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Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure

BACKGROUND: The identification of endogenous signals that lead to microglial activation is a key step in understanding neuroinflammatory cascades. As ATP release accompanies mechanical strain to neural tissue, and as the P2X7 receptor for ATP is expressed on microglial cells, we examined the morphol...

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Autores principales: Campagno, Keith E., Lu, Wennan, Jassim, Assraa Hassan, Albalawi, Farraj, Cenaj, Aurora, Tso, Huen-Yee, Clark, Sophia P., Sripinun, Puttipong, Gómez, Néstor Más, Mitchell, Claire H.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8454080/
https://www.ncbi.nlm.nih.gov/pubmed/34544431
http://dx.doi.org/10.1186/s12974-021-02251-7
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author Campagno, Keith E.
Lu, Wennan
Jassim, Assraa Hassan
Albalawi, Farraj
Cenaj, Aurora
Tso, Huen-Yee
Clark, Sophia P.
Sripinun, Puttipong
Gómez, Néstor Más
Mitchell, Claire H.
author_facet Campagno, Keith E.
Lu, Wennan
Jassim, Assraa Hassan
Albalawi, Farraj
Cenaj, Aurora
Tso, Huen-Yee
Clark, Sophia P.
Sripinun, Puttipong
Gómez, Néstor Más
Mitchell, Claire H.
author_sort Campagno, Keith E.
collection PubMed
description BACKGROUND: The identification of endogenous signals that lead to microglial activation is a key step in understanding neuroinflammatory cascades. As ATP release accompanies mechanical strain to neural tissue, and as the P2X7 receptor for ATP is expressed on microglial cells, we examined the morphological and molecular consequences of P2X7 receptor stimulation in vivo and in vitro and investigated the contribution of the P2X7 receptor in a model of increased intraocular pressure (IOP). METHODS: In vivo experiments involved intravitreal injections and both transient and sustained elevation of IOP. In vitro experiments were performed on isolated mouse retinal and brain microglial cells. Morphological changes were quantified in vivo using Sholl analysis. Expression of mRNA for M1- and M2-like genes was determined with qPCR. The luciferin/luciferase assay quantified retinal ATP release while fura-2 indicated cytoplasmic calcium. Microglial migration was monitored with a Boyden chamber. RESULTS: Sholl analysis of Iba1-stained cells showed retraction of microglial ramifications 1 day after injection of P2X7 receptor agonist BzATP into mouse retinae. Mean branch length of ramifications also decreased, while cell body size and expression of Nos2, Tnfa, Arg1, and Chil3 mRNA increased. BzATP induced similar morphological changes in ex vivo tissue isolated from Cx3CR1(+/GFP) mice, suggesting recruitment of external cells was unnecessary. Immunohistochemistry suggested primary microglial cultures expressed the P2X7 receptor, while functional expression was demonstrated with Ca(2+) elevation by BzATP and block by specific antagonist A839977. BzATP induced process retraction and cell body enlargement within minutes in isolated microglial cells and increased Nos2 and Arg1. While ATP increased microglial migration, this required the P2Y12 receptor and not P2X7 receptor. Transient elevation of IOP led to microglial process retraction, cell body enlargement, and gene upregulation paralleling changes observed with BzATP injection, in addition to retinal ATP release. Pressure-dependent changes were reduced in P2X7(−/−) mice. Death of retinal ganglion cells accompanied increased IOP in C57Bl/6J, but not P2X7(−/−) mice, and neuronal loss showed some association with microglial activation. CONCLUSIONS: P2X7 receptor stimulation induced rapid morphological activation of microglial cells, including process retraction and cell body enlargement, and upregulation of markers linked to both M1- and M2-type activation. Parallel responses accompanied IOP elevation, suggesting ATP release and P2X7 receptor stimulation influence the early microglial response to increased pressure. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12974-021-02251-7.
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spelling pubmed-84540802021-09-21 Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure Campagno, Keith E. Lu, Wennan Jassim, Assraa Hassan Albalawi, Farraj Cenaj, Aurora Tso, Huen-Yee Clark, Sophia P. Sripinun, Puttipong Gómez, Néstor Más Mitchell, Claire H. J Neuroinflammation Research BACKGROUND: The identification of endogenous signals that lead to microglial activation is a key step in understanding neuroinflammatory cascades. As ATP release accompanies mechanical strain to neural tissue, and as the P2X7 receptor for ATP is expressed on microglial cells, we examined the morphological and molecular consequences of P2X7 receptor stimulation in vivo and in vitro and investigated the contribution of the P2X7 receptor in a model of increased intraocular pressure (IOP). METHODS: In vivo experiments involved intravitreal injections and both transient and sustained elevation of IOP. In vitro experiments were performed on isolated mouse retinal and brain microglial cells. Morphological changes were quantified in vivo using Sholl analysis. Expression of mRNA for M1- and M2-like genes was determined with qPCR. The luciferin/luciferase assay quantified retinal ATP release while fura-2 indicated cytoplasmic calcium. Microglial migration was monitored with a Boyden chamber. RESULTS: Sholl analysis of Iba1-stained cells showed retraction of microglial ramifications 1 day after injection of P2X7 receptor agonist BzATP into mouse retinae. Mean branch length of ramifications also decreased, while cell body size and expression of Nos2, Tnfa, Arg1, and Chil3 mRNA increased. BzATP induced similar morphological changes in ex vivo tissue isolated from Cx3CR1(+/GFP) mice, suggesting recruitment of external cells was unnecessary. Immunohistochemistry suggested primary microglial cultures expressed the P2X7 receptor, while functional expression was demonstrated with Ca(2+) elevation by BzATP and block by specific antagonist A839977. BzATP induced process retraction and cell body enlargement within minutes in isolated microglial cells and increased Nos2 and Arg1. While ATP increased microglial migration, this required the P2Y12 receptor and not P2X7 receptor. Transient elevation of IOP led to microglial process retraction, cell body enlargement, and gene upregulation paralleling changes observed with BzATP injection, in addition to retinal ATP release. Pressure-dependent changes were reduced in P2X7(−/−) mice. Death of retinal ganglion cells accompanied increased IOP in C57Bl/6J, but not P2X7(−/−) mice, and neuronal loss showed some association with microglial activation. CONCLUSIONS: P2X7 receptor stimulation induced rapid morphological activation of microglial cells, including process retraction and cell body enlargement, and upregulation of markers linked to both M1- and M2-type activation. Parallel responses accompanied IOP elevation, suggesting ATP release and P2X7 receptor stimulation influence the early microglial response to increased pressure. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12974-021-02251-7. BioMed Central 2021-09-20 /pmc/articles/PMC8454080/ /pubmed/34544431 http://dx.doi.org/10.1186/s12974-021-02251-7 Text en © The Author(s) 2021 https://creativecommons.org/licenses/by/4.0/Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) . The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/ (https://creativecommons.org/publicdomain/zero/1.0/) ) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
spellingShingle Research
Campagno, Keith E.
Lu, Wennan
Jassim, Assraa Hassan
Albalawi, Farraj
Cenaj, Aurora
Tso, Huen-Yee
Clark, Sophia P.
Sripinun, Puttipong
Gómez, Néstor Más
Mitchell, Claire H.
Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure
title Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure
title_full Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure
title_fullStr Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure
title_full_unstemmed Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure
title_short Rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by P2X7 receptor stimulation and increased intraocular pressure
title_sort rapid morphologic changes to microglial cells and upregulation of mixed microglial activation state markers induced by p2x7 receptor stimulation and increased intraocular pressure
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8454080/
https://www.ncbi.nlm.nih.gov/pubmed/34544431
http://dx.doi.org/10.1186/s12974-021-02251-7
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