Acteoside attenuates TSLP-induced mast cell proliferation via down-regulating MDM2.

Acteoside (verbascoside) is extensively distributed in Abeliophyllum distichum and has antimicrobial and anti-inflammatory properties. Thymic stromal lymphopoietin (TSLP) has a pivotal function in the pathogeneses of inflammatory diseases through increasing the mast cell proliferation via the activation of murine double minute 2 (MDM2). Here, we investigate whether acteoside attenuates the MDM2 expression in a TSLP-stimulated human mast cell line (HMC-1 cells). In these cells, TSLP induced the up-regulation of MDM2 and the down-regulation of p53; however, in the TSLP-stimulated HMC-1 cells, the acteoside down-regulated the MDM2 and up-regulated the p53. Increases in the phosphorylation of the single transducer and activation of transcription 6 and 5 via TSLP are decreased by acteoside. The interleukin (IL)-13 (a mast cell growth factor), IL-6, tumor necrosis factor-α, and IL-1β levels are significantly reduced by the acteoside in the TSLP-stimulated HMC-1 cells, and the acteoside significantly induces the activation of caspase-3, the cleavage of poly-ADP-ribose polymerase, and the reduction of the procaspase-3 and Bcl2. Furthermore, the mRNA expressions of the TSLP receptor and IL-7 receptor that increase due to TSLP are reduced by the acteoside. In conclusion, these results indicate that acteoside is a specific regulator of MDM2 activation in TSLP-stimulated mast cells, which indicates its potential use for the treatment of mast cell-mediated inflammatory diseases.