Research progress of natural plant active ingredients in reversing tumor multidrug resistance by down-regulating P-gp / 中国临床药理学与治疗学

Multidrug resistance (MDR) is the main factor of tumor recurrence and chemotherapy failure in clinical practice. Its mechanism is relatively complex, and one of the most thoroughly studied mechanism is the overexpression of P-glycoprotein (P-gp) on tumor cell membrane. Most of the chemotherapy drugs are p-gp substrates, and tumor cells will transport the chemotherapy drugs to the extracellular through p-gp mediated active transport, so that the concentration of effective drugs in the cell is reduced, resulting in drug resistance, leading to the decline of clinical efficacy. The reversal agent of P-gp can reduce the intracellular pumping of chemotherapeutic drugs by regulating the expression and transport activity of P-gp, and enhance the sensitivity of tumor cells to chemotherapeutic drugs, thus improving the therapeutic effect. In this paper, we will summarize the natural plant active ingredients that can reverse P-gp mediated MDR to provide reference for clinical and related studies.

Study on role of HDAC5 in P-gp expression in rats in high-altitude low oxygen environment and its effect on phenytoin sodium pharmacokinetics / 中国药理学通报

Aim To explore the important role of HDAC5 in P-gp expression in rats in high-altitude low oxygen environment and its effect on phenytoin sodium pharmacokinetics. Methods Wistar rats were transported to Batang, Yushu, Qinghai, at an altitude of 4010 m, with 6 rats in each group, divided into 1 d and 3 d groups. Different groups were given phenytoin, phenytoin combined with hypericin, and phenytoin combined with verapamil. Plasma and liver tissues were collected at different time after taking the drug in the plateau area. The concentration of phenytoin sodium in plasma was determined by UFLC-MS method. Changes in protein expression were detected by Western blot. Results The results of UFLC-MS showed that the AUC

Extract of Codiaeum luzonicum Merr. overcomes multidrug resistance in human colon cancer cells by modulating P-glycoprotein

Objective: To investigate anti-multidrug resistance (MDR) activity and safety of the bioactive fraction (CL11) from Codiaeum luzonicum crude leaf extract. Methods: Cytotoxic activity of CL11 against MDR and non- resistant colon cancer cells was assessed using MTT assay. Mode of cell death was investigated by annexin V-propidium iodide staining, TUNEL, and JC-1 assays. To examine mechanism of action, the effect on the expression and function of the MDR-implicated protein P-glycoprotein was tested using Western blotting and calcein assay, respectively. Results: CL11 had an EC 50 of 0.18, 1.03 and 38.52 μg/mL against HCT-15, HCT-15/Dox and HCT116, respectively. Cytotoxicity was mediated by inhibition of P-glycoprotein function and expression. The mode of cell death involved mitochondrial membrane depolarization and was mostly non-apoptotic at EC 50 concentrations against HCT-15 and HCT-15/Dox. Conclusions: Fraction CL11 of Codiaeum luzonicum induces non- apoptotic cell death in MDR cancer cells by overcoming MDR through inhibition of P-glycoprotein expression and function.

Z-guggulsterone reversed multi-drug resistance of hepatocarcinoma chemotherapy through down-regulating a PXR/P-gp pathway / 中国药理学通报

Aim To investigate the improved effects of Z-guggulsterone on the chemotherapy agents-induced proliferation and apoptosis through regulating PXR(pregnane X receptor)/P-gp(P-glycoprotein)signaling pathway in human hepatocellular carcinoma cells.Methods HepG2 cells were treated with Z-guggulsterone, DDP(cis-platinum)and 5-FU(5-fluorouracil)alone or in combination.CCK-8(Cell Counting Kit-8), Annexin-FITC/PI(Annexin V-fluorescein isothiocyanate isomer/propidium iodide)flow cytometry, RT-qPCR(Real-time quantitively Polymerase Chain Reaction)and Western blot were used to determine cell proliferation, apoptosis, the expression of MDR1 mRNA, PXR and P-gp respectively.Results Compared to DDP or 5-FU treatment alone, Z-guggulsterone(30 μmol·L-1)enhanced the inhibitory effects of DDP or 5-FU on the proliferation and apoptosis of HepG2 cells.Z-guggulsterone(30 μmol·L-1)also significantly reduced the expression levels of PXR,P-gp and MDR1 mRNA in HepG2 cells.Further research demonstrated that rifampicin, one agonist of PXR, increased the expression of PXR and P-gp, while Z-guggulsterone reversed its effects.Meanwhile, the expressions of PXR and P-gp were reduced by ketoconazole, one antagonist of PXR, and further decreased by co-administration with Z-guggulsterone.Conclusion Z-guggulsterone can improve the effects of chemotherapy on the proliferation and apoptosis of hepatocellular carcinoma cell lines by down-regulating the PXR/P-gp signaling pathway.

Effect of Notoginseng Total Saponins on Changing Multidrug Resistance in HepG2/ Adriamycin Cells Through ERK/Akt Signaling / 中国实验方剂学杂志

Objective:To investigate the effect of notoginseng total saponins （TNS） on adriamycin （Adr） resistance in HepG2/Adr cells and the expression and activity of the mechanisms as the modulators of multi-drug resistance， so as to explore the possible mechanism of extracellular signal-regulated kinase （ERK） and protein kinase B （Akt） signaling pathways in reversing the resistance of HepG2/Adr cells mechanism. Method:Effect of TNS on HepG2/Adr cell proliferation was detected by thiazole blue （MTT） method. HepG2/Adr cells were treated with different concentrations （100， 50， 25， 0 mg·L^-1） of TNS and （20 μmol·L^-1） Adr respectively， and a blank group was set. The high-content screening platform was used to detect the accumulation of Adr in HepG2/Adr cells after 40 minutes， 3 hours and 6 hours. Western blot was used to detect the expression of P-glycoprotein /multidrug resistance/ATP binding cassette subfamily B member 1（P-gp/MDR1/ABCB1） and other drug resistance-related proteins and the main protein expression of ERK/Akt signaling pathway. The change of MDR1 on cell membranes was observed by laser confocal microscopy. Result:Compared with HepG2 cells， the expression of MDR1 in HepG2/Adr cells was significantly increased （<italic>P</italic><0.01）. Compared with the Adr group， the half-inhibitory concentration （IC₅₀） of TNS （25， 50， 100 mg·L^-1） and Adr （20 μmol·L^-1） co-administration group on HepG2/Adr cells <italic>in vitro</italic> significantly reduced （<italic>P</italic><0.01）， and the highest reversal multiple was 10 times. Compared with the Adr group， the co-administration group could significantly increase the accumulation of Adr in the cells （<italic>P</italic><0.05） in a dose-dependent manner. Compared with the blank group， the co-administration group could significantly reduce MDR1， ABC semitransporter （ABCG2）， multidrug resistance associated protein （MRP1）， ERK， phosphorylated extracellular regulatory protein kinase （p-ERK）， Akt， phosphorylated protein kinase B （p-Akt）， mammals， rapamycin target protein （mTOR） and phosphorylated mammalian rapamycin target protein （p-mTOR） （<italic>P</italic><0.05）， with the same results in the doxorubicin group. Compared with the blank group， there was no significant difference in the distribution and fluorescence intensity of MDR1 on the cell membrane between the Adr group and the notoginseng total saponins （25 mg·L^-1） group. Compared with the blank group and the doxorubicin group， TNS could significantly reduce the distribution of MDR1 on the cell membrane （<italic>P</italic><0.05）. Conclusion:TNS can inhibit the ERK/Akt pathway， reduce the expression of MDR1， and significantly increase the accumulation of doxorubicin in HepG2/Adr cells， which may be one of the mechanisms of notoginseng total saponins in reversing resistance.

Study on rat small intestinal absorption characteristics of gallic acid based on single-pass perfusion model / 中国药理学通报

Aim To investigate the absorption characteristics of gallic acid in the intestine, and to provide a theoretical basis for improving the bioavailability of tannins. Methods Single-pass intestinal perfusion (SPIP) model was used for rat in situ and HPLC to determine the concentration of gallic acid. The absorption rate constant Ka and effective apparent permeability coefficient Peff of gallic acid in each intestinal segment were calculated. The effects of different intestinal segments, drug concentrations, pH value, P-glycoprotein (P-gp), and multidrug resistance protein2 (MRP2) on intestinal absorption were assessed. Results The absorption rate constant (Ka) of gallic acid decreased following the sequence of jejunum > duodenum > ileum ≈ colon. With the increase of drug concentration, there was no significant difference in the absorption of gallic acid. The acidic environment (pH 5. 5) was conducive to the absorption of gallic acid. After the addition of P-gp and MRP2 inhibitors, the absorption of gallic acid was significantly different from that without P-gp and MRP2 inhibitors (P < 0. 05). Conclusions Gallic acid can be well absorbed in the intestine of rats, and is best absorbed in jejunum. The absorption mechanism is determined to be passive diffusion. The gallic acid absorption process is affected by the efflux of P-gp and MRP2, which may be the P-gp and MRP2 substrates.

Effects of verapamil on pharmacokinetics of Y101 in vivo in rats / 中国药理学通报

Aim To develop a liquid chromatography electrospray-ionization tandem mass spectrometry (LC- MS/MS) method for simultaneous determination of bentysrepinine (Y101) and its metabolites M8 and M9 in rat plasma and to investigate the effect of verapamil, an inhibitor of P-glycoprotein (P-gp) , on the pharma¬cokinetics of Y101, a substrate of P-gp, in rats. Methods SD rats were divided randomly into two groups; ( 1) Y101 only as a control group, received an oral dose of 60 mg • kg"1 Y101; (2) Verapamil plus Y101 as an experimental group, received an oral dose of 60 mg • kg"1 Y101 in combination of 25 mg • kg"1 verapamil. The plasma concentrations of Y101 and its metabolites were determined by LC-MS/MS method af¬ter intragastric administration, and the pharmacokinetic parameters were calculated using non-compartmental a- nalysis. Results We successfully developed and fully validated a LC-MS/MS method, which simultaneously determined the concentration of Y101 and its metabo¬lites in rat plasma. The AUC0_t for Y101 and M9 in experimental group increased to 1.71-fold and 1.58- fold in comparison of control group. At the same time, the plasma clearance of Y101 and M9 decreased to 60% of control. However, we did not find any differ¬ence in AUC0_l and plasma clearance for M8 between two groups. Conclusions The validated LC-MS/MS method is sensitive and rapid for the determination of Y101 and its metabolites in rat plasma and was suc¬cessfully applied to the pharmacokinetic study in rats. Verapamil, a P-gp inhibitor, significantly increases the exposure of Y101 and its metabolites in vivo, indicating the adjustment of Y101 dosage for combined adminis¬tration is needed in clinical practice.

Intestinal absorption characteristics of Polygonum orientale extract in normal and isoproterenol-induced myocardial ischemia model rats via everted intestinal sac models / 中国中药杂志

The present study is to investigate the absorption characteristics of the main components in Polygonum orientale extract in normal and isoproterenol-induced myocardial ischemia model rats with everted intestinal sac models. Intestinal sac fluid samples were collected in different part of intestine(duodenum, jejunum, ileum, colon) at different time after administration of different concentration of P. orientale extract(5.0,10.0, 20.0 mg·mL~(-1)). An UPLC-TQD method was employed for the determination of six components including orientin, isoorientin, vitexin, protocatechuic acid, kaempferol-3-O-β-D-glucoside and quercitrin in the intestinal sac samples. The absorption rate and cumulative absorption were calculated to analyze the intestinal absorption characteristics of six components in normal and myocardial ischemia model rats. The P-glycoprotein(P-gp) inhibitor was applied to investigate influence of intestinal absorption of six components in P. orientale extract. The results showed that the main absorption sites were concentrated on the duodenum at low concentration, while they were the colon at the medium concentration and the ileum at high concentration in control groups. In the condition of myocardial ischemia model, the main absorption sites focus on the ileum and jejunum at low concentration; the main absorption sites were in the ileum at the medium concentration and main absorption sites were the duodenum and ileum at high concentration. Compared with the normal group, the absorption rate and cumulative absorption of the six components significantly decreased in the model group. P-gp inhibitor markedly increased the absorption rate and cumulative absorption of six components in the model group, inferring that the 6 components may be the substrates of P-gp, and the mechanism needs further study. In this study, it is revealed that the six components of P. orientale extract can be absorbed into the intestinal sac, and it is an effective method to assess the intestinal absorption characteristics of P. orientale extract through everted intestinal sac model, providing data support for the clinical application and further development of P. orientale.

Sensitization of hepatocellular carcinoma cells towards doxorubicin and sorafenib is facilitated by glucosedependent alterations in reactive oxygen species, P-glycoprotein and DKK4

Altered glucose uptake and metabolism is the key characteristic of cancer cells including hepatocellularcarcinoma (HCC). However, role of glucose availability in chemotherapeutic outcome of HCC is unclear. Thepresent study investigates the effect of glucose facilitated sensitization of HCC cells towards doxorubicin(DOX) and sorafenib (SORA). In HCC cells, we observed that hyperglycemic culture condition (HG) isassociated with increased sensitivity towards DOX and SORA. P-glycoprotein (P-gp), a transporter involved indrug efflux, was elevated in HCC cells in NG, rendering them less susceptible to DOX and SORA. Further, thisstudy demonstrated that knockdown of dickkopf protein 4 (DKK4), a Wnt antagonist protein, causes enhancedglucose uptake and reduction in P-gp level rendering HCC cells in NG sensitive to DOX and SORA.Moreover, HG elevates the level of intracellular reactive oxygen species (ROS), which regulates P-gp.Alteration in intracellular ROS did not directly affect regulation of DKK4 in HCC cells. Functional assayssuggest that alterations in DKK4 and P-gp level in HCC cells are dependent on glucose availability andchanges in ROS level because of enhanced glucose utilization, respectively. Collectively, the present studyhighlights direct involvement of glucose-induced ROS, DKK4 and P-gp in altering the sensitivity of HCC cellstowards DOX and SORA.

Effects of vitamin C on reversing cisplatin resistance in oral squamous cell carcinoma / 中国肿瘤生物治疗杂志

@#Objective: To study the effects of vitamin C (VC) on reversing cisplatin (DDP) resistance in oral squamous cell carcinoma (OSCC) and the mechanism. Methods: Human OSCC CAL27 cells were cultured in vitro and DDP-resistant CAL27 cell line (CAL27/ DDP) was screened by increasing concentration gradient method. Plate clone formation assay, CCK-8, Wound healing assay, Annexin V-FITC/PI staining flow cytometry were used to determine the effects of DDP alone or in combination with VC on colony formation, proliferation, migration and apoptosis of CAL27/DDP cells. Western blotting was used to detect the expression level of P-gp protein in CAL27 cells, CAL27/DDP cells and VC treated CAL27/DDP cells. Results: The inhibition concentration (IC50) of DDP increased significantly in CAL27/DDP cells as compared with that in CAL27 cells (P<0.05), indicating CAL27/DDP was DDP-resistant.After the combination with VC, the IC50 of DDP on CAL27/DDP cells was significantly reduced compared with that of DDP alone (P<0.05). DDP combined with VC significantly inhibited the migration of CAL27/DDP cells (P<0.01), and promoted the apoptosis rate (P<0.01). The expression level of P-gp protein in CAL27/DDP cells was increased compared with that in CAL27 cells (P<0.05), but decreased after VC intervention (P<0.05). Conclusion: VC can reverse DDP-resistance in OSCC cells by inhibiting P-gp protein expression.

Effects and mechanism of Ligusticum chuanxiong volatile oil in combination with temozolomide in treatment of glioma by regulating P-gp protein / 中草药

Objective: To investigate the anti-tumor effect of Ligusticum chuanxiong volatile oil in combination with temozolomide (TMZ) in the treatment of glioma, and illuminate its possible mechanism. Methods: After C6 glioma animal model was successfully finished, changes of body weight, survival status, tumor volume, and the tumor inhibition rate of rats were detected in the TMZ group and the compatibility group of the volatile oil of L. chuanxiong and TMZ. The concentration of TMZ in the internal and external fluids of U87-MG cells was measured by HPLC after the administration of TMZ and the combination of volatile oil of L. chuanxiong and TMZ, and the differences of the content were analyzed statistically. Western blotting was used to study the effects of TMZ monotherapy, L. chuanxiong volatile oil and TMZ on the expression of P-gp protein of U87-MG cells.Results: Compared with TMZ group, the tumor volume of rats in the compatibility group was significantly decreased (P < 0.05), which was positively correlated with the amount of volatile oil. At the same time, the weight gain of the rats in the compatibility group was increased and the survival status was better. Volatile oil of L. chuanxiong can promote the entry of TMZ into U87-MG cells, and with the increase concentration of volatile oil, the promoting effect was stronger. Volatile oil at 6.25 × 10-3 μL/mL can significantly increase the accumulation of TMZ in the internal fluid (P < 0.05). Western blotting analysis showed that P-gp expressions of cells treated with combination treatment with TMZ (20 μg/mL) and volatile oil [(3.125 × 10-3), (6.25 × 10-3) μL/mL] were markedly down-regulated (P < 0.01), when compared with TMZ group. Conclusion: The volatile oil of L. chuanxiong can promote TMZ entry into glioma cells and then enhance TMZ-induced anticancer efficiency in vivo by inhibiting P-gp expression.

Role of kaempferol to increase bioavailability and pharmacokinetics of nifedipine in rats / 中国天然药物

Herein, the purpose of this study is to evaluate the effects of kaempferol on bioavailability and pharmacokinetics of nifedipine and its metabolite dehydronifedipine in rats. The experimental design is based on with or without kaempferol in the oral and intravenous administration of nifedipine in rats. Moreover, the pharmacokinetic parameters including nifedipine and dehydronifedipine were evaluated in rats.The in vitro studies ofkaempferol were investigated on P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 activity. Kaempferol reduced a 50% inhibitory concentration (IC) of 8.6 μmol·L on CYP3A4 enzyme activity. Moreover, kaempferol clearly improved the cell internalization of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp. Depending on increased concentrations of kaempferol, the areas under the plasma concentration-time curve (AUC) and the peak concentration (C) of nifedipine were increased after oral and intravenous administration. Moreover, the absolute bioavailability (AB) and relative bioavailability (RB) of nifedipine in the presence of kaempferol was significantly higher than those of the control group after oral and intravenous administration. Improvement of bioavailability of nifedipine by kaempferol may be mainly because of the inhibition of the P-gp-mediated efflux transporter in the small intestine and CYP3A4-mediated metabolism in the small intestine or liver, or both.

Curcumin Reverses 5-Fluorouracil Resistance by Promoting Human Colon Cancer HCT-8/5-FU Cell Apoptosis and Down-regulating Heat Shock Protein 27 and P-Glycoprotein / 中国结合医学杂志

OBJECTIVE@#To investigate the potential mechanisms that curcumin reverses 5-fluorouracil (5-FU) multidrug resistance (MDR).@*METHODS@#Cell growth and the inhibitory rate of curcumin (2-25 μg/mL) and/or 5-FU (0.05-1000 μg/mL) on human colon cancer HCT-8 and HCT-8/5-FU (5-FU-resistant cell line) were determined using cell counting kit-8 (CCK-8) assay. Apoptosis and cell cycle after 5-FU and/or curcumin treatment were detected by flow cytometry (FCM) and transmission electron microscopy (TEM). The expression of the multidrug resistance related factors p-glycoprotein (P-gp) and heat shock protein 27 (HSP-27) genes and proteins were analyzed by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting (WB), respectively.@*RESULTS@#The inhibitory rate of curcumin or 5-FU on HCT-8 and HCT-8/5-FU cells proliferation at exponential phase were in a dosedependent manner, HCT-8 cell line was more sensitive to curcumin or 5-FU when compared the inhibitory rate of HCT-8/5-FU. The 50% inhibitory concentration (IC) of combination 5-FU and curcumin (4.0 μg/mL) in HCT-8/5-FU was calculated as 179.26 μg/mL, with reversal fold of 1.85. Another IC of combination 5-FU and curcumin (5.5 μg/mL) in HCT-8/5-FU was calculated as 89.25 μg/mL, with reversal fold of 3.71. Synergistic effect of 5-FU and curcumin on HCT-8 and HCT-8/5-FU cells were found. The cell cycle analysis performed by FCM showed that HCT-8 and HCT-8/5-FU cells mostly accumulated at G/G phase, which suggested a synergistic effect of curcumin and 5-FU to induce apoptosis. FCM analysis found that the percentage of apoptosis of cells treated with curcumin, 5-FU and their combination were significantly increased compared to the control group (P<0.05), and the percentage of apoptosis of the combination groups were slightly higher than other groups (P<0.05). The mRNA levels of P-gp (0.28±0.02) and HSP-27 (0.28±0.09) in HCT-8/5-FU cells treated with combination drugs were lower than cells treated with 5-FU alone (P-gp, 0.48±0.07, P=0.009; HSP-27, 0.57±0.10, P=0.007). The protein levels of P-gp (0.25±0.06) and HSP-27 (0.09±0.02) in HCT-8/5-FU cells treated with combination drugs were decreased when compared to 5-FU alone (P-gp, 0.46±0.02, P=0.005; HSP-27, 0.43±0.01, P=0.000).@*CONCLUSIONS@#Curcumin can inhibit the proliferation of human colon cancer cells. Curcumin has the ability of reversal effects on the multidrug resistance of human colon cancer cells lines HCT-8/5-FU. Down-regulation of P-gp and HSP-27 may be the mechanism of curcumin reversing the drug resistance of HCT-8/5-FU to 5-FU.

The epigallocatechin gallate derivative Y reverses drug resistance mediated by the ABCB1 transporter both and

Previously, we reported that Y, a new epigallocatechin gallate derivative, is efficacious in reversing doxorubicin (DOX)--mediated resistance in hepatocellular carcinoma BEL-7404/DOX cells. In this study, we evaluated the efficacy of Y in reversing drug resistance both and by determining its effect on the adenosine triphosphate-binding cassette protein B1 transporter (ABCB1 or P-glycoprotein, P-gp). Our results showed that Y significantly sensitized cells overexpressing the ABCB1 transporter to anticancer drugs that are ABCB1 substrates. Y significantly stimulated the adenosine triphosphatase activity of ABCB1. Furthermore, Y exhibited a higher docking score as compared with epigallocatechin gallate inside the transmembrane domain of ABCB1. In addition, in the nude mouse tumor xenograft model, Y (110 mg/kg, intragastric administration), in combination with doxorubicin (2 mg/kg, intraperitoneal injection), significantly inhibited the growth of BEL-7404/DOX cell xenograft tumors, compared to equivalent epigallocatechin gallate. In conclusion, Y significantly reversed ABCB1-mediated multidrug resistance and its mechanisms of action may result from its competitive inhibition of the ABCB1 drug efflux function.

Overcoming chemotherapy resistance simultaneous drug-efflux circumvention and mitochondrial targeting

Multidrug resistance (MDR) has been considered as a huge challenge to the effective chemotherapy. Therefore, it is necessary to develop new strategies to effectively overcome MDR. Here, based on the previous research of -(2-hydroxypropyl)methacrylamide (HPMA) polymer-drug conjugates, we designed an effective system that combined drug-efflux circumvention and mitochondria targeting of anticancer drug doxorubicin (Dox). Briefly, Dox was modified with mitochondrial membrane penetrating peptide (MPP) and then attached to (HPMA) copolymers (P-M-Dox). Our study showed that macromolecular HPMA copolymers successfully bypassed drug efflux pumps and escorted Dox into resistant MCF-7/ADR cells endocytic pathway. Subsequently, the mitochondria accumulation of drugs was significantly enhanced with 11.6-fold increase by MPP modification. The excellent mitochondria targeting then resulted in significant enhancement of reactive oxygen species (ROS) as well as reduction of adenosine triphosphate (ATP) production, which could further inhibit drug efflux and resistant cancer cell growth. By reversing Dox resistance, P-M-Dox achieved much better suppression in the growth of 3D MCF-7/ADR tumor spheroids compared with free Dox. Hence, our study provides a promising approach to treat drug-resistant cancer through simultaneous drug efflux circumvention and direct mitochondria delivery.

Combination of tetrandrine and paclitaxel overcomes multidrug resistance on C6/MDR glioma cells / 中草药

Objective To investigate the feasibility of tetrandrine combined with paclitaxel (PTX) in multidrug resistance reversal on C6/MDR glioma cells, and explore the potential molecular mechanisms. Methods Through the comparison of non-resistant glioma C6 cells and drug-resistant glioma C6/MDR cells, the cytotoxicity of against C6/MDR (or C6) cells were assayed by MTT method. The intracellular accumulation of PTX and Rhodamine 123 (R123) were determined by high performance liquid chromatography (HPLC) and flow cytometry, respectively. The cell apoptosis induction of C6/MDR (or C6) cells was detected by AnnexinV-PE/7-AAD staining method after various intervention of PTX, tetrandrine, and PTX + HfA. P-glycoprotein (P-gp) expression and P-gp ATPase activity were evaluated through P-gp antibody binding assay kit and Pgp-GloTM assay systems, respectively. Results The half maximal inhibitory concentration (IC50) of tetrandrine + PTX against C6/MDR cells were (5.88 ± 0.43) nmol/L. The C6/MDR intracellular accumulation of PTX and R123 were increased by 9.4-fold and 12.3-fold in the presence of 10 μmol/L tetrandrine. Accordingly, the apoptosis rate of C6/MDR cells treated with tetrandrine + PTX was 2.3-fold higher than PTX treatment. The tetrandrine-mediated multidrug resistance reversal was involved with the downregulation of P-gp expression and the stimulation of P-gp ATPase activity. Conclusion The combination of tetrandrine and PTX had a potential of overcoming multidrug resistance on C6/MDR glioma cells in vitro.

Effect of six bioactive lignans of Wuzhi tablet (Schisandra sphenanthera extract) on P-glycoprotein and its herb-drug interaction with digoxin / 药学学报

This study was aimed to investigate the effects of six Schisandra lignans of Wuzhi tablet (WZ, a preparation of ethanol extract of Schisandra sphenanthera) on the pharmacokinetic process of digoxin (DG, a classical P-gp substrate) after intravenous and oral administration in rats. The effect of Schisandra lignans on the transportion of DG in Caco-2 cells was further elucidated. Our data showed that the plasma concentrations of DG were increased to different extent following co-administration of schisandrin A, schisandrin B, schisandrol B and schisantherin A, respectively. Schisandrol B showed the most potent effect among the six lignans. However, schisandrin C and schisandrol A showed little effect on pharmacokinetic of DG. Schisandrol B led to 99.0% (P < 0.05) and 109.2% (P < 0.05) increase in the AUC after orally or intravenously administered of DG, suggesting that co-administration of schisandrol B induced a more potent effect on increasing hepatic bioavailability of DG than that of intestinal. Furthermore, in vitro transport experiment showed that schisandrin A, schisandrin B, schisandrol B and schisantherin A inhibited P-gp-mediated efflux of DG, suggested that these lignans inhibited the P-gp-mediated efflux of DG. In conclusion, the exposure of DG in rats was increased when co-administered with Schisandra lignans, and schisandrol B showed the strongest effect. The dramatic increase in oral bioavailability of digoxin in the presence of schisandrol B may be due to the inhibition of hepatic/renal P-gp activity.

Transport characteristics of Shuxiong prescription across Caco-2 cell monolayer model / 中国中药杂志

Shuxiong prescription (Notoginseng Radix et Rhizoma, Chuanxiong Rhizome and Carthami Flos) has the function of activating blood circulation to dissipate blood stasis, activating meridians to stop pain. This paper was mainly aimed to discuss the transport characteristics of Shuxiong prescription across Caco-2 cell monolayer. Safe concentration range of Shuxiong prescription against Caco-2 cell monolayer model was determined by MTT assay. The mechanism of Shuxiong prescription bidirectional transport was investigated by Caco-2 cell monolayer model. The apparent permeability coefficient Papp of digoxin was determined by high performance liquid chromatography (HPLC). The test results showed that the Papp of extract from Notoginseng Radix et Rhizoma, Chuanxiong Rhizome, Carthami Flos, Chuanxiong Rhizome+Carthami Flos and Shuxiong prescription transport from apical (AP) side to basolateral (BL) side was (3.12±0.73)×10⁻⁶, (2.58±0.41)×10⁻⁶, (4.97±0.64)×10⁻⁶, (4.63±0.57)×10⁻⁶, (5.79±0.68)×10⁻⁶ cm·s⁻¹, respectively, indicating that the transport of digoxin across Caco-2 cell monolayer model was active absorption, and the P-gp protein took part in the process. Chuanxiong Rhizome could significantly decrease the transport of digoxin from BL→AP(<0.01) and increase its transport from AP→BL(<0.05) significantiy. After the addition of Shuxiong prescription, the transport of digoxin from BL→AP was significantly inhibited(<0.01). The results suggested that the extract of safflower had no effect on P-gp transport, nor on the independence diffusion of digoxin. The transport of digoxin could be degraded by the extract of Chuanxiong Rhizome and the extract of Shuxiong prescription from BL→AP(<0.01), significantly; pseudo-ginseng had no effect on the independence diffusion of digoxin; the extract of safflower+Chuanxiong Rhizome had the same experimental result as Chuanxiong Rhizome extract.

Mechanism of Berberine in the Regulation of CYP3A4 and P-gp via PXR Signaling Pathway / 中国药师

Objective: To investigate the regulation of CYP3A4 and P-gp by berberine hydrochloride ( BBR) via pregnane X re-ceptor (PXR) pathway. Methods: pLKO. 1-PXR vector, a lentivirus plasmid expressing PXR shRNA, was packaged into 293T cells. Human hepatoma (HepG2) cells were infected with the lentivirus and the cell clones stably expressing PXR shRNA were selected by puromycin according to pLKO. 1 vector characteristics. Real-time RT-PCR and Western blot were used to evaluate CYP3A4 and P-gp mRNA and protein in berberine treated HepG2 cells and PXR-silenced HepG2 cells. Results: The PXR expression in PXR silenced cells significantly decreased (P<0.01) when compared with that in HepG2 cells, while there was no significant difference (P >0. 05) in the expression of CYP3A4 and P-gp between the groups. Compared with that in HepG2 cells, the inhibition of berberine on the mRNA and protein expression of CYP3A4 and P-gp in PXR-silenced HepG2 cells was weakened (P<0. 05 or P<0. 01). Conclu-sion: Berberine can regulate the expression of CYP3A4 and P-gp via PXR signaling pathway, while it is not the only one.

Synthesis and tumor resistance reverse activities ofα-hederagenin-type ring-A fused pyrazine derivatives / 中国药理学与毒理学杂志

α-Hederagenin (H), derived from Hedera nepalensis var.sinensis, is a pentacyclic oleane-type triterpenoid that exhibits clear cytotoxicity to different tumor cell lines.In this study,a series of novel C-28 derivatives of hederagenin (H) were designed and synthesized in attempt to develop potent tumor resistance reverse activities agents. Previous research showed that H6 displayed robust reverse activity for paclitaxel resistance in KBV cells. Importantly, Co-treatment of paclitaxel with H6 significantly reduced the tumor weight to 42%. Pleasingly, H6 enhanced the efficacy of paclitaxel against KBV cancer cell-derived xenograft tumors in nude mice.Mechanism studies had found that H6 activated permeability glycoprotein(P-gp)ATPase,reduced intracellular ATP levels and inhibited efflux of P-gp substrates,thus enhancing the antitumor activity of paclitaxel on KBV cells.Molecular docking analysis of homology P-gp and H6 then conducted using the Surflex-Dock module.H6 showed a high binding affinity docking score with a total score of 5.4148,much higher than that of H(0.1414).The nov-el C-28 derivatives of H was synthesized from H6 via three-step reaction. The reversal activity of all synthesized H derivatives were tested using the MTT assay.The results showed that the derivatives of nitrogen groups at C-28 displayed same even potent activity than parent compound H6.In addition,its underlying mechanism of action and in vivo activity are in explore.