title: Secretion of bioactive hepcidin-25 by liver cells correlates with its gene transcription and points towards synergism between iron and inflammation signaling pathways.
abstract: Hepcidin is a small liver-derived peptide central in the regulation of systemic iron homeostasis. Although the gene regulation has been extensively studied at transcriptional level, the corresponding effects on the production of bioactive peptide are largely unknown. We therefore applied a proteomics-based approach by combining immunocapture with time-of-flight mass spectrometry to characterize hepcidin-25 produced by hepatocyte-derived cell lines. Similar to its transcriptional regulation, mature hepcidin-25 was strongly secreted upon stimulation with BMPs and IL-6. The immunocaptured peptide down-modulated iron-exporter ferroportin on the monocyte/macrophage surface. Further mass spectrometry-based analyses indicated that hepcidin-25 in its bioactive conformation was very stable in serum and urine and not converted into its smaller isoforms. Hepcidin-25 was processed in the Golgi apparatus from its precursor, while the unprocessed prohepcidin was secreted only when furin-like protease activity was intracellularly inhibited. Furthermore, the amounts of hepatocytic secretion of hepcidin-25 are highly correlated with the gene transcript levels. An unexpected observation was the synergistic effect of BMPs and IL-6 on hepcidin-25 secretion, which points towards cross-talk between iron and inflammatory stimuli. The study underscores hepcidin-25 quantification as a valuable tool to unravel regulatory pathways in iron metabolism.
authors.affiliation: Department of Clinical Chemistry, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Apriliana E R
authors.initials: AE
authors.lastname: Kartikasari
authors.forename: Rian
authors.initials: R
authors.lastname: Roelofs
authors.forename: Renée M J
authors.initials: RM
authors.lastname: Schaeps
authors.forename: Erwin H J M
authors.initials: EH
authors.lastname: Kemna
authors.forename: Wilbert H M
authors.initials: WH
authors.lastname: Peters
authors.forename: Dorine W
authors.initials: DW
authors.lastname: Swinkels
authors.forename: Harold
authors.initials: H
authors.lastname: Tjalsma
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000378:metabolism*; D019485:Bone Morphogenetic Proteins / Q000819:agonists / Q000494:pharmacology; D027682:Cation Transport Proteins / Q000378:metabolism; D002460:Cell Line; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects; D006056:Golgi Apparatus / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism*; D064451:Hepcidins; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D015850:Interleukin-6 / Q000819:agonists / Q000494:pharmacology; D007501:Iron / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D000098742:Ferroportin
chemical_list: D023181:Antimicrobial Cationic Peptides; D019485:Bone Morphogenetic Proteins; D027682:Cation Transport Proteins; C578702:HAMP protein, human; D064451:Hepcidins; C508600:IL6 protein, human; D015850:Interleukin-6; D011498:Protein Precursors; D000098742:Ferroportin; D007501:Iron