Glutathione peroxidase activity and mRNA expression in eosinophils and neutrophils of asthmatic and non-asthmatic subjects.

Asthma has been reported to be associated with a reduction in the activity of glutathione peroxidase (GSH-Px), an important antioxidant enzyme. However, the expression of GSH-Px enzyme activity has not previously been investigated in human eosinophils, which are important inflammatory cells involved in asthma. Reverse transcriptase-polymerase chain reaction and Southern blotting demonstrated that eosinophils express GSH-Px mRNA and the relative expression of GSH-Px was greater in eosinophils than in neutrophils for both asthmatic and non-asthmatic subjects. The presence of GSH-Px protein in eosinophil and neutrophil lysates was confirmed by size exclusion chromatography and by Western blotting. GSH-Px enzyme activity as measured by a spectrophotometric assay was greater in eosinophil (48.4+/-1.6 micromol NADPH oxidized x min(-1) x g(-1) protein) than in neutrophil lysates (18.1+/-0.4, n = 24, P < 0.0001). GSH-Px activities of eosinophils and neutrophils from asthmatic subjects did not differ from those of non-asthmatic subjects. Eosinophil GSH-Px activity was correlated with peripheral blood eosinophil count only in asthmatic subjects (rs = 0.59, n = 12, P = 0.04). Increased GSH-Px expression in eosinophils compared with neutrophils of asthmatic patients may provide antioxidant protection against the greater amounts of reactive oxygen species generated by these cells and may enhance the survival of eosinophils at sites of inflammation in asthma.