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Vojnits K, de León A, Rathore H, Liao S, Zhao M, Gibon J, Pakpour S. ROS-dependent degeneration of human neurons induced by environmentally relevant levels of micro- and nanoplastics of diverse shapes and forms. J Hazard Mater 2024; 469:134017. [PMID: 38518696 DOI: 10.1016/j.jhazmat.2024.134017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 03/08/2024] [Accepted: 03/11/2024] [Indexed: 03/24/2024]
Abstract
Our study explores the pressing issue of micro- and nanoplastics (MNPs) inhalation and their subsequent penetration into the brain, highlighting a significant environmental health concern. We demonstrate that MNPs can indeed penetrate murine brain, warranting further investigation into their neurotoxic effects in humans. We then proceed to test the impact of MNPs at environmentally relevant concentrations, with focusing on variations in size and shape. Our findings reveal that these MNPs induce oxidative stress, cytotoxicity, and neurodegeneration in human neurons, with cortical neurons being more susceptible than nociceptors. Furthermore, we examine the role of biofilms on MNPs, demonstrating that MNPs can serve as a vehicle for pathogenic biofilms that significantly exacerbate these neurotoxic effects. This sequence of investigations reveals that minimal MNPs accumulation can cause oxidative stress and neurodegeneration in human neurons, significantly risking brain health and highlights the need to understand the neurological consequences of inhaling MNPs. Overall, our developed in vitro testing battery has significance in elucidating the effects of environmental factors and their associated pathological mechanisms in human neurons.
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Affiliation(s)
- Kinga Vojnits
- School of Engineering, University of British Columbia, Kelowna, BC, Canada
| | - Andrés de León
- School of Engineering, University of British Columbia, Kelowna, BC, Canada; Department of Biology, University of British Columbia, Kelowna, BC, Canada
| | - Harneet Rathore
- School of Engineering, University of British Columbia, Kelowna, BC, Canada
| | - Sophia Liao
- School of Engineering, University of British Columbia, Kelowna, BC, Canada
| | - Michael Zhao
- School of Engineering, University of British Columbia, Kelowna, BC, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia, Kelowna, BC, Canada; Office of Vice-Principal, Research and Innovation, McGill University, Montreal, Quebec, Canada
| | - Sepideh Pakpour
- School of Engineering, University of British Columbia, Kelowna, BC, Canada.
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Da Silva DE, Richards CM, McRae SA, Riar I, Yang S(S, Zurfluh NE, Gibon J, Klegeris A. Extracellular mixed histones are neurotoxic and modulate select neuroimmune responses of glial cells. PLoS One 2024; 19:e0298748. [PMID: 38630734 PMCID: PMC11023449 DOI: 10.1371/journal.pone.0298748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 01/29/2024] [Indexed: 04/19/2024] Open
Abstract
Although histone proteins are widely known for their intranuclear functions where they organize DNA, all five histone types can also be released into the extracellular space from damaged cells. Extracellular histones can interact with pattern recognition receptors of peripheral immune cells, including toll-like receptor 4 (TLR4), causing pro-inflammatory activation, which indicates they may act as damage-associated molecular patterns (DAMPs) in peripheral tissues. Very limited information is available about functions of extracellular histones in the central nervous system (CNS). To address this knowledge gap, we applied mixed histones (MH) to cultured cells modeling neurons, microglia, and astrocytes. Microglia are the professional CNS immunocytes, while astrocytes are the main support cells for neurons. Both these cell types are critical for neuroimmune responses and their dysregulated activity contributes to neurodegenerative diseases. We measured effects of extracellular MH on cell viability and select neuroimmune functions of microglia and astrocytes. MH were toxic to cultured primary murine neurons and also reduced viability of NSC-34 murine and SH-SY5Y human neuron-like cells in TLR4-dependent manner. MH did not affect the viability of resting or immune-stimulated BV-2 murine microglia or U118 MG human astrocytic cells. When applied to BV-2 cells, MH enhanced secretion of the potential neurotoxin glutamate, but did not modulate the release of nitric oxide (NO), tumor necrosis factor-α (TNF), C-X-C motif chemokine ligand 10 (CXCL10), or the overall cytotoxicity of lipopolysaccharide (LPS)- and/or interferon (IFN)-γ-stimulated BV-2 microglial cells towards NSC-34 neuron-like cells. We demonstrated, for the first time, that MH downregulated phagocytic activity of LPS-stimulated BV-2 microglia. However, MH also exhibited protective effect by ameliorating the cytotoxicity of LPS-stimulated U118 MG astrocytic cells towards SH-SY5Y neuron-like cells. Our data demonstrate extracellular MH could both damage neurons and alter neuroimmune functions of glial cells. These actions of MH could be targeted for treatment of neurodegenerative diseases.
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Affiliation(s)
- Dylan E. Da Silva
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Christy M. Richards
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Seamus A. McRae
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Ishvin Riar
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Sijie (Shirley) Yang
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Noah E. Zurfluh
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Andis Klegeris
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
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Glasgow SD, Fisher TAJ, Wong EW, Lançon K, Feighan KM, Beamish IV, Gibon J, Séguéla P, Ruthazer ES, Kennedy TE. Acetylcholine synergizes with netrin-1 to drive persistent firing in the entorhinal cortex. Cell Rep 2024; 43:113812. [PMID: 38377003 DOI: 10.1016/j.celrep.2024.113812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/18/2023] [Accepted: 02/01/2024] [Indexed: 02/22/2024] Open
Abstract
The ability of the mammalian brain to maintain spatial representations of external or internal information for short periods of time has been associated with sustained neuronal spiking and reverberatory neural network activity in the medial entorhinal cortex. Here, we show that conditional genetic deletion of netrin-1 or the netrin receptor deleted-in-colorectal cancer (DCC) from forebrain excitatory neurons leads to deficits in short-term spatial memory. We then demonstrate that conditional deletion of either netrin-1 or DCC inhibits cholinergic persistent firing and show that cholinergic activation of muscarinic receptors expressed by entorhinal cortical neurons promotes persistent firing by recruiting DCC to the plasma membrane. Together, these findings indicate that normal short-term spatial memory function requires the synergistic actions of acetylcholine and netrin-1.
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Affiliation(s)
- Stephen D Glasgow
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Teddy A J Fisher
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Edwin W Wong
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Kevin Lançon
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Kira M Feighan
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Ian V Beamish
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Julien Gibon
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Philippe Séguéla
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Edward S Ruthazer
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada.
| | - Timothy E Kennedy
- Department of Neurology & Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, Montréal, QC H3A 2B4, Canada.
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McRae SA, Richards CM, Da Silva DE, Riar I, Yang SS, Zurfluh NE, Gibon J, Klegeris A. Pro-neuroinflammatory and neurotoxic potential of extracellular histones H1 and H3. Neurosci Res 2024:S0168-0102(24)00008-7. [PMID: 38278218 DOI: 10.1016/j.neures.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 12/23/2023] [Accepted: 01/17/2024] [Indexed: 01/28/2024]
Abstract
Histones organize DNA within cellular nuclei, but they can be released from damaged cells. In peripheral tissues extracellular histones act as damage-associated molecular patterns (DAMPs) inducing pro-inflammatory activation of immune cells. Limited studies have considered DAMP-like activity of histones in the central nervous system (CNS); therefore, we studied the effects of extracellular histones on microglia, the CNS immunocytes, and on neuronal cells. Both the linker histone H1 and the core histone H3 induced pro-inflammatory activation of microglia-like cells by upregulating their secretion of NO and cytokines, including interferon-γ-inducible protein 10 (IP-10) and tumor necrosis factor-α (TNF). The selective inhibitors MMG-11 and TAK-242 were used to demonstrate involvement of toll-like receptors (TLR) 2 and 4, respectively, in H1-induced NO secretion by BV-2 microglia. H1, but not H3, downregulated the phagocytic activity of BV-2 microglia. H1 was also directly toxic to all neuronal cell types studied. We conclude that H1, and to a lesser extent H3, when released extracellularly, have the potential to act as a CNS DAMPs. Inhibition of the DAMP-like effects of extracellular histones on microglia and their neurotoxic activity represents a potential strategy for combating neurodegenerative diseases that are characterized by the adverse activation of microglia and neuronal death.
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Affiliation(s)
- Seamus A McRae
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Christy M Richards
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Dylan E Da Silva
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Ishvin Riar
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Sijie Shirley Yang
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Noah E Zurfluh
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada
| | - Andis Klegeris
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, BC V1V 1V7, Canada.
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Yang SS, Simtchouk S, Gibon J, Klegeris A. Regulation of the phagocytic activity of astrocytes by neuroimmune mediators endogenous to the central nervous system. PLoS One 2023; 18:e0289169. [PMID: 37498903 PMCID: PMC10374099 DOI: 10.1371/journal.pone.0289169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 07/11/2023] [Indexed: 07/29/2023] Open
Abstract
The phagocytic activity of glial cells is essential for maintaining normal brain activity, and its dysfunction may contribute to the central nervous system (CNS) pathologies, including neurodegenerative diseases. Phagocytic activity is one of the well-established neuroimmune functions of microglia. Although emerging evidence indicates that astrocytes can also function as CNS phagocytes in humans and rodents, limited information is available about the molecular mechanism regulating this function. To address this knowledge gap, we studied modulation of the phagocytic activity of human U118 MG astrocytic cells and murine primary astrocytes by four CNS inflammatory mediators and bacterial endotoxin lipopolysaccharide (LPS). LPS and cytochrome c (CytC) upregulated, while interferon (IFN)-γ downregulated, phagocytosis of latex beads by human astrocytic cells and phagocytosis of synaptosomes by murine primary astrocytes. Interleukin (IL)-1β and tumor necrosis factor (TNF)-α had no effect on the phagocytic activity of human astrocytic cells but upregulated this function in murine astrocytes. Varying effects of combinations of the above inflammatory mediators were observed in these two cell types. LPS- and CytC-induced phagocytic activity of human astrocytic cells was partially mediated by activation of toll-like receptor 4 (TLR4). By monitoring other functions of astrocytes, we concluded there were no correlations between the effects of the mediators studied on astrocyte phagocytic activity and their secretion of cytokines, cytotoxins, or glutamate. Our study identified four candidate CNS regulators of astrocyte phagocytic activity. Future investigation of molecular mechanisms behind this regulation could identify novel therapeutic targets allowing modulation of this astrocyte-mediated clearance mechanism in CNS pathologies.
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Affiliation(s)
- Sijie Shirley Yang
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Svetlana Simtchouk
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
| | - Andis Klegeris
- Department of Biology, University of British Columbia Okanagan Campus, University Way, Kelowna, British Columbia, Canada
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Barnett JA, Josephson JK, Bandy ML, Haskey N, Gibon J, Chiang H, Gibson DL. A55 YOU ARE WHAT YOUR GREAT, GREAT GRANDPARENTS PARENTS ATE: PRE-NATAL GLYPHOSATE EXPOSURE INDUCES DYSBIOSIS, METABOLIC DYSFUNCTION AND BEHAVIOURAL ABNORMALITIES THREE GENERATIONS AFTER EXPOSURE. J Can Assoc Gastroenterol 2023. [PMCID: PMC9991229 DOI: 10.1093/jcag/gwac036.055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/09/2023] Open
Abstract
Background Canada is one of the most prolific users of the herbicide glyphosate (tradename Roundup®), with over 25 million kilograms purchased annually. Glyphosate is commonly applied pre-harvest as a desiccant, leading to higher residues in many foods consumed within Canada, including wheat, cereals, legumes, and soy products. Glyphosate prevents the synthesis of aromatic amino acids by inhibiting the Shikimate pathway, which, besides killing weeds, can also inhibit bacterial growth and promote bacterial dysbiosis. Dysbiosis has been associated with multiple disease states, including intestinal inflammation and metabolic dysfunction, which both include anxiety, depression, and cognitive dysfunction as co-morbidities. Purpose My goal is to clarify if there are harmful glyphosate effects on the gut bacteriome, resulting in altered metabolic health, damaging intestinal inflammation, and behaviour changes through the gut-brain axis. We explored two environmentally relevant doses throughout our experiments: (1) the acceptable daily intake currently set by the Environmental Protection Agency (EPA) (1.75mg/kg body weight/day); (2) the North American dose calculated with a registered dietician based on literature values of glyphosate within items that make up a typical Canadian diet (0.01mg/kg body weight/day.) Method Breeding pairs consisting of Muc2-/- (colitis susceptible) and Muc2+/- (littermate control) mice were exposed to glyphosate during pregnancy. A subset of each generation underwent behavioural testing to characterize anxiety, memory, and locomotor activity. Animals also underwent metabolic testing, including oral glucose and insulin tolerance tests. Only the parental generation of animals received glyphosate. In total, three generations of animals were raised. Result(s) Our results show that healthy mice whose great-grandparents were exposed to glyphosate at levels currently deemed safe by the EPA exhibited decreased locomotor activity. Furthermore, mice whose parents were exposed to either North American or EPA glyphosate levels exhibit symptoms of metabolic dysfunction in healthy and colitis-susceptible mice, including higher fasting blood glucose, an inability to efficiently clear glucose and impaired insulin response. Additionally, Muc2-/- mice whose parents were exposed to levels of glyphosate found within the North American diet during pregnancy showed significant impairments in working memory. Conclusion(s) This study is the first to highlight the transgenerational effects of glyphosate at levels previously deemed safe for human exposure on locomotor activity, working memory and metabolism. Additionally, this study highlights how environmental toxins within our food system, such as glyphosate, may play a vital role in the etiology of many diseases in healthy and colitis-susceptible populations by promoting a sedentary lifestyle, metabolic dysfunction, and behavioural deficits. Please acknowledge all funding agencies by checking the applicable boxes below CAG, CCC, Other Please indicate your source of funding; NSERC Disclosure of Interest None Declared
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Affiliation(s)
| | | | | | | | | | | | - D L Gibson
- Biology,Medicine , University of British Columbia, Kelowna, Canada
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Wenzel TJ, Murray TE, Noyovitz B, Narayana K, Gray TE, Le J, He J, Simtchouk S, Gibon J, Alcorn J, Mousseau DD, Zandberg WF, Klegeris A. Cardiolipin released by microglia can act on neighboring glial cells to facilitate the uptake of amyloid-β (1-42). Mol Cell Neurosci 2023; 124:103804. [PMID: 36592800 DOI: 10.1016/j.mcn.2022.103804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 11/16/2022] [Accepted: 12/24/2022] [Indexed: 12/31/2022] Open
Abstract
Cardiolipin is a mitochondrial phospholipid that is also detected in serum inferring its extracellular release; however, this process has not been directly demonstrated for any of the brain cell types. Nevertheless, extracellular cardiolipin has been shown to modulate several neuroimmune functions of microglia and astrocytes, including upregulation of their endocytic activity. Low cardiolipin levels are associated with brain aging, and may thus hinder uptake of amyloid-β (Αβ) in Alzheimer's disease. We hypothesized that glial cells are one of the sources of extracellular cardiolipin in the brain parenchyma where this phospholipid interacts with neighboring cells to upregulate the endocytosis of Αβ. Liquid chromatography-mass spectrophotometry identified 31 different species of cardiolipin released from murine BV-2 microglial cells and revealed this process was accelerated by exposure to Aβ42. Extracellular cardiolipin upregulated internalization of fluorescently-labeled Aβ42 by primary murine astrocytes, human U118 MG astrocytic cells, and murine BV-2 microglia. Increased endocytic activity in the presence of extracellular cardiolipin was also demonstrated by studying uptake of Aβ42 and pHrodo™ Bioparticles™ by human induced pluripotent stem cells (iPSCs)-derived microglia, as well as iPSC-derived human brain organoids containing microglia, astrocytes, oligodendrocytes and neurons. Our observations indicate that Aβ42 augments the release of cardiolipin from microglia into the extracellular space, where it can act on microglia and astrocytes to enhance their endocytosis of Aβ42. Our observations suggest that the reduced glial uptake of Aβ due to the decreased levels of cardiolipin could be at least partially responsible for the extracellular accumulation of Aβ in aging and Alzheimer's disease.
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Affiliation(s)
- Tyler J Wenzel
- Cell Signalling Laboratory, Department of Psychiatry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada; College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Taryn E Murray
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Benjamin Noyovitz
- Department of Chemistry, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Kamal Narayana
- Department of Chemistry, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Taylor E Gray
- Department of Chemistry, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Jennifer Le
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada
| | - Jim He
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada
| | - Svetlana Simtchouk
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Jane Alcorn
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Darrell D Mousseau
- Cell Signalling Laboratory, Department of Psychiatry, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
| | - Wesley F Zandberg
- Department of Chemistry, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
| | - Andis Klegeris
- Department of Biology, University of British Columbia Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada.
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de León A, Gibon J, Barker PA. APP Genetic Deficiency Alters Intracellular Ca 2+ Homeostasis and Delays Axonal Degeneration in Dorsal Root Ganglion Sensory Neurons. J Neurosci 2022; 42:6680-6691. [PMID: 35882556 PMCID: PMC9436018 DOI: 10.1523/jneurosci.0162-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 06/08/2022] [Accepted: 07/11/2022] [Indexed: 11/21/2022] Open
Abstract
The activation of self-destructive cellular programs helps sculpt the nervous system during development, but the molecular mechanisms used are not fully understood. Prior studies have investigated the role of the APP in the developmental degeneration of sensory neurons with contradictory results. In this work, we sought to elucidate the impact of APP deletion in the development of the sensory nervous system in vivo and in vitro. Our in vivo data show an increase in the number of sciatic nerve axons in adult male and female APP-null mice, consistent with the hypothesis that APP plays a pro-degenerative role in the development of peripheral axons. In vitro, we show that genetic deletion of APP delays axonal degeneration triggered by nerve growth factor deprivation, indicating that APP does play a pro-degenerative role. Interestingly, APP depletion does not affect caspase-3 levels but significantly attenuates the rise of axoplasmic Ca2+ that occurs during degeneration. We examined intracellular Ca2+ mechanisms that could be involved and found that APP-null DRG neurons had increased Ca2+ levels within the endoplasmic reticulum and enhanced store-operated Ca2+ entry. We also observed that DRG axons lacking APP have more mitochondria than their WT counterparts, but these display a lower mitochondrial membrane potential. Finally, we present evidence that APP deficiency causes an increase in mitochondrial Ca2+ buffering capacity. Our results support the hypothesis that APP plays a pro-degenerative role in the developmental degeneration of DRG sensory neurons, and unveil the importance of APP in the regulation of calcium signaling in sensory neurons.SIGNIFICANCE STATEMENT The nervous system goes through a phase of pruning and programmed neuronal cell death during development to reach maturity. In such context, the role played by the APP in the peripheral nervous system has been controversial, ranging from pro-survival to pro-degenerative. Here we present evidence in vivo and in vitro supporting the pro-degenerative role of APP, demonstrating the ability of APP to alter intracellular Ca2+ homeostasis and mitochondria, critical players of programmed cell death. This work provides a better understanding of the physiological function of APP and its implication in developmental neuronal death in the nervous system.
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Affiliation(s)
- Andrés de León
- University of British Columbia Okanagan, Kelowna, British Columbia V1V 1V7, Canada
| | - Julien Gibon
- University of British Columbia Okanagan, Kelowna, British Columbia V1V 1V7, Canada
| | - Philip A Barker
- University of British Columbia Okanagan, Kelowna, British Columbia V1V 1V7, Canada
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Kievit B, Johnstone AD, Gibon J, Barker PA. Mitochondrial Reactive Oxygen Species Mediate Activation of TRPV1 and Calcium Entry Following Peripheral Sensory Axotomy. Front Mol Neurosci 2022; 15:852181. [PMID: 35370552 PMCID: PMC8973397 DOI: 10.3389/fnmol.2022.852181] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 02/17/2022] [Indexed: 12/03/2022] Open
Abstract
Axons that are physically separated from their soma activate a series of signaling events that results in axonal self-destruction. A critical element of this signaling pathway is an intra-axonal calcium rise that occurs just prior to axonal fragmentation. Previous studies have shown that preventing this calcium rise delays the onset of axon fragmentation, yet the ion channels responsible for the influx, and the mechanisms by which they are activated, are largely unknown. Axonal injury can be modeled in vitro by transecting murine dorsal root ganglia (DRG) sensory axons. We coupled transections with intra-axonal calcium imaging and found that Ca2+ influx is sharply reduced in axons lacking trpv1 (for transient receptor potential cation channel vanilloid 1) and in axons treated with capsazepine (CPZ), a TRPV1 antagonist. Sensory neurons from trpv1–/– mice were partially rescued from degeneration after transection, indicating that TRPV1 normally plays a pro-degenerative role after axonal injury. TRPV1 activity can be regulated by direct post-translational modification induced by reactive oxygen species (ROS). Here, we tested the hypothesis that mitochondrial ROS production induced by axotomy is required for TRPV1 activity and subsequent axonal degeneration. We found that reducing mitochondrial depolarization with NAD+ supplementation or scavenging ROS using NAC or MitoQ sharply attenuates TRPV1-dependent calcium influx induced by axotomy. This study shows that ROS-dependent TRPV1 activation is required for Ca2+ entry after axotomy.
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Affiliation(s)
- Bradley Kievit
- Department of Biology, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Aaron D. Johnstone
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia Okanagan, Kelowna, BC, Canada
- *Correspondence: Julien Gibon,
| | - Philip A. Barker
- Department of Biology, University of British Columbia Okanagan, Kelowna, BC, Canada
- Philip A. Barker,
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Abbasian M, Langlois A, Gibon J. Sexual Dimorphism in Balance and Coordination in p75NTRexonIII Knock-Out Mice. Front Behav Neurosci 2022; 16:842552. [PMID: 35283743 PMCID: PMC8907914 DOI: 10.3389/fnbeh.2022.842552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 01/31/2022] [Indexed: 11/13/2022] Open
Abstract
The p75 neurotrophin receptor (p75NTR) is implicated in various biological functions during development and adulthood. Several animal models have been developed to identify the roles of p75NTR in vivo and in vitro. P75NTRExonIII knock-out mice are widely used to study the neurotrophin receptor and its signaling pathways. Similar to other models of p75NTR knock-out (p75NTRExon IV KO) or conditional knock-out (p75NTRfl/fl) mice, p75NTRExonIII knock-out mice present severe abnormalities in walking, gait, balance and strength. The present study identifies a sexual dimorphism in the p75NTRExonIII knock-out strain regarding balance and coordination. Using Kondziela’s inverted grid test, we observed that p75NTRExonIII knock-out males performed poorly at the task, whereas p75NTRExonIII knock-out females did not exhibit any defects. We also observed that female p75NTRExonIII knock-out mice performed significantly better than male p75NTRExonIII knock-out mice at the beam balance test. There were no differences in strength, skin innervation, or the number of ulcers on the toes between p75NTRExonIII knock-out males and females. The literature regarding the role of p75NTR in behavior is controversial; our results suggest that studies investigating the role of p75NTR in vivo using p75NTR knock-out mice should systematically report data from males and females.
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Glasgow SD, Labrecque S, Beamish IV, Aufmkolk S, Gibon J, Han D, Harris SN, Dufresne P, Wiseman PW, McKinney RA, Séguéla P, De Koninck P, Ruthazer ES, Kennedy TE. Activity-Dependent Netrin-1 Secretion Drives Synaptic Insertion of GluA1-Containing AMPA Receptors in the Hippocampus. Cell Rep 2018; 25:168-182.e6. [DOI: 10.1016/j.celrep.2018.09.028] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 05/30/2018] [Accepted: 09/06/2018] [Indexed: 11/28/2022] Open
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Abstract
Axons normally degenerate during development of the mammalian nervous system, but dysregulation of the same genetically-encoded destructive cellular machinery can destroy crucial structures during adult neurodegenerative diseases. Nerve growth factor (NGF) withdrawal from dorsal root ganglia (DRG) axons is a well-established in vitro experimental model for biochemical and cell biological studies of developmental degeneration. Definitive methods for measuring axon degeneration have been lacking and here we report a novel method of axon degeneration quantification from bulk cultures of DRG that enables objective and automated measurement of axonal density over the entire field of radial axon outgrowth from the ganglion. As proof of principal, this new method, written as an R script called Axoquant 2.0, was used to examine the role of extracellular Ca2+ in the execution of cytoskeletal disassembly during degeneration of NGF-deprived DRG axons. This method can be easily applied to examine degenerative or neuroprotective effects of gene manipulations and pharmacological interventions.
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Affiliation(s)
- Aaron D. Johnstone
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Department of Biology, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Robin M. Hallett
- The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Andrés de Léon
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- Department of Biology, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Bruno Carturan
- Department of Biology, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Julien Gibon
- Department of Biology, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Philip A. Barker
- Department of Biology, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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Abstract
Neurotrophins have been intensively studied and have multiple roles in the brain. Neurotrophins are first synthetized as proneurotrophins and then cleaved intracellularly and extracellularly. Increasing evidences demonstrate that proneurotrophins and mature neurotrophins exerts opposing role in the central nervous system. In the present review, we explore the role of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4) and their respective proform in cellular processes related to learning and memory. We focused on their roles in synaptic activity and plasticity in the brain with an emphasis on long-term potentiation, long-term depression, and basal synaptic transmission in the hippocampus and the temporal lobe area. We also discuss new findings on the role of the Val66Met polymorphism on the BDNF propeptide on synaptic activity.
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Affiliation(s)
- Julien Gibon
- Department of Biology, University of British Columbia, Kelowna, BC, Canada
| | - Philip A. Barker
- Department of Biology, University of British Columbia, Kelowna, BC, Canada
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14
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Gibon J, Kang MS, Aliaga A, Sharif B, Rosa-Neto P, Séguéla P, Barker PA, Kostikov A. Towards the PET radiotracer for p75 neurotrophin receptor: [(11)C]LM11A-24 shows biological activity in vitro, but unfavorable ex vivo and in vivo profile. Bioorg Med Chem 2016; 24:4759-4765. [PMID: 27567078 DOI: 10.1016/j.bmc.2016.08.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 08/08/2016] [Accepted: 08/12/2016] [Indexed: 12/13/2022]
Abstract
Mature neurotrophins as well as their pro forms are critically involved in the regulation of neuronal functions. They are signaling through three distinct types of receptors: tropomyosin receptor kinase family (TrkA/B/C), p75 neurotrophin receptor (p75(NTR)) and sortilin. Aberrant expression of p75(NTR) in the CNS is implicated in a variety of neurodegenerative diseases, including Alzheimer's disease. The goal of this work was to evaluate one of the very few reported p75(NTR) small molecule ligands as a lead compound for development of novel PET radiotracers for in vivo p75(NTR) imaging. Here we report that previously described ligand LM11A-24 shows significant inhibition of carbachol-induced persistent firing (PF) of entorhinal cortex (EC) pyramidal neurons in wild-type mice via selective interaction with p75(NTR). Based on this electrophysiological assay, the compound has very high potency with an EC50<10nM. We optimized the radiosynthesis of [(11)C]LM11A-24 as the first attempt to develop PET radioligand for in vivo imaging of p75(NTR). Despite some weak interaction with CNS tissues, the radiolabeled compound showed unfavorable in vivo profile presumably due to high hydrophilicity.
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Affiliation(s)
- Julien Gibon
- University of British Columbia, 3187 University Way, Kelowna, BC V1V1V7, Canada; Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A2B4, Canada
| | - Min Su Kang
- Translational Neuroimaging Laboratory, McGill University Research Centre for Studies in Aging, Douglas Mental Health University Institute, 6875 Boulevard LaSalle, Montreal, QC H4H 1R3, Canada
| | - Arturo Aliaga
- Translational Neuroimaging Laboratory, McGill University Research Centre for Studies in Aging, Douglas Mental Health University Institute, 6875 Boulevard LaSalle, Montreal, QC H4H 1R3, Canada
| | - Behrang Sharif
- Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A2B4, Canada
| | - Pedro Rosa-Neto
- Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A2B4, Canada; Translational Neuroimaging Laboratory, McGill University Research Centre for Studies in Aging, Douglas Mental Health University Institute, 6875 Boulevard LaSalle, Montreal, QC H4H 1R3, Canada
| | - Philippe Séguéla
- Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A2B4, Canada
| | - Philip A Barker
- University of British Columbia, 3187 University Way, Kelowna, BC V1V1V7, Canada
| | - Alexey Kostikov
- Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, QC H3A2B4, Canada.
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15
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Gibon J, Unsain N, Gamache K, Thomas RA, De Leon A, Johnstone A, Nader K, Séguéla P, Barker PA. The X-linked inhibitor of apoptosis regulates long-term depression and learning rate. FASEB J 2016; 30:3083-90. [PMID: 27189977 DOI: 10.1096/fj.201600384r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 05/12/2016] [Indexed: 12/22/2022]
Abstract
Hippocampal long-term depression (LTD) is an active form of synaptic plasticity that is necessary for consolidation of spatial memory, contextual fear memory, and novelty acquisition. Recent studies have shown that caspases (CASPs) play an important role in NMDA receptor-dependent LTD and are involved in postsynaptic remodeling and synaptic maturation. In the present study, we examined the role of X-linked inhibitor of apoptosis (XIAP), a putative endogenous CASP inhibitor, in synaptic plasticity in the hippocampus. Analysis in acute brain slices and in cultured hippocampal neurons revealed that XIAP deletion increases CASP-3 activity, enhances α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor internalization, sharply increases LTD, and significantly reduces synapse density. In vivo behaviors related to memory were also altered in XIAP(-/-) mice, with faster acquisition of spatial object location and increased fear memory observed. Together, these results indicate that XIAP plays an important physiologic role in regulating sublethal CASP-3 activity within central neurons and thereby facilitates synaptic plasticity and memory acquisition.-Gibon, J., Unsain, N., Gamache, K., Thomas, R. A., De Leon, A., Johnstone, A., Nader, K., Séguéla, P., Barker, P. A. The X-linked inhibitor of apoptosis regulates long-term depression and learning rate.
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Affiliation(s)
- Julien Gibon
- Biology Unit, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada; Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Nicolas Unsain
- Laboratorio de Neurobiología, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Karine Gamache
- Department of Psychology, McGill University, Montreal, Quebec, Canada; and
| | - Rhalena A Thomas
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Andres De Leon
- Biology Unit, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada; Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Aaron Johnstone
- Biology Unit, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada; Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Karim Nader
- Department of Psychology, McGill University, Montreal, Quebec, Canada; and
| | - Philippe Séguéla
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada;
| | - Philip A Barker
- Biology Unit, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada; Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada;
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16
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Gaub P, de Léon A, Gibon J, Soubannier V, Dorval G, Séguéla P, Barker PA. HBpF-proBDNF: A New Tool for the Analysis of Pro-Brain Derived Neurotrophic Factor Receptor Signaling and Cell Biology. PLoS One 2016; 11:e0150601. [PMID: 26950209 PMCID: PMC4780767 DOI: 10.1371/journal.pone.0150601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 02/17/2016] [Indexed: 01/12/2023] Open
Abstract
Neurotrophins activate intracellular signaling pathways necessary for neuronal survival, growth and apoptosis. The most abundant neurotrophin in the adult brain, brain-derived neurotrophic factor (BDNF), is first synthesized as a proBDNF precursor and recent studies have demonstrated that proBDNF can be secreted and that it functions as a ligand for a receptor complex containing p75NTR and sortilin. Activation of proBDNF receptors mediates growth cone collapse, reduces synaptic activity, and facilitates developmental apoptosis of motoneurons but the precise signaling cascades have been difficult to discern. To address this, we have engineered, expressed and purified HBpF-proBDNF, an expression construct containing a 6X-HIS tag, a biotin acceptor peptide (BAP) sequence, a PreScission™ Protease cleavage site and a FLAG-tag attached to the N-terminal part of murine proBDNF. Intact HBpF-proBDNF has activities indistinguishable from its wild-type counterpart and can be used to purify proBDNF signaling complexes or to monitor proBDNF endocytosis and retrograde transport. HBpF-proBDNF will be useful for characterizing proBDNF signaling complexes and for deciphering the role of proBDNF in neuronal development, synapse function and neurodegenerative disease.
