The role of nitric oxide and cyclooxygenase-2 in attenuating apoptosis.
The production of nitric oxide (NO) is an essential determinant in auto- and paracrine signaling. NO is generated under inflammatory conditions and may serve as a cytotoxic molecule to produce cell demise along an apoptotic or necrotic pathway. NO also gained attention as a regulator of immune function and a death inhibitor. Cytotoxicity because of substantial NO-formation is established to initiate apoptosis, characterized by upregulation of the tumor suppressor p53, changes in the expression of pro- and antiapoptotic Bcl-2 family members, cytochrome c relocation, activation of caspases, and DNA fragmentation. However, NO-toxicity is not a constant value and NO may protect several cell types from entering programmed cell death. Preactivation of macrophages with a nontoxic dose of S-nitrosoglutathione (200 microM) or lipopolysaccharide/interferon-gamma/N(G)-monomethyl-L-arginine for 15 hours attenuated death in response to various agonists, suppressed p53 accumulation, and abrogated caspase activation. Prestimulation of macrophages with cytokines or low-level NO activated the transcription factor NF-kappaB as well as AP-1 and promoted immediate early gene expression of cyclooxygenase-2 (COX-2). NF-kappaB activation comprised p50/p65-heterodimer formation, IkappaB degradation, and activation of a luciferase reporter construct, that contained four copies of the NF-kappaB-site derived from the murine COX-2 promoter. A NF-kappaB decoy approach (oligonucleotides directed against NF-kappaB) or transfection of a dominant-negative c-Jun mutant (TAM67) abrogated not only the COX-2 expression but also the inducible protection. Blocking NO- or cytokine-mediated inducible protection at the level of NF-kappaB and/or AP-1 restored the occurrence of apoptotic features. Our experiments underscore the role of COX-2 in attenuating natural occurring cell death (i.e., apoptosis).
Brüne
Bernhard
B
University of Kaiserslautern, Faculty of Biology, Department of Cell Biology, Germany. bruene@rhrk.uni-kl.de
von Knethen
Andreas
A
D017209:Apoptosis / Q000502:physiology*; D018929:Cell Culture Techniques; D051546:Cyclooxygenase 2; D016207:Cytokines / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation; D007527:Isoenzymes / Q000494:pharmacology*; D008264:Macrophages / Q000502:physiology; D008565:Membrane Proteins; D009569:Nitric Oxide / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000494:pharmacology*; D015398:Signal Transduction; D014157:Transcription Factors
D016207:Cytokines; D007527:Isoenzymes; D008565:Membrane Proteins; D014157:Transcription Factors; D009569:Nitric Oxide; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases