Genetic variation at the catalytic subunit of glutamate cysteine ligase contributes to the susceptibility to sporadic colorectal cancer: a pilot study.

BACKGROUND: Glutathione is a tripeptide detoxifying a variety of exogenous and endogenous free radicals and carcinogens, and a deficiency of glutathione is associated with an increased host susceptibility to oxidative stress, a pathological condition implicated in the development and progression of cancer. The catalytic subunit of glutamate-cysteine ligase (GCLC) is an enzyme responsible for the initial and rate-limiting step of glutathione biosynthesis. METHODS AND RESULTS: The aim of this pilot study was to investigate whether genetic variation at the GCLC gene contributes to the risk of colorectal cancer (CRC). DNA samples from 681 unrelated Russian individuals (283 patients with CRC and 398 age- and sex-matched healthy controls) were genotyped for six common functional SNPs of the GCLC gene (SNPs) such as rs12524494, rs17883901, rs606548, rs636933, rs648595 and rs761142 of the GCLC gene using the MassARRAY-4 system. We found that genotype rs606548-C/T is significantly associated with increased risk of CRC regardless of sex and age (OR 2.24; 95% CI 1.24-4.03; P = 0.007, FDR = 0.04). Moreover, ten GCLC genotype combinations showed association with the risk of CRC (P < 0.05). Functional SNP annotation enabled establishing the CRC-associated polymorphisms are associated with a decreased GCLC expression that may be attributed to epigenetic effects of histone modifications operating in a colon-specific manner. CONCLUSIONS: The present study was the first to show that genetic variation at the catalytic subunit of glutamate-cysteine ligase may contribute to the risk of colorectal cancer risk. However, further genetic association studies with a larger sample size are required to substantiate the role of GCLC gene polymorphisms in the development of sporadic colorectal cancer.

A comprehensive study revealed SNP-SNP interactions and a sex-dependent relationship between polymorphisms of the CYP2J2 gene and hypertension risk.

This study investigated whether common polymorphisms of cytochrome P450 2J2 (CYP2J2), a major enzyme that controls the biosynthesis of vasoactive epoxyeicosatrienoic acids, are collectively involved in the molecular basis of essential hypertension (EH). A total of 2314 unrelated Russian subjects from the Kursk (discovery sample: 913 EH patients and 645 controls) and Belgorod (replication sample: 345 EH patients and 411 controls) regions were recruited for this study. Eight single nucleotide polymorphisms (SNPs), including rs890293, rs11572182, rs10493270, rs1155002, rs2280275, rs7515289, rs11572325, and rs10889162, of CYP2J2 were genotyped using the MassARRAY 4 system and TaqMan-based assays. Significant associations were identified among the SNPs rs890293 (OR = 2.17, 95%CI 1.30-3.65), rs2280275 (OR = 1.59, 95%CI 1.10-2.37) and rs11572325 (OR = 1.89, 95%CI 1.22-2.95) and the risk of EH in females from the Kursk population. Sixteen CYP2J2 genotype combinations only showed significant associations with EH risk only in females. A common haplotype, T-T-G-C-C-C-T-A, increased the risk of EH in females. The bioinformatic analysis enabled identification of the SNPs that possess regulatory potential and/or are located within the binding sites for multiple transcription factors that play roles in the pathways involved in hypertension pathogenesis. Moreover, the polymorphisms rs890293, rs2280275, and rs11572325 were found to be significantly associated with hypertension risk in the Belgorod population. In conclusion, the rs2280275 and rs11572325 SNPs of CYP2J2 may be considered novel genetic markers of hypertension, at least in Russian women. However, sex-specific associations between CYP2J2 gene polymorphisms and hypertension require further investigation to clarify the specific genetic and/or environmental factors that are responsible for the increased disease susceptibility of women compared to that of men.

A comprehensive contribution of genes for aryl hydrocarbon receptor signaling pathway to hypertension susceptibility.

OBJECTIVE: The present study was designed to investigate whether genetic polymorphisms of the aryl hydrocarbon receptor (AHR) signaling pathway are involved in the molecular basis of essential hypertension (EH). METHODS: A total of 2160 unrelated Russian individuals comprising 1341 EH patients and 819 healthy controls were recruited into the study. Seven common AHR pathway single-nucleotide polymorphisms (SNPs) such as rs2066853, rs2292596, rs2228099, rs1048943, rs762551, rs1056836, and rs1800566 were genotyped by TaqMan-based allele discrimination assays. RESULTS: We found that SNP rs2228099 of ARNT is associated with an increased risk of EH (odds ratio=1.20 95% confidence interval: 1.01-1.44, P=0.043) in a dominant genetic model, whereas polymorphism rs762551 of CYP1A2 showed an association with a decreased risk of disease in a recessive genetic model (odds ratio=0.68, 95% confidence interval: 0.52-0.89, P=0.006). A log-likelihood ratio test enabled identification of epistatic interaction effects on EH susceptibility for all SNPs. MB-MDR analysis showed that cigarette smoking, rs1048943, rs762551, rs1056836, and rs2228099 were significant contributing factors in 19, 18, 13, 13, and 11 interaction models, respectively. The best MDR model associated with EH risk included rs1048943, rs762551, rs1056836, and cigarette smoking (cross-validation consistency 100%, prediction error 45.7%, Ppermutation<0.0001). The mRNA expression and in-silico function prediction analyses have confirmed a regulatory potential for a majority of SNPs associated with EH susceptibility. CONCLUSION: Our pilot study was the first to show that gene-gene and gene-environment interactions in the AHR signaling pathway represent important determinants for the development of EH, and the pathway may become an attractive target for a pharmacological intervention in hypertensive patients in the future.

