KGF PREVENTS HYDROGEN PEROXIDE-INDUCED INCREASES IN AIRWAY EPITHELIAL-CELL PERMEABILITY

Keratinocyte growth factor (KGF) has recently been shown to protect ra ts from hyperoxia-induced lung injury. However, the mechanism of the p rotective effect of KGF remains unclear. To elucidate the mechanism of action of KGF, we determined the effect of KGF on the barrier functio n of epithelial monolayers exposed to H2O2. Calu-3 (human airway epith elial cells) were grown on Transwell membranes,and the permeability to fluorescein isothiocyanate-albumin was measured. Exposure to 0.5 mM H 2O2 significantly increased permeability from 1.50 +/- 0.09 to 24.8 +/ - 1.5 (mean +/- SE x 10(-6) cm/s; P < 0.001). Incubation of monolayers with 50 ng/ml KGF for 24 h significantly reduced basal albumin flux ( 0.85 +/- 0.09; P < 0.001), and pretreatment with KGF completely abolis hed the H2O2-induced permeability increase (1.08 +/- 0.09). The protec tive effect of KGF was dose dependent and was observed at concentratio ns as low as 1 ng/ml. Partial amelioration of the H2O2-induced permeab ility increase occurred after 1 h of exposure to KGF. Treatment of cel ls with calphostin C, an inhibitor of protein kinase C (PKC), had no e ffect on the permeability of control or H2O2-treated cells. Calphostin C abolished both the KGF-mediated decrease in basal albumin flux and the protective effect of KGF against H2O2-induced increases in permeab ility. KGF pretreatment also prevented H2O2-induced disruption of F-ac tin staining patterns, suggesting stabilization of the cytoskeleton. T hese studies demonstrate that KGF decreases albumin flux across airway epithelial monolayers and prevents H2O2-induced increases in permeabi lity by a PKC-dependent process that may involve stabilization of the cytoskeleton.