Influenza A virus and TLR7 activation potentiate NOX2 oxidase-dependent ROS production in macrophages

• Published in: Free radical research Vol. 48; no. 8; pp. 940 - 947
• Main Authors: To, E. E., Broughton, B. R. S., Hendricks, K. S., Vlahos, R., Selemidis, S.
• Format: Journal Article
• Language: English
• Published: England Informa Healthcare 01.08.2014; Taylor & Francis
• Subjects: Animals; Humans; imiquimod; Influenza A virus - genetics; Influenza A virus - metabolism; lung pathology; Macrophages - metabolism; Male; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred C57BL; NADPH Oxidase 2; NADPH Oxidases - metabolism; Oxidative Stress; Phosphorylation; poly I:C; Reactive Oxygen Species - metabolism; Signal Transduction; superoxide; Toll-Like Receptor 7 - genetics; Toll-Like Receptor 7 - metabolism; superoxide; poly I:C; oxidative stress; imiquimod; lung pathology
• DOI: 10.3109/10715762.2014.927579
• ISSN: 1071-5762

Abstract Influenza A virus infects resident alveolar macrophages in the respiratory tract resulting in Toll like receptor 7 (TLR7) activation that triggers an inflammatory response to resolve the infection. Macrophages are also major sources of reactive oxygen species (ROS) via the NOX2-containing NADPH oxidase. Although ROS are crucial for pathogen clearance, in response to influenza A virus, ROS are touted as being culprit mediators of the lung tissue injury. The aim of the present study was to determine whether influenza A virus infection and TLR7 activation of macrophages, results in alterations in their ROS production. Here we demonstrate using immunofluorescence that influenza A virus (Hong Kong X-31 strain; H3N2) internalizes in RAW264.7 cells and mouse alveolar macrophages within 1 h, resulting in a significant enhancement in the stimulated NOX2 oxidase-dependent oxidative burst, although virus had no effect on basal ROS. The specific TLR7 agonist imiquimod (10 μg/ml) elevated basal superoxide production and, in a similar fashion to influenza A virus, enhanced NOX2 oxidase-dependent oxidative burst. By contrast, the TLR3 agonist, poly I:C (1-100 μg/ml) failed to influence the oxidative burst to NOX2 oxidase. A peptide corresponding to the region 337-348 on p47phox conjugated to a HIV-tat, designed to inhibit the phosphorylation of Ser346 on p47phox suppressed the influenza A virus- and imiquimod-induced enhancement in the oxidative burst. In conclusion, this study demonstrates for the first time that influenza A virus and TLR7 activation enhance the NOX2 oxidase-dependent oxidative burst in macrophages, which might underpin the acute lung injury to influenza A virus infection.