EPO

Anemia of Inflammation.

Anemia of inflammation (AI), also known as anemia of chronic disease, is the most common anemia in hospitalized patients and considered to be the second most common anemia worldwide after iron deficiency anemia (IDA). The hallmark of AI is iron restriction within macrophages of the mononuclear phagocyte system (MPS) resulting in hypoferremia and hyperferritinemia together with suppression of erythropoiesis and shortened erythrocyte lifespan. Symptoms are comparable to other anemia entities and often related to the underlying disease. Patients usually present with normocytic, normochromic, hypoproliferative, mild-to-moderate anemia, reduced circulating iron levels (transferrin saturation), and increased stored iron (serum ferritin). However, AI is often associated with true iron deficiency on the basis of inflammatory diseases and blood losses of different reasons, which is why the correct identification of these patients, and their iron needs is a diagnostic challenge. Treatment of the underlying disease that causes immune activation is the primary therapeutic approach for AI which normally results in its resolution over time. Concomitant pathologies and factors contributing to the AI severity should be considered and, when feasible, specifically corrected. Iron supplementation is the first-line therapy for AI+IDA patients, while intravenously applied iron is trapped in macrophages of the MPS during advanced inflammation in patients with solely AI, whereas orally supplemented iron is not properly absorbed. Effectiveness of erythropoiesis-stimulating agents is limited in AI due to inflammation-mediated suppression of erythropoietin (Epo) signaling and impaired erythroid cell proliferation and differentiation, while red blood cell transfusion should primarily be used in life-threatening anemia. Clinical studies on hypoxia-inducible factor prolyl hydroxylase inhibitors seem promising although concerns about their safety and efficacy in AI arose within recent years. New treatment strategies aim to modify the hepcidin-ferroportin axis, yet clinical trials are still outstanding.

How do we treat life-threatening anemia in a Jehovah's Witness patient?

The refusal of allogeneic human blood and blood products by Jehovah's Witness (JW) patients complicates the treatment of life-threatening anemia. For JW patients, when hemoglobin (Hb) levels decrease beyond traditional transfusion thresholds (<7&#x2009;g/dL), alternative methods to allogeneic blood transfusion can be utilized to augment erythropoiesis and restore endogenous Hb levels. The use of erythropoietin-stimulating agents and intravenous iron has been shown to restore red blood cell and Hb levels in JW patients, although these effects may be significantly delayed. When JW patients have evidence of life-threatening anemia (Hb <5&#x2009;g/dL), oxygen-carrying capacity can be supplemented with the administration of Hb-based oxygen carriers (HBOCs). Although HBOCs are not Food and Drug Administration (FDA) approved, they may be obtained and administered with FDA, institutional review board, and patient approval. We describe a protocol-based algorithm to the management of life-threatening anemia in JW patients and review time to anemia reversal and patient outcomes using this approach.

Ineffective erythropoiesis and its treatment.

The erythroid marrow and circulating red blood cells (RBCs) are the key components of the human erythron. Abnormalities of the erythron that are responsible for anemia can be separated into 3 major categories: erythroid hypoproliferation, ineffective erythropoiesis, and peripheral hemolysis. Ineffective erythropoiesis is characterized by erythropoietin-driven expansion of early-stage erythroid precursors, associated with apoptosis of late-stage precursors. This mechanism is primarily responsible for anemia in inherited disorders like &#x3b2;-thalassemia, inherited sideroblastic anemias, and congenital dyserythropoietic anemias, as well as in acquired conditions like some subtypes of myelodysplastic syndrome (MDS). The inherited anemias that are due to ineffective erythropoiesis are also defined as iron-loading anemias because of the associated parenchymal iron loading caused by the release of erythroid factors that suppress hepcidin production. Novel treatments specifically targeting ineffective erythropoiesis are being developed. Iron restriction through enhancement of hepcidin activity or inhibition of ferroportin function has been shown to reduce ineffective erythropoiesis in murine models of &#x3b2;-thalassemia. Luspatercept is a transforming growth factor-&#x3b2; ligand trap that inhibits SMAD2/3 signaling. Based on preclinical and clinical studies, this compound is now approved for the treatment of anemia in adult patients with &#x3b2;-thalassemia who require regular RBC transfusions. Luspatercept is also approved for the treatment of transfusion-dependent anemia in patients with MDS with ring sideroblasts, most of whom carry a somatic SF3B1 mutation. While the long-term effectiveness and safety of luspatercept need to be evaluated in &#x3b2;-thalassemia and MDS, defining the molecular mechanisms of ineffective erythropoiesis in different disorders might allow the discovery of new effective compounds.

Doping and sports endocrinology: growth hormone, IGF-1, insulin, and erythropoietin.

Among the substances prohibited by the World Anti-Doping Agency, "peptide hormones, growth factors, related substances, and mimetics" are classified as prohibited both in- and out-of-competition in section S2. This work reviews growth hormone and its releasing peptides, insulin-like growth factor 1 as the main growth factor, insulin, and erythropoietin and other agents that affect erythropoiesis. This review analyzes the prevalence of use among professional athletes and gym clients, the forms of use, dosing, ergogenic effects and effects on physical performance, as well as side effects and anti-doping detection methods.

Erythropoietin.

Total hemoglobin (Hb) mass is an important determinant of aerobic power. The glycoprotein erythropoietin (Epo) promotes the production of red blood cells (RBCs). The present article reviews the regulation of erythropoiesis and ways of its manipulation. The various Epos, e.g. recombinant human (rh)Epo and (epoetin), and their long-acting analogues can be misused by cheating athletes, but the drugs are detectable by chemical tests, because their glycan isoform structures differ from those of endogenous Epo. Still, anti-doping control has become more difficult, since additional erythropoiesis-stimulating agents have become available (Epo mimetics, activin inhibitors, and small-molecule chemical drugs activating EPO expression). A major problem is created by hypoxia-inducible factor (HIF) stabilizers (e.g. &#x3b1;-ketoglutarate competitors and Co2+ salt) which activate HIFs and thus increase EPO expression. Direct EPO transfer is theoretically also possible but medically little advanced. To overcome weaknesses of direct testing of biological fluids, the World Anti-Doping Agency has implemented the Athlete Biological Passport for continuous monitoring of RBC parameters of athletes. Blood doping is assumed when distinct parameters (blood Hb concentration and reticulocytes) change in a nonphysiological way.

Recombinant erythropoietin.

Cloning and expression of the human gene encoding erythropoietin has resulted in the availability of recombinant erythropoietin for clinical and laboratory investigation. Results of such investigations are clarifying the mechanisms that regulate production of erythropoietin in health and disease. It seems likely that erythropoietin administration will reduce, if not replace, erythrocyte transfusions for certain pediatric patients. Those with the anemia of end-state renal disease and anemia of prematurity may be most likely to benefit. Clearly, additional well-controlled studies to assess the risks and benefits of erythropoietin administration will be needed prior to widespread usage of erythropoietin for anemic children.

Hepcidin.

Hepcidin is an iron-regulating peptide hormone made in the liver. It controls the delivery of iron to blood plasma from intestinal cells absorbing iron, from erythrocyte-recycling macrophages, and from iron-storing hepatocytes. Hepcidin acts by binding to and inactivating the sole cellular iron exporter, ferroportin, which delivers iron to plasma from all iron-transporting cells. In a classical endocrine feedback system, hepcidin production is stimulated by plasma iron and iron stores. Reflecting a likely role of hepcidin in innate immunity, hepcidin is also induced by inflammation. Increased erythropoietic activity suppresses hepcidin, which leads to increased iron absorption and release of iron from stores, matching iron supply to increased demand. This suppression of hepcidin is in part mediated by erythroferrone, a hormone produced by erythropoietin-stimulated erythroblasts. Hereditary hemochromatosis is caused by hepcidin deficiency or resistance to hepcidin, and hepcidin deficiency also mediates the hyperabsorption of iron in &#x3b2;-thalassemia and other iron-loading anemias. Pathologically increased concentrations of hepcidin are seen in iron-refractory iron deficiency anemia, in anemia of inflammation, and anemia of chronic kidney disease where increased hepcidin limits the availability of iron for erythropoiesis. Its central involvement in a variety of iron disorders makes hepcidin an important target for diagnostic and therapeutic applications.

[Erythropoietin and neuroprotection].

Erythropoietin (Epo) has long been recognised for its role in the control of erythropoiesis and therefore in the treatment of anemia including anemia of prematurity. The erythropoietin receptor (Epo-R) though is expressed in many other organs including the CNS. This review focuses on the role of erythropoietin during the development of the CNS and its potential role as a neuroprotective agent. Epo-R is expressed in many different cellules of the CNS during development including neural progenitor cells, neurons, astrocytes and oligodendrocytes. In the event of hypoxia CNS cells respond with increase of erythropoietin release with subsequent stimulation of neurogenesis through Epo-R on neural progenitor cells. In an Epo-R knock-out model therefore cerebral development is severely impaired. In models of hypoxia-ischemia exogenous Epo has been shown to reduce lesion size and improve structural and functional recovery. Human studies are emerging using Epo as a neuroprotective agent both for the term infant with hypoxia-ischemia as well as for the extremely preterm infant.

Sports haematology.

While the crucial role of haemoglobin in aerobic exercise has been well accepted, there is still a great deal of controversy about the optimal haematological parameters in the athletic population. The initial part of this review will examine the question of anaemia in athletes. The most common finding in athletes is a dilutional pseudoanaemia that is caused by a plasma volume expansion, rather than an actual blood loss. It is not a pathological state and normalises with training cessation in 3 to 5 days. This entity should be distinguished from conditions associated with lowered blood counts, such as intravascular haemolysis or iron deficiency anaemia. The evaluation of true anaemia states in the athlete must take into account not only blood losses secondary to exercise, such as foot strike haemolysis or iron losses through sweat, but non-athletic causes as well. Depending on the age and sex of the athlete, consideration must be given to evaluation of the gastrointestinal or genitourinary systems for blood loss. Finally, a comprehensive nutritional history must be taken, as athletes, especially women, are frequently not consuming adequate dietary iron. The second section of the paper will deal with the very contentious issue of sickle cell trait. While there have been studies demonstrating an increased risk of sudden death in people with sickle cell trait, it is still quite rare and should not be used as a restriction to activity. Further, studies have demonstrated that patients with sickle cell trait have an exercise capacity that is probably normal or near normal. However, in the cases of sudden death, it has been secondary to rhabdomyolysis occurring among sickle cell trait athletes performing at intense exertion under hot conditions, soon after arriving at altitude. The recommendations are that athletes with sickle cell trait adhere to compliance with the general guidelines for fluid replacement and acclimatisation to hot conditions and altitude. The final section of the paper examines the issue of haematological manipulation for the purposes of ergogenic improvement. Although experiments with blood doping revealed improvements in running time to exhaustion and maximal oxygen uptake, the introduction of recombinant erythropoietin has rendered blood doping little more than a historical footnote. However, the improvements in performance are not without risk, and the use of exogenous erythropoietin has the potential for increased viscosity of the blood and thrombosis with potentially fatal results. Until a definitive test is developed for detection of exogenous erythropoietin, it will continue to be a part of elite athletics.

Erythropoietin: current status.

Understanding the regulation of red blood cell production has been greatly enhanced by the cloning and expression of the gene for human erythropoietin (Epo) and its receptor. The availability of recombinant human erythropoietin (rhEpo) for administration to patients has ushered in a new era in molecular medicine. Intravenous or subcutaneous administration of rhEpo can reliably cure the anemia of chronic renal failure and may be effective in the treatment of anemias secondary to chronic inflammation, malignancy, and marrow suppression from chemotherapy. In addition, rhEpo therapy will probably play a prominent role in transfusion medicine, both in preparing patients for auto-transfusions as well as in minimizing red cell transfusion requirements in the post-operative period.

The use of darbepoetin to stimulate erythropoiesis in anemia of chronic kidney disease in cats: 25 cases.

Anemia is present in 30-65% in cats with chronic kidney disease (CKD) and few long-term treatment options exist. Darbepoetin is effective in treating anemia of kidney disease in humans and may be used in cats. To evaluate the use of darbepoetin, a recombinant analog of human erythropoietin, to stimulate erythropoiesis, and to effectively treat anemia of kidney disease in cats. Twenty-five of 66 cats that received &#x2265; 2 doses of darbepoetin at the Animal Medical Center between January 2005 and December 2009 were included in this study. Cats were included in the study if they received darbepoetin and follow-up data were available for at least 56 days and had CKD as a primary clinical diagnosis. Cats were excluded if they were treated with darbepoetin but did not have kidney disease. Response to treatment was defined as reaching or exceeding a target packed red blood cell volume or hematocrit of 25%. Fourteen of 25 cats responded. Thirteen of those 14 cats received a dosage of 1 &#x3bc;g/kg/wk or higher. Presumptive adverse effects included vomiting, hypertension, seizures, and fever. Darbepoetin is effective for treatment of anemia of kidney disease in cats. Pure red cell aplasia appears to be less common with darbepoetin than with epoetin usage.

Erythropoietin and iron-restricted erythropoiesis.

Twenty five years ago, Finch summarized knowledge gained primarily from studies of normal individuals, patients with hereditary hemolytic anemias, and patients with hemochromatosis [1]. Under conditions of basal erythropoiesis in normal subjects, plasma iron turnover (as an index of marrow erythropoietic response) is little affected, whether transferrin saturation ranges from very low to very high levels. In contrast, the erythropoietic response in individuals with congenital hemolytic anemia, in whom erythropoiesis is chronically raised up to sixfold over basal levels [2], is affected (and limited) by serum iron levels and by transferrin saturation [3]. Patients with hemochromatosis who underwent serial phlebotomy were observed to mount erythropoietic responses of up to eightfold over basal rates, attributed to the maintenance of very high serum iron and transferrin saturation levels in these patients [4], whereas normal individuals were shown to have difficulty providing sufficient iron to support rates of erythropoiesis greater than three times basal rates [5]. These observations led Finch to identify a "relative iron deficiency" state, also known as "functional iron deficiency," which he defined as circumstances in which increased erythron iron requirements exceed the available supply of iron [6]. In another clinical setting, patients undergoing autologous blood donation represent a model for perisurgical blood loss and the erythropoietic response. Insights gained over the last 20 years regarding the relationship between erythropoietin, iron, and erythropoiesis, along with implications for clinical management, will be reviewed.

Brain Injury Outcomes after Adjuvant Erythropoietin Neuroprotection for Moderate or Severe Neonatal Hypoxic-Ischemic Encephalopathy: A Report from the HEAL Trial.

Erythropoietin (Epo) is a putative neuroprotective therapy that did not improve overall outcomes in a phase 3 randomized controlled trial for neonates with moderate or severe hypoxic-ischemic encephalopathy (HIE). However, HIE is a heterogeneous disorder, and it remains to be determined whether Epo had beneficial effects on a subset of perinatal brain injuries. This study was a secondary analysis of neuroimaging data from the High-dose Erythropoietin for Asphyxia and Encephalopathy (HEAL) Trial, which was conducted from 2016 to 2021 at 17 sites involving 23 US academic medical centers. Participants were neonates &gt;36 weeks' gestation undergoing therapeutic hypothermia for moderate or severe HIE who received 5 doses of study drug (Epoetin alpha 1,000 U/kg/dose) or placebo in the first week of life. Treatment assignment was stratified by trial site and severity of encephalopathy. The primary outcome was the locus, pattern, and acuity of brain injury as determined by three independent readers using a validated HIE Magnetic Resonance Imaging (MRI) scoring system. Of the 500 infants enrolled in HEAL, 470 (94%) had high quality MRI data obtained at a median of 4.9 days of age (IQR: 4.5-5.8). The incidence of injury to the deep gray nuclei, cortex, white matter, brainstem and cerebellum was similar between Epo and placebo groups. Likewise, the distribution of injury patterns was similar between groups. Among infants imaged at less than 8 days (n = 414), 94 (23%) evidenced only acute, 93 (22%) only subacute and 89 (21%) both acute and subacute injuries, with similar distribution across treatment groups. Adjuvant erythropoietin did not reduce the incidence of regional brain injury. Subacute brain injury was more common than previously reported, which has key implications for the development of adjuvant neuroprotective therapies for this population.

Erythropoietin therapy.

Erythropoiesis and iron.

Iron and erythropoiesis are inextricably linked. Erythropoiesis is a dynamic process that requires 30-40 mg of iron per day. In normal circumstances this is met from red cell destruction but in anaemia this will not be the case. Reduced iron stores will limit iron supply to erythroblasts but normal or raised iron stores may not be able to supply iron fast enough. This is particularly true when the marrow is stimulated by erythropoietin therapy; the most common cause of failure to respond is "functional iron deficiency"'. This entity can only be effectively addressed by intravenous iron therapy. While haemoglobin and serum ferritin concentrations reflect the major iron pools, iron supply to erythroid cells can only be assessed by measuring effective haemoglobinization through the percentage of hypochromic red cells in the circulation.

Erythropoietin overview--1993.

Knowledge continues to grow on the biology of endogenous erythropoietin (EPO), its effects on red blood cell physiology, and the use of the recombinant form of the hormone. In addition to oxygen delivery, oxygen consumption may be important in stimulating EPO production. This production is likely mediated by an intracellular messenger system other than cAMP. Once released, EPO prevents programmed cell death of BFU-E and CFU-E cells. Recent evidence suggests that lack of EPO, rather than the presence of EPO inhibitors, is the cause of the anemia seen in renal patients. Recombinant EPO has been available clinically since mid 1989. Nearly two thirds of dialysis patients are receiving this agent, although low doses are the rule, with the average hematocrit achieved of only 31%. EPO dosing has been subjected to kinetic modeling that has revealed a wide range in RBC half-life from patient to patient. This accounts in part for the varying maintenance dosing requirements. An additional modulating factor in the response to EPO is severe, secondary hyperparathyroidism with bone marrow fibrosis which may be reversible with medical or surgical parathyroidectomy. Hypertension continues to occur in 20-35% of patients given EPO. This effect may be mediated by endothelin which appears to be stimulated by EPO administration. Treatment of the anemia of renal failure leads to many organ system benefits including improved muscle metabolism, decreased left ventricular hypertrophy, enhanced immune responses to hepatitis vaccine, and improved brain electrophysiology. he optimal target hematocrit to achieve the greatest benefits for the patient at an acceptable cost remains to be determined.

Roxadustat: First Global Approval.

Roxadustat (Ai Rui Zhuo&#xae; in China) is an orally administered, small molecule hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor that is being developed by FibroGen, in collaboration with Astellas and AstraZeneca, for the treatment of anaemia in patients with dialysis-dependent chronic kidney disease (CKD), non-dialysis-dependent CKD and in patients with myelodysplastic syndromes. The drug reversibly binds to and inhibits HIF-prolyl hydroxylase enzymes that are responsible for the degradation of transcription factors in the HIF family under normal oxygen conditions. Inhibition of these enzymes reduces HIF breakdown and promotes HIF activity, leading to an increase in endogenous erythropoietin production, thereby enhancing erythropoiesis. It also reduces the expression of the peptide hormone hepcidin, improves iron availability and increases haemoglobin levels. HIF regulates the expression of genes in response to reduced oxygen levels, including genes required for erythropoiesis and iron metabolism. Roxadustat is approved in China and is under regulatory review in Japan for the treatment of anaemia in patients with dialysis-dependent CKD. Studies are underway to investigate long-term cardiovascular outcomes with roxadustat versus placebo (for non-dialysis-dependent CKD) or standard of care (for dialysis-dependent CKD). This article summarizes the milestones in the development of roxadustat leading to this first approval.

Erythropoiesis, erythropoietin, and iron.

Erythropoietic regulators of iron metabolism.

Erythropoiesis is the predominant consumer of iron in humans and other vertebrates. By decreasing the transcription of the gene encoding the iron-regulatory hormone hepcidin, erythropoietic activity stimulates iron absorption, as well as the release of iron from recycling macrophages and from stores in hepatocytes. The main erythroid regulator of hepcidin is erythroferrone (ERFE), synthesized and secreted by erythroblasts in the marrow and extramedullary sites. The production of ERFE is induced by erythropoietin (EPO) and is also proportional to the total number of responsive erythroblasts. ERFE acts on hepatocytes to suppress the production of hepcidin, through an as yet unknown mechanism that involves the bone morphogenetic protein pathway. By suppressing hepcidin, ERFE facilitates iron delivery during stress erythropoiesis but also contributes to iron overload in anemias with ineffective erythropoiesis. Although most of these mechanisms have been defined in mouse models, studies to date indicate that the pathophysiology of ERFE is similar in humans. ERFE antagonists and mimics may prove useful for the prevention and treatment of iron disorders.

Reticulocyte hemoglobin content.

Under normal conditions, reticulocytes are the youngest erythrocytes released from the bone marrow into circulating blood. They mature for 1-3 days within the bone marrow and circulate for 1-2 days before becoming mature erythrocytes. Measurement of cellular hemoglobin concentration has long been reported by automated hematology analyzers as one of the red blood cell indices. The reticulocyte hemoglobin content (CHr or Ret-He) provides an indirect measure of the functional iron available for new red blood cell production over the previous 3-4 days. Measurement of reticulocyte hemoglobin content in peripheral blood samples is useful for diagnosis of iron deficiency in adults (Mast et al., Blood 2002;99:1489-1491) and children (Brugnara et al., JAMA 1999;281:2225-2230; Ullrich et al., JAMA 2005;294:924-930; Bakr and Sarette, Eur J Pediatr 2006;165:442-445). It provides an early measure of the response to iron therapy increasing within 2-4 days of the initiation of intravenous iron therapy (Brugnara et al., Blood 1994;83:3100-3101). Sequential measurements of reticulocyte hemoglobin content in patients with iron deficiency anemia provide a rapid means for assessing the erythropoietic response to iron replacement therapy (Brugnara et al., Blood 1994;83:3100-3101). It is also an early indicator or iron-restricted erythropoiesis in patients receiving erythropoietin therapy (Fishbane et al., Kidney Int 1997;52:217-222; Fishbane et al., Kidney Int 2001;60:2406-2411; Mittman et al., Am J Kidney Dis 1997;30:912-922; Tsuchiya et al., Clin Nephrol 2003;59:115-123; Chuang et al., Nephrol Dial Transplant 2003;18:370-377). Thus, reticulocyte hemoglobin content is a recent addition to an expanding list of biomarkers that can be used to differentiate iron deficiency from other causes of anemia.

BRAF inhibitors enhance erythropoiesis and treat anemia through paradoxical activation of MAPK signaling.

Erythropoiesis is a crucial process in hematopoiesis, yet it remains highly susceptible to disruption by various diseases, which significantly contribute to the global challenges of anemia and blood shortages. Current treatments like erythropoietin (EPO) or glucocorticoids often fall short, especially for hereditary anemias such as Diamond-Blackfan anemia (DBA). To uncover new erythropoiesis-stimulating agents, we devised a screening system using primary human hematopoietic stem and progenitor cells (HSPCs). We discovered that BRAF inhibitors (BRAFi), commonly used to treat BRAFV600E melanoma, can unexpectedly and effectively promote progenitor cell proliferation by temporarily delaying erythroid differentiation. Notably, these inhibitors exhibited pronounced efficacy even under cytokine-restricted conditions and in patient samples of DBA. Mechanistically, although these BRAFi inhibit the MAPK cascade in BRAFV600E mutant cells, they paradoxically act as amplifiers in wild-type BRAF cells, potently enhancing the cascade. Furthermore, we found that while the oncogenic BRAFV600E mutation disrupts hematopoiesis and erythropoiesis through AP-1 hyperactivation, BRAFi minimally impact HSPC self-renewal and differentiation. In vivo studies have shown that BRAFi can enhance human hematopoiesis and erythropoiesis in severe immunodeficient mouse models and alleviate anemia in the Rpl11 haploinsufficiency DBA model, as well as other relevant anemia models. This discovery underscores the role of the MAPK pathway in hematopoiesis and positions BRAFi as a promising therapeutic option for improving hematopoietic reconstitution and treating anemias, including DBA.

Erythropoietin in obstetrics.

Our objective was to discuss the role of erythropoietin in fetal erythropoiesis and to review its clinical uses in perinatal medicine. All relevant articles compiled through a MEDLINE search (years 1986-1997) were reviewed. Erythropoietin is essential for fetal erythropoiesis and is produced in response to hypoxia and anemia. Cord blood erythropoietin is purely fetal and reflects tissue oxygenation. It has been found to be increased in many complicated pregnancies with underlying fetal hypoxia. Erythropoietin could be used as a marker of fetal hypoxia because its concentration rises rapidly by increased production in response to hypoxia. Its measurement might enable more accurate timing of hypoxic injury. In addition, erythropoietin levels have been well correlated with perinatal brain damage and may facilitate treatment of high risk neonates. Erythropoietin has also been used successfully in anemia of prematurity, decreasing the transfusion requirement. However, studies are still needed to determine the optimal doses of erythropoietin and iron supplementations required for maximizing the red blood cell response. Erythropoietin has been examined as potential maternal therapy in various disorders during pregnancy. These include end-stage renal disease, severe antepartum iron deficiency anemia, and postpartum anemia. Erythropoietin has been found to be effective and well tolerated in these conditions. An additional promising use lies in the optimization of maternal red blood cell mass to allow autologous blood donation. This may be critical in cases where a large amount of bleeding might be anticipated, as with placenta previa. This would also minimize the donor transfusion-related hazards. Erythropoietin with its wide clinical applications could improve maternal and neonatal outcome.

Blood doping at the Olympic Games.

The objective of this paper was to review our knowledge of athletes who have, are believed to have or have attempted to engage in blood doping to enhance their performance at an Olympic Games. The paper focused on the Games from Munich 1972 to London 2012 and the author had a medical role at each of the Olympics that is discussed. The study revealed that Olympic athletes have benefitted from manipulating their blood by re-infusion of autologous or infusion of homologous blood and by administering erythropoiesis stimulating agents, notably the three generations of erythropoietins. Fifty seven athletes have been sanctioned with 12 athletes forfeiting 17 Olympic medals including 12 gold medals because of blood doping. Until 1986, the infusion of blood was not prohibited in sport but considered unethical. Erythropoietin was prohibited by the International Olympic Committee's Medical Commission in 1990. There has been a change as to how Olympic athletes have enhanced performance by blood doping, commencing with blood infusion and later administering erythropoiesis stimulating agents and significant advances have occurred in detecting such misuse. Currently, the hematological component of World Anti-Doping Agency's athlete biological passport is an important but not infallible mechanism to identify athletes who cheat by blood doping.

The mutual crosstalk between iron and erythropoiesis.

Iron homeostasis and erythropoiesis are strongly interconnected. On one side iron is essential to terminal erythropoiesis for hemoglobin production, on the other erythropoiesis may increase iron absorption through the production of erythroferrone, the erythroid hormone that suppresses hepcidin expression Also erythropoietin production is modulated by iron through the iron regulatory proteins-iron responsive elements that control the hypoxia inducible factor 2-&#x3b1;. The second transferrin receptor, an iron sensor both in the liver and in erythroid cells modulates erythropoietin sensitivity and is a further link between hepcidin and erythropoiesis. When erythropoietin is decreased in iron deficiency the erythropoietin sensitivity is increased because the second transferrin receptor is removed from cell surface. A deranged balance between erythropoiesis and iron/hepcidin may lead to anemia, as in the case of iron deficiency, defective iron uptake and erythroid utilization or subnormal recycling. Defective control of hepcidin production may cause iron deficiency, as in the recessive disorder iron refractory iron deficiency anemia or in anemia of inflammation, or in iron loading anemias, which are characterized by excessive but ineffective erythropoiesis. The elucidation of the mechanisms that regulates iron homeostasis and erythropoiesis is leading to the development of drugs for the benefit of both iron and erythropoiesis disorders.

Anemia of chronic disease.

Anemia of chronic disease (ACD) or inflammation may be secondary to infections, autoimmune disorders, chronic renal failure, or malignancies. It is characterized by an immune activation with an increase in inflammatory cytokines and resultant increase in hepcidin levels. In addition, inappropriate erythropoietin levels or hyporesponsiveness to erythropoietin and reduced red blood cell survival contribute to the anemia. Hepcidin being the central regulator of iron metabolism plays a key role in the pathophysiology of ACD. Hepcidin binds to the iron export protein, ferroportin, present on macrophages, hepatocytes, and enterocytes, causing degradation of the latter. This leads to iron trapping within the macrophages and hepatocytes, resulting in functional iron deficiency. Production of hepcidin is in turn regulated by iron stores, inflammation, and erythropoiesis via the BMP-SMAD and JAK-STAT signaling pathways. Treatment of anemia should primarily be directed at the underlying disease, and conventional therapy such as red blood cell transfusions, iron, erythropoietin, and novel agents targeting the hepcidin-ferroportin axis and signaling pathways (BMP-SMAD, JAK-STAT) involved in hepcidin production also may be considered.

Second-generation non-hematopoietic erythropoietin-derived peptide for neuroprotection.

Erythropoietin (EPO) is a well-known erythropoietic cytokine having a tissue-protective effect in various tissues against hypoxic stress, including the brain. Thus, its recombinants may function as neuroprotective compounds. However, despite considerable neuroprotective effects, the EPO-based therapeutic approach has side effects, including hyper-erythropoietic and tumorigenic effects. Therefore, some modified forms and derivatives of EPO have been proposed to minimize the side effects. In this study, we generated divergently modified new peptide analogs derived from helix C of EPO, with several amino acid replacements that interact with erythropoietin receptors (EPORs). This modification resulted in unique binding potency to EPOR. Unlike recombinant EPO, among the peptides, ML1-h3 exhibited a potent neuroprotective effect against oxidative stress without additional induction of cell-proliferation, owing to a differential activating mode of EPOR signaling. Furthermore, it inhibited neuronal death and brain injury under hypoxic stress in vitro and in an in vivo ischemic brain injury model. Therefore, the divergent modification of EPO-derivatives for affinity to EPOR could provide a basis for a more advanced and optimal neuroprotective strategy.

Developmental biology of erythropoiesis.

A newborn infant represents the culmination of developmental events from conception through organogenesis. Red cells are critically important for survival and growth of the embryo. During development, erythropoiesis occurs in two distinct forms. The first 'primitive' form consists of nucleated erythroblasts that differentiate within the blood vessels of the extraembryonic yolk sac. The second 'definitive' form consists of anucleate erythrocytes that differentiate within the liver and third trimester bone marrow of the fetus. While adult bone marrow and cord blood now serve as sources of stem cells for the treatment by transplantation of genetic and malignant diseases, the developmental origin of hematopoietic stem cells has not been determined. During the third trimester the fetus grows rapidly and the production of red cells is approximately 3-5 times that of adult steady state levels. Birth brings dramatic changes in oxygenation and erythropoietin production that result in a tenfold drop in red cell production and in a transient 'physiologic' anemia. Other causes of fetal and infant anemias have their origins in development processes. These include globin gene switching in alpha and beta thalassemia, the expression of red cell antigens in alloimmune hemolytic disease, and the poorly understood defects in the regulation of erythropoiesis in Diamond Blackfan anemia. Even in the adult, vestiges of fetal erythropoiesis are evident during transient states of accelerated erythroid expansion. A better understanding of the development of erythropoiesis will bring improvements in the treatment of anemia, not only in the newborn, but also in the fetus and the adult.

Erythropoietin update 2011.

Traditionally, erythropoietin (EPO) is described as a hematopoietic cytokine, regulating proliferation and differentiation and survival of the erythroid progenitors. The recent finding of new sites of EPO production and the wide spread distribution of EPO receptors (EPO-R) on endothelial cells, cardiomyocytes, renal cells as well as the central and peripheral nervous system raised the possibility that EPO may exert pleiotropic actions on several targets. Indeed studies (mainly preclinical) have documented protective, non-hematopoietic, abilities of EPO in a variety of tissue. However, the data obtained from clinical studies are more skeptical about these properties. This article provides a comprehensive overview of EPO and its derivatives.

Androgens and erythropoiesis: past and present.

