Akt protects mouse hepatocytes from TNF-alpha- and Fas-mediated apoptosis through NK-kappa B activation.
To determine the role of phosphatidylinositol 3-kinase (PI3K)/Akt and nuclear factor-kappa B (NF-kappa B) in protecting hepatocytes from tumor necrosis factor-alpha (TNF-alpha)- and Fas-mediated apoptosis, we pretreated primary cultures of mouse hepatocytes with pharmacological and adenovirus-mediated inhibitors of the PI3K/Akt and NF-kappa B pathways followed by treatment with TNF-alpha or Jo2, an anti-Fas antibody. Jo2 and, to a lesser extent, TNF-alpha phosphorylate Akt. The PI3K inhibitor LY-294002 blocks TNF-alpha- and Fas-mediated Akt phosphorylation. LY-294002 pretreatment reduces NF-kappa B binding activity and transcriptional activity and NF-kappa B-responsive gene expression by TNF-alpha or Jo2. LY-294002 promotes apoptosis after TNF-alpha or Jo2. The expression of dominant-negative Akt blocks NF-kappa B activation and sensitizes hepatocytes to TNF-alpha- and Fas-mediated apoptosis. The expression of constitutively active Akt rescues LY-294002-pretreated cells from TNF-alpha- and Fas-mediated apoptosis. Active Akt induces NF-kappa B transcriptional activity but not NF-kappa B binding activity or I kappa B degradation. Furthermore, LY-294002 pretreatment blocks TNF-alpha- and Jo2-induced Bcl-xL levels in hepatocytes, with no effect on the phosphorylation levels of Bad. Bcl-xL overexpression protects hepatocytes from Fas- but not TNF-alpha-induced apoptosis after sensitization by actinomycin D or the I kappa B superrepressor. Together, the PI3K/Akt pathway has a protective role in Fas-mediated apoptosis, which requires NF-kappa B activation, partially through the subsequent induction of Bcl-xL.
Hatano
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Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Brenner
D A
DA
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D022781:Hepatocytes / Q000502:physiology*; D020672:I-kappa B Proteins / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009025:Morpholines / Q000494:pharmacology; D016328:NF-kappa B / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*; D051020:bcl-X Protein; D019014:fas Receptor / Q000276:immunology / Q000502:physiology*
D000906:Antibodies; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D020672:I-kappa B Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009025:Morpholines; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; D019014:fas Receptor; C494812:Bcl2l1 protein, mouse; C506387:Cflar protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one