TUMOR-NECROSIS-FACTOR-ALPHA STIMULATES HUMAN CLARA CELL SECRETORY PROTEIN-PRODUCTION BY HUMAN AIRWAY EPITHELIAL-CELLS

Clara cell secretory protein (CCSP), or CC10, is an inhibitor of secre tory phospholipase A(2) which may be produced by phagocytic cells and by a variety of other cells in the airway. Tumor necrosis factor-alpha (TNF-alpha) is capable of activating phospholipases and inducing the expression of a variety of genes in the airway epithelium which may mo dulate the airway inflammatory response. Therefore, it was of interest to determine whether this proinflammatory cytokine could induce the p roduction of a counterregulatory protein such as CCSP which might modu late the production of eicosanoid mediators in the airway. Using a hum an bronchial epithelial cell line (BEAS-2B), CCSP messenger RNA (mRNA) levels were detected by ribonuclease protection assay. TNF treatment of these cells increased CCSP mRNA levels in a time- and dose-dependen t manner. The CCSP mRNA level increased in response to TNF-alpha (20 n g/ml) stimulation after 8 to 36 h with the peak increase at 18 h. Immu noblotting of CCSP protein released into the culture media demonstrate d that TNF-alpha induced the synthesis and secretion of CCSP protein i n a time-dependent manner over 8 to 18 h. The results of a CCSP report er gene activity assay, nuclear run-on assay, and CCSP mRNA half-life assay indicated that the TNF-alpha-induced increases in CCSP gene expr ession are regulated at the post-transcriptional level. We conclude th at TNF-alpha induces airway epithelial cell expression of human CCSP p rotein and may modulate airway inflammatory responses in this manner.