Ouratea spectabilis and its Biflavanone Ouratein D Exert Potent Anti-inflammatory Activity in MSU Crystal-induced Gout in Mice

Gouty arthritis (GA) is an inflammatory arthritis triggered by the deposition of monosodium urate monohydrate (MSU) crystals, causing pain, inflammation, and joint damage. Several drugs are currently employed to manage acute flares of GA, but they either have limited effectiveness or induce severe adverse reactions. Ouratea spectabilis is traditionally used in Brazil to treat gastric ulcers and rheumatism. The ethanolic extract of O. spectabilis stems (OSpC) and four biflavanones (ouratein A - D) isolated thereof were evaluated in a murine model of GA induced by the injection of MSU crystals. The underlying mechanism of action of ouratein D was investigated in vitro in cell cultures by measurement of IL-1β levels by ELISA and Western blot analysis. The administration of OSpC (10, 30 or 100 mg/Kg, p. o.) reduced the migration of total inflammatory cells, monocytes, and neutrophils and diminished the levels of IL-1β and CXCL1 in the synovial tissue. Among the tested compounds, only ouratein D (1 mg/Kg) reduced the migration of the inflammatory cells and it was shown to be active up to 0.01 mg/Kg (equivalent to 0.34 nM/Kg, p. o.). Treatment of pre-stimulated THP-1 cells (differentiated into macrophages) or BMDMs with ouratein D reduced the release of IL-1β in both macrophage lines. This biflavanone reduced the activation of caspase-1 (showed by the increase in the cleaved form) in supernatants of cultured BMDMs, evidencing its action in modulating the inflammasome pathway. The obtained results demonstrate the anti-gout properties of O. spectabilis and point out ouratein D as the bioactive component of the assayed extract.

Therapeutic potential of the FPR2/ALX agonist AT-01-KG in the resolution of articular inflammation

The resolution of inflammation is a dynamic process, characterized by the biosynthesis of pro-resolving mediators, including the lipid Lipoxin A4 (LXA₄). LXA₄ acts on the N-formyl peptide receptor 2 (FPR2/ALX) to mediate anti-inflammatory and pro-resolving effects. In order to exploit the therapeutic potential of endogenous LXA₄ in the context of inflammation we have recently developed synthetic LXA₄ mimetics (sLXms) including a dimethyl-imidazole-containing FPR2/ALX agonist designated AT-01-KG. Here, we have investigated the effect of treatment with AT-01-KG in established models of articular inflammation. In a model of gout, mice were injected with MSU crystals and treated with AT-01-KG at the peak of inflammatory response. The treatment decreased the number of neutrophils in the knee exudate, an effect which was accompanied by low levels of myeloperoxidase, CXCL1 and IL-1β in periarticular tissue. AT-01-KG treatment led to reduced tissue damage and hypernociception. The effects of AT-01-KG on neutrophil accumulation were not observed in MSU treated FPR2/3^-/-mice. Importantly, AT-01-KG induced resolution of articular inflammation by increasing neutrophil apoptosis and subsequent efficient efferocytosis. In a model of antigen-induced arthritis, AT-01-KG treatment also attenuated inflammatory responses. These data suggest that AT-01-KG may be a potential new therapy for neutrophilic inflammation of the joints.