IMMUNOREACTIVE ENDOTHELIN-1 IN THE VITREOUS HUMOR AND EPIRETINAL MEMBRANES OF PATIENTS WITH PROLIFERATIVE DIABETIC RETINOPATHY

[The role of endothelin-1 in the pathogenesis of familial exudative vitreoretinopathy]

Familial exudative vitreoretinopathy (FEVR) is a rare hereditary disease characterized by pathological retinal vascularization with a progressive and variable course. The mechanisms of disease progression remain unclear. One substance that plays an important role in the pathogenesis of retinal vascular diseases is endothelin (ET). It was found that tissue hypoxia enhances the expression of the gene encoding ET-1, and ET-1 can be locally produced in the eye.

PURPOSE

The study evaluates the possible role of endothelin-1 in the pathogenesis of FEVR.

MATERIAL AND METHODS

The study included 85 patients with FEVR aged from 1 months to 17 years who were examined in Helmholtz National Medical Research Center of Eye Diseases. The concentration of ET-1 was evaluated in 19 patients with FEVR in the blood serum (n=17), lacrimal fluid (n=18) and 16 patients from the control group.

RESULTS

The median of ET-1 in the lacrimal fluid in patients with FEVR was 13.74 pg/mL, respectively, which exceeded the same indicator of the control group 4.66 pg/mL by 2.5 times (p<0.001). The median of ET-1 in the blood serum exceeded the control group by 2.4 times (21.61 pg/mL and 9.21 pg/mL, respectively, p<0.001).

CONCLUSIONS

An increase in the concentration of ET-1 in the lacrimal fluid and blood serum of patients with FEVR in comparison with the control group indicates its involvement in the pathogenesis of the disease.

Elevated aqueous endothelin-1 concentrations in advanced diabetic retinopathy

Purpose

Endothelin-1 (ET-1) is a potent vasoconstrictor which seems to be involved in the pathogenesis of diabetic retinopathy (DR). However, studies on intraocular ET-1 in DR have been limited. Thus, we investigated aqueous ET-1 levels in patients with DR.

Methods

A total 85 subjects were included in this prospective study. Those were classified into three groups: advanced DR group included those with severe nonproliferative DR or proliferative DR, whereas early DR group included those with mild nonproliferative DR or moderative nonproliferative DR. Those who underwent cataract surgery and had no concomitant ocular disease were included in the control group. Aqueous humor levels of ET-1 were obtained before intravitreal bevacizumab injection (IVB) and after 1 month for the DR patients, and at the time of cataract surgery for the control group.

Results

Advanced DR group included 40 eyes (47.1%), whereas early DR group did 19 eyes (22.4%), and control group (26 eyes, 30.5%). Mean aqueous ET-1 level was 10.1±4.1 pg/mL (6.0–21.0 pg/mL) in advanced DR group, 1.9±0.7 pg/mL (0.6–2.8 pg/mL) in early DR group, and 2.1±1.0 pg/mL (0.7–3.9 pg/mL) in control group (P < 0.001). Advanced DR group was further subdivided into severe nonproliferative DR (15 eyes, 12.8%) and proliferative DR (25 eyes, 34.3%). Mean aqueous ET-1 level was 10.1±4.3 pg/mL (6.0–20.1 pg/mL) in patients with severe nonproliferative DR, and 10.0±4.0 pg/mL (6.0–21.0 pg/mL) in those with proliferative DR (P = 0.928) at baseline. Mean ET-1 level at 1 month after intravitreal injection was 2.5±1.0 pg/mL (0.3–4.8 pg/mL) in patients with severe proliferative DR and 2.9±1.7 pg/mL (1.0–7.0 pg/mL) in those with proliferative DR (P = 0.443). Mean aqueous ET-1 level was significantly reduced in both groups (P < 0.001, respectively).

Conclusion

The mean aqueous ET-1 level was significantly higher in the eyes with advanced DR than those with early DR and the control group. The mean aqueous ET-1 level was significantly reduced after intravitreal injections in the advanced DR group. Based on our results, future studies on the exact role of ET-1 in the pathogenesis of DR and future implication for intervention would be helpful for managing DR.

Contributions of Sodium-Hydrogen Exchanger 1 and Mitogen-Activated Protein Kinases to Enhanced Retinal Venular Constriction to Endothelin-1 in Diabetes

Diabetes elevates endothelin-1 (ET-1) in the vitreous and enhances constriction of retinal venules to this peptide. However, mechanisms contributing to ET-1-induced constriction of retinal venules are incompletely understood. We examined roles of sodium-hydrogen exchanger 1 (NHE1), protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and extracellular calcium (Ca²⁺) in retinal venular constriction to ET-1 and the impact of diabetes on these signaling molecules. Retinal venules were isolated from control pigs and pigs with streptozocin-induced diabetes for in vitro studies. ET-1-induced vasoconstriction was abolished in the absence of extracellular Ca²⁺ and sensitive to c-Jun N-terminal kinase (JNK) inhibitor SP600125 but unaffected by extracellular signal-regulated kinase (ERK) inhibitor PD98059, p38 kinase inhibitor SB203580, or broad-spectrum PKC inhibitor Gö 6983. Diabetes (after 2 weeks) enhanced venular constriction to ET-1, which was insensitive to PD98059 and Gö 6983 but was prevented by NHE1 inhibitor cariporide, SB203580, and SP600125. In conclusion, extracellular Ca²⁺ entry and activation of JNK, independent of ERK and PKC, mediate constriction of retinal venules to ET-1. Diabetes activates p38 MAPK and NHE1, which cause enhanced venular constriction to ET-1. Treatments targeting these vascular molecules may lessen retinal complications in early diabetes.

Endothelin-1 levels are decreased in pediatric Type 1 diabetes and negatively correlate with the carotid intima media thickness

AIMS

Better understanding of the timeline and risk factors for the appearance of complications in pediatric Type-1-diabetes is key for developing prevention strategies. We studied endothelial markers and their determinants in adolescents with Type-1-diabetes at different time points from diagnosis.

METHODS

A cross-sectional study of 58 adolescents, mean age 15.0 ± 2.4 years; 20 with recent-onset Type-1-diabetes, 20 with over 7 years of Type-1-diabetes and 18 controls. Clinical and biochemical data were collected. Fingertip arterial reactive hyperemia (EndoPAT) and carotid intima-media-thickness (cIMT) were measured to assess endothelial function and structure.

RESULTS

Compared to controls, individuals with prolonged Type-1-diabetes had higher mean cIMT (0.49 ± 0.07 mm vs. 0.43 ± 0.05 mm p = 0.021) and maximal cIMT (0.61 ± 0.08 mm 0.52 ± 0.08 mm, p = 0.025). Endothelin-1 levels were significantly lower in subjects with prolonged Type-1-diabetes (1.2 ± 1.0 pg/ml) compared to controls (3.0 ± 1.7, p = 0.008 pg/ml); they negatively correlated with the mean cIMT (c = - 0.291, p = 0.031) and mean 6 months hemoglobin A1c (c = - 0.301, p = 0.022) and positively correlated with mean c-peptide levels (c = 0.356, p = 0.006) and the weekly exercise time (c = 0.485, p < 0.001). Endothelin-1 levels did not correlate with EndoPAT results.

CONCLUSIONS

Our results suggest that the early years after the diagnosis of Type-1-diabetes are an important window for prevention of arterial damage in the pediatric population. The trajectories of relationships of Endothelin-1 with metabolic and vascular measures were opposite from the anticipated, yet consistent. Endothelin-1 related indirectly to adverse measures and directly to favorable measures. Decreased Endothelin-1 levels might reflect early stages in endothelial impairment in Type-1-diabetes, yet its' exact role in the development of complications is yet to be unraveled.

Constriction of Retinal Venules to Endothelin-1: Obligatory Roles of ETA Receptors, Extracellular Calcium Entry, and Rho Kinase

Purpose

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide implicated in retinal venous pathologies such as diabetic retinopathy and retinal vein occlusion. However, underlying mechanisms contributing to venular constriction remain unknown. Thus, we examined the roles of ET-1 receptors, extracellular calcium (Ca²⁺), L-type voltage-operated calcium channels (L-VOCCs), Rho kinase (ROCK), and protein kinase C (PKC) in ET-1-induced constriction of retinal venules.

Methods

Porcine retinal venules were isolated and pressurized for vasoreactivity study using videomicroscopic techniques. Protein and mRNA were analyzed using molecular tools.

Results

Retinal venules developed basal tone and constricted concentration-dependently to ET-1. The ET_A receptor (ET_AR) antagonist BQ123 abolished venular constriction to ET-1, but ET_B receptor (ET_BR) antagonist BQ788 had no effect on vasoconstriction. The ET_BR agonist sarafotoxin S6c did not elicit vasomotor activity. In the absence of extracellular Ca²⁺, venules lost basal tone and ET-1–induced constriction was nearly abolished. Although L-VOCC inhibitor nifedipine also reduced basal tone and blocked vasoconstriction to L-VOCC activator Bay K8644, constriction of venules to ET-1 remained. The ROCK inhibitor H-1152 but not PKC inhibitor Gö 6983 prevented ET-1-induced vasoconstriction. Protein and mRNA expressions of ET_ARs and ET_BRs, along with ROCK1 and ROCK2 isoforms, were detected in retinal venules.

Conclusions

Extracellular Ca²⁺ entry via L-VOCCs is essential for developing and maintaining basal tone of porcine retinal venules. ET-1 causes significant constriction of retinal venules by activating ET_ARs and extracellular Ca²⁺ entry independent of L-VOCCs. Activation of ROCK signaling, without involvement of PKC, appears to mediate venular constriction to ET-1 in the porcine retina.

Topical Administration of Bosentan Prevents Retinal Neurodegeneration in Experimental Diabetes

Experimental evidence suggests that endothelin 1 (ET-1) is involved in the development of retinal microvascular abnormalities induced by diabetes. The effects of ET-1 are mediated by endothelin A- and B-receptors (ETA and ETB). Endothelin B-receptors activation mediates retinal neurodegeneration but there are no data regarding the effectiveness of ETB receptor blockage in arresting retinal neurodegeneration induced by diabetes. The main aim of the present study was to assess the usefulness of topical administration of bosentan (a dual endothelin receptor antagonist) in preventing retinal neurodegeneration in diabetic (db/db) mice. For this purpose, db/db mice aged 10 weeks were treated with one drop of bosentan (5 mg/mL, n = 6) or vehicle (n = 6) administered twice daily for 14 days. Six non-diabetic (db/+) mice matched by age were included as the control group. Glial activation was evaluated by immunofluorescence using specific antibodies against glial fibrillary acidic protein (GFAP). Apoptosis was assessed by TUNEL method. A pharmacokinetic study was performed in rabbits. We found that topical administration of bosentan resulted in a significant decrease of reactive gliosis and apoptosis. The results of the pharmacokinetic study suggested that bosentan reached the retina through the trans-scleral route. We conclude that topical administration of bosentan was effective in preventing neurodegeneration in the diabetic retina and, therefore, could be a good candidate to be tested in clinical trials.

Endothelin-1 is associated with fibrosis in proliferative diabetic retinopathy membranes

Purpose

To characterize the relationship between endothelin-1 and fibrosis in epiretinal membranes in proliferative diabetic retinopathy and explore the role of endothelial-mesenchymal transition in these membranes.

Methods

Membranes were obtained from eyes undergoing pars plana vitrectomy for complicated proliferative diabetic retinopathy or idiopathic epiretinal membrane. Through standard immunohistochemical techniques, we labeled membranes to explore the distribution of endothelin-1 and endothelin receptor B, comparing proliferative diabetic retinopathy and idiopathic epiretinal membranes. In addition, membranes were also labeled with markers for fibroblasts, endothelial, and glial cells and studied with confocal laser scanning microscopy. The intensity of endothelin-1 labeling was quantified using standard image analysis software.

Results

Fourteen membranes were included in the analysis, nine from eyes with proliferative diabetic retinopathy and five idiopathic membranes. Flatmount diabetic membranes showed co-localization of endothelin-1 with S100A4 and CD31. Immunohistochemistry and quantitative analysis of cross-sectional membranes showed significantly higher endothelin-1 labeling in proliferative diabetic retinopathy membranes compared to idiopathic membranes (p<0.05). Diabetic membranes showed more elements staining positive for S100A4 compared to idiopathic membranes.

Conclusion

Epiretinal membrane formation in proliferative diabetic retinopathy involves higher tissue levels of endothelin-1 and fibroblastic activity. Furthermore, endothelin-1, endothelial and fibroblastic staining appear to be correlated, suggestive of endothelial-to-mesenchymal transition in proliferative diabetic retinopathy.

