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

Changes in the ocular surface microbiome of patients with coronavirus disease 2019 (COVID-19)

Purpose

To elucidate the reasons behind the increased incidence of ocular disease in patients with coronavirus disease 2019 (COVID-19), this study delved deeper into the specific effects of COVID-19 on patients' ocular surface microbiome (OSM) and investigated its relationship with the increased incidence of ocular disease.

Methods

In this study, conjunctival sac swabs were collected from 43 participants for 16S rRNA amplicon sequencing. The participants were categorized into three groups based on their COVID-19 status: the control group (C group) consisted of 15 participants who showed no evidence of COVID-19, the experimental group (E group) included 15 participants who tested positive for COVID-19, and the COVID-19 recovery period group (R group) comprised 13 participants.

Results

In the comparison of alpha diversity, group E had a higher Shannon, Chao1 and Goods coverage index. When comparing beta diversity, groups E and R were more similar to each other. At the phylum level, although the OSM of the three groups was dominated by Proteobacteria, Actinobacteriota, Bacteroidota and Firmicutes, the compositional proportions were significantly different. At the genus level, the dominant species in the three OSM groups were significantly different, with Pseudomonas becoming the dominant genus in groups E and R compared to group C, and the abundance of Ralstonia decreasing significantly.

Conclusion

This study provides additional evidence supporting the association between the OSM and COVID-19, which contributes to our understanding of the potential mechanisms underlying ocular symptoms and complications associated with COVID-19 in the future.

Unveiling the gut-eye axis: how microbial metabolites influence ocular health and disease

The intricate interplay between the gut microbiota and ocular health has surpassed conventional medical beliefs, fundamentally reshaping our understanding of organ interconnectivity. This review investigates into the intricate relationship between gut microbiota-derived metabolites and their consequential impact on ocular health and disease pathogenesis. By examining the role of specific metabolites, such as short-chain fatty acids (SCFAs) like butyrate and bile acids (BAs), herein we elucidate their significant contributions to ocular pathologies, thought-provoking the traditional belief of organ sterility, particularly in the field of ophthalmology. Highlighting the dynamic nature of the gut microbiota and its profound influence on ocular health, this review underlines the necessity of comprehending the complex workings of the gut-eye axis, an emerging field of science ready for further exploration and scrutiny. While acknowledging the therapeutic promise in manipulating the gut microbiome and its metabolites, the available literature advocates for a targeted, precise approach. Instead of broad interventions, it emphasizes the potential of exploiting specific microbiome-related metabolites as a focused strategy. This targeted approach compared to a precision tool rather than a broad-spectrum solution, aims to explore the therapeutic applications of microbiome-related metabolites in the context of various retinal diseases. By proposing a nuanced strategy targeted at specific microbial metabolites, this review suggests that addressing specific deficiencies or imbalances through microbiome-related metabolites might yield expedited and pronounced outcomes in systemic health, extending to the eye. This focused strategy holds the potential in bypassing the irregularity associated with manipulating microbes themselves, paving a more efficient pathway toward desired outcomes in optimizing gut health and its implications for retinal 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.

Pharmacotherapy and Nutritional Supplements for Neovascular Eye Diseases

In this review, we aim to provide an overview of the recent findings about the treatment of neovascular retinal diseases. The use of conventional drugs and nutraceuticals endowed with antioxidant and anti-inflammatory properties that may support conventional therapies will be considered, with the final aim of achieving risk reduction (prevention) and outcome improvement (cooperation between treatments) of such sight-threatening proliferative retinopathies. For this purpose, we consider a medicinal product one that contains well-defined compound(s) with proven pharmacological and therapeutic effects, usually given for the treatment of full-blown diseases. Rarely are prescription drugs given for preventive purposes. A dietary supplement refers to a compound (often an extract or a mixture) used in the prevention or co-adjuvant treatment of a given pathology. However, it must be kept in mind that drug-supplement interactions may exist and might affect the efficacy of certain drug treatments. Moreover, the distinction between medicinal products and dietary supplements is not always straightforward. For instance, melatonin is formulated as a medicinal product for the treatment of sleep and behavioral problems; at low doses (usually below 1 mg), it is considered a nutraceutical, while at higher doses, it is sold as a psychotropic drug. Despite their lower status with respect to drugs, increasing evidence supports the notion of the beneficial effects of dietary supplements on proliferative retinopathies, a major cause of vision loss in the elderly. Therefore, we believe that, on a patient-by-patient basis, the administration of nutraceuticals, either alone or in association, could benefit many patients, delaying the progression of their disease and likely improving the efficacy of pharmaceutical drugs.

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.

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.

Natural killer cell homing and trafficking in tissues and tumors: from biology to application

Natural killer (NK) cells, a subgroup of innate lymphoid cells, act as the first line of defense against cancer. Although some evidence shows that NK cells can develop in secondary lymphoid tissues, NK cells develop mainly in the bone marrow (BM) and egress into the blood circulation when they mature. They then migrate to and settle down in peripheral tissues, though some special subsets home back into the BM or secondary lymphoid organs. Owing to its success in allogeneic adoptive transfer for cancer treatment and its "off-the-shelf" potential, NK cell-based immunotherapy is attracting increasing attention in the treatment of various cancers. However, insufficient infiltration of adoptively transferred NK cells limits clinical utility, especially for solid tumors. Expansion of NK cells or engineered chimeric antigen receptor (CAR) NK cells ex vivo prior to adoptive transfer by using various cytokines alters the profiles of chemokine receptors, which affects the infiltration of transferred NK cells into tumor tissue. Several factors control NK cell trafficking and homing, including cell-intrinsic factors (e.g., transcriptional factors), cell-extrinsic factors (e.g., integrins, selectins, chemokines and their corresponding receptors, signals induced by cytokines, sphingosine-1-phosphate (S1P), etc.), and the cellular microenvironment. Here, we summarize the profiles and mechanisms of NK cell homing and trafficking at steady state and during tumor development, aiming to improve NK cell-based cancer immunotherapy.

Lycium barbarum polysaccharide promotes corneal Re-epithelialization after alkaline injury

Chemical injury of the cornea results in epithelial defect and subsequent stromal scarring and infection. Our study aims to evaluate the effectiveness of pre-treatment of Lycium barbarum polysaccharide (LBP) in promoting corneal re-epithelialization after alkaline burn. The corneas of C57BL/6J mice were pre-treated with topical phosphate-buffered saline or LBP (0.2/2/20 mg/mL) for 7 days, following by 0.1M sodium hydroxide injury for 30 s and washing with distilled water for another 30 s. Area of epithelial defect and thickness of cornea were evaluated. Inflammatory cytokines and water channel expression levels were assessed using immunohistochemistry and Western blot. Compared to the injury group, mice with 2 mg/mL LBP pre-treatment revealed a significant decrease in fluorescein stained area after injury (p = 0.025), with increased epithelial layer thickness (p = 0.004). The corneal opacity was significantly reduced in the group with 2 mg/mL LBP pre-treatment followed by injury (p = 0.02). The expression of matrix metalloproteinase 12 (p = 0.033), platelet derived growth factor-BB (p = 0.031), and aquaporin 5 (p = 0.022) resulted in a decrease in expression level in group with 2 mg/mL LBP pre-treatment. Our results showed that 2 mg/mL LBP, with no apoptotic effect on corneal cells, promoted corneal epithelial growth and minimized disruption of the collagen architecture after injury in vivo. We suggest that LBP, as a natural Traditional Chinese Medicine, may potentially be a novel topical pre-treatment option for patients highly susceptible to ocular injury.

New Understanding of Diagnosis, Treatment and Prevention of Endometriosis

For 100 years, pelvic endometriosis has been considered to originate from the implantation of endometrial cells following retrograde menstruation or metaplasia. Since some observations, such as the clonal aspect, the biochemical variability of lesions and endometriosis in women without endometrium, the genetic-epigenetic (G-E) theory describes that endometriosis only begins after a series of cumulative G-E cellular changes. This explains that the endometriotic may originate from any pluripotent cell apart from the endometrium, that 'endometrium-like cells' can harbour important G-E differences, and that the risk is higher in predisposed women with more inherited incidents. A consequence is a high risk after puberty which decreases progressively thereafter. Considering a 10-year delay between initiation and performing a laparoscopy, this was observed in the United Arab Emirates, Belgium, France and USA. The subsequent growth varies with the G-E changes and the environment but is self-limiting probably because of the immunologic reaction and fibrosis. That each lesion has a different set of G-E incidents explains the variability of pain and the response to hormonal treatment. New lesions may develop, but recurrences after surgical excision are rare. The fibrosis around endometriosis belongs to the body and does not need to be removed. This suggests conservative excision or minimal bowel without safety margins and superficial treatment of ovarian endometriosis. This G-E concept also suggests prevention by decreasing oxidative stress from retrograde menstruation or the peritoneal microbiome. This suggests the prevention of vaginal infections and changes in the gastrointestinal microbiota through food intake and exercise. In conclusion, a higher risk of initiating endometriosis during adolescence was observed in UAE, France, Belgium and USA. This new understanding and the limited growth opens perspectives for earlier diagnosis and better treatment.