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Fanikos M, Kohn SA, Stamato R, Brenhouse HC, Gildawie KR. Impacts of age and environment on postnatal microglial activity: Consequences for cognitive function following early life adversity. PLoS One 2024; 19:e0306022. [PMID: 38917075 PMCID: PMC11198844 DOI: 10.1371/journal.pone.0306022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 06/10/2024] [Indexed: 06/27/2024] Open
Abstract
Early life adversity (ELA) increases the likelihood of later-life neuropsychiatric disorders and cognitive dysfunction. Importantly, ELA, neuropsychiatric disorders, and cognitive deficits all involve aberrant immune signaling. Microglia are the primary neuroimmune cells and regulate brain development. Microglia are particularly sensitive to early life insults, which can program their responses to future challenges. ELA in the form of maternal separation (MS) in rats alters later-life microglial morphology and the inflammatory profile of the prefrontal cortex, a region important for cognition. However, the role of microglial responses during MS in the development of later cognition is not known. Therefore, here we aimed to determine whether the presence of microglia during MS mediates long-term impacts on adult working memory. Clodronate liposomes were used to transiently deplete microglia from the brain, while empty liposomes were used as a control. We hypothesized that if microglia mediate the long-term impacts of ELA on working memory in adulthood, then depleting microglia during MS would prevent these deficits. Importantly, microglial function shifts throughout the neonatal period, so an exploratory investigation assessed whether depletion during the early versus late neonatal period had different effects on adult working memory. Surprisingly, empty liposome treatment during the early, but not late, postnatal period induced microglial activity changes that compounded with MS to impair working memory in females. In contrast, microglial depletion later in infancy impaired later life working memory in females, suggesting that microglial function during late infancy plays an important role in the development of cognitive function. Together, these findings suggest that microglia shift their sensitivity to early life insults across development. Our findings also highlight the potential for MS to impact some developmental processes only when compounded with additional neuroimmune challenges in a sex-dependent manner.
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Affiliation(s)
- Michaela Fanikos
- Department of Psychology, Northeastern University, Boston, Massachusetts, United States of America
| | - Skylar A. Kohn
- Department of Psychology, Northeastern University, Boston, Massachusetts, United States of America
| | - Rebecca Stamato
- Department of Psychology, Northeastern University, Boston, Massachusetts, United States of America
| | - Heather C. Brenhouse
- Department of Psychology, Northeastern University, Boston, Massachusetts, United States of America
| | - Kelsea R. Gildawie
- Department of Psychology, Northeastern University, Boston, Massachusetts, United States of America
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2
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Power D, Elstrott J, Schallek J. Photoreceptor loss does not recruit neutrophils despite strong microglial activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.25.595864. [PMID: 38854151 PMCID: PMC11160676 DOI: 10.1101/2024.05.25.595864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
In response to central nervous system (CNS) injury, tissue resident immune cells such as microglia and circulating systemic neutrophils are often first responders. The degree to which these cells interact in response to CNS damage is poorly understood, and even less so, in the neural retina which poses a challenge for high resolution imaging in vivo. In this study, we deploy fluorescence adaptive optics scanning light ophthalmoscopy (AOSLO) to study fluorescent microglia and neutrophils in mice. We simultaneously track immune cell dynamics using label-free phase-contrast AOSLO at micron-level resolution. Retinal lesions were induced with 488 nm light focused onto photoreceptor (PR) outer segments. These lesions focally ablated PRs, with minimal collateral damage to cells above and below the plane of focus. We used in vivo (AOSLO, SLO and OCT) imaging to reveal the natural history of the microglial and neutrophil response from minutes-to-months after injury. While microglia showed dynamic and progressive immune response with cells migrating into the injury locus within 1-day after injury, neutrophils were not recruited despite close proximity to vessels carrying neutrophils only microns away. Post-mortem confocal microscopy confirmed in vivo findings. This work illustrates that microglial activation does not recruit neutrophils in response to acute, focal loss of photoreceptors, a condition encountered in many retinal diseases.
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3
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Singh S, Bensalem J, Hein LK, Casey A, Mäkinen VP, Sargeant TJ. epHero - a tandem-fluorescent probe to track the fate of apoptotic cells during efferocytosis. Cell Death Discov 2024; 10:179. [PMID: 38632247 PMCID: PMC11024195 DOI: 10.1038/s41420-024-01952-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 04/01/2024] [Accepted: 04/08/2024] [Indexed: 04/19/2024] Open
Abstract
The efficient removal of apoptotic cells via efferocytosis is critical for maintaining optimal tissue function. This involves the binding and engulfment of apoptotic cells by phagocytes and the subsequent maturation of the phagosome, culminating in lysosomal fusion and cargo destruction. However, current approaches to measure efferocytosis rely on labelling apoptotic targets with fluorescent dyes, which do not sufficiently distinguish between changes to the engulfment and acidification of apoptotic material. To address this limitation, we have developed a genetically coded ratiometric probe epHero which when expressed in the cytoplasm of target cells, bypasses the need for additional labelling steps. We demonstrate that epHero is a pH-sensitive reporter for efferocytosis and can be used to simultaneously track changes to apoptotic cell uptake and acidification, both in vitro and in mice. As proof-of-principle, we modify extracellular nutrition to show how epHero can distinguish between changes to cargo engulfment and acidification. Thus, tracking efferocytosis with epHero is a simple, cost-effective improvement on conventional techniques.
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Affiliation(s)
- Sanjna Singh
- South Australian Health and Medical Research Institute, Adelaide, SA, Australia
- University of Adelaide, Adelaide, SA, Australia
| | - Julien Bensalem
- South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Leanne K Hein
- South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Aaron Casey
- South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Ville-Petteri Mäkinen
- Research Unit of Population Health, Faculty of Medicine, University of Oulu, Oulu, Finland
- Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Timothy J Sargeant
- South Australian Health and Medical Research Institute, Adelaide, SA, Australia.
- University of Adelaide, Adelaide, SA, Australia.
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4
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Márquez-Ropero M, Sierra A. Interferons: Invited guests at the brain's gala banquet. Neuron 2024; 112:1205-1207. [PMID: 38608706 DOI: 10.1016/j.neuron.2024.03.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 03/10/2024] [Accepted: 03/11/2024] [Indexed: 04/14/2024]
Abstract
Removal of toxic debris that can hinder brain function is performed primarily by microglia, the brain's professional phagocytes. A recent study in Cell1 identified that viral response interferons are required for priming microglia, ensuring competent phagocytosis and proper circuit wiring.
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Affiliation(s)
- Mar Márquez-Ropero
- Achucarro Basque Center for Neuroscience, Scientific Park UPV/EHU, Barrio Sarriena s/n, 48940 Bilbao, Spain; Department of Neurosciences, University of the Basque Country EHU/UPV, Barrio Sarriena s/n, 48940 Bilbao, Spain
| | - Amanda Sierra
- Achucarro Basque Center for Neuroscience, Scientific Park UPV/EHU, Barrio Sarriena s/n, 48940 Bilbao, Spain; Department of Biochemistry and Molecular Biology, University of the Basque Country EHU/UPV, Barrio Sarriena s/n, 48940 Bilbao, Spain; Ikerbasque Foundation, Euskadi Plaza, 5, 48009 Bilbao, Spain.
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Bull D, Matte JC, Navarron CM, McIntyre R, Whiting P, Katan M, Ducotterd F, Magno L. The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function - Insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation. Biochim Biophys Acta Mol Basis Dis 2024; 1870:166978. [PMID: 38061598 DOI: 10.1016/j.bbadis.2023.166978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 10/29/2023] [Accepted: 11/27/2023] [Indexed: 12/30/2023]
Abstract
Phospholipase C-gamma 2 (PLCγ2) is highly expressed in hematopoietic and immune cells, where it is a key signalling node enabling diverse cellular functions. Within the periphery, gain-of-function (GOF) PLCγ2 variants, such as the strongly hypermorphic S707Y, cause severe immune dysregulation. The milder hypermorphic mutation PLCγ2 P522R increases longevity and confers protection in central nervous system (CNS) neurodegenerative disorders, implicating PLCγ2 as a novel therapeutic target for treating these CNS indications. Currently, nothing is known about what consequences strong PLCγ2 GOF has on CNS functionality, and more precisely on the specific biological functions of microglia. Using the PLCγ2 S707Y variant as a model of chronic activation we investigated the functional consequences of strong PLCγ2 GOF on human microglia. PLCγ2 S707Y expressing human inducible pluripotent stem cells (hiPSC)-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, compared to PLCγ2 wild type. Despite the increase in PLCγ2 enzymatic activity, the PLCγ2 S707Y hiPSC-derived microglia display diminished functionality for key microglial processes including phagocytosis and cytokine secretion upon inflammatory challenge. RNA sequencing revealed a downregulation of genes related to innate immunity and response, providing molecular support for the phenotype observed. Our data suggests that chronic activation of PLCγ2 elicits a detrimental phenotype that is contributing to unfavourable CNS functions, and informs on the therapeutic window for targeting PLCγ2 in the CNS. Drug candidates targeting PLCγ2 will need to precisely mimic the effects of the PLCγ2 P522R variant on microglial function, but not those of the PLCγ2 S707Y variant.
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Affiliation(s)
- Daniel Bull
- Alzheimer's Research UK UCL Drug Discovery Institute, University College London, The Cruciform Building, Gower Street, London WC1E 6BT, United Kingdom
| | - Julie C Matte
- Wellcome Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, United Kingdom
| | - Carmen M Navarron
- Alzheimer's Research UK UCL Drug Discovery Institute, University College London, The Cruciform Building, Gower Street, London WC1E 6BT, United Kingdom
| | - Rebecca McIntyre
- Wellcome Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, United Kingdom
| | - Paul Whiting
- Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
| | - Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Fiona Ducotterd
- Alzheimer's Research UK UCL Drug Discovery Institute, University College London, The Cruciform Building, Gower Street, London WC1E 6BT, United Kingdom
| | - Lorenza Magno
- Alzheimer's Research UK UCL Drug Discovery Institute, University College London, The Cruciform Building, Gower Street, London WC1E 6BT, United Kingdom.
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Lorimer IAJ. Potential roles for efferocytosis in glioblastoma immune evasion. Neurooncol Adv 2024; 6:vdae012. [PMID: 38616895 PMCID: PMC11012614 DOI: 10.1093/noajnl/vdae012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024] Open
Abstract
Glioblastoma is an aggressive and incurable brain cancer. This cancer establishes both local and systemic immunosuppression that creates a major obstacle to effective immunotherapies. Many studies point to tumor-resident myeloid cells (primarily microglia and macrophages) as key mediators of this immunosuppression. Myeloid cells exhibit a high level of plasticity with respect to their phenotype and are capable of both stimulating and repressing immune responses. How glioblastomas recruit myeloid cells and exploit them to avoid the immune system is an active area of research. Macrophages can acquire an immunosuppressive phenotype as a consequence of exposure to cytokines such as TGFB1 or IL4; in addition, macrophages can acquire an immunosuppressive phenotype as a consequence of the engulfment of apoptotic cells, a process referred to as efferocytosis. There is substantial evidence that glioblastoma cells are able to secrete cytokines and other factors that induce an immunosuppressive phenotype in macrophages and microglia. However, less is known about the contribution of efferocytosis to immunosuppression in glioblastoma. Here I review the literature in this area and discuss the potential of efferocytosis inhibition to improve glioblastoma response to immunotherapy.
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Affiliation(s)
- Ian A J Lorimer
- Cancer Research Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
- Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
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7
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Plaza-Zabala A, Sierra A. Studying Autophagy in Microglia: Overcoming the Obstacles. Methods Mol Biol 2024; 2713:45-70. [PMID: 37639114 DOI: 10.1007/978-1-0716-3437-0_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
In this chapter, we provide an overview of the main techniques and experimental approaches that can be used to analyze autophagy flux in microglia, the brain-resident macrophages. For this purpose, we first briefly introduce the main peculiarities of microglial biology, describe the basic mechanisms and functions of autophagy, and summarize the evidence accumulated so far on the role of autophagy in the regulation of microglial survival and functions, mainly phagocytosis and inflammation. Then, we highlight conceptual and technical aspects of autophagic recycling and microglial physiology that need to be taken into account for the accurate evaluation of autophagy flux in microglia. Finally, we describe the main assays that can be used to analyze the complete sequence of autophagosome formation and degradation or autophagy flux, mainly in cultured microglia and in vivo. The main approaches include indirect tracking of autophagosomes by autophagic enzymes such as LC3 by western blot and fluorescence-based confocal microscopy, as well as direct analysis of autophagic vesicles by electron microscopy. We also discuss the advantages and disadvantages of using these methods in specific experimental contexts and highlight the need to complement LC3 and/or electron microscopy data with analysis of other autophagic effectors and lysosomal proteins that participate in the initiation and completion of autophagy flux, respectively. In summary, we provide an experimental guide for the analysis of autophagosome turnover in microglia, emphasizing the need to combine as many markers and complementary approaches as possible to fully characterize the status of autophagy flux in microglia.
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Affiliation(s)
- Ainhoa Plaza-Zabala
- Achucarro Basque Center for Neuroscience, Leioa, Spain.
- Department of Pharmacology, University of the Basque Country (UPV/EHU), Leioa, Spain.
| | - Amanda Sierra
- Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Leioa, Spain
- Ikerbasque Foundation, Bilbao, Spain
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8
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Gu X, Zhao Z, Chen X, Zhang L, Fang H, Zhao T, Ju S, Gao W, Qian X, Wang X, Zhang J, Cheng H. Imaging microglia surveillance during sleep-wake cycles in freely behaving mice. eLife 2023; 12:RP86749. [PMID: 38132088 PMCID: PMC10746140 DOI: 10.7554/elife.86749] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023] Open
Abstract
Microglia surveillance manifests itself as dynamic changes in cell morphology and functional remodeling. Whether and how microglia surveillance is coupled to brain state switches during natural sleep-wake cycles remains unclear. To address this question, we used miniature two-photon microscopy (mTPM) to acquire time-lapse high-resolution microglia images of the somatosensory cortex, along with EEG/EMG recordings and behavioral video, in freely-behaving mice. We uncovered fast and robust brain state-dependent changes in microglia surveillance, occurring in parallel with sleep dynamics and early-onset phagocytic microglial contraction during sleep deprivation stress. We also detected local norepinephrine fluctuation occurring in a sleep state-dependent manner. We showed that the locus coeruleus-norepinephrine system, which is crucial to sleep homeostasis, is required for both sleep state-dependent and stress-induced microglial responses and β2-adrenergic receptor signaling plays a significant role in this process. These results provide direct evidence that microglial surveillance is exquisitely tuned to signals and stressors that regulate sleep dynamics and homeostasis so as to adjust its varied roles to complement those of neurons in the brain. In vivo imaging with mTPM in freely behaving animals, as demonstrated here, opens a new avenue for future investigation of microglia dynamics and sleep biology in freely behaving animals.
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Affiliation(s)
- Xiaochun Gu
- PKU-Nanjing Institute of Translational Medicine, Nanjing Raygen HealthNanjingChina
- National Platform for Medical Engineering Education Integration, Southeast UniversityNanjingChina
- Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast UniversityNanjingChina
- Key Laboratory of Developmental Genes and Human Diseases, Department of Histology Embryology, Medical School, Southeast UniversityNanjingChina
| | - Zhong Zhao
- Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical CollegeBeijingChina
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational MedicineNanjingChina
| | - Xueli Chen
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational MedicineNanjingChina
| | - Lifeng Zhang
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational MedicineNanjingChina
| | - Huaqiang Fang
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational MedicineNanjingChina
| | - Ting Zhao
- PKU-Nanjing Institute of Translational Medicine, Nanjing Raygen HealthNanjingChina
| | - Shenghong Ju
- Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast UniversityNanjingChina
| | - Weizheng Gao
- Academy of Advanced Interdisciplinary Study, College of Engineering, Peking UniversityBeijingChina
| | - Xiaoyu Qian
- Academy of Advanced Interdisciplinary Study, College of Engineering, Peking UniversityBeijingChina
| | - Xianhua Wang
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational MedicineNanjingChina
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking UniversityBeijingChina
| | - Jue Zhang
- Academy of Advanced Interdisciplinary Study, College of Engineering, Peking UniversityBeijingChina
| | - Heping Cheng
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational MedicineNanjingChina
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking UniversityBeijingChina
- National Biomedical Imaging Center, State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, College of Future Technology, Peking UniversityBeijingChina
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9
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Li X, Ding Z, Liu K, Wang Q, Song L, Chai Z, Yu J, Ma D, Xiao B, Ma C. Astrocytic phagocytosis of myelin debris and reactive characteristics in vivo and in vitro. Biol Cell 2023; 115:e202300057. [PMID: 37851997 DOI: 10.1111/boc.202300057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/24/2023] [Accepted: 10/12/2023] [Indexed: 10/20/2023]
Abstract
BACKGROUND INFORMATION Persistent myelin debris can inhibit axonal regeneration, thereby hindering remyelination. Effective removal of myelin debris is essential to eliminate the interference of myelin debris in oligodendrocyte progenitor cell (OPC) activation, recruitment to demyelinating sites and/or differentiation into mature oligodendrocytes (OLs). In addition to microglia, it has been reported that astrocytic phagocytosis of myelin debris is a feature of early demyelination. RESULTS In the present study, astrocytes effectively phagocytized myelin debris in vitro and in vivo. On the 5th day after injecting myelin debris into the brain, astrocytes were enriched in the area injected with myelin debris compared with microglia, and their ability to engulf myelin debris was stronger than that of microglia. When exposed to myelin debris, astrocytes phagocytizing myelin debris triggered self-apoptosis, accompanied by the activation of NF-κB, down-regulation of Nrf2, and the increase of ciliary neurotrophic factor (CNTF) and basic fibroblast growth factor (bFGF). However, the activation of astrocytic NF-κB did not influence the inflammatory cytokines IL-1β, IL-6, and TNF-α, and the anti-inflammatory factor IL-10. The proliferation of astrocytes and mobilization of OPCs in the subventricular zone were elevated on the 5th day after intracerebral injection of myelin debris. CONCLUSIONS The results suggested that myelin phagocytosis of astrocytes should help improve the microenvironment and promote myelin regeneration by increasing CNTF and bFGF within the central nervous system. SIGNIFICANCE However, the molecular interaction of astrocytes acting as phagocytes remains to be further explored. Therefore, an improvement of astrocytes to phagocytize myelin debris may be a promising treatment measure to prevent demyelination and promote remyelination in MS and other diseases with prominent myelin injury.
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Affiliation(s)
- Xiaohui Li
- The Key Research Laboratory of Benefiting Qi for Acting Blood Circulation Method to Treat Multiple, Sclerosis of State Administration of Traditional Chinese Medicine, Research Center of Neurobiology, Shanxi University of Chinese Medicine, Jinzhong, China
| | - Zhibin Ding
- Department of Neurology, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University, Taiyuan, China
| | - Kexin Liu
- The Key Research Laboratory of Benefiting Qi for Acting Blood Circulation Method to Treat Multiple, Sclerosis of State Administration of Traditional Chinese Medicine, Research Center of Neurobiology, Shanxi University of Chinese Medicine, Jinzhong, China
| | - Qing Wang
- The Key Research Laboratory of Benefiting Qi for Acting Blood Circulation Method to Treat Multiple, Sclerosis of State Administration of Traditional Chinese Medicine, Research Center of Neurobiology, Shanxi University of Chinese Medicine, Jinzhong, China
| | - Lijuan Song
- The Key Research Laboratory of Benefiting Qi for Acting Blood Circulation Method to Treat Multiple, Sclerosis of State Administration of Traditional Chinese Medicine, Research Center of Neurobiology, Shanxi University of Chinese Medicine, Jinzhong, China
- The Key Laboratory of Nervous System Disease Prevention and Treatment under Health Commission of Shanxi Province, Sinopharm Tongmei General Hospital, Datong, China
| | - Zhi Chai
- The Key Research Laboratory of Benefiting Qi for Acting Blood Circulation Method to Treat Multiple, Sclerosis of State Administration of Traditional Chinese Medicine, Research Center of Neurobiology, Shanxi University of Chinese Medicine, Jinzhong, China
| | - Jiezhong Yu
- Institute of Brain Science, Shanxi Key Laboratory of Inflammatory Neurodegenerative Diseases, Medical School of Shanxi Datong University, Datong, China
| | - Dong Ma
- The Key Laboratory of Nervous System Disease Prevention and Treatment under Health Commission of Shanxi Province, Sinopharm Tongmei General Hospital, Datong, China
| | - Baoguo Xiao
- Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
| | - Cungen Ma
- The Key Research Laboratory of Benefiting Qi for Acting Blood Circulation Method to Treat Multiple, Sclerosis of State Administration of Traditional Chinese Medicine, Research Center of Neurobiology, Shanxi University of Chinese Medicine, Jinzhong, China
- Institute of Brain Science, Shanxi Key Laboratory of Inflammatory Neurodegenerative Diseases, Medical School of Shanxi Datong University, Datong, China
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Tang J, Jin Y, Jia F, Lv T, Manaenko A, Zhang LF, Zhang Z, Qi X, Xue Y, Zhao B, Zhang X, Zhang JH, Lu J, Hu Q. Gas6 Promotes Microglia Efferocytosis and Suppresses Inflammation Through Activating Axl/Rac1 Signaling in Subarachnoid Hemorrhage Mice. Transl Stroke Res 2023; 14:955-969. [PMID: 36324028 DOI: 10.1007/s12975-022-01099-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/17/2022] [Accepted: 10/19/2022] [Indexed: 11/05/2022]
Abstract
Early brain injury (EBI) following subarachnoid hemorrhage (SAH) is characterized by rapid development of neuron apoptosis and dysregulated inflammatory response. Microglia efferocytosis plays a critical role in the clearance of apoptotic cells, attenuation of inflammation, and minimizing brain injury in various pathological conditions. Here, using a mouse SAH model, we aim to investigate whether microglia efferocytosis is involved in post-SAH inflammation and to determine the underlying signaling pathway. We hypothesized that TAM receptors and their ligands regulate this process. To prove our hypothesis, the expression and cellular location of TAM (Tyro3, Axl, and Mertk) receptors and their ligands growth arrest-specific 6 (Gas6) and Protein S (ProS1) were examined by PCR, western blots, and fluorescence immunostaining. Thirty minutes after SAH, mice received an intraventricular injection of recombinant Gas6 (rGas6) or recombinant ProS1 (rPros1) and underwent evaluations of inflammatory mediator expression, neurological deficits, and blood-brain barrier integrity at 24 h. Microglia efferocytosis of apoptotic neurons was analyzed in vivo and in vitro. The potential mechanism was determined by inhibiting or knocking down TAM receptors and Rac1 by specific inhibitors or siRNA. SAH induced upregulation of Axl and its ligand Gas6. The administration of rGas6 but not rPros1 promoted microglia efferocytosis, alleviated inflammation, and ameliorated SAH-induced BBB breakdown and neurological deficits. The beneficial effects of rGas6 were arrogated by inhibiting or knocking down Axl and Rac1. We concluded that rGas6 attenuated the development of early brain injury in mice after SAH by facilitating microglia efferocytosis and preventing inflammatory response, which is partly dependent on activation of Axl and Rac1.
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Affiliation(s)
- Junjia Tang
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
- Department of Neurosurgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 201620, China
| | - Yichao Jin
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Feng Jia
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Tao Lv
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Anatol Manaenko
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Lin-Feng Zhang
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Zeyu Zhang
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Xin Qi
- Discipline of Neuroscience, Department of Physiology and Anatomy, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yajun Xue
- Department of Neurosurgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 201620, China
| | - Bin Zhao
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Xiaohua Zhang
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - John H Zhang
- Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Jianfei Lu
- Discipline of Neuroscience, Department of Physiology and Anatomy, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
- Songjiang Institute and Songjiang Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 201600, China.
| | - Qin Hu
- Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China.
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11
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Lopez-Ortiz AO, Eyo UB. Astrocytes and microglia in the coordination of CNS development and homeostasis. J Neurochem 2023:10.1111/jnc.16006. [PMID: 37985374 PMCID: PMC11102936 DOI: 10.1111/jnc.16006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 10/20/2023] [Accepted: 10/20/2023] [Indexed: 11/22/2023]
Abstract
Glia have emerged as important architects of central nervous system (CNS) development and maintenance. While traditionally glial contributions to CNS development and maintenance have been studied independently, there is growing evidence that either suggests or documents that glia may act in coordinated manners to effect developmental patterning and homeostatic functions in the CNS. In this review, we focus on astrocytes, the most abundant glia in the CNS, and microglia, the earliest glia to colonize the CNS highlighting research that documents either suggestive or established coordinated actions by these glial cells in various CNS processes including cell and/or debris clearance, neuronal survival and morphogenesis, synaptic maturation, and circuit function, angio-/vasculogenesis, myelination, and neurotransmission. Some molecular mechanisms underlying these processes that have been identified are also described. Throughout, we categorize the available evidence as either suggestive or established interactions between microglia and astrocytes in the regulation of the respective process and raise possible avenues for further research. We conclude indicating that a better understanding of coordinated astrocyte-microglial interactions in the developing and mature brain holds promise for developing effective therapies for brain pathologies where these processes are perturbed.
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Affiliation(s)
- Aída Oryza Lopez-Ortiz
- Center for Brain Immunology and Glia, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Ukpong B Eyo
- Center for Brain Immunology and Glia, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia, USA
- Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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12
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Ito T, Degawa T, Okumura N. Brazilian green propolis prevent Alzheimer's disease-like cognitive impairment induced by amyloid beta in mice. BMC Complement Med Ther 2023; 23:416. [PMID: 37978479 PMCID: PMC10656927 DOI: 10.1186/s12906-023-04247-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 11/04/2023] [Indexed: 11/19/2023] Open
Abstract
BACKGROUND The increasing incidence of cognitive impairment has become a health problem in the aging society. Owing to its antioxidant and anti-inflammatory properties, Brazilian green propolis-derived from Baccharis dracunculifolia-is anticipated to possess anticognitive properties. However, the preventive effect of Brazilian green propolis on cognitive impairment remains unexplained. This study aimed to investigate the effect of Brazilian green propolis on cognitive impairment using a mouse model of Alzheimer's disease (AD) induced by intracerebroventricular injection of amyloid beta (Aβ)25‒35. METHODS Five-week-old male Slc:ddY mice were randomly divided into five groups (n = 8). The groups were pretreated with vehicle and propolis at a dose of 100, 300 and 900 mg/kg body weight for 8 days, then AD-like phenotypes were induced by intracerebroventricular (ICV) injection of Aβ25‒35. A sham operation group was set as the control. Memory and learning ability were measured at 7 to 8 days after ICV injection. Gene expression and histological studies were performed at the endpoint of the study. RESULTS In a passive avoidance test, the administration of Brazilian green propolis prevented the impairment of learning and memory function. Furthermore, comprehensive gene expression analysis in the hippocampus and forebrain cortex revealed that Brazilian green propolis suppressed Aβ25-35-induced inflammatory and immune responses. In particular, Brazilian green propolis prevented alterations in gene expressions of microglial and astrocytic markers such as Trem2 and Lcn2 induced by Aβ25‒35 injection, suggesting the suppression of excessive activation of glial cells in the brain. In addition, Brazilian green propolis suppressed the elevation of plasma interleukin (IL)-6 levels induced by Aβ25‒35 injection. CONCLUSIONS The results suggest that the prophylactic administration of Brazilian green propolis has a preventive effect against AD by suppressing excessive inflammation and immune response in glial cells. To our knowledge, this study is the first to demonstrate that Brazilian green propolis may inhibit the hyperactivation of microglia and astrocytes as a mechanism of action to prevent AD. Thus, it is a promising ingredient for preventing AD-type dementia.
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Affiliation(s)
- Takashi Ito
- Institute for Bee Products & Health Science, Yamada Bee Company, Inc, Okayama, Japan
| | - Tomomi Degawa
- Institute for Bee Products & Health Science, Yamada Bee Company, Inc, Okayama, Japan
| | - Nobuaki Okumura
- Institute for Bee Products & Health Science, Yamada Bee Company, Inc, Okayama, Japan.
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13
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Burstyn-Cohen T, Fresia R. TAM receptors in phagocytosis: Beyond the mere internalization of particles. Immunol Rev 2023; 319:7-26. [PMID: 37596991 DOI: 10.1111/imr.13267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/18/2023] [Indexed: 08/21/2023]
Abstract
TYRO3, AXL, and MERTK constitute the TAM family of receptor tyrosine kinases, activated by their ligands GAS6 and PROS1. TAMs are necessary for adult homeostasis in the immune, nervous, reproductive, skeletal, and vascular systems. Among additional cellular functions employed by TAMs, phagocytosis is central for tissue health. TAM receptors are dominant in providing phagocytes with the molecular machinery necessary to engulf diverse targets, including apoptotic cells, myelin debris, and portions of live cells in a phosphatidylserine-dependent manner. Simultaneously, TAMs drive the release of anti-inflammatory and tissue repair molecules. Disruption of the TAM-driven phagocytic pathway has detrimental consequences, resulting in autoimmunity, male infertility, blindness, and disrupted vascular integrity, and which is thought to contribute to neurodegenerative diseases. Although structurally and functionally redundant, the TAM receptors and ligands underlie complex signaling cascades, of which several key aspects are yet to be elucidated. We discuss similarities and differences between TAMs and other phagocytic pathways, highlight future directions and how TAMs can be harnessed therapeutically to modulate phagocytosis.
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Affiliation(s)
- Tal Burstyn-Cohen
- The Institute for Biomedical and Oral Research, Faculty of Dental Medicine, The Hebrew University, Jerusalem, Israel
| | - Roberta Fresia
- The Institute for Biomedical and Oral Research, Faculty of Dental Medicine, The Hebrew University, Jerusalem, Israel
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14
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Lana D, Magni G, Landucci E, Wenk GL, Pellegrini-Giampietro DE, Giovannini MG. Phenomic Microglia Diversity as a Druggable Target in the Hippocampus in Neurodegenerative Diseases. Int J Mol Sci 2023; 24:13668. [PMID: 37761971 PMCID: PMC10531074 DOI: 10.3390/ijms241813668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/31/2023] [Accepted: 09/02/2023] [Indexed: 09/29/2023] Open
Abstract
Phenomics, the complexity of microglia phenotypes and their related functions compels the continuous study of microglia in disease animal models to find druggable targets for neurodegenerative disorders. Activation of microglia was long considered detrimental for neuron survival, but more recently it has become apparent that the real scenario of microglia morphofunctional diversity is far more complex. In this review, we discuss the recent literature on the alterations in microglia phenomics in the hippocampus of animal models of normal brain aging, acute neuroinflammation, ischemia, and neurodegenerative disorders, such as AD. Microglia undergo phenomic changes consisting of transcriptional, functional, and morphological changes that transform them into cells with different properties and functions. The classical subdivision of microglia into M1 and M2, two different, all-or-nothing states is too simplistic, and does not correspond to the variety of phenotypes recently discovered in the brain. We will discuss the phenomic modifications of microglia focusing not only on the differences in microglia reactivity in the diverse models of neurodegenerative disorders, but also among different areas of the brain. For instance, in contiguous and highly interconnected regions of the rat hippocampus, microglia show a differential, finely regulated, and region-specific reactivity, demonstrating that microglia responses are not uniform, but vary significantly from area to area in response to insults. It is of great interest to verify whether the differences in microglia reactivity may explain the differential susceptibility of different brain areas to insults, and particularly the higher sensitivity of CA1 pyramidal neurons to inflammatory stimuli. Understanding the spatiotemporal heterogeneity of microglia phenomics in health and disease is of paramount importance to find new druggable targets for the development of novel microglia-targeted therapies in different CNS disorders. This will allow interventions in three different ways: (i) by suppressing the pro-inflammatory properties of microglia to limit the deleterious effect of their activation; (ii) by modulating microglia phenotypic change to favor anti-inflammatory properties; (iii) by influencing microglia priming early in the disease process.
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Affiliation(s)
- Daniele Lana
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
| | - Giada Magni
- Institute of Applied Physics “Nello Carrara”, National Research Council (IFAC-CNR), Via Madonna del Piano 10, 50019 Florence, Italy;
| | - Elisa Landucci
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
| | - Gary L. Wenk
- Department of Psychology, The Ohio State University, Columbus, OH 43210, USA;
| | - Domenico Edoardo Pellegrini-Giampietro
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
| | - Maria Grazia Giovannini
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
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15
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Yu C, Deng XJ, Xu D. Microglia in epilepsy. Neurobiol Dis 2023; 185:106249. [PMID: 37536386 DOI: 10.1016/j.nbd.2023.106249] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/07/2023] [Accepted: 07/31/2023] [Indexed: 08/05/2023] Open
Abstract
Epilepsy is one of most common chronic neurological disorders, and the antiseizure medications developed by targeting neurocentric mechanisms have not effectively reduced the proportion of patients with drug-resistant epilepsy. Further exploration of the cellular or molecular mechanism of epilepsy is expected to provide new options for treatment. Recently, more and more researches focus on brain network components other than neurons, among which microglia have attracted much attention for their diverse biological functions. As the resident immune cells of the central nervous system, microglia have highly plastic transcription, morphology and functional characteristics, which can change dynamically in a context-dependent manner during the progression of epilepsy. In the pathogenesis of epilepsy, highly reactive microglia interact with other components in the epileptogenic network by performing crucial functions such as secretion of soluble factors and phagocytosis, thus continuously reshaping the landscape of the epileptic brain microenvironment. Indeed, microglia appear to be both pro-epileptic and anti-epileptic under the different spatiotemporal contexts of disease, rendering interventions targeting microglia biologically complex and challenging. This comprehensive review critically summarizes the pathophysiological role of microglia in epileptic brain homeostasis alterations and explores potential therapeutic or modulatory targets for epilepsy targeting microglia.
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Affiliation(s)
- Cheng Yu
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, Hubei Province 430022, China
| | - Xue-Jun Deng
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, Hubei Province 430022, China
| | - Da Xu
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Avenue, Wuhan, Hubei Province 430022, China.
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16
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Sola-Sevilla N, Mesa-Lombardo A, Aleixo M, Expósito S, Diaz-Perdigón T, Azqueta A, Zamani F, Suzuki T, Maioli S, Eroli F, Matton A, Ramírez MJ, Solas M, Tordera RM, Martín ED, Puerta E. SIRT2 Inhibition Rescues Neurodegenerative Pathology but Increases Systemic Inflammation in a Transgenic Mouse Model of Alzheimer's Disease. J Neuroimmune Pharmacol 2023; 18:529-550. [PMID: 37698780 PMCID: PMC10577113 DOI: 10.1007/s11481-023-10084-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 08/18/2023] [Indexed: 09/13/2023]
Abstract
Sirtuin 2 (SIRT2) has been proposed to have a central role on aging, inflammation, cancer and neurodegenerative diseases; however, its specific function remains controversial. Recent studies propose SIRT2 pharmacological inhibition as a therapeutic strategy for several neurodegenerative diseases including Alzheimer's disease (AD). Surprisingly, none of these published studies regarding the potential interest of SIRT2 inhibition has assessed the peripheral adverse side consequences of this treatment. In this study, we demonstrate that the specific SIRT2 inhibitor, the compound 33i, does not exhibit genotoxic or mutagenic properties. Moreover, pharmacological treatment with 33i, improved cognitive dysfunction and long-term potentiation, reducing amyloid pathology and neuroinflammation in the APP/PS1 AD mouse model. However, this treatment increased peripheral levels of the inflammatory cytokines IL-1β, TNF, IL-6 and MCP-1. Accordingly, peripheral SIRT2 inhibition with the blood brain barrier impermeable compound AGK-2, worsened the cognitive capacities and increased systemic inflammation. The analysis of human samples revealed that SIRT2 is increased in the brain but not in the serum of AD patients. These results suggest that, although SIRT2 pharmacological inhibition may have beneficial consequences in neurodegenerative diseases, its pharmacological inhibition at the periphery would not be recommended and the systemic adverse side effects should be considered. This information is essential to maximize the therapeutic potential of SIRT2 inhibition not only for AD but also for other neurodegenerative diseases.
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Affiliation(s)
- Noemi Sola-Sevilla
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | - Alberto Mesa-Lombardo
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
- Department of Anatomy, Histology and Neurosciences, Medical School, Autonoma University of Madrid, 28029, Madrid, Spain
| | - Mikel Aleixo
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | - Sara Expósito
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Teresa Diaz-Perdigón
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | - Amaya Azqueta
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | | | | | - Silvia Maioli
- Department of Neurobiology, Care Sciences and Society, Division of Neurogeriatrics, Center for Alzheimer Research, Karolinska Institutet, Stockholm, Sweden
| | - Francesca Eroli
- Department of Neurobiology, Care Sciences and Society, Division of Neurogeriatrics, Center for Alzheimer Research, Karolinska Institutet, Stockholm, Sweden
| | - Anna Matton
- Department of Neurobiology, Care Sciences and Society, Division of Neurogeriatrics, Center for Alzheimer Research, Karolinska Institutet, Stockholm, Sweden
| | - Maria J Ramírez
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | - Maite Solas
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | - Rosa M Tordera
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain
| | - Eduardo D Martín
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Elena Puerta
- Department of Pharmacology and Toxicology, University of Navarra, Navarra Institute for Health Research (IdiSNA), C/ Irunlarrea, 1, 31008, Pamplona, Spain.
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17
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Andrews SJ, Renton AE, Fulton-Howard B, Podlesny-Drabiniok A, Marcora E, Goate AM. The complex genetic architecture of Alzheimer's disease: novel insights and future directions. EBioMedicine 2023; 90:104511. [PMID: 36907103 PMCID: PMC10024184 DOI: 10.1016/j.ebiom.2023.104511] [Citation(s) in RCA: 63] [Impact Index Per Article: 63.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/20/2023] [Indexed: 03/12/2023] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is a complex multifactorial neurodegenerative disorder and the most common form of dementia. AD is highly heritable, with heritability estimates of ∼70% from twin studies. Progressively larger genome-wide association studies (GWAS) have continued to expand our knowledge of AD/dementia genetic architecture. Until recently these efforts had identified 39 disease susceptibility loci in European ancestry populations. RECENT DEVELOPMENTS Two new AD/dementia GWAS have dramatically expanded the sample sizes and the number of disease susceptibility loci. The first increased total sample size to 1,126,563-with an effective sample size of 332,376-by predominantly including new biobank and population-based dementia datasets. The second, expands on an earlier GWAS from the International Genomics of Alzheimer's Project (IGAP) by increasing the number of clinically-defined AD cases/controls in addition to incorporating biobank dementia datasets, resulting in a total sample size to 788,989 and an effective sample size of 382,472. Collectively both GWAS identified 90 independent variants across 75 AD/dementia susceptibility loci, including 42 novel loci. Pathway analyses indicate the susceptibility loci are enriched for genes involved in amyloid plaque and neurofibrillary tangle formation, cholesterol metabolism, endocytosis/phagocytosis, and the innate immune system. Gene prioritization efforts for the novel loci identified 62 candidate causal genes. Many of the candidate genes from known and newly discovered loci play key roles in macrophages and highlight phagocytic clearance of cholesterol-rich brain tissue debris by microglia (efferocytosis) as a core pathogenetic hub and putative therapeutic target for AD. WHERE NEXT?: While GWAS in European ancestry populations have substantially enhanced our understanding of AD genetic architecture, heritability estimates from population based GWAS cohorts are markedly smaller than those from twin studies. While this missing heritability is likely due to a combination of factors, it highlights that our understanding of AD genetic architecture and genetic risk mechanisms remains incomplete. These knowledge gaps result from several underexplored areas in AD research. First, rare variants remain understudied due to methodological issues in identifying them and the cost of generating sufficiently powered whole exome/genome sequencing datasets. Second, sample sizes of non-European ancestry populations in AD GWAS remain small. Third, GWAS of AD neuroimaging and cerebrospinal fluid endophenotypes remains limited due to low compliance and high costs associated with measuring amyloid-β and tau levels and other disease-relevant biomarkers. Studies generating sequencing data, including diverse populations, and incorporating blood-based AD biomarkers are set to substantially improve our knowledge of AD genetic architecture.
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Affiliation(s)
- Shea J Andrews
- Department of Psychiatry and Behavioral Sciences, University of California San Francisco, San Francisco, CA, USA.
| | - Alan E Renton
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Brian Fulton-Howard
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Anna Podlesny-Drabiniok
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Edoardo Marcora
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Alison M Goate
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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18
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Escoubas CC, Dorman LC, Nguyen PT, Lagares-Linares C, Nakajo H, Anderson SR, Cuevas B, Vainchtein ID, Silva NJ, Xiao Y, Lidsky PV, Wang EY, Taloma SE, Nakao-Inoue H, Schwer B, Andino R, Nowakowski TJ, Molofsky AV. Type I interferon responsive microglia shape cortical development and behavior. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2021.04.29.441889. [PMID: 35233577 PMCID: PMC8887080 DOI: 10.1101/2021.04.29.441889] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Microglia are brain resident phagocytes that can engulf synaptic components and extracellular matrix as well as whole neurons. However, whether there are unique molecular mechanisms that regulate these distinct phagocytic states is unknown. Here we define a molecularly distinct microglial subset whose function is to engulf neurons in the developing brain. We transcriptomically identified a cluster of Type I interferon (IFN-I) responsive microglia that expanded 20-fold in the postnatal day 5 somatosensory cortex after partial whisker deprivation, a stressor that accelerates neural circuit remodeling. In situ, IFN-I responsive microglia were highly phagocytic and actively engulfed whole neurons. Conditional deletion of IFN-I signaling (Ifnar1fl/fl) in microglia but not neurons resulted in dysmorphic microglia with stalled phagocytosis and an accumulation of neurons with double strand DNA breaks, a marker of cell stress. Conversely, exogenous IFN-I was sufficient to drive neuronal engulfment by microglia and restrict the accumulation of damaged neurons. IFN-I deficient mice had excess excitatory neurons in the developing somatosensory cortex as well as tactile hypersensitivity to whisker stimulation. These data define a molecular mechanism through which microglia engulf neurons during a critical window of brain development. More broadly, they reveal key homeostatic roles of a canonical antiviral signaling pathway in brain development.
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Affiliation(s)
- Caroline C. Escoubas
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Leah C. Dorman
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- Department of Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA
| | - Phi T. Nguyen
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- Department of Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA
| | - Christian Lagares-Linares
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Haruna Nakajo
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Sarah R. Anderson
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Beatriz Cuevas
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- Department of Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA
| | - Ilia D. Vainchtein
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Nicholas J. Silva
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Yinghong Xiao
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA
| | - Peter V. Lidsky
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA
| | - Ellen Y. Wang
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- UCSF SRTP program, University of California, San Francisco, San Francisco, CA
| | - Sunrae E. Taloma
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- Department of Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA
| | - Hiromi Nakao-Inoue
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
| | - Bjoern Schwer
- Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA
- Department of Neurosurgery, University of California, San Francisco, San Francisco, CA
| | - Raul Andino
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA
| | - Tomasz J. Nowakowski
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA
- Department of Anatomy, University of California, San Francisco, San Francisco, CA
- Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA
- Chan-Zuckerberg Biohub, San Francisco, CA
| | - Anna V. Molofsky
- Department of Psychiatry and Behavioral Sciences/ Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA
- Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA
- Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA
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Sierra-Martín A, Navascués J, Neubrand VE, Sepúlveda MR, Martín-Oliva D, Cuadros MA, Marín-Teva JL. LPS-stimulated microglial cells promote ganglion cell death in organotypic cultures of quail embryo retina. Front Cell Neurosci 2023; 17:1120400. [PMID: 37006469 PMCID: PMC10050569 DOI: 10.3389/fncel.2023.1120400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 02/27/2023] [Indexed: 03/17/2023] Open
Abstract
During development microglia colonize the central nervous system (CNS) and play an important role in programmed cell death, not only because of their ability to remove dead cells by phagocytosis, but also because they can promote the death of neuronal and glial cells. To study this process, we used as experimental systems the developing in situ quail embryo retina and organotypic cultures of quail embryo retina explants (QEREs). In both systems, immature microglia show an upregulation of certain inflammatory markers, e.g., inducible NO synthase (iNOS), and nitric oxide (NO) under basal conditions, which can be further enhanced with LPS-treatment. Hence, we investigated in the present study the role of microglia in promoting ganglion cell death during retinal development in QEREs. Results showed that LPS-stimulation of microglia in QEREs increases (i) the percentage of retinal cells with externalized phosphatidylserine, (ii) the frequency of phagocytic contacts between microglial and caspase-3-positive ganglion cells, (iii) cell death in the ganglion cell layer, and (iv) microglial production of reactive oxygen/nitrogen species, such as NO. Furthermore, iNOS inhibition by L-NMMA decreases cell death of ganglion cells and increases the number of ganglion cells in LPS-treated QEREs. These data demonstrate that LPS-stimulated microglia induce ganglion cell death in cultured QEREs by a NO-dependent mechanism. The fact that phagocytic contacts between microglial and caspase-3-positive ganglion cells increase suggests that this cell death might be mediated by microglial engulfment, although a phagocytosis-independent mechanism cannot be excluded.
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20
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Morrison VE, Bix GJ. The meal Maketh the Microglia: Why studying microglial phagocytosis is critical to stroke research. Neurochem Int 2023; 164:105488. [PMID: 36707032 DOI: 10.1016/j.neuint.2023.105488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 01/15/2023] [Accepted: 01/15/2023] [Indexed: 01/25/2023]
Affiliation(s)
- Vivianne E Morrison
- Tulane University School of Medicine Center for Clinical Neuroscience Research Center, United States
| | - Gregory J Bix
- Tulane University School of Medicine Center for Clinical Neuroscience Research Center, United States.
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Xing YL, Poh J, Chuang BH, Moradi K, Mitew S, Richardson WD, Kilpatrick TJ, Osanai Y, Merson TD. High-efficiency pharmacogenetic ablation of oligodendrocyte progenitor cells in the adult mouse CNS. CELL REPORTS METHODS 2023; 3:100414. [PMID: 36936074 PMCID: PMC10014347 DOI: 10.1016/j.crmeth.2023.100414] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 10/11/2022] [Accepted: 01/30/2023] [Indexed: 03/02/2023]
Abstract
Approaches to investigate adult oligodendrocyte progenitor cells (OPCs) by targeted cell ablation in the rodent CNS have limitations in the extent and duration of OPC depletion. We have developed a pharmacogenetic approach for conditional OPC ablation, eliminating >98% of OPCs throughout the brain. By combining recombinase-based transgenic and viral strategies for targeting OPCs and ventricular-subventricular zone (V-SVZ)-derived neural precursor cells (NPCs), we found that new PDGFRA-expressing cells born in the V-SVZ repopulated the OPC-deficient brain starting 12 days after OPC ablation. Our data reveal that OPC depletion induces V-SVZ-derived NPCs to generate vast numbers of PDGFRA+NG2+ cells with the capacity to proliferate and migrate extensively throughout the dorsal anterior forebrain. Further application of this approach to ablate OPCs will advance knowledge of the function of both OPCs and oligodendrogenic NPCs in health and disease.
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Affiliation(s)
- Yao Lulu Xing
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Jasmine Poh
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Bernard H.A. Chuang
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Kaveh Moradi
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC 3052, Australia
| | - Stanislaw Mitew
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - William D. Richardson
- Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
| | - Trevor J. Kilpatrick
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC 3052, Australia
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia
| | - Yasuyuki Osanai
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
| | - Tobias D. Merson
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia
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22
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Saavedra J, Nascimento M, Liz MA, Cardoso I. Key brain cell interactions and contributions to the pathogenesis of Alzheimer's disease. Front Cell Dev Biol 2022; 10:1036123. [PMID: 36523504 PMCID: PMC9745159 DOI: 10.3389/fcell.2022.1036123] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Accepted: 11/14/2022] [Indexed: 06/22/2024] Open
Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide, with the two major hallmarks being the deposition of extracellular β-amyloid (Aβ) plaques and of intracellular neurofibrillary tangles (NFTs). Additionally, early pathological events such as cerebrovascular alterations, a compromised blood-brain barrier (BBB) integrity, neuroinflammation and synaptic dysfunction, culminate in neuron loss and cognitive deficits. AD symptoms reflect a loss of neuronal circuit integrity in the brain; however, neurons do not operate in isolation. An exclusively neurocentric approach is insufficient to understand this disease, and the contribution of other brain cells including astrocytes, microglia, and vascular cells must be integrated in the context. The delicate balance of interactions between these cells, required for healthy brain function, is disrupted during disease. To design successful therapies, it is critical to understand the complex brain cellular connections in AD and the temporal sequence of their disturbance. In this review, we discuss the interactions between different brain cells, from physiological conditions to their pathological reactions in AD, and how this basic knowledge can be crucial for developing new therapeutic strategies.
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Affiliation(s)
- Joana Saavedra
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | - Mariana Nascimento
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Faculdade de Medicina, Universidade do Porto, Porto, Portugal
| | - Márcia A. Liz
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
| | - Isabel Cardoso
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal
- Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
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Abstract
Neurons in the developing brain undergo extensive structural refinement as nascent circuits adopt their mature form. This physical transformation of neurons is facilitated by the engulfment and degradation of axonal branches and synapses by surrounding glial cells, including microglia and astrocytes. However, the small size of phagocytic organelles and the complex, highly ramified morphology of glia have made it difficult to define the contribution of these and other glial cell types to this crucial process. Here, we used large-scale, serial section transmission electron microscopy (TEM) with computational volume segmentation to reconstruct the complete 3D morphologies of distinct glial types in the mouse visual cortex, providing unprecedented resolution of their morphology and composition. Unexpectedly, we discovered that the fine processes of oligodendrocyte precursor cells (OPCs), a population of abundant, highly dynamic glial progenitors, frequently surrounded small branches of axons. Numerous phagosomes and phagolysosomes (PLs) containing fragments of axons and vesicular structures were present inside their processes, suggesting that OPCs engage in axon pruning. Single-nucleus RNA sequencing from the developing mouse cortex revealed that OPCs express key phagocytic genes at this stage, as well as neuronal transcripts, consistent with active axon engulfment. Although microglia are thought to be responsible for the majority of synaptic pruning and structural refinement, PLs were ten times more abundant in OPCs than in microglia at this stage, and these structures were markedly less abundant in newly generated oligodendrocytes, suggesting that OPCs contribute substantially to the refinement of neuronal circuits during cortical development.
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24
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Sun Y, Wang Y, Ye F, Cui V, Lin D, Shi H, Zhang Y, Wu A, Wei C. SIRT1 activation attenuates microglia-mediated synaptic engulfment in postoperative cognitive dysfunction. Front Aging Neurosci 2022; 14:943842. [PMID: 36437988 PMCID: PMC9685341 DOI: 10.3389/fnagi.2022.943842] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 09/14/2022] [Indexed: 07/21/2023] Open
Abstract
BACKGROUND Postoperative cognitive dysfunction (POCD) is a debilitating neurological complication in surgical patients. Current research has focused mainly on microglial activation, but less is known about the resultant neuronal synaptic changes. Recent studies have suggested that Sirtuin-1 (SIRT1) plays a critical role in several different neurological disorders via its involvement in microglial activation. In this study, we evaluate the effects of SIRT1 activation in a POCD mouse model. MATERIALS AND METHODS Exploratory laparotomy was performed in mice aged 12-14 months under sevoflurane anesthesia to establish our animal POCD model. Transcriptional changes in the hippocampus after anesthesia and surgery were evaluated by RNA sequencing. SIRT1 expression was verified by Western Blot. Mice were treated with SIRT1 agonist SRT1720 or vehicle after surgery. Changes in microglia morphology, microglial phagocytosis, presence of dystrophic neurites, and dendritic spine density were evaluated. Cognitive performance was evaluated using the Y maze and Morris water maze (MWM). RESULTS Sirtuin-1 expression levels were downregulated in POCD. Exposure to anesthesia and surgery lead to alteration in microglia morphology, increased synaptic engulfment, dendritic spine loss, and cognitive deficits. These effects were alleviated by SRT1720 administration. CONCLUSION This study suggests an important neuroprotective role for SIRT1 in POCD pathogenesis. Increasing SIRT1 function represents a promising therapeutic strategy for prevention and treatment of POCD.
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Affiliation(s)
- Yi Sun
- Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Yuzhu Wang
- Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Fan Ye
- Department of Anesthesiology, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Xiangyang, China
| | - Victoria Cui
- Department of General Surgery, MedStar Georgetown University Hospital, Washington, DC, United States
| | - Dandan Lin
- Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Hui Shi
- Department of Clinical Psychology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing, China
| | - Anshi Wu
- Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Changwei Wei
- Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
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25
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Romero-Molina C, Garretti F, Andrews SJ, Marcora E, Goate AM. Microglial efferocytosis: Diving into the Alzheimer's disease gene pool. Neuron 2022; 110:3513-3533. [PMID: 36327897 DOI: 10.1016/j.neuron.2022.10.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/04/2022] [Accepted: 10/07/2022] [Indexed: 11/07/2022]
Abstract
Genome-wide association studies and functional genomics studies have linked specific cell types, genes, and pathways to Alzheimer's disease (AD) risk. In particular, AD risk alleles primarily affect the abundance or structure, and thus the activity, of genes expressed in macrophages, strongly implicating microglia (the brain-resident macrophages) in the etiology of AD. These genes converge on pathways (endocytosis/phagocytosis, cholesterol metabolism, and immune response) with critical roles in core macrophage functions such as efferocytosis. Here, we review these pathways, highlighting relevant genes identified in the latest AD genetics and genomics studies, and describe how they may contribute to AD pathogenesis. Investigating the functional impact of AD-associated variants and genes in microglia is essential for elucidating disease risk mechanisms and developing effective therapeutic approaches.
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Affiliation(s)
- Carmen Romero-Molina
- Ronald M. Loeb Center for Alzheimer's Disease, 1 Gustave L. Levy Place, New York, NY 10029-6574, USA; Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Francesca Garretti
- Ronald M. Loeb Center for Alzheimer's Disease, 1 Gustave L. Levy Place, New York, NY 10029-6574, USA; Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Shea J Andrews
- Ronald M. Loeb Center for Alzheimer's Disease, 1 Gustave L. Levy Place, New York, NY 10029-6574, USA; Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Psychiatry and Behavioral Sciences, University of California San Francisco, San Francisco, CA, USA
| | - Edoardo Marcora
- Ronald M. Loeb Center for Alzheimer's Disease, 1 Gustave L. Levy Place, New York, NY 10029-6574, USA; Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Alison M Goate
- Ronald M. Loeb Center for Alzheimer's Disease, 1 Gustave L. Levy Place, New York, NY 10029-6574, USA; Department of Genetics & Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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26
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Li S, Wernersbach I, Harms GS, Schäfer MKE. Microglia subtypes show substrate- and time-dependent phagocytosis preferences and phenotype plasticity. Front Immunol 2022. [PMID: 36105813 DOI: 10.3389/fimmu.2022b.945485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Microglia are phagocytosis-competent CNS cells comprising a spectrum of subtypes with beneficial and/or detrimental functions in acute and chronic neurodegenerative disorders. The heterogeneity of microglia suggests differences in phagocytic activity and phenotype plasticity between microglia subtypes. To study these issues, primary murine glial cultures were cultivated in the presence of serum, different growth factors and cytokines to obtain M0-like, M1-like, and M2-like microglia as confirmed by morphology, M1/M2 gene marker expression, and nitric oxide assay. Single-cell analysis after 3 hours of phagocytosis of E.coli particles or IgG-opsonized beads showed equal internalization by M0-like microglia, whereas M1-like microglia preferably internalized E.coli particles and M2-like microglia preferably internalized IgG beads, suggesting subtype-specific preferences for different phagocytosis substrates. Time-lapse live-cells imaging over 16 hours revealed further differences between microglia subtypes in phagocytosis preference and internalization dynamics. M0- and, more efficiently, M1-like microglia continuously internalized E.coli particles for 16 hours, whereas M2-like microglia discontinued internalization after approximately 8 hours. IgG beads were continuously internalized by M0- and M1-like microglia but strikingly less by M2-like microglia. M2-like microglia initially showed continuous internalization similar to M0-like microglia but again discontinuation of internalization after 8 hours suggesting that the time of substrate exposure differently affect microglia subtypes. After prolonged exposure to E.coli particles or IgG beads for 5 days all microglia subtypes showed increased internalization of E.coli particles compared to IgG beads, increased nitric oxide release and up-regulation of M1 gene markers, irrespectively of the phagocytosis substrate, suggesting phenotype plasticity. In summary, microglia subtypes show substrate- and time-dependent phagocytosis preferences and phenotype plasticity. The results suggest that prolonged phagocytosis substrate exposure enhances M1-like profiles and M2-M1 repolarization of microglia. Similar processes may also take place in conditions of acute and chronic brain insults when microglia encounter different types of phagocytic substrates.
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Affiliation(s)
- Shuailong Li
- Department of Anesthesiology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Isa Wernersbach
- Department of Anesthesiology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Gregory S Harms
- Cell Biology Unit, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany.,Departments of Biology and Physics, Wilkes University, Wilkes Barre, PA, United States
| | - Michael K E Schäfer
- Department of Anesthesiology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany.,Focus Program Translational Neurosciences (FTN), Johannes Gutenberg-University Mainz, Mainz, Germany.,Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
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27
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Li S, Wernersbach I, Harms GS, Schäfer MKE. Microglia subtypes show substrate- and time-dependent phagocytosis preferences and phenotype plasticity. Front Immunol 2022; 13:945485. [PMID: 36105813 PMCID: PMC9465456 DOI: 10.3389/fimmu.2022.945485] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 08/04/2022] [Indexed: 11/16/2022] Open
Abstract
Microglia are phagocytosis-competent CNS cells comprising a spectrum of subtypes with beneficial and/or detrimental functions in acute and chronic neurodegenerative disorders. The heterogeneity of microglia suggests differences in phagocytic activity and phenotype plasticity between microglia subtypes. To study these issues, primary murine glial cultures were cultivated in the presence of serum, different growth factors and cytokines to obtain M0-like, M1-like, and M2-like microglia as confirmed by morphology, M1/M2 gene marker expression, and nitric oxide assay. Single-cell analysis after 3 hours of phagocytosis of E.coli particles or IgG-opsonized beads showed equal internalization by M0-like microglia, whereas M1-like microglia preferably internalized E.coli particles and M2-like microglia preferably internalized IgG beads, suggesting subtype-specific preferences for different phagocytosis substrates. Time-lapse live-cells imaging over 16 hours revealed further differences between microglia subtypes in phagocytosis preference and internalization dynamics. M0- and, more efficiently, M1-like microglia continuously internalized E.coli particles for 16 hours, whereas M2-like microglia discontinued internalization after approximately 8 hours. IgG beads were continuously internalized by M0- and M1-like microglia but strikingly less by M2-like microglia. M2-like microglia initially showed continuous internalization similar to M0-like microglia but again discontinuation of internalization after 8 hours suggesting that the time of substrate exposure differently affect microglia subtypes. After prolonged exposure to E.coli particles or IgG beads for 5 days all microglia subtypes showed increased internalization of E.coli particles compared to IgG beads, increased nitric oxide release and up-regulation of M1 gene markers, irrespectively of the phagocytosis substrate, suggesting phenotype plasticity. In summary, microglia subtypes show substrate- and time-dependent phagocytosis preferences and phenotype plasticity. The results suggest that prolonged phagocytosis substrate exposure enhances M1-like profiles and M2-M1 repolarization of microglia. Similar processes may also take place in conditions of acute and chronic brain insults when microglia encounter different types of phagocytic substrates.
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Affiliation(s)
- Shuailong Li
- Department of Anesthesiology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Isa Wernersbach
- Department of Anesthesiology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Gregory S. Harms
- Cell Biology Unit, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
- Departments of Biology and Physics, Wilkes University, Wilkes Barre, PA, United States
| | - Michael K. E. Schäfer
- Department of Anesthesiology, University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
- Focus Program Translational Neurosciences (FTN), Johannes Gutenberg-University Mainz, Mainz, Germany
- Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany
- *Correspondence: Michael K. E. Schäfer,
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28
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Abstract
Mounting evidence indicates that microglia, which are the resident immune cells of the brain, play critical roles in a diverse array of neurodevelopmental processes required for proper brain maturation and function. This evidence has ultimately led to growing speculation that microglial dysfunction may play a role in neurodevelopmental disorder (NDD) pathoetiology. In this review, we first provide an overview of how microglia mechanistically contribute to the sculpting of the developing brain and neuronal circuits. To provide an example of how disruption of microglial biology impacts NDD development, we also highlight emerging evidence that has linked microglial dysregulation to autism spectrum disorder pathogenesis. In recent years, there has been increasing interest in how the gut microbiome shapes microglial biology. In the last section of this review, we put a spotlight on this burgeoning area of microglial research and discuss how microbiota-dependent modulation of microglial biology is currently thought to influence NDD progression.
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Affiliation(s)
- John R Lukens
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia, USA;
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, Virginia, USA
| | - Ukpong B Eyo
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia, USA;
- Center for Brain Immunology and Glia, University of Virginia, Charlottesville, Virginia, USA
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29
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Anderson SR, Roberts JM, Ghena N, Irvin EA, Schwakopf J, Cooperstein IB, Bosco A, Vetter ML. Neuronal apoptosis drives remodeling states of microglia and shifts in survival pathway dependence. eLife 2022; 11:e76564. [PMID: 35481836 PMCID: PMC9071266 DOI: 10.7554/elife.76564] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 04/27/2022] [Indexed: 01/13/2023] Open
Abstract
Microglia serve critical remodeling roles that shape the developing nervous system, responding to the changing neural environment with phagocytosis or soluble factor secretion. Recent single-cell sequencing (scRNAseq) studies have revealed the context-dependent diversity in microglial properties and gene expression, but the cues promoting this diversity are not well defined. Here, we ask how interactions with apoptotic neurons shape microglial state, including lysosomal and lipid metabolism gene expression and dependence on Colony-stimulating factor 1 receptor (CSF1R) for survival. Using early postnatal mouse retina, a CNS region undergoing significant developmental remodeling, we performed scRNAseq on microglia from mice that are wild-type, lack neuronal apoptosis (Bax KO), or are treated with CSF1R inhibitor (PLX3397). We find that interactions with apoptotic neurons drive multiple microglial remodeling states, subsets of which are resistant to CSF1R inhibition. We find that TAM receptor Mer and complement receptor 3 are required for clearance of apoptotic neurons, but that Mer does not drive expression of remodeling genes. We show TAM receptor Axl is negligible for phagocytosis or remodeling gene expression but is consequential for microglial survival in the absence of CSF1R signaling. Thus, interactions with apoptotic neurons shift microglia toward distinct remodeling states and through Axl, alter microglial dependence on survival pathway, CSF1R.
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Affiliation(s)
| | | | - Nathaniel Ghena
- Department of Neurobiology, University of UtahSalt Lake CityUnited States
- Interdepartmental Program in Neuroscience, University of UtahSalt Lake CityUnited States
| | - Emmalyn A Irvin
- Department of Neurobiology, University of UtahSalt Lake CityUnited States
| | - Joon Schwakopf
- Department of Neurobiology, University of UtahSalt Lake CityUnited States
| | | | - Alejandra Bosco
- Department of Neurobiology, University of UtahSalt Lake CityUnited States
| | - Monica L Vetter
- Department of Neurobiology, University of UtahSalt Lake CityUnited States
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30
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Thiel WA, Blume ZI, Mitchell DM. Compensatory engulfment and Müller glia reactivity in the absence of microglia. Glia 2022; 70:1402-1425. [PMID: 35451181 DOI: 10.1002/glia.24182] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 04/05/2022] [Accepted: 04/08/2022] [Indexed: 01/25/2023]
Abstract
Microglia are known for important phagocytic functions in the vertebrate retina. Reports also suggest that Müller glia have phagocytic capacity, though the relative levels and contexts in which this occurs remain to be thoroughly examined. Here, we investigate Müller glial engulfment of dying cells in the developing zebrafish retina in the presence and absence of microglia, using a genetic mutant in which microglia do not develop. We show that in normal conditions clearance of dying cells is dominated by microglia; however, Müller glia do have a limited clearance role. In retinas lacking intact microglial populations, we found a striking increase in the engulfment load assumed by the Müller glia, which displayed prominent cellular compartments containing apoptotic cells, several of which localized with the early phagosome/endosome marker Rab5. Consistent with increased engulfment, lysosomal staining was also increased in Müller glia in the absence of microglia. Increased engulfment load led to evidence of Müller glia reactivity including upregulation of gfap but did not trigger cell cycle re-entry by differentiated Müller glia. Our work provides important insight into the phagocytic capacity of Müller glia and the ability for compensatory functions and downstream effects. Therefore, effects of microglial deficiency or depletion on other glial cell types should be well-considered in experimental manipulations, in neurodegenerative disease, and in therapeutic approaches that target microglia. Our findings further justify future work to understand differential mechanisms and contexts of phagocytosis by glial cells in the central nervous system, and the significance of these mechanisms in health and disease.
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Affiliation(s)
- Whitney A Thiel
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
| | - Zachary I Blume
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
| | - Diana M Mitchell
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, USA
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31
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Fixemer S, Ameli C, Hammer G, Salamanca L, Uriarte Huarte O, Schwartz C, Gérardy JJ, Mechawar N, Skupin A, Mittelbronn M, Bouvier DS. Microglia phenotypes are associated with subregional patterns of concomitant tau, amyloid-β and α-synuclein pathologies in the hippocampus of patients with Alzheimer's disease and dementia with Lewy bodies. Acta Neuropathol Commun 2022; 10:36. [PMID: 35296366 PMCID: PMC8925098 DOI: 10.1186/s40478-022-01342-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 03/02/2022] [Indexed: 12/26/2022] Open
Abstract
The cellular alterations of the hippocampus lead to memory decline, a shared symptom between Alzheimer’s disease (AD) and dementia with Lewy Bodies (DLB) patients. However, the subregional deterioration pattern of the hippocampus differs between AD and DLB with the CA1 subfield being more severely affected in AD. The activation of microglia, the brain immune cells, could play a role in its selective volume loss. How subregional microglia populations vary within AD or DLB and across these conditions remains poorly understood. Furthermore, how the nature of the hippocampal local pathological imprint is associated with microglia responses needs to be elucidated. To this purpose, we employed an automated pipeline for analysis of 3D confocal microscopy images to assess CA1, CA3 and DG/CA4 subfields microglia responses in post-mortem hippocampal samples from late-onset AD (n = 10), DLB (n = 8) and age-matched control (CTL) (n = 11) individuals. In parallel, we performed volumetric analyses of hyperphosphorylated tau (pTau), amyloid-β (Aβ) and phosphorylated α-synuclein (pSyn) loads. For each of the 32,447 extracted microglia, 16 morphological features were measured to classify them into seven distinct morphological clusters. Our results show similar alterations of microglial morphological features and clusters in AD and DLB, but with more prominent changes in AD. We identified two distinct microglia clusters enriched in disease conditions and particularly increased in CA1 and DG/CA4 of AD and CA3 of DLB. Our study confirms frequent concomitance of pTau, Aβ and pSyn loads across AD and DLB but reveals a specific subregional pattern for each type of pathology, along with a generally increased severity in AD. Furthermore, pTau and pSyn loads were highly correlated across subregions and conditions. We uncovered tight associations between microglial changes and the subfield pathological imprint. Our findings suggest that combinations and severity of subregional pTau, Aβ and pSyn pathologies transform local microglia phenotypic composition in the hippocampus. The high burdens of pTau and pSyn associated with increased microglial alterations could be a factor in CA1 vulnerability in AD.
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32
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Cuadros MA, Sepulveda MR, Martin-Oliva D, Marín-Teva JL, Neubrand VE. Microglia and Microglia-Like Cells: Similar but Different. Front Cell Neurosci 2022; 16:816439. [PMID: 35197828 PMCID: PMC8859783 DOI: 10.3389/fncel.2022.816439] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/17/2022] [Indexed: 12/12/2022] Open
Abstract
Microglia are the tissue-resident macrophages of the central nervous parenchyma. In mammals, microglia are thought to originate from yolk sac precursors and posteriorly maintained through the entire life of the organism. However, the contribution of microglial cells from other sources should also be considered. In addition to “true” or “bona-fide” microglia, which are of embryonic origin, the so-called “microglia-like cells” are hematopoietic cells of bone marrow origin that can engraft the mature brain mainly under pathological conditions. These cells implement great parts of the microglial immune phenotype, but they do not completely adopt the “true microglia” features. Because of their pronounced similarity, true microglia and microglia-like cells are usually considered together as one population. In this review, we discuss the origin and development of these two distinct cell types and their differences. We will also review the factors determining the appearance and presence of microglia-like cells, which can vary among species. This knowledge might contribute to the development of therapeutic strategies aiming at microglial cells for the treatment of diseases in which they are involved, for example neurodegenerative disorders like Alzheimer’s and Parkinson’s diseases.
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Affiliation(s)
- Miguel A Cuadros
- Department of Cell Biology, Faculty of Science, University of Granada, Granada, Spain
| | - M Rosario Sepulveda
- Department of Cell Biology, Faculty of Science, University of Granada, Granada, Spain
| | - David Martin-Oliva
- Department of Cell Biology, Faculty of Science, University of Granada, Granada, Spain
| | - José L Marín-Teva
- Department of Cell Biology, Faculty of Science, University of Granada, Granada, Spain
| | - Veronika E Neubrand
- Department of Cell Biology, Faculty of Science, University of Granada, Granada, Spain
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33
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Konishi H, Koizumi S, Kiyama H. Phagocytic astrocytes: Emerging from the shadows of microglia. Glia 2022; 70:1009-1026. [PMID: 35142399 PMCID: PMC9305589 DOI: 10.1002/glia.24145] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 12/18/2021] [Accepted: 01/07/2022] [Indexed: 12/12/2022]
Abstract
Elimination of dead or live cells take place in both a healthy and diseased central nervous system (CNS). Dying or dead cells are quickly cleared by phagocytosis for the maintenance of a healthy CNS or for recovery after injury. Live cells or parts thereof, such as the synapses and myelin, are appropriately eliminated by phagocytosis to maintain or refine neural networks during development and adulthood. Microglia, the specific population of resident macrophages in the CNS, are classically considered as primary phagocytes; however, astrocytes have also been highlighted as phagocytes in the last decade. Phagocytic targets and receptors are reported to be mostly common between astrocytes and microglia, which raises the question of how astrocytic phagocytosis differs from microglial phagocytosis, and how these two phagocytic systems cooperate. In this review, we address the consequences of astrocytic phagocytosis, particularly focusing on these elusive points.
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Affiliation(s)
- Hiroyuki Konishi
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, University of Yamanashi, Yamanashi, Japan.,GLIA Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Hiroshi Kiyama
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Chavda V, Singh K, Patel V, Mishra M, Mishra AK. Neuronal Glial Crosstalk: Specific and Shared Mechanisms in Alzheimer’s Disease. Brain Sci 2022; 12:brainsci12010075. [PMID: 35053818 PMCID: PMC8773743 DOI: 10.3390/brainsci12010075] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/21/2021] [Accepted: 12/27/2021] [Indexed: 02/04/2023] Open
Abstract
The human brain maintains billions of neurons functional across the lifespan of the individual. The glial, supportive cells of the brain are indispensable to neuron elasticity. They undergo various states (active, reactive, macrophage, primed, resting) and carefully impose either quick repair or the cleaning of injured neurons to avoid damage extension. Identifying the failure of these interactions involving the relation of the input of glial cells to the inception and/or progression of chronic neurodegenerative diseases (ND) is crucial in identifying therapeutic options, given the well-built neuro-immune module of these diseases. In the present review, we scrutinize different interactions and important factors including direct cell–cell contact, intervention by the CD200 system, various receptors present on their surfaces, CXC3RI and TREM2, and chemokines and cytokines with special reference to Alzheimer’s disease (AD). The present review of the available literature will elucidate the contribution of microglia and astrocytes to the pathophysiology of AD, thus evidencing glial cells as obligatory transducers of pathology and superlative targets for interference.
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Affiliation(s)
- Vishal Chavda
- Division of Anesthesia, Dreamzz IVF Center and Women’s Care Hospital, Ahmedabad 382350, Gujarat, India;
| | - Kavita Singh
- Centre for Translational Research, Jiwaji University, Gwalior 474011, Madhya Pradesh, India;
| | - Vimal Patel
- Department of Pharmaceutics, Nirma University, Ahmedabad 382481, Gujarat, India;
| | - Meerambika Mishra
- Department of Infectious Diseases and Pathology, University of Florida, Gainesville, FL 32611, USA
- Correspondence: (M.M.); (A.K.M.)
| | - Awdhesh Kumar Mishra
- Department of Biotechnology, Yeungnam University, Gyeongsan 38541, Gyeongbuk, Korea
- Correspondence: (M.M.); (A.K.M.)
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35
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Abstract
Alzheimer's disease (AD) is characterized by the presence of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs), neuronal and synaptic loss and inflammation of the central nervous system (CNS). The majority of AD research has been dedicated to the understanding of two major AD hallmarks (i.e. Aβ and NFTs); however, recent genome-wide association studies (GWAS) data indicate neuroinflammation as having a critical role in late-onset AD (LOAD) development, thus unveiling a novel avenue for AD therapeutics. Recent evidence has provided much support to the innate immune system's involvement with AD progression; however, much remains to be uncovered regarding the role of glial cells, specifically microglia, in AD. Moreover, numerous variants in immune and/or microglia-related genes have been identified in whole-genome sequencing and GWAS analyses, including such genes as TREM2, CD33, APOE, API1, MS4A, ABCA7, BIN1, CLU, CR1, INPP5D, PICALM and PLCG2. In this review, we aim to provide an insight into the function of the major LOAD-associated microglia response genes.
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Affiliation(s)
- Lauren A. Jonas
- Weill Cornell, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10065, USA,Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Tanya Jain
- Weill Cornell, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10065, USA,Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Yue-Ming Li
- Weill Cornell, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10065, USA,Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
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36
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Zhao J, Zhang W, Wu T, Wang H, Mao J, Liu J, Zhou Z, Lin X, Yan H, Wang Q. Efferocytosis in the Central Nervous System. Front Cell Dev Biol 2021; 9:773344. [PMID: 34926460 PMCID: PMC8678611 DOI: 10.3389/fcell.2021.773344] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 10/25/2021] [Indexed: 11/23/2022] Open
Abstract
The effective clearance of apoptotic cells is essential for maintaining central nervous system (CNS) homeostasis and restoring homeostasis after injury. In most cases of physiological apoptotic cell death, efferocytosis prevents inflammation and other pathological conditions. When apoptotic cells are not effectively cleared, destruction of the integrity of the apoptotic cell membrane integrity, leakage of intracellular contents, and secondary necrosis may occur. Efferocytosis is the mechanism by which efferocytes quickly remove apoptotic cells from tissues before they undergo secondary necrosis. Cells with efferocytosis functions, mainly microglia, help to eliminate apoptotic cells from the CNS. Here, we discuss the impacts of efferocytosis on homeostasis, the mechanism of efferocytosis, the associations of efferocytosis failure and CNS diseases, and the current clinical applications of efferocytosis. We also identify efferocytosis as a novel potential target for exploring the causes and treatments of CNS diseases.
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Affiliation(s)
- Jiayi Zhao
- Department of Anesthesia, Zhejiang Hospital, Hangzhou, China
| | - Weiqi Zhang
- The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Tingting Wu
- The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Hongyi Wang
- The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Jialiang Mao
- The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Jian Liu
- The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Ziheng Zhou
- The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Xianfeng Lin
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Huige Yan
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Qingqing Wang
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China
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37
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Honig MG, Del Mar NA, Henderson DL, O'Neal D, Doty JB, Cox R, Li C, Perry AM, Moore BM, Reiner A. Raloxifene Modulates Microglia and Rescues Visual Deficits and Pathology After Impact Traumatic Brain Injury. Front Neurosci 2021; 15:701317. [PMID: 34776838 PMCID: PMC8585747 DOI: 10.3389/fnins.2021.701317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 09/07/2021] [Indexed: 11/29/2022] Open
Abstract
Mild traumatic brain injury (TBI) involves widespread axonal injury and activation of microglia, which initiates secondary processes that worsen the TBI outcome. The upregulation of cannabinoid type-2 receptors (CB2) when microglia become activated allows CB2-binding drugs to selectively target microglia. CB2 inverse agonists modulate activated microglia by shifting them away from the harmful pro-inflammatory M1 state toward the helpful reparative M2 state and thus can stem secondary injury cascades. We previously found that treatment with the CB2 inverse agonist SMM-189 after mild TBI in mice produced by focal cranial blast rescues visual deficits and the optic nerve axon loss that would otherwise result. We have further shown that raloxifene, which is Food and Drug Administration (FDA)-approved as an estrogen receptor modulator to treat osteoporosis, but also possesses CB2 inverse agonism, yields similar benefit in this TBI model through its modulation of microglia. As many different traumatic events produce TBI in humans, it is widely acknowledged that diverse animal models must be used in evaluating possible therapies. Here we examine the consequences of TBI created by blunt impact to the mouse head for visual function and associated pathologies and assess raloxifene benefit. We found that mice subjected to impact TBI exhibited decreases in contrast sensitivity and the B-wave of the electroretinogram, increases in light aversion and resting pupil diameter, and optic nerve axon loss, which were rescued by daily injection of raloxifene at 5 or 10 mg/ml for 2 weeks. Raloxifene treatment was associated with reduced M1 activation and/or enhanced M2 activation in retina, optic nerve, and optic tract after impact TBI. Our results suggest that the higher raloxifene dose, in particular, may be therapeutic for the optic nerve by enhancing the phagocytosis of axonal debris that would otherwise promote inflammation, thereby salvaging less damaged axons. Our current work, together with our prior studies, shows that microglial activation drives secondary injury processes after both impact and cranial blast TBI and raloxifene mitigates microglial activation and visual system injury in both cases. The results thus provide a strong basis for phase 2 human clinical trials evaluating raloxifene as a TBI therapy.
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Affiliation(s)
- Marcia G Honig
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Nobel A Del Mar
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Desmond L Henderson
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Dylan O'Neal
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - John B Doty
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Rachel Cox
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Chunyan Li
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Aaron M Perry
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Bob M Moore
- Department of Pharmaceutical Sciences, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - Anton Reiner
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN, United States.,Department of Ophthalmology, The University of Tennessee Health Science Center, Memphis, TN, United States
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38
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VanRyzin JW. Phagocytic microglia in development: Are they what they eat? Brain Behav Immun Health 2021; 18:100373. [PMID: 34761244 PMCID: PMC8566956 DOI: 10.1016/j.bbih.2021.100373] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 09/29/2021] [Accepted: 10/13/2021] [Indexed: 12/30/2022] Open
Abstract
Microglia, the innate immune cells of the brain, are indispensable for proper brain development. As professional phagocytes, microglia engulf other cells within distinct developmental niches to sculpt the architecture of the brain. Here, I highlight the age-, brain region-, and substrate-dependent diversity of developmental phagocytosis, and pose the idea that phagocytosis may, in turn, drive changes in microglia phenotype. Ultimately, phagocytosis might be just as important for shaping microglia function as it is for shaping the brain.
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Affiliation(s)
- Jonathan W VanRyzin
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD, United States
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39
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Trzeciak A, Wang YT, Perry JSA. First we eat, then we do everything else: The dynamic metabolic regulation of efferocytosis. Cell Metab 2021; 33:2126-2141. [PMID: 34433074 PMCID: PMC8568659 DOI: 10.1016/j.cmet.2021.08.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 06/07/2021] [Accepted: 08/02/2021] [Indexed: 12/13/2022]
Abstract
Clearance of apoptotic cells, or "efferocytosis," is essential for diverse processes including embryonic development, tissue turnover, organ regeneration, and immune cell development. The human body is estimated to remove approximately 1% of its body mass via apoptotic cell clearance daily. This poses several intriguing cell metabolism problems. For instance, phagocytes such as macrophages must induce or suppress metabolic pathways to find, engulf, and digest apoptotic cells. Then, phagocytes must manage the potentially burdensome biomass of the engulfed apoptotic cell. Finally, phagocytes reside in complex tissue architectures that vary in nutrient availability, the types of dying cells or debris that require clearance, and the neighboring cells they interact with. Here, we review advances in our understanding of these three key areas of phagocyte metabolism. We end by proposing a model of efferocytosis that integrates recent findings and establishes a new paradigm for testing how efferocytosis prevents chronic inflammatory disease and autoimmunity.
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Affiliation(s)
- Alissa Trzeciak
- Immunology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Ya-Ting Wang
- Immunology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Justin Shaun Arnold Perry
- Immunology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, 417 E 68th Street, New York, NY 10065, USA; Department of Immunology and Microbial Pathogenesis, Weill Cornell Medical College, 417 E 68th Street, New York, NY 10065, USA.
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40
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Huisman Y, Uphoff K, Berger M, Dobrindt U, Schelhaas M, Zobel T, Bussmann J, van Impel A, Schulte-Merker S. Meningeal lymphatic endothelial cells fulfill scavenger endothelial cell function and cooperate with microglia in waste removal from the brain. Glia 2021; 70:35-49. [PMID: 34487573 DOI: 10.1002/glia.24081] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 08/16/2021] [Accepted: 08/18/2021] [Indexed: 12/13/2022]
Abstract
Brain lymphatic endothelial cells (BLECs) constitute a group of loosely connected endothelial cells that reside within the meningeal layer of the zebrafish brain without forming a vascular tubular system. BLECs have been shown to readily endocytose extracellular cargo molecules from the brain parenchyma, however, their functional relevance in relation to microglia remains enigmatic. We here compare their functional uptake efficiency for several macromolecules and bacterial components with microglia in a qualitative and quantitative manner in 5-day-old zebrafish embryos. We find BLECs to be significantly more effective in the uptake of proteins, polysaccharides and virus particles as compared to microglia, while larger particles like bacteria are only ingested by microglia but not by BLECs, implying a clear distribution of tasks between the two cell types in the brain area. In addition, we compare BLECs to the recently discovered scavenger endothelial cells (SECs) of the cardinal vein and find them to accept an identical set of substrate molecules. Our data identifies BLECs as the first brain-associated SEC population in vertebrates, and demonstrates that BLECs cooperate with microglia to remove particle waste from the brain.
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Affiliation(s)
- Yvonne Huisman
- Institute of Cardiovascular Organogenesis and Regeneration, WWU Münster, Münster, Germany.,Faculty of Medicine, WWU Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence, WWU Münster, Münster, Germany
| | - Katharina Uphoff
- Institute of Cardiovascular Organogenesis and Regeneration, WWU Münster, Münster, Germany.,Faculty of Medicine, WWU Münster, Münster, Germany
| | | | | | - Mario Schelhaas
- Faculty of Medicine, WWU Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence, WWU Münster, Münster, Germany.,Institute of Cellular Virology, ZMBE, Münster, Germany
| | - Thomas Zobel
- Cells-in-Motion Cluster of Excellence, WWU Münster, Münster, Germany.,Imaging Network, Cells in Motion Interfaculty Centre, WWU Münster, Germany
| | - Jeroen Bussmann
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, Einsteinweg 55, Leiden, 2333CC, The Netherlands
| | - Andreas van Impel
- Institute of Cardiovascular Organogenesis and Regeneration, WWU Münster, Münster, Germany.,Faculty of Medicine, WWU Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence, WWU Münster, Münster, Germany
| | - Stefan Schulte-Merker
- Institute of Cardiovascular Organogenesis and Regeneration, WWU Münster, Münster, Germany.,Faculty of Medicine, WWU Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence, WWU Münster, Münster, Germany
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41
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Takata K, Ginhoux F, Shimohama S. Roles of microglia in Alzheimer's disease and impact of new findings on microglial heterogeneity as a target for therapeutic intervention. Biochem Pharmacol 2021; 192:114754. [PMID: 34480881 DOI: 10.1016/j.bcp.2021.114754] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 12/25/2022]
Abstract
Microglia are specialized macrophages that reside within the central nervous system and play key roles in brain immunity, development and homeostasis. Recent studies also revealed functions of microglia in neuroprotection and neuroinflammation, leading to the discovery that microglia are involved in several brain pathologies including Alzheimer's disease (AD). However, the beneficial and detrimental actions of this intriguing cell population can be challenging to dissect: the advent of single-cell and single-nucleus transcriptomic technologies has revolutionized our understanding of the heterogeneity of multiple cell types and is now being applied to the study of microglia in health and disease. Here, we review recent findings on microglial biology, focusing on insights from single cell transcriptomic studies and the heterogeneity that they reveal, and consider the impact of these findings on our understanding of AD. We also discuss how microglia might represent a next-generation therapeutic target for treatment of AD and other neuroinflammatory conditions.
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Affiliation(s)
- Kazuyuki Takata
- Division of Integrated Pharmaceutical Sciences, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Florent Ginhoux
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore 138648, Singapore; Shanghai Institute of Immunology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China; Translational Immunology Institute, SingHealth/Duke-NUS, Academic Medical Centre, The Academia, Singapore 169856, Singapore
| | - Shun Shimohama
- Department of Neurology, Sapporo Medical University, School of Medicine, Sapporo 060-8543, Japan
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42
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Glial contribution to cyclodextrin-mediated reversal of cholesterol accumulation in murine NPC1-deficient neurons in vivo. Neurobiol Dis 2021; 158:105469. [PMID: 34364974 DOI: 10.1016/j.nbd.2021.105469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 07/17/2021] [Accepted: 08/02/2021] [Indexed: 12/11/2022] Open
Abstract
Niemann-Pick type C disease is a rare and fatal lysosomal storage disorder presenting severe neurovisceral symptoms. Disease-causing mutations in genes encoding either NPC1 or NPC2 protein provoke accumulation of cholesterol and other lipids in specific structures of the endosomal-lysosomal system and degeneration of specific cells, notably neurons in the central nervous system (CNS). 2-hydroxypropyl-beta-cyclodextrin (CD) emerged as potential therapeutic approach based on animal studies and clinical data, but the mechanism of action in neurons has remained unclear. To address this topic in vivo, we took advantage of the retina as highly accessible part of the CNS and intravitreal injections as mode of drug administration. Coupling CD to gold nanoparticles allowed us to trace its intracellular location. We report that CD enters the endosomal-lysosomal system of neurons in vivo and enables the release of lipid-laden lamellar inclusions, which are then removed from the extracellular space by specific types of glial cells. Our data suggest that CD induces a concerted action of neurons and glial cells to restore lipid homeostasis in the central nervous system.
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43
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Microglial Extracellular Vesicles as Vehicles for Neurodegeneration Spreading. Biomolecules 2021; 11:biom11060770. [PMID: 34063832 PMCID: PMC8224033 DOI: 10.3390/biom11060770] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/17/2021] [Accepted: 05/18/2021] [Indexed: 12/12/2022] Open
Abstract
Microglial cells are the neuroimmune competent cells of the central nervous system. In the adult, microglia are responsible for screening the neuronal parenchyma searching for alterations in homeostasis. Chronic neuroinflammation plays a role in neurodegenerative disease. Indeed, microglia-mediated neuroinflammation is involved in the onset and progression of several disorders in the brain and retina. Microglial cell reactivity occurs in an orchestrated manner and propagates across the neural parenchyma spreading the neuroinflammatory signal from cell to cell. Extracellular vesicles are important vehicles of intercellular communication and act as message carriers across boundaries. Extracellular vesicles can be subdivided in several categories according to their cellular origin (apoptotic bodies, microvesicles and exosomes), each presenting, different but sometimes overlapping functions in cell communication. Mounting evidence suggests a role for extracellular vesicles in regulating microglial cell action. Herein, we explore the role of microglial extracellular vesicles as vehicles for cell communication and the mechanisms that trigger their release. In this review we covered the role of microglial extracellular vesicles, focusing on apoptotic bodies, microvesicles and exosomes, in the context of neurodegeneration and the impact of these vesicles derived from other cells in microglial cell reactivity.
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44
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Neuroimmune cleanup crews in brain injury. Trends Immunol 2021; 42:480-494. [PMID: 33941486 DOI: 10.1016/j.it.2021.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/05/2021] [Accepted: 04/06/2021] [Indexed: 12/21/2022]
Abstract
Traumatic brain injury (TBI) is a leading cause of death and disability. Mounting evidence indicates that the immune system is critically involved in TBI pathogenesis, where it is deployed to dispose of neurotoxic material generated from head trauma and to instruct the wound healing process. However, the immune response to brain damage must be carefully held in check as aberrant regulation of immune signaling can lead to deleterious neuroinflammation, brain pathology, and neurological dysfunction. Efficient clearance of neurotoxic material by microglia (the brain's resident phagocytes) and the glymphatic-meningeal lymphatic drainage system are paramount to keeping the immune system in balance following head trauma. In this review, we highlight emerging evidence that defines pivotal roles for microglia and the recently discovered glymphatic-meningeal lymphatic system in TBI pathogenesis.
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45
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Ann Butler C, Thornton P, Charles Brown G. CD33M inhibits microglial phagocytosis, migration and proliferation, but the Alzheimer's disease-protective variant CD33m stimulates phagocytosis and proliferation, and inhibits adhesion. J Neurochem 2021; 158:297-310. [PMID: 33720433 DOI: 10.1111/jnc.15349] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 01/28/2021] [Accepted: 03/11/2021] [Indexed: 12/13/2022]
Abstract
CD33 is a Siglec (sialic acid-binding immunoglobulin-type lectin) receptor on microglia. Human CD33 can be alternatively spliced into two isoforms: the long isoform (CD33M) and a shorter isoform (CD33m) that lacks the sialic acid-binding site. CD33m appears to protect against Alzheimer's disease; however, it remains unclear how. To investigate potential mechanisms by which CD33m may confer protection, we expressed the CD33m and CD33M isoforms of human CD33 in mouse BV-2 and human CHME3 microglial cells and assessed microglia functions. In the BV-2 cells, CD33M inhibited microglial phagocytosis of beads, synapses, debris and dead cells, while CD33m increased phagocytosis of beads, debris and cells. RNAi knockdown of the endogenous mouse CD33 increased phagocytosis and prevented CD33m's (but not CD33M's) effect on phagocytosis. CD33M increased cell attachment but inhibited cell proliferation, while CD33m did the opposite. We also found that CD33M inhibited cell migration. In human CHME3 cells, CD33M increased cell attachment, but inhibited phagocytosis, proliferation and migration, whereas CD33m did the opposite. We conclude that CD33M inhibits microglial phagocytosis, inhibits migration and increases adhesion, while CD33m increases phagocytosis, proliferation and inhibits adhesion. Thus, CD33m might protect against Alzheimer's disease by increasing microglial proliferation, movement and phagocytosis of debris and dead cells.
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Affiliation(s)
- Claire Ann Butler
- Department of Biochemistry, University of Cambridge, Cambridge, UK.,AstraZeneca, Cambridge, UK
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46
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Abstract
PURPOSE OF REVIEW The aim of this study was to provide an update on the role of the innate immune system and neuroinflammation in the pathogenesis of Alzheimer's disease, with an emphasis on microglial receptors CD33 and TREM2. RECENT FINDINGS Genome-wide association studies (GWAS) have identified many Alzheimer's disease risk genes related to immune response and microglia including the phagocytic receptors CD33 and TREM2. Recent GWAS and pathway analyses emphasize the crucial role of the innate immune system and neuroinflammation in the pathogenesis of Alzheimer's disease. Disease-associated microglia have been characterized by TREM2-dependent upregulation of phagocytic and lipid metabolism genes. Impaired microglial phagocytosis results in amyloid beta (Aβ) accumulation leading to neuroinflammation that is the primary cause of neurodegeneration. CD33 and TREM2 modulate neuroinflammation in Alzheimer's disease and have emerged as therapeutic targets in Alzheimer's disease. Progress has been made to inhibit CD33 by gene therapy, small molecules or immunotherapy, and to increase TREM2 activity by immunotherapy. Finally, mAbs against CD33 and TREM2 have entered clinical trials and may reduce neuroinflammation in Alzheimer's disease brain. SUMMARY Targeting neuroinflammation via CD33 inhibition and/or TREM2 activation may have important implications for neurodegeneration in Alzheimer's disease and may be an addition to monoclonal anti-Aβ antibody treatments that remove plaques without reducing neuroinflammation.
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Affiliation(s)
- Ana Griciuc
- Genetics and Aging Research Unit, McCance Center for Brain Health, Mass General Institute for Neurodegenerative Disease, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
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47
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Campagno KE, Mitchell CH. The P2X 7 Receptor in Microglial Cells Modulates the Endolysosomal Axis, Autophagy, and Phagocytosis. Front Cell Neurosci 2021; 15:645244. [PMID: 33790743 PMCID: PMC8005553 DOI: 10.3389/fncel.2021.645244] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 02/22/2021] [Indexed: 01/18/2023] Open
Abstract
Microglial cells regulate neural homeostasis by coordinating both immune responses and clearance of debris, and the P2X7 receptor for extracellular ATP plays a central role in both functions. The P2X7 receptor is primarily known in microglial cells for its immune signaling and NLRP3 inflammasome activation. However, the receptor also affects the clearance of extracellular and intracellular debris through modifications of lysosomal function, phagocytosis, and autophagy. In the absence of an agonist, the P2X7 receptor acts as a scavenger receptor to phagocytose material. Transient receptor stimulation induces autophagy and increases LC3-II levels, likely through calcium-dependent phosphorylation of AMPK, and activates microglia to an M1 or mixed M1/M2 state. We show an increased expression of Nos2 and Tnfa and a decreased expression of Chil3 (YM1) from primary cultures of brain microglia exposed to high levels of ATP. Sustained stimulation can reduce lysosomal function in microglia by increasing lysosomal pH and slowing autophagosome-lysosome fusion. P2X7 receptor stimulation can also cause lysosomal leakage, and the subsequent rise in cytoplasmic cathepsin B activates the NLRP3 inflammasome leading to caspase-1 cleavage and IL-1β maturation and release. Support for P2X7 receptor activation of the inflammasome following lysosomal leakage comes from data on primary microglia showing IL-1β release following receptor stimulation is inhibited by cathepsin B blocker CA-074. This pathway bridges endolysosomal and inflammatory roles and may provide a key mechanism for the increased inflammation found in age-dependent neurodegenerations characterized by excessive lysosomal accumulations. Regardless of whether the inflammasome is activated via this lysosomal leakage or the better-known K+-efflux pathway, the inflammatory impact of P2X7 receptor stimulation is balanced between the autophagic reduction of inflammasome components and their increase following P2X7-mediated priming. In summary, the P2X7 receptor modulates clearance of extracellular debris by microglial cells and mediates lysosomal damage that can activate the NLRP3 inflammasome. A better understanding of how the P2X7 receptor alters phagocytosis, lysosomal health, inflammation, and autophagy can lead to therapies that balance the inflammatory and clearance roles of microglial cells.
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Affiliation(s)
- Keith E Campagno
- Department of Basic and Translational Science, University of Pennsylvania, Philadelphia, PA, United States
| | - Claire H Mitchell
- Department of Basic and Translational Science, University of Pennsylvania, Philadelphia, PA, United States.,Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, United States.,Department of Physiology, University of Pennsylvania, Philadelphia, PA, United States
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Triviño JJ, von Bernhardi R. The effect of aged microglia on synaptic impairment and its relevance in neurodegenerative diseases. Neurochem Int 2021; 144:104982. [PMID: 33556444 DOI: 10.1016/j.neuint.2021.104982] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 01/31/2021] [Accepted: 02/01/2021] [Indexed: 02/07/2023]
Abstract
Microglia serve key functions in the central nervous system (CNS), participating in the establishment and regulation of synapses and the neuronal network, and regulating activity-dependent plastic changes. As the neuroimmune system, they respond to endogenous and exogenous signals to protect the CNS. In aging, one of the main changes is the establishment of inflamm-aging, a mild chronic inflammation that reduces microglial response to stressors. Neuroinflammation depends mainly on the increased activation of microglia. Microglia over-activation may result in a reduced capacity for performing normal functions related to migration, clearance, and the adoption of an anti-inflammatory state, contributing to an increased susceptibility for neurodegeneration. Oxidative stress contributes both to aging and to the progression of neurodegenerative diseases. Increased production of reactive oxygen species (ROS) and neuroinflammation associated with age- and disease-dependent mechanisms affect synaptic activity and neurotransmission, leading to cognitive dysfunction. Astrocytes prevent microglial cell cytotoxicity by mechanisms mediated by transforming growth factor β1 (TGFβ1). However, TGFβ1-Smad3 pathway is impaired in aging, and the age-related impairment of TGFβ signaling can reduce protective activation while facilitating cytotoxic activation of microglia. A critical analysis on the effect of aging microglia on neuronal function is relevant for the understanding of age-related changes on neuronal function. Here, we present evidence in the context of the "microglial dysregulation hypothesis", which leads to the reduction of the protective functions and increased cytotoxicity of microglia, to discuss the mechanisms involved in neurodegenerative changes and Alzheimer's disease.
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Affiliation(s)
- Juan José Triviño
- Department of Neurology, Pontificia Universidad Católica de Chile School of Medicine, Laboratory of Neuroscience. Marcoleta 391, Santiago, Chile
| | - Rommy von Bernhardi
- Department of Neurology, Pontificia Universidad Católica de Chile School of Medicine, Laboratory of Neuroscience. Marcoleta 391, Santiago, Chile; Faculty of Health Sciences, Universidad San Sebastián, Lota 2465, Santiago, Chile.
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Patkar OL, Caruso M, Teakle N, Keshvari S, Bush SJ, Pridans C, Belmer A, Summers KM, Irvine KM, Hume DA. Analysis of homozygous and heterozygous Csf1r knockout in the rat as a model for understanding microglial function in brain development and the impacts of human CSF1R mutations. Neurobiol Dis 2021; 151:105268. [PMID: 33450391 PMCID: PMC7941205 DOI: 10.1016/j.nbd.2021.105268] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 01/06/2021] [Accepted: 01/07/2021] [Indexed: 12/11/2022] Open
Abstract
Mutations in the human CSF1R gene have been associated with dominant and recessive forms of neurodegenerative disease. Here we describe the impacts of Csf1r mutation in the rat on development of the brain. Diffusion imaging indicated small reductions in major fiber tracts that may be associated in part with ventricular enlargement. RNA-seq profiling revealed a set of 105 microglial markers depleted in all brain regions of the Csf1rko rats. There was no evidence of region or sex-specific expression of microglia-associated transcripts. Other than the microglial signature, Csf1rko had no effect on any neuronal or region-specific transcript cluster. Expression of markers of oligodendrocytes, astrocytes, dopaminergic neurons and Purkinje cells was minimally affected. However, there were defects in dendritic arborization of doublecortin-positive neurogenic precursors and expression of poly-sialylated neural cell adhesion molecule (PS-NCAM) in the dentate gyrus of the hippocampus. Heterozygous Csf1rko rats had no detectable brain phenotype. We conclude that most brain developmental processes occur normally in the absence of microglia and that CSF1R haploinsufficiency is unlikely to cause leukoencephalopathy.
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Affiliation(s)
- Omkar L Patkar
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Melanie Caruso
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Ngari Teakle
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Sahar Keshvari
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Stephen J Bush
- Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Clare Pridans
- University of Edinburgh Centre for Inflammation Research, Edinburgh, UK and Simons Initiative for the Developing Brain, Centre for Discovery Brain Sciences, University of Edinburgh, UK
| | - Arnauld Belmer
- School of Clinical Sciences, Queensland University of Technology, Brisbane, Australia
| | - Kim M Summers
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Katharine M Irvine
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - David A Hume
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia.
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Rombaut B, Kessels S, Schepers M, Tiane A, Paes D, Solomina Y, Piccart E, Hove DVD, Brône B, Prickaerts J, Vanmierlo T. PDE inhibition in distinct cell types to reclaim the balance of synaptic plasticity. Theranostics 2021; 11:2080-2097. [PMID: 33500712 PMCID: PMC7797685 DOI: 10.7150/thno.50701] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 11/17/2020] [Indexed: 02/06/2023] Open
Abstract
Synapses are the functional units of the brain. They form specific contact points that drive neuronal communication and are highly plastic in their strength, density, and shape. A carefully orchestrated balance between synaptogenesis and synaptic pruning, i.e., the elimination of weak or redundant synapses, ensures adequate synaptic density. An imbalance between these two processes lies at the basis of multiple neuropathologies. Recent evidence has highlighted the importance of glia-neuron interactions in the synaptic unit, emphasized by glial phagocytosis of synapses and local excretion of inflammatory mediators. These findings warrant a closer look into the molecular basis of cell-signaling pathways in the different brain cells that are related to synaptic plasticity. In neurons, intracellular second messengers, such as cyclic guanosine or adenosine monophosphate (cGMP and cAMP, respectively), are known mediators of synaptic homeostasis and plasticity. Increased levels of these second messengers in glial cells slow down inflammation and neurodegenerative processes. These multi-faceted effects provide the opportunity to counteract excessive synapse loss by targeting cGMP and cAMP pathways in multiple cell types. Phosphodiesterases (PDEs) are specialized degraders of these second messengers, rendering them attractive targets to combat the detrimental effects of neurological disorders. Cellular and subcellular compartmentalization of the specific isoforms of PDEs leads to divergent downstream effects for these enzymes in the various central nervous system resident cell types. This review provides a detailed overview on the role of PDEs and their inhibition in the context of glia-neuron interactions in different neuropathologies characterized by synapse loss. In doing so, it provides a framework to support future research towards finding combinational therapy for specific neuropathologies.
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