Regulation of soluble epoxide hydrolase in renal-associated diseases: insights from potential mechanisms to clinical researches

In recent years, numerous experimental studies have underscored the pivotal role of soluble epoxide hydrolase (sEH) in renal diseases, demonstrating the reno-protective effects of sEH inhibitors. The nexus between sEH and renal-associated diseases has garnered escalating attention. This review endeavors to elucidate the potential molecular mechanisms of sEH in renal diseases and emphasize the critical role of sEH inhibitors as a prospective treatment modality. Initially, we expound upon the correlation between sEH and Epoxyeicosatrienoic acids (EETs) and also addressing the impact of sEH on other epoxy fatty acids, delineate prevalent EPHX2 single nucleotide polymorphisms (SNPs) associated with renal diseases, and delve into sEH-mediated potential mechanisms, encompassing oxidative stress, inflammation, ER stress, and autophagy. Subsequently, we delineate clinical research pertaining to sEH inhibition or co-inhibition of sEH with other inhibitors for the regulation of renal-associated diseases, covering conditions such as acute kidney injury, chronic kidney diseases, diabetic nephropathy, and hypertension-induced renal injury. Our objective is to validate the potential role of sEH inhibitors in the treatment of renal injuries. We contend that a comprehensive comprehension of the salient attributes of sEH, coupled with insights from clinical experiments, provides invaluable guidance for clinicians and presents promising therapeutic avenues for patients suffering from renal diseases.

Hepatic Transcriptome and Its Regulation Following Soluble Epoxide Hydrolase Inhibition in Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is a serious public health problem with limited pharmacologic options. The goal of the current study was to investigate the efficacy of pharmacologic inhibition of soluble epoxide hydrolase (sEH), an enzyme involved in lipid metabolism, in experimental ALD, and to examine the underlying mechanisms. C57BL/6J male mice were subjected to acute-on-chronic ethanol (EtOH) feeding with or without the sEH inhibitor 4-[[trans-4-[[[[4-trifluoromethoxy phenyl]amino]carbonyl]-amino]cyclohexyl]oxy]-benzoic acid (TUCB). Liver injury was assessed by multiple end points. Liver epoxy fatty acids and dihydroxy fatty acids were measured by targeted metabolomics. Whole-liver RNA sequencing was performed, and free modified RNA bases were measured by mass spectrometry. EtOH-induced liver injury was ameliorated by TUCB treatment as evidenced by reduced plasma alanine aminotransferase levels and was associated with attenuated alcohol-induced endoplasmic reticulum stress, reduced neutrophil infiltration, and increased numbers of hepatic M2 macrophages. TUCB altered liver epoxy and dihydroxy fatty acids and led to a unique hepatic transcriptional profile characterized by decreased expression of genes involved in apoptosis, inflammation, fibrosis, and carcinogenesis. Several modified RNA bases were robustly changed by TUCB, including N6-methyladenosine and 2-methylthio-N6-threonylcarbamoyladenosine. These findings show the beneficial effects of sEH inhibition by TUCB in experimental EtOH-induced liver injury, warranting further mechanistic studies to explore the underlying mechanisms, and highlighting the translational potential of sEH as a drug target for this disease.

Overexpression of Human Soluble Epoxide Hydrolase Exacerbates Coronary Reactive Hyperemia Reduction in Angiotensin-II-Treated Mouse Hearts

ABSTRACT

Coronary reactive hyperemia (CRH) is impaired in cardiovascular diseases, and angiotensin-II (Ang-II) exacerbates it. However, it is unknown how Ang-II affects CRH in Tie2-sEH Tr (human-sEH-overexpressed) versus wild-type (WT) mice. sEH-overexpression resulted in CRH reduction in Tie2-sEH Tr versus WT. We hypothesized that Ang-II exacerbates CRH reduction in Tie2-sEH Tr versus WT. The Langendorff system measured coronary flow in Tie2-sEH Tr and WT. The hearts were exposed to 15-second ischemia, and CRH was assessed in 10 mice each. Repayment volume was reduced by 40.50% in WT treated with Ang-II versus WT (7.42 ± 0.8 to 4.49 ± 0.8 mL/g) and 48% in Tie2-sEH Tr treated with Ang-II versus Tie2-sEH Tr (5.18 ± 0.4 to 2.68 ± 0.3 mL/g). Ang-II decreased repayment duration by 50% in WT-treated with Ang-II versus WT (2.46 ± 0.5 to 1.24 ± 0.4 minutes) and 54% in Tie2-sEH Tr treated with Ang-II versus Tie2-sEH Tr (1.66 ± 0.4 to 0.76 ± 0.2 minutes). Peak repayment flow was reduced by 11.2% in WT treated with Ang-II versus WT (35.98 ± 0.7 to 32.11 ± 1.4 mL/g) and 4% in Tie2-sEH Tr treated with Ang-II versus Tie2-sEH Tr (32.18 ± 0.6 to 30.89 ± 1.5 mL/g). Furthermore, coronary flow was reduced by 43% in WT treated with Ang-II versus WT (14.2 ± 0.5 to 8.15 ± 0.8 mL/min/g) and 32% in Tie2-sEH Tr treated with Ang-II versus Tie2-sEH Tr (12.1 ± 0.8 to 8.3 ± 1.2 mL/min/g). Moreover, the Ang-II-AT 1 -receptor and CYP4A were increased in Tie2-sEHTr. Our results demonstrate that Ang-II exacerbates CRH reduction in Tie2-sEH Tr mice.

Hepatic soluble epoxide hydrolase activity regulates cerebral Aβ metabolism and the pathogenesis of Alzheimer's disease in mice

Alzheimer's disease (AD) is caused by a complex interaction between genetic and environmental factors. However, how the role of peripheral organ changes in response to environmental stimuli during aging in AD pathogenesis remains unknown. Hepatic soluble epoxide hydrolase (sEH) activity increases with age. Hepatic sEH manipulation bidirectionally attenuates brain amyloid-β (Aβ) burden, tauopathy, and cognitive deficits in AD mouse models. Moreover, hepatic sEH manipulation bidirectionally regulates the plasma level of 14,15-epoxyeicosatrienoic acid (-EET), which rapidly crosses the blood-brain barrier and modulates brain Aβ metabolism through multiple pathways. A balance between the brain levels of 14,15-EET and Aβ is essential for preventing Aβ deposition. In AD models, 14,15-EET infusion mimicked the neuroprotective effects of hepatic sEH ablation at biological and behavioral levels. These results highlight the liver's key role in AD pathology, and targeting the liver-brain axis in response to environmental stimuli may constitute a promising therapeutic approach for AD prevention.

Genetic deletion or pharmacological inhibition of soluble epoxide hydrolase attenuated particulate matter 2.5 exposure mediated lung injury

Air pollution represented by particulate matter 2.5 (PM2.5) is closely related to diseases of the respiratory system. Although the understanding of its mechanism is limited, pulmonary inflammation is closely correlated with PM2.5-mediated lung injury. Soluble epoxide hydrolase (sEH) and epoxy fatty acids play a vital role in the inflammation. Herein, we attempted to use the metabolomics of oxidized lipids for analyzing the relationship of oxylipins with lung injury in a PM2.5-mediated mouse model, and found that the cytochrome P450 oxidases/sEH mediated metabolic pathway was involved in lung injury. Furthermore, the sEH overexpression was revealed in lung injury mice. Interestingly, sEH genetic deletion or the selective sEH inhibitor TPPU increased levels of epoxyeicosatrienoic acids (EETs) in lung injury mice, and inactivated pulmonary macrophages based on the MAPK/NF-κB pathway, resulting in protection against PM2.5-mediated lung injury. Additionally, a natural sEH inhibitor luteolin from Inula japonica displayed a pulmonary protective effect towards lung injury mediated by PM2.5 as well. Our results are consistent with the sEH message and protein being both a marker and mechanism for PM2.5-induced inflammation, which suggest its potential as a pharmaceutical target for treating diseases of the respiratory system.

Enhancement of the liver's neuroprotective role ameliorates traumatic brain injury pathology

Traumatic brain injury (TBI) is a pervasive problem worldwide for which no effective treatment is currently available. Although most studies have focused on the pathology of the injured brain, we have noted that the liver plays an important role in TBI. Using two mouse models of TBI, we found that the enzymatic activity of hepatic soluble epoxide hydrolase (sEH) was rapidly decreased and then returned to normal levels following TBI, whereas such changes were not observed in the kidney, heart, spleen, or lung. Interestingly, genetic downregulation of hepatic Ephx2 (which encodes sEH) ameliorates TBI-induced neurological deficits and promotes neurological function recovery, whereas overexpression of hepatic sEH exacerbates TBI-associated neurological impairments. Furthermore, hepatic sEH ablation was found to promote the generation of A2 phenotype astrocytes and facilitate the production of various neuroprotective factors associated with astrocytes following TBI. We also observed an inverted V-shaped alteration in the plasma levels of four EET (epoxyeicosatrienoic acid) isoforms (5,6-, 8,9-,11,12-, and 14,15-EET) following TBI which were negatively correlated with hepatic sEH activity. However, hepatic sEH manipulation bidirectionally regulates the plasma levels of 14,15-EET, which rapidly crosses the blood-brain barrier. Additionally, we found that the application of 14,15-EET mimicked the neuroprotective effect of hepatic sEH ablation, while 14,15-epoxyeicosa-5(Z)-enoic acid blocked this effect, indicating that the increased plasma levels of 14,15-EET mediated the neuroprotective effect observed after hepatic sEH ablation. These results highlight the neuroprotective role of the liver in TBI and suggest that targeting hepatic EET signaling could represent a promising therapeutic strategy for treating TBI.

