Proteomic Biomarkers of Retinal Inflammation in Diabetic Retinopathy. Int J Mol Sci. 2019;20. [PMID: 31557880 PMCID: PMC6801709 DOI: 10.3390/ijms20194755]

NADH-Cytochrome B5 reductase 2 suppresses retinal vascular dysfunction through regulation of vascular endothelial growth factor A in diabetic retinopathy

Diabetic retinopathy (DR) is a progressive vascular complication of diabetes mellitus (DM) and is related to retinal vascular abnormalities. NADH-Cytochrome B5 Reductase 2 (CBR2) has been implicated in angiogenesis, but the effect of CBR2 on angiogenesis and endothelial cell biological behavior in DR remains unclear. Here, we aimed to explore the effect of CBR2 on retinal vascular dysfunction under diabetic conditions. The histological analyses were performed to explore the effect of CBR2 on pathological change in streptozotocin (STZ)-induced diabetic rat retinas. The effect of CBR2 on endothelial cell function was explored by CCK-8, scratch wound, transwell, tube formation, and immunofluorescence assays in high glucose (HG)-stimulated human retinal microvascular endothelial cells (HRMECs). CBR2 expression was significantly downregulated in DM rat retinas and HG-stimulated HRMECs. Intravitreal injection of CBR2-expressing lentivirus under diabetic conditions reduced retinal angiogenesis, acellular capillary formation, and pericyte loss, along with decreased expression of hypoxia-inducible factor-1α (HIF-1α), cluster of differentiation 31 (CD31), and vascular endothelial growth factor A (VEGFA) in vivo. Moreover, CBR2 overexpression inhibited cell growth and tube formation and led to decreased expression of HIF-1α and VEGFA in HG-induced HRMECs. Interestingly, the repressive effects of CBR2 on cell proliferation, migration, and tube formation under HG conditions were strongly reversed when VEGFA was overexpressed. Overall, the key findings of our study suggested that CBR2 might alleviate retinal vascular dysfunction and abnormal endothelial proliferation during the process of DR by regulating VEGFA, providing a piece of potent evidence for DR therapy.

A Mechanistic Exploratory Study on the Therapeutic Efficacy of Astragaloside IV Against Diabetic Retinopathy Revealed by Network Pharmacology

Purpose: Diabetic retinopathy (DR) is a serious complication of diabetes mellitus, which nearly happens to all the diabetic sufferers. This study aims to identify the preliminary molecular regulation involved in the therapeutic efficacy of astragaloside IV (AS- IV) for DR.

Methods: Diabetic rat models were established and treated with AS-IV. Optical coherence tomography (OCT) and Hematoxylin-eosin (HE) staining was employed to demonstrate the histopathological changes. The main targets of AS-IV were identified by searching from public databases of traditional Chinese medicine (GeneCards, PharmMapper and Swiss Target Prediction). Besides, disease targets of DR were also obtained by integrated data from GEO datasets and predicted from public databases. Protein-protein interaction (PPI) network was constructed by Cytoscape with overlapping genes and 10 core targets were selected, on which Gene Ontology (GO) along with Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were conducted. The interaction between AS-IV and these crucial genes were analyzed using molecular docking. RT-qPCR and western blot were used to verify the expression variation of core targets.

Results: OCT imaging and HE staining demonstrated that AS-IV administration significantly increased retinal thickness in diabetic rats, obviously alleviating DR induced histopathological changes as well as elevated blood glucose levels. 107 common targets of AS-IV and DR were determined after intersection. PPI network analysis filtered 10 hub genes potentially targeted by AS-IV, including VEGFA, CASP3, HIF1α, STAT3, CTNNB1, SRC, AKT1, EGFR, IL1β and IL6. Enrichment analysis indicated that these genes were mainly enriched in biological processes like T cell activation, epithelial cell proliferation and protein kinase B signaling, and involved in oxidative stress, apoptosis and inflammation-related pathways. The molecular docking prediction suggested that AS-IV exhibited stable binding to these core targets. In addition, mRNA levels of core targets in diabetic rats were differentially expressed before and after AS-IV treatment. Western blot further revealed that AS-IV treatment elevated DR-depressed protein levels of PI3K and AKT.

Conclusion: Our study elucidated the effect of AS-IV in attenuating retinopathy induced by diabetes in rats and preliminarily unveiled the therapeutic efficacy of AS-IV in the treatment of DR might be attributed to activation of PI3K-AKT signaling pathway.

Differences in Vitreous Protein Profiles in Patients With Proliferative Diabetic Retinopathy Before and After Ranibizumab Treatment

Proliferative diabetic retinopathy (PDR) accounts for severe impact on vision, its mechanism is still poorly understood. To compare the differences of vitreous protein profiles in PDR patients before and after a complete anti-vascular endothelial growth factor (VEGF) loading dose with ranibizumab treatment. Twelve vitreous humor (VH) samples were collected from six PDR patients before (set as pre group) and after (set as post group) intravitreal injection of ranibizumab (IVR) treatment. LC-MS/MS and bioinformatics analysis were performed to identify differentially expressed proteins. Proteins were validated with targeted proteomics using parallel reaction monitoring (PRM) in a validation set consisting of samples from the above patients. A total of 2680 vitreous proteins were identified. Differentially expressed proteins were filtrated with fold change ≥2.0 (post group/ pre group protein abundance ratio ≥2 or ≤ 0.5) and p-value <0.05. 11 proteins were up-regulated and 17 proteins were down-regulated, while consistent presence/absence expression profile group contains one elevated protein and nine reduced proteins, among which seven proteins were identified as potential biomarkers for IVR treatment through PRM assays. Bioinformatics analysis indicated the up-regulated proteins were significantly enriched in "GnRH secretion" and "Circadian rhythm" signaling pathway. This report represents the first description of combined label-free quantitative proteomics and PRM analysis of targeted proteins for discovery of different proteins before and after IVR treatment in the same patient. IVR treatment may protect against PDR by promoting SPP1 expression through "GnRH secretion" and "Circadian rhythm" signaling pathway.

Putative Biomarkers in Tears for Diabetic Retinopathy Diagnosis

Purpose

Tear fluid biomarkers may offer a non-invasive strategy for detecting diabetic patients with increased risk of developing diabetic retinopathy (DR) or increased disease progression, thus helping both improving diagnostic accuracy and understanding the pathophysiology of the disease. Here, we assessed the tear fluid of nondiabetic individuals, diabetic patients with no DR, and diabetic patients with nonproliferative DR (NPDR) or with proliferative DR (PDR) to find putative biomarkers for the diagnosis and staging of DR.

Methods

Tear fluid samples were collected using Schirmer test strips from a cohort with 12 controls and 54 Type 2 Diabetes (T2D) patients, and then analyzed using mass spectrometry (MS)-based shotgun proteomics and bead-based multiplex assay. Tear fluid-derived small extracellular vesicles (EVs) were analyzed by transmission electron microscopy, Western Blotting, and nano tracking.

