Cytochrome P450 Pathway Contributes to Methanandamide-induced Vasorelaxation in Rat Aorta
Purpose The generation of hyperpolarising vasorelaxant endothelial cytochrome P450 epoxygenase (CYP)¿derived metabolites of arachidonic may provide beneficial effects for the treatment of cardiovascular diseases in which the bioavailability of NO is impaired. The cannabinoid methanandamide has vasodilatory properties linked to hyperpolarisation. The aim of the present work was to investigate the vasorelaxant effects of methanandamide in rat aorta, focusing on the role of cytochrome P450 pathway. Methods Changes in isometric tension in response to a cumulative concentration-response curve of methanandamide (1 nM¿100 ¿M) were recorded in aortic rings from male Wistar rats. The involvement of cannabinoid receptors, endothelial nitric oxide (NO)-, prostacyclin- and some hyperpolarising-mediated pathways were investigated. The activation of large-conductance Ca2+-activated K+ (BKCa) channels have also been evaluated. Results Methanandamide provoked an endothelium-dependent vasorelaxation in rat aorta, reaching a maximal effect (Rmax) of 67%±2.6%. This vasorelaxation was clearly inhibited by the combination of CB1 and CB2 cannabinoid antagonists (Rmax: 21.6%±1.3%) and by the combination of guanylate cyclase and CYP inhibitors (Rmax: 16.7%±1.1%). The blockade induced separately by guanylate cyclase (31.3%± 2.8%) or CYP (36.3%±6.6%) inhibitors on methanandamide vasorelaxation was not significantly modified by either CB1 or CB2 inhibition. BKCa channels inhibition caused a partial and significant inhibition of the methanandamide vasorelaxation (Rmax: 39.9%±3.3%). Conclusions Methanandamide endothelium-dependent vasorelaxation is mediated by CB1 and CB2 cannabinoid receptors. The NO- and CYP-mediated pathways contribute in a concurrent manner in this vascular effect. Stimulation of both cannabinoid receptor subtypes is indistinctly linked to NO or CYP routes to cause vasorelaxation.