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Expansion of CAG trinucleotide repeats in ATXN1 causes spinocerebellar ataxia type 1 (SCA1), a neurodegenerative disease that impairs coordination and cognition. While ATXN1 is associated with increased Alzheimer's disease (AD) risk, CAG repeat number in AD patients is not changed. Here, we investigated the consequences of ataxin-1 loss of function and discovered that knockout of Atxn1 reduced CIC-ETV4/5-mediated inhibition of Bace1 transcription, leading to increased BACE1 levels and enhanced amyloidogenic cleavage of APP, selectively in AD-vulnerable brain regions. Elevated BACE1 expression exacerbated Aß deposition and gliosis in AD mouse models and impaired hippocampal neurogenesis and olfactory axonal targeting. In SCA1 mice, polyglutamine-expanded mutant ataxin-1 led to the increase of BACE1 post-transcriptionally, both in cerebrum and cerebellum, and caused axonal-targeting deficit and neurodegeneration in the hippocampal CA2 region. These findings suggest that loss of ataxin-1 elevates BACE1 expression and Aß pathology, rendering it a potential contributor to AD risk and pathogenesis.
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Enfermedad de Alzheimer/patología , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Ataxina-1/metabolismo , Encéfalo/metabolismo , Enfermedad de Alzheimer/metabolismo , Secretasas de la Proteína Precursora del Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Ataxina-1/deficiencia , Ataxina-1/genética , Encéfalo/patología , Región CA2 Hipocampal/metabolismo , Región CA2 Hipocampal/patología , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Modelos Animales de Enfermedad , Femenino , Frecuencia de los Genes , Humanos , Masculino , Ratones , Ratones Transgénicos , Neurogénesis , Proteínas Proto-Oncogénicas c-ets/genética , Proteínas Proto-Oncogénicas c-ets/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción Genética , Repeticiones de Trinucleótidos/genética , Regulación hacia ArribaRESUMEN
The stimulator of interferon genes (STING) pathway has been implicated in neurodegenerative diseases, including Parkinson's disease and amyotrophic lateral sclerosis (ALS). While prior studies have focused on STING within immune cells, little is known about STING within neurons. Here, we document neuronal activation of the STING pathway in human postmortem cortical and spinal motor neurons from individuals affected by familial or sporadic ALS. This process takes place selectively in the most vulnerable cortical and spinal motor neurons but not in neurons that are less affected by the disease. Concordant STING activation in layer V cortical motor neurons occurs in a mouse model of C9orf72 repeat-associated ALS and frontotemporal dementia (FTD). To establish that STING activation occurs in a neuron-autonomous manner, we demonstrate the integrity of the STING signaling pathway, including both upstream activators and downstream innate immune response effectors, in dissociated mouse cortical neurons and neurons derived from control human induced pluripotent stem cells (iPSCs). Human iPSC-derived neurons harboring different familial ALS-causing mutations exhibit increased STING signaling with DNA damage as a main driver. The elevated downstream inflammatory markers present in ALS iPSC-derived neurons can be suppressed with a STING inhibitor. Our results reveal an immunophenotype that consists of innate immune signaling driven by the STING pathway and occurs specifically within vulnerable neurons in ALS/FTD.
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Esclerosis Amiotrófica Lateral , Demencia Frontotemporal , Células Madre Pluripotentes Inducidas , Enfermedad de Pick , Animales , Humanos , Ratones , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/metabolismo , Proteína C9orf72/genética , Demencia Frontotemporal/genética , Demencia Frontotemporal/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Neuronas Motoras/metabolismoRESUMEN
INTRODUCTION: Despite strong evidence linking amyloid beta (Aß) to Alzheimer's disease, most clinical trials have shown no clinical efficacy for reasons that remain unclear. To understand why, we developed a quantitative systems pharmacology (QSP) model for seven therapeutics: aducanumab, crenezumab, solanezumab, bapineuzumab, elenbecestat, verubecestat, and semagacestat. METHODS: Ordinary differential equations were used to model the production, transport, and aggregation of Aß; pharmacology of the drugs; and their impact on plaque. RESULTS: The calibrated model predicts that endogenous plaque turnover is slow, with an estimated half-life of 2.75 years. This is likely why beta-secretase inhibitors have a smaller effect on plaque reduction. Of the mechanisms tested, the model predicts binding to plaque and inducing antibody-dependent cellular phagocytosis is the best approach for plaque reduction. DISCUSSION: A QSP model can provide novel insights to clinical results. Our model explains the results of clinical trials and provides guidance for future therapeutic development.
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Enfermedad de Alzheimer , Péptidos beta-Amiloides , Simulación por Computador , Farmacología en Red , Preparaciones Farmacéuticas , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/inmunología , Secretasas de la Proteína Precursora del Amiloide/uso terapéutico , Péptidos beta-Amiloides/efectos de los fármacos , Péptidos beta-Amiloides/metabolismo , Anticuerpos Monoclonales Humanizados/uso terapéutico , HumanosRESUMEN
Activity-dependent synaptic plasticity plays a critical role in the refinement of circuitry during postnatal development and may be disrupted in conditions that cause intellectual disability, such as Down syndrome (DS). To test this hypothesis, visual cortical plasticity was assessed in Ts65Dn mice that harbor a chromosomal duplication syntenic to human chromosome 21q. We find that Ts65Dn mice demonstrate a defect in ocular dominance plasticity (ODP) following monocular deprivation. This phenotype is similar to that of transgenic mice that express amyloid precursor protein (APP), which is duplicated in DS and in Ts65DN mice; however, normalizing APP gene copy number in Ts65Dn mice fails to rescue plasticity. Ts1Rhr mice harbor a duplication of the telomeric third of the Ts65Dn-duplicated sequence and demonstrate the same ODP defect, suggesting a gene or genes sufficient to drive the phenotype are located in that smaller duplication. In addition, we find that Ts65Dn mice demonstrate an abnormality in olfactory system connectivity, a defect in the refinement of connections to second-order neurons in the olfactory bulb. Ts1Rhr mice do not demonstrate a defect in glomerular refinement, suggesting that distinct genes or sets of genes underlie visual and olfactory system phenotypes. Importantly, these data suggest that developmental plasticity and connectivity are impaired in sensory systems in DS model mice, that such defects may contribute to functional impairment in DS, and that these phenotypes, present in male and female mice, provide novel means for examining the genetic and molecular bases for neurodevelopmental impairment in model mice in vivoSIGNIFICANCE STATEMENT Our understanding of the basis for intellectual impairment in Down syndrome is hindered by the large number of genes duplicated in Trisomy 21 and a lack of understanding of the effect of disease pathology on the function of neural circuits in vivo This work describes early postnatal developmental abnormalities in visual and olfactory sensory systems in Down syndrome model mice, which provide insight into defects in the function of neural circuits in vivo and provide an approach for exploring the genetic and molecular basis for impairment in the disease. In addition, these findings raise the possibility that basic dysfunction in primary sensory circuitry may illustrate mechanisms important for global learning and cognitive impairment in Down syndrome patients.
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Síndrome de Down/fisiopatología , Vías Olfatorias/fisiopatología , Olfato , Visión Ocular , Vías Visuales/fisiopatología , Animales , Ceguera/fisiopatología , Proteínas del Citoesqueleto/genética , Predominio Ocular , Femenino , Masculino , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso/genética , Plasticidad Neuronal , Corteza Visual/fisiopatologíaRESUMEN
OBJECTIVE: The objective of this study was to relate a novel test of identifying and recalling odor percepts to biomarkers of Alzheimer's disease (AD) in well-characterized elderly individuals, ranging from cognitively normal to demented. METHODS: One hundred eighty-three participants (cognitively normal: n = 70; subjective cognitive concerns: n = 74; mild cognitive impairment [MCI]: n = 29, AD dementia: n = 10) were administered novel olfactory tests: the Odor Percept IDentification (OPID) and the Percepts of Odor Episodic Memory (POEM) tests. Univariate cross-sectional analyses of performance across diagnoses; logistic regression modeling, including covariates of age, sex, education, APOE genotype, and neuropsychological test scores; and linear mixed modeling of longitudinal cognitive scores were performed. Amyloid deposition and MRI volumetrics were analyzed in a subset of participants. RESULTS: Accuracy of identification and episodic memory of odor percepts differed significantly across diagnosis and age, with progressively worse performance across degrees of impairment. Among the participants who were cognitively normal or had subjective cognitive concerns, poorer than expected performance on the POEM test (based on the same individual's performance on the OPID and odor discrimination tests) was associated with higher frequencies of the APOE ε4 allele, thinner entorhinal cortices, and worse longitudinal trajectory of Logical Memory scores. INTERPRETATION: Selective impairment of episodic memory of odor percepts, relative to identification and discrimination of odor percepts revealed by this novel POEM battery, is associated with biomarkers of AD in a well-characterized pre-MCI population. These affordable, noninvasive olfactory tests offer potential to identify clinically normal individuals who have greater likelihood of future cognitive decline. Ann Neurol 2016;80:846-857.
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Enfermedad de Alzheimer/psicología , Apolipoproteína E4/genética , Disfunción Cognitiva/psicología , Memoria Episódica , Pruebas Neuropsicológicas , Percepción Olfatoria , Placa Amiloide/patología , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/patología , Atrofia/patología , Biomarcadores , Estudios de Casos y Controles , Disfunción Cognitiva/genética , Disfunción Cognitiva/patología , Estudios Transversales , Corteza Entorrinal/patología , Femenino , Hipocampo/patología , Humanos , Imagen por Resonancia Magnética , Masculino , Neuroimagen , Tomografía Computarizada por Tomografía de Emisión de PositronesRESUMEN
Recent evidence indicates that sensory and motor changes may precede the cognitive symptoms of Alzheimer's disease (AD) by several years and may signify increased risk of developing AD. Traditionally, sensory and motor dysfunctions in aging and AD have been studied separately. To ascertain the evidence supporting the relationship between age-related changes in sensory and motor systems and the development of AD and to facilitate communication between several disciplines, the National Institute on Aging held an exploratory workshop titled "Sensory and Motor Dysfunctions in Aging and AD." The scientific sessions of the workshop focused on age-related and neuropathologic changes in the olfactory, visual, auditory, and motor systems, followed by extensive discussion and hypothesis generation related to the possible links among sensory, cognitive, and motor domains in aging and AD. Based on the data presented and discussed at this workshop, it is clear that sensory and motor regions of the central nervous system are affected by AD pathology and that interventions targeting amelioration of sensory-motor deficits in AD may enhance patient function as AD progresses.
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Envejecimiento/fisiología , Enfermedad de Alzheimer/fisiopatología , Trastornos del Movimiento/fisiopatología , Trastornos de la Sensación/fisiopatología , Enfermedad de Alzheimer/diagnóstico , Progresión de la Enfermedad , Diagnóstico Precoz , Humanos , Trastornos del Movimiento/diagnóstico , National Institute on Aging (U.S.) , Trastornos de la Sensación/diagnóstico , Estados UnidosRESUMEN
Neuroinflammation is a pathological feature of many neurodegenerative diseases, including Alzheimer's disease (AD)1,2 and amyotrophic lateral sclerosis (ALS)3, raising the possibility of common therapeutic targets. We previously established that cytoplasmic double-stranded RNA (cdsRNA) is spatially coincident with cytoplasmic pTDP-43 inclusions in neurons of patients with C9ORF72-mediated ALS4. CdsRNA triggers a type-I interferon (IFN-I)-based innate immune response in human neural cells, resulting in their death4. Here, we report that cdsRNA is also spatially coincident with pTDP-43 cytoplasmic inclusions in brain cells of patients with AD pathology and that type-I interferon response genes are significantly upregulated in brain regions affected by AD. We updated our machine-learning pipeline DRIAD-SP (Drug Repurposing In Alzheimer's Disease with Systems Pharmacology) to incorporate cryptic exon (CE) detection as a proxy of pTDP-43 inclusions and demonstrated that the FDA-approved JAK inhibitors baricitinib and ruxolitinib that block interferon signaling show a protective signal only in cortical brain regions expressing multiple CEs. Furthermore, the JAK family member TYK2 was a top hit in a CRISPR screen of cdsRNA-mediated death in differentiated human neural cells. The selective TYK2 inhibitor deucravacitinib, an FDA-approved drug for psoriasis, rescued toxicity elicited by cdsRNA. Finally, we identified CCL2, CXCL10, and IL-6 as candidate predictive biomarkers for cdsRNA-related neurodegenerative diseases. Together, we find parallel neuroinflammatory mechanisms between TDP-43 associated-AD and ALS and nominate TYK2 as a possible disease-modifying target of these incurable neurodegenerative diseases.
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Post-Acute Sequelae of COVID-19 (PASC) encompasses persistent neurological symptoms, including olfactory and autonomic dysfunction. Here, we report chronic neurological dysfunction in mice infected with a virulent mouse-adapted SARS-CoV-2 that does not infect the brain. Long after recovery from nasal infection, we observed loss of tyrosine hydroxylase (TH) expression in olfactory bulb glomeruli and neurotransmitter levels in the substantia nigra (SN) persisted. Vulnerability of dopaminergic neurons in these brain areas was accompanied by increased levels of proinflammatory cytokines and neurobehavioral changes. RNAseq analysis unveiled persistent microglia activation, as found in human neurodegenerative diseases. Early treatment with antivirals (nirmatrelvir and molnupiravir) reduced virus titers and lung inflammation but failed to prevent neurological abnormalities, as observed in patients. Together these results show that chronic deficiencies in neuronal function in SARS-CoV-2-infected mice are not directly linked to ongoing olfactory epithelium dysfunction. Rather, they bear similarity with neurodegenerative disease, the vulnerability of which is exacerbated by chronic inflammation.
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The direct access of olfactory afferents to memory-related cortical systems has inspired theories about the role of the olfactory pathways in the development of cortical neurodegeneration in Alzheimer's disease (AD). In this study, we used baseline olfactory identification measures with longitudinal flortaucipir and PiB PET, diffusion MRI of 89 cognitively normal older adults (73.82 ± 8.44 years; 56% females), and a transcriptomic data atlas to investigate the spatiotemporal spreading and genetic vulnerabilities of AD-related pathology aggregates in the olfactory system. We find that odor identification deficits are predominantly associated with tau accumulation in key areas of the olfactory pathway, with a particularly strong predictive power for longitudinal tau progression. We observe that tau spreads from the medial temporal lobe structures toward the olfactory system, not the reverse. Moreover, we observed a genetic background of odor perception-related genes that might confer vulnerability to tau accumulation along the olfactory system.
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Envejecimiento , Enfermedad de Alzheimer , Percepción Olfatoria , Tomografía de Emisión de Positrones , Proteínas tau , Humanos , Femenino , Proteínas tau/metabolismo , Proteínas tau/genética , Masculino , Anciano , Percepción Olfatoria/fisiología , Envejecimiento/fisiología , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/fisiopatología , Anciano de 80 o más Años , Vías Olfatorias/metabolismo , Vías Olfatorias/diagnóstico por imagen , Olfato/fisiología , Encéfalo/metabolismo , Encéfalo/diagnóstico por imagen , Lóbulo Temporal/metabolismo , Lóbulo Temporal/diagnóstico por imagen , Persona de Mediana EdadRESUMEN
Amyloid-ß (Aß)-induced changes in synaptic function in experimental models of Alzheimer's disease (AD) suggest that Aß generation and accumulation may affect fundamental mechanisms of synaptic plasticity. To test this hypothesis, we examined the effect of APP overexpression on a well characterized, in vivo, developmental model of systems-level plasticity, ocular dominance plasticity. Following monocular visual deprivation during the critical period, mice that express mutant alleles of amyloid precursor protein (APPswe) and Presenilin1 (PS1dE9), as well as mice that express APPswe alone, lack ocular dominance plasticity in visual cortex. Defects in the spatial extent and magnitude of the plastic response are evident using two complementary approaches, Arc induction and optical imaging of intrinsic signals in awake mice. This defect in a classic paradigm of systems level synaptic plasticity shows that Aß overexpression, even early in postnatal life, can perturb plasticity in cerebral cortex, and supports the idea that decreased synaptic plasticity due to elevated Aß exposure contributes to cognitive impairment in AD.
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Enfermedad de Alzheimer/fisiopatología , Plasticidad Neuronal/fisiología , Privación Sensorial/fisiología , Sinapsis/fisiología , Visión Ocular/fisiología , Enfermedad de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Animales , Enucleación del Ojo , Fluorescencia , Humanos , Procesamiento de Imagen Asistido por Computador , Inmunohistoquímica , Hibridación in Situ , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuronas/fisiología , Estimulación Luminosa , Reacción en Cadena de la Polimerasa , Presenilina-1/genética , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Corteza Visual/citología , Corteza Visual/fisiologíaRESUMEN
BACKGROUND AND OBJECTIVE: Competing risks data arise in both observational and experimental clinical studies with time-to-event outcomes, when each patient might follow one of the multiple mutually exclusive competing paths. Ignoring competing risks in the analysis can result in biased conclusions. In addition, possible confounding bias of the treatment-outcome relationship has to be addressed, when estimating treatment effects from observational data. In order to provide tools for estimation of average treatment effects on time-to-event outcomes in the presence of competing risks, we developed the R package causalCmprsk. We illustrate the package functionality in the estimation of effects of a right heart catheterization procedure on discharge and in-hospital death from observational data. METHODS: The causalCmprsk package implements an inverse probability weighting estimation approach, aiming to emulate baseline randomization and alleviate possible treatment selection bias. The package allows for different types of weights, representing different target populations. causalCmprsk builds on existing methods from survival analysis and adapts them to the causal analysis in non-parametric and semi-parametric frameworks. RESULTS: The causalCmprsk package has two main functions: fit.cox assumes a semiparametric structural Cox proportional hazards model for the counterfactual cause-specific hazards, while fit.nonpar does not impose any structural assumptions. In both frameworks, causalCmprsk implements estimators of (i) absolute risks for each treatment arm, e.g., cumulative hazards or cumulative incidence functions, and (ii) relative treatment effects, e.g., hazard ratios, or restricted mean time differences. The latter treatment effect measure translates the treatment effect from probability into more intuitive time domain and allows the user to quantify, for example, by how many days or months the treatment accelerates the recovery or postpones illness or death. CONCLUSIONS: The causalCmprsk package provides a convenient and useful tool for causal analysis of competing risks data. It allows the user to distinguish between different causes of the end of follow-up and provides several time-varying measures of treatment effects. The package is accompanied by a vignette that contains more details, examples and code, making the package accessible even for non-expert users.
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Modelos Estadísticos , Humanos , Mortalidad Hospitalaria , Modelos de Riesgos Proporcionales , Análisis de Supervivencia , ProbabilidadRESUMEN
BACKGROUND: Olfactory dysfunction is one of the earliest signs of Alzheimer's disease (AD), highlighting its potential use as a biomarker for early detection. It has also been linked to progression from mild cognitive impairment (MCI) to dementia. OBJECTIVE: To study olfactory function and its associations with markers of AD brain pathology in non-demented mutation carriers of an autosomal dominant AD (ADAD) mutation and non-carrier family members. METHODS: We analyzed cross-sectional data from 16 non-demented carriers of the Presenilin1 E280A ADAD mutation (mean age [SD]: 40.1 [5.3], and 19 non-carrier family members (mean age [SD]: 36.0 [5.5]) from Colombia, who completed olfactory and cognitive testing and underwent amyloid and tau positron emission tomography (PET) imaging. RESULTS: Worse olfactory identification performance was associated with greater age in mutation carriers (râ=â-0.52 pâ=â0.037). In carriers, worse olfactory identification performance was related to worse MMSE scores (râ=â0.55, pâ=â0.024) and CERAD delayed recall (râ=â0.63, pâ=â0.007) and greater cortical amyloid-ß (râ=â-0.53, pâ=â0.042) and tau pathology burden (entorhinal: râ=â-0.59, pâ=â0.016; inferior temporal: râ=â-0.52, pâ=â0.038). CONCLUSION: Worse performance on olfactory identification tasks was associated with greater age, a proxy for disease progression in this genetically vulnerable ADAD cohort. In addition, this is the first study to report olfactory dysfunction in ADAD mutation carriers with diagnosis of MCI and its correlation with abnormal accumulation of tau pathology in the entorhinal region. Taken together, our findings suggest that olfactory dysfunction has promise as an early marker of brain pathology and future risk for dementia.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Trastornos del Olfato , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/metabolismo , Biomarcadores , Encéfalo/patología , Disfunción Cognitiva/diagnóstico por imagen , Disfunción Cognitiva/genética , Disfunción Cognitiva/patología , Estudios Transversales , Humanos , Imagen por Resonancia Magnética/métodos , Trastornos del Olfato/etiología , Trastornos del Olfato/genética , Tomografía de Emisión de Positrones/métodos , Proteínas tau/genética , Proteínas tau/metabolismoRESUMEN
Metformin, a diabetes drug with anti-aging cellular responses, has complex actions that may alter dementia onset. Mixed results are emerging from prior observational studies. To address this complexity, we deploy a causal inference approach accounting for the competing risk of death in emulated clinical trials using two distinct electronic health record systems. In intention-to-treat analyses, metformin use associates with lower hazard of all-cause mortality and lower cause-specific hazard of dementia onset, after accounting for prolonged survival, relative to sulfonylureas. In parallel systems pharmacology studies, the expression of two AD-related proteins, APOE and SPP1, was suppressed by pharmacologic concentrations of metformin in differentiated human neural cells, relative to a sulfonylurea. Together, our findings suggest that metformin might reduce the risk of dementia in diabetes patients through mechanisms beyond glycemic control, and that SPP1 is a candidate biomarker for metformin's action in the brain.
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Demencia , Diabetes Mellitus Tipo 2 , Metformina , Humanos , Metformina/farmacología , Metformina/uso terapéutico , Reposicionamiento de Medicamentos , Farmacología en Red , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Diabetes Mellitus Tipo 2/complicaciones , Compuestos de Sulfonilurea , Hipoglucemiantes/farmacología , Hipoglucemiantes/uso terapéutico , Demencia/tratamiento farmacológico , Demencia/etiología , Registros MédicosRESUMEN
BACKGROUND: The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O). METHODS: Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus. RESULTS: The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies. CONCLUSION: This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.
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Hipersensibilidad , Olfato , Consenso , Costo de Enfermedad , HumanosRESUMEN
BACKGROUND: The mechanisms by which any upper respiratory virus, including SARS-CoV-2, impairs chemosensory function are not known. COVID-19 is frequently associated with olfactory dysfunction after viral infection, which provides a research opportunity to evaluate the natural course of this neurological finding. Clinical trials and prospective and histological studies of new-onset post-viral olfactory dysfunction have been limited by small sample sizes and a paucity of advanced neuroimaging data and neuropathological samples. Although data from neuropathological specimens are now available, neuroimaging of the olfactory system during the acute phase of infection is still rare due to infection control concerns and critical illness and represents a substantial gap in knowledge. RECENT DEVELOPMENTS: The active replication of SARS-CoV-2 within the brain parenchyma (ie, in neurons and glia) has not been proven. Nevertheless, post-viral olfactory dysfunction can be viewed as a focal neurological deficit in patients with COVID-19. Evidence is also sparse for a direct causal relation between SARS-CoV-2 infection and abnormal brain findings at autopsy, and for trans-synaptic spread of the virus from the olfactory epithelium to the olfactory bulb. Taken together, clinical, radiological, histological, ultrastructural, and molecular data implicate inflammation, with or without infection, in either the olfactory epithelium, the olfactory bulb, or both. This inflammation leads to persistent olfactory deficits in a subset of people who have recovered from COVID-19. Neuroimaging has revealed localised inflammation in intracranial olfactory structures. To date, histopathological, ultrastructural, and molecular evidence does not suggest that SARS-CoV-2 is an obligate neuropathogen. WHERE NEXT?: The prevalence of CNS and olfactory bulb pathosis in patients with COVID-19 is not known. We postulate that, in people who have recovered from COVID-19, a chronic, recrudescent, or permanent olfactory deficit could be prognostic for an increased likelihood of neurological sequelae or neurodegenerative disorders in the long term. An inflammatory stimulus from the nasal olfactory epithelium to the olfactory bulbs and connected brain regions might accelerate pathological processes and symptomatic progression of neurodegenerative disease. Persistent olfactory impairment with or without perceptual distortions (ie, parosmias or phantosmias) after SARS-CoV-2 infection could, therefore, serve as a marker to identify people with an increased long-term risk of neurological disease.
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COVID-19/complicaciones , COVID-19/diagnóstico por imagen , Trastornos del Olfato/diagnóstico por imagen , Trastornos del Olfato/etiología , Mucosa Olfatoria/diagnóstico por imagen , Encéfalo/diagnóstico por imagen , Encéfalo/fisiopatología , Encéfalo/virología , COVID-19/fisiopatología , Humanos , Enfermedades Neurodegenerativas/diagnóstico por imagen , Enfermedades Neurodegenerativas/etiología , Enfermedades Neurodegenerativas/fisiopatología , Trastornos del Olfato/fisiopatología , Trastornos del Olfato/virología , Mucosa Olfatoria/fisiopatología , Mucosa Olfatoria/virología , Estudios Prospectivos , Olfato/fisiologíaRESUMEN
Clinical trials of novel therapeutics for Alzheimer's Disease (AD) have consumed a large amount of time and resources with largely negative results. Repurposing drugs already approved by the Food and Drug Administration (FDA) for another indication is a more rapid and less expensive option. We present DRIAD (Drug Repurposing In AD), a machine learning framework that quantifies potential associations between the pathology of AD severity (the Braak stage) and molecular mechanisms as encoded in lists of gene names. DRIAD is applied to lists of genes arising from perturbations in differentiated human neural cell cultures by 80 FDA-approved and clinically tested drugs, producing a ranked list of possible repurposing candidates. Top-scoring drugs are inspected for common trends among their targets. We propose that the DRIAD method can be used to nominate drugs that, after additional validation and identification of relevant pharmacodynamic biomarker(s), could be readily evaluated in a clinical trial.
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Enfermedad de Alzheimer/tratamiento farmacológico , Drogas en Investigación/farmacología , Aprendizaje Automático , Proteínas del Tejido Nervioso/genética , Fármacos Neuroprotectores/farmacología , Nootrópicos/farmacología , Medicamentos bajo Prescripción/farmacología , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Corteza Cerebral/patología , Reposicionamiento de Medicamentos , Drogas en Investigación/química , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Ensayos Analíticos de Alto Rendimiento , Humanos , Proteínas del Tejido Nervioso/antagonistas & inhibidores , Proteínas del Tejido Nervioso/metabolismo , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Neuronas/patología , Fármacos Neuroprotectores/química , Nootrópicos/química , Farmacogenética/métodos , Farmacogenética/estadística & datos numéricos , Polifarmacología , Medicamentos bajo Prescripción/química , Cultivo Primario de Células , Índice de Severidad de la EnfermedadRESUMEN
Triggers of innate immune signaling in the CNS of patients with amyotrophic lateral sclerosis and frontotemporal degeneration (ALS/FTD) remain elusive. We report the presence of cytoplasmic double-stranded RNA (cdsRNA), an established trigger of innate immunity, in ALS-FTD brains carrying C9ORF72 intronic hexanucleotide expansions that included genomically encoded expansions of the G4C2 repeat sequences. The presence of cdsRNA in human brains was coincident with cytoplasmic TAR DNA binding protein 43 (TDP-43) inclusions, a pathologic hallmark of ALS/FTD. Introducing cdsRNA into cultured human neural cells induced type I interferon (IFN-I) signaling and death that was rescued by FDA-approved JAK inhibitors. In mice, genomically encoded dsRNAs expressed exclusively in a neuronal class induced IFN-I and death in connected neurons non-cell-autonomously. Our findings establish that genomically encoded cdsRNAs trigger sterile, viral-mimetic IFN-I induction and propagated death within neural circuits and may drive neuroinflammation and neurodegeneration in patients with ALS/FTD.
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Esclerosis Amiotrófica Lateral , Proteína C9orf72 , Demencia Frontotemporal , Esclerosis Amiotrófica Lateral/genética , Animales , Encéfalo/metabolismo , Proteína C9orf72/genética , Expansión de las Repeticiones de ADN , Demencia Frontotemporal/genética , Humanos , Ratones , ARN BicatenarioRESUMEN
The main neurological manifestation of COVID-19 is loss of smell or taste. The high incidence of smell loss without significant rhinorrhea or nasal congestion suggests that SARS-CoV-2 targets the chemical senses through mechanisms distinct from those used by endemic coronaviruses or other common cold-causing agents. Here we review recently developed hypotheses about how SARS-CoV-2 might alter the cells and circuits involved in chemosensory processing and thereby change perception. Given our limited understanding of SARS-CoV-2 pathogenesis, we propose future experiments to elucidate disease mechanisms and highlight the relevance of this ongoing work to understanding how the virus might alter brain function more broadly.