Vascular endothelial over-expression of soluble epoxide hydrolase (Tie2-sEH) enhances adenosine A1 receptor-dependent contraction in mouse mesenteric arteries: role of ATP-sensitive K+ channels

Abstract

Soluble epoxide hydrolase (sEH) converts epoxyeicosatrienoic acids that are endothelium-derived hyperpolarizing factors into less active dihydroxyeicosatrienoic acids. Previously, we reported a decrease in adenosine A1 receptor (A1AR) protein levels in sEH knockout (sEH−/−) and an increase in sEH and A1AR protein levels in A2AAR−/− mice. Additionally, KATP channels are involved in adenosine receptor (AR)-dependent vascular relaxation. Thus, we hypothesize that a potential relationship may exist among sEH overexpression, A1AR up-regulation, inactivation of KATP channels and increased in vascular tone. We performed DMT myograph muscle tension measurements and western blot analysis in isolated mouse mesenteric arteries (MAs) from wild type (WT) and endothelial over-expression of sEH (Tie2-sEH Tr) mice. Our data revealed that NECA (a non-selective adenosine receptors agonist)-induced relaxation was significantly reduced in Tie2-sEH Tr mice, and CCPA (A1AR agonist)-induced contraction was increased in Tie2-sEH Tr mice. A1AR-dependent contraction in Tie2-sEH Tr mice was significantly attenuated by pharmacological inhibition of CYP4A (HET0016, 10 μM), PKCα (GO6976, 1 μM), and ERK1/2 (PD58059, 1 μM). Our western blot analysis revealed significantly higher basal protein expression of CYP4A, A1AR, and reduced p-ERK in MAs of Tie2-sEH Tr mice. Notably, pinacidil (KATP channel opener)-induced relaxation was also significantly reduced in MAs of Tie2-sEH Tr mice. Furthermore, KATP channel-dependent relaxation in MAs was enhanced by inhibition of PKCα and ERK1/2 in WT but not Tie2-sEH Tr mice. In conclusion, our data suggests that over-expression of sEH enhances A1AR-dependent contraction and reduces KATP channel-dependent relaxation in MAs. These results suggest a possible interaction between sEH, A1AR, and KATP channels in regulating vascular tone.

Vascular Endothelial Over-Expression of Human Soluble Epoxide Hydrolase (Tie2-sEH Tr) Attenuates Coronary Reactive Hyperemia in Mice: Role of Oxylipins and ω-Hydroxylases

“…This in turn could lead to higher levels of 20-HETE. This possibility is supported by the finding that CYP4A’s expression was increased in the mesenteric arteries of Tie2-sEH Tr mice [12]. The levels of 20-HETE were too low to be detected in heart perfusates from WT or Tie2-sEH Tr mice.…”

“…CYP4A is an ω-hyroxylase involved in metabolizing AA to the potent vasoconstrictor 20-HETE [16]. Yadav et al has recently reported that CYP4A level was increased in the mesenteric arteries of Tie2-sEH Tr mice [12]. These data suggest that while the decrease in mid-chain HETEs observed in the heart perfusates of Tie2-sEH Tr mice should have enhanced CRH, the reported increased expression of CYP4A in the same mice may have overridden the effect of decreased mid-chain HETEs and caused a net effect of decreased CRH.…”

“…The levels of 20-HETE were too low to be detected in heart perfusates from WT or Tie2-sEH Tr mice. Upregulation of CYP4A [12], may contribute to reduced CRH in Tie2-sEH Tr compared to WT mice. As mentioned earlier, the temporary pharmacological inhibition of sEH could not completely restore CRH in Tie2-sEH Tr to that in WT mice.…”

“…While sEH is the main pathway of EET metabolism [6], some EETs, such as 5,6- and 8,9-EET, are substrates for the cyclooxygenase (COX) pathway [7]. Different approaches of targeting sEH to study the effects of EETs have been utilized, including genetic deletion [8–11], endothelial expression [12, 13], and pharmacologic inhibition of sEH [11, 14] or CYP epoxygenases [15]. Increased EET generation in mouse cardiomyocytes was shown to exert cardioprotective effects against ischemia/reperfusion injury [8].…”

“…CYP4A is one of the ω-hyroxylases involved in metabolizing AA to ω-terminal HETEs, including the potent vasoconstrictor 20-HETE (hydroxyeicosatetraenoic acid) [16]. In addition to regulating EET levels, sEH expression also impacts CYP ω-hydroxylase pathway; as reported by Yadav et al, CYP4A level was increased in the mesenteric arteries of mice with endothelial expression of sEH (Tie2-sEH Tr mice) [12]. sEH activity also affects the levels of other arachidonic- and linoleic- acids derived oxylipins, such as mid-chain hydroxyeicosatetraenoic acids (HETEs), prostaglandins (PGs), epoxyoctadecaenoic acids (EpOMEs), and hydroxyoctadecadienoic acids (HODEs) [11, 17–20].…”