Nitration of respiratory epithelial cells by myeloperoxidase depends on extracellular nitrite.
To investigate peroxidase induced 3'-nitrotyrosine (3NT) formation, neutrophil derived myeloperoxidase (MPO) (0.025 microM) was directly administered to A549 epithelial cells with or without H(2)O(2) (150 microM). Little evidence of 3NT was found. In contrast, there was a dose dependent increase in intracellular NO (p<0.001, n=8) following MPO (0.025 microM) treatment, which was further enhanced (p<0.0003, n=8) by addition of H(2)O(2). Extracellular NO also increased after MPO (p<0.002, n=5) and with MPO and H(2)O(2) (p<0.004, n=5). Substantial 3NT formation was only detected following addition of nitrite (NO(2)(-), > or =100 microM), which induced a dose dependent increase in epithelial 3NT. In contrast, protein carbonyl formation and increased GSSG/GSH ratios were associated with MPO treatment even in the absence of NO(2)(-). Co-culture of A549 epithelial cells with polymorphonuclear leukocytes (PMN) (10(6)/ml) led to immunocytochemical detection of epithelial 3NT and induction of nitric oxide synthase (NOS2). However, in a Transwell system direct contact between PMN and A549 cells was necessary for immunodetection of 3NT but not of NOS2 consistent with a role for high local nitrite concentrations. These findings demonstrate dissociation between epithelial endogenous NO production and 3NT formation. Although MPO can influence cellular oxidative stress, particularly in the presence of H(2)O(2), 3NT formation requires the presence of high concentrations of NO(2)(-) in the milieu.
Govindaraju
Karuthapillai
K
Meakins-Christie Laboratories and Respiratory Division, Department of Medicine, McGill University and McGill University Health Centre Research Institute, Room A3.09, 687 Pine Avenue West, Montreal, Que., Canada H3A 1A1.
Shan
Jichuan
J
Levesque
Kathy
K
Hussain
Sabah N A
SN
Powell
William S
WS
Eidelman
David H
DH
D015153:Blotting, Western; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007120:Immunochemistry; D009504:Neutrophils / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000032:analysis / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000032:analysis; D009573:Nitrites / Q000032:analysis / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D009195:Peroxidase / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000096:biosynthesis
D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D006861:Hydrogen Peroxide; D009195:Peroxidase; D019001:Nitric Oxide Synthase; D005978:Glutathione