Neutrophil Necroptosis Is Triggered by Ligation of Adhesion Molecules following GM-CSF Priming

Abstract

Apoptosis is the most common form of neutrophil death under both physiological and inflammatory conditions. However, forms of nonapoptotic neutrophil death have also been observed. In the current study, we report that human neutrophils undergo necroptosis after exposure to GM-CSF followed by the ligation of adhesion receptors such as CD44, CD11b, CD18, or CD15. Using a pharmacological approach, we demonstrate the presence of a receptor-interacting protein kinase-3 (RIPK3)-a mixed lineage kinase-like (MLKL) signaling pathway in neutrophils which, following these treatments, first activates p38 MAPK and PI3K, that finally leads to the production of high levels of reactive oxygen species (ROS). All these steps are required for necroptosis to occur. Moreover, we show that MLKL undergoes phosphorylation in neutrophils in vivo under inflammatory conditions. This newly identified necrosis pathway in neutrophils would imply that targeting adhesion molecules could be beneficial for preventing exacerbation of disease in the neutrophilic inflammatory response.

Necroptosis directly induces the release of full‐length biologically active IL‐33 in vitro and in an inflammatory disease model

“…To this end, we examined the role of necroptosis in an A. fumigatus extract ( Asp . )‐induced allergic airway inflammation, using a recently discovered murine necroptosis inhibitor, GW80 . Treatment with GW80 resulted in delayed cell death kinetics for TSZ‐, but not TS‐, treated IL‐33‐GFP‐expressing L929 or HaCaT cells, thus confirming its ability to inhibit necroptotic cell death in vitro (Fig.…”

The role of neutrophil death in chronic inflammation and cancer

“…This necroptosis is coordinated by RIPK1, RIPK3, and MLKL, which finally results in a compromised membrane integrity and the release of cytosolic components 20 . Necroptosis can be triggered by engagement of CD44, CD11b, CD18, or CD15 on GM-CSF-primed neutrophils 21 or by autophagy 22 .…”

In vivo evidence for extracellular DNA trap formation

“…If the source of infection/stimulation persists, the released mtDNA, having similarity to viral and bacterial DNA (enriched in unmethylated CpG motifs), acts as a danger signal and triggers cytokine production for a protective and regulated immune response 7,55 . b Cytolysis: Under pathological conditions, such as the persistent presence of foreign antigens 104 , "too large to be trapped antigens", such as fungal hyphae 60,61 , strong adhesion receptor activation [153][154][155] , presence of monosodium urate (MSU) 88 , or phorbol-myristate-acetate (PMA) stimulation 2,12 , results in an excess of reactive oxygen species (ROS), leading to neutrophil cytolysis. Similarly, excessive increases in intracellular calcium [Ca 2+ ] i by ionomycin results in non-apoptotic neutrophil death 12,81 .…”