The effects of cigarette smoke exposure on bleomycin-induced lung injury in rats

Abstract

Pulmonary fibrosis is considered to as a disease caused by persistent lung injury and inflammation. Cigarette smoke (CS) exposure is known to be associated with development of inflammatory lung diseases. The present study investigated whether the inflammatory response by CS repeated exposure may be involved in exacerbation of bleomycin (BLM)-induced lung injury in rats. Rats were exposed nose-only inhalation to CS (0, 100, 200 or 300 μg/L) for 4 weeks (4 hours/day, 7 days/week), and received intratracheal BLM (single dose on first day). The following eight experimental groups (n=6) were evaluated: vehicle control (VC), BLM, CS 100, 200, 300 and BLM + CS 100, 200, 300. After 4 weeks, in the lung tissues of BLM groups exhibited histopathological changes, including alveolar macrophage aggregation, chronic inflammation and fibrosis. These changes were exacerbated in the lungs tissues of BLM + CS groups in a concentration-dependent manner of CS. The expression of inflammatory cytokines was markedly increased in the bronchoalveolar lavage fluid (BALF) of BLM + CS groups compared to BLM or CS alone, and similar was observed in the lung tissues. On the other hand, there were no significant differences in the levels of these cytokines in the serum of BLM and CS groups compared with VC group. These results suggest that repeated exposure to CS produces an inflammatory response that may contribute to the development of BLM-induced pulmonary fibrosis.

This research was supported by a grant (19183MFDS463) from the Ministry of Food and Drug Safety in 2020.