Patent Application
20090305258
This invention relates to studies on cause-effect relationships between alterations of cholesterol homeostasis, the ageing process and the development of proliferative diseases (such as atherosclerosis and neoplasms) and/or conformational diseases (such as Alzheimer's disease (AD) and prion-related diseases) in humans and/or other mammals.
This invention describes methods allowing to distinguish healthy subjects from subjects affected by, or at risk of developing, the above mentioned proliferative and/or conformational diseases.
More specifically, the present invention provides methods for assessing cholesterol trafficking and metabolism in peripheral cells, such as peripheral blood mononuclear cells (PBMCs) or skin fibroblasts. The methods encompass in vitro assays aimed at determining the levels of the following parameters:
i) total cholesterol, HDL- and LDL-cholesterol in serum, which can be used for differential diagnosis;
ii) free cholesterol (FC) in plasma membranes and esterified cholesterol (EC) in the cell cytoplasm;
iii) proteins (SREBP2, LDL-R, HMG-CoA-R, MDR1-Pgp, ACAT, nCEH, caveolin-1 and ABCA-1) and related mRNAs involved in the intracellular trafficking and metabolism of cholesterol;
iv) proteins (APP, Neprilysin, β-secretase, PrP, tumor suppressor proteins, oncoproteins) and related mRNAs involved in the pathogenesis of specific proliferative and/or conformational diseases;
v) pro-inflammatory cytokines (TNFα, IL-1α, IFNγ) and related mRNAs.
As summarized in
Most of the newly synthesized FC participates to the physiological turnover of cholesterol in the rafts (c), and/or to the biogenesis of new membrane domains in ER and Golgi.
If plasma membrane FC exceeds a threshold level, the excess FC is rapidly transported to the ER (d) by a P-glycoprotein (MDR1-Pgp, firstly described for its ability to catalyse ATP-dependent efflux of cytotoxic agents from tumour cells) (1-3), encoded by the multidrug resistance (MDR1) gene. Then, the ER-resident enzyme acyl-coenzyme-A cholesterol-acyl-transferase (ACAT) (e) converts FC into cholesteryl-esters (CE), which are stored in droplets in the cytoplasm (4-6). Although neosynthesized FC in the ER could be efficiently used for esterification by virtue of its proximity to ACAT, only a small percentage of it is directly esterified. Virtually all the esterified FC derives from the plasma membrane.
If cells require cholesterol, CE is re-hydrolyzed to FC by the enzyme neutral cholesterol-esters-hydrolase (nCEH) (f) and re-delivered to the plasma membrane by caveolin-1. If in excess, FC is eliminated from the cells through an efflux pathway spanning from the ER to the plasma membrane and involving caveolin-1, the ATP-Binding Cassette of the sub-family A, member 1 (ABC-A1), and plasma HDLs (g) (4-9).
Recent work has led to a new way of considering biological membranes, which are now viewed as a “mosaic of lipid domains”, rather than as an “homogeneous fluid mosaic”. It appears that cholesterol is not uniformly distributed within membranes, but is distributed into cholesterol-poor and cholesterol-rich domains. Among the latter, those containing saturated sphingolipids are referred to as lipid rafts (10), which float freely in plasma membranes carrying a few passenger proteins. When the passenger proteins are activated by a ligand, lipid rafts coalesce to form larger platforms where many different proteins converge in order to perform specific functions, such as signalling, processing or transport (10, 11).
Examples of raft passenger proteins are receptors for growth factors, signal transducing proteins (P21Ras), chemokine receptors, proteins of the MHC classes, antigen receptors, and various proteins with yet undefined functions, such as the amyloid precursor protein (APP) and the cellular prion protein (PrPc) involved in AD and Prion-related disorders, respectively. Interestingly, the amount of cholesterol associated with these domains exerts profound effects on the functions of the raft-resident proteins. For instance, perduring low levels of cholesterol in lipid rafts lead to a continuous stimulus for cell growth promotion (12), or induce APP and cellular prion protein PrPc to undergo pathologic processes leading to the generation of their corresponding pathogenic forms: the amyloidogenic A-beta peptide and the scrapie prion protein (PrPsc), respectively (13, 14).
The initial studies of the authors on cholesterol trafficking and metabolism in proliferative diseases have been carried out in: i), rat acinar cell pancreatic carcinoma and ascite hepatoma (15, 16); ii) tissue biopsies from human solid and haematologic neoplasms (17-20); iii) cell lines derived from various human and animal tumours (21-23) and, iv) vessel tissues from healthy and atherosclerotic patients (24, 25).
In these in vivo and in vitro models the authors have demonstrated that the rate of cell proliferation correlates: i) positively, with the levels of MDR1-Pgp and ACAT and related mRNAs, leading to FC esterification; and ii) negatively, with the levels of nCEH and caveolin-1 and relative mRNAs, leading to intracellular CE accumulation (Table 1).
Accordingly, when compared to healthy controls, subjects affected by the above mentioned proliferative diseases possess lower FC levels, significantly higher CE levels and lower HDL-cholesterol levels.
However such an experimental approach, based on the analysis of tissue samples, is not readily applicable to the elaboration of an easy and fast test for the diagnosis and/or prognosis of proliferative or conformational diseases. The authors disclose in the present invention that PBMCs and/or fibroblasts, preferably PBMCs, are good starting materials to perform assays aimed at the identification of mRNAs and/or its protein products involved in intracellular cholesterol homeostasis.
Among the increasing number of neurodegenerative pathologies classified as conformational diseases, AD and Prion-related disorders (also known as Transmissible Spongiform Encephalopaties, TSEs) can be considered prototypes of non-transmissible and transmissible cerebral amyloidoses, respectively (25-27).
Although there are obvious differences in the aetiology and pathogenesis of these diseases, intracellular CE accumulation is a common hallmark indicating a link between these pathogenetic processes and the alteration of cholesterol homeostasis.
All the above diseases have reached serious proportions in terms of incidence. However, no conclusive means of diagnosis, therapy or prevention are available yet for AD and prion-related disorders (28-30).
The present invention:
a) is useful to identify a cell phenotype possibly predisposing to pathological conditions;
b) contributes to the early diagnosis of suspected AD and TSE by providing a sensitive test before signs and symptoms become fully apparent;
c) represents a tool to assess the risk of developing AD among relatives of AD patients;
d) provides an easy method to study several cellular and plasma parameters involved in cholesterol metabolism, which are altered in various conformational and proliferative diseases, and then serves as an indicator of the effectiveness of therapy.
This invention allows to distinguish between clinically normal individuals and individuals affected by, or at risk to develop, proliferative and/or conformational diseases characterized by alterations in CE metabolism, which influences raft-associated protein function. This invention provides means for the diagnosis, prophylaxis, therapy and therapy monitoring of proliferative and/or conformational diseases.
In addition, it provides means for predicting/establishing the therapeutic/prophylactic value of existing or of new, synthetic or natural compounds/active principles for the ageing process, proliferative or conformational diseases.
In any event, when used either alone or in conjunction with other tests (i.e. ApoE aplotype), the methods of the present invention will improve the probability of correctly diagnosing the presence, the risk, or the absence of proliferative diseases, conformational diseases, such as AD, or prion-related diseases, such as TSE.
The present invention includes novel approaches for detecting the above diseases or the individual susceptibility to the above diseases by using plasma, skin fibroblasts and/or PBMCs. These approaches involve the evaluation of total cholesterol, HDL-cholesterol and LDL-cholesterol levels in plasma, and of FC and CE content, and of cholesterol trafficking and metabolism indicators in both non-proliferating and proliferating peripheral cells.
Diagnosis of disease, or of risk of disease, will be made through the comparison of the relative values of the above parameters in suspected cases with those of appropriate standardized age-matched controls.
Therefore it is an object of the present invention, a method to diagnose and/or to make prognostic predictions and/or to monitor the efficacy of a therapy of a proliferative or conformational disease, or to establish the state of ageing in a subject, comprising the steps of:
a) collecting a blood sample from the subject;
b) separating plasma and isolating peripheral blood lymphocytes (PBMCs) from the blood sample;
c) measuring the level of HDL-cholesterol in the plasma;
d) culturing PBMCs and promoting their proliferation by stimulation with an appropriate efficient amount of a stimulating agent to get a sufficient amount of cultured PBMCs;
e) isolating the lipid fraction from the cultured PBMCs;
f) determining the amount of free and esterified cholesterol from the isolated lipid fraction of cultured PBMCs;
g) detecting at least one mRNA and/or its translated protein involved in intracellular cholesterol homeostasis in the cultured PBMCs; and, optionally
h) detecting at least one mRNA and/or its translated protein involved in the pathogenesis of specific proliferative or conformational diseases in the cultured PBMCs; and, optionally
i) detecting at least one mRNA and/or its translated protein of pro-inflammatory cytokines in the cultured PBMCs;
j) comparing the results of steps c), f), g), h), i) with standardized values from an age-matched control sample.
Preferably, the proliferative disease is selected from the group of: atherosclerosis, restenosis after angioplastic, hematologic neoplasms, solid tumors. More preferably, hematologic neoplasms are selected from the group of: Hodgkin and non-Hodgkin lymphomas, acute and chronic leukemias, eritroleukemias, mielomas or policytemias. Even more preferably, the solid tumors are selected from the group of: brain, headneck, nasopharyngeal, breast, ling, gastrointestinal, colon, kidney or liver tumor.
