We have earlier shown that the treatment of A10 vascular smooth muscle cells with S-nitroso- N-acetyl-penicillamine (SNAP); nitric oxide donor (NO) for 24 h decreased the expression of natriuretic peptide receptor C (NPR-C) and adenylyl cyclase signaling. The present study was undertaken to examine the implication of different signaling mechanisms in a NO-induced response. The treatment of A10 vascular smooth muscle cells with SNAP decreased the expression of NPR-C and Giα proteins in a time-dependent manner. The expression of Giα proteins was decreased at 6 h, whereas the expression of NPR-C was attenuated at 2 h. The NPR-C-mediated inhibition of adenylyl cyclase was attenuated (∼50%) after 2 h of treatment and was completely abolished after 6 h of treatment. The decreased expression of NPR-C and NPR-C-mediated attenuation of adenylyl cyclase after 2 h of treatment was reversed to control levels by PD-98059, a MEK inhibitor. SNAP also modulated the ERK1/2 phosphorylation in a time-dependent manner; an increase was observed up to 2 h, and, thereafter, the ERK1/2 phosphorylation was decreased. On the other hand, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one and KT-5823 inhibitor of soluble guanylyl cyclase and protein kinase G, respectively, and Mn(III)tetrakis(4-benzoic acid)porphyrin, a scavenger of peroxynitrite, were unable to restore the SNAP-induced decreased expression of NPR-C protein and increased ERK1/2 phosphorylation to control levels. However, the decreased levels of phosphorylated ERK1/2 and Giα proteins were restored to control levels by 8-bromo-cAMP. These results indicate that a temporal relationship follows between a NO-induced decreased expression of NPR-C and Giα proteins. The decreased expression of NPR-C is mediated through cGMP-independent but MAPK-dependent pathway, whereas NO-induced decreased levels of cAMP may contribute to the decreased activation of MAPK and thereby decreased the expression of Giα proteins.
Knockdown of natriuretic peptide receptor-A enhances receptor C expression and signalling in vascular smooth muscle cells