Progress of studies on ATP-binding cassette transporters and transportation of secondary metabolites in medicinal plants / 中国中药杂志

ATP-binding cassette(ABC) transporters are one of the largest protein families in organisms, with important effects in regulating plant growth and development, root morphology, transportation of secondary metabolites and resistance of stress. Environmental stress promotes the biosynthesis and accumulation of secondary metabolites, which determines the quality of medicinal plants. Therefore, how to improve the accumulation of secondary metabolites has been a hotspot in studying medicinal plants. Many studies have showed that ABC transporters are extremely related to the transportation and accumulation of secondary metabolites in plants. Recently, with the great development of genomics and transcriptomic sequencing technology, the regulatory mechanisms of ABC transporters on secondary metabolites have attached great attentions in medicinal plants. This paper reviewed the mechanisms of different groups of ABC transporters in transporting secondary metabolites through cell membranes. This paper provided key theoretical basis and technical supports in studying the mechanisms of ABC transporters in medicinal plant, and promoting the accumulation of secondary metabolites, in order to improve the quality of medicinal plants.

Recent advances for plant secondary metabolite transporters / 中草药

Plants produce a series of secondary metabolites in cells. These secondary metabolites will be transported to specific organelles for storage or secreted extracellularly. Transporters are a class of membrane proteins that mediate transmembrane transport of chemicals and intracellular signal exchange, and also play an important role in transmembrane transport of plant secondary metabolites. Identification of the function of the secondary metabolite transporters of medicinal plants will help to elucidate the biosynthetic pathways of secondary metabolites in medicinal plants and the molecular mechanism of the transport process of bioactive compounds. In this review, the structure and classification of plant transporters are described in detail. The research progress of plant secondary metabolic transporters and the methods for functional verification of transporter, which have been summarized in this article, will provide a basis for elucidating the biosynthetic pathways and utilization of secondary metabolites in medicinal plants.

Characterisation of an ABC transporter of a resistant Candida glabrata clinical isolate

BACKGROUND Candida glabrata ranks second in epidemiological surveillance studies, and is considered one of the main human yeast pathogens. Treatment of Candida infections represents a contemporary public health problem due to the limited availability of an antifungal arsenal, toxicity effects and increasing cases of resistance. C. glabrata presents intrinsic fluconazole resistance and is a significant concern in clinical practice and in hospital environments. OBJECTIVE The aim of this study was to characterise the azole resistance mechanism presented by a C. glabrata clinical isolate from a Brazilian university hospital. METHODS Azole susceptibility assays, chemosensitisation, flow cytometry and mass spectrometry were performed. FINDINGS Our study demonstrated extremely high resistance to all azoles tested: fluconazole, voriconazole, posaconazole and itraconazole. This isolate was chemosensitised by FK506, a classical inhibitor of ABC transporters related to azole resistance, and Rhodamine 6G extrusion was observed. A mass spectrometry assay confirmed the ABC protein identification suggesting the probable role of efflux pumps in this resistance phenotype. MAIN CONCLUSIONS This study emphasizes the importance of ABC proteins and their relation to the resistance mechanism in hospital environments and they may be an important target for the development of compounds able to unsettle drug extrusion.

Comparative untargeted proteomic analysis of ADME proteins and tumor antigens for tumor cell lines

In the present study, total membrane proteins from tumor cell lines including HepG2, Hep3B2, H226, Ovcar3 and N87 were extracted and digested with LysC and trypsin. The resulting peptide lysate were pre-fractionated and subjected to untargeted quantitative proteomics analysis using a high resolution mass spectrometer. The mass spectra were processed by the MaxQuant and the protein abundances were estimated using total peak area (TPA) method. A total of 6037 proteins were identified, and the analysis resulted in the identification of 2647 membrane proteins. Of those, tumor antigens and absorption, metabolism, disposition and elimination (ADME) proteins including UDP-glucuronosyltransferase, cytochrome P450, solute carriers and ATP-binding cassette transporters were detected and disclosed significant variations among the cell lines. The principal component analysis was performed for the cluster of cell lines. The results demonstrated that H226 is closely related with N87, while Hep3B2 aligned with HepG2. The protein cluster of Ovcar3 was apart from that of other cell lines investigated. By providing for the first time quantitative untargeted proteomics analysis, the results delineated the expression profiles of membrane proteins. These findings provided a useful resource for selecting targets of choice for anticancer therapy through advancing data obtained from preclinical tumor cell line models to clinical outcomes.

Papel de la superfamilia ABC en la resistencia farmacológica / Role of the superfamily of ABC transports in pharmacological resistance / Papel da superfamília ABC na resistência a drogas / Rôle de la superfamille ABC dans la résistance pharmacologique

Resumen Objetivo: Actualizar los conocimientos acerca de los transportadores de la superfamilia ABC vinculados con la resistencia farmacológica. Materiales y métodos: Se realizó un estudio donde se aplicó el método cualitativo, mediante una revisión bibliográfica y documental sobre el tema en fuentes de datos digitales. Se usaron los descriptores DeCs-MeSH: transportadores ABC, superfamilia ABC, resistencia farmacológica, ATP binding- cassette. Se revisaron artículos publicados sobre el tema, a través de los buscadores habituales (Google, PubMed, Cochrane, Future Medicine, Scielo, entre otros), teniendo en cuenta la calidad y la actualidad de ellos. Resultados: Se destaca la importancia clínica de estos transportadores que se relacionan con la aterosclerosis, enfermedades hepáticas, enfermedad de Alzheimer, entre otras. Esto los convierte en dianas atractivas para el diseño de nuevos medicamentos; pero al mismo tiempo, pueden expulsarlos de la célula, haciéndola resistente como a los antitumorales, antimicrobianos y antivirales. Conclusiones: Los transportadores ABC tienen una función central en los efectos adversos que diferentes sustancias, entre ellas los fármacos, tienen sobre la célula. Además, el polimorfismo genético en esta superfamilia se asocia con alteraciones farmacocinéticas que pueden desencadenar resistencia farmacológica; el impacto de estas modificaciones es el centro de recientes investigaciones que las sitúan como posible blanco terapéutico.

Abstract Objective: To update the knowledge about the ABC transporters superfamily linked to drug resistance. Materials and methods: A qualitative study where the method was applied, using a bibliographical and documentary review on the subject of digital data sources was conducted. ABC transporters, ABC superfamily, and drug resistance, binding- ATP cassette: the DECS-MeSH descriptors were using published articles on the subject through the usual search engines (Google, PubMed, Cochrane, Future Medicine, Scielo, among others), counting on the quality and timeliness of them were review. Results: The clinical significance of these transporters is stress as they relate to atherosclerosis, liver disease, Alzheimer's disease, among other conditions. This makes them attractive targets for new drug design; but at the same time, they can expel the cell making it resistant as antitumor, antimicrobial and antiviral. Conclusions: ABC transporters have central role in the adverse effects of different substances, including drugs, have on the cell. In addition, the genetic polymorphism in this superfamily is associated with pharmacokinetic changes that can trigger drug resistance; the impact of these changes is the focus of recent research that place them as a possible therapeutic target.

Resumo Objectivo: Atualizar o conhecimento sobre os transportadores de superfamilia ABC ligada a resistência a drogas. Materiais e métodos: Foi realizado um estudo qualitativo, através de uma revisão da literatura e documental sobre o tema em fontes de dados digitais. Foram utilizados os descritores DeCs-MeSH: transportadores ABC, superfamilia ABC, resistência farmacológica, ATP binding- cassette. Foram pesquisados artigos sobre o tema, através dos motores de busca (Google, PubMed, Cochrane, Future Medicine, Scielo, entre outros), tendo em conta a qualidade e a sua atualidade. Resultados: Destacou-se a importãncia clínica destes transportadores que se relacionam com a aterosclerose, doen9as hepáticas, de Alzheimer, entre outras. Isso os torna alvos atraentes para o design de novos fármacos, mas ao mesmo tempo, os fármacos podem ser expulsos da célula, tornando-a resistente aos antitumorais, antimicrobianos e antivirais. Conclusões: Os transportadores ABC têm uma função central nos efeitos adversos que diferentes substãncias, tais como os fármacos, possuem sobre a célula. Além disso, o polimorfismo genético desta superfamilia está associado as alterações farmacocinéticas que podem desencadear a resistência aos medicamentos; o impacto dessas mudanças é o centro de pesquisas recentes que os coloca como um possível alvo terapéutico.

Résumé Objectif: Actualiser les connaissances sur les transporteurs de la superfamille ABC liés a la résistance pharmacologique. Matériaux et méthodes: Une étude qualitative a été réalisée au moyen d'une recherche bibliographique et documentaire dans différentes sources de données numériques avec les moteurs de recherche habituels (Google, PubMed, Cochrane, Medicine Future, Scielo, entre autres). Les descripteurs DeCs-MeSH utilisés ont été: transporteurs ABC, superfamille ABC, résistance pharmacologique, ATP binding- cassette. Un certain nombre d'articles relatifs au sujet ont été sélectionnés en fonction de leur qualité et de leur actualité. Résultats: Les résultats mettent en avant l'importance clinique de ces transporteurs du fait de leur relation avec l'athérosclérose, certaines maladies hépatiques, la maladie d'Alzheimer, et d'autres affections. Cela en fait des cibles attrayantes pour la conception de nouveaux médicaments; mais en meme temps, ils peuvent expulser des médicaments de la cellule et la rendre résistante aux antitumoraux, antimicrobiens et antiviraux, par exemple. Conclusions: Les transporteurs ABC jouent un role central dans les conséquences néfastes de différentes substances, y compris les médicaments, sur la cellule. En outre, le polymorphisme génétique dans cette superfamille est associé a des modifications pharmacocinétiques qui peuvent déclencher une résistance aux médicaments; l'impact de ces modifications est l'objet de recherches récentes qui les placent comme cible thérapeutique possible.

Correlation of minimal residual disease and multidrug resistance genes expression in acute myeloid leukemia / 基础医学与临床

Objective To explore the correlation of minimal residual disease ( MRD) and ABC genes expression in acute myeloid leukemia ( AML) .Methods 52 de novo AML bone marrow samples were used to detect the expres-sion of ABCB1,ABCC1,ABCC4 andABCG2 by real-time PCR at diagnosis.Meanwhile, followed up these patients to monitor MRD with MFC at the points of finishing the first induction cause as well as the third ,the sixth and the ninth month after chemotherapy .Results The expression level of 4 ABC transporters among three MRD level de-tected after induction cause are correlated significantly with ABCB1(P<0.01), ABCC1(P<0.01), ABCC4(P<0.01) and ABCG2(P<0.01).Further more, after nine months follow-up, the patients whose MRD turned into positive again were detected a high ABC transports expression level , comparing with those MRD remained negative for nine months,which was of a statistically significance for ABCB1(P<0.05), ABCC1(P<0.05), ABCC4(P<0.01) and ABCG2(P<0.01).Conclusions A positive correlation of MRD and ABC transporters level in AML is found.

Thermodynamics of ABC transporters

ABC transporters form the largest of all transporter families, and their structural study has made tremendous progress over recent years. However, despite such advances, the precise mechanisms that determine the energy-coupling between ATP hydrolysis and the conformational changes following substrate binding remain to be elucidated. Here, we present our thermodynamic analysis for both ABC importers and exporters, and introduce the two new concepts of differential-binding energy and elastic conformational energy into the discussion. We hope that the structural analysis of ABC transporters will henceforth take thermodynamic aspects of transport mechanisms into account as well.

Role and molecular mechanisms of SET mediated pachtaxel resistance in MCF-7/PTX cells / 中国药学杂志

OBJECTIVE: To investigate the resistance mechanisms related to SET in paclitaxel-induced human breast cancer cells. METHODS: The different expressions of SET and ABC transporters between MCF-7/S and paclitaxel resistant MCF-7/PTX cells were identified using Western blot. We adopted siRNA method to knockdown SET in MCF-7/PTX cells and plasmid transfection analysis to up-regulated SET in MCF-7/S cells. The cell viability to paclitaxel was assessed by MTT assay. The cell apoptosis was analyzed by flow cytometry. The levels of ABC transporters were analyzed using Western blot and Real-time PCR, respectively. RESULTS: We found that higher levels of SET and ABC transporters in MCF-7/PTX cells. Knockdown of SET not only significantly sensitized MCF-7/PTX cells to paclitaxel, but also induced cell apoptosis. The levels of the ABC transporters were also reduced. Upregulated SET in MCF-7/S cells expressed resistant to paclitaxel and decreased cell apoptosis. High expression of the SET significantly promotes the mRNA and protein level of ABC transporters. CONCLUSION: The above results demonstrate that SET is associated with paclitaxel resistance in MCF-7/PTX cells. The SET is expected to be one of novel biological targets of overcoming paclitaxel resistant in breast cancer treatment.

Evaluation of the role of ATP-binding cassette transporters as a defence mechanism against temephos in populations of Aedes aegypti

The role of ATP-binding cassette (ABC) transporters in the efflux of the insecticide, temephos, was assessed in the larvae of Aedes aegypti. Bioassays were conducted using mosquito populations that were either susceptible or resistant to temephos by exposure to insecticide alone or in combination with sublethal doses of the ABC transporter inhibitor, verapamil (30, 35 and 40 μM). The best result in the series was obtained with the addition of verapamil (40 μM), which led to a 2x increase in the toxicity of temephos, suggesting that ABC transporters may be partially involved in conferring resistance to the populations evaluated.

Efeito de hipolipemiantes sobre a expressão de genes envolvidos no transporte reverso do colesterol / Statin effects on expression of genes involved in reverse cholesterol transport

A eficácia das estatinas em reduzir o risco de eventos coronarianos não é completamente explicada por seus efeitos em diminuir colesterol de lipoproteína de baixa densidade (LDL-C). Um dos seus efeitos adicionais pode ser decorrente da modificação na concentração de lipoproteína de alta densidade (HDL), reconhecida como ateroprotetora, principalmente por seu papel no transporte reverso do colesterol (TRC). Os transportadores de membrana do tipo ATP-binding cassette, ABCA1 e ABCG1, e o scavenger receptor BI (SRBI) são proteínas importantes envolvidas no TRC e seus genes são regulados por vários fatores de transcrição, entre eles os liver-x-receptors (LXRs). Com a finalidade de avaliarmos os efeitos dos hipolipemiantes sobre expressão dos transportadores ABC e do receptor SRBI, a expressão de RNAm do ABCA1, ABCG1, SCARB1, NR1H3 (LXRα) e NR1H2 (LRXβ) foi avaliada por PCR em tempo real em células das linhagens HepG2 (origem hepática) e Caco-2 (origem intestinal) tratadas com atorvastatina ou sinvastatina (10 µM) e/ou ezetimiba (até 5 µM) por até 24 horas. Além disso, a expressão desses genes também foi avaliada em células mononucleares do sangue periférico (CMSP) de 50 pacientes normolipidêmicos (NL) e 71 hipercolesterolêmicos (HC) tratados com atorvastatina (10mg/dia/4semanas, n=48) ou sinvastatina e/ou ezetimiba (10mg/dia/4 ou 8 semanas, n=23). A possível associação entre os polimorfismos ABCA1 C-14T e R219K e a expressão de RNAm em CMSP também foi avaliada por PCR-RFLP. O SCARB1 foi o gene mais expresso nas células HepG2 e Caco-2, seguido por NR1H2, NR1H3, ABCG1 e ABCA1 em HepG2 ou por ABCA1 e ABCG1 em Caco-2. O tratamento com estatinas (1 ou 10 µM) ou ezetimiba (5 µM), por 12 ou 24 horas, aumentou a expressão de RNAm do ABCG1, mas não de ABCA1 e SCARB1, em células HepG2. Ainda nesta linhagem, o aumento na transcrição dos genes NR1H2 e NR1H3 foi observado somente com a maior concentração de atorvastatina (10 µM) e, ao contrário, o tratamento com ezetimiba...

The efficacy of statins in reducing the risk of coronary events is not completely explained by their effects in decreasing cholesterol low-density lipoprotein (LDL-C). One of their additional effects may result from the change in concentration of high-density lipoprotein (HDL), recognized as atheroprotective, mainly for the role in reverse cholesterol transport (RCT). The membrane transporters, as ATP-binding cassette, ABCA1 and ABCG1, and scavenger receptor BI (SRBI) are important proteins involved in the RCT and their genes are regulated by various transcription factors, including the liver-X-receptors (LXRs) . In order to evaluate the effects of lipid lowering on expression of ABC transporters and SRBI receptor, the mRNA expression of ABCA1, ABCG1, SCARB1, NR1H3 (LXRα) and NR1H2 (LRXβ) was assessed by real time PCR in HepG2 (hepatic origin) and Caco-2 (intestinal origin) cells treated with atorvastatin or simvastatin (10 µM) and/or ezetimibe (up to 5 µM) for 24 hours. Furthermore, the expression of these genes was evaluated in peripheral blood mononuclear cells (PBMC) of 50 normolipidemic (NL) and 71 hypercholesterolemic (HC) patients treated with atorvastatin (10mg/d/4 weeks, n = 48) or simvastatin and/or ezetimibe (10mg/d/4 or 8 weeks, n = 23). The possible association between ABCA1 C-14T and R219K polymorphisms and mRNA expression in PBMC was also evaluated by PCR-RFLP. SCARB1 was the most expressed in HepG2 and Caco-2 cells, followed by NR1H2, NR1H3, ABCG1 and ABCA1 in HepG2 or by ABCG1 and ABCA1 in Caco-2. The treatment with statins (1 or 10 µM) or ezetimibe (5 µM) for 12 or 24 hours, increased mRNA expression of ABCG1 but not ABCA1 and SCARB1 in HepG2 cells. Moreover, in HepG2 cells, atorvastatin also upregulated NR1H2 and NR1H3 only at 10.0 µM, meanwhile ezetimibe downregulated NR1H2 but did not change NR1H3 expression. In Caco-2 cells, atorvastatin or simvastatin treatment for 12 or 24 hours reduced the amount of ABCA1 transcript and did not ...

Efeito de hipolipemiantes sobre a expressão de genes envolvidos no transporte reverso do colesterol / Statin effects on expression of genes involved in reverse cholesterol transport

A eficácia das estatinas em reduzir o risco de eventos coronarianos não é completamente explicada por seus efeitos em diminuir colesterol de lipoproteína de baixa densidade (LDL-C). Um dos seus efeitos adicionais pode ser decorrente da modificação na concentração de lipoproteína de alta densidade (HDL), reconhecida como ateroprotetora, principalmente por seu papel no transporte reverso do colesterol (TRC). Os transportadores de membrana do tipo ATP-binding cassette, ABCA1 e ABCG1, e o scavenger receptor BI (SRBI) são proteínas importantes envolvidas no TRC e seus genes são regulados por vários fatores de transcrição, entre eles os liver-x-receptors (LXRs). Com a finalidade de avaliarmos os efeitos dos hipolipemiantes sobre expressão dos transportadores ABC e do receptor SRBI, a expressão de RNAm do ABCA1, ABCG1, SCARB1, NR1H3 (LXRα) e NR1H2 (LRXß) foi avaliada por PCR em tempo real em células das linhagens HepG2 (origem hepática) e Caco-2 (origem intestinal) tratadas com atorvastatina ou sinvastatina (10 µM) e/ou ezetimiba (até 5 µM) por até 24 horas. Além disso, a expressão desses genes também foi avaliada em células mononucleares do sangue periférico (CMSP) de 50 pacientes normolipidêmicos (NL) e 71 hipercolesterolêmicos (HC) tratados com atorvastatina (10mg/dia/4semanas, n=48) ou sinvastatina e/ou ezetimiba (10mg/dia/4 ou 8 semanas, n=23). A possível associação entre os polimorfismos ABCA1 C-14T e R219K e a expressão de RNAm em CMSP também foi avaliada por PCR-RFLP. O SCARB1 foi o gene mais expresso nas células HepG2 e Caco-2, seguido por NR1H2, NR1H3, ABCG1 e ABCA1 em HepG2 ou por ABCA1 e ABCG1 em Caco-2. O tratamento com estatinas (1 ou 10 µM) ou ezetimiba (5 µM), por 12 ou 24 horas, aumentou a expressão de RNAm do ABCG1, mas não de ABCA1 e SCARB1, em células HepG2. Ainda nesta linhagem, o aumento na transcrição dos genes NR1H2 e NR1H3 foi observado somente com a maior concentração de atorvastatina (10 µM) e, ao contrário, o tratamento com ezetimiba causou redução na transcrição de NR1H2, sem alteração de NR1H3. Em células Caco-2, o tratamento com atorvastatina ou sinvastatina por 12 ou 24 horas reduziu a quantidade do transcrito ABCA1 e não alterou a expressão do SCARB1 e do ABCG1, embora, para este último, tenha havido uma tendência à diminuição da expressão após tratamento com sinvastatina (p=0,07). Após tratamento com ezetimiba isolada (até 5 µM) nenhuma alteração de expressão de RNAm foi observada em células Caco-2; no entanto, após 24 horas de tratamento com sinvastatina e ezetimiba, foi reduzida a taxa de transcrição de ABCA1 e ABCG1, mas não de SCARB1. Ao contrário das linhagens celulares, em CMSP os genes NR1H2 e ABCG1 foram os mais expressos, seguidos pelos genes SCARB1 e ABCA1 e, finalmente, pelo NR1H3. Indivíduos HC tiveram maior expressão basal de NR1H2 e NR1H3, mas não de outros genes, quando comparados aos NL (p<0,05). Além disso, nos indivíduos HC, a expressão basal de ABCA1 foi maior em portadores do alelo -14T do polimorfismo ABCA1 -14C>T quando comparados aos portadores do genótipo -14CC (p=0,034). O tratamento com estatinas, com ezetimiba ou com a terapia combinada diminuiu a transcrição de ABCA1 e ABCG1. Para o SCARB1, NR1H2 e NR1H3, nenhuma alteração de expressão de RNAm em CMSP foi detectada após os tratamentos in vivo. Após todas as fases de tratamento, ABCA1 e ABCG1 e também NR1H2 e NR1H3 foram significativamente correlacionados entre si, mas nenhuma correlação com perfil lipídico sérico foi relevante. Coletivamente, esses resultados dão indícios de que os hipolipemiantes analisados (estatinas e ezetimiba) têm um importante papel na regulação da expressão de genes envolvidos no transporte reverso do colesterol e sugerem a existência de regulação tecido-específica para os dois transportadores ABC. Além disso, o efeito das estatinas ou da ezetimiba sobre a expressão do ABCA1, do ABCG1 ou do SCARB1 não sofreu influencia de alterações diretas da transcrição dos LXRs

The efficacy of statins in reducing the risk of coronary events is not completely explained by their effects in decreasing cholesterol low-density lipoprotein (LDL-C). One of their additional effects may result from the change in concentration of high-density lipoprotein (HDL), recognized as atheroprotective, mainly for the role in reverse cholesterol transport (RCT). The membrane transporters, as ATP-binding cassette, ABCA1 and ABCG1, and scavenger receptor BI (SRBI) are important proteins involved in the RCT and their genes are regulated by various transcription factors, including the liver-X-receptors (LXRs) . In order to evaluate the effects of lipid lowering on expression of ABC transporters and SRBI receptor, the mRNA expression of ABCA1, ABCG1, SCARB1, NR1H3 (LXRα) and NR1H2 (LRXß) was assessed by real time PCR in HepG2 (hepatic origin) and Caco-2 (intestinal origin) cells treated with atorvastatin or simvastatin (10 µM) and/or ezetimibe (up to 5 µM) for 24 hours. Furthermore, the expression of these genes was evaluated in peripheral blood mononuclear cells (PBMC) of 50 normolipidemic (NL) and 71 hypercholesterolemic (HC) patients treated with atorvastatin (10mg/d/4 weeks, n = 48) or simvastatin and/or ezetimibe (10mg/d/4 or 8 weeks, n = 23). The possible association between ABCA1 C-14T and R219K polymorphisms and mRNA expression in PBMC was also evaluated by PCR-RFLP. SCARB1 was the most expressed in HepG2 and Caco-2 cells, followed by NR1H2, NR1H3, ABCG1 and ABCA1 in HepG2 or by ABCG1 and ABCA1 in Caco-2. The treatment with statins (1 or 10 µM) or ezetimibe (5 µM) for 12 or 24 hours, increased mRNA expression of ABCG1 but not ABCA1 and SCARB1 in HepG2 cells. Moreover, in HepG2 cells, atorvastatin also upregulated NR1H2 and NR1H3 only at 10.0 µM, meanwhile ezetimibe downregulated NR1H2 but did not change NR1H3 expression. In Caco-2 cells, atorvastatin or simvastatin treatment for 12 or 24 hours reduced the amount of ABCA1 transcript and did not alter the ABCG1 and SCARB1 expressions, despite the tendency to decrease ABCG1 mRNA expression after simvastatin treatment (p = 0.07). After treatment with ezetimibe alone (up to 5 µM) no change in mRNA expression was observed in Caco-2 cells; however, after 24 hours- simvastatin and ezetimibe treatments decreased the transcription of ABCA1 and ABCG1, but not of SCARB1. Unlike cell lines, in PBMC, NR1H2 and ABCG1 were the most expressed, followed by SCARB1 and ABCA1 and finally by the NR1H3. HC patients showed higher NR1H2 and NR1H3 basal expressions, but not of other genes, compared to NL (p <0.05). Moreover, in HC individuals, the ABCA1 basal expression was higher in individuals carrying -14T allele of -14C> T polymorphism when compared with -14CC carriers (p = 0.034). Treatment with statins, ezetimibe, or combined therapy downregulated ABCA1 and ABCG1 expression. For SCARB1, NR1H2 and NR1H3, no change in mRNA expression in PBMC was detected after treatments. After all phases of treatment, ABCA1 and ABCG1 as well as NR1H2 and NR1H3 were significantly correlated, but no correlation with serum lipid profile was relevant. Collectively, these results provide evidences that the lipid lowering (statins and ezetimibe) have an important role in mRNA expression regulation of genes involved in reverse cholesterol transport and suggest the existence of tissue-specific regulation for the ABC transporters. Furthermore, the effect of statins or ezetimibe on ABCA1, ABCG1 or SCARB1 expression was not directly influenced by changes of LXR transcription

Identification of citrus expressed sequence tags (ESTs) encoding pleiotropic drug resistance (PDR)-like proteins

Pleiotropic drug resistance (PDR) proteins, a subfamily of the ATP-binding cassette (ABC) transporters, have been recently shown to play a role in plant defense against biotic and abiotic stresses. However, nothing is known about their expression in citrus. To investigate the occurrence of PDR homologues in citrus species, we have surveyed EST sequences from different tissues and conditions of the Citrus Expressed Sequence Tags (CitEST) database, through sequence similarity search analyses and inspections for characteristic PDR domains. Multiple sequence alignments, prediction of transmembrane topology and phylogenetic analysis of PDR-like proteins were additionally performed. This study allowed the identification of nine putative proteins showing characteristic PDR features in citrus species under various conditions, which may indicate a potential correlation between PDRs and stress and metabolism of citrus plants. Moreover, a tissue-specific putative PDR-like protein was found in sweet orange fruits. To our knowledge, this is the first report regarding the identification of citrus ESTs encoding PDR-like proteins as well as the first to identify a putative full ABC transporter with specific expression in fruits.

Expression of Ten ABC Transporters in Cisplatin-resistant Nasopharyngeal Carcinoma Cell Lines / 生物化学与生物物理进展

Ten ATP binding cassette (ABC) transporters are confirmed to be associated with resistance against anticancer drugs. To investigate the relationship between these ten ABC transporters and the nasopharyngeal carcinoma cell line CNE2 resistant to cisplatin, cisplatin and cisplatin with 5-fluorouracil were used to induce the CNE2 cell to acquire the drug-resistance for 1 year. After these cells were cultured without drugs for 2 months, the MTT assay method was used to determine the dose-effect relationship of cisplatin and resistant index. Quantitative real time polymerase chain reaction was used to detect the mRNA expression of ten ABC transporters in CNE2 and the drug-resistant CNE2 cells, and the result was confirmed by immunocytochemical method. The results of MTT method showed that two cell lines resistant to cisplatin (named as CNE2/DDP) and cisplatin with 5-fluorouracil (named as CNE2/DDP+5Fu) were established, with resistant index 2.58 and 5.31, respectively. Of ten ABC transporters, only ABCC2 was found to be up-regulated both in CNE2/DDP and CNE2/DDP+5Fu cells, for increasing about 2.50 and 4.08 folds, respectively. The results of immunocytochemical method also confirmedthat the expression of ABCC2 in CNE2/DDP and CNE2/DDP+5Fu cells were stronger that that in CNE2 cell. Furthermore, ABCC2 protein was found to be located at nuclear membrane of CNE2/DDP +5Fu cell but not at nuclear membrane of CNE2 cell. The results suggest that ABCC2 may play an important role in cisplatinresistance of nasopharyngeal carcinoma cell line CNE2.

Expression and Function of ABC Transporters as Multidrug Resistance Mechansims in Gastric Cancer Cells

PURPOSE: Multidrug resistance (MDR) is a phenomenon whereby tumor cell acquire resistance to a broad range of structurally and functionally diverse chemotherapeutic drugs. The most widely implicated mechanism of MDR is that of altered membrane transporter in tumor cells. P-glycoprotein (Pgp), multidrug resistance protein (MRP), and breast cancer-resistance protein (BCRP) are well known membrane transporters, which pump out antitumor agents via an ATP-dependent process, the so called ATP-binding cassette (ABC) superfamily or transporter. This study was undertaken to test the prevalence of each ABC transporter, and which of then exhibit functional activity in various gastric cancer cells. METHODS: The expressions of Pgp, MRP, and BCRP mRNA were determined by RT-PCR assay on 10 gastric cancer cells. The sensitivity to anticancer agents, substrates for each ABC transporter in the gastric cancer cells was determined using the MTT assay. The intracellular accumulation of fluorescent compounds for the functional detection of each ABC transporter was determined using flow cytometry. RESULTS: The Pgp mRNA was expressed at various levels in 9 out of the 10 gastric cancer cells tested, but significantly low. MRP mRNA was constitutively expressed in all the cells. BCRP mRNA was differentially expressed in 5 of the gastric cancer cells. There was no relation between the expressions of Pgp and MRP and the cytotoxicity to each substrate. It was observed that the accumulations of paclitaxel and VP-16 were significantly increased on the additions of PSC833 and probenecid, respectively, in all tested cells. The reversal effect of drug accumulation by each inhibitor was much higher in the MRP than Pgp. With BCRP, the observed cytotoxic effect and amount of mitoxanthrone accumulation were less than in the cells expressing the highest levels of BCRP compared to those that did not. However the mitoxanthrone accumulation was not increased on the addition of FTC in the either cell type. CONCLUSION: This study suggests that of the ABC transporters, MRP has primarily functional activity, whereas that of Pgp is only slight, in the gastric cancer cells. Other possible MDR mechanisms involved will have to be explored in further studies.