Over Expression Of IFI16 Increased Inflammatory Response In Hepatitis B Virus-Associated Glomerulonephritis By Regulating Caspase-1 And IL-1β

[Background]Hepatitis B virus(HBV)infection is an important public health problem worldwide.HBV infection leads both hepatic and extrahepatic organ injures.Hepatitis B virus-associated glomerulonephritis(HBV-GN)is common extrahepatic performance of HBV-infection and remains one of the most common secondary glomerular diseases[1].Ever since HBV-associated-glomerular,by Combes et al.in 1971[2,3].Subsequently,most studies focused on the immune complex deposition induced by HBV infection[3,4].However,the pathogenesis of HBV-GN is not entirely clear.IF116(Interferon-g-inducible protein 16)belongs to Pyrin-Hin200 family(PHI-200),playing important role in innate immune and oncogenesis[5].As innate immune sensors,IFI16 recognizes both cytosolic and nuclear double-stranded DNA(dsDNA)from invaded DNA viruses such as vaccinia virus(VACV)herpes simplex virus 1(HSV-1),and Kaposi sarcoma-associated herpesvirus(KSHV)[6,7,8].DNA recognition by IFI16 triggers downstream stimulator of interferon genes-TANK-binding kinase 1-interferon regulatory factor 3(STING-TBK1-IRF3)signaling to induce type I interferon(IFN-1)or apoptosis-associated speck-like protein containing a CARD(ASC)-caspase-1-dependent inflammasome to produce interleukin-1β(IL-1β)[8,9].Both IFN-I and IL-1β are important inflammatory cytokines playing critical roles in the host immunity against viral infection.However,over activation of IFN-a/b receptor(IFNAR)or caspase-1 induced excessive production of IFN-I or IL-113 and lead to autoimmune diseases such as systemic lupus erythematosus(SLE)and Sjogren syndrome[10,11].Although IFI16 induces the ASC-dependent inflammasome pathway and the IFN-b pathway through the STING-TBK1-IRF3 axis is well understood,the specific pathogenesis associated IFI16 against HBV invaded is unclear.HBV contains a circular and partially double-stranded DNA(dsDNA).Previous studies have found that HBV particles can be detected in the kidneys of HBV-GN patients[3,12,13].After sensing ds DNA,IFI16 leads to the formation of inflammasomes,lead to the activation of caspase-1 and the maturation and secretion ofIL-1 β,which may be responsible for the renal damage seen in HBV-GN patients.In this study,We used immunohistochemistry to determine the level of IFI16 in the cytoplasm of glomerular intrinsic cells infected with HBV and its relationship with caspase-1,IL-1 β inflammatory cytokines and renal inflammation.Moreover,The effects of IFI16,caspase-1 and IL-1β expression status in primary human glomerular mesangial(HGM)cells and HEK-293T cells transfected with HBVDNA and IFI16 or vector control or empty were also investigated.Our results showed that IFI16 expression is high in HBV-GN compared with CGN,IFI16 expression was positive correlation with caspase-1 and IL-1β expression.Furthermore,over-expression of IFI16 increased expression of caspase-1 and IL-1β in vitro.Thus,the combination of IFI16 and ds DNA,leads to the formation of inflammasomes,which,by activating caspase-1,leads to the formation of IL-1 β and other inflammatory cytokines,causing tissue cell damage and playing an important role in the pathogenesis and inflammatory response process of HBV-GN.[Methods]A total 75 patients with chronic nephritis(CN)including 50 with HBV-GN and 25 with chronic glomerulonephritis(CCN)involved in this study.Each CN patient undergoing renal biopsy,and the expression of IFI16,caspase-1 and il-1 was detected by immunohistochemistry(including IHC)[3].Following IFI16 was transfected in HBV-infected and HBV-uninfected human glomerular mesangial(HGM)cell line and HEK-293T cell line,expression of Caspase-1 and IL-1β were detected by Western blot and ELISA.Results of the study were analyzed by SPSS 22.0 software(version 22.0).Measurement data was described as mean± standard deviation.Fisher’s exact probability test and Chisquare test(categorical data)analysis of immunohistochemical results and the relationship between clinical pathological indicators.Comparison between the two groups using paired t test,multiple pairwise comparisons between samples using single factor analysis of variance.Spearman’s two-tailed test was used for correlation analysis and differences were regarded as significant if the p value was less than 0.05 on either side.[Results]1.IFI16 was expressed in the cytoplasm of glomerular endothelial cells and mesangial cells;2.The positive expression rate of IFI16 in HBV-GN patients was significantly higher than in CGN patients(80%versus 24%,p<0.05);3.Expression of IFI16 have no correlation with pathological type of HBV-GN and the status of HBV-associated antigen deposited in kidney(p=0.510,p=0.997);4.Expression of IFI16 was correlated with Caspase-1(rs=0.998,p<0.01)and IL-1β(rs=0.953,p<0.05);5.Over expression IFI16 increased Caspase-1 and IL-1 β expression in HBV-infected HGM and HEK-293T;[Conclusion]The elevation of IFI16 may be one of the important causes of kidney damage thus provides a possible therapeutic target and a new approach for studying the pathogenesis and clinical treatment of HBV-GN.