Oxidative Stress Suppresses Cellular Autophagy in Corneal Epithelium

Reticulated Retinoic Acid Synthesis is Implicated in the Pathogenesis of Dry Eye in Aqp5 Deficiency Mice

Purpose

Abnormalities in aquaporins are implicated in the pathological progression of dry eye syndrome. Retinoic acid (RA) regulates cellular proliferation, differentiation, and apoptosis in the cornea, thereby being associated with dry eye disease (DED). The objective of this study is to explore the underlying mechanisms responsible for RA metabolic abnormalities in corneas lacking aquaporin 5 (AQP5).

Methods

Dry eye (DE) models were induced via subcutaneous scopolamine hydrobromide. Aqp5 knockout (Aqp5-/-) mice and DE mice were utilized to assess corneal epithelial alterations. Tear secretion, goblet cell counts, and corneal punctate defects were evaluated. The impact of Aqp5 on RA-related enzymes and receptors was investigated using pharmacological RA or SR (A JunB inhibitor), a transcription factor JunB inhibitor, treatment in mouse corneal epithelial cells (CECs), or human corneal epithelial cells (HCECs). The HCECs and NaCl-treated HCECs underwent quantitative real-time PCR (qRT-PCR), immunofluorescent, Western blot, and TUNEL assays. The regulation of transcription factor JunB on Aldh1a1 was explored via ChIP-PCR.

Results

Aqp5 and Aldh1a1 were reduced in both CECs of DE mice and NaCl-induced HCECs. Aqp5-/- mice exhibited DE phenotype and reduced Aldh1a1. RA treatment reduced apoptosis, promoted proliferation, and improved the DE phenotype in Aqp5-/- mice. JunB enrichment in the Aldh1a1 promoter was identified by ChIP-PCR. SR significantly increased Aldh1a1 expression, Ki67, and ΔNp63-positive cells, and decreased TUNEL-positive cells in CECs and HCECs.

Conclusions

Our findings demonstrated the downregulation of Aqp5 expression and aberrant RA metabolism in DE conditions. Knockout of Aqp5 resulted in reduced production of RA through activation of JunB, subsequently leading to the manifestation of DE symptoms.

Differential Efficacy of Small Molecules Dynasore and Mdivi-1 for the Treatment of Dry Eye Epitheliopathy or as a Countermeasure for Nitrogen Mustard Exposure of the Ocular Surface

The ocular surface comprises the wet mucosal epithelia of the cornea and conjunctiva, the associated glands, and the overlying tear film. Epitheliopathy is the common pathologic outcome when the ocular surface is subjected to oxidative stress. Whether different stresses act via the same or different mechanisms is not known. Dynasore and dyngo-4a, small molecules developed to inhibit the GTPase activity of classic dynamins DNM1, DNM2, and DNM3, but not mdivi-1, a specific inhibitor of DNM1L, protect corneal epithelial cells exposed to the oxidant tert-butyl hydroperoxide (tBHP). Here we report that, while dyngo-4a is the more potent inhibitor of endocytosis, dynasore is the better cytoprotectant. Dynasore also protects corneal epithelial cells against exposure to high salt in an in vitro model of dysfunctional tears in dry eye. We now validate this finding in vivo, demonstrating that dynasore protects against epitheliopathy in a mouse model of dry eye. Knockdown of classic dynamin DNM2 was also cytoprotective against tBHP exposure, suggesting that dynasore's effect is at least partially on target. Like tBHP and high salt, exposure of corneal epithelial cells to nitrogen mustard upregulated the unfolded protein response and inflammatory markers, but dynasore did not protect against nitrogen mustard exposure. In contrast, mdivi-1 was cytoprotective. Interestingly, mdivi-1 did not inhibit the nitrogen mustard-induced expression of inflammatory cytokines. We conclude that exposure to tBHP or nitrogen mustard, two different oxidative stress agents, cause corneal epitheliopathy via different pathologic pathways. SIGNIFICANCE STATEMENT: Results presented in this paper, for the first time, implicate the dynamin DNM2 in ocular surface epitheliopathy. The findings suggest that dynasore could serve as a new topical treatment for dry eye epitheliopathy and that mdivi-1 could serve as a medical countermeasure for epitheliopathy due to nitrogen mustard exposure, with potentially increased efficacy when combined with anti-inflammatory agents and/or UPR modulators.

The cGAS-STING pathway-dependent sensing of mitochondrial DNA mediates ocular surface inflammation

The innate immune response is the main pathophysiological process of ocular surface diseases exposed to multiple environmental stresses. The epithelium is central to the innate immune response, but whether and how innate immunity is initiated by ocular epithelial cells in response to various environmental stresses in ocular surface diseases, such as dry eye, is still unclear. By utilizing two classic experimental dry eye models-a mouse ocular surface treated with benzalkonium chloride (BAC) and a mouse model with surgically removed extraorbital lachrymal glands, as well as dry eye patient samples-along with human corneal epithelial cells (HCE) exposed to hyperosmolarity, we have discovered a novel innate immune pathway in ocular surface epithelial cells. Under stress, mitochondrial DNA (mtDNA) was released into the cytoplasm through the mitochondrial permeability transition pore (mPTP) and further activated the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, aggravating downstream inflammatory responses and ocular surface damage. Genetic deletion or pharmacological suppression of STING and inhibition of mtDNA release reduced inflammatory responses, whereas mtDNA transfection supported cytoplasmic mtDNA-induced inflammatory responses by activating the cGAS-STING pathway. Our study clarified the cGAS-STING pathway-dependent sensing of mitochondrial DNA-mediated ocular surface inflammation, which elucidated a new mechanism of ocular surface diseases in response to multiple environmental stresses.

The mTOR signalling in corneal diseases: A recent update

Corneal diseases affect 4.2 million people worldwide and are a leading cause of vision impairment and blindness. Current treatments for corneal diseases, such as antibiotics, steroids, and surgical interventions, have numerous disadvantages and challenges. Thus, there is an urgent need for more effective therapies. Although the pathogenesis of corneal diseases is not fully understood, it is known that injury caused by various stresses and postinjury healing, such as epithelial renewal, inflammation, stromal fibrosis, and neovascularization, are highly involved. Mammalian target of rapamycin (mTOR) is a key regulator of cell growth, metabolism, and the immune response. Recent studies have revealed that activation of mTOR signalling extensively contributes to the pathogenesis of various corneal diseases, and inhibition of mTOR with rapamycin achieves promising outcomes, supporting the potential of mTOR as a therapeutic target. In this review, we detail the function of mTOR in corneal diseases and how these characteristics contribute to disease treatment using mTOR-targeted drugs.

Nanocarriers for the Delivery of Neuroprotective Agents in the Treatment of Ocular Neurodegenerative Diseases

Retinal neurodegeneration is considered an early event in the pathogenesis of several ocular diseases, such as diabetic retinopathy, age-related macular degeneration, and glaucoma. At present, there is no definitive treatment to prevent the progression or reversal of vision loss caused by photoreceptor degeneration and the death of retinal ganglion cells. Neuroprotective approaches are being developed to increase the life expectancy of neurons by maintaining their shape/function and thus prevent the loss of vision and blindness. A successful neuroprotective approach could prolong patients' vision functioning and quality of life. Conventional pharmaceutical technologies have been investigated for delivering ocular medications; however, the distinctive structural characteristics of the eye and the physiological ocular barriers restrict the efficient delivery of drugs. Recent developments in bio-adhesive in situ gelling systems and nanotechnology-based targeted/sustained drug delivery systems are receiving a lot of attention. This review summarizes the putative mechanism, pharmacokinetics, and mode of administration of neuroprotective drugs used to treat ocular disorders. Additionally, this review focuses on cutting-edge nanocarriers that demonstrated promising results in treating ocular neurodegenerative diseases.

AUTOPHAGY IN THE EYE: FROM PHYSIOLOGY TO PATHOPHYSOLOGY

Autophagy is a catabolic self-degradative pathway that promotes the degradation and recycling of intracellular material through the lysosomal compartment. Although first believed to function in conditions of nutritional stress, autophagy is emerging as a critical cellular pathway, involved in a variety of physiological and pathophysiological processes. Autophagy dysregulation is associated with an increasing number of diseases, including ocular diseases. On one hand, mutations in autophagy-related genes have been linked to cataracts, glaucoma, and corneal dystrophy; on the other hand, alterations in autophagy and lysosomal pathways are a common finding in essentially all diseases of the eye. Moreover, LC3-associated phagocytosis, a form of non-canonical autophagy, is critical in promoting visual cycle function. This review collects the latest understanding of autophagy in the context of the eye. We will review and discuss the respective roles of autophagy in the physiology and/or pathophysiology of each of the ocular tissues, its diurnal/circadian variation, as well as its involvement in diseases of the eye.

Loss of aquaporin 5 contributes to the corneal epithelial pathogenesis via Wnt/β-catenin pathway

AQP5 plays a crucial role in maintaining corneal transparency and the barrier function of the cornea. Here, we found that in the corneas of Aqp5-/- mice at older than 6 months, loss of AQP5 significantly increased corneal neovascularization, inflammatory cell infiltration, and corneal haze. The results of immunofluorescence staining showed that upregulation of K1, K10, and K14, and downregulation of K12 and Pax6 were detected in Aqp5-/- cornea and primary corneal epithelial cells. Loss of AQP5 aggravated wound-induced corneal neovascularization, inflammation, and haze. mRNA sequencing, western blotting, and qRT-PCR showed that Wnt2 and Wnt6 were significantly decreased in Aqp5-/- corneas and primary corneal epithelial cells, accompanied by decreased aggregation in the cytoplasm and nucleus of β-catenin. IIIC3 significantly suppressed corneal neovascularization, inflammation, haze, and maintained corneal transparent epithelial in Aqp5-/- corneas. We also found that pre-stimulated Aqp5-/- primary corneal epithelial cells with IIIC3 caused the decreased expression of K1, K10, and K14, the increased expression of K12, Pax6, and increased aggregation in the cytoplasm and nucleus of β-catenin. These findings revealed that AQP5 may regulate corneal epithelial homeostasis and function through the Wnt/β-catenin signaling pathway. Together, we uncovered a possible role of AQP5 in determining corneal epithelial cell fate and providing a potential therapeutic target for corneal epithelial dysfunction.

Autophagy in the normal and diseased cornea

The cornea and covering tear film are together the 'objective lens' of the eye through which 80% of light is refracted. Despite exposure to a physically harsh and at times infectious or toxic environment, transparency essential for sight is in most cases maintained. Such resiliency makes the avascular cornea a superb model for the exploration of autophagy in the regulation of homeostasis with relevancy to all organs. Nonetheless, missense mutations and inflammation respectively clog or apparently overwhelm autophagic flux to create dystrophies much like in neurodegenerative diseases or further exacerbate inflammation. Here there is opportunity to generate novel topical therapies towards the restoration of homeostasis with potential broad application.

Exosomes and autophagy in ocular surface and retinal diseases: new insights into pathophysiology and treatment

BACKGROUND

Ocular surface and retinal diseases are widespread problems that cannot be ignored in today's society. However, existing prevention and treatment still have many shortcomings and limitations, and fail to effectively hinder the occurrence and development of them.

MAIN BODY

The purpose of this review is to give a detailed description of the potential mechanism of exosomes and autophagy. The eukaryotic endomembrane system refers to a range of membrane-bound organelles in the cytoplasm that are interconnected structurally and functionally, which regionalize and functionalize the cytoplasm to meet the needs of cells under different conditions. Exosomal biogenesis and autophagy are two important components of this system and are connected by lysosomal pathways. Exosomes are extracellular vesicles that contain multiple signaling molecules produced by multivesicular bodies derived from endosomes. Autophagy includes lysosome-dependent degradation and recycling pathways of cells or organelles. Recent studies have revealed that there is a common molecular mechanism between exosomes and autophagy, which have been, respectively, confirmed to involve in ocular surface and retinal diseases.

CONCLUSION

The relationship between exosomes and autophagy and is mostly focused on fundus diseases, while a deeper understanding of them will provide new directions for the pathological mechanism, diagnosis, and treatment of ocular surface and retinal diseases.

Beneficial Effects of Polydeoxyribonucleotide (PDRN) in an In Vitro Model of Fuchs Endothelial Corneal Dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a bilateral, hereditary syndrome characterized by progressive irreversible injury in the corneal endothelium; it is the most frequent cause for corneal transplantation worldwide. Oxidative stress induces the apoptosis of corneal endothelial cells (CECs), and has a crucial function in FECD pathogenesis. The stimulation of the adenosine A_2A receptor (A_2Ar) inhibits oxidative stress, reduces inflammation and modulates apoptosis. Polydeoxyribonucleotide (PDRN) is a registered drug that acts through adenosine A_2Ar. Thus, the goal of this study was to assess the effect of PDRN in an in vitro FECD model. Human Corneal Endothelial Cells (IHCE) were challenged with H₂O₂ (200 μM) alone or in combination with PDRN (100 μg/mL), PDRN plus ZM241385 (1 μM) as an A_2Ar antagonist, and CGS21680 (1 μM) as a well-known A_2Ar agonist. H₂O₂ reduced the cells’ viability and increased the expression of the pro-inflammatory markers NF-κB, IL-6, IL-1β, and TNF-α; by contrast, it decreased the expression of the anti-inflammatory IL-10. Moreover, the pro-apoptotic genes Bax, Caspase-3 and Caspase-8 were concurrently upregulated with a decrease of Bcl-2 expression. PDRN and CGS21680 reverted the negative effects of H₂O₂. Co-incubation with ZM241385 abolished the effects of PDRN, indicating that A_2Ar is involved in the mode of action of PDRN. These data suggest that PDRN defends IHCE cells against H₂O₂-induced damage, potentially as a result of its antioxidant, anti-inflammatory and antiapoptotic properties, suggesting that PDRN could be used as an FECD therapy.

The interplay between oxidative stress and autophagy: focus on the development of neurological diseases

Regarding the epidemiological studies, neurological dysfunctions caused by cerebral ischemia or neurodegenerative diseases (NDDs) have been considered a pointed matter. Mount-up shreds of evidence support that both autophagy and reactive oxygen species (ROS) are involved in the commencement and progression of neurological diseases. Remarkably, oxidative stress prompted by an increase of ROS threatens cerebral integrity and improves the severity of other pathogenic agents such as mitochondrial damage in neuronal disturbances. Autophagy is anticipated as a cellular defending mode to combat cytotoxic substances and damage. The recent document proposes that the interrelation of autophagy and ROS creates a crucial function in controlling neuronal homeostasis. This review aims to overview the cross-talk among autophagy and oxidative stress and its molecular mechanisms in various neurological diseases to prepare new perceptions into a new treatment for neurological disorders. Furthermore, natural/synthetic agents entailed in modulation/regulation of this ambitious cross-talk are described.

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.

Oxidative and antioxidative stress markers in keratoconus: a systematic review and meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis on the levels of oxidative stress markers and antioxidants in keratoconus compared to healthy subject.

METHOD

The PubMed, Cochrane Library, Embase, Science Direct and Google Scholar databases were searched on 1st June 2020 for studies reporting oxidative and antioxidative stress markers in keratoconus and healthy controls. Main meta-analysis was stratified by type of biomarkers, type of samples (tears, cornea, aqueous humour and blood) and type of corneal samples (stromal cells, epithelium and endothelium).

RESULTS

We included 36 articles, for a total of 1328 keratoconus patients and 1208 healthy controls. There is an overall increase in oxidative stress markers in keratoconus compared with healthy controls (standard mean deviation (SMD) = 0.94, 95% confidence interval (95% CI) 0.55-1.33), with a significant increase in reactive oxygen and nitrogen species (1.09, 0.41-1.78) and malondialdehyde (1.78, 0.83-2.73). There is an overall decrease in antioxidants in keratoconus compared with healthy controls (-0.63, -0.89 to -0.36), with a significant decrease in total antioxidant capacity/status (-1.65, -2.88 to -0.43), aldehyde/NADPH dehydrogenase (-0.77, -1.38 to -0.17), lactoferrin/transferrin/albumin (-1.92, -2.96 to -0.89) and selenium/zinc (-1.42, -2.23 to -0.61). Oxidative stress markers were higher in tears and in cornea of keratoconus than in aqueous humour, and antioxidants were decreased in tears, aqueous humour and blood without difference between sample type. Oxidative stress markers increased in stromal cells and antioxidants decreased in endothelium.

CONCLUSION

Oxidative stress markers and antioxidants were dysregulated in keratoconus, involving an imbalance of redox homeostasis in tears, cornea, aqueous humour and blood.

