Two exonic single nucleotide polymorphisms in the microsomal epoxide hydrolase gene are jointly associated with preeclampsia

EPHX1 mutations cause a lipoatrophic diabetes syndrome due to impaired epoxide hydrolysis and increased cellular senescence

Epoxide hydrolases (EHs) regulate cellular homeostasis through hydrolysis of epoxides to less-reactive diols. The first discovered EH was EPHX1, also known as mEH. EH functions remain partly unknown, and no pathogenic variants have been reported in humans. We identified two de novo variants located in EPHX1 catalytic site in patients with a lipoatrophic diabetes characterized by loss of adipose tissue, insulin resistance, and multiple organ dysfunction. Functional analyses revealed that these variants led to the protein aggregation within the endoplasmic reticulum and to a loss of its hydrolysis activity. CRISPR-Cas9-mediated EPHX1 knockout (KO) abolished adipocyte differentiation and decreased insulin response. This KO also promoted oxidative stress and cellular senescence, an observation confirmed in patient-derived fibroblasts. Metreleptin therapy had a beneficial effect in one patient. This translational study highlights the importance of epoxide regulation for adipocyte function and provides new insights into the physiological roles of EHs in humans.

Oxidative stress-related genes (EPHX1 and MnSOD) polymorphism and risk of pre-eclampsia: a meta-analysis

BACKGROUND

Previous studies have detected the association of polymorphisms in oxidative stress-related genes EPHX1 and MnSOD with pre-eclampsia (PE) risk, but the results are inconsistent among studies. Thus, a meta-analysis was performed to obtain more conclusive results.

METHODS

Eligible studies were retrieved in PubMed, Web of Science, EMBASE, Scopus, and CNKI. Odds ratios (ORs) with 95% confidence intervals (CIs) were utilized to evaluate the relationship between EPHX1 rs1051740, EPHX1 rs2234922, MnSOD rs4880 polymorphisms, and PE susceptibility in the genetic models. The subgroup analysis was also performed.

RESULTS

Fourteen studies with a total of 4250 participants were included, including 1784 PE patients and 2466 healthy women. There was a statistically significant association between EPHX1 rs1051740 polymorphism and PE in Caucasians within the allele, dominant, heterozygous, and homozygous models (OR = 0.79, 95% CI = 0.64-0.98; OR = 0.64, 95% CI = 0.47-0.87; OR = 0.61, 95% CI = 0.44-0.85; OR = 0.63, 95% CI = 0.42-0.97, respectively). There was a statistically significant association between EPHX1 rs2234922 polymorphism and PE in Middle Easterners within the recessive and homozygous models (OR = 3.59, 95% CI = 1.25-10.32; OR = 3.99, 95% CI = 1.38-11.49, respectively). There was no statistically significant association between MnSOD rs4880 polymorphism and PE within five genetic models. Subgroup analysis didn't reveal any association between MnSOD rs4880 polymorphism and PE in Asians, Caucasians, or Middle Easterners.

CONCLUSIONS

This meta-analysis shows a significant association between the EPHX1 rs1051740 and PE risk in Caucasians. Meantime, there was a statistically significant association between EPHX1 rs2234922 polymorphism and PE in Middle Easterners.

Regulation of cardiovascular biology by microsomal epoxide hydrolase

Microsomal epoxide hydrolase/epoxide hydrolase 1 (mEH/EPHX1) works in conjunction with cytochromes P450 to metabolize a variety of compounds, including xenobiotics, pharmaceuticals and endogenous lipids. mEH has been most widely studied for its role in metabolism of xenobiotic and pharmaceutical compounds where it converts hydrophobic and reactive epoxides to hydrophilic diols that are more readily excreted. Inhibition or genetic disruption of mEH can be deleterious in the face of many industrial, environmental or pharmaceutical exposures and EPHX1 polymorphisms are associated with the development of exposure-related cancers. The role of mEH in endogenous epoxy-fatty acid (EpFA) metabolism has been less well studied. In vitro, mEH metabolizes most EpFAs at a far slower rate than soluble epoxide hydrolase (sEH) and has thus been generally considered to exert a minor role in EpFA metabolism in vivo. Indeed, sEH inhibitors or sEH-deficiency increase EpFA levels and are protective in animal models of cardiovascular disease. Recently, however, mEH was found to have a previously unrecognized and substantial role in EpFA metabolism in vivo. While few studies have examined the role of mEH in cardiovascular homeostasis, there is now substantial evidence that mEH can regulate cardiovascular function through regulation of EpFA metabolism. The discovery of a prominent role for mEH in epoxyeicosatrienoic acid (EET) metabolism, in particular, suggests that additional studies on the role of mEH in cardiovascular biology are warranted.

