Background: Euphorbia L. is a traditionally used herb and contains many newly identified compounds with novel chemical structures. EFL2, a diterpenoid derived from Euphorbia seeds, is reported to alleviate acute lung injury and arthritis by exerting anti-inflammatory effects [1,2]. However, its inhibitory activity on the NLRP3 inflammasome and its direct regulatory target are still unknown.

Objectives: In this study, we aimed to test the therapeutic benefit and mechanisms of EFL2 in NLRP3 inflammasome-mediated murine gouty models and identified the potential molecular mechanism.

Methods: An air pouch and acute gouty murine model was used to evaluate EFL2’s antiarthritic effect. The inhibitory effect of this compound on inflammatory cell infiltration was determined by flow cytometry in vivo. Cytokine levels were measured using ELISA. The mechanism by which EFL2 activates the NLRP3 inflammasome signalling pathway was evaluated by Western blotting, coimmunoprecipitation, immunofluorescence staining and transmission electron microscopy. Discovery Studio was used to visualize the interaction between the binding target and EFL2, followed by drug affinity responsive target stability and cellular thermal shift assays.

Results: In vitro, EFL2 specifically reduced NLRP3 inflammasome-mediated IL-1β production in bone marrow-derived macrophages. It also significantly alleviated MSU crystal-induced arthritis and inflammatory cell infiltration in the air pouch in mice in an NLRP3 inflammasome-dependent manner. Mechanistically, EFL2 robustly downregulated NF-κB p65 phosphorylation and subsequent NLRP3 inflammasome expression by binding to glucocorticoid receptors. Moreover, EFL2 could specifically suppress the lysosome damage-mediated NLRP3 inflammasome activation process.

Conclusion: Overall, EFL2 is able to suppress both the priming and activation of the NLRP3 inflammasome and has therapeutic potential as a candidate for NLRP3 inflammasome-mediated diseases.

REFERENCES: [1] Zhang, Q. et al. Euphorbia factor L2 alleviates lipopolysaccharide-induced acute lung injury and inflammation in mice through the suppression of NF-κB activation. Biochem Pharmacol 155, 444-454, doi:10.1016/j.bcp.2018.07.025 (2018).

[2] Tang, J. et al. Euphorbia Factor L2 ameliorates the Progression of K/BxN Serum-Induced Arthritis by Blocking TLR7 Mediated IRAK4/IKKβ/IRF5 and NF-kB Signaling Pathways. Front Pharmacol 12, 773592, doi:10.3389/fphar.2021.773592 (2021).

Acknowledgements: NIL.

Disclosure of Interests: None declared.