Erythropoietin: physiology and pharmacology update

Erythropoiesis suppression is associated with anthrax lethal toxin-mediated pathogenic progression

Anthrax is a disease caused by the bacterium Bacillus anthracis, which results in high mortality in animals and humans. Although some of the mechanisms are already known such as asphyxia, extensive knowledge of molecular pathogenesis of this disease is deficient and remains to be further investigated. Lethal toxin (LT) is a major virulence factor of B. anthracis and a specific inhibitor/protease of mitogen-activated protein kinase kinases (MAPKKs). Anthrax LT causes lethality and induces certain anthrax-like symptoms, such as anemia and hypoxia, in experimental mice. Mitogen-activated protein kinases (MAPKs) are the downstream pathways of MAPKKs, and are important for erythropoiesis. This prompted us to hypothesize that anemia and hypoxia may in part be exacerbated by erythropoietic dysfunction. As revealed by colony-forming cell assays in this study, LT challenges significantly reduced mouse erythroid progenitor cells. In addition, in a proteolytic activity-dependent manner, LT suppressed cell survival and differentiation of cord blood CD34⁺-derived erythroblasts in vitro. Suppression of cell numbers and the percentage of erythroblasts in the bone marrow were detected in LT-challenged C57BL/6J mice. In contrast, erythropoiesis was provoked through treatments of erythropoietin, significantly ameliorating the anemia and reducing the mortality of LT-treated mice. These data suggested that suppressed erythropoiesis is part of the pathophysiology of LT-mediated intoxication. Because specific treatments to overcome LT-mediated pathogenesis are still lacking, these efforts may help the development of effective treatments against anthrax.

Constitutive excessive erythrocytosis causes inflammation and increased vascular permeability in aged mouse brain

Excessive erythrocytosis results in severely increased blood viscosity that may compromise the vascular endothelium. Using our transgenic mouse model of excessive erythrocytosis we previously showed that despite altered brain endothelial cell morphology and an activated vasculature, brain vascular integrity was largely maintained up to 4-5 months of age. We now present data showing that persistent long-term damage of the vascular wall during the later stages of adulthood (9-12 months) results in a chronic detrimental inflammatory phenotype and increased vessel permeability that likely contributes to the reduced life span of our erythropoietin overexpressing transgenic mouse. In aged transgenic animals inflammatory cells were detected in brain tissue and elevated RNA and protein levels of inflammatory markers such as IL-6 and TNFα were observed in both brain tissue and blood plasma. Additionally, increased expression of p53 and other pro-apoptotic markers, as well as decreased Bcl-xL expression in the brain vasculature, indicated ongoing cell death within the vascular compartment. Finally, abnormally elevated vascular permeability in all organs was detected in correlation with decreased expression of the tight junction protein occludin and the adherens junction protein β-catenin in brain. Thus chronic erythrocytosis results in sustained activation of inflammatory pathways, vascular dysfunction and blood-brain barrier disruption.

The role and regulation of erythropoietin (EPO) and its receptor in skeletal muscle: how much do we really know?

Erythropoietin (EPO) primarily activates erythroid cell proliferation and growth and is active in several types of non-hematopoietic cells via its interaction with the EPO-receptor (EPO-R). This review focuses on the role of EPO in skeletal muscle. The EPO-R is expressed in skeletal muscle cells and EPO may promote myoblast differentiation and survival via the activation of the same signaling cascades as in hematopoietic cells, such as STAT5, MAPK and Akt. Inconsistent results exist with respect to the detection of the EPO-R mRNA and protein in muscle cells, tissue and across species and the use of non-specific EPO-R antibodies contributes to this problem. Additionally, the inability to reproducibly detect an activation of the known EPO-induced signaling pathways in skeletal muscle questions the functionality of the EPO-R in muscle in vivo. These equivocal findings make it difficult to distinguish between a direct effect of EPO on skeletal muscle, via the activation of its receptor, and an indirect effect resulting from a better oxygen supply to the muscle. Consequently, the precise role of EPO in skeletal muscle and its regulatory mechanism/s remain to be elucidated. Further studies are required to comprehensively establish the importance of EPO and its function in skeletal muscle health.

Use of high-dose erythropoietin for repair after injury: A comparison of outcomes in heart and kidney

CONTEXT

There is a need to define the exact benefits and contraindications of use of high-dose recombinant human erythropoietin (EPO) for its non-hematopoietic function as a cytokine that enhances tissue repair after injury. This review compares the outcomes from use of EPO in the injured heart and kidney, two organs that are thought, traditionally, to have intrinsically-different repair mechanisms.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

Ongoing work by us on EPO protection of ischemia-reperfusion-injured kidneys indicated, first, that EPO acutely enhanced kidney repair via anti-apoptotic, pro-regenerative mechanisms, and second, that EPO may promote chronic fibrosis in the long term. Work by others on the ischaemia-injured heart has also indicated that EPO promotes repair. Although myocardial infarcts are made up mostly of necrotic tissue, many publications state EPO is anti-apoptotic in the heart, as well as promoting healing via cell differentiation and stimulation of granulation tissue. In the case of the heart, promotion of fibrosis may be advantageous where an infarct has destroyed a zone of cardiomyocytes, but if EPO stimulates progressive fibrosis in the heart, this may promote cardiac failure.

CONCLUSIONS

A major concern in relation to the use of EPO in a cytoprotective role is its stimulation of long-term inflammation and fibrosis. EPO usage for cytoprotection is undoubtedly advantageous, but it may need to be offset with an anti-inflammatory agent in some organs, like kidney and heart, where progression to chronic fibrosis after acute injury is often recorded.

Enhanced preservation of pig cardiac allografts by combining erythropoietin with glyceryl trinitrate and zoniporide

Erythropoietin has a tissue-protective effect independent of its erythropoietic effect that may be enhanced by combining it with the nitric oxide donor glyceryl trinitrate (GTN) and the sodium-hydrogen exchange inhibitor zoniporide in rat hearts stored with an extracellular-based preservation solution (EBPS). We thus sought to test this combination of agents in a porcine model of orthotopic heart transplantation incorporating donor brain death and total ischaemic time of approximately 260 min. Pig hearts were stored in one of four storage solutions: unmodified EBPS (CON), EBPS supplemented with GTN and zoniporide (GZ), EBPS supplemented with erythropoietin and zoniporide (EZ), or EBPS supplemented with all three agents (EGZ). A total of 4/5 EGZ hearts were successfully weaned from cardiopulmonary bypass compared with only 2/5 GZ hearts, 0/5 CON hearts and 0/5 EG hearts (p = 0.017). Following weaning from bypass EGZ hearts demonstrated superior contractility and haemodynamics than GZ hearts. All weaned hearts displayed impaired diastolic function. Release of troponin I from EGZ hearts was lower than all other groups. In conclusion, supplementation of EBPS with erythropoietin, glyceryl trinitrate and zoniporide provided superior donor heart preservation than all other strategies tested.

Erythropoietin in the neurology ICU

OPINION STATEMENT

Erythropoietin (EPO) is an approved drug that is used in the treatment of chronic anemia associated with chronic renal failure. In the Neuro ICU, there are 2 potential uses for treatment with EPO. Anemia is common in patients with acute neurological disorders and may be a cause of secondary insults. Studies of EPO to treat anemia associated with critical illness have not conclusively shown a beneficial risk/benefit ratio. The relatively small reduction in transfusion requirement with EPO in critically ill patients is likely due to the 7-10 days required to see an effect of EPO on hematocrit. For these reasons, EPO is not recommended to treat anemia of critical illness. Neuroprotection is the other potential use for EPO in the Neuro ICU. Many experimental studies demonstrate neuroprotective effects with EPO in a variety of acute neurological disorders. To date, no clinical studies have confirmed beneficial effects of EPO on neurological outcome although some studies have suggested a reduction in mortality rate in trauma patients treated with EPO. Additional clinical studies are needed before EPO administration can be recommended for cytoprotection in neurological disorders.

Anemia in chronic heart failure: can we treat? What to treat?

Even though anemia is a significant comorbidity regularly observed in patients with chronic heart failure (HF), only in recent years systematic therapeutic research has been started. This article aims to review the aspects of anemia in chronic HF that are relevant for making treatment decisions, beginning with the definition of anemia and its incidence and prevalence of anemia in patients with chronic HF. Considering the etiology and prognostic impact of anemia in chronic HF, several treatment options will be considered. The latter are the application of erythropoiesis-stimulating agents (erythropoietin or darbepoetin alfa) or in the application of intravenous iron (e.g., iron carboxymaltose). According to the results seen in the FAIR-HF trial, iron supplementation should be particularly considered to improve symptoms and quality of life. Intravenous iron application may result in higher compliance and much faster treatment response than oral iron. The RED-HF study will show whether use of darbepoetin alfa in anemic patients with chronic HF will reduce the combined endpoint of death for any reason or hospitalization for heart failure.

Hypoxia-inducible factor-1 alpha in the heart: a double agent?

Hypoxia-inducible factor (HIF) is a set of transcription factors that regulate the cellular response to hypoxia. There is a great body of evidence supporting the protective role of HIF-1α in cardiovascular pathophysiology, however, newer studies are hinting at a maladaptive and deleterious role of this transcription factor that merits further investigation. There is a general agreement, however, that HIF-mediated responses appear to differ under conditions of acute and chronic oxygen deprivation. The intensity and sustainability of HIF-1α activation are major determinants of whether the responses are pathological or beneficial. HIF activation is seen to be beneficial in the setting of acute myocardial ischemia and deleterious in chronic conditions. In this review, we will focus on recent insights into the role of HIF-1α in the heart and especially in the setting of ischemic heart disease.

Targeting erythropoietin for chronic neurodegenerative diseases

INTRODUCTION

Since erythropoietin (EPO) and EPO receptor (EPOR) are expressed in the central nervous system (CNS) beyond hematopoietic system, EPO illustrates a robust biological function in maintaining neuronal survival and regulating neurogenesis and may play a crucial role in neurodegenerative diseases.

AREAS COVERED

EPO is capable of modulating multiple cellular signal transduction pathways to promote neuronal survival and enhance the proliferation and differentiation of neuronal progenitor cells. Initially, EPO binds to EPOR to activate the Janus-tyrosine kinase 2 (Jak2) protein followed by modulation of protein kinase B (Akt), mammalian target of rapamycin, signal transducer and activators of transcription 5, mitogen-activated protein kinases, protein tyrosine phosphatases, Wnt1 and nuclear factor κB. As a result, EPO may actively prevent the progression of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, epilepsy, multiple sclerosis and motor neuron diseases.

EXPERT OPINION

Novel knowledge of the cell signaling pathways regulated by EPO in the CNS will allow us to establish the foundation for the development of therapeutic strategies against neurodegenerative diseases. Further investigation of the role of EPO in neurodegenerative diseases can not only formulate EPO as a therapeutic candidate, but also further identify novel therapeutic targets for these disorders.

Population pharmacodynamic analysis of erythropoiesis in preterm infants for determining the anemia treatment potential of erythropoietin

A population pharmacokinetics/pharmacodynamic (PK/PD) model was developed to describe changes in erythropoiesis as a function of plasma erythropoietin (EPO) concentration over the first 30 days of life in preterm infants who developed severe anemia requiring red blood cell (RBC) transfusion. Several covariates were tested as possible factors influencing the responsiveness to EPO. Discarded blood samples in 27 ventilated preterm infants born at 24-29 wk of gestation were used to construct plasma EPO, hemoglobin (Hb), and RBC concentration-time profiles. The amount of Hb removed for laboratory testing and that transfused throughout the study period were recorded. A population PK/PD model accounting for the dynamic Hb changes experienced by these infants was simultaneously fitted to plasma EPO, Hb, and RBC concentrations. A covariate analysis suggested that the erythropoietic efficacy of EPO is increased for preterm infants at later gestational ages. The PD analysis showed a sevenfold difference in maximum Hb production rate dependent on gestational age and indicated that preterm infants, when stimulated by EPO, have the capacity to produce additional Hb that may result in a decrease in RBC transfusions. The present model has utility in clinical trial simulations investigating the treatment potential of erythropoietic stimulating agents in the treatment of anemia of prematurity.

Relationship between hemoglobin, serum retinol and habitual meat consumption in the elderly: a population-based study

Considering the scarcity of data on the relationship between hemoglobin, serum retinol and habitual meat consumption in the elderly, a cross-sectional population-based study was performed, which was representative of the population of a state capital in Northeastern Brazil, including 176 elderly aged between 60 and 90 years, who responded to questionnaires about habitual food consumption and socioeconomic aspects. Blood counts and serum retinol analyses were carried out. The prevalence of anemia was 9.58%, and 96% of elderly showing adequate serum retinol levels. The consumption of vitamin A and iron was adequate in 93.75% and 85%, respectively. There was no correlation between serum retinol and hemoglobin values (p=0.56), and as expected, there was a positive association between meat consumption and hemoglobin (p=0.02). Based on results obtained in this study, it was concluded that the maintenance of adequate vitamin A and meat intake in this population should be encouraged, which appears to be an effective intervention strategy to achieve appropriate serum retinol and hemoglobin values, and hence lower iron deficiency anemia rates.

The low number of red blood cells is an important risk factor for all-cause mortality in the general population

Patients with advanced chronic kidney disease (CKD) show decreased hemoglobin levels. We aimed to verify the changes of red blood cell (RBC) number according to glomerular filtration rate (GFR) levels and its influence on the clinical outcome. With the data from routine health checkups of 114,496 adults, we grouped the subjects according to quartile levels of RBC number in each gender. Mortality data were from the National Statistical Office. RBC number was increased with decreasing GFR and/or the presence of a component of metabolic syndrome (MS) in subjects with GFR ≥ 50 ml/min/1.73 m². The estimated mean RBC number of subjects with GFR 89-50 ml/min/1.73 m² was higher compared to those with GFR ≥ 100 ml/min/1.73 m² by ANCOVA. In men, the death rate was the highest in the 1st quartile group (1Q) of RBC number (1.22%), followed by the 2nd quartile group (2Q, 0.42%), the 3rd quartile group (3Q, 0.39%), and the 4th quartile group (4Q, 0.29%) (p < 0.001). The hazard ratio (HR) of death in 2Q, 3Q and 4Q was 0.446, 0.580, and 0.440, respectively, compared to 1Q (p < 0.001). Among men in 1Q group, subjects with hemoglobin < 14.0 g/dL showed higher mortality rate than those with hemoglobin 14.0-14.9 g/dL or ≥ 15.0 g/dL (2.3% : 0.8% : 1.1%, respectively, p < 0.001). In conclusion, the RBC number was increased according to declines of GFR in the range of GFR ≥ 50 ml/min/1.73 m² and was an important risk factor for mortality.

Can the normobaric oxygen paradox (NOP) increase reticulocyte count after traumatic hip surgery?

STUDY OBJECTIVE

To determine if the normobaric oxygen paradox (NOP) was effective in increasing reticulocyte count and reducing postoperative requirements for allogeneic red blood cell transfusion after traumatic hip surgery.

DESIGN

Prospective, randomized, double blinded, multi-center study.

SETTING

Surgical wards of two academic hospitals.

PATIENTS

85 ASA physical status 1 and 2 patients undergoing surgery for traumatic hip fracture.

INTERVENTIONS

Patients were randomly assigned to receive 30 minutes of air [air group (control); n = 40] or 30 minutes of 100% oxygen (O2 group; n = 14) at 15 L/min every day from the first postoperative day (POD 1) until discharge.

MEASUREMENTS

Venous blood samples were taken at admission and after surgery on POD 1, POD 3, and POD 7. Hemoglobin (Hb), hematocrit (Hct), reticulocytes, hemodynamic variables, and transfusion requirements were recorded, as were hospital length of stay (LOS) and mortality.

MAIN RESULTS

Full analysis was obtained for 80 patients. On hospital discharge, the mean increase in reticulocyte count was significantly higher in the O2 group than the air group. Percent variation also increased: 184.9% ± 41.4% vs 104.7% ± 32.6%, respectively; P < 0.001. No difference in Hb or Hct levels was noted at discharge. Allogeneic red blood cell transfusion was 7.5% in the O2 group versus 35% in the air group (P = 0.0052). Hospital LOS was significantly shorter in the O2 group than the air group (7.2 ± 0.7 days vs 7.8 ± 1.6 days, respectively; P < 0.05).

CONCLUSIONS

Transient O2 administration increases reticulocyte count after traumatic hip surgery. Hospital LOS also was shorter in the O2 group than the control group. Allogeneic red blood cell transfusion was reduced in the O2 group but it was not due to the NOP mechanism.

Erythropoietin and engineered innate repair activators

Erythropoietin (EPO) is a pleiotropic type I cytokine that has been identified as a major endogenous tissue protective molecule. In response to injury, EPO and a distinct receptor are expressed with a characteristic temporal and spatial expression pattern. Together, these serve to limit injury and to initiate repair. Administration of EPO in the setting of injury has been shown to be beneficial in a multitude of preclinical models. However, translation into the clinic has been hampered by EPO's adverse effects, including promotion of thrombosis. Recently, engineered molecules based on EPO's structure-activity relationships have been developed that are devoid of hematopoietic effects. These compounds are promising candidates for treatment of a wide variety of acute and chronic diseases.

Epo and non-hematopoietic cells: what do we know?

The hematopoietic growth factor erythropoietin (Epo) circulates in plasma and controls the oxygen carrying capacity of the blood (Fisher. Exp Biol Med (Maywood) 228:1-14, 2003). Epo is produced primarily in the adult kidney and fetal liver and was originally believed to play a role restricted to stimulation of early erythroid precursor proliferation, inhibition of apoptosis, and differentiation of the erythroid lineage. Early studies showed that mice with targeted deletion of Epo or the Epo receptor (EpoR) show impaired erythropoiesis, lack mature erythrocytes, and die in utero around embryonic day 13.5 (Wu et al. Cell 83:59-67, 1995; Lin et al. Genes Dev. 10:154-164, 1996). These animals also exhibited heart defects, abnormal vascular development as well as increased apoptosis in the brain suggesting additional functions for Epo signaling in normal development of the central nervous system and heart. Now, in addition to its well-known role in erythropoiesis, a diverse array of cells have been identified that produce Epo and/or express the Epo-R including endothelial cells, smooth muscle cells, and cells of the central nervous system (Masuda et al. J Biol Chem. 269:19488-19493, 1994; Marti et al. Eur J Neurosci. 8:666-676, 1996; Bernaudin et al. J Cereb Blood Flow Metab. 19:643-651, 1999; Li et al. Neurochem Res. 32:2132-2141, 2007). Endogenously produced Epo and/or expression of the EpoR gives rise to autocrine and paracrine signaling in different organs particularly during hypoxia, toxicity, and injury conditions. Epo has been shown to regulate a variety of cell functions such as calcium flux (Korbel et al. J Comp Physiol B. 174:121-128, 2004) neurotransmitter synthesis and cell survival (Velly et al. Pharmacol Ther. 128:445-459, 2010; Vogel et al. Blood. 102:2278-2284, 2003). Furthermore Epo has neurotrophic effects (Grimm et al. Nat Med. 8:718-724, 2002; Junk et al. Proc Natl Acad Sci U S A. 99:10659-10664, 2002), can induce an angiogenic phenotype in cultured endothelial cells and is a potent angiogenic factor in vivo (Ribatti et al. Eur J Clin Invest. 33:891-896, 2003) and might enhance ventilation in hypoxic conditions (Soliz et al. J Physiol. 568:559-571, 2005; Soliz et al. J Physiol. 583, 329-336, 2007). Thus multiple functions have been identified breathing new life and exciting possibilities into what is really an old growth factor.This review will address the function of Epo in non-hematopoietic tissues with significant emphasis on the brain and heart.

Running economy and maximal oxygen consumption after 4 weeks of oral Echinacea supplementation

The purpose of this investigation was to determine the effects of 4 weeks of oral Echinacea (ECH) supplementation on erythropoietin (EPO), red blood cell (RBC) count, running economy (RE), and VO2max. Twenty-four men aged 24.9 ± 4.2 years, height 178.9 ± 7.9 cm, weight 87.9 ± 14.6 kg, body fat 19.3 ± 6.5% were grouped using a double-blind design and self-administered an 8,000-mg·d(-1) dosage of either ECH or placebo (PLA) in 5 × 400 mg × 4 times per day for 28 days. Blood samples were collected and analyzed for RBCs and EPO using automated flow cytometery and enzyme-linked immunosorbent assay. Maximal graded exercise tests (GXTs) were administered to measure VO2max, RE, and heart-rate responses. Analysis of variance was used to determine statistically significant differences (P ≤ 0.05). The EPO increased significantly in ECH at 7 days (ECH: 15.75 ± 0.64, PLA: 10.01 ± 0.73 mU·ml(-1)), 14 days (ECH: 18.88 ± 0.71, PLA: 11.02 ± 0.69 mU·ml(-1)), and 21 days (ECH: 16.06 ± 0.55, PLA: 9.20 ± 0.55 mU·ml(-1)). VO2max increased significantly in ECH (ECH: 1.47 ± 1.28, PLA: -0.13 ± 0.52%). Running economy improved significantly in ECH as indicated by a decrease in submaximal VO2max during the first 2 stages of the GXT (stage 1: ECH -1.50 ± 1.21, PLA 0.60 ± 1.95%; stage 2: ECH -1.67 ± 1.43, PLA 0.01 ± 1.03%). These data suggest that ECH supplementation results in significant increases in EPO, VO2max, and running economy.

Kidney EPO expression during chronic hypoxia in aged mice

In order to maintain normal cellular function, mammalian tissue oxygen concentrations must be tightly regulated within a narrow physiological range. The hormone erythropoietin (EPO) is essential for maintenance of tissue oxygen supply by stimulating red blood cell production and promoting their survival. In this study we compared the effects of 290 Torr atmospheric pressure on the kidney EPO protein levels in young (4-month-old) and aged (24-month-old) C57BL/6 mice. The mice were sacrificed after being anesthetized, and kidney samples were collected and processed by Western blot analysis. Relatively low basal expression of EPO during normoxia in young mice showed significant upregulation in hypoxia and stayed upregulated throughout the hypoxic period (threefold compared to normoxic control), showing a slight decline toward the third week. Whereas, a relatively higher normoxic basal EPO protein level in aged mice did not show significant increase until seventh day of hypoxia, but showed significant upregulation in prolonged hypoxia. Hence, we confirmed that there is a progressively increased accumulation of EPO during chronic hypoxia in young and aged mouse kidney, and the EPO upregulation during hypoxia showed a similarity with the pattern of increase in hematocrit, which we have reported previously.

The combined effect of recombinant human epidermal growth factor and erythropoietin on full-thickness wound healing in diabetic rat model

Diabetic wound is a chronic wound in which normal process of wound healing is interrupted. Lack of blood supply, infection and lack of functional growth factors are assumed as some of the conditions that lead to non-healing environment. Epidermal growth factor (EGF) acts primarily to stimulate epithelial cell growth across wound. Erythropoietin (EPO) is a haematopoietic factor, which stimulates the production, differentiation and maturation of erythroid precursor cells. This study hypothesised combining these two factors, non-healing process of diabetic wound will be compensated and eventually lead to acceleration of wound healing compared with single growth factor treatment. A total of 30 diabetic Sprague-Dawley rats were divided into three treatment groups (single treatment of rh-EPO or rh-EGF or combined treatment on a full-thickness skin wound). To assess the wound healing effects of the components, the wound size and the healing time were measured in each treatment groups. The skin histology was examined by light microscopy and immunohistochemical analysis of proliferating markers was performed. The combined treatment with rh-EPO and rh-EGF improved full-thickness wound significantly (P < 0·05) accelerating 50% healing time with higher expression of Ki-67 compared with single growth factor-treated groups. The combined treatment failed to accelerate the total healing time when compared with single growth factor treatments. However, the significant improvement were found in wound size reduction in the combined treatment group on day 4 against single growth factor-treated groups (P < 0·05). This study demonstrated that the combined treatment of rh-EPO and rh-EGF improved the wound healing possibly through a synergistic action of each growth factor. This application provides further insight into combined growth factor therapy on non-healing diabetic wounds.

Acute hemodynamic effects of erythropoietin do not mediate its cardioprotective properties

Activation of nitric oxide (NO) signaling is considered, at list partially, a mechanistic basis for EPO-induced cardioprotection. Surprisingly, hemodynamic response subsequent to NO activation after EPO administration has never been reported. The objectives of this study were to evaluate the acute hemodynamic and cardiovascular responses to EPO administration, to confirm their NO genesis, and to test the hypothesis that EPO-induced cardioprotection is mediated through cardiovascular changes related to NO activation. In Experiment 1, after 3000 U/kg of rhEPO was administered intravenously to Wistar rats, arterial blood pressure, monitored via indwelling catheter, progressively declined almost immediately until it leveled off 90 minutes after injection at 20% below control level. In Experiment 2 the 25% reduction of mean blood pressure, compared to control group, was observed 2 hours after intravenous injection of either 3000 or 150 U/kg of rhEPO. Detailed pressure–volume loop analyses of cardiac performance (Experiment 3) 2 hours after intravenous injection of human or rat recombinant EPO (3000 U/kg) revealed a significant reduction of systolic function (PRSW was 33% less than control). Reduction of arterial blood pressure and systolic cardiac function in response to rhEPO were blocked in rats pretreated with a non-selective inhibitor of nitric oxide synthase (L-NAME). In Experiment 4, 24 hours after a permanent ligation of a coronary artery, myocardial infarction (MI) measured 26±3.5% of left ventricle in untreated rats. MI in rats treated with 3000 U/kg of rhEPO immediately after coronary ligation was 56% smaller. Pretreatment with L-NAME did not attenuate the beneficial effect of rhEPO on MI size, while MI size in rats treated with L-NAME alone did not differ from control. Therefore, a single injection of rhEPO resulted in a significant, NO-mediated reduction of systemic blood pressure and corresponding reduction of cardiac systolic function. However, EPO-induced protection of myocardium from ischemic damage is not associated with NO activation or NO-mediated hemodynamic responses.

Erythropoietin is detectable in the ascitic fluid in patients with ovarian tumors

BACKGROUND AND OBJECTIVE

Erythropoietin (Epo) is a glycoprotein that stimulates proliferation and migration of human endothelial cells and promotes angiogenesis, which are crucial phenomena in cancer biology. The objective of this study was to investigate whether Epo is detectable in the ascitic fluid of patients with ovarian tumors.

PATIENTS AND METHODS

We investigated the presence of Epo in the ascitic fluid of 100 women undergoing laparotomy for an ovarian tumor. Epo concentration was quantitated with an immunochemiluminometric assay.

RESULTS

Ten women had a benign tumor, 13 women had a borderline tumor, and 77 women had ovarian cancer. Epo was detected in all ascitic fluid samples, in similar amounts as in corresponding serum samples. Ascitic fluid Epo concentration did not differ between the 3 study groups (P = 0.081), but in multiple comparisons, ascitic fluid Epo was higher in the women with cancer than in the women with a benign tumor (P = 0.006). Ascitic fluid Epo concentration correlated positively with serum Epo (P < 0.0001) and the volume of ascites (P < 0.0001). In regression analyses, serum Epo, volume of ascites, blood hemoglobin, plasma CA125, tumor stage, tumor grade, and the presence of residual tumor after surgery had no significant independent effect on ascitic fluid Epo.

CONCLUSION

Considerable amounts of Epo are present in the ascitic fluid of women with ovarian tumors. The origin of Epo in the ascitic fluid of women with ovarian tumors as well as the clinical relevance of our finding remain to be clarified.

Renal variant of Fabry disease with sporadic GLA gene mutation: role of early renal biopsy

Fabry disease (FD) is a rare, X-linked inherited disease of glycosphingolipid metabolism due to deficiency of lysosomal α-galactosidase A activity. Scarce activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide (Gb3) within lysosomes, believed to trigger a flow of cellular changes that lead to the clinical manifestation of the disease. We present a 23-year-old male with renal variant of FD who was born from non-affected parents, which, to the best of our knowledge, has not been reported in the literature so far. In conclusion, FD can occur due to sporadic GLA gene mutation. Pure renal involvement might be associated with progressive disease which leads to end-stage renal disease within a short period. Physicians should have a high index of suspicion for FD especially in male cases with unexplained renal failure that are slowly progressive in nature, even in the absence of a clear hereditary component. Early renal biopsy is recommended in any progressive renal impairment.

Erythropoietin improves neuronal proliferation in dentate gyrus of hippocampal formation in an animal model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a prevalent disorder with severe learning and memory defects. Because it has been demonstrated that erythropoietin (EPO) has positive effects on the central nervous system, the aim of this study was to evaluate the effect of EPO on neuronal proliferation in dentate gyrus of hippocampal formation in a well-defined model for AD.

MATERIALS AND METHODS

A rat model of sporadic dementia of Alzheimer's type was established by a bilateral intracerebroventricular injection of streptozotocin (ICV-STZ). Impairment of learning and memory was confirmed 2 weeks after ICV-STZ injection by passive avoidance learning test and then rats were divided into fourgroups:Control, control-EPO, Alzheimer and Alzheimer-EPO. EPO was injected intraperitoneally every other day with a dose of 5000 IU/kg and, finally, the rats were anesthetized and decapitated for immunohistochemical study and neurogenesis investigation (by Ki67 method) in dentate gyrus of hippocampal formation.

RESULTS

The results driven from the histological study showed that EPO significantly increases neuronal proliferation in dentate gyrus of hippocampus in the Alzheimer-EPO group compared with the control, control-EPO and Alzheimer groups; however, there were no differences between the other groups.

CONCLUSION

Our results show that even though EPO in intact animals doesnot change neurogenesis in dentate gyrus, it can nonetheless significantly increase neurogenesis if there is an underlying disorder like neurodegenerative diseases.

Modeling of red blood cell life-spans in hematologically normal populations

Despite the impact of red blood cell (RBC) Life-spans in some disease areas such as diabetes or anemia of chronic kidney disease, there is no consensus on how to quantitatively best describe the process. Several models have been proposed to explain the elimination process of RBCs: random destruction process, homogeneous life-span model, or a series of 4-transit compartment model. The aim of this work was to explore the different models that have been proposed in literature, and modifications to those. The impact of choosing the right model on future outcomes prediction--in the above mentioned areas--was also investigated. Both data from indirect (clinical data) and direct life-span measurement (biotin-labeled data) methods were analyzed using non-linear mixed effects models. Analysis showed that: (1) predictions from non-steady state data will depend on the RBC model chosen; (2) the transit compartment model, which considers variation in life-span in the RBC population, better describes RBC survival data than the random destruction or homogenous life-span models; and (3) the additional incorporation of random destruction patterns, although improving the description of the RBC survival data, does not appear to provide a marked improvement when describing clinical data.

Decreased VEGF expression and microvascular density, but increased HIF-1 and 2α accumulation and EPO expression in chronic moderate hyperoxia in the mouse brain

Normal brain function is dependent on continuous and controlled oxygen delivery. Chronic moderate hypoxia leads to angiogenesis, suggesting a modulatory role for oxygen in determining capillary density. The objective of this study was to determine physiologic and brain angiogenic adaptational changes during chronic moderate normobaric hyperoxia in mice. Four-month old C56BL/6J mice were kept in a normobaric chamber at 50% O(2) for up to 3 weeks. Normoxic littermates were kept in the same room outside the chamber. Freshly collected or fixed brain specimens were analyzed by RT-PCR, Western blot analysis and immunohistochemistry. Results show accumulation of hypoxia inducible factors 1 and 2α (HIF-1 and 2α), and increased expression of erythropoietin (EPO), cyclooxygenase-2 (COX-2) and angiopoietin-2 (Ang-2). Conversely, vascular endothelial growth factor (VEGF), and VEGF receptor-2 (KDR/Flk-1), Peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) and prolylhydroxylase-2 (PHD-2) expressions were decreased. VEGF mRNA level was diminished but there was no change in HIF-1α mRNA and von Hippel Lindau E3 ubiquitin ligase (VHL) protein expression. Microvascular density was significantly diminished by the end of the 3rd week of hyperoxia. Overall, our results are: (1) increased expression of the potent neuroprotective molecule, EPO; (2) diminished expression of the potent angiogenic factor, VEGF; and (3) decreased microvascular density. We can, therefore, conclude that brain microvascular density can be controlled by HIF-independent mechanisms, and that brain capillary density is a continuously adjusted variable with tissue oxygen availability as one of the controlling modulators.

Aliskiren improves insulin resistance and ameliorates diabetic renal vascular complications in STZ-induced diabetic rats

Aliskiren, a direct renin inhibitor (DRI), has therapeutic effects in patients with hypertension and associated complications, but its potential mechanism in diabetic nephropathy is lacking. The effects of aliskiren in Streptozotocin (STZ)-induced renal complication in diabetic rats were investigated. Aliskiren treatment for eight weeks at the dose of 10 mg/kg/day, via osmotic mini-pump, induced improvement in blood glucose levels, systolic blood pressure (BP) and serum creatinine. Improvement of insulin resistance by aliskiren was confirmed by increased glucose translocation in liver and muscle and hence insulin levels. The treated group also showed improvement in glomerulosclerosis and tubulointerstitial injury. Aliskiren treatment also improved albumin levels in plasma, suppressed profibrotic and proinflammatory cytokine synthesis viz TNF-α and TGF-β and angiogenesis by a decrease in VEGF. In addition, the level of total proteins and GFR via cystatin c and beta-2microglobulin along with adiponectin and erythropoietin were also improved. These results suggest that the beneficial organ protective effect of aliskiren is mediated by improvement in insulin resistance as well as a direct anti-fibrotic effect in the target organ in STZ-induced diabetic rats with a slight effect on blood pressure. Aliskiren may be a useful therapeutic agent in the treatment of type 2 diabetes and diabetic nephropathy.

N-Glycosylation engineering of tobacco plants to produce asialoerythropoietin

Erythropoietin (EPO) is a glycoprotein hormone that displays both hematopoietic and tissue-protective functions by binding to two distinct receptors. Recombinant human EPO (rhuEPO) is widely used for the treatment of anemia, but its use for tissue protection is limited because of potentially harmful increases in red blood cell mass when higher doses of rhuEPO are used. Recent studies have shown that asialoerythropoietin (asialo-rhuEPO), a desialylated form of rhuEPO, lacks hematopoietic activity, but retains cytoprotective activity. Currently, a small amount of asialo-rhuEPO is produced by enzymatic desialylation of rhuEPO. The prohibitive cost of rhuEPO, however, is a major limitation of this method. Plants have the ability to synthesize complex N-glycans, but lack enzymatic activities to add sialic acid and β1,4-galactose to N-glycan chains. Plants could be genetically engineered to produce asialo-rhuEPO by introducing human β1,4-galactosyltransferase. The penultimate β1,4-linked galactose residues are important for in vivo biological activity. In this proof of concept study, we show that tobacco plants co-expressing human β1,4-galactosyltransferase and EPO genes accumulated asialo-rhuEPO. Purified asialo-rhuEPO binds to an Erythrina cristagalli lectin column, indicating that its N-glycan chains bear terminal β1,4-galactose residues and that the co-expressed GalT is functionally active. Asialo-rhuEPO interacted with the EPO receptor (EPOR) with similar affinity as rhuEPO, implying that it was properly folded. The strategy described here provides a straightforward way to produce asialo-rhuEPO for research and therapeutic purposes.

KEY MESSAGE

N-glycosylation pathway in tobacco plants could be genetically engineered to produce a tissue-protective cytokine, asialoerythropoietin (a desialylated form of human hormone erythropoietin).

Clinical and histological outcome predictors in renal limited pauci-immune crescentic glomerulonephritis: a single centre experience

Renal-limited vasculitis is a pauci-immune crescentic glomerulonephritis with no signs of systemic involvement, representing one of the most common causes of rapidly progressive glomerulonephritis. The study aims to examine clinical and histological features in twenty-four patients with RLV diagnosed by the Nephrology Department of Sapienza University of Rome, Italy, evaluating the role of these parameters in predicting renal survival. Patients details, clinical and histological features and outcomes were recorded at the time of renal biopsy and over a mean follow-up period of 36±6 months. In our study, serum creatinine at presentation was significantly higher in patients who had a poor outcome than in those who survived with independent renal function (6.3±2.47 mg/dl vs 2.84±2.01 mg/dl, P= 0.002). The presence of C3c was found in the area of glomerular fibrinoid necrosis and in small arteries and arterioles with fibrinoid necrosis in 17 patients (P= 0.018). In conclusion, serum creatinine at presentation and focal C3c depositions in areas of glomerular and arteriolar fibrinoid necrosis were the best determinants of poor renal outcome, maybe underlining the pathogenic role of alternative pathway activation of complement system but also demonstrating the focal distribution of necrotizing lesions.

Expression profiling reveals novel hypoxic biomarkers in peripheral blood of adult mice exposed to chronic hypoxia

Hypoxia induces a myriad of changes including an increase in hematocrit due to erythropoietin (EPO) mediated erythropoiesis. While hypoxia is of importance physiologically and clinically, lacunae exist in our knowledge of the systemic and temporal changes in gene expression occurring in blood during the exposure and recovery from hypoxia. To identify these changes expression profiling was conducted on blood obtained from cohorts of C57Bl-10 wild type mice that were maintained at normoxia (NX), exposed for two weeks to normobaric chronic hypoxia (CH) or two weeks of CH followed by two weeks of normoxic recovery (REC). Using stringent bioinformatic cut-offs (0% FDR, 2 fold change cut-off), 230 genes were identified and separated into four distinct temporal categories. Class I) contained 1 transcript up-regulated in both CH and REC; Class II) contained 202 transcripts up-regulated in CH but down-regulated after REC; Class III) contained 9 transcripts down-regulated both in CH and REC; Class IV) contained 18 transcripts down-regulated after CH exposure but up-regulated after REC. Profiling was independently validated and extended by analyzing expression levels of selected genes as novel biomarkers from our profile (e.g. spectrin alpha-1, ubiquitin domain family-1 and pyrroline-5-carboxylate reductase-1) by performing qPCR at 7 different time points during CH and REC. Our identification and characterization of these genes define transcriptome level changes occurring during chronic hypoxia and normoxic recovery as well as novel blood biomarkers that may be useful in monitoring a variety of physiological and pathological conditions associated with hypoxia.

Human mesenchymal stromal cells could deliver erythropoietin and migrate to the basal layer of hair shaft when subcutaneously implanted in a murine model

Mesenchymal stromal cells (MSC) are an attractive cell-targeting vehicle for gene delivery. MIDGE (an acronym for Minimalistic, Immunologically Defined Gene Expression) construct is relatively safer than the viral or plasmid expression system as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. The objective of this study was to test the ability of the human MSC (hMSC) to deliver the erythropoietin (EPO) gene in a nude mice model following nucleofection using a MIDGE construct. hMSC nucleofected with MIDGE encoding the EPO gene was injected subcutaneously in Matrigel at the dorsal flank of nude mice. Subcutaneous implantation of nucleofected hMSC resulted in increased hemoglobin level with presence of human EPO in the peripheral blood of the injected nude mice in the first two weeks post-implantation compared with the control groups. The basal layer of the hair shaft in the dermal layer was found to be significantly positive for immunohistochemical staining of a human EPO antibody. However, only a few basal layers of the hair shaft were found to be positively stained for CD105. In conclusion, hMSC harboring MIDGE-EPO could deliver and transiently express the EPO gene in the nude mice model. These cells could be localized to the hair follicle and secreted EPO protein might have possible role in hair regeneration.

Erythropoietin: still on the neuroprotection road

Acute stroke is one of the major causes of death and disabilities. Since the 1980s many clinical studies have been conducted to evaluate neuroprotective approaches to treat this important brain vascular event. However, to date the only drug approved (recombinant tissue plasminogen activator [rtPA]) represents a thrombolytic, nonneuroprotective approach. An important neuroprotective strategy is based on erythropoietin (EPO). Exogenously administered EPO exhibits neuroprotective effects in numerous animal models, through the activation of anti-apoptotic, anti-oxidant and anti-inflammatory pathways as well as through the stimulation of angiogenic and neurogenic events. The capability of EPO to cross the blood-brain barrier after systemic administration and its effective therapeutic window are advantages for human acute stroke therapy. However, a multicenter stroke trial where recombinant human EPO (rhEPO) was combined with rtPA had negative outcomes. The present paper reviews the EPO neuroprotective strategy and its mechanisms in ischemic stroke and in other human nervous system diseases.

