Protective effects of statin on cardiac fibrosis and apoptosis in adrenomedullin-knockout mice treated with angiotensin II and high salt loading

Statins exert pleiotropic effects, including antioxidative and cellular protective effects. Endogenous adrenomedullin (AM) induces anti-inflammatory, anti-fibrotic and proangiogenic effects. We examined the effects of simvastatin on cardiac fibrosis and apoptosis in AM heterozygous knockout (AM +/− ) mice treated with angiotensin (Ang) II and high salt loading. Seven-week-old AM +/− mice were infused with Ang II while on a high-salt diet with or without simvastatin for 2 weeks. Hearts were stained by hematoxylin-eosin or Masson's trichrome, and were immunostained with isolectin B 4 and α-smooth muscle actin antibodies. Expression of c-Kit and Sca-1 messenger RNA (mRNA) was evaluated by real-time PCR analysis. Apoptotic cells in hearts were identified by terminal deoxynucleotidyl transferase-mediated UTP end labeling (TUNEL) staining. Hearts from Ang II/salt loading AM +/− mice showed marked perivascular fibrosis around coronary arteries. Treatment with simvastatin significantly inhibited the fibrosis around coronary arteries in Ang II/salt-loading AM +/− mice. Expression of c-Kit and Sca-1 mRNAs in hearts from Ang II/salt-loading AM +/− mice was significantly lower than in hearts from wild-type mice. Treatment with simvastatin significantly increased the suppressed expression of c-Kit and Sca-1 mRNAs. In addition, treatment with simvastatin significantly increased the number of isolectin B 4 -positive capillary arteries in hearts from Ang II/salt-loading AM +/− mice. Ang II/high salt significantly increased apoptotic cells in hearts from AM +/− mice; this trend was reversed by treatment with simvastatin. Thus, statins have potent cardioprotective effects that may be associated with anti-fibrotic, proangiogenic and anti-apoptotic effects in Ang II/salt-loading AM +/− mice.