Oxidized vitamin E and glutathione as markers of clinical status in asthma

Abstract

Antioxidant status is disturbed in asthma. Measurement of both oxidized and reduced forms of antioxidants provides important information regarding the oxidant/antioxidant balance. The aim of this study was to investigate the clinical relevance of key antioxidants (alpha-tocopherol and glutathione) in asthma, by measuring the oxidized and reduced forms, in the airways (induced sputum) and systemically (peripheral blood). This cross-sectional study examines stable asthmatics (n=44) and healthy controls (n=31) recruited through John Hunter Hospital, NSW, Australia. We collected peripheral blood and induced sputum during hypertonic saline challenge. Alpha-tocopherol and alpha-tocopherol quinone were measured by HPLC. Total glutathione and glutathione disulfide were determined by a colorimetric assay. Plasma alpha-tocopherol was low in asthma versus controls. Subjects with asthma had higher levels of whole blood alpha-tocopherol quinone and %alpha-tocopherol quinone than controls and %alpha-tocopherol quinone correlated with asthma control (p=0.009). Sputum supernatant levels of total, reduced and oxidized glutathione were elevated in asthma versus controls. Oxidized glutathione in sputum supernatant negatively correlated with FEV(1)/FVC% (p=0.029). In asthma, both systemic and airway antioxidant defences are disturbed. Oxidized forms of alpha-tocopherol and glutathione are associated with clinical asthma outcomes, and should be further investigated as a tool for monitoring asthma.