Cellular protection by erythropoietin: new therapeutic implications?

Adequacy of an Altitude Fitness Program (Living and Training) plus Intermittent Exposure to Hypoxia for Improving Hematological Biomarkers and Sports Performance of Elite Athletes: A Single-Blind Randomized Clinical Trial

Athletes incorporate altitude training programs into their conventional training to improve their performance. The purpose of this study was to determine the effects of an 8-week altitude training program that was supplemented with intermittent hypoxic training (IHE) on the blood biomarkers, sports performance, and safety profiles of elite athletes. In a single-blind randomized clinical trial that followed the CONSORT recommendations, 24 male athletes were randomized to an IHE group (HA, n = 12) or an intermittent normoxia group (NA, n = 12). The IHE consisted of 5-min cycles of hypoxia−normoxia with an FIO2 of between 10−13% for 90 min every day for 8 weeks. Hematological (red blood cells, hemoglobin, hematocrit, hematocrit, reticulated hemoglobin, reticulocytes, and erythropoietin), immunological (leukocytes, monocytes, and lymphocytes), and renal (urea, creatinine, glomerular filtrate, and total protein) biomarkers were assessed at the baseline (T1), day 28 (T2), and day 56 (T3). Sports performance was evaluated at T1 and T3 by measuring quadriceps strength and using three-time trials over the distances of 60, 400, and 1000 m on an athletics track. Statistically significant increases (p < 0.05) in erythropoietin, reticulocytes, hemoglobin, and reticulocyte hemoglobin were observed in the HA group at T3 with respect to T1 and the NA group. In addition, statistically significant improvements (p < 0.05) were achieved in all performance tests. No variations were observed in the immunological or renal biomarkers. The athletes who were living and training at 1065 m and were supplemented with IHE produced significant improvements in their hematological behavior and sports performance with optimal safety profiles.

Effects of perioperative erythropoietin administration on acute kidney injury and red blood cell transfusion in patients undergoing cardiac surgery: A systematic review and meta-analysis

BACKGROUND

The renoprotective effects of erythropoietin (EPO) are well-known; however, the optimal timing of EPO administration remains controversial. Red blood cell (RBC) transfusion is an independent risk factor for cardiac surgery-associated acute kidney injury (CSA-AKI). We aimed to evaluate the efficacy of EPO on CSA-AKI and RBC transfusion according to the timing of administration.

METHODS

We searched the Cochrane Library, EMBASE, and MEDLINE databases for randomized controlled trials. The primary outcome was the incidence of CSA-AKI following perioperative EPO administration, and the secondary outcomes were changes in serum creatinine, S-cystatin C, S-neutrophil gelatinase-associated lipocalin, urinary neutrophil gelatinase-associated lipocalin, length of hospital and intensive care unit (ICU) stay, volume of RBC transfusion, and mortality. The subgroup analysis was stratified according to the timing of EPO administration in relation to surgery.

RESULTS

Eight randomized controlled trials with 610 patients were included in the study. EPO administration significantly decreased the incidence of CSA-AKI (odds ratio: 0.60, 95% confidence interval [CI]: 0.43-0.85, P = .004; I2 = 52%; P for heterogeneity = .04), intra-operative RBC transfusion (standardized mean difference: -0.30, 95% CI: -0.55 to -0.05, P = .02; I2 = 15%, P for heterogeneity = .31), and hospital length of stay (mean difference: -1.54 days, 95% CI: -2.70 to -0.39, P = .009; I2 = 75%, P for heterogeneity = .001) compared with control groups. Subgroup analyses revealed that pre-operative EPO treatment significantly reduced the incidence of CSA-AKI, intra-operative RBC transfusion, serum creatinine, and length of hospital and ICU stay.

CONCLUSION

Pre-operative administration of EPO may reduce the incidence of CSA-AKI and RBC transfusion, but not in patients administered EPO during the intra-operative or postoperative period. Therefore, pre-operative EPO treatment can be considered to improve postoperative outcomes by decreasing the length of hospital and ICU stay in patients undergoing cardiac surgery.

The effect of intermittent hypoxic exposure on erythropoietic response and hematological variables in elite athletes

This study aimed to evaluate the changes in the erythropoietin level and hematological variables in wrestlers after intermittent hypoxic exposure (IHE). Twelve wrestlers were assigned into two groups: hypoxia (sports training combined with IHE, n=6) and control (sports training, n=6). An IHE was performed for 10 days, with one day off after 6 days, once a day for about an hour. The concentrations of hydrogen peroxide ( H(2)O(2) ), nitric oxide (NO), vascular endothelial growth factor (VEGF) and erythropoietin (EPO), as well as total creatine kinase activity (CK) were measured. Also, the hematological markers (Hb - hemoglobin, Ht - hematocrit, RBC - red blood cell, WBC - white blood cell, Ret - reticulocytes) were analyzed. The 6-day IHE caused an increase in the levels of H(2)O(2), NO and VEGF. Similarly, the EPO level and WBC count reached the highest value after 6 days of IHE. The total Ret number increase constantly during 10 days of IHE. The hypoxia group showed a higher CK activity compared to the control. In conclusion, 10-day IHE in combination with wrestling training elevates levels of H(2)O(2), NO and VEGF, and improves the oxygen transport capacity by the release of EPO and Ret in circulation.

Erythropoietin Alleviates Burn-induced Muscle Wasting

Background: Burn injury induces long-term skeletal muscle pathology. We hypothesized EPO could attenuate burn-induced muscle fiber atrophy. Methods: Rats were allocated into four groups: a sham burn group, an untreated burn group subjected to third degree hind paw burn, and two burn groups treated with weekly or daily EPO for four weeks. Gastrocnemius muscle was analyzed at four weeks post-burn. Results: EPO attenuated the reduction of mean myofiber cross-sectional area post-burn and the level of the protective effect was no significant difference between two EPO-treated groups (p=0.784). Furthermore, EPO decreased the expression of atrophy-related ubiquitin ligase, atrogin-1, which was up-regulated in response to burn. Compared to untreated burn rats, those receiving weekly or daily EPO groups had less cell apoptosis by TUNEL assay. EPO decreased the expression of cleaved caspase 3 (key factor in the caspase-dependent pathway) and apoptosis-inducing factor (implicated in the caspase-independent pathway) after burn. Furthermore, EPO alleviated connective tissue overproduction following burn via transforming growth factor beta 1-Smad2/3 pathway. Daily EPO group caused significant erythrocytosis compared with untreated burn group but not weekly EPO group. Conclusion: EPO therapy attenuated skeletal muscle apoptosis and fibrosis at four weeks post-burn. Weekly EPO may be a safe and effective option in muscle wasting post-burn.

