Hypoxia-inducible factor-2α and iron absorptive gene expression in Belgrade rat intestine

Abstract

The divalent metal transporter (DMT1, Slc11a2) is an important molecule for intestinal iron absorption. In the Belgrade (b/b) rat, the DMT1 G185R mutation markedly decreases intestinal iron absorption. We used b/b rats as a model to examine the genes that could be compensatory for decreased iron absorption. When tissue hypoxia was assayed by detecting pimonidazole HCl adducts, the b/b liver and intestine exhibited more adducts than the +/+ rats, suggesting that hypoxia might signal altered gene expression. Total RNA in the crypt-villus bottom (C-pole) and villus top (V-pole) of +/+, b/b, and iron-fed b/b rats was isolated for gene array analyses. In addition, hepatic hepcidin and intestinal hypoxia-inducible factor-α (Hifα) expression were examined. The results showed that expression of hepatic hepcidin was significantly decreased and intestinal Hif2α was significantly increased in b/b and iron-fed b/b than +/+ rats. In b/b rats, the expression of Tfrc mRNA in the C-pole and of DMT1, Dcytb, FPN1, Heph, Hmox1, and ZIP14 mRNAs in the V-pole were markedly enhanced with increases occurring even in the C-pole. After iron feeding, the increased expression found in b/b rats persisted, except for Heph and ZIP14, which returned to normal levels. Thus in b/b rats depressed liver hepcidin production and activated intestinal Hif2α starting at the C-pole resulted in increasing expression of iron transport genes, including DMT1 G185R, in an attempt to compensate for the anemia in Belgrade rats.

Glucose metabolism in the Belgrade rat, a model of iron-loading anemia

“…The b/b and ϩ/b groups were established at the time of weaning and fed with the iron-supplemented diet. Belgrade rat genotype was verified by both visual discrimination and PCR genotyping (49). Body weight and daily food intake were measured two times a week from 3 to 18 wk old.…”

Hypoxia of the growing liver accelerates regeneration

“…Pimonidazole was dissolved in normal saline (100 mg/mL), and 60 mg were injected intravenously 1 hour prior to harvesting the organs. 15 Pimonidazole undergoes chemical reduction under hypoxic conditions, binds irreversibly to SH-containing molecules, such as glutathione and proteins, and the resulting complexes accumulate in hypoxic tissue. The pimonidazole bound in tissue was visualized with monoclonal antibodies using immunofluorescence.…”

Physiologic implications of metal-ion transport by ZIP14 and ZIP8

“…A few studies have provided limited evidence for this, but the data are inconsistent. For example, ZIP14 mRNA levels have been reported to be upregulated in the duodenum of iron-deficient Belgrade rats (Yeh et al 2011), iron-deficient pigs (Hansen et al 2009), and Hfe knockout mice (Coppin et al 2007). A microarray analysis of iron-deficient rat duodenum, however, did not identify ZIP14 as being differentially expressed (Collins et al 2005).…”