Baicalein links macrophage M2 polarization with reduced synovial inflammation to alleviate gouty arthritis

Gouty arthritis (GA) is an inflammatory disease caused by abnormal uric acid metabolism, with its pathological mechanism involving inflammatory cell infiltration and abnormal expression of pro-inflammatory factors. Monosodium urate (MSU) crystals activate the NLRP3 inflammasome, promoting the abnormal release of pro-inflammatory cytokines such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), as well as the expression of mediators like monocyte chemoattractant protein-1 (MCP-1) and high mobility group box 1 (HMGB1), thereby amplifying local inflammatory responses. Additionally, MSU crystals activate Toll-like receptors (TLRs) and their downstream signaling pathways, including nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK), driving the aggregation of inflammatory cells such as neutrophils and macrophages into the joint cavity, mediating synovial tissue damage, and causing oxidative stress imbalance. This study, based on the traditional Chinese medicine (TCM) theory of "accumulated toxins," investigates the therapeutic effects and molecular mechanisms of the Chinese herbal monomer baicalein on gouty arthritis in mice through both in vivo and in vitro experiments.

(1) In Vivo Experiments: Thirty BALB/c male mice were randomly divided into five groups: Control, Model, low-dose baicalein (Low,50 mg/kg), medium-dose baicalein (Middle,100 mg/kg), and high-dose baicalein (High,200 mg/kg). A mouse model of gouty arthritis was induced by intra-articular injection of MSU crystals. Behavioral scoring, gait analysis, joint swelling measurement, and histopathological analysis were used to evaluate the anti-inflammatory effects of baicalein. Molecular biology techniques were employed to detect serum and joint tissue levels of inflammatory cytokines (IL-1β, TNF-α, iNOS), immune regulatory markers (CD86, CD206). (2) In Vitro Experiments: RAW264.7 macrophages were cultured and divided into blank control, model (RAW264.7 cells treated with LPS 0.1 mg/ml and MSU 0.7 μmol/L), low-dose baicalein intervention (Low,10 μmol/L), medium-dose baicalein intervention (Middle,20 μmol/L), and high-dose baicalein intervention (High,30 μmol/L) groups. Real-time fluorescence quantitative PCR (RT-qPCR) was used to detect mRNA expression levels of IL-1β, TNF-α, iNOS, CD86, CD206 and IL-10. Cell proliferation was assessed using the CCK-8 assay. Protein expression levels of TNF-α and iNOS were determined by Western blotting. Immunofluorescence was used to observe the effect of baicalein on M1-type polarization of RAW264.7 cells. Cell migration was evaluated through a cell migration assay.

Baicalein intervention significantly alleviated joint swelling and inflammatory infiltration in a dose-dependent manner (P < 0.05). Molecular studies revealed that baicalein inhibited iNOS-mediated oxidative stress, downregulated the activation of the NF-κB signaling pathway, reduced the secretion of pro-inflammatory cytokines (IL-1β, TNF-α), and suppressed iNOS expression. Furthermore, baicalein regulated the expression of surface markers CD86 and CD206, thereby inhibiting M1 polarization and promoting the transition from an M1 to an M2 phenotype.

This study demonstrates that baicalein improves the inflammatory microenvironment of gouty arthritis through multi-target and multi-pathway synergistic effects, including the inhibition of oxidative stress, immune regulation, and modulation of key signaling pathways. These findings provide experimental evidence supporting the clinical application of baicalein in the treatment of gouty arthritis.