HRelaxin-2 fusion protein treatment prevents isoproterenol-induced hypertrophy and fibrosis

Abstract

Cardiac hypertrophy accompanies many forms of heart disease, including ischemic disease, hypertension, and heart failure. Anti-fibrotic therapy is promising for prevention and treatment of hypertrophic cardiomyopathy as the disease is associated with interstitial fibrosis. The search for new drugs for symptom relief and to improve long-term outcomes in heart failure has led to development of serelaxin, a recombinant human relaxin-2 hormone, and hRelaxin-2 fusion protein (hRLX-2). Comparatively, hRLX-2 has an extended half-life, potential superior efficacy, and convenient dosing, which suggests an improved safety profile. The purpose of this study was to test whether hRLX-2 is protective in cardiac hypertrophy and fibrosis. Isoproterenol was used to induce cardiac hypertrophy model in C57BL6J mice. Vehicle or isoproterenol (15 mg/kg/day) was delivered via Alzet minipumps for 14 days, and hRLX-2 (30 mg/kg) was given twice by subcutaneous injection at day 0 and 7. For comparison, a group with serelaxin (500 mg/kg/day, un-modified recombinant human relaxin-2) or enalapril (2.5 mg/kg/day, an ACE inhibitor) was co-infused with isoproterenol. Isoproterenol increased cardiac hypertrophy (as measured by heart weight/body weight, heart weight/tibial length, and echocardiography) and fibrosis (collagen content and histological assessment) compared to vehicle. H-RLX-2, enalapril or serelaxin treatments attenuated the isoproterenol induced cardiac hypertrophy and fibrosis. Isoproterenol-induced hypertrophy significantly increased TGFβ1/Smad-induced fibrotic signaling, which was attenuated by hRLXn-2. Consistent with a previous study using seralaxin, we found that hRLX-2 significantly increased AKT/eNOS signaling. In addition, hRLX-2 treatment increased protein S-nitrosylation, which has been shown in other cardioprotective models. These findings support a potential role for hRLX-2 in the treatment of hypertrophic myocardiopathy.