Ratio of the vitreous vascular endothelial growth factor and pigment epithelial-derived factor in Eales disease

PEDF is an endogenous inhibitor of VEGF-R2 angiogenesis signaling in endothelial cells

Pigment epithelium derived factor (PEDF), an endogenous inhibitor of angiogenesis, targets the growth of aberrant blood vessels in many tissues, including the eye. In this study we show that PEDF prevented early mitogenic signals of vascular endothelial growth factor (VEGF-A) in primate retinal endothelial cells, blocking proliferation, migration and tube formation. PEDF inhibited the phosphorylation and activation of five major downstream VEGF-A signaling partners, namely phosphoinositide-3-OH Kinase (PI3K), AKT, FAK, Src (Y416), and PLC-γ. It did so by binding to the extracellular domain of VEGF-R2, blocking VEGF-A-induced tyrosine phosphorylation (Tyr 951 and Tyr 1175), and inhibiting VEGF-R2 receptor kinase activity. PEDF had no effect on the transcription or translation of VEGF-R2 in cultured HUVECs. PEDF also bound to the extracellular domain of VEGF-R1. We conclude that PEDF blocks the growth of new blood vessels, in part, by reducing VEGF-A activation of its key mitogenic receptor, VEGF-R2, and by preventing its downstream signals in endothelial cells.

Secretogranin III as a disease-associated ligand for antiangiogenic therapy of diabetic retinopathy

LeBlanc et al. uncover secretogranin III (Scg3) as a unique disease-associated vascular permeability and angiogenic factor using comparative ligandomics. Scg3-neutralizing antibodies alleviate vascular leakage in diabetic retinopathy mice and retinal neovascularization in oxygen-induced retinopathy mice with high efficacy.

Diabetic retinopathy (DR) is a leading cause of vision loss with retinal vascular leakage and/or neovascularization. Current antiangiogenic therapy against vascular endothelial growth factor (VEGF) has limited efficacy. In this study, we applied a new technology of comparative ligandomics to diabetic and control mice for the differential mapping of disease-related endothelial ligands. Secretogranin III (Scg3) was discovered as a novel disease-associated ligand with selective binding and angiogenic activity in diabetic but not healthy vessels. In contrast, VEGF bound to and induced angiogenesis in both diabetic and normal vasculature. Scg3 and VEGF signal through distinct receptor pathways. Importantly, Scg3-neutralizing antibodies alleviated retinal vascular leakage in diabetic mice with high efficacy. Furthermore, anti-Scg3 prevented retinal neovascularization in oxygen-induced retinopathy mice, a surrogate model for retinopathy of prematurity (ROP). ROP is the most common cause of vision impairment in children, with no approved drug therapy. These results suggest that Scg3 is a promising target for novel antiangiogenic therapy of DR and ROP.

Low blood and vitreal BDNF, LXA4 and altered Th1/Th2 cytokine balance are potential risk factors for diabetic retinopathy

OBJECTIVE

The study was conducted to observe the serum and vitreous levels of LXA4, BDNF and Th1/Th2 cytokines in type 2 diabetes mellitus (DM) and changes associated with diabetic retinopathy (DR). Further, the in vitro study was performed to analyze the exposure of BDNF and LXA4 on LPS-induced pro-inflammatory state in ARPE 19 cells.

MATERIALS AND METHODS

Totally 114 individuals were recruited in a prospective case control study. Of these, 27 were type 2 DM cases with no complications, 30 cases were type 2 DM with non proliferative diabetic retinopathy (NPDR), 30 were type 2 DM with proliferative diabetic retinopathy (PDR), and 27 were healthy control. ELISA was done to estimate the serum and vitreous levels of BDNF, VEGF and PEDF. FACS cytometric Bead Array system was used to analyze the serum cytokines.

RESULTS

The serum BDNF and LXA4 levels were significantly reduced in both NPDR and PDR cases compared to control (p=0.005, 0.01; p=0.033, 0.015). Serum IL-6 was significantly increased in the PDR group (p=0.04). BDNF showed a significant negative correlation with VEGF levels (r=-0.522, p<0.01) and positive correlation with IL-10 (r=0.67, p<0.05) in serum. A significant odds ratio for the serum BDNF (OR: 3.20, p=0.025) as well as serum IL-6 (OR: 1.244, p=0.042) indicated them as potential risk factors for progression of type 2 DM to DR. A significant decrease in both the LXA4 (p=0.013) and BDNF (p=0.0008) with increase in cytokines IL-6 and IL-10 levels were observed in the vitreous of PDR cases ((p=0.04, 0.01). In vitro studies showed that both LXA4 (10 nmol/L) and BDNF (500 pg) decreased the IL-6 levels (p=0.036, 0.0002), in LPS induced pro-inflammatory condition in ARPE 19 cells, thereby their anti-inflammatory effect.

