Hepcidin-25 (human)

The human hepcidin-25 hormone has a key role in iron regulation in blood. The clinical relevance of this hepatic ~2.8 kDa cysteine-rich peptide is rapidly increasing, since altered levels can be associated with inflammatory events and iron dysfunctions, such as hereditary hemochromatosis and iron overload. Moreover, hepcidin has also attracted the anti-doping field for its possible role as indirect marker of erythropoietin blood doping. Methods currently reported are based on immunoassays (ELISA and RIA), or various types of mass spectroscopy (MS)-based protocols, semi-quantitative or quantitative. Despite the great effort in optimizing robust and simple assays measuring hepcidin in real matrices, at present this challenge remains still an open issue. To explore the possibility to face hepcidin detection through the development of affinity-based biosensors, we set up a comparative study by surface plasmon resonance (SPR) technology. An immuno-based, on anti-hepcidin-25 IgG, and a biomimetic-based, on a synthetic peptide corresponding to the hepcidin-binding site on ferroportin (HBD), biosensors were developed. Here we report behaviors and analytical performances of the two systems, discussing limits and potentialities.

Hepcidin is a key regulator controlling iron intestinal absorption and distribution through the body. The article by van der Putten et al. examined the association between hepcidin-25 and erythropoietin responsiveness and inflammation in erythropoietin-naive, iron-replete patients with chronic heart failure and chronic kidney disease. A cross-sectional observation revealed that serum hepcidin-25 was elevated almost twofold when compared with levels in healthy subjects. Hepcidin-25 was inversely correlated with hemoglobin (r(2) = 0.18; p < 0.02), and positively with ferritin (r(2) = 0.51; p < 0.01) and transferrin saturation (r(2) = 0.14; p < 0.03), while it did not correlate with levels of IL-6 and highly sensitive C-reactive protein. They found that 2-week erythropoietin therapy (50 IU/kg/week) significantly decreased hepcidin-25 levels. The magnitude of the decrease in hepcidin-25 levels correlated with the increase in reticulocytes (r(2) = 0.23; p < 0.03) and soluble transferrin receptor (r(2) = 0.23; p = 0.03), but not with inflammatory markers. A decline in hepcidin-25 correlated with the increment of hemoglobin after 6 months (r(2) = 0.49; p < 0.01). The findings convincingly suggest that hepcidin-25 may be useful in predicting erythropoietin responsiveness in stable chronic heart failure patients. However, further studies will be needed to establish clinically available methods to reliably measure hepcidin-25 level.

Hepcidin was first identified as an antimicrobial peptide present in human serum and urine. It was later demonstrated that hepcidin is the long-sought hormone that regulates iron homeostasis in mammals. Recombinant human Hepcidin-25 (Hepc25) was expressed in Pichia pastoris using a modified version of the pPICZαA vector. Hepc25 was then purified by a simple two-step chromatographic process to obtain 1.9 mg of soluble recombinant human Hepc25 per liter of culture at 96% purity. The sequence of Hepc25 and the presence of four disulfide bridges were confirmed by mass spectrometry analyses, and the recombinant Hepc25 exhibited antibacterial activity. This protocol of production and purification is the first step toward the production of human Hepc25 at a greater scale.