Induction of vascular endothelial growth factor by 4-hydroxynonenal and its prevention by glutathione precursors in retinal pigment epithelial cells

Advanced nanomedicines for the treatment of age-related macular degeneration

The critical and unmet medical need for novel therapeutic advancements in the treatment of age-related macular degeneration (AMD) cannot be overstated, particularly given the aging global population and the increasing prevalence of this condition. Current AMD therapy involves intravitreal treatments that require monthly or bimonthly injections to maintain optimal efficacy. This underscores the necessity for improved approaches, prompting recent research into developing advanced drug delivery systems to prolong the intervals between treatments. Nanoparticle-based therapeutic approaches have enabled the controlled release of drugs, targeted delivery of therapeutic materials, and development of smart solutions for the harsh microenvironment of diseased tissues, offering a new perspective on ocular disease treatment. This review emphasizes the latest pre-clinical treatment options in ocular drug delivery to the retina and explores the advantages of nanoparticle-based therapeutic approaches, with a focus on AMD, the leading cause of irreversible blindness in the elderly.

The Role of Glutathione in Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is a chronic disease that usually develops in older people. Pathogenetic changes in this disease include anatomical and functional complexes. Harmful factors damage the retina and macula. These changes may lead to partial or total loss of vision. The disease can occur in two clinical forms: dry (the progression is slow and gentle) and exudative (wet-progression is acute and severe), which usually starts in the dry form; however, the coexistence of both forms is possible. The etiology of AMD is not fully understood, and the precise mechanisms of the development of this illness are still unknown. Extensive genetic studies have shown that AMD is a multi-factorial disease and that genetic determinants, along with external and internal environmental and metabolic-functional factors, are important risk factors. This article reviews the role of glutathione (GSH) enzymes engaged in maintaining the reduced form and polymorphism in glutathione S-transferase theta-1 (GSTT1) and glutathione S-transferase mu-1 (GSTM1) in the development of AMD. We only chose papers that confirmed the influence of the parameters on the development of AMD. Because GSH is the most important antioxidant in the eye, it is important to know the influence of the enzymes and genetic background to ensure an optimal level of glutathione concentration. Numerous studies have been conducted on how the glutathione system works till today. This paper presents the current state of knowledge about the changes in GSH, GST, GR, and GPx in AMD. GST studies clearly show increased activity in ill people, but for GPx, the results relating to activity are not so clear. Depending on the research, the results also suggest higher and lower GPx activity in patients with AMD. The analysis of polymorphisms in GST genes confirmed that mutations lead to weaker antioxidant barriers and may contribute to the development of AMD; unfortunately, a meta-analysis and some research did not confirm that connection. Unspecific results of many of the parameters that make up the glutathione system show many unknowns. It is so important to conduct further research to understand the exact mechanism of defense functions of glutathione against oxidative stress in the human eye.

Reactive Carbonyl Species and Protein Lipoxidation in Atherogenesis

Atherosclerosis is a multifactorial disease of medium and large arteries, characterized by the presence of lipid-rich plaques lining the intima over time. It is the main cause of cardiovascular diseases and death worldwide. Redox imbalance and lipid peroxidation could play key roles in atherosclerosis by promoting a bundle of responses, including endothelial activation, inflammation, and foam cell formation. The oxidation of polyunsaturated fatty acids generates various lipid oxidation products such as reactive carbonyl species (RCS), including 4-hydroxy alkenals, malondialdehyde, and acrolein. RCS covalently bind to nucleophilic groups of nucleic acids, phospholipids, and proteins, modifying their structure and activity and leading to their progressive dysfunction. Protein lipoxidation is the non-enzymatic post-translational modification of proteins by RCS. Low-density lipoprotein (LDL) oxidation and apolipoprotein B (apoB) modification by RCS play a major role in foam cell formation. Moreover, oxidized LDLs are a source of RCS, which form adducts on a huge number of proteins, depending on oxidative stress intensity, the nature of targets, and the availability of detoxifying systems. Many systems are affected by lipoxidation, including extracellular matrix components, membranes, cytoplasmic and cytoskeletal proteins, transcription factors, and other components. The mechanisms involved in lipoxidation-induced vascular dysfunction are not fully elucidated. In this review, we focus on protein lipoxidation during atherogenesis.

Lipofuscin, Its Origin, Properties, and Contribution to Retinal Fluorescence as a Potential Biomarker of Oxidative Damage to the Retina

Lipofuscin accumulates with age as intracellular fluorescent granules originating from incomplete lysosomal digestion of phagocytosed and autophagocytosed material. The purpose of this review is to provide an update on the current understanding of the role of oxidative stress and/or lysosomal dysfunction in lipofuscin accumulation and its consequences, particularly for retinal pigment epithelium (RPE). Next, the fluorescence of lipofuscin, spectral changes induced by oxidation, and its contribution to retinal fluorescence are discussed. This is followed by reviewing recent developments in fluorescence imaging of the retina and the current evidence on the prognostic value of retinal fluorescence for the progression of age-related macular degeneration (AMD), the major blinding disease affecting elderly people in developed countries. The evidence of lipofuscin oxidation in vivo and the evidence of increased oxidative damage in AMD retina ex vivo lead to the conclusion that imaging of spectral characteristics of lipofuscin fluorescence may serve as a useful biomarker of oxidative damage, which can be helpful in assessing the efficacy of potential antioxidant therapies in retinal degenerations associated with accumulation of lipofuscin and increased oxidative stress. Finally, amendments to currently used fluorescence imaging instruments are suggested to be more sensitive and specific for imaging spectral characteristics of lipofuscin fluorescence.

Antioxidative effects of polypyrimidine tract-binding protein-associated splicing factor against pathological retinal angiogenesis through promotion of mitochondrial function

Reactive oxygen species (ROS), a by-product of oxygen metabolism mainly originating from mitochondria, participate in many pathological processes related to ophthalmopathy. Excessive production of ROS leads to oxidative stress, which influences the permeability, proliferation, migration, and tube formation of human retinal microcapillary endothelial cells (HRMECs). The molecular mechanisms underlying the effects of ROS are not clear. In Vldlr-/- mice, we used fundus fluorescein angiography and retinal flat mount staining to observe the effect of polypyrimidine tract-binding protein-associated splicing factor (PSF) on pathological retinal neovascularization in vivo. Additionally, in human retinal microvascular endothelial cells treated with 4-HNE, cell viability, tube formation, wound healing, and Transwell assays were performed to study the effect of PSF on the proliferation, migration, and tube formation of retinal vascular endothelial cells in vitro. Moreover, reactive oxygen species assay, real-time PCR, and Western blot were included to analyze the potential mechanism of PSF in the above series of effects. PSF ameliorated intraretinal neovascularization (IRNV) in vivo in Vldlr-/- mice. Under 4-hydroxynonenal (4-HNE) conditions in vitro, PSF reprogrammed mitochondrial bioenergetic and glycolytic profiles. It also reduced ROS levels and inhibited 4-HNE-induced angiogenesis, which involves the proliferation, migration, and tube formation of HRMECs. These results suggest that PSF participates in the regulation of HRMECs proliferation and migration during the development of pathological angiogenesis. We demonstrated that PSF enhanced Nrf2 activation and heme oxygenase-1 (HO-1) expression via extracellular signal-regulated kinase (ERK) and Akt signaling in HRMECs, which subsequently resulted in intracellular ROS scavenging. PSF restored endoplasmic reticulum (ER) redox homeostasis, which was indicated by an increase in protein disulfide isomerase (PDI) and Ero-1α and a reduction in GRP78 and C/EBP homologous protein (CHOP). PSF also attenuated ER stress via regulation of the protein kinase R (PKR)-like endoplasmic reticulum kinase PERK/eukaryotic translation factor 2 alpha (eIF2α)/activating transcription factor 4 (ATF4) pathway in 4-HNE-treated HRMECs. Our research shows that PSF may be a potential antioxidant that regulates pathological angiogenesis through ERK-AKT/Nrf2/HO-1 and PERK/eIF2α/ATF4 signal regulation. KEY MESSAGES: Reactive oxygen species (ROS) mainly originating from mitochondria is a by-product of oxygen metabolism in the body and participates in the pathological process related to multiple blindness-related ophthalmopathy. Moreover , excessive production of ROS will lead to oxidative stress. Consequently, oxidative stress influences the permeability, proliferation, migration, and tube formation of human retinal microcapillary endothelial cells (HRMECs). The molecular mechanisms underlying the effects of ROS remain unclear. Here, we reveal that Polypyrimidine tract-binding protein-associated splicing factor (PSF) ameliorates intraretinal neovascularization (IRNV) in vivo in Vldlr-/- mice. Furthermore, under 4-HNE conditions in vitro, PSF reprograms mitochondrial bioenergetic and glycolytic profiles, reduces ROS levels, and inhibits 4-HNE-induced angiogenesis, which involves the proliferation, migration, and tube formation of HRMECs, suggesting that it participates in regulating the proliferation and migration of HRMECs during the development of pathological angiogenesis. Furthermore, PSF enhances Nrf2 activation and HO-1 expression through ERK and AKT signaling in HRMECs, resulting in intracellular ROS scavenging. PSF restores endoplasmic reticulum (ER) redox homeostasis, as indicated by an increase in PDI and Ero-1α and a reduction in GRP78 and CHOP. PSF also attenuates ER stress by regulating the PERK/eIF2α/ATF4 pathway in 4-HNE-treated HRMECs.

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.

Post-translational inhibition of YAP oncogene expression by 4-hydroxynonenal in bladder cancer cells

The transcriptional regulator YAP plays an important role in cancer progression and is negatively controlled by the Hippo pathway. YAP is frequently overexpressed in human cancers, including bladder cancer. Interestingly, YAP expression and activity can be inhibited by pro-oxidant conditions; moreover, YAP itself can also affect the cellular redox status through multiple mechanisms. 4-Hydroxynonenal (HNE), the most intensively studied end product of lipid peroxidation, is a pro-oxidant agent able to deplete GSH and has an anti-tumoral effect by affecting multiple signal pathways, including the down-regulation of oncogene expressions. These observations prompted us to investigate the effect of HNE on YAP expression and activity. We demonstrated that HNE inhibited YAP expression and its target genes in bladder cancer cells through a redox-dependent mechanism. Moreover, the YAP down-regulation was accompanied by an inhibition of proliferation, migration, invasion, and angiogenesis, as well as by an accumulation of cells in the G2/M phase of cell cycle and by an induction of apoptosis. We also established the YAP role in inhibiting cell viability and inducing apoptosis in HNE-treated cells by using an expression vector for YAP. Furthermore, we identified a post-translational mechanism for the HNE-induced YAP expression inhibition, involving an increase of YAP phosphorylation and ubiquitination, leading to proteasomal degradation. Our data established that HNE can post-translationally down-regulate YAP through a redox-dependent mechanism and that this modulation can contribute to determining the specific anti-cancer effects of HNE.

Bioceramic akermanite enhanced vascularization and osteogenic differentiation of human induced pluripotent stem cells in 3D scaffolds in vitro and vivo

A growing number of studies suggest that the modulation of cell differentiation by biomaterials is critical for tissue engineering. In previous work, we demonstrated that human induced pluripotent stem cells (iPSCs) are remarkably promising seed cells for bone tissue engineering. In addition, we found that the ionic products of akermanite (Aker) are potential inducers of osteogenic differentiation of iPSCs. Furthermore, composite scaffolds containing polymer and bioceramics have more interesting properties compared to pure bioceramic scaffolds for bone tissue engineering. The characteristic of model biomaterials in bone tissue engineering is their ability to control the osteogenic differentiation of stem cells and simultaneously induce the angiogenesis of endothelia cells. Thus, this study aimed at investigating the effects of poly(lactic-co-glycolic acid)/Aker (PLGA-Aker) composite scaffolds on angiogenic and osteogenic differentiation of human iPSCs in order to optimize the scaffold compositions. The results from Alizarin Red S staining, qRT-PCR analysis of osteogenic genes (BMP2, RUNX2, ALP, COL1 and OCN) and angiogenic genes (VEGF and CD31) demonstrated that PLGA/Aker composite scaffolds containing 10% Aker exhibited the highest stimulatory effects on the osteogenic and angiogenic differentiation of human iPSCs among all scaffolds. After the scaffolds were implanted in nu/nu mice subcutaneous pockets and calvarial defects, H&E staining, BSP immunostaining, qRT-PCR analysis and micro-CT analysis (BMD, BV/TV) indicated that PLGA + 10% Aker scaffolds enhanced the vascularization and osteogenic differentiation of human iPSCs and stimulated the repair of bone defects. Taken together, our work indicated that combining scaffolds containing silicate bioceramic Aker and human iPSCs is a promising approach for the enhancement of bone regeneration.

Bioceramics akermanite enhanced vascularization and osteogenic differentiation of human iPSCs in 3D scaffolds in vitro and vivo.

Distribution of 4-Hydroxynonenal-Protein Conjugates as a Marker of Lipid Peroxidation and Parameter of Malignancy in Astrocytic and Ependymal Tumors of the Brain

Aims and Background

Lipid peroxidation (LPO) is an autocatalytic process caused by oxidative stress. It results in the production of 4-hydroxynonenal (HNE), which plays a crucial role in hypoxic brain injury, neuronal degeneration and apoptosis. The aim of this study was to evaluate the expression of HNE in 120 astrocytic and 40 ependymal tumors in relation to tumor type, grade of malignancy, angiogenesis, and presence of necrosis and apoptosis.

Methods

Immunohistochemical staining was performed using a monoclonal antibody for the detection of HNE-modified proteins.

Results

HNE-protein adducts were found in all tumors. The incidence of HNE-im-munopositive tumor cells increased with increasing grades of malignancy. Significantly higher HNE expression was found in tumor cells of glioblastomas multiforme than in cells of pilocytic astrocytomas ( P <0.005), and in anaplastic ependymomas than in benign ependymomas ( P <0.01). HNE-immunopositive tumor cells were distributed more diffusely than in perivascular locations ( P <0.05). Pronounced HNE-protein adducts were detected in mitotic, necrotic, and apoptotic cells. HNE was expressed in the endothelium of almost all tumor vessels, but its expression in the walls of the vessels was significantly higher in diffuse and anaplastic astrocytomas than in pilocytic astrocytomas and glioblastomas multiforme ( P <0.05). The number of microvessels containing HNE in their endothelium and walls was significantly associated with the grade of malignancy in both astrocytic ( P <0.001) and ependymal tumors ( P <0.05), although microvessels in pilocytic astrocytomas were significantly more numerous ( P <0.05) than in diffuse astrocytomas.

Conclusions

LPO seems to be a common pathological process in astrocytic and ependymal glial tumors, proportional to the level of malignancy and neovascularization. Therefore, HNE might be involved in the damage of brain cells and the induction of malignancy.

Proatherogenic effects of 4-hydroxynonenal

4-hydroxy-2-nonenal (HNE) is a α,β-unsaturated hydroxyalkenal generated by peroxidation of n-6 polyunsaturated fatty acid. This reactive carbonyl compound exhibits a huge number of biological properties that result mainly from the formation of HNE-adducts on free amino groups and thiol groups in proteins. In the vascular system, HNE adduct accumulation progressively leads to cellular dysfunction and tissue damages that are involved in the progression of atherosclerosis and related diseases. HNE contributes to the atherogenicity of oxidized LDL, by forming HNE-apoB adducts that deviate the LDL metabolism to the scavenger receptor pathway of macrophagic cells, and lead to the formation of foam cells. HNE activates transcription factors (Nrf2, NF-kappaB) that (dys)regulate various cellular responses ranging from hormetic and survival signaling at very low concentrations, to inflammatory and apoptotic effects at higher concentrations. Among a variety of cellular targets, HNE can modify signaling proteins involved in atherosclerotic plaque remodeling, particularly growth factor receptors (PDGFR, EGFR), cell cycle proteins, mitochondrial and endoplasmic reticulum components or extracellular matrix proteins, which progressively alters smooth muscle cell proliferation, angiogenesis and induces apoptosis. HNE adducts accumulate in the lipidic necrotic core of advanced atherosclerotic lesions, and may locally contribute to macrophage and smooth muscle cell apoptosis, which may induce plaque destabilization and rupture, thereby increasing the risk of athero-thrombotic events.

4-Hydroxy-7-oxo-5-heptenoic Acid Lactone Induces Angiogenesis through Several Different Molecular Pathways

Oxidative stress and angiogenesis have been implicated not only in normal phenomena such as tissue healing and remodeling but also in many pathological processes. However, the relationships between oxidative stress and angiogenesis still remain unclear, although oxidative stress has been convincingly demonstrated to influence the progression of angiogenesis under physiological and pathological conditions. The retina is particularly susceptible to oxidative stress because of its intensive oxygenation and high abundance of polyunsaturated fatty acyls. In particular, it has high levels of docosahexanoates, whose oxidative fragmentation produces 4-hydroxy-7-oxo-5-heptenoic acid lactone (HOHA-lactone). Previously, we found that HOHA-lactone is a major precursor of 2-(ω-carboxyethyl)pyrrole (CEP) derivatives, which are tightly linked to age-related macular degeneration (AMD). CEPs promote the pathological angiogenesis of late-stage AMD. We now report additional mechanisms by which HOHA-lactone promotes angiogenesis. Using cultured ARPE-19 cells, we observed that HOHA-lactone induces secretion of vascular endothelial growth factor (VEGF), which is correlated to increases in reactive oxygen species and decreases in intracellular glutathione (GSH). Wound healing and tube formation assays provided, for the first time, in vitro evidence that HOHA-lactone induces the release of VEGF from ARPE-19 cells, which promotes angiogenesis by human umbilical vein endothelial cells (HUVEC) in culture. Thus, HOHA-lactone can stimulate vascular growth through a VEGF-dependent pathway. In addition, results from MTT and wound healing assays as well as tube formation experiments showed that GSH-conjugated metabolites of HOHA-lactone stimulate HUVEC proliferation and promote angiogenesis in vitro. Previous studies demonstrated that HOHA-lactone, through its CEP derivatives, promotes angiogenesis in a novel Toll-like receptor 2-dependent manner that is independent of the VEGF receptor or VEGF expression. The new studies show that HOHA-lactone also participates in other angiogenic signaling pathways that include promoting the secretion of VEGF from retinal pigmented epithelial cells.

Malondialdehyde induces autophagy dysfunction and VEGF secretion in the retinal pigment epithelium in age-related macular degeneration

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries and is closely related to oxidative stress, which leads to lipid peroxidation. Malondialdehyde (MDA) is a major byproduct of polyunsaturated fatty acid (PUFA) peroxidation. Increased levels of MDA have been reported in eyes of AMD patients. However, little is known about the direct relationship between MDA and AMD. Here we show the biological importance of MDA in AMD pathogenesis. We first confirmed that MDA levels were significantly increased in eyes of AMD patients. In ARPE-19 cells, a human retinal pigment epithelial cell line, MDA treatment induced vascular endothelial growth factor (VEGF) expression alternation, cell junction disruption, and autophagy dysfunction that was also observed in eyes of AMD patients. The MDA-induced VEGF increase was inhibited by autophagy-lysosomal inhibitors. Intravitreal MDA injection in mice increased laser-induced choroidal neovascularization (laser-CNV) volumes. In a mouse model fed a high-linoleic acid diet for 3 months, we found a significant increase in MDA levels, autophagic activity, and laser-CNV volumes. Our study revealed an important role of MDA, which acts not only as a marker but also as a causative factor of AMD pathogenesis-related autophagy dysfunction. Furthermore, higher dietary intake of linoleic acid promoted CNV progression in mice with increased MDA levels.

Akermanite bioceramics promote osteogenesis, angiogenesis and suppress osteoclastogenesis for osteoporotic bone regeneration

It is a big challenge for bone healing under osteoporotic pathological condition with impaired angiogenesis, osteogenesis and remodeling. In the present study, the effect of Ca, Mg, Si containing akermanite bioceramics (Ca2MgSi2O7) extract on cell proliferation, osteogenic differentiation and angiogenic factor expression of BMSCs derived from ovariectomized rats (BMSCs-OVX) as well as the expression of osteoclastogenic factors was evaluated. The results showed that akermanite could enhance cell proliferation, ALP activity, expression of Runx2, BMP-2, BSP, OPN, OCN, OPG and angiogenic factors including VEGF and ANG-1. Meanwhile, akermanite could repress expression of osteoclastogenic factors including RANKL and TNF-α. Moreover, akermanite could activate ERK, P38, AKT and STAT3 signaling pathways, while crosstalk among these signaling pathways was evident. More importantly, the effect of akermanite extract on RANKL-induced osteoclastogenesis was evaluated by TRAP staining and real-time PCR assay. The results showed that akermanite could suppress osteoclast formation and expression of TRAP, cathepsin K and NFATc1. The in vivo experiments revealed that akermanite bioceramics dramatically stimulated osteogenesis and angiogenesis in an OVX rat critical-sized calvarial defect model. All these results suggest that akermanite bioceramics with the effects of Mg and Si ions on osteogenesis, angiogenesis and osteoclastogenesis are promising biomaterials for osteoporotic bone regeneration.

Evaluation of osteogenesis and angiogenesis of icariin loaded on micro/nano hybrid structured hydroxyapatite granules as a local drug delivery system for femoral defect repair

Icariin has been identified to promote osteogenic differentiation of bone mesenchymal stem cells (BMSCs). However, whether icariin could enhance angiogenic factor expression of BMSCs, which may be vital for bone repair, needs to be explored. Moreover, how to construct a delivery system of icariin and its repair capability in bone defects are still unknown. In the present study, the effects of icariin on the osteogenic differentiation and angiogenic factor expression of BMSCs were firstly evaluated. Moreover, new micro/nano hybrid structured HAp (micro/nano HAp) granules were fabricated to construct the delivery system of icariin, and the osteogenesis and angiogenesis of icariin loaded on micro/nano HAp granules in a rat femoral plug defect model were evaluated by micro-CT measurements, sequential fluorescent labeling and the histological assay. The in vitro results showed that icariin significantly improved osteogenic differentiation of rat BMSCs demonstrated by the enhanced alkaline phosphatase (ALP) activity and gene expression of runt-related transcription factor-2 (Runx2), ALP, collagen type I (Col I), osteocalcin (OCN) and OCN protein secretion. Moreover, icariin induced the angiogenic genes expression of BMSCs, such as vascular endothelial growth factor (VEGF) and angiotensin 1 (ANG1). Furthermore, the activation of the AKT signaling pathway was observed in BMSCs upon treatment with icariin, and these enhancement effects could be blocked by LY294002, which suggested that the AKT signaling pathway was involved in the osteogenic differentiation and angiogenic factor expression of BMSCs induced by icariin. More importantly, micro/nano HAp granules with rod-like shapes were successfully fabricated and acted as delivery carriers for icariin. Consequently, icariin loaded on micro/nano HAp granules could promote new bone formation and blood vessel formation. These results demonstrated that icariin could enhance osteogenic differentiation and angiogenic factor expression of BMSCs via the AKT signaling pathway, moreover, the novel micro/nano HAp granules could act as carriers for icariin to repair bone defects via enhancing osteogenesis and angiogenesis.

Influence of vascular endothelial growth factor and Cysteamine on in vitro bovine oocyte maturation and subsequent embryo development

The objective of this study was to investigate the effect of VEGF and Cysteamine during in vitro maturation (IVM) of bovine oocytes on GSH content and developmental competence. For this purpose, experiments were designed to evaluate the effect of 0, 100, 300, and 500 ng/mL VEGF in IVM medium on: GSH content in oocytes and cumulus cells (Exp. 1) and subsequent embryo development (Exp. 2). Also, influence of adding 500 ng/mL VEGF and 100 μM Cysteamine to IVM medium on GSH content in oocytes and cumulus cells (Exp. 3) and oocyte developmental capacity (Exp. 4) were evaluated. Oocytes were matured in: a) Control; b) VEGF 0-3 h; c) Cysteamine 4-24 h; d) VEGF 0-3 h + Cysteamine 4-24 h; and e) VEGF + Cysteamine 24 h. The results showed that: i) VEGF did not alter GSH content in oocytes and cumulus cells; (ii) supplementation of 300 and 500 ng/mL VEGF increased blastocyst yield; (iii) the presence of VEGF + Cysteamine simultaneously during 24 h improved GSH content but not embryo development; and (iv) the presence of VEGF during the first 3 h + Cysteamine from 4 to 24 h increased GSH concentrations and subsequent embryo development. In conclusion, the addition of VEGF and Cysteamine in two sequential steps to maturation medium result in an improvement of cytoplasmic maturation, with a positive impact on oocyte developmental capacity by increasing the efficiency of in vitro blastocyst production. However, the effect was detrimental when both VEGF and Cysteamine were present during 24 of IVM.

4-Hydroxy-7-oxo-5-heptenoic Acid (HOHA) Lactone is a Biologically Active Precursor for the Generation of 2-(ω-Carboxyethyl)pyrrole (CEP) Derivatives of Proteins and Ethanolamine Phospholipids

2-(ω-Carboxyethyl)pyrrole (CEP) derivatives of proteins were previously shown to have significant pathological and physiological relevance to age-related macular degeneration, cancer and wound healing. Previously, we showed that CEPs are generated in the reaction of ε-amino groups of protein lysyl residues with 1-palmityl-2-(4-hydroxy-7-oxo-5-heptenoyl)-sn-glycero-3-phosphatidylcholine (HOHA-PC), a lipid oxidation product uniquely generated by oxidative truncation of docosahexanenate-containing phosphatidylcholine. More recently, we found that HOHA-PC rapidly releases HOHA-lactone and 2-lyso-PC (t1/2 = 30 min at 37 °C) by nonenzymatic transesterification/deacylation. Now we report that HOHA-lactone reacts with Ac-Gly-Lys-OMe or human serum albumin to form CEP derivatives in vitro. Incubation of human red blood cell ghosts with HOHA-lactone generates CEP derivatives of membrane proteins and ethanolamine phospholipids. Quantitative analysis of the products generated in the reaction HOHA-PC with Ac-Gly-Lys-OMe showed that HOHA-PC mainly forms CEP-dipeptide that is not esterified to 2-lysophosphatidycholine. Thus, the HOHA-lactone pathway predominates over the direct reaction of HOHA-PC to produce the CEP-PC-dipeptide derivative. Myleoperoxidase/H2O2/NO2(-) promoted in vitro oxidation of either 1-palmityl-2-docosahexaneoyl-sn-glycero-3-phosphatidylcholine (DHA-PC) or docosahexaenoic acid (DHA) generates HOHA-lactone in yields of 0.45% and 0.78%, respectively. Lipid oxidation in human red blood cell ghosts also releases HOHA-lactone. Oxidative injury of ARPE-19 human retinal pigmented epithelial cells by exposure to H2O2 generated CEP derivatives. Treatment of ARPE-19 cells with HOHA-lactone generated CEP-modified proteins. Low (submicromolar), but not high, concentrations of HOHA-lactone promote increased vascular endothelial growth factor (VEGF) secretion by ARPE-19 cells. Therefore, HOHA-lactone not only serves as an intermediate for the generation of CEPs but also is a biologically active oxidative truncation product from docosahexaenoate lipids.

Oxidative stress in myopia

Myopia affected approximately 1.6 billion people worldwide in 2000, and it is expected to increase to 2.5 billion by 2020. Although optical problems can be corrected by optics or surgical procedures, normal myopia and high myopia are still an unsolved medical problem. They frequently predispose people who have them to suffer from other eye pathologies: retinal detachment, glaucoma, macular hemorrhage, cataracts, and so on being one of the main causes of visual deterioration and blindness. Genetic and environmental factors have been associated with myopia. Nevertheless, lack of knowledge in the underlying physiopathological molecular mechanisms has not permitted an adequate diagnosis, prevention, or treatment to be found. Nowadays several pieces of evidence indicate that oxidative stress may help explain the altered regulatory pathways in myopia and the appearance of associated eye diseases. On the one hand, oxidative damage associated with hypoxia myopic can alter the neuromodulation that nitric oxide and dopamine have in eye growth. On the other hand, radical superoxide or peroxynitrite production damage retina, vitreous, lens, and so on contributing to the appearance of retinopathies, retinal detachment, cataracts and so on. The objective of this review is to suggest that oxidative stress is one of the key pieces that can help solve this complex eye problem.

Decline in cellular clearance systems induces inflammasome signaling in human ARPE-19 cells

Retinal pigment epithelium (RPE) plays a major role in the maintenance of photoreceptors, and degeneration of RPE results in the development of age-related macular degeneration (AMD). Accumulation of intracellular protein aggregates, increased oxidative stress, and chronic inflammation are all factors damaging the functionality of aged RPE cells. Here, we report that inhibition of proteasomal degradation with MG-132 and autophagy with bafilomycin A1 resulted in the release of IL-1β but not that of IL-18 in human ARPE-19 cells. NLRP3 receptor became upregulated, and caspase-1, the functional component of an inflammasome complex, was activated. In addition to accumulating intracellular protein aggregates, inhibition of degradation systems induced oxidative stress which was demonstrated by elevated amounts of intracellular 4-hydroxynonenal (HNE)-protein adducts. Along with IL-1β, exposure to MG-132 and bafilomycin A1 resulted in the secretion of IL-8. A low concentration (1pg/ml) of IL-1β was capable of triggering significant IL-8 production which also became attenuated by treatment with a specific caspase-1 inhibitor. These results suggest that decline in intracellular degradation systems results not only in increased amounts of intracellular protein aggregates and oxidative stress but also in the activation of NLRP3 inflammasomes, arisen as a result of elevated production of biologically active IL-1β.

Cellular and molecular mechanisms of age-related macular degeneration: from impaired autophagy to neovascularization

Age-related macular degeneration (AMD) is a complex, degenerative and progressive disease involving multiple genetic and environmental factors. It can result in severe visual loss e.g. AMD is the leading cause of blindness in the elderly in the western countries. Although age, genetics, diet, smoking, and many cardiovascular factors are known to be linked with this disease there is increasing evidence that long-term oxidative stress, impaired autophagy clearance and inflammasome mediated inflammation are involved in the pathogenesis. Under certain conditions these may trigger detrimental processes e.g. release of vascular endothelial growth factor (VEGF), causing choroidal neovascularization e.g. in wet AMD. This review ties together these crucial pathological threads in AMD.

Successful tumour necrosis factor (TNF) blocking therapy suppresses oxidative stress and hypoxia-induced mitochondrial mutagenesis in inflammatory arthritis

Introduction

To examine the effects of tumour necrosis factor (TNF) blocking therapy on the levels of early mitochondrial genome alterations and oxidative stress.

Methods

Eighteen inflammatory arthritis patients underwent synovial tissue oxygen (tpO₂) measurements and clinical assessment of disease activity (DAS28-CRP) at baseline (T0) and three months (T3) after starting biologic therapy. Synovial tissue lipid peroxidation (4-HNE), T and B cell specific markers and synovial vascular endothelial growth factor (VEGF) were quantified by immunohistochemistry. Synovial levels of random mitochondrial DNA (mtDNA) mutations were assessed using Random Mutation Capture (RMC) assay.

Results

4-HNE levels pre/post anti TNF-α therapy were inversely correlated with in vivo tpO₂ (P < 0.008; r = -0.60). Biologic therapy responders showed a significantly reduced 4-HNE expression (P < 0.05). High 4-HNE expression correlated with high DAS28-CRP (P = 0.02; r = 0.53), tender joint count for 28 joints (TJC-28) (P = 0.03; r = 0.49), swollen joint count for 28 joints (SJC-28) (P = 0.03; r = 0.50) and visual analogue scale (VAS) (P = 0.04; r = 0.48). Strong positive association was found between the number of 4-HNE positive cells and CD4+ cells (P = 0.04; r = 0.60), CD8+ cells (P = 0.001; r = 0.70), CD20+ cells (P = 0.04; r = 0.68), CD68+ cells (P = 0.04; r = 0.47) and synovial VEGF expression (P = 0.01; r = 063). In patients whose in vivo tpO₂ levels improved post treatment, significant reduction in mtDNA mutations and DAS28-CRP was observed (P < 0.05). In contrast in those patients whose tpO₂ levels remained the same or reduced at T3, no significant changes for mtDNA mutations and DAS28-CRP were found.

Conclusions

High levels of synovial oxidative stress and mitochondrial mutation burden are strongly associated with low in vivo oxygen tension and synovial inflammation. Furthermore these significant mitochondrial genome alterations are rescued following successful anti TNF-α treatment.

NBHA reduces acrolein-induced changes in ARPE-19 cells: possible involvement of TGFβ

PURPOSE

Acrolein, a toxic, reactive aldehyde formed metabolically and environmentally, has been implicated in the damage to and dysfunction of the retinal pigment epithelium (RPE) that accompanies age-related macular degeneration (AMD). Our purpose was to investigate the potential of acrolein to influence the release of transforming growth factor beta-2 (TGFβ2) and vascular endothelial growth factor (VEGF), to assess the ability of N-benzylhydroxylamine (NBHA) to prevent the effect of acrolein on cytokine release and reduction of viable cells, and to explore the pathway by which acrolein might be causing the increase of VEGF.

MATERIALS AND METHODS

Confluent ARPE-19 cells were treated with acrolein and/or NBHA. They were also pretreated with SIS3, a specific inhibitor of SMAD 3, and ZM39923, a JAK3 inhibitor, before being treated with acrolein. Viable cells were counted; ELISA was used to measure the TGFβ2 and/or VEGF in the conditioned media.

RESULTS

Acrolein was shown to reduce the number of viable ARPE-19 cells and to upregulate the release of the proangiogenic cytokines TGFβ2 and VEGF. Co-treatment with 200 μM NBHA significantly reduced the effects of acrolein on viable cell number and TGFβ2 release. Pretreatment of the cells with SIS3 partially blocked the action of acrolein on decreased viable cell number and VEGF upregulation, suggesting that part of the effects of acrolein are mediated by the increased levels of TGFβ and its signaling.

CONCLUSIONS

Our results suggest that the action of acrolein on the reduction of viability and VEGF increase by ARPE-19 cells is partially mediated by TGFβ2. By reducing the effects of acrolein, NBHA and SIS3 could be potential pharmacological agents in the prevention and progression of acrolein-induced damage to the RPE that relates to AMD.

The "two-faced" effects of reactive oxygen species and the lipid peroxidation product 4-hydroxynonenal in the hallmarks of cancer

Reacytive Oxygen Species (ROS) have long been considered to be involved in the initiation, progression and metastasis of cancer. However, accumulating evidence points to the benefical role of ROS. Moreover, ROS production, leading to apoptosis, is the mechanism by which many chemotherapeutic agents can act. Beside direct actions, ROS elicit lipid peroxidation, leading to the production of 4-hydroxynoneal (HNE). Interestingly, HNE also seems to have a dual behaviour with respect to cancer. In this review we present recent literature data which outline the "two-faced" character of oxidative stress and lipid peroxidation in carcinogenesis and in the hallmarks of cancer.

Intratracheal budesonide-poly (lactide-co-glycolide) microparticles reduce oxidative stress, VEGF expression, and vascular leakage in a benzo(a)pyrene-fed mouse model

The purpose of this study was to determine whether intratracheally instilled polymeric budesonide microparticles could sustain lung budesonide levels for one week and inhibit early biochemical changes associated with benzo(a)pyrene (B[a]P) feeding in a mouse model for lung tumours. Polymeric microparticles of budesonide-poly (dl-lactide-co-glycolide) (PLGA 50:50) were prepared using a solvent evaporation technique and characterized for their size, morphology, encapsulation efficiency, and in-vitro release. The microparticles were administered intratracheally (i.t.) to B[a]P-fed A/J mice. At the end of one week drug levels in the lung tissue and bronchoalveolar lavage (BAL) were estimated using HPLC and compared with systemic (intramuscular) administration. In addition, in-vivo end points including malondialdehyde (MDA), glutathione (GSH), total protein levels and vascular endothelial growth factor (VEGF) in BAL, and VEGF and c-myc mRNA levels in the lung tissue were assessed at the end of one week following intratracheal administration of budesonide microparticles. Budesonide-PLGA microparticles (1–2 μm), with a budesonide loading efficiency of 69–94%, sustained in-vitro budesonide release for over 21 days. Compared with the intramuscular route, intratracheally administered budesonide-PLGA microparticles resulted in higher budesonide levels in the BAL and lung tissue. In-vivo, B[a]P-feeding increased BAL MDA, lung VEGF mRNA, lung c-myc mRNA, BAL total protein, and BAL VEGF levels by 60, 112, 71, 154, and 78%, respectively, and decreased BAL GSH by 62%. Interestingly, intratracheally administered budesonide-PLGA particles inhibited these biochemical changes. Thus, biodegradable budesonide microparticles sustained budesonide release and reduced MDA accumulation, GSH depletion, vascular leakage, and VEGF and c-myc expression in B[a]P-fed mice, indicating the potential of locally delivered sustained-release particles for inhibiting angiogenic factors in lung cancer.

Molecular regulation of cigarette smoke induced-oxidative stress in human retinal pigment epithelial cells: implications for age-related macular degeneration

Cigarette smoke is the most important environmental risk factor for developing age-related macular degeneration (AMD). Damage to the retinal pigment epithelium (RPE) caused by cigarette smoke may underlie the etiology of AMD. This study investigated the molecular and cellular effects of cigarette smoke exposure on human RPE cells. ARPE-19 or primary human RPE cells were exposed to cigarette smoke extract (CSE) or hydroquinone (HQ), a component of cigarette smoke. The effect of this exposure on key aspects of RPE vitality including viability, cell size, mitochondrial membrane potential (DeltaPsi(m)), superoxide production, 4-hydroxy-2-nonenal (4-HNE), vascular endothelial growth factor (VEGF), and heme oxygenase-1 (HO-1) expression was determined. Exposure of RPE cells to CSE or HQ caused oxidative damage and apoptosis, characterized by a reduction in cell size and nuclear condensation. Evidence of oxidative damage also included increased lipid peroxidation (4-HNE) and mitochondrial superoxide production, as well as a decrease in intracellular glutathione (GSH). Exogenous administration of antioxidants (GSH and N-acetyl-cysteine) prevented oxidative damage to the RPE cells caused by CSE. Cigarette smoke also induced expression of VEGF, HO-1, and the transcription factor nuclear factor erythroid-derived 2, like 2 (NRF2). However, NRF2 was only modestly involved in CSE-induced HO-1 expression, as shown by the NRF2 small interfering RNA studies. These new findings demonstrate that cigarette smoke is a potent inducer of oxidative damage and cell death in human RPE cells. These data support the hypothesis that cigarette smoke contributes to AMD pathogenesis by causing oxidative damage and cell death to RPE cells.

Effect of diabetes on transscleral delivery of celecoxib

PURPOSE

To investigate the effects of diabetes on transscleral retinal delivery of celecoxib in albino and pigmented rats.

METHODS

Albino (Sprague Dawley-SD) and pigmented (Brown Norway-BN) rats were made diabetic by a single intraperitoneal injection of streptozotocin (60 mg/kg) following 24 h of fasting and diabetes was confirmed (blood glucose>250 mg/dL). Two months after diabetes induction, the integrity of blood-retinal-barrier in control versus diabetic rats from both strains was compared by using FITC-dextran leakage assay. Fifty microliter suspension of celecoxib (3 mg/rat) was injected periocularly in both the strains in one eye, 2 months following diabetes induction. The animals were euthanized at the end of 0.25, 0.5, 1, 2, 3, 4, 8, and 12 h post-dosing and celecoxib levels in ocular tissues and plasma were estimated using a HPLC assay.

RESULTS

Diabetes (2-month duration) resulted in 2.4 and 3.5 fold higher blood-retinal barrier leakage in diabetic SD and BN rats, respectively, compared to controls. The area under tissue celecoxib concentration versus time curves (AUC) for sclera, cornea, and lens were not significantly different between control and diabetic animals. However, retinal and vitreal AUCs of celecoxib in treated eyes were approximately 1.5-fold and 2-fold higher in diabetic SD and BN rats, respectively, as compared to the controls.

CONCLUSIONS

Transscleral retinal and vitreal delivery of celecoxib is significantly higher in diabetic animals of both strains. The increase in retinal delivery of celecoxib due to diabetes is higher in pigmented rats compared to albino rats. Higher delivery of celecoxib in diabetic animals compared to control animals can be attributed to the disruption of blood-retinal barrier due to diabetes.

Self-regulatory role of 4-hydroxynonenal in signaling for stress-induced programmed cell death

Within the last two decades, 4-hydroxynonenal has emerged as an important second messenger involved in the regulation of various cellular processes. Our recent studies suggest that HNE can induce apoptosis in various cells through the death receptor Fas (CD95)-mediated extrinsic pathway as well as through the p53-dependent intrinsic pathway. Interestingly, through its interaction with the nuclear protein Daxx, HNE can self-limit its apoptotic role by translocating Daxx to cytoplasm where it binds to Fas and inhibits Fas-mediated apoptosis. In this paper, after briefly describing recent studies on various biological activities of HNE, based on its interactions with Fas, Daxx, and p53, we speculate on possible mechanisms through which HNE may affect a multitude of cellular processes and draw a parallel between signaling roles of H(2)O(2) and HNE.

[Oxidative stress in association with risk factors for the occurrence and development of age-related macular degeneration]

<zakljucak> Niz rezultata potvrdjuje ulogu oksidativnog stresa u etiopatogenezi AMD i to bilo kao inicijalnog ili izolovanog uzrocnog faktora, ili kao dodatnog cinioca u sklopu drugih faktora rizika. Bolje poznavanje ove oblasti prosiruje mogucnosti prevencije ove, ali i drugih bolesti starijeg zivotnog doba.

The proteasome: a target of oxidative damage in cultured human retina pigment epithelial cells

PURPOSE

Dysfunction of the ubiquitin-proteasome pathway (UPP) is associated with several age-related degenerative diseases. The objective of this study was to investigate the effect of oxidative stress on the UPP in cultured human retina pigment epithelial cells.

METHODS

To mimic physiological oxidative stress, ARPE-19 cells were exposed to continuously generated H2O(2) or A2E-mediated photooxidation. Proteasome activity was monitored using fluorogenic peptides as substrates. The ubiquitin conjugation activity and activities of E1 and E2 were determined by the thiolester assays. Levels of ubiquitin and ubiquitin conjugates were determined by Western blotting.

RESULTS

Exposure of ARPE-19 cells to 40 to 50 microM H2O(2) for 4 hours resulted in a 30% to 50% reduction in all three peptidase activities of the proteasome. Similarly, exposure of A2E-loaded ARPE-19 cells to blue light resulted in a 40% to 60% reduction in proteasome activity. Loading of A2E or exposure to blue light alone had little effect on proteasome activity. In contrast, exposure of ARPE-19 to low levels of H2O(2) (10 microM) stimulated ubiquitin conjugation activity. Loading of A2E, with or without exposure to blue light, upregulated the levels of ubiquitin-activating enzyme and increased conjugation activity. Exposure to H2O(2) or A2E-mediated photooxidation also resulted in a twofold to threefold increase in levels of endogenous ubiquitin conjugates.

CONCLUSIONS

These data show that the proteasome in ARPE-19 is susceptible to oxidative inactivation, whereas activities of the ubiquitin-conjugating enzymes are more resistant to oxidative stress. Oxidative inactivation of the proteasome appears to be one of the mechanisms underlying stress-induced accumulation of ubiquitin conjugates in the cells.

Phototoxicity in human retinal pigment epithelial cells promoted by hypericin, a component of St. John's wort

St. John's wort (SJW), an over-the-counter antidepressant, contains hypericin, which absorbs light in the UV and visible ranges. In vivo studies have determined that hypericin is phototoxic to skin and our previous in vitro studies with lens tissues have determined that it is potentially phototoxic to the human lens. To determine if hypericin might also be phototoxic to the human retina, we exposed human retinal pigment epithelial (hRPE) cells to 10(-7) to 10(-5) M hypericin. Fluorescence emission detected from the cells (lambda(ex) = 488 nm; lambda(em) = 505 nm) confirmed hypericin uptake by human RPE. Neither hypericin exposure alone nor visible light exposure alone reduced cell viability. However when irradiated with 0.7 J cm(-2) of visible light (lambda > 400 nm) there was loss of cell viability as measured by MTS and lactate dehydrogenase assays. The presence of hypericin in irradiated hRPE cells significantly changed the redox equilibrium of glutathione and a decrease in the activity of glutathione reductase. Increased lipid peroxidation as measured by the thiobarbituric acid reactive substances assay correlated to hypericin concentration in hRPE cells and visible light radiation. Thus, ingested SJW is potentially phototoxic to the retina and could contribute to retinal or early macular degeneration.

AQ4, an antitumor anthracenedione, inhibits endothelial cell proliferation and vascular endothelial growth factor secretion: implications for the therapy of ocular neovascular disorders

Current clinical options for the treatment of neovascular disorders of the posterior segment of the eye have several drawbacks. Photocoagulation lasers can impair peripheral and night vision. Photodynamic therapies as well as intravitreal macromolecule injections (Macugen and Lucentis) require frequent, invasive administrations. Above all, only modest improvement in vision is achieved with any of the existing treatments. In order to overcome these limitations in the long run, this study investigated the antiangiogenic potential of AQ4, a low molecular weight anthracenedione. The results indicate that AQ4 enters the cell nucleus and inhibits proliferation of choroid-retina endothelial (RF/6A) cells and human retinal pigment epithelial (ARPE-19) cells under hypoxic (1% O(2)) as well as normoxic (21% O(2)) conditions. The IC(50) for these effects ranges from 5.5 to 6.9 muM. AQ4 does not affect the viability of non-dividing RF/6A or ARPE-19 cells up to 0.1 mM. Further, AQ4 (20 muM) reduces vascular endothelial growth factor (VEGF) protein secretion by about 50% in ARPE-19 cells under normoxia as well as hypoxia, possibly by reducing VEGF transcription. AQ4 arrests the growth of endothelial cells in S phase, consistent with interference of AQ4 with DNA replication. These results for the first time suggest that AQ4 can potentially alleviate the neovascularization of choroid/retina by a dual mechanism of inhibiting the proliferation of endothelial cells and by reducing mitogenic VEGF stimulus from retinal pigment epithelial cells.

Bone morphogenetic protein-4 enhances vascular endothelial growth factor secretion by human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells secrete vascular endothelial growth factor (VEGF), a cytokine known to promote angiogenesis. Results from RNase protection assays (RPAs) show that RPE from non-diabetic human donors and from adult retinal pigment epithelium-19 (ARPE-19) cells expressed significant bone morphogenetic protein-4 (BMP-4) message. In addition, ARPE-19 cells cultured in high glucose (25 mM), compared to those in physiological glucose (5.5 mM) released significantly more BMP-4 into the conditioned media (CM). However, the effect of BMP-4 on the release of VEGF by ARPE-19 cells has not been studied. Accordingly, ARPE-19 cells were treated with BMP-4 to determine VEGF secretion. BMP-4 and VEGF levels in the CM and cell lysates were measured by enzyme-linked immunosorbent assay (ELISA). Cells treated with exogenous BMP-4 had higher VEGF in the CM and this treatment effect was dose- and time-dependent, while cell lysates had low levels of VEGF. Addition of cycloheximide (CHX) or actinomycin-D (ACT) significantly reduced VEGF secretion from cells treated with BMP-4, suggesting that the BMP-4-induced secretion of VEGF requires new RNA and protein synthesis. Our results suggest that BMP-4 may play a role in the regulation of ocular angiogenesis associated with diabetic retinopathy (DR) by stimulating VEGF release from RPE cells.

Thiol regulation of vascular endothelial growth factor-A and its receptors in human retinal pigment epithelial cells

We investigated the secretion and expression of VEGF-A and its receptors in human retinal pigment epithelial cells (RPE) under conditions of oxidative stress induced by glutathione (GSH) depletion. RPE cells were treated with 500 microM DL-buthionine-(S,R)-sulfoximine (BSO) for varying times up to 24 h. Cellular GSH levels, GSH:GSSG ratios, VEGF-A mRNA and protein expression, as well as VEGF-A secretion, and VEGFR-1 and VEGFR-2 receptor expression were determined. Treatment with BSO caused a significant decrease in intracellular GSH and in GSH/GSSG ratios. Treatment with BSO increased VEGF-A mRNA linearly with time which was significant at 24h (p<0.01 vs untreated controls). An increase was also found for VEGF-A secretion with BSO treatment; incubation of RPE with GSH monoethyl ester (GSH-MEE) caused an 84% decrease in VEGF-A secretion. Further, thiol depletion by BSO caused a significant induction of VEGFR-1 and VEGFR-2. Thus, our studies show that cellular redox status plays an important role in VEGF regulation in RPE cells.

Nanoparticle formulation enhances the delivery and activity of a vascular endothelial growth factor antisense oligonucleotide in human retinal pigment epithelial cells

The objective of this study was to investigate the delivery and activity of a vascular endothelial growth factor (VEGF) antisense oligonucleotide in a human retinal pigment epithelial cell line (ARPE-19) using a biodegradable nanoparticulate delivery system. A 19-mer antisense phosphorothioate oligonucleotide (PS-ODN) complementary to bases 6-24 relative to the translational start site of the VEGF mRNA, a sense PS-ODN and a mismatch PS-ODN were examined for the inhibition of secretion and mRNA expression of VEGF using an enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction, respectively. Nanoparticles of the antisense oligonucleotides were formulated using a poly(lactide-co-glycolide) (50:50) copolymer using a double emulsion solvent evaporation method. After preparing nanoparticles, drug loading, encapsulation efficiency and particle size were determined. The cells were exposed to either plain solution of oligonucleotide or nanoparticles of oligonucleotide from Day 3 through Day 6. Alternatively, the cells were incubated with PS-ODNs and lipofectin for 4 h on Day 4. In all studies, VEGF secretion and mRNA expression were determined on Day 6. The particle size, drug loading and encapsulation efficiency were 252 nm, 5.5% and 16.5%, respectively. The antisense PS-ODN inhibited VEGF mRNA and protein secretion when delivered using nanoparticles or lipofectin but not in its free form. This was consistent with the ability of nanoparticles and lipofectin to elevate the cellular uptake of the oligonucleotide by 4-fold and 13-fold, respectively. Neither mismatch nor sense oligonucleotides inhibited VEGF secretion. In conclusion, biodegradable nanoparticles enhance cellular delivery of a VEGF antisense oligonucleotide and inhibit VEGF secretion and mRNA expression in a human retinal pigment epithelial cell line.

Indirect Antioxidant Protection Against Photooxidative Processes Initiated in Retinal Pigment Epithelial Cells by a Lipofuscin Pigment

Oxidative mechanisms are considered to contribute to the aging changes in retinal pigment epithelial (RPE) cells that underlie the pathogenesis of age-related macular degeneration. An important source of oxidative damage is likely to be the photoreactive pigments that progressively accumulate and constitute the lipofuscin of retinal pigment epithelial cells. Evidence for a link between RPE lipofuscin and cellular dysfunction is also provided by the understanding of disease progression in Stargardt disease. Using a culture model previously used to demonstrate photooxidative damage to retinal pigment epithelial cells that have accumulated the lipofuscin fluorophore A2E, it was shown that the propensity for cell death is increased under conditions that deplete cellular levels of glutathione. Additionally, sulforaphane, a phytochemical and inducer of phase 2 enzymes, protected RPE cells that accumulated A2E and were irradiated at 430 nm. The protection afforded by sulforaphane was paralleled by elevated levels of glutathione and increases in the activities of the phase 2 enzymes NAD(P)H:quinone reductase and glutathione-S-transferases. Moreover, transcriptional induction of NAD(P)H:quinone reductase was indicated by the increases in mRNA determined by real time RT-PCR. There has been considerable interest in the intake of carotenoids and antioxidant vitamins and the related incidence of age-related macular degeneration. The present results indicate that the indirect antioxidant activity of plant-derived phase 2 inducers also may be potentially important.

Single periocular injection of celecoxib-PLGA microparticles inhibits diabetes-induced elevations in retinal PGE2, VEGF, and vascular leakage

PURPOSE

To determine whether celecoxib inhibits VEGF secretion from ARPE-19 cells and to investigate further the safety and effectiveness of periocular celecoxib-poly (lactide-co-glycolide; PLGA) microparticles in inhibiting elevations in retinal PGE(2), VEGF, and blood-tissue barrier leakage at the end of 60 days in a streptozotocin diabetic rat model.

METHODS

VEGF mRNA and protein expression in ARPE-19 cells was evaluated in the presence of 0 to 10 microM celecoxib, and cytotoxicity of celecoxib on ARPE-19 and RF6A cells was evaluated over a 0- to 100-microM concentration range. Celecoxib-PLGA microparticles were prepared by a modified solvent evaporation technique, sterilized by 25 kGy of gamma-irradiation, and characterized for size, zeta potential, drug loading, and in vitro release. Normal and streptozotocin-diabetic male Sprague-Dawley rats were divided into five groups: normal, diabetic, diabetic+placebo, normal+celecoxib, and diabetic+celecoxib. Phosphate-buffered saline (PBS) containing celecoxib-PLGA microparticles, placebo PLGA microparticles, or plain PBS in one eye was injected into the posterior subconjunctival (periocular) space in rats under anesthesia. Sixty days after administration, the animals were killed, and retinal PGE2 secretion, VEGF protein, and blood-retinal barrier leakage were estimated. Blood cell counts, blood chemistry and histology were used to assess the safety of the microparticulate system.

RESULTS

Celecoxib (up to 25 microM) did not cause significant cytotoxicity in ARPE-19 or RF6A cells. Nanomolar concentrations of celecoxib reduced VEGF mRNA and VEGF protein secretion. Celecoxib-PLGA microparticles (diameter: 1140 +/- 15 nm), containing 14.93% +/- 0.21% of celecoxib sustained in vitro drug release and in vivo drug levels in the retina for 60 days. Diabetes elevated PGE2 secretion, VEGF protein, the vitreous-plasma protein ratio, and blood-retinal barrier leakage by 3-, 1.7-, 3.1-, and 2.7-fold, and celecoxib-PLGA microparticles significantly reduced these elevations by 40%, 50%, 40%, and 50%, respectively. Neither the placebo-treated eyes nor the contralateral eyes in celecoxib-PLGA microparticle-treated rats showed significant effects. Celecoxib-PLGA or placebo-PLGA particles had no effect on the body weight or blood sugar level of rats. The celecoxib-PLGA microparticles did not cause any changes in blood cell counts or chemistry and caused no histopathological damage to the retina or periocular tissues.

CONCLUSIONS

Nanomolar concentrations of celecoxib can inhibit VEGF mRNA and protein expression from ARPE-19 cells. Periocular celecoxib microparticles are useful sustained drug delivery systems for inhibiting diabetes-induced elevations in PGE2, VEGF, and blood-retinal barrier leakage. The periocular celecoxib-PLGA microparticles are safe and do not cause any damage to the retina.

Lipid peroxidation and renal cell carcinoma: further supportive evidence and new mechanistic insights

We have recently proposed lipid peroxidation as a unifying mechanistic pathway by which several seemingly unrelated risk/protective factors (obesity, hypertension, diabetes, smoking, oophorectomy/hysterectomy, parity, antioxidants) affect renal cell carcinoma development. In experimental studies, increased lipid peroxidation is a principal mechanistic pathway in renal carcinogenesis induced by different chemicals. In this communication, we provide additional lines of evidence that further support a role for lipid peroxidation on renal cell cancer development. (1) Lipid peroxidation may explain the role of other risk (analgesic use, pre-eclampsia) or protective (alcohol intake, oral contraceptives) factors for renal cell carcinoma. (2) Additional experimental evidence supports lipid peroxidation as an important mechanism in renal carcinogenesis, and (3) Existing evidence support a cross-talk between the lipid peroxidation pathway and other pathways that are relevant to renal carcinogenesis, such as apoptosis, VHL, and possibly other pathways.

Oxidative stress in fibroblasts from patients with pseudoxanthoma elasticum: possible role in the pathogenesis of clinical manifestations

Pseudoxanthoma elasticum (PXE) is a genetic disease characterized by calcification and fragmentation of elastic fibres of the skin, cardiovascular system and eye, caused by mutations of the ABCC6 gene, which encodes the membrane transporter MRP6. The pathogenesis of the lesions is unknown. Based on studies of similar clinical and histopathological damage present in haemolytic disorders, our working hypothesis is that PXE lesions may result from chronic oxidative stress occurring in PXE cells as a consequence of MRP6 deficiency. Our results show that PXE fibroblasts suffer from mild chronic oxidative stress due to the imbalance between production and degradation of oxidant species. The findings also show that this imbalance results, at least in part, from the loss of mitochondrial membrane potential (DeltaPsi(m)) with overproduction of H2O2. Whether mitochondrial dysfunction is the main factor responsible for the oxidative stress in PXE cells remains to be elucidated. However, mild chronic generalized oxidative stress could explain the great majority of structural and biochemical alterations already reported in PXE.

Mechanisms for the induction of HNE- MDA- and AGE-adducts, RAGE and VEGF in retinal pigment epithelial cells

Pathological features of age-related macular degeneration such as the formation of extracellular deposits and neovascularization are frequently viewed as outcomes of compromising processes within retinal pigment epithelial cells, but the initiating circumstances are poorly understood. Here we tested the hypothesis that photooxidation events initiated by A2E, a blue light-excitable aging fluorophore of the retinal pigment epithelium, can set the stage for altered cellular signaling and changes in the expression of genes that can impact the extracellular milieu. Proteins modified by lipid peroxidation products (4-hydroxynonenal; malondialdhyde) and advanced glycation end products were detected at sites of blue light irradiation both in association with the cultured A2E-laden retinal pigment epithelial cells and within the fibronectin substrate on which the cells were grown. RAGE, the cell surface receptor that transduces the effects of advanced glycation end products, was also upregulated, and RAGE expression co-localized with the deposition of advanced glycation end products. Blue light triggered alterations in gene expression was also evidenced by elevations in both transcripts and protein for vascular endothelial growth factor, a potent angiogenic and permeability-enhancing factor. These findings indicate that cell associated and extracellular modification of proteins by lipid peroxidation products and advanced glycation end products together with increased expression of RAGE and vascular endothelial growth factor may be induced consequent to blue light illumination of A2E-burdened retinal pigment epithelial cells. Thus, photooxidative events that are not an immediate threat to retinal pigment epithelial cell viability may nevertheless elicit sustained perturbation that could ultimately alter neighboring tissues and impact retinal pigment epithelial cell function.

Subconjunctivally administered celecoxib-PLGA microparticles sustain retinal drug levels and alleviate diabetes-induced oxidative stress in a rat model

We have previously reported that repeated oral doses of celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, reduced diabetes-induced retinal vascular endothelial growth factor (VEGF) expression [Ayalasomayajula, S.P., Kompella, U.B., 2003. Celecoxib, a selective cyclooxygenase-2 inhibitor, inhibits retinal vascular endothelial growth factor expression and vascular leakage in a streptozotocin-induced diabetic rat model. Eur J Pharmacol 458, 283-289] and that retinal celecoxib delivery can be improved by several-fold following subconjunctival administration [Ayalasomayajula, S.P., Kompella, U.B., 2004. Retinal delivery of celecoxib is several-fold higher following subconjunctival administration compared to systemic administration. Pharm Res 21, 1797-1804]. The objective of the current study was to determine whether polymeric microparticles of celecoxib sustain retinal drug levels following subconjunctival administration and alleviate diabetes-induced oxidative stress in a streptozotocin-induced diabetic rat model. Biodegradable poly (lactide-co-glycolide) (PLGA; 85:15) microparticles of celecoxib were prepared using solvent evaporation method and characterized for their size, morphology, encapsulation efficiencies, and in vitro release. The celecoxib-PLGA microparticles or solution containing 75 microg of celecoxib was administered subconjunctivally to one eye (ipsilateral) of Sprague Dawley rats and drug levels in the retina, vitreous, lens, and cornea of ipsilateral and contralateral eyes were determined on 1, 7, and 14 days using high-performance liquid chromatography (HPLC). The effect of subconjunctivally administered celecoxib-PLGA microparticles on oxidative stress in day 14 diabetic rat retinas was determined by measuring the retinal glutathione (reduced (GSH) and oxidized (GSSG)), thiobarbituric acid reactive substances, and 4-hydroxynonenal levels using spectrofluorometric and colorimetric methods. Solvent evaporation method produced spherical celecoxib-PLGA microparticles with mean diameters of 3.9+/-0.6 microm and 68.5% loading efficiency. These microparticles sustained celecoxib release during the 49-day in vitro release study. Subconjunctivally administered celecoxib-PLGA microparticles sustained retinal and other ocular tissue drug levels during the 14-day study in rats. No detectable celecoxib levels were observed in the contralateral eye. The celecoxib-PLGA microparticles significantly inhibited the diabetes-induced increases in thiobarbituric acid reactive substance (P=0.012) and 4-hydroxynonenal levels (P=0.029). The particles also inhibited the GSH depletion and the increase in GSSH/GSH ratio associated with diabetes but the effects were not statistically significant (P=0.12). Thus, following subconjunctival administration, celecoxib-PLGA microparticles sustained retinal celecoxib delivery and inhibited diabetes-induced retinal oxidative damage, indicating their potential usefulness in treating diabetes-induced retinal abnormalities.

Resveratrol protects against 4-HNE induced oxidative stress and apoptosis in Swiss 3T3 fibroblasts

Here we report on the marked protective effect of resveratrol on 4-hydroxynonenal (4-HNE) induced oxidative stress and apoptotic death in Swiss 3T3 fibroblasts. 4-HNE, one of the major aldehydic products of the peroxidation of membrane w-6 polyunsaturated fatty acids, has been suggested to contribute to oxidant stress mediated cell injury. Indeed, in vitro treatment of 3T3 fibroblasts with 4-HNE induced a condition of oxidative stress as monitored by the oxidation of dichlorofluorescein diacetate; this reaction was prevented when cells were pretreated with resveratrol. Further, 4-HNE-treated fibroblasts eventually underwent apoptotic death as determined by differential staining and internucleosomal DNA fragmentation. Resveratrol pretreatment also prevented 4-HNE induced DNA fragmentation and apoptosis. These observations are consistent with a potential role of lipid peroxidation-derived products in programmed cell death and demonstrate that resveratrol can counteract this effect by quenching cell oxidative stress.

Acute hyperoxia-induced transcriptional response in the mouse RPE/choroid

Oxidative stress has been studied in the retinal pigmented epithelium (RPE) in vitro but not in vivo. Our purpose, therefore, was to develop an in vivo model of acute oxidative stress in the C57BL/6J mouse. Mice were exposed to > or = 98% oxygen for 0, 2, or 6 h, and amplified total RNA from the RPE/choroid was applied to microarrays examining about 2200 unique genes. Statistical analysis determined that 642 genes, out of a total of 1349 expressed, were significantly downregulated at only 2 h, only 6 h, or both 2 and 6 h, and a single gene, ubiquitin, was upregulated. These genes are involved in all aspects of cellular functions, and there are no major differences among the three groups. The effect of hyperoxia on the RPE/choroid in vivo appears to be very similar to oxidative stress studies performed with an RPE cell line in vitro. All 11 genes identified as being regulated by all three oxidants in our previous study, and were expressed by mouse, were also differentially regulated by hyperoxia. At least for the initial response to an oxidative challenge, the in vitro ARPE-19 cell line is a reasonable model for in vivo studies.

4-hydroxynonenal as a bioactive marker of pathophysiological processes

The review is focused on the currently major aspect of 4-hydroxynonenal (HNE) research--studies that combine biological activities of the aldehyde together with the methods of its identification in cells and tissues. Because there were some excellent reviews on HNE published in recent years, starting in 1990 and 1991 with supreme reviews done by Hermann Esterbauer, who discovered the aldehyde, and colleagues from the Institute of Biochemistry in Graz, this article pays most of attention to the most recent articles, published in the last 15 months. Additionally, an overview on the relevance of HNE is given with respect to the research and publication trends in the period of 10 years (1993-2002) according to the data in the Current Contents and Medline data bases. It is obvious that HNE started in 1993 as a "toxic product of lipid peroxidation" and "second toxic messenger of free radicals", to become in 2002 a reliable marker of oxidative stress, a possible causative agent of several diseases (such as Alzheimer's disease), growth modulating factor and a signaling molecule. Novel analytical methods developed suitable pathways for HNE to become a clinically applicable marker of lipid peroxidation on one side and on the other a standardized parameter of food quality control. As it is also present physiologically in various cells and tissues, it is likely that HNE will soon become one of the most attractive factors for those who search for a small and reactive molecular link between genomics and proteomics.

Celecoxib, a selective cyclooxygenase-2 inhibitor, inhibits retinal vascular endothelial growth factor expression and vascular leakage in a streptozotocin-induced diabetic rat model

Overexpression of vascular endothelial growth factor (VEGF) is implicated in the development of vascular leakage and retinal neovascularization in diabetic subjects. The objective of this study was to determine whether celecoxib, a selective cyclooxygenase-2 enzyme inhibitor, reaches ocular tissues following oral administration and inhibits the retinal VEGF expression and vascular leakage in a streptozotocin-induced diabetic rat model. After administering a single intraperitoneal injection of streptozotocin (60 mg/kg) to Sprague-Dawley rats and ensuring the induction of diabetes at the end of 24 h, celecoxib was administered b.i.d. by oral gavage (50 mg/kg). On day 8, the animals were sacrificed and the retinal VEGF and cyclooxygenase-2 mRNA levels, ocular tissue celecoxib concentrations, and the vitreous/plasma protein ratio were determined. In diabetic rats, the retinal VEGF mRNA expression was 2.3-fold compared to controls, with a corresponding increase in cyclooxygenase-2 mRNA expression. Celecoxib treatment inhibited VEGF mRNA expression without any significant reduction in cyclooxygenase-2 mRNA. Furthermore, the retinal vascular leakage estimated as vitreous to plasma protein ratio increased in diabetic animals from 0.35+/-0.1 to 1.1+/-0.1 and celecoxib treatment significantly decreased this ratio to 0.4+/-0.1. Celecoxib levels were 24.8+/-6.6, 1.9+/-1, 1.7+/-0.8, and 6.9+/-0.9 ng/mg in the retina, vitreous, lens, and cornea, respectively. The plasma celecoxib levels were 85+/-24 ng/ml. Thus, celecoxib reaches the retina after oral administration and reduces diabetes-induced retinal VEGF mRNA expression and vascular leakage by inhibiting the activity of cyclooxygenase-2 enzyme.