Influenza A virus-induced apoptosis in bronchiolar epithelial (NCI-H292) cells limits pro-inflammatory cytokine release.
Infection of cells with influenza A virus results in cell death with apoptotic characteristics. Apoptosis is regarded as a non-inflammatory process. However, during influenza an inflammatory response occurs in the airway epithelium. An examination of this apparent paradox was made using influenza A virus infection of human nasal and bronchiolar epithelial cells. Some cytokine genes (IL-18, CCL2 and CCL5) were expressed constitutively in nasal cells but no cytokine was released. In bronchiolar cells, IL-1 beta, IL-6 and CXCL8 expression was constitutive, whilst CCL2 and CCL5 expression was upregulated following influenza virus infection. IL-6, CXCL8 and CCL5 were released but IL-1 beta and CCL2 were not. In bronchiolar cells, cell death was inhibited by the caspase-8 (Z-IETD-fmk) and pan-caspase (Z-VAD-fmk) inhibitors and these inhibitors enhanced expression of CCL5 and increased the levels of the three secreted cytokines significantly. Thus, the amount of each cytokine released from bronchiolar cells is reduced during cell death, implying that the observed inflammatory response in influenza would be greater if cell death did not occur. Reduced cytokine release is also associated with fragmentation of the Golgi body, as the caspase inhibitors also rescued influenza A virus-induced fragmentation of the Golgi ribbon.
Brydon
Edward W A
EWA
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Smith
Harry
H
The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Sweet
Clive
C
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D002460:Cell Line; D018932:Chemokine CCL2 / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D018946:Chemokine CCL5 / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D016207:Cytokines / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D009980:Influenza A virus / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D020545:Respiratory Mucosa / Q000276:immunology / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D018932:Chemokine CCL2; D018946:Chemokine CCL5; D015853:Cysteine Proteinase Inhibitors; D016207:Cytokines; D009842:Oligopeptides; D012333:RNA, Messenger; C403753:benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9