Erythropoietin: physiology and pharmacology update

Progress toward a nonviral gene therapy protocol for the treatment of anemia

Anemia frequently accompanies chronic diseases such as progressive renal failure, acquired immunodeficiency syndrome, and cancer. Patients are currently treated with erythropoietin (EPO) replacement therapy, using various recombinant human EPO protein formulations. Although this treatment is effective, gene therapy could be more economical and more convenient for the long-term management of the disease. The objective of this study was to develop a naked DNA-based gene therapy protocol that could fill this need. Hydrodynamic limb vein technology has been shown to be an effective and safe procedure for delivering naked plasmid DNA (pDNA) into the skeletal muscles of limbs. Using this method, we addressed the major challenge of an EPO-based gene therapy of anemia: maintaining stable, long-term expression at a level that sufficiently promotes erythropoiesis without leading to polycythemia. The results of our study, using a rat anemia model, provide proof of principle that repeated delivery of small pDNA doses has an additive effect and can gradually lead to the correction of anemia without triggering excessive hematopoiesis. This simple method provides an alternative approach for regulating EPO expression. EPO expression was also proportional to the injected pDNA dose in nonhuman primates. In addition, long-term (more than 450 days) expression was obtained after delivering rhesus EPO cDNA under the transcriptional control of the muscle-specific creatine kinase (MCK) promoter. In conclusion, these data suggest that the repeated delivery of small doses of EPO expressing pDNA into skeletal muscle is a promising, clinically viable approach to alleviate the symptoms of anemia.

Effects of recombinant human erythropoietin on antiplatelet action of aspirin and clopidogrel in healthy subjects: results of a double-blind, placebo-controlled randomized trial

BACKGROUND

Recombinant human erythropoietin (rHuEpo) reduces myocardial injury in experimental ischemia and has been proposed as a cardioprotective agent for potential use in acute coronary syndromes. Its safety profile in clinical acute ischemic settings is uncertain because rHuEpo has been reported to increase platelet reactivity and the risk of thromboembolism in some disease populations. Whether prothrombotic effects of rHuEpo mitigate the effects of antiplatelet agents used in acute coronary syndrome patients is unknown.

METHODS

Recombinant human erythropoietin 100, 200, 400 U/kg, or placebo was given intravenously once daily for 3 consecutive days in a double-blind randomized trial in 96 healthy subjects. A single oral dose of aspirin 325 mg or clopidogrel 300 mg was given immediately after the last dose of study drug. Bleeding time and in vitro high shear stress platelet function assays (PFA)-100 were determined before; 5 hours; and 1, 5, and 7 days after aspirin or clopidogrel.

RESULTS

Recombinant human erythropoietin at doses of 100 and 200 U/kg did not alter bleeding time or PFA-100 closure times at any time point when compared with placebo. Recombinant human erythropoietin at a dose of 400 U/kg significantly blunted the post-aspirin increase in bleeding time when compared with placebo (P = .03) but did not alter post-clopidogrel bleeding times nor PFA closure times. The 400-U/kg dose did not change hematocrit but did significantly increase the platelet count at 5 days after study drug administration when compared with placebo (P = .014).

CONCLUSION

Short-term rHuEpo at doses up to 200 U/kg did not mitigate the effects of administration of aspirin or clopidogrel on either in vivo or in vitro measures of platelet function in healthy subjects. The 400-U/kg dose attenuated the effects of aspirin on bleeding time and increased the platelet count. Studies of the effects of rHuEpo on platelet function in patients with coronary artery disease are warranted to further characterize dose/safety profile.

Erythropoietin and treatment of non-anemic conditions--cardiovascular protection

The well-established physiological function of erythropoietin (EPO) is the induction of erythropoiesis. A growing body of evidence indicates that EPO has tissue-protective effects and prevents tissue damage during ischemia and inflammation. Tissue protection after ischemia and injury has been found in the brain, heart, and kidney. It has been speculated that EPO has anti-apoptotic effects in cardiovascular cells. These novel effects of EPO seem to be independent of its erythropoietic activity. Unclear is the role of the known EPO receptor or whether other signaling pathways are involved; a novel EPO receptor might be involved in tissue protection by this hormone. This review article summarizes present knowledge of cardiovascular and renal protective effects of EPO and discusses possible underlying mechanisms.

Erythropoietin and other blood-boosting methods

Dating back to the earliest Olympics, athletes have been searching for a performance edge. Recombinant human erythropoietin was made commercially available in 1987 to treat various diseases associated with anemia. Within a few years, elite endurance athletes capitalized on its potential as an undetectable performance-enhancing agent. Although antidoping agencies have developed a test to detect its use, there are pitfalls. More importantly, athletes continue to add more sophisticated doping practices to their armamentarium, challenging regulatory agencies, putting their health at great risk, and tainting the spirit of fair competition.

Darbepoetin alfa protects podocytes from apoptosis in vitro and in vivo

Detachment or apoptosis of podocytes leads to proteinuria and glomerulosclerosis. There are no current interventions for diabetic or non-diabetic glomerular diseases specifically preventing podocyte apoptosis. Binding of erythropoiesis stimulating proteins (ESPs) to receptors on non-hematopoietic cells has been shown to have anti-apoptotic effects in vitro, in vivo, and in preliminary human studies. Recently, erythropoietin receptors were identified on podocytes; therefore, we tested effects of darbepoetin alfa in preventing podocyte apoptosis. Cultured immortalized mouse podocytes were treated with low-dose ultraviolet-C (uv-C) irradiation to induce apoptosis in the absence or presence of darbepoetin alfa. Apoptosis was quantified by Hoechst staining and by caspase 3 cleavage assessed by Western blots. Pretreatment with darbepoetin alfa significantly reduced podocyte apoptosis with this effect involving intact Janus family protein kinase-2 (JAK2) and AKT signaling pathways. Additionally, darbepoetin alfa was found protective against transforming growth factor-beta1 but not puromycin aminonucleoside induced apoptosis. Mice with anti-glomerular antibody induced glomerulonephritis had significantly less proteinuria, glomerulosclerosis, and podocyte apoptosis when treated with darbepoetin alfa. Our studies show that treatment of progressive renal diseases characterized by podocyte apoptosis with ESPs may be beneficial in slowing progression of chronic kidney disease.

Renal sympathetic nerves modulate erythropoietin plasma levels after transient hemorrhage in rats

In contrast to other sympathetic outflow tracts, renal sympathetic nerve activity (RSNA) decreases in response to hypotensive hemorrhage. The functional significance of this "paradox" is not known. We tested the hypothesis that RSNA modulates renal perfusion and thus erythropoietin (EPO) release after transient hypotensive hemorrhage in anesthetized rats. Plasma EPO was measured before and after 30 min of transient hypotensive hemorrhage (i.e., -40 mmHg from mean baseline blood pressure, followed by reinfusion of shed blood) and 120 min thereafter in sham-denervated rats, and after renal denervation (DNX) or bilateral cervical vagotomy (VX) to abolish/blunt the RSNA decrease mediated by a cardiopulmonary reflex. RSNA, renal Doppler flow, renal vascular resistance (RVR), resistance index, and oxygen delivery/uptake (Do(2)/Vo(2)) were measured. RSNA decreased in intact animals (-40 +/- 5% from baseline, P < 0.05). This was blunted by VX. With intact nerves, EPO level did not increase. In DNX rats, EPO was increased at minute 120 (49 +/- 3 vs. 74 +/- 2 mU/ml; P < 0.05), in VX rats this (47 +/- 2 vs. 62 +/- 4 mU/ml; P < 0.05) was less pronounced. Do(2) in DNX rats was lower compared with intact and VX rats (0.25 +/- 0.04 vs. 0.51 +/- 0.06 and 0.54 +/- 0.05 ml O(2)/min; P < 0.05) due to lower Doppler flow and increased RVR. RVR and Do(2) were similar in intact and VX rats, but resistance index differed between all groups (0.70 +/- 0.02 vs. 0.78 +/- 0.02 vs. 0.85 +/- 0.02; P < 0.05, intact vs. VX vs. DNX), indicating differential reactivity of renal vasculature. Vo(2) was unaffected by VX and DNX. Renal sympathoinhibition during hypotensive hemorrhage might help to preserve sufficient oxygenation of renal tissue by modulation of hemodynamic mechanisms that act to adapt renal oxygen availability to demand.

