Distinct iron homeostasis in Th1- and Th2-biased mouse strains

Abstract

Abstract Iron is a proinflammatory transition metal ion, yet limited information is documented on the differences in iron homeostasis under Th1 and Th2 biased conditions. We used C57BL/6 (BL6) and Balb/C (BB) strains, which exhibit prototypical Th1 and Th2 immune responses, to investigate the extent to which Th1 and Th2 biased responses dictate iron homeostasis during healthy and inflammatory conditions. Systemic and tissue iron levels were assessed in age and gender matched BL6 and BB mice. Gene expression for iron absorption, transport, and storage proteins were quantified in duodenum and liver. Intracellular labile iron pool (LIP) was assessed in bone marrow-derived macrophages (BMDM) and neutrophils (BMDN). Hypoferremia of inflammation was assessed by measuring serum iron before and after LPS treatment. BB mice displayed significantly higher levels of systemic and storage iron than BL6 mice. Although the expression of hepcidin and ferroportin were comparable between the two strains, hepcidin-independent iron absorption is more prominent in BB mice, as indicated by higher expression of genes involved in iron absorption and transport: DcytB, DMT1, SFT, and hephaestin. Similarly, hepatic TfR1, TfR2, transferrin, and DMT1 expression was higher in BB mice. Moreover, the basal levels of LIP in BB BMDM and BMDN were 3.4 and 2.6 folds higher than BL6, respectively. The LPS-induced hypoferremia of inflammation is more pronounced in BL6 than BB mice. Taken together, iron homeostasis is distinct between these two strains during both healthy and inflammatory conditions. BB mice showed more iron load than BL6 mice, which could be explained, in part, by the higher expression of iron uptake genes and also reduced Th1 responses in BB mice.