Abstract: Objective To assess the role of N-acetyl-L-cysteine (NAC) on the expression of autophagy in rat NR8383 cells exposed to silicon dioxide (SiO₂).Methods NR8383 cells were cultured routinely and exposed to SiO₂ dust (50 mg/L) for 3,6,12,20, and 24 hours,respectively,and then tumor necrosis factor-α (TNF-α) and transforming growth factor-βⅠ(TGF-βⅠ) in culture supernatant were detected with double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) to determined the optimal time for following NAC treatment (10 mmol/L).Light chain 3 (LC3) level in NR8383 cells was determined with Western blot and immunofluorescence with confocal microscopy.Results The optimal exposure time to SiO₂ dust was 20 hours in the rat NR8383 cell model.The TNF-α level in the silica exposure group with NAC treatment was significantly lower than that in the group without NAC treatment (116.82±8.98 vs.1 823.58±764.85 pg/mL,P<0.05)but the level of TGF-βⅠwas not significantly different between the two groups (8.27±3.62 vs.14.28±5.71 pg/mL,P>0.05).The LC3 protein levels in both the silica exposure groups with and without NAC treatment (3.52±0.57 and 3.84±0.53 pg/mL)were higher than that in the control group (2.24±0.56 pg/mL).Immunofluorescence confocal microscopy analysis demonstrated that LC3 expression in NR8383 cells with silica exposure for 20 hours was stronger than that of the control group but was not different from that of the exposure group with NAC treatment.Conclusion SiO₂ can enhance autophagy in rat NR8383 cells and NAC can reduce TNF-α in cell culture supernatant,suggesting that NAC might be involved in the inflammatory response of the cells exposed to SiO₂.