Erythropoietin Increases GABAA Currents in Human Cortex from TLE Patients

Erythropoietin (EPO) is a hematopoietic growth factor that has an important role in the erythropoiesis. EPO and its receptor (EPO-R) are expressed all over in the mammalian brain. Furthermore, it has been reported that EPO may exert neuroprotective effect in animal models of brain disorders as ischemia and epilepsy. Here, we investigate whether EPO could modulate the GABA-evoked currents (I_GABA) in both human epileptic and non-epileptic control brain tissues. Therefore, we transplanted in Xenopus oocytes cell membranes obtained from autoptic and surgical brain tissues (cortex) of seven temporal lope epilepsy (TLE) patients and of five control patients. Two microelectrodes voltage-clamp technique has been used to record I_GABA. Moreover, qRT-PCR assay was performed in the same human tissues to quantify the relative gene expression levels of EPO/EPO-R. To further confirm experiments in oocytes, we performed additional experiments using patch-clamp recording in slices obtained from rat cerebellum. We show that exposure to EPO significantly increased the amplitude of the I_GABA in all the patients analyzed. No differences in the expression of EPO and EPO-R in both TLE and control patients have been found. Notably, the increase of I_GABA has been recorded also in rat cerebellar slices. Our findings show a new modulatory action of EPO on GABA_A receptors (GABA_A-Rs). This effect could be relevant to balance the GABAergic dysfunction in human TLE. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.

Identification of methionine oxidation in human recombinant erythropoietin by mass spectrometry: Comparative isoform distribution and biological activity analysis

BACKGROUND

Oxidative degradation of human recombinant erythropoietin (hrEPO) may occur in manufacturing process or therapeutic applications. This unfavorable alteration may render EPO inefficient or inactive. We investigated the effect of methionine/54 oxidative changes on the amino acid sequences, glycoform distribution and biological activity of hrEPO.

METHODS

Mass spectrometry was applied to verify the sequence and determine the methionine oxidation level of hrEPO. Isoform distribution was studied by capillary zone electrophoresis method. In vivo normocythemic mice assay was used to assess the biological activity of three different batches (A, B, and C) of the proteins.

RESULTS

Nano-LC/ESI/MS/MS data analyses confirmed the amino acid sequences of all samples. The calculated area percent of three isoforms (2-4 of the 8 obtained isoforms) were decreased in samples of C, B, and A with 27.3, 16.7, and 6.8% of oxidation, respectively. Specific activities were estimated as 53671.54, 95826.47, and 112994.93 mg/mL for the samples of A, B, and C, respectively.

CONCLUSION

The observed decrease in hrEPO biological activity, caused by increasing methionine oxidation levels, was rather independent of its amino acid structure and mainly associated with the higher contents of acidic isoforms.

Induction of erythropoietin gene expression in epithelial cells by chemicals identified in GATA inhibitor screenings

Erythropoietin (EPO) is a hormone that promotes proliferation, differentiation and survival of erythroid progenitors. EPO gene expression is regulated in a tissue-specific and hypoxia-inducible manner and is mainly restricted to renal EPO-producing cells after birth. Chronic kidney disease (CKD) confers high risk for renal anemia due to lower EPO production from injured kidneys. In transgenic reporter lines of mice, disruption of a GATA-binding motif within the Epo gene promoter-proximal region restores constitutive reporter expression in epithelial cells. Here, mitoxantrone and its analogues, identified as GATA factor inhibitors through high-throughput chemical library screenings, markedly induce EPO/Epo gene expression in epithelium-derived cell lines and mice regardless of oxygen levels. In contrast, mitoxantrone interferes with hypoxia-induced EPO gene expression in Hep3B cells. Cryptic promoters are created for the EPO/Epo gene expression in epithelial cells upon mitoxantrone treatment, and consequently, unique 5'-untranslated regions are generated. The mitoxantrone-induced aberrant transcripts contribute to the reporter protein production in epithelial cells that carry the reporter gene in the proper reading frame of mouse Epo gene. Thus, EPO production in uninjured adult epithelial cells may be a therapeutic approach for renal anemia in patients with CKD.

Erythropoietin and sildenafil protect against ischemia/reperfusion injury following testicular torsion in adult rats

Testicular torsion/detorsion causes severe tissue damage due to ischemia/reperfusion injury. The present study investigated the protective effect of erythropoietin and sildenafil against ischemia/reperfusion injury following unilateral testicular torsion/detorsion in adult rats. A total of 28 adult male rats were included, and were divided into the following groups: Group A (n=5), sham operated; groups B (n=5), C (n=5), D (n=5) and E (n=8), undergoing right testis torsion and detorsion after 90 min. Group B received no drug treatment. Rats in the groups C and D received low-dose (1,000 IU/kg) or high-dose (3,000 IU/kg) erythropoietin, while those in group E received sildenafil (0.7 mg/kg), through intraperitoneal injection after 60 min of torsion. The right testis was extracted 24 h after detorsion, and the tissue was subjected to histopathological examination and immunohistochemical assessment of cleaved caspase-3 expression. Histological alterations and the quality of spermatogenesis were scored according to the Cosentino and the Johnsen scoring systems, respectively. The results demonstrated normal testicular architecture in group A, while the other groups showed ischemic cellular damages, with the worst scores observed in group B. Groups D and E presented better scores compared with group C. Regarding the quality of spermatogenesis, the best scores were observed in group A, and the worst in group B. Groups C, D and E presented similar results, which were improved in comparison to group B, however, not compared to group A. Furthermore, cleaved caspase-3 levels were lower in groups A, D and E, with equal results observed. Group C had higher levels of cleaved caspase-3 compared with these groups, but lower than group B, which presented the highest cleaved caspase-3 levels. In conclusion, erythropoietin and sildenafil protect testis from ischemia/reperfusion injury by decreasing cellular damage and attenuating apoptosis.

Erythropoietin-induced cytoprotection in intestinal epithelial cells is linked to system Xc<sup/>

Necrotizing enterocolitis is a common but serious complication among premature babies. Currently, there are limited treatment options. These include intensive supportive care and surgical intervention. In this study, we hypothesize that erythropoietin (Epo) could be protective against cell necrosis by increasing the levels of glutathione. This can be regulated by increasing the activity of system xC^-. This was demonstrated using intestinal epithelial cells (IEC-6) as a model system. S4-CPG and sulfasalazine pharmacologically inhibit xCT, which induced cell death. Our data showed a dose dependent decrease in cell viability when treated with both inhibitors. In addition, the IEC-6 cells displayed a dose dependent increase when treated with Epo. In conclusion, Epo can be protective against cell death and ultimately be considered as a treatment option for intestinal epithelial cell death.

A comprehensive review of the neonatal Fc receptor and its application in drug delivery

Advances in the understanding of neonatal Fc receptor (FcRn) biology and function have demonstrated that this receptor, primarily identified for the transfer of passive immunity from mother infant, is involved in several biological and immunological processes. In fact, FcRn is responsible for the long half-life of IgG and albumin in the serum, by creating an intracellular protein reservoir, which is protected from lysosomal degradation and, importantly, trafficked across the cell. Such discovery has led researchers to hypothesize the role for this unique receptor in the controlled delivery of therapeutic agents. A great amount of FcRn-based strategies are already under extensive investigation, in which FcRn reveals to have profound impact on the biodistribution and half-life extension of therapeutic agents. This review summarizes the main findings on FcRn biology, function and distribution throughout different tissues, together with the main advances on the FcRn-based therapeutic opportunities and model systems, which indicate that this receptor is a potential target for therapeutic regimen modification.

Helix B Surface Peptide Protects against Acute Myocardial Ischemia-Reperfusion Injury via the RISK and SAFE Pathways in a Mouse Model

OBJECTIVE

This study explores the effects of helix B surface peptide (HBSP) on myocardial infarct size (IS), cardiac function, cardiomyocyte apoptosis and oxidative stress damage in mouse hearts subjected to myocardial ischemia-reperfusion injury (MIRI) and also the mechanisms underlying the effects.

METHOD

Male adult mice were subjected to 45 min of ischemia followed by 2 h of reperfusion; 5 min before the reperfusion, they were treated with HBSP or vehicle. MIRI-induced IS, cardiomyocyte apoptosis and cardiac functional impairment were determined and compared. Western blot analysis was then conducted to elucidate the mechanism of HBSP after treatment.

RESULTS

HBSP administration before reperfusion significantly reduced the myocardial IS, decreased cardiomyocyte apoptosis, reduced the activities of superoxide dismutase and malondialdehyde and partially preserved heart function. As demonstrated by the Western blot analysis, HBSP after treatment upregulated Akt/GSK-3β/ERK and STAT-3 phosphorylation; these inhibitors, in turn, weakened the beneficial effects of HBSP.

CONCLUSION

HBSP plays a protective role in MIRI in mice by inhibiting cardiomyocyte apoptosis, reducing the MIRI-induced IS, oxidative stress and improving the heart function after MIRI. The mechanism underlying these effects of HBSP is related to the activation of the RISK (reperfusion injury salvage kinase, Akt/GSK-3β/ERK) and SAFE (STAT-3) pathways.

Early biomarkers of renal injury and protective effect of erythropoietin on kidneys of asphyxiated newborn rats

BACKGROUND

The aims of this study were to determine which of the two biomarkers of renal injury, kidney injury molecule-1 or cystatin C, is more sensitive and to evaluate whether erythropoietin protects kidneys injured by perinatal asphyxia.

METHODS

Animals were split into three groups designated as follows: AE, pups that survived perinatal asphyxia and subsequently received 2.5 μg (0.1 ml) of darbepoetin-α (i.p.); A, the pups that survived perinatal asphyxia and received 0.1 ml of 0.9% NaCl; and C, control group. The pups were killed at different ages of life (6 h, 24 h, 48 h, 7 d, and 14 d of age; 10 rats in each subgroup). Immunohistopathological evaluation of kidneys was performed.

RESULTS

At 48 h and on days 7 and 14, absolute injury scores were significantly lower in group AE as measured by both biomarkers. Cystatin C expression was the most intensive 6 h after the hypoxic event (average value of absolute injury score was 2.82) and declined over time. Expression of kidney injury molecule-1 was less intensive, with the average value of absolute injury score being 2.02 at 6 h and 2.105 at 24 h; the peak value (2.155) was recorded 48 h after the hypoxic event.

CONCLUSION

Erythropoietin has a protective effect on hypoxic kidneys. Cystatin C is more sensitive as an early biomarker of acute kidney injury in comparison with kidney injury molecule-1.

Does erythropoietin have a role in the treatment of β-hemoglobinopathies?

This review presents the indications and contraindications (pros and cons) for the potential use of erythropoietin (Epo) as a treatment in β-thalassemia and sickle cell anemia (SCA). Its high cost and route of administration (by injection) are obvious obstacles, especially in underdeveloped countries, where thalassemia is prevalent. We believe that from the data summarized in this review, the time has come to define, by studying in vitro and in vivo models, as well as by controlled clinical trials, the rationale for treating patients with various forms of thalassemia and SCA with Epo alone or in combination with other medications.

Effect of erythropoietin on the incidence of acute kidney injury following complex valvular heart surgery: a double blind, randomized clinical trial of efficacy and safety

Introduction

Recombinant human erythropoietin (EPO) is known to provide organ protection against ischemia-reperfusion injury through its pleiotropic properties. The aim of this single-site, randomized, case-controlled, and double-blind study was to investigate the effect of pre-emptive EPO administration on the incidence of postoperative acute kidney injury (AKI) in patients with risk factors for AKI undergoing complex valvular heart surgery.

Methods

We studied ninety-eight patients with preoperative risk factors for AKI. The patients were randomly allocated to either the EPO group (n = 49) or the control group (n = 49). The EPO group received 300 IU/kg of EPO intravenously after anesthetic induction. The control group received an equivalent volume of normal saline. AKI was defined as an increase in serum creatinine >0.3 mg/dl or >50% from baseline. Biomarkers of renal injury were serially measured until five days postoperatively.

Results

Patient characteristics and operative data, including the duration of cardiopulmonary bypass, were similar between the two groups. Incidence of postoperative AKI (32.7% versus 34.7%, P = 0.831) and biomarkers of renal injury including cystatin C and neutrophil gelatinase-associated lipocalin showed no significant differences between the groups. The postoperative increase in interleukin-6 and myeloperoxidase was similar between the groups. None of the patients developed adverse complications related to EPO administration, including thromboembolic events, throughout the study period.

Conclusions

Intravenous administration of 300 IU/kg of EPO did not provide renal protection in patients who are at increased risk of developing AKI after undergoing complex valvular heart surgery.

Trial registration

Clinical Trial.gov, NCT01758861

CNTO 530 increases expression of HbA and HbF in murine models of β-thalassemia and sickle cell anemia

CNTO 530 is an erythropoietin receptor agonist MIMETIBODY^TM construct. CNTO 530 has been shown to be active in a number of rodent models of acquired anemia (e.g. renal insufficiency and chemotherapy induced anemia). We investigated the efficacy of CNTO 530 in murine models of β-thalassemia and sickle cell anemia (Berkeley mice). β- thalassemic mice are deficient in expression of α-globin chain and heterozygous mice are characterized by a clinical syndrome similar to the human β-thalassemia intermedia. Berkeley mice are knocked out for murine alpha and beta globin and are transgenic for human alpha, beta (sickle) and gamma globin genes. Berkeley mice thus express human sickle hemoglobin A (HbS) and can also express human fetal hemoglobin. These mice express a severe compensated hypochromic microcytic anemia and display the sickle cell phenotype. To test the effectiveness of CNTO 530, mice from both genotypes received a single subcutaneous (s.c.) dose of CNTO 530 or darbepoetin-α (as a comparator) at 10,000 U/kg, a dose shown to cause a similar increase in reticulocytes and hemoglobin in normal mice. Hematologic parameters were evaluated over time. CNTO 530, but not darbepoetin-α, increased reticulocytes, red blood cells and total hemoglobin in β- thalassemic mice. In Berkeley mice CNTO 530 showed an increase in reticulocytes, red blood cells, F-cells, total hemoglobin and fetal hemoglobin. In conclusion, CNTO 530 is effective in murine models of β-thalassemia and sickle cell anemia. These data suggest that CNTO 530 may have beneficial effects in patients with genetically mediated hemoglobinopathies.

Pharmacokinetics and pharmacodynamics of recombinant human EPO-Fc fusion protein in vivo

In this study, the in vivo pharmacokinetics and pharmacodynamics of a novel recombinant human erythropoietin (rhEPO) Fc fusion protein, rhEPO-Fc, were studied in both rodents and rhesus monkeys. Animal models of anemia induced by irradiation, cyclophosphamide and partial renal ablation were used to evaluate therapeutic effects of rhEPO-Fc. We have demonstrated that serum half-life of rhEPO-Fc was 29.5 to 38.9 h at doses of 8, 25, 80 µg/kg in rhesus monkeys and 35.5 to 43.5 h at doses of 16, 50, 160 µg/kg in rats. In anemia animal models, rhEPO-Fc dose-dependently (7.5–30.0 µg/kg in mice, 5.4–21.4 µg/kg in rats and 5.0–10.0 µg/kg in rhesus monkeys) increased reticulocyte level, followed by an increase of RBC count, hemoglobin and hematocrit levels. At reduced intervention frequency of weekly treatments, rhEPO-Fc showed similar hematopoietic effects as compared with rhEPO given three times a week. These results indicated that rhEPO-Fc could potentially be used in treatment of anemia and warrants future clinical trials.

Effects of massage under hypoxic conditions on exercise-induced muscle damage and physical strain indices in professional soccer players

Reports based on experiences from masseurs and players, mostly without any scientific background, suggest that the combination of a classical regeneration method (i.e. massage) with exposure to hypoxia may enhance regeneration in soccer. The aim of this study was to evaluate whether this specific combination could affect blood parameters related to muscle damage and physical strain after a soccer game. Approximately 15 hours after two separate championship games, 10 professional male outfield players of the first Austrian division were exposed to normobaric hypoxia (FiO2 13.5% ∼ 4000m) or normoxia for 1 hour (30 minutes rest followed by 30 min massage) (cross-over design). Creatine kinase (CK), urea and uric acid (UA) were measured 4 days before the first game, and 15 and 63 hours after the two games. Match play increased CK values independently of the intervention. No effect of the massage in combination with hypoxia was seen. A trend was found between Δ UA ([UA] 48 hours after exposure minus [UA] before exposure) in response to hypoxia and SaO2 measured in hypoxia (r=0.612, p=0.06). Results show that massage under hypoxic conditions had no additional positive effect on the measured parameters compared to massage alone. Solely the trend of a relationship for Δ UA and SaO2 might indicate that redox alterations are a potential consequence of hypoxic exposure.

Erythropoietin attenuated vascular dysfunction and inflammation by inhibiting NADPH oxidase-derived superoxide production in nitric oxide synthase-inhibited hypertensive rat aorta

Erythropoietin (EPO), used clinically for renal anemia, reportedly exerts beneficial pleiotropic effects in various tissues. Recent studies suggest that nitric oxide (NO) plays an important role in EPO-induced tissue protection. The present study investigated whether recombinant human EPO (rHuEPO) exhibits vasoprotective effects even in the NO synthase-inhibited state. Rats that received a NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), in drinking water (0.7 mg/ml) were treated with rHuEPO (75 U/kg, s.c.) three times a week for 2 weeks. The administration of rHuEPO to L-NAME-treated rats had no effect on hematocrit values or increased blood pressure. Vasodilation in response to acetylcholine in the aortic ring was impaired in the L-NAME-treated rats, and improved by rHuEPO. Immunohistochemical staining revealed that infiltration by macrophages and expression of osteopontin were enhanced in the L-NAME-treated rat aorta, and the overexpression was suppressed by rHuEPO. rHuEPO also attenuated medial hyperplasia. Activation of Akt signaling was evident in rHuEPO-treated rats as the increased expression of phosphorylated Akt. rHuEPO enhanced the expression of antioxidant enzymes such as Cu/Zn-superoxide dismutase and heme oxygenase-1 in the aorta. In addition, rHuEPO reduced NADPH oxidase-dependent superoxide production and enhanced the expression of suppressor of cytokine signaling-1(SOCS-1) in the L-NAME-treated rat aorta. These results suggest that a low dose of rHuEPO results in the normalization of endothelial function and vascular inflammation beyond hematopoiesis even in a pharmacologically NO synthase-inhibited state. These effects might be due to the antioxidant properties of rHuEPO. SOCS-1 overexpression would play an important role in suppressing NADPH oxidase activation.

