The involvement of a stress-activated pathway in equine influenza virus-mediated apoptosis.
We have shown elsewhere that equine-2 influenza virus (EIV; subtype H3N8) induced pronounced cell death in infected cells through apoptosis as demonstrated by DNA fragmentation assay and a combined TUNEL and immunostaining scheme. In this study, we investigated the mechanism of EIV-mediated cytotoxicity on a permissive mammalian epithelial cell line, Madin-Darby canine kidney (MDCK) cells. EIV infection increased the cellular levels of oxidative stress and c-Jun/AP-1 protein (which is known to be affected by oxidative stress), as well as its DNA binding activity. Increased production of TGF-beta1, an inducer of c-Jun N-terminal kinase or stress-activated protein kinase (JNK/SAPK) activation, was also detected in EIV-infected MDCK cells. It has been reported that TGF-beta may initiate a signaling cascade leading to JNK/SAPK activation. Addition of c-Jun antisense oligodeoxynucleotide, antioxidant N-acetyl-cysteine (NAC), JNK/SAPK inhibitor carvedilol, or TGF-beta-neutralizing antibody effectively blocked c-Jun/AP-1 upregulation and TGF-beta1 production mediated by EIV infection. These treatments also attenuated EIV-induced cytopathogenic effects (CPE) and apoptosis. Our results suggest that a stress-activated pathway is involved in apoptosis mediated by EIV infection. It is likely that EIV infection turns on the JNK/SAPK cascade, which modulates the activity of apoptosis-promoting regulatory factor c-Jun/AP-1 and epithelial growth inhibitory cytokine TGF-beta.
Lin
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The Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington 40508, USA. chengbin.lin@spcorp.com
Zimmer
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Lu
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Holland
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Dong
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Chambers
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D000818:Animals; D017209:Apoptosis; D002227:Carbazoles / Q000494:pharmacology; D000077261:Carvedilol; D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D053938:DNA Fragmentation; D004285:Dogs; D004789:Enzyme Activation; D020287:In Situ Nick-End Labeling; D009980:Influenza A virus; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D009976:Orthomyxoviridae Infections / Q000201:enzymology*; D018384:Oxidative Stress; D011412:Propanolamines / Q000494:pharmacology; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000096:biosynthesis; D014779:Virus Replication / Q000187:drug effects
D002227:Carbazoles; D020319:Oligodeoxyribonucleotides, Antisense; D011412:Propanolamines; D016212:Transforming Growth Factor beta; D000077261:Carvedilol; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases