Endotoxin and Kupffer cell activation in alcoholic liver disease.

One central component in the complex network of processes leading to the development of alcoholic liver disease is the activation of immune cells residing in the liver (i.e., Kupffer cells) by a substance called endotoxin, which is released by bacteria living in the intestine. Alcohol consumption can lead to increased endotoxin levels in the blood and liver. When activated, Kupffer cells produce signaling molecules (i.e., cytokines) that promote inflammatory reactions as well as molecules called reactive oxygen species (ROS), which can damage liver cells. Endotoxin activates Kupffer cells by interacting with a complex of protein molecules that are located on the outside of the Kupffer cell or which extend into the cell. Binding of endotoxin alters the activities of the proteins in this complex so that they trigger a cascade of biochemical signals in the Kupffer cell, resulting in cytokine and ROS production and, ultimately, liver damage. Because alcohol can enhance endotoxin release and, therefore, Kupffer cell activation, novel approaches to inhibit these processes might help prevent or ameliorate alcoholic liver disease.