Activated Protein C Ameliorates Aortic Dissection Via YB1/OGT/p66Shc/ROS Axis

Objective:Aortic dissection is a serious aortic disease in which the blood in the lumen enters the middle layer of the arterial wall through the intimal breach after the aortic intimal tear,forms a dissection hematoma,and expands along the long axis of the blood vessel,forming the pathological changes of the true and false lumen of the artery.At present,the pathophysiological mechanism of aortic dissection has not yet been elucidated.Therefore,further research on the pathogenesis of aortic dissection is of great significance for clinical prevention and treatment.Adaptor protein p66Shc is a mitochondrial redox state sensing protein,which is closely related to mitochondrial oxidative stress.Studies have shown that coagulation protease activated protein C（a PC）can ameliorate diabetic nephropathy by epigenetically regulating p66Shc expression.So whether a PC can also regulate the expression of p66Shc,affect the formation of ROS in vascular wall and protect aortic dissection,and how a PC regulates the expression of p66Shc remains to be clarified.This study will provide a new theoretical basis and early prevention and treatment ideas for the pathogenesis of aortic dissection.Methods:8-week-old male C57BL/6N background Apo E^-/-mice（wild type）and TM^p/p×Apo E^-/-mice（mutant type）with impaired protein C activation in vivo were selected.Mice were divided into four groups:saline group,protein C（PC）group,angiotensin II+saline（Ang II+saline）group and angiotensin II+protein C（Ang II+PC）group.First,Wild type and mutant mice were givenβ-aminopropionitrile（BAPN）at a concentration of 0.1%for3 weeks in drinking water and infused via osmotic mini pumps with either saline or 2500ng/kg/min angiotensin II（Ang II）for 2 weeks.Wild type and mutant mice were given PC treatment for weeks.PC was freshly prepared in physiological saline and administered to mice at a dose of 1 mg/kg every day through intraperitoneal injection.Results:This study confirmed that a PC can effectively prevent the occurrence and development of aortic dissection.The results of in vitro experiments further elucidate the specific molecular mechanism of the protective effect of a PC on aortic dissection.Firstly,in human umbilical vein endothelial cells,a PC can alter the epigenetics of p66Shc by reducing acetylated histones to reduce its expression,while reducing the expression of matrix metalloproteinase（MMP2/9）,inflammatory indicators（ICAM1 and VCAM1）and the level of oxidative stress.Secondly,a PC can inhibit the mitochondria translocation of p66Shc induced by Ang II and the decrease of mitochondrial membrane potential caused by Ang II;thirdly,a PC promotes the expression of glycosyltransferase by regulating the expression of YB1 protein,increases the O-glycosylation modification level of p66Shc protein and then inhibits the translocation of p66Shc mitochondria.Thus,the production of mitochondrial ROS and the decrease of mitochondrial membrane potential were inhibited.The point mutation of the 29th amino acid on p66Shc protein（O-glycosylation modification site,threonine mutation to alanine）showed that a PC inhibited its translocation mainly by regulating the O-glycosylation modification of the 29th amino acid on p66Shc protein.Conclusions:On the one hand,a PC reduces its expression by regulating the epigenetics of p66Shc,and on the other hand,it regulates the expression of YB1 protein to up-regulate the expression of glycosyltransferase and increases the level of O-glycosylation of p66Shc protein and inhibits its mitochondrial translocation,thereby inhibiting the decrease of mitochondrial membrane potential and the generation of ROS,and finally inhibiting the occurrence and development of aortic dissection.