Characterization of porcine NLRP3 inflammasome activation and its upstream mechanism

Inflammasomes, which are intracellular sensors of endogenous or exogenous danger signals, activate caspase-1, resulting in interleukin (IL)-1 beta maturation. Although most studies on inflammasomes have been performed in human and/or mouse-derived macrophages, porcine inflammasome activation has not been elucidated even though pigs are considered one of the best animal models for translational and preclinical investigations. In this study, we optimized detection of porcine IL-1 beta secretion, which is the most well established indicator of inflammasome activation, and compared inflammasome activation between miniature and domestic pigs as well as between porcine and murine macrophages. In our results, anti-sera against murine IL-1 beta had higher affinity to porcine IL-1 beta than anti-sera against human IL-1 beta, even though the amino acid sequence of porcine IL-1 beta was more similar to that of human IL-1 beta. In addition, there was no significant difference in inflammasome activation between miniature and domestic pigs. Furthermore, well established inflammasome triggers (ATP, nigericin, and crystals) in humans and mice had similar effects on porcine NLRP3 inflammasome activation. We further elucidated the upstream signaling pathway of porcine inflammasome activation using pharmacological inhibitors. Similar to the mechanisms of inflammasome activation in humans and mice, potassium efflux and reactive oxygen species generation were confirmed as key pathways in porcine inflammasome activation. Thus, inflammasome activation in pigs is not different from that in humans or mice.