Subchronic inhalation toxicity study of 3R4F reference cigarette smoke in rats

This study aimed to investigate the subchronic exposure toxicity of smoke from 3R4F reference cigarettes. Male and female Sprague-Dawley rats were exposed to cigarette smoke at total particulate matter (TPM) concentrations of 50, 100, or 200 μg/L for a period of 13 weeks. Body weight gain of male rats significantly decreased upon exposure to 200 μg TPM/L of smoke. All smoke-exposed groups showed increase in blood carboxyhemoglobin, urinary nicotine and its metabolites, and inflammatory cytokines relative to the control group. Increased alveolar macrophages, pigmented and thickened alveolar walls, and hypertrophy/hyperplasia were observed in the lungs at concentrations above 50 μg TPM/L. These changes were related to the increase in absolute or relative lung weights. Histopathological examination revealed cigarette smoke-related changes in the nasal cavity, larynx, and trachea. The respiratory tract was adversely affected by inhalation of cigarette smoke. We identified that blood carboxyhemoglobin, urinary nicotine and its metabolites were tobacco-specific biomarkers, and suggested that CXCL1, CCL2, IL-1β, IL-10, TIMP-1, TIMP-2 were useful biomarkers for cigarette smoke. These results may serve as reference data to compare toxicity of tobacco products.