Expression And Significance Of CHOP/KLF4 In Hepatic Fibrosis Induced By Schistosoma Japonicum

Human schistosomiasis is a zoonotic parasitic disease that has been epidemic for a long time,and has brought enormous health and socio-economic burdens to mankind.China is one of the main endemic areas of Schistosoma japonicum(S.japonicum)with a wide epidemic range.After the cercariae of japonicum infect human host,the worms lodging within the veins will produce hundreds to thousands of eggs daily.Once entering the host liver through blood circulation,schistosome eggs deposit in liver and produce soluble egg antigen(SEA)continuously,evoking severe granulomatous inflammatory reaction.Gradual formation of granulomas precipitates development of liver fibrosis which increases portal blood pressure,and ultimately contributes to the mortality of schistosomiasis.Inhibition of egg granulomas and alleviation or even prevention of fibrosis is significant for improving the living quality of patients and reducing the mortality.However,the mechanisms of the formation of S.japonicum induced hepatic granulomas and fibrosis are complicated,with multiple cells and chemokines involved in regulation and exerting integrated effect.It is still a vital scientific problem in schistosomiasis research.The pathology of hepatic fibrosis attributes to the constant immune response of CD4~+T cells to SEA stimulation,while CD4~+Th2 immune response is dominant.Furthermore,hepatic stellate cells(HSCs)are identified as major cellular contributor to fibrotic process in which they transdifferentiate into myofibroblast marked with extracellular matrix(ECM)production.The deposition of massive ECM in liver leads to the development of hepatic fibrosis.Recent research found that Krüppel-like factor 4(KLF4)may be involved in hepatic fibrosis via inhibiting HSCs activation.It was reported previously that the transcription factor C/EBP homologous protein(CHOP),a pivotal pro-apoptotic regulatory factor,facilitated the formation of fibrosis in the lung,kidney,heart,and fibrosis induced by liver injury.However,there are no prior published studies in which the involvement of CHOP in hepatic fibrosis during schistosomiasis has been considered.Based on the previous research,we speculate that CHOP should play a role in schistosome induced liver fibrosis.Therefore,this study takes CHOP as the main point.We established C57BL/6 mice as experimental schistosomiasis models for S.japonicum to analyze how CHOP correlates with hepatic fibrosis formation and the possible underlying mechanisms.The ultimate purpose of this study is to provide new insights into the strategy interfering with hepatic fibrosis caused by S.japonicum.Objective:To observe the expression change of CHOP,and evaluate its role and the possible mechanism in the development of schistosome induced liver fibrosis.Methods:The SPF C57BL/6 mice(8 weeks)were randomly divided into control and infection group.Experimental model of hepatic fibrosis during schistosomiasis japonicum was established by infecting mice with cercariae of S.japonicum.Mice were sacrificed at 4,6,8,10,12 weeks post-infection and liver samples were collected.HE staining and MASSON staining were conducted with paraffin sections of liver tissue,and then,average granuloma area and average expression of collagen fibers were respectively analysed for the change of granuloma size and the degree of fibrosis.The expression of CHOP and KLF4 protein in liver at increasing time-points were detected with Western Blot.Results:(1)Observation indexes showed that,compared with the control group,mouse weight increased at 4-10 weeks post-infection with S.japonicum,and there were an increase in liver weight and a significant increase(P<0.05,P<0.01)in liver index(%)with time dependence at all weeks post-infection.(2)Pathological changes of liver showed that,compared with the control group,the average granuloma area of liver tissue increased significantly(P<0.01)at 6-12 weeks post-infection,and the average expression of collagen fibers increased significantly(P<0.01)at 8-12 weeks post-infection.Compared with the 10-week infection group,there was some decrease in the average granuloma area and expression of collagen fibers at 12 weeks.(3)Compared with the control group,the expression of CHOP protein was significantly higher at 6-12 weeks post-infection,and increased with the exacerbation of hepatic fibrosis.However,there was some decrease in CHOP protein expression at 12 weeks.(4)Compared with the control group,the expression of KLF4 protein was significantly lower at 6-12 weeks post-infection,and reached the minimum at 10 weeks post-infection when the degree of fibrosis is severe.Conclusion:(1)Our study found that CHOP is involved in the development of S.japonicum induced hepatic fibrosis.(2)Down-regulation of KLF4 is involved in the development of S.japonicum induced hepatic fibrosis.(3)Above study provided experimental basis for the intervention strategy based on CHOP and KLF4.