Induction of nitric oxide synthase regulates atrial natriuretic peptide receptors in vascular smooth muscle cells

Abstract

In a previous study, we reported that cyclic GMP (cGMP) selectively down-regulates the atrial natriuretic peptide clearance receptor (ANP C receptor) in the vascular endothelial cells. The aim of the present study is to determine whether nitric oxide (NO) regulates ANP receptor by accumulating intracellular cGMP in cultured rabbit aortic smooth muscle cells. Treatment with interleukin-1β (IL-1), a cytokine known to induce NO synthase, dose-dependently increased the basal level of intracellular cGMP with a concomitant increase of nitrite in the conditioned media. These effects of IL-1 were attenuated in the presence of N ω-nitro-L-arginine. IL-1 (40 pM) significantly (P < 0.01) decreased [ 125I]atriopeptin III binding to the cells, an effect that was inhibited by N ω-nitro-L-arginine. Treatment with sodium nitroprusside (SNP) which releases NO also decreased [ 125I]atriopeptin III binding to the cells. In addition, further decrease in [ 125I]atriopeptin III binding following IL-1 or SNP treatment was observed in the presence of 0.1 mM zaprinast, a cGMP-specific phosphodiesterase inhibitor. Scatchard analysis of the binding data in the treated cells showed a decrease in B max without a significant change in K d. Affinity cross-linking of [ 125I]atriopeptin III to the treated cells demonstrated a decrease in 70-kDa band corresponding to the ANP C receptor. Meanwhile, intracellular cGMP response to atriopeptin III was significantly (P < 0.01) enhanced in the cells pretreated with IL-1 or SNP despite the decrease in receptor density. These findings suggest that NO down-regulates the ANP C receptor by the accumulation of intracellular cGMP in cultured rabbit aortic smooth muscle cells. Enhanced cGMP response to atriopeptin III in the treated cells indicates that the membrane type guanylate cyclase-coupled receptor (ANP B receptor) is regulated in a differential manner.