Biological responses in rats exposed to cigarette smoke and Middle East sand (dust)

Abstract

Respiratory symptoms are frequently reported in personnel deployed to the Middle East. This project characterized the respiratory toxicity of inhaled Iraqi sand (IS). Adult rats underwent a 6-wk inhalation to air or mainstream cigarette smoke (MSCS) (3 h/d, 5 d/wk) that included exposure to IS or crystalline silica (1 mg/m³, 19 h/d, 7 d/wk) or air during the last 2 weeks. Assessments included motor activity, whole-body plethysmography, cytological and biochemical analysis of bronchoalveolar lavage fluid, lung metal burden, nasal and lung pathology, and changes in lung protein and gene expression. A number of metals including nickel, manganese, vanadium, and chromium were detected in IS. Elevated lung parenchyma aluminum, silica, barium, manganese, and vanadium concentrations were seen in IS-exposed rats, suggesting that several metals present in IS are bioavailable. Rats exposed to IS only developed mild inflammation in the anterior nose and lung. Silica inhalation was associated with some pulmonary responses that were not seen in IS-exposed rats, such as mild laryngeal and tracheal inflammation, mild tracheal epithelial hyperplasia, and elevated lung silica concentrations. MSCS inhalation with or without co-exposure to either IS or silica resulted in changes consistent with pulmonary inflammation and stress response. Rats exposed to MSCS and silica had more widespread airway lesions when compared with rats exposed to MSCS only. Silica-exposed rats had more robust pulmonary gene expression and proteomic responses than that seen in IS-exposed rat. Our studies show that the respiratory toxicity of IS is qualitatively similar to or less than that seen following short-term silica exposure.

Keywords::

• Particle toxicity
• nanoparticles
• rat
• in vivo
• in vitro
• pulmonary toxicity
• cytotoxicity
• dust inhalation

Acknowledgments

The authors would like to thank Kay C. Roberts, Carl U. Parkinson, Earl W. Tewksbury, and Jason Frye of Inhalation Facility, Paul W. Ross and the animal care staff, Betsy Gross Bermudez and the necropsy/histology staff, Linda J. Pluta and Victoria A. Wong, of The Hamner Institutes for Health Sciences for conducting the in-life components of this study. Melanie Foster, North Carolina State University, conducted the FOB studies (at The Hamner Institutes for Health Sciences). Gabrielle Willson of Experimental Pathology Laboratories performed the histological evaluations.

Declarations of interest

This study was sponsored and funded by the Office of Naval Research and Global War on Terrorism, the USAMRMC and the Military Operational Medicine Research Program. The views expressed are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of the Army, Department of Defense or the US Government. Citation of commercial organizations or trade names in this report do not constitute an official Department of the Navy or Department of the Army endorsement or approval of the products or services of these organizations.