. We investigated the effects of NO donor on hypoxia-induced acute lung injury that occurs when transgenic sickle cell SAD mice are exposed to chronic hypoxia, a model for lung vasoocclusive sickle cell events. In wild-type and SAD mice, intraperitoneal injection of S-nitrosoalbumin (NO-Alb) produced no significant hematologic changes under room air conditions, whereas it induced mild temporary hypotension and inhibition of platelet aggregation. NO-Alb administration (300 mg/kg ip twice a day, equivalent to 7.5 M NO) in wild-type and SAD mice exposed to 46 h of hypoxia (8% oxygen) followed by 2 h of normoxia resulted in 1) reduction of the hypoxiainduced increase in blood neutrophil count, 2) prevention of hypoxiainduced increased IL-6 and IL-1 levels in bronchoalveolar lavage, 3) reduction of the lung injury induced by hypoxia-reoxygenation, 4) prevention of thrombus formation, and 5) prevention of hypoxiainduced increase of lung matrix metalloproteinase-9 gene expression. These effects provide new insights into the possible use of NO-Alb in the treatment of acute lung injury in SCD. transgenic sickle cell SAD mice; hypoxic lung injury; nitric oxide; nitrite NITRIC OXIDE (NO) is a potent vasodilator, an inhibitor of vascular remodeling, and a modulator of the cascade of events involved in leukocyte, platelet, and endothelial activation (8,9,21). Sickle cell disease patients show reduced NO metabolites during either vasoocclusive crisis associated with severe pain or acute chest syndrome as well as a decreased exhaled NO, suggesting a possible role of a relative NO lung deficiency in the pathogenesis of sickle cell-related pulmonary complications (25).