Protective Effect Of Endostatin On Acute Lung Injury In Septic Mice And Its Mechanism

BACKGROUND AND OBJECTIVE: Existing research have shown that oxidative stress and inflammation can lead to endothelial injury,which is closely related to coagulation disorders.In sepsis organ dysfunction,the lung is the most vulnerable target organ.Therefore,this experiment aims to study the protective effect of endostatin on acute lung injury in septic mice and explore its mechanism.METHODS: Sepsis model was established by cecal ligation and puncture(CLP).Male Balb/C mice aged 8 weeks were randomly divided into four groups: sham operation+ solvent control group(Sham+V),sham operation + endostatin group(Sham+ES),sepsis model + solvent control group(CLP+V),sepsis model+endostatin group(CLP+ES).The endostatin group was treated with endostatin(2mg/kg,intraperitoneal injection)immediately after operation.The solvent control group was given the same dose of normal saline at the same time point.The serum,lung tissue and alveolar lavage fluid of the mice were collected 24 hours after the operation.HE staining was used to observe the pathological changes of lung tissue;Pulmonary capillary leakage was detected by lung wet / dry weight ratio and Evans blue leakage test;Enzyme linked immunosorbent assay(ELISA)was used to detect early inflammatory factor(IL-1β,IL-6,TNF-α)and endothelial glycocalyx markers [syndecan-1,heparan sulfate(HS),thrombomodulin(TM)] of mouse serum and alveolar lavage fluid.ELISA also was used to detect serum coagulation related indexes [thrombin antithrombin complex(TAT),plasminogen activator inhibitor-1(PAI-1),D-dimer].Neutrophil infiltration in lung tissue was detected by immunohistochemistry.The activity of myeloperoxidase(MPO),malondialdehyde(MDA)and superoxide dismutase(SOD)in lung tissues were determined by colorimetry.RESULTS: The morphology of lung tissue in Sham + V group and Sham + ES group was generally normal,and the inflammatory factors,endothelial glycocalyx markers and coagulation related indexes were at the baseline level.There was no significant difference between the two groups.Compared with Sham+V group and Sham+ES group,lung tissue in CLP+V group showed significant morphological changes.The content of Evans blue in lung tissue was increased(p < 0.05),and the ratio of lung wet to dry weight was increased(p < 0.05),indicating that pulmonary capillary injury resulted in increased leakage in CLP+V group.The levels of inflammatory factors(IL-1β,IL-6 and TNF-α)in alveolar lavage fluid and serum were significantly increased(p < 0.01),the activity of MPO in lung tissue was increased(p < 0.01),and the infiltration of neutrophils was increased,indicating that pulmonary and systemic inflammation occurred in CLP+V group.The levels of syndecan-1,HS and TM in alveolar lavage fluid and serum were significantly increased(p < 0.01),indicating that endothelial integrity was impaired in CLP+V group.The level of MDA in lung tissue was increased(p < 0.05)and the level of SOD activity was decreased(p < 0.05),indicating that lung tissue of mice in CLP+V group was damaged by oxidative stress.Serum TAT,PAI-1 and D-Dimer levels were significantly increased(p < 0.05),indicating that the mice in CLP+V group had coagulation dysfunction.Compared with CLP+V group,the lung tissue morphological damage in CLP+ES group was significantly reduced,and the content of Evans blue and the ratio of lung wet-dry weight were decreased(p < 0.05),suggesting that endostatin intervention could reduce lung capillary leakage in CLP mice.The levels of inflammatory factors(IL-1β,IL-6 and TNF-α)in alveolar lavage fluid and serum were significantly decreased(p < 0.01),the activity of MPO in lung tissue was decreased(p < 0.01),and neutrophil infiltration was decreased,indicating that endostatin inhibited pulmonary and systemic inflammation in mice.The levels of syndecan-1,HS and TM in alveolar lavage fluid and serum were significantly decreased(p < 0.01),indicating that endostatin intervention protected the endothelial integrity of CLP mice.The content of MDA in lung tissue decreased(p < 0.05)and the activity of SOD increased(p < 0.05),suggesting that endostatin alleviated oxidative stress injury in CLP mice.Serum TAT,PAI-1 and D-Dimer levels were significantly decreased(p < 0.05),indicating that endostatin improved coagulation function in CLP mice.CONCLUSIONS: Endostatin has a protective effect on acute lung injury in septic mice.Its mechanism may be related to inhibition of excessive inflammatory response,reduction of oxidative stress injury,protection of endothelial glycocalyx and reduction of capillary leakage,while the corrected coagulation disorder may be closely related to the integrity of endothelial injury.