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Affiliation(s)
- Perrine Gaub
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Andrès de Léon
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Julien Gibon
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Vincent Soubannier
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Geneviève Dorval
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Philippe Séguéla
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Philip A. Barker
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, H3A 2B4, Canada
- * E-mail:
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Gibon J, Barker PA, Séguéla P. Opposing presynaptic roles of BDNF and ProBDNF in the regulation of persistent activity in the entorhinal cortex. Mol Brain 2016; 9:23. [PMID: 26932787 PMCID: PMC4774087 DOI: 10.1186/s13041-016-0203-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 02/25/2016] [Indexed: 11/15/2022] Open
Abstract
Background Sustained, persistent firing (PF) of cortical pyramidal neurons following a short depolarization is a crucial cellular mechanism required for spatial and working memory. Pyramidal neurons in the superficial and deep layers of the medial and lateral entorhinal cortex (EC) display this property of prolonged firing activity. Here, we focused on the regulation of this activity in EC neurons by mature brain derived neurotrophic factor (BDNF) and its precursor proBDNF. Results Using patch clamp electrophysiology in acute mouse cortical slices, we observed that BDNF facilitates cholinergic PF in pyramidal neurons in layer V of the medial EC. Inhibition of TrkB with K252a blocks the potentiating effect of BDNF whereas inhibition of p75NTR with function-blocking antibodies does not. By recording spontaneous excitatory post-synaptic currents (sEPSC), we find that BDNF acts pre-synaptically via TrkB to increase glutamate release whereas proBDNF acting via p75NTR acts to reduce it. MPEP abolished the facilitating effect of BDNF on PF, demonstrating that the metabotropic glutamate receptor mGluR5 plays a critical role in the BDNF effect. In contrast, paired pulse ratio and EPSC measurements indicated that proBDNF, via presynaptic p75NTR, is a negative regulator of glutamate release in the EC. Conclusions Taken together, our findings demonstrate that the BDNF/TrkB pathway facilitates persistent activity whereas the proBDNF/p75NTR pathway inhibits this mnemonic property of entorhinal pyramidal neurons.
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Affiliation(s)
- Julien Gibon
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Suite 778, Montreal, Quebec, H3A 2B4, Canada.
| | - Philip A Barker
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Suite 778, Montreal, Quebec, H3A 2B4, Canada.
| | - Philippe Séguéla
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Suite 778, Montreal, Quebec, H3A 2B4, Canada.
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Gibon J, Buckley SM, Unsain N, Kaartinen V, Séguéla P, Barker PA. proBDNF and p75NTR Control Excitability and Persistent Firing of Cortical Pyramidal Neurons. J Neurosci 2015; 35:9741-53. [PMID: 26134656 PMCID: PMC6605143 DOI: 10.1523/jneurosci.4655-14.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 05/19/2015] [Accepted: 05/29/2015] [Indexed: 02/07/2023] Open
Abstract
Persistent firing of entorhinal cortex (EC) pyramidal neurons is a key component of working and spatial memory. We report here that a pro-brain-derived neurotrophic factor (proBDNF)-dependent p75NTR signaling pathway plays a major role in excitability and persistent activity of pyramidal neurons in layer V of the EC. Using electrophysiological recordings, we show that proBDNF suppresses persistent firing in entorhinal slices from wild-type mice but not from p75NTR-null mice. Conversely, function-blocking proBDNF antibodies enhance excitability of pyramidal neurons and facilitate their persistent firing, and acute exposure to function-blocking p75NTR antibodies results in enhanced firing activity of pyramidal neurons. Genetic deletion of p75NTR specifically in neurons or during adulthood also induces enhanced excitability and persistent activity, indicating that the proBDNF-p75NTR signaling cascade functions within adult neurons to inhibit pyramidal activity. Phosphatidylinositol 4,5-bisphosphate (PIP2)-sensitive transient receptor potential canonical channels play a critical role in mediating persistent firing in the EC and we hypothesized that proBDNF-dependent p75NTR activation regulates PIP2 levels. Accordingly, proBDNF decreases cholinergic calcium responses in cortical neurons and affects carbachol-induced depletion of PIP2. Further, we show that the modulation of persistent firing by proBDNF relies on a p75NTR-Rac1-PI4K pathway. The hypothesis that proBDNF and p75NTR maintain network homeostasis in the adult CNS was tested in vivo and we report that p75NTR-null mice show improvements in working memory but also display an increased propensity for severe seizures. We propose that the proBDNF-p75NTR axis controls pyramidal neuron excitability and persistent activity to balance EC performance with the risk of runaway activity. SIGNIFICANCE STATEMENT Persistent firing of entorhinal cortex (EC) pyramidal neurons is required for working memory. We report here that pro-brain-derived neurotrophic factor (proBDNF) activates p75NTR to induce a Rac1-dependent and phosphatidylinositol 4,5-bisphosphate-dependent signaling cascade that suppresses persistent activity. Conversely, using loss-of-function approaches, we find that endogenous proBDNF or p75NTR activation strongly decreases pyramidal neuron excitability and persistent firing, suggesting that a physiological role of this proBDNF-p75NTR cascade may be to regulate working memory in vivo. Consistent with this, mice rendered null for p75NTR during adulthood show improvements in working memory but also display an increased propensity for severe seizures. We propose that by attenuating EC network performance, the proBDNF-p75NTR signaling cascade reduces the probability of epileptogenesis.
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Affiliation(s)
- Julien Gibon
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada H3A2B4, and
| | - Shannon M Buckley
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada H3A2B4, and
| | - Nicolas Unsain
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada H3A2B4, and
| | - Vesa Kaartinen
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, Michigan 48109
| | - Philippe Séguéla
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada H3A2B4, and
| | - Philip A Barker
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada H3A2B4, and
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Plett JM, Gibon J, Kohler A, Duffy K, Hoegger PJ, Velagapudi R, Han J, Kües U, Grigoriev IV, Martin F. Phylogenetic, genomic organization and expression analysis of hydrophobin genes in the ectomycorrhizal basidiomycete Laccaria bicolor. Fungal Genet Biol 2012; 49:199-209. [PMID: 22293303 DOI: 10.1016/j.fgb.2012.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 11/30/2011] [Accepted: 01/17/2012] [Indexed: 11/19/2022]
Abstract
Hydrophobins are morphogenetic, small secreted hydrophobic fungal proteins produced in response to changing development and environmental conditions. These proteins are important in the interaction between certain fungi and their hosts. In mutualistic ectomycorrhizal fungi several hydrophobins form a subclass of mycorrhizal-induced small secreted proteins that are likely to be critical in the formation of the symbiotic interface with host root cells. In this study, two genomes of the ectomycorrhizal basidiomycete Laccaria bicolor strains S238N-H82 (from North America) and 81306 (from Europe) were surveyed to construct a comprehensive genome-wide inventory of hydrophobins and to explore their characteristics and roles during host colonization. The S238N-H82 L. bicolor hydrophobin gene family is composed of 12 genes while the 81306 strain encodes nine hydrophobins, all corresponding to class I hydrophobins. The three extra hydrophobin genes encoded by the S238N-H82 genome likely arose via gene duplication and are bordered by transposon rich regions. Expression profiles of the hydrophobin genes of L. bicolor varied greatly depending on life stage (e.g. free living mycelium vs. root colonization) and on the host root environment. We conclude from this study that the complex diversity and range of expression profiles of the Laccaria hydrophobin multi-gene family have likely been a selective advantage for this mutualist in colonizing a wide range of host plants.
