ANIT toxicity toward mouse hepatocytes in vivo is mediated primarily by neutrophils via CD18

Exploration of Emodin to treat alpha-naphthylisothiocyanate-induced cholestatic hepatitis via anti-inflammatory pathway

Emodin, 1,3,8-trihydroxy-6-methyl-anthraquinone, is an anthraquinone derivative from the roots of Rheum officinale Baill that has been used to treat many diseases in digestive system for thousands of years. This study is to disclose the mechanism of Emodin to treat cholestatic hepatitis via anti-inflammatory pathway. Rats were divided into Emodin, ursodeoxycholic acid, Dexamethasone, model and blank control groups with treatment of respective agent after administration of alpha-naphthylisothiocyanate. At 24 h, 48 h and 72 h time points after administration, liver function, pathological changes of hepatic tissue, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, myeloperoxidase (MPO), malondialdehyde (MDA), superoxide dismutase (SOD), cytokine-induced neutrophil chemoattractant (CINC)-1, macrophage inflammatory protein (MIP)-2, intercellular adhesion molecule (ICAM)-1, nuclear factor (NF)-kappaB and early growth response (Egr)-1, nitric oxide (NO) and inducible nitric oxide synthase (iNOS) were detected. As a result, compared to the controls, Emodin had a notable effect on rat's living condition, pathological manifestation of hepatic tissue, total bilirubin, direct bilirubin, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (P<0.05), but had little effect on alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT) and total bile acid. With Emodin intervention, levels of TNF-alpha, IL-6, MPO, MDA, CINC-1, MIP-2, ICAM-1 and translocation of NF-kappaB were remarkably decreased, and levels of NO and iNOS were markedly increased (P<0.05). Emodin had no effect on Egr-1. In conclusion, Emodin has a protective effect on hepatocytes and a restoring activity on cholestatic hepatitis by anti-inflammation. The effects are mainly due to antagonizing pro-inflammatory cytokines and mediators, inhibiting oxidative damage, improving hepatic microcirculation, reducing impairment signals, and controlling neutrophil infiltration.

Role of neutrophils in the pathogenesis of acute inflammatory liver injury

Polymorphonuclear leukocytes (neutrophils) are essential in the defense against invading microorganisms, tissue trauma or any inciting inflammatory signals. Hepatic infiltration of neutrophils is an acute response to recent or ongoing liver injury, hepatic stress or unknown systemic inflammatory signals. Once neutrophils reach the liver, they can cause mild-to-severe tissue damage and consequent liver failure. For neutrophils to appear in the liver, neutrophils have to undergo systemic activation (priming) by inflammatory mediators such as cytokines, chemokines, complement factors, immune complexes, opsonized particles and other biologically active molecules, e.g., platelet activating factor. Neutrophils accumulated in the hepatic microvasculature (sinusoids and postsinusoidal venules) can extravasate (transmigrate) into the hepatic parenchyma if they receive a signal from distressed cells. Transmigration can be mediated by a chemokine gradient established towards the hepatic parenchyma and generally involves orchestration by adhesion molecules on neutrophils (beta(2) integrins) and on endothelial cells (intracellular adhesion molecules, ICAM-1). After transmigration, neutrophils adhere to distressed hepatocytes through their beta(2) integrins and ICAM-1 expressed on hepatocytes. Neutrophil contact with hepatocytes mediate oxidative killing of hepatocytes by initiation of respiratory burst and neutrophil degranulation leading to hepatocellular oncotic necrosis. Neutrophil-mediated liver injury has been demonstrated in a variety of diseases and chemical/drug toxicities. Relevant examples are discussed in this review.