Abstract: Objective To investigate the effect of N-acetylcysteine(NAC) on ameliorating testicular injury of rats caused by subacute exposure to atmospheric fine particulate matter(PM2.5). 
Methods A total of 30 Wistar rats were randomly divided into three groups:saline control group, PM2.5 exposure group and PM2.5+NAC group. The rats in PM2.5 exposure group were exposed to a dose of 5.0 mg/kg PM2.5 suspension by intratracheal instillation, once a week for 8 weeks. Rats in the PM2.5+NAC groups were given 150 mg·kg-1·d-1 NAC by intragastric gavage continuously on the basis of PM2.5 exposure. Saline control group was given the same volume of saline(1 mL/kg). After modeling, the pathological sections of testicular tissue were prepared by hematoxylin-eosin staining(HE). Terminal deoxynucleotidyl transferase dUTP nick end labeling(TUNEL) method was used to detect testicular apoptosis in rats. Superoxide dismutase(SOD), glutathione(GSH) and malondialdehyde(MDA) indicators were measured using spectrophotometer method. The levels of interleukin-10(IL-10) and testosterone were measured by enzyme-linked immunosorbent assay(ELISA) method.
Results Serum testosterone levels and testicular tissue GSH, SOD, IL-10 levels of rats in the PM2.5 exposure group and PM2.5+NAC group were lower than those in the saline control group, while MDA levels in the testicular tissue were increased; The testosterone levels and testicular tissue GSH, SOD, IL-10 levels were higher in the PM2.5+NAC group than in PM2.5 exposure group, while MDA level in testicular tissue was decreased(P＜0.05). In the PM2.5 exposure group, multiple nuclei in the seminiferous tubules showed obvious dark brown staining, and the TUNEL positive cell count was significantly higher than that of the saline control group and the PM2.5+NAC group(P＜0.05). The number of apoptotic cells in the PM2.5+NAC group was significantly lower than that of the PM2.5 control group, but higher than that of the saline control group(P＜0.05). The apoptosis index of testicular cells in the PM2.5 exposure group and PM2.5+NAC group was higher than that of the saline control group, and the index was lower in the PM2.5+NAC group than in the PM2.5 exposure group(P＜0.05). 
Conclusion Subacute exposure to PM2.5 can induce pathological injury of testicular tissue, testicular cell apoptosis, and changes in indicators of inflammation and oxidative stress. NAC, as an antioxidant, can obviously ameliorate PM2.5-induced testicular injury, and has an antagonistic effect on the PM2.5-induced toxic effects on the testis of rats. 

Key words: particulate matter(PM)2.5, N-acetylcysteine, oxidativestress, inflammation, apoptosis