The role of Th17 immunity in chronic ocular surface disorders

A Rabbit Dry Eye Model Induced by Subcutaneous Scopolamine

PURPOSE

To establish and characterize a dry eye model in New Zealand rabbits by subcutaneous injections of scopolamine hydrobromide (SCOP).

METHODS

Twenty New Zealand male rabbits were injected subcutaneously SCOP for 14 consecutive days; subcutaneous saline was used as a negative control. The correlated clinical parameters of ocular surface dryness were detected in vivo using tear secretion and corneal fluorescein staining. The expression of IL-1β and TNF-α on the ocular surface and in lacrimal glands were analyzed by real-time PCR and western blot on the 14th day. The expression of Mucin-5 subtype AC (MUC5AC) was detected by Immunofluorescence staining in conjunctival tissue.

RESULTS

The SCOP-treated rabbits exhibited significantly decreased aqueous tear secretion and increased corneal fluorescein staining scores over time. Both the mRNA expression levels and the protein expression levels of IL-1β and TNF-α were significantly increased after SCOP treatment compared with those after saline treatment. The loss of conjunctival MUC5AC was found in the SCOP-injected rabbits. Some infiltrated inflammatory cells and atrophic acinar cells were observed in the lacrimal gland after SCOP treatment. The disordered structures of the ocular surface and lacrimal glands were also observed.

CONCLUSIONS

This study showed that repeated subcutaneous SCOP injections successfully elicited some of the typical dry eye symptoms commonly seen in humans.

RNF213 promotes Treg cell differentiation by facilitating K63-linked ubiquitination and nuclear translocation of FOXO1

Autoreactive CD4+ T helper cells are critical players that orchestrate the immune response both in multiple sclerosis (MS) and in other neuroinflammatory autoimmune diseases. Ubiquitination is a posttranslational protein modification involved in regulating a variety of cellular processes, including CD4+ T cell differentiation and function. However, only a limited number of E3 ubiquitin ligases have been characterized in terms of their biological functions, particularly in CD4+ T cell differentiation and function. In this study, we found that the RING finger protein 213 (RNF213) specifically promoted regulatory T (Treg) cell differentiation in CD4+ T cells and attenuated autoimmune disease development in an FOXO1-dependent manner. Mechanistically, RNF213 interacts with Forkhead Box Protein O1 (FOXO1) and promotes nuclear translocation of FOXO1 by K63-linked ubiquitination. Notably, RNF213 expression in CD4+ T cells was induced by IFN-β and exerts a crucial role in the therapeutic efficacy of IFN-β for MS. Together, our study findings collectively emphasize the pivotal role of RNF213 in modulating adaptive immune responses. RNF213 holds potential as a promising therapeutic target for addressing disorders associated with Treg cells.

Immunopeptides: immunomodulatory strategies and prospects for ocular immunity applications

Immunopeptides have low toxicity, low immunogenicity and targeting, and broad application prospects in drug delivery and assembly, which are diverse in application strategies and drug combinations. Immunopeptides are particularly important for regulating ocular immune homeostasis, as the eye is an immune-privileged organ. Immunopeptides have advantages in adaptive immunity and innate immunity, treating eye immune-related diseases by regulating T cells, B cells, immune checkpoints, and cytokines. This article summarizes the application strategies of immunopeptides in innate immunity and adaptive immunity, including autoimmunity, infection, vaccine strategies, and tumors. Furthermore, it focuses on the mechanisms of immunopeptides in mediating ocular immunity (autoimmune diseases, inflammatory storms, and tumors). Moreover, it reviews immunopeptides' application strategies and the therapeutic potential of immunopeptides in the eye. We expect the immune peptide to get attention in treating eye diseases and to provide a direction for eye disease immune peptide research.

Mechanic study based on untargeted metabolomics of Pi-pa-run-fei-tang on pepper combined with ammonia induced chronic cough model mice

ETHNOPHARMACOLOGICAL RELEVANCE

Pi-pa-run-fei-tang (PPRFT), a traditional Chinese medicine formula with long-standing history, demonstrated beneficial effect on chronic cough. However, the mechanism underlying efficacy unclear. In current research, we explored the impact and molecular mechanism of chronic cough mouse stimulating with capsaicin combined with ammonia.

AIM OF THE STUDY

To investigate the metabolic modulating effects, and potential mechanisms underlying the therapeutic effect of PPRFT in chronic cough.

MATERIALS AND METHODS

Chronic cough mouse models were created by stimulating mice by capsaicin combined with ammonia. Number of coughs and cough latency within 2 min were recorded. With lung tissue and serum samples collected for histopathology, metabolomics, RT-qPCR, immunohistochemistry, and WB analysis. Lymphocytes were isolated and flow cytometric assays were conducted to evaluate the differentiation between Th17 and Treg cell among CD4+ cells.

RESULTS

Results indicated that PPRFT obviously reduced the number of coughs, prolonged cough latency, reduced inflammatory cell infiltration and lung tissues damage, and decreased the serum level of IL-6, IL-1β, TNF-α, and IL-17 while increasing IL-10 levels. Notably, PPRFT suppressed Th17 cell divergence and promoted Treg cell divergence. Furthermore, serum metabolomic assays showed that 46 metabolites differed significantly between group, with 35 pathways involved. Moreover, mRNA levels of IL-6, NF-κB, IL-17, RORγT, JAK2, STAT3, PI3K and AKT in lung tissues remarkably reduced and mRNA levels of IL-10 and FOXP3 were elevated after PPRFT pretreatment. Additionally, PPRFT treatments decreased the protein levels of IL-6, NF-κB, IL-17, RORγT, p-JAK2, p-STAT3, p-PI3K, and p-AKT and increased the protein levels of IL-10 and FOXP3, but no significantly effects to the levels on JAK2, STAT3, PI3K, and AKT in the lungs.

CONCLUSION

Conclusively, our result suggested the effect with PPRFT on chronic cough may be mediated through IL-6/JAK2/STAT3 and PI3K/AKT/NF-κB pathway, which regulate the differentiation between Th17 and Treg cell. This beneficial effect of PPRFT in capsaicin and ammonia-stimulated chronic cough mice indicates its potential application in treating chronic cough.

Local administration of myeloid-derived suppressor cells prevents progression of immune-mediated dry eye disease

Myeloid derived suppressor cells (MDSCs) are a heterogenous population of immature hematopoietic precursors with known immunoregulatory functions. The immunosuppressive role of MDSCs has been highlighted in several inflammatory ophthalmic disorders; however, their therapeutic application in suppressing the immune-mediated changes in dry eye disease (DED) has not been studied. We observed significant reduction in antigen presenting cell (APC) frequencies and their maturation in the presence of MDSCs. Moreover, co-culturing MDSCs with T helper 17 cells (Th17) resulted in reduced Th17 frequencies and their IL-17 expression. On the contrary, MDSCs maintained regulatory T cell frequencies and enhanced their function in-vitro. Furthermore, we delineated the role of interleukin-10 (IL-10) secreted by MDSCs in their immunoregulatory functions. We confirmed these results by flow cytometry analysis and observed that treatment with MDSCs in DED mice effectively suppressed the maturation of APCs, pathogenic Th17 response, and maintained Treg function and significantly ameliorated the disease. The results in this study highlight the potential therapeutic application of MDSCs in treating refractory DED.

The Various Roles of PEDF in Cancer

Pigment epithelium-derived factor (PEDF) is a natural immunomodulator, anti-inflammatory, anti-angiogenic, anti-tumour growth and anti-metastasis factor, which can enhance tumour response to PEDF but can also conversely have pro-cancerous effects. Inflammation is a major cause of cancer, and it has been proven that PEDF has anti-inflammatory properties. PEDF's functional activity can be investigated through measuring metastatic and metabolic biomarkers that will be discussed in this review.

Comparison of Transcriptomic Analysis of the Conjunctiva in Glaucoma-Treated Eyes with Dry Eyes and Healthy Controls

Ocular surface disease (OSD) associated with topical glaucoma drugs is a common issue impacting treatment adherence. We aimed to identify conjunctival transcriptomic changes in glaucoma and dry eye patients, comparing them to healthy controls. Bulbar conjunctival specimens were collected via impression cytology from 33 patients treated for glaucoma, 9 patients with dry eye, and 14 healthy controls. RNA extraction and bulk RNA sequencing were performed, followed by bioinformatics analysis to detect gene dysregulation. Ingenuity pathways analysis (IPA) identified pathways and biological processes associated with these transcriptomic changes. Sequencing analysis revealed 200 modified genes in glaucoma patients compared to healthy individuals, 233 differentially expressed genes in dry eye patients versus controls, and 650 genes in treated versus dry eye samples. In glaucoma patients, 79% of altered pathways were related to host defense, while dry eye patients showed a 39% involvement of host response, 15% in cellular proliferation and integrity, and 16% of mitochondrial dysfunction. These findings were validated through qRT-PCR. Glaucoma patients showed an intensified conjunctival immune response as a potential cause of OSD, whereas in dry eye patients, in addition to the immune response, other mechanisms such as mitochondrial dysfunction or reduced cellular proliferation were observed.

TRIM11 attenuates Treg cell differentiation by p62-selective autophagic degradation of AIM2

Ubiquitination is an important protein modification that regulates diverse biological processes, including CD4+ T cell differentiation and functions. However, the function of most E3 ubiquitin ligases in CD4+ T cell differentiation and CD4+ T cell-mediated pathological diseases remains unclear. In this study, we find that tripartite motif-containing motif 11 (TRIM11) specifically negatively regulates regulatory T (Treg) cell differentiation in CD4+ T cells and promotes autoimmune disease development in an AIM2-dependent manner. Mechanistically, TRIM11 interacts with absent in melanoma 2 (AIM2) and promotes the selective autophagic degradation of AIM2 by inducing AIM2 ubiquitination and binding to p62 in CD4+ T cells. AIM2 attenuates AKT and FOXO1 phosphorylation, MYC signaling, and glycolysis, thereby promoting the stability of Treg cells during experimental autoimmune encephalomyelitis (EAE). Our findings suggest that TRIM11 serves as a potential target for immunotherapeutic intervention for dysregulated immune responses that lead to autoimmunity and cancers.

