Rita Török

Association of vitamin D receptor gene polymorphisms and Parkinson's disease in Hungarians

Vitamin D receptor (VDR) gene encodes a transcription factor that influences calcium homeostasis and immunoregulation, and may play a role in neurological disorders including Parkinsons disease (PD). The investigations of the association between VDR and PD in different populations revealed various results. In a present study 100 PD patients and 109 healthy controls from the Hungarian population were genotyped for four polymorphic sites (BsmI, ApaI, FokI and TaqI) in the VDR gene. The polymorphisms were determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). Our results demonstrate an association between the FokI C allele and PD; the frequency of the C allele was significantly higher in PD patients than in controls, suggesting that this polymorphism may have a role in the development of PD in these patients.

An assessment of the frequency of mutations in the GBA and VPS35 genes in Hungarian patients with sporadic Parkinson's disease.

Parkinsons disease (PD) is the second most common neurodegenerative disorder, with cases of either familial or sporadic origin. Several polymorphisms in a number of genes have been proved to have an important role in the development of PD. Particular attention has recently been paid to genes of the glucocerebrosidase (GBA) and the vacuolar protein sorting-associated protein 35 (VPS35). In this study, the three most common mutations (L444P, N370S and R120W) of the GBA gene and the D620N mutation of the VPS35 gene were examined in 124 Hungarian patients diagnosed with sporadic PD (SPD) and 122 control subjects. The frequency of the L444P mutation of the GBA gene proved to be higher in the PD patients (2.4%) than in the controls (0%), although the difference was not statistically significant. All the patients who carried the mutant allele were in the early-onset PD (EOPD) group. However, neither the R120W nor the N370S variant of the GBA gene nor D620N mutation of the VPS35 gene were detected among the PD cases or the controls. Even though these results suggest that the studied mutations are quite rare in SPD patients, the most frequent L444P mutation of the GBA gene may be associated with the development of EOPD in the Hungarian population.

Central nervous system-specific alterations in the tryptophan metabolism in the 3-nitropropionic acid model of Huntington's disease

Experiments on human samples and on genetic animal models of Huntingtons disease (HD) suggest that a number of neuroactive metabolites in the kynurenine (KYN) pathway (KP) of the tryptophan (TRP) catabolism may play a role in the development of HD. Our goal in this study was to assess the concentrations of TRP, KYN, kynurenic acid and 3-hydroxykynurenine (3-OHK) in the serum and brain of 5-month-old C57Bl/6 mice in the widely used 3-nitropropionic acid (3-NP) toxin model of HD. We additionally investigated the behavioral changes through open-field, rotarod and Y-maze tests. Our findings revealed an increased TRP catabolism via the KP as reflected by elevated KYN/TRP ratios in the striatum, hippocampus, cerebellum and brainstem. As regards the other examined metabolites of KP, we found only a significant decrease in the 3-OHK level in the cerebellum of the 3-NP-treated mice. The open-field and rotarod tests demonstrated that treatment with 3-NP resulted in a reduced motor ability, though this had almost totally disappeared a week after the last injection, similarly as observed previously in most murine 3-NP studies. The relevance of the alterations observed in our biochemical and behavioral analyses is discussed. We propose that the identified biochemical alterations could serve as applicable therapeutic endpoints in studies of drug effects on delayed-type neurodegeneration in a relatively fast and cost-effective toxin model of HD.

The Genetic Link between Parkinson's Disease and the Kynurenine Pathway Is Still Missing.

Background. There is substantial evidence that the kynurenine pathway (KP) plays a role in the normal physiology of the brain and is involved in the pathology of neurodegenerative disorders such as Huntingtons disease and Parkinsons disease (PD). Objective. We set out to investigate the potential roles in PD of single nucleotide polymorphisms (SNPs) from one of the key enzymes of the KP, kynurenine 3-monooxygenase (KMO). Methods. 105 unrelated, clinically definitive PD patients and 131 healthy controls were enrolled to investigate the possible effects of the different alleles of KMO. Fluorescently labeled TaqMan probes were used for allele discrimination. Results. None of the four investigated SNPs proved to be associated with PD or influenced the age at onset of the disease. Conclusions. The genetic link between the KP and PD is still missing. The investigated SNPs presumably do not appear to influence the function of KMO and probably do not contain binding sites for regulatory proteins of relevance in PD. This is the first study to assess the genetic background behind the biochemical alterations of the kynurenine pathway in PD, directing the attention to this previously unexamined field.

Protein kinase inhibitor as a potential candidate for epilepsy treatment

Purpose:  Effects of the “VID‐82925” kinase inhibitor molecule were investigated both during the developing phase as well as during the stable phase of the focus with spontaneous recurrent seizures using the 4‐AP‐induced in vivo epilepsy model in anesthetized rats.

