Particulate Matter-Induced Lysosomal Rupture-Mediated Pyroptosis in Human Vocal Fold Fibroblasts

Exposure to air pollution, specifically to particulate matter (PM), is a significant global health hazard. Recent studies have shown that PM triggers NLRP3-mediated pyroptosis. However, whether cathepsin B (CTSB), a protease released from ruptured lysosomes, activates the NLRP3 inflammasome is unclear. This study investigated the involvement of CTSB and NLRP3 inflammasome activation in PM-exposed human vocal fold fibroblasts (hVFFs).

Pyroptotic cell death was evaluated based on LDH release and PI staining and NLRP3 inflammasome activation via western blotting and immunofluorescence staining. The inflammatory response during pyroptosis was analyzed in an ELISA assay and lysosomal stability by LysoTracker staining.

PM exposure was shown to induce cell membrane rupture and pyroptosis in hVFFs, through a mechanism involving NLRP3, cleaved caspase-1, gasdermin D (GSDMD), IL-1β, lysosomal-associated membrane protein 2a, and CTSB. These results suggested that PM causes pyroptosis in hVFFs via NLRP3 inflammasome activation and lysosomal destabilization. Treatment of the PM-exposed cells with MCC950, an NLRP3-specific inhibitor, suppressed this pathway, providing further evidence of the involvement of the NLRP3 inflammasome in PM-induced pyroptosis. A role for CTSB in NLRP3 inflammasome activation and pyroptosis was implied by the finding that treatment with CA-074-me, a CTSB-specific inhibitor, reduced CTSB expression and suppressed NLRP3, cleaved caspase-1, GSDMD, IL-1β, and CTSB in PM-exposed hVFFs.

Our study shows that both the NLRP3 inflammasome and CTSB participate in PM-induced pyroptosis in hVFFs. Targeting these pathways could yield novel therapeutic agents able to mitigate the detrimental effects of PM exposure on respiratory health.