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

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 kinaselike (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.