Endothelial nitric oxide synthase genotypes in the etiology of retinopathy of prematurity in premature infants

Potential role of eNOS and EDN-1 gene polymorphisms in the development and progression of retinopathy of prematurity

The aim of this study was to investigate the association between selected polymorphisms of nitric oxide synthetase (eNOS) and endothelin-1 (EDN-1) with the occurrence and progression of retinopathy of prematurity (ROP). A prospective study was conducted on 90 preterm infants (44 female), comparing 39 cases with ROP and 51 controls without ROP. Patients who developed ROP were further divided into two subgroups-those with spontaneous regression of the disease and those with ROP requiring treatment. We found that preterm infants with TT genotype eNOS 894G > T had a 12.8-fold higher risk of developing ROP requiring treatment (p = 0.02). Our results showed that allele T of eNOS894G > T polymorphism was significantly more prevalent in ROP patients requiring treatment (p = 0.029). We also investigated preterm infants with TC genotype eNOS - 786 T > C and found an 8.8-fold higher risk developing of ROP requiring treatment (p = 0.021). Our results didn't show any association between EDN-1 5665G > T polymorphism and ROP development. The eNOS polymorphisms appears to influence incidence of ROP requiring treatment in preterm infants. Future research on single nucleotide polymorphisms may provide important information about the pathogenetic mechanisms underlying the development of ROP.

Retinopathy of prematurity: contribution of inflammatory and genetic factors

Retinopathy of prematurity (ROP) is a retinal vasoproliferative disorder that represents an important cause of childhood visual impairment and blindness. Although oxidative stress has long been implicated in ROP etiology, other prenatal and perinatal factors are also involved. This review focuses on current research involving inflammation and genetic factors in the pathogenesis of ROP. Increasing evidence suggests that perinatal inflammation or infection contributes to ROP pathogenesis. Cytokines and chemokines with a fundamental role in inflammatory responses and that significantly contributing to angiogenesis are analyzed. Microglia cells, the retinal-resident macrophages, are crucial for retinal homeostasis, however, under sustained pathological stimuli release exaggerated amounts of inflammatory mediators and can promote pathological neovascularization. Current modulation of angiogenic cytokines, such as treatment with antibodies to vascular endothelial growth factor (anti-VEGF), has shown efficacy in the treatment of ocular neovascularization; however, some patients are refractory to anti-VEGF agents, suggesting that other angiogenic or anti-angiogenic cytokines need to be identified. Much evidence suggests that genetic factors contribute to the phenotypic variability of ROP. Several studies have implicated the involvement of candidate genes from different signaling pathways in the development of ROP. However, a genetic component with a major impact on ROP has not yet been discovered. Most studies have limitations and did not replicate results. Future research involving bioinformatics, genomics, and proteomics may contribute to finding more genes associated with ROP and may allow discovering better solutions in the management and treatment of ROP.

Endothelial nitric oxide synthase G894T, intron 4 VNTR, and T786C polymorphisms in retinopathy of prematurity

BACKGROUND

Our objective in this study was to assess the association between eNOS gene, that achieves synthesis of nitric oxide especially in the endothelial cells known to have an important role in angiogenesis and vasculogenesis, G894T, intron 4 VNTR (27-bp repeat) and T786C functional polymorphisms and retinopathy of prematurity (ROP), which is an important cause of morbidity in premature or low birth weight babies.

METHODS

A total of 139 babies who were followed up in our neonatal intensive care unit because of premature birth in our hospital or admitted to our unit. 69 of them had retinopathy of prematurity and comprised the patients group. The remaining 70 babies who did not have ROP comprised the control group. An additional of 1 ml of blood samples were drawn from babies who were in the study groups during routine laboratory analysis. eNOS gene polymorphisms were determined by using polymerase chain reaction method.

RESULTS

eNOS G894T, intron 4 VNTR and T786C gene polymorphisms did not differ between the patient and control groups (p >  0.05). Using logistic regression analysis; while gender did not differ between two groups; gestational age, birth weight, time on mechanical ventilation differ between two groups. After adjustment for variables other than eNOS gene polymorphisms, we found no significant difference in the genotype distribution of eNOS G894T, intron 4 VNTR and T786C polymorphisms (p >  0.05).

CONCLUSION

We observed no association between ROP and eNOS gene polymorphisms but needs more investigation.

Nitric Oxide Interaction with the Eye

Nitric oxide (NO) is acknowledged as a vital intercellular messenger in multiple systems in the body. Medicine has focused on its functions and therapeutic applications for decades, especially in cardiovascular and nervous systems, and its role in immunological responses. This review was composed to demonstrate the prevalence of NO in components of the ocular system, including corneal cells and multiple cells in the retina. It discussed NO's assistance during the immune, inflammation and wound-healing processes. NO is identified as a vascular endothelial relaxant that can alter the choroidal blood flow and prompt or suppress vascular changes in age-related macular degeneration and diabetes, as well as the blood supply to the optic nerve, possibly influencing the progression of glaucoma. It will provide a deeper understanding of the role of NO in ocular homeostasis, the delicate balance between overproduction or underproduction and the effect on the processes from aqueous outflow and subsequent intraocular pressure to axial elongation and the development of myopia. This review also recognized the research and investigation of therapies being developed to target the NO complex and treat various ocular diseases.

Association of eNOS and ACE Polymorphisms with Retinopathy of Prematurity: A Systematic Review and Meta-Analysis

Background: We performed a meta-analysis to clarify the association of endothelial nitric oxide synthase (eNOS) and angiotensin I-converting enzyme (ACE) gene polymorphisms with retinopathy of prematurity (ROP) risk. Methods: PubMed, Medline, and Embase literatures up to June 01, 2019, were reviewed. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the strength of associations. Results: Eighteen case-control studies including 14 studies (810 cases and 1754 controls) on eNOS polymorphisms and four studies (1014 cases and 1215 controls) on ACE I/D polymorphism were selected. Overall, analysis showed that infants with the ACE I/D polymorphism have an increased susceptibility to ROP. No association of eNOS 27-bp, 894 G > T and -786 T > C polymorphisms with ROP risk was found. Conclusion: ACE I/D polymorphism may serve as genetic biomarker of increased ROP risk. The eNOS polymorphisms do not appear to influence susceptibility to ROP.

Vascular and Neuronal Protection in the Developing Retina: Potential Therapeutic Targets for Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a common retinal disease in preterm babies. To prolong the lives of preterm babies, high oxygen is provided to mimic the oxygen level in the intrauterine environment for postnatal organ development. However, hyperoxia-hypoxia induced pathological events occur when babies return to room air, leading to ROP with neuronal degeneration and vascular abnormality that affects retinal functions. With advances in neonatal intensive care, it is no longer uncommon for increased survival of very-low-birth-weight preterm infants, which, therefore, increased the incidence of ROP. ROP is now a major cause of preventable childhood blindness worldwide. Current proven treatment for ROP is limited to invasive retinal ablation, inherently destructive to the retina. The lack of pharmacological treatment for ROP creates a great need for effective and safe therapies in these developing infants. Therefore, it is essential to identify potential therapeutic agents that may have positive ROP outcomes, especially in preserving retinal functions. This review gives an overview of various agents in their efficacy in reducing retinal damages in cell culture tests, animal experiments and clinical studies. New perspectives along the neuroprotective pathways in the developing retina are also reviewed.

The genetics of retinopathy of prematurity: a model for neovascular retinal disease

TOPIC

Retinopathy of prematurity (ROP) is a proliferative retinal vascular disease in premature infants, and is a major cause of childhood blindness worldwide. In addition to known clinical risk factors such as low birth weight and gestational age, there is a growing body of evidence supporting a genetic basis for ROP.

CLINICAL RELEVANCE

While comorbidities and environmental factors have been identified as contributing to ROP outcomes in premature infants, most notably gestational age and oxygen, some infants progress to severe disease despite absence of these clinical risk factors. The contribution of genetic factors may explain these differences and allow better detection and treatment of infants at risk for severe ROP.

METHODS

To comprehensively review genetic factors that potentially contribute to the development and severity of ROP, we conducted a literature search focusing on the genetic basis for ROP. Terms related to other heritable retinal vascular diseases like "familial exudative vitreoretinopathy", as well as to genes implicated in animal models of ROP, were also used to capture research in diseases with similar pathogenesis to ROP in humans with known genetic components.

RESULTS

Contributions across several genetic domains are described including vascular endothelial growth factor, the Wnt signaling pathway, insulin-like growth factor 1, inflammatory mediators, and brain-derived neurotrophic factor.

CONCLUSIONS

Most candidate gene studies of ROP have limitations such as inability to replicate results, conflicting results from various studies, small sample size, and differences in clinical characterization. Additional difficulty arises in separating the contribution of genetic factors like Wnt signaling to ROP and prematurity. Although studies have implicated involvement of multiple signaling pathways in ROP, the genetics of ROP have not been clearly elucidated. Next-generation sequencing and genome-wide association studies have potential to expand future understanding of underlying genetic risk factors and pathophysiology of ROP.

Retinopathy of prematurity: a review of risk factors and their clinical significance

Retinopathy of prematurity (ROP) is a retinal vasoproliferative disease that affects premature infants. Despite improvements in neonatal care and management guidelines, ROP remains a leading cause of childhood blindness worldwide. Current screening guidelines are primarily based on two risk factors: birth weight and gestational age; however, many investigators have suggested other risk factors, including maternal factors, prenatal and perinatal factors, demographics, medical interventions, comorbidities of prematurity, nutrition, and genetic factors. We review the existing literature addressing various possible ROP risk factors. Although there have been contradictory reports, and the risk may vary between different populations, understanding ROP risk factors is essential to develop predictive models, to gain insights into pathophysiology of retinal vascular diseases and diseases of prematurity, and to determine future directions in management of and research in ROP.

Genetic association of single nucleotide polymorphisms of FZD4 and BDNF genes with retinopathy of prematurity

BACKGROUND

Retinopathy of prematurity (ROP) is a multifactorial disease occurring in preterm neonates, caused by incorrect development of retinal blood vessels. It has been suggested that, in addition to gestational age, weight, and oxygen supplementation, genetic factors can play a role in the pathogenesis of ROP.

METHODS

In the present prospective study, 97 neonates were enrolled based on the gestational age and weight, and genomic DNA from patients diagnosed with ROP and premature newborns without ROP was collected. The DNA sequence of protein coding and 5´and 3´ untranslated regions (UTRs) of the frizzled-4 (FZD4) gene and the genotype of the locus rs7934165:G˃A (NM_170731.4: c.3 + 10976 C˃T) within the brain-derived neurotrophic factor gene (BDNF) were determined.

RESULTS

We detected a significant association between rs61749246:C˃A (NM_012193.3: c.*2G˃T) and ROP in a general genetic model as well as in a multiplicative model and by the Cochran-Armitage test for trend. Moreover, rs61749246 was strongly associated with ROP, requiring surgical intervention.

CONCLUSION

We suggest that rs61749246:C˃A of the FZD4 gene is likely associated with the development of ROP. It is necessary to confirm this suggestion in larger studies.

Race Effects of Inhaled Nitric Oxide in Preterm Infants: An Individual Participant Data Meta-Analysis

OBJECTIVE

To assess whether inhaled nitric oxide (iNO) improves survival without bronchopulmonary dysplasia (BPD) for preterm African American infants.

STUDY DESIGN

An individual participant data meta-analysis was conducted, including 3 randomized, placebo-controlled trials that enrolled infants born at  <34 weeks of gestation receiving respiratory support, had at least 15% (or a minimum of 10 infants in each trial arm) of African American race, and used a starting iNO of >5  parts per million with the intention to treat for 7 days minimum. The primary outcome was a composite of death or BPD. Secondary outcomes included death before discharge, postnatal steroid use, gross pulmonary air leak, pulmonary hemorrhage, measures of respiratory support, and duration of hospital stay.

RESULTS

Compared with other races, African American infants had a significant reduction in the composite outcome of death or BPD with iNO treatment: 49% treated vs 63% controls (relative risk, 0.77; 95% CI, 0.65-0.91; P = .003; interaction P = .016). There were no differences between racial groups for death. There was also a significant difference between races (interaction P = .023) of iNO treatment for BPD in survivors, with the greatest effect in African American infants (P = .005). There was no difference between racial groups in the use of postnatal steroids, pulmonary air leak, pulmonary hemorrhage, or other measures of respiratory support.

CONCLUSION

iNO therapy should be considered for preterm African American infants at high risk for BPD. iNO to prevent BPD in African Americans may represent an example of a racially customized therapy for infants.

A Pathogenic Relationship of Bronchopulmonary Dysplasia and Retinopathy of Prematurity? A Review of Angiogenic Mediators in Both Diseases

Bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) are common and significant morbidities of prematurely born infants. These diseases have in common altered and pathologic vascular formation in the face of incomplete organ development. Therefore, it is reasonable to question whether factors affecting angiogenesis could have a joint pathogenic role for both diseases. Inhibition or induced expression of a single angiogenic factor is unlikely to be 100% causative or protective of either of BPD or ROP. It is more likely that interactions of multiple factors leading to disordered angiogenesis are present, increasing the likelihood of common pathways in both diseases. This review explores this possibility by assessing the evidence showing involvement of specific angiogenic factors in the vascular development and maldevelopment in each disease. Theoretical interactions of specific factors mutually contributing to BPD and ROP are proposed and, where possible, a timeline of the proposed relationships between BPD and ROP is developed. It is hoped that future research will be inspired by the theories put forth in this review to enhance the understanding of the pathogenesis in both diseases.

Genomics in the neonatal nursery: Focus on ROP

Retinopathy of prematurity (ROP) is a complex disease that is influenced by both genetic and environmental factors. Several small studies have found genetic variants in EPAS1, VEGF, SOD, and members of the WNT family in association with ROP. Design in genetic studies is challenging because of changing recommendations for the management of prematurity and ROP, the fact ROP is rare, and that availability of resources for managing premature infants can vary throughout the world. In addition, there is a shortage of ophthalmologists with the ability to diagnose and characterize severe ROP. Careful determination of the degree of prematurity is important when evaluating genetic studies. Controlling for significant epidemiologic factors and multiple comparisons is also important to consider when evaluating genetic studies. One large candidate gene study controlled for degree of prematurity, significant epidemiologic factors, and multiple comparisons and found variants within the intron of BDNF associated with severe ROP. Future studies using unbiased techniques to assess genetic risk are important as are in-depth study of BDNF through deep sequencing and associated mechanistic studies using appropriate experimental models.

Genetic and Environmental Influences on Retinopathy of Prematurity

OBJECTIVE

The goals were to isolate and study the genetic susceptibility to retinopathy of prematurity (ROP), as well as the gene-environment interaction established in this disease.

METHODS

A retrospective study (2000-2014) was performed about the heritability of retinopathy of prematurity in 257 infants who were born at a gestational age of ≤ 32 weeks. The ROP was studied and treated by a single pediatric ophthalmologist. A binary logistic regression analysis was completed between the presence or absence of ROP and the predictor variables.

RESULTS

Data obtained from 38 monozygotic twins, 66 dizygotic twins, and 153 of simple birth were analyzed. The clinical features of the cohorts of monozygotic and dizygotic twins were not significantly different. Genetic factors represented 72.8% of the variability in the stage of ROP, environmental factors 23.08%, and random factors 4.12%. The environmental variables representing the highest risk of ROP were the number of days of tracheal intubation (p < 0.001), postnatal weight gain (p = 0.001), and development of sepsis (p = 0.0014).

CONCLUSION

The heritability of ROP was found to be 0.73. The environmental factors regulate and modify the expression of the genetic code.

Infantile hemangiomas, retinopathy of prematurity and cancer: a common pathogenetic role of the β-adrenergic system

The serendipitous demonstration that the nonselective β-adrenergic receptor (β-AR) antagonist propranolol promotes the regression of infantile hemangiomas (IHs) aroused interest around the involvement of the β-adrenergic system in angiogenic processes. The efficacy of propranolol was related to the β2-AR blockade and the consequent inhibition of the production of vascular endothelial growth factor (VEGF), suggesting the hypothesis that propranolol could also be effective in treating retinopathy of prematurity (ROP), a retinal pathology characterized by VEGF-induced neoangiogenesis. Consequent to the encouraging animal studies, a pilot clinical trial showed that oral propranolol protects newborns from ROP progression, even though this treatment is not sufficiently safe. Further, animal studies clarified the role of β3-ARs in the development of ROP and, together with several preclinical studies demonstrating the key role of the β-adrenergic system in tumor progression, vascularization, and metastasis, prompted us to also investigate the participation of β3-ARs in tumor growth. The aim of this review is to gather the recent findings on the role of the β-adrenergic system in IHs, ROP, and cancer, highlighting the fact that these different pathologies, triggered by different pathogenic noxae, share common pathogenic mechanisms characterized by the presence of hypoxia-induced angiogenesis, which may be contrasted by targeting the β-adrenergic system. The mechanisms characterizing the pathogenesis of IHs, ROP, and cancer may also be active during the fetal-neonatal development, and a great contribution to the knowledge on the role of β-ARs in diseases characterized by chronic hypoxia may come from research focusing on the fetal and neonatal period.

The pathophysiology of retinopathy of prematurity: an update of previous and recent knowledge

Retinopathy of prematurity (ROP) is a disease that can cause blindness in very low birthweight infants. The incidence of ROP is closely correlated with the weight and the gestational age at birth. Despite current therapies, ROP continues to be a highly debilitating disease. Our advancing knowledge of the pathogenesis of ROP has encouraged investigations into new antivasculogenic therapies. The purpose of this article is to review the findings on the pathophysiological mechanisms that contribute to the transition between the first and second phases of ROP and to investigate new potential therapies. Oxygen has been well characterized for the key role that it plays in retinal neoangiogenesis. Low or high levels of pO2 regulate the normal or abnormal production of hypoxia-inducible factor 1 and vascular endothelial growth factors (VEGF), which are the predominant regulators of retinal angiogenesis. Although low oxygen saturation appears to reduce the risk of severe ROP when carefully controlled within the first few weeks of life, the optimal level of saturation still remains uncertain. IGF-1 and Epo are fundamentally required during both phases of ROP, as alterations in their protein levels can modulate disease progression. Therefore, rhIGF-1 and rhEpo were tested for their abilities to prevent the loss of vasculature during the first phase of ROP, whereas anti-VEGF drugs were tested during the second phase. At present, previous hypotheses concerning ROP should be amended with new pathogenetic theories. Studies on the role of genetic components, nitric oxide, adenosine, apelin and β-adrenergic receptor have revealed new possibilities for the treatment of ROP. The genetic hypothesis that single-nucleotide polymorphisms within the β-ARs play an active role in the pathogenesis of ROP suggests the concept of disease prevention using β-blockers. In conclusion, all factors that can mediate the progression from the avascular to the proliferative phase might have significant implications for the further understanding and treatment of ROP.

The prevalence of platelet activating factor acetylhydrolase single nucleotide polymorphisms in relationship to necrotizing enterocolitis in Northwest Louisiana infants

PURPOSE

Studies documented that platelet activating factor (PAF) and the enzyme platelet activating factor acetylhydrolase (PAFAH) play a very important role in the pathogenesis of neonatal necrotizing enterocolitis (NEC). In this retrospective, case-controlled pilot study, the authors investigated the prevalence of single nucleotide polymorphisms (Ile198Thr and Ala379Val) of the PAFAH gene.

SUBJECTS AND METHODS

We screened 570 blood samples from both Caucasian and African-American preterm infants in the Northwest Louisiana population for the above mentioned PAFAH gene polymorphisms. Out of 570 infants, 36 had stage I or II NEC based on diagnostic coding, the International Classification of Diseases, 9th revision, Clinical Modification, 2009 (ICD-9-CM). The remaining infants without an ICD-9-CM diagnosis of NEC were recruited as control population. The DNA was isolated and restriction fragment length polymorphism microplate polymerase chain reaction assay was performed.

RESULTS

Variants of the PAFAH gene polymorphism (Ile198Thr and Ala379Val) frequencies were not significantly different between the infants with NEC and the control group (P value of 0.26 by either multiple logistic regression analysis or the Cochran-Mantel-Haenszel test).

CONCLUSIONS

This is the first study of its kind in exploring the relationship between NEC and single nucleotide polymorphisms in the coding genes of the enzyme PAFAH. Our preliminary data demonstrated that adjusted for the effect of race, PAFAH polymorphisms (Ile198Thr and Ala379Val) have no significant effect on NEC.

Common polymorphisms in angiogenesis

A wide variety of diseases have a significant genetic component, including major causes of morbidity and mortality in the western world. Many of these diseases are also angiogenesis dependent. In humans, common polymorphisms, although more subtle in effect than rare mutations that cause Mendelian disease, are expected to have greater overall effects on human disease. Thus, common polymorphisms in angiogenesis-regulating genes may affect the response to an angiogenic stimulus and thereby affect susceptibility to or progression of such diseases. Candidate gene studies have identified several associations between angiogenesis gene polymorphisms and disease. Similarly, emerging pharmacogenomic evidence indicates that several angiogenesis-regulating polymorphisms may predict response to therapy. In contrast, genome-wide association studies have identified only a few risk alleles in obvious angiogenesis genes. As in other traits, regulatory polymorphisms appear to dominate the landscape of angiogenic responsiveness. Rodent assays, including the mouse corneal micropocket assay, tumor models, and a macular degeneration model have allowed the identification and comparison of loci that directly affect the trait. Complementarity between human and animal approaches will allow increased understanding of the genetic basis for angiogenesis-dependent disease.