title: The effects of hypochlorous acid and neutrophil proteases on the structure and function of extracellular superoxide dismutase.
abstract: Extracellular superoxide dismutase (EC-SOD) is expressed by both macrophages and neutrophils and is known to influence the inflammatory response. Upon activation, neutrophils generate hypochlorous acid (HOCl) and secrete proteases to combat invading microorganisms. This produces a hostile environment in which enzymatic activity in general is challenged. In this study, we show that EC-SOD exposed to physiologically relevant concentrations of HOCl remains enzymatically active and retains the heparin-binding capacity, although HOCl exposure established oxidative modification of the N-terminal region (Met32) and the formation of an intermolecular cross-link in a fraction of the molecules. The cross-linking was also induced by activated neutrophils. Moreover, we show that the neutrophil-derived proteases human neutrophil elastase and cathepsin G cleaved the N-terminal region of EC-SOD irrespective of HOCl oxidation. Although the cleavage by elastase did not affect the quaternary structure, the cleavage by cathepsin G dissociated the molecule to produce EC-SOD monomers. The present data suggest that EC-SOD is stable and active at the site of inflammation and that neutrophils have the capacity to modulate the biodistribution of the protein by generating EC-SOD monomers that can diffuse into tissue.
authors.affiliation: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Karla
authors.initials: K
authors.lastname: Morales
authors.affiliation: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Mads Nikolaj
authors.initials: MN
authors.lastname: Olesen
authors.affiliation: Department of Molecular Biology and Genetics, Interdisciplinary Nanoscience Center and Center for Insoluble Protein Structures, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Ebbe Toftgaard
authors.initials: ET
authors.lastname: Poulsen
authors.affiliation: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Ulrike G
authors.initials: UG
authors.lastname: Larsen
authors.affiliation: Department of Molecular Biology and Genetics, Interdisciplinary Nanoscience Center and Center for Insoluble Protein Structures, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Enghild
authors.affiliation: Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark. Electronic address: svp@biomed.au.dk.
authors.forename: Steen Vang
authors.initials: SV
authors.lastname: Petersen
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D056649:Cathepsin G / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D005110:Extracellular Space / Q000737:chemistry / Q000201:enzymology; D006493:Heparin / Q000737:chemistry; D006801:Humans; D006997:Hypochlorous Acid / Q000378:metabolism / Q000494:pharmacology*; D019272:Leukocyte Elastase / Q000737:chemistry* / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D010084:Oxidation-Reduction; D061251:Primary Cell Culture; D011485:Protein Binding; D020836:Protein Structure, Quaternary / Q000187:drug effects; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D006997:Hypochlorous Acid; D006493:Heparin; D013482:Superoxide Dismutase; C534094:CTSG protein, human; D056649:Cathepsin G; D019272:Leukocyte Elastase
keywords: Antioxidant; Cathepsin G; Extracellular matrix protein; Free radicals; Hypochlorous acid; Inflammation; Neutrophil; Superoxide dismutase