Erythropoietin induces heme oxygenase-1 expression and attenuates oxidative stress

Identification of Cytoprotective Small-Molecule Inducers of Heme-Oxygenase-1

Acute kidney injury (AKI) is a major public health concern with significant morbidity and mortality and no current treatments beyond supportive care and dialysis. Preclinical studies have suggested that heme-oxygenase-1 (HO-1), an enzyme that catalyzes the breakdown of heme, has promise as a potential therapeutic target for AKI. Clinical trials involving HO-1 products (biliverdin, carbon monoxide, and iron), however, have not progressed beyond the Phase ½ level. We identified small-molecule inducers of HO-1 that enable us to exploit the full therapeutic potential of HO-1, the combination of its products, and yet-undefined effects of the enzyme system. Through cell-based, high-throughput screens for induction of HO-1 driven by the human HO-1 promoter/enhancer, we identified two novel small molecules and broxaldine (an FDA-approved drug) for further consideration as candidate compounds exhibiting an Emax ≥70% of 5 µM hemin and EC50 <10 µM. RNA sequencing identified shared binding motifs to NRF2, a transcription factor known to regulate antioxidant genes, including HMOX1. In vitro, the cytoprotective function of the candidates was assessed against cisplatin-induced cytotoxicity and apoptosis. In vivo, delivery of a candidate compound induced HO-1 expression in the kidneys of mice. This study serves as the basis for further development of small-molecule HO-1 inducers as preventative or therapeutic interventions for a variety of pathologies, including AKI.

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.

Effects of Allicin on Pathophysiological Mechanisms during the Progression of Nephropathy Associated to Diabetes

This study aimed to assess the impact of allicin on the course of diabetic nephropathy. Study groups included control, diabetes, and diabetes-treated rats. Allicin treatment (16 mg/kg day/p.o.) started after 1 month of diabetes onset and was administered for 30 days. In the diabetes group, the systolic blood pressure (SBP) increased, also, the oxidative stress and hypoxia in the kidney cortex were evidenced by alterations in the total antioxidant capacity as well as the expression of nuclear factor (erythroid-derived 2)-like 2/Kelch ECH associating protein 1 (Nrf2/Keap1), hypoxia-inducible factor 1-alpha (HIF-1α), vascular endothelial growth factor (VEGF), erythropoietin (Epo) and its receptor (Epo-R). Moreover, diabetes increased nephrin, and kidney injury molecule-1 (KIM-1) expression that correlated with mesangial matrix, the fibrosis index and with the expression of connective tissue growth factor (CTGF), transforming growth factor-β1 (TGF-β1), and α-smooth muscle actin (α-SMA). The insulin levels and glucose transporter protein type-4 (GLUT4) expression were decreased; otherwise, insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) expression was increased. Allicin increased Nrf2 expression and decreased SBP, Keap1, HIF-1α, and VEGF expression. Concurrently, nephrin, KIM-1, the mesangial matrix, fibrosis index, and the fibrotic proteins were decreased. Additionally, allicin decreased hyperglycemia, improved insulin levels, and prevented changes in (GLUT4) and IRSs expression induced by diabetes. In conclusion, our results demonstrate that allicin has the potential to help in the treatment of diabetic nephropathy. The cellular mechanisms underlying its effects mainly rely on the regulation of antioxidant, antifibrotic, and antidiabetic mechanisms, which can contribute towards delay in the progression of renal disease.

Advances in Understanding the Effects of Erythropoietin on Renal Fibrosis

Renal fibrosis is the common manifestation of the pathogenesis of end-stage renal disease that results from different types of renal insult, and is a hallmark of chronic kidney disease (CKD). The main pathologic characteristics of renal fibrosis are renal interstitial fibroblast hyperplasia and the aberrant and excessive deposition of extracellular matrix, pathologies that lead to the destruction of normal renal tubules and interstitial structures. However, the biological significance of fibrosis during the progression of CKD is not clear, and there are no approved clinical treatments for delaying or reversing renal fibrosis. Studies of the mechanism of renal fibrosis and of potential measures of prevention and treatment have focused on erythropoietin (EPO), a hormone best known as a regulator of red blood cell production. These recent studies have found that EPO may also provide efficient protection against renal fibrosis. Future therapeutic approaches using EPO offer new hope for patients with CKD. The aim of the present review is to briefly discuss the role of EPO in renal fibrosis, to identify its possible mechanisms in preventing renal fibrosis, and to provide novel ideas for the use of EPO in future treatments of renal fibrosis.

DMOG, a Prolyl Hydroxylase Inhibitor, Increases Hemoglobin Levels without Exacerbating Hypertension and Renal Injury in Salt-Sensitive Hypertensive Rats

Prolyl hydroxylase (PHD) inhibitors are being developed as alternatives to recombinant human erythropoietin (rHuEPO) for the treatment of anemia in patients with chronic kidney disease (CKD). However, the effects of PHD inhibitors and rHuEPO on blood pressure and CKD in animal models susceptible to hypertension and nephropathy have not been studied. The present study compared the effects of dimethyloxaloylglycine (DMOG), a PHD inhibitor, and rHuEPO on the development of hypertension and renal injury in Dahl salt-sensitive rats fed an 8% salt diet for 3 weeks. DMOG and rHuEPO were equally effective at raising hemoglobin levels. Systolic blood pressure rose to a greater extent in rHuEPO-treated rats (267 ± 10 vs. 226 ± 4 mm Hg) than in rats given DMOG (189 ± 8 mm Hg). Urinary protein excretion increased to 568 ± 54 versus 353 ± 25 mg/day in rats treated with rHuEPO and vehicle; however, it only rose to 207 ± 21 mg/day in rats receiving DMOG. DMOG significantly attenuated the degree of glomerulosclerosis and renal interstitial fibrosis as compared with that in vehicle and rHuEPO-treated rats. This was associated with lower renal levels of monocyte chemoattractant protein-1 and interleukin-1β and increased vascular endothelial growth factor expression in cortex and medulla. These results indicate that DMOG and rHuEPO are equally effective in increasing hemoglobin levels in Dahl S rats; however, rHuEPO aggravates hypertension and renal injury, whereas DMOG has marked renoprotective effects. These results suggest that PHD inhibitors may have a therapeutic advantage for the treatment of anemia in CKD. SIGNIFICANCE STATEMENT: Prolyl hydroxylase (PHD) inhibitors are in phase 3 clinical trials as alternatives to recombinant human erythropoietin (rHuEPO) for the treatment of anemia in chronic kidney disease (CKD). The present study reveals that dimethyloxaloylglycine (DMOG), a PHD inhibitor, and rHuEPO are equally effective in increasing hemoglobin levels in Dahl S rats; however, rHuEPO aggravated hypertension and renal injury, whereas DMOG attenuated the development of hypertension and prevented renal injury. PHD inhibitors may provide a safer therapeutic option for the treatment of anemia in CKD.

Additional effects of erythropoietin pretreatment, ischemic preconditioning, and N-acetylcysteine posttreatment in rat kidney reperfusion injury

Background/aim

Since the nature of ischemia/reperfusion (IR)-induced tissue damage is multifactorial and complex, in the current study, the effects of multiple treatment strategies via concomitant administration of erythropoietin (EPO) and N-acetylcysteine (NAC) with an ischemic preconditioning (IPC) regimen on renal IR injury were examined.

Materials and methods

Thirty male Wistar rats were subjected to bilateral occlusion of the renal pedicles for 50 min followed by reperfusion. EPO (1000 IU/kg) was administered for 3 days, as well as IPC before the IR and NAC (150 mg/kg) administration for 4 days after IR. The animals were randomly allocated into 6 groups (n = 5): sham, IR, EPO+IR, IPC+IR, NAC+IR, and EPO+IPC+NAC+IR. Kidney tissues and blood samples were obtained for oxidative stress, proinflammatory cytokines, and renal functional evaluations.

Results

IR caused significant inflammatory response, oxidative stress, and reduced renal function. Treatment with EPO, IPC, and NAC or a combination of two of them attenuated renal dysfunction and reduced the oxidative stress and inflammatory markers. Rats treated with the combination of EPO, IPC, and NAC showed a higher degree of protection compared to the other groups.

Conclusion

These results showed that concomitant administration of EPO and IPC along with posttreatment NAC may have additive beneficial effects on kidney IR injury during IR-induced acute renal failure.

Hydrogen sulfide treatment protects against renal ischemia-reperfusion injury via induction of heat shock proteins in rats

OBJECTIVES

Hydrogen sulfide (H2S) attenuates ischemia-reperfusion injury (IRI) in different organs. However, its mechanism of action in renal IRI remains unclear. The present study investigated the hypothesis that H2S attenuates renal IRI via the induction of heat shock proteins (HSPs).

MATERIALS AND METHODS

Adult Wistar rats were subjected to unilateral renal ischemia for 45 min followed by reperfusion for 6 hr. One group of rats underwent I/R without treatment, one group was administered 150 μmol/l sodium hydrosulfide (NaHS) prior to I/R, one group was injected with 100 mg/kg quercetin (an HSP inhibitor) intraperitoneally prior to I/R, and another group received quercetin prior to I/R and treatment with NaHS following I/R. Two other groups underwent a sham operation and one of them received 150 μmol/l NaHS following the sham operation whereas the other received no treatment. Renal function and histological changes were compared and relevant indices of oxidative stress, apoptosis, and inflammation were examined.

RESULTS

IRI increased serum creatinine and blood urea nitrogen concentrations, promoted lipid peroxidation by elevating malondialdehyde levels, suppressed superoxide dismutase activity, stimulated inflammation by inducing NF-kB, IL-2, and TLR-4 expression, and increased renal apoptosis. Levels of HSP 70, heme-oxygenase-1 (HO-1) and HSP 27 were increased following IRI and reversed following H2S treatment. H2S attenuated changes observed in pathology, lipid peroxidation, inflammation, and apoptosis following IRI. The administration of quercetin reversed all protective effects of H2S.

CONCLUSION

The present study indicated that H2S protected renal tissue against IRI induced lipid peroxidation, inflammation, and apoptosis, which may be attributed to the upregulation of HSP 70, HO-1, and HSP 27.

Safety and effectiveness of long-term use of darbepoetin alfa in non-dialysis patients with chronic kidney disease: a post-marketing surveillance study in Japan

Background

This post-marketing surveillance (PMS) study evaluated the safety and effectiveness of long-term darbepoetin alfa (darbepoetin) for the treatment of renal anemia in Japanese non-dialysis chronic kidney disease patients.

Methods

Patients were treated with darbepoetin and followed up for 3 years. Adverse events (AEs), adverse drug reactions (ADRs), hemoglobin (Hb) levels, and renal function were assessed. Patients were stratified by Hb level at the time of occurrence of cardiovascular-related AEs. Statistical analyses were performed to explore factors affecting the occurrence of AEs, cardiovascular-related AEs, and composite renal endpoints.

Results

In the safety analysis set (5547 patients), AEs and ADRs occurred in 44.4 and 7.1% of patients, respectively. Cardiovascular-related AEs were observed in 12.6% of the overall population. The proportion of patients who presented cardiovascular-related AEs was lower among those with a higher Hb level at the time of occurrence. In the effectiveness analysis set (5024 patients), mean Hb levels remained between 10.0 and 10.6 g/dL (Weeks 4–156). Three months after darbepoetin administration, patients with Hb ≥ 11 g/dL presented fewer composite renal endpoints than those with Hb < 11 g/dL (p = 0.0013), and the cumulative proportion of renal survival was higher in those with Hb ≥ 11 g/dL vs. Hb < 11 g/dL (p < 0.0001).

Conclusions

This PMS study showed the safety and effectiveness of long-term use of darbepoetin in a large number of patients. Patients with Hb ≥ 11 g/dL presented fewer composite renal endpoints than those with Hb < 11 g/dL, without an increase in the incidence of cardiovascular-related AEs.

