Abstract 96: Simvastatin Prevents TGF-β1-induced SMAD2/3 Phosphorylation Involved in Ventricular Fibrosis: Role of Protein Phosphatases

Abstract

Background: Ventricular fibrosis leads to progressive cardiac dysfunction and heart failure (HF). Statins are reported to reduce cardiac fibrosis through the cholesterol-independent pathway, but mechanisms remain elusive. We hypothesize simvastatin reduced TGF-β1-induced ventricular fibrosis through activation of SMAD protein phosphatase Mg 2+ /Mn 2+ -1A (PPM1A), -2A (PP2A). Methods: In the absence and presence of TGF-β1 (5ng) with or without simvastatin (1μM), the rate of fibroblast proliferation (doubling time), myofibroblast differentiation (ICC), α-SMA mRNA (RT-PCR) and protein expression (Western blot) and the release of collagen synthesis markers, pro-collagen type I C-terminal peptide (PICP) and pro-collagen type III N-terminal peptide (PIIINP), in the media (ELISA) were determined along with protein interaction between SMAD2/3 and PPM1A or PP2A (Co-IP) and SMAD2/3 phosphorylation (Western blot). Results: Simvastatin reduced the effect of TGF-β1 on hVF proliferation by 47% (50000 to 26500), p<0.01; myofibroblast differentiated population from 48% (avg 48/100) to 11% (avg 11/100), p<0.01; expression of α-SMA mRNA by 76%, p<0.01; and protein by 60%, p<0.05. Simvastatin also decreased release of PICP by 66%, p<0.01, and PIIINP by 83%, p<0.01, into the media. Time-dependent increases in SMAD2/3 phosphorylation were reduced by simvastatin through activation of protein phosphatases PPM1A and PP2A by interacting with SMAD2/3. Conclusion: Involvement of PPM1A and PP2A in the anti-fibrotic effect of simvastatin reveals novel signaling mediators that may be selectively targeted for prevention of myocardial injury-induced ventricular fibrosis and HF.