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 µg·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 β (TGF-β) 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 α-smooth muscle actin (α-SMA) and transforming growth factor-β1 (TGF-β1), and increased the expression of cluster of differentiation-31 (CD31) in rats with isoprenaline-induced myocardial fibrosis. In vitro, compared with TGF-β treatment, relaxin and spironolactone used alone or combined with TGF-β decreased cell mobility, α-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.