Results

Proteomics analysis revealed that among the 682 reliably quantified proteins in tear fluid, 42 and 26 were differentially expressed in NPDR and PDR, respectively, comparing to the control group. Data are available via ProteomeXchange with identifier PXD033101. By multicomparison analyses, we also found significant changes in 32 proteins. Gene ontology (GO) annotations showed that most of these proteins are associated with oxidative stress and small EVs. Indeed, we also found that tear fluid is particularly enriched in small EVs. T2D patients with NPDR have higher IL-2/-5/-18, TNF, MMP-2/-3/-9 concentrations than the controls. In the PDR group, IL-5/-18 and MMP-3/-9 concentrations were significantly higher, whereas IL-13 was lower, compared to the controls.

Conclusions

Overall, the results show alterations in tear fluid proteins profile in diabetic patients with retinopathy. Promising candidate biomarkers identified need to be validated in a large sample cohort.

Mechanistic Pathogenesis of Endothelial Dysfunction in Diabetic Nephropathy and Retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR) are microvascular complications of diabetes. Microvascular endothelial cells are thought to be the major targets of hyperglycemic injury. In diabetic microvasculature, the intracellular hyperglycemia causes damages to the vascular endothelium, via multiple pathophysiological process consist of inflammation, endothelial cell crosstalk with podocytes/pericytes and exosomes. In addition, DN and DR diseases development are involved in several critical regulators including the cell adhesion molecules (CAMs), the vascular endothelial growth factor (VEGF) family and the Notch signal. The present review attempts to gain a deeper understanding of the pathogenesis complexities underlying the endothelial dysfunction in diabetes diabetic and retinopathy, contributing to the development of new mechanistic therapeutic strategies against diabetes-induced microvascular endothelial dysfunction.

The potential effects and mechanisms of hispidulin in the treatment of diabetic retinopathy based on network pharmacology

Background

Diabetic retinopathy (DR), one of the most common and severe microvascular complication of diabetes mellitus (DM), is mainly caused by diabetic metabolic disorder. So far, there is no effective treatment for DR. Eriocauli Flos, a traditional Chinese herb, has been used in treating the ophthalmic diseases including DR. However, the active ingredients and molecular mechanisms of Eriocauli Flos to treat diabetic retinopathy remain elusive.

Methods

Here, the systems pharmacology model was developed via constructing network approach. 8 active components which were screened by oral bioavailability (OB ≥ 30%) and drug-likeness (DL ≥ 0.18) and 154 targets were selected from Eriocauli Flos through TCMSP database. Another 3593 targets related to DR were obtained from Genecards, OMIM, TTD, and Drugbank databases. The 103 intersecting targets of DR and Eriocauli Flos were obtained by Draw Venn Diagram. In addition, protein-protein interaction network was established from STRING database and the compound-target network was constructed by Cytoscape which screened top 12 core targets with cytoNCA module. Then the overlapping targets were analyzed by GO and KEGG enrichment. Moreover, two core targets were selected to perform molecular docking simulation. Subsequently, CCK8 assay, RT-PCR and Western blotting were applied to further reveal the mechanism of new candidate active component from Eriocauli Flos in high glucose-induced HRECs.

Results

The results showed that the overlapping targets by GO analysis were enriched in cellular response to chemical stress, response to oxidative stress, response to reactive oxygen species, reactive oxygen species metabolic process and so on. Besides, the overlapping targets principally regulated pathways such as AGE-RAGE signaling pathway in diabetic complications, lipid atherosclerosis, fluid shear stress and atherosclerosis, and PI3K-Akt signaling pathway. Molecular docking exhibited that VEGFA and TNF-α, had good bindings to the great majority of compounds, especially the compound hispidulin. In vitro, hispidulin ameliorated high-glucose induced proliferation by down-regulating the expression of p-ERK, p-Akt, and VEGFA; meanwhile inhibited the mRNA levels of TNF-α.

Conclusions

In this study, through network pharmacology analysis and experimental validation, we found that hispidulin maybe has a potential targeted therapy effect for DR by decreasing the expression of p-Akt, p-ERK, and VEGFA, which resulted in ameliorating the proliferation in HRECs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03593-2.

Lab-on-a-chip technologies for minimally invasive molecular sensing of diabetic retinopathy

Diabetic retinopathy (DR) is the most common diabetic eye disease and the worldwide leading cause of vision loss in working-age adults. It progresses from mild to severe non-proliferative or proliferative DR based on several pathological features including the magnitude of blood-retinal barrier breakdown and neovascularization. Available pharmacological and retinal laser photocoagulation interventions are mostly applied in the advanced stages of DR and are inefficient in halting disease progression in a significantly high percentage of patients. Yet, recent evidence has shown that some therapies could potentially limit DR progression if applied at early stages, highlighting the importance of early disease diagnostics. In the past few decades, different imaging modalities have proved their utility for examining retinal and optic nerve changes in patients with retinal diseases. However, imaging based-methodologies solely rely on morphological examination of the retinal vascularization and are not suitable for recurrent and personalized patient evaluation. This raises the need for new technologies to enable accurate and early diagnosis of DR. In this review, we critically discuss the potential clinical benefit of minimally-invasive molecular biomarker identification and profiling of diabetic patients who are at risk of developing DR. We provide a comparative overview of conventional and recently developed lab-on-a-chip technologies for quantitative assessment of potential DR molecular biomarkers and discuss their advantages, current limitations and challenges for future practical implementation and continuous patient monitoring at the point-of-care.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Transcriptomics Coupled to Proteomics Reveals Novel Targets for the Protective Role of Spermine in Diabetic Cardiomyopathy

Background

Diabetic cardiomyopathy (DbCM) is the main complication and the cause of high mortality of diabetes. Exploring the transcriptomics and proteomics of DbCM is of great significance for understanding the biology of the disease and for guiding new therapeutic targets for the potential therapeutic effect of spermine (SPM).

Methods and Results

By using a mouse DbCM model, we analyzed the overall transcriptome and proteome of the myocardium, before/after treatment with SPM. The general state and cardiac structure and function changes of each group were also compared. Diabetes induced an increased blood glucose and serum triglyceride content, a decreased body weight, serum insulin level, and cardiac function-related indexes, accompanied by disrupted myocardial tissue morphology and ultrastructure damage. Using RNA sequencing (RNA-seq), we identified thousands of differentially expressed genes (DEGs) in DbCM with or without SPM treatment. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that the DEGs were significantly enriched in lipid metabolism and amino acid metabolism pathways. Specifically, quantitative real-time PCR (qRT-PCR) confirmed that SPM protected DbCM by reversing the expressions of lipid metabolism and amino acid metabolism-related genes, including Alox15, Gm13033, pla2g12a, Ptges, Pnpla2, and Acot1. To further reveal the pathogenesis of DbCM, we used proteome-based data-independent acquisition (DIA) and identified 139 differentially expressed proteins (DEPs) with 67 being upregulated and 72 being downregulated in DbCM. Venn intersection analysis showed 37 coexpressed genes and proteins in DbCM, including 29 upregulation and 8 downregulation in DbCM. In the protein-protein interaction (PPI) network constructed by the STRING database, the metabolism-related coexpressed genes and proteins, such as Acot2, Ephx2, Cyp1a1, Comt, Acox1, Hadhb, Hmgcs2, Acot1, Inmt, and Cat, can interact with the identified DEGs and DEPs.

Conclusion

The biomarkers and canonical pathways identified in this study may hold the key to understand the mechanisms of DbCM pathobiology and provide new targets for the therapeutic effect of SPM against DbCM by targeting lipid and amino acid metabolism pathways.

Aqueous Lumican Correlates with Central Retinal Thickness in Patients with Idiopathic Epiretinal Membrane: A Proteome Study

Idiopathic epiretinal membrane (iERM) is a pathological fibrocellular change in the vitreoretinal junction over the macular area; however, possible pathogenic mechanisms remain unclear. Changes in the differential protein composition of the aqueous humor (AH) may represent potential molecular changes associated with iERM. To gain new insights into the molecular mechanisms of iERM pathology, a sensitive label-free proteomics analysis was performed to compare AH protein expressions in patients with cataracts with or without iERM. This study employed nanoflow ultra-high-performance liquid chromatography-tandem mass spectrometry to investigate protein compositions of the AH obtained from individual human cataract eyes from 10 patients with iERM and 10 age-matched controls without iERM. Eight proteins were differentially expressed between the iERM and control samples, among which six proteins were upregulated and two were downregulated. A gene ontology (GO) analysis revealed that iERM was closely associated with several biological processes, such as immunity interactions, cell proliferation, and extracellular matrix remodeling. Additionally, multiple proteins, including lumican, cyclin-dependent kinase 13, and collagen alpha-3(VI) chain, were correlated with the central retinal thickness, indicating a multifactorial response in the pathogenic process of iERM. Changes in the AH level of lumican between iERM and control samples were also confirmed by an enzyme-linked immunosorbent assay. In conclusion, several pathological pathways involved in iERM were identified in the AH by a proteomic analysis, including immune reactions, cell proliferation, and remodeling of the extracellular matrix. Lumican is a potential aqueous biomarker for predicting iERM development and monitoring its progression. More clinical parameters also need to be identified to complete the analysis, and those could provide additional targets for treating and preventing iERM.

A novel miR-338-3p/SLC1A5 axis reprograms retinal pigment epithelium to increases its resistance to high glucose-induced cell ferroptosis

BACKGROUND

Oxidative stress-induced cell ferroptosis occurs during the pathogenesis of diabetic retinopathy (DR), but the detailed molecular mechanisms are still unclear. The present study aimed to investigate this issue.

MATERIALS AND METHODS

The retinal pigment epithelium (RPE) was treated with high glucose (30 mM) in vitro to mimic the realistic conditions of DR progression in vivo. Cell viability was determined by MTT assay and trypan blue staining assay. Gene expressions were examined by Real-Time qPCR and Western Blot analysis. FCM was used to detect cell apoptosis and ROS generation. Dual-luciferase reporter gene system assay was used to verify the targeting sites.

RESULTS

High glucose increased reactive oxygen species (ROS) levels, promoted cell ferroptosis, and suppressed cell proliferation and viability in RPE, which were reversed by co-treating cells with both a ferroptosis inhibitor ferrostatin-1 and an ROS scavenger, N-acetyl-L-Cysteine (NAC). In addition, we screened out a miR-338-3p/ASCT2 (SLC1A5) axis that played an important role in this process. Mechanistically, miR-338-3p targeted the 3' untranslated regions (3'UTR) of SLC1A5 for its inhibition and degradation, and high glucose downregulated SLC1A5 by upregulating miR-338-3p in RPE cells. Next, the miR-338-3p inhibitor and SLC1A5 overexpression vectors were delivered into the RPE cells, and the following gain- and loss-of-function experiments validated that both miR-338-3p ablation and SLC1A5 upregulation abrogated the regulating effects of high glucose on cell proliferation, viability, ferroptosis and ROS production in RPE cells.

CONCLUSIONS

Collectively, data in the present study indicated that targeting the miR-338-3p/SLC1A5 axis could block high glucose-induced ferroptosis in RPE cells.

Spectropathologic endorsement of ocular carotenoids for early detection of diabetic retinopathy

Diabetic retinopathy (DR) is a common health concern. Unfortunately, the metabolic pathway causing DR is yet to be understood. The carotenoid level in the human body is known to protect the health of the eyes. In this work, resonance Raman spectroscopy and multivariate analysis of the spectral data of human serum are reported as next-generation spectropathologic tools to detect retinal degeneration efficiently. The proposed technique shows promise by endorsing ocular carotenoids as a critical biomarker for such pathosis. Furthermore, the multivariate analysis of the spectral data distinguishes between two different stages of the disease. The machine learning algorithm is used to estimate a significant accuracy of 94% of the proposed model for the classification. As the carotenoid level can be controlled by dietary intake, we believe that the reported results also indicate a therapeutic role of the same in DR.

Sirt5-mediated desuccinylation of OPTN protects retinal ganglion cells from autophagic flux blockade in diabetic retinopathy

Retinal neurodegeneration develops early in the course of diabetic retinopathy (DR), and our previous research showed that succinate accumulation results in retinal ganglion cells (RGCs) dysfunction in the retinas of rats with DR. Succinate can enhance lysine succinylation, but the succinylation of DR is not well understood. In this study, we investigated the role of the succinylome in DR and identified the key factor in this process. TMT labeling and LC–MS/MS analysis were combined to quantify the differentially succinylated proteins between vitreous humor (VH) samples from DR and non-DR patients. A total of 74 sites in 35 proteins were differentially succinylated between DR and non-DR vitreous humor samples, among which succinylation of the K108 site of optineurin (OPTN K108^su) in the defense response was enriched by GO analysis based on the biological process category. Then, using a streptozotocin (STZ)-induced diabetic rat model, R28 cells and primary rat RGCs (rRGCs), we demonstrated that OPTN underwent lysine succinylation in the retinas of rats with DR and that OPTN K108^su mediated autophagic flux blockade under high-glucose (HG) conditions. Sirt5 can desuccinylate OPTN K108^su, thus protecting RGCs function from high glucose-induced RGCs autophagic flux blockade in the diabetic retina. Overall, desuccinylation of OPTN is an essential adaptive mechanism for ameliorating autophagic flux blockade in RGCs under DR conditions, and targeting the Sirt5-desuccK108-OPTN axis may thus open an avenue for therapeutic intervention in RCGs dysfunction.

