Abstract
Purpose: :
Recent studies show that epidermal growth factor (EGF) stimulates the synthesis of Lipoxin A4 (LxA4), a promoter of epithelial wound healing (ARVO 2008). EGF is a potent inducer of 12-lipoxygenase (12-LOX) in rabbit corneal epithelial cells (RCEC)(Exp.Eye.Res.76:613,2003).This enzyme converts arachidonic acid to 12(S)HETE and is also involved in the synthesis of LxA4. Here we demonstrate that activation of the EGF receptor (EGF-R) is needed for the induction of LxA4 and that 12/15-LOX plays a fundamental role in EGF-induced wound healing.
Methods: :
RCEC were pretreated with the EGF-R inhibitor AG 1478 (10µM) before stimulation with EGF(10ng/ml) for 36 h. Total RCE cell homogenate was incubated with (20µM) LTA4, and the synthesis of 12(S)HETE and LxA4 was analyzed by LC-ESI-MS/MS. To assess corneal epithelial wound healing, 2mm epithelial debridement wounds were made in 12/15-LOX-deficient mice (ALOX-15 knockout mice). Mice corneas were stimulated with EGF or LxA4 for 24 h.
Results: :
Inhibition of EGF-R decreased during the synthesis of 12(S)HETE and LxA4 by almost 75% and 80% respectively, compared with EGF-stimulated RCE cells. ALOX-15 knockout mice showed a 2-fold decrease in wound healing promoted by EGF, compared to wild type stimulated with EGF. However, stimulation with LxA4 induced similar wound healing in both mice.
Conclusions: :
Our results demonstrate that activation of the EGF-R induces the synthesis of LxA4 and that the presence of 12/15-LOX is essential to promoting epithelial wound healing activated by EGF.
Keywords: wound healing • growth factors/growth factor receptors • lipids