Redox-Dependent Activation of Matrix Metalloproteinases Regulates Influenza A Virus Replication in Neuronal Cells.

Background: Influenza A virus (IAV) is a major respiratory pathogen with the potential to invade the central nervous system (CNS), leading to neurological complications. However, the mechanisms underlying IAV neurotropism and its impact on neuronal cells remain poorly understood. This study is aimed at establishing a reliable in vitro model using differentiated SH-SY5Y human neuroblastoma cells to investigate IAV infection in the CNS, with a specific focus on oxidative stress and matrix metalloproteinases (MMPs) production. Methods: Differentiated SH-SY5Y cells were infected with Influenza A/NWS/33 (H1N1) strain. Redox state was assessed by measuring intracellular glutathione (GSH) levels, Glutaredoxin 1 (Grx1) expression, and Prdx1 release. The activation of oxidative stress-responsive MMPs (MMP-2, MMP-9) was analyzed via western blot, gelatin zymography, and qRT-PCR. The effect of MMPs inhibition on viral replication was evaluated using Batimastat (BB-94) and siRNA-mediated downmodulation. Results: IAV efficiently infects and replicates in differentiated SH-SY5Y cells, inducing oxidative stress, as evidenced by decreased GSH levels, increased glutathionylated proteins and Grx1 expression, and Prdx1 release. Additionally, IAV infection enhances the production and activation of MMP-2 and MMP-9, a process regulated by redox balance, as demonstrated by the inhibitory effects of redox modulators. Finally, postinfection treatment with BB-94, an MMPs inhibitor, and siRNA-mediated downmodulation significantly reduces viral replication and infectivity. Conclusions: These findings demonstrate that IAV infection modulates neuronal redox balance and promotes MMPs activation, fostering a cellular environment that enhances viral replication and spread within neuronal-like cells.