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. CONCLUSION: 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.

Astragalus polysaccharides can regulate cytokine and P-glycoprotein expression in H22 tumor-bearing mice.

AIM: To investigate the adjunct anticancer effect of Astragalus polysaccharides in H22 tumor-bearing mice. METHODS: To establish a solid tumor model, 5.0 × 10(6)/mL H22 hepatoma cells were inoculated subcutaneously into the right armpit region of Kunming mice (6-12 wk old, 18-22 g). When the tumors reached a size of 100 mm(3), the animals were treated as indicated, and the mice were randomly assigned to seven groups (n = 10 each). After ten days of treatment, blood samples were collected from mouse eyes, and serum was harvested by centrifugation. Mice were sacrificed, and the whole body, tumor, spleen and thymus were weighed immediately. The rate of tumor inhibition and organ indexes were calculated. The expression levels of serum cytokines, P-glycoprotein (P-GP) and multidrug resistance (MDR) 1 mRNA in tumor tissues were detected using enzyme-linked immunosorbent assay, Western blotting, and quantitative myeloid-derived suppressor cells reverse transcription-polymerase chain reaction, respectively. RESULTS: The tumor inhibition rates in the treatment groups of Adriamycin (ADM) + Astragalus polysaccharides (APS) (50 mg/kg), ADM + APS (100 mg/kg), and ADM + APS (200 mg/kg) were significantly higher than in the ADM group (72.88% vs 60.36%, P = 0.013; 73.40% vs 60.36%, P = 0.010; 77.57% vs 60.36%, P = 0.001). The spleen indexes of the above groups were also significantly higher than in the ADM group (0.65 ± 0.22 vs 0.39 ± 0.17, P = 0.023; 0.62 ± 0.34 vs 0.39 ± 0.17, P = 0.022; 0.67 ± 0.20 vs 0.39 ± 0.17, P = 0.012), and the thymus indexes of the ADM + APS (100 mg/kg) and ADM + APS (200 mg/kg) groups were significantly higher than in the ADM group (0.20 ± 0.06 vs 0.13 ± 0.04, P = 0.029; 0.47 ± 0.12 vs 0.13 ± 0.04, P = 0.000). APS was found to exert a synergistic anti-tumor effect with ADM and to alleviate the decrease in the sizes of the spleen and thymus induced by AMD. The expression of interleukin-1α (IL-1α), IL-2, IL-6, and tumor necrosis factor-α (TNF-α) was significantly higher in the ADM + APS (50 mg/kg), ADM + APS (100 mg/kg) and ADM + APS (200 mg/kg) groups than in the ADM group; and IL-10 was significantly lower in the above groups than in the ADM group. APS could increase IL-1α, IL-2, IL-6, and TNF-α expression and decrease IL-10 levels. Compared with the ADM group, APS treatment at a dose of 50-200 mg/kg could down-regulate MDR1 mRNA expression in a dose-dependent manner (0.48 ± 0.13 vs 4.26 ± 1.51, P = 0.000; 0.36 ± 0.03 vs 4.26 ± 1.51, P = 0.000; 0.21 ± 0.04 vs 4.26 ± 1.51, P = 0.000). The expression level of P-GP was significantly lower in the ADM + APS (200 mg/kg) group than in the ADM group (137.35 ± 9.20 mg/kg vs 282.19 ± 20.54 mg/kg, P = 0.023). CONCLUSION: APS exerts a synergistic anti-tumor effect with ADM in H22 tumor-bearing mice. This may be related to its ability to enhance the expression of IL-1α, IL-2, IL-6, and TNF-α, decrease IL-10, and down-regulate MDR1 mRNA and P-GP expression levels.

Ent-kauranoids from Isodon rubescens var. taihangensis.

Two new compounds, rubescensins Q and R (1 and 2), and a new acetonide derivative (3) of lasiodonin, together with thirteen known analogues, oridonin (4), ponicidin (5), wikstroemioidin B (6), lasiodonin (7), lasiokaurin (8), enmenol (9), 1-O-beta-D-glucopyranosyl-enmenol (10), trichokaurin (11), the acetonide of maoyecrystal F (12), rabdoternins A-D (13-16), have been isolated from Isodon rubescens var. taihangensis. The structures of the new compounds were elucidated on the basis of spectroscopic methods, especially the 2D NMR spectral analysis. Compound 3 exhibited cytotoxicity against K562, Bcap37, CA, CNE, BIU87, BGC823, and HeLa cell lines.