Trichothecene mycotoxins activate NLRP3 inflammasome through a P2X7 receptor and Src tyrosine kinase dependent pathway

Abstract

Inflammasome is an intracellular molecular platform of the innate immunity that is a key mediator of inflammation. The inflammasome complex detects pathogens and different danger signals, and triggers cysteine protease caspase-1-dependent processing of pro-inflammatory cytokines IL-1β, and IL-18 in dendritic cells and macrophages. Previously, we have shown that water-damaged building associated trichothecene mycotoxins, including roridin A, trigger IL-1β and IL-18 secretion in human macrophages. However, the molecular basis as well as mechanism behind this trichothecene-induced cytokine secretion has remained uncharacterized. Here, we show that the trichothecene-induced IL-1β secretion is dependent on NLRP3 inflammasome in human primary macrophages. Pharmacological inhibition and small interfering RNA approach showed that the trichothecene-induced NLRP3 inflammasome activation is mediated through ATP-gated P2X7 receptor. Moreover, we show that trichothecene-triggered NLRP3 inflammasome activation is dependent on Src tyrosine kinase activity. In addition, gene silencing of c-Cbl, a negative autophagy-related regulator of c-Src, resulted in enhanced secretion of IL-1β and IL-18 in response to trichothecene mycotoxin stimulation in human macrophages. In conclusion, our results suggest that roridin A, a fungal trichothecene mycotoxin, acts as microbial danger signals that trigger activation of NLRP3 inflammasome through P2X7R and Src tyrosine kinase signaling dependent pathway in human primary macrophages.

Keywords: 4-amino-3-(4-chlorophenyl)-1-(t-butyl)-1H-pyrazolo[3,4-d]pyrimidine, RLR, RIG-I-like receptors; AG126; AZ; AZ11645373; DAMP; NLR; NLR family, Pyrin domain containing; NLRP; NOD-like nucleotide-binding oligomerization domain; PP2; RU; danger associated molecular pattern; relative unit; siRNA; small ribonucleic acid interference; tyrphostin AG 126.