Identification of chemokines and growth factors in proliferative diabetic retinopathy vitreous

Identifying Therapeutic Targets and Potential Drugs for Diabetic Retinopathy: Focus on Oxidative Stress and Immune Infiltration

Background

Diabetic retinopathy (DR), a microvascular disorder linked to diabetes, is on the rise globally. Oxidative stress and immune cell infiltration are linked to illness initiation and progression, according to recent study. This study investigated biomarkers connected to DR and oxidative stress and their connection with immune cell infiltration using bioinformatics analysis and found possible therapeutic medications.

Methods

The Gene Expression Omnibus (GEO) database was used to obtain the gene expression data for DR. Differentially expressed genes (DEGs) and oxidative stress (OS)-related genes were intersected. The Enrichment analyses concentrate on OS-related differentially expressed genes (DEOSGs). Analysis of protein-protein interaction (PPI) networks and machine learning algorithms were used to identify hub genes. Single-gene Gene Set Enrichment Analysis (GSEA) identified biological functions, while nomograms and ROC curves assessed diagnostic potential. Immune infiltration analysis and regulatory networks were constructed. Drug prediction was validated through molecular docking, and hub gene expression was confirmed in dataset and animal models.

Results

Compared to the control group, 91 DEOSGs were found. Enrichment analyses showed that these DEOSGs were largely connected to oxidative stress response, PI3K/Akt pathway, inflammatory pathways, and immunological activation. Four hub genes were found via PPI networks and machine learning. These hub genes were diagnostically promising according to nomogram and ROC analysis. Analysis of immune cell infiltration highlighted the role of immune cells. Gene regulatory networks for transcription factor (TF) and miRNA were created. Using structural data, molecular docking shows potential drugs and hub genes have high binding affinity. Dataset analysis, Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR) and Western Blot (WB) confirmed the CCL4 expression difference between DR and controls.

Conclusion

CCL4 was identified as potential oxidative stress-related biomarker in DR, providing new insights for DR diagnosis and treatment.

Therapeutic effects of Mudan granules on diabetic retinopathy: Mitigating fibrogenesis caused by FBN2 deficiency and inflammation associated with TNF-α elevation

ETHNOPHARMACOLOGICAL RELEVANCE

Mudan granules (MuD), a time-honored traditional Chinese patent medicine (TCPM), are widely utilized in the clinical treatment of diabetic peripheral neuropathy (DPN). In the field of biomedical diagnostics, both diabetic retinopathy (DR) and DPN are recognized as critical microvascular complications associated with diabetes. According to the principles of traditional Chinese medicine (TCM), these conditions are primarily attributed to a deficiency in Qi and the obstruction of collaterals. Despite this, the protective effects of MuD on DR and the underlying mechanisms remain to be comprehensively elucidated.

AIMS OF THE STUDY

The purpose of this study was to investigate the effect of MuD on DR and to further explore the promising therapeutic targets.

METHODS

A diabetic mouse model was established by administering 60 mg/kg of streptozotocin (STZ) via intraperitoneal injection for five consecutive days. The therapeutic efficacy of MuD was evaluated using a comprehensive approach, which included electroretinogram (ERG) analysis, histopathological examination, and assessment of serum biochemical markers. Then, the pharmacodynamic mechanisms of MuD were systematically analyzed using Tandem Mass Tags-based proteomics. Meanwhile, the candidate compounds of MuD were analyzed by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and molecular docking was applied to estimate the affinity of the active ingredient to their potential key targets. In addition, the functional mechanisms identified through bioinformatics analysis were confirmed by molecular biological methods.

RESULTS

We demonstrated that MuD provided significant protection to retinal function and effectively mitigated the reduction in retinal thickness observed in the animal model. Through proteomic analysis, we identified a substantial regulation by MuD of 70 biomarkers associated with diabetic retinal damage. These proteins were notably enriched in the tumor necrosis factor (TNF) signaling pathway, a critical mediator in inflammatory processes. A particularly intriguing finding was the significant downregulation of fibrillin-2 (FBN2) in the diabetic retina compared to the control group (0.36 times the level), and its most pronounced upregulation (3.26 times) in the MuD treatment group. This suggests that FBN2 may play a pivotal role in the protective effects of MuD. Molecular docking analyses have unveiled a robust interplay between the components of MuD and TNF-α. Further corroboration was provided by molecular biological methods, which confirmed that MuD could suppress TNF-mediated inflammation and prevent retinal neovascularization and fibrogenesis.

CONCLUSION

MuD have the potential to alleviate diabetic retinal dysfunction by effectively curbing the fibrogenesis-associated neoangiogenesis and mitigating the inflammatory response, thereby restoring retinal health and function.

Human Antigen R -mediated modulation of Transforming Growth Factor Beta 1 expression in retinal pathological milieu

The fate and stability of messenger RNA (mRNA), from transcription to degradation is regulated by a dynamic shuttle of epigenetic modifications and RNA binding proteins in maintaining healthy cellular homeostasis and disease development. While Transforming Growth Factor Beta 1 (TGFβ1) has been implicated as a key regulator for diabetic retinopathy, a microvascular complication of diabetes, the RNA binding proteins post-transcriptionally regulating its expression remain unreported in the ocular context. Further, dysfunction of TGFβ1 signalling is also strongly associated with angiogenesis, inflammatory responses and tissue fibrosis in many eye conditions leading to vision loss. In this study, computational and molecular simulations were initially carried out to identify Human Antigen R (HuR) binding sites in TGFβ1 mRNA and predict the structural stability of these RNA-protein interactions. These findings were further validated through in vitro experiments utilizing Cobalt Chloride (CoCl2) as a hypoxia mimetic agent in human retinal microvascular endothelial cells (HRMVEC). In silico analysis revealed that HuR preferentially binds to the 5'-UTR of TGFβ1 and displayed more stable interaction than the 3'UTR. Consistent with in silico analysis, RNA immunoprecipitation demonstrated a robust association between HuR and TGFβ1 mRNA specifically under hypoxic conditions. Further, silencing of HuR significantly reduced TGFβ1 protein expression upon CoCl2 treatment. Thus, for the first time in ocular pathological milieu, direct evidence of HuR- TGFβ1 mRNA interaction under conditions of hypoxia has been reported in this study providing valuable insights into RNA binding proteins as therapeutic targets for ocular diseases associated with TGFβ1 dysregulation.

An Association between HTRA1 and TGF-β2 in the Vitreous Humor of Patients with Chorioretinal Vascular Diseases

Background: The aim of this paper was to investigate the protein concentrations of high-temperature requirement A 1 (HTRA1) and transforming growth factor-β (TGF-β) in the vitreous humor of patients with chorioretinal vascular diseases. Methods: This study measured protein concentrations of HTRA1, TGF-β1-3, and vascular endothelial growth factor A (hereinafter called VEGF) in the vitreous humor from seven eyes of patients with chorioretinal vascular diseases (age-related macular degeneration, diabetic macular edema, and retinal vein occlusion) and six control eyes (idiopathic epiretinal membrane and macular hole). We analyzed the mutual relationship among the protein levels. Results: The protein levels of HTRA1 and VEGF were significantly increased in the chorioretinal vascular disease group compared with the control group (1.57 ± 0.79 ×10-9 mol/mL vs. 0.68 ± 0.79 ×10-9 mol/mL, p = 0.039; 3447.00 ± 3423.47 pg/mL vs. 35.33 ± 79.01 pg/mL, p = 0.046, respectively). TGF-β2 levels were not significantly different between groups (2222.71 ± 1151.25 pg/mL for the chorioretinal vascular disease group vs. 1918.83 ± 744.01 pg/mL for the control group, p = 0.62). The concentration of HTRA1 was strongly associated with TGF-β2 levels in the vitreous humor, independent of VEGF (r = 0.80, p = 0.0010). Conclusions: We revealed that vitreous HTRA1 was increased in patients with chorioretinal vascular diseases and strongly correlated with TGF-β2.

Microvascular destabilization and intricated network of the cytokines in diabetic retinopathy: from the perspective of cellular and molecular components

Microvascular destabilization is the primary cause of the inner blood-retinal barrier (iBRB) breakdown and increased vascular leakage in diabetic retinopathy (DR). Microvascular destabilization results from the combinational effects of increased levels of growth factors and cytokines, involvement of inflammation, and the changed cell-to-cell interactions, especially the loss of endothelial cells and pericytes, due to hyperglycemia and hypoxia. As the manifestation of microvascular destabilization, the fluid transports via paracellular and transcellular routes increase due to the disruption of endothelial intercellular junctional complexes and/or the altered caveolar transcellular transport across the retinal vascular endothelium. With diabetes progression, the functional and the structural changes of the iBRB components, including the cellular and noncellular components, further facilitate and aggravate microvascular destabilization, resulting in macular edema, the neuroretinal damage and the dysfunction of retinal inner neurovascular unit (iNVU). Although there have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying the microvascular destabilization, some still remain to be fully elucidated. Recent data indicate that targeting the intricate signaling pathways may allow to against the microvascular destabilization. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in the microvascular destabilization in DR. In this review, we discuss: (1) the brief introduction of DR and microvascular destabilization; (2) the cellular and molecular components of iBRB and iNVU, and the breakdown of iBRB; (3) the matrix and cell-to-cell contacts to maintain microvascular stabilization, including the endothelial glycocalyx, basement membrane, and various cell-cell interactions; (4) the molecular mechanisms mediated cell-cell contacts and vascular cell death; (5) the altered cytokines and signaling pathways as well as the intricate network of the cytokines involved in microvascular destabilization. This comprehensive review aimed to provide the insights for microvascular destabilization by targeting the key molecules or specific iBRB cells, thus restoring the function and structure of iBRB and iNVU, to treat DR.

Cell and molecular targeted therapies for diabetic retinopathy

Diabetic retinopathy (DR) stands as a prevalent complication in the eye resulting from diabetes mellitus, predominantly associated with high blood sugar levels and hypertension as individuals age. DR is a severe microvascular complication of both type I and type II diabetes mellitus and the leading cause of vision impairment. The critical approach to combatting and halting the advancement of DR lies in effectively managing blood glucose and blood pressure levels in diabetic patients; however, this is seldom achieved. Both human and animal studies have revealed the intricate nature of this condition involving various cell types and molecules. Aside from photocoagulation, the sole therapy targeting VEGF molecules in the retina to prevent abnormal blood vessel growth is intravitreal anti-VEGF therapy. However, a substantial portion of cases, approximately 30-40%, do not respond to this treatment. This review explores distinctive pathophysiological phenomena of DR and identifiable cell types and molecules that could be targeted to mitigate the chronic changes occurring in the retina due to diabetes mellitus. Addressing the significant research gap in this domain is imperative to broaden the treatment options available for managing DR effectively.

Nutraceuticals for Diabetic Retinopathy: Recent Advances and Novel Delivery Systems

Diabetic retinopathy (DR) is a major vision-threatening disease among the working-age population worldwide. Present therapeutic strategies such as intravitreal injection of anti-VEGF and laser photocoagulation mainly target proliferative DR. However, there is a need for early effective management in patients with early stage of DR before its progression into the more severe sight-threatening proliferative stage. Nutraceuticals, natural functional foods with few side effects, have been proposed to be beneficial in patients with DR. Over the decades, many studies, either in vitro or in vivo, have demonstrated the advantages of a number of nutraceuticals in DR with their antioxidative, anti-inflammatory, neuroprotective, or vasoprotective effects. However, only a few clinical trials have been conducted, and their outcomes varied. The low bioavailability and instability of many nutraceuticals have indeed hindered their utilization in clinical use. In this context, nanoparticle carriers have been developed to deliver nutraceuticals and to improve their bioavailability. Despite its preclinical nature, research of interventive nutraceuticals for DR may yield promising information in their clinical applications.

CC Chemokine Family Members' Modulation as a Novel Approach for Treating Central Nervous System and Peripheral Nervous System Injury-A Review of Clinical and Experimental Findings

Despite significant progress in modern medicine and pharmacology, damage to the nervous system with various etiologies still poses a challenge to doctors and scientists. Injuries lead to neuroimmunological changes in the central nervous system (CNS), which may result in both secondary damage and the development of tactile and thermal hypersensitivity. In our review, based on the analysis of many experimental and clinical studies, we indicate that the mechanisms occurring both at the level of the brain after direct damage and at the level of the spinal cord after peripheral nerve damage have a common immunological basis. This suggests that there are opportunities for similar pharmacological therapeutic interventions in the damage of various etiologies. Experimental data indicate that after CNS/PNS damage, the levels of 16 among the 28 CC-family chemokines, i.e., CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11, CCL12, CCL17, CCL19, CCL20, CCL21, and CCL22, increase in the brain and/or spinal cord and have strong proinflammatory and/or pronociceptive effects. According to the available literature data, further investigation is still needed for understanding the role of the remaining chemokines, especially six of them which were found in humans but not in mice/rats, i.e., CCL13, CCL14, CCL15, CCL16, CCL18, and CCL23. Over the past several years, the results of studies in which available pharmacological tools were used indicated that blocking individual receptors, e.g., CCR1 (J113863 and BX513), CCR2 (RS504393, CCX872, INCB3344, and AZ889), CCR3 (SB328437), CCR4 (C021 and AZD-2098), and CCR5 (maraviroc, AZD-5672, and TAK-220), has beneficial effects after damage to both the CNS and PNS. Recently, experimental data have proved that blockades exerted by double antagonists CCR1/3 (UCB 35625) and CCR2/5 (cenicriviroc) have very good anti-inflammatory and antinociceptive effects. In addition, both single (J113863, RS504393, SB328437, C021, and maraviroc) and dual (cenicriviroc) chemokine receptor antagonists enhanced the analgesic effect of opioid drugs. This review will display the evidence that a multidirectional strategy based on the modulation of neuronal-glial-immune interactions can significantly improve the health of patients after CNS and PNS damage by changing the activity of chemokines belonging to the CC family. Moreover, in the case of pain, the combined administration of such antagonists with opioid drugs could reduce therapeutic doses and minimize the risk of complications.

TGF-β Signaling Pathways in the Development of Diabetic Retinopathy

Diabetic retinopathy (DR), a prevalent complication of diabetes mellitus affecting a significant portion of the global population, has long been viewed primarily as a microvascular disorder. However, emerging evidence suggests that it should be redefined as a neurovascular disease with multifaceted pathogenesis rooted in oxidative stress and advanced glycation end products. The transforming growth factor-β (TGF-β) signaling family has emerged as a major contributor to DR pathogenesis due to its pivotal role in retinal vascular homeostasis, endothelial cell barrier function, and pericyte differentiation. However, the precise roles of TGF-β signaling in DR remain incompletely understood, with conflicting reports on its impact in different stages of the disease. Additionally, the BMP subfamily within the TGF-β superfamily introduces further complexity, with BMPs exhibiting both pro- and anti-angiogenic properties. Furthermore, TGF-β signaling extends beyond the vascular realm, encompassing immune regulation, neuronal survival, and maintenance. The intricate interactions between TGF-β and reactive oxygen species (ROS), non-coding RNAs, and inflammatory mediators have been implicated in the pathogenesis of DR. This review delves into the complex web of signaling pathways orchestrated by the TGF-β superfamily and their involvement in DR. A comprehensive understanding of these pathways may hold the key to developing targeted therapies to halt or mitigate the progression of DR and its devastating consequences.

GMFB/AKT/TGF-β3 in Müller cells mediated early retinal degeneration in a streptozotocin-induced rat diabetes model

Retinal degeneration, characterized by Müller cell gliosis and photoreceptor apoptosis, is considered an early event in diabetic retinopathy (DR). Our previous study proposed that GMFB may mediate diabetic retinal degeneration. This study identified GMFB as a sensitive and functional gliosis marker for DR. Compared to the wild type (WT) group, Gmfb knockout (KO) significantly improved visual function, attenuated gliosis, reduced the apoptosis of neurons, and decreased the mRNA levels of tumor necrosis factor α (Tnf-α) and interleukin-1β (Il-1β) in diabetic retinas. Tgf-β3 was enriched by hub genes using RNA sequencing in primary WT and KO Müller cells. Gmfb KO significantly upregulated the transforming growth factor (TGF)-β3 protein level via the AKT pathway. The protective effect of TGF-β3 in the vitreous resulted in significantly improved visual function and decreased the number of apoptotic cells in the diabetic retina. The protection of Gmfb KO in primary Müller cells against high glucose (HG)-induced photoreceptor apoptosis was partially counteracted by TGF-β3 antibody and administration of TGFBR1/2 inhibitors. Nuclear receptor subfamily 3 group C member 1 (NR3C1) binds to the promoter region of Gmfb and regulates Gmfb mRNA at the transcriptional level. NR3C1 was increased in the retinas of early diabetic rats but decreased in the retinas of late diabetic rats. N'-[(1E)-(3-Methoxyphenyl)Methylene]-3-Methyl-1H-Pyrazole-5-Carbohydrazide (DS-5) was identified as an inhibitor of GMFB, having a protective role in DR. We demonstrated that GMFB/AKT/TGF-β3 mediated early diabetic retinal degeneration in diabetic rats. This study provides a novel therapeutic strategy for treating retinal degeneration in patients with DR.

Targeting Members of the Chemokine Family as a Novel Approach to Treating Neuropathic Pain

Neuropathic pain is a debilitating condition that affects millions of people worldwide. Numerous studies indicate that this type of pain is a chronic condition with a complex mechanism that tends to worsen over time, leading to a significant deterioration in patients' quality of life and issues like depression, disability, and disturbed sleep. Presently used analgesics are not effective enough in neuropathy treatment and may cause many side effects due to the high doses needed. In recent years, many researchers have pointed to the important role of chemokines not only in the development and maintenance of neuropathy but also in the effectiveness of analgesic drugs. Currently, approximately 50 chemokines are known to act through 20 different seven-transmembrane G-protein-coupled receptors located on the surface of neuronal, glial, and immune cells. Data from recent years clearly indicate that more chemokines than initially thought (CCL1/2/3/5/7/8/9/11, CXCL3/9/10/12/13/14/17; XCL1, CX3CL1) have pronociceptive properties; therefore, blocking their action by using neutralizing antibodies, inhibiting their synthesis, or blocking their receptors brings neuropathic pain relief. Several of them (CCL1/2/3/7/9/XCL1) have been shown to be able to reduce opioid drug effectiveness in neuropathy, and neutralizing antibodies against them can restore morphine and/or buprenorphine analgesia. The latest research provides irrefutable evidence that chemokine receptors are promising targets for pharmacotherapy; chemokine receptor antagonists can relieve pain of different etiologies, and most of them are able to enhance opioid analgesia, for example, the blockade of CCR1 (J113863), CCR2 (RS504393), CCR3 (SB328437), CCR4 (C021), CCR5 (maraviroc/AZD5672/TAK-220), CXCR2 (NVPCXCR220/SB225002), CXCR3 (NBI-74330/AMG487), CXCR4 (AMD3100/AMD3465), and XCR1 (vMIP-II). Recent research has shown that multitarget antagonists of chemokine receptors, such as CCR2/5 (cenicriviroc), CXCR1/2 (reparixin), and CCR2/CCR5/CCR8 (RAP-103), are also very effective painkillers. A multidirectional strategy based on the modulation of neuronal-glial-immune interactions by changing the activity of the chemokine family can significantly improve the quality of life of patients suffering from neuropathic pain. However, members of the chemokine family are still underestimated pharmacological targets for pain treatment. In this article, we review the literature and provide new insights into the role of chemokines and their receptors in neuropathic pain.

The role of inflammation in immune system of diabetic retinopathy: Molecular mechanisms, pathogenetic role and therapeutic implications

Diabetic retinopathy is one of the most common complications of diabetes mellitus and the leading cause of low vision and blindness worldwide. Mounting evidence demonstrates that inflammation is a key mechanism driving diabetes-associated retinal disturbance, yet the pathophysiological process and molecular mechanisms of inflammation underlying diabetic retinopathy are not fully understood. Cytokines, chemokines, and adhesion molecules interact with each other to form a complex molecular network that propagates the inflammatory and pathological cascade of diabetic retinopathy. Therefore, it is important to understand and elucidate inflammation-related mechanisms behind diabetic retinopathy progression. Here, we review the current understanding of the pathology and pathogenesis of inflammation in diabetic retinopathy. In addition, we also summarize the relevant clinical trials to further suggest inflammation-targeted therapeutics for prevention and management of diabetic retinopathy.

The palliative effects of folic acid on retinal microvessels in diabetic retinopathy via regulating the metabolism of DNA methylation and hydroxymethylation

Diabetic retinopathy (DR) is one of the severe microvascular complications of diabetes. The protective effects of FA on retinal vascular endothelial cells against high glucose levels involve in multiple aspects in DR; however, the underlying mechanism is not fully elucidated. In present study, we investigated the transcriptome as well as genome-wide DNA methylation and hydroxymethylation signature in human retinal microvascular endothelial ACBRI 181 cells cultured within high glucose (HG) medium supplemented with or without FA by RNA-seq, MeDIP-seq, and hMeDIP-seq. Total 3308 differential expressed genes (DEGs) were involved in multiple biological processes and molecular functions containing angiogenesis, inflammation, S-adenosyl methionine metabolism, and hypoxia response. Moreover, the global DNA methylation and hydroxymethylation in ACBRI 181 cells with FA treatment were both compromised compared to HG. Combined with transcriptome data, four subclusters of DEGs with hyper- or hypomethylated promoters were further verified. Unexpectedly, promoters of these 487 genes all displayed a pattern of increased DNA hydroxymethylation. Furthermore, hyperglycemia rat model was established and administered with FA. The DNA methylation and hydroxymethylation changes of selected target genes COL1A1, ITGA7, MMP-14, and VEGFB confirmed by MeDIP-qPCR were consistent with the results in human ACBRI 181 cells. Finally, the presence of activated DNMT1 and TET2 induced by FA was determined in ACBRI 181 cells and hyperglycemia rat. Taken together, this research provided a resource of expression and epigenetic profiles in retinal microvascular endothelial cell, emphasizing a pharmacological mechanism of FA on DNA methylation and hydroxymethylation regulation in retinal microvessel cells of DR.

Multiplex protein analysis for the study of glaucoma

INTRODUCTION

Glaucoma, a leading cause of irreversible blindness in the world, is a chronic neurodegenerative disease of multifactorial origin. Extensive research is ongoing to better understand, prevent, and treat progressive degeneration of retinal ganglion cells in glaucoma. While experimental models of glaucoma and postmortem tissues of human donors are analyzed for pathophysiological comprehension and improved treatment of this blinding disease, clinical samples of intraocular biofluids and blood collected from glaucoma patients are analyzed to identify predictive, diagnostic, and prognostic biomarkers. Multiplexing techniques for protein analysis offer a valuable approach for translational glaucoma research.

AREAS COVERED

This review provides an overview of the increasing applications of multiplex protein analysis for glaucoma research and also highlights current research challenges in the field and expected solutions from emerging technological advances.

EXPERT OPINION

Analytical techniques for multiplex analysis of proteins can help uncover neurodegenerative processes for enhanced treatment of glaucoma and can help identify molecular biomarkers for improved clinical testing and monitoring of this complex disease. This evolving field and continuously growing availability of new technologies are expected to broaden the comprehension of this complex neurodegenerative disease and speed up the progress toward new therapeutics and personalized patient care to prevent blindness from glaucoma.

Association between diabetic retinopathy and polymorphisms of cytokine genes: a systematic review and meta-analysis

INTRODUCTION

Diabetic retinopathy (DR) is a medical condition caused by damage to the blood vessels of retina tissue due to diabetes mellitus. DR leads to injury in neural and vascular structures and is reported to be significantly influenced by inflammation and inflammatory mediators like cytokines. In this study, a systematic review and meta-analysis were performed to analyze the association between cytokine gene polymorphisms and DR.

METHODS

We identified relevant studies from Scopus, PubMed, and Google scholar databases. Allele and genotype frequencies were pooled. Heterogeneity and publication bias were explored. The odds ratio (OR) and corresponding 95% confidence intervals (CIs) were calculated to estimate the relation.

RESULTS

A total of 3337 cases and 4945 controls in 19 eligible studies were included in the meta-analysis. Overall, results indicated the negative association between the cytokine gene polymorphisms and DR susceptibility in the allelic model (IFN-γ (rs2430561): OR 0.64, [CI]: 0.5 to 0.82; and TGF-β (rs1800471): [OR] = 0.15, [CI]: 0.03 to 0.79); and also, in the dominant model (IFN-γ (rs2430561): OR = 0.4, [CI]: 0.22 to 0.75; and TGF-β (rs1800471): OR = 0.14, [CI]: 0.05 to 0.4).

CONCLUSION

The present study suggests that IFN-γ (rs2430561) and TGF-β (rs1800471) polymorphisms are associated with decreased susceptibility to DR.

Protective role and molecular mechanism of action of Nesfatin-1 against high glucose-induced inflammation, oxidative stress and apoptosis in retinal epithelial cells

Diabetic retinopathy (DR) is a major complication of diabetes mellitus that may cause severe visual impairment. It has been reported that the levels of nesfatin-1 in the serum and vitreous humor were negatively correlated with DR; however, its role in DR has not been fully elucidated. Therefore, the present study was performed to investigate the effect of nesfatin-1 on high glucose-treated human retinal epithelial cells (ARPE-19) and explore the underlying mechanism. The effects of nesfatin-1 on cell viability, inflammation, oxidative stress and apoptosis were examined under high glucose conditions. The Cell Counting Kit-8 assay was used to determine cell viability. The levels of inflammatory cytokines were evaluated using ELISA kits. The reactive oxygen species and malondialdehyde content was estimated using commercial assay kits. Flow cytometry was performed to detect apoptotic cells and western blot analysis was employed to evaluate the expression of apoptosis-associated proteins. Moreover, the levels of NF-κB, NACHT, LRR and PYD domains-containing protein 3 (NLRP3) and high-mobility group protein B1 (HMGB1) were determined via western blot analysis. The results revealed that nesfatin-1 enhanced cell viability and suppressed inflammation, oxidative stress and apoptosis in the presence of high glucose concentration. Moreover, the activation of the NF-κB/NLRP3 inflammasome signaling and the expression of HMGB1 were inhibited by nesfatin-1. Furthermore, HMGB1 overexpression partially abrogated the inactivation of the NF-κB/NLRP3 inflammasome pathway caused by nesfatin-1. Taken together, these findings demonstrated that nesfatin-1 inhibited the activation of the NF-κB/NLRP3 inflammasome signaling via modulating HMGB1 and exerted a protective effect on ARPE-19 cells against high glucose-induced inflammation, oxidative stress and apoptosis.

Involvement of Müller Glial Autoinduction of TGF-β in Diabetic Fibrovascular Proliferation Via Glial-Mesenchymal Transition

Purpose

Müller glial–mesenchymal transition (GMT) is reported as the fibrogenic mechanism promoted by TGF-β–SNAIL axis in Müller cells transdifferentiated into myofibroblasts. Here we show the multifaceted involvement of TGF-β in diabetic fibrovascular proliferation via Müller GMT and VEGF-A production.

Methods

Surgically excised fibrovascular tissues from the eyes of patients with proliferative diabetic retinopathy were processed for immunofluorescence analyses of TGF-β downstream molecules. Human Müller glial cells were used to evaluate changes in gene and protein expression with real-time quantitative PCR and ELISA, respectively. Immunoblot analyses were performed to detect TGF-β signal activation.

Results

Müller glial cells in patient fibrovascular tissues were immunopositive for GMT-related molecular markers, including SNAIL and smooth muscle protein 22, together with colocalization of VEGF-A and TGF-β receptors. In vitro administration of TGF-β1/2 upregulated TGFB1 and TGFB2, both of which were suppressed by inhibitors for nuclear factor-κB, glycogen synthase kinase-3, and p38 mitogen-activated protein kinase. Of the various profibrotic cytokines, TGF-β1/2 application exclusively induced Müller glial VEGFA mRNA expression, which was decreased by pretreatment with small interfering RNA for SMAD2 and inhibitors for p38 mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Supporting these findings, TGF-β1/2 stimulation to Müller cells increased the phosphorylation of these intracellular signaling molecules, all of which were also activated in Müller glial cells in patient fibrovascular tissues.

Conclusions

This study underscored the significance of Müller glial autoinduction of TGF-β as a pathogenic cue to facilitate diabetic fibrovascular proliferation via TGF-β–driven GMT and VEGF-A–driven angiogenesis.

Immunological biomarkers of the vitreous responsible for proliferative alteration in the different forms of retinal detachment

Background

The purpose of the study was to explore the immunological components that are responsible for the proliferative alterations in the different forms of retinal detachment (RD).

Methods

Vitreous fluids were collected during 23G pars plana vitrectomy from 54 eyes of 54 patients with different RD types, such as rhegmatogenous RD (RRD) without proliferative vitreoretinopathy (PVR) (n = 30), PVR (n = 16) and proliferative diabetic retinopathy (PDR) with tractional RD (n = 8). Vitreous fluids were obtained from 19 eyes with epiretinal membrane (ERM), which were used as control samples. A multiplex chemiluminescent immunoassay was performed to evaluate the concentrations of 48 cytokines, chemokines and growth factors.

Results

The expression levels of eotaxin, IFN-gamma, IL-6, IL-8, IL-16, MCP-1, MIF and MIP-1 beta were significantly higher in all RD groups than in the ERM group. The levels of CTACK, IP-10, SCGF-beta, and SDF-1 alpha were significantly higher in patients with diabetic tractional RD and PVR than in other patients. The upregulation of VEGF and IL-18 was detected in PDR.

Conclusions

Our results indicate that complex and significant immunological mechanisms are associated with the pathogenesis of different forms of RD: selected cytokines, chemokines and growth factors are upregulated in the vitreous of eyes with RD. The detected proteins are present in different concentrations both in RRD and PVR. In the presence of PVR and PDR, the majority of cytokines are upregulated; thus, they may serve as biomarkers to estimate the progression or severity level of proliferation and later to develop personalized therapeutic strategies to slow down or prevent pathological changes.

Angiogenesis-Inflammation Cross Talk in Diabetic Retinopathy: Novel Insights From the Chick Embryo Chorioallantoic Membrane/Human Vitreous Platform

Pathological angiogenesis of the retina is a key component of irreversible causes of blindness, as observed in proliferative diabetic retinopathy (PDR). The pathogenesis of PDR is complex and involves vascular, inflammatory, and neuronal mechanisms. Several structural and molecular alterations associated to PDR are related to the presence of inflammation that appears to play a non-redundant role in the neovascular response that characterizes the retina of PDR patients. Vascular endothelial growth factor (VEGF) blockers have evolved over time for the treatment of retinal neovascularization. However, several limitations to anti-VEGF interventions exist. Indeed, the production of other angiogenic factors and pro-inflammatory mediators may nullify and/or cause resistance to anti-VEGF therapies. Thus, appropriate experimental models are crucial for dissecting the mechanisms leading to retinal neovascularization and for the discovery of more efficacious anti-angiogenic/anti-inflammatory therapies for PDR patients. This review focuses on the tight cross talk between angiogenesis and inflammation during PDR and describe how the chick embryo chorioallantoic membrane (CAM) assay may represent a cost-effective and rapid in vivo tool for the study of the relationship between neovascular and inflammatory responses elicited by the vitreous humor of PDR patients and for the screening of novel therapeutic agents.

Comparative Analysis of Multiplex Platforms for Detecting Vitreous Biomarkers in Diabetic Retinopathy

Purpose

To evaluate the feasibility of using the Proximity Extension Assay (PEA) platform to detect biomarkers in vitreous and to compare the findings with results obtained with an electrochemiluminescent (ECL) sandwich immunoassay.

Methods

Vitreous samples from patients with proliferative diabetic retinopathy (PDR) and non-diabetic controls were tested using two different proteomics platforms. Forty-one assays were completed with the ECL platform and 459 with the PEA platform. Spearman's rank correlation coefficient (r_s) was used to determine the direction and strength of the relationship between protein levels detected by both platforms.

Results

Three hundred sixty-six PEA assays detected the tested protein in at least 25% of samples, and the difference in protein abundance between PDR and controls was statistically significant for 262 assays. Seventeen ECL assays yielded a detection rate ≥ 25%, and the difference in protein concentration between PDR and controls was statistically significant for 13 proteins. There was a subset of proteins that were detected by both platforms, and for those the Spearman's correlation coefficient was higher than 0.8.

Conclusions

PEA is suitable for the analysis of vitreous samples, showing a strong correlation with the ECL platform. The detection rate of PEA panels was higher than the panels tested with ECL. The levels of several proinflammatory and angiogenic cytokines were significantly higher in PDR vitreous compared to controls.

Translational Relevance

This study provides new information on the yields of small-volume assays that can detect proteins of interest in ocular specimens, and it identifies patterns of cytokine dysregulation in PDR.

Correlations between vitreous cytokine levels and inflammatory cells in fibrovascular membranes of patients with proliferative diabetic retinopathy

Purpose

The purpose of this study was to investigate the levels of cytokines in the vitreous, and their correlation with the density of inflammatory cells in fibrovascular membranes (FVMs) in patients with proliferative diabetic retinopathy (PDR) to evaluate intraocular inflammatory conditions with regard to disease activity.

Methods

Thirty-three patients (33 eyes) with PDR requiring vitreoretinal surgery because of FVMs and tractional detachment were enrolled in the study, and compared with 20 patients (20 eyes) with macular hole (MH; control group). All patients underwent complete ophthalmological examinations before surgery. The activity of the disease was noted in patients with PDR. Samples of vitreous and blood were taken, and cytokine (MCP-1, IL-8, IL-6, VEGF, IL-1β, TNF-α, MIP-1α, MIP-1β, IL-10, and IL-12) levels were measured using cytometric bead array (CBA). Samples of FVMs were analyzed with immunohistochemical methods for the presence of inflammatory cells (CD45+, CD14+, CD3+, CD4+, CD8+, and CD19+ cells), and the numerical areal density was calculated (NA). Spearman's correlation was used to assess the association between variables. The Mann-Whitney test was used to assess the differences between independent groups. The Wilcoxon signed-rank test was used for assessing differences between two related groups. A p value of less than 0.05 was considered statistically significant.

Results

Patients with active PDR had statistically significantly higher levels of MCP-1 (p = 0.003), VEGF (p = 0.009), and IL-8 (p = 0.02) in the vitreous in comparison with those with inactive PDR. CD45+, CD14+, CD3+, CD4+, CD8+, and CD19+ cells were identified in FVMs for patients with PDR. Statistically significantly higher numerical areal density of T lymphocytes (CD3+, CD4+, and CD8+) was demonstrated in patients with active PDR in comparison with patients with inactive PDR. Moderate to strong correlations were found between either MCP-1 or IL-8 in the vitreous, and the numerical areal density of cells (CD45+, CD3+, CD4+, and CD8+) in the FVMs, and weaker between either MCP-1 or IL-8 in the vitreous and the numerical areal density of CD14+ cells in the FVMs.

Conclusions

The correlation of cytokine (MCP-1 and IL-8) vitreous levels with the density of inflammatory cells in FVMs, and differences in cytokine levels in the vitreous between patients with active and inactive PDR, and between the vitreous and serum in PDR indicate the importance of local intraocular inflammation in patients with PDR.

Transforming growth factor-β signaling, a potential mechanism associated with diabetes mellitus and pancreatic cancer?

Pancreatic cancer is a common malignant digestive disease. Epidemiological and clinical studies have demonstrated that pancreatic cancer is closely related to diabetes mellitus. Diabetic patients are more likely to develop pancreatic cancer, which is linked with poor outcomes. Pancreatic cancer is complicated with abnormal blood sugar and insulin resistance and promotes the development of diabetes mellitus. Understanding the molecular mechanisms linking diabetes mellitus and pancreatic cancer is essential for the treatment of diabetes cancer patients. The transforming growth factor-β (TGF-β) signaling pathway is deregulated in cancer and has a dual role in different stages of cancer as a suppressor or a promoter. More important, The TGF-β signaling pathway is also another important reason for diabetic complications. This review summarizes the relationship between diabetes and pancreatic cancer, in particular, focusing on the role of the TGF-β signaling pathway. It is possible to find drugs like metformin that can prevent and treat pancreatic cancer by targeting the TGF-β signaling pathway.

Current management of diabetic tractional retinal detachments

Twenty-five percent of diabetes-related vision loss stems from complications of proliferative diabetic retinopathy (PDR). Panretinal photocoagulation has been the preferred treatment of high-risk PDR for decades and more recently intravitreal injections of drugs that inhibit the actions of vascular endothelial growth factor have become popular. But despite these treatments PDR may progress uncontrollably to advanced pathologies such as traction retinal detachments (TRDs), combined traction/rhegmatogenous retinal detachments (TRD/RRDs), vitreous hemorrhages, rubeosis iridis, and traction maculopathies, which produce mild-to-severe loss of vision. TDR have long been the most common indication for PDR-related vitreoretinal surgery. Vitrectomy surgery is indicated for recent (<6 months duration) TRD involving the macula, progressive TRD that threatens the macula, and recent data suggest that chronic macula-involving TRDs (>6 months duration) may also benefit. Combined TRD/RRD represents a particularly challenging surgical condition but advances in surgical instrumentation, dissection techniques, and post-operative tamponade have produced excellent success rates. The recent development of small-gauge vitrectomy systems has persuaded most surgeons to switch platforms since these appear to produce shorter surgical times and quicker post-operative recoveries. Pre-operative injections of bevacizumab are frequently administered for persistent neovascularization to facilitate surgical dissection of pre-retinal fibrosis and reduce the incidence of post-operative hemorrhages. Recent trends toward earlier surgical intervention and expanded indications are likely to continue as surgical instrumentation and techniques are further developed.

Inhibition of stromal cell-derived factor-1α/CXCR4 signaling restores the blood-retina barrier in pericyte-deficient mouse retinas

In diabetic retinopathy (DR), pericyte dropout from capillary walls is believed to cause the breakdown of the blood-retina barrier (BRB), which subsequently leads to vision-threatening retinal edema. While various proinflammatory cytokines and chemokines are upregulated in eyes with DR, their distinct contributions to disease progression remain elusive. Here, we evaluated roles of stromal cell-derived factor-1α (SDF-1α) and its receptor CXCR4 in the BRB breakdown initiated by pericyte deficiency. After inhibition of pericyte recruitment to developing retinal vessels in neonatal mice, endothelial cells (ECs) upregulated the expression of SDF-1α. Administration of CXCR4 antagonists, or EC-specific disruption of the CXCR4 gene, similarly restored the BRB integrity, even in the absence of pericyte coverage. Furthermore, CXCR4 inhibition significantly decreased both the expression levels of proinflammatory genes (P < 0.05) and the infiltration of macrophages (P < 0.05) into pericyte-deficient retinas. Taken together, EC-derived SDF-1α induced by pericyte deficiency exacerbated inflammation through CXCR4 in an autocrine or paracrine manner and thereby induced macrophage infiltration and BRB breakdown. These findings suggest that the SDF-1α/CXCR4 signaling pathway may be a potential therapeutic target in DR.

The Controversial Role of TGF-β in Neovascular Age-Related Macular Degeneration Pathogenesis

The multifunctional transforming growth factors-beta (TGF-βs) have been extensively studied regarding their role in the pathogenesis of neovascular age-related macular degeneration (nAMD), a major cause of severe visual loss in the elderly in developed countries. Despite this, their effect remains somewhat controversial. Indeed, both pro- and antiangiogenic activities have been suggested for TGF-β signaling in the development and progression of nAMD, and opposite therapies have been proposed targeting the inhibition or activation of the TGF-β pathway. The present article summarizes the current literature linking TGF-β and nAMD, and reviews experimental data supporting both pro- and antiangiogenic hypotheses, taking into account the limitations of the experimental approaches.

Chebulagic acid and Chebulinic acid inhibit TGF-β1 induced fibrotic changes in the chorio-retinal endothelial cells by inhibiting ERK phosphorylation

PURPOSE

Diabetic retinopathy (DR) is characterized by pro-inflammatory, pro-angiogenic and pro-fibrotic environment during the various stages of the disease progression. Basement membrane changes in the retina and formation of fibrovascular membrane are characteristically seen in DR. In the present study the effect of Alcoholic (AlE) extracts of Triphala an ayurvedic herbal formulation and its chief compounds, Chebulagic (CA), Chebulinic (CI) and Gallic acid (GA) were evaluated for TGFβ1-induced anti-fibrotic activity in choroid-retinal endothelial cells (RF/6A).

METHOD

RF/6A cells were treated with TGFβ1 alone or co-treated with AlE, CA, CI or GA. The mRNA and protein expression of fibrotic markers (αSMA, CTGF) were assessed by qPCR and western blot/ELISA. Functional changes were assessed using proliferation assay and migration assay. To deduce the mechanism of action, downstream signaling was assessed by western blot analysis along with in silico docking studies.

RESULT

AlE (50 μg/ml) CA and CI at 10 μM reduced the expression of pro-fibrotic genes (αSMA and CTGF) induced by TGFβ1, by inhibiting ERK phosphorylation. GA did not inhibit TGFβ1 mediated changes in RF/6A cells. In silico experiments shows that CA and CI has favourable binding energy to bind with TGFβ receptor and inhibit the downstream signaling, while GA did not.

CONCLUSION

Hence this study identifies Triphala and its chief compounds CA and CI as potential adjuvants in the management of DR.

Identification of genes related to proliferative diabetic retinopathy through RWR algorithm based on protein-protein interaction network

Proliferative diabetic retinopathy (PDR) is one of the most common complications of diabetes and can lead to blindness. Proteomic studies have provided insight into the pathogenesis of PDR and a series of PDR-related genes has been identified but are far from fully characterized because the experimental methods are expensive and time consuming. In our previous study, we successfully identified 35 candidate PDR-related genes through the shortest-path algorithm. In the current study, we developed a computational method using the random walk with restart (RWR) algorithm and the protein-protein interaction (PPI) network to identify potential PDR-related genes. After some possible genes were obtained by the RWR algorithm, a three-stage filtration strategy, which includes the permutation test, interaction test and enrichment test, was applied to exclude potential false positives caused by the structure of PPI network, the poor interaction strength, and the limited similarity on gene ontology (GO) terms and biological pathways. As a result, 36 candidate genes were discovered by the method which was different from the 35 genes reported in our previous study. A literature review showed that 21 of these 36 genes are supported by previous experiments. These findings suggest the robustness and complementary effects of both our efforts using different computational methods, thus providing an alternative method to study PDR pathogenesis.

Inflammation and N-formyl peptide receptors mediate the angiogenic activity of human vitreous humour in proliferative diabetic retinopathy

AIMS/HYPOTHESIS

Angiogenesis and inflammation characterise proliferative diabetic retinopathy (PDR), a major complication of diabetes mellitus. However, the impact of inflammation on the pathogenesis of PDR neovascularisation has not been elucidated. Here, we assessed the capacity of PDR vitreous fluid to induce pro-angiogenic/proinflammatory responses in endothelium and the contribution of the inflammation-related pattern recognition N-formyl peptide receptors (FPRs) in mediating these responses.

METHODS

Pooled and individual pars plana vitrectomy-derived PDR vitreous fluid ('PDR vitreous') samples were assessed in endothelial cell proliferation, motility, sprouting and morphogenesis assays, and for the capacity to induce proinflammatory transcription factor activation, reactive oxygen species production, intercellular junction disruption and leucocyte-adhesion molecule upregulation in these cells. In vivo, the pro-angiogenic/proinflammatory activity of PDR vitreous was tested in murine Matrigel plug and chick embryo chorioallantoic membrane (CAM) assays. Finally, the FPR inhibitors Boc-Phe-Leu-Phe-Leu-Phe (Boc-FLFLF) and Ac-L-Arg-Aib-L-Arg-L-Cα(Me)Phe-NH₂ tetrapeptide (UPARANT) were evaluated for their capacity to affect the biological responses elicited by PDR vitreous.

RESULTS

PDR vitreous activates a pro-angiogenic/proinflammatory phenotype in endothelial cells. Accordingly, PDR vitreous triggers a potent angiogenic/inflammatory response in vivo. Notably, the different capacity of individual PDR vitreous samples to induce neovessel formation in the CAM correlates with their ability to recruit infiltrating CD45⁺ cells. Finally, the FPR inhibitor Boc-FLFLF and the novel FPR antagonist UPARANT inhibit neovessel formation and inflammatory responses triggered by PDR vitreous in the CAM assay.

CONCLUSIONS/INTERPRETATION

This study provides evidence that inflammation mediates the angiogenic activity of PDR vitreous and paves the way for the development of FPR-targeting anti-inflammatory/anti-angiogenic approaches for PDR therapy.

Histone Deacetylase Inhibition Restores Retinal Pigment Epithelium Function in Hyperglycemia

In diabetic individuals, macular edema is a major cause of vision loss. This condition is refractory to insulin therapy and has been attributed to metabolic memory. The retinal pigment epithelium (RPE) is central to maintaining fluid balance in the retina, and this function is compromised by the activation of advanced glycation end-product receptors (RAGE). Here we provide evidence that acute administration of the RAGE agonist, glycated-albumin (gAlb) or vascular endothelial growth factor (VEGF), increased histone deacetylase (HDAC) activity in RPE cells. The administration of the class I/II HDAC inhibitor, trichostatin-A (TSA), suppressed gAlb-induced reductions in RPE transepithelial resistance (in vitro) and fluid transport (in vivo). Systemic TSA also restored normal RPE fluid transport in rats with subchronic hyperglycemia. Both gAlb and VEGF increased HDAC activity and reduced acetyl-α-tubulin levels. Tubastatin-A, a relatively specific antagonist of HDAC6, inhibited gAlb-induced changes in RPE cell resistance. These data are consistent with the idea that RPE dysfunction following exposure to gAlb, VEGF, or hyperglycemia is associated with increased HDAC6 activity and decreased acetyl-α-tubulin. Therefore, we propose inhibiting HDAC6 in the RPE as a potential therapy for preserving normal fluid homeostasis in the hyperglycemic retina.

Lecithin-Bound Iodine Prevents Disruption of Tight Junctions of Retinal Pigment Epithelial Cells under Hypoxic Stress

Aim. We investigated whether lecithin-bound iodine (LBI) can protect the integrity of tight junctions of retinal pigment epithelial cells from hypoxia. Method. Cultured human retinal pigment epithelial (ARPE-19) cells were pretreated with LBI. To mimic hypoxic conditions, cells were incubated with CoCl2. We compared the integrity of the tight junctions (TJs) of control to cells with either LBI alone, CoCl2 alone, or LBI + CoCl2. The levels of cytokines in the conditioned media were also determined. Results. Significant decrease in the zonula occludens-1 (ZO-1) intensity in the CoCl2 group compared to the control (5787.7 ± 4126.4 in CoCl2 group versus 29244.6 ± 2981.2 in control; average ± standard deviation). But the decrease was not significant in the LBI + CoCl2 (27189.0 ± 11231.1). The levels of monocyte chemoattractant protein-1 (MCP-1) and Chemokine (C-C Motif) Ligand 11 (CCL-11) were significantly higher in the CoCl2 than in the control (340.8 ± 43.3 versus 279.7 ± 68.3 pg/mL for MCP-1, and 15.2 ± 12.9 versus 12.5 ± 6.1 pg/mL for CCL-11. With LBI pretreatment, the levels of both cytokines were decreased to 182.6 ± 23.8 (MCP-1) and 5.46 ± 1.9 pg/mL for CCL-11). Blockade of MCP-1 or CCL-11 also shows similar result representing TJ protection from hypoxic stress. Conclusions. LBI results in a protective action from hypoxia.

The Vitreomacular Interface in Diabetic Retinopathy

Diabetic retinopathy (DR) is a leading health concern and a major cause of blindness. DR can be complicated by scar tissue formation, macular edema, and tractional retinal detachment. Optical coherence tomography has found that patients with DR often have diffuse retinal thickening, cystoid macular edema, posterior hyaloid traction, and tractional retinal detachment. Newer imaging techniques can even detect fine tangential folds and serous macular detachment. The interplay of the vitreous and the retina in the progression of DR involves multiple chemokine and other regulatory factors including VEGF. Understanding the cells infiltrating pathologic membranes at the vitreomacular interface has opened up the possibility of new targets for pharmacotherapy. Vitrectomies for DR remain a vital tool to help relieve tension on the macula by removing membranes, improving edema absorption, and eliminating the scaffold for new membrane formation. Newer treatments such as triamcinolone acetonide and VEGF inhibitors have become essential as a rapid way to control DR at the vitreomacular interface, improve macular edema, and reduce retinal neovascularization. These treatments alone, and in conjunction with PRP, help to prevent worsening of the VMI in patients with DR.