Reactive oxygen and ischemia/reperfusion injury of the liver

Pharmacological experiments suggested that reactive oxygen species contribute to ischemia-reperfusion injury of the liver. Since there is no evidence that quantitatively sufficient amounts of reactive oxygen are generated intracellularly to overwhelm the strong antioxidant defense mechanisms in the liver and cause parenchymal cell injury, the role of reactive oxygen in the pathogenesis remains controversial. This paper reviews the data and conclusions obtained with pharmacological intervention studies in vivo, the sources of reactive oxygen in the liver as well as the growing evidence for the importance of liver macrophages (Kupffer cells) and infiltrating neutrophils in the pathogenesis. A comprehensive hypothesis is presented that focuses on the extracellular generation of reactive oxygen in the hepatic sinusoids, where Kupffer cell-derived reactive oxygen species seem to be involved in the initial vascular and parenchymal cell injury and indirectly also in the recruitment of neutrophils into the liver. Reactive oxygen species may also contribute to the subsequent neutrophil-dependent injury phase as one of the toxic mediators released by these inflammatory cells.