Method for diagnosing neuronal deseases and for treating primary hemostasis deficiency

Abstract

The invention relates to a method for diagnosing neuronal diseases and for treating primary hemostasis deficiency. The invention further relates to a method for suppressing the immune system, which is inter alia significant for transplantation medicine and for the treatment of allergies. The invention is used in the field of medicine and in the pharmaceutical industry. The invention is worked according to the claims. The invention is based on the discovery that serotonin is synthesized by TPH isoenzymes that are differently expressed in the neurons in the peripheral tissues. Gene targeting was used to show that an isoform, the peripheral enzyme (referred to in the following as TPH), is responsible for maintaining primary hemostasis and T-cell mediated immune responses. Another isoform, the newly identified neuron-specific TPH (referred to as nTPH) synthesizes serotonin irrespective thereof in the central nervous system. The invention further relates to the newly identified neuronal tryptophan hydroxylase (nTPH) that differs from the TPH known so far in the regulatory domain.

Description

[0001] The present invention relates to a method for diagnosing neuronal diseases and or treating primary hemostasis deficiency. The invention further relates to a method for suppressing the immune system, which is inter alia significant for transplantation medicine and for the treatment of allergies. The invention is used in the field of medicine and pharmaceutical industry.

[0002] Several behavioral disorders, such as depressions, alcoholism, drug abuse, isomnia and nutritional disturbances, are disorders tightly connected to the central nervous system. The tissue hormone serotonin plays an essential role at many levels. Serotonin is a neurotransmitter inter alia for the stimulation of the peristalsis, the vasodilatation and—constriction (dosage depending), respectively, and the increase of the tonicity in the respiratory tract. It is not only a neurotransmitter in the CNS, but, in addition, a compound that can be found everywhere in the periphery, where serotonin was first discovered due to its activity as strong vascular constrictor (Rapport et al., J. Biol. Chem. 176:1237, 1948).

[0003] In addition, serotonin plays an essential role in primary hemostasis, that is, the inhibition of bleedings. The serotonin that is stored in the platelets is excreted at sites of vascular lesion, whereupon it interferes with the primary hemostasis (Holland, Proc. Soc. Exp. Biol. Med. 151:32-39, 1976).

[0004] Furthermore, the serotonin of the platelets further mediates between components of the immune system (Geba et al., J. Immunol. 157:557-565, 1996). The mechanisms that thereby take place are yet unknown.

[0005] It is known that the enzyme tryptophan-hydroxylase (TPH), an enzyme that is expressed in neurons and pheripheric tissue, catalyses the yield-limiting step in the biosynthesis of serotonin, and is therefore essential for the function of the serotonergic system in the CNS and the periphery (Boadle-Biber, Prog. Biophys. Mol. Bio. 60:1-15, 1993).

[0006] There are already some medical applications, which rely on the effect of serotonin in the body. The increased release of serotonin by Rauwolfia-Alkoloides, and the retardation of the serotonin decay using MAO (Monoaminooxidase) inhibitors, respectively are used for the treatment of mental depressions, while its antagonist, methysergide, find its application in the treatment of migraine.

[0007] It has not yet been achieved to control the serotonin production in the body in such a manner that an effective treatment of the above-mentioned and other pathological phenomena are possible.

[0008] It is therefore a problem of the invention to improve the diagnosis of neuronal diseases of the above-mentioned kind. It is a further object to develop agents for the treatment of the primary hemostasis deficiency as well as agents for suppressing the immune system based on new findings of the effect of serotonin.

[0009] The invention is worked according to the claims. The invention is based on the essential discovery that serotonin is synthesized in the body by TPH isoenzymes that are differently expressed in the neurons and the peripheric tissues. Gene targeting was used to show that an isoform, the peripheral enzyme (referred to in the following as TPH), is responsible for maintaining the primary hemostasis and T-cell mediated immune responses. Another isoform, the newly identified neuron specific TPH (referred to as nTPH) synthesizes serotonin independently thereof in the CNS.

[0010] Furthermore, some mechanisms could be elucidated. It was found

[0011] a) that the major step of serotonin in the primary hemostasis is mediated by the von Willebrand-factor. Furthermore, it was established that

[0012] b) the serotonin in the platelets is essential for the normal number of circulating CD4+ cells, as well as for their normal activity, and thus provides a new target for an immune suppressive treatment.

[0013] In summary, it can be established that two separately regulated serotonergic systems exist in the CNS and the periphery which are defined by the peripheral isoform TPH and the neuronal isoform nTPH, respectively. This result is an important contribution for the use of these systems within the scope of the present invention.

[0014] The dichotomy of the serotonin-biosynthesis on the molecular level results in unexpected diagnostic and therapeutic possibilities. This relates to correlations between peripheric and central nervous serotonergic metabolites. In addition, this relates to possibilities of diagnostic fine-correlations, since the subtractive determination of the concentrations of the metabolites as present allows for the ascertainment of the CNS metabolites in the periphery. The peripheral serotonin-biosynthesis can thus transiently be inhibited specifically in order to subsequently determine the peripheral metabolite concentrations that stem from the CNS. The advantages of such a diagnostic method, in particular in the case of persisting psychiatric disorders, should outbalance the transient risk of bleeding episodes and distorted cell-mediated immune responses, since an improved therapy can follow after a more precise diagnosis.

[0015] The invention primarily relates to inhibitors or promoters, respectively of both TPH-isoforms which can be used for diagnosing neuronal diseases and for treating primary hemostasis deficiency. Furthermore, the invention relates to the use of these inhibitors for suppressing the immune system, which is of importance inter alia for transplantation medicine and for the treatment of allergies.

[0016] The method is characterized by a modulation of the regulation of nTPH and/or TPH and thus the specific serotonin production in the body. It was shown that the peripheral TPH is essential for primary hemostasis and for the T-cell-mediated immune response, whereas the newly identified nTPH, which is independently expressed and synthesizes serotonin in the CNS is responsible for the serotonergic effects in behavioral physiology. This results in new pharmacological possibilities for immune suppression and for the therapeutic manipulation of hemostasis.

[0017] The modulation of the nTPH- and/or TPH-regulation takes place in the following ways:

[0018] Specific inhibitors of the peripheral TPH-isoforms were developed that rely on the molecular differences of the TPH-isoforms as described, and also inhibitors that cannot pass the blood-brain-barrier. Specific inhibitors for the TPH-isoforms can be found in vitro using fairly simple screening methods, since the cDNAs of the two isoforms that were obtained can be used for the specific expression of the pure isoforms using expression systems. These inhibitors, in addition to a diagnostic use, account also for therapeutical uses, since increased serotonin levels in the blood are found in a plurality of complications.

[0019] a) In this context it is worth mentioning that during the use of SSRI (serotonin specific reuptake inhibitors)-antidepressive agents in the psychopharmacological therapy, as side effects in some cases serious bleeding complications became known (Goldberg, Arch. Fam. Med. 7:78-84, 1998). These side effects can be traced back to the decreased serotonin-level in platelets due to said therapy (Bottlender et al., Fortschr. Neurol. Psychiatr. 66:32-35, 1998). Also associated with this field of application are the new findings of the participation of serotonin in primary hemostasis. One side effect of antidepressive agents which act in a blocking fashion on the serotonin-transporter is the incidence of acute bleeding episodes, apparently due to the insufficient serotonin storage in the thrombocytes of the patients that are treated. That is to say that the serotonin-transporter of the thrombocytes is identical with the specific target of the antidepressive agents, the serotonin-transporter of the CNS. In the case of such bleeding episodes the antidepressants are usually displaced, which results in a decline of the status of the afflicted patients and an increase of the depression-induced risk for suicide. This can be avoided if commercially available von Willebrand-factor (vWF) is infused during such an acute bleeding episode.

[0020] b) Increased serotonin-concentrations during the pre-eclampsia correlate with the increase of the CD4+-T-cell-subpopulations. Using specific inhibitors of the peripheral TPH-isoform, an early treatment of the imminent pre-eclampsia is enabled, which neither exerts an influence on the serotonin-biosynthesis in the maternal nor in the fetal brain.

[0021] c) In addition to these applications, a positive influence of only peripherally acting inhibitors on transplantation medicine also can be achieved. An essential limitation in a common immune suppressive therapy is given by the nephro-, hepato- and neurotoxic side effects of the most commonly used substance clyclosporin A (CsA). More recent immune suppressants of natural origin, such as FK506 and rapamycin in combination preparations together with CsA thus allow a more effective (additive) immune suppresive treatment having lower side effects, since CsA is thus applied at a lower dosage.

[0022] The immune suppressive effect of lowered serotonin levels in the blood can be used in order to apply toxic substances, CsA, FK 506, and rapamycin, at a lower dose.