Selective modulation of the erythropoietic and tissue-protective effects of erythropoietin: time to reach the full therapeutic potential of erythropoietin

Erythropoietin (EPO) has been used clinically both as an erythropoietic stimulating agent in the treatment of anemia and as a tissue-protective agent in diverse clinical settings including stroke, multiple sclerosis, acute myocardial infarction and others. However, use of EPO or EPO-analogues leads to simultaneous targeting of both the erythropoietic and tissue-protective properties of EPO, and this strategy has been associated with several problems. Specifically, the benefit of correction of cancer-related anemia can be offset by the tissue-protective effects of EPO, which may lead to stimulation of cancer cell proliferation. Conversely, the benefit of tissue-protection in patients with stroke or myocardial infarction can be offset by adverse effects associated with the erythropoietic effects of EPO such as elevation of red blood cell mass, hypertension and prothrombotic phenomena. The finding that the erythropoietic and tissue-protective properties of EPO are conferred via two distinct receptor systems raises the interesting possibility of discovering novel drugs that selectively stimulate either the erythropoietic or the tissue-protective activities of EPO. This article reviews the current status of the clinical use of EPO and EPO-analogues in the treatment of cancer-related anemia and for tissue protection, outlines the distinct molecular biology of the tissue-protective and erythropoietic effects of EPO and discusses strategies of selective targeting of these activities with the goal of exploiting the full therapeutic potential of EPO.

Neuronal apoptosis following cerebral ischaemia: pathophysiology and possible therapeutic implications

PURPOSE OF REVIEW

Neuronal apoptosis following cerebral ischaemia has become an issue of extraordinary scientific interest in the past decade. Besides necrosis, this highly relevant pathomechanism has been shown to be markedly involved in the pathogenesis of delayed postischaemic neuronal damage. As a result, a variety of possible neuroprotective strategies and therapeutic options subsequent to cerebral ischaemia have emerged. This article provides an overview of the pathophysiologic mechanisms underlying delayed neuronal apoptotic degeneration after cerebral ischaemia. Based on these facts, selected therapeutic implications are discussed in detail.

RECENT FINDINGS

Recent findings from experimental studies have demonstrated a new therapeutic neuroprotective potential of pharmaceutical blockade of death-inducing ligands (e.g. Fas/CD95 ligand), enhancement of survival signal transduction with endogenous ligands (e.g. erythropoietin) and therapeutically modulating the balance between intracellular anti- and proapoptotic Bcl proteins with intriguing molecular techniques after cerebral ischaemia.

SUMMARY

Neuronal apoptosis is highly relevant in the pathophysiology of neurodegenerative disorders, neurotrauma and cerebral ischaemia/reperfusion. Within the past few years, a variety of therapeutic strategies have emerged based on our increasing knowledge of the pathophysiology of apoptosis. Whereas inhibition of single factors in apoptotic cascades (e.g. proteases) has produced rather unsatisfying results, new opportunities have emerged at the molecular level due to advances in molecular medicine. These approaches offer promising opportunities for neuroprotective therapeutic strategies subsequent to cerebral ischaemia. It is tempting to speculate that a combination ('cocktail') of these antiapoptotic interventions might even increase their neuroprotective potential.

Soluble erythropoietin receptor is present in the mouse brain and is required for the ventilatory acclimatization to hypoxia

While erythropoietin (Epo) and its receptor (EpoR) have been widely investigated in brain, the expression and function of the soluble Epo receptor (sEpoR) remain unknown. Here we demonstrate that sEpoR, a negative regulator of Epo's binding to the EpoR, is present in the mouse brain and is down-regulated by 62% after exposure to normobaric chronic hypoxia (10% O2 for 3 days). Furthermore, while normoxic minute ventilation increased by 58% in control mice following hypoxic acclimatization, sEpoR infusion in brain during the hypoxic challenge efficiently reduced brain Epo concentration and abolished the ventilatory acclimatization to hypoxia (VAH). These observations imply that hypoxic downregulation of sEpoR is required for adequate ventilatory acclimatization to hypoxia, thereby underlying the function of Epo as a key factor regulating oxygen delivery not only by its classical activity on red blood cell production, but also by regulating ventilation.

Functional conservation of erythropoietin signaling in zebrafish

Erythropoietin (Epo) and its cognate receptor (EpoR) are required for maintaining adequate levels of circulating erythrocytes during embryogenesis and adulthood. Here, we report the functional characterization of the zebrafish epo and epor genes. The expression of epo and epor was evaluated by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization, revealing marked parallels between zebrafish and mammalian gene expression patterns. Examination of the hypochromic mutant, weissherbst, and adult hypoxia-treated hearts indicate that zebrafish epo expression is induced by anemia and hypoxia. Overexpression of epo mRNA resulted in severe polycythemia, characterized by a striking increase in the number of cells expressing scl, c-myb, gata1, ikaros, epor, and betae1-globin, suggesting that both the erythroid progenitor and mature erythrocyte compartments respond to epo. Morpholino-mediated knockdown of the epor caused a slight decrease in primitive and complete block of definitive erythropoiesis. Abrogation of STAT5 blocked the erythropoietic expansion by epo mRNA, consistent with a requirement for STAT5 in epo signaling. Together, the characterization of zebrafish epo and epor demonstrates the conservation of an ancient program that ensures proper red blood cell numbers during normal homeostasis and under hypoxic conditions.

Carboxymethyl chitosan-coated capillary and its application in CE of proteins

A hydrophilic basic polysaccharide, carboxymethyl chitosan (CMC) as a capillary coating is presented with a simple preparation procedure. The CMC-coated capillary showed a long lifetime of more than 100 runs, and had good tolerance to some organic solvents, 0.1 M HCl, 0.1 M NaOH, and 5 M urea. The run-to-run, day-to-day, and capillary-to-capillary RSDs for the CMC-coated capillary were all below 2.0% for the determination of EOF. Moreover, the coatings with different concentrations and molecular weights of CMC were also investigated. The CMC-coated capillary was successfully applied to separate basic proteins and recombinant human erythropoietin (rhEPO). Furthermore, several experimental parameters, such as the concentration and pH of the running buffer, temperature, and applied voltage, were optimized for the separation of rhEPO glycoforms. Comparison of an uncoated capillary with chitosan- and CMC-coated capillaries for the separation of rhEPO glycoforms was also discussed. The results demonstrated that rhEPO glycoforms can be well separated by a CMC-coated capillary within 8 min with good reproducibility and resolution. Finally, the volatile BGE HAc-NH4Ac was utilized to separate rhEPO for its further application with CE-MS, achieving a satisfactory result.

Anti-EPO and anti-NESP antibodies raised against synthetic peptides that reproduce the minimal amino acid sequence differences between EPO and NESP

Erythropoietin (EPO) is a hormone that regulates red blood cell production. Recombinant human EPO (rHuEPO) and NESP (novel erythropoiesis stimulating protein) have been produced for therapeutic purposes and also to improve sports performance. The primary sequences of rHuEPO and NESP differ by just five amino acids. Due to the high homology, no antibodies that are able to discriminate between both molecules have been obtained until now. The aim of the present work was to design synthetic peptides corresponding to the sequence that differs between EPO and NESP (87-90aa), that can then be used as immunogens to develop specific rabbit polyclonal antibodies for selectively detecting EPO and NESP. Three peptides were synthesized: EPO (81-95), NESP (81-95), and NESP (86-104), and these were coupled to KLH and OVA for immunization and screening purposes, respectively. The sera obtained were tested by ELISA on synthetic peptide-OVA conjugates and purified by immunoaffinity chromatography against the corresponding synthetic peptide. The specific purified antibodies were characterized by ELISA, SDS-PAGE, and isoelectric focusing, followed by western blot. Antisera raised against EPO (81-95) recognized rHuEPO but not NESP. In contrast, anti-NESP (84-106) sera gave a specific anti-NESP response only after immunoaffinity purification on a NESP (86-91) column. An efficient strategy for generating specific antibodies against EPO and NESP can be achieved by selecting suitable synthetic peptides. The antibodies obtained are able to differentiate between rHuEPO and NESP, and may be particularly useful for screening purposes in both therapeutic and antidoping contexts.

