OBJECTIVETo investigate the autophagy of effector cells in lung tissue at different time points when rats were exposed to free SiO2 dust.

METHODSSixty Wistar rats (220∼230 g) were selected and allocated to experimental group (n = 30) and control group (n = 30). In the experimental group, a rat silicosis model was established by infusing SiO2 suspension into the trachea of rats. Six rats in each group were sacrificed on days 1, 7, 14, 21, or 28 of dust exposure. Lung tissue samples were collected to prepare lung tissue sections. The pulmonary inflammation and fibrosis were observed by HE staining. The proautophagosome, autophagosome, and autophagolysosome in lung tissue sections were observed under a transmission electron microscope.

RESULTSOn day 1 of dust exposure, many proautophagosomes and autophagosomes were seen in both experimental group and control group. On day 7 of dust exposure, the experimental group had more autophagosomes in lung tissue than the control group. On day 14 of dust exposure, the experimental group had fewer autophagosomes than the control group. On days 21 and 28, autophagolysosomes were seen in macrophage plasma in both experimental group and control group; the autophagolysosomes in experimental group showed cloudy swelling and expansion, and some were vacuolated, and these changes were more significant on day 28.

CONCLUSIONFree SiO2 dust can induce autophagy in the lung tissue of rats, with varying degrees at different time points of dust exposure.