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

Lens Densitometry after Corneal Cross-linking in Patients with Keratoconus Using a Scheimpflug Camera

PURPOSE

To evaluate changes in crystalline lens densitometry following corneal cross-linking (CXL) in keratoconic patients.

METHODS

In a quasi-experimental study, three-dimensional lens densitometry was performed using the Pentacam Scheimpflug camera (Oculus Optikgerate GmbH, Wetzlar, Germany) at baseline and six months after CXL. Densitometry was performed in a fixed area of 2 inch × 1 inch of the anterior capsule and anterior lens cortex. The subject group included patients with progressive keratoconus who underwent CXL (n = 40) and the control group was comprised of aged-matched patients with non-progressive keratoconus (n = 36).

RESULTS

Mean age of the case and control groups was 25.8 ± 4.0 and 25.0 ± 4.1 years, respectively (P = 0.392). Mean lens density in the CXL group was 6.68% ± 0.58% at baseline and 6.77% ± 0.53% at the last visit (P = 0.352). Corresponding figures in the control group were 6.53% ± 0.27% and 6.39% ± 0.31%, respectively (P = 0.213). There was no significant difference between the study groups at baseline or six months later (P = 0.96).

CONCLUSION

In this short term study with six months' follow-up, we observed no significant impact on lens density following exposure of the crystalline lens to ultraviolet A and riboflavin free radicals in the CXL procedure.

Light, lipids and photoreceptor survival: live or let die?

Due to its constant exposure to light and its high oxygen consumption the retina is highly sensitive to oxidative damage, which is a common factor in inducing the death of photoreceptors after light damage or in inherited retinal degenerations. The high content of docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, has been suggested to contribute to this sensitivity. DHA is crucial for developing and preserving normal visual function. However, further roles of DHA in the retina are still controversial. Current data support that it can tilt the scale either towards degeneration or survival of retinal cells. DHA peroxidation products can be deleterious to the retina and might lead to retinal degeneration. However, DHA has also been shown to act as, or to be the source of, a survival molecule that protects photoreceptors and retinal pigment epithelium cells from oxidative damage. We have established that DHA protects photoreceptors from oxidative stress-induced apoptosis and promotes their differentiation in vitro. DHA activates the retinoid X receptor (RXR) and the ERK/MAPK pathway, thus regulating the expression of anti and pro-apoptotic proteins. It also orchestrates a diversity of signaling pathways, modulating enzymatic pathways that control the sphingolipid metabolism and activate antioxidant defense mechanisms to promote photoreceptor survival and development. A deeper comprehension of DHA signaling pathways and context-dependent behavior is required to understand its dual functions in retinal physiology.

Clinical analysis of risk factors contributing to recurrence of pterygium after excision and graft surgery

AIM

To find the risk factors related to the reproliferation of the pterygial tissue after excision and graft surgery.

METHODS

Charts of 130 eyes of 130 patients who had pterygial excision from March 2006 to April 2011 were reviewed. Preoperative pterygium morphology, surgical methods, and adjunctive treatments were statistically analyzed for their relationship with recurrence.

RESULTS

During the follow-up period, recurrence was observed in 20 eyes (15.4%). None of the preoperative morphologic features were affected the rate of the recurrence. However, an age < 40y [P =0.085, odds ratio (OR) 3.609, 95% confidence interval (CI) 0.838-15.540] and amniotic membrane graft instead of conjunctival autograft (P =0.002, OR 9.093, 95% CI 2.316-35.698) were statistically significant risk factors for recurrence. Multivariate analysis revealed that intraoperative mitomycin C (MMC) (P=0.072, OR 0.298, 95% CI 0.080-1.115) decreased the rate of recurrence.

CONCLUSION

Younger age is a risk factor for reproliferation of pterygial tissue after excision and amniotic membrane transplantation (AMT) are less effective in preventing recurrence of pterygium after excision based on the comparison between conjunctival autograft and AMT. Intraoperative MMC application and conjunctival autograft reduce recurrence.

