Immunosuppressive effect of voacamine from Voacanga africana Stapf based on SPRi experiment

Purpose: To investigate the affinity of a bis-indole alkaloid -voacamine from Voacanga Africana Stapf for IL-2R alpha - and its immunosuppressive effect on concanavalin A-induced T cell proliferation and lipopolysaccharide -induced B cell proliferation in vitro. Methods: Surface plasmon resonance imaging (SPRi) was used to screen the target protein of voacamine, while CCK-8 kit was used to evaluate cytotoxicity. Mitogen-induced proliferation assay was carried out to assess the inhibitory effect of voacamine on Con A-induced T cell proliferation and LPS-induced B cell proliferation. The binding characteristics of voacamine were investigated using a binding model with IL-2R alpha constructed based on molecular docking simulation. Results: Voacamine had a high-affinity for IL-2R alpha with an equilibrium dissociation constant (KD) of 1.85x10(-8) M. Cytotoxicity data showed that voacamine did not exhibit cytotoxicity at concentrations lower than 0.32 mu M. However, it exerted significant immunosuppressive effect on B cells at a lower concentration, but had no influence on proliferation of T cells. Autodock results indicate that voacamine has a good interaction with the enzyme active site. Conclusion: Voacamine and its analogues exert influence on the immune system.