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Tsui CT, Mirkiani S, Roszko DA, Churchward MA, Mushahwar VK, Todd KG. In vitro biocompatibility evaluation of functional electrically stimulating microelectrodes on primary glia. Front Bioeng Biotechnol 2024; 12:1351087. [PMID: 38314352 PMCID: PMC10834782 DOI: 10.3389/fbioe.2024.1351087] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/10/2024] [Indexed: 02/06/2024] Open
Abstract
Neural interfacing devices interact with the central nervous system to alleviate functional deficits arising from disease or injury. This often entails the use of invasive microelectrode implants that elicit inflammatory responses from glial cells and leads to loss of device function. Previous work focused on improving implant biocompatibility by modifying electrode composition; here, we investigated the direct effects of electrical stimulation on glial cells at the electrode interface. A high-throughput in vitro system that assesses primary glial cell response to biphasic stimulation waveforms at 0 mA, 0.15 mA, and 1.5 mA was developed and optimized. Primary mixed glial cell cultures were generated from heterozygous CX3CR-1+/EGFP mice, electrically stimulated for 4 h/day over 3 days using 75 μm platinum-iridium microelectrodes, and biomarker immunofluorescence was measured. Electrodes were then imaged on a scanning electron microscope to assess sustained electrode damage. Fluorescence and electron microscopy analyses suggest varying degrees of localized responses for each biomarker assayed (Hoescht, EGFP, GFAP, and IL-1β), a result that expands on comparable in vivo models. This system allows for the comparison of a breadth of electrical stimulation parameters, and opens another avenue through which neural interfacing device developers can improve biocompatibility and longevity of electrodes in tissue.
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Affiliation(s)
- Christopher T. Tsui
- Department of Biomedical Engineering, University of Alberta, Edmonton, AB, Canada
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute (NMHI), University of Alberta, Edmonton, AB, Canada
- Sensory Motor Adaptive Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, AB, Canada
| | - Soroush Mirkiani
- Neuroscience and Mental Health Institute (NMHI), University of Alberta, Edmonton, AB, Canada
- Sensory Motor Adaptive Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, AB, Canada
| | - David A. Roszko
- Neuroscience and Mental Health Institute (NMHI), University of Alberta, Edmonton, AB, Canada
- Sensory Motor Adaptive Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, AB, Canada
| | - Matthew A. Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute (NMHI), University of Alberta, Edmonton, AB, Canada
- Sensory Motor Adaptive Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, AB, Canada
- Department of Biological and Environmental Sciences, Concordia University of Edmonton, Edmonton, AB, Canada
| | - Vivian K. Mushahwar
- Neuroscience and Mental Health Institute (NMHI), University of Alberta, Edmonton, AB, Canada
- Sensory Motor Adaptive Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, AB, Canada
- Division of Physical Medicine and Rehabilitation, Department of Medicine, University of Alberta, Edmonton, AB, Canada
| | - Kathryn G. Todd
- Department of Biomedical Engineering, University of Alberta, Edmonton, AB, Canada
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute (NMHI), University of Alberta, Edmonton, AB, Canada
- Sensory Motor Adaptive Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, AB, Canada
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Gupta SJ, Churchward MA, Todd KG, Winship IR. Pleiotrophin Signals Through ALK Receptor to Enhance the Growth of Neurons in the Presence of Inhibitory Chondroitin Sulfate Proteoglycans. Neurosci Insights 2023; 18:26331055231186993. [PMID: 37465214 PMCID: PMC10350765 DOI: 10.1177/26331055231186993] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 06/23/2023] [Indexed: 07/20/2023] Open
Abstract
Chondroitin sulfate proteoglycans (CSPGs), one of the major extracellular matrix components of the glial scar that surrounds central nervous system (CNS) injuries, are known to inhibit the regeneration of neurons. This study investigated whether pleiotrophin (PTN), a growth factor upregulated during early CNS development, can overcome the inhibition mediated by CSPGs and promote the neurite outgrowth of neurons in vitro. The data showed that a CSPG matrix inhibited the outgrowth of neurites in primary cortical neuron cultures compared to a control matrix. PTN elicited a dose-dependent increase in the neurite outgrowth even in the presence of the growth inhibitory CSPG matrix, with optimal growth at 15 ng mL-1 of PTN (114.8% of neuronal outgrowth relative to laminin control). The growth-promoting effect of PTN was blocked by inhibition of the receptor anaplastic lymphoma kinase (ALK) by alectinib in a dose-dependent manner. Neurite outgrowth in the presence of this CSPG matrix was induced by activation of the protein kinase B (AKT) pathway, a key downstream mediator of ALK activation. This study identified PTN as a dose-dependent regulator of neurite outgrowth in primary cortical neurons cultured in the presence of a CSPG matrix and identified ALK activation as a key driver of PTN-induced growth.
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Affiliation(s)
- Somnath J Gupta
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Matthew A Churchward
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Department of Biology and Environmental Sciences, Concordia University of Edmonton, Edmonton, AB, Canada
| | - Kathryn G Todd
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Ian R Winship
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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Churchward MA, Michaud ER, Mullish BH, Miguens Blanco J, Garcia Perez I, Marchesi JR, Xu H, Kao D, Todd KG. Short-chain fatty and carboxylic acid changes associated with fecal microbiota transplant communally influence microglial inflammation. Heliyon 2023; 9:e16908. [PMID: 37484415 PMCID: PMC10360965 DOI: 10.1016/j.heliyon.2023.e16908] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 05/24/2023] [Accepted: 05/31/2023] [Indexed: 07/25/2023] Open
Abstract
The intestinal microbiota has been proposed to influence human mental health and cognition through the gut-brain axis. Individuals experiencing recurrent Clostridioides difficile infection (rCDI) frequently report depressive symptoms, which are improved after fecal microbiota transplantation (FMT); however, mechanisms underlying this association are poorly understood. Short-chain fatty acids and carboxylic acids (SCCA) produced by the intestinal microbiota cross the blood brain barrier and have been proposed to contribute to gut-brain communication. We hypothesized that changes in serum SCCA measured before and after successful FMT for rCDI influences the inflammatory response of microglia, the resident immune cells of the central nervous system. Serum SCCA were quantified using gas chromatography-mass spectroscopy from 38 patients who participated in a randomized trial comparing oral capsule-vs colonoscopy-delivered FMT for rCDI, and quality of life was assessed by SF-36 at baseline, 4, and 12 weeks after FMT treatment. Successful FMT was associated with improvements in mental and physical health, as well as significant changes in a number of circulating SCCA, including increased butyrate, 2-methylbutyrate, valerate, and isovalerate, and decreased 2-hydroxybutyrate. Primary cultured microglia were treated with SCCA and the response to a pro-inflammatory stimulus was measured. Treatment with a combination of SCCA based on the post-FMT serum profile, but not single SCCA species, resulted in significantly reduced inflammatory response including reduced cytokine release, reduced nitric oxide release, and accumulation of intracellular lipid droplets. This suggests that both levels and diversity of SCCA may be an important contributor to gut-brain communication.
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Affiliation(s)
- Matthew A. Churchward
- Department of Biological and Environmental Sciences, Concordia University of Edmonton, AB, T5B 4E4, Canada
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2R3, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2R3, Canada
| | - Emily R. Michaud
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2R3, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2R3, Canada
| | - Benjamin H. Mullish
- Division of Digestive Diseases, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, W2 1NY, UK
| | - Jesús Miguens Blanco
- Division of Digestive Diseases, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, W2 1NY, UK
| | - Isabel Garcia Perez
- Division of Digestive Diseases, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, W2 1NY, UK
| | - Julian R. Marchesi
- Division of Digestive Diseases, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, W2 1NY, UK
| | - Huiping Xu
- Department of Biostatistics and Health Data Science, Indiana University School of Medicine Indianapolis, IN, USA, 46202
| | - Dina Kao
- Division of Gastroenterology, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, T6G 2R3, Canada
| | - Kathryn G. Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2R3, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2R3, Canada
- Department of Biomedical Engineering, University of Alberta, Edmonton, AB, T6G 2R3, Canada
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Koss KM, Son T, Li C, Hao Y, Cao J, Churchward MA, Zhang ZJ, Wertheim JA, Derda R, Todd KG. Toward discovering a novel family of peptides targeting neuroinflammatory states of brain microglia and astrocytes. J Neurochem 2023:10.1111/jnc.15840. [PMID: 37171455 PMCID: PMC10640667 DOI: 10.1111/jnc.15840] [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: 12/16/2022] [Revised: 04/17/2023] [Accepted: 04/19/2023] [Indexed: 05/13/2023]
Abstract
Microglia are immune-derived cells critical to the development and healthy function of the brain and spinal cord, yet are implicated in the active pathology of many neuropsychiatric disorders. A range of functional phenotypes associated with the healthy brain or disease states has been suggested from in vivo work and were modeled in vitro as surveying, reactive, and primed sub-types of primary rat microglia and mixed microglia/astrocytes. It was hypothesized that the biomolecular profile of these cells undergoes a phenotypical change as well, and these functional phenotypes were explored for potential novel peptide binders using a custom 7 amino acid-presenting M13 phage library (SX7) to identify unique peptides that bind differentially to these respective cell types. Surveying glia were untreated, reactive were induced with a lipopolysaccharide treatment, recovery was modeled with a potent anti-inflammatory treatment dexamethasone, and priming was determined by subsequently challenging the cells with interferon gamma. Microglial function was profiled by determining the secretion of cytokines and nitric oxide, and expression of inducible nitric oxide synthase. After incubation with the SX7 phage library, populations of SX7-positive microglia and/or astrocytes were collected using fluorescence-activated cell sorting, SX7 phage was amplified in Escherichia coli culture, and phage DNA was sequenced via next-generation sequencing. Binding validation was done with synthesized peptides via in-cell westerns. Fifty-eight unique peptides were discovered, and their potential functions were assessed using a basic local alignment search tool. Peptides potentially originated from proteins ranging in function from a variety of supportive glial roles, including synapse support and pruning, to inflammatory incitement including cytokine and interleukin activation, and potential regulation in neurodegenerative and neuropsychiatric disorders.
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Affiliation(s)
- K M Koss
- Comprehensive Transplant Center and Department of Surgery, Feinberg School of Medicine, Northwestern University, Illinois, Chicago, USA
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Alberta, Edmonton, Canada
- Department of Surgery, University of Arizona College of Medicine, Arizona, Tucson, USA
| | - T Son
- Comprehensive Transplant Center and Department of Surgery, Feinberg School of Medicine, Northwestern University, Illinois, Chicago, USA
| | - C Li
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr NW, Edmonton, AB T6G 2G2, Canada
| | - Y Hao
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr NW, Edmonton, AB T6G 2G2, Canada
| | - J Cao
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr NW, Edmonton, AB T6G 2G2, Canada
- 48Hour Discovery Inc, 11421 Saskatchewan Dr NW, Edmonton, AB T6G 2M9, Canada
| | - M A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Alberta, Edmonton, Canada
- Department of Biology and Environmental Sciences, Concordia University of Edmonton, Alberta, Edmonton, Canada
| | - Z J Zhang
- Comprehensive Transplant Center and Department of Surgery, Feinberg School of Medicine, Northwestern University, Illinois, Chicago, USA
| | - J A Wertheim
- Comprehensive Transplant Center and Department of Surgery, Feinberg School of Medicine, Northwestern University, Illinois, Chicago, USA
- Department of Surgery, University of Arizona College of Medicine, Arizona, Tucson, USA
| | - R Derda
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Dr NW, Edmonton, AB T6G 2G2, Canada
- 48Hour Discovery Inc, 11421 Saskatchewan Dr NW, Edmonton, AB T6G 2M9, Canada
| | - K G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Alberta, Edmonton, Canada
- Department of Biomedical Engineering, University of Alberta, Alberta, Edmonton, Canada
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Tsui CT, Lal P, Fox KVR, Churchward MA, Todd KG. The effects of electrical stimulation on glial cell behaviour. BMC Biomed Eng 2022; 4:7. [PMID: 36057631 PMCID: PMC9441051 DOI: 10.1186/s42490-022-00064-0] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 08/09/2022] [Indexed: 12/05/2022] Open
Abstract
Neural interface devices interact with the central nervous system (CNS) to substitute for some sort of functional deficit and improve quality of life for persons with disabilities. Design of safe, biocompatible neural interface devices is a fast-emerging field of neuroscience research. Development of invasive implant materials designed to directly interface with brain or spinal cord tissue has focussed on mitigation of glial scar reactivity toward the implant itself, but little exists in the literature that directly documents the effects of electrical stimulation on glial cells. In this review, a survey of studies documenting such effects has been compiled and categorized based on the various types of stimulation paradigms used and their observed effects on glia. A hybrid neuroscience cell biology-engineering perspective is offered to highlight considerations that must be made in both disciplines in the development of a safe implant. To advance knowledge on how electrical stimulation affects glia, we also suggest experiments elucidating electrochemical reactions that may occur as a result of electrical stimulation and how such reactions may affect glia. Designing a biocompatible stimulation paradigm should be a forefront consideration in the development of a device with improved safety and longevity.
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Affiliation(s)
- Christopher T Tsui
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Biomedical Engineering, University of Alberta, Edmonton, AB, T6G 2V2, Canada
| | - Preet Lal
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Katelyn V R Fox
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Matthew A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.,Department of Biological and Environmental Sciences, Concordia University of Edmonton, Edmonton, AB, T5B 4E4, Canada
| | - Kathryn G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB, T6G 2G3, Canada. .,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada. .,Department of Biomedical Engineering, University of Alberta, Edmonton, AB, T6G 2V2, Canada.
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Jesudasan SJB, Gupta SJ, Churchward MA, Todd KG, Winship IR. Inflammatory Cytokine Profile and Plasticity of Brain and Spinal Microglia in Response to ATP and Glutamate. Front Cell Neurosci 2021; 15:634020. [PMID: 33889075 PMCID: PMC8057348 DOI: 10.3389/fncel.2021.634020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 03/10/2021] [Indexed: 11/27/2022] Open
Abstract
Microglia are the primary cells in the central nervous system that identify and respond to injury or damage. Such a perturbation in the nervous system induces the release of molecules including ATP and glutamate that act as damage-associated molecular patterns (DAMPs). DAMPs are detected by microglia, which then regulate the inflammatory response in a manner sensitive to their surrounding environment. The available data indicates that ATP and glutamate can induce the release of pro inflammatory factors TNF (tumor necrosis factor), IL-1β (interleukin 1 beta), and NO (nitric oxide) from microglia. However, non-physiological concentrations of ATP and glutamate were often used to derive these insights. Here, we have compared the response of spinal cord microglia (SM) relative to brain microglia (BM) using physiologically relevant concentrations of glutamate and ATP that mimic injured conditions in the central nervous system. The data show that ATP and glutamate are not significant modulators of the release of cytokines from either BM or SM. Consistent with previous studies, spinal microglia exhibited a general trend toward reduced release of inflammatory cytokines relative to brain-derived microglia. Moreover, we demonstrate that the responses of microglia to these DAMPs can be altered by modifying the biochemical milieu in their surrounding environment. Preconditioning brain derived microglia with media from spinal cord derived mixed glial cultures shifted their release of IL-1ß and IL-6 to a less inflammatory phenotype consistent with spinal microglia.
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Affiliation(s)
- Sam Joshva Baskar Jesudasan
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Somnath J. Gupta
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Matthew A. Churchward
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Department of Biology and Environmental Sciences, Concordia University of Edmonton, Edmonton, AB, Canada
| | - Kathryn G. Todd
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Ian R. Winship
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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Tsui CT, MacGillivray SR, Weber SM, McAllister L, Churchward MA, Dennison CR, Todd KG. Applying a novel 3D hydrogel cell culture to investigate activation of microglia due to rotational kinematics associated with mild traumatic brain injury. J Mech Behav Biomed Mater 2020; 114:104176. [PMID: 33184015 DOI: 10.1016/j.jmbbm.2020.104176] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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: 06/23/2020] [Revised: 08/25/2020] [Accepted: 10/23/2020] [Indexed: 10/23/2022]
Abstract
Many investigations on mild traumatic brain injury (mTBI) aim to further understand how cells in the brain react to the mechanical forces associated with the injury. While it is known that rapid head rotation is a mechanism contributing to mTBI, establishing definitive thresholds for head rotation has proved challenging. One way to advance determining mechanisms and thresholds for injury is through in vitro models. Here, an apparatus has been designed that is capable of delivering rotational forces to three-dimensional (3D) hydrogel cell cultures. Using an in vitro model, we test the hypothesis that rotational kinematics can activate microglia suspended in a 3-dimensional mixed glia environment (absent neurons). The impact apparatus was able to deliver peak angular velocities of approximately 45 rad/s, a magnitude for angular velocity that in select literature is associated with diffuse brain injury. However, no measurable glial cell reactivity was observed in response to the rotational kinematics through any of the chosen metrics (nitric oxide, pro-inflammatory cytokine release and proportion of amoeboid activated microglia). The results generated from this study suggest that rotation of the glia alone did not cause activation - in future work we will investigate the effect of neuronal contributions in activating glia.
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Affiliation(s)
- Christopher T Tsui
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Department of Biomedical Engineering, University of Alberta, Edmonton, AB T6G 2V2, Canada.
| | - Samantha R MacGillivray
- Biomedical Instrumentation Lab, Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
| | - Savannah M Weber
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada.
| | - Lowell McAllister
- Biomedical Instrumentation Lab, Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
| | - Matthew A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada.
| | - Christopher R Dennison
- Biomedical Instrumentation Lab, Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
| | - Kathryn G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Department of Biomedical Engineering, University of Alberta, Edmonton, AB T6G 2V2, Canada.
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Churchward MA, Michaud ER, Todd KG. Supporting microglial niches for therapeutic benefit in psychiatric disorders. Prog Neuropsychopharmacol Biol Psychiatry 2019; 94:109648. [PMID: 31078613 DOI: 10.1016/j.pnpbp.2019.109648] [Citation(s) in RCA: 4] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 05/06/2019] [Accepted: 05/08/2019] [Indexed: 12/27/2022]
Abstract
Inflammation is an essential tissue response to injury, stress, or infection resulting in debris and/or pathogen clearance intended to promote healing and recovery. Due to the status as an immune 'privileged' tissue, microglia serve as endogenous regulators of inflammation in the central nervous system, but maintain communication with peripheral immune system to enable recruitment of peripheral immune cells in case of injury or infection. While microglia retain the functional capacity for a full range of inflammatory functions - microglia express a range of pattern-recognition receptors and function as innate immune cells, carry out phagocytosis of pathogens, and act as antigen presenting cells - in the healthy central nervous system (CNS) these functions are rarely engaged. Subsequently microglia are being recognized to occupy an increasing number of homeostatic niches, and in many cases have adopted immune or inflammatory mechanisms to carry out these niche functions absent immune activation. These sterile inflammatory functions are challenging long-held views of the role of inflammation in the central nervous system while simultaneously expanding the potential for the development of truly novel therapeutic interventions for a range of neuroinflammatory, neurodegenerative, and neuropsychiatric disorders. In the present review we discuss recent preclinical evidence for conserved niche functions for microglia whose disruption may causally contribute to various psychiatric disorders, and prospective targets for restoring disrupted niches.
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Affiliation(s)
- M A Churchward
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada; Neuroscience and Mental Health Institute, Faculty of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada.
| | - E R Michaud
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada; Neuroscience and Mental Health Institute, Faculty of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - K G Todd
- Neurochemical Research Unit, Department of Psychiatry, Faculty of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada; Neuroscience and Mental Health Institute, Faculty of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada; Department of Biomedical Engineering, University of Alberta, Edmonton, AB T6G2R3, Canada
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Dhami KS, Churchward MA, Baker GB, Todd KG. Fluoxetine and its metabolite norfluoxetine induce microglial apoptosis. J Neurochem 2019; 148:761-778. [DOI: 10.1111/jnc.14661] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 11/28/2022]
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Tsui C, Koss K, Churchward MA, Todd KG. Biomaterials and glia: Progress on designs to modulate neuroinflammation. Acta Biomater 2019; 83:13-28. [PMID: 30414483 DOI: 10.1016/j.actbio.2018.11.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [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: 07/20/2018] [Revised: 10/05/2018] [Accepted: 11/06/2018] [Indexed: 02/06/2023]
Abstract
Microglia are multi-functional cells that play a vital role in establishing and maintaining the function of the nervous system and determining the fate of neurons following injury or neuropathology. The roles of microglia are diverse and essential to the capacity of the nervous system to recover from injury, however sustained inflammation can limit recovery and drive chronic disease processes such as neurodegenerative disorders. When assessing implantable therapeutic devices in the central nervous system, an improved lifetime of the implant is considered achievable through the attenuation of microglial inflammation. Consequently, there is a tremendous underexplored potential in biomaterial and engineered design to modulate neuroinflammation for therapeutic benefit. Several strategies for improving device compatibility reviewed here include: biocompatible coatings, improved designs in finer and flexible shapes to reduce tissue shear-related scarring, and loading of anti-inflammatory drugs. Studies about microglial cell cultures in 3D hydrogels and nanoscaffolds to assess various injuries and disorders are also discussed. A variety of other microglia-targeting treatments are also reviewed, including nanoparticulate systems, cellular backpacks, and gold plinths, with the intention of delivering anti-inflammatory drugs by targeting the phagocytic nature of microglia. Overall, this review highlights recent advances in biomaterials targeting microglia and inflammatory function with the potential for improving implant rejection and biocompatibility studies. STATEMENT OF SIGNIFICANCE: Microglia are the resident immune cells of the central nervous system, and thus play a central role in the neuroinflammatory response against conditions than span acute injuries, neuropsychiatric disorders, and neurodegenerative disorders. This review article presents a summary of biomaterials research that target microglia and other glial cells in order to attenuate neuroinflammation, including but not limited to: design of mechanically compliant and biocompatible stimulation electrodes, hydrogels for high-throughput 3D modelling of nervous tissue, and uptake of nanoparticle drug delivery systems. The goal of this paper is to identify strengths and gaps in the relevant literature, and to promote further consideration of microglia behaviour and neuroinflammation in biomaterial design.
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Affiliation(s)
- C Tsui
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2R3, Canada; Department of Biomedical Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - K Koss
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2R3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - M A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2R3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - K G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2R3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2R3, Canada; Department of Biomedical Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada.
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Koss KM, Churchward MA, Jeffery AF, Mushahwar VK, Elias AL, Todd KG. Improved 3D Hydrogel Cultures of Primary Glial Cells for In Vitro Modelling of Neuroinflammation. J Vis Exp 2017. [PMID: 29286415 DOI: 10.3791/56615] [Citation(s) in RCA: 7] [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] [Indexed: 12/17/2022] Open
Abstract
In the central nervous system, numerous acute injuries and neurodegenerative disorders, as well as implanted devices or biomaterials engineered to enhance function result in the same outcome: excess inflammation leads to gliosis, cytotoxicity, and/or formation of a glial scar that collectively exacerbate injury or prevent healthy recovery. With the intent of creating a system to model glial scar formation and study inflammatory processes, we have generated a 3D cell scaffold capable of housing primary cultured glial cells: microglia that regulate the foreign body response and initiate the inflammatory event, astrocytes that respond to form a fibrous scar, and oligodendrocytes that are typically vulnerable to inflammatory injury. The present work provides a detailed step-by-step method for the fabrication, culture, and microscopic characterization of a hyaluronic acid-based 3D hydrogel scaffold with encapsulated rat brain-derived glial cells. Further, protocols for characterization of cell encapsulation and the hydrogel scaffold by confocal immunofluorescence and scanning electron microscopy are demonstrated, as well as the capacity to modify the scaffold with bioactive substrates, with incorporation of a commercial basal lamina mixture to improved cell integration.
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Affiliation(s)
- Kyle M Koss
- Department of Psychiatry, University of Alberta; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta
| | - Matthew A Churchward
- Department of Psychiatry, University of Alberta; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta
| | - Andrea F Jeffery
- Department of Psychiatry, University of Alberta; Department of Chemical and Materials Engineering, University of Alberta
| | - Vivian K Mushahwar
- Department of Psychiatry, University of Alberta; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta; Division of Physical Medicine and Rehabilitation, University of Alberta
| | - Anastasia L Elias
- Department of Chemical and Materials Engineering, University of Alberta
| | - Kathryn G Todd
- Department of Psychiatry, University of Alberta; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta; Centre for Neuroscience, University of Alberta;
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12
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Sridar S, Churchward MA, Mushahwar VK, Todd KG, Elias AL. Peptide modification of polyimide-insulated microwires: Towards improved biocompatibility through reduced glial scarring. Acta Biomater 2017; 60:154-166. [PMID: 28735029 DOI: 10.1016/j.actbio.2017.07.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [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: 04/06/2017] [Revised: 07/01/2017] [Accepted: 07/18/2017] [Indexed: 01/12/2023]
Abstract
The goal of this study is to improve the integration of implanted microdevices with tissue in the central nervous system (CNS). The long-term utility of neuroprosthetic devices implanted in the CNS is affected by the formation of a scar by resident glial cells (astrocytes and microglia), limiting the viability and functional stability of the devices. Reduction in the proliferation of glial cells is expected to enhance the biocompatibility of devices. We demonstrate the modification of polyimide-insulated microelectrodes with a bioactive peptide KHIFSDDSSE. Microelectrode wires were functionalized with (3-aminopropyl) triethoxy silane (APTES); the peptide was then covalently bonded to the APTES. The soluble peptide was tested in 2D mixed cultures of astrocytes and microglia, and reduced the proliferation of both cell types. The interactions of glial cells with the peptide-modified wires was then examined in 3D cell-laden hydrogels by immunofluorescence microscopy. As expected for uncoated wires, the microglia were first attracted to the wire (7days) followed by astrocyte recruitment and hypertrophy (14days). For the peptide-treated wires, astrocytes coated the wires directly (24h), and formed a thin, stable coating without evidence of hypertrophy, and the attraction of microglia to the wire was significantly reduced. The results suggest a mechanism to improve tissue integration by promoting uniform coating of astrocytes on a foreign body while lessening the reactive response of microglia. We conclude that the bioactive peptide KHIFSDDSSE may be effective in improving the biocompatibility of neural interfaces by both reducing acute glial reactivity and generating stable integration with tissue. STATEMENT OF SIGNIFICANCE The peptide KHIFSDDSSE has previously been shown in vitro to both reduce the proliferation of astrocytes, and to increase the adhesion of astrocyte to glass substrates. Here, we demonstrate a method to apply uniform coatings of peptides to microwires, which could readily be generalized to other peptides and surfaces. We then show that when peptide-modified wires are inserted into 3D cell-laden hydrogels, the normal cellular reaction (microglial activation followed by astrocyte recruitment and hypertrophy) does not occur, rather astrocytes are attracted directly to the surface of the wire, forming a relatively thin and uniform coating. This suggests a method to improve tissue integration of implanted devices to reduce glial scarring and ultimately reduce failure of neural interfaces.
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Affiliation(s)
- Sangita Sridar
- Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta, AB, Canada
| | - Matthew A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta, AB, Canada
| | - Vivian K Mushahwar
- Division of Physical Medicine and Rehabilitation, University of Alberta, Edmonton, AB T6G 2E1, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta, AB, Canada
| | - Kathryn G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta, AB, Canada
| | - Anastasia L Elias
- Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada; Alberta Innovates-Health Solutions Interdisciplinary Team in Smart Neural Prostheses (Project SMART), University of Alberta, AB, Canada.
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13
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Churchward MA, Tchir DR, Todd KG. Microglial Function during Glucose Deprivation: Inflammatory and Neuropsychiatric Implications. Mol Neurobiol 2017; 55:1477-1487. [PMID: 28176274 PMCID: PMC5820372 DOI: 10.1007/s12035-017-0422-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Accepted: 01/25/2017] [Indexed: 12/23/2022]
Abstract
Inflammation is increasingly recognized as a contributor to the pathophysiology of neuropsychiatric disorders, including depression, anxiety disorders and autism, though the factors leading to contextually inappropriate or sustained inflammation in pathological conditions are yet to be elucidated. Microglia, as the key mediators of inflammation in the CNS, serve as likely candidates in initiating pathological inflammation and as an ideal point of therapeutic intervention. Glucose deprivation, as a component of the pathophysiology of ischemia or occurring transiently in diabetes, may serve to modify microglial function contributing to inflammatory injury. To this end, primary microglia were cultured from postnatal rat brain and subject to glucose deprivation in vitro. Microglia were characterized for their proliferation, phagocytic function and secretion of inflammatory factors, and tested for their capacity to respond to a potent inflammatory stimulus. In the absence of glucose, microglia remained capable of proliferation, phagocytosis and inflammatory activation and showed increased release of inflammatory factors after presentation of an inflammatory stimulus. Glucose-deprived microglia demonstrated increased phagocytic activity and decreased accumulation of lipids in lipid droplets over a 48-h timecourse, suggesting they may use scavenged lipids as a key alternate energy source during metabolic stress. In the present manuscript, we present novel findings that glucose deprivation may sensitize microglial release of inflammatory mediators and prime microglial functions for both survival and inflammatory roles, which may contribute to psychiatric comorbidities of ischemia, diabetes and/or metabolic disorder.
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Affiliation(s)
- Matthew A Churchward
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, 116th St and 85th Ave NW, Edmonton, AB T6G2R3, Canada
| | - Devan R Tchir
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, 116th St and 85th Ave NW, Edmonton, AB T6G2R3, Canada
| | - Kathryn G Todd
- Neurochemical Research Unit, Department of Psychiatry, University of Alberta, 116th St and 85th Ave NW, Edmonton, AB T6G2R3, Canada. .,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB T6G 2R3, Canada.
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14
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Churchward MA, Todd KG. Statin treatment affects cytokine release and phagocytic activity in primary cultured microglia through two separable mechanisms. Mol Brain 2014; 7:85. [PMID: 25424483 PMCID: PMC4247600 DOI: 10.1186/s13041-014-0085-7] [Citation(s) in RCA: 38] [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: 07/03/2014] [Accepted: 11/08/2014] [Indexed: 12/14/2022] Open
Abstract
Background As the primary immune cells of the central nervous system, microglia contribute to development, homeostasis, and plasticity of the central nervous system, in addition to their well characterized roles in the foreign body and inflammatory responses. Increasingly, inappropriate activation of microglia is being reported as a component of inflammation in neurodegenerative and neuropsychiatric disorders. The statin class of cholesterol-lowering drugs have been observed to have anti-inflammatory and protective effects in both neurodegenerative diseases and ischemic stroke, and are suggested to act by attenuating microglial activity. Results We sought to investigate the effects of simvastatin treatment on the secretory profile and phagocytic activity of primary cultured rat microglia, and to dissect the mechanism of action of simvastatin on microglial activity. Simvastatin treatment altered the release of cytokines and trophic factors from microglia, including interleukin-1-β, tumour necrosis factor-α, and brain derived neurotrophic factor in a cholesterol-dependent manner. Conversely, simvastatin inhibited phagocytosis in microglia in a cholesterol-independent manner. Conclusions The disparity in cholesterol dependence of cytokine release and phagocytosis suggests the two effects occur through distinct molecular mechanisms. These two pathways may provide an opportunity for further refinement of pharmacotherapies for neuroinflammatory, neurodegenerative, and neuropsychiatric disorders.
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Affiliation(s)
- Matthew A Churchward
- Neurochemical Research Unit, University of Alberta Faculty of Medicine, Edmonton, AB, Canada, T6G 2R3. .,Department of Psychiatry, University of Alberta Faculty of Medicine, Edmonton, AB, Canada, T6G 2R3.
| | - Kathryn G Todd
- Neurochemical Research Unit, University of Alberta Faculty of Medicine, Edmonton, AB, Canada, T6G 2R3. .,Department of Psychiatry, University of Alberta Faculty of Medicine, Edmonton, AB, Canada, T6G 2R3. .,Neuroscience and Mental Health Institute, University of Alberta Faculty of Medicine, Edmonton, AB, Canada, T6G 2R3.
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15
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Jeffery AF, Churchward MA, Mushahwar VK, Todd KG, Elias AL. Hyaluronic Acid-Based 3D Culture Model for In Vitro Testing of Electrode Biocompatibility. Biomacromolecules 2014; 15:2157-65. [DOI: 10.1021/bm500318d] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Andrea F. Jeffery
- Chemical
and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada
- Alberta Innovates-Health
Solutions Interdisciplinary Team in Smart Neural Prostheses (Project
SMART), University of Alberta, AB, Canada
| | - Matthew A. Churchward
- Department
of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada
- Alberta Innovates-Health
Solutions Interdisciplinary Team in Smart Neural Prostheses (Project
SMART), University of Alberta, AB, Canada
| | - Vivian K. Mushahwar
- Division
of Physical Medicine and Rehabilitation, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Centre
for Neuroscience, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Alberta Innovates-Health
Solutions Interdisciplinary Team in Smart Neural Prostheses (Project
SMART), University of Alberta, AB, Canada
| | - Kathryn G. Todd
- Department
of Psychiatry, University of Alberta, Edmonton, AB T6G 2G3, Canada
- Centre
for Neuroscience, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Alberta Innovates-Health
Solutions Interdisciplinary Team in Smart Neural Prostheses (Project
SMART), University of Alberta, AB, Canada
| | - Anastasia L. Elias
- Chemical
and Materials Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada
- Alberta Innovates-Health
Solutions Interdisciplinary Team in Smart Neural Prostheses (Project
SMART), University of Alberta, AB, Canada
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16
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Rogasevskaia TP, Churchward MA, Coorssen JR. Anionic lipids in Ca(2+)-triggered fusion. Cell Calcium 2012; 52:259-69. [PMID: 22516687 DOI: 10.1016/j.ceca.2012.03.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [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: 02/13/2012] [Revised: 03/20/2012] [Accepted: 03/25/2012] [Indexed: 01/30/2023]
Abstract
Anionic lipids are native membrane components that have a profound impact on many cellular processes, including regulated exocytosis. Nonetheless, the full nature of their contribution to the fast, Ca(2+)-triggered fusion pathway remains poorly defined. Here we utilize the tightly coupled quantitative molecular and functional analyses enabled by the cortical vesicle model system to elucidate the roles of specific anionic lipids in the docking, priming and fusion steps of regulated release. Studies with cholesterol sulfate established that effectively localized anionic lipids could contribute to Ca(2+)-sensing and even bind Ca(2+) directly as effectors of necessary membrane rearrangements. The data thus support a role for phosphatidylserine in Ca(2+) sensing. In contrast, phosphatidylinositol would appear to serve regulatory functions in the physiological fusion machine, contributing to priming and thus the modulation and tuning of the fusion process. We note the complexities associated with establishing the specific roles of (anionic) lipids in the native fusion mechanism, including their localization and interactions with other critical components that also remain to be more clearly and quantitatively defined.
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Affiliation(s)
- Tatiana P Rogasevskaia
- Department of Chemical & Biological Sciences, Mount Royal University, 4825 Mount Royal Gate SW, Calgary, AB, T3E 6K6 Canada
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Furber KL, Churchward MA, Rogasevskaia TP, Coorssen JR. Identifying critical components of native Ca2+-triggered membrane fusion. Integrating studies of proteins and lipids. Ann N Y Acad Sci 2009; 1152:121-34. [PMID: 19161383 DOI: 10.1111/j.1749-6632.2008.03993.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ca(2+)-triggered membrane fusion is the defining step of exocytosis. Despite realization that the fusion machinery must include lipids and proteins working in concert, only of late has work in the field focused more equally on both these components. Here we use isolated sea urchin egg cortical vesicles (CV), a stage-specific preparation of Ca(2+)-sensitive release-ready vesicles that enables the tight coupling of molecular and functional analyses necessary to dissect molecular mechanisms. The stalk-pore hypothesis proposes that bilayer merger proceeds rapidly via transient, high-negative curvature, intermediate membrane structures. Consistent with this, cholesterol, a major component of the CV membrane, contributes to a critical local negative curvature that supports formation of lipidic fusion intermediates. Following cholesterol depletion, structurally dissimilar lipids having intrinsic negative curvature greater than or equal to cholesterol recover the ability of CV to fuse but do not recover fusion efficiency (Ca(2+) sensitivity and kinetics). Conversely, cholesterol- and sphingomyelin-enriched microdomains regulate the efficiency of the fusion mechanism, presumably by contributing spatial and functional organization of other critical lipids and proteins at the fusion site. Critical proteins are thought to participate in Ca(2+) sensing, initiating membrane deformations, and facilitating fusion pore expansion. Capitalizing on a novel effect of the thiol-reactive reagent iodoacetamide (IA), potentiation of the Ca(2+) sensitivity and kinetics, a fluorescently tagged IA has been used to enhance fusion efficiency and simultaneously label the proteins involved. Isolation of cholesterol-enriched CV membrane fractions, using density gradient centrifugation, is being used to narrow the list of protein candidates potentially critical to the mechanism of fast Ca(2+)-triggered membrane fusion.
