Patología vascular: ¿causa o efecto en la enfermedad de Alzheimer? / Vascular pathology: Cause or effect in Alzheimer disease?

Introducción: La enfermedad de Alzheimer (EA) es la principal enfermedad neurodegenerativa cortical. Su incidencia aumenta con la edad, lo que provoca importantes problemas médicos, sociales y económicos, especialmente en países con población envejecida. Objetivo: El objetivo de esta revisión es poner de manifiesto las evidencias que existen sobre el modo en que la disfunción vascular puede contribuir al deterioro cognitivo en la EA, así como las posibilidades terapéuticas que de ello podrían derivarse. Desarrollo: La hipótesis vascular ha surgido como alternativa a la hipótesis de la cascada amiloide como explicación de la fisiopatología de la EA. Esta hipótesis sitúa en los vasos sanguíneos el origen de una serie de estímulos patogénicos que llevarían a la lesión neuronal y la demencia. La destrucción de la organización de la barrera hematoencefálica, la disminución del flujo sanguíneo cerebral y el establecimiento de un contexto inflamatorio serían responsables de un consecuente daño neuronal a causa de favorecer la agregación del péptido β-amiloide en el cerebro. Las vías que relacionan la disfunción vascular con la neurodegeneración han proporcionado nuevos enfoques terapéuticos y dianas farmacológicas con las que avanzar en la búsqueda de tratamientos para la EA. Conclusiones: Resulta difícil determinar si el componente vascular de la EA es la causa o el efecto de la enfermedad, pero no cabe duda de que la enfermedad vascular tiene una relación importante con la EA. Es probable que la disfunción vascular actúe sinérgicamente con los cambios neurodegenerativos en un ciclo que agrava el deterioro cognitivo propio de la EA (AU)

Introduction: Alzheimer disease (AD) is the main cortical neurodegenerative disease. The incidence of this disease increases with age, causing significant medical, social and economic problems, especially in countries with ageing populations. Objective: This review aims to highlight existing evidence of how vascular dysfunction may contribute to cognitive impairment in AD, as well as the therapeutic possibilities that might arise from this evidence. Development: The vascular hypothesis emerged as an alternative to the amyloid cascade hypothesis as an explanation for the pathophysiology of AD. This hypothesis locates blood vessels as the origin for a variety of pathogenic pathways that lead to neuronal damage and dementia. Destruction of the organisation of the blood brain barrier, decreased cerebral blood flow, and the establishment of an inflammatory context would thus be responsible for any subsequent neuronal damage since these factors promote aggregation of Beta-amyloid peptide in the brain. The link between neurodegeneration and vascular dysfunction pathways has provided new drug targets and therapeutic approaches that will add to the treatments for AD. Conclusions: It is difficult to determine whether the vascular component in AD is the cause or the effect of the disease, but there is no doubt that vascular pathology has an important relationship with AD. Vascular dysfunction is likely to act synergistically with neurodegenerative changes in a cycle that exacerbates the cognitive impairment found in AD (AU)

Vascular pathology: Cause or effect in Alzheimer disease? / Patología vascular: ¿causa o efecto en la enfermedad de Alzheimer?

INTRODUCTION: Alzheimer disease (AD) is the main cortical neurodegenerative disease. The incidence of this disease increases with age, causing significant medical, social and economic problems, especially in countries with ageing populations. OBJECTIVE: This review aims to highlight existing evidence of how vascular dysfunction may contribute to cognitive impairment in AD, as well as the therapeutic possibilities that might arise from this evidence. DEVELOPMENT: The vascular hypothesis emerged as an alternative to the amyloid cascade hypothesis as an explanation for the pathophysiology of AD. This hypothesis locates blood vessels as the origin for a variety of pathogenic pathways that lead to neuronal damage and dementia. Destruction of the organisation of the blood brain barrier, decreased cerebral blood flow, and the establishment of an inflammatory context would thus be responsible for any subsequent neuronal damage since these factors promote aggregation of ß-amyloid peptide in the brain. The link between neurodegeneration and vascular dysfunction pathways has provided new drug targets and therapeutic approaches that will add to the treatments for AD. CONCLUSIONS: It is difficult to determine whether the vascular component in AD is the cause or the effect of the disease, but there is no doubt that vascular pathology has an important relationship with AD. Vascular dysfunction is likely to act synergistically with neurodegenerative changes in a cycle that exacerbates the cognitive impairment found in AD.

Oxidative stress triggers cytokinesis failure in hepatocytes upon isolation.

Primary hepatocytes are highly differentiated cells and proliferatively quiescent. However, the stress produced during liver digestion seems to activate cell cycle entry by proliferative/dedifferentiation programs that still remain unclear. The aim of this work was to assess whether the oxidative stress associated with hepatocyte isolation affects cell cycle and particularly cytokinesis, the final step of mitosis. Hepatocytes were isolated from C57BL/6 mice by collagenase perfusion in the absence and presence of N-acetyl cysteine (NAC). Polyploidy, cell cycle, and reactive oxygen species (ROS) were studied by flow cytometry (DNA, phospho-histone 3, and CellROX(®) Deep Red) and Western blotting (cyclins B1 and D1, and proliferating cell nuclear antigen). mRNA expression of cyclins A1, B1, B2, D1, and F by reverse transcription (RT)-PCR was also assessed. Glutathione levels were measured by mass spectrometry. Here we show that hepatocyte isolation enhanced cell cycle entry, increased hepatocyte binucleation, and caused marked glutathione oxidation. Addition of 5 mM NAC to the hepatocyte isolation media prevented glutathione depletion, partially blocked ROS production and cell cycle entry of hepatocytes, and avoided the blockade of mitosis progression, abrogating defective cytokinesis and diminishing the formation of binucleated hepatocytes during isolation. Therefore, addition of NAC to the isolation media decreased the generation of polyploid hepatocytes confirming that oxidative stress occurs during hepatocyte isolation and it is responsible, at least in part, for cytokinesis failure and hepatocyte binucleation.

p38 MAPK: a dual role in hepatocyte proliferation through reactive oxygen species.

p38 MAPKs are important mediators of signal transduction that respond to a wide range of extracellular stressors such as UV radiation, osmotic shock, hypoxia, pro-inflammatory cytokines, and oxidative stress. The most abundant family member is p38α, which helps to couple cell proliferation and growth in response to certain damaging stimuli. In fact, increased proliferation and impaired differentiation are hallmarks of p38α-deficient cells. It has been reported that reactive oxygen species (ROS) play a critical role in cytokine-induced p38α activation. Under physiological conditions, p38α can function as a mediator of ROS signaling and either activate or suppress cell cycle progression depending on the activation stimulus. The interplay between cell proliferation, p38 MAPK activation, and ROS production plays an important role in hepatocytes. In fact, low levels of ROS seem to be needed to activate several signaling pathways in response to hepatectomy and to orchestrate liver regeneration. p38 MAPK works as a sensor of oxidative stress and cells that have developed mechanisms to uncouple p38 MAPK activation from oxidative stress are more likely to become tumorigenic. So far, p38α influences the redox balance, determining cell survival, terminal differentiation, proliferation, and senescence. Further studies would be necessary in order to clarify the precise role of p38 MAPK signaling as a redox therapeutical target.

Human mesenchymal stem cells from adipose tissue: Differentiation into hepatic lineage.

Adipose tissue represents an accessible source of mesenchymal stem cells (ADSCs), with similar characteristics to bone marrow-derived stem cells. The aim of this work was to investigate the transdifferentiation of ADSCs into hepatic lineage cells in vitro. ADSCs were obtained from human adipose tissue from lipectomy. Cells were grown in medium containing 15% AB human serum. Cultures were serum deprived for two days and exposed to a two-step protocol with two different media using growth factors and cytokines. Hepatic differentiation was assessed by RT-PCR of liver-marker genes. ADSCs exhibited a fibroblastic morphology that changed to a cuboidal shape when cells differentiated. Expression of liver genes increased when using one of the two studied media consisting of DMEM supplemented with HGF, bFGF and nicotinamide for 14 days. The results indicate that, under certain specific inducing conditions, ADSCs can be induced to differentiate into hepatic lineage in vitro. Adipose tissue may be an ideal source of high amounts of autologous stem cells.

Quinolonas y Streptococcus pneumoniae. Mecanismo de acción y resistencia / Quinolones and Streptococcus pneumoniae. Mechanisms of action and resistance

Streptococcus pneumoniae se considera el principal agente causal de la neumonía adquirida en la comunidad, además de estar implicado con frecuencia en exacerbaciones de bronquitis crónica, otitis media aguda, sinusitis, meningitis y otras infecciones. Durante los últimos años, en búsqueda de nuevas sustancias debido a la aparición de resistencias en este microorganismo, se han estudiado, entre otros agentes antibacterianos, las fluoroquinolonas. Asimismo, la biología molecular ha ayudado a estudiar y comprender casi todos los mecanismos bioquímicos de resistencia y las rutas para la diseminación de la información genética entre las bacterias. En esta revisión se repasa el mecanismo de acción de las quinolonas y los mecanismos causantes de la resistencia de S. pneumoniae a ellas, por su importancia clínica y epidemiológica. S. pneumoniae es un caso peculiar, puesto que en este microorganismo la actividad bactericida puede producirse a través de la girasa, la topoisomerasa IV o ambas, dependiendo de la estructura de la quinolona, lo cual implica una influencia de la estructura en el logro del éxito antimicrobiano. Es importante, pues, conocer el prototipo de resistencia para hacer una recomendación de la antibioticoterapia adecuada, cuando esté indicada. (AU)

Las quinolonas: relación estructura-efectos adversos e interacciones con otros fármacos / Quinolone antibacterials: structure-side effects relationship and interactions with other drugs

Las quinolonas en conjunto pueden considerarse como un grupo con un buen balance beneficio/riesgo pues, en general, los derivados quinolónicos son seguros y bien tolerados. Frecuentemente, los efectos adversos disminuyen con la reducción de la dosis y la duración de la terapia. Sólo es necesaria la interrupción del tratamiento en el 1-3 por ciento de los pacientes. Las reacciones adversas más frecuentes son molestias del tracto gastrointestinal, estimulación del sistema nervioso central y alergias. No obstante, algunas quinolonas como el temafloxacino, el grepafloxacino y el trovafloxacino han sido retiradas del mercado por problemas de toxicidad grave. En el presente trabajo se revisa la relación estructura-efectos adversos e interacciones con otros fármacos de estos antibacterianos. El objetivo fundamental es identificar los grupos estructurales que determinan la aparición de reacciones adversas importantes para destacar las configuraciones moleculares exentas de riesgos y que, potencialmente, pueden ser valiosos instrumentos en la terapéutica antiinfecciosa (AU)

Mecanismos de resistencia bacteriana a las quinolonas / Mechanisms of bacterial resistance to quinolones

Para ejercer su efecto citotóxico las quinolonas deben penetrar a través de la membrana bacteriana y alcanzar su diana celular, la DNA girasa o la topoisomerasa IV, e inducir la muerte de la célula. Por ello, los mecanismos de resistencia a las fluoroquinolonas incluyen mutaciones en los genes que codifican la DNA girasa y la topoisomerasa IV dando lugar a las QRDR, alteraciones en la permeabilidad de la membrana que disminuyen la penetración intracelular del fármaco y actividad de transportadores activos endógenos que provocan la expulsión de los antimicrobianos desde la membrana celular al medio exterior. Estos mecanismos de resistencia pueden manifestarse solos o en combinación, si bien parece que in vivo el aumento en el grado de resistencia a las quinolonas es producto de varios mecanismos simultáneos. En el presente trabajo se revisan estos mecanismos de resistencia y se establece, en la medida de lo posible, una relación con la estructura de la quinolona. (AU)

[Mechanisms of bacterial resistance to quinolones]. / Mecanismos de resistencia bacteriana a las quinolonas.

In order to produce their cytotoxic effect, quinolones must enter the cell through the bacterial membrane to reach their target, DNA-gyrase or topoisomerase IV, and induce cell death. The mechanisms of resistance to fluoroquinolones include: those mediated by gene mutations codifying for DNA gyrase and topoisomerase IV and leading to QRDR; those characterized by changes in the permeability of the outer membrane which decrease intracellular penetration of the drug; and those caused by active endogenous carriers responsible for drug efflux. These resistance mechanisms can occur alone or in combination; in fact, it is believed that high resistance levels to quinolones in vivo are associated with simultaneous mechanisms. This article reviews such resistance mechanisms and establishes, when possible, their relation to the structure of quinolones.

[Quinolones and Streptococcus pneumoniae. Mechanisms of action and resistance]. / Quinolonas y Streptococcus pneumoniae. Mecanismo de acción y resistencia.

Streptococcus pneumoniae is considered the most frequent bacterial cause of community-acquired pneumonia, and is involved in a significant number of cases of acute exacerbations of chronic bronchitis, acute otitis, sinusitis, meningitis and other infectious diseases. Fluoroquinolones have been extensively investigated in recent years in the search for new agents that has been prompted by the emergence of resistance in this microorganism. Furthermore, the study of resistance from a molecular biology standpoint has helped in elucidating almost all the biochemical mechanisms of resistance and the routes of dissemination of genetic information between bacteria. This short review is focused on the mechanism of action of quinolones and on the mechanisms responsible for resistance of S. pneumoniae to them, given their clinical and epidemiological relevance. S. pneumoniae is a case apart because bactericidal activity against this microorganism can be produced through gyrase, topoisomerase IV or both, depending on the quinolone structure, which shows that structure has an influence on the success of treatment. Knowledge of the resistance prototype is therefore important so that the appropriate antibiotic therapy can be recommended when indicated.