Expression of erythropoietin receptor in human epiretinal membrane of proliferative diabetic retinopathy

PURPOSE

It is widely accepted that intravitreous levels of erythropoietin (Epo) are elevated in patients with ischaemic retinal diseases such as proliferative diabetic retinopathy (PDR). The aim of this study was to examine the expression of Epo and the Epo receptor (EpoR) in epiretinal membranes with and without diabetes.

METHODS

Eighteen epiretinal membranes (PDR (n = 10), idiopathic epiretinal membranes (IERMs) without diabetes (n = 4) and inner limiting membranes (ILMs) (n = 4)) were obtained during pars plana vitrectomy. Formalin-fixed and paraffin-embedded tissues were examined by immunohistochemistry with anti-Epo and EpoR antibodies.

RESULTS

The histopathological findings demonstrated that PDR membranes consisted of a variety of endothelial cells forming a microvascular cavity with red blood cells and non-vascular stromal mononuclear cells. Membranous and cytoplasmic immunoreactivity for EpoR was strongly detected in endothelial cells and stromal cells in all PDR patients. Although microvessels were not observed in IERMs and ILMs, immunoreactivity for EpoR was noted in the cellular component of IERMs, and was weakly detected in ILMs. Epo was not expressed in any membrane.

CONCLUSION

EpoR was strongly expressed in microvessels of all PDR membranes. The in vivo evidence in this study suggests that Epo in the vitreous binds to EpoR in PDR membranes, which subsequently leads to the proliferation of new retinal vessels. EpoR immunoreactivity in non-vascular stromal cells in PDR membranes, and IERMs and ILMs might be indirectly correlated with ischaemia.

The relationship between human fetal cardiovascular hemodynamics and serum erythropoietin levels in growth-restricted fetuses

OBJECTIVE

We hypothesized that in growth restricted fetuses, erythropoietin (EPO) secretion is increased in proportion to the severity of cardiovascular compromise.

STUDY DESIGN

Thirty-eight growth restricted fetuses underwent Doppler ultrasonography of cardiovascular hemodynamics. An umbilical artery (UA) blood sample was taken at delivery for EPO analysis. Group 1 fetuses (n=9) had normal UA and ductus venosus (DV) velocimetries. Group 2 fetuses (n=18) showed an abnormal UA and a normal DV velocimetry. Group 3 fetuses (n=11) had abnormal UA and DV velocimetries. Normal EPO values were determined in 19 uncomplicated pregnancies (control group).

RESULTS

In group 3, EPO levels were higher (P<.05) than in groups 1 and 2. All fetuses in group 3 had EPO concentrations above the 90th percentile EPO value in the control group. The corresponding incidences were 44% and 50% in groups 1 and 2. Fetuses with retrograde aortic isthmus net blood flow had greater (P<.001) EPO levels than fetuses with antegrade net blood flow. Descending aorta, UA, DV and left hepatic vein pulsatility index values correlated significantly with EPO concentrations.

CONCLUSION

In fetal growth restriction, serum EPO concentration is increased in proportion to the severity of fetal cardiovascular compromise. Furthermore, in fetuses with retrograde aortic isthmus net blood flow, EPO levels are increased.

Darbepoetin-Alpha Does Not Promote Microvascular Thrombus Formation in Mice

Objective— Erythropoietin (EPO) treatment has become the standard treatment of renal anemia. Though a link between hematopoiesis-stimulating drugs and thrombosis has not been proven, it is generally assumed that systemic application of EPO and its analogues increases the risk for thrombotic events.

Methods and Results— Here we show in C57BL/6J mice that 4-week treatment with the long-lasting EPO analogue darbepoetin-alpha (DPO) at a dose of 10 μg/kg/week induces a reduction of platelet reactivity using flow cytometry and Western blot analysis of tyrosine-specific platelet phosphorylation. Additionally, immunohistochemistry of endothelial adhesion molecule expression and ELISA of circulating endothelial activation markers demonstrated a reduced endothelial activation. Immunohistochemistry and RT-PCR analysis revealed a significant ( P <0.05) increase of eNOS expression. Further, DPO did not exert prothrombogenic effects in a murine intravital microscopic thrombosis model of the cremaster muscle. The role of eNOS in prevention of DPO-mediated microvascular thrombosis is further underlined by a significantly accelerated thrombus formation on DPO treatment in eNOS (−/−) mice.

Conclusion— Thus, DPO-related erythropoiesis with a raised hematocrit is not associated with an increased risk for thrombosis as long as endothelial NO production serves as compensatory mechanism.

Increased erythropoietin elimination in fetal sheep following chronic phlebotomy

PURPOSE

To determine by pharmacokinetic (PK) means the role of erythropoietin-receptor (EPO-R) upregulation in fetuses on the elimination of erythropoietin (EPO).

MATERIALS AND METHODS

Six fetal sheep were catheterized at a gestational age of 125-127 days and phlebotomized daily for 6 days. Paired tracer PK studies using recombinant human EPO (rHuEPO) were conducted in the sheep fetuses at baseline and post-phlebotomy, 7 days later. A PK model with Michaelis-Menten elimination was simultaneously fit to the PK data at baseline and post-phlebotomy for each fetus.

RESULTS

Daily phlebotomies reduced the hemoglobin levels from baseline values of 10.8 (5%) (mean (C.V.)) g/dl to a nadir of 4.5 (17%) g/dl post-phlebotomy. The endogenous EPO concentration rapidly increased after the first phlebotomy and remained elevated, although variable, thereafter. The Michaelis-Menten maximal rHuEPO elimination rate parameter, V(max), was significantly greater post-phlebotomy than at baseline (p < 0.05), increasing 1.31 fold. The fetal baseline "linear" clearance at very low concentrations of rHuEPO was determined to be 117 ml/kg/h, similar to that determined in newborn sheep but 2-3 fold higher than that determined in adult sheep.

CONCLUSIONS

The observed increase in V(max) is consistent with an up-regulation of EPO-R due to a positive feedback resulting from the phlebotomy-induced anemia.

Specific activities of poetam preparation (superlow-doses of antibodies to erythropoietin) and recombinant erythropoietin

We compared the capacity of superlow-dose of antibodies to erythropoietin (Poetam) and recombinant erythropoietin (Recormon) to stimulate the recovery of adriamycin-suppressed erythropoiesis in mice. Both preparations exhibited high erythron activation capacity and considerably increased the content of erythrocytes and reticulocytes in the peripheral blood and content of erythrokaryocytes and erythroid precursors in the hemopoietic tissue of experimental animals. The effect of Recormon manifested immediately after injection, while the effect of Poetam was somewhat delayed, but more lasting (due to activation of host erythropoietin system).

Change in erythropoietin pharmacokinetics following hematopoietic transplantation

Pre-clinical studies have demonstrated that bone marrow ablation has a profound effect in decreasing erythropoietin (EPO) elimination. The study's objective was to determine in humans if EPO pharmacokinetics (PKs) are perturbed following bone marrow ablation. EPO PK studies were performed in eight subjects, aged 4 to 61 years, undergoing fully myeloablative hematopoietic stem cell transplantation. Serial PK studies using intravenous injection of recombinant human EPO (92+/-2.0 U/kg) (mean+/-SEM) were carried out during four periods of altered marrow integrity: baseline pre-ablation, post-ablation pre-transplant, early post-transplant pre-engraftment, and late post-transplant full engraftment. Compared with baseline, post-ablation pre-transplant and early post-transplant EPO PKs demonstrated declines in clearance increases in terminal elimination half-life of 36 and 95%, respectively. Clearance and half-life returned to baseline following full engraftment. The association of EPO elimination with decreased bone marrow activity in patients undergoing transplantation conclusively establishes the bone marrow as a key determinant of EPO elimination in humans.

