STUDY ON THE SIGNAL TRANSDUCTION AND REGULATION IN ERYTHROPOIESIS BY TOTAL SAPONINS OF PANAX GINSENG / 解剖学报

ABSTRACT

Objective To investgate the signal transduction and regulation in erythropoiesis by total saponins of Panax ginseng(TSPG) to clarify the mechanism for Panax Ginseng promoting hematopoiesis.Methods The colony-forming ability of mononuclear cells(MNCs) from human umbilical cord blood was assayed in methylcellulose assay systems,various dilutions of TSPG(0,10-100mg/L) were then added to each methylcellulose culture mixture;MNC proliferation in response to erythropoietin(Epo) was measured by MTT;To investigate whether the preferential differentiation of MNCs into erythroid lineage cells was caused by an increase in the expression of erythropoietin receptor(EpoR) on the cells,immunoblotting analyses were performed;Immunoprecipitation of JAK_2/STAT_5 was used for the effect of TSPG on Epo/EpoR-induced tyrosine phosphorylation of JAK_2/STAT_5. Results 1.TSPG(10-75mg/L) can promote the colony formation of BFU-E,CFU-E,and the preferential differentiation into erythroid lineage cells was induced from 25mg/L of TSPG;2.Using the colorimetric MTT assay,MNCs exhibited proliferous responses to Epo(2?10~3-5?10~4IU/L) reaching maximum at 5?10~3IU/L Epo;3.The addition of TSPG did not increase the expression of EpoR;4.After MNCs were incubated in the presence of with or without TSPG for 24 h,the cells were stimulated with Epo for 0,2,5,30min,and tyrosine phosphorylation JAK_2/STAT_5 was measured.The pretreatment with TSPG enhanced Epo-induced tyrosine phosphorylation of JAK_2 and STAT_5(STAT_(5a) and STAT_(5b)).Conclusion In the present study,we have shown that the Epo/EpoR-mediated signals are enhanced,and JAK_2/STAT_5 signals plays an essential role in the effect of TSPG on erythropoiesis,whereas the expression level of EpoR remains unchanged.