Paraoxonase 1 (PON1) polymorphisms and risk for essential tremor

Background: The polymorphic enzyme human serum paraoxonase 1 (PON1), encoded by the gene PON1 (chromosome 7q21.3), plays a major role in the metabolism of organophosphorus compounds. We investigated the possible association between the PON1 genotype and allelic variants of the polymorphisms Leu55Met and Glu192Arg, and the risk for essential tremor (ET). Methods: We studied the frequency of the PON1 genotypes and allelic variants in 201 patients with ET and 220 healthy controls using a PCR‐RLFP method. Results: The frequencies of the PON1 genotypes and allelic variants of the polymorphisms Leu55Met and Gln192Arg did not differ significantly between patients with ET and controls. These polymorphisms were unrelated with the age of onset of ET. Conclusions: PON1 polymorphisms are not related with the risk for ET.     

Paraoxonase gene polymorphisms and stroke severity

Background: Paraoxonase (PON) is an HDL‐associated enzyme that prevents low‐density lipoprotein oxidation, playing a major role in the pathogenesis of atherosclerosis. PON genes polymorphisms may affect the corresponding enzyme activity. In this study, we examined the association of ischemic stroke with the three PON genes. Methods: One hundred and seventy‐eight patients hospitalized for ischemic stroke and 181 age‐ and sex‐matched healthy controls were recruited. PON1(Q/R) 192, PON1(M/L) 55, and PON2(S/C) 311 polymorphisms were analyzed. Results: The presence of the PON2 311C allele was significantly increased in patients with severe forms of ischemic stroke according to Modified Rankin Scale (P = 0.02, odds ratio = 2.215). No significant differences in genotype and allele distribution were observed between patients and controls. Conclusions: The PON2 311C allele was suggested as a possible predisposing factor for severe cases of ischemic stroke. Large‐scale multicenter‐controlled prospective studies are warranted to further explore the effects of PON polymorphisms on stroke susceptibility and severity.     

Dopamine receptor 3(DRD3) polymorphism and risk for migraine

Background/objectives: Dopamine has been implicated in the pathogenesis of migraine. We investigated the possible association between the polymorphism 312G>A (rs6280) in the DRD3 gene(essential tremor 1‐ETM1‐ locus, chromosome 3q13) and the risk for migraine and for triggering migraine attacks by alcohol. Methods: We studied the frequency of the DRD3 genotypes and allelic variants in 197 patients with migraine and 282 healthy controls using a polymerase chain reaction and MlsI‐restriction fragment length polymorphisms method. Results: The frequencies of the DRD3 genotypes and DRD3Gly9 were similar in patients with migraine and controls and were unrelated to the age of onset of migraine, gender, family history of migraine and triggering of migraine attacks by alcohol. The frequency of the genotype DRD3Gly9Gly9 was significantly higher in patients with migraine with aura when compared with patients with migraine without aura, but not with controls. Conclusion: DRD3 genotype and allelic variants were not related to the risk for migraine in Caucasian Spanish people.     

对氧磷酶1基因多态性与缺血性脑卒中的关联研究

目的探讨对氧磷酶1(PON1)基因的rs2299262标签位点(tag SNP)多态性与缺血性脑卒中的相关性。方法本研究共纳入705例缺血性脑卒中患者和406例对照组人群,按TOAST分型标准,分为动脉粥样硬化性脑梗死406例、腔隙性脑梗死299例。以位于PON1基因的rs2299262位点为遗传标记,采用聚合酶链反应(PCR)和限制性片段长度多态性(RFLP)技术检测PON1基因的多态性。结果缺血性脑卒中组、动脉粥样硬化性脑梗死组、腔隙性脑梗死组和对照组的PON1基因型及等位基因频率与对照组的差异无统计学意义(P>0.05)。经性别分层后也未见显著差异。结论PON1基因与缺血性脑卒中的发病可能无关。     

Genetic polymorphism of paraoxonase 1 (PON1) and susceptibility to Parkinson''s disease

Toxicologists have thought that the paraoxonase (PON) enzyme polymorphism might contribute to effects of pollutants and other environmental chemicals on susceptibility to cancer, birth defects and Parkinson's disease (PD). We studied a biallelic PON1 polymorphism at codon 192 (A and B alleles) in 166 patients with sporadic idiopathic PD. The frequency of the B (Arg) allele of PON1 was significantly increased in patients with PD than in healthy controls (χ²=8.75, df=1, P<0.005). The relative risk of PD in homozygotes for the B allele was 1.60 fold higher than individuals with the A (Gln) allele (χ²=7.38, df=1, P<0.01). Our data suggest that environmental neurotoxins metabolized by PON1 might be responsible for neurodegeneration with aging and that the B (Arg) allele form might have genetic susceptibility to PD.     