Altered erythrocyte membrane protein composition mirrors pleiotropic effects of hypertension susceptibility genes and disease pathogenesis.

OBJECTIVE: The study was designed to assess the effects of polymorphisms in genes associated with essential hypertension on the variation of erythrocyte membrane proteins (EMPs) in hypertensive patients. METHODS: Major EMPs content was analyzed in blood from 1162 unrelated Russians (235 hypertensive patients, 176 healthy controls, and 751 random individuals from the Central Russia population). Essential hypertension patients were genotyped for 11 polymorphisms of essential hypertension susceptibility genes including ADD1 (rs4961), GNB3 (rs5443, rs16932941), NOS3 (rs1799983, rs2070744), ACE (rs5186), AGTR1 (rs5186), AGT (rs699, rs4762), MR (rs5534), and TGFB1 (rs1800471). EMP contents and their relationship with the genetic loci were analyzed using various statistical tests. RESULTS: Sex-specific differences in EMP contents between the cases and controls were observed. Regardless of sex, hypertensives exhibited mainly decreased levels of alpha (SPTA1) and beta-spectrin (SPTB) and increased levels of glucose transporter (GLUT1) as compared with healthy subjects (P ≤ 0.001). EMP correlated differently in essential hypertension patients and controls. Almost 70% of the joint variation in the EMP levels is explained by five gender-specific principal components. The essential hypertension susceptibility genes showed considerable effects on the levels of spectrins and glucose transporter. A joint variation of the genes explained about half the total polygenic variance in the GLUT1, SPTA1, and SPTB levels in hypertensives. CONCLUSIONS: The study showed that essential hypertension susceptibility genes are the important factors of the inherited EMP variation, and their pleitropic effects may be mirrored in the altered expression of genes encoding cytoskeletal proteins and those related to intracellular glucose metabolism.

Synergism between the N-acetyltransferase 2 gene and oxidant exposure increases the risk of idiopathic male infertility.

N-acetyltransferase (NAT2) is a phase-II xenobiotic-metabolizing enzyme participating in the detoxification of toxic arylamines, aromatic amines and hydrazines. The present study was designed to investigate whether two common single-nucleotide polymorphisms (SNP) of the NAT2 gene (481C>T, rs1799929; 590G>A, rs1799930) are associated with susceptibility to idiopathic male infertility and to assess if the risk is modified by oxidant and antioxidant exposures. A total 430 DNA samples (203 infertile patients and 227 fertile men) were genotyped for the polymorphisms by PCR and restriction fragment length polymorphism. No association was found between the NAT2 polymorphisms and idiopathic male infertility. However, gene-environment interaction analysis revealed that a low-acetylation genotype, 590GA, was significantly associated with increased disease risk in men who had environmental risk factors such as cigarette smoking (OR 1.71, 95% CI 1.02-2.87, P = 0.042), alcohol abuse (OR 2.14, 95% CI 1.08-4.27, P = 0.029) and low fruit/vegetable intake (OR 1.68, 95% CI 1.01-2.79, P = 0.04). This pilot study found, as far as is known for the first time, that the polymorphism 590G>A of NAT2 is a novel genetic marker for susceptibility to idiopathic male infertility, but the risk is potentiated by exposure to various environmental oxidants.

Antioxidant defense enzyme genes and asthma susceptibility: gender-specific effects and heterogeneity in gene-gene interactions between pathogenetic variants of the disease.

Oxidative stress resulting from an increased amount of reactive oxygen species and an imbalance between oxidants and antioxidants plays an important role in the pathogenesis of asthma. The present study tested the hypothesis that genetic susceptibility to allergic and nonallergic variants of asthma is determined by complex interactions between genes encoding antioxidant defense enzymes (ADE). We carried out a comprehensive analysis of the associations between adult asthma and 46 single nucleotide polymorphisms of 34 ADE genes and 12 other candidate genes of asthma in Russian population using set association analysis and multifactor dimensionality reduction approaches. We found for the first time epistatic interactions between ADE genes underlying asthma susceptibility and the genetic heterogeneity between allergic and nonallergic variants of the disease. We identified GSR (glutathione reductase) and PON2 (paraoxonase 2) as novel candidate genes for asthma susceptibility. We observed gender-specific effects of ADE genes on the risk of asthma. The results of the study demonstrate complexity and diversity of interactions between genes involved in oxidative stress underlying susceptibility to allergic and nonallergic asthma.

