Bone morphogenetic protein (BMP) signaling induces hepatic expression of the peptide hormone hepcidin. Hepcidin reduces serum iron levels by promoting degradation of the iron exporter ferroportin. A relative deficiency of hepcidin underlies the pathophysiology of many of the genetically distinct iron overload disorders, collectively termed hereditary hemochromatosis. Conversely, chronic inflammatory conditions and neoplastic diseases can induce high hepcidin levels, leading to impaired mobilization of iron stores and the anemia of chronic disease. Two BMP type I receptors, Alk2 (Acvr1) and Alk3 (Bmpr1a), are expressed in murine hepatocytes. We report that liver-specific deletion of either Alk2 or Alk3 causes iron overload in mice. The iron overload phenotype was more marked in Alk3-than in Alk2-deficient mice, and Alk3 deficiency was associated with a nearly complete ablation of basal BMP signaling and hepci- IntroductionThe hepatic hormone hepcidin regulates serum iron levels in mice and humans by inducing degradation of the iron exporter, ferroportin. 1,2 Low ferroportin levels reduce intestinal iron absorption and the release of iron from macrophage stores. Human hereditary hemochromatosis is characterized by low hepcidin levels, leading to iron accumulation in liver, heart, and endocrine organs. 1,3 Similarly, hepcidin deficiency causes hepatic iron overload in mice. 2,4 In contrast, high hepcidin levels contribute to the anemia of chronic disease (ACD) by reducing iron bioavailability for erythropoiesis. 5,6 Recent studies have demonstrated a critical role for bone morphogenetic protein (BMP) signaling in the regulation of hepcidin expression by iron. [7][8][9][10][11] Binding of BMP ligands to type I and type II BMP receptors induces the type II receptor to phosphorylate and activate the type I receptor. The activated type I receptor, in turn, phosphorylates intracellular signaling molecules, including SMADs 1, 5, and 8. Phosphorylated SMADs 1, 5, and 8 bind SMAD4 and together translocate to the nucleus, where they activate the expression of genes, including hepcidin and the Id family of transcription factors. 12 Deficiency of Smad4, 10 the BMP coreceptor hemojuvelin, 13,14 or BMP6 15,16 in hepatocytes reduces expression of hepcidin 17,18 and induces iron overload. In addition, BMP signaling appears to have an important role in the induction of hepcidin expression by inflammatory mediators that are involved in ACD. 11,19,20 There are 4 type I BMP receptors: Alk1, Alk2, Alk3, and Alk6. The identity of the type I BMP receptor(s) responsible for iron-dependent signaling and the regulation of hepcidin expression in hepatocytes are unknown. Alk1 is predominantly expressed in the endothelium. Alk6 is expressed at low levels in murine liver, 21 and global Alk6 deficiency does not induce iron overload in mice (D. R. Campagna, P. J. Schmidt, and M.D.F., unpublished observations, January 2011). In contrast, Alk2 and Alk3 are abundantly expressed in hepatocytes. 21 To identify the type I BMP receptor required for th...

Anemia of inflammation develops in settings of chronic inflammatory, infectious, or neoplastic disease. In this highly prevalent form of anemia, inflammatory cytokines, including IL-6, stimulate hepatic expression of hepcidin, which negatively regulates iron bioavailability by inactivating ferroportin. Hepcidin is transcriptionally regulated by IL-6 and bone morphogenetic protein (BMP) signaling. We hypothesized that inhibiting BMP signaling can reduce hepcidin expression and ameliorate hypoferremia and anemia associated with inflammation. In human hepatoma cells, IL-6-induced hepcidin expression, an effect that was inhibited by treatment with a BMP type I receptor inhibitor, LDN-193189, or BMP ligand antagonists noggin and ALK3-Fc. In zebrafish, the induction of hepcidin expression by transgenic expression of IL-6 was also reduced by LDN-193189 IntroductionAnemia of inflammation (AI), also known as anemia of chronic disease (ACD), is the most prevalent form of anemia after iron-deficient anemia (IDA). 1,2 AI frequently occurs in patients with a broad array of infectious, autoimmune, or inflammatory disorders, as well as cancer and kidney disease, and can contribute to the morbidity associated with these conditions. 3 In contrast to IDA, AI is typically normochromic and normocytic with hemoglobin (Hb) levels greater than 8 g/dL; however, severe AI can lead to microcytosis. 1,2 Patients with AI have diminished serum iron levels and transferrin saturations, whereas ferritin levels are normal or elevated. 3 Erythropoietin levels are typically elevated, but lower than those seen in patients with a similar degree of anemia attributable to iron deficiency. While a mild degree of anemia may be tolerated in patients who are otherwise healthy, anemia in patients with cardiovascular or pulmonary disease can impair systemic oxygen delivery, thereby worsening angina or dyspnea, or reducing exercise tolerance. Moreover, anemia is associated with worsened prognosis in cancer, 4 chronic kidney disease, 5-7 and congestive heart failure. 5,8,9 When treatment of the underlying disease is incomplete or not feasible, blood transfusions, erythropoiesis-stimulating agents (ESAs), and iron supplementation have been used to increase Hb levels in AI. However, there are known risks associated with blood transfusion, and iron supplementation in AI requires intravenous (IV) administration. Moreover, aggressive treatment with ESAs can increase the cardiovascular events and mortality in patients with kidney disease 10 and may accelerate tumor progression in patients with cancer. 11 Thus, additional therapeutic options are needed for patients with AI.A common feature of the disorders associated with AI is immune activation and production of inflammatory cytokines, such as IL-1␤, IL-6, TNF␣, and IFN␥. IL-6 is especially potent in regulating the expression of the peptide hormone hepcidin, a central regulator of systemic iron balance. [12][13][14][15] Hepcidin binds to and initiates degradation of ferroportin-1, the sole elemental iron exporter...

