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New Insight into the NO‐mediated Signaling to Modulate Neutrophil Free Radical Generation
Author(s) -
Patel Satyananda,
Kumar Sachin,
Barthwal Manoj Kumar,
Dikshit Madhu
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a623
Subject(s) - chemistry , peroxynitrite , reactive nitrogen species , nadph oxidase , superoxide , reactive oxygen species , nitric oxide , hypochlorous acid , biochemistry , propidium iodide , myeloperoxidase , peroxynitrous acid , inflammation , apoptosis , enzyme , immunology , programmed cell death , biology , organic chemistry
Neutrophils (PMNs) and nitric oxide (NO) play an important role in pathogen killing as well as in various pathological conditions associated with inflammation, hypoxia/ischemia and reoxygenation injury by generating reactive oxygen (ROS) and reactive nitrogen (RNS) species. Previous work from this lab has shown that NO modulates neutrophil NADPH‐oxidase (NOX) activity and thus modulates ROS production. The present study has been undertaken to assess signalling mechanisms involved in NO mediated effect on PMNs by flowcytometry (DCF‐DA, DHE, propidium iodide, CBA Flex array), biochemical (H 2 O 2 , hypochlorous acid [HOCl], nitryl chloride [NO 2 Cl], dityrosine) and molecular (Western blotting) measurements. NO donors, SNP and SNAP (10 μM to 1 mM) inhibited the NADPH‐oxidase activity but enhanced DCF‐DA fluorescence in a concentration and time dependent manner, with no adverse effect on the cell viability. The effect was significantly blocked by NOS inhibitors and was partially blocked by ERK and MPO inhibitors. NO at the concentrations used seems to activate futile cycle generating peroxynitrite (ONOO)/NO 3 − , which subsequently uncouples NOS and generate superoxide radicals and H 2 O 2 . H 2 O 2 thus formed leads to the formation of HOCl by MPO catalysis, which further reacts with nitrite (NO 2 − ) to generate NO 2 Cl, a more potent oxidant and nitrating agent. The results obtained thus suggest that NO mediated augmentation in neutrophil free radical production involves ERK signalling.