Electronic supplementary material

The online version of this article (10.1007/s10157-018-1632-9) contains supplementary material, which is available to authorized users.

Brain-derived erythropoietin protects from intermittent hypoxia-induced cardiorespiratory dysfunction and oxidative stress in mice

Study Objectives

Based on the fact that erythropoietin (Epo) administration in rodents protects against spatial learning and cognitive deficits induced by chronic intermittent hypoxia (CIH)-mediated oxidative damage, here we tested the hypothesis that Epo in the brain protects against cardiorespiratory disorders and oxidative stress induced by CIH in adult mice.

Methods

Adult control and transgenic mice overexpressing Epo in the brain only (Tg21) were exposed to CIH (21%-10% O2-10 cycles/hour-8 hours/day-7 days) or room air. After CIH exposure, we used the tail cuff method to measure arterial pressure, and whole-body plethysmography to assess the frequency of apneic episodes at rest, minute ventilation, and ventilatory responses to hypoxia and hypercapnia. Finally, the activity of pro-oxidant (XO-xanthine oxidase, and NADPH) and antioxidant (super oxide dismutase) enzymes was evaluated in the cerebral cortex and brainstem.

Results

Exposure of control mice to CIH significantly increased the heart rate and arterial pressure, the number of apneic events, and the ventilatory response to hypoxia and hypercapnia. Furthermore, CIH increased the ratio of pro-oxidant to antioxidant enzymes in cortex and brainstem tissues. Both physiological and molecular changes induced by CIH were prevented in transgenic Tg21 mice.

Conclusions

We conclude that the neuroprotective effect of Epo prevents oxidative damage in the brain and cardiorespiratory disorders induced by CIH. Considering that Epo is used in clinics to treat chronic kidney disease and stroke, our data show convincing evidence suggesting that Epo may be a promising alternative drug to treat sleep-disorder breathing.

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.

Heme Oxygenase 1 as a Therapeutic Target in Acute Kidney Injury

A common clinical condition, acute kidney injury (AKI) significantly influences morbidity and mortality, particularly in critically ill patients. The pathophysiology of AKI is complex and involves multiple pathways, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Recent evidence suggests that a single insult to the kidney significantly enhances the propensity to develop chronic kidney disease. Therefore, the generation of effective therapies against AKI is timely. In this context, the cytoprotective effects of heme oxygenase 1 (HO-1) in animal models of AKI are well documented. HO-1 modulates oxidative stress, autophagy, and inflammation and regulates the progression of cell cycle via direct and indirect mechanisms. These beneficial effects of HO-1 induction during AKI are mediated in part by the by-products of the HO reaction (iron, carbon monoxide, and bile pigments). This review highlights recent advances in the molecular mechanisms of HO-1-mediated cytoprotection and discusses the translational potential of HO-1 induction in AKI.

Targeting Iron Homeostasis in Acute Kidney Injury

Iron is an essential metal involved in several major cellular processes required to maintain life. Because of iron's ability to cause oxidative damage, its transport, metabolism, and storage is strictly controlled in the body, especially in the small intestine, liver, and kidney. Iron plays a major role in acute kidney injury and has been a target for therapeutic intervention. However, the therapies that have been effective in animal models of acute kidney injury have not been successful in human beings. Targeting iron trafficking via ferritin, ferroportin, or hepcidin may offer new insights. This review focuses on the biology of iron, particularly in the kidney, and its implications in acute kidney injury.

Cytoprotective effect of glutaraldehyde erythropoietin on HEK293 kidney cells after silver nanoparticle exposure

The toxic effects from exposure to silver nanoparticles (AgNPs), which are broadly present in many consumer products, have long raised concerns. Many studies have focused on the mechanisms of nanosilver, which cause toxicity in human cells, but little is known about prevention of this type of injury. This study investigated the in vitro effects of glutaraldehyde erythropoietin (GEPO), a cytoprotective compound derived from erythropoietin, in terms of cell protection against AgNP-induced injury. HEK293 cells were pretreated with or without GEPO before administration of AgNPs. The protective effects of GEPO in this cell line were assessed by the percentage of viable cells, alterations of cell morphology, and the proliferative capability of the cells. In addition, we assessed the role of GEPO in lowering cellular oxidative stress and regulating expression of the anti-apoptotic protein Bcl2. The results showed rescue effects on the percentage of viable and proliferative cells among GEPO pretreated cells. Pretreatment with GEPO maintained the normal cell shape and ultrastructural morphology. Moreover, GEPO reduced the generation of reactive oxygen species in cells and activated expression of Bcl2, which are the major mechanisms in protection against cellular toxicity induced by AgNPs. In conclusion, our study showed that the cytotoxic effects from exposure to AgNPs can be prevented by GEPO.

Effects of long-acting erythropoietin analog darbepoetin-α on adriamycin-induced chronic nephropathy

OBJECTIVES

To study the effects of darbepoetin-α (DPO-α) (erythropoietin analog) on adriamycin (ADR)-induced chronic nephropathy in rats.

METHODS

Sixty-nine male Sprague-Dawley rats divided into 3 groups (23 rats each): negative control group: normal rats received saline as a vehicle; positive control (ADR) group: rats received 2 iv injection of ADR via penile vein at 14-day interval without treatment; and DPO-α group: as ADR group but rats received sc DPO-α (0.3 μg/kg bw) once weekly for 12 weeks. By the end of experiment hemoglobin (Hb) content, serum creatinine, BUN, albumin, triglycerides and cholesterol, urinary protein excretion and kidney injury molecule-1 (KIM-1). GSH, malondialdehyde, caspase-3 expression histopathological and electron microscopic examinations for kidney tissues were done.

RESULTS

DPO-α significantly improved the animal survival rate and body weight, Hb, serum BUN, triglycerides, cholesterol, and albumin and urinary protein excretion and KIM-1 in urine. Also, administration of DPO-α improved the morphological damage in glomeruli and renal tubules as well as caspase-3 expression and markers of oxidative stress in kidney tissues.

CONCLUSION

Administration of DPO-α alleviates ADR nephropathy and this might due to improvement of Hb content, hyperlipidemia, enhancement of endogenous antioxidants, reduction of apoptosis and tubulointerstitial injury and maintaining the integrity of glomerular membrane.

Epoetin beta pegol alleviates oxidative stress and exacerbation of renal damage from iron deposition, thereby delaying CKD progression in progressive glomerulonephritis rats

The increased deposition of iron in the kidneys that occurs with glomerulopathy hinders the functional and structural recovery of the tubules and promotes progression of chronic kidney disease (CKD). Here, we evaluated whether epoetin beta pegol (continuous erythropoietin receptor activator: CERA), which has a long half‐life in blood and strongly suppresses hepcidin‐25, exerts renoprotection in a rat model of chronic progressive glomerulonephritis (cGN). cGN rats showed elevated urinary total protein excretion (uTP) and plasma urea nitrogen (UN) from day 14 after the induction of kidney disease (day 0) and finally declined into end‐stage kidney disease (ESKD), showing reduced creatinine clearance with glomerulosclerosis, tubular dilation, and tubulointerstitial fibrosis. A single dose of CERA given on day 1, but not on day 16, alleviated increasing uTP and UN, thereby delaying ESKD. In the initial disease phase, CERA significantly suppressed urinary 8‐OHdG and liver‐type fatty acid–binding protein (L‐FABP), a tubular damage marker. CERA also inhibited elevated plasma hepcidin‐25 levels and alleviated subsequent iron accumulation in kidneys in association with elevated urinary iron excretion and resulted in alleviation of growth of Ki67‐positive tubular and glomerular cells. In addition, at day 28 when the exacerbation of uTP occurs, a significant correlation was observed between iron deposition in the kidney and urinary L‐FABP. In our study, CERA mitigated increasing kidney damage, thereby delaying CKD progression in this glomerulonephritis rat model. Alleviation by CERA of the exacerbation of kidney damage could be attributable to mitigation of tubular damage that might occur with lowered iron deposition in tubules.

Antioxidant and antiapoptotic effects of darbepoetin-α against traumatic brain injury in rats

INTRODUCTION

In this study, we tried to determine whether darbepoetin-α would protect the brain from oxidative stress and apoptosis in a rat traumatic brain injury model.

MATERIAL AND METHODS

The animals were randomized into four groups; group 1 (sham), group 2 (trauma), group 3 (darbepoetin α), group 4 (methylprednisolone). In the sham group only the skin incision was performed. In all the other groups, a moderate traumatic brain injury modelwas applied.

RESULTS

Following trauma both glutathione peroxidase, superoxide dismutase levels decreased (p < 0.001 for both); darbepoetin-α increased the activity of both antioxidant enzymes (p = 0.001 and p < 0.001 respectively). Trauma caused significant elevation in the nitric oxide synthetase and xanthine oxidase levels (p < 0.001 for both). Administration of darbepoetin-α significantly decreased the levels of nitric oxide synthetase and xanthine oxidase (p < 0.001 for both). Also, trauma caused significant elevation in the nitric oxide levels (p < 0.001); darbepoetin-α administration caused statistically significant reduction in the nitric oxide levels (p < 0.001). On the other hand, malondialdehyde levels were increased following trauma (p < 0.001), and darbepoetin α significantly reduced the malondialdehyde levels (p < 0.001). Due to the elevated apoptotic activity following the injury, caspase-3 activity increased significantly. Darbepoetin-α treatment significantly inhibited apoptosis by lowering the caspase-3 activity (p < 0.001). In the darbepoetin group, histopathological score was lower than the trauma group (p = 0.016).

CONCLUSIONS

In this study, darbepoetin-α was shown to be at least as effective as methylprednisolone in protecting brain from oxidative stress, lipid peroxidation and apoptosis.

Rhodiola crenulata- and Cordyceps sinensis-based supplement boosts aerobic exercise performance after short-term high altitude training

High altitude training is a widely used strategy for improving aerobic exercise performance. Both Rhodiola crenulata (R) and Cordyceps sinensis (C) supplements have been reported to improve exercise performance. However, it is not clear whether the provision of R and C during high altitude training could further enhance aerobic endurance capacity. In this study, we examined the effect of R and C based supplementation on aerobic exercise capacity following 2-week high altitude training. Alterations to autonomic nervous system activity, circulatory hormonal, and hematological profiles were investigated. Eighteen male subjects were divided into two groups: Placebo (n=9) and R/C supplementation (RC, n=9). Both groups received either RC (R: 1400 mg+C: 600 mg per day) or the placebo during a 2-week training period at an altitude of 2200 m. After 2 weeks of altitude training, compared with Placebo group, the exhaustive run time was markedly longer (Placebo: +2.2% vs. RC: +5.7%; p<0.05) and the decline of parasympathetic (PNS) activity was significantly prevented in RC group (Placebo: -51% vs. RC: -41%; p<0.05). Red blood cell, hematocrit, and hemoglobin levels were elevated in both groups to a comparable extent after high altitude training (p<0.05), whereas the erythropoietin (EPO) level remained higher in the Placebo group (∼48% above RC values; p<0.05). The provision of an RC supplement during altitude training provides greater training benefits in improving aerobic performance. This beneficial effect of RC treatment may result from better maintenance of PNS activity and accelerated physiological adaptations during high altitude training.

The administration of erythropoietin attenuates kidney injury induced by ischemia/reperfusion with increased activation of Wnt/β-catenin signaling

BACKGROUND/PURPOSE

Understanding the mechanisms of protecting the kidneys from injury is of great importance because there are no effective therapies that promote repair and the kidneys frequently do not repair adequately. Evidence has shown that erythropoietin (EPO) has a vital renoprotective role, independent of its erythropoietic effect. However, whether EPO can contribute to kidney repair after injury and the potential mechanisms are not fully understood.

