Abstract
Purpose: :
The barrier function of epithelia depends primarily on tight junctions, of which zonula occludens (ZO)-1 is a major component. 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 in vitro and corneal epithelial wound healing in vivo. We have now investigated the effect of PHSRN on ZO-1 expression in cultured human corneal epithelial cells.
Methods: :
Simian virus 40-transformed human corneal epithelial (HCE) cells were cultured with PHSRN or the control peptide NRSHP. Expression of ZO-1 was determined at the mRNA and protein levels by reverse transcription-polymerase chain reaction analysis and by both immunoblot analysis and flow cytometry, respectively. Phosphorylation of the signaling proteins ERK, JNK, p38 MAPK, and c-Jun was measured with the Bio-Plex system (Bio-Rad) and by immunoblot analysis.
Results: :
Exposure of HCE cells to PHSRN increased the abundance of ZO-1 mRNA in a concentration- and time-dependent manner. Incubation of the cells with the control peptide NRSHP had no effect on the amount of ZO-1 mRNA. PHSRN, but not NRSHP, also increased the abundance of ZO-1 protein in a concentration- and time-dependent manner. Exposure of the cells to PHSRN increased the phosphorylation of ERK, JNK, p38 MAPK, and c-Jun.
Conclusions: :
The fibronectin-derived peptide PHSRN up-regulates the expression of ZO-1 at the protein and mRNA levels in cultured human corneal epithelial cells. The effect of PHSRN on ZO-1 expression was accompanied by activation of mitogen-activated protein kinase cascades and the transcription factor c-Jun. In addition to its stimulation of the migration of corneal epithelial cells, PHSRN may thus also promote the formation of tight junctions between these cells.
Keywords: cornea: epithelium • wound healing • cell adhesions/cell junctions