Protective roles of NF-kappa B for chromium(VI)-induced cytotoxicity is revealed by expression of Ikappa B kinase-beta mutant.
To delineate the molecular mechanisms of NF-kappaB-mediated regulation of chromium(VI)-induced cell death, the signaling pathway leading to the activation of NF-kappaB was interrupted by stable transfection of a kinase-mutated form of IkappaB kinase beta (IKKbeta-KM). Here we demonstrate a novel role for the NF-kappaB transcription factor in inhibiting chromium(VI)-induced cell death. Inhibition of NF-kappaB by IKKbeta-KM or IKKbeta gene deficiency resulted in a spontaneous cleavage of Bcl-xL antiapoptotic protein due to the elevated caspase-3 activity. DNA microarray assay suggested a decreased expression of genes encoding antiapoptotic proteins, cIAP1 and cIAP2, in the cells overexpressing IKKbeta-KM. Chromium(VI) treatment of these NF-kappaB-inhibited cells induced necrotic-like cell death. Such chromium(VI)-induced cell killing could be partially inhibited by expression of exogenous cIAP1, an inhibitor of caspases, indicating that caspases along with others may be involved in chromium(VI)-induced cell death. These results suggest that NF-kappaB is essential for inhibiting toxic metal-induced cytotoxicity. Such inhibition may involve up-regulation of the expression of anti-death proteins including cIAP1 that prevents spontaneous caspase activation and subsequent cleavage of Bcl-xL protein.
Chen
Fei
F
Health Effects Laboratory Division, NIOSH, Morgantown, West Virginia 26505, USA. lfd3@cdc.gov
Bower
Jacquelyn
J
Leonard
Stephen S
SS
Ding
Min
M
Lu
Yongju
Y
Rojanasakul
Yon
Y
Kung
Hsiang-fu
HF
Vallyathan
Val
V
Castranova
Vince
V
Shi
Xianglin
X
D017209:Apoptosis / Q000235:genetics*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002857:Chromium / Q000633:toxicity*; D017931:DNA Primers; D005786:Gene Expression Regulation; D006801:Humans; D051550:I-kappa B Kinase; D051034:Inhibitor of Apoptosis Proteins; D007700:Kinetics; D016328:NF-kappa B / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D011506:Proteins / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D020545:Respiratory Mucosa; D014162:Transfection; D044767:Ubiquitin-Protein Ligases
D017931:DNA Primers; D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D011506:Proteins; D011994:Recombinant Proteins; D002857:Chromium; C074702:chromium hexavalent ion; C494833:BIRC2 protein, human; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases