Britannin as a novel NLRP3 inhibitor, suppresses inflammasome activation in macrophages and alleviates NLRP3-related diseases in mice.

Overactivation of the NLRP3 inflammasomes induces production of pro-inflammatory cytokines and drives pathological processes. Pharmacological inhibition of NLRP3 is an explicit strategy for the treatment of inflammatory diseases. Thus far no drug specifically targeting NLRP3 has been approved by the FDA for clinical use. This study was aimed to discover novel NLRP3 inhibitors that could suppress NLRP3-mediated pyroptosis. We screened 95 natural products from our in-house library for their inhibitory activity on IL-1ß secretion in LPS + ATP-challenged BMDMs, found that Britannin exerted the most potent inhibitory effect with an IC50 value of 3.630 µM. We showed that Britannin (1, 5, 10 µM) dose-dependently inhibited secretion of the cleaved Caspase-1 (p20) and the mature IL-1ß, and suppressed NLRP3-mediated pyroptosis in both murine and human macrophages. We demonstrated that Britannin specifically inhibited the activation step of NLRP3 inflammasome in BMDMs via interrupting the assembly step, especially the interaction between NLRP3 and NEK7. We revealed that Britannin directly bound to NLRP3 NACHT domain at Arg335 and Gly271. Moreover, Britannin suppressed NLRP3 activation in an ATPase-independent way, suggesting it as a lead compound for design and development of novel NLRP3 inhibitors. In mouse models of MSU-induced gouty arthritis and LPS-induced acute lung injury (ALI), administration of Britannin (20 mg/kg, i.p.) significantly alleviated NLRP3-mediated inflammation; the therapeutic effects of Britannin were dismissed by NLRP3 knockout. In conclusion, Britannin is an effective natural NLRP3 inhibitor and a potential lead compound for the development of drugs targeting NLRP3.

Endothelial deubiquinatase YOD1 mediates Ang II-induced vascular endothelial-mesenchymal transition and remodeling by regulating ß-catenin.

Hypertension is a prominent contributor to vascular injury. Deubiquinatase has been implicated in the regulation of hypertension-induced vascular injury. In the present study we investigated the specific role of deubiquinatase YOD1 in hypertension-induced vascular injury. Vascular endothelial endothelial-mesenchymal transition (EndMT) was induced in male WT and YOD1-/- mice by administration of Ang II (1 µg/kg per minute) via osmotic pump for four weeks. We showed a significantly increased expression of YOD1 in mouse vascular endothelial cells upon Ang II stimulation. Knockout of YOD1 resulted in a notable reduction in EndMT in vascular endothelial cells of Ang II-treated mouse; a similar result was observed in Ang II-treated human umbilical vein endothelial cells (HUVECs). We then conducted LC-MS/MS and co-immunoprecipitation (Co-IP) analyses to verify the binding between YOD1 and EndMT-related proteins, and found that YOD1 directly bound to ß-catenin in HUVECs via its ovarian tumor-associated protease (OTU) domain, and histidine at 262 performing deubiquitination to maintain ß-catenin protein stability by removing the K48 ubiquitin chain from ß-catenin and preventing its proteasome degradation, thereby promoting EndMT of vascular endothelial cells. Oral administration of ß-catenin inhibitor MSAB (20 mg/kg, every other day for four weeks) eliminated the protective effect of YOD1 deletion on vascular endothelial injury. In conclusion, we demonstrate a new YOD1-ß-catenin axis in regulating Ang II-induced vascular endothelial injury and reveal YOD1 as a deubiquitinating enzyme for ß-catenin, suggesting that targeting YOD1 holds promise as a potential therapeutic strategy for treating ß-catenin-mediated vascular diseases.