Aflatoxin B1 Increases Soluble Epoxide Hydrolase in the Brain and Induces Neuroinflammation and Dopaminergic Neurotoxicity

Parkinson's disease (PD) is an increasingly common neurodegenerative movement disorder with contributing factors that are still largely unexplored and currently no effective intervention strategy. Epidemiological and pre-clinical studies support the close association between environmental toxicant exposure and PD incidence. Aflatoxin B1 (AFB1), a hazardous mycotoxin commonly present in food and environment, is alarmingly high in many areas of the world. Previous evidence suggests that chronic exposure to AFB1 leads to neurological disorders as well as cancer. However, whether and how aflatoxin B1 contributes to the pathogenesis of PD is poorly understood. Here, oral exposure to AFB1 is shown to induce neuroinflammation, trigger the α-synuclein pathology, and cause dopaminergic neurotoxicity. This was accompanied by the increased expression and enzymatic activity of soluble epoxide hydrolase (sEH) in the mouse brain. Importantly, genetic deletion or pharmacological inhibition of sEH alleviated the AFB1-induced neuroinflammation by reducing microglia activation and suppressing pro-inflammatory factors in the brain. Furthermore, blocking the action of sEH attenuated dopaminergic neuron dysfunction caused by AFB1 in vivo and in vitro. Together, our findings suggest a contributing role of AFB1 to PD etiology and highlight sEH as a potential pharmacological target for alleviating PD-related neuronal disorders caused by AFB1 exposure.

Genetic polymorphisms of microsomal epoxide hydrolase and UDP-glucuronosyltransferase (UGT) and its effects on plasma carbamazepine levels and metabolic ratio in persons with epilepsy of South India: A cross-sectional genetic association study

OBJECTIVES

Carbamazepine (CBZ), an anti-seizure drug, is widely prescribed for the management of focal seizures. At a given therapeutic dose, CBZ exhibits marked interindividual variation in the plasma CBZ levels. The aim wasto study the influence of EPHX1 c.337 T>C and UGT2B7*2 genetic polymorphisms on plasma carbamazepine (CBZ) levels in persons with epilepsy (PWE) from South India.

METHODS

115 PWE belong to South India origin who are on carbamazepine monotherapy were recruited. Genotyping of the two variants weredone using RT-PCR method. PWE who had seizure freedom for one year and their last dose which was not changed for one year duration were included and their plasma levels of CBZ and its active metabolite CBZ 10,11 epoxide were analysed by reverse phase HPLC.

RESULTS

In EPHX1 c. 337 (T>C) polymorphism, the PWE carrying CC had lower plasma CBZ levels when compared to CT genotype (2.45 μg/ml vs 3.15 μg/ml. In UGT2B7*2, PWE carrying homozygous mutant TT had higher levels when compared with CT (3.09 μg/ml vs 2.74 μg/ml) genotype but found no statistical significance. Mutant genotype of EPHX1 (CC) had higher metabolic ratio compared to TT genotype (1.33 vs 1.17) but not found to be statistically significant. Mutant genotype of UGT2B7*2 (TT) was found to be having lower metabolic ratio when compared with CC genotype (1.18 vs 1.35; p value =0.08).

CONCLUSION

PWE carrying EPHX1 c.337 T>C (rs1051740) and UGT2B7*2 (rs7439366) genetic polymorphisms did not affect the plasma CBZ levels and metabolic ratio of PWE of South Indian origin. However, this finding should be confirmed in a larger sample size which may help in optimization and personalized CBZ therapy in South Indians.

Cloning and characterization of Aedes aegypti juvenile hormone epoxide hydrolases (JHEHs)

Juvenile hormone epoxide hydrolase (JHEH) plays an important role in the metabolism of juvenile hormone III (JH III) in insects. To study the role that JHEH plays in female Aedes aegypti JHEH 1, 2, and 3 complementary DNA (cDNAs) were cloned and sequenced. Northern blot analyses show that the three transcripts are expressed in the head thorax, the gut, the ovaries, and the fat body of females. Molecular modeling shows that the enzyme is a homodimer that binds JH III acid (JH IIIA) at the catalytic groove better than JH III. The cDNA of JHEH 1 and 2 are very similar indicating close relationship. Knocking down of jheh 1, 2, and 3 in adult female and larval Ae. aegypti using double-stranded RNA (dsRNA) did not affect egg development or caused adult mortality. Larvae that were fed bacterial cells expressing dsRNA against jheh 1, 2, and 3 grew normally. Treating blood-fed female Ae. aegypti with [12-³ H](10R) JH III and analyzing the metabolites by C₁₈ reversed phase chromatography showed that JHEH preferred substrate is not JH III but JH IIIA. Genomic analysis of jheh 1, 2, and 3 indicate that jheh 1 and 2 are transcribed from a 1.53 kb DNA whereas jheh 3 is transcribed from a 10.9 kb DNA. All three genes are found on chromosome two at distinct locations. JHEH 2 was expressed in bacterial cells and purified by Ni affinity chromatography. Sequencing of the recombinant protein by MS/MS identified JHEH 2 as the expressed recombinant protein.

Decreased Expression of Soluble Epoxide Hydrolase Suppresses Murine Choroidal Neovascularization

Neovascular or "wet" age-related macular degeneration (nAMD) is a leading cause of blindness among older adults. Choroidal neovascularization (CNV) is a major pathological feature of nAMD, in which abnormal new blood vessel growth from the choroid leads to irreversible vision loss. There is a critical need to develop novel therapeutic strategies to address limitations of the current anti-vascular endothelial growth factor biologics. Previously, we identified soluble epoxide hydrolase (sEH) as a possible therapeutic target for CNV through a forward chemical genetic approach. The purpose of this study was to validate sEH as a target by examining retinal expression of sEH protein and mRNA by immunohistochemistry and RNAscope in situ hybridization, respectively, and to assess the efficacy of an adeno-associated virus (AAV) vector designed to knock down the sEH gene, Ephx2, in the murine laser-induced (L-) CNV model. nAMD patient postmortem eye tissue and murine L-CNV showed overexpression of sEH in photoreceptors and retinal pigment epithelial cells. Ephx2 knockdown significantly reduced CNV and normalized mRNA expression levels of CNV-related inflammatory markers. Thus, this study further establishes sEH as a promising therapeutic target against CNV associated with nAMD.

Cardiomyocyte-specific disruption of soluble epoxide hydrolase limits inflammation to preserve cardiac function

Endotoxemia elicits a multiorgan inflammatory response that results in cardiac dysfunction and often leads to death. Inflammation-induced metabolism of endogenous N-3 and N-6 polyunsaturated fatty acids generates numerous lipid mediators, such as epoxy fatty acids (EpFAs), which protect the heart. However, EpFAs are hydrolyzed by soluble epoxide hydrolase (sEH), which attenuates their cardioprotective actions. Global genetic disruption of sEH preserves EpFA levels and attenuates cardiac dysfunction in mice following acute lipopolysaccharide (LPS)-induced inflammatory injury. In leukocytes, EpFAs modulate the innate immune system through the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. However, the mechanisms by which both EpFAs and sEH inhibition exert their protective effects in the cardiomyocyte are still elusive. This study investigated whether cardiomyocyte-specific sEH disruption attenuates inflammation and cardiac dysfunction in acute LPS inflammatory injury via modulation of the NLRP3 inflammasome. We use tamoxifen-inducible CreER recombinase technology to target sEH genetic disruption to the cardiomyocyte. Primary cardiomyocyte studies provide mechanistic insight into inflammasome signaling. For the first time, we demonstrate that cardiomyocyte-specific sEH disruption preserves cardiac function and attenuates inflammatory responses by limiting local cardiac inflammation and activation of the systemic immune response. Mechanistically, inhibition of cardiomyocyte-specific sEH activity or exogenous EpFA treatment do not prevent upregulation of NLRP3 inflammasome machinery in neonatal rat cardiomyocytes. Rather, they limit downstream activation of the pathway leading to release of fewer chemoattractant factors and recruitment of immune cells to the heart. These data emphasize that cardiomyocyte sEH is vital for mediating detrimental systemic inflammation.NEW & NOTEWORTHY The cardioprotective effects of genetic disruption and pharmacological inhibition of sEH have been demonstrated in a variety of cardiac disease models, including acute LPS inflammatory injury. For the first time, it has been demonstrated that sEH genetic disruption limited to the cardiomyocyte profoundly preserves cardiac function and limits local and systemic inflammation following acute LPS exposure. Hence, cardiomyocytes serve a critical role in the innate immune response that can be modulated to protect the heart.

