ENFERMEDAD DE CHAGAS: NOVEDADES EN NANOMEDICINAS COMO ESTRATEGIA TERAPÉUTICA / Chagas disease: an update on nanomedicine as a novel therapeutical strategy

La enfermedad de Chagas, tripanosomiasis americana o simplemente Chagas, es una infección parasitaria que afecta a más de 8 millones de personas a nivel mundial. La Organización Mundial de la Salud ha incluido a esta patología dentro de la categoría de enfermedades tropicales desatendidas (junto a la malaria, leishmaniasis y dengue, entre otras), ya que afecta mayoritariamente a grupos vulnerables de la sociedad sin acceso a condiciones adecuadas de sanidad ni tratamientos médicos, y en contacto continuo con los vectores de contagio. La terapia actual incluye fármacos utilizados desde hace ya más de 50 años que, si bien son efectivos en la fase inicial de la enfermedad, fallan en la erradicación total del parásito, a la vez que generan graves efectos adversos. En vista de este panorama, surge la necesidad de nuevas estrategias de bajo costo para optimizar la terapia. Una posible alternativa para mejorar el tratamiento, diagnóstico y prevención surge desde la nanotecnología: el presente artículo revisa el estado actual de la investigación de nanomedicinas para tratar la enfermedad de Chagas. Cabe mencionar que, si bien se ha avanzado enormemente en dirección a una terapia que disminuya los efectos adversos de la droga, aún no se ha logrado diseñar y producir un nanovehículo farmacéutico óptimo contra el agente etiológico de la enfermedad.

Chagas disease, American trypanosomiasis or Chagas disease, is a parasitic infection that affects more than 8 million people worldwide. This pathology was included by the World Health Organization within the category of neglected tropical diseases (along with malaria, leishmaniasis and dengue, among others), since it mainly affects vulnerable groups in society without access to adequate health conditions nor medical treatments, and in continuous contact with the transmission vectors. Current therapy includes drugs used for more than 50 years that, although effective in the initial phase of the disease, fail in the total eradication of the parasite, while generating serious adverse effects. In light of this situation, new low-cost approach strategies are necessary to optimize therapy. A possible alternative to improve treatment, diagnosis and prevention arises from nanotechnology: this article reviews the current state of research in nanomedicines to treat Chagas disease. It is worth mentioning that, although great progress has been made towards a therapy that reduces the adverse effects of the drug, it has not yet been possible to design and produce an optimal pharmaceutical nanovehicle against the etiologic agent of the disease.

Puesta a punto de la técnica de Ussing Chamber para estudios de permeabilidad intestinal en tejido de cerdo / Optimization of the Ussing Chamber Technique for studies of intestinal permeability in pig tissue

El Sistema de Clasificación Biofarmacéutica es un marco científico para clasificar ingredientes farmacéuticos activos en base a su solubilidad acuosa y su permeabilidad intestinal, que cuando se combina con la disolución del producto toma en cuenta los tres factores principales que gobiernan la velocidad y el alcance de la absorción de un fármaco a partir de formas posológicas orales sólidas de liberación inmediata. Cuando los fármacos cumplen con determinados criterios biofarmacéuticos este sistema permite reemplazar los estudios in vivo de biodisponibilidad / bioequivalencia por estudios in vitro. La permeabilidad intestinal de los IFAs puede ser estudiada por diferentes métodos, uno de ellos es la técnica de Ussing Chamber que utiliza una porción de tejido intestinal. La ventaja de esta técnica es que permite conservar las capacidades funcionales de los tejidos. En la puesta a punto de esta nueva técnica se obtuvieron datos concordantes con bibliografía. Se evaluó la permeabilidad de ibuprofeno, metoprolol y atenolol (drogas de alta y baja permeabilidad) utilizando Ussing Chamber con intestino delgado de cerdo. Contar con esta técnica en el Departamento de Farmacología representa un valioso complemento a las metodologías ya utilizadas: estudios in vitro (células Caco-2 y MDCK) e in situ (perfusión intestinal en rata).

The Biopharmaceutical Classification System is a scientific framework for classifying Active Pharmaceutical Ingredients based on their aqueous solubility and their intestinal permeability which, when combined with the dissolution of the product takes into account the three main factors that govern the absorption speed and extent of a drug from immediate-release solid oral dosage form. When drugs meet certain biopharmaceutical criteria, this system allows in vivo bioavailability / bioequivalence studies to be replaced by in vitro studies. The intestinal permeability of APIs can be studied by different methods, one of them is the Ussing Chamber technique that uses a portion of intestinal tissue. The advantage of this technique is that it allows to conserve the functional capacities of tissues. In the development of this new technique, concordant data with bibliography was obtained. The permeability of ibuprofen, metoprolol and atenolol (high and low permeability drugs) was evaluated utilizing the Ussing Chamber Technique with pig small intestine. To have this technique in the Department of Pharmacology represents a valuable complement to the methodologies already used; both in vitro (Caco-2 and MDCK cells) and in situ (intestinal perfusion in rat) studies.

Computer-Aided Recognition of ABC Transporters Substrates and Its Application to the Development of New Drugs for Refractory Epilepsy.

Despite the introduction of more than 15 third generation antiepileptic drugs to the market from 1990 to the moment, about one third of the epileptic patients still suffer from refractory to intractable epilepsy. Several hypotheses seek to explain the failure of drug treatments to control epilepsy symptoms in such patients. The most studied one proposes that drug resistance might be related with regional overactivity of efflux transporters from the ATP-Binding Cassette (ABC) superfamily at the blood-brain barrier and/or the epileptic foci in the brain. Different strategies have been conceived to address the transporter hypothesis, among them inhibiting or down-regulating the efflux transporters or bypassing them through a diversity of artifices. Here, we review scientific evidence supporting the transporter hypothesis along with its limitations, as well as computer-assisted early recognition of ABC transporter substrates as an interesting strategy to develop novel antiepileptic drugs capable of treating refractory epilepsy linked to ABC transporters overactivity.

Transepithelial transport of biperiden hydrochloride in Caco-2 cell monolayers.

The aim of this research has been to determine the biperiden hydrochloride permeability in Caco-2 model, in order to classify it based on the Biopharmaceutics Classification System (BCS). The World Health Organization (WHO) as well as many other authors have provisionally assigned the drug as BCS class I (high solubility-high permeability) or III (high solubility-low permeability), based on different methods. We determined biperiden BCS class by comparing its permeability to 5 pre-defined compounds: atenolol and ranitidine hydrochloride (low permeability group) and metoprolol tartrate, sodium naproxen and theophylline (high permeability group). Since biperiden permeability was higher than those obtained for high permeability drugs, we classified it as a BCS class I compound. On the other hand, as no differences were obtained for permeability values when apical to basolateral and basolateral to apical fluxes were studied, this drug cannot act as a substrate of efflux transporters. As a consequence of our results, we suggest that the widely used antiparkinsonian drug, biperiden, should be candidate for a waiver of in vivo bioequivalence studies.

Prediction of drug intestinal absorption by new linear and non-linear QSPR.

In order to minimize the high attrition rate that usually characterizes drug research and development projects, current medicinal chemists aim to characterize both pharmacological and ADME profiles at the beginning of drug R&D initiatives. Thus, the development of ADME High-Throughput Screening in vitro and in silico ADME models has become an important growing research area. Here we present new linear and non-linear predictive QSPR models to predict the human intestinal absorption rate, which are derived from a medium sized, balanced and diverse training set of organic compounds. The structure-property relationships so obtained involve only 4 molecular descriptors, and display an excellent ratio of number of cases to number of descriptors. Their adjustment of the training set data together with the performance achieved during the internal and external validation procedures are comparable to previously reported modeling efforts.

Characterization of 5-HT receptor subtypes mediating contraction in human umbilical vein. 1. Evidence of involvement of 5-HT2A receptors using functional and radioligand binding assays.

This study attempted to characterize pharmacologically the involvement of 5-HT(2A) receptors in 5-HT-induced contractile responses in human umbilical vein (HUV) rings employing functional and radioligand binding assays. In HUV rings, prazosin 1 micro M did not affect contractile responses elicited by 5-HT, ruling out the involvement of alpha(1)-adrenoceptors in contractile responses to 5-HT. 5-HT-induced contractions were competitively blocked by ketanserin, a 5-HT(2A)-selective antagonist. The apparent pA(2) value was 9.8 and the Schild slope significantly less than unity, suggesting that 5-HT-induced responses are mediated by a heterogeneous receptor population. Alpha-methyl-5-HT, a selective 5-HT(2) receptor agonist, induced contractions that were antagonized in a competitive manner by ketanserin. The slope regression was not significantly different from unity and the pA(2) value was 8.8. The selective 5-HT(2A) ligand spiperone produced a parallel rightward shift on 5-HT CRCs in HUV rings. The calculated pA(2) was 9.0, which is in accord for an interaction with the 5-HT(2A) receptor subtype. Alpha-methyl-5-HT CRCs were competitively blocked by spiperone treatment. The Schild analysis yielded a pA(2) of 9.1 with a slope not significantly different from unity. The 5-HT(2C/2A) antagonist mesulergine 10 nM did not affect 5-HT CRCs, suggesting that 5-HT(2C) receptors are not involved in 5-HT-elicited contractions. Higher concentrations of mesulergine showed a parallel rightward shift on 5-HT responses. The calculated pA(2) was 7.44, which suggests an interaction with the 5-HT(2A) receptor subtype. In addition, mesulergine competitively blocked alpha-methyl-5-HT CRCs. The Schild slope was not significantly different from unity and the p A(2) value was 7.98. The binding of [(3)H]ketanserin to HUV membranes was saturable and of high affinity. Ketanserin displayed a monophasic curve which was best fit with a single component of binding. Nonlinear least squares analysis of the binding curves revealed a high affinity K(d) of 0.30 nM and a B(max) of 134 fmol/mg protein. These findings provide strong pharmacological evidence of the involvement of 5-HT(2A) receptors in 5-HT-induced vasoconstriction in HUV. In addition, the contribution of another receptor population cannot be excluded. The results also suggest that this receptor population is neither an alpha(1)-adrenoceptor nor a 5-HT(2C) receptor subtype.