April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Immune priming and experimental glaucoma: The effect of prior systemic lipopolysaccharide challenge on tissue outcomes after optic nerve injury
Author Affiliations & Notes
  • Daniel Narayan
    Ophthalmology, University of Adelaide, Adelaide, SA, Australia
    South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Adelaide, SA, Australia
  • Robert James Casson
    Ophthalmology, University of Adelaide, Adelaide, SA, Australia
    South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Adelaide, SA, Australia
  • Andreas Ebneter
    Ophthalmology, University of Adelaide, Adelaide, SA, Australia
    South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Adelaide, SA, Australia
  • Glyn Chidlow
    Ophthalmology, University of Adelaide, Adelaide, SA, Australia
    South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Adelaide, SA, Australia
  • Peter M Grace
    Physiology, University of Adelaide, Adelaide, SA, Australia
  • Mark R Hutchinson
    Physiology, University of Adelaide, Adelaide, SA, Australia
  • John P M Wood
    Ophthalmology, University of Adelaide, Adelaide, SA, Australia
    South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Adelaide, SA, Australia
  • Footnotes
    Commercial Relationships Daniel Narayan, None; Robert Casson, None; Andreas Ebneter, None; Glyn Chidlow, None; Peter Grace, None; Mark Hutchinson, None; John Wood, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 1667. doi:
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      Daniel Narayan, Robert James Casson, Andreas Ebneter, Glyn Chidlow, Peter M Grace, Mark R Hutchinson, John P M Wood; Immune priming and experimental glaucoma: The effect of prior systemic lipopolysaccharide challenge on tissue outcomes after optic nerve injury. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1667.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

Microglial activation is a prominent feature throughout the optic pathway in experimental glaucoma. Pro-inflammatory microglial activation can contribute to neurodegeneration through the release of pro-inflammatory cytokines and other inflammatory mediators. Systemic administration of lipopolysaccharide (LPS), a constituent of gram-negative bacteria, stimulates microglia to produce pro-inflammatory cytokines and chemoattractants. A preliminary investigation demonstrated pro-inflammatory microglial activation throughout the optic pathway in rats following systemic LPS challenge (Fig.1). The aim of the current work was to investigate whether microglial priming with LPS would exacerbate optic nerve injury in rats following experimental glaucoma.

 
Methods
 

Adult female Sprague-Dawley rats were divided into LPS treatment (n = 15) and saline treatment groups (n = 15). Microglial priming was induced with a 2.5 mg/kg intraperitoneal injection of LPS; control animals received saline. Experimental glaucoma was induced 48 hours later in the right eyes of animals by laser photocoagulation of the trabecular meshwork. Animals were sacrificed nine days after laser treatment, and globes and optic nerves were harvested for histology and immunohistochemistry. Toluidine-blue stained sections were used to count optic nerve axons.

 
Results
 

The estimated number of axons per optic nerve was 51 327 ± 3868 (mean ± SEM) in the LPS group and 54 569 ± 6687 (mean ± SEM) in the saline group (Fig.2). Estimated optic nerve axon counts were not significantly different between groups (p = 0.67).

 
Conclusions
 

Systemic LPS challenge had no discernible effect on optic nerve injury in laser-induced experimental glaucoma. This finding does not support the hypothesis that this model of experimental glaucoma involves inflammation and instead suggests that microglial activation may occur secondary to chronic neurodegeneration.

 
 
Photomicrographs of ED1 immunolabelling in the rat retina 48 hours after systemic saline administration (A) and systemic LPS administration (B). Marked microglial activation is seen in the LPS treated retina compared to the saline treated retina.
 
Photomicrographs of ED1 immunolabelling in the rat retina 48 hours after systemic saline administration (A) and systemic LPS administration (B). Marked microglial activation is seen in the LPS treated retina compared to the saline treated retina.
 
 
Oil-immersion micrographs of toluidine-blue stained cross sections from experimental glaucoma optic nerves in rats treated with systemic saline administration (A) and systemic LPS administration (B).
 
Oil-immersion micrographs of toluidine-blue stained cross sections from experimental glaucoma optic nerves in rats treated with systemic saline administration (A) and systemic LPS administration (B).
 
Keywords: 595 microglia • 615 neuroprotection • 555 immunomodulation/immunoregulation  
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