Synergistic effect with Phe‐Gly‐Leu‐Met‐NH 2 of the C‐terminal of substance P and insulin‐like growth factor‐1 on epithelial wound healing of rabbit cornea

We previously reported that substance P and insulin‐like growth factor‐1 (IGF‐1) synergistically stimulate corneal epithelial wound healing in vitro and in vivo . We wished to identify which portion of the amino acid sequence of substance P might be responsible for this synergism. Corneal epithelial migration was not affected by the addition of any one of the following factors: substance P; Phe‐Gly‐Leu‐Met‐NH 2 (C‐terminal of substance P); Val‐Gly‐Leu‐Met‐NH 2 (C‐terminal of neurokinin A, neurokinin B, and kassinin); Tyr‐Gly‐Leu‐Met‐NH 2 (C‐terminal of physalaemin); Ile‐Gly‐Leu‐Met‐NH 2 (C‐terminal of eledoisin); or Gly‐Leu‐Met‐NH 2 (common C‐terminal of tachykinins). In the presence of IGF‐1, only substance P and Phe‐Gly‐Leu‐Met‐NH 2 were synergistic in stimulating corneal epithelial migration in a dose‐dependent fashion. The combination of Phe‐Gly‐Leu‐Met‐NH 2 and IGF‐1 did not affect the incorporation of [ 3 H]‐thymidine into corneal epithelial cells. Treatment with Phe‐Gly‐Leu‐Met‐NH 2 and IGF‐1, but not with Phe‐Gly‐Leu‐Met‐NH 2 or IGF‐1 alone, increased attachment of corneal epithelial cells to a fibronectin matrix. The levels of α5 and β1 integrin were not affected by Phe‐Gly‐Leu‐Met‐NH 2 or IGF‐1 alone, but they were significantly increased by the combination of Phe‐Gly‐Leu‐Met‐NH 2 and IGF‐1. Topical application of the same combination facilitated corneal epithelial wound closure in vivo . These results demonstrated that Phe‐Gly‐Leu‐Met‐NH 2 , a sequence of 4 amino‐acids of the C‐terminal of substance P, is the minimum sequence necessary to produce the synergistic effects of substance P and IGF‐1 on corneal epithelial wound healing.British Journal of Pharmacology (1999) 127 , 489–497; doi: 10.1038/sj.bjp.0702550