Paraoxonase 1 and cytochrome P450 polymorphisms in susceptibility to acute organophosphorus poisoning in Egyptians

BackgroundOrganophosphates are the basis of many insecticides, herbicides, and nerve agents. They were listed as highly acutely toxic agents. Findings in knockout mice suggest that paraoxonase 1 may modulate the toxicity resulting from exposure to organophosphorus compounds. In human, there is no enough data about genetic modulation of acute organophosphorus intoxication. CYP2D6 is involved in the metabolism of about 30% of xenobiotics. Prompt accurate management of OP acute intoxication can promote patient's survival.Design and methodsForty acute organophosphorus intoxicated patients were divided according to presence of clinical toxicity manifestations and serum level of pseudo-cholinesterase into two groups of acute symptomatic and acute asymptomatic patients. A third group of 29 healthy volunteers served as control. Paraoxonase 1 Q192R and CYP2D6 G1934A polymorphisms, (QQ, QR, and RR for PON1) and (GG, GA, and AA for CYP2D6), were studied using polymerase chain reaction-restriction fragment length polymorphism technique. Serum paraoxonase 1 and pseudo-cholinesterase activities were measured spectrophotometrically.ResultsSerum pseudo-cholinesterase was significantly reduced in both acute intoxication groups compared to the controls (p = 0.000). Paraoxonase 1 was significantly reduced in the symptomatic acute intoxication patients in comparison to the asymptomatic group (p = 0.002). There was a significant increase in paraoxonase 1 192 RR genotype and R allele in the symptomatic patients in comparison to the controls and asymptomatic patients (p = 0.006 and p = 0.01, respectively). For CYP2D6 G1934A genotypes and alleles, no significant difference was found between groups (p = 0.3 and p = 0.18, respectively). However, one case of the two recorded fatalities was for a symptomatic female patient with the only traced AA genotype. The combination of both single nucleotide polymorphisms revealed a significant distribution difference between groups, with QQ + GG genotypes being more represented in the controls, while RR + GA genotypes were exclusively present in the group of symptomatic patients (p = 0.04), none of the participants was found to have RR + AA genotypes.Some nicotinic (fasciculation and weakness), and muscarinic symptoms (bronchospasm, salivation, lacrimation, and diarrhea), increased with high significance in the symptomatic group compared to the asymptomatic one (p < 0.001 for all). Convulsions also showed significant increase (p = 0.02).ConclusionParaoxonase 1 Q192R modulates patient's response, and CYP2D6 may be related to the acute organophosphorus intoxication in the context of other genetic-environmental factors. Paraoxonase 1 enzyme level is related to symptom severity in acute OP poisoning, while pseudo-cholinesterase level indicates exposure to OP rather than severity of clinical manifestations.     

Gamma-aminobutyric acid (GABA) receptor rho (GABRR) polymorphisms and risk for essential tremor

Some clinical and experimental data suggest a possible role of gamma-aminobutyrate (GABA)-ergic mechanisms in the pathophysiology of essential tremor (ET), such as the improvement of ET with some GABAergic drugs and the development of an experimental model of ET in GABA A receptor alpha-1 knockout mice (postural and kinetic tremor and motor incoordination similar to human ET). To investigate the possible association between the GABA receptor subtype rho1, rho2, and rho3 (GABRR1, GABRR2, and GABRR3) genotypes and allelic variants of the single nucleotide polymorphisms GABRR1-M26V (Met26Val, rs12200969), GABRR1-H27R (His26Arg, rs1186902), GABRR2-T455M (Thr55Met, rs282129), and GABRR3-Y205X (Tyr205X, rs832032), and the risk for ET, we studied the frequency of the previously mentioned GABRR genotypes and allelic variants in 200 patients with ET and 250 healthy controls using TaqMan genotyping. The frequencies of the GABBR1 genotypes and allelic variants of the studied polymorphisms did not differ significantly between patients with ET and controls, and were unrelated with the age at onset of tremor, gender, localization of tremor, and response of tremor to ethanol. These data suggest that the single nucleotide polymorphisms studied in the GABBR genes are not related to the risk for ET.     

