Bax Inhibitor-1 Acts as an Anti-Influenza Factor by Inhibiting ROS Mediated Cell Death and Augmenting Heme-Oxygenase 1 Expression in Influenza Virus Infected Cells

Influenza virus remains a major health concern worldwide, and there have been continuous efforts to develop effective antivirals despite the use of annual vaccination programs. The purpose of this study was to determine the anti-influenza activity of Bax inhibitor-1 (BI-1). Madin-Darby Canine Kidney (MDCK) cells expressing wild type BI-1 and a non-functional BI-1 mutant, BI-1 Delta C (with the C-terminal 14 amino acids deleted) were prepared and infected with A/PR/8/34 influenza virus. BI-1 overexpression led to the suppression of virus-induced cell death and virus production compared to control Mock or BI-1 Delta C overexpression. In contrast to BI-1 Delta C-overexpressing cells, BI-1 overexpressing cells exhibited markedly reduced virus-induced expression of several viral genes, accompanied by a substantial decrease in ROS production. We found that treatment with a ROS scavenging agent, N-acetyl cysteine (NAC), led to a dramatic decrease in virus production and viral gene expression in control MDCK and BI-1 Delta C-overexpressing cells. In contrast, NAC treatment resulted in the slight additional suppression of virus production and viral gene expression in BI-1-overexpressing cells but was statistically significant. Moreover, the expression of heme oxygenase-1 (HO-1) was also significantly increased following virus infection in BI-1-overexpressing cells compared to control cells. Taken together, our data suggest that BI-1 may act as an anti-influenza protein through the suppression of ROS mediated cell death and upregulation of HO-1 expression in influenza virus infected MDCK cells.