Association between androgens and erythropoiesis has been known for more than seven decades. Androgens stimulate hematopoietic system by various mechanisms. These include stimulation of erythropoietin release, increasing bone marrow activity and iron incorporation into the red cells. Before the discovery of recombinant erythropoietin (rhEpo), androgens were used in the treatment of anemia associated with renal disease, bone marrow suppression, and hypopituitarism. Anabolism is an additional advantage of androgen therapy. Furthermore, in light of recent reports regarding adverse effects of rhEpo, the role of androgen therapy in various types of anemias should be readdressed. Polycythemia remains a known side effect of androgen therapy. In this review, we will briefly discuss the initial animal and human studies which demonstrated the role of androgens in the treatment of anemia, their mechanism of action, a detailed account of the efficacy of androgens in the treatment of various anemias, the erythropoietic side effects of androgens and finally, the relationship between hematocrit levels and cardiovascular disease.

Erythropoietin and erythropoiesis stimulating agents.

Erythropoietin (EPO) is the main hormonal regulator of red blood cell production. Recombinant EPO has become the leading drug for treatment of anaemia from a variety of causes; however, it is sometimes misused in sport with the aim of improving performance and endurance. This paper presents an introductory overview of EPO, its receptor, and a variety of recombinant human EPOs/erythropoiesis stimulating agents (ESAs) available on the market (e.g. epoetins and their long acting analogs--darbepoetin alfa and continuous erythropoiesis receptor activator). Recent efforts to improve on EPO's pharmaceutical properties and to develop novel replacement products are also presented. In most cases, these efforts have emphasized a reduction in frequency of injections or complete elimination of intravenous or subcutaneous injections of the hormone (biosimilars, EPO mimetic peptides, fusion proteins, endogenous EPO gene activators and gene doping). Isoelectric focusing (IEF) combined with double immunoblotting can detect the subtle differences in glycosylation/sialylation, enabling differentiation among endogenous and recombinant EPO analogues. This method, using the highly sensitive anti-EPO monoclonal antibody AE7A5, has been accepted internationally as one of the methods for detecting misuse of ESAs in sport.

Erythropoiesis-stimulating agents: past and future.

Renal anemia is a well-recognized complication of chronic kidney disease (CKD), and the deficiency of erythropoietin (EPO) is the primary cause. Observational population-based studies continue to demonstrate the association of low hemoglobin with adverse outcomes, and renal failure, cardiac failure, and anemia all may interact to cause or worsen each other, the so-called cardio-renal anemia syndrome. Treatment of anemia can be successfully achieved with the use of erythropoiesis-stimulating agents (ESAs). From a mechanistic point of view, however, the therapeutic benefits of ESA could be far beyond the correction of anemia. ESA modulates a broad array of cellular processes that include progenitor stem cell development, cellular integrity, and angiogenesis. A pleiotropic effect of EPO has been shown in the central nervous system, the cardiovascular system, and the kidney. While recent results of randomized controlled trials have established that there is little support for normalizing hemoglobin in CKD patients, the results of these studies do not negate renoprotective effects of EPO. A large number of patients with CKD will benefit from early recognition and appropriate correction of anemia with ESA.

Erythropoietic agents and the elderly.

Erythropoietin (Epo) is a peptide hormone that stimulates erythropoiesis. There are several agents in clinical use and in development that either act as ligands for the cell surface receptors of Epo or promote Epo production, which stimulates erythropoiesis. These are known as erythropoietic agents. The agents already in use include epoetin alfa, epoetin beta, and darbepoetin alfa. Newer agents under active investigation include continuous erythropoietin receptor activator (CERA) or proline hydroxylase inhibitors that increase hypoxia-inducible factor-1 (HIF-1), thereby stimulating Epo production and iron availability and supply. Erythropoietic agents have been shown to promote neuronal regeneration and to decrease post-stroke infarct size in mouse models. They have also been reported to shorten survival when used to treat anemia in many cancer patients and to increase thromboembolism. In contrast, rapid decrease of Epo levels as observed in astronauts and high-altitude dwellers upon rapid descent to sea level leads to the decrease of erythroid mass, a phenomenon known as "neocytolysis." The relative decrease in the serum Epo level is known to occur in some subjects with otherwise unexplained anemia of aging. Anemia by itself is a predictor of poor physical function in the elderly and is a significant economic burden on society. One out of every five persons in the United States will be elderly by 2050. Erythropoietic agents, by preventing and treating otherwise unexplained anemias of the elderly and anemia associated with other disease conditions of the elderly, have the potential to improve the functional capacity and to decrease the morbidity and mortality in the elderly, thereby alleviating the overall burden of medical care in society.

[Erythropoietin].

New data on erythropoietin and regulation of erythropoiesis are presented; the possibility to treat anaemia in patients with chronic renal disease by erythropoietin is stressed.

Hematologic disorders in renal failure.

Anemia is a frequent complication of renal failure. As in anemias of other origin, the resulting tissular hypoxia is partially compensated by an increased production of 2,3-diphosphoglycerate in red cells and a shift to the right of the oxygen hemoglobin dissociation curve. Two mechanisms are implicated in this anemia: increased hemolysis and depressed production of red cells. Decreased production of erythropoietin is probably the cause of reduced erythropoiesis, but the role of uremic intoxication has not been unequivocally excluded. In the course of chronic hemodialysis, iron deficiency anemia and occasionally hypersplenism develop. It is noteworthy that blood requirements in anephric patients are two to three times greater than those of nonanephric hemodialyzed patients. Accordingly, bilateral nephrectomy should be restricted to carefully selected cases. At the present time, androgens seem to be the best treatment of renal anemia. Qualitative anomalies of platelets are the main factor responsible for uremic bleeding and are corrected by hemodialysis.