Association of Four Missense SNPs with Preeclampsia in Saudi Women

Objective:

The objective of this study was to investigate the association of rs1051740, rs2234922 (in microsomal epoxide hydrolase 1; EPHX1), rs268 (in lipoprotein lipase; LPL) and rs6025 (in Factor V Leiden; F5) genetic variants with the risk of preeclampsia development in Saudi women.

Materials and Methods:

This case–control study recruited 233 Saudi women (94 preeclampsia cases and 139 healthy controls) who visited the Gynecology and Obstetrics Departments of two hospitals in Jeddah, Saudi Arabia, for routine postpregnancy clinical follow-ups. All the women underwent thorough clinical and biochemical investigations conducted according to the standard clinical guidelines. Genotyping of the study participants was done using real-time polymerase chain reaction-based TaqMan allelic discrimination assay. The strength of the association between genetic variants and disease development was assessed using chi-square, odds ratio, 95% confidence interval and multifactor dimensionality reduction tests.

Result:

The minor alleles “G” in rs268 (LPL) and “A” in rs6025 (F5) were absent in Saudi women. The frequencies of rs1051740 and rs2234922 of EPHX1, both in the homozygous and allelic forms, were not significantly different between preeclampsia patients and healthy controls (for all tests, P > 0.05). The multifactor dimensionality reduction analysis also indicated that the interaction between the four studied single-nucleotide polymorphisms (SNPs) had no significant association with preeclampsia risk.

Conclusion:

This study found that none of the studied genetic variants (neither the single SNP nor the SNP–SNP interactions) explain the development of preeclampsia in the Saudi population. These findings not only underscore the disease heterogeneity but also highlight the need to develop population-specific diagnostic genetic biomarkers for preeclampsia.

Non-additive effects of ACVR2A in preeclampsia in a Philippine population

BACKGROUND

Multiple interrelated pathways contribute to the pathogenesis of preeclampsia, and variants in susceptibility genes may play a role among Filipinos, an ethnically distinct group with high prevalence of the disease. The objective of this study was to examine the association between variants in maternal candidate genes and the development of preeclampsia in a Philippine population.

METHODS

A case-control study involving 29 single nucleotide polymorphisms (SNPs) in 21 candidate genes was conducted in 150 patients with preeclampsia (cases) and 175 women with uncomplicated normal pregnancies (controls). Genotyping for the GRK4 and DRD1 gene variants was carried out using the TaqMan Assay, and all other variants were assayed using the Sequenom MassARRAY Iplex Platform. PLINK was used for SNP association testing. Multilocus association analysis was performed using multifactor dimensionality reduction (MDR) analysis.

RESULTS

Among the clinical factors, older age (P <  1 × 10-4), higher BMI (P <  1 × 10-4), having a new partner (P = 0.006), and increased time interval from previous pregnancy (P = 0.018) associated with preeclampsia. The MDR algorithm identified the genetic variant ACVR2A rs1014064 as interacting with age and BMI in association with preeclampsia among Filipino women.

CONCLUSIONS

The MDR algorithm identified an interaction between age, BMI and ACVR2A rs1014064, indicating that context among genetic variants and demographic/clinical factors may be crucial to understanding the pathogenesis of preeclampsia among Filipino women.

Preeclampsia and Related Cardiovascular Risk: Common Genetic Background

PURPOSE OF REVIEW

Preeclampsia (PE) is a hypertensive disorder exclusive for pregnancy. It affects women all over the world and poses a great threat to life, both for mother and child. No definitive treatment exists and placenta delivery comprises the only known cure for PE. One of the most severe complications observed in preeclamptic women is the occurrence of cardiovascular diseases (CVDs) later in life.

RECENT FINDINGS

Both PE and CVDs share some of their pathogenic pathways and gene variations. Thus far, a number of publications have examined those relationships; however, almost all of them focus only on common risk factors. The precise pathomechanism and genetic basis of PE and its associated cardiovascular complications remain unknown. Therefore, the aim of this review is to unify and clarify the current state of knowledge and provide direction for future studies, especially those regarding the genetic aspect.

Beyond detoxification: a role for mouse mEH in the hepatic metabolism of endogenous lipids

Microsomal and soluble epoxide hydrolase (mEH and sEH) fulfill apparently distinct roles: Whereas mEH detoxifies xenobiotics, sEH hydrolyzes fatty acid (FA) signaling molecules and is thus implicated in a variety of physiological functions. These epoxy FAs comprise epoxyeicosatrienoic acids (EETs) and epoxy-octadecenoic acids (EpOMEs), which are formed by CYP epoxygenases from arachidonic acid (AA) and linoleic acid, respectively, and then are hydrolyzed to their respective diols, the so-called DHETs and DiHOMEs. Although EETs and EpOMEs are also substrates for mEH, its role in lipid signaling is considered minor due to lower abundance and activity relative to sEH. Surprisingly, we found that in plasma from mEH KO mice, hydrolysis rates for 8,9-EET and 9,10-EpOME were reduced by 50% compared to WT plasma. This strongly suggests that mEH contributes substantially to the turnover of these FA epoxides—despite kinetic parameters being in favor of sEH. Given the crucial role of liver in controlling plasma diol levels, we next studied the capacity of sEH and mEH KO liver microsomes to synthesize DHETs with varying concentrations of AA (1–30 μM) and NADPH. mEH-generated DHET levels were similar to the ones generated by sEH, when AA concentrations were low (1 μM) or epoxygenase activity was curbed by modulating NADPH. With increasing AA concentrations sEH became more dominant and with 30 μM AA produced twice the level of DHETs compared to mEH. Immunohistochemistry of C57BL/6 liver slices further revealed that mEH expression was more widespread than sEH expression. mEH immunoreactivity was detected in hepatocytes, Kupffer cells, endothelial cells, and bile duct epithelial cells, while sEH immunoreactivity was confined to hepatocytes and bile duct epithelial cells. Finally, transcriptome analysis of WT, mEH KO, and sEH KO liver was carried out to discern transcriptional changes associated with the loss of EH genes along the CYP-epoxygenase–EH axis. We found several prominent dysregulations occurring in a parallel manner in both KO livers: (a) gene expression of Ephx1 (encoding for mEH protein) was increased 1.35-fold in sEH KO, while expression of Ephx2 (encoding for sEH protein) was increased 1.4-fold in mEH KO liver; (b) Cyp2c genes, encoding for the predominant epoxygenases in mouse liver, were mostly dysregulated in the same manner in both sEH and mEH KO mice, showing that loss of either EH has a similar impact. Taken together, mEH appears to play a leading role in the hydrolysis of 8,9-EET and 9,10-EpOME and also contributes to the hydrolysis of other FA epoxides. It probably profits from its high affinity for FA epoxides under non-saturating conditions and its close physical proximity to CYP epoxygenases, and compensates its lower abundance by a more widespread expression, being the only EH present in several sEH-lacking cell types.

The Tyr113His T/C rs1051740 and 'very slow' phenotype of the EPHX1 gene alters miR-26b-5p and miR-1207-5p expression in pregnancy

BACKGROUND

Environmental insults and microsomal epoxide hydrolase 1 (EPHX1) single nucleotide polymorphisms (SNPs), Tyr113His T/C rs1051740 and His139Arg A/G rs2234922, aberrantly alters microRNA (miR) expression and are linked to low birthweights (LBW).

OBJECTIVES

To investigate the interplay between pollution, EPHX1 SNPs and miRs during pregnancy and associated LBW outcomes.