血清对氧磷酶L55M基因多态性与动脉粥样硬化性脑梗死的关系

目的 探讨中国湖南汉族人群血清对氧磷酶（PON1）L55M基因多态性与动脉粥样硬化性脑梗死（ACI）的关系。方法 筛选153例ACI及153名健康人群为研究对象。采用聚合酶链式-限制性片段长度多态性办法检测PON1-L55M基因多态性。结果 在研究总人群中没有发现MM基因型。ACI组LL、LM基因犁频率分别为96．7％、3．3％,L、M等位基因频率分别为0．991、0．016;正常对照组LL、LM基因型频率为93.5％和6．5％．L、M等位基因频率分别为0．968和0．032。PON1-L55M各基因型和等位基因频率在ACI和正常对照组分布差异无显著性。结论 PON1-L55M基因多态性可能与中国湖南汉族人群ACI发病无关。     

Paraoxonase 1 gene promoter polymorphisms are associated with the extent of stenosis in coronary arteries

HDL-associated paraoxonase1 (PON1) is believed to be an important anti-oxidative enzyme in the retardation of atherosclerosis. In this study, we determined haplotypes of three SNPs within the PON1 gene promoter to elucidate association of functional sites with coronary artery disease (CAD). We applied a direct haplotyping procedure through ARMS (Amplification Refractory Mutation System) and RFLP (Restriction Fragment Length Polymorphism) analysis techniques. The haplotypes of the G(− 907)C, A(− 162)G and C(− 107)T polymorphisms within the 5' region of the PON1 gene were determined in 99 patients and 66 controls who were evaluated angiographically for the presence and extent of stenosis in coronary arteries. The genotype and haplotype distributions had significant differences between patient subgroups (One-, Two- and Three-vessel disease) but not between the patient and control groups. Multivariate analyses suggested decreased arylesterase activity is the most important independent factor in the CAD severity. The increase of high activity variants [G(− 907) and C(− 107)] within the two-allelic haplotypes was reversely associated with the extent of stenosis in coronary arteries. However, we could not determine the independent involvement each of the C(− 107)T and G(− 907)C polymorphisms on the extent of stenosis. We found no significant association between the A(− 162)G polymorphism and the extent of stenosis in vessels. The study indicated the association of polymorphic variations within the PON1 gene promoter haplotypes with the serum arlyesterase activity. The arlyesterase activity was also associated with the extent of stenosis in coronary arteries but not with primary development of atherosclerosis.     

Thymidylate synthase promoter tandem repeat and MTHFD1 R653Q polymorphisms modulate the risk for migraine conferred by the MTHFR T677 allele

There is growing evidence that folate metabolism is involved in migraine pathophysiology, mainly in migraine with aura. Even though folate metabolism is regulated by a number of enzymes, only two functional polymorphisms have been tested in association studies with migraine. Here, we have explored the possible role in migraine of other folate-metabolizing enzymes which are in close interdependency with 5',10'-methylenetetrahydrofolate reductase analyzing functional polymorphisms of these enzymes in a case-control study. Individually, thymidylate synthase (TS), methenyltetrahydrofolate cyclohydrolase formyltetrahydrofolate synthase (MTHFD1), or methionine synthase (MS) polymorphisms did not modify the general risk for suffering migraine. Nevertheless, we observed a strong interaction between TS and MTHFR mutated genotypes, which increased over 8-fold the risk for experiencing aura among migraineurs; MTHFD1 and MTHFR mutated genotypes also increased together the risk for migraine in general (OR = 3.08; 95% CI = 1.3-7.4). We conclude that the pathogenetic role of the MTHFR T677 allele in migraine is modulated by functional polymorphisms of TS and MTHFD1.     

Paraoxonase polymorphisms, pesticide exposure and Parkinson's disease in a Caucasian population

Summary. Parkinson's disease (PD) has been associated with exposure to pesticides and oxidative injury. The involvement of paraoxonase in both pesticide metabolism and lipid peroxidation suggests that it may play a role in the pathogenesis of PD. We examined the frequency of polymorphic alleles of the PON1 and PON2 genes in a sample of caucasian subjects with PD. The frequency distribution of these genotypes did not differ significantly between patients and controls, including those who had reported exposure to pesticides. Received August 20, 1999; accepted January 18, 2000     

GABA-A2 receptor subunit gene (GABRA2) polymorphisms and risk for alcohol dependence

