title: Knockout of ccr2 alleviates photoreceptor cell death in a model of retinitis pigmentosa.
abstract: Neuroinflammation involving CC chemokines such as monocyte chemoattractant protein-1 (MCP-1) has been demonstrated in the pathological process of retinitis pigmentosa (RP), an inherited degenerative retinal disease. However, the mechanism of MCP-1 and its receptor CCR2 involvement in the disease remains unclear. To investigate the role of MCP1/CCR2 in RP pathogenesis, ccr2 mutant RP mice (ccr2(-/-) rd10) were created and analyzed. The expression of MCP-1, RANTES, stromal cell-derived factor (SDF-1), and tumor necrosis factor-α (TNF-α) in the retinas of wild-type, rd10, and ccr2(-/-) rd10 mice was analyzed using quantitative RT-PCR. Photoreceptor apoptosis (TUNEL staining) and the number of microglia (positive for the F4/80 antibody) in the retina were examined. Retinal function was assessed using electroretinograms, and the structure of the whole retina was analyzed from images obtained using optical coherence tomography (OCT) and by histological examination. The expression levels of MCP-1, RANTES, and SDF-1 increased with time in the rd10 mice but not in the wild-type mice. Rearing the mice in the dark prevented degeneration and resulted in thicker photoreceptor layers at each time point. In those mice, the peaks of chemokine expression shifted to a later time with degeneration, suggesting that the expression of these chemokines was induced during the progression of degeneration. Although the difference was not so obvious, the retina in the ccr2(-/-) rd10 mice was consistently and significantly thicker than that in the rd10 (ccr2(+/+) rd10) mice at all time points. Rhodopsin gene expression was also higher in the ccr2(-/-) rd10 mice than in rd10 (ccr2(+/+) rd10) mice, suggesting photoreceptor survival in the former. Retinal function was also better preserved in the ccr2(-/-) rd10 mice than in the rd10 mice. The number of microglia in the retinas of the ccr2(-/-) rd10 mice was significantly lower than that in the retinas of the rd10 mice. Interestingly, the MCP-1 induction that was observed in the retinas of the rd10 mice was diminished in the retinas of the ccr2(-/-) rd10 mice. Our results suggest that the MCP-1/CCR2 system plays a role in retinal degeneration in rd mouse retinas. Retinal MCP-1 expression in the rd mouse retina may be partially controlled by ccr2-positive circulating cells.
authors.affiliation: Department of Ophthalmology, Kyoto University Graduate School of Medicine, 54-Kawaharacho, Shogoin, Kyoto 606-8507, Japan.
authors.forename: Congrong
authors.initials: C
authors.lastname: Guo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Otani
authors.forename: Akio
authors.initials: A
authors.lastname: Oishi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kojima
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Makiyama
authors.forename: Satoko
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Nagahisa
authors.initials: N
authors.lastname: Yoshimura
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers / Q000378:metabolism; D002470:Cell Survival; D018932:Chemokine CCL2 / Q000502:physiology; D018946:Chemokine CCL5 / Q000378:metabolism; D054377:Chemokine CXCL12 / Q000378:metabolism; D003623:Dark Adaptation; D004195:Disease Models, Animal; D004596:Electroretinography; D019084:Fluorescent Antibody Technique, Indirect; D060005:Genotyping Techniques; D020287:In Situ Nick-End Labeling; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D054390:Receptors, CCR2 / Q000502:physiology*; D012174:Retinitis Pigmentosa / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D041623:Tomography, Optical Coherence; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015415:Biomarkers; C491768:Ccl2 protein, mouse; C503460:Ccl5 protein, mouse; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D018946:Chemokine CCL5; D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D012333:RNA, Messenger; D054390:Receptors, CCR2; D014409:Tumor Necrosis Factor-alpha