NITRIC-OXIDE DECREASES SURFACTANT PROTEIN-A GENE-EXPRESSION IN H441 CELLS

Objective: To study the effects of nitric oxide (NO) on surfactant pro tein A (SP-A) gene expression, Design: In vitro study, Subjects: A hum an lung tumor cell line (H441) representative of distal respiratory ep ithelium, Interventions: Cells were treated with the NO donor S-nitros o-N-acetyl penicillamine (SNAP) at concentrations ranging from 0.3 to 3.0 mM for 24 hrs, Measurements and Main Results: Northern blot analys es using a radiolabeled cDNA probe for human SP-A demonstrated that SN AP modestly (similar to 30%) decreased SP-A mRNA expression in a dose- dependent manner, Western blot analyses using a polyclonal anti-human SP-A antibody demonstrated that SNAP also decreased SP-A peptide expre ssion. mRNA stability assays demonstrated that SNAP did not affect the half-life of SP A mRNA, Cell viability assays demonstrated that SNAP slightly decreased cell viability compared with control cells. There w ere no significant differences in cell viability among cells treated w ith the different concentrations of SNAP, Conclusions: NO decreases in vitro SP-A gene expression by similar to 30% in a human lung tumor ce ll line representative of distal respiratory epithelium. This effect d oes not occur at the posttranscriptional level and cannot be entirely accounted for by changes in cell viability, The inhibitory effect of N O demonstrated in this study is of relatively small magnitude and it i s therefore difficult to make strong conclusions regarding biological relevance. However, these data, coupled with previous data demonstrati ng that NO negatively affects surfactant function, suggest that NO has the potential to negatively impact surfactant homeostasis.