Gamma-aminobutyric acid (GABA) A receptors are believed to mediate some of the physiological and behavioral actions of ethanol. Recent studies have suggested that genetic variants of the GABA-A receptor alpha2 subunit gene (GABRA2) are associated with alcohol dependence. The aim of this study is to confirm and extend the role of GABRA2 haplotypes in the liability to alcohol dependence. 291 (231 male) treatment-seeking alcohol-dependent individuals and 295 (153 male) control subjects were enrolled into the study. Characteristics of alcohol dependence were obtained using the SSAGA (semi-structured assessment of the genetics of alcoholism, German Version). Genotyping of 10 SNPs across the GABRA2 gene was performed following previous reports and using PCR. One genetic variant was detected to significantly differ between alcohol-dependent subjects and controls. Two common 8 SNP haplotypes and their complementary alleles were identified containing this SNP and were present in 89.9% of controls and 93.4% of the alcohol-dependent individuals. One of the haplotypes (T-C-A-C-A-T-T-C) was significantly associated with alcohol dependence and characteristics of alcohol withdrawal and severity of alcohol dependence (delirium tremens, withdrawal seizures). These findings support and extend the three previous studies implicating a GABA-A receptor subunit as contributing to the genetic risk for alcohol dependence. Possible implications of these findings are discussed.     

Positive correlation of paraoxonase 1 (PON1) activity with serum insulin level and HOMA-IR in dementia. A possible advantageous role of PON1 in dementia development

Paraoxonase 1 (PON1) activity and metabolic syndrome traits were evaluated in 169 demented patients (81 recognized as AD, 32 as VaD, 56 as MD) and in 64 control individuals. Paraoxonase activity was determined spectrophotometrically using phenyloacetate as substrate. Metabolic syndrome was recognized according to AHA/NHLBI criteria.In the whole group with dementia significant positive correlation between PON1 activity/HDL cholesterol ratio (i.e. HDL corrected PON1 activity) and insulin level as well as HOMA IR index, was observed. The multivariate analysis showed that the PON1/HDL-C ratio was also significantly positively associated with the presence of metabolic syndrome (with insulin resistance as a major underlying trait) both in dementia and in control group. High insulin level and HOMA-IR are considered to be the traits of insulin resistance. It has however to be taken into account that they both could also depend on insulin production and release which, as was recently stated in cell experiments, are enhanced by PON1. The observed positive correlation suggests an advantageous role of the enzyme in metabolic syndrome influence on dementia development.     

Genetic and temporal determinants of pesticide sensitivity: role of paraoxonase (PON1)

Susceptibility to organophosphorus (OP) insecticides and nerve agents is strongly influenced by genetic and developmental factors. A number of organophosphorothioate insecticides are detoxified in part via a two-step pathway involving bioactivation of the parent compound by the cytochrome P450 systems, then hydrolysis of the resulting oxygenated metabolite (oxon) by serum and liver paraoxonases (PON1). Serum PON1 has been shown to be polymorphic in human populations. The Arg192 isoform (PON1R192) of this HDL-associated protein hydrolyzes paraoxon (POX) at a high rate, while the Gln192 isoform (PON1Q192) hydrolyzes paraoxon at a low rate. The effect of the polymorphism is reversed for the hydrolysis of diazoxon (DZO), soman and particularly sarin. Phenylacetate is hydrolyzed at approximately the same rate by both PON1 isoforms and chlorpyrifos oxon (CPO) slightly faster by the PON1R192 isoform. In addition to the effect of the amino acid substitution on rates of toxicant hydrolysis, two other factors influence these rates. The expression of PON1 is developmentally regulated. Newborns have very low levels of PON1. Adult levels in rats and mice are reached at 3 weeks of age and in humans, sometime after 6 months of age. In addition, among individuals of a given genotype, there is at least a 13-fold difference in expression of PON1 that is stable over time. Dose/response experiments with normal mice injected with purified PON1 and with PON1 knockout mice have clearly demonstrated that the observed differences of in vitro rates of hydrolysis are significant in determining differential sensitivities to specific insecticides processed through the P450/PON1 pathway. Injection of purified rabbit PON1 protects mice from cholinesterase inhibition by chlorpyrifos (CPS) and CPO. Knockout mice are much more sensitive to CPO and DZO than are their PON1+/+ littermates or wild-type mice. A number of recent reports have also indicated that the PON1R192 isoform may be a risk factor for cardiovascular disease. Studies with PON1 knockout mice are also consistent with a role of PON1 in preventing vascular disease.