Hepcidin regulates iron metabolism by down-regulating ferroportin-1 (Fpn1). We demonstrated that hepcidin is complexed to the blood transport protein, α2-macroglobulin (α2M) (Peslova, G., Petrak, J., Kuzelova, K., Hrdy, I., Halada, P., Kuchel, P. W., Soe-Lin, S., Ponka, P., Sutak, R., Becker, E., Huang, M. L., Suryo Rahmanto, Y., Richardson, D. R., and Vyoral, D. (2009) Blood 113, 6225-6236). However, nothing is known about the mechanism of hepcidin binding to α2M or the effects of the α2M·hepcidin complex in vivo. We show that decreased Fpn1 expression can be mediated by hepcidin bound to native α2M and also, for the first time, hepcidin bound to methylamine-activated α2M (α2M-MA). Passage of high molecular weight α2M·hepcidin or α2M-MA·hepcidin complexes (≈725 kDa) through a Sephadex G-25 size exclusion column retained their ability to decrease Fpn1 expression. Further studies using ultrafiltration indicated that hepcidin binding to α2M and α2M-MA was labile, resulting in some release from the protein, and this may explain its urinary excretion. To determine whether α2M-MA·hepcidin is delivered to cells via the α2M receptor (Lrp1), we assessed α2M uptake and Fpn1 expression in Lrp1(-/-) and Lrp1(+/+) cells. Interestingly, α2M·hepcidin or α2M-MA·hepcidin demonstrated similar activities at decreasing Fpn1 expression in Lrp1(-/-) and Lrp1(+/+) cells, indicating that Lrp1 is not essential for Fpn1 regulation. In vivo, hepcidin bound to α2M or α2M-MA did not affect plasma clearance of α2M/α2M-MA. However, serum iron levels were reduced to a significantly greater extent in mice treated with α2M·hepcidin or α2M-MA·hepcidin relative to unbound hepcidin. This effect could be mediated by the ability of α2M or α2M-MA to retard kidney filtration of bound hepcidin, increasing its half-life. A model is proposed that suggests that unlike proteases, which are irreversibly bound to activated α2M, hepcidin remains labile and available to down-regulate Fpn1.

• Klíčová slova
• Iron, Iron Metabolism, Metalloproteins, Metals, Protein Metal Ion Interaction, α2-Macroglobulin,
• MeSH
• alfa-makroglobuliny genetika   metabolismus   MeSH
• biologické modely * MeSH
• buněčné linie MeSH
• ferroportin MeSH
• hepcidiny krev   genetika   MeSH
• LDL-receptory genetika   metabolismus   MeSH
• lidé MeSH
• multiproteinové komplexy krev   genetika   MeSH
• myši knockoutované MeSH
• myši MeSH
• nádorové supresorové proteiny genetika   metabolismus   MeSH
• protein 1 související s LDL-receptory genetika   metabolismus   MeSH
• proteiny přenášející kationty biosyntéza   genetika   MeSH
• regulace genové exprese fyziologie   MeSH
• železo krev   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• alfa-makroglobuliny MeSH
• ferroportin MeSH
• hepcidiny MeSH
• LDL-receptory MeSH
• LRP1 protein, human MeSH Prohlížeč
• Lrp1 protein, mouse MeSH Prohlížeč
• multiproteinové komplexy MeSH
• nádorové supresorové proteiny MeSH
• protein 1 související s LDL-receptory MeSH
• proteiny přenášející kationty MeSH
• železo MeSH

Disturbances of iron metabolism are observed in chronic liver diseases. In the present study, we examined gene expression of duodenal iron transport molecules and hepcidin in patients with hereditary hemochromatosis (HHC) (treated and untreated), involving various genotypes (genotypes which represent risk for HHC were examined), and in patients with iron deficiency anaemia (IDA). Gene expressions of DMT1, ferroportin, Dcytb, hephaestin, HFE and TFR1 were measured in duodenal biopsies using real-time PCR and Western blot. Serum hepcidin levels were measured using ELISA. DMT1, ferroportin and TFR1 mRNA levels were significantly increased in post-phlebotomized hemochromatics relative to controls. mRNAs of all tested molecules were significantly increased in patients with IDA compared to controls. The protein expression of ferroportin was increased in both groups of patients but not significantly. Spearman rank correlations showed that DMT1 versus ferroportin, Dcytb versus hephaestin and DMT1 versus TFR1 mRNAs were positively correlated regardless of the underlying cause, similarly to protein levels of ferroportin versus Dcytb and ferroportin versus hephaestin. Serum ferritin was negatively correlated with DMT1 mRNA in investigated groups of patients, except for HHC group. A decrease of serum hepcidin was observed in IDA patients, but this was not statistically significant. Our data showed that although untreated HHC patients do not have increased mRNA levels of iron transport molecules when compared to normal subjects, the expression is relatively increased in relation to body iron stores. On the other hand, post-phlebotomized HHC patients had increased DMT1 and ferroportin mRNA levels possibly due to stimulated erythropoiesis after phlebotomy.

• MeSH
• biologický transport MeSH
• deficit železa * MeSH
• dospělí MeSH
• duodenum metabolismus   MeSH
• fenotyp MeSH
• hemochromatóza krev   genetika   metabolismus   MeSH
• hepcidiny MeSH
• kationické antimikrobiální peptidy krev   metabolismus   MeSH
• lidé středního věku MeSH
• lidé MeSH
• messenger RNA genetika   metabolismus   MeSH
• proteiny přenášející kationty genetika   metabolismus   MeSH
• regulace genové exprese MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• studie případů a kontrol MeSH
• železo metabolismus   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• HAMP protein, human MeSH Prohlížeč
• hepcidiny MeSH
• kationické antimikrobiální peptidy MeSH
• messenger RNA MeSH
• proteiny přenášející kationty MeSH
• železo MeSH