TY - JOUR
T1 - Hepatocytes sensitized to tumor necrosis factor-α cytotoxicity undergo apoptosis through caspase-dependent and caspase-independent pathways
AU - Jones, Brett E.
AU - Lo, Chau R.
AU - Liu, Hailing
AU - Srinivasan, Anu
AU - Streetz, Konrad
AU - Valentino, Karen L.
AU - Czaja, Mark J.
PY - 2000/1/7
Y1 - 2000/1/7
N2 - Hepatocytes can be sensitized to tumor necrosis factor (TNF)-α toxicity by repression of NF-κB activation or inhibition of RNA synthesis. To determine whether both forms of sensitization lead to TNF-α cytotoxicity by similar mechanisms, TNF-α-induced cell death in RALA255-10G hepatocytes was examined following infection with an adenovirus, Ad5IκB, that blocks NF-κB activation or following cotreatment with actinomycin D (ActD). TNF-α treatment of Ad5IκB-infected cells resulted in 44% cell death within 6 h. ActD/TNF-α induced no death within 6 h but did lead to 37% cell death by 24 h. In both instances, cell death occurred by apoptosis and was associated with caspase activation, although caspase activation in ActD-sensitized cells was delayed. CrmA and chemical caspase inhibitors blocked Ad5IκB/TNF-α- induced cell death but did not inhibit ActD/TNF-α-induced apoptosis. A Fas- associated protein with death domain (FADD) dominant negative decreased Ad5IκB/TNF-αand ActD/TNF-α-induced cell death by 81 and 47%, respectively. However, downstream events differed, since Ad5IκB/TNF-α but not ActD/TNF-α treatment caused mitochondrial cytochrome c release. These results suggest that NF-κB inactivation and inhibition of RNA synthesis sensitize RALA255- 10G hepatocytes to TNF-α toxicity through distinct cell death pathways that diverge below the level of FADD. ActD-induced hepatocyte sensitization to TNF-α cytotoxicity occurs through a FADD-dependent, caspase-independent pathway of apoptosis.
AB - Hepatocytes can be sensitized to tumor necrosis factor (TNF)-α toxicity by repression of NF-κB activation or inhibition of RNA synthesis. To determine whether both forms of sensitization lead to TNF-α cytotoxicity by similar mechanisms, TNF-α-induced cell death in RALA255-10G hepatocytes was examined following infection with an adenovirus, Ad5IκB, that blocks NF-κB activation or following cotreatment with actinomycin D (ActD). TNF-α treatment of Ad5IκB-infected cells resulted in 44% cell death within 6 h. ActD/TNF-α induced no death within 6 h but did lead to 37% cell death by 24 h. In both instances, cell death occurred by apoptosis and was associated with caspase activation, although caspase activation in ActD-sensitized cells was delayed. CrmA and chemical caspase inhibitors blocked Ad5IκB/TNF-α- induced cell death but did not inhibit ActD/TNF-α-induced apoptosis. A Fas- associated protein with death domain (FADD) dominant negative decreased Ad5IκB/TNF-αand ActD/TNF-α-induced cell death by 81 and 47%, respectively. However, downstream events differed, since Ad5IκB/TNF-α but not ActD/TNF-α treatment caused mitochondrial cytochrome c release. These results suggest that NF-κB inactivation and inhibition of RNA synthesis sensitize RALA255- 10G hepatocytes to TNF-α toxicity through distinct cell death pathways that diverge below the level of FADD. ActD-induced hepatocyte sensitization to TNF-α cytotoxicity occurs through a FADD-dependent, caspase-independent pathway of apoptosis.
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U2 - 10.1074/jbc.275.1.705
DO - 10.1074/jbc.275.1.705
M3 - Article
C2 - 10617670
AN - SCOPUS:0034614526
SN - 0021-9258
VL - 275
SP - 705
EP - 712
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 1
ER -