Effects of atrial natriuretic peptide and sodium nitroprusside on epidermal growth factor-stimulated wound repair in rabbit corneal epithelial cells

Abstract

Purpose. Treatment of rabbit corneal epithelial cells (RCEC) with epidermal growth factor (EGF) stimulates cell proliferation and wound repair in a cell culture model system. Studies have also shown that atrial natriuretic peptide (ANP) and sodium nitroprusside (SNP), a nitric oxide-generating agent, inhibit proliferation of a variety of cell types. The aim of the present work was to examine whether ANP or SNP has any effect on EGF-stimulated proliferation of RCEC involved in wound repair. Methods. The SV-40 immortalized RCEC were cultured in 24-well plates until they became confluent. Wounds of uniform size (8 mm diameter) were created and the cells allowed to grow in the presence and absence of EGF and/or other agents. At prescribed time intervals, the cells were stained by Giemsa and the wound areas digitized and quantified by Sigma Image Scan System. The cGMP contents in RCEC, treated with or without ANP or SNP, were measured by radioimmunoassay. Results. Addition of EGF (1–100 ng/ml) to RCEC stimulated cell proliferation which significantly reduced the time required for wound closure. Addition of ANP (1 nM to 10 µM) or SNP (10 µM to 1 mM), in the presence of EGF, dose-dependently inhibited the growth factor-stimulated wound closure in RCEC. When added alone to the cells, ANP or SNP increased cGMP accumulation in a dose-dependent manner. Addition of ANP (1 µM) or SNP (1 mM) to primary corneal epithelial cells, in the presence and absence of EGF, also inhibited the wound closure with a corresponding increase in cGMP contents. Treatment of the cells with ODQ (10 nM to 10 µM), a soluble guanylate cyclase inhibitor, dose-dependently decreased the SNP-induced accumulation of cGMP, and reversed the inhibitory effect of SNP on EGF-stimulated wound closure. Addition of membrane-permeable cGMP analog, 8-bromo-cGMP, to RCEC inhibited the EGF-stimulated wound closure in a dose-dependent manner. Treatment of RCEC with mitomycin C (5 µM) exerted a marked inhibitory effect on wound closure in the presence and absence of EGF, and also abrogated the inhibitory effect of 8-bromo-cGMP on wound closure in the EGF-treated and untreated cells. Conclusions. The results demonstrate that ANP and SNP inhibit the EGF-stimulated wound repair in RCEC. The effect of these agents is mediated via activation of guanylate cyclases that generate cGMP. Cyclic GMP appears to exert its inhibitory effect at the level of cell proliferation and not cell migration. The data suggest an important role for cGMP-dependent protein kinase in proliferation of RCEC stimulated by EGF.