Inhibition of P‐glycoprotein function by procyanidine on blood–brain barrier

The inhibitory effects of procyanidine, one of the components from the bark of Pinus massoniana Lamb, on the P‐glycoprotein (P‐gp) function of the blood–brain barrier (BBB) were studied using in vitro rat brain microvessel endothelial cells (RBMECs) and nude mice transplanted with human cerebroma. Quantitative accumulation and efflux of rhodamine 123 (Rh123), a P‐gp substrate, were determined using a fluorescence spectrophotometer as a measure of P‐gp function. Procyanidine markedly increased the accumulation of Rh123 by inhibiting its efflux in a dose‐dependent manner. A 5‐fold increase in cellular Rh123 was observed for procyanidine at 10 µmol/L. The verapamil‐stimulated ATPase activity in plasma membrane vesicles from the RBMECs was estimated by measuring inorganic phosphate liberation. Procyanidine significantly inhibited the verapamil‐induced P‐gp ATPase activity by 78% when pretreated with 10 µmol/L in a concentration‐dependent manner. The inhibition of P‐gp by procyanidine was suggested to be at least partly due to its inhibition of P‐gp ATPase. Procyanidine markedly improved the therapeutic effects of adriamycin (ADM) on nude mice transplanted with human cerebroma, compared with solitary treatment of ADM. The combination of 80 mg/kg procyanidine with 2 mg/kg ADM significantly elevated the days of survival with an increase in life span of 76%. The findings suggested that procyanidine was a potent inhibitor of P‐gp on BBB and could improve the therapeutic effects on cerebral tumors of some drugs which are difficult to accumulate in the brain. Copyright © 2009 John Wiley & Sons, Ltd.     

Potent modulation of P‐glycoprotein activity by naturally occurring phenylbutenoids from Zingiber cassumunar

Five phenylbutenoid derivatives from the rhizomes of Zingiber cassumunar Roxb. (Zingiberaceae) were evaluated for their P‐glycoprotein (P‐gp) inhibitory effects in a P‐gp over‐expressing multidrug resistant (MDR) human breast cancer cell line, MCF‐7/ADR. As a result, a phenylbutenoid dimer, (±)‐trans‐3‐(3,4‐dimethoxyphenyl)‐4‐[(E)‐3,4‐dimethoxystyryl]cyclohex‐1‐ene (1), exhibited highly potent P‐gp inhibitory activity, decreasing the IC₅₀ value of daunomycin (DNM) to 4.31 ± 0.40 µm in the cells (DNM IC₅₀ = 37.1 ± 0.59 µm ). The positive control, verapamil decreased the IC₅₀ value of DNM to 6.94 ± 0.40 µm . Three phenylbutenoid monomers, 2–4 from this plant, also resulted in a significant decrease in the IC₅₀ values of DNM compared with the control. In particular, compound 1 markedly enhanced [³H]‐DNM accumulation and significantly reduced [³H]‐DNM efflux compared with the control, and this effect was more potent than that of verapamil, a well‐known P‐gp inhibitor. These results suggest that compound 1 of Z. cassumunar can be developed as a potent chemo‐sensitizing agent that reverses P‐gp‐mediated MDR in human cancer chemotherapy. Copyright © 2008 John Wiley & Sons, Ltd.     

Trametenolic Acid B Reverses Multidrug Resistance in Breast Cancer Cells Through Regulating the Expression Level of P‐Glycoprotein

Trametenolic acid B (TAB) is the main active composition of Trametes lactinea (Berk.) Pat which possesses anti‐tumor activities. There was no report its antitumor effect through regulating P‐glycoprotein (P‐gp) so far, due to P‐gp over expression is one of the most important mechanisms contributing to the multiple drug resistance phenotype. The present aim was to investigate the effects of TAB on P‐gp in multidrug‐resistant cells; Paclitaxel‐resistant cell line MDA‐MB‐231/Taxol was established by stepwise exposure for 10 months. MDA‐MB‐231 cells and MDA‐MB‐231/Taxol cells were treated with TAB, and their growth was evaluated using MTT assays. Paclitaxel accumulation in the cells was analyzed by high performance liquid chromatogram (HPLC). The activity of P‐gp was detected by intracellular accumulation of rhodamine123 (Rho123), and the protein expression of P‐gp was evaluated using western blot. Results indicated that the IC₅₀ of MDA‐MB‐231/Taxol to paclitaxel (Taxol) was 33 times higher than that of nature MDA‐MB‐231. TAB increased the intracellular concentration of Taxol and inhibited the activity of P‐gp and suppressed the expression of P‐gp in MDA‐MB‐231/Taxol cells. Our present results showed that TAB could reverse Taxol resistance in MDA‐MB‐231/Taxol cells, mainly inhibiting the activity of P‐gp and down‐regulating the expression level of P‐gp, and then enhancing the accumulation of chemotherapy agents. © 2013 The Authors Phytotherapy Research Published by John Wiley & Sons Ltd.     

Rutin,a Quercetin Glycoside,Restores Chemosensitivity in Human Breast Cancer Cells

Several studies have documented the ability of flavonoids to sensitize cancer cells to chemotherapeutics and reverse multidrug resistance by inhibition of efflux pumps (adenosine triphosphate‐binding cassette transporters), apoptosis activation, and cell cycle arrest. In this study, the flavonoid rutin (quercetin 3‐O‐β‐d ‐rutinoside) was investigated as chemosensitizer towards two different human epithelial breast cancer cell lines: (i) MB‐MDA‐231, selected as representative for triple‐negative breast cancer and (ii) MCF‐7 used as a well‐characterized model of HER2‐negative breast cancer. To assess the cytocompatibility of rutin against non‐cancer cells, primary human mammary fibroblasts were used as control and non‐target cells. In MDA‐MB‐231 cells, 20 μM rutin enhanced cytotoxicity related to cyclophosphamide and methotrexate. Rutin significantly (p < 0.05) increased the anticancer activity of both chemotherapeutics, at 24–48–72 h, and decreased the activity of the adenosine triphosphate‐binding cassette transporters, namely, P‐glycoprotein (P‐gp) and breast cancer resistance protein (BCRP). Flow cytometry analysis showed 20 μM and 50 μM rutin arrested cell cycle at G2/M and G0/G1 phases, respectively, significantly promoting cell apoptosis. Rutin, via non‐selective inhibition of P‐gp and BCRP pumps, efficiently reverses multidrug resistance and restores chemosensitivity to cyclophosphamide and cyclophosphamide of human chemoresistant, triple‐negative breast cancer cells, successfully arresting cell cycle progression. Copyright © 2017 John Wiley & Sons, Ltd.     

卡莫氟在 Caco - 2 细胞模型中的吸收和转运特性

  目的 应用 Caco-2 细胞模型对卡莫氟 （ carmofur , 1-hexylcarbamoyl-5-fluorouracil , HCFU ） 的吸收、转运特性及其机制进行研究。 方法 分别考察时间、 pH 、浓度及抑制剂对 HCFU 吸收的影响;测定药物在不同时间双向转运的速度,计算 HCFU 的表观渗透系数,研究不同药物浓度对其转运的影响。 结果 Caco-2 细胞对 HCFU 的吸收在 20 min 内呈线性,药物摄取时间定为 10 min ; pH 对 HCFU 的吸收没有显著影响,浓度依赖性结果显示, HCFU 的吸收由一个饱和成分和一个非饱和成分组成; P- 糖蛋白（ P-glycoprotein , P-gp ）抑制剂维拉帕米对 HCFU 的吸收基本没有影响,而耐药相关性蛋白（ MRP ）抑制剂 MK571 的存在可显著增加对 HCFU 的吸收（ P <0.05 ）。双向转运的表观渗透性存在方向性差异,且受浓度的影响。 结论 HCFU 在 Caco-2 细胞中以主动和被动 2 种形式吸收,其吸收存在外排机制, MRP2 可能对 HCFU 的吸收有外排作用。     

