RESUMO
HSV infection of adult humans occasionally results in life-threatening herpes simplex encephalitis (HSE) for reasons that remain to be defined. An animal system that could prove useful to model HSE could be microRNA-155 knockout (miR-155KO) mice. Thus, we observe that mice with a deficiency of miR-155 are highly susceptible to HSE with a majority of animals (75-80%) experiencing development of HSE after ocular infection with HSV-1. The lesions appeared to primarily represent the destructive consequences of viral replication, and animals could be protected from HSE by acyclovir treatment provided 4 d after ocular infection. The miR-155KO animals were also more susceptible to development of zosteriform lesions, a reflection of viral replication and dissemination within the nervous system. One explanation for the heightened susceptibility to HSE and zosteriform lesions could be because miR-155KO animals develop diminished CD8 T cell responses when the numbers, functionality, and homing capacity of effector CD8 T cell responses were compared. Indeed, adoptive transfer of HSV-immune CD8 T cells to infected miR-155KO mice at 24 h postinfection provided protection from HSE. Deficiencies in CD8 T cell numbers and function also explained the observation that miR-155KO animals were less able than control animals to maintain HSV latency. To our knowledge, our observations may be the first to link miR-155 expression with increased susceptibility of the nervous system to virus infection.
Assuntos
Encéfalo/metabolismo , Encefalite por Herpes Simples/genética , Predisposição Genética para Doença/genética , MicroRNAs/genética , Aciclovir/farmacologia , Transferência Adotiva , Animais , Antivirais/farmacologia , Encéfalo/patologia , Encéfalo/virologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Linfócitos T CD8-Positivos/transplante , Encefalite por Herpes Simples/terapia , Encefalite por Herpes Simples/virologia , Feminino , Citometria de Fluxo , Herpesvirus Humano 1/efeitos dos fármacos , Herpesvirus Humano 1/imunologia , Herpesvirus Humano 1/fisiologia , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Análise de Sobrevida , Replicação Viral/efeitos dos fármacosRESUMO
Huntington disease (HD) is an inherited progressive neurodegenerative disorder, characterized by motor, cognitive, and psychiatric deficits as well as neurodegeneration and brain atrophy beginning in the striatum and the cortex and extending to other subcortical brain regions. The genetic cause is an expansion of the CAG repeat stretch in the HTT gene encoding huntingtin protein (htt). Here, we generated an HD transgenic rat model using a human bacterial artificial chromosome (BAC), which contains the full-length HTT genomic sequence with 97 CAG/CAA repeats and all regulatory elements. BACHD transgenic rats display a robust, early onset and progressive HD-like phenotype including motor deficits and anxiety-related symptoms. In contrast to BAC and yeast artificial chromosome HD mouse models that express full-length mutant huntingtin, BACHD rats do not exhibit an increased body weight. Neuropathologically, the distribution of neuropil aggregates and nuclear accumulation of N-terminal mutant huntingtin in BACHD rats is similar to the observations in human HD brains. Aggregates occur more frequently in the cortex than in the striatum and neuropil aggregates appear earlier than mutant htt accumulation in the nucleus. Furthermore, we found an imbalance in the striatal striosome and matrix compartments in early stages of the disease. In addition, reduced dopamine receptor binding was detectable by in vivo imaging. Our data demonstrate that this transgenic BACHD rat line may be a valuable model for further understanding the disease mechanisms and for preclinical pharmacological studies.
Assuntos
Cromossomos Artificiais Bacterianos/genética , Doença de Huntington/genética , Doença de Huntington/patologia , Proteínas do Tecido Nervoso/genética , Processamento Alternativo , Animais , Ansiedade/genética , Ansiedade/psicologia , Comportamento Animal/fisiologia , Western Blotting , Peso Corporal/fisiologia , Ingestão de Alimentos/fisiologia , Transtornos Neurológicos da Marcha/psicologia , Dosagem de Genes , Humanos , Proteína Huntingtina , Doença de Huntington/psicologia , Imuno-Histoquímica , Atividade Motora/fisiologia , Tomografia por Emissão de Pósitrons , Equilíbrio Postural/fisiologia , Regiões Promotoras Genéticas , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Ratos , Ratos Sprague-Dawley , Ratos Transgênicos , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Posttranslational amyloid-ß (Aß) modification is considered to play an important role in Alzheimer's disease (AD) etiology. An N-terminally modified Aß species, pyroglutamate-amyloid-ß (pE3-Aß), has been described as a major constituent of Aß deposits specific to human AD but absent in normal aging. Formed via cyclization of truncated Aß species by glutaminyl cyclase (QC; QPCT) and/or its isoenzyme (isoQC; QPCTL), pE3-Aß aggregates rapidly and is known to seed additional Aß aggregation. To directly investigate pE3-Aß toxicity in vivo, we generated and characterized transgenic TBA2.1 and TBA2.2 mice, which express truncated mutant human Aß. Along with a rapidly developing behavioral phenotype, these mice showed progressively accumulating Aß and pE3-Aß deposits in brain regions of neuronal loss, impaired long-term potentiation, microglial activation, and astrocytosis. Illustrating a threshold for pE3-Aß neurotoxicity, this phenotype was not found in heterozygous animals but in homozygous TBA2.1 or double-heterozygous TBA2.1/2.2 animals only. A significant amount of pE3-Aß formation was shown to be QC-dependent, because crossbreeding of TBA2.1 with QC knock-out, but not isoQC knock-out, mice significantly reduced pE3-Aß levels. Hence, lowering the rate of QC-dependent posttranslational pE3-Aß formation can, in turn, lower the amount of neurotoxic Aß species in AD.
Assuntos
Precursor de Proteína beta-Amiloide/biossíntese , Transtornos Heredodegenerativos do Sistema Nervoso/genética , Transtornos Heredodegenerativos do Sistema Nervoso/patologia , Hipocampo/patologia , Ácido Pirrolidonocarboxílico/metabolismo , Envelhecimento/patologia , Envelhecimento/psicologia , Doença de Alzheimer/patologia , Animais , Comportamento Animal , Encéfalo/patologia , Ensaio de Imunoadsorção Enzimática , Gliose/patologia , Transtornos Heredodegenerativos do Sistema Nervoso/psicologia , Humanos , Imuno-Histoquímica , Cinética , Potenciação de Longa Duração/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Camundongos Transgênicos , Microscopia Eletrônica , Plasticidade Neuronal/genética , Plasticidade Neuronal/fisiologia , Fenótipo , Equilíbrio Postural/fisiologia , Processamento de Proteína Pós-Traducional , Reflexo de Sobressalto/fisiologia , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Huntington Disease (HD) is a fatal neurodegenerative disorder, caused by a mutation in the Huntington gene. Although HD is most often diagnosed in mid-life, the key to its clinical expression may be found during brain maturation. In the present work, we performed in vivo diffusion kurtosis imaging (DKI) in order to study brain microstructure alterations in developing transgenic HD rat pups. Several developing brain regions, relevant for HD pathology (caudate putamen, cortex, corpus callosum, external capsule and anterior commissure anterior), were examined at postnatal days 15 (P15) and 30 (P30), and DKI results were validated with histology. At P15, we observed higher mean (MD) and radial (RD) diffusivity values in the cortex of transgenic HD rat pups. In addition, at the age of P30, lower axial kurtosis (AK) values in the caudate putamen of transgenic HD pups were found. At the level of the external capsule, higher MD values at P15 but lower MD and AD values at P30 were detected. The observed DKI results have been confirmed by myelin basic protein immunohistochemistry, which revealed a reduced fiber staining as well as less ordered fibers in transgenic HD rat pups. These results indicate that neuronal development in young transgenic HD rat pups occurs differently compared to controls and that the presence of mutant huntingtin has an influence on postnatal brain development. In this context, various diffusivity parameters estimated by the DKI model are a powerful tool to assess changes in tissue microstructure and detect developmental changes in young transgenic HD rat pups.
Assuntos
Envelhecimento/patologia , Encéfalo/crescimento & desenvolvimento , Encéfalo/patologia , Imagem de Difusão por Ressonância Magnética/métodos , Modelos Animais de Doenças , Doença de Huntington/patologia , Doença de Huntington/fisiopatologia , Animais , Medicina Baseada em Evidências , Humanos , Ratos , Ratos Transgênicos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
We report a retrospective case series of four patients with genetically confirmed Huntington's disease (HD) and sporadic amyotrophic lateral sclerosis (ALS), examining the brain and spinal cord in two cases. Neuropathological assessment included a polyglutamine recruitment method to detect sites of active polyglutamine aggregation, and biochemical and immunohistochemical assessment of TDP-43 pathology. The clinical sequence of HD and ALS varied, with the onset of ALS occurring after the mid-50's in all cases. Neuropathologic features of HD and ALS coexisted in both cases examined pathologically: neuronal loss and gliosis in the neostriatum and upper and lower motor neurons, with Bunina bodies and ubiquitin-immunoreactive skein-like inclusions in remaining lower motor neurons. One case showed relatively early HD pathology while the other was advanced. Expanded polyglutamine-immunoreactive inclusions and TDP-43-immunoreactive inclusions were widespread in many regions of the CNS, including the motor cortex and spinal anterior horn. Although these two different proteinaceous inclusions coexisted in a small number of neurons, the two proteins did not co-localize within inclusions. The regional distribution of TDP-43-immunoreactive inclusions in the cerebral cortex partly overlapped with that of expanded polyglutamine-immunoreactive inclusions. In the one case examined by TDP-43 immunoblotting, similar TDP-43 isoforms were observed as in ALS. Our findings suggest the possibility that a rare subset of older HD patients is prone to develop features of ALS with an atypical TDP-43 distribution that resembles that of aggregated mutant huntingtin. Age-dependent neuronal dysfunction induced by mutant polyglutamine protein expression may contribute to later-life development of TDP-43 associated motor neuron disease in a small subset of patients with HD.
Assuntos
Esclerose Lateral Amiotrófica/complicações , Doença de Huntington/complicações , Adulto , Esclerose Lateral Amiotrófica/patologia , Encéfalo/metabolismo , Encéfalo/patologia , Proteínas de Ligação a DNA/metabolismo , Feminino , Humanos , Doença de Huntington/patologia , Macrófagos/patologia , Masculino , Pessoa de Meia-Idade , Neuroglia/patologia , Neurônios/patologia , Peptídeos/metabolismo , Estudos Retrospectivos , Medula Espinal/metabolismo , Medula Espinal/patologiaRESUMO
The formation of polyglutamine aggregates occupies a central role in the pathophysiology of neurodegenerative diseases caused by expanded trinucleotide repeats encoding the amino acid glutamine. This chapter describes sensitive histological methods for detection of tissue sites that are capable of further recruitment of polyglutamine and for sites rich in polyglutamine defined immunohistochemically. These methods have been found to be applicable in a number of diseases and animal models of disease. Recruitment, which is a property of highly ordered, amyloid-like aggregates, is most commonly found in punctate sites, termed aggregation foci (AF), in the neuronal perikaryonal cytoplasm. As expected, these AF correspond to sites containing polyglutamine aggregates detected using the antibody 1C2. Interestingly, however, many of the latter sites, including most neuropil aggregates and neuronal intranuclear inclusions, exhibit a limited ability to support polyglutamine recruitment. Thus there is limited correlation between the distribution of polyglutamine aggregates and recruitment activity, suggesting functional heterogeneity among polyglutamine aggregates. These methods should prove useful in explaining the relationship between aggregation reactions, aggregate formation, and the development of symptomatic disease and should be adaptable to the study of other protein aggregation disorders.
Assuntos
Encéfalo/metabolismo , Peptídeos/genética , Encéfalo/patologia , Humanos , Imuno-Histoquímica , Peptídeos/química , Peptídeos/metabolismo , Expansão das Repetições de TrinucleotídeosRESUMO
The role of aggregate formation in the pathophysiology of Huntington's disease (HD) remains uncertain. However, the temporal appearance of aggregates tends to correlate with the onset of symptoms and the numbers of neuropil aggregates correlate with the progression of clinical disease. Using highly sensitive immunohistochemical methods we have detected the appearance of diffuse aggregates during embryonic development in the R6/2 and YAC128 mouse models of HD. These are initially seen in developing axonal tracts and appear to spread throughout the cerebrum in the early neonate.
Assuntos
Encéfalo/embriologia , Encéfalo/metabolismo , Proteína Huntingtina/metabolismo , Doença de Huntington/embriologia , Doença de Huntington/metabolismo , Animais , Axônios/metabolismo , Axônios/patologia , Encéfalo/patologia , Modelos Animais de Doenças , Doença de Huntington/patologia , Imuno-Histoquímica , Camundongos Transgênicos , Agregação Patológica de Proteínas/embriologia , Agregação Patológica de Proteínas/metabolismo , Agregação Patológica de Proteínas/patologiaRESUMO
BACKGROUND: Unusually large CAG repeat expansions (>60) in exon one of Huntingtin (HTT) are invariably associated with a juvenile-onset form of Huntington's disease (HD), characterized by a more extensive and rapidly progressing neuropathology than the more prevalent adult-onset form. However, existing mouse models of HD that express the full-length Htt gene with CAG repeat lengths associated with juvenile HD (ranging between ~75 to ~150 repeats in published models) exhibit selective neurodegenerative phenotypes more consistent with adult-onset HD. Objective: To determine if a very large CAG repeat (>200) in full-length Htt elicits neurodegenerative phenotypes consistent with juvenile HD. METHODS: Using a bacterial artificial chromosome (BAC) system, we generated mice expressing full-length mouse Htt with ~225 CAG repeats under control of the mouse Htt promoter. Mice were characterized using behavioral, neuropathological, biochemical and brain imaging methods. RESULTS: BAC-225Q mice exhibit phenotypes consistent with a subset of features seen in juvenile-onset HD: very early motor behavior abnormalities, reduced body weight, widespread and progressive increase in Htt aggregates, gliosis, and neurodegeneration. Early striatal pathology was observed, including reactive gliosis and loss of dopamine receptors, prior to detectable volume loss. HD-related blood markers of impaired energy metabolism and systemic inflammation were also increased. Aside from an age-dependent progression of diffuse nuclear aggregates at 6 months of age to abundant neuropil aggregates at 12 months of age, other pathological and motor phenotypes showed little to no progression. CONCLUSIONS: The HD phenotypes present in animals 3 to 12 months of age make the BAC-225Q mice a unique and stable model of full-length mutant Htt associated phenotypes, including body weight loss, behavioral impairment and HD-like neurodegenerative phenotypes characteristic of juvenile-onset HD and/or late-stage adult-onset HD.
Assuntos
Comportamento Animal , Encéfalo/patologia , Doença de Huntington/genética , Camundongos , Neurônios/patologia , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Expansão das Repetições de Trinucleotídeos/genética , Animais , Atrofia , Encéfalo/metabolismo , Cromossomos Artificiais Bacterianos , Modelos Animais de Doenças , Progressão da Doença , Doença de Huntington/patologia , Doença de Huntington/fisiopatologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/metabolismo , Fenótipo , Regiões Promotoras GenéticasRESUMO
We have serendipitously established a mouse that expresses an N-terminal human huntingtin (htt) fragment with an expanded polyglutamine repeat (approximately 120) under the control of the endogenous human promoter (shortstop). Frequent and widespread htt inclusions occur early in shortstop mice. Despite these inclusions, shortstop mice display no clinical evidence of neuronal dysfunction and no neuronal degeneration as determined by brain weight, striatal volume, and striatal neuronal count. These results indicate that htt inclusions are not pathogenic in vivo. In contrast, the full-length yeast artificial chromosome (YAC) 128 model with the identical polyglutamine length and same level of transgenic protein expression as the shortstop demonstrates significant neuronal dysfunction and loss. In contrast to the YAC128 mouse, which demonstrates enhanced susceptibility to excitotoxic death, the shortstop mouse is protected from excitotoxicity, providing in vivo evidence suggesting that neurodegeneration in Huntington disease is mediated by excitotoxic mechanisms.