Carbon monoxide protects hepatocytes from TNF-alpha/Actinomycin D by inhibition of the caspase-8-mediated apoptotic pathway.
We have previously shown that carbon monoxide (CO) (250 ppm) prevented tumor necrosis factor-alpha (TNFalpha)-induced apoptosis and activated the transcription factor NF-kappaB in hepatocytes both in vivo and in vitro. These studies were conducted to further determine the mechanisms by which CO suppresses apoptotic signaling in TNFalpha (10 ng/ml) and Actinomycin D (ActD, 200 ng/ml)-treated hepatocytes. Consistent with our previous findings, CO protected against TNFalpha/ActD-induced cell death, which is in part dependent on NF-kappaB activation. This was associated with a reduction in mitochondrial damage, a decrease in cytochrome c release, and an inhibition of translocation of Bcl proteins to mitochondria. In conjugation with inhibition of these mitochondrial events, CO also suppressed caspases-8 and -3 cleavage in response to TNFalpha/ActD. Inhibition of NF-kappaB activation resulted in diminished CO-induced cFLIP expression and increased caspase-8 cleavage from cells treated with TNFalpha/ActD. These data indicate that CO interferes with apoptotic signaling at a proximal step.
Kim
Hoe Suk
HS
Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
Loughran
Patricia A
PA
Kim
Peter K
PK
Billiar
Timothy R
TR
Zuckerbraun
Brian S
BS
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002248:Carbon Monoxide / Q000494:pharmacology*; D053181:Caspase 8; D061945:Caspase Inhibitors; D002478:Cells, Cultured; D003609:Dactinomycin / Q000037:antagonists & inhibitors / Q000633:toxicity; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects*; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000633:toxicity; D015854:Up-Regulation
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D061945:Caspase Inhibitors; C506387:Cflar protein, mouse; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; D002248:Carbon Monoxide; C505526:Casp8 protein, mouse; D053181:Caspase 8