Still preferably, the conformational disease is selected from the group of: prion-related disorders, Alzheimer's disease, Parkinson's disease, Huntington disease, amyotrophic lateral sclerosis or spinocerebellar degenerations. More preferably, the prion-related disorders are selected from the group of: Creutzfeldt-Jacob disease, new variant Creutzfeldt-Jacob disease, Gerstmann-Straussler Sheinker syndrome, fatal familial insomnia, bovine spongiform encephalopathy, scrapie, chronic wasting disease, feline spongiform encephalopathy.
Preferably, the stimulating agent is a mitogenic agent. More preferably, the mitogenic agent is phytohemagglutinin or Concanavalin A.
In one embodiment, steps d)-j) of the method described above are substituted by the following steps:
d′) isolating fibroblasts from the subject;
e′) culturing, synchronizing and optionally stimulating isolated fibroblasts to obtain a sufficient amount of cells;
f′) isolating lipid fraction from cultured fibroblasts;
g′) determining the amount of free and esterified cholesterol in the isolated lipid fraction or in the cultured fibroblasts;
h′) detecting at least one mRNA and/or translated protein involved in intracellular cholesterol homeostasis in the cultured fibroblasts; and, optionally
i′) detecting at least one mRNA and/or translated protein involved in the pathogenesis of specific proliferative or conformational diseases in the cultured fibroblasts; and, optionally
j′) detecting at least one mRNA or translated protein of pro-inflammatory cytokines in the cultured fibroblasts;
k′) comparing the results of steps c), g′), h′), i′) and j′) with standardized values from an age-matched control sample.
Preferably, the synchronizing fibroblasts step of e′) is performed by serum deprivation. More preferably, the stimulating fibroblasts step of e′) is performed by addition of fetal calf serum or at least one mitogen. Preferably, the mitogen is β-FGF.
Still preferably, the esterified cholesterol is measured by staining of cells with oil red O.
Yet preferably, the mRNA and/or translated protein involved in intracellular cholesterol homeostasis is comprised in the group of LDL-R, HMGCoA-R, SREBP2, MDR1, ACAT-1, Caveolin-1, nCEH and ABCA1.
Preferably, the mRNA and/or translated protein involved in the pathogenesis of the proliferative and conformational is comprised in the group of: APP, Neprilysin, β-secretase; PrP protein; tumor suppressor genes such as p16, p53, PTEN and oncogenes such as cMyc, Cyclin D1, ErbB2, EGF-R and Bcl2.
More preferably, the mRNA and/or translated protein of pro-inflammatory cytokines is selected in the group of: Tumour Necrosis Factor alpha (TNFα), Interleukin-1 alpha (IL-1α) and Interferon-gamma (IFNγ).
Preferably, the methods above described further comprises the step of determining the ApoE aplotype.
It is an object of the invention a method to screen drugs for therapeutical effect of a proliferative or conformational disease, comprising the steps of:
a) collecting a blood sample from an affected subject;
b) separating plasma and isolating peripheral blood lymphocytes (PBMCs) from the blood sample;
c) culturing PBMCs and promoting their proliferation by stimulation with an appropriate efficient amount of a stimulating agent to get a sufficient amount of cultured PBMCs;
d) incubating PBMCs with each of drugs at appropriate conditions and dosages;
e) detecting at least one mRNA and/or its translated protein involved in intracellular cholesterol homeostasis in the cultured PBMCs;
f) detecting at least one mRNA and/or its translated protein involved in the pathogenesis of specific proliferative or conformational diseases in the cultured PBMCs;
g) detecting at least one mRNA and/or its translated protein of pro-inflammatory cytokines in the cultured PBMCs;
h) comparing the results of steps e), f), g) with reference drugs and proper controls.
A further object of the invention is a method to screen drugs for therapeutical effect of a proliferative or conformational disease, comprising the steps of:
a) isolating fibroblasts from the subject;
b) culturing, synchronizing and optionally stimulating isolated fibroblasts to obtain a sufficient amount of cells;
c) incubating cultured fibroblasts with each of drugs at appropriate conditions and dosages;
d) detecting at least one mRNA and/or translated protein involved in intracellular cholesterol homeostasis in the cultured fibroblasts;
e) detecting at least one mRNA and/or translated protein involved in the pathogenesis of specific proliferative or conformational diseases in the cultured fibroblasts;
f) detecting at least one mRNA or translated protein of pro-inflammatory cytokines in the cultured fibroblasts;
g) comparing the results of steps d), e), f) with reference drugs and proper controls.
