Enhanced release of superoxide from polymorphonuclear neutrophils in obstructive sleep apnea - Impact of continuous positive airway pressure therapy

Obstructive sleep apnea (OSA) is associated with increased cardiovascular m orbidity and mortality. Free oxygen radicals have been implicated in the pa thogenesis of cardiovascular disorders. Therefore, we aimed to test the hyp othesis that increased oxidative stress constitutes one underlying mechanis m for the connection between OSA and cardiovascular disease. In 18 patients with OSA the release of superoxide from polymorphonuclear neutrophils was determined after stimulation with the bacterial tripeptide formylmethionyll eucylphenylalanine (fMLP) and the calcium ionophore A23. Superoxide product ion was measured as superoxide dismutase-inhibitable reduction of cytochrom e c. Blood samples were obtained before and after two nights of CPAP therap y and after 4.8 +/- 0.6 mo of follow-up. Ten healthy young volunteers and 1 0 lung cancer patients without OSA but a similar spectrum of comorbidity se rved as controls. Before CPAP, neutrophil superoxide generation was markedl y enhanced in OSA when compared with both control groups. Effective CPAP th erapy led to a rapid and long-lasting decrease of superoxide release in OSA . In conclusion, OSA is linked with a "priming" of neutrophils for enhanced respiratory burst. The increased superoxide generation, which might have m ajor impact on the development of cardiovascular disorders, is virtually fu lly reversed by effective CPAP therapy.