RESUMEN
Ribavirin is a broad-spectrum nucleoside-derived antiviral drug used in combination pharmacotherapy treatment of hepatitis C virus infection. Current evidence indicates that ribavirin-associated teratogenicity is not significant in humans, but more information about the developmental toxicity and mechanisms involved in ribavirin placental kinetics is required to assure its safe use in pregnancy. Thus, we have investigated potential roles of equilibrative nucleoside transporters (ENTs, SLC29A), Na+-dependent influx-mediating concentrative nucleoside transporters (CNTs, SLC28A), and ATP-binding cassette (ABC) efflux pumps, in ribavirin placental pharmacokinetics. Our data indicate that ENT1 participates in uptake of ribavirin by BeWo cells, fresh human placental villous fragments and microvillous plasma membrane (MVM) vesicles while activity of CNTs (probably CNT2) was only observed in BeWo cells. In situ dual perfusion experiments with rat term placenta in an open circuit setup showed that ENT inhibition significantly decreases total ribavirin maternal-to-foetal and foetal-to-maternal clearances. In contrast, no contribution of ABC transporters, p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), or multidrug resistance-associated protein (ABCC2) was detected in assays with MDCKII cells overexpressing them, or in closed circuit dual perfusion experiments with rat term placenta. In summary, our data show that ribavirin placental pharmacokinetics are largely controlled by ENT1 activity and independent of ABCB1, ABCG2, and ABCC2 efflux pumps.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/fisiología , Antimetabolitos/metabolismo , Nucleósidos/fisiología , Placenta/metabolismo , Ribavirina/metabolismo , Animales , Antimetabolitos/farmacología , Línea Celular Tumoral , Perros , Relación Dosis-Respuesta a Droga , Tranportador Equilibrativo 1 de Nucleósido/metabolismo , Femenino , Humanos , Células de Riñón Canino Madin Darby , Proteína 2 Asociada a Resistencia a Múltiples Medicamentos , Placenta/efectos de los fármacos , Embarazo , Transporte de Proteínas/efectos de los fármacos , Transporte de Proteínas/fisiología , Ratas , Ratas Wistar , Ribavirina/farmacología , Especificidad de la EspecieRESUMEN
INTRODUCTION: Zidovudine (AZT) and emtricitabine (FTC) are effective and well tolerated antiretroviral drugs, routinely used in the prevention of perinatal HIV transmission. However, precise mechanism(s) involved in their transfer from mother to fetus are not fully elucidated. Since both drugs are nucleoside analogues, we hypothesized that the mechanisms of their transplacental passage might include equilibrative nucleoside transporters, ENT1 and/or ENT2. METHODS: To address this issue, we performed in vitro accumulation assays in the BeWo placental trophoblast cell line, ex vivo uptake studies in fresh villous fragments isolated from human placenta and in situ dually perfused rat term placenta experiments. RESULTS: Applying this complex array of methods, we did not prove that ENTs play a significant role in transfer of AZT or FTC across the placenta. DISCUSSION: We conclude that the transplacental passage of AZT and FTC is independent of ENTs. Disposition of either compound into the fetal circulation should thus not be affected by ENT-mediated drug-drug interactions or placental expression of the transporters.
Asunto(s)
Emtricitabina/farmacocinética , Proteínas de Transporte de Nucleósido Equilibrativas/metabolismo , Placenta/metabolismo , Inhibidores de la Transcriptasa Inversa/farmacocinética , Zidovudina/farmacocinética , Animales , Línea Celular Tumoral , Femenino , Humanos , Embarazo , Ratas WistarRESUMEN
Endoglin, a transforming growth factor ß (TGF-ß) receptor type III, is co-expressed with endothelial nitric oxide synthase (eNOS) in aortic endothelium in atherosclerotic plaques of mice. Interestingly, atorvastatin (ATV) is able to increase both endoglin and eNOS expression and reduce plaque size beyond its lipid lowering effects but by unknown mechanisms. We hypothesized whether inflammation modulates ATV-dependent induction of endoglin and eNOS expression in vitro in endothelial cells and whether ATV-induced eNOS expression is regulated via endoglin. After treatment of human umbilical vein endothelial cells (HUVECs) with TNF-α, endoglin and eNOS protein expression was reduced, concomitantly with increased levels of cell surface VCAM-1 and soluble endoglin, as determined by flow cytometry, Western blot and ELISA analyses. By contrast, ATV treatment increased endoglin and eNOS protein expression, while preventing TNF-α-mediated downregulation of endoglin and eNOS protein levels. Moreover, suppression of endoglin using small interfering RNA (siRNA), but not inhibition of TGF-ß signaling with SB431542, abrogated ATV-induced eNOS expression. These results suggest that ATV treatment prevents inflammation-reduced endoglin and eNOS expression in endothelial cells and that ATV-induced eNOS expression strongly depends on the proper expression of endoglin in HUVECs. Possible implications of these findings might be reflected in pathological conditions characterized by reduced expression of endoglin and eNOS as for example in hereditary hemorrhagic telangiectasia or in other endothelial dysfunctions.
Asunto(s)
Antígenos CD/metabolismo , Atorvastatina/farmacología , Células Endoteliales de la Vena Umbilical Humana/efectos de los fármacos , Óxido Nítrico Sintasa de Tipo III/metabolismo , Receptores de Superficie Celular/metabolismo , Antígenos CD/genética , Células Cultivadas , Endoglina , Expresión Génica , Células Endoteliales de la Vena Umbilical Humana/metabolismo , Humanos , ARN Interferente Pequeño/genética , Especies Reactivas de Oxígeno/metabolismo , Receptores de Superficie Celular/genética , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
The placental trophoblast at different stages of pregnancy contains some drug transporters and xenobiotic-metabolising enzymes, as well as ligand-activated nuclear receptors, which control their inducible transcriptional regulation. Glucocorticoid receptor alpha (GRalpha) is expressed in both placental syncytiotrophoblast and cytotrophoblast. GRalpha was shown to control inducible expression of several enzymes of the cytochrome P-450 family (CYP) and the drug transporter P-glycoprotein in the liver. However, GRalpha-mediated transcriptional regulation of drug transporters and CYPs has not been studied in the placental trophoblast. In this study, we examined the expression and activity of GRalpha in the transcriptional regulation of P-glycoprotein, CYP3A4, and CYP2C9 in placental trophoblast cell lines. Employing RT-PCR, Western blotting, and luciferase gene reporter assay, we detected the expression and activity of GRalpha in JEG3 and BeWo cell lines. However, we observed that only MDR1 mRNA was up-regulated after treatment of placental cells with dexamethasone. Accordingly, only the promoter of the MDR1 gene was activated by dexamethasone in gene reporter assays in placental cells and the activation was abolished by RU486, an antagonist of GRalpha. CYP3A4 and CYP2C9 promoters were activated in placental cells only after co-transfection with hepatocyte nuclear factor 4alpha (HNF4alpha), which indicates the hepatocyte-specific character of GRalpha-mediated regulation of the genes. On the other hand, coexpression of HNF4alpha had no effect on the activation of the MDR1 gene promoter, suggesting HNF4alpha-independent regulation via GRalpha. We conclude that GRalpha may be involved in the transcriptional regulation of P-glycoprotein in the placental trophoblast. We also indicate that the CYP3A4 and CYP2C9 genes are not inducible through GRalpha in placental cell lines, due to the lack of HNF4alpha expression and possibly some additional hepatocyte-specific transcriptional factors.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/biosíntesis , Hidrocarburo de Aril Hidroxilasas/biosíntesis , Sistema Enzimático del Citocromo P-450/biosíntesis , Receptores de Glucocorticoides/fisiología , Trofoblastos/metabolismo , Línea Celular , Línea Celular Tumoral , Citocromo P-450 CYP2C9 , Citocromo P-450 CYP3A , Dexametasona/farmacología , Femenino , Factor Nuclear 4 del Hepatocito/fisiología , Humanos , Embarazo , Regiones Promotoras Genéticas/fisiología , ARN Mensajero/metabolismo , Activación Transcripcional/fisiologíaRESUMEN
The present paper is concerned with the linguistic aspect of the new anatomical nomenclature (Terminologia Anatomica 1998). Orthographic, morphological, syntactic, lexical, and terminological comments are presented. In the authors' opinion, shortcomings might have been effectively avoided by cooperation with linguists.