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-β1, 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-β 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-β-neutralizing antibody effectively blocked c-Jun/AP-1 upregulation and TGF-β1 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-β.
|Number of pages||12|
|State||Published - Aug 15 2001|
Bibliographical noteFunding Information:
We thank Drs. Zhen Pang, Mansoor Ahmed, Howard Glauert, and Steve Estus, and Steve Sells and Lynn Tudor for helpful comments and assistance. We also thank Dr. Judith Appleton (James A. Baker Institute for Animal Health, Cornell University) for the generous gift of F90 5 H1.25 antibody. This work was supported in part by USDA/CRIS project No. Ky 014006. The investigation reported in this paper is in connection with a project (No. 99-14-123) of the Kentucky Agricultural Experiment Station and is published with approval of the director.
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