Introduction: Pyroptosis, a form of inflammatory cell death, has been linked as a substantial contributor to various types of sterile inflammation, including atherosclerosis, myocardial ischemia-reperfusion injury and diabetes. Mediated by inflammasomes, it results in the release of pro-inflammatory cytokines such as IL-1β.
Aim: Currently, no selective inflammasome inhibitors are available for human use. Therefore, we aimed to identify and validate novel inhibitors through compound screening.
Methods: A total of 6,280 drugs and drug-like compounds were screened using a medium-throughput approach using propidium iodide fluorescence as a pyroptosis readout. Among the 22 'hits', the quinone compound 2,6-dimethoxybenzoquinone (DMBQ) was identified as a promising candidate. To examine DMBQs inhibitory properties on NLRP3-dependent pyroptosis, THP-1 cells were primed with 1 µg ml-1 LPS for three hours prior to the addition of 5 µg ml-1 nigericin for one hour.
Results: A concentration of 10 µM DMBQ led to a significant reduction in cell death, as well as a substantial decrease in IL-1β secretion (222.6 pg/ml vs. 11.19 pg/ml, p < 0.05). These effects were not associated with any signs of toxicity, as determined via WST-assay at the given concentration. In addition, the intracellular formation of inflammasome specks was significantly reduced by DMBQ by 83.4% (vs. solvent control, p < 0.05) as well as the cleavage of the pore-forming protein Gasdermin D compared to the solvent control (ratio of Gasdermin D full-length:cleaved 66.58 vs. 5.71) in LPS- and nigericin-treated THP-1 cells.The addition of DMBQ to LPS-treated monocytes did not alter the NF-κB pathway, as analysed by IKBα phosphorylation and p65 nuclear translocation. No inhibitory effect on the NLRC4 inflammasome, a member of the NLR family such as NLRP3, was observed in DMBQ, indicating a specificity for NLRP3.
Conclusion: DMBQ is a novel inhibitor of NLRP3-mediated pyroptosis that interferes with inflammasome assembly and potently reduces IL-1β release.
