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      A Role for Heme Oxygenase-1 in the Antioxidant and Antiapoptotic Effects of Erythropoietin: The Start of a Good News/Bad News Story?

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          Abstract

          Erythropoietin (EPO) is the major regulator of erythropoiesis. EPO’s actions have been shown to be antiapoptotic and dependent on JAK2 signaling and Akt phosphorylation. These effects serve as link between EPO and heme oxygenase-1 (HO-1). HO-1 is an inducible enzyme with potent antioxidant and antiapoptotic activities which are regulated by Akt signaling. EPO’s ability to alter cellular systems that involve apoptosis and oxidants suggests that EPO treatments are likely to have multiple and different effects which may start a good news/bad news story. Recombinant human EPO is the recognized treatment of choice to address anemia and to stimulate erythropoiesis in chronic renal failure patients, through its antiapoptotic action which likely involves HO-1. On the other hand, EPO treatment to address anemia in cancer patients, while providing significant improvements in cancer patients’ quality of life, its effects on survival are equivocal, likely due to its linkage with HO-1. Two clinical trials of EPO in patients with solid tumors have, in fact, shown specific negative effects on survival. However, EPO’s effect on tumor growth and survival is not uniformily pro growth and pro survival, as EPO may act synergistically with chemotherapy to induce apoptosis. Finally, compounds have been synthesized that do not trigger EPO receptor and thus may allow experimental distinction and, therefore, at least potentially affect at the clinical level the tissue-protective effects of EPO (e.g., antiapoptosis) without provoking its other potentially detrimental effects.

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          Most cited references 33

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          Number and migratory activity of circulating endothelial progenitor cells inversely correlate with risk factors for coronary artery disease.

          Recent studies provide increasing evidence that postnatal neovascularization involves bone marrow-derived circulating endothelial progenitor cells (EPCs). The regulation of EPCs in patients with coronary artery disease (CAD) is unclear at present. Therefore, we determined the number and functional activity of EPCs in 45 patients with CAD and 15 healthy volunteers. The numbers of isolated EPCs and circulating CD34/kinase insert domain receptor (KDR)-positive precursor cells were significantly reduced in patients with CAD by approximately 40% and 48%, respectively. To determine the influence of atherosclerotic risk factors, a risk factor score including age, sex, hypertension, diabetes, smoking, positive family history of CAD, and LDL cholesterol levels was used. The number of risk factors was significantly correlated with a reduction of EPC levels (R=-0.394, P=0.002) and CD34-/KDR-positive cells (R=-0.537, P<0.001). Analysis of the individual risk factors demonstrated that smokers had significantly reduced levels of EPCs (P<0.001) and CD34-/KDR-positive cells (P=0.003). Moreover, a positive family history of CAD was associated with reduced CD34-/KDR-positive cells (P=0.011). Most importantly, EPCs isolated from patients with CAD also revealed an impaired migratory response, which was inversely correlated with the number of risk factors (R=-0.484, P=0.002). By multivariate analysis, hypertension was identified as a major independent predictor for impaired EPC migration (P=0.043). The present study demonstrates that patients with CAD revealed reduced levels and functional impairment of EPCs, which correlated with risk factors for CAD. Given the important role of EPCs for neovascularization of ischemic tissue, the decrease of EPC numbers and activity may contribute to impaired vascularization in patients with CAD. The full text of this article is available at http://www.circresaha.org.
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            Erythropoietin to treat head and neck cancer patients with anaemia undergoing radiotherapy: randomised, double-blind, placebo-controlled trial.

            Anaemia is associated with poor cancer control, particularly in patients undergoing radiotherapy. We investigated whether anaemia correction with epoetin beta could improve outcome of curative radiotherapy among patients with head and neck cancer. We did a multicentre, double-blind, randomised, placebo-controlled trial in 351 patients (haemoglobin <120 g/L in women or <130 g/L in men) with carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx. Patients received curative radiotherapy at 60 Gy for completely (R0) and histologically incomplete (R1) resected disease, or 70 Gy for macroscopically incompletely resected (R2) advanced disease (T3, T4, or nodal involvement) or for primary definitive treatment. All patients were assigned to subcutaneous placebo (n=171) or epoetin beta 300 IU/kg (n=180) three times weekly, from 10-14 days before and continuing throughout radiotherapy. The primary endpoint was locoregional progression-free survival. We assessed also time to locoregional progression and survival. Analysis was by intention to treat. 148 (82%) patients given epoetin beta achieved haemoglobin concentrations higher than 140 g/L (women) or 150 g/L (men) compared with 26 (15%) given placebo. However, locoregional progression-free survival was poorer with epoetin beta than with placebo (adjusted relative risk 1.62 [95% CI 1.22-2.14]; p=0.0008). For locoregional progression the relative risk was 1.69 (1.16-2.47, p=0.007) and for survival was 1.39 (1.05-1.84, p=0.02). Epoetin beta corrects anaemia but does not improve cancer control or survival. Disease control might even be impaired. Patients receiving curative cancer treatment and given erythropoietin should be studied in carefully controlled trials.
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              Derivatives of erythropoietin that are tissue protective but not erythropoietic.

              Erythropoietin (EPO) is both hematopoietic and tissue protective, putatively through interaction with different receptors. We generated receptor subtype-selective ligands allowing the separation of EPO's bioactivities at the cellular level and in animals. Carbamylated EPO (CEPO) or certain EPO mutants did not bind to the classical EPO receptor (EPOR) and did not show any hematopoietic activity in human cell signaling assays or upon chronic dosing in different animal species. Nevertheless, CEPO and various nonhematopoietic mutants were cytoprotective in vitro and conferred neuroprotection against stroke, spinal cord compression, diabetic neuropathy, and experimental autoimmune encephalomyelitis at a potency and efficacy comparable to EPO.
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                Author and article information

                Journal
                NEP
                Nephron Physiol
                10.1159/issn.1660-2137
                Nephron Physiology
                S. Karger AG
                1660-2137
                2006
                June 2006
                22 June 2006
                : 103
                : 3
                : 107-111
                Affiliations
                Departments of aClinical and Experimental Medicine, Clinica Medica 4, and bMedical and Surgical Sciences, Nephrology, University of Padova, Padova, Italy; cDepartment of Nutrition, University of California, Davis, Calif., USA
                Article
                92213 Nephron Physiol 2006;103:107–111
                10.1159/000092213
                16554668
                © 2006 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                References: 45, Pages: 5
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/92213
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