Suppression of the pro-inflammatory NLRP3/interleukin-1β pathway in macrophages by the thioredoxin reductase inhibitor auranofin

• The involvement of thioredoxin reductase in Toll-like receptor signaling in macrophages was studied.
• The thioredoxin reductase inhibitor auranofin blocked LPS-mediated induction of IL-1-related genes.
• Auranofin suppressed the induction of pro-IL-1β and the inflammasome receptor NLRP3.
• Thioredoxin reductase may positively regulate the Toll-like receptor 4/IL-1β pathway.

BackgroundThe thioredoxin/thioredoxin reductase system, which is best known for its essential role in antioxidant defense and redox homeostasis, is increasingly implicated in the regulation of multiple cellular signaling pathways. In the present study, we asked if the thioredoxin system in macrophages might regulate toll-like receptor 4 (TLR4)-dependent gene expression and consequent responses.MethodsUsing microarray analysis we analyzed the effect of auranofin, a highly potent and specific inhibitor of thioredoxin reductase, on the transcriptional program activated in J774 macrophages by the TLR4 agonist, lipopolysaccharide (LPS). We used quantitative real-time PCR (qPCR), Western blotting, ELISA and cytotoxicity assays to confirm and extend the microarray results.ResultsGlobal transcriptional profiling revealed that macrophage treatment with auranofin exerted a selective effect on LPS-induced gene expression, suppressing the induction of a small number of genes. Interestingly, among these suppressed genes were three members of the interleukin-1 (IL-1) family of genes, among which IL-1β was most affected. qPCR analyses confirmed the repressive effects of auranofin on IL-1 genes. In addition, qPCR and Western blot analyses showed that auranofin impaired TLR4-dependent induction of the inflammasome receptor NLRP3, which plays a critical role in IL-1β processing. Consistent with these findings, inflammasome-dependent release of IL-1β from stimulated macrophages was suppressed by auranofin as was inflammasome-mediated cell death.ConclusionsOur findings suggest a regulatory role for the thioredoxin system in macrophage inflammatory signaling. Inhibition of the thioredoxin system in macrophages exerts an anti-inflammatory effect by repressing the activation of the NLRP3/IL-1β pathway.