title: Oxidation of calprotectin by hypochlorous acid prevents chelation of essential metal ions and allows bacterial growth: Relevance to infections in cystic fibrosis.
abstract: Calprotectin provides nutritional immunity by sequestering manganese and zinc ions. It is abundant in the lungs of patients with cystic fibrosis but fails to prevent their recurrent infections. Calprotectin is a major protein of neutrophils and composed of two monomers, S100A8 and S100A9. We show that the ability of calprotectin to limit growth of Staphylococcus aureus and Pseudomonas aeruginosa is exquisitely sensitive to oxidation by hypochlorous acid. The N-terminal cysteine residue on S100A9 was highly susceptible to oxidation which resulted in cross-linking of the protein monomers. The N-terminal methionine of S100A8 was also readily oxidized by hypochlorous acid, forming both the methionine sulfoxide and the unique product dehydromethionine. Isolated human neutrophils formed these modifications on calprotectin when their myeloperoxidase generated hypochlorous acid. Up to 90% of the N-terminal amine on S100A8 in bronchoalveolar lavage fluid from young children with cystic fibrosis was oxidized. Oxidized calprotectin was higher in children with cystic fibrosis compared to disease controls, and further elevated in those patients with infections. Our data suggest that oxidative stress associated with inflammation in cystic fibrosis will stop metal sequestration by calprotectin. Consequently, strategies aimed at blocking extracellular myeloperoxidase activity should enable calprotectin to provide nutritional immunity within the airways.
authors.affiliation: Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Magon
authors.affiliation: Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand.
authors.forename: Rufus
authors.initials: R
authors.lastname: Turner
authors.affiliation: Department of Medicine, University of Otago, Christchurch, New Zealand.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Gearry
authors.affiliation: Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Hampton
authors.affiliation: Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand; Department of Medicine, University of Otago, Christchurch, New Zealand.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Sly
authors.affiliation: Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand. Electronic address: tony.kettle@otago.ac.nz.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Kettle
mesh_terms: D000595:Amino Acid Sequence; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000382:microbiology; D006801:Humans; D006997:Hypochlorous Acid / Q000737:chemistry*; D007223:Infant; D039841:Leukocyte L1 Antigen Complex / Q000737:chemistry* / Q000502:physiology; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000276:immunology / Q000382:microbiology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000254:growth & development; D013211:Staphylococcus aureus / Q000254:growth & development
chemical_list: D039841:Leukocyte L1 Antigen Complex; D006997:Hypochlorous Acid
keywords: Calprotectin; Dehydromethionine; Hypochlorous acid; Methionine; Methionine sulfoxide; Nutritional immunity; S100A8; S100A9