Effects of Astragalus polysaccharides on P-glycoprotein efflux pump function and protein expression in H22 hepatoma cells in vitro.
BACKGROUND
Astragalus polysaccharides (APS) are active constituents of Astragalus membranaceus. They have been widely studied, especially with respect to their immunopotentiating properties, their ability to counteract the side effects of chemotherapeutic drugs, and their anticancer properties. However, the mechanism by which APS inhibit cancer and the issue of whether that mechanism involves the reversal of multidrug resistance (MDR) is not completely clear. The present paper describes an investigation of the effects of APS on P-glycoprotein function and expression in H22 hepatoma cell lines resistant to Adriamycin (H22/ADM).


METHODS
H22/ADM cell lines were treated with different concentrations of APS and/or the most common chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine. Chemotherapeutic drug sensitivity, P-glycoprotein function and expression, and MDR1 mRNA expression were detected using MTT assay, flow cytometry, Western blotting, and quantitative RT-PCR.


RESULTS
When used alone, APS had no anti-tumor activity in H22/ADM cells in vitro. However, it can increase the cytotoxicity of certain chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine, in H22/ADM cells. It acts in a dose-dependent manner. Compared to a blank control group, APS increased intracellular Rhodamine-123 retention and decreased P-glycoprotein efflux function in a dose-dependent manner. These factors were assessed 24 h, 48 h, and 72 h after administration. APS down regulated P-glycoprotein and MDR1 mRNA expression in a concentration-dependent manner within a final range of 0.8-500 mg/L and in a time-dependent manner from 24-72 h.


CONCLUSIONS
APS can enhance the chemosensitivity of H22/ADM cells. This may involve the downregulation of MDR1 mRNA expression, inhibition of P-GP efflux pump function, or both, which would decrease the expression of the MDR1 protein.
Clinical Pharmacy and Pharmacology Research Institute, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.
Qing E
QE
Tian
Huan
H
De Li
Miao
M
Yan
Hua-Lin
HL
Cai
Qin-You
QY
Tan
Wen-Yuan
WY
Zhang
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000302:isolation & purification / Q000494:pharmacology*; D027883:Astragalus Plant / Q000737:chemistry*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D011134:Polysaccharides / Q000302:isolation & purification / Q000494:pharmacology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D010936:Plant Extracts; D011134:Polysaccharides