Abstract
Purpose: :
Corneal epithelial cells are subject to various insults and turnover continuously through apoptosis. We have previously shown that the peptide PHSRN, which corresponds to the second cell-binding domain of fibronectin, stimulates both migration of the corneal epithelium and corneal epithelial wound healing. We have now investigated the effect of the PHSRN peptide on apoptosis in cultured human corneal epithelial cells.
Methods: :
Simian virus 40-transformed human corneal epithelial (HCE) cells were incubated with sodium nitroprusside (SNP), a nitric oxide donor and inducer of apoptosis, in the absence or presence of the PHSRN peptide. Apoptosis was detected by flow cytometric analysis of cells stained with annexin V and propidium iodide. Phosphorylation of the protein kinase Akt, which plays an important role in antiapoptotic signaling, was assessed by immunoblot analysis. Cell death was also quantified by measurement of the release of lactate dehydrogenase (LDH) into culture supernatants, and cell proliferation was evaluated by measurement of [3H]thymidine incorporation.
Results: :
SNP (1 mM) induced the release of LDH from HCE cells as well as an increase in the proportion of apoptotic (annexin V+, propidium iodide-) cells, and both of these effects were inhibited by the PHSRN peptide (1 µg/ml). The inhibitory effects of the PHSRN peptide on SNP-induced LDH release and apoptosis were blocked by LY294002 (10 µM), an inhibitor of phosphatidylinositol 3-kinase. The PHSRN peptide also induced the phosphorylation of Akt, but it had no effect on HCE cell proliferation.
Conclusions: :
The fibronectin-derived peptide PHSRN suppresses the induction of apoptosis in cultured human corneal epithelial cells, and this effect may be mediated by the activation of phosphatidylinositol 3-kinase and Akt.
Keywords: apoptosis/cell death • extracellular matrix • cornea: epithelium