Abstract
Augmented endothelium-dependent contractions (EDC) contributes to endothelial dysfunction and vascular disease progression. An early signal in EDC is cytosolic [Ca2+]i rise in endothelial cells, which stimulates the production of contractile prostanoids, leading to vascular contraction. In this study, the molecular identity of Ca2+-permeable channels in endothelial cells and its function were investigated. Vascular tension was measured by wire myograph. EDCs were elicited by acetylcholine (ACH) in the presence of NG-nitro-l-arginine methyl ester (L-NAME). [Ca2+]i was measured using a Ca2+-sensitive fluorescence dye. Enzyme Immunoassay (EIA) was used for prostaglandin measurement. Immunohistochemical staining found the expression of transient receptor potential channel C5 (TRPC5) in endothelial and smooth muscle cells of mouse carotid arteries. ACH-induced EDC in male mouse carotid arteries was found to be substantially reduced in TRPC5 knockout (KO) mice than in wild-type (WT) mice. TRPC5 inhibitors clemizole and ML204 also reduced the EDC. Furthermore, ACH-induced Ca2+ entry in endothelial cells was lower in TRPC5 KO mice than in WT mice. Moreover, the EDC was abolished by a cyclooxygenase-2 (COX-2) inhibitor NS-398, but not affected by a COX-1 inhibitor valeryl salicylate (VAS). Enzyme immunoassay results showed that TRPC5 stimulated the COX-2-linked production of prostaglandin F2α (PGF2α), prostaglandin E2 (PGE2), and prostaglandin D2 (PGD2). Exogeneous PGF2α, PGE2, and PGD2 could induce contractions in carotid arteries. Our present study demonstrated that TRPC5 in endothelial cells contributes to EDC by stimulating the production of COX-2-linked prostanoids. The finding extends our knowledge about EDC.