Oxidative stress plays an important role in the pathogenesis of asthma via the upregulation of local inflammatory mediators and/or promoting Th2-skewing during Ag sensitization. Thioredoxin (TRX), a 12 kDa redox-active protein with antioxidative property, has been recently shown to play a protective role in various inflammatory diseases. Using a mouse model of asthma, we show here that IL-13 and eotaxin production are decreased in TRX-Tg mice leading to reduced eosinophils recruitment and mucus metaplasia. The reduction in airway inflammation occurs without the attenuation of systemic Th2 immunity in that comparable levels of Th2-type cytokines and Ig were detected in LN and serum, respectively, from TRX-Tg and WT mice. Likewise, CD4 1 T cells from both strains of mice developed similar Th1 and Th2 responses in vitro. Asthmatic lungs of TRX-Tg and WT mice contained similar amounts of GATA-3 1 and Foxp3 1 T cells. Finally, production of MIF, an upstream modulator of airway inflammation, was significantly reduced in the lungs of TRX-Tg mice. Our data suggest that TRX suppresses airway inflammation by inhibiting MIF production thereby limiting the downstream recruitment of eosinophils to the lung independently of modulating systemic Th1/Th2 immunity.

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