Lipopolysaccharide/adenosine triphosphate-mediated signal transduction in the regulation of NLRP3 protein expression and caspase-1-mediated interleukin-1β secretion.

OBJECTIVE: Reactive oxygen species (ROS) plays a critical role in the regulation of NLRP3 inflammasome activation. However, the ROS-mediated signaling pathways controlling NLRP3 inflammasome activation are not well defined.

METHODS: Using lipopolysaccharide (LPS) and adenosine triphosphate (ATP) activated murine macrophages as the testing model, cytokine release and protein expression were quantified by enzyme-linked immunosorbent assay and Western blot, respectively. ROS was scavenged by N-acetyl cysteine; NADPH oxidase, the major source of ROS, was inhibited by diphenyliodonium, apocynin or gp91-phox siRNA transfection; and protein kinase was inhibited by its specific inhibitor.

RESULTS: LPS-induced NLRP3 protein expression was regulated through the NADPH oxidase/ROS/NF-κB-dependent, JAK2/PI3-kinase/AKT/NF-κB-dependent, and MAPK-dependent pathways, while ATP-induced caspase-1 activation was regulated through the NADPH oxidase/ROS-dependent pathway.

CONCLUSIONS: These results demonstrate that ROS regulates not only the priming stage, but also the activation stage, of NLRP3 inflammasome activation in LPS + ATP-activated macrophages.