Hesperetin Inhibits Sphingosylphosphorylcholine-Induced Vascular Smooth Muscle Contraction by Regulating the Fyn/Rho-Kinase Pathway

Cardiovascular diseases are the leading cause of mortality and disability worldwide. We have previously found that sphingosylphosphorylcholine (SPC) is the key molecule leading to vasospasm. We have also identified the SPC/Src family protein tyrosine kinase Fyn/Rho-kinase (ROK) pathway as a novel signaling pathway for Ca(2+) sensitization of vascular smooth muscle (VSM) contraction. This study aimed to investigate whether hesperetin can inhibit the SPC-induced contraction with little effect on 40 mM K(+)-induced Ca(2+)-dependent contraction and to elucidate the underlying mechanisms. Hesperetin significantly inhibited the SPC-induced contraction of porcine coronary artery smooth muscle strips with little effect on 40 mM K(+)-induced contraction. Hesperetin blocked the SPC-induced translocation of Fyn and ROK from the cytosol to the membrane in human coronary artery smooth muscle cells (HCASMCs). SPC decreased the phosphorylation level of Fyn at Y531 in both VSMs and HCASMCs and increased the phosphorylation levels of Fyn at Y420, myosin phosphatase target subunit 1 at T853, and myosin light chain (MLC) at S19 in both VSMs and HCASMCs, which were significantly suppressed by hesperetin. Our results indicate that hesperetin inhibits the SPC-induced contraction at least in part by suppressing the Fyn/ROK pathway, suggesting that hesperetin can be a novel drug to prevent and treat vasospasm.