Abstract

Objective Patients with diabetes are at an increased risk for developing corneal complications and delayed wound healing. This study investigated the effects of high glucose (HG) on epidermal growth factor receptor (EGFR) signaling and on epithelial wound healing in the cornea.

Research Design and Methods Effects of HG on wound healing and on EGFR signaling were investigated in cultured porcine corneas, human corneal epithelial cells (CECs), and human corneas using Western blotting and immunofluorescence. Effects of HG on reactive oxygen species (ROS) and glutathione (GSH) levels and on EGFR pathways were assessed in porcine and primary human CECs, respectively. The effects of EGFR ligands and antioxidants on HG-delayed epithelial wound healing were assessed in cultured porcine corneas.

Results HG impaired ex vivo epithelial wound healing and disturbed cell responses and EGFR signaling to wounding. HG suppressed AKT phosphorylation in an ROS sensitive manner and decreased intracellular GSH in cultured porcine corneas. Exposure to HG for 24 hrs resulted in an increase in ROS positive cells in primary human CECs. While heparin-binding EGF-like growth factor and antioxidant N-acetylcysteine had beneficial effects on epithelial wound closure, their combination significantly accelerated HG-delayed wound healing to a level similar to that seen in controls. Finally, AKT signaling pathway was perturbed in the epithelia of human diabetic corneas, but not in the corneas of non-diabetic, age-matched donors.

Conclusions HG, likely through ROS, impairs EGFR-phosphatidylinositol 3-kinase-AKT pathway, resulting in delayed corneal epithelial wound healing. Antioxidants in combination with EGFR ligands may be promising potential therapeutics for diabetic keratopathy.