METHODS

South African pregnant women (n=241) were recruited in the MACE birth cohort study in Durban, a city with high levels of industry and traffic related pollutants. EPHX1 SNPs were genotyped using PCR-RFLP and grouped into their respective phenotypes, i.e. normal (N), slow (S), very slow (VS) and fast (F). EPHX1, miR-26b-5p, miR-193b-3p and miR-1207-5p expression were determined using quantitative PCR.

RESULTS

Mothers with the Tyr113His SNP had low iron levels [TT vs. TC+CC: mean difference (MD)=0.67g/dl; p=0.0167], LBW [TT vs. TC+CC: MD=189.30g; p=0.0067], and low EPHX1 expression; p<0.0001. miR-26b-5p and miR-1207-5p expression were significantly higher in the CC genotypes compared to TT+TC groups; p<0.0001. The opposite trend occurred for miR-193b-3p; p=0.0045. Mothers with the VS phenotype had low iron levels [N vs. VS and VS vs. F: MD=2.03 and -1.96g/dl; p=0.0021, respectively], decreased gestational age [VS vs. F: MD=-2.14weeks; p=0.0051, respectively], and LBW [N vs. VS, VS vs. F and S vs. VS: MD=1000, -940.30 and 968.80g; p<0.0001, respectively]; F phenotype had the highest EPHX1 expression [N vs. F, VS vs. F and S vs. F: MD=-1.067, -1.854 and -1.379; p=0.0002, respectively]; and N phenotype had low miR-26b-5p [N vs. VS: MD=-0.6100; p=0.0159] and miR-1207-5p [N vs. VS and VS vs. F: MD=-0.834 and 1.103; p=0.0007, respectively] expression. miR-193b-3p expression between phenotypes remained unchanged.

CONCLUSION

The Tyr113His T/C variant of rs1051740 and VS phenotype alters EPHX1, miR-26b-5p and miR-1207-5p expression, and contributes towards low blood iron levels and LBW.

Low-Activity Haplotype of the Microsomal Epoxide Hydrolase Gene Is Protective Against Placental Abruption

OBJECTIVE

We wanted to determine whether genetic variability in the gene encoding microsomal epoxide hydrolase (EPHX) contributes to individual differences in susceptibility to the occurrence of placental abruption.

METHODS

The study involved 117 women with placental abruption and 115 healthy control pregnant women who were genotyped for two single nucleotide polymorphisms (SNPs), T-->C (Tyr113His) in exon 3 and A-->G (His139Arg) in exon 4, in the EPHX gene. Chi-square analysis was used to assess genotype and allele frequency differences between the women with placental abruption and the control group. In addition, single-point analysis was expanded to pair of loci haplotype analysis to examine the estimated haplotype frequencies of the two SNPs, of unknown phase, among the women with placental abruption and the control group. Estimated haplotype frequencies were assessed using the maximum-likelihood method, employing an expectation-maximization algorithm.

RESULTS

Single-point allele and genotype distributions in exons 3 and 4 of the EPHX gene were not statistically different between the groups. However, in the haplotype estimation analysis we observed a significantly decreased frequency of haplotype C-A (His113-His139) among the placental abruption group compared with the control group (P = .007). The odds ratio for placental abruption associated with the low-activity haplotype C-A (His113-His139) was 0.552 (95% confidence interval, 0.358 to 0.851).

CONCLUSIONS

The use of two intragenic SNPs jointly in haplotype analysis of association demonstrated that the genetically determined low-activity haplotype C-A (His113-His139) was significantly less frequent in women with placental abruption.

Microsomal epoxide hydrolase 1 (EPHX1): Gene, structure, function, and role in human disease

Microsomal epoxide hydrolase (EPHX1) is an evolutionarily highly conserved biotransformation enzyme for converting epoxides to diols. Notably, the enzyme is able to either detoxify or bioactivate a wide range of substrates. Mutations and polymorphic variants in the EPHX1 gene have been associated with susceptibility to several human diseases including cancer. This review summarizes the key knowledge concerning EPHX1 gene and protein structure, expression pattern and regulation, and substrate specificity. The relevance of EPHX1 for human pathology is especially discussed.

The role of epoxide hydrolases in health and disease

Epoxide hydrolases (EH) are ubiquitously expressed in all living organisms and in almost all organs and tissues. They are mainly subdivided into microsomal and soluble EH and catalyze the hydration of epoxides, three-membered-cyclic ethers, to their corresponding dihydrodiols. Owning to the high chemical reactivity of xenobiotic epoxides, microsomal EH is considered protective enzyme against mutagenic and carcinogenic initiation. Nevertheless, several endogenously produced epoxides of fatty acids function as important regulatory mediators. By mediating the formation of cytotoxic dihydrodiol fatty acids on the expense of cytoprotective epoxides of fatty acids, soluble EH is considered to have cytotoxic activity. Indeed, the attenuation of microsomal EH, achieved by chemical inhibitors or preexists due to specific genetic polymorphisms, is linked to the aggravation of the toxicity of xenobiotics, as well as the risk of cancer and inflammatory diseases, whereas soluble EH inhibition has been emerged as a promising intervention against several diseases, most importantly cardiovascular, lung and metabolic diseases. However, there is reportedly a significant overlap in substrate selectivity between microsomal and soluble EH. In addition, microsomal and soluble EH were found to have the same catalytic triad and identical molecular mechanism. Consequently, the physiological functions of microsomal and soluble EH are also overlapped. Thus, studying the biological effects of microsomal or soluble EH alterations needs to include the effects on both the metabolism of reactive metabolites, as well as epoxides of fatty acids. This review focuses on the multifaceted role of EH in the metabolism of xenobiotic and endogenous epoxides and the impact of EH modulations.

eNOSI4 and EPHX1 polymorphisms affect maternal susceptibility to preeclampsia: analysis of five polymorphisms predisposing to cardiovascular disease in 279 Caucasian and 241 African women

PURPOSE

The aim of this study was to evaluate possible associations of genetic polymorphisms predisposing to cardiovascular disease with the development and/or the severity of preeclampsia.

METHODS

A two hospital-based prospective case-control study was performed in Germany and Ghana. 470 blood samples of 250 Caucasian and 220 black African have been genotyped by pyrosequencing and fragment length analysis. We evaluated the distribution of the epoxide hydrolase 1 (EPHX1) polymorphism on exon 3, the endothelial nitric oxide synthase (eNOS) polymorphisms on exon 7 and on intron 4, the angiotensinogen polymorphism on exon 2 and the estrogen receptor 1 polymorphism in intron 1.

RESULTS

74 Caucasian and 84 African were classified as preeclampsia with 27 Caucasian developing a hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome and 17 African women experiencing eclampsia. Multivariate logistic regression analysis adjusting for ethnicity, age and parity revealed for carriers of eNOSI4 VNTR4a a 1.7-fold increased (95% CI 1.10-2.711, p = 0.016) risk to develop preeclampsia and a 3.6-fold increase for carriers of the EPHX1 113Tyr (95% CI 1.366-8.750, p = 0.009) to develop severest preeclampsia.

CONCLUSION

Our finding of eNOSI4 polymorphism predisposing to preeclampsia independently of ethnicity, age and parity supports the concept of NO being involved in the endothelial disorder preeclampsia. Since EPHX1 is highly expressed in the liver, can interact with various signaling pathways and is involved in central nervous system disorders, the association of EPHX1 polymorphism with the HELLP syndrome and eclampsia may hint to EPHX being a further key player in the pathogenesis of preeclampsia.

The role of genetics in pre-eclampsia and potential pharmacogenomic interventions

The pregnancy-specific condition pre-eclampsia not only affects the health of mother and baby during pregnancy but also has long-term consequences, increasing the chances of cardiovascular disease in later life. It is accepted that pre-eclampsia has a placental origin, but the pathogenic mechanisms leading to the systemic endothelial dysfunction characteristic of the disorder remain to be determined. In this review we discuss some key factors regarded as important in the development of pre-eclampsia, including immune maladaptation, inadequate placentation, oxidative stress, and thrombosis. Genetic factors influence all of these proposed pathophysiological mechanisms. The inherited nature of pre-eclampsia has been known for many years, and extensive genetic studies have been undertaken in this area. Genetic research offers an attractive strategy for studying the pathogenesis of pre-eclampsia as it avoids the ethical and practical difficulties of conducting basic science research during the preclinical phase of pre-eclampsia when the underlying pathological changes occur. Although pharmacogenomic studies have not yet been conducted in pre-eclampsia, a number of studies investigating treatment for essential hypertension are of relevance to therapies used in pre-eclampsia. The pharmacogenomics of antiplatelet agents, alpha and beta blockers, calcium channel blockers, and magnesium sulfate are discussed in relation to the treatment and prevention of pre-eclampsia. Pharmacogenomics offers the prospect of individualized patient treatment, ensuring swift introduction of optimal treatment whilst minimizing the use of inappropriate or ineffective drugs, thereby reducing the risk of harmful effects to both mother and baby.

Development of fluorescent substrates for microsomal epoxide hydrolase and application to inhibition studies

The microsomal epoxide hydrolase (mEH) plays a significant role in the metabolism of numerous xenobiotics. In addition, it has a potential role in sexual development and bile acid transport, and it is associated with a number of diseases such as emphysema, spontaneous abortion, eclampsia, and several forms of cancer. Toward developing chemical tools to study the biological role of mEH, we designed and synthesized a series of absorbent and fluorescent substrates. The highest activity for both rat and human mEH was obtained with the fluorescent substrate cyano(6-methoxy-naphthalen-2-yl)methyl glycidyl carbonate (11). An in vitro inhibition assay using this substrate ranked a series of known inhibitors similarly to the assay that used radioactive cis-stilbene oxide but with a greater discrimination between inhibitors. These results demonstrate that the new fluorescence-based assay is a useful tool for the discovery of structure-activity relationships among mEH inhibitors. Furthermore, this substrate could also be used for the screening chemical library with high accuracy and with a Z' value of approximately 0.7. This new assay permits a significant decrease in labor and cost and also offers the advantage of a continuous readout. However, it should not be used with crude enzyme preparations due to interfering reactions.

The genetics of pre-eclampsia and other hypertensive disorders of pregnancy

Hypertension is the most frequent medical complication occurring during pregnancy. In this chapter, we aim to address the genetic contribution to these disorders, with specific focus on pre-eclampsia. The pathogenic mechanisms underlying pre-eclampsia remain to be elucidated; however, immune maladaptation, inadequate placental development and trophoblast invasion, placental ischaemia, oxidative stress and thrombosis are all thought to represent key factors in the development of disease. Furthermore, all of these components have genetic factors that may be involved in the pathogenic changes occurring. The familial nature of pre-eclampsia has been known for many years and, as such, extensive genetic research has been carried out in this area using strategies that include candidate gene studies and linkage analysis. Interactions between fetal and maternal genotypes, the effect of environmental factors, and epistasis will also be considered.

CDKN1C mutations in HELLP/preeclamptic mothers of Beckwith-Wiedemann Syndrome (BWS) patients

Preeclampsia is the development of new-onset hypertension with proteinuria after 20 weeks of gestation. HELLP syndrome (haemolysis, elevated liver enzymes, and low platelet count) is a severe form of preeclampsia with high rates of neonatal and maternal morbidity. In recent years, loss of function of cdkn1c (a tight-binding inhibitor of G1 cyclin/cyclin-dependent kinase complexes and a negative regulator of cell proliferation) has been observed in several mouse models of preeclampsia. In this paper, we report on three women with HELLP/preeclampsia who had children with Beckwith Wiedemann syndrome, a complex genetic disorder characterised, among other findings, by overgrowth, omphalocele and macroglossia. All three children displayed mutations in CDKN1C predicted to generate truncated proteins. Two of the mutations were maternally inherited while the third was de novo. This finding suggests a fetal contribution to the maternal disease. To the best of our knowledge this is the first report of CDKN1C mutations in children born to women with preeclampsia/HELLP syndrome, thus suggesting the involvement of an imprinted gene in the pathophysiology of preeclampsia.

