Figure 1

Cristobalite silica increases caspase-1 transcript levels and caspase -1 cleavage products in primary human bronchial epithelial cells. A. Caspase-1 mRNA levels in primary normal human bronchial epithelial (NHBE) cells after 24 h exposure to 15 (SIL15) and 75 × 10⁶μm²/cm² (SIL75) cristobalite silica, expressed as mean fold change ± SEM (indicated by error bars) with *p-value <0.05 compared to unexposed control cells (UC) and normalized to the housekeeping gene HPRT (N= 3). B. Western blot analysis of caspase-1 cleaved products was conducted on whole cell lysates of NHBE cells after 24 h of exposure. p20 subunits were detected after a longer exposure compared to pro-caspase-1 (14 min versus 30 s). Glass beads (GB) and unexposed cells (UC) were included as controls, and β-actin was used as a loading control. C, Caspase-1 enzymatic activity was assayed in cell lysates of NHBE cells exposed to the indicated silica concentrations for 24 h with. Caspase-1 activities are expressed as arbitrary units (O.D. 405 nm/μg protein) with *p-value <0.05 compared to UC.