NF-kappaB-mediated up-regulation of Bcl-X(S) and Bax contributes to cytochrome c release in cyanide-induced apoptosis.
Cyanide induces apoptosis through cytochrome c activated caspase cascade in primary cultured cortical neurons. The underlying mechanism for cytochrome c release from mitochondria after cyanide treatment is still unclear. In this study, the roles of endogenous Bcl-2 proteins in cyanide-induced apoptosis were investigated. After cyanide (100-500 microm) treatment for 24 h, two pro-apoptotic Bcl-2 proteins, Bcl-X(S) and Bax were up-regulated as shown by western blot and RT-PCR analysis. The expression levels of two antiapoptotic Bcl-2 proteins, Bcl-2 and Bcl-X(L), remained unchanged after cyanide treatment, whereas the mRNA levels of Bcl-X(S) and Bax began to increase within 2 h and their protein levels increased 6 h after treatment. NF-kappaB, a redox-sensitive transcription factor activated after cyanide treatment, is responsible for the up-regulation of Bcl-X(S) and Bax. SN50, which is a synthetic peptide that blocks translocation of NF-kappaB from cytosol to nucleus, inhibited the up-regulation of Bcl-X(S) and Bax. Similar results were obtained using a specific kappaB decoy DNA. NMDA receptor activation and reactive oxygen species (ROS) generation are upstream events of NF-kappaB activation, as blockade of these two events by MK801, l-NAME or PBN inhibited cyanide-induced up-regulation of Bcl-X(S) and Bax. Up-regulation of pro-apoptotic Bcl-X(S) and Bax contributed to cyanide-induced cytochrome c release, because SN50 and a specific Bax antisense oligodeoxynucleotide significantly reduced release of cytochrome c from mitochondria as shown by western blot analysis. It was concluded that NF-kappaB-mediated up-regulation of Bcl-X(S) and Bax is involved in regulating cytochrome c release in cyanide-induced apoptosis.
Shou
Yan
Y
Neurotoxicology Laboratory, Department of Medicinal Chemistry and Molecular Pharmacology, Department of Basic Medical Sciences, Purdue University, West Lafayette, IN 47907-1333, USA.
Li
Nianyu
N
Li
Li
L
Borowitz
Joseph L
JL
Isom
Gary E
GE
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D003486:Cyanides / Q000633:toxicity*; D003574:Cytochrome c Group / Q000378:metabolism*; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010084:Oxidation-Reduction; D010455:Peptides / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494828:Bax protein, rat; C494813:Bcl2l1 protein, rat; D003486:Cyanides; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D016376:Oligonucleotides, Antisense; D010455:Peptides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C118258:SN50 peptide; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D020169:Caspases