Design, synthesis, and characterization of cyclic analogues of the iron regulatory peptide hormone hepcidin

Structural and functional characterisation of HepTH1-5 peptide as a potential hepcidin replacement

Hepcidin is a principal regulator of iron homeostasis and its dysregulation has been recognised as a causative factor in cancers and iron disorders. The strategy of manipulating the presence of hepcidin peptide has been used for cancer treatment. However, this has demonstrated poor efficiency and has been short-lived in patients. Many studies reported using minihepcidin therapy as an alternative way to treat hepcidin dysregulation, but this was only applied to non-cancer patients. Highly conserved fish hepcidin protein, HepTH1-5, was investigated to determine its potential use in developing a hepcidin replacement for human hepcidin (Hepc25) and as a therapeutic agent by targeting the tumour suppressor protein, p53, through structure-function analysis. The authors found that HepTH1-5 is stably bound to ferroportin, compared to Hepc25, by triggering the ferroportin internalisation via Lys42 and Lys270 ubiquitination, in a similar manner to the Hepc25 activity. Moreover, the residues Ile24 and Gly24, along with copper and zinc ligands, interacted with similar residues, Lys24 and Asp1 of Hepc25, respectively, showing that those molecules are crucial to the hepcidin replacement strategy. HepTH1-5 interacts with p53 and activates its function through phosphorylation. This finding shows that HepTH1-5 might be involved in the apoptosis signalling pathway upon a DNA damage response. This study will be very helpful for understanding the mechanism of the hepcidin replacement and providing insights into the HepTH1-5 peptide as a new target for hepcidin and cancer therapeutics.Communicated by Ramaswamy H. Sarma.

Small cyclic agonists of iron regulatory hormone hepcidin

Minihepcidins are in vitro and in vivo active mimetics of iron-regulatory hormone hepcidin. They contain various unusual amino acids including: N-substituted, β-homo-, and d-amino acids with their combination depending on particular minihepcidin. In the current study, we sought to limit the use of unusual/more expensive amino acids derivatives by peptide cyclization. Novel cyclic mimetics of hepcidin were synthesized and tested in vitro and showed activity at low nanomolar concentration. Nonetheless, the most active cyclic compound (mHS17) is approximately ten times less active than the parental minihepcidin PR73. Collectively, our findings suggest that cyclization is viable approach in the synthesis of hepcidin mimetics.

Hepcidin regulation in prostate and its disruption in prostate cancer

Hepcidin is a circulating peptide hormone made by the liver that is a central regulator of systemic iron uptake and recycling. Here, we report that prostate epithelial cells also synthesize hepcidin, and that synthesis and secretion of hepcidin are markedly increased in prostate cancer cells and tissue. Prostatic hepcidin functions as an autocrine hormone, decreasing cell surface ferroportin, an iron exporter, increasing intracellular iron retention, and promoting prostate cancer cell survival. Synthesis of hepcidin in prostate cancer is controlled by a unique intersection of pathways that involves BMP4/7, IL6, Wnt, and the dual BMP and Wnt antagonist, SOSTDC1. Epigenetic silencing of SOSTDC1 through methylation is increased in prostate cancer and is associated with accelerated disease progression in patients with prostate cancer. These results establish a new connection between iron metabolism and prostate cancer, and suggest that prostatic dysregulation of hepcidin contributes to prostate cancer growth and progression.

Serum hepcidin levels in women infected with HIV-1 under antiviral therapy

Accumulating data suggest that iron may have a role in the regulation of HIV-infection. In the present study, we determined by radioimmunoassay the levels of hepcidin, a key regulator of iron homeostasis, in sera of 182 women infected with HIV-1 under highly active antiretroviral therapy (HAART). In the total cohort, hepcidin levels were lower in individuals infected with HIV than in controls (3.20 ± 3.06 vs. 5.68 ± 3.66 nmol/L, P = 0.009). Serum hepcidin concentrations were strongly correlated positively with iron, ferritin, urea, and uric acid. In the total cohort of patients with abnormal viral load and CD4 cell count <500 cells/mm(3) , a strong positive correlation was found between hepcidin and viral load. Hepcidin level was significantly higher in HIV-patients with high viremia than in patients with undetectable viral load. Iron level was significantly lower in HIV-patients with high viral load compared with patients with undetectable viral load. This study suggests that hepcidin controls serum iron, especially in response of iron utilization by HIV for viral replication. The possibility of using inhibitors of hepcidin expression as adjunct therapy for HIV-patients is discussed.

The pathophysiology and pharmacology of hepcidin

Inappropriate production of the iron-regulatory hormone hepcidin contributes to the pathogenesis of common iron disorders. Absolute or relative deficiency of hepcidin causes iron overload in hereditary hemochromatosis and iron-loading anemias. Elevated hepcidin causes iron restriction in inflammatory conditions including autoimmune disease, critical illness, some cancers, and chronic kidney disease. Multiple agents targeting hepcidin and its regulators are under development as novel therapeutics for iron disorders. This review summarizes hepcidin biology and discusses the current landscape for hepcidin-targeting therapeutic strategies.