The role of erythropoietin in the "stroke belt" phenomenon

Global geographic disparities in stroke mortality rates are substantial. In the US alone, higher stroke mortality rates are reported in the Southeast part particularly along the coastline while lower rates have been observed in the Mountain region. The phenomenon has been called the "stroke belt". Although many theories have attempted to explain such nonrandom distribution of stroke mortality rates, no conclusive explanations have been drawn so far. I hypothesize that this nonrandom stroke distribution is related to regional differences in individual levels of erythropoietin (EPO), a hormone, which production depends on the tissue hypoxia due to variation in altitude. If successful, future studies based on this hypothesis may open up new avenues for treatment of such an important health issue as stroke. More importantly, future studies based on this theory may shed the lights on the mechanism of stroke as well as other diseases which have nonrandom geographic distribution not only in the US but also internationally.

Erythropoietin increases survival and attenuates fulminant hepatic failure injury induced by D-galactosamine/lipopolysaccharide in mice

BACKGROUND

Liver transplantation is the only therapy of proven benefit in fulminant hepatic failure (FHF). Lipopolysaccharide (LPS), d-galactosamine (GalN)-induced FHF is a well-established model of liver injury in mice. Erythropoietin has a powerful tissue-protective effect in animal models. The aim of this study was to investigate the effect and mechanism of recombinant human erythropoietin (rhEPO) administration in FHF mice.

METHODS

C57BL/6 (n=42) mice were studied in vivo in a fulminant model induced by GalN/LPS. rhEPO was administered 30 min after the induction of FHF. Serum liver enzymes and hepatic tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels were determined. Histologic analysis was performed, and apoptotic cells were identified by immunohistochemistry for caspase-3. Nuclear factor (NF)-κB and c-Jun-N-terminal kinase (JNK) activation were studied using Western blot analysis.

RESULTS

After the induction of FHF, all control mice died within 12 hr of GalN/LPS administration. However, 83% of mice that were administered rhEPO were alive 2 weeks later, and overall survival improved (Kaplan-Meier, P<0.001). The serum liver enzymes, hepatic TNF-α and IL-1β levels, liver histologic injury, and apoptotic hepatocytes were significantly reduced in FHF mice that were administered rhEPO compared with untreated mice. A significant decrease in hepatic NF-κB and JNK activation was noted in FHF rhEPO-treated mice compared with FHF untreated mice.

CONCLUSIONS

The administration of rhEPO brought about increased survival and attenuation of the hepatic injury. This was associated with decreased hepatic NF-κB and JNK activation and thus TNF-α and IL-1β levels. These findings have important implications for the potential use of rhEPO in FHF.

Erythropoietin: a hormone with multiple functions

Erythropoietin (EPO), the main hemopoietic hormone synthesized by the kidney as well as by the liver in fetal life, is implicated in mammalian erythropoiesis. Production and secretion of EPO and the expression of its receptor (EPO-R) are regulated by tissue oxygenation. EPO and EPO-R, expressed in several tissues, exert pleiotropic activities and have different effects on nonhemopoietic cells. EPO is a cytokine with antiapoptotic activity and plays a potential neuroprotective and cardioprotective role against ischemia. EPO is also involved in angiogenesis, neurogenesis, and the immune response. EPO can prevent metabolic alterations, neuronal and vascular degeneration, and inflammatory cell activation. Consequently, EPO may be of therapeutic use for a variety of disorders. Many tumors express EPO and/or EPO-R, but the action of EPO on tumor cells remains controversial. It has been suggested that EPO promotes the proliferation and survival of cancer cells expressing EPO-R. On the other hand, other reports have concluded that EPO-R plays no role in tumor progression. This review provides a detailed insight into the nonhemopoietic role of EPO and its mechanism(s) of action which may lead to a better understanding of its potential therapeutic value in diverse clinical settings.

Renovascular protective effects of erythropoietin in patients with chronic kidney disease

BACKGROUND/AIMS

Erythropoietin (EPO) has been widely used for the treatment of anemia in chronic kidney disease (CKD). A growing body of evidence indicates that the therapeutic benefits of EPO could extend beyond the improvement of anemia. The aim of the present study was to determine whether EPO affects renovascular and oxidative stress biomarkers in pre-dialysis CKD patients with anemia.

METHODS

The study was a single-arm prospective study. Fifteen CKD patients (9 males and 6 females, mean age 63 years) with anemia (mean Hb: 8.1 g/dL) were treated with recombinant human EPO; 12,000 U administered subcutaneously once every 2 weeks. Various parameters were measured before and 6 months after treatment. These included serum hemoglobin (Hb), creatinine, estimated glomerular filtration rate (eGFR), proteinuria, urinary liver-type fatty acid binding protein (L-FABP--a biomarker of renal injury), urinary 8-hydroxydeoxyguanosine (8-OHdG--a marker of oxidative stress), serum asymmetrical dimethylarginine (ADMA), carotid artery intima-media thickness (IMT) and brachial-ankle pulse wave velocity (baPWV) as vascular markers and plasma brain natriuretic peptide (BNP) levels and left ventricular ejection fraction (LVEF) as cardiac function markers and cardio-thoracic ratio (CTR) and inferior vena cava dimension (IVCS) as extra fluid retention markers.

RESULTS

After 6 months, serum Hb was significantly increased (p<0.001) and urinary levels of protein, L-FABP and 8-OHdG, carotid IMT, baPWV, plasma BNP and serum ADMA levels were significantly decreased (p<0.001). Serum creatinine, eGFR, LVEF, CTR and IVCS showed little difference throughout the experimental period.

CONCLUSION

These data suggest that recombinant human EPO may ameliorate renal injury, oxidative stress and progression of atherosclerosis in addition to improving anemia in CKD patients.

The antioxidant effect of erythropoietin on thalassemic blood cells

Because of its stimulating effect on RBC production, erythropoietin (Epo) is used to treat anemia, for example, in patients on dialysis or on chemotherapy. In β-thalassemia, where Epo levels are low relative to the degree of anemia, Epo treatment improves the anemia state. Since RBC and platelets of these patients are under oxidative stress, which may be involved in anemia and thromboembolic complications, we investigated Epo as an antioxidant. Using flow-cytometry technology, we found that in vitro treatment with Epo of blood cells from these patients increased their glutathione content and reduced their reactive oxygen species, membrane lipid peroxides, and external phosphatidylserine. This resulted in reduced susceptibility of RBC to undergo hemolysis and phagocytosis. Injection of Epo into heterozygous (Hbb(th3/+)) β-thalassemic mice reduced the oxidative markers within 3 hours. Our results suggest that, in addition to stimulating RBC and fetal hemoglobin production, Epo might alleviate symptoms of hemolytic anemias as an antioxidant.

A small nonerythropoietic helix B surface peptide based upon erythropoietin structure is cardioprotective against ischemic myocardial damage

Strong cardioprotective properties of erythropoietin (EPO) reported over the last 10 years have been difficult to translate to clinical applications for ischemic cardioprotection owing to undesirable parallel activation of erythropoiesis and thrombogenesis. A pyroglutamate helix B surface peptide (pHBP), recently engineered to include only a part of the EPO molecule that does not bind to EPO receptor and thus, is not erythropoietic, retains tissue protective properties of EPO. Here we compared the ability of pHBP and EPO to protect cardiac myocytes from oxidative stress in vitro and cardiac tissue from ischemic damage in vivo. HBP, similar to EPO, increased the reactive oxygen species (ROS) threshold for induction of the mitochondrial permeability transition by 40%. In an experimental model of myocardial infarction induced by permanent ligation of a coronary artery in rats, a single bolus injection of 60 μg/kg of pHBP immediately after coronary ligation, similar to EPO, reduced apoptosis in the myocardial area at risk, examined 24 h later, by 80% and inflammation by 34%. Myocardial infarction (MI) measured 24 h after coronary ligation was similarly reduced by 50% in both pHBP- and EPO-treated rats. Two wks after surgery, left ventricular remodeling (ventricular dilation) and functional decline (fall in ejection fraction) assessed by echocardiography were significantly and similarly attenuated in pHBP- and EPO-treated rats, and MI size was reduced by 25%. The effect was retained during the 6-wk follow-up. A single bolus injection of pHBP immediately after coronary ligation was effective in reduction of MI size in a dose as low as 1 μg/kg, but was ineffective at a 60 μg/kg dose if administered 24 h after MI induction. We conclude that pHBP is equally cardioprotective with EPO and deserves further consideration as a safer alternative to rhEPO in the search for therapeutic options to reduce myocardial damage following blockade of the coronary circulation.

Association between breast milk erythropoietin and reduced risk of mother-to-child transmission of HIV

We examined the prospective associations between breast milk concentrations of erythropoietin, a factor with trophic effects on infant gut epithelia, and the risk of mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) through breast-feeding in a study of 59 MTCT cases and 116 controls nested within a cohort of antiretroviral-naive HIV-infected Tanzanian women. Controls were matched to cases on the basis of the time from birth when the breast milk sample was collected. The risk of MTCT was inversely related to breast milk erythropoietin concentration (adjusted odds ratio for highest vs lowest erythropoietin concentration tertile, 0.34 [95% confidence interval, 0.14-0.82]; P = .02). These results suggest a protective effect of breast milk erythropoietin against MTCT.

Soluble erythropoietin receptor contributes to erythropoietin resistance in end-stage renal disease

BACKGROUND

Erythropoietin is a growth factor commonly used to manage anemia in patients with chronic kidney disease. A significant clinical challenge is relative resistance to erythropoietin, which leads to use of successively higher erythropoietin doses, failure to achieve target hemoglobin levels, and increased risk of adverse outcomes. Erythropoietin acts through the erythropoietin receptor (EpoR) present in erythroblasts. Alternative mRNA splicing produces a soluble form of EpoR (sEpoR) found in human blood, however its role in anemia is not known.

METHODS AND FINDINGS

Using archived serum samples obtained from subjects with end stage kidney disease we show that sEpoR is detectable as a 27kDa protein in the serum of dialysis patients, and that higher serum sEpoR levels correlate with increased erythropoietin requirements. Soluble EpoR inhibits erythropoietin mediated signal transducer and activator of transcription 5 (Stat5) phosphorylation in cell lines expressing EpoR. Importantly, we demonstrate that serum from patients with elevated sEpoR levels blocks this phosphorylation in ex vivo studies. Finally, we show that sEpoR is increased in the supernatant of a human erythroleukaemia cell line when stimulated by inflammatory mediators such as interleukin-6 and tumor necrosis factor alpha implying a link between inflammation and erythropoietin resistance.

CONCLUSIONS

These observations suggest that sEpoR levels may contribute to erythropoietin resistance in end stage renal disease, and that sEpoR production may be mediated by pro-inflammatory cytokines.

Erythropoietin-induced neuroprotection requires cystine glutamate exchanger activity

Erythropoietin (Epo) has been used for many years in neonates for the treatment of anemia of prematurity. Epo has also been proposed for treatment of neonatal brain injury, as mounting evidence suggests neuroprotective properties for Epo. However, Epo's neuroprotective mechanism of action is poorly understood. In this study we hypothesized that Epo may confer neuroprotection by enhancing cellular redox defense brought about by cellular glutathione (GSH). This was examined in cultures of differentiated cortical neural stem cells and using the B104 cell line as model systems. Our data shows that Epo causes a time- and dose-dependent increase in expression and activity of system Xc(-), the transporter responsible for uptake of cystine for the production of glutathione. Cystine uptake increases 3-5 fold in differentiated neural stem cells and B104 cells treated with Epo. Exposure of cells to 100 microM kainate suppressed cellular GSH and caused excitotoxicity, but GSH levels and cell viability were completely restored by Epo in the continued presence of kainate. This rescue effect of Epo vanished if system Xc(-) was inhibited pharmacologically using S4-CPG in the presence of Epo leading to marked cell death of B104 cells and cultured mouse cortical neural stem cells. This could also be achieved using xCT siRNA to decrease xCT expression. This data suggests that system Xc(-) activity and protein expression are positively regulated by Epo directly explaining its neuroprotective effect.

