Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 15 de 15
Filtrar
Más filtros











Base de datos
Intervalo de año de publicación
1.
Artículo en Inglés | MEDLINE | ID: mdl-38397617

RESUMEN

BACKGROUND: Colorectal cancer (CRC) screening is effective in the prevention and early detection of cancer. Implementing evidence-based screening guidelines remains a challenge, especially in Federally Qualified Health Centers (FQHCs), where current rates (43%) are lower than national goals (80%), and even lower in populations with limited English proficiency (LEP) who experience increased barriers to care related to systemic inequities. METHODS: This quality improvement (QI) initiative began in 2016, focused on utilizing patient navigation and practice facilitation to addressing systemic inequities and barriers to care to increase CRC screening rates at an urban FQHC, with two clinical locations (the intervention and control sites) serving a diverse population through culturally tailored education and navigation. RESULTS: Between August 2016 and December 2018, CRC screening rates increased significantly from 31% to 59% at the intervention site (p < 0.001), with the most notable change in patients with LEP. Since 2018 through December 2022, navigation and practice facilitation expanded to all clinics, and the overall CRC screening rates continued to increase from 43% to 50%, demonstrating the effectiveness of patient navigation to address systemic inequities. CONCLUSIONS: This multilevel intervention addressed structural inequities and barriers to care by implementing evidence-based guidelines into practice, and combining patient navigation and practice facilitation to successfully increase the CRC screening rates at this FQHC.


Asunto(s)
Neoplasias Colorrectales , Navegación de Pacientes , Humanos , Detección Precoz del Cáncer , Promoción de la Salud , Instituciones de Salud , Neoplasias Colorrectales/diagnóstico , Neoplasias Colorrectales/prevención & control , Neoplasias Colorrectales/epidemiología , Tamizaje Masivo
2.
ACG Case Rep J ; 10(6): e01087, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37342653

RESUMEN

With endoscopic advancements, the number of detected intestinal lymphangiectasias has been on the rise. They are generally considered benign and incidental; occasionally, these lesions carry complications, and best management options need to be established. Bleeding intestinal lymphangiectasias should be considered a rare cause in the differential diagnosis for gastrointestinal bleeding. References in the literature primarily indicate surgical treatment in these situations. In this study, we report an uncommon case of a man with esophageal adenocarcinoma who developed acute gastrointestinal bleeding from duodenal lymphangiectasias that were successfully banded.

3.
Cancers (Basel) ; 13(18)2021 Sep 16.
Artículo en Inglés | MEDLINE | ID: mdl-34572881

RESUMEN

PURPOSE: The incidence of esophageal adenocarcinoma (EAC) has risen substantially in recent decades, while the average 5-year survival remains only ~20%. Disease stage and treatment are the strongest prognostic factors. The role of lifestyle factors in relation to survival remains uncertain, with a handful of studies to date investigating associations with obesity, smoking, physical activity, diet, or medications. METHODS: This study included patients diagnosed with primary adenocarcinoma of the esophagus, gastroesophageal junction, or cardia (N = 371) at Roswell Park Comprehensive Cancer Center between 2003 and 2019. Leveraging extensive data abstracted from electronic medical records, epidemiologic questionnaires, and a tumor registry, we analyzed clinical, behavioral, and environmental exposures and evaluated stage-specific associations with survival. Survival distributions were visualized using Kaplan-Meier curves. Cox proportional hazards regression models adjusted for age, sex, stage, treatment, and comorbidities were used to estimate the association between each exposure and all-cause or cancer-specific mortality. RESULTS: Among patients presenting with localized/regional tumors (stages I-III), current smoking was associated with increased overall mortality risk (HR = 2.5 [1.42-4.53], p = 0.002), while current physical activity was linked to reduced risk (HR = 0.58 [0.35-0.96], p = 0.035). Among patients with stage IV disease, individuals reporting pre-diagnostic use of statins (HR = 0.62 [0.42-0.92], p = 0.018) or NSAIDs (HR = 0.61 [0.42-0.91], p = 0.016) had improved overall survival. Exploratory analyses suggested that high pre-diagnostic dietary consumption of broccoli, carrots, and fiber correlated with prolonged overall survival in patients with localized/regional disease. CONCLUSION: Our data suggest that lifestyle exposures may be differentially associated with EAC survival based on disease stage. Future investigation of larger, diverse patient cohorts is essential to validate these findings. Our results may help inform the development of lifestyle-based interventions to improve EAC prognosis and quality of life.

