The expression of erythropoietin triggered by Danggui Buxue Tang, a Chinese herbal decoction prepared from Radix Astragali and Radix Angelicae Sinensis, is mediated by the hypoxia-inducible factor in cultured HEK293T cells

Abstract

Danggui buxue tang (DBT), a Chinese medicinal decoction that is being commonly used as hematopoietic medicine to treating woman menopausal irregularity, contains two herbs: radix Astragali and radix Angelicae Sinensis. Pharmacological results indicate that DBT can stimulate the production of erythropoietin (EPO), a specific hematopoietic growth factor, in cultured cells. In order to reveal the mechanism of DBT's hematopoietic function, this study investigated the activity of the DBT-induced EPO expression and the upstream regulatory cascade of EPO via hypoxia-induced signaling in cultured kidney fibroblasts (HEK293T). DBT-induced mRNA expressions were revealed by real-time PCR, while the change of protein expressions were analyzed by Western blotting. For the analysis of hypoxia-dependent signaling, a luciferase reporter was used to report the transcriptional activity of hypoxia response element (HRE). The plasmid containing HRE, being transfected into HEK293T, was highly responsive to the challenge of DBT application. To account for the transcriptional activation of HRE, DBT treatment was shown to increase the mRNA and protein expressions of hypoxia-inducible factor-1α (HIF-1α). In addition, the activation of Raf/MEK/ERK signaling pathway by DBT could also enhance the translation of HIF-1α, suggesting the dual actions of DBT in stimulating the EPO expression in kidney cells. Our study indicates that HIF pathway plays an essential role in directing DBT-induced EPO expression in kidney. These results provide one of the molecular mechanisms of this ancient herbal decoction for its hematopoietic function.