Neopterin, Inflammation, and Oxidative Stress: What Could We Be Missing?

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Abstract

Neopterin has been extensively used as a clinical marker of immune activation during inflammation in a wide range of conditions and stresses. However, the analysis of neopterin alone neglects the cellular reactions that generate it in response to interferon-γ. Neopterin is the oxidation product of 7,8-dihydroneopterin, which is a potent antioxidant generated by interferon-γ-activated macrophages. 7,8-Dihydroneopterin can protect macrophage cells from a range of oxidants through a scavenging reaction that generates either neopterin or dihydroxanthopterin, depending on the oxidant. Therefore, plasma and urinary neopterin levels are dependent on both macrophage activation to generate 7,8-dihydroneopterin and subsequent oxidation to neopterin. This relationship is clearly shown in studies of exercise and impact-induced injury during intense contact sport. Here, we argue that neopterin and total neopterin, which is the combined value of 7,8-dihydroneopterin and neopterin, could provide a more comprehensive analysis of clinical inflammation than neopterin alone.

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Immune response-associated production of neopterin. Release from macrophages primarily under control of interferon-gamma

J Troppmair, D. Niederwieser, P. Swetly … (1984)

Neopterin, a compound derived from GTP, represents a precursor molecule of biopterin that is an essential cofactor in neurotransmitter synthesis. We have recently reported that in vivo as well as in vitro immune responses are accompanied by an increased release of neopterin and that this phenomenon can be used for the biochemical monitoring of diseases accompanied by hyperimmune stimulation. This article deals with the cellular origin and the control of this immune response- associated neopterin release in vitro. Using highly purified or monoclonal cellular reagents we demonstrate that macrophages (M phi) stimulated with supernatants from activated T cells release large amounts of neopterin into culture supernatants. Further experiments involving induction of neopterin release from M phi with various human recombinant interferons (IFNs) or neutralization of the effect of T cell supernatants with various monoclonal anti-IFN antibodies revealed immune IFN as the active principle. It thus appears that a metabolic pathway so far exclusively known in context with the generation of an essential cofactor of neurotransmitter-synthesis during immune responses is also activated in M phi under stringent control by immune IFN-like lymphokines.

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A chronic inflammatory response dominates the skeletal muscle molecular signature in dystrophin-deficient mdx mice.

P Merriam, J. Porter, Chelliah Richmonds … (2002)

Mutations in dystrophin cause Duchenne muscular dystrophy (DMD), but absent dystrophin does not invariably cause necrosis in all muscles, life stages and species. Using DNA microarray, we established a molecular signature of dystrophinopathy in the mdx mouse, with evidence that secondary mechanisms are key contributors to pathogenesis. We used variability controls, adequate replicates and stringent analytic tools, including significance analysis of microarrays to estimate and manage false positive rates. In leg muscle, we identified 242 differentially expressed genes, >75% of which have not been previously reported as altered in human or animal dystrophies. Data provide evidence for coordinated activity of numerous components of a chronic inflammatory response, including cytokine and chemokine signaling, leukocyte adhesion and diapedesis, invasive cell type-specific markers, and complement system activation. Selective chemokine upregulation was confirmed by RT-PCR and immunoblot, and may be a key determinant of the nature of the inflammatory response in dystrophic muscle. Up-regulation of secreted phosphoprotein 1 (minopontin, osteopontin) mRNA and protein in dystrophic muscle identified a novel linkage between inflammatory cells and repair processes. Extracellular matrix genes were up-regulated in mdx to levels similar to those in DMD. Since, unlike DMD, mdx exhibits little fibrosis, data suggest that collagen regulation at post-transcriptional stages mediates extensive fibrosis in DMD. Taken together, these data identify a relatively neglected aspect of DMD, suggest new treatment avenues, and highlight the value of genome-wide profiling in study of complex disease processes.

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Myeloperoxidase: a key regulator of neutrophil oxidant production.

A Kettle, C Winterbourn (1997)

Myeloperoxidase plays a fundamental role in oxidant production by neutrophils. This heme enzyme uses hydrogen peroxide and chloride to catalyze the production of hypochlorous acid, which is the major strong oxidant generated by neutrophils in appreciable amounts. In addition to chlorination, myeloperoxidase displays several other activities. It readily oxidizes thiocyanate to hypothiocyanite, converts a myriad of organic substrates to reactive free radicals, and hydroxylates aromatic compounds. Depending on the concentration of its competing substrates and the conditions of the local environment, myeloperoxidase could substantially affect oxidant production by neutrophils. Superoxide is undoubtedly a physiological substrate for myeloperoxidase. Its interactions with the enzyme are key factors in determining how neutrophils use superoxide to kill pathogens and promote inflammatory tissue damage. Superoxide modulates the chlorination and peroxidation activities of myeloperoxidase. It also reacts with the enzyme to form oxymyeloperoxidase which is catalytically active and hydroxylates phenolic substrates. Myeloperoxidase reacts rapidly with nitric oxide and peroxynitrite so that at sites of inflammation there is a strong possibility that these reactions will impact on oxidative damage caused by neutrophils. Under certain conditions, many substrates of myeloperoxidase act as inhibitors and regulate oxidant production by the enzyme. Given the numerous reactions of myeloperoxidase, all its activities should be considered when assessing the injurious oxidants produced by neutrophils.

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Journal

Journal ID (nlm-ta): Antioxidants (Basel)

Journal ID (iso-abbrev): Antioxidants (Basel)

Journal ID (publisher-id): antioxidants

Title: Antioxidants

Publisher: MDPI

ISSN (Electronic): 2076-3921

Publication date (Electronic): 26 June 2018

Publication date Collection: July 2018

Volume: 7

Issue: 7

Electronic Location Identifier: 80

Affiliations

[1 ]Free Radical Biochemistry Laboratory, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand; greg.parker@ 123456pg.canterbury.ac.nz

[2 ]Department of Radiology, University of Otago Christchurch, Christchurch 8011, New Zealand

[3 ]Division of Rehabilitation Science and Division of Physical Therapy, Department of Rehabilitation Medicine, University of Minnesota, Minneapolis, MN 55455, USA; alindsay@ 123456umn.edu

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[* ]Correspondence: Steven.Gieseg@ 123456canterbury.ac.nz ; Tel.: +64-3-364-2860; Fax: +64-3-364-2024

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Steven P. Gieseg https://orcid.org/0000-0002-3862-1385

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Publisher ID: antioxidants-07-00080

DOI: 10.3390/antiox7070080

PMC ID: 6071275

PubMed ID: 29949851

SO-VID: 0003b49d-10fa-4121-ac6d-64a0712c93cd

License:

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

Neopterin, Inflammation, and Oxidative Stress: What Could We Be Missing?

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Abstract

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Most cited references 83

Immune response-associated production of neopterin. Release from macrophages primarily under control of interferon-gamma

A chronic inflammatory response dominates the skeletal muscle molecular signature in dystrophin-deficient mdx mice.

Myeloperoxidase: a key regulator of neutrophil oxidant production.

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