Cytochrome P-450 metabolites of 2-arachidonoylglycerol play a role in Ca2+-induced relaxation of rat mesenteric arteries

Abstract

The perivascular sensory nerve (PvN) Ca2+-sensing receptor (CaR) is implicated in Ca2+-induced relaxation of isolated, phenylephrine (PE)-contracted mesenteric arteries, which involves the vascular endogenous cannabinoid system. We determined the effect of inhibition of diacylglycerol (DAG) lipase (DAGL), phospholipase A2 (PLA2), and cytochrome P-450 (CYP) on Ca2+-induced relaxation of PE-contracted rat mesenteric arteries. Our findings indicate that Ca2+-induced vasorelaxation is not dependent on the endothelium. The DAGL inhibitor RHC 802675 (1 μM) and the CYP and PLA2 inhibitors quinacrine (5 μM) (EC50: RHC 802675 2.8 ± 0.4 mM vs. control 1.4 ± 0.3 mM; quinacrine 4.8 ± 0.4 mM vs. control 2.0 ± 0.3 mM; n = 5) and arachidonyltrifluoromethyl ketone (AACOCF3, 1 μM) reduced Ca2+-induced relaxation of mesenteric arteries. Synthetic 2-arachidonoylglycerol (2-AG) and glycerated epoxyeicosatrienoic acids (GEETs) induced concentration-dependent relaxation of isolated arteries. 2-AG relaxations were blocked by iberiotoxin (IBTX) (EC50: control 0.96 ± 0.14 nM, IBTX 1.3 ± 0.5 μM) and miconazole (48 ± 3%), and 11,12-GEET responses were blocked by IBTX (EC50: control 55 ± 9 nM, IBTX 690 ± 96 nM) and SR-141716A. The data suggest that activation of the CaR in the PvN network by Ca2+ leads to synthesis and/or release of metabolites of the CYP epoxygenase pathway and metabolism of DAG to 2-AG and subsequently to GEETs. The findings indicate a role for 2-AG and its metabolites in Ca2+-induced relaxation of resistance arteries; therefore this receptor may be a potential target for the development of new vasodilator compounds for antihypertensive therapy.