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Retinal neuroinflammatory induced neuronal degeneration - Role of toll-like receptor-4 and relationship with gliosis

Ghosh, Fredrik LU ; Abdshill, Hodan LU ; Arnér, Karin LU ; Voss, Ulrikke LU and Taylor, Linnéa LU (2018) In Experimental Eye Research 169. p.99-110
Abstract

The purpose of this study was to explore retina-intrinsic neuroinflammatory reactions, effects on neuronal survival, relationship with classic gliosis, and possible role of the toll-like receptor 4 (TLR4). To isolate the adult retina from the systemic immune system, a previously described large animal explant culture model was used in which full-thickness porcine retinal sheets can be kept in vitro for extended time periods. Explants were kept for 5 days in vitro (DIV) and were treated with either; lipopolysaccharide (LPS), a Toll-like receptor-4 (TLR4) inhibitor (CLI-095), LPS + CLI-095, or solvent vehicle throughout the culture period after which retinal sections were examined with hematoxylin and eosin staining and extensive... (More)

The purpose of this study was to explore retina-intrinsic neuroinflammatory reactions, effects on neuronal survival, relationship with classic gliosis, and possible role of the toll-like receptor 4 (TLR4). To isolate the adult retina from the systemic immune system, a previously described large animal explant culture model was used in which full-thickness porcine retinal sheets can be kept in vitro for extended time periods. Explants were kept for 5 days in vitro (DIV) and were treated with either; lipopolysaccharide (LPS), a Toll-like receptor-4 (TLR4) inhibitor (CLI-095), LPS + CLI-095, or solvent vehicle throughout the culture period after which retinal sections were examined with hematoxylin and eosin staining and extensive immunohistochemistry. In addition, the culture medium of all explants was assayed for a panel of cytokines at 2 and 5DIV. Compared with in vivo controls, vehicle controls (CT) as well as CLI-095 explants displayed moderate reduction of total thickness and number of retinal neurons with upregulation of glial fibrillary acidic protein (GFAP) throughout the Müller cells. In contrast, LPS and LPS + CLI-095 treated counterparts showed extensive overall thinning with widespread neuronal degeneration but only minimal signs of classical Müller cell gliosis (limited upregulation of GFAP and no downregulation of glutamine synthetase (GS). These specimens also displayed a significantly increased expression of galectin-3 and TGF-beta activated kinase 1 (TAK1). Multiplex proteomic analysis of culture medium at 2DIV revealed elevated levels of IL-1β, IL-6, IL-4 and IL-12 in LPS-treated explants compared to CLI-095 and CT counterparts. LPS stimulation of the isolated adult retina results in substantial neuronal cell death despite only minimal signs of gliosis indicating a retina-intrinsic neuroinflammatory response directly related to the degenerative process. This response is characterized by early upregulation of several inflammatory related cytokines with subsequent upregulation of Galectin-3, TLR4 and TAK1. Pharmacological block of TLR4 does not attenuate neuronal loss indicating that LPS induced retinal degeneration is mediated by TLR4 independent neuroinflammatory pathways.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galectin 3, Gliosis, Lipopolysaccharide, Retinal neuroinflammation, Toll-like receptor 4
in
Experimental Eye Research
volume
169
pages
12 pages
publisher
Elsevier
external identifiers
  • scopus:85041519440
ISSN
0014-4835
DOI
10.1016/j.exer.2018.02.002
language
English
LU publication?
yes
id
f0805972-e09c-49b0-a558-784d4d43e9c8
date added to LUP
2018-02-20 11:50:26
date last changed
2018-05-29 11:03:53
@article{f0805972-e09c-49b0-a558-784d4d43e9c8,
  abstract     = {<p>The purpose of this study was to explore retina-intrinsic neuroinflammatory reactions, effects on neuronal survival, relationship with classic gliosis, and possible role of the toll-like receptor 4 (TLR4). To isolate the adult retina from the systemic immune system, a previously described large animal explant culture model was used in which full-thickness porcine retinal sheets can be kept in vitro for extended time periods. Explants were kept for 5 days in vitro (DIV) and were treated with either; lipopolysaccharide (LPS), a Toll-like receptor-4 (TLR4) inhibitor (CLI-095), LPS + CLI-095, or solvent vehicle throughout the culture period after which retinal sections were examined with hematoxylin and eosin staining and extensive immunohistochemistry. In addition, the culture medium of all explants was assayed for a panel of cytokines at 2 and 5DIV. Compared with in vivo controls, vehicle controls (CT) as well as CLI-095 explants displayed moderate reduction of total thickness and number of retinal neurons with upregulation of glial fibrillary acidic protein (GFAP) throughout the Müller cells. In contrast, LPS and LPS + CLI-095 treated counterparts showed extensive overall thinning with widespread neuronal degeneration but only minimal signs of classical Müller cell gliosis (limited upregulation of GFAP and no downregulation of glutamine synthetase (GS). These specimens also displayed a significantly increased expression of galectin-3 and TGF-beta activated kinase 1 (TAK1). Multiplex proteomic analysis of culture medium at 2DIV revealed elevated levels of IL-1β, IL-6, IL-4 and IL-12 in LPS-treated explants compared to CLI-095 and CT counterparts. LPS stimulation of the isolated adult retina results in substantial neuronal cell death despite only minimal signs of gliosis indicating a retina-intrinsic neuroinflammatory response directly related to the degenerative process. This response is characterized by early upregulation of several inflammatory related cytokines with subsequent upregulation of Galectin-3, TLR4 and TAK1. Pharmacological block of TLR4 does not attenuate neuronal loss indicating that LPS induced retinal degeneration is mediated by TLR4 independent neuroinflammatory pathways.</p>},
  author       = {Ghosh, Fredrik and Abdshill, Hodan and Arnér, Karin and Voss, Ulrikke and Taylor, Linnéa},
  issn         = {0014-4835},
  keyword      = {Galectin 3,Gliosis,Lipopolysaccharide,Retinal neuroinflammation,Toll-like receptor 4},
  language     = {eng},
  pages        = {99--110},
  publisher    = {Elsevier},
  series       = {Experimental Eye Research},
  title        = {Retinal neuroinflammatory induced neuronal degeneration - Role of toll-like receptor-4 and relationship with gliosis},
  url          = {http://dx.doi.org/10.1016/j.exer.2018.02.002},
  volume       = {169},
  year         = {2018},
}