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Hammond BP, Manek R, Kerr BJ, Macauley MS, Plemel JR. Regulation of microglia population dynamics throughout development, health, and disease. Glia 2021; 69:2771-2797. [PMID: 34115410 DOI: 10.1002/glia.24047] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/20/2021] [Accepted: 05/28/2021] [Indexed: 12/11/2022]
Abstract
The dynamic expansions and contractions of the microglia population in the central nervous system (CNS) to achieve homeostasis are likely vital for their function. Microglia respond to injury or disease but also help guide neurodevelopment, modulate neural circuitry throughout life, and direct regeneration. Throughout these processes, microglia density changes, as does the volume of area that each microglia surveys. Given that microglia are responsible for sensing subtle alterations to their environment, a change in their density could affect their capacity to mobilize rapidly. In this review, we attempt to synthesize the current literature on the ligands and conditions that promote microglial proliferation across development, adulthood, and neurodegenerative conditions. Microglia display an impressive proliferative capacity during development and in neurodegenerative diseases that is almost completely absent at homeostasis. However, the appropriate function of microglia in each state is critically dependent on density fluctuations that are primarily induced by proliferation. Proliferation is a natural microglial response to insult and often serves neuroprotective functions. In contrast, inappropriate microglial proliferation, whether too much or too little, often precipitates undesirable consequences for nervous system health. Thus, fluctuations in the microglia population are tightly regulated to ensure these immune cells can execute their diverse functions.
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Affiliation(s)
- Brady P Hammond
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Rupali Manek
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Bradley J Kerr
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Anesthesiology & Pain Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Matthew S Macauley
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Jason R Plemel
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Medicine, Division of Neurology, University of Alberta, Edmonton, Alberta, Canada
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Understanding stress: Insights from rodent models. CURRENT RESEARCH IN NEUROBIOLOGY 2021; 2:100013. [PMID: 36246514 PMCID: PMC9559100 DOI: 10.1016/j.crneur.2021.100013] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/30/2021] [Accepted: 05/08/2021] [Indexed: 02/01/2023] Open
Abstract
Through incorporating both physical and psychological forms of stressors, a variety of rodent models have provided important insights into the understanding of stress physiology. Rodent models also have provided significant information with regards to the mechanistic basis of the pathophysiology of stress-related disorders such as anxiety disorders, depressive illnesses, cognitive impairment and post-traumatic stress disorder. Additionally, rodent models of stress have served as valuable tools in the area of drug screening and drug development for treatment of stress-induced conditions. Although rodent models do not accurately reproduce the biochemical or physiological parameters of stress response and cannot fully mimic the natural progression of human disorders, yet, animal research has provided answers to many important scientific questions. In this review article, important studies utilizing a variety of stress models are described in terms of their design and apparatus, with specific focus on their capabilities to generate reliable behavioral and biochemical read-out. The review focusses on the utility of rodent models by discussing examples in the literature that offer important mechanistic insights into physiologically relevant questions. The review highlights the utility of rodent models of stress as important tools for advancing the mission of scientific research and inquiry. Stressful life events may lead to the onset of severe psychopathologies in humans. Rodents may model many features of stress exposure in human populations. Induction of stress via pharmacological and psychological manipulations alter rodent behavior. Mechanistic rodent studies reveal key molecular targets critical for new therapeutic targets.
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Microglia, Lifestyle Stress, and Neurodegeneration. Immunity 2020; 52:222-240. [PMID: 31924476 DOI: 10.1016/j.immuni.2019.12.003] [Citation(s) in RCA: 175] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 11/26/2019] [Accepted: 12/09/2019] [Indexed: 02/06/2023]
Abstract
Recent years have witnessed a revolution in our understanding of microglia biology, including their major role in the etiology and pathogenesis of neurodegenerative diseases. Technological advances have enabled the identification of microglial signatures in health and disease, including the development of new models to investigate and manipulate human microglia in vivo in the context of disease. In parallel, genetic association studies have identified several gene risk factors associated with Alzheimer's disease that are specifically or highly expressed by microglia in the central nervous system (CNS). Here, we discuss evidence for the effect of stress, diet, sleep patterns, physical activity, and microbiota composition on microglia biology and consider how lifestyle might influence an individual's predisposition to neurodegenerative diseases. We discuss how different lifestyles and environmental factors might regulate microglia, potentially leading to increased susceptibility to neurodegenerative disease, and we highlight the need to investigate the contribution of modern environmental factors on microglia modulation in neurodegeneration.
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Leem YH, Chang H. Arc/Arg3.1 protein expression in dorsal hippocampal CA1, a candidate event as a biomarker for the effects of exercise on chronic stress-evoked behavioral abnormalities. J Exerc Nutrition Biochem 2017; 21:45-51. [PMID: 29370673 PMCID: PMC5772070 DOI: 10.20463/jenb.2017.0033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 12/16/2017] [Indexed: 12/19/2022] Open
Abstract
[Purpose] Chronic stress is a risk factor for behavioral deficits, including impaired memory processing and depression. Exercise is well known to have beneficial impacts on brain health. [Methods] Mice were forced to treadmill running (4-week) during chronic restraint stress (6h/21d), and then behavioral tests were conducted by Novel object recognition, forced swimming test: FST, sociality test: SI. Dissected brain was stained with anti-calbindin-d28k and anti-Arc antibodies. Also, mice were treated with CX546 intraperitoneally during chronic restraint stress, and behavioral tests were assessed using Morris water maze, FST, and SI. Dissected brain was stained with anti-Arc antibody. [Results] The current study demonstrated that chronic stress-induced impairment of memory consolidation and depression-like behaviors, along with the changes in calbindin-d28k and Arc protein levels in the hippocampal CA1 area, were attenuated by regular treadmill running. Further, prolonged ampakine treatment prevented chronic stress-evoked behavioral abnormalities and nuclear Arc levels in hippocampal CA1 neurons. Nuclear localization of Arc protein in hippocampal CA1 neurons, but not total levels, was correlated with behavioral outcome in chronically stressed mice in response to a regular exercise regimen. [Conclusion] These results suggest that nuclear levels of Arc are strongly associated with behavioral changes, and highlight the role of exercise acting through an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR)-mediated mechanisms in a chronic stress-induced maladaptive condition.
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Tian L, Hui CW, Bisht K, Tan Y, Sharma K, Chen S, Zhang X, Tremblay ME. Microglia under psychosocial stressors along the aging trajectory: Consequences on neuronal circuits, behavior, and brain diseases. Prog Neuropsychopharmacol Biol Psychiatry 2017; 79:27-39. [PMID: 28095309 DOI: 10.1016/j.pnpbp.2017.01.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 12/30/2016] [Accepted: 01/13/2017] [Indexed: 12/18/2022]
Abstract
Mounting evidence indicates the importance of microglia for proper brain development and function, as well as in complex stress-related neuropsychiatric disorders and cognitive decline along the aging trajectory. Considering that microglia are resident immune cells of the brain, a homeostatic maintenance of their effector functions that impact neuronal circuitry, such as phagocytosis and secretion of inflammatory factors, is critical to prevent the onset and progression of these pathological conditions. However, the molecular mechanisms by which microglial functions can be properly regulated under healthy and pathological conditions are still largely unknown. We aim to summarize recent progress regarding the effects of psychosocial stress and oxidative stress on microglial phenotypes, leading to neuroinflammation and impaired microglia-synapse interactions, notably through our own studies of inbred mouse strains, and most importantly, to discuss about promising therapeutic strategies that take advantage of microglial functions to tackle such brain disorders in the context of adult psychosocial stress or aging-induced oxidative stress.
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Affiliation(s)
- Li Tian
- Neuroscience Center, University of Helsinki, Viikinkaari 4, Helsinki FIN-00014, Finland; Psychiatry Research Center, Beijing Huilongguan Hospital, Peking University, Beijing, China.
| | - Chin Wai Hui
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada
| | - Kanchan Bisht
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada
| | - Yunlong Tan
- Psychiatry Research Center, Beijing Huilongguan Hospital, Peking University, Beijing, China
| | - Kaushik Sharma
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada
| | - Song Chen
- Psychiatry Research Center, Beijing Huilongguan Hospital, Peking University, Beijing, China; Beijing Key Laboratory of Mental Disorders and Center of Schizophrenia, Beijing Institute for Brain Disorders, Beijing Anding Hospital, Capital Medical University, China
| | - Xiangyang Zhang
- Psychiatry Research Center, Beijing Huilongguan Hospital, Peking University, Beijing, China; Department of Psychiatry and Behavioral Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Marie-Eve Tremblay
- Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, Canada.
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Psychosocial stress on neuroinflammation and cognitive dysfunctions in Alzheimer's disease: the emerging role for microglia? Neurosci Biobehav Rev 2017; 77:148-164. [PMID: 28185874 DOI: 10.1016/j.neubiorev.2017.01.046] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 01/20/2017] [Accepted: 01/31/2017] [Indexed: 01/22/2023]
Abstract
Chronic psychosocial stress is increasingly recognized as a risk factor for late-onset Alzheimer's disease (LOAD) and associated cognitive deficits. Chronic stress also primes microglia and induces inflammatory responses in the adult brain, thereby compromising synapse-supportive roles of microglia and deteriorating cognitive functions during aging. Substantial evidence demonstrates that failure of microglia to clear abnormally accumulating amyloid-beta (Aβ) peptide contributes to neuroinflammation and neurodegeneration in AD. Moreover, genome-wide association studies have linked variants in several immune genes, such as TREM2 and CD33, the expression of which in the brain is restricted to microglia, with cognitive dysfunctions in LOAD. Thus, inflammation-promoting chronic stress may create a vicious cycle of aggravated microglial dysfunction accompanied by increased Aβ accumulation, collectively exacerbating neurodegeneration. Surprisingly, however, little is known about whether and how chronic stress contributes to microglia-mediated neuroinflammation that may underlie cognitive impairments in AD. This review aims to summarize the currently available clinical and preclinical data and outline potential molecular mechanisms linking stress, microglia and neurodegeneration, to foster future research in this field.
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Alhaider IA, Alkadhi KA. Caffeine treatment prevents rapid eye movement sleep deprivation-induced impairment of late-phase long-term potentiation in the dentate gyrus. Eur J Neurosci 2016; 42:2843-50. [PMID: 26449851 DOI: 10.1111/ejn.13092] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 09/28/2015] [Accepted: 09/29/2015] [Indexed: 02/06/2023]
Abstract
The CA1 and dentate gyrus (DG) are physically and functionally closely related areas of the hippocampus, but they differ in various respects, including their reactions to different insults. The purpose of this study was to determine the protective effects of chronic caffeine treatment on late-phase long-term potentiation (L-LTP) and its signalling cascade in the DG area of the hippocampus of rapid eye movement sleep-deprived rats. Rats were chronically treated with caffeine (300 mg/L drinking water) for 4 weeks, after which they were sleep-deprived for 24 h. L-LTP was induced in in anaesthetized rats, and extracellular field potentials from the DG area were recorded in vivo. The levels of L-LTP-related signalling proteins were assessed by western blot analysis. Sleep deprivation markedly reduced L-LTP magnitude, and basal levels of total cAMP response element-binding protein (CREB), phosphorylated CREB (P-CREB), and calcium/calmodulin kinase IV (CaMKIV). Chronic caffeine treatment prevented the reductions in the basal levels of P-CREB, total CREB and CaMKIV in sleep-deprived rats. Furthermore, caffeine prevented post-L-LTP sleep deprivation-induced downregulation of P-CREB and brain-derived neurotrophic factor in the DG. The current findings show that caffeine treatment prevents acute sleep deprivation-induced deficits in brain function.
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Affiliation(s)
- Ibrahim A Alhaider
- Department of Pharmacological and Pharmaceutical Sciences, 521E Science and Research 2 Bldg, College of Pharmacy, University of Houston, Houston, TX 77204-5037, USA
| | - Karim A Alkadhi
- Department of Pharmacological and Pharmaceutical Sciences, 521E Science and Research 2 Bldg, College of Pharmacy, University of Houston, Houston, TX 77204-5037, USA
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Alkadhi KA, Alhaider IA. Caffeine and REM sleep deprivation: Effect on basal levels of signaling molecules in area CA1. Mol Cell Neurosci 2016; 71:125-31. [DOI: 10.1016/j.mcn.2015.12.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 12/16/2015] [Accepted: 12/31/2015] [Indexed: 01/19/2023] Open
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