Monika Białecka

Association of Nrf2-encoding NFE2L2 haplotypes with Parkinson's disease

BackgroundOxidative stress is heavily implicated in the pathogenic process of Parkinsons disease. Varying capacity to detoxify radical oxygen species through induction of phase II antioxidant enzymes in substantia nigra may influence disease risk. Here, we hypothesize that variation in NFE2L2 and KEAP1, the genes encoding the two major regulators of the phase II response, may affect the risk of Parkinsons disease.MethodsThe study included a Swedish discovery case-control material (165 cases and 190 controls) and a Polish replication case-control material (192 cases and 192 controls). Eight tag single nucleotide polymorphisms representing the variation in NFE2L2 and three representing the variation in KEAP1 were chosen using HapMap data and were genotyped using TaqMan Allelic Discrimination.ResultsWe identified a protective NFE2L2 haplotype in both of our European case-control materials. Each haplotype allele was associated with five years later age at onset of the disease (p = 0.001) in the Swedish material, and decreased risk of PD (p = 2 × 10-6), with an odds ratio of 0.4 (95% CI 0.3-0.6) for heterozygous and 0.2 (95% CI 0.1-0.4) for homozygous carriers, in the Polish material. The identified haplotype includes a functional promoter haplotype previously associated with high transcriptional activity. Genetic variation in KEAP1 did not show any associations.ConclusionThese data suggest that variation in NFE2L2 modifies the Parkinsons disease process and provide another link between oxidative stress and neurodegeneration.

The association of functional catechol-O-methyltransferase haplotypes with risk of Parkinson's disease, levodopa treatment response, and complications.

Introduction Differences in catechol-O-methyltransferase (COMT) activity and genotype may determine individual variations in the therapeutic response to levodopa or Parkinsons disease (PD) susceptibility. The role of functional COMT haplotypes in PD susceptibility and treatment response has not been examined. Objectives In this case–control study, we investigated the association of the most common COMT gene haplotypes (formed by single nucleotide polymorphisms (SNPs): rs6269:A>G; rs4633C>T; rs4818:C>G; and rs4680:A>G) with PD risk and the association of the COMT haplotypes with the dose and complications of levodopa therapy in PD patients. Methods A total of 679 study participants (322 PD and 357 controls) were included. Each participant was genotyped for four SNPs in the COMT gene, located in a common haploblock, that has been shown to influence COMT enzymatic activity. The influence of COMT haplotypes on the dose of levodopa administered during fifth year of treatment, and occurrence of motor complications were examined in PD patients. The EH program (Jurg Ott, Rockefeller University, New York, USA) was used to estimate haplotype frequencies. Results The estimated frequencies of low (A_C_C_G) and medium (A_T_C_A) activity haplotypes tended to be slightly lower among PD patients when compared with controls (P=0.09, G_C_G_G-high activity haplotype as reference). The frequency of G_C_G_G (high activity) haplotype carriers was higher in late onset PD patients (P=0.04) compared with controls. The mean levodopa dose increased with the activity of the functional haplotypes (low<medium<high). Doses prescribed for G_C_G_G (high activity) haplotype carriers (mean 604.2±261.9 mg) were significantly higher than those for the noncarriers (mean 512.2±133.5 mg, P<0.05). The COMT haplotype seemed to have little influence on the development of levodopa-induced dyskinesias. Conclusion Our study showed a possible association of functional COMT haplotypes with the risk of PD. Both nonsynonymous and synonymous SNPs within functional COMT haplotype blocks may be more relevant than individual SNPs in conferring PD susceptibility. The doses of levodopa treatment can be influenced by specific COMT haplotypes and this may be useful in instituting individualized therapy for PD patients.

The effect of monoamine oxidase B (MAOB) and catechol-O-methyltransferase (COMT) polymorphisms on levodopa therapy in patients with sporadic Parkinson's disease

Objectives –  The etiology of sporadic idiopathic Parkinsons disease (PD) is considered multifactorial with both genetic and environmental factors modifying the disease expression. Recent studies suggest that polymorphism in monoamine oxidase B (MAOB) and catechol‐O‐methyltransferase (COMT) might influence the risk and treatment of PD. The aim of the study was to evaluate the effect of MAOB and COMT genetic polymorphism on effective daily dose of levodopa applied during the first 5 years of treatment, and to find out if a relationship exists between MAOB and COMT haplotypes and motor disturbances onset in PD patients treated with levodopa preparations.

Interleukin-10 (IL10) and tumor necrosis factor α (TNF) gene polymorphisms in Parkinson's disease patients

Recent studies revealed that inflammatory processes might play an important role in the pathogenesis of Parkinsons disease (PD). We hypothesized that genetically determined differences in the immune response, especially in anti- and pro-inflammatory cytokines production might influence the risk for the development and/or onset of sporadic PD. In the present study, we investigated the genetic polymorphisms of the IL10 (-1082 and -519) and TNF (-308) genes in relation to the risk of PD, and their associations with age of PD onset in a group of 316 patients, divided into two subgroups: Group 1: patients with early onset PD (EOPD), i.e. before 50 years of age (102 patients), and group 2: patients with onset of PD after 50 years of age comprising 214 subjects. Control samples were obtained from 300 randomly selected healthy individuals from the same geographical region with no signs of Parkinsonism as evaluated by a neurologist. PCR-RFLP methods were used for genotyping. No statistically significant differences between PD patients and controls were found in the frequency of a single locus of IL10 promoter. We found TNF -308A allele significantly more frequent in EOPD patients compared to the controls (p=0.007). The overrepresentation of the A allele was reflected by a significant increase in AA homozygous individuals in EOPD patients compared to the controls (p=0.0021). The results from our study revealed that the TNF -308AA genotype might increase the risk of early onset of PD.

Association of COMT, MTHFR, and SLC19A1(RFC-1) polymorphisms with homocysteine blood levels and cognitive impairment in Parkinson's disease.

Introduction Elevated plasma homocysteine (Hcy) concentration is an independent risk factor for cardiovascular disease, and its involvement in endothelial cell dysfunction is well established. However, the role of Hcy and folate in the pathogenesis of Parkinson’s disease (PD) remains controversial. Objectives The study was aimed at evaluating the relationships between Hcy, vitamin B12, and folic acid levels in the blood and cognitive status in PD patients with the genetic polymorphisms of MTHFR (rs1801133: C>T-677C>T, rs1801131: A>C-1298A>C), COMT (rs4680: A>G-Val158Met, rs6269: A>G, rs4633: C>T, rs4818: C>G), or SLC19A1 (rs1051266: G>A-80G>A). Methods A total of 502 participants (248 with PD and 254 age-matched and sex-matched controls) were included in the study. The Unified Parkinson’s Disease Rating Scale score, Hoehn–Yahr staging, and the Schwab–England scale were used to assess motor abilities and activity during daily life. Complex psychological examination with a battery of tests was used to classify patients into groups with (PDD) and without (nPDD) dementia. Blood samples were examined for Hcy, vitamin B12, and folic acid levels, as well as polymorphisms in genes related to Hcy metabolism, such as COMT, MTHFR, and SLC19A1(RFC-1). Results The frequency of homozygous COMT rs4680G and rs4633C allele carriers was significantly decreased in PD patients in comparison with the controls (P=0.015; odds ratio=0.60; 95% confidence interval 0.41–0.90 and P=0.020; odds ratio=0.619; 95% confidence interval 0.42–0.92, respectively). No significant differences in the distribution of MTHFR 677C>T, 1298A>C, and SLC19A1 80G>A alleles and genotypes between PD patients and the controls were found. Hcy levels were significantly increased in PD patients (18±7.8 &mgr;mol/l) as compared with the controls (14.0±9.6 &mgr;mol/l, P=10–8) and were significantly associated with the MTHFR 677C>T polymorphism both in PD patients and controls, in which T allele carriers were characterized by markedly elevated Hcy plasma concentrations. No association was observed between Hcy plasma level and COMT and SLC19A polymorphisms. The results of multivariate logistic regression analysis revealed age (P=0.0003) and Hcy plasma levels (P=0.07) as independent risk factors predisposing individuals to PD dementia. The studied polymorphisms were not associated with cognitive status in PD patients. Conclusion The genetic factors studied were not associated with cognitive status in PD patients. Only age and Hcy plasma levels were found to be independent risk factors predisposing individuals to PD dementia. However, COMT: rs4680: A>G and rs4633: C>T polymorphisms were found to significantly affect PD risk, and the MTHFR 677C>T polymorphism helped determine plasma Hcy concentrations.

CARD15 variants in patients with sporadic Parkinson's disease

Recent reports have proven the importance of genetic factors and inflammation in the pathogenesis of sporadic Parkinsons disease (PD). In the current study, the frequency of CARD15/NOD2 gene variants (R702W, G908R, L1007fs), previously associated with Crohns disease--a common inflammatory bowel disease, have been examined in a group of 308 sporadic PD patients and 220 healthy controls. Significantly higher frequency of total CARD15 variant alleles in PD patients (13.0%) compared to the controls (8.0%, p<0.02) was observed. 24.0% of PD patients carried at least one CARD15 variant allele compared to 15.5% of healthy controls (p<0.02, OR=1.73). The results of the study suggest, that the polymorphism in CARD15/NOD2 gene may be a risk factor for sporadic PD development, and support the concept of inflammatory pathogenesis of PD.

Analysis of LRRK2 G2019S and I2020T mutations in Parkinson's disease

Mutations in the leucine-rich repeat kinase 2 (LRRK2), encoding dardarin protein, have been demonstrated to be linked to autosomal dominant Parkinsons disease (PD). In the present study the entire exon 41 of LRRK2 gene was evaluated in a series of 174 PD patients recruited from Polish population, aged at the time of diagnosis 54.0 ± 39.1 years, 21 of them had positive family history of PD with mean onset of the disease of 51.9 ± 11.7 years as well as in 190 healthy controls aged 73.7 ± 6.0 years. The mutations were evaluated by direct sequencing for mutations in exon 41 of LRRK2 gene. In the studied patients no known mutations in exon 41 of LRRK2 gene, including G2019S and I2020T were found, both in PD patients as well as in the controls. It can be concluded that the G2019S and I2020T mutations in exon 41 of LRRK2 gene are rare causes of Parkinson disease in a Polish population.

