Effects of desferrioxamine on serum erythropoietin and ventilatory sensitivity to hypoxia in humans

Clinical trial of deferiprone iron chelation therapy in beta-thalassaemia/haemoglobin E patients in Thailand

Nine patients with either beta-thalassaemia/haemoglobin E (7) or homozygous beta-thalassaemia (2) not requiring regular transfusions were treated with the oral iron chelator, deferiprone 25-50 mg/kg/d for between 17 and 86 weeks (mean 49 weeks). There were significant decreases in serum ferritin (initial mean +/- standard deviation 2168 +/- 1142, final 418 +/- 247 micro g/l; t-test for paired samples, P = 0.005), hepatic iron (initial 20.3 +/- 6.26, final 11.7 +/- 4.83 mg/g/dry weight; P = < 0.02), red cell membrane iron (initial 76.2 +/- 3.64, final 7.2 +/- 0.56 mmol/mg protein; P = < 0.0005) and serum non-transferrin bound iron (initial 9.0 +/- 0.56, final 5.9 +/- 0.89 micro mol/l; P = < 0.0005). There was also a significant rise in serum erythropoietin (initial 240 +/- 195.1, final 433.2 +/- 269.2 U/l; P = 0.034). The haemoglobin level rose in three patients and transfusion requirements were reduced substantially in four patients. Serum thiobarbituric acid reactive substance (TBARS) also fell in six of eight patients. Patients generally improved clinically, with weight gain observed. Side-effects were mild and included gastrointestinal symptoms (6) and arthralgia (1), not requiring withdrawal of the drug. One patient died at 17 weeks of therapy as a result of an intercurrent infection. His neutrophil count was normal. We conclude that deferiprone is an effective, well-tolerated iron chelator for patients with thalassaemia intermedia. Further studies are needed to determine the optimum dose and length of treatment needed to reduce iron burden to a safe level in these patients.

A novel iron chelator that does not induce HIF-1 activity

Human skin cells (FEK-4) have been shown to undergo an immediate and transient release of low molecular mass iron (LMrFe) when subjected to UVA (320-380 nm) irradiation and this iron may act as a pro-oxidant and increase tissue injury. In order to decrease this transient release of LMrFe, cells were treated with the iron chelators desferrioxamine (DFO) and salicylaldehyde isonicotinoyl hydrazone (SIH). However, although the iron pool decreased, an increase in the DNA binding activity of the hypoxia inducible factor-1 (HIF-1) was observed when DFO and SIH were administered to normal growing FEK-4 cells. The induction of HIF-1 activates the expression of several genes associated with hypoxia and iron homeostasis. HIF-1 induction has also been associated with protection against certain forms of oxidative stress. Therefore, it is difficult to use a conventional HIF-1 activating iron chelator (such as DFO) for mechanistic studies of protection against iron-mediated oxidative stress since any protection observed could be a consequence of either the chelation of LMrFe or the induction of protective genes associated with the hypoxic response. In order to observe the effect of iron chelation on cell function without the induction of hypoxia responsive genes, cells were treated with the novel iron chelator N-(2-hydroxybenzyl)-L-serine (HBSer). Although this compound is an effective iron chelator under the conditions employed in this experiment, it does have a lower iron-binding constant than either DFO or SIH. This may be the major determinant of the observation that the compound does not induce HIF-1 binding or activate HIF-1 responsive transcriptional promoters.

Erythropoietin in human milk: physiology and role in infant health

Human milk contains substantial concentrations of erythropoietin, a hormone best known for its role in the regulation of erythropoiesis. Recent studies show that erythropoietin receptors are widely distributed in human tissues, including the gastrointestinal tract, endothelial cells, spinal cord, and brain, suggesting that erythropoietin plays a wider role in infant development. Mammary epithelial cells contribute to the production of erythropoietin in human milk, and erythropoietin concentrations appear to rise slowly in human milk during the first few months of lactation. Current data suggest that erythropoietin in human milk may play a pleiomorphic role in erythropoiesis, neurodevelopment, maturation of the gut, apoptosis, and immunity in the infant.

