BCL-2 protects peroxynitrite-treated thymocytes from poly(ADP-ribose) synthase (PARS)-independent apoptotic but not from PARS-mediated necrotic cell death.
In thymocytes, peroxynitrite induces poly(ADP-ribose) synthetase (PARS) activation, which results in necrotic cell death. In the absence of PARS, however, peroxynitrite-treated thymocytes die by apoptosis. Because Bcl-2 has been reported to inhibit not only apoptotic but also some forms of necrotic cell death, here we have investigated how Bcl-2 regulates the peroxynitrite-induced apoptotic and necrotic cell death. We have found that Bcl-2 did not provide protection against peroxynitrite-induced necrotic death, as characterized by propidium iodide uptake, mitochondrial membrane potential decrease, secondary superoxide production, and cardiolipin loss. In the presence of a PARS inhibitor, peroxynitrite-treated thymocytes from Bcl-2 transgenic mice showed no caspase activation or DNA fragmentation and displayed smaller mitochondrial membrane potential decrease. These data show that Bcl-2 protects thymocytes from peroxynitrite-induced apoptosis at a step proximal to mitochondrial alterations but fails to prevent PARS-mediated necrotic cell death. Activation of tissue transglutaminase (tTG) occurs in various forms of apoptosis. Peroxynitrite did not induce transglutaminase activity in thymocytes and did not have a direct inhibitory effect on the purified tTG. Basal tTG was not different in Bcl-2 transgenic and wild type cells.
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Inotek Corporation, Beverly, MA 01915, USA.
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D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D020169:Caspases / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D019254:Genes, bcl-2; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009336:Necrosis; D009566:Nitrates / Q000633:toxicity*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D011503:Transglutaminases / Q000378:metabolism
D009566:Nitrates; D019253:Proto-Oncogene Proteins c-bcl-2; C039642:peroxynitric acid; D011503:Transglutaminases; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases