The anemia of inflammation is a common co-morbid condition associated with various infections, autoimmune disorders, and other chronic disease states. In general, hemoglobin levels are mildly to moderately decreased. In vitro studies have demonstrated that pro-inflammatory cytokines can inhibit erythropoiesis at various stages of development, but many of these studies are limited to the analysis of early developmental stages and primarily assess proliferation as opposed to maturation or survival. Sufficient data from in vivo studies and whole animal models are lacking. We characterized the anemia in 8–10 week old C57BL/6 mice with turpentine oil-induced sterile abscess. We found that following 3 weeks of sterile abscess, the mice had a normocytic, normochromic anemia.
Using in vivo biotin-labeling of peripheral blood, we found the coefficient describing erythrocyte life span significantly decreased from -0.044 ± 0.002 SE in control mice to -0.048 ± 0.002 SE in mice with sterile abscess (p = 0.04). In further support of the mechanism of increased erythrocyte turnover, we found that splenic macrophages isolated from mice with abscess significantly increased expression of Heme-regulated gene 1 (Hrg-1) 2.5 fold, (p < .001) and significantly increased expression of Ferroportin (Fpn) 2.76 fold (p = 0.003).
Oxidative stress can lead to increased erythrocyte turnover and can inhibit erythroid maturation. To determine whether erythrocytes from mice with sterile abscess had impaired capacity for survival, we assessed staining of peripheral blood and erythroid precursors with chloromethyl dichlorodihydrofluorescein diacetate, acetyl ester (DCF). DCF fluoresces upon oxidation. We found that mean DCF fluorescence intensity (MFI) in peripheral blood increased from 3.2 ± 1.0 in control mice to 5.5 ± 0.6 in mice with abscess (p=0.004). Similarly, we found a greater percentage of bone marrow derived erythroid precursors from mice with abscess had high DCF staining (16.2 ± 3.9%) when compared to control mice (6.7 ± 1.9%, p=0.003). In conclusion, these data support the hypothesis that increased oxidative stress in erythroid precursors of mice with sterile abscess results in increased erythrocyte turnover and normocytic, normochromic anemia. Future studies will investigate whether pro-inflammatory cytokines inhibit the expression of key erythrocyte anti-oxidant enzymes or whether reactive oxygen species from neighboring granulocytes damage erythroid precursors in the bone marrow.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.