Project description:Advances in nanotechnology have enabled the design of nanotherapeutic platforms that could address the challenges of targeted delivery of active therapeutic agents to the central nervous system (CNS). While the majority of previous research studies on CNS nanotherapeutics have focused on neurons and endothelial cells, the predominant resident immune cells of the CNS, microglia, are also emerging as a promising cellular target for neurodegeneration considering their prominent role in neuroinflammation. Under normal physiological conditions, microglia protect neurons by removing pathological agents. However, long-term exposure of microglia to stimulants will cause sustained activation and lead to neuronal damage due to the release of pro-inflammatory agents, resulting in neuroinflammation and neurodegeneration. This Perspective highlights criteria to be considered when designing microglia-targeting nanotherapeutics for the treatment of neurodegenerative disorders. These criteria include conjugating specific microglial receptor-targeting ligands or peptides to the nanoparticle surface to achieve targeted delivery, leveraging microglial phagocytic properties, and utilizing biocompatible and biodegradable nanomaterials with low immune reactivity and neurotoxicity. In addition, certain therapeutic agents for the controlled inhibition of toxic protein aggregation and for modulation of microglial activation pathways can also be incorporated within the nanoparticle structure without compromising stability. Overall, considering the multifaceted disease mechanisms of neurodegeneration, microglia-targeted nanodrugs and nanotherapeutic particles may have the potential to resolve multiple pathological determinants of the disease and to guide a shift in the microglial phenotype spectrum toward a more neuroprotective state.
Project description:Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS) are the most common human adult-onset neurodegenerative diseases. They are characterized by prominent age-related neurodegeneration in selectively vulnerable neural systems. Some forms of AD, PD, and ALS are inherited, and genes causing these diseases have been identified. Nevertheless, the mechanisms of the neuronal cell death are unresolved. Morphological, biochemical, genetic, as well as cell and animal model studies reveal that mitochondria could have roles in this neurodegeneration. The functions and properties of mitochondria might render subsets of selectively vulnerable neurons intrinsically susceptible to cellular aging and stress and overlying genetic variations, triggering neurodegeneration according to a cell death matrix theory. In AD, alterations in enzymes involved in oxidative phosphorylation, oxidative damage, and mitochondrial binding of Aβ and amyloid precursor protein have been reported. In PD, mutations in putative mitochondrial proteins have been identified and mitochondrial DNA mutations have been found in neurons in the substantia nigra. In ALS, changes occur in mitochondrial respiratory chain enzymes and mitochondrial cell death proteins. Transgenic mouse models of human neurodegenerative disease are beginning to reveal possible principles governing the biology of selective neuronal vulnerability that implicate mitochondria and the mitochondrial permeability transition pore. This review summarizes how mitochondrial pathobiology might contribute to neuronal death in AD, PD, and ALS and could serve as a target for drug therapy.
Project description:The infectious template-mediated protein conversion is a unique mechanism for the onset of rare and fatal neurodegenerative disorders known as transmissible spongiform encephalopathies, or prion diseases, which affect humans and other animal species. However, emerging studies are now demonstrating prion-like mechanisms of self-propagation of protein misfolding in a number of common, non-infectious neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. It has been proposed that distinct and unrelated proteins (beta-amyloid, tau, ?-synuclein, TAR DNA-binding protein 43 and huntingtin, etc.) associated with common neurodegenerative disorders can seed conversion and spread via cell-to-cell transfer, sustaining the transmission of neurotoxic agents along a stereotypic route, sharing features at the heart of the intrinsic nature of prions. Here we review the most recent development on both the molecular mechanisms underlying the pathogenesis of prion-like neurodegenerative diseases as well as innovative methods and strategies for potential therapeutic applications.
Project description:The most common neurodegenerative diseases are Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, frontotemporal lobar degeneration, and the motor neuron diseases, with AD affecting approximately 6% of people aged 65 years and older, and PD affecting approximately 1% of people aged over 60 years. Specific proteins are associated with these neurodegenerative diseases, as determined by both immunohistochemical studies on post-mortem tissue and genetic screening, where protein misfolding and aggregation are key hallmarks. Many of these proteins are shown to misfold and aggregate into soluble non-native oligomers and large insoluble protein deposits (fibrils and plaques), both of which may exert a toxic gain of function. Proteotoxicity has been examined intensively in cell culture and in in vivo models, and clinical trials of methods to attenuate proteotoxicity are relatively new. Therapies to enhance cellular protein quality control mechanisms such as upregulation of chaperones and clearance/degradation pathways, as well as immunotherapies against toxic protein conformations, are being actively pursued. In this article, we summarize the common pathophysiology of neurodegenerative disease, and review therapies in early-phase clinical trials that target the proteotoxic component of several neurodegenerative diseases.
Project description:Cognitive training (CT) is an increasingly popular, non-pharmacological intervention for improving cognitive functioning in neurodegenerative diseases and healthy aging. Although meta-analyses support the efficacy of CT in improving cognitive functioning, the neural mechanisms underlying the effects of CT are still unclear. We performed a systematic review of literature in the PubMed, Embase and PsycINFO databases on controlled CT trials (N >?20) in aging and neurodegenerative diseases with pre- and post-training functional MRI outcomes up to November 23rd 2018 (PROSPERO registration number CRD42019103662). Twenty articles were eligible for our systematic review. We distinguished between multi-domain and single-domain CT. CT induced both increases and decreases in task-related functional activation, possibly indicative of an inverted U-shaped curve association between regional brain activity and task performance. Functional connectivity within 'cognitive' brain networks was consistently reported to increase after CT while a minority of studies additionally reported increased segregation of frontoparietal and default mode brain networks. Although we acknowledge the large heterogeneity in type of CT, imaging methodology, in-scanner task paradigm and analysis methods between studies, we propose a working model of the effects of CT on brain activity and connectivity in the context of current knowledge on compensatory mechanisms that are associated with aging and neurodegenerative diseases.
Project description:Mammalian asparagine endopeptidase (AEP) is a cysteine protease that cleaves its protein substrates on the C-terminal side of asparagine residues. Converging lines of evidence indicate that AEP may be involved in the pathogenesis of several neurological diseases, including Alzheimer's disease, Parkinson's disease, and frontotemporal dementia. AEP is activated in the aging brain, cleaves amyloid precursor protein (APP) and promotes the production of amyloid-? (A?). We renamed AEP to ?-secretase to emphasize its role in APP fragmentation and A? production. AEP also cleaves other substrates, such as tau, ?-synuclein, SET, and TAR DNA-binding protein 43, generating neurotoxic fragments and disturbing their physiological functions. The activity of ?-secretase is tightly regulated at both the transcriptional and posttranslational levels. Here, we review the recent advances in the role of ?-secretase in neurodegenerative diseases, with a focus on its biochemical properties and the transcriptional and posttranslational regulation of its activity, and discuss the clinical implications of ?-secretase as a diagnostic biomarker and therapeutic target for neurodegenerative diseases.
Project description:Neurodegenerative diseases are a major global health burden particularly with the increasing ageing population. Hereditary predisposition and environmental risk factors contribute to the heterogeneity of existing pathological phenotypes. Traditional clinical interventions focused on the use of small drugs have often led to failures due to the difficulties in crossing the blood-brain barrier and reaching the brain. In this regard, nanosystems can specifically deliver drugs and improve their bioavailability, overcoming some of the major challenges in neurodegenerative disease treatment. This review focuses on the use of nanosystems as an encouraging therapeutic approach targeting molecular pathways involved in localized and systematic neurodegenerative diseases. Among the latter, Friedreich's ataxia is an untreatable complex multisystemic disorder and the most widespread type of ataxia; it represents a test case to validate the clinical potential of therapeutic strategies based on nanoparticles with pleiotropic effects.
Project description:Several common psychiatric and neurodegenerative diseases share epidemiologic risk; however, whether they share pathophysiology is unclear and is the focus of our investigation. Using 25 GWAS results and LD score regression, we find eight significant genetic correlations between psychiatric and neurodegenerative diseases. We integrate the GWAS results with human brain transcriptomes (n = 888) and proteomes (n = 722) to identify cis- and trans- transcripts and proteins that are consistent with a pleiotropic or causal role in each disease, referred to as causal proteins for brevity. Within each disease group, we find many distinct and shared causal proteins. Remarkably, 30% (13 of 42) of the neurodegenerative disease causal proteins are shared with psychiatric disorders. Furthermore, we find 2.6-fold more protein-protein interactions among the psychiatric and neurodegenerative causal proteins than expected by chance. Together, our findings suggest these psychiatric and neurodegenerative diseases have shared genetic and molecular pathophysiology, which has important ramifications for early treatment and therapeutic development.
Project description:Neurodegenerative diseases are rarely caused by a mutation in a single gene but rather influenced by a combination of genetic, epigenetic and environmental factors. Emerging high-throughput technologies such as RNA sequencing have been instrumental in deciphering the molecular landscape of neurodegenerative diseases, however, the interpretation of such large amounts of data remains a challenge. Network biology has become a powerful platform to integrate multiple omics data to comprehensively explore the molecular networks in the context of health and disease. In this review article, we highlight recent advances in network biology approaches with an emphasis in brain-networks that have provided insights into the molecular mechanisms leading to the most prevalent neurodegenerative diseases including Alzheimer's (AD), Parkinson's (PD) and Huntington's diseases (HD). We discuss how integrative approaches using multi-omics data from different tissues have been valuable for identifying biomarkers and therapeutic targets. In addition, we discuss the challenges the field of network medicine faces toward the translation of network-based findings into clinically actionable tools for personalized medicine applications.
Project description:Social feedback can selectively enhance learning in diverse domains. Relevant neurocognitive mechanisms have been studied mainly in healthy persons, yielding correlational findings. Neurodegenerative lesion models, coupled with multimodal brain measures, can complement standard approaches by revealing direct multidimensional correlates of the phenomenon. To this end, we assessed socially reinforced and non-socially reinforced learning in 40 healthy participants as well as persons with behavioural variant frontotemporal dementia (n = 21), Parkinson's disease (n = 31) and Alzheimer's disease (n = 20). These conditions are typified by predominant deficits in social cognition, feedback-based learning and associative learning, respectively, although all three domains may be partly compromised in the other conditions. We combined a validated behavioural task with ongoing EEG signatures of implicit learning (medial frontal negativity) and offline MRI measures (voxel-based morphometry). In healthy participants, learning was facilitated by social feedback relative to non-social feedback. In comparison with controls, this effect was specifically impaired in behavioural variant frontotemporal dementia and Parkinson's disease, while unspecific learning deficits (across social and non-social conditions) were observed in Alzheimer's disease. EEG results showed increased medial frontal negativity in healthy controls during social feedback and learning. Such a modulation was selectively disrupted in behavioural variant frontotemporal dementia. Neuroanatomical results revealed extended temporo-parietal and fronto-limbic correlates of socially reinforced learning, with specific temporo-parietal associations in behavioural variant frontotemporal dementia and predominantly fronto-limbic regions in Alzheimer's disease. In contrast, non-socially reinforced learning was consistently linked to medial temporal/hippocampal regions. No associations with cortical volume were found in Parkinson's disease. Results are consistent with core social deficits in behavioural variant frontotemporal dementia, subtle disruptions in ongoing feedback-mechanisms and social processes in Parkinson's disease and generalized learning alterations in Alzheimer's disease. This multimodal approach highlights the impact of different neurodegenerative profiles on learning and social feedback. Our findings inform a promising theoretical and clinical agenda in the fields of social learning, socially reinforced learning and neurodegeneration.