Activation of transient receptor potential vanilloid 1 decreases endothelial nitric oxide synthase phosphorylation at Thr497 by protein phosphatase 2 B-dependent dephosphorylation of protein kinase C.

Aims We investigated the effects and underlying molecular mechanism of transient receptor potential vanilloid 1 ( TRPV1), a calcium (Ca²⁺)-permeable non-selective cation channel, on phosphorylation of endothelial nitric oxide synthase (e NOS) at threonine 497 (Thr497) in bovine aortic endothelial cells ( BAECs) and in mice. Methods Western blotting and immunoprecipitation were used for the evaluation of protein phosphorylation; protein phosphatase 2 B ( PP2B) activity was assessed by convention kit; Griess assay was for NO production; tube formation and Matrigel plug assay were used for angiogenesis. Results In BAECs, treatment with the TRPV1 ligand evodiamine decreased the phosphorylation of e NOS at Thr497, protein kinase Cα ( PKCα) at Serine 657 (Ser657) and PKCβ2 at Ser660. Evodiamine increased protein phosphatase 2B (PP2B) activity and promoted the formation of a PP2B- PKC complex. Inhibition of TRPV1 activation by the pharmacological antagonists, removal of extracellular Ca²⁺ or pharmacological inhibition of PI3K/Akt/calmodulin-dependent protein kinase II/ AMP-activated protein kinase signalling pathway abolished the evodiamine-induced alterations in phosphorylation of e NOS at Thr497, PKCα at Ser657, PKCβ2 at Ser660 and PP2B activity, as well as the formation of a PP2B- PKC complex. Inhibition of PP2B activation partially reduced the evodiamine-induced NO bioavailability and tube formation in endothelial cells ( ECs) and angiogenesis in mice. Moreover, evodiamine decreased the phosphorylation of e NOS at Thr497, PKCα at Ser657 and PKCβ2 at Ser660 in apolipoprotein E (ApoE)-deficient mouse aortas but not TRPV1-deficient or ApoE/ TRPV1 double-knockout mice. Conclusion TRPV1 activation in ECs may elicit a Ca²⁺-dependent effect on PP2B- PKC signalling, which leads to dephosphorylation of e NOS at Thr497 in ECs and in mice. [ABSTRACT FROM AUTHOR]