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

SummaryBackground & aimsAntioxidant 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 (α-tocopherol and glutathione) in asthma, by measuring the oxidized and reduced forms, in the airways (induced sputum) and systemically (peripheral blood).MethodsThis 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. α-tocopherol and α-tocopherol quinone were measured by HPLC. Total glutathione and glutathione disulfide were determined by a colorimetric assay.ResultsPlasma α-tocopherol was low in asthma versus controls. Subjects with asthma had higher levels of whole blood α-tocopherol quinone and %α-tocopherol quinone than controls and %α-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 FEV1/FVC% (p = 0.029).ConclusionsIn asthma, both systemic and airway antioxidant defences are disturbed. Oxidized forms of α-tocopherol and glutathione are associated with clinical asthma outcomes, and should be further investigated as a tool for monitoring asthma.