Correlative Research Between Leptin And Tgf-β1 And The Recovery On CCl₄ Induced Hepatic Fibrosis In Rats

The liver is an metabolism and biotransformation organ in our body.It susceptible to be invasion by pathogens and stimulating factors stimulatied,for rich blood supply,which lead to liver damage and inflammation.The liver long time is at the damage condition, often lead to liver fibrosis(hepatic fibrosis). Hepatic fibrosis characterized by excessive deposition of extracellular matrix (ECM) proteins,, altered hepatocyte regeneration, deranged microvascular architecture and cirrhosis.A wealth of evidence now indicated that this process was irreversible. Key to this is the discovery that reversion of fibrosis is accompanied by clearance of activated hepatic stellate cell (HSC) by apoptosis. Therefore, modulation of apoptosis of activated HSC could be an important complementary pathway in preventing hepatic fibrosis.Recent studies demonstrated that the Leptin and its receptor(OB-Rb) was increased during the hepatic fibrosis.Leptin may activates the HSC directly by combining OB-Rb on HSC. It also could integrate OB-Rb on Kuffer cell(KC),stimulating KC to secrete fibrosis factors such as transforming growth factorβ1(TGF-β1) and so on. But the HSC proliferation and cell factors secrete whether affected by the change of Leptin and OB-Rb during regression of hepatic fibrosis is still far from being fully understood.In view of the significance of Leptin,our research are based on the recovery of CCl4 induced hepatic fibrosis. By OBserving the change of Leptin and OB-Rb, we might investigate the relationships between Leptin and the recovery of hepatic fibrosis.We also try to reveal the mechanism of by which way the change affect the recovery of hepatic fibrosis. The main contents are divided into two sections, as follows:1. Correlative research between leptin and TGF-β1 and the recovery on CCl4 induced hepatic fibrosis in ratsCarbon Tetrachloride(CCl4) is a classical inducer of hepatic fibrosis.It could injury hepatic cell directly and induction hepatic fibrosis through gathering inflammatory corpuscle ,releasing cytokines and stimulating extracellular matrix deposition.However,after stopping CCl4 injection,the degree of hepatic injury declined and the hepatic fibrosis recovered.The progress may be affected by many kinds of factors.We established hepatic fibrosis by subcutaneous injections CCl4 twelve weeks inrats. After stopping CCl4 injection,rats were sacrificed on week 0,2,4,6,8. Following dynamic OBservation the change of pathologic histology, the levels of ALT,AST, HA andⅣ-C in serum and Hyp in liver, we definited that the model of progression and recovery of hepatic fibrosis was rats with CCl4 12 week and 4 week spontaneous recovery after injecting CCl4 12 weeks.Leptin and TGF-β1 play an important role in the formation of hepatic fibrosis.Leption is one of the initiating agent in hepatic fibrosis.It promotes hepatic fibrosis by combine with OB-Rb on HSC and KC,which could activating HSC to secrete cytokine. TGF-β1 could regulation the formation and degradation of ECM through conbined with TGF-βRⅠ,which can activation HSC by Smad signal transduction channel in.During the recovery of hepatic fibrosis, Leptin and TGF-β1 were declined not only in serm but also in liver tissue.The downtrend of Leptin and TGF-β1 were significant correlative with HA,CⅣand Hyp.It indicated that the decline of Leptin and TGF-β1 were postived to the regression of hepatic fibrosis. The expression of OB-Rb and TGF-βRⅠmRNA and NF-κb protein were also decreased in liver. Therefore, the downtrend of Leptin and TGF-β1 leaded to the decline of OB-Rb and TGF-βRⅠexpression which may affected the actvation of NF-κb and those maybe one of the mechanism of the recovery of hepatic fibrosis.2.The changing of JAK-STAT signal transduction pathway and the effect of Leptin induced TGF-β1 secerte in HSC in the recovery of hepatic fibrosisJAK-STAT is the principle signal transduction pathway of Leptin. JAK and STAT proceed to phosphorylation after Leptin combined with OB-Rb and regulated gene expression in nuclear.The activation of JAK-STAT signal transduction pathway played a significance role in hepatic fibrosis which could proliferation HSC and promoted fibrosis cytokine releasing.However,the alteration of this signal transduction pathway in the recovery of hepatic fibrosis wasn't reported until present.In this section,HSC were separated by liver perfusion in situ and density gradient centrifugation. OB-Rb, phosphorylation JAK and STAT protein could be detected in each group and the highest expression was in model group.They declined at 4w spontaneous recovery group vs model.Leptin(100ng·mL-1) can stimulat HSC to secrete TGF-β1,the level is higher in Leptin than and Leptin+AG490 treated HSC.Thus,the declining of Leptin could decreased the OB-Rb, JAK and STAT protein expression and affected the secreting of TGF-β1.These changing might affect the recovery of hepatic fibrosis.