One of the major consequences of chronic alcohol abuse in the brain is increased inflammation that leads to neurodegeneration with associated cognitive defects and ultimately dementia. In brain, the neuroimmune system is composed of astrocytes and microglial cells that act in concert to fend off infection, respond to injury and remodel after neuronal damage. Recent work has shown that ethanol elicits a diverse set of responses by the neuroimmune system. Ethanol treatment activates astrocyte signaling pathways mediated by toll-like receptors and up-regulates the secretion of inflammatory mediators regulated by mitogen activated protein kinases (MAPK);the consequence is a chronic increase in release of proinflammatory mediators. The c-Jun NH2-terminal kinase (JNK) signal transduction pathway is one of the MAPK signal transduction pathways that controls the innate immune response and is composed of upstream kinases, JNKs, scaffolding proteins (JIP), and its down stream target, c-Jun. The recent discovery that loss of the JNK1 gene protects the brain against the untoward effects of autoimmune encephalomyelitis highlights the potential role that the JNK signal transduction pathway plays in controlling the neuroimmune response. We hypothesize that ethanol provokes a neuroinflammatory state by altering cytokine production and/or the cellular response of astrocytes and microglial cells through the JNK signal transduction pathway. To explore the effects of alcohol on JNK pathway function in astrocytes and microglial cells, we make use of our colony of JNK pathway mutants that lack one or more of the signaling kinases. We will first define the role of the JNK signal transduction pathway in mediating ethanol-induced cytokine production/secretion by astrocytes. Astrocytes will be prepared from neonates derived from our colony of mouse mutants deficient in one or more of the components in the JNK pathway. The effects of ethanol on resting, TGF-1 and LPS-stimulated cytokine production and secretion will be systematically evaluated. We will then examine the role of the JNK pathway in mediating the ethanol- induced changes in microglial biology. The effects of ethanol on cytokine induced microglial motility, cytokine production by resting, TGF-1 and LPS-stimulated cells, and matrix metalloproteinase (MMP) production will be evaluated. We will finish our studies by evaluating the effects of chronic alcohol treatment on the JNK mediated neuroinflammatory response in vivo, using experimental autoimmune encephalomyelitis (EAE), and lysophosphatidic acid induced reactive gliosis as model diseases. The results of the proposed studies will define the role of JNK dependent cytokine expression in astrocytes and microglial cells and its participation in the neuroinflammatory response associated with alcohol abuse. This discovery will identify the JNK pathway as a potential target for therapeutic intervention that will alleviate or prevent additional brain cell loss in recovering alcoholics and/or to prevent further neurodegeneration.
Ethanol induced neuroinflammation is one of the major causes of the brain damage found after chronic alcohol abuse. The goal of this proposal is to identify and characterize the MAPK signaling pathways used by ethanol to provoke the neuroimmune system into a chronic proinflammatory state.
