Gene Expression, Secretion, and Autocrine Action of C-Type Natriuretic Peptide in Cultured Adult Rat Cardiac Fibroblasts

Abstract

C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, is known to be synthesized in the central nervous system and vascular endothelial cells, in contrast to atrial natriuretic peptide and brain natriuretic peptide. However, there have been no studies concerning CNP production in cultured cardiac cells. Here, we examined the production and the local effect of CNP in cultured ventricular cells. Under serum-free conditions, adult rat cardiac fibroblasts secreted immunoreactive CNP time dependently. TGF-beta1, basic fibroblast growth factor, and endothelin-1 significantly stimulated CNP secretion. Northern blot analysis detected significant expressions of CNP and its specific receptor (guanylyl cyclase-B) mRNA in cardiac fibroblasts. CNP stimulated intracellular cGMP production in fibroblasts more intensely than atrial and brain natriuretic peptides. CNP inhibited both DNA and collagen syntheses of cardiac fibroblasts, and these inhibitory effects by CNP were stronger than by atrial and brain natriuretic peptides. The inhibition by CNP of DNA and collagen syntheses was reproduced by a cGMP analog, 8-bromo cGMP. The present findings demonstrate that CNP is synthesized in and secreted from cardiac fibroblasts and suggest that CNP has a suppressive effect on fibroblast proliferation and extracellular matrix production, probably via the guanylyl cyclase-B-mediated cGMP-dependent process. CNP produced by cardiac fibroblasts may play a role as an autocrine regulator against excessive cardiac fibrosis.

Cardiomyocyte‐restricted over‐expression of C‐type natriuretic peptide prevents cardiac hypertrophy induced by myocardial infarction in mice

“…Furthermore, that the CNP/NPRB axis is responsible for the cardiac CNP effects is also supported by cell-based studies. CNP modulates the growth, proliferation, and hypertrophy of smooth muscle cells, cardiomyocytes and fibroblasts [31][32][33], and cGMP is implicated in all of these studies when CNP binds to its receptor NPRB. Additionally, our data on increased cGMP in the hearts of CNP-transgenic mice is congruent with findings in isolated rat and rabbit cardiomyocytes generating cGMP after CNP stimulation [34,35].…”

C-type natriuretic peptide attenuates bleomycin-induced pulmonary fibrosis in mice

“…Interestingly, CNP infusion markedly inhibited Ki-67-positive cells in fibrotic lesions of the lung. An in vitro study showed that CNP directly inhibited proliferation of cardiac fibroblasts through a guanylate cyclase-B-mediated cGMP-dependent pathway (7). Thus it is possible that the reduction of pulmonary fibrosis by CNP infusion may be mediated by a direct antiproliferative effect of CNP on fibroblasts in the lung.…”

“…Recently, CNP has been shown to suppress inflammation through inhibition of macrophage infiltration in injured carotid arteries of rabbits (20). Interestingly, CNP has been shown to directly inhibit cardiac fibroblast proliferation through a guanylate cyclase-B-mediated cGMP-dependent pathway (7). These findings suggest that CNP plays an important role in regulation of the cardiovascular system.…”

Natriuretic Peptides in the Regulation of Cardiovascular Physiology and Metabolic Events

“…Furthermore, transgenic overexpression of CNP in cardiomyocytes has been shown to prevent development of LV hypertrophy post‐MI 89. The cGMP‐dependent signaling appears to be central for antifibrotic effects of CNP 88, 90. Evidence from Burnett's laboratory suggests that a non‐cGMP‐dependent pathway also mediates the antifibrotic effects of CNP 78.…”