Co-stimulatory effect of nitric oxide on endothelial NF-kappaB implies a physiological self-amplifying mechanism.
Here we investigated the effects of the second messenger molecule NO at various concentrations on the activation of transcription factor NF-kappaB, IkappaB-alpha kinase (IKK-alpha), Jun N-terminal kinase (JNK) and apoptosis in murine endothelial cells. Low concentrations of NO alone failed to activate NF-kappaB, IKK-alpha and JNK. When NF-kappaB was prestimulated by TNF-alpha or phorbol 12-myristate 13-acetate, the addition of NO at low concentrations enhanced the activation of NF-kappaB. This provides a mechanism for a self-amplifying signal in the inflammatory response, since the inducible NO synthase in endothelial cells is regulated by NF-kappaB. The co-stimulatory effect of NO on NF-kappaB activation was also evident from IKK-alpha kinase assays and reporter gene experiments in endothelial cells. High doses of NO impaired the TNF-alpha-induced DNA-binding activity of NF-kappaB. Accordingly, these high amounts of NO also repressed the TNF-alpha-induced transactivation by NF-kappaB as efficient as dexamethasone. The doses of NO required for the inhibition of NF-kappaB are not cytotoxic for the endothelial cells, enabling the establishment of an autoregulatory loop for NF-kappaB signaling.
Umansky
V
V
German Cancer Research Center, Department of Cellular Immunology, Heidelberg.
Hehner
S P
SP
Dumont
A
A
Hofmann
T G
TG
Schirrmacher
V
V
Dröge
W
W
Schmitz
M L
ML
D000818:Animals; D017209:Apoptosis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D004727:Endothelium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D051550:I-kappa B Kinase; D007249:Inflammation / Q000209:etiology; D048031:JNK Mitogen-Activated Protein Kinases; D008156:Luciferases / Q000235:genetics; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B / Q000378:metabolism* / Q000502:physiology; D009569:Nitric Oxide / Q000494:pharmacology* / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases