Homozygosity for the EPHX2 K55R polymorphism increases the long-term risk of ischemic stroke in men: a study in Swedes

Overexpression of soluble epoxide hydrolase reduces post-ischemic recovery of cardiac contractile function

Cytochromes P450 can metabolize endogenous fatty acids, such as arachidonic acid, to bioactive lipids such as epoxyeicosatrienoic acids (EETs) that have beneficial effects. EETs protect hearts against ischemic damage, heart failure or fibrosis; however, their effects are limited by hydrolysis to less active dihydroxy oxylipins by soluble epoxide hydrolase (sEH), encoded by the epoxide hydrolase 2 gene (EPHX2, EC 3.3.2.10). Pharmacological inhibition or genetic disruption of sEH/EPHX2 have been widely studied for their impact on cardiovascular diseases. Less well studied is the role of increased EPHX2 expression, which occurs in a substantial human population that carries the EPHX2 K55R polymorphism or after induction by inflammatory stimuli. Herein, we developed a mouse model with cardiomyocyte-selective expression of human EPHX2 (Myh6-EPHX2) that has significantly increased total EPHX2 expression and activity. Myh6-EPHX2 hearts exhibit strong, cardiomyocyte-selective expression of EPHX2. EPHX2 mRNA, protein, and epoxide hydrolysis measurements suggest that Myh6-EPHX2 hearts have 12-fold increase in epoxide hydrolase activity relative to wild type (WT) hearts. This increased activity significantly decreased epoxide:diol ratios in vivo. Isolated, perfused Myh6-EPHX2 hearts were not significantly different from WT hearts in basal parameters of cardiac function; however, compared to WT hearts, Myh6-EPHX2 hearts demonstrated reduced recovery of heart contractile function after ischemia and reperfusion (I/R). This impaired recovery after I/R correlated with reduced activation of PI3K/AKT and GSK3β signaling pathways in Myh6-EPHX2 hearts compared to WT hearts. In summary, the Myh6-EPHX2 mouse line represents a novel model of cardiomyocyte-selective overexpression of EPHX2 that has detrimental effects on cardiac function.

CYP metabolic pathway related gene polymorphism increases the risk of embolic and atherothrombotic stroke and vulnerable carotid plaque in southeast China

OBJECTIVE

To investigate the association of CYP metabolic pathway-related genetic polymorphisms with the susceptibility to ischemic stroke and stability of carotid plaque in southeast China.

METHODS

We consecutively enrolled 294 acute ischemic stroke patients with carotid plaque and 282 controls from Wenling First People's Hospital. The patients were divided into the carotid vulnerable plaque group and stable plaque group according to the results of carotid B-mode ultrasonography. Polymorphisms of CYP3A5 (G6986A, rs776746), CYP2C9*2 (C430T, rs1799853), CYP2C9*3 (A1075C, rs1057910), and EPHX2 (G860A, rs751141) were determined using polymerase chain reaction and mass spectrometry analysis.

RESULTS

EPHX2 GG may reduce the susceptibility to ischemic stroke (OR = 0.520, 95% CI: 0.288 ∼ 0.940, P = 0.030) and AA+AG may increase the risk for ischemic stroke (OR = 1.748, 95% CI: 1.001 ∼ 3.052, P = 0.050). The distribution of CYP3A5 genotypes showed significant differences between the vulnerable plaque and stable plaque groups (P = 0.026). Multivariate logistic regression analysis found that CYP3A5 GG could reduce the risk of vulnerable plaques (OR = 0.405, 95% CI: 0.178 ∼ 0.920, P = 0.031).

CONCLUSION

EPHX2 G860A polymorphism may reduce the stroke susceptibility, while other SNPs of CYP genes are not associated with ischemic stroke in southeast China. Furthermore CYP3A5 polymorphism was related with carotid plaque instability.

SERPINE1 mRNA Binding Protein 1 Is Associated with Ischemic Stroke Risk: A Comprehensive Molecular-Genetic and Bioinformatics Analysis of SERBP1 SNPs

The SERBP1 gene is a well-known regulator of SERPINE1 mRNA stability and progesterone signaling. However, the chaperone-like properties of SERBP1 have recently been discovered. The present pilot study investigated whether SERBP1 SNPs are associated with the risk and clinical manifestations of ischemic stroke (IS). DNA samples from 2060 unrelated Russian subjects (869 IS patients and 1191 healthy controls) were genotyped for 5 common SNPs-rs4655707, rs1058074, rs12561767, rs12566098, and rs6702742 SERBP1-using probe-based PCR. The association of SNP rs12566098 with an increased risk of IS (risk allele C; p = 0.001) was observed regardless of gender or physical activity level and was modified by smoking, fruit and vegetable intake, and body mass index. SNP rs1058074 (risk allele C) was associated with an increased risk of IS exclusively in women (p = 0.02), non-smokers (p = 0.003), patients with low physical activity (p = 0.04), patients with low fruit and vegetable consumption (p = 0.04), and BMI ≥25 (p = 0.007). SNPs rs1058074 (p = 0.04), rs12561767 (p = 0.01), rs12566098 (p = 0.02), rs6702742 (p = 0.036), and rs4655707 (p = 0.04) were associated with shortening of activated partial thromboplastin time. Thus, SERBP1 SNPs represent novel genetic markers of IS. Further studies are required to confirm the relationship between SERBP1 polymorphism and IS risk.

Crosstalk between adenosine receptors and CYP450-derived oxylipins in the modulation of cardiovascular, including coronary reactive hyperemic response

Adenosine is a ubiquitous endogenous nucleoside or autacoid that affects the cardiovascular system through the activation of four G-protein coupled receptors: adenosine A₁ receptor (A₁AR), adenosine A_2A receptor (A_2AAR), adenosine A_2B receptor (A_2BAR), and adenosine A₃ receptor (A₃AR). With the rapid generation of this nucleoside from cellular metabolism and the widespread distribution of its four G-protein coupled receptors in almost all organs and tissues of the body, this autacoid induces multiple physiological as well as pathological effects, not only regulating the cardiovascular system but also the central nervous system, peripheral vascular system, and immune system. Mounting evidence shows the role of CYP450-enzymes in cardiovascular physiology and pathology, and the genetic polymorphisms in CYP450s can increase susceptibility to cardiovascular diseases (CVDs). One of the most important physiological roles of CYP450-epoxygenases (CYP450-2C & CYP2J2) is the metabolism of arachidonic acid (AA) and linoleic acid (LA) into epoxyeicosatrienoic acids (EETs) and epoxyoctadecaenoic acid (EpOMEs) which generally involve in vasodilation. Like an increase in coronary reactive hyperemia (CRH), an increase in anti-inflammation, and cardioprotective effects. Moreover, the genetic polymorphisms in CYP450-epoxygenases will change the beneficial cardiovascular effects of metabolites or oxylipins into detrimental effects. The soluble epoxide hydrolase (sEH) is another crucial enzyme ubiquitously expressed in all living organisms and almost all organs and tissues. However, in contrast to CYP450-epoxygenases, sEH converts EETs into dihydroxyeicosatrienoic acid (DHETs), EpOMEs into dihydroxyoctadecaenoic acid (DiHOMEs), and others and reverses the beneficial effects of epoxy-fatty acids leading to vasoconstriction, reducing CRH, increase in pro-inflammation, increase in pro-thrombotic and become less cardioprotective. Therefore, polymorphisms in the sEH gene (Ephx2) cause the enzyme to become overactive, making it more vulnerable to CVDs, including hypertension. Besides the sEH, ω-hydroxylases (CYP450-4A11 & CYP450-4F2) derived metabolites from AA, ω terminal-hydroxyeicosatetraenoic acids (19-, 20-HETE), lipoxygenase-derived mid-chain hydroxyeicosatetraenoic acids (5-, 11-, 12-, 15-HETEs), and the cyclooxygenase-derived prostanoids (prostaglandins: PGD₂, PGF_2α; thromboxane: Txs, oxylipins) are involved in vasoconstriction, hypertension, reduction in CRH, pro-inflammation and cardiac toxicity. Interestingly, the interactions of adenosine receptors (A_2AAR, A₁AR) with CYP450-epoxygenases, ω-hydroxylases, sEH, and their derived metabolites or oxygenated polyunsaturated fatty acids (PUFAs or oxylipins) is shown in the regulation of the cardiovascular functions. In addition, much evidence demonstrates polymorphisms in CYP450-epoxygenases, ω-hydroxylases, and sEH genes (Ephx2) and adenosine receptor genes (ADORA1 & ADORA2) in the human population with the susceptibility to CVDs, including hypertension. CVDs are the number one cause of death globally, coronary artery disease (CAD) was the leading cause of death in the US in 2019, and hypertension is one of the most potent causes of CVDs. This review summarizes the articles related to the crosstalk between adenosine receptors and CYP450-derived oxylipins in vascular, including the CRH response in regular salt-diet fed and high salt-diet fed mice with the correlation of heart perfusate/plasma oxylipins. By using A_2AAR^-/-, A₁AR^-/-, eNOS^-/-, sEH^-/- or Ephx2^-/-, vascular sEH-overexpressed (Tie2-sEH Tr), vascular CYP2J2-overexpressed (Tie2-CYP2J2 Tr), and wild-type (WT) mice. This review article also summarizes the role of pro-and anti-inflammatory oxylipins in cardiovascular function/dysfunction in mice and humans. Therefore, more studies are needed better to understand the crosstalk between the adenosine receptors and eicosanoids to develop diagnostic and therapeutic tools by using plasma oxylipins profiles in CVDs, including hypertensive cases in the future.

Plasma epoxyeicosatrienoic acids and diabetes-related cardiovascular disease: The cardiovascular health study

Background

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid that may impact atherosclerosis, and animal experimental studies suggest EETs protect cardiac function. Plasma EETs are mostly esterified to phospholipids and part of an active pool. To address the limited information about EETs and CVD in humans, we conducted a prospective study of total plasma EETs (free + esterified) and diabetes-related CVD in the Cardiovascular Health Study (CHS).

Methods

We measured 4 EET species and their metabolites, dihydroxyepoxyeicosatrienoic acids (DHETs), in plasma samples from 892 CHS participants with type 2 diabetes. We determined the association of EETs and DHETs with incident myocardial infarction (MI) and ischemic stroke using Cox regression.

Findings

During follow-up (median 7.5 years), we identified 150 MI and 134 ischemic strokes. In primary, multivariable analyses, elevated levels of each EET species were associated with non-significant lower risk of incident MI (for example, hazard ratio for 1 SD higher 14,15-EET: 0.86, 95% CI: 0.72–1.02; p=0.08). The EETs-MI associations became significant in analyses further adjusted for DHETs (hazard ratio for 1 SD higher 14,15-EET adjusted for 14,15-DHET: 0.76, 95% CI: 0.63–0.91; p=0.004). Elevated EET levels were associated with higher risk of ischemic stroke in primary but not secondary analyses. Three DHET species were associated with higher risk of ischemic stroke in all analyses.

Interpretation

Findings from this prospective study complement the extensive studies in animal models showing EETs protect cardiac function and provide new information in humans. Replication is needed to confirm the associations.

Funding

US National Institutes of Health.

CRISPR/Cas9-mediated inactivation of the phosphatase activity of soluble epoxide hydrolase prevents obesity and cardiac ischemic injury

INTRODUCTION

Although the physiological role of the C-terminal hydrolase domain of the soluble epoxide hydrolase (sEH-H) is well investigated, the function of its N-terminal phosphatase activity (sEH-P) remains unknown.

OBJECTIVES

This study aimed to assess in vivo the physiological role of sEH-P.

METHODS

CRISPR/Cas9 was used to generate a novel knock-in (KI) rat line lacking the sEH-P activity.

RESULTS

The sEH-P KI rats has a decreased metabolism of lysophosphatidic acids to monoacyglycerols. KI rats grew almost normally but with less weight and fat mass gain while insulin sensitivity was increased compared to wild-type rats. This lean phenotype was more marked in males than in female KI rats and mainly due to decreased food consumption and enhanced energy expenditure. In fact, sEH-P KI rats had an increased lipolysis allowing to supply fatty acids as fuel to potentiate brown adipose thermogenesis under resting condition and upon cold exposure. The potentiation of thermogenesis was abolished when blocking PPARγ, a nuclear receptor activated by intracellular lysophosphatidic acids, but also when inhibiting simultaneously sEH-H, showing a functional interaction between the two domains. Furthermore, sEH-P KI rats fed a high-fat diet did not gain as much weight as the wild-type rats, did not have increased fat mass and did not develop insulin resistance or hepatic steatosis. In addition, sEH-P KI rats exhibited enhanced basal cardiac mitochondrial activity associated with an enhanced left ventricular contractility and were protected against cardiac ischemia-reperfusion injury.

CONCLUSION

Our study reveals that sEH-P is a key player in energy and fat metabolism and contributes together with sEH-H to the regulation of cardiometabolic homeostasis. The development of pharmacological inhibitors of sEH-P appears of crucial importance to evaluate the interest of this promising therapeutic strategy in the management of obesity and cardiac ischemic complications.

No impact of soluble epoxide hydrolase rs4149243, rs2234914 and rs751142 genetic variants on the development of type II diabetes and its hypertensive complication among Jordanian patients

BACKGROUND

Human soluble epoxide hydrolase plays a major role in cardiovascular homoeostasis. Genetic variants in the EPHX2 gene among different ethnic groups are associated with cardiovascular complications, such as hypertension. However, no reports regarding the association of EPHX2 genotype with hypertension among type II diabetic (T2D) patients of Middle Eastern Jordanian origin exist.

