Genetic deletion of COX-2 diminishes VEGF production in mouse retinal Müller cells

Abstract

Non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit COX activity, reduce the production of retinal VEGF and neovascularization in relevant models of ocular disease. We hypothesized that COX-2 mediates VEGF production in retinal Müller cells, one of its primary sources in retinal neovascular disease. The purpose of this study was to determine the role of COX-2 and its products in VEGF expression and secretion. These studies have more clearly defined the role of COX-2 and COX-2-derived prostanoids in retinal angiogenesis. Müller cells derived from wild-type and COX-2 null mice were exposed to hypoxia for 0–24 hours. COX-2 protein and activity were assessed by western blot analysis and GC-MS, respectively. VEGF production was assessed by ELISA. Wild-type mouse Müller cells were treated with vehicle (0.1% DMSO), 10 µM PGE2, or PGE2 + 5 µM H-89 (a PKA inhibitor), for 12 hours. VEGF production was assessed by ELISA. Hypoxia significantly increased COX-2 protein (p ≤ 0.05) and activity (p ≤ 0.05), and VEGF production (p ≤ 0.0003). COX-2 null Müller cells produced significantly less VEGF in response to hypoxia (p ≤ 0.05). Of the prostanoids, PGE2 was significantly increased by hypoxia (p ≤ 0.02). Exogenous PGE2 significantly increased VEGF production by Müller cells (p ≤ 0.0039), and this effect was inhibited by H-89 (p ≤ 0.055). These data demonstrate that hypoxia induces COX-2, prostanoid production, and VEGF synthesis in Müller cells, and that VEGF production is at least partially COX-2-dependent. Our study suggests that PGE2, signaling through the EP2 and/or EP4 receptor and PKA, mediates the VEGF response of Müller cells.

Mitigation of Oxygen-Induced Retinopathy in α2β1 Integrin-Deficient Mice

“…33,34 In contrast, GFAP expression had a more modest increase at P18 in a2-null mice after hypoxia (Fig. 3A).…”

“…4A). 23,30,33,34 Although a2-null retinas also developed a central avascular area due to capillary loss near the optic nerve, the avascular region was significantly diminished compared to the WT (Fig. 4A), indicating that a2b1 integrin-deletion protected from early vessel attenuation during hyperoxia.…”

“…Given that NV in OIR is considered to be primarily driven by VEGF-A overproduction, our findings strongly suggest that the integrin's contribution to the pathogenesis of OIR is from the Müller compartment. 31,34,38 However, without cell-type-specific a2-null mice, it is not possible to rule out contributing roles in the endothelium or other cell types.…”

“…33,34 To determine WT and ITGA2 À/À mice raised in normal air or relative hypoxia (6 days after hyperoxia in OIR) were evaluated by immunofluorescence microscopy using anti-GFAP (Müller cells: red) or anti-CD31 (ECs: green) and DAPI (nuclei: blue). Images were taken at 340 magnification and are representative of three separate trials.…”

Fluorocoxib A enables targeted detection of cyclooxygenase-2 in laser-induced choroidal neovascularization

“…Also, COX-2 may be a valuable molecular imaging biomarker for early detection of retinal diseases, staging of disease severity, and monitoring therapeutic response in patients with retinal disease including AMD and diabetic retinopathy. 12 …”