CONCLUSIONS

This study reports that low serum BDNF and higher IL-6 levels are potential risk factors for DR in type 2 DM. This study supports the role of BDNF in modulating the pro- and anti-inflammatory cytokines, and low level of BDNF is associated with development of diabetic retinopathy.

Growth factors/chemokines in diabetic vitreous and aqueous alter the function of bone marrow-derived progenitor (CD34⁺) cells in humans

Ocular ischemic microenvironment plays a critical role in the progression of diabetic retinopathy (DR). In this study, we investigated the effect of vitreous and aqueous obtained from proliferative DR patients on the function of CD34⁺ cells derived from healthy humans. Human CD34⁺ cells were incubated with vitreous or aqueous of subjects with PDR. After incubation, cell migration of CD34⁺ was evaluated with CXCL12. Intracellular levels of nitric oxide (NO) were measured with DAF-FM. Tube formation assay was used to evaluate the effect of treated CD34⁺ cells on in vitro angiogenesis. Angiogenic protein array and mass spectrometry (MS) were performed to ascertain the factors secreted by healthy nondiabetic CD34⁺ cells exposed to diabetic vitreous or aqueous. PDR vitreous/aqueous reduced migration of CD34⁺ cells (672.45 ± 42.1/736.75 ± 101.7 AFU; P < 0.01) and attenuated intracellular NO levels (182 ± 1.4/184.5 ± 6.3 AFU, P = 0.002). Pretreatment with PDR vitreous suppressed tube formation of human retinal endothelial cells (64 ± 1.6 vs. 80 ± 2.5). CD34⁺ exposed to PDR vitreous resulted in the increased expression of CXCL4 and serpin F1, whereas CD34⁺ exposed to PDR aqueous showed increased expression of CXCL4, serpin F1, and endothelin-1 (ET-1). MS analysis of CD34⁺ (exposed to PDR vitreous) expressed J56 gene segment, isoform 2 of SPARC-related modular calcium-binding protein 2, isoform 1 of uncharacterized protein c1 orf167, integrin α-M, and 40s ribosomal protein s21. Exposure of healthy nondiabetic CD34⁺ cells to PDR vitreous and aqueous resulted in decreased migration, reduced generation of NO, and altered paracrine secretory function. Our results suggest that the contribution of CD34⁺ cells to the aberrant neovascularization observed in PDR is driven more by the proangiogenic effects of the retinal cells rather than the influence of the vitreous.

Eales' disease - current concepts in diagnosis and management

Eales' disease, first described by the British ophthalmologist Henry Eales in 1880, is characterized by three overlapping stages of venous inflammation (vasculitis), occlusion, and retinal neovascularization. Diagnosis is mostly clinical and requires exclusion of other systemic or ocular conditions that could present with similar retinal features. In recent years, immunological, molecular biological, and biochemical studies have indicated the role of human leukocyte antigen, retinal autoimmunity, Mycobacterium tuberculosis genome, and free radical-mediated damage in the etiopathogenesis of this disease. However, its etiology appears to be multifactorial. The management depends on the stage of the disease and consists of medical treatment with oral corticosteroids in the active inflammatory stage and laser photocoagulation in the advanced retinal ischemia and neovascularization stages.

High glucose induced differential expression of lysyl oxidase and its isoform in ARPE-19 cells

PURPOSE

Lysyl oxidase (LOX) stabilizes the extracellular matrix (ECM) by cross-linking collagen and elastin molecules. In proliferative diabetic retinopathy (PDR), there is ECM remodeling with neovascularization and basement membrane changes. While protease activities are well reported, the role of LOX in the pathogenesis of diabetic retinopathy is less studied. This study was done to see the effect of high glucose on the activity and expression of LOX and its isoforms in ARPE-19 cells.

MATERIALS AND METHODS

ARPE-19 cells were exposed to high glucose up to 48 h, and LOX activity was determined by N-acetyl-3,7-dihydroxyphenoxazine assay. The mRNA expression of LOX and its isoforms was done by real-time PCR and the protein expression by ELISA. Immunohistochemistry for LOX was done in epiretinal membrane from PDR.

RESULTS

With an increase in glucose concentration LOX activity and protein was reduced significantly at 30 mM glucose at 48 h. mRNA expression of LOX, LOXL1, and LOXL2 varied with time and concentration of glucose. Vascular endothelial growth factor (VEGF) increased the LOX activity as well as the mRNA expression. Pigment epithelium-derived factor (PEDF) downregulated the mRNA expression of LOX, LOXL1, and LOXL2. The matrix metalloprotease (MMP) activity increased significantly with the increase in glucose concentration. The diabetic neovascular membrane showed increased immunostaining of LOX.

CONCLUSIONS

This study suggests that although the LOX activity, which is composite of all the isoforms, was reduced under high glucose conditions, there was a differential mRNA expression with increased LOX and LOXL1 and decreased LOXL2 expression.

Comparative modeling of retinol-binding protein-3 and retinal S-antigen in Eales' disease and prediction of their binding sites using computational methods

Retinal S-antigen and interphotoreceptor retinoid-binding protein-3 play a significant role in the etiopathogenesis of Eales' disease. Protein 3D structures are functionally very important and play a significant role in progression of the disease, hence these 3D structures are better target for further drug designing and relative studies. We developed 3D model structure of retinol-binding protein-3 and retinal S-antigen protein of human involved in Eales' disease. Functional site prediction is a very important and related step; hence, in the current course of analysis, we predicted putative functional site residues in the target proteins. Molecular models of these proteins of Eales' disease as documented in this study may provide a valuable aid for designing an inhibitor or better ligand against Eales' disease and could play a significant role in drug design.

Total antioxidant capacity in Eales' disease, uveitis & cataract

BACKGROUND & OBJECTIVES

The human system possesses antioxidants that act harmoniously to neutralize the harmful oxidants. This study was aimed to evaluate the serum total antioxidant capacity (TAC) as a single parameter in Eales' disease (ED) and in an acute inflammatory condition such as uveitis and in cataract which is chronic, compared to healthy controls.

METHODS

The TAC assay was done spectrophotometrically in the serum of Eales' disease cases (n=20) as well as in other ocular pathologies involving oxidative stress namely, uveitis and cataract (n=20 each). The oxidative stress measured in terms of TBARS, was correlated with the TAC. Individual antioxidants namely vitamin C, E and glutathione were also estimated and correlated with TAC.

RESULTS

TAC was found to be significantly lower in Eales' disease with active vasculitis (0.28 ± 0.09 mM, P<0.001), Eales' disease with healed vasculitis (0.67 ± 0.09 mM), uveitis (0.46 ± 0.09 mM, P<0.001) and cataract (0.53 ± 0.1 mM, P=0.001) compared to the healthy controls, with a TAC level of 0.77 ± 0.09 mM. The TAC was found to correlate positively with vitamin E levels (P=0.05), GSH (P=0.02) but not with vitamin C, as seen in ED cases. In ED cases supplemented with vitamin E and C, there was a significant increase in the TAC level (P=0.02).

INTERPRETATION & CONCLUSIONS

The TAC measurement provided a comprehensive assay for establishing a link between the antioxidant capacity and the risk of disease as well as monitoring antioxidant therapy. This method is a good substitute for assay of individual antioxidants as it clearly gives the status of the oxidative stress in the disease process.

The yin and yang of VEGF and PEDF: multifaceted neurotrophic factors and their potential in the treatment of Parkinson's Disease

Over the last few decades, vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) have emerged as multifaceted players in not only the pathogenesis, but potential treatment, of numerous diseases. They activate diverse intracellular signaling cascades known to have extensive crosstalk, and have been best studied for their effects in cardiology and cancer biology. Recent work with the two factors indicates that the activity of one growth factor is often directly related to the action of the other. Their respective neuroprotective effects, in particular, raise important questions regarding the treatment of neurodegenerative disorders, including Parkinson’s disease.

Eales' disease: diagnosis and management

Eales' disease is an idiopathic inflammatory venous occlusive disease. It primarily affects young adults and is often bilateral. It is characterized by three overlapping stages of venous inflammation (vasculitis), occlusion, and retinal neovascularization. Diagnosis is mostly clinical and requires exclusion of other systemic or ocular conditions that could present with similar retinal features. Recurrent vitreous haemorrhage is the hall mark of Eales' disease. Treatment is usually corticosteroids in the inflammation stage and photocoagulation in the proliferative stage of the disease. Visual prognosis is good if treated early in the course of the disease.