T Cell-Mediated Autoimmunity in Glaucoma Neurodegeneration

Rag1-/- mice with T and B lymphocyte deficiency exhibit milder retinal inflammatory response and retinal ganglion cell injury after optic nerve crush

Bourgeoning literature verified the essential contribution of neuroinflammation in optic nerve injury, here, we aim to investigate the effect of lymphocyte deficiency on retinal ganglion cells (RGCs) survival after optic nerve crush (ONC). 48 wide type (WT) and 48 Rag1-/- mice were used to establish the ONC model. AAV2-hSyn1-eGFP was employed to inject into the vitreous body to transfect RGCs 4 weeks before ONC modeling, the confocal scanning laser ophthalmoscopy was utilized to visualize the RGCs in vivo. RBPMS, Iba-1 and GFAP expression were detected by immunofluorescence. The expression of retinal glial biomarkers was detected by qRT-PCR, and the protein expression of occludin and CD3 was detected by WB. Electroretinography and optomotor response were used to evaluate the visual function. Our results showed that a milder RGC loss and GCC thickness decrease were found in Rag1-/- mice than in WT mice after ONC in vivo and in vitro (p < 0.05). The morphologic and molecular feature analyses of retinal glial cells showed that the lack of lymphocytes significantly inhibited the number and activation level of microglia after ONC (p < 0.05). Besides, Occludin was significantly decreased and CD3 was upregulated at week 4 after ONC in WT mice compared with Rag1-/- mice (p < 0.01). Visual function assessment showed a better visual condition in Rag1-/- mice with ONC at week 4 (p < 0.05). Altogether, Rag1-/- mice with lymphocyte deficiency exhibit less RGC loss, milder retinal glial activation and better visual function when compared with WT mice after ONC.

Integration of single-cell and bulk transcriptomics reveals β-hydroxybutyrylation-related signatures in primary open-angle glaucoma

The pathophysiology of primary open-angle glaucoma (POAG), the most prevalent glaucoma type, is poorly understood. Although it is well known that epigenetic factors affect the progression of POAG, the impact of β-hydroxybutyrylation (Kbhb) on POAG remains unknown. Based on POAG-related datasets (GSE27276, GSE4316, and GSE231749) retrieved from the Gene Expression Omnibus (GEO) database, four biomarkers (FABP5, GLS, PDLIM1, and TAGLN) with a diagnostic value for POAG were identified by combining differential expression analysis, machine learning algorithms, and receiver operating characteristic (ROC) analysis. Immune infiltration analysis demonstrated significant differences in the infiltration abundances of 10 immune cells between POAG and controls, including regulatory T cells, monocytes, and macrophages, with notable positive correlations between TAGLN expression and these immune cells. Subsequently, single-cell analysis revealed that GLS, PDLIM1, and TAGLN were higher expressed in chondrocytes, smooth muscle cells, and endothelial cells. In addition, in vitro cellular experiments and animal models revealed that the TAGLN expression trend was consistent with the data from GSE27276 and GSE4316. In conclusion, TAGLN may play an important role in understanding of the molecular mechanisms of POAG and exploration of therapeutic targets.

Profiling of the Peripheral Blood Mononuclear Cells Proteome by Shotgun Proteomics Identifies Alterations of Immune System Components, Proteolytic Balance, Autophagy, and Mitochondrial Metabolism in Glaucoma Subjects

Glaucoma is a chronic optic neuropathy and is the second cause of irreversible blindness worldwide. Although the pathogenesis of the disease is not fully understood, the death of retinal ganglion cells and degeneration of the optic nerve are likely promoted by a combination of local and systemic factors. Growing attention has been paid to nonintraocular pressure risk factors, including mechanisms of inflammation and neuroinflammation. Phenotypical and molecular alterations of circulating immune cells, in particular, lymphocyte subsets, have been documented in murine models of glaucoma and in human subjects. Very recently, oxygen consumption rate and nicotinamide adenine dinucleotide levels of human peripheral blood mononuclear cells (PBMC) have been proposed as biomarkers of disease progression, thus suggesting that immune cells of glaucoma subjects present severe molecular and metabolic alterations. In this framework, this pilot study aimed to be the first to characterize global proteome perturbations of PBMC of patients with primary open-angle glaucoma (POAG) compared to nonglaucomatous controls (control) by shotgun proteomics. The approach identified >4,500 proteins and a total of 435 differentially expressed proteins between POAG and control subjects. Clustering and rationalization of proteomic data sets and immunodetection of selected proteins by Western blotting highlighted significant alterations of immune system compartments (i.e., complement factors, regulators of immune functions, and lymphocyte activation) and pathways serving key roles for immune system such as proteolysis (i.e., matrix metalloproteinases and their inhibitors), autophagy (i.e., beclin-1 and LC3B), cell proliferation (Bcl2), mitochondrial (i.e., sirtuin), and energetic/redox metabolism (i.e., NADK). Based on these findings, this proteomic study suggests that circulating immune cells suffer from heterogeneous alterations of central pathways involved in cell metabolism and homeostasis. Larger, properly designed studies are required to confirm specifically how immune cellular alterations may be involved in the pathogenesis of both neuroinflammation and glaucomatous disease.

Cannabinoids as Multitarget Drugs for the Treatment of Autoimmunity in Glaucoma

Diseases of multifactorial origin like neurodegenerative and autoimmune diseases require a multitargeted approach. The discovery of the role of autoimmunity in glaucoma and retinal ganglionic cell (RGC) death has led to a paradigm shift in our understanding of the etiopathology of glaucoma. Glaucoma can cause irreversible vision loss that affects up to an estimated 3% of the population over 40 years of age. The current pharmacotherapy primarily aims to manage only intraocular pressure (IOP), a modifiable risk factor in the glaucomatous neurodegeneration of RGCs. However, neurodegeneration continues to happen in normotensive patients (where the IOP is below a reference value), and the silent nature of the disease can cause significant visual impairment and take a massive toll on the healthcare system. Cannabinoids, although known to reduce IOP since the 1970s, have received renewed interest due to their neuroprotective, anti-inflammatory, and immunosuppressive effects on autoimmunity. Additionally, the role of the gut-retina axis and abnormal Wnt signaling in glaucoma makes cannabinoids even more relevant because of their action on multiple targets, all converging in the pathogenesis of glaucomatous neurodegeneration. Cannabinoids also cause epigenetic changes in immune cells associated with autoimmunity. In this Review, we are proposing the use of cannabinoids as a multitargeted approach for treating autoimmunity associated with glaucomatous neurodegeneration, especially for the silent nature of glaucomatous neurodegeneration in normotensive patients.

Rho Kinase (ROCK) Inhibitors in the Treatment of Glaucoma and Glaucoma Surgery: A Systematic Review of Early to Late Phase Clinical Trials

Background/Objectives: Primary open-angle glaucoma (POAG) is an anterior optic neuropathy that can lead to irreversible vision loss if untreated. Prostaglandin analogues are the first-line treatment, but new drug classes, such as rho kinase (ROCK) inhibitors, are being explored. This review evaluates the efficacy and safety of ROCK inhibitors in treating POAG based on completed trials, comparing results with available natural history data and identifying areas for further research. Methods: A systematic database search was conducted in Ovid MEDLINE and Ovid Embase on 5 April 2022 using the following keywords: 'glaucoma', 'rho kinase inhibitor', 'rho-kinase inhibitor', 'rock inhibitor', 'ripasudil', 'netarsudil', and 'fasudil'. Abstracts were screened for relevant studies and results summarized in tables. Results: The analysis of trials conducted for ROCK inhibitors reveals that they are a safe and efficacious drug to treat POAG, demonstrating non-inferiority to existing medical treatments. Comparison of data to natural history studies was inconclusive due to the lack of natural history studies and their limitations. The results showed ROCK inhibitors to be effective when combined with existing medical treatments. However, questions remain regarding the optimal dosage, patient selection, and cost-effectiveness. Outcome measures for future trials should be expanded to include additional methods of monitoring disease progression as well as patient quality-of-life. Conclusions: ROCK inhibitors have emerged with a favorable safety profile, efficaciously attenuating intraocular pressure. To elucidate their long-term therapeutic value and safety comprehensively, further independent, large-scale, prospective randomized controlled trials are warranted. Such studies are pivotal to augment our understanding of this emergent medication class.

Proteome-Wide Analysis of Autoantibodies in Open-Angle Glaucoma in Japanese Population: A Pilot Study

Objectives: The objective of this study was to identify novel autoantibodies specific for open-angle glaucoma (OAG), including normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG), using proteome-wide autoantibody screening and to determine their utility for diagnosis. Methods: We conducted proteome-wide autoantibody screening by wet protein arrays. Autoantibody reactivity in the plasma of OAG patients (50 NTG and 69 POAG patients) was quantitatively analyzed and compared to that of controls (35 cataract patients). The area under the curve (AUC) of the receiver operating characteristic (ROC) and multivariate analyses were used to determine diagnostic potential in patients with OAG. Results: Based on differences in autoantibody titers and positivity rates, four autoantibodies against ETNK1, VMAC, NEXN, and SUN1 were selected as potential biomarkers to discriminate OAG and cataract. In discrimination between POAG and cataract, the AUCs of ETNK1 and VMAC were calculated to be 0.820 (95%CI: 0.733-0.907) and 0.889 (95%CI: 0.818-0.959), respectively. Furthermore, the combination of these four antibodies demonstrated diagnostic potential for OAG with an AUC of 0.828 (95%CI: 0.757-0.898) by multivariate analysis. Conclusions: Four new glaucoma-associated autoantibodies were identified in this study. The differences in autoantibody patterns in the plasma between glaucoma and cataract patients support their potential utility as biomarkers for glaucoma screening.

Association between 91 circulating inflammatory proteins and the risk of glaucoma: A Mendelian randomization study

Glaucoma is a leading cause of irreversible blindness worldwide, with its pathogenesis incompletely understood. Inflammation, as an important aspect of glaucoma, has attracted increasing attention. In this study, we performed a Mendelian randomization (MR) analysis to investigate the association between 91 circulating inflammatory proteins and glaucoma. First, a bidirectional MR was employed to screen for inflammatory proteins that potentially influence glaucoma risk, with the findings further confirmed by a replication sample MR. Then, a mediation analysis was employed to assess the mediating effects of glaucoma endophenotypes on glaucoma. Finally, we performed a subgroup MR to investigate the association between circulating proteins and glaucoma subtypes, including primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). The bidirectional MR suggested 7 out of the 91 proteins were possibly related with glaucoma risk, with T-cell surface glycoprotein CD5 (CD5) (odds ratio (OR) = 0.87; 95% confidence interval (CI): 0.81-0.94; P = 2.46 × 10-4) passing false discovery rate correction. This result was verified by the replication sample MR. The mediation analysis revealed that intraocular pressure (IOP) (β=-0.05; 95% CI: -0.02--0.09; P = 1.56 × 10-3) was a mediator of CD5's protective effect on glaucoma. The subgroup MR indicated that CD5 conferred a protective causal effect specifically on POAG, not PACG. Moreover, IOP served as a mediator in the association between CD5 and POAG, explaining a proportion of 38.29% of CD5's protective effect against POAG. Our findings suggest a negative causal association between circulating CD5 and POAG risk, which is partially mediated by IOP. This indicates that targeted CD5 therapy may be beneficial to POAG eyes.

The adaptive immune system in the retina of diabetics

As the prevalence of diabetes mellitus increases each year, its most common microvascular complication, diabetic retinopathy (DR), is also on the rise. DR is now regarded as an inflammatory disease in which innate immunity plays a crucial role, and a large number of innate immune cells with associated cytokines are involved in the pathologic process of DR. The role of adaptive immunity in DR is seldom mentioned, probably due to the general perception of the immune privileged environment of the retina; however, in recent years there has been a gradual increase in research on the role of adaptive immunity in DR, and with the discovery of the retinal lymphatic system, it seems that the role of adaptive immunity can no longer be ignored. Here, we discuss the immunosuppressive environment of the retina, the phenomenon and potential mechanisms of lymphocyte infiltration in DR, and the role of the adaptive immune system in the diabetic retina, which may point the way for future research.

Exploring the causal influence of 731 immune cells on 4 different glaucoma subtypes using a two-sample mendelian randomization method

In the pathological progression of glaucoma, damage to the ocular nerves and associated tissue alterations can induce a systemic immune response, leading to the activation of various immune cells such as T cells, B cells, and macrophages. This complex process has the potential to intensify the clinical manifestations of glaucoma. Utilising Mendelian randomisation methods to identify the types and quantities of activated immune cells in different glaucoma-related lesions could provide robust evidence for the development of novel immunomodulators and immunosuppressants tailored to specific types of glaucoma, thereby facilitating personalised treatment strategies. We used five Mendelian randomisation (MR) methods-inverse variance weighted (IVW), MR-Egger, simple model, weighted median, and weighted mediation model - to assess causal relationships between immune cells and four glaucoma subtypes: neovascular glaucoma (NVG), primary open-angle glaucoma (POAG), primary closed-angle glaucoma (PACG), and normal-tension glaucoma (NTG). IVW aggregated causal estimates using Wald ratios and variance-weighted meta-analysis. MR-Egger considered horizontal pleiotropy under the InSIDE assumption. The weighted median model required ≥ 50% valid instrumental variables (IVs) for robust inference, while the weighted mediation model adjusted for SNP correlations. The simple model provided additional insight into causality. Glaucoma GWAS data were obtained from FinnGen ( https://finngen.gitbook.io/documentation/ ). Summary statistics for immune cell phenotypes (GWAS IDs: GCST90001391-GCST90002121) were obtained from the GWAS catalogue ( https://www.ebi.ac.uk/gwas/studies/GCST90002121 ). The study has identified a causal relationship between various immune cells and different types of glaucoma. It was found that 21 different types of immune cells had a causal relationship with NVG, 37 types of immune cells had a causal relationship with POAG, 40 different types of immune cells had a causal relationship with PACG, and 24 different types of immune cells had a causal relationship with NTG.

LCN2 deficiency mitigates the neuroinflammatory damage following acute glaucoma

Rationale: Acute high intraocular pressure (IOP) induces retinal ischemia/reperfusion (RI/R) that further initiates neuroinflammatory responses. This event can cause retinal tissue damage and neuronal death, ultimately resulting in irreversible blindness worldwide that lacks effective therapies, validated treatment targets and underlying mechanisms. We sought to explore the potential mechanisms on the causal link between the neuroinflammatory response and neurodegeneration following acute high IOP. Methods: A rat model of RI/R induced by acute high IOP was used to investigate the spatiotemporal profiles of blood-retinal barrier (BRB) disruption, peripheral immune cell infiltration, and innate immune cell response following acute glaucomatous injury. RNA sequencing and in vivo transfection with adeno-associated virus (AAV) were used to explore the pathogenic mechanisms of acute high IOP-induced neuroinflammation. Results: Disruption of the inner BRB and infiltration of macrophages and lymphocytes occurred during the early stage after acute high IOP. These events were accompanied by an innate immune response. RNA sequencing revealed that Lipocalin-2 (Lcn2) was one of the most significantly up-regulated inflammation-related genes. Lcn2 knockdown ameliorated inner BRB disruption, peripheral immune cell infiltration, and innate immune cell response, resulting in neuroprotective effects. Furthermore, we found that acute glaucomatous injury triggers high expression of LCN2 in the peripheral serum, which is strongly associated with the severity of the neuroinflammatory response in the retina. Conclusions: A "neuroinflammatory cascade" characterized by breakdown of inner BRB, peripheral immune cell infiltration, and innate immune cell response occurs during the initial stage following glaucomatous injury. We also identified a novel mechanism for LCN2 in acute high IOP-induced neuroinflammation. LCN2 has the potential to serve as a candidate biomarker for predicting the severity of the neuroinflammatory response following acute glaucoma, which may provide new evidence to retinal repair strategies for better visual function recovery at intervention time points and new targets.

Ocular neuroinflammatory response secondary to SARS-CoV-2 infection-a review

With the consistent occurrence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the prevalence of various ocular complications has increased over time. SARS-CoV-2 infection has been shown to have neurotropism and therefore to lead to not only peripheral inflammatory responses but also neuroinflammation. Because the receptor for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2), can be found in many intraocular tissues, coronavirus disease 2019 (COVID-19) may also contribute to persistent intraocular neuroinflammation, microcirculation dysfunction and ocular symptoms. Increased awareness of neuroinflammation and future research on interventional strategies for SARS-CoV-2 infection are important for improving long-term outcomes, reducing disease burden, and improving quality of life. Therefore, the aim of this review is to focus on SARS-CoV-2 infection and intraocular neuroinflammation and to discuss current evidence and future perspectives, especially possible connections between conditions and potential treatment strategies.

The Role of Gut Microbiota in the Pathogenesis of Glaucoma: Evidence from Bibliometric Analysis and Comprehensive Review

The relationship between gut microbiota and glaucoma has garnered significant interest, with emerging evidence suggesting that gut dysbiosis, inflammation, and immune mechanisms may contribute to glaucoma pathogenesis. Understanding these interactions through the gut-retina axis offers new insights into disease progression and potential therapeutic options. This study combines bibliometric analysis and literature review to evaluate research trends and key research areas related to gut microbiota's role in glaucoma. Our data were collected from the Web of Science Core Collection (WoSCC) and included the English original articles and reviews published between 1 January 2008, and 6 August 2024. Visual and statistical analyses were conducted using VOSviewer and CiteSpace. The analyses comprised 810 citations from leading journals, representing contributions from 23 countries/regions, 111 institutions, 40 journals, and 321 authors. Among the countries and regions involved, the USA and China were the leading contributors, publishing the most articles and being major research hubs. The Experimental Eye Research and Investigative Ophthalmology & Visual Science were the top journals in citation and co-citations that produced high-quality publications. The top 10 highly cited articles were published in high-ranking, top-quartile journals. The frequently occurring keywords were "glaucoma", "microbiota", "gut microbiota", "inflammation", "gut-retina axis", and "probiotics". Our study highlights the growing interest in the association between gut microbiota and glaucoma. It summarizes the possible ways gut microbiota dysbiosis, systemic and neuroinflammation, and autoimmune mechanisms contribute to glaucomatous pathogenesis. Future research should focus on mechanistic studies to elucidate the pathways linking gut microbiota to glaucoma development and progression.

The gut-retina axis: Uncovering the role of autoimmunity in glaucoma development

Glaucoma, a leading cause of irreversible blindness worldwide, is characterized by progressive loss of retinal ganglion cells (RGCs) and optic nerve damage. While elevated intraocular pressure (IOP) is the only known modifiable risk factor, normal-tension glaucoma (NTG) challenges this notion, suggesting other mechanisms beyond IOP may contribute to its development. Emerging evidence support the hypothesis that glaucoma may be an autoimmune disease. This review summarizes evidence for this hypothesis, focusing on the gut-retina axis. We discuss how antigens of gut bacterial prime peripheral T cells to breach the blood-retina barrier (BRB) and initiate cross-reactivity with ocular tissues via molecular mimicry, resulting in autoimmune RGC damage. Understanding these mechanisms may uncover new diagnostic biomarkers and therapeutic strategies targeting immune pathways alongside conventional IOP-lowering treatments.

α-1 antitrypsin is promising for the identification of glaucoma severity and is associated with glaucomatous neural damage

Aim: To investigate the association between plasma AAT level and glaucoma.Methods: 163 glaucoma patients and 111 healthy controls were recruited. The plasma AAT levels were measured by ELISA.Results: Plasma AAT level was significantly higher in glaucoma patients than those in healthy controls (p < 0.001). Patients with higher plasma AAT level exhibited severer disease stage (early vs. severe: p < 0.05; H-P-A; early vs. severe: p < 0.05; early vs. end-stage: p < 0.01; AGIS). ROC curves yielded that AAT can distinguish patients with early glaucoma from those with advanced glaucoma (early vs. severe: AUC: 0.616; H-P-A; early vs. severe: AUC: 0.763; early vs. end-stage: AUC: 0.660; AGIS).Conclusion: Plasma AAT is a useful biomarker for the identification of glaucoma severity.

