IRG1 Regulatesmitochondrial Ros Production During Respiratory Syncytial Virus Infection Of Airway Epithelial Cells

Respiratory syncytial virus(RSV)is a negative sense,single strand RNA(ssRNA)virus and is the most common cause of childhood infection.Although proinflammatory cytokine production has been identified as a primary cause of RSV diseases,accumulating evidence indicate that reactive oxygen species(ROS)production is a major factor to pulmonary inflammation and tissue damage.The immune responsive gene 1(IRG1)was first identified as an LPS-stimulated gene and has recently been shown to modulate innate immune response against bacterial pathogens through the conversion of cis-aconitate,an intermediate of tricarboxylic acid cycle,to itaconic acid.IRG1 also regulates mitochondrial ROS(mROS)production through ?-oxidation of fatty acids.Viral and bacterial infection promotes IRG1 expression.We investigated IRG1 expression during RSV infection inA549 cells.We found that RSV infection induced IRG1 expression.Overexpression of IRG1 had no significant effect on RSV infectivity,although IRG1 was reported with antiviral activity against some ssRNA viruses.Suppression of IRG1 induction by siRNA resulted in reduced expression of proinflammatory cytokines and mROS production in RSV infected cells.Further experiments show that treated with antioxidant N-acetyl-L-cysteine(NAC)and Glutathione(GSH)down-regulated ROS levels and inhibited RSV infection effectively.While buthionine sulfoximine(BSO),a GSH synthesis inhibitor,could upregulated ROS levels,did not promote RSV replication.Besides,RSV increased glucose uptake and glycolysis significantly,while no itaconic acid accumulation was detected.These data therefore implicate IRG1 induction to ROS production by RSV infection,while RSV replication was not replied on pre-existing IRG1 or ROS.In conclusion,this paper proved that RSV infection can significantly induce IRG1 expression,andthe important role of IRG1 gene in the process of ROS production,which may be a potential therapy to RSV infection.