Another object of the invention is a method to assess drugs response profile of a subject affected by a proliferative or conformational disease, comprising the steps of:
a) collecting a blood sample from the affected subject;
b) separating plasma and isolating peripheral blood lymphocytes (PBMCs) from the blood sample;
c) culturing PBMCs and promoting their proliferation by stimulation with an appropriate efficient amount of a stimulating agent to get a sufficient amount of cultured PBMCs;
d) incubating PBMCs with each of drugs at appropriate conditions and dosages;
e) detecting at least one mRNA and/or its translated protein involved in intracellular cholesterol homeostasis in the cultured PBMCs;
f) detecting at least one mRNA and/or its translated protein involved in the pathogenesis of specific proliferative or conformational diseases in the cultured PBMCs;
g) detecting at least one mRNA and/or its translated protein of pro-inflammatory cytokines in the cultured PBMCs;
h) comparing the results of steps e), f), g) with reference drugs, proper controls and among tested drugs.
A further object of the invention is a method to assess drugs response profile of a subject affected by a proliferative or conformational disease, comprising the steps of:
a) isolating fibroblasts from the subject;
b) culturing, synchronizing and optionally stimulating isolated fibroblasts to obtain a sufficient amount of cells;
c) incubating cultured fibroblasts with each of drugs at appropriate conditions and dosages;
d) detecting at least one mRNA and/or translated protein involved in intracellular cholesterol homeostasis in the cultured fibroblasts;
e) detecting at least one mRNA and/or translated protein involved in the pathogenesis of specific proliferative or conformational diseases in the cultured fibroblasts;
f) detecting at least one mRNA or translated protein of pro-inflammatory cytokines in the cultured fibroblasts;
g) comparing the results of steps d), e), f) with reference drugs, proper controls, and among tested drugs.
Another object of the invention is a kit for measuring the esterified cholesterol in the cell including means for cell staining with oil red O.
A further object of the invention is a kit for the detection of at least one mRNA involved in intracellular cholesterol homeostasis including:
Another object of the invention is a kit for the detection of at least one mRNA involved in the pathogenesis of the proliferative or conformational diseases including:
Another object of the invention is a kit for the detection of at least one mRNA of pro-inflammatory cytokines, including:
Another object of the invention is a kit for the detection of at least one protein involved in intracellular cholesterol homeostasis including at least a ligand specific for one of the proteins comprised in the group: LDL-R, HMGCoA-R, SREBP2, MDR1, ACAT-1, Caveolin-1, nCEH and ABCA1.
Still object of the invention is kit for the detection of at least one protein involved in the pathogenesis of the proliferative or conformational diseases including at least a ligand specific for one of the proteins comprised in the group of: APP, Neprilysin and β-Secretase for Alzheimer's disease; PrP protein for prion-related diseases; tumor suppressor genes such as p16, p53, PTEN and oncogenes such as cMyc, Cyclin D1, ErbB2, EGF-R and Bcl2 for hematologic neoplasms and solid tumors.
A further object of the invention is a kit for the detection of at least one pro-inflamatory cytokine, including at least one ligand for cytokines comprised but not limited to the group of: Tumour Necrosis Factor alpha (TNFα), Interleukin-1 alpha (IL-1α) and Interferon-gamma (IFNγ).
Another object of the invention is a diagnostic platform to diagnose, and/or to make prognostic predictions, and/or to monitor the efficacy of a therapy, and/or to screen drugs for therapeutical effect, and/or to assess drugs response profile of a subject affected by a proliferative or conformational disease, or to establish the state of ageing in a subject, including all of kits according to claims 22 to 28.
In the present invention proliferative and conformational diseases comprise, but are not limited to, the diseases indicated in Table 2.
The invention will be now described by non limiting examples referring to the following figures:
Intracellular cholesterol derives from i) endogenous neosynthesis in the ergastoplasmic reticulum (ER) through the activity of HMGCoA-reductase (HMGCoA-R) (1); ii) circulating low density lipoproteins (LDL) (2), which are first internalised via LDL receptors (a) and then hydrolytically processed in lysosomes to generate free cholesterol (FC) through the activity of acid cholesterol ester hydrolase (aCEH) (b). Most of the newly synthesized FC, or LDL-bound FC released in the lysosomes, rapidly emerges at cell surface caveolae, from where it may be used for cellular functions (c). If plasma membrane FC exceeds a threshold level, the excess FC is rapidly transported to the ER (d) by a P-glycoprotein (MDR1-Pgp) encoded by the multidrug resistance (MDR1) gene. Then, the ER-resident enzyme acyl-coenzyme A-cholesterol-acyl-transferase (ACAT) (e) converts FC into cholesteryl esters (CE), which are stored in cytoplasmic droplets. If cells require cholesterol, CE is re-hydrolyzed to FC by the enzyme neutral cholesterol-esters-hydrolase (nCEH) (f) and transported to the plasma membrane by caveolin-1. If in excess, FC is eliminated from the cells through an efflux pathway spanning from the ER to the plasma membrane and involving caveolin-1, the ABCA1 receptor, and plasma HDLs (g).
bis: Alterations of cholesterol homeostasis in pathologic conditions.
