Format

Send to

Choose Destination
Free Radic Biol Med. 2015 Dec;89:1024-35. doi: 10.1016/j.freeradbiomed.2015.10.398. Epub 2015 Nov 4.

Neutrophil NET formation is regulated from the inside by myeloperoxidase-processed reactive oxygen species.

Author information

1
The Phagocyte Research Group, Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
2
Department of Bioscience, CVMD iMed, AstraZeneca R&D Mölndal, Mölndal, Sweden.
3
Department of Pediatrics, The Queen Silvia Children's Hospital, Gothenburg, Sweden.
4
The Phagocyte Research Group, Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; Department of Oral Microbiology and Immunology, Institute of Odontology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden. Electronic address: johan.bylund@gu.se.

Abstract

AIM:

Neutrophil extracellular traps (NETs) are mesh-like DNA fibers clad with intracellular proteins that are cast out from neutrophils in response to certain stimuli. The process is thought to depend on reactive oxygen species (ROS) generated by the phagocyte NADPH-oxidase and the ROS-modulating granule enzyme myeloperoxidase (MPO), but when, how, and where these factors contribute is so far uncertain. The neutrophil NADPH-oxidase can be activated at different cellular sites and ROS may be produced and processed by MPO within intracellular granules, even in situations where a phagosome is not formed, e.g., upon stimulation with phorbol myristate acetate (PMA).

OBJECTIVES:

We investigated the subcellular location of ROS production and processing by MPO in the context of PMA-induced NET formation.

RESULTS:

Complete neutralization of extracellular ROS was not sufficient to block NET formation triggered by PMA, indicating that intragranular ROS are critical for NETosis. Employing a set of novel MPO-inhibitors, inhibition of NET formation correlated with inhibition of intragranular MPO activity. Also, extracellular addition of MPO was not sufficient to rescue NET formation in completely MPO-deficient neutrophils and specific neutralization by luminol of MPO-processed ROS within intracellular granules led to a complete block of PMA-triggered NET formation.

CONCLUSION:

We show for the first time that inhibition of intragranular MPO activity, or neutralization of intragranular MPO-processed ROS by luminol effectively block NET formation. Our data demonstrate that ROS must be formed and processed by MPO in order to trigger NET formation, and that these events have to occur within intracellular granules.

KEYWORDS:

Granulocyte; Heterotypic granule fusion; Inflammation; NADPH-oxidase; Phagocyte; Subcellular localization

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center