MyD88 Deficiency Protects Against Dry Eye-Induced Damage

BMSC-derived exosomes regulate the Treg/Th17 balance through the miR-21-5p/TLR4/MyD88/NF-κB pathway to alleviate dry eye symptoms in mice

Bone marrow mesenchymal stem cell (BMSC)-derived exosomes (BMSC-Exos) have a variety of biological functions and are extensively involved in the regulation of inflammatory diseases, as well as tissue repair and regeneration. However, the mechanism of action of these compounds in dry eye disease (DED) in mice is still unclear. This study demonstrated that the Treg/Th17 ratio was strongly imbalanced in DED clinical samples. BMSC-Exos can modulate the Treg/Th17 balance, improve the integrity of the corneal epithelial layer, and ameliorate DED progression in mice. Mechanistically, BMSC-Exos dramatically decreased the levels of IL-17 and IL-22; increased the levels of IL-4, IL-10, and TGF-β1; and increased tear secretion and the number of goblet cells in the conjunctiva in mice, thus alleviating the progression of DED. This effect is achieved by BMSC-Exos through the delivery of miR-21-5p to target and restrain TLR4, thereby restraining the MyD88/NF-κB pathway. Our study showed that the upregulation of miR-21-5p in BMSC-Exos may be a therapeutic target for DED. These findings support new ideas and a basis for treating DED, as well as for further study of the application value of exosomes in alleviating DED.

A PEDF peptide mimetic effectively relieves dry eye in a diabetic murine model by restoring corneal nerve, barrier, and lacrimal gland function

PURPOSE

The study investigated effectiveness of a novel PEDF peptide mimetic to alleviate dry eye-like pathologies in a Type I diabetic mouse model established using streptozotocin.

METHODS

Mice were treated topically for 3-6 weeks with Ppx (a 17-mer PEDF mimetic) 2x/day or vehicle. Corneal sensitivity, tear film, epithelial and endothelial injury were measured using Cochet-Bonnet esthesiometer, phenol red cotton thread wetting, fluorescein sodium staining, and ZO1 expression, respectively. Inflammatory and parasympathetic nerve markers and activation of the MAPK/JNK pathways in the lacrimal glands were measured.

RESULTS

Diabetic mice exhibited features of dry eye including reduced corneal sensation and tear secretion and increased corneal epithelium injury, nerve degeneration, and edema. Ppx reversed these pathologies and restored ZO1 expression and morphological integrity of the endothelium. Upregulation of IL-1β and TNFα, increased activation of P-38, JNK, and ERK, and higher levels of M3ACHR in diabetic lacrimal glands were also reversed by the peptide treatment.

CONCLUSION

The study demonstrates that topical application of a synthetic PEDF mimetic effectively alleviates diabetes-induced dry eye by restoring corneal sensitivity, tear secretion, and endothelial barrier and lacrimal gland function. These findings have significant implications for the potential treatment of dry eye using a cost-effective and reproducible approach with minimal invasiveness and no obvious side effects.

Saikosaponin F ameliorates depression-associated dry eye disease by inhibiting TRIM8-induced TAK1 ubiquitination

AIMS

Saikosaponin F (SsF) is one of the major active ingredients of Radix Bupleuri, an herb widely used in the treatment of depression. Studies have shown that dry eye disease often occurs together with depression. The aim of this study is to investigate whether SsF can improve depression-associated dry eye disease and explore the underlying mechanism.

METHODS

Behavioral test was used to verify the effect of SsF on CUMS-induced depression-like behaviors in mice. Corneal fluorescein staining, phenol red cotton thread test and periodic acid-Schiff (PAS) staining were used to observe the effect of SsF on depression-associated dry eye disease. Western blot (WB) was performed to observe the expression of TAK1 protein and key proteins of NF-κB and MAPK (P38) inflammatory pathways in the hippocampus and cornea. Immunohistochemical staining was used to observe the expression of microglia, and immunoprecipitation was used to observe K63-linked TAK1 ubiquitination. Subsequently, we constructed a viral vector sh-TAK1 to silence TAK1 protein to verify whether SsF exerted its therapeutic effect based on TAK1. The expression of inflammatory factors such as IL-1β, TNF-α and IL-18 in hippocampus and cornea were detected by ELISA. Overexpression of TRIM8 (OE-TRIM8) by viral vector was used to verify whether SsF improved depression-associated dry eye disease based on TRIM8.

RESULTS

SsF treatment significantly improved the depression-like behavior, increased tear production and restored corneal injury in depression-related dry eye model mice. SsF treatment downregulated TAK1 expression and TRIM8-induced K63-linked TAK1 polyubiquitination, while inhibiting the activation of NF-κB and MAPK (P38) inflammatory pathways and microglial expression. In addition, selective inhibition of TAK1 expression ameliorated depression-associated dry eye disease, while overexpression of TRIM8 attenuated the therapeutic effect of SsF on depression-associated dry eye disease.

CONCLUSION

SsF inhibited the polyubiquitination of TAK1 by acting on TRIM8, resulting in the downregulation of TAK1 expression, inhibition of inflammatory response, and improvement of CUMS-induced depression-associated dry eye disease.

Region-resolved multi-omics of the mouse eye

The eye is a complex organ consisting of multiple compartments with unique and specialized properties, and small disturbances in one eye region can result in impaired vision and blindness. Although there have been advancements in ocular research, the hierarchical molecular network in region-wide resolution, indicating the division of labor and crosstalk among different eye regions, is not yet comprehensively illuminated. Here, we present an atlas of region-resolved proteome and lipidome of mouse eye. Multiphoton microscopy-guided laser microdissection combined with in-depth label-free proteomics identifies 13,536 proteins across various mouse eye regions. Further integrative analysis of spectral imaging, label-free proteome, and imaging mass spectrometry of the lipidome and phosphoproteome reveals distinctive molecular features, including proteins and lipids of various anatomical mouse eye regions. These deposited datasets and our open proteome server integrating all information provide a valuable resource for future functional and mechanistic studies of mouse eye and ocular disease.

The influenza-injured lung microenvironment promotes MRSA virulence, contributing to severe secondary bacterial pneumonia

Influenza infection is substantially worsened by the onset of secondary pneumonia caused by bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). The bidirectional interaction between the influenza-injured lung microenvironment and MRSA is poorly understood. By conditioning MRSA ex vivo in bronchoalveolar lavage fluid collected from mice at various time points of influenza infection, we found that the influenza-injured lung microenvironment dynamically induces MRSA to increase cytotoxin expression while decreasing metabolic pathways. LukAB, a SaeRS two-component system-dependent cytotoxin, is particularly important to the severity of post-influenza MRSA pneumonia. LukAB's activity is likely shaped by the post-influenza lung microenvironment, as LukAB binds to (and is activated by) heparan sulfate (HS) oligosaccharide sequences shed from the epithelial glycocalyx after influenza. Our findings indicate that post-influenza MRSA pneumonia is shaped by bidirectional host-pathogen interactions: host injury triggers changes in bacterial expression of toxins, the activity of which may be shaped by host-derived HS fragments.

Bacteria and Dry Eye: A Narrative Review

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

Mussel-Inspired Microgel Encapsulated NLRP3 Inhibitor as a Synergistic Strategy Against Dry Eye

The inflammatory response mediated by oxidative stress is the main pathogenesis of dry eye, but clinical observations have shown that scavenging oxygen-free radicals alone has limited therapeutic effect. Moreover, the unique anatomy and physiology of the ocular surface result in low bioavailability of drugs, and higher concentration is required to achieve the desired efficacy, which, however, may bring systemic side effects. These problems pose a challenge, but the revelation of the ROS-NLRP3-IL-1β signaling axis opens up new possibilities. In this investigation, an NLRP3 inhibitor was successfully encapsulated in polydopamine-based microgels and used for dry eye treatment. It was demonstrated that the well-designed microgels exhibited good biocompatibility, prolonged drug retention time on the ocular surface, and effective inhibition of corneal epithelial damage and cell apoptosis. In addition, due to the synergistic effect, the NLRP3 inhibitor–loaded microgels could exert enhanced oxygen radical scavenging and inflammation-inhibiting effects at a lower dose than monotherapy. These findings suggest that polydopamine-based microgels have advantages as ocular surface drug delivery platforms and have promising applications in oxidative damage–related inflammatory diseases in synergy with anti-inflammatory drugs.

Altered Intrinsic Regional Spontaneous Brain Activity in Patients With Severe Obesity and Meibomian Gland Dysfunction: A Resting-State Functional Magnetic Resonance Imaging Study

Purpose

To evaluate potential regional homogeneity (ReHo) cerebrum function lesions in people with severe obesity and meibomian gland dysfunction (SM) and probe the connection between aberrant cerebrum activity and clinical manifestations.

Patients and Methods

An aggregation of 12 patients with SM, and 12 healthy controls (HCs) closely matched in age and gender were enrolled. We applied corneal confocal microscopy and fundus angiography to compare imaging distinctions between the two groups. SMs were required to carefully fill out the Hospital Anxiety Depression Scale (HADS) forms, and a correlation analysis was performed. ReHo was also utilized to appraise partial differences in spontaneous cerebrum function. Receiver operating characteristic (ROC) curves were created to partition ReHo values between patients with SM and the HCs.

Results

ReHo values for the left cerebellum (LC), right fusiform gyrus (RFG), left inferior temporal gyrus (LITG), left rectus gyrus (LRG), right thalamus (RT), right caudate (RC), left insula (LI), and left thalamus (LT) of subjects with SM were notably higher than those of the HCs (P < 0.05). ReHo values of the right middle frontal gyrus (RMFG) in subjects with SM were decreased notably compared to the HCs (P < 0.05). ReHo values for the RMFG showed a negative correlation with the anxiety scores (ASs; r = −0.961, P < 0.001) and ReHo values for the RFG showed a positive correlation with the depression scores (DSs; r = 0.676, P = 0.016). The areas under the ROC curve were 1.000 (P < 0.001) for the RMFG, LC, LITG, LRG, RC, LI, and LT and 0.993 (P < 0.001) for the RFG and RT. The results from the ROC curve analysis indicated that changes in the ReHo values of some brain regions may help diagnose SM.

Conclusion

Our research emphasized that patients with SM had lesions in synchronized neural activity in many encephalic areas. Our discoveries may provide beneficial information for exploring the neuromechanics of SM.

Mucosal immunology of the ocular surface

The eye is a sensory organ exposed to the environment and protected by a mucosal tissue barrier. While it shares a number of features with other mucosal tissues, the ocular mucosal system, composed of the conjunctiva, Meibomian glands, and lacrimal glands, is specialized to address the unique needs of (a) lubrication and (b) host defense of the ocular surface. Not surprisingly, most challenges, physical and immunological, to the homeostasis of the eye fall into those two categories. Dry eye, a dysfunction of the lacrimal glands and/or Meibomian glands, which can both cause, or arise from, sensory defects, including those caused by corneal herpes virus infection, serve as examples of these perturbations and will be discussed ahead. To preserve vision, dense neuronal and immune networks sense various stimuli and orchestrate responses, which must be tightly controlled to provide protection, while simultaneously minimizing collateral damage. All this happens against the backdrop of, and can be modified by, the microorganisms that colonize the ocular mucosa long term, or that are simply transient passengers introduced from the environment. This review will attempt to synthesize the existing knowledge and develop trends in the study of the unique mucosal and immune elements of the ocular surface.

Immune signaling in rosacea

Rosacea is a common chronic skin disease affecting mostly people aged 40 and above, with currently no cure. When it affects the eyelids and periocular skin, it leads to dry eye and potentially corneal damage. Research performed over the last decade shed light into the potential mechanisms leading to skin hypersensitivity and provided promising avenues for development of novel, rational therapeutics aimed at reducing the skin inflammatory state. In this review, we discuss the current knowledge on the mechanisms of rosacea in general and of periocular skin-affecting disease in particular, identify key questions that remain to be answered in future research, and offer a disease model that can explain the key characteristics of this disease, with particular emphasis on a potential positive feedback loop that could explain both the acute and chronic features of rosacea.

PEDF Gene Deletion Disrupts Corneal Innervation and Ocular Surface Function

Purpose

The cornea is richly innervated by the trigeminal ganglion (TG) and its function supported by secretions from the adjacent lacrimal (LG) and meibomian glands (MG). In this study we examined how pigment epithelium–derived factor (PEDF) gene deletion affects the cornea structure and function.

