scholarly journals Exosomes: Innocent Bystanders or Critical Culprits in Neurodegenerative Diseases

Author(s):  
Margarida Beatriz ◽  
Rita Vilaça ◽  
Carla Lopes

Extracellular vesicles (EVs) are nano-sized membrane-enclosed particles released by cells that participate in intercellular communication through the transfer of biologic material. EVs include exosomes that are small vesicles that were initially associated with the disposal of cellular garbage; however, recent findings point toward a function as natural carriers of a wide variety of genetic material and proteins. Indeed, exosomes are vesicle mediators of intercellular communication and maintenance of cellular homeostasis. The role of exosomes in health and age-associated diseases is far from being understood, but recent evidence implicates exosomes as causative players in the spread of neurodegenerative diseases. Cells from the central nervous system (CNS) use exosomes as a strategy not only to eliminate membranes, toxic proteins, and RNA species but also to mediate short and long cell-to-cell communication as carriers of important messengers and signals. The accumulation of protein aggregates is a common pathological hallmark in many neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and prion diseases. Protein aggregates can be removed and delivered to degradation by the endo-lysosomal pathway or can be incorporated in multivesicular bodies (MVBs) that are further released to the extracellular space as exosomes. Because exosome transport damaged cellular material, this eventually contributes to the spread of pathological misfolded proteins within the brain, thus promoting the neurodegeneration process. In this review, we focus on the role of exosomes in CNS homeostasis, their possible contribution to the development of neurodegenerative diseases, the usefulness of exosome cargo as biomarkers of disease, and the potential benefits of plasma circulating CNS-derived exosomes.

2021 ◽  
Vol 15 ◽  
Author(s):  
Luyao Huo ◽  
Xinzhe Du ◽  
Xinrong Li ◽  
Sha Liu ◽  
Yong Xu

Intercellular communication in the central nervous system (CNS) is essential for brain growth, development, and homeostasis maintenance and, when dysfunctional, is involved in the occurrence and development of neurodegenerative diseases. Increasing evidence indicates that extracellular vesicles, especially exosomes, are critical mediators of intercellular signal transduction. Under physiological and pathological conditions, neural cells secret exosomes with the influence of many factors. These exosomes can carry specific proteins, lipids, nucleic acids, and other bioactive substances to the recipient cells to regulate their function. Depending on the CNS environment, as well as the origin and physiological or pathological status of parental cells, exosomes can mediate a variety of different effects, including synaptic plasticity, nutritional metabolic support, nerve regeneration, inflammatory response, anti-stress effect, cellular waste disposal, and the propagation of toxic components, playing an important role in health and neurodegenerative diseases. This review will discuss the possible roles of exosomes in CNS intercellular communication in both physiologic and neurodegenerative conditions.


2014 ◽  
Vol 33 (4) ◽  
Author(s):  
Guylaine Hoffner ◽  
William André ◽  
Christophe Sandt ◽  
Philippe Djian

AbstractThe accumulation of misfolded proteins in the form of aggregates characterizes a number of diseases of the central nervous system such as Alzheimer’s disease, Parkinson’s disease, prion diseases, and the diseases of polyglutamine expansion. Recent evidence obtained


Cells ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 150
Author(s):  
Shofiul Azam ◽  
Md. Ezazul Haque ◽  
In-Su Kim ◽  
Dong-Kug Choi

Microglia are brain-dwelling macrophages and major parts of the neuroimmune system that broadly contribute to brain development, homeostasis, ageing and injury repair in the central nervous system (CNS). Apart from other brain macrophages, they have the ability to constantly sense changes in the brain’s microenvironment, functioning as housekeepers for neuronal well-being and providing neuroprotection in normal physiology. Microglia use a set of genes for these functions that involve proinflammatory cytokines. In response to specific stimuli, they release these proinflammatory cytokines, which can damage and kill neurons via neuroinflammation. However, alterations in microglial functioning are a common pathophysiology in age-related neurodegenerative diseases, such as Alzheimer’s, Parkinson’s, Huntington’s and prion diseases, as well as amyotrophic lateral sclerosis, frontotemporal dementia and chronic traumatic encephalopathy. When their sentinel or housekeeping functions are severely disrupted, they aggravate neuropathological conditions by overstimulating their defensive function and through neuroinflammation. Several pathways are involved in microglial functioning, including the Trem2, Cx3cr1 and progranulin pathways, which keep the microglial inflammatory response under control and promote clearance of injurious stimuli. Over time, an imbalance in this system leads to protective microglia becoming detrimental, initiating or exacerbating neurodegeneration. Correcting such imbalances might be a potential mode of therapeutic intervention in neurodegenerative diseases.


2021 ◽  
Vol 14 ◽  
Author(s):  
Xiaomin Huang ◽  
Yixun Su ◽  
Nan Wang ◽  
Hui Li ◽  
Zhigang Li ◽  
...  

Astrocytes play a crucial role in the maintenance of the normal functions of the Central Nervous System (CNS). During the pathogenesis of neurodegenerative diseases, astrocytes undergo morphological and functional remodeling, a process called reactive astrogliosis, in response to the insults to the CNS. One of the key aspects of the reactive astrocytes is the change in the expression and function of connexins. Connexins are channel proteins that highly expressed in astrocytes, forming gap junction channels and hemichannels, allowing diffusional trafficking of small molecules. Alterations of astrocytic connexin expression and function found in neurodegenerative diseases have been shown to affect the disease progression by changing neuronal function and survival. In this review, we will summarize the role of astroglial connexins in neurodegenerative diseases including Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis. Also, we will discuss why targeting connexins can be a plausible therapeutic strategy to manage these neurodegenerative diseases.


Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 846 ◽  
Author(s):  
Oscar F. Sánchez ◽  
Andrea V. Rodríguez ◽  
José M. Velasco-España ◽  
Laura C. Murillo ◽  
Jhon-Jairo Sutachan ◽  
...  

Gap junction (GJ) channels and their connexins (Cxs) are complex proteins that have essential functions in cell communication processes in the central nervous system (CNS). Neurons, astrocytes, oligodendrocytes, and microglial cells express an extraordinary repertory of Cxs that are important for cell to cell communication and diffusion of metabolites, ions, neurotransmitters, and gliotransmitters. GJs and Cxs not only contribute to the normal function of the CNS but also the pathological progress of several diseases, such as cancer and neurodegenerative diseases. Besides, they have important roles in mediating neuroprotection by internal or external molecules. However, regulation of Cx expression by epigenetic mechanisms has not been fully elucidated. In this review, we provide an overview of the known mechanisms that regulate the expression of the most abundant Cxs in the central nervous system, Cx30, Cx36, and Cx43, and their role in brain cancer, CNS disorders, and neuroprotection. Initially, we focus on describing the Cx gene structure and how this is regulated by epigenetic mechanisms. Then, the posttranslational modifications that mediate the activity and stability of Cxs are reviewed. Finally, the role of GJs and Cxs in glioblastoma, Alzheimer’s, Parkinson’s, and Huntington’s diseases, and neuroprotection are analyzed with the aim of shedding light in the possibility of using Cx regulators as potential therapeutic molecules.


2021 ◽  
Vol 22 (9) ◽  
pp. 4630
Author(s):  
Agnieszka Kulczyńska-Przybik ◽  
Piotr Mroczko ◽  
Maciej Dulewicz ◽  
Barbara Mroczko

Reticulons (RTNs) are crucial regulatory factors in the central nervous system (CNS) as well as immune system and play pleiotropic functions. In CNS, RTNs are transmembrane proteins mediating neuroanatomical plasticity and functional recovery after central nervous system injury or diseases. Moreover, RTNs, particularly RTN4 and RTN3, are involved in neurodegeneration and neuroinflammation processes. The crucial role of RTNs in the development of several neurodegenerative diseases, including Alzheimer’s disease (AD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or other neurological conditions such as brain injury or spinal cord injury, has attracted scientific interest. Reticulons, particularly RTN-4A (Nogo-A), could provide both an understanding of early pathogenesis of neurodegenerative disorders and be potential therapeutic targets which may offer effective treatment or inhibit disease progression. This review focuses on the molecular mechanisms and functions of RTNs and their potential usefulness in clinical practice as a diagnostic tool or therapeutic strategy.


2010 ◽  
Vol 2010 ◽  
pp. 1-12 ◽  
Author(s):  
Dorit Trudler ◽  
Dorit Farfara ◽  
Dan Frenkel

Toll-like receptors (TLRs) are known to be expressed by innate immune response cells and to play a critical role in their activation against foreign pathogens. It was recently suggested that TLRs have an important role in the crosstalk between neurons and glial cells in the central nervous system (CNS). TLR signaling was reported to be associated with a yin-yang effect in the CNS. While TLR signaling was linked to neurogenesis, it was also found to be involved in the pathogenesis of neurodegenerative diseases. This paper will focus on TLR signaling in glial cells in neurodegenerative diseases such as Alzheimer's disease, prion diseases, amyotrophic lateral sclerosis, and Parkinson's disease. Understanding the pattern of TLR signaling in the glial cells may lead to the identification of new targets for therapeutic application.


2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Valerio Chiurchiù ◽  
Antonio Orlacchio ◽  
Mauro Maccarrone

The central nervous system is particularly sensitive to oxidative stress due to many reasons, including its high oxygen consumption even under basal conditions, high production of reactive oxygen and nitrogen species from specific neurochemical reactions, and the increased deposition of metal ions in the brain with aging. For this reason, along with inflammation, oxidative stress seems to be one of the main inducers of neurodegeneration, causing excitotoxicity, neuronal loss, and axonal damage, ultimately being now considered a key element in the onset and progression of several neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, multiple sclerosis, and hereditary spastic paraplegia. Thus, the present paper reviews the role of oxidative stress and of its mechanistic insights underlying the pathogenesis of these neurodegenerative diseases, with particular focus on current studies on its modulation as a potential and promising therapeutic strategy.


Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 953
Author(s):  
Federica Piancone ◽  
Francesca La Rosa ◽  
Ivana Marventano ◽  
Marina Saresella ◽  
Mario Clerici

Neurodegenerative diseases are chronic, progressive disorders that occur in the central nervous system (CNS). They are characterized by the loss of neuronal structure and function and are associated with inflammation. Inflammation of the CNS is called neuroinflammation, which has been implicated in most neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). Much evidence indicates that these different conditions share a common inflammatory mechanism: the activation of the inflammasome complex in peripheral monocytes and in microglia, with the consequent production of high quantities of the pro-inflammatory cytokines IL-1β and IL-18. Inflammasomes are a group of multimeric signaling complexes that include a sensor Nod-like receptor (NLR) molecule, the adaptor protein ASC, and caspase-1. The NLRP3 inflammasome is currently the best-characterized inflammasome. Multiple signals, which are potentially provided in combination and include endogenous danger signals and pathogens, trigger the formation of an active inflammasome, which, in turn, will stimulate the cleavage and the release of bioactive cytokines including IL-1β and IL-18. In this review, we will summarize results implicating the inflammasome as a pivotal player in the pathogenesis of neurodegenerative diseases and discuss how compounds that hamper the activation of the NLRP3 inflammasome could offer novel therapeutic avenues for these diseases.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jia-zhe Lin ◽  
Ming-rui Duan ◽  
Nuan Lin ◽  
Wei-jiang Zhao

Abstract Chondroitin sulfate (CS) is a kind of linear polysaccharide that is covalently linked to proteins to form proteoglycans. Chondroitin sulfate proteoglycans (CSPGs) consist of a core protein, with one or more CS chains covalently attached. CSPGs are precisely regulated and they exert a variety of physiological functions by binding to adhesion molecules and growth factors. Widely distributed in the nervous system in human body, CSPGs contribute to the major component of extracellular matrix (ECM), where they play an important role in the development and maturation of the nervous system, as well as in the pathophysiological response to damage to the central nervous system (CNS). While there are more than 30 types of CSPGs, this review covers the roles of the most important ones, including versican, aggrecan, neurocan and NG2 in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and multiple sclerosis. The updated reports of the treatment of neurodegenerative diseases are involving CSPGs.


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