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Intervention with an erythropoietin-derived peptide protects against neuroglial and vascular degeneration during diabetic retinopathy.

McVicar CM, Hamilton R, Colhoun LM, Gardiner TA, Brines M, Cerami A, Stitt AW - Diabetes (2011)

Bottom Line: In the diabetic retina, Müller glial expression of glial fibrillary acidic protein was increased when compared with nondiabetic controls, but pHBSP significantly reduced this stress-related response (P < 0.001).CD11b+ microglia and proinflammatory cytokines were elevated in diabetic retina responses, and some of these responses were attenuated by pHBSP (P < 0.01-0.001). pHBSP significantly reduced diabetes-linked DNA damage as determined by 8-hydroxydeoxyguanosine and transferase-mediated dUTP nick-end labeling positivity and also prevented acellular capillary formation (P < 0.05).In OIR, pHBSP had no effect on preretinal neovascularization at any dose.

View Article: PubMed Central - PubMed

Affiliation: Centre for Vision and Vascular Science, Queen’s University Belfast, Belfast, Northern Ireland, UK.

ABSTRACT

Objective: Erythropoietin (EPO) may be protective for early stage diabetic retinopathy, although there are concerns that it could exacerbate retinal angiogenesis and thrombosis. A peptide based on the EPO helix-B domain (helix B-surface peptide [pHBSP]) is nonerythrogenic but retains tissue-protective properties, and this study evaluates its therapeutic potential in diabetic retinopathy.

Research design and methods: After 6 months of streptozotocin-induced diabetes, rats (n = 12) and age-matched nondiabetic controls (n = 12) were evenly split into pHBSP and scrambled peptide groups and injected daily (10 μg/kg per day) for 1 month. The retina was investigated for glial dysfunction, microglial activation, and neuronal DNA damage. The vasculature was dual stained with isolectin and collagen IV. Retinal cytokine expression was quantified using real-time RT-PCR. In parallel, oxygen-induced retinopathy (OIR) was used to evaluate the effects of pHBSP on retinal ischemia and neovascularization (1-30 μg/kg pHBSP or control peptide).

Results: pHBSP or scrambled peptide treatment did not alter hematocrit. In the diabetic retina, Müller glial expression of glial fibrillary acidic protein was increased when compared with nondiabetic controls, but pHBSP significantly reduced this stress-related response (P < 0.001). CD11b+ microglia and proinflammatory cytokines were elevated in diabetic retina responses, and some of these responses were attenuated by pHBSP (P < 0.01-0.001). pHBSP significantly reduced diabetes-linked DNA damage as determined by 8-hydroxydeoxyguanosine and transferase-mediated dUTP nick-end labeling positivity and also prevented acellular capillary formation (P < 0.05). In OIR, pHBSP had no effect on preretinal neovascularization at any dose.

Conclusions: Treatment with an EPO-derived peptide after diabetes is fully established can significantly protect against neuroglial and vascular degenerative pathology without altering hematocrit or exacerbating neovascularization. These findings have therapeutic implications for disorders such as diabetic retinopathy.

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pHBSP and microglial activation in the diabetic retina. Retinal microglia were labeled using CD11b immunoreactivity in retinal sections and visualized using confocal microscopy. Cntl, control; Sc, scrambled pHBSP; and Db, diabetic. A: Mean cell counts of CD11b-positive cells were taken from three separate points within the central retina. There was a significant increase in microglial numbers after 7.5 months of diabetes (*P < 0.05; **P < 0.01). pHBSP (10 μg/kg) had no significant effect on this diabetes-related increase (P > 0.05). B: After subdividing the total number of microglial cell counts, there is a significant difference in the number of dendritic (nonactivated) and amoeboid (activated) cells between control and diabetic rats (*P < 0.05). Compared with diabetic rats treated with the scrambled peptide, there are more dendritic microglia and fewer amoeboid in the retinae of the diabetic rats that received the scrambled pHBSP (**P < 0.01 and *P < 0.05). Data are mean ± SEM; n = 6 per group. Sc’pHBSP, scrambled pHBSP. C–F: Images of CD11b-positive cells: control and Sc (C), control and pHBSP (D), diabetic and Sc (E), and diabetic and pHBSP (F). (A high-quality color representation of this figure is available in the online issue.)
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Figure 4: pHBSP and microglial activation in the diabetic retina. Retinal microglia were labeled using CD11b immunoreactivity in retinal sections and visualized using confocal microscopy. Cntl, control; Sc, scrambled pHBSP; and Db, diabetic. A: Mean cell counts of CD11b-positive cells were taken from three separate points within the central retina. There was a significant increase in microglial numbers after 7.5 months of diabetes (*P < 0.05; **P < 0.01). pHBSP (10 μg/kg) had no significant effect on this diabetes-related increase (P > 0.05). B: After subdividing the total number of microglial cell counts, there is a significant difference in the number of dendritic (nonactivated) and amoeboid (activated) cells between control and diabetic rats (*P < 0.05). Compared with diabetic rats treated with the scrambled peptide, there are more dendritic microglia and fewer amoeboid in the retinae of the diabetic rats that received the scrambled pHBSP (**P < 0.01 and *P < 0.05). Data are mean ± SEM; n = 6 per group. Sc’pHBSP, scrambled pHBSP. C–F: Images of CD11b-positive cells: control and Sc (C), control and pHBSP (D), diabetic and Sc (E), and diabetic and pHBSP (F). (A high-quality color representation of this figure is available in the online issue.)

Mentions: As depicted in retinal sections, diabetes was associated with an increase in CD11b-positive microglia in the neuropile, especially within the IPL (P < 0.05) (Fig. 4A and B). There was also a significant shift in phenotype toward activated, amoeboid cells (Fig. 4C–F). pHBSP had no influence on overall microglia numbers, but this treatment significantly increased the proportion of cells with a dendritic phenotype and reduced amoeboid cells when compared with diabetic rats treated with the scrambled pHBSP (P < 0.05) (Fig. 4A and B). Lectin-stained microglia also showed that diabetes was associated with an increase in microglia compared with the controls in the inner plexus in the central (P < 0.01) and peripheral retina (P < 0.05) (Supplementary Fig. 4).


Intervention with an erythropoietin-derived peptide protects against neuroglial and vascular degeneration during diabetic retinopathy.

McVicar CM, Hamilton R, Colhoun LM, Gardiner TA, Brines M, Cerami A, Stitt AW - Diabetes (2011)

pHBSP and microglial activation in the diabetic retina. Retinal microglia were labeled using CD11b immunoreactivity in retinal sections and visualized using confocal microscopy. Cntl, control; Sc, scrambled pHBSP; and Db, diabetic. A: Mean cell counts of CD11b-positive cells were taken from three separate points within the central retina. There was a significant increase in microglial numbers after 7.5 months of diabetes (*P < 0.05; **P < 0.01). pHBSP (10 μg/kg) had no significant effect on this diabetes-related increase (P > 0.05). B: After subdividing the total number of microglial cell counts, there is a significant difference in the number of dendritic (nonactivated) and amoeboid (activated) cells between control and diabetic rats (*P < 0.05). Compared with diabetic rats treated with the scrambled peptide, there are more dendritic microglia and fewer amoeboid in the retinae of the diabetic rats that received the scrambled pHBSP (**P < 0.01 and *P < 0.05). Data are mean ± SEM; n = 6 per group. Sc’pHBSP, scrambled pHBSP. C–F: Images of CD11b-positive cells: control and Sc (C), control and pHBSP (D), diabetic and Sc (E), and diabetic and pHBSP (F). (A high-quality color representation of this figure is available in the online issue.)
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Figure 4: pHBSP and microglial activation in the diabetic retina. Retinal microglia were labeled using CD11b immunoreactivity in retinal sections and visualized using confocal microscopy. Cntl, control; Sc, scrambled pHBSP; and Db, diabetic. A: Mean cell counts of CD11b-positive cells were taken from three separate points within the central retina. There was a significant increase in microglial numbers after 7.5 months of diabetes (*P < 0.05; **P < 0.01). pHBSP (10 μg/kg) had no significant effect on this diabetes-related increase (P > 0.05). B: After subdividing the total number of microglial cell counts, there is a significant difference in the number of dendritic (nonactivated) and amoeboid (activated) cells between control and diabetic rats (*P < 0.05). Compared with diabetic rats treated with the scrambled peptide, there are more dendritic microglia and fewer amoeboid in the retinae of the diabetic rats that received the scrambled pHBSP (**P < 0.01 and *P < 0.05). Data are mean ± SEM; n = 6 per group. Sc’pHBSP, scrambled pHBSP. C–F: Images of CD11b-positive cells: control and Sc (C), control and pHBSP (D), diabetic and Sc (E), and diabetic and pHBSP (F). (A high-quality color representation of this figure is available in the online issue.)
Mentions: As depicted in retinal sections, diabetes was associated with an increase in CD11b-positive microglia in the neuropile, especially within the IPL (P < 0.05) (Fig. 4A and B). There was also a significant shift in phenotype toward activated, amoeboid cells (Fig. 4C–F). pHBSP had no influence on overall microglia numbers, but this treatment significantly increased the proportion of cells with a dendritic phenotype and reduced amoeboid cells when compared with diabetic rats treated with the scrambled pHBSP (P < 0.05) (Fig. 4A and B). Lectin-stained microglia also showed that diabetes was associated with an increase in microglia compared with the controls in the inner plexus in the central (P < 0.01) and peripheral retina (P < 0.05) (Supplementary Fig. 4).

Bottom Line: In the diabetic retina, Müller glial expression of glial fibrillary acidic protein was increased when compared with nondiabetic controls, but pHBSP significantly reduced this stress-related response (P < 0.001).CD11b+ microglia and proinflammatory cytokines were elevated in diabetic retina responses, and some of these responses were attenuated by pHBSP (P < 0.01-0.001). pHBSP significantly reduced diabetes-linked DNA damage as determined by 8-hydroxydeoxyguanosine and transferase-mediated dUTP nick-end labeling positivity and also prevented acellular capillary formation (P < 0.05).In OIR, pHBSP had no effect on preretinal neovascularization at any dose.

View Article: PubMed Central - PubMed

Affiliation: Centre for Vision and Vascular Science, Queen’s University Belfast, Belfast, Northern Ireland, UK.

ABSTRACT

Objective: Erythropoietin (EPO) may be protective for early stage diabetic retinopathy, although there are concerns that it could exacerbate retinal angiogenesis and thrombosis. A peptide based on the EPO helix-B domain (helix B-surface peptide [pHBSP]) is nonerythrogenic but retains tissue-protective properties, and this study evaluates its therapeutic potential in diabetic retinopathy.

Research design and methods: After 6 months of streptozotocin-induced diabetes, rats (n = 12) and age-matched nondiabetic controls (n = 12) were evenly split into pHBSP and scrambled peptide groups and injected daily (10 μg/kg per day) for 1 month. The retina was investigated for glial dysfunction, microglial activation, and neuronal DNA damage. The vasculature was dual stained with isolectin and collagen IV. Retinal cytokine expression was quantified using real-time RT-PCR. In parallel, oxygen-induced retinopathy (OIR) was used to evaluate the effects of pHBSP on retinal ischemia and neovascularization (1-30 μg/kg pHBSP or control peptide).

Results: pHBSP or scrambled peptide treatment did not alter hematocrit. In the diabetic retina, Müller glial expression of glial fibrillary acidic protein was increased when compared with nondiabetic controls, but pHBSP significantly reduced this stress-related response (P < 0.001). CD11b+ microglia and proinflammatory cytokines were elevated in diabetic retina responses, and some of these responses were attenuated by pHBSP (P < 0.01-0.001). pHBSP significantly reduced diabetes-linked DNA damage as determined by 8-hydroxydeoxyguanosine and transferase-mediated dUTP nick-end labeling positivity and also prevented acellular capillary formation (P < 0.05). In OIR, pHBSP had no effect on preretinal neovascularization at any dose.

Conclusions: Treatment with an EPO-derived peptide after diabetes is fully established can significantly protect against neuroglial and vascular degenerative pathology without altering hematocrit or exacerbating neovascularization. These findings have therapeutic implications for disorders such as diabetic retinopathy.

Show MeSH
Related in: MedlinePlus