Sensitive and precise regulation of haemoglobin after gene transfer of erythropoietin to muscle tissue using electroporation

Electroporation-based gene transfer (electro gene transfer (EGT)) is gaining increasing momentum, in particular for muscle tissue, where long-term high-level expression is obtainable. Induction of expression using the Tet-On system was previously established; however, attempts to reach a predefined target dose - a prescription, have not been reported. We set three target haemoglobin levels (10, 12 and 14 mmol/l, base level was 8.2 mmol/l) and aimed at them by transferring the erythropoietin (EPO) gene to mouse tibialis cranialis (TC) muscle, and varying (1) DNA amount, (2) muscle mass transfected and (3) induction with the Tet-On system. Results showed that (a) using GFP, luciferase and EPO low DNA amounts were needed. In fact, 0.5 microg of DNA to one TC muscle led to significant Hgb elevation - this amount extrapolates to 1.4 mg of DNA in humans, (b) three prescribers hit the targets with average Hgb of 10.5, 12.0 and 13.7 mmol/l, (c) different approaches could be used, (d) undershooting could be corrected by retransferring, and (e) overshooting could be alleviated by reducing dose of inducer (doxycycline (dox)). In conclusion, this study shows that using EGT to muscle, a preset level of protein expression can be reached. This is of great interest for future clinical use.

Detection window of Darbepoetin-α following one single subcutaneous injection

BACKGROUND

The current official direct recombinant erythropoietin (rHuEPO) detection anti-doping test based on 1D isoelectric focusing (IEF) of urinary proteins was performed to determine the detection window of Darbepoietin-alpha when applying the positivity criteria established by the World Anti-Doping Agency (WADA).

RESULTS

Following WADA's positivity criteria, the IEF based urinary EPO test enabled to determine that the detection window after a single subcutaneous injection of Darbepoietin-alpha (40 microg of ARANESP injected) is close to 7 days, that is to say approximately two times more than for rHuEPO-beta (4000 IU of Recormon injected). The detection window can be different from one subject to another, because the actual positivity criteria take into consideration in someway the endogenous EPO production rate which differs enormously from one subject to another. That means, all subjects with a naturally elevated or stimulated EPO production rate (altitude training, hypoxic tent,...) have a reduced detection window for bone marrow stimulators such as Darbepoietin-alpha.

CONCLUSION

Darbepoietin-alpha has a much longer detection window in urine than any other available EPOs, which is a major disadvantage for illegal use in sports. The positivity criteria used up to now by all anti-doping laboratories are very conservative. Furthermore all athletes tested for rHuEPO are not equal regarding the actual test. For that reason, the criteria could be slightly adapted in the future, but further experiments are needed.

Erythropoietin in cerebrospinal fluid: age-related reference values and relevance in neurological disease

We aimed to establish age-related reference values for Erythropoietin (EPO) in cerebrospinal fluid (CSF) and to evaluate concentrations in neurological diseases. CSF and serum EPO was measured in controls with tension-type headache (CTTH), in patients with ALS, dementia and depression using ELISA technique. Stability experiments showed CSF EPO to be stable for two and a half months and over two thaw/freeze cycles. A positive correlation of CSF EPO with age was found (P<0.01). We found a CSF/serum EPO concentration ratio of 0.126, pointing towards an intrathecal synthesis of EPO. The ALS group showed significantly lowered CSF EPO compared to age-matched CTTH (P<0.012), whereas the dementia and depression group showed no significant differences compared to CTTH.The establishment of age-related reference values in a large cohort of controls will improve the interpretation of future CSF EPO evaluations in neurological diseases.

Erythropoietin reduces ischemia-reperfusion injury in the rat liver

BACKGROUND

Human recombinant erythropoietin (Epo) has recently been shown to be a potent protector of ischemic damage in various organ systems. A significant reduction of stroke injury following cerebral ischemia has been postulated as well as improved cardiomyocyte function after myocardial infarction in tissue pretreated with Epo. It was the aim of this study to evaluate the effects of Epo in liver ischemia.

MATERIAL AND METHODS

Rats were subjected to 45 min of warm hepatic ischemia. Animals were either pretreated with 1,000 IU of Epo in three doses or received 1,000 IU into the portal vein 30 min before ischemia. Control animals received saline at the same time points before ischemia. Animals were than sacrificed 6, 12, 24, 48 h and 7 days after surgery and transaminases were measured. Liver specimens were evaluated regarding apoptosis, necrosis and regeneration capacity.

RESULTS

Apoptosis rates were dramatically reduced in animals pretreated with Epo while mRNA of tumor necrosis factor-alpha and STAT-3 were upregulated in all groups. Intraportal venous injection displayed superiority to subcutaneous preconditioning. Transaminases were significantly reduced among the Epo-treated animals after 6 and 12 h.

CONCLUSION

Our data suggests a protective effect of Epo in warm hepatic ischemia and reperfusion injury in the rat.

Renal disease: the anesthesiologist's perspective

The kidney is a remarkable organ whose functions include maintaining fluid and electrolyte balance, excreting metabolic waste products, and controlling vascular tone. Blood flow within the kidney is very heterogeneous, which places the metabolically active medulla at high risk for ischemic injury. A number of mediators play a role in the modulation of renal blood flow, including angiotensin II, dopamine, vasopressin, prostaglandins, atrial natriuretic peptide, endothelin, and nitric oxide. Early markers of renal injury elicit strong interest, although currently there is no reliable marker available. Surgery causes the release of catecholamines, renin, angiotensin, and AVP that lead to a redistribution of renal blood flow and a decrease in GFR. Additionally, general anesthesia often results in some degree of hypotension and depressed cardiac output, which further reduces renal perfusion and potentially jeopardizes renal function. A careful anesthetic plan is imperative in the patient with renal insufficiency or failure because acute renal failure in the perioperative period is associated with a high morbidity and mortality. Factors including advanced age, diabetes, underlying renal insufficiency, and heart failure place a patient at high risk for developing acute renal failure. It is imperative to maintain euvolemia, normotension, and cardiac output, and to avoid nephrotoxic agents to optimize renal blood flow and renal perfusion as the best prevention of renal dysfunction. Further studies are needed to establish if any therapies exist to prevent or treat renal dysfunction effectively.

Reduced cerebral blood flow but elevated cerebral glucose metabolic rate in erythropoietin overexpressing transgenic mice with excessive erythrocytosis

To examine the impact of excessive erythrocytosis on local cerebral blood flow (CBF) and cerebral glucose metabolic rate (CMR(glc)), we made use of our constitutively erythropoietin (Epo)-overexpressing transgenic mouse line (tg-6) that reach a mean hematocrit of 0.87. Compared with wild-type (wt) control siblings, CBF decreased by 44% in tg-6 mice, while upon hemodilution (tg-6-HD) to a physiologic hematocrit (e.g., 0.44) tg-6-HD mice returned the CBF to wt levels. Cerebral blood flow was determined in another transgenic mouse line that overexpresses human Epo in the brain only (tg-21): CBF increased by 17% compared with wt controls. However, oxygen delivery was similar in all four mouse groups tested (wt, tg-6, tg-6-HD and tg-21). Mean CMR(glc) was higher in tg-6 (+72%), tg-6-HD mice (+43%) and tg-21 (+22%) than in wt mice. Local CMR(glc) was higher in all 40 brain regions in tg-6 but only in 15 and 8 regions in tg-6-HD and tg-21 mice. These results show that prolonged increases in hematocrit did not alter cerebral oxygen delivery at a decreased CBF and increased CMR(glc). Hemodilution suggests that high blood viscosity is a cause of the decrease in CBF and partly of the increase in CMR(glc). Cerebral glucose metabolic rate may also be increased by a direct effect of Epo in the brain (tg-21 mice).

An assessment of recombinant human erythropoietin effect on reticulocyte production rate and lifespan distribution in healthy subjects

PURPOSE

An empirical pharmacodynamic model was developed to assess the effect of recombinant human erythropoietin (rHu-EPO) treatment on the reticulocyte production rate and lifespan distribution.

MATERIALS AND METHODS

Single doses of rHu-EPO at levels 20, 40, 60, 90, 120, and 160 kIU were administered to healthy volunteers (n = 8 per dose level). Erythropoietin plasma concentrations as well as hematologic responses were measured up to 42 days. The hematological data were used to determine explicit relationships between reticulocyte and red blood cell counts (RBC) and the reticulocytes' production rate and lifespan distribution.

RESULTS

The parameter estimates obtained by simultaneous fitting of the model to the reticulocyte and RBC data revealed that rHu-EPO transiently increased the reticulocyte lifespan from the baseline value of 1.7 days to 3.4 days and the effect lasted for 8.3 days. The dose dependent increase in the reticulocyte production had the maximal value of 77.5 10(9) cells/l/day and was followed by a rebound that was less than 9% of the baseline value. Both reticulocyte and RBC responses were preceded by a dose-independent lag time of 1.7 days.

