Keratinocyte growth factor promotes alveolar epithelial cell DNA repair after H2O2 exposure.
Alveolar epithelial cell (AEC) injury and repair are important in the pathogenesis of oxidant-induced lung damage. Keratinocyte growth factor (KGF) prevents lung damage and mortality in animals exposed to various forms of oxidant stress, but the protective mechanisms are not yet established. Because DNA strand break (DNA-SB) formation is one of the earliest cellular changes that occurs after cells are exposed to an oxidant stress, we determined whether KGF reduces H2O2-induced pulmonary toxicity by attenuating AEC DNA damage. KGF (10-100 ng/ml) decreased H2O2 (0.05-0.5 mM)-induced DNA-SB formation in cultured A549 and rat alveolar type II cells measured by an alkaline unwinding, ethidium bromide fluorometric technique. The protective effects of KGF were independent of alterations in catalase, glutathione (GSH), or the expression of bcl-2 and bax, two protooncogenes known to regulate oxidant-induced apoptosis. Actinomycin D and cycloheximide abrogated protective effects of KGF. Furthermore, protection by KGF was completely blocked by 1) genistein, a tyrosine kinase inhibitor; 2) staurosporine and calphostin C, protein kinase C (PKC) inhibitors; and 3) aphidicolin, butylphenyl dGTP, and 2',3'-dideoxythymidine 5'-triphosphate, inhibitors of DNA polymerase. We conclude that KGF attenuates H2O2-induced DNA-SB formation in cultured AECs by mechanisms that involve tyrosine kinase, PKC, and DNA polymerases. These data suggest that the ability of KGF to protect against oxidant-induced lung injury is partly due to enhanced AEC DNA repair.
Pulmonary and Critical Care Medicine, Veterans Affairs Chicago Health Care System (Lakeside Division) and Northwestern University Medical School, Chicago, Illinois 60611, USA.
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Wu
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Pollack
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Panos
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Sporn
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D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects*; D003609:Dactinomycin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051526:Fibroblast Growth Factor 10; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D019833:Genistein / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology* / Q000502:physiology; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D007700:Kinetics; D008175:Lung Neoplasms; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D019311:Staurosporine / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; C496453:FGF7 protein, human; C496455:Fgf7 protein, rat; D051526:Fibroblast Growth Factor 10; D006133:Growth Substances; D009281:Naphthalenes; D051523:Fibroblast Growth Factor 7; D003609:Dactinomycin; D016590:Aphidicolin; D005346:Fibroblast Growth Factors; D003513:Cycloheximide; D006861:Hydrogen Peroxide; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D019311:Staurosporine; C058819:calphostin C