Cepharanthine synergistically promotes methylprednisolone pharmacodynamics against human peripheral blood mononuclear cells possibly via regulation of P-glycoprotein/glucocorticoid receptor translocation.

Background: Cepharanthin^® alone or in combination with glucocorticoid (GC) has been used to treat chronic immune thrombocytopenia (ITP) since the 1990s. Cepharanthine (CEP) is one of the main active components of Cepharanthin^®. The purpose of this study was to investigate the effects of CEP on GC pharmacodynamics on immune cells and analyse the possible action mechanism of their interactions. Methods: Peripheral blood mononuclear cells (PBMCs), T lymphocytic leukemia MOLT-4 cells and daunorubicin resistant MOLT-4 cells (MOLT-4/DNR) were used to evaluate the pharmacodynamics and molecular mechanisms. Drug pharmacodynamics was evaluated by WST-8 assay. P-glycoprotein function was examined by rhodamine 123 assay. CD4⁺CD25⁺Foxp3⁺ regulatory T cells and Th1/Th2/Th17 cytokines were detected by flow cytometry. P-glycoprotein expression and GC receptor translocation were examined by Western blot. Results: CEP synergistically increased methylprednisolone (MP) efficacy with the suppressive effect on the cell viability of PBMCs. 0.3 and 1 μM of CEP significantly inhibited P-glycoprotein efflux function of CD4⁺ cells, CD8⁺ cells, and lymphocytes (P<0.05). 0.03~3 μM of CEP also inhibited the P-glycoprotein efflux function in MOLT-4/DNR cells in a concentration-dependent manner (P<0.001). However, 0.03~3 μM of CEP did not influence P-glycoprotein expression. 0.03~0.3 μM of CEP significantly increased the GC receptor distribution from the cytoplasm to the nucleus in a concentration-dependent manner in MOLT-4/DNR cells. The combination did not influence the frequency of CD4⁺, CD4⁺CD25⁺ and CD4⁺CD25⁺Foxp3⁺ T cells or the secretion of Th1/Th2/Th17 cytokines from PBMCs. In contrast, CEP alone at 1 μM decreased the percentage of CD4⁺ T cell significantly (P<0.01). It also inhibited the secretion of IL-6, IL-10, IL-17, TNF-α, and IFN-γ. Conclusions: CEP synergistically promoted MP pharmacodynamics to decrease the cell viability of the mitogen-activated PBMCs, possibly via inhibiting P-glycoprotein function and potentiating GC receptor translocation. The present study provides new evidence of the therapeutic effect of Cepharanthin^® alone or in combination with GC for the management of chronic ITP. [ABSTRACT FROM AUTHOR]