CONCLUSIONS

The effect of rHu-EPO on the reticulocyte production rate and lifespan distribution was characterized. The results of the present study can be further utilized in building more mechanistic pharmacodynamic models of rHu-EPO stimulatory effects.

Effect of prolactin on inositol uptake in mouse mammary gland explants

Studies were carried out to assess the role of insulin (I), cortisol (H), and prolactin (P or PRL) in regulating myoinositol (inositol) uptake in the mammary gland. Using cultured mammary gland explants from pregnant mice (12-14 days into gestation), insulin and prolactin were found to stimulate inositol uptake, while cortisol impaired inositol uptake. Optimal inositol uptake was observed when tissues were treated with all three lactogenic hormones (I, H, and PRL). Further studies were designed primarily to characterize the PRL stimulation of inositol transport. Inositol uptake in the mammary explants increased linearly for 4 h, both in IH treated tissues and those treated with IHP; distribution ratios of greater than 14 were achieved at 4 h, suggesting an active inositol transport mechanism. The PRL effect on inositol uptake is sodium-dependent, temperature-dependent, and ouabain sensitive. DIDS and furosemide did not impair inositol uptake or the PRL effect on inositol uptake. PRL stimulated inositol uptake employing PRL concentrations of 10-1000 ng/ml. The PRL effect was manifested at all PRL-treatment times of 12 h or longer, but not at earlier times. PRL thus appears to be an important and essential hormone for the stimulation of inositol accumulation in milk during lactogenesis.

Determination of human erythropoietin by on-line immunoaffinity capillary electrophoresis: a preliminary report

Several CE methodologies have been described for the analysis of rHuEPO in concentrated solutions, but the inherently limited concentration sensitivity of CE precludes the detection of EPO at the levels found in biological fluids. In this work, we have investigated an on-line immunoaffinity solid-phase extraction capillary electrophoresis (IA-CE) methodology for the selective preconcentration of EPO in diluted solutions. The preliminary results obtained using a custom-made immunoaffinity sorbent prepared from an anti-human EPO polyclonal antibody and glutaraldehyde-glass beads show the potential of this novel approach. The summarized findings are discussed in detail as a starting point for our ongoing investigations.

Sodium butyrate alters erythropoietin glycosylation via multiple mechanisms

Recombinant human erythropoietin (rHuEPO) produced in a human kidney fibrosarcoma cell line, HT1080, was used as a model to study the effects of sodium butyrate (SB) on protein glycosylation. Treatment with 2 mM SB resulted in complex changes with respect to sugar nucleotide pools including an increase in UDP-Gal and a decrease in UDP-GlcNac. In addition, polylactosamine structures present on rHuEPO increased after SB treatment. To determine if these phenotypic changes correlated with changes in mRNA abundance, we profiled mRNA levels over a 24-h period in the presence or absence of SB using oligonucleotide microarrays. By filtering our data through a functional glycomics gene list associated with the processes of glycan degradation, glycan synthesis, and sugar nucleotide synthesis and transport we identified 26 genes with significantly altered mRNA levels. We were able to correlate the changes in message in six of these genes with measurable phenotypic changes within our system including: neu1, b3gnt6, siat4b, b3gnt1, slc17a5, and galt. Interestingly, for the two genes: cmas and gale, our measurable phenotypic changes did not correlate with changes in mRNA expression. These data demonstrate both the utility and pit falls of coupling biochemical analysis with high throughput oligonucleotide microarrays to predict how changes in cell culture environments will impact glycoprotein oligosaccharide content.

Delayed erythropoietin therapy reduces post-MI cardiac remodeling only at a dose that mobilizes endothelial progenitor cells

We examined the cardiac effects of chronic erythropoietin (EPO) therapy initiated 7 days after myocardial infarction (MI) in rats. A single high dose of EPO has been shown to reduce infarct size by preventing apoptosis when injected immediately after myocardial ischemia. The proangiogenic potential of EPO has also been reported, but the effects of chronic treatment with standard doses after MI are unknown. In this study, rats underwent coronary occlusion followed by reperfusion or a sham procedure. Infarcted rats were assigned to one of three treatment groups: 1) 0.75 μg/kg darbepoetin (MI+darb 0.75, n = 12); 2) 1.5 μg/kg darbepoetin (MI+darb 1.5, n = 12); 3) vehicle (MI+PBS, n = 16), once a week from day 7 postsurgery. Sham rats received the vehicle alone ( n = 10). After 8 wk of treatment, the animals underwent echocardiography, left ventricular pressure-volume measurements, and peripheral blood endothelial progenitor cell (EPC) counting. MI size and capillary density in the border zone and the area at risk (AAR) were measured postmortem. The AAR was similar in the three MI groups. Compared with MI+PBS, the MI+darb 1.5 group showed a reduction in the MI-to-AAR ratio (20.8% vs. 38.7%; P < 0.05), as well as significantly reduced left ventricle dilatation and improved cardiac function. This reduction in post-MI remodeling was accompanied by increased capillary density ( P < 0.05) and by a higher number of EPC ( P < 0.05). Both darbepoetin doses increased the hematocrit, whereas MI+darb 0.75 did not increase EPC numbers or capillary density and had no functional effect. We found that chronic EPO treatment reduces MI size and improves cardiac function only at a dose that induces EPC mobilization in blood and that increases capillary density in the infarct border zone.

A statistical pattern recognition approach for determining cellular viability and lineage phenotype in cultured cells and murine bone marrow

BACKGROUND

Cellular binding of annexin V and membrane permeability to 7-aminoactinomycin D (7AAD) are important tools for studying apoptosis and cell death by flow cytometry. Combining viability markers with cell surface marker expression is routinely used to study various cell lineages. Current classification methods using strict thresholds, or "gates," on the fluorescent intensity of these markers are subjective in nature and may not fully describe the phenotypes of interest. We have developed objective criteria for phenotypic boundary recognition through the application of statistical pattern recognition. This task was achieved using artificial neural networks (ANNs) that were trained to recognize subsets of cells with known phenotypes, and then used to determine decision boundaries based on statistical measures of similarity. This approach was then used to test the hypothesis that erythropoietin (EPO) inhibits apoptosis and cell death in erythroid precursor cells in murine bone marrow.

METHODS

Our method was developed for classification of viability using an in vitro cell system and then applied to an ex vivo analysis of murine late-stage erythroid progenitors. To induce apoptosis and cell death in vitro, an EPO-dependent human leukemic cell line, UT-7(EPO) cells were incubated without recombinant human erythropoietin (rhEPO) for 72 h. Five different ANNs were trained to recognize live, apoptotic, and dead cells using a "known" subset of the data for training, and a K-fold cross validation procedure for error estimation. The ANNs developed with the in vitro system were then applied to classify cells from an ex vivo study of rhEPO treated mice. Tg197 (human tumor necrosis-alpha transgenic mice, a model of anemia of chronic disease) received a single s.c. dose of 10,000 U/kg rhEPO and femoral bone marrow was collected 1, 2, 4, and 8 days after dosing. Femoral bone marrow cells were stained with TER-119 PE, CD71 APC enable identification of erythroid precursors, and annexin V FITC and 7AAD to identify the apoptotic and dead cells. During classification forward and side angle light scatter were also input to all pattern recognition systems.

RESULTS

Similar decision boundaries between live, apoptotic, and dead cells were consistently identified by the neural networks. The best performing network was a radial basis function multi-perceptron that produced an estimated average error rate of 4.5% +/- 0.9%. Using these boundaries, the following results were reached: depriving UT-7(EPO) cells of rhEPO induced apoptosis and cell death while the addition of rhEPO rescued the cells in a dose-dependent manner. In vivo, treatment with rhEPO resulted in an increase of live erythroid cells in the bone marrow to 119.8% +/- 9.8% of control at the 8 day time point. However, a statistically significant transient increase in TER-119(+) CD71(+) 7AAD(+) dead erythroid precursors was observed at the 1 and 2 day time points with a corresponding decrease in TER-119(+) CD71(+) 7AAD(-) Annexin V(-) live erythroid precursors, and no change in the number of TER-119(+) CD71(+) annexin V(+) 7AAD(-) apoptotic erythroid precursors in the bone marrow.

