The CCR6/CCL20 axis mediates Th17 cell migration to the ocular surface in dry eye disease

Immunosenescence, immunotolerance and rejection: clinical aspects in solid organ transplantation

As a consequence of increased lifespan and rising number of elderly individuals developing end-stage organ disease, the higher demand for organs along with a growing availability for organs from older donors pose new challenges for transplantation. During aging, dynamic adaptations in the functionality and structure of the biological systems occur. Consistently, immunosenescence (IS) accounts for polydysfunctions within the lymphocyte subsets, and the onset of a basal but persistent systemic inflammation characterized by elevated levels of pro-inflammatory mediators. There is an emerging consensus about a causative link between such hallmarks and increased susceptibility to morbidities and mortality, however the role of IS in solid organ transplantation (SOT) remains loosely addressed. Dissecting the immune-architecture of immunologically-privileged sites may prompt novel insights to extend allograft survival. A deeper comprehension of IS in SOT might unveil key standpoints for the clinical management of transplanted patients.

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.

Prostaglandin E2 may clinically alleviate dry eye disease by inducing Th17 cell differentiation

Dry eye (DE) is a multifactorial ocular surface disease characterised by an imbalance in tear homeostasis. The pathogenesis of DE is complex and related to environmental, immunological (e.g., T helper 17 cells) and other factors. However, the DE disease pathogenesis remains unclear, thereby affecting its clinical treatment. This study aimed to explore the mechanism through which prostaglandin E2 (PGE2) affects DE inflammation by regulating Th17. The DE mouse model was established through subcutaneous injection of scopolamine hydrobromide. The tear secretion test and break-up time (BUT) method were used to detect tear secretion and tear film BUT, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to detect the concentrations of PGE2, interleukin (IL)-17, IL-6 and tumour necrosis factor (TNF-α) in tear fluid and those of PGE2 and IL-17 in the serum. RT-qPCR and western blotting were used to test the mRNA and protein expression levels of IL-17 and retinoid-related orphan receptor-γt (RORγt). PGE2 was highly expressed in the DE mouse model. The mRNA and protein levels of IL-17 and the key Th17 transcription factor RORγt were increased in tissues of the DE mice. Moreover, PGE2 promoted tear secretion, reduced the BUT, increased the IL-17 concentration in tears and increased the Th17 cell proportion in DE, whereas the PGE2 receptor inhibitor AH6809 reversed the effects of PGE2 on tear secretion, BUT, and the Th17 cell proportion in draining lymph node (DLN) cells. Taken together, the study findings indicate that PGE2 could induce DE-related symptoms by promoting Th17 differentiation.

New developments in the management of persistent corneal epithelial defects

A persistent epithelial defect (PED) is a corneal epithelial defect that failed to heal after 2weeks. It is a condition that carries much morbidity, and our understanding of PED remains poor, with current treatment methods often having unsatisfactory outcomes. With PEDs becoming more prevalent, more efforts are required to establish reliable treatment modalities. Our reviews describe the causes of PEDs and the different approaches developed to manage them, as well as their associated limitations. Emphasis is placed on understanding various advances in the development of new treatment modalities. We have also described a case of a woman with a background of graft-versus-host disease on long-term topical corticosteroids who developed complicated PED involving both eyes. The current approach to managing PEDs generally involves exclusion of an active infection, followed by treatment modalities that aim to encourage corneal epithelial healing. Success rates, however, remain far from desirable, as treatment remains challenging due to multiple underlying etiologies. In summary, advances in the development of new therapies may be able to facilitate progress in the understanding and treatment of PED.

Thymosin β4 Alleviates Autoimmune Dacryoadenitis via Suppressing Th17 Cell Response

Purpose

We investigated the therapeutic effect of recombinant thymosin β4 (rTβ4) on rabbit autoimmune dacryoadenitis, an animal model of SS dry eye, and explore its mechanisms.

Methods

Rabbits were treated topically with rTβ4 or PBS solution after disease onset for 28 days, and clinical scores were determined by assessing tear secretion, break-up time, fluorescein, hematoxylin and eosin staining, and periodic acid-Schiff. The expression of inflammatory mediators in the lacrimal glands were measured by real-time PCR. The expression of T helper 17 (Th17) cell-related transcription factors and cytokines were detected by real-time PCR and Western blotting. The molecular mechanism underlying the effects of rTβ4 on Th17 cell responses was investigated by Western blotting.

Results

Topical administration of rTβ4 after disease onset efficiently ameliorated the ocular surface inflammation and relieved the clinical symptoms. Further analysis revealed that rTβ4 treatment significantly inhibited the expression of Th17-related genes (RORC, IL-17A, IL-17F, IL-1R1, IL-23R, and granulocyte-macrophage colony-stimulating factor) and IL-17 protein in lacrimal glands, and meanwhile decreased the inflammatory mediators expression. Mechanistically, we demonstrated that rTβ4 repressed the phosphorylation of signal transducer and activator of transcription 3 (STAT3) both in vivo and in vitro. Activation of the STAT3 signal pathway by Colivelin partly reversed the suppressive effects of rTβ4 on IL-17 expression in vitro.

Conclusions

rTβ4 could alleviate ongoing autoimmune dacryoadenitis in rabbits, probably by suppressing Th17 response via partly affecting the STAT3 pathway. These data may provide a new insight into the therapeutic effect and mechanism of rTβ4 in dry eye associated with Sjögren's syndrome.

Distinct Serum Immune Profiles Define the Spectrum of Acute and Chronic Pancreatitis From the Multicenter Prospective Evaluation of Chronic Pancreatitis for Epidemiologic and Translational Studies (PROCEED) Study

BACKGROUND & AIMS

Pancreatitis is a disease continuum, starting with acute pancreatitis (AP) and progressing in some cases to recurrent acute pancreatitis (RAP) and chronic pancreatitis (CP). Currently, there are no approved therapies or early diagnostic or prognostic biomarkers for pancreatitis. The current study examined whether patient serum immune profiling could identify noninvasive biomarkers and provide mechanistic insight into the disease continuum of pancreatitis.

METHODS

Using Olink immunoassay, we assessed the protein levels of 92 immune markers in serum samples from participants enrolled in the Prospective Evaluation of Chronic Pancreatitis for Epidemiologic and Translational Studies (PROCEED) study of the Chronic Pancreatitis, Diabetes, and Pancreatic Cancer (CPDPC) consortium. Samples (N = 231) were obtained from individuals without pancreatic disease (n = 56) and from those with chronic abdominal pain (CAP) (n = 24), AP (n = 38), RAP (n = 56), and CP (n = 57).

RESULTS

A total of 33 immune markers differentiated the combined pancreatitis groups from controls. Immune markers related to interleukin (IL) 17 signaling distinguished CP from AP and RAP. Similarly, the serum level of IL17A and C-C motif chemokine ligand 20 differentiated CP from CAP, suggesting the involvement of T helper 17 cells in CP pathogenesis. The receiver operator characteristic curve with 2 immune markers (IL17A and sulfotransferase 1A1) could differentiate CP from CAP (optimistic area under the curve = 0.78). The macrophage classical activation pathway elevated along the continuum of pancreatitis, suggesting an accumulation of proinflammatory signals over disease progression. Several immune markers were associated with smoking, alcohol, and diabetes status.

CONCLUSIONS

Immune profiling of serum samples from a large pancreatitis cohort led to identifying distinct immune markers that could serve as potential biomarkers to differentiate the varying pancreatitis disease states. In addition, the finding of IL17 signaling in CP could provide insight into the immune mechanisms underlying disease progression.

