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Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway

BACKGROUND: α7 nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the central nervous system and are reported to have neuroprotective properties. α7 nAChRs are expressed on astrocytes, which are key regulators of neuroinflammation and oxidative stress in several neurodegene...

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Autores principales: Patel, Hiral, McIntire, Jessica, Ryan, Sarah, Dunah, Anthone, Loring, Ralph
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615458/
https://www.ncbi.nlm.nih.gov/pubmed/28950908
http://dx.doi.org/10.1186/s12974-017-0967-6
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author Patel, Hiral
McIntire, Jessica
Ryan, Sarah
Dunah, Anthone
Loring, Ralph
author_facet Patel, Hiral
McIntire, Jessica
Ryan, Sarah
Dunah, Anthone
Loring, Ralph
author_sort Patel, Hiral
collection PubMed
description BACKGROUND: α7 nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the central nervous system and are reported to have neuroprotective properties. α7 nAChRs are expressed on astrocytes, which are key regulators of neuroinflammation and oxidative stress in several neurodegenerative diseases. However, the anti-inflammatory and antioxidant properties of astroglial α7 nAChRs are not well studied. Therefore, we evaluated the role of astroglial α7 nAChR activation in neuroinflammation. METHODS: Anti-inflammatory and antioxidant effects of α7 nAChR activation were evaluated in an in vitro mouse model of neuroinflammation using lipopolysaccharide (LPS) in primary astrocyte cultures. α7 nAChR anti-inflammatory effects on the NF-κB pathway were evaluated using ELISA, gene expression analysis, immunofluorescence, and western blotting. Antioxidant effect of α7 nAChR activation on expression profiles of canonical Nrf2 target genes was examined by quantitative PCR and western blotting. The role of the Nrf2 pathway in α7 nAChR-mediated anti-inflammatory response was evaluated using Nrf2 knockout astrocytes. Brain ex vivo NF-κB luciferase signals were evaluated after treatment with an α7 nAChR agonist in lipopolysaccharide (LPS)-injected NF-κB luciferase reporter mouse model. RESULTS: Astrocytes treated with the α7 nAChR partial agonist (GTS21) showed significantly reduced LPS-mediated secretion of inflammatory cytokines and this effect was reversed by the α7 nAChR antagonist methyllycaconitine (MLA) and by knockdown of α7 nAChR expression with a short hairpin RNA. Further, α7 nAChR activation blocked LPS-mediated NF-κB nuclear translocation indicating that the observed anti-inflammatory effect may be mediated through inhibition of the NF-κB pathway. Treatment with GTS21 also upregulated canonical Nrf2 antioxidant genes and proteins suggesting antioxidant properties of α7 nAChR in astrocytes. Using an astrocyte conditioned media approach, we demonstrated reduction in neuronal apoptosis when astrocytes were pretreated with GTS21. Finally, in an in vivo neuroinflammation model using LPS in NF-κB luciferase reporter mice, we demonstrated reduction in LPS-induced NF-κB activity and pro-inflammatory cytokines with GTS21 treatment in brain tissue. CONCLUSION: Our results suggest that activating astroglial α7 nAChRs may have a role in neuroprotection by decreasing inflammation and oxidative stress, and therefore could have therapeutic implication for disease modifying treatments of neurodegenerative diseases.
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spelling pubmed-56154582017-09-28 Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway Patel, Hiral McIntire, Jessica Ryan, Sarah Dunah, Anthone Loring, Ralph J Neuroinflammation Research BACKGROUND: α7 nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the central nervous system and are reported to have neuroprotective properties. α7 nAChRs are expressed on astrocytes, which are key regulators of neuroinflammation and oxidative stress in several neurodegenerative diseases. However, the anti-inflammatory and antioxidant properties of astroglial α7 nAChRs are not well studied. Therefore, we evaluated the role of astroglial α7 nAChR activation in neuroinflammation. METHODS: Anti-inflammatory and antioxidant effects of α7 nAChR activation were evaluated in an in vitro mouse model of neuroinflammation using lipopolysaccharide (LPS) in primary astrocyte cultures. α7 nAChR anti-inflammatory effects on the NF-κB pathway were evaluated using ELISA, gene expression analysis, immunofluorescence, and western blotting. Antioxidant effect of α7 nAChR activation on expression profiles of canonical Nrf2 target genes was examined by quantitative PCR and western blotting. The role of the Nrf2 pathway in α7 nAChR-mediated anti-inflammatory response was evaluated using Nrf2 knockout astrocytes. Brain ex vivo NF-κB luciferase signals were evaluated after treatment with an α7 nAChR agonist in lipopolysaccharide (LPS)-injected NF-κB luciferase reporter mouse model. RESULTS: Astrocytes treated with the α7 nAChR partial agonist (GTS21) showed significantly reduced LPS-mediated secretion of inflammatory cytokines and this effect was reversed by the α7 nAChR antagonist methyllycaconitine (MLA) and by knockdown of α7 nAChR expression with a short hairpin RNA. Further, α7 nAChR activation blocked LPS-mediated NF-κB nuclear translocation indicating that the observed anti-inflammatory effect may be mediated through inhibition of the NF-κB pathway. Treatment with GTS21 also upregulated canonical Nrf2 antioxidant genes and proteins suggesting antioxidant properties of α7 nAChR in astrocytes. Using an astrocyte conditioned media approach, we demonstrated reduction in neuronal apoptosis when astrocytes were pretreated with GTS21. Finally, in an in vivo neuroinflammation model using LPS in NF-κB luciferase reporter mice, we demonstrated reduction in LPS-induced NF-κB activity and pro-inflammatory cytokines with GTS21 treatment in brain tissue. CONCLUSION: Our results suggest that activating astroglial α7 nAChRs may have a role in neuroprotection by decreasing inflammation and oxidative stress, and therefore could have therapeutic implication for disease modifying treatments of neurodegenerative diseases. BioMed Central 2017-09-26 /pmc/articles/PMC5615458/ /pubmed/28950908 http://dx.doi.org/10.1186/s12974-017-0967-6 Text en © The Author(s). 2017 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Patel, Hiral
McIntire, Jessica
Ryan, Sarah
Dunah, Anthone
Loring, Ralph
Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway
title Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway
title_full Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway
title_fullStr Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway
title_full_unstemmed Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway
title_short Anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the NF-κB pathway and activation of the Nrf2 pathway
title_sort anti-inflammatory effects of astroglial α7 nicotinic acetylcholine receptors are mediated by inhibition of the nf-κb pathway and activation of the nrf2 pathway
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615458/
https://www.ncbi.nlm.nih.gov/pubmed/28950908
http://dx.doi.org/10.1186/s12974-017-0967-6
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