Altered dietary iron intake is a strong modulator of renal DMT1 expression
AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY
Authors: Wareing, M; Ferguson, CJ; Delannoy, M; Cox, AG; McMahon, RFT; Green, R; Riccardi, D; Smith, CP
Abstract
Divalent metal transporter1 (DMT1; also known as DCT1 or NRAMP2) is an important component of the cellular machinery responsible for dietary iron absorption in the duodenum. DMT1 is also highly expressed in the kidney where it has been suggested to play a role in urinary iron handling. In this study, we determined the effect on renal DMT1 expression of feeding an iron-restricted diet ( 50 mg/kg) or an iron-enriched diet ( 5 g/kg) for 4 wk and measured urinary and fecal iron excretion rates. Feeding the low-iron diet caused a reduction in serum iron concentration and fecal iron output rate with an increase in renal DMT1 expression. Feeding an iron-enriched diet had the converse effect. Therefore, DMT1 expression in the kidney is sensitive to dietary iron intake, and the level of expression is inversely related to the dietary iron content. Changes in DMT1 expression occurred intracellularly in the proximal tubule and in the apical membrane and subapical region of the distal convoluted tubule. Increased DMT1 expression was accompanied by a decrease in urinary iron excretion rate and vice versa when DMT1 expression was reduced. Together, these findings suggest that modulation of renal DMT1 expression may influence renal iron excretion rate.
Phenotypic expression of pyruvate kinase deficiency and protection against malaria in a mouse model
GENES AND IMMUNITY
Authors: Min-Oo, G; Fortin, A; Tam, MF; Gros, P; Stevenson, MM
Abstract
The recombinant congenic mouse strains AcB55 and AcB61 are extremely resistant to malaria ( Plasmodium chabaudi AS) despite the presence of susceptibility alleles at the known Char1/Char2 resistance loci. Resistance in AcB55 and AcB61 is controlled by a locus on chromosome 3 (Char4) shown to be allelic with or tightly linked to a loss-of-function mutation in pyruvate kinase (Pklr). AcB55 and AcB61 show important splenomegaly prior to infection caused by the expansion of the red pulp, and display histological signs of extramedullary erythropoiesis in the liver. Examination of splenic cell populations by flow cytometry demonstrates elevated numbers of TER119-positive erythroid precursor cells (>30% of total spleen cells), while RNA expression studies show elevated expression of erythrocyte-specific transcripts such as globin, transferrin receptor, and Nramp2/Slc11a2 in the spleen of both strains. Hematological profiling in both strains is consistent with the presence of anemia as evidenced by low total erythrocyte counts, decreased hemoglobin, as well as abnormally high numbers of circulating reticulocytes ( 15 - 20%). These results strongly suggest that the mutant Pklr allele (Pklr(269A)) of AcB55/61 strains causes hemolytic anemia compensated by constitutive erythropoiesis, which in turn protects the mice against P. chabaudi infection. The possible molecular basis of the Pklr protective effect is discussed and is under current investigation in these two strains.