Nanoceria-Mediated Cyclosporin A Delivery for Dry Eye Disease Management through Modulating Immune-Epithelial Crosstalk.

Dry eye disease (DED) affects a substantial worldwide population with increasing frequency. Current single-targeting DED management is severely hindered by the existence of an oxidative stress-inflammation vicious cycle and complicated intercellular crosstalk within the ocular microenvironment. Here, a nanozyme-based eye drop, namely nanoceria loading cyclosporin A (Cs@P/CeO2), is developed, which possesses long-term antioxidative and anti-inflammatory capacities due to its regenerative antioxidative activity and sustained release of cyclosporin A (CsA). In vitro studies showed that the dual-functional Cs@P/CeO2 not only inhibits cellular reactive oxygen species production, sequentially maintaining mitochondrial integrity, but also downregulates inflammatory processes and repolarizes macrophages. Moreover, using flow cytometric and single-cell sequencing data, the in vivo therapeutic effect of Cs@P/CeO2 was systemically demonstrated, which rebalances the immune-epithelial communication in the corneal microenvironment with less inflammatory macrophage polarization, restrained oxidative stress, and enhanced epithelium regeneration. Collectively, our data proved that the antioxidative and anti-inflammatory Cs@P/CeO2 may provide therapeutic insights into DED management.

Analysis of the mucosal chemokines CCL28, CXCL14, and CXCL17 in dry eye disease: An in vitro and clinical investigation.

Mucosal chemokines have antimicrobial properties and play an important role in mucosal immunity. However, little is known about their expression on the ocular surface. This study aimed to analyze the expression of the mucosal chemokines CCL28, CXCL14 and CXCL17 in corneal and conjunctival epithelial cells under in vitro dry eye (DE) conditions, and in conjunctival samples from healthy subjects and DE patients. Human corneal epithelial cells (HCE) and immortalized human conjunctival epithelial cells (IM-HConEpiC) were incubated under hyperosmolar (400-500 mOsM) or inflammatory (TNF-α 25 ng/mL) conditions for 6 h and 24 h to measure CCL28, CXCL14, and CXCL17 gene expression by RT-PCR and their secretion by immunobead-based analysis (CCL28, CXCL14) and ELISA (CXCL17). Additionally, twenty-seven DE patients and 13 healthy subjects were included in this study. DE-related questionnaires (OSDI, mSIDEQ and NRS) evaluated symptomatology. Ocular surface integrity was assessed using vital staining. Tactile sensitivity was measured with Cochet-Bonnet esthesiometer, and mechanic and thermal (heat and cold) sensitivity using Belmonte's non-contact esthesiometer. Subbasal nerve plexus and dendritic cell density were analyzed by in vivo confocal microscopy. Conjunctival cells from participants were collected by impression cytology to measure mucosal chemokines gene expression by RT-PCR. Our results showed that HCE and IM-HConEpiC cells increased CCL28, CXCL14, and CXCL17 secretion under hyperosmolar conditions. The gene expression of CCL28 was significantly upregulated in conjunctival samples from DE patients. CCL28 expression correlated positively with symptomatology, corneal staining, heat sensitivity threshold, and dendritic cell density. CXCL14 expression correlated positively with age, ocular pain, conjunctival staining, tactile sensitivity, and image reflectivity. CXCL17 expression correlated positively with corneal staining. These results suggest that corneal and conjunctival epithelial cells could be a source of CCL28, CXCL14, and CXCL17 on the ocular surface and that CCL28 might be involved in DE pathogenesis.

Assessment of Mucin-Associated Gene Expression Levels on the Ocular Surface.

The ocular surface is covered with a mucus layer. The mucin-associated genes expressed in the ocular surface cells include MUC1, MUC4, MUC5AC, and MUC16. Impression cytology is useful for collecting specimens from the ocular surface, their histological examination, and measuring mucin-associated gene expression levels. The expression of mucin-associated gene levels was assessed by quantitative polymerase chain reaction. The expression levels of these mucin-associated genes are potential biomarkers for ocular surface diseases, including dry eye disease.

ER-1 deficiency induces inflammation and lipid deposition in meibomian gland and lacrimal gland.

PURPOSE: To investigated the role of estrogen receptor-1 (ER-1) in maintaining homeostasis in ocular surface. METHODS: ER-1-knockout (ER-1KO) mice were studied at 4 months of age. The ocular surface was examined using a slit lamp. Histological alterations in the meibomian gland (MG) and lacrimal gland (LG) were observed with H&E staining. Protein levels of P-ERK, peroxisome proliferator-activated receptor gamma (PPAR-γ), p-NFκB-P65, IL-1ß, aquaporin 5 (AQP-5), fatty acid-binding protein 5 (Fabp5) and K10 were determined by immunofluorescence and Western blotting. Gene expressions of APO-F, APO-E, K10, ELOVL4, PPAR-γ, SCD-1, and SREBP1 were quantified by qPCR. Conjunctival (CJ) goblet cell alterations were detected by PAS staining. Lipid metabolism in MG and LG was assessed using LipidTox. Apoptosis in MG and LG was analyzed through the TUNEL assay. RESULTS: Both male and female ER-1KO mice demonstrated increased corneal fluorescence staining scores. MG showed abnormal lipid metabolism and ductal dilation. LG displayed lipid deposition and reduced AQP-5 expression. CJ experienced goblet cell loss. MG, LG exhibited signs of inflammation and apoptosis. CONCLUSION: ER1 is pivotal for ocular surface homeostasis in both genders of mice. ER1 deficiency induces inflammation and lipid deposition to MG and LG, culminating in dry eye-like manifestations on the ocular surface.

Evaluation of Dry Eye Severity and Ocular Surface Inflammation in Patients with Pemphigus and Pemphigoid.

PURPOSE: To evaluate ocular surface involvement, tear cytokine levels, and histopathological changes in pemphigus and pemphigoid patients. METHODS: A total of 22 patients (15 pemphigus and 7 pemphigoids) and 21 non-diseased controls were enrolled in our study. All participants underwent ocular surface evaluation, which included ocular surface disease index test, slit lamp observation, dry eye-related examination, tear multicytokine analysis, and conjunctival impression cytology. RESULTS: Pemphigus and pemphigoid patients presented much more severe conjunctivochalasis, corneal epithelial defects, corneal opacity, symblepharon   and dry eye. Severe ocular surface squamous metaplasia and a significant increase of tear macrophage inflammatory protein-1beta, tumor necrosis factor-alpha, interleukin (IL)-1ß, IL -6, and IL-8 occurred in pemphigus and pemphigoid patients. CONCLUSIONS: Our results revealed that ocular surface inflammation and dry eye persist in most pemphigus and pemphigoid patients, and do not occur in parallel with the systemic course. Regular ophthalmological examinations and local anti-inflammatory should be provided for pemphigus and pemphigoid patients.

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-1ß 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.

The Anti-Inflammatory Effect of Multi-Wavelength Light-Emitting Diode Irradiation Attenuates Dry Eye Symptoms in a Scopolamine-Induced Mouse Model of Dry Eye.

Dry eye disease is a common condition in patients of all ages, causing discomfort and potential visual problems. Current treatments, including artificial tears and anti-inflammatory drugs, have certain limitations, encouraging research into alternative therapies. We investigated the therapeutic potential of multi-wavelength light-emitting diode (LED) irradiation of mice with dry eye. First, we showed that multi-wavelength LED irradiation was non-toxic to human corneal epithelial cells and improved cell viability. We then used a scopolamine-induced mouse model of dry eye to assess the effects of multi-wavelength LED irradiation on various clinical parameters. This treatment increased the tear volume and reduced corneal irregularity, thus improving dry eye. Histological analysis revealed that multi-wavelength LED irradiation protected against corneal epithelial damage and the associated reduction in epithelial thickness and would thus improve the corneal health of dry eye patients. Multi-wavelength LED irradiation significantly reduced the corneal levels of pro-inflammatory cytokines IL-6, IL-1ß, and TNF-α; the treatment was thus anti-inflammatory. Our results suggest that multi-wavelength LED irradiation may serve as a safe and effective treatment for dry eye, alleviating symptoms, reducing inflammation, and promoting corneal health.

The potential benefits of polyphenols for corneal diseases.

The cornea functions as the primary barrier of the ocular surface, regulating temperature and humidity while providing protection against oxidative stress, harmful stimuli and pathogenic microorganisms. Corneal diseases can affect the biomechanical and optical properties of the eye, resulting in visual impairment or even blindness. Due to their diverse origins and potent biological activities, plant secondary metabolites known as polyphenols offer potential advantages for treating corneal diseases owing to their anti-inflammatory, antioxidant, and antibacterial properties. Various polyphenols and their derivatives have demonstrated diverse mechanisms of action in vitro and in vivo, exhibiting efficacy against a range of corneal diseases including repair of tissue damage, treatment of keratitis, inhibition of neovascularization, alleviation of dry eye syndrome, among others. Therefore, this article presents a concise overview of corneal and related diseases, along with an update on the research progress of natural polyphenols in safeguarding corneal health. A more comprehensive understanding of natural polyphenols provides a novel perspective for secure treatment of corneal diseases.

Pathohistological features of the aging human lacrimal gland.

AIM: To assess sex-related differences in the pathohistological features of the human lacrimal gland and to investigate age-related and sex-related differences in stereologically measured volume density of the secretory tissue, connective tissue, and fat. METHODS: We performed an observational analysis of acinar atrophy, periacinar fibrosis, periductal fibrosis, ductal dilation, ductal proliferation, fatty infiltration, and lymphocyte infiltration of hematoxylin and eosin-stained lacrimal gland samples from 81 cornea donors. Stereological analysis of the volume density of the secretory tissue, connective tissue, and fat was performed on samples from 66 donors. RESULTS: Up to 69% of all samples showed degenerative changes. Female samples had a higher frequency of all observed degenerative changes, except ductal dilation. While acinar atrophy was significantly more prevalent in women, ductal dilation was significantly more prevalent in men. Stereological analysis indicated lower portions of acini and higher portions of connective tissue and fat, as well as a more pronounced age-related progression of degenerative changes in female samples. CONCLUSION: Female lacrimal glands are more susceptible to degeneration, and this susceptibility could play an important role in the higher incidence of dry eye disease in older women. A further stereological analysis using more samples from younger age groups is needed to elucidate age-related and sex-related differences in the structure of the human lacrimal gland and their impact on dry eye disease.

Disrupted Neural Regeneration in Dry Eye Secondary to Ankylosing Spondylitis-With a Theoretical Link between Piezo2 Channelopathy and Gateway Reflex, WDR Neurons, and Flare-Ups.

This study aimed at analyzing the corneal neural regeneration in ankylosing spondylitis patients using in vivo corneal confocal microscopy in correlation with Langerhans cell density, morphology, and dry eye parameters. Approximately 24 ankylosing spondylitis subjects and 35 age- and gender-matched control subjects were enrolled. Data analysis showed that all corneal nerve-fiber descriptives were lower in the ankylosing spondylitis group, implicating disrupted neural regeneration. Peripheral Langerhans cell density showed a negative correlation with nerve fiber descriptions. A negative correlation between tear film break-up time and corneal nerve fiber total branch density was detected. The potential role of somatosensory terminal Piezo2 channelopathy in the pathogenesis of dry eye disease and ankylosing spondylitis is highlighted in our study, exposing the neuroimmunological link between these diseases. We hypothesized earlier that spinal neuroimmune-induced sensitization due to this somatosensory terminal primary damage could lead to Langerhans cell activation in the cornea, in association with downregulated Piezo1 channels on these cells. This activation could lead to a Th17/Treg imbalance in dry eye secondary to ankylosing spondylitis. Hence, the corneal Piezo2 channelopathy-induced impaired Piezo2-Piezo1 crosstalk could explain the disrupted neural regeneration. Moreover, the translation of our findings highlights the link between Piezo2 channelopathy-induced gateway to pathophysiology and the gateway reflex, not to mention the potential role of spinal wide dynamic range neurons in the evolution of neuropathic pain and the flare-ups in ankylosing spondylitis and dry eye disease.

