Effect of High Glucose on Ocular Surface Epithelial Cell Barrier and Tight Junction Proteins

Abstract

PURPOSE. Patients with diabetes mellitus are reported to have ocular surface defects, impaired ocular surface barrier function, and a higher incidence of corneal and conjunctival infections. Tight junctions are critical for ocular surface barrier function. The present study was designed to investigate the effect of high glucose exposure on human corneal and conjunctival epithelial cell barrier function and tight junction proteins. METHODS. Human corneal and conjunctival epithelial cells were exposed to 15 mM and 30 mM glucose for 24 and 72 hours. The barrier function was measured using transepithelial electrical resistance (TEER). The cell migration was quantified using scratch assay. The cells were harvested for protein extraction and mRNA isolation. Gene and protein expression of claudins, zonula occludens (ZOs), and occludin was quantified using realtime PCR and Western blot. RESULTS. Glucose caused a significant decrease in TEER after 72 hours of exposure in both corneal and conjunctival epithelial cells. Glucose did not cause any notable change in migration of either corneal or conjunctival epithelial cells. Glucose exposure did not cause any notable change in protein expression of claudin-1, ZO-1, ZO-2, ZO-3, or occludin. On the other hand, 15 mM glucose caused an increase in gene expression of claudin-1, claudin-3, ZO-2, ZO-3, and occludin, a likely response to osmotic stress since 15 mM mannitol also caused consistently similar increase in gene expression of these proteins. CONCLUSIONS. High glucose exposure causes impairment of corneal and conjunctival epithelial cell barrier function, but this detrimental effect is not caused by a decrease in expression of tight junction proteins: claudin-1, ZO-1, ZO-2, ZO-3, and occludin.

Chronic Hyperglycemia Compromises Mitochondrial Function in Corneal Epithelial Cells: Implications for the Diabetic Cornea

“…The impact of hyperglycemia on cellular migration in the published literature is equivocal. Although a recent report evaluating the effects of high glucose on corneal and conjunctival epithelial cells reported similar findings to ours, others have found a hyperglycemia-induced delay in migration and growth [ 49 , 50 ]. Culture conditions and the cell type used may impact the cellular response to hyperglycemia and hyperosmolarity.…”

Design of an L-Valine-Modified Nanomicelle-Based Drug Delivery System for Overcoming Ocular Surface Barriers

“…In surface cells, ZO proteins and claudins are mainly expressed. ZO-1 is the marker protein of tight junctions in the corneal epithelium, and claudin-1 is the main protein expressed in claudins [43][44][45]. The effects of ophthalmic preparations on tight junction proteins can be determined by PCR, WB or immunofluorescence staining [45][46][47].…”

“…ZO-1 is the marker protein of tight junctions in the corneal epithelium, and claudin-1 is the main protein expressed in claudins [43][44][45]. The effects of ophthalmic preparations on tight junction proteins can be determined by PCR, WB or immunofluorescence staining [45][46][47]. In this study, the expression changes of ZO-1 and claudin-1 were detected with WB, proving that the cellular uptake mechanism of nanomicelles inhibits the overexpression of ZO-1 and claudin-1 induced by drug stimulation, which is a novel and noteworthy discovery.…”

“…The study results showed that BC induced the upregulation of tight junction protein expression in corneal epithelial cells. This phenomenon occurred due to the stimulation of the ocular surface by 15 mM glucose, which may be a compensatory cellular response to negative stress [45]. However, few studies have reported stimulation by therapeutic agents, which not only reflected the advantage of using nanomicelles to deliver drugs but also provided a new idea for studying the ocular delivery obstacles of ophthalmic drugs in the future.…”

Glucose-Impaired Corneal Re-Epithelialization Is Promoted by a Novel Derivate of Dimethyl Fumarate

“…Diabetic condition elicits a chronic oxidative stress and an inflammatory status that supports the progressive cellular dysfunction and the alterations of physiological processes of the eye [ 12 ]. High concentration of glucose was shown to compromise corneal barrier function without an associated decrease in the levels of zonula occludens proteins (ZO-1, ZO-2, ZO-3), tight junction proteins (claudin-1) and occludin [ 13 ]. Such an effect is due to the loss of laminin-5, one of the main constituents of corneal basement membrane, under a HG condition: clinical features of diabetic keratopathy were shown to correlate with decreased adhesion between epithelial cells [ 14 ].…”