Barbigerone reverses multidrug resistance in breast MCF‐7/ADR cells

Development of agents to overcome multidrug resistance (MDR) is one of the important strategies in cancer chemotherapy, and P‐glycoprotein (P‐gp) correlates with the degree of resistance. As a naturally occurring isoflavone, whether barbigerone (BA) could reverse MDR, is unknown. In this paper, we evaluated effects of BA on reversing P‐gp mediated MDR of adriamycin (ADR)‐resistant human breast carcinoma (MCF‐7/ADR) cells. BA (0.5 μM) treatment showed strong potency to increase ADR cytotoxicity toward MCF‐7/ADR cells. It was also demonstrated that BA time‐ and dose‐dependently increased accumulations of ADR and reduced the efflux in MCF‐7/ADR cells, pretreatment of these cells with BA might relocalized ADR to the nuclei. Furthermore, the results also revealed that BA did not affect P‐gp, but alter P‐gp ATPase activity. Intravenous administration of BA significantly increased anticancer efficacy of ADR to MCF‐7/ADR xenograft model in nude mice. These results revealed that BA might reverse P‐gp mediated MDR through inhibition of ATPase activity, which indicated a novel use of BA as a potent candidate for cancer chemotherapy.     

Caco‐2 Cell methodology and inhibition of the P‐glycoprotein transport of digoxin by Aloe vera Juice

The aims of this study were to carry out a thorough quality control setup for essential Caco‐2 cell characteristics in P‐glycoprotein (P‐gp) inhibition studies and to explore if Aloe vera juice (AVJ) inhibits the bidirectional transport of the P‐gp substrate digoxin (30 nm ). Seven AVJ concentrations (0.00001‐1.0 mg/mL), anticipated to cover a clinically relevant range, were tested and digoxin apparent permeability coefficients (Papp), net Papp values (Papp_Net) and net flux values (J_Net) were calculated. Relevant validation parameters for P‐gp inhibition studies in Caco‐2 cells are suggested to include, as a minimum, an assay linearity test with and without a known P‐gp inhibitor, cell cytotoxicity testing (MTT‐test) for substrates and inhibitors, and cell integrity testing by TEER and mannitol transport measurements. The question is also raised whether a minimum effect of a reference P‐gp inhibitor as verapamil should be demanded. Cell cytotoxicity was seen for digoxin at concentrations ≥3 µm and for AVJ at 10 mg/mL. AVJ did not inhibit the P‐gp transport of digoxin in any of the concentrations tested. This indicates that AVJ is no inhibitor of the P‐gp mediated transport of digoxin in vitro if AVJ is present in clinically relevant concentrations. Copyright © 2008 John Wiley & Sons, Ltd.     

Evaluation of First‐Pass Cytochrome P4503A (CYP3A) and P‐glycoprotein Activities Using Felodipine and Hesperetin in Combination in Wistar Rats and Everted Rat Gut Sacs in Vitro

The effects of hesperetin on the pharmacokinetics and the role of P‐glycoprotein (P‐gp) in the transport of felodipine were investigated in rats and in vitro. Felodipine was administered orally (10 mg/kg) without or with hesperetin (25, 50 and 100 mg/kg) to rats for 15 consecutive days. Blood samples were collected at different time intervals on 1^st day in single dose pharmacokinetic study (SDS) and on 15^th day in multiple dose pharmacokinetic study (MDS). The area under the plasma concentration–time curve (AUC_0–∞) and the peak plasma concentration (C_max) of felodipine were dose‐dependently increased in SDS and MDS with hesperetin compared to control ( p < 0.001). The half‐life (t_1/2) and mean residence time was longer than the control group in both studies. The role of P‐gp determined using everted rat gut sacs in vitro by incubating felodipine with or without hesperetin and verapamil (typical P‐gp and CYP3A4 inhibitor). The in vitro experiments revealed that the verapamil and hesperetin increased the intestinal absorption of felodipine (p < 0.01). Concurrent use of hesperetin dramatically altered the pharmacokinetics of felodipine leading to an increase in systemic exposure. The likely mechanism is inhibition of CYP3A4‐mediated first‐pass metabolism and P‐gp in the intestine and the liver. Copyright © 2013 John Wiley & Sons, Ltd.     

The beta‐carboline alkaloid harmine inhibits BCRP and can reverse resistance to the anticancer drugs mitoxantrone and camptothecin in breast cancer cells

Multidrug resistance (MDR), mediated by highly expressed ABC transporters, is one of the most important mechanisms in tumor cells. Breast cancer resistance protein (BCRP) is a member of the ABC transporter family. This transporter expels different kinds of lipophilic anticancer drugs, which have diffused into the cells. In this study, 96‐well plate based assays and flow cytometry analysis were employed to screen natural products for BCRP inhibition. The beta‐carboline alkaloid harmine inhibited BCRP in a BCRP overexpressing breast cancer cell line (MDA‐MB‐231). Harmine reduced resistance to the anticancer drugs mitoxantrone and camptothecin mediated by BCRP and might be an interesting new reversal agent. Harmine did not inhibit P‐glycoprotein (P‐gp) mediated drug efflux. Copyright © 2009 John Wiley & Sons, Ltd.     

Mechanisms of improvement of intestinal transport of baicalin and puerarin by extracts of Radix Angelicae Dahuricae

Radix Angelicae Dahuricae is the dried root of Angelicae Dahurica (Fisch.ex Hoffm.)Benth.et Hook.f. var.formosana (Boiss.) Shan et Yuan (Fam.Umbelliferae). The total coumarins (Cou) and volatile oil (VO) were main active components that drived from Radix Angelicae Dahuricae. Our previous studies have shown that Cou and VO could increase intestinal absorption for transmucosal drug delivery with unknown mechanism. The aim of this study was to investigate the molecular mechanism of Radix Angelicae Dahuricae for improving drug intestinal transport. Caco‐2 cell model was used to study the effect of Radix Angelicae Dahurica on transepithelial electrical resistance. Western blot was used to study its effect on the expression of the actin and ZO‐1, tight junction proteins. The effect of Radix Angelicae Dahurica on the expression of P‐gp protein was investigated using flow cytometry. VO (0.036–2.88 μL/mL) and Cou (0.027–0.54 mg/mL) caused a reversible, time‐ and dose‐dependent decrease in transepithelial electrical resistance. VO and/or Cou could inhibit the expression of the tight junction protein, ZO‐1 and actin. VO and/or Cou also could inhibit the expression of P‐gp. These data suggested that Radix Angelicae Dahurica increased cell permeability by affecting the expression of actin, ZO‐1 or P‐gp, opening the tight junction or inhibiting the efflux induced by P‐gp. Copyright © 2014 John Wiley & Sons, Ltd.     

Quercetin reversed MDR in breast cancer cells through down‐regulating P‐gp expression and eliminating cancer stem cells mediated by YB‐1 nuclear translocation

Overexpression of P‐glycoprotein (P‐gp) plays an important role in mediating multidrug resistance (MDR), resulting in chemotherapy failure of tumor patients and enhancement of cancer stem cell characteristics. By preparing doxorubicin (Dox) resistant human breast cancer MCF‐7 cells, here, we wanted to evaluate the effects of quercetin (Que) on MDR reversal activity and investigate its possible mechanism. MCF‐7 and MCF‐7/dox cells were respectively treated by Dox, paclitaxel (Pac), or vincristine (Vcr) with or without Que intervention for 24 hr. Cell viability, cell apoptosis, cell cycle, intracellular drug accumulation, the expression of P‐gp and Y‐box binding protein 1 (YB‐1), and breast cancer stem cells (BCSCs) were then assessed. The results showed that Que significantly enhanced the antitumor activities of Dox, Pac, and Vcr in breast cancer cells. In addition, combined treatment of Dox, Pac, or Vcr with Que significantly downregulated P‐gp expression and eliminated BCSCs. Furthermore, combined treatment of Dox, Pac, or Vcr with Que significantly inhibited nuclear translocation of YB‐1. Thus, we speculated that Que reversed MDR in breast cancer cells through downregulating P‐gp expression and eliminating cancer stem cells mediated by YB‐1 nuclear translocation.     

Euphorbiasteroid reverses P‐glycoprotein‐mediated multi‐drug resistance in human sarcoma cell line MES‐SA/Dx5

In this study, we evaluated whether euphorbiasteroid isolated from Euphorbia lathyris has the potential to reverse P‐glycoprotein (P‐gp)‐mediated multi‐drug resistance (MDR) by using the drug‐sensitive human sarcoma cell line MES‐SA and its MDR counterpart MES‐SA/Dx5. Interestingly, even at low concentrations of euphorbiasteroid (1–3 μM), it efficiently restored the toxicities of anticancer drugs including vinblastine, taxol and doxorubicin in MES‐SA/Dx5 cells. Additionally, the computational Bayesian model for predicting potential P‐gp substrates or inhibitors revealed that euphorbiasteroid showed 97% probability for substrate likeness having similar molecular features with 50 P‐gp substrates. Consistent with this result, the substrate likeness of euphorbiasteroid was also experimentally confirmed by P‐gp ATPase activity assay. In conclusion, our finding suggested that euphorbiasteroid could be a transport substrate for P‐gp that can effectively inhibit P‐gp‐mediated drug transport and reverse resistance to anticancer drugs in MES‐SA/Dx5 cells. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantitative Evaluation of the Mechanism Underlying the Biotransportation of the Active Ingredients in Puerariae lobatae Radix and Chuanxiong rhizoma

The objective of this study was to establish a quantitative method to evaluate the biotransportation of a drug across the cell membrane. Through the application of the law of mass conservation, the drug transportation rate was calculated based on Fick's law of passive diffusion and the Michaelis–Menten equation. The overall membrane‐transportation rate was the sum of the passive diffusion rate and the carrier‐mediated diffusion rate, which were calculated as the transportation mass divided by the respective rate. The active ingredients of Puerariae lobatae Radix and Chuanxiong rhizoma, namely, puerarin and ferulic acid, respectively, were used as two model drugs. The transportation rates of puerarin and ferulic acid were obtained by fitting a model that includes both Fick's law of diffusion and the Michaelis–Menten equation. Compared with the overall transportation, the carrier‐mediated transport and passive diffusion of 1.59 mmol/L puerarin were ?35.07% and 64.93%, respectively, whereas the respective transportation modes of 0.1 mmol/L ferulic acid were ?35.40% and 64.60%, respectively. Verapamil and MK‐571 increased the overall transport rate and ratio, and MK‐571 treatment changed the carrier‐mediated transport from negative to positive. However, the transport rate and ratio of ferulic acid did not change significantly. The cell transportation mechanisms of puerarin and ferulic acid primarily involve simple passive diffusion and carrier‐mediated transportation. Moreover, P‐glycoprotein and multidrug resistance‐associated protein efflux proteins, and other transportation proteins were found to be involved in the transportation of puerarin. Copyright © 2015 John Wiley & Sons, Ltd.     

Modulation of P‐glycoprotein ATPase activity by some phytoconstituents

In the present investigation 16 phytoconstituents, which are active moieties found in several medicinal herbs, have been evaluated for their P‐glycoprotein (P‐gp) stimulation/inhibition profiles using a P‐gp‐dependent ATPase assay in rat jejunal membrane (in vitro). Acteoside, agnuside, catechin, chlorogenic acid, picroside ‐II and santonin showed an inhibitory effect. Negundoside, picroside ‐I and oleanolic acid caused a stimulatory effect. Andrographolide, apocyanin, berberine, glycyrrhizin, magniferin and piperine produced a biphasic response (stimulation at low concentration and inhibition at high concentration). The results suggested that a possible interaction of these phytoconstituents at the level of P‐gp, could be an important parameter in determining their role in several key pharmacodynamic events. Copyright © 2009 John Wiley & Sons, Ltd.     

普流罗尼克对P-gp底物罗丹明123在Caco-2细胞蓄积的影响

 目的 研究普流罗尼克（Pluronic F127,F68,P85,P123对小肠P-糖蛋白（P-gp的调控作用。方法 采用MTT法检测不同质量浓度的Pluronic对Caco-2细胞生长抑制作用;以P-gp底物罗丹明123(R-123为荧光探针,评价各种Pluronic辅料和P-gp抑制剂维拉帕米对R-123细胞蓄积的影响,细胞内的R-123浓度采用高效液相-荧光检测。同时考察了Pluronic P123和F127对P-gp ATP酶活性的影响。结果 除了L61,经Pluronic处理后的细胞生存率都在80％以上,表明在蓄积实验中的细胞活性没有受到Pluronic的影响。在抑制剂维拉帕米和不同浓度的Pluronic(0.001~50 mg·mL-1作用下,可在不同程度上提高R-123在Caco-2细胞的蓄积作用,同时具有浓度依赖性,在接近或超过临界胶束浓度(CMC后,细胞蓄积达到最大值,然后随着Pluronic浓度的继续增大,蓄积作用又逐渐减弱。不同浓度的Pluronic P123和F127对P-gp ATP酶活性具有抑制作用。结论 蓄积实验结果表明,Pluronic F127,F68,P85和P123可以通过抑制P-gp的作用改善药物的吸收,抑制P-gp ATP酶活性可能是原因之一。因此,联合使用Pluronic,有望提高P-gp底物药物的口服生物利用度。     

Combination of tanshinone IIA and doxorubicin possesses synergism and attenuation effects on doxorubicin in the treatment of breast cancer

Doxorubicin (Dox) is a first‐line drug for breast cancer chemotherapy. However, with the prolongation of chemotherapy cycle, breast cancer cells are increasingly tempt to resist Dox, and meanwhile, high cumulative dose of Dox brings enhancing toxic side effects, and these effects may lead to chemotherapy failure. Hence, it is necessary to search an agent in combination medication with Dox, which can not only enhance the chemosensitivity of Dox but also reduce the toxic side effects. Tanshinone IIA (Tan IIA) is reported to have antitumor activity in addition to its cardiovascular protective effects. We employed human breast cancer MCF‐7 and MCF‐7/dox cells in order to assess whether Tan IIA might perform such function. Our in vitro studies showed that Tan IIA could enhance the sensitivity of breast cancer cells to Dox through inhibiting the PTEN/AKT pathway and downregulating the expression of efflux ABC transporters including P‐gp, BCRP, and MRP1. In addition, our in vivo studies showed Tan IIA enhanced the chemotherapeutic effect of Dox against breast cancer while reducing its toxic side effects including weight loss, myelosuppression, cardiotoxicity, and nephrotoxicity. Therefore, Tan IIA could be used as a novel agent combined with Dox in breast cancer therapy.     

Potentiating Effect of the Flavonolignan (‐)‐Hydnocarpin in Combination with Vincristine in a Sensitive and P‐gp‐Expressing Acute Lymphoblastic Leukemia Cell Line

The potentiating action of the flavonolignan, (‐)‐hydnocarpin, in combination with vincristine was evaluated in the 697 acute lymphoblastic leukemia cell line and a P‐gp‐expressing variant, 697‐R. Vincristine at 3 nM caused nearly complete growth inhibition in 697 cells versus a 17% growth inhibition in 697‐R cells. When combined with (‐)‐hydnocarpin at concentrations of 10 and 5 μM, vincristine‐mediated growth inhibition in the 697‐R cells increased significantly over the sum of the individual agents to 72% (p ≤ 0.0001) and 41% (p = 0.0256), respectively. Vincristine at 1.5 nM (66% growth inhibition) and 0.75 nM (39% growth inhibition) combined with (‐)‐hydnocarpin at 10 μM (42% growth inhibition) in the 697 cells caused a significant increase in growth inhibition to 83% (p = 0.03) and to 61% (p < 0.0001), respectively, when compared to vincristine treatment as a single agent. To investigate the mechanism for the vincristine re‐sensitization caused by (‐)‐hydnocarpin, the P‐gp inhibitory effect of (‐)‐hydnocarpin was evaluated. Copyright © 2012 John Wiley & Sons, Ltd.     

