NMN intervention regulates the expression of ROS and GSH in silica-induced lung injury. (A) Histogram of ROS levels from flow cytometry after exposure to silica for 7 d; (B) histogram of ROS levels from flow cytometry after exposure to silica for 28 d; (C) expression of ROS in lung tissue at 7 d, analyzed using mean fluorescence intensity from flow cytometry; (D) expression of ROS in lung tissue at 28 d, analyzed using mean fluorescence intensity from flow cytometry; (E) expression of GSH in lung tissue at 7 d; (F) expression of GSH in lung tissue at 28 d. # indicates p < 0.05, ### p < 0.001, #### p < 0.0001 vs. Vehicle; ** p < 0.01, *** p < 0.001, NMN-H vs NMN-L. ROS: reactive oxygen species, GSH: glutathione. Sham: saline + saline; Vehicle: silica + saline; NMN-H: silica + NMN (1000 mg/kg); NMN-L: silica + NMN (500 mg/kg); NMN-Con: saline + NMN (1000 mg/kg).