Proceedings of The Physiological Society
Newcastle University (2009) Proc Physiol Soc 16, PC11
Copper loading and depletion regulate iron transporter expression in Caco-2 cells.
K. Pourvali1,2, P. Sharp1
1. Nutritional Sciences Division, King's College London, London, United Kingdom. 2. Shaheed Beheshti Medical University, Tehran, Iran.
Copper is an essential trace metal in the body required for many physiological functions. The intimate relationship between copper and iron metabolism has been known for many years (Sharp, 2004). In in vitro intestinal epithelial cell models, experimental evidence suggests that copper and iron may compete for uptake via divalent metal transporter 1 (DMT1) (Tennant et al 2002). Furthermore, in the same cells hephaestin, a copper-containing ferrioxidase, is required for iron efflux (Vulpe et al 1999). The aim of this study was to investigate the effects of copper on the protein and mRNA expression of the iron transporters DMT1 and ferroportin, and the ferrioxidase hephaestin in intestinal Caco-2 cells. Fully-differentiated Caco-2 cells (used for experiments 21 days post-seeding) were treated with 50 µM copper chloride, for 4, 8, and 24 hours. In addition, the effect of treating cells with 0.5 mM of Triethylenetetramine dihydrochloride (TETA), a copper chelator, over the same time scale was investigated. We examined the changes in the whole cell levels of transport proteins by western blotting and mRNA expression by Real Time PCR. Western blotting data were semi-quantified using Scion Image software for were analysed by one-way ANOVA and Tukey’s post hoc test (significant at p<0.05). Following exposure to copper for 24h there was a significant decrease in DMT1 mRNA expression (-42%; p< 0.05) compared with control. Ferroportin and hephaestin were not altered under copper-loading conditions. Treatment with TETA (0.5mM) for 24h, significantly increased DMT1 (+380%; p<0.006) and hephaestin mRNA expression (+1420%; p<0.04). In addition, there was a significant increase in hephaestin protein expression (+183%; p<0.05) in TETA treated cells. These data show that the expression of iron transporters is altered by modulating cellular copper levels and provide further evidence that copper nutrition exerts an important influence on iron homeostasis.
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