METHODS

To investigate the renoprotective mechanism of EPO, a kidney ischemia/reperfusion injury (IRI) model was induced in adult male Sprague-Dawley rats. The rats were subsequently randomly treated with EPO or a vehicle 6 hours after the kidney IRI. The rats were sacrificed on Day 3, Day 5, and Day 7 post kidney IRI. Renal function and histological alterations were examined. Renal interstitial macrophage infiltration, cell proliferation, apoptosis, and angiogenesis were evaluated by immunostaining. Furthermore, the effects of EPO on the Wnt/β-catenin pathway and IRI-related micro-RNAs were investigated.

RESULTS

The administration of EPO significantly improved renal function and reduced tubular injury. Furthermore, EPO treatment significantly prevented tubular cell apoptosis and promoted cell proliferation after IRI. Erythropoietin significantly suppressed macrophage infiltration, compared to the vehicle. In addition, treatment with EPO markedly prevented the loss of microvasculature. We have also demonstrated that, compared to the vehicle, EPO administration enhanced the expression of Wnt7b and β-catenin, and downregulated miR-21, -214, -210, and -199a.

CONCLUSION

Erythropoietin protects the kidneys against IRI by attenuating injury of the renal microvasculature and tubule epithelial cells, by promoting Wnt/β-catenin pathway activation, and by regulating miRNA expression.

Erythropoietin Attenuates Pulmonary Vascular Remodeling in Experimental Pulmonary Arterial Hypertension through Interplay between Endothelial Progenitor Cells and Heme Oxygenase

BACKGROUND

Pulmonary arterial hypertension (PAH) is a pulmonary vascular disease with a high mortality, characterized by typical angio-proliferative lesions. Erythropoietin (EPO) attenuates pulmonary vascular remodeling in PAH. We postulated that EPO acts through mobilization of endothelial progenitor cells (EPCs) and activation of the cytoprotective enzyme heme oxygenase-1 (HO-1).

METHODS

Rats with flow-associated PAH, resembling pediatric PAH, were treated with HO-1 inducer EPO in the presence or absence of the selective HO-activity inhibitor tin-mesoporphyrin (SnMP). HO activity, circulating EPCs and pulmonary vascular lesions were assessed after 3 weeks.

RESULTS

In PAH rats, circulating EPCs were decreased and HO activity was increased compared to control. EPO treatment restored circulating EPCs and improved pulmonary vascular remodeling, as shown by a reduced wall thickness and occlusion rate of the intra-acinar vessels. Inhibition of HO activity with SnMP aggravated PAH. Moreover, SnMP treatment abrogated EPO-induced amelioration of pulmonary vascular remodeling, while surprisingly further increasing circulating EPCs as compared with EPO alone.

CONCLUSION

In experimental PAH, EPO treatment restored the number of circulating EPCs to control level, improved pulmonary vascular remodeling, and showed important interplay with HO activity. Inhibition of increased HO activity in PAH rats exacerbated progression of pulmonary vascular remodeling, despite the presence of restored number of circulating EPCs. We suggest that both EPO-induced HO-1 and EPCs are promising targets to ameliorate the pulmonary vasculature in PAH.

Ischemic postconditioning prevents renal ischemia reperfusion injury through the induction of heat shock proteins in rats

Ischemic postconditioning (IPo) attenuates ischemia-reperfusion injuries (IRI) in various organs, of both animals and humans. This study tested the hypothesis that IPo attenuates renal IRI through the upregulation of heat shock protein (HSP)70, HSP27 and heme oxygenase-1 (HO-1, also known as HSP 32) expression. Adult Sprague Dawley rats were subjected to bilateral renal ischemia for 45 min followed by reperfusion for up to 48 h. One group of rats received IPo prior to restoring full perfusion. Another group was administered 100 mg/kg HSP inhibitor quercetin, injected intraperitoneally 1 h prior to ischemia. Control rats received sham operations. Renal IR resulted in severe morphological and pathological changes, with increased serum creatinine and blood urea nitrogen concentrations. IR resulted in increased inflammation by inducing plasma tumor necrosis factor-α and renal nuclear factor kappa-light-chain-enhancer of activated B cells expression. IR also increased lipid peroxidation, as indicated by elevated malondialdehyde content, reduced superoxide dismutase activity and increased renal apoptosis. Renal HSP70, HSP27 and HO-1 mRNA and protein levels were increased by IR and further elevated by IPo. IPo attenuated these changes observed in pathology, lipid peroxidation, apoptosis and inflammation. Quercetin treatment abolished all the protective effects of IPo. In conclusion, this study showed that IPo can attenuate lipid peroxidation, apoptosis and inflammation as well as renal IRI by upregulating the expression of HSP70, HSP27 and HO-1.

Recombinant human erythropoietin in amyotrophic lateral sclerosis: a pilot study of safety and feasibility

Background and Purpose

It has been shown that erythropoietin is neuroprotective in animal models of neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). The aim of this study was to determine the safety and feasibility of repetitive high-dose recombinant human erythropoietin (rhEPO) therapy in ALS patients.

Methods

Two consecutive studies were conducted. We first recruited 26 subjects for an initial single-arm safety study. After a lead-in period of 3 months to assess the disease progression, rhEPO was infused intravenously (35,000 IU) once per month for 3 months, and the subjects were followed for an additional 3 months. The ALS Functional Rating Scale-Revised (ALSFRS-R) was used for clinical assessment. After confirming the safety of rhEPO, 60 subjects were recruited for the second controlled study (rhEPO and control groups), which involved a total of 6 infusions at a rate of 1/month.

Results

There were no serious adverse events in the first study. The mean rate of decline in the ALSFRS-R score was lower during the treatment period than during the lead-in period (mean±SD: 2.6±1.8 and 3.7±2.6, respectively; p=0.02). However, the rate of decline during the subsequent 3 months returned to that observed in the lead-in period. In the second study, the mean rate of decline in ALSFRS-R score was significantly lower in the rhEPO group than in the control group (during months 0-3, 1.8±1.7 vs. 3.1±2.3, p=0.03; during months 4-6, 2.1±2.2 vs. 3.5±2.3, p=0.02).

Conclusions

Intravenous high-dose rhEPO is both safe and feasible for the treatment of ALS. Further investigation using different intervals and doses should be considered.

Activation of hypoxia-inducible factors prevents diabetic nephropathy

Hyperglycemia results in increased oxygen consumption and decreased oxygen tension in the kidney. We tested the hypothesis that activation of hypoxia-inducible factors (HIFs) protects against diabetes-induced alterations in oxygen metabolism and kidney function. Experimental groups consisted of control and streptozotocin-induced diabetic rats treated with or without chronic cobalt chloride to activate HIFs. We elucidated the involvement of oxidative stress by studying the effects of acute administration of the superoxide dismutase mimetic tempol. Compared with controls, diabetic rats displayed tissue hypoxia throughout the kidney, glomerular hyperfiltration, increased oxygen consumption, increased total mitochondrial leak respiration, and decreased tubular sodium transport efficiency. Diabetic kidneys showed proteinuria and tubulointerstitial damage. Cobalt chloride activated HIFs, prevented the diabetes-induced alterations in oxygen metabolism, mitochondrial leak respiration, and kidney function, and reduced proteinuria and tubulointerstitial damage. The beneficial effects of tempol were less pronounced after activation of HIFs, indicating improved oxidative stress status. In conclusion, activation of HIFs prevents diabetes-induced alteration in kidney oxygen metabolism by normalizing glomerular filtration, which reduces tubular electrolyte load, preventing mitochondrial leak respiration and improving tubular transport efficiency. These improvements could be related to reduced oxidative stress and account for the reduced proteinuria and tubulointerstitial damage. Thus, pharmacologic activation of the HIF system may prevent development of diabetic nephropathy.

Protective effects of erythropoietin in traumatic spinal cord injury by inducing the Nrf2 signaling pathway activation

BACKGROUND

Erythropoietin has demonstrated neuroprotective effects against traumatic spinal cord injury (SCI), but the underlying mechanisms remain unclear. The signaling pathway of an antioxidant transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), has been shown to play an important role in protecting SCI-induced secondary spinal cord damage. This study was undertaken to explore the effect of recombinant human erythropoietin (rhEPO) on the activation of Nrf2 signaling pathway and secondary spinal cord damage in rats after SCI.

METHODS

Adult male Sprague-Dawley rats were subjected to laminectomy at T8-T9 and compression with a vascular clip. Three groups were analyzed: (1) sham group, (2) SCI group, and (3) SCI + rhEPO group (n = 16 per group). In the SCI + rhEPO group, rhEPO was administered at a dose of 5,000 IU/kg at 30 minutes after SCI. Spinal cord samples were extracted at 72 hours after the trauma.

RESULTS

As a result, we found that the treatment with rhEPO markedly up-regulated the messenger RNA expressions and activities of Nrf2 signaling pathway-related agents, including Nrf2, NAD(P)H:quinone oxidoreductase 1(NQO1), and glutathione S-transferase. The administration of rhEPO also significantly ameliorated the secondary spinal cord damage, as shown by a decreased severity of locomotion deficit, spinal cord edema, and apoptosis.

CONCLUSION

Post-SCI rhEPO administration induces Nrf2-mediated cytoprotective response in the injured spinal cord, and this may be a mechanism whereby rhEPO improves the outcome following SCI.

Recombinant human erythropoietin preconditioning attenuates liver ischemia reperfusion injury through the phosphatidylinositol-3 kinase/AKT/endothelial nitric oxide synthase pathway

BACKGROUND

The exact mechanism by which erythropoietin protects the liver from ischemia reperfusion (I/R) injury is not yet known. In the present study, we examined the role of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in the protective effect of recombinant human erythropoietin (rHuEPO) on I/R injury of the liver.

MATERIALS AND METHODS

We used a liver in situ I/R model. One hundred twenty adult male Sprague-Dawley rats were divided randomly into six groups. rHuEPO and (or) LY294002 were injected in the tail vein before the operation, and its effect was assessed by measuring the serum levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, nitric oxide (NO), and endothelin-1 (ET-1) and by histologic analysis. The expression of erythropoietin receptor (EPOR) and eNOS was measured by real-time polymerase chain reaction. Total AKT and eNOS and phosphorylated AKT and eNOS were examined by western blot.

RESULTS

rHuEPO dramatically attenuated the functional and morphologic injuries. The serum levels of alanine aminotransferase and lactate dehydrogenase were significantly decreased, but the amount of NO in the serum was increased in the I/R + rHuEPO group. Accordingly, rHuEPO administration significantly ameliorated the histologic damages at 6 h after reperfusion. rHuEPO significantly stimulated the phosphorylation of AKT and eNOS in the rats after liver I/R.

CONCLUSIONS

The protective effect of rHuEPO in I/R injury is mediated via the activation of the phosphatidylinositol-3 kinase/AKT/eNOS signaling pathway, at least in part, by increasing p-AKT and p-eNOS and leads to the maintenance of an elevated level of NO.

How the duration period of erythropoietin treatment influences the oxidative status of hemodialysis patients

BACKGROUND

End-stage renal disease is a state of enhanced oxidative stress (OS) and hemodialysis (HD) and renal anemia further augment this disbalance. Anemia correction with erythropoietin (EPO) may improve oxidative status. However, there is no evidence of time dependent effects of EPO therapy on redox status of HD patients.

OBJECTIVE

The aim of this study was to evaluate whether the duration of EPO treatment may affect OS parameters in uremic patients.

PATIENTS AND METHODS

104 HD patients and 29 healthy volunteers were included. Patients were divided into 3 groups according to the duration of EPO treatment. Forth group consisted of HD patients without EPO treatment. Plasma and erythrocyte malondialdehyde (MDA, MDA(rbc)), reactive carbonyl groups (RCG), plasma sulfhydryl (-SH) groups and total antioxidative capacity (TAC) levels were evaluated.

