The small molecule, genistein, increases hepcidin expression in human hepatocytes

Authors


  • This work was supported by the National Institutes of Health (R01 DK085250-01A1 and 3P30 DK034 854-24S1; to P.G.F.), the Cooley's Anemia Foundation (to P.G.F.), the March of Dimes Research Foundation Basil O'Connor Starter Scholar Research Award (to P.G.F.), Harvard College Research Program (to N.N.), and the Institute for Collaborative Biotechnologies Grant W9111NF-09-001 from the U.S. Army Research Office (to S.M. and E.F.). The content of the information does not necessarily reflect the position or policy of the government, and no official endorsement should be inferred.

  • Potential conflict of interest: Nothing to report.

Address reprint requests to: Paula Fraenkel, M.D., Division of Hematology/Oncology, Beth Israel Deaconess Medical Center, SLD 423B, 330 Brookline Avenue, Boston, MA 02215. E-mail: pfraenke@bidmc.harvard.edu; fax: 866-345-0065.

Abstract

Hepcidin, a peptide hormone that decreases intestinal iron absorption and macrophage iron release, is a potential drug target for patients with iron overload syndromes because its levels are inappropriately low in these individuals. Endogenous stimulants of Hepcidin transcription include bone morphogenic protein 6 (BMP6) and interleukin-6 (IL-6) by effects on mothers against decapentaplegic homolog (Smad)4 or signal transducer and activator of transcription (Stat)3, respectively. We conducted a small-scale chemical screen in zebrafish embryos to identify small molecules that modulate hepcidin expression. We found that treatment with the isoflavone, genistein, from 28-52 hours postfertilization in zebrafish embryos enhanced Hepcidin transcript levels, as assessed by whole-mount in situ hybridization and quantitative real-time reverse-transcriptase polymerase chain reaction. Genistein's stimulatory effect was conserved in human hepatocytes: Genistein treatment of HepG2 cells increased both Hepcidin transcript levels and promoter activity. We found that genistein's effect on Hepcidin expression did not depend on estrogen receptor signaling or increased cellular iron uptake, but was impaired by mutation of either BMP response elements or the Stat3-binding site in the Hepcidin promoter. RNA sequencing of transcripts from genistein-treated hepatocytes indicated that genistein up-regulated 68% of the transcripts that were up-regulated by BMP6; however, genistein raised levels of several transcripts involved in Stat3 signaling that were not up-regulated by BMP6. Chromatin immunoprecipitation and ELISA experiments revealed that genistein enhanced Stat3 binding to the Hepcidin promoter and increased phosphorylation of Stat3 in HepG2 cells. Conclusion: Genistein is the first small-molecule experimental drug that stimulates Hepcidin expression in vivo and in vitro. These experiments demonstrate the feasibility of identifying and characterizing small molecules that increase Hepcidin expression. Genistein and other candidate molecules may subsequently be developed into new therapies for iron overload syndromes. (Hepatology 2013;58:1315–1325)

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