Erythropoietin in the control of red cell production

The cytokine receptor CRLF3 is a human neuroprotective EV-3 (Epo) receptor

The evolutionary conserved orphan cytokine receptor-like factor 3 (CRLF3) has been implicated in human disease, vertebrate hematopoiesis and insect neuroprotection. While its specific functions are elusive, experimental evidence points toward a general role in cell homeostasis. Erythropoietin (Epo) is a major regulator of vertebrate hematopoiesis and a general cytoprotective cytokine. Erythropoietic functions mediated by classical Epo receptor are understood in great detail whereas Epo-mediated cytoprotective mechanisms are more complex due to involvement of additional Epo receptors and a non-erythropoietic splice variant with selectivity for certain receptors. In the present study, we show that the human CRLF3 mediates neuroprotection upon activation with the natural Epo splice variant EV-3. We generated CRLF3 knock-out iPSC lines and differentiated them toward the neuronal lineage. While apoptotic death of rotenone-challenged wild type iPSC-derived neurons was prevented by EV-3, EV-3-mediated neuroprotection was absent in CRLF3 knock-out neurons. Rotenone-induced apoptosis and EV-3-mediated neuroprotection were associated with differential expression of pro-and anti-apoptotic genes. Our data characterize human CRLF3 as a receptor involved in Epo-mediated neuroprotection and identify CRLF3 as the first known receptor for EV-3.

Traumatic optic neuropathy: a review of current studies

Traumatic optic neuropathy (TON) is a serious complication of craniofacial trauma that directly or indirectly damages the optic nerve and can cause severe vision loss. The incidence of TON has been gradually increasing in recent years. Research on the protection and regeneration of the optic nerve after the onset of TON is still at the level of laboratory studies and which is insufficient to support clinical treatment of TON. And, due to without clear guidelines, there is much ambiguity regarding its diagnosis and management. Clinical interventions for TON include observation only, treatment with corticosteroids alone, or optic canal (OC) decompression (with or without steroids). There is controversy in clinical practice concerning which treatment is the best. A review of available studies shows that the visual acuity of patients with TON can be significantly improved after OC decompression surgery (especially endoscopic transnasal/transseptal optic canal decompression (ETOCD)) with or without the use of corticosteroids. And new findings of laboratory studies such as mitochondrial therapy, lipid change studies, and other studies in favor of TON therapy have also been identified. In this review, we discuss the evolving perspective of surgical treatment and experimental study.

Erythropoietin and G-csf Receptors in Human Tumor Cells: Expression and Aspects regarding Functionality

Aims and Background

Recombinant human erythropoietin (Epo) and granulocyte-colony-stimulating factor (G-CSF) are used to stimulate hematopoiesis in patients with malignant diseases. These cytokines transduce their biological signal via the Epo receptor (EpoR) and G-CSF receptor (G-CSF-R) into the cell. We therefore investigated in human tumor cell lines the expression of these receptors in tumor cells as well as their response to Epo and G-CSF.

Methods and Study Design

The expression of EpoR and G-CSF-R mRNA was analyzed with reverse transcription-polymerase chain reaction (RT-PCR). EpoR protein expression was further monitored with Western blot and immunocytochemistry analysis. The cellular response to various concentrations of Epo was evaluated using 3[H]-thymidine uptake, Northern blot of c-fos expression and tyrosine kinase activity assay. The proliferation after G-CSF incubation was analyzed with the MTS assay.

Results

In this study EpoR mRNA and protein were detected in various human tumor cell lines. Treatment with Epo did not influence the proliferation rate of examined EpoR-positive tumor cell lines. Epo did not stimulate the tyrosine kinase activity nor did it affect the c-fos mRNA in these cell lines. G-CSF-R mRNA was only detected in two myeloid cell lines. Treatment with G-CSF did not increase the proliferation of these cells.

Conclusions

These results demonstrate that Epo and G-CSF did not modulate the growth rate of examined receptor-positive tumor cell lines; the presence of the Epo receptor seems not essential for cell growth of these tumor cells in cell culture.

Erythropoietin-Mediated Neuroprotection in Insects Suggests a Prevertebrate Evolution of Erythropoietin-Like Signaling

The cytokine erythropoietin (Epo) mediates protective and regenerative functions in mammalian nervous systems via activation of poorly characterized receptors that differ from the "classical" homodimeric Epo receptor expressed on erythroid progenitor cells. Epo genes have been identified in vertebrate species ranging from human to fish, suggesting that Epo signaling evolved earlier than the vertebrate lineage. Studies on insects (Locusta migratoria, Chorthippus biguttulus, Tribolium castaneum) revealed Epo-mediated neuroprotection and neuroregeneration. Recombinant human Epo (rhEpo) prevents apoptosis by binding to a janus kinase-associated receptor, stimulation of STAT transcription factors, and generation of factors that prevent the activation of proapoptotic caspases. Insect neurons were also protected by a neuroprotective but nonerythropoietic Epo splice variant, suggesting similarity with mammalian neuroprotective but not with homodimeric "classical" Epo receptors. Additionally, rhEpo promotes the regeneration of neurites in primary cultured insect brain neurons and after nerve crush in an in vivo preparation. In contrast to neuroprotective and regenerative effects shared with mammalian species, no evidence for a role of Epo signaling in the regulation of neuro- or gliogenesis was found in insects. Similar structural and functional characteristics of the Epo binding receptors, partly shared transduction pathways that prevent apoptosis and the functional implication in neuroprotective and neuroregenerative processes in both mammalian and insect species, suggest that Epo-like signaling was already established in their last common ancestor. Originally functioning as a tissue-protective response to unfavorable physiological situations, cell injury, and pathogen invasion, Epo was later adapted as a humoral regulator of erythropoiesis in the vertebrate lineage.

Melatonin rescues cardiovascular dysfunction during hypoxic development in the chick embryo

There is a search for rescue therapy against fetal origins of cardiovascular disease in pregnancy complicated by chronic fetal hypoxia, particularly following clinical diagnosis of fetal growth restriction (FGR). Melatonin protects the placenta in adverse pregnancy; however, whether melatonin protects the fetal heart and vasculature in hypoxic pregnancy independent of effects on the placenta is unknown. Whether melatonin can rescue fetal cardiovascular dysfunction when treatment commences following FGR diagnosis is also unknown. We isolated the effects of melatonin on the developing cardiovascular system of the chick embryo during hypoxic incubation. We tested the hypothesis that melatonin directly protects the fetal cardiovascular system in adverse development and that it can rescue dysfunction following FGR diagnosis. Chick embryos were incubated under normoxia or hypoxia (14% O2) from day 1 ± melatonin treatment (1 mg/kg/day) from day 13 of incubation (term ~21 days). Melatonin in hypoxic chick embryos rescued cardiac systolic dysfunction, impaired cardiac contractility and relaxability, increased cardiac sympathetic dominance, and endothelial dysfunction in peripheral circulations. The mechanisms involved included reduced oxidative stress, enhanced antioxidant capacity and restored vascular endothelial growth factor expression, and NO bioavailability. Melatonin treatment of the chick embryo starting at day 13 of incubation, equivalent to ca. 25 wk of gestation in human pregnancy, rescues early origins of cardiovascular dysfunction during hypoxic development. Melatonin may be a suitable antioxidant candidate for translation to human therapy to protect the fetal cardiovascular system in adverse pregnancy.