4.
Front Oncol ; 11: 679177, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33996609

RESUMEN

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy. Nivolumab, an anti-PD-1 monoclonal antibody, markedly improved overall survival in advanced renal cell carcinoma (RCC). However, ICIs can rarely trigger massive inflammation, a phenomenon characterized by rapid acceleration in radiographic tumor growth, the mechanisms underlying which are largely unknown. We report three patients with metastatic RCC who experienced rapid radiographic progression and clinical deterioration following treatment with nivolumab. However, histological analysis revealed no viable cancer despite the evidence of radiological progression. Instead, extensive necrosis and lymphohistiocytic infiltration were noted, as described previously in patients with ICI-induced pseudoprogression. Based on these observations, we postulate that exuberant antitumor inflammatory responses may contribute to adverse clinical outcomes in some patients with ICI-induced radiographic progression. Prospective studies incorporating tumor biopsies may shed more light on this rare phenomenon.

5.
ACG Case Rep J ; 7(4): e00360, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32548190

RESUMEN

Immune checkpoint inhibitors (ICIs) can result in immune-related adverse events which require rapid identification and treatment. Gastrointestinal immune-related adverse events are among the most frequent and severe of these events. ICI colitis can be refractory to current therapies such as corticosteroids and biologic therapy. Fecal microbiota transplantation (FMT) is currently used in cases of recurrent Clostridioides difficile colitis. Many investigations are underway to test the utility of FMT for additional indications, including inflammatory bowel disease (IBD). We present a 71-year-old man with ICI colitis that was nonresponsive to currently defined management options and treated with benefit from FMT.

6.
Antimicrob Agents Chemother ; 58(3): 1713-22, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24379203

RESUMEN

The blood-testis barrier and blood-brain barrier are responsible for protecting the male genital tract and central nervous system from xenobiotic exposure. In HIV-infected patients, low concentrations of antiretroviral drugs in cerebrospinal fluid and seminal fluid have been reported. One mechanism that may contribute to reduced concentrations is the expression of ATP-binding cassette drug efflux transporters, such as P-glycoprotein (P-gp). The objective of this study was to investigate in vivo the tissue distribution of the HIV protease inhibitor atazanavir in wild-type (WT) mice, P-gp/breast cancer resistance protein (Bcrp)-knockout (Mdr1a-/-, Mdr1b-/-, and Abcg2-/- triple-knockout [TKO]) mice, and Cyp3a-/- (Cyp) mice. WT mice and Cyp mice were pretreated with a P-gp/Bcrp inhibitor, elacridar (5 mg/kg of body weight), and the HIV protease inhibitor and boosting agent ritonavir (2 mg/kg intravenously [i.v.]), respectively. Atazanavir (10 mg/kg) was administered i.v. Atazanavir concentrations in plasma (Cplasma), brain (Cbrain), and testes (Ctestes) were quantified at various times by liquid chromatography-tandem mass spectrometry. In TKO mice, we demonstrated a significant increase in atazanavir Cbrain/Cplasma (5.4-fold) and Ctestes/Cplasma (4.6-fold) ratios compared to those in WT mice (P<0.05). Elacridar-treated WT mice showed a significant increase in atazanavir Cbrain/Cplasma (12.3-fold) and Ctestes/Cplasma (13.5-fold) ratios compared to those in vehicle-treated WT mice. In Cyp mice pretreated with ritonavir, significant (P<0.05) increases in atazanavir Cbrain/Cplasma (1.8-fold) and Ctestes/Cplasma (9.5-fold) ratios compared to those in vehicle-treated WT mice were observed. These data suggest that drug efflux transporters, i.e., P-gp, are involved in limiting the ability of atazanavir to permeate the rodent brain and genital tract. Since these transporters are known to be expressed in humans, they could contribute to the low cerebrospinal and seminal fluid antiretroviral concentrations reported in the clinic.


Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/fisiología , Encéfalo/metabolismo , Inhibidores de la Proteasa del VIH/farmacocinética , Oligopéptidos/farmacocinética , Piridinas/farmacocinética , Túbulos Seminíferos/metabolismo , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2 , Transportadoras de Casetes de Unión a ATP/fisiología , Animales , Sulfato de Atazanavir , Química Encefálica , Citocromo P-450 CYP3A , Sistema Enzimático del Citocromo P-450/fisiología , Inhibidores de la Proteasa del VIH/análisis , Inhibidores de la Proteasa del VIH/sangre , Masculino , Ratones , Ratones Noqueados , Oligopéptidos/análisis , Oligopéptidos/sangre , Piridinas/análisis , Piridinas/sangre , Ritonavir/análisis , Ritonavir/sangre , Ritonavir/farmacocinética , Túbulos Seminíferos/química , Testículo/química , Testículo/metabolismo
7.
Biochem Biophys Res Commun ; 444(4): 531-6, 2014 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-24472536

RESUMEN

P-glycoprotein (P-gp, product of Mdr1a and Mdr1b genes), multidrug resistance associated proteins (Mrps), and breast cancer resistance protein (Bcrp), all members of the ATP-binding cassette (ABC) membrane-associated drug transporters superfamily, can significantly restrict the entry of antiretroviral drugs (ARVs) into organs which exhibit a barrier function such as the central nervous system (CNS) and the male genital tract (MGT). In vitro, HIV-1 viral proteins such as glycoprotein-120 (gp120) and transcriptional transactivator (tat) have been shown to alter the expression of these transporters and ARVs permeability. The objective of this study was to compare mRNA expression of these transporters, in vivo, in several tissues obtained from HIV-1 transgenic rats (Tg-rat) (8 and 24 weeks) with those of age-matched wild-type rats. At 24 weeks, significant changes in several drug transporter mRNA expressions were observed, in particular, in brain, kidney, liver and testes. These findings suggest that HIV-1 viral proteins can alter the expression of ABC drug transporters, in vivo, in the context of HIV-1 and further regulate ARVs permeability in several organs including the CNS and MGT, two sites which have been reported to display very low ARVs permeability in the clinic.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/genética , VIH-1/fisiología , Interacciones Huésped-Patógeno , Ratas/genética , Ratas/virología , Proteínas Virales/genética , Animales , Expresión Génica , VIH-1/genética , Masculino , ARN Mensajero/genética , Ratas Sprague-Dawley , Ratas Transgénicas
8.
Curr Pharm Des ; 20(10): 1543-63, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-23789949

RESUMEN

Membrane-associated drug transporters are important determinants of antiretroviral drug disposition in the central nervous system during HIV-1 infection. A number of influx and efflux transport proteins expressed at the blood-brain barrier, blood-cerebrospinal fluid barrier and in brain parenchyma cellular compartments (i.e., astrocytes, microglia) have been implicated in the traffic of many antiretroviral drugs into and out of the brain. In particular, members of the ATP-binding cassette membrane associated transporter superfamily and Solute Carrier family are known to be involved in the efflux and/or influx of drugs, respectively. As a result, changes in the functional expression of these transporters can alter the disposition and distribution of drugs in the brain. Moreover, antiretroviral therapy itself and/or pathological events (i.e., inflammation, oxidative stress) associated with viral infection may affect the functional expression of these transporters. This review summarizes recent knowledge on the role of drug transporters in regulating brain antiretroviral drug transport in the context of HIV-1 infection.


Asunto(s)
Fármacos Anti-VIH/uso terapéutico , Barrera Hematoencefálica/metabolismo , Sistemas de Liberación de Medicamentos , Infecciones por VIH/virología , VIH-1 , Proteínas de Transporte de Membrana/metabolismo , Enfermedades del Sistema Nervioso/tratamiento farmacológico , Enfermedades del Sistema Nervioso/metabolismo , Animales , Barrera Hematoencefálica/efectos de los fármacos , Infecciones por VIH/complicaciones , Infecciones por VIH/tratamiento farmacológico , Humanos , Enfermedades del Sistema Nervioso/etiología
9.
J Clin Pharmacol ; 53(9): 934-45, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23856938

RESUMEN

The use of antiretroviral therapy (ART) as pre-exposure prophylaxis (PrEP) has gained global attention as a promising HIV prevention strategy in men who have sex with men. Permeability of these agents in the rectal mucosa may be partially regulated by interactions with drug efflux transporters, P-glycoprotein (P-gp), multidrug resistance-associated proteins (MRPs) and/or breast cancer resistance protein (BCRP). The objective of this work was to investigate the expression of drug efflux transporters in recto-sigmoid colon tissues of HIV-infected and uninfected men, and evaluate the association of ART and/or HIV infection with drug transporter expression. MDR1/P-gp, MRPs (1-4) and BCRP mRNA and protein expression were detected in sigmoid colon biopsies of HIV-uninfected individuals. Biopsies from HIV-infected, ART-naïve participants revealed a significant downregulation of P-gp and MRP2 protein levels compared to HIV-uninfected individuals. Biopsies from HIV-infected ART-treated patients showed 1.9-fold higher P-gp protein expression and 1.5-fold higher MRP2 protein expression compared to the ones obtained from the HIV-infected ART-naïve patients. This is a first report demonstrating that HIV infection or ART could alter expression of drug efflux transporters in gut mucosa which in turn could affect the permeability of PrEP antiretroviral agents across this barrier, a highly vulnerable site of HIV transmission.


Asunto(s)
Antirretrovirales/farmacología , Colon Sigmoide/metabolismo , Infecciones por VIH/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Adulto , Anciano , Antirretrovirales/uso terapéutico , Recuento de Linfocito CD4 , Colon Sigmoide/inmunología , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/inmunología , Infecciones por VIH/virología , Humanos , Recuento de Linfocitos , Masculino , Proteínas de Transporte de Membrana/genética , Persona de Mediana Edad , ARN Mensajero/metabolismo , Carga Viral , Adulto Joven
10.
Mol Pharmacol ; 81(4): 598-609, 2012 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-22266374

RESUMEN

Breast cancer resistance protein (BCRP/ABCG2), an ATP-binding cassette (ABC) membrane-associated drug efflux transporter, is known to localize at the blood-brain barrier (BBB) and can significantly restrict xenobiotic permeability in the brain. The objective of this study is to investigate the regulation of BCRP functional expression by peroxisome proliferator-activated receptor alpha (PPARα), a ligand-activated transcription factor primarily involved in lipid metabolism, in a cerebral microvascular endothelial cell culture system (hCMEC/D3), representative of human BBB. We demonstrate that PPARα-selective ligands (i.e., clofibrate, GW7647) significantly induce BCRP mRNA and protein expression in a time- and concentration-dependent manner, whereas pharmacological inhibitors (i.e., MK886, GW6471) prevent this induction. Using [(3)H]mitoxantrone, an established BCRP substrate, we observe a significant reduction in its cellular accumulation by monolayer cells treated with clofibrate, suggesting increased BCRP efflux activity. In addition, we show a significant decrease in BCRP protein expression and function when PPARα is down-regulated by small interfering RNA. Applying chromatin immunoprecipitation and quantitative real-time polymerase chain reaction, we observe that clofibrate treatment increases PPARα binding to the peroxisome proliferator response element within the ABCG2 gene promoter. This study provides the first evidence of direct BCRP regulation by PPARα in a human in vitro BBB model and suggests new targeting strategies for either improving drug brain bioavailability or increasing neuroprotection.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/fisiología , Encéfalo/irrigación sanguínea , Endotelio Vascular/metabolismo , Microvasos/metabolismo , Proteínas de Neoplasias/fisiología , PPAR alfa/fisiología , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2 , Secuencia de Bases , Disponibilidad Biológica , Barrera Hematoencefálica , Línea Celular Transformada , Inmunoprecipitación de Cromatina , Cartilla de ADN , Endotelio Vascular/citología , Técnica del Anticuerpo Fluorescente , Humanos , Microvasos/citología , Reacción en Cadena en Tiempo Real de la Polimerasa
11.
J Pharmacol Exp Ther ; 340(1): 96-108, 2012 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-21990609

RESUMEN

The blood-testis barrier (BTB), composed primarily of Sertoli cells, is responsible for protecting developing germ cells from xenobiotic exposure. ATP-binding cassette (ABC) membrane-associated drug efflux transporters, P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and the multidrug resistance-associated proteins (Mrps), have been shown to restrict antiretroviral drug permeability at blood-tissue barriers such as the blood-brain barrier. However, it remains unclear whether these transporters are functional at the level of Sertoli cells and can regulate anti-HIV drug permeability at the BTB. This study investigated the functional expression of ABC transporters in a mouse Sertoli cell line system (TM4) and in primary cultures of human Sertoli cells (HSECs). Expression of multidrug resistance Mdr1a/1b/MDR1/P-gp, Mrp1/MRP1, and Mrp4/MRP4 is confirmed by quantitative polymerase chain reaction and immunoblotting analysis in TM4 cells and HSECs. Immunofluorescence studies revealed plasma membrane localization of P-gp, Mrp1/MRP1, and Mrp4/MRP4 in both cell systems. However, Bcrp expression and localization was only detected in rodent cells. Accumulation of 1) rhodamine-6G (R-6G), a fluorescent P-gp substrate, 2) [³H]atazanavir, a HIV protease inhibitor and known P-gp substrate, 3) 2'7'-bis-(2-carboxyethyl)-5-(and-6)carboxyfluorescein (BCECF), a fluorescent Mrp substrate, and 4) [³H]mitoxantrone, a BCRP substrate, by TM4 monolayer cells in the presence of established inhibitors demonstrates that these transporters are functional. In addition, several anti-HIV drugs significantly enhance the accumulation of R-6G, [³H]atazanavir, BCECF, and [³H]mitoxantrone by TM4 cells. This study provides the first evidence of ABC transporter expression and activity in Sertoli cells and suggests that these transporters could play an important role in restricting antiretroviral drug permeability at the BTB.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/biosíntesis , Fármacos Anti-VIH/farmacocinética , Barrera Hematotesticular/efectos de los fármacos , Células de Sertoli/metabolismo , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/biosíntesis , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2 , Transportadoras de Casetes de Unión a ATP/genética , Animales , Western Blotting , Línea Celular , Células Cultivadas , ADN Complementario/biosíntesis , ADN Complementario/genética , Femenino , Técnica del Anticuerpo Fluorescente , Humanos , Masculino , Ratones , Ratones Endogámicos BALB C , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/biosíntesis , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Proteínas de Neoplasias/biosíntesis , Proteínas de Neoplasias/genética , Permeabilidad , Reacción en Cadena de la Polimerasa , ARN/biosíntesis , ARN/aislamiento & purificación , Células de Sertoli/efectos de los fármacos , Células de Sertoli/ultraestructura
12.
Trends Pharmacol Sci ; 31(1): 22-35, 2010 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-20004485

RESUMEN

Treatment of human immunodeficiency virus (HIV) infection involves a combination of several antiviral agents belonging to different pharmacological classes. This combination is referred to as highly active antiretroviral therapy (HAART). This treatment has proved to be very effective in suppressing HIV replication, but antiretroviral drugs have complex pharmacokinetic properties involving extensive drug metabolism and transport by membrane-associated drug carriers. Combination drug therapy often introduces complex drug-drug interactions that can result in toxic or sub-therapeutic drug concentrations, compromising treatment. This review focuses on the role of ATP-binding cassette (ABC) membrane-associated efflux transporters and solute carrier (SLC) uptake transporters in antiretroviral drug disposition, and identifies clinically important antiretroviral drug-drug interactions associated with changes in drug transport.


Asunto(s)
Fármacos Anti-VIH/farmacología , Infecciones por VIH/tratamiento farmacológico , Proteínas de Transporte de Membrana/efectos de los fármacos , Transportadoras de Casetes de Unión a ATP/efectos de los fármacos , Transportadoras de Casetes de Unión a ATP/metabolismo , Animales , Fármacos Anti-VIH/efectos adversos , Fármacos Anti-VIH/farmacocinética , Terapia Antirretroviral Altamente Activa/métodos , Transporte Biológico/efectos de los fármacos , Interacciones Farmacológicas , Humanos , Proteínas de Transporte de Membrana/metabolismo
13.
Mol Pharmacol ; 74(1): 264-73, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18413666

RESUMEN

Mammalian cells require specific transport mechanisms for the cellular uptake and release of endogenous nucleosides such as adenosine, and nucleoside analogs used in chemotherapy. We have identified a novel splice variant of the mouse equilibrative nucleoside transporter, mENT1, that results from the exclusion of exon 11 during pre-RNA processing. This variant encodes a truncated protein (mENT1Delta11) missing the last three transmembrane domains of the full-length mENT1. The mENT1Delta11 transcript and protein were found to be differentially distributed among tissues relative to full-length mENT1. PK15-NTD (nucleoside transport deficient) cells were transfected with mENT1 or mENT1Delta11 and assessed for nucleoside transport function. No significant differences were observed between the mENT1 and mENT1Delta11 in terms of transport function or inhibitor binding affinity. PK15-mENT1Delta11 transfected cells bound the ENT1 probe [3H]nitrobenzylthioinosine (NBMPR) with high affinity and mediated the cellular accumulation of both [3H]2-chloroadenosine and [3H]uridine. The only significant differences between the mENT1 variants were that mENT1Delta11 could not be photolabeled with [3H]NBMPR and that mENT1Delta11 was insensitive to the transporter-modifying effects of N-ethylmaleimide. These data suggest that the last three transmembrane domains of mENT1 are not necessary for transport activity, but this region does contain the cysteines responsible for the sensitivity of mENT1 to sulfhydryl reagents, and the residues important for covalent modification of the protein with NBMPR. These results provide important guidelines for future mutagenesis studies aimed at elucidating the tertiary structure of the ENT1 protein and the domains involved in inhibitor binding and substrate translocation.


Asunto(s)
Empalme Alternativo , Tranportador Equilibrativo 1 de Nucleósido/genética , Tranportador Equilibrativo 1 de Nucleósido/metabolismo , Proteínas de Transporte de Nucleósidos/genética , Proteínas de Transporte de Nucleósidos/metabolismo , Secuencia de Aminoácidos , Animales , Línea Celular , Línea Celular Tumoral , Tranportador Equilibrativo 1 de Nucleósido/química , Cinética , Masculino , Ratones , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Proteínas de Transporte de Nucleósidos/química , Plásmidos , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Porcinos , Distribución Tisular , Transcripción Genética , Transfección
14.
Microvasc Res ; 75(3): 351-7, 2008 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-18048066

RESUMEN

The cardioprotective actions of adenosine are terminated by its uptake into endothelial cells with subsequent metabolism through hypoxanthine to uric acid. This process involves xanthine oxidase-mediated generation of reactive oxygen species (ROS), which have been implicated in the vascular dysfunction observed in ischemia-reperfusion injury. The equilibrative nucleoside transporter, ENT2, mediates the transfer of hypoxanthine into cells. We hypothesize that ENT2 also mediates the cellular release of hypoxanthine, which would limit the amount of intracellular hypoxanthine available for xanthine oxidase-mediated ROS production. Rat microvascular endothelial cells (MVECs) were isolated from skeletal muscle by lectin-affinity purification. The transport of [(3)H]hypoxanthine was assessed using an oil-stop method, and hypoxanthine metabolites were identified by thin-layer chromatography. MVECs accumulated hypoxanthine with a K(m) of 300 microM and a V(max) of 2.8 pmol microl(-1) s(-1). ATP-depleted cells loaded with [(3)H]hypoxanthine released the radiolabel with kinetics similar to that obtained for [(3)H]hypoxanthine influx. The uptake and release of [(3)H]hypoxanthine were both blocked by ENT2 inhibitors with similar order of potency. Thus, ENT2 mediates both the influx and efflux of hypoxanthine. Inhibition of ENT2 in MVECs might be expected to increase the amount of intracellular hypoxanthine available for metabolism by xanthine oxidase and enhance the intracellular production of ROS.


Asunto(s)
Endotelio Vascular/metabolismo , Transportador Equilibrativo 2 de Nucleósido/metabolismo , Hipoxantina/metabolismo , Músculo Esquelético/irrigación sanguínea , Alopurinol/farmacología , Animales , Antimetabolitos/farmacología , Transporte Biológico , Células Cultivadas , Cromatografía en Capa Delgada , Desoxiglucosa/farmacología , Tranportador Equilibrativo 1 de Nucleósido/metabolismo , Transportador Equilibrativo 2 de Nucleósido/antagonistas & inhibidores , Hipoxantina/análisis , Masculino , Microcirculación/citología , Microcirculación/metabolismo , Ratas , Ratas Wistar , Rotenona/farmacología , Tritio , Desacopladores/farmacología
15.
Mol Membr Biol ; 24(4): 294-303, 2007.
Artículo en Inglés | MEDLINE | ID: mdl-17520485

RESUMEN

Nucleosides are accumulated by cells via a family of equilibrative transport proteins (ENTs). An alternative splice variant of the most common subtype of mouse ENT (ENT1) has been identified which is missing a protein kinase CK2 (casein kinase 2) consensus site (Ser(254)) in the central intracellular loop of the protein. We hypothesized that this variant (mENT1a) would be less susceptible to modulation by CK2-mediated phosphorylation compared to the variant containing the serine at position 254 (mENT1b). Each splice variant was transfected into nucleoside transporter deficient PK15 cells, and stable transfectants assessed for their ability to bind the ENT1-selective probe [(3)H]nitrobenzylthioinosine (NBMPR) and to mediate the cellular uptake of [(3)H]2-chloroadenosine, with or without treatment with the CK2 selective inhibitor, 4,5,6,7-tetrabromobenzotriazole (TBB). mENT1a had a higher affinity for NBMPR relative to mENT1b - measured both directly by the binding of [(3)H]NBMPR, and indirectly via inhibition of [(3)H]2-chloroadenosine influx by NBMPR. Furthermore, incubation of mENT1b-expressing cells with 10 microM TBB for 48 h decreased both the K(D) and B(max) of [(3)H]NBMPR binding, as well as the V(max) of 2-chloroadenosine uptake, whereas similar treatment of mENT1a-expressing cells with TBB had no effect. PK15 cells transfected with hENT1, which has Ser(254), was similar to mENT1b in its response to TBB. In conclusion, inhibition of CK2 activity, or deletion of Ser(254) from mENT1, enhances transporter affinity for the inhibitor, NBMPR, and reduces the number of ENT1 proteins functioning at the level of the plasma membrane.


Asunto(s)
Quinasa de la Caseína II/fisiología , Proteínas de Transporte de Nucleósidos/metabolismo , 2-Cloroadenosina/farmacocinética , Animales , Quinasa de la Caseína II/antagonistas & inhibidores , Línea Celular , Inhibidores Enzimáticos/farmacología , Tranportador Equilibrativo 1 de Nucleósido , Cinética , Ratones , Proteínas de Transporte de Nucleósidos/análisis , Proteínas de Transporte de Nucleósidos/genética , Unión Proteica , Isoformas de Proteínas/metabolismo , Serina , Transfección
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA