Chronic oxidative stress reduces the respiratory burst response of neutrophils from beta‐thalassaemia patients

Summary Beta‐thalassaemia patients are susceptible to infections by mechanisms that are not fully understood. Polymorphonuclear neutrophils (PMN) destroy microbes by producing a burst of reactive oxygen species (ROS) (respiratory burst) in response to bacterial components, as well as to phorbol‐myristate‐acetate (PMA). In the present study, we compared ROS generation by normal and β‐thalassaemia PMN and assessed their response to PMA. Blood cells were subjected to gelatin separation, staining with dichlorofluorescin‐diacetate and flow cytometry. At basal level, the fluorescence (mean fluorescence channel) of normal and thalassaemia PMN were 12·7 ± 4·5 and 95·6 ± 19·8 respectively; it changed to 283·4 ± 72·5 and 39·5 ± 14·3, respectively, upon PMA stimulation, indicating that thalassaemia PMN have a higher basal ROS but a reduced response to PMA. When normal PMN were treated with the oxidants hydrogen peroxide and butyl‐hydroxyperoxide, as well as iron and haemin, which are elevated in thalassaemia, their basal ROS increased 5–22‐fold, but the PMA response was abolished. Treating thalassaemic PMN with antioxidants (N‐acetyl‐l‐cysteine or vitamins C and E) reduced their basal ROS but enhanced their PMA response. Our findings indicate that chronically stressed PMN, e.g. in thalassaemia, have reduced capacity to elicit a respiratory burst, which may compromise their antibacterial capacity, and imply prophylactic treatment with antioxidants for recurrent infections.