Expression and localization of hepcidin in macrophages: a role in host defense against tuberculosis.

Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
Journal of Leukocyte Biology (Impact Factor: 4.3). 11/2007; 82(4):934-45. DOI: 10.1189/jlb.0407216
Source: PubMed

ABSTRACT Hepcidin is an antimicrobial peptide produced by the liver in response to inflammatory stimuli and iron overload. Hepcidin regulates iron homeostasis by mediating the degradation of the iron export protein ferroportin 1, thereby inhibiting iron absorption from the small intestine and release of iron from macrophages. Here, we examined the expression of hepcidin in macrophages infected with the intracellular pathogens Mycobacterium avium and Mycobacterium tuberculosis. Stimulation of the mouse RAW264.7 macrophage cell line and mouse bone marrow-derived macrophages with mycobacteria and IFN-gamma synergistically induced high levels of hepcidin mRNA and protein. Similar results were obtained using the human THP-1 monocytic cell line. Stimulation of macrophages with the inflammatory cytokines IL-6 and IL-beta did not induce hepcidin mRNA expression. Iron loading inhibited hepcidin mRNA expression induced by IFN-gamma and M. avium, and iron chelation increased hepcidin mRNA expression. Intracellular protein levels and secretion of hepcidin were determined by a competitive chemiluminescence ELISA. Stimulation of RAW264.7 cells with IFN-gamma and M. tuberculosis induced intracellular expression and secretion of hepcidin. Furthermore, confocal microscopy analyses showed that hepcidin localized to the mycobacteria-containing phagosomes. As hepcidin has been shown to possess direct antimicrobial activity, we investigated its activity against M. tuberculosis. We found that hepcidin inhibited M. tuberculosis growth in vitro and caused structural damage to the mycobacteria. In summary, our data show for the first time that hepcidin localizes to the phagosome of infected, IFN-gamma-activated cells and has antimycobacterial activity.

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    ABSTRACT: Hepcidin inhibits ferroportin-mediated iron efflux, leading to intracellular macrophage iron retention, possibly favoring Mycobacterium tuberculosis iron acquisition and tuberculosis (TB) pathogenesis. Plasma hepcidin was measured at human immunodeficiency virus (HIV) diagnosis in a retrospective HIV-prevalent, antiretroviral-naïve African cohort to investigate the association with incident pulmonary and/or extra-pulmonary TB. One hundred ninety-six participants were followed between 5 August 1992 and 1 June 2002, with 32 incident TB cases identified. Greater hepcidin was associated with significantly increased likelihood of TB after a median time to TB of 6 months. Elucidation of iron-related causal mechanisms and time-sensitive biomarkers that identify individual changes in TB risk are needed.
    The International Journal of Tuberculosis and Lung Disease 11/2014; 18(11). · 2.76 Impact Factor
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    ABSTRACT: The human hepcidin 25 (hep-25) and its isoform hepcidin 20 (hep-20) are histidine-containing, cystein rich, β-sheet structured peptides endowed with antimicrobial activity. We previously reported that, similar to other histidine-containing peptides, the microbicidal effects of hep-25 and hep-20 are highly enhanced at acidic pH. In the present study, we investigated whether pH influences the mode of action of hep-25 and hep-20 on Escherichia coli American Type Culture Collection 25922 and model membranes. A striking release of β-galactosidase by hepcidin-treated E. coli was observed at pH 5.0, whereas no inner membrane permeabilization capacity was seen at pH 7.4, even at bactericidal concentrations. Similar results were obtained by flow cytometry when assessing the internalization of propidium iodide by hepcidin-treated E. coli. Scanning electron microscope imaging revealed that both peptides induced the formation of numerous blebs on the surface of bacterial cells at acidic pH but not at neutral pH. Moreover, a phospholipid/polydiacetylene colourimetric vesicle assay revealed a more evident membrane damaging effect at pH 5.0 than at pH 7.4. The leakage of entrapped dextrans of increasing molecular size from liposomes was also assessed at pH 7.4. Consistent with the lack of β-galactosidase release from whole E. coli observed at such a pH value, evident leakage of only the smallest 4-kDa dextran (and not of dextrans of 20 or 70 kDa) was observed, indicating a poor ability of hepcidin peptides to permeabilize liposome vesicles at pH 7.4. Altogether, the data obtained in the present study using different approaches strongly suggest that the ability of hepcidins to perturb bacterial membranes is markedly pH-dependent.
    FEBS Journal 06/2013; 280(12). · 3.99 Impact Factor
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    ABSTRACT: Hepcidin has a regulatory role in inflammation, the immune system, and iron metabolism. It has been shown that proinflammatory cytokine interleukin 6 (IL-6) is an important inducer of hepcidin synthesis during infection and inflammation. Aim of the work To study the relationship between serum hepcidin level and hypoxemia in the COPD patients and its relation to COPD severity. Patients and methods A prospective case control study to compare serum hepcidin levels and other parameters in 70 COPD patients treated at the Pulmonology Department, King Fahad Hospital Dammam, with 34 age and sex matched healthy controls. All subjects participating in the study underwent a complete physical examination and detailed pulmonary function tests (PFTs). A sample from the radial artery for arterial blood gas analysis was done. As well as a panel of other tests including hemoglobin, hematocrit (hct), Iron, CRP, ferritin and total iron binding capacity. A hepcidin prohormone enzyme immunoassay kit (RE 54051, IBL) was used for serum hepcidin measurement. Results COPD patients had significantly lower serum hepcidin level compared to the control group (204.60 ± 53.12 and 280.81 ± 50.61, respectively). Furthermore there was a significantly greater reduction in serum hepcidin level in patients with severe COPD compared to patients with mild COPD. A positive correlation was found between serum hepcidin levels and arterial oxygen saturation (SaO2, %) and FEV1 level (P = 0.005). There was a negative correlation between serum hepcidin level and the ages of patients and packs of cigarettes consumed per year (P = 0.003). Conclusion Our study demonstrated a significant reduction in serum hepcidin levels in COPD patients, and the degree of reduction correlated with the severity of COPD and hypoxemia.
    Egyptian Journal of Chest Diseases and Tuberculosis. 10/2014;

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