Helicobacter pylori infection and eye diseases: a systematic review

The connection between Helicobacter pylori (Hp) infection and eye diseases has been increasingly reported in the literature and in active research. The implication of this bacterium in chronic eye diseases, such as blepharitis, glaucoma, central serous chorioretinopathy and others, has been hypothesized. Although the mechanisms by which this association occurs are currently unknown, this review describes shared pathogenetic mechanisms in an attempt to identify a lowest common denominator between eye diseases and Hp infection. The aim of this review is to assess whether different studies could be compared and to establish whether or not Hp infection and Eye diseases share common pathogenetic aspects. In particular, it has been focused on oxidative damage as a possible link between these pathologies. Text word search in Medline from 1998 to July 2014. 152 studies were included in our review. Were taken into considerations only studies that related eye diseases more frequent and/or known. Likely oxidative stress plays a key role. All of the diseases studied seem to follow a common pattern that implicates a cellular response correlated with a sublethal dose of oxidative stress. These alterations seem to be shared by both Hp infections and ocular diseases and include the following: decline in mitochondrial function, increases in the rate of reactive oxygen species production, accumulation of mitochondrial DNA mutations, increases in the levels of oxidative damage to DNA, proteins and lipids, and decreases in the capacity to degrade oxidatively damaged proteins and other macromolecules. This cascade of events appears to repeat itself in different diseases, regardless of the identity of the affected tissue. The trabecular meshwork, conjunctiva, and retina can each show how oxidative stress may acts as a common disease effector as the Helicobacter infection spreads, supported by the increased oxidative damage and other inflammation.

Oxidant/antioxidant state in tissue of prymary and recurrent pterygium

BACKGROUND

Pterygium is a disorder of the ocular surface induced by chronic exposure to UV-light. Abundant data is available from patients with primary pterygium, but scarce from those with recurrent pterygium. The present study aimed to explore the oxidant/antioxidant status in tissue of primary and recurrent pterigium in men and women.

METHODS

Pathological tissue samples were taken during surgery on patients with primary and recurrent pterygium. Healthy conjunctive tissue samples were taken during cataract surgery. After homogenization of 77 tissue samples, evaluation was made of thiobarbituric reactive substances (TBARS), nitric oxide (NO), total antioxidant status (TAS) and the activity of the three main antioxidant enzymes: glutathione peroxidase, superoxide dismutase and catalase. Gender differences were evaluated.

RESULTS

Compared to the control group, in the primary pterygium group there was an increase in NO and TAS, and a tendency to a decrease of all antioxidant enzymes, indicating an increase in non-enzymatic antioxidant activity. Compared to the control group, in the recurrent pterygium group there was a significant decrease in the level of TAS and antioxidant enzymes. A high positive correlation was found between most of measured parameters within the control group and the recurrent pterygium group, but not within the primary pterygium group. Compared to men, a significant difference was observed in the elevated NO level and low TAS level of women in the prymary pterygium group.

CONCLUSIONS

The diminished antioxidant defense in the recurrent pterygium group, possibly determined mainly by decreased non-enzymatic activity, supports the idea that oxidative stress plays an important role in the recurrence of this disorder.

Human retinal transmitochondrial cybrids with J or H mtDNA haplogroups respond differently to ultraviolet radiation: implications for retinal diseases

Background

It has been recognized that cells do not respond equally to ultraviolet (UV) radiation but it is not clear whether this is due to genetic, biochemical or structural differences of the cells. We have a novel cybrid (cytoplasmic hybrids) model that allows us to analyze the contribution of mitochondrial DNA (mtDNA) to cellular response after exposure to sub-lethal dose of UV. mtDNA can be classified into haplogroups as defined by accumulations of specific single nucleotide polymorphisms (SNPs). Recent studies have shown that J haplogroup is high risk for age-related macular degeneration while the H haplogroup is protective. This study investigates gene expression responses in J cybrids versus H cybrids after exposure to sub-lethal doses of UV-radiation.

Methodology/Principal Findings

Cybrids were created by fusing platelets isolated from subjects with either H (n = 3) or J (n = 3) haplogroups with mitochondria-free (Rho⁰) ARPE-19 cells. The H and J cybrids were cultured for 24 hours, treated with 10 mJ of UV-radiation and cultured for an additional 120 hours. Untreated and treated cybrids were analyzed for growth rates and gene expression profiles. The UV-treated and untreated J cybrids had higher growth rates compared to H cybrids. Before treatment, J cybrids showed lower expression levels for CFH, CD55, IL-33, TGF-A, EFEMP-1, RARA, BCL2L13 and BBC3. At 120 hours after UV-treatment, the J cybrids had decreased CFH, RARA and BBC3 levels but increased CD55, IL-33 and EFEMP-1 compared to UV-treated H cybrids.

Conclusion/Significance

In cells with identical nuclei, the cellular response to sub-lethal UV-radiation is mediated in part by the mtDNA haplogroup. This supports the hypothesis that differences in growth rates and expression levels of complement, inflammation and apoptosis genes may result from population-specific, hereditary SNP variations in mtDNA. Therefore, when analyzing UV-induced damage in tissues, the mtDNA haplogroup background may be important to consider.

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.

Reactive oxygen species activated NLRP3 inflammasomes prime environment-induced murine dry eye

Tear film hyperosmolarity along with exposure to oxidant stress are factors that can induce chronic ocular surface inflammation and pain. However, there is limited information on how increases in reactive oxygen species (ROS) generated by oxidant exposure can induce inflammation. There is emerging evidence in other tissues that innate immune responses to a variety of environmental stresses stem from ROS-induced cytosolic NLRP3 inflammasome activation. Once this occurs, pro-caspase-1 is converted into its catalytic active form, which in turn cleaves pro-IL-1β thereby generating its bioactive form. We determined the role of ROS generation in mediating increases in IL-1β secretion through caspase-1 activation caused by NLRP3 inflammasome activation in an environment-induced murine dry eye (DE) model. An intelligently controlled environmental system (ICES) induced evaporative DE in female 4-6 week old C57BL/6J mice. Increases in ROS production preceded rises in corneal and conjunctival gene expression of NLRP3 inflammasome components and IL-1β that were identified using real-time PCR. Confocal microscopy evaluated concomitant increases in NLPR3, caspase-1 and IL-1β immunostaining. Increases in caspase-1 activity were used as an indicator of inflammasome activation. Rises in ROS generation occurred after 1 week of ICES exposure, which preceded increases in gene expression of three NLRP3 inflammasome components (i.e. NLRP3, ASC and caspase-1) leading to rises in bioactive IL-1β release. Increases in caspase-1 activity occurred after 2 weeks of ICES exposure. Eyedrops containing 0.3% N-acetyl-l-cysteine (NAC) were applied to quench ROS generation by mice kept in the ICES for 2 weeks. This scavenger reduced corneal fluorescein staining and decreased ROS production. NAC also down-regulated both increases in NLRP3, ASC, caspase-1 and IL-1β mRNA levels, along with their immunostaining. It robustly attenuated rises in inflammasome mediated increases in caspase-1 catalytic activity. We show in a dessicating DE disease murine model that rises in ROS generation trigger NLRP3 inflammasome complexation and activation leading to increases in bioactive IL-1β secretion. These results prompt us to suggest that the ROS-NLRP3-IL-1β signaling pathway might play a priming role in environment-induced DE progression. Finally, our findings provide a basis for developing novel strategies that may improve the management of patients requiring treatment for environment-induced dry eye disease.

Effects of eye drops containing a mixture of omega-3 essential fatty acids and hyaluronic acid on the ocular surface in desiccating stress-induced murine dry eye

PURPOSE

To investigate the efficacy of the topical application of omega-3 essential fatty acids (EFAs) and hyaluronic acid (HA) mixtures in a mouse model of experimental dry eye (EDE).

METHODS

Eye drops consisting of 0.1% HA, 0.02%, or 0.2% omega-3 EFAs alone and mixture of 0.02%, or 0.2% omega-3 EFAs and 0.1% HA were applied in desiccating stress-induced murine dry eye. Corneal irregularity scores and fluorescein staining scores were measured 5 and 10 days after treatment. Levels of interleukin (IL)-1β, -17, and interferon gamma-induced protein (IP)-10 were measured in the conjunctiva at 10 days using a multiplex immunobead assay. The concentrations of hexanoyl-lys (HEL) and 4-hydroxynonenal (4-HNE) in conjunctiva tissue were measured with enzyme-linked immunosorbent assays.

RESULTS

Mice treated with the mixture containing 0.2% omega-3 EFAs showed a significant improvement in corneal irregularity scores and corneal fluorescein staining scores compared with EDE, HA, 0.02% or 0.2% omega-3 EFAs alone, and 0.02% omega-3 EFAs mixture-treated mice. A significant decrease in the levels of IL-1β, -17, and IP-10 were observed in the 0.2% EFAs mixture-treated group, compared with the other groups. In the mice treated with the mixture containing 0.2% omega-3 EFAs, the concentration of 4-HNE was also lower than the other groups. Although 0.2% omega-3 EFAs alone group also had a significant improvement in corneal irregularity scores and IL-17, IL-10, and 4 HNE levels compared with the other groups, the efficacy was lower than 0.2% omega-3 mixture group.

CONCLUSIONS

Topically applied eye drops containing a mixture of omega-3 EFAs and HA could improve corneal irregularity and corneal epithelial barrier disruption, and decrease inflammatory cytokines and oxidative stress markers on the ocular surface. Topical omega-3 EFAs and HA mixture may have a greater therapeutic effect on clinical signs and inflammation of dry eye compared with HA artificial tears.