Ferroportin inhibition attenuates plasma iron, oxidant stress, and renal injury following red blood cell transfusion in guinea pigs.

Background: Red blood cell (RBC) transfusions result in the sequestration and metabolism of storage-damaged RBCs within the spleen and liver. These events are followed by increased plasma iron concentrations that can contribute to oxidant stress and cellular injury. We hypothesized that administration of a ferroportin inhibitor (FPN-INH) immediately after acute RBC exchange transfusion could attenuate posttransfusion circulatory compartment iron exposure, by retaining iron in spleen and hepatic macrophages.

Electron paramagnetic resonance oximetry as a novel approach to monitor the effectiveness and quality of red blood cell transfusions.

Background: The goal of red blood cell transfusion is to improve tissue oxygenation. Assessment of red blood cell quality and individualised therapeutic needs can be optimised using direct oxygen (O) measurements to guide treatment. Electron paramagnetic resonance oximetry is capable of accurate, repeatable and minimally invasive measurements of tissue pO.

Revisiting the putative role of heme as a trigger of inflammation.

Activation of the innate immune system by free heme has been proposed as one of the principal consequences of cell-free hemoglobin (Hb) exposure. Nonetheless, in the absence of infection, heme exposures within a hematoma, during hemolysis, or upon systemic administration of Hb (eg, as a Hb-based oxygen carrier) are typically not accompanied by uncontrolled inflammation, challenging the assumption that heme is a major proinflammatory mediator in vivo. Because of its hydrophobic nature, heme liberated from oxidized hemoglobin is rapidly transferred to alternative protein-binding sites (eg, albumin) or to hydrophobic lipid compartments minimizing protein-free heme under in vivo equilibrium conditions.

Evaluation of renal oxygen homeostasis in a preclinical animal model to elucidate difference in blood quality after transfusion.

Background: Red blood cell (RBC) oxygen (O ) delivery may be impacted at the tissue, cellular, and molecular levels after storage duration, preservation strategies, and pathogen reduction. Collectively, the preclinical measurement of arterial and venous PO , systemic blood flow, tissue hypoxia-inducible factors (HIFs), pimonidazole adduction, and erythropoietin (EPO) regulation can serve to elucidate differential RBC quality after storage and processing.

Study Design And Methods: Donor guinea pig blood was collected, leukoreduced, and stored at 4°C in AS-3 for 1 (fresh) or 14 (stored) days.

Iron accelerates hemoglobin oxidation increasing mortality in vascular diseased guinea pigs following transfusion of stored blood.

Non-transferrin-bound iron (NTBI) and free hemoglobin (Hb) accumulate in circulation following stored RBC transfusions. This study investigated transfusion, vascular disease, and mortality in guinea pigs after stored RBC transfusion alone and following cotransfusion with apo-transferrin (apo-Tf) and haptoglobin (Hp). The effects of RBC exchange transfusion dose (1, 3, and 9 units), storage period (14 days), and mortality were evaluated in guinea pigs with a vascular disease phenotype.

Hemoglobinuria-related acute kidney injury is driven by intrarenal oxidative reactions triggering a heme toxicity response.

Intravascular hemolysis can result in hemoglobinuria with acute kidney injury. In this study we systematically explored two in vivo animal models and a related cell culture system to identify hemoglobinuria-triggered damage pathways. In models of stored blood transfusion and hemoglobin (Hb) exposure in guinea pigs and beagle dogs we found that hemoglobinuria led to intrarenal conversion of ferrous Hb(Fe(2+)) to ferric Hb(Fe(3+)), accumulation of free heme and Hb-cross-linking products, enhanced 4-hydroxynonenal reactivity in renal tissue, and acute tubule injury.

Different target specificities of haptoglobin and hemopexin define a sequential protection system against vascular hemoglobin toxicity.

Free hemoglobin (Hb) triggered vascular damage occurs in many hemolytic diseases, such as sickle cell disease, with an unmet need for specific therapeutic interventions. Based on clinical observations the Hb and heme scavenger proteins haptoglobin (Hp) and hemopexin (Hx) have been characterized as a sequential defense system with Hp as the primary protector and Hx as a backup when all Hp is depleted during more severe intravascular hemolysis. In this study we present a mechanistic rationale for this paradigm based on a combined biochemical and cell biological approach directed at understanding the unique roles of Hp and Hx in Hb detoxification.

Reversal of hemochromatosis by apotransferrin in non-transfused and transfused Hbbth3/+ (heterozygous B1/B2 globin gene deletion) mice.

Intermediate beta-thalassemia has a broad spectrum of sequelae and affected subjects may require occasional blood transfusions over their lifetime to correct anemia. Iron overload in intermediate beta-thalassemia results from a paradoxical intestinal absorption, iron release from macrophages and hepatocytes, and sporadic transfusions. Pathological iron accumulation in parenchyma is caused by chronic exposure to non-transferrin bound iron in plasma.

Proteasome inhibition and oxidative reactions disrupt cellular homeostasis during heme stress.

Dual control of cellular heme levels by extracellular scavenger proteins and degradation by heme oxygenases is essential in diseases associated with increased heme release. During severe hemolysis or rhabdomyolysis, uncontrolled heme exposure can cause acute kidney injury and endothelial cell damage. The toxicity of heme was primarily attributed to its pro-oxidant effects; however additional mechanisms of heme toxicity have not been studied systematically.