LPS/IFNgamma-induced RAW 264.7 apoptosis is regulated by both nitric oxide-dependent and -independent pathways involving JNK and the Bcl-2 family.
Lipopolysaccharide (LPS) and interferon-gamma (IFNgamma) stimulate macrophages to produce nitric oxide (NO) via inducible nitric oxide synthase (iNOS) and activate stress signaling cascades including the c-jun-N-terminal kinase (JNK) pathway. These events trigger an apoptotic cascade that ultimately results in death. Since JNK regulates pro-apoptotic and anti-apoptotic Bcl-2 family members, the role of NO in LPS/IFNgamma-induced activation of JNK and its effects on the Bcl-2 family was examined in RAW 264.7 macrophage-like cells. Inhibition of JNK by siRNA verified a role for JNK in LPS/IFNgamma-induced apoptosis. Suppression of NO production by a pharmacologic agent, i.e., iNOS inhibitor L-NIL, altered the kinetics of JNK activation by LPS/IFNgamma. Examination of mitochondrial and nuclear compartments of RAW 264.7 cells demonstrated NO-dependent activation of mitochondrial JNK by LPS/IFNgamma, but NO-independent, cytokine-induced phosphorylation of Bim. NO did not affect phosphorylation, but did inhibit Bax phosphorylation. These results suggest a novel mechanism of LPS/IFNgamma-induced apoptosis in macrophages involving NO-independent phosphorylation of Bim and NO-dependent dephosphorylation of Bax.
Seminara
Aurora R
AR
Division of Cell Signaling, Institute of Molecular Medicine, Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas, USA.
Ruvolo
Peter P
PP
Murad
Ferid
F
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D051028:bcl-2-Associated X Protein; D009569:Nitric Oxide; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; D048031:JNK Mitogen-Activated Protein Kinases