Micronutrient Laboratory, Nutrition Institute and Food Technology, Macul, Santiago, Chile.
Eur J Nutr. 2011 Aug;50(5):363-71. doi: 10.1007/s00394-010-0144-5. Epub 2010 Nov 16.
Heme iron is found in the diet mainly in the form of hemoglobin and myoglobin. It is known that heme iron (heme-Fe) and inorganic iron are absorbed differently. Intracellularly, heme oxygenase-1 (HO1) participates in the cleavage of the heme ring producing biliverdin, CO and ferrous iron. Iron released from heme becomes part of labile iron pool, and it can be stored in ferritin or released through the basolateral membrane. The mechanism by which heme-Fe is metabolized within cells is not completely understood.
This study focused on the uptake and transport of heme iron and on the role of heme oxygenase-1 on heme iron metabolism.
Caco-2 cells were incubated with different concentrations of heme-Fe. A full-length heme oxygenase-1 cDNA was expressed in Caco-2 cells and intracellular iron and heme-Fe content, heme uptake, heme and iron transport and heme oxygenase-1 immunolocalization were assessed in these cells.
Heme-Fe was bioavailable and induced an intracellular increase in iron, ferritin and HO1 levels and a decrease in DMT1 expression. In cells overexpressing HO1, heme-Fe uptake and transepithelial Fe transport was higher than in controls. Most heme-Fe was metabolized to free iron, most of which was found mainly in the basolateral chamber. However, there is a fraction of heme that is delivered intact to the basolateral side. In a high heme-Fe condition, HO1 is found near the plasma membrane.
These results suggest that heme oxygenase-1 catabolizes most of the heme-Fe and favors iron influx and efflux in intestinal cells.
膳食中的血红素铁主要以血红蛋白和肌红蛋白的形式存在。已知血红素铁（血红素-Fe）和无机铁的吸收方式不同。细胞内，血红素加氧酶-1（HO1）参与血红素环的裂解，生成胆绿素、CO 和亚铁。从血红素释放的铁成为不稳定铁池的一部分，它可以储存在铁蛋白中或通过基底外侧膜释放。血红素-Fe 在细胞内代谢的机制尚不完全清楚。
本研究专注于血红素铁的摄取和转运，以及血红素加氧酶-1 在血红素铁代谢中的作用。
用不同浓度的血红素-Fe 孵育 Caco-2 细胞。在 Caco-2 细胞中表达全长血红素加氧酶-1 cDNA，并评估这些细胞内的细胞内铁和血红素-Fe 含量、血红素摄取、血红素和铁转运以及血红素加氧酶-1 免疫定位。
血红素-Fe 是生物可利用的，诱导细胞内铁、铁蛋白和 HO1 水平增加，DMT1 表达降低。在过表达 HO1 的细胞中，血红素-Fe 摄取和跨上皮铁转运高于对照组。大多数血红素-Fe 被代谢为游离铁，其中大部分主要存在于基底外侧室。然而，有一部分血红素完整地递送到基底外侧。在高血红素-Fe 条件下，HO1 位于质膜附近。
这些结果表明，血红素加氧酶-1 代谢大部分血红素-Fe，并有利于肠道细胞中铁的内流和外流。
