Age-related changes in superoxide dismutase, glutathione peroxidase, catalase and xanthine oxidoreductase/xanthine oxidase activities in the rabbit cornea

Corneal epithelium models for safety assessment in drug development: Present and future directions

The human corneal epithelial barrier plays a crucial role in drug testing studies, including drug absorption, distribution, metabolism, and excretion (ADME), as well as toxicity testing during the preclinical stages of drug development. However, despite the valuable insights gained from animal and current in vitro models, there remains a significant discrepancy between preclinical drug predictions and actual clinical outcomes. Additionally, there is a growing emphasis on adhering to the 3R principles (refine, reduce, replace) to minimize the use of animals in testing. To tackle these challenges, there is a rising demand for alternative in vitro models that closely mimic the human corneal epithelium. Recently, remarkable advancements have been made in two key areas: microphysiological systems (MPS) or organs-on-chips (OoCs), and stem cell-derived organoids. These cutting-edge platforms integrate four major disciplines: stem cells, microfluidics, bioprinting, and biosensing technologies. This integration holds great promise in developing powerful and biomimetic models of the human cornea.

Nanozyme-Cosmetic Contact Lenses for Ocular Surface Disease Prevention

Efficiently balancing excess reactive oxygen species (ROS) caused by various factors on the ocular surface is a promising strategy for preventing the development of ocular surface diseases (OSDs). Nevertheless, the conventional topical administration of antioxidants is limited in efficacy due to poor absorption, rapid metabolism, and irreversible depletion, which impede their performance. To address this issue, contact lenses embedded with antioxidant nanozymes that can continuously scavenge ROS, thereby providing an excellent preventive effect against OSDs are developed. Specifically, Prussian blue family nanozymes are chosen based on their multiple antioxidant enzyme-like activities and excellent biocompatibility. The diverse range of colors made them promising candidates for the development of cosmetic contact lenses (CCLs) as a substitute for conventional pigments. The efficacy of nanozyme-CCLs is demonstrated in rabbits and rats exposed to a high risk of developing OSDs. These OSDs' prevention nanozyme-CCLs can pave the way for CCLs toward powerful wearable biomedical devices and provide novel strategies for the rational utilization of nanomaterials in clinical practice.

Oxidative Stress in the Anterior Ocular Diseases: Diagnostic and Treatment

The eye is a metabolically active structure, constantly exposed to solar radiations making its structure vulnerable to the high burden of reactive oxygen species (ROS), presenting many molecular interactions. The biomolecular cascade modification is caused especially in diseases of the ocular surface, cornea, conjunctiva, uvea, and lens. In fact, the injury in the anterior segment of the eye takes its origin from the perturbation of the pro-oxidant/antioxidant balance and leads to increased oxidative damage, especially when the first line of antioxidant defence weakens with age. Furthermore, oxidative stress is related to mitochondrial dysfunction, DNA damage, lipid peroxidation, protein modification, apoptosis, and inflammation, which are involved in anterior ocular disease progression such as dry eye, keratoconus, uveitis, and cataract. The different pathologies are interconnected through various mechanisms such as inflammation, oxidative stress making the diagnostics more relevant in early stages. The end point of the molecular pathway is the release of different antioxidant biomarkers offering the potential of predictive diagnostics of the pathology. In this review, we have analysed the oxidative stress and inflammatory processes in the front of the eye to provide a better understanding of the pathomechanism, the importance of biomarkers for the diagnosis of eye diseases, and the recent treatment of anterior ocular diseases.

Neurobiological Mechanisms of Cognitive Decline Correlated with Brain Aging

Cognitive decline has emerged as one of the greatest health threats of old age. Meanwhile, aging is the primary risk factor for Alzheimer's disease (AD) and other prevalent neurodegenerative disorders. Developing therapeutic interventions for such conditions demands a greater understanding of the processes underlying normal and pathological brain aging. Despite playing an important role in the pathogenesis and incidence of disease, brain aging has not been well understood at a molecular level. Recent advances in the biology of aging in model organisms, together with molecular- and systems-level studies of the brain, are beginning to shed light on these mechanisms and their potential roles in cognitive decline. This chapter seeks to integrate the knowledge about the neurological mechanisms of age-related cognitive changes that underlie aging.

Intracellular reactive oxygen species level in blood cells of atomic bomb survivors is increased due to aging and radiation exposure

Although reactive oxygen species (ROS) play important roles in immune responses, excessive ROS production and accumulation might enhance the risk of inflammation-related diseases. Moreover, impaired immune function and the acceleration of pre-clinically persistent inflammation due to aging and radiation exposure have been observed in atomic bomb (A-bomb) survivors more than 60 years post-exposure. Meanwhile, the effects of aging and radiation exposure on ROS production in immune cells have not been characterized. This study investigated the relationship between intracellular ROS (H₂O₂ and O₂^•-) levels in blood cells or T cell subsets and serum iron, ferritin, and C-reactive protein (CRP) levels, as well as how these variables are affected by age and radiation exposure in A-bomb survivors. We examined 2495 Hiroshima A-bomb survivors. Multiple linear regression models adjusted for confounding factors indicated that intracellular O₂^•- levels in monocytes, granulocytes, and lymphocytes, and particularly in memory CD8⁺ T cells, including effector memory and terminally differentiated effector memory CD8⁺ T cells, increased with radiation dose. Additionally, serum iron, ferritin, and CRP levels affected intracellular ROS levels in specific blood cell types and T cell subsets. Serum CRP levels increased significantly with increasing age and radiation dose. Finally, when divided into three groups according to serum CRP levels, dose-dependent increases in the intracellular O₂^•- levels in blood cells and central memory and effector memory CD8⁺ T cells were most prominently observed in the high-CRP group. These results suggest that an increase in the levels of certain intracellular ROS, particularly after radiation exposure, might be linked to enhanced inflammatory status, including elevated serum CRP levels and reduced serum iron levels. This study reveals that aging and radiation exposure increase oxidative stress in blood cells, which is involved in impaired immune function and accelerated pre-clinically persistent inflammation in radiation-exposed individuals.

Spatiotemporal determination of metabolite activities in the corneal epithelium on a chip

The corneal epithelial barrier maintains the metabolic activities of the ocular surface by regulating membrane transporters and metabolic enzymes responsible for the homeostasis of the eye as well as the pharmacokinetic behavior of drugs. Despite its importance, no established biomimetic in vitro methods are available to perform the spatiotemporal investigation of metabolism and determine the transportation of endogenous and exogenous molecules across the corneal epithelium barrier. This study introduces multiple corneal epitheliums on a chip namely, Corneal Epithelium on a Chip (CEpOC), which enables the spatiotemporal collection as well as analysis of micro-scaled extracellular metabolites from both the apical and basolateral sides of the barriers. Longitudinal samples collected during 48 h period were analyzed using untargeted liquid chromatography-mass spectrometry metabolomics method, and 104 metabolites were annotated. We observed the spatiotemporal secretion of biologically relevant metabolites (i.e., antioxidant, glutathione and uric acid) as well as the depletion of essential nutrients such as amino acids and vitamins mimicking the in vivo molecules trafficking across the human corneal epithelium. Through the shifts of extracellular metabolites and quantitative analysis of mRNA associated with transporters, we were able to investigate the secretion and transportation activities across the polarized barrier in a correlation with the expression of corneal transporters. Thus, CEpOC can provide a non-invasive, simple, yet effectively informative method to determine pharmacokinetics and pharmacodynamics as well as to discover novel biomarkers for drug toxicological and safety tests as advanced experimental model of the human corneal epithelium.

Antioxidant Defenses in the Human Eye: A Focus on Metallothioneins

The human eye, the highly specialized organ of vision, is greatly influenced by oxidants of endogenous and exogenous origin. Oxidative stress affects all structures of the human eye with special emphasis on the ocular surface, the lens, the retina and its retinal pigment epithelium, which are considered natural barriers of antioxidant protection, contributing to the onset and/or progression of eye diseases. These ocular structures contain a complex antioxidant defense system slightly different along the eye depending on cell tissue. In addition to widely studied enzymatic antioxidants, including superoxide dismutase, glutathione peroxidase, catalase, peroxiredoxins and selenoproteins, inter alia, metallothioneins (MTs) are considered antioxidant proteins of growing interest with further cell-mediated functions. This family of cysteine rich and low molecular mass proteins captures and neutralizes free radicals in a redox-dependent mechanism involving zinc binding and release. The state of the art of MTs, including the isoforms classification, the main functions described to date, the Zn-MT redox cycle as antioxidant defense system, and the antioxidant activity of Zn-MTs in the ocular surface, lens, retina and its retinal pigment epithelium, dependent on the number of occupied zinc-binding sites, will be comprehensively reviewed.

Effect of hydrogen peroxide on the oxidative burst of neutrophils in pigs and ruminants

Background and Aim

Neutrophils represent between 20% and 75% of white blood cells in animals and play a key role in an effective immune response. The generation of reactive oxygen species (ROS) is commonly referred to as an oxidative burst and is crucial under healthy and disease conditions. Interestingly, ROS are emerging as regulators of several neutrophil functions, including their oxidative burst. The present study aimed to investigate the effect of hydrogen peroxide on the oxidative burst of neutrophils, collected from domestic animal species (namely, pig, cattle, and sheep), and exposed to different stimuli.

Materials and Methods

A total of 65 slaughtered animals were included in the present study: Twenty-two pigs, 21 cattle, and 22 sheep. Blood samples were collected at bleeding and neutrophils were then purified using ad hoc developed and species-specific protocols. Neutrophils were treated with hydrogen peroxide at micromolar-to-millimolar concentrations, alone, or combined with other stimuli (i.e., opsonized yeasts, and phorbol 12-myristate 13-acetate). The generation of ROS was evaluated using a luminol-derived chemiluminescence (CL) assay. For each animal species, data were aggregated and reported as mean area under curve±standard deviation. Finally, data were statistically analyzed by one-way ANOVA, followed by Tukey's post hoc test.

Results

Exposure of bovine and ovine neutrophils to hydrogen peroxide alone resulted in a dose-dependent enhancement of the CL response, which was significantly stronger at its highest concentration and proved particularly prominent in sheep. Opsonized yeasts and phorbol 12-myristate 13-acetate both proved capable of stimulating the generation of ROS in all animal species under study. Hydrogen peroxide negatively modulated the oxidative burst of neutrophils after exposure to those stimuli, observed response patterns varying between pigs and ruminants. Porcine neutrophils, pre-exposed to micromolar concentrations of hydrogen peroxide, showed a decreased CL response only to opsonized yeasts. Conversely, pre-exposure to hydrogen peroxide reduced the CL response of ruminant neutrophils both to yeasts and phorbol 12-myristate 13-acetate, the effect being most prominent at 1 mM concentration.

Conclusion

These results indicate that hydrogen peroxide is capable of modulating the oxidative bursts of neutrophils in a species-specific and dose-dependent manner, substantial differences existing between pigs and ruminants. Further investigation is required to fully comprehend such modulation, which is crucial for the proper management of the generation of ROS under healthy and disease conditions.

Pro-Aging Effects of Xanthine Oxidoreductase Products

The senescence process is the result of a series of factors that start from the genetic constitution interacting with epigenetic modifications induced by endogenous and environmental causes and that lead to a progressive deterioration at the cellular and functional levels. One of the main causes of aging is oxidative stress deriving from the imbalance between the production of reactive oxygen (ROS) and nitrogen (RNS) species and their scavenging through antioxidants. Xanthine oxidoreductase (XOR) activities produce uric acid, as well as reactive oxygen and nitrogen species, which all may be relevant to such equilibrium. This review analyzes XOR activity through in vitro experiments, animal studies and clinical reports, which highlight the pro-aging effects of XOR products. However, XOR activity contributes to a regular level of ROS and RNS, which appears essential for the proper functioning of many physiological pathways. This discourages the use of therapies with XOR inhibitors, unless symptomatic hyperuricemia is present.

Genetic parameter estimates for plasma oxidative status traits in slaughter pigs

The aim of the present study was to assess the effect of sex and to estimate genetic parameters for several traits related to plasma oxidative status in slaughter pigs, i.e., ferric reducing ability of plasma (FRAP), concentrations of α-tocopherol and malondialdehyde (MDA), and glutathione peroxidase (GPx) activity. Blood samples were collected at slaughter from 477 Piétrain × (Landrace × Large White intercross) pigs of 2 performance test stations. Heritabilities (±SE) of plasma oxidative status traits as well as their phenotypic and additive genetic correlations with animal performance traits were estimated with multiple-trait REML animal models using VCE software. Results displayed no significant difference between barrows and gilts for FRAP and α-tocopherol in plasma. However, gilts had a significantly higher concentration of MDA and lower GPx activity compared with barrows. Heritability estimates were high for GPx (0.55 ± 0.05), and medium to low for α-tocopherol (0.30 ± 0.06), FRAP (0.22 ± 0.05), and MDA (0.15 ± 0.04). Estimated additive genetic and phenotypic correlations between these four traits were generally low, except for a negative additive genetic correlation between FRAP and GPx of -0.45 (±0.23). Additive genetic correlations between plasma oxidative status traits and animal performance traits were also generally absent or low with maximum values of ~0.3. Parameter estimates in this study have to be interpreted with caution because of the small size of the dataset. Nevertheless, it may be concluded that there is considerable additive genetic variance for plasma oxidative status traits in slaughter pigs. More research is warranted on the genetic determination of oxidative stress in farm animals and its relevance in breeding programs.

Microdot Accumulation in the Anterior Cornea with Aging - Quantitative Analysis with in Vivo Confocal Microscopy

PURPOSE

Degenerative 'microdot' deposits in healthy and hypoxic corneas are believed to represent lipofuscin-like material aggregation in the stroma. To accurately assess microdot deposits in a clinical setting, we sought to quantify these deposits for the first time using the non-invasive clinical imaging technique of in vivo confocal microscopy (IVCM).

METHODS

The corneas of 102 healthy subjects aged 15-88 years were examined by IVCM and microdot density was quantified using a 6-point grading scale by two masked, trained examiners. Microdot density was analyzed with respect to age, sex and stromal depth, and inter-eye and inter-observer differences were evaluated.

RESULTS

In healthy subjects, microdot density decreased from the anterior to posterior stroma, with the greatest accumulation observed in the most anterior stroma (subepithelial region). In this region, microdot density correlated strongly with age (P < .0001), with increased microdot deposition in older subjects (>60 years) relative to younger ones (<45 years) (P < .001). Microdot density between eyes of the same subject was highly correlated (r = 0.92, P < .0001), while no association with sex was noted (P ≥ 0.05). The mean inter-observer difference in microdot assessment was 0.62 ± 0.09 grades, with a high correlation of grading between observers (r = 0.77, P < .0001).

CONCLUSIONS

IVCM can be used to non-invasively quantify microdot deposits in the subepithelial corneal stroma with good inter-observer reproducibility. Microdot assessment may provide a novel means of quantifying age-related or pathologic degeneration of the corneal stroma in a clinical setting.

Depletion of the Third Complement Component Ameliorates Age-Dependent Oxidative Stress and Positively Modulates Autophagic Activity in Aged Retinas in a Mouse Model

The aim of the study was to investigate the influence of complement component C3 global depletion on the biological structure and function of the aged retina. In vivo morphology (OCT), electrophysiological function (ERG), and the expression of selected oxidative stress-, apoptosis-, and autophagy-related proteins were assessed in retinas of 12-month-old C3-deficient and WT mice. Moreover, global gene expression in retinas was analyzed by RNA arrays. We found that the absence of active C3 was associated with (1) alleviation of the age-dependent decrease in retinal thickness and gradual deterioration of retinal bioelectrical function, (2) significantly higher levels of antioxidant enzymes (catalase and glutathione reductase) and the antiapoptotic survivin and Mcl-1/Bak dimer, (3) lower expression of the cellular oxidative stress marker-4HNE-and decreased activity of proapoptotic caspase-3, (4) ameliorated retinal autophagic activity with localization of ubiquitinated protein conjugates commonly along the retinal pigment epithelium (RPE) layer, and (5) significantly increased expression of several gene sets associated with maintenance of the physiological functions of the neural retina. Our findings shed light on mechanisms of age-related retinal alterations by identifying C3 as a potential therapeutic target for retinal aging.

Mitochondrial dysfunction and oxidative stress in corneal disease

The cornea is the anterior transparent surface and the main refracting structure of the eye. Mitochondrial dysfunction and oxidative stress are implicated in the pathogenesis of inherited (e.g. Kearns Sayre Syndrome) and acquired corneal diseases (e.g. keratoconus and Fuchs endothelial corneal dystrophy). Both antioxidants and reactive oxygen species are found in the healthy cornea. There is increasing evidence of imbalance in the oxidative balance and mitochondrial function in the cornea in disease states. The cornea is vulnerable to mitochondrial dysfunction and oxidative stress due to its highly exposed position to ultraviolet radiation and high oxygen tension. The corneal endothelium is vulnerable to accumulating mitochondrial DNA (mtDNA) damage due to the post- mitotic nature of endothelial cells, yet their mitochondrial genome is continually replicating and mtDNA mutations can develop and accumulate with age. The unique physiology of the cornea predisposes this structure to oxidative damage, and there is interplay between inherited and acquired mitochondrial dysfunction, oxidative damage and a number of corneal diseases. By targeting mitochondrial dysfunction in corneal disease, emerging treatments may prevent or reduce visual loss.

KCa 3.1 upregulation preserves endothelium-dependent vasorelaxation during aging and oxidative stress

Endothelial oxidative stress develops with aging and reactive oxygen species impair endothelium-dependent relaxation (EDR) by decreasing nitric oxide (NO) availability. Endothelial KCa 3.1, which contributes to EDR, is upregulated by H2 O2 . We investigated whether KCa 3.1 upregulation compensates for diminished EDR to NO during aging-related oxidative stress. Previous studies identified that the levels of ceramide synthase 5 (CerS5), sphingosine, and sphingosine 1-phosphate were increased in aged wild-type and CerS2 mice. In primary mouse aortic endothelial cells (MAECs) from aged wild-type and CerS2 null mice, superoxide dismutase (SOD) was upregulated, and catalase and glutathione peroxidase 1 (GPX1) were downregulated, when compared to MAECs from young and age-matched wild-type mice. Increased H2 O2 levels induced Fyn and extracellular signal-regulated kinases (ERKs) phosphorylation and KCa 3.1 upregulation. Catalase/GPX1 double knockout (catalase(-/-) /GPX1(-/-) ) upregulated KCa 3.1 in MAECs. NO production was decreased in aged wild-type, CerS2 null, and catalase(-/-) /GPX1(-/-) MAECs. However, KCa 3.1 activation-induced, N(G) -nitro-l-arginine-, and indomethacin-resistant EDR was increased without a change in acetylcholine-induced EDR in aortic rings from aged wild-type, CerS2 null, and catalase(-/-) /GPX1(-/-) mice. CerS5 transfection or exogenous application of sphingosine or sphingosine 1-phosphate induced similar changes in levels of the antioxidant enzymes and upregulated KCa 3.1. Our findings suggest that, during aging-related oxidative stress, SOD upregulation and downregulation of catalase and GPX1, which occur upon altering the sphingolipid composition or acyl chain length, generate H2 O2 and thereby upregulate KCa 3.1 expression and function via a H2 O2 /Fyn-mediated pathway. Altogether, enhanced KCa 3.1 activity may compensate for decreased NO signaling during vascular aging.

Oxidative stress in the trabecular meshwork (Review)

Glaucoma is the second leading cause of blindness worldwide and elevated intraocular pressure (IOP) is the most important risk factor. High IOP usually occurs as a result of an increase in aqueous humor outflow resistance at the trabecular meshwork (TM). An abnormal TM contributes to the development of glaucoma. Oxidative stress and vascular damage are considered two major cellular factors that lead to alterations in the TM. In this review, we discuss the findings related to oxidative damage to the TM, including the sources of oxidative stress in the TM such as the mitochondria, peroxisomes, endoplasmic reticulum, membrane, cytosol and exogenous factors. We also discuss antioxidants and clinical studies related to protection against oxidative stress in the TM. Although many questions remain unanswered, it is becoming increasingly clear that oxidative stress-induced damage to the TM is related to glaucoma. This may inspire new studies to find better and more stable antioxidants, and better models with which to elucidate the mechanisms involved, and to determine whether in vitro findings translate into in vivo observations. The regulation of the oxidative/redox balance may be the ultimate target for protecting the TM from oxidative stress and preventing glaucoma.

Bacterial and fungal keratitis in Upper Egypt: in vitro screening of enzymes, toxins and antifungal activity

Purpose:

This work was conducted to study the ability of bacterial and fungal isolates from keratitis cases in Upper Egypt to produce enzymes, toxins, and to test the isolated fungal species sensitivity to some therapeutic agents.

Materials and Methods:

One hundred and fifteen patients clinically diagnosed to have microbial keratitis were investigated. From these cases, 37 bacterial isolates and 25 fungal isolates were screened for their ability to produce extra-cellular enzymes in solid media. In addition, the ability of fungal isolates to produce mycotoxins and their sensitivity to 4 antifungal agents were tested.

Results:

Protease, lipase, hemolysins, urease, phosphatase, and catalase were detected respectively in 48.65%, 37.84%, 59.46%, 43.24%, 67.57%, and 100% out of 37 bacterial isolates tested. Out of 25 fungal isolates tested during the present study, 80% were positive for protease, 84% for lipase and urease, 28% for blood hemolysis, and 100% for phosphatase and catalase enzymes. Thirteen fungal isolates were able to produce detectable amounts of 7 mycotoxins in culture medium (aflatoxins (B1, B2, G1, and G2), sterigmatocystin, fumagillin, diacetoxyscirpenol, zearalenone, T-2 toxin, and trichodermin). Among the antifungal agents tested in this study, terbinafine showed the highest effect against most isolates in vitro.

Conclusion:

In conclusion, the ability of bacterial and fungal isolates to produce extracellular enzymes and toxins may be aid in the invasion and destruction of eye tissues, which, in turn, lead to vision loss.

Effect of ageing and oxidative stress on antioxidant enzyme activity in different regions of the rat kidney

Oxidative stress has been implicated in ageing and the pathogenesis of chronic kidney disease. We examined levels of antioxidant enzymes glutathione peroxidase, glutathione reductase, glutathione S-transferase, catalase and superoxide dismutase as modulated by age and oxidative stress in different regions of the kidney. Antioxidant enzymes were examined in different regions of the kidney in male Wistar rats. Kidneys from rats of different ages (5, 12, 36 and 60 weeks) were dissected into cortex, outer medulla and inner medulla. Tissues were incubated for 30 min with or without 0.2 mM H2O2 to induce oxidative stress. Antioxidant enzyme activities progressively decreased with age under both control and stress conditions (P < 0.05) after peaking at 12 weeks. Antioxidant enzyme activities were greater in the cortex (P < 0.05) by comparison with the outer and inner medulla, respectively.

Polymorphisms of the apoptosis-related FAS and FAS ligand genes in keratoconus and Fuchs endothelial corneal dystrophy

Keratoconus (KC) is a non-inflammatory eye disease characterized by progressive corneal thinning and asymmetrical conical protrusion of the cornea. Fuchs endothelial corneal dystrophy (FECD) is a degenerative, slowly progressive disease of the corneal endothelium that is characterized by alteration in corneal endothelial cell morphology and progressive loss of these cells. They are unrelated eye diseases that may ultimately lead to vision loss. Their pathogenesis is largely unknown, although impaired apoptosis has been suggested to be responsible for both diseases. Therefore, we studied the frequency of the c.-671A>G polymorphism of the apoptosis-related FAS gene and the c.-844T>C polymorphism of the FAS ligand (FASLG) gene in patients with FECD (221 individuals) or KC (264) and controls (300). Each polymorphism is located within the putative cis-acting element of the respective promoter. Risk of KC or FECD was estimated with unconditional multiple logistic regression with adjustment for various factors, including age, sex, allergies, and family history. The T/T genotype and the T allele of the c.-844T>C polymorphism were associated with increased occurrence of KC, while the C allele was associated with decreased KC occurrence. The G allele of the c.-671A>G polymorphism was associated with increased occurrence of FECD, while the A allele was associated with decreased FECD occurrence. The C/C-A/A combined genotype was associated with reduced risk of FECD, whereas the T/T-G/A combined genotype increased risk of KC. In conclusion, variability in the expression of the FAS and FASLG genes may be involved in the pathogenesis of KC and FECD.

Focus on molecular events in the anterior chamber leading to glaucoma

Primary open-angle glaucoma is a multifactorial disease that affects the retinal ganglion cells, but currently its therapy is to lower the eye pressure. This indicates a definite involvement of the trabecular meshwork, key region in the pathogenesis of glaucoma. This is the first target of glaucoma, and its functional complexity is a real challenge to search. Its functions are those to allow the outflow of aqueous humor and not the reflux. This article describes the morphological and functional changes that happen in anterior chamber. The "primus movens" is oxidative stress that affects trabecular meshwork, particularly its endothelial cells. In these develops a real mitochondriopaty. This leads to functional impotence, the trabecular meshwork altering both motility and cytoarchitecture. Its cells die by apoptosis, losing barrier functions and altering the aqueous humor outflow. All the morphological alterations occur that can be observed under a microscope. Intraocular pressure rises and the malfunctioning trabecular meshwork endotelial cells express proteins that completely alter the aqueous humor. This is a liquid whose functional proteomics complies with the conditions of the trabecular meshwork. Indeed, in glaucoma, it is possible detect the presence of proteins which testify to what occurs in the anterior chamber. There are six classes of proteins which confirm the vascular endothelium nature of the anterior chamber and are the result of the morphofunctional trabecular meshwork decay. It is possible that, all or in part, these proteins can be used as a signal to the posterior pole.

Age-related decrease in human corneal γ-glutamyltranspeptidase activity

PURPOSE

To investigate age-related effects on human corneal γ-glutamyltranspeptidase (GGT) (ectoenzyme important to maintaining corneal hydration and antioxidant potential via glutathione recapture).

METHODS

Age-related differences between total, endothelial, and epithelial GGT activity and endothelial cell density were determined for corneas from 29 donors (mean age, 53 ± 17 years; age range, 13-83 years). GGT activity was determined using a standard colorimetric assay based on the transpeptidation reaction. Corneal GGT localization and expression was determined by immunohistochemistry.

RESULTS

Total corneal, endothelial, and epithelial GGT activities in the young (<50 years) donor corneas were 37% (P = 0.02), 44% (P = 0.001), and 36% (P = 0.06) higher, respectively, than in the senior (≥50 years) corneas. The age-related rates of decline for GGT activity were 1.0 unit per year for total cornea, 0.4 to 0.5 unit per year for endothelium, and 0.3 to 0.4 unit per year for epithelium. Notably, endothelial cell density in the young corneas was 14% (P = 0.001) higher than in the senior corneas declining about 100 cells per square millimeter per decade (0.3% per year). GGT activity per 10 endothelial cells decreased at about 0.2 units per year and GGT activity per 10 endothelial cells in the young corneas was 41% higher (P = 0.01) than in the senior corneas. Fewer immunoreactive GGT-positive epithelial cells were detected in senior cornea.

CONCLUSION

The age-related loss of human corneal GGT activity was associated with reductions in endothelial and epithelial GGT activity, being because of reduced number of GGT-positive endothelial and epithelial cells and reduced GGT activity per endothelial cell.

Environmental light and endogenous antioxidants as the main determinants of non-cancer ocular diseases

The human eye is constantly exposed to sunlight and artificial lighting. Exogenous sources of reactive oxygen species (ROS) such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins contribute to oxidative damage in ocular tissues. Long-term exposure to these insults places the aging eye at considerable risk for pathological consequences of oxidative stress. Furthermore, in eye tissues, mitochondria are an important endogenous source of ROS. Over time, all ocular structures, from the tear film to the retina, undergo oxidative stress, and therefore, the antioxidant defenses of each tissue assume the role of a safeguard against degenerative ocular pathologies. The ocular surface and cornea protect the other ocular tissues and are significantly exposed to oxidative stress of environmental origin. Overwhelming of antioxidant defenses in these tissues clinically manifests as pathologies including pterygium, corneal dystrophies, and endothelial Fuch's dystrophy. The crystalline lens is highly susceptible to oxidative damage in aging because its cells and their intracellular proteins are not turned over or replaced, thus providing the basis for cataractogenesis. The trabecular meshwork, which is the anterior chamber tissue devoted to aqueous humor drainage, has a particular susceptibility to mitochondrial oxidative injury that affects its endothelium and leads to an intraocular pressure increase that marks the beginning of glaucoma. Photo-oxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelium followed by death of the overlying photoreceptors. Accordingly, converging evidence indicates that mutagenic mechanisms of environmental and endogenous sources play a fundamental pathogenic role in degenerative eye diseases.