[0023] According to the invention, the manipulation of the nTPH- and/or TPH-regulation can take place in the following ways:

[0024] The specific down-regulation of nTPH and/or pTPH using molecular biology takes place with ribozymes, antisense-oligonucleotides or by antisense-RNA-expression, wherein the differences in the sequences of the isoform-mRNAs allow for the modulation of only one of each mRNA at once. In addition, according to the invention, also pharmacological preparations are employed using specific TPH-inhibitors, such as, for example, p-chlorophenylalanine or p-ethynylphenylalanine.

[0025] The serotonin production is preferably stimulated by tissue specific over-expression of the TPH-isoforms using molecular biology, pharmacologically, for example, the precursor-compound 5-hydroxytryptophan, and also substituted analogues, and, last but not least, also serotonin itself can be administered.

[0026] The method according to the present invention for diagnosing neuronal diseases is characterized in that a specific inhibition of the peripheral serotonin-biosynthesis is performed, subsequently the metabolite concentrations derived from the CNS are determined, and based on a comparative curve the grade of the disease is ascertained. For this, it is required to use compounds that cannot pass the blood-brain-barrier.

[0027] The invention further relates to the newly identified neuronal tryptophan-hydroxylase (nTPH) that differs from the known TPH its regulatory domain (the catalytic domain is identical). nTPH has the amino acid sequence, that is depicted in FIG. 9.

[0028] The invention shall be described in detail in the following based on embodiments (figures).

[0029] FIG. 1. Production of TPH(−/−)-mice

[0030] A. Schematic representation of the targeting-method. The first four of the 11 exons of the TPH-gene are depicted. The knock-out construct was integrated by homologous recombination in one allele of the ES-cells, whereby the first coding exon of the TPH-gene was inactivated. Furthermore, the integrated neomycin resistance-cassette contained a transcriptional-stop-sequence. The positions of the analytic amplicons are depicted for wild-type and knock-out-indentification, as well as the positions of the internal and external Southern blot probes. Identical Eco-RI-sites that enable the identification of wild-type and knock-out-animals in Southern blots are depicted in bold (RI). Restriction sites: RI: Eco RI; Hd: Hind III; Bm: Bam HI; Sc:Sac I.

[0031] B. Agarose gel-electrophoresis of analytical PCR-products. As stated in A, a 1.1 kb-fragment for the wild-type-allele, and a 1.3 kb-fragment for the knock-out-allele is obtained, respectively.

[0032] C. Southern blot-examination of Eco RI-digested genomic DNA. As stated in A, both probes detect a 10 kb-fragment for the wild-type allele and an 8 kb-fragment for the knock-out-allele.

[0033] FIG. 2. Quantification of trypthophan (Trp) and serotonin (5-HT) in peripheral tissues and of Trp, 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in selected areas of the brain.

[0034] A. Trp and 5-HT in whole blood and in duodenum-samples of 129SvJ-, C57BL/6-, TPH(−/−)-, and TPH(+/+)-mice. N.d: not detectable (<25 fg/μl). *: statistically significant compared to all other mice-straines (p<0.05).

[0035] B. Trp, 5-HT and 5-HIAA in hippocampus- and frontal cortex-samples of 129SvJ-, C57BL/6-, TPH(−/−)-, and TPH(+/+)-mice. *: statistically significant compared to all other mice-strains (p<0.05). 5-HT is significantly lowered in the hippocampus of TPH(−/−)-mice compared with TPH(+/+)-mice, nevertheless not compared with the other laboratory-mice-strains.

[0036] FIG. 3. Disturbed hemostasis in TPH(−/−)-mice.

[0037] A. Prolonged bleeding times of TPH(−/−)-animals. Normal bleeding times of control-animals are at 8-11 min, whereas TPH(−/−)-mice bleed at an average of 35 min.

[0038] B. Healing of the phenotype by intracardial 5-HT-injection. The 5-HT-amounts applied result in {fraction (1/10)} and the ten-fold of the normal blood concentrations.

[0039] C. Healing of the phenotype by intracardial von Willebrand-factor injection. The effect is specific for the TPH(−/−)-mice, whereas control-animals are not affected.

[0040] FIG. 4. Disturbed T-cell-mediated immune responses in TPH(−/−)-mice.

[0041] A. Time course of the net swelling of ears after oxazolone treatment, indicative for T-cell-mediated hypersensitivity of the late type. TPH(−/−)-mice do not exhibit an allergic swelling reaction.

[0042] B. Determination of leucocyte-subpopulations in the peripheral blood of TPH(−/−)-animals using flow-cytometry. Only CD+4-T-cells (CD4+/CD3+) are significantly reduced (p<0.05), but not CD8+-T-cells.

[0043] C. Exemplary illustration of the rejection of skin-second-order-transplants. Arrowheads indicate the sensitizing transplants of the first order, arrows the transplants of the second order. In comparison with the well-healing transplants on TPH(−/−)-animals, the transplants on TPH(+/+)- and C57BL/6-animals can at the outer edges of wounds (white rejection) be identified by insufficient revascularization and infections at the same time or are already completely rejected (transplant of first order and two of the transplants of second order on the C57BL/6-animal).

[0044] FIG. 5. Complexity of TPH-expression in the mouse.

[0045] A. Sequence alignment of the published cDNA (Stoll et al., 1990) of the cloned alternatively spliced cDNA having a 34 bp-elongation of exon 3 and genomic DNA. Chromosomal DNA has the 34 bp-elongation directly after the splicing-donor-site of exon 3, whereupon an obligatory GT-dinuclotide follows; the elongated exon 3 is in the following designated exon 3b.

[0046] B. RNase protection assays of 80 μg total-RNA of the organs as indicated and 10 μg of the mastocytoma-cells P815 (2x) with the cDNA described in 5A. The probe clearly identifies six splice variants of the mouse-TPH-mRNA. It has to be noted that only a set of three variants is expressed in the TPH-KO-mice. The weak band at the position of the known TPH-mRNA that can be seen in the duodenum and lung of TPH-KO(−/−)-animals results from a high sequence homology of the variants. The P815-RNAs show how comparatively low the expression of TPH is in tissues, namely nearly at the level of detectability.

[0047] C. Alternative splicing between exon 3 and exon 4. The splicing-donor-(SDS)- and splicing-acceptor-sites (SAS) that are involved are indicated. The parts of the sequence of the published sequence are marked as exon 3a and exon 4a. Splicing of SDS2 on SAS 1 results in the C-variants, which only code for the regulatory domain of the TPH-isoforms (cf. FIG. 7B). The splicing of SDS2 on the internal SAS2 of exon 4 eliminates the frame shift that would be the result of the additional 34 bp of exon 3b. The constant regions are shaded in light grey, the alternative segments in dark grey. Furthermore, the alternative segments as well as flanking intron-sequences are indicated in italic.

[0048] FIG. 6. Characterization of the new exon 2b

[0049] A. Genomic sequence of exon 2b of the mouse with flanking sequences. The ORF in the trinucleotide-notation is marked in bold. In the 5′-flanking region, a part of the putative new promoter is shown, wherein one TATA-box and the most probable start of transcription (+1) are indicated. In the 3′-region, the splicing-donor-site of exon 2b is depicted. Intron-sequences have been indicated in small letters in italic, wherein the short intron of 53 bp was symbolically bridged from the segments of the ORF using a line. For clarity, the respective consensus-sequences are indicated below the splicing-donor-sites, -branching-sites, and -accepting-sites, respectively that are involved.

[0050] B. Examination of the exon-intron-structure of the new exon 2. Five out of eight nucleotides in the mouse are identical with the consensus-sequence of splicing-donor-sites (bold and underlined), four in the rat and three in human. The intron between the new exon 2 and exon 3 has an exact length of 948 bp in the mouse, similarly as in rat and in human.

[0051] FIG. 7. Schematic depiction of the TPH-gene-structure

[0052] A. Schematic comparision of the known splicing-structure (top) with the structure that was obtained in the present work for the gene segments of the regulatory domain (bottom). The promoter position that is supported by experimental evidence, was marked with P2.

[0053] B. Assembly of all newly discovered mRNA-variants. The promoter 1 is primarily active in the periphery, whereas the new promoter 2 is responsible for expression in CNS.

[0054] The mRNA that is indicated as variant A is the known form of the TPH-mRNA. The variant A′ was already cloned and codes for an active TPH-Isoform. The variants B and B′ are not yet cloned, nevertheless, they have been clearly identified for several times now using RPA-assays. Variants C and C′ lead to the expression of only the regulatory domains. For clarity, the mRNAs are only depicted up to the 6th exon of the overall 11 exons.

[0055] FIG. 8. Amino acid-sequence-alignment of the new regulatory domain of TPH with other AAAHs

[0056] The upper part of the sequences shows the new segment of TPH. Below, the conserved parts of the sequence of the regulatory domains of the AAAHs are indicated. The sequences have each been aligned with another using the clustal W-program and have been assembled manually. In doing so, larger gaps were partially allowed in order to indicate the identical structural elements. Noticeable sequence motifs are framed and individually named. Four of the five motifs are identical with elements of the secondary structure of the PAH. Overlapping in part with the IEDN-motif, a region of the regulatory domain is framed and shaded in gray that reaches into the groove of the catalytic centre, as it is known from christallographic examinations of the PAH. Further explanations in the text. The sequences used are: nstph=neuron-specific TPH (the new variant) of the mouse, musth=TH of the mouse, muspah and humpah=murine and human PAH, ptph=peripheral TPH of the mouse (known variant).

