The Effects Of All-trans-retinoic Acid On Expression Of Myosin Light Chain Kinase In The Artery Wall Of Diabetic Rats And Its Molecular Mechanism

Objective To investigate whether the expression of myosin light chain kinase (MLCK) in the artery wall of diabetic rats is regulated by the all-trans-retinoic acid (ATRA) through the pathway of extracellular signal regulated kinase (ERK). Methods Sixty-five SD rats were randomly divided into normal group, high-lipid group, diabetic group, insulin group, ATRA group and insulin+ATRA group.The rat model of diabetes was induced by high-lipid diet and intraperitoneal injection of streptozotocin (STZ). The glucose, triglyceride and cholesterol levels in the serum of each group were measured after 12 weeks. The expression of MLCK in the artery wall was detected by immunohistochemistry and western blot. Meanwhile, the phosphorylation of MLC and ERK in the artery wall was also detected by western blot. HVSMC were cultured in vitro. Treatments for the 8 groups were: cell group, DMSO group, high glucose group, ox-LDL(75mg/L) group, high glucose+ox-LDL group, high glucose+ox-LDL+0.1μg/ml ATRA group, high glucose+ox-LDL+1μg/ml ATRA group, high glucose+ox-LDL+10μg/ml ATRA group. The expression of MLCK and the phosphorylation of MLC and ERK were detected by western blot. Results The rat model of diabetes was established successfully. The glucose and cholesterol levels in the serum of diabetic group increased markedly compared with that of normal and high-lipid group (P<0.05). Compared with diabetic group, the insulin group, ATRA group and insulin+ATRA group of the glucose and cholesterol levels in the serum significantly decreased (P<0.05). Both immunohistochemistry and western blot show that the MLCK expression in the artery wall of diabetic group significantly increased compared with normal and high-lipid group (P<0.05), while the expression of MLCK was decreased in insulin group, ATRA group and insulin+ATRA group (P<0.05). In addition, western blot also shows the level of phosphorylated MLC and phosphorylated ERK showed the same pattern as MLCK. The rerult of HVSMC in vitro reported that high glucose and ox-LDL can stimulate the expression of MLCK increased in vascular smooth muscle cells, and both have a synergistic effect (P<0.05). The high expression of MLCK can regulate by all-trans retinoic acid treatment (P<0.05), moreover, the phosphorylation level of MLC and ERK showed the same pattern as the expression of MLCK in vascular smooth muscle cells. Conclusion During the onset of diabetes, the expression of MLCK in the artery was significantly increased. However, ATRA therapy could down-regulate abnormal MLCK expression in the artery. Furthermore, this expression of MLCK in the artery might be regulatede through ERK signalling pathway.