PBM-Study ClinicalTrials.gov, NCT01820949.

Iron is an essential element in our daily diet. Most iron is required for the de novo synthesis of red blood cells, where it plays a critical role in oxygen binding to hemoglobin. Thus, iron deficiency causes anemia, a major public health burden worldwide. On the other extreme, iron accumulation in critical organs such as liver, heart, and pancreas causes organ dysfunction due to the generation of oxidative stress. Therefore, systemic iron levels must be tightly balanced. Here we focus on the regulatory role of the hepcidin/ferroportin circuitry as the major regulator of systemic iron homeostasis. We discuss how regulatory cues (e.g., iron, inflammation, or hypoxia) affect the hepcidin response and how impairment of the hepcidin/ferroportin regulatory system causes disorders of iron metabolism.

Background During extended storage, erythrocytes undergo functional changes. These changes reduce the viability of erythrocytes leading to release of oxyhemoglobin, a potent scavenger of nitric oxide. We hypothesized that transfusion of ovine packed erythrocytes (PRBC) stored for prolonged periods would induce pulmonary vasoconstriction in lambs, and that reduced vascular nitric oxide concentrations would increase this vasoconstrictor effect. Methods We developed a model of autologous stored blood transfusion in lambs (n=36). Leukoreduced blood was stored for either 2 days (fresh PRBC) or 40 days (stored PRBC). Fresh or stored PRBC were transfused into donors instrumented for awake hemodynamic measurements. Hemodynamic effects of PRBC transfusion were also studied after infusion of NG-nitro-L-arginine methyl-ester (25 mg/kg) or during inhalation of nitric oxide (80 ppm). Results Cell-free hemoglobin levels were higher in the supernatant of stored PRBC than in supernatant of fresh PRBC (Mean±SD, 148±20 versus 41±13 mg/dl, respectively, P<0.001). Pulmonary artery pressure during transfusion of stored PRBC transiently increased from 13±1 to 18±1 mmHg (P<0.001) and was associated with increased plasma hemoglobin concentrations. NG-nitro-L-arginine methyl-ester potentiated the increase in pulmonary arterial pressure induced by transfusing stored PRBC, whereas inhalation of nitric oxide prevented the vasoconstrictor response. Conclusions Our results suggest that patients with reduced vascular nitric oxide levels due to endothelial dysfunction may be more susceptible to adverse effects of transfusing blood stored for prolonged periods. These patients might benefit from transfusion of fresh PRBC, when available, or inhaled nitric oxide supplementation to prevent the pulmonary hypertension associated with transfusion of stored PRBC.

The authors dissect the transcriptional regulatory pathway by which the iron regulatory hormone hepcidin is suppressed by erythroferrone in response to erythropoietin.

Blood transfusions are a daily practice in hospitals. Since these products are limited in availability and have various, harmful side effects, researchers have pursued the goal to develop artificial blood components for about 40 years. Development of oxygen therapeutics and stem cells are more recent goals. Medline

BACKGROUND Stored red blood cells (RBCs) undergo progressive deleterious functional, biochemical, and structural changes. The mechanisms responsible for the adverse effects of transfusing stored RBCs remain incompletely elucidated. STUDY DESIGN AND METHODS Awake wild-type (WT) mice, WT mice fed a high-fat diet (HFD-fed WT) for 4 to 6 weeks, and diabetic (db/db) mice were transfused with syngeneic leukoreduced RBCs or supernatant with or without oxidation (10% of total blood volume) after storage for not more than 24 hours (FRBCs) or 2 weeks (SRBCs). Inhaled nitric oxide (NO) at 80 parts per million was administered to a group of mice transfused with SRBCs. Blood and tissue samples were collected 2 hours after transfusion to measure iron and cytokine levels. RESULTS SRBCs had altered RBC morphology and a reduced P50. Transfusion of SRBCs into WT or HFD-fed WT mice did not produce systemic hemodynamic changes. In contrast, transfusion of SRBCs or supernatant from SRBCs into db/db mice induced systemic hypertension that was prevented by concurrent inhalation of NO. Infusion of washed SRBCs or oxidized SRBC supernatant into db/db mice did not induce hypertension. Two hours after SRBC transfusion, plasma hemoglobin (Hb), interleukin-6, and serum iron levels were increased. CONCLUSION Transfusion of syngeneic SRBCs or the supernatant from SRBCs produces systemic hypertension and vasoconstriction in db/db mice. It is likely that RBC storage, by causing in vitro hemolysis and posttransfusion hemoglobinemia, produces sustained NO scavenging and vasoconstriction in mice with endothelial dysfunction. Vasoconstriction is prevented by oxidizing the supernatant of SRBCs or breathing NO during SRBC transfusion.