Metabolic reprogramming in polyol pathway contributes to anti-inflammatory effect of glucosamine salts on synovial fibroblasts

Abstract The upregulation of cyclooxygenase-2 (COX-2) and the subsequent production of prostaglandin E 2 (PGE 2 ) in synovial tissue are hallmarks of autoimmune arthritis, including rheumatoid arthritis (RA). While glucosamine (GlcN) derivatives modulate RA symptoms, their specific anti-inflammatory mechanisms in synovial fibroblasts (SFBs) are poorly understood. In this study, we evaluated the anti-inflammatory efficacy of various GlcN derivatives: glucosamine hydrochloride (GlcN-HCl), glucosamine sulfate (GlcN-S), glucosaminate (GlcNA), and N-acetylglucosamine (GlcNAc). GlcN-HCl and GlcN-S inhibited IL-1β-induced PGE 2 release and the expression of COX-2 at both protein and mRNA levels, whereas GlcNA and GlcNAc exhibited no such inhibitory activity. Structure-activity relationship analysis using GlcN-HCl epimers revealed that whereas the C-4 epimer, galactosamine hydrochloride (GalN-HCl), retained potent anti-inflammatory effects, the C-2 epimer, mannosamine hydrochloride (ManN-HCl), showed significantly diminished bioactivity, highlighting the critical role of the C-2 stereochemical configuration in modulating inflammatory responses. Mechanistically, we demonstrated that GlcN-HCl-mediated COX-2 suppression occurs via epigenetic silencing rather than mRNA destabilization. GlcN-HCl treatment significantly reduced the enrichment of active chromatin marks, H3K27ac and H3K4me3, at the COX-2 promoter, whereas mRNA stability remained unaffected. Given that metabolic dysregulation is intrinsically linked to inflammatory pathogenesis, we characterized the metabolic profile of GlcN-HCl-treated SFBs. We found that GlcN-HCl triggers metabolic reprogramming of the polyol pathway by modulating the expression of AKR1B1 and sorbitol dehydrogenase ( SORD ), resulting in elevated intracellular sorbitol levels. Pharmacological inhibition of AKR1B1 effectively abrogated the anti-inflammatory effects of GlcN-HCl, indicating that polyol pathway activation is essential for its efficacy. We confirmed the evolutionary conservation of these findings in human SFBs, demonstrating the translational relevance of the GlcN-HCl-mediated metabolic and epigenetic axis. Our findings demonstrate that GlcN-HCl induces metabolic reprogramming of the polyol pathway in synovial fibroblasts, facilitating the epigenetic silencing of inflammatory mediators. This metabolic-epigenetic axis suggests a mechanistic rationale for pharmacological metabolic intervention in RA, shifting the therapeutic paradigm toward targeted reprogramming of synovial fibroblast metabolism.