Unsupervised Learning Based on Meibography Enables Subtyping of Dry Eye Disease and Reveals Ocular Surface Features.

Purpose: This study aimed to establish an image-based classification that can reveal the clinical characteristics of patients with dry eye using unsupervised learning methods. Methods: In this study, we analyzed 82,236 meibography images from 20,559 subjects. Using the SimCLR neural network, the images were categorized. Data for each patient were averaged and subjected to mini-batch k-means clustering, and validated through consensus clustering. Statistical metrics determined optimal category numbers. Using a UNet model, images were segmented to identify meibomian gland (MG) areas. Clinical features were assessed, including tear breakup time (BUT), tear meniscus height (TMH), and gland atrophy. A thorough ocular surface evaluation was conducted on 280 cooperative patients. Results: SimCLR neural network achieved clustering patients with dry eye into six image-based subtypes. Patients in different subtypes harbored significantly different noninvasive BUT, significantly correlated with TMH. Subtypes 1 and 5 had the most severe MG atrophy. Subtype 2 had the highest corneal fluorescent staining (CFS). Subtype 4 had the lowest TMH, whereas subtype 5 had the highest. Subtypes 3 and 6 had the largest MG areas, and the upper MG areas of a person's bilateral eyes were highly correlated. Image-based subtypes are related to meibum quality, CFS, and morphological characteristics of MG. Conclusions: In this study, we developed an unsupervised neural network model to cluster patients with dry eye into image-based subtypes using meibography images. We annotated these subtypes with functional and morphological clinical characteristics.

Evaluation of aqueous-deficient and evaporative dry eye cases with confocal microscopy.

INTRODUCTION: Dry eye disease (DED) is an important health problem affecting hundreds of millions of people worldwide. In vivo confocal microscopy (IVCM) is a non-invasive imaging tool that can visualize ocular surface diseases. In this study, we aimed to evaluate corneal structures and inflammatory cells with IVCM in DED patients. MATERIAL AND METHODS: The patients were divided into three subgroups: group 1, consisting of 22 patients with aqueous tear insufficiency; group 2, consisting of 21 patients with evaporative type DED; and group 3, consisting of 20 healthy patients. Imaging was performed with IVCM. The corneal epithelium, nerves, stroma, endothelial and inflammatory cells were compared between groups. RESULTS: There was a significant decrease in corneal epithelial cell density in cases with DED, and there was a significant increase in corneal basal epithelial cell density in the aqueous-deficient type. Keratocyte density was significantly increased in the aqueous-deficient type. A significant decrease in the number and density of sub-basal nerves was found in aqueous-deficient cases, and an increase was found in neural pilling and folding. Dendritic cell density, size, number and area were significantly increased in the aqueous-deficient type. There was also decreased corneal endothelial cell density in DED. CONCLUSION: We evaluated pathological changes in DED on the corneal surface by IVCM. This methodology is valuable in terms of objectively evaluating how the corneal surface is affected in accordance with disease severity and in predicting poor response to treatment.

Insulin-like growth factor binding protein-3 mediates hyperosmolar stress-induced mitophagy through the mechanistic target of rapamycin.

Hyperosmolarity of the ocular surface triggers inflammation and pathological damage in dry eye disease (DED). In addition to a reduction in quality of life, DED causes vision loss and when severe, blindness. Mitochondrial dysfunction occurs as a consequence of hyperosmolar stress. We have previously reported on a role for the insulin-like growth factor binding protein-3 (IGFBP-3) in the regulation of mitochondrial ultrastructure and metabolism in mucosal surface epithelial cells; however, this appears to be context-specific. Due to the finding that IGFBP-3 expression is decreased in response to hyperosmolar stress in vitro and in an animal model of DED, we next sought to determine whether the hyperosmolar stress-mediated decrease in IGFBP-3 alters mitophagy, a key mitochondrial quality control mechanism. Here we show that hyperosmolar stress induces mitophagy through differential regulation of BNIP3L/NIX and PINK1-mediated pathways. In corneal epithelial cells, this was independent of p62. The addition of exogenous IGFBP-3 abrogated the increase in mitophagy. This occurred through regulation of mTOR, highlighting the existence of a new IGFBP-3-mTOR signaling pathway. Together, these findings support a novel role for IGFBP-3 in mediating mitochondrial quality control in DED and have broad implications for epithelial tissues subject to hyperosmolar stress and other mitochondrial diseases.

Increased METTL3 expression and m6A RNA methylation may contribute to the development of dry eye in primary Sjögren's syndrome.

BACKGROUND: Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder defined by xerostomia and keratoconjunctivitis sicca, and its etiology remains unknown. N6-methyladenosine (m6A) is the predominant posttranscriptional modification in eukaryotic mRNAs and is dynamically regulated by m6A regulators. Dysregulation of m6A modification is closely associated with several autoimmune disorders, but the role of m6A modification in pSS remains unknown. This study investigated the potential role of m6A and m6A-related regulators in pSS patients with dry eye. METHODS: This cross-sectional study included forty-eight pSS patients with dry eye and forty healthy controls (HCs). Peripheral blood mononuclear cells (PBMCs) were isolated, and the level of m6A in total RNA was measured. The expression of m6A regulators was determined utilizing real-time PCR and western blotting. The serological indicators detected included autoantibodies, immunoglobulins (Igs), complement factors (Cs), and inflammatory indicators. Dry eye symptoms and signs were measured, including the ocular surface disease index, Schirmer's test (ST), corneal fluorescein staining score (CFS), and tear break-up time. Spearman's correlation coefficient was employed to assess the associations of m6A and m6A-related regulator expression with clinical characteristics. RESULTS: The expression level of m6A was markedly increased in the PBMCs of pSS patients with dry eye compared to HCs (P value<0.001). The relative mRNA and protein expression levels of the m6A regulators methyltransferase-like 3 (METTL3) and YT521-B homology domains 1 were markedly elevated in pSS patients with dry eye (both P value<0.01). The m6A RNA level was found to be positively related to METTL3 expression in pSS patients (r = 0.793, P value<0.001). Both the m6A RNA level and METTL3 mRNA expression correlated with the anti-SSB antibody, IgG, ST, and CFS (all P values < 0.05). The m6A RNA level was associated with C4 (r = -0.432, P value = 0.002), while METTL3 mRNA expression was associated with C3 (r = -0.313, P value = 0.030). CONCLUSIONS: Our work revealed that the upregulation of m6A and METTL3 was associated with the performance of serological indicators and dry eye signs in pSS patients with dry eye. METTL3 may contribute to the pathogenesis of dry eye related to pSS.

Suppression of NLRP3/Caspase-1/GSDMD Mediated Corneal Epithelium Pyroptosis Using Melatonin-Loaded Liposomes to Inhibit Benzalkonium Chloride-Induced Dry Eye Disease.

Introduction: Benzalkonium chloride (BAC) is widely employed as a preservative in eye drops, which will cause the death of corneal epithelial cells due to ROS production, DNA strand breakage, and mitochondrial dysfunction, resulting in dry eye disease (DED)-like changes in ocular surface tissues. In this study, Melatonin (MT) liposomes (TAT-MT-LIPs) designed by loading MT into TAT-modified liposomes have been developed, characterized, and used for inhibiting BAC-induced DED (BAC-DED). Methods: The TAT was chemically grafted onto the Mal-PEG2000-DSPE by Michael's addition between the sulfhydryl group in TAT and the maleimide group in Mal-PEG2000-DSPE. TAT-MT-LIPs were prepared using film dispersion followed by the extrusion method and topically treated in rats once a day. BAC-DED was induced in rats by topical administration with 0.2% BAC twice daily. Defects, edema, and inflammation of the corneas, as well as IOP, were examined. Histologic analyses of corneas were performed to assess the change of mitochondrial DNA oxidation and NLRP3/Caspase-1/GSDMD signaling transduction. Results: After topical administration, TAT-MT-LIPs significantly alleviated DED-clinical symptoms of experimental animals by inhibiting tissue inflammation and preventing the loss of the corneal epithelium and conjunctival goblet cells. Our data suggested continuous ocular surface exposure of BAC-induced NLRP3/Caspase-1/GSDMD mediated corneal epithelium pyroptosis, which was not reported before. BAC caused substantial mt-DNA oxidation, which promoted the transduction of NLRP3/Caspase-1/GSDMD and consequent corneal epithelium pyroptosis. TAT-MT-LIPs could efficiently suppress the BAC-induced corneal epithelium pyroptosis and inflammation by inhibiting mt-DNA oxidation and the subsequent signal transmission. Conclusion: NLRP3/Caspase-1/GSDMD mediated corneal epithelium pyroptosis is involved in the development of BAC-DED. The present study provided new insights into the adverse effects of BAC, which can serve as a new target for protecting corneal epithelium when applying BAC as a preservative in eye drops. The developed TAT-MT-LIPs can efficiently inhibit BAC-DED and give great potential to be developed as a new DED treatment.

Impact of Plasma Rich in Growth Factors (PRGF) Eye Drops on Ocular Redness and Symptomatology in Patients with Dry Eye Disease.

Background and Objectives: Dry eye disease (DED) is a common and very symptomatic pathology that affects normal daily activity. The aim of the study was to evaluate the efficacy of plasma rich in growth factors (PRGF) added to one routine treatment protocol for DED (artificial tears substitutes, lid hygiene, and anti-inflammatory therapy). Materials and Methods: Patients were divided into two groups of treatment: standard treatment group (n = 43 eyes) and PRGF group (n = 59). Patients' symptomatology (inferred from OSDI and SANDE questionnaires), ocular inflammation, tear stability, and ocular surface damage were analyzed at baseline and after 3 months of treatment. Results: OSDI test scores were significantly lower in both groups (p < 0.001). SANDE frequency test scores also improved statistically, with differences between groups (p = 0.0089 SANDE frequency and p < 0.0119 SANDE severity). There was a greater reduction in ocular redness (ocular inflammation) in the PRGF group (p < 0.0001) and fluorescein tear break-up time was significantly improved in the PRGF group (p = 0.0006). No significant changes were found in terms of ocular surface damage. No adverse events were obtained in either group. Conclusions: The addition of PRGF to the standard treatment of DED, according to the results obtained, proved to be safe and produced an improvement in ocular symptomatology and signs of inflammation, particularly in moderate and severe cases, when compared to standard treatment.

Neurosensory abnormalities and stability of a mouse model of dry eye disease.

This study aimed to use a mouse model of dry eye disease (DED) induced by topical administration of benzalkonium chloride (BAK) and assess its stability and the presence of neurosensory abnormalities, including ocular pain. Eight-week-old C57BL6/6 N male mice were used in this study. Mice were treated with 10 µL of 0.2% BAK dissolved in artificial tears (AT), administered twice daily for 7 days. After one week, animals were randomized into two groups: one was administered with 0.2% BAK in AT once per day for 7 days, while the other was not further treated. Corneal epitheliopathy was quantified at days 0, 3, 7, 12, and 14. Moreover, tear secretions, corneal nociception, and corneal nerve integrity were measured after BAK treatment. After sacrifice, corneas were dissected to assess nerve density and leukocyte infiltration by immunofluorescence. Topical BAK instillation for 14 days significantly increased corneal fluorescein staining (p < 0.0001) compared to day 0. On the other hand, interruption of BAK instillation was associated with improvement of corneal epitheliopathy (day 12, p < 0.0001; day 14, p < 0.001). BAK treatment increased ocular pain (p < 0.0001) and resulted in a significant increase in leukocyte infiltration in the cornea (p < 0.01). Moreover, corneal sensitivity was reduced (p < 0.0001), together with corneal nerve density (p < 0.0001) and tear secretion (p < 0.0001). One week twice a day, followed by one additional week once a day, of 0.2% BAK topical administration induces stable clinical and histological signs of DED, which is associated with neurosensory abnormalities, including pain.

Autophagy in dry eye disease: Therapeutic implications of autophagy modulators on the ocular surface.

