Cigarette smoke (CS) is a key contributor of chronic obstructive pulmonary disease (COPD)
however, its role in the pathogenesis of COPD has not been fully elucidated. N‑acetyl‑L‑cysteine (NAC), as an antioxidant, has been used in the treatment of COPD
however, the mechanisms of action of NAC are not fully understood. Alveolar epithelial type 2 (ATII) cells serve an essential role in the maintenance of alveolar integrity. The aim of the present study was to identify the effect of CS on rat lungs and ATII cells. A subacute lung injury model of Wistar rats was established using CS exposure for 4 weeks. Interalveolar septa widening, infiltration of inflammatory cells, edema fluid in airspaces and abnormal enlargement of airspaces were observed through H&E staining. ELISA revealed that NAC could protect against CS‑induced increases in serum levels of malondialdehyde and decreases in serum levels of superoxide dismutase. Additionally, 8‑hydroxy‑deoxyguanosine was detected using immunohistochemical staining, and this was also expressed at increased levels in the lung tissue of the CS‑exposed group. In addition, the expression levels of Bcl‑2, BAX and caspase‑3 p12 in lung tissue were detected by western blotting or immunohistochemical staining. The expression levels of Bcl‑2 decreased and those of caspase3 p12 were increased in response to CS exposure when compared with those in the control group. These effects were prevented by treatment with NAC.