Anti-Vascular Endothelial Growth Factors Protect Retinal Pigment Epithelium Cells Against Oxidation by Modulating Nitric Oxide Release and Autophagy

Membrane Blue Dual Protects Retinal Pigment Epithelium Cells/Ganglion Cells-Like through Modulation of Mitochondria Function

Although recent data highlight the greater protective effects exerted by Membrane Blue Dual (MBD), a precise analysis of the mechanisms of action is missing. We examined the effects of MBD with/without polyethylene glycol (PEG) on both human retinal pigment epithelial cells (ARPE-19) and retinal ganglion cells-like (RGC-5) cultured in the presence/absence of ultraviolet B (UVB) treatment on mitochondria function, oxidants, and apoptosis. In ARPE-19/RGC-5 cells either treated or not with UVB, the effects of MBD with/without PEG were evaluated by specific assays for viability, mitochondrial membrane potential and mitochondrial reactive oxygen species (mitoROS) release. Annexin V was used to detect apoptosis, whereas trypan blue and the scratch assay were used for proliferation/migration. In both physiologic conditions and in the presence of UVB, MBD with/without PEG increased cell viability, mitochondrial membrane potential, proliferation and migration in both ARPE-19 and RGC-5 cells. In general, the effects of MBD with PEG were greater than those caused by MBD without PEG. Our results suggest that, in particular, MBD with PEG is a safe and effective dye for vitreoretinal surgery through the modulation of mitochondrial function.

Oxidative Stress Implication in Retinal Diseases-A Review

Oxidative stress (OS) refers to an imbalance between free radicals (FRs), namely highly reactive molecules normally generated in our body by several pathways, and intrinsic antioxidant capacity. When FR levels overwhelm intrinsic antioxidant defenses, OS occurs, inducing a series of downstream chemical reactions. Both reactive oxygen species (ROS) and reactive nitrogen species (RNS) are produced by numerous chemical reactions that take place in tissues and organs and are then eliminated by antioxidant molecules. In particular, the scientific literature focuses more on ROS participation in the pathogenesis of diseases than on the role played by RNS. By its very nature, the eye is highly exposed to ultraviolet radiation (UVR), which is directly responsible for increased OS. In this review, we aimed to focus on the retinal damage caused by ROS/RNS and the related retinal pathologies. A deeper understanding of the role of oxidative and nitrosative stress in retinal damage is needed in order to develop targeted therapeutic interventions to slow these pathologies.

MicroRNA-184 attenuates hypoxia and oxidative stress-related injury via suppressing apoptosis, DNA damage and angiogenesis in an in vitro age-related macular degeneration model

Age-related macular degeneration (AMD) is one of the leading causes of blindness worldwide, particularly in developed countries. Recently, microRNAs (miRs) have become popular research area to develop new treatment options of AMD. However, interaction between hsa-miR-184 and AMD remain largely unexplored. In this study, sub-lethal levels of Deforoxamine Mesylate salt (DFX) and H₂O₂ were applied to ARPE-19 cells to establish a severe in vitro AMD model, via durable hypoxia and oxidative stress. We found that up-regulation of miR-184 level in AMD can suppress hypoxia-related angiogenic signals through HIF-1α/VEGF/MMPs axis. Also, miR-184 suppressed the hypoxia sensor miR-155 and genes in the EGFR/PI3K/AKT pathway, which is an alternative pathway in angiogenesis. To investigate the mechanism behind this protective effect, we evaluated the impact of miR-184 on retinal apoptosis in a model of AMD. miR-184 inhibited retinal apoptosis by upregulating BCL-2 and downregulating pro-apoptototic BAX, TRAIL, Caspase 3 and 8 signals as well as p53. Taken together, miR-184 attenuates retinal cell damage induced by severe AMD pathologies through suppressing hypoxia, angiogenesis and apoptosis. The safety profile of miR-184 was observed to be similar to Bevacizumab, which is in wide use clinically, but miR-184 was found to provide a more effective therapeutic potential by regulating simultaneously multiple pathologies.

Alpha-Tocopherol Protects Human Dermal Fibroblasts by Modulating Nitric Oxide Release, Mitochondrial Function, Redox Status, and Inflammation

BACKGROUND

The altered balance between oxidants/antioxidants and inflammation, changes in nitric oxide (NO) release, and mitochondrial function have a role in skin aging through fibroblast modulation. Tocopherol is promising in counteracting the abovementioned events, but the effective mechanism of action needs to be clarified.

OBJECTIVE

The aim of this study was to examine the effects of α-tocopherol on cell viability/proliferation, NO release, mitochondrial function, oxidants/antioxidants, and inflammation in human dermal fibroblasts (HDF) subjected to oxidative stress.

METHODS

HDF were treated with H2O2 in the presence or absence of 1-10 μM α-tocopherol. Cell viability, reactive oxygen species (ROS), NO release, and mitochondrial membrane potential were measured; glutathione (GSH), superoxide dismutase (SOD)-1 and -2, glutathione peroxidase-1 (GPX-1), inducible NO synthase (iNOS), and Ki-67 were evaluated by RT-PCR and immunofluorescence; cell cycle was analyzed using FACS. Pro- and anti-inflammatory cytokine gene expression was analyzed through qRT-PCR.

RESULTS

α-Tocopherol counteracts H2O2, although it remains unclear whether this effect is dose dependent. Improvement of cell viability, mitochondrial membrane potential, Ki-67 expression, and G0/G1 and G2/M phases of the cell cycle was observed. These effects were accompanied by the increase of GSH content and the reduction of SOD-1 and -2, GPX-1, and ROS release. Also, iNOS expression and NO release were inhibited, and pro-inflammatory cytokine gene expression was decreased, confirming the putative role of α-tocopherol against inflammation.

CONCLUSION

α-Tocopherol exerts protective effects in HDF which underwent oxidative stress by modulating the redox status, inflammation, iNOS-dependent NO release, and mitochondrial function. These observations have a potential role in the prevention and treatment of photoaging-related skin cancers.

Exposure to Plasma From Non-alcoholic Fatty Liver Disease Patients Affects Hepatocyte Viability, Generates Mitochondrial Dysfunction, and Modulates Pathways Involved in Fat Accumulation and Inflammation

Changes of lipidic storage, oxidative stress and mitochondrial dysfunction may be involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Although the knowledge of intracellular pathways has vastly expanded in recent years, the role and mechanisms of circulating triggering factor(s) are debated. Thus, we tested the hypothesis that factors circulating in the blood of NAFLD patients may influence processes underlying the disease. Huh7.5 cells/primary human hepatocytes were exposed to plasma from 12 NAFLD patients and 12 healthy subjects and specific assays were performed to examine viability, H₂O₂ and mitochondrial reactive oxygen species (ROS) release, mitochondrial membrane potential and triglycerides content. The involvement of NLRP3 inflammasome and of signaling related to peroxisome-proliferator-activating-ligand-receptor-γ (PPARγ), sterol-regulatory-element-binding-protein-1c (SREBP-1c), nuclear-factor-kappa-light-chain-enhancer of activated B cells (NF-kB), and NADPH oxidase 2 (NOX2) was evaluated by repeating the experiments in the presence of NLRP3 inflammasome blocker, MCC950, and through Western blot. The results obtained shown that plasma of NAFLD patients was able to reduce cell viability and mitochondrial membrane potential by about 48 and 24% (p < 0.05), and to increase H₂O₂, mitochondrial ROS, and triglycerides content by about 42, 19, and 16% (p < 0.05), respectively. An increased expression of SREBP-1c, PPARγ, NF-kB and NOX2 of about 51, 121, 63, and 46%, respectively, was observed (p < 0.05), as well. Those effects were reduced by the use of MCC950. Thus, in hepatocytes, exposure to plasma from NAFLD patients induces a NAFLD-like phenotype by interference with NLRP3-inflammasome pathways and the activation of intracellular signaling related to SREBP-1c, PPARγ, NF-kB and NOX2.

Oxidative and Nitrosative Stress in Age-Related Macular Degeneration: A Review of Their Role in Different Stages of Disease

Although the exact pathogenetic mechanisms leading to age-related macular degeneration (AMD) have not been clearly identified, oxidative damage in the retina and choroid due to an imbalance between local oxidants/anti-oxidant systems leading to chronic inflammation could represent the trigger event. Different in vitro and in vivo models have demonstrated the involvement of reactive oxygen species generated in a highly oxidative environment in the development of drusen and retinal pigment epithelium (RPE) changes in the initial pathologic processes of AMD; moreover, recent evidence has highlighted the possible association of oxidative stress and neovascular AMD. Nitric oxide (NO), which is known to play a key role in retinal physiological processes and in the regulation of choroidal blood flow, under pathologic conditions could lead to RPE/photoreceptor degeneration due to the generation of peroxynitrite, a potentially cytotoxic tyrosine-nitrating molecule. Furthermore, the altered expression of the different isoforms of NO synthases could be involved in choroidal microvascular changes leading to neovascularization. The purpose of this review was to investigate the different pathways activated by oxidative/nitrosative stress in the pathogenesis of AMD, focusing on the mechanisms leading to neovascularization and on the possible protective role of anti-vascular endothelial growth factor agents in this context.

Inhibition of nitric oxide synthase aggravates brain injury in diabetic rats with traumatic brain injury

Studies have shown that hyperglycemia aggravates brain damage by affecting vascular endothelial function. However, the precise mechanism remains unclear. Male Sprague-Dawley rat models of diabetes were established by a high-fat diet combined with an intraperitoneal injection of streptozotocin. Rat models of traumatic brain injury were established using the fluid percussion method. Compared with traumatic brain injury rats without diabetic, diabetic rats with traumatic brain injury exhibited more severe brain injury, manifested as increased brain water content and blood-brain barrier permeability, the upregulation of heme oxygenase-1, myeloperoxidase, and Bax, the downregulation of occludin, zona-occludens 1, and Bcl-2 in the penumbra, and reduced modified neurological severity scores. The intraperitoneal injection of a nitric oxide synthase inhibitor N(5)-(1-iminoethyl)-L-ornithine (10 mg/kg) 15 minutes before brain injury aggravated the injury. These findings suggested that nitric oxide synthase plays an important role in the maintenance of cerebral microcirculation, including anti-inflammatory, anti-oxidative stress, and anti-apoptotic activities in diabetic rats with traumatic brain injury. The experimental protocols were approved by the Institutional Animal Care Committee of Harbin Medical University, China (approval No. ky2017-126) on March 6, 2017.

Imbalance Between Oxidative Stress and Growth Factors in Human High Myopia

Myopia is one of the commonest eye pathologies that could affect 2.56 billion people by 2020. Today high myopia is a leading cause of blindness worldwide due to associated ocular illness. Nevertheless, the cellular bases for these diseases to develop are unclear in many areas. We conducted a prospective study of oxidative stress and growth factors in human myopic and non myopic eyes in an attempt to increase our understanding of the underlying physiopathological conditions to adequately early diagnose, prevent and treat the retina problem that derives from myopia. Aqueous humor samples were obtained from 41 patients being operated for cataracts in our hospital. Axial length, refractive status and complete ophthalmologic examination were recorded. The VEGF and HGF levels were determined by an ELISA kit. Total antioxidant capacity and total nitrites/nitrate levels were established with a lab kit. We show for the first time an increase in the total nitrite levels in high myopia. We also propose for the first time the concurrence of three factors: myopia, oxidative stress, and oxidative stress together with growth factors in the same group of patients. In this way, it would not be accurate to envision high myopia as a type of normal myopia, but one with more diopters or longer axial length.

A Review of Macular Atrophy of the Retinal Pigment Epithelium in Patients with Neovascular Age-Related Macular Degeneration: What is the Link? Part II

Introduction

To explore the potential link between macular atrophy (MA) of the retinal pigment epithelium (RPE) in patients with neovascular age-related macular degeneration (nAMD) and anti-vascular endothelial growth factor (anti-VEGF) treatment.

Methods

Through a balanced overview of the field from a largely clinical perspective, we looked at available evidence on the topic of MA correlation with anti-VEGF therapy and examined possible risk factors for MA development in the context of nAMD treatment with anti-VEGF.

Results

Links have been reported to connect both MA incidence and progression to treatment frequency and to the anti-VEGF drug type.

Conclusions

All reports agree on the fact that de novo development of MA in anti-VEGF-treated eyes is frequent and multifactorial. Research data shows an expansion of atrophy during anti-VEGF treatment. There are mixed conclusions about the correlation of MA incidence or progression with treatment-related risk factors. It mostly appears that there is no straightforward link. More clinical research is still needed to further understand this association.

Nitrosative Stress in Retinal Pathologies: Review

Nitric oxide (NO) is a gas molecule with diverse physiological and cellular functions. In the eye, NO is used to maintain normal visual function as it is involved in photoreceptor light transduction. In addition, NO acts as a rapid vascular endothelial relaxant, is involved in the control of retinal blood flow under basal conditions and mediates the vasodilator responses of different substances such as acetylcholine, bradykinin, histamine, substance P or insulin. However, the retina is rich in polyunsaturated lipid membranes and is sensitive to the action of reactive oxygen and nitrogen species. Products generated from NO (i.e., dinitrogen trioxide (N₂O₃) and peroxynitrite) have great oxidative damaging effects. Oxygen and nitrogen species can react with biomolecules (lipids, proteins and DNA), potentially leading to cell death, and this is particularly important in the retina. This review focuses on the role of NO in several ocular diseases, including diabetic retinopathy, retinitis pigmentosa, glaucoma or age-related macular degeneration (AMD).

The subthreshold micropulse laser treatment of the retina restores the oxidant/antioxidant balance and counteracts programmed forms of cell death in the mice eyes

PURPOSE

Subthreshold micropulse laser (SMPL) has been increasingly used for the treatment of different retinal and choroidal macular disorders. However, the exact mechanisms of action have not yet been clearly defined. Therefore, we aimed to examine the role of SMPL treatment in the modulation of oxidant/antioxidant systems, apoptosis and autophagy in the mice eyes.

METHODS

A specific laser contact lens for retina was positioned on the cornea of 40 mice (20 young and 20 old) in order to focus the laser on the eye fundus for SMPL treatment. Within 6 months, 20 animals received one treatment only, whereas the others were treated three times. Eye specimens underwent histological analysis and were used for thiobarbituric acid reactive substances (TBARS) and glutathione (GSH) quantification, as well as for the superoxide dismutase 1 (SOD1) and the selenoprotein thioredoxin reductase 1 (TrxR1) expression evaluation. Western blot was performed for nitric oxide synthase (NOS) subtypes detection and to examine changes in apoptotic/autophagy proteins expression.

RESULTS

SMPL treatment reduced TBARS and increased GSH and SOD1 in the mice eyes. It also reduced cytochrome c, caspase 3 expression and activity and cleaved caspase 9, and increased Beclin 1, p62 and LC3β. The effects were more relevant in the elderly animals.

CONCLUSION

Our results showed that SMPL therapy restored the oxidant/antioxidant balance within retinal layers and modulated programmed forms of cell death. Further studies may confirm these data and could evaluate their relevance in clinical practice.

Effects of Genistein on Differentiation and Viability of Human Visceral Adipocytes

Obesity can lead to pathological growth of adipocytes by inducing inflammation and oxidative stress. Genistein could be a potential candidate for the treatment of obesity due to its antioxidant properties. Specific kits were used to examine the effects of genistein vs adiponectin on human visceral pre-adipocytes differentiation, cell viability, mitochondrial membrane potential, and oxidative stress in pre-adipocytes and in white/brown adipocytes. Western Blot was performed to examine changes in protein activation/expression. Genistein increased human visceral pre-adipocytes differentiation and browning, and caused a dose-related improvement of cell viability and mitochondrial membrane potential. Similar effects were observed in brown adipocytes and in white adipocytes, although in white cells the increase of cell viability was inversely related to the dose. Moreover, genistein potentiated AMP-activated protein kinase (AMPK)/mitofusin2 activation/expression in pre-adipocytes and white/brown adipocytes and protected them from the effects of hydrogen peroxide. The effects caused by genistein were similar to those of adiponectin. The results obtained showed that genistein increases human visceral pre-adipocytes differentiation and browning, protected against oxidative stress in pre-adipocytes and white/brown adipocytes through mechanisms related to AMPK-signalling and the keeping of mitochondrial function.

Kinsenoside Ameliorates Oxidative Stress-Induced RPE Cell Apoptosis and Inhibits Angiogenesis via Erk/p38/NF-κB/VEGF Signaling

The pathological superoxidative condition that retinal pigment epithelium (RPE) cells experience contributed to the advancement of age-related macular degeneration (AMD), which was accompanied by significant neovascularization. Therefore, the discovery of novel pharmacological candidates to ameliorate oxidative damage (H₂O₂) against RPE cells and inhibit the following angiogenesis simultaneously is urgently needed. Herein, we found that kinsenoside (Kin), an active component derived from Anoectochilus roxburghii, was able to protect RPE cells effectively and attenuate subsequent angiogenesis. In this study, H₂O₂-induced oxidative injury reduced RPE cell viability and increased cell apoptosis, which was significantly rescued by the treatment with Kin. Compared with H₂O₂ alone, Kin decreased the levels of Bax and increased the production of Bcl-2 in RPE cells. H₂O₂-stimulated VEGF up-regulation was inhibited by Kin treatment. Human umbilical vein endothelial cell (HUVEC) neovascularization induced by conditioned medium (CM) from H₂O₂-stimulated RPE cells was attenuated by treatment with Kin, VEGF antagonist, NF-κB, Erk-MAPK, and p38-MAPK inhibitors. Additionally, H₂O₂-activated phosphorylated expression of IκBα, p65, Erk, and p38 in RPE cells was inhibited by treatment with Kin. Taken together, Kin protected RPE from apoptosis against oxidative stress while simultaneously decreasing apoptosis-related neovascularization. This could be ascribed to the inhibition of Erk/p38/NF-κB signaling by Kin that contributed to the resulting decreased VEGF expression in H₂O₂-treated RPE cells.