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Amanda C. Rehorn, D'Anne S. Duncan, Monet Stanford, Gwynne Davis, Rebecca M. Sappington; Differential Expression of CCL5 Receptors in Acute and Chronic Murine Models of Glaucoma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6598.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal ganglion cell (RGC)-glial cell interactions are a key component of glaucomatous pathology. Our previous work suggests that the chemokine CCL5 could contribute to RGC-glial interactions and may mediate events like microglia recruitment. In this study, we sought to identify targets for CCL5 by examining expression and localization of CCL5 receptors in both acute and chronic mouse models of glaucoma.
We confirmed expression of CCR1, CCR3 and CCR5 in mouse retina, using PCR and immunohistochemistry. We examined proteinexpression/localization for CCR1, CCR3 and CCR5 in retina from the DBA/2 (chronic) and Microbead Occlusion (acute) mouse models of glaucoma. DBA/2 mice and C57 controls were examined at 4 or 9 months of age. Unilateral microbead occlusion was conducted for 4 weeks in C57 mice. Using immunohistochemistry, we co-labeled CCR1, CCR3 and CCR5 with cell type-specific markers for microglia (Iba-1), astrocytes (GFAP), Muller cells (glutamine synthetase) and RGCs (SMI-31). Labeling intensity for CCL5 receptors was quantified in both the outer and inner retina, using quantitative digital microscopy and image analysis software.
CCR1 was not detectable in normal mouse retina. In contrast, CCR3 and CCR5 mRNA and protein were constitutively expressed in multiple retinal layers. Constitutive expression of CCR3 and CCR5 was noted primarily in microglia and RGCs with some CCR5 expression also present in vasculature. In the chronic model, CCR3 intensity increased up to 5-fold in the inner retina for a subset of 9 month DBA/2 mice, compared to C57 and DBA/2 mice of both ages (p<0.05). Similarly, CCR5 label in the inner retina increased 2.5-fold in 9 month DBA/2 mice, as compared to 4 month DBA/2 mice and all C57 mice (p<0.05). For both CCR3 and CCR5, increased label was most attributable to induced expression in Muller cells and astrocytes. In the Microbead Occlusion Model, CCR3 label decreased by 27% in the inner retina of microbead-injected eyes, as compared to saline-injected eyes (p<0.01). This decrease was primarily observed in RGCs.Qualitatively, CCL5 intensity appeared to decrease in the inner retina of microbead-injected eyes, but this observation failed to reach statistical significance (p>0.05). For both chronic and acute models, CCR3 and CCR5 intensity remained unaltered in the outer retina.
These data support a functional role for CCL5 that is both constitutive and inducible. The differential effects of IOP exposure further suggest that CCL5 is relevant to the pathophysiology of glaucoma, particularly RGC-glia interactions.
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