Aqueous humor endothelin-1 and total retinal blood flow in patients with non-proliferative diabetic retinopathy

PurposeThe purpose of this study was to determine the association between aqueous ET-1 levels and total retinal blood flow (TRBF) in patients with non-insulin-dependent type 2 diabetes mellitus (T2DM) and early non-proliferative diabetic retinopathy (NPDR).Patients and methodsA total of 15 age-matched controls and 15 T2DM patients with NPDR were recruited into the study. Aqueous humor (~80-120 μl) was collected before cataract surgery to measure the levels of ET-1 using suspension multiplex array technology. Four weeks post surgery, six images were acquired to assess TRBF using the prototype RTVue Doppler FD-OCT (Optovue, Inc., Fremont, CA, USA) with a double circular scan protocol. At the same visit, forearm blood was collected to determine plasma glycosylated hemoglobin (A1c) levels.ResultsAqueous ET-1 was significantly elevated in the NPDR group compared with the control group (3.5±1.8 vs 2.2±0.8, P=0.02). TRBF was found to be significantly reduced in the NPDR group compared with the control group (34.5±9.1 vs 44.1±4.6 μl/min, P=0.002). TRBF and aqueous ET-1 were not correlated within the NPDR group (r=-0.24, P=0.22). In a multivariate analysis, high A1c was associated with reduced TRBF and aqueous ET-1 levels across control and NPDR groups (P<0.01).ConclusionAqueous ET-1 levels were increased while TRBF was reduced in patients with NPDR compared with the control group. Although not directly associated, the vasoconstrictory effects of ET-1 are consistent with a reduced TRBF observed in early DR. ET-1 dysregulation may contribute to a reduction in retinal blood flow during early DR.

Level of Vascular Endothelial Growth Factor in the Vitreous Fluid of Proliferative Diabetic Retinopathy Patients and Prognosis after Vitrectomy

PURPOSE

The aim of this study was to evaluate the relationship between the intravitreal vascular endothelial growth factor (VEGF) level and prognosis of proliferative diabetic retinopathy (PDR).

METHODS

The study involved 136 eyes of 114 PDR patients who underwent an initial vitrectomy between 2006 and 2008. Intravitreal VEGF levels were determined using Bio-Plex® (Bio-Rad), with levels of 5,000 pg/mL or more classified as high-VEGF (45 eyes) and levels lower than 5,000 pg/mL as low-VEGF (91 eyes). Diabetic control, PDR severity, and frequency of postoperative complications were compared between the groups.

RESULTS

There was no significant difference in preoperative status between the groups. In the low-VEGF group, a reoperation was required due to postoperative complications in 2 eyes (2.2%); 1 with vitreous hemorrhage (VH) and 1 with retinal detachment (RD). In contrast, a reoperation was required in 8 eyes (17.8%) in the high-VEGF group; 3 with VH, 2 with RD, and 3 with neovascular glaucoma. The difference between the groups was significant. There was a statistically lower postoperative corrected visual acuity logMAR (6 months after surgery) in the high-VEGF than in the low-VEGF group (p = 0.02, unpaired t test).

CONCLUSION

Current findings indicate that careful observation is needed in patients with elevated VEGF levels.

Biomarkers for Diabetic Retinopathy - Could Endothelin 2 Be Part of the Answer?

Purpose

The endothelins are a family of three highly conserved and homologous vasoactive peptides that are expressed across all organ systems. Endothelin (Edn) dysregulation has been implicated in a number of pathophysiologies, including diabetes and diabetes-related complications. Here we examined Edn2 and endothelin receptor B (Endrb) expression in retinae of diabetic mouse models and measured serum Edn2 to assess its biomarker potential.

Materials and Methods

Edn2 and Ednrb mRNA and Edn2 protein expression were assessed in young (8wk) and mature (24wk) C57Bl/6 (wild type; wt), Kimba (model of retinal neovascularisation, RNV), Akita (Type 1 diabetes; T1D) and Akimba mice (T1D plus RNV) by qRT-PCR and immunohistochemistry. Edn2 protein concentration in serum was measured using ELISA.

