SYNERGISTIC CYTOTOXICITY FROM NITRIC-OXIDE AND HYPEROXIA IN CULTURED LUNG-CELLS

Exogenous nitric oxide (NO) is being tested clinically for the treatme nt of pulmonary hypertension in infants and children. In mast cases, t hese patients receive simultaneous oxygen (O-2) therapy. However, litt le is known about the combined toxicity of NO+hyperoxia. To test this potential toxicity, human alveolar epithelial cells (A549 cells) and h uman lung microvascular endothelial lung cells were cultured in room a ir (control), hyperoxia (95% O-2), NO (derived from chemical donors), or combined hyperoxia+NO. Control cells grew normally over a 6-day stu dy period. In contrast, cell death from hyperoxia was evident after 4- 5 days, whereas cells neither died nor divided in NO alone. However, c ells exposed to both NO and hyperoxia began to die on day 2 and died r apidly thereafter. This cytotoxic effect was clearly synergistic, and cell death did not occur via apoptosis. As an indicator of peroxynitri te formation, nitrotyrosine-containing proteins were assayed using ant i-nitrotyrosine antibodies. Two protein bands, at molecular masses of 25 and 35 kDa, were found to be increased in A549 cells exposed to NO or NO+hyperoxia. These results indicate that combined NO+hyperoxia has a synergistic cytotoxic effect on alveolar epithelial and lung vascul ar endothelial cells in culture.