Neurodegenerative disorders are characterized by the progressive loss of specific populations of neurons with consequent deterioration of brain's function and dramatic impact on human behavior. At present, there are no effective cures for neurodegenerative diseases. Because unambiguous diagnosis is possible only after manifestation of symptoms, when a large proportion of neurons has been already lost, therapies are necessarily confined to alleviation of symptoms. Development of cures halting the disease course is hampered by our rudimentary understanding of the etiopathology. Most neurodegenerative disorders are sporadic and age-related and - even for those of known genetic origin - the mechanisms influencing disease onset and progression have not been fully characterized. The different diseases, however, share important similarities in the mechanisms responsible for neuronal loss, which is caused by a combination of endogenous and exogenous challenges. Trophic deprivation, oxidative stress, accumulation of abnormal protein aggregates, and bioenergetics defects have been described in most, if not all, neurodegenerative disease. To counterbalance these noxious stimuli cells deploy, at least during the initial pathogenic states, intrinsic neuroprotective responses. These are general compensatory mechanisms, common to several neurodegenerative conditions, which reprogram cellular physiology to overcome stress. Adaptation includes strategies to optimize energetic resources, for instance reduction of rRNA synthesis to repress translation, suppression of transcription, and bioenergetics and metabolic redesign. Additional mechanisms include potentiation of antioxidant capacity, induction of endoplasmic reticulum (ER) stress, and activation of protein quality control systems and autophagy. Ineffective execution of these compensatory strategies severely threatens cellular homeostasis and favors onset of pathology. Therefore, a better understanding of these "buffering" mechanisms and of their interconnections may help to devise more effective therapeutic tools to prolong neuronal survival and activity, independently of the original genetic mutations and stress insults. This Research Topic focuses on the initial compensatory responses protecting against failure of those mechanisms that sustain neuronal survival and activity. The collection intends to summarize the state-of-the-art in this field and to propose novel research contributes, with the ultimate goal of inspiring innovative studies aimed to contrast progression of neurodegenerative diseases.
Traumatic brain injury (TBI) remains a significant source of death and permanent disability, contributing to nearly one-third of all injury related deaths in the United States and exacting a profound personal and economic toll. Despite the increased resources that have recently been brought to bear to improve our understanding of TBI, the developme
"Written by two experts in the field, this book provides information useful to physicians for assessing and managing chemosensory disorders - with appropriate case-histories - and summarizes the current scientific knowledge of human olfaction. It will be of particular interest to neurologists, otolaryngologists, psychologists, psychiatrists, and neuroscientists."--BOOK JACKET.
This is the first book to assemble the leading researchers in the field of LRRK2 biology and neurology and provide a snapshot of the current state of knowledge, encompassing all major aspects of its function and dysfunction. The contributors are experts in cell biology and physiology, neurobiology, and medicinal chemistry, bringing a multidisciplinary perspective on the gene and its role in disease. The book covers the identification of LRRK2 as a major contributor to the pathogenesis of Parkinson's Disease. It also discusses the current state of the field after a decade of research, putative normal physiological roles of LRRK2, and the various pathways that have been identified in the search for the mechanism(s) of its induction of neurodegeneration.
Provides a timely overview of critical advances in molecular and cellular neurobiology, covers key methodologies driving progress, and highlights key future directions for research on neuronal injury and neurodegeneration relevant to neuronal brain pathologies. The editors bring together contributions from internationally recognized workers in the field to provide an up to date account of how and why molecular and cellular neurobiology is such an important area for clinical neuroscience. Understanding the molecular aspects of a number of neurodegenerative conditions such as Parkinson's or Alzheimer's disease for the purpose of improving patient management remains a major challenge of neurobiology be it from the basic or clinical perspective. A strategic evaluation of research contributions and the power of modern methods will help advance knowledge over the next years.
Cyclin Dependent Kinase 5 provides a comprehensive and up-to-date collection of reviews on the discovery, signaling mechanisms and functions of Cdk5, as well as the potential implication of Cdk5 in the treatment of neurodegenerative diseases. Since the identification of this unique member of the Cdk family, Cdk5 has emerged as one of the most important signal transduction mediators in the development, maintenance and fine-tuning of neuronal functions and networking. Further studies have revealed that Cdk5 is also associated with the regulation of neuronal survival during both developmental stages and in neurodegenerative diseases. These observations indicate that precise control of Cdk5 is essential for the regulation of neuronal survival. The pivotal role Cdk5 appears to play in both the regulation of neuronal survival and synaptic functions thus raises the interesting possibility that Cdk5 inhibitors may serve as therapeutic treatment for a number of neurodegenerative diseases.
Possible new breakthroughs in understanding the aging mind that can be used to benefit older people are now emerging from research. This volume identifies the key scientific advances and the opportunities they bring. For example, science has learned that among older adults who do not suffer from Alzheimer's disease or other dementias, cognitive decline may depend less on loss of brain cells than on changes in the health of neurons and neural networks. Research on the processes that maintain neural health shows promise of revealing new ways to promote cognitive functioning in older people. Research is also showing how cognitive functioning depends on the conjunction of biology and culture. The ways older people adapt to changes in their nervous systems, and perhaps the changes themselves, are shaped by past life experiences, present living situations, changing motives, cultural expectations, and emerging technology, as well as by their physical health status and sensory-motor capabilities. Improved understanding of how physical and contextual factors interact can help explain why some cognitive functions are impaired in aging while others are spared and why cognitive capability is impaired in some older adults and spared in others. On the basis of these exciting findings, the report makes specific recommends that the U.S. government support three major new initiatives as the next steps for research.
Written by leading experts, this book offers a picture of how HIV impairs the brain, focusing on emerging areas including genetic strains of the virus, interactions between advanced age and HIV, and the impact of HIV on the brain during antiretroviral therapy.
This book describes recent developments concerning structural, functional and possible therapeutic aspects of one particular CAM, the neural cell adhesion molecule (NCAM).
Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the two most common neurodegenerative diseases with rates increasing along with the ageing global population. Despite best efforts, we still do not understand the etiopathogenesis of these diseases and there are no effective disease-modifying treatments. Cognitive deficiencies or motor complications that emerge during AD and PD are thought to be the result of the accumulation of misfolded, aggregate-prone proteins, such as amyloid-? (A?) and tau or ?-synuclein (?-syn), respectively. Growing evidence suggests that prefibrillar oligomers of A? and ?-syn (oA? and o?-syn) are key contributors to the progression of these diseases. The progressive accumulation of these proteins leads to a gradual spread of pathology throughout interconnected brain regions, but the mechanisms by which this spreading occurs are still largely unknown. Neuroinflammation has been recognised as an important contributor to neurodegenerative disease. It is hypothesised that a pro-inflammatory environment initiated by the innate immune system, either through activation from A? itself or indirectly through neuronal injury signals in AD. These phenomena are thought to either cause or accelerate AD, such that an anti-inflammatory approach may be neuroprotective. In paper I, we investigated whether different inflammatory environments affected the transfer of oA? between neuron-like cells, in addition to investigating inter- and intracellular protein changes. This study demonstrated that an anti-inflammatory environment reduces the transfer of oA? between cells. We also provide evidence that these cells begin to take on the “phenotype” of the inflammatory milieu, while also demonstrating that the expression profile of endosomal/lysosomal and protein trafficking proteins is altered during these conditions. Small extracellular vesicles called exosomes, which are key players in cell to cell communication, have been proposed to play an influential role in spreading neurodegenerative proteins between cells. Exosomes are small membranous vesicles that are formed by the inward budding of multivesicular bodies (MVBs). These MVBs can then merge with the plasma membrane to be released into the extracellular environment as vesicles, which serve as vehicles for transferring proteins, lipids, and mRNAs between cells. The ESCRT-dependent pathway is the most understood mechanism underlying exosome biogenesis. However, exosomes can also be formed through ESCRT-independent pathways, including through the hydrolysis of sphingomyelin by neutral sphingomyelinase 2 (nSMase2), which produces ceramide. Paper II investigated whether exosomes formed through an ESCRT-independent pathway plays a significant role in the transfer of o?-syn between neuron-like cells. As oxidative stress is a common feature in PD brains, which in turn dysregulates nSMase2 activity, we also tested our model under hypoxic conditions. Inhibition of nSMase2 significantly reduced the transfer of o?-syn between cells but also resulted in decreased ?-syn aggregation. Hypoxia did not influence o?-syn transfer, however, it significantly dysregulated the sphingolipid composition, which may be important for ?-syn binding to exosomes and exosome communication. During AD and PD, there is a noted reduction in the effectiveness of autophagy, a process critical to cellular proteostasis. Recent studies have uncovered shared regulatory mechanisms of exosome biogenesis and autophagy, suggesting that they are closely linked. Previous findings have shown that inhibition of autophagy in AD mice mediates A? trafficking through altering the secretion of A? in MVBs. To further study this effect, we investigated the interplay between autophagy and exosome secretion using ATG7 knock-out x APPNL-F knock-in AD mice in paper III. These autophagy-deficient AD mice had a reduced extracellular A? plaque load, but increased intracellular A?, which was found to be assembled into higher-ordered assemblies. While exosomal secretion was dysregulated in these mice, the amount of A? packaged into the exosomes was unchanged. Lastly, one of the biggest challenges in developing effective treatments for AD is the lack of early diagnosis of living patients. As the connection between exosomes and the spread of neurodegenerative proteins is still relatively new, there remains a diagnostic potential to be explored with exosomes. Paper IV aimed to develop a new diagnostic assay to detect oA? in exosomes isolated from human cerebrospinal fluid. Although exosomal oA? was readily detected in some of these samples, the assay’s sensitivity requires additional optimisation before it can be further validated for the clinic. In summary, the studies presented in this thesis have furthered our understanding of how inflammation, autophagy, and exosomes contribute to the intercellular transmission of AD and PD associated proteins. We have shown that an anti-inflammatory approach may slow down the progression of AD through reducing the transfer of oA? between cells. We also provide novel findings relating to the biogenesis of exosomes, which in turn affected the ability of exosomes to transmit neurodegenerative proteins between cells, and their association with autophagic processes. Finally, we have investigated the feasibility of exosomes as an early AD diagnostic marker. This work has helped to elucidate some of the mechanisms underlying the progression of neurodegenerative diseases, which may be useful targets for the investigation of new therapeutic avenues.