RESULTS

HD patients both with and without EPO treatment, showed a significant increase in all oxidative parameters without significance between EPO treated and -untreated group. The decrease in MDA and MDA(rbc) levels coincided with the duration of EPO treatment. A negative correlation was observed between the duration of EPO treatment and serum MDA (r=-0.309, p=0.003). Increasing periods of EPO treatment were associated with decrease in RCG, without significance between EPO groups. Increase in TAC accompanied increasing durations of EPO treatment, with EPO treatment for more than 24 months causing the most striking changes (p<0.05). There were no significant differences in -SH levels between EPO subgroups.

CONCLUSION

Our results suggest that long term administration of EPO attenuated the lipid peroxidation process and restored the levels of antioxidants.

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.

Carbon monoxide induced erythroid differentiation of K562 cells mimics the central macrophage milieu in erythroblastic islands

Growing evidence supports the role of erythroblastic islands (EI) as microenvironmental niches within bone marrow (BM), where cell-cell attachments are suggested as crucial for erythroid maturation. The inducible form of the enzyme heme oxygenase, HO-1, which conducts heme degradation, is absent in erythroblasts where hemoglobin (Hb) is synthesized. Yet, the central macrophage, which retains high HO-1 activity, might be suitable to take over degradation of extra, harmful, Hb heme. Of these enzymatic products, only the hydrophobic gas molecule - CO can transfer from the macrophage to surrounding erythroblasts directly via their tightly attached membranes in the terminal differentiation stage.

Based on the above, the study hypothesized CO to have a role in erythroid maturation. Thus, the effect of CO gas as a potential erythroid differentiation inducer on the common model for erythroid progenitors, K562 cells, was explored. Cells were kept under oxygen lacking environment to mimic BM conditions. Nitrogen anaerobic atmosphere (N₂A) served as control for CO atmosphere (COA). Under both atmospheres cells proliferation ceased: in N₂A due to cell death, while in COA as a result of erythroid differentiation. Maturation was evaluated by increased glycophorin A expression and Hb concentration. Addition of 1%CO only to N₂A, was adequate for maintaining cell viability. Yet, the average Hb concentration was low as compared to COA. This was validated to be the outcome of diversified maturation stages of the progenitor's population.

In fact, the above scenario mimics the in vivo EI conditions, where at any given moment only a minute portion of the progenitors proceeds into terminal differentiation. Hence, this model might provide a basis for further molecular investigations of the EI structure/function relationship.

Erythropoietin administration modulates pulmonary Nrf2 signaling pathway after traumatic brain injury in mice

BACKGROUND

In our previous studies, antioxidant transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway has been shown to play an important role in protecting traumatic brain injury (TBI)-induced acute lung injury (ALI). This study was designed to explore whether recombinant human erythropoietin (rhEPO) administration modulates pulmonary Nrf2 signaling pathway in a murine TBI model.

METHODS

Closed head injury was made by Hall's weight-dropping method. The rhEPO was administered at a dose of 5,000 IU/kg 30 minutes after TBI. Pulmonary capillary permeability, wet or dry weight ratio, apoptosis, Nrf2 and its downstream cytoprotective enzymes including NAD(P)H:quinone oxidoreductase 1, and glutathione S-transferase were investigated at 24 hours after TBI.

RESULTS

We found that treatment with rhEPO markedly ameliorated TBI-induced ALI, as characterized by decreased pulmonary capillary permeability, wet or dry weight ratio, and alveolar cells apoptosis. Administration of rhEPO also significantly upregulated the mRNA expressions and activities of Nrf2 signaling pathway-related agents, including Nrf2, NAD(P)H:quinone oxidoreductase 1, and glutathione S-transferase.

CONCLUSIONS

The results of this study suggest that post-TBI rhEPO administration may induce Nrf2-mediated cytoprotective response in the lung, and this may be a mechanism whereby rhEPO reduces TBI-induced ALI.

Reactive Oxygen Species Modulation of Na/K-ATPase Regulates Fibrosis and Renal Proximal Tubular Sodium Handling

The Na/K-ATPase is the primary force regulating renal sodium handling and plays a key role in both ion homeostasis and blood pressure regulation. Recently, cardiotonic steroids (CTS)-mediated Na/K-ATPase signaling has been shown to regulate fibrosis, renal proximal tubule (RPT) sodium reabsorption, and experimental Dahl salt-sensitive hypertension in response to a high-salt diet. Reactive oxygen species (ROS) are an important modulator of nephron ion transport. As there is limited knowledge regarding the role of ROS-mediated fibrosis and RPT sodium reabsorption through the Na/K-ATPase, the focus of this review is to examine the possible role of ROS in the regulation of Na/K-ATPase activity, its signaling, fibrosis, and RPT sodium reabsorption.

Influence of erythropoietin on arterial stiffness and endothelial function in renal transplant recipients

BACKGROUND/AIMS

Recent retrospective studies suggest an association of therapy with erythropoiesis-stimulating agents (ESAs) and increased mortality in renal transplant recipients (RTR). Large artery structure and function are significantly impaired in RTR which contributes to their high cardiovascular morbidity and could be altered by erythropoietin. We aimed to examine the influence of ESA therapy on large artery stiffness and endothelial function in RTR.

METHODS

63 RTR with chronic allograft dysfunction and renal anemia were randomized to a group receiving darbepoetin alfa (Dar) and a control group (Co). At baseline and after 8 months of treatment (cumulative Dar dose 11.1 µg/kg b.w.) brachial and common carotid artery distensibility coefficients, aortic pulse wave velocity, brachial artery flow-mediated and nitroglycerin-mediated vasodilation were measured as well as the following biomarkers of vascular function: vWF, sVCAM, sICAM, E-selectin, t-PA and PAI-1.

RESULTS

23 patients in the Dar group and 17 patients in the Co group were available for per-protocol analysis. Hemoglobin increased significantly from 10.9 to 12.6 g/dl after 8 months in the Dar group, whereas it remained stable at 11.3 g/dl in the Co group. Effects on large artery stiffness, endothelial function and biomarkers of vascular function did not differ significantly between the two groups.