Antioxidant defenses in the ocular surface

The human eye is subjected constantly to oxidative stress due to daily exposure to sunlight, high metabolic activities, and oxygen tension. Reactive oxygen species generated from environmental insults and pathological conditions render the human eye particularly vulnerable to oxidative damage. The ocular surface composed of the tear film, the cornea, and the aqueous humor forms the first physical and biochemical barrier of the eye and plays a pivotal role in combating free radicals. These ocular compartments are enriched in certain antioxidants in the form of metabolic enzymes or small molecules. Such an antioxidant defense system in the ocular surface is essential for the maintenance of redox homeostasis in the eye and protection against oxidative damage. Herein, we review the properties and functions of key constituent antioxidants of the ocular surface.

The aged-related increase in xanthine oxidase expression and activity in several tissues from mice is not shown in long-lived animals

Xanthine oxidase (XO) is an important source of oxidant production and plays an essential role in several oxidative stress-related diseases. Aging is associated with a progressive deregulation of homeostasis as a result of a chronic oxidative stress situation. In the present work the age-related changes in XO expression and activity, as well as the activities of superoxide dismutase and catalase have been investigated in liver, kidney and thymus from four different age groups of mice, including long-lived animals. Furthermore, we have evaluated the contribution of the XO to the oxidative stress-associated with aging, in comparison to another enzymatic key source of oxidant generation, the NADPH oxidase, in peritoneal leukocytes from old mice. In all the tissues analyzed, the old mice showed higher activity and expression of XO, and decreased or unchanged superoxide dismutase and catalase activities as compared with adult mice. Moreover, the inhibition of reactive oxygen species with allopurinol or apocynin in peritoneal leukocytes from old mice, suggest that both XO and NADPH oxidase contribute to the generation of superoxide anion, whereas the XO may have a special relevance in the production of hydrogen peroxyde. Finally, long-lived animals showed a well-preserved redox state, in terms of antioxidant defenses and oxidant compounds in tissues and immune cells, which may be related to the ability of these subjects to reach a very advanced age in healthy condition. These results confirm that XO plays an important role in the age-related oxidative stress in tissues and immune cells.

Antioxidants and the integrity of ocular tissues

Oxygen-derived free radicals are normally generated in many pathways. These radicals can interact with various cellular components and induce cell injury. When free radicals exceed the antioxidant capacity, cell injury causes diverse pathologic changes in the organs. The imbalance between the generation of free radicals and antioxidant defence is known as oxidative stress. The eye can suffer the effect of oxidative damage due to the etiopathogenesis of some pathological changes related to oxidative stress. This paper reviews the role of oxidative stress in the onset and progression of damage in different eye structures, the involvement of the antioxidant network in protecting and maintaining the homeostasis of this organ, and the potential assessment methodologies used in research and in some cases in clinical practice.

Biliverdin Rescues the HO-2 Null Mouse Phenotype of Unresolved Chronic Inflammation Following Corneal Epithelial Injury

PURPOSE. The heme oxygenase system (HO-1 and HO-2) represents an intrinsic cytoprotective and anti-inflammatory pathway based on its ability to modulate leukocyte migration and to inhibit the expression of inflammatory cytokines and proteins by its products biliverdin/bilirubin and carbon monoxide. Corneal injury in HO-2 null mice leads to impaired healing and chronic inflammatory complications, including ulceration and neovascularization. The authors examined whether topically administered biliverdin can counteract the effects of HO deficiency in a corneal epithelial injury model. METHODS. HO-2 null mice were treated with biliverdin 1 hour before epithelial injury and twice a day thereafter. Reepithelialization and neovascularization were assessed by fluorescein staining and vital microscopy, respectively, and were quantified by image analysis. Inflammation was quantified by histology and Gr-1-specific immunofluorescence, and oxidative stress was assessed by DHE fluorescence. RESULTS. Treatment with biliverdin accelerated wound closure, inhibited neovascularization and reduced epithelial defects. It also reduced inflammation, as evidenced by a reduction in the appearance of inflammatory cells and the expression levels of inflammatory and oxidant proteins, including KC and NOXs. CONCLUSIONS. The results clearly show that biliverdin, directly or through its metabolism to bilirubin by biliverdin reductase-the expression of which is increased after injury-rescues the aberrant inflammatory phenotype, further underscoring the importance of the HO system in the cornea for the execution of an ordered inflammatory and reparative response.

Age-related gene response of human corneal endothelium to oxidative stress and DNA damage

PURPOSE

Nuclear oxidative DNA damage increases with age in human corneal endothelial cells (HCECs) and contributes to their decreased proliferative capacity. These studies investigated whether HCECs respond to this damage by upregulating their expression of oxidative stress and DNA damage-signaling genes in an age-dependent manner.

METHODS

HCECs were dissected from the corneas of young (30 years and younger) and older (50 years and older) donors. Total RNA was isolated and reverse-transcribed. Oxidative stress and DNA damage-signaling gene expression were analyzed using commercial PCR-based microarrays. Western blot analyses were conducted on selected proteins to verify the microarray results. Nuclear DNA damage foci were detected in the endothelium of ex vivo corneas by immunostaining for H2AX-Ser139.

RESULTS

Four of 84 genes showed a statistically significant age-related difference in the expression of oxidative stress-related genes; however, Western blot analysis demonstrated an age-related increase in only 2 (cytoglobin and GPX-1) of 11 proteins tested. No age-related differences were detected in the expression of DNA damage-signaling genes. Western blot analysis of seven DNA damage-related proteins verified this finding. Intense nuclear staining of DNA damage foci was observed in nuclei within the central endothelium of older donors. Central endothelium from young donors consistently showed a low level of positive staining.

CONCLUSIONS

HCECs respond to age-related increases in oxidative nuclear DNA damage by forming DNA damage repair foci; however, they do not vigorously defend against or repair this damage by upregulating the expression of multiple oxidative stress or DNA damage-signaling genes.

Emerging role of antioxidants in the protection of uveitis complications

Current understanding of the role of oxidative stress in ocular inflammatory diseases indicates that antioxidant therapy may be important to optimize the treatment. Recently investigated antioxidant therapies for ocular inflammatory diseases include various vitamins, plant products and reactive oxygen species scavengers. Oxidative stress plays a causative role in both non-infectious and infectious uveitis complications, and novel strategies to diminish tissue damage and dysfunction with antioxidant therapy may ameliorate visual complications. Preclinical studies with experimental animals and cultured cells demonstrate significant anti-inflammatory effects of a number of promising antioxidant agents. Many of these antioxidants are under clinical trial for various inflammatory diseases other than uveitis such as cardiovascular, rheumatoid arthritis and cancer. Well planned interventional clinical studies in the field of ocular inflammation will be necessary to sufficiently investigate the potential medical benefits of antioxidant therapies for uveitis. This review summarizes the recent investigations of novel antioxidant agents for ocular inflammation, with selected studies focused on uveitis.

Biogerontology in the Czech Republic

Authors provide results of their review of research in the field of biogerontology. Despite the fact that the term "biogerontology" is not commonly used in Czech scientific practice, there have been many research efforts in this field. Up to present, the Czech research teams have focused on the theoretical and biological models of ageing, its immunological aspects, the risk factors of unsuccessfull human ageing, and also metabolic and nutritional factors. Many research teams are dealing with the mechanisms of the neurodegeneration. The authors conclude that better coordination and systematic funding of research in gerontology is needed because of the actual demographic challenges.

Aging decreases expression and activity of glutathione peroxidase-1 in human endothelial progenitor cells

The mechanisms underlying effects of aging on functions of pro-angiogenic endothelial progenitor cells (EPCs) are poorly understood. Previous studies demonstrated that human EPCs express high levels of antioxidant enzymes as compared to mature endothelial cells. Here, we hypothesized that aging impairs antioxidant capacity of EPCs. So called "early EPCs" derived from cultured blood mononuclear cells were obtained from healthy young (average=24 years old) and old (average=72 years old) subjects. In EPCs of old subjects, the levels of glutathione peroxidase-1 (GPX1) protein and enzymatic activity were significantly reduced. The serum selenium levels in young and old subjects were not significantly different. Increasing selenium concentration in the cell culture also did not affect the protein levels of GPX1, suggesting the reduced GPX1 in old subject's EPCs is selenium independent. Expressions of catalase, Mn-superoxide dismutase (MnSOD), and CuZnSOD were not affected by aging. EPCs of old subjects were more sensitive to oxidative stress induced by H(2)O(2) as compared with EPCs of young subjects, suggesting that impairment of GPX1 during aging may contribute to low survival ability of EPCs in response to oxidative stress. The results indicate that GPX1 may represent a potential therapeutic target for enhancement of regenerative capacity of EPCs in old subjects.

Age-accelerated atherosclerosis correlates with failure to upregulate antioxidant genes

Excess food intake leads to obesity and diabetes, both of which are well-known independent risk factors for atherosclerosis, and both of which are growing epidemics in an aging population. We hypothesized that aging enhances the metabolic and vascular effects of high fat diet (HFD) and therefore examined the effect of age on atherosclerosis and insulin resistance in lipoprotein receptor knockout (LDLR(-/-)) mice. We found that 12-month-old (middle-aged) LDLR(-/-) mice developed substantially worse metabolic syndrome, diabetes, and atherosclerosis than 3-month-old (young) LDLR(-/-) mice when both were fed HFD for 3 months, despite similar elevations in total cholesterol levels. Microarray analyses were performed to analyze the mechanism responsible for the marked acceleration of atherosclerosis in middle-aged mice. Chow-fed middle-aged mice had greater aortic expression of multiple antioxidant genes than chow-fed young mice, including glutathione peroxidase-1 and -4, catalase, superoxide dismutase-2, and uncoupling protein-2. Aortic expression of these enzymes markedly increased in young mice fed HFD but decreased or only modestly increased in middle-aged mice fed HFD, despite the fact that systemic oxidative stress and vascular reactive oxygen species generation, measured by plasma F2alpha isoprostane concentration (systemic) and dihydroethidium conversion and p47phox expression (vascular), were greater in middle-aged mice fed HFD. Thus, the mechanism for the accelerated vascular injury in older LDLR(-/-) mice was likely the profound inability to mount an antioxidant response. This effect was related to a decrease in vascular expression of 2 key transcriptional pathways regulating the antioxidant response, DJ-1 and forkhead box, subgroup O family (FOXOs). Treatment of middle-aged mice fed HFD with the antioxidant apocynin attenuated atherosclerosis, whereas treatment with the insulin sensitizer rosiglitazone attenuated both metabolic syndrome and atherosclerosis. Both treatments decreased oxidative stress. A novel effect of rosiglitazone was to increase expression of Nrf2 (nuclear factor [erythroid-derived 2]-like 2), a downstream target of DJ-1 contributing to enhanced expression of vascular antioxidant enzymes. This investigation underscores the role of oxidative stress when multiple atherosclerotic risk factors, particularly aging, converge on the vessel wall and emphasizes the need to develop effective strategies to inhibit oxidative stress to protect aging vasculature.

Oxidative stress in diseases of the human cornea

Intense exposure to light, robust metabolic activity, and high oxygen tension render the human eye particularly vulnerable to oxidative damage and the list of ophthalmological disorders implicating reactive oxygen and nitrogen species is rapidly expanding. Here, we review the roles of oxidative stress in the etiopathogeneses and pathophysiology of diseases of the human cornea including pterygium, keratoconus, trauma and chemical injury, and a host of inflammatory, metabolic, degenerative, and iatrogenic conditions. Data from animal and tissue culture experimentation germane to these conditions are also adduced.

Effects of Vitamin E, Pentoxifylline and Aprotinin on Light-Induced Retinal Injury

PURPOSE

A considerable amount of clinical and experimental evidence exists suggesting the involvement of reactive oxygen species (ROS) in the etiology of light-induced retinal injury. The aim of this study was to investigate the protective role of vitamin E, pentoxifylline (PTX) and aprotinin against light-induced retinal injury in guinea pigs.

METHODS

Thirty adult male guinea pigs were divided into 5 groups of 6 animals each. The first group was used as control. The guinea pigs were kept in cyclic light for 2 weeks before the experiments. The animals were maintained in 12-hour light-dark cycles, before and after exposure to intense white fluorescent light, for as long as 12 h and then returned to cyclic light. Groups 3-5 received intraperitoneal injections of vitamin E, PTX and aprotinin, respectively. One eye of each animal was selected for histopathological evaluation and the other for biochemical assay. Retinal malondialdehyde (MDA) levels and the thickness of the outer nuclear layers were measured.

RESULTS

The compounds had the following relationships: vitamin E more than PTX more than aprotinin in preventing light-induced retinal damage. All 3 gave significant protection against the formation of MDA. Retinas of all 3 treatment groups had been protected from light-induced injury.

CONCLUSION

The intraperitoneal vitamin E, PTX and aprotinin supplementations may strengthen the antioxidant defense system because of decreased ROS, and these agents may play a role in treating light-induced retinal injury.

Cytoprotective effect against UV-induced DNA damage and oxidative stress: Role of new biological UV filter

The majority of chemical solar filters are cytotoxic, particularly on sensitive ocular cells (corneal and conjunctival cells). Consequently, a non-cytotoxic UV filter would be interesting in dermatology, but more especially in ophthalmology. In fact, light damage to the eye can be avoided thanks to a very efficient ocular antioxidant system; indeed, the chromophores absorb light and dissipate its energy. After middle age, a decrease in the production of antioxidants and antioxidative enzymes appears with accumulation of endogenous molecules that are phototoxic. UV radiations can induce reactive oxygen species formation, leading to various ocular diseases. Because most UV filters are cytotoxic for the eye, we investigated the anti-UV properties of Calophyllum inophyllum oil in order to propose it as a potential vehicle, free of toxicity, with a natural UV filter action in ophthalmic formulation. Calophyllum inophyllum oil, even at low concentration (1/10,000, v/v), exhibited significant UV absorption properties (maximum at 300nm) and was associated with an important sun protection factor (18-22). Oil concentrations up to 1% were not cytotoxic on human conjunctival epithelial cells, and Calophyllum inophyllum oil appeared to act as a cytoprotective agent against oxidative stress and DNA damage (85% of the DNA damage induced by UV radiations were inhibited with 1% Calophyllum oil) and did not induce in vivo ocular irritation (Draize test on New Zealand rabbits). Calophyllum inophyllum oil thus exhibited antioxidant and cytoprotective properties, and therefore might serve, for the first time, as a natural UV filter in ophthalmic preparations.

Differential expressions of antioxidant status in aging rats: the role of transcriptional factor Nrf2 and MAPK signaling pathway

Antioxidant enzymes (AOEs) play an important role in the protection of cells against reactive oxygen species and facilitate the prevention of oxidative stress-induced aging. In the present study, the antioxidant indices, including the content of peroxidation product and the expression of AOEs in rat livers of varying ages (2, 12 and 18-24 months old) were evaluated. Erythrocytes haemolysis induced by free radicals showed significant age-dependent increases (P < 0.05). The content of oxidation products in livers showed that increasing age was associated with serious oxidative injury. The activities of AOEs decreased with increasing age. Expression of the antioxidant and age-related gene, klotho, decreased with increasing age. Western blot assay showed that aged rats experience higher levels of oxidative stress. Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) exhibited an age-dependent decrease. Additionally, the mitogen-activated protein kinase cascade (MAPK) played a regulatory role in signaling transduction. Overall, we suggest that age-related declines of the antioxidant defense are closely involved with the expression of Nrf2 and are regulated by the MAPK family.

Cataract surgery in Fuchs?? dystrophy

PURPOSE OF REVIEW

Corneal decompensation after cataract surgery can occur in patients with Fuchs' endothelial dystrophy. This paper reviews the pathogenesis of corneal edema in Fuchs' dystrophy, the preoperative and perioperative risk factors for corneal endothelial cell loss during cataract surgery, and indications for cataract surgery alone or cataract surgery combined with keratoplasty for patients with visually significant cataracts and Fuchs' dystrophy.

RECENT FINDINGS

Accelerated loss of corneal endothelial cells in Fuchs' dystrophy is multifactorial, with apoptosis and altered gene regulation of aquaporin proteins playing a role. Preoperative factors contributing to decreased endothelial cell count include age, sex, diabetes, a history of ocular trauma or inflammation, and contact lens wear. Intra-operative measures shown to protect endothelial cells include the use of the soft-shell viscoelastic technique for very dense cataracts, efficient cataract removal techniques (phaco-chop, use of oscillatory handpiece), and surgery by an experienced surgeon. A triple procedure should be performed with preoperative corneal epithelial decompensation and considered with preoperative pachymetry greater than 640 mum. Otherwise, it is reasonable to attempt cataract surgery alone with proper patient education.

SUMMARY

Fuchs' dystrophy is a progressive disorder. Cataract surgery in the setting of Fuchs' dystrophy can be performed successfully, especially when the surgeon is aware of the preoperative and intraoperative factors that affect the number of functioning endothelial cells. All patients should be aware of the progressive nature of this disease and the possibility of keratoplasty at some point in their lifetime.