Metabolomics of various samples advancing biomarker discovery and pathogenesis elucidation for diabetic retinopathy

Diabetic retinopathy (DR) is a universal microvascular complication of diabetes mellitus (DM), which is the main reason for global sight damage/loss in middle-aged and/or older people. Current clinical analyses, like hemoglobin A1c, possess some importance as prognostic indicators for DR severity, but no effective circulating biomarkers are used for DR in the clinic currently, and studies on the latent pathophysiology remain lacking. Recent developments in omics, especially metabolomics, continue to disclose novel potential biomarkers in several fields, including but not limited to DR. Therefore, based on the overview of metabolomics, we reviewed progress in analytical technology of metabolomics, the prominent roles and the current status of biomarkers in DR, and the update of potential biomarkers in various DR-related samples via metabolomics, including tear as well as vitreous humor, aqueous humor, retina, plasma, serum, cerebrospinal fluid, urine, and feces. In this review, we underscored the in-depth analysis and elucidation of the common biomarkers in different biological samples based on integrated results, namely, alanine, lactate, and glutamine. Alanine may participate in and regulate glucose metabolism through stimulating N-methyl-D-aspartate receptors and subsequently suppressing insulin secretion, which is the potential pathogenesis of DR. Abnormal lactate could cause extensive oxidative stress and neuroinflammation, eventually leading to retinal hypoxia and metabolic dysfunction; on the other hand, high-level lactate may damage the structure and function of the retinal endothelial cell barrier via the G protein-coupled receptor 81. Abnormal glutamine indicates a disturbance of glutamate recycling, which may affect the activation of Müller cells and proliferation via the PPP1CA-YAP-GS-Gln-mTORC1 pathway.

Diagnostic and Therapeutic Application of Exosomal microRNAs Inducing Inflammation in Type 2 Diabetes Mellitus

Diabetes mellitus is a class of noncommunicable chronic metabolic disorders marked by hyperglycemia due to insulin production, insulin action or both and has reached epidemic levels around the world. The two most frequent types of diabetes are type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Despite substantial improvements in the knowledge and treatment of DM, the associated incidence and mortality rates remain steadily increased. Reliable markers for the early detection, monitoring and focused treatment of DM are desperately required. Conversely, microRNAs (miRNAs) have received much significance due to their regulatory involvement in gene expression. Fascinatingly, exosomes can be enclosed into miRNAs to transport or distribute them into the target cells or tissues in which they have a physiological regulatory action. Thus, exosomal miRNAs are proving to be important regulators in the establishment and maintenance of DM, however, further mode of action will be needed to investigate in order to fully comprehend the pathophysiological process. Hereby, this review outlines the recent findings on the role of exosomal miRNAs intending to understand the precise function in diagnostic and therapeutic aspects in T2DM disease.

Aqueous humor proteomic analysis of acute angle-closure glaucoma with visual field loss

Background

Acute angle-closure glaucoma (AACG) is an ophthalmic emergency that occurs over the course of hours or days and may cause irreversible blindness if not treated immediately. In most cases, optic nerve damage is the cause of visual field (VF) loss in AACG. There has been no reliable biomarker found to evaluate optic nerve damage to date. Aqueous humor (AH) proteome analysis might reveal the proteomic alterations in AACG and provide helpful clues in the search for an AH biomarker of optic nerve damage and VF loss.

Methods

In this study, we used the AH proteome to explore the functions of differentially expressed proteins (DEPs) during disease progression. The AH proteins from the early-stage group and late-stage group were extracted and analyzed by the data-independent acquisition (DIA) method. The DEPs functions were annotated, and parallel reaction monitoring (PRM) was used to validate the key DEPs.

Results

A total of 87 DEPs were found. Gene Ontology analysis showed that most DEPs were enriched in immunology, hemodynamics, and apoptosis. Ingenuity pathway analysis found that vascular endothelial growth factor (VEGF) signaling, the production of reactive oxygen species (ROS) in macrophages, and the nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress response were active pathways in the late stage of AACG. The mechanism of retinal ganglion cell (RGC) death was hypothesized on the basis of DEP functional analysis. A total of 20 DEPs were validated by using PRM, and prostaglandin-H2 D-isomerase was found to have the potential to evaluate optic nerve damage.

Conclusions

This study showed that AH proteomic analysis could reveal the proteomic alterations in the pathogenesis of VF loss in AACG and help to provide objective protein biomarkers to evaluate VF loss. These findings will benefit the application of the AH proteome to clinical research.

High-Fat Diet Alters the Retinal Transcriptome in the Absence of Gut Microbiota

The relationship between retinal disease, diet, and the gut microbiome has shown increasing importance over recent years. In particular, high-fat diets (HFDs) are associated with development and progression of several retinal diseases, including age-related macular degeneration (AMD) and diabetic retinopathy. However, the complex, overlapping interactions between diet, gut microbiome, and retinal homeostasis are poorly understood. Using high-throughput RNA-sequencing (RNA-seq) of whole retinas, we compare the retinal transcriptome from germ-free (GF) mice on a regular diet (ND) and HFD to investigate transcriptomic changes without influence of gut microbiome. After correction of raw data, 53 differentially expressed genes (DEGs) were identified, of which 19 were upregulated and 34 were downregulated in GF-HFD mice. Key genes involved in retinal inflammation, angiogenesis, and RPE function were identified. Enrichment analysis revealed that the top 3 biological processes affected were regulation of blood vessel diameter, inflammatory response, and negative regulation of endopeptidase. Molecular functions altered include endopeptidase inhibitor activity, protease binding, and cysteine-type endopeptidase inhibitor activity. Human and mouse pathway analysis revealed that the complement and coagulation cascades are significantly affected by HFD. This study demonstrates novel data that diet can directly modulate the retinal transcriptome independently of the gut microbiome.

Importance of Identifying Novel Biomarkers of Microvascular Damage in Type 1 Diabetes

Microvascular complications of type 1 diabetes, which primarily include diabetic kidney disease, retinopathy, and neuropathy, are characterized by damage to the microvasculature of the kidney, retina, and neurons. The pathogenesis of these complications is multifactorial, and several pathways are implicated. These complications are often silent during their early stages, and once symptoms develop, there might be little to be done to cure them. Thus, there is a strong need for novel biomarkers to identify individuals at risk of microvascular complications at an early stage and guide the implementation of new therapeutic options for preventing their development and progression. Recent advancements in proteomics, metabolomics, and other 'omics' have led to the identification of several potential biomarkers of microvascular complications. However, biomarker discovery has met several challenges and, up to now, there are no new biomarkers that have been implemented into clinical practice. This highlights the need for further work in this area to move towards better diagnostic and prognostic approaches.

Metabolomics in Diabetic Retinopathy: A Systematic Review

Purpose

Diabetic retinopathy (DR), a common microvascular complication of diabetes, is the leading cause of acquired blindness in the working-age population. Individuals with diabetes still develop DR despite appropriate glycemic and blood pressure control, highlighting the pressing need to identify useful biomarkers for risk stratification. The purpose of this review is to systematically summarize potential metabolic biomarkers and pathways of DR, which could facilitate developing an understanding of the disease mechanisms, as well as new therapeutic measures.

Methods

We searched PubMed and Web of Science for relevant metabolomics studies on humans published before September 30, 2020. Information regarding authors, title, publication date, study subjects, analytical platforms, methods of statistical analysis, biological samples, directions of change of potential metabolic biomarkers, and predictive values of metabolic biomarker panels was extracted, and the quality of the studies was assessed. Pathway analysis, including enrichment analysis and topology analysis, was derived from integrating differential metabolites using MetaboAnalyst 3.0, based on the Kyoto Encyclopedia of Genes and Genomes and Human Metabolome Database.

Results

We found nine studies focused on the identification of potential biomarkers. Repeatedly identified metabolites including l-glutamine, l-lactic acid, pyruvic acid, acetic acid, l-glutamic acid, d-glucose, l-alanine, l-threonine, citrulline, l-lysine, and succinic acid were found to be potential biomarkers of DR. It was observed that l-glutamine and citrulline changed in all biological samples. Dysregulation of metabolic pathways involved amino acid and energy metabolism.

Conclusions

This review summarizes potential biomarkers and metabolic pathways, providing insights into new pathogenic pathways for this microvascular complication of diabetes.

Role of interferons in diabetic retinopathy

Diabetic retinopathy (DR) is one of the major causes of visual impairment and irreversible blindness in developed regions. Aside from abnormal angiogenesis, inflammation is the most specific and might be the initiating factor of DR. As a key participant in inflammation, interferon-gamma (IFN-γ) can be detected in different parts of the eye and is responsible for the breakdown of the blood-retina barrier and activation of inflammatory cells and other cytokines, which accelerate neovascularization and neuroglial degeneration. In addition, IFN-γ is involved in other vascular complications of diabetes mellitus and angiogenesis-dependent diseases, such as diabetic nephropathy, cerebral microbleeds, and age-related macular degeneration. Traditional treatments, such as anti-vascular endothelial growth factor agents, vitrectomy, and laser photocoagulation therapy, are more effective for angiogenesis and not tolerable for every patient. Many ongoing clinical trials are exploring effective drugs that target inflammation. For instance, IFN-α acts against viruses and angiogenesis and is commonly used to treat malignant tumors. Moreover, IFN-α has been shown to contribute to alleviating the progression of DR and other ocular diseases. In this review, we emphasize the roles that IFNs play in the pathogenesis of DR and discuss potential clinical applications of IFNs in DR, such as diagnosis, prognosis, and therapeutic treatment.

The Vitreous Ecosystem in Diabetic Retinopathy: Insight into the Patho-Mechanisms of Disease

Diabetic retinopathy is one of the leading causes of blindness in the world with the incidence of disease ever-increasing worldwide. The vitreous humor represents an extensive and complex interactive arena for cytokines in the diabetic eye. In recent decades, there has been significant progress in understanding this environment and its implications in disease pathophysiology. In this review, we investigate the vitreous ecosystem in diabetic retinopathy at the molecular level. Areas of concentration include: the current level of knowledge of growth factors, cytokine and chemokine mediators, and lipid-derived metabolites in the vitreous. We discuss the molecular patho-mechanisms of diabetic retinopathy based upon current vitreous research.

Changes in tear protein profile in dogs with keratoconjunctivitis sicca following topical treatment using cyclosporine A

Background and Aim

Keratoconjunctivitis sicca (KCS) is a chronic inflammatory ocular disease that occurs in many dog breeds worldwide. This study aimed to investigate the tear protein pattern of healthy dogs, KCS dogs, and KCS dogs after treatment with cyclosporine A (CsA).

Materials and Methods

Twenty-eight dogs of any breed were enrolled in the study. The subjects were divided into three groups: Healthy, KCS, and CsA-treated dogs. Tear samples were collected using Schirmer strips. Tear proteins extracted from the strips were analyzed using two-dimensional electrophoresis. For the first dimension, total protein from tears was separated by isoelectric focusing. The second dimension was performed using 12.5% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The gel images were analyzed and the protein spots of differential expression were manually cut for protein annotation using mass spectrometry.

Results

In total, 12 protein spots were excised and subjected to protein identification. Associated with KCS, six protein spots were a downregulated protein, namely, lysozyme. The other six protein spots were upregulated in KCS dogs, consisting of heat shock protein beta-1, protein S100-A12, and keratin type II cytoskeletal 1 and 5. After treatment with CsA for 45 days, the lysozyme protein was still decreasing and the inflammation protein (S100-A12) was not identified.

Conclusion

Inflammatory tear proteins and proteins involved in cellular stress were present in KCS dogs and appeared to be reduced in medicated eyes. Treatment with topical CsA in the short term may not improve the activity of antibacterial proteins. Changes in the expression patterns of these four proteins might be useful for disease severity and progression assessment, as well as for exploring a novel method for dry eye management in dogs.

Proteome Characterization of Glaucoma Aqueous Humor

Glaucoma is the leading cause of irreversible blindness worldwide. The proteome characterization of glaucoma is not clearly understood. A total of 175 subjects, including 57 primary acute angle-closure glaucoma (PAACG), 50 primary chronic angle-closure glaucoma (PCACG), 35 neovascular glaucoma (NVG), and 33 cataract patients, were enrolled and comparison proteomic analysis was provided. The samples were randomly divided into discovery group or validation group, whose aqueous humor proteome was analyzed by data-independent acquisition or by parallel reaction monitoring. The common proteome features of three types of glaucoma were immune response, lipid metabolism, and cell death. Three proteins, VTN, SERPIND1, and CD14, showed significant upregulation in glaucoma and could discriminate glaucoma from cataract. Mutual differential proteomic analysis of PAACG, PCACG, and NVG showed different proteome characterization of the three types of glaucoma. NVG was characterized with activated angiogenesis. PAACG was characterized with activation of inflammation response. SERPIND1 was discovered to play vital role in glaucoma occurrences, which is associated with eye transparency decrease and glucose metabolism. This study would provide insights in understanding proteome characterization of glaucoma and benefit the clinical application of AH proteome.

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Aqueous humor proteome of different glaucoma (PACG, NVG) was profiled.

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Potential protein biomarkers for glaucoma were proposed.

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Potential mechanism of glaucoma was described.

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SERPIND1 was discovered to have potential value for glaucoma diagnosis.

Sex-Based Analysis of Potential Inflammation-Related Protein Biomarkers in the Aqueous Humor of Patients With Diabetes Mellitus

Purpose

To investigate whether men have higher inflammatory protein biomarker concentrations in their aqueous humor (AH) compared with women in groups of patients with varying levels of diabetic disease.

Methods

This cross-sectional study included AH specimens from 59 adult patients comprised of three groups: no diabetes mellitus (DM), DM without diabetic retinopathy (DR), and DM with proliferative diabetic retinopathy (PDR). Protein biomarker concentration values were quantified using a commercial proximity extension assay-based technique.

Results

Intersex comparisons of concentration values for each protein biomarker revealed no discoveries in patients with no DM or with PDR. In contrast, 24 discoveries were detected in patients with DM without DR. The mean concentration value for all 24 protein biomarkers was higher in men compared with women. Of these 24 proteins, 12 demonstrated a significant association with sex on multivariate linear regression analysis. The β coefficient results demonstrated a positive association between male sex and concentration value for all 12 of these proteins.

Conclusions

Higher AH concentration levels of several potential biomarkers, including chemokines, proteases, proteins involved in programmed cell death, and a T-cell surface protein, were detected in men with DM with no DR. These findings suggest that men may have a more inflammatory disease phenotype compared with women in this group of patients.

Translational Relevance

The findings of this study help explain differences in epidemiologic patterns of diabetic retinopathy development between men and women.

Galectins in the Pathogenesis of Common Retinal Disease

Diseases of the retina are major causes of visual impairment and blindness in developed countries and, due to an ageing population, their prevalence is continually rising. The lack of effective therapies and the limitations of those currently in use highlight the importance of continued research into the pathogenesis of these diseases. Vascular endothelial growth factor (VEGF) plays a major role in driving vascular dysfunction in retinal disease and has therefore become a key therapeutic target. Recent evidence also points to a potentially similarly important role of galectins, a family of β-galactoside-binding proteins. Indeed, they have been implicated in regulating fundamental processes, including vascular hyperpermeability, angiogenesis, neuroinflammation, and oxidative stress, all of which also play a prominent role in retinopathies. Here, we review direct evidence for pathological roles of galectins in retinal disease. In addition, we extrapolate potential roles of galectins in the retina from evidence in cancer, immune and neuro-biology. We conclude that there is value in increasing understanding of galectin function in retinal biology, in particular in the context of the retinal vasculature and microglia. With greater insight, recent clinical developments of galectin-targeting drugs could potentially also be of benefit to the clinical management of many blinding diseases.

Assessment of biomarkers associated with rapid renal decline in the detection of retinopathy and its progression in type 2 diabetes: The Fremantle Diabetes Study Phase II

AIMS

To determine whether biomarkers for diabetic kidney disease (DKD) can be used to determine the prevalence, progression and/or incidence of diabetic retinopathy (DR) complicating type 2 diabetes.

METHODS

Proteomic biomarkers were measured in baseline fasting plasma from 958 Fremantle Diabetes Study Phase II participants whose baseline and, in those returning for follow-up (n = 764), Year 4 fundus photographs were graded for DR presence/severity. The performance of PromarkerD (three biomarkers and readily available clinical variables which identify prevalent DKD and predict incident DKD and estimated glomerular filtration rate decline ≥30% over four years) for detecting DR prevalence, progression and incidence was assessed using the area under the receiver operating curve (AUC). Logistic regression determined whether individual proteins were associated with DR outcomes after adjusting for the most parsimonious model.

RESULTS

Plasma apolipoprotein A-IV (APOA4) was independently associated with moderate non-proliferative DR at baseline (OR (95% CI): 1.64 (1.01, 2.67), P = 0.047). Model discrimination was poor for all PromarkerD predicted probabilities against all DR outcomes (AUC ≤0.681).

CONCLUSIONS

PromarkerD and its constituent biomarkers were not consistently associated with DR prevalence or temporal change. APOA4 was associated with prevalent DR, but not DR incidence or progression. Distinct pathophysiological mechanisms may underlie DKD and DR.

Association of serum and aqueous humor myonectin concentrations with diabetic retinopathy

Myonectin, a newly discovered myokine, enhances fatty acid uptake in cultured adipocytes and hepatocytes and suppresses circulating levels of free fatty acids in mice. This study is performed to evaluate the association between serum and aqueous humor myonectin concentrations with diabetic retinopathy (DR). This study was performed in a population of 228 patients with type 2 diabetes (T2DM) and 72 control subjects. Diabetic patients were then divided into T2DM patients without DR, non-proliferative diabetic retinopathy (NPDR) patients, and proliferative diabetic retinopathy (PDR) patients. Serum and aqueous humor myonectin concentrations were significantly lower in the case group than in the control group. PDR patients showed significantly decreased serum and aqueous humor myonectin concentrations than in the other two T2DM patients. In addition, NPDR patients showed significantly lower serum and aqueous humor myonectin concentrations than T2DM patients without DR. Logistic regression analysis demonstrated that serum and aqueous humor myonectin was correlated with a decreased risk of T2DM and DR. Simple linear regression analysis showed that serum myonectin was negatively correlated with duration of disease, body mass index (BMI), and HbA1c. Duration of disease and BMI were still correlated with the serum myonectin after a multiple linear regression analysis. Aqueous humor myonectin was negatively correlated with duration of disease, systolic blood pressure (SBP), and diastolic blood pressure. Duration of disease and SBP was still correlated with the aqueous humor myonectin after a multiple linear regression analysis. Our investigation indicates an inverse association of serum and aqueous humor myonectin with DR.

Gambogic acid ameliorates high glucose- and palmitic acid-induced inflammatory response in ARPE-19 cells via activating Nrf2 signaling pathway: ex vivo

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes. Gambogic acid has been reported to have anti-inflammatory effect. However, the effect of GA on inflammatory response of ARPE-19 cells remains unclear. In our study, ARPE-19 cells were stimulated by palmitic acid (PA) induction in the presence of 30 mM glucose and then treated with 0.5, 1, 2, 5, 10, or 20 μM GA. CCK-8 assay showed that cell viability was increased by GA treatment at doses of 0.5, 1, and 2 μM instead of higher doses. ELISA analysis found that GA dose-dependently reduced the production of pro-inflammatory mediators TNF-α and IL-1β. Western blot indicated that GA downregulated the expression of NLRP3 inflammasome components including TXNIP, NLRP3, ASC, cleaved-caspase-1, and cleaved-IL-1β in a dose-dependent manner. In addition, Western blot and immunofluorescence analysis suggested that GA effectively increased the protein level of nuclear factor E2-related factor-2 (Nrf2). RT-qPCR showed that GA significantly increased the mRNA levels of Heme oxygenase-1 (HO-1) and NADPH:quinone oxidoreductase1 (NQO1). Furthermore, Nrf2 siRNA transfection confirmed the above effects of GA. In total, subtoxic doses of GA significantly flattened the inflammatory response induced by HG and PA in ARPE-19 cells via modulating the Nrf2 signaling pathway.

Proteomic Analysis of Plasma sEVs Reveals That TNFAIP8 Is a New Biomarker of Cell Proliferation in Diabetic Retinopathy

Small extracellular vesicles (sEVs) derived from the plasma have been increasingly recognized as important vehicles of intercellular communication and potential sources of new biomarkers for multiple diseases. In this study, proteomic profiles of plasma sEVs from normal subjects and diabetic patients with or without diabetic retinopathy (DR) were systematically compared using iTRAQ-based quantitative proteomics. Among a total of 901 identified proteins in plasma sEVs (false discovery rate (FDR) < 1%), 90 proteins were found to have significantly changed levels in DR. Based on the findings from the proteomic analysis, the role of tumor necrosis factor-α-induced protein 8 (TNFAIP8) in promoting human retinal microvascular endothelial cell (HRMEC) proliferation was investigated. The enzyme-linked immunosorbent assay (ELISA) showed that TNFAIP8 levels in plasma sEVs and vitreous are elevated in DR, whereas not statistically different in large EVs (lEVs) and plasma. In addition, in vitro experiments demonstrated that 4-hydroxynonenal (4-HNE) increased the expression of TNFAIP8 in HRMECs. TNFAIP8 significantly increased HRMECs cell viability and promote cell migration and tube formation, and the depletion of TNFAIP8 impaired HRMEC proliferation. We demonstrated that TNFAIP8 in plasma sEVs could be used as a potential biomarker of DR. Functional studies suggested that TNFAIP8 might be an important mediator of angiogenesis in DR.

The effects of Bushen Yiqi Huoxue prescription and its disassembled prescriptions on a diabetic retinopathy model in Sprague Dawley rats

BACKGROUND

Diabetic retinopathy (DR) is one of the most serious complications in the late stages of diabetes, with a complex mechanism. As a complication affecting local lesions, few studies have compared differences of cytokine expression in the serum and retina. Owing to the specific value of traditional Chinese medicine (TCM) to complex diseases, TCM research has recently boomed in the prevention and treatment of diabetes. Bushen Yiqi Huoxue (BYH) prescription is a Chinese herbal compound that has been independently developed by our research group and has been proved to have a positive effect on DR; however, its specific mechanism and compatibility rule remain to be further explored.

OBJECTIVE

To construct a DR model of Sprague Dawley (SD) rats, simultaneously detect multiple factor expression in the serum and retina of rats, explore the effect of BYH prescription and its disassembled prescriptions on DR, and discuss the influence of various compatibility combinations.

METHODS

BYH prescription was disassembled into two new compatibilities in the absence of Rehmanniae Radix (Yiqi Huoxue prescription, YH prescription) or Ginseng Radix et Rhizoma (Bushen Huoxue prescription, BH prescription). Male SD rats were induced using streptozotocin + high-fat and high-sugar diet to establish DR models and were divided into groups, then the intragastric administration and sampling. The body weight and fasting blood glucose of rats were continuously recorded during feeding; pathophysiological status observation of the retina by haematoxylin and eosin (HE) staining; advanced glycation end products (AGEs) and haemoglobin A1c (HbA1c) level detection in the rat serum by enzyme-linked immunosorbent assay; and the Luminex technique was used to detect the ICAM-1, IL-1β, IL-6, TNF-α and vascular endothelial growth factor (VEGF) expression concentrations in the retinal tissue and serum.

RESULTS

The results of blood glucose, body weight and HE staining proved that the model was successfully constructed, and the three combinations could reduce the retinal injury in DR rats. Serum AGEs and HbA1c levels of the model group increased compared with the control group (CG). Compared with the DR model group, only AGEs decreased in the BYH group, while the AGEs and HbA1c levels were significantly inhibited in the YH and BH groups, showing a significant correlation between the expression of AGEs and HbA1c in the serum of DR rats. In the serum of rats, IL-1β, IL-6, TNF-α and VEGF concentrations in the DR model group increased, although no statistical difference was observed in the ICAM-1 data compared with the CG. Compared with the DR model group, the IL-1β, IL-6 and TNF-α expression decreased in the BYH group. Moreover, the IL-6 and TNF-α expression decreased in the YH group and only the IL-6 expression decreased in the BH group. In the retina tissue, the model group had higher ICAM-1, IL-1β, IL-6, TNF-α and VEGF levels than the CG. Compared with the DR model group, TNF-α in the BYH group rats decreased, and the ICAM-1, IL-6 and TNF-α concentrations decreased in the YH and BH groups. Furthermore, differences in the ICAM-1 and VEGF expression in the serum and retina existed.

CONCLUSION

BYH compound and its disassembled prescriptions could improve the DR model rats induced with streptozotocin + high-fat and high-sugar diet, respectively, by inhibiting chronic blood glucose, AGEs, or inflammation response. The expression level and location of each factor are different, confirming that the effect of TCM prescriptions is not the simple addition of each single drug or its chemical components, but the rationality of its internal compatibility combination. Further, ICAM-1 and VEGF have exactly different expression levels, suggesting more attention to be paid by other researchers or doctors in future studies.

Increased vitreal levels of interleukin-10 in diabetic retinopathy: a Meta-analysis

AIM

To conduct a Meta-analysis for the change of interleukin-10 (IL-10) concentration in vitreous samples of patients with diabetic retinopathy (DR).

METHODS

Systemic search for literature was conducted from the databases of PubMed, Web of Science and Cochrane Library by August 2019. Statistical analyses including standard mean difference (SMD) and its 95% confidence interval (CI) were performed by using RevMan 5.3 software.

RESULTS

Totally 194 studies were screened and finally 11 studies were included in the Meta-analysis. The concentration of IL-10 in the DR group was higher than in the control group (P=0.003, SMD: 0.77, 95%CI: 0.25-1.28). Significant heterogeneity was found among all studies (P<0.00001, I ²=92%). The subgroup analysis showed that the concentration of IL-10 increased in vitreous samples from patients with DR compared to the non-DR controls (P=0.004, SMD: 1.44, 95%CI: 0.46-2.42). Moreover, the concentration of IL-10 in samples of proliferative diabetic retinopathy (PDR) patients was significantly higher than that of non-proliferative diabetic retinopathy (NPDR) patients (P=0.01, SMD: 0.61, 95%CI: 0.13-1.08).

CONCLUSION

The vitreal concentration of IL-10 is significantly increased in patients with DR. Further studies are needed to reveal the mechanisms of IL-10 in DR.

Extracellular Vesicles and MicroRNA: Putative Role in Diagnosis and Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is a complex, progressive, and heterogenous retinal degenerative disease associated with diabetes duration. It is characterized by glial, neural, and microvascular dysfunction, being the blood-retinal barrier (BRB) breakdown a hallmark of the early stages. In advanced stages, there is formation of new blood vessels, which are fragile and prone to leaking. This disease, if left untreated, may result in severe vision loss and eventually legal blindness. Although there are some available treatment options for DR, most of them are targeted to the advanced stages of the disease, have some adverse effects, and many patients do not adequately respond to the treatment, which demands further research. Oxidative stress and low-grade inflammation are closely associated processes that play a critical role in the development of DR. Retinal cells communicate with each other or with another one, using cell junctions, adhesion contacts, and secreted soluble factors that can act in neighboring or long-distance cells. Another mechanism of cell communication is via secreted extracellular vesicles (EVs), through exchange of material. Here, we review the current knowledge on deregulation of cell-to-cell communication through EVs, discussing the changes in miRNA expression profiling in body fluids and their role in the development of DR. Thereafter, current and promising therapeutic agents for preventing the progression of DR will be discussed.

Elevated vitreous Lipocalin-2 levels of patients with proliferative diabetic retinopathy

BACKGROUND

Lipocalin-2 (LCN2) is a novel adipokine with potential roles in obesity, insulin resistance, and inflammation. This study aims to assess the concentrations of LCN2 and vascular endothelial growth factor (VEGF) expressed in the vitreous humors of patients with proliferative diabetic retinopathy (PDR).

