Abstract 17105: Constitutively Active NPR-B (Type-B Human Natriuretic Peptide Receptor) Inhibits Cardiomyocyte Hypertrophy and Cardiac Fibroblast Fibrosis
Introduction: Cyclic GMP (cGMP) has been suggested to be a negative regulator of cardiac hypertrophy and fibrosis. Intracellular cGMP levels can be elevated by the stimulation of nitric oxide (NO) or natriuretic peptides, and by inhibiting cGMP-degrading phosphodiesterases (PDE). Type-B natriuretic peptide receptor (NPR-B) synthesizes cGMP in response to C-type natriuretic peptide (CNP) binding. We have identified a novel missense mutation in the NPR-B gene (2647G>A; Val 883 Met) in a family case showing overgrowth and bone anomalies. Overexpression of this mutant NPR-B (MT-NPR-B) induced significant increase in intracellular cGMP levels without CNP binding. We investigated a hypothesis that overexpression of MT-NPR-B inhibits cardiomyocyte hypertrophy and cardiac fibrosis in vitro.
Methods: MT-NPR-B, wild-type NPR-B (WT-NPR-B), or GFP control were transfected into neonatal Wistar rat cardiomyocytes (CMs) and cardiac fibroblasts (CFs) by using recombinant adenoviral vectors. Transfected CMs were incubated with endothelin-1 (ET1) or Angiotensin-II (ATII), then the Cell size and hypertrophic signals, as well as cGMP levels, were investigated. Next, transfected CFs were incubated with TGF-β1, then the expression of collagen-1 mRNA and cGMP levels were investigated.
Results: Overexpression of MT-NPR-B in CMs and CFs induced significant increases in cGMP levels compared to WT-NPR-B or GFP control. Overexpression of MT-NPR-B in CMs inhibited ATII- or ET1-induced increase in cell size and increase in ANP, BNP, and βMHC mRNA expression (Cell size (%): GFP, 192±15; WT-NPR-B, 178±17; MT-NPR-B, 121±13 n=5, ANP/GAPDH (-fold): GFP, 2.51±0.35; WT-NPR-B, 2.66±0.27; MT-NPR-B, 1.13±0.25 n=7).
Moreover, overexpression of MT-NPR-B in CFs suppressed TGF-β1-induced increase in collagen-1 mRNA expression (Collagen-1/GAPDH (-fold): GFP, 2.72±0.28; WT-NPR-B, 2.30±0.59; MT-NPR-B, 0.94±0.18 n=7).
Conclusion: Mutant NPR-B with a novel gain-of-function mutation induced significant increase in intracellular cGMP levels in both CMs and CFs. Overexpression of MT-NPR-B inhibited hypertrophy of CMs and CFs-induced fibrosis in vitro. The NPR-B may be an additional therapeutic target in the treatment of cardiac hypertrophy and fibrosis.
- © 2013 by American Heart Association, Inc.