Association of Ocular Surface Immune Cells With Dry Eye Signs and Symptoms in the Dry Eye Assessment and Management (DREAM) Study

Purpose

Dry eye disease (DED) is a multifactorial, heterogeneous disease of the ocular surface with one etiology being ocular surface inflammation. Studies using animal models demonstrate the role of ocular surface immune cells in the inflammatory pathway leading to DED, but few have evaluated humans. This study described the white blood cell population from the ocular surface of patients with DED and assessed its association with DED signs and symptoms in participants of the Dry Eye Assessment and Management (DREAM) study.

Methods

Participants were assessed for symptoms using the Ocular Surface Disease Index, signs via corneal staining, conjunctival staining, tear break-up time, and Schirmer test, and Sjögren's syndrome (SS) based on the 2012 American College of Rheumatology classification criteria. Impression cytology of conjunctival cells from each eye was evaluated using flow cytometry: T cells, helper T cells (Th), regulatory T cells (Tregs), cytotoxic T cells, and dendritic cells.

Results

We assessed 1049 eyes from 527 participants. White blood cell subtype percentages varied widely across participants. Significant positive associations were found for Th and conjunctival staining (mean score of 2.8 for 0% Th and 3.1 for >4.0% Th; P = 0.007), and corneal staining (mean score of 3.5 for 0% Th and 4.3 for >4.0% Th; P = 0.01). SS was associated with higher percent of Tregs (median 0.1 vs. 0.0; P = 0.01).

Conclusions

Th were associated with more severe conjunctival and corneal staining, possibly indicating their role in inflammation leading to damage of the ocular surface. There is no consistent conclusion about Tregs in SS, but these results support that Tregs are elevated in SS.

RNF157 attenuates CD4+ T cell-mediated autoimmune response by promoting HDAC1 ubiquitination and degradation

Background: CD4⁺ T cells play an important role in body development and homeostasis. Quantitative and functional changes in CD4⁺ T cells result in abnormal immune responses, which lead to inflammation, cancer, or autoimmune diseases, such as multiple sclerosis (MS). Ubiquitination plays an essential role in the differentiation and functioning of CD4⁺ T cells. However, the function of several E3 ubiquitin ligases in CD4⁺ T cell differentiation and T cell-mediated pathological diseases remains unclear. Methods: RNA sequencing data were analyzed to identify the E3 ubiquitin ligases that participate in the pathogenesis of MS. Furthermore, conditional knockout mice were generated. Specifically, flow cytometry, qPCR, western blot, CO-IP and cell transfer adoptive experiments were performed. Results: In this study, we identified The RING finger 157 (RNF157) as a vital regulator of CD4⁺ T cell differentiation; it promoted Th1 differentiation but attenuated Th17 differentiation and CCR4 and CXCR3 expressions in CD4⁺ T cells, thereby limiting experimental autoimmune encephalomyelitis development. Mechanistically, RNF157 in CD4⁺ T cells targeted HDAC1 for K48-linked ubiquitination and degradation. Notably, RNF157 expression was significantly decreased and showed a significant negative correlation with RORγt expression in patients with MS. Conclusions: Our study highlights the critical role of RNF157 in regulating CD4⁺ T cell functions in autoimmune diseases and suggests RNF157 as a potential target in adaptive immune responses against MS and other autoimmune disorders.

Salidroside alleviates oxidative stress in dry eye disease by activating autophagy through AMPK-Sirt1 pathway

Dry eye disease (DED) is a multifactorial disease, and oxidative stress plays a crucial role in its pathogenesis. Recently, multiple studies have shown that upregulation of autophagy can protect the cornea from oxidative stress damage. The present study investigated the therapeutic effects of salidroside, the main component of Rhodiola crenulata, in both in vivo and in vitro dry eye models. The results showed that topical eye drop treatment with salidroside restored corneal epithelium damage, increased tear secretion, and reduced cornea inflammation in the DED mice. Salidroside activated autophagy through AMP-activated protein kinase (AMPK)-sirtuin-1 (Sirt1) signaling pathway, which promoted the nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2) and increased the expression of downstream antioxidant factors heme oxygenase-1 (HO-1) and NAD(P)H quinone dehydrogenase 1 (NQO1). This process restored antioxidant enzyme activity, reduced reactive oxygen species (ROS) accumulation, and alleviated oxidative stress. The application of autophagy inhibitor chloroquine and AMPK inhibitor Compound C reversed the therapeutic efficacy of salidroside, validating the above findings. In conclusion, our data suggest that salidroside is a promising candidate for DED treatment.

Extending the use of biologics to mucous membranes by attachment of a binding domain

Biologics are almost exclusively administered systemically, but localized delivery is preferable as it minimizes off-target exposure and allows more aggressive treatments. Topical application of biologics to epithelia is generally ineffective because most are covered with fluids and biologics are washed out too quickly to have significant therapeutic effects. Here we explore the idea that attaching a binding domain can serve as an "anchor" to extend the residency time of biologics on wet epithelia, allowing their effective use even with infrequent applications. We use topical application to the ocular surface as a challenging test since foreign substances are washed out especially efficiently by tear flow and blinking. Our results demonstrate that conjugation of antibodies to wheat germ agglutinin, which binds GlcNAc and sialic acid that are ubiquitously present in tissues, increases their half-life 350-fold upon application to the ocular surface in a mouse model of dry eye, a common and onerous disease in humans. Importantly, antibodies to IL-17A, IL-23, and IL-1β conjugated to the agglutinin reduces manifestations of dry eye, even when applied just once daily. In contrast, unconjugated antibodies are ineffective. Attaching an anchor to biologics is a simple means to overcome washout and to extend their therapeutic use.

T-Cell Repertoire Analysis in the Conjunctiva of Murine Dry Eye Model

Purpose

Dry eye is closely related to the activation and proliferation of immune cells, especially T cells. However, the determination of the preferential T-cell clonotypes is technically challenging. This study aimed to investigate the characterization of T-cell receptor (TCR) repertoire in the conjunctiva during dry eye.

Methods

A desiccating stress animal model was established using C57/BL6 mice (8-10 weeks, female). After 7 days of stress stimulation, the slit-lamp image and Oregon-green-dextran staining were used to evaluate the ocular surface injury. Periodic acid-Schiff staining was used to measure the number of goblet cells. Flow cytometry was used to detect the activation and proliferation of T cells in the conjunctiva and cervical lymph nodes. Next-generation sequencing was used to detect the αβ TCR repertoire of the conjunctiva.

Results

The αβ TCR diversity increased significantly in the dry eye group, including the higher CDR3 amino acid length, marked gene usage on TCR V and J gene segments, extensive V(D)J recombination, and distinct CDR3 aa motifs. More important, several T-cell clonotypes were uniquely identified in dry eye. Furthermore, these perturbed rearrangements were reversed after glucocorticoid administration.

Conclusions

A comprehensive analysis of the αβ TCR repertoire in the conjunctiva of the dry eye mouse model was performed. Data in this study contributed significantly to the research on dry eye pathogenesis by demonstrating the TCR gene distribution and disease-specific TCR signatures. This study further provided some potential predictive T-cell biomarkers for future studies.

METTL3 inhibits autoreactive Th17 cell responses in experimental autoimmune uveitis via stabilizing ASH1L mRNA

Methyltransferase like 3 (METTL3), a primary N6-methyladenosine (m6A) methyltransferase, has been implicated in various biological and pathological processes including immune responses. However, the functions and mechanisms of METTL3 in pathogenic T helper (Th)17 cells are poorly understood. Here we found significantly decreased METTL3 expression along with reduced m6A levels in eyeballs and T cells of experimental autoimmune uveitis (EAU). Overexpression of METTL3 ameliorated the development of EAU and suppressed pathogenic Th17 cell responses in vivo and in vitro. Mechanistically, METTL3 promoted the expression of absent, small, or homeotic-like 1 (ASH1L) via enhancing its stability in a YT521-B homology domain containing 2 (YTHDC2)-dependent manner, which further decreased the expression of IL-17 and IL-23 receptor (IL-23R), resulting in reduced pathogenic Th17 responses. Together, our data reveal a pivotal role of METTL3 in regulating pathogenic Th17 responses, which may contribute to human uveitis therapy.

USP1-regulated reciprocal differentiation of Th17 cells and Treg cells by deubiquitinating and stabilizing TAZ

The balance between inflammatory T helper type 17 (Th17) and immunosuppressive regulatory T (Treg) cells is critical for maintaining immune homeostasis in the human body and is tightly regulated under healthy conditions. An increasing number of studies have reported that deubiquitinases (DUBs) play a vital role in regulating Th17- and Treg-cell differentiation. However, the biological functions of only a small fraction of DUBs in Th17- and Treg-cell differentiation are well defined. In this study, we identified ubiquitin-specific peptidase 1 (USP1) as a vital regulator of CD4+ T-cell differentiation. USP1 promoted Th17-cell differentiation but attenuated Treg-cell differentiation, thereby promoting the development of inflammatory diseases. Mechanistically, USP1 in CD4+ T cells enhanced the activity of RORγt but promoted the proteasomal degradation of Foxp3 through deubiquitination and stabilization of TAZ in vitro and in vivo. Notably, ML323, a specific inhibitor of the USP1/UAF1 deubiquitinase complex, inhibited Th17-cell differentiation and promoted Treg-cell differentiation in vitro and in vivo, indicating that ML323 might be a promising candidate for the treatment of diseases associated with an imbalance between Th17 and Treg cells. Our study highlights the critical role of USP1 in regulating adaptive immune responses and suggests that USP1 might be a drug target for the treatment of diseases associated with an imbalance between Th17 and Treg cells.

Meibomian Gland Dysfunction: A Route of Ocular Graft-Versus-Host Disease Progression That Drives a Vicious Cycle of Ocular Surface Inflammatory Damage

PURPOSE

To investigate the role of aggressive meibomian gland dysfunction (MGD) in the immune pathogenesis of ocular graft-vs-host disease (GVHD).

METHODS

In mice, an allogeneic GVHD model was established by transferring bone marrow (BM) and purified splenic T cells from C57BL/6J mice into irradiated C3-SW.H2b mice (BM+T). Control groups received BM only. Mice were scored clinically across the post-transplantation period. MGD severity was categorized using the degree of atrophy on harvested lids. Immune disease was analyzed using flow cytometry of tissues along with fluorescent tracking of BM cells onto the ocular surface. In humans, parameters from 57 patients with ocular GVHD presenting to the Duke Eye Center were retrospectively reviewed. MGD was categorized using the degree of atrophy on meibographs. Immune analysis was done using high-parameter flow cytometry on tear samples.

RESULTS

Compared with BM only, BM+T mice had higher systemic disease scores that correlated with tear fluid loss and eyelid edema. BM+T had higher immune cell infiltration in the ocular tissues and higher CD4+-cell cytokine expression in draining lymph nodes. BM+T mice with worse MGD scores had significantly worse corneal staining. In patients with ocular GVHD, 96% had other organs affected. Patients with ocular GVHD had abnormal parameters on dry eye testing, high matrix metalloproteinase-9 positivity (92%), and abundance of immune cells in tear samples. Ocular surface disease signs were worse in patients with higher MGD severity scores.

CONCLUSIONS

Ocular GVHD is driven by a systemic, T-cell-dependent process that causes meibomian gland damage and induces a robust form of ocular surface disease that correlates with MGD severity. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Qi Jing Mingmu decoction inhibits the p38 signaling pathway in conjunctivochalasis fibroblasts by down-regulation of Th17 cell differentiation

ETHNOPHARMACOLOGICAL RELEVANCE

Qi Jing Mingmu (QJMM) decoction is a traditional Chinese medicine that has been widely used for the clinical treatment of conjunctivochalasis (CCH). It is an effective treatment to relieve ocular symptoms including improving tear film and promoting tear secretion. However, its effects and molecular mechanisms need to be elucidated.

AIM OF THE STUDY

To determine whether QJMM decoction affected T helper 17 (Th17) cell differentiation of CCH patients.

MATERIALS AND METHODS

Blood samples and conjunctival tissues were collected from CCH patients and normal controls. The fibroblasts were separately induced, and CD4⁺ T cells were incubated with increasing concentrations of QJMM decoction and co-cultured with CCH fibroblasts. Th17 cell numbers were then analyzed using flow cytometry. Serum levels of interleukin 17 (IL-17) and IL-22 were detected using enzyme-linked immunosorbent assays. The expressions of signal proteins and genes were detected using western blotting and quantitative real-time PCR.

RESULTS

Compared with normal controls, Th17 cell numbers and serum levels of IL-17 and IL-22 were elevated in patients with CCH. QJMM decoction down-regulated the expressions of IL-17, IL-22, and STAT3 of CD4⁺T cells from CCH patients, suggesting that QJMM decoction impeded Th17 cell differentiation. QJMM decoction-treated CD4⁺ T cells inhibited the expression of p38 in CCH fibroblasts.

CONCLUSION

QJMM decoction inhibited Th17 cell differentiation of CD4⁺T cells from CCH patients, and QJMM decoction-treated CD4⁺T cells down-regulated the p38 signal pathway in CCH fibroblasts. Our study showed that Th17 cells may be good candidates for clinical treatment of CCH.

Bacteria and Dry Eye: A Narrative Review

(1) Background: Dry eye is a multifactorial disease of the ocular surface, the incidence of which has been increasing sharply. The pathogenesis of dry eye, especially in terms of the bacterial flora, has drawn great attention. Additionally, the potential treatment methods need to be explored. (2) Methods: We reviewed more than 100 studies and summarized them briefly in a review. (3) Results: We summarized the bacterial communities found on the ocular surface in the general population and patients with dry eye and found a relationship between dry eye and antibiotic therapy. We identified the possible mechanisms of bacteria in the development of dry eye by discussing factors such as the destruction of the antibacterial barrier, infectious diseases, microbiome homeostasis, inflammatory factors on the ocular surface and vitamin deficiency. (4) Conclusion: We systematically reviewed the recent studies to summarize the bacterial differences between patients with dry eye and the general population and brought up several possible mechanisms and possible treatment targets.

Impact of aging on the pathophysiology of dry eye disease: A systematic review and meta-analysis

PURPOSE

Dry eye disease (DED) is a common age-related ocular surface disease. However, it is unknown how aging influences the ocular surface microenvironment. This systematic review aims to investigate how the aging process changes the ocular surface microenvironment and impacts the development of DED.

METHODS

An article search was performed in PubMed, EMBASE, and Web of Science. 44 studies reporting on age-related ocular changes and 14 large epidemiological studies involving the prevalence of DED were identified. 8 out of 14 epidemiological studies were further analyzed with meta-analysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines were followed. Study-specific estimates (impact of aging on the prevalence of DED) were combined using one-group meta-analysis in a random-effects model.

RESULTS

Meta-analysis revealed the prevalence of DED in the elderly aged 60 years old or older was 5519 of 60107 (9.2%) and the odds ratio of aging compared to younger age was 1.313 (95% confidence interval [CI]; 1.107, 1.557). With increasing age, the integrity of the ocular surface and tear film stability decreased. Various inflammatory cells, including senescent-associated T-cells, infiltrated the ocular surface epithelium, lacrimal gland, and meibomian gland, accompanied by senescence-related changes, including accumulation of 8-OHdG and lipofuscin-like inclusions, increased expression of p53 and apoptosis-related genes, and decreased Ki67 positive cells.

CONCLUSIONS

The aging process greatly impacts the ocular surface microenvironment, consequently leading to DED.

Corneal Epithelium-Derived Netrin-1 Alleviates Dry Eye Disease via Regulating Dendritic Cell Activation

Purpose

To investigate the expression of corneal epithelium-derived netrin-1 (NTN-1) and its immunoregulatory function in dry eye disease (DED) using a DED mouse model.

Methods

We generated DED mouse models with desiccating stress under scopolamine treatment. RNA sequencing was performed to identify differentially expressed genes (DEGs) in the corneal epithelium of DED mice. NTN-1 expression was analyzed via real-time PCR, immunofluorescence staining, and immunoblotting. The DED mice were then treated with recombinant NTN-1 or neutralizing antibodies to investigate the severity of the disease, dendritic cell (DC) activation, and inflammatory cytokine expression.

Results

A total of 347 DEGs (292 upregulated and 55 downregulated) were identified in the corneal epithelium of DED mice: corneal epithelium-derived NTN-1 expression was significantly decreased in DED mice compared to that in control mice. Topical recombinant NTN-1 application alleviated the severity of the disease, accompanied by restoration of tear secretion and goblet cell density. In addition, NTN-1 decreased the number of DCs, inhibited the activation of the DCs and Th17 cells, and reduced the expression of inflammatory factors in DED mice. In contrast, blocking endogenous NTN-1 activity with an anti-NTN-1 antibody aggravated the disease, enhanced DC activation, and upregulated the inflammatory factors in the conjunctivae of DED mice.

Conclusions

We identified decreased NTN-1 expression in the corneal epithelium of DED mice. Our findings elucidate the role of NTN-1 in alleviating DED and impeding DC activation, thereby indicating its therapeutic potential in suppressing ocular inflammation in DED.

Interleukin-17 Receptor E and C-C Motif Chemokine Receptor 10 Identify Heterogeneous T Helper 17 Subsets in a Mouse Dry Eye Disease Model

Dry eye disease (DED) features the inflammatory response of the ocular surface. Pro-inflammatory T helper 17 (Th17) cells are important for the pathogenesis of DED. In the present study a mouse DED model was used to discover two Th17 subsets in draining lymph nodes and conjunctivae based on the expression of IL-17 receptor E (IL-17RE) and CCR10: IL-17RE^lowCCR10^- Th17 and IL-17RE^highCCR10⁺ Th17. IL-17RE^highCCR10⁺ Th17 expressed more retinoic acid-related orphan receptor gamma t but fewer T-box-expressed-in-T-cells than IL-17RE^lowCCR10^- Th17. In addition, the former expressed higher IL-17A, IL-21, and IL-22 but fewer IFN-γ than the latter. Further analysis showed that IL-17RE^highCCR10⁺ Th17 did not express IFN-γ in vivo, whereas IL-17RE^lowCCR10^- Th17 contained IFN-γ-expressing Th17/Th1 cells. Moreover, IL-17RE^highCCR10⁺ Th17 possessed more phosphorylated p38 mitogen-activated protein kinase (MAPK) and Jnk than IL-17RE^lowCCR10^- Th17, suggesting higher activation of MAPK signaling in IL-17RE^highCCR10⁺ Th17. In vitro treatment with IL-17C effectively maintained IL-17A expression in Th17 cells through p38 MAPK rather than Jnk MAPK. Furthermore, the adoptive transfer of the two Th17 subpopulations indicated their equivalent pathogenicity in DED. Interestingly, IL-17RE^highCCR10⁺ Th17 cells were able to phenotypically polarize to IL-17RE^lowCCR10^- Th17 cells in vivo. In conclusion, the current study revealed novel Th17 subsets with differential phenotypes, functions, and signaling status in DED, thus deepening the understanding of Th17 pathogenicity, and exhibited Th17 heterogeneity in DED.

Emerging therapies for dry eye disease

INTRODUCTION

Dry Eye Disease (DED) is defined as a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and a vicious cycle of inflammation on the ocular surface. Despite its high prevalence and standing as one of the most common eye conditions seen by practitioners, the current treatment options available to patients have not proven adequate.

AREAS COVERED

This review will discuss the burden of DED, its pathophysiology, as well as emerging therapies. These therapies include immunosuppressants, immunomodulators, anti-inflammatory drugs, and corticosteroids. The mechanisms of these drugs will be discussed, as well as their phase of development and results from recent clinical trials. The literature search was performed using PubMed, Cochrane Library, Web of Science, ClinicalTrials.gov, and the Springer AdisInsight database.

EXPERT OPINION

The optimal therapy for DED is associated with improved bioavailability, minimal ocular side effects, and effective dosing. The ideal treatment has not yet been established, but this paper outlines a number of promising therapies. Continued development of therapies targeting the inflammation cascade, as well as the establishment of objective markers to quantify DED severity, are important aspects in the progression of treatment.

Immune responses to injury and their links to eye disease

The eye is regarded as an immune privileged site. Since the presence of a vasculature would impair vision, the vasculature of the eye is located outside of the central light path. As a result, many regions of the eye evolved mechanisms to deliver immune cells to sites of dysgenesis, injury, or in response to the many age-related pathologies. While the purpose of these immune responses is reparative or protective, cytokines released by immune cells compromise visual acuity by inducing inflammation and fibrosis. The response to traumatic or pathological injury is distinct in different regions of the eye. Age-related diseases impact both the anterior and posterior segment and lead to reduced quality of life and blindness. Here we focus attention on the role that inflammation and fibrosis play in the progression of age-related pathologies of the cornea and the lens as well as in glaucoma, the formation of epiretinal membranes, and in proliferative vitreoretinopathy.

The Role of Neuropeptides in Pathogenesis of Dry Dye

Neuropeptides are known as important mediators between the nervous and immune systems. Recently, the role of the corneal nerve in the pathogenesis of various ocular surface diseases, including dry eye disease, has been highlighted. Neuropeptides are thought to be important factors in the pathogenesis of dry eye disease, as suggested by the well-known role between the nervous and immune systems, and several recently published studies have elucidated the previously unknown pathogenic mechanisms involved in the role of the neuropeptides secreted from the corneal nerves in dry eye disease. Here, we reviewed the emerging concept of neurogenic inflammation as one of the pathogenic mechanisms of dry eye disease, the recent results of related studies, and the direction of future research.

Autoimmunity in dry eye disease - An updated review of evidence on effector and memory Th17 cells in disease pathogenicity

The classic Th1/Th2 dogma has been significantly reshaped since the subsequent introduction of several new T helper cell subsets, among which the most intensively investigated during the last decade is the Th17 lineage that demonstrates critical pathogenic roles in autoimmunity and chronic inflammation - including the highly prevalent dry eye disease. In this review, we summarize current concepts of Th17-mediated disruption of ocular surface immune homeostasis that leads to autoimmune inflammatory dry eye disease, by discussing the induction, activation, differentiation, migration, and function of effector Th17 cells in disease development, highlighting the phenotypic and functional plasticity of Th17 lineage throughout the disease initiation, perpetuation and sustention. Furthermore, we emphasize the most recent advance in Th17 memory formation and function in the chronic course of dry eye disease, a major area to be better understood for facilitating the development of effective treatments in a broader field of autoimmune diseases that usually present a chronic course with recurrent episodes of flare in the target tissues or organs.

CD4+ T-Cell Plasticity in Non-Infectious Retinal Inflammatory Disease

Non-infectious uveitis (NIU) is a potentially sight-threatening disease. Effector CD4+ T cells, especially interferon-γ-(IFNγ) producing Th1 cells and interleukin-17-(IL-17) producing Th17 cells, are the major immunopathogenic cells, as demonstrated by adoptive transfer of disease in a model of experimental autoimmune uveitis (EAU). CD4+FoxP3+CD25+ regulatory T cells (Tregs) were known to suppress function of effector CD4+ T cells and contribute to resolution of disease. It has been recently reported that some CD4+ T-cell subsets demonstrate shared phenotypes with another CD4+ T-cell subset, offering the potential for dual function. For example, Th17/Th1 (co-expressing IFNγ and IL-17) cells and Th17/Treg (co-expressing IL-17 and FoxP3) cells have been identified in NIU and EAU. In this review, we have investigated the evidence as to whether these 'plastic CD4+ T cells' are functionally active in uveitis. We conclude that Th17/Th1 cells are generated locally, are resistant to the immunosuppressive effects of steroids, and contribute to early development of EAU. Th17/Treg cells produce IL-17, not IL-10, and act similar to Th17 cells. These cells were considered pathogenic in uveitis. Future studies are needed to better clarify their function, and in the future, these cell subsets may in need to be taken into consideration for designing treatment strategies for disease.

A Novel Rabbit Dry Eye Model Induced by a Controlled Drying System

Purpose

To establish an environment-induced dry eye model in rabbits using a controlled drying system (CDS).

Methods

Rabbits were randomly divided into two groups. The rabbits in the dry group were housed in the CDS, in which the relative humidity, airflow, and temperature were controlled at 22% ± 4%, 3 to 4 m/s, and 23°C to 25°C for 14 days. The rabbits in the control group were housed in a normal environment at the same time. A Schirmer test, fluorescein staining, and lissamine green staining were performed. On day 14, the eyeballs and lacrimal glands were processed for evaluating the corneal epithelial thickness, inflammatory cell infiltration index, goblet cell density, and expression of the MUC5AC protein and caspase-3 protein. The mRNA expression of the involved inflammatory genes was analyzed.