The Brain’s Microvascular Response to High Glycemia and to the Inhibition of Soluble Epoxide Hydrolase Is Sexually Dimorphic

Biological sex and a high glycemic diet (HGD) contribute to dementia, yet little is known about the operative molecular mechanisms. Our goal was to understand the differences between males and females in the multi-genomic response of the hippocampal microvasculature to the HGD, and whether there was vasculoprotection via the inhibition of soluble epoxide hydrolase (sEHI). Adult wild type mice fed high or low glycemic diets for 12 weeks, with or without an sEHI inhibitor (t-AUCB), had hippocampal microvessels isolated by laser-capture microdissection. Differential gene expression was determined by microarray and integrated multi-omic bioinformatic analyses. The HGD induced opposite effects in males and females: the HGD-upregulated genes were involved in neurodegeneration or neuroinflammation in males, whereas in females they downregulated the same pathways, favoring neuroprotection. In males, the HGD was associated with a greater number of clinical diseases than in females, the sEHI downregulated genes involved in neurodegenerative diseases to a greater extent with the HGD and compared to females. In females, the sEHI downregulated genes involved in endothelial cell functions to a greater extent with the LGD and compared to males. Our work has potentially important implications for sex-specific therapeutic targets for vascular dementia and cardiovascular diseases in males and females.

TPPU Downregulates Oxidative Stress Damage and Induces BDNF Expression in PC-12 Cells

Objective

Ischemia-reperfusion is an ongoing clinical challenge that can lead to a series of pathological changes including oxidative stress. The inhibition of soluble epoxide hydrolase inhibitor (sEH) by 1-(1-propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea (TPPU) results in an anti-inflammatory, cardioprotective, and blood vessel growth-promoting effects. Therefore, this study focused on the protective effect of TPPU on a rat pheochromocytoma (PC-12) cell oxidative stress model induced by H2O2.

Methods

CCK-8 and Hoechst 33342 were used to evaluate cell apoptosis and western blot to detect the apoptotic proteins and brain-derived neurotrophic factor (BDNF) expression.

Result

The incubation with 100 μM, 50 μM, and 25 μM TPPU significantly increased PC-12 cell viability. Epoxyeicosatrienoic acid (EET) pretreatment also protected PC-12 cells from oxidative stress. In addition, TPPU reduced caspase-3 and Bax expression and induced Bcl-2 expression, and EETs exerted the same effect on caspase-3 expression as TPPU. A positive relationship was found between TPPU or EET incubation and BDNF expression.

Conclusion

These results revealed that TPPU reduced PC-12 cell oxidative stress injury induced by H2O2 and promoted BDNF expression.

Genetic analyses of circulating PUFA-derived mediators identifies heritable dihydroxyeicosatrienoic acid species

Estimates of heritability are the first step in identifying a trait with substantial variation due to genetic factors. Large-scale genetic analyses can identify the DNA variants that influence the levels of circulating lipid species and the statistical technique Mendelian randomisation can use these DNA variants to address potential causality of these lipids in disease. We estimated the heritability of plasma eicosanoids, octadecanoids and docosanoids to identify those lipid species with substantial heritability. We analysed plasma lipid mediators in 31 White British families (196 participants) ascertained for high blood pressure and deeply clinically and biochemically phenotyped over a 25-year period. We found that the dihydroxyeicosatrienoic acid (DHET) species, 11,12-DHET and 14,15-DHET, products of arachidonic acid metabolism by cytochrome P450 (CYP) monooxygenase and soluble epoxide hydrolase (sEH), exhibited substantial heritability (h2 = 33%-37%; Padj<0.05). Identification of these two heritable bioactive lipid species allows for future large-scale, targeted, lipidomics-genomics analyses to address causality in cardiovascular and other diseases.

Evolution of tunnels in α/β-hydrolase fold proteins—What can we learn from studying epoxide hydrolases?

The evolutionary variability of a protein’s residues is highly dependent on protein region and function. Solvent-exposed residues, excluding those at interaction interfaces, are more variable than buried residues whereas active site residues are considered to be conserved. The abovementioned rules apply also to α/β-hydrolase fold proteins—one of the oldest and the biggest superfamily of enzymes with buried active sites equipped with tunnels linking the reaction site with the exterior. We selected soluble epoxide hydrolases as representative of this family to conduct the first systematic study on the evolution of tunnels. We hypothesised that tunnels are lined by mostly conserved residues, and are equipped with a number of specific variable residues that are able to respond to evolutionary pressure. The hypothesis was confirmed, and we suggested a general and detailed way of the tunnels’ evolution analysis based on entropy values calculated for tunnels’ residues. We also found three different cases of entropy distribution among tunnel-lining residues. These observations can be applied for protein reengineering mimicking the natural evolution process. We propose a ‘perforation’ mechanism for new tunnels design via the merging of internal cavities or protein surface perforation. Based on the literature data, such a strategy of new tunnel design could significantly improve the enzyme’s performance and can be applied widely for enzymes with buried active sites.

So far very little is known about proteins tunnels evolution. The goal of this study is to evaluate the evolution of tunnels in the family of soluble epoxide hydrolases—representatives of numerous α/β-hydrolase fold enzymes. As a result two types of tunnels evolution analysis were proposed (a general and a detailed approach), as well as a ‘perforation’ mechanism which can mimic native evolution in proteins and can be used as an additional strategy for enzymes redesign.

Clinical and Preclinical Evidence for Roles of Soluble Epoxide Hydrolase in Osteoarthritis Knee Pain

OBJECTIVE

Chronic pain due to osteoarthritis (OA) is a major clinical problem, and existing analgesics often have limited beneficial effects and/or adverse effects, necessitating the development of novel therapies. Epoxyeicosatrienoic acids (EETs) are endogenous antiinflammatory mediators, rapidly metabolized by soluble epoxide hydrolase (EH) to dihydroxyeicosatrienoic acids (DHETs). We undertook this study to assess whether soluble EH-driven metabolism of EETs to DHETs plays a critical role in chronic joint pain associated with OA and provides a new target for treatment.

METHODS

Potential associations of chronic knee pain with single-nucleotide polymorphisms (SNPs) in the gene-encoding soluble EH and with circulating levels of EETs and DHETs were investigated in human subjects. A surgically induced murine model of OA was used to determine the effects of both acute and chronic selective inhibition of soluble EH by N-[1-(1-oxopropy)-4-piperidinyl]-N'-(trifluoromethoxy)phenyl]-urea (TPPU) on weight-bearing asymmetry, hind paw withdrawal thresholds, joint histology, and circulating concentrations of EETs and DHETs.

RESULTS

In human subjects with chronic knee pain, 3 pain measures were associated with SNPs of the soluble EH gene EPHX2, and in 2 separate cohorts of subjects, circulating levels of EETs and DHETs were also associated with 3 pain measures. In the murine OA model, systemic administration of TPPU both acutely and chronically reversed established pain behaviors and decreased circulating levels of 8,9-DHET and 14,15-DHET. EET levels were unchanged by TPPU administration.

CONCLUSION

Our novel findings support a role of soluble EH in OA pain and suggest that inhibition of soluble EH and protection of endogenous EETs from catabolism represents a potential new therapeutic target for OA pain.

A thiol redox sensor in soluble epoxide hydrolase enables oxidative activation by intra-protein disulfide bond formation

Soluble epoxide hydrolase (sEH), an enzyme that broadly regulates the cardiovascular system, hydrolyses epoxyeicosatrienoic acids (EETs) to their corresponding dihydroxyeicosatrienoic acids (DHETs). We previously showed that endogenous lipid electrophiles adduct within the catalytic domain, inhibiting sEH to lower blood pressure in angiotensin II-induced hypertensive mice. As angiotensin II increases vascular H2O2, we explored sEH redox regulation by this oxidant and how this integrates with inhibition by lipid electrophiles to regulate vasotone. Kinetics analyses revealed that H2O2 not only increased the specific activity of sEH but increased its affinity for substrate and increased its catalytic efficiency. This oxidative activation was mediated by formation of an intra-disulfide bond between C262 and C264, as determined by mass spectrometry and substantiated by biotin-phenylarsinate and thioredoxin-trapping mutant assays. C262S/264S sEH mutants were resistant to peroxide-induced activation, corroborating the disulfide-activation mechanism. The physiological impact of sEH redox state was determined in isolated arteries and the effect of the pro-oxidant vasopressor angiotensin II on arterial sEH redox state and vasodilatory EETs indexed in mice. Angiotensin II induced the activating intra-disulfide in sEH, causing a decrease in plasma EET/DHET ratios that is consistent with the pressor response to this hormone. Although sEH C262-C264 disulfide formation enhances hydrolysis of vasodilatory EETs, this modification also sensitized sEH to inhibition by lipid electrophiles. This explains why angiotensin II decreases EETs and increases blood pressure, but when lipid electrophiles are also present, that EETs are increased and blood pressure lowered.

Alteration in antioxidant status in slow and fast alleles of EPHX1 gene polymorphisms among wood workers

Occupational wood dust exposure may be associated with various health effects, especially in wood industry. These effects may be due to inducing oxidative stress which is related to inflammations. Biochemical assessment of antioxidant enzyme activities illustrated role of oxidative stress (OS) on its depletion. Super oxide dismutase, glutathione peroxidase (GPx) and catalase (CAT) were analyzed in 50 exposed workers and 50 control subjects. Also, macrophage inflammatory protein-2 was assessed among these workers as it was produced upon dust exposure. Microsomal epoxide hydrolase (EPHX1) enzyme shared in the protective mechanism against wood dust oxidative stress. It plays a dual role in the metabolism of environmental pollutants, detoxification, and bioactivation. Gene polymorphisms of EPHX1 may be associated with variations in enzyme activity. Polymorphisms in exons 3 and 4 have resulted in either decreased (slow conjugating allele) or increased (fast conjugating allele) activity in vitro. We aimed to evaluate the associations between EPHX1 polymorphisms and change in antioxidant status (SOD, CAT, and GPx) among wood dust exposed workers. EPHX1 genotyping in exon 3 and exon 4 polymorphisms was carried out by PCR-RFLP. Our result shows a significant reduction in enzymatic antioxidants (SOD, CAT, and GPx) levels with significant rise in MIP-2 levels in worker group. Also, there are significant variations in SOD, CAT, and GPx levels as well as in MIP-2 in different genotypes of EPHX polymorphisms in exon 3 or 4 (specially in Hist-Hist genotypes in both exons). We can conclude an alteration in antioxidant status in both slow and fast allele of EPHX gene polymorphisms with release of MIP-2 protein in wood workers.

Genetic deficiency or pharmacological inhibition of soluble epoxide hydrolase ameliorates high fat diet-induced pancreatic β-cell dysfunction and loss

Pancreatic β-cells are crucial regulators of systemic glucose homeostasis, and their dysfunction and loss are central features in type 2 diabetes. Interventions that rectify β-cell dysfunction and loss are essential to combat this deadly malady. In the current study, we sought to delineate the role of soluble epoxide hydrolase (sEH) in β-cells under diet-induced metabolic stress. The expression of sEH was upregulated in murine and macaque diabetes models and islets of diabetic human patients. We postulated that hyperglycemia-induced elevation in sEH leads to a reduction in its substrates, epoxyeicosatrienoic acids (EETs), and attenuates the function of β-cells. Genetic deficiency of sEH potentiated glucose-stimulated insulin secretion in mice, likely in a cell-autonomous manner, contributing to better systemic glucose control. Consistent with this observation, genetic and pharmacological inactivation of sEH and the treatment with EETs exhibited insulinotropic effects in isolated murine islets ex vivo. Additionally, sEH deficiency enhanced glucose sensing and metabolism with elevated ATP and cAMP concentrations. This phenotype was associated with attenuated oxidative stress and diminished β-cell death in sEH deficient islets. Moreover, pharmacological inhibition of sEH in vivo mitigated, albeit partly, high fat diet-induced β-cell loss and dedifferentiation. The current observations provide new insights into the role of sEH in β-cells and information that may be leveraged for the development of a mechanism-based intervention to rectify β-cell dysfunction and loss.

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.

Association of microsomal epoxide hydrolase gene (fast genotype) with lung functions impairment in wood workers

OBJECTIVES

Exposure to wood dust may lead to impairment of the lung functions. Microsomal epoxide hydrolase enzyme (EPHX1) was shown to take part in protection against oxidative stress. An alteration in enzyme activity might be associated with its gene polymorphisms. In vitro polymorphisms in exons 3 (His113Tyr) and 4 (Arg139His) lead to reduced activity (slow allele) and increased activity (fast allele). Macrophage inflammatory protein 2 (MIP-2) is produced in rat lung epithelial cells after exposure to fine particles. We aimed to investigate the associations between mEPHX1 polymorphisms (in exon 3 and 4) and lung function in furniture workers and assessment of MIP-2 effect.

METHODS

Our study was performed on 70 wood dust exposed male workers and 70 matched normal controls subjects. Ventilatory function tests were measured by spirometer, MIP-2 was performed by ELISA methods and EPHX gene was done by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods for each participant.

RESULTS

Significant reduction in forced vital capacity (FVC%) and forced expiratory volume in the first second (FEV1) levels in Tyr-Tyr and Tyr-Hist genotypes of EPHX (exon 3) was observed. Reduced peak expiratory flow (PEF) levels and significant rise in MIP-2 levels were detected in Tyr-Tyr genotype. While high significant reduction in FVC% and FEV1 levels were shown in different genotypes in exon 4. Significant rise was observed in MIP-2 levels in Hist-Hist genotype of exon 4. An increase in duration of exposure showed positive correlation with fall in ventilatory functions.

CONCLUSIONS

It was concluded that in Hist139Arg of EPHX gene, fast genotype (Arg-Arg) was associated with impaired ventilatory functions.

Cord blood acrylamide levels and birth size, and interactions with genetic variants in acrylamide-metabolising genes

BACKGROUND

Up to now, 3 epidemiological studies have shown clear inverse associations between prenatal acrylamide exposure and birth size. In addition to studying the association between acrylamide and birth size, we investigated the interaction between acrylamide and polymorphisms in acrylamide-metabolising genes, with the aim of probing the causality of the inverse relationship between acrylamide and fetal growth.

METHODS

We investigated the association between prenatal acrylamide exposure (acrylamide and glycidamide hemoglobin adduct levels (AA-Hb and GA-Hb) in cord blood) and birth weight, length and head circumference in 443 newborns of the ENVIRONAGE (ENVIRonmental influence ON AGEing in early life) birth cohort. In addition, we studied interaction with single nucleotide polymorphisms (SNPs) in CYP2E1, EPHX1 and GSTP1, using multiple linear regression analysis.

RESULTS

Among all neonates, the body weight, length and head circumference of neonates in the highest quartile was - 101 g (95% CI: - 208, 7; p for trend = 0.12), - 0.13 cm (95% CI: - 0.62, 0.36; p for trend = 0.69) and - 0.41 cm (- 0.80, - 0.01; p for trend = 0.06) lower, respectively, compared to neonates in the lowest quartile of AA-Hb in cord blood, For GA-Hb, the corresponding effect estimates were - 222 g (95% CI: - 337, - 108; p for trend = 0.001), - 0.85 (95% CI: - 1.38, - 0.33; p for trend = 0.02) and - 0.55 (95% CI: - 0.98, - 0.11; p for trend = 0.01), respectively. The associations for GA-Hb were similar or stronger in newborns of non-smoking mothers. There was no statistically significant interaction between acrylamide exposure and the studied genetic variations but there was a trend of stronger inverse associations with birth weight and head circumference among newborns with homozygous wildtypes alleles for the CYP2E1 SNPS and with variant alleles for a GSTP1 SNP (rs1138272).

CONCLUSIONS

Prenatal dietary acrylamide exposure, specifically in the form of its metabolite glycidamide, was inversely associated with birth weight, length and head circumference. The interaction pattern with SNPs in CYP2E1, although not statistically significant, is an indication for the causality of this association. Other studies are needed to corroborate this finding.

Elevated cerebrospinal fluid cytokine levels in tuberculous meningitis predict survival in response to dexamethasone

Adjunctive treatment with antiinflammatory corticosteroids like dexamethasone increases survival in tuberculosis meningitis. Dexamethasone responsiveness associates with a C/T variant in Leukotriene A4 Hydrolase (LTA4H), which regulates expression of the proinflammatory mediator leukotriene B4 (LTB4). TT homozygotes, with increased expression of LTA4H, have the highest survival when treated with dexamethasone and the lowest survival without. While the T allele is present in only a minority of the world's population, corticosteroids confer modest survival benefit worldwide. Using Bayesian methods, we examined how pretreatment levels of cerebrospinal fluid proinflammatory cytokines affect survival in dexamethasone-treated tuberculous meningitis. LTA4H TT homozygosity was associated with global cytokine increases, including tumor necrosis factor. Association between higher cytokine levels and survival extended to non-TT patients, suggesting that other genetic variants may also induce dexamethasone-responsive pathological inflammation. These findings warrant studies that tailor dexamethasone therapy to pretreatment cerebrospinal fluid cytokine concentrations, while searching for additional genetic loci shaping the inflammatory milieu.

Machine Learning Enables Selection of Epistatic Enzyme Mutants for Stability Against Unfolding and Detrimental Aggregation

Machine learning (ML) has pervaded most areas of protein engineering, including stability and stereoselectivity. Using limonene epoxide hydrolase as the model enzyme and innov'SAR as the ML platform, comprising a digital signal process, we achieved high protein robustness that can resist unfolding with concomitant detrimental aggregation. Fourier transform (FT) allows us to take into account the order of the protein sequence and the nonlinear interactions between positions, and thus to grasp epistatic phenomena. The innov'SAR approach is interpolative, extrapolative and makes outside-the-box, predictions not found in other state-of-the-art ML or deep learning approaches. Equally significant is the finding that our approach to ML in the present context, flanked by advanced molecular dynamics simulations, uncovers the connection between epistatic mutational interactions and protein robustness.

