Figure 1.

SiO₂ induced the activation and apoptosis of U937 cell-derived macrophages. (a–d) Representative Western blot and densitometric analyses showing the effects of SiO₂ on the expression of the M1 marker NOS2, the M2a marker ARG1, the M2c marker SOCS3 (a and b) and the apoptosis-associated proteins, BAX, BCL2L1 and cleaved-CASP3 (c and d) in U937 cells. The results suggested that SiO₂ induced NOS2, ARG1, SOCS3, BAX, BCL2L1 and cleaved-CASP3 expression in a time-dependent manner. Data are presented as the mean±S.E.M. (n=5); *P<0.05; **P<0.01 versus the 0-h group (two-way ANOVA). (e) MTT assay results showing that the SiO₂-induced decrease in cell viability occurred in a time-dependent manner in U937 cells. Data are presented as the mean±SEM (n=5); *P<0.05 versus the 0-h group (Student's t-test)