Oxidized Phospholipids and Neutrophil Elastase Coordinately Play Critical Roles in NET Formation

Abstract

Neutrophil extracellular traps (NETs) are web-like structures consisting of decondensed chromatin DNA and contents of granules, such as myeloperoxidase (MPO) and neutrophil elastase (NE). NETs are usually released from neutrophils undergoing NETosis, a neutrophil-specific cell death mode characterized by the collapse and disappearance of cell membranes and nuclear envelopes. It is well known that production of reactive oxygen species (ROS) triggers NETosis and NET formation. However, details of intracellular signaling downstream of ROS production during NETosis and NET formation remains uncertain. Here, we demonstrated that the peroxidation of phospholipids plays a critical role in NETosis and NET formation induced by phorbol 12-myristate13-acetate (PMA) or immune complex in vitro and by lipopolysaccharide (LPS) in vivo. This phospholipid peroxidation is mediated by the enzymatic activity of MPO. On the other hand, NE, which was previously reported to be released from granules to cytosol by MPO during NET formation, is not required for either the peroxidation of phospholipids or the execution of NETosis, but contributes to chromatin decondensation and nuclear swelling independently of MPO-mediated oxidized phospholipids. Analysis of isolated nuclei clearly demonstrated that oxidized phospholipids and NE differently yet synergistically execute chromatin decondensation and nuclear swelling, and the subsequent release of nuclear contents. These findings indicate the dual roles of MPO in NETosis and NET formation, and provide new insight into the molecular mechanism of these phenomena.

Increased MPO in Colorectal Cancer Is Associated With High Peripheral Neutrophil Counts and a Poor Prognosis: A TCGA With Propensity Score-Matched Analysis

“…Neutrophils play a tumor-promoting role through the formation of neutrophil extracellular traps (NETs) within the tumor, known as NETosis ( 43 ). NETs are involved in the deterioration of a variety of diseases such as cancer, autoimmune diseases, and thrombosis ( 44 ). Most evidence shows that neutrophils can promote tumors, and the degree of neutrophil infiltration is related to poor prognosis; however, a few studies have observed that neutrophils can improve or did not affect prognosis ( 24 , 25 , 45 ).…”

Formation of Blood Neutrophil Extracellular Traps Increases the Mastitis Risk of Dairy Cows During the Transition Period

“…The concentration of serum myeloperoxidase (MPO, #A044-1-1, inter-assay CV is 1.3% and intra-assay CV is 1.3%) was measured using an MPO kit (Nanjing Jiancheng Bioengineering Institute) and the contents of deoxyribonuclease I (DNase I, #CK-EN77261, inter-assay CV is 10% and intra-assay CV is 15%) and neutrophil elastase (NE, #CK-EN78022, inter-assay CV is 10% and intra-assay CV is 15%) in serum samples were determined using corresponding ELISA kits (Quanzhou Ruixin Science & Technology, Quanzhou, China) ( 29 , 30 ).…”

Diverse Roles of NETosis in the Pathogenesis of Lupus

“…The correlation between the presence of NETs and Endo-MT in the nephritic MRL/lpr mice further suggests a role of NET-triggered Endo-MT in the pathogenesis of lupus ( 47 ). Notwithstanding, neutrophil elastase may not always be required in the execution of NETosis ( 48 ). Further studies are needed to decipher the role of neutrophil elastase in NET-induced Endo-MT.…”