When alterations in cholesterol homeostasis occur, such as excessive cholesterol synthesis and uptake, more cholesterol is transported to the ER by MDR1-Pgp. Cholesterol overloading in the ER leads to activation of the ACAT enzyme which, in turn, esterifies cholesterol. Cholesterol esters (CE) are then accumulated in the cytoplasm as lipid droplets, and foam-like cells are formed (Schemes 2 A, B, and C). On the other hand, excessive accumulation of cholesterol in the form of esters reduces the cholesterol pool that can be transported by caveolin-1 to the plasma membrane (rafts) for excretion. This leads to a decreased cholesterol efflux via ABCA-1 receptors and, thus, to lower HDL-cholesterol levels in plasma (Schemes 2 A, B, and C). Lower levels of FC into the rafts may also lead to a continuous activation of raft-protein functions in membrane signalling, protein and lipid processing and transport, thus triggering a variety of pathologic processes including atherosclerosis (
Panel A shows ApoE genotype (table) and mRNA levels of ACAT-1, nCEH, ABCA-1, MDR1, Caveolin-1, LDL-R and β-actin genes in skin fibroblasts from AD patients (AD), their relatives (Rel) and control healthy donors (C). Panel B shows Western blotting analysis of caveolin-1 and ACAT-1 expression in skin fibroblasts from AD, their relatives and controls.
PBMC from AD patients (A1-A3), their relatives (B1-B3) and healthy individuals (C1-C3, control group) stained for neutral lipid by the ORO method at 0 (A1, B1, C1), 24 (A2, B2, C2) and 48 (A3, B3, C3) hours after PHA stimulation.
Individuals with clinical diagnosis or at risk of AD (or TSE). Clinical diagnoses of AD are made according to the NINCDS-ADRDA criteria. Additional measures include the MMSE and Dementia Severity Rating Scale (DSRS). Routine laboratory studies, including magnetic resonance imaging, are performed to rule out other causes of cognitive impairment. The Reisberg Global Deterioration Scale (GDS) is used to indicate the severity of the cognitive impairment of AD patients. Abnormal GDS levels start from level 3 and maximal deterioration grade corresponds to level 7. First degree relatives of AD patients of different ages and with no cognitive decline are recruited in the study after informed consent. An age-matched group of control subjects with no cognitive decline is recruited at affiliated hospitals or from blood donor lists (AVIS).
Peripheral blood Mononuclear cells (PBMCs) are collected from peripheral blood samples Dermal biopsies are obtained from the upper forearm of the subjects by a 2-mm punch after local anesthesia with 2% xylocaine.
Eighteen patients with chronic lymphocytic leukemia (CLL) (aged 45-65 years) and twelve patients with acute lymphocytic leukemia (ALL) (aged 40-60 years) were recruited at diagnosis in local hospitals. Fifteen healthy age-matched subjects were also recruited as controls. Ten patients (7 with CLL and 3 with ALL) were randomly chosen to perform kinetic and molecular analyses. Informed written consent was obtained from all patients and healthy controls before initiating the study according to the policies of the hospitals Institutional Review Boards.
All subjects enrolled in the various studies did not receive any pharmacological treatment prior to blood or punch sampling.
10 naturally scrapie-affected Sarda breed sheep with the scrapie-susceptible ARQ/ARQ genotypes and 10 experimentally scrapie-infected sheep with ARQ/ARQ genotype were used (all named as ARQ/ARQ+). All sheep were at the terminal clinical stage of the disease. The sheep were euthanized with a barbiturate followed by 4 ml of embutramide and mebenzonico-iodide (Hoechst Roussel Vet). Peripheral blood samples and skin biopsies were collected from the animals. The brains were collected and transverse sections taken for PrPSc detection by Western Blot. The same procedure was performed on 10 scrapie-resistant ARR/ARR genotype sheep and 10 ARQ/ARQ scrapie-free sheeps (ARQ/ARQ−).