Genes and the preeclampsia syndrome

Preeclampsia is specific to pregnancy and is still a leading cause of maternal and perinatal mortality and morbidity, affecting about 3% of women, but the underlying pathogenetic mechanisms still remain unclear. Immune maladaptation, placental ischemia and increased oxidative stress represent the main components discussed to be of etiologic importance, and they all may have genetic implications. Since the familial nature of preeclampsia is known for many years, extensive research on the genetic contribution to the pathogenesis of this severe pregnancy disorder has been performed. In this review, we will overview the linkage and candidate gene studies carried out so far as well as summarize important historical notes on the genetic hypotheses generated in preeclampsia research. Moreover, the influence of maternal and fetal genes and their interaction as well as the role of genomic imprinting in preeclampsia will be discussed.

Association of microsomal epoxide hydrolase gene polymorphism and pre-eclampsia in Turkish women

AIM

To assess the association between human epoxide hydrolase exon 3 and 4 polymorphisms and pre-eclampsia by carrying out a case-control study in Turkish women.

METHODS

DNA was extracted from peripheral blood leukocytes, and genotype distribution of exon 3 and exon 4 of epoxide hydrolase gene (EPHX) was carried out in 271 patients and 155 controls.

RESULTS

There was no statistically significant difference in the distribution of genotypes between pre-eclampsia without HELLP and pre-eclampsia plus HELLP cases and controls for the exon 3 and 4 polymorphism of EPHX. However, we found a significant association between the predicted enzyme activity level and pre-eclampsia (P = 0.018). The distribution of subjects with predicted high, intermediate and low microsomal epoxide hydrolase enzyme (EPHX) activity were 23.2, 38.8 and 38% in cases and 12, 47.3 and 40.7% in controls, respectively.

CONCLUSION

Although we could not find any association between genetic variability in exon 3 and 4 of EPHX and pre-eclampsia, genetic variability in these two exons jointly modifies the predicted enzyme activity and may be a risk factor for pre-eclampsia.

Candidate-gene association study of mothers with pre-eclampsia, and their infants, analyzing 775 SNPs in 190 genes

Pre-eclampsia (PE) affects 5-7% of pregnancies in the US, and is a leading cause of maternal death and perinatal morbidity and mortality worldwide. To identify genes with a role in PE, we conducted a large-scale association study evaluating 775 SNPs in 190 candidate genes selected for a potential role in obstetrical complications. SNP discovery was performed by DNA sequencing, and genotyping was carried out in a high-throughput facility using the MassARRAY(TM) System. Women with PE (n = 394) and their offspring (n = 324) were compared with control women (n = 602) and their offspring (n = 631) from the same hospital-based population. Haplotypes were estimated for each gene using the EM algorithm, and empirical p values were obtained for a logistic regression-based score test, adjusted for significant covariates. An interaction model between maternal and offspring genotypes was also evaluated. The most significant findings for association with PE were COL1A1 (p = 0.0011) and IL1A (p = 0.0014) for the maternal genotype, and PLAUR (p = 0.0008) for the offspring genotype. Common candidate genes for PE, including MTHFR and NOS3, were not significantly associated with PE. For the interaction model, SNPs within IGF1 (p = 0.0035) and IL4R (p = 0.0036) gave the most significant results. This study is one of the most comprehensive genetic association studies of PE to date, including an evaluation of offspring genotypes that have rarely been considered in previous studies. Although we did not identify statistically significant evidence of association for any of the candidate loci evaluated here after adjusting for multiple testing using the false discovery rate, additional compelling evidence exists, including multiple SNPs with nominally significant p values in COL1A1 and the IL1A region, and previous reports of association for IL1A, to support continued interest in these genes as candidates for PE. Identification of the genetic regulators of PE may have broader implications, since women with PE are at increased risk of death from cardiovascular diseases later in life.

EPHX1 polymorphisms and the risk of lung cancer: a HuGE review

BACKGROUND

Microsomal epoxide hydrolase 1 (EPHX1) plays an important role in both the activation and detoxification of tobacco-derived carcinogens. Polymorphisms at exons 3 and 4 of the EPHX1 gene have been reported to be associated with variations in EPHX1 activity. The aim of this study is to review and summarize the available molecular epidemiologic studies of lung cancer and EPHX1.

METHODS

We searched MEDLINE, Current Contents, and Web of Science databases for studies published before August 2004. We conducted a systematic review and meta-analysis of 13 case-control studies. Summary odds ratios and summary prevalence of the variant allele (genotype) of both polymorphisms in the EPHX1 gene were calculated using the DerSimonian and Laird method.

