Cytokine-stimulated inducible nitric oxide synthase expression in astroglia: role of Erk mitogen-activated protein kinase and NF-kappaB.
Expression of inducible nitric oxide synthase (iNOS), which leads to the production of nitric oxide (NO), is stimulated by proinflammatory cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha). Here we report on the roles of nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein (MAP) kinases in IL-1beta/TNF-alpha-induced iNOS expression in adult rat astroglia. Cytokine-induced increases in nitrite accumulation (an index of NO production) and iNOS expression were attenuated by inhibition of NF-kappaB with pyrrolidine dithiocarbamate (PDTC). Similar attenuation of these cytokine-induced responses was produced by inhibition of MAP kinase (MEK), the immediate upstream activator of Erk, using PD098,059. Combined treatment of astroglia with PDTC and PD098,059 completely abolished the cytokine-induced increases in iNOS expression and nitrite accumulation. By contrast, the selective p38 kinase inhibitor SB203,580 amplified the effects of IL-1beta/TNF-alpha on nitrite accumulation. In accordance with these findings, IL-1beta- and TNF-alpha-induced a time-dependent increase in Erk1/Erk2 activation. This cytokine action was completely abolished by PD098,059 but was not altered by PDTC. Finally, IL-1beta and TNF-alpha induced degradation of NF-kappaB's bound inhibitory protein, IkappaB-alpha, leading to translocation of NF-kappaB into the nucleus. IkappaB-alpha expression was not restored to control levels by inhibition of MEK. Furthermore, inhibition of MEK with PD098,059 did not alter IL-1beta- and TNF-alpha-induced expression of active NF-kappaB. The results demonstrate that autonomous Erk and NF-kappaB pathways mediate cytokine-induced increases in iNOS expression in astroglia.
Marcus
Joshua S
JS
Department of Physiology and Functional Genomics and McKnight Brain Institute, University of Florida, Gainesville, Florida 32610, USA.
Karackattu
Sharon L
SL
Fleegal
Melissa A
MA
Sumners
Colin
C
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000378:metabolism* / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000187:drug effects / Q000378:metabolism; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology; D048369:MAP Kinase Kinase 1; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D016207:Cytokines; D020672:I-kappa B Proteins; D007375:Interleukin-1; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases