Inflammation and Neurodegeneration in Glaucoma: Isolated Eye Disease or a Part of a Systemic Disorder? - Serum Proteomic Analysis

Introduction

Glaucoma is the most common optic neuropathy and the leading cause of irreversible blindness worldwide, which affects 3.54% of the population aged 40-80 years. Despite numerous published studies, some aspects of glaucoma pathogenesis, serum biomarkers, and their potential link with other diseases remain unclear. Recent articles have proposed that autoimmune, oxidative stress and inflammation may be involved in the pathogenesis of glaucoma.

Methods

We investigated the serum expression of 92 inflammatory and neurotrophic factors in glaucoma patients. The study group consisted of 26 glaucoma patients and 192 healthy subjects based on digital fundography.

Results

Patients with glaucoma had significantly lower serum expression of IL-2Rβ, TWEAK, CX3CL1, CD6, CD5, LAP TGF-beta1, LIF-R, TRAIL, NT-3, and CCL23 and significantly higher expression of IL-22Rα1.

Conclusion

Our results indicate that patients with glaucoma tend to have lower levels of neuroprotective proteins and higher levels of neuroinflammatory proteins, similar to those observed in psychiatric, neurodegenerative and autoimmune diseases, indicating a potential link between these conditions and glaucoma pathogenesis.

Role of exosome-derived miRNAs in diabetic wound angiogenesis

Chronic wounds with high disability are among the most common and serious complications of diabetes. Angiogenesis dysfunction impair wound healing in patients with diabetes. Compared with traditional therapies that can only provide symptomatic treatment, stem cells-owing to their powerful paracrine properties, can alleviate the pathogenesis of chronic diabetic wounds and even cure them. Exosome-derived microRNAs (miRNAs), important components of stem cell paracrine signaling, have been reported for therapeutic use in various disease models, including diabetic wounds. Exosome-derived miRNAs have been widely reported to be involved in regulating vascular function and have promising applications in the repair and regeneration of skin wounds. Therefore, this article aims to review the current status of the pathophysiology of exosome-derived miRNAs in the diabetes-induced impairment of wound healing, along with current knowledge of the underlying mechanisms, emphasizing the regulatory mechanism of angiogenesis, we hope to document the emerging theoretical basis for improving wound repair by restoring angiogenesis in diabetes.

Changes in aqueous and vitreous inflammatory cytokine levels in proliferative diabetic retinopathy: a systematic review and meta-analysis

BACKGROUND

Diabetic retinopathy is a major complication of diabetes mellitus, where in its most advanced form ischemic changes lead to the development of retinal neovascularization, termed proliferative diabetic retinopathy (PDR). While the development of PDR is often associated with angiogenic and inflammatory cytokines, studies differ on which cytokines are implicated in disease pathogenesis and on the strength of these associations. We therefore conducted a systematic review and meta-analysis to quantitatively assess the existing body of data on intraocular cytokines as biomarkers in PDR.

METHODS

A comprehensive search of the literature without year limitation was conducted to January 18, 2021, which identified 341 studies assessing vitreous or aqueous cytokine levels in PDR, accounting for 10379 eyes with PDR and 6269 eyes from healthy controls. Effect sizes were calculated as standardized mean differences (SMD) of cytokine concentrations between PDR and control patients.

RESULTS

Concentrations (SMD, 95% confidence interval, and p-value) of aqueous IL-1β, IL-6, IL-8, MCP-1, TNF-α, and VEGF, and vitreous IL-2, IL-4, IL-6, IL-8, angiopoietin-2, eotaxin, erythropoietin, GM-CSF, GRO, HMGB-1, IFN-γ, IGF, IP-10, MCP-1, MIP-1, MMP-9, PDGF-AA, PlGF, sCD40L, SDF-1, sICAM-1, sVEGFR, TIMP, TNF-α, and VEGF were significantly higher in patients with PDR when compared to healthy nondiabetic controls. For all other cytokines no differences, failed sensitivity analyses or insufficient data were found.

CONCLUSIONS

This extensive list of cytokines speaks to the complexity of PDR pathogenesis, and informs future investigations into disease pathogenesis, prognosis, and management.

Comparative transcriptome analysis of human and murine choroidal neovascularization identifies fibroblast growth factor inducible-14 as phylogenetically conserved mediator of neovascular age-related macular degeneration

BACKGROUND

Visual outcome of patients with neovascular age-related macular degeneration has significantly improved during the last years following the introduction of anti-vascular endothelial growth factor (VEGF) therapy. However, about one third of patients show persistent exudation and decreasing visual acuity despite recurrent anti-VEGF treatment, which implies a role of other, still unknown proangiogenic mediators.

METHODS

The present study applied transcriptional profiling of human and mouse (C57BL/6J wildtype) choroidal neovascularization (CNV) membranes each with reference to healthy control tissue to identify yet unrecognized mediators of CNV formation. Key factors were further investigated by immunohistochemistry as well as by intravitreal inhibition experiments and multiplex protein assays in the laser-induced CNV mouse model.

FINDINGS

Transcriptional profiles of CNV membranes were characterized by enhanced activation of blood vessel development, cytoskeletal organization, and cytokine production, with angiogenesis and wound healing processes predominating in humans and activation of immune processes in mice. Besides several species-specific factors, 95 phylogenetically conserved CNV-associated genes were detected, among which fibroblast growth factor inducible-14 (FN14), a member of the tumor necrosis factor (TNF) receptor family, was identified as a key player of CNV formation. Blocking the pathway by intravitreal injection of a FN14 decoy receptor modulated the cytokine profile - most notably IL-6 - and led to a significant reduction of CNV size in vivo.

INTERPRETATION

This study characterizes the transcriptome of human and mouse CNV membranes in an unprejudiced manner and identifies FN14 as a phylogenetically conserved mediator of CNV formation and a promising new therapeutic target for neovascular AMD.

FUNDING

This study was funded by the Helmut Ecker Foundation and the Volker Homann Foundation.

Intraocular tumour necrosis factor ligand related molecule 1 A links disease progression of proliferative diabetic retinopathy after primary vitrectomy

Tumour necrosis factor ligand related molecule 1 A (TL1A), a member of tumour necrosis factor superfamily, has been identified as a crucial regulator for vascular homeostasis and inflammation. However, the function of TL1A in diabetic retinopathy (DR) is largely unknown. This study aims to examine levels of TL1A in serum and intraocular fluid in patients with proliferative diabetic retinopathy (PDR), and to explore the correlation of intraocular TL1A with the prognosis of PDR progression after primary vitrectomy. Seventy-five patients (75 eyes) with PDR who underwent pars plana vitrectomy (PPV) and 19 patients (19 eyes) who received vitrectomy for idiopathic macular holes (IMH) as non-diabetic control group were enrolled in this prospective study. Serum, aqueous and vitreous fluid samples were collected during cataract and PPV surgery. Protein expressions of TL1A as well as other angiogenic and inflammatory cytokines in serum and intraocular fluid were measured. Correlations of intraocular TL1A concentrations with inflammatory cytokines were analyzed. We found both aqueous and vitreous TL1A levels were significantly higher in the PDR group than in control group (P_aqueous  = 0.026; P_vitreous <0.001). Angiogenic and inflammatory cytokines such as VEGF, IL-6, IL-8, MCP-1, MIP-1α, and MIP-1β were significantly higher in intraocular fluid in PDR group than in controls, which MCP-1 and MIP-1α showed positive correlation with intraocular TL1A levels. There is no significant difference in the levels of serum TL1A as well as other inflammatory cytokines between PDR patients and controls. Intraocular levels of TL1A were significantly lower in PDR progression group than in the stable group (P_aqueous <0.001; P_vitreous <0.001). Multivariate logistic regression analyses revealed that lower levels of intraocular TL1A was an important risk factor for predicting PDR progression after primary PPV (OR_aqueous  = 0.717, P_aqueous  = 0.001; OR_vitreous  = 0.684; P_vitreous  = 0.002). In conclusion, TL1A and multiple inflammatory cytokines were highly enriched in the intraocular fluid of PDR patients compared with the controls. Lower levels of intraocular TL1A were associated with development of PDR complications after primary PPV and might be used as prognostic factor in predicting the vitrectomy outcome in PDR patients.

Evaluation of soluble TNF-like weak inducer of apoptosis (sTWEAK) levels to predict preeclampsia in early weeks of pregnancy

INTRODUCTION

Soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) is linked to endothelial dysfunction; a key factor in pre-eclamptic pathogenesis. This study aimed to compare sTWEAK levels during pregnancy to assess for its prognostic ability.

MATERIALS AND METHODS

Sixty three high risk pregnant women were followed up from 12 weeks of gestation till term. Serum levels of sTWEAK and platelet derived growth factor (PlGF), blood pressure, serum glucose, uric acid, urea/creatinine and liver function tests were measured. Subjects were stratified according to the ACOG criteria as women who developed PE, or PIH or remained normotensive at term. A negative control group of normotensive healthy pregnant women (n = 17) was also recruited for comparison.

RESULTS

Baseline sTWEAK levels were lower (4.03 ± 0.37 ng/dl) in HR cohort that developed PE and further reduced at term (1.93 ± 0.23 ng/dl) as compared to HR subjects who remained normotensive and negative control group (30.53 ± 0.79 ng/dl; p < 0.01). Likewise PlGF levels were significantly lower (74.22 ± 10.11 pg/ml) in HR cohort that developed PE (p = 0.013). At term 39.68% (n = 22) HR subjects with low sTWEAK developed PIH and 34.92% (n = 24) developed PE. In terms of high risk characteristics observed in the HR group; 73% of the subjects were multiparous, whereas 26.98% reported to have developed PE in previous pregnancies.

CONCLUSION

sTWEAK levels at early pregnancy weeks were found to be low in high risk females who developed PE at follow up versus normotensive pregnant women. Baseline TWEAK might serve as an independent variable for prediction of pre-eclampsia; however longitudinal studies with larger sample size are required to ascertain the causal relation.

