title: Microglial NADPH oxidase activation mediates rod cell death in the retinal degeneration in rd mice.
abstract: Accumulating evidence supports that nicotinamide adenine dinucleotide phosphate (NADPH) oxidase contributes to microglia-mediated neurotoxicity in the CNS neurodegenerative diseases. Several studies, including ours, suggest that microglial activation is involved in the retinal degeneration in the animal models of retinitis pigmentosa (RP). In the present study, we investigated the activation of NADPH oxidase in the rod degeneration in rd mice and further explored its role in the microglia-mediated photoreceptor apoptosis. Expression of gp91phox protein, a major subunit of NAPDH oxidase in the whole retina of rd mice at postnatal days (P) 8, 10, 12, 14, 16 and 18 was assessed by western blot analysis. Location of gp91phox in the rd retina at each age group and its cellular source were studied by immunohistochemical analysis and double labeling respectively. The generation of superoxide radicals in the rd retinas was demonstrated by intraperitoneal injection of hydroethidine. Apocynin was applied intraperitoneally in the rd mice from P8 to P14 to inhibit the activity of NAPDH oxidase and the outer nuclear layer (ONL) thickness was measured before and after apocynin treatment. Our results demonstrated that during the rod degenerative process, the expression of gp91phox started to increase in the outer part of rd retina at P10 and reached a peak at P14. Double labeling of gp91phox with CD11b showed co-localization of gp91phox in the retinal microglial cells. Increasing generation of superoxide radicals visualized by hydroethidine was noted at P8 and reached a peak at P14. Apocynin markedly reduced the production of superoxide radicals and preserved the rod cells. The results suggested that NADPH oxidase might play an important role in the rod degeneration in the rd mice. Inhibition of NAPDH oxidase could be a possible approach to treat RP in the early degenerative stage.
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Science Key Laboratory, Beijing 100730, China. Electronic address: zhydr@hotmail.com.
authors.forename: H
authors.initials: H
authors.lastname: Zeng
authors.affiliation: Department of Ophthalmology Teaching and Research Section of Wei Fang Medical University, Weifang 261053, China.
authors.forename: M
authors.initials: M
authors.lastname: Ding
authors.affiliation: Plastic Surgery Research Center of Wei Fang Medical University, Weifang 261053, China.
authors.forename: X-X
authors.initials: XX
authors.lastname: Chen
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Science Key Laboratory, Beijing 100730, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Lu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051379:Mice; D017628:Microglia / Q000201:enzymology*; D019255:NADPH Oxidases / Q000378:metabolism*; D012162:Retinal Degeneration / Q000201:enzymology* / Q000473:pathology; D017948:Retinal Rod Photoreceptor Cells / Q000201:enzymology* / Q000473:pathology; D013481:Superoxides / Q000378:metabolism
chemical_list: D013481:Superoxides; D019255:NADPH Oxidases
keywords: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; EDTA; EGTA; FITC; GCL; H.E.; HEPES; INL; NADPH; NADPH oxidase; Nox; ONL; OPL; PBS; ROS; RP; RPE; TNF; TRITC; ethylene glycol tetraacetic acid; ethylenediaminetetraacetic acid; fluorescein isothiocyanate; ganglion cell layer; hematoxylin and eosin; inner nuclear layer; microglia; nicotinamide adenine dinucleotide phosphate; outer nuclear layer; outer plexiform layer; phosphate buffered saline; rd mice; reactive oxygen species; retinal pigment epithelium; retinitis pigmentosa; rod degeneration; tetramethylrhodamine isothiocyanate; tumor necrosis factor