Subchronic inhalation of coal dust particulate matter 10 induces bronchoalveolar hyperplasia and decreases MUC5AC expression in male Wistar rats

Coal dust is a pollutant found in coal mines that are capable of inducing oxidative stress and inflammation, but the effects on lung metaplasia as an early step of carcinogenesis remain unknown. The purpose of the present study was to evaluate the effects of PM₁₀ coal dust on lung histology, MUC5AC expression, epidermal growth factor (EGF) expression, and epidermal growth factor receptor (EGFR) expression. An experimental study was done on male Wistar rats, which were divided into the following groups: control groups exposed to coal dust for 14 days (at doses of 6.25 mg/m³, 12.5 mg/m³, and 25 mg/m³), and the groups exposed to coal dust for 28 days (at doses of 6.25 mg/m³, 12.5 mg/m³, and 25 mg/m³). EGF expressions in rat lungs were measured by ELISA. EGFR and MUC5AC were measured by a confocal laser scanning microscope. The bronchoalveolar epithelial image of the group exposed to coal dust for 14 and 28 days showed a epithelial rearrangement, hyperplastic (metaplastic) goblet cells, and scattered massive inflammatory cells. The pulmonary parenchymal image of the group of exposed to coal dust for 14 and 28 days showed scattered inflammatory cells filling up the pulmonary alveolar networks, leading to an appearance of thickened parenchymal alveoli until emphysema-like structure. There was no significant difference in MUC5AC, EGF, and EGFR expressions for 14-d exposure (p > 0.05). There was no significant difference in EGF and EGFR expressions for 28-d exposure (p > 0.05), but there was a significant difference in MUC5AC expression (p < 0.05). We concluded that subchronic inhalation of coal dust particulate matter 10 induces bronchoalveolar reactive hyperplasia and rearrangement of epithelial cells which accompanied by decrease expression MUC5AC in male rats.