Peroxynitrite inhibits the expression of Giα protein and adenylyl cyclase signaling in vascular smooth muscle cells

Abstract

We previously showed that S-nitroso- N-acetylpenicillamine, a nitric oxide donor, decreased the levels and functions of Giα proteins by formation of peroxynitrite (ONOO−) in vascular smooth muscle cells (VSMC). The present studies were undertaken to investigate whether ONOO−can modulate the expression of Giα protein and associated adenylyl cyclase signaling in VSMC. Treatment of A-10 and aortic VSMC with ONOO−for 24 h decreased the expression of Giα-2 and Giα-3, but not Gsα, protein in a concentration-dependent manner; expression was restored toward control levels by111Mn-tetralis(benzoic acid porphyrin) and uric acid, but not by 1 H[1,2,4]oxadiazole[4,3-a]quinoxaline-1-one (ODQ) and KT-5823. cGMP levels were increased by ∼50% and 150% by 0.1 and 0.5 mM ONOO−, respectively, and attenuated toward control levels by ODQ. In addition, 0.5 mM ONOO−attenuated the inhibition of adenylyl cyclase by ANG II and C-type atrial natriuretic peptide (C-ANP4–23), as well as the inhibition of forskolin-stimulated adenylyl cyclase activity by GTPγS, whereas, the Gs-mediated stimulations were augmented. In addition, 0.5 mM ONOO−decreased phosphorylation of ERK1/2 and p38 MAP kinase and enhanced JNK phosphorylation but did not affect AKT1/3 phosphorylation. These results suggest that ONOO−decreased the expression of Giproteins and associated functions in VSMC through a cGMP-independent mechanism and may involve the MAP kinase signaling pathway.