title: Diclofenac enhances proinflammatory cytokine-induced phagocytosis of cultured microglia via nitric oxide production.
abstract: Influenza-associated encephalopathy (IAE) is a central nervous system complication with a high mortality rate, which is increased significantly by the non-steroidal anti-inflammatory drug diclofenac sodium (DCF). In the present study, we investigated the effects of DCF on brain immune cells (i.e. microglia) stimulated with three proinflammatory cytokines, namely tumor necrosis factor-α, interleukin-1β, and interferon-γ. Similar to previous findings in astrocytes, all three cytokines induced the expression of inducible NO synthase (iNOS), as well as NO production, in microglia. The addition of DCF to the culture system augmented iNOS expression and NO production. Immunocytochemical analysis and the phagocytosis assay revealed that cytokine treatment induced morphological changes to and phagocytosis by the microglia. The addition of DCF to the culture system enhanced microglial activation, as well as the phagocytic activity of cytokine-stimulated microglia. Inhibitors of nuclear factor (NF)-κB inhibited iNOS gene expression in cytokine-stimulated microglia with or without DCF, suggesting that the NF-κB pathway is one of the main signaling pathways involved. The iNOS inhibitor N(G)-monomethyl-l-arginine (l-NMMA) reduced both cytokine-induced phagocytosis and phagocytosis induced by the combination of cytokines plus DCF. Furthermore, the NO donor sodium nitroprusside induced phagocytosis, indicating that NO production is a key regulator of microglial phagocytosis. In conclusion, DCF acts synergistically with proinflammatory cytokines to increase the production of NO in microglia, leading to phagocytic activity of the activated microglia. These findings, together with previous observations regarding astrocytes, may explain the significant increase in mortality of IAE patients treated with DCF.
authors: Department of Molecular Neurobiology, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.
authors: Hiroki
authors: H
authors: Kakita
authors: Mineyoshi
authors: M
authors: Aoyama
authors: Yoshiaki
authors: Y
authors: Nagaya
authors: Hayato
authors: H
authors: Asai
authors: Mohamed Hamed
authors: MH
authors: Hussein
authors: Mieko
authors: M
authors: Suzuki
authors: Shin
authors: S
authors: Kato
authors: Shinji
authors: S
authors: Saitoh
authors: Kiyofumi
authors: K
authors: Asai
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000633:toxicity*; D001927:Brain Diseases / Q000401:mortality; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004008:Diclofenac / Q000633:toxicity*; D015232:Dinoprostone / Q000096:biosynthesis; D006801:Humans; D007251:Influenza, Human / Q000150:complications; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D010587:Phagocytosis / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D016207:Cytokines; D004008:Diclofenac; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone