Leonurine Promotes the Maturation of Healthy Donors and Multiple Myeloma Patients Derived-Dendritic Cells

Abstract: Objective Leonurine is an agent from Leonurus japonicus Houtt , which potentially has immunomodulatory effects. The immunomodulatory effect of leonurine on dendritic cells (DCs) is not clear up to date. In the current study, the effect of leonurine on the maturation of monocyte derived dendritic cells (moDCs) from healthy donors (HDs) and multiple myeloma (MM) patients will be investigated for the first time. Method Peripheral blood mononuclear cells (PBMCs) were isolated from the peripheral blood of HDs and MM patients. The generation of moDCs from monocytes in PBMCs was conducted by the incubation of 7 days in a medium consisting of RPMI 1640 medium, 5% human serum, 800U/mL GM-CSF, 500U/mL IL-4, 100U/mL penicillin and 0.1mg/mL streptomycin. During this period, the incubation system was administrated with leonurine at 1 µM or 1×PBS as the control group. On the 8 th day, cells were harvested, and the immunophenotyping of cells were analyzed by the flow cytometry. The CD80+CD86+ cell population in total cells is gated as DCs in the FACS analyzing system. Then, the median fluorescence intensity (MFI) of surface markers CD40, CD83 and HLA-DR on DCs were analyzed respectively. Results The proportion of DCs in the harvested cells was significantly higher in HD group (n=14) than that in MM patient group (n=11) (75.55%±9.69% vs 61.39%±4.86%, P=0.000). When analyzing all the HD-derived moDCs (n=14), leonurine significantly enhanced the MFI of CD40 (2.11×105±0.92×105 vs 1.81×105±0.72×105, P = 0.049), CD83 (2.41×105±2.06×105 vs 2.14×105±1.71×105, P=0.042) and HLA-DR (12.21×105±4.20×105 vs 11.11×105±3.94×105, P=0.013) on moDCs when compared with the control group. When analyzing all the MM patients-derived moDCs (n=11), leonurine also significantly enhanced the MFI of CD40 (1.99×105±0.98×105 vs 1.72×105±0.78×105, P = 0.025), CD83 (0.30×105±0.18×105 vs 0.27×105±0.16×105, P = 0.020) and HLA-DR (7.49×105±2.58×105 vs 6.80×105±2.18×105, P = 0.006) on moDCs when compared with the control group. Conclusions Regarding the moDCs generated in vitro, a smaller number of MM patients-derived moDCs can be generated compared with HD-derived moDCs. Leonurine at 1 µM in vitro can promote the maturation of both HD-derived moDCs and MM patients-derived moDCs. Leonurine shows potential to be a DC adjuvant for DC-based therapeutic strategies, such as DC vaccine and DC cell-therapy in MM. Key words: Leonurine; Monocyte derived Dendritic Cells; Multiple Myeloma; DC Adjuvant