Sergio Claudio Saccà

Fluctuations of Intraocular Pressure during the Day in Open-Angle Glaucoma, Normal-Tension Glaucoma and Normal Subjects

Purpose: The aim of the present paper is to describe the variations in intraocular pressure (IOP) during the day in normals, in patients with primary open-angle glaucoma (POAG) and in patients with normal-tension glaucoma (NTG). IOP represents one of the most important risk factors for glaucoma. However the IOP value is not constant during the day and IOP fluctuation could influence the diagnostic and prognostic evaluation of the glaucomatous disease. Methods: For this purpose IOP was evaluated every 2 h from 8 a.m. to 8 p.m. in one randomized eye of 33 normal subjects, 95 POAG and 50 NTG patients. Results: The results show that the highest IOP values were detectable in the morning in all three groups. The lowest values were found in the early afternoon hours. These variations were most evident in POAG patients. The daily IOP fluctuations were directly proportional to IOP level. Conclusion: The study evidents that a single tonometric evaluation, especially if done in the first hours of the afternoon, is not sufficient to correctly evaluate the IOP-related risk in glaucoma patients. If the pressure peaks are important in determining the extent of glaucomatous damage in NTG patients IOP should not have an important role in optic nerve head damage. The use of diurnal curves seems to be mandatory for the assessment of IOP-related risk and of efficiency of the therapeutic approach.

Oxidative stress and glaucoma: injury in the anterior segment of the eye.

The perturbation of the pro-oxidant/antioxidant balance can lead to increased oxidative damage, especially when the first line of antioxidant defense weakens with age. Chronic changes in the composition of factors present in aqueous or vitreous humor may induce alterations both in trabecular cells and in cells of the optic nerve head. Free radicals and reactive oxygen species are able to affect the cellularity of the human trabecular meshwork (HTM). These findings suggest that intraocular pressure increase, which characterizes most glaucomas, is related to oxidative and degenerative processes affecting the HTM and, more specifically, its endothelial cells. This supports the theory that glaucomatous damage is the pathophysiological consequence of oxidative stress. Glaucomatous subjects might have a genetic predisposition, rendering them more susceptible to reactive oxygen species-induced damage. It is likely that specific genetic factors contribute to both the elevation of IOP and susceptibility of the optic nerve/retinal ganglion cells (RGCs) to degeneration. Thus, oxidative stress plays a fundamental role during the arising of glaucoma-associated lesions, first in the HTM and then, when the balance between nitric oxide and endothelins is broken, in neuronal cell. Vascular damage and hypoxia, often associated with glaucoma, lead to apoptosis of RGCs and may also contribute to the induction of oxidative damage to the HTM. On the whole, these findings support the hypothesis that oxidative damage is an important step in the pathogenesis of primary open-angle glaucoma and might be a relevant target for both prevention and therapy.

Mitochondrial Damage in the Trabecular Meshwork of Patients With Glaucoma

OBJECTIVES To analyze the frequency of mitochondrial DNA (mtDNA) damage in patients with primary open-angle glaucoma. Oxidative damage plays a major role in glaucoma pathogenesis. Since no environmental risk factor for glaucoma is recognized, we focused our attention on mitochondria, the main endogenous source of reactive oxygen species. METHODS Mitochondrial damage was evaluated analyzing a common mtDNA deletion by real-time polymerase chain reaction in trabecular meshwork collected at surgery from 79 patients with primary open-angle glaucoma and 156 unaffected matched controls. In the same samples, polymorphisms of genes encoding for antioxidant defenses (GSTM1), repair of oxidative DNA damage (OGG1), and apoptosis (FAS) were tested. RESULTS Mitochondrial DNA deletion was dramatically increased (5.32-fold; P = .01) in trabecular meshwork of patients with glaucoma vs controls. This finding was paralleled by a decrease in the number of mitochondria per cell (4.83-fold; P < .001) and by cell loss (16.36-fold; P < .01). Patients with glaucoma bearing the GSTM1-null genotype showed increased amounts of mtDNA deletion and a decreased number of mitochondria per cell as compared with GSTM1-positive subjects. Patients bearing a FAS homozygous mutation showed only a decreased number of mitochondria per cell. CONCLUSIONS Obtained results indicate that mitochondrion is targeted by the glaucomatous pathogenic processes. Some subjects bearing adverse genetic assets are more susceptible to this event. Clinical Relevance Oxidative damage to the trabecular meshwork exerts a pathogenic role in glaucoma inducing mitochondrial damage and triggering apoptosis and cell loss. This issue may be useful to develop new glaucoma molecular biomarkers and to identify high-risk subjects.

Gene-environment interactions in ocular diseases.

Degenerative ocular diseases are widespread in the population and represent a major cause of reversible and irreversible blindness. Scientific evidences have been accumulating supporting the role of genotoxic damage and gene environment interactions in the pathogenesis of these diseases mainly including glaucoma, age-related macular degeneration, and cataract. Glaucoma, in its degenerative form, is characterized by the degeneration of the trabecular meshwork, the tissue of the anterior chamber of the eye devoted to aqueous-humour outflow. Such a degenerative process results in intra-ocular pressure increase and progressive damage of optic nerve head. Oxidative stress and DNA damage play an important role in inducing the degeneration of these well differentiated target tissues in which DNA damage results in a progressive cell loss. Macular degeneration is a common age-related disease affecting the central regions of the retina inducing progressive accumulation of oxidized lipoproteins and neovascularization. Environmental genotoxic risk factors include diet, light, and cigarette smoke paralleled by individual susceptibility as determined by adverse genetic assets. Cataract is a progressive opacity of the crystalline lens resulting from molecular damages induced by various risk factors including UV-containing light. This disease has been related to a failure in antioxidant defences. Experimental study provides evidence that cataract patients possess higher basal level of DNA damage, as evaluated by Comet test, in lymphocytes than controls. This finding is paralleled by the higher susceptibility to oxidative stress observed in the same patients. These novel experimental data further support the role of DNA damage as a main factor contributing to cataract onset. In conclusion, the examined degenerative ocular diseases recognise environmental risk factors often displaying genotoxic attitudes. Whenever these factors target individuals who are susceptible due their genetic assets the results is the onset of a specific eye disease depending on the affected ocular tissue.

New proteins as vascular biomarkers in primary open angle glaucomatous aqueous humor.

PURPOSE The aim of this study was to investigate the expression level of several biomarkers in the in the aqueous humor of 14 patients with primary open angle glaucoma who underwent glaucoma surgery, and 11 nonglaucomatous normals who underwent cataract extraction surgery. METHODS The aqueous humor proteome of 25 patients was analyzed using an antibody microarray. Fourteen patients with uncontrolled intraocular pressure-despite profound therapeutic interventions-who underwent filtering procedures and 11 control subjects who underwent surgery for senile cataracts were included in the present study. Protein expression was evaluated using Cy3/Cy5 labeling, column purification, and hybridization on antibody-spotted glass microarrays. Fluorescent signals were detected by fluorescence laser scanning. RESULTS The levels of 13 proteins were significantly increased in the aqueous humor of glaucomatous patients compared with expression levels in healthy controls. One of the 13 proteins (ELAM 1) was involved in inflammation. Two of these proteins (apolipoprotein B and E) were involved in the delivery of cholesterol to cells. Five of the 13 proteins (myotrophin, myoblast determination protein 1, myogenin, vasodilator-stimulated phosphoprotein, and ankyrin-2) were involved in muscle cell differentiation and function. Three proteins (heat shock 60 kilodaltons (kDa) and 90 kDa proteins, and ubiquitin fusion degradation 1-like) were involved in stress response and the removal of damaged proteins; and two proteins (phospholipase C β and γ) were involved in signal transduction and neural development. CONCLUSIONS The expressions of these proteins in the aqueous humor of glaucomatous patients reflect the damage occurring in anterior chamber endothelia, mainly including the trabecular meshwork, which is the main structure of this ocular segment injured by glaucoma.

Mitochondrial damage in the trabecular meshwork occurs only in primary open-angle glaucoma and in pseudoexfoliative glaucoma.

Background Open-angle glaucoma appears to be induced by the malfunction of the trabecular meshwork cells due to injury induced by oxidative damage and mitochondrial impairment. Here, we report that, in fact, we have detected mitochondrial damage only in primary open-angle glaucoma and pseudo-exfoliation glaucoma, among several glaucoma types compared. Methodology/Principal Findings Mitochondrial damage was evaluated by analyzing the common mitochondrial DNA deletion by real-time PCR in trabecular meshwork specimens collected at surgery from glaucomatous patients and controls. Glaucomatous patients included 38 patients affected by various glaucoma types: primary open-angle, pigmented, juvenile, congenital, pseudoexfoliative, acute, neovascular, and chronic closed-angle glaucoma. As control samples, we used 16 specimens collected from glaucoma-free corneal donors. Only primary open-angle glaucoma (3.0-fold) and pseudoexfoliative glaucoma (6.3-fold) showed significant increases in the amount of mitochondrial DNA deletion. In all other cases, deletion was similar to controls. Conclusions/Significance Despite the fact that the trabecular meshwork is the most important tissue in the physiopathology of aqueous humor outflow in all glaucoma types, the present study provides new information regarding basic physiopathology of this tissue: only in primary open-angle and pseudoexfoliative glaucomas oxidative damage arising from mitochondrial failure play a role in the functional decay of trabecular meshwork.

The dysfunction of the trabecular meshwork during glaucoma course.

Primary open angle glaucoma is a multi‐tissue disease that targets, in an ascending order, the trabecular meshwork, the optic nerve head, the lateral geniculate nuclei, and the visual cortex. Oxidative stress and vascular damage play major roles in triggering apoptotic cell loss in these tissues. Molecular alterations occurring in the ocular anterior chamber during the early course of glaucoma trigger this cell loss. These molecular events are mainly of endogenous origin and related to the long‐term accumulation of oxidative damages arising from mitochondrial failure and endothelial dysfunction. This situation results in decreased antioxidant defences in aqueous humour and apoptosis activation in trabecular meshwork cells as triggered by severe mitochondrial damage altering tissue function and integrity. The presence of neural proteins in glaucomatous aqueous humour indicate that a molecular interconnection exists between the anterior and the posterior chamber tissues. Trabecular meshwork and lamina cribrosa share a common neuro‐ectodermal embryological, which contribute to explain the interconnection between anterior and the posterior chamber during glaucoma pathogenesis. During glaucoma, proteins deriving from the damage occurring in endothelial trabecular meshwork cells are released into aqueous humour. Accordingly, aqueous humour composition is characterised in glaucomatous patients by the presence of proteins deriving from apoptosis activation, mitochondrial damage, loss of intercellular connections, antioxidant decrease. Many questions remain unanswered, but molecular events illuminate TM damage and indicate that trabecular cell protection plays a role in the treatment and prevention of glaucoma. J. Cell. Physiol. 230: 510–525, 2015.

The Outflow Pathway: A Tissue With Morphological and Functional Unity

The trabecular meshwork (TM) plays an important role in high‐tension glaucomas. Indeed, the TM is a true organ, through which the aqueous humor flows from the anterior chamber to Schlemms canal (SC). Until recently, the TM, which is constituted by endothelial‐like cells, was described as a kind of passive filter. In reality, it is much more. The cells delineating the structures of the collagen framework of the TM are endowed with a cytoskeleton, and are thus able to change their shape. These cells also have the ability to secrete the extracellular matrix, which expresses proteins and cytokines, and are capable of phagocytosis and autophagy. The cytoskeleton is attached to the nuclear membrane and can, in millionths of a second, send signals to the nucleus in order to alter the expression of genes in an attempt to adapt to biomechanical insult. Oxidative stress, as happens in aging, has a deleterious effect on the TM, leading eventually to cell decay, tissue malfunction, subclinical inflammation, changes in the extracellular matrix and cytoskeleton, altered motility, reduced outflow facility, and (ultimately) increased IOP. TM failure is the most relevant factor in the cascade of events triggering apoptosis in the inner retinal layers, including ganglion cells. J. Cell. Physiol. 231: 1876–1893, 2016.

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 Fuchs 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.

Glaucoma and Helicobacter pylori infection: correlations and controversies.

A possible association between Helicobacter pylori infection (fig 1) and eye diseases, including Sjögren syndrome, blepharitis, central serous chorioretinopathy and uveitis, has been proposed. Glaucoma is the second leading cause of blindness in the world, after cataracts, and the leading cause of irreversible blindness, but many aspects of its pathogenesis remain unknown. H pylori infection may influence the pathophysiology of glaucoma by releasing various proinflammatory and vasoactive substances, as well as by influencing the apoptotic process, parameters that may also exert their own effects in the induction and/or progression of glaucomatous neuropathy. It is difficult to understand how H pylori infection can be linked to such varied pathologies. Systemic H pylori-induced oxidative damage may be the mechanism which links oxidative stress, H pylori infection and the damage to the trabecular meshwork and optical nerve head that results in glaucoma.