Iron overload is the main cause of morbidity and mortality in hereditary hemochromatosis, 2-thalassemia and various anemias that require chronic transfusions. Alternatives to current treatments of iron overload are a high priority, as reflected in a recent NIH initiative (PAS-10-046). Hepcidin deficiency is the direct cause of iron overload in nearly all cases of hereditary hemochromatosis and in ?-thalassemia intermedia, and may contribute to iron overload and maldistribution in ?-thalassemia major. Hepcidin therapy is a rational experimental approach to the prevention and treatment of iron overload in these disorders. Natural hepcidin is expensive, rapidly cleared from circulation and not orally absorbable. We developed 7-9 amino acid peptides, """"""""minihepcidins"""""""" that mimic the activity of hepcidin and exceed its potency. Some have been engineered for oral absorption, and have shown considerable activity by oral route in mice. We will determine the potential of minihepcidins to prevent iron overload or reverse its toxic effects in hemochromatosis and ?-thalassemia, and examine the effects of hepcidin agonists on ?-thalassemic erythropoiesis in mouse models and in bone marrow cultures and identify those mechanisms that could ameliorate anemia. Specifically, we will: 1. Select a parenteral and an oral minihepcidin for subsequent studies based on the dose-response relationship and duration of hypoferremic effect in C57BL/6 mice and hepcidin knockout mice. 2. Define the effects of minihepcidins in animal models of hereditary hemochromatosis. a. Can minihepcidins started after weaning prevent the development of iron overload in mouse models of severe (hepcidin knockout) or moderate (HFE knockout) hereditary hemochromatosis? b. Can minihepcidin treatment of mice with established iron overload (hepcidin or HFE knockouts) redistribute iron away from vulnerable cells and tissues (hepatocytes, pancreatic islet cells, cardiomyocytes) to relatively iron-resistant macrophages? c. Can minihepcidins reverse iron overload-related liver damage in the gerbil model of iron-induced hepatic cirrhosis? 3. Define the effects of minihepcidins in animal models of ?-thalassemia. a. Can minihepcidins prevent iron overload in a mouse model of ?-thalassemia intermedia, while improving (or not worsening) anemia? b. Can minihepcidins ameliorate iron overload in transfused mice with ?-thalassemia major and redistribute iron to less vulnerable locations, without worsening anemia? c. Identify mechanisms by which minihepcidins can improve ?-thalassemic erythropoiesis. This project would establish minihepcidins as viable drug leads for further development, and would eventually help patients with iron overload disorders by providing them with improved therapeutic options.
Iron overload diseases are an important medical problem in need of new treatments. Building on recent advances in the understanding of iron metabolism, we propose to develop and test new kinds of medications for the treatment of iron overload in hereditary hemochromatosis and Cooley's anemia.
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