CRISPR-CasRx-mediated disruption of Aqp1/Adrb2/Rock1/Rock2 genes reduces intraocular pressure and retinal ganglion cell damage in mice

Glaucoma affects approximately 80 million individuals worldwide, a condition for which current treatment options are inadequate. The primary risk factor for glaucoma is elevated intraocular pressure. Intraocular pressure is determined by the balance between the secretion and outflow of aqueous humor. Here we show that using the RNA interference tool CasRx based on shH10 adenovirus-associated virus can reduce the expression of the aqueous humor circulation related genes Rock1 and Rock2, as well as aquaporin 1 and β2 adrenergic receptor in female mice. This significantly reduced intraocular pressure in female mice and provided protection to the retina ganglion cells, ultimately delaying disease progression. In addition, we elucidated the mechanisms by which the knockdown of Rock1 and Rock2, or aquaporin 1 and β2 adrenergic receptor in female mice, reduces the intraocular pressure and secures the retina ganglion cells by single-cell sequencing.

Role of T cell-induced autoimmune response in the pathogenesis of glaucoma

PURPOSE

This review aims to elucidate the role of T cell-induced autoimmune responses in the pathogenesis of glaucoma, focusing on the immunological changes contributing to retinal ganglion cell (RGC) damage.

METHODS

A comprehensive review of recent studies examining immunological mechanisms in glaucoma was conducted. This included analyses of T cell interactions, heat shock proteins (HSPs), and resultant autoimmune responses. Key findings from experimental models and clinical observations were synthesized to present a coherent understanding of immune dynamics in glaucoma.

RESULTS

Glaucoma is a neurodegenerative disease marked by optic nerve atrophy and irreversible vision loss due to RGC damage. The disease is etiologically heterogeneous, with multiple risk factors and pathogenic mechanisms. Recent research highlights the dual immunomodulatory role of T cells in immune protection and injury. T cells, pre-sensitized by bacterial HSPs, can cross-react with endogenous HSPs in RGCs under stress, leading to autoimmune damage. Elevated levels of HSP autoantibodies and abnormal T cell activity have been observed in glaucoma patients, indicating a significant autoimmune component in disease progression.

CONCLUSIONS

T cell-induced autoimmune responses are crucial in the pathogenesis of glaucoma, contributing to RGC degeneration beyond the effects of elevated intraocular pressure. Understanding these immunological mechanisms is vital for developing targeted neuroprotective therapies for glaucoma.

Regulated Necrosis in Glaucoma: Focus on Ferroptosis and Pyroptosis

Glaucoma is one of the most common causes of irreversible blindness worldwide. This neurodegenerative disease is characterized by progressive and irreversible damage to retinal ganglion cells (RGCs) and optic nerves, which can lead to permanent loss of peripheral and central vision. To date, maintaining long-term survival of RGCs using traditional treatments, such as medication and surgery, remains challenging, as these do not promote optic nerve regeneration. Therefore, it is of great clinical and social significance to investigate the mechanisms of optic nerve degeneration in depth and find reliable targets to provide pioneering methods for the prevention and treatment of glaucoma. Regulated necrosis is a form of genetically programmed cell death associated with the maintenance of homeostasis and disease progression in vivo. An increasing body of innovative evidence has recognized that aberrant activation of regulated necrosis pathways is a common feature in neurodegenerative diseases, such as Alzheimer's, Parkinson's, and glaucoma, resulting in unwanted loss of neuronal cells and function. Among them, ferroptosis and pyroptosis are newly discovered forms of regulated cell death actively involved in the pathophysiological processes of RGCs loss and optic nerve injury. This was shown by a series of in vivo and in vitro studies, and these mechanisms have been emerging as a key new area of scientific research in ophthalmic diseases. In this review, we focus on the molecular mechanisms of ferroptosis and pyroptosis and their regulatory roles in the pathogenesis of glaucoma, with the aim of exploring their implications as potential therapeutic targets and providing new perspectives for better clinical decision-making in glaucoma treatment.

Th1 cells contribute to retinal ganglion cell loss in glaucoma in a VCAM-1-dependent manner

Glaucoma is a complex neurodegenerative disorder characterized by the progressive loss of retinal ganglion cells (RGC) and optic nerve axons, leading to irreversible visual impairment. Despite its clinical significance, the underlying mechanisms of glaucoma pathogenesis remain poorly understood. In this study, we aimed to unravel the multifaceted nature of glaucoma by investigating the interaction between T cells and retinas. By utilizing clinical samples, murine glaucoma models, and T cell transfer models, we made several key findings. Firstly, we observed that CD4+ T cells from glaucoma patients displayed enhanced activation and a bias towards T helper (Th) 1 responses, which correlated with visual impairment. Secondly, we identified the infiltration of Th1 cells into the retina, where they targeted RGC and integrated into the pro-inflammatory glial network, contributing to progressive RGC loss. Thirdly, we discovered that circulating Th1 cells upregulated vascular cell adhesion protein 1 (VCAM-1) on retinal microvessels, facilitating their entry into the neural retina. Lastly, we found that Th1 cells underwent functional reprogramming before reaching the retina, acquiring a phenotype associated with lymphocyte migration and neurodegenerative diseases. Our study provides novel insights into the role of peripheral CD4+ T cells in glaucoma pathogenesis, shedding light on the mechanisms underlying their infiltration into the retina and offering potential avenues for innovative therapeutic interventions in this sight-threatening disease.