CONCLUSION

Therapy with Dar during 8 months did not significantly impact parameters of large artery stiffness and endothelial function in RTR. These data suggest that therapy with erythropoietin does not deteriorate arterial stiffness and endothelial function in RTR.

Recombinant human erythropoietin reduces aggregation of mutant Cu/Zn-binding superoxide dismutase (SOD1) in NSC-34 cells

Human erythropoietin (hEPO) has multiple actions in non-hematopoietic tissues, including neurotrophic, anti-oxidant, anti-apoptotic, and anti-inflammatory effects. To examine the effect of EPO in an vitro model of amyotrophic lateral sclerosis (ALS), we stably overexpressed wild SOD1 and a mutant form, SOD1/G93A, in NSC-34 motoneuron-like cells. Transformants harboring the wild and mutant forms of SOD1 were selected by G418 selection and immunoblot analysis. RT-PCR analysis showed that cox-2 expression was increased in the NSC-34/mSOD1s, and MTT assays and BrdU-ELISAs revealed reduced cell growth and proliferation in the NSC-34/mSOD1 cell line. Incubation with 5 or 10IU/mL rhEPO increased the viability and decreased the cox-2 expression in the dNSC-34/mSOD1s cells. Immunocytochemical staining with anti-SOD1 antibody revealed the presence of aggregates of mSOD1 protein in dNSC-34/mSOD1 cells. Incubation with10IU/mL rhEPO reduced the proportion of cells containing such aggregates. Our findings suggest that the anti-oxidant and anti-inflammatory effects of EPO increase the survival of NSC-34/mSOD1 cells and reduce aggregation of the mutant SOD1 protein.

Erythropoietin ameliorates renal ischemia and reperfusion injury via inhibiting tubulointerstitial inflammation

BACKGROUND

Tubulointerstitial inflammation is the characteristics of renal ischemia reperfusion injury (IRI) that is inevitable in kidney transplantation. Erythropoietin (EPO) has recently been shown to have protective effects on renal IRI by anti-apoptosis and anti-oxidation. Here, the effect and mechanism of EPO on renal IRI were further investigated, with a focus on tubulointerstitial inflammation.

MATERIALS AND METHODS

Male Sprague-Dawley rats were administrated with saline or EPO prior to IRI induced by bilateral renal pedicle clamping. Twenty-four hours following reperfusion, the effects of EPO on renal IRI were assessed by renal function and structure, tubulointerstitial myeloperoxidase (MPO) positive neutrophils, and proinflammatory mediator gene expression. The translocation and activity of NF-κB in renal tissues were also evaluated.

RESULTS

Compared with control groups, the EPO treated group exhibited lower serum urea and creatinine levels, limited tubular necrosis with a lower score of renal histological lesion. MPO positive cells in the tubulointerstitial area were greatly increased by IRI, but significantly reduced by the treatment of EPO. The gene expression of proinflammatory cytokines (IL-1β, IL-6, IL-10, and TNF-α) and chemokine (MCP-1) was also significantly decreased by EPO. In addition, less activation and nuclear-translocation of NF-κB was observed in the kidney treated by EPO as well.

CONCLUSION

EPO improved renal function and structure in IRI rats via reducing neutrophils in the tubulointerstitium, the production of proinflammatory cytokines and chemokine, as well as the activation and nuclear-translocation of NF-κB. EPO may have potential clinical applications as an anti-inflammation agent clinically for a wide range of injury.

Darbepoetin alfa suppresses tumor necrosis factor-α-induced endothelin-1 production through antioxidant action in human aortic endothelial cells: role of sialic acid residues

Recombinant human erythropoietin (r-HuEPO) is widely used to correct anemia in end-stage renal disease patients, who commonly suffer from atherosclerosis. Endothelin-1 (ET-1) has been implicated in the pathogenesis of atherosclerosis. Here, we tested whether darbepoetin alfa, a hypersialylated analogue of r-HuEPO, regulates tumor necrosis factor-α (TNF-α)-induced ET-1 production in human aortic endothelial cells, and sought to identify the signal pathways involved. Darbepoetin alfa attenuated TNF-α-induced ET-1 production. It also diminished TNF-α-induced reactive oxygen species (ROS) accumulation and subsequent activation of c-Jun NH2-terminal kinase (JNK), which regulates the DNA-binding activities of both AP-1 and NF-κB required for ET-1 gene transcription. Like a JNK inhibitor, darbepoetin alfa did not affect IκBα degradation or p65 nuclear translocation, but did inhibit mitogen- and stress-activated protein kinase 1 (MSK1) activation and attenuated p65 phosphorylation (serine 276), effects that may account for the reduction in NF-κB DNA-binding activity. Desialylation completely abolished darbepoetin alfa's inhibitory effects on TNF-α-induced ROS accumulation, MSK1 activation, and ET-1 gene expression, without affecting its stimulation of STAT5 activity. These data demonstrate that darbepoetin alfa suppresses TNF-α-induced ET-1 production through its antioxidant action and suggest that the sialic acid residues of darbepoetin alfa are essential for its antioxidant effect, possibly by scavenging ROS.

Erythropoietin protects against apoptosis and increases expression of non-neuronal cell markers in the hypoxia-injured developing brain

Erythropoietin (EPO) is a cytokine hormone with cytoprotective effects in many tissues including the brain. Although the benefits of administration of recombinant human EPO (rhEPO) for neonatal hypoxic brain injury have been demonstrated in neuronal tissue, the effect on non-neuronal cell populations is unclear. We tested the hypothesis that rhEPO would not only protect neuronal cells but also glial cells at a stage of brain development where their maturation was particularly sensitive, and also protect the vasculature. This was evaluated in a rat model of hypoxic injury. 1000 IU/kg rhEPO was delivered intraperitoneally at the start of 4 h hypoxia or normoxia. Treatment groups of neonatal rats (day of birth, at least N = 10 per group) were as follows: normoxia; normoxia plus rhEPO; hypoxia (8% FiO(2) delivered in temperature-controlled chambers); and hypoxia plus rhEPO. Day of birth in rats is equivalent to human gestation of 28-32 weeks. The effects of rhEPