Growth Differentiation Factor 15 Prevents Lipopolysaccharide-and D-galactosamine-induced Inflammation And Acute Liver Injury In Mice

OBJECT:Sepsis is a clinical syndrome of host organ dysfunction due to the imbalance of host infection.The main organ damage is the main cause of death due to sepsis,especially the liver.At present,the pathogenesis of septic liver injury is still obscure,and the clinical effect is not ideal.Previous research shows GDF-15 is a new TGF-β superfamily member,which function involves in immunosuppression,anti-apoptosis and anti-inflammatory.GDF-15 is significantly higher in patients with heart,liver and renal failure,and overexpression of GDF-15 can protect the kidneys and heart from LPS induced organ damage.Further experiments are needed to confirm its role and the potential mechanism.In this study,we investigate whether GDF-15 play a role and its mechanism in endotoxin induced liver injury after the mouse were stimulated by lipopolysaccharide(LPS)and D-galactosamine(D-GalN).METHODS:The model of acute liver injury was induced by intraperitoneal injection of LPS and D-GalN in mice.To investigate liver function with automatic biochemical analyzer,to observe the morphologic changes of the liver tissue of mice with HE staining,to detect proinflammatory cytokines in serum and liver tissue with ELISA,to detecte MDA and MPO in liver tissues by thiobarbituric acid method and four methyl benzidine method.To confirm the potential mechanism,we detected iNOS positive cell rate in liver tissue of mice by fluoreused imnunofluorescence staining and flow cytometry,invstigated the expression of iNOS mRNA in Kupffer cells by fluorescence quantitative PCR,detected the expression of COX-2 and MCP-1 in the culture supernatant of the liver tissue of mice and Kupffer cells,detected NF-kB signal pathway by Western blot.RESULTS:Hepatocyte injury and infiltration of inflammatory cells in the liver tissue of the mice were obvious after LPS/D-Ga1N stimulation.The levels of MDA,MPO and pro-inflammatory factors(IL-6,TNF-αand IL-1β)in liver tissue were significantly increased,and the same with serum ALT/AST and pro-inflammatory factor.GDF-15 significantly reduced the severity of on 1iver injury induced by LPS/D-GalN and the level of pro-inflammatory factors.In further study,GDF-15 significantly reduced the ratio of iNOS-positive macrophages in both and the liver tissue and the expression of iNOS mRNA in Kupffer cells after LPS induction.In addition,macrophage related proinflammatory cytokines COX-2 and MCP-1 expression was also significantly reduced.GDF-15 significantly downregulated the protein level of NF-kB p65,p-TAK1,P50 and p-IκBα in LPS-induced Kupffer cells.CONCLUSION:In sumrary,our study is the first to show that GDF15 plays a protective role in LPS-induced septic liver damage by reducing the level of proinlammation.GDF15 may serve its protective function by reducing the number and activation of pro-inflammation macrophages in liver,which potential mechanism is inhibiting the activation of IκBα-NF-κB signaling pathway by blocking the phosphorylation of transforming growth factor kinase 1(TAK1).