RESULTS

The low-activity (variant) genotype of EPHX1 polymorphism at exon 3 was associated with decreased risk of lung cancer (odds ratio = 0.65; 95% confidence interval = 0.44-0.96) in lung cancer risk among whites. In white populations, the high-activity (variant) genotype of EPHX1 polymorphism at exon 4 was associated with a modest increase in risk of lung cancer (1.22; 0.79-1.90) and the predicted low activity was associated with a modest decrease in risk (0.72; 0.43-1.22).

CONCLUSIONS

EPHX1 enzyme may act as a phase I enzyme in lung carcinogenesis. The low-activity genotype of EPHX1 gene is associated with decreased risk of lung cancer among whites.

Maternal and fetal single nucleotide polymorphisms in the epoxide hydrolase and gluthatione S-transferase P1 genes are not associated with pre-eclampsia in the Coloured population of the Western Cape, South Africa

Oxidative stress is thought to play an important role in the pathophysiology of pre-eclampsia. A defect in certain enzymes responsible for detoxification may cause prolonged exposure to reactive by-products and contribute to maternal endothelial as well as placental damage. Two polymorphisms affecting the function of the biotransformation enzymes epoxide hydrolase and glutathione S-transferase P1 were shown previously to be associated with pre-eclampsia in a Dutch population. The aim of this study was to determine if these two polymorphisms (maternal or fetal) contribute to pre-eclampsia in an anthropologically distinct population (the Western Cape region of South Africa) with a high incidence of the disease. Genomic DNA of mother - infant pairs with severe pre-eclampsia (n = 144), a population control group (n = 156) and control mother - infant pairs with uncomplicated pregnancy outcome (n = 45) were analysed for the EPHX and GSTP1 polymorphisms by polymerase chain reaction amplification and restriction enzyme digestion. Each polymorphism had a similar distribution in case and control subjects (mother and infant). The Val105/Val105 genotype of GSTP1 occurred at a higher frequency than reported for other populations. Neither maternal nor fetal EPHX Tyr113His and GSTP1 Ile105Val polymorphisms appear to contribute significantly to the pathophysiology of pre-eclampsia in the Coloured population of the Western Cape region of South Africa.

Epoxide hydrolases: mechanisms, inhibitor designs, and biological roles

Organisms are exposed to epoxide-containing compounds from both exogenous and endogenous sources. In mammals, the hydration of these compounds by various epoxide hydrolases (EHs) can not only regulate their genotoxicity but also, for lipid-derived epoxides, their endogenous roles as chemical mediators. Recent findings suggest that the EHs as a family represent novel drug discovery targets for regulation of blood pressure, inflammation, cancer progression, and the onset of several other diseases. Knowledge of the EH mechanism provides a solid foundation for the rational design of inhibitors, and this review summarizes the current understanding of the catalytic mechanism of the EHs. Although the overall EH mechanism is now known, the molecular basis of substrate selectivity, possible allosteric regulation, and many fine details of the catalytic mechanism remain to be solved. Finally, recent development in the design of EH inhibitors and the EH biological role are discussed.

Epoxide hydrolases: their roles and interactions with lipid metabolism

The epoxide hydrolases (EHs) are enzymes present in all living organisms, which transform epoxide containing lipids by the addition of water. In plants and animals, many of these lipid substrates have potent biologically activities, such as host defenses, control of development, regulation of inflammation and blood pressure. Thus the EHs have important and diverse biological roles with profound effects on the physiological state of the host organisms. Currently, seven distinct epoxide hydrolase sub-types are recognized in higher organisms. These include the plant soluble EHs, the mammalian soluble epoxide hydrolase, the hepoxilin hydrolase, leukotriene A4 hydrolase, the microsomal epoxide hydrolase, and the insect juvenile hormone epoxide hydrolase. While our understanding of these enzymes has progressed at different rates, here we discuss the current state of knowledge for each of these enzymes, along with a distillation of our current understanding of their endogenous roles. By reviewing the entire enzyme class together, both commonalities and discrepancies in our understanding are highlighted and important directions for future research pertaining to these enzymes are indicated.