ABSTRACT
Background Our previous study demonstrated that microglial activation is closely associated with photoreceptor apoptosis in rd mice.Recent studies on central nervous system (CNS) showed that activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase plays a key role in the microglia activation and neural cell death.However,the mechanism of NADPH oxidase during the retinal degeneration and the effect of NADPH oxidase inhibitor on photoreceptor apoptosis are concerned.Objective The aim of this study was to further explore the production of reactive oxygen species (ROS) by NADPH oxidase in the retinal degenerative process of rd mice and protection of NADPH oxidase inhibitor on photoreceptors.Methods Sixty rd mice at postnatal day 9 (P9) were randomized into the experimental group and the control group by throwing coins method.Apocynin,a NADPH oxidase inhibitor,was intraperitoneally injected in the dose of 10 mg/kg (0.01 ml/kg) once daily for 5 days (P13) in the experimental group,and the equal amount of PBS was used in the same way in the control group,and 10 C57BL/6N mice without injection of any drugs served as the wild type mice group.All the mice were sacrificed in P14 for the preparation of retinal sections.The expression of ROS in the retina was detected by dihydroethidium (DHE) fluorescence staining.Expression level of rhodopsin mRNA in the photoreceptor of the mice was determined by real-time PCR,and the thickness of retinal outer nuclear layer (ONL) in the mice of the experimental group and the control group was measured using hematoxylin & eosin staining.The use and care of the animals complied with the Statement of Association for Research in Vision and Ophthalmology.Results DHE staining showed that the ROS presented with the red fluorescence in the mouse retinas.In the rd mice of the experimental group,the ROS fluorescence intensity was dramatically enhanced in comparison with C57BL/6N mice,but weakened in comparison with the rd mice of the control group.Real-time PCR revealed that the relative expressing level of rhodopsin mRNA in the photoreceptor was (4.21±0.33) in the experimental group and (0.93±0.24) in the control group,showing a significant difference between them (t =2.360,P =0.000).The thickness value of retinal ONL was (35.95±1.63)μm in the mice of the experimental group,which was significantly higher than that in the mice of the control group ([23.17±1.38] μm) (t=3.850,P=0.016).Conclusions In the retinal degeneration of rd mice,activation of NADPH oxidase increases the ROS production.Apocynin can slow the apoptosis procedure of photoreceptor cells of rd mice.
ABSTRACT
Background Studies showed that activation of microglia-derived nicotinamide adenine dinucleotide phosphate (NADPH) oxidase plays a key role in the neurodegenerative diseases and neural cell death in central nervous system.The effect of NADPH on cone degeneration have been determined in rd rats,its role in rod degeneration is relatively less studied.Objective This study was to study the expression of NADPH oxidase in the retinal degenerative process in rd mice and further explore its role in the photoreceptor degeneration.Methods rd Mice at postnatal day 8 (P8),P10,P12,P14,P16 and P18 were collected.The mice were sacrificed,and retinal sections,RNAs and proteins were prepared in above-mentioned time points.The expressions of the gp91 phox,a major subunit of NADPH oxidase,in transcript level and protein level in the retinas were semi-quantitatively detected by real-time PCR and Western blot respectively.Expression of gp91phox was localized in the rd retinas as ageing by immunohistochemstry,and the co-expression of gp91phox with CD11b,a specific marker of microglial cells,was assayed by immunofluorescent double labeling.The C57BL/6N mice were served as controls.The use and care of the animals complied with the Guideline of ARVO.Results Real-time PCR showed that gp91phox mRNA was not expressed in the retinas of C57BL/6N mice.Gp91phox mRNA was found to have less expressed in retinas of P8 rd mice.With aging,the expression level of gp91phox mRNA (gp91phox mRNA/β-actin) in rd mouse retinas was gradually increased with the highest level in P14 mice(1.136±0.370).A significant difference was seen in the gp91 phox mRNA expression among various groups of mice (F=17.81,P =0.00),and gp91phox mRNA expression was significantly elevated in P10,P12,P14,P16 and P18 rd mice compared with P8 rd mice(all at P＜0.05).The expression level of gp91phox protein (A value) in the retinas presented with a similar trend in the rd mice,with a significant difference among the various ages of rd mice and C57BL/6N mice (F =354.00,P＜0.01).The expression level of gp91 phox protein was increased in the rd mice in comparison with the C57BL/6N mice (all at P＜0.05).Immunochemistry revealed that the positive response cells for gp91phox increased in the inner layers of retinas in P10 rd mice and peaked in P14 mice.Immunofluorescent double labeling exhibited that gp91phox were seen to present a co-expression with CD11b,showing an orange fluorescence.Conclusions Expression of NADPH oxidase in the rctinas in the rd mice up-regulates and is parallels to the microglial activation and photoreceptor degeneration,suggesting that NADPH oxidase plays a role in the retinal dystrophy associated with microglial activation.
ABSTRACT
Objective To study the development of hereditary dystrophic retina of rd mice and photoreceptors apoptosis. Methods Retinal sections of rd mice and their controls at different ages ranging from postnatal days 5 to 40 were examined by morphological(light and electronic microscope), morphometric and TUNEL analysis. Results Compared with age-matched control mice, the retinal dystrophy of rd mice began at postnatal days 10, resulting in rapid loss of photoreceptors and reaching a peak at postnatal days 18. TUNEL postitive nucleus of photoreceptor cells emerged from postnatal days 10 and reached a peak at postnatal days 14 and 16. Ultrastructure of photoreceptor cell layer showed marked nuclear pyknotosis and chromatin margination. Apoptotic bodies of photoreceptor cells were observed.Conclusion Rd mice retina degenerated during the process of maturity. Photoreceptor cell death occurred through apoptosis.