NADPH oxidases (NOXs) are major players in generating reactive oxygen species (ROS) and are implicated in various neurodegenerative ocular pathologies. The aim of this study was to investigate the role of a NOX4 inhibitor (GLX7013114) in two in vivo, experimental streptozotocin (STZ) paradigms depicting the early events of diabetic retinopathy (DR). Animals in the diabetic treated group received GLX7013114 topically (20 μL/eye, 10 mg/mL, once daily) for 14 days (paradigm A: preventive) and 7 days (paradigm B: treated) at 48 h and 4 weeks after STZ injection, respectively. Several methodologies were used (immunohistochemistry, Western blot, real-time PCR, ELISA, pattern electroretinography [PERG]) to assess the diabetes-induced early events of DR, namely oxidative stress, neurodegeneration, and neuroinflammation, and the effect of GLX7013114 on the diabetic insults. GLX7013114, administered as eye drops (paradigms A and B), was beneficial in treating the oxidative nitrative stress, activation of caspase-3 and micro- and macroglia, and attenuation of neuronal markers. It also attenuated the diabetes-induced increase in vascular endothelial growth factor, Evans blue dye leakage, and proinflammatory cytokine (TNF-α protein, IL-1β/IL-6 mRNA) levels. PERG amplitude values suggested that GLX7013114 protected retinal ganglion cell function (paradigm B). This study provides new findings regarding the pharmacological profile of the novel NOX4 inhibitor GLX7013114 as a promising therapeutic candidate for the treatment of the early stage of DR. Article Highlights: NADPH oxidases (NOXs) are implicated in the early pathological events of diabetic retinopathy (DR). The NOX4 inhibitor GLX7013114, topically administered, reduced oxidative damage and apoptosis in the rat streptozotocin model of DR. GLX7013114 protected retinal neurons and retinal ganglion cell function and reduced the expression of pro-inflammatory cytokines in the diabetic retina. GLX7013114 diminished the diabetes-induced increase in vascular endothelial growth factor levels and Evans blue dye leakage in retinal tissue. GLX7013114 exhibits neuroprotective, anti-inflammatory, and vasculoprotective properties that suggest it may have a role as a putative therapeutic for the early events of DR.

BNN27, a C17-spiroepoxy derivative of DHEA, was shown to have anti-apoptotic properties via mechanisms involving the NGF receptors (TrkA/ p75^NTR). In this study we examined the effects of BNN27 on neural/glial cell function, apoptosis and inflammation in the experimental rat streptozotocin (STZ)-model of diabetic retinopathy (DR). The ability of BNN27 to activate the TrkA receptor and regulate p75^NTR expression was investigated. BNN27 (2,10,50mg/kg,7days,i.p.) administration four weeks post STZ-injection (Paradigm A) reversed the diabetes-induced glial activation, loss of function of amacrine cells (bNOS/TH expression) and ganglion cell axons via a TrkAR-dependent mechanism. BNN27 activated/phosphorylated the TrkA^Y490 residue in the absence but not the presence of TrkAR inhibitor and abolished the diabetes-induced increase in p75^NTR expression. However, it had no effect on retinal cell death (TUNEL⁺ cells). A similar result was observed when BNN27(10mg/kg,i.p.) was administered at the onset of diabetes, every other day for four weeks (Paradigm B). However, BNN27 decreased the activation of caspase-3 in both paradigms. Finally, BNN27 reduced the pro-inflammatory (TNFα,IL_1β) and increased the anti-inflammatory (IL-10,IL-4) cytokine levels. These findings suggest that BNN27 has the pharmacological profile of a therapeutic for diabetic retinopathy, since it targets both the neurodegenerative and inflammatory components of the disease.