IRT5 Probiotics Changes Immune Modulatory Protein Expression in the Extraorbital Lacrimal Glands of an Autoimmune Dry Eye Mouse Model

The microbiome and the eye: a new era in ophthalmology

The human microbiome has progressively been recognised for its role in various disease processes. In ophthalmology, complex interactions between the gut and distinct ocular microbiota within each structure and microenvironment of the eye has advanced our knowledge on the multi-directional relationships of these ecosystems. Increasingly, studies have shown that modulation of the microbiome can be achieved through faecal microbiota transplantation and synbiotics producing favourable outcomes for ophthalmic diseases. As ophthalmologists, we are obliged to educate our patients on measures to cultivate a healthy gut microbiome through a range of holistic measures. Further integrative studies combining microbial metagenomics, metatranscriptomics and metabolomics are necessary to fully characterise the human microbiome and enable targeted therapeutic interventions.

Multidimensional immunotherapy for dry eye disease: current status and future directions

Dry Eye Disease (DED) is a multifactorial condition driven by tear film hyperosmolarity, immune dysregulation, and neuro-immune interactions. The immune system plays a central role in its pathogenesis, influencing both inflammation and ocular surface damage. While traditional immunotherapies like anti-inflammatory agents and immunosuppressants offer symptom relief, their long-term use is limited by side effects. This review focuses on emerging immunotherapies, including biologics, stem cell therapy, gene therapy, nanotechnology, and exosome-based treatments, all of which hold promise in modulating immune responses and promoting tissue repair. The relationship between the ocular microbiome and DED is also explored, with an emphasis on personalized immunotherapy. Key challenges for future research include identifying novel therapeutic targets, optimizing clinical translation, and evaluating the long-term efficacy of these innovative treatments.

Gut microbiota and eye diseases: A review

Recent studies reveal that alterations in gut microbiota play a significant role in the progression of various diseases, including those affecting the eyes. The association between gut microbiota and eye health is an emerging focus of research. This review seeks to summarize the connection between the gut microbiome and specific eye conditions, such as ocular surface diseases, funduscopic disorders and immune-mediated eye diseases. Gut microbiota may influence these conditions by regulating the immune system or altering metabolites, thereby contributing to disease development. Strategies like probiotics, antibiotics, dietary modifications, and fecal transplants show promise in addressing these issues. This review examines how the gut microbiome may be linked to the pathogenesis of eye diseases, providing fresh therapeutic perspectives for ophthalmology.

Microbiome as an endocrine organ and its relationship with eye diseases: Effective factors and new targeted approaches

Microbiome is an endocrine organ that refers to both the complicated biological system of microbial species that colonize our bodies and their genomes and surroundings. Recent studies confirm the connection between the microbiome and eye diseases, which are involved in the pathogenesis of eye diseases, including age-related macular disorders, diabetic retinopathy, glaucoma, retinitis pigmentosa, dry eye, and uveitis. The aim of this review is to investigate the microbiome in relation to eye health. First, a brief introduction of the characteristics of the gut microorganisms terms of composition and work, the role of dysbiosis, the gut microbiome and the eye microbiome in the progression of eye illnesses are highlighted, then the relationship among the microbiome and the function of the immune system and eye diseases, the role of inflammation and aging and the immune system, It has been reviewed and finally, the control and treatment goals of microbiome and eye diseases, the role of food factors and supplements, biotherapy and antibiotics in relation to microbiome and eye health have been reviewed.

Gut Microbiota and Probiotics in Perioperative Management: A Narrative Review

The human gut is the abode of several complex and diverse microbes. It is a fact that the human brain is interconnected with the spinal cord and sense organs; however, there is also a possibility of a connection between the brain and the gut microbiome. The human gut can be altered in various ways, the principal method being the intake of prebiotics, probiotics and synbiotics. Can this alteration in the gut microbiome be clinically utilised in the perioperative period? We conducted a literature search related to this topic using databases and search engines (Medical Literature Analysis and Retrieval System Online {MEDLINE}, Embase, Scopus, PubMed and Google Scholar). The search revealed some preclinical and clinical studies in animals and humans that demonstrate the alteration of the gut microbiome with the use of anxiolysis, probiotics/prebiotics and other perioperative factors including opioids, anaesthetics and perioperative stress. The significant effects of this alteration have been seen on preoperative anxiety and postoperative delirium/cognitive dysfunction/pain. These effects are described in this narrative review, which opens up newer vistas for high-quality research related to the gut microbiome, gut-brain axis, the related signaling pathways and their clinical application in the perioperative period.

Tear Fluid as a Matrix for Biomonitoring Environmental and Chemical Exposures

PURPOSE

Exposures to hazardous chemicals have been linked to many detrimental health effects and it is therefore critical to have effective biomonitoring methods to better evaluate key environmental exposures that increase the risk of chronic disease and death. Traditional biomonitoring utilizing blood and urine is limited due to the specialized skills and invasiveness of collecting these fluid samples. This systematic review focuses on tear fluid, which is largely under-researched, as a promising complementary matrix to the traditional fluids used for biomonitoring. The objective is to evaluate the practicability of using human tear fluid for biomonitoring environmental exposures, highlighting potential pitfalls and opportunities.

RECENT FINDING

Tear fluid biomonitoring represents a promising method for assessing exposures because it can be collected with minimal invasiveness and tears contain exposure markers from both the external and internal environments. Tear fluid uniquely interfaces with the external environment at the air-tear interface, providing a surface for airborne chemicals to diffuse into the ocular environment and interact with biomolecules. Tear fluid also contains molecules from the internal environment that have travelled from the blood to tears by crossing the blood-tear barrier. This review demonstrates that tear fluid can be used to identify hazardous chemicals from the external environment and differentiate exposure groups.

Probiotic LB101 alleviates dry eye in mice by suppressing matrix metalloproteinase-9 expression through the regulation of gut microbiota-involved NF-κB signaling

Tear matrix metalloproteinase (MMP)-9 is an inflammatory signal in patients with dry eye (DE). In the present study, to understand the action mechanism of probiotic LB101 (Lactobacillus plantarum NK151 and Bifidobacterium bifidum NK175 [4:1] mix) against DE, we investigated its effect on tear amount and inflammatory marker expression levels in mice with unilateral exorbital lacrimal gland excision/atropine-benzalkonium chloride application (EB) or fecal microbiota transplantation from mice with EB (eFMT). Oral gavage of LB101 increased EB-suppressed tear amount and decreased EB-induced blinking number. Furthermore, LB101 decreased EB-induced TNF-α, IL-1β, and MMP-9 expression, TNF-α+ and NF-κB+CD11c+ cell populations, and edema in the conjunctiva, while EB-suppressed IL-10 and occludin expression increased. LB101 also decreased EB-induced TNF-α and IL-1β expression and NF-κB+CD11c+ cell population in the colon. eFMT also decreased tear amount and increased blinking number in the transplanted mice. eFMT increased TNF-α, IL-1β, and MMP-9 expression and TNF-α+ and NF-κB+CD11c+ cell populations in the conjunctiva and TNF-α and IL-1β expression and NF-κB+CD11c+ cell populations in the colon. Oral gavage of LB101 increased eFMT-suppressed tear amount and decreased eFMT-induced blinking number. Furthermore, LB101 decreased TNF-α, IL-1β, and MMP-9 expression, TNF-α+ and NF-κB+CD11c+ cell populations, and edema in the conjunctiva and TNF-α and IL-1β expression and NF-κB+CD11c+ cell population in the colon, while eFMT-suppressed IL-10 and occludin expression decreased. Furthermore, LB101 increased eFMT-suppressed Muribaculaceae, Prevotellaceae, and Lactobacillaceae populations in the gut microbiota, while eFMT-induced Bacteroidaceae population decreased. These findings suggest that DE may cause gut dysbiosis, which may be a risk factor for DE, and LB101 may alleviate DE with gut inflammation by suppressing the expression of MMP-9 and proinflammatory cytokines TNF-α and IL-1β with the regulation of gut microbiota-involved NF-κB signaling.

Efficacy of RCI001 as a therapeutic candidate of dry eye disease in a modified mixed dry eye model

BACKGROUND

To evaluate the therapeutic effects of topical RCI001 (RCI) and compare its efficacy with that of 1% prednisolone acetate (PDE) and 5% Lifitegrast in a modified mixed dry eye disease (DED) model.

METHODS

The environmental DED model was induced in BALB/c mice in a dry chamber with scopolamine. The eyes of the mice were treated topically with phosphate buffered saline (PBS), PDE, Lifitegrast or RCI twice daily for 1 week. Ocular surface staining (OSS), tear secretion, inflammatory cytokines in the ocular surface and lacrimal gland, and immunofluorescence staining in the conjunctiva and cornea(CC) were assessed.

RESULTS

The RCI group demonstrated better improvement of OSS and tear secretion than the PBS group (OSS, PBS: 13.0 ± 1.6, RCI: 9.4 ± 3.0; tear secretion, PBS: 5.0 ± 0.4 mm, RCI: 7.0 ± 0.3 mm, each P < 0.001) and better clinical efficacy than PDE and Lifitegrast groups on Day 7 (improvement rate of OSS, RCI: 32.45%, Lifitegrast: 13.13%, PDE: 12.25%). The RCI group resulted in significantly lower expression of oxidative stress markers in the CC than the PBS group (4-HNE, NOX2, and NOX4 in the conjunctiva; NOX2 in the cornea, each P < 0.05). However, the PDE and Lifitegrast groups did not show significant differences compared with the PBS group. There were no significant differences of inflammatory cytokines in the ocular surface and lacrimal gland between all groups.

CONCLUSION

Topical RCI001 showed excellent therapeutic effects in environmental DED models by stimulating tear secretion, modulating oxidative stress and improving corneal epithelial healing compared to 1% PDE and 5% Lifitegrast.

Recommendations for nutritional supplements for dry eye disease: current advances

Dry eye disease (DED) represents a prevalent ocular surface disease. The development of effective nutritional management strategies for DED is crucial due to its association with various factors such as inflammation, oxidative stress, deficiencies in polyunsaturated fatty acids (PUFAs), imbalanced PUFA ratios, and vitamin insufficiencies. Extensive research has explored the impact of oral nutritional supplements, varying in composition and dosage, on the symptoms of DED. The main components of these supplements include fish oils (Omega-3 fatty acids), vitamins, trace elements, and phytochemical extracts. Beyond these well-known nutrients, it is necessary to explore whether novel nutrients might contribute to more effective DED management. This review provides a comprehensive update on the therapeutic potential of nutrients and presents new perspectives for combination supplements in DED treatment.

How gut microbiota may impact ocular surface homeostasis and related disorders

Changes in the bacterial flora in the gut, also described as gut microbiota, are readily acknowledged to be associated with several systemic diseases, especially those with an inflammatory, neuronal, psychological or hormonal factor involved in the pathogenesis and/or the perception of the disease. Maintaining ocular surface homeostasis is also based on all these four factors, and there is accumulating evidence in the literature on the relationship between gut microbiota and ocular surface diseases. The mechanisms involved are mostly interconnected due to the interaction of central and peripheral neuronal networks, inflammatory effectors and the hormonal system. A better understanding of the influence of the gut microbiota on the maintenance of ocular surface homeostasis, and on the onset or persistence of ocular surface disorders could bring new insights and help elucidate the epidemiology and pathology of ocular surface dynamics in health and disease. Revealing the exact nature of these associations could be of paramount importance for developing a holistic approach using highly promising new therapeutic strategies targeting ocular surface diseases.

Targeting the Gut-Eye Axis: An Emerging Strategy to Face Ocular Diseases

The human microbiota refers to a large variety of microorganisms (bacteria, viruses, and fungi) that live in different human body sites, including the gut, oral cavity, skin, and eyes. In particular, the presence of an ocular surface microbiota with a crucial role in maintaining ocular surface homeostasis by preventing colonization from pathogen species has been recently demonstrated. Moreover, recent studies underline a potential association between gut microbiota (GM) and ocular health. In this respect, some evidence supports the existence of a gut-eye axis involved in the pathogenesis of several ocular diseases, including age-related macular degeneration, uveitis, diabetic retinopathy, dry eye, and glaucoma. Therefore, understanding the link between the GM and these ocular disorders might be useful for the development of new therapeutic approaches, such as probiotics, prebiotics, symbiotics, or faecal microbiota transplantation through which the GM could be modulated, thus allowing better management of these diseases.

Lessons from Animal Models in Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a connective tissue disease characterized by a wide spectrum of clinical features, extending from a benign glandular disease to an aggressive systemic disorder and/or lymphoma. The pathogenesis of Sjögren's syndrome (SS) is not completely understood, but it is assumed that pathogenesis of SS is multifactorial. The studies based on the animal models of SS provided significant insight in SS disease pathogenesis and management. The aim of this review is to summarize current studies on animal models with primary SS-like symptoms and discuss the impact of these studies on better understanding pathogenesis and management of Sjögren's syndrome. Databases PubMed, Web of Science, Scopus and Cochrane library were searched for summarizing studies on animal models in SS. Available data demonstrate that animal models are highly important for our understanding of SS disease.

Gut microbiota and eye diseases: a bibliometric study and visualization analysis

Introduction

Recently the role of gut microbial dysbiosis in many ocular disorders, including but not limited to uveitis, age-related macular degeneration (AMD), diabetic retinopathy (DR), dry eye, keratitis and orbitopathy is a hot research topic in the field. Targeting gut microbiota to treat these diseases has become an unstoppable trend. Bibliometric study and visualization analysis have become essential methods for literature analysis in the medical research field. We aim to depict this area's research hotspots and future directions by bibliometric software and methods.

Methods

We search all the related publications from the Web of Science Core Collection. Then, CiteSpace was applied to analyze and visualize the country distributions, dual-map overlay of journals, keyword bursts, and co-cited references. VOSviewer was employed to identify authors, co-cited authors, journals and co-cited journals and display the keyword co-occurrence networks.

Results

A total of 284 relevant publications were identified from 2009 to 2023. The number of studies has been small in the first five years and has grown steadily since 2016. These studies were completed by 1,376 authors from 41 countries worldwide, with the United States in the lead. Lin P has published the most papers while Horai R is the most co-cited author. The top journal and co-cited journal are both Investigative Ophthalmology & Visual Science. In the keyword co-occurrence network, except gut microbiota, inflammation becomes the keyword with the highest frequency. Co-citation analyses reveal that gut dysbiosis is involved in common immune- and inflammation-mediated eye diseases, including uveitis, diabetic retinopathy, age-related macular degeneration, dry eye, and Graves' orbitopathy, and the study of microbiomes is no longer limited to the bacterial populations. Therapeutic strategies that target the gut microbiota, such as probiotics, healthy diet patterns, and fecal microbial transplantation, are effective and critical to future research.

Conclusions

In conclusion, the bibliometric analysis displays the research hotspots and developmental directions of the involvement of gut microbiota in the pathogenesis and treatment of some ocular diseases. It provides an overview of this field's dynamic evolution and structural relationships.

The Link Between Gastrointestinal Microbiome and Ocular Disorders

The gut-eye axis has been hypothesized to be a factor in many eye pathologies. This review examines papers from PubMed about this topic. Bacterial commensals could either be protective by regulating the immune system or prove to be damaging to the gut mucosal wall and incite an inflammatory process. The balance between the two appears to be crucial in maintaining eye health. Imbalances have been implicated in ophthalmologic conditions. The use of probiotics, dietary modifications, antibiotics, and faecal microbiota transplant in mice with pathologies such as those encountered in our practice appears to reverse disease course or at least prevent its progression. Clinical trials are currently underway to investigate their clinical significance in diseased patients.

TFOS Lifestyle: Impact of nutrition on the ocular surface

Nutrients, required by human bodies to perform life-sustaining functions, are obtained from the diet. They are broadly classified into macronutrients (carbohydrates, lipids, and proteins), micronutrients (vitamins and minerals) and water. All nutrients serve as a source of energy, provide structural support to the body and/or regulate the chemical processes of the body. Food and drinks also consist of non-nutrients that may be beneficial (e.g., antioxidants) or harmful (e.g., dyes or preservatives added to processed foods) to the body and the ocular surface. There is also a complex interplay between systemic disorders and an individual's nutritional status. Changes in the gut microbiome may lead to alterations at the ocular surface. Poor nutrition may exacerbate select systemic conditions. Similarly, certain systemic conditions may affect the uptake, processing and distribution of nutrients by the body. These disorders may lead to deficiencies in micro- and macro-nutrients that are important in maintaining ocular surface health. Medications used to treat these conditions may also cause ocular surface changes. The prevalence of nutrition-related chronic diseases is climbing worldwide. This report sought to review the evidence supporting the impact of nutrition on the ocular surface, either directly or as a consequence of the chronic diseases that result. To address a key question, a systematic review investigated the effects of intentional food restriction on ocular surface health; of the 25 included studies, most investigated Ramadan fasting (56%), followed by bariatric surgery (16%), anorexia nervosa (16%), but none were judged to be of high quality, with no randomized-controlled trials.

Perioperative probiotics attenuates postoperative cognitive dysfunction in elderly patients undergoing hip or knee arthroplasty: A randomized, double-blind, and placebo-controlled trial

Background

Postoperative cognitive dysfunction (POCD) is a common complication in elderly patients following surgery. The preventive and/or treatment strategies for the incidence remain limited.

Objective

This study aimed to investigate the preventive effect of perioperative probiotic treatment on POCD in elderly patients undergoing hip or knee arthroplasty.

Methods

After obtaining ethical approval and written informed consent, 106 patients (age ≥60 years) were recruited, who scheduled elective hip or knee arthroplasty, from 16 March 2021 to 25 February 2022 for this randomized, double-blind, and placebo-controlled trial. They were randomly assigned with a 1:1 ratio to receive either probiotics or placebo treatment (four capsules, twice/day) from hospital admission until discharge. Cognitive function was assessed with a battery of 11 neuropsychological tests on the admission day and the seventh day after surgery, respectively.

Results

A total of 96 of 106 patients completed the study, and their data were finally analyzed. POCD occurred in 12 (26.7%) of 45 patients in the probiotic group and 29 (56.9%) of 51 patients in the placebo group (relative risk [RR], 0.47 [95% confidence interval [CI], 0.27 to 0.81]; P = 0.003). Among them, mild POCD occurred in 11 (24.4%) in the probiotic group and 24 (47.1%) in the placebo group (RR, 0.52 [95% CI, 0.29 to 0.94]; P = 0.022). No significant difference in severe POCD incidence was found between the two groups (P = 0.209). Compared with the placebo group, the verbal memory domain cognitive function was mainly improved in the probiotic group.

Conclusion

Probiotics may be used perioperatively to prevent POCD development and improve verbal memory performance in elderly patients receiving hip or knee arthroplasty.

Clinical trial registration

www.chictr.org.cn, identifier: ChiCTR2100045620.

Probiotics Mechanism of Action on Immune Cells and Beneficial Effects on Human Health

Immune cells and commensal microbes in the human intestine constantly communicate with and react to each other in a stable environment in order to maintain healthy immune activities. Immune system-microbiota cross-talk relies on a complex network of pathways that sustain the balance between immune tolerance and immunogenicity. Probiotic bacteria can interact and stimulate intestinal immune cells and commensal microflora to modulate specific immune functions and immune homeostasis. Growing evidence shows that probiotic bacteria present important health-promoting and immunomodulatory properties. Thus, the use of probiotics might represent a promising approach for improving immune system activities. So far, few studies have been reported on the beneficial immune modulatory effect of probiotics. However, many others, which are mainly focused on their metabolic/nutritional properties, have been published. Therefore, the mechanisms behind the interaction between host immune cells and probiotics have only been partially described. The present review aims to collect and summarize the most recent scientific results and the resulting implications of how probiotic bacteria and immune cells interact to improve immune functions. Hence, a description of the currently known immunomodulatory mechanisms of probiotic bacteria in improving the host immune system is provided.

The Gut-Eye Axis: Correlation Between the Gut Microbiota and Autoimmune Dry Eye in Individuals With Sjögren Syndrome

ABSTRACT

The impact of gut microbiota on human health, autoimmunity, and disease occurrence has long been recognized since the advancement of metagenomic sequencing technology has enabled a new level of perspective on the human microbiome. Emerging findings also suggest the existence of a gut-eye axis, wherein gut dysbiosis may be a crucial factor affecting the onset and progression of multiple ocular diseases. Sjögren syndrome (SS) is a chronic autoimmune disease mainly affecting the exocrine glands, primarily the lacrimal gland in the eye, resulting in severe dry eye. Although there are currently various treatments for environmental dry eye, the efficacy for SS-related autoimmune dry eye is limited, and new and more effective therapies still need to be explored. The latest studies have demonstrated that the gut microbiota plays a key role in the pathogenesis of autoimmune dry eye. This review describes the effect of gut microbiota on the ocular surface of autoimmune dry eye; introduces the presumable pathways forming the "gut dysbiosis-ocular surface-lacrimal gland axis"; discusses the advantages of restoring intestinal microecology to treat dry eye by fecal microbiota transplantation or probiotics, which are expected to provide perspectives into the correlation between the gut microbiome and dry eye; enhance our understanding of the pathogenesis in autoimmune dry eye; and be useful in the development of future interventions of dry eye by regulating the gut microbiota.

Gastrointestinal microbiome and primary Sjögren's syndrome: a review of the literature and conclusions

The recognition of the profound impact of the human gastrointestinal microbiome (GM) on human autoimmune diseases has gradually increased thanks to deeper research efforts. As a systemic autoimmune disease, primary Sjögren's syndrome (pSS) cannot be completely cured. Human studies have revealed that GM species and diversity are altered in patients with pSS compared with healthy individuals. Animal studies have provided possible mechanisms for the association between pSS and GM. The potential role of GM in pSS is exerted through several mechanisms. GM dysbiosis leads to increased intestinal permeability, which increases the risk of GM antigen exposure and activates specific autoreactive T lymphocytes via "molecular mimicry". In addition, GM antigen exposure and intestinal immune tolerance loss caused by GM dysbiosis together induce chronic local gut mucosal inflammation, which deteriorates to systemic chronic non-specific inflammation with the circulation of pro-inflammatory lymphocytes and cytokines. These factors eventually activate autoreactive B lymphocytes and lead to pSS. If GM plays a key role in the pathogenesis of pSS, clarifying the underlying mechanisms will be helpful for the development of new therapies targeting GM for dry eye associated with pSS. This review summarizes the latest knowledge about the relationship between GM and pSS, with the aim of contributing to future research and to the development of new clinical applications.

Shotgun metagenomic sequencing analysis of ocular surface microbiome in Singapore residents with mild dry eye

The ocular surface microbiome has implications for ocular surface inflammation and immunology. Previous shotgun metagenomics analyses were performed in China, showing results that differed according to environment and age. Patients with Sjogren's syndrome were reported to have altered conjunctival microbiome, but such studies have not been done in milder dry eye. The aim of this study is to describe the conjunctival microbiome in people with mild dry eye in Singapore. Samples were collected from 14 participants with mild dry eye and 10 age-matched comparison participants recruited from Singapore National Eye Centre (SNEC) clinics. Shotgun metagenomic sequencing analysis was employed to evaluate the conjunctival microbiome composition. Proteobacteria formed the predominant phylum in the conjunctiva. As in a study from a coastal city in China, Achromobacter spp. was numerically most abundant. Compared to age-matched controls, the conjunctival microbial composition in mild dry eye was similar. Several microorganisms, including Streptococcus spp. increased in representation with age, and the abundance of Staphylococcus correlated with Schirmer readings. In addition, when cultured corneal epithelial cells were exposed to three strains of Achromobacter xylosoxidans, cytokines such as TNF-α and IL-6 were upregulated in the cell lysates and supernatants. Ourresults suggest that age is an important factor that affects composition of the conjunctival microbiome, and relative abundance of specific microorganism may vary according to the environment of the human host.

The Impact of Probiotics and Prebiotics on Dry Eye Disease Signs and Symptoms

Dry eye is considered an inflammatory disease. Gut microbiota are important in the regulation of low-grade chronic inflammation, including in the eye. Probiotics and prebiotics are increasingly used to regulate chronic-disease-associated gut dysbiosis. Therefore, this double-masked, randomized controlled clinical trial aimed to explore the potential of oral probiotics and prebiotics in the management of dry eye disease. In total, 41 participants with dry eye received probiotic and prebiotic supplements (treatment group, n = 23) or respective placebos (control group, n = 18) for 4 months. Dry eye symptoms and signs were evaluated using the Ocular Surface Disease Index (OSDI), Dry Eye Questionnaire 5, osmolarity, non-invasive keratograph break-up time (NIKBUT), ocular surface staining, tear meniscus height (TMH), lipid layer thickness, and conjunctival redness. After 4 months, the average OSDI score of the treatment group was significantly better compared to that of the controls (16.8 ± 5.9 vs. 23.4 ± 7.4; p < 0.001). The NIKBUT and TMH did not change significantly with treatment (p = 0.31 and p = 0.84) but reduced significantly for controls on average by −5.5 ± 1.0 secs (p = 0.03) and 0.2 ± 0.1 mm (p = 0.02). These data suggest that probiotics and prebiotics might be effective in the management of dry eye disease.

Gut Microbiome and Its Influence On Ocular Surface and Ocular Surface Diseases

ABSTRACT

The gut microbiome plays a substantial immunologic and pathophysiologic role in maintaining the health of the host, and dysregulation of this dynamic ecosystem has been associated with several inflammatory conditions. Many studies have explored the influence of gut microbiota on the ocular surface and whether gut microbiota impact the pathophysiology of ophthalmic conditions. These findings have highlighted the advantages of enhancing gut microbes through probiotics, prebiotics, diet, vitamin supplementations, and fecal microbial transplant in clinical practice. The purpose of this review article was to provide an up-to-date overview of the knowledge on this topic. Further exploration of this area of research is important to help guide new therapeutic targets to develop treatment and prevention of certain ocular surface diseases.

Gut Microbiota and Autoimmune Diseases: A Charming Real World Together with Probiotics

BACKGROUND

The role of gut microbiota in human disease is fascinating for hundreds of researchers worldwide. Many works have highlighted that gut microbiota modulates the immune system and that its disruption can trigger autoimmune and inflammatory immune-mediated diseases. Probiotics are able to positively modify microbiota composition.

OBJECTIVE

The aim of this review is to report the most important findings regarding the effects of probiotics administration in the most common autoimmune disease and inflammatory immune-mediated diseases.

METHODS

Literature research was performed in PubMed, Google Scholar, and Medline, as well as in specific journal websites using the keywords: "autoimmunity", "microbiota", and "probiotics". The article selection has been made independently by three authors, and controversies have been solved by a fourth researcher. Only English-language articles were included and preference was given to clinical trials, meta-analysis, and case series. After the review process, 68 articles have been considered.

RESULTS

Relying on this evidence, many studies have investigated the potential of probiotics in restoring gut eubiosis, thus affecting pathogenesis, clinical manifestations, and course of these pathologies. Even in the light of few and sometimes contradictory studies, physicians should start to consider these preliminary findings when approaching patients suffering from autoimmune disease. After an accurate case-by-case evaluation of potential candidates, probiotics might be introduced besides the standard therapeutic plan as supportive measures.

The gut microbiota in retinal diseases

The gut microbiota is a complex ecosystem that inhabits the gastrointestinal tract and consists of archaea, fungi, viruses, and bacteria, with bacteria being dominant. From birth onwards, it coevolves dynamically together with the host. The composition of the gut microbiota is under the influence of a complex interplay between both host and environmental factors. Scientific advances in the past few decades have shown that it is essential in maintaining homeostasis and tipping the balance between health and disease. In addition to its role in food digestion, the gut microbiota is implicated in regulating multiple physiological processes in the host gut mucosa and in distant organs such as the brain. Persistent imbalance between gut microbial communities, termed "dysbiosis," has been associated with several inflammatory and metabolic diseases as well as with central nervous system disorders. In this review, we present the state of the art of current knowledge on an emerging concept, the microbiota-retina axis, and the potential role of its disturbance in the development of retinopathies. We also describe several microbiota-targeting strategies that could constitute preventive and therapeutic tools for retinopathies.

Microbiota and Ocular Diseases

Recent advances have identified significant associations between the composition and function of the gut microbiota and various disorders in organ systems other than the digestive tract. Utilizing next-generation sequencing and multiomics approaches, the microbial community that possibly impacts ocular disease has been identified. This review provides an overview of the literature on approaches to microbiota analysis and the roles of commensal microbes in ophthalmic diseases, including autoimmune uveitis, age-related macular degeneration, glaucoma, and other ocular disorders. In addition, this review discusses the hypothesis of the "gut-eye axis" and evaluates the therapeutic potential of targeting commensal microbiota to alleviate ocular inflammation.

A Review of the Impact of Alterations in Gut Microbiome on the Immunopathogenesis of Ocular Diseases

Recent studies have highlighted the association between ocular diseases and microbiota profiles of the host intestinal tract and oral cavity. There is mounting evidence supporting the existence of a 'gut-eye axis', whereby changes in gut microbiome alter host immunity, with consequential implications for ocular health and disease. In this review, we examined recent published findings on the association between gut microbiome and ocular morbidity, based on 25 original articles published between 2011 to 2020. The review included both clinical and in vivo animal studies, with particular focus on the influence of the microbiome on host immunity and metabolism. Significant associations between altered intestinal microbiome and specific ocular diseases and pathological processes, including Behçet's syndrome, autoimmune uveitis, age-related macular degeneration, choroidal neovascularization, bacterial keratitis, and Sjögren-like lacrimal keratoconjunctivitis have been demonstrated. Furthermore, alterations in the gut microbiome resulted in quantifiable changes in the host immune response, suggesting immunopathogenesis as the basis for the link between intestinal dysbiosis and ocular disease. We also examined and compared different techniques used in the identification and quantification of gut microorganisms. With our enhanced understanding of the potential role of gut commensals in ophthalmic disease, the stage is set for further studies on the underlying mechanisms linking the gut microbiome, the host immune response, and the pathogenesis of ophthalmic disease.

Aquaporin5-Targeted Treatment for Dry Eye Through Bioactive Compounds and Gut Microbiota

Dry eye and dry mouth are the principal sources of morbidity for patients with Sjögren's syndrome (SS). There are few effective treatments, particularly systemic ones. Targeting aquaprin-5 (AQP5)-mediated tear secretion has been tested as a novel ancillary strategy and has proved promising. Patients have a great interest in using complementary medicine, including nutraceuticals and bioactive compounds to alleviate their symptoms. Potential mechanisms by which phytocompounds and bioactive compounds may benefit SS ocular and mouth symptoms through modulation of AQP5 activity are presented within this review. Supplementation with prebiotics (such as polyphenols with high bioavailability) in SS patients with lower Firmicutes/Bacteroides (F/B) community ratio phenotype, through administration of butyrate-producing diets, is proposed as ancillary strategy for dry eye and mouth. The potential use of natural bioactive compounds to treat dry eye could also apply to dry mouth occurring in the context of aging and SS. This novel hypothesis could have implications with respect to planning a successful dietary regimen for achieving and maintaining a normal gut microbiota in SS patients. This regimen would include augmenting butyrate-producing foodstuffs and/or polyphenol-rich syrups, and high amounts of some specific probiotic-rich foodstuffs such as yogurt, soy yogurt, or as probiotic supplements. There are applications for pharmaceutical and nutraceutical products aiming to relieve dry eye and mouth.

Dry eye disease: an (in)convenient truth

The salient rise of chronic disease from the mid-twentieth century threatens to overwhelm public health systems in an increasing number of countries and is now considered an epidemic. Dry eye disease is an underappreciated disorder that bears all the hallmarks of chronic disease. Preventative health care seeks improved and sustainable patient engagement in the self-management of health to limit the progress and extent of chronic disease. Anthropogenic environments engendering lifestyles and behaviours that can be detrimental to human health, can be considered as direct or indirect threats to successful preventative health strategies. Chronic disease can be viewed as the result of physiological responses of the human body to the modern environment. The quest for an increasingly convenient, global, and disease-free lifestyle is ironically threatening to undo the gains in health and quality of life made over the last one hundred years. Considering dry eye disease as an anthropogenic chronic disease, contributions of diet (food and beverages consumed) and nutrition (extending to relationships with self, community, and nature) to development of dry eye disease are explored in this review. Evidence of environmental and behavioural instigators of chronic disease with an emphasis on production, disbursement, and preservation of food, is presented. Furthermore, evidence of traditional food practices that offer resistance to the development of chronic systemic inflammatory disorders are reviewed as an exemplar of potential strategies that can be put into practice by individuals and communities to reinstate a balanced life, community and planet.

Age-Dependent Distinct Distributions of Dendritic Cells in Autoimmune Dry Eye Murine Model

We investigated whether aging-dependent changes in dendritic cell (DC) distributions are distinct in autoimmune dry eye compared with an aging-related murine model. Corneal staining and tear secretion were evaluated in young and aged C57BL/6 (B6) and NOD.B10.H2b mice (NOD). In the corneolimbus, lacrimal gland (LG), and mesenteric lymph node (MLN), CD11b- and CD11b+ DCs, CD103+ DCs and MHC-IIhi B cells were compared between young and aged B6 and NOD mice. With increased corneal staining, tear secretion decreased in both aged B6 and NOD mice (p < 0.001). In both aged B6 and NOD mice, the percentages of corneolimbal CD11b+ DCs were higher (p < 0.05) than those in young mice. While, the percentages of lymph nodal CD103+ DCs were higher in aged B6 and NOD mice (p < 0.05), the percentages of corneolimbal CD103+ DCs were only higher in aged NOD mice (p < 0.05). In aged NOD mice, the proportions of lacrimal glandial and lymph nodal MHC-IIhi B cells were also higher than those in young mice (p < 0.05). It indicates that corneolimbal or lacrimal glandial distribution of CD103+ DCs or MHC-IIhi B cells may be distinct in aged autoimmune dry eye models compared to those in aged immune competent murine models.

MAIT Cells and Microbiota in Multiple Sclerosis and Other Autoimmune Diseases

The functions of mucosal-associated invariant T (MAIT) cells in homeostatic conditions include the interaction with the microbiota and its products, the protection of body barriers, and the mounting of a tissue-repair response to injuries or infections. Dysfunction of MAIT cells and dysbiosis occur in common chronic diseases of inflammatory, metabolic, and tumor nature. This review is aimed at analyzing the changes of MAIT cells, as well as of the microbiota, in multiple sclerosis and other autoimmune disorders. Common features of dysbiosis in these conditions are the reduced richness of microbial species and the unbalance between pro-inflammatory and immune regulatory components of the gut microbiota. The literature concerning MAIT cells in these disorders is rather complex, and sometimes not consistent. In multiple sclerosis and other autoimmune conditions, several studies have been done, or are in progress, to find correlations between intestinal permeability, dysbiosis, MAIT cell responses, and clinical biomarkers in treated and treatment-naïve patients. The final aims are to explain what activates MAIT cells in diseases not primarily infective, which interactions with the microbiota are potentially pathogenic, and their dynamics related to disease course and disease-modifying treatments.

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.

Lactobacillus plantarum and Bifidobacterium bifidum alleviate dry eye in mice with exorbital lacrimal gland excision by modulating gut inflammation and microbiota

In order to understand the efficacy of probiotics against dry eye syndrome, we selected anti-inflammatory probiotics Lactobacillus plantarum NK151 and Bifidobacterium bifidum NK175, which increased the ratio of IL-10 to TNF-α expression, from the human gut bacteria collection and examined their effects on tear secretion and cornea/conjunctiva inflammation in mice with excision of the unilateral exorbital lacrimal gland and 1% atropine and 0.1% benzalkonium chloride solution (ELA)-induced dry eye. Exposure to ELA significantly reduced tear secretion in mice, assessed by the phenol red thread tear test. However, oral gavage of NK151 and/or NK175 significantly increased ELA-suppressed tear secretion, IL-10 expression, and goblet cell population and decreased the ELA-induced corneal fluorescein-staining score, IL-1β and TNF-α expression in the conjunctiva. They also suppressed ELA-induced myeloperoxidase, IL-1β, and TNF-α expression. In particular, they increased the ratio of IL-10 to TNF-α expression in the colon. Their treatments increased ELA-induced α-diversity reduction to that of the control group and partially restored ELA-shifted β-diversity to that of the control group. Oral gavage of NK151 and/or NK175 reduced ELA-induced Verrucomicrobia and Actinobacteria populations at the phylum level. Furthermore, they reduced ELA-induced Bacteroidaceae, Akkemansiaceae, and AC160630_f populations and increased ELA-suppressed Lactobacillaceae and Muribaculaceae populations at the family level. These gut bacteria populations exhibited significant correlation with the tear secretion volume. In conclusion, NK151 and/or NK175 alleviated dry eye by modulating the expression ratio of pro-inflammatory cytokines such as TNF-α and anti-inflammatory cytokines such as IL-10 and gut microbiota composition.

Effect of IRT5 probiotics on dry eye in the experimental dry eye mouse model

Objective

To investigate the clinical effects of IRT5 probiotics in the environmental dry eye model.

Methods

Eight week old male C57BL/6 mice were randomly divided into two groups; control group (n = 16) received oral gavage of 300 μL phosphate-buffered saline (PBS) alone once daily, IRT5 group (n = 9) received oral gavage of 1 x 10⁹ CFU IRT5 probiotics powder in 300 μL PBS once daily, both groups for 11 to 12 days. Simultaneously, all mice underwent dry eye induction. Tear secretion, corneal staining and conjunctival goblet cell density were evaluated. Quantative real-time polymerase chain reaction (RT-PCR) for inflammation-related markers was performed. 16S ribosomal RNA of fecal microbiome was analyzed and compositional difference, alpha and beta diversities were assessed.

Results

There was no difference in NEI score but significant increase in tear secretion was observed in IRT5 group (p < 0.001). There was no significant difference in goblet cell density between groups. Quantative RT-PCR of cornea and conjunctiva revealed increased TNF-α expression in IRT5 group (p < 0.001) whereas other markers did not significantly differ from control. IRT5 group had significantly increased species diversity by Shannon index (p = 0.041). Beta diversity of genus by UniFrac principle coordinates analysis showed significant distance between groups (p = 0.001). Compositional differences between groups were observed and some were significantly associated with tear secretion. Multivariate linear regression analysis revealed Christensenellaceae (p = 0.009), Lactobacillus Helveticus group (p = 0.002) and PAC001797_s (p = 0.011) to strongly influence tear secretion.

Conclusion

In experimental dry eye model, IRT5 probiotics treatment partially improves experimental dry eye by increasing tear secretion which was associated with and influenced by the change in intestinal microbiome. Also, intestinal microbiome may affect the lacrimal gland through a different mechanism other than regulating inflammation.

Can Gut Microbiota Affect Dry Eye Syndrome?

Using metagenomics, continuing evidence has elicited how intestinal microbiota trigger distant autoimmunity. Sjögren's syndrome (SS) is an autoimmune disease that affects the ocular surface, with frequently unmet therapeutic needs requiring new interventions for dry eye management. Current studies also suggest the possible relation of autoimmune dry eye with gut microbiota. Herein, we review the current knowledge of how the gut microbiota interact with the immune system in homeostasis as well as its influence on rheumatic and ocular autoimmune diseases, and compare their characteristics with SS. Both rodent and human studies regarding gut microbiota in SS and environmental dry eye are explored, and the effects of prebiotics and probiotics on dry eye are discussed. Recent clinical studies have commonly observed a correlation between gut dysbiosis and clinical manifestations of SS, while environmental dry eye portrays characteristics in between normal and autoimmune. Moreover, a decrease in both the Firmicutes/Bacteroidetes ratio and genus Faecalibacterium have most commonly been observed in SS subjects. The presumable pathways forming the "gut dysbiosis-ocular surface-lacrimal gland axis" are introduced. This review may provide perspectives into the link between the gut microbiome and dry eye, enhance our understanding of the pathogenesis in autoimmune dry eye, and be useful in the development of future interventions.

Intestinal Dysbiosis in, and Enteral Bacterial Therapies for, Systemic Autoimmune Diseases

Recent studies have shown that a number of common autoimmune diseases have perturbations of their intestinal microbiome (dysbiosis). These include: Celiac Disease (CeD), Multiple Sclerosis (MS), Rheumatoid Arthritis (RA), Sjogren’s Syndrome (SS), and Type 1 diabetes (T1D). All of these have intestinal microbiomes that are different from healthy controls. There have been numerous studies using animal models of single probiotics (monoclonal) or mixtures of probiotics (polyclonal) and even complete microbiota transfer (fecal microbial transfer-FMT) to inhibit or delay the onset of autoimmune diseases such as the aforementioned common ones. However, proportionally, fewer clinical trials have utilized monoclonal therapies or FMT than polyclonal therapies for treating autoimmune diseases, even though bacterial mono-therapies do inhibit the development of autoimmune diseases and/or delay the onset of autoimmune diseases in rodent models of those autoimmune diseases. In this review then, we review the previously completed and currently ongoing clinical trials that are testing bacterial therapies (FMT, monoclonal, and polyclonal) to treat common autoimmune dseases and discuss the successes in using bacterial monotherapies to treat rodent models of these common autoimmune diseases.