Myosin light chain kinase inhibitor attenuates atherosclerosis and permeability via reduced endothelial tight junction in rabbits.

Abstract： The development of atherosclerosis is a multifactorial process in which elevated plasma cholesterol levels play a central role. This study analyzed the effects of myosin light chain kinase (MLCK) inhibitor (ML7) on endothelial permeability and gap formation and junction proteins expression in the artery wall of rabbits after feeding with a high-cholesterol diet. Further, we tested to determine whether that effects are involved in MLCK expression and MLC phosphorylation.We investigated the role of ML7 in the development of atherosclerotic lesions in New Zealand White rabbits fed an atherogenic diet for 12 weeks. Histopathological examination demonstrated that ML7 reduced the size of aortic lesions, lipid contents and endothelial permeability. Electron microscopy revealed ML7 attenuated gap formation in the endothelial tight junction. Immunohistochemistry indicated that ML7 decreased the expression of tight junction protein in the artery wall of rabbits fed with a high-cholesterol diet. Western blotting demonstrated that ML7 reduced occludin expression in the precipitation, but increased its expression in the supernatant of lysed aortas which indicated occludin occurred remodeling from cell membrane to cytoplasm. Further mechanistic studies showed ML7 attenuated endothelial barrier dysfunction through both MLCK expression and myosin light chain phosphorylation in aortic endothelial cells. We Concluded that ML7 contributes to atherosclerosis and endothelial barrier function by regulating tight junction proteins via mechanisms involving not only MLCK expression but also MLC phosphorylation.?????