Topically Administered NOX4 Inhibitor, GLX7013114, Is Efficacious in Treating the Early Pathological Events of Diabetic Retinopathy.

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-1ß/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.

A small molecule inhibitor of Nox2 and Nox4 improves contractile function after ischemia-reperfusion in the mouse heart.

The NADPH oxidase enzymes Nox2 and 4, are important generators of Reactive oxygen species (ROS). These enzymes are abundantly expressed in cardiomyocytes and have been implicated in ischemia-reperfusion injury. Previous attempts with full inhibition of their activity using genetically modified animals have shown variable results, suggesting that a selective and graded inhibition could be a more relevant approach. We have, using chemical library screening, identified a new compound (GLX481304) which inhibits Nox 2 and 4 (with IC50 values of 1.25 µM) without general antioxidant effects or inhibitory effects on Nox 1. The compound inhibits ROS production in isolated mouse cardiomyocytes and improves cardiomyocyte contractility and contraction of whole retrogradely (Langendorff) perfused hearts after a global ischemia period. We conclude that a pharmacological and partial inhibition of ROS production by inhibition of Nox 2 and 4 is beneficial for recovery after ischemia reperfusion and might be a promising venue for treatment of ischemic injury to the heart.

A novel NADPH oxidase inhibitor targeting Nox4 in TGFß-induced lens epithelial to mesenchymal transition.

Many of the small molecule-based inhibitors of NADPH oxidase activity are largely inadequate to substantiate broad claims, often exhibiting a lack of Nox-isoform-specificity, and sometimes only acting as scavengers of reactive oxygen species (ROS). In the present study, we use a newly developed highly selective Nox4 inhibitor, GLX7013114, to modulate TGFß-induced lens epithelial to mesenchymal transition (EMT). Rat lens epithelial explants were pre-treated with 0.3  µM of GLX7013114, and then treated with 200 pg/ml of TGF-ß2 to induce lens EMT. ROS production was visualized microscopically using the superoxide fluorogenic probe, dihydroethidium (DHE). The EMT process was documented using phase-contrast microscopy, and molecular EMT markers were immunolabeled. qPCR was also performed to observe changes in EMT-associated genes. TGFß-induced ROS was evident at 8 h of culture and its intensity was found to be significantly reduced when GLX7013114 was applied, comparable to ROS levels measured in untreated explants. Using phase-contrast microscopy to follow TGFß-induced EMT over 5 days in the presence of the inhibitor, lens epithelial cells in explants became myofibroblastic by day 2 and underwent progressive apoptosis to reveal a bare lens capsule by day 5. Explants treated with TGFß and GLX7013114 had some increased cell survival; however, these differences were not significant. For the first time, Nox4 inhibition by GLX7013114 was shown to reduce the TGFß-induced gene expression of α-smooth muscle actin (αSMA), collagen 1a and fibronectin. GLX7013114, given that it appears to block aspects of TGFß-induced EMT, including ROS production, may be a new useful Nox4-selective inhibitor for further studies.

The novel NADPH oxidase 4 selective inhibitor GLX7013114 counteracts human islet cell death in vitro.

It has been proposed that pancreatic beta-cell dysfunction in type 2 diabetes is promoted by oxidative stress caused by NADPH oxidase (Nox) over-activity. The aim of the present study was to evaluate the efficacy of novel Nox inhibitors as protective agents against cytokine- or high glucose + palmitate-induced human beta-cell death. The Nox2 protein was present mainly in the cytoplasm and was induced by cytokines. Nox4 protein immunoreactivity, with some nuclear accumulation, was observed in human islet cells, and was not affected by islet culture in the presence of cytokines or high glucose + palmitate. Nox inhibitors with partial or no isoform selectivity (DPI, dapsone, GLX351322, and GLX481372) all reduced ROS production of human islet cells exposed to high glucose + palmitate. This was paralleled by improved viability and reduced caspase 3 activation. The Nox1 selective inhibitor ML171 failed to reduce human islet cell death in response to both cytokines and high glucose + palmitate. The selective Nox2 inhibitor Phox-I2 also failed to protect against cytokines, but protected partially against high glucose + palmitate-induced cellular death. The highly selective Nox4 inhibitor GLX7013114 protected islet cells against both cytokines and high glucose + palmitate. However, as no osmotic control for high glucose was used, we cannot exclude the possibility that the high glucose effect was due to osmosis. It is concluded that Nox4 may participate in stress-induced islet cell death in human islets in vitro. We propose that Nox4 mediates pro-apoptotic effects in intact islets under stressful conditions and that selective Nox4-inhibition may be a therapeutic strategy in type 2 diabetes.

FOXC2 controls Ang-2 expression and modulates angiogenesis, vascular patterning, remodeling, and functions in adipose tissue.

Adipogenesis is spatiotemporally coupled to angiogenesis throughout adult life, and the interplay between these two processes is communicated by multiple factors. Here we show that in a transgenic mouse model, increased expression of forkhead box C2 (FOXC2) in the adipose tissue affects angiogenesis, vascular patterning, and functions. White and brown adipose tissues contain a considerably high density of microvessels appearing as vascular plexuses, which show redistribution of vascular smooth muscle cells and pericytes. Dysfunction of these primitive vessels is reflected by impairment of skin wound healing. We further provide a mechanistic insight of the vascular phenotype by showing that FOXC2 controls Ang-2 expression by direct activation of its promoter in adipocytes. Remarkably, an Ang-2-specific antagonist almost completely reverses this vascular phenotype. Thus, the FOXC2-Ang-2 signaling system is crucial for controlling adipose vascular function, which is part of an adaptation to increased adipose tissue metabolism.

Insulin and IGF-1 mediated inhibition of apoptosis in CHO cells grown in suspension in a protein-free medium.

When Chinese hamster ovary (CHO) cells were grown in suspension and deprived of serum, 40% of them became apoptotic after 72 hours, as determined by flow cytometry analysis of TUNEL-labelled cells. Cell viability, assessed by erythrocin B staining, decreased correspondingly. An increase in the total fraction of cells expressing interleukin converting enzyme (ICE; caspase 1), B-cell lymphoma 2 protein (Bcl-2,) and Bcl-2 associated x protein (Bax) was shown by antibody probing and subsequent flow cytometry. The p53 tumour suppressor gene product level remained low within the cell population. Insulin-like growth factor-1 (IGF-1) inhibited cell death in a concentration-dependent manner, and at 20 ng/ml, cell viability was maintained close to 100% and no apoptotic cells were detected. Also, insulin was shown to inhibit cell death - at 1.0 microg/ml, cell viability was 95%, whereas 10% of the cells stained for apoptosis. At the highest concentrations of IGF-1 and insulin, the expression of ICE, Bcl-2 and Bax was fully suppressed, whereas the p53 product level increased, despite still being detectable in a minority of cells. Under these conditions, IGF-1 may increase p53 expression to restrain abnormal cell proliferation. It is concluded that special attention should be paid to exposure and culture conditions that induce acquired susceptibility to a toxic insult, during the development and validation of cell-based assays.