CONCLUSIONS

A statistical pattern recognition approach to viability classification provides an objective rationale for setting decision boundaries between "positive" and "negative" intensity measures in cytometric data. Using this approach we have confirmed that rhEPO inhibits apoptosis and cell death in an EPO dependent cell line in vitro, but failed to do so in vivo, suggesting EPO may not act as a simple antiapoptotic agent in the bone marrow. Rather, homeostatic mechanisms may regulate the pharmacodynamic response to rhEPO.

Early goal-directed therapy in severe sepsis and septic shock revisited: concepts, controversies, and contemporary findings

Studies of acute myocardial infarction, trauma, and stroke have been translated into improved outcomes by earlier diagnosis and application of therapy at the most proximal stage of hospital presentation. Most therapies for these diseases are instituted prior to admission to an ICU; this approach to the sepsis patient has been lacking. In response, a trial comparing early goal-directed therapy (EGDT) vs standard care was performed using specific criteria for the early identification of high-risk sepsis patients, verified definitions, and a consensus-derived protocol to reverse the hemodynamic perturbations of hypovolemia, vasoregulation, myocardial suppression, and increased metabolic demands. Five years after the EGDT publication, there has been much discussion generated with regard to the concepts of EGDT, as well as debate fueled regarding diagnostic and therapeutic interventions. However, during this time period further investigations by the primary investigators and others have brought additional contemporary findings. EGDT modulates some of the components of inflammation, as reflected by improved organ function. The end points used in the EGDT protocol, the outcome results, and the cost-effectiveness have subsequently been externally validated, revealing similar or even better findings than those from the original trial. Although EGDT is faced with challenges, a coordinated approach to sepsis management is necessary to duplicate the progress in outcomes seen in patients with conditions such as acute myocardial infarction, stroke, and trauma.

Comparison of neuroprotective effects of erythropoietin (EPO) and carbamylerythropoietin (CEPO) against ischemia-like oxygen-glucose deprivation (OGD) and NMDA excitotoxicity in mouse hippocampal slice cultures

In addition to its well-known hematopoietic effects, erythropoietin (EPO) also has neuroprotective properties. However, hematopoietic side effects are unwanted for neuroprotection, underlining the need for EPO-like compounds with selective neuroprotective actions. One such compound, devoid of hematopoietic bioactivity, is the chemically modified, EPO-derivative carbamylerythropoietin (CEPO). For comparison of the neuroprotective effects of CEPO and EPO, we subjected organotypic hippocampal slice cultures to oxygen-glucose deprivation (OGD) or N-methyl-d-aspartate (NMDA) excitotoxicity. Hippocampal slice cultures were pretreated for 24 h with 100 IU/ml EPO (=26 nM) or 26 nM CEPO before OGD or NMDA lesioning. Exposure to EPO and CEPO continued during OGD and for the next 24 h until histology, as well as during the 24 h exposure to NMDA. Neuronal cell death was quantified by cellular uptake of propidium iodide (PI), recorded before the start of OGD and NMDA exposure and 24 h after. In cultures exposed to OGD or NMDA, CEPO reduced PI uptake by 49+/-3 or 35+/-8%, respectively, compared to lesion-only controls. EPO reduced PI uptake by 33+/-5 and 15+/-8%, respectively, in the OGD and NMDA exposed cultures. To elucidate a possible mechanism involved in EPO and CEPO neuroprotection against OGD, the integrity of alpha-II-spectrin cytoskeletal protein was studied. Both EPO and CEPO significantly reduced formation of spectrin cleavage products in the OGD model. We conclude that CEPO is at least as efficient neuroprotectant as EPO when excitotoxicity is modeled in mouse hippocampal slice cultures.

Protective Effects of Erythropoietin in Cardiac Ischemia

Erythropoietin (EPO) is a hypoxia-induced hormone produced in the kidneys that stimulates hematopoiesis in the bone marrow. However, recent studies have also shown important nonhematopoietic effects of EPO. A functional EPO receptor is found in the cardiovascular system, including endothelial cells and cardiomyocytes. In animal studies, treatment with EPO during ischemia/reperfusion in the heart has been shown to limit the infarct size and the extent of apoptosis. In the longer term, EPO may promote ischemia-induced neovascularization, either by stimulating endothelial cells in situ or by mobilizing endothelial progenitor cells from bone marrow. The effects of EPO in the ischemic heart support the concept of EPO as a pleiotropic, tissue-protective agent for other organs expressing the EPO receptor. We recently performed a first randomized clinical study showing the safety and feasibility of EPO administration in patients with acute myocardial infarction. Future clinical studies are warranted to translate the beneficial effects of EPO from basic experiments to cardiac patients.

Mechanisms of disease: erythropoietin--an old hormone with a new mission?

The major physiological function of erythropoietin is the induction of erythropoiesis. A growing body of evidence indicates, however, that this hormone has tissue-protective effects and prevents tissue damage during ischemia and inflammation. This review article summarizes the present knowledge on the cardiovascular and renal protective effects of erythropoietin and discusses the possible underlying mechanisms.

Erythropoietin and blood doping

OBJECTIVE AND METHOD

To outline the direct and indirect approaches in the fight against blood doping in sports, the different strategies that have been used and are currently being used to fight efficiently against blood doping are presented and discussed.

RESULTS AND CONCLUSIONS

The paper outlines the different approaches and diagnostic tools that some federations have to identify and target sports people demonstrating abnormal blood profiles. Originally blood tests were introduced for medical reasons and for limiting misuse of recombinant human erythropoietin (rHuEPO). In this way it became possible to prevent athletes with haematocrit levels well above normal, and potentially dangerous for their health, competing in sport. Today, with nearly a decade of blood testing experience, sports authorities should be familiar with some of the limitations and specially the ability of blood tests performed prior to competitions to fight efficiently against the misuse of rHuEPO, blood transfusion, and artificial haemoglobin.

Erythropoietin and cerebral vascular protection: role of nitric oxide

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is a major clinical problem causing cerebral ischemia and infarction. The pathogenesis of vasospasm is related to a number of pathological processes including endothelial damage and alterations in vasomotor function leading to narrowing of arterial diameter and a subsequent decrease in cerebral blood flow. Discovery of the tissue protective effects of erythropoietin (EPO) stimulated the search for therapeutic application of EPO for the prevention and treatment of cerebrovascular disease. Recent studies have identified the role of EPO in vascular protection mediated by the preservation of endothelial cell integrity and stimulation of angiogenesis. In this review, we discuss the EPO-induced activation of endothelial nitric oxide (NO) synthase and its contribution to the prevention of cerebral vasospasm.

Biochemistry, physiology, and complications of blood doping: facts and speculation

Competition is a natural part of human nature. Techniques and substances employed to enhance athletic performance and to achieve unfair success in sport have a long history, and there has been little knowledge or acceptance of potential harmful effects. Among doping practices, blood doping has become an integral part of endurance sport disciplines over the past decade. The definition of blood doping includes methods or substances administered for non-medical reasons to healthy athletes for improving aerobic performance. It includes all means aimed at producing an increased or more efficient mechanism of oxygen transport and delivery to peripheral tissues and muscles. The aim of this review is to discuss the biochemistry, physiology, and complications of blood doping and to provide an update on current antidoping policies.

Spotlight on darbepoetin alfa in the treatment of anemia in patients with cancer receiving chemotherapy

Darbepoetin alfa (Aranesp) is an analog of recombinant human erythropoietin (rHuEPO) produced using recombinant DNA technology. The high number of sialic acid moieties in darbepoetin alfa results in a prolonged half-life and enhanced in vivo biologic activity compared with rHuEPO (as demonstrated in animal studies), and permits a reduction in the frequency of administration. Subcutaneous darbepoetin alfa 2.25 microg/kg once weekly or 500microg once every 3 weeks (with a provision for dosage adjustments) is an effective and well tolerated erythropoietic agent in anemic patients with cancer receiving chemotherapy. In randomized, controlled clinical trials, the drug increased hemoglobin levels and reduced the need for blood transfusions in patients with various types of nonmyeloid malignancies, and also ameliorated anemia-related fatigue, thereby improving their health-related quality of life scores. The once-every-3-weeks dosage regimen provides further convenience by offering the possibility of synchronizing its administration with most chemotherapy regimens. Direct comparisons between approved dosages of darbepoetin alfa and other erythropoietic agents have not been conducted. Such comparisons would be very helpful in formulating definitive conclusions about their relative efficacy and cost effectiveness. Darbepoetin alfa provides an effective and well tolerated treatment option for the treatment of anemia in patients with cancer receiving chemotherapy.