PBMCs are collected from peripheral blood of patients and controls and separated by Ficoll-Hypaque density gradient. After extensive washings, cells are resuspended (1×106 cells/ml) in RPMI-1640 with 10% FCS and incubated overnight. For assay purposes, 2×105 cells/ml nonadherent cells (lymphocytes) are incubated at 37° C. in RPMI-1640 10% FCS supplemented with PHA (Phythohemoagglutinin, 10 μg/ml, cat. number L8902, SIGMA). Viability is evaluated after a time course by counting cells using trypan blue exclusion. Cells are harvested at different time points of incubations.
For fibroblasts isolation, biopsies are plated into 6 well plates for 2 hours. After 2 hours of adhesion, a few drops of Dulbecco's modified Eagle's medium (DMEM) (Gibco Lab NY, USA) supplemented with 10% fetal bovine serum (FBS) (Sigma), 100 U/ml penicillin/streptomycin (Sigma), and fungizone (Life Technologies, Inc.) covering each fragment are added. The next day, the tissue fragments are covered with culture medium and maintained in a humidified incubator (37° C., 5% CO2). The medium is changed every 2 days. After 5 to 6 days, fibroblasts begin to proliferate from the fragment margin (“halo of cells”) and create a monolayer of spindle-shaped cells. After 4 weeks, fibroblasts are purified by repeat trypsinization (trypsin-EDTA-0.05%/0.02%) and passaging to achieve a homogenous population of spindle cells. Purified fibroblasts are washed two times with PBS and centrifuged. 1×106 cells are then seeded into 25 cm2 culture flask and grown to confluence. At this time cells are used for “in vitro” staining experiments, or transferred into vials containing cryo-preservation medium at a density of 1×107 cells/ml. After swift freezing, vials are transferred into liquid nitrogen for long-term storage. When needed for analysis cryopreserved cells are removed from liquid nitrogen and cultured as described above.
For analysis, skin fibroblasts are plated at a density of 5000 cell/cm2 in 6 well plates and then incubated for 48 h in MEM 199 containing 0.2% FCS to force cells into a quiescent state. Before each assay, quiescent cells are stimulated to proliferate synchronously by adding FCS (10%) or in alternative a potent mytogen, such as β-FGF (β-fibroblast growth factor), and incubated for 12, 24, 48 and 72 hours in presence or in absence of different drugs.
All assays are conducted using fibroblasts between passages two to four.
Cell proliferation was measured by 3H-thymidine incorporation. Cells were labeled with 3H-thymidine (2.5 μCi/ml) during the last 6 hours of culture and harvested at the time points indicated, see
Cholesterol esterification was evaluated by incubating cells for 6 hours in medium containing [1-14C] oleic acid (Dupont, NEN 55 mCi/mmol), bound to bovine serum albumin (BSA). After incubation cells were washed with PBS and lipids extracted with acetone. Lipid subclasses were separated by thin layer chromatography (TLC) on kiesegel plates using a solvent system containing n-heptane/isopropyl ether/formic acid (60:40:2, v/v/v). Cholesterol ester bands were identified by comparison with reference standard run simultaneously side-by-side and visualized under iodine vapors. For scintillation counting, the bands were excised and added directly to counting vials containing 10 ml Econofluor (DuPont NEN) liquid scintillation fluid.
The molecular characterization of the aplotype for APOE, is performed on DNA extracted from lymphocytes obtained from peripheral blood samples. DNA is purified according to the QiAmp Blood kit procedure (Quiagen), followed by PCR amplification using sets of primers and standard experimental conditions.
Determination of relative mRNA expression levels for: SREBP2, LDL-R, HMG-CoA-R, MDR1-Pgp, ACAT-1, nCEH, caveolin-1 ABCA-1, APP, Neprilysin, β-secretase, PrP, p16, p53, PTEN, cMyc, Cyclin D1, ErbB2, EGF-R, Bcl2, TNFα, IL-1α and IFNγ is performed on samples of total RNA, purified with the TRIZOL reagent (GIBCO) according to established procedures, by a macroarray system.
Macroarrays are prepared by printing purified PCR products, suspended in DR.DiY spotting buffer, using the Fast Spotter macroarrayer (Dr, Chip Biotechnologies). Printing is done on aminosilane-treated slides (ex. CMT-GAPS™ from Corning). After printing, slides are allowed to dry at room temperature and then UV-crosslinked with a UVC 500 crosslinker (Hoefer) and used immediately or stored desiccated at room temperature.
Preparation of Labelled cDNAs (in Each of 2 Separate 0.5 ml Eppendorf Tubes)
The reactions are mixed, the tubes are wrapped in aluminum foil and incubated at 42° C. for 2 hours.
Tubes are then pulse-spun and 1.5 μl of EDTA are added to stop the reaction
Labeling reactions are loaded onto filtration columns (ex. Microspin™ G-50, Amersham Pharmacia) and washed according to the protocol provided by the manufacturer. Eluted probes are collected in clean tubes, wrapped in foil, and stored at −20° C. if not used immediately.
