Pigment epithelium-derived factor inhibits retinal microvascular dysfunction induced by 12/15-lipoxygenase-derived eicosanoids

We recently demonstrated that 12/15-lipoxygenase (LOX) derived metabolites, hydroxyeicosatetraenoic acids (HETEs), contribute to diabetic retinopathy (DR) via NADPH oxidase (NOX) and disruption of the balance in retinal levels of the vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF). Here, we test whether PEDF ameliorates retinal vascular injury induced by HETEs and the underlying mechanisms. Furthermore, we pursue the causal relationship between LOX–NOX system and regulation of PEDF expression during DR. For these purposes, we used an experimental eye model in which normal mice were injected intravitreally with 12-HETE with/without PEDF. Thereafter, fluorescein angiography (FA) was used to evaluate the vascular leakage, followed by optical coherence tomography (OCT) to assess the presence of angiogenesis. FA and OCT reported an increased vascular leakage and pre-retinal neovascularization, respectively, in response to 12-HETE that were not observed in the PEDF-treated group. Moreover, PEDF significantly attenuated the increased levels of vascular cell and intercellular adhesion molecules, VCAM-1 and ICAM-1, elicited by 12-HETE injection. Accordingly, the direct relationship between HETEs and PEDF has been explored through in-vitro studies using Müller cells (rMCs) and human retinal endothelial cells (HRECs). The results showed that 12- and 15-HETEs triggered the secretion of TNF-α and IL-6, as well as activation of NFκB in rMCs and significantly increased permeability and reduced zonula occludens protein-1 (ZO-1) immunoreactivity in HRECs. All these effects were prevented in PEDF-treated cells. Furthermore, interest in PEDF regulation during DR has been expanded to include NOX system. Retinal PEDF was significantly restored in diabetic mice treated with NOX inhibitor, apocynin, or lacking NOX2 up to 80% of the control level. Collectively, our findings suggest that interfering with LOX–NOX signaling opens up a new direction for treating DR by restoring endogenous PEDF that carries out multilevel vascular protective functions.National Eye Institute 5R01EY023315-02, Qatar National Research Fund NPRP 4-1046-3-284, and Vision Discovery Institute (MA), Mr. and Mrs. Richards travel award (ASI)

A System for Inducible Gene Expression in Retinal Ganglion Cells

PURPOSE. To develop a system for inducible gene expression in retinal ganglion cells, Thy1 and ckit promoters were used to direct expression of a second-generation reverse tetracycline transactivator (rtTA2(S)-M2). METHODS. Transgenic mice were generated that harbor rtTA2(S)-M2 under the control of either the Thy1 or ckit promoter. These animals were crossed with mice transgenic for the LacZ gene downstream of a cassette of tet operator (TRE) binding sites. Induction of the LacZ reporter gene in vivo after either oral or subcutaneous doxycycline administration and in vitro in cultured retinal cells was assessed. To examine induction of a secreted protein, expression of pigment epitheliumderived factor (PEDF) in mice harboring Thy1-rtTA and TRE-PEDF constructs was quantified. RESULTS. Five of seven Thy1-rtTA lines showed induction with subcutaneous doxycycline: maximum induction in one line (Thy1-C), moderate in one line (Thy1-F), and minimal in three lines. There was no detectable retinal LacZ expression in the ckit-rtTA lines, despite expression of the ckit-rtTA transgene at the RNA level. In Thy1-rtTA lines, LacZ reporter expression as measured by X-gal staining was evenly dispersed throughout all quadrants of the retina, present in a subpopulation of retinal ganglion cell (RGC) bodies, RGC axons projecting through the retina and optic nerve, and some cells in the inner nuclear layer. Immunostaining for ␤-galactosidase demonstrated more uniform expression in RGCs and cells of the inner aspect of the inner nuclear layer, which, by double staining with anti-␤-galactosidase and anti-calretinin antibodies, were consistent with amacrine cells. More than 95% of Thy-1 antigen-positive cells in the retina expressed the induced transgene. Subcutaneous doxycycline resulted in a more robust induction of LacZ than did oral administration. In vitro, the number of cells induced in culture increased in a dose-dependent manner, with maximum expression at 10 g/mL at a level 3.4-fold over background. Thy1-rtTA/TRE-PEDF mice treated with doxycycline had 1000-fold induction in their retinal PEDF expression in comparison with nontransgenic mice and 600-fold induction over noninduced Thy1-rtTA/TRE-PEDF mice. CONCLUSIONS. A transgenic system for inducible RGC expression has been developed that demonstrates minimal leakiness and significant induction with doxycycline. This system will be useful for several applications. (Invest Ophthalmol Vis Sci

TNFα Is Required for Late BRB Breakdown in Diabetic Retinopathy, and Its Inhibition Prevents Leukostasis and Protects Vessels and Neurons from Apoptosis

The absence of TNFα protects against diabetes-associated blood–retinal barrier breakdown, leukostasis, and apoptosis in the retina, making it a good therapeutic target for the prevention of the progressive BRB breakdown, inflammation, and apoptosis associated with diabetic retinopathy

Plasma Vascular Endothelial Growth Factor Concentrations after Intravitreous Anti-Vascular Endothelial Growth Factor Therapy for Diabetic Macular Edema

To assess systemic vascular endothelial growth factor (VEGF)-A levels after treatment with intravitreous aflibercept, bevacizumab, or ranibizumab. Comparative-effectiveness trial with participants randomly assigned to 2 mg aflibercept, 1.25 mg bevacizumab, or 0.3 mg ranibizumab after a re-treatment algorithm. Participants with available plasma samples (N = 436). Plasma samples were collected before injections at baseline and 4-week, 52-week, and 104-week visits. In a preplanned secondary analysis, systemic-free VEGF levels from an enzyme-linked immunosorbent assay were compared across anti-VEGF agents and correlated with systemic side effects. Changes in the natural log (ln) of plasma VEGF levels. Baseline free VEGF levels were similar across all 3 groups. At 4 weeks, mean ln(VEGF) changes were -0.30±0.61 pg/ml, -0.31±0.54 pg/ml, and -0.02±0.44 pg/ml for the aflibercept, bevacizumab, and ranibizumab groups, respectively. The adjusted differences between treatment groups (adjusted confidence interval [CI]; P value) were -0.01 (-0.12 to +0.10; P = 0.89), -0.31 (-0.44 to -0.18; P < 0.001), and -0.30 (-0.43 to -0.18; P < 0.001) for aflibercept-bevacizumab, aflibercept-ranibizumab, and bevacizumab-ranibizumab, respectively. At 52 weeks, a difference in mean VEGF changes between bevacizumab and ranibizumab persisted (-0.23 [-0.38 to -0.09]; P < 0.001); the difference between aflibercept and ranibizumab was -0.12 (P = 0.07) and between aflibercept and bevacizumab was +0.11 (P = 0.07). Treatment group differences at 2 years were similar to 1 year. No apparent treatment differences were detected at 52 or 104 weeks in the cohort of participants not receiving injections within 1 or 2 months before plasma collection. Participants with (N = 9) and without (N = 251) a heart attack or stroke had VEGF levels that appeared similar. These data suggest that decreases in plasma free-VEGF levels are greater after treatment with aflibercept or bevacizumab compared with ranibizumab at 4 weeks. At 52 and 104 weeks, a greater decrease was observed in bevacizumab versus ranibizumab. Results from 2 subgroups of participants who did not receive injections within at least 1 month and 2 months before collection suggest similar changes in VEGF levels after stopping injections. It is unknown whether VEGF levels return to normal as the drug is cleared from the system or whether the presence of the drug affects the assay's ability to accurately measure free VEGF. No significant associations between VEGF concentration and systemic factors were noted