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Affiliation(s)
- Kendra L Furber
- Department of Physiology and Biophysics, University of Calgary, Faculty of Medicine, Calgary, Canada
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18
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Abstract
Proteomic analyses using two-dimensional gel electrophoresis (2DE) depend heavily upon the quality of protein stains for sensitive detection. Indeed, detection rather than protein resolution is likely a current limiting factor in 2DE. The recent development of fluorescent protein stains has dramatically improved the sensitivity of in-gel protein detection and has enabled more accurate protein quantification. Here, we have evaluated the overall quality and relative cost of five commercially available fluorescent stains, Krypton, Deep Purple, Rubeo, Flamingo, and the most commonly used stain, Sypro Ruby (SR). All stains were found to be statistically comparable with regard to number of protein spots detected, but SR was superior with regard to fluorophore stability (e.g., capacity for repeated use of the stain solution). Notably, colloidal Coomassie Blue was also found to be comparable to SR when detected using an infrared fluorescence imaging system rather than standard densitometry. Thus, depending on available equipment and operating budgets, there are at least two high-sensitivity alternatives to achieve the best currently available in-gel protein detection: Sypro Ruby or Coomassie Blue.
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Affiliation(s)
- Lauren R Harris
- Department of Physiology & Biophysics, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, AB, T2N 4N1, Canada
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Churchward MA, Rogasevskaia T, Höfgen J, Bau J, Coorssen JR. Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion. J Cell Sci 2005; 118:4833-48. [PMID: 16219690 DOI: 10.1242/jcs.02601] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The process of regulated exocytosis is defined by the Ca2+-triggered fusion of two apposed membranes, enabling the release of vesicular contents. This fusion step involves a number of energetically complex steps and requires both protein and lipid membrane components. The role of cholesterol has been investigated using isolated release-ready native cortical secretory vesicles to analyze the Ca2+-triggered fusion step of exocytosis. Cholesterol is a major component of vesicle membranes and we show here that selective removal from membranes, selective sequestering within membranes, or enzymatic modification causes a significant inhibition of the extent, Ca2+ sensitivity and kinetics of fusion. Depending upon the amount incorporated, addition of exogenous cholesterol to cholesterol-depleted membranes consistently recovers the extent, but not the Ca2+ sensitivity or kinetics of fusion. Membrane components of comparable negative curvature selectively recover the ability to fuse, but are unable to recover the kinetics and Ca2+ sensitivity of vesicle fusion. This indicates at least two specific positive roles for cholesterol in the process of membrane fusion: as a local membrane organizer contributing to the efficiency of fusion, and, by virtue of its intrinsic negative curvature, as a specific molecule working in concert with protein factors to facilitate the minimal molecular machinery for fast Ca2+-triggered fusion.
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Affiliation(s)
- Matthew A Churchward
- Department of Physiology and Biophysics, Hotchkiss Brain Institute, University of Calgary, Health Sciences Centre, Faculty of Medicine, Calgary, Alberta, T2N 4N1, Canada
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Churchward MA, Butt RH, Lang JC, Hsu KK, Coorssen JR. Enhanced detergent extraction for analysis of membrane proteomes by two-dimensional gel electrophoresis. Proteome Sci 2005; 3:5. [PMID: 15941475 PMCID: PMC1184097 DOI: 10.1186/1477-5956-3-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2005] [Accepted: 06/07/2005] [Indexed: 11/29/2022] Open
Abstract
Background The analysis of hydrophobic membrane proteins by two-dimensional gel electrophoresis has long been hampered by the concept of inherent difficulty due to solubility issues. We have optimized extraction protocols by varying the detergent composition of the solubilization buffer with a variety of commercially available non-ionic and zwitterionic detergents and detergent-like phospholipids. Results After initial analyses by one-dimensional SDS-PAGE, quantitative two-dimensional analyses of human erythrocyte membranes, mouse liver membranes, and mouse brain membranes, extracted with buffers that included the zwitterionic detergent MEGA 10 (decanoyl-N-methylglucamide) and the zwitterionic lipid LPC (1-lauroyl lysophosphatidylcholine), showed selective improvement over extraction with the common 2-DE detergent CHAPS (3 [(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate). Mixtures of the three detergents showed additive improvements in spot number, density, and resolution. Substantial improvements in the analysis of a brain membrane proteome were observed. Conclusion This study demonstrates that an optimized detergent mix, coupled with rigorous sample handling and electrophoretic protocols, enables simple and effective analysis of membrane proteomes using two-dimensional electrophoresis.
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Affiliation(s)
- Matthew A Churchward
- Dept. of Physiology and Biophysics, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
| | - R Hussain Butt
- Dept. of Physiology and Biophysics, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
| | - John C Lang
- Dept. of Physiology and Biophysics, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
| | - Kimberly K Hsu
- Dept. of Physiology and Biophysics, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
| | - Jens R Coorssen
- Dept. of Physiology and Biophysics, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
- Dept. of Biochemistry and Molecular Biology, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
- Hotchkiss Brain Institute, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary AB, T2N 4N1, CANADA
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