Peroxiredoxin-2: A Novel Regulator of Iron Homeostasis in Ineffective Erythropoiesis.

AIMS: Iron overload (IO) is a life-threatening complication of chronic hemolytic disorders such as ß-thalassemia. IO results in severe cellular oxidative damage, leading to organ failure. Peroxiredoxin-2 (Prx2), a typical 2-cysteine-(Cys)-peroxiredoxin, is an important component of the cytoprotective system, but its response to IO is still to be fully defined. RESULTS: We studied the effects of IO on Prx2-knockout mice (Prx2-/-). The absence of Prx2 enhanced toxicity due to IO on erythropoiesis. We found that IO failed to induce the typical hepcidin (Hamp) upregulation in Prx2-/- mice due to its failure to activate the signal transducer and activator of transcription-3 (STAT3) with intact Jak2 signaling. In Prx2-/- mice, the loss of Hamp response was also observed after administration of a single dose of oral iron. When lipopolysaccharide (LPS) was used to explore IL6-STAT3 activation in Prx2-/- mice, STAT3 activation and Hamp upregulation were once again defective. Treatment with PEP-fusion-recombinant-Prx2 (PEP Prx2) significantly increased STAT3 activation with upregulation of Hamp expression in both IO- and LPS-exposed Prx2-/- mice. We also confirmed the beneficial effects of PEP Prx2 on Hamp expression through STAT3 activation in ß-thalassemic mice. INNOVATION: We propose that Prx2 plays a key role in responding to cytotoxicity of IO, directly targeting STAT3-transcriptional factor in a Jak2-independent fashion and regulating Hamp in response to canonical stimuli. CONCLUSION: Collectively, our data highlight a novel role of Prx2 in iron homeostasis. Prx2 is a key cytoprotector against IO that is induced either by iron supplementation or due to chronic hemolysis as in ß-thalassemia. Prx2 is required to support STAT3 transcriptional activity and regulation of Hamp expression. Antioxid. Redox Signal. 28, 1-14.

Hepcidin is a key mediator of anemia of inflammation in Crohn's disease.

UNLABELLED: Anemia often complicates the course of Inflammatory Bowel Disease (IBD). Hepcidin, a liver-produced peptide hormone, is a key mediator of anemia of chronic disease (ACD). We hypothesized that hepcidin is significantly elevated in anemic CD patients and that hepcidin may cause iron restriction and, therefore, mediate ACD. METHODS: We enrolled 17 patients with CD and ACD recruited from the Cedars-Sinai IBD Center. Routine blood tests included hemoglobin (Hgb), hematocrit, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Anemia was defined as hemoglobin <12g/dL and <13.5g/dL, in men and women, respectively. ACD was diagnosed on the basis of a combination of the following: a) normal or elevated ferritin b) lowered serum iron and total iron binding capacity and c) normal percent iron saturation. Serum and urine hepcidin, as well as IL-6 levels were also measured. Patients with documented iron-deficiency anemia were excluded. RESULTS: There was an excellent correlation between urine (expressed as ng/mg of creatinine) and serum hepcidin levels expressed as ng/ml (r=0.853, p<0.001). We also found a strong positive correlation between serum hepcidin and ferritin levels (r=0.723, p=0.0015). There was a positive correlation between serum hepcidin and IL-6 levels (r=0.546, p=0.023). We found a strong negative correlation between serum hepcidin concentrations and Hgb levels (r=0.528, p=0.029). CONCLUSION: We demonstrate that ACD in CD is characterized by high serum IL-6 and hepcidin levels, which negatively correlate with Hgb levels. Our data support the hypothesis that IL-6-driven hepcidin production mediates ACD in patients with CD.