Regulation of surfactant proteins A and B by TNF-α and phorbol ester independent of NF-κB.

Acute lung inflammation is complicated by altered pulmonary surfactant phospholipid and protein composition. The proinflammatory cytokine tumor necrosis factor-α (TNF-α) and the phorbol ester 12- O-tetradecanoyl phorbol-13-acetate (TPA) inhibit expression of surfactant-associated proteins A and B (SP-A and SP-B), both important for normal surfactant function. The transcription factor nuclear factor-κB (NF-κB) frequently mediates regulation of gene expression by TPA and TNF-α. In the present study, electrophoretic mobility shift assays (EMSAs) and pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-κB activation, were utilized to determine the role of NF-κB activation in TPA and TNF-α inhibition of the surfactant proteins in NCI-H441 cells. Pentoxifylline (PTX), which inhibits TNF-α cellular effects without preventing NF-κB activation, was also tested. By EMSA, TPA and TNF-α increased nuclear NF-κB binding activity in temporally distinct patterns. PDTC decreased TPA- and TNF-α-induced NF-κB binding activity but did not limit their inhibition of SP-A and SP-B mRNAs. PDTC independently decreased both SP-A and SP-B mRNAs. PTX partially reversed TNF-α- but not TPA-mediated inhibition of SP-A and SP-B mRNAs without altering NF-κB binding. The effects of PDTC and PTX on NF-κB and the surfactant proteins suggest that NF-κB activation does not mediate TPA or TNF-α inhibition of SP-A and SP-B mRNA accumulation.