The Effect And Mechanism Of SIRT1 In The Inflammation Process Of Acute Respiratory Distress Syndrome

Background and objectives:Acute respiratory distress syndrome(ARDS)is a severe and acute clinical syndrome featured with severe respiratory distress and progressive respiratory failure.The main pathological features,including the diffuse damage of alveolar epithelial barrier and pulmonary capillary endothelial barrier,leads to the leakage of protein,pulmonary edema,infiltration of inflammatory cell and the formation of hyaline membrane.The activation of inflammatory cells and the release of a large number of inflammatory mediators from direct or indirect lung injury,would trigger the inflammatory cascade,and result in the loss of control of systemic inflammation.Although similar clinical factors and therapeutic schedule were administrated to ARDS patients,the probability of developed ARDS,the severity of inflammation,the progress and prognosis were also different.Therefore,the in-depth study of gene related to the occurrence of inflammation in ARDS would provide a new direction in the prevention and treatment of ARDS.SIRT1 is class III histone deacetylase(HDAC).Recent studies have confirmed that SIRT1 could initiate the inflammation with deacetylase NF-?B,FOXO3,p53 and other histone or nonhistone.It is reported that SIRT1 can inhibit the activation of inflammatory factors,but the sustained high level of SIRT1 would result in suppressive immunity and increased cells mortality.The environment would influence the role of SIRT1 in inflammation.The differences of disease stages and therapeutic targets would effect SIRT1 to regulate the body's inflammation and disease outcome.But the intrinsic role of SIRT1 in ARDS is not clear.Integrating the p38 MAPK signal pathway is the main inflammatory regulatory pathway of ARDS,we speculated that p38 MAPK signaling pathway may be involved in the regulation of SIRT1 to the ARDS.The study used mice in different background ploygene including SIRT1+/-gene konckdown mice and wild-type mice to establish ARDS model with lipopolysaccharide(LPS),based on the evaluation of SIRT1 gene knockdown on lung injury of inflammation and the expression changes of p38 MAPK signal pathway and observation in lung tissue,we sought to preliminary study the specific role of SIRT1 in the ARDS development and its possible mechanism induced by LPS.Methods:1.the SIRT1 gene+/-konckdown mice were adopted to pairs breed,then a sufficient number of SIRT1+/-mice were selected by using the PCR method to identify the genotype for follow-up study.2.The q RT-PCR and Western Blot test were performed to detect the differences of two SIRT1 expression in lung tissue of the SIRT1+/-gene konckdown mice and wild type mice.3.The ARDS model was established by intraperitoneal injection of LPS.The lung tissue pathological changes of two different SIRT1 gene background of mice were observed,and the wet to dry ratio(W/D ratio)of lung was calculated,the total number of leucocytes in the bronchoalveolar lavage fluid(BALF)was counted,the total protein concentration in BALF was detected with the BCA method;the levels of inflammatory factor TNF-? and IL-6 in BALF and plasma were reported by ELISA;the expression of p-p38 MAPK and p-ATF2 in lung tissue was detected by Western Blot and immunohistochemical statining in two mouse.results:1.Compared with wild-type mice(WT),the m RNA and protein expressions of SIRT1 in lung tissues of heterozygote mice(HET)with SIRT1+/-gene konckdown were significantly decreased(P<0.01).2.The pathological observation of HET+LPS group and WT+LPS group showed obvious damage to lung tissue compared with the control group of saline respectively,meanwhile the scores of lung tissues were significantly increased,and the lung tissue is more serious damaged in HET+LPS group,the scores of lung tissues also show a further increase.The lung W/D ratio,total number of leucocytes and total protein concentration in BALF,the levels of inflammation factor TNF-? and IL-6 in the plasma and BALF,were significantly increased in HET +LPS group and WT+LPS group compared with the control group,respectively(P<0.05),and the indexes mentioned above were increased more significantly in HET+LPS group compared with WT+LPS group(P<0.05).3.The expression of p-p38 MAPK and p-ATF2 in lung tissue were increased in HET+LPS group and WT+LPS group compared with the control group of saline,respectively(P<0.05),and the protein expression mentioned above was increased more obviously in HET+LPS group compared with WT+LPS group(P<0.05).Conclusions:1.The expression of SIRT1 in lung tissue of SIRT1+/-mice was significantly decreased,which could provide the necessary premise and effective protection for subsequent study.2.Compared with wild-type mice,the SIRT1+/-mice showed more severe inflammation in the disease model induced by LPS in ARDS,suggesting that the knockdown of SIRT1 had proinflammatory effects on ARDS mice induced by LPS,and SIRT1 plays a protective role in the ARDS inflammatory induced by LPS.3.Compared with wild-type mice,the expression of the p-p38 MAPK and p-ATF2 in lung tissues of SIRT1+/-mice were significantly increased,suggesting that p38 MAPK-p-ATF2 signaling pathway may be involved in the inflammatory regulation effect of SIRT1 on ARDS induced by LPS.