Macro- and microvascular endothelial dysfunction in diabetes

Endothelial cells, as well as their major products nitric oxide (NO) and prostacyclin, play a key role in the regulation of vascular homeostasis. Diabetes mellitus is an important risk factor for cardiovascular disease. Diabetes-induced endothelial dysfunction is a critical and initiating factor in the genesis of diabetic vascular complications. The present review focuses on both large blood vessels and the microvasculature. The endothelial dysfunction in diabetic macrovascular complications is characterized by reduced NO bioavailability, poorly compensated for by increased production of prostacyclin and/or endothelium-dependent hyperpolarizations, and increased production or action of endothelium-derived vasoconstrictors. The endothelial dysfunction of microvascular complications is primarily characterized by decreased release of NO, enhanced oxidative stress, increased production of inflammatory factors, abnormal angiogenesis, and impaired endothelial repair. In addition, non-coding RNAs (microRNAs) have emerged as participating in numerous cellular processes. Thus, this reviews pays special attention to microRNAs and their modulatory role in diabetes-induced vascular dysfunction. Some therapeutic strategies for preventing and restoring diabetic endothelial dysfunction are also highlighted.

Soluble plasma proteins ST2 and CD163 as early biomarkers of nephropathy in Swedish patients with diabetes, 15-34 years of age: a prospective cohort study

BACKGROUND

The aim of this study was to investigate plasma levels of sST2 and sCD163 to determine whether they at an early stage could predict development of diabetic nephropathy and/or diabetic retinopathy in patients at clinical onset.

METHODS

Patients diagnosed with diabetes mellitus at age 15-34 years between 1987 and 1988 (n = 220) were included. Data such as BMI, smoking, HbA1c and islet cell antibodies were collected at time of diagnosis. Within the 10 year follow-up period, 112 patients (51%) developed following diabetes related complications; retinopathy (n = 91), nephropathy (n = 12) or both (n = 9). Plasma concentrations of sST2 and sCD163 were measured at time of diagnosis and levels compared between different complication groups.

RESULTS

Plasma levels of sST2 were significantly higher in patients who later developed nephropathy (n = 21; 1012 [773-1493] pg/ml) compared to those who did not (n = 199; 723 [449-1084] pg/ml; p = 0.006). A tendency for higher plasma levels of sCD163 was observed but not statistically significant (p = 0.058).

CONCLUSIONS

sST2 and sCD163 show promise as potential biomarkers for the development of nephropathy already at clinical onset. sST2 and/or sCD163 could possibly be part of a biomarker panel aimed to find patients at high risk of developing nephropathy. Both markers need to be investigated in a larger prospective study.

TNFSF15 Inhibits Blood Retinal Barrier Breakdown Induced by Diabetes

Tumor necrosis factor superfamily 15 (TNFSF15) is an endogenous neovascularization inhibitor and an important negative regulator of vascular homeostasis. This study aimed to explore the potential role of TNFSF15 in diabetic retinopathy. Vitreous TNFSF15 and VEGF levels in proliferative diabetic retinopathy (PDR) patients were detected by ELISA. Retinal expression of TNFSF15 and the content of tight junction proteins (TJPs) in rats were detected by immunohistochemistry and Western blot, respectively. The blood retinal barrier (BRB) permeability was evaluated using Evans Blue (EB) dye. The TNFSF15/VEGF ratio was decreased in the vitreous fluid of patients with PDR relative to the controls, even though the expression levels of TNFSF15 were higher. TNFSF15 was dramatically decreased one month later after diabetes induction (p < 0.001), and then increased three months later and thereafter. TNFSF15 treatment significantly protected the BRB in the diabetic animals. Diabetes decreased TJPs levels in the retina, and these changes were inhibited by TNFSF15 treatment. Moreover, TNFSF15 decreased activation of VEGF both in mRNA and protein levels caused by diabetes. These results indicate that TNFSF15 is an important inhibitor in the progression of DR and suggest that the regulation of TNFSF15 shows promise for the development of diabetic retinopathy treatment strategies.

Neuroretinal hypoxic signaling in a new preclinical murine model for proliferative diabetic retinopathy

Diabetic retinopathy (DR) affects approximately one-third of diabetic patients and, if left untreated, progresses to proliferative DR (PDR) with associated vitreous hemorrhage, retinal detachment, iris neovascularization, glaucoma and irreversible blindness. In vitreous samples of human patients with PDR, we found elevated levels of hypoxia inducible factor 1 alpha (HIF1α). HIFs are transcription factors that promote hypoxia adaptation and have important functional roles in a wide range of ischemic and inflammatory diseases. To recreate the human PDR phenotype for a preclinical animal model, we generated a mouse with neuroretinal-specific loss of the von Hippel Lindau tumor suppressor protein, a protein that targets HIF1α for ubiquitination. We found that the neuroretinal cells in these mice overexpressed HIF1α and developed severe, irreversible ischemic retinopathy that has features of human PDR. Rapid progression of retinopathy in these mutant mice should facilitate the evaluation of therapeutic agents for ischemic and inflammatory blinding disorders. In addition, this model system can be used to manipulate the modulation of the hypoxia signaling pathways, for the treatment of non-ocular ischemic and inflammatory disorders.