Classical ROS-dependent and early/rapid ROS-independent release of Neutrophil Extracellular Traps triggered by Leishmania parasites

Abstract

Neutrophil extracellular traps (NETs) extruded from neutrophils upon activation are composed of chromatin associated with cytosolic and granular proteins, which ensnare and kill microorganisms. This microbicidal mechanism named classical netosis has been shown to dependent on reactive oxygen species (ROS) generation by NADPH oxidase and also chromatin decondensation dependent upon the enzymes (PAD4), neutrophil elastase (NE) and myeloperoxidase (MPO). NET release also occurs through an early/rapid ROS-independent mechanism, named early/rapid vital netosis. Here we analyze the role of ROS, NE, MPO and PAD4 in the netosis stimulated by Leishmania amazonensis promastigotes in human neutrophils. We demonstrate that promastigotes induce a classical netosis, dependent on the cellular redox imbalance, as well as by a chloroamidine sensitive and elastase activity mechanism. Additionally, Leishmania also induces the early/rapid NET release occurring only 10 minutes after neutrophil-parasite interaction. We demonstrate here, that this early/rapid mechanism is dependent on elastase activity, but independent of ROS generation and chloroamidine. A better understanding of both mechanisms of NET release, and the NETs effects on the host immune system modulation, could support the development of new potential therapeutic strategies for leishmaniasis.

Multimodal Regulation of NET Formation in Pregnancy: Progesterone Antagonizes the Pro-NETotic Effect of Estrogen and G-CSF

“…Interestingly, in vitro application of hCG leads to a significant increase in PAD4 expression, without a major increment in citH3 levels. Furthermore, ROS production, a further key element in the NETotic cascade, was not significantly elevated by hCG treatment, underlining a possible ROS-independent mechanism driving the generation of NETs as described recently (45). As gestation advances, it becomes apparent that a discrete interaction between G-CSF and steroid sex hormones modulates pro-NETotic activity.…”

Pancreatic Cancer-Induced Neutrophil Extracellular Traps: A Potential Contributor to Cancer-Associated Thrombosis

“…Similarly, the generation of ROS is thought to be indispensable for forming NETs; however, a few studies have also reported ROS-independent release of NETs [37,38,39]. The majority of NET-inducers studied thus far, stimulate a NET-releasing mechanism that requires at least 3 h of stimulation and is dependent on the generation of ROS [1,22,23].…”

Beneficial and Deleterious Effects of Neutrophil Extracellular Traps on Infection

“…PAD4 activity is only relevant during classic NETosis. Promastigotes viability after treatment of parasites with a NETs-rich supernatant, obtained from either the early and rapid or the classic pathways, shows a reduction of about 42% [41].…”

“…These authors observed that Leishmania promastigotes promote a redox disbalance in neutrophils. The exposure of neutrophils to H 2 O 2 induces histone deamination mediated by PAD4, and the redox disbalance takes place independently of the parasite viability, thus suggesting that Leishmania induces the production of ROS through an NADPH oxidase-dependent mechanism [41].…”