DSpace Community: RectorRectorhttp://hdl.handle.net/20.500.12323/57212024-03-29T12:47:47Z2024-03-29T12:47:47ZCeruloplasmin Is an Endogenous Inhibitor of MyeloperoxidaseChapman, Anna L. P.Mocatta, Tessa J.Shiva, SrutiSeidel, AntoniaChen, BrianKhalilova, IradaPaumann-Page, Martina E.Jameson, Guy N. L.Winterbourn, Christine C.Kettle, Anthony J.http://hdl.handle.net/20.500.12323/74052024-03-18T10:46:56Z2013-01-10T00:00:00ZTitle: Ceruloplasmin Is an Endogenous Inhibitor of Myeloperoxidase
Authors: Chapman, Anna L. P.; Mocatta, Tessa J.; Shiva, Sruti; Seidel, Antonia; Chen, Brian; Khalilova, Irada; Paumann-Page, Martina E.; Jameson, Guy N. L.; Winterbourn, Christine C.; Kettle, Anthony J.
Abstract: Myeloperoxidase is a neutrophil enzyme that promotes oxidative stress in numerous inflammatory pathologies. It uses hydrogen peroxide to catalyze the production of strong oxidants including chlorine bleach and free radicals. A physiological defense against the inappropriate action of this enzyme has yet to be identified. We found that myeloperoxidase oxidized 75% of the ascorbate in plasma from ceruloplasmin knock-out mice, but there was no significant loss in plasma from wild type animals. When myeloperoxidase was added to human plasma it became bound to other proteins and was reversibly inhibited. Ceruloplasmin was the predominant protein associated with myeloperoxidase. When the purified proteins were mixed, they became strongly but reversibly associated. Ceruloplasmin was a potent inhibitor of purified myeloperoxidase, inhibiting production of hypochlorous acid by 50% at 25 nm. Ceruloplasmin rapidly reduced Compound I, the Fe(V) redox intermediate of myeloperoxidase, to Compound II, which has Fe(IV) in its heme prosthetic groups. It also prevented the fast reduction of Compound II by tyrosine. In the presence of chloride and hydrogen peroxide, ceruloplasmin converted myeloperoxidase to Compound II and slowed its conversion back to the ferric enzyme. Collectively, our results indicate that ceruloplasmin inhibits myeloperoxidase by reducing Compound I and then trapping the enzyme as inactive Compound II. We propose that ceruloplasmin should provide a protective shield against inadvertent oxidant production by myeloperoxidase during inflammation.2013-01-10T00:00:00ZHypochlorous acid inactivates myeloperoxidase inside phagocytosing neutrophilsPaumann-Page, MartinaV. Ashby, LouisaKhalilova, IradaMagon, Nicholas J.Hofbauer, StefanPaton, Louise N.Furtmüller, Paul G.Obinger, ChristianKettle, Anthony J.http://hdl.handle.net/20.500.12323/67912023-09-04T09:05:13Z2023-12-01T00:00:00ZTitle: Hypochlorous acid inactivates myeloperoxidase inside phagocytosing neutrophils
Authors: Paumann-Page, Martina; V. Ashby, Louisa; Khalilova, Irada; Magon, Nicholas J.; Hofbauer, Stefan; Paton, Louise N.; Furtmüller, Paul G.; Obinger, Christian; Kettle, Anthony J.
Abstract: When neutrophils phagocytose bacteria, they release myeloperoxidase (MPO) into phagosomes to catalyse the
conversion of superoxide to the potent antimicrobial oxidant hypochlorous acid (HOCl). Here we show that
within neutrophils, MPO is inactivated by HOCl. In this study, we aimed to identify the effects of HOCl on the
structure and function of MPO, and determine the enzyme’s susceptibility to oxidative inactivation during
phagocytosis. When hydrogen peroxide was added to a neutrophil granule extract containing chloride, MPO
activity was rapidly lost in a HOCl-dependent reaction. With high concentrations of hydrogen peroxide, western
blotting demonstrated that MPO was both fragmented and converted to high molecular weight aggregates. Using
the purified enzyme, we showed that HOCl generated by MPO inactivated the enzyme by destroying its prosthetic heme groups and releasing iron. MPO protein was additionally modified by forming high molecular weight
aggregates. Before inactivation occurred, MPO chlorinated itself to convert most of its amine groups to
dichloramines. When human neutrophils phagocytosed Staphylococcus aureus, they released MPO that was
largely inactivated in a process that required production of superoxide. Enzyme inactivation occurred inside
neutrophils because it was not blocked when extracellular HOCl was scavenged with methionine. The inactivated
enzyme contained a chlorinated tyrosine residue, establishing that it had reacted with HOCl. Our results
demonstrate that MPO will substantially inactivate itself during phagocytosis, which may limit oxidant production inside phagosomes. Other neutrophil proteins are also likely to be inactivated. The chloramines formed
on neutrophil proteins may contribute to the bactericidal milieu of the phagosome.2023-12-01T00:00:00ZOxidized glutathione and uric acid as biomarkers of early cystic fibrosis lung diseaseDickerhof, NinaTurner, RufusKhalilova, IradaFantino, EmmanuelleSly, Peter DKettle, Anthony Jhttp://hdl.handle.net/20.500.12323/47532022-06-03T06:02:37Z2017-03-01T00:00:00ZTitle: Oxidized glutathione and uric acid as biomarkers of early cystic fibrosis lung disease
Authors: Dickerhof, Nina; Turner, Rufus; Khalilova, Irada; Fantino, Emmanuelle; Sly, Peter D; Kettle, Anthony J
Abstract: Background: In cystic fibrosis (CF) there is an urgent need for earlier diagnosis of pulmonary infections and inflammation using blood- and urinebased biomarkers.
Methods: Using mass spectrometry, oxidation products of glutathione and uric acid were measured in matched samples of bronchoalveolar lavage
(BAL), serum and urine from 36 infants and children with CF, and related to markers of neutrophilic inflammation and infection in BAL.
Results: Oxidation products of glutathione (glutathione sulfonamide, GSA) and uric acid (allantoin), were elevated in BAL of children with
pulmonary infections with Pseudomonas aeruginosa (PsA) compared to those without (p b 0.05) and correlated with other markers of neutrophilic
inflammation. Serum GSA was significantly elevated in children with PsA infections (p b 0.01). Urinary GSA correlated with pulmonary GSA
(r = 0.42, p b 0.05) and markers of neutrophilic inflammation.
Conclusions: This proof-of-concept study demonstrates that urinary GSA but not allantoin shows promise as a non-invasive marker of neutrophilic
inflammation in early CF lung disease.2017-03-01T00:00:00ZUric acid and thiocyanate as competing substrates of lactoperoxidaseSeidel, AntoniaTurner, RufusDickerhof, NinaKhalilova, Irada S.Wilbanks, Sigurd M.Kettle, Anthony J.Jameson, Guy N. L.Parker, Heatherhttp://hdl.handle.net/20.500.12323/47522022-06-03T06:01:34Z2014-08-01T00:00:00ZTitle: Uric acid and thiocyanate as competing substrates of lactoperoxidase
Authors: Seidel, Antonia; Turner, Rufus; Dickerhof, Nina; Khalilova, Irada S.; Wilbanks, Sigurd M.; Kettle, Anthony J.; Jameson, Guy N. L.; Parker, Heather
Abstract: The physiological function of urate is poorly understood. It
may act as a danger signal, an antioxidant, or a substrate for
heme peroxidases. Whether it reacts sufficiently rapidly with
lactoperoxidase (LPO) to act as a physiological substrate remains unknown. LPO is a mammalian peroxidase that plays a
key role in the innate immune defense by oxidizing thiocyanate
to the bactericidal and fungicidal agent hypothiocyanite. We
now demonstrate that urate is a good substrate for bovine LPO.2014-08-01T00:00:00Z