Enterovirus 71 induces integrin β1/EGFR-Rac1-dependent oxidative stress in SK-N-SH cells: role of HO-1/CO in viral replication.

Oxidative stress became emerged as a key player in the development and progression of many pathological conditions including virus-induced encephalitis. Heme oxygenase-1 (HO-1) plays a crucial role in defending the body against oxidant-induced injury during inflammatory processes. Therefore, we investigated the induction of HO-1 level in host cells, which may exert a beneficial effect to minimize viral replication in SK-N-SH cells. In this study, we found that enterovirus 71 (EV71) induced the generation of reactive oxygen species (ROS) and activation of NADPH oxidase. EV71-induced ROS generation was mediated through activation of integrin β1, an epidermal growth factor receptor (EGFR), Rac1 and NADPH oxidase which revealed by using selective pharmacological inhibitors or transfection with respective siRNAs. In addition, the reduction of viral load was observed with NADPH oxidase inhibitors (apocynin and diphenyleneiodonium chloride), ROS scavenger (N-acetylcysteine), and transfection with p47(phox) siRNA in Western blot and real-time PCR analyses. Consistently, overexpression of HO-1 attenuated EV71-induced NADPH oxidase/ROS generation and EV71 replication which were abrogated by pretreatment with an HO-1 inhibitor, zinc protoporphyrin IX (ZnPP IX). Moreover, metabolite of HO-1, carbon monoxide (CO), also diminished ROS formation and EV71 replication which were reversed by pretreatment with a CO scavenger (hemoglobin) and a cyclic GMP-dependent protein kinase (PKG) inhibitor (KT5823). These findings suggest that up-regulation of HO-1 exerts as a host cellular defense mechanism against EV71 infection in SK-N-SH cells.