Association of Common Variants in eNOS Gene with Primary Open Angle Glaucoma: A Meta-Analysis

PREDICTING THE OCCURRENCE OF PRIMARY OPEN-ANGLE GLAUCOMA DEPENDING ON THE GENETIC POLYMORPHISM ENDOTHELIAL NO SYNTHASE (NOS3) GENE

OBJECTIVE

The aim: To develop the model for predicting primary open - angle glaucoma (POAG) depending on the presence of the genetic polymorphism in the endothelial NO-synthase (NOS3) gene.

PATIENTS AND METHODS

Materials and methods: The results of genotyping 153 patients (153 eyes) with POAG are included in this investigation. 47 patients were in the control group. Their age was 65,0±13,1 years, duration of disease - 4,9±5,3 years. The polymerase chain reaction was carried out in the patients' blood in the real time mode (Gene Amp® PCR System 7500 amplifier; USA) with the help of the TaqMan Mutation Detection Assays Life-Technology test system (USA). The program Statistica 10 (StatSoft, Inc., USA) was used for mathematical testing of the obtained results.

RESULTS

Results: The regression analysis confirmed the effect of rs1799983 and rs2070744 polymorphisms of the NOS3 gene on the development of POAG. Calculating their specific gravity based on the degree of the impact on the probability of developing the disease showed that rs2070744 - 72.2% had the greater impact than rs1799983 - 38.5%. The regression model of POAG risk depending on the genotypes of the NOS3 gene rs1799983 and rs2070744 polymorphisms was constructed with the satisfactory quality of mathematical prediction (-2log=202.59; χ2=28.91; P<0.001). The value of probability of developing POAG exceeded the limit value (Cut-off=0.8), respectively, OR 4.39 (95% CI 1.00-19.30; P=0.048) and OR 14.15 (95% CI 1.88-106.28; P<0.001) in carriers of the rs1799983 and rs2070744 GT-CC and TT-CC haplotypes.

CONCLUSION

Conclusions: The results of the study proved the importance of risk genotypes (TT rs1799983 and CC rs 2070744) for the development of POAG in patients from the Ukrainian population. It has been shown that the significant increase in the risk of POAG exists for carriers of the GT-CC and TT-CC haplotypes.

The role of polymorphisms rs2070744 and rs1799983 eNOS gene in patients with POAG: a systematic review and meta-analysis

BACKGROUND

Glaucoma is a progressive disease of the optic nerve that has several underlying causes, but in most cases, the cause is unknown. Given the importance of the role of nitric oxide in the occurrence of ocular nerve damage and the effect of eNOS gene polymorphic sites on protein function, to better understand the mechanism of formation of POAG, the relationship between polymorphisms rs2070744 and rs1799983 eNOS gene with POAG risk was investigated in this study using meta-analysis.

METHODS

In this study, systematic review and meta-analysis of study data related to the study of polymorphisms rs2070744 and rs1799983 eNOS gene in patients with POAG using the keywords eNOS, NOS3, Gluuc8898, POAG, primary open-angle glaucoma. It was extracted from SID, MagIran, IranMedex, IranDoc, ScienceDirect, Embase, Scopus, PubMed, Web of Science, and Google Scholar search engines without a time limit until May 2020. To perform the analysis of qualified studies, the model of random effects was used and the inconsistency of studies with the I² index was investigated. Data analysis was performed with Comprehensive Meta-Analysis (Version 2).

RESULTS

In a review of 16 studies (9 studies on polymorphism rs2070744 and seven studies on polymorphism rs1799983) with a sample size of 1631 subjects and a control group of 2405 subjects related to polymorphism rs2070744 and a group of 1456 subjects and a control group of 2240 subjects related to polymorphism 9997 rs1, the odds ratio of TT, CT, and CC genotypes was reported to be 0.95, 1.01, and 1.14, respectively, and the odds ratio of GG, GT and TT genotypes to be 0.88, 0.97, and 1.31, respectively, was reported in patients with POAG.

CONCLUSION

The results of our systematic review and meta-analysis study show that the eNOS gene polymorphisms rs2070744 and rs1799983 may increase the risk of POAG among individuals. However, further studies are needed to confirm these findings.

NADPH oxidase-induced oxidative stress in the eyes of hypertensive rats

Purpose

Increased reactive oxygen species (ROS) released by NADPH oxidase and inflammation are associated with arterial hypertension and eye diseases associated with high blood pressure, including glaucoma, retinopathies (e.g., age-related macular degeneration), and choroidopathies affecting ocular function; however, the mechanisms underlying these adverse outcomes remain undefined. The present study was designed to highlight the importance of oxidative stress in severe hypertension-related eye damage.

Methods

Male Wistar rats (n = 7, unless otherwise specified for specific experiments) were administered an oral dose of 30 mg of Nω-nitro-L-arginine methyl ester (L-NAME) per kilogram of bodyweight and day for 3 weeks; chronic administration with L-NAME is a validated experimental approach resulting in severe hypertension secondary to nitric oxide (NO) depletion and subsequent vasoconstriction in the systemic circulation. Upon treatment completion, histomorphometric studies, NADPH oxidase activity, and ROS production were measured in eyecup homogenates and paraffin-embedded sections from control and L-NAME-treated animals. In addition, immunohistofluorescence, western blotting, and real-time PCR (RT-qPCR) analyses were performed in the eye and the retina to evaluate the expression of i) NADPH oxidase main isoforms (NOX1, NOX2, and NOX4) and subunits (p22phox and p47phox); ii) glial fibrillary acidic protein (GFAP), as a marker of microglial activation in the retina; iii) antioxidant enzymes; and iv) endothelial constitutive (eNOS) and inflammation inducible (iNOS) nitric oxide synthase isoforms, and nitrotyrosine as a versatile biomarker of oxidative stress.

Results

Increased activity of NADPH oxidase and superoxide anion production, accompanied by transcriptional upregulation of this enzyme isoforms, was found in the retina and choroid of the hypertensive rats in comparison with the untreated controls. Histomorphometric analyses revealed a significant reduction in the thickness of the ganglion cell layer and the outer retinal layers in the hypertensive animals, which also showed a positive strong signal of GFAP in the retinal outer segment and plexiform layers. In addition, L-NAME-treated animals presented with upregulation of nitric oxide synthase (including inducible and endothelial isoforms) and abnormally elevated nitrotyrosine levels. Experiments on protein and mRNA expression of antioxidant enzymes revealed depletion of superoxide dismutase and glutathione peroxidase in the eyes of the hypertensive animals; however, glutathione reductase was significantly higher than in the normotensive controls.

Conclusions

The present study demonstrated structural changes in the retinas of the L-NAME-treated hypertensive animals and strengthens the importance of NADPH oxidase as a major ROS-generating enzyme system in the oxidative and inflammatory processes surrounding hypertensive eye diseases. These observations might contribute to unveiling pathogenic mechanisms responsible for developing ocular disturbances in the context of severe hypertension.

ABCA1 Regulates IOP by Modulating Cav1/eNOS/NO Signaling Pathway

Purpose

This study aimed to investigate the role and pathophysiological mechanism of ATP binding cassette transporter A1 (ABCA1) in regulating the IOP and aqueous humor outflow.

Methods

ABCA1 expression was measured in trabecular meshwork samples obtained from patients with POAG and human donor eyes by Western blot. To further evaluate the functional significance of ABCA1, porcine angular aqueous plexus (AAP) cells, which are equivalent to human Schlemm's canal endothelial cells, were either treated with ABCA1 agonist GW3965 or transduced with lentivirus expressing ABCA1-shRNA. Transendothelial electrical resistance, protein expression, and nitric oxide (NO) concentration were measured. GW3965 was administered by intracameral injection. IOP and aqueous humor outflow facility were also measured.

Results

ABCA1 expression was significantly higher in the trabecular meshwork tissue of patients with POAG compared with controls. ABCA1 upregulation in angular aqueous plexus cells decreased the transendothelial electrical resistance in the angular aqueous plexus monolayers accompanied by a 0.56-fold decrease in caveolin-1 expression and a 2.85-fold and 1.17-fold increase in endothelial NO synthase expression and NO concentration, respectively (n = 3, P < 0.05). Conversely, ABCA1 downregulation increased transendothelial electrical resistance and caveolin-1 expression and decreased endothelial NO synthase expression and NO production (n = 3, P < 0.05). GW3965 decreased IOP and significantly increased conventional outflow facility (P < 0.05).

Conclusions

Regulation of aqueous humor outflow via the caveolin-1/endothelial NO synthase/NO pathway is a newly defined function of ABCA1 that is different from its traditional role in mediating cholesterol efflux. ABCA1 is a compelling, novel therapeutic candidate for the treatment of glaucoma and ocular hypertension.

Sunitinib-induced oxidative imbalance and retinotoxic effects in rats

AIMS

Sunitinib (Su), a tyrosine kinase inhibitor, is one of the most commonly used anti-angiogenic drugs. Some studies have described retinal detachment and photoreceptor damage following systemic exposure to Su, despite beneficial effects achieved with local treatment of ocular pathologies. The aim of this study was to explore the role of NADPH oxidase system and oxidative stress in eyes from Su-treated animals.

MAIN METHODS

Male Wistar rats were administered 25 mg Su/kg body weight/day incorporated in the chow for 3 weeks. Upon treatment completion, NADPH oxidase activity and ROS levels were measured in ocular tissue by chemiluminescence and dihydroethidium (DHE) staining, respectively. The expression of NADPH oxidase isoforms (NOX1, NOX2 and NOX4), antioxidant enzymes and endothelial/inducible nitric oxidase isoforms (eNOS/iNOS) in the eyecup and/or retina were measured via immunofluorescence, immunoblotting and RT-qPCR.

KEY FINDINGS

NADPH oxidase activity/expression increased in eyecup and retinas from Su-treated rats. Immunohistofluorescence studies in retinal layer confirmed a higher signal of NADPH oxidase isoforms after Su treatment. Treated animals also presented with reductions in NO levels and eNOS expression, whereas iNOS was upregulated. Finally, a significant depletion of antioxidant enzyme glutathione peroxidase was measured in eyecups of rats following Su exposure, and the opposite pattern was seen for glutathione reductase and superoxide dismutase.

SIGNIFICANCE

This study demonstrates that Su treatment is associated with NADPH oxidase-derived oxidative stress in the eye. Long-term treatment of Su should be properly monitored to avoid retinotoxic effects that might result in ocular pathologies and sight-threatening conditions.

NOS3 Deletion in Cav1 Deficient Mice Decreases Drug Sensitivity to a Nitric Oxide Donor and Two Nitric Oxide Synthase Inhibitors

Purpose

This study aims to investigate the pharmacologic consequence of genetic deletion of nitric oxide synthase 3 (NOS3) in caveolin 1 (Cav1)-/- mice (double knockout [DKO]) in response to a nitric oxide (NO) donor and two NOS inhibitors.

Methods

NO donor sodium nitroprusside (SNP; 10-40 mg/mL), NOS inhibitor L-NG-nitroarginine methyl ester (L-NAME; 10-200 μM), and cavtratin (10-75 μM ) was administered topically to the eye while the contralateral eyes were vehicle controls. Intraocular pressure (IOP) was measured in both eyes by tonometry. Cyclic guanosine monophosphate (cGMP) level in outflow tissue was measured by ELISA assay. Protein expression were analyzed by western blot.

Results

Inducible NOS (iNOS) expression significantly increased in the DKO mice compared with the wild type (WT), Cav1 knockout (Cav1 KO), and NOS3 KO mice. In contrast to WT, Cav1 KO and NOS3 KO mice, SNP concentration of up to 30 mg/mL did not significantly affect IOP in DKO mice. However, higher concentration (40 mg/mL) SNP significantly reduced IOP by 14% (n = 8, P < 0.01). Similarly, only 200 μM L-NAME produced a significant increase in IOP (n = 10, P < 0.05). Cavtratin did not significantly change IOP in DKO and NOS3 KO mice. cGMP activity in DKO mice was significantly lower than Cav1 KO mice (n = 4, P < 0.05).

Conclusions

In conclusion, our results demonstrated that genetic deletion of NOS3 in Cav1 deficient mice resulted in reduced sensitivity to the NO donor SNP and the two NOS inhibitors possibly due to compromised NOS and cGMP activity.

Association of endothelial nitric oxide synthase (NOS3) gene polymorphisms with primary open-angle glaucoma in a Saudi cohort

Aim

To investigate the association of endothelial nitric oxide synthase (NOS3) gene polymorphisms in patients with primary open-angle glaucoma (POAG) of Saudi origin.

Methods

This case-control study included 173 patients with POAG (94 men and 79 women) and 171 controls (98 men and 73 women). Genotyping of rs2070744 (T-786C) and rs1799983 (G894T) variants of the NOS3 gene was performed using TaqMan^® assay.

Results

Rs1799983 genotypes showed a significant association with POAG but did not survive Bonferroni correction (p_correction = 0.01). The minor ‘T’ allele was significantly associated with the risk of POAG among men (p = 0.025, odds ratio (OR) = 1.77, 95% confidence interval (CI) = 1.07–2.94). Likewise, the genotypes were significantly associated with POAG among men in dominant (p = 0.030, OR = 1.92, 95% CI = 1.06–3.48) and log-additive models (p = 0.022, OR = 1.82, 95% CI = 1.08–3.07), and after adjustment for age and smoking. Genotype and allele frequencies of rs2070744 were not significantly different between POAG cases and controls, and after sex stratification. CG haplotype was significantly protective (p = 0.011, OR = 0.52, 95% CI = 0.32–0.87) and CT haplotype conferred significantly increased risk of POAG (p = 0.016, OR = 2.60, 95% CI = 1.16–5.82) among men. Rs1799983 showed trend (p = 0.054) towards risk of POAG independent of age, gender, smoking, and rs2070744 polymorphism in logistic regression analysis. Both the polymorphisms showed no association with POAG phenotypes such as intraocular pressure and cup/disc ratio.

Conclusion

Our results suggest that the polymorphism rs1799983 and the haplotypes of rs20707440 and rs1799983 in the NOS3 gene may significantly modulate the risk of POAG in Saudi’s, particularly among men. Further larger studies are needed to confirm these findings.

Apolipoprotein E Deficiency Causes Endothelial Dysfunction in the Mouse Retina

Objective

Atherogenic lipoproteins may impair vascular reactivity consecutively causing tissue damage in multiple organs via abnormal perfusion and excessive reactive oxygen species generation. We tested the hypothesis that chronic hypercholesterolemia causes endothelial dysfunction and cell loss in the retina.

Methods

Twelve-month-old apolipoprotein E-deficient (ApoE-/-) mice and age-matched wild-type controls were used in this study (n = 8 per genotype for each experiment). Intraocular pressure, blood pressure, and ocular perfusion pressure were determined. Retinal arteriole responses were studied in vitro, and reactive oxygen and nitrogen species were quantified in the retinal and optic nerve cryosections. The expression of the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) and the NADPH oxidase isoforms, NOX1, NOX2, and NOX4, were determined in retinal cryosections by immunofluorescence microscopy. Pro- and antioxidant redox genes were quantified in retinal explants by PCR. Moreover, cell number in the retinal ganglion cell layer and axon number in the optic nerve was calculated.

Results

Responses to the endothelium-dependent vasodilator, acetylcholine, were markedly impaired in retinal arterioles of ApoE-/- mice (P < 0.01). LOX-1 (P = 0.0007) and NOX2 (P = 0.0027) expressions as well as levels of reactive oxygen species (P = 0.0022) were increased in blood vessels but not in other retinal structures. In contrast, reactive nitrogen species were barely detectable in both mouse genotypes. Messenger RNA for HIF-1α, VEGF-A, NOX1, and NOX2, but also for various antioxidant redox genes was elevated in the retina of ApoE-/- mice. Total cell number in the retinal ganglion cell layer did not differ between ApoE-/- and wild-type mice (P = 0.2171). Also, axon number in the optic nerve did not differ between ApoE-/- and wild-type mice (P = 0.6435).

Conclusion

Apolipoprotein E deficiency induces oxidative stress and endothelial dysfunction in retinal arterioles, which may trigger hypoxia in the retinal tissue. Oxidative stress in nonvascular retinal tissue appears to be prevented by the upregulation of antioxidant redox enzymes, resulting in neuron preservation.

Pharmacological regulation of outflow resistance distal to Schlemm's canal

The trabecular meshwork (TM) and Schlemm's canal generate the majority of outflow resistance; however, the distal regions of the conventional outflow pathway account for 25-50% of total resistance. Sections of distal vessels are surrounded by α-smooth muscle actin-containing cells, indicating that they may be vasoregulated. This study examined the effect of a potent vasodilator, nitric oxide (NO), and its physiological antagonist, endothelin-1 (ET-1), on the regulation of outflow resistance in the distal regions of the conventional outflow pathway. Using a physiological model of the conventional outflow pathway, human and porcine anterior segments were perfused in organ culture under constant flow conditions, while intrachamber pressure was continually monitored. For porcine anterior segments, a stable baseline outflow facility with TM intact was first achieved before anterior segments were removed and a trabeculotomy was performed. For human anterior segments, a trabeculotomy was immediately performed. In human anterior segments, 100 nM ET-1 significantly decreased distal outflow facility from 0.49 ± 0.26 to 0.31 ±  0.18 (mean ± SD) µl·min^-1·mmHg, P < 0.01. Perfusion with 100 µM diethylenetriamine-NO in the presence of 1 nM ET-1 immediately reversed ET-1 effects, significantly increasing distal outflow facility to 0.54 ± 0.35 µl·min^-1·mmHg, P = 0.01. Similar results were obtained in porcine anterior segment experiments. Therefore, data show a dynamic range of resistance generation by distal vessels in both the human and the porcine conventional outflow pathways. Interestingly, maximal contraction of vessels in the distal outflow tract of trabeculotomized eyes generated resistance very near physiological levels for both species having an intact TM.

The Relation Between Endothelial Nitric Oxide Synthase Polymorphisms and Normal Tension Glaucoma

PURPOSE

We investigated whether polymorphisms of the endothelial NO synthase (eNOS) gene are associated with normal tension glaucoma (NTG). We also investigated whether the eNOS polymorphisms are associated with NTG subgroups [NTG with and without optic disc hemorrhage (DH)].

METHODS

A total of 251 patients with NTG and 245 healthy volunteers were enrolled in this study. DNA from peripheral blood leukocytes was extracted, and the genotypes of 4 polymorphisms (rs2070744, rs1549758, rs1799983, and rs2566514) in the eNOS gene were determined using restriction fragment length polymorphism and the SNaPshot method. The primary outcome was to investigate the relation between eNOS polymorphisms and NTG. The secondary outcome was to compare the frequencies of the polymorphic genotypes among the NTG subgroups. Bonferroni correction was used to adjust for type I error.

RESULTS

In all subjects, the genotype distribution was in accordance with Hardy-Weinberg equilibrium. None of the 4 polymorphisms showed any significant difference in the frequencies of alleles or genotypes between the NTG patients and controls. In the further analysis comparing the genotypic frequencies between NTG with DH and normal controls, the CC/CT genotype of rs2070744 was significantly associated with DH in NTG patients (genotypic association test, P-value=0.0041). On the multiple logistic regression analysis adjusted for covariates such as sex and age, the NTG with DH was associated with polymorphic genotypes of rs2070744 with a borderline significance (additive genetic model, P=0.0070).

CONCLUSIONS

Our results indicates that eNOS rs2070744 can be associated with NTG patients with DH. This finding suggests that the eNOS polymorphism may be a genetic risk factor in the development of DH in NTG patients.