Effect of Inhibitors of Arachidonic Acid Metabolism on Corneal Reepithelialization in the Rat

Abstract

We examined the ability of inhibitors of arachidonic acid metabolism to influence the rate of healing of organ-cultured rat corneas with 3-mm diameter central epithelial abrasions. In control corneas, and in the presence of the cyclooxygenase inhibitors indomethacin (1 μM) or flurbiprofen (1 μM), the defect was completely reepithelialized by 25 hr. In contrast, corneas cultured with the lipoxygenase inhibitors quercetin (100 μM), esculetin (100 μM), or baicalein (10 μM) or the dual cyclooxygenase/lipoxygenase inhibitors BW 755C (100 μM) or BW A540C (100 μM) had significantly delayed epithelial healing rates when compared with the controls; complete healing of the epithelial defects required 32·5-40 hr. Dose-response studies with esculetin and BW 755C demonstrated that the concentrations for 50% inhibition of reepithelialization (65·3 μM for esculetin, 39·6 μM for BW 755C) were significantly greater than those for inhibition of 12-lipoxygenase activity (16·6 μM for esculetin, 21·1 μM for BW 755C), the major lipoxygenase activity in normal rat cornea. Addition of 12(S)-5,8,10,14-hydroxyeicosatetraenoic acid [12(S)-HETE, 0·01-10 μM], the main 12-lipoxygenase metabolite of arachidonic acid in normal rat cornea, to the organ cultures did not influence the rate of epithelial wound healing in the absence or presence of 100 μM esculetin. Our results suggest that lipoxygenase activity is an important factor in regulating corneal epithelial wound healing in the rat, presumably by influencing epithelial cell migration. The lipoxygenase enzyme and metabolite(s) responsible for regulating reepithelialization, and the mechanism of action, remain to be determined.