LRP-1 Pathway Targeted Inhibition of Vascular Abnormalities in the Retina of Diabetic Mice

Abstract

Purpose The cell surface LDL (low-density lipoprotein) receptor-related protein-1 (LRP-1) is important for lipid transport and several cell signaling processes. Human apolipoprotein E (apoE) is a ligand of LRP-1. We previously reported that a short peptide (apoEdp) mimicking the LRP-1 binding region of apoE prevents hyperglycemia-induced retinal endothelial cell dysfunction in vitro. The in-vivo outcome of apoE-based peptidomimetic inhibition of LRP-1 in the treatment of diabetic retinopathy is unknown. Methods Six months after streptozotocin induction of diabetes, male C57Bl/6 mice were intravitreally inoculated with apoEdp in a controlled release formulation. On the 15th day post-apoEdp treatment, mouse retinas were harvested to examine (1) blood–retinal–barrier (BRB) permeability by Evans blue dye, inflammatory leukostasis by concanavalin staining of leukocytes and LRP-1 pathway-related protein expression by Western blot analysis and gelatin zymography. Results Intravitreal apoEdp treatment of diabetic mice significantly reduced Evans blue extravasation and the number of adherent leukocytes in the diabetic mouse retinas. ApoEdp treatment inhibited the expression of extracellular matrix (ECM) degrading proteases heparanase and MMP-2, and restores the BRB tight junction proteins occludin and ZO-1. ApoEdp treatment also inhibited Wnt/β-catenin-related expression of pro-inflammatory molecules ICAM-1, HIF-1α, and VEGF through negative regulation by LRP-1. Conclusion Intravitreal apoEdp treatment of diabetic mice resulted a significant decrease in retinal vascular abnormalities through downregulation of LRP-1-related ECM protein degradation and Wnt/β-catenin-related pro-angiogenic molecules.

Longitudinal In Vivo Characterization of the Streptozotocin-Induced Diabetic Mouse Model: Focus on Early Inner Retinal Responses

“…The observed rapid increase in adherent leukocyte number starting at 2 weeks that still persisted at 4 and 8 weeks after diabetes onset in the murine retina is in line with other STZ studies also indicating a start of leukostasis around 1 to 2 weeks 60,88 and persisting up to 3 months. 51 Although one report describes high leukocyte numbers at 6 months in the mouse STZ model, 89 which contrasts our data that clearly reveal a reduction in the number of adherent leukocytes during late-term diabetes. The reason for this is unknown; however a decline in leukocyte number back to baseline levels is also described in the diabetic Ins2 Akita model at 20 weeks after diabetes onset.…”

Loss of β-catenin via activated GSK3β causes diabetic retinal neurodegeneration by instigating a vicious cycle of oxidative stress-driven mitochondrial impairment

“…Extract supernatants were measured by a spectrophotometer at 620 nm and 740 nm, respectively. Retinal vascular permeability was expressed as microgram of EB per milligram of retinal proteins after normalization by concentrations of total retinal protein as previously described [ 54 ].…”

Is leukostasis a crucial step or epiphenomenon in the pathogenesis of diabetic retinopathy?

“…Recently, additional evidence for a causal role of leukocyteinduced vascular damage in PCDR in rodents was reported by various research groups, who demonstrated that after several intervention methods, decreased leukostasis led to decreased diabetic sequelae in diabetic animal models [5,[7][8][9][10], which will be further discussed in the "Experimental evidence for the role of leukostasis in the development of vascular pathology in DR" section.…”