Oxidative stress: Biomarkers and novel therapeutic pathways

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO) and members of the mammalian forkhead transcription factors of the O class (FoxOs) may offer the greatest promise for new treatment regimens since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. However, biological outcome with EPO and FoxOs may sometimes be both unexpected and undesirable that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as complicated role EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

Use of agents stimulating erythropoiesis in digestive diseases

Anemia is the most common complication of inflammatory bowel disease (IBD). Control and inadequate treatment leads to a worse quality of life and increased morbidity and hospitalization. Blood loss, and to a lesser extent, malabsorption of iron are the main causes of iron deficiency in IBD. There is also a variable component of anemia related to chronic inflammation. The anemia of chronic renal failure has been treated for many years with recombinant human erythropoietin (rHuEPO), which significantly improves quality of life and survival. Subsequently, rHuEPO has been used progressively in other conditions that occur with anemia of chronic processes such as cancer, rheumatoid arthritis or IBD, and anemia associated with the treatment of hepatitis C virus. Erythropoietic agents complete the range of available therapeutic options for treatment of anemia associated with IBD, which begins by treating the basis of the inflammatory disease, along with intravenous iron therapy as first choice. In cases of resistance to treatment with iron, combined therapy with erythropoietic agents aims to achieve near-normal levels of hemoglobin/hematocrit (11-12 g/dL). New formulations of intravenous iron (iron carboxymaltose) and the new generation of erythropoietic agents (darbepoetin and continuous erythropoietin receptor activator) will allow better dosing with the same efficacy and safety.

Erythropoietin, forkhead proteins, and oxidative injury: biomarkers and biology

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO), and members of the mammalian forkhead transcription factors of the O class (FoxOs), may offer the greatest promise for new treatment regimens, since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. Yet, EPO and FoxOs may sometimes have unexpected and undesirable effects that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as the complex role that EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

Morg1 heterozygous mice are protected from acute renal ischemia-reperfusion injury

Renal ischemia and reperfusion injury leads to acute renal failure when proinflammatory and apoptotic processes in the kidney are activated. The increase in hypoxia-inducible transcription factor-alpha (HIF-alpha), an important transcription factor for several genes, can attenuate ischemic renal injury. We recently identified a novel WD-repeat protein designated Morg1 (MAPK organizer 1) that interacts with prolyl hydroxylase 3 (PHD3), an important enzyme involved in the regulation of HIF-1alpha and HIF-2alpha expression. While homozygous Morg1 -/- mice are embryonic lethal, heterozygous Morg1 +/- mice have a normal phenotype. We show here that Morg1 +/- were partially protected from renal ischemia-reperfusion injury compared with wild-type Morg1 +/+ animals. Morg1 +/- mice compared with wild-type animals revealed a stronger increase in HIF-1alpha and HIF-2alpha expression in the ischemic-reperfused kidney associated with enhanced serum erythropoietin levels. However, no significant expression of HIF-1alpha and HIF-2alpha was found in nonischemic kidneys without any difference between Morg1 +/- and Morg1 +/+ mice. Ischemic kidneys of Morg1 +/- mice expressed more erythropoietin mRNA than ischemic kidneys from wild-type animals. Renal ischemia in Morg1 +/- mice resulted in a decrease in renal inflammation and reduction of proinflammatory cytokines (MCP-1, IP-10, MIP-2) compared with wild-type mice. Furthermore, there was significantly less apoptosis and tubular damage in Morg1 +/- kidneys after ischemia-reperfusion, and this was also reflected in significantly improved renal function compared with wild-type. Thus Morg1 may be a novel therapeutic target to limit renal injury after ischemia-reperfusion.

Thrombopoietin limits IL-6 release but fails to attenuate liver injury in two hepatic stress models

OBJECTIVE

Various pleiotropic substances have been suggested as candidates that directly reduce the severity of liver injury after hepatic ischemia/reperfusion (I/R) and upon acute liver failure (ALF). Herein, we studied whether thrombopoietin (TPO), the main regulator of megakaryopoiesis and thrombopoiesis, showed hepatoprotective effects and might mediate an antiapoptotic function in liver tissue under stress.

METHODS/RESULTS

In livers with ALF or undergoing warm hepatic I/R, injury was quantified by intravital fluorescence microscopy, chemical, and immunohistochemical analysis as well as western immunoblot. Induction of both ALF and I/R injury led to hepatocellular expression of c-mpl, the receptor of TPO. Exogenous application of recombinant TPO in a low (12.5 microg/kg) as well as a high (75 microg/kg) dose, however, did not ameliorate postischemic perfusion and leukocyte endothelial cell interaction, but slightly aggravated transaminase release upon I/R. Similarly, TPO was unable to dampen hepatic microcirculatory deteriorations after the induction of ALF, but caused an increase of leukocyte accumulation and transaminase activity when applied in high dose. Low dose of TPO did not influence the amount of hepatocellular apoptosis, whereas high-dose TPO slightly diminished the activation of caspase 3. Interestingly, exogenous TPO application completely reversed the stress-induced increase of plasma IL-6 levels, suggesting a negative feedback of TPO on IL-6 release.

CONCLUSION

Although the existence of the TPO-receptor on target liver cells TPO plays only a minor role in mediating hepatocyte apoptosis and does not provide protection against hepatic injury, contrasting the efficacy of the related hematopoietic growth factor erythropoietin.

Erythropoietin improved initial resuscitation and increased survival after cardiac arrest in rats

INTRODUCTION

Recent data have demonstrated potent cardioprotective and neuroprotective effects of the application of growth hormones like erythropoietin (EPO) after focal cardiac or cerebral ischemia. In order to assess possible benefits regarding survival and resuscitation conditions, EPO was tested against placebo in a model of cardiac arrest in the rat.

METHODS

Thirty-four male Wistar rats were randomized into two groups (EPO versus control; n=17 per group). Under anesthesia, cardiac arrest was induced by asphyxia after neuromuscular blockade. After 6 min of global ischemia, animals were resuscitated by external chest compression combined with epinephrine administration. An intravenous bolus of recombinant human EPO (rhEPO, 3000 UIkg(-1) body weight, i.v.) or saline (in control group) was performed 15 min before cardiac arrest, by a blinded investigator. Restoration of spontaneous circulation (ROSC), survival at 1, 24, 48 and 72 h and hemodynamic changes after cardiac arrest were studied.

RESULTS

Survival to 72 h was significantly improved in the EPO group (n=15/17) compared to the control group (n=7/17). All the EPO-treated rats were successfully resuscitated whereas only 13 of 17 control animals resuscitated. EPO-treated animals required a significantly smaller dose of epinephrine before resuscitation, compared to control rats. Time course of systolic arterial blood pressure after resuscitation revealed no significant differences between both groups.

