NOX2 inhibitor baicalein alleviates rheumatoid arthritis and inactivating mitochondrial oxidative stress-mediated cGAS-STING signaling in fibroblast-like synoviocytes.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune disease with a complex pathogenesis, leading to pain, disability, and even death. Baicalein, a constituent of Scutellaria baicalensis, has been identified as a potential therapeutic agent for multiple autoimmune diseases, including RA. Nevertheless, the precise molecular mechanism and its direct cellular targets remain unclear.

PURPOSE: This study aimed to reveal the therapeutic efficacy and molecular mechanism of baicalein in RA treatment.

METHODS: In vivo experiments were conducted using a collagen-induced arthritis (CIA) rat model to assess the alleviation of RA pathology, adverse effects, and underlying mechanisms of baicalein treatment. In vitro assays included the CCK8 assay, transwell migration assay, Western blotting, mtDNA detection, mitochondrial reactive oxygen species (mtROS) detection, Seahorse energy metabolism, CETSA and biotin pulldown assay to evaluate the therapeutic effects and mechanistic action of baicalein on RA- fibroblast-like synoviocytes (FLS).

RESULTS: It was found that FLS developed into invasive synovial cells and produced inflammatory cytokines by activating mitochondrial oxidative stress (MOS)-mediated cGAS-STING signaling. And this led to the progression of RA. Baicalein was identified as a novel NADPH oxidase 2 (NOX2) inhibitor, which decreased mtROS levels and suppressed MOS-mediated VDAC1 oligomerization as well as mtDNA release. This, in turn, led to the inactivation of cGAS-STING signaling. Consequently, baicalein effectively alleviated arthritis pathology of CIA rats with few side effects.

CONCLUSION: The present study posits that baicalein functions as a pharmaceutical agent for RA by modulating the NOX2-cGAS-STING signaling in RA-FLS, and clarify a novel activation mechanism of cGAS through mtROS-mediated VDAC1 oligomerization.