Regulation Of TRPV1 And TRPV4 Channels In Mouse Lung Vasculature

Background: The transient receptor potential vanilloid-1(TRPV1) and transient receptor potential vanilloid-4(TRPV4) calcium channels are non-selective cation channels protein found on the cell membrane or intracellular organelle membrane, widely studied on the regulation of vascular function in recent years. They play an important role on the regulation of vascular function. Resent study have shown that TRPV1 and TRPV4 channels exist in the endothelial cells of mouse mesenteric arteries, and activated these channels could produce endothelium-dependent vasodilation However, the research on the regulation in pulmonary microcirculation was largely unknown, and lacked of integrity and unity. Furthermore, no vascular function studies on TRPV1 and TRPV4 in mouse lung microvasculature was reported international, and there was still contradiction and dispute at their role in pulmonary arterial hypertension.Objective:To investigate the existence of TRPV1 and TRPV4 in Mouse Lung Vasculature and their roles in vascular regulation, and further explore the mechanisms in vascular regulation.Materials and methods:Experiments were performed in male wild-type and Trpv1-/- mice, all on C57BL/6J background. We studied the function effect of TRPV1 and TRPV4 channels in the second branches of pulmonary arteries by myograph experiment and lung microvasculature by vitro isolated lung perfusion experiment. Mesenteric arteries served as vessel control,Result: 1. TRPV1 agonist capsaicin relaxed the mesenteric arteries with an EC50 of 9.3 n M in an endothelium-dependent manner. This vasodilatory effect was nearly abolished by the TRPV1 antagonist capsazepine and in Trpv1-/-mice.2. TRPV1 agonist capsaicin induced concentration-dependent relaxation of large pulmonary arteries, but the effect occurred at ~1000-fold higher concentrations(EC50, 9.88μM) than in mesenteric arteries(EC50, 9.3n M). The effect was not different from removal of the endothelium(EC50, 16.8μM,P >0.05) and in Trpv1-/- mice(EC50, 30.47μM,P >0.05).3. Capsaicin induced concentration-dependent relaxation of lung microvasculature, but the effect occurred at ~3000-fold higher concentrations(EC50, 30.9 μM) than in mesenteric arteries(EC50, 9.3 n M, P <0.05). The effect was not different from Trpv1-/- mice(EC50, 14.58 μM,P >0.05).4. TRPV4 agonist GSK1016790 A relaxed the mesenteric arteries with an EC50 of 50.6 n M in an endothelium-dependent manner. This vasodilatory effect of GSK1016790 A was reduced by the TRPV4 antagonist AB159908(EC50, 296 n M, P<0.05). This was agreed with the previous literature.5. GSK1016790 A relaxed the large pulmonary arteries with an EC50 of 40 n M in an endothelium-dependent manner. This vasodilatory effect of GSK1016790 A was reduced by AB159908(EC50, 241 n M, P<0.05) and was nearly abolished by the e NOS inhibitor L-NAME(EC50, 134μM, P<0.05) or by IKCa /SKCa inhibitor Charybdotoxin and Apamin(EC50, 104 μM, P<0.05).6. Opposed to our expectations, GSK1016790 A caused vasoconstriction of the mouse lung microvasculation in a dose-dependent manner. The effect was inhibited by AB159908(P<0.05), it also inhibited by the e NOS inhibitor L-NAME or by IKCa /SKCa inhibitor Charybdotoxin and Apamin(P<0.05).Conclusion:Our results first demonstrate that TRPV4 channels have sites of opposite vasoregulatory function in the mouse lung vasculature through the e NOS and the IKCa /SKCa pathway which induced vasocontraction of lung microvasculature and vasodilation of large pulmonary arteries in a compensatory manner. TRPV1 channels have no function in mouse lung vasculature.