ENDOGENOUS NITRIC-OXIDE LIMITS CYTOKINE-INDUCED DAMAGE OF MURINE LUNGEPITHELIAL-CELLS

This study investigated whether endogenous nitric oxide (NO) limits cy tokine-induced damage to the murine lung epithelial cell Line LA-4. NO production was assessed as nitrite using the Griess reaction, and cel l damage was assessed using ethidium homodimer-l. Cytotoxicity was fir st detected after a 24-h incubation with a combination of tumor necros is factor-alpha, interleukin-1 beta, and interferon-gamma (cytomix). N itrite production increased to 78.0 +/- 0.5 nmol/10(6) cells at 24 h. Coincubation of LA-4 with cytomix and NO synthase inhibitors, aminogua nidine (3-1,000 mu M) and N-G-monomethyl-L-arginine (10-1,000 mu M), b ut not NG-monomethyl-D-arginine, or a soluble guanylate cyclase inhibi tor, 1H-[1,2,4] oxadiazole [4,3-a] quinoxalin-1-one, reduced cytomix-i nduced nitrite production and increased cytotoxicity up to twofold (24 h). Removal of L-arginine from the medium increased damage; reintrodu ction of 1,000 mu M L-arginine, but not D-arginine, reversed this. In aminoguanidine-treated cells, replacement of NO with an NO donor, S-ni trosoglutathione (30 mu M), reversed, in part, the cell damage observe d in aminoguanidine/cytomix-treated cells. These results suggest that endogenous NO Limits cytokine-induced lung epithelial damage.