壞死細胞引發之嗜中性白血球胞外陷阱

When cells are stimulated by physical or chemical stress, cells may undergo necrosis and release damage-associated molecular patterns (DAMPs) that can induce inflammation. This kind of inflammation, which occurs in the absence of microbial infection, is called sterile inflammation and is characterized by the recruitment of neutrophils to site of tissue damage. Neutrophils can phagocytose and clear the injured cells; however, the release of reactive oxygen and nitrogen intermediates and granular contents also cause harm to the healthy tissue. The aim of this study is to investigate whether necrotic cells could stimulate neutrophils to form the neutrophil extracellular traps (NETs). Human blood neutrophils treated with necrotic human HL60 cells clearly showed the formation of NETs, which could be visualized by the immunofluorescent staining of extracellular DNA and myeloperoxidase, and quantified by measuring the release of neutrophil DNA after DNase treatment. Necrotic cell-stimulated neutrophils showed increased generation of reactive oxygen species (ROS), which could be responsible for causing NET formation. Necrotic cell-induced NET formation was markedly attenuated when total DNA or protein components in the lysates were depleted by enzyme digestion, suggesting that cellular DNA and proteins could both serve as DAMPs for inducing NET formation. IL-1α has been postulated as a DAMP, and we found that neutrophils could also be induced by recombinant IL-1α to form NETs. In addition, we also observed NET formation when purified mouse bone marrow neutrophils were stimulated with necrotic murine EL4 cells, although it required a longer time of treatment. Taken together, our data demonstrated that neutrophils could be stimulated by necrotic cells to form NETs, indicating that there is a dynamic interplay between the injured cells and the recruited neutrophils during sterile inflammation. Further investigation should be done to elucidate how this interaction may affect tissue homeostasis or pathogenesis.