CCR6 as a Potential Target for Therapeutic Antibodies for the Treatment of Inflammatory Diseases

The CC chemokine receptor 6 (CCR6) is a G protein-coupled receptor (GPCR) involved in a wide range of biological processes. When CCR6 binds to its sole ligand CCL20, a signaling network is produced. This pathway is implicated in mechanisms related to many diseases, such as cancer, psoriasis, multiple sclerosis, HIV infection or rheumatoid arthritis. The CCR6/CCL20 axis plays a fundamental role in immune homeostasis and activation. Th17 cells express the CCR6 receptor and inflammatory cytokines, including IL-17, IL-21 and IL-22, which are involved in the spread of inflammatory response. The CCL20/CCR6 mechanism plays a crucial role in the recruitment of these pro-inflammatory cells to local tissues. To date, there are no drugs against CCR6 approved, and the development of small molecules against CCR6 is complicated due to the difficulty in screenings. This review highlights the potential as a therapeutic target of the CCR6 receptor in numerous diseases and the importance of the development of antibodies against CCR6 that could be a promising alternative to small molecules in the treatment of CCR6/CCL20 axis-related pathologies.

E. coli LPS/TLR4/NF-κB Signaling Pathway Regulates Th17/Treg Balance Mediating Inflammatory Responses in Oral Lichen Planus

Oral lichen planus (OLP) is a chronic inflammatory autoimmune disease mediated by T cells. The imbalance of microflora has potential impacts on the onset and development of OLP, but the mechanism is still unclear. Here, we investigated the effects of Escherichia coli (E. coli) lipopolysaccharide (LPS) simulating the microbial enrichment state of OLP on T cell immune functions in vitro. Effect of E. coli LPS on the viability of T cell using CCK8 assay. After E. coli LPS pretreatment, the expression of the toll-like receptor 4 (TLR4), nuclear factor-kappa B p65 (NF-κB p65), cytokines, retinoic acid-related orphan receptor γt (RORγt), and forkhead box p3 (Foxp3) in the peripheral blood of OLP patients and normal controls (NC) were assessed using quantitative RT-PCR (qRT-PCR), western blot, and enzyme-linked immunosorbent assay (ELISA). Finally, Th17 and Treg cells were detected by flow cytometry. We found that the TLR4/NF-κB pathway was activated and the expression of interleukin (IL)-6 and IL-17 was increased in both groups after E. coli LPS stimulation. CC chemokine ligand (CCL)20 and CC chemokine receptor (CCR)4 expression was increased in OLP after E. coli LPS treatment, while no difference was found in CCR6 and CCL17 expression of both groups. Moreover, E. coli LPS treatment enhanced the proportion of Th17 cells, Th17/Treg ratio, and RORγt/Foxp3 ratio in OLP. In conclusion, E. coli LPS regulated Th17/Treg balance to mediate the inflammatory responses of OLP through the TLR4/NF-κB pathway in vitro, indicating that oral microbiota dysbiosis affected the chronic inflammatory state of OLP.

Effect of TRPM8 Functional Loss on Corneal Epithelial Wound Healing in Mice

Purpose

To reveal the role of cold-sensing transient receptor potential melastatin 8 (TRPM8) channels in corneal epithelial wound healing.

Methods

Cold sensitivity, tear production, corneal thickness, and corneal opacity assessments were used to evaluate the effect of Trpm8 knockout on the ocular surface. A corneal epithelial wounding model was generated by scraping the corneal epithelium once or multiple times using C57BL/6J (wild-type [WT]) and Trpm8-/- mice. The processes of corneal epithelial repair and corneal epitheliopathy were observed and recorded. Corneas were collected for sequencing, immunofluorescence staining, hematoxylin and eosin staining, and quantitative PCR.

Results

The perception of coldness, basal tear secretion, and corneal thickness were decreased in young Trpm8-/- mice compared with those in WT mice, except for the corneal sensitivity. Corneal opacity and increased corneal thickness were observed in aged Trpm8-/- mice. TRPM8 deficiency promoted corneal epithelial wound closure, consistent with the observed increase in Ki67-positive epithelial cells, and the pharmacological activation of TRPM8 in WT mice delayed corneal re-epithelization. After subjecting mice to multiple injuries, squamous metaplasia emerged in Trpm8-/- corneas, as verified by cytokeratin-1 and small proline-rich protein 1B-positive staining. The IFN-β and IFN-γ signaling pathways were significantly activated in Trpm8-/- mice, which was confirmed based on the up-regulated expression of the key mediators, signal transducer and activator of transcription-1 and phosphor-signal transducer and activator of transcription-1, as well as the induction of IFN-stimulated genes, compared with levels in WT mice.

Conclusions

In corneal wound healing, the loss of TRPM8 function could promote epithelial repair, but predispose the cornea to epithelial lesions.

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.

Recent Developments About the Pathogenesis of Dry Eye Disease: Based on Immune Inflammatory Mechanisms

Dry eye disease is a common and frequently occurring ophthalmology with complex and diverse causes, and its incidence is on the upward trend. The pathogenesis of DED is still completely clear. However, the immune response based on inflammation has been recognized as the core basis of this disease. In this review, we will systematically review the previous research on the treatment of DED in immune inflammation, analyze the latest views and research hotspots, and provide reference for the prevention and treatment of DED.

Differentially Expressed Gene Pathways in the Conjunctiva of Sjögren Syndrome Keratoconjunctivitis Sicca

Sjögren syndrome (SS) is an autoimmune condition that targets the salivary and lacrimal glands, with cardinal clinical signs of dry eye (keratoconjunctivitis sicca, KCS) and dry mouth. The conjunctiva of SS patients is often infiltrated by immune cells that participate in the induction and maintenance of local inflammation. The purpose of this study was to investigate immune-related molecular pathways activated in the conjunctiva of SS patients. Female SS patients (n=7) and controls (n=19) completed a series of oral, ocular surface exams. Symptom severity scores were evaluated using validated questionnaires (OSDI and SANDE). All patients fulfilled the ACR/EULAR criteria for SS and the criteria for KCS. Fluorescein and lissamine green dye staining evaluated tear-break-up time (TBUT), corneal and conjunctival disease, respectively. Impression cytology of the temporal bulbar conjunctiva was performed to collect cells lysed and subjected to gene expression analysis using the NanoString Immunology Panel. 53/594 differentially expressed genes (DEGs) were observed between SS and healthy controls; 49 DEGs were upregulated, and 4 were downregulated (TRAF5, TGFBI, KLRAP1, and CMKLRI). The top 10 DEGs in descending order were BST2, IFITM1, LAMP3, CXCL1, IL19, CFB, LY96, MX1, IL4R, CDKN1A. Twenty pathways had a global significance score greater or equal to 2. Spearman correlations showed that 29/49 upregulated DEGs correlated with either TBUT (inverse) or OSDI or conjunctival staining score (positive correlations). Venn diagrams identified that 26/29 DEGs correlated with TBUT, 5/26 DEGs correlated with OSDI, and 16/26 correlated with conjunctival staining scores. Five upregulated DEGs (CFB, CFI, IL1R1, IL2RG, IL4R) were uniquely negatively correlated with TBUT. These data indicate that the conjunctiva of SS patients exhibits a phenotype of immune activation, although some genes could be inhibitory. Some of the DEGs and pathways overlap with previous DEGs in salivary gland biopsies, but new DEGs were identified, and some of these correlated with symptoms and signs of dry eye. Our results indicate that gene analysis of conjunctiva imprints is a powerful tool to understand the pathogenesis of SS and develop new therapeutic targets.

Cigarette Smoke Specifically Affects Small Airway Epithelial Cell Populations and Triggers the Expansion of Inflammatory and Squamous Differentiation Associated Basal Cells

Smoking is a major risk factor for chronic obstructive pulmonary disease (COPD) and causes remodeling of the small airways. However, the exact smoke-induced effects on the different types of small airway epithelial cells (SAECs) are poorly understood. Here, using air–liquid interface (ALI) cultures, single-cell RNA-sequencing reveals previously unrecognized transcriptional heterogeneity within the small airway epithelium and cell type-specific effects upon acute and chronic cigarette smoke exposure. Smoke triggers detoxification and inflammatory responses and aberrantly activates and alters basal cell differentiation. This results in an increase of inflammatory basal-to-secretory cell intermediates and, particularly after chronic smoke exposure, a massive expansion of a rare inflammatory and squamous metaplasia associated KRT6A⁺ basal cell state and an altered secretory cell landscape. ALI cultures originating from healthy non-smokers and COPD smokers show similar responses to cigarette smoke exposure, although an increased pro-inflammatory profile is conserved in the latter. Taken together, the in vitro models provide high-resolution insights into the smoke-induced remodeling of the small airways resembling the pathological processes in COPD airways. The data may also help to better understand other lung diseases including COVID-19, as the data reflect the smoke-dependent variable induction of SARS-CoV-2 entry factors across SAEC populations.

Toll-like receptor 2 induces pathogenicity in Th17 cells and reveals a role for IPCEF in regulating Th17 cell migration

Pathogenic Th17 cells drive inflammation in autoimmune disease, yet the molecular programming underlying Th17 cell pathogenicity remains insufficiently understood. Activation of Toll-like receptor 2 (TLR2) increases Th17 cell inflammatory potential, but little is known regarding the mechanistic outcomes of TLR2 signaling in Th17 cells. Here, we demonstrate that TLR2 is comparable to IL-23 in inducing pathogenicity and increasing the migratory capacity of Th17 cells. We perform RNA sequencing of Th17 cells stimulated though the TLR2 pathway and find differential expression of several genes linked with the Th17 genetic program as well as genes not previously associated with pathogenic Th17 cells, including Ipcef1. Enforced expression of Ipcef1 in Th17 cells abolishes the TLR2-dependent increases in migratory capacity and severely impairs the ability of Th17 cells to induce experimental autoimmune encephalomyelitis. This study establishes the importance of the TLR2 signaling pathway in inducing Th17 cell pathogenicity and driving autoimmune inflammation.

Proteoglycan 4 (PRG4) expression and function in dry eye associated inflammation

Dry eye disease (DED) affects hundreds of millions of people worldwide. It is characterized by the production of inflammatory cytokines and chemokines as well as damaging matrix metalloproteinases (MMPs) at the ocular surface. While proteoglycan 4 (PRG4), a mucin-like glycoprotein present at the ocular surface, is most well known as a boundary lubricant that contributes to ocular surface integrity, it has been shown to blunt inflammation in various cell types, suggesting a dual mechanism of action. Recently, full-length recombinant human PRG4 (rhPRG4) has been shown to improve signs and symptoms of DED in humans. However, there remains a significant need for basic science research on rhPRG4's biological properties and its potential therapeutic mechanisms of action in treating DED. Therefore, the objectives of this study were to characterize endogenous PRG4 expression by telomerase-immortalized human corneal epithelial (hTCEpi) cells, examine whether exogenous rhPRG4 modulates cytokine and chemokine secretion in response to dry eye associated inflammation (TNFα and IL-1β), explore interactions between rhPRG4 and MMP-9, and understand how experimental dry eye (EDE) in mice affects PRG4 expression. PRG4 secretion from hTCEpi cells was quantified by Western blot and expression visualized by immunocytochemistry. Cytokine/chemokine production was measured by ELISA and Luminex, while rhPRG4's effect on MMP-9 activity, binding, and expression was quantified using an MMP-9 inhibitor kit, surface plasmon resonance, and reverse transcription polymerase chain reaction (RT-PCR), respectively. Finally, EDE was induced in mice, and PRG4 was visualized by immunohistochemistry in the cornea and by Western blot in lacrimal gland lysate. In vitro results demonstrate that hTCEpi cells synthesize and secrete PRG4, and PRG4 secretion is inhibited by TNFα and IL-1β. In response to these pro-inflammatory stresses, exogenous rhPRG4 significantly reduced the stimulated production of IP-10, RANTES, ENA-78, GROα, MIP-3α, and MIG, and trended towards a reduction of MIP-1α and MIP-1β. The hTCEpi cells were also able to internalize fluorescently-labelled rhPRG4, consistent with a mechanism of action that includes downstream biological signaling pathways. rhPRG4 was not digested by MMP-9, and it did not modulate MMP-9 gene expression in hTCEpi cells, but it was able to bind to MMP-9 and inhibited in vitro activity of exogenous MMP-9 in the presence of human tears. Finally, in vivo results demonstrate that EDE significantly decreased immunolocalization of PRG4 on the corneal epithelium and trended towards a reduction of PRG4 in lacrimal gland lysate. Collectively these results demonstrate rhPRG4 has anti-inflammatory properties on corneal epithelial cells, particularly as it relates to mitigating chemokine production, and is an inhibitor of MMP-9 activity, as well as that in vivo expression of PRG4 can be altered in preclinical models of DED. In conclusion, these findings contribute to our understanding of PRG4's immunomodulatory properties in the context of DED inflammation and provide the foundation and motivation for further mechanistic research of PRG4's properties on the ocular surface as well as expanding clinical evaluation of its ability as a multifunctional therapeutic agent to effectively provide relief to those who suffer from DED.

Pigment epithelium-derived factor (PEDF) plays anti-inflammatory roles in the pathogenesis of dry eye disease

PURPOSE

To investigate the expression of pigment epithelium-derived factor (PEDF) in ocular surface in dry eye disease (DED) and its anti-inflammatory roles and mechanisms, clinically and by experiments in vivo and in vitro.

METHODS

A cross-sectional study was conducted to detect the expression of PEDF in tears of dry eye patients by enzyme-linked immunosorbent assay (ELISA). Using dry eye mouse model and human corneal epithelial cells (hCECs) stimulated by hyperosmolarity or inflammatory cytokines, expression of PEDF in corneal epithelial cells, stroma and conjunctiva was quantified by real-time polymerase chain reaction, ELISA and Western blot. Next, either dry eye mice or hyperosmotic hCECs were treated with recombinant PEDF or neutralizing antibodies, and the expressions of inflammatory cytokines and immune cells were detected. Finally, Western blot was performed on MAPK and NF-κB to investigate the signaling pathways by which PEDF played its roles.

RESULTS

Concentrations of PEDF were increased in tears of dry eye patients. Increased PEDF was observed in corneal epithelial cells (CECs) rather than corneal stroma or conjunctiva in dry eye mice. Furthermore, hCECs exposed to hyperosmolarity showed upregulation of PEDF. In vivo and in vitro studies showed that PEDF suppressed the expression of inflammatory cytokines including IL-1β, IL-6, TNF-α and IL-17A, as well as the percentage of Th17 cells in DED. Further investigation showed that PEDF inhibited the phosphorylation of MAPK p38 and JNK in hyperosmotic hCECs.

CONCLUSIONS

CECs derived PEDF is increased in DED. PEDF plays anti-inflammatory and immunoregulatory roles in the pathogenesis of DED.

A Review of the Mechanism of Action of Cyclosporine A: The Role of Cyclosporine A in Dry Eye Disease and Recent Formulation Developments

Dry eye disease (DED) is a multifactorial disease of the ocular surface and tear film that has gained awareness as a public health problem. Characteristics of DED include tear film instability, hyperosmolarity, and ocular surface inflammation, which can occur independently or may be a sequela of numerous ocular diseases, ocular surgery or contact lens wear. Much has been learned about the impact of the disease to help affected individuals who report symptoms of poor vision, pain, and tearing. Recently, new research highlights the importance of the role of ocular surface inflammation and damage in DED-leading to a vicious cycle of inflammation as well as loss of tear film homeostasis. DED immunopathophysiology is characterized by four stages: initiation, amplification, recruitment, and re-initiation. Cyclosporine is proven to be a valuable ophthalmic therapeutic for DED through its immunomodulatory actions and regulation of the adaptive immune response. Cyclosporine mechanism of action is well described in the published literature and the myriad of benefits in all four stages lend a broad-based immunomodulatory function particularly suitable for addressing DED. Furthermore, cyclosporine has unique goblet cell density improvement capabilities as well as anti-apoptotic properties. Topical formulations of cyclosporine are centered around addressing the highly lipophilic nature of the molecule. The poor aqueous solubility of cyclosporine traditionally presented technical challenges in drug delivery to the ocular surface. Newer formulations such as cationic emulsions and nanomicellar aqueous solutions address formulation, tissue concentration, and drug delivery challenges.

Aged Mice Exhibit Severe Exacerbations of Dry Eye Disease with an Amplified Memory Th17 Cell Response

The prevalence as well as the severity of dry eye disease increase with age. Memory T helper 17 (Th17) cells (CD4+IL-17A+CD44+) drive the chronic and relapsing course of dry eye disease. Here, we investigated the contribution of memory Th17 cells to age-related dry eye disease, and evaluated memory Th17 cell depletion with anti-IL-15 antibody as a strategy to abrogate the severe exacerbations of dry eye disease observed in aged mice. After initial exposure to desiccating stress, aged mice maintained higher frequencies of memory Th17 cells in the draining lymph nodes relative to young mice. Upon secondary exposure to desiccating stress, aged mice developed more severe corneal epitheliopathy than young mice, which is associated with increased local frequencies of Th17 cells (CD4+IL-17A+). Treatment with anti-IL-15 antibody decreased the enlarged memory Th17 pool in aged mice to frequencies comparable with young mice. Furthermore, anti-IL-15-treated mice showed significantly reduced conjunctival infiltration of Th17 cells and lower corneal fluorescein staining scores compared with saline-treated control mice. Our data suggest that age-related increases in the memory Th17 compartment predispose aged mice toward the development of severe corneal epithelial disease after exposure to a dry environment. Selectively targeting memory Th17 cells may be a viable therapeutic approach in the treatment of age-related dry eye disease.

The role of Th17 immunity in chronic ocular surface disorders

Th17 cells have been implicated in the pathogenesis of numerous inflammatory and autoimmune conditions. At the ocular surface, Th17 cells have been identified as key effector cells in chronic ocular surface disease. Evidence from murine studies indicates that following differentiation and expansion, Th17 cells migrate from the lymphoid tissues to the eye, where they release inflammatory cytokines including, but not limited to, their hallmark cytokine IL-17A. As the acute phase subsides, a population of long-lived memory Th17 cells persist, which predispose hosts both to chronic inflammation and severe exacerbations of disease; of great interest is the small subset of Th17/1 cells that secrete both IL-17A and IFN-γ in acute-on-chronic disease exacerbation. Over the past decade, substantial progress has been made in deciphering how Th17 cells interact with the immune and neuroimmune pathways that mediate chronic ocular surface disease. Here, we review (i) the evidence for Th17 immunity in chronic ocular surface disease, (ii) regulatory mechanisms that constrain the Th17 immune response, and (iii) novel therapeutic strategies targeting Th17 cells.

Dry Eye Disease: Emerging Approaches to Disease Analysis and Therapy

Dry eye disease (DED) is among the most common ocular disorders affecting tens of millions of individuals worldwide; however, the condition remains incompletely understood and treated. Valuable insights have emerged from multidisciplinary approaches, including immunometabolic analyses, microbiome analyses, and bioengineering. Furthermore, we have seen new developments in clinical assessment approaches and treatment strategies in the recent past. Here, we review the emerging frontiers in the pathobiology and clinical management of DED.

Age-associated antigen-presenting cell alterations promote dry-eye inducing Th1 cells

Aging is a significant risk factor for dry eye. Here we used a murine aging model to investigate the effects of aging on antigen presenting cells (APCs) and generation of pathogenic T helper (Th)-1 cells. Our results showed that APCs from aged mice accumulate at the conjunctiva, have higher levels of co-activation marker CD86 and lower aldehyde dehydrogenase activity. Using topical ovalbumin peptide as a surrogate antigen, we observed an increased number of antigen-loaded APCs in the draining cervical lymph nodes in the aged group and loss of tight junction protein occludin in the conjunctiva. Aged cervical lymph nodes APCs showed a greater generation of Th1 cells than young APCs in antigen-presentation assays in vitro. Aged lacrimal glands, and draining nodes showed an accumulation of IFN-γ producing CD4+T cells, while Th-17 cells were present only in aged draining nodes. There was also an age-related increase in CD4+CXCR3+IFN-γ+ cells in the conjunctiva, nodes, and lacrimal glands while CD4+CCR6+IL-17A+ cells increased in the draining nodes of aged mice. Adoptive transfer of aged CD4+CXCR3+ cells into young, naive immunodeficient recipients caused greater goblet cell loss than young CD4+CXCR3+ donor cells. Our results demonstrate that age-associated changes in APCs are critical for the pathogenesis of age-related dry eye.

CCL20-CCR6 axis modulated traumatic brain injury-induced visual pathologies

BACKGROUND

Traumatic brain injury (TBI) is a major cause of death and disability in the USA and the world; it constitutes 30% of injury-related deaths (Taylor et al., MMWR Surveill Summ 66:1-16, 2017). Contact sports athletes often experience repetitive TBI (rTBI), which exerts a cumulative effect later in life. Visual impairment is a common after-effect of TBI. Previously, we have shown that C-C chemokine 20 (CCL20) plays a critical role in neurodegeneration and inflammation following TBI (Das et al., J Neuroinflammation 8:148, 2011). C-C chemokine receptor 6 (CCR6) is the only receptor that CCL20 interacts with. The objective of the present study was to investigate the role of CCL20-CCR6 axis in mediating rTBI-induced visual dysfunction (TVD).

METHODS

Wild type (WT) or CCR6 knock out (CCR6-/-) mice were subjected to closed head rTBI. Pioglitazone (PG) is a peroxisome proliferator-activated receptor γ (PPARγ) agonist which downregulates CCL20 production. Subsets of WT mice were treated with PG following final rTBI. A subset of mice was also treated with anti-CCL20 antibody to neutralize the CCL20 produced after rTBI. Histopathological assessments were performed to show cerebral pathologies, retinal pathologies, and inflammatory changes induced by rTBI.

RESULTS

rTBI induced cerebral neurodegeneration, retinal degeneration, microgliosis, astrogliosis, and CCL20 expression. CCR6-/- mice showed reduced retinal degeneration, microgliosis, and inflammation. Treatment with CCL20 neutralization antibody or PG showed reduced CCL20 expression along with reduced retinal degeneration and inflammation. rTBI-induced GFAP-positive glial activation in the optic nerve was not affected by knocking out CCR6.

CONCLUSION

The present data indicate that rTBI-induced retinal pathology is mediated at least in part by CCL20 in a CCR6-dependent manner.

Rebamipide ophthalmic solution modulates the ratio of T helper cell 17/regulatory T cells in dry eye disease mice

The aim of the present study was to confirm the effect of 2% rebamipide ophthalmic solution on a scopolamine‑induced dry eye (DE) mouse model, and to investigate its effect on the ratio of T helper cell 17 (Th17)/regulatory T cell (Treg) numbers. C57BL/6 mice received subcutaneous injections of scopolamine and were exposed to a low‑humidity environment in order to establish a DE model. Rebamipide eye drops (2%) administered four times daily for 2 weeks, significantly reduced the corneal staining scores and increased the tear film breakup time and tear production in the DE mice. Pathologically, the rebamipide restored the histological changes induced by DE in the cornea, conjunctiva and lacrimal gland. At a molecular level, it downregulated pro‑inflammatory and upregulated anti‑inflammatory cytokines in the conjunctiva and lacrimal gland. Furthermore, the increased Th17 and Treg levels were restored following treatment with rebamipide. In conclusion, the anti‑inflammatory and Th17/Treg balance‑preserving effects of rebamipide may contribute to the treatment of DE in mice.

Interaction Between CCR6+ Th17 Cells and CD34+ Fibrocytes Promotes Inflammation: Implications in Graves' Orbitopathy in Chinese Population

Purpose

Recent reports suggest that Th17 immunity and bone marrow-derived CD34+ fibrocytes contribute to the pathogenesis of Graves' orbitopathy (GO). This study investigated interactions between Th17 cells and fibrocytes in GO inflammation in Chinese subjects.

Methods

Th17 cells and fibrocytes were derived from blood samples from Chinese GO patients and healthy controls. Proportions and phenotypes of Th17 cells, regulatory T cells (Tregs), and fibrocytes were examined by flow cytometry. Exogenous IL-17A was used to study inflammatory activity of fibrocytes from GO patients and control subjects. Coculture, quantitative RT-PCR, Luminex, and transwell assays were performed to investigate the relationship between Th17 cells and fibrocytes.

Results

CC-chemokine receptor 6 (CCR6+) Th17 cells were increased in both active (P < 0.001) and inactive (P < 0.05) GO patients, compared with healthy controls. There was a positive correlation between number of CCR6+ Th17 cells and GO clinical activity score (P < 0.0001, r = 0.8176). Further, CD34+ fibrocytes were increased in GO patients, with increased expression of IL-17RA (P < 0.05), CD80 (P < 0.05), and CD86 (P < 0.05). A decreased population of effector Treg cells (P < 0.01) and increased CTLA-4 expression on naïve Treg cells (P < 0.05) were observed in GO patients. IL-17A stimulated cytokine production in fibrocytes; GO fibrocytes exhibited more robust production than normal fibrocytes. Autologous Th17 cells promoted inflammatory and antigen-presenting functions of GO fibrocytes; conversely, fibrocytes enhanced Th17 cell-function and recruited Th17 cells in a macrophage inflammatory protein 3 (MIP-3)/CCR6-dependent manner.

Conclusions

The crosstalk between CCR6+ Th17 cells and fibrocytes plays a role in the pathogenesis of GO. Suppressing these interactions may be a candidate molecular target for therapeutic approaches of GO.

Innate and Adaptive Cell Populations Driving Inflammation in Dry Eye Disease

Dry eye disease (DED) is the most common ocular disease and affects millions of individuals worldwide. DED encompasses a heterogeneous group of diseases that can be generally divided into two forms including aqueous-deficient and evaporative DED. Evidence suggests that these conditions arise from either failure of lacrimal gland secretion or low tear film quality. In its secondary form, DED is often associated with autoimmune diseases such as Sjögren's syndrome and rheumatoid arthritis. Current treatment strategies for DED are limited to anti-inflammatory medications that target the immune system as the source of deleterious inflammation and tissue injury. However, there is a lack of understanding of the underlying pathogenesis of DED, and subsequently, there are very few effective treatment strategies. The gap in our knowledge of the etiology of primary DED is in part because the majority of research in DED focused on secondary autoimmune causes. This review focuses on what is currently understood about the contribution of innate and adaptive immune cell populations in the pathogenesis of DED and highlights the need to continue investigating the central role of immunity driving DED.

Pleiotropic Immune Functions of Chemokine Receptor 6 in Health and Disease

C-C chemoattractant cytokine (chemokine) receptor 6 (CCR6) and its exclusive binding molecule CCL20 is an extremely important chemokine receptor-ligand pair which controls cell migration and immune induction during inflammatory disease. Not many scientific studies have been undertaken to study its immune mechanisms in detail, but its unique contribution to steady state cell chemotaxis in upholding immune tolerance and regulating immune homeostasis during inflammation is evident in multiple systems in the human body, including skin, liver, lung, kidney, brain, eye, joints, gonads and the gut. The role of CCR6 is constitutively expressed as a series of much debilitating severe inflammatory and autoimmune diseases, Human Immunodeficiency Virus (HIV) and cancer metastasis. CD4⁺ T cells, the central organizers of adaptive immunity, are stringently mobilized by the CCR6/CCL20 axis also induced by cytokines and a host of other factors in a carefully executed immune modulation scenario, to bring about a delicate balance between inflammation inducing T_H17 cells and regulatory T_reg cells. Although the exact immune regulatory role is not elucidated as yet, the CCR6/CCL20 axis is implicated as a front runner which determines the polarization of T_H17 and regulatory T_reg cells, upon which depends the resolution or progression of many debilitating disorders. This review therefore aims at emphasizing the pleiotropic significance of the chemokines CCR6 and CCL20 in immunologic function in multiple organ systems, thereby hoping to accentuate its value in future therapeutic modalities.

When Clarity Is Crucial: Regulating Ocular Surface Immunity

The ocular surface is a unique mucosal immune compartment in which anatomical, physiological, and immunological features act in concert to foster a particularly tolerant microenvironment. These mechanisms are vital to the functional competence of the eye, a fact underscored by the devastating toll of excessive inflammation at the cornea - blindness. Recent data have elucidated the contributions of specific anatomical components, immune cells, and soluble immunoregulatory factors in promoting homeostasis at the ocular surface. We highlight research trends at this distinctive mucosal barrier and identify crucial gaps in our current knowledge.

The Pathophysiology of Dry Eye Disease: What We Know and Future Directions for Research

Clinical and laboratory studies performed over the past few decades have discovered that dry eye is a chronic inflammatory disease that can be initiated by numerous extrinsic or intrinsic factors that promote an unstable and hyperosmolar tear film. These changes in tear composition, in some cases combined with systemic factors, lead to an inflammatory cycle that causes ocular surface epithelial disease and neural stimulation. Acute desiccation activates stress signaling pathways in the ocular surface epithelium and resident immune cells. This triggers production of innate inflammatory mediators that stimulate the production of matrix metalloprotease, inflammatory cell recruitment, and dendritic cell maturation. These mediators, combined with exposure of autoantigens, can lead to an adaptive T cell-mediated response. Cornea barrier disruption develops by protease-mediated lysis of epithelial tight junctions, leading to accelerated cell death; desquamation; an irregular, poorly lubricated cornea surface; and exposure and sensitization of epithelial nociceptors. Conjunctival goblet cell dysfunction and death are promoted by the T helper 1 cytokine interferon gamma. These epithelial changes further destabilize the tear film, amplify inflammation, and create a vicious cycle. Cyclosporine and lifitegrast, the 2 US Food and Drug Administration-approved therapies, inhibit T-cell activation and cytokine production. Although these therapies represent a major advance in dry eye therapy, they are not effective in improving discomfort and corneal epithelial disease in all patients. Preclinical studies have identified other potential therapeutic targets, biomarkers, and strategies to bolster endogenous immunoregulatory pathways. These discoveries will, it is hoped, lead to further advances in diagnostic classification and treatment.

Lacrimal gland-derived IL-22 regulates IL-17-mediated ocular mucosal inflammation

Inflammatory damage of mucosal surface of the eye is a hallmark of dry eye disease (DED) and, in severe cases, can lead to significant discomfort, visual impairment, and blindness. DED is a multifactorial autoimmune disorder with a largely unknown pathogenesis. Using a cross-sectional patient study and a well-characterized murine model of DED, herein we investigated the immunoregulatory function of interleukin-22 (IL-22) in the pathogenesis of DED. We found that IL-22 levels were elevated in lacrimal fluids of DED patients and inversely correlated with severity of disease. Acinar cells of the lacrimal glands (LGs), not inflammatory immune cells, are the primary source of IL-22, which suppresses inflammation in ocular surface epithelial cells upon desiccating stress. Moreover, loss of function analyses using IL-22 knockout mice demonstrated that IL-22 is essential for suppression of ocular surface infiltration of Th17 cells and inhibition of DED induction. Our novel findings elucidate immunoregulatory function of LG-derived IL-22 in inhibiting IL-17-mediated ocular surface epitheliopathy in DED thus making IL-22 a new relevant therapeutic target.

