Eosinophils generate brominating oxidants in allergen-induced asthma
Weijia Wu, … , Serpil C. Erzurum, Stanley L. Hazen
Weijia Wu, … , Serpil C. Erzurum, Stanley L. Hazen
Published May 15, 2000
Citation Information: J Clin Invest. 2000;105(10):1455-1463. https://doi.org/10.1172/JCI9702.
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Article

Eosinophils generate brominating oxidants in allergen-induced asthma

Abstract

Eosinophils promote tissue injury and contribute to the pathogenesis of allergen-triggered diseases like asthma, but the chemical basis of damage to eosinophil targets is unknown. We now demonstrate that eosinophil activation in vivo results in oxidative damage of proteins through bromination of tyrosine residues, a heretofore unrecognized pathway for covalent modification of biologic targets in human tissues. Mass spectrometric studies demonstrated that 3-bromotyrosine serves as a specific “molecular fingerprint” for proteins modified through the eosinophil peroxidase-H2O2 system in the presence of plasma levels of halides. We applied a localized allergen challenge to model the effects of eosinophils and brominating oxidants in human lung injury. Endobronchial biopsy specimens from allergen-challenged lung segments of asthmatic, but not healthy control, subjects demonstrated significant enrichments in eosinophils and eosinophil peroxidase. Baseline levels of 3-bromotyrosine in bronchoalveolar lavage (BAL) proteins from mildly allergic asthmatic individuals were modestly but not statistically significantly elevated over those in control subjects. After exposure to segmental allergen challenge, lung segments of asthmatics, but not healthy control subjects, exhibited a >10-fold increase in BAL 3-bromotyrosine content, but only two- to threefold increases in 3-chlorotyrosine, a specific oxidation product formed by neutrophil- and monocyte-derived myeloperoxidase. These results identify reactive brominating species produced by eosinophils as a distinct class of oxidants formed in vivo. They also reveal eosinophil peroxidase as a potential therapeutic target for allergen-triggered inflammatory tissue injury in humans.

Authors

Weijia Wu, Michael K. Samoszuk, Suzy A.A. Comhair, Mary Jane Thomassen, Carol F. Farver, Raed A. Dweik, Mani S. Kavuru, Serpil C. Erzurum, Stanley L. Hazen

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Effect of localized allergen challenge on allergic asthmatic airway and ...
Effect of localized allergen challenge on allergic asthmatic airway and BAL proteins. An allergic asthmatic subject underwent fiberoptic bronchoscopy and ragweed allergen was instilled into a specific segment of one lung. A segment in the contralateral lung was similarly challenged with normal saline. Forty-eight hours later, fiberoptic bronchoscopy was repeated and both allergen- and normal saline–challenged lung segments were lavaged with normal saline and biopsied. (a and b) Hematoxylin and eosin staining of (a) normal saline- and (b) allergen-challenged lung segments reveals intense leukocyte infiltration and red granular debris from eosinophils in the allergen-challenged segment. High-power magnification view (data not shown) demonstrated that the majority of leukocytes recruited to the allergen-challenged airways were eosinophils. (c and d) Histological analysis of (c) normal saline– and (d) allergen-challenged lung segments by in situ fluorescence microscopy under conditions specific for the heme moiety of EPO reveals intense fluorescence signal in the allergen-challenged segment. (e and f) Protein recovered in BAL fluid from (e) normal saline– and (f) allergen-challenged lung segments of an asthmatic subject were analyzed by stable isotope dilution GC-MS for the presence of 3-bromotyrosine (BrY) using selected ion monitoring mode. The chromatograms shown were monitored at m/z 445, the base ion for the n-propyl, per pentafluoroproprionyl derivative of 3-bromotyrosine (Figure 1c), as well as the corresponding isotopically enriched counterpart at m/z 451 derived from the internal standard, 3-bromo[13C6]tyrosine.