Redox Regulation of Soluble Epoxide Hydrolase by 15-Deoxy-Δ-Prostaglandin J ₂ Controls Coronary Hypoxic Vasodilation

Abstract

Rationale 15-deoxy-Δ-prostaglandin J2 (15d-PGJ2) is an electrophilic oxidant that dilates the coronary vasculature. This lipid can adduct to redox active protein thiols to induce oxidative post-translational modifications that modulate protein and tissue function. Objective To investigate the role of oxidative protein modifications in 15d-PGJ2-mediated coronary vasodilation and define the distal signaling pathways leading to enhanced perfusion. Methods and Results Proteomic screening with biotinylated 15d-PGJ2 identified novel vascular targets to which it adducts, most notably soluble Epoxide Hydrolase (sEH). 15d-PGJ2 inhibited sEH by specifically adducting to a highly conserved thiol (Cys521) adjacent to the catalytic centre of the hydrolase. Indeed a Cys521Ser sEH ‘redox-dead’ mutant was resistant to 15d-PGJ2-induced hydrolase inhibition.15d-PGJ2 dilated coronary vessels and a role for hydrolase inhibition was supported by two structurally different sEH antagonists each independently inducing vasorelaxation. Furthermore, 15d-PGJ2 and sEH antagonists also increased coronary effluent epoxyeicosatrienoic acids (EETs) consistent with their vasodilatory actions. Indeed 14,15 EET alone induced relaxation and 15d-PGJ2-mediated vasodilation was blocked by the EET receptor antagonist 14,15-EEZE. Additionally the coronary vasculature of sEH null mice was basally dilated compared to wild-type controls and failed to vasodilate in response to 15d-PGJ2. Coronary vasodilation to hypoxia in wild-types was accompanied by 15d-PGJ2 adduction to and inhibition of sEH. Consistent with the importance of hydrolase inhibition sEH null mice failed to vasodilate during hypoxia. Conclusion This represents a new paradigm for the regulation of sEH by an endogenous lipid, which is integral to the fundamental physiological response of coronary hypoxic vasodilation.

Protection from hypertension in mice by the Mediterranean diet is mediated by nitro fatty acid inhibition of soluble epoxide hydrolase

“…Consequently, sEH activity was measured in heart tissue, where NO 2 -OA treatment was observed to inhibit hydrolase activity in WT but not KI. It was also noted that the sEH activity in the KI was slightly less than WT, consistent with previous studies in transfected cells where it was observed that the cysteine-to-serine mutation similarly reduced EET hydrolysis (1). This suggests the explanation that the Cys521 thiol may provide protons necessary for EET hydrolysis and the addition of electrophiles to this thiol abrogates catalytic activity.…”

“…This "redox-inactive" sEH thiol mutant, rendered insensitive to adductive inhibition by lipid electrophiles in vitro, provided a novel model system for testing the impact of lipid nitroalkenes on sEH hydrolysis of vasoactive EET species and downstream physiological responses (1). The data reveal that nitro fatty acids, applied exogenously as a pharmacological agent or generated endogenously as part of the Mediterranean diet, inhibit sEH to elevate plasma EETs, which in turn lower BP.…”

“…This cysteine can undergo Michael addition with electrophilic lipids, which inhibits hydrolysis of the enzyme's epoxyeicosatrienoic acid (EET) substrates (1). This in turn elevates EET levels, which mediate blood vessel dilation and lowers blood pressure (BP), especially in the setting of hypertension (2,3).…”

“…The endogenous lipid electrophile 10-nitrooctadec-9-enoic acid (nitro-oleic acid, NO 2 -OA) inhibits sEH in vitro (1). NO 2 -OA and other fatty acid nitroalkenes appear to signal via pleiotropic mechanisms including targeting and activating peroxisome proliferator-activated receptor gamma (PPARγ), the Kelch-like erythroid cell-derived protein with CNC homology (EHC)-associated protein-1 (Keap1), and nuclear factor (erythroidderived)-like-2 (Nrf2)-regulated antioxidant response genes and inhibiting proinflammatory gene expression regulated by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) (15,16).…”

Metabolomic Profiling of Lipids for Biomarker Discovery

“…This indicates that the ratios of EpETrEs/DiHETrEs are closely related with the function of sEHI. Other studies using lipids metabolic profiling also revealed that either the ratios of EpETrEs/ DiHETrEs or the increased EpETrEs is correlated with sEHI treatment and may be used as a potential biomarker to evaluate the engagement of sEHI [13][14][15][16][17].…”