Mechanisms of cadmium-mediated acute hepatotoxicity.

The mechanism of cadmium-mediated acute hepatotoxicity has been the subject of numerous investigations and although some uncertainties persist, sufficient evidence has emerged to provide a reasonable account of the toxic process. Acute hepatotoxicity involves two pathways, one for the initial injury produced by direct effects of cadmium and the other for the subsequent injury produced by inflammation. Primary injury appears to be caused by the binding of Cd2+ to sulfhydryl groups on critical molecules in mitochondria. Thiol group inactivation causes oxidative stress, the mitochondrial permeability transition, and mitochondrial dysfunction. Although cadmium may injure hepatocytes directly, there are compelling reasons to believe that hepatocellular injury is produced in vivo as the result of ischemia caused by damage to endothelial cells. Secondary injury from acute cadmium exposure is thought to occur from the activation of Kupffer cells and a cascade of events involving several types of liver cells and a large number of inflammatory and cytotoxic mediators. In this regard, it is clear that Kupffer cell activation and neutrophil infiltration are important events in the toxic process, and the involvement of proinflammatory cytokines and chemokines has also been implicated. The precise roles of the soluble mediators of inflammation warrant further investigation.