Moringa oleifera leaf polysaccharide alleviates ulcerative colitis by inhibiting glycolysis mediated M1 macrophages polarization

Objective We aimed to investigate the therapeutic effects of Moringa oleifera leaf polysaccharide (MOLP) in ulcerative colitis (UC) and the underlying mechanism involving macrophages polarization. Methods Dextran sodium sulfate (DSS)-induced colitis mouse model, as well as lipopolysaccharide (LPS) and interferon-γ (IFN-γ) stimulated macrophages (PMA-differentiated THP-1 cells) were used for investigations. Therapeutic effect of MOLP was evaluated by measuring disease activity index (DAI), myeloperoxidase (MPO) activity and histological morphology in mice, with 5-aminosalicylic acid as positive control. Macrophages were determined by flow cytometry and immunofluorescence staining. Glycolysis activity was determined by measuring lactic acid content, extracellular acidification rate (ECAR) and the uptake of fluorescent deoxyglucose analog 2-NBDG. Results MOLP effectively alleviated colitis symptoms of DSS-induced UC mice, as demonstrated by reduced DAI score and MPO activity, alleviation of colon shortening, and mitigated colonic histopathological damage. Besides, MOLP decreased the proportion of M1 macrophages and the mRNA expression of their specific factors (TNF-α, IL-1β and iNOS), while increasing M2 macrophages and their specific factors (CD206, Arg1 and Chil3). Based on LPS and IFNγ-stimulated macrophages, MOLP treatment suppressed M1 macrophages polarization by inhibiting the glycolysis activity, which was confirmed by the glycolysis inhibitor 2-DG. Mechanistically, HMGB1 was down-regulated by MOLP, and recombinant HMGB1 protein treatment could offset the curative effects of MOLP on UC. Furthermore, HMGB1 interacted with HAVCR2, and the latter mediated macrophage glycolysis by PI3K/Akt/HIF-1α pathway, thereby regulating M1 macrophages polarization. Conclusion MOLP could alleviate UC by regulating macrophages M1 polarization through HMGB1/HAVCR2 mediated glycolysis.