Abstract
Introduction: Targeted-ablation of guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) gene ( Npr1 ) in mice exhibits hypertension and provokes congestive heart failure; however, the underlying mechanisms are not well understood. Hypothesis: To determine whether transforming growth factor-beta 1 (TGF)-β1 receptor antagonist, GW788388 inhibits the development of cardiac fibrosis and remodeling in GC-A/NPRA gene-disrupted mice. Methods: The adult male (16-20 weeks) Npr1 null mutant ( Npr1 -/- , 0-copy), heterozygous ( Npr1 +/- , 1-copy), and wild-type ( Npr1 +/+ , 2-copy) mice were orally administered with TGF-β1 receptor antagonist, GW788388 (2 mg/kg/day) for 28 days. The expression of cardiac fibrotic markers was analyzed using real-time PCR and Western blot. Heart weight-to-body weight (HW/BW) ratios were determined and heart functions were measured by echocardiographic analysis. Results: The Npr1 -/- mice showed markedly increased cardiac fibrosis and HW/BW ratio with increased expression of collagen-1α (3.5-fold), monocyte chemoattractant protein (4-fold), connective tissue growth factor (CTGF, 5-fold), α-smooth muscle actin (α-SMA, 4-fold), TGF-βRI (4-fold), TGF-βRII (3.5-fold) and SMAD proteins (SMAD-2, 5-fold; SMAD-3, 3-fold) compared with Npr1 +/+ mice. The expression of phosphorylated extracellular-regulated kinase (pERK1/2) was also up-regulated in Npr1 -/- mice. The treatment of Npr1 -/- mice with GW788388 significantly prevented the development of cardiac fibrosis and down-regulated the expression of fibrotic markers and SMAD proteins compared to vehicle-treated mice. In contrast, the expression of pERK1/2 proteins was unaffected in GW7885388-treated mice excluding the involvement of non-genomic pathway. The left ventricular dimensions (systole and diastole) and fractional shortening were significantly improved in the drug-treated Npr1 -/- mice. Conclusions: The results suggest that the cardiac fibrosis, remodeling, and dysfunction in Npr1 -/- mice are regulated through TGF-β-mediated SMAD-dependent canonical pathway. The findings will be important for the development of new molecular therapeutic targets for the treatment of cardiac fibrosis, remodeling, and dysfunction in human patients.
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