Health Potential of Aloe vera against Oxidative Stress Induced Corneal Damage: An "In Vitro" Study

Fuchs endothelial corneal dystrophy (FECD) is characterized by the gradual deterioration of corneal endothelial cells (CECs) and is the most common cause of corneal transplantation worldwide. CECs apoptosis caused by oxidative stress plays a pivotal role in the pathogenesis of FECD. Antioxidant compounds have been of considerable significance as a candidate treatment in the management of corneal diseases. Based on these findings, the objective of this study was to evaluate the effects of an aloe extract with antioxidant properties, in an “in vitro” model of FECD. Human corneal epithelial (HCE) cells were preincubated with aloe extract 100 μg/mL, two hours before hydrogen peroxide (H₂O₂) stimulus. H₂O₂ challenge significantly reduced the cell viability, increased the generation of Reactive Oxygen Species (ROS) and malondialdehyde levels. Moreover, m-RNA expression and activity of Nrf-2, Catalase and Superoxide dismutase (SOD) were reduced together with an enhanced expression of IL-1β, tumor necrosis factor-α (TNF-α), IL-6, and cyclooxygenase 2 (COX-2). Furthermore, Bcl-2, Caspase-3 and Caspase-8 expression were down-regulated while Bax was up-regulated by H₂O₂ stimulus. Aloe extract blunted the oxidative stress-induced inflammatory cascade triggered by H₂O₂ and modulated apoptosis. Aloe extract defends HCE cells from H₂O₂-induced injury possibly due its antioxidant and anti-inflammatory activity, indicating that eye drops containing aloe extract may be used as an adjunctive treatment for FECD.

Role of autophagy and oxidative stress to astrocytes in fenpropathrin-induced Parkinson-like damage

Fenpropathrin is an insecticide that is widely used in agriculture. It remains unknown whether fenpropathrin exposure increases the risk of Parkinson's disease. We found that fenpropathrin increased oxidative stress both in vitro and in vivo. Additionally, fenpropathrin increased production of ROS, NOS2, and HO-1, and decreased SOD and GSH in astrocytes. We further found that fenpropathrin-mediated oxidative stress might inhibit autophagic flow, including decreased expression of LC3A/B and enhanced expression of SQSTM1 via down-regulation of CDK-5, an upstream marker of autophagy. In mice, autophagy was slightly different from that found in astrocytes, as reflected in the increased expressions of LC3A/B and SQSTM1. Our findings elucidate the toxicological phenomena and pathogenic mechanisms of fenpropathrin and may provide guidance for improved pesticide control and environmental protection.

Modulation of Oxidative Stress and Inflammation in the Aged Lacrimal Gland

Inflammation and oxidative stress accompany aging. This study investigated the interplay between oxidative stress and inflammation in the lacrimal gland. C57BL/6 mice were used at 2 to 3, 12, and 24 months of age. Nuclear factor erythroid derived-2-related factor 2 (Nrf2)^-/- and corresponding wild-type mice were used at 2 to 3 and 12 to 13 months of age. A separate group of 15.5 to 17 months of age C57BL/6 mice received a diet containing an Nrf2 inducer (Oltipraz) for 8 weeks. Aged C57BL/6 lacrimal glands showed significantly greater lymphocytic infiltration, higher levels of MHC II, IFN-γ, IL-1β, TNF-α, and cathepsin S (Ctss) mRNA transcripts, and greater nitrotyrosine and 4-hydroxynonenal protein. Young Nrf2^-/- mice showed an increase in IL-1β, IFN-γ, MHC II, and Ctss mRNA transcripts compared with young wild-type mice and greater age-related changes at 12 to 13 months of age. Oltipraz diet significantly decreased nitrotyrosine and 4-hydroxynonenal and decreased the expression of IL-1β and TNF-α mRNA transcripts, while decreasing the frequency of CD45⁺CD4⁺ cells in lacrimal glands and significantly increasing conjunctival goblet cell density compared with a standard diet. The findings provide novel insight into the development of chronic, low-grade inflammation and oxidative stress in age-related dry eye. New therapies targeting oxidative stress pathways will be valuable in treating age-related dry eye.

NOX1 down-regulation attenuated the autophagy and oxidative damage in pig intestinal epithelial cell following transcriptome analysis of transport stress

The previous study indicated that transport stress resulted in oxidative damage and autophagy/mitophagy elevation, companied by NOX1 over- expression in the jejunal tissues of pigs. However, the transportation-related gene expression profile and NOX1 function in intestine remain to be explicated. In the current study, differentially expressed genes involved in PI3K-Akt and NF-κB pathways, oxidative stress and autophagy process have been identified in pig jejunal tissues after transcriptome analysis following transportation. The physiological functions of NOX1 down-regulation were explored against oxidative damage and excessive autophagy in porcine intestinal epithelial cells (IPEC-1) following NOX1 inhibitor ML171 and H₂O₂ treatments. NOX1 down-regulation could decrease the content of Malondialdehyde (MDA), Lactic dehydrogenase (LDH) activity and reactive oxygen species (ROS) level, and up-regulate superoxide dismutase (SOD) activity. Furthermore, mitochondrial membrane potential and content were restored, and the expressions of tight junction proteins (Claudin-1 and ZO-1) were also increased. Additionally, NOX1 inhibitior could down-regulate the expression of autophagy-associated proteins (ATG5, LC3, p62), accompanied by activating SIRT1/PGC-1α pathway. NOX1 down-regulation might alleviate oxidative stress-induced mitochondria damage and intestinal mucosal injury via modulating excessive autophagy and SIRT1/PGC-1α signaling pathway. The data will shed light on the molecular mechanism of NOX1 on intestine oxidative damage following pig transportation.

Autophagy modulation in animal models of corneal diseases: a systematic review

Autophagy is an intracellular catabolic process implicated in the recycling and degradation of intracellular components. Few studies have defined its role in corneal pathologies. Animal models are essential for understanding autophagy regulation and identifying new treatments to modulate its effects. A systematic review (SR) was conducted of studies employing animal models for investigations of autophagy in corneal diseases. Studies were identified using a structured search strategy (TS = autophagy AND cornea*) in Web of Science, Scopus, and PubMed from inception to September 2019. In this study, 230 articles were collected, of which 28 were analyzed. Mouse models were used in 82% of the studies, while rat, rabbit, and newt models were used in the other 18%. The most studied corneal layer was the epithelium, followed by the endothelium and stroma. In 13 articles, genetically modified animal models were used to study Fuch endothelial corneal dystrophy (FECD), granular corneal dystrophy type 2 (GCD2), dry eye disease (DED), and corneal infection. In other 13 articles, animal models were experimentally induced to mimic DED, keratitis, inflammation, and surgical scenarios. Furthermore, in 50% of studies, modulators that activated or inhibited autophagy were also investigated. Protective effects of autophagy activators were demonstrated, including rapamycin for DED and keratitis, lithium for FECD, LYN-1604 for DED, cysteamine and miR-34c antagomir for damaged corneal epithelium. Three autophagy suppressors were also found to have therapeutic effects, such as aminoimidazole-4-carboxamide-riboside (AICAR) for corneal allogeneic transplantation, celecoxib and chloroquine for DED.

Effects of Eurya japonica extracts on human corneal epithelial cells and experimental dry eye

Eurya japonica (EJ) leaves have been indicated to exert anti-oxidative and anti-inflammatory effects. Dry eye disease (DED) is a chronic inflammatory disease and oxidative stress is closely associated with DED. The aim of the present study was to analyze the therapeutic efficacy of EJ in DED using human corneal epithelial (HCE) cells and a mouse model of experimental dry eye (EDE). EJ extracts (0.001, 0.01 and 0.1%) were used to treat HCE cells. Cell viability and mitochondrial function were detected using a EZ-Cytox cell viability assay kit and mitochondrial membrane potential assays. Dichlorofluorescein diacetate (DCF-DA) assay was used to measure cellular reactive oxygen species (ROS) levels. Subsequently, eye drops consisting of BSS or 0.001%, 0.01 and 0.1% EJ extracts were applied for treatment of EDE. At 7 days, conjunctival ROS production was measured using a DCF-DA assay. Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, 10 kDa interferon gamma-induced protein 10 (IP-10) and monokine induced by interferon-γ (MIG) levels in the conjunctiva were analyzed using a multiplex immunobead assay. Tear film and ocular surface parameters were measured. Treatment with EJ extracts in HCE cells effectively improved cell viability, ROS levels and mitochondrial function. Mice treated with 0.01 and 0.1% EJ extracts indicated a significant decrease in ROS, TNF-α, IL-1β, IP-10 and MIG levels compared with the EDE or BSS groups. Furthermore, a significant improvement in all clinical parameters was observed in the 0.01 and 0.1% EJ extract groups. EJ extracts could decrease cytotoxicity and ROS production in HCE cells. Additionally, topical EJ extracts reduced oxidative damage and inflammation and improved clinical signs of EDE, suggesting that EJ extracts may be used as an adjunctive therapy for DED.

The protective effect of EGF-activated ROS in human corneal epithelial cells by inducing mitochondrial autophagy via activation TRPM2

Oxidative stress is a major pathogenesis of some ocular surface diseases. Our previous study demonstrated that epidermal growth factor (EGF)-activated reactive oxygen species (ROS) could protect against human corneal epithelial cell (HCE) injury. In the present study, we aimed to explore the role and mechanisms of oxidative stress and mitochondrial autophagy in HCE cells subjected to scratch injury. CCK-8 assays, EdU assays, Western blot analysis, wound-healing assays, and flow cytometry were conducted to determine cell viability, proliferation, protein expression, cell apoptosis, and intracellular ROS levels, respectively. The results showed that EGF could promote damage repair and inhibit cell apoptosis in scratch injured HCE cells by upregulating ROS (**p < .01, ***p < .001). EGF also induced mitochondrial autophagy and alleviated mitochondrial damage. Interestingly, the combination of the mitochondrial autophagy inhibitor and mitochondrial division inhibitor 1 (MDIVI-1) with EGF could reduce cell proliferation, viability, and the ROS level (*p < .05, **p < .01, ***p < .001). Treatment using the ROS inhibitor N-acetyl- l-cysteine abrogated the increase in mitochondrial membrane potential after EGF treatment. (*p < .05). Taken together, these findings indicated that EGF plays an important role in HCE damage repair and could activate ROS to protect against HCE injury by inducing mitochondrial autophagy via activation of TRPM2.

New micelle myricetin formulation for ocular delivery: improved stability, solubility, and ocular anti-inflammatory treatment

Myricetin (Myr) is a naturally occurring flavonoid exhibiting diverse biological and pharmacological properties, but its characteristics such as water insolubility, poor aqueous stability, and poor bioavailability limit its clinical application, including in ophthalmology. To increase its clinical application in ophthalmology, Myr was designed to be encapsulated in a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (PVCL-PVA-PEG) polymeric micelles to increases its aqueous solubility, stability, and corneal permeability to promote its efficacy in eye disease treatments. Thus, the Myr micelle ophthalmic solution was prepared and characterized encapsulation efficiency (EE), micelle size, and zeta potential. The chemical stability of Myr and the short-term storage stability of the Myr micelle ophthalmic solution were evaluated, followed by in vitro cytotoxicity and in vivo ocular irritation; in vitro cellular uptake and in vivo corneal permeation; and in vitro antioxidant activity and in vivo anti-inflammatory efficacy were also further evaluated. Myr could be incorporated into micelles with high EE. PVCL-PVA-PEG micelles significantly enhanced Myr's aqueous solubility and chemical stability. The Myr micelle ophthalmic solution also showed high storage stability. In rabbits, the Myr micelle ophthalmic solution displayed good in vitro cellular tolerance. Remarkable improvements in in vitro cellular uptake and in vivo corneal permeation were also observed in the Myr micelle ophthalmic solution, and significant improvements in the in vitro antioxidant activity and in vivo anti-inflammatory efficacy were also obtained. Overall, these results supported that the Myr micelle ophthalmic solution could be a promising nanomedicine for ocular tissues.

Oxidative stress in corneal injuries of different origin: Utilization of 3D human corneal epithelial tissue model

The purpose of the current work was to utilize a three dimensional (3D) corneal epithelial tissue model to study dry eye disease and oxidative stress-related corneal epithelial injuries for the advancement of ocular therapeutics. Air-liquid interface cultures of normal human corneal epithelial cells were used to produce 3D corneal epithelial tissues appropriate for physiologically relevant exposure to environmental factors. Oxidative stress was generated by exposing the tissues to non-toxic doses of ultraviolet radiation (UV), hydrogen peroxide, vesicating agent nitrogen mustard, or desiccating conditions that stimulated morphological, cellular, and molecular changes relevant to dry eye disease. Corneal specific responses, including barrier function, tissue viability, reactive oxygen species (ROS) accumulation, lipid peroxidation, cytokine release, histology, and gene expression were evaluated. 3D corneal epithelial tissue model structurally and functionally reproduced key features of molecular responses of various types of oxidative stress-induced ocular damage. The most pronounced effects for different treatments were: UV irradiation - intracellular ROS accumulation; hydrogen peroxide exposure - barrier impairment and IL-8 release; nitrogen mustard exposure - lipid peroxidation and IL-8 release; desiccating conditions - tissue thinning, a decline in mucin expression, increased lipid peroxidation and IL-8 release. Utilizing a PCR gene array, we compared the effects of corneal epithelial damage on the expression of 84 oxidative stress-responsive genes and found specific molecular responses for each type of damage. The topical application of lubricant eye drops improved tissue morphology while decreasing lipid peroxidation and IL-8 release from tissues incubated at desiccating conditions. This model is anticipated to be a valuable tool to study molecular mechanisms of corneal epithelial damage and aid in the development of therapies against dry eye disease, oxidative stress- and vesicant-induced ocular injuries.

Ultra-small micelles based on polyoxyl 15 hydroxystearate for ocular delivery of myricetin: optimization, in vitro, and in vivo evaluation

The aim was to develop a nanocarrier based on polyoxyl 15 hydroxystearate (Kolliphor® HS15, HS15) micelles for the solubility, stability, and ocular delivery of myricetin (Myr). An optimized ratio of HS15 and Myr was prepared to fabricate HS15-Myr micelle ophthalmic solution. Myr-encapsulating HS15 micelles (HS15-Myr micelles) were subjected to physicochemical characterizations. The chemical stability of Myr in HS15 micelles and storage stability of HS15-Myr micelle ophthalmic solutions were evaluated. In vitro parallel artificial membrane permeability assay and antioxidant activity of Myr in HS15 micelles were also measured. In vivo ocular tolerance, corneal permeation, and anti-inflammatory efficacy studies were conducted following ocular topical administration. HS15-Myr micelles were successfully prepared and presented transparent appearance with high encapsulation (96.12 ± 0.31%), ultra-small micelle size (a mean diameter of 12.17 ± 0.73 nm), uniform size distribution (polydispersity index [PDI] = 0.137 ± 0.013), and negative surface charge (- [4.28 ± 0.42] mV). Myr in HS15 micelle solution demonstrated higher aqueous stability than the free Myr solution among the accepted pH range for eyedrops. HS15-Myr micelle ophthalmic solution demonstrated high storage stability at 4 °C and 25 °C. HS15 micelles could significantly improve in vitro antioxidant activity and faster membrane permeation of Myr. No irritations or corneal damage were revealed in rabbit eyes after ocular administration of HS15-Myr micelle solution. In vivo corneal permeation study demonstrated that HS15-Myr micelles could penetrate the cornea efficiently in mouse eyes. Further, HS15-Myr micelles also demonstrated significant in vivo anti-inflammatory activity. It can be concluded that HS15 micelles are a potential ophthalmic delivery nanocarrier for poorly soluble drugs such as Myr.

Bone marrow mesenchymal stem cells-derived conditioned medium protects cardiomyocytes from hypoxia/reoxygenation-induced injury through Notch2/mTOR/autophagy signaling

Bone marrow mesenchymal stem cells (BMSC) can ameliorate ischemic injury of various tissues. However, the molecular mechanisms involved remain to be clarified. In this study, we intend to investigate the effects of BMSC-derived conditioned medium (BMSC-CM) on hypoxia/reoxygenation (H/R)-induced injury of H9c2 myocardial cells, and the potential mechanisms. Cell injury was determined through level of cell viability, lactate dehydrogenase (LDH) release, total intracellular reactive oxygen species (ROS), mitochondrial membrane potential (Δψm), and cell apoptosis. Autophagic activity of cells was detected through levels of the autophagy-associated proteins and autophagic flux. Results showed that BMSC-CM alleviated H/R-induced injury in H9c2 cells, as demonstrated by increased cell viability and Δψm, decreased ROS production, LDH release, and cell apoptosis. Furthermore, the H/R treatment induced a decrease in autophagic activity and an increase in Notch2 signaling activation in H9c2 cells. In the presence of BMSC-CM, the autophagic activity impaired by the H/R treatment was upregulated with decreased phosphorylation of mTOR, and the activation of Notch2 signaling was downregulated. These effects of BMSC-CM could be replicated by Notch signaling inhibitor. In contrast, inhibitors of cell autophagy including chloroquine (CQ) and 3-methyladenine, diminished the protective effects of BMSC-CM. Taken together results, our study showed that BMSC-CM could protect H9c2 cells from H/R-induced injury potentially through regulating Notch2/mTOR/autophagy signaling. These findings may provide a novel insight into the mechanisms of BMSC-CM in therapy of myocardial ischemia/reperfusion injury as well as other ischemic diseases.