Keratinocyte Growth Factor Stimulates CLC-2 Expression in Primary Fetal Rat Distal Lung Epithelial Cells

Keratinocyte growth factor (KGF) is mitogenic for epithelial cells and induces cystic dilation of fetal lung explants through cystic fibrosis transmembrane conductance regulator-independent chloride channels. One candidate fetal lung chloride channel that is highly expressed on the apical surface of the respiratory epithelium and markedly downregulated after birth is CLC-2. We hypothesized that KGF regulates CLC-2 expression in the fetal lung. Primary fetal rat distal lung epithelial cell monolayers were grown in medium containing 10 ng/ml KGF for 48 h. CLC-2 protein was increased by Western blot analysis of whole-cell lysates in KGF-treated cultures. Similarly, KGF stimulated CLC-2 messenger RNA (mRNA) by Northern blot analysis. This enhanced expression was dose-dependent and maximal at 48 h with 10 ng/ml KGF. Promoter-reporter gene experiments demonstrated that KGF did not stimulate gene transcription. By inhibition of new mRNA synthesis with actinomycin D, evidence was obtained that KGF stabilizes CLC-2 mRNA. We speculate that KGF may positively influence pulmonary chloride and fluid secretion by a secondary pathway affecting CLC-2 degradation.