Cytokine and Complement Response in the Glaucomatous βB1-CTGF Mouse Model

Complement Component C5a and Fungal Pathogen Induce Diverse Responses through Crosstalk between Transient Receptor Potential Channel (TRPs) Subtypes in Human Conjunctival Epithelial Cells

The conjunctiva has immune-responsive properties to protect the eye from infections. Its innate immune system reacts against external pathogens, such as fungi. The complement factor C5a is an important contributor to the initial immune response. It is known that activation of transient-receptor-potential-vanilloid 1 (TRPV1) and TRP-melastatin 8 (TRPM8) channels is involved in different immune reactions and inflammation in the human body. The aim of this study was to determine if C5a and mucor racemosus e voluminae cellulae (MR) modulate Ca2+-signaling through changes in TRPs activity in human conjunctival epithelial cells (HCjECs). Furthermore, crosstalk was examined between C5a and MR in mediating calcium regulation. Intracellular Ca2+-concentration ([Ca2+]i) was measured by fluorescence calcium imaging, and whole-cell currents were recorded using the planar-patch-clamp technique. MR was used as a purified extract. Application of C5a (0.05-50 ng/mL) increased both [Ca2+]i and whole-cell currents, which were suppressed by either the TRPV1-blocker AMG 9810 or the TRPM8-blocker AMTB (both 20 µM). The N-terminal peptide C5L2p (20-50 ng/mL) blocked rises in [Ca2+]i induced by C5a. Moreover, the MR-induced rise in Ca2+-influx was suppressed by AMG 9810 and AMTB, as well as 0.05 ng/mL C5a. In conclusion, crosstalk between C5a and MR controls human conjunctival cell function through modulating interactions between TRPV1 and TRPM8 channel activity.

Retinal debris triggers cytotoxic damage in cocultivated primary porcine RPE cells

Introduction

One of the most common causes of vision loss in the elderly population worldwide is age-related macular degeneration (AMD). Subsequently, the number of people affected by AMD is estimated to reach approximately 288 million by the year 2040. The aim of this study was to develop an ex vivo model that simulates various aspects of the complex AMD pathogenesis.

Methods

For this purpose, primary porcine retinal pigment epithelial cells (ppRPE) were isolated and cultured. One group was exposed to medium containing sodium iodate (NaIO3) to induce degeneration. The others were exposed to different supplemented media, such as bovine serum albumin (BSA), homogenized porcine retinas (HPR), or rod outer segments (ROOS) for eight days to promote retinal deposits. Then, these ppRPE cells were cocultured with porcine neuroretina explants for another eight days. To assess the viability of ppRPE cells, live/dead assay was performed at the end of the study. The positive RPE65 and ZO1 area was evaluated by immunocytochemistry and the expression of RLBP1, RPE65, and TJP1 was analyzed by RT-qPCR. Additionally, drusen (APOE), inflammation (ITGAM, IL6, IL8, NLRP3, TNF), oxidative stress (NFE2L2, SOD1, SOD2), and hypoxia (HIF1A) markers were investigated. The concentration of the inflammatory cytokines IL-6 and IL-8 was determined in medium supernatants from day 16 and 24 via ELISA.

Results

Live/dead assay suggests that especially exposure to NaIO3 and HPR induced damage to ppRPE cells, leading in a significant ppRPE cell loss. All supplemented media resulted in decreased RPE-characteristic markers (RPE65; ZO-1) and gene expression like RLBP1 and RPE65 in the cultured ppRPE cells. Besides, some inflammatory, oxidative as well as hypoxic stress markers were altered in ppRPE cells cultivated with NaIO3. The application of HPR induced an enhanced APOE expression. Pre-exposure of the ppRPE cells led to a diminished number of cones in all supplemented media groups compared to controls.

Discussion

Overall, this novel coculture model represents an interesting initial approach to incorporating deposits into coculture to mimic AMD pathogenesis. Nevertheless, the effects of the media used need to be investigated in further studies.

Proteomics Analyses of Small Extracellular Vesicles of Aqueous Humor: Identification and Validation of GAS6 and SPP1 as Glaucoma Markers

Cataracts and glaucoma account for a high percentage of vision loss and blindness worldwide. Small extracellular vesicles (sEVs) are released into different body fluids, including the eye's aqueous humor. Information about their proteome content and characterization in ocular pathologies is not yet well established. In this study, aqueous humor sEVs from healthy individuals, cataracts, and glaucoma patients were studied, and their specific protein profiles were characterized. Moreover, the potential of identified proteins as diagnostic glaucoma biomarkers was evaluated. The protein content of sEVs from patients' aqueous humor with cataracts and glaucoma compared to healthy individuals was analyzed by quantitative proteomics. Validation was performed by western blot (WB) and ELISA. A total of 828 peptides and 192 proteins were identified and quantified. After data analysis with the R program, 8 significantly dysregulated proteins from aqueous humor sEVs in cataracts and 16 in glaucoma showed an expression ratio ≥ 1.5. By WB and ELISA using directly aqueous humor samples, the dysregulation of 9 proteins was mostly confirmed. Importantly, GAS6 and SPP1 showed high diagnostic ability of glaucoma, which in combination allowed for discriminating glaucoma patients from control individuals with an area under the curve of 76.1% and a sensitivity of 65.6% and a specificity of 87.7%.

In a novel autoimmune and high-pressure glaucoma model a complex immune response is induced

Background

The neurodegenerative processes leading to glaucoma are complex. In addition to elevated intraocular pressure (IOP), an involvement of immunological mechanisms is most likely. In the new multifactorial glaucoma model, a combination of high IOP and optic nerve antigen (ONA) immunization leads to an enhanced loss of retinal ganglion cells accompanied by a higher number of microglia/macrophages in the inner retina. Here, we aimed to evaluate the immune response in this new model, especially the complement activation and the number of T-cells, for the first time. Further, the microglia/macrophage response was examined in more detail.

Methods

Six-week-old wildtype (WT+ONA) and βB1-connective tissue growth factor high-pressure mice (CTGF+ONA) were immunized with 1 mg ONA. A wildtype control (WT) and a CTGF group (CTGF) received NaCl instead. Six weeks after immunization, retinae from all four groups were processed for immunohistology, RT-qPCR, and flow cytometry, while serum was used for microarray analyses.

Results

We noticed elevated numbers of C1q+ cells (classical complement pathway) in CTGF and CTGF+ONA retinae as well as an upregulation of C1qa, C1qb, and C1qc mRNA levels in these groups. While the complement C3 was only increased in CTGF and CTGF+ONA retinae, enhanced numbers of the terminal membrane attack complex were noted in all three glaucoma groups. Flow cytometry and RT-qPCR analyses revealed an enhancement of different microglia/macrophages markers, including CD11b, especially in CTGF and CTGF+ONA retinae. Interestingly, increased retinal mRNA as well as serum levels of the tumor necrosis factor α were found throughout the different glaucoma groups. Lastly, more T-cells could be observed in the ganglion cell layer of the new CTGF+ONA model.

Conclusion

These results emphasize an involvement of the complement system, microglia/macrophages, and T-cells in glaucomatous disease. Moreover, in the new multifactorial glaucoma model, increased IOP in combination with autoimmune processes seem to enforce an additional T-cell response, leading to a more persistent pathology. Hence, this new model mimics the pathomechanisms occurring in human glaucoma more accurately and could therefore be a helpful tool to find new therapeutic approaches for patients in the future.

The Role of Complement Dysregulation in Glaucoma

Glaucoma is a progressive neurodegenerative disease characterized by damage to the optic nerve that results in irreversible vision loss. While the exact pathology of glaucoma is not well understood, emerging evidence suggests that dysregulation of the complement system, a key component of innate immunity, plays a crucial role. In glaucoma, dysregulation of the complement cascade and impaired regulation of complement factors contribute to chronic inflammation and neurodegeneration. Complement components such as C1Q, C3, and the membrane attack complex have been implicated in glaucomatous neuroinflammation and retinal ganglion cell death. This review will provide a summary of human and experimental studies that document the dysregulation of the complement system observed in glaucoma patients and animal models of glaucoma driving chronic inflammation and neurodegeneration. Understanding how complement-mediated damage contributes to glaucoma will provide opportunities for new therapies.

Enhanced glaucomatous damage accompanied by glial response in a new multifactorial mouse model

Introduction

Glaucoma is a complex, multifactorial neurodegenerative disease, which can lead to blindness if left untreated. It seems that, among others, immune processes, elevated intraocular pressure (IOP), or a combination of these factors are responsible for glaucomatous damage. Here, we combined two glaucoma models to examine if a combination of risk factors (IOP and immune response) results in a more severe damage of retinal ganglion cells (RGCs) and the optic nerves as well as an additional glia activation.

Methods

Six-week-old wildtype (WT+ONA) and βB1-Connective Tissue Growth Factor (CTGF) mice (CTGF+ONA) were immunized with 1 mg ONA (optic nerve antigen). A WT and a CTGF control group (CTGF) received sodium chloride instead. IOP was measured before and every two weeks after immunization. After six weeks, electroretinogram (ERG) measurements were performed. Then, retinae and optic nerves were processed for (immuno-) histology. Further, mRNA levels of corresponding genes in optic nerve and retina were analyzed via RT-qPCR.

Results

Six weeks after immunization, the IOP in CTGF and CTGF+ONA mice was increased. The optic nerve of CTGF+ONA animals displayed the most severe cell inflammation, demyelination, and macroglia activation. Fewer numbers of oligodendrocytes were only observed in WT+ONA optic nerves, while more apoptotic cells triggered by the extrinsic pathway could be revealed in all three glaucoma groups. The number of microglia/macrophages was not altered within the optic nerves of all groups. The loss of neuronal cells, especially RGCs was most pronounced in CTGF+ONA retinae in the central part and this was accompanied by an enhanced activation of microglia/macrophages. Also, Müller cell activation could be noted in CTGF and CTGF+ONA retinae.

Discussion

In this new model, an additive degeneration could be noted in optic nerves as well as in the number of RGCs. These results suggest a potential additive role of high IOP and immune factors in glaucoma development, which will aid for understanding this multifactorial disease more precisely in the future.

Heat Shock Protein Upregulation Supplemental to Complex mRNA Alterations in Autoimmune Glaucoma

Glaucomatous optic neuropathy is a common cause for blindness. An elevated intraocular pressure is the main risk factor, but also a contribution of the immune system seems likely. In the experimental autoimmune glaucoma model used here, systemic immunization with an optic nerve homogenate antigen (ONA) leads to retinal ganglion cell (RGC) and optic nerve degeneration. We processed retinae for quantitative real-time PCR and immunohistology 28 days after immunization. Furthermore, we performed mRNA profiling in this model for the first time. We detected a significant RGC loss in the ONA retinae. This was accompanied by an upregulation of mRNA expression of genes belonging to the heat shock protein family. Furthermore, mRNA expression levels of the genes of the immune system, such as C1qa, C1qb, Il18, and Nfkb1, were upregulated in ONA animals. After laser microdissection, inner retinal layers were used for mRNA microarrays. Nine of these probes were significantly upregulated in ONA animals (p < 0.05), including Hba-a1 and Cxcl10, while fifteen probes were significantly downregulated in ONA animals (p < 0.05), such as Gdf15 and Wwox. Taken together, these findings provide further insights into the pivotal role of the immune response in glaucomatous optic neuropathy and could help to identify novel diagnostic or therapeutic strategies.