Alloimmunity and Tolerance in Corneal Transplantation

Corneal transplantation is one of the most prevalent and successful forms of solid tissue transplantation. Despite favorable outcomes, immune-mediated graft rejection remains the major cause of corneal allograft failure. Although low-risk graft recipients with uninflamed graft beds enjoy a success rate ∼90%, the rejection rates in inflamed graft beds or high-risk recipients often exceed 50%, despite maximal immune suppression. In this review, we discuss the critical facets of corneal alloimmunity, including immune and angiogenic privilege, mechanisms of allosensitization, cellular and molecular mediators of graft rejection, and allotolerance induction.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

IFN-γ-Expressing Th17 Cells Are Required for Development of Severe Ocular Surface Autoimmunity

Th17 cells are critical effectors mediating the ocular surface autoimmunity in dry eye disease (DED). Increased IFN-γ has also been implicated in DED; however, it remains unclear to what extent Th1 cells contribute to DED pathogenesis. In this study, we investigated the cellular source of IFN-γ and assessed its contribution to corneal epitheliopathy in DED mice. We discovered a significant IL-17A⁺IFN-γ⁺ (Th17/1) population and determined that these cells are derived from Th17 precursors. Adoptive transfer of Th17/1, but not Th1, cells confers the disease to naive recipients as effectively as do Th17 cells alone. DED-induced IL-12 and IL-23 are required for in vivo transition of pathogenic Th17 cells to IFN-γ producers. Furthermore, using IFN-γ-deficient Th17 cells, we demonstrate the disease-amplifying role of Th17-derived IFN-γ in DED pathogenesis. These results clearly demonstrate that Th17 cells mediate ocular surface autoimmunity through both IL-17A and IFN-γ.

T Cell-Derived Granulocyte-Macrophage Colony-Stimulating Factor Contributes to Dry Eye Disease Pathogenesis by Promoting CD11b+ Myeloid Cell Maturation and Migration

Purpose

Growing evidence suggests that granulocyte-macrophage colony-stimulating factor (GM-CSF) contributes to T helper 17 (Th17) cell-associated immunoinflammatory diseases. The purpose of this study was to evaluate the effect of T cell-derived GM-CSF on CD11b+ myeloid cell function in dry eye disease (DED).

Methods

In a murine model of DED, quantitative real-time PCR and ELISA were used to measure GM-CSF expression at the ocular surface, and flow cytometry was used to enumerate GM-CSF producing Th17 cells. A granulocyte-macrophage colony-stimulating factor neutralizing antibody was used topically in vivo and in an in vitro culture system to evaluate the role of GM-CSF in recruiting and maturing CD11b+ cells. Clinical disease severity was evaluated after topical administration of GM-CSF neutralizing antibody.

Results

In dry eye disease, GM-CSF is significantly upregulated at the ocular surface and the frequency of GM-CSF producing Th17 cells is significantly increased in the draining lymph nodes. In vitro neutralization of GM-CSF from CD4+ T cells derived from DED mice suppresses major histocompatibility complex II expression by CD11b+ cells and CD11b+ cell migration. Topical neutralization of GM-CSF in a murine model of DED suppresses CD11b+ maturation and migration, as well as Th17 cell induction, yielding a reduction in clinical signs of disease.

Conclusions

T helper 17 cell-derived GM-CSF contributes to DED pathogenesis by promoting CD11b+ cell activation and migration to the ocular surface.

Mucosal immune tolerance at the ocular surface in health and disease

The ocular surface is constantly exposed to environmental irritants, allergens and pathogens, against which it can mount a prompt immune response to preserve its integrity. But to avoid unnecessary inflammation, the ocular surface's mucosal immune system must also discriminate between harmless and potentially dangerous antigens, a seemingly complicated task. Despite its unique features, the ocular surface is a mucosal lining, and as such, it shares some homeostatic and pathophysiological mechanisms with other mucosal surfaces. The purpose of this review is to explore the mucosal homeostatic immune function of the ocular surface in both the healthy and diseased states, with a special focus on mucosal immunology concepts. The information discussed in this review has been retrieved by PubMed searches for literature published from January 1981 to October 2016.

Ageing and ocular surface immunity

The prevalence of ocular surface immunopathologies is enhanced in the elderly. This increased prevalence has been attributed to age-related dysregulation of innate and adaptive immune system responses. Age-related changes in ocular surface immunity have similar and distinct characteristics to those changes seen in other mucosal tissues. This mini review provides a brief outline of key findings in the field of ocular ageing, draws comparisons with other mucosal tissues and, finally, discusses age-related changes in the context of immunopathogenesis of infectious keratitis and dry eye disease, two of the most common inflammatory disorders of the ocular surface.

Relationship Between Dynamic Changes in Expression of IL-17/IL-23 in Lacrimal Gland and Ocular Surface Lesions in Ovariectomized Mice

PURPOSE

An ovariectomized mouse model was constructed to observe the dynamic effects of hormone changes on the expression of interleukin (IL)-17A and IL-23 in the lacrimal glands.

METHODS

The ovariectomized mouse model was constructed by bilateral ovary removal. The concentrations of serum estradiol and testosterone in mouse cardiac blood were detected by radioimmunoassay. Mice in both groups underwent the phenol red cotton thread test and corneal fluorescein staining to assess the ocular surface, whereas Th17 cells in blood and spleen were detected by flow cytometry. IL-17A and IL-23 expression in the lacrimal glands was detected by immunohistochemistry, enzyme-linked immunosorbent assay, and real-time fluorescence quantitative polymerase chain reaction.

RESULTS

Serum estradiol and testosterone levels were significantly lower in the ovariectomized group compared with those in the control group. There was lymphocytic infiltration in the lacrimal gland of the ovariectomized group mice. At 6 months after the surgery, aqueous tear production was significantly lower, and statistically significant corneal fluorescein staining was found in the ovariectomized group, compared with that in the control group. In the ovariectomized group, IL-17A and the IL-23 expression in the lacrimal glands and the Th17 expression in the blood and spleen were significantly higher than in the control group.

CONCLUSION

The hormone levels are significantly reduced and lymphocytic infiltration in the lacrimal gland in ovariectomized mice, whereas the frequency of Th17 cells in the blood and spleen and IL-17A and IL-23 expression in the lacrimal glands are increased, leading to reduced tear production and positive fluorescein staining in the cornea.

C-C motif chemokine ligand 20 regulates neuroinflammation following spinal cord injury via Th17 cell recruitment

Background

Spinal cord injury (SCI) is a severe traumatic injury that often leads to paralysis. The neuroinflammation following SCI plays an important role during the secondary injury phase. C-C motif chemokine ligand 20 (CCL20) works like a magnet to attract inflammatory cells and subsequently regulate inflammation. However, the role and mechanisms of CCL20 in neuroinflammation following traumatic injury are poorly understood.

Methods

A modified Allen’s weight drop method was applied to induce a rat moderate contusion injury model. HE staining was used to assess spinal cord histopathology, and the water content test was used to estimate spinal cord edema. Motor function scores were quantified to evaluate locomotor ability, and leukocyte infiltration was observed by CD45 immunofluorescence and flow cytometry. Additionally, qRT-PCR and ELISA were used to determine inflammatory mediator gene expression. Th17 cell recruitment was identified by flow cytometry.

Results

Compared with the injury control groups, histological analysis of the lesion area and tissue edema revealed reduced spinal cord edema and decreased lesion volume in the group administrated with CCL20 neutralizing antibody. Locomotor activity, as assessed by Basso, Beattie, and Bresnahan (BBB) score, showed that CCL20 blockade was beneficial for motor function recovery. Results also showed that leukocyte infiltration was reduced by neutralizing CCL20 at 7 days post-injury. More importantly, expression levels of IL-1β, IL-6, and TNF-α at 24 h after SCI demonstrated that a reduced inflammatory reaction in the CCL20 antibody group compared with the injury controls. Although CCL20 altered the expression of IL-1β, IL-6, and TNF-α, it had no effect on anti-inflammatory IL-10 expression at 24 h after damage. Notably, tissue flow cytometry confirmed that Th17 cell recruitment in the CCL20 antibody group was decreased compared with the control groups at 14 days post-injury. Additionally, IL-17A expression, which is mainly secreted by Th17 cell, suggested that CCL20 blockade also reduced IL-17A levels at 14 days after SCI.