Erythropoietin produced by the retina: its role in physiology and diabetic retinopathy

Erythropoietin (Epo) is the principal regulator of erythropoiesis by inhibiting apoptosis and by stimulating the proliferation and differentiation of erythroid precursor cells. However, Epo also performs extra-erythropoietic actions of which the neuroprotective effects are among the most relevant. Apart from kidney and liver, Epo is also produced by the brain and the retina. In addition, Epo receptor (Epo-R) expression has also been found in the brain and in the retina, thus suggesting an autocrine/paracrine action which seems essential for the physiological homeostasis of both brain and retina. In this review, we will give an overview of the current concepts of the physiology of Epo and will focus on its role in the retina in both normal conditions and in the setting of diabetic retinopathy. Finally, the reasons as to why Epo could be contemplated as a potential new treatment for the early stages of diabetic retinopathy will be given.

Therapeutic use of a cationic antimicrobial peptide from the spider Acanthoscurria gomesiana in the control of experimental candidiasis

Background

Antimicrobial peptides are present in animals, plants and microorganisms and play a fundamental role in the innate immune response. Gomesin is a cationic antimicrobial peptide purified from haemocytes of the spider Acanthoscurria gomesiana. It has a broad-spectrum of activity against bacteria, fungi, protozoa and tumour cells. Candida albicans is a commensal yeast that is part of the human microbiota. However, in immunocompromised patients, this fungus may cause skin, mucosal or systemic infections. The typical treatment for this mycosis comprises three major categories of antifungal drugs: polyenes, azoles and echinocandins; however cases of resistance to these drugs are frequently reported. With the emergence of microorganisms that are resistant to conventional antibiotics, the development of alternative treatments for candidiasis is important. In this study, we evaluate the efficacy of gomesin treatment on disseminated and vaginal candidiasis as well as its toxicity and biodistribution.

Results

Treatment with gomesin effectively reduced Candida albicans in the kidneys, spleen, liver and vagina of infected mice. The biodistribution of gomesin labelled with technetium-99 m showed that the peptide is captured in the kidneys, spleen and liver. Enhanced production of TNF-α, IFN-γ and IL-6 was detected in infected mice treated with gomesin, suggesting an immunomodulatory activity. Moreover, immunosuppressed and C. albicans-infected mice showed an increase in survival after treatment with gomesin and fluconazole. Systemic administration of gomesin was also not toxic to the mic

Conclusions

Gomesin proved to be effective against experimental Candida albicans infection. It can be used as an alternative therapy for candidiasis, either alone or in combination with fluconazole. Gomesin's mechanism is not fully understood, but we hypothesise that the peptide acts through the permeabilisation of the yeast membrane leading to death and/or releasing the yeast antigens that trigger the host immune response against infection. Therefore, data presented in this study reinforces the potential of gomesin as a therapeutic antifungal agent in both humans and animals.

Evaluation of functional erythropoietin receptor status in skeletal muscle in vivo: acute and prolonged studies in healthy human subjects

BACKGROUND

Erythropoietin receptors have been identified in human skeletal muscle tissue, but downstream signal transduction has not been investigated. We therefore studied in vivo effects of systemic erythropoietin exposure in human skeletal muscle.

METHODOLOGY/PRINCIPAL FINDINGS

The protocols involved 1) acute effects of a single bolus injection of erythropoietin followed by consecutive muscle biopsies for 1-10 hours, and 2) a separate study with prolonged administration for 16 days with biopsies obtained before and after. The presence of erythropoietin receptors in muscle tissue as well as activation of Epo signalling pathways (STAT5, MAPK, Akt, IKK) were analysed by western blotting. Changes in muscle protein profiles after prolonged erythropoietin treatment were evaluated by 2D gel-electrophoresis and mass spectrometry. The presence of the erythropoietin receptor in skeletal muscle was confirmed, by the M20 but not the C20 antibody. However, no significant changes in phosphorylation of the Epo-R, STAT5, MAPK, Akt, Lyn, IKK, and p70S6K after erythropoietin administration were detected. The level of 8 protein spots were significantly altered after 16 days of rHuEpo treatment; one isoform of myosin light chain 3 and one of desmin/actin were decreased, while three isoforms of creatine kinase and two of glyceraldehyd-3-phosphate dehydrogenase were increased.

CONCLUSIONS/SIGNIFICANCE

Acute exposure to recombinant human erythropoietin is not associated by detectable activation of the Epo-R or downstream signalling targets in human skeletal muscle in the resting situation, whereas more prolonged exposure induces significant changes in the skeletal muscle proteome. The absence of functional Epo receptor activity in human skeletal muscle indicates that the long-term effects are indirect and probably related to an increased oxidative capacity in this tissue.

Erythropoietin administration acutely stimulates resting energy expenditure in healthy young men

Treatment with recombinant human erythropoietin (rHuEpo) improves insulin sensitivity in patients with end-stage renal disease, and animal studies indicate that Epo increases fat oxidation. However, the metabolic effects of rHuEpo have never been experimentally studied in healthy humans. The aim was to investigate the effects of an acute rHuEpo bolus on substrate metabolism and insulin sensitivity in healthy young men. Ten healthy young men were studied in a single-blinded, randomized crossover design with a 2-wk washout period receiving 400 IU/kg rHuEpo or placebo. Substrate metabolism was evaluated by indirect calorimetry and tracer infusions, and insulin sensitivity by a hyperinsulinemic euglycemic clamp; and PCR and Western blotting measured protein expression and content, respectively. Resting energy expenditure (REE) increased significantly after rHuEpo [basal: 1,863.3 ± 67.2 (kcal/day) (placebo) vs. 2,041.6 ± 81.2 (rHuEpo), P < 0.001; clamp: 1,903.9 ± 68.3 (placebo) vs. 2,015.7 ± 114.4 (rHuEpo), P = 0.03], but the increase could not be explained by changes in mRNA levels of uncoupling protein 2 or 3. Fat oxidation in the basal state tended to be higher after rHuEpo but could not be explained by changes in mRNA levels of CPT1 and PPARα or AMPK and ACC protein phosphorylation. Insulin-stimulated glucose disposal, glucose metabolism, and whole body and forearm protein metabolism did not change significantly in response to rHuEpo. In conclusion, a single injection of rHuEpo acutely increases REE in healthy human subjects. This calorigenic effect is not accompanied by distinct alterations in the pattern of substrate metabolism or insulin sensitivity.

Renoprotective effect of erythropoietin in ischemia/reperfusion injury: possible roles of the Akt/endothelial nitric oxide synthase-dependent pathway

OBJECTIVES

It has been reported that erythropoietin protects the kidneys from ischemia/reperfusion injury. In the present study, we examined the role of Akt and endothelial nitric oxide synthase in the protective effect of erythropoietin on ischemia/reperfusion injury of the kidney.

METHODS

Erythropoietin was injected in the peritoneal space of ICR mice after ischemia/reperfusion injury and its effect was assessed by measuring blood urea nitrogen and creatinine, and by histological analysis. Phosphorylation of Akt and endothelial nitric oxide synthase was examined by western blot analysis. Endothelial nitric oxide synthase gene null mice were also used to examine the role of endothelial nitric oxide synthase in the renoprotective effect of erythropoietin.

RESULTS

Erythropoietin administration significantly inhibited the increase in blood urea nitrogen and creatinine after ischemia/reperfusion injury compared with control mice. Accordingly, erythropoietin administration significantly ameliorated the histological damages, including apoptotic cell death. Erythropoietin significantly stimulated phosphorylation of Akt and endothelial nitric oxide synthase in the kidneys. When endothelial nitric oxide synthase gene null mice were subjected to ischemia/reperfusion injury, erythropoietin did not significantly suppress the increase in blood urea nitrogen or creatinine.

CONCLUSIONS

Erythropoietin seems to activate the Akt/endothelial nitric oxide synthase-dependent pathway in the kidneys. This pathway might be implicated in the renoprotective effect of erythropoietin in the ischemia/reperfusion injury model.

Treating anemia associated with chronic renal failure with erythropoiesis stimulators: recombinant human erythropoietin might be the best among the available choices

Chronic renal failure (CRF) is a widespread medical problem commonly accompanied by a hypoproliferative anemia ("renal anemia") due to erythropoietin deficiency. Anemia greatly contributes to reduced quality of life (Hr-QoL) and high morbidity and mortality in CRF patients. Recombinant human erythropoietin (rHu-Epo) was introduced to medical practice some 20years ago. It enables correction of anemia (hemoglobin levels, Hb) with dramatic immediate (Hr-QoL improvement) and long-term effects (reduced morbidity and mortality). Newer experimental data suggest that long-term benefits could be due not only to antianemic effect, but also to a direct organoprotective effect of (rHu)-Epo mediated through a receptor complex different from the "erythropoietic" erythropoietin receptor. During the last decade, two alternative treatments for renal anemia have been approved: darbepoetin and CERA. Both are direct agonists of the "erythropoietic" receptors and both were derived from rHu-Epo. Molecularly, they differ from rHu-Epo in that they are much larger molecules (darbepoetin is genetically modified rHu-Epo with a higher sugar content and CERA is pegylated rHu-Epo) with lower affinity for the erythropoietin receptor but with a longer circulating time. In terms of renal anemia correction, they are non-inferior to rHu-Epo and allow for less frequent dosing. They have never been compared to rHu-Epo regarding the long-term outcomes. It is hypothesized that regarding the long-term outcomes (morbidity, mortality), rHu-Epo might be superior to those larger molecules. The hypothesis is based on two types of observations. First, experimental data emphasize the role of small, erythropoietically less valuable rHu-Epo isoforms in its organoprotective effects. Second, clinical observations suggest that rHu-Epo enables for less variable Hb correction than the larger molecules, and pronounced within-subject Hb variability has been suggested as an independent predictor of poor long-term outcomes of renal anemia management.

Herpesvirus entry mediator regulates hypoxia-inducible factor-1α and erythropoiesis in mice

Erythropoiesis, the production of red blood cells, must be tightly controlled to ensure adequate oxygen delivery to tissues without causing thrombosis or stroke. Control of physiologic and pathologic erythropoiesis is dependent predominantly on erythropoietin (EPO), the expression of which is regulated by hypoxia-inducible factor (HIF) activity in response to low oxygen tension. Accumulating evidence indicates that oxygen-independent mediators, including inflammatory stimuli, cytokines, and growth factors, also upregulate HIF activity, but it is unclear whether these signals also result in EPO production and erythropoiesis in vivo. Here, we found that signaling through herpesvirus entry mediator (HVEM), a molecule of the TNF receptor superfamily, promoted HIF-1α activity in the kidney and subsequently facilitated renal Epo production and erythropoiesis in vivo under normoxic conditions. This Epo upregulation was mediated by increased production of NO by renal macrophages. Hvem-deficient mice displayed impaired Epo expression and aggravated anemia in response to erythropoietic stress. These data reveal that HVEM signaling functions to promote HIF-1α activity and Epo production, and thus to regulate erythropoiesis. Furthermore, our findings suggest that this molecular mechanism could represent a therapeutic target for Epo-responsive diseases, including anemia.

Optimization of erythropoietin production with controlled glycosylation-PEGylated erythropoietin produced in glycoengineered Pichia pastoris

Pichia pastoris is a methylotropic yeast that has gained great importance as an organism for protein expression in recent years. Here, we report the expression of recombinant human erythropoietin (rhEPO) in glycoengineered P. pastoris. We show that glycosylation fidelity is maintained in fermentation volumes spanning six orders of magnitude and that the protein can be purified to high homogeneity. In order to increase the half-life of rhEPO, the purified protein was coupled to polyethylene glycol (PEG) and then compared to the currently marketed erythropoiesis stimulating agent, Aranesp(®) (darbepoetin). In in vitro cell proliferation assays the PEGylated protein was slightly, and the non-PEGylated protein was significantly more active than comparator. Pharmacodynamics as well as pharmacokinetic activity of PEGylated rhEPO in animals was comparable to that of Aranesp(®). Taken together, our results show that glycoengineered P. pastoris is a suitable production host for rhEPO, yielding an active biologic that is comparable to those produced in current mammalian host systems.

Organ-protective and immunomodulatory effects of erythropoietin--an update on recent clinical trials

Erythropoietin (EPO) belongs to a group of pharmacological agents with multifunctional effects. EPO was originally acknowledged as the main regulator of erythropoiesis, but it also exhibits several extra haematopoietic properties, such as promoting the maintenance of homeostasis of cells under stress. These pleiotropic effects have been extensively investigated in preclinical models including models of ischaemic-reperfusions injuries, inflammation, neuroprotection, neovascularisation and wound healing. Promising effects of EPO have especially been reported in models of ischaemic-reperfusions injuries. The mechanisms by which EPO exerts these organ-protective effects are not completely understood, although anti-apoptotic, anti-inflammatory and anti-oxidative properties have been described. Activation of the EPO receptor initiates several intracellular signalling systems, such as, phosphatidylinositol 3-kinase, STAT5, mitogen-activated protein kinase and nuclear factor-kappa B. These pathways are recognized as involved in the cellular response to stress and regulation of apoptosis. Although EPO has been demonstrated to be effective in animal models, the effect has not been clearly demonstrated in clinical trials. This MiniReview gives a brief introduction to the pleiotropic effects of EPO, the evidence of organ protection in animal models, and discusses the disappointing results obtained from recent clinical trials.