Serotonin hormonally regulates lacrimal gland secretory function via the serotonin type 3a receptor

Mental burden of ocular surface discomfort

OBJECTIVE

This research investigates the associations between Dry Eye Disease (DED), pain perception, and mental health, focusing on how neuropathic pain influences treatment efficacy and patients' quality of life.

METHODS AND RESULTS

The study delves into the complexity of DED by assessing the correlation between ocular pain, depression, PTSD, and systemic pain conditions. It highlights the role of chronic neuropathic pain in DED and the nociceptive hypothesis, which suggests that psychological stress can exacerbate DED symptoms. Additionally, it explores diagnostic and management strategies for DED, emphasizing the importance of considering psychological aspects to improve patient care.

CONCLUSIONS

The intricate nature of DED, closely linked to mental health issues, requires a comprehensive diagnostic and therapeutic approach. Addressing neuropathic pain and psychological factors is crucial for effective DED management. Future efforts should focus on developing specific interventions targeting DED's physical and emotional impacts to enhance overall patient well-being.

Real Life Impact of Dry Eye Disease

Dry Eye Disease (DED) is an increasingly common condition that affects between 5% and 50% of the global population. Even though DED is most frequently diagnosed in older people, it has also been diagnosed in young adults and adolescents more frequently in recent years (employees, gamers). People can experience different types of symptoms and find it challenging to read, watch TV, cook, climb stairs, and meet friends. Mild and severe dry eye can reduce quality of life similarly to mild psoriasis and moderate-to-severe angina. Furthermore, DED patients experience serious difficulties driving vehicles, especially at night, and show a decrease in work productivity, which, when combined with the relevant indirect cost that this condition produces, poses a serious challenge in our days. In addition, DED patients are more likely to develop depression and suicidal ideations and experience frequent sleep disorders. Finally, it is discussed how lifestyle changes, such as increased physical activity, blinking exercises, and a proper diet, have positive implications for the management of this condition. Our aim is to draw attention to the negative effects of dry eye in real life, which are unique to each patient, especially as they relate to the non-visual symptoms experienced by DED patients.

Congenital aniridia beyond black eyes: From phenotype and novel genetic mechanisms to innovative therapeutic approaches

Congenital PAX6-aniridia, initially characterized by the absence of the iris, has progressively been shown to be associated with other developmental ocular abnormalities and systemic features making congenital aniridia a complex syndromic disorder rather than a simple isolated disease of the iris. Moreover, foveal hypoplasia is now recognized as a more frequent feature than complete iris hypoplasia and a major visual prognosis determinant, reversing the classical clinical picture of this disease. Conversely, iris malformation is also a feature of various anterior segment dysgenesis disorders caused by PAX6-related developmental genes, adding a level of genetic complexity for accurate molecular diagnosis of aniridia. Therefore, the clinical recognition and differential genetic diagnosis of PAX6-related aniridia has been revealed to be much more challenging than initially thought, and still remains under-investigated. Here, we update specific clinical features of aniridia, with emphasis on their genotype correlations, as well as provide new knowledge regarding the PAX6 gene and its mutational spectrum, and highlight the beneficial utility of clinically implementing targeted Next-Generation Sequencing combined with Whole-Genome Sequencing to increase the genetic diagnostic yield of aniridia. We also present new molecular mechanisms underlying aniridia and aniridia-like phenotypes. Finally, we discuss the appropriate medical and surgical management of aniridic eyes, as well as innovative therapeutic options. Altogether, these combined clinical-genetic approaches will help to accelerate time to diagnosis, provide better determination of the disease prognosis and management, and confirm eligibility for future clinical trials or genetic-specific therapies.

Neurostimulation for dry eye disease

PURPOSE OF REVIEW

To review the neuroanatomy and physiology of the basal and reflex tearing and present the available and developing therapies using the concept of neurostimulation in dry eye disease (DED).

RECENT FINDINGS

The most prevalent current DED treatments seek to supplement low tear volume and tear components or reduce inflammation. Neurostimulation is a unique approach gaining momentum in recent years, geared toward increasing the production of all basal tear components by stimulating the nerves responsible for producing the various tear components. The neuroanatomy of the lacrimal unit provides several possible access points to stimulate tear production through two arms of the sensory trigeminal nerves. Modes of stimulation include chemical or energy in electrical or magnetic form. Research thus far has shown that neurostimulation can achieve lacrimal, goblet cell, and meibomian gland stimulation. Subjectively it improves symptoms of DED. Clinically, neurostimulation has improved the signs and symptoms of DED by increasing basal tear production and tear volume.

SUMMARY

Neurostimulation using electrical, mechanical, or chemical means is a novel concept to increase tear production and was demonstrated to be an effective, safe, and well-tolerated method for managing DED.

Role of ocular surface neurobiology in neuronal-mediated inflammation in dry eye disease

Inflammation is the consequence of dry eye disease regardless of its etiology. Several injurious or harmless processes to the ocular surface neurons promote ocular surface neurogenic inflammation, leading to the vicious cycle of dry eye disease. These processes include the regular release of neuromediators during the conduction of ocular surface sensations, hyperosmolarity-induced ocular surface neuronal damage, neuro-regenerative activities, and neuronal-mediated dendritic cell activities. Neurogenic inflammation appears to be the main culprit, instigating the self-perpetuating inflammation observed in patients with dry eye disease.

Dry eye disease and psychiatric disorders: A systematic review and meta-analysis

The association between dry eye disease (DED) and psychiatric conditions is a highly researched topic. This work reviews the literature on this relationship, examining the prevalence and correlations of depression and anxiety with dry eye signs and symptoms. A comprehensive literature search of MEDLINE, EMBASE, PsycINFO, and gray literature was conducted, with keywords for dry eye and mood disorders, depression, anxiety, and suicide. Eligible studies underwent quality assessment using the Newcastle-Ottawa Scale. Meta-analysis was performed using STATA 15.0. Fixed- and random-effects models were computed based on the presence of heterogeneity. Thirty-two studies were included, with 31 reporting on depression and 19 on anxiety. Meta-analysis results found a depression prevalence of 40% (CI: [0.29, 0.52]) in DED patients, with 1.81 times higher odds of prevalence compared to controls (CI: [1.61, 2.02]). Prevalence of anxiety was 39% (CI: [0.15, 0.64]), with 2.32 times higher odds of prevalence compared to controls (CI: [1.67, 3.23]). Depression scores were significantly higher in patients with DED in all studies. Anxiety scores were significantly higher in DED patients in studies using all scales except the Hospital Anxiety and Depression Scale-Anxiety Subscale. DED symptom scores were significantly associated with depression (ES = 0.43; CI: [0.31, 0.55]) and anxiety (ES = 0.41; CI: [0.32, 0.50]) scores. In conclusion, depression and anxiety are more prevalent and severe in DED patients and are correlated with dry eye symptoms but not signs. These findings highlight the interrelationship between these disorders and have important implications for providing appropriate care to these patients.

Disruption of autophagy by increased 5-HT alters gut microbiota and enhances susceptibility to experimental colitis and Crohn's disease

Autophagy, an essential intracellular recycling process, is linked to the pathogenesis of various diseases including Crohn’s disease (CD). Factors that lead to the development of impaired autophagy during intestinal inflammation remain largely unexplored. Here, we report the impact of the interaction between serotonin [5-hydroxytryptamine;(5-HT)] and autophagy in colitis in mouse and human studies. In mice, increased gut 5-HT inhibited autophagy and led to enhanced colitis susceptibility. Reciprocally, mice with reduced 5-HT exhibited up-regulated autophagy via the mammalian target of rapamycin pathway, which resulted in significantly decreased colitis. Deletion of autophagy gene, Atg7, in an epithelial-specific manner, in concert with reduced 5-HT, promoted the development of a colitogenic microbiota and abolished the protective effects conferred by reduced 5-HT. Notably, in control and patient peripheral blood mononuclear cells, we uncovered that 5-HT treatment inhibited autophagy. Our findings suggest 5-HT as a previously unidentified therapeutic target in intestinal inflammatory disorders such as CD that exhibits dysregulated autophagy.

Dry Those Crying Eyes: The Role of Depression and Antidepressants in Dry Eye Disease

PURPOSE/BACKGROUND

Several clinic-based and large population studies have associated a depression diagnosis or depression severity with dry eye disease (DED) or symptoms. On the other hand, several other large population studies have found that antidepressant use was also associated with DED. Unfortunately, many of the studies finding associations between depression and DED did not control for concomitant antidepressant use, whereas the ones that found associations between antidepressant use and DED did not control for severity of depression or other psychiatric indications for selective serotonin inhibitor use. The purpose of this review was to identify whether depression and antidepressants play an independent role from one another in the onset of DED.

METHODS/PROCEDURES

A systematic literature review was conducted searching for DED studies that adjusted for concomitant antidepressant use in depressed patients, that adjusted for depressive symptoms in patients taking antidepressants, and that enrolled depressed patients who were not taking psychiatric medications at the time of the study. Additionally, the prescribing information of marketed antidepressants was reviewed to determine rates of dry eyes reported during clinical trials.

FINDINGS/RESULTS

The literature review initially identified 43 studies with 13 fitting the inclusion criteria. Although these studies varied in their quality, 7 revealed statistically significant associations between depression and DED, whereas 7, including 1 randomized trial, revealed significant associations between antidepressants and DED. Sixteen percent of the antidepressant package inserts inspected reported DED symptoms as an infrequent risk.

IMPLICATIONS/CONCLUSIONS

This review suggests that independent of one another, both depression and antidepressant use are associated with DED.

Establishment of functional epithelial organoids from human lacrimal glands

Background

Tear deficiency due to lacrimal gland (LG) dysfunction is one of the major causes of dry eye disease (DED). Therefore, LG stem cell-based therapies have been extensively reported to regenerate injured lacrimal tissue; however, the number of stem cells in the LG tissue is low, and 2D long-term cultivation reduces the differentiation capacity of stem cells. Nevertheless, 3D LG organoids could be an alternative for a DED therapy because it is capable of prolonged growth while maintaining the characteristics of the LG tissue. Here, we report the development of LG organoids and their application as cell therapeutics.

Methods

Digested cells from human LG tissue were mixed with Matrigel and cultured in five different media modified from human prostate/salivary organoid culture media. After organoid formation, the growth, specific marker expression, and histological characteristics were analyzed to authenticate the formation of LG organoids. The secretory function of LG organoids was confirmed  through calcium influx or proteomics analysis after pilocarpine treatment. To explore the curability of the developed organoids, mouse-derived LG organoids were fabricated and transplanted into the lacrimal tissue of a mouse model of DED.

Results

The histological features and specific marker expression of LG organoids were similar to those of normal LG tissue. In the pilocarpine-treated LG organoid, levels of internal Ca²⁺ ions and β-hexosaminidase, a lysosomal protein in tear fluid, were increased. In addition, the secreted proteins from pilocarpine-treated lacrimal organoids were identified through proteomics. More than 70% of the identified proteins were proven to exosome through gene ontology analysis. These results indicate that our developed organoid was pilocarpine reactive, demonstrating the function of LG. Additionally, we developed LG organoids from patients with Sjogren’s syndrome patients (SS) and confirmed that their histological features were similar to those of SS-derived LG tissue. Finally, we confirmed that the mouse LG organoids were well engrafted in the lacrimal tissue two weeks after transplantation.

Conclusion

This study demonstrates that the established LG organoids resemble the characteristics of normal LG tissue and may be used as a therapy for patients with DED.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02133-y.

Tryptophan as a Safe Compound in Topical Ophthalmic Medications: In Vitro and In Vivo Studies

Background: To evaluate the effects of tryptophan (TRP) on normal human corneal and conjunctival epithelium in vitro and the re-epithelization of corneal erosion in rabbits.Materials and methods: Corneal epithelial cell (10.014 pRSV-T) and conjunctival epithelial cell (HC0597) cultures were used. The cellular metabolism, viability, secretion of IL-1β, IL-6, IL-10, cytoskeleton organization, transwell migration were determined. Cells were incubated in the presence of TRP at 1-100 μM. After corneal de-epithelization rabbits received TRP drops (100 μM), 5 times a day.Results: TRP increased conjunctival epithelium metabolism at 50 μM and increased the viability of corneal epithelium at 100 μM. TRP (10 μM) enhanced the production of IL-6 by the corneal epithelium and had no effect on IL-1β and IL-10.Conclusions: TRP had no influence on the cellular cytoskeleton but induced a significant pseudopodia projection in both epithelia. TRP did not influence corneal re-epithelization in vivo. TRP was not toxic for corneal and conjunctival epithelia.

Pathophysiological Role and Drug Modulation of Calcium Transport in Ocular Surface Cells

The ocular surface structure and extraocular accessory organs constitute the ocular surface system, which includes the cornea, conjunctiva, eyelids, lacrimal organs, and lacrimal passages. This system is composed of, and stabilized by, the corneal epithelium, conjunctival cells, conjunctival goblet cells, lacrimal acinar cells and Tenon's fibroblasts, all of which maintain the healthy eyeball surface system. Ocular surface diseases are commonly referred to corneal and conjunctival disease and external ocular disease, resulting from damage to the ocular surface structure. A growing body of evidence has indicated that abnormal activation of the KCa3.1 channel and Ca2+/ calmodulin-dependent kinase initiates ocular injury. Signaling pathways downstream of the irregular Ca2+ influx induce cell progression and migration, and impair tight junctions, epithelial transport and secretory function. In this overview, we summarize the current knowledge regarding ocular surface disease in terms of physical and pathological alteration of the ocular system. We dissect in-depth, the mechanisms underlying disease progression, and we describe the current calcium transport therapeutics and the obstacles that remain to be solved. Finally, we summarize how to integrate the research results into clinical practice in the future.

Corneal Sensory Experience via Transient Receptor Potential Vanilloid 1 Accelerates the Maturation of Neonatal Tearing

Tearing maturates rapidly after birth, and external environmental challenges play a key role in promoting lacrimal functional maturation. However, little is known about the facilitative factors underlying this developmental process or the potential of application of these factors to treat hypofunction of the lacrimal gland. In this study, eye opening and the subsequent ocular surface sensory experience, which is thought to be involved in postnatal maturation of lacrimal function, were investigated. Our results demonstrated that eye opening after birth is essential for the maturation of neonatal tearing. The maturation process of lacrimal function is dependent on the ocular surface sensory experience via transient receptor potential cation channel subfamily member 1 after birth. This study provides, for the first time, important evidence of the sensory experience of the ocular surface in relation to the maturation of functional tear secretion during the postnatal period.

"Smart Eye Camera": An innovative technique to evaluate tear film breakup time in a murine dry eye disease model

Tear film breakup time (TFBUT) is an essential parameter used to diagnose dry eye disease (DED). However, a robust method for examining TFBUT in murine models has yet to be established. We invented an innovative device, namely, the "Smart Eye Camera", which addresses several problems associated with existing methods and is capable of evaluating TFBUT in a murine DED model. We compared images taken by existing devices and the Smart Eye Camera in a graft-versus-host disease-related DED murine model. We observed that the quality of the images obtained by the Smart Eye Camera were sufficient for practical use. Moreover, this new technique could be used to obtain measurements for several consecutive ocular phenotypes in a variety of environments. Here, we demonstrate the effectiveness of our new invention in the examination of ocular phenotypes, including TFBUT in a murine model. We highlight the potential for future translational studies adopting the Smart Eye Camera in clinical settings.

Autophagy: roles in intestinal mucosal homeostasis and inflammation

The intestinal mucosa is a site of multiple stressors and forms the barrier between the internal and external environment. In the intestine, a complex interplay between the microbiota, epithelial barrier and the local immune system maintains homeostasis and promotes a healthy gut. One of the major cellular catabolic processes that regulate this homeostasis is autophagy. Autophagy is required to maintain anti-microbial defense, epithelial barrier integrity and mucosal immune response. Dysregulation of the autophagy process causes disruption of several aspects of the intestinal epithelium and the immune system that can lead to an inappropriate immune response and subsequent inflammation. Genome-wide association studies have found an association between several risk loci in autophagy genes and inflammatory bowel disease. The aim of the current review is to provide an update on the role of autophagy in intestinal mucosal physiology and in the control of inappropriate inflammation.