Administration of poly-D-glutamic acid induces proliferation of erythropoietin-producing peritubular cells in rat kidney

Erythropoietin (EPO), a 34-kDa glycoprotein, is produced predominantly by peritubular interstitial cells (PIC) in the renal cortex and is physiologically released when ambient oxygen pressure falls. However, the exact nature of EPO-producing cells in the kidney is not well understood. We discovered that brief administration of a low-molecular-weight synthetic peptide, poly-D-glutamic acid (PDG), induced prompt and robust expansion of EPO-producing PIC in rat kidney, without evidence of tubular cell necrosis/apoptosis or fibrotic reaction. Proliferating PIC in PDG-treated rats were noninflammatory, alpha-smooth muscle actin negative, and specifically expressed CD73 (ecto-5'-nucleotidase), EPO mRNA, and protein. Increased numbers of EPO-positive PIC persisted even after the cessation of PDG treatment. No erythropoietic effects of EPO were detected, potentially suggesting maintained physiological control of EPO secretion in this normoxic model. We showed previously that PDG is readily filtered and is rapidly taken up and stored in lysosomes of proximal tubular cells (PTC), resulting in an apparently nonnoxious lysosomal storage condition by virtue of its nonhydrolyzable nature (Kishore BK, Maldague P, Tulkens PM, Courtoy PJ. Lab Invest 74: 1013-1023, 1996). Based on these findings, we suggest that unknown signaling molecules, produced by PTC in response to lysosomal PDG storage, appear to specifically stimulate the proliferation of EPO-producing PIC. We conclude that this model is uniquely suited to investigate the biology of EPO production by PIC and may thus facilitate the development of novel and more economical therapies of anemias and other EPO-responsive conditions.

Comparison of two epoetin brands in anemic hemodialysis patients: results of two efficacy trials and a single-dose pharmacokinetic study

Epoetin alpha is recombinant human erythropoietin with established efficacy and safety in the treatment of renal anemia. Epoetin omega is recombinant erythropoietin that differs from epoetin alpha in the sugar moiety. We compared the two epoetins in two 12-week efficacy studies (S1, S2) with twice-weekly dosing, and a single-dose crossover pharmacokinetic (PK) study in severely anemic hemodialysis patients. Epoetins were delivered subcutaneously in all studies. S1 was randomized (omega n = 39, alpha n = 38), while S2 included the patients from S1 (omega n = 32, alpha n = 24) with 'switched' treatments (omegaleft arrow over right arrowalpha). In the intent-to-treat analysis, average weekly difference in hemoglobin vs. the baseline value was higher in omega-treated patients in both studies: 1.94 +/- 0.81 vs. 1.23 +/- 0.62 g/dL in S1 and 1.44 +/- 0.72 vs. 0.95 +/- 0.62 g/dL in S2. The unadjusted and adjusted omega-alpha differences in S1 were 0.71 g/dL (95% CI 0.38-1.04; P < 0.001) and 0.78 g/dL (95% CI 0.49-1.08; P < 0.001), respectively. Differences in S2 were 0.48 g/dL (95% CI 0.11-0.86; P = 0.012) and 0.46 g/dL (95% CI 0.1-0.82; P = 0.025), unadjusted and adjusted, respectively. Average weekly epoetin dose was lower in the omega groups in both studies: 87 +/- 25 vs. 108 +/- 21 IU/kg in S1 and 106 +/- 25 vs. 125 +/- 20 IU/kg in S2. The unadjusted and adjusted omega-alpha differences in S1 were -21 IU/kg (95% CI -32 to -11; P < 0.001) and -24 IU/kg (95% CI -35 to -13; P < 0.001), respectively. Differences in S2 were -19 IU/kg (95% CI -31 to -6; P = 0.006) and -15 IU/kg (95% CI -28 to -2; P = 0.04), unadjusted and adjusted, respectively. In the PK study (n = 17), the peak and total exposure to epoetin after 50 IU/kg of either drug was approximately twice greater for epoetin omega: C(max) omega/alpha 2.19 (95% CI 1.55-3.11), AUC omega/alpha 2.24 (95% CI 1.64-3.06). Epoetins were comparably well tolerated. In hemodialysis patients, subcutaneous epoetin omega apparently provides greater bioavailability and anti-anemic effect per administered dose (IU) than epoetin alpha.

Estimation of the composition of recombinant human erythropoietin mixtures using capillary electrophoresis and multivariate calibration methods

A multivariate calibration method using partial least-squares (PLS) is proposed in order to characterize binary mixtures of two types of recombinant human erythropoietin (epoetin alpha and beta), based on the analysis of the highly overlapped UV-electrophoretic profiles obtained with the CE methodology recommended by the European Pharmacopoeia (EurPh). A two-factor PLS-1 model was developed and validated using mixtures of alpha and beta epoetins. Glycoforms were identified according to their effective electrophoretic mobility values and the normalized area values of each glycoform peak were used as multivariate data. Calibration and validation results were satisfactory. The PLS-1 model was successfully used for determination of epoetin alpha and beta contents in the rHuEPO provided by the EurPh as a biological reference product.

Pharmacokinetic and pharmacodynamic modeling of recombinant human erythropoietin after intravenous and subcutaneous administration in rats

The pharmacokinetics (PK) and pharmacodynamics (PD) of recombinant human erythropoietin (rHuEPO) were studied in rats after single i.v. and s.c. administration at three dose levels (450, 1350, and 4050 IU/kg). The plasma concentrations of rHuEPO and its erythropoietic effects including reticulocyte (RET), red blood cell (RBC), and hemoglobin (Hb) levels were determined. A two-compartment model with dual input rate and nonlinear disposition was used to characterize the PK of rHuEPO. The catenary indirect response model with several compartments reflecting the bone marrow and circulating erythropoietic cells was applied. The s.c. doses exhibited slow absorption (T(max) = 12 h) and incomplete bioavailability (F = 0.59). In placebo groups, RBC and Hb values gradually increased over time with growth of the rats, and the changes in the baselines monitored from 8 to 32 weeks of age were described by a nonlinear growth function. All doses resulted in dose-dependent increases in RET counts followed by an immediate decline below the baseline at around 6 days and returned to the predose level in 21-24 days after dosing. A subsequent steady increase of RBC and Hb levels followed and reached peaks at 6 days. A tolerance phenomenon observed at all dose levels was modeled by a negative feedback inhibition with the relative change in Hb level. The PK/PD model well described the erythropoietic effects of rHuEPO as well as tolerance, thereby yielding important PD parameters (S(max) = 1.87 and SC(50) = 65.37 mIU/ml) and mean lifespans of major erythropoietic cell populations in rats.

Cytokines in the differentiation therapy of leukemia: from laboratory investigations to clinical applications

Differentiation therapy of leukemia is the treatment of leukemia cells with biological or chemical agents that induce the terminal differentiation of the cancer cells. It is regarded as a novel and targeted approach to leukemia treatment, based on our better understanding of the hematopoietic process and the mechanisms of its deregulation during leukemogenesis. Clinically, differentiation therapy has been most successful in acute promyelocytic leukemia using all-trans-retinoic acid as the inducer, either alone or in combination with chemotherapy. This review presents evidence that a number of hematopoietic cytokines play important roles in both normal and aberrant hematopoietic processes. In vitro laboratory investigations in the past two decades using well-characterized myeloid leukemic cell lines and primary blast cells from leukemia patients have revealed that many hematopoietic cytokines can trigger lineage-specific differentiation of leukemia cells, which may have important implications in the clinical setting. Moreover, our current understanding of cytokine interactions and the molecular mechanisms of cytokine-induced leukemic cell differentiation will be discussed in the light of recent findings. Finally, ways in which laboratory research on cytokines in the differentiation therapy of leukemia can lead to the improved design of protocols for future clinical applications to leukemia therapy will also be addressed.

