Alcoholic liver disease (ALD) is a major health problem, but well-established and effective forms of therapy are lacking. Our long-term goal is to develop therapeutic agents that effectively correct the fundamental cellular disturbances resulting from excessive alcohol consumption. A number of hypotheses regarding the mechanisms by which alcohol causes cell injury have been suggested, with oxidative stress being a leading putative etiologic factor. Thus, antioxidant therapy has gained increasing attention in prevention of ALD. Zinc is an essential trace element with potent antioxidant functions. Cellular zinc homeostasis is regulated by metallothionein (MT). The MT-bound zinc can be released under oxidative stress condition. Hepatic zinc depletion in liver has long been noted in alcoholic liver disease. A mechanistic link between hepatic zinc depletion and cell injury, however, has not been established. This project proposes to test the hypothesis that hepatic zinc depletion is a critical mediator in alcohol-induced oxidative stress, thus zinc supplementation should attenuate alcohol-induced oxidative liver injury. A novel MT-null (MT-KO) mouse model along with wild type 129/Sv mice will be chronically fed liquid alcohol diet.
The specific aims are as follow: (1) To define the importance of hepatic zinc depletion in the development of ALD, the effect of dietary zinc deficiency and its supplementation on hepatic zinc status and oxidative liver injury will be determined in mice after chronic alcohol exposure: (2) To evaluate the therapeutic potential of zinc in controlling ALD, the effects of dietary zinc supplementation on alcohol-induced liver injury in mice previously exposed to alcohol will be examined; (3) To determine whether zinc protects against ALD through inhibition of oxidative stress, the effects of dietary zinc supplementation on ROS accumulation, ROS-generating and ROS-scavenging systems in the liver will be analyzed in mice after chronic alcohol exposure; (4) To understand the molecular mechanisms by which zinc inhibits alcohol-induced oxidative stress, the effects of dietary zinc supplementation on gene expression in the liver will be determined by DMA microarray and Real-Time RTPCR. The effects of zinc on the activities of zinc finger transcription factors also will be examined. These studies will provide fundamental understanding of the role of zinc in the pathophysiology of ALD, and pave the way to novel therapeutical approaches to prevention and treatment of this disease.
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