Paris saponin VII induces cell cycle arrest and apoptosis by regulating Akt/MAPK pathway and inhibition of P‐glycoprotein in K562/ADR cells

Paris saponinVII (PSVII) is a steroidal saponin isolated from the roots and rhizomes of Trillium tschonoskii Maxim. We found that PSVII could inhibit the growth of adriamycin‐resistant human leukemia cells (K562/ADR) in a dose‐dependent manner. Furthermore, the molecular mechanism underlying the cytotoxicity and downregulation of P‐glycoprotein (P‐gp) expression by PSVII was clarified. PSVII significantly suppressed cell proliferation by cell cycle arrest in the G0/G1 phase, which was associated with an obvious decrease in cyclin B1/D1 and CDK2/4/6 protein expression. Moreover, PSVII could attenuate mitochondrial membrane potential, increase the expression of apoptosis‐related proteins, such as Bax and cytochrome c, and decrease the protein expression levels of Bcl‐2, caspase‐9, caspase‐3, PARP‐1, and p‐Akt. We also found that JNK, ERK1/2, and p38 were regulated by PSVII in K562/ADR cells. And further studies indicated that the decrease in the reactive oxygen species level inhibited intrinsic P‐gp expression. Therefore, PSVII‐induced apoptosis in K562/ADR cells was associated with Akt/MAPK and the inhibition of P‐gp. In addition, PSVII induced a robust autophagy in K562/ADR cells as demonstrated by the degradation of LC3‐I. These results provide a biochemical basis for possible clinical applications of PSVII in the treatment of leukemia.     

Modulation of P-glycoprotein-mediated resistance by kaempferol derivatives isolated from Zingiber zerumbet

This study examined the effects of the kaempferol derivatives extracted from Zingiber zerumbet on the accumulation and efflux of [(3)H]-daunomycin (DNM) in P-glycoprotein (P-gp) overexpressing multidrug resistant (MDR) human breast cancer cells, MCF-7/ADR. Of six kaempferol derivatives extracted from Z. zerumbet, kaempferol-3-O-methyl ether (1) and kaempferol-3,4'-O-dimethyl ether (2) showed a potent P-gp inhibitory effect as great as verapamil, a well-known P-gp inhibitor. The P-gp inhibitory activity of these two compounds was through a 3-fold increase of the level of [(3)H]-DNM accumulation and a decrease of P-gp-mediated efflux. These results suggest that the kaempferol derivative components of Z. zerumbet can be used as a scaffold for developing agents that reverse P-gp-mediated MDR in human cancer chemotherapy.     

连翘脂苷A抑制Caco-2细胞膜上P-糖蛋白的外排功能及作用机制探讨

目的:探讨连翘脂苷A对人克隆结肠癌细胞(Caco-2)细胞膜上P-糖蛋白(P-gp)的外排功能及作用机制。方法:采用刃天青法检测不同质量浓度连翘脂苷A对Caco-2的细胞毒性作用。以P-gp底物罗丹明123(Rh-123)为荧光探针,采用流式细胞术评价不同质量浓度连翘脂苷A对Rh-123细胞蓄积的影响,考察不同质量浓度连翘脂苷A对P-gp三磷酸腺苷(ATP)酶活性的影响。结果:连翘脂苷A在1~80 mg·L-1时,与阴性组比较,差异无统计学意义,细胞存活率90%,对Caco-2细胞形态无影响。连翘脂苷A的荧光强度较空白组显著增加,其中80 mg·L-1连翘脂苷A荧光强度(223.43±5.6)%增加最多。连翘脂苷A不同质量浓度均有抑制P-gp ATP酶耗能的作用。结论:连翘脂苷A可通过抑制P-gp ATP酶产生抑制P-gp外排的作用。