Han Okhee, Wessling-Resnick Marianne
Department of Nutrition, Harvard School of Public Health, Boston, MA 02115, USA.
Am J Physiol Gastrointest Liver Physiol. 2002 Mar;282(3):G527-33. doi: 10.1152/ajpgi.00414.2001.
The influence of copper status on Caco-2 cell apical iron uptake and transepithelial transport was examined. Cells grown for 7-8 days in media supplemented with 1 microM CuCl(2) had 10-fold higher cellular levels of copper compared with control. Copper supplementation did not affect the integrity of differentiated Caco-2 cell monolayers grown on microporous membranes. Copper-repleted cells displayed increased uptake of iron as well as increased transport of iron across the cell monolayer. Northern blot analysis revealed that expression of the apical iron transporter divalent metal transporter-1 (DMT1), the basolateral transporter ferroportin-1 (Fpn1), and the putative ferroxidase hephaestin (Heph) was upregulated by copper supplementation, whereas the recently identified ferrireductase duodenal cytochrome b (Dcytb) was not. These results suggest that DMT1, Fpn1, and Heph are involved in the iron uptake process modulated by copper status. Although a clear role for Dcytb was not identified, an apical surface ferrireductase was modulated by copper status, suggesting that its function also contributes to the enhanced iron uptake by copper-repleted cells. A model is proposed wherein copper promotes iron depletion of intestinal Caco-2 cells, creating a deficiency state that induces upregulation of iron transport factors.
研究了铜状态对Caco-2细胞顶端铁摄取和跨上皮转运的影响。在补充有1 microM CuCl₂的培养基中培养7 - 8天的细胞，其细胞内铜水平比对照高10倍。补充铜不影响在微孔膜上生长的分化Caco-2细胞单层的完整性。铜充足的细胞显示出铁摄取增加以及铁跨细胞单层的转运增加。Northern印迹分析显示，顶端铁转运蛋白二价金属转运体1（DMT1）、基底外侧转运体铁转运蛋白1（Fpn1）和假定的铁氧化酶血浆铜蓝蛋白（Heph）的表达通过补充铜而上调，而最近鉴定的铁还原酶十二指肠细胞色素b（Dcytb）则没有。这些结果表明，DMT1、Fpn1和Heph参与了由铜状态调节的铁摄取过程。虽然未确定Dcytb的明确作用，但顶端表面铁还原酶受铜状态调节，表明其功能也有助于铜充足细胞增强铁摄取。提出了一个模型，其中铜促进肠道Caco-2细胞的铁消耗，产生一种诱导铁转运因子上调的缺乏状态。
