Arejian M, Li Y, Anand-Srivastava MB. Nitric oxide attenuates the expression of natriuretic peptide receptor C and associated adenylyl cyclase signaling in aortic vascular smooth muscle cells: role of MAPK. Am J Physiol Heart Circ Physiol 296: H1859 -H1867, 2009. First published February 27, 2009 doi:10.1152/ajpheart.01108.2008We 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 Gi␣ proteins in a time-dependent manner. The expression of Gi␣ 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 (ϳ50%) 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 SNAPinduced decreased expression of NPR-C protein and increased ERK1/2 phosphorylation to control levels. However, the decreased levels of phosphorylated ERK1/2 and Gi␣ 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 Gi␣ 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 Gi␣ proteins. G proteins; mitogen-activated protein kinase NATRIURETIC PEPTIDES (NPs) are a family of three peptide hormones termed atrial NP (ANP), brain NP, and C-type NP, all of which are produced in mammalian hearts, including human hearts (31). ANP regulates a variety of physiological parameters, including blood pressure (7), by interacting with receptors on plasma membrane either to generate second messengers such as cAMP (2, 3) and cGMP (20,48) or to affect ion channels (7). Three types of NP receptors (NPRs) have been cloned; NPR-A (16) and NPR-B (15) subtypes are membranebound guanylate cyclases (130-180 kDa) that mediate the biological actions of NP through a regulation of intracellular cGMP levels (7), whereas NPR-C (4, 17) is a disulfide-bridged homodimer of 67-an...

We have recently shown that cyclic GMP (cGMP) decreased the expression of natriuretic peptide receptor C (NPR‐C) in vascular smooth muscle cells (VSMC). Since cGMP is the second messenger of nitric oxide (NO), the present studies were undertaken to investigate if NO can mimic the effect of cGMP in attenuating the expression and associated Gia‐adenylyl cyclase signaling of NPR‐C in aortic VSMC.Treatment of VSMC with SNAP (100 μM) decreased the expression of NPR‐C, Gia‐2 and Gia‐3 proteins in a time‐dependent manner, as determined by Western Blotting. The maximal inhibition of Gia‐2, Gia‐3 and NPR‐C proteins was between 30–35%. The NO‐induced decreased levels of NPR‐C and Giá proteins at 24 h was also reflected in decreased NPR‐C‐mediated adenylyl cyclase inhibition, as determined by C‐ANP4‐23‐mediated inhibition of adenylyl cyclase. Furthermore, ODQ, an inhibitor of soluble guanylyl cyclase, KT5823, an inhibitor of protein kinase G, and MnTBAP, a scavenger of peroxynitrite, were unable to restore the SNAP‐induced decreased expression of NPR‐C protein to control levels, suggesting that SNAP‐mediated decreased expression of NPR‐C is not through peroxynitrite or cGMP‐dependent mechanism. These results suggest that NO decreases NPR‐C expression and that the NO‐induced decreased expression of NPR‐C is mediated through a cGMP‐independent pathway. (Supported by Canadian Institutes of Health Research)