Research

Cigarette smoke worsens lung inflammation and impairs resolution of influenza infection in mice

Rosa C Gualano^1,4 , Michelle J Hansen^1,4 , Ross Vlahos^1,4 , Jessica E Jones^1,4 , Ruth A Park-Jones^1,4 , Georgia Deliyannis³ , Stephen J Turner³ , Karen A Duca⁵ and Gary P Anderson^1,2,4

¹  Department of Pharmacology, The University of Melbourne, Parkville 3010, Victoria, Australia

²  Department of Medicine, The University of Melbourne & The Royal Melbourne Hospital, Parkville 3050, Victoria, Australia

³  Department of Microbiology & Immunology, The University of Melbourne, Parkville 3010, Victoria, Australia

⁴  Co-Operative Research Centre for Chronic Inflammatory Diseases, Parkville 3052, Victoria, Australia

⁵  Virginia Bioinformatics Institute, Blacksburg, Virginia, USA

author email corresponding author email

Respiratory Research 2008, 9:53doi:10.1186/1465-9921-9-53

Published:	15 July 2008

Abstract

Background

Cigarette smoke has both pro-inflammatory and immunosuppressive effects. Both active and passive cigarette smoke exposure are linked to an increased incidence and severity of respiratory virus infections, but underlying mechanisms are not well defined. We hypothesized, based on prior gene expression profiling studies, that upregulation of pro-inflammatory mediators by short term smoke exposure would be protective against a subsequent influenza infection.

Methods

BALB/c mice were subjected to whole body smoke exposure with 9 cigarettes/day for 4 days. Mice were then infected with influenza A (H3N1, Mem71 strain), and analyzed 3 and 10 days later (d3, d10). These time points are the peak and resolution (respectively) of influenza infection.

Results

Inflammatory cell influx into the bronchoalveolar lavage (BALF), inflammatory mediators, proteases, histopathology, viral titres and T lymphocyte profiles were analyzed. Compared to smoke or influenza alone, mice exposed to smoke and then influenza had more macrophages, neutrophils and total lymphocytes in BALF at d3, more macrophages in BALF at d10, lower net gelatinase activity and increased activity of tissue inhibitor of metalloprotease-1 in BALF at d3, altered profiles of key cytokines and CD4+ and CD8+ T lymphocytes, worse lung pathology and more virus-specific, activated CD8+ T lymphocytes in BALF. Mice smoke exposed before influenza infection had close to 10-fold higher lung virus titres at d3 than influenza alone mice, although all mice had cleared virus by d10, regardless of smoke exposure. Smoke exposure caused temporary weight loss and when smoking ceased after viral infection, smoke and influenza mice regained significantly less weight than smoke alone mice.

Conclusion

Smoke induced inflammation does not protect against influenza infection.

In most respects, smoke exposure worsened the host response to influenza. This animal model may be useful in studying how smoke worsens respiratory viral infections.