The C718T polymorphism in the 3'-untranslated region of glutathione peroxidase-4 gene is a predictor of cerebral stroke in patients with essential hypertension.

In the present study we have investigated the association of three single nucleotide polymorphisms in glutathione peroxidase (GPx) genes GPX1 rs1050450 (P198L), GPX3 rs2070593 (G930A) and GPX4 rs713041 (T718C) with the risk of cerebral stroke (CS) in patients with essential hypertension (EH). A total of 667 unrelated EH patients of Russian origin, including 306 hypertensives (the EH-CS group) who suffered from CS and 361 people (the EH-CS group) who did not have cerebrovascular accidents, were enrolled in the study. The variant allele 718C of the GPX4 gene was found to be significantly associated with an increased risk of CS in hypertensive patients (odds ratio (OR) 1.53, 95% confidence interval (CI) 1.23-1.90, P(adj) = 0.0003). The prevalence of the 718TC and 718CC genotypes of the GPX4 gene was higher in the EH-CS group than the EH-alone group (OR = 2.12, 95%CI 1.42-3.16, P(adj) = 0.0018). The association of the variant GPX4 genotypes with the increased risk of CS in hypertensives remained statistically significant after adjusting for confounding variables such as sex, body mass index (BMI), blood pressure and antihypertensive medication use (OR = 2.18, 95%CI 1.46-3.27, P = 0.0015). Multiple logistic regression analysis did not reveal any interaction between various combinations of GPX1, GPX3 and GPX4 genotypes regarding the risk of CS in patients with EH. The study demonstrated for the first time that the C718T polymorphism in the 3'-untranslated region of the GPX4 gene could be considered as a genetic marker of susceptibility to CS in patients with EH.

Genetic variation of genes for xenobiotic-metabolizing enzymes and risk of bronchial asthma: the importance of gene-gene and gene-environment interactions for disease susceptibility.

The aim of our pilot study was to evaluate the contribution of genes for xenobiotic-metabolizing enzymes (XMEs) for the development of bronchial asthma. We have genotyped 25 polymorphic variants of 18 key XME genes in 429 Russians, including 215 asthmatics and 214 healthy controls by a polymerase chain reaction, followed by restriction fragment length polymorphism analyses. We found for the first time significant associations of CYP1B1 V432L (P=0.045), PON1 Q192R (P=0.039) and UGT1A6 T181A (P=0.025) gene polymorphisms with asthma susceptibility. Significant P-values were evaluated through Monte-Carlo simulations. The multifactor-dimensionality reduction method has obtained the best three-locus model for gene-gene interactions between three loci, EPHX1 Y113H, CYP1B1 V432L and CYP2D6 G1934A, in asthma at a maximum cross-validation consistency of 100% (P=0.05) and a minimum prediction error of 37.8%. We revealed statistically significant gene-environment interactions (XME genotypes-smoking interactions) responsible for asthma susceptibility for seven XME genes. A specific pattern of gametic correlations between alleles of XME genes was found in asthmatics in comparison with healthy individuals. The study results point to the potential relevance of toxicogenomic mechanisms of bronchial asthma in the modern world, and may thereby provide a novel direction in the genetic research of the respiratory disease in the future.

A common polymorphism G-50T in cytochrome P450 2J2 gene is associated with increased risk of essential hypertension in a Russian population.

The present study was designed to test whether common polymorphism G-50T within the promoter of human CYP2J2 gene is associated with increased risk of essential hypertension in a Russian population. We studied 576 unrelated subjects, including 295 patients with hypertension and 281 healthy subjects. Genotyping for polymorphism G-50T of the CYP2J2 gene was performed by polymerase chain reaction and restriction fragment length polymorphism techniques. The frequency of a -50T variant allele of CYP2J2 gene was significantly higher in patients with hypertension versus healthy controls (OR 4.03 95%CI 1.80-9.04 p=0.0004). The association of a -50GT genotype with hypertension remained significant after adjustment for age, gender and family history of hypertension by multivariate logistic regression (OR 4.78 95%CI 1.87-12.27 p=0.001). It has been found that OR for -50GT genotype x gender interaction (OR 4.48 95%CI 1.93-10.39 p=0.00048) was slightly higher than OR for -50GT genotype (OR 4.43 95%CI 1.91-10.29 p=0.00052), suggesting a weak effect of gender on the risk of hypertension in the heterozygous carriers of -50GT genotype. A family history of hypertension has no effect on the association between a -50GT genotype and hypertension. In present study we demonstrate for the first time that a CYP2J2*7 allele of the CYP2J2 gene is clearly associated with an increased risk of essential hypertension. Furthermore, this study highlights the importance of P-450 epoxygenase pathway of arachidonic acid metabolism in the pathogenesis of hypertensive disease.