Purpose: Substance P (SP) is present in the sensory nerve fibers of the corneal epithelium. Various biological agents, including epidermal growth factor, fibronectin, interleukin-6, and the combination of SP and insulin-like growth factor (IGF)-1, promote the healing of corneal epithelial wounds. The role of SP in corneal epithelial migration was examined.
Methods: The effects of various agents on corneal epithelial migration were investigated with the rabbit cornea in an organ culture system.
Results: An SP-derived tetrapeptide, FGLM-amide, shifted the dose-response relations for the induction of corneal epithelial migration not only by an IGF-1-derived peptide (C-domain peptide) but also by fibronectin or interleukin-6 to lower concentrations. This action of SP was prevented by inhibitors of phospholipase C, of the inositol 1,4,5-trisphosphate receptor-mediated release of Ca(2+) from intracellular stores, and of Ca(2+)- and calmodulin-dependent protein kinase II (CaM-PK II).
Conclusions: These results indicate that SP, acting at the neurokinin type 1 receptor, functions as an important modulator of corneal epithelial wound healing by activating CaM-PK II in epithelial cells and thereby sensitizing them to the induction of migration by various biological agents. They also provide important insight into a new strategy for the treatment of corneal wounds.