Abstract
BackgroundThe release by neutrophils of DNA-based extracellular traps (NETs) is a recently recognized innate immune phenomenon that contributes significantly to control of bacterial pathogens at tissue foci of infection. NETs have also been implicated in the pathogenesis of non-infectious diseases such as small vessel vasculitis, lupus and cystic fibrosis lung disease. Reactive oxygen species (ROS) are important mediators of NET generation (NETosis). Neutrophils with reduced ROS production, such as those from patients with chronic granulomatous disease or myeloperoxidase (MPO) deficiency, produce fewer NETs in response to inflammatory stimuli. To better understand the roles of various ROS in NETosis, we explore the role of MPO, its substrates chloride ion (Cl−) and hydrogen peroxide (H2O2), and its product hypochlorite (HOCl) in NETosis.FindingsIn human peripheral blood neutrophils, pharmacologic inhibition of MPO decreased NETosis. Absence of extracellular Cl−, a substrate for MPO, also reduced NETosis. While exogenous addition of H2O2 and HOCl stimulated NETosis, only exogenous HOCl could rescue NETosis in the setting of MPO inhibition. Neither pharmacological inhibition nor genetic deletion of MPO in murine neutrophils blocked NETosis, in contrast to findings in human neutrophils.ConclusionsOur results pinpoint HOCl as the key ROS involved in human NETosis. This finding has implications for understanding innate immune function in diseases in which Cl− homeostasis is disturbed, such as cystic fibrosis. Our results also reveal an example of significant species-specific differences in NET phenotypes, and the need for caution in extrapolation to humans from studies of murine NETosis.
Highlights
When epithelial barriers are breached by microbial pathogens, a critical first responder of the innate immune response is the neutrophil
Our results pinpoint HOCl as the key Reactive oxygen species (ROS) involved in human NETosis
Our results reveal an example of significant species-specific differences in neutrophils of DNA-based extracellular traps (NETs) phenotypes, and the need for caution in extrapolation to humans from studies of murine NETosis
Summary
When epithelial barriers are breached by microbial pathogens, a critical first responder of the innate immune response is the neutrophil. Preloaded with a potent antimicrobial armamentarium, neutrophils are activated to kill pathogens through phagocytosis, generation of reactive oxygen and nitrogen species, and release of antimicrobial peptides and proteases into the extracellular space [1]. Another more recently described mechanism of microbial killing by neutrophils at the site of infection is the formation of neutrophil extracellular traps (NETs), the endproduct of a distinct form of programmed cell death termed ‘‘NETosis’’ [2,3,4]. To better understand the roles of various ROS in NETosis, we explore the role of MPO, its substrates chloride ion (Cl2) and hydrogen peroxide (H2O2), and its product hypochlorite (HOCl) in NETosis
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.