RESUMEN
The gastrointestinal epithelium functions as a selective barrier to absorb nutrients, electrolytes and water, but at the same time restricts the passage into the systemic circulation of intraluminal potentially toxic compounds. This epithelium maintains its selective barrier function through the presence of very selective and complex intercellular junctions and the ability of the absorptive cells to reject those compounds. Accordingly, the enterocytes metabolize orally incorporated xenobiotics and secrete the hydrophilic metabolites back into the intestinal lumen through specific transporters localized apically. In the recent decades, there has been increasing recognition of the existence of the intestinal cellular barrier. In the present review we focus on the role of the multidrug resistance-associated protein 2 (MRP2, ABCC2) in the apical membrane of the enterocytes, as an important component of this intestinal barrier, as well as on its regulation. We provide a detailed compilation of significant contributions demonstrating that MRP2 expression and function vary under relevant physiological and pathophysiological conditions. Because MRP2 activity modulates the availability and pharmacokinetics of many therapeutic drugs administered orally, their therapeutic efficacy and safety may vary as well.
Asunto(s)
Intestinos/fisiología , Intestinos/fisiopatología , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Animales , Humanos , Proteína 2 Asociada a Resistencia a Múltiples MedicamentosRESUMEN
The multi-xenobiotics resistance (MXR) mechanisms are the first line of defense against toxic substances in aquatic organisms and present great importance in the adaptation related to contaminated environments. Methyl parathion (MP) is a widely used organophosphate pesticide, which has been associated to various toxic effects in organisms. In the present work, we studied the main genes related to efflux transporters in zebrafish liver (ZFL) cells exposed to MP with and without an inhibitor of ABC transporters (verapamil). The results concerning transporters activity showed that the MXR mechanism is activated to detoxify from methyl parathion. The toxic effects of MP on ZFL cells were increased in the presence of the efflux transporter inhibitor, once cell viability was significantly decreased in co-exposure experiments. The combined exposure to MP and the inhibitor caused an increase in gene expression of P-gp1 (Abcb1) and MRP4 (Abcc4), suggesting that these transporters isoforms are associated with MP efflux. In general, the expression of genes related to the antioxidant defense system (ADS) was significantly increased in ZFL cells co-exposed to MP and verapamil. These data provide useful insights for better understanding of MP detoxification mechanism in fish hepatocytes.
Asunto(s)
Hígado/metabolismo , Metil Paratión/metabolismo , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Proteínas de Pez Cebra/fisiología , Transportadoras de Casetes de Unión a ATP , Animales , Línea Celular , Supervivencia Celular , Relación Dosis-Respuesta a Droga , Hígado/fisiología , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Pez Cebra/metabolismo , Proteínas de Pez Cebra/metabolismoRESUMEN
UNLABELLED: Galectin-1 (Gal-1), a widely expressed ß-galactoside-binding protein, exerts pleiotropic biological functions. Gal-1 is up-regulated in hepatocarcinoma cells, although its role in liver pathophysiology remains uncertain. We investigated the effects of Gal-1 on HepG2 hepatocellular carcinoma (HCC) cell adhesion and polarization. Soluble and immobilized recombinant Gal-1 (rGal-1) promoted HepG2 cell adhesion to uncoated plates and also increased adhesion to laminin. Antibody-mediated blockade experiments revealed the involvement of different integrins as critical mediators of these biological effects. In addition, exposure to rGal-1 markedly accelerated the development of apical bile canaliculi as shown by TRITC-phalloidin labeling and immunostaining for multidrug resistance associated-protein 2 (MRP2). Notably, rGal-1 did not interfere with multidrug resistance protein 1/P-glycoprotein or MRP2 apical localization, neither with transfer nor secretion of 5-chloromethylfluorescein diacetate through MRP2. Stimulation of cell adhesion and polarization by rGal-1 was abrogated in the presence of thiodigalactoside, a galectin-specific sugar, suggesting the involvement of protein-carbohydrate interactions in these effects. Additionally, Gal-1 effects were abrogated in the presence of wortmmanin, PD98059 or H89, suggesting involvement of phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase and cyclic adenosine monophosphate-dependent protein kinase signaling pathways in these functions. Finally, expression levels of this endogenous lectin correlated with HCC cell adhesion and polarization and up-regulation of Gal-1-favored growth of hepatocarcinoma in vivo. CONCLUSION: Our results provide the first evidence of a role of Gal-1 in modulating HCC cell adhesion, polarization, and in vivo tumor growth, with critical implications in liver pathophysiology.
Asunto(s)
Carcinoma Hepatocelular/fisiopatología , Polaridad Celular/fisiología , Proliferación Celular , Galectina 1/fisiología , Neoplasias Hepáticas/fisiopatología , Adhesión Celular/fisiología , Línea Celular Tumoral , Proteínas Quinasas Dependientes de AMP Cíclico/fisiología , Humanos , Proteínas Quinasas Activadas por Mitógenos/fisiología , Proteína 2 Asociada a Resistencia a Múltiples Medicamentos , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Fosfatidilinositol 3-Quinasas/fisiología , Transducción de Señal/fisiologíaAsunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Transporte Biológico/efectos de los fármacos , Hipertensión/tratamiento farmacológico , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/metabolismo , Subfamilia B de Transportador de Casetes de Unión a ATP/fisiología , Animales , Antihipertensivos/uso terapéutico , Transporte Biológico/fisiología , Sistemas de Liberación de Medicamentos , Femenino , Humanos , Hipertensión/metabolismo , Absorción Intestinal/efectos de los fármacos , Absorción Intestinal/fisiología , Masculino , Ratones , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Farmacogenética , Medición de Riesgo , Sensibilidad y Especificidad , Resultado del TratamientoRESUMEN
The mechanisms involved in spironolactone (SL, 200 micromol/kg body weight, 3 days i.p.)-induced choleresis were explored in vivo by evaluating bile salt export pump (Bsep)-, multidrug resistance-associated protein 2 (Mrp2)-, and anion exchanger 2 (AE2)-mediated secretory processes in rat liver. Hepatic bile salt metabolism was also analyzed. Total bile flow was significantly increased by SL, primarily due to an increase in bile salt-independent bile flow, whereas bile salt secretion was decreased. SL did not produce any choleresis in TR(-) rats. SL decreased the de novo bile salt synthesis rate in concordance with impaired microsomal cholesterol 7 alpha-hydroxylase activity, thus leading to a decrease in endogenous bile salt pool size. In contrast, the maximum secretory rate of tauroursodeoxycholate as well as expression of Bsep protein detected by Western blotting were not affected. Thus, decreased bile salt availability for canalicular transport rather than transport capability itself likely explains reduced biliary secretion of bile salts. Biliary secretion of glutathione, an endogenous substrate of Mrp2, and HCO(3)(-), the AE2 substrate, were increased by SL, as a main factor explaining enhanced bile salt-independent bile flow. Western blot studies revealed increased expression of Mrp2 in response to SL whereas AE2 content remained unchanged. Enhanced activity and expression of Mrp2 was confirmed by analyzing the excretion rate of dinitrophenyl S-glutathione, an exogenous substrate of Mrp2, in isolated hepatocytes and by immunofluorescence microscopy, respectively. We conclude that SL increased bile flow mainly by increasing the biliary secretion of glutathione species and HCO(3)(-); increased expression of Mrp2 is also involved.
Asunto(s)
Bilis/efectos de los fármacos , Proteínas de Transporte de Membrana/fisiología , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Espironolactona/farmacología , Miembro 11 de la Subfamilia B de Transportador de Casetes de Unión al ATP , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/fisiología , Animales , Proteínas de Transporte de Anión/genética , Proteínas de Transporte de Anión/fisiología , Antiportadores/genética , Antiportadores/fisiología , Bilis/metabolismo , Transporte Biológico , Hepatocitos/metabolismo , Masculino , Proteínas de Transporte de Membrana/genética , Proteína 2 Asociada a Resistencia a Múltiples Medicamentos , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Ratas , Ratas Wistar , Proteínas SLC4ARESUMEN
CPT-11 is a topoisomerase I (Topo I) inhibitor which was initially described as active in multi-drug resistance (MDR) tumors. The MDR phenomenon is characterized by the overexpression of efflux pumps which are able to extrude a range of drugs non-related chemical or functionally. In this work, we treated leukemic cells with CPT-11 300 microM at 24h and compared its cytotoxicity with the activity of efflux pumps and with cell cycle phase. Our findings show that CPT-11 has a potent anti-tumor activity in leukemic cells regardless MDR phenotype and the cell cycle phase, suggesting new avenues to be explored in leukemia treatment.