OBJECTIVE

The current study aimed to elucidate the association of the EPHX2 allele, genotype and haplotype with T2D, hypertension and parameters of lipid profile parameters among Jordanian T2D patients.

METHODS

Ninety-three genomic DNA samples of non-diabetic controls and 97 samples from T2D patients were genotyped for EPHX2 rs4149243, rs2234914 and rs751142 genetic variants. The DNA samples were amplified using polymerase chain reaction (PCR) and then sequenced using Applied Biosystems Model (ABI3730x1). The functionality of intronic EPHX2 variants was predicted using the in silico Berkely Drosophila Genome Project software.

RESULTS

We found no significant (P >.05) association between the EPHX2 rs4149243, rs2234914 and rs751142 allele, genotype and haplotype and the incidence of T2D and hypertension. Additionally, no association (P >.05) between these EPHX2 genetic variants with the baseline total cholesterol, low- and high-density lipoproteins and triglycerides among both non-diabetic and diabetic volunteers was found. However, we found an inter-ethnic variation (χ² -test, P value ˂ .05) in the allele frequency of the EPHX2 rs4149243 and rs2234914 variants between Jordanians and other ethnic populations. Also, the in silico Berkely Drosophila Genome Project software predicted that the intronic EPHX2 rs4149243 could alter the splicing of intron 7.

CONCLUSIONS

It can be concluded from this study that EPHX2 rs4149243, rs2234914 and rs751142 genetic variants do not play a role in the development of T2D and hypertension among Jordanian T2D patients. Further genetic studies with larger sample sizes are needed to find out the association of other functional EPHX2 variants with cardiovascular diseases among T2D patients in Jordan.

Age and Sex Differences in Hearts of Soluble Epoxide Hydrolase Null Mice

Biological aging is an inevitable part of life that has intrigued individuals for millennia. The progressive decline in biological systems impacts cardiac function and increases vulnerability to stress contributing to morbidity and mortality in aged individuals. Yet, our understanding of the molecular, biochemical and physiological mechanisms of aging as well as sex differences is limited. There is growing evidence indicating CYP450 epoxygenase-mediated metabolites of n-3 and n-6 polyunsaturated fatty acids (PUFAs) are active lipid mediators regulating cardiac homeostasis. These epoxy metabolites are rapidly hydrolyzed and inactivated by the soluble epoxide hydrolase (sEH). The current study characterized cardiac function in young and aged sEH null mice compared to the corresponding wild-type (WT) mice. All aged mice had significantly increased cardiac hypertrophy, except in aged female sEH null mice. Cardiac function as assessed by echocardiography demonstrated a marked decline in aged WT mice, notably significant decreases in ejection fraction and fractional shortening in both sexes. Interestingly, aged female sEH null mice had preserved systolic function, while aged male sEH null mice had preserved diastolic function compared to aged WT mice. Assessment of cardiac mitochondria demonstrated an increased expression of acetyl Mn-SOD levels that correlated with decreased Sirt-3 activity in aged WT males and females. Conversely, aged sEH null mice had preserved Sirt-3 activity and better mitochondrial ultrastructure compared to WT mice. Consistent with these changes, the activity level of SOD significantly decreased in WT animals but was preserved in aged sEH null animals. Markers of oxidative stress demonstrated age-related increase in protein carbonyl levels in WT and sEH null male mice. Together, these data highlight novel cardiac phenotypes from sEH null mice demonstrating a sexual dimorphic pattern of aging in the heart.

Association of the sEH gene promoter polymorphisms and haplotypes with preeclampsia

Background

The epoxyeicosatrienoic acids (EETs) have antihypertensive, anti-inflammatory, and organ protective properties and their circulation levels are related to hypertension, diabetes mellitus, cardiovascular diseases, and preeclampsia. Soluble epoxide hydrolase (sEH) catalyses the degradation of EETs to less biologically active dihydroxyeicosatrienoic acids. Here, we sequenced the promoter region of EPHX2 to investigate the association between promoter sequence alterations that we thought to affect the expression levels of the enzyme and preeclampsia (PE).

Methods

Nucleotide sequencing of the promoter region of the EPHX2, spanning from position -671 to +30, was performed on 100 pregnant women with PE and, 20 or more weeks pregnant normotensive, healthy women (n=100).

Results

Pregnant women who carry rs4149235, rs4149232, rs73227309, and rs62504268 polymorphisms have 4.4, 2.4, 2.3, and 2.8 times significantly increased risk of PE, respectively. CCGG (OR: 3.11; 95% CI: 1.12-8.62) and CCCA (OR: 0.45; 95% CI: 0.36-0.55) haplotypes were associated with an increased and decreased risk of PE, respectively.

Conclusions

Four SNPs (rs4149232, rs4149235, rs73227309, and rs62504268) in the promoter region of the EPHX2, and CCGG and CCCA haplotypes of these 4 SNPs were significantly associated with PE. These SNPs in the promoter region may affect sEH expression and thus enzyme activity and may play a role in PE pathogenesis by causing individual differences in EET levels. However, future studies are needed to confirm our findings and examine the effect of these SNPs on the sEH expression and/or enzyme activity.

Epoxy Fatty Acids Are Promising Targets for Treatment of Pain, Cardiovascular Disease and Other Indications Characterized by Mitochondrial Dysfunction, Endoplasmic Stress and Inflammation

Bioactive lipid mediators resulting from the metabolism of polyunsaturated fatty acids (PUFA) are controlled by many pathways that regulate the levels of these mediators and maintain homeostasis to prevent disease. PUFA metabolism is driven primarily through three pathways. Two pathways, the cyclooxygenase (COX) and lipoxygenase (LO) enzymatic pathways, form metabolites that are mostly inflammatory, while the third route of metabolism results from the oxidation by the cytochrome P450 enzymes to form hydroxylated PUFA and epoxide metabolites. These epoxygenated fatty acids (EpFA) demonstrate largely anti-inflammatory and beneficial properties, in contrast to the other metabolites formed from the degradation of PUFA. Dysregulation of these systems often leads to chronic disease. Pharmaceutical targets of disease focus on preventing the formation of inflammatory metabolites from the COX and LO pathways, while maintaining the EpFA and increasing their concentration in the body is seen as beneficial to treating and preventing disease. The soluble epoxide hydrolase (sEH) is the major route of metabolism of EpFA. Inhibiting its activity increases concentrations of beneficial EpFA, and often disease states correlate to mutations in the sEH enzyme that increase its activity and decrease the concentrations of EpFA in the body. Recent approaches to increasing EpFA include synthetic mimics that replicate biological activity of EpFA while preventing their metabolism, while other approaches focus on developing small molecule inhibitors to the sEH. Increasing EpFA concentrations in the body has demonstrated multiple beneficial effects in treating many diseases, including inflammatory and painful conditions, cardiovascular disease, neurological and disease of the central nervous system. Demonstration of efficacy in so many disease states can be explained by the fundamental mechanism that EpFA have of maintaining healthy microvasculature and preventing mitochondrial and endoplasmic reticulum stress. While there are no FDA approved methods that target the sEH or other enzymes responsible for metabolizing EpFA, current clinical efforts to test for efficacy by increasing EpFA that include inhibiting the sEH or administration of EpFA mimics that block metabolism are in progress.

The differences in brain stem transcriptional profiling in hypertensive ISIAH and normotensive WAG rats

BACKGROUND

The development of essential hypertension is associated with a wide range of mechanisms. The brain stem neurons are essential for the homeostatic regulation of arterial pressure as they control baroreflex and sympathetic nerve activity. The ISIAH (Inherited Stress Induced Arterial Hypertension) rats reproduce the human stress-sensitive hypertensive disease with predominant activation of the neuroendocrine hypothalamic-pituitary-adrenal and sympathetic adrenal axes. RNA-Seq analysis of the brain stems from the hypertensive ISIAH and normotensive control WAG (Wistar Albino Glaxo) rats was performed to identify the differentially expressed genes (DEGs) and the main central mechanisms (biological processes and metabolic pathways) contributing to the hypertensive state in the ISIAH rats.

RESULTS

The study revealed 224 DEGs. Their annotation in databases showed that 22 of them were associated with hypertension and blood pressure (BP) regulation, and 61 DEGs were associated with central nervous system diseases. In accordance with the functional annotation of DEGs, the key role of hormonal metabolic processes and, in particular, the enhanced biosynthesis of aldosterone in the brain stem of ISIAH rats was proposed. Multiple DEGs associated with several Gene Ontology (GO) terms essentially related to modulation of BP were identified. Abundant groups of DEGs were related to GO terms associated with responses to different stimuli including response to organic (hormonal) substance, to external stimulus, and to stress. Several DEGs making the most contribution to the inter-strain differences were detected including the Ephx2, which was earlier defined as a major candidate gene in the studies of transcriptional profiles in different tissues/organs (hypothalamus, adrenal gland and kidney) of ISIAH rats.

CONCLUSIONS

The results of the study showed that inter-strain differences in ISIAH and WAG brain stem functioning might be a result of the imbalance in processes leading to the pathology development and those, exerting the compensatory effects. The data obtained in this study are useful for a better understanding of the genetic mechanisms underlying the complexity of the brain stem processes in ISIAH rats, which are a model of stress-sensitive form of hypertension.

Role of epoxy-fatty acids and epoxide hydrolases in the pathology of neuro-inflammation

Neuroinflammation is a physiologic response aimed at protecting the central nervous system during injury. However, unresolved and chronic neuroinflammation can lead to long term damage and eventually neurologic disease including Parkinson's disease, Alzheimer's disease and dementia. Recently, enhancing the concentration of epoxyeicosatrienoic acids (EETs) through blocking their hydrolytic degradation by soluble epoxide hydrolase (sEH) has been applied towards reducing the long-term damage associated with central neurologic insults. Evidence suggests this protective effect is mediated, at least in part, through polarization of microglia to an anti-inflammatory phenotype that blocks the inflammatory actions of prostaglandins and promotes wound repair. This mini-review overviews the epidemiologic basis for using sEH inhibition towards neuroinflammatory disease and pharmacologic studies testing sEH inhibition in several neurologic diseases. Additionally, the combination of sEH inhibition with other eicosanoid signaling pathways is considered as an enhanced approach for developing potent neuroprotectants.

Association between the EPHX2 p.Lys55Arg polymorphism and prognosis following an acute coronary syndrome

Inhibition of soluble epoxide hydrolase (sEH, EPHX2) elicits potent cardiovascular protective effects in preclinical models of ischemic cardiovascular disease (CVD), and genetic polymorphisms in EPHX2 have been associated with developing ischemic CVD in humans. However, it remains unknown whether EPHX2 variants are associated with prognosis following an ischemic CVD event. We evaluated the association between EPHX2 p.Lys55Arg and p.Arg287Gln genotype with survival in 667 acute coronary syndrome (ACS) patients. No association with p.Arg287Gln genotype was observed (P = 0.598). Caucasian EPHX2 Arg55 carriers (Lys/Arg or Arg/Arg) had a significantly higher risk of 5-year mortality (adjusted hazard ratio [HR] 1.61, 95% confidence interval [CI] 1.01-2.55, P = 0.045). In an independent population of 2712 ACS patients, this association was not replicated (adjusted HR 0.92, 95% CI 0.70-1.21, P = 0.559). In a secondary analysis, Caucasian homozygous Arg55 allele carriers (Arg/Arg) appeared to exhibit a higher risk of cardiovascular mortality (adjusted HR 2.60, 95% CI 1.09-6.17). These results demonstrate that EPHX2 p.Lys55Arg and p.Arg287Gln polymorphisms do not significantly modify survival after an ACS event. Investigation of other sEH metabolism biomarkers in ischemic CVD appears warranted.

Metabolic/inflammatory/vascular comorbidity in psychiatric disorders; soluble epoxide hydrolase (sEH) as a possible new target

The common and severe psychiatric disorders, including major depressive disorder (MDD) and bipolar disorder (BD), are associated with inflammation, oxidative stress and changes in peripheral and brain lipid metabolism. Those pathways are implicated in the premature development of vascular and metabolic comorbidities, which account for considerable morbidity and mortality, including increased dementia risk. During endoplasmic reticulum stress, the soluble epoxide hydrolase (sEH) enzyme converts anti-inflammatory fatty acid epoxides generated by cytochrome p450 enzymes into their corresponding and generally less anti-inflammatory, or even pro-inflammatory, diols, slowing the resolution of inflammation. The sEH enzyme and its oxylipin products are elevated post-mortem in MDD, BD and schizophrenia. Preliminary clinical data suggest that oxylipins increase with symptoms in seasonal MDD and anorexia nervosa, requiring confirmation in larger studies and other cohorts. In rats, a soluble sEH inhibitor mitigated the development of depressive-like behaviors. We discuss sEH inhibitors under development for cardiovascular diseases, post-ischemic brain injury, neuropathic pain and diabetes, suggesting new possibilities to address the mood and cognitive symptoms of psychiatric disorders, and their most common comorbidities.

