Hepcidin is a key iron regulatory hormone that controls expression of the iron exporter ferroportin to increase the iron supply when needed to support erythropoiesis and other essential functions, but to prevent the toxicity of iron excess. Abnormally low hepcidin expression leads to the iron overload disorder hereditary hemochromatosis and contributes to iron loading anemias such as b-thalassemia. Excess hepcidin contributes to iron restricted erythropoiesis and anemia in a number of chronic diseases. A key unanswered question is how the liver senses iron levels in the body to appropriately coordinate hepcidin expression. We previously discovered that the bone morphogenetic protein (BMP)6-SMAD signaling pathway is a central regulator of hepcidin transcription in response to iron. Moreover, modulators of the BMP6-SMAD pathway regulate hepcidin expression to treat hemochromatosis and anemia of chronic disease in animal models. These studies have already yielded important insights into the pathophysiology of hemochromatosis and have identified the BMP6-SMAD pathway as a viable therapeutic target for iron disorders. However, it remains largely unknown how iron is sensed by the liver to regulate BMP6-SMAD signaling and thereby hepcidin production. In the last funding period, we discovered that liver endothelial cells are a key source for BMP6 in the regulation of hepcidin production. We also established a primary liver endothelial cell culture model and demonstrated that BMP6 transcription in liver endothelial cells is governed by intracellular iron content. Finally, we used this cell culture model in conjunction with quantitative proteomics and RNA-seq screens to identify iron transporters and transcription factor pathways that we hypothesize play a key role in mediating BMP6 production in response to iron to control hepcidin expression and systemic iron homeostasis.
In Specific Aim I, we will use primary liver endothelial cultures and genetic mouse models to establish the role of specific iron transporters in controlling liver endothelial cell iron content and iron-regulated pathways to govern BMP6 expression.
In Specific Aim II, we will use primary liver endothelial cell cultures, chromatin immunoprecipitation, reporter assays, pharmacologic approaches, and endothelial conditional knockout mouse models to determine the role of candidate transcription factor pathways and their mechanism of activation in controlling BMP6 production in response to iron. The long-term goals of this project are to understand how the BMP signaling pathway is modulated by different signals to regulate hepcidin expression and systemic iron balance, to gain insights into the physiology and pathophysiology of iron homeostasis in health and disease, and ultimately to develop new therapeutic strategies for treating disorders of iron metabolism.

Public Health Relevance

Iron balance in the body must be closely controlled to provide this essential nutrient for red blood cell production, but to prevent the damaging effects of too much iron on a number of organs including the liver, heart, and pancreas. This proposal will investigate how the liver senses iron levels in the body to control production of a hormone called hepcidin that is critical to keep body iron in balance. Our work will help to understand how iron balance is disrupted in diseases of too little or too much iron including anemia, hemochromatosis, and b- thalassemia, with the ultimate goal to identify new ways to treat these diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK087727-11A1
Application #
10118347
Study Section
Integrative Nutrition and Metabolic Processes Study Section (INMP)
Program Officer
Hattangadi, Shilpa Manohar
Project Start
2010-07-01
Project End
2025-06-30
Budget Start
2020-09-21
Budget End
2021-06-30
Support Year
11
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02114
Canali, Susanna; Wang, Chia-Yu; Zumbrennen-Bullough, Kimberly B et al. (2017) Bone morphogenetic protein 2 controls iron homeostasis in mice independent of Bmp6. Am J Hematol 92:1204-1213
Wang, Chia-Yu; Core, Amanda B; Canali, Susanna et al. (2017) Smad1/5 is required for erythropoietin-mediated suppression of hepcidin in mice. Blood 130:73-83
Dev, Som; Babitt, Jodie L (2017) Overview of iron metabolism in health and disease. Hemodial Int 21 Suppl 1:S6-S20
David, Valentin; Francis, Connor; Babitt, Jodie L (2017) Ironing out the cross talk between FGF23 and inflammation. Am J Physiol Renal Physiol 312:F1-F8
Canali, Susanna; Zumbrennen-Bullough, Kimberly B; Core, Amanda B et al. (2017) Endothelial cells produce bone morphogenetic protein 6 required for iron homeostasis in mice. Blood 129:405-414
He, Qing; Bouley, Richard; Liu, Zun et al. (2017) Large G protein ?-subunit XL?s limits clathrin-mediated endocytosis and regulates tissue iron levels in vivo. Proc Natl Acad Sci U S A 114:E9559-E9568
David, Valentin; Martin, Aline; Isakova, Tamara et al. (2016) Inflammation and functional iron deficiency regulate fibroblast growth factor 23 production. Kidney Int 89:135-46
Theurl, Igor; Hilgendorf, Ingo; Nairz, Manfred et al. (2016) On-demand erythrocyte disposal and iron recycling requires transient macrophages in the liver. Nat Med 22:945-51
Canali, Susanna; Core, Amanda B; Zumbrennen-Bullough, Kimberly B et al. (2016) Activin B Induces Noncanonical SMAD1/5/8 Signaling via BMP Type I Receptors in Hepatocytes: Evidence for a Role in Hepcidin Induction by Inflammation in Male Mice. Endocrinology 157:1146-62
Canali, Susanna; Vecchi, Chiara; Garuti, Cinzia et al. (2016) The SMAD Pathway Is Required for Hepcidin Response During Endoplasmic Reticulum Stress. Endocrinology 157:3935-3945

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