The Relationship of Dry Eye Disease with Depression and Anxiety: A Naturalistic Observational Study

Purpose

In recent years, the relationship between dry eye disease (DED) and psychiatric disorders has been gaining attention. The relationship between dry eye symptoms and psychiatric symptoms has been reported in multiple retrospective studies. However, in previous studies there have been limitations to these observations, such as a lack of close examination of either DED or mood symptoms.

Methods

In this study, we evaluated the psychological state and social functionality of DED patients by administering validated psychiatric tests as well as ophthalmologic examinations twice during the course of DED treatment. Forty subjects (61.3 ± 18.1-years old) received the primary psychiatric assessments and 26 received the secondary psychiatric assessments.

Results

In a cross-sectional examination, we found patients with depressive and/or anxiety symptoms had higher Dry Eye Related Quality of Life Score (DEQ) scores, whereas the objective symptoms of DED did not differ between groups. We also found a positive relationship between depression/anxiety scores and DED subjective symptoms. On the other hand, in longitudinal examination, we found psychiatric symptoms had no impact on subjective and objective DED symptoms throughout the course of DED symptoms.

Conclusions

We found depression and anxiety were related to the subjective symptoms of DED but not the objective symptoms.

Translational Relevance

It is important to pay attention to psychiatric symptoms in patients with DED and an investigation into appropriate treatment strategies for patients with DED in combination with psychiatric symptoms is needed in the future.

Neurological and Inflammatory Manifestations in Sjögren's Syndrome: The Role of the Kynurenine Metabolic Pathway

For decades, neurological, psychological, and cognitive alterations, as well as other glandular manifestations (EGM), have been described and are being considered to be part of Sjögren's syndrome (SS). Dry eye and dry mouth are major findings in SS. The lacrimal glands (LG), ocular surface (OS), and salivary glands (SG) are linked to the central nervous system (CNS) at the brainstem and hippocampus. Once compromised, these CNS sites may be responsible for autonomic and functional disturbances that are related to major and EGM in SS. Recent studies have confirmed that the kynurenine metabolic pathway (KP) can be stimulated by interferon-γ (IFN-γ) and other cytokines, activating indoleamine 2,3-dioxygenase (IDO) in SS. This pathway interferes with serotonergic and glutamatergic neurotransmission, mostly in the hippocampus and other structures of the CNS. Therefore, it is plausible that KP induces neurological manifestations and contributes to the discrepancy between symptoms and signs, including manifestations of hyperalgesia and depression in SS patients with weaker signs of sicca, for example. Observations from clinical studies in acquired immune deficiency syndrome (AIDS), graft-versus-host disease, and lupus, as well as from experimental studies, support this hypothesis. However, the obtained results for SS are controversial, as discussed in this study. Therapeutic strategies have been reexamined and new options designed and tested to regulate the KP. In the future, the confirmation and application of this concept may help to elucidate the mosaic of SS manifestations.

Intravital Two-photon Imaging of Ca2+ signaling in Secretory Organs of Yellow Cameleon Transgenic Mice

Intracellular calcium ([Ca²⁺]i) signaling regulates physiological functions in most cells. In secretory organs, such as the pancreas, salivary gland, and lacrimal gland (LG), [Ca²⁺]i elevation in acinar cells triggers fluid secretion, which plays vital roles in the maintenance of functional health across the life-course. It is important to understand the secretory mechanism of secretory organs, but lack of analytic systems available for living animals limits the scope of research to gain deeper insights into the precise mechanism of secretion. We established an intravital imaging system for specific cell types of secretory organs to monitor the [Ca²⁺]i changes using mouse line expressing Yellow Cameleon 3.60, a genetically encoded Ca²⁺ indicator. Elevation of [Ca²⁺]i in specific cell types of secretory organs could be monitored after cholinergic stimulation ex vivo and intravitally. We found that a marked attenuation of LG [Ca²⁺]i response to cholinergic stimulation was induced under pathological conditions by postganglionic denervation. Intravital Ca²⁺ imaging in secretory organs will broaden our understanding of the cellular mechanisms in animal models of secretory diseases.