Ethanol metabolism generates oxidative stress and chronic ethanol exposure alters mitochondrial function. The central question extant is what events and processes link alcohol-induced mitochondrial dysfunction and ROS generation to local and distal tissue damage. We do not yet know how mitochondria are damaged by ethanol metabolism and ROS formation, the molecular identity(ies) of the toxic materials, nor their specific targets. How ethanol metabolism by the liver leads to damage to surrounding and distal tissue also remains opaque. We also lack reliable circulating markers of the propensity for tissue damage. We recently identified specific oxidatively-fragmented phospholipids that are readily transported into cells, where they intercalate into mitochondrial membranes to initiate mitochondrial-dependent apoptosis. We now find these lipids, the lipid inflammatory mediator Platelet-activating Factor (PAF), and distinctive hydroxylated phospholipids are all increased in the circulation of rats chronically ingesting ethanol. Early results suggest this occurs early in the human syndrome as well. These lipids are therefore circulating markers of endogenous oxidative processes resulting from liver metabolism of ethanol. Moreover, they themselves may induce proximal and distal tissue damage through dysregulation of their selective target, energized mitochondria.
The aims of this application are 1) Define the source, identity, and amounts of circulating lipid oxidation products circulating in animals and human chronically ingesting ethanol. 2) Determine how oxidized lipids affect mitochondrial function, and whether mitochondrial function is compromised in a cell specific fashion. 3) Determine whether PAF acetylhydrolase, an enzyme that specifically hydrolyzes oxidatively-modified phospholipids, protects mitochondrial function of liver cells during ethanol metabolism. Alcoholic liver and tissue damage is a significant public health issue, yet adequate markers of the progression of accruing damage are not available until late in the disease process. This project will validate novel circulating lipids as disease associated markers, but, significantly, because these same lipids induce tissue damage, we will be able to accurately assess future organ damage.
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