Tangeretin formulated in a self-nano-emulsifying drug-delivery system (SNEDDS) alleviates symptoms of rheumatoid arthritis by antagonizing M1 macrophages polarization.

As targeting glycolytic reprogramming for antagonizing the polarization and functions of M1 macrophages represents a novel therapeutic strategy, finding new targets or drug candidate on glycolytic modulation is appealing. Tangeretin (TG), a natural polymethoxylated flavone with broad anti-inflammatory bioactivities, however, its low solubility limits its therapeutic applications in rheumatoid arthritis (RA). This study aimed to develop a self-nano-emulsifying drug-delivery system (SNEDDS) for enhancing the bioavailability and the anti-arthritic effects of TG, and to reveal the mechanisms underlying the inhibition of M1 macrophage polarization by targeting glycolytic reprogramming. In vivo pharmacokinetic and the anti-arthritic effect in adjuvant-induced arthritis (AIA) rats were evaluated for the optimized TG-SNEDDS formulation. Moreover, the inhibiting effects of TG on M1 macrophages polarization and function via modulating glycolytic reprogramming were evaluated In vivo and in vitro with Raw264.7 macrophages and bone marrow-derived macrophages (BMDMs). SNEDDS improved the bioavailability of TG compared to 0.5 % CMCNa or a surfactant solvent system, which leads to a significant enhancement of the therapeutic outcomes for RA symptoms and reduced the joint infiltration of M1 macrophage in AIA rats. Moreover, TG prevented M1 polarization and inhibited M1 markers including iNOS, TNF-α, and IL-6. Mechanistically, TG modulated the energy metabolism including the decreased basal and maximal respiration as well as the secretion of lactate during M1 polarization or after M1 polarization by down-regulating the glycolysis level via inhibiting LDHA, G6PD, PDH and HIF-1α. Furthermore, we revealed that TG suppressed M1 macrophage polarization by targeting LDHA, which was confirmed by DARTS and BLI experiments as well as siRNA interference. In sum, by using the formulation of SNEDDS which enhanced the solubility and bioavailability of TG, we demonstrated that TG suppressed the polarization and function of M1 macrophages via modulating metabolic reprogramming as the inhibitor of LDHA, providing a promising approach to effectively inhibit M1 macrophages polarization and alleviate symptoms of rheumatoid arthritis.