Bacteroides fragilis Enterotoxin Activates NLRP3 Inflammasomes through NF-κB Signaling and Mitophagy Suppression in Intestinal Epithelial Cells

Background/Aims: enterotoxin (BFT). Although inflammasomes are critical for maintaining intestinal homeostasis and modulating inflammation, their roles remain poorly characterized during ETBF infection. This study investigated the pathways involved in inflammasome formation in BFT-exposed intestinal epithelial cells (IECs). Methods: Human colon epithelial cells HCT-116 and CCD 841 CoN were used as IEC models. To investigate inflammasome formation and activation, BFT-treated cells were analyzed by immunoblotting, disuccinimidyl suberate cross-linking, immunofluorescence microscopy, colocalization assays, and enzyme-linked immunosorbent assay. Results: BFT stimulation significantly upregulated the expression of NLR family pyrin domain containing 3 (NLRP3), pro-interleukin (IL)-1β, pro-IL-18, and cleaved caspase-1 in both cell lines. Inflammasome complexes were confirmed by apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization and colocalization of ASC with NLRP3, accompanied by increased IL-1β and IL-18 secretion. Two pathways were involved in inflammasome activation: first, nuclear factor kappa B (NF-κB) signaling regulated NLRP3, pro-IL-1β, and pro-IL-18 expression, promoting caspase-1 activation; second, p53/BAG5 axis activation suppressed Parkin-mediated mitophagy and drove reactive oxygen species accumulation, engaging the inflammasome complex. Conclusions: These findings demonstrate that the formation of inflammasomes may occur via two pathways, namely, NF-κB-mediated signaling and p53/BAG5-associated suppression of mitophagy.