SOCS1-derived peptide administered by eye drops prevents retinal neuroinflammation and vascular leakage in experimental diabetes

Diabetic retinopathy; Neuroinflammation; Suppressors of cytokine signalingRetinopatía diabética; Neuroinflamación; Supresores de señalizadores de citoquinasRetinopatia diabètica; Neuroinflamació; Supressors de senyalitzadors de citoquinesCurrent treatments for diabetic retinopathy (DR) target late stages when vision has already been significantly affected. Accumulating evidence suggests that neuroinflammation plays a major role in the pathogenesis of DR, resulting in the disruption of the blood-retinal barrier. Suppressors of cytokine signaling (SOCS) are cytokine-inducible proteins that function as a negative feedback loop regulating cytokine responses. On this basis, the aim of the present study was to evaluate the effect of a SOCS1-derived peptide administered by eye drops (2 weeks) on retinal neuroinflammation and early microvascular abnormalities in a db/db mouse model. In brief, we found that SOCS1-derived peptide significantly reduced glial activation and neural apoptosis induced by diabetes, as well as retinal levels of proinflammatory cytokines. Moreover, a significant improvement of electroretinogram parameters was observed, thus revealing a clear impact of the histological findings on global retinal function. Finally, SOCS1-derived peptide prevented the disruption of the blood-retinal barrier. Overall, our results suggest that topical administration of SOCS1-derived peptide is effective in preventing retinal neuroinflammation and early microvascular impairment. These findings could open up a new strategy for the treatment of early stages of DR.This study was supported by grants from the Ministerio de Economia y Competitividad (PI16/00541, SAF2015-63696-R, PI14/00386, PI17/01495 and DTS-2017/00203). Cristina Sola-Adell is a recipient of a Predoctoral Research Grant from MINECO (BES-2013-064944). Joel Sampedro is a recipient of a Predoctoral Research Grant from AGAUR

Effects of liposomal formulation of citicoline in experimental diabetes-induced retinal neurodegeneration

Diabetic retinopathy (DR) has been classically considered a microcirculatory disease of the retina. However, there is growing evidence to suggest that retinal neurodegeneration is also an early event in the pathogenesis of DR. Citicoline has been successfully used as a neuroprotective agent in the treatment of glaucoma but their effects on DR remain to be elucidated. On this basis, the main aim of the present study was to evaluate the effect of topical administration of citicoline in liposomal formulation on retinal neurodegeneration in db/db mouse and to investigate the underlying mechanisms of action. The treatment (citicoline or vehicle) was topically administered twice daily for 15 days. Retinal analyses were performed in vivo by electroretinography and ex vivo by using Western blot and immunofluorescence measurements. We found that the liposomal formulation of citicoline prevented glial activation and neural apoptosis in the diabetic retina. The main mechanism implicated in these beneficial effects were the inhibition of the downregulation of synaptophysin and its anti-inflammatory properties by means of preventing the upregulation of NF-κB and TNF-α (Tumor Necrosis Factor α) induced by diabetes. Overall, these results suggest that topical administration of citicoline in liposomal formulation could be considered as a new strategy for treating the early stages of DR

Topical administration of bosentan prevents retinal neurodegeneration in experimental diabetes

Experimental evidence suggests that endothelin 1 (ET-1) is involved in the development of retinal microvascular abnormalities induced by diabetes. The effects of ET-1 are mediated by endothelin A- and B-receptors (ETA and ETB). Endothelin B-receptors activation mediates retinal neurodegeneration but there are no data regarding the effectiveness of ETB receptor blockage in arresting retinal neurodegeneration induced by diabetes. The main aim of the present study was to assess the usefulness of topical administration of bosentan (a dual endothelin receptor antagonist) in preventing retinal neurodegeneration in diabetic (db/db) mice. For this purpose, db/db mice aged 10 weeks were treated with one drop of bosentan (5 mg/mL, n = 6) or vehicle (n = 6) administered twice daily for 14 days. Six non-diabetic (db/+) mice matched by age were included as the control group. Glial activation was evaluated by immunofluorescence using specific antibodies against glial fibrillary acidic protein (GFAP). Apoptosis was assessed by TUNEL method. A pharmacokinetic study was performed in rabbits. We found that topical administration of bosentan resulted in a significant decrease of reactive gliosis and apoptosis. The results of the pharmacokinetic study suggested that bosentan reached the retina through the trans-scleral route. We conclude that topical administration of bosentan was effective in preventing neurodegeneration in the diabetic retina and, therefore, could be a good candidate to be tested in clinical trials

Effects of liposomal formulation of citicoline in experimental diabetes-induced retinal neurodegeneration

Diabetic retinopathy (DR) has been classically considered a microcirculatory disease of the retina. However, there is growing evidence to suggest that retinal neurodegeneration is also an early event in the pathogenesis of DR. Citicoline has been successfully used as a neuroprotective agent in the treatment of glaucoma but their effects on DR remain to be elucidated. On this basis, the main aim of the present study was to evaluate the effect of topical administration of citicoline in liposomal formulation on retinal neurodegeneration in db/db mouse and to investigate the underlying mechanisms of action. The treatment (citicoline or vehicle) was topically administered twice daily for 15 days. Retinal analyses were performed in vivo by electroretinography and ex vivo by using Western blot and immunofluorescence measurements. We found that the liposomal formulation of citicoline prevented glial activation and neural apoptosis in the diabetic retina. The main mechanism implicated in these beneficial effects were the inhibition of the downregulation of synaptophysin and its anti-inflammatory properties by means of preventing the upregulation of NF-κB and TNF-α (Tumor Necrosis Factor α) induced by diabetes. Overall, these results suggest that topical administration of citicoline in liposomal formulation could be considered as a new strategy for treating the early stages of DR

New Insights into the Mechanisms of Action of Topical Administration of GLP-1 in an Experimental Model of Diabetic Retinopathy

The main goals of this work were to assess whether the topical administration of glucagon-like peptide-1 (GLP-1) could revert the impairment of the neurovascular unit induced by long-term diabetes (24 weeks) in diabetic mice and to look into the underlying mechanisms. For that reason, db/db mice were treated with eye drops of GLP-1 or vehicle for 3 weeks. Moreover, db/+ mice were used as control. Studies performed in vivo included electroretinogramand the assessment of vascular leakage by using Evans Blue. NF-κB, GFAP and Ki67 proteins were analyzed by immunofluorescence (IF). Additionally, caspase 9, AMPK, IKBα, NF-κB, AKT, GSK3, β-catenin, Bcl-xl, and VEGF were analyzed by WB. Finally, VEGF, IL-1β, IL-6, TNF-α, IL-18, and NLRP3 were studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. We found that topical administration of GLP-1 reverted reactive gliosis and albumin extravasation, and protected against apoptosis and retinal dysfunction. Regarding the involved mechanisms, GLP-1 exerted an anti-inflammatory action by decreasing NF-κB, inflammosome, and pro-inflammatory factors. In addition, it also decreased VEGF expression. Furthermore, GLP-1 promoted cell survival by increasing the anti-apoptotic protein Bcl-xl and the signaling pathway Akt/GSK3b/β-catenin. Finally, Ki67 results revealed that GLP-1 treatment could induce neurogenesis. In conclusion, the topical administration of GLP-1 reverts the impairment of the neurovascular unit by modulating essential pathways involved in the development of diabetic retinopathy (DR). These beneficial effects on the neurovascular unit could pave the way for clinical trials addressed to confirm the effectiveness of GLP-1 in early stages of DR

New insights into the mechanisms of action of topical administration of GLP-1 in an experimental model of diabetic retinopathy

The main goals of this work were to assess whether the topical administration of glucagon-like peptide-1 (GLP-1) could revert the impairment of the neurovascular unit induced by long-term diabetes (24 weeks) in diabetic mice and to look into the underlying mechanisms. For that reason, db/db mice were treated with eye drops of GLP-1 or vehicle for 3 weeks. Moreover, db/+ mice were used as control. Studies performed in vivo included electroretinogramand the assessment of vascular leakage by using Evans Blue. NF-κB, GFAP and Ki67 proteins were analyzed by immunofluorescence (IF). Additionally, caspase 9, AMPK, IKBα, NF-κB, AKT, GSK3, β-catenin, Bcl-xl, and VEGF were analyzed by WB. Finally, VEGF, IL-1β, IL-6, TNF-α, IL-18, and NLRP3 were studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. We found that topical administration of GLP-1 reverted reactive gliosis and albumin extravasation, and protected against apoptosis and retinal dysfunction. Regarding the involved mechanisms, GLP-1 exerted an anti-inflammatory action by decreasing NF-κB, inflammosome, and pro-inflammatory factors. In addition, it also decreased VEGF expression. Furthermore, GLP-1 promoted cell survival by increasing the anti-apoptotic protein Bcl-xl and the signaling pathway kt/GSK3b/β-catenin. Finally, Ki67 results revealed that GLP-1 treatment could induce neurogenesis. In conclusion, the topical administration of GLP-1 reverts the impairment of the neurovascular unit by modulating essential pathways involved in the development of diabetic retinopathy (DR). These beneficial effects on the neurovascular unit could pave the way for clinical trials addressed to confirm the effectiveness of GLP-1 in early stages of DR

Calcium Dobesilate Prevents Neurodegeneration and Vascular Leakage in Experimental Diabetes

<p><i>Purpose</i>: The mechanisms involved in the reported beneficial effects of Calcium dobesilate monohydrate (CaD) for the treatment of diabetic retinopathy (DR) remain to be elucidated. The main aim of the present study is to examine whether CaD prevents early events in the pathogenesis of DR such as neurodegeneration and vascular leakage. In addition, putative mediators of both neurodegeneration (glutamate/GLAST, ET-1/ETB receptor) and early microvascular impairment (ET-1/ETA receptor, oxidative stress, VEGF, and the PKC-delta-p38 MAPK pathway) have been examined.</p> <p><i>Methods</i>: Diabetic (db/db) mice were randomly assigned to daily oral treatment with CaD (200 mg/Kg/day) (<i>n</i> = 12) or vehicle (<i>n</i> = 12) for 14 days. In addition, 12 non-diabetic (db/+) mice matched by age were used as the control group. Functional abnormalities were assessed by electroretinography. Neurodegeneration and microvascular abnormalities were evaluated by immunohistochemistry and Western blot. Glutamate was determined by HPLC.</p> <p><i>Results</i>: CaD significantly decreased glial activation and apoptosis and produced a significant improvement in the electroretinogram parameters. Mechanistically, CaD prevented the diabetes-induced up-regulation of ET-1 and its cognate receptors (ETA-R and ETB-R), which are involved in microvascular impairment and neurodegeneration, respectively. In addition, treatment with CaD downregulated GLAST, the main glutamate transporter, and accordingly prevented the increase in glutamate. Finally, CaD prevented oxidative stress, and the upregulation of VEGF and PKC delta-p38 MAPK pathway induced by diabetes, thus resulting in a significant reduction in vascular leakage.</p> <p><i>Conclusions</i>: Our findings demonstrate for the first time that CaD exerts neuroprotection in an experimental model of DR. In addition, we provide first evidence that CaD prevents the overexpression of ET-1 and its receptors in the diabetic retina. These beneficial effects on the neurovascular unit could pave the way for clinical trials addressed to confirm the effectiveness of CaD in very early stages of DR.</p

SOCS1-derived peptide administered by eye drops prevents retinal neuroinflammation and vascular leakage in experimental diabetes

Current treatments for diabetic retinopathy (DR) target late stages when vision has already been significantly affected. Accumulating evidence suggests that neuroinflammation plays a major role in the pathogenesis of DR, resulting in the disruption of the blood-retinal barrier. Suppressors of cytokine signaling (SOCS) are cytokine-inducible proteins that function as a negative feedback loop regulating cytokine responses. On this basis, the aim of the present study was to evaluate the effect of a SOCS1-derived peptide administered by eye drops (2 weeks) on retinal neuroinflammation and early microvascular abnormalities in a db/db mouse model. In brief, we found that SOCS1-derived peptide significantly reduced glial activation and neural apoptosis induced by diabetes, as well as retinal levels of proinflammatory cytokines. Moreover, a significant improvement of electroretinogram parameters was observed, thus revealing a clear impact of the histological findings on global retinal function. Finally, SOCS1-derived peptide prevented the disruption of the blood-retinal barrier. Overall, our results suggest that topical administration of SOCS1-derived peptide is effective in preventing retinal neuroinflammation and early microvascular impairment. These findings could open up a new strategy for the treatment of early stages of DR