Glaucomatous tissue stress and the regulation of immune response through glial Toll-like receptor signaling.
OBJECTIVE
To determine the regulation of immune system activity associated with Toll-like receptor (TLR) signaling in glaucoma.


METHODS
Retinal protein samples obtained from human donor eyes with (n = 10) or without (n = 10) glaucoma were analyzed by a quantitative proteomic approach involving mass spectrometry. Cellular localization of TLR2, -3, and -4 was also determined by immunohistochemical analysis of an additional group of human donor eyes with glaucoma (n = 34) and control eyes (n = 20). In addition, in vitro experiments were performed in rat retinal microglia and astrocytes to determine glial TLR expression and immunoregulatory function after exposure to exogenous heat shock proteins (HSPs) and H(2)O(2)-induced oxidative stress.


RESULTS
Proteomic analyses of the human retina detected expression and differential regulation of different TLRs in glaucomatous samples. Parallel to the upregulation of TLR signaling, proteomic findings were also consistent with a prominent increase in the expression of HSPs in glaucoma. Immunohistochemical analysis supported upregulated expression of TLRs on both microglia and astrocytes in the glaucomatous retina. In vitro experiments provided additional evidence that HSPs and oxidative stress upregulate glial TLR and MHC class II expression and cytokine production through TLR signaling and stimulate proliferation and cytokine secretion of co-cultured T cells during antigen presentation.


CONCLUSIONS
The findings of this study support the upregulation of TLR signaling in human glaucoma, which may be associated with innate and adaptive immune responses. In vitro findings showed that components of glaucomatous tissue stress, including upregulated HSPs and oxidative stress, may initiate the immunostimulatory signaling through glial TLRs.
Luo
Cheng
C
Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
Yang
Xiangjun
X
Kain
Angela D
AD
Powell
David W
DW
Kuehn
Markus H
MH
Tezel
Gülgün
G
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D005902:Glaucoma, Open-Angle / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D007107:Immune System / Q000502:physiology*; D007150:Immunohistochemistry; D007429:Intraocular Pressure; D008213:Lymphocyte Activation; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress; D040901:Proteomics; D051381:Rats; D011914:Rats, Inbred BN; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology; D053719:Tandem Mass Spectrometry; D051193:Toll-Like Receptors / Q000378:metabolism*; D015854:Up-Regulation
D051193:Toll-Like Receptors; D006861:Hydrogen Peroxide