Nitric oxide is necessary for a switch from stationary to locomoting phenotype in epithelial cells

The restitution of epithelial integrity is accomplished in part by cell migration. Studying this process, we have found that nitric oxide (NO) release from migrating epithelial BSC-1 cells displayed a biphasic response to the inflicted wounds; an initial transient release of NO is followed by a delayed sustained elevation. Whereas the constitutive endothelial NO synthase (NOS) did not show any spatial or temporal changes associated with wounding, the inducible NOS became expressed 3 h after wounding and showed higher abundance at the edges of epithelial wounds. L-Arginine (L-Arg) or NO-donor, S-nitroso-N-acetyl-DL-penicillamine, exerted motogenic effect in epithelial and endothelial cells. Inhibition of NOS with N-G-nitro-L-arginine methyl ester (L-NAME) or a selective knockout of inducible NOS with antisense oligodeoxynucleotides reduced the rate of spontaneous or epidermal growth factor (EGF)-induced BSC-1 cell migration. Migrating cells showed the polarized expression of NOS, suggesting a head-to-rear NO gradient. Several growth factors (EGF, insulin-like growth factor I, hepatocyte growth factor, and fibroblast growth factor) were motogenic for BSC-1 cells, but this effect was abrogated by pretreatment with L-NAME. We conclude that endogenous NO production is a prerequisite for BSC-1 cell migration. A vectorial NO release may be essential for the spatially and temporally coordinated reciprocal phenomena that occur at the leading and trailing edge of locomoting epithelial cells. Although the exact mode of NO action remains uncertain, it is conceivable that the production of NO serves as a cellular switch from the stationary to the locomoting epithelial phenotype.