Equal volumes (10 μl) of the two probes are combined in a 0.5 ml Eppendorf tube and then are added:
Probes are denatured by heating at 95° C. for 3 min. and then combined with an equal volume of hybridization buffer (10×SSC, 50% formamide, 0.2% SDS).
Just before use, slides are prehybridized in a Coplin jar with Pre-hyb buffer (5×SSC, 0.1% SDS and 1% BSA) for 30 min at 42° C.
Slides are dipped in filtered Milli-Q water and then in isopropanol and allowed to dry at room temperature. Thirty μl of probe mix are overlaid onto the macroarray and covered with a 22×60 mm hydrofobic coverslip. Slides are set in Hybridization chambers which are then sealed with the lid and placed in a water bath at 42° C. and incubated for 16-20 hours in the dark. After hybridization slides are placed in a Petri dish, submerged in wash buffer (1×SSC, 0.2% SDS) at 42%. The coverslips are lifted gently and removed while the slides are submerged and these are then washed with stringency buffer (0.1×SSC, 0.2% SDS). After washing the slides are allowed to dry at room temperature and immediately scanned with a GenePix® 4000B Fluorescent scanner and analyzed with the GenePix Pro software. Relative levels of expression are calculated as red-to-green signal ratio, after normalization and background subtraction.
Validation of markers is accomplished according to criteria established by the Working Group on Molecular and Biochemical Markers of Alzheimer's Disease and worth to evaluate (i) sensitivity (refers to the capacity of a biomarker to identify a substantial percentage of patients with the disease), (ii) specificity (refers to the capacity of a test to distinguish AD from normal aging, other causes of cognitive disorders and dementias); (iii) predictive (positive or negative) value (represents the percentage of people with a positive/negative test who subsequently at autopsy prove to have/not to have the disease).
Heparinized plasma specimens are collected for lipid testing after an overnight fast and analyzed on the same day. Total cholesterol (TC), triglycerides (TG) and phospholipid (PL) levels are determined enzymatically (Boehringer Mannheim Diagnostics, Indianapolis, Ind.). High-density lipoprotein cholesterol (HDL-C) are determined after precipitation of the apolipoprotein B (Apo-B) containing particles by magnesium chloride and dextran sulfate.
For lipid cell content determinations, neutral lipids extracted from isolated cultured PBMCs and skin fibroblasts with cold acetone, are separated by thyn layer chromatography (TLC). Free cholesterol (FC), cholesterol esters (CE), triglycerides (TG) and phospholipids (PH) mass are determined by enzymatic standard assay methods.
For neutral lipid staining, isolated PBMC and skin fibroblasts are cultured as described above. At different times of incubation, the cells are washed three times with PBS and fixed by soaking in 10% formalin. The cells are treated with isopropylic alcohol (60%), washed and nuclei and intracellular neutral lipid droplets are then stained with Mayer's hematoxylin solution and oil red O, respectively. The stained cells are then examined and photographed under the light microscopy. Lipid-bound ORO was quantified in intact cells or in cell extracts by the Scion image analysis software (NIH Image 1.63 Analysis Software program) or after chloroform/methanol (2:1) extraction of lipids and OD reading at 520 nm, respectively.
Table 4 shows lipid content in primary Acute and Chronic Lymphocytic Leukemia (ALL and CLL, respectively) cells, as well as lipid profiles of sera from patients with CLL (18 patients, ages 45-65 years), or ALL (12 patients, ages 40-60 years), at diagnosis. Age-matched healthy subjects (n=15) were used as controls. The authors found that constitutive cholesterol ester levels were higher in leukemia cells than in controls. A strong decrease in FC:CE molar ratio (1.1 in CLL and 0.85 in ALL vs. 3.6 in controls) was also observed in leukemia cells. No significant changes in other cellular lipid parameters were seen. HDL-C were significantly reduced (P<0.05) in leukemia patients compared with age-matched healthy controls. Total serum cholesterol (TC), LDL-C, TG, and PL levels were not significantly different between control subjects and tumor patients, although a trend toward hypocholesterolemia and hypertriglyceridemia was observed in the latter group (data not shown).
These results support the notion that changes in lipid content, mainly in the levels of cellular cholesterol esters and plasma HDL-C, represent an identifiable profile for proliferative diseases.
To reinforce these results, the authors analyzed the cytoplasm lipid content in normal lymphocytes and in leukemic PBMCs, using the oil-red O staining method.
