( 3, 4) NETs have been well described in infectious states, where they serve a beneficial role in host defense against bacteria, fungi, and protozoa ( 5) capture and destruction of circulating pathogens by NETs limits dissemination and minimizes virulence. ( 3, 4) NETs are extracellular scaffolds composed of nuclear DNA studded with granule proteins, histones and cytoplasmic antimicrobials. ( 1, 2) A novel mechanism of neutrophil response to perceived threats in the circulation is formation of neutrophil extracellular traps (NETs). Neutrophils are highly specialized innate immune cells and are recognized as critical effectors of the immune response to sepsis and hepatitis, as well as to oxidative stress of the liver. Our study demonstrates a requirement for TLR-4 and NOX in superoxide-induced NETs, and suggests involvement of superoxide-induced NETs in pathophysiologic settings. To reduce circulating superoxide, we pretreated mice undergoing I/R with allopurinol and N-acetylcysteine, which resulted in decreased NETs and ameliorated liver injury. When mice were subjected to warm liver I/R, we found significant NET formation associated with liver necrosis and increased serum ALT in TLR-4 WT but not TLR-4 KO mice. Inhibition of superoxide generation by allopurinol and inhibition of NOX by diphenyleneiodonium prevented NET formation.

We treated neutrophils with extracellular superoxide and observed NET DNA release, histone H3 citrullination and increased levels of MPO-DNA complexes occurring in a TLR-4-dependent manner. We hypothesize that superoxide induces NET formation through a signaling cascade involving Toll-like receptor 4 (TLR-4) and neutrophil NADPH oxidase (NOX). While extracellular superoxide recruits neutrophils to the liver and initiates sterile inflammatory injury, it is unknown whether superoxide induces the formation of NETs.

Superoxide is a radical intermediate of oxygen metabolism produced by parenchymal and nonparenchymal hepatic cells, and is a hallmark of oxidative stress after liver ischemia-reperfusion (I/R). Neutrophil extracellular traps (NETs) are a novel mechanism to counter pathogenic invasion and sequelae of ischemia, including cell death and oxidative stress. Neutrophils constitute the early innate immune response to perceived infectious and sterile threats.

Nox for mac infection