Mitochondrial transcription factor A variants and the risk of Parkinson's disease.

The mitochondrial transcription factor A (TFAM) has been recently shown to decrease reactive oxygen species (ROS) generation. It is also known that mitochondrial DNA (mtDNA) haplogroups might confer different coupling properties, resulting in different ROS levels. We hypothesized that potentially functional TFAM variants could influence PD risk depending on haplogroup background. To test this we assessed the role of six TFAM variants on PD risk in 326 PD patients and 316 controls, and correlated it with mtDNA haplogroup clusters (HV, JTKU and a putative functionally different group U4U5a1KJ1cJ2, connected previously with partial uncoupling of oxidative phosphorylation). Both genotype and haplotype analysis showed that intronic variant rs2306604 modifies PD risk. Multivariate logistic regression analysis confirmed that rs2306604 G/G genotype is an independent risk factor for PD (OR 1.789, 95% CI 1.162-2.755, p=0.008). There was a borderline interaction between G/G genotype and HV haplogroup (p=0.075). Haplotype analysis showed that all three haplotypes containing rs2306604 allele A occurred at higher frequencies in controls, but only one of them reached statistical significance (chi(2) 4.523, p=0.0334). Conversely, four of five haplotypes containing allele G had higher frequencies in PD group, with no statistical significance.

The impact of MRI white matter hyperintensities on dementia in Parkinson's disease in relation to the homocysteine level and other vascular risk factors.

Background: The role of white matter hyperintensities (WMH) and homocysteine (Hcy) and other vascular risk factors in the pathogenesis of Parkinsons disease (PD) dementia (PDD) remains unclear. Objective: The aim of the study was to assess the impact of WMH, Hcy and other biochemical and vascular risk factors on PDD. Methods: A total of 192 patients with PD and 184 age- and sex-matched healthy controls were included. A semistructured interview was used to assess demographic and clinical variables with respect to vascular risk factors (arterial hypertension, diabetes mellitus, atrial fibrillation, ischemic heart disease, obliterative atherosclerosis, hypercholesterolemia, smoking, alcohol intake). Unified Parkinsons Disease Rating Scale score, Hoehn-Yahr staging and the Schwab-England activities of daily living scale were used to assess motor abilities and activities of daily living. A complex neuropsychological examination with a battery of tests was used to classify patients into a group with dementia (PDD) and a group without dementia (PD). Neuroradiological examination of MRI scans included visual rating scales for WMH (according to the Wahlund and Erkinjunntti rating scales) and the Scheltens scale for hippocampal atrophy. Blood samples for Hcy, folate, vitamin B12, fibrinogen, lipids, glucose, creatinine, transaminases and thyroid stimulating hormone (TSH) were examined. Results: Among all patients, 57 (29.7%) fulfilled the diagnostic criteria for dementia. Significantly higher Hcy plasma levels were noted in PD and PDD groups compared to controls (p < 0.05) and in PDD when compared to PD (p < 0.05). According to multivariate regression analysis, WMH (Erkinjuntti scale), high Hcy, low vitamin B12 and folate plasma levels were independent risk factors for PDD. Vascular risk factors did not play any role in the pathogenesis of PDD and WMH. Conclusions: WMH along with Hcy, folate and vitamin B12 may impact cognition in PD. Therapy with vitamin B12, folate and catechol-O-methyltransferase inhibitors may play a potential protective role against PDD.

BDNF G196A (Val66Met) polymorphism associated with cognitive impairment in Parkinson's disease

Brain-derived neurotrophic factor (BDNF) is a neurotrophin widely expressed in the mammalian brain, regulating neuronal survival and known to influence dopaminergic neurons and cognitive processes. The present study investigated the BDNF Val66Met polymorphism associations with PD risk, and cognitive impairment in PD. A total of 486 study subjects (244 PD and 242 age and sex matched controls) were included in the study. UPDRS score, Hoehn-Yahr staging and the Schwab-England scale were used to assess motor abilities and activity during daily life. The patients were classified into groups with dementia (PDD, n=69) and without it (nPDD, n=166) on the basis of neuropsychological assessment. The most common functional polymorphism in BDNF Val66Met (rs6265, G196A) gene was determined using TaqMan real-time PCR assay. Frequencies of evaluated BDNF alleles and genotypes were similar in PD and the controls. The mean age of disease onset among BDNF Met/Met carriers was later (65.00±6.13) in comparison to Val/Val (57.45±10.68) and Val/Met (56.33±10.91) subjects (p=0.077). The studied BDNF polymorphism was not associated with cognitive status in PD patients. However, patients with Met/Met alleles demonstrated better delayed recall of information than patients with Val/Val alleles. The results of multivariate logistic regression analysis revealed age (p=0.0003) and the disease stage (p=0.002) as independent risk factors predisposing to PD dementia.