No abstract

One of the Important functions of the cornea Is to maintain normal vision by refracting light onto the lens and retina. This property is dependent In part on the ability of the corneal epithelium to undergo continuous renewal. Epithelial renewal is essential because It enables this tissue to act as a barrier that protects the corneal Interior from becoming infected by noxious environmental agents. Furthermore, the smooth optical properties of the corneal epithelial surface are sustained through this renewal process. The rate of renewal Is dependent on a highly Integrated balance between the processes of corneal epithelial proliferation, differentiation, and cell death. One experimental approach to characterize these three aspects of the renewal process has been to study the kinetics and dynamlcs of corneal re-epithelializatlon In a wound-healing model. This effort has employed In vivo and In vitro studies. From such studies It Is evident that the appropriate Integration and coordination of corneal epithelial proliferation, adhesion, migration, and cell demise is dependent on the actions of a myriad of cytoklnes. Our goal here is to provide an overview into how these mediators and environmental tactors elicit control of eel-lUlar proliferation, adhesion, migration, and apoptosls. To this end we review the pertinent literature dealing with the receptor and the cell signaling events that are responsible for medi• atlng cytoklne control of corneal epithelial renewal. It Is our hope that a better appreciation can be obtained about the complexity of the control processes that are responsible for assuring continuous corneal epithelial renewal in health and disease.

Worldwide, myopia is the leading cause of visual impairment. It results from inappropriate extension of the ocular axis and concomitant declines in scleral strength and thickness caused by extracellular matrix (ECM) remodeling. However, the identities of the initiators and signaling pathways that induce scleral ECM remodeling in myopia are unknown. Here, we used single-cell RNA-sequencing to identify pathways activated in the sclera during myopia development. We found that the hypoxia-signaling, the eIF2-signaling, and mTOR-signaling pathways were activated in murine myopic sclera. Consistent with the role of hypoxic pathways in mouse model of myopia, nearly one third of human myopia risk genes from the genome-wide association study and linkage analyses interact with genes in the hypoxia-inducible factor-1α (HIF-1α)-signaling pathway. Furthermore, experimental myopia selectively induced HIF-1α up-regulation in the myopic sclera of both mice and guinea pigs. Additionally, hypoxia exposure (5% O) promoted myofibroblast transdifferentiation with down-regulation of type I collagen in human scleral fibroblasts. Importantly, the antihypoxia drugs salidroside and formononetin down-regulated HIF-1α expression as well as the phosphorylation levels of eIF2α and mTOR, slowing experimental myopia progression without affecting normal ocular growth in guinea pigs. Furthermore, eIF2α phosphorylation inhibition suppressed experimental myopia, whereas mTOR phosphorylation induced myopia in normal mice. Collectively, these findings defined an essential role of hypoxia in scleral ECM remodeling and myopia development, suggesting a therapeutic approach to control myopia by ameliorating hypoxia.

In certain epithelial tissues, activation of transient receptor potential (TRP) vanilloid subtype 1 (TRPV1) by noxious stimuli induces proinflammatory cytokine release, which helps to mitigate the challenge. While the corneal epithelium elicits such responses to a variety of challenges, it remains unknown whether TRPV1 mediates pro-inflammatory cytokine secretion. Accordingly, we probed for TRPV1 expression and function in human (HCEC) and rabbit corneal epithelial cell (RCEC) lines, in their primary counterparts, and in human and mouse corneal epithelium in situ. Cell membrane and perinuclear TRPV1 expression was detected in all preparations and its identity verified by Western blot analysis. Capsaicin (CAP) (1-10 mM) increased nonselective cation channel whole cell currents (2.5-fold AE 0.5-fold between À60 and 130 mV), resulting in calcium transients that were fully blocked by the TRPV1 antagonists capsazepine (CPZ) and ruthenium red, or removal of extracellular calcium. Another signaling event involved transient activation of global mitogen-activated protein kinase (MAPK) superfamily, which was followed by up to 3.3-and 9-fold increases in interleukins (IL)-6 and -8 release, respectively. Such increases in inflammatory mediators' release were suppressed by exposure to CPZ or MAPK inhibitors, or removal of Ca 2þ . Taken together, TRPV1 receptors may play a role in mediating corneal epithelial inflammatory mediator secretion and subsequent hyperalgesia.

We examined whether absence or blocking of transient receptor potential vanilloid subtype 1 (TRPV1) affects the level of inflammation and fibrosis/scarring during healing of injured tissue using an alkali burn model of cornea in mice. A cornea burn was produced with 1 N NaOH instilled into one eye of TRPV1-/- (KO) (n = 88) or TRPV1+/+ (n = 94) mice. Examinations of the corneal surface and eye globe size suggested that the loss of TRPV1 suppressed inflammation and fibrosis/scarring after alkali burn, and this was confirmed by histology, IHC, and gene expression analysis. The loss of TRPV1 inhibited inflammatory cell invasion and myofibroblast generation in association with reduction of expression of proinflammatory and profibrogenic components. Experiments of bone marrow transplantation between either genotype of mice showed that KO corneal tissue resident cells, but not KO bone marrow-derived cells, are responsible for KO-type wound healing with reduced inflammation and fibrosis. The absence of TRPV1 attenuated expression of transforming growth factor β 1 (TGFβ1) and other proinflammatory gene expression in cultured ocular fibroblasts, but did not affect TGFβ1 expression in macrophages. Loss of TRPV1 inhibited myofibroblast transdifferentiation in cultured fibroblasts. Systemic TRPV1 antagonists reproduced the KO type of healing. In conclusion, absence or blocking of TRPV1 suppressed inflammation and fibrosis/scarring during healing of alkali-burned mouse cornea. TRPV1 is a potential drug target for improving the outcome of inflammatory/fibrogenic wound healing.

PurposeThis study compares signs, symptoms and predictive tools used to diagnose dry eye disease (DED) and ocular surface disorders in six systemic well-defined and non-overlapping diseases. It is well known that these tests are problematic because of a lack of agreement between them in identifying these conditions. Accordingly, we provide here a comparative clinical profile analysis of these different diseases.MethodsA spontaneous and continuous sample of patients with Sjögren's syndrome (SS) (n = 27), graft-versus-host-disease (GVHD) (n = 28), Graves orbitopathy (n = 28), facial palsy (n = 8), diabetes mellitus without proliferative retinopathy (n = 14) and glaucoma who chronically received topical drugs preserved with benzalkonium chloride (n = 20) were enrolled. Evaluation consisted of a comprehensive protocol encompassing: (1) structured questionnaire - Ocular Surface Disease Index (OSDI); (2) tear osmolarity (TearLab Osmolarity System - Ocusense); (3) tear film break-up time (TBUT); (4) fluorescein and lissamine green staining; (5) Schirmer test and (6) severity grading.ResultsOne hundred and twenty five patients (aged 48.8 years-old±14.1, male:female ratio = 0.4) were enrolled in the study, along with 24 age and gender matched controls. Higher scores on DED tests were obtained in Sjögren Syndrome (P<0.05), except for tear film osmolarity that was higher in diabetics (P<0.001) and fluorescein staining, that was higher in facial palsy (P<0.001). TFBUT and OSDI correlated better with other tests. The best combination of diagnostic tests for DED was OSDI, TBUT and Schirmer test (sensitivity 100%, specificity 95% and accuracy 99.3%).ConclusionsDED diagnostic test results present a broad range of variability among different conditions. Vital stainings and TBUT correlated best with one another whereas the best test combination to detect DED was: OSDI/TBUT/Schirmer.

Hypertonic stress-elicited TRPV1 channel stimulation mediates increases in a proinflammatory cytokine IL-6 and a chemoattractant IL-8 by eliciting EGFR transactivation, MAPK, and NF-κB activation. Selective drug modulation of either TRPV1 activity or its signaling mediators may yield a novel approach to suppressing inflammatory responses occurring in dry eye syndrome.

Peroxisome proliferator-activated receptors (PPARs) are members of a superfamily of nuclear transcription factors. They are involved in mediating numerous physiological effects in humans, including glucose and lipid metabolism. PPARα ligands effectively treat dyslipidemia and have significant antiinflammatory and anti-atherosclerotic activities. These effects and their ligand-dependent activity make nuclear receptors obvious targets for drug design. Here, we present the structure of the human PPARα in complex with WY14643, a member of fibrate class of drug, and a widely used PPAR activator. The crystal structure of this complex suggests that WY14643 induces activation of PPARα in an unusual bipartite mechanism involving conventional direct helix 12 stabilization and an alternative mode that involves a second ligand in the pocket. We present structural observations, molecular dynamics and activity assays that support the importance of the second site in WY14643 action. The unique binding mode of WY14643 reveals a new pattern of nuclear receptor ligand recognition and suggests a novel basis for ligand design, offering clues for improving the binding affinity and selectivity of ligand. We show that binding of WY14643 to PPARα was associated with antiinflammatory disease in a human corneal cell model, suggesting possible applications for PPARα ligands.