Results

The CDS was able to maintain a dry environment, in which the tear production decreased, and the ocular surface staining increased over time in the rabbits. In the dry group, the corneal epithelium became thinner, inflammatory cells were noted, goblet cells and MUC5AC proteins decreased, and the increased levels of caspase-3 proteins and inflammatory cytokines were observed in the ocular surface tissues and lacrimal glands.

Conclusions

This CDS could create a dry environment, in which the rabbits exhibited a pathological change in dry eye similar to that in humans.

Translational Relevance

This model would be helpful in offering a platform to identify and test candidate therapies for environment-induced dry eye and to explore its underlying mechanisms.

Association between aging-dependent gut microbiome dysbiosis and dry eye severity in C57BL/6 male mouse model: a pilot study

BACKGROUND

While aging is a potent risk factor of dry eye disease, age-related gut dysbiosis is associated with inflammation and chronic geriatric diseases. Emerging evidence have demonstrated that gut dysbiosis contributes to the pathophysiology or exacerbation of ocular diseases including dry eye disease. However, the relationship between aging-related changes in gut microbiota and dry eye disease has not been elucidated. In this pilot study, we investigated the association between aging-dependent microbiome changes and dry eye severity in C57BL/6 male mice.

RESULTS

Eight-week-old (8 W, n = 15), one-year-old (1Y, n = 10), and two-year-old (2Y, n = 8) C57BL/6 male mice were used. Dry eye severity was assessed by corneal staining scores and tear secretion. Bacterial genomic 16 s rRNA from feces was analyzed. Main outcomes were microbiome compositional differences among the groups and their correlation to dry eye severity. In aged mice (1Y and 2Y), corneal staining increased and tear secretion decreased with statistical significance. Gut microbiome α-diversity was not different among the groups. However, β-diversity was significantly different among the groups. In univariate analysis, phylum Firmicutes, Proteobacteria, and Cyanobacteria, Firmicutes/Bacteroidetes ratio, and genus Alistipes, Bacteroides, Prevotella, Paraprevotella, and Helicobacter were significantly related to dry eye severity. After adjustment of age, multivariate analysis revealed phylum Proteobacteria, Firmicutes/Bacteroidetes ratio, and genus Lactobacillus, Alistipes, Prevotella, Paraprevotella, and Helicobacter to be significantly associated with dry eye severity.

CONCLUSIONS

Our pilot study suggests that aging-dependent changes in microbiome composition are related to severity of dry eye signs in C57BL/6 male mice.

Nicotinamide Mononucleotide Alleviates Hyperosmolarity-Induced IL-17a Secretion and Macrophage Activation in Corneal Epithelial Cells/Macrophage Co-Culture System

Background

Hyperosmosis stress (HS) was a key pathological factor in the development of dry eye disease (DED). Nicotinamide mononucleotide (NMN) demonstrated protective effects in the corneal damage, however, its role in the HS-induced DED remained unclear.

Methods

A NaCl based HS in-vitro model (500 mOsm) was generated and used in a co-culture system including corneal epithelial cells (CEC) and macrophage cell line RAW264.7. The effect of NMN on NAD+ metabolism and the expression of HS biomarker, tonicity-responsive element binding protein (TonEBP), was studied in the CEC. The cellular activity, including cell viability, apoptosis status and lactate dehydrogenase (LDH) release through trypan blue staining, flow cytometry and LDH assay, respectively. The mitochondrial membrane potential (MMP) assay would be conducted using the JC1 kit. The expression of IL-17a were detected using RT-PCR, ELISA and Western blot. After co-culture with the CEC in different group for 24 h, the phagocytosis ability and macrophage polarization were assessed in RAW264.7 cells co-cultured with CEC with or without HS or NMN treatment. Besides, the involvement of Notch pathway in the RAW264.7 would be analyzed. The potential involvement of Sirtuin 1 (SIRT1) and IL-17a in the crosstalk between CEC and macrophage was studied with SIRT1 inhibitor EX 527 and anti-IL-17a monoclonal antibody, respectively.

Results

NMN treatment increased NAD+ concentration and thus improved cell viability, reduced apoptotic rate and decreased the LDH release in HS-treated CEC. Besides, NMN alleviated HS-induced MMP, intracellular ROS and LDH release. Besides, it was confirmed NMN improve SIRT1 function and decreased the HS related IL-17a expression in CEC and then alleviated macrophage phagocytosis ability and M1 polarization based on a CEC-macrophage co-culture system. Moreover, NMN treatment of CEC in the CEC could moderate the subsequent macrophage activation through Notch pathway. SIRT1 activation and IL-17a inhibition was regarded as key progress in the function of NMN based on the application of EX 527 and anti-IL-17a antibody in the CEC-macrophage co-culture system.

Conclusion

The findings demonstrated that NMN could alleviated HS-induced DED status through regulating the CEC/macrophage interaction. Our data pointed to the role of SIRT1, IL-17a and Notch pathway in the function of NMN and then provided updated knowledge of potential NMN application in the management of DED.