title: p38 mitogen-activated protein kinase-dependent hyperinduction of tumor necrosis factor alpha expression in response to avian influenza virus H5N1.
abstract: Avian influenza A virus subtype H5N1 can infect humans to cause a severe viral pneumonia with mortality rates of more than 30%. The biological basis for this unusual disease severity is not fully understood. We previously demonstrated that in contrast to human influenza A virus subtypes including H1N1 or H3N2, the H5N1 virus associated with the "bird flu" outbreak in Hong Kong in 1997 (H5N1/97) hyperinduces proinflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha), in primary human macrophages in vitro. To delineate the molecular mechanisms involved, we analyzed the role of transcription factor NF-kappaB and cellular kinases in TNF-alpha dysregulation. H5N1 and H1N1 viruses did not differ in the activation of NF-kappaB or degradation of IkappaB-alpha in human macrophages. However, we demonstrated that unlike H1N1 virus, H5N1/97 strongly activates mitogen-activated protein kinase (MAPK), including p38 MAPK and extracellular signal-regulated kinases 1 and 2. Specific inhibitors of p38 MAPK significantly reduced the H5N1/97-induced TNF-alpha expression in macrophages. Taken together, our findings suggest that H5N1/97-mediated hyperinduction of cytokines involves the p38 MAPK signaling pathway. These results may provide insights into the pathogenesis of H5N1 disease and rationales for the development of novel therapeutic strategies.
authors.affiliation: Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Davy C W
authors.initials: DC
authors.lastname: Lee
authors.forename: Chung-Yan
authors.initials: CY
authors.lastname: Cheung
authors.forename: Anna H Y
authors.initials: AH
authors.lastname: Law
authors.forename: Chris K P
authors.initials: CK
authors.lastname: Mok
authors.forename: Malik
authors.initials: M
authors.lastname: Peiris
authors.forename: Allan S Y
authors.initials: AS
authors.lastname: Lau
mesh_terms: D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype; D009980:Influenza A virus / Q000472:pathogenicity*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D011956:Receptors, Cell Surface / Q000502:physiology; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases