Mechanisms Of MTOR Signal Pathway In The Early Phase Of Cirrhotic Portal Hypertension

Part I: THE ACTIVATION AND SIGNIFICANCE OF MTORSIGNAL PATHWAY IN THE EARLY PHASE OF CIRRHOTICPORTAL HYPERTENSIONObjective: This study is aimed to investigate the activation andsignificance of mTOR signal pathway in the early phase of cirrhotic portalhypertension.Methods: Cirrhotic portal hypertension was induced by bile ductligation (BDL). Male SD rats were randomly divided into sham-operatedgroup and model group. Liver fibrosis, inflammation, and portal veinpressure were accessed by histopathology, morphology and hemodynamics.mRNA expressions of α-smooth muscle actin (α-SMA), procollagen-a1(PC-α1), transforming growth factor-β1(TGF-β1) and platelet-derivedgrowth factor (PDGF) were quantified by RT-PCR. The expressions ofP70S6K, P-P70S6K, S6and P-S6were examined by western blot assay.Results: Early cirrhotic portal hypertension was stably induced by bileduct ligation (BDL) for three weeks, when portal vein pressure and spleensize were significantly increased but intrahepatic nodules and fiber spacing had not yet formed. Compared with sham-operated group, the expressionsof P-P70S6K (P<0.05) and P-S6(P<0.05) increased significantly in the ratlivers of model group. The activation and proliferation of hepatic stellatecells (HSCs) and biliary cells was apparent, the liver fibrogenic genes such asPC-α1(P<0.05), α-SMA (P<0.05), TGF-β1(P<0.05), and PDGF (P<0.05)were upregulated, and interstitial collagen synthesis was increased.Conclusion: Early cirrhotic portal hypertension was stably induced byBDL for three weeks. mTOR signal pathway was mainly involved in theformation of cirrhotic portal hypertension in phosphorylation of functionalstatus. Blocking the signal pathway would be a potential target fortherapeutic intervention in this disease. Part Ⅱ: INTERVENTION STUDY OF RAPAMYCIN BLOCKINGMTOR SIGNALING IN THE EARLY PHASE OF CIRRHOTICPORTAL HYPERTENSIONObjective: To investigate the therapeutic effect of rapamycin blockingmTOR signal pathway in the early phase of cirrhotic portal hypertension, aswell as to explore its possible mechanism.Methods: Male SD rats were randomly divided into sham-operatedgroup, model group and rapamycin-treated model group. Early cirrhoticportal hypertension was induced by BDL for three weeks. BDL rats receivedrapamycin (2mg kg-1day-1) by intraperitoneal injection over a2-week period,starting one week after ligation. Liver fibrosis and portal vein pressure wereaccessed by histopathology, morphology and hemodynamics. mRNAexpressions of PC-α1，α-SMA, TGF-β1and PDGF were quantified byRT-PCR. α-SMA and antigen Ki67were detected by immunohistochemistry.Expressions of α-SMA, P70S6K, P-P70S6K, S6and P-S6were examined bywestern blot assay.Results: The activation and proliferation of biliary cells andα-SMA-positive cells was apparent (P<0.05). The sizes of liver and spleen, aswell as portal hypertension, markedly increased. The liver fibrogenic geneswere upregulated significantly (P<0.05), as well as the expression of proteinsα-SMA (P<0.05), Ki67(P<0.05), P-P70S6K (P<0.05), and P-S6(P<0.05).However, mTOR blockage by rapamycin profoundly inhibited the expressionof α-SMA, Ki67, P-P70S6K, and P-S6, and improved liver function, fibrosis,portal pressure and splenomegaly (P<0.05).Conclusions: mTOR signal pathway played an important role in the formation of early cirrhotic portal hypertension in rats. Blocking the signalpathway could be considered as a potential target for treating the early phaseof this disease.