Superoxide anion production by monocytes of corticosteroid-treated asthmatic patients

Reactive oxygen species play an important role in promoting inflammation. Blood monocytes have been described to release higher amounts of superoxide anion in uncontrolled and untreated asthmatics. Corticosteroids are widely used in asthma, but little is known about their molecular mechanism of action. The aim of our study was to analyse the ex vivo effect of corticosteroid treatments on superoxide anion release by blood monocytes. Superoxide anion release was measured by a spectrophotometric method based on the superoxide dismutase (SOD) -inhibitable reduction of ferricytochrome C by blood monocytes from untreated patients and asthmatics treated with i.v., inhaled and oral corticosteroids. Monocytes from uncontrolled and untreated asthmatics, released high amounts of superoxide anions. After short-term treatment with i.v., corticosteroids, this release was found to decrease significantly (1.410 versus 0.340 nM, p<0.05). Cells from asthmatics who had undergone long-term treatment with inhaled or oral steroids presented low amounts of superoxide anion production, with a significant difference as compared to untreated asthmatics (0.375 nM p<0.01 and 0.620 nM p<0.02 respectively). In general, patients with controlled asthma (treated with short-term oral steroids, or with long-term inhaled steroids) released lesser amounts of superoxide anion than uncontrolled and untreated asthmatics. In the case of steroid-dependent asthmatics there was no difference between patients with a controlled or uncontrolled disease.