Abstract
Purpose:
Glucocorticoids exert their functions through the nuclear receptor, the glucocorticoid receptor (GR), and have been widely used to treat diseases pertaining to the cornea. However, chronic use of glucocorticoids is sometimes associated with the risk of development of cataracts and glaucoma. Thus, understanding of the role of glucocorticoid receptor signaling in the eye and specifically the cornea is needed to improve therapeutic strategies.
Methods:
Immortalized human corneal epithelial cells (HCE-T) from RIKEN were used for all studies and were treated with the synthetic glucocorticoid, Dexamethasone or vehicle. hGRα 59 antibody was used for detecting glucocorticoid receptor in immunoblotting and nuclear trafficking studies. Microarrays were preformed using Agilent Whole Genome chips. Scratch assay and FITC-Dextran permeability assays were used to evaluate the effect of Dexamethasone on wound healing and epithelial barrier function, respectively.
Results:
HCE-T cells expressed the glucocorticoid receptor, which trafficked to the nucleus upon stimulation by Dexamethasone. Genome-wide microarray revealed that glucocorticoids significantly regulated 8399 probes, of which 97% of the probes were repressed, suggesting that transrepression is a predominant function of glucocorticoids in these human corneal epithelial cells. Ingenuity Pathway Analysis identified cell movement and cell-to-cell signaling as the top significant glucocorticoid-regulated biological functions. The Notch signaling pathway, a mediator of cell-cell communication, was repressed by glucocorticoids. Treatment of HCE cells with Dexamethasone exhibited a remarkable delay in wound healing. This effect was reversible with the GR antagonist RU486. Interestingly, epithelial barrier function was improved in cells treated with Dexamethasone, suggesting that wound healing in the presence of glucocorticoids enhances epithelial barrier integrity.
Conclusions:
Glucocorticoids significantly alter the gene expression profile of corneal epithelial cells, which are manifested in biological outcomes including delayed wound healing with improved barrier function. We are now generating cornea-specific GR knockout mice to elucidate the role of glucocorticoid receptor in the cornea during embryonic and postnatal development.
Keywords: 482 cornea: epithelium •
765 wound healing •
739 transcription factors