Figure 1.

Silica induces COX-2 but not COX-1 protein in human lung fibroblasts. Fibroblasts in culture were treated for 24 h with the indicated concentrations of amorphous (AS) or crystalline (CS) silica. Carbon black (CB, 100 μg/ml) was included as a negative control. Total cell protein was analyzed by Western blot for expression of COX-2, COX-1 and actin (to confirm equal protein loading). Amorphous silica induces COX-2 slightly at 2.5 μg/ml and strongly at 10 μg/ml. 10-fold higher concentrations of crystalline silica are required to produce similar elevations in COX-2 protein. Neither form of silica alters the constitutive expression of COX-1.