Respiratory syncytial virus infection of human respiratory epithelial cells enhances inducible nitric oxide synthase gene expression.
The induction kinetics of the mRNA of interferon regulatory factor 1 (IRF-1), inducible nitric oxide synthase (iNOS), and proinflammatory cytokines in respiratory syncytial virus (RSV)-infected human type 2 alveolar epithelial cells (A549 cells) were analyzed semiquantitatively by RT-PCR. RSV enhanced IRF-1 and iNOS mRNA expression as early as 4 h after RSV infection and this enhancement lasted several hours. No IFN-gamma gene expression was observed during the whole course of the infection. Expression of IFN-beta, IL-1beta, and TNF-alpha genes was observed slightly at 4 h and became marked 7 h after infection. Addition of neutralizing antibodies to these cytokines to the culture had no effect on the induction of iNOS mRNA. The iNOS transcriptional activity in RSV-infected cells was significantly enhanced by an exogenous cytokine mixture (IL-1beta, TNF-alpha, and IFN-gamma). An apparent nitric oxide (NO) production was identified only when cytokines were added together with RSV infection. A significant increase of iNOS gene expression was observed in nasopharyngeal exudate cells obtained from infants during the acute phase of RSV bronchiolitis. These observations suggest that RSV infection of human respiratory epithelial cells induces the iNOS gene both in vitro and in vivo; this induction may occur rather promptly and involves transcriptional activator IRF-1 induced by the RSV infection itself. The iNOS gene, which is initially induced by RSV infection, may be further enhanced in a paracrine fashion by proinflammatory cytokines released by infection-activated inflammatory cells.
Department of Pediatrics, Sapporo Medical University School of Medicine, Japan.
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Tsutsumi
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Takeuchi
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Ohsaki
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Seki
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Chiba
D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000235:genetics; D004790:Enzyme Induction; D004847:Epithelial Cells; D005122:Exudates and Transudates; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007223:Infant; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha / Q000235:genetics; D016899:Interferon-beta / Q000096:biosynthesis / Q000235:genetics; D007371:Interferon-gamma / Q000235:genetics / Q000494:pharmacology; D007375:Interleukin-1 / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D009305:Nasopharynx / Q000201:enzymology; D009500:Neutralization Tests; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics; D011650:Pulmonary Alveoli / Q000166:cytology; D018357:Respiratory Syncytial Virus Infections / Q000201:enzymology* / Q000276:immunology; D018113:Respiratory Syncytial Virus, Human / Q000276:immunology*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha; D007375:Interleukin-1; D009573:Nitrites; D010750:Phosphoproteins; D014409:Tumor Necrosis Factor-alpha; D016899:Interferon-beta; D007371:Interferon-gamma; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II