Proteína tau como biomarcador en Alzheimer preclínico / Tau protein as a biomarker in preclinical Alzheimer's disease

El desarrollo de biomarcadores de la proteína tau para el diagnóstico temprano de la enfermedad de Alzheimer (EA) emerge como un desafío fundamental, pudiendo mejorar la efectividad de un tratamiento preventivo o que enlentezca la progresión de la enfermedad. Esta revisión analiza las evidencias que justificarían el uso de la proteína tau como biomarcador en Alzheimer preclínico. Para esto se seleccionaron artículos científicos (2011-2021) que incluyeran a la proteína tau en plasma y plaquetas como biomarcador. La presencia de la proteína tau fosforilada en el líquido cefalorraquídeo presenta limitaciones por su carácter invasivo mientras que las técnicas de imagen son costosas. La medición de tau en plaquetas se correlaciona con la severidad de la demencia, y sería útil en el seguimiento de la EA. Sin embargo, la pertinencia de su uso en la detección temprana de EA se mantiene en discusión. La presencia de proteína tau fosforilada en plasma correspondería al biomarcador con mayor nivel de desarrollo, respecto de beta amiloide. La proteína tau plasmática detecta la EA con gran precisión en casos de demencia y ha sido validada por estudios neuropatológicos. p-tau217 plasmática medida por primera vez junto a técnicas de imagen, fue importante en la etapa preclínica de EA pudiendo predecir la formación de ovillos neurofibrilares. La correlación entre especies fosforiladas de tau en plasma y EA preclínica ha sido bien establecida, por lo que su uso como biomarcador podría ser de utilidad para la comprensión del proceso fisiopatológico de la neurodegeneración y la detección temprana de EA

The development of tau protein biomarkers for the early diagnosis of Alzheimer's disease (AD) emerges as a fundamental challenge, which may improve the effectiveness of preventive treatment or slow the progression of the disease. This review analyzes the evidence that would justify the use of tau protein as a biomarker in preclinical Alzheimer's disease. For this purpose, we selected scientific articles (2011-2021) that included tau protein in plasma and platelets as a biomarker. Phosphorylated tau protein in cerebrospinal fluid has limitations due to its invasiveness, while imaging techniques are expensive. The tau measurement in platelets correlates with the severity of dementia and would be helpful in the follow-up of AD. However, the relevance of its use in the early detection of AD remains under discussion. Plasma phosphorylated tau protein would correspond to the biomarker with the highest level of development for beta-amyloid. Plasma tau protein detects AD with high accuracy in cases of dementia, and neuropathological studies validate its use. Plasma p-tau217 measured for the first time with imaging techniques was important in preclinical AD and could predict the formation of neurofibrillary tangles. The correlation between plasma phosphorylated tau species and preclinical AD is well-established, so its use as a biomarker would help understand the pathophysiological process of neurodegeneration and early AD detection.

Doença de Alzheimer de início precoce (DAIP): características neuropatológicas e variantes genéticas associadas / Early-onset Alzheimer's Disease (EOAD): neuropathological characteristics and associated genetic variants

RESUMO A doença neurodegenerativa mais comum no mundo é a doença de Alzheimer (DA), e 10% dos casos apresentam sintomas antes dos 65 anos, quase todos com associação genética, com hereditariedade autossômica dominante e penetrância entre 92 a 100% dos portadores. Na presente revisão, realizamos uma busca sobre as variantes genéticas associadas à doença de Alzheimer de início precoce (DAIP), enfatizando as características associadas mais importantes e as principais mutações já descritas. Os genes mais comumente relacionados com o surgimento da DAIP são APP, PSEN1, PSEN2 e MAPT, e mutações nestes afetam o metabolismo e a estrutura destas proteínas, resultando em acúmulos de peptídeo Aβ que causam inflamação e toxicidade no cérebro, levando à ativação da micróglia e promovendo a liberação de fatores neurotóxicos e pró-inflamatórios que aceleram a neurodegeneração. O gene PSEN1 é responsável por 70% das mutações conhecidas da DAIP, sendo a L166P associada à idade de ocorrência da doença abaixo dos 30 anos. Mutações em APP levam à agregação da proteína em placas neurodegenerativas. Todas as mutações descritas para MAPT estão associadas a um aumento dos emaranhados neurofibrilares. O polimorfismo E4 da Apolipoproteína E (APOE) influencia o aumento no risco de DAIP elevando as chances em três vezes para portadores heterozigotos e entre oito a dez vezes para os homozigotos. Apenas 5% das mutações associadas à DAIP são conhecidas, e novos estudos apresentam outros genes candidatos, bem como a importância de alterações epigenéticas na gênese desta doença.

SUMMARY The most common neurodegenerative disease in the world is Alzheimer's Disease (AD). Ten percent of Alzheimer patients experience symptoms before the age of 65, and almost all of them present genetic features of autosomal dominant inheritance nature, and penetrance of 92 to 100%. In the present review, we searched for genetic variants associated with early onset Alzheimer's disease (EOAD), emphasizing the most important characteristics and the main mutations. The genes most commonly related to the onset of EOAD are APP, PSEN1, PSEN2 and MAPT, whose mutations affect the metabolism and structure of these proteins. This process results in accumulations of Aβ peptide that leads to activation of the microglia and release of neurotoxic and pro-inflammatory factors that accelerate neurodegeneration. The PSEN1 gene is responsible for 70% of the known mutations in EOAD, while L166P is associated with below 30 years as the starting age of occurrence. APP mutations lead to protein aggregation in neurodegenerative plaques. All of the mutations described for MAPT are associated with an increase in neurofibrillary tangles. The E4 polymorphism of Apolipoprotein E (APOE) influences an increased risk of EOAD increasing up to three times the chances for heterozygous, and between eight and ten times for homozygotes carriers. Only 5% of the mutations associated with EOAD are known; new studies will show other candidate genes, as well as the importance of epigenetic factors changes in the etio-pathogenesis of this disease.

Salivary biomarkers in Alzheimer´s disease / Biomarcadores salivales en la enfermedad de Alzheimer

The hypotheses currently considered the most likely causes of Alzheimer's disease (AD) are amyloid beta peptide deposition in the cerebral cortex and hyperphosphorylation of the Tau protein, with the consequent formation of neurofibrillary tangles. In clinical practice, although not accurate, AD diagnosis is based on the exclusion of other diseases, behavioural assessments and complementary examinations, such as imaging and blood tests. Advances in the field of biotechnology have created exciting prospects for the early detection of AD via biomarker assessment, which is considered a safer and more efficient procedure. Molecules recognised as biomarkers can be expressed in some body fluids, including cerebrospinal fluid, saliva and blood. The presence of amyloid beta peptide and Tau can be confirmed in saliva, which is also an easily and non-invasively collectable material with an accessible cost. The objective was evaluate the concentrations of the t-Tau protein and Ab42 peptide in the saliva of elderly individuals with and without dementia of the AD type Method: The objective of this case-control study, involving a total of 120 individuals, was to analyse whether a correlation exists between variations in the concentrations of the t-Tau and Ab42 biomarkers in the saliva of patients with confirmed AD and individuals in the inclusion group but without AD . We found that t-Tau expression in AD patients is significantly lower than that in individuals without AD, whereas the salivary concentration of Ab42 is higher in patients with AD but not significantly different from that of the group without AD. Conclusion: Thus, we demonstrate the feasibility of using salivary biomarkers as predictive markers for diagnosis of Alzheimer's disease.

Las hipótesis consideradas actualmente como las causas más probables de la enfermedad de Alzheimer (EA) son la deposición de péptido beta amiloide en la corteza cerebral y la hiperfosforilación de la proteína Tau, con la consiguiente formación de ovillos neurofibrilares. En la práctica clínica, aunque no es precisa, el diagnóstico de la EA se basa en la exclusión de otras enfermedades, evaluaciones de comportamiento y exámenes complementarios, como imágenes y análisis de sangre. Los avances en el campo de la biotecnología han creado interesantes perspectivas para la detección temprana de la EA a través de la evaluación de biomarcadores, que se considera un procedimiento más seguro y más eficiente. Las moléculas reconocidas como biomarcadores se pueden expresar en algunos fluidos corporales, incluidos el líquido cerebroespinal, la saliva y la sangre. La presencia del péptido beta amiloide (AB) y la proteína Tau (t-Tau) se puede confirmar en la saliva, que también es un material fácil y no invasivo de recolección con un costo accesible. El objetivo fue evaluar las concentraciones de la proteína t-Tau y el péptido Ab42 en la saliva de las personas de edad avanzada con y sin demencia del tipo de tipo EA. El estudio de casos y controles, se realizó en un total de 120 personas, para analizar si existe una correlación entre las variaciones en las concentraciones de los biomarcadores t-Tau y Ab42 en la saliva de pacientes con EA confirmada e individuos en el grupo de inclusión pero sin AD. Encontramos que la expresión de t-Tau en pacientes con EA es significativamente menor que en individuos sin EA, mientras que la concentración salival de Ab42 es mayor en pacientes con EA pero no significativamente diferente de la del grupo sin la enfermedad . Por lo tanto, se demuestra la viabilidad del uso de biomarcadores salivales como marcadores predictivos para el diagnóstico de la enfermedad de Alzheimer.

Enfermedad de Creutzfeldt-Jakob / Creutzfeldt-Jakob disease

Resumen: La enfermedad de Creutzfeldt-Jakob es una afección neuroselectiva y neurodegenerativa, de curso fatal, poco frecuente, que representa un desafío para el diagnóstico clínico. Se comunica el caso de un paciente de 52 años de edad con antecedente de ingesta de mamíferos silvestres durante su vida, con cuadro de disminución de la agudeza visual, demencia rápidamente progresiva, mioclonías, movimientos anormales y disfunción motora; con estudios auxiliares de diagnóstico diferencial dentro de parámetros normales y la determinación de la proteína TAU reactiva.

Abstract: Creutzfeldt-Jakob disease is a neuroselective and neurodegenerative illness, with fatal course, which is rare and represents a challenge for clinical diagnosis. This paper reports the case of a 52-year-old male with a history of ingestion of wild mam- mals during his life, with a picture of diminished visual acuity, rapidly progressive dementia, myoclonus, abnormal movements and motor dysfunction; with auxiliary studies of differential diagnosis within normal parameters and the determination of reactive TAU protein.

Increased CSF levels of total Tau in patients with subcortical cerebrovascular pathology and cognitive impairment / Aumento dos níveis de CSF de Tau total em pacientes com patologia subcutânea cerebrovascular e comprometimento cognitivo

ABSTRACT. Cognitive impairment includes mild cognitive decline and dementia, such as Alzheimer's disease (AD) and cerebrovascular-related pathologies. Objective: To investigate the profile of AD-related CSF biomarkers in a sample of cognitively impaired and unimpaired older adults with concomitant subcortical cerebrovascular burden. Methods: Seventy-eight older adults attending an outpatient psychogeriatric clinic were enrolled. Diagnoses were based on clinical, neuropsychological, laboratory, and neuroimaging data. Participants were classified into: cognitively normal (controls, n = 30), mild cognitive impairment (MCI, n = 34), and dementia (AD, n = 14). All subjects were submitted to CSF analyses for determination of amyloid-beta (Aß1-42), total tau (t-tau), phosphorylated tau (p-tau) and Aß1-42/p-tau ratio according to the Luminex method. MRI was performed in all individuals, and was scored independently by two experts according to Fazekas scale. Statistical analyses were conducted with the aid of general linear model procedures, and the Chi-squared test. Results: T-tau levels were significantly associated with subcortical lesion pattern when Fazekas was considered as a group factor. CSF biomarkers were not associated with MCI, AD, or controls when considered separately. There was a tendency for reduction in CSF Aß1-42 together with increasing Fazekas scores, but without statistical significance. Comparisons of Aß1-42 and t-tau with each clinical group or with each neuroimaging pattern did not reach statistical differences. Likewise, Fazekas scores had no impact on CAMCOG scores. Conclusion: We found a significant association between t-tau levels and subcortical lesions when all Fazekas classifications were considered as a single group; comparisons of Fazekas subgroups and CSF biomarkers did not reach significance.

RESUMO. O comprometimento cognitivo inclui alterações leves da cognição e demência, como doença de Alzheimer (DA) e patologias vasculares associadas. Objetivo: Investigar o perfil de biomarcadores da DA no líquor e doença cerebrovascular concomitante em idosos com e sem alterações cognitivas. Métodos: Foram incluídos 78 sujeitos de um ambulatório de psicogeriatria. Efetuaram-se os diagnósticos com base em dados clínicos, neuropsicológicos, laboratoriais e neuroimagem. Os participantes foram classificados em: cognitivamente normais (controles, n = 30), comprometimento cognitivo leve (CCL, n = 34) e demência (DA, n = 14). Todos foram submetidos ao exame liquórico para determinação de ß-amiloide (Aß1-42), tau total (t-tau), tau fosforilada (p-tau) e razão Aß1-42/p-tau, segundo o método de Luminex. RM foi efetuada em todos os indivíduos. Dois especialistas independentes avaliaram as imagens segundo a escala de Fazekas. As análises estatísticas basearam-se em modelo linear geral e teste qui-quadrado. Resultados: T-tau foi significantemente associada ao padrão de lesão subcortical quando o grau de Fazekas foi considerado como fator grupal. Não houve associação entre biomarcadores e diagnóstico clínico de CCL, DA e grupo controle, considerados individualmente. Observou-se uma tendência de redução de Aß1-42 concomitante com elevação dos escores de Fazekas, sem correlação significante. Comparações entre Aß1-42 e tau e diagnóstico clínico ou neuroimagem não foram significantes. Os resultados de Fazekas não influenciaram os escores do CAMCOG. Conclusão: Como principal resultado, observou-se associação significante entre os níveis de t-tau e lesões subcorticais quando as classificações de Fazekas foram incluídas em um único grupo. As comparações dos subgrupos de Fazekas e biomarcadores liquóricos não foram significantes.

Biomarcadores y marcadores de imagen de la enfermedad de Alzheimer / Biomarkers and image markers of Alzheimer's disease

Este artículo presenta un análisis desde el punto de vista bibliográfico de marcadores y biomarcadores de la enfermedad de Alzheimer (EA). Las metodologías usadas fueron los marcadores de imágenes (Resonancia Magnética y Tomografía por emisión de positrones) y biomarcadores de la proteína BA42, de la proteína Tau y de la Apoliproteína E (ALPE). De esta manera, son de importancia los niveles de BA42 disminuidos, la Tau incrementada, los polimorfismos de ALPE y las alteraciones constatadas en los marcadores de imagen, como factores de riesgo esenciales para el desarrollo de la EA. Se realiza una revisión de la literatura con respecto a los hallazgos clínicos de esta enfermedad.

This article presents a bibliographical analysis of markers and biomarkers of Alzheimer's disease (AD). The methodologies used were the imaging markers (Magnetic Resonance and Positron Emission Tomography) and biomarkers of the BA42 protein, Tau protein and Apoliprotein E (ALPE). Thus, decreased levels of BA42, increased Tau, ALPE polymorphisms, and alterations in imaging markers are important as risk factors for the development of AD. A review of the literature is made regarding the clinical findings of this disease.

Biología molecular de la enfermedad de Alzheimer / Molecular biology of Alzheimer's disease

Resumen:La enfermedad de Alzheimer (EA) es una enfermedad neurodegenerativa asociada con una disminución cognitiva y es la forma más común de demencia en los ancianos. Un gran número de factores se asocian con un riesgo aumentado de EA, no obstante, la edad representa, por mucho, el riesgo individual más grande en la etiología de la EA. La variante genética más fuerte para la EA típica de inicio tardío es la apolipoproteína E (APOE). Mutaciones raras en tres genes han sido implicadas en la enfermedad familiar de inicio temprano: APP, PSEN1 y PSEN2. Las placas amiloides extracelulares y los ovillos neurofibrilares intraneurales (NFT) son las dos lesiones características de esta enfermedad fatal. La proteína tau está involucrada en el ensamblaje y estabilización de los microtúbulos.La fosforilación anormal de tau, una característica prominente del cerebro con EA, decrece su habilidad de unión a los microtúbulos, pudiendo desestabilizar los microtúbulos y causar daño celular. Un grupo heterogéneo de péptidos Aβ monoméricos de entre 37 a 43 aminoácidos se genera a partir de la proteína precursora amiloide transmembrana (APP) por el corte mediado por las secretasas β y ץ. El monómero tiene una alta tendencia a autoagregarse formando agregados grandes y fibrillas. In vivoexiste una sopa de oligómeros de Aβ consistiendo de una gran variedad de formas intercambiables rápidamente, que difieren en tamaño, conformación, desorden intrínseco y toxicidad. Evidencia creciente sugiere que las formas más dañinas de los péptidos del amiloide β son los oligómeros solubles y que los depósitos amorfos e insolubles o fibrilares representan una forma inactivada menos peligrosa del péptido. Varios mecanismos han sido propuestos para explicar las anormalidades en la EA, incluyendo la toxicidad por Aβ, deficiencias del transporte axónico y el estrés oxidativo.

Abstract:Alzheimer disease (AD is a progressive neurodegenerative disease associated with cognitive decline and is the most common form of dementia in the enderly. A large number of factors has been associated with increased risk of AD, however, age represents, by far, the single greatest risk factor in the etiology of AD. The strongest common genetic variant for typical late-onset AD is apoliprotein E (APOE). Rare mutations in three genes have been implicated in familial early-onset disease: APP, PSEN1, and PSEN2.Extracellular amyloid plaques and intraneuronal neurofibrillary tangles (NFT) are two major hallmark lesions of this fatal pathology.Tau protein is involved in microtubule assembly and stabilization. Abnormal phosphorylation of tau, a prominent feature of AD brain, decreases its microtubule binding ability, which may destabilize microtubules and results in cellular damage.A heterogeneous pool of monomeric Aβ peptide varying in length from 37 to 43 amino acids is generated from the transmembrane amyloid precursor protein (APP) by β- and ץ-secretase-mediated cleavage. The Aβ monomer has a high tendency to self-assemble into large aggregates and fibrils.A diverse "Aβ oligomeric soup" exists, consisting of a large variety of rapidly exchangeable polymorphs that differ in size, conformation, intrinsic disorder, and toxicity.Growing evidence suggests that the most detrimental forms of amyloid β peptides are the soluble oligomers and that the insoluble amorphous or fibrillar deposits represent a less harmful inactivated form of the peptide.Several mechanisms have been proposed to account for abnormalities in AD, including Aβ toxicity, axonal transport deficiencies, and oxidative stress.

Revisión de Creutzfeld-Jakob a propósito de dos casos clínicos en el Hospital Universitario San Ignacio / Creutzfeldt-Jakob review based on two clinical cases in Hospital Universitario San Ignacio

La enfermedad de Creutzfeld-Jakob es una patología neurodegenerativa fatal e intratable, que hace parte de las denominadas encefalopatías espongiformes y se produce por la acumulación anormal de la PrP (proteína priónica patogénica),denominada PrPsc, a nivel del sistema nervioso central. La enfermedad priónica humana más común es la forma esporádica de la enfermedad de Creutzfeld-Jakob, cuya aparición se ha relacionado con los efectos ambientales desconocidos o los sucesos aleatorios y genéticos, que resultan en la producción espontánea de PrP en el cerebro. A continuación se presentan dos casos clínicos de dos mujeres que consultan al servicio de urgencias del Hospital Universitario San Ignacio, en quienes se sospechó encefalopatía rápidamente progresiva, compatible con enfermedad de Creutzfeld-Jakob.

Creutzfeldt-Jakob disease is a fatal and untreatable neurodegenerative disorder that is part of the so-called spongiform encephalopathies, which is caused by the abnormal accumulation of PrP protein (called PrPSc) in the central nervous system. The most common human prion disease is sporadic form of Creutzfeldt-Jakob, whose appearance has been associated with environmental effects or unknown and random genetic events that result in the spontaneous production of PrP in the brain. In this work we will present two Clinical cases of two woman who visited the emergency room of the hospital Universitario San Ignacio, in which a rapidly progressive encephalopathy caused by Creutzfeldt-Jakob disease is suspected.

Neurodegenerative changes in the brainstem and olfactory bulb in people older than 50 years old: a descriptive study / Alterações neurodegenerativas no tronco cerebral e bulbo olfatório em indivíduos acima de 50 anos: um estudo descritivo

With the increase in life expectancy in Brazil, concerns have grown about the most prevalent diseases in elderly people. Among these diseases are neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases. Protein deposits related to the development of these diseases can pre-date the symptomatic phases by years. The tau protein is particularly interesting: it might be found in the brainstem and olfactory bulb long before it reaches the limbic cortex, at which point symptoms occur. Of the 14 brains collected in this study, the tau protein was found in the brainstems of 10 (71.42%) and in olfactory bulbs of 3 out 11. Of the 7 individuals who had a final diagnosis of Alzheimer’s disease (AD), 6 presented tau deposits in some region of the brainstem. Our data support the idea of the presence of tau protein in the brainstem and olfactory bulb in the earliest stages of AD.

Com o aumento da expectativa de vida no Brasil e no mundo, crescem as preocupações com as doenças mais prevalentes entre os idosos, dentre elas as doenças neurodegenerativas (DN) como a doença de Alzheimer (DA) e a doença de Parkinson (DP). Sabe-se que os depósitos proteicos relacionados com o desenvolvimento destas doenças podem preceder a fase sintomática em anos. A proteína tau é de particular interesse, uma vez que parece ser encontrada no tronco encefálico e bulbo olfatório muito antes de atingir o córtex límbico, quando ocorrem os primeiros sintomas. Dos 14 encéfalos coletados neste estudo, a proteína tau foi encontrada, no tronco encefálico, em 10 (71,42%) e no bulbo olfatório em 3 de 11. Dos 7 indivíduos que tiveram diagnóstico final de DA, todos apresentavam depósitos de tau em alguma região do tronco encefálico. Nossos dados estão de acordo com a literatura mais recente, que tem confirmado a presença de proteína tau no tronco encefálico e bulbo olfatório nos estágios mais precoces da DA.

La teoría de la neuroinmunomodulación en enfermedades neurodegenerativas: nuevas evidencias científicas / Neuroinmmunomodulation in neurodegenerative diseases: new scientific evidence

Microglial cells play a major role in the innate immunity of the central nervous system. Alterations in the normal cross-talks between microglia and brain neuronal cells may lead to serious disturbances and neurodegenerative diseases. We have postulated that neuroinflammatory processes are a critical factor triggering the pathological cascade leading to neuronal degeneration. In our neuroimmunomodulation theory, external or internal damage signals activate microglial cells, producing cytotoxic factors that induce neuronal degeneration. These factors activate protein-kinases, that lead to tau hyperphosphorylation, and its consequent oligomerization. The tau aggregates released into the extracellular medium favor a positive feedback mechanism that determines neurodegeneration. Nowadays, natural components with a string anti-inflammatory activity and that cross the blood brain barrier appears as candidates for prevention and treatment of degenerative brain disorders such as Alzheimers'disease.

Las células microgliales juegan un papel importante en la inmunidad innata del sistema nervioso central. Las alteraciones en la normal diafonía celular, entre microglias y células neuronales cerebrales, pueden conducir a graves disturbios y enfermedades neurodegenerativas. En este contexto, hemos postulado que los procesos neuroinflamatorios son un factor crítico a desencadenar la cascada patológica que conduce a la degeneración neuronal. En nuestra teoría Neuroinmunomoduladora, señales de daños externos o internos activan las células microgliales, favoreciendo la producción de factores citotóxicos que inducen la degeneración neuronal. Estos factores activan la proteína-quinasas, que conducen a la hiperfosforilación de la proteína tau, y su consecuente oligomerización. Estos agregados de tau liberados al medio extracelular, al activar a la célula microglial, provocarían un mecanismo de retroalimentación positiva favoreciendo la neurodegeneración. Hoy en día, compuestos de origen natural con una fuerte actividad anti-inflamatoria, capaces de cruzar la barrera hematoencefálica del cerebro, aparecen como candidatos para la prevención y el tratamiento de trastornos neurodegenerativos tales como la enfermedad de Alzheimer.

Aspectos da fisiopatologia da doença de Alzheimer esporádica / Pathophysiological features of sporadic Alzheimer's disease

A doença de Alzheimer (DA) é a forma de demência degenerativa esporádica mais comum. Caracteristicamente ocorre expressiva perda neuronal progressiva em locais específicos nas pessoas atingidas. O distúrbio degenerativo progressivo se caracteriza pela perda de sinapses, de neurônios cerebrais e por depósitos de fibrilas de peptídeos de beta-amilóide extraneuronais, constituindo as placas senis e a presença de agregados intraneuronais da proteína tau, formando os emaranhados neurofibrilares. Fatores genéticos, metabólicos, neuroinflamação, alterações mitocondriais, distúrbios vasculares e processos oxidativos estão envolvidos no desencadear e manutenção de várias doenças neurodegenerativas, incluindo a DA. Todas essas alterações participam no processo fisiopatológico da doença. O objetivo desta revisão é mostrar a associação das várias causas subjacentes ao processo fisiopatológico da DA, com vistas ao desenvolvimento de marcadores biológicos e estratégias terapêuticas.

Alzheimer's disease (AD) is the most common form of sporadic degenerative dementia. Characteristically there is an expressive neuronal loss in specific sites in the affected persons. The progressive degenerative disorder is characterized by synaptic loss, of brain neurons, and by extraneuronal deposition of beta-amyloid fibrils, constituting the senile plaques, and the presence of intraneuronal aggregates of tau protein, forming the neurofibrillary tangles. Genetic factors, metabolic, neuroinflammation, mitochondrial disturbances, vascular disorders and oxidative processes are involved in the onset and maintenance of several neurodegenerative disorders, including AD. All these disturbances participate in the pathophysiological process of the disease. The aim of this review is to show the association of the varied causes underlying the pathophysiological process of AD, having in view the development of biological markers and therapeutic strategies.

Detección de b-Amiloide, proteína TAU hiperfosforilada y ubiquitina por técnica de inmunohistoquímica en cerebros de caninos mayores de 10 años / Detection b-Amiloid, hyperphosphorylate TAU protein and ubiquitin for technique the immunohistochemistry in brains in dogs over 10 years

El interés en el estudio del proceso de envejecimiento cerebral y los cambios comportamentales relacionados con la edad en caninos y felinos geriátricos ha aumentado en la última década (Mentzel, 2005a; Ingram & Williams, 2010). Las alteraciones del comportamiento canino que responden a cambios fisiopatológicos relacionados con la edad y que involucran distintas esferas conductuales y cognitivas, se engloban bajo la denominación de Síndrome de Disfunción Cognoscitiva (SDC) (Mentzel, 2005b). El cual fue descrito en 1997 y se observó en perros de más de 9 años (Ingram & Williams). El Síndrome de Disfunción Cognoscitivo (SDC) es también llamado Alzheimer canino por las similitudes histopatológicas cerebrales y conductuales relacionadas. En el presente estudio, los caninos geriátricos presentaron los mismos depósitos proteicos anormales presentes en la enfermedad de Alzheimer, como las placas seniles, los cuerpos ubiquitinados y la angiopatía amiloide, pero no presentaron los ovillos neurofibrilares, los cuales son los responsables de la demencia que se padece en la enfermedad. Las únicas herramientas de evaluación prácticas en clínica para esta patología son las encuestas y formularios relacionados con aspectos comportamentales. Además existen exámenes diagnósticos postmortem que permiten identificar de una manera eficaz la presencia de elementos anormales involucrados en la neuropatología, uno de ellos es la inmunohistoquímica. En este estudio se utilizaron los anticuerpos monoclonales de uso humano anti-b-amiloide, anti-proteína tau y anti-ubiquitina en muestras de cerebros de perros mayores de 10 años. El modelo canino hoy en día está constituyendo un significado indispensable para el estudio de los procesos de neurodegeneración porque ha permitido un acercamiento a la teoría del problema desde nuevas perspectivas (Dimakopoulos & Mayer, 2002).

The interest in the study of the process of cerebral aging and the changes in the behaviour related to age in geriatric canine and feline has increased in the last decade (Mentzel, 2005a; Ingram & Williams, 2010). The alterations of the canine behaviour that respond to physiopathological changes related to the age and which involve different conducts and cognitive spheres are included under the denomination of Canine Cognitive Dysfunction Syndrome (CDS) called canine Alzheimer, considering the cerebral and histopathologic behavioural similarities. In the present study the geriatric patients displayed the same abnormal protein deposits present in Alzheimer disease, such as senile plaques ubiquitinate bodies and the amyloid angiopathy. However they did not display the balls of neurofibrillary tangles which are characteristic of the disease. The only practical tools of evaluation in clinic for this pathology are the surveys and forms related to behavioural aspects. In addition there are post mortem exams such as those in inmunohistochemistry, that allow an effective identification of abnormal elements present in the neuropathology. In this study the monoclonal antibodies were used anti-b-amyloid, anti-protein tau and anti-ubiquitin in samples of brains in dogs over 10 years of age. The canine model constitutes an indispensable meaning for the study of the neurodegeneration processes because it has allowed an approach to the theory of the problem from a new perspective (Dimakopoulos & Mayer, 2002).

La neuroinflamación como factor detonante del desarrollo de la enfermedad de alzheimer: [revisión] / Neuroinflammation as a triggering factor for alzheimer's disease: [review]

The progressive increase in life expectancy of the world population has fostered a major concern in order to find effective avenues for diagnosis of treatment of Alzheimer's disease (AD). Even tough AD pathogenesis is still unclear, new advances have allowed to understand that exposure of individuals to a series of environmental risk factors, named to as damage signals, play a main role in triggering the disease. This is important for AD prevention but also for the search of new treatment approaches. Activation of innate immunity in the central nervous system (CNS), essentially microglial cells, appears to be a key element in the neurodegenerative pathway As a matter of fact, when microglia cells are exposed continuously to damage signals such as metabolites from conditions of hyperlipidemia, hyperglycemia, oxidative stress, head injury and trauma, recurrent infections, in addition to supramolecular aggregates such as tau filaments or b-amyloid oligomers, among other anomalous protein filaments, they respond by triggering the inflammatory cascade. On this basis, we have postulated the neuroimmunomodulation hypothesis for Alzheimer's Disease. Therefore, we postulates that a long-term activation of brain innate immunity by a converging set of damage signals constitute a unifying mechanism that triggers the inflammatory cascade, thus leading to irreversible alteration in the neuronal cytoskeleton. These concerted alterations in signaling mechanisms will lead in neuronal cells to a final common pathway, tau hyperphosphorylations, with the consequent self-aggregation of modified tau and formation of paired helical filaments (PHFs), as the main triggering event for neurodegenration in AD.

El constante aumento en la expectativa de vida en la población mundial ha incrementado la preocupación hacia la búsqueda de la comprensión de la Enfermedad de Alzheimer (EA), así como de su diagnóstico temprano y tratamiento. Actualmente la etiopatogenia que conduce al desarrollo de la EA es aún difusa, pero se ha llegado a comprender que la exposición a una serie de distintos factores de riesgo, o señales de daño, está asociada al desencadenamiento de la EA. Esto es muy importante no solo para la prevención de esta devastadora enfermedad sino también para la búsqueda de avenidas efectivas para su tratamiento. En efecto, la activación de la inmunidad innata en el sistema nervioso central (SNC), esencialmente por las células microgliales, son un elemento clave en el proceso neurodegenerativo, cuando éstas son expuestas por períodos prolongados a señales de daño. Entre éstas están la hiperlipidemia, hiperglicemia, estrés oxidativo, traumatismos, infecciones recurrentes, oligomeros de -amiloide, agregados de tau, entre otros factores, los que desencadenarían una respuesta pro-inflamatoria persistente que conduce a la cascada neurodegenerativa. En base a esto, hemos postulado la teoría de la neuroinmunomodulación en la EA, y proponemos que la activación a largo plazo del sistema inmune innato por un conjunto de señales de daño constituye un mecanismo unificado que gatillo, una cascada inflamatoria que conduce a alteraciones irreversibles en el citoesqueleto. Estos mecanismos anómalos de señalización molecular llevarían a una vía final común que es la hiperfosforilación de la proteína tau, su autoagregación y formación de los PHFs, como desencadenantes claves en la neurodegeneración y desarrollo de la EA.

Influência genética sobre a doença de Alzheimer de início precoce / Genetic influence on early onset Alzeimer's disease

CONTEXTO: A doença de Alzheimer de início precoce (DAIP) representa 5 por cento de todos os casos de doença de Alzheimer e está relacionada a mutações gênicas. OBJETIVO: Apresentar a influência de mutações gênicas na DAIP. MÉTODOS: Revisão da literatura, a partir de 1992, empregando o banco de dados PubMed. RESULTADOS: O alelo E*4 do gene da apolipoproteína E interfere na DAIP. No gene da proteína precursora da amiloide, foram descritas 20 mutações, que causam cerca de 10 por cento a 15 por cento dos casos de DAIP. Mutações no gene das presenilinas 1 e 2 causam 30 por cento a 70 por cento dos casos de DAIP. No gene da PSN1, há 30 mutações de troca de aminoácidos e três inserções/deleções. O gene da PSEN2 apresenta seis mutações de troca de aminácidos. No gene MAPT, apenas uma mutação se relaciona exclusivamente com a DA. CONCLUSÕES: O uso de informações genéticas para a detecção precoce de possíveis pacientes com DAIP ainda é bastante limitado. A heterogeneidade genética é ampla. Algumas mutações descritas nesta revisão foram responsáveis pela doença de Alzheimer em apenas algumas poucas famílias. A aplicação clínica desses métodos no rastreamento de indivíduos em risco para a DAIP ainda exige cautela.

BACKGROUND: Early onset Alzheimer's disease (EOAD) represents 5 percent of all cases of Alzheimer's disease, and it is connected to genic mutations. OBJECTIVES: To present the influence of genic mutations in EOAD. METHODS: Review of current literature, starting from 1992, utilizing the PubMed data bank. RESULTS: The E*4 allele of the apolipoprotein E gene interferes in EOAD. In the gene of the Amyloid Precursor Protein, 20 mutations were described, causing 10 percent to 15 percent of the cases of EOAD. Mutations in the gene of presenilins 1 and 2 cause 30 percent to 70 percent of the cases of EOAD. In PSN1 gene, 30 aminoacid change mutations and 3 insertions/deletions are known. In the PSEN2 gene, there are 6 aminoacid change mutations. Only one mutation in the MAPT gene is selectively associated with Alzheimer's disease. CONCLUSIONS: The use of genetic information for early detection of possible pacients of EOAD is still very limited. Genetic heterogeneity is broad. Some mutations described in this review were responsible for Alzheimer's disease only in a few families. The clinical utilization of these methods for screening individuals at risk for EOAD still asks for caution.

Papel da proteína Tau na fisiopatologia da demência frontotemporal / The role of TAU protein in the pathophysiology of frontotemporal dementia

CONTEXTO: Sob a denominação demência frontotemporal (DFT) enquadram-se importantes síndromes demenciais de natureza degenerativa progressiva que acometem os lobos frontais e temporais em ambos os hemisférios. As DFTs podem ser agrupadas, segundo seus aspectos clínicos dominantes, em variante frontal, afasia progressiva não fluente e demência semântica. A proteína Tau tem papel importante na patogenia desses transtornos, e anormalidades conformacionais estão presentes em até 50 por cento dos casos de DFT esporádica. Do ponto de vista neuropatológico, as DFTs podem ser classificadas em Tau negativas e Tau positivas, estas últimas também classificadas entre as tauopatias. OBJETIVO: Neste trabalho será revisto o papel da proteína Tau na patogenia das DFTs. MÉTODOS: Busca simples no Scielo e na Pubmed por meio das palavras-chave: "tauopatias", "demência frontotemporal" e "proteína Tau". Foram revisados os artigos publicados a partir de 2000, e artigos anteriores de maior relevância, identificados a partir das referências estudadas. RESULTADOS: Dentre os trabalhos incluídos nesta análise, 12 abordam as tauopatias, sendo dez originais e sete de revisão. Foram identificados 20 artigos sobre DFT, sendo 16 artigos originais e quatro de revisão. CONCLUSÃO: A proteína Tau tem papel fundamental na patogenia das DFTs e outras doenças neurodegenerativas. O conhecimento desses mecanismos fisiopatológicos é o passo inicial para o desenvolvimento de estratégias terapêuticas.

BACKGROUND: Frontotemporal dementia (FTD) represents an important group of neurodegenerative diseases, affecting temporal and frontal lobes of both hemispheres. FTD can be divided into three clinical subsyndromes: frontal variant, non-fluent progressive aphasia, and semantic dementia. Abnormalities of the metabolism of Tau protein are present in the physiopathology of FTD, and is found in approximately 50 percent of sporadic cases, supporting the classification of the FTDs into Tau-negative and Tau-positive subtypes, the latter also called "Tauopathies". OBJECTIVE: To review the role of Tau in the pathophysiology of FTD. METHODS: Review of the literature on FTD published in the Pubmed and Scielo databases since the year 2000, using the keywords: Tau, Tauopathies, frontotemporal dementia. Relevant references previously published, as indicated in the reference list of selected articles, were also included. RESULTS: Through electronic search we identified 12 articles addressing Tauopathies (ten containing original data and seven reviews), and 20 articles (16 with original data and four reviews) on FTDs. CONCLUSIONS: There is consistent evidence in the literature to support the notion that Tau protein plays a crucial role in the pathogenesis of FTDs and other neurodegenerative dementias, and the knowledge on these mechanisms is necessary for the development of more specific therapies.

La melatonina: un coadyuvante potencial en el tratamiento de las demencias / Melatonin: A potential coadyuvant in dementia treatment

Alzheimer's disease is characterized by a progressive neuronal death and a lost of memory and cognition that unable the patient to perform daily tasks. Cytoskeleton alterations, identified as a major histopathologic hallmark of neurodegenerative diseases, occur in dementia. In this disease, neurons have pathologic inclusions containing fibrillar aggregates of hyperphosphorylated tau protein in absence of amyloid deposits. Abundant senile plaques and neurofibrillary tangles constitute the two major neuropathologic lesions present in hippocampal, neocortical, and forebrain cholinergic brain regions of Alzheimer's patients. Hyperphosphorylated tau and the subsequent formation of paired helical filaments loses the capabilities for maintaining highly asymmetrical neuronal polarity. Thus, in brains with a high content of hyperphosphorylated tau, microtubules are disassembled, the highly asymmetrical neural shape is lost and an impairment of axonal transport is produced together with a lost of dendrite arborizations. In addition, brain damage caused by free radicals occurs in Alzheimer's disease. This illness involves a reduction of the endogenous antioxidant enzyme system, increased senile-plaque formation, cytoskeletal collapse, and neuronal apoptosis induced by oxidative stress. Acetylcholinesterase inhibitors are the most commonly used compounds in the treatment of neurodegenerative diseases. However, despite their wide use in the treatment of Alzheimer's disease, these compounds have limited therapeutic effects and cause undesirable effects. Therefore it is necessary to investigate new alternatives in the Alzheimer's disease treatment. Considering that neurodegenerative diseases are cytoskeleton disorders, this cellular structure could be a drug target for therapeutic approaches by restoring normal cytoskeleton structure and by precluding damage caused by oxygen-reactive species. In this regard, melatonin, the indole secreted by the pineal gland during the dark phase of the photoperiod, has two important properties that may be useful for the treatment of mental disorders. One is that melatonin is a potent free-radical scavenger and the other is that this indole is a cytoskeletal modulator. A neuroprotective role for melatonin was initially suggested due to its free-radical scavenger properties. Melatonin detoxifies the highly toxic hydroxyl radical as well as the peroxyl radical, peroxynitrite anion, nitric oxide, and singlet oxygen, all of which can damage brain macromolecules. Moreover, melatonin stimulates the activity of antioxidative enzymes including superoxide dismutase, glutathione peroxidase, and glutathione reductase. Also, it is a lipophilic molecule able to cross the blood-brain barrier. All these properties make melatonin a highly effective pharmacologic agent against free-radical damage in the brain. Also, it is a useful neuroprotector in dementia because it synchronize the body rhythms with the photoperiod, which are altered in Alzheimer's disease and because normal circadian secretion of melatonin and sleep-wake cycle can be restored by the indolamine administration. Additionally, cytoskeletal modulation by melatonin is another relevant property of the indole for neurodegenerative diseases treatment. Direct assessment of melatonin effects on cytoskeletal organization in neuronal cells indicated that the indole promotes neuritogenesis in N1E-115 neuroblastoma cells at plasma melatonin concentration. Neurite formation is a complex process critical to establish synaptic connectivity that is lost in Alzheimer's disease. Neuritogenesis takes place by a dynamic cytoskeletal organization that involves microtubule enlargement, microfilament arrangement, and intermediate-filament reorganization. In particular, microtubule assembly participates in neurite formation elicited by melatonin through antagonism to calmodulin. Also, selective activation of protein kinase C (PKC) alpha by melatonin participates in vimentin intermediate filament rearrangements and actin dynamics for neurite outgrowth in neuroblastoma cells. In N1E-115 cells, melatonin at plasma and cerebrospinal fluid concentration caused an increase in microfilament arrays in stress fibers and their thickening, as well as increased growth cone formation, and augmented number of cells with microspikes. Recently, it was demonstrated that melatonin increased both the number of N1E-115 cells with filopodia and with long neurites through both PKC activation and Rho-associated kinase (ROCK) stimulation. The utility of melatonin to prevent damage in the cytoskeletal structure produced by neurodegenerative processes was demonstrated in N1E-115 neuroblastoma cells cultured with okadaic acid (OA), a specific inhibitor of the serine/threonine proteins phosphatases 1 and 2A that induces molecular and structural changes similar to those found in Alzheimer's disease. Melatonin prevented microtubule disruption followed by cell-shape changes and increased lipid peroxidation and apoptosis induced by OA. Melatonin effects on altered cytoskeletal organization induced by OA are dose-dependent and effects were observed at plasma -and cerebrospinal-fluid concentrations of the indole. These data support that melatonin can be useful in the treatment of neurodegenerative diseases by both its action on the cytoskeleton and by its free-radical scavenger properties.

La enfermedad de Alzheimer es una enfermedad neurodegenerativa progresiva que cursa con una deficiencia en las capacidades cognitivas, así como con la presencia de síntomas psiquiátricos y alteraciones conductuales. Las características histopatológicas más importantes en la enfermedad de Alzheimer son la formación de placas seniles, los ovillos neurofibrilares y un incremento en el estrés oxidativo. La polaridad estructural y la morfología neuronal se pierden en la enfermedad de Alzheimer. La proteína tau se encuentra anormalmente fosforilada, los microtúbulos se despolimerizan, se pierden la forma asimétrica de las neuronas y la conectividad sináptica, y se interrumpe el transporte axoplasmático. Asimismo, se ha sugerido que la inhibición o la pérdida en el balance de la formación de neuronas en el hipocampo puede participar en la fisiopatología de la enfermedad de Alzheimer debido a que el cerebro no puede reparar el daño neuronal y consecuentemente induce la pérdida de la cognición. Los agentes colinérgicos son los medicamentos más aceptados en el tratamiento de la enfermedad de Alzheimer en una etapa en que los síntomas se clasifican de medios a moderados. Sin embargo, el tratamiento de pacientes con enfermedad de Alzheimer grave es limitado. Por lo anterior se requiere la búsqueda de nuevas alternativas para el tratamiento de esta enfermedad. La melatonina es una indolamina que actúa como un potente antioxidante, como un modulador de la organización del citoesqueleto así como un factor de diferenciación celular. Diversos estudios han sugerido que la melatonina tiene un efecto neuroprotector por su capacidad de captar radicales libres. La melatonina disminuye la lipoperoxidación y la apoptosis producida por la administración de ácido ocadáico (AO) o peróxido de hidrógeno (H2O2). Se sabe que las especies reactivas de oxígeno producen alteraciones en la organización del citoesqueleto e influyen el estado de fosforilación de la proteína tau y que la melatonina previene la fosforilación de la proteína tau debido a su actividad antioxidante. Se ha descrito que la melatonina modula el arreglo de los microfilamentos de actina y la formación de fibras de tensión en las células Madin-Darby canine kidney (MDCK) por medio de una interacción concertada de la indolamina con la calmodulina y con la proteína cinasa C (PKC) y la participación de la proteína cinasa dependiente de Rho (ROCK). Asimismo, la melatonina participa en las etapas tempranas de la formación de neuritas en las células N1E-115 por medio de ROCK. Otros estudios han indicado que la melatonina previene el daño en el citoesqueleto producido por el AO en las células N1E-115. El AO se ha utilizado para reproducir en células en cultivo las alteraciones en el citoesqueleto y el incremento en el estrés oxidativo que ocurren en las neuronas de pacientes con enfermedad de Alzheimer. La melatonina en estas células previene la retracción del citoesqueleto, efecto del AO. La red del citoesqueleto se mantiene en el citoplasma y en las neuritas de las células N1E-115 cultivadas con melatonina, no obstante que sean tratadas con el AO posteriormente. Recientemente, se demostró que en las células de neuroblastoma N1E-115 incubadas con melatonina se previene la hiperfosforilación de la proteína tau causada por el AO. Aunado a lo anterior, se ha demostrado que la melatonina modula la formación de neuronas nuevas en un modelo in vitro utilizando células embrionarias y de corteza cerebral de ratón. La formación de neuronas inducida por la melatonina se corroboró utilizando células precursoras aisladas de animales adultos así como en animales adultos, y se encontró que la indolamina moduló la sobrevida de las células nuevas formadas, así como la diferenciación de éstas en neuronas nuevas. Las evidencias presentadas en esta revisión indican que la melatonina puede ser útil como un coadyuvante en el tratamiento de las demencias.