RESUMO
Objective@#To investigate the changes in the levels of interleukin-6 (IL-6) and let-7e in rats induced by coal mine dust, so as to provide the basis for the mechanism of coal worker's pneumoconiosis (CWP).@*Methods@#Sixty-four clean and healthy male Sprague-Dawley rats were randomly divided into the control group, coal dust group, mixed dust group (mixed coal and silica dust) and quartz group. The rats in the control group were exposed to 1 mL physiological saline by non-exposure tracheal perfusion, and the rats in the dust-exposed groups were exposed to 1 mL dust suspension. Rats were sacrificed by anesthesia after 1 month and 6 months, lung tissue was observed using hematoxylin-eosin staining, the pathological change in the lungs was scored using the Szapiel scoring system, the levels of IL-6 in the bronchoalveolar lavage fluid were detected using enzyme-linked immunosorbent assay, and the expression of let-7e was determined by quantitative real-time PCR.@*Results@#A month after exposure, a small amount of coal spots and inflammatory exudation were observed in the lung tissue of the coal dust group and the mixed dust group. The quartz group showed tissue structure destruction and mild fibrosis and thickening of alveolar septum. Six months after exposure, there were more coal spots and slightly thickened alveolar septum in the coal dust group, and hyperplasia of pulmonary interstitial fibers, destruction of alveolar structure and silica nodules were observed in the mixed dust group. In the quartz group, the alveolar structure was obviously destroyed, the interstitial fiber proliferation was significant and silica nodules were seen. Two-factor analysis of variance showed that the interaction between duration of exposure and dust type significantly influenced the pathological score of lung tissue, IL-6 levels, and let-7e expression levels (P<0.05). Under the same dust type, the pathological score of lung tissue and IL-6 levels were higher at 6 months after exposure than at 1 month, while the relative expression of let-7e was lower at 6 months after exposure than at 1 month (all P<0.05). Under the same duration of exposure, the pathological score of lung tissue and IL-6 levels were higher in the dust-exposed groups than in the control group, while the relative expression of let-7e was lower in the dust-exposed groups than in the control group (all P<0.05).@*Conclusions@#Coal dust can cause an increase in levels of IL-6 and a decrease in let-7e expression in rats. The type of dust and duration of exposure can interactively affect IL-6 and let-7e.