Results

Fold-changes in Edn2 and Ednrb mRNA were seen only in young Kimba (Edn2: 5.3; Ednrb: 6.0) and young Akimba (Edn2: 7.9, Ednrb: 8.8) and in mature Kimba (Edn2:9.2, Ednrb:11.2) and mature Akimba (Edn2:14.0, Ednrb:17.5) mice. Co-localisation of Edn2 with Müller-cell-specific glutamine synthetase demonstrated Müller cells and photoreceptors as the major cell types for Edn2 expression in all animal models. Edn2 serum concentrations in young Kimba, Akita and Akimba mice were not elevated compared to wt. However, in mature mice, Edn2 serum concentration was increased in Akimba (6.9pg/mg total serum protein) compared to wt, Kimba and Akita mice (3.9, 4.6, and 3.8pg/mg total serum protein, respectively; p<0.05).

Conclusions

These results demonstrated that long-term hyperglycaemia in conjunction with VEGF-driven RNV increased Edn2 serum concentration suggesting Edn2 might be a candidate biomarker for vascular changes in diabetic retinopathy.

Alterations in circulating angiogenic and anti-angiogenic factors in type 2 diabetic patients with neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most common diabetic chronic complications. There is an increased attention directed towards the role of angiogenic factors including vascular endothelial growth factor (VEGF) and anti-angiogenic factors including soluble endoglin (sEng) as contributors to diabetic microvascular complications including neuropathy. The purposes of this study were to determine the role of these angiogenesis regulators in the prognosis of DPN. The study group included 60 patients with type 2 diabetes mellitus (T2DM) and 20 clinically healthy individuals. The patients were divided into two groups. Group I included 20 T2DM patients without peripheral neuropathy, and Group II consisted of 40 T2DM patients with DPN. In all groups, plasma VEGF, sEng and endothelin-1 (ET-1), nitric oxide and ET-1 mRNA were estimated. Plasma levels of VEGF, sEng, ET-1 and nitric oxide were significantly elevated in diabetic patients (Groups I and II) compared with healthy control subjects, with a higher increase in their levels in patients with DPN compared with diabetic patients without peripheral neuropathy. Measurement of plasma levels of angiogenesis-related biomarkers in high-risk diabetic patients might identify who later develop DPN, thus providing opportunities for early detection and targets for novel treatments.

Role of intravitreal inflammatory cytokines and angiogenic factors in proliferative diabetic retinopathy

OBJECTIVE

Inflammatory reaction has been shown to involve the progress of type 2 (non-insulin-dependent) diabetes. We, therefore, examined the effects of inflammatory cytokines and angiogenic factors in the pathogenesis of proliferative diabetic retinopathy (PDR) in type 2 diabetes.

PATIENTS AND METHODS

Vitreous fluid samples were obtained by vitrectomy from 62 eyes of PDR patients with type 2 diabetes and from 20 eyes of age-matched non-diabetic patients. The concentrations of interleukin 1 beta (IL1B), IL6, IL8, IL10, chemokine (C-C motif) ligand 2 (CCL2), endothelin 1 (EDN1), vascular endothelial growth factor (VEGF), and tumor necrosis factor (TNF) in the vitreous samples were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The concentrations of LI1B, IL6, IL8, CCL2, EDN1, VEGF, and TNF in the vitreous samples were considerably higher in PDR patients in comparison with the controls. However, the level of IL10 in PDR patients was similar to that obtained in the controls. Analysis of the correlations of the studied factors revealed the correlation of VEGF and IL6, VEGF and EDN1, IL8 and CCL2, and EDN1 and TNF in PDR patients. In addition, a significant positive correlation was observed between vitreous TNF as well as EDN1 and serum HbA(1)c levels in PDR patients.

CONCLUSIONS

The inflammatory cytokines and angiogenic factors IL1B, IL6, IL8, CCL2, EDN1, VEGF, and TNF are increased in the vitreous of PDR patients without an increase in IL-10. These results add support to the role of inflammatory cytokines and angiogenic factors in the genesis of PDR. Understanding the implication of these cytokines may provide diagnostic tools and therapeutic targets for treatment and prevention of PDR.

Endothelin-induced changes in blood flow in STZ-diabetic and non-diabetic rats: relation to nitric oxide synthase and cyclooxygenase inhibition

In this study, using the microsphere method, the hemodynamic response to endothelin-1 (ET-1) in healthy and streptozotocin (STZ)-diabetic rats was evaluated as well as the influences of inhibition of nitric oxide (NO)-synthase using L-NAME (Nω-nitro-L: -arginine methyl ester) and the cyclooxygenase inhibitor indomethacin. Blood flow (Q) was measured in tissues of interest for vascular complications in diabetes such as kidney, eye, brain, heart and skeletal muscle with the main focus on ophthalmic circulation. Under resting conditions, evidence for renal vasoconstriction was found in diabetic animals. In both groups, administration of L-NAME reduced Q in all investigated tissues indicating a basal NO influence. In the normal rats, ET-1 induced a significant increase in blood pressure and intense vasoconstriction in all tissues except in the choroid of the eye and in the brain, where it induced an increased Q. In the STZ-diabetic rats, effects of ET-1 were less pronounced. Pretreatment with L-NAME, but not the cyclooxygenase inhibitor, abolished the ET-1-induced vasodilation in the choroid of both groups. Administration of ET A receptor antagonist BQ-123 reduced the ET-1-induced vasodilation in the choroid only in diabetic animals. In conclusion, evidence for altered vascular endothelial response to ET-1 in STZ-diabetic animals was found particularly in the ophthalmic circulation. The findings suggest differential involvement of receptors in the response to ET-1 in normal and STZ-diabetic animals.

Thrombin-induced endothelin-1 synthesis and secretion in retinal pigment epithelial cells is rho kinase dependent

PURPOSE

The retinal pigment epithelium (RPE) is a major source for endothelin-1 (ET-1), a potent vasoactive peptide, at the outer blood–retinal barrier. Factors that regulate ET-1 synthesis at this site may help identify its normal function and its role in pathologic states accompanying retinal injury. Thrombin is one such factor that might act on the RPE after injury and breakdown of the blood–retinal barrier. The present study was conducted to identify signaling intermediates in thrombin-induced ET-1 synthesis and secretion in primary human RPE (hRPE) and transformed RPE cells (ARPE-19) and a possible pharmacological strategy to block excess release of ET-1.

METHODS

Cultured hRPE cells were treated with different concentrations of thrombin and thrombin receptor agonists, and a time course to measure levels of preproET-1 (ppET-1) mRNA and secreted mature ET-1 was performed. Levels of secondary messengers [Ca²+]i and RhoA were measured and pharmacologically inhibited to determine how receptor-mediated thrombin activity lead to changes in ET-1 levels.

RESULTS

Thrombin primarily acts via the protease-activated receptor-1 (PAR-1) subtype in RPE to induce ET-1 synthesis. Thrombin and other receptor agonists increased both [Ca²+]<]i and active RhoA. PAR-1-dependent rho/Rho kinase activation led to increase in ppET-1 mRNA and mature ET-1 secretion.

CONCLUSIONS

Transient intracellular calcium mobilization and protein kinase C activation by thrombin play a minor role, if any, in ET-1 synthesis in RPE. Instead, rho/Rho kinase activation after PAR-1 stimulation strongly increased ppET-1 mRNA and ET-1 secretion in hRPE cells.

Roles of endothelin-1 and selected proinflammatory cytokines in the pathogenesis of proliferative diabetic retinopathy: Analysis of vitreous samples

PURPOSE

To investigate the roles of endothelin-1(ET-1), TNF-alpha, IL-6 in the pathogenesis of proliferative diabetic retinopathy (PDR) in type 2 diabetes.

METHODS

Vitreous and blood serum samples were collected during vitrectomy from 19 patients with PDR and 15 patients who underwent vitrectomy for other reasons. The concentrations of ET-1, TNF-alpha, IL-6, vWF, sE-selectin were determined by ELISA.

RESULTS

Intraocular and serous concentrations of ET-1, TNF-alpha, IL-6, vWF, sE-selectin were higher in patients with PDR than in the control group. The vitreous ET-1/plasma ET-1 ratios the group of diabetic patients and in the control group were similar. Also TNF-alpha, IL-6 vitreous/plasma ratio were not statistically different between the analysed groups. Correlation between intraocular ET-1 and TNF-alpha concentrations in patients with PDR and between the increases in both factors in the vitreous and HbA(1)c concentration were shown. In the vitreous the increase in vWF depended on elevated levels of vWF in the serum. E-selectin concentration correlated with diastolic blood pressure.

CONCLUSION

These data provide evidence of the activation of the local synthesis of ET-1, TNF-alpha, IL-6 in PDR. The relationship between the increase in vitreous ET-1, TNF-alpha concentrations and HbA(1)c concentration is a important confirmation of the necessity to optimise diabetes treatment.