Cytokines—Central Factors in Alcoholic Liver Disease

Many processes related to the consumption or breakdown of alcohol that contribute to alcohol-induced liver disease are mediated by small proteins known as cytokines, which are produced and secreted by liver cells and many other cells throughout the body. Through a variety of actions, cytokines regulate certain biochemical processes in the cells that produce them as well as in neighboring cells. For example, in case of an infection, they attract white blood cells to the tissues, triggering an inflammatory response. In the liver, persistent cytokine secretion resulting in chronic inflammation leads to conditions such as hepatitis, fibrosis, and cirrhosis. Cytokines also regulate a process known as programmed cell death, or apoptosis, which is in part responsible for alcohol-induced destruction of liver tissue. Two cytokines— tumor necrosis factor alpha and transforming growth factor beta—play prominent roles in apoptosis. Finally, a cytokine network mediates the harmful effects of a bacterial protein called endotoxin on the liver. Because of their diverse functions, cytokines might make attractive targets in the prevention or treatment of alcoholic liver disease, and researchers already have obtained encouraging results when testing such approaches.