Lack of age-related clinical progression in PGC-1α-deficient mice – implications for mitochondrial encephalopathies

Impaired peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) function has been demonstrated in several neurodegenerative diseases, and murine whole-body knockouts of PGC-1α have been considered as models for Huntingtons disease. Recent neuropathological studies, however, rather propose these animals to be morphological models of mitochondrial encephalopathies, with special reminiscence of Kearns-Sayre syndrome. PGC-1α-deficient animals have already been subjected to behavioral assessments; however, the contradictory findings and the paucity of data assessing long-term progression necessitated further examinations. This study provides a comprehensive neurological phenotypic profiling of full-length-(FL-)PGC-1α-deficient mice in a broad age spectrum, with special focus on previously controversial findings, the issue of long-term phenotypic progression, the histopathological assessment of previously non-characterized tissues of potential clinicopathological relevance, and the gene expression profile of novel brain-specific isoforms of PGC-1α. Our findings demonstrate moderate hypomotility with signs of gait and trunk ataxia in addition to severe impairments in coordination and muscle strength in FL-PGC-1α-deficient mice, phenotypic features consistent of a mitochondrial disease. Intriguingly, however, these early alterations did not progress with age, the understanding of which may unveil mechanisms of potential therapeutic relevance, as discussed. The observed phenotype did not associate with retinal or spinal cord alterations, and was accompanied by mild myopathic changes. Based on these, FL-PGC-1α-deficient mice can be regarded not only as morphological but behavioral models of mitochondrial encephalopathies, with an important temporal limitation that has now been clarified. The mechanisms capable of halting a potentially lethal phenotype are to be unveiled, as they may hold therapeutic value for mitochondrial diseases.

Investigation of vitamin D receptor polymorphisms in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) patients manifest aberrations in the vitamin D endocrine system, with a vitamin D deficiency. Genetic investigations have identified those proteins which link vitamin D to ALS pathology: major histocompatibility complex class II molecules, toll‐like receptors, poly(ADP ribose) polymerase‐1, haeme oxygenase‐1, the reduced form of nicotinamide adenine dinucleotide phosphate and calcium‐binding proteins. Vitamin D additionally impacts ALS through cell‐signalling mechanisms: glutamate, matrix metalloproteinases, the Wnt/β‐catenin signalling pathway, mitogen‐activated protein kinase pathways, prostaglandins, reactive oxygen species and nitric oxide synthase, but its role has been only poorly investigated.

Effect of MPTP on mRNA expression of PGC-1α in mouse brain

The peroxisome proliferator-activated receptor-γ (PPARγ) coactivator 1α (PGC-1α) is a key regulator of mitochondrial biogenesis, respiration and adaptive thermogenesis. Besides the full-length protein (FL-PGC-1α), several other functionally active PGC-1α isoforms were identified as a result of alternative splicing (e.g., N-truncated PGC-1α; NT-PGC-1α) or alternative promoter usage (e.g., central nervous system-specific PGC-1α isoforms; CNS-PGC-1α). Achieving neuroprotection via CNS-targeted pharmacological stimulation is limited due to poor penetration of the blood brain barrier (BBB) by the proposed pharmaceutical agents, so preconditioning emerged as another option. The current study aimed to examine of how the expression levels of FL-, NT-, CNS- and reference PGC-1α isoforms change in different brain regions following various 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment regimens, including chronic low-dose treatment for preconditioning. Ninety minutes following the acute treatment regimen, the expression levels of FL-, NT- and CNS-PGC-1α isoforms increased significantly in the striatum, cortex and cerebellum. However, this elevation diminished 7days following the last MPTP injection in the acute treatment regimen. The chronic low-dose administration of MPTP, which did not cause significant toxic effects in light of the relatively unaltered dopamine levels, did not result in any significant change of PGC-1α expression. The elevation of PGC-1α levels following acute treatment may demonstrate a short-term compensatory mechanism against mitochondrial damage induced by the complex I inhibitor MPTP. However, drug-induced preconditioning by chronic low-dose MPTP seems not to induce protective responses via the PGC-1α system.

L13 Stimulation of the PGC-1A expression in mouse brain

Background Mitochondrial dysfunction play a significant role in the patomechanism of several neurodegenerative disorders, including Huntington’s disease. PGC-1α is a master regulator of mitochondrial biogenesis, thus it could serve as a potential therapeutic target in these disorders. Due to the several tissue-specific isoforms and the limitation of the blood-brain barrier penetration, the brain specific stimulation of the expression of this transcriptional factor is difficult. Methods We have used several different paradigms including physical and chemical factors in wild-type mice to stimulate the expression of PGC-1α in certain brain areas affected most in neurodegenerative disorders. Results Administration of mitochondrial toxin MPTP produce a significant elevation of brain specific as well as full length and NT isoforms in several brain regions. The long term, but not the short term rotarod training produced a moderate, but significant increase of expression of all isoforms exclusively in the cerebellum. However the calorie restriction, the cold challenge or vitamin D administration did not alter the PGC-1α expression in any region of the brain. Conclusion These data produce evidence that brain specific stimulation of this mitochondrial key regulator is not easily feasible. So further studies are needed with blood-brain barrier penetrating molecules. This work was supported by grants KTIA_13_NAP-A-II/17 of National Brain Research Program.