Nitration of respiratory epithelial cells by myeloperoxidase depends on extracellular nitrite
- 作者：Karuthapillai Govindaraju ; Jichuan Shan ; Kathy Levesque ; Sabah N.A. Hussain ; William S. Powell ; David H. Eidelman
- 关键词：Neutrophils ; Myeloperoxidase ; Epithelial cells ; Nitric oxide ; Oxidative stress ; Nitrotyrosine
- 刊名：Nitric Oxide
- 出版年：2008
- 期刊代码：181_10898603
- 类别：bio
- 出版时间：May 2008
- 卷：18
- 期：3
- 页码：184-194
- 文件大小：1124 K
摘要
To investigate peroxidase induced 3′-nitrotyrosine (3NT) formation, neutrophil derived myeloperoxidase (MPO) (0.025 μM) was directly administered to A549 epithelial cells with or without H<sub>2sub>O<sub>2sub> (150 μM). 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 μM) treatment, which was further enhanced (p < 0.0003, n = 8) by addition of H<sub>2sub>O<sub>2sub>. Extracellular NO also increased after MPO (p < 0.002, n = 5) and with MPO and H<sub>2sub>O<sub>2sub> (p < 0.004, n = 5). Substantial 3NT formation was only detected following addition of nitrite (NO<sub>2sub><sup>−sup>, ![]()
src="http://www.sciencedirect.com/scidirimg/entities/2a7e.gif" alt="greater-or-equal, slanted" title="greater-or-equal, slanted" border="0">100 μM), 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<sub>2sub><sup>−sup>. Co-culture of A549 epithelial cells with polymorphonuclear leukocytes (PMN) (10<sup>6sup>/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<sub>2sub>O<sub>2sub>, 3NT formation requires the presence of high concentrations of NO<sub>2sub><sup>−sup> in the milieu.