Elsevier

Free Radical Biology and Medicine

Volume 49, Issue 9, 15 November 2010, Pages 1354-1360
Free Radical Biology and Medicine

Original Contribution
Identifying peroxidases and their oxidants in the early pathology of cystic fibrosis

https://doi.org/10.1016/j.freeradbiomed.2010.07.010Get rights and content

Abstract

We aimed to determine whether myeloperoxidase (MPO) is the main peroxidase present in the airways of children with cystic fibrosis (CF) and to assess which oxidants it produces and whether they are associated with clinical features of CF. Children with CF (n = 54) and without CF (n = 16) underwent bronchoscopy and bronchoalveolar lavage (BAL) for assessment of pulmonary infection and inflammation. BAL fluid was analyzed for MPO, halogenated tyrosines as markers of hypohalous acids, thiocyanate, and protein carbonyls. MPO was the only peroxidase detected in BAL samples from children with CF and its concentration was markedly higher than in controls. Levels of 3-chlorotyrosine and 3-bromotyrosine in proteins were higher in the CF group. They correlated with neutrophils and MPO. The concentration of thiocyanate in BAL samples was below 1 μM. Protein carbonyl levels correlated with MPO and halogenated tyrosines in patients with CF. Levels of MPO and halogenated tyrosines were higher in children with infections, especially Pseudomonas aeruginosa, and in the presence of respiratory symptoms. They also correlated with the Kanga clinical score. Our findings suggest that MPO produces hypobromous acid as well as hypochlorous acid in the airways of children with CF and that these oxidants are involved in the early pathogenesis of CF.

Section snippets

Materials

Potassium thiocyanate was supplied by Ajax Chemicals (Sydney, Australia) and 3,3′,5,5′-tetramethylbenzidine (TMB) was from Fluka Chemie GmbH (Buchs, Switzerland). p-Nitrophenyl phosphate was supplied by Strem Chemicals (Newburyport, MA, USA). Riboflavin was obtained from Eastman Organic Chemicals (Rochester, NY, USA) and crystal violet was from Peking Chemical Works (Peking, China). L-Tyrosine-U-13C9 and L-tyrosine-ring-13C6 were obtained from Cambridge Isotope Laboratories (Andover, MA, USA).

Characteristics of the study population

Subject characteristics are shown in Table 1. Children in the NCF group were on average 1.5 years older than those in the CF group; the majority (88%) had respiratory symptoms at the time of BAL and almost half had pulmonary infection. Children with CF had an increased number of neutrophils compared to the NCF group, even after adding age as a confounding variable (p = 0.013). Eosinophils were detected in the BALF of 29 children with CF (group geometric mean (95% CI): 5.30 (3.01, 9.33) × 103/ml) and

Discussion

In an earlier study we demonstrated that myeloperoxidase was the predominant peroxidase in BAL from infants with CF and that it produced HOCl [7]. We have now confirmed these findings in a different population of children with CF and extended our work to show that MPO also actively produces HOBr within the airways, and that levels of MPO as well as biomarkers of HOCl and HOBr were increased in the presence of infection and respiratory symptoms. They also correlated with the Kanga score, a

Acknowledgments

We thank the Health Research Council of New Zealand and the Australian Cystic Fibrosis Research Trust for supporting this work. Eline Thomson was supported by the Christchurch School of Medicine and Health Sciences on a McGee Scholarship. Dr. Kettle has received speaking honoraria from AstraZeneca and Lilly and has received research grant support from AstraZeneca. The full authorship of this article includes the members of AREST CF: Elizabeth Balding, Luke J. Berry, Dr. Siobhain Brennan,

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