ANTIHYPERTENSIVE AND CARDIOPROTECTIVE EFFECTS OF EPOXYEICOSATRIENOIC ACID ANALOGS AND SOLUBLE EPOXIDE HYDROLASE INHIBITORS (REVIEW)

In the present article is considered antihypertensive and cardioprotective action of epoxieicosatrienoic acids (EETs) analogues and soluble epoxide hydrolase (sEH) inhibitors. Being epoxygenase products of arachidonic acid metabolism EETs provide a wide spectrum of biological activity in different organs implicated in the regulation of arterial pressure, including vascular endothelium (VE), heart and kidney. EETs are acting as autocrine or paracrine agents producing vasodilation, reduction in salt and fluid retention. EETs exert vasodilatory properties by activation of the smooth muscle large conductance Ca2+ -activated K+ channels in different vascular beds. In experimental and clinical studies EETs provide beneficial influence in hypertensive states alleviating vascular endothelium function associated with reduction of inflammation and increased Na+ excretion, prevented cardiovascular and renal complications accompanied arterial hypertension (AH). In animals studies using Dahl-salt-sensitive (Dss) hypertensive rats EETs analogues displayed renoprotective effect, reducing mRNA expression of tumor growth factor-"B" as well as concomitant oxidative stress and fibrotic changes in the heart and kidneys. In cultered endothelial cells also was demonstrated anti-inflammatory action of EETs when they significantly decreased TNF-α-induced high level of monocyte chemoattractant protein-1, which was reversed by EETs antagonist. sEH is another new target for therapeutic intervention in cardiovascular diseases. In several experimental models of AH sEH inhibitors (sEHI) significantly reduce AP which was associated with their anti-inflammatory and renoprotective action. sEHI showed cardiovascular effect related to CYP2J2overexpression during myocardial ischemia-reperfusion injury. It should be noted that EETs demonstrate binding ability to PPAR receptor "Y" stimulating it's transcription process in endothelial cells facilitating by sEHI. It is suggested that EETs and sEH are involved in the regulation of the cardiovascular function playing significant role in vascular homeostasis.

Endothelial Nox4 dysfunction aggravates atherosclerosis by inducing endoplasmic reticulum stress and soluble epoxide hydrolase

BACKGROUND AND AIMS

Our previous findings have demonstrated the protective effect of endothelial Nox4-based NADPH oxidase on atherosclerosis. One of the possible mechanisms is the inhibition of soluble epoxide hydrolase (sEH), a proinflammatory and atherogenic factor. Our goal was to investigate whether in vivo inhibition of sEH by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) alleviates endothelial Nox4 dysfunction caused atherosclerosis and the regulatory mechanism of endothelial Nox4 on sEH.

METHODS

& results: We used endothelial human Nox4 dominant-negative (EDN) transgenic mice in ApoE deficient background to mimic the dysfunction of endothelial Nox4 in atherosclerosis-prone conditions. In EDN aortic endothelium, sEH and the inflammatory marker vascular cell adhesion molecule 1 (VCAM1) were upregulated. TPPU reduced atherosclerotic lesions in EDN mice. In EDN endothelial cells (ECs), the endoplasmic reticulum (ER) stress markers (BIP, IRE1α, phosphorylation of PERK, ATF6) were upregulated, and they can be suppressed by ER stress inhibitor 4-phenyl butyric acid (4-PBA). In EDN ECs, 4-PBA downregulated the expression of sEH and VCAM1, suppressed inflammation, and its application in vivo reduced atherosclerotic lesions of EDN mice.

CONCLUSIONS

Endothelial Nox4 dysfunction upregulated sEH to enhance inflammation, probably by its induction of ER stress. Inhibition of ER stress or sEH is beneficial to alleviate atherosclerosis caused by endothelial Nox4 dysfunction.

Mutation of an atypical oxirane oxyanion hole improves regioselectivity of the α/β-fold epoxide hydrolase Alp1U

Epoxide hydrolases (EHs) have been characterized and engineered as biocatalysts that convert epoxides to valuable chiral vicinal diol precursors of drugs and bioactive compounds. Nonetheless, the regioselectivity control of the epoxide ring opening by EHs remains challenging. Alp1U is an α/β-fold EH that exhibits poor regioselectivity in the epoxide hydrolysis of fluostatin C (compound 1) and produces a pair of stereoisomers. Herein, we established the absolute configuration of the two stereoisomeric products and determined the crystal structure of Alp1U. A Trp-186/Trp-187/Tyr-247 oxirane oxygen hole was identified in Alp1U that replaced the canonical Tyr/Tyr pair in α/β-EHs. Mutation of residues in the atypical oxirane oxygen hole of Alp1U improved the regioselectivity for epoxide hydrolysis on 1. The single site Y247F mutation led to highly regioselective (98%) attack at C-3 of 1, whereas the double mutation W187F/Y247F resulted in regioselective (94%) nucleophilic attack at C-2. Furthermore, single-crystal X-ray structures of the two regioselective Alp1U variants in complex with 1 were determined. These findings allowed insights into the reaction details of Alp1U and provided a new approach for engineering regioselective epoxide hydrolases.

Highly regio- and enantio-selective hydrolysis of two racemic epoxides by GmEH3, a novel epoxide hydrolase from Glycine max

A novel epoxide hydrolase from Glycine max, designated GmEH3, was excavated based on the computer-aided analysis. Then, gmeh3, a GmEH3-encoding gene, was cloned and successfully expressed in E. coli Rosetta(DE3). Among the ten investigated rac-epoxides, GmEH3 possessed the highest and best complementary regioselectivities (regioselectivity coefficients, αS = 93.7% and βR = 97.2%) in the asymmetric hydrolysis of rac-m-chlorostyrene oxide (5a), and the highest enantioselectivity (enantiomeric ratio, E = 55.6) towards rac-phenyl glycidyl ether (7a). The catalytic efficiency (kcatS/KmS = 2.50 mM-1 s-1) of purified GmEH3 for (S)-5a was slightly higher than that (kcatR/KmR = 1.52 mM-1 s-1) for (R)-5a, whereas the kcat/Km (5.16 mM-1 s-1) for (S)-7a was much higher than that (0.09 mM-1 s-1) for (R)-7a. Using 200 mg/mL wet cells of E. coli/gmeh3 as the biocatalyst, the scale-up enantioconvergent hydrolysis of 150 mM rac-5a at 25 °C for 1.5 h afforded (R)-5b with 90.2% eep and 95.4% yieldp, while the kinetic resolution of 500 mM rac-7a for 2.5 h retained (R)-7a with over 99% ees and 43.2% yields. Furthermore, the sources of high regiocomplementarity of GmEH3 for (S)- and (R)-5a as well as high enantioselectivity towards rac-7a were analyzed via molecular docking (MD) simulation.

14,15-Epoxyeicosatrienoic Acid Alleviates Pathology in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of late-onset dementia, and there exists an unmet medical need for effective treatments for AD. The accumulation of neurotoxic amyloid-β (Aβ) plaques contributes to the pathophysiology of AD. EPHX2 encoding soluble epoxide hydrolase (sEH)-a key enzyme for epoxyeicosatrienoic acid (EET) signaling that is mainly expressed in lysosomes of astrocytes in the adult brain-is cosited at a locus associated with AD, but it is unclear whether and how it contributes to the pathophysiology of AD. In this report, we show that the pharmacologic inhibition of sEH with 1-trifluoromethoxyphenyl- 3-(1-propionylpiperidin-4-yl) urea (TPPU) or the genetic deletion of Ephx2 reduces Aβ deposition in the brains of both male and female familial Alzheimer's disease (5×FAD) model mice. The inhibition of sEH with TPPU or the genetic deletion of Ephx2 alleviated cognitive deficits and prevented astrocyte reactivation in the brains of 6-month-old male 5×FAD mice. 14,15-EET levels in the brains of these mice were also increased by sEH inhibition. In cultured adult astrocytes treated with TPPU or 14,15-EET, astrocyte Aβ clearance was increased through enhanced lysosomal biogenesis. Infusion of 14,15-EET into the hippocampus of 5×FAD mice prevented the aggregation of Aβ. Notably, a higher concentration of 14,15-EET (200 ng/ml) infusion into the hippocampus reversed Aβ deposition in the brains of 6-month-old male 5×FAD mice. These results indicate that EET signaling, especially 14,15-EET, plays a key role in the pathophysiology of AD, and that targeting this pathway is a potential therapeutic strategy for the treatment of AD.SIGNIFICANCE STATEMENT There are limited treatment options for Alzheimer's disease (AD). EPHX2 encoding soluble epoxide hydrolase (sEH) is located at a locus that is linked to late-onset AD, but its contribution to the pathophysiology of AD is unclear. Here, we demonstrate that sEH inhibition or Ephx2 deletion alleviates pathology in familial Alzheimer's disease (5×FAD) mice. Inhibiting sEH or increasing 14,15-epoxyeicosatrienoic acid (EET) enhanced lysosomal biogenesis and amyloid-β (Aβ) clearance in cultured adult astrocytes. Moreover, the infusion of 14,15-EET into the hippocampus of 5×FAD mice not only prevented the aggregation of Aβ, but also reversed the deposition of Aβ. Thus, 14,15-EET plays a key role in the pathophysiology of AD and therapeutic strategies that target this pathway may be an effective treatment.

Identification and catalytic properties of new epoxide hydrolases from the genomic data of soil bacteria

Epoxide hydrolases (EHs) catalyse the conversion of epoxides into vicinal diols. These enzymes have extensive value in biocatalysis as they can generate enantiopure epoxides and diols which are important and versatile synthetic intermediates for the fine chemical and pharmaceutical industries. Despite these benefits, they have seen limited use in the bioindustry and novel EHs continue to be reported in the literature. We identified twenty-nine putative EHs within the genomes of soil bacteria. Eight of these EHs were explored in terms of their activity. Two limonene epoxide hydrolases (LEHs) and one ⍺/β EH were active on a model compound styrene oxide and its ring-substituted derivatives, with low to good percentage conversions of 18-86%. Further exploration of the substrate scope with enantiopure (R)-styrene oxide and (S)-styrene oxide, showed different epoxide ring opening regioselectivities. Two enzymes, expressed from plasmids pQR1984 and pQR1990 de-symmetrised the meso-epoxide cyclohexene oxide, forming the (R,R)-diol with high enantioselectivity. Two LEHs, from plasmids pQR1980 and pQR1982 catalysed the hydrolysis of (+) and (-) limonene oxide, with diastereomeric preference for the (1S,2S,4R)- and (1R,2R,4S)-diol products, respectively. The enzyme from plasmid pQR1982 had a good substrate scope for a LEH, being active towards styrene oxide, its analogues, cyclohexene oxide and 1,2-epoxyhexane in addition to (±)-limonene oxide. The enzymes from plasmids pQR1982 and pQR1984 had good substrate scopes and their enzymatic properties were characterised with respect to styrene oxide. They had comparable temperature optima and pQR1984 had 70% activity in the presence of 40% of the green solvent MeOH, a useful property for bio-industrial applications. Overall, this study has provided novel EHs with potential value in industrial biocatalysis.

Identification of Human Leukotriene A4 Hydrolase Inhibitors Using Structure-Based Pharmacophore Modeling and Molecular Docking

Leukotriene B4 (LTB4) is a potent, proinflammatory lipid mediator implicated in the pathologies of an array of inflammatory diseases and cancer. The biosynthesis of LTB4 is regulated by the leukotriene A4 hydrolase (LTA₄H). Compounds capable of limiting the formation of LTB4, through selective inhibition of LTA₄H, are expected to provide potent anti-inflammatory and anti-cancer agents. The aim of the current study is to obtain potential LTA₄H inhibitors using computer-aided drug design. A hybrid 3D structure-based pharmacophore model was generated based on the crystal structure of LTA₄H in complex with bestatin. The generated pharmacophore was used in a virtual screen of the Maybridge database. The retrieved hits were extensively filtered, then docked into the active site of the enzyme. Finally, they were consensually scored to yield five hits as potential LTA₄H inhibitors. Consequently, the selected hits were purchased and their biological activity assessed in vitro against the epoxide hydrolase activity of LTA₄H. The results were very promising, with the most active compound showing 73.6% inhibition of the basal epoxide hydrolase activity of LTA₄H. The results from this exploratory study provide valuable information for the design and development of more potent and selective inhibitors.

A novel interaction between soluble epoxide hydrolase and the AT1 receptor in retinal microvascular damage

Clinical studies have suggested that the renin-angiotensin system (RAS) may be a promising therapeutic target in treating diabetic retinopathy (DR). While AT1 receptor blockade decreased the incidence of DR in the DIRECT trial, it did not reduce the DR progression. Lack of understanding of the molecular mechanism of retinal microvascular damage induced by RAS is a critical barrier to the use of RAS blockade in preventing or treating DR. The purpose of this study is to investigate the interaction between soluble epoxide hydrolase (sEH) and the AT1 receptor in Angiotensin II (Ang II)- and diabetes-induced retinal microvascular damage. We demonstrate that Ang II increases retinal sEH levels, which is blunted by an AT1 blocker; administration of 11,12-epoxyeicosatrienoic acid (EET) exacerbates intravitreal Ang II-induced retinal albumin leakage; while sEH knockout (KO) and blockade reduce Ang II-induced retinal vascular remodeling, sEH KO causes retinal vascular leakage in Ang II-sEH KO mice; and sEH KO potentiates diabetes-induced retinal damage via promoting retinal vascular endothelial growth factor (VEGF) but reducing expression of tight junction proteins (ZO-1 and occludin). Our studies hold the promise of providing a new strategy, the use of combined EETs blockade with AT1 blocker, to prevent or reduce DR.

Single-Nucleotide Polymorphisms (SNPs) Both Associated with Hypertension and Contributing to Accelerated-Senescence Traits in OXYS Rats

Aging is a major risk factor of numerous human diseases. Adverse genetic variants may contribute to multiple manifestations of aging and increase the number of comorbid conditions. There is evidence of links between hypertension and age-related diseases, although the genetic relationships are insufficiently studied. Here, we investigated the contribution of hypertension to the development of accelerated-senescence syndrome in OXYS rats. We compared transcriptome sequences of the prefrontal cortex, hippocampus, and retina of OXYS rats with the genotypes of 45 rat strains and substrains (which include models with hypertension) to find single-nucleotide polymorphisms (SNPs) both associated with hypertension and possibly contributing to the development of age-related diseases. A total of 725 polymorphisms were common between OXYS rats and one or more hypertensive rat strains/substrains being analyzed. Multidimensional scaling detected significant similarities between OXYS and ISIAH rat genotypes and significant differences between these strains and the other hypertensive rat strains/substrains. Nonetheless, similar sets of SNPs produce a different phenotype in OXYS and ISIAH rats depending on hypertension severity. We identified 13 SNPs causing nonsynonymous amino-acid substitutions having a deleterious effect on the structure or function of the corresponding proteins and four SNPs leading to functionally significant structural rearrangements of transcripts in OXYS rats. Among them, SNPs in genes Ephx1, Pla2r1, and Ccdc28b were identified as candidates responsible for the concomitant manifestation of hypertension and signs of accelerated aging in OXYS rats.

Computational Design of Enantiocomplementary Epoxide Hydrolases for Asymmetric Synthesis of Aliphatic and Aromatic Diols

The use of enzymes in preparative biocatalysis often requires tailoring enzyme selectivity by protein engineering. Herein we explore the use of computational library design and molecular dynamics simulations to create variants of limonene epoxide hydrolase that produce enantiomeric diols from meso‐epoxides. Three substrates of different sizes were targeted: cis‐2,3‐butene oxide, cyclopentene oxide, and cis‐stilbene oxide. Most of the 28 designs tested were active and showed the predicted enantioselectivity. Excellent enantioselectivities were obtained for the bulky substrate cis‐stilbene oxide, and enantiocomplementary mutants produced (S,S)‐ and (R,R)‐stilbene diol with >97 % enantiomeric excess. An (R,R)‐selective mutant was used to prepare (R,R)‐stilbene diol with high enantiopurity (98 % conversion into diol, >99 % ee). Some variants displayed higher catalytic rates (k_cat) than the original enzyme, but in most cases K_M values increased as well. The results demonstrate the feasibility of computational design and screening to engineer enantioselective epoxide hydrolase variants with very limited laboratory screening.

Dual Farnesoid X Receptor/Soluble Epoxide Hydrolase Modulators Derived from Zafirlukast

The nuclear farnesoid X receptor (FXR) and the enzyme soluble epoxide hydrolase (sEH) are validated molecular targets to treat metabolic disorders such as non-alcoholic steatohepatitis (NASH). Their simultaneous modulation in vivo has demonstrated a triad of anti-NASH effects and thus may generate synergistic efficacy. Here we report dual FXR activators/sEH inhibitors derived from the anti-asthma drug Zafirlukast. Systematic structural optimization of the scaffold has produced favorable dual potency on FXR and sEH while depleting the original cysteinyl leukotriene receptor antagonism of the lead drug. The resulting polypharmacological activity profile holds promise in the treatment of liver-related metabolic diseases.

The effect on congenital heart diseases of maternal EPHX1 polymorphisms modified by polycyclic aromatic hydrocarbons exposure

Polycyclic aromatic hydrocarbons (PAHs) may be 1 of etiologic factors responsible for congenital heart diseases (CHDs). Variations of the microsomal epoxide hydrolase (EPHX1) gene, as well as their possible interactions with PAHs exposure, may increase susceptibility to CHDs.This case-control study investigated the risk of CHDs in relation to the EPHX1 polymorphisms and assessed the interactions between these polymorphisms and PAHs exposure in 357 mothers of CHDs fetuses and 270 control mothers. Logistic regression models for the risk of CHDs were applied to determine the effect of genetic polymorphisms using additive, recessive, and dominant genetic models, as well as gene-exposure interactions. Multiple testing was adjusted by applying the false discovery rate (FDR).None of the maternal genetic polymorphisms of EPHX1 was associated with CHDs occurrence. Only the single nucleotide polymorphism rs1051740 was associated with an increased risk of right-sided obstructive malformations under the recessive model (adjusted odds ratio [aOR] = 1.852, 95% confidence interval [CI]: 1.065, 3.22) before FDR correction. A possible modifying effect of PAHs exposure on genetic polymorphisms of EPHX1 was found in susceptibility to CHDs, though no multiplicative-scale interactions between maternal exposure to PAHs and polymorphisms of EPHX1 gene were seento affect the risk of CHDs.The role of EPHX1 gene polymorphisms for CHDs need to be further evaluated, in particularly by interacting with PAHs exposure.

15-deoxy-Δ12,14-Prostaglandin J2 inhibits human soluble epoxide hydrolase by a dual orthosteric and allosteric mechanism

Human soluble epoxide hydrolase (hsEH) is an enzyme responsible for the inactivation of bioactive epoxy fatty acids, and its inhibition is emerging as a promising therapeutical strategy to target hypertension, cardiovascular disease, pain and insulin sensitivity. Here, we uncover the molecular bases of hsEH inhibition mediated by the endogenous 15-deoxy-Δ12,14-Prostaglandin J2 (15d-PGJ2). Our data reveal a dual inhibitory mechanism, whereby hsEH can be inhibited by reversible docking of 15d-PGJ2 in the catalytic pocket, as well as by covalent locking of the same compound onto cysteine residues C423 and C522, remote to the active site. Biophysical characterisations allied with in silico investigations indicate that the covalent modification of the reactive cysteines may be part of a hitherto undiscovered allosteric regulatory mechanism of the enzyme. This study provides insights into the molecular modes of inhibition of hsEH epoxy-hydrolytic activity and paves the way for the development of new allosteric inhibitors.

A machine learning approach for reliable prediction of amino acid interactions and its application in the directed evolution of enantioselective enzymes

Directed evolution is an important research activity in synthetic biology and biotechnology. Numerous reports describe the application of tedious mutation/screening cycles for the improvement of proteins. Recently, knowledge-based approaches have facilitated the prediction of protein properties and the identification of improved mutants. However, epistatic phenomena constitute an obstacle which can impair the predictions in protein engineering. We present an innovative sequence-activity relationship (innov'SAR) methodology based on digital signal processing combining wet-lab experimentation and computational protein design. In our machine learning approach, a predictive model is developed to find the resulting property of the protein when the n single point mutations are permuted (2n combinations). The originality of our approach is that only sequence information and the fitness of mutants measured in the wet-lab are needed to build models. We illustrate the application of the approach in the case of improving the enantioselectivity of an epoxide hydrolase from Aspergillus niger. n = 9 single point mutants of the enzyme were experimentally assessed for their enantioselectivity and used as a learning dataset to build a model. Based on combinations of the 9 single point mutations (29), the enantioselectivity of these 512 variants were predicted, and candidates were experimentally checked: better mutants with higher enantioselectivity were indeed found.

Eicosanoid signaling in carcinogenesis of colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death in the USA. It is of practical importance to identify novel therapeutic targets of CRC to develop new anti-cancer drugs and to discover novel biomarkers of CRC to develop new detection methods. Eicosanoids, which are metabolites of polyunsaturated fatty acids produced by cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) enzymes, are important lipid-signaling molecules involved in the regulation of inflammation and tumorigenesis. Substantial studies have shown that the profiles of eicosanoids are deregulated in CRC, and the enzymes, metabolites, and receptors in the eicosanoid signaling cascade play critical roles in regulating colonic inflammation and colon tumorigenesis. In this review, we discuss the roles of the COX, LOX, and CYP pathways in the carcinogenesis of CRC.

Leukotriene biosynthetic enzymes as therapeutic targets

Leukotrienes are powerful immune-regulating lipid mediators with established pathogenic roles in inflammatory allergic diseases of the respiratory tract - in particular, asthma and hay fever. More recent work indicates that these lipids also contribute to low-grade inflammation, a hallmark of cardiovascular, neurodegenerative, and metabolic diseases as well as cancer. Biosynthesis of leukotrienes involves oxidative metabolism of arachidonic acid and proceeds via a set of soluble and membrane enzymes that are primarily expressed by cells of myeloid origin. In activated immune cells, these enzymes assemble at the endoplasmic and perinuclear membrane, constituting a biosynthetic complex. This Review describes recent advances in our understanding of the components of the leukotriene-synthesizing enzyme machinery, emerging opportunities for pharmacological intervention, and the development of new medicines exploiting both antiinflammatory and pro-resolving mechanisms.

Inhibition of Soluble Epoxide Hydrolase 2 Ameliorates Diabetic Keratopathy and Impaired Wound Healing in Mouse Corneas

EPHX2 (encoding soluble epoxide hydrolase [sEH]) converts biologically active epoxyeicosatrienoic acids (EETs), anti-inflammatory and profibrinolytic effectors, into the less biologically active metabolites, dihydroxyeicostrienoic acids. We sought to characterize the expression and the function of EPHX2 in diabetic corneas and during wound healing. The expression of EPHX2 at both mRNA and protein levels, as well as sEH enzymatic activity, was markedly upregulated in the tissues/cells, including corneal epithelial cells as well as the retina of human type 2 and mouse type 1 (streptozotocin [STZ] induced) and/or type 2 diabetes. Ephx2 depletion had no detectable effects on STZ-induced hyperglycemia but prevented the development of tear deficiency. Ephx2-/- mice showed an acceleration of hyperglycemia-delayed epithelium wound healing. Moreover, inhibition of sEH increased the rate of epithelium wound closure and restored hyperglycemia-suppressed STAT3 activation and heme oxygenase-1 (HO-1) expression in the diabetic corneas. Treatment of diabetic corneas with cobalt protoporphyrin, a well-known HO-1 inducer, restored wound-induced HO-1 upregulation and accelerated delayed wound healing. Finally, Ephx2 depletion enhanced sensory innervation and regeneration in diabetic corneas at 1 month after epithelial debridement. Our data suggest that increased sEH activity may be a contributing factor for diabetic corneal complications; targeting sEH pharmacologically or supplementing EETs may represent a new, adjunctive therapy for treating diabetic keratopathy.

Sensitivity of Arbor Acres broilers and chemoprevention of aflatoxin B1-induced liver injury by curcumin, a natural potent inducer of phase-II enzymes and Nrf2

In this study, we scrutinized the effects of curcumin and AFB₁ supplemented diet alone or in combination on phase-ӀӀ enzymes. Histopathological examination showed that after 28 days, AFB1 (5.0 mg/kg diet) induced liver injury in broilers, but curcumin supplementation partially ameliorated liver injury in a dose-dependent manner. RT-PCR data revealed that AFB₁ significantly (p < 0.01) down-regulated Nrf2 and its downstream genes mRNA expression level. Moreover, Western blot analysis showed that Nrf2, GSTM2, and GSTA3 protein expression level was markedly (p < 0.01) reduced in AFB₁-fed group. However, curcumin supplementation ameliorated AFB₁-induced liver injury via enhancing phase-ӀӀ enzymes expressions and activity. HPLC results showed that curcumin increased AFB₁-GSH conjugation in-vitro in liver cytosol. Surprisingly, similar trends were noted in mRNA, protein expression level of Nrf2 and its downstream genes at day 35, one week after the withdrawal of AFB₁ and curcumin from the diet, showing the preventive effects of curcumin.

Co-exposure to environmental carcinogens in vivo induces neoplasia-related hallmarks in low-genotoxicity events, even after removal of insult

Addressing the risk of mixed carcinogens in vivo under environmentally-realistic scenarios is still a challenge. Searching for adequate biomarkers of exposure requires understanding molecular pathways and their connection with neoplasia-related benchmark pathologies. Subjecting the zebrafish model to realistic concentrations of two genotoxicants and carcinogens, cadmium and benzo[a]pyrene, isolated and combined, yielded low levels of DNA damage. Altogether, the organisms' mechanisms of DNA repair, oxidative stress and phases I and II were not overwhelmed after two weeks of treatment. Still, transcriptional responses related to detoxification (epoxide hydrolase and UDP-glucuronosyltransferase) were higher in animals subjected to the combination treatment, inclusively following depuration. Nonetheless, inflammation and formation of hyperplasic foci in fish epithelia were more severe in animals exposed to the combined substances, showing slower recovery during depuration. Additionally, the combination treatment yielded unexpected increased expression of a ras-family oncogene homologue after depuration, with evidence for increased tp53 counter-response in the same period. The findings indicate that oncogene expression, cell proliferation and inflammation, may not require noticeable DNA damage to occur. Furthermore, albeit absent proof for neoplasic growth, the removal of chemical insult may promote tissue recovery but does not entirely clear molecular and histopathological endpoints that are commonly associated to neoplasia.

Association of EPHX2 R287Q Polymorphism with Diabetic Nephropathy in Chinese Type 2 Diabetic Patients

The aim of this study was to investigate the relationship between EPHX2 rs751141 (R287Q polymorphism) and diabetic nephropathy (DN) in Chinese type 2 diabetes (T2D). This case-control study explored the association between EPHX2 rs751141 and DN in a total of 870 Chinese T2D patients (406 T2D patients with DN and 464 T2D patients without DN). DNA was extracted from peripheral leukocytes of the patients and rs751141 was genotyped. The A allele frequency of rs751141 was significantly lower in DN patients (20.94%) compared with non-DN controls (27.8%) (P = 0.001), and the A allele of rs751141 was associated with a significantly lower risk of DN after adjustment for multiple covariates in the additive genetic model (OR = 0.68, 95% CI = 0.52-0.88, P = 0.004). Significant association between rs751141 and homocysteine (Hcy) level on the risk of DN was observed, indicating that in patients with the highest Hcy levels, the A allele showed marked association with lower risk of DN in all three genetic models. In conclusion, the A allele of exonic polymorphism in EPHX2 rs751141 is negatively associated with the incidence of DN in the Chinese T2D population, which could be modulated by Hcy level status.

Maternal Smoking during Early Pregnancy, GSTP1 and EPHX1 Variants, and Risk of Isolated Orofacial Clefts

Objective:

To examine the interactions between four fetal xenobiotic metabolizing gene polymorphisms, maternal cigarette smoking, and risk for oral cleft defects.

Design and Participants:

California population–based case-control study of 431 infants born with isolated orofacial clefts and 299 nonmalformed controls.

Main Outcome Measures:

Infants were genotyped for functional polymorphisms of the detoxification enzymes microsomal epoxide hydrolase-1 (EPHX1 T→C [Tyr113His], and A→G [His139Arg]), and glutathione-S transferase Pi-1 (GSTP1 A→G [Ile105Val] and C→T [Ala114Val]), and risks for cleft outcomes were measured for gene only and gene-maternal smoking effects.

Results:

Although smoking was associated with an increased risk for isolated cleft lip ± palate, we found no independent associations of genotypes of EPHX1-codon 113 or GSTP1-codon 105 polymorphisms for either isolated cleft lip ± palate or isolated cleft palate. The heterozygote genotype for the EPHX1-codon 139 polymorphism was associated with an increased risk of isolated cleft palate (odds ratio = 1.6 [95% confidence interval, 1.0 to 2.6]). Infant EPHX1 and GTSP1 polymorphic variants did not appreciably alter the risks for clefts associated with maternal smoking, nor were any EPHX1 combined genotype-specific risks found. Infant genotypes of the GSTP1-codon 105 polymorphism, combined with glutathione-S-transferase-μ-1 null genotypes, did not appreciably alter the risk of orofacial clefts.

Conclusions:

Our results suggest that genetic variation of the detoxification enzymes EPHX1 and GSTP1 did not increase the risks of orofacial clefting, nor do they influence the risks associated with maternal smoking.

Association of prenatal passive smoking and metabolic gene polymorphisms with child growth from birth to 3years of age in the Hokkaido Birth Cohort Study on Environment and Children's Health

Although the effects of prenatal passive smoking on birth weight have been reported, the effects of metabolic gene polymorphisms on passive smoking have not been studied. Therefore, we investigated the effects of maternal passive smoking and metabolic gene polymorphisms on child growth up to 3years of age using cotinine as a biomarker. We included 1356 Japanese participants in a prospective cohort between 2003 and 2007 (cotinine levels at the third trimester≤0.21ng/mL and 0.22 to 11.48ng/mL for non-passive and passive smokers, respectively), and measured child outcomes such as weight, length, head circumference, and Kaup index. Additionally, we analyzed cytochrome P450 1A1 (CYP1A1), epoxide hydrolase 1 (EPHX1), and two N-acetyltransferase 2 (NAT2) genotypes using real-time polymerase chain reaction methods. Associations were investigated using multiple regression models. Kaup index gain from birth up to 3years of age was significantly smaller in children born to passive smokers than in those born to non-passive smokers (-0.34kg/m²; 95% confidence interval: -0.67, -0.01). Maternal CYP1A1 genotype was not associated with prenatal passive smoking and Kaup index gain, but was significantly associated with prenatal passive smoking and head circumference gain from birth up to 3years of age (-0.75cm; 95% confidence interval: -1.39, -0.12). Thus, this study suggests that prenatal passive smoking may have potent effects on postnatal growth from birth up to 3years of age. Moreover, children with maternal CYP1A1 genotype may be more susceptible to the effects of prenatal passive smoking.

Stereoselective Hydrolysis of Epoxides by reVrEH3, a Novel Vigna radiata Epoxide Hydrolase with High Enantioselectivity or High and Complementary Regioselectivity

To provide more options for the stereoselective hydrolysis of epoxides, an epoxide hydrolase (VrEH3) gene from Vigna radiata was cloned and expressed in Escherichia coli. Recombinant VrEH3 displayed the maximum activity at pH 7.0 and 45 °C and high stability at pH 4.5-7.5 and 55 °C. Notably, reVrEH3 exhibited high and complementary regioselectivity toward styrene oxides 1a-3a and high enantioselectivity (E = 48.7) toward o-cresyl glycidyl ether 9a. To elucidate these interesting phenomena, the interactions of the three-dimensional structure between VrEH3 and enantiomers of 1a and 9a were analyzed by molecular docking simulation. Using E. coli/vreh3 whole cells, gram-scale preparations of (R)-1b and (R)-9a were performed by enantioconvergent hydrolysis of 100 mM rac-1a and kinetic resolution of 200 mM rac-9a in the buffer-free water system at 25 °C. These afforded (R)-1b with >99% ee_p and 78.7% overall yield after recrystallization and (R)-9a with >99% ee_s, 38.7% overall yield, and 12.7 g/L/h space-time yield.

Silencing of juvenile hormone epoxide hydrolase gene (Nljheh) enhances short wing formation in a macropterous strain of the brown planthopper, Nilaparvata lugens

The rice brown planthopper, Nilaparvata lugens, is an important migratory pest in many rice planting areas of Asia. The typical wing dimorphism of N. lugens gives them flexibility to adapt to different environmental cues. As an important hormone in the insect's endocrine regulation, juvenile hormone (JH) has previously been shown to participate in the wing morph determination of N. lugens. In this paper, we investigated the possible wing morph determination roles of two JH metabolic enzymes, JH esterase (JHE) and JH epoxide hydrolase (JHEH). A 1957-bp full-length cDNA sequence encoding JHEH in N. lugens (NlJHEH) was first cloned from a hemipteran insect. Except for an uncertain transmembrane segment prediction, the deduced 454-amino-acid sequence of Nljheh has all of the conserved domains of JHEHs such as the H¹⁴⁷GWP¹⁵⁰, Tyr293 and Tyr368 motif corresponding to the oxyanion hole and the residues Asp222, Glu398, and His425 in the catalytic triad. qRT-PCR results showed that both Nljhe and Nljheh had different expression timeframes between a predominantly brachypterous strain (BS) and a macropterous strain (MS) of N. lugens, indicating that these two enzymes may participate in wing dimorphism regulation in brown planthopper. Silencing Nljheh expression by dsRNA injection enhanced short wing formation in the macropterous strain of N. lugens, while the brachypterizing individuals were mainly females. Compared to the dsgfp injection control, silencing Nljhe had no brachypterizing effect. Our results indicated that NlJHEH plays an important role in the wing morph determination of N. lugens.

LTA4H regulates cell cycle and skin carcinogenesis

Leukotriene A4 hydrolase (LTA4H), a bifunctional zinc metallo-enzyme, is reportedly overexpressed in several human cancers. Our group has focused on LTA4H as a potential target for cancer prevention and/or therapy. In the present study, we report that LTA4H is a key regulator of cell cycle at the G0/G1 phase acting by negatively regulating p27 expression in skin cancer. We found that LTA4H is overexpressed in human skin cancer tissue. Knocking out LTA4H significantly reduced skin cancer development in the 7,12-dimethylbenz(a)anthracene (DMBA)-initiated/12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted two-stage skin cancer mouse model. LTA4H depletion dramatically decreased anchorage-dependent and -independent skin cancer cell growth by inducing cell cycle arrest at the G0/G1 phase. Moreover, our findings showed that depletion of LTA4H enhanced p27 protein stability, which was associated with decreased phosphorylation of CDK2 at Thr160 and inhibition of the CDK2/cyclin E complex, resulting in down-regulated p27 ubiquitination. These findings indicate that LTA4H is critical for skin carcinogenesis and is an important mediator of cell cycle and the data begin to clarify the mechanisms of LTA4H's role in cancer development.

Arabidopsis thaliana EPOXIDE HYDROLASE1 (AtEH1) is a cytosolic epoxide hydrolase involved in the synthesis of poly-hydroxylated cutin monomers

Epoxide hydrolases (EHs) are present in all living organisms. They have been extensively characterized in mammals; however, their biological functions in plants have not been demonstrated. Based on in silico analysis, we identified AtEH1 (At3g05600), a putative Arabidopsis thaliana epoxide hydrolase possibly involved in cutin monomer synthesis. We expressed AtEH1 in yeast and studied its localization in vivo. We also analyzed the composition of cutin from A. thaliana lines in which this gene was knocked out. Incubation of recombinant AtEH1 with epoxy fatty acids confirmed its capacity to hydrolyze epoxides of C18 fatty acids into vicinal diols. Transfection of Nicotiana benthamiana leaves with constructs expressing AtEH1 fused to enhanced green fluorescent protein (EGFP) indicated that AtEH1 is localized in the cytosol. Analysis of cutin monomers in loss-of-function Ateh1-1 and Ateh1-2 mutants showed an accumulation of 18-hydroxy-9,10-epoxyoctadecenoic acid and a concomitant decrease in corresponding vicinal diols in leaf and seed cutin. Compared with wild-type seeds, Ateh1 seeds showed delayed germination under osmotic stress conditions and increased seed coat permeability to tetrazolium red. This work reports a physiological role for a plant EH and identifies AtEH1 as a new member of the complex machinery involved in cutin synthesis.