New genetic and physiological factors for excessive erythrocytosis and Chronic Mountain Sickness

In the last few years, genetic and functional studies have provided important insight on the pathophysiology of excessive erythrocytosis (EE), the main sign of Chronic Mountain Sickness (CMS). The recent finding of the association of the CMS phenotype with a single-nucleotide polymorphism (SNP) in the Sentrin-specific Protease 1 (SENP1) gene, and its differential expression pattern in Andean highlanders with and without CMS, has triggered large interest in high-altitude studies because of the potential role of its gene product in the control of erythropoiesis. The SENP1 gene encodes for a protease that regulates the function of hypoxia-relevant transcription factors such as Hypoxia-Inducible Factor (HIF) and GATA, and thus might have an erythropoietic regulatory role in CMS through the modulation of the expression of erythropoietin (Epo) or Epo receptors. The different physiological patterns in the Epo-EpoR system found among Andeans, even among highlanders with CMS, together with their different degrees of erythropoietic response, might indicate specific underlying genetic backgrounds, which in turn might reflect different levels of adaptation to lifelong high-altitude hypoxia. This minireview discusses recent genetic findings potentially underlying EE and CMS, and their possible physiological mechanisms in Andean highlanders.

Erythropoietin-mediated protection of insect brain neurons involves JAK and STAT but not PI3K transduction pathways

The cytokine erythropoietin (Epo) initiates adaptive cellular responses to both moderate environmental challenges and tissue damaging insults in various non-hematopoietic mammalian tissues including the nervous system. Neuroprotective and neuroregenerative functions of Epo in mammals are mediated through receptor-associated Janus kinase 2 and intracellular signaling cascades that modify the transcription of Epo-regulated genes. Signal transducers and activators of transcription (STAT) and phosphoinositol-3-kinase (PI3K) represent key components of two important Epo-induced transduction pathways. Our previous study on insects revealed neuroprotective and regenerative functions of recombinant human Epo (rhEpo) similar to those in mammalian nervous tissues. Here we demonstrate that rhEpo effectively rescues primary cultured locust brain neurons from apoptotic cell death induced by hypoxia or the chemical compound H-7. The Janus kinase inhibitor AG-490 and the STAT inhibitor sc-355797 abolished protective effects of rhEpo on locust brain neurons. In contrast, inhibition of PI3K with LY294002 had no effect on rhEpo-mediated neuroprotection. The results indicate that rhEpo mediates the protection of locust brain neurons through interference with apoptotic pathways by the activation of a Janus kinase-associated receptor and STAT transcription factor(s). The involvement of similar transduction pathways in mammals and insects for the mediation of neuroprotection and support of neural regeneration by Epo indicates that an Epo/Epo receptor-like signaling system with high structural and functional similarity exists in both groups of animals. Epo-like signaling involved in tissue protection appears to be an ancient beneficial function shared by vertebrates and invertebrates.

Intravitreal injection of soluble erythropoietin receptor exacerbates photoreceptor cell apoptosis in a rat model of retinal detachment

PURPOSE

To evaluate the effects of intravitreal injection of soluble erythropoietin (EPO) receptor (sEPOR) on photoreceptor cell apoptosis in an animal model of retinal detachment (RD).

METHODS

Various dosages of sEPOR (2, 20, or 200 ng) were injected into the vitreous cavities of normal rats. Three days after injection, retinal function was measured by flash electroretinography (ERG). On day 7, histopathology and retinal morphology were examined by light and transmission electron microscopy (TEM), respectively. Rat models of RD were successfully established by injection of 1.4% sodium hyaluronate into the subretinal space, followed by immediate injection of phosphate-buffered saline (PBS) or sEPOR into the vitreous cavity. On day 3, photoreceptor cell apoptosis was evaluated using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and caspase-3 activity assayed by Western blotting and immunofluorescence. Light microscopic examination of retinal histopathology was used to determine the thickness of the outer nuclear layer (ONL) 14 days after establishment of RD.

RESULTS

There were no significant differences in the latency and amplitude of maximal a, b and oscillatory potential (OP) wave responses by flash ERG before or 3 days after sEPOR injection (p > 0.05). Retinal tissues showed no obvious pathological changes by either light or transmission electron microscopy. Both Western blotting and immunofluorescence indicated consistent sEPOR enhanced caspase-3 activation aggravated apoptosis of photoreceptor cells in RD rat retinas. On day 14, RD ONLs were thinner, according to increasing dosages of sEPOR.

CONCLUSION

Intravitreal injection of sEPOR exacerbates photoreceptor cell apoptosis in RD models via activation of caspase-3.

Effects of supplemental erythropoietin on its receptor expression and signal transduction pathways in rat model of retinal detachment

PURPOSE

The aim of this study was to investigate the effects of supplemental erythropoietin (EPO) on its receptor (EPOR) and signal transduction pathways in rat model of retinal detachment (RD).

METHODS

To investigate the effect of EPO on EPOR expression in RD rats 100, 200 or 400 ng EPO was injected into the vitreous cavity immediately after RD model was induced. Western blot and immunohistochemistry analyses were performed to measure EPOR expression. To investigate the effect of EPO on signal transduction pathways in RD rats single dose of 400 ng EPO was injected into the vitreous cavity immediately after RD model was induced. The total and phosphorylated levels of JAK2, Akt, ERK-1/2, STAT5 and NF-κB were assessed by western blot.

RESULTS

Western blot analysis showed that, compared with the normal control group, EPOR expression in the neurosensory retina was significantly increased in experimental RD groups (P < 0.05), but the differences were not significant between experimental RD groups (P > 0.05). Immunohistochemical examination indicated that EPOR staining on retinas became strongly positive 3 days after RD, with no significant difference in staining intensities between the treatment groups. Phosphorylated levels of JAK2, Akt, ERK-1/2, STAT5, and NF-κB were enhanced 3 days after RD, but only JAK2, Akt, and ERK-1/2 phosphorylation was further enhanced by 400 ng EPO treatment (P < 0.05).

CONCLUSIONS

Supplementary EPO cannot affect EPOR expression in detached retina, but EPO may activate both PI-3K/Akt and MAPK/ERK-1/2 signal transduction pathways in RD model.

Safety and efficacy of intravitreal injection of recombinant erythropoietin for protection of photoreceptor cells in a rat model of retinal detachment

PURPOSE

To elucidate the safety and efficacy of exogenous erythropoietin (EPO) for the protection of photoreceptor cells in a rat model of retinal detachment (RD).

METHODS

Recombinant rat EPO (400 ng) was injected into the vitreous cavity of normal rats to observe the eye manifestations. Retinal function was assessed by flash electroretinograms. Histopathological examination of retinal tissue was performed at 14 days and 2 months after injection, respectively. To investigate the inhibitory effect of EPO on photoreceptor cell apoptosis in RD rats, 100, 200, or 400 ng EPO was injected into the vitreous cavity immediately after RD model establishment. Apoptosis of photoreceptor cells was determined at 3 days after injection. Caspase-3 activation was measured by western blot analysis and immunofluorescence, respectively, and the level of Bcl-X(L) expression was analyzed by western blot.

RESULTS

Intravitreal injection of EPO 400 ng into normal rats had no significant impact on retinal function, morphology, or structure. Apoptosis of retinal photoreceptor cells apparently increased after RD and was significantly reduced following EPO treatment. The thickness of the outer nuclear layer in the RD + 400 ng group was significantly thicker than that in other experimental RD groups both at 14 days and at 2 months after RD (P < 0.05). Western blot and immunofluorescence analyses showed decreased caspase-3 activation and increased Bcl-X(L) expression following EPO treatment.

CONCLUSION

Intravitreal injection of EPO 400 ng is safe, and EPO may suppress caspase-3 activation and enhance Bcl-X(L) expression, resulting in inhibition of apoptosis and protection of photoreceptor cells.

High glucose stimulates the expression of erythropoietin in rat glomerular epithelial cells

It has been reported that the levels of erythropoietin are associated with diabetes mellitus. Glomerular epithelial cells, located in the renal cortex, play an important role in the regulation of kidney function and hyperglycemia-induced cell loss of glomerular epithelial cells is implicated in the onset of diabetic nephropathy. This study investigated the effect of high glucose on erythropoietin and erythropoietin receptor expression in rat glomerular epithelial cells. We found that 25 mM D-glucose, but not mannitol or L-glucose, stimulated erythropoietin mRNA and protein expression in a time dependent manner (>4 h) in rat glomerular epithelial cells. In addition, 25 mM glucose, but not mannitol or L-glucose, also increased the phosphorylation of erythropoietin receptor, suggesting a role for erythropoietin receptor phosphorylation in erythropoietin synthesis. We conclude that high glucose stimulates erythropoietin production and erythropoietin receptor phosphorylation in rat glomerular epithelial cells.

Recombinant human erythropoietin treatment of chronic renal failure patients normalizes altered phenotype and proliferation of CD4-positive T lymphocytes

Patients with chronic renal failure (CRF) receive recombinant human erythropoietin (rhEPO) for the correction of anemia. However, rhEPO also has an immunomodulatory effect. Detailed changes of phenotype and function of CD4(+) T lymphocytes in CRF patients receiving rhEPO have not been reported yet; their study may bring insight into understanding of this immunomodulatory action of rhEPO. Two groups of CRF patients were included into the study: those treated; and those not receiving rhEPO. The expression of activation markers on CD4(+) lymphocytes was measured with flow cytometry, both ex vivo and in vitro. The kinetics of CD4(+) T lymphocytes proliferation was calculated using a dividing cells tracing method and numerical approach. Significantly higher percentages of CD4(+)CD95(+), CD4(+)HLA-DR(+) cells, and lower percentages of CD4(+)CD69(+) and CD4(+)CD28(+) cells were observed in both rhEPO-treated and untreated patients when compared with healthy controls. Changes in the proportions of CD4(+)CD28(+) and CD4(+)HLA-DR(+) subpopulations were dependent on the type of rhEPO, being more pronounced for rhEPObeta. CD4(+) lymphocytes from untreated patients exhibited decreased expression of CD28 and CD69 after stimulation in vitro, whereas the expression of these antigens on lymphocytes of rhEPO-treated patients was similar to that observed in healthy controls. Fewer CD4(+)CD28(+) T lymphocytes of untreated patients proliferated in vitro; these cells had longer G0-->G1 time, which negatively correlated with surface expression of CD28. Our study confirms that rhEPO treatment normalizes activation parameters of CD4(+) T lymphocytes and their proliferative capacity, which could explain earlier described immunomodulatory effects of rhEPO in patients suffering from CRF.

Neuroprotective role of erythropoietin by antiapoptosis in the retina

Erythropoietin (EPO) stimulates red blood cell production, in part by inhibiting apoptosis of the red blood cell precursors. The erythropoietic effects of EPO are circadian stage dependent. Retinal injury due to light occurs through oxidative mechanisms and is manifest by retinal and retinal pigment epithelium (RPE) cells apoptosis. The visual cycle might be circadian coordinated as a means of effectively protecting the retina from the detrimental effects of light-induced, oxygen-dependent, free radical-mediated damage, especially at the times of day when light is more intense. We show that the retinal expression of EPO and its receptor (EPOR), as well as subsequent Janus kinase 2 (Jak2) phosphorylations, are each tightly linked to a specific time after oxidative stress and in anticipation of daily light onset. This is consistent with physiological protection against daily light-induced, oxidatively mediated retinal apoptosis. In vitro, we verify that EPO protects RPE cells from light, hyperoxia, and hydrogen peroxide-induced retinal cell apoptosis, and that these stimuli increase EPO and EPOR expression in cultured RPE cells. Together, these data support the premise that EPO and its EPOR interactions represent an important retinal shield from physiologic and pathologic light-induced oxidative injury.

Expression Pattern of Erythropoietin and Erythropoietin Receptor in Experimental Model of Retinal Detachment

PURPOSE

Erythropoietin (EPO), known for its role in erythroid cell differentiation, has been suggested to have a neuroprotective effect on retinal neurons. The aim of the current study was to investigate the expression pattern of EPO and erythropoietin receptor (EPOR) in the detached retina of a rat model of retinal detachment (RD).

METHODS

Forty-eight albino Sprague-Dawley rats were randomized into normal control group (n = 6) and RD model group (n = 42). The rat RD model was established by slow injection of 1.4% sodium hyaluronate into the upper half of the subretinal space, in which the upper half of the neurosensory retina was detached from the underlying retinal pigment epithelium (RPE). The expression of EPO and EPOR mRNA/protein was determined at 1, 3, 6, 12, 24, 48, and 72 hr after sodium hyaluronate injection by semiquantitative RT-PCR and Western blot analysis, respectively. Meanwhile, the distributions of EPO and EPOR were examined by immunohistochemistry.

RESULTS

EPO and EPOR mRNA levels increased gradually after sodium hyaluronate injection and peaked 48 hr later. EPO mRNA level became significantly higher than that in the normal control group at 12 hr after injection, and EPOR mRNA level became significantly higher at 6 hr (p < 0.05). Moreover, the protein levels of EPO and EPOR presented a similar tendency to the mRNA level and became significantly higher than those in normal control group at 3 hr after injection (p < 0.05). Immunohistochemical results showed that both EPO and EPOR were strongly expressed all over the neurosensory retina 48 hr after injection, but EPOR was not found in the rod outer segment. Only weak expression of EPO and EPOR was noticed in the retina of normal control group.

CONCLUSIONS

The levels of EPO and EPOR in detached retina increase with the duration of retinal detachment and reach their peaks at 48 hr; most layers of detached neurosensory retina can express EPO and EPOR. It is indicated that the EPO/EPOR system might play an important role in protection of retinal neurons during RD; supplementation with exogenous EPO might promote the survival of retinal neurons.

Design and fabrication of 3D porous scaffolds to facilitate cell-based gene therapy

Biomaterials capable of efficient gene delivery by embedded cells provide a fundamental tool for the treatment of acquired or hereditary diseases. A major obstacle is maintaining adequate nutrient and oxygen diffusion to cells within the biomaterial. In this study, we combined the solid free-form fabrication and porogen leaching techniques to fabricate three-dimensional scaffolds, with bimodal pore size distribution, for cell-based gene delivery. The objective of this study was to design micro-/macroporous scaffolds to improve cell viability and drug delivery. Murine bone marrow-derived mesenchymal stromal cells (MSCs) genetically engineered to secrete erythropoietin (EPO) were seeded onto poly-L-lactide (PLLA) scaffolds with different microporosities. Over a period of 2 weeks in culture, an increase in cell proliferation and metabolic activity was observed with increasing scaffold microporosity. The concentration of EPO detected in supernatants also increased with increasing microporosity level. Our study shows that these constructs can promote cell viability and release of therapeutic proteins, and clearly demonstrates their capacity for a dual role as scaffolds for tissue regeneration and as delivery systems for soluble gene products.

Differentiation of the local structure around tryptophan 51 and 64 in recombinant human erythropoietin by tryptophan phosphorescence

Recombinant human erythropoietin is a 4-helix bundle, glycosylated cytokine containing three tryptophan residues at positions 51, 64 and 88 whose phosphorescence emission may represent a sensitive probe of the structure at multiple sites near or at the protein surface. This report characterizes the phosphorescence properties (spectral energy, thermal spectral relaxation and phosphorescence lifetime), from low temperature glasses to ambient temperature, of the native protein plus that of three single point mutation analogs where each Trp was replaced by Phe. The structural information inferred from the phosphorescence parameters was essentially in good agreement with the structure of the Escherichia coli-produced nonglycosylated protein determined by nuclear magnetic resonance (Cheetham et al., Nat Struct Biol [1998] 5:861). The results showed that the fluorescence and phosphorescence spectra of the native protein were entirely due to independent contributions of Trp51 and Trp64 and that Trp88 was quenched under all conditions. The phosphorescence emissions of Trp51 and Trp64 were differentiated by their unique spectra at 77 K with Trp64 exhibiting an unusually blueshifted spectrum likely due to the attractive interaction of Arg110 and Lys116 with the ground state dipole of Trp64. In the native protein the room temperature phosphorescence lifetime of Trp64 was relatively short with a time of 1.62 ms whereas the lifetime of Trp51 was five-fold longer. Characterization of the single point mutation analogs showed that each lifetime was composed of multiple components revealing the presence of multiple stable conformations of the protein at these surface sites.

A comparative study of stimulation of erythropoiesis during renal anemia with the preparation of antibodies against erythropoietin in ultralow doses and Recormon

We compared the stimulatory effects of a preparation of antibodies against erythropoietin in ultralow doses (Poetam) and recombinant erythropoietin (Recormon) on erythropoiesis that was suppressed by carboplatin. Both drugs possessed high erythropoiesis-stimulating activity, which was manifested in an increase in the number of erythrokaryocytes and erythroid precursors in hemopoietic tissue and count of erythrokaryocytes and reticulocytes in the peripheral blood during postcytostatic recovery. Recormon produced a rapid and short-term stimulatory effect on the erythron. The effect of Poetam developed slowly, but persisted for a longer time.

Deconvoluting lung evolution: from phenotypes to gene regulatory networks

Speakers in this symposium presented examples of respiratory regulation that broadly illustrate principles of evolution from whole organ to genes. The swim bladder and lungs of aquatic and terrestrial organisms arose independently from a common primordial "respiratory pharynx" but not from each other. Pathways of lung evolution are similar between crocodiles and birds but a low compliance of mammalian lung may have driven the development of the diaphragm to permit lung inflation during inspiration. To meet the high oxygen demands of flight, bird lungs have evolved separate gas exchange and pump components to achieve unidirectional ventilation and minimize dead space. The process of "screening" (removal of oxygen from inspired air prior to entering the terminal units) reduces effective alveolar oxygen tension and potentially explains why nonathletic large mammals possess greater pulmonary diffusing capacities than required by their oxygen consumption. The "primitive" central admixture of oxygenated and deoxygenated blood in the incompletely divided reptilian heart is actually co-regulated with other autonomic cardiopulmonary responses to provide flexible control of arterial oxygen tension independent of ventilation as well as a unique mechanism for adjusting metabolic rate. Some of the most ancient oxygen-sensing molecules, i.e., hypoxia-inducible factor-1alpha and erythropoietin, are up-regulated during mammalian lung development and growth under apparently normoxic conditions, suggesting functional evolution. Normal alveolarization requires pleiotropic growth factors acting via highly conserved cell-cell signal transduction, e.g., parathyroid hormone-related protein transducing at least partly through the Wingless/int pathway. The latter regulates morphogenesis from nematode to mammal. If there is commonality among these diverse respiratory processes, it is that all levels of organization, from molecular signaling to structure to function, co-evolve progressively, and optimize an existing gas-exchange framework.

Lack of effect of extracellular adenosine generation and signaling on renal erythropoietin secretion during hypoxia

Previous studies have yielded conflicting results as to whether extracellular adenosine generation and signaling contributes to hypoxia-induced increases in renal erythropoietin (EPO) secretion. In this study, we combined pharmacological and genetic approaches to elucidate a potential contribution of extracellular adenosine to renal EPO release in mice. To stimulate EPO secretion, we used murine carbon monoxide exposure (400 and 750 parts per million CO, 4 h), ambient hypoxia (8% oxygen, 4 h), or arterial hemodilution. Because the ecto-5-nucleotidase (CD73, conversion of AMP to adenosine) is considered the pacemaker of extracellular adenosine generation, we first tested the effect of blocking extracellular adenosine generation with the specific CD73-inhibitor adenosine 5'-(alpha,beta-methylene) diphosphate (APCP) or by gene-targeted deletion of cd73. These studies showed that neither APCP-treatment nor targeted deletion of cd73 resulted in changes of stimulated EPO mRNA or serum levels, although the increases of adenosine levels in the kidney following CO exposure were attenuated in mice with APCP treatment or in cd73(-/-) mice. Moreover, pharmacological studies using specific inhibitors of individual adenosine receptors (A1 AR, DPCPX; A 2A AR, DMPX; A 2B AR, PSB 1115; A3AR, MRS 1191) showed no effect on stimulated increases of EPO mRNA or serum levels. Finally, stimulated EPO secretion was not attenuated in gene-targeted mice lacking A1A(-/-, A2A AR-/-, A2BAR(-/-), or A3AR-/-. Together, these studies combine genetic and pharmacological in vivo evidence that increases of EPO secretion during limited oxygen availability are not affected by extracellular adenosine generation or signaling.

Up-regulated Endogenous Erythropoietin/Erythropoietin Receptor System and Exogenous Erythropoietin Rescue Retinal Ganglion Cells after Chronic Ocular Hypertension

AIMS

Recent studies have showed that erythropoietin (EPO) is a neuroprotectant for central nerve system neurons in addition to being a hematopoietic cytokine in response to hypoxia. In this study, we investigate the role of the EPO/EPO receptor (EPOR) system in the rat retina after ocular hypertension injury that mimics glaucoma.

METHODS

Elevated intraocular pressure was induced by laser coagulation of the episcleral and limbal veins. Expression of EPO and EPOR in the normal and glaucomous retinas was investigated by immunohistochemistry and Western blot. To examine the effects of endogenous EPO on the survival of retinal ganglion cells (RGCs) subjected to hypertensive injury, soluble EPOR was directly injected into the vitreous body. Recombinant human EPO was both intravitreally and systemically administrated to study the effect of exogenous EPO on the survival of RGCs after ocular hypertension injury.

RESULTS

Immunohistochemistry studies identified Müller cells as the main source of EPO in the normal retina. Expression of EPO and EPOR proteins was increased significantly 2 weeks after ocular hypertension. RGCs, amacrine and bipolar cells all demonstrated an increased expression of EPOR after ocular hypertension. Neutralization of endogenous EPO with soluble EPOR exacerbated ocular hypertensive injury, suggesting a role of the EPO/EPOR system in the survival of RGCs after injury. Similarly, topical and systemic administration of recombinant human EPO rescues RGCs after chronic ocular hypertension.

CONCLUSIONS

These results indicate that an endogenous EPO/EPOR system participates in intrinsic recovery mechanisms after retina injury and RGCs might be rescued by exogenous administration of EPO.

Systemically delivered Erythropoietin transiently enhances adult hippocampal neurogenesis

Erythropoietin is a primary regulator of erythropoiesis in the hematopoietic system. More recently erythropoietin has been shown to play a role in neurogenesis and provide neurotrophic support to injured CNS tissue. Here the effects of large systemic doses of erythropoietin on basal levels of adult hippocampal neurogenesis in mice were examined. A 7-day period of recombinant human erythropoietin (rhEPO) administration increased the number of bromodeoxyuridine [BrdU(+)] cells in the sub-granular zone (SGZ) by 30%. Analysis of cell phenotype revealed an increase in mitotically active doublecortin(+) neuronal progenitor cells and glial fibrillary acidic protein(+) SGZ radial astrocytes/stem cells but not mature S100beta(+) astrocytes. These effects appeared to be mediated, in part, by mitogen-activated protein kinase signaling and potentially regulated by suppressor of cytokine signaling-3. Hippocampal levels of phosphorylated extracellular signal-related kinase 42/44 and suppressor of cytokine signaling-3 were increased 2-6 h after a single systemic rhEPO injection. However, rhEPO had no observed effect on the long-term survival of new born cells in the SGZ, with similar numbers of BrdU(+) cells and BrdU(+)/NeuN(+) co-labeled cells after 4 weeks. Therefore, systemically delivered rhEPO transiently increased adult hippocampal neurogenesis without any apparent long-term effects.

De novo erythropoietin receptor (EPO-R) expression in human neoplastic glial cells decreases with grade of malignancy but is favourably associated with patient survival

The erythropoietin receptor (EPO-R) is mainly known as a regulator of erythropoiesis. However, recent studies revealed that the EPO-R is not exclusively expressed in haematopoietic tissues but also in various cancer cell types and normal tissue such as the central nervous system (CNS). EPO-R is up-regulated under hypoxia and is able to counteract the deleterious effects of hypoxia on tumour growth, metastasis and treatment resistance. Therefore, the EPO-EPO-R signalling pathway is considered as a possible target for tumour treatment. Here, we investigated brain tumour samples obtained from patients between 1993 and 2003 to study EPO-R expression in vivo. Tissue samples included 194 gliomas of different WHO grades, additionally 25 infiltration zone samples and 31 relapses of WHO grade IV glioblastomas as well as 23 normal CNS tissue specimens to address the in vivo situation. Immunohistochemistry of the tissue microarray samples revealed significantly higher levels of EPO-R expression in neoplastic glial cells compared with glial cells derived from normal brain. EPO-R expression showed a highly significant decrease from low- to high-grade gliomas. Age-stratified Kaplan-Meier analysis revealed longer survival for patients exhibiting high EPO-R status in high-grade gliomas. Our results show a grade-dependent EPO-R down-regulation and might contribute to the understanding of high-grade glioma resistance to radio- and chemotherapy as both were shown to be improved by a well functioning EPO-EPO-R pathway in previous studies. Further studies are needed to investigate to what extent the decreased mortality in age-stratified patient groups with high EPO-R levels reflects a direct beneficial role of EPO-R expression.

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).

Erythropoietin attenuates the development of experimental autoimmune myocarditis

OBJECTIVE

Erythropoietin (EPO) has been shown to not only have cardioprotective effects but also attenuate autoimmune diseases. In the present study, we investigated the effect of EPO on cardiac inflammation and function, inflammatory cell infiltration, and cytokine expression in a rat model of experimental autoimmune myocarditis (EAM).

METHODS AND RESULTS

Male Lewis rats (6-8 weeks old) were immunized on day 0 with porcine cardiac myosin to establish EAM. The rats were subcutaneously administered either vehicle (saline) or human recombinant EPO (6,000 U/kg, 3 days/week) from day 0 to 20, and they were evaluated on day 21. In the EPO group, the inflammation area and heart weight/body weight ratio were significantly attenuated as compared with those in the vehicle group. Blood pressure and cardiac function were also improved in the EPO group. Immunohistochemistry revealed that EPO decreased the infiltration of macrophages and CD4 T cells, and degranulated mast cells in the myocardium. Real-time RT-PCR analysis demonstrated that inflammatory cytokine expression in the myocardium and lymphocytes was suppressed in the EPO group. However, in vitro experiments showed that EPO had no effect on antigen-induced proliferation and cytokine expression in lymphocytes.

CONCLUSION

EPO attenuates inflammatory cell infiltration and cytokine expression, and it improves cardiac function and reduces cardiac inflammation in EAM. This beneficial effect of EPO is unlikely to arise from a direct anti-inflammatory action on lymphocytes. These findings suggest the therapeutic potential of EPO for the treatment of myocarditis.

Biophysical comparability of the same protein from different manufacturers: a case study using Epoetin alfa from Epogen and Eprex

This study focuses on the development and application of biophysical methodology to characterize conformations of Epogen and Eprex, the injectable formulations of recombinant human Epoetin alfa produced by different manufacturers and commonly used for the treatment of renal anemia. In these studies Eprex, from prefilled syringes, and Epogen bulk product formulated in a buffer similar to the Eprex formulation, were purified by anion-exchange chromatography. Analytical ultracentrifugation studies of the purified main peak from each sample demonstrated that Epogen contains a single component with an s value of 2.51 while Eprex contains a single component with the same molecular weight but with an s value of 2.44 suggesting a slight difference in hydrodynamic structure. The degree of alpha-helicity was compared by far-UV circular dichroism and shown to contain slight differences. Intrinsic tryptophan fluorescence and near-UV circular dichroism were assessed and demonstrated additional differences between the proteins. Finally, the global stability of the proteins was monitored using thermal unfolding monitored by far-UV circular dichroism. The Epoetin alfa of Epogen demonstrated complete reversibility while the Epoetin alfa purified from Eprex demonstrated only 80%-85% thermal reversibility when heated to 100 degrees C. Together the data indicate that the proteins are not structurally identical.

Inverse relationship between serum erythropoietin and blood lead concentrations in Kathmandu tricycle taxi drivers

OBJECTIVE

Kathmandu tricycle taxi drivers, whose environmental lead (Pb) exposure is ascribable mainly to vehicular exhaust, were studied to examine a dose-response relationship between blood Pb (Pb-B) and serum erythropoietin (sEPO) concentrations.

METHODS

Subjects were 27 drivers and 9 non-drivers. They were non-anemic healthy men with normal renal function. Pb-B was measured by an atomic absorption spectrometer with a graphite furnace, and sEPO was determined with a sandwich-type enzyme-linked immunosorbent assay.

RESULTS

sEPO levels in drivers were lower than those of non-drivers, while Pb-B levels in drivers were higher than those of non-drivers. There was an inverse relationship between Pb-B and sEPO.

CONCLUSIONS

The data suggest that Pb inhibits renal EPO production in a dose-dependent manner in persons with subclinical Pb toxicity. sEPO may serve as an early biochemical marker of subclinical Pb toxicity.

Role of Renal Nerves and Salt Intake on Erythropoietin Secretion in Rats following Carbon Monoxide Exposure

Because the data from the literature contain conflicting results regarding the role of renal nerves and angiotensin II in hypoxia-induced erythropoietin (EPO) secretion, we evaluated the effect of renal nerves and salt intake in rats on EPO secretion stimulated by carbon monoxide (CO). Serum levels and renal mRNA content of EPO were similarly elevated by exposure to different CO concentrations in a dose-dependent manner in rats with bilateral renal denervation (DNX) and in sham-denervated controls (INN). However, at 600 ppm CO, serum concentrations and mRNA of EPO were significantly higher in DNX compared with INN rats (p < 0.05). This increase of EPO secretion in DNX rats could be blocked by administration of neuropeptide Y (NPY) (p < 0.05), whereas the NPY receptor antagonist did not enhance EPO secretion in INN rats after CO exposure. Agonists and antagonists of beta-adrenergic receptors had no effect on EPO secretion. High-salt (HS) diet reduced EPO secretory response at 600 ppm CO by 55% compared with INN rats on normal salt diet (p < 0.01). In addition, DNX increased EPO secretion in rats on low-salt and HS diet, whereas plasma renin activity did not correlate with EPO levels under these experimental conditions. In summary, our data suggest that renal nerves contribute to the half-maximal EPO secretory response to CO exposure, possibly via NPY receptors.

Pharmacological approaches to repair the injured spinal cord

Acute traumatic spinal cord injury (SCI) results in a devastating loss of neurological function below the level of injury and adversely affects multiple systems within the body. The pathobiology of SCI involves a primary mechanical insult to the spinal cord and activation of a delayed secondary cascade of events, which ultimately causes progressive degeneration of the spinal cord. Whereas cell death from the mechanical injury is predominated by necrosis, secondary injury events trigger a continuum of necrotic and apoptotic cell death mechanisms. These secondary events include vascular abnormalities, ischemia-reperfusion, glutamate excitotoxicity and disturbances in ionic homeostasis, oxidative cell injury, and a robust inflammatory response. No gold standard therapy for SCI has been established, although clinical trials with methylprednisolone (NASCIS II and III) and GM-1 ganglioside (Maryland and Sygen) have demonstrated modest, albeit potentially important therapeutic benefits. In light of the overwhelming impact of SCI on the individual, other therapeutic interventions are urgently needed. A number of promising pharmacological therapies are currently under investigation for neuroprotective abilities in animal models of SCI. These include the sodium (Na+) channel blocker riluzole, the tetracycline derivative minocycline, the fusogen copolymer polyethylene glycol (PEG), and the tissue-protective hormone erythropoietin (EPO). Moreover, clinical trials investigating the putative neuroprotective and neuroregenerative properties ascribed to the Rho pathway antagonist, Cethrin (BioAxone Therapeutic, Inc.), and implantation of activated autologous macrophages (ProCord; Proneuron Biotechnologies) in patients with thoracic and cervical SCI are now underway. We anticipate that these studies will harken an era of renewed interest in translational clinical trials. Ultimately, due to the multi-factorial pathophysiology of traumatic SCI, effective therapies will require combined approaches.

Emerging therapies in multiple sclerosis

Multiple sclerosis (MS) is the most common neurological cause of disability in young people. The disease-modifying treatments, IFN-beta and glatiramer acetate, have been widely available over the last decade and have shown a beneficial effect on relapse rate and magnetic resonance imaging parameters of disease activity; however, their effect on disease progression and disability is modest. Therefore, the search for alternative treatment strategies continues. As understanding of the heterogeneous pathophysiology of MS has increased, emphasis has shifted to more selective therapy that targets components of the inflammatory cascade and the promotion of remyelination and neuroprotection. These agents target the blood-brain barrier, systemic immune dysfunction, local inflammation and neurodegeneration. Combination therapies are being investigated for patients who fail first-line treatments. Many new drugs are being developed and tested that address these issues with the aim of finding a more effective and convenient therapy. These include humanized monoclonal antibodies such as daclizumab (IL-2 antagonist), oral immunomodulators such as sirolimus and statins and neuroprotective agents such as NMDA antagonists and Na+-channel blockers. Many of the treatments discussed in this review are still at early stages of development, but provide exciting potential treatment options; others have proved disappointing in larger extended-phase studies.

Novel tissue remodelling roles for human recombinant erythropoietin

rHuEPO (recombinant human erythropoietin) is a haemopoietic growth factor and a primary regulator of erythropoiesis that is used for the treatment of chronic anaemia associated with RA (rheumatoid arthritis). Erythropoietin also appears to modulate a broad array of cellular processes, including progenitor stem-cell development, cellular integrity, angiogenesis and oxidative damage. These diverse activities suggest the exciting possibility of multiple roles for rHuEPO therapy in a variety of disorders other than RA, including cerebral ischaemia, myocardial infarction, chronic congestive heart failure and cancer. Thus it appears that rHuEPO may be a pleiotropic agent, capable of influencing tissue remodelling independently of its established erythropoietic role. Whereas these effects may be largely beneficial, dose-related side effects could have implications for the safe therapeutic use of rHuEPO and its illegal use as a performance-enhancing agent in endurance sports.

Erythropoietin treatment improves neurological functional recovery in EAE mice

Erythropoietin (EPO), originally recognized for its central role in erythropoiesis, has been shown to improve neurological outcome after stroke. Here, we investigated the treatment of experimental autoimmune encephalomyelitis (EAE) in mice with EPO. Mice were treated with recombinant human EPO (rhEPO) upon onset of paresis. Neurological functional tests were scored daily by grading of clinical signs (score 0-5). Hematoxylin and eosin (HE) staining of cerebral tissue was performed to detect inflammatory infiltrates. Double staining for Luxol fast blue and Bielshowsky was used to demonstrate myelin and axons, respectively. Immunohistochemistry was performed to measure the expression of bromodeoxyuridine (BrdU, a marker for cell proliferation), NG2 (a marker for oligodendrocyte progenitor cells) and brain-derived neurotrophic factor (BDNF). Treatment with rhEPO significantly improved neurological functional recovery, reduced inflammatory infiltrates and demyelination, and increased oligodendrocyte progenitor cell proliferation and BDNF+ cells compared to the EAE controls. These data indicate that rhEPO treatment improved functional recovery after EAE in mice, possibly, via stimulating oligodendrogenesis, downregulating proinflammatory infiltrates and by elevating BDNF expression.

Erythropoietin on a tightrope: balancing neuronal and vascular protection between intrinsic and extrinsic pathways

Enthusiasm for erythropoietin (EPO) as a broad cytoprotective agent continues to increase at an almost exponential rate. The premise that EPO was required only for erythropoiesis was eventually shed by recent work demonstrating the existence of EPO and its receptor in other organs and tissues outside of the liver and the kidney, such as the brain and heart. As a result, EPO has been identified as a possible candidate in the formulation of therapeutic strategies for both cardiac and nervous system diseases. EPO has been shown to mediate an array of vital cellular functions that involve progenitor stem cell development, cellular protection, angiogenesis, DNA repair, and cellular longevity. An important requirement to achieve the goal of preventing or even reducing cellular injury by any cytoprotective agent is the ability to uncover the cellular pathways that ultimately drive a cell to its demise. We present for consideration several critical cellular pathways modulated by EPO that involve Janus kinase 2 (Jak2), the serine-threonine kinase Akt, forkhead transcription factors, glycogen synthase kinase-3beta (GSK-3beta), cellular calcium, protein kinase C, caspases, as well as the control of inflammatory microglial activation. As we continue to gain new insight into these pathways, EPO should emerge as a critical agent for the development, maturation, and survival of cells throughout the body.

Hypoxia-induced Synthesis of Hemoglobin in the Crustacean Daphnia magna Is Hypoxia-inducible Factor-dependent

Of the four known globin genes that exist in the fresh-water crustacean Daphnia magna, several are individually induced by hypoxia, lending pale normoxic animals a visible red color when challenged by oxygen deprivation. The promoter regions of the Daphnia globin genes each contain numerous hypoxia response elements (HREs) as potential binding sites for hypoxia-inducible factors (HIFs). Daphnia HIF, bound to human HRE sequences, was detected in extracts from hypoxic (red), but not normoxic (pale), animals. Taking advantage of the phylogenetically conserved HIF/HRE recognition, we employed heterologous transfections of HIF-expressing human and Drosophila cells to model HIF signaling in Daphnia. These experiments revealed that three functional HREs within the promoter of the D. magna globin-2 gene cooperate for maximal hypoxic induction of a downstream luciferase reporter gene. Two of these three cis-elements, at promoter positions -258 and -107, are able to specifically bind human, Drosophila, or Daphnia HIF complexes in vitro. The same two sites are also necessary for maximal induction of reporter transcription under low oxygen tension in the presence of either endogenous human or overexpressed Drosophila HIF proteins. The third motif of the globin-2 gene promoter, a CACGTG palindrome at position -146, functions as a docking site for an unknown constitutive transcription factor. In human cells, this -146 complex interferes with HIF occupancy at the adjacent -107 HRE and thus controls the extent of HIF-mediated hypoxic activation of the downstream target.

Nucleotide sequence of equine erythropoietin and characterization of region-specific antibodies

OBJECTIVE

To determine the full-length complementary DNA (cDNA) sequence of equine erythropoietin (EPO) and to develop region-specific antibodies to differentiate equine EPO (eEPO) and human EPO (hEPO).

SAMPLE POPULATION

RNA and lysate extracted from renal tissues of an adult Thoroughbred.

PROCEDURE

Full-length cDNA was determined by use of a reverse transcriptase-polymerase chain reaction assay and a rapid amplification of cDNA ends method. The deduced amino acid sequence was compared with sequences of EPO reported for other species. Furthermore, 4 synthetic peptides were designed in 2 distinctive parts of the eEPO and hEPO amino acid sequences to obtain antibodies specific for eEPO and hEPO. Specificity of the antibodies was tested against supernatant of homogenized equine kidney and recombinant hEPO (rhEPO) by use of western immunoblotting techniques.

RESULTS

Analysis of the 1,181 bp in the nucleotide sequence revealed that eEPO was a residue of 192 amino acids. Similarity of eEPO with amino acid sequences of EPO from other species was 81.0% to 90.6%. Antibodies were specifically recognized by eEPO or rhEPO molecules. Anti-hEPO (161 to 165) antibody specifically recognized rhEPO. In contrast, anti-eEPO (133 to 144) antibody reacted with the equine kidney lysate.

CONCLUSIONS AND CLINICAL RELEVANCE

We determined the cDNA and amino acid sequence of eEPO and developed region-specific antibodies that specifically recognized eEPO or rhEPO. These antibodies may be useful in distinguishing rhEPO from eEPO in a test to detect the misuse of rhEPO in racehorses.

Drugs for increasing oxygen and their potential use in doping: a review

Blood oxygenation is a fundamental factor in optimising muscular activity. Enhancement of oxygen delivery to tissues is associated with a substantial improvement in athletic performance, particularly in endurance sports. Progress in medical research has led to the identification of new chemicals for the treatment of severe anaemia. Effective and promising molecules have been created and sometimes used for doping purposes. The aim of this review is to present methods, and drugs, known to be (or that might be) used by athletes to increase oxygen transport in an attempt to improve endurance capacity. These methods and drugs include: (i) blood transfusion; (ii) endogenous stimulation of red blood cell production at altitude, or using hypoxic rooms, erythropoietins (EPOs), EPO gene therapy or EPO mimetics; (iii) allosteric effectors of haemoglobin; and (iv) blood substitutes such as modified haemoglobin solutions and perfluorochemicals. Often, new chemicals are used before safety tests have been completed and athletes are taking great health risks. Such new chemicals have also created the need for new instrumental strategies in doping control laboratories, but not all of these chemicals are detectable. Further progress in analytical research is necessary.

Recombinant human erythropoietin protects the myocardium from ischemia-reperfusion injury and promotes beneficial remodeling

Erythropoietin (EPO), originally identified for its critical hormonal role in promoting erythrocyte survival and differentiation, is a member of the large and diverse cytokine superfamily. Recent studies have identified multiple paracrineautocrine functions of EPO that coordinate local responses to injury by maintaining vascular autoregulation and attenuating both primary (apoptotic) and secondary (inflammatory) causes of cell death. Experimental evidence also supports a role for EPO in repair and regeneration after brain and spinal cord injury, including the recruitment of stem cells into the region of damage. Tissue expression of the EPO receptor is widespread, especially during development, and includes the heart. However, it is currently unknown as to whether EPO plays a physiological function in adult myocardial tissue. We have assessed the potential protective role of EPO in vitro with adult rat cardiomyocytes, and in vivo in a rat model of myocardial infarction with reperfusion. The results show that EPO markedly prevents the apoptosis of cultured adult rat myocardiocytes subjected to 28 h of hypoxia (approximately 3% normal oxygen). Additional studies employing a rat model of coronary ischemia-reperfusion showed that the administration of recombinant human EPO (5,000 units/kg of body weight; i.p. daily for 7 days) reduces cardiomyocyte loss by approximately 50%, an extent sufficient to normalize hemodynamic function within 1 week after reperfusion. These observations not only suggest a potential therapeutic role for recombinant human EPO in the treatment of myocardial ischemia and infarction by preventing apoptosis and attenuating postinfarct deterioration in hemodynamic function, but also predict that EPO is likely a tissue-protective cytokine in other organs as well.

Angiogenesis and plasticity: role of erythropoietin in vascular systems

One of the principal functions of erythropoietin (EPO) is to stimulate the maturation of erythroid precursors. Yet EPO has recently been shown to modulate a host of cellular signal transduction pathways in pluripotent stem cells to perform multiple functions other than erythropoiesis. The production of EPO is tightly modulated by the loss of oxygen and the hypoxia-inducible factor 1. Once generated, EPO becomes a robust stimulus which regulates endothelial cell proliferation and migration as well as erythropoiesis and vascular resistance. Further downstream in the signal transduction cascade, EPO engages diverse cellular pathways--such as those involving Janus kinase 2, signal transducers and activators of transcription (STATs), mitogen-activated protein kinases (MAPKs), Bcl-x(L), protein kinase B, protein kinase C, and cysteine proteases--to provide "plasticity" to vascular systems through highly conserved mechanisms. EPO also has recently been demonstrated to inhibit the induction of apoptosis through two distinct components that involve the maintenance of the integrity of genomic DNA and the preservation of cellular membrane asymmetry. Recognition of the multipotential attributes of EPO for vascular systems may further the progress of the development of therapeutic strategies to delay the onset of degenerative diseases.

Recombinant human erythropoietin in the treatment of head and neck tumour anaemia

At the time of first diagnosis, patients with squamous cell carcinoma in the head and neck are often in the advanced stage of their disease, therefore surgery is not a viable option for treatment. These patients also present frequently a high grade of anaemia as a result of either the malignant process itself or of the following therapy. The incidence of anaemia and the need for transfusion depends on several factors, such as the type and intensity of radiotherapy and radiochemotherapy. Multimode therapeutic concepts such as radio-chemotherapy are being applied with increasing frequency, resulting in an ever increasing need for transfusion with great effects on the patient's quality of life. Even more important to tumour patients is the role of the haemaglobin (Hb) value as a prognostic factor for survival and/or local tumour control. A large number of studies show that recombinant human erythropoietin (r-HuEPO) is effective in the treatment of tumour-induced anaemia and prevention and correction of chemotherapy and radiotherapy-induced anaemia. The simultaneous application of r-HuEPO with chemotherapy can prevent patients with head and neck tumours from developing anaemia or can reduce the extent of the anaemia and the need for transfusion. Comparable effects were observed both in patients undergoing platinum-based and non-platinum-based chemotherapy. The direct correlation between anaemia, tumour hypoxia and poor response to radio and/or chemotherapy has been clinically proven. Recombinant human erythropoietin administration improves the therapeutic outcome and the patients' prognosis.

Anemia with erythropoietin deficiency occurs early in diabetic nephropathy

OBJECTIVE

The normochromic normocytic anemia of erythropoietin (EPO) deficiency is recognized in advanced renal failure but not in early renal disease. The aim of this study was to determine whether anemia with EPO deficiency is found in type 1 diabetic patients with diabetic nephropathy in the absence of advanced renal failure and to compare them with patients with nondiabetic renal disease of similar severity.

RESEARCH DESIGN AND METHODS

A total of 27 type 1 diabetic patients with diabetic nephropathy (DN), defined as having persistent proteinuria (mean 1,086 mg/day [CI 120-5,1901), a serum creatinine < or = 180 micromol/l, and retinopathy, were compared with 26 nondiabetic patients with glomerulonephritis (GN) and persistent proteinuria (1,874 mg/day [349-5,005]). The Hb concentration, red cell indexes, and serum EPO levels were measured, and other causes for the anemia were excluded. The EPO values were compared with a normal reference range obtained from nondiabetic patients with a microcytic anemia. The DN patients were tested for signs of diabetic peripheral and autonomic neuropathy.

RESULTS

We found that 13 of the 27 DN patients were anemic (Hb 10.6 +/- 0.9 g/dl) in marked contrast to none of the GN patients (Hb 13.7 +/- 1.4 g/dl, P < 0.005). In the DN group, serum EPO concentrations failed to increase in response to anemia compared with the response seen in patients with microcytic anemia. Thus, the anemia of the DN group was associated with EPO deficiency. The anemic DN patients showed evidence of more severe proteinuria and diabetic neuropathy than the nonanemic DN patients.

CONCLUSIONS

Anemia associated with EPO deficiency can occur early in DN before the onset of advanced renal failure, but does not normally occur in nondiabetic renal disease of similar severity. The pathogenesis requires elucidation.

Correlation between erythropoietin and lactate in humans during altitude exposure

The plasma concentrations of both immunoreactive erythropoietin (EPO) and lactate were determined in four healthy untrained subjects at sea level and on the 2nd or 3rd day at altitudes (1,300 and 3,500 m). The mean plasma EPO (18.8 +/- 1.6 mU/ml at sea level) increased significantly on the 3rd day at 1,300 m (25.5 +/- 2.0 mU/ml, p < 0. 05) and showed an almost three-fold increase on the 2nd day at 3,500 m (53.5 +/- 3.7 mU/ml, p < 0.001). Likewise, the mean plasma lactate at 3,500 m (3.98 +/- 0.27 mmol/l) was 3.6 times as high as that at sea level (1.11 +/- 0.05 mmol/l) (p < 0.001). The plasma EPO concentrations were found to correlate well with the lactate concentrations at sea level and altitudes (r = 0.86, p < 0.01). These results are consistent with the well-known EPO/lactate response to altitudes and suggest that the circulating EPO concentration as well as blood lactate concentration can be used as an index of anaerobic condition.

Angiotensin II increases erythropoietin production in healthy human volunteers

BACKGROUND

A number of animal studies and our own clinical trials point towards a possible influence of the renin-angiotensin-system (RAS) on erythropoietin (EPO) production. In this study we investigated the role of angiotensin II in the regulation of EPO production in humans.

METHODS

After a hemorrhage of 750 ml as a basic physiological stimulus 72 healthy male volunteers received in a parallel design either placebo (physiologic electrolyte solution) for 6 h, angiotensin II i.v. for 6 h (1-3 microgram min-1, sufficient to increase systolic blood pressure by 20 mmHg), the selective AT1-receptor antagonist losartan, the ACE-inhibitor captopril, angiotensin II + losartan, or angiotensin II + captopril.

RESULTS

Administration of angiotensin II alone and in combination with captopril resulted in a significantly higher Cmax EPO (67% higher vs. placebo, P < 0.05) and AUCEPO (0-24h) (40% higher vs. placebo, P < 0.05). In the groups receiving losartan or captopril alone or the combination of angiotensin II + losartan no significant difference of Cmax EPO and AUCEPO(0-24h) compared to placebo could be detected.

CONCLUSIONS

This study shows in a model of controlled, basic physiological stimulation of renal EPO production that angiotensin II is able to increase EPO levels in humans. This effect of angiotensin II can be blocked by the specific AT1-receptor antagonist losartan but not by the ACE-inhibitor captopril. The result may be interpreted as a hint that one signal for the control of EPO production in humans may be mediated by angiotensin II (AT1)-receptors.

Evidence against a major role for Ca2+ in hypoxia-induced gene expression in human hepatoma cells (Hep3B)

1. The human hepatoma cell line Hep3B is a widely used model for studies of hypoxia-related gene expression. Cytosolic free calcium concentration ([Ca2+]i) has been implicated in cellular oxygen-sensing processes. We investigated whether calcium ions have a significant impact on the production of erythropoietin (EPO) and vascular endothelial growth factor (VEGF). 2. We found that the calcium ionophore ionomycin induced a rapid and sustained increase of [Ca2+]i while thapsigargin, an inhibitor of endoplasmic reticulum calcium ATPase, only caused a 20 % elevation of [Ca2+]i within 10 min after application. However, the calcium content of intracellular stores was considerably reduced by thapsigargin after an incubation period of 24 h. 3. Variations in [Ca2+]o did not result in altered EPO or VEGF secretion rates. Ionomycin decreased EPO production while the lowering of VEGF production was not statistically significant. In the presence of extracellular Ca2+ the membrane permeant calcium chelator BAPTA-AM stimulated the production of EPO (P < 0.05) but not of VEGF while EGTA-AM, a closely related agent, affected neither EPO nor VEGF formation under these conditions. Incubation with thapsigargin resulted in decreased EPO synthesis (P < 0.05) but stimulated VEGF secretion (P < 0.05). 4. In the absence of extracellular calcium, EGTA-AM led to an accumulation of hypoxia-inducible factor-1alpha (HIF-1alpha). This treatment significantly stimulated VEGF synthesis but also decreased EPO secretion (P < 0.05). 5. Our data suggest that the calcium transient and the cytosolic Ca2+ concentration do not play a key role in hypoxia-induced EPO and VEGF production in Hep3B cells.

Erythropoietin production in anemia associated with experimental cancer

Serum erythropoietin (EPO) concentrations reportedly are depressed in patients with chronic disorders such as cancer, rheumatoid arthritis, and acquired immunodeficiency syndrome. We evaluated serum EPO levels in mice with tumors and found that the EPO response was appropriate for the associated anemia during the major part of the disease process. The levels of the hormone increased as the anemia worsened in association with progression of the disease. The increased EPO levels were comparable to those of controls with a similar degree of experimentally induced anemia. Only during the terminal stages of cancer, when the animals were severely cachectic, were serum EPO concentrations lower than in controls with a similar degree of anemia. These findings suggest that a blunted EPO response in experimental cancer occurs only in association with advanced disease.