Rui-Hua Zhang1, Hong-Liang Zhang2, Pei-Yao Li1, Chun-Hong Li1, Jing-Ping Gao1, Jun Li3, Tong Xu4, Xue-Jing Wang5, Cun-Lian Wang1, Hui-Chen Zhang6, Ming-Ju Xu1, Shu-Fei Tian1. 1. Key Laboratory of Preventive Veterinary Medicine, Department of Veterinary Medicine, Animal Science College, Hebei North University, Zhangjiakou, 075131, Hebei, People's Republic of China. 2. Department of Veterinary Medicine, Inner Mongolia Agricultural University, Hohhot, 010018, Inner Mongolia, People's Republic of China. 3. Shandong Provincial Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, 250100, Shandong, People's Republic of China. Lijun05318@163.com. 4. Key Laboratory of Preventive Veterinary Medicine, Department of Veterinary Medicine, Animal Science College, Hebei North University, Zhangjiakou, 075131, Hebei, People's Republic of China. xutong1969@sohu.com. 5. The Animal Husbandry and Veterinary Institute of Hebei, Baoding, 071001, Hebei, People's Republic of China. 6. He He Animal Husbandry Development Co. Ltd., Zhenlai, 137300, Jilin, People's Republic of China.
Abstract
BACKGROUND: Oxidative stress is an important pathogenic factor in influenza A virus infection. It has been found that reactive oxygen species induced by the H9N2 influenza virus is associated with viral replication. However, the mechanisms involved remain to be elucidated. METHODS: In this study, the role of autophagy was investigated in H9N2 influenza virus-induced oxidative stress and viral replication in A549 cells. Autophagy induced by H9N2 was inhibited by an autophagy inhibitor or RNA interference, the autophagy level, viral replication and the presence of oxidative stress were detected by western blot, TCID50 assay, and Real-time PCR. Then autophagy and oxidative stress were regulated, and viral replication was determined. At last, the Akt/TSC2/mTOR signaling pathways was detected by western blot. RESULTS: Autophagy was induced by the H9N2 influenza virus and the inhibition of autophagy reduced the viral titer and the expression of nucleoprotein and matrix protein. The blockage of autophagy suppressed the H9N2 virus-induced increase in the presence of oxidative stress, as evidenced by decreased reactive oxygen species production and malonaldehyde generation, and increased superoxide dismutase 1 levels. The changes in the viral titer and NP mRNA level caused by the antioxidant, N-acetyl-cysteine (NAC), and the oxidizing agent, H2O2, confirmed the involvement of oxidative stress in the control of viral replication. NAC plus transfection with Atg5 siRNA significantly reduced the viral titer and oxidative stress compared with NAC treatment alone, which confirmed that autophagy was involved in the replication of H9N2 influenza virus by regulating oxidative stress. Our data also revealed that autophagy was induced by the H9N2 influenza virus through the Akt/TSC2/mTOR pathway. The activation of Akt or the inhibition of TSC2 suppressed the H9N2 virus-induced increase in the level of LC3-II, restored the decrease in the expression of phospho-pAkt, phospho-mTOR and phospho-pS6 caused by H9N2 infection, suppressed the H9N2-induced increase in the presence of oxidative stress, and resulted in a decrease in the viral titer. CONCLUSION: Autophagy is involved in H9N2 virus replication by regulating oxidative stress via the Akt/TSC2/mTOR signaling pathway. Thus, autophagy maybe a target which may be used to improve antiviral therapeutics.
BACKGROUND: Oxidative stress is an important pathogenic factor in influenza A virusinfection. It has been found that reactive oxygen species induced by the H9N2 influenza virus is associated with viral replication. However, the mechanisms involved remain to be elucidated. METHODS: In this study, the role of autophagy was investigated in H9N2 influenza virus-induced oxidative stress and viral replication in A549 cells. Autophagy induced by H9N2 was inhibited by an autophagy inhibitor or RNA interference, the autophagy level, viral replication and the presence of oxidative stress were detected by western blot, TCID50 assay, and Real-time PCR. Then autophagy and oxidative stress were regulated, and viral replication was determined. At last, the Akt/TSC2/mTOR signaling pathways was detected by western blot. RESULTS: Autophagy was induced by the H9N2 influenza virus and the inhibition of autophagy reduced the viral titer and the expression of nucleoprotein and matrix protein. The blockage of autophagy suppressed the H9N2 virus-induced increase in the presence of oxidative stress, as evidenced by decreased reactive oxygen species production and malonaldehyde generation, and increased superoxide dismutase 1 levels. The changes in the viral titer and NP mRNA level caused by the antioxidant, N-acetyl-cysteine (NAC), and the oxidizing agent, H2O2, confirmed the involvement of oxidative stress in the control of viral replication. NAC plus transfection with Atg5 siRNA significantly reduced the viral titer and oxidative stress compared with NAC treatment alone, which confirmed that autophagy was involved in the replication of H9N2 influenza virus by regulating oxidative stress. Our data also revealed that autophagy was induced by the H9N2 influenza virus through the Akt/TSC2/mTOR pathway. The activation of Akt or the inhibition of TSC2 suppressed the H9N2 virus-induced increase in the level of LC3-II, restored the decrease in the expression of phospho-pAkt, phospho-mTOR and phospho-pS6 caused by H9N2 infection, suppressed the H9N2-induced increase in the presence of oxidative stress, and resulted in a decrease in the viral titer. CONCLUSION: Autophagy is involved in H9N2 virus replication by regulating oxidative stress via the Akt/TSC2/mTOR signaling pathway. Thus, autophagy maybe a target which may be used to improve antiviral therapeutics.
Authors: S Braber; K A T Verheijden; P A J Henricks; A D Kraneveld; G Folkerts Journal: Am J Physiol Lung Cell Mol Physiol Date: 2010-10-08 Impact factor: 5.464