Ca2+ dependent but PKC independent signalling mediates UTP induced contraction of rat mesenteric arteries

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

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 A_2AAR^-/- mice. Additionally, K_ATP channels are involved in adenosine receptor (AR)-dependent vascular relaxation. Thus, we hypothesize that a potential relationship may exist among sEH over-expression, A₁AR upregulation, inactivation of K_ATP 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 (K_ATP channel opener)-induced relaxation was also significantly reduced in MAs of Tie2-sEH Tr mice. Furthermore, K_ATP 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 suggest that over-expression of sEH enhances A₁AR-dependent contraction and reduces K_ATP channel-dependent relaxation in MAs. These results suggest a possible interaction between sEH, A₁AR, and K_ATP channels in regulating vascular tone.