Inhibition of Nox2 Oxidase Activity Ameliorates Influenza A Virus-Induced Lung Inflammation

Ross Vlahos,Steven Bozinovski,Stavros Selemidis,John Stambas,Grant R Drummond,Brad R S Broughton,Stacey Schultz-Cherry

doi:10.1371/journal.ppat.1001271

Ross Vlahos, Steven Bozinovski + Show 5 more

Open Access

https://doi.org/10.1371/journal.ppat.1001271

Copy DOI

Abstract

Influenza A virus pandemics and emerging anti-viral resistance highlight the urgent need for novel generic pharmacological strategies that reduce both viral replication and lung inflammation. We investigated whether the primary enzymatic source of inflammatory cell ROS (reactive oxygen species), Nox2-containing NADPH oxidase, is a novel pharmacological target against the lung inflammation caused by influenza A viruses. Male WT (C57BL/6) and Nox2−/y mice were infected intranasally with low pathogenicity (X-31, H3N2) or higher pathogenicity (PR8, H1N1) influenza A virus. Viral titer, airways inflammation, superoxide and peroxynitrite production, lung histopathology, pro-inflammatory (MCP-1) and antiviral (IL-1β) cytokines/chemokines, CD8+ T cell effector function and alveolar epithelial cell apoptosis were assessed. Infection of Nox2−/y mice with X-31 virus resulted in a significant reduction in viral titers, BALF macrophages, peri-bronchial inflammation, BALF inflammatory cell superoxide and lung tissue peroxynitrite production, MCP-1 levels and alveolar epithelial cell apoptosis when compared to WT control mice. Lung levels of IL-1β were ∼3-fold higher in Nox2−/y mice. The numbers of influenza-specific CD8+DbNP366+ and DbPA224+ T cells in the BALF and spleen were comparable in WT and Nox2−/y mice. In vivo administration of the Nox2 inhibitor apocynin significantly suppressed viral titer, airways inflammation and inflammatory cell superoxide production following infection with X-31 or PR8. In conclusion, these findings indicate that Nox2 inhibitors have therapeutic potential for control of lung inflammation and damage in an influenza strain-independent manner.

Highlights

The early host innate immune response directed against influenza A virus infection in the absence of pre-existing immunity is typically characterised by activation of airway epithelium and resident alveolar macrophages, and release of inflammatory mediators resulting in the trafficking of additional macrophages, neutrophils and T lymphocytes into the lung [1]
An important paradigm strongly suggests that the lung damage arising from influenza A viruses but other pathogens including, but not restricted to, SARS, parainfluenza viruses, human respiratory syncytial virus and Streptococcus pneumoniae consists of an excessive host response characterised by a rapid, influx of inflammatory cells into the lungs leading to excessive reactive oxygen species (ROS) production
Our study demonstrates that the primary enzymatic source of inflammatory cell ROS, Nox2-containing NADPH oxidase, promotes airways inflammation to low and high pathogenicity influenza A virus infection and impedes with the host’s ability to clear the virus

Summary

Introduction

The early host innate immune response directed against influenza A virus infection in the absence of pre-existing immunity is typically characterised by activation of airway epithelium and resident alveolar macrophages, and release of inflammatory mediators resulting in the trafficking of additional macrophages, neutrophils and T lymphocytes into the lung [1]. Recent evidence suggests that much of the acute lung injury caused by H5N1 can be attributed to excessive ROS production (i.e. oxidative stress) initiated by an overactive innate immune response [3], [4]. Identification of the enzymatic sources of ROS may pave the way for therapies that combat the oxidative stress-dependent lung injury caused by influenza A virus infection

Methods

Results

Discussion

Conclusion