Patent Application
20180118699
The present invention provides, inter alia, SK and IK channel activators and compositions containing such compounds. Methods for using such compounds or compositions are also provided.
In the initial phases of the heart failure (HF) syndrome, small resistance vessels, especially nonessential circulations such as the renal, splanchnic (e.g. mesenteric) and cutaneous vascular beds, constrict in order to maintain systemic blood pressure. For patients with HF, the body's adaptation can be more detrimental than the initial insult. As the HF syndrome progresses, the elevated vascular tone in coronary arteries and peripheral vessels becomes excessive and maladaptive, increasing cardiac workload, reducing myocardial perfusion, and predisposing the heart to ischemia (Zelis et al. 1982, Katz et al, 1992, Schrier et al. 1999). The reduction in myocardial blood flow and the increased cardiac workload conspire to impair cardiac output and ventricular remodeling, accelerating the progression to decompensated HF (Mroz et al. 2012, Duvvuri et al. 2012, He et al. 2011, Smith et al 2012). The increase in vascular tone reflects high levels of circulating vasoactive hormones and cytokines, formation of reactive oxygen species (ROS), and endothelial dysfunction. The endothelial dysfunction is manifested by reduced endothelial-mediated dilatation caused by diminished bioavailability of nitric oxide (NO) and endothelial-derived hyperpolarizing factors (EDHF) (Katz et al. 1992). Reducing this excessive vascular tone is an important therapeutic goal in the treatment of patients with HF, but in many cases the drugs, which do not directly target the molecules responsible for the dysfunction, lack efficacy and/or have side effects that can detrimentally affect cardiac function.
An unappreciated contributor to the increased vasoconstriction in HF is the intrinsic dysfunction of vascular smooth muscle (VSM) cells within resistance vessels. In mice with HF, VSM cells have abnormal electrical properties, namely reduced expression and activity of voltage- and Ca2+-activated large conductance K+ (BK) channels, increased depolarization of the membrane potential, and increased intracellular Ca2+ concentration, leading to enhanced pressure-induced vasoconstriction (myogenic tone) (Wan et al, 2013). Mice with deletion of the smooth muscle-specific BK β1 regulatory subunit also have markedly reduced survival and worsened HF after ligation of their left coronary artery (Brenner et al. 2000, Kumar et al. 2005). Without the BK β1 subunit, small vessels are hypercontractile in response to increases in luminal pressure and norepinephrine, the latter being markedly elevated after myocardial infarction (MI) and in HF (Xu et al. 2011, Graham et al. 2004, McAlpine et al. 1988, Sigurdsson et al. 1993, Lymperopoulos et al. 2010). The phenotype of decreased survival and cardiac function in BK β1 null mice is thus likely due to the failure to blunt coronary and/or peripheral vasoconstriction. This hypothesis offers an explanation for the increased incidence and severity of MI and HF in animals and humans with diabetes and hypertension. Diabetes and hypertension have been shown in most, but not all animal models to be associated with reduced expression and/or function of the pore-forming BK α subunit and its β1 regulatory subunit (Rusch 2009, Phillips et al. 2005, Dong et al. 2009, Liu et al. 2009, Nieves-Cintron et al, 2008, Amberg et al, 2003(a), Amberg et al. 2003(b), Bagi et al. 2005, Lagaud et al 2001, McGahon et al. 2007(a), McGahon et al. 2007(b), Lu et al. 2008, Dong et al. 2008, Yang et al. 2012).
An important approach to treat HF is to reduce vascular resistance, but most therapies do not specifically target the intrinsic dysfunctions within endothelial and VSM cells. Nitrates can reduce vascular contractility, but the benefits of nitrates, shown in animal and human studies, are short-lived due to the development of tolerance and pseudotolerance (Gupta et al. 2013). Since BK channels play a central role in the mediation of the vasodilator response to NO and other nitrates, the findings of their reduced expression and function provide a mechanism to explain, at least in part, the limited effectiveness of nitrates (Bychkov et al. 1998). Many other vasodilators either decrease cardiac contractility (e.g. Ca2+ channel antagonists), which preclude their use in patients with HF, or can increase heart rate, arrhythmias and long-term mortality (e.g. dobutamine, milrinone). BK channels are especially attractive targets because of their critical function in the peripheral vasculature, their putative cardioprotective role in mitochondria of cardiomyocytes, and their absence in the plasma membrane of cardiomyocytes (Wan et al. 2013, Babu et al. 2007, Clements et al. 2011, Singh et al, 2013). These characteristics are particularly important for designing treatments for HF patients.
The present invention is provided to overcome, inter alia, the challenges noted above.
Drugs that enhance endothelial derived hyperpolarizing factor (EDHF), an alternative pathway that is both not dependent upon the function of BK channels and not affected by tolerance, may represent a new class of agents for HF patients. Activation of endothelial Ca2+-activated small and intermediate conductance K+ channels (SK3 and IK1) can indirectly hyperpolarize the underlying VSM cells. Whereas endothelial-derived vasodilators, such as P450-derived epoxyeicosatrienoic acids (EET), NO, prostacyclin, lipoxygenase products and hydrogen peroxide, hyperpolarize and relax VSM cells by activating BK channels, BK channels are not required for EDHF-mediated vasodilation. Increasing SK3 and IK1 currents by transgenic or pharmacological approaches decreased myogenic tone, increased acetylcholine-induced relaxation of rat cremaster arterioles, and restored the attenuated EDHF-type relaxation in mesenteric arteries from Zucker diabetic rats. Activating SK3 and IK1 channels induced dilation and increased coronary flow in Langendorff-perfused rat hearts. SKA-31, a specific activator of SK3 and IK1 channels, caused dilation of mesenteric resistance vessels isolated from mice with HF. The present invention describes improved SK and IK agonist compounds which are shown herein to activate heterologously expressed SK3 channels.
One embodiment of the present invention is a compound having formula (I):
wherein
A and B are independently selected from the group consisting of S or N;
R1, R2, R3, R4, and R6 are independently selected from the group consisting of H, halogen, alkyl, ester, ether, thioether, aryl, heteroaryl, CN, NO2, and amine;
R5, is selected from the group consisting of H, ester, thioether, aryl, heteroaryl, NO2, and amine;
Another embodiment of the present invention is a compound having the structure:
or a crystalline form, hydrate, or pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a compound having the structure:
or a crystalline form, hydrate, or pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound of the present invention.
Another embodiment of the present invention is a method for treating or ameliorating the effects of a condition in a subject in need thereof comprising administering to the subject an effective amount of a compound of the present invention or a pharmaceutical composition of the present invention.
Another embodiment of the present invention is a method for treating or ameliorating the effects of heart failure syndrome (HF) in a subject in need thereof comprising administering to the subject an effective amount of a pharmaceutical composition of the invention.
Another embodiment of the present invention is a kit for treating or ameliorating the effects of a condition in a subject in need thereof, the kit comprising an effective amount of a compound of the present invention or a pharmaceutical composition of the present invention, packaged together with instructions for its use.
Another embodiment of the present invention is a kit for treating or ameliorating the effects of heart failure syndrome (HF) in a subject in need thereof, the kit comprising an effective amount of a pharmaceutical composition of the present invention, packaged together with instructions for its use.
Another embodiment of the present invention is a composition comprising a compound of the present invention.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.
One embodiment of the present invention is a compound having formula (I):
wherein
A and B are independently selected from the group consisting of S or N;
R1, R2, R3, R4, and R6 are independently selected from the group consisting of H, halogen, alkyl, ester, ether, thioether, aryl, heteroaryl, CN, NO2, and amine;
R5, is selected from the group consisting of H, ester, thioether, aryl, heteroaryl, NO2, and amine;
The term “aryl” as used herein includes substituted or unsubstituted single-ring aromatic groups in which each atom of the ring is carbon. Preferably the ring is a 3- to 8-membered ring, more preferably a 6-membered ring. The term “aryl” also includes polycyclic ring systems having two or more cyclic rings in which two or more carbons are common to two adjoining rings wherein at least one of the rings is aromatic, e.g., the other cyclic rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls, heteroaryls, and/or heterocyclyls. Aryl groups include benzene, naphthalene, phenanthrene, phenol, aniline, and the like.
The term “substituted” means moieties having substituents replacing a hydrogen on one or more carbons of the backbone. It will be understood that “substitution” or “substituted with” includes the implicit proviso that such substitution is in accordance with the permitted valence of the substituted atom and the substituent, and that the substitution results in a stable compound, e.g., which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc. The permissible substituents can be one or more and the same or different for appropriate organic compounds.
As used herein, a “halide” means a halogen atom such as fluorine, chlorine, bromine, iodine, or astatine.
As used herein, an “aromatic ring” is an aryl or a heteroaryl. The term “heteroaryl” includes substituted or unsubstituted aromatic single ring structures, preferably 3- to 8-membered rings, more preferably 5- to 7-membered rings, even more preferably 5- to 6-membered rings, whose ring structures include at least one heteroatom, preferably one to four heteroatoms, more preferably one or two heteroatoms. The term “heteroaryl” also includes polycyclic ring systems having two or more cyclic rings in which two or more carbons are common to two adjoining rings wherein at least one of the rings is heteroaromatic, e.g., the other cyclic rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls, heteroaryls, and/or heterocyclyls. Heteroaryl groups include, for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, pyrazole, pyridine, pyrazine, pyridazine, and pyrimidine, and the like.
The term “heteroatom” as used herein means an atom of any element other than carbon or hydrogen. Preferred heteroatoms are nitrogen, oxygen, and sulfur; more preferably, nitrogen and oxygen or nitrogen and sulfur.
The terms “amine” and “amino” are art-recognized and refer to both unsubstituted and substituted amines and salts thereof, e.g., a moiety that can be represented by
wherein R7, R8, and R8′ each independently represent a hydrogen or a hydrocarbyl group, or R7 and R8 taken together with the N atom to which they are attached complete a heterocycle having from 4 to 8 atoms in the ring structure. The term “primary” amine means only one of R7 and R8 or one of R7, R8, and R8′ is a hydrocarbyl group. Secondary amines have two hydrocarbyl groups bound to N. In tertiary amines, all three groups, R7, R8, and R8′, are replaced by hydrocarbyl groups.
As used herein, the term “heterocycle” means substituted or unsubstituted non aromatic ring structures. Preferably the heterocycle comprises 3 to 8 membered rings, and at least one heteroatom, preferably one to four heteroatoms, more preferably one or two heteroatoms. Such heterocycles may include at least one ring nitrogen. The term “heterocycle” also includes polycyclic ring systems having two or more cyclic rings in which two or more carbons are common to two adjoining rings wherein at least one of the rings is heterocyclic, e.g., the other cyclic ring(s) can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls, heteroaryls, and/or heterocyclyls. Heterocycle groups of the present invention include, for example, piperidine, piperazine, pyrrolidine, morpholine, lactones, lactams, and the like.
The term “alkyl” means the radical of saturated aliphatic groups that does not have a ring structure, including straight-chain alkyl groups, and branched-chain alkyl groups. In certain embodiments, a straight chain or branched chain alkyl has 6 or fewer carbon atoms such as 4 or fewer carbon atoms in its backbone (e.g., C1-C6 for straight chains, C3-C6 for branched chains).
The term “ether”, as used herein, means a hydrocarbyl group linked through an oxygen to another hydrocarbyl group. Accordingly, an ether substituent of a hydrocarbyl group may be hydrocarbyl-O—. Ethers may be either symmetrical or unsymmetrical. Examples of ethers include, but are not limited to, heterocycle-O-heterocycle and aryl-O-heterocycle. Ethers include “alkoxyalkyl” groups, which may be represented by the general formula alkyl-O-alkyl.
The term “thioether”, as used herein, means a hydrocarbyl group linked through an sulfur to another hydrocarbyl group. Accordingly, an ether substituent of a hydrocarbyl group may be hydrocarbyl-S—. Thioethers may be either symmetrical or unsymmetrical. Examples of thioethers include, but are not limited to, heterocycle-S-heterocycle and aryl-S-heterocycle. Thioethers include groups, which may be represented by the general formula alkyl-S-alkyl.
The term “aliphatic”, as used herein, means a group composed of carbon and hydrogen atoms that does not contain aromatic rings. Accordingly, aliphatic groups include alkyl, alkenyl, alkynyl, and carbocyclyl groups. A preferred C1-4 aliphatic is a vinyl moiety.
The term “alkenyl”, as used herein, means an aliphatic group containing at least one double bond.
The term “alkynyl”, as used herein, means an aliphatic group containing at least one triple bond.
In the present invention, the term “crystalline form” means the crystal structure of a compound. A compound may exist in one or more crystalline forms, which may have different structural, physical, pharmacological, or chemical characteristics. Different crystalline forms may be obtained using variations in nucleation, growth kinetics, agglomeration, and breakage. Nucleation results when the phase-transition energy barrier is overcome, thereby allowing a particle to form from a supersaturated solution. Crystal growth is the enlargement of crystal particles caused by deposition of the chemical compound on an existing surface of the crystal. The relative rate of nucleation and growth determine the size distribution of the crystals that are formed. The thermodynamic driving force for both nucleation and growth is supersaturation, which is defined as the deviation from thermodynamic equilibrium. Agglomeration is the formation of larger particles through two or more particles (e.g., crystals) sticking together and forming a larger crystalline structure.
The term “hydrates”, as used herein, means a solid or a semi-solid form of a chemical compound containing water in a molecular complex. The water is generally in a stoichiometric amount with respect to the chemical compound.
As used herein, “pharmaceutically acceptable salts” refer to derivatives of the compounds disclosed herein wherein the compounds are modified by making acid or base salts thereof. Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines; alkali or organic salts of acidic residues such as carboxylic acids; and the like. For example, such salts include salts from ammonia, L-arginine, betaine, benethamine, benzathine, calcium hydroxide, choline, deanol, diethanolamine (2,2′-iminobis(ethanol)), diethylamine, 2-(diethylamino)-ethanol, 2-aminoethanol, ethylenediamine, N-ethyl-glucamine, hydrabamine, 1H-imidazole, lysine, magnesium hydroxide, 4-(2-hydroxyethyl)-morpholine, piperazine, potassium hydroxide, 1-(2-hydroxy-ethyl)-pyrrolidine, sodium hydroxide, triethanolamine (2,2′,2″-nitrilotris(ethanol)), tromethamine, zinc hydroxide, acetic acid, 2.2-dichloro-acetic acid, adipic acid, alginic acid, ascorbic acid, L-aspartic acid, benzenesulfonic acid, benzoic acid, 2,5-dihydroxybenzoic acid, 4-acetamido-benzoic acid, (+)-camphoric acid, (+)-camphor-10-sulfonic acid, carbonic acid, cinnamic acid, citric acid, cyclamic acid, decanoic acid, dodecylsulfuric acid, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-hydroxy-ethanesulfonic acid, ethylenediamonotetraacetic acid, formic acid, fumaric acid, galacaric acid, gentisic acid, D-glucoheptonic acid, D-gluconic acid, D-glucuronic acid, glutamic acid, glutantic acid, glutaric acid, 2-oxo-glutaric acid, glycero-phosphoric acid, glycine, glycolic acid, hexanoic acid, hippuric acid, hydrobromic acid, hydrochloric acid isobutyric acid, DL-lactic acid, lactobionic acid, lauric acid, lysine, maleic acid, (−)-L-malic acid, malonic acid, DL-mandelic acid, methanesulfonic acid, galactaric acid, naphthalene-1,5-disulfonic acid, naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid, nitric acid, octanoic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, pamoic acid (embonic acid), phosphoric acid, propionic acid, (−)-L-pyroglutamic acid, salicylic acid, 4-amino-salicylic acid, sebacic acid, stearic acid, succinic acid, sulfuric acid, tannic acid, (+)-L-tartaric acid, thiocyanic acid, p-toluenesulfonic acid and undecylenic acid. Further pharmaceutically acceptable salts can be formed with cations from metals like aluminum, calcium, lithium, magnesium, potassium, sodium, zinc and the like. (also see Pharmaceutical salts, Berge, S. M. et al., J. Pharm. Sci., (1977), 66, 1-19).
The pharmaceutically acceptable salts of the present invention can be synthesized from a compound disclosed herein which contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a sufficient amount of the appropriate base or acid in water or in an organic diluent like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile, or a mixture thereof.
Another embodiment of the present invention is a compound having the formula (II)
wherein
A and B are independently selected from the group consisting of S or N;
R1, R2, R3, R4, and R6 are independently selected from the group consisting of H, halogen, C1-6alkyl, —X—C1-6alkyl, CN, —NO2, —C(O)—R7 and —N(R7)(R8);
R5, is selected from the group consisting of H, —NO2, —C(O)—R7 and N(R7)(R8);
The term “Cx-y” when used in conjunction with a chemical moiety, such as, alkyl, alkenyl, or alkoxy is meant to include groups that contain from x to y carbons in the chain. For example, the term “Cx-yalkyl” means substituted or unsubstituted saturated hydrocarbon groups, including straight-chain alkyl and branched-chain alkyl groups that contain from x to y carbons in the chain, including haloalkyl groups such as trifluoromethyl and 2,2,2-trifluoroethyl, etc. The terms “C2-yalkenyl” and “C2-yalkynyl” refer to substituted or unsubstituted unsaturated aliphatic groups analogous in length and possible substitution to the alkyls described above, but that contain at least one double or triple bond respectively.
Another embodiment of the present invention is a compound selected from the group consisting of
and crystalline forms, hydrates, or pharmaceutically acceptable salts thereof.
Another embodiment of the present invention is a compound having the structure:
or a crystalline form, hydrate, or pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a compound having the structure:
or a crystalline form, hydrate, or pharmaceutically acceptable salt thereof.
Another embodiment of the present invention is a pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound of the present invention.
The compounds or compositions, including pharmaceutical compositions of the present invention may be administered in any desired and effective manner: for oral ingestion, or as an ointment or drop for local administration to the eyes, or for parenteral or other administration in any appropriate manner such as intraperitoneal, subcutaneous, topical, intradermal, inhalation, intrapulmonary, rectal, vaginal, sublingual, intramuscular, intravenous, intraarterial, intrathecal, or intralymphatic. Further, compounds or compositions, including pharmaceutical compositions of the present invention may be administered in conjunction with other treatments. Compounds or compositions, including pharmaceutical compositions of the present invention may be encapsulated or otherwise protected against gastric or other secretions, if desired.
