Sodium nitroprusside augments human lung fibroblast collagen gel contraction independently of NO-cGMP pathway

Nitric oxide (NO) relaxes vascular smooth muscle in part through an accumul ation of cGMP in the target cells. We hypothesized that a similar effect ma y also exist on collagen gel contraction mediated by human fetal lung (HFL1 ) fibroblasts, a model of wound contraction. To evaluate this, HFL1 cells w ere cultured in three-dimensional type I collagen gels and floated in serum -free DMEM with and without various NO donors. Gel size was measured with a n image analyzer. Sodium nitroprusside (SNP, 100 mu M) significantly augmen ted collagen gel contraction by HFL1 cells (78.5 +/- 0.8 vs. 58.3 +/- 2.1, P < 0.01), whereas S-nitroso-N-acetylpenicillamine, 5-amino-3-(4-morpholiny l)-1,2,3-oxadiazolium chloride, NONOate, and N-G-monomethyl-L-arginine did not affect the contraction. Sodium ferricyanide, sodium nitrate, or sodium nitrite was not active. The augmentory effect of SNP could not be blocked b y 1H-[1,2,4]-oxadiazolo-[4,3-alpha]-quinoxalin-1-one, whereas it was partia lly reversed by 8-(4-chlorophenylthio) (CPT)-cGMP. To further explore the m echanisms by which SNP acted, fibronectin and PGE(2) production were measur ed by immunoassay after 2 days of gel contraction. SNP inhibited PGE(2) pro duction and increased fibronectin production by HFL1 cells in a concentrati on-dependent manner. CPT-cGMP had opposite effects on fibronectin and PGE2 production. Addition of exogenous PGE2 blocked SNP-augmented contraction an d fibronectin production by HFL1 cells. Therefore, SNP was able to augment human lung fibroblast-mediated collagen gel contraction, an effect that app ears to be independent of NO production and not mediated through cGMP. Decr eased PGE2 production and augmented fibronectin production may have a role in this effect. These data suggest that human lung fibroblasts in three-dim ensional type I collagen gels respond distinctly to SNP by mechanisms unrel ated to the NO-cGMP pathway.