Lipopolysaccharide and proinflammatory cytokines require different astrocyte states to induce nitric oxide production.
Nitric oxide (NO) production by astrocytes is a significant factor affecting brain physiology and pathology, but the mechanism by which it is regulated is not known. Previous studies using different specimens and stimuli might have described different aspects of a complex system. We investigated the effect of culture and stimulus conditions on NO production by cultured astrocytes and identified two combinations of these allowing NO production. Lipopolysaccharide (LPS)-induced NO production required a high seeding cell density and was independent of the serum concentration, whereas that induced by proinflammatory cytokines required simultaneous treatment with interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma and low-serum conditions but was less affected by the seeding density. These two pathways showed differential sensitivity to protein kinase inhibitors. Both LPS and cytokines induced expression of inducible nitric oxide synthase (iNOS). Although LPS-induced iNOS expression required a high seeding cell density, cytokine-induced iNOS expression, in contrast to NO production, was not affected by the serum concentration. These results suggest that astrocytes interact with the environment and alter their responsiveness to NO production-inducing stimuli by regulating iNOS expression and activity. This is the first evidence for the selective use of two different regulatory pathways in any cell type.
Kozuka
Nagisa
N
Laboratory of Cellular Neurobiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo, Japan.
Itofusa
Rurika
R
Kudo
Yoshihisa
Y
Morita
Mitsuhiro
M
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D002450:Cell Communication / Q000502:physiology; D002452:Cell Count; D002478:Cells, Cultured; D003470:Culture Media / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism* / Q000494:pharmacology; D004660:Encephalitis / Q000378:metabolism* / Q000503:physiopathology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000378:metabolism* / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000187:drug effects / Q000378:metabolism; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D003470:Culture Media; D016207:Cytokines; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D011494:Protein Kinases