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Affiliation(s)
- Jonathan M Plett
- INRA, UMR 1136 INRA - University Henri Poincaré, Interactions Arbres/Microorganismes, INRA-Nancy, 54280 Champenoux, France.
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Gibon J, Richaud P, Bouron A. Hyperforin changes the zinc-storage capacities of brain cells. Neuropharmacology 2011; 61:1321-6. [DOI: 10.1016/j.neuropharm.2011.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 07/19/2011] [Accepted: 08/03/2011] [Indexed: 01/12/2023]
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Vincent D, Kohler A, Claverol S, Solier E, Joets J, Gibon J, Lebrun MH, Plomion C, Martin F. Secretome of the Free-living Mycelium from the Ectomycorrhizal Basidiomycete Laccaria bicolor. J Proteome Res 2011; 11:157-71. [DOI: 10.1021/pr200895f] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Annegret Kohler
- INRA, UMR1136 Interactions Arbres/Micro-Organismes, Nancy, France
| | | | - Emilie Solier
- Plate-forme Protéomique, Université Bordeaux 2, Bordeaux, France
| | - Johann Joets
- UMR Génétique Végétale du Moulon, Gif-sur-Yvette, France
| | - Julien Gibon
- INRA, UMR1136 Interactions Arbres/Micro-Organismes, Nancy, France
| | | | | | - Francis Martin
- INRA, UMR1136 Interactions Arbres/Micro-Organismes, Nancy, France
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Bohic S, Ghersi-Egea JF, Gibon J, Paoletti P, Arnaud J, Hunot S, Boom A, Bouron A. [Biological roles of trace elements in the brain with special focus on Zn and Fe]. Rev Neurol (Paris) 2010; 167:269-79. [PMID: 21056442 DOI: 10.1016/j.neurol.2010.07.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 06/14/2010] [Accepted: 07/20/2010] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Many metals like iron (Fe), copper (Cu) or zinc (Zn) fulfil various essential biological functions and are thus vital for all living organisms. For instance, they play important roles in nervous tissue, participating in a wide range of processes such as neurotransmitter synthesis, myelination or synaptic transmission. STATE OF THE ART As in other tissues, brain cells tightly control the concentration of metals but any excess or deficit can lead to deleterious responses and alter cognitive functions. Of note, certain metals such as Zn, Fe or Cu accumulate in specific brain structures over lifespan and several neurodegenerative diseases are associated with a dysregulation of the homeostatic mechanisms controlling the concentration of these cations. CONCLUSION AND PERSPECTIVES This review will address some of the cellular and molecular processes controlling the entry and distribution of selected metals (mainly Zn and Fe) in the brain, as well as their roles in synaptic transmission, in the pathogenesis of some neurologic diseases such as Parkinson's disease and Alzheimer's disease, and their impact on cognitive functions.
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Affiliation(s)
- S Bohic
- Inserm U836, équipe 6 Rayonnement synchrotron et recherches médicales, Grenoble institut des neurosciences, 38054 Grenoble, France
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23
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Gibon J, Tu P, Frazzini V, Sensi SL, Bouron A. The thiol-modifying agent N-ethylmaleimide elevates the cytosolic concentration of free Zn(2+) but not of Ca(2+) in murine cortical neurons. Cell Calcium 2010; 48:37-43. [PMID: 20667413 DOI: 10.1016/j.ceca.2010.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 06/22/2010] [Accepted: 06/22/2010] [Indexed: 10/19/2022]
Abstract
The membrane permeant alkylating agent N-ethylmaleimide (NEM) regulates numerous biological processes by reacting with thiol groups. Among other actions, NEM influences the cytosolic concentration of free Ca(2+) ([Ca(2+)]i). Depending on the cell type and the concentration used, NEM can promote the release of Ca(2+), affect its extrusion, stimulate or block its entry. However, most of these findings were obtained in experiments that employed fluorescent Ca(2+) probes and one major disadvantage of such experimental setting derives from the lack of specificity of the probes as all the so-called "Ca(2+)-sensitive" indicators also bind metals like Zn(2+) or Mn(2+) with higher affinities than Ca(2+). In this study, we examined the effects of NEM on the [Ca(2+)]i homeostasis of murine cortical neurons. We performed live-cell Ca(2+) and Zn(2+) imaging experiments using the fluorescent probes Fluo-4, FluoZin-3 and RhodZin-3 and found that NEM does not affect the neuronal [Ca(2+)]i homeostasis but specifically increases the cytosolic and mitochondrial concentration of free Zn(2+)([Zn(2+)]i). In addition, NEM triggers some neuronal loss that is prevented by anti-oxidants such as N-acetylcysteine or glutathione. NEM-induced toxicity is dependent on changes in [Zn(2+)]i levels as chelation of the cation with the cell-permeable heavy metal chelator, N,N,N'N'-tetrakis(-)[2-pyridylmethyl]-ethylenediamine (TPEN), promotes neuroprotection of cortical neurons exposed to NEM. Our data indicate that NEM affects [Zn(2+)]i but not [Ca(2+)]i homeostasis and shed new light on the physiological actions of this alkylating agent on central nervous system neurons.
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24
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Gibon J, Tu P, Bouron A. Store-depletion and hyperforin activate distinct types of Ca(2+)-conducting channels in cortical neurons. Cell Calcium 2010; 47:538-43. [PMID: 20621761 DOI: 10.1016/j.ceca.2010.05.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Revised: 05/04/2010] [Accepted: 05/06/2010] [Indexed: 11/29/2022]
Abstract
Cortical neurons embryos (E13) from murine brain have a wide diversity of plasma membrane Ca(2+)-conducting channels. For instance, they express several types of transient receptor potential channels of C-type (TRPC) and hyperforin, a potent TRPC6-channel activator, controls the activity of TRPC6-like channels. In addition, E13 cortical neurons possess plasma membrane channels activated in response to the depletion of internal Ca(2+) pools. Since some TRPC channels seem to be involved in the activity of store-depletion-activated channels, we investigated whether hyperforin and the depletion of the Ca(2+) stores control similar or distinct Ca(2+) routes. Calcium imaging experiments performed with the fluorescent Ca(2+) indicator Fluo-4 showed that the TRPC3 channel blocker Pyr3 potently inhibits with an IC(50) of 0.5microM the entry of Ca(2+) triggered in response to the thapsigargin-dependent depletion of the Ca(2+) stores. On the other hand, Pyr3 does not block the hyperforin-sensitive Ca(2+) entry. In contrast to the hyperforin responses, the Ca(2+) entry through the store-depletion-activated channels is down-regulated by the competitive tyrosine kinase inhibitors genistein and PP2. In addition, the immunosuppressant FK506, known to modulate several classes of Ca(2+)-conducting channels, strongly attenuates the entry of Ca(2+) through the store-depletion-activated channels, leaving the hyperforin-sensitive responses unaffected. Hence, the Zn(2+) chelator TPEN markedly attenuated the hyperforin-sensitive responses without modifying the thapsigargin-dependent Ca(2+) signals. Pyr3-insensitive channels are key components of the hyperforin-sensitive channels, whereas the thapsigargin-dependent depletion of the Ca(2+) stores of the endoplasmic reticulum activates Pyr3-sensitive channels. Altogether, these data support the notion that hyperforin and the depletion of the Ca(2+) pools control distinct plasma membrane Ca(2+)-conducting channels. This report further illustrates that, at the beginning of the corticogenesis, immature cortical neurons express diverse functional Ca(2+) channels.
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Vincent D, Balesdent MH, Gibon J, Claverol S, Lapaillerie D, Lomenech AM, Blaise F, Rouxel T, Martin F, Bonneu M, Amselem J, Dominguez V, Howlett BJ, Wincker P, Joets J, Lebrun MH, Plomion C. Hunting down fungal secretomes using liquid-phase IEF prior to high resolution 2-DE. Electrophoresis 2010; 30:4118-36. [PMID: 19960477 DOI: 10.1002/elps.200900415] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The secreted proteins (secretome) of fungi play a key role in interactions of pathogenic and symbiotic fungi with plants. Using the plant pathogenic fungus Leptosphaeria maculans and symbiont Laccaria bicolor grown in culture, we have established a proteomic protocol for extraction, concentration and resolution of the fungal secretome. As no proteomic data were available on mycelium tissues from both L. maculans and L. bicolor, mycelial proteins were studied; they also helped verifying the purity of secretome samples. The quality of protein extracts was initially assessed by both 1-DE and 2-DE using first a broad pH range for IEF, and then narrower acidic and basic pH ranges, prior to 2-DE. Compared with the previously published protocols for which only dozens of 2-D spots were recovered from fungal secretome samples, up to approximately 2000 2-D spots were resolved by our method. MS identification of proteins along several pH gradients confirmed this high resolution, as well as the presence of major secretome markers such as endopolygalacturonases, beta-glucanosyltransferases, pectate lyases and endoglucanases. Shotgun proteomic experiments evidenced the enrichment of secreted protein within the liquid medium. This is the first description of the proteome of L. maculans and L. bicolor, and the first application of liquid-phase IEF to any fungal extracts.
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Abstract
Hyperforin, an extract of the medicinal plant hypericum perforatum (also named St John's wort), possesses antidepressant properties. Recent data showed that it elevates the intracellular concentration of Ca(2+) by activating diacylglycerol-sensitive C-class of transient receptor potential (TRPC6) channels without activating the other isoforms (TRPC1, TRPC3, TRPC4, TRPC5, and TRPC7). This study was undertaken to further characterize the cellular neuronal responses induced by hyperforin. Experiments conducted on cortical neurons in primary culture and loaded with fluorescent probes for Ca(2+) (Fluo-4) and Zn(2+) (FluoZin-3) showed that it not only controls the activity of plasma membrane channels but it also mobilizes these two cations from internal pools. Experiments conducted on isolated brain mitochondria indicated that hyperforin, like the inhibitor of oxidative phosphorylation, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), collapses the mitochondrial membrane potential. Furthermore, it promotes the release of Ca(2+) and Zn(2+) from these organelles via a ruthenium red-sensitive transporter. In fact, hyperforin exerts complex actions on CNS neurons. This antidepressant not only triggers the entry of cations via plasma membrane TRPC6 channels but it displays protonophore-like properties. As hyperforin is now use to probe the functions of native TRPC6 channels, our data indicate that caution is required when interpreting results obtained with this antidepressant.
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Affiliation(s)
- Peng Tu
- UMR CNRS 5249, Grenoble, France
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Cortes MAM, Gibon J, Chanteloup NK, Moulin-Schouleur M, Gilot P, Germon P. Inactivation of ibeA and ibeT results in decreased expression of type 1 fimbriae in extraintestinal pathogenic Escherichia coli strain BEN2908. Infect Immun 2008; 76:4129-36. [PMID: 18591231 PMCID: PMC2519445 DOI: 10.1128/iai.00334-08] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 04/25/2008] [Accepted: 06/21/2008] [Indexed: 12/21/2022] Open
Abstract
IbeA in extraintestinal pathogenic Escherichia coli (ExPEC) strains was previously described for its role in invasion. Here we investigated the role of IbeA and IbeT, encoded by a gene located downstream of ibeA, in the adhesion of the avian ExPEC strain BEN2908 to human brain microvascular endothelial cells (HBMEC). The DeltaibeA mutant was less adhesive to HBMEC than the wild-type strain BEN2908 was. Because strain BEN2908 also expresses type 1 fimbriae, we measured the adhesion specifically due to IbeA by comparing the adhesive properties of a Deltafim derivative of strain BEN2908 to those of a double Deltafim DeltaibeA mutant. No differences were observed, indicating that the reduction of adhesion in BEN2908 DeltaibeA could be due to a decrease in type 1 fimbria expression. We indeed showed that the decreased adhesion of BEN2908 DeltaibeA was correlated with a decrease in type 1 fimbria expression. Accordingly, more bacteria had a fim promoter orientated in the off position in a culture of BEN2908 DeltaibeA than in a culture of BEN2908. Expression of fimB and fimE, two genes encoding recombinases participating in controlling the orientation of the fim promoter, was decreased in BEN2908 DeltaibeA. A reduction of type 1 fimbria expression due to a preferential orientation of the fim promoter in the off position was also seen in an ibeT mutant of strain BEN2908. We finally suggest a role for IbeA and IbeT in modulating the expression of type 1 fimbriae through an as yet unknown mechanism.
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Affiliation(s)
- Mélanie A M Cortes
- INRA, UR 1282 Infectiologie Animale et Santé Publique, Laboratoire de Pathogénie Bactérienne, Nouzilly, France
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Tardif C, Pasquis P, Fourneyron V, Gibon J. Régime ventilatoire du rameur en activité simulée. Sci Sports 1986. [DOI: 10.1016/s0765-1597(86)80033-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Vincent A, Gibon J, Ghosez JP. [Surgical treatment of scoliosis]. Acta Orthop Belg 1973; 39:514-34. [PMID: 4724987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Vincent A, Ghosez JP, Gibon J. [Modification of Harrington's hooks]. Acta Orthop Belg 1972; 38:377-85. [PMID: 4656148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Ghosez JP, Vincent A, Gibon J. [Neurologic complication of adult idiopathic kyphoscoliosis]. Acta Orthop Belg 1972; 38:386-9. [PMID: 4656149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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