Epithelial-mesenchymal transition (EMT): principles and clinical impact in cancer therapy / Transición epitelio-mesenquimática (TEM): principios e impacto clínico en la terapia contra el cáncer

The epithelial-mesenchymal transition (EMT) is a biological phenomenon responsible for the formation of different tissues and organs during normal metazoan development. Because of the connection of the EMT with the pathogenesis of certain diseases, such as cancer, the attention of the scientific community has been directed towards the search for and identification of effective therapeutic targets. These targets include signal transduction in cancerous stem cells and the use of microRNAs, which would inhibit EMT-associated phenotypic changes and tumoral progression. In an attempt to compile relevant and current information, this work addresses concepts that define the EMT and the advances in this field. The wealth of knowledge gained from areas such as the loss of cell polarity and intracellular adhesion complexes, the signaling pathways implicated, microRNA participation in this process, and stemness acquisition in embryonic and cancerous cells, all of which allow for the visualization of promising perspectives, particularly, methods for targeting advanced malignancies, are presented herein.

La transición epitelio-mesenquimática (TEM) es el fenómeno biológico responsable de la formación de los diferentes tejidos y órganos durante el desarrollo normal de los organismos metazoarios. En razón de su conexión con la patogénesis de ciertas enfermedades como el cáncer, la atención de la comunidad científica se ha redireccionado hacia la búsqueda e identificación de blancos terapéuticos efectivos, como la transducción de señales de las células madre cancerosas o la utilización de microARNs, que permitirían bloquear los cambios fenotípicos asociados con la TEM y, por ende, la progresión tumoral. En un intento por recopilar información relevante y actualizada, el presente trabajo aborda conceptos que definen a la TEM y avances alcanzados en este campo. El acervo de conocimiento obtenido en aspectos como pérdida de la polaridad celular y de los complejos de adhesión intercelular, vías de señalización implicadas y participación de los microARNs en el proceso, así como adquisición de stemness o troncalidad, tanto en células embrionarias como cancerosas, hace posible visualizar perspectivas promisorias, en especial en lo que se refiere a las terapias contra las malignidades de alto grado.

The role of the SLAM-SAP signaling pathway in the modulation of CD4+ T cell responses

The signaling lymphocytic activation molecule (SLAM), present on the surface of hematopoietic cells, can regulate some events of the immune responses. This modulatory action is associated with the capacity of SLAM to interact with an intracytoplasmic adapter, such as SLAM-associated protein (SAP). SLAM is constitutively expressed in most of these cells, is rapidly induced after antigenic or inflammatory stimuli, and participates in the immunological synapse. Defects in the function of the SLAM-SAP pathway contribute to immunological abnormalities, resulting in autoimmune diseases, tumors of the lymphoid tissues and inadequate responses to infectious agents. Initially, the role of SLAM was investigated using an anti-SLAM monoclonal antibody (α-SLAM mAb) identified as an agonist of the SLAM-SAP pathway, which could induce the production of interferon-γ and could redirect the immune response to a T helper 1 (Th1) cell profile. However, in this review we postulate that the SLAM-SAP pathway primarily induces a Th2 response and secondarily suppresses the Th1 response.

Tissue engineering and its implications in dentistry.

Tissue engineering is a novel and highly exciting field of research. With tissue engineering techniques it may be possible to repair damaged tissues or even create replacement organs. This article reviews the principles underlying key tissue engineering strategies and the typical components used. Examples of tissue engineering include passive approaches, such as dental implants, and inductive approaches, in which specific molecular signals are used to activate cells.

Down syndrome critical region 1 enhances the proteolytic cleavage of calcineurin

Down syndrome critical region 1 (DSCR1), an oxidative stress-response gene, interacts with calcineurin and represses its phosphatase activity. Recently it was shown that hydrogen peroxide inactivates calcineurin by proteolytic cleavage. Based on these facts, we investigated whether oxidative stress affects DSCR1-mediated inactivation of calcineurin. We determined that overexpression of DSCR1 leads to increased proteolytic cleavage of calcineurin. Convertsely, knockdown of DSCR1 abolished calcineurin cleavage upon treatment with hydrogen peroxide. The PXIIXT motif in the COOH-terminus of DSCR1 is responsible for both binding and cleavage of calcineurin. The knockdown of overexpressed DSCR1 in DS fibroblast cells also abrogated calcineurin proteolysis by hydrogen peroxide. These results suggest that DSCR1 has the ability to inactivate calcineurin by inducing proteolytic cleavage of calcineurin upon oxidative stress.

Hipocretinas, péptidos relacionados con la narcolepsia / Hypocretins, peptides associated with narcolepsy

La narcolepsia es un trastorno del sueño caracterizado por excesiva somnolencia diurna, transiciones prematuras de la vigila al sueño de movimientos oculares rápidos, alucinaciones hipnagógicas y cataplexia. Evidencias experimentales indican que la narcolepsia en humanos es una enfermedad neurodegenerativa asociada con la pérdida de neuronas hipocretinérgicas localizadas en el hipotálamo lateral. Además, se sabe que los pacientes narcolépticos presentan reducción significativa en la concentración de hipocretinas (HCRT) en el líquido cefalorraquídeo. Nuestro laboratorio ha generado un nuevo modelo experimental de narcolepsia en rata, que nos permite estudiar la enfermedad desde un enfoque histológico y neuroquímico. Hemos demostrado que la toxina hipocretina 2/saporina destruye selectivamente las neuronas hipocretinérgicas. Además, la pérdida de estas neuronas induce un cuadro conductual similar al observado en otros modelos experimentales o narcolepsia en humanos. En la presente revisión abordamos aspectos generales de la narcolepsia, del sistema hipocretinérgico, así como de los modelos experimentales de narcolepsia y el uso de los transplantes como alternativa para tratar la enfermedad.

Narcolepsy is a chronic disease characterized by excessive somnolence, abrupt transitions from wakefulness to rapid eye movement sleep stage and cataplexy. Experimental evidence show that narcolepsy in humans is a neurodegenerative disease associated with the lost of hypocretin (HCRT) neurons in the lateral hypothalamus. Narcoleptic patients also display a significant diminution in HCRT contents of cerebrospinal fluid. In order to study narcolepsy, several experimental models have been developed. Murine and canine models currently allow us to study this disease. Our laboratory has developed a new experimental rat model of narcolepsy. This model allows us to study the disease from a histological and neurochemical perspective. Elsewhere we have reported that the use of the toxin hypocretin2/saporine (HCRT2/ SAP) selectively destroys hypocretinergic neurons. The loss of these neurons induces a similar behavioural profile as the one observed in other experimental models of narcolepsy. In the present review we describe an overview on narcolepsy, the hypocretinergic system, experimental models in narcolepsy and the use of transplants as an alternative therapeutic tool.

Transducción de la señal, pivote de la integración neurobiológica de la memoria: Una propuesta diferente a la tradicional hipótesis del sistema colinérgico / Signal transduction, pillar of the neurobiological integration of memory: An alternative view to the cholinergic hypothesis

Los procesos neurofisiológicos, bioquímicos y moleculares descritos en la integración de la memoria, más que estar relacionados con la actividad colinérgica involucran fundamentalmente a neurotransmisores como la serotonina y el glutamato, así como a diversos canales iónicos como los del calcio y los del potasio. De hecho, los receptores de estos neurotransmisores están ligados directamente con la activación de la potenciación a largo plazo (LTP), mecanismo que contribuye a la preservación de la memoria. De esta forma que la activación del receptor 5HT desencadena una señal de transducción que al influenciar bioquímicamente al núcleo produce diversos cambios presinápticos con los que se expulsa al magnesio del área postsináptica, despolarizando a la neurona y activando simultáneamente a los receptores N metilD Aspartato dependientes (NMDAR), contribuyendo en esta forma a perpetuar el mecanismo de LTP en sus distintas fases: LTP1 que depende de la activación de proteincinasas; LTP2 ligada con la traslación genética; y LTP3 relacionada con la transcripción. A este poderoso mecanismo de activación neuronal, se contrapone el fenómeno de depresión a largo plazo (LTD), que se inicia cuando la neurona pre sináptica activa al inhibidor 1 en el momento en que detecta una reducción en el influjo de calcio, promoviendo en esta forma la defosforilación de una proteincinasa tipo II calcio calmodulin dependiente, lo que detiene el desarrollo del proceso de autofosforilación y con ello, el mecanismo de LTP. No obstante lo difundido de la hipótesis colinérgica en la enfermedad de Alzheimer, la integración de la memoria depende fundamentalmente de la intervención de otros sistemas de neurotransmisión como lo son el serotonérgico y el glutamatérgico, los que no han sido debidamente considerados en el tratamiento de esta enfermedad; sin embargo más allá de estos sistemas, se encuentran los mecanismos de autofosforilación de distintas proteincinasas cuyo control, además de repercutir sobre la expresión genética, podría restituir algunos de los trastornos que afectan la función cognoscitiva.

Neurophysiological, biochemical and molecular processes described in the integration of memory are closely related with neurotransmitters such as glutamate and serotonin (5HT) and with the function of calcium and potassium ion channels more than with cholinergic activity. In fact, glutamate and 5 HT receptors are closely related with Long-Term Potentiation (LTP) processes, the mechanism by which memory is preserved throughout time. That is, the activation of the 5 HT4 receptor triggers a transduction signal that after influencing nuclear cell activity, provokes several presynaptic changes, which leads to the displacement of magnesium from the postsynaptic area depolarizing the neuron and leading to the activation of N methyl -D-aspartate receptors (NMDA). As a whole, this process contributes to the support and perpetuation of LTP, which consists of the following processes: LTP1 that depends on protein kinase activity; LTP2 linked to translation of genes; and LTP3 closely related to genes transcription. On the opposite side but in perfect balance, we find the mechanism of Long Term depression (LTD), which is triggered instead when the Ca++ flow decreases in the presynaptic neuron activating the inhibitor 1 enzyme that promotes the dephosphorylation of a calmodulin dependent protein kinase II and as a result, the inhibition of autophosphorylation and consequently of LTP too. Despite the widespread dissemination of the cholinergic hypothesis in Alzheimer's disease, memory build up rather than involving acetylcholine essentially depends on the participation of other neurotransmitters such as 5 HT and glutamate, which have not been adequately considered in the treatment of this disease. However, beyond neurotransmission, it is the cellular mechanism of autophosphorylation of several protein kinases, the process susceptible of being activated or controlled by the action of distinct substances. In such a case, it would be possible to exert some influence on gene expression improving perhaps, some of the physiopathological deficits that characterize memory disruption.

Marcadores biológicos de tumores tiroidianos / Biological markers in thyroid tumors

Um marcador biológico ideal deve ser específico e sensível para identificar o tipo tumoral e caracterizar o estágio da progressão neoplásica. Os tumores de tiróide originam-se de dois tipos celulares: 1) carcinoma medular originário de células parafoliculares; e 2) as neoplasias de células epiteliais foliculares, que incluem bócio, adenomas, carcinomas diferenciados (carcinoma papilífero e carcinoma folicular) e carcinoma indiferenciado (carcinoma anaplásico). O comportamento biológico distinto faz com que cada tipo tumoral necessite de uma conduta terapêutica específica. O conhecimento acumulado ao longo destes anos, utilizando métodos de biologia molecular e, mais recentemente, a genômica, identificou mutações específicas de câncer de tiróide e, atualmente, entendemos muito das alterações que ocorrem na expressão de fatores de crescimento, seus receptores e proteínas sinalizadoras intracelular nas neoplasias tiroidianas. Contudo, apesar desses, até o momento não dispomos de um marcador eficiente que auxilie no diagnóstico e prognóstico e, conseqüentemente, para indicação de uma terapêutica mais adequada. Nesta revisão, discutiremos os principais aspectos relacionados à tumorigênese tiroidiana, avaliando o potencial destes fatores como marcador em neoplasia folicular de tiróide.