title: Signal transduction pathways of nitric oxide release in primary microglial culture challenged with gram-positive bacterial constituent, lipoteichoic acid.
abstract: Between one-third and one-half of all cases of sepsis are known to be caused by gram-positive microorganisms through the cell wall component, e.g. lipoteichoic acid (LTA). Gram-positive bacteria are also known to induce encephalomyelitis and meningeal inflammation, and enhance the production of nitric oxide (NO) via expression of inducible nitric oxide synthase (iNOS) in murine tissue macrophages. It remains to be explored if LTA could activate microglia considered to be resident brain macrophages. We report here that LTA derived from gram-positive bacteria (Staphylococcus aureus) significantly induces NO release and iNOS expression in primary microglia. LTA-induced NO accumulation was detected at 2 h in microglial culture and was significantly attenuated by pretreatment with anti-CD14, complement receptor type 3 (CR3) or scavenger receptor (SR) antibodies. LTA activated mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase, p38 MAPK or c-Jun N-terminal kinase in cultured microglia. LTA-elicited microglial NO production was also drastically suppressed by SB203580 (p38 MAPK inhibitor) or pyrrolidine dithiocarbamate (an inhibitor of nuclear factor kappaB), indicating that p38 MAPK and nuclear factor kappaB were involved in microglial NO release after LTA challenge. These results suggest that gram-positive bacterial product such as LTA can activate microglia to release NO via the signal transduction pathway involving multiple LTA receptors (e.g. CD14, CR3 or SR), p38 MAPK and nuclear factor kappaB. The in vivo study further confirmed that administered intracerebrally LTA induced considerable noticeable iNOS, phospho-IkappaB and phospho-p38 MAPK expression in microglia/macrophages.
authors.affiliation: Department of Surgery, College of Medicine, National Taiwan University, 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan.
authors.forename: H F
authors.initials: HF
authors.lastname: Chien
authors.forename: K Y
authors.initials: KY
authors.lastname: Yeh
authors.forename: Y F
authors.initials: YF
authors.lastname: Jiang-Shieh
authors.forename: I H
authors.initials: IH
authors.lastname: Wei
authors.forename: C Y
authors.initials: CY
authors.lastname: Chang
authors.forename: M L
authors.initials: ML
authors.lastname: Chang
authors.forename: C H
authors.initials: CH
authors.lastname: Wu
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002230:Carbidopa / Q000276:immunology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005136:Eye Proteins / Q000276:immunology; D005455:Fluorescent Antibody Technique / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects; D020672:I-kappa B Proteins / Q000378:metabolism; D007211:Indoles; D037102:Lectins / Q000378:metabolism; D007980:Levodopa / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D017628:Microglia / Q000187:drug effects* / Q000201:enzymology; D009419:Nerve Tissue Proteins / Q000276:immunology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects*; D013682:Teichoic Acids / Q000494:pharmacology*; D013997:Time Factors; D051845:gamma-Synuclein; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000906:Antibodies; D004338:Drug Combinations; D005136:Eye Proteins; D020672:I-kappa B Proteins; D007211:Indoles; D037102:Lectins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D009419:Nerve Tissue Proteins; D009573:Nitrites; D013682:Teichoic Acids; C009265:carbidopa, levodopa drug combination; D051845:gamma-Synuclein; D009569:Nitric Oxide; D007980:Levodopa; C007293:DAPI; C009900:lipoteichoic acid; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D048051:p38 Mitogen-Activated Protein Kinases; D002230:Carbidopa