HBXIP Regulation Of Macrophage Lysosomal Function And Its Role In Autoimmune Diseases

Background:Autoimmune diseases are a series of disorders caused by the immune response to autoantigen,resulting in the dysfunction of multiple organs and tissues.The onset of autoimmune diseases is closely related to multiple factors such as heredity,loss of immune tolerance and so on.Recent studies have demonstrated that abnormal autophagy or dysfunction of lysosome in immune cells have influence on the process of autoimmune diseases,in consequence,it is important to search for a molecular participating in autophagy-lysosome pathway for the prevention of autoimmune diseases and reveal relevant mechanism.Previous studies have found a phenotype of autoimmunity in HBXIP conditional knockout mice(HBXIP△LysM),however,its mechanism is not clear.Objective:The study intends to confirm the significant role of HBXIP in the progression of autoimmune response and inflammation and reveal the related mechanism.Methods:The spleens of 4-month-old HBXIP conditional knockout mice(HBXIP△LysM)and HBXIPfl/fl control were weighed and their cell population was analyzed by flow cytometry.Meanwhile,Blood was tested for routine,biochemical and immunological indicators and tissues were pathologically evaluated for the inflammatory cell infiltration.To explore the effect of macrophage function with the loss of HBXIP,bone marrow cells isolated from the hind legs of HBXIP △LysM and HBXIPfl/fl mice and induced by the cytokine M-CSFs into BMDMs.The expression of LC3 and p62,markers of autophagy,were measured by western blotting and the fluorescence intensity of double fluorescent plasmid RFP-GFP-LC3 was detected by immunofluorescence.For changes in lysosome function,the expression of CTSD was detected by western blotting.Molecular probes,including DQ green BSA,Lysosensor and LysoTracker,were used to detect the degradation capacity of cell and acidity of lysosome.In mechanism,the catalytic activity of V-ATPase was measured with the method of malachite green phosphate.The probable interactions between HBXIP and V-ATPase subunits were detected by co-immunoprecipitation.Human peripheral blood monocyte cells(PBMCs)were isolated to test the gene expression of HBXIP and the correlation between the expression level and clinical indexes was analyzed.Results:HBXIP△LysM mice showed a series of symptoms,consisting of enlarged spleen and lymph nodes,increased serum levels of anti-DS-DNA antibodies,IgM and IgG,gross changes and inflammatory cell infiltration in major organs such as skin,lung,colorectal and joint,indicating the phenotype of autoimmune disease and development of systemic inflammation.Loss of HBXIP blocked the process of autophagy flux in macrophages and impaired degradation ability and acidic environment of lysosomes,affecting the catalytic activity of V-ATPase on lysosomes.The molecular mechanism studies have shown that the HBXIP had an interaction with ATP6V1A.Conclusion:HBXIP can have a protective effect on the function of lysosome in macrophages and autoimmune diseases further,providing a new strategy for the treatment of autoimmune diseases.HBXIP was significantly lower in the patients with systemic lupus erythematosus(SLE),affecting the progression of autoimmune disease...