Figure 1

Asbestos primes and activates NLRP3 in HMC. (A) Crocidolite asbestos fibers (arrows in left panel) and GB (arrows in right panel) interact with differentiated LP9 mesothelial cells that are characterized by long microvilli both in vivo and in vitro. Bars = 10 μm. (B) Crocidolite asbestos (Asb) and the soluble tumor promoter, TPA cause increased trends in NLRP3 mRNA levels, as demonstrated by qRT-PCR. In contrast, non-pathogenic GB at identical SA concentrations have no effects (N = 2 samples/group/time point; N = 3 for control, 8 + 24 h (0) group). (C) A time course study shows the protracted nature of NLRP3 transcription by asbestos (75) (N = 2 samples/group/time point; N = 4 for control (0)). (D) Caspase-1 activity is significantly increased by asbestos (75) at 24 and 48 h (N = 4 samples/group/time point; combined data from two experiments). A randomized block ANOVA was used to determine significance for this experiment. * = significantly different p ≤ 0.05) from untreated control group (0). (E) Asbestos-induced NLRP3 protein levels in HMC. (F) Western blot analysis of secreted p20 subunit of caspase-1 (an indicator of caspase-1 activation) in medium in response to asbestos exposure in HMC (N = 2 samples/group/time point). (G) HMGB1 release in medium from HMC cells in response to asbestos exposure. (H) IL-1β released into the medium of HMC in response to asbestos exposure as measured by ELISA, and IL-18 (I) released over time as measured by ELISA (N = 2 samples/group/time point). * = significantly different (p ≤ 0.05) from 0 control at same time point; † = significantly different (p ≤ 0.05) from 8 h asbestos group.