Koumine alleviates rheumatoid arthritis by regulating macrophage polarization.

ETHNOPHARMACOLOGICAL RELEVANCE: The imbalance between M1-and M2-polarized macrophages is one of the major pathophysiological changes in RA. Therefore, targeted macrophage polarization may be an effective therapy for RA. Koumine, an alkaloid monomer with the highest content and low toxicity in Gelsemium elegans Benth., has the effect of treating RA by playing an immunomodulatory role by influencing various immune cells. However, whether koumine affects macrophage polarization in RA and the associated molecular mechanisms remain unknown. AIM OF THE STUDY: To investigate the mechanism of the anti-RA effect of koumine on macrophage polarization. MATERIALS AND METHODS: The effect of koumine on macrophage polarization was investigated in vivo and in vitro. We first explored the effects of koumine on AIA rats and detected the levels of M1/M2 macrophage polarization markers in the spleen by western blotting. Then, we explored the regulatory effect of koumine on M1/M2 macrophage polarization and the effect on the PI3K/AKT signaling pathway in vitro. Finally, we verified the effects of koumine on macrophage polarization in CIA mice. RESULTS: We found that koumine alleviated symptoms, including relieving pain, reducing joint redness and swelling in AIA rats and restoring the M1/M2 macrophage balance in vivo. Interestingly, koumine had an inhibitory effect on both M1 and M2 macrophage polarization in vitro, but it had a stronger inhibitory effect on M1 macrophage. In a mixed polarization experiment, koumine mainly inhibited M1 macrophage polarization and had an inhibitory effect on the PI3K/AKT signaling pathway. Finally, we found that koumine had therapeutic effects on CIA mice, regulated macrophage polarization and inhibited the PI3K/AKT signaling pathway. CONCLUSIONS: Our results reveal that koumine regulates macrophage polarization through the PI3K/AKT signaling pathway. This may be one of the important mechanisms of its anti-RA effect, which provides a theoretical and scientific basis for the possible clinical application of koumine.

The immunomodulatory effect of koumine on B cells under dependent and independent responses by T cells.

Dysregulated activation of polyclonal B cells and production of pathogenic antibodies are involved in the development of rheumatoid arthritis (RA). Therefore, targeted B cell therapy is effective against RA. Gelsemium elegans (Gardn. & Champ.) Benth., a toxic plant widely distributed in Southeast Asia, has been used for treating rheumatoid pain, neuropathic pain, spasticity, skin ulcers, and cancers for many years in traditional Chinese medicine. Koumine, an alkaloid monomer from Gelsemium elegans Benth., exerts therapeutic effects against RA. However, whether koumine affects B cells remains unknown. In this study, the effect of koumine on B cells under T cell-independent (TI) and T cell-dependent (TD) immune responses is investigated in vitro and in vivo. Mouse primary B cells were obtained by immunomagnetic bead sorting, and immunomodulatory effects of koumine on the activation, proliferation, and differentiation of B cells were determined in TI and TD models induced by lipopolysaccharide (LPS) and anti-CD40 antibodies in vitro, respectively. The humoral immune responses of TI and TD were established using NP-AECM-FICOLL and NP-CGG in C57BL/6J mice, respectively. We found that koumine inhibited B cell differentiation in the TI model and inhibited B cell activation and proliferation in the TD model in vitro. Koumine also inhibited antibody secretion in TI immune response, TD initial immune response, and in TD secondary immune response. Our results reveal that koumine has a direct and indirect immune regulatory effect on B cells, showing that it can directly inhibit the differentiation and secretion of autoantibodies after abnormal activation of B cells, and indirectly inhibit the activation and proliferation of TD B cells to reduce the secretion of antibodies. It may be an important mechanism for its anti-RA effect in mice, providing a rationale and laboratory data support for the application of koumine in anti-human RA therapy.