Methods

We used PEDF hemizygous and homozygous knockout mice to study effects of PEDF deficiency on corneal innervation assessed by beta tubulin staining, mRNA expression of trophic factors, and PEDF receptors by adjacent supporting glands, corneal sensitivity measured using a Cochet-Bonnet esthesiometer, and tear production using phenol red cotton thread wetting.

Results

Loss of PEDF was accompanied by reduced corneal innervation and sensitivity, increased corneal surface injury and tear production, thinning of the corneal stroma and loss of stromal cells. PEDF mRNA was expressed in the cornea and its supporting tissues, the TG, LG, and MG. Deletion of one or both PEDF alleles resulted in decreased expression of essential trophic support in the TG, LG, and MG including nerve growth factor, brain-derived neurotrophic growth factor, and GDNF with significantly increased levels of NT-3 in the LG and decreased EGF expression in the cornea. Decreased transcription of the putative PEDF receptors, adipose triglyceride lipase, lipoprotein receptor–related protein 6, laminin receptor, PLXDC1, and PLXDC2 was also evident in the TG, LG and MG with the first three showing increased levels in corneas of the Pedf^+/− and Pedf^−/− mice compared to wildtype controls. Constitutive inactivation of ERK1/2 and Akt was pronounced in the TG and cornea, although their protein levels were dramatically increased in Pedf^−/− mice.

Conclusions

This study highlights an essential role for PEDF in corneal structure and function and confirms the reported rescue of exogenous PEDF treatment in corneal pathologies. The pleiotropic effects of PEDF deletion on multiple trophic factors, receptors and signaling molecules are strong indications that PEDF is a key coordinator of molecular mechanisms that maintain corneal function and could be exploited in therapeutic options for several ocular surface diseases.

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.

The artemisinin analog SM934 alleviates dry eye disease in rodent models by regulating TLR4/NF-κB/NLRP3 signaling

Dry eye disease (DED) is a multifactorial disorder of the tears and ocular surface characterized by manifestations of dryness and irritation. Although the pathogenesis is not fully illuminated, it is recognized that inflammation has a prominent role in the development and deterioration of DED. β-aminoarteether maleate (SM934) is a water-soluble artemisinin derivative with anti-inflammatory and immunosuppressive activities. In this study, we established scopolamine hydrobromide (SCOP)-induced rodent model as well as benzalkonium chloride (BAC)-induced rat model to investigate the therapeutic potential of SM934 for DED. We showed that topical application of SM934 (0.1%, 0.5%) significantly increased tear secretion, maintained the number of conjunctival goblet cells, reduced corneal damage, and decreased the levels of inflammatory mediators (TNF-α, IL-6, IL-10, or IL-1β) in conjunctiva in SCOP-induced and BAC-induced DED models. Moreover, SM934 treatment reduced the accumulation of TLR4-expressing macrophages in conjunctiva, and suppressed the expression of inflammasome components, i.e., myeloid differentiation factor88 (MyD88), Nod-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing CARD (ASC), and cleaved caspase 1. In LPS-treated RAW 264.7 cells, we demonstrated that pretreatment with SM934 (10 μM) impeded the upregulation of TLR4 and downstream NF-κB/NLRP3 signaling proteins. Collectively, artemisinin analog SM934 exerts therapeutic benefits on DED by simultaneously reserving the structural integrity of ocular surface and preventing the corneal and conjunctival inflammation, suggested a further application of SM934 in ophthalmic therapy, especially for DED.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

Myeloid differentiation factor 88 expression in eyelid specimens of rosacea

Purpose: Rosacea is a common cause of ocular surface disease. Specific immunologic features have been implicated in its pathogenesis, including toll-like receptors, mitogen-associated kinase, and nuclear factor kappa-B. Myeolid differentiation factor 88 (MYD88) has been associated with these elements, suggesting a role for this protein in rosacea. This study was designed to compare the expression of MYD88 in the eyelids of patients with and without this disease.Methods: Western blotting for MYD88 was performed in 14 control patients and 15 patients with rosacea. Bands were quantified and normalized to actin. Immunohistochemical staining for MYD88 was performed in a different cohort of 12 patients with rosacea and 12 controls, and positively-staining cells were counted across five consecutive 40x fields. Statistical analyses compared the differences between the two groups via a dedicated software package.Results: On western blotting, the mean ratios of MYD88 to actin were 13.8 (standard deviation = 14.1) and 44.3 (standard deviation = 39.6) in control and rosacea patients, respectively (p = .002). On immunohistochemistry, the mean numbers of positively-staining cells were 12.1/40x field (standard deviation = 9.61/40x field) and 27.4/40x (standard deviation = 18.7/40x field) in control and rosacea patients, respectively (p = .0438).Conclusions: MYD88 is enriched in eyelid specimens of rosacea. This finding further implicates the innate immune system in the pathogenesis of rosacea, and is consistent with previous reports regarding the role of this protein in ocular surface disease and the previously-implicated cellular features of the disease. Inhibition of MYD88 may be a successful treatment strategy to manage rosacea.

Obese Mice with Dyslipidemia Exhibit Meibomian Gland Hypertrophy and Alterations in Meibum Composition and Aqueous Tear Production

BACKGROUND

Dyslipidemia may be linked to meibomian gland dysfunction (MGD) and altered meibum lipid composition. The purpose was to determine if plasma and meibum cholesteryl esters (CE), triglycerides (TG), ceramides (Cer) and sphingomyelins (SM) change in a mouse model of diet-induced obesity where mice develop dyslipidemia.

METHODS

Male C57/BL6 mice (8/group, age = 6 wks) were fed a normal (ND; 15% kcal fat) or an obesogenic high-fat diet (HFD; 42% kcal fat) for 10 wks. Tear production was measured and meibography was performed. Body and epididymal adipose tissue (eAT) weights were determined. Nano-ESI-MS/MS and LC-ESI-MS/MS were used to detect CE, TG, Cer and SM species. Data were analyzed by principal component analysis, Pearson's correlation and unpaired t-tests adjusted for multiple comparisons; significance set at p ≤ 0.05.

RESULTS

Compared to ND mice, HFD mice gained more weight and showed heavier eAT and dyslipidemia with higher levels of plasma CE, TG, Cer and SM. HFD mice had hypertrophic meibomian glands, increased levels of lipid species acylated by saturated fatty acids in plasma and meibum and excessive tear production.

CONCLUSIONS

The majority of meibum lipid species with saturated fatty acids increased with HFD feeding with evidence of meibomian gland hypertrophy and excessive tearing. The dyslipidemia is associated with altered meibum composition, a key feature of MGD.

Cluster Analysis of Dry Eye Disease Models Based on Immune Cell Parameters - New Insight Into Therapeutic Perspective

Dry eye disease (DED) can be represented as a display of disease in the mucosal part of the eye. It is quite distinct from the retinal side of the eye which connects with the neurons and thus represents the neuroimmunological disease. DED can occur either by the internal damage of the T cells inside the body or by microbial infections. Here we summarize the most common animal model systems used for DED relating to immune factors. We aimed to identify the most important immune cell/cytokine among the animal models of the disease. We also show the essential immune factors which are being tested for DED treatment. In our results, both the mechanism and the treatment of its animal models indicate the involvement of Th1 cells and the pro-inflammatory cytokine (IL-1β and TNF-α) related to the Th1-cells. The study is intended to increase the knowledge of the animal models in the field of the ocular surface along with the opening of a dimension of thoughts while designing a new animal model or treatment paradigm for ocular surface inflammatory disorders.

The gut-eye-lacrimal gland-microbiome axis in Sjögren Syndrome

The bacterial communities that collectively inhabit our body are called the microbiome. Virtually all body surface harbors bacteria. Recent advances in next-generation sequencing that have provided insight into the diversity, composition of bacterial communities, and their interaction are discussed in this review, as well as the current knowledge of how the microbiome promotes ocular health. The ocular surface is a site of low bacterial load. Sjögren Syndrome is an autoimmune disease that affects the exocrine glands, causing dry mouth and dry eye. Systemic antibiotic treatment and germ-free mice have demonstrated that commensal bacteria have a protective role for the ocular surface and lacrimal gland. The existence of a gut-eye-lacrimal gland axis-microbiome is discussed.

Dysbiosis Modulates Ocular Surface Inflammatory Response to Liposaccharide

Purpose

The purpose of this study was to investigate the inflammatory response of cornea and conjunctiva to topically applied lipopolysaccharide (LPS) in mice with and without antibiotic (antibiotic cocktail, ABX) induced dysbiosis.

Methods

Dysbiosis was induced by oral antibiotics for 14 days in a group of conventional female C57BL/6J (B6) mice. 16S rRNA sequencing investigated microbiome composition. Intestinal microbiome differences were assessed using 16S rRNA sequencing of fecal pellet DNA. Blood was collected after euthanasia. CD86 expression in draining nodes was examined by flow cytometry. At day 15, a single dose of LPS or vehicle was topically applied to ABX and naïve mice. Corneal epithelium and conjunctiva were obtained after 4 hours and processed for gene expression analysis. A separate group of germ-free (GF) B6 mice was also topically challenged with LPS.

Results

Antibiotic treatment significantly decreased intestinal diversity and increased serum levels of LPS. This was accompanied by a significant increase in CD86⁺MHC II⁺CD11c⁺CD11b⁺ cells in draining nodes. Compared to vehicle, topically applied LPS increased IL-1β, TNF-α, and CXCL10 mRNA transcripts in cornea and IL-1β, TNF-α, and CXCL10 in the conjunctiva in conventional and antibiotic-treated groups. However, there was higher TNF-α, CXCL10, and IL-12 expression in the cornea of LPS-treated ABX mice compared to LPS-treated mice with intact microbiota. LPS stimulation on GF conjunctiva mirrored the results in ABX mice, although greater IL-12 and IFN-γ expression was observed in GF conjunctiva compared to conventional LPS-treated mice.

Conclusions

Acute depletion of commensals through antibiotics or germ-free environment worsens the inflammatory response to LPS.

Amelioration of dry eye syndrome in db/db mice with diabetes mellitus by treatment with Tibetan Medicine Formula Jikan Mingmu Drops

ETHNOPHARMACOLOGICAL RELEVANCE

Jikan Mingmu Drops (JMD), a traditional Tibetan medicine containing six herbs, has been used to treat dry eye syndrome (DES) in individuals with diabetes mellitus.

AIM OF STUDY

However, the activity of JMD ameliorates DES with diabetes mellitus has not been previously examined. The aim of the study is to investigate the molecular mechanism of JMD on db/db mice.

MATERIALS AND METHODS

The main chemical constituents of JMD were analyzed by high-performance liquid chromatography and gas chromatography-mass spectrometry. DES was then induced in db/db mice by applying 0.2% benzalkonium chloride to the ocular surface for 7 days. Eye drops containing JMD (0.25, 0.5, or 1 g/mL) or vehicle subsequently were administered three times daily for another 7 days, and the therapeutic effects were evaluated by phenol red thread tear and sodium fluorescein tests. Conjunctival specimens were subjected to hematoxylin and eosin staining and periodic acid-Schiff staining to examine pathological changes and number of goblet cells. ELISA was performed to assess the levels of various inflammatory cytokines.

RESULTS

JMD contains hydroxysafflor yellow A, magnoflorine, jatrorrhizine hydrochloride, palmatine hydrochloride, berberine hydrochloride, gallic acid, ellagic acid, tauroursodeoxycholic acid, camphor, isoborneol, borneol, trans-cinnamic acid, and muscone. JMD treatment significantly increased the tear volume, decreased the corneal fluorescein staining score, restored the morphology and structure of conjunctival epithelial cells, and markedly downregulated the levels of interleukin (IL)-6, IL-17α, IL-1β, tumor necrosis factor-α, and vascular endothelial growth factor in the conjunctiva. Further data showed that these protective effects were accompanied by inhibition of inflammation in a dose-dependent manner.

CONCLUSIONS

Amelioration of DES in db/db mice with diabetes mellitus by treatment with Tibetan medicine formula JMD maybe related to its anti-inflammatory effects.

Dyslipidemia and Meibomian Gland Dysfunction: Utility of Lipidomics and Experimental Prospects with a Diet-Induced Obesity Mouse Model

Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease and loss of ocular surface homeostasis. Increasingly, several observational clinical studies suggest that dyslipidemia (elevated blood cholesterol, triglyceride or lipoprotein levels) can initiate the development of MGD. However, conclusive evidence is lacking, and an experimental approach using a suitable model is necessary to interrogate the relationship between dyslipidemia and MGD. This systematic review discusses current knowledge on the associations between dyslipidemia and MGD. We briefly introduce a diet-induced obesity model where mice develop dyslipidemia, which can serve as a potential tool for investigating the effects of dyslipidemia on the meibomian gland. Finally, the utility of lipidomics to examine the link between dyslipidemia and MGD is considered.

Selective Serotonin Reuptake Inhibitors Aggravate Depression-Associated Dry Eye Via Activating the NF-κB Pathway

Purpose

Our study aimed to evaluate the side effects of selective serotonin reuptake inhibitors (SSRIs) on the ocular surface.

Methods

Twenty patients with depression and dry eye disease (DED) were randomly picked to receive SSRI treatment, whereas another 20 patients received placebo treatment. The serotonin, inflammatory cytokine, and proapoptotic protein levels were determined by using protein chip, qRT-PCR, and ELISA analyses. A rat depression model was established, and SSRIs were applied for 3 or 6 weeks. Tear production and corneal epithelial barrier function were evaluated. The serotonin and inflammatory cytokine levels were analyzed by qRT-PCR, immunohistochemical staining, and ELISA. Human corneal epithelial cells were subjected to serotonin, a HTR antagonist, and/or an NF-κB signaling inhibitor. The inflammatory cytokine and proapoptotic protein levels were determined by qRT-PCR, Western blot analysis, and ELISA. The cell apoptosis rate was assessed by using flow cytometry.

Results

The SSRI group had higher tear serotonin levels and more serious inflammation and cell apoptosis on the ocular surface. In the rat depression model, depression decreased tear secretion and increased IL-1β and TNF-α production, whereas the serotonin, TLR2, and TLR4 levels were not increased. SSRI aggravated DED, disrupted the corneal epithelial barrier, and promoted an inflammatory response on the ocular surface by increasing the tear serotonin levels. In addition, serotonin induced an inflammatory response and cell apoptosis in corneal epithelial cells by activating NF-κB signaling.

Conclusions

SSRIs aggravate depression-associated DED via activating the NF-κB pathway. The antagonist of HTRs or the inhibitor of NF-κB signaling presents a potential therapeutic strategy for depression-associated DED. (Trial registration number, ChiCTR1800015592).

Corneal autophagy and ocular surface inflammation: A new perspective in dry eye

Dry eye disease (DED), a multifactorial ocular surface disorder affecting millions of individuals worldwide, is characterized by inflammation and damage to the ocular surface. It is unclear whether corneal autophagy participates in ocular surface inflammation observed in DED. To test this involvement, dry eye (DE) was induced in female C57BL/6 mice housed in a controlled environment by subcutaneous injection of scopolamine. Expression of the autophagy-related proteins LC3B and ATG5 and activation of autophagy were detected in the corneas of these mice. Treatment with LYN-1604, an activator of autophagy, alleviated the clinical indications in DE mice, including tear production and corneal fluorescence staining. LYN-1604 also reduced the corneal levels of inflammatory response products, including tumor necrosis factor alpha (TNF-α) and matrix metalloproteinases-3 and -9. By contrast, treatment of DE mice with the autophagy inhibitor 3-MA, exacerbated the clinical indications of DE and increased the levels of inflammatory response products. This is the first study to show that autophagy could regulate the level of ocular surface inflammation, suggesting that agents that regulate autophagy could relieve ocular surface inflammation and treat DED.

Adaptive eyeglasses for presbyopia correction: an original variable-focus technology

We propose an original variable-focus technology specially designed for presbyopia-correcting adaptive eyeglasses. It has been thought through to offer vision comfort without cutting on aesthetics. It relies on a fluid-filled variable-focus lens (presenting 2 liquids and 1 ultra-thin membrane) assisted by a low-power, high-volume microfluidic actuator. It also features a distance-sensing system to provide automatic focusing. We demonstrate the qualities of this novel technology on our first prototype. Our prototype achieves the necessary 3-diopter-high power variation on a 20-millimeter-wide variable zone with low actuation pressures (~200 Pa at most), and the preliminary optical quality analysis shows the spatial resolution is much better than the one specified by classic eye charts. We discuss further improvements in terms of optics, aesthetics and portability. In particular, we point out that this variable technology is compatible with standard base curves, and we highlight an optimal configuration where the power consumption of our opto-fluidic engine is about 25 mW peak.