ABSTRACT
BackgroundOur previous study showed that erythropoietin (EPO) protects the photoreceptor from apoptosis in retinal detachment(RD) rat,but its signal transduction pathway remains unknown.Objective The present study was to investigate the effects of EPO on signal transduction pathway in RD.MethodsTwentyfour albino clean Sprague-Dawley(SD) rats were randomly divided into 4 groups.5 μl PBS was injected into vitreous cavity of rats in RD+PBS group,and 400 ng EPO(5 μl) was used at the same way in RD+EPO group.Three days later,the rats were sacrificed and the retina was isolated in each group.The expression levels of Janus kinase 2 (JAK2),p-JAK2,Akt,p-Akt,extracellular regulated protein kinase-1/2 ( ERK-1/2 ),p-ERK-1/2,signal transducer and activator of transcription 5 ( STAT5 ),p-STAT5,nuclear factor-kB (NF-sB) and p-NF-kB were detected by Western blot assay.The administration of experimental animals followed the Standard of ARVO.ResultsThree days after RD,the expression levels of JAK2,Akt and ERK-1,ERK-2 in retinas among normal group,RD,RD+PBS,RD+EPO groups were statistically insignificant different ( F =0.298,P =0.826 ; F =0.681,P =0.588 ; F =0.978,P=0.450;F=1.115,P=0.399 ),but the levels of p-JAK2,p-Akt,p-Erk-1 and p-Erk-2 among these 4 groups were significant difference ( F=24.435,P =0.000; F=48.163,P =0.000;F =19.092,P =0.001; F =14.393,P=0.001 ),and those in RD+EPO group was significantly higher than that in RD and RD+PBS groups( P＜0.05 ).The expression levels of STAT5 and NF-kB among the 4 groups were no significantly differences (F =1.136,P=0.391 ;F=0.696,P=0.580),but after the phosphorylation of STAT5 and NF-kB,the differences was significant ( F =14.189,P =0.001 ; F =40.103,P =0.000 ).Those in RD,RD + PBS,RD + EPO groups did not increase either (P＞0.05).Although the levels of p-STAT5 and p-NF-kB in RD,RD+PBS,RD+EPO groups were significantly higher than those in normal control group( P＜0.05 ),the level of p-STAT5 in RD+EPO group was not significantly higher than that in RD and RD + PBS groups (P ＞ 0.05 ). Conclusions PI3K/Akt and MAPK/ERK-1/2 signal transduction pathways might participate in the protecting process of EPO to photoreceptor in RD rats.
ABSTRACT
Erythropoietin(EPO) has an anti-apoptotic effect,and promotes the proliferation and differentiation of erythroid progenitor cells. Several studies have indicated that EPO can protect photoreceptor cells from the lightinduced retinal degeneration ;protect retinal neurons from ischemia-reperfusion injury and retinal ganglion cells after acute and chronic ocular hypertension; promote ganglion cell survival and axonal regeneration after optic nerve transaction; attenuate inflammation in multiple sclerosis optic neuritis; reduce the permeability of the retinal barrier and protect retinal neurons in diabetic retinopathy; enhance the stability of hypoxic retinal vessels in retinopathy of prematurity. Herein,we review the distribution of EPO and its receptor in retina,their expression in animal model of retinal diseases,and their effects and mechanisms in protection of retinal neurons and optic nerve.
ABSTRACT
Background Erythropoietin (EPO) has a protective effect on retinal neurons in many retinal diseases,but regarding the effect of EPO on apoptosis of retinal photoreceptor cells in retinal detachment (RD) is uncompletely clear.Objective This study was to investigate the protective effect of endogenous EPO on photoreceptors in a rat model of RD and explore its possible mechanism.Methods Seventy-two Sprague- Dawley (SD) rats were randomly assigned to control group,RD group,RD+PBS group,RD+erythropoietin soluble receptor (EPOsR) 2, 20, 200ng groups with 12 rats for each group.1.4% hyaluronic acid was slowly injected into the subretinal space to induce RD in rats,and PBS or 2,20 or 200ng EPOsR was then injected into the vitreous space.On day 3 after RD,apoptotic photoreceptors were detected using transferase-mediated dUTP nickend labeling (TUNEL),and caspase-3 activity was assessed by Western-blot and immunofluorescence staining.On day 14 after RD,retinal histopathologic examination was carried out and outer nuclear layer (ONL) thickness was measured under the light microscope.The use of animals complied with the Statement of Association for Research in Vision and Ophthalmology. Results Apoptotic photoreceptors were seen in ONL of rats of the RD group.Apoptotic photoreceptors were gradually increased with the elevation of EPOsR dose in the vitreous cavity.Western blot and immunofluorescence consistently showed that the gray scale of caspase-3 activity was 0.15±0.04,0.49±0.03,0.50±0.07,0.63±0.03,0.69±0.04 and 0.83±0.04 in the normal group,RD group,RD +PBS group,RD+EPOsR 2,20,200ng groups respectively with statistically significant differences (F=76.016;P=0.000),and caspase-3 activity was considerably stronger in the RD+EPOsR 200ng group than the other groups (P＜0.01).On day 14 after RD,the ONL thicknesses in the normal control group,RD group,RD+PBS group,RD+EPOsR 2,20,200ng groups were (47.39±3.39)μm,(33.96±3.54)μm,(31.83±5.21)μm,(31.40±2.63)μm,(24.99±2.06)μm and (19.30±3.71)μm,showing significant differences among these groups (F=44.733,P=0.000).ONL thicknesses the groups treated with different doses of EPOsR were markedly thinner than that of the RD group and RD +PBS group (P＜0.01).Conclusion EPOsR induces apoptosis of retinal cells and enhances the activity of caspase-3 in a dose-dependent manner.Endogenous EPO can protect photoreceptors against anoxia-mediated damage in RD eyes through decreasing caspase-3 activity and inhibiting apoptosis.