Eales' disease: oxidant stress and weak antioxidant defence

Oxidative Stress Implication in Retinal Diseases-A Review

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

To Study the Role of Serum Homocysteine Levels and Ocular Involvement in Retinal Vasculitis

Idiopathic retinal vasculitis is a chronic disease of unknown aetiology which results in ocular morbidity in patients of productive age group. Homocysteine has been implicated in various ocular conditions like age-related macular degeneration, retinal vein occlusions, diabetic retinopathy, and optic nerve diseases. We conducted a study to investigate the relation between serum homocysteine levels and retinal vasculitis at a tertiary care centre in North India. In this case-control study, 32 cases and 64 controls were included and the duration was from June 2017 to March 2019. Serum homocysteine of cases and controls was detected by reflectance photometry using VITROS Chemistry Products HCY 2 (Homocysteine) and the normal range of serum homocysteine as per this method was 6.60 to 14.80 micro mol per litre. Our study found that of the total 32 retinal vasculitis patients, serum homocysteine was raised in 65.62% (21 cases out of 32) and in 70.31% of control group (45 out of 64). Chi square test results showed that there was no significant association found between S. homocysteine levels and Reticular vasculitis (P: 0.64). The two groups were comparable in terms of the age with mean ± SD in cases being 33.47 ± 8.336 years and controls being 35.16 ± 8.568 years with a P value of 0.37 being statistically insignificant. The data collected was analysed using SSPS-16 (Statistical Package for Social Sciences Version 16) software and test of association was Odd's ratio. Power of study was 80% and P < 0.05 is considered statistically significant. We found that there is no significant association between raised serum homocysteine and retinal vasculitis (with P < 0.64). Odds ratio was 0.80(0.33-1.99) implying that the cases and controls were statistically significantly different with respect to homocysteine levels.

Localization of Human Copper Transporter 1 in the Eye and its Role in Eales Disease

PURPOSE

Copper (Cu) is an essential trace element; however excess is toxic due to the pro-oxidant activity. Increased intracellular Cu levels in vitreous and monocyte were reported in Eales disease (ED) previously. Copper transporter1 (CTR1) maintains copper homeostasis and hence, we studied the presence of CTR1 in ocular tissues and its role in ED.

METHODS

Real-time PCR, ELISA and Western blot experiments were performed in donor eyeballs tissues and PBMCs isolated from controls and ED. Immunostaining were performed for CTR1 from donor eyeballs and one ED case.

RESULTS

CTR1 protein was expressed in all ocular tissues. PBMCs showed a three-fold increase in CTR1 protein in ED when compared with controls. Retinal sections from ED patients also revealed increased CTR1 protein expression in retinal tissues, compared with control.

CONCLUSIONS

CTR1 was significantly increased in ED when compared with controls, indicating its considerable role in the ED pathology.

Increased homocysteine, homocysteine-thiolactone, protein homocysteinylation and oxidative stress in the circulation of patients with Eales' disease

BACKGROUND

Eales' disease (ED) is an idiopathic retinal vascular disorder. It presents with inflammation and neovascularization in the retina. Adult men, aged between 15 and 40 years are more susceptible than women. Homocysteine has been implicated in other ocular diseases including age-related macular degeneration (ARMD), central retinal vein occlusion (CRVO) and optic neuropathy. The present study investigates the role of homocysteine in ED.

METHODS

Forty male subjects, 20 with ED and 20 healthy controls, were recruited to the study. Their blood samples were used to measure thiobarbituric acid reactive substances (TBARS), glutathione (GSH), homocysteine, homocysteine-thiolactone, extent of homocysteine conjugation with proteins and plasma copper concentration.

RESULTS

In the ED group, plasma homocysteine (18.6 ± 1.77 µmol/L, P < 0.001) and homocysteine-thiolactone (45.3 ± 6.8 nmol/L, P < 0.0001) concentrations were significantly higher compared to homocysteine (11.2 ± 0.64 µmol/L) and homocysteine-thiolactone (7.1 ± 0.94 nmol/L) concentrations in control subjects. TBARS (P < 0.011) and protein homocysteinylation (P < 0.030) were higher in the ED group while GSH (5.9 ± 0.44 µmol/L, P < 0.01) and copper (6.6 ± 0.42 µmol/L, P < 0.001) were lower compared to GSH (8.1 ± 0.41 µmol/L) and copper (15.4 ± 0.73 µmol/L) concentrations in control subjects.

CONCLUSIONS

Increased homocysteine, and its metabolite thiolactone, is associated with the functional impairment of protein due to homocysteinylation in ED.

Angiogenic activity of sera from pulmonary tuberculosis patients in relation to IL-12p40 and TNFα serum levels

The role of angiogenesis in the pathogenesis of tuberculosis (TB) is not clear. The aim of this study was to examine the effect of sera from TB patients on angiogenesis induced by different subsets of normal human mononuclear cells (MNC) in relation to IL-12p40 and TNFα serum levels. Serum samples from 36 pulmonary TB patients and from 22 healthy volunteers were evaluated. To assess angiogenic reaction the leukocytes-induced angiogenesis test according to Sidky and Auerbach was performed. IL-12p40 and TNFα serum levels were evaluated by ELISA. Sera from TB patients significantly stimulated angiogenic activity of MNC compared to sera from healthy donors and PBS (p < 0.001). The number of microvessels formed after injection of lymphocytes preincubated with sera from TB patients was significantly lower compared to the number of microvessels created after injection of MNC preincubated with the same sera (p < 0.016). However, the number of microvessels created after the injection of lymphocytes preincubated with sera from healthy donors or with PBS alone was significantly higher (p < 0.017). The mean levels of IL-12p40 and TNFα were significantly elevated in sera from TB patients compared to healthy donors. We observed a correlation between angiogenic activity of sera from TB patients and IL-12p40 and TNFα serum levels (p < 0.01). Sera from TB patients constitute a source of mediators that participate in angiogenesis and prime monocytes for production of proangiogenic factors. The main proangiogenic effect of TB patients’ sera is mediated by macrophages/monocytes. TNFα and IL-12p40 may indirectly stimulate angiogenesis in TB.

Antioxidant supplementation improves platelet membrane fluidity in idiopathic retinal periphlebitis (Eales' disease)

PURPOSE

Oxidative damage to cellular membranes plays an important role in the pathobiology of tissue injury. Retinal photoreceptors and platelets are an easy target of oxidants because of high proportion of polyunsaturated fatty acids. A tertiary-care center-based prospective study was undertaken to study the effect of antioxidant supplementation over membrane fluidity in platelets in idiopathic retinal periphlebitis (Eales' disease) for the first time.

METHODS

Assay of thiobarbituric acid reactive substances (TBARS) levels was done following a standard protocol and membrane fluidity in platelets was estimated using a fluorescent probe, 1,6-diphenyl-1,3,5-hexatrience, in 15 cases and 12 healthy controls. Prednisolone (1 mg/kg) in a weekly tapering dose for 6 weeks and a commercially available antioxidant preparation [lutein 3.2 mg (containing zeaxanthin 256 mcg), L-glutathione 5 mg, vitamin E 15 IU, vitamin C 150 mg, zinc 40 mg, copper 2 mg, selenium 40 mcg, and manganese 5 mg] was administered once a day for 3 months to all the cases. Pre- and postantioxidant supplementation platelet TBARS and membrane fluidity levels were assessed in all the cases.

RESULTS

Significant increase was observed in TBARS levels in the cases when compared with controls (P = 0.01). Platelet fluorescence polarization was significantly higher in cases, indicating decreased membrane fluidity, when compared with controls (P = 0.005). Antioxidant supplementation led to marked decrease in TBARS levels (P = 0.01) and improved levels of platelet membrane fluidity (P = 0.001).

CONCLUSION

Antioxidant supplementation leads to significant decrease in oxidative stress and a significant improvement in platelet membrane fluidity, thereby helping to prevent retinal photoreceptor dysfunction.

Prediction of diabetic retinopathy: role of oxidative stress and relevance of apoptotic biomarkers

Diabetic retinopathy (DR) is the foremost cause of blindness in working-aged worldwide; it is characterized by vascular and neuronal degeneration. Features of DR include leukocyte adhesion, increased vascular permeability, neovascularization and neuronal cell death. Early diagnosis and intervention are important to prevent or at least ameliorate the development of DR. Recent reports indicate that pathophysiological mechanisms leading to diabetic retinopathy include oxidative stress and retinal cell death cascades. Circulating biomarkers of oxidative stress such as malondialdehyde (MDA), thiobarbituric acid reacting substances (TBARS), conjugated diene (CD), advanced oxidation protein products (AOPP), protein carbonyl, 8-hydroxydeoxyguanosin (8-OHdG), nitrotyrosine, and F(2) isoprostanes and pro-apoptosis molecules (caspase-3, Fas, and Bax) are associated with increased susceptibility to develop DR in diabetic subjects. Thus, identification of oxidative stress and cell death biomarkers in diabetic patients could be in favor of predicting, diagnosis, and prevention of DR, and to target for novel therapeutic interventions.

Ratio of the vitreous vascular endothelial growth factor and pigment epithelial-derived factor in Eales disease

Eales disease (ED) is an idiopathic inflammatory venous occlusion of the peripheral retina. As neovascularization is prominent in ED, this study attempts to look at the ratio of VEGF, the angiogenic factor, and PEDF, an anti-angiogenic factor in the vitreous of ED patients in comparison with the macular hole (MH) and Proliferative Diabetic Retinopathy (PDR). Vitreous levels of VEGF and PEDF were determined in the undiluted vitreous specimen obtained from 26 ED cases, 17 PDR, and seven patients with MH. The vitreous levels of VEGF and PEDF were estimated by ELISA. The immunohistochemistry (IHC) for VEGF and PEDF were done in the epiretinal membrane of ED and PDR case. The VEGF/PEDF ratio was found to be significantly increased in ED (p = 0.014) and PDR (p = 0.000) compared to MH. However the ratio was 3.5-fold higher in PDR than ED (p = 0.009). The IHC data on the ERM specimen from ED showed the presence of VEGF and PEDF similar to PDR. The high angiogenic potential seen as the ratio of VEGF/PEDF correlates with the peak clinical onset of the disease in the age group 21–30 years and the diseases usually self-resolves above the age of 40, which is reflected by the low ratio of VEGF/PEDF. The study shows that the VEGF/PEDF ratio is significantly increased in ED though the angiogenic potential is higher in PDR than in ED. Clinically Eales Disease is known as a self-limiting disease, while PDR is a progressive disease.

Increase in Fe3+/Fe2+ ratio and iron-induced oxidative stress in Eales disease and presence of ferrous iron in circulating transferrin

Eales disease was shown to be associated with oxidant stress and weak antioxidant defense. Total iron, ferrous iron, thiobarbituric acid reactive substances (TBARS), and ceruloplasmin were estimated in the blood samples of patients with inflammation, perivasculitis, and venous insufficiency. Levels of ferric iron were determined from the difference in those of total iron and ferrous iron. All biochemical parameters were estimated in age and sex-matched controls. Fe3+/Fe2+ ratio was greater in patients with Eales disease than in normal controls. Similar increase in TBARS and ceruloplasmin levels were noted. The patients were treated with prednisone and vitamins E and C, then Fe3+/Fe2+ ratios and TBARS decreased progressively; the active state of the disease was reduced to 16%. So Fe3+/Fe2+ ratio in addition to TBARS levels could be considered an index of the active state of the disease. Circulating transferrin in blood did contain ferrous iron. Binding of ferrous iron to transferrin was confirmed by estimating iron-binding capacity using ferrous ammonium sulphate.