Deletion of soluble epoxide hydrolase enhances coronary reactive hyperemia in isolated mouse heart: role of oxylipins and PPARγ

Abstract

The relationship between soluble epoxide hydrolase (sEH) and coronary reactive hyperemia (CRH) response to a brief ischemic insult is not known. Epoxyeicosatrienoic acids (EETs) exert cardioprotective effects in ischemia/reperfusion injury. sEH converts EETs into dihydroxyeicosatrienoic-acids (DHETs). Therefore, we hypothesized that knocking out sEH enhances CRH through modulation of oxylipin profiles, including an increase in EET/DHET ratio. Compared with sEH, sEH mice showed enhanced CRH, including greater repayment volume (RV; 28% higher, P < 0.001) and repayment/debt ratio (32% higher, P < 0.001). Oxylipins from the heart perfusates were analyzed by LC-MS/MS. The 14,15-EET/14,15-DHET ratio was 3.7-fold higher at baseline (P < 0.001) and 5.6-fold higher post-ischemia (P < 0.001) in sEH compared with sEH mice. Likewise, the baseline 9,10- and 12,13-EpOME/DiHOME ratios were 3.2-fold (P < 0.01) and 3.7-fold (P < 0.001) higher, respectively in sEH compared with sEH mice. 13-HODE was also significantly increased at baseline by 71% (P < 0.01) in sEH vs. sEH mice. Levels of 5-, 11-, 12-, and 15-hydroxyeicosatetraenoic acids were not significantly different between the two strains (P > 0.05), but were decreased postischemia in both groups (P = 0.02, P = 0.04, P = 0.05, P = 0.03, respectively). Modulation of CRH by peroxisome proliferator-activated receptor gamma (PPARγ) was demonstrated using a PPARγ-antagonist (T0070907), which reduced repayment volume by 25% in sEH (P < 0.001) and 33% in sEH mice (P < 0.01), and a PPARγ-agonist (rosiglitazone), which increased repayment volume by 37% in both sEH (P = 0.04) and sEH mice (P = 0.04). l-NAME attenuated CRH in both sEH and sEH These data demonstrate that genetic deletion of sEH resulted in an altered oxylipin profile, which may have led to an enhanced CRH response.

Vascular endothelial overexpression of human CYP2J2 (Tie2-CYP2J2 Tr) modulates cardiac oxylipin profiles and enhances coronary reactive hyperemia in mice

“…Physiological levels of EpOMEs protected against hypoxia/reoxygenation injury [20, 22], whereas their hydrated metabolites, DiHOMEs, may have been shown to be less active or cytotoxic [7, 20, 27]. The changes in oxylipin levels and CRH in Tie2-CYP2J2 Tr hearts were similar to those seen in sEH –/– [11] or sEH inhibitor-treated mice [17]. Oxylipin levels confirm that Tie2-CYP2J2 Tr hearts increase overall oxylipin production, while sEH –/– hearts have altered epoxide hydrolysis.…”

Reduced coronary reactive hyperemia in mice was reversed by the soluble epoxide hydrolase inhibitor ( t -AUCB): Role of adenosine A 2A receptor and plasma oxylipins

“…A 2A AR–activation resulted in increased EETs' release [32], and A 2A AR −/− (A 2A -null) mice had increased expression of EETs'–metabolizing enzyme sEH [33]. Additionally, our lab has reported that sEH −/− mice had increased aortic expression of A 2A AR [41] and increased EET levels [10]. At the functional level, sEH −/− mice demonstrated more aortic relaxation in response to an A 2A AR–agonist, which is consistent with the increased expression of A 2A AR [41], and enhanced CRH, which is in line with the increase in EET levels [10].…”

“…Additionally, our lab has reported that sEH −/− mice had increased aortic expression of A 2A AR [41] and increased EET levels [10]. At the functional level, sEH −/− mice demonstrated more aortic relaxation in response to an A 2A AR–agonist, which is consistent with the increased expression of A 2A AR [41], and enhanced CRH, which is in line with the increase in EET levels [10]. In this study, blocking A 2A AR attenuated CRH in sEH −/− mice such that it became comparable to that of wild type.…”

“…EETs are hydrated to their corresponding metabolites, DHETs, by sEH [42]. Increased EETs or EET/DHET ratios partly mediate the enhanced CRH in sEH–deleted [10] and in sEH–inhibited mouse heart in response to brief ischemia [9]. At the same time, endothelial over-expression of human sEH decreased CRH in isolated mouse heart [3], increased conversion of EETs to DHETs, and impaired endothelium-dependent cerebral vasodilation in mice [18].…”

“…The final concentrations, after standardization of dose (0.01, 0.1, 1, & 10 μM) response for the used drugs were 0.1 μM SCH-58261, selective A 2A AR-antagonist, and 1 μM DDMS (dibromo-dodecenyl-methylsulfimide, CYP4A-blocker), and 10 μM t -AUCB ( trans -4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (a selective sEH-inhibitor, University of California, Davis) [36]. These concentrations were less than or equal to concentrations used in earlier studies: t -AUCB, 10 μM; [3, 9, 10, 37], DDMS, 1 μM [38]. …”