5-methylthiopentyl Isothiocyanate, a Sulforaphane Analogue, Inhibits Pro-inflammatory Cytokines by Regulating LPS/ATP-mediated NLRP3 Inflammasome Activation

Background: Pro-inflammatory cytokines secreted from activated macrophages and astrocytes are crucial mediators of inflammation for host defense. Among them, the secretion of IL-1β, a major pro-inflammatory cytokine, is especially mediated by the activation of NLRP3 inflammasome. Pro-IL-1β, which is produced in response to the invaded pathogens, such as LPS, is cleaved and matured in the NLRP3 inflammasome by the recognition of ATP. Excessively activated IL-1β induces other immune cells, resulting in the up-regulation of inflammation. Therefore, regulation of NLRP3 inflammasome can be a good strategy for alleviating inflammation. Objective: Our study aimed to examine whether 5-methylthiopentyl isothiocyanate, a sulforaphane analogue (berteroin), has an anti-inflammatory effect on the NLRP3 inflammasome activation induced by LPS and ATP. Methods: Primary bone marrow-derived macrophages (BMDMs) and astrocytes were stimulated by LPS and ATP with the treatment of 5-methylthiopentyl isothiocyanate, a sulforaphane analogue. The secretion of pro-inflammatory cytokines was measured by ELISA, and the expression level of NLRP3 inflammasome-associated proteins was detected by western blot. The association of NLRP3 inflammasome was assessed by co-immunoprecipitation, and the formation of ASC specks was evaluated by fluorescent microscope. Results: 5-methylthiopentyl isothiocyanate, a sulforaphane analogue (berteroin), decreased the release of pro-inflammatory cytokines, IL-1β, and IL-6 in the BMDMs. Berteroin notably prevented the formation of both NLRP3 inflammasome and ASC specks, which reduced the secretion of IL-1β. Additionally, berteroin reduced the IL-1β secretion and cleaved IL-1β expression in the primary astrocytes. Discussion and Conclusion: These results indicated the anti-inflammatory effects of 5- methylthiopentyl isothiocyanate (berteroin) by regulating NLRP3 inflammasome activation, suggesting that berteroin could be the potential natural drug candidate for the regulation of inflammation.