As shown in
Similar results were obtained in mitogen-induced proliferating PBMCs from atherosclerotic patients compared with mononuclear cells from healthy control subjects (
In vitro studies on cellular trafficking and metabolism of cholesterol (reported in FIG. 5 and 5Bis) reveal that skin fibroblasts from AD patients have an increased capacity to esterify and accumulate cholesterol when compared to fibroblasts from healthy donors. Moreover, the authors found higher intracellular levels of mRNA for MDR1-Pgp and ACAT-1, with lower levels of mRNA for nCEH, caveolin-1 and ABCA1, in fibroblasts from the same AD patients compared to healthy controls (
The data reported in
Similar correlations were also found in brain tissue (
In conclusion, the presence of high intracellular CE levels and, consequently, low plasma membrane FC is indicative of a cell phenotype predisposing to several pathological conditions (FIG. 2A,B,C), including formation/deposition of structurally aberrant proteins in conformational diseases (
In addition, the authors had already shown that some of the above parameters also correlate with the ageing phenomenon (36). In fact, using a rat model, the authors proved that, as the age of animals increases, the levels of MDR1-Pgp and ACAT mRNAs significantly increase in several organs (liver, brain, hearth, kidney, arteries). By contrast, the expression levels of mRNA for nCEH and caveolin-1 significantly decrease with age, leading to intracellular CE accumulation and to decreased levels of plasma membrane FC, coupled with low circulating HDL-cholesterol (36). The present results demonstrate that the above correlations can also be found in PBMCs and skin fibroblasts, thus allowing a prompt evaluation of the risk of developing the above defined age-related diseases.
An exemplificative kit for measuring the amount of cytoplasmic CE accumulation in a pheripheral blood sample may take advantage of the ORO staining method, and may include:
a) means for isolating PBMCs from whole blood samples, i.e. according to the following procedure:
An exemplificative kit for the relative quantification of at least one mRNA involved in intracellular cholesterol homeostasis may include means for the specific reverse amplification of mRNA through cDNA or fragment thereof.
An exemplificative Polymerase Chain Reaction (PCR) reaction reagent mix includes:
PCR products are loaded onto filtration columns (ex. Microspin™ G-50, Amersham Pharmacia) and washed according to the protocol provided by the manufacturer.
Eluted amplicons are collected in clean tubes, and stored at −20° C. if not used immediately.
Macroarrays are prepared by printing purified PCR products, suspended in DR.DiY spotting buffer, using the Fast Spotter macroarrayer. Printing is done on aminosilane-treated slides (ex. CMT-GAPS™ from Corning). After printing, slides are allowed to dry at room temperature and then UV-crosslinked with a UVC 500 crosslinker (Hoefer) and used immediately or stored dessicated at room temperature.
Preparation of Labelled cDNAs (in Each of 2 Separate 0.5 ml Eppendorf Tubes)
The reactions are mixed, the tubes are wrapped in aluminum foil and incubated at 42° C. for 2 hours.
Tubes are then pulse-spun and 1.5 μl of EDTA are added to stop the reaction
Labeling reactions are loaded onto filtration columns (ex. Microspin™ G-50, Amersham Pharmacia) and washed according to the protocol provided by the manufacturer.
Eluted probes are collected in clean tubes, wrapped in foil, and stored at −20° C. if not used immediately.
Equal volumes (10 μl) of the two probes are combined in a 0.5 ml Eppendorf tube and then are added:
Probes are denatured by heating at 95° C. for 3 min. and then combined with an equal volume of hybridization buffer (10×SSC, 50% formamide, 0.2% SDS).
Just before use, slides are prehybridized in a Coplin jar with Pre-hyb buffer (5×SSC, 0.1% SDS and 1% BSA) for 30 min at 42° C.
Slides are dipped in filtered Milli-Q water and then in isopropanol and allowed to dry at room temperature.
Thirty μl of probe mix are overlaid onto the macroarray and covered with a 22×60 mm hydrophobic coverslip.
Slides are set in Hybridization chambers which are then sealed with the lid and placed in a water bath at 42° C. and incubated for 16-20 hours in the dark.
After hybridization slides are placed in a Petri dish, submerged in wash buffer (1×SSC, 0.2% SDS) at 42%.
The coverslips are lifted gently and removed while the slides are submerged and these are then washed with stringency buffer (0.1×SSC, 0.2% SDS).
After washing the slides are allowed to dry at room T and immediately scanned with a GenePix® 4000B Fluorescent scanner and analyzed with the GenePix Pro software. Relative levels of expression are calculated as red-to-green signal ratio, after normalization and background subtraction.
| Number | Date | Country | Kind |
|---|---|---|---|
| RM2006 A 000285 | May 2006 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IT07/00110 | 2/19/2007 | WO | 00 | 5/19/2009 |
| Number | Date | Country | |
|---|---|---|---|
| 60774311 | Feb 2006 | US |
