Search

Hepcidin is a liver-derived antimicrobial peptide that regulates iron absorption and is also an integral part of the acute phase response. In a previous report, we found evidence that this peptide could also be induced by toxic heavy metals and xenobiotics, thus broadening its teleological role as a defensin. However it remained unclear how its sensing of disparate biotic and abiotic stressors might be integrated at the transcriptional level. We hypothesized that its function in cytoprotection may be regulated by NFE2-related factor 2 (Nrf2), the master transcriptional controller of cellular stress defenses. In this report, we show that hepcidin regulation is inextricably linked to the acute stress response through Nrf2 signaling. Nrf2 regulates hepcidin expression from a prototypical antioxidant response element in its promoter, and by synergizing with other basic leucine-zipper transcription factors. We also show that polyphenolic small molecules or phytoestrogens commonly found in fruits and vegetables including the red wine constituent resveratrol can induce hepcidin expression in vitro and post-prandially, with concomitant reductions in circulating iron levels and transferrin saturation by one such polyphenol quercetin. Furthermore, these molecules derepress hepcidin promoter activity when its transcription by Nrf2 is repressed by Keap1. Taken together, the data show that hepcidin is a prototypical antioxidant response or cytoprotective gene within the Nrf2 transcriptional circuitry. The ability of phytoestrogens to modulate hepcidin expression in vivo suggests a novel mechanism by which diet may impact iron homeostasis., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

Hepcidin is a small acute phase peptide that regulates iron absorption. It is induced by inflammation and infection, but is repressed by anaemia and hypoxia. Here we further reveal that hepcidin transcription also involves interactions between functional metal response elements (MREs) in its promoter, and the MRE-binding transcription factor-1. Analysis of hepcidin mRNA and protein levels in hepatoma cells suggests that its expression may be regulated by divalent metal ions, with zinc inducing maximal effects on hepcidin levels. These data suggest that this peptide may be a pleiotropic sensor of divalent metals, some of which are xenobiotic environmental toxins., (Copyright 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

The role of Vitamin D in the regulation of calcium absorption in the intestine is well recognized but the mechanisms of the effects on human genes are surprisingly poorly understood. We have determined the expression of transcripts of the apical membrane calcium transporter TRPV6, the cytoplasmic calcium binding protein calbindin-D9k, the basolateral plasma membrane Ca(2+)-ATPase (PMCA1) and the Vitamin D receptor (VDR) in normal endoscopic duodenal mucosal biopsies using quantitative real-time RT-PCR and related baseline expression to Vitamin D metabolites. TRPV6 transcript levels have been shown to be significantly correlated with serum 1,25(OH)(2)D levels in men, but not overall in women, where negative effects of age predominate. TRPV6 and VDR expression were significantly related in both men and women, but were significantly lower in older women. Associations with bone mineral density and fractional calcium absorption were also studied. In a second series of subjects, duodenal biopsies were incubated in organ culture for 6h with Vitamin D metabolites. TRPV6 expression was significantly increased by 1,25(OH)(2)D(3) (10(-9)mol/l) as was PMCA1 to a much smaller extent. TRPV6 expression also increased with 25(OH)D(3). CYP27B1 expression was found in all samples, and CYP24 transcripts were detected after incubation with 1,25(OH)(2)D(3) or 25(OH)D(3).

Unlabelled: Intestinal absorption of calcium affects bone mineralization and varies greatly. In human duodenum, expression of the calcium channel TRPV6 was directly related to blood 1,25-dihydroxyvitamin D in men, but effects of age with lower median vitamin D receptor levels were more significant in women., Introduction: The TRPV6 calcium channel/transporter is implicated in animal studies of intestinal calcium absorption, but in humans, its role and relationship to differences in mineral metabolism is unclear. We aimed to characterize TRPV6 expression in human intestine including defining relationships to the vitamin D endocrine system., Materials and Methods: TRPV6 transcript expression was determined in endoscopic mucosal biopsies obtained from normal duodenum. Expression was compared with that in ileum and with in situ hybridization in archival tissues and related to sequence variants in genomic DNA. TRPV6 expression was related in 33 subjects to other transcripts involved in calcium absorption including the vitamin D receptor (VDR) and to blood vitamin D metabolites including 1,25-dihydroxyvitamin D [1,25(OH)(2)D]., Results: TRPV6 transcripts were readily detected in duodenum but not in ileum. Expression was highest in villous epithelial cells. Sequence variants in the coding and upstream regions of the gene did not affect TRPV6 expression. The relationship between duodenal TRPV6 expression and 1,25(OH)(2)D differed in men and women. In men, linear regression showed a strong association with 1,25(OH)(2)D (r = 0.87, p < 0.01), which was unaffected by age. In women, there was no significant overall relationship with 1,25(OH)(2)D, but there was a significant decrease with age (r = -0.69, p < 0.001). Individual expression of TRPV6 and VDR was significantly correlated. The group of older women (>50) had lower median levels of both TRPV6 and VDR transcripts than younger women (p < 0.001 and 0.02, respectively)., Conclusions: Duodenal TRPV6 expression is vitamin D dependent in men, but not in older women, where expression of TRPV6 and VDR are both reduced. These findings can explain, at least in part, the lower fractional calcium absorption seen in older postmenopausal women.

The advent of DNA array technology and proteomics has revolutionised biology by allowing global analysis of cellular events. So far, the benefits from these new techniques have primarily been realised for well-characterised species. These organisms are rarely the most relevant for environmental biology and ecotoxicology. Thus, there is a need to explore new ways to exploit transcriptomics and proteomics for non-model species. In the present study, rainbow trout (Oncorhynchus mykiss) were exposed to a sublethal concentration of waterborne zinc for up to 6 days. The response in gill tissue was investigated by differential screening of a heterologous cDNA array and by protein profiling using Surface Enhanced Laser Desorption/Ionisation (SELDI). The cDNA array, which was a high-density spotted library of cDNA from Fugu rubripes gill, revealed differentially expressed genes related to energy production, protein synthesis, paracellular integrity, and inflammatory response. SELDI analysis yielded seven proteins that were consistently present only in zinc-exposed gills, and four proteins unique to gills from control fish. A further 11 proteins were differentially regulated. Identification of these proteins by bioinformatics proved difficult in spite of detailed information on molecular mass, charge and zinc-binding affinity. It is concluded that these approaches are viable to non-model species although both have clear limitations.