Caspase 3 inhibition attenuates hydrogen peroxide-induced DNA fragmentation but not cell death in neuronal PC12 cells.
Exposure of neurons to H(2)O(2) results in both necrosis and apoptosis. Caspases play a pivotal role in apoptosis, but exactly how they are involved in H(2)O(2)-mediated cell death is unknown. We examined H(2)O(2)-induced toxicity in neuronal PC12 cells and the effects of inducible overexpression of the H(2)O(2)-scavenging enzyme catalase on this process. H(2)O(2) caused cell death in a time- and concentration-dependent manner. Cell death induced by H(2)O(2) was found to be mediated in part through an apoptotic pathway as H(2)O(2)-treated cells exhibited cell shrinkage, nuclear condensation and marked DNA fragmentation. H(2)O(2) also triggered activation of caspase 3. Genetic up-regulation of catalase not only significantly reduced cell death but also suppressed caspase 3 activity and DNA fragmentation. While the caspase 3 inhibitor DEVD inhibited both caspase 3 activity and DNA fragmentation induced by H(2)O(2) it did not prevent cell death. Treatment with the general caspase inhibitor ZVAD, however, resulted in complete attenuation of H(2)O(2)-mediated cellular toxicity. These results suggest that DNA fragmentation induced by H(2)O(2) is attributable to caspase 3 activation and that H(2)O(2) may be critical for signaling leading to apoptosis. However, unlike inducibly increased catalase expression and general caspase inhibition both of which protect cells from cytotoxicity, caspase 3 inhibition alone did not improve cell survival suggesting that prevention of DNA fragmentation is insufficient to prevent H(2)O(2)-mediated cell death.
Neurogerontology Division, Andrus Gerontology Center, University of Southern California, Los Angeles, California, USA.
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Jiang
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Boonplueang
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Andersen
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation; D005978:Glutathione / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000633:toxicity*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D016716:PC12 Cells; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D006861:Hydrogen Peroxide; D002374:Catalase; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D005978:Glutathione