Neuroimmune consequences of chronic alcohol exposure: relationship to stress

Alcoholism is characterized by tolerance to alcohol, withdrawal signs or symptoms, and continued use despite detrimental physical or psychological consequences. Studies have illustrated the deleterious effects of prolonged and excessive alcohol use extend to many organs including the liver, lungs, stomach, and brain. While the brain represents the most important organ in the development and maintenance of alcoholism, the neurobiological mechanisms underlying its role are not sufficiently understood to permit effective and timely intervention. Recent work has demonstrated that alcohol-associated changes in neuroimmune function may contribute to the progression of alcoholism. To better understand the role of alcohol in neuroimmune system dysregulation, changes in cytokine expression were determined after alcohol exposure in rats. While acute alcohol administration did not increase proinflammatory cytokines measured in the cerebral cortex, chronic alcohol administration produced a robust effect. Additionally, HMGB1, an endogenous activator of the neuroimmune system, was elevated following chronic alcohol administration. Stress, a major contributor to relapse in abstinent alcoholics, activates the neuroimmune system and, like alcohol, has been shown to increase cytokines in brain. The effects of stress and chronic alcohol on brain cytokines were examined in combination. A stress challenge following chronic alcohol exposure caused a more pronounced increase inbrain cytokines. Because HMBG1 was elevated following chronic alcohol exposure, the possibility that stress was contributing to the release of HMGB1 was examined. Blockade of HMBG1 with two different antagonists reduced stress-induced increases in cytokines following chronic alcohol exposure. This work illustrates that 1) chronic alcohol exposure increases neuroimmune activity and 2) stress following chronic alcohol exposure causes a greater activation of the neuroimmune system. Blockade of HMGB1 blocked the stress-induced production of cytokines following chronic ethanol exposure. Therefore, this work highlights a critical pathway of activation associated with chronic alcohol use and provides a valuable target system for future therapies.Doctor of Philosoph