CONCLUSION

EPO, when administrated before cardiac arrest, improved initial resuscitation and increased the duration of post-resuscitation survival.

No evidence for protective erythropoietin alpha signalling in rat hepatocytes

BACKGROUND

Recombinant human erythropoietin alpha (rHu-EPO) has been reported to protect the liver of rats and mice from ischemia-reperfusion injury. However, direct protective effects of rHu-EPO on hepatocytes and the responsible signalling pathways have not yet been described. The aim of the present work was to study the protective effect of rHu-EPO on warm hypoxia-reoxygenation and cold-induced injury to hepatocytes and the rHu-EPO-dependent signalling involved.

METHODS

Loss of viability of isolated rat hepatocytes subjected to hypoxia/reoxygenation or incubated at 4 degrees C followed by rewarming was determined from released lactate dehydrogenase activity in the absence and presence of rHu-EPO (0.2-100 U/ml). Apoptotic nuclear morphology was assessed by fluorescence microscopy using the nuclear fluorophores H33342 and propidium iodide. Erythropoietin receptor (EPOR), EPO and Bcl-2 mRNAs were quantified by real time PCR. Activation of JAK-2, STAT-3 and STAT-5 in hepatocytes and rat livers perfused in situ was assessed by Western blotting.

RESULTS

In contrast to previous in vivo studies on ischemia-reperfusion injury to the liver, rHu-EPO was without any protective effect on hypoxic injury, hypoxia-reoxygenation injury and cold-induced apoptosis to isolated cultured rat hepatocytes. EPOR mRNA was identified in these cells but specific detection of the EPO receptor protein was not possible due to the lack of antibody specificity. Both, in the cultured rat hepatocytes (10 U/ml for 15 minutes) and in the rat liver perfused in situ with rHu-EPO (8.9 U/ml for 15 minutes) no evidence for EPO-dependent signalling was found as indicated by missing effects of rHu-EPO on phosphorylation of JAK-2, STAT-3 and STAT-5 and on the induction of Bcl-2 mRNA.

CONCLUSION

Together, these results indicate the absence of any protective EPO signalling in rat hepatocytes. This implies that the protection provided by rHu-EPO in vivo against ischemia-reperfusion and other causes of liver injury is most likely indirect and does not result from a direct effect on hepatocytes.

Hyperhomocysteinemia, paraoxonase concentration and cardiovascular complications in Tunisian patients with nondiabetic renal disease

OBJECTIVES

Hyperhomocysteinemia is associated with an increased risk of cardiovascular diseases. We determine homocysteine levels (Hcy), paraoxonase (PON1) concentration and their relationship on cardiovascular complications in patients with chronic renal disease (CRD).

DESIGN AND METHODS

The study population included 100 CRD patients and 120 healthy controls. Renal function was assessed using the eGFR by the MDRD study equation. Patients were considered to have CRD when the eGFR was <60 mL/min/1.73 m(2). Hcy concentrations were determined by direct chemiluminescence assay. PON1 concentration was measured spectrophotometrically using phenylacetate as a substrate.

RESULTS

We found an increased Hcy levels and a decreased eGFR and PON1 concentration in CRD patients compared to the control group (P<0.001, P<0.001, P<0.01 respectively). Patients with cardiovascular complications showed an increased Hcy levels and a lower PON1 concentration than patients without cardiovascular complications (P<0.001, P<0.01 respectively).

CONCLUSION

We showed that hyperhomocysteinemia and low PON1 concentration are associated with CRD and markedly associated in patients with cardiovascular complications. Additional effects contribute to the severity of renal disease and increase the incidence of cardiovascular disease.

The role of erythropoietin in the acute phase of trauma management: evidence today

Trauma patients often present in a state of haemorrhagic shock. Blood products remain the gold standard of resuscitation, but allogeneic blood transfusions (ABTs) are associated with several risks. The stimulating effect of recombinant-erythropoietin (EPO-A) on erythropoiesis has raised interest in its administration as an alternative. The existing evidence on the early use of EPO-A in the acute phase of trauma patients management consists of only 14 publications. The level of evidence of these studies and the number of treated patients was not found to be adequate to support its generalised use, despite their favourable results. Its safety profile, the preliminary proofs of its efficacy, and the additional cyto-protective properties of EPO-A strongly encourage further controlled studies assessing its use in the acute setting of initial trauma management.

Emerging concepts in acute kidney injury following cardiac surgery

Acute kidney injury (AKI) remains a significant cause of morbidity and mortality following cardiac surgery. Through a more thorough understanding of perioperative genomics and the evolving role of early biomarkers of AKI, the authors seek to improve meaningful outcomes among cardiac surgery patients. In this review, the focus will be on advances in risk stratification, evolving definitions and improving early diagnosis of AKI, identification of effective individualized therapies, and future directions.

Ser9 phosphorylation of mitochondrial GSK-3beta is a primary mechanism of cardiomyocyte protection by erythropoietin against oxidant-induced apoptosis

The aim of this study was to determine the role of GSK-3beta in cardiomyocyte protection afforded by erythropoietin (EPO) against oxidant stress-induced apoptosis. Treatment with EPO (10 units/ml) induced Ser473 phosphorylation of Akt and Ser9 phosphorylation of GSK-3beta and significantly reduced the proportion of apoptotic H9c2 cardiomyocytes after exposure to H2O2 from 38.3 +/- 2.7% to 26.0 +/- 2.9%. This protection was not detected in cells transfected with constitutively active GSK-3beta (S9A), which lacks Ser9 for inhibitory phosphorylation. The antiapoptotic effect of EPO was mimicked completely by GSK-3beta knockdown using small interfering RNA and partly by the transfection with kinase-deficient GSK-3beta (K85R). The level of colocalization of intracellular GSK-3beta with mitochondria assessed by enhanced green fluorescent protein-tagged GSK-3beta or immunocytochemistry was not altered by EPO treatment. However, EPO increased the level of Ser9-phospho-GSK-3beta colocalized with mitochondria by 50% in a phosphatidylinositol 3-kinase-dependent manner. Mitochondrial translocation of Bcl-2-associated X protein (BAX) after exposure to H2O2 was inhibited by EPO pretreatment and by GSK-3beta knockdown. These results suggest that the suppression of GSK-3beta activity by Akt-mediated Ser9 phosphorylation in the mitochondria affords cardiomyocytes tolerance against oxidant-induced apoptosis, possibly by inhibiting the access of BAX to the mitochondria.