Nitroaspirins and morpholinosydnonimine but not aspirin inhibit the formation of superoxide and the expression of gp91phox induced by endotoxin and cytokines in pig pulmonary artery vascular smooth muscle cells and endothelial cells

Background-Although nonsteroidal antiinflammatory drugs (NSAIDs) are ineffective in treating acute respiratory distress syndrome (ARDS), inhalational NO has proved to be useful. NO-donating NSAIDs may therefore be more effective in treating ARDS than NSAIDs alone. Because oxidant stress is central to the pathophysiology of ARDS, the effect of nitroaspirins (NCX 4016, NCX 4040, and NCX 4050) compared with morpholinosydnonimine (SIN-1; an NO donor) and aspirin (ASA) on superoxide (O-2(circle-)) formation and gp91(phox) (an active catalytic subunit of NADPH oxidase) expression in pig pulmonary artery vascular smooth muscle cells (PAVSMCs) and endothelial cells (PAECs) was investigated. Methods and Results - Cultured PAVSMCs and PAECs were incubated with lipopolysaccharide (LPS), tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1alpha (with or without NO-ASA, SIN-1, or ASA) for 16 hours, and O-2(circle-) release was measured by use of the reduction of ferricytochrome c. The expression of gp91(phox) was assessed by use of Western blotting. LPS, TNF-alpha, and IL-1alpha all stimulated the formation of O-2(circle-) and expression of gp91(phox) in both PAVSMCs and PAECs, an effect inhibited by NADPH oxidase inhibitors, diphenyleneiodonium, and apocynin. SIN-1, NCX 4016, and NCX 4050 but not ASA alone inhibited the formation of O-2(circle-) and expression of gp91(phox). Conclusions - LPS and cytokines promote the formation of O-2(circle-) in PAVSMCs and PAECs through an augmentation of NADPH oxidase activity, which in turn is prevented by NO. Thus, NO may play a protective role in preventing excess O-2(circle-) formation, but its negation by O-2(circle-) may augment the progress of ARDS. The inhibitory effect of nitroaspirins suggests that they may be therapeutically useful in treating ARDS through the suppression of NADPH oxidase upregulation and O-2(circle-) formation.