Toxicity And Autophagy In Neurodegenerative Disorders

Comprehensive overview of different aspects of autophagy as it relates to neurodegenerative diseases. The pathogenesis of the main neurodegenerative disorders includes either the accumulation of altered or misfolded proteins or exposure to several toxics. Autophagy constitute one of the two principal cellular pathways implicate in the clearance of these material and can serve as a neuroprotective mechanism. Topics include: the role of autophagy in the brain, the role of autophagy in the principal neurodegenerative disorders, and the mechanism by which different molecules cause neurotoxicity and the role autophagy plays.

To date, three forms of autophagy – macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA) – have been identified. Recently, we discovered a novel type of autophagy, “RNautophagy,” in which RNA is taken up directly into lysosomes for degradation. Gain of toxic functions of accumulated misfolded proteins or abnormal RNAs in CNS participate to a considerable degree in the pathogenesis of various neurodegenerative diseases. Thus, degradation and clearance of the toxic species by autophagy systems may be important for the maintenance of neurons and prevention of neurodegenerative diseases. We showed that amyotrophic lateral sclerosis (ALS)-linked mutant SOD1 is degraded not only by the proteasome but also by macroautophagy, and that macroautophagy reduces mutant SOD1-mediated toxicity. We found that Parkinson’s disease-associated mutant UCH-L1 interacts with LAMP-2A and Hsc70, which are the components of CMA machinery, and inhibits CMA. Because RNAs containing aberrant repeats are thought to cause some of ALS or spinocerebellar ataxia (SCA), RNautophagy may also play significant roles in the pathology of neurodegenerative diseases.

What is autophagy? Why would neurons digest parts of themselves through autophagy? How can autophagy save the lives of cells under some conditions, but act as an accomplice to cell death in others? By what mechanisms are autophagy-related processes dysregulated in neurological diseases, and are there therapeutic strategies to correct or compensate for their dysfunction? This book provides an expert view of major concepts in autophagy research with a focus on autophagy in neurons. Experimental evidence for evolutionarily conserved and specialized regulatory mechanisms for autophagy in the mammalian nervous system will be presented, including recent data on braking mechanisms. Areas of intersection with cell death, the ubiquitin-proteasome system, chaperone-mediated autophagy, and the endocytic pathway will be reviewed, along with emerging areas of mitochondrial autophagy (mitophagy) and the autophagic regulation of neuritic/synaptic processes. Advances in delineating mechanisms by which autophagy is involved in the pathophysiology of neurological disorders, including Alzheimer's, Parkinson's, Huntington's, amyotrophic lateral sclerosis, ischemia/hypoxia and lysosomal storage diseases, will be discussed along with current drug development strategies targeting autophagy.

The Molecular and Cellular Basis of Neurodegenerative Diseases: Underlying Mechanisms presents the pathology, genetics, biochemistry and cell biology of the major human neurodegenerative diseases, including Alzheimer’s, Parkinson’s, frontotemporal dementia, ALS, Huntington’s, and prion diseases. Edited and authored by internationally recognized leaders in the field, the book's chapters explore their pathogenic commonalities and differences, also including discussions of animal models and prospects for therapeutics. Diseases are presented first, with common mechanisms later. Individual chapters discuss each major neurodegenerative disease, integrating this information to offer multiple molecular and cellular mechanisms that diseases may have in common. This book provides readers with a timely update on this rapidly advancing area of investigation, presenting an invaluable resource for researchers in the field. Covers the spectrum of neurodegenerative diseases and their complex genetic, pathological, biochemical and cellular features Focuses on leading hypotheses regarding the biochemical and cellular dysfunctions that cause neurodegeneration Details features, advantages and limitations of animal models, as well as prospects for therapeutic development Authored by internationally recognized leaders in the field Includes illustrations that help clarify and consolidate complex concepts

The editor of this volume, having research interests in the field of ROS production and the damage to cellular systems, has identified a number of enzymes showing ·OH scavenging activities details of which are anticipated to be published in the near future as confirmatory experiments are awaited. It is hoped that the information presented in this book on NDs will stimulate both expert and novice researchers in the field with excellent overviews of the current status of research and pointers to future research goals. Clinicians, nurses as well as families and caregivers should also benefit from the material presented in handling and treating their specialised cases. Also the insights gained should be valuable for further understanding of the diseases at molecular levels and should lead to development of new biomarkers, novel diagnostic tools and more effective therapeutic drugs to treat the clinical problems raised by these devastating diseases.

This book provides a cutting-edge review of polyglutamine disorders. It primarily focuses on two main aspects: (1) the mechanisms underlying the pathologies’ development and progression, and (2) the therapeutic strategies that are currently being explored to stop or delay disease progression. Polyglutamine (polyQ) disorders are a group of inherited neurodegenerative diseases with a fatal outcome that are caused by an abnormal expansion of a coding trinucleotide repeat (CAG), which is then translated in an abnormal protein with an elongated glutamine tract (Q). To date, nine polyQ disorders have been identified and described: dentatorubral-pallidoluysian atrophy (DRPLA); Huntington’s disease (HD); spinal–bulbar muscular atrophy (SBMA); and six spinocerebellar ataxias (SCA 1, 2, 3, 6, 7, and 17). The genetic basis of polyQ disorders is well established and described, and despite important advances that have opened up the possibility of generating genetic models of the disease, the mechanisms that cause neuronal degeneration are still largely unknown and there is currently no treatment available for these disorders. Further, it is believed that the different polyQ may share some mechanisms and pathways contributing to neurodegeneration and disease progression.

The health of the proteome depends upon protein quality control to regulate the proper synthesis, folding, translocation, and clearance of proteins. The cell is challenged constantly by environmental and physiological stress, aging, and the chronic expressions of disease associated misfolded proteins. Substantial evidence supports the hypothesis that the expression of damaged proteins initiates a cascade of molecular events that leads to Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and other diseases of protein conformation.

This monograph describes the progress in neuropathological HD research made during the last century, the neuropathological hallmarks of HD and their pathogenic relevance. Starting with the initial descriptions of the progressive degeneration of the striatum as one of the key events in HD, the worldwide practiced Vonsattel HD grading system of striatal neurodegeneration will be outlined. Correlating neuropathological data with results on the functional neuroanatomy of the human brain, subsequent chapters will highlight recent HD findings: the neuronal loss in the cerebral neo-and allocortex, the neurodegeneration of select thalamic nuclei, the affection of the cerebellar cortex and nuclei, the involvement of select brainstem nuclei, as well as the pathophysiological relevance of these pathologies for the clinical picture of HD. Finally, the potential pathophysiological role of neuronal huntingtin aggregations and the most important and enduring challenges of neuropathological HD research are discussed.