Rosmarinic acid attenuates cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling

Agonists of peroxisome proliferator-activated receptor gamma (PPAR-gamma) can activate 5' AMP-activated protein kinase alpha (AMPK alpha) and exert cardioprotective effects. A previous study has demonstrated that rosmarinic acid (RA) can activate PPAR-gamma, but its effect on cardiac remodeling remains largely unknown. Our study aimed to investigate the effect of RA on cardiac remodeling and to clarify the underlying mechanism. Mice were subjected to aortic banding to generate pressure overload induced cardiac remodeling and then were orally administered RA (100 mg/kg/day) for 7 weeks beginning 1 week after surgery. The morphological examination, echocardiography, and molecular markers were used to evaluate the effects of RA. To ascertain whether the beneficial effect of RA on cardiac fibrosis was mediated by AMPK alpha, AMPK alpha 2 knockout mice were used. Neonatal rat cardiomyocytes and fibroblasts were separated and cultured to validate the protective effect of RA in vitro. RA-treated mice exhibited a similar hypertrophic response as mice without RA treatment, but had an attenuated fibrotic response and improved cardiac function after pressure overload. Activated AMPKa was essential for the anti-fibrotic effect of RA via inhibiting the phosphorylation and nuclear translocation of Smad3 in vivo and in vitro, and AMPKa deficiency abolished RA-mediated protective effects. Small interfering RNA against Ppar-gamma (siPpar-gamma) and GW9662, a specific antagonist of PPAR-gamma, abolished RA-mediated AMPKa phosphorylation and alleviation of fibrotic response in vitro. RA attenuated cardiac fibrosis following long-term pressure overload via AMPK alpha/Smad3 signaling and PPAR-gamma was required for the activation of AMPK alpha. RA might be a promising therapeutic agent against cardiac fibrosis.