The compositions, including pharmaceutical compositions of the invention may comprise one or more active ingredients in admixture with one or more pharmaceutically-acceptable diluents or carriers and, optionally, one or more other compounds, drugs, ingredients and/or materials. Regardless of the route of administration selected, the agents/compounds of the present invention are formulated into pharmaceutically-acceptable dosage forms by conventional methods known to those of skill in the art. See, e.g., Remington, The Science and Practice of Pharmacy (21st Edition, Lippincott Williams and Wilkins, Philadelphia, Pa.).
Pharmaceutically acceptable diluents or carriers are well known in the art (see, e.g., Remington, The Science and Practice of Pharmacy (21st Edition, Lippincott Williams and Wilkins, Philadelphia, Pa.) and The National Formulary (American Pharmaceutical Association, Washington, D.C.)) and include sugars (e.g., lactose, sucrose, mannitol, and sorbitol), starches, cellulose preparations, calcium phosphates (e.g., dicalcium phosphate, tricalcium phosphate and calcium hydrogen phosphate), sodium citrate, water, aqueous solutions (e.g., saline, sodium chloride injection, Ringer's injection, dextrose injection, dextrose and sodium chloride injection, lactated Ringer's injection), alcohols (e.g., ethyl alcohol, propyl alcohol, and benzyl alcohol), polyols (e.g., glycerol, propylene glycol, and polyethylene glycol), organic esters (e.g., ethyl oleate and triglycerides), biodegradable polymers (e.g., polylactide-polyglycolide, poly(orthoesters), and poly(anhydrides)), elastomeric matrices, liposomes, microspheres, oils (e.g., corn, germ, olive, castor, sesame, cottonseed, and groundnut), cocoa butter, waxes (e.g., suppository waxes), paraffins, silicones, talc, salicylate, etc. Each pharmaceutically acceptable diluent or carrier used in a pharmaceutical composition of the invention must be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not injurious to the subject. Diluents or carriers suitable for a selected dosage form and intended route of administration are well known in the art, and acceptable diluents or carriers for a chosen dosage form and method of administration can be determined using ordinary skill in the art.
The compositions, including pharmaceutical compositions of the invention may, optionally, contain additional ingredients and/or materials commonly used in pharmaceutical compositions. These ingredients and materials are well known in the art and include (1) fillers or extenders, such as starches, lactose, sucrose, glucose, mannitol, and silicic acid; (2) binders, such as carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone, hydroxypropylmethyl cellulose, sucrose and acacia; (3) humectants, such as glycerol; (4) disintegrating agents, such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, sodium starch glycolate, cross-linked sodium carboxymethyl cellulose and sodium carbonate; (5) solution retarding agents, such as paraffin; (6) absorption accelerators, such as quaternary ammonium compounds; (7) wetting agents, such as cetyl alcohol and glycerol monostearate; (8) absorbents, such as kaolin and bentonite clay; (9) lubricants, such as talc, calcium stearate, magnesium stearate, solid polyethylene glycols, and sodium lauryl sulfate; (10) suspending agents, such as ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth; (11) buffering agents; (12) excipients, such as lactose, milk sugars, polyethylene glycols, animal and vegetable fats, oils, waxes, paraffins, cocoa butter, starches, tragacanth, cellulose derivatives, polyethylene glycol, silicones, bentonites, silicic acid, talc, salicylate, zinc oxide, aluminum hydroxide, calcium silicates, and polyamide powder; (13) inert diluents, such as water or other solvents; (14) preservatives; (15) surface-active agents; (16) dispersing agents; (17) control-release or absorption-delaying agents, such as hydroxypropylmethyl cellulose, other polymer matrices, biodegradable polymers, liposomes, microspheres, aluminum monostearate, gelatin, and waxes; (18) opacifying agents; (19) adjuvants; (20) wetting agents; (21) emulsifying and suspending agents; (22), solubilizing agents and emulsifiers, such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (in particular, cottonseed, groundnut, corn, germ, olive, castor and sesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan; (23) propellants, such as chlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, such as butane and propane; (24) antioxidants; (25) agents which render the formulation isotonic with the blood of the intended recipient, such as sugars and sodium chloride; (26) thickening agents; (27) coating materials, such as lecithin; and (28) sweetening, flavoring, coloring, perfuming and preservative agents. Each such ingredient or material must be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not injurious to the subject. Ingredients and materials suitable for a selected dosage form and intended route of administration are well known in the art, and acceptable ingredients and materials for a chosen dosage form and method of administration may be determined using ordinary skill in the art.
The compositions, including pharmaceutical compositions of the present invention suitable for oral administration may be in the form of capsules, cachets, pills, tablets, powders, granules, a solution or a suspension in an aqueous or non-aqueous liquid, an oil-in-water or water-in-oil liquid emulsion, an elixir or syrup, a pastille, a bolus, an electuary or a paste. These formulations may be prepared by methods known in the art, e.g., by means of conventional pan-coating, mixing, granulation or lyophilization processes.
Solid dosage forms for oral administration (capsules, tablets, pills, dragees, powders, granules and the like) may be prepared, e.g., by mixing the active ingredient(s) with one or more pharmaceutically-acceptable diluents or carriers and, optionally, one or more fillers, extenders, binders, humectants, disintegrating agents, solution retarding agents, absorption accelerators, wetting agents, absorbents, lubricants, and/or coloring agents. Solid compositions of a similar type may be employed as fillers in soft and hard-filled gelatin capsules using a suitable excipient. A tablet may be made by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared using a suitable binder, lubricant, inert diluent, preservative, disintegrant, surface-active or dispersing agent. Molded tablets may be made by molding in a suitable machine. The tablets, and other solid dosage forms, such as dragees, capsules, pills and granules, may optionally be scored or prepared with coatings and shells, such as enteric coatings and other coatings well known in the pharmaceutical-formulating art. They may also be formulated so as to provide slow or controlled release of the active ingredient therein. They may be sterilized by, for example, filtration through a bacteria-retaining filter. These compositions may also optionally contain opacifying agents and may be of a composition such that they release the active ingredient only, or preferentially, in a certain portion of the gastrointestinal tract, optionally, in a delayed manner. The active ingredient can also be in microencapsulated form.
Liquid dosage forms for oral administration include pharmaceutically-acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. The liquid dosage forms may contain suitable inert diluents commonly used in the art. Besides inert diluents, the oral compositions may also include adjuvants, such as wetting agents, emulsifying and suspending agents, sweetening, flavoring, coloring, perfuming and preservative agents. Suspensions may contain suspending agents.
The compositions, including pharmaceutical compositions of the present invention for rectal or vaginal administration may be presented as a suppository, which may be prepared by mixing one or more active ingredient(s) with one or more suitable nonirritating diluents or carriers which are solid at room temperature, but liquid at body temperature and, therefore, will melt in the rectum or vaginal cavity and release the active compound. The pharmaceutical compositions of the present invention which are suitable for vaginal administration also include pessaries, tampons, creams, gels, pastes, foams or spray formulations containing such pharmaceutically-acceptable diluents or carriers as are known in the art to be appropriate.
Dosage forms for the topical or transdermal administration include powders, sprays, ointments, pastes, creams, lotions, gels, solutions, patches, drops and inhalants. The active agent(s)/compound(s) may be mixed under sterile conditions with a suitable pharmaceutically-acceptable diluent or carrier. The ointments, pastes, creams and gels may contain excipients. Powders and sprays may contain excipients and propellants.
The compositions, including pharmaceutical compositions of the present invention suitable for parenteral administrations may comprise one or more agent(s)/compound(s) in combination with one or more pharmaceutically-acceptable sterile isotonic aqueous or non-aqueous solutions, dispersions, suspensions or emulsions, or sterile powders which may be reconstituted into sterile injectable solutions or dispersions just prior to use, which may contain suitable antioxidants, buffers, solutes which render the formulation isotonic with the blood of the intended recipient, or suspending or thickening agents. Proper fluidity can be maintained, for example, by the use of coating materials, by the maintenance of the required particle size in the case of dispersions, and by the use of surfactants. These pharmaceutical compositions may also contain suitable adjuvants, such as wetting agents, emulsifying agents and dispersing agents. It may also be desirable to include isotonic agents. In addition, prolonged absorption of the injectable pharmaceutical form may be brought about by the inclusion of agents which delay absorption.
In some cases, in order to prolong the effect of a drug (e.g., pharmaceutical formulation), it is desirable to slow its absorption from subcutaneous or intramuscular injection. This may be accomplished by the use of a liquid suspension of crystalline or amorphous material having poor water solubility.
The rate of absorption of the active agent/drug then depends upon its rate of dissolution which, in turn, may depend upon crystal size and crystalline form. Alternatively, delayed absorption of a parenterally-administered agent/drug may be accomplished by dissolving or suspending the active agent/drug in an oil vehicle. Injectable depot forms may be made by forming microencapsule matrices of the active ingredient in biodegradable polymers. Depending on the ratio of the active ingredient to polymer, and the nature of the particular polymer employed, the rate of active ingredient release can be controlled. Depot injectable formulations are also prepared by entrapping the drug in liposomes or microemulsions which are compatible with body tissue. The injectable materials can be sterilized for example, by filtration through a bacterial-retaining filter. Any formulation of the invention may be presented in unit-dose or multi-dose sealed containers, for example, ampules and vials, and may be stored in a lyophilized condition requiring only the addition of the sterile liquid diluent or carrier, for example water for injection, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the type described above.
In some aspects of this embodiment, the pharmaceutical composition comprises one or more additional active agents. In a preferred aspect of this embodiment, the additional active agents are selected from the group consisting of nitrates, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers, beta-adrenergic blockers, and aldosterone receptor antagonists.
As used herein, a “blocker”, “antagonist” or “inhibitor” means a substance which can reduce the activity or the expression of the target protein. As used herein, an “agonist” means a substance which can activate a receptor.
In one aspect of this embodiment, the additional active agent is a nitrate. Nitrates are venodialators that are thought to reduce the workload of the heart. Nitrates include, without limitation, nitroglycerin, isorbide mononitrate, isosorbide dinitrate, pentaerythrityl tetranitrate, sodium nitroprusside, molsidomine, and SIN-1.
In another aspect of this embodiment, the additional active agent is an ACE inhibitor. ACE inhibitors block the conversion of angiotensin I (AI) to angiotensin II (AII). ACE inhibitors include, without limitation, alacepril, alatriopril, altiopril calcium, ancovenin, benazepril, benazepril hydrochloride, benazeprilat, benzoylcaptopril, captopril, captopril-cysteine, captopril-glutathione, ceranapril, ceranopril, ceronapril, cilazapril, cilazaprilat, delapril, delapril-diacid, enalapril, enalaprilat, enapril, epicaptopril, foroxymithine, fosfenopril, fosenopril, fosenopril sodium, fosinopril, fosinopril sodium, fosinoprilat, fosinoprilic acid, glycopril, hemorphin-4, idrapril, imidapril, indolapril, indolaprilat, libenzapril, lisinopril, lyciumin A, lyciumin B, mixanpril, moexipril, moexiprilat, moveltipril, muracein A, muracein B, muracein C, pentopril, perindopril, perindoprilat, pivalopril, pivopril, quinapril, quinapril hydrochloride, quinaprilat, ramipril, ramiprilat, spirapril, spirapril hydrochloride, spiraprilat, spiropril, spiropril hydrochloride, temocapril, temocapril hydrochloride, teprotide, trandolapril, trandolaprilat, utibapril, zabicipril, zabiciprilat, zofenopril, zofenoprilat, casokinins, lactokinins and lactotripeptides such as Val-Pro-Pro and Ile-Pro-Pro.
In another aspect of this embodiment, the additional active agent is an angiotensin receptor blocker. Angiotensin receptors are a class of G protein-coupled receptors with angiotensin II as their ligands. There are at least four subtypes of angiotensin receptors, type 1, type 2, type 3, and type 4. Angiotensin receptor blockers include, without limitation, candesartan, candesartan cilexetil, losartan, valsartan, irbesartan, tasosartan, telmisartan, eprosartan, L158,809, saralasin and olmesartan.
In another aspect of this embodiment, the additional active agent is a beta-adrenergic blocker. Beta-adrenergic blocker are beta-adrenoreceptor antagonists which include, without limitation, acebutolol, atenolol, betaxolol, bevantolol, bisoprolol, celiprolol, cetamolol, epanolol, esmolol, levobetaxolol, practolol, propranolol, bucindolol, carteolol, carvedilol, nadolol, oxyprenolol, penbutolol, pindolol, sotalol, timolol, metoprolol, nebivolol, butaxamine, IC-118,551 and SR59230A.
In a further aspect of this embodiment, the additional active agent is a aldosterone receptor antagonist. Aldosterone receptor antagonists are diuretics that help the body get rid of extra water. Aldosterone receptor antagonists include, without limitation, spironolactone, eplerenone, canrenone, propenone and mexrenone.
In the present invention, the additional active agents may be used as a single agent together with the compounds and compositions, including pharmaceutical compositions of the present invention. The additional active agents may also be used with one or more additional active agents together with the compounds and compositions, including pharmaceutical compositions.
Another embodiment of the present invention is a method for treating or ameliorating the effects of a condition in a subject in need thereof comprising administering to the subject an effective amount of a compound of the present invention or a pharmaceutical composition of the present invention. In a preferred aspect of this embodiment, the condition is high blood pressure or diabetes. In a more preferred aspect of this embodiment, the condition is heart failure syndrome.
In the present invention, an “effective amount” or a “therapeutically effective amount” of a compound or composition, including pharmaceutical compositions disclosed herein is an amount of such compound or composition that is sufficient to effect beneficial or desired results as described herein when administered to a subject. Effective dosage forms, modes of administration, and dosage amounts may be determined empirically, and making such determinations is within the skill of the art. It is understood by those skilled in the art that the dosage amount will vary with the route of administration, the rate of excretion, the duration of the treatment, the identity of any other drugs being administered, the age, size, and species of mammal, e.g., human patient, and like factors well known in the arts of medicine and veterinary medicine. In general, a suitable dose of a compound or composition, including pharmaceutical compositions according to the invention will be that amount of the compound or composition which is the lowest dose effective to produce the desired effect. The effective dose of a compound or composition, including pharmaceutical compositions of the present invention may be administered as two, three, four, five, six or more sub-doses, administered separately at appropriate intervals throughout the day.
A suitable, non-limiting example of a dosage of any of the compounds or compositions, including pharmaceutical compositions disclosed herein is from about 1 mg/kg to about 2400 mg/kg per day, such as from about 1 mg/kg to about 1200 mg/kg per day, 75 mg/kg per day to about 300 mg/kg per day, including from about 1 mg/kg to about 100 mg/kg per day. Other representative dosages of such agents include about 1 mg/kg, 5 mg/kg, 10 mg/kg, 15 mg/kg, 20 mg/kg, 25 mg/kg, 30 mg/kg, 35 mg/kg, 40 mg/kg, 45 mg/kg, 50 mg/kg, 60 mg/kg, 70 mg/kg, 75 mg/kg, 80 mg/kg, 90 mg/kg, 100 mg/kg, 125 mg/kg, 150 mg/kg, 175 mg/kg, 200 mg/kg, 250 mg/kg, 300 mg/kg, 400 mg/kg, 500 mg/kg, 600 mg/kg, 700 mg/kg, 800 mg/kg, 900 mg/kg, 1000 mg/kg, 1100 mg/kg, 1200 mg/kg, 1300 mg/kg, 1400 mg/kg, 1500 mg/kg, 1600 mg/kg, 1700 mg/kg, 1800 mg/kg, 1900 mg/kg, 2000 mg/kg, 2100 mg/kg, 2200 mg/kg, and 2300 mg/kg per day. The effective dose of compounds or compositions, including pharmaceutical compositions disclosed herein, may be administered as two, three, four, five, six or more sub-doses, administered separately at appropriate intervals throughout the day.
As used herein, the terms “ameliorate”, “ameliorating” and grammatical variations thereof mean to decrease the severity of the symptoms of a disease in a subject.
As used herein, the terms “treat,” “treating,” “treatment” and grammatical variations thereof mean subjecting an individual subject to a protocol, regimen, process or remedy, in which it is desired to obtain a physiologic response or outcome in that subject, e.g., a patient. In particular, the methods and compositions, including pharmaceutical compositions of the present invention may be used to slow the development of disease symptoms or delay the onset of the disease or condition, or halt the progression of disease development. However, because every treated subject may not respond to a particular treatment protocol, regimen, process or remedy, treating does not require that the desired physiologic response or outcome be achieved in each and every subject or subject population, e.g., patient population. Accordingly, a given subject or subject population, e.g., patient population, may fail to respond or respond inadequately to treatment.
As used herein, a “subject” is a mammal, preferably, a human. In addition to humans, categories of mammals within the scope of the present invention include, for example, primates, farm animals, domestic animals, laboratory animals, etc. Some examples of agricultural animals include cows, pigs, horses, goats, etc. Some examples of domestic animals include dogs, cats, etc. Some examples of laboratory animals include primates, rats, mice, rabbits, guinea pigs, etc.
Another embodiment of the present invention is a method for treating or ameliorating the effects of heart failure syndrome (HF) in a subject in need thereof comprising administering to the subject an effective amount of a pharmaceutical composition of the invention. In this embodiment, the subject is a mammal as described above, preferably a human.
Another embodiment of the present invention is a kit for treating or ameliorating the effects of a condition in a subject in need thereof. In this embodiment, the kit comprises an effective amount of a compound of the present invention or a pharmaceutical composition of the present invention, packaged together with instructions for its use. In a preferred aspect of this embodiment, the condition is high blood pressure or diabetes. In a more preferred aspect of this embodiment, the condition is heart failure syndrome.
The kits of the present invention may also include suitable storage containers, e.g., ampules, vials, tubes, etc., for the compounds and compositions, including pharmaceutical compositions of the present invention and other active agents and/or reagents, e.g., buffers, balanced salt solutions, etc., for use in administering the compounds and compositions to subjects. The compounds and compositions, including pharmaceutical compositions of the present invention may be present in the kits in any convenient form, such as, e.g., in a solution or in a powder form. The kits may further include a packaging container, optionally having one or more partitions for housing the compounds and pharmaceutical compositions and other optional reagents.
Another embodiment of the present invention is a kit for treating or ameliorating the effects of heart failure syndrome (HF) in a subject in need thereof. In this embodiment, the kit comprises an effective amount of a pharmaceutical composition of the present invention, packaged together with instructions for its use.
Another embodiment of the present invention is a composition comprising a compound of the present invention. In one aspect of this embodiment, the composition is a research reagent. As used herein, a “research reagent” is any compound or composition used in the execution of investigational activities.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
For recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the numbers 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.
The following examples are provided to further illustrate certain aspects of the present invention. These examples are illustrative only and are not intended to limit the scope of the invention in any way.
As shown below, the substituted tetralone compounds (0.5 mmol), thiourea (0.5 mmol), PTSA (2.5 mmol) and iodine (0.15 mmol) were mixed in a round bottom flask. DMSO (2 mL) was added and the reaction mixture was stirred under oxygen at 75° C. for 24 hours. The reaction mixture was cooled down and diluted with ethyl acetate. The organic phase was washed with aqueous sodium bicarbonate, water and brine. The resulting organic phase was dried over sodium sulfate and concentrated. The crude product was purified with preparative TLC with ethyl acetate and dichloromethane (ratio 1:3) to provide the product. Compound identities were confirmed by 1HNMR.
XX-03-52, 1HNMR (400 MHz, CDCl3) δ 8.37 (d, J=8.8 Hz, 1H), 7.61 (d, J=8.8 Hz, 1H), 7.50 (d, J=8.4 Hz, 1H), 7.21 (d, J=9.6 Hz, 1H), 7.19 (s, 1H), 5.55 (br s, 2H), 3.93 (s, 3H).
XX-03-53, 1HNMR (400 MHz, CDCl3) δ 7.80 (d, J=2.8 Hz, 1H), 7.75 (d, J=9.2 Hz, 1H), 7.53 (d, J=8.8 Hz, 1H), 7.50 (d, J=8.4 Hz, 1H), 7.14 (d, J=8.8 Hz, 1H), 7.13 (d, J=8.8 Hz, 1H), 5.70 (br s, 2H), 3.97 (s, 3H); 13CNMR (100 MHz, CDCl3) δ 166.1, 158.1, 146.7, 129.7, 127.9, 127.4, 126.9, 122.5, 118.0, 116.2, 102.1, 55.5.
XX-03-54, 1HNMR (400 MHz, CDCl3) δ 8.09 (dd, J=2.4, 10.0 Hz, 1H), 7.85 (dd, J=5.6, 9.2 Hz, 1H), 7.62 (d, J=8.8 Hz, 1H), 7.59 (d, J=9.2 Hz, 1H), 7.25 (dt, J=2.8, 8.6 Hz, 1H), 5.47 (br s, 2H).
XX-03-55, 1HNMR (400 MHz, CDCl3) δ 8.48 (d, J=2.0 Hz, 1H), 7.79 (d, J=8.8 Hz, 1H), 7.66 (d, J=8.8 Hz, 1H), 7.57 (d, J=8.8 Hz, 1H), 7.42 (dd, J=2.0, 8.8 Hz, 1H), 5.38 (br s, 2H).
XX-03-56, 1HNMR (400 MHz, CDCl3) δ 8.43 (d, J=9.2 Hz, 1H), 7.85 (s, 1H), 7.69 (d, J=8.4 Hz, 1H), 7.52 (d, J=8.4 Hz, 1H), 7.49 (d, J=9.2 Hz, 1H), 5.36 (br s, 2H).
XX-03-68, 1HNMR (400 MHz, CDCl3) δ 8.65 (d, J=1.2 Hz, 1H), 7.73 (d, J=8.8 Hz, 1H), 7.67 (d, J=8.8 Hz, 1H), 7.56 (d, J=8.8 Hz, 1H), 7.55 (d, J=8.4 Hz, 1H), 5.37 (br s, 2H).
XX-03-69, 1HNMR (400 MHz, Acetone-d6) δ 8.58 (d, J=8.4 Hz, 1H), 8.45 (s, 1H), 7.97 (d, J=9.2 Hz, 1H), 7.74 (d, J=9.2 Hz, 1H), 7.74 (d, J=9.2 Hz, 1H), 7.18 (br s, 2H).
XX-03-70, 1HNMR (400 MHz, Acetone-d6) δ 8.05 (d, J=8.0 Hz, 1H), 7.93 (d, J=9.2 Hz, 1H), 7.73 (d, J=8.8 Hz, 1H), 7.43 (t, J=8.0 Hz, 1H), 7.06 (br s, 2H), 6.92 (d, J=7.2 Hz, 1H), 4.00 (s, 3H); 13CNMR (100 MHz, Acetone-d6) δ 167.2, 155.6, 148.2, 127.7, 126.7, 125.8, 123.9, 117.9, 116.2, 115.2, 103.6, 55.0.
XX-03-71, 1HNMR (400 MHz, Acetone-d6) δ 8.51 (d, J=8.8 Hz, 1H), 7.92 (d, J=9.2 Hz, 1H), 7.89 (d, J=8.8 Hz, 1H), 7.80 (d, J=7.2 Hz, 1H), 7.42 (d, J=8.0 Hz, 1H), 7.10 (br s, 2H); 13CNMR (100 MHz, Acetone-d6) δ 168.1, 148.7, 130.4, 129.3, 127.7, 127.1, 126.0, 124.1, 122.2, 120.6, 119.7.
XX-03-72, 1HNMR (400 MHz, Acetone-d6) δ 8.14 (d, J=1.6 Hz, 1H), 7.76 (d, J=8.4 Hz, 1H), 7.69 (d, J=8.4 Hz, 1H), 7.66 (d, J=9.2 Hz, 1H), 7.61 (dd, J=1.6, 9.0 Hz, 1H), 7.00 (br s, 2H).
XX-03-73, 1HNMR (400 MHz, Acetone-d6) δ 7.79 (dd, J=5.6, 8.4 Hz, 1H), 7.77 (d, J=8.4 Hz, 1H), 7.65 (d, J=8.4 Hz, 1H), 7.65 (d, J=8.4 Hz, 1H), 7.37 (dt, J=2.4, 8.8 Hz, 1H), 6.91 (br s, 2H).
Macroscopic currents were recorded from HEK293 cells transfected with GFP-tagged human KCNN3, transcript variant 1 cDNA (Accession # NM_002249) in the whole-cell patch clamp configuration at 22-24° C. Currents were activated by 200 msec depolarizing ramps between −120 mV and +30 mV, from a holding potential of −90 mV, and then deactivated by repolarization to the holding potential. Voltage ramps were applied every 5 seconds. The bath solution was 140 mM NaCl, 4 mM KCl, 0.1 mM CaCl2, 3 mM Mg Cl2, 10 mM HEPES (pH 7.4) and the pipette solution was 150 mM KCl, 5 mM TES (pH 7.2), 2 mM HEDTA, and 1 μM free Ca2+. The free Ca2+ concentration was calculated using the Max Chelator program and confirmed using a Ca2+ electrode (Orion). Agonists were superfused in the bath solution. Results are shown in
Small arteries constrict in response to increases in luminal pressure, and dilate with decreased pressure, a process referred to as myogenic tone (Bayliss 1902). Arteriolar myogenic tone is an intrinsic property of arterial smooth muscle and occurs independently of systemic factors such as nervous and hormonal inputs. Importantly, myogenic tone underlies the local autoregulation of microvascular blood flow and sets the vascular diameter upon which vasodilators and vasoconstrictors act (Johnson 1986, Hill et al. 2009). Its measurement ex vivo reflects the intrinsic contractility of the small vessels that are fundamental for setting the systemic vascular resistance. Abnormalities in myogenic tone are linked to hypertension, diabetes, stroke and vasospasm (see
Membrane potential, Ca2+ influx and the cytosolic Ca2+ concentration within VSM cells are key regulators of myogenic tone and vascular contractility (Hill et al. 2006). Myogenic tone requires pressure and stretch activation of transient receptor potential (TRP) channels, leading to VSM cell depolarization, opening of voltage-gated Ca2+ channels, and Ca2+ influx, which causes myosin light chain (MLC) phosphorylation and contraction (Earley et al. 2010, Fernandez-Tenorio et al. 2011) (see, e.g.,
Male C57BL/6 mice underwent left anterior descending (LAD) artery ligation to cause a large MI (see
Strong hyperpolarizing currents are required to prevent excessive contraction in response to intraluminal pressure and vasoconstrictors, and for relaxation in response to vasodilators. BK channels are especially important contributors to these hyperpolarizing currents by virtue of their large conductance and Ca2+ sensitivity (Nelson et al. 1995). In smooth muscle, BK α associates with its (31 regulatory subunit, priming the channel for activation by Ca2+ sparks from the nearby ryanodine receptors (see
The increased circulating hormones and cytokines, and formation of ROS are important contributors to the HF syndrome, and are the likely effectors, at least in part, of the reduced expression and function of BK channels. There is precedent for this: for instance, the expression of BK subunits is transcriptionally regulated by circulating angiotensin II (Ang II), aldosterone, and the cytokine IL-1β (Amberg et al. 2003a, Amberg et al. 2003b, Layne et al. 2008, Nieves-Cintron et al. 2007, Ambroisine et al. 2007, Gao et al. 2010). BK β1 expression is a direct target of serum response factor-myocardin transactivation (Long et al. 2009). Forced expression of myocardin increased BK β1 expression, and knockdown of serum response factor decreased BK β1 expression. Although mice with HF had no change in the mRNA expression of serum response factor and myocardin compared to sham controls (assessed using an Affymetrix GeneChip Gene 1.0 ST Array, see below), HF may cause changes in the post translational mechanisms regulating myocardin's protein stability or transcriptional activity (Xie et al. 2009, Morita et al. 2014, Mack 2011, Choi et al. 2010). Miano and colleagues also showed that BK α mRNA expression was not dependent upon myocardin, implying distinct transcriptional control mechanisms of the two BK subunits (Long et al. 2009). The loss of protection from depolarizing influences in the vasculature of HF animals is analogous to altered expression and function of K+ channels in cardiomyocytes occurring in conditions such as HF and cardiac hypertrophy (Tomaselli et al. 2004).
Inhibitors of circulating hormones may restore normal expression and function of BK α and β1. If normalizing BK channel expression/function is therapeutic, the transcriptional regulation of BK subunits are explored. BK β1 association with BK α may also be dynamically regulated, based upon a recent study demonstrating that antegrade trafficking of β1 subunit-containing Rab11A-positive recycling endosomes and subsequent association with surface BK α is the primary mechanism by which NO activates BK channels and induces vasodilation (Leo et al. 2014).
Decreased Vascular BK Channel Activity Reduces Survival and Heart Function after MI.
In the setting of acute myocardial ischemia, coronary vasodilation is an important means of enhancing oxygen delivery to threatened myocardium in order to limit infarct size. 10- to 12-week old male mice with deletion of BK β1 were found to have markedly reduced survival after LAD-ligation (see
The coronary anatomy of WT and β1 null mice, assessed using plastic replica casts, were grossly indistinguishable, insofar as the number of major vessels were equal (see
Since the sole validated function of BK β1 is to modulate the open probability of BK α in smooth muscle, and BK β1 is not expressed in adult cardiomyocytes, these findings reveal an important protective role for vascular BK channels in the peri-MI period (Brenner et al. 2000, Long et al. 2009, Jiang et al. 1999, Behrens et al. 2000). Activating BK channels may be a novel approach to treat coronary spasm and myocardial hypoperfusion after MI.
Whereas endothelial-derived vasodilators, such as P450-derived epoxyeicosatrienoic acids (EET), NO, prostacyclin, lipoxygenase products and hydrogen peroxide, hyperpolarize and relax VSM cells by activating BK channels, BK channels are not required for EDHF-mediated vasodilation (Feletou 2009, Larsen et al. 2006, Liu et al. 2011). Increasing SK3 and IK1 currents by transgenic or pharmacological approaches decreased myogenic tone, increased acetylcholine-induced relaxation of rat cremaster arterioles, and restored the attenuated EDHF-type relaxation in mesenteric arteries from Zucker diabetic rats (Taylor et al. 2003, Brondum et al. 2010). Activating SK3 and IK1 channels induced dilation and increased coronary flow in Langendorff-perfused rat hearts (Mishra et al. 2012). Enhancing EDHF by activating endothelial SK3 and IK1 channels is an innovative and unique approach to circumvent the dysfunctional control of the VSM membrane potential caused by decreased BK channel expression and function in HF. SKA-31, a specific activator of SK3 and IK1 channels, caused dilation of mesenteric resistance vessels isolated from mice with HF. Indirectly hyperpolarizing the underlying VSM cells through enhancing EDHF (see, e.g.,
VSM Plasma Membrane Potential is Depolarized in Mesenteric Arteries of Mice with HF.
The plasma membrane potential of VSM cells was directly measured in intact vessels by impaling them through the adventitia with glass microelectrodes. At three intraluminal pressures, the degree of depolarization was significantly greater in vessels from mice with HF than sham-controls (see
RNA, from third-order mesenteric arteries of mice 6 weeks after sham or LAD-ligation, was hybridized to an Affymetrix GeneChip Gene 1.0 ST Array. For the primary analysis, in which the hypotheses were pre-specified for candidate ion channels and pumps, the type I error rate was controlled at 0.01. The conclusions are: (1) of the 88 detectable K+ channels and related regulatory proteins, 4 K+ channels were reduced by >1.4-fold, SK3, IK1, BK α and KV1.5 (see
Decreased Expression and Function of Vascular BK Channels in Mice with HF.
Immunohistochemistry (IHC) was used to semi-quantitatively assess the expression of BK α and β1 in the tunica media layer of mesenteric arteries. The antibodies were deemed specific based upon the failure to detect BK α and β1 in immunoblots and IHC of arterial extracts of BK α and β1 null mice, respectively (see
Spontaneous transient outward currents (STOCs), the simultaneous openings of BK channels in response to localized Ca2+ sparks, were measured in freshly isolated third-order mesenteric VSM cells (see
In mesenteric arteries isolated from mice without HF, paxilline, a specific BK channel blocker, increased constriction by 10.9%, a relative increase of 51.9% in myogenic tone (see
If the increased myogenic tone of HF was due to diminished BK currents secondary to reduced expression of BK channel subunits, HF should have a minimal effect on the already elevated myogenic tone in BK β1 null mice. To test this premise, the myogenic tone of sham-operated and LAD artery-ligated BK β1 null mice was compared. Despite having severely reduced LV function (see
Characterization of the Vasoreactivity and Electrical Profiles of Coronary Septal Arteries and Third-Order Mesenteric Resistance Arteries Early after MI and During the Progression to Severe HF.
The myogenic tone of mesenteric vessels were measured, 4-months post-MI. The myogenic tone in mesenteric vessels was 36%, 42% and 43% at 40, 80 and 120 mm Hg, respectively, which was greater than at 6-weeks post-MI for 40 and 80 mm Hg. These results are consistent with the hypothesis that as HF worsens, vascular resistance increases.
Four time-points are used: 2 days, 2 weeks, 6 weeks and 4 months post-MI or post-sham operations. LV function is assessed by echocardiography, and post-mortem cardiac histopathology and lung to body weight ratio. Two vascular beds are studied: (i) coronary septal arteries and (ii) third-order mesenteric arteries. Coronary septal arteries, which are identified as described (Sankaranarayanan et al. 2009, Edwards et al. 1998, Davis et al. 2012), are not perturbed during LAD-ligation because they are branches of the right coronary artery (see FIGS. 5A and 1 in Kumar et al. 2005) and not the LAD as they are in humans. Myogenic tone and VSM Ca2+ concentration are determined simultaneously using the Ionoptix system (Wan et al. 2013). The VSM cell membrane potential is measured in intact vessels as shown in
Real-time qPCR, semi-quantitative immunoblotting and immunohistochemistry are performed (using DAB-IHC and Duolink—see
Duolink has >100-times higher signal:noise ratio than standard immunofluorescence (0-link manual, page 8). Frozen sections of mice aortas were incubated first with anti-BK α monoclonal antibody, and then with two distinct anti-mouse secondary antibodies. These secondary antibodies are known as proximity ligation assay (PLA) probes, and each is attached to a unique short DNA strand. When the two PLA probes are in close proximity (<40 nm) to one another, the DNA strands interact and are amplified several-hundredfold by a polymerase. Each distinct spot represents either a single BK α tetramer or closely apposed tetramers. Using the Duolink image tool, individual spots were automatically identified (see
Mesenteric and coronary VSM cells are isolated from HF and sham mice for in-depth electrophysiological analysis: (a) voltage-dependent Ca2+ currents are measured using whole-cell technique (Navedo et al. 2007). K+ currents are inhibited using 1 μM paxilline and 10 mM 4-aminopyridine, and CsCl in the pipette. (b) KV channels are measured using whole-cell voltage clamp. BK channels are blocked with paxilline. (c) Ca2+-activated Cl− currents (TMEM16a) are measured using whole-cell configuration with Cs+ replacing K+ in the intracellular solution (Manoury et al. 2010, Hartzell et al 2009). Cells are dialyzed with solutions containing either 17 or 600 nM free Ca2+. (d) Mechanosensitive cation channels (TRP) are recorded using cell-attached configuration, applying mild negative pressure of 7.5-15 mm Hg. The bath and pipette solution contain 140 mM CsCl (Ozgen et al. 2007).
If the Ca2+-activated Cl− currents mediated by TMEM16a are increased in HF, for example, reducing these currents using an inhibitor, T16Ainh-A01 (aminophenylthiazole), may normalize myogenic tone in vitro (Bulley et al. 2012, Davis et al. 2012). A similar approach is used for mechanosensitive (TRP) channels.
The reduction in STOCs (see
BK channels integrate the signals of multiple kinases activated by classical neurohormonal pathways, including the sympathetic nervous system and RAAS. PKA and PKG phosphorylation increase BK channel activity, whereas PKC and c-Src phosphorylation decrease BK channel activity (Schubert et al. 2001, Alioua et al. 2002). PKC and c-Src inhibitors are used, anticipating that if the channels are inhibited because of PKC or c-Src phosphorylation in VSM cells from HF mice, BK currents increase upon inhibition of PKC or c-Src. Similarly, oxidative stress within the vessel wall may be responsible for depolarization and reduced amplitude and frequency of STOCs in VSM cells from HF mice. Because of the non-specificity of Nox inhibitors, two inhibitors are tested: diphenylene iodonium (Lu et al. 2010) and apocynin, anticipating that if BK channels are inhibited due to oxidation in VSM cells from HF mice, BK currents increase after NAPDH oxidase inhibition. The results are compared to VSM cells isolated from sham mice, as PKC, c-Src or Nox antagonists should have minimal effects on these channels.
Conversely, Ang II (2 μM) or phenylephrine (10 μM) may differentially modulate channel function in VSM cells isolated from HF mice. Ang II inhibits BK channel function through its effects on PKC, c-Src and Nox (Lu et al. 2010). Ang II causes less inhibition if BK channels are already modified by PKC, c-Src or Nox pathways, as compared to the effect on BK channels from control VSM cells, in which Ang II suppressed BK current by 50% (see
Two determinants of BK activity are used: STOCs and whole-cell current density. BK currents are a very large fraction of the total K+ currents in freshly isolated mesenteric VSM cells (see
Ang II, aldosterone and cytokine IL-1β, which are elevated in HF, are known to decrease the expression of BK α and β1 mRNA (Amberg et al. 2003a, Amberg et al. 2003b, Layne et al. 2008, Nieves-Cintron et al. 2007, Ambroisine et al. 2007, Gao et al. 2010). Spironolactone prevents the aldosterone-induced decrease in BK α mRNA in cultured rat VSM cells (Ambroisine et al. 2007). The activated RAAS and neurohumoral system is hypothesized to be responsible for the reduction in BK α and β1 mRNA expression. It will be determined whether in vivo administration of spironolactone and lisinopril can restore BK α and β1 expression and normalize myogenic tone. Angiotensin converting enzyme and aldosterone antagonists are mainstays of HF therapy. Changes in myogenic tone by these drugs may be due to their effects on transcriptional regulation of BK α and β1, and/or effects on channel gating.
Three groups of mice, each with 10 animals are used for this study. Two groups of mice undergo LAD ligation and the third group undergo sham ligation. After 6 weeks, LV function is assessed by echocardiography. For the HF groups, only those mice with EF less than 40% are used. One LAD-ligated/HF group is treated with both lisinopril (66 mg/L-Sigma) and spironolactone (250 mg/L-Sigma) in the drinking water. This combination has been used in mice and the concentrations are in the effective range for mice: 10 mg/kg/day for lisinopril and 37.5 mg/kg/day for spironolactone (Thomas-Gatewood et al. 2011). Five mice in each group are euthanized at 1 week and 3 weeks post-initiation of the drugs. LV function is assessed by echocardiography prior to euthanasia. Endpoints will include BK α and β1 expression in mesenteric and coronary vessels, assessed using real time qPCR, immunohistochemistry and immunoblot, and the myogenic tone of mesenteric vessels. Electrophysiological studies of isolated VSM cells from mesenteric and coronary vessels are performed if myogenic tone is normalized.
PKC phosphorylation of BK channels not only reduces BK currents, but also renders the channels insensitive to PKA and PKG stimulation (Zhou et al. 2010). If HF renders the BK channels relatively resistant to vasodilators that are dependent upon PKA and PKG signaling, the vasodilators sodium nitroprusside, salbutamol or milrinone are applied to VSM cells. If the channels are relatively resistant to PKA or PKG-stimulation, the PKC, c-Src or Nox inhibitors may normalize the response of BK channels to PKA- and PKG-dependent vasodilators. These studies will explore the recent finding (Leo et al. 2014) that BK β1 association with BK α may be dynamically regulated, and that NO activates BK channels by inducing the association of BK α and β1 at the surface membrane.
There are important differences between the hearts of mice and larger animals, especially in regards to metabolic and heart rate. HF frequently develops insidiously in humans over several years, whereas in most animal models, it occurs subacutely over weeks to months. Human vessels are obtained from HF patients (e.g. heart transplant recipients or HF patients undergoing surgical procedures such as ICD implantation) to determine whether HF causes elevation of myogenic tone and reduced expression of BK subunits.
Doxycycline-inducible, VSM cell-specific BK α-expressing Tg mice were created. Founders were identified and were crossed with SM22α-rtTA mice to create double Tg mice (see
Doxycycline-inducible VSM-specific BK β1-expressing Tg mice were also created. Multiple founders were identified and these mice were also crossed with SM22α-rtTA mice, yielding double Tg mice (see
For both BK α and BK β1, there are four groups: Group 1: BK α or β1 expression starting 72 hours after LAD-ligation and continued to 6 weeks; Group 2: BK α or β1 expression starting 5 weeks after LAD-ligation; Group 3 (control): No doxycycline; Group 4 (control): Doxycycline in non-Tg (littermate). (see
BK Current Density Measured in VSM Cells Isolated from Mice with HF.
The transgenes are likely not susceptible to HF-induced changes in transcription, unlike endogenous channels, confirmed by real time qPCR and immunohistochemistry. The primary endpoints are the extent of myogenic tone and the membrane potential of VSM cells in mesenteric arterial vessels. If the reduction in BK currents is responsible for the increased myogenic tone, restoration of BK current density (Groups 1 or 2) reduces myogenic tone and restores the normal membrane potential compared to Groups 3 and 4. These studies are complemented with determinations of Ca2+ concentration and STOCs. Secondary endpoints include LV function, assessed by echocardiography 2 days, and 1 and 3 weeks post-MI and by echocardiography and pressure-volume loops at 6 weeks post-MI. During post-mortem analysis, the severity of HF is inferred from lung weight, heart weight, and body weight ratios (Wan et al. 2013, Jones et al. 2003, Fraccarollo et al. 2008), and cardiac histopathological studies. Echocardiograms are performed using a Vevo 2100. High-frequency speckle tracking echocardiography derived LV ejection fraction, mass, volume, global and regional strain analyses are performed as described in Bhan et al. 2014. Infarct size is determined by 2,3,5-triphenyltetrazolium (TTC) staining. In addition, plasma BNP levels are determined by ELISA (Kamiya Biomedical). The study is sufficiently powered to detect an improvement in ejection fraction of 10% with a power of 0.8, a of 0.05 and standard deviation of 12. Mortality is tracked, but additional mice are required to detect a survival benefit: for instance, 58 mice in Group 1 are needed to achieve a power of 0.7 to detect a significant (a 0.05) improvement to 0.90 from 0.72.
Expression of K+ channels may worsen mortality or outcomes, perhaps due to hypotension. Adverse effects on blood pressure or survival have not been detected with a 30-50% increased expression of either BK α or β1 in mice prior to MI or HF. Titration and appropriate timing of expression of BK channels, however, may be important for the mice after MI and in HF.
Sufficiency of Increased Expression of BK Channels to Normalize Myogenic Tone and Improve LV Function in Mice with Pre-Existing HF.
For these experiments, it will be determined whether increasing BK currents when the HF syndrome is already established can reduce myogenic tone and improve cardiac function. This timing more closely mimics clinical practice. For both BK a or β1 Tg mice, there are four groups of mice, each with 10 animals (see
SM22α-rtTA/tetO-BK β1 mice (see
Three groups of mice are studied, each with 25 mice (see
The operator and all data collection will be blinded. The primary endpoint is mortality: Group 1 and Group 2 vs. Group 3. Additional endpoints are: (a) Clinical severity of HF- to be assessed as described above; (b) Histopathological analysis of infarct size and LV dimensions; (c) Cardiac function—assessed using echocardiography 2 days and 1, 3, and 6 weeks after MI and by pressure-volume loops 6 weeks after MI. An improvement in survival can be detected to 60% in Group 1 or Group 2 vs. Group 3 with a power of 0.7 and a type I error probability of 0.05. An improvement in ejection fraction of 9% can be detected at day 2 with a power of 0.8, assuming 20 mice survive per group.
It is also important to determine whether expression of BK β1 in VSM cells prior to LAD ligation alters the ratio of infarct size (IS) to area-at-risk (AAR). Five additional mice in groups 1, 2 and 3 are used to assess the early effects of BK β1 expression. This ratio is expected to be reduced with BK β1 expression. AAR and IS are performed as previously described (Redfors et al. 2012, Moon et al. 2003, Takagawa et al. 2007). Seventy-two hours after LAD ligation, 2 ml of 5% Evans blue is injected into the RV chamber. The mice are subsequently euthanized with 4 ml of 0.5 M KCl. Serial 6-μM-thick cryostat sections are prepared. Well-perfused myocardium are outlined in blue. Unstained areas contain a combination of infarcted and unperfused, but viable myocardium (AAR). Sections are then incubated in TTC; AAR is stained red and dead tissue is white.
In addition to crossing the BK α and β1 Tg mice to co-express both BK α and β1, a doxycycline-inducible BK α-β1 Tg mouse line was developed using an internal ribosomal entry site. Co-expression of both BK α and β1 may be necessary to normalize myogenic tone and improve LV function. Expression of BK α and β1 subunits should increase the amplitude and frequency of STOCs. If the STOCs are not increased and membrane potential is not normalized, Ca2+ sparks and the ratio between Ca2+ sparks and STOCs are measured, which represents the coupling gain. HF may affect the coupling gain.
Rottlerin (mallotoxin) was identified as a potent activator of BK channels (Zakharov et al. 2005). Rottlerin increased BK currents in rodent and human VSM cells and decreased myogenic tone. These effects are β1 subunit-independent (Zakharov et al. 2005), an ideal property to circumvent the HF-induced reduction in BK β1 expression. Rottlerin markedly attenuated methacholine-induced airway hyperreactivity in two murine models of asthma without any apparent adverse effects (Goldklang et al. 2013). If experiments using Tg BK mice show a beneficial effect, the effects of rottlerin on myogenic tone and LV function will be studied. Plasma rottlerin levels were measured two hours after IP injection of 100 μg (5 μg/g) using LC/MS and a plasma level of 2.9 μg/mL was found (see Goldklang et al. 2013), which is more than the EC50 for BK channel activation (Zakharov et al. 2005). Rottlerin is injected via IP injection 1 hour prior to LAD-ligation and its administration continued via daily IP injections for 1 week. If survival is improved, the experiments are continued for up to 6 weeks (without rottlerin injections) to determine if LV function is improved. If survival is improved but LV function is not improved, then experiments will be performed in which rottlerin is continued for the entire 6-week experimental period. Any beneficial effect of rottlerin may be multifactorial, since at relatively high concentrations, rottlerin can inhibit several cellular kinases including PKC (Gschwendt et al. 1994, Soltoff 2001, Soltoff 2007). Another BK agonist, NS11021 (Neurosearch) (Bentzen et al. 2007), is used for confirmation. If myogenic tone is normalized, and survival and LV function are not improved by VSM-specific re-expression of BK β1, but they are improved with pharmacological activation of BK channels, this suggests that non-vascular BK channels, perhaps in the cardiomyocyte mitochondria, might be responsible.
Indirect Hyperpolarization of VSM can Improve Survival and HF after MI in the WT and BK β1 Null Mice.
Another approach to correct the HF-induced depolarization of VSM cells is to enhance EDHF. Activation of endothelial SK3 and IK1 channels and the resulting hyperpolarization of endothelial cells is a crucial step for initiation of EDHF-mediated hyperpolarization of the VSM membrane potential and vasodilatation (Taylor et al. 2003, Edwards et al. 1998). SKA-31 (naphtha[1,2-d]thiazol-2-ylamine) is a potent activator of IK1 (EC50 of 250 nM) and SK channels (EC50 in low μM range) (Sankaranarayanan et al. 2009). SKA-31, which exhibits excellent selectivity for SK and IK1 channels, is not cytotoxic at concentrations up to 100 μM and has no acute toxicity in rats and mice. After administering SKA-31 (10 mg/kg) IP to mice, plasma concentrations were 5.5 μM at 2 h, 1.4 μM at 4 h and 500 nM at 24 h, of which 39% was plasma protein-bound and 61% was free, with higher concentrations in plasma than tissue. A single IP injection of 10 mg/kg SKA-31 lowered blood pressure by 4 mm Hg at 24 h, likely because the free plasma level of SKA-31 was 300 nM. A higher dose of 30 mg/kg lowered mean arterial pressure by 6 mm Hg in normal mice and by 12 mm Hg in mice with hypertension. Based upon these data, the initial dose of SKA-31 used was 30 mg/kg IP every 24 h.
Endothelial cells were isolated from third-order mesenteric arteries of mice using enzymatic digestion followed by labeling the endothelial cells with CD34 antibody-labeled magnetic beads, collecting them using a magnet and then releasing them from the beads by competition. To measure both SK3 and IK1 currents, the cells were dialyzed with KCl-solution containing 3 μM free Ca2+ and currents elicited using voltage ramps and by the activator NS-309 (see
Activation of SK3 and IK1 Channels Reduces Myogenic Tone in Mesenteric Resistance Vessels of Mice with HF and Controls.
Intraluminal infusion of either 250 nM or 1 μM SKA-31 effectively dilated the vessels from both control mice and mice with HF (see
Augmentation of EDHF via activation of SK3 and IK1 channels was tested to see if it can relax phenylephrine-constricted mesenteric resistance vessels of BK β1 null mice, similar to the effects in WT mice. Perfusion of SKA-31 caused dilatation of vessels from β1 null mice to a similar extent as vessels from WT mice (see
In vivo administration of SKA-31 may improve remodeling after MI. Two sets of experiments will be performed, one in which SKA-31 (30 mg/kg) or vehicle is administered IP daily to WT mice starting 72 hours after MI for 6 weeks, and the other in which SKA-31 is administered to WT mice with LV ejection fraction less than 40%, starting 6 weeks after LAD-ligation (see
Pharmacologic activation of EDHF may improve survival after LAD-ligation in BK β1 null mice. 30 mg/kg SKA-31 is injected daily via IP injections for 3 days prior to LAD-ligation. On the third day, the LAD is ligated in SKA-31-treated and vehicle-injected animals. SKA-31 is continued for 1 week after MI. If survival is improved, the experiments are continued for up to 6 weeks (without continued SKA-31) to determine if LV function is improved. If survival is improved but LV function is not improved, another set of experiments is performed in which SKA-31 treatment is started before LAD-ligation and continued throughout the 6-week-protocol. The primary endpoint is mortality. Additional endpoints are: (a) Clinical severity of HF; (b) Histopathological analysis; (c) Cardiac function, assessed at 2 days and 1, 3, and 6 weeks after MI by echocardiography and by pressure-volume loops at 6 weeks after MI.
To facilitate these studies, SKA-31 is administered via Alzet osmotic pumps. There is conflicting data about the role of SK channels in either promoting or preventing atrial fibrillation, perhaps dependent upon the species (Ozgen et al. 2007, Diness et al. 2010, Ellinor et al. 2010). Most pertinent for the studies in mice is the finding that genetic ablation of SK2 promoted atrial arrhythmias (Li et al. 2009), suggesting that atrial arrhythmias in SKA-31 treated mice are not increased. SK1 and SK2 channels are down-regulated in the atrium of patients with atrial fibrillation (Yu et al. 2012). SK currents play little role in the regulation of the action potential in normal ventricles, but are up-regulated in epicardial cells of the failing rabbit ventricle (Chua et al. 2011). During rapid pacing or fibrillation in failing ventricles, increased Ca2+ may activate SK channels and shorten the action potential, increasing the risk of ventricular fibrillation. Thus, telemeters will be implanted (Morrow et al. 2011) to determine whether SKA-31 increases the incidence of arrhythmias in the mice with HF.
Afterload Reduction Improves Cardiac Work in an Animal with Systolic Heart Failure
In this experiment, a wildtype mouse with heart failure (FAC 38%) was given an IV bolus of SKA-31 (3 mg/kg) through the left internal jugular vein during simultaneous recording of left ventricular pressure and volume using a Milar conductance catheter inserted through the right carotid artery. (
BK channel deficient mice and wildtype littermates developed an ischemic cardiomyopathy after surgical ligation of the left anterior descending coronary artery. Systolic heart failure was confirmed six weeks later by noting a fractional area of change (FAC) of 40% or lower on 2D echocardiography (Visualsonics Vevo 2100). Mice with heart failure were laid supine on a heated pad under isoflurane anesthesia and mechanically depilated. The left internal jugular vein was isolated by blunt dissection and cannulated with a custom-built catheter made from PET tubing (McMaster). Blood loss and insensible losses were treated with a slow infusion of NS (0.1-0.5 ml) intravenously and/or subcutaneously. The right common carotid artery was isolated by blunt dissection and a 1 Fr conductance catheter (PVR-1045 made by Milar) was introduced and carefully advanced into the left ventricle (LV). Continuous LV pressure and volume measurements were recorded (MPVS Ultra by Milar with PowerLab 4/35 and LabChart by ADInstruments). After stable baseline LV measurements were recorded, vehicle (Cremophor EL made by Calbiochem) was infused intravenously into the cannulated internal jugular vein as a single bolus in the same volume later used to deliver an intravenous bolus of SKA-31 (Tocris) at 3 mg/kg. Volume measurements were calibrated by administration of 0.1 ml hypertonic saline and with blood obtained from cardiac puncture in a standardized cuvette (Milar).
As seen in
All patents, patent applications, and publications cited above are incorporated herein by reference in their entirety as if recited in full herein.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention and all such modifications are intended to be included within the scope of the following claims.
This patent application is a continuation in part of PCT international application no. PCT/US2016/033584, filed May 20, 2016, which claims the benefit of U.S. Provisional Patent Application No. 62/165,628, filed May 22, 2015, which applications are incorporated by reference herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 62165628 | May 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2016/033584 | May 2016 | US |
| Child | 15819732 | US |