Erythropoietin.

Role of erythropoietin in the brain.

Multi-tissue erythropoietin receptor (EPO-R) expression provides for erythropoietin (EPO) activity beyond its known regulation of red blood cell production. This review highlights the role of EPO and EPO-R in brain development and neuroprotection. EPO-R brain expression includes neural progenitor cells (NPC), neurons, glial cells and endothelial cells. EPO is produced in brain in a hypoxia sensitive manner, stimulates NPC proliferation and differentiation, and neuron survival, and contributes to ischemic preconditioning. Mice lacking EPO or EPO-R exhibit increased neural cell apoptosis during development before embryonic death due to severe anemia. EPO administration provides neural protection in animal models of brain ischemia and trauma, reducing the extent of injury and damage. Intrinsic EPO production in brain and EPO stimulation of endothelial cells contribute to neuroprotection and these are of particular importance since only low levels of EPO appear to cross the blood-brain barrier when administered at high dose intravenously. The therapeutic potential of EPO for brain ischemia/trauma and neurodegenerative diseases has shown promise in early clinical trial and awaits further validation.

Erythropoietin and neuroprotection: a therapeutic perspective.

Recombinant erythropoietin (EPO) is used to correct for anaemia caused by chronic renal failure or cancer therapy. Improvement of the quality of life of anaemic patients treated with EPO was recently demonstrated and preliminary clinical results suggest an improvement of cognitive functions in patients receiving EPO. High expression of EPO and its receptor in the brain during embryonic development has led to the investigation of not only the neurotrophic role of EPO but also its neuroprotective properties. The neuroprotective effects of EPO have various complementary actions including antagonism of the effects of glutamate, increased expression of antioxidant enzymes, changes in production of neurotransmitters and induction of neuroglobin. Convincing experimental results suggest a blood-brain transport of EPO whereas clinical pharmacokinetic data do not as yet support this. The neuroprotective effects of EPO and its therapeutic promise need to be underlined.

Pathophysiology of perioperative anaemia.

Perioperative anaemia is a common clinical entity. It is usually due to combination of various mechanisms, including: pre-existing anaemia prior to surgery; anaemia due to impaired erythropoiesis, including alterations of metabolism of iron and erythropoietin (EPO); anaemia due to increased destruction of red blood cells (RBCs); and anaemia due to iatrogenic causes. Postoperatively, anaemia resembles anaemia of chronic disease and is probably related to the effects of inflammatory mediators released during and after surgery on the production and survival of RBCs. Pro-inflammatory cytokines, such as tumour necrosis factor, impair erythropoietin-dependent signalling and iron homeostasis. Iatrogenic causes, notably excessive phlebotomies, remain a major cause of perioperative anaemia. With increasing emphasis on restrictive blood transfusion strategies, understanding these mechanisms is important for the clinician.

The mutual control of iron and erythropoiesis.

Iron is essential for hemoglobin synthesis during terminal erythropoiesis. To supply adequate iron the carrier transferrin is required together with transferrin receptor endosomal cycle and normal mitochondrial iron utilization. Iron and iron protein deficiencies result in different types of anemia. Iron-deficiency anemia is the commonest anemia worldwide due to increased requirements, malnutrition, chronic blood losses and malabsorption. Mutations of transferrin, transferrin receptor cycle proteins, enzymes of the first step of heme synthesis and iron sulfur cluster biogenesis lead to rare anemias, usually accompanied by iron overload. Hepcidin plays an indirect role in erythropoiesis by controlling plasma iron. Inappropriately high hepcidin levels characterize the rare genetic iron-refractory iron-deficiency anemia (IRIDA) and the common anemia of chronic disease. Iron modulates both effective and ineffective erythropoiesis: iron restriction reduces heme and alpha-globin synthesis that may be of benefit in thalassemia. This review relies on the analysis of the most recent literature and personal data. Erythropoiesis controls iron homeostasis, by releasing erythroferrone that inhibits hepcidin transcription to increase iron acquisition in iron deficiency, hypoxia and EPO treatment. Erythroferrone, produced by EPO-stimulated erythropoiesis, inhibits hepcidin only when the activity of BMP/SMAD pathway is low, suggesting that EPO somehow modulates the latter signaling. Erythroblasts sense circulating iron through the second transferrin receptor (TFR2) that, in animal models, modulates the sensitivity of the erythroid cells to EPO. The advanced knowledge of the regulation of systemic iron homeostasis and erythropoiesis-mediated hepcidin regulation is leading to the development of targeted therapies for anemias and iron disorders.

Erythropoiesis-stimulating protein delivery in providing erythropoiesis and neuroprotection.

Erythropoietin (EPO), a glycoprotein, plays an important role in erythropoiesis and neuroprotection. EPO therapies for anemia or neurodegenerative diseases require frequent injections or high-dose systemic administration which may cause unwanted side effects. Various strategies for EPO delivery have been investigated for increasing EPO bioavailability and decreasing side effects, including nano/micro particles, PEGylation of EPO and transport-mediated delivery systems. Nano/micro particles provide EPO with long-term effect and protect EPO against proteolytic cleavage. PEGylated EPO prolong circulating time and reduce injection frequency of anemia treatment. A transport-mediated delivery system enables protein to cross biological barriers. Presently, there is no report about an effective delivery system of EPO for neuroprotection. This review focuses on EPO delivery systems for erythropoiesis or neuroprotection with prolonged duration and enhanced bioavailability.