Desferrioxamine elevates pulmonary vascular resistance in humans: potential for involvement of HIF-1

Hypoxia-inducible factor (HIF)-1 is stabilized by hypoxia and iron chelation. We hypothesized that HIF-1 might be involved in pulmonary vascular regulation and that infusion of desferrioxamine over 8 h would consequently mimic hypoxia and elevate pulmonary vascular resistance. In study A, we characterized the pulmonary vascular response to 4 h of isocapnic hypoxia; in study B, we measured the pulmonary vascular response to 8 h of desferrioxamine infusion. For study A, 11 volunteers undertook two protocols: 1) 4 h of isocapnic hypoxia (end-tidal PO(2) = 50 Torr), followed by 2 h of recovery with isocapnic euoxia (end-tidal PO(2) = 100 Torr), and 2) 6 h of air breathing (control). For study B, nine volunteers undertook two protocols while breathing air: 1) continuous infusion of desferrioxamine (4 g/70 kg) over 8 h and 2) continuous infusion of saline over 8 h (control). In both studies, pulmonary vascular resistance was assessed at 0.5- to 1-h intervals by Doppler echocardiography via the maximum pressure gradient during systole across the tricuspid valve. Results show a progressive rise in pressure gradient over the first 3-4 h with both isocapnic hypoxia (P < 0.001) and desferrioxamine infusion (P < 0.005) to increases of ~16 and 4 Torr, respectively. These results support a role for HIF-regulated gene activation in human hypoxic pulmonary vasoconstriction.

Extra- and intracellular free iron and the carotid body responses

The hypothesis that chelation of free iron, by decreasing reactive oxygen species (ROS), might mimic hypoxia and stimulate the carotid body was tested. We used the iron chelators, desferrioxamine (DFO, 200-400 microM) initially, and later ciclopirox olamine (CPX, 2.5-5.0 microM), on rat carotid body in vitro and measured chemosensory activity and [Ca2+]i in isolated cultured glomus cell clusters during normoxia and hypoxia. Although acute treatment of DFO might not penetrate the cell, and extracellular DFO would not influence these activities whereas CPX significantly increased chemosensory activities as well as increased [Ca2+]i in normoxia. We concluded that chelation of extracellular free iron did not alter ROS formation and oxygen sensing. Chelation of intracellular free iron and, therefore, a decrease in intracellular ROS appears to influence oxygen sensing in the carotid body.

Iron deficiency anemia is highly prevalent among human immunodeficiency virus-infected and uninfected infants in Uganda

Although anemia is a common finding among human immunodeficiency (HIV)-infected infants in sub-Saharan Africa, the factors contributing to the pathogenesis of anemia have not been well characterized. We sought to characterize the relative contribution of iron deficiency and chronic disease to the anemia among infants. Hemoglobin, ferritin, erythropoietin, tumor necrosis factor-alpha (TNF-alpha), neopterin, CD4(+) lymphocyte count and plasma HIV load were measured in 165 HIV-infected and 39 uninfected 9-mo-old infants seen in an outpatient pediatric clinic in Kampala, Uganda. Among HIV-infected and uninfected infants, the prevalence of anemia (hemoglobin < 110 g/L) was 90.9 and 76.9%, respectively (P = 0.015), and the prevalence of iron deficiency anemia (hemoglobin < 110 g/L and ferritin < 12 microg/L) was 44.3 and 45.4%, respectively (P = 0.92). The relatively higher prevalence of anemia among HIV-infected infants was attributed to the anemia of chronic disease. Among infants with and without iron deficiency, the fitted regression line was log(10) plasma erythropoietin = 2.86 - 0.016.hemoglobin, and log(10) plasma erythropoietin = 4.11 - 0.028.hemoglobin, respectively, with a difference in the slope of the regression lines between log(10) erythropoietin and hemoglobin among infants with and without iron deficiency (P = 0.049). Infants in Uganda have an extremely high prevalence of anemia, and nearly half of the anemia is due to iron deficiency. The erythropoietin response to anemia appears to be upregulated among infants with iron deficiency.