GR-Mediated DNA Repair Mechanisms in Human Corneal Epithelial Cells

Abstract:

Ultraviolet Rays (UV) such as UVB are responsible for non-melanoma skin cancer, making up 4-5% of cancers in the United States. DNA breakage caused by UV light is responsible for mutations such as cyclobutane pyrimidine dimers (CPD) that lead to cancer. These dimers are observed in the skin as well as the cornea of the eye. When UVB penetrates the eye, it passes through the cornea and could cause damage including ocular tumors, dry eye syndrome, and other DNA damage and mutations. Glucocorticoids (GC) are steroid hormones with anti-inflammatory properties used in treating eye diseases to target and repress inflammation. GCs exert their action by binding to a transcription factor, the glucocorticoid receptor (GR). GCs bind to GR which then regulates the transcription of genes involved in bodily functions such as stress, inflammatory response, and metabolism. Dexamethasone (Dex) is a synthetic glucocorticoid that has been linked to DNA damage repair in past studies which suggests that the response to DNA damage is mediated by the GR pathway. The glucocorticoid Dex will be used with UVB-treated human corneal cells (HCET) with and without GR present using siRNA to determine if DNA repair is mediated through the GR pathway. CPD clearance will be measured using slot blot assay and the change in gene expression involved in DNA repair will be calculated using RT-PCR. The research proposed will give more insight into how GCs play a role in the effect of UVB-induced mutations in HCET cells through the GR pathway. We predict that the use of Dex will aid in DNA repair which decreases the potential for corneal cells to undergo UVB-induced DNA damage, therefore preventing the development of ocular inflammation and disease.