Vitamin A supplementation in children with poor vitamin A and iron status increases erythropoietin and hemoglobin concentrations without changing total body iron

BACKGROUND

Vitamin A deficiency impairs iron metabolism; vitamin A supplementation of vitamin A-deficient populations may reduce anemia. The mechanism of these effects is unclear. In vitro and in animal models, vitamin A treatment increases the production of erythropoietin (EPO), a stimulant of erythropoiesis.

OBJECTIVE

We measured the effect of vitamin A supplementation on hemoglobin, iron status, and circulating EPO concentrations in children with poor iron and vitamin A status.

DESIGN

In a double-blind, randomized trial, Moroccan schoolchildren (n = 81) were given either vitamin A (200,000 IU) or placebo at baseline and at 5 mo. At baseline, 5 mo, and 10 mo, hemoglobin, indicators of iron and vitamin A status, and EPO were measured.

RESULTS

At baseline, 54% of children were anemic; 77% had low vitamin A status. In the vitamin A group at 10 mo, serum retinol improved significantly compared with the control group (P < 0.02). Vitamin A treatment increased mean hemoglobin by 7 g/L (P < 0.02) and reduced the prevalence of anemia from 54% to 38% (P < 0.01). Vitamin A treatment increased mean corpuscular volume (P < 0.001) and decreased serum transferrin receptor (P < 0.001), indicating improved iron-deficient erythropoiesis. Vitamin A decreased serum ferritin (P < 0.02), suggesting mobilization of hepatic iron stores. Calculated from the ratio of transferrin receptor to serum ferritin, overall body iron stores remained unchanged. In the vitamin A group at 10 mo, we observed an increase in EPO (P < 0.05) and a decrease in the slope of the regression line of log10(EPO) on hemoglobin (P < 0.01).

CONCLUSION

In children deficient in vitamin A and iron, vitamin A supplementation mobilizes iron from existing stores to support increased erythropoiesis, an effect likely mediated by increases in circulating EPO.

Erythropoietin is expressed in the human retina and it is highly elevated in the vitreous fluid of patients with diabetic macular edema

OBJECTIVE

Erythropoietin has been recently found to be increased in the vitreous fluid from ischemic retinal diseases such as proliferative diabetic retinopathy (PDR). The aims of the present study were 1) to measure erythropoietin levels in the vitreous fluid from patients with diabetic macular edema (DME), a condition in which the ischemia is not a predominant event, and 2) to compare erythropoietin mRNA expression between human retinas from nondiabetic and diabetic donors without retinopathy.

RESEARCH DESIGN AND METHODS

Vitreous samples from 12 type 2 diabetic patients with DME without significant retinal ischemia and 12 PDR patients were prospectively analyzed. Ten nondiabetic patients with macular holes served as the control group. Erythropoietin was assessed by radioimmunoassay (milliunits per milliliter). Erythropoietin mRNA expression was measured by quantitative real-time RT-PCR analysis in the retina from eight nondiabetic and eight age-matched diabetic donors without diabetic retinopathy

RESULTS

Intravitreal erythropoietin concentration was higher in both PDR and DME patients than in nondiabetic control subjects (PDR vs. control subjects: median 302 [range 117-1,850] vs. 30 mU/ml [10-75], P < 0.01; DME vs. control subjects: 430 [41-3,000] vs. 30 mU/ml [10-75], P < 0.01). However, no significant differences were found between DME and PDR patients. Erythropoietin mRNA expression was detected in the human retina, and it was higher in the retina from diabetic than from nondiabetic donors.

CONCLUSIONS

As occurs in PDR, intravitreous erythropoietin concentrations are strikingly higher in DME. Erythropoietin is expressed in the human retina, and it is upregulated in diabetic patients even without retinopathy. These findings suggest that other factors apart from ischemia are involved in the overexpression of erythropoietin in diabetic retinopathy.

Pleiotropic role of histone deacetylases in the regulation of human adult erythropoiesis

Histone acetylation and deacetylation play fundamental roles in transcriptional regulation. We investigated the role of histone deacetylases (HDACs) in human adult haematopoiesis, using the structurally distinct HDAC inhibitors FK228 (depsipeptide) and Trichostatin A. When CD34+ cells were cultured with interleukin (IL)-3 or stem cell factor (SCF) + IL-3, FK228 (0.5 ng/ml) specifically enhanced the generation of immature erythroid cells with a CD36+ glycophorin A (GPA)low phenotype. In semisolid cultures, FK228 promoted the formation of erythroid colonies by CD34+ cells with IL-3 and SCF + IL-3. Furthermore, upon exposure to FK228, CD34+ cell-derived CD36+ GPA- cells were induced to form erythroid colonies with IL-3 alone. Conversely, FK228 inhibited the generation of CD36+ GPAhigh relatively mature erythroid cells from CD34+ cells in the presence of erythropoietin (EPO) and SCF + EPO. FK228 suppressed the EPO-mediated survival of CD36+ GPAlow/- and CD36+ GPAhigh cells and induced their apoptosis. Similar effects were observed for trichostatin A in the generation of erythroid cells in IL-3- and EPO-containing cultures. These data suggest that HDACs negatively regulate the IL-3-mediated growth of early erythroid precursors by suppressing their responsiveness to IL-3, while playing an important role in EPO-mediated differentiation and survival of erythroid precursors. Our data revealed that HDACs have diverse functions in human adult erythropoiesis.

Elevated serum erythropoietin levels in patients with Budd-Chiari syndrome secondary to polycythemia vera: clinical implications for the role of JAK2 mutation analysis

PURPOSE

It is widely accepted that an increased serum endogenous erythropoietin (Epo) level in a patient presenting with an elevated red cell mass makes a diagnosis of clonal polycythemia vera (PV) extremely unlikely. However, until the recent description of the constitutively activating V617F point mutation of the Janus 2 tyrosine kinase (JAK2)--a high-frequency molecular marker that is extremely specific for clonal chronic myeloproliferative disorders--distinction of PV from secondary erythrocytosis or other conditions has often been difficult. The purpose of this study was to use JAK2 V617F analysis to re-evaluate the validity of elevated Epo levels as a PV-exclusion criterion in patients with hepatic vein thrombosis [Budd-Chiari syndrome (BCS)].

PATIENTS AND METHODS

We reviewed clinical data from 30 patients at our institution who presented with erythrocytosis and BCS. We isolated myeloid cells from fresh or archival bone marrow samples from four patients with BCS and an elevated serum Epo level, and analyzed them for the presence of the JAK2 V617F mutation.

RESULTS

All four samples were positive for JAK2 V617F, confirming the presence of a clonal hematopoietic disorder consistent with PV.

CONCLUSION

In the presence of BCS, elevated serum Epo levels do not exclude the diagnosis of PV.

Ionene-dynamically coated capillary for analysis of urinary and recombinant human erythropoietin by capillary electrophoresis and online electrospray ionization mass spectrometry

In this article, a series of ionene polymers were synthesized and used to coat fused-silica capillaries for the separation of recombinant and urinary human erythropoietin (rhEPO and uEPO) standards by CE. The influence of the charge density of coatings on the separation of rhEPO and uEPO glycoforms was investigated. Then, we further studied the method for fast separation and detection of rhEPO and uEPO standards by CE-ESI-MS. The influence of several CE and MS operating parameters, such as the concentration of CE running buffer, applied external pressure, and the composition and flow rate of sheath liquid on CE-ESI-MS was studied. The results demonstrated that when the capillary was permanently coated with 6,6-ionene and the pH value of acetic acid-ammonium acetate running buffer was 4.80 and 5.50, respectively, a significantly reproducible separation was achieved for rhEPO and uEPO glycoforms. In the online CE-ESI-MS experiments, we not only achieved the online MS signal of uEPO, but also obtained baseline separation of three major rhEPO glycoforms successfully and reproducibly on the 6,6-ionene-coated capillaries. Furthermore, the standard mixture of rhEPO and uEPO was separated, and two incompletely resolved peaks that were identified to be rhEPO and uEPO by the unique MS "fingerprint" were obtained. Additionally, the molecular weight of rhEPO and uEPO were verified and compared to the results by MALDI-TOF-MS. It can be concluded that, in contrast to other indirect methods, the online CE-ESI-MS technique with the combination of the advantages of both CE and MS shows great potential for the separation and detection of rhEPO doping directly in competitive sports.