The Role Of P53 In The Inhibition Of Abdominal Aortic Aneurysm By Caloric Restriction

Background and Purpose:Abdominal aortic aneurysm?AAA?is a degenerative vascular disease characterized by progressive segmental abdominal aortic dilation.Because of the rupture of the aneurysm,the mortality rate is very high in the population.Surgery therapy is recommended to prevent large AAA rupture.However,there is still no effective drug to prevent the progression of AAA.Angiotensin II?Ang II?can induce the formation of oxygen free radicals,the expression of inflammatory factors and the synthesis of matrix metalloproteinases by activating downstream signal molecules,leading to the inflammatory reaction of abdominal aortic wall and the degradation of collagen and the necrosis of the media of the artery,which account for the gradual expansion of the aneurysm and the formation of aneurysms.Caloric restriction?CR?refers to reducing the body's energy intake by about 30%⁴0%on the premise of ensuring the basic nutritional needs of the body.As a convenient dietary intervention,long-term CR can significantly reduce the incidence of cardiovascular and cerebrovascular diseases in humans and primates.Recent studies have shown that CR,as a non-drug intervention,can resist AAA formation induced by Ang II.Therefore,as an important protective factor,clarifying the mechanism of CR's resistance to AAA formation is of great significance for preventing the risk of AAA rupture and reducing its mortality.Senescent of vascular smooth muscle cells?VSMCs?is often accompanied by the formation of AAA.Cellular senescence secretes a series of cytokines,chemokines and proteases,which participate in vascular structural and functional disorders,and promote the occurrence and development of AAA.P53,as an important transcription factor in cells,regulates the expression of many important downstream molecules through the changes of expression level and modification status,thus participating in regulating various cell activities.P53 plays an important role in maintaining cell homeostasis and genomic stability.The deletion or mutation of p53 gene results in tumorigenesis,while overexpression of p53leads to aging and apoptosis.Evidence suggests that p53-dependent VSMCs senescence is the key pathological process of AAA.Previous studies have shown that the formation of AAA is often accompanied by overexpression of p53 in vascular smooth muscle cells.However,the role of p53 in CR antagonizing AAA formation remains unknown.Mitochondria are key sites for intracellular ATP production and redox.The number,distribution and activity of mitochondria are important factors to maintain cell homeostasis,and their dysfunction is one of the main causes of cell senescence.Studies have shown that appropriate expression levels of p53 also play a decisive role in the normal functioning of mitochondria.Too high or too low expression of p53 can cause mitochondrial dysfunction,where impaired mitochondrial oxidative respiratory chain function leads to overproduction of reactive oxygen species?ROS?,which aggravates the occurrence of inflammation and aging.Recent studies have shown that CR can significantly inhibit the increase of p53expression in the aorta of Ang II-induced mice,but whether CR can inhibit mitochondrial dysfunction and antagonize vascular aging by regulating p53 remains to be further explored.Materials and Methods:This study is to investigate the role of p53 in the inhibition of AAA in CR,and it is divided into two parts:in vitro and in vivo.In vitro experiments were performed on primary vascular smooth muscle cells of mice.Wild-type mice(P53^+/+)and P53 knockout(P53^-/-)mice with C57BL/6J background were used in the body experiment.After limiting energy intake or free feeding for 12 weeks,the experimental group was given an Ang II infusion.At 4 weeks,AAA formation was induced,and the control group was given an equal volume of saline.1.The p53^+/+and p53^-/-mice were subjected to CR for 12 weeks to examine body weight,blood pressure,and glucose metabolism.2.The incidence of AAAs in each group and the maximum diameter,weight and body weight ratio of the arteries were measured.The elastin degradation of aortic in each group was detected by van Gieson staining.3.SA-?-gal staining was used to detect senescence of vascular wall cells;intracellular ROS production was detected by DHE probe and intracellular ATP,H2O2 content was detected by corresponding kits.4.The high-resolution mitochondrial respiratory function assay system?O-2k?was used to detect the effects of mitochondrial respiratory function in vascular smooth muscle cells treated with serum from CR and p53^-/-mice.Result:1.Compared with AL,CR can improve glucose metabolism and reduce body weight in mice,but has no significant effect on blood pressure.p53 knockout does not affect the beneficial effects of CR on body weight and glucose metabolism.2.CR significantly increased the incidence of AAA formation,arterial diameter and aortic weight ratio increased,accompanied by elastin destruction and fragmentation in p53^-/-mice.3.CR significantly increased the senescence of the abdominal aortic wall,increased production of reactive oxygen species in cells and mitochondria,and ATP production was significantly reduced in p53^-/-mice.4.Mitochondrial respiratory function analysis showed that in CR serum treatment of vascular smooth muscle cells,p53 knockout resulted in decreased function of mitochondrial respiratory chain complex enzyme IV.In conclusion:1.CR reduces Ang II-induced AAA formation in mice in a p53-dependent manner.In the context of deletion of the p53 gene,CR in turn aggravated Ang II-induced AAA formation.2.The dysfunction of the complex mitochondrial IV on the mitochondrial respiratory chain during p53 knockout aggravates the oxidative stress,inflammatory response and senescence of VSMCs,and thus blocks the protective effect of CR on AAA.P53-dependent mitochondrial normal function plays a key role in regulating the protective effect of CR on AAA formation.