Exosome-based crosstalk in glaucoma pathogenesis: a focus on oxidative stress and neuroinflammation

Impact of Oral Citicoline, Antioxidant Vitamins, and Blackcurrant Supplementation on Primary Open-Angle Glaucoma: An OCT and OCTA Study

Purpose: We sought to evaluate the long-term effects of oral citicoline; vitamins A, B, C, and E; and blackcurrant therapy in patients with primary open-angle glaucoma (POAG) using optical coherence tomography (OCT), OCT angiography (OCTA), and microperimetry parameters. Materials and Methods: Fifteen patients with POAG (the treated group) received one soluble liquid sachet of a complementary dietary supplement containing, in a fixed combination, citicoline; vitamins A, B, C, and E; and blackcurrant (Citizin®, Bruschettini s.r.l., Genova, Italy) daily for 20 days a month for 1 year. Fifteen age-matched patients with POAG were given a placebo and served as a control group. The patients underwent best-corrected visual acuity (BCVA) analysis, Goldmann applanation tonometry, microperimetry examination, OCT, and OCTA at the beginning of the study and then 1, 6, and 12 months later. Results: A significant improvement in the overall retinal nerve fiber layer (RNFL) thickness values (compared with the control group) was recorded at the 6- (p < 0.009) and 12 (p < 0.001)-month follow-ups in the treated group. The ganglion cell complex (GCC) increased in thickness (compared with the control group) at the 12-month follow-up (p < 0.0001) in the treated group. The mean macular vessel density (MVD) and the mean peripapillary vessel density (PVD) in the treated group were significantly higher than those in the control group at the 12-month follow-up. Microperimetry examination, BCVA, and Goldmann applanation tonometry showed no statistically significant alterations. Conclusions: A fixed combination of citicoline; vitamins A, B, C, and E; and blackcurrant administered orally may have a positive impact on RNFL, GCC, MVD, and PVD in patients with POAG.

Changes in the Protein Composition of the Aqueous Humor in Patients with Glaucoma: An Update Review

The study of the aqueous humor (AH) plays a key role in understanding the pathophysiology of glaucoma. The AH provides nutrition, maintains the appropriate intraocular pressure, and provides important information about the mechanisms of the disease. The development of modern technologies has allowed the use of more accurate analytical methods, which has proven to be a key factor in determining the changes occurring in the proteome of the aqueous humor of glaucoma patients. Recently, researchers have observed changes in the levels of proteins associated with inflammation, oxidative stress, the complement system, and extracellular matrix remodeling. They have also shown that these changes may be variable for different types of glaucoma. The objective of this review is to collect and summarize the current knowledge on the potential biomarkers and pathomechanisms involved in the pathogenesis of glaucoma. We hope that our review will contribute to the improvement of current diagnostic methods in this illness and, through a better understanding of the changes occurring during the progression of the disease, will enable the development of more effective preventive and therapeutic strategies in the future.

IFNγ preconditioning improves neuroprotection of MSC-derived vesicles on injured retinal ganglion cells by suppressing microglia activation via miRNA-dependent ribosome activity

Aim: Microglial activation plays a pivotal role in the pathogenesis of retinal ganglion cell (RGC) degeneration resulting from optic nerve crush (ONC). Small extracellular vesicles (sEVs) secreted by mesenchymal stem cells (MSCs) have the potential to prevent retinal degeneration by modulating microglial activation. In this study, we elucidated the specific effects of sEVs derived from IFN-γ-primed MSCs on the phenotypic transition of microglia and the associated pathways in ONC mice. Methods: The ONC mice model was established and administered intravitreal injection with the sEVs derived from native MSCs (native sEVs) and the sEVs derived from MSCs primed with IFN-γ (IFNγ-sEVs). Their respective effects on the survival of the retinal ganglion cells (RGCs) and the transition of microglia phenotypes were determined through visual function testing and immunohistochemical staining. Combined with mRNA seq and microRNA seq techniques, we elucidated the mechanism of modulation of microglia phenotypic transformation by sEVs derived from MSCs primed by IFNγ. Results: It demonstrated that IFNγ-sEVs exhibited superior protective effects against RGC loss and reduced inflammatory responses in the ONC retina compared to native sEVs. Both types of sEVs promoted microglia activation to disease-associated microglia (DAM) phenotype, while IFNγ-sEVs especially suppressed interferon-responsive microglia (IRM) activation during RGCs degeneration. Subsequent miRNA sequencing suggested that miR-423-5p, which exhibited the most significant differential expression between the two sEVs types and elevated expression in IFNγ-sEVs, inhibited the expression of IRM and ribosomal genes. Conclusion: These findings suggest that IFN-γ-preconditioned MSCs may enhance sEVs of neuroprotection on RGCs by suppressing IRM activation through the secretion of sEVs containing specific microRNAs in ONC mice.

Extracellular Vesicles and Glaucoma: Opportunities and Challenges

PURPOSE

Glaucoma is one of the leading causes of irreversible blindness, characterized by progressive visual field loss. Several risk factors are associated with developing the disease. However, the exact mechanisms or pathological pathways involved are still unknown. There is an urgent need to find the mechanisms and biomarkers for early detection and therapy to halt progression or cure the disease. Extracellular vesicles (EVs), specifically exosomes, have emerged as a crucial player in all aspects of glaucoma, including pathogenesis to therapeutic application with their cell-cell communication properties.

METHODS

We performed a literature search on PubMed, Google Scholar, and Web of Science using different keywords. Next, we reviewed the literature with studies focusing on the role of EVs as a causative factor in disease progression, biomarker discovery based on their contents, and protection from glaucoma.

RESULTS

Studies summarized here provide reports of differential EV miRNA and protein expression alterations when communicating with aqueous humor drainage tissues. We described how EV contents are involved in various pathways, including extracellular matrix remodeling and miRNA-mediated oxidative stress transmission between outflow tissues, thereby contributing to glaucoma. Extracellular vesicles, mainly derived from mesenchymal stem cells protecting the optic nerve from degeneration, have also been discussed as potential therapies for glaucoma.

CONCLUSIONS

Overall, this review provides a comprehensive discussion of the role of extracellular vesicles in glaucoma. We identified the challenges in finding major signaling molecules of glaucoma etiology. Lastly, we highlighted future directions to improve the treatment of glaucoma by extracellular vesicles.

Exploration of potential drug targets for Glaucoma by plasma proteome screening

BACKGROUND

Glaucoma is the leading cause of irreversible blindness. However, the current available treatment methods are still unsatisfactory. Therefore, the exploration of new drug targets for the treatment of glaucoma is of paramount importance.

METHODS

We conducted two-sample Mendelian randomization (MR) using plasma protein quantitative trait loci (pQTL) data from two datasets (n = 734, n = 4907) and their instrumental variables to investigate the causal relationship between plasma proteins and glaucoma. The analysis was validated by replacing the exposure and outcome cohorts. Additionally, we utilized protein-protein interaction networks to assess the associations between these potential drug targets and existing drug targets.

RESULTS

Through two-sample Mendelian randomization analysis, we identified causal relationships between Glaucoma and the following proteins: AZU1, OBP2B, ENPP5, INPP5B, KREMEN1, LYPLAL1, and PTPRJ. External validation confirmed the protective effect of LYPLAL1 on Glaucoma, while ENPP5, KREMEN1, and PTPRJ increased the risk of Glaucoma. Reverse MR and Steiger filtering did not indicate any reverse causal associations of the aforementioned proteins with Glaucoma.

CONCLUSION

Our study demonstrates a causal impact of ENPP5, KREMEN1, PTPRJ, and LYPLAL1 on the risk of Glaucoma. These findings suggest that these four proteins may serve as promising drug targets for Glaucoma treatment.

SIGNIFICANCE

Currently, the pharmacological treatment of glaucoma primarily focuses on lowering intraocular pressure, which has its limitations. Targeted therapy is a personalized treatment approach that aims to inhibit or block the development and progression of diseases such as cancer and inflammation by selectively acting on specific biomolecules or signaling pathways. Our research employs a two-sample Mendelian randomization (MR) method, integrating a large amount of GWAS and pQTL data to perform MR analysis. This has enabled us to explore several plasma proteins as potential drug targets for glaucoma, providing direction and a research foundation for future investigations into glaucoma drug targets.

Identification and validation of oxidative stress-related genes in primary open-angle glaucoma by weighted gene co-expression network analysis and machine learning

Primary open-angle glaucoma (POAG) is a common ocular disease, and there is currently no effective treatment for POAG therapy. Thus, identifying some effective diagnostic markers is beneficial to the treatment of patients. The expression profile was obtained from Gene Expression Omnibus (GEO) database. The functional enrichment was analyzed using Gene Ontology, Kyoto Encyclopedia of Genes and Genomes and gene set enrichment analysis. Co-expressed genes were identified using weighted gene co-expression network analysis (WGCNA). Hub genes were screened through Lasso regression, support vector machine-recursive feature elimination (SVM-RFE) and Random Forest, and receiver operating characteristic curve was used to assess diagnostic value. Immune cell infiltration was calculated using IOBR package. The regulatory network was constructed through STRING, miRactDB and Cytoscape. The oncoPredict package was employed to predict the candidate chemotherapy agents. According to GSE27276 database, 541 differentially expressed genes were identified. Five oxidative stress-related genes with high area under the curve value, namely HBB, MAOA, ACOX2, ALDH7A1 and TYMP, were determined using WGCNA and machine learning. Infiltration level of NK cells, CD4 T cells and dendritic cells were significantly increased in POAG group compared with normal group, while CD8 T cells and Tregs cells were significantly decreased. HBB was closely related to most immune cells. Hub genes were all targeted by 16 miRNAs. Drug sensitivity analysis exhibited that some drugs were more sensitivity for POAG, such as Acetalax_1804, Ibrutinib_1799 and OSI_027_1594. We identified 5 oxidative stress-related genes with high diagnostic value for POAG.

Intracellular Zn2+ promotes extracellular matrix remodeling in dexamethasone-treated trabecular meshwork

Given the widespread application of glucocorticoids in ophthalmology, the associated elevation of intraocular pressure (IOP) has long been a vexing concern for clinicians, yet the underlying mechanisms remain inconclusive. Much of the discussion focuses on the extracellular matrix (ECM) of trabecular meshwork (TM). It is widely agreed that glucocorticoids impact the expression of matrix metalloproteinases (MMPs), leading to ECM deposition. Since Zn2+ is vital for MMPs, we explored its role in ECM alterations induced by dexamethasone (DEX). Our study revealed that in human TM cells treated with DEX, the level of intracellular Zn2+ significantly decreased, accompanied by impaired extracellular Zn2+ uptake. This correlated with changes in several Zrt-, Irt-related proteins (ZIPs) and metallothionein. ZIP8 knockdown impaired extracellular Zn2+ uptake, but Zn2+ chelation did not affect ZIP8 expression. Resembling DEX's effects, chelation of Zn2+ decreased MMP2 expression, increased the deposition of ECM proteins, and induced structural disarray of ECM. Conversely, supplementation of exogenous Zn2+ in DEX-treated cells ameliorated these outcomes. Notably, dietary zinc supplementation in mice significantly reduced DEX-induced IOP elevation and collagen content in TM, thereby rescuing the visual function of the mice. These findings underscore zinc's pivotal role in ECM regulation, providing a novel perspective on the pathogenesis of glaucoma.NEW & NOTEWORTHY Our study explores zinc's pivotal role in mitigating extracellular matrix dysregulation in the trabecular meshwork and glucocorticoid-induced ocular hypertension. We found that in human trabecular meshwork cells treated with dexamethasone, intracellular Zn2+ significantly decreased, accompanied by impaired extracellular Zn2+ uptake. Zinc supplementation rescues visual function by modulating extracellular matrix proteins and lowering intraocular pressure, offering a direction for further exploration in glaucoma management.

Human adipose tissue-derived stem cell extracellular vesicles attenuate ocular hypertension-induced retinal ganglion cell damage by inhibiting microglia- TLR4/MAPK/NF-κB proinflammatory cascade signaling

