Pathogenesis And Targeted Therapy Of Liver Injury In Systemic Lupus Erythematous

Systemic lupus erythematosus(SLE)is a chronic autoimmune disease characterized by high levels of autoantibodies and multi-organ tissue damage,including kidney and skin.The liver as an important part of the body's immune system is the largest digestive and metabolic organ,but also the largest organ to generate complement,gradually attracting attention in the organs involved in SLE.Since the complexity of internal and external factors that affect liver damage,there is less research on SLE-related liver involvement,and no direct evidence that SLE disease itself can mediate liver injury at present.However,the mechanism of the cellular interaction involved in the pathogenesis of lupus liver diseases remains unclear.In order to clarify the involvement of liver in lupus erythematosus disease,a retrospective analysis of 404 cases of SLE patients was performed,on the other hand,we investigated the pathological and serological changes of liver in a transgenic lupus mouse model(MRL/lpr)to confirm that lupus disease can mediate liver injury by itself.The animal model of deposited lupus IgG-induced liver inflammation through intrahepatic injection of lupus serum in normal mice is a useful tool to investigate the pathogenesis of liver damage in SLE.We examined the liver injury by determining serum transaminase ALT levels and liver pathologic changes.By cell depletion,effects of the specific lymphocyte population and cellular interactions in the process of liver injury were investigated.The FACS analysis provided us with the precise information about lymphocyte phenotype,activation and cytokine production.We used ELISA to examine cytokine levels in serum and cell supernatant.Moreover,we also applied cell co-culture system,specific blocking with antibodies and gene knock-out mice to explore the potential mechanisms involved in the cell-to-cell communication.The major methods and results of our experiments are shown as follows:1.Spontaneous established liver damage in lupus diseaseWe analyzed the medical record of 404 patients with SLE.There were 91 lupus patients with liver dysfunction(LD),which includes changes of several serum biochemical parameters of liver function.Histopathological examination demonstrated that a large amount of inflammatory cell infiltrate around the portal areas of the livers in lupus-prone mice.We also investigated changes in serum biochemical parameters of liver function in lupus-prone mice and found that serum ALT and AST peaked at the age of 20 to 22 weeks,and decreased with the progression of the disease.We found that hepatic apoptosis and fibrosis development in the livers of lupus-prone mice.These findings suggest that liver damage develops spontaneously in lupus-prone mice.2.Liver inflammation is triggered by hepatic deposited lupus IgGImmunohistochemical analysis revealed that mouse IgG are widely distributed around the normal hepatic portal area and abundant IgG are deposited within the inflamed site in the liver of active lupus mice.Lupus IgG deposition in liver of normal mice by performing intrahepatic injection of serum from lupus patients and lupus-prone mice can induce hepatic lesions.Liver inflammation in this model was not caused by LPS contamination of lupus serum or by the surgical procedure.Liver inflammation only developed following local injection of lupus serum and not after systemic injection of lupus serum.We found that liver inflammation was significantly decreased in mice injected with lupus sera depleted of IgG or IgG-containing complexes compared with lupus sera without IgG depletion.The same dose of IgG from lupus serum mediated more severe liver damage than did IgG from healthy subjects.These data demonstrated that liver IgG deposition is a major pathological factor to initiate liver inflammation.3.Liver inflammation induced by hepatic deposited lupus IgG depends on marophages and NK cellsImmunohistochemical and FACS analysis demonstrated that macrophage cells,dendritic cells and T cells were increased in the liver of lupus-prone mice compared to normal mice.Experiments on Rag-1-deficient mice indicated that lymphocytes are attracted to the inflamed liver but not required for the initiation of the pathology.We evaluated the role of macrophages in the development of lupus IgG-induced liver lesions by using macrophage-depleted mice that were pretreated with clodronate liposomes.We found that the severity of the liver lesions and liver enzymes levels induced by lupus IgG were significantly reduced in macrophage-depleted mice compared to normal mice.FACS analysis suggest that an accumulation and activation of NK cells in the livers of lupus-prone mice and in the livers of mice treated with an intrahepatic injection of lupus serum or IgG compared to controls.The requirement of NK cells in liver inflammation induced by lupus IgG was confirmed by NK cell depletion experiments.4.Synergic effect of macrophage/TNF-?,and NK cells/IFN-? on hepatic apoptosis induced by lupus IgGImmunohistochemical staining showed that TNF-? and IFN-y were expressed around the inflammatory sites of livers in lupus-prone mice.Furthermore,the induction of these cytokines was enhanced both systemically and intrahepatically following serum or IgG treatment.The study demonstrated that after IgG intrahepatic injection,IFN-y was mainly produced by liver NK cells,and NK cell depletion could significantly inhibit IFN-? production in the serum.The immunofluorescent staining of liver sections showed that TNF-? was produced mainly by macrophages.The levels of TNF-? or IFN-y are abrogated following IgG intrahepatic transferring in mice with macrophage or NK cells depletion,respectively.We found that hepatic inflammation was markedly attenuated in TNF-?-/-and NK cell-depleted mice and even hepatic apoptosis was abolished in TNF-?-/-mice with NK cell depletion.These data suggest that TNF-? and IFN-y have a synergic effect on liver injury induced by lupus IgG.5.Blocking IgG/Syk signaling suppressed liver inflammation induced by hepatic deposited lupus IgGThe effect of deposited IgG on hepatic inflammation was investigated by using FcyRIIb-deficient mice and FcyRIII-deficient mice in vivo.We found that lupus IgG stimulated Syk activation in bone marrow derived macrophages(BMDMs)in vitro,and this process have suppressed by Syk inhibitor R406.We assessed intracellular signaling pathways induced by lupus-IgG and found that phosphorylation and degradation of I?B? for the activation of NF-?B were inhibited in the condition of Syk signaling blocked,indicating that Syk activation is required for lupus IgG-induced liver disease.Syk inhibitor treatment led to a significant reduction in liver inflammation and hepatic apoptosis induced by deposited lupus IgG in mice.These data indicate that Syk plays an important role in liver inflammation induced by deposited lupus IgG.Conclusion:Although abnormal liver function in SLE patients has been well documented during the past several decades,the pathogenesis of liver injury in SLE remains unclear.Our clinical study of patients with SLE and our animal studies demonstrate that liver injury was caused by SLE and that hepatic deposited lupus IgG deposition is an important pathological factor in the development of liver injury in SLE.Additionally,macrophages and NK cells and their products play a major role in liver injury regulated by Syk in SLE.