[0057] FIG. 9. Amino acid-sequence of the nTPH

Claims

1. Method for the modulation of the serotonin level by specifically regulating the TPH- and/or the nTPH-activity.

2. Method of diagnosing neuronal diseases as well as for the treatment of primary hemo stasis deficiency, characterized in that the serotonin production is increased or decreased by modulating the TPH- and/or the nTPH-regulation.

3. Method of diagnosing neuronal diseases according to claim 2, characterized in that the specific inhibition of the peripheral serotonin-biosynthesis is performed, subsequently the metabolite concentrations stemming from the CNS are determined, and the grade of the disease is determined using a comparative curve.

4. Method for the treatment of the primary hemostasis deficiency according to claim 2, characterized in that the serotonin production is increased by the modulation of the TPH-regulation.

5. Method for the treatment of the primary hemostasis deficiency according to claim 2, characterized in that the serotonin production is increased or serotonin is administered.

6. Method for the treatment of the primary hemostasis deficiency according to claim 5, characterized in that the serotonin production is increased by tissue-specific over-expression.

7. Method for the treatment of the primary hemostasis deficiency according to claim 5 and 6, characterized in that the serotonin production is increased by administering the precursor-compound 5-hydroxytrypthophan.

8. Method for the treatment of the primary hemostasis deficiency according to claim 5 and 6, characterized in that the serotonin production is increased by the addition of substituted analogues of 5-hydroxytryptophan.

9. Method for the treatment of arteriosclerosis/thrombosis, characterized in that the serotonin production is lowered.

10. Method for the treatment of arteriosclerosis/thrombosis according to claim 9, characterized in that the serotonin production is lowered by ribozymes.

11. Method for the treatment of arteriosclerosis/thrombosis according to claim 9, characterized in that the serotonin production is lowered by antisense-oligonucleotides.

12. Method for the treatment of arteriosclerosis/thrombosis according to claim 9, characterized in that the serotonin production is lowered by antisense-RNA-expression.

13. Method for the treatment of arteriosclerosis/thrombosis according to claim 9, characterized in that the serotonin production is lowered by using specific TPH-inhibitors, such as p-chlorophenylalanine, or p-ethynylphenylalanine.

14. Method for the treatment of arteriosclerosis/thrombosis occurring during diabetes mellitus according to claims 9, 10, 11, 12, and 13.

15. Method for the treatment of overreactions or unwanted normal reactions of the immune system (e.g. allergies, immune- as well as auto-immune diseases, risk-bearing pregnancies, such as pre-eclampsia as well as in transplantation medicine for immune-suppressive therapy), characterized in that the serotonin production is lowered.

16. Preparation for the treatment of pre-eclampsia according to claim 15, containing inhibitors (ribozymes, antisense-oligonucleotides, antisense-RNA-expression, p-chlorophenylalanine or p-ethynylphenylalanine), by which the serotonin production is lowered.

17. Preparation for the treatment of allergies according to claim 15, containing inhibitors (ribozymes, antisense-oligonucleotides, antisense-RNA-expression, p-chlorophenylalanine or p-ethynylphenylalanine), by which the serotonin production is lowered.

18. Preparation for the treatment of immune- as well as auto-immune-diseases according to claim 15, containing inhibitors (e.g.: ribozymes, antisense-oligonucleotides, antisense-RNA-expression, p-chlorophenylalanine or p-ethynylphenylalanine), by which the serotonin production is lowered.

19. Combination preparation for the treatment of bleeding episodes in the psychopharmacological treatment of depressions using antidepressive agents, that act on the serotonin-reuptake-transporter, containing antidepressive agents and von Willebrand-factor.

20. Combination preparation for the immune-suppressive therapy in transplantations, containing common immune-suppressive agents (e.g.: CsA, FK506 or rapamycin) and inhibitors (e.g.: ribozymes, antisense-oligonucleotides, antisense-RNA-expression, p-chlorophenylalanine or p-ethynylphenylalanine), by which the serotonin production is lowered.

21. Sequence of the neuronal THP, as indicated in FIG. 9.

22. DNA construct for the production of peripherally serotonin-deficient animals, as depicted in FIG. 1.