Suppressed endothelin-1 by anti-VEGF therapy is important for patients with BRVO-related macular edema to improve their vision

Anti-Vascular Endothelial Growth Factor Treatment for Macular Edema in Eyes with Branch Retinal Vein Occlusion with vs Without Glaucoma – Does Glaucoma Affect Visual Outcome in Eyes with BRVO-ME After antiVEGF Injections?

Purpose

To compare the therapeutic effects of anti-vascular endothelial growth factor (anti-VEGF) agents in eyes with macular edema associated with branch retinal vein occlusion (BRVO-ME) with glaucoma to those without glaucoma.

Patients and Methods

This retrospective study was conducted using the medical records of Mie University Hospital from 2013 to 2017. Patients were recruited if they had received anti-VEGF agents for BRVO-ME treatment and included 30 patients (30 eyes) without glaucoma (G[-] group) and 27 patients (27 eyes) with glaucoma (G[+] group). The central retinal thickness (CRT) and best-corrected visual acuity (BCVA) at 3 months after a single injection of anti-VEGF agents were compared between the two groups.

Results

Before treatment, the mean±standard deviation of the CRT was 514.2±117.3 μm for the G[-] group, which was not significantly different from that for the G[+] group (533.4±171.4 μm). The CRT in the G[-] and G[+] groups significantly reduced to 321.1±114.6 μm and 347.8±134.7 μm, respectively, at 1 month after the injection and to 360.4±159.5 μm and 352.4±151.9 μm, respectively, at 3 months after the injection (P<0.01 for each group). The difference in the degree of CRT reduction between the two groups was not significant. Before treatment, the BCVA was 0.42±0.32 logMAR units in the G[-] group and 0.57±0.33 logMAR units in the G[+] group, showing no significant difference. The BCVA in the G[-] and G[+] groups improved significantly to 0.27±0.26 logMAR units and 0.34±0.42 logMAR units, respectively, at 1 month, and to 0.18±0.20 logMAR units and 0.39±0.34 logMAR units, respectively, at 3 months (P<0.01). The BCVA in the G[-] group was significantly better than that in the G[+] group at 3 months (P=0.02).

Conclusion

The therapeutic response of anti-VEGF agents for BRVO-ME is affected by the presence of glaucoma.

ENDOTHELIN-1 AS A RISK FACTOR IN RETINAL VEIN OCCLUSION

PURPOSE

Retinal vein occlusion (RVO) risk factors largely coincide with cardiovascular risk factors. Endothelin-1 (ET-1), the most potent vasoconstrictor with proinflammatory properties, is a known cardiovascular risk factor. In this study, we explore the role of serum ET-1 as a potential risk factor for RVO.

METHODS

Endothelin-1 serum levels were measured in patients with RVO and control subjects. Samples were measured using the sandwich enzyme-linked immunosorbent assay for the quantitative determination of human big endothelin-1 (Biomedica Group, Austria).

RESULTS

The study consisted of 147 RVO patients and 150 control subjects. Median serum ET-1 was significantly higher in RVO patients (0.26 pmol/L; range, 0.19-0.37 pmol/L) compared with control subjects (0.10 pmol/L; range, 0.05-0.22 pmol/L) (P < 0.0001) independent of the occlusion site. The difference remained significant after adjusting for arterial hypertension, diabetes mellitus, history of stroke, history of myocardial infarction, history of venous thromboembolism, glomerular filtration rate, and c-reactive protein.

CONCLUSION

In conclusion, our results suggest that ET-1 is a potential risk factor for all types of RVO.

Epithelial-mesenchymal transition-related serum markers ET-1, IL-8 and TGF-β2 are elevated in a Finnish wet age-related macular degeneration cohort

PURPOSE

It has been hypothesized that epithelial-mesenchymal transition (EMT) may occur in the retinal pigment epithelium of advanced stage age-related macular degeneration (AMD). Various serum and plasma growth factors and inflammatory mediators have been linked to AMD. We were interested in finding out whether systemic levels of EMT-associated markers were altered in the serum of wet AMD patients. Serum biomarkers associated with the various pathological processes of AMD may present an avenue towards identifying and characterizing the birth mechanisms of wet AMD, its progression and severity, paving the way towards the application of precision medicine.

METHODS

We chose to measure the serum levels of known biomarkers of EMT - EGF (epidermal growth factor), ET-1 (endothelin 1), IL-8 (interleukin 8), TGF-β1 and TGF-β2 (transforming growth factor-beta 1 and 2) and VEGF-A (vascular endothelial growth factor A) - using enzyme-linked immunosorbent assays. We measured them from 71 Finnish wet AMD patients who were receiving intravitreal anti-VEGF-A injection treatments, as well as 64 age-adjusted controls.

RESULTS

We found significantly elevated levels of ET-1, IL-8 and TGF-β2 in the serums of wet AMD patients.

CONCLUSIONS

ET-1, IL-8 and TGF-β2 appear to be useful serum biomarkers in understanding active wet AMD. However, we cannot conclude that local retinal EMT-processes could be observed from the corresponding systemic serum biomarkers in patients undergoing anti-VEGF-A treatments.

Significant elevation of aqueous endothelin-1 in central retinal vein occlusion

PURPOSE

To investigate aqueous humor concentrations of endothelin-1 (ET-1) in patients with central retinal vein occlusion (CRVO) compared with patients with branch retinal vein occlusion (BRVO) and a normal control group.

METHODS

A total 80 subjects were included in this prospective study, including 15 patients with CRVO, 20 patients with BRVO, and 45 patients who underwent cataract surgery and had no concomitant ocular disease. Aqueous humor levels of ET-1 were obtained before intravitreal bevacizumab injection (IVB) and after 1 month.

RESULTS

At baseline, the mean aqueous ET-1 level was 12.7±3.6 pg/mL in the CRVO group, 8.0±2.3 pg/mL in the BRVO group, and 2.0±0.9 pg/mL in the control group (P<0.001). After IVB, the mean aqueous level of ET-1 was 3.4±1.9 pg/mL (0.5-6.9 pg/mL) in the CRVO group and 1.8±1.0 pg/mL (0.3-3.2 pg/mL) in the BRVO group (P = 0.008). The mean aqueous ET-1 level was significantly reduced in both the patients with CRVO and those with BRVO (P<0.001).

CONCLUSION

The mean aqueous humor ET-1 level was significant higher in the patients with CRVO than those with BRVO and in the control group. After IVB, the mean level was significantly reduced in both the patients with CRVO and those with BRVO.

Retinal venous pressure is decreased after anti-VEGF therapy in patients with retinal vein occlusion-related macular edema

Purpose

The pathomechanism leading to retinal vein occlusion (RVO) is unclear. Mechanical compression, thrombosis, and functional contractions of veins are discussed as the reasons for the increased resistance of venous outflow. We evaluated changes in the retinal venous pressure (RVP) following intravitreal injection of anti-vascular endothelial growth factor (VEGF) agent to determine the effect on RVO-related macular edema.

Methods

Twenty-six patients with RVO-related macular edema (16 branch RVOs [BRVOs] and 10 central RVOs [CRVOs], age 72.5 ± 8.8 years) who visited our hospital were included in this prospective study. Visual acuity (VA), intraocular pressure (IOP), central retinal thickness (CRT) determined by macular optical coherence tomography, and RVP measured using an ophthalmodynamometer were obtained before intravitreal injection of ranibizumab (IVR) and 1 month later.

Results

Comparison of the BRVOs and CRVOs showed that VA was significantly improved by a single injection in BRVOs (P < 0.0001; P = 0.1087 for CRVOs), but CRT and RVP were significantly decreased without significant difference in IOP after the treatment in both groups (P < 0.0001).

Conclusion

The anti-VEGF treatment resulted in a significant decrease in the RVP, but the RVP remained significantly higher than the IOP. An increased RVP plays a decisive role in the formation of macula edema, and reducing it is desirable.

[The role of the endothelin system in the pathogenesis of eye diseases]

The endothelin system (ES) plays a complex role in the pathogenesis of various eye diseases as a local regulator of vascular tone as well as many other physiological processes. Components of ES - endothelins and their receptors - can be found nearly in all cellular structures of the eye, their concentration increases in the presence of many eye diseases. In glaucoma, ES is involved in the mechanisms of eye hypertension by influencing the secretion and outflow of aqueous humor. The increase of endothelin level leads to the decrease of perfusion pressure, hypoxia, astrocyte proliferation, increase of density and rigidity of lamina cribrosa, apoptosis of neural cells, and has a profibrogenic effect. In retinal pathology, increase of endothelins disturbs autoregulation of retinal blood vessels changing the neurovascular interactions, breaks intercellular contacts in the retina, promotes neoangiogenesis. In diabetic retinopathy, ES contributes to the development of microangiopathy and proliferative vitreoretinopathy. The review discusses the possibility of correcting ES activity in the eye with medications by influencing its synthesis, cleavage and receptor binding.

Protective effects of hydrogen gas in a rat model of branch retinal vein occlusion via decreasing VEGF-α expression

Background

Oxidative stress (OS) is an essential factor in the pathogenesis of branch retinal vein occlusion (BRVO). Studies have demonstrated the role of hydrogen gas in the regulation of OS. This study was designed to evaluate the efficacy of hydrogen gas on the BRVO rat model.

Methods

Twenty-four BRVO rats were randomly divided into two groups: the hydrogen gas (H) group (42% H₂, 21% O₂, 37% N₂) and the model (M) group (21% O₂, 79% N₂). Rats in the H group inhaled hydrogen gas for 8 h every day up to 30 d post-occlusion. Twelve age-matched healthy rats served as the control (C) group. Retinal function and morphology were detected at 1, 7, 14 and 30 d post-occlusion. Furthermore, the expression of vascular endothelial growth factor (VEGF-α) was detected by immunofluorescent staining.

Results

Full-field electroretinography (ffERG) revealed that the amplitude of the b-wave (dark-adaptation 3.0 response), the amplitude of the OPs2 wave and the light-adapted flicker response in the H group were all higher than those in the M group at 7 d post-occlusion (all p < 0.05). The reopen time of occlusive retinal vessels in the H group was 2.235 ± 1.128 d, which was shorter than that in the M group (4.234 ± 2.236 d, p < 0.05). The rats in the H group had a thinner IPL + GCL + NFL and an increased total retina compared with those in the M group at 3 d post-occlusion (p < 0.05), while the rats in the H group had a thicker INL, IPL + GCL + NFL and total retina compared with those at 7, 14 and 30 d post-occlusion (p < 0.05). Moreover, the flow velocity of ear vein blood was increased in the H group compared with that in the M group (p < 0.05). The expression of VEGF-α in the H group was dramatically decreased compared with that in the M group at 1, 7 and 14 d post-occlusion (p < 0.05), while the expression kept in similar level at 30 d post-occlusion (p > 0.05).

Conclusions

Our findings demonstrate that inhalation of hydrogen gas could alleviate retinal oedema, shorten reopen time and improve retinal function, and the potential mechanism might be related to a decrease in VEGF-α expression.

Short-term effect of intravitreal conbercept injection on major and macular branch retinal vein occlusion

OBJECTIVE

To evaluate the effectiveness of intravitreal conbercept injection on major and macular branch retinal vein occlusion (BRVO).

METHODS

This retrospective analysis involved 43 patients with BRVO (major BRVO n = 24; macular BRVO, n = 19) who were diagnosed by fluorescein fundus angiography (FFA) and injected with intravitreal conbercept. The following outcomes were measured at baseline and follow-up (1-6 months): best-corrected visual acuity (BCVA), central foveal thickness (CFT), total retinal volume in a 6-mm diameter section of the macula, choroidal thickness under the central fovea of the macula, relative area of retinal hemorrhage, complications, and times when repeated injection was performed.

RESULTS

There were significant differences between the two groups in terms of BCVA, CFT, and total retinal volume in a 6-mm diameter section of the macula at 6 months after treatment. Choroidal thickness under the central fovea of the macula and relative area of retinal hemorrhage showed no significant differences between the two groups at 6 months after treatment; however, they significantly differed from baseline measurements.

CONCLUSION

In general, intravitreal injection of conbercept may have a better short-term effect in patients with macular BRVO than in patients with major BRVO.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Mystery of Retinal Vein Occlusion: Vasoactivity of the Vein and Possible Involvement of Endothelin-1

Retinal vein occlusion (RVO) is a common vascular disease of retina; however, the pathomechanism leading to RVO is not yet clear. In general, increasing age, hypertension, arteriosclerosis, diabetes mellitus, dyslipidemia, cardiovascular disorder, and cerebral stroke are systemic risk factors of RVO. However, RVO often occur in the unilateral eye and sometimes develop in young subjects who have no arteriosclerosis. In addition, RVO show different variations on the degrees of severity; some RVO are resolved without any treatment and others develop vision-threatening complications such as macular edema, combined retinal artery occlusion, vitreous hemorrhage, and glaucoma. Clinical conditions leading to RVO are still open to question. In this review, we discuss how to treat RVO in practice by presenting some RVO cases. We also deliver possible pathomechanisms of RVO through our clinical experience and animal experiments.

The discovery of the Flammer syndrome: a historical and personal perspective

This review describes the clinical and basic research that led to the description of Flammer syndrome. It is narrated from a personal perspective. This research was initiated by the observation of an increased long-term fluctuation of visual fields in a subgroup of glaucoma patients. As these patients had strikingly cold hands, peripheral blood flow was tested with a capillary microscopy, and vasospastic syndrome (VS) was diagnosed. Further studies on these patients revealed frequently weakened autoregulation of ocular blood flow and increased flow resistivity in retroocular vessels. Their retinal vessels were more rigid and irregular and responded less to flickering light. Holistic investigation demonstrated low blood pressure, silent myocardial ischaemia, altered beat-to-beat variation, altered gene expression in the lymphocytes, slightly increased plasma endothelin level and increased systemic oxidative stress. This combination of signs and symptoms was better described by the term primary vascular dysregulation (PVD) than by VS. Subsequent studies showed additional symptoms frequently related to PVD, such as low body mass index, cold extremities combined with slightly increased core temperature, prolonged sleep onset time, reduced feelings of thirst, increased sensitivity to smell and also for certain drugs and increased retinal venous pressure. To better characterise this entire syndrome, the term Flammer syndrome (FS) was introduced. Most subjects with FS were healthy. Nevertheless, FS seemed to increase the risk for certain eye diseases, particularly in younger patients. This included normal-tension glaucoma, anterior ischaemic optic neuropathy, retinal vein occlusions, Susac syndrome and central serous chorioretinopathy. Hereditary diseases, such as Leber’s optic neuropathy or retinitis pigmentosa, were also associated with FS, and FS symptoms and sings occurred more frequent in patients with multiple sclerosis or with acute hearing loss. Further research should lead to a more concise definition of FS, a precise diagnosis and tools for recognizing people at risk for associated diseases. This may ultimately lead to more efficient and more personalised treatment.