Involvement of Bcl-2 family and caspase-3-like protease in NO-mediated neuronal apoptosis.
To clarify mechanisms of neuronal death in the postischemic brain, we examined whether astrocytes exposed to hypoxia/reoxygenation exert a neurotoxic effect, using a coculture system. Neurons cocultured with astrocytes subjected to hypoxia/reoxygenation underwent apoptotic cell death, the effect enhanced by a combination of interleukin-1beta with hypoxia. The synergistic neurotoxic activity of hypoxia and interleukin-1beta was dependent on de novo expression of inducible nitric oxide synthase (iNOS) and on nitric oxide (NO) production in astrocytes. Further analysis to determine the neurotoxic mechanism revealed decreased Bcl-2 and increased Bax expression together with caspase-3 activation in cortical neurons cocultured with NO-producing astrocytes. Inhibition of NO production in astrocytes by N(G)-monomethyl-L-arginine, an inhibitor of NOS, significantly inhibited neuronal death together with changes in Bcl-2 and Bax protein levels and in caspase-3-like activity. Moreover, treatment of neurons with a bax antisense oligonucleotide inhibited the caspase-3-like activation and neuronal death induced by an NO donor, sodium nitroprusside. These data suggest that NO produced by astrocytes after hypoxic insult induces apoptotic death of neurons through mechanisms involving the caspase-3 activation after down-regulation of Bcl-2 and up-regulation of Bax protein levels.
Tamatani
M
M
Department of Anatomy and Neuroscience, Osaka University Medical School, Suita, Japan.
Ogawa
S
S
Niitsu
Y
Y
Tohyama
M
M
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001253:Astrocytes / Q000502:physiology; D053148:Caspase 3; D020169:Caspases; D015687:Cell Hypoxia / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D003546:Cysteine Endopeptidases / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects / Q000502:physiology; D007375:Interleukin-1 / Q000494:pharmacology; D005810:Multigene Family; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D007375:Interleukin-1; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases