The deubiquitinase USP44 promotes Treg function during inflammation by preventing FOXP3 degradation.

The transcription factor forkhead box P3 (FOXP3) is essential for the development of regulatory T cells (Tregs) and their function in immune homeostasis. Previous studies have shown that in natural Tregs (nTregs), FOXP3 can be regulated by polyubiquitination and deubiquitination. However, the molecular players active in this pathway, especially those modulating FOXP3 by deubiquitination in the distinct induced Treg (iTreg) lineage, remain unclear. Here, we identify the ubiquitin-specific peptidase 44 (USP44) as a novel deubiquitinase for FOXP3. USP44 interacts with and stabilizes FOXP3 by removing K48-linked ubiquitin modifications. Notably, TGF-ß induces USP44 expression during iTreg differentiation. USP44 co-operates with USP7 to stabilize and deubiquitinate FOXP3. Tregs genetically lacking USP44 are less effective than their wild-type counterparts, both in vitro and in multiple in vivo models of inflammatory disease and cancer. These findings suggest that USP44 plays an important role in the post-translational regulation of Treg function and is thus a potential therapeutic target for tolerance-breaking anti-cancer immunotherapy.

Neobavaisoflavone inhibits allergic inflammatory responses by suppressing mast cell activation.

Neobavaisoflavone (NBIF), a monomolecular compound extracted from Psoralea corylifolia (Leguminosae), is commonly used in traditional Chinese medicine for multiple purposes. NBIF is known to exert anti-fungal and anti-tumor effects, and promote bone formation. Whether NBIF exhibits anti-allergic effects by regulating mast cell activation remains unclear. Therefore, we designed this study to investigate the anti-allergic effects of NBIF on IgE/Ag-induced mouse bone marrow-derived mast cells and ovalbumin-induced asthma, and the passive systemic anaphylaxis (PSA) reaction in mice. Our results showed that NBIF suppresses the production of leukotriene C4, prostaglandin D2 and inflammatory cytokines, and decreases the degranulation of BMMCs stimulated by IgE/Ag. A thorough investigation ascertained that NBIF suppresses the phosphorylation of mitogen-activated protein kinases, and represses the nuclear factor-κB-related signaling pathway. In addition, the oral administration of NBIF in mice inhibited the IgE-induced PSA reaction in a dose-dependent manner. Overall, we provide new insights into how NBIF regulates the IgE/Ag-mediated signaling pathways. Moreover, our investigation promotes the potential use of NBIF in treating allergy and asthma.

Inhibition of human thrombin by the constituents of licorice: inhibition kinetics and mechanistic insights through in vitro and in silico studies.

Thrombin inhibition therapy is a practical strategy to reduce thrombotic and cardiovascular risks via blocking the formation of blood clots. This study aimed to identify naturally occurring thrombin inhibitors from licorice (one of the most popular edible herbs), as well as to investigate their inhibitory mechanisms. Among all tested licorice constituents, licochalcone A was found as the most efficacious agent against human thrombin (IC50 = 7.96 µM). Inhibition kinetic analyses demonstrated that licochalcone A was a mixed inhibitor against thrombin-mediated Z-Gly-Gly-Arg-AMC acetate hydrolysis, with a K i value of 12.23 µM. Furthermore, mass spectrometry-based chemoproteomic assays and molecular docking simulations revealed that licochalcone A could bind to human thrombin at both exosite I and the catalytic site. In summary, our findings demonstrated that the chalcones isolated from licorice were a new class of direct thrombin inhibitors, also suggesting that licochalcone A was a promising lead compound for developing novel anti-thrombotic agents.