Iron transport across the human placenta is regulated by hepcidin.

BACKGROUND: Transport of iron across the placenta is critical for appropriate development of the fetus. Iron deficiency during pregnancy remains a major public health concern, particularly in low- and middle-income countries, often exacerbated by infectious diseases leading to altered iron trafficking via inflammatory responses. Herein, we investigate the role of hepcidin, a master regulator of iron homeostasis, on regulation of iron transport across trophoblast cells. METHODS: We utilized the Jeg-3 choriocarcinoma cell line for analysis of the expression of transferrin receptor, ferritin, and ferroportin as well as the export of 59Fe in the presence of hepcidin. Placental tissue from human term pregnancies was utilized for immunohistochemistry. RESULTS: Hepcidin treatment of Jeg-3 cells decreased the expression of ferroportin and transferrin receptor (TfR) and reduced the cellular export of iron. Lower expression of TfR on the syncytiotrophoblast was associated with the highest levels of hepcidin in maternal circulation, and ferroportin expression was positively associated with placental TfR. Placentas from small-for-gestational-age newborns had significantly lower levels of ferroportin and ferritin gene expression at delivery. CONCLUSIONS: Our data suggest that hepcidin plays an important role in the regulation of iron transport across the placenta, making it a critical link in movement of iron into fetal circulation. IMPACT: Hepcidin has a direct impact on iron transport across the human placenta. This study provides the first evidence of direct regulation of iron efflux from human trophoblast cells by hepcidin. These data extend our understanding of iron transport across the maternal-fetal interface, a process critical for fetal health and development.

Copper chaperone for superoxide dismutase is essential to activate mammalian Cu/Zn superoxide dismutase.

Recent studies in Saccharomyces cerevisiae suggest that the delivery of copper to Cu/Zn superoxide dismutase (SOD1) is mediated by a cytosolic protein termed the copper chaperone for superoxide dismutase (CCS). To determine the role of CCS in mammalian copper homeostasis, we generated mice with targeted disruption of CCS alleles (CCS(-/-) mice). Although CCS(-/-) mice are viable and possess normal levels of SOD1 protein, they reveal marked reductions in SOD1 activity when compared with control littermates. Metabolic labeling with (64)Cu demonstrated that the reduction of SOD1 activity in CCS(-/-) mice is the direct result of impaired Cu incorporation into SOD1 and that this effect was specific because no abnormalities were observed in Cu uptake, distribution, or incorporation into other cuproenzymes. Consistent with this loss of SOD1 activity, CCS(-/-) mice showed increased sensitivity to paraquat and reduced female fertility, phenotypes that are characteristic of SOD1-deficient mice. These results demonstrate the essential role of any mammalian copper chaperone and have important implications for the development of novel therapeutic strategies in familial amyotrophic lateral sclerosis.

Brain copper content and cuproenzyme activity do not vary with prion protein expression level.

Prion diseases are neurodegenerative disorders that result from conformational transformation of a normal cell surface glycoprotein, PrP(C), into a pathogenic isoform, PrP(Sc). Although the normal physiological function of PrP(C) has remained enigmatic, the recent observation that the protein binds copper ions with micromolar affinity suggests a possible role in brain copper metabolism. In this study, we have used mice that express 0, 1, and 10 times the normal level of PrP to assess the effect of PrP expression level on the amount of brain copper and on the properties of two brain cuproenzymes. Using mass spectrometry, we find that the amount of ionic copper in subcellular fractions from brain is similar in all three lines of mice. In addition, the enzymatic activities of Cu-Zn superoxide dismutase and cytochrome c oxidase in brain extracts are similar in these groups of animals, as is the incorporation of (64)Cu into Cu-Zn superoxide dismutase both in cultured cerebellar neurons and in vivo. Our results differ from those of another set of published studies, and they require a re-evaluation of the role of PrP(C) in copper metabolism.

The role of copper in neurodegenerative disease.

Copper is an essential trace metal which plays a fundamental role in the biochemistry of the human nervous system. Menkes disease and Wilson disease are inherited disorders of copper metabolism and the dramatic neurodegenerative phenotypes of these two diseases underscore the essential nature of copper in nervous system development as well as the toxicity of this metal when neuronal copper homeostasis is perturbed. Ceruloplasmin contains 95% of the copper found in human plasma and inherited loss of this essential ferroxidase is associated with progressive neurodegeneration of the retina and basal ganglia. Gain-of-function mutations in the cytosolic copper enzyme superoxide dismutase result in the motor neuron degeneration of amyotrophic lateral sclerosis and current evidence suggests a direct pathogenic role for copper in this process. Recent studies have also implicated copper in the pathogenesis of neuronal injury in Alzheimer's disease and the prion-mediated encephalopathies, suggesting that further elucidation of the mechanisms of copper trafficking and metabolism within the nervous system will be of direct relevance to our understanding of the pathophysiology and treatment of neurodegenerative disease.

Characterization of the nitric oxide reductase-encoding region in Rhodobacter sphaeroides 2.4.3.

A gene cluster which includes genes required for the expression of nitric oxide reductase in Rhodobacter sphaeroides 2.4.3 has been isolated and characterized. Sequence analysis indicates that the two proximal genes in the cluster are the Nor structural genes. These two genes and four distal genes apparently constitute an operon. Mutational analysis indicates that the two structural genes, norC and norB, and the genes immediately downstream, norQ and norD, are required for expression of an active Nor complex. The remaining two genes, nnrT and nnrU, are required for expression of both Nir and Nor. The products of norCBQD have significant identity with products from other denitrifiers, whereas the predicted nnrT and nnrU gene products have no similarity with products corresponding to other sequences in the database. Mutational analysis and functional complementation studies indicate that the nnrT and nnrU genes can be expressed from an internal promoter. Deletion analysis of the regulatory region upstream of norC indicated that a sequence motif which has identity to a motif in the gene encoding nitrite reductase in strain 2.4.3 is critical for nor operon expression. Regulatory studies demonstrated that the first four genes, norCBQD, are expressed only when the oxygen concentration is low and nitrate is present but that the two distal genes, nnrTU, are expressed constitutively.