Erianin inhibits proliferation of activated T cells by downregulating CyclinB1

Abstract Objective To investigate the inhibitory effect of erianin on T cell proliferation and its underlying mechanism. Methods Peripheral blood mononuclear cells (PBMCs) were isolated using density gradient centrifugation, and T cells were purified by magnetic-activated cell sorting (MACS) with immunomagnetic beads, followed by being activated with anti-human CD3 antibodies and anti-human CD28 antibodies. The activated T cells were labeled with carboxyfluorescein succinimidyl ester (CFSE), and the effects of erianin (0.05~0.20 μmol/L) on the proliferation, apoptosis, expression of activation marker cluster of differentiation 25 (CD25), cell cycle distribution of activated T cells, as well as the survival rate of resting T cells were assessed using flow cytometry. Enzyme-linked immunosorbent assay (ELISA) was applied to determine the secretion levels of IL-2 and IL-17 in the culture supernatant of erianin-treated activated T cells. Western blotting was employed to examine the impact of erianin on the protein expression of cell division cycle protein 2 (CDC2), phosphorylated CDC2 (p-CDC2), and Cyclin B1. The differences were observed between the erianin-treated group and the positive control group (activation with CD3/CD28 antibodies). Results CFSE proliferation assay demonstrated that the proliferative rate of activated T cells was in a concentration-dependent decline after 0.05~0.20 μmol/L erianin treatment (P<0.0001), with a half-maximal inhibitory concentration (IC50) of 0.09±0.10 μmol/L. No significant differences were observed in apoptotic rates or survival rates among the erianin-treated groups (activated and resting T cells) and the positive control cells. Analysis of T cell activation markers revealed that erianin had no impact on CD25 expression or IL-2 secretion. However, ELISA results indicated erianin exerted a significant suppression on the secretion of pro-inflammatory cytokine IL-17 (P<0.0001). Cell cycle analysis showed that erianin arrested activated T cells at the G2/M phase (P<0.05). Further mechanistic investigations demonstrated that while erianin did not alter CDC2 phosphorylation or total CDC2 expression, but it markedly down-regulated CyclinB1 expression (P<0.01). Conclusion Erianin exhibits potent immunomodulatory activity by suppressing activated T cell proliferation through down-regulating Cyclin B1.