Conclusions

These results suggested that CCL20 aggravates neuroinflammation following SCI via regulation of Th17 cell recruitment and IL-17A level. Thus, CCL20-target therapy could be a promising clinical application for the treatment of SCI.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0630-7) contains supplementary material, which is available to authorized users.

Age-related Defects in Ocular and Nasal Mucosal Immune System and the Immunopathology of Dry Eye Disease

Dry eye disease (DED) is a prevalent public health concern that affects up to 30% of adults and is particularly chronic and severe in the elderly. Two interconnected mechanisms cause DED: (1) an age-related dysfunction of lacrimal and meibomian glands, which leads to decreased tear production and/or an increase in tear evaporation; and (2) an age-related uncontrolled inflammation of the surface of the eye triggered by yet-to-be-determined internal immunopathological mechanisms, independent of tear deficiency and evaporation. In this review we summarize current knowledge on animal models that mimic both the severity and chronicity of inflammatory DED and that have been reliably used to provide insights into the immunopathological mechanisms of DED, and we provide an overview of the opportunities and limitations of the rabbit model in investigating the role of both ocular and nasal mucosal immune systems in the immunopathology of inflammatory DED and in testing novel immunotherapies aimed at delaying or reversing the uncontrolled age-related inflammatory DED.

Altered Mucosal Microbiome Diversity and Disease Severity in Sjögren Syndrome

There is mounting evidence that the microbiome has potent immunoregulatory functions. We assessed the effects of intestinal dysbiosis in a model of Sjögren syndrome (SS) by subjecting mice to desiccating stress (DS) and antibiotics (ABX). We characterized the conjunctival, tongue and fecal microbiome profiles of patients with SS. Severity of ocular surface and systemic disease was graded. 16S ribosomal RNA gene sequencing characterized the microbiota. ABX + DS mice had a significantly worse dry eye phenotype compared to controls, a decrease in Clostridium and an increase in Enterobacter, Escherichia/Shigella, and Pseudomonas in stool after ABX + DS for 10 days. Goblet cell density was significantly lower in ABX treated groups compared to controls. Stool from SS subjects had greater relative abundances of Pseudobutyrivibrio, Escherichia/Shigella, Blautia, and Streptococcus, while relative abundance of Bacteroides, Parabacteroides, Faecalibacterium, and Prevotella was reduced compared to controls. The severity of SS ocular and systemic disease was inversely correlated with microbial diversity. These findings suggest that SS is marked by a dysbiotic intestinal microbiome driven by low relative abundance of commensal bacteria and high relative abundance of potentially pathogenic genera that is associated with worse ocular mucosal disease in a mouse model of SS and in SS patients.

The C-C chemokine receptor 6 (CCR6) is crucial for Th2-driven allergic conjunctivitis

Allergic conjunctivitis from an allergen-driven Th2 response is characterized by conjunctival eosinophilic infiltration. Although CCL20-CCR6 axis has been reported to play a proinflammatory role in several murine models of autoimmune diseases including allergic diseases, their underlying mechanism needs to be investigated. We here examined whether CCL20-CCR6 axis could play a role in the development of allergic conjunctival inflammation using murine experimental allergic conjunctivitis (EAC) model induced by ovalbumin (OVA) allergen. Mice were challenged with consecutive 10days of OVA via conjunctival sac after systemic challenge with OVA and cholera toxin in alum. Several indicators for allergy were comparatively evaluated in wild-type and CCR6 KO EAC mice. Wild-type mice challenged with OVA via conjunctival sac following systemic challenge with OVA in alum had severe allergic conjunctivitis. The absence of CCR6 suppressed IgE secretion and allergic conjunctival inflammation. Reduced allergic inflammation was ascribable to reduced cytokine responses from Th-2 type in draining lymph node although Th17, regulatory T cells and dendritic cell subsets are not affected by the absence of CCR6. In addition, neutralization of CCR6 ligand, CCL20 could repress allergic conjunctival inflammation. Our findings suggested that CCR6 might be crucial for optimal development of Th2 immune responses and further allergic conjunctival inflammation in EAC model.

VEGF-trap aflibercept significantly improves long-term graft survival in high-risk corneal transplantation

BACKGROUND

Graft failure because of immune rejection remains a significant problem in organ transplantation, and lymphatic and blood vessels are important components of the afferent and efferent arms of the host alloimmune response, respectively. We compare the effect of antihemangiogenic and antilymphangiogenic therapies on alloimmunity and graft survival in a murine model of high-risk corneal transplantation.

METHODS

Orthotopic corneal transplantation was performed in hemevascularized and lymph-vascularized high-risk host beds, and graft recipients received subconjunctival vascular endothelial growth factor (VEGF)-trap, anti-VEGF-C, sVEGFR-3, or no treatment, beginning at the time of surgery. Fourteen days after transplantation, graft hemeangiogenesis and lymphangiogenesis were evaluated by immunohistochemistry. The frequencies of Th1 cells in regional lymphoid tissue and graft-infiltrating immune cells were evaluated by flow cytometry. Long-term allograft survival was compared using Kaplan-Meier curves.

RESULTS

VEGF-trap significantly decreased graft hemangiogenesis as compared to the control group and was most effective in reducing the frequency of graft-infiltrating immune cells. Anti-VEGF-C and sVEGFR3 significantly decreased graft lymphangiogenesis and lymphoid Th1 cell frequencies as compared to control. VEGF-trap (72%), anti-VEGF-C (25%), and sVEGFR-3 (11%) all significantly improved in the 8-week graft survival compared to control (0%), although VEGF-trap was significantly more effective than both anti-VEGF-C (P < 0.05) and sVEGFR-3 (P < 0.05).

CONCLUSION

In a clinically relevant model of high-risk corneal transplantation in which blood and lymphatic vessels are present and treatment begins at the time of transplantation, VEGF-trap is significantly more effective in improving long-term graft survival as compared to anti-VEGF-C and sVEGFR-3, but all approaches improve survival when compared to untreated control.

Inflammatory Chemokines MIP-1δ and MIP-3α Are Involved in the Migration of Multipotent Mesenchymal Stromal Cells Induced by Hepatoma Cells

In vivo, bone marrow-derived multipotent mesenchymal stromal cells (MSC) have been identified at sites of tumors, suggesting that specific signals mobilize and activate MSC to migrate to areas surrounding tumors. The signals and migratory mechanisms that guide MSC are not well understood. Here, we investigated the migration of human MSC induced by conditioned medium of Huh-7 hepatoma cells (Huh-7 CM). Using a transwell migration system, we showed that human MSC migration was increased in the presence of Huh-7 CM. Using a human cytokine antibody array, we detected increased levels of MIP-1δ and MIP-3α in Huh-7 CM. Recombinant chemokines MIP-1δ and MIP-3α induced MSC migration. Anti-MIP-1δ and anti-MIP-3α antibodies added to Huh-7 CM decreased MSC migration, further suggesting that MIP-1δ and MIP-3α were implicated in the Huh-7 CM-induced MSC migration. By real-time polymerase chain reaction, we observed an absence of chemokine receptors CCR2 and CXCR2 and low expression of CCR1, CCR5, and CCR6 in MSC. Expression of these chemokine receptors was not regulated by Huh-7 CM. Furthermore, matrix metalloproteinase 1 (MMP-1) expression was strongly increased in MSC after incubation with Huh-7 CM, suggesting that MSC migration depends on MMP-1 activity. The signaling pathway MAPK/ERK was activated by Huh-7 CM but its inhibition by PD98059 did not impair Huh-7 CM-induced MSC migration. Further, long-term incubation of MSC with MIP-1δ increased α-smooth muscle actin expression, suggesting its implication in the Huh-7 CM-induced evolvement of MSC into myofibroblasts. In conclusion, we report that two inflammatory cytokines, MIP-1δ and MIP-3α, are able to increase MSC migration in vitro. These cytokines might be responsible for migration and evolvement of MSC into myofibroblasts around tumors.

