Iron absorption and distribution in TNFΔARE/+ mice, a model of chronic inflammation

Hemizygous TNFΔARE/+ mice are a murine model for chronic inflammation. We utilized these animals to study iron-kinetics and corresponding protein expression in an iron-deficient and iron-adequate setting. 59Fe-absorption was determined in ligated duodenal loops in vivo. Whole body distribution of i.v. injected 59Fe was analysed, and the organ specific expression of ferroportin, transferrin receptor-1, hepcidin and duodenal DMT-1 was quantified by real-time PCR and Western blotting.Duodenal 59Fe-lumen-to-body transport was not affected by the genotype. Duodenal 59Fe-retention was increased in TNFΔARE/+ mice, suggesting higher 59Fe-losses with defoliated enterocytes. Iron-deficiency increased duodenal 59Fe-lumen-to-body transport, and higher duodenal 59Fe-tissue retention went along with higher duodenal DMT-1, ferroportin, and liver hepcidin expression. TNFΔARE/+ mice significantly increase their 59Fe-content in inflamed joints and ilea, and correspondingly reduce splenic 59Fe-content. Leukocyte infiltrations in the joints suggest a substantial shift of iron-loaded RES cells to inflamed tissues as the underlying mechanism. This finding was paralleled by increased non-haem iron content in joints and reduced haemoglobin and haematocrit concentrations in TNFΔARE/+ mice.In conclusion, erythropoiesis in inflamed TNFΔARE/+ mice could be iron-limited due to losses with exfoliated iron-loaded enterocytes and/or to increased iron-retention in RES cells that shift from the spleen to inflamed tissues.