Constitutive overexpression of human erythropoietin protects the mouse retina against induced but not inherited retinal degeneration (original) (raw)
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2013
Elevation of erythropoietin (Epo) concentrations by hypoxic preconditioning or application of recombinant human Epo (huEpo) protects the mouse retina against light-induced degeneration by inhibiting photoreceptor cell apoptosis. Because photoreceptor apoptosis is also the common path to cell loss in retinal dystrophies such as retinitis pigmentosa (RP), we tested whether high levels of huEpo would reduce apoptotic cell death in two mouse models of human RP. We combined the two respective mutant mouse lines with a transgenic line (tg6) that constitutively overexpresses huEpo mainly in neural tissues. Transgenic expression of huEpo caused constitutively high levels of Epo in the retina and protected photoreceptors against light-induced degeneration; however, the presence of high levels of huEpo did not affect the course or the extent of retinal degeneration in a light-independent (rd1) and a light-accelerated (VPP) mouse model of RP. Similarly, repetitive intraperitoneal injections of...
Neuroprotective role of erythropoietin by antiapoptosis in the retina
Journal of Neuroscience Research, 2009
Erythropoietin (EPO) stimulates red blood cell production, in part by inhibiting apoptosis of the red blood cell precursors. The erythropoietic effects of EPO are circadian stage dependent. Retinal injury due to light occurs through oxidative mechanisms and is manifest by retinal and retinal pigment epithelium (RPE) cells apoptosis. The visual cycle might be circadian coordinated as a means of effectively protecting the retina from the detrimental effects of light-induced, oxygendependent, free radical-mediated damage, especially at the times of day when light is more intense. We show that the retinal expression of EPO and its receptor (EPOR), as well as subsequent Janus kinase 2 (Jak2) phosphorylations, are each tightly linked to a specific time after oxidative stress and in anticipation of daily light onset. This is consistent with physiological protection against daily light-induced, oxidatively mediated retinal apoptosis. In vitro, we verify that EPO protects RPE cells from light, hyperoxia, and hydrogen peroxide-induced retinal cell apoptosis, and that these stimuli increase EPO and EPOR expression in cultured RPE cells. Together, these data support the premise that EPO and its EPOR interactions represent an important retinal shield from physiologic and pathologic light-induced oxidative injury.
Constant or intense light degenerates the retina and retinal pigment epithelial cells. Light generates reactive oxygen species and nitric oxide leading to initial reactions of retinal degeneration. Apoptosis is the primary mechanism of abnormal death of photoreceptors, retinal ganglion cells, or retinal pigment epithelium (RPE) in degenerative retinal diseases, including diabetic retinopathy and age-related macular degeneration. The current study evaluated the function of erythropoietin (EPO) on angiogenesis and apoptosis in the retina and RPE under oxidative stress. We determined the pro-angiogenic and antiapoptotic mechanism of EPO under stress conditions using a conditional EPO knockdown model using siRNA, EPO addition, proteomics, immunocytochemistry, and bioinformatic analysis. Our studies verified that EPO protected retinal cells from light-, hypoxia-, hyperoxia-, and hydrogen peroxide-induced apoptosis through caspase inhibition, whereas up-regulated angiogenic reactions through vascular endothelial growth factor (VEGF) and angiotensin pathway. We demonstrated that the EPO expression in the retina and subsequent serine/threonine/tyrosine kinase phosphorylations might be linked to oxidative stress response tightly to determining angiogenesis and apoptosis. Neuroprotective roles of EPO may involve the balance between antiapoptotic and proangiogenic signaling molecules, including BCL-xL, c-FOS, caspase-3, nitric oxide, angiotensin, and VEGF receptor. Our data indicate a new therapeutic application of EPO toward retinal degeneration based on the dual roles in apoptosis and angiogenesis at the molecular level under oxidative stress.
2021
Erythropoietin (EPO) protects cells by inhibiting apoptosis, oxidative stress and inflammation in several models of retinal degeneration. In this study, we demonstrate the effects of recombinant Adeno Associated Virus (AAV) vector-mediated delivery of a modified form of erythropoietin (EPO-R76E) in an established mouse model of dry-AMD in which retinal degeneration is induced by RPE oxidative stress. Experimental vector AAV-EPO-R76E and control vector AAV-GFP were packaged into serotype-1 (AAV1) to enable RPE selective expression. RPE oxidative stress-mediated retinal degeneration was induced by exon specific deletion of the protective enzyme MnSOD (encoded by Sod2) by cre/lox mechanism. Experimental mice received subretinal injection of AAV-EPO-R76E in the right eye and AAV-GFP in the left eye. Western blotting of RPE/Choroid protein samples from AAV-EPO-R76E injected eyes showed RPE specific exogenous protein expression. Retinal degeneration was monitored by electroretinography (E...
Experimental eye research, 2009
The primary objectives of this study were to determine if erythropoietin (EPO) is neuroprotective to the photoreceptors in the retinal degeneration slow (rds) mouse in the absence of an increase in hematocrit and to determine if deglycosylated EPO (DEPO) is less neuroprotective. We performed subretinal injections of 10U EPO, DEPO or hyperglycosylated EPO (HEPO) in postnatal day 7 rds mice. Whole eye EPO levels were quantified by ELISA at specified time points post-injection. TUNEL analysis, hematocrit, and immunohistochemistry were performed at postnatal day 20. Half of the amount of EPO measured immediately after injection was detected less than one hour later. Twenty four hours later, EPO levels were 1000 times lower than the amount originally detected. Uninjected rds mice contained 36±2 TUNEL-positive cells/mm retina and PBS injected mice contained 17±3 TUNEL-positive cells/mm retina. EPO, DEPO, and HEPO treated rds retinas contained 5±2, 9±2, and 3±1 TUNEL-positive cells/mm retina, respectively. The hematocrit was 43% in control and 41% in treated rds mice Previous studies have shown neuroprotection of the retina by treatment with as little as 24–39mU EPO/mg total protein in the eye. In this study, we detected 40mU/mg EPO in the eye 11 hours after injecti on of 10U EPO. Treatment with all forms of EPO tested was neuroprotective to the photoreceptors without a concomitant increase in hematocrit.
Antioxidants, 2021
Erythropoietin (EPO) plays an important role in erythropoiesis by its action in blocking apoptosis of progenitor cells and protects both photoreceptors and retinal ganglion cells from induced or inherited degeneration. A modified form of EPO, EPO-R76E has attenuated erythropoietic activity but is effective in inhibiting apoptosis, oxidative stress, and inflammation in several models of retinal degeneration. In this study, we used recombinant Adeno Associated Virus (AAV) to provide long-term sustained delivery of EPO-R76E and demonstrated its effects in a mouse model of dry-AMD in which retinal degeneration is induced by oxidative stress in the retinal pigment epithelial (RPE) cells. Experimental vector AAV-EPO-R76E and control vector AAV-GFP were packaged into serotype-1 (AAV1) to enable RPE selective expression. RPE oxidative stress-mediated retinal degeneration was induced by exon specific deletion of the protective enzyme MnSOD (encoded by Sod2) by cre/lox mechanism. Experimental...
Experimental Eye Research, 2007
Erythropoietin (Epo) had been shown to have a neuroprotective effect independent from its erythropoietic properties. In this study, we tested whether Epo could protect the retina from damage induced by a long period of moderate light insult and how it protected. First, rats were injected intraperitoneally (i.p.) by human recombinant Epo at 5000 or 30,000 U/kg to assess Epo concentration in plasma and retina. Second, rats were untreated or injected i.p. with Epo at 30,000 U/kg, 1 or 4 h before being placed in constant light (24 h; 2200 lux). Electroretinograms (ERG) were recorded before treatment, 1 day and 15 days (D15) after light exposure. After the last ERG, eyes were taken for histology. In parallel, we tested Epo protection against oxidative stressors on isolated retinas and its effect on caspase-9 activity. Epo injected at 30,000 U/kg body weight, 4 h before exposure to the damaging light, protected retinal function and structure against light damage and induced an increase in caspase-9 activity and expression. Epo had no direct or indirect protective effect against free radicals-induced death on isolated retinas. Epo protected the retina from a long period of moderate light exposure through a mechanism independent from a free radical scavenging property or an antioxidant facilitating activity. The activation of caspase-9, 4 h after Epo injection, corresponding to the start of light exposure, suggests that caspase-9 plays a role in neuroprotection.
The anemia of the newborn induces erythropoietin expression in the developing mouse retina
AJP: Regulatory, Integrative and Comparative Physiology, 2010
The hematopoietic hormone erythropoietin (Epo), regularly produced by the kidneys and the liver, is also expressed in neuronal tissue, where it has been found to mediate paracrine neuroprotective effects. In most studies exploring the rescue effects of Epo, apoptosis was exogenously induced by different cell death stimuli. Herein, we set out to study the expression and function of Epo in physiologically occurring apoptosis in a model of retinal development. We made use of an organotypic retinal wholemount culture system that resembles the physiological in vivo situation with cell connections still retained. Epo mRNA expression in the retina, liver, and kidney showed a significant increase during early development, coinciding with the anemia of the newborn. In the retina of Epo-green fluorescent protein transgenic mice, Epo-expressing cells were identified and found to be distributed in the retinal ganglion cell layer. Treatment of retinal wholemount cultures with recombinant Epo res...