METHODS

The concentrations of LCN2 and VEGF were measured from the vitreous of 67 patients undergoing vitrectomy (20 controls and 47 PDR) via enzyme-linked immunosorbent assay (ELISA). Patients with non-ocular pathology that could elevate the LCN2 level in the vitreous were excluded. PDR activity and a history of panretinal photocoagulation were used for further grouping analysis.

RESULTS

The vitreous concentration of LCN2 was statistically significantly higher in the PDR group compared to the control group (63,522 (30,009) pg/ml versus 1663 (1191) pg/ml, respectively; P < 0.001). VEGF level was also significantly higher in the PDR group than in the control group (1038 (1326) pg/ml versus 9 pg/ml, respectively; P < 0.001). The mean vitreous LCN2 and VEGF levels in active PDR patients were significantly higher than that of the inactive PDR patients. The mean LCN2 concentration in vitreous humor was significantly lower in the 28 PDR patients with a history of complete PRP (37,304 (16,651) pg/mL) in comparison with 19 PDR patients without preperformed panretinal photocoagulation or with preperformed incomplete panretinal photocoagulation (79,796 (24,391) pg/mL). A significant correlation between the vitreous LCN2 level and VEGF level was found in patients with PDR (R = 0.34; P = 0.019).

CONCLUSIONS

This report shows a significant increase of LCN2 in the vitreous fluid of patients with PDR and present a significant correlation between LCN2 and VEGF, suggesting LCN2 might be involved in the pathogenesis of PDR.

The unique association between the level of peripheral blood monocytes and the prevalence of diabetic retinopathy: a cross-sectional study

OBJECTIVE

The attraction and influx of monocytes into the retina has been considered a critical step in the development of diabetic retinopathy (DR). However, large population studies about the association between peripheral blood monocyte levels, an inexpensive and easily measurable laboratory index, and DR are limited. Thus, we aimed to investigate the association between peripheral blood monocyte levels and DR.

METHODS

A total of 3223 participants out of 3277 adults with diabetes were enrolled from seven communities in China in this cross-sectional survey. Participants underwent several medical examinations, including the measurement of anthropometric factors, blood pressure, routinely analyzed leukocyte characteristics, glucose, lipid profiles, urine albumin/creatinine ratio and fundus photographs.

RESULTS

The prevalence of DR among the participants in the highest quartile of peripheral blood monocyte levels significantly decreased by 41% (OR 0.59; 95% CI 0.43, 0.81) compared with the participants in the first quartile (P for trend < 0.05). However, there were no associations between the monocyte level and the prevalence of cardiovascular and cerebrovascular diseases (CVD) and diabetic kidney disease (DKD) (both P for trend > 0.05). Associations between leukocyte, neutrophil and lymphocyte levels and DR were also not found (all P for trend > 0.05). These associations were all fully adjusted for age, sex, education status, duration of diabetes history, current smoking, BMI, HbA1c, dyslipidemia, systolic blood pressure and insulin therapy.

CONCLUSION

Decreased peripheral blood monocyte levels were associated with increased odds of DR after adjusting for potential confounders in diabetic adults. However, causation remains to be demonstrated.

Dysregulation of trophic factors contributes to diabetic retinopathy in the Ins2Akita mouse

Diabetic retinopathy (DR) is considered as a diabetes-related complication that can lead to severe visual impairments. By 2030, it is expected that 1 in 5 adults will suffer from the disease. Suitable animal models for chronic DR are essential for a better understanding of the pathophysiology and to further develop new treatments. The Ins2^Akita mouse is a type 1 diabetes model that shows signs of both early and late stages of DR, including pericyte loss, increased vascular permeability, increased acellular capillaries and neovascularization. To further characterize DR in the Ins2^Akita mouse model, we have evaluated the protein levels of the angiogenesis inducers vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) and the angiogenesis inhibitor pigment epithelium-derived factor (PEDF). Additionally, we have analyzed the protein expression profile of the glial markers ionized calcium binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) as well as of the chemokine monocyte chemoattractant protein 1 (MCP-1). In this study we demonstrate that, with disease progression, there is the development of an inflammatory response and an unbalanced expression of pro- and antiangiogenic factors in the neural retina and in the retinal pigment epithelium (RPE) of Ins2^Akita mice. Therefore, our data provide support for the diabetic retinopathy features detected in the Ins2^Akita retina, reflecting what is observed in the human pathology.

High Density Display of an Anti-Angiogenic Peptide on Micelle Surfaces Enhances Their Inhibition of αvβ3 Integrin-Mediated Neovascularization In Vitro

Diabetic retinopathy (DR), Retinopathy of Pre-maturity (ROP), and Age-related Macular Degeneration (AMD) are multifactorial manifestations associated with abnormal growth of blood vessels in the retina. These three diseases account for 5% of the total blindness and vision impairment in the US alone. The current treatment options involve heavily invasive techniques such as frequent intravitreal administration of anti-VEGF (vascular endothelial growth factor) antibodies, which pose serious risks of endophthalmitis, retinal detachment and a multitude of adverse effects stemming from the diverse physiological processes that involve VEGF. To overcome these limitations, this current study utilizes a micellar delivery vehicle (MC) decorated with an anti-angiogenic peptide (aANGP) that inhibits αvβ3 mediated neovascularization using primary endothelial cells (HUVEC). Stable incorporation of the peptide into the micelles (aANGP-MCs) for high valency surface display was achieved with a lipidated peptide construct. After 24 h of treatment, aANGP-MCs showed significantly higher inhibition of proliferation and migration compared to free from aANGP peptide. A tube formation assay clearly demonstrated a dose-dependent angiogenic inhibitory effect of aANGP-MCs with a maximum inhibition at 4 μg/mL, a 1000-fold lower concentration than that required for free from aANGP to display a biological effect. These results demonstrate valency-dependent enhancement in the therapeutic efficacy of a bioactive peptide following conjugation to nanoparticle surfaces and present a possible treatment alternative to anti-VEGF antibody therapy with decreased side effects and more versatile options for controlled delivery.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Review of Three-Dimensional Liquid Chromatography Platforms for Bottom-Up Proteomics

Proteomics is a large-scale study of proteins, aiming at the description and characterization of all expressed proteins in biological systems. The expressed proteins are typically highly complex and large in abundance range. To fulfill high accuracy and sensitivity of proteome analysis, the hybrid platforms of multidimensional (MD) separations and mass spectrometry have provided the most powerful solution. Multidimensional separations provide enhanced peak capacity and reduce sample complexity, which enables mass spectrometry to analyze more proteins with high sensitivity. Although two-dimensional (2D) separations have been widely used since the early period of proteomics, three-dimensional (3D) separation was barely used by low reproducibility of separation, increased analysis time in mass spectrometry. With developments of novel microscale techniques such as nano-UPLC and improvements of mass spectrometry, the 3D separation becomes a reliable and practical selection. This review summarizes existing offline and online 3D-LC platforms developed for proteomics and their applications. In detail, setups and implementation of those systems as well as their advances are outlined. The performance of those platforms is also discussed and compared with the state-of-the-art 2D-LC. In addition, we provide some perspectives on the future developments and applications of 3D-LC in proteomics.