DGAT1 regulates macrophage pyroptosis during Klebsiella pneumoniae infection

Klebsiella pneumoniae (Kp) is a Gram-negative opportunistic pathogen that causes severe infections, including pneumonia and sepsis, yet the molecular mechanisms governing macrophage cell death during Kp infection are incompletely understood. Here, we identify diacylglycerol acyltransferase-1 (DGAT1) as a critical regulator of macrophage pyroptosis during infection with a classical Kp (cKp) isolate. cKp infection induced lipid droplet (LD) accumulation in murine macrophages, whereas pharmacological inhibition or genetic suppression of DGAT1 attenuated LD formation and pyroptotic cell death. Mechanistically, DGAT1-dependent LD accumulation was associated with lysosomal dysfunction and mitochondrial reactive oxygen species (ROS) production, which together facilitated NLRP3 inflammasome activation and pyroptosis. Furthermore, LD accumulation, ROS production, and mTOR signaling were mutually interconnected, as inhibition of any one component attenuated the others, collectively sustaining pyroptotic signaling during cKp infection. Small RNA sequencing further identified miR-155-5p as a ROS-dependent microRNA up-regulated during cKp infection, which promoted LD accumulation in a DGAT1-dependent manner and contributed to pyroptotic cell death. Collectively, these findings identify DGAT1 as a key immunometabolic regulator of macrophage pyroptosis and suggest that targeting DGAT1 may represent a potential therapeutic strategy to mitigate Kp infection-induced macrophage pyroptosis.