P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) family of transporters, plays a crucial role in the development of multi-drug resistance (MDR) in cancer treatment. P-gp actively pumps chemotherapeuti...P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) family of transporters, plays a crucial role in the development of multi-drug resistance (MDR) in cancer treatment. P-gp actively pumps chemotherapeutic drugs out of cancer cells, reducing their intracellular concentrations and thereby diminishing their efficacy. This review explores the mechanisms by which P-gp contributes to MDR, including intrinsic and acquired resistance. It also discusses various strategies to inhibit P-gp, such as blocking drug binding sites, interfering with ATP hydrolysis, and altering cell membrane integrity. The potential of fourth-generation P-gp inhibitors and other novel approaches to enhance the effectiveness of cancer therapies is also examined. Understanding and overcoming P-gp-mediated MDR is essential for improving therapeutic outcomes in cancer patients.展开更多
介绍了一个新的基于优化推导出的核偏最小二乘(kernel partial least squares,K-PLS)的算法原理和实现步骤,并且给出了利用K-PLS法构建P-糖蛋白(P-glycoprotein,P-gp)黄酮类抑制剂的定量构效关系(QSAR)模型.利用该方法结合几个简单的分...介绍了一个新的基于优化推导出的核偏最小二乘(kernel partial least squares,K-PLS)的算法原理和实现步骤,并且给出了利用K-PLS法构建P-糖蛋白(P-glycoprotein,P-gp)黄酮类抑制剂的定量构效关系(QSAR)模型.利用该方法结合几个简单的分子拓扑参数,构建了具有高准确率的预测模型.该模型将有助于P-gp黄酮类抑制剂的虚拟筛选和理性设计.结果证明K-PLS是一个十分稳定可靠的方法,将会在化学计量学领域得到较好的应用和推广.展开更多
肿瘤多药耐药性(multiple drug resistance,MDR)的发生往往伴随着多药耐药基因如MDR1、MRP1和BCRP等高表达,其中MDR1基因编码的P-糖蛋白(P-glycoprotein,P-gp)是目前公认可以诱发癌细胞发生MDR的重要分子。传统研究认为P-gp主要是作为...肿瘤多药耐药性(multiple drug resistance,MDR)的发生往往伴随着多药耐药基因如MDR1、MRP1和BCRP等高表达,其中MDR1基因编码的P-糖蛋白(P-glycoprotein,P-gp)是目前公认可以诱发癌细胞发生MDR的重要分子。传统研究认为P-gp主要是作为一个药物泵将化疗药物从细胞内排出从而导致MDR。然而系列研究发现,除了介导MDR以外,P-gp还能够调节癌细胞的生长、增殖、凋亡、迁移和侵袭等其他生物学行为;而且研究表明P-gp的这些作用可以依赖,也可以不依赖于其药物泵的功能。这些结果表明P-gp能够通过一些新的机制促进肿瘤的进展。本文主要针对P-gp在促进肿瘤进展中的作用进行综述。展开更多
To study the effect of the different interventional treatment on P Glycoprotein (Pgp) in different histopathological types of primary hepatocellular carcinoma (PHC), 98 surgically and histologically verified PHC spec...To study the effect of the different interventional treatment on P Glycoprotein (Pgp) in different histopathological types of primary hepatocellular carcinoma (PHC), 98 surgically and histologically verified PHC specimens were obtained. The patients included 57 patients treated by surgical resection alone and 41 patients receiving second stage surgical resection after four kinds of interventional treatment. SABC immunohistochemical staining with a monoclonal antibody against human Pgp was used to observe the Pgp in all specimens. The positive rate of Pgp was 100 % in group of chemotherapy alone ( P <0.05), 62.5 % in group of chemotherapy combined with iodized oil ( P >0.05), 46.6 % in group of chemotherapy combined with iodized oil and spongia gelatini absorbens (Sga) ( P >0.05), 18.18 % in group of chemotherapy combined with Ethanol iodized oil and Sga ( P <0.05) and 52.63 % in group of surgical resection alone. The positive rate of Pgp varied with different histopathological types, with rate of clear cell PHC being the lowest, and that of poorly differentiated or undifferentiated PHC the highest. The positive rate of Pgp was increased as pathological grades increased. Overexpression of Pgp may be responsible for the intrinsic and acquired drug resistance of PHC. Multidrug resistance (MDR) varied with different histological types. Therapy of PHC should be tailored according to individual. Local chemotherapy combined with ethanol iodized oil and Sga embolization may become a new way to overcome MDR of PHC.展开更多
INTRODUCTIONMost advanced hepatocellular garcinoma (HCC) isinsensitive to most anticancer drugs which might berelated to the high frequency of expression of themultidrug resistance-1(MDR1) gene and itsproduct,P-glycop...INTRODUCTIONMost advanced hepatocellular garcinoma (HCC) isinsensitive to most anticancer drugs which might berelated to the high frequency of expression of themultidrug resistance-1(MDR1) gene and itsproduct,P-glycoprotein (p-gp).p-gp expressionmay also be concerned with tumor progression anddifferentiation.In the present study。展开更多
BACKGROUND:Multidrug resistance(MDR)is extremely common in hepatocellular carcinoma(HCC)and is a major problem in cancer eradication by limiting the efficacy of chemotherapy.Modulation of c-Jun NH2-terminal kinase(JNK...BACKGROUND:Multidrug resistance(MDR)is extremely common in hepatocellular carcinoma(HCC)and is a major problem in cancer eradication by limiting the efficacy of chemotherapy.Modulation of c-Jun NH2-terminal kinase(JNK)activation could be a new method to reverse MDR.However,the relationship between JNK activity and MDR in HCC cells is unknown.This study aimed to explore the relationship between MDR and JNK in HCC cell lines with different degrees of MDR.METHODS:A MDR human HCC cell line,SMMC-7721/ ADM,was developed by exposing parental cells to gradually increasing concentrations of adriamycin.The MTT assay was used to determine drug sensitivity.Flow cytometry was used to analyze the cell cycle distribution and to measure the expression levels of P-glycoprotein(P-gp)and MDR-related protein(MRP)-1 in these cells.JNK1,JNK2 and JNK3 mRNA expression levels were quantified by real-time PCR.Expression and phosphorylation of JNK1,JNK2,and JNK3 were analyzed by Western blotting.RESULTS:The MDR of SMMC-7721/ADM cells resistant to 0.05 mg/L adriamycin was mainly attributed to the overexpression of P-gp but not MRP1.In addition,these cells had a significant increase in percentage in the S phase,accompanied by a decrease in percentage in the G0/G1 phase,which is likely associated with a reduced ability for cell proliferation and MDR generation.We found that JNK1,JNK2,and JNK3 activities were negatively correlated with the degree of MDR in HCC cells.CONCLUSION:This study suggests that JNK1,JNK2,and JNK3 activities are negatively correlated with the degree of MDR in HCC cells.展开更多
Imatinib,a breakpoint cluster region(BCR)-Abelson murine leukemia(ABL) tyrosine kinase inhibitor(TKI),has revolutionized the treatment of chronic myelogenous leukemia(CML).However,development of multidrug resistance(M...Imatinib,a breakpoint cluster region(BCR)-Abelson murine leukemia(ABL) tyrosine kinase inhibitor(TKI),has revolutionized the treatment of chronic myelogenous leukemia(CML).However,development of multidrug resistance(MDR) limits the use of imatinib.In the present study,we aimed to investigate the mechanisms of cellular resistance to imatinib in CML.Therefore,we established an imatinib-resistant human CML cell line(K562-imatinib) through a stepwise selection process.While characterizing the phenotype of these cells,we found that K562-imatinib cells were 124.6-fold more resistant to imatinib than parental K562 cells.In addition,these cells were cross-resistant to second-and third-generation BCR-ABL TKIs.Western blot analysis and reverse transcription-polymerase chain reaction(RT-PCR) demonstrated that P-glycoprotein(P-gp) and MDR1 mRNA levels were increased in K562-imatinib cells.In addition,accumulation of [14C]6-mercaptopurine(6-MP) was decreased,whereas the ATP-dependent efflux of [14C]6-MP and [3H]methotrexate transport were increased in K562-imatinib cells.These data suggest that the overexpression of P-gp may play a crucial role in acquired resistance to imatinib in CML K562-imatinib cells.展开更多
The main purpose of treatment of rheumatoid arthritis(RA) with disease modifying antirheumatic drugs(DMARDs) is to control activation of lymphocytes,although some patients do not respond adequately to such treatment. ...The main purpose of treatment of rheumatoid arthritis(RA) with disease modifying antirheumatic drugs(DMARDs) is to control activation of lymphocytes,although some patients do not respond adequately to such treatment. Among various mechanisms of multidrug resistance, P-glycoprotein(P-gp), a member of ATP-binding cassette transporters, causes drugresistance by efflux of intracellular drugs. Certain stimuli,such as tumor necrosis factor-α, activate lymphocytes and induce P-gp expression on lymphocytes, as evident in active RA. Studies from our laboratories showed spontaneous nuclear accumulation of human Y-boxbinding protein-1, a multidrug resistance 1 transcription factor, in unstimulated lymphocytes, and surface overexpression of P-gp on peripheral lymphocytes of RA patients with high disease activity. The significant correlation between P-gp expression level and RA disease activity is associated with active efflux of drugs from the lymphocyte cytoplasm and in drugresistance.However, the use of biological agents that reduce P-gp expression as well as P-gp antagonists(e.g., cyclosporine) can successfully reduce the efflux of corticosteroids from lymphocytes in vitro, suggesting that both types of drugs can be used to overcome drug-resistance and improve clinical outcome. We conclude that lymphocytes activated by various stimuli in RA patients with highly active disease acquire P-gpmediated multidrug resistance against corticosteroids and probably some DMARDs, which are substrates of P-gp. Inhibition/reduction of P-gp could overcome such drug resistance. Expression of P-gp on lymphocytes is a promising marker of drug resistance and a suitable therapeutic target to prevent drug resistance in patients with active RA.展开更多
AIM： To investigate the role of oxidative stress in regulating the functional expression of P-glycoprotein（P-gp） in mitochondria of D407 cells.METHODS： D407 cells were exposed to different ranges of concentrations...AIM： To investigate the role of oxidative stress in regulating the functional expression of P-glycoprotein（P-gp） in mitochondria of D407 cells.METHODS： D407 cells were exposed to different ranges of concentrations of H2O2. The mitochondrial location of P-gp in the cells subjected to oxidative stress was detected by confocal analysis. Expression of P-gp in isolated mitochondria was assessed by Western blot. The pump activity of P-gp was evaluated by performing the efflux study on isolated mitochondria with Rhodamine 123（Rho-123） alone and in the presence of P-gp inhibitor（Tariquidar） using flow cytometry analysis. The cells were pretreated with 10 mmol/L N-acetylcysteine（NAC） for 30 min before exposing to H2O2, and analyzed the mitochondrial extracts by Western blot and flow cytometry.RESULTS： P-gp was co-localized in the mitochondria by confocal laser scanning microscopy, and it was also detected in the mitochondria of D407 cells using Western blot. Exposure to increasing concentrations of H2O2 led to gradually increased expression and location of P-gp in the mitochondria of cells. Rho-123 efflux assay showed higher uptake of Rho-123 on isolated mitochondria in the presence of Tariquidar both in normal and oxidative stress state. H2O2 up-regulated P-gp in D407 cells, which could be reversed by NAC treatment. CONCLUSION： H2O2 could up-regulate the functional expression of P-gp in mitochondria of D407 cells, while antioxidants might suppress oxidative-stress-induced over-expression of functional P-gp. It is indicative that limiting the mitochondrial P-gp transport in retinal pigment epithelium cells would be to improve the effect of mitochondria-targeted antioxidant therapy in age-related macular degeneration-like retinopathy.展开更多
Epileptic seizures induce overexpression of P-glycoprotein in the blood-brain barrier. However, it is unclear whether hippocampal neurons also overexpress P-glycoprotein following seizure. This study confirmed that th...Epileptic seizures induce overexpression of P-glycoprotein in the blood-brain barrier. However, it is unclear whether hippocampal neurons also overexpress P-glycoprotein following seizure. This study confirmed that the clinical manifestation, pathological characteristics and electroencephalography in the rat model of lithium-pilocarpine-induced mesial temporal lobe epilepsy were consistent with clinical reports of mesial temporal lobe epilepsy in humans.Immunohistochemistry staining demonstrated that P-glycoprotein positive staining was found in neurons in the pyramidal layer of the hippocampus. Westem blot assay and real-time polymerase chain reaction revealed that P-glycoprotein overexpression was exhibited in the CA1, CA3, and dentate gyrus of the hippocampus at 24 and 60 days following model induction, but no significant dffierence was detected in the same region at various time points. These results indicate that seizures led to overexpression of P-glycoprotein in neurons of the hippocampus, but no evidence was found for a positive association between P-glycoprotein expression and seizure frequency.展开更多
Objective： To investigate the expression of MDR-1 P-glycoprotein（MDR-1 Pgp） in breast cancer and analyze its correlation to the biological behavior and prognosis of the disease. Methods：The expression of MDR-1 Pgp...Objective： To investigate the expression of MDR-1 P-glycoprotein（MDR-1 Pgp） in breast cancer and analyze its correlation to the biological behavior and prognosis of the disease. Methods：The expression of MDR-1 Pgp was examined in 75 cases of breast cancer patients by using three different monoclonal antibodies（JSB1, C219 and C494） with S-P immunohistochemisty. These patients were followed up for 5 years, and the correlation between MDR-1 Pgp expression, survival rate and lymph metastasis was analyzed. Results： Positive detection of MDR-1 Pgp by JSB1, C219 and C494 in 75 cases of breast cancer was 86.7%, 48% and 85.3%, respectively. MDR-1 Pgp expression was not related to ages of patients （P 〉 0.05）. JSBl-detected expression of MDR-1 Pgp was related to lymph node metastasis（P〈 0.05）; while C219 and C494 were not（P 〉 0.05）. The patients with MDR-1 Pgp expression positively detected by either two of the three antibodies, had five-year survival rate that was significantly higher than those positively detected by all the three antibodies（P 〈 0.05）. Conclusion：Three antibodies should be used simultaneously to detect MDR-1 Pgp expression in breast cancer. Positive MDR-1 Pgp expression in breast cancer detected by all the three antibodies may represent a poor prognosis; while positive MDR-1 Pgp detection by JSB1 and C494 is associated with lymph metastasis.展开更多
Over-expression of P-glycoprotein(P-gp),an ATP-dependent drug efflux pump,represents one of the major mechanisms that contribute to multidrug resistance(MDR) in cancer cells.This study examined the effects of troglita...Over-expression of P-glycoprotein(P-gp),an ATP-dependent drug efflux pump,represents one of the major mechanisms that contribute to multidrug resistance(MDR) in cancer cells.This study examined the effects of troglitazone,a ligand of peroxisome proliferator-activated receptor gamma(PPARγ),on P-gp-mediated MDR in SGC7901/VCR cells(a vincristine-resistant human gastric cancer cell line).The expression of P-gp was detected by RT-PCR and Western blotting,respectively.The SGC7901/VCR cells were treated with 0.1 mg/L vincristine(VCR) alone or in combination with 1,5,10 μmol/L troglitazone for 24 h.PPARγ was measured by electrophoretic mobility shift assay(EMSA).The intracellular concentration of Rhodamine123(Rh123,a fluorescent P-gp substrate) was assayed to evaluate the activity of P-gp.The cell cycle and apoptosis were measured by flow cytometry.The results showed that the P-gp was increasingly expressed in SGC7901,BGC823 and SGC7901/VCR cells in turn,suggesting that MDR in the SGC7901/VCR cells was mediated by the increased expression of P-gp.In the SGC7901/VCR cells,the expression level of total PPARγ was increased,however,the protein level and activity of PPARγ in the nuclei of cells decreased significantly.Troglitazone elevated the PPARγ activity in SGC7901/VCR cells in a dose-dependent manner.Troglitazone decreased the P-gp expression and markedly enhanced the accumulation of Rh123 in SGC7901/VCR cells in a dose-dependent manner.We also found that troglitazone significantly increased the percentage of SGC7901/VCR cells in the G2/M phase and decreased the cell percentage in G1 and S phase in a dose-dependent manner.Troglitazone significantly increased the apoptotic rate of SGC7901/VCR cells treated by VCR or ADR in a dose-dependent manner.It was concluded that P-gp-overexpressed SGC7901/VCR cells have minor endogenous PPARγ activity.Elevation of the PPARγ activity by troglitazone can reverse P-gp-mediated MDR via down-regulating the expression and activity of P-gp in SGC7901/VCR cells.It was suggested that troglitazone can dramatically enhance the sensitivity of P-gp-mediated MDR cancer cells to chemotherapeutic agents.展开更多
文摘P-glycoprotein (P-gp), a member of the ATP-binding cassette (ABC) family of transporters, plays a crucial role in the development of multi-drug resistance (MDR) in cancer treatment. P-gp actively pumps chemotherapeutic drugs out of cancer cells, reducing their intracellular concentrations and thereby diminishing their efficacy. This review explores the mechanisms by which P-gp contributes to MDR, including intrinsic and acquired resistance. It also discusses various strategies to inhibit P-gp, such as blocking drug binding sites, interfering with ATP hydrolysis, and altering cell membrane integrity. The potential of fourth-generation P-gp inhibitors and other novel approaches to enhance the effectiveness of cancer therapies is also examined. Understanding and overcoming P-gp-mediated MDR is essential for improving therapeutic outcomes in cancer patients.
文摘介绍了一个新的基于优化推导出的核偏最小二乘(kernel partial least squares,K-PLS)的算法原理和实现步骤,并且给出了利用K-PLS法构建P-糖蛋白(P-glycoprotein,P-gp)黄酮类抑制剂的定量构效关系(QSAR)模型.利用该方法结合几个简单的分子拓扑参数,构建了具有高准确率的预测模型.该模型将有助于P-gp黄酮类抑制剂的虚拟筛选和理性设计.结果证明K-PLS是一个十分稳定可靠的方法,将会在化学计量学领域得到较好的应用和推广.
文摘肿瘤多药耐药性(multiple drug resistance,MDR)的发生往往伴随着多药耐药基因如MDR1、MRP1和BCRP等高表达,其中MDR1基因编码的P-糖蛋白(P-glycoprotein,P-gp)是目前公认可以诱发癌细胞发生MDR的重要分子。传统研究认为P-gp主要是作为一个药物泵将化疗药物从细胞内排出从而导致MDR。然而系列研究发现,除了介导MDR以外,P-gp还能够调节癌细胞的生长、增殖、凋亡、迁移和侵袭等其他生物学行为;而且研究表明P-gp的这些作用可以依赖,也可以不依赖于其药物泵的功能。这些结果表明P-gp能够通过一些新的机制促进肿瘤的进展。本文主要针对P-gp在促进肿瘤进展中的作用进行综述。
基金This project was supported by a grand from National re-search project foundation of China(No.96 - 90 7- 0 3- 0 1)
文摘To study the effect of the different interventional treatment on P Glycoprotein (Pgp) in different histopathological types of primary hepatocellular carcinoma (PHC), 98 surgically and histologically verified PHC specimens were obtained. The patients included 57 patients treated by surgical resection alone and 41 patients receiving second stage surgical resection after four kinds of interventional treatment. SABC immunohistochemical staining with a monoclonal antibody against human Pgp was used to observe the Pgp in all specimens. The positive rate of Pgp was 100 % in group of chemotherapy alone ( P <0.05), 62.5 % in group of chemotherapy combined with iodized oil ( P >0.05), 46.6 % in group of chemotherapy combined with iodized oil and spongia gelatini absorbens (Sga) ( P >0.05), 18.18 % in group of chemotherapy combined with Ethanol iodized oil and Sga ( P <0.05) and 52.63 % in group of surgical resection alone. The positive rate of Pgp varied with different histopathological types, with rate of clear cell PHC being the lowest, and that of poorly differentiated or undifferentiated PHC the highest. The positive rate of Pgp was increased as pathological grades increased. Overexpression of Pgp may be responsible for the intrinsic and acquired drug resistance of PHC. Multidrug resistance (MDR) varied with different histological types. Therapy of PHC should be tailored according to individual. Local chemotherapy combined with ethanol iodized oil and Sga embolization may become a new way to overcome MDR of PHC.
基金the China Medical Board of New York,Inc.,USA,Grant No.90-534
文摘INTRODUCTIONMost advanced hepatocellular garcinoma (HCC) isinsensitive to most anticancer drugs which might berelated to the high frequency of expression of themultidrug resistance-1(MDR1) gene and itsproduct,P-glycoprotein (p-gp).p-gp expressionmay also be concerned with tumor progression anddifferentiation.In the present study。
基金supported by grants from the Medical Innovation Fundation of Fujian Province(No.2007-CXB-7)the Natural Science Foundation of Fujian Province(No.2009D010)
文摘BACKGROUND:Multidrug resistance(MDR)is extremely common in hepatocellular carcinoma(HCC)and is a major problem in cancer eradication by limiting the efficacy of chemotherapy.Modulation of c-Jun NH2-terminal kinase(JNK)activation could be a new method to reverse MDR.However,the relationship between JNK activity and MDR in HCC cells is unknown.This study aimed to explore the relationship between MDR and JNK in HCC cell lines with different degrees of MDR.METHODS:A MDR human HCC cell line,SMMC-7721/ ADM,was developed by exposing parental cells to gradually increasing concentrations of adriamycin.The MTT assay was used to determine drug sensitivity.Flow cytometry was used to analyze the cell cycle distribution and to measure the expression levels of P-glycoprotein(P-gp)and MDR-related protein(MRP)-1 in these cells.JNK1,JNK2 and JNK3 mRNA expression levels were quantified by real-time PCR.Expression and phosphorylation of JNK1,JNK2,and JNK3 were analyzed by Western blotting.RESULTS:The MDR of SMMC-7721/ADM cells resistant to 0.05 mg/L adriamycin was mainly attributed to the overexpression of P-gp but not MRP1.In addition,these cells had a significant increase in percentage in the S phase,accompanied by a decrease in percentage in the G0/G1 phase,which is likely associated with a reduced ability for cell proliferation and MDR generation.We found that JNK1,JNK2,and JNK3 activities were negatively correlated with the degree of MDR in HCC cells.CONCLUSION:This study suggests that JNK1,JNK2,and JNK3 activities are negatively correlated with the degree of MDR in HCC cells.
基金supported by start-up funding from St.John's University(Z.S.Chen)
文摘Imatinib,a breakpoint cluster region(BCR)-Abelson murine leukemia(ABL) tyrosine kinase inhibitor(TKI),has revolutionized the treatment of chronic myelogenous leukemia(CML).However,development of multidrug resistance(MDR) limits the use of imatinib.In the present study,we aimed to investigate the mechanisms of cellular resistance to imatinib in CML.Therefore,we established an imatinib-resistant human CML cell line(K562-imatinib) through a stepwise selection process.While characterizing the phenotype of these cells,we found that K562-imatinib cells were 124.6-fold more resistant to imatinib than parental K562 cells.In addition,these cells were cross-resistant to second-and third-generation BCR-ABL TKIs.Western blot analysis and reverse transcription-polymerase chain reaction(RT-PCR) demonstrated that P-glycoprotein(P-gp) and MDR1 mRNA levels were increased in K562-imatinib cells.In addition,accumulation of [14C]6-mercaptopurine(6-MP) was decreased,whereas the ATP-dependent efflux of [14C]6-MP and [3H]methotrexate transport were increased in K562-imatinib cells.These data suggest that the overexpression of P-gp may play a crucial role in acquired resistance to imatinib in CML K562-imatinib cells.
基金Supported by In part by research Grants-In-Aid for Scientific Research by the Ministry of Health,Labor and Welfare of Japanthe Ministry of Education,Culture,Sports,Science and Technology of JapanUniversity of Occupational and Environmental Health,Japan
文摘The main purpose of treatment of rheumatoid arthritis(RA) with disease modifying antirheumatic drugs(DMARDs) is to control activation of lymphocytes,although some patients do not respond adequately to such treatment. Among various mechanisms of multidrug resistance, P-glycoprotein(P-gp), a member of ATP-binding cassette transporters, causes drugresistance by efflux of intracellular drugs. Certain stimuli,such as tumor necrosis factor-α, activate lymphocytes and induce P-gp expression on lymphocytes, as evident in active RA. Studies from our laboratories showed spontaneous nuclear accumulation of human Y-boxbinding protein-1, a multidrug resistance 1 transcription factor, in unstimulated lymphocytes, and surface overexpression of P-gp on peripheral lymphocytes of RA patients with high disease activity. The significant correlation between P-gp expression level and RA disease activity is associated with active efflux of drugs from the lymphocyte cytoplasm and in drugresistance.However, the use of biological agents that reduce P-gp expression as well as P-gp antagonists(e.g., cyclosporine) can successfully reduce the efflux of corticosteroids from lymphocytes in vitro, suggesting that both types of drugs can be used to overcome drug-resistance and improve clinical outcome. We conclude that lymphocytes activated by various stimuli in RA patients with highly active disease acquire P-gpmediated multidrug resistance against corticosteroids and probably some DMARDs, which are substrates of P-gp. Inhibition/reduction of P-gp could overcome such drug resistance. Expression of P-gp on lymphocytes is a promising marker of drug resistance and a suitable therapeutic target to prevent drug resistance in patients with active RA.
基金Supported by National Natural Science Foundation of China(No.81400424)Guangdong Medical Science Foundation(No.A2015151)
文摘AIM： To investigate the role of oxidative stress in regulating the functional expression of P-glycoprotein（P-gp） in mitochondria of D407 cells.METHODS： D407 cells were exposed to different ranges of concentrations of H2O2. The mitochondrial location of P-gp in the cells subjected to oxidative stress was detected by confocal analysis. Expression of P-gp in isolated mitochondria was assessed by Western blot. The pump activity of P-gp was evaluated by performing the efflux study on isolated mitochondria with Rhodamine 123（Rho-123） alone and in the presence of P-gp inhibitor（Tariquidar） using flow cytometry analysis. The cells were pretreated with 10 mmol/L N-acetylcysteine（NAC） for 30 min before exposing to H2O2, and analyzed the mitochondrial extracts by Western blot and flow cytometry.RESULTS： P-gp was co-localized in the mitochondria by confocal laser scanning microscopy, and it was also detected in the mitochondria of D407 cells using Western blot. Exposure to increasing concentrations of H2O2 led to gradually increased expression and location of P-gp in the mitochondria of cells. Rho-123 efflux assay showed higher uptake of Rho-123 on isolated mitochondria in the presence of Tariquidar both in normal and oxidative stress state. H2O2 up-regulated P-gp in D407 cells, which could be reversed by NAC treatment. CONCLUSION： H2O2 could up-regulate the functional expression of P-gp in mitochondria of D407 cells, while antioxidants might suppress oxidative-stress-induced over-expression of functional P-gp. It is indicative that limiting the mitochondrial P-gp transport in retinal pigment epithelium cells would be to improve the effect of mitochondria-targeted antioxidant therapy in age-related macular degeneration-like retinopathy.
基金the Science and Technology Foundation of Guangdong Province,No.2009B060700049,2008B060600063the National Natural Science Foundation of China,No.10671213
文摘Epileptic seizures induce overexpression of P-glycoprotein in the blood-brain barrier. However, it is unclear whether hippocampal neurons also overexpress P-glycoprotein following seizure. This study confirmed that the clinical manifestation, pathological characteristics and electroencephalography in the rat model of lithium-pilocarpine-induced mesial temporal lobe epilepsy were consistent with clinical reports of mesial temporal lobe epilepsy in humans.Immunohistochemistry staining demonstrated that P-glycoprotein positive staining was found in neurons in the pyramidal layer of the hippocampus. Westem blot assay and real-time polymerase chain reaction revealed that P-glycoprotein overexpression was exhibited in the CA1, CA3, and dentate gyrus of the hippocampus at 24 and 60 days following model induction, but no significant dffierence was detected in the same region at various time points. These results indicate that seizures led to overexpression of P-glycoprotein in neurons of the hippocampus, but no evidence was found for a positive association between P-glycoprotein expression and seizure frequency.
基金This work was supported by the Science Development Foundation of the Nanjing Medical University(2006NMUZ023)The research in Dr. W. Zhang's laboratory was supported by funding from the National Research Council of Canada and a Canadian Research Program spon- sored by CIHR, HSFC, ASC and Pfizer(PG-04-0248)
文摘Objective： To investigate the expression of MDR-1 P-glycoprotein（MDR-1 Pgp） in breast cancer and analyze its correlation to the biological behavior and prognosis of the disease. Methods：The expression of MDR-1 Pgp was examined in 75 cases of breast cancer patients by using three different monoclonal antibodies（JSB1, C219 and C494） with S-P immunohistochemisty. These patients were followed up for 5 years, and the correlation between MDR-1 Pgp expression, survival rate and lymph metastasis was analyzed. Results： Positive detection of MDR-1 Pgp by JSB1, C219 and C494 in 75 cases of breast cancer was 86.7%, 48% and 85.3%, respectively. MDR-1 Pgp expression was not related to ages of patients （P 〉 0.05）. JSBl-detected expression of MDR-1 Pgp was related to lymph node metastasis（P〈 0.05）; while C219 and C494 were not（P 〉 0.05）. The patients with MDR-1 Pgp expression positively detected by either two of the three antibodies, had five-year survival rate that was significantly higher than those positively detected by all the three antibodies（P 〈 0.05）. Conclusion：Three antibodies should be used simultaneously to detect MDR-1 Pgp expression in breast cancer. Positive MDR-1 Pgp expression in breast cancer detected by all the three antibodies may represent a poor prognosis; while positive MDR-1 Pgp detection by JSB1 and C494 is associated with lymph metastasis.
基金supported by grants from Natural Sciences Foundation of Hubei Province (No.2007ABA065)Science and Technology Key Project of Health Bureau of Hubei Province (No.JX1B006)
文摘Over-expression of P-glycoprotein(P-gp),an ATP-dependent drug efflux pump,represents one of the major mechanisms that contribute to multidrug resistance(MDR) in cancer cells.This study examined the effects of troglitazone,a ligand of peroxisome proliferator-activated receptor gamma(PPARγ),on P-gp-mediated MDR in SGC7901/VCR cells(a vincristine-resistant human gastric cancer cell line).The expression of P-gp was detected by RT-PCR and Western blotting,respectively.The SGC7901/VCR cells were treated with 0.1 mg/L vincristine(VCR) alone or in combination with 1,5,10 μmol/L troglitazone for 24 h.PPARγ was measured by electrophoretic mobility shift assay(EMSA).The intracellular concentration of Rhodamine123(Rh123,a fluorescent P-gp substrate) was assayed to evaluate the activity of P-gp.The cell cycle and apoptosis were measured by flow cytometry.The results showed that the P-gp was increasingly expressed in SGC7901,BGC823 and SGC7901/VCR cells in turn,suggesting that MDR in the SGC7901/VCR cells was mediated by the increased expression of P-gp.In the SGC7901/VCR cells,the expression level of total PPARγ was increased,however,the protein level and activity of PPARγ in the nuclei of cells decreased significantly.Troglitazone elevated the PPARγ activity in SGC7901/VCR cells in a dose-dependent manner.Troglitazone decreased the P-gp expression and markedly enhanced the accumulation of Rh123 in SGC7901/VCR cells in a dose-dependent manner.We also found that troglitazone significantly increased the percentage of SGC7901/VCR cells in the G2/M phase and decreased the cell percentage in G1 and S phase in a dose-dependent manner.Troglitazone significantly increased the apoptotic rate of SGC7901/VCR cells treated by VCR or ADR in a dose-dependent manner.It was concluded that P-gp-overexpressed SGC7901/VCR cells have minor endogenous PPARγ activity.Elevation of the PPARγ activity by troglitazone can reverse P-gp-mediated MDR via down-regulating the expression and activity of P-gp in SGC7901/VCR cells.It was suggested that troglitazone can dramatically enhance the sensitivity of P-gp-mediated MDR cancer cells to chemotherapeutic agents.
