The Protective Effect And Mechanism Research Of Melatonin On Nicotine-related Abdominal Aortic Aneurysm

Objective: Abdominal aortic Aneurysm(AAA)refers to a diameter greater than 50%(or greater than 30 mm)of the diameter of the abdominal aorta after dilation.The incidence of AAA is higher than 5% in people over 65 years of age,and it is highly likely to cause death if ruptured.At present,the abdominal aortic aneurysm with a diameter greater than 50 mm is mainly treated with Open Surgical Repair(OSR)and Endovascular Aortic Aneurysm Repair(EVAR).However,for early AAA,several studies have shown that early surgical interventions do not have the expected benefits.Currently,small-diameter AAA is mainly monitored by imaging techniques.For the early stage,it is the best time to control the expansion of AAA with drugs,but there is currently no effective drug treatment for AAA in the clinic.Therefore,exploring the pathogenesis of AAA and finding effective drugs have great clinical significance.Classical histological changes in AAA include massive inflammatory cell infiltration,degradation of extracellular matrix,destruction of arterial wall structure,and dysfunction of vascular smooth muscle cells.As a chronic inflammatory disease,the inflammatory microenvironment is closely related to AAA.Our previous experiments showed that the inflammatory microenvironment of the arterial wall promotes AAA development through related signaling pathways.Vascular smooth muscle cells(VSMC)are an important component of the arterial wall.VSMC has two phenotypes,a contractile phenotype and a synthetic phenotype.The contractile phenotype of VSMC have a very important role in maintaining the normal elasticity of the vessel wall and the pressure of the vessel wall.When exposed to external stimuli,the contractile phenotype of VSMC will switch to a synthetic phenotype,which is also the basis of vascular disease.AAA is a chronic inflammatory disease,autophagy is closely related to inflammation,suggesting that autophagy is involved in the formation of abdominal aortic aneurysm.Studies have reported that autophagy-related genes are up-regulated in abdominal aortic tissue,but the mechanism of abdominal aortic aneurysm on autophagy is still a blank.Melatonin is a steroid hormone secreted mainly by the pineal gland at night.Its main function is to regulate the circadian rhythm.Studies have shown that melatonin is currently the strongest endogenous antioxidant in the body,with a strong anti-inflammatory effect,regulating blood sugar metabolism and blood lipids and other broad physiological and pharmacological effects.In recent years,it has been found that melatonin plays a very important role in regulating other organ functions,especially cardiovascular diseases,such as hypertension,ischemic heart disease and atherosclerosis,and evidence suggests that endogenous melatonin levels are associated with multiple cardiovascular diseases including myocardial infarction.but there is currently no association study between endogenous melatonin levels and abdominal aortic aneurysms.Smoking is a major risk factor for the development abdominal aortic aneurysm(AAA).Studies have shown that smoking can increase the incidence of AAA and the risk of rupture,but there is no report on how smoking regulates abdominal aortic aneurysm.So how does nicotine as a major component of cigarette smoke affect AAA,and whether melatonin has a therapeutic effect on nicotine-related AAA requires further exploration.Therefore,this study studied the changes of melatonin and inflammation levels in AAA patients,and studied the regulation mechanism of nicotine on abdominal aortic aneurysm and the treatment of melatonin on nicotine-related aneurysms,aiming to provide experimental basis for the pathogenesis of AAA.And it provides new therapeutic strategies and new targets for clinical treatment of AAA.Methods: 1)Blood samples from AAA patients and control group were obtained.The changes of serum melatonin levels in the two groups were measured.The serum inflammatory index tumor necrosis factor-?(TNF-?)and the difference in antioxidant capacity levels were measured in AAA patients and control group and performed a correlation analysis of melatonin levels and antioxidant capacity in AAA patients.AAA patients were divided into smoking group and non-smoking group,and changes in melatonin levels were measured in the two groups.2)The model of abdominal aortic aneurysm of SD rats was established by using the method of elastase perfusion.The experiment was divided into two groups: inactivated elastase sham operation group and active elastase operation group.Western blotting was used to detect expression levels of AKT and p-m TOR proteins at 14 days postoperatively.and simultaneous detection of expression levels of autophagy-related proteins LC3 II,LC3I,and p62 proteins.At the same time,the expression levels of vascular smooth muscle contractile proteins SM22?,?-SMA and the expression of synthetic protein OPN protein were detected in each group.The phenotypic switch of vascular smooth muscle cells during AAA formation was observed.3)Nicotine and melatonin were separately used to construct AAA model.The experiment was divided into three groups: abdominal aortic aneurysm model group,nicotine-related aneurysm group,melatonin treatment for nicotine-related aneurysm group,and detection of rat rats in each group.The diameters of abdominal aorta in each group were measured,and the changes of elastic fibers in each group were detected.The expression levels of pAKT and p-m TOR protein in each group were detected by Western blotting,and the expression levels of autophagy-related proteins LC3 II,LC3I and p62 were detected.Finally,the expression levels of vascular smooth muscle contractile proteins SM22? and ?-SMA and the expression of synthetic protein OPN protein in each group were detected.The effect of nicotine on AAA and the regulation mechanism of melatonin on nicotinerelated abdominal aortic aneurysm were investigated.Results: 1)ELISA results showed that compared with the control group,the level of melatonin in AAA patients was significantly lower,the difference was statistically significant,and the level of TNF-? in AAA patients was also significantly higher than that in the control group,but the level of antioxidant capacity in AAA patients was lower than in the control group.There is a positive correlation between melatonin levels and antioxidant capacity in AAA patients.At the same time,we detected that the level of melatonin in smoking AAA patients was lower than that in non-smoking AAA patients.2)Our results showed that the expression levels of p-AKT and p-m TOR protein were increased in the AAA model rats,and the ratio of autophagy-associated protein LC3II/LC3 I was increased,autophagy substrate protein p62 increased,and the expression of vascular smooth muscle contractile protein SM22?,?-SMA decreased,and the expression of synthetic protein OPN protein increased.3)Nicotine treatment will accelerate AAA dilation,while melatonin will inhibit the dilation of nicotine-related abdominal aortic aneurysm and restore the structure of blood vessels.Compared with the aneurysm model group,the nicotine-treated group further activated the AKT-m TOR pathway,the autophagy-associated protein LC3II/LC3 I ratio increased,the autophagy substrate protein p62 was increased,the expression levels of vascular smooth muscle contractile proteins SM22? and ?-SMA decreased,and the expression of synthetic protein OPN protein increased.After melatonin treatment,it inhibits AKT-m TOR pathway,decreases autophagy-related protein LC3II/LC3 I ratio,decreases autophagy substrate protein p62,and increases the expression of vascular smooth muscle contractile protein SM22?,?-SMA,and decreases the expression of synthetic protein OPN protein.Conclusion: This study demonstrates that there is insufficient melatonin level in AAA patients,and the level of inflammation in AAA patients increased,the antioxidant capacity decreased,and the level of melatonin in smoking AAA patients decreased further.There is a positive correlation between melatonin levels and antioxidant capacity in AAA patients.During the formation of AAA,the AKT-m TOR signaling pathway is activated,autophagy is dysfunctional,and the vascular smooth muscle cell phenotype is contracted to synthetic,and nicotine accelerates AAA dilation,which further aggravates the above process,while melatonin Inhibit the dilation of nicotine-related abdominal aortic aneurysm by restoring vascular smooth muscle cell phenotype expression.