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AIM:To analyze the role of CYLD for receptor-mediated cell death of murine hepatocytes in acute liver injury models.METHODS:Hepatocyte cell death in CYLD knockout mice(CYLD-/-)was analyzed by application of liver injury models for CD95-(Jo2)and tumor necrosis factor(TNF)-α-[D-Gal N/lipopolysaccharide(LPS)]induced apoptosis.Liver injury was assessed by measurement of serum transaminases and histological analysis.Apoptosis induction was quantified by cleaved PARP staining and Western blotting of activated caspases.Nuclear factor(NF)-κB,ERK,Akt and jun amino-terminal kinases signaling were assessed.Primary Hepatocytes were isolated by two step-collagenase perfusion and treated with recombinant TNF-αand with the CD95-ligand Jo2.Cell viability was analyzed by MTT-assay.RESULTS:Livers of CYLD-/-mice showed increased anti-apoptotic NF-κB signaling.In both applied liver injury models CYLD-/-mice showed a significantly reduced apoptosis sensitivity.After D-Gal N/LPS treatment CYLD-/-mice exhibited significantly lower levels of alanine aminotransferase(ALT)(295 U/L vs 859 U/L,P<0.05)and aspartate aminotransferase(AST)(560 U/L vs 1025 U/L,P<0.01).After Jo injection CYLD-/-mice showed 2-fold lower ALT(50 U/L vs 110 U/L,P<0.01)and lower AST(250 U/L vs 435 U/L,P<0.01)serumlevels compared to WT mice.In addition,isolated CYLD-/-primary murine hepatocytes(PMH)were less sensitive towards death receptor-mediated apoptosis and showed increased levels of Bcl-2,XIAP,c IAP1/2,survivin and c-FLIP expression upon TNF-and CD95-receptor triggering,respectively.Inhibition of NF-κB activation by the inhibitor of NF-κB phosphorylation inhibitor BAY 11-7085 inhibited the expression of antiapoptotic proteins and re-sensitized CYLD-/-PMH towards TNF-and CD95-receptor mediated cell death.CONCLUSION:CYLD is a central regulator of apoptotic cell death in murine hepatocytes by controlling NF-κB dependent anti-apoptotic signaling.
AIM: To analyze the role of CYLD for receptor-mediated cell death of murine hepatocytes in acute liver injury models. METHODS: Hepatocyte cell death in CYLD knockout mice (CYLD - / -) was analyzed by application of liver injury models for CD95- ( Jo2) and tumor necrosis factor (TNF) -α- [D-Gal N / lipopolysaccharide (LPS)] induced apoptosis. Liver injury was assessed by measurement of serum transaminases and histological analysis. Apoptosis induction was quantified by cleaved PARP staining and Western blotting of activated caspases. Nuclear factor (NF) -κB, ERK, Akt and jun amino-terminal kinases signaling were measured. Primary Hepatocytes were isolated by two step-collagenase perfusion and treated with recombinant TNF-αand with the CD95-ligand Jo2.Cell The viability was analyzed by MTT-assay. RESULTS: Livers of CYLD - / - mice showed increased anti-apoptotic NF-κB signaling. Both applied liver injury models CYLD - / - mice showed a significantly reduced apoptosis sensitivity. After D-Gal N / LPS treatment CYLD - / - mice ex hibly significantly lower levels of alanine aminotransferase (ALT) (295 U / L vs 859 U / L, P <0.05) and aspartate aminotransferase (AST) CYLD - / - mice showed 2-fold lower ALT (50 U / L vs 110 U / L, P <0.01) and lower AST (250 U / L vs 435 U / L, P <0.01) serum levels compared to WT mice. In addition, isolated CYLD - / - primary murine hepatocytes (PMH) were less sensitive towards death receptor-mediated apoptosis and showed increased levels of Bcl-2, XIAP, c IAP1 / 2, survivin and c-FLIP expression upon TNF- and CD95 -receptor triggering, respectively. Inhibition of NF-κB activation by the inhibitor of NF-κB phosphorylation inhibitor BAY 11-7085 inhibited the expression of antiapoptotic proteins and re-sensitized CYLD - / - PMH towards TNF-and CD95-receptor mediated cell death .CONCLUSION: CYLD is a central regulator of apoptotic cell death in murine hepatocytes by controlling NF-κB dependent anti-apoptotic signaling.