Microglia-mediated neuroinflammatory responses are recognized as a predominant factor during high intraocular pressure (IOP)-induced retinal and optic nerve injury along with potential therapeutic targets for the disease. Our previous research indicated that mesenchymal stem cell (MSC) treatment could reduce high IOP-induced neuroinflammatory responses through the TLR4 pathway in a rat model without apparent cell replacement and differentiation, suggesting that the anti-neuroinflammatory properties of MSCs are potentially mediated by paracrine signaling. This study aimed to evaluate the anti-neuroinflammatory effect of human adipose tissue-derived extracellular vesicles (ADSC-EVs) in microbead-induced ocular hypertension (OHT) animals and to explore the underlying mechanism since extracellular vesicles (EVs) are the primary transporters for cell secretory action. The anti-neuroinflammatory effect of ADSC-EVs on LPS-stimulated BV-2 cells in vitro and OHT-induced retinal and optic nerve injury in vivo was investigated. According to the in vitro research, ADSC-EV treatment reduced LPS-induced microglial activation and the TLR4/NF-κB proinflammatory cascade response axis in BV-2 cells, such as CD68, iNOS, TNF-α, IL-6, and IL-1β, TLR4, p-38 MAPK, NF-κB. According to the in vivo data, intravitreal injection of ADSC-EVs promoted RGC survival and function, reduced microglial activation, microglial-derived neuroinflammatory responses, and TLR4/MAPK/NF-κB proinflammatory cascade response axis in the OHT mice. Our findings provide preliminary evidence for the RGC protective and microglia-associated neuroinflammatory reduction effects of ADSC-EVs by inhibiting the TLR4/MAPK/NF-κB proinflammatory cascade response in OHT mice, indicating the therapeutic potential ADSC-EVs or adjunctive therapy for glaucoma.

The Role and Mechanism of Nicotinamide Riboside in Oxidative Damage and a Fibrosis Model of Trabecular Meshwork Cells

Purpose

To investigate the potential effects and mechanism of nicotinamide riboside (NR) on the oxidative stress and fibrosis model of human trabecular meshwork (HTM) cell line cells.

Methods

HTM cells were pretreated with NR, followed by the induction of oxidative injury and fibrosis by hydrogen peroxide (H2O2) and TGF-β2, respectively. Cell viability was tested using Hoechst staining and MTT assays, cell proliferation was assessed by EdU assay, and cell apoptosis was detected by flow cytometry and western blotting. DCFH-DA and DHE probes were used to measure the level of reactive oxygen species (ROS), and MitoTracker staining was used to measure the mitochondrial membrane potential (MMP). Fibrotic responses, including cell migration and deposition of extracellular matrix (ECM) proteins, were detected via Transwell assays, qRT-PCR, and immunoblotting.

Results

NR pretreatment improved the viability, proliferation, and MMP of H2O2-treated HTM cells. Compared to cells treated solely with H2O2, HTM cells treated with both NR and H2O2, exhibited a reduced rate of apoptosis and generation of ROS. Compared with H2O2 pretreatment, NR pretreatment upregulated expression of the JAK2/Stat3 pathway but inhibited mitogen-activated protein kinase (MAPK) pathway expression. Moreover, 10-ng/mL TGF-β2 promoted cell proliferation and migration, which were inhibited by NR pretreatment. Both qRT-PCR and immunoblotting showed that NR inhibited the expression of fibronectin in a TGF-β2-induced fibrosis model.

Conclusions

NR has a protective effect on oxidative stress and fibrosis in HTM cells, which may be related to the JAK2/Stat3 pathway and MAPK pathway.

Translational Relevance

Our research provides the ongoing data for potential therapy of NAD+ precursors in glaucoma.

Exosomes in neuron-glia communication: A review on neurodegeneration

Introduction

Exosomes, a subset of extracellular vesicles (EVs), are crucial for intercellular communication in various contexts. Despite their small size, they carry diverse cargo, including RNA, proteins, and lipids. Internalization by recipient cells raises concerns about potential disruptions to cellular functions. Notably, the ability of exosomes to traverse the blood-brain barrier (BBB) has significant implications.

Methods

To conduct a thorough investigation into the existing academic literature on exosomes within the framework of neuron-glia communication, a comprehensive search strategy was implemented across the PubMed, Google Scholar, and Science Direct databases. Multiple iterations of the keywords "exosome," "neuron-glia communication," and "neurological disorders" were employed to systematically identify relevant publications. Furthermore, an exploration of the Clinicaltrials.gov database was undertaken to identify clinical trials related to cellular signaling, utilizing analogous terminology.

Results

Although the immediate practical applications of exosomes are somewhat limited, their potential as carriers of pathogenic attributes offers promising opportunities for the development of precisely targeted therapeutic strategies for neurological disorders. This review presents a comprehensive overview of contemporary insights into the pivotal roles played by exosomes as agents mediating communication between neurons and glial cells within the central nervous system (CNS).

Conclusion

By delving into the intricate dynamics of exosomal communication in the CNS, this review contributes to a deeper understanding of the roles of exosomes in both physiological and pathological processes, thereby paving the way for potential therapeutic advancements in the field of neurological disorders.