KCa3.1 differentially regulates trachea and bronchi epithelial gene expression in a chronic-asthma mouse model.

Ion channels are potentially exploitable as pharmacological targets to treat asthma. This study evaluated the role of KCa3.1 channels, encoded by Kcnn4, in regulating the gene expression of mouse airway epithelium and the development of asthma traits. We used the ovalbumin (OVA) challenge as an asthma model in wild-type and Kcnn4-/- mice, performed histological analysis, and measured serum IgE to evaluate asthma traits. We analyzed gene expression of isolated epithelial cells of trachea or bronchi using mRNA sequencing and gene ontology and performed Ussing chamber experiments in mouse trachea to evaluate anion secretion. Gene expression of epithelial cells from mouse airways differed between trachea and bronchi, indicating regional differences in the inflammatory and transepithelial transport properties of proximal and distal airways. We found that Kcnn4 silencing reduced mast cell numbers, mucus, and collagen in the airways, and reduced the amount of epithelial anion secretion in the OVA-challenged animals. In addition, gene expression was differentially modified in the trachea and bronchi, with Kcnn4 genetic silencing significantly altering the expression of genes involved in the TNF pathway, supporting the potential of KCa3.1 as a therapeutic target for asthma.

Resistencia a medicamentos en mycobacterium tuberculosis: contribución de mecanismos constitutivos y adquiridos / Drug resistance in mycobacterium tuberculosis: contribution of constituent and acquired mechanisms

RESUMEN En presencia de aislamientos de Mycobacterium tuberculosis (MTB) multifármaco-resistentes (MTB-MDR) y con resistencia extendida (MTB-XDR) las tasas de fracaso de los esquemas estandarizados de tratamiento son altas, constituyéndose en un verdadero problema de salud pública a nivel mundial. La fármaco-resistencia en MTB se debe principalmente a mutaciones en genes blanco; sin embargo, una proporción de aislamientos fármaco-resistentes no presentan mutaciones en dichos genes, sugiriendo la participación de otros mecanismos, tales como permeabilidad reducida de la pared celular, modificación enzimática y/o bombas de eflujo. La resistencia clínica a los medicamentos anti-tuberculosos (anti-TB) ocurre en gran parte como resultado de la selección de mutantes resistentes durante la falta de adherencia del paciente al tratamiento, inapropiados seguimientos y prescripción médica, dosis subóptimas de fármacos y dificultad de acceso a los servicios de salud y al tratamiento. Los Avances de la biología molecular y la secuenciación del genoma de MTB han contribuido a mejorar el entendimiento de los mecanismos de resistencia a los principales medicamentos anti-TB. Un mejor conocimiento de los mecanismos de fármaco-resistencia en MTB contribuirá a la identificación de nuevos blancos terapéuticos, al diseño de nuevos medicamentos, al desarrollo de nuevos métodos diagnósticos y/o mejorar las técnicas que actualmente están disponibles para la detección rápida de TB fármaco-resistente. Este artículo presenta una revisión actualizada de los mecanismos y las bases moleculares de la resistencia de MTB a medicamentos anti-TB.(AU)

ABSTRACT Due to the emergence of multi-drug resistant (MDR-MTB) and extensively drug-resistant (XDR-MTB) Mycobacterium tuberculosis (MTB) isolates, the failure rates of standard treatment regimens are high, thus becoming a major public health challenge worldwide. Resistance to anti-tuberculous (anti-TB) drugs is attributed mainly to specific mutations in target genes; however, a proportion of drug-resistant MTB isolates do not have mutations in these genes, which suggests the involvement of other mechanisms, such as the low permeability of the mycobacterial cell wall, enzymatic modification and/or efflux pumps. Clinical drug resistance to anti-TB drugs occurs largely as a result of the selection of resistant mutants caused by poor patient adherence to treatment, inappropriate follow-ups and prescriptions, suboptimal doses of drugs and poor access to health services and treatment. Major advances in molecular biology tools and the availability of the complete genome sequences of MTB have contributed to improve understanding of the mechanisms of resistance to the main anti-TB drugs. Better knowledge of the drug-resistance of MTB will contribute to the identification of new therapeutic targets to design new drugs, develop new diagnostic tests and/or improve methods currently available for the rapid detection of drug-resistant TB. This article presents an updated review of the mechanisms and molecular basis of drug resistance in MTB.(AU)

[Drug resistance in Mycobacterium tuberculosis: contribution of constituent and acquired mechanisms]. / Resistencia a Medicamentos en Mycobacterium tuberculosis: contribución de mecanismos constitutivos y adquiridos.

Due to the emergence of multi-drug resistant (MDR-MTB) and extensively drug-resistant (XDR-MTB) Mycobacterium tuberculosis (MTB) isolates, the failure rates of standard treatment regimens are high, thus becoming a major public health challenge worldwide. Resistance to anti-tuberculous (anti-TB) drugs is attributed mainly to specific mutations in target genes; however, a proportion of drug-resistant MTB isolates do not have mutations in these genes, which suggests the involvement of other mechanisms, such as the low permeability of the mycobacterial cell wall, enzymatic modification and/or efflux pumps. Clinical drug resistance to anti-TB drugs occurs largely as a result of the selection of resistant mutants caused by poor patient adherence to treatment, inappropriate follow-ups and prescriptions, suboptimal doses of drugs and poor access to health services and treatment. Major advances in molecular biology tools and the availability of the complete genome sequences of MTB have contributed to improve understanding of the mechanisms of resistance to the main anti-TB drugs. Better knowledge of the drug-resistance of MTB will contribute to the identification of new therapeutic targets to design new drugs, develop new diagnostic tests and/or improve methods currently available for the rapid detection of drug-resistant TB. This article presents an updated review of the mechanisms and molecular basis of drug resistance in MTB.

En presencia de aislamientos de Mycobacterium tuberculosis (MTB) multifármaco-resistentes (MTB-MDR) y con resistencia extendida (MTB-XDR) las tasas de fracaso de los esquemas estandarizados de tratamiento son altas, constituyéndose en un verdadero problema de salud pública a nivel mundial. La fármaco-resistencia en MTB se debe principalmente a mutaciones en genes blanco; sin embargo, una proporción de aislamientos fármaco-resistentes no presentan mutaciones en dichos genes, sugiriendo la participación de otros mecanismos, tales como permeabilidad reducida de la pared celular, modificación enzimática y/o bombas de eflujo. La resistencia clínica a los medicamentos anti-tuberculosos (anti-TB) ocurre en gran parte como resultado de la selección de mutantes resistentes durante la falta de adherencia del paciente al tratamiento, inapropiados seguimientos y prescripción médica, dosis subóptimas de fármacos y dificultad de acceso a los servicios de salud y al tratamiento. Los Avances de la biología molecular y la secuenciación del genoma de MTB han contribuido a mejorar el entendimiento de los mecanismos de resistencia a los principales medicamentos anti-TB. Un mejor conocimiento de los mecanismos de fármaco-resistencia en MTB contribuirá a la identificación de nuevos blancos terapéuticos, al diseño de nuevos medicamentos, al desarrollo de nuevos métodos diagnósticos y/o mejorar las técnicas que actualmente están disponibles para la detección rápida de TB fármaco-resistente. Este artículo presenta una revisión actualizada de los mecanismos y las bases moleculares de la resistencia de MTB a medicamentos anti-TB.

Estandarización de una reacción en cadena de la polimerasa en tiempo real (qPCR) para la detección de strongyloides stercoralis en muestras de materia fecal / Standardization of a real-time polymerase chain reaction (qPCR) for the detection of strongyloides stercoralis in stool samples

Introducción: el diagnóstico de estrongiloidiasis se realiza de rutina en los laboratoriosclínicos; sin embargo, su detección se dificulta debido a la baja excreción parasitaria y la baja sensibilidad de las pruebas parasitológicas empleadas. Objetivo:diseñar y estandarizar una PCR en tiempo real (qPCR) para la detección de ADN de Strongyloides stercoralis en muestras de materia fecal. Materiales y métodos: se establecieron las condiciones de qPCR y se evaluaron: a) la especificidadanalítica mediante análisis BLASTn de secuencias obtenidas de muestras positivas para Strongyloides stercoralis, b) sensibilidad analítica mediante dilucionesseriadas de muestras que contenían larvas de Strongyloides stercoralis y c) la ocurrencia de reacciones cruzadas con otros parásitos e inhibidores de la amplificación. Resultados: se amplificó un fragmento de 101 pb del gen 18S del ARN ribosomal. El valor de Ct osciló entre 23 y 29, tomando un Ct ≤35 como el punto de corte para muestras positivas. El análisis BLASTn de las secuencias obtenidas mostró un porcentaje de identidad del 98% con secuencias 18S del ARN ribosomal de Strongyloides stercoralis reportadas en la NCBI. El límite inferiorde detección de la qPCR fue 0,9 ng/μL. No se evidenció reacción cruzada con Ascaris lumbricoides, Trichuris trichiura, Uncinarias, Hymenolepis nana, Entamoeba histolytica/Entamoeba dispar, Entamoeba hartmanni, Giardia intestinalis e Iodamoeba bütschlii. No se detectaron inhibidores en las muestras de materia fecal. Conclusiones: la sensibilidad y la especificidad analítica de la qPCR comparado con el examen directo de heces son del 100%; sin embargo, aún no es posible interpretar su utilidad clínica.

Introduction: the diagnosis of strongyloidiasis is performing routinely in clinical laboratories; however, its detection is difficult due to low parasitic excretion and low sensitivity of the parasitological tests employed. Objective: to design and standardize a real-time PCR (qPCR) for the detection of Strongyloides stercoralis DNA in stool samples. Materials and methods: qPCR conditions were established and it were assessed: a) analytical specificity by BLASTn analysis of sequences obtained from samples positive for Strongyloides stercoralis, b) analytical sensitivity by serial dilutions of samples containing Strongyloides stercoralislarvae and c) the occurrence of cross-reactions with other parasites and amplification inhibitors. Results: a 101 bp fragment of the 18S ribosomal RNA gene was amplified. The value of Ct ranged from 23 and 29, with a Ct value ≤35 as a cut-off point for positive samples. BLASTn analysis of the obtained sequences showed an identity percentage of 98% with 18S ribosomal RNA sequences of Strongyloides stercoralis reported in the NCBI. The qPCR lower limit of detection was 0.9 ng/ μL. There was no cross-reaction with Ascaris lumbricoides, Trichuristrichiura, Uncinarias, Hymenolepis nana, Entamoeba histolytica/Entamoeba dispar, Entamoeba hartmanni, Giardia intestinalis, and Iodamoeba bütschlii. No inhibitors were detected in the stool samples. Conclusion: the sensitivity and analytical specificity of qPCR compared to direct examination of feces are 100%; however, it is still not possible to interpret their clinical utility.

[Thin layer agar represents a cost-effective alternative for the rapid diagnosis of multi-drug resistant tuberculosis]. / Agar de capa delgada: Una opción costo-efectiva para el diagnóstico rápido de tuberculosis multirresistente.

OBJECTIVE: Using cost-benefit analysis for comparing the thin-layer agar culture method to the standard multiple proportion method used in diagnosing multidrug-resistant tuberculosis (MDR TB). METHODS: A cost-benefit evaluation of two diagnostic tests was made at the Corporación para Investigaciones Biológicas (CIB) in Medellín, Colombia. RESULTS: 100 patients were evaluated; 10.8% rifampicin resistance and 14.3% isoniazid resistance were found. A computer-based decision tree model was used for cost-effectiveness analysis (Treeage Pro); the thin-layer agar culture method was most cost-effective, having 100% sensitivity, specificity and predictive values for detecting rifampicin and isoniazid resistance. The multiple proportion method value was calculated as being US$ 71 having an average 49 day report time compared to US$ 18 and 14 days for the thin-layer agar culture method. DISCUSSION: New technologies have been developed for diagnosing tuberculosis which are apparently faster and more effective; their operating characteristics must be evaluated as must their effectiveness in terms of cost-benefit. The present study established that using thin-layer agar culture was cheaper, equally effective and could provide results more quickly than the traditional method. This implies that a patient could receive MDR TB treatment more quickly.

SVCT2 transporter expression is post-natally induced in cortical neurons and its function is regulated by its short isoform.

Different studies have demonstrated the importance of micronutrients, such as vitamins, for normal adult brain function and development. Vitamin C is not synthesized in the brain, but high levels are detected in this organ because of the existence of specific uptake mechanisms, which concentrate ascorbic acid from the bloodstream to the cerebrospinal fluid and then into neurons and glial cells. Two different isoforms of sodium-vitamin C cotransporters (SVCT1 and SVCT2) have been cloned. SVCT2 expression has been observed in the adult hippocampus and cortical neurons by in situ hybridization. In addition, the localization of SVCT2 in the rat fetal brain has been studied by immunohistochemistry and in situ hybridization, demonstrating that SVCT2 is highly expressed in the ventricular and subventricular areas of the brain cortex. However, there are currently no immunohistochemical data regarding SVCT2 expression and function in the post-natal brain. Therefore, we analyzed SVCT2 expression in the developing brain cortex of mice, and demonstrated an increase in SVCT2 mRNA in mice at 1-15 days of age. The expression of a short isoform, SVCT2sh, was also detected within the same period. SVCT2 expression was concentrated in neurons within the inner layer of the brain cortex. Both SVCT2 isoforms were coexpressed in N2a cells to obtain functional data. Fluorescence resonance energy transfer analysis revealed a molecular interaction between SVCT2wt and SVCT2sh. Finally, differences in transport ratios suggested that SVCT2sh expression inhibited ascorbic acid uptake in N2a cells when both isoforms were coexpressed. The sodium-vitamin C cotransporter, SVCT2, is induced in neurons within the inner layer of the brain cortex during post-natal development, mainly in pyramidal cortex neurons. Two different isoforms, SVCT2wt and SVCT2sh, were detected. Using in vitro studies, we suggest a molecular interaction between SVCT2wt and SVCT2sh, which may regulate the affinity of vitamin C uptake.

Agar de capa delgada: Una opción costo-efectiva para el diagnóstico rápido de tuberculosis multirresistente / Thin layer agar represents a cost-effective alternative for the rapid diagnosis of multi-drug resistant tuberculosis

Objetivo Realizar un análisis de costo efectividad comparando el método de cultivo en agar de capa delgada y el método estándar de proporciones múltiples, utilizados en el diagnóstico de Tuberculosis Multi-drogorresistente (TB MDR). Métodos Estudio de evaluación económica en el cual se evalúan los costos y la efectividad de dos pruebas diagnósticas, ejecutado en la Corporación para Investigaciones Biológicas-CIB en Medellín, Colombia. Resultados Se evaluaron 100 pacientes, encontrando una prevalencia de resistencia a la Rifampicina de 10,8 % y resistencia a Isoniazida de 14,3 %. Se presenta un análisis en términos de costo-efectividad mediante el diseño de un árbol de decisiones (Treeage Pro ®), resultando ser la prueba basada en cultivo en agar de capa delgada más costo-efectiva; con valores de sensibilidad, especificidad y predictivos del 100 % para detectar resistencia a Rifampicina e Isoniazida. El valor del método de las proporciones múltiples fue calculado en US$ 71, con una media de tiempo para ser reportado de 49 días versus US$ 18 y 14 días respectivamente para el cultivo en agar de capa delgada. Discusión Se han desarrollado nuevas tecnologías para el diagnóstico de Tuberculosis, aparentemente más rápidas y efectivas, que deben ser evaluadas no solo en sus características operativas, sino también en términos de costo-efectividad. El presente estudio establece que el empleo de la capa delgada es menos costoso, igualmente efectivo, y puede aportar resultados más rápidamente; cuando se compara con el método tradicional. Esto implica, entre otros aspectos, que el paciente pueda recibir más oportunamente el tratamiento dirigido para TB MDR.

