The Role Of HIPPO Pathway In Liver Fibrosis Caused By Schistosoma Japonicum Infection

Objectives: After schistosome infection,the eggs are deposited in the hepatic sinusoid.Multiple inflammatory cells are recruited around the eggs,participating in the inflammatory response and releasing a variety of cytokines that activate HSCs and play an important role in the process of liver fibers.The HIPPO signaling pathway is a kinase chain consisting of a series of conserved protein kinases and transcription factors,which are closely related to cell proliferation,polarization,transdifferentiation and apoptosis.HIPPO signal influence the occurrence and progression of liver fibrosis through affecting the transdifferentiation,proliferation and apoptosis of non-parenchymal cells.It is still unclear which mechanism HIPPO signaling pathway work on the development of liver fibrosis caused by schistosome infection.This study was to investigate the mechanism of HIPPO signaling pathway on hepatic fibrosis in mice infected with schistosome by inhibiting the function of YAP.Methods: Female 8-week-old BALB/c mice were infected with 16 S.japonicum cercariaes through skin to construct a model of schistosome infection.The HSCs of mice were isolated from 4,8 and 15 weeks after infection,to detect the expression of HIPPO signal marker YAP.After infection for 4 weeks,VP(Verteporfin)were injected intravenously.8 and 10 week s after infection,the change of liver fibrosis in mice after YAP inhibited were observed,and the expression of profibrotic genes and proteins in the liver were detected.The HSCs were isolated to detect expression levels and activation levels of fibrosis.To investigate the role HIPPO signaling play in hepatic macrophage activation after infection,the Kupffer cells were isolated to observe the differentiation phenotype.The LX-2 was cultured with the supernatant of Kupffer cells to observe the role of Kupffer cells play on the activation of HSCs.Results: Obvious egg granulomaswere in the liver of mice,After 6 weeks of schistosome infection.After 4,8,and 15 weeks of infection,the levels of HIPPO signaling-related molecule YAP increased in HSCs,and YAP was accumulated into the nucleus inimmunofluorescence staining.To further understand the role of HIPPO signaling in liver fibrosis duringschistosomiasis,we injected VP 4 weeks after schistosoma infection,and collected liver and HSCs in mice 4 and 6 weeks later.The severity of liver fibrosis was reduced,the mRNA level of a-SMA,Collagen1-a(16)and TGF-b1 in liver tissue was decreased,while the levels of a-SMA,Collagen1-a(16)and CTGF in HSCs were also decreased.Meanwhile,we found Inhibition of YAP decreased mRNA expression levels of Arg1 and CTGF in Kupffer cells.In vitro,supression of YAP also reduced the mRNA levels of Arg1,CTGF and TGF-b in the RAW264.7.To clarify the role YAP inhibition plays onKupffer cells activating HSCs,we injected a YAP inhibitor or vehicle for 4 or 6 weeks,and collected cultured supernatants of Kupffer cells to culture LX-2.The mRNA levels of a-SMA,Collagen1-a(16)and CTGF of HSCs decreased,these showed YAP inhibitors slowed the process of Kupffer cell supernatant to aggravate the activation of HSCs in infected mice.Conclusion: The YAP of HSCs increased at the level of transcription and translation,and aggregated into the nucleus,after schistosomoa infection.These results indicates that liver fibrosis caused byschistosomiasis is accompanied by inhibition of HIPPO signaling and activation of YAP in HSCs.Inhibition of YAP in vivo reduces liver fibrosis in infected mice,indicating that the HIPPO signal pathway affects the development of liver fibrosis.Supression of YAP not only inhibits the activation of HSCs,but also represses the transdifferentiation Kuppfer cells to M2-type and reduces the secretion of pro-fibrotic factors.In addition,in vitro,the culture supernatant of Kupffer cells isolated from mice infectedcan aggravate the activation of HSCs,while inhibiting the YAP of Kupffer cells can alleviate this progression,suggesting that activation of HIPPO signal can inhibit the activation of HSCs,and affects the formation ofliver fibrosis by affecting the inflammatory microenvironment around HSCs.