TY - JOUR
T1 - The effects of hypochlorous acid and neutrophil proteases on the structure and function of extracellular superoxide dismutase
AU - Morales, Karla
AU - Olesen, Mads Nikolaj
AU - Poulsen, Ebbe Toftgaard
AU - Larsen, Ulrike G
AU - Enghild, Jan Johannes
AU - Petersen, Steen Vang
N1 - Copyright © 2015. Published by Elsevier Inc.
PY - 2015/4
Y1 - 2015/4
N2 - 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 where enzymatic activity in general is challenged. In this study, we show that EC-SOD exposed to physiological 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 suggests 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.
AB - 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 where enzymatic activity in general is challenged. In this study, we show that EC-SOD exposed to physiological 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 suggests 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.
U2 - 10.1016/j.freeradbiomed.2014.12.027
DO - 10.1016/j.freeradbiomed.2014.12.027
M3 - Journal article
C2 - 25582887
SN - 0891-5849
VL - 81
SP - 38
EP - 46
JO - Free Radical Biology & Medicine
JF - Free Radical Biology & Medicine
ER -