LBP Protected Hepatic Mitochondria From Sepsis-induced Damage Via MTOR Signaling Pathway In Rat Sepsis Model

[Background]Sepsis,as a disease of host organ dysfunction caused by infection,has more than 19 million sepsis patients worldwide each year,with a mortality rate of more than 25%.After the occurrence of sepsis,it can cause fever,muscle soreness,organ dysfunction,septic shock and eventually death.Lipopolysaccharide（LPS）,the outermost structure of the cell wall of Gram-negative bacteria,is one of the main pathogenic factors of sepsis.When LPS invades the body,the lipopolysaccharide binding protein（LBP）secreted by the body specifically binds LPS,to promote the binding of LPS to TLR4 and CD14 on the cell membrane surface,forming LPS/TLR4/CD14 complex and causing inflammation.Anti-inflammatory therapy is often used to treat sepsis.Blocking the binding of LBP and LPS or knocking out LBP can reduce the inflammation caused by LPS.But the therapeutic effect in sepsis is controversial.Metabolic homeostasis is the very important role for maintaining cell function.Sepsis can also cause cell metabolic dysfunction and lead to death.Liver plays a complex role in the pathogenesis of sepsis.Hepatic metabolic disorders are caused by inhibited glycolysis in the later stage of sepsis.Thus,we speculate that knockout LBP can reduce inflammation,but sepsis will cause metabolic disorders,which is one of the reasons for poor anti-inflammatory effect.[Research Contents]1.Knockout of LBP gene in SD rats by Crispr-Cas9 technique 2.Serum biochemical analysis,Real-time PCR,histochemistry,transmission electron microscope and flow cytometry were used to compare the effects of WT and LBP^-/-rats on inflammatory response and liver structure and function induced by LPS.3.Transcriptome sequencing was used to analyze the changes of m RNA expression levels in WT rats and LBP^-/-at different time points（0h,6h,24h）after LPS injecting.4.Using Rapamycin to inhibit m TOR signal pathway,regulating metabolic function in septic rats,and detecting the changes of liver mitochondrial function in LBP^-/-rats.To explore the role and mechanism of LBP in sepsis caused by LPS.[Results]1.In the LPS-inducing sepsis rats model,knockout of LBP could reduce the liver injury（AST,ALT,p<0.05）and m RNA expression of inflammatory factors（TNF-α,IL-6,p<0.05）after LPS injecting for 1h,6h.2.After LPS injecting for 24 h,the liver morphology showed that there was hepatic edema in LBP^-/-rats.Comparing with WT rats,the number of hepatocyte mitochondria decreased,ROS increased,mitochondrial damage increased.3.Transcriptome analysis showed that the activation of NF-κB signal pathway decreased in LBP^-/-rats after LPS injecting for 6 hours.But the lipid metabolism pathway and cellular oxidation related genes were abnormal in LBP^-/-rats after LPS injecting for 24 hours.4.The inhibition of m TOR signal pathway by rapamycin can reduce the mitochondrial damage induced by LPS stimulation for 24 hours,reduce ROS and enhance the oxidative respiratory and glycolysis function of mitochondria in LBP^-/-rats.Therefore,the edema of liver tissue and the decrease of the number and function of liver mitochondria in LBP^-/-rats after LPS injecting for 24 h were caused by abnormal lipid metabolism and cell oxidation.[Conclusion]1,Knockout of LBP alleviated the liver injury and reduced the expression of inflammatory factors induced by LPS.2,LPS induced edema of liver cells,decrease of number and function of mitochondria in LBP^-/-rats,and aggravation of mitochondrial damage in hepatocytes.3,After LPS injecting for 24 h,the hepatic metabolism and cellular oxidative transcriptome of LBP^-/-rats were changed.4,LBP protected rats’ liver mitochondria from sepsis-induced damage via m TOR signaling pathway.