Anti-Fibrosis Effect of Relaxin and Spironolactone Combined on Isoprenaline-Induced Myocardial Fibrosis in Rats via Inhibition of Endothelial-Mesenchymal Transition

Background: The effect of relaxin and spironolactone combined on myocardial fibrosis has not been reported. Thus, we investigated the effect of the combined therapy on isoprenaline-induced myocardial fibrosis and the mechanism. Methods: Rats were injected subcutaneously with isoprenaline to induce myocardial fibrosis and underwent subcutaneous injection with relaxin (2 mu g.kg(-1).d(-1)) and given a gavage of spironolactone (30 mg.kg(-1).d(-1)) alone or combined for 14 days. In vitro, the endothelial mesenchymal transition was induced with transforming growth factor beta (TGF-beta) in human umbilical vein endothelial cells (HUVECs) pretreated with relaxin, 200 ng/ml, and/or spironolactone, 1uM. Results: Relaxin and spironolactone used alone or combined improved cardiac function and decreased cardiac weight indices; reduced fibrous tissue proliferation; reduced levels of type I and III collagen; decreased the expression of a smooth muscle actin (alpha-SMA) and transforming growth factor-beta 1 (TGF-beta 1), and increased the expression of cluster of differentiation-31 (CD31) in rats with isoprenaline-induced myocardial fibrosis. In vitro, compared with TGF-beta treatment, relaxin and spironolactone used alone or combined with TGF-beta decreased cell mobility, a-SMA and vimentin levels but increased vascular endothelial cadherin (VE-cadherin) and endothelial CD31levels. Especially, combined therapy had more remarkable effect than relaxin and spironolactone used alone both in vitro and in vivo. Conclusion: Relaxin and spironolactone combined affected isoprenaline-induced myocardial fibrosis in rats that the mechanism might be inhibition of the cardiac endothelial mesenchymal transition. (C) 2017 The Author(s)