Dry eye disease (DED) is a chronic ocular surface disorder, associated with inflammation, which can cause severe morbidity, visual compromise, and loss of quality of life, affecting up to 5-50% of the world population. In DED, ocular surface damage and tear film instability due to abnormal tear secretion lead to ocular surface pain, discomfort, and epithelial barrier disruption. Studies have shown the involvement of autophagy regulation in dry eye disease as a pathogenic mechanism along with the inflammatory response. Autophagy is a self-degradation pathway in mammalian cells that reduces the excessive inflammation driven by the secretion of inflammatory factors in tears. Specific autophagy modulators are already available for the management of DED currently. However, growing studies on autophagy regulation in DED might further encourage the development of autophagy modulating drugs that reduce the pathological response at the ocular surface. In this review, we summarize the role of autophagy in the pathogenesis of dry eye disease and explore its therapeutic application.

Hyperglycemia Induces Tear Reduction and Dry Eye in Diabetic Mice through the Norepinephrine-α1 Adrenergic Receptor-Mitochondrial Impairment Axis of Lacrimal Gland.

Dry eye syndrome is a common complication in diabetic patients with a prevalence of up to 54.3%. However, the pathogenic mechanisms underlying hyperglycemia-induced tear reduction and dry eye remain less understood. The present study indicated that both norepinephrine (NE) and tyrosine hydroxylase levels were elevated in the lacrimal gland of diabetic mice, accompanied by increased Fos proto-oncogene (c-FOS)+ cells in the superior cervical ganglion. However, the elimination of NE accumulation by surgical and chemical sympathectomy significantly ameliorated the reduction in tear production, suppressed abnormal inflammation of the lacrimal gland, and improved the severity of dry eye symptoms in diabetic mice. Among various adrenergic receptors (ARs), the α1 subtype played a predominant role in the regulation of tear production, as treatments of α1AR antagonists improved tear secretion in diabetic mice compared with ßAR antagonist propranolol. Moreover, the α1AR antagonist alfuzosin treatment also alleviated functional impairments of the meibomian gland and goblet cells in diabetic mice. Mechanically, the α1AR antagonist rescued the mitochondrial bioenergetic deficit, increased the mitochondrial DNA copy numbers, and elevated the glutathione levels of the diabetic lacrimal gland. Overall, these results deciphered a previously unrecognized involvement of the NE-α1AR-mitochondrial bioenergetics axis in the regulation of tear production in the lacrimal gland, which may provide a potential strategy to counteract diabetic dry eye by interfering with the α1AR activity.

PM2.5 exposure increases dry eye disease risks through corneal epithelial inflammation and mitochondrial dysfunctions.

Dry eye disease (DED) is the most common disease affecting vision and quality of life. PM2.5 was a potential risk of DED. Herein, we conducted animal exposure and cell-based studies to evaluate the pathogenic effect of PM2.5 exposure on the ocular surface and DED etiological mechanisms. C57 mice were exposed to filtered air and PM2.5 aerosol. We assessed health conditions and inflammation of the ocular surface by corneal fluorescein staining and immunohistochemistry. In parallel, cultured human corneal epithelial cells (HCETs) were treated with PM2.5, followed by characterization of cell viability, intracellular ATP level, mitochondrial activities, and expression level of DED relevant mRNA and proteins. In mice, PM2.5 exposure induced severe superficial punctate keratopathy and inflammation in their cornea. In HCETs, cell proliferation and ROS generation followed dose-response and time-dependent manner; meanwhile, mitochondrial ROS (mtROS) level increased and mitochondrial membrane potential (MMP) level decreased. Inflammation cascade was triggered even after short-term exposure. The reduction of ATP production was alleviated with Nrf2 overexpression, NF-κB P65 knockdown, or ROS clearance. Nrf2 overexpression and P65 knockdown reduced inflammatory reaction through decreasing expression of P65 and increasing of Nrf2, respectively. They partly alleviated changes of ROS/mtROS/MMP. This research proved that PM2.5 would cause DED-related inflammation reaction on corneal epithelial cells and further explored its mechanism: ROS from mitochondrial dysfunctions of corneal epithelial cells after PM2.5 exposure partly inhibited the expression of anti-inflammatory protein Nrf2 led the activation of inflammatory protein P65 and its downstream molecules, which finally caused inflammation reaction.