Soluble epoxide hydrolase as a therapeutic target for pain, inflammatory and neurodegenerative diseases

Eicosanoids are biologically active lipid signaling molecules derived from polyunsaturated fatty acids. Many of the actions of eicosanoid metabolites formed by cyclooxygenase and lipoxygenase enzymes have been characterized, however, the epoxy-fatty acids (EpFAs) formed by cytochrome P450 enzymes are newly described by comparison. The EpFA metabolites modulate a diverse set of physiologic functions that include inflammation and nociception among others. Regulation of EpFAs occurs primarily via release, biosynthesis and enzymatic transformation by the soluble epoxide hydrolase (sEH). Targeting sEH with small molecule inhibitors has enabled observation of the biological activity of the EpFAs in vivo in animal models, greatly contributing to the overall understanding of their role in the inflammatory response. Their role in modulating inflammation has been demonstrated in disease models including cardiovascular pathology and inflammatory pain, but extends to neuroinflammation and neuroinflammatory disease. Moreover, while EpFAs demonstrate activity against inflammatory pain, interestingly, this action extends to blocking chronic neuropathic pain as well. This review outlines the role of modulating sEH and the biological action of EpFAs in models of pain and inflammatory diseases.

Integrating multi-omics biomarkers and postprandial metabolism to develop personalized treatment for anorexia nervosa

BACKGROUND

Anorexia Nervosa (AN) is a serious mental illness characterized by emaciation, an intense fear of gaining weight despite being underweight, and distorted body image. Few treatments reverse the core symptoms in AN such as profound aversion to food and food avoidance. Consequently, AN has a chronic and relapsing course and the highest mortality rate of any psychiatric illness. A more complete understanding of the disease pathogenesis is needed in order to develop better treatments and improve AN outcome. The pathogenesis and psychopathophysiology of AN can be better elucidated by combining longitudinal phenotyping with multiple "omics" techniques, including genomics, proteomics, lipidomics, and metabolomics.

DESIGN

This paper summarizes the key findings of a series of interrelated studies including new experimental data and previously published data, and describes our current initiatives and future directions.

RESULTS

Exon sequencing data was analyzed in 1205 AN and 1948 controls. Targeted metabolomics, lipidomics, and proteomics data were collected in two independent convenience samples consisting of 75 subjects with eating disorders and 61 sex- and age-matched healthy controls. Study participants were female and the mean age was 22.9 (4.9 [SD]) years. Epoxide hydrolase 2 (EPHX2) genetic variations were significantly associated with AN risk, and epoxide hydrolase (sEH) activity was elevated in AN compared to controls. The polyunsaturated fatty acids (PUFAs) and eicosanoids data revealed that cytochrome P450 pathway was implicated in AN, and AN displayed a dysregulated postprandial metabolism of PUFAs and sEH-dependent eicosanoids.

IMPLICATION AND CURRENT INITIATIVES

Collectively, our data suggest that dietary factors may contribute to the burden of EPHX2-associated AN susceptibility and affect disease outcome. We are implementing new investigations using a longitudinal study design in order to validate and develop an EPHX2 multi-omics biomarker system. We will test whether sEH-associated postprandial metabolism increases AN risk and affects treatment outcome through an ω-6 rich breakfast challenge. Participants will include 100 ill AN patients, 100 recovered AN patients, and 100 age- and race-matched healthy women. These data will allow us to investigate 1) how genetic and dietary factors independently and synergistically contribute to AN risk and progression, and 2) if clinical severity and treatment response in AN are affected by sEH activity and eicosanoid dysregulation. Results of our study will 1) identify clinically relevant biomarkers, 2) unravel mechanistic functions of sEH, and 3) delineate contributory roles of dietary PUFAs and cytochrome P450 pathway eicosanoids for the purpose of developing novel AN treatments and improving disease prognosis.

Ischemic Stroke and Six Genetic Variants in CRP, EPHX2, FGA, and NOTCH3 Genes: A Meta-Analysis

BACKGROUND

Ischemic stroke (IS) is a leading cause of death and disability worldwide. As genetic heritability for IS is estimated at about 35%-40%, the identification of genetic variants associated with IS risk is of great importance. The main objective of this study was to carry out a meta-analysis for polymorphisms in CRP, EPHX2, FGA, and NOTCH3 genes and the risk for IS.

METHODS

Literature search for 6 candidate polymorphisms and IS was conducted using HuGE Navigator, PubMed, and Google Scholar databases. Meta-Analyst program was used to calculate pooled odds ratios (ORs) with a random effects model.

RESULTS

Twenty-five published studies for 6 candidate polymorphisms were included: CRP-rs1800947 (5 studies), CRP-rs1205 (3 studies), EPHX2-rs751141 (5 studies), FGA-rs6050 (6 studies), NOTCH3-rs3815188 (3 studies), and NOTCH3-rs1043994 (3 studies), for a total number of 7,825 IS cases and 56,532 control subjects. We did not find significant pooled ORs (P values > .05) for any of the genetic variants evaluated in this work.

CONCLUSIONS

Our meta-analysis results did not show significant associations between these 6 polymorphisms in 4 candidate genes and IS, despite the functional role of some of these single nucleotide polymorphisms (e.g., rs6050 in FGA gene). Future studies are needed to identify additional main genetic risk factors for IS in different populations.

Disrupting Dimerization Translocates Soluble Epoxide Hydrolase to Peroxisomes

The epoxyeicosatrienoic acid (EET) neutralizing enzyme soluble epoxide hydrolase (sEH) is a neuronal enzyme, which has been localized in both the cytosol and peroxisomes. The molecular basis for its dual localization remains unclear as sEH contains a functional peroxisomal targeting sequence (PTS). Recently, a missense polymorphism was identified in human sEH (R287Q) that enhances its peroxisomal localization. This same polymorphism has also been shown to generate weaker sEH homo-dimers. Taken together, these observations suggest that dimerization may mask the sEH PTS and prevent peroxisome translocation. In the current study, we test the hypothesis that dimerization is a key regulator of sEH subcellular localization. Specifically, we altered the dimerization state of sEH by introducing substitutions in amino acids responsible for the dimer-stabilizing salt-bridge. Green Fluorescent Protein (GFP) fusions of each of mutants were co-transfected into mouse primary cultured cortical neurons together with a PTS-linked red fluorescent protein to constitutively label peroxisomes. Labeled neurons were analyzed using confocal microscopy and co-localization of sEH with peroxisomes was quantified using Pearson's correlation coefficient. We find that dimer-competent sEH constructs preferentially localize to the cytosol, whereas constructs with weakened or disrupted dimerization were preferentially targeted to peroxisomes. We conclude that the sEH dimerization status is a key regulator of its peroxisomal localization.

Interactions Among CYP2C8, EPHX2, and CYP4A11 Variants and CYP Plasma Metabolite Levels in Ischemic Stroke

Aim: To better understand the relationship between the interactions among rs17110453, rs751141, and rs9333025 variants and plasma levels of cytochrome P450 (CYP) metabolites, i.e., 20-hydroxyeicosatetraenoic acid (20-HETE), epoxyeicosatrienoic acids (EETs), and dihydroxyeicosatrienoic acids (DiHETEs) in ischemia stroke (IS).

Methods: We measured plasma CYP metabolite levels in 218 acute IS cases and 126 controls, and a subset of samples were assessed to further understand the association between relevant variants and IS risk in our previous study. We assessed the associations between variant interactions and levels of 20-HETE, EETs, and DiHETEs as well as the associations between levels of 20-HETE, EETs, and DiHETEs and IS risk after adjusting for other potential confounders. Furthermore, the association between variant interactions and IS risk after adjusting for other covariates, including CYP metabolites levels, was evaluated.

Results: The interactions among variants rs17110453, rs751141, and rs9333025 were significantly associated with high 20-HETE, high DiHETEs, and low EETs after adjusting for the status of diabetes mellitus and hypertension. High 20-HETE, high DiHETEs, and low EETs were independent risk factors for IS after adjusting for hypertension, diabetes mellitus, and the interactions among rs17110453, rs751141, and rs9333025. Furthermore, the interactions among rs17110453, rs751141, and rs9333025 were significantly associated with a higher risk of IS after adjusting for CYP metabolites (OR= 2.02, 95% CI: 1.28–5.27, P = 0.007).

Conclusion: The association between the interactions among rs17110453, rs751141, and rs9333025 and IS risk in Chinese population may be partly but not exclusively mediated by plasma levels of 20-HETE, EETs, and DHETs. Further well-designed studies are warranted to replicate this finding.

Dysregulation of soluble epoxide hydrolase and lipidomic profiles in anorexia nervosa

Individuals with anorexia nervosa (AN) restrict eating and become emaciated. They tend to have an aversion to foods rich in fat. Because epoxide hydrolase 2 (EPHX2) was identified as a novel AN susceptibility gene, and because its protein product, soluble epoxide hydrolase (sEH), converts bioactive epoxides of polyunsaturated fatty acid (PUFA) to the corresponding diols, lipidomic and metabolomic targets of EPHX2 were assessed to evaluate the biological functions of EPHX2 and their role in AN. Epoxide substrates of sEH and associated oxylipins were measured in ill AN, recovered AN and gender- and race-matched controls. PUFA and oxylipin markers were tested as potential biomarkers for AN. Oxylipin ratios were calculated as proxy markers of in vivo sEH activity. Several free- and total PUFAs were associated with AN diagnosis and with AN recovery. AN displayed elevated n-3 PUFAs and may differ from controls in PUFA elongation and desaturation processes. Cytochrome P450 pathway oxylipins from arachidonic acid, linoleic acid, alpha-linolenic acid and docosahexaenoic acid PUFAs are associated with AN diagnosis. The diol:epoxide ratios suggest the sEH activity is higher in AN compared with controls. Multivariate analysis illustrates normalization of lipidomic profiles in recovered ANs. EPHX2 influences AN risk through in vivo interaction with dietary PUFAs. PUFA composition and concentrations as well as sEH activity may contribute to the pathogenesis and prognosis of AN. Our data support the involvement of EPHX2-associated lipidomic and oxylipin dysregulations in AN, and reveal their potential as biomarkers to assess responsiveness to future intervention or treatment.

The role of epoxyeicosatrienoic acids in the cardiovascular system

There is increasing evidence suggesting that epoxyeicosatrienoic acids (EETs) play an important role in cardioprotective mechanisms. These include regulating vascular tone, modulating inflammatory responses, improving cardiomyocyte function and reducing ischaemic damage, resulting in attenuation of animal models of cardiovascular risk factors. This review discusses the current knowledge on the role of EETs in endothelium-dependent control of vascular tone in the healthy and in subjects with cardiovascular risk factors, and considers the pharmacological potential of targeting this pathway.

Beneficial effects of ω-3 PUFA in children on cardiovascular risk factors during childhood and adolescence

Omega-3 polyunsatured fatty acids (ω-3 PUFA) are essential nutrients mainly derived from fish and seafood but present also in vegetables such as nuts and seed-oils. Some epidemiological and clinical studies indicate a protection of ω-3 FA against cardiovascular disease and a favourable effect on cardiovascular risk factors control in adults. The evidences of their effects in children and adolescents are scanty but a possible beneficial role, especially for insulin sensitivity and blood pressure control, has been proposed. In this review we want to focus especially on the evidences, which could justify the assumption of ω-3 in children and adolescents, and to underline the aspects which need further investigation. Mechanisms through which ω-3 FA act are manifolds and still a matter of investigation: beside their interaction with ion channel and their influence on plasma membrane fluidity, probably the main effect is acting as competitor for cytochrome P-450 (CYP) with respect to ω-6 FA. Thus, they can modulate the biosynthesis of eicosanoids and other lipid mediators, which likely exert a protective action. Another suggestive hypothesis is that their beneficial effect is not dependent only on the intake of ω-3 FA, but also on the complex interaction between different nutrients including ω-3 and other FAs with polymorphisms in genes involved in ω-3 FA modulation. This complex interaction has seldom been explored in children and adolescents. Further studies are needed to investigate all these points in order to find a better collocation of ω-3 FA on the available armamentarium for preventive, possibly individualized, medicine.

Soluble epoxide hydrolase gene deletion improves blood flow and reduces infarct size after cerebral ischemia in reproductively senescent female mice

Soluble epoxide hydrolase (sEH), a key enzyme in the metabolism of vasodilatory epoxyeicosatrienoic acids (EETs), is sexually dimorphic, suppressed by estrogen, and contributes to underlying sex differences in cerebral blood flow and injury after cerebral ischemia. We tested the hypothesis that sEH inhibition or gene deletion in reproductively senescent (RS) female mice would increase cerebral perfusion and decrease infarct size following stroke. RS (15–18 month old) and young (3–4 month old) female sEH knockout (sEHKO) mice and wild type (WT) mice were subjected to 45 min middle cerebral artery occlusion (MCAO) with laser Doppler perfusion monitoring. WT mice were treated with vehicle or a sEH inhibitor t-AUCB at the time of reperfusion and every 24 h thereafter for 3 days. Differences in regional cerebral blood flow were measured in vivo using optical microangiography (OMAG). Infarct size was measured 3 days after reperfusion. Infarct size and cerebral perfusion 24 h after MCAO were not altered by age. Both sEH gene deletion and sEH inhibition increased cortical perfusion 24 h after MCAO. Neither sEH gene deletion nor sEH inhibition reduced infarct size in young mice. However, sEH gene deletion, but not sEH inhibition of the hydrolase domain of the enzyme, decreased infarct size in RS mice. Results of these studies show that sEH gene deletion and sEH inhibition enhance cortical perfusion following MCAO and sEH gene deletion reduces damage after ischemia in RS female mice; however this neuroprotection in absent is young mice.

Genetic variation in soluble epoxide hydrolase: association with outcome after aneurysmal subarachnoid hemorrhage

OBJECT

Patients with aneurysmal subarachnoid hemorrhage (SAH) are at high risk for delayed cerebral ischemia (DCI) and stroke. Epoxyeicosatrienoic acids (EETs) play an important role in cerebral blood flow regulation and neuroprotection after brain injury. Polymorphisms in the gene for the enzyme soluble epoxide hydrolase (sEH), which inactivates EETs, are associated with ischemic stroke risk and neuronal survival after ischemia. This prospective observational study of patients with SAH compares vital and neurologic outcomes based on functional polymorphisms of sEH.

METHODS

Allelic discrimination based on quantitative real-time polymerase chain reaction was used to differentiate wild-type sEH from K55R heterozygotes (predictive of increased sEH activity and reduced EETs) and R287Q heterozygotes (predictive of decreased sEH activity and increased EETs). The primary outcome was new stroke after SAH. Secondary outcomes were death, Glasgow Outcome Scale score, and neurological deterioration attributable to DCI.

RESULTS

Multivariable logistic regression models adjusted for age at admission and Glasgow Coma Scale scores revealed an increase in the odds of new stroke (OR 5.48 [95% CI 1.51-19.91]) and death (OR 7.52 [95% CI 1.27-44.46]) in the K55R group, but no change in the odds of new stroke (OR 0.56 [95% CI 0.16-1.96]) or death (OR 3.09 [95% CI 0.51-18.52]) in patients with R287Q genotype, compared with wild-type sEH. The R287Q genotype was associated with reduced odds of having a Glasgow Outcome Scale score of ≤ 3 (OR 0.23 [95% CI 0.06-0.82]). There were no significant differences in the odds of neurological deterioration due to DCI.

CONCLUSIONS

Genetic polymorphisms of sEH are associated with neurological and vital outcomes after aneurysmal SAH.

Epoxyeicosatrienoic acids and cardioprotection: the road to translation

Cardiovascular disease, including acute myocardial infarction (AMI), is the leading cause of morbidity and mortality globally, despite well-established treatments. The discovery and development of novel therapeutics that prevent the progression of devastating consequences following AMI are thus important in reducing the global burden of this devastating disease. Scientific evidence for the protective effects of epoxyeicosatrienoic acids (EETs) in the cardiovascular system is rapidly emerging and suggests that promoting the effects of these cytochrome P450-derived epoxyeicosanoids is a potentially viable clinical therapeutic strategy. Through a translational lens, this review will provide insight into the potential clinical utility of this therapeutic strategy for AMI by 1) outlining the known cardioprotective effects of EETs and underlying mechanisms demonstrated in preclinical models of AMI with a particular focus on myocardial ischemia-reperfusion injury, 2) describing studies in human cohorts that demonstrate a relationship between EETs and associated pathways with coronary artery disease risk, and 3) discussing preclinical and clinical areas that require further investigation in order to increase the probability of successfully translating this rapidly emerging body of evidence into a clinically applicable therapeutic strategy for AMI.

Variations in the human soluble epoxide hydrolase gene and recurrence of atrial fibrillation after catheter ablation

BACKGROUND

Single nucleotide polymorphisms (SNPs) of EPHX2 alter sEH activity and are associated with increased [rs41507953 (K55R)] or reduced [rs751141 (R287Q)] cardiovascular risk via modulation of fibrosis, inflammation or cardiac ion channels. This indicates an effect on development and therapy response of AF. This study tested the hypothesis that variations in the EPHX2 gene encoding human soluble epoxide hydrolase (sEH) are associated with atrial fibrillation (AF) and recurrence of atrial fibrillation after catheter ablation.

METHODS AND RESULTS

A total of 218 consecutive patients who underwent catheter ablation for drug refractory AF and 268 controls were included. Two SNPs, rs41507953 and rs751141, were genotyped by direct sequencing. In the ablation group, holter recordings 3, 12 and 24 months after ablation were used to detect AF recurrence. No significant association of the SNPs and AF at baseline was detected. In the ablation group, recurrence of AF occurred in 20% of the patients 12 months after ablation and in 35% 24 months after ablation. The presence of the rs751141 polymorphism significantly increased the risk of AF recurrence 12 months (odds ratio [OR]: 3.2, 95% confidence interval [CI]: 1.237 to 8.276, p=0.016) and 24 months (OR: 6.076, 95% CI: 2.244 to 16.451, p<0.0001) after catheter ablation.

CONCLUSIONS

The presence of rs751141 polymorphism is associated with a significantly increased risk of AF recurrence after catheter ablation. These results point to stratification of catheter ablation by genotype and differential use of sEH-inhibitory drugs in the future.

Soluble epoxide hydrolase: gene structure, expression and deletion

Mammalian soluble epoxide hydrolase (sEH) converts epoxides to their corresponding diols through the addition of a water molecule. sEH readily hydrolyzes lipid signaling molecules, including the epoxyeicosatrienoic acids (EETs), epoxidized lipids produced from arachidonic acid by the action of cytochrome p450s. Through its metabolism of the EETs and other lipid mediators, sEH contributes to the regulation of vascular tone, nociception, angiogenesis and the inflammatory response. Because of its central physiological role in disease states such as cardiac hypertrophy, diabetes, hypertension, and pain sEH is being investigated as a therapeutic target. This review begins with a brief introduction to sEH protein structure and function. sEH evolution and gene structure are then discussed before human small nucleotide polymorphisms and mammalian gene expression are described in the context of several disease models. The review ends with an overview of studies that have employed the sEH knockout mouse model.

Vanin-1 T26I polymorphism, hypertension and cardiovascular events in two large urban-based prospective studies in Swedes

BACKGROUND AND AIMS

Vanin-1 (gene name VNN1) is an enzyme with pantetheinase activity generating the amino-thiol cysteamine which is implicated in the regulation of red-ox status through its effect on glutathione. We tested the hypothesis that the rs2294757 VNN1 T26I polymorphism could affect blood pressure (BP) levels, hypertension prevalence, and risk of incident cardiovascular events.

METHODS AND RESULTS

The VNN1 T26I polymorphism was genotyped in 5664 participants of the cardiovascular cohort of the "Malmö Diet and Cancer" (MDC-CVA) study and successively in 17874 participants of the "Malmö Preventive project"(MPP). The incidence of cardiovascular events was monitored for an average of nearly 12 years of follow-up in the MDC-CVA and for 25 years in the MPP. Both before and after adjustment for sex, age and BMI in the MDC-CVA the polymorphism had a mild lowering effect on diastolic BP and hypertension, especially in females. However in MPP no effect on BP phenotypes was detectable. Before and after adjustment for major cardiovascular risk factors, the hazard ratio for incident ischemic stroke and coronary events in the MDC-CVA was not significantly different in carriers of different genotypes.

CONCLUSIONS

Our data do not support a major role for the VNN1 T26I variant in determining BP level and incident ischemic events.

Development of an HTS assay for EPHX2 phosphatase activity and screening of nontargeted libraries

The EPXH2 gene encodes soluble epoxide hydrolase (sEH), which has two distinct enzyme activities: epoxide hydrolase (Cterm-EH) and phosphatase (Nterm-phos). The Cterm-EH is involved in the metabolism of arachidonic acid epoxides that play important roles in blood pressure, cell growth, inflammation, and pain. While recent findings suggested complementary biological roles for Nterm-phos, research is limited by the lack of potent bioavailable inhibitors of this phosphatase activity. Also, a potent bioavailable inhibitor of this activity could be important in the development of therapy for cardiovascular diseases. We report herein the development of an HTS enzyme-based assay for Nterm-phos (Z'>0.9) using AttoPhos as the substrate. This assay was used to screen a wide variety of chemical entities, including a library of known drugs that have reached through clinical evaluation (Pharmakon 1600), as well as a library of pesticides and environmental toxins. We discovered that ebselen inhibits sEH phosphatase activity. Ebselen binds to the N-terminal domain of sEH (K(I)=550 nM) and chemically reacts with the enzyme to quickly and irreversibly inhibit Nterm-phos, and subsequently Cterm-EH, and thus represents a new class of sEH inhibitor.

Attenuation of cisplatin-induced renal injury by inhibition of soluble epoxide hydrolase involves nuclear factor κB signaling

Acute kidney injury is associated with a significant inflammatory response that has been the target of renoprotection strategies. Epoxyeicosatrienoic acids (EETs) are anti-inflammatory cytochrome P450-derived eicosanoids that are abundantly produced in the kidney and metabolized by soluble epoxide hydrolase (sEH; Ephx2) to less active dihydroxyeicosatrienoic acids. Genetic disruption of Ephx2 and chemical inhibition of sEH were used to test whether the anti-inflammatory effects of EETs, and other lipid epoxide substrates of sEH, afford protection against cisplatin-induced nephrotoxicity. EET hydrolysis was significantly reduced in Ephx2(-/-) mice and was associated with an attenuation of cisplatin-induced increases in serum urea nitrogen and creatinine levels. Histological evidence of renal tubular damage and neutrophil infiltration was also reduced in the Ephx2(-/-) mice. Likewise, cisplatin had no effect on renal function, neutrophil infiltration, or tubular structure and integrity in mice treated with the potent sEH inhibitor 1-adamantan-1-yl-3-(1-methylsulfonyl-piperidin-4-yl-urea) (AR9273). Consistent with the ability of EETs to interfere with nuclear factor-κB (NF-κB) signaling, the observed renoprotection was associated with attenuation of renal NF-κB activity and corresponding decreases in the expression of tumor necrosis factor (TNF) α, TNF receptor (TNFR) 1, TNFR2, and intercellular adhesive molecule-1 before the detection of tubular injury. These data suggest that EETs or other fatty acid epoxides can attenuate cisplatin-induced kidney injury and sEH inhibition is a novel renoprotective strategy.

Role of soluble epoxide hydrolase phosphatase activity in the metabolism of lysophosphatidic acids

The EPXH2 gene encodes for the soluble epoxide hydrolase (sEH), which has two distinct enzyme activities: epoxide hydrolase (Cterm-EH) and phosphatase (Nterm-phos). The Cterm-EH is involved in the metabolism of epoxides from arachidonic acid and other unsaturated fatty acids, endogenous chemical mediators that play important roles in blood pressure regulation, cell growth, inflammation and pain. While recent findings suggested complementary biological roles for Nterm-phos, its mode of action is not well understood. Herein, we demonstrate that lysophosphatidic acids are excellent substrates for Nterm-phos. We also showed that sEH phosphatase activity represents a significant (20-60%) part of LPA cellular hydrolysis, especially in the cytosol. This possible role of sEH on LPA hydrolysis could explain some of the biology previously associated with the Nterm-phos. These findings also underline possible cellular mechanisms by which both activities of sEH (EH and phosphatase) may have complementary or opposite roles.

Cytochrome P450 eicosanoids and cerebral vascular function

The eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs), which are generated from the metabolism of arachidonic acid by cytochrome P450 (CYP) enzymes, possess a wide array of biological actions, including the regulation of blood flow to organs. 20-HETE and EETs are generated in various cell types in the brain and cerebral blood vessels, and contribute significantly to cerebral blood flow autoregulation and the coupling of regional brain blood flow to neuronal activity (neurovascular coupling). Investigations are beginning to unravel the molecular and cellular mechanisms by which these CYP eicosanoids regulate cerebral vascular function and the changes that occur in pathological states. Intriguingly, 20-HETE and the soluble epoxide hydrolase (sEH) enzyme that regulates EET levels have been explored as molecular therapeutic targets for cerebral vascular diseases. Inhibition of 20-HETE, or increasing EET levels by inhibiting the sEH enzyme, decreases cerebral damage following stroke. The improved outcome following cerebral ischaemia is a consequence of improving cerebral vascular structure or function and protecting neurons from cell death. Thus, the CYP eicosanoids are key regulators of cerebral vascular function and novel therapeutic targets for cardiovascular diseases and neurological disorders.

Genetic variation in soluble epoxide hydrolase (EPHX2) is associated with forearm vasodilator responses in humans

Cytochrome P450-derived epoxyeicosatrienoic acids are potent vasodilators in preclinical models and are hydrolyzed by soluble epoxide hydrolase (EPHX2). Associations between the EPHX2 Lys55Arg and Arg287Gln polymorphisms and cardiovascular disease risk have been reported; however, their impact on vascular function in humans has not been investigated. In 265 volunteers (198 white, 67 black American), forearm blood flow was measured by strain-gauge venous occlusion plethysmography at baseline and in response to bradykinin, methacholine, and sodium nitroprusside. Forearm vascular resistance was calculated as mean arterial pressure/forearm blood flow. In white Americans, Lys55Arg genotype was associated with vasodilator response to bradykinin, such that forearm blood flow was significantly lower (P = 0.043) and forearm vascular resistance was significantly higher (P = 0.013) in Arg55 variant allele carriers compared to wild-type individuals. Significant associations were also observed with methacholine and sodium nitroprusside. In contrast, no relationship was observed in black Americans. In black Americans, Arg287Gln genotype was associated with vasodilator response to bradykinin. Although the difference in forearm blood flow did not reach statistical significance (P = 0.058), forearm vascular resistance was significantly lower (P = 0.037) in Gln287 variant allele carriers compared to wild-type individuals. Significant associations were also observed with methacholine and sodium nitroprusside. In white Americans, Gln287 variant allele carriers did not exhibit significantly higher forearm blood flow (P = 0.128) or lower forearm vascular resistance (P = 0.080). Genetic variation in EPHX2 is associated with forearm vasodilator responses in a bradykinin receptor- and endothelium-independent manner, suggesting an important role for soluble epoxide hydrolase in the regulation of vascular function in humans.