Expression of 15–lipoxygenases in the Human Cornea

Abstract

Abstract: : Purpose: 15S–hydroxyeicosatetraenoic acid (15S–HETE) is a major arachidonic acid metabolite produced by human corneal epithelium. There are two human 15–lipoxygenases (LOX), 15–LOX–1 and 15–LOX–2, which convert arachidonic acid to 15–HETE. The presence of both 15–lipoxygenases in the human cornea prompted this study to better delineate their roles in the human corneal epithelium. Methods: Human corneal epithelium from eye banked corneas and a human corneal epithelial cell line (HCE) were used in [1–¹⁴C]arachidonic acid incubations, Western analysis, and quantitative real time RT–PCR. Cell cultures of HCE were treated with 15S–HETE to measure its effect on cellular proliferation (BrdU uptake) and apoptosis (TUNEL assay). Results: 15–LOX–2 but not 15–LOX–1 was detected by Western blot analyses, although we were able to detect similar levels of both 15–LOX mRNAs by real–time quantitative RT–PCR. [1–¹⁴C]Arachidonic acid incubations revealed 15S–HETE as the major lipoxygenase product in the human corneal epithelium. Treatment with 15S–HETE (5–10 µM) reduced growth rate and induced apoptosis of cultured HCE cells in a dose dependent manner. Conclusions: These findings indicate that 15–LOX–2 is the predominant 15–lipoxygenase protein in human corneal epithelium, and its product, 15S–HETE, may play a role in maintenance of the corneal epithelium through cellular apoptosis.

Keywords: cell death/apoptosis • cornea: epithelium • cornea: basic science