A New Recombinant PACAP-Derived Peptide Efficiently Promotes Corneal Wound Repairing and Lacrimal Secretion

A new recombinant pituitary adenylate cyclase-activating polypeptide (PACAP)-derived peptide, MPAPO, which has higher stability and PAC1-specific potency, was generated. The actions of MPAPO on corneal wound repairing and lacrimal secretion were examined.

MPAPO was prepared and identified by gene recombination, high-performance liquid chromatography (HPLC), and electrospray ionization mass spectrometry (ESI-MS). Stability assay was performed by HPLC-ESI-MS. PAC1-specific binding and potency assays were performed using PAC1-CHO cells. C57BL/6 mice and Japanese white rabbits were respectively used to analyze the effects of MPAPO on corneal wound repairing and lacrimal fluid secretion. Tetrazolium-based colorimetric assay (MTT), immunofluorescence, gene microarrays, and Western blot assay were performed to measure the effects of MPAPO on corneal epithelial cell proliferation, synapse growth, and gene differential expression of trigeminal ganglion cells.

As compared with the wild PACAP, the in vitro stability and PAC1-specific potency of MPAPO with four mutations (M17L, L27K and M, K, respectively, added to the N- and C-terminus) were increased approximately 31- and 2-fold, respectively. MPAPO can significantly promote the proliferation of mouse corneal epithelium cells and the synapse growth of trigeminal ganglion cells. In experimental animals, MPAPO performed a complete corneal epithelial wound closure in 30 hours and significantly inhibited corneal neovascularization, and the effects were obviously stronger than for wild PACAP and recombinant bovine (rb)-bFGF (an anti-corneal wound drug). Furthermore, MPAPO can increase the lacrimal secretion, which may efficiently improve dry eye.

MPAPO may represent a promising external therapeutic peptide for corneal wound repairing or dry eye.