Sigma receptor 1 activation attenuates release of inflammatory cytokines MIP1γ, MIP2, MIP3α, and IL12 (p40/p70) by retinal Müller glial cells

The high-affinity sigma receptor 1 (σR1) ligand (+)-pentazocine ((+)-PTZ) affords profound retinal neuroprotection in vitro and in vivo by a yet-unknown mechanism. A common feature of retinal disease is Müller cell reactive gliosis, which includes cytokine release. Here, we investigated whether lipopolysaccharide (LPS) stimulates cytokine release by primary mouse Müller cells and whether (+)-PTZ alters release. Using a highly sensitive inflammatory antibody array we observed significant release of macrophage inflammatory proteins (MIP1γ, MIP2, MIP3α) and interleukin-12 (IL12 (p40/p70)) in LPS-treated cells compared to controls, and a significant decrease in secretion upon (+)-PTZ treatment. Müller cells from σR1 knockout mice demonstrated increased MIP1γ, MIP2, MIP3α and IL12 (p40/p70) secretion when exposed to LPS compared to LPS-stimulated WT cells. We investigated whether cytokine secretion was accompanied by cytosolic-to-nuclear NFκB translocation and whether endothelial cell adhesion/migration was altered by released cytokines. Cells exposed to LPS demonstrated increased NFκB nuclear location, which was reduced significantly in (+)-PTZ-treated cells. Media conditioned by LPS-stimulated-Müller cells induced leukocyte-endothelial cell adhesion and endothelial cell migration, which was attenuated by (+)-PTZ treatment. The findings suggest that release of certain inflammatory cytokines by Müller cells can be attenuated by σR1 ligands providing insights into the retinal neuroprotective role of this receptor.

Fasudil mediates cell therapy of EAE by immunomodulating encephalomyelitic T cells and macrophages

Although Fasudil has shown therapeutic potential in EAE mice, the mechanism of action are still not fully understood. Here, we examined the immunomodulatory effect of Fasudil on encephalitogenic mononuclear cells (MNCs), and tested the therapeutic potential of Fasudil-treated MNCs in active EAE. Fasudil inhibited expression of CCL20 on T cells and migration of T cells, decreased CD4(+) IFN-γ(+) and CD4(+) IL-17(+) T cells, but increased CD4(+) IL-10(+) and CD4(+) TGF-β(+) T cells. Fasudil reduced expression of CD16/32 and IL-12, while elevating expression of CD206, CD23, and IL-10. Fasudil also decreased levels of iNOS/NO, enhanced levels of Arg-1, and inhibited the TLR-4/NF-κB signaling and TNF-α, shifting M1 macrophage to M2 phenotype. These modulatory effects of Fasudil on T cells and macrophages were not altered by adding autoantigen MOG35-55 to the culture, i.e., autoantigen-independent. Further, we observed that, in vitro, Fasudil inhibited the capacity of encephalitogenic MNCs to adoptively transfer EAE and reduced TLR-4/p-NF-κB/p65 and inflammatory cytokines in spinal cords. Importantly, Fasudil-treated encephalitogenic MNCs exhibited therapeutic potential when injected into actively induced EAE mice. Together, our results not only provide evidence that Fasudil mediates the polarization of macrophages and the regulation of T cells, but also reveal a novel strategy for cell therapy in MS.

CCL20/MIP-3 alpha mRNA expression in the conjunctival epithelium of normal individuals and patients with vernal keratoconjunctivitis

Background

CCL20, the single chemokine ligand for CCR6, contributes to recruiting CCR6-expressing memory B cells, memory T cells, Th17 cells and dendritic cells, and is involved in regulating immune responses, homeostasis, and inflammation in mucosal tissues.

Methods

CCL20 messenger RNA (mRNA) expression was analyzed in the conjunctival epithelium in an in vivo study of patients with vernal keratoconjunctivitis (VKC group) and healthy volunteers (control group) using impression cytology. In vitro analysis of CCL20 mRNA was performed using cultured conjunctival epithelial cells (CECs). Real-time polymerase chain reaction was used to assess IL-8 and eotaxin-2 mRNA expression for comparison with CCL20 mRNA expression.

Results

In the control group, CCL20 mRNA expression was present in all conjunctival locations. However, CCL20 mRNA expression was significantly higher in the upper palpebral conjunctiva in the severe VKC group than in the mild VKC and control groups (p < 0.05, Steel test). In vitro stimulation of CECs with lipopolysaccharide (LPS) significantly increased CCL20 expression in a concentration-dependent manner that was significantly correlated with expression of IL-8 (p < 0.001, Spearman’s rank correlation coefficient), but not eotaxin-2.

Conclusion

We conclude that CCL 20 mRNA expression in the conjunctival epithelium plays a crucial role in regulating homeostasis at the ocular surface and in exacerbation of VKC.

Managing Sjögren's Syndrome and non-Sjögren Syndrome dry eye with anti-inflammatory therapy

Dry eye from Sjögren’s syndrome is a multifactorial disease that results in dysfunction of the lacrimal functional unit. Studies have shown changes in tear composition, including inflammatory cytokines, chemokines, and metalloproteinase. T-lymphocytes have been shown to increase in the conjunctiva and lacrimal glands in patient and animal models. This inflammation is in part responsible for the pathogenesis of the disease, which results in symptoms of eye irritation, ocular surface epithelial disease, and loss of corneal barrier function. There are a number of anti-inflammatory approaches for treating this disease. The current study reviews details of immune response and anti–inflammatory therapies used to control this disease.

The role and treatment of inflammation in dry eye disease

Dry eye syndrome is a common ocular surface problem, affects 10-30 % of the population, especially in those who are older than 40 years. As a consequence of the demographic pressure created by the aging population, its prevalence is expected to increase as well as its burden on ophthalmologic practices. Thus, understanding the complex underlying mechanisms and development of thoughtful, effective strategies that involve these mechanisms are critical. Many factors causing ocular surface damage and inflammation have been shown to contribute to the etiopathogenesis. Increased osmolarity induces ocular surface inflammation leading to disruption of both the quality and quantity of tears. Pathologic tear function and the ocular surface inflammation affects the neural arcade and increases apoptosis in the ocular surface cells thus creating a viscous cycle for dry eye by causing unstable and hyperosmolar tears. Thus, the treatment objective is to prevent severe dry eye complications via preventing inflammation and apoptosis of the ocular surface cells. The ultimate target is a normalized ocular surface, increased tear stability, and decreased osmolarity of the tear film. In the light of current literature, this review aims to elucidate the role of inflammation as the main etiological factor in dry eye disease and discuss current therapeutic approaches to overcome it.

Ocular surface disease and dacryoadenitis in aging C57BL/6 mice

Dry eye in humans displays increased prevalence in the aged and in women. Here, we investigated the ocular surfaces and lacrimal glands of aged mice of both sexes. We surveyed three different ages [young, middle-aged (6 to 9 months), and elderly] by investigating severity markers of dry eye disease (DED). We observed an age-dependent dry eye phenotype as early as 6 to 9 months: increased corneal surface irregularity, increased corneal barrier disruption, conjunctival CD4(+) T-cell infiltration, and loss of mucin-filled goblet cells. Expression of interferon-γ, IL-17 mRNA transcripts was increased in the conjunctiva and IL-17A, matrix metallopeptidase 9, and chemokine ligand 20 in the corneas of elderly mice. Elderly male mice develop more of a skewed response of type 1 T helper cell, whereas female mice have a bias toward type 17 T helper cell in the conjunctiva. In the lacrimal gland, an increase in CD4(+) and CD8(+) T cells and B cells and a decrease in activated dendritic cells were observed. Adoptive transfer of CD4(+) T cells isolated from elderly mice transferred DED into young immunodeficient recipients, which was more pronounced from male donors. Our findings show the development of DED in aging mice. Pathogenic CD4(+) T cells that develop with aging are capable of transferring DED from older mice to naive immunodeficient recipients. Taken together, our results indicate that age-related autoimmunity contributes to development of DED with aging.