Objective Using cost-benefit analysis for comparing the thin-layer agar culture method to the standard multiple proportion method used in diagnosing multidrug-resistant tuberculosis (MDR TB). Methods A cost-benefit evaluation of two diagnostic tests was made at the Corporación para Investigaciones Biológicas (CIB) in Medellín, Colombia. Results 100 patients were evaluated; 10.8 % rifampicin resistance and 14.3 % isoniazid resistance were found. A computer-based decision tree model was used for cost-effectiveness analysis (Treeage Pro); the thin-layer agar culture method was most cost-effective, having 100 % sensitivity, specificity and predictive values for detecting rifampicin and isoniazid resistance. The multiple proportion method value was calculated as being US$ 71 having an average 49 day report time compared to US$ 18 and 14 days for the thin-layer agar culture method. Discussion New technologies have been developed for diagnosing tuberculosis which are apparently faster and more effective; their operating characteristics must be evaluated as must their effectiveness in terms of cost-benefit. The present study established that using thin-layer agar culture was cheaper, equally effective and could provide results more quickly than the traditional method. This implies that a patient could receive MDR TB treatment more quickly.

The splice variant of the V2 vasopressin receptor adopts alternative topologies.

The V2 receptor gene encodes two receptor variants by alternative splicing, the canonical V2 receptor (V2a receptor) and V2b. The V2b variant has an amino acid sequence identical to that of the V2a receptor up to the sixth transmembrane domain, but the V2b sequences corresponding to the putative seventh transmembrane domain and the carboxyl terminus are different from those of the V2a receptor. Here we investigate the topology and subcellular distribution of the V2b variant. We found that, in contrast to the V2a receptor, the V2b adopted two topologies: one with six transmembrane segments with the C-terminus on the extracellular side of the membrane and another with seven transmembrane segments with the C-terminus on the intracellular side, similar to typical G-protein-coupled receptors. Furthermore, we observed that both topological isoforms oligomerized with the V2a canonical receptor. Unlike the V2a receptor, V2b did not move to the plasma membrane, but it is retained in the ER--Golgi compartments. These findings indicate that the C-terminal sequence beyond the sixth transmembrane of the V2a is required for the stabilization of the seven-transmembrane topology of the receptor and is also essential for the trafficking of the receptor to the plasma membrane.

Postnatal expression of V2 vasopressin receptor splice variants in the rat cerebellum.

The V(2) vasopressin receptor gene contains an alternative splice site in exon-3, which leads to the generation of two splice variants (V(2a) and V(2b)) first identified in the kidney. The open reading frame of the alternatively spliced V(2b) transcript encodes a truncated receptor, showing the same amino acid sequence as the canonical V(2a) receptor up to the sixth transmembrane segment, but displaying a distinct sequence to the corresponding seventh transmembrane segment and C-terminal domain relative to the V(2a) receptor. Here, we demonstrate the postnatal expression of V(2a) and V(2b) variants in the rat cerebellum. Most importantly, we showed by in situ hybridization and immunocytochemistry that both V(2) splice variants were preferentially expressed in Purkinje cells, from early to late postnatal development. In addition, both variants were transiently expressed in the neuroblastic external granule cells and Bergmann fibers. These results indicate that the cellular distributions of both splice variants are developmentally regulated, and suggest that the transient expression of the V(2) receptor is involved in the mechanisms of cerebellar cytodifferentiation by AVP. Finally, transfected CHO-K1 expressing similar amounts of both V(2) splice variants, as that found in the cerebellum, showed a significant reduction in the surface expression of V(2a) receptors, suggesting that the differential expression of the V(2) splice variants regulates the vasopressin signaling in the cerebellum.

Vasopressin up-regulates the expression of growth-related immediate-early genes via two distinct EGF receptor transactivation pathways.

Activation of V(1a) receptor triggers the expression of growth-related immediate-early genes (IEGs), including c-Fos and Egr-1. We found that pre-treatment of rat vascular smooth muscle A-10 cell line with the EGF receptor inhibitor AG1478 or the over-expression of an EGFR dominant negative mutant (HEBCD533) blocked the vasopressin-induced expression of IEGs, suggesting that activation of these early genes mediated by V(1a) receptor is via transactivation of the EGF receptor. Importantly, the inhibition of the metalloproteinases, which catalyzed the shedding of the EGF receptor agonist HB-EGF, selectively blocked the vasopressin-induced expression c-Fos. On the other hand, the inhibition of c-Src selectively blocked the vasopressin-induced expression of Egr-1. Interestingly, in contrast to the expression of c-Fos, the expression of Egr-1 was mediated via the Ras/MEK/MAPK-dependent signalling pathway. Vasopressin-triggered expression of both genes required the release of intracellular calcium, activation of PKC and beta-arrestin 2. These findings demonstrated that vasopressin up-regulated the expression of c-Fos and Erg-1 via transactivation of two distinct EGF receptor-dependent signalling pathways.

Differential distribution of the vasopressin V receptor along the rat nephron during renal ontogeny and maturation.

BACKGROUND: Ontogeny and cellular distribution of vasopressin receptors in the kidney are key factors determining the role of vasopressin in renal physiology. Expression of vasopressin V(2) receptor (V(2)R) mRNA and the immunoreactive protein in rat kidney were investigated. METHODS: An antiserum directed to epitope TLD25 of the rat V(2)R sequence was characterized by Western blotting. Expression of V(2)R mRNA was assessed by reverse transcription-polymerase chain reaction (RT-PCR), and on protein level by immunohistochemistry. RESULTS: Specificity of the antiserum was documented by Western blots from cells expressing a fusion protein of V(2)R and GFP. Using lysates of rat kidney and of native cell lines expressing V(2)R but not V(1)R, our antiserum to peptide TLD25 revealed a major band of 55 kD corresponding to the monomeric form of V(2)R, and a band of 110 kD most likely representing the homodimeric form of the receptor. This highly specific antiserum allowed us to localize the V(2)R in thick ascending limbs, distal convoluted and connecting tubules, and in collecting ducts. During ontogeny, immunoreactivity was first observed at the luminal membrane on prenatal day 20, emerging at the basolateral side from postnatal day 5 on. RT-PCR demonstrated V(2)R transcripts from prenatal day 18 to gradually increasing thereafter. CONCLUSION: Expression of V(2)R is first detectable in the late embryonic stage of rat ontogeny starting from day E18 and gradually increasing with kidney maturation. In the adult kidney, V(2)R is differentially distributed in the various nephron segments.

Novel down-regulatory mechanism of the surface expression of the vasopressin V2 receptor by an alternative splice receptor variant.

In rat kidney, two alternatively spliced transcripts are generated from the V2 vasopressin receptor gene. The large transcript (1.2 kb) encodes the canonical V2 receptor, whereas the small transcript encodes a splice variant displaying a distinct sequence corresponding to the putative seventh transmembrane domain and the intracellular C terminus of the V2 receptor. This work showed that the small spliced transcript is translated in the rat kidney collecting tubules. However, the protein encoded by the small transcript (here called the V2b splice variant) is retained inside the cell, in contrast to the preferential surface distribution of the V2 receptor (here called the V2a receptor). Cells expressing the V2b splice variant do not exhibit binding to 3H-labeled vasopressin. Interestingly, we found that expression of the splice variant V2b down-regulates the surface expression of the V2a receptor, most likely via the formation of V2a.V2b heterodimers as demonstrated by co-immunoprecipitation and fluorescence resonance energy transfer experiments between the V2a receptor and the V2b splice variant. The V2b splice variant would then be acting as a dominant negative. The effect of the V2b splice variant is specific, as it does not affect the surface expression of the G protein-coupled interleukin-8 receptor (CXCR1). Furthermore, the sequence encompassing residues 242-339, corresponding to the C-terminal domain of the V2b splice variant, also down-regulates the surface expression of the V2a receptor. We suggest that some forms of nephrogenic diabetes insipidus are due to overexpression of the splice variant V2b, which could retain the wild-type V2a receptor inside the cell via the formation of V2a.V2b heterodimers.