Role of Inflammation in Canine Primary Glaucoma

Primary glaucoma is a painful, progressive, and blinding disease reported in many canine breeds, characterized by intraocular pressure (IOP) elevation in the absence of antecedent intraocular disease. Clinical observations of dogs with primary glaucoma suggest that many affected eyes develop concurrent intraocular inflammation in addition to elevated IOP. In this work, we summarize the current knowledge that relates inflammation to primary glaucoma in dogs, reviewing studies focused on genetics, physiology, histopathology, bioanalysis of ocular fluids, therapeutics, and clinical outcomes of glaucomatous patients. Through disruption of the blood-aqueous and blood-retinal barriers, pigment dispersion, and biochemical changes to the aqueous humor and tear film, the pathogenesis of canine primary glaucoma appears to involve inflammatory changes to various extents and with various consequences from the front to the back of the eye. Among others, inflammation further impacts IOP by reducing aqueous humor outflow at the level of the iridocorneal angle and accelerates vision loss by promoting neuronal degeneration. As such, the vicious cycle of ocular inflammation and IOP elevation might warrant the use of anti-inflammatory medications as a core component of the treatment regime for dogs with primary glaucoma, either therapeutically (i.e., actively glaucomatous eye) or prophylactically in the yet unaffected contralateral eye.

Tea polyphenols protect bovine intestinal epithelial cells from the adverse effects of heat-stress in vitro

Heat-stress (HS) leads to impaired gut health, adversely affecting milk production of dairy cows. In the present study, we investigated the protective effects of tea polyphenols (TP) against HS-induced damage in bovine intestinal epithelial cells (BIECs) and explored the underlying mechanisms. Primary BIECs were isolated from bovine duodenum, cultured and treated as follows: (1) control cells incubated in complete medium at 37 °C for 12 h, (2) TP group incubated in medium containing 100 μg/mL TP at 37 °C for 12 h, (3) HS group incubated in medium at 37 °C for 6 h followed by 6 h at 42 °C, and (4) HS + TP group incubated with 100 μg/mL TP for 6 h at 37 °C and 6 h at 42 °C. TP improved cell viability and antioxidant capacity, and decreased apoptosis and LDH activity. TP led to upregulation of Nrf2 and its target antioxidant genes HO-1, NQO1 and SOD1 expression. TP significantly decreased the expression of proinflammatory cytokine genes (NF-κB, IL-6 and TNF-α), and increased expression of the anti-inflammatory cytokine gene, IL-10. The above results suggested that TP protected BIECs from HS-induced adverse effects by alleviating oxidative stress and inflammatory responses, indicating that TP can alleviate HS-induced intestinal damage in dairy cows.

Cerebrospinal Fluid Pressure Reduction Induces Glia-Mediated Retinal Inflammation and Leads to Retinal Ganglion Cell Injury in Rats

Low intracranial pressure (LICP)-induced translaminar cribrosa pressure difference (TLCPD) elevation has been proven as a risk factor in glaucomatous neurodegeneration, whereas the underlying retinal immune features of LICP-induced retinal ganglion cells (RGC) injury remain elusive. Here, we identified the retinal immune characteristics of LICP rats, and minocycline (Mino) treatment was utilized to analyze its inhibitory role in glia-mediated retinal inflammation of LICP rats. The results showed that retrograde axonal transport was decreased in LICP rats without significant RGC loss, indicating the RGC injury was at an early stage before the morphological loss. The activation of retinal microglia and astrocytes with morphologic and M1 or A1-marker alternations was detected in TLCPD elevation rats, the activation level is more dramatic in HIOP rats than in the LICP rats (P<0.05). Besides, we detected reduced retinal tight junction protein expressions, accompanied by specific imbalance patterns of T lymphocytes in the retina of both LICP and HIOP rats (P<0.05). Further Mino treatment showed an effective inhibitory role in glia-driven inflammatory responses in LICP rats, including improving retrograde axonal transport, inhibiting retinal glial activation and proinflammatory subtype polarization, and alleviating the blood-retina barrier compromise. This study identified the glia-mediated retinal inflammation features triggered by LICP stimulus, and Mino application exhibited an effective role in the inhibition of retinal glia-mediated inflammation in LICP-induced TLCPD elevation rats.

Assessing the role of T cells in response to retinal injury to uncover new therapeutic targets for the treatment of retinal degeneration

BACKGROUND

Retinal degeneration is a disease affecting the eye, which is an immune-privileged site because of its anatomical and physiological properties. Alterations in retinal homeostasis-because of injury, disease, or aging-initiate inflammatory cascades, where peripheral leukocytes (PL) infiltrate the parenchyma, leading to retinal degeneration. So far, research on PL's role in retinal degeneration was limited to observing a few cell types at specific times or sectioning the tissue. This restricted our understanding of immune cell interactions and response duration.

METHODS

In vivo microscopy in preclinical mouse models can overcome these limitations enabling the spatio-temporal characterization of PL dynamics. Through in vivo imaging, we assessed structural and fluorescence changes in response to a focal injury at a defined location over time. We also utilized minimally invasive techniques, pharmacological interventions, and knockout (KO) mice to determine the role of PL in local inflammation. Furthermore, we investigated PL abundance and localization during retinal degeneration in human eyes by histological analysis to assess to which extent our preclinical study translates to human retinal degeneration.

RESULTS

We demonstrate that PL, especially T cells, play a detrimental role during retinal injury response. In mice, we observed the recruitment of helper and cytotoxic T cells in the parenchyma post-injury, and T cells also resided in the macula and peripheral retina in pathological conditions in humans. Additionally, we found that the pharmacological PL reduction and genetic depletion of T-cells reduced injured areas in murine retinas and rescued the blood-retina barrier (BRB) integrity. Both conditions promoted morphological changes of Cx3cr1+ cells, including microglial cells, toward an amoeboid phenotype during injury response. Interestingly, selective depletion of CD8+ T cells accelerated recovery of the BRB compared to broader depletions. After anti-CD8 treatment, the retinal function improved, concomitant to a beneficial immune response.

CONCLUSIONS

Our data provide novel insights into the adaptive immune response to retinal injury in mice and human retinal degeneration. Such information is fundamental to understanding retinal disorders and developing therapeutics to modulate immune responses to retinal degeneration safely.

Emerging roles of air pollution and meteorological factors in autoimmune eye diseases

Autoimmune eye diseases (AEDs), a collection of autoimmune inflammatory ocular conditions resulting from the dysregulation of immune system at the ocular level, can target both intraocular and periorbital structures leading to severe visual deficit and blindness globally. The roles of air pollution and meteorological factors in the initiation and progression of AEDs have been increasingly attractive, among which the systemic and local mechanisms are both involved in. Exposure to excessive air pollution and extreme meteorological conditions including PM2.5/PM0.1, environmental tobacco smoke, insufficient sunshine, and high temperature, etc., can disturb Th17/Treg balance, regulate macrophage polarization, activate neutrophils, induce systemic inflammation and oxidative stress, decrease retinal blood flow, promote tissue fibrosis, activate sympathetic nervous system, adversely affect nutrients synthetization, as well as induce heat stress, therefore may together deteriorate AEDs. The crosstalk among inflammation, oxidative stress and dysregulated immune system appeared to be prominent. In the present review, we will concern and summarize the potential mechanisms underlying linkages of air pollution and meteorological factors to ocular autoimmune and inflammatory responses. Moreover, we concentrate on the specific roles of air pollutants and meteorological factors in several major AEDs including uveitis, Graves' ophthalmopathy (GO), ocular allergic disease (OAD), glaucoma, diabetic retinopathy (DR), etc.

Gut-licensed β7+ CD4+ T cells contribute to progressive retinal ganglion cell damage in glaucoma

Glaucoma is the leading cause of irreversible blindness. Currently, most therapeutic strategies aim to reduce elevated intraocular pressure (EIOP), but this does not always halt disease progression. Evidence suggests a role for T cells in glaucoma pathogenesis, but the underlying mechanisms remain largely unknown. Here, we found that the percentage of circulating CD4+ T cells expressing a gut-homing integrin β7 was increased in patients with glaucoma and was associated with disease stage. In an EIOP-triggered glaucoma mouse model, β7+ CD4+ T cells infiltrated the retina in the progressive phase of glaucoma via eliciting retinal endothelial cell expression of mucosal vascular addressin cell adhesion molecule 1 (MAdCAM-1). MAdCAM-1 was minimally detected in retinas of healthy mice, and neutralization with an MAdCAM-1 antibody ameliorated retinal ganglion cell (RGC) loss and glial activity in mice with glaucoma. We furthermore found that EIOP-induced β7+ CD4+ T cells homed to the gut during the acute phase of glaucoma, which was essential for progressive RGC damage in diseased mice. Gut-homing β7+ CD4+ T cells underwent transcriptional reprogramming, showing up-regulated pathways enriched in autoimmune diseases, bacteria responses, mucosal immunity, and glial activity. Gut-homing β7+ CD4+ T cells gained the competence to induce retinal MAdCAM-1 expression and to cross the blood-retina barrier. Together, our study reveals a role of gut-licensed β7+ CD4+ T cells and MAdCAM-1 in RGC degeneration and emphasizes the importance of the "gut-retina" axis in glaucoma.

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

Exosomes are membrane-bound tiny particles that are released by all live cells that contain multiple signal molecules and extensively participate in numerous normal physical activities and pathologies. In glaucoma, the crucial role of exosome-based crosstalk has been primarily revealed in animal models and ex vivo cell studies in the recent decade. In the aqueous drainage system, exosomes derived from non-pigment ciliary epithelium act in an endocrine manner and specifically regulate the function of the trabecular meshwork to cope with persistent oxidative stress challenges. In the retina, a more complicated regulatory network among microglia, retinal neurons, retinal ganglial cells, retinal pigment epithelium, and other immune effector cells by exosomes are responsible for the elaborate modulation of tissue homeostasis under physical state and the widespread propagation of neuroinflammation and its consequent neurodegeneration in glaucoma pathogenesis. Accumulating evidence indicates that exosome-based crosstalk depends on numerous factors, including the specific cargos they carried (particularly micro RNA), concentration, size, and ionization potentials, which largely remain elusive. In this narrative review, we summarize the latest research focus of exosome-based crosstalk in glaucoma pathogenesis, the current research progress of exosome-based therapy for glaucoma and provide in-depth perspectives on its current research gap.

Oxidative Stress and Antioxidants in Age-Related Macular Degeneration

Oxidative stress plays a crucial role in aging-related eye diseases, including age-related macular degeneration (AMD), cataracts, and glaucoma. With age, antioxidant reparative capacity decreases, and excess levels of reactive oxygen species produce oxidative damage in many ocular cell types underling age-related pathologies. In AMD, loss of central vision in the elderly is caused primarily by retinal pigment epithelium (RPE) dysfunction and degeneration and/or choroidal neovascularization that trigger malfunction and loss of photo-sensing photoreceptor cells. Along with various genetic and environmental factors that contribute to AMD, aging and age-related oxidative damage have critical involvement in AMD pathogenesis. To this end, dietary intake of antioxidants is a proven way to scavenge free radicals and to prevent or slow AMD progression. This review focuses on AMD and highlights the pathogenic role of oxidative stress in AMD from both clinical and experimental studies. The beneficial roles of antioxidants and dietary micronutrients in AMD are also summarized.

Protective effects of blocking PD-1 pathway on retinal ganglion cells in a mouse model of chronic ocular hypertension

Purpose

In this study, we aimed to investigate whether Programmed cell death 1 ligand 1/programmed cell death 1 ligand 2 (PD-L1/PD-L2) double knockout (dKO) has a protective effect on RGCs in a mouse model of chronic ocular hypertension (COHT).

Methods

We used superparamagnetic iron oxide to induce COHT in mice. Apoptosis of retinal ganglion cells (RGCs) and activation of microglia were evaluated using western blotting (WB) and immunofluorescence staining of the mouse retina. In addition, we also conducted transcriptome sequencing and further gene expression analyses using the gene ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) database.

Results

In the mouse model of COHT, PD-L1/PD-L2 prevented the apoptosis of RGCs to some extent. Blocking the programmed cell death 1 (PD-1) pathway also increased the number of anti-inflammatory M2-activated microglia and enhanced the phosphorylation of its related pathway signal transducer and activator of transcription (STAT)6. Sequencing results showed that this protective effect may have been achieved by regulating the NF-B, tumour necrosis factor (TNF), PI3K/Akt and toll-like receptor signaling pathway etc.

Conclusion

Blocking the PD-1 pathway has a protective effect on RGCs in the mouse model of COHT induced by superparamagnetic iron oxide.

A New Concept of Associations between Gut Microbiota, Immunity and Central Nervous System for the Innovative Treatment of Neurodegenerative Disorders

Nerve cell death accounts for various neurodegenerative disorders, in which altered immunity to the integrated central nervous system (CNS) might have destructive consequences. This undesirable immune response often affects the progressive neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, schizophrenia and/or amyotrophic lateral sclerosis (ALS). It has been shown that commensal gut microbiota could influence the brain and/or several machineries of immune function. In other words, neurodegenerative disorders may be connected to the gut-brain-immune correlational system. The engrams in the brain could retain the information of a certain inflammation in the body which might be involved in the pathogenesis of neurodegenerative disorders. Tactics involving the use of probiotics and/or fecal microbiota transplantation (FMT) are now evolving as the most promising and/or valuable for the modification of the gut-brain-immune axis. More deliberation of this concept and the roles of gut microbiota would lead to the development of stupendous treatments for the prevention of, and/or therapeutics for, various intractable diseases including several neurodegenerative disorders.

A Review on the Application of Stem Cell Secretome in the Protection and Regeneration of Retinal Ganglion Cells; a Clinical Prospect in the Treatment of Optic Neuropathies

PURPOSE

Retinal ganglion cells (RGCs) are one the most specialized neural tissues in the body. They transmit (and further process) chemoelectrical information originating in outer retinal layers to the central nervous system. In fact, the optic nerve is composed of RGC axons. Like other neural cells, RGCs will not completely heal after the injury, leading to irreversible vision loss from disorders such as glaucoma that primarily affect these cells. Several methods have been developed to protect or regenerate RGCs during or after the insult has occurred. This study aims to review the most recent clinical, animal and laboratory experiments designed for the regeneration of RGC that apply the stem cell-derived secretome.

METHODS

We extracted the studies from Web of Science (ISI), Medline (PubMed), Scopus, Embase, and Google scholar from the first record to the last report registered in 2022, using the following keywords; "secretome" OR "conditioned medium" OR "exosome" OR "extracellular vesicle" AND "stem cell" AND "RGC" OR "optic neuropathy". Any registered clinical trials related to the subject were also extracted from clinicaltrial.gov. All published original studies that express the effect of stem cell secretome on RGC cells in optic neuropathy, whether in vitro, in animal studies, or in clinical trials were included in this survey.

RESULTS

In this review, we provided an update on the existing reports, and a brief description of the details applied in the procedure. Compared to cell transplant, applying stem cell-derived secretome has the advantage of minimized immunogenicity yet preserving efficacy via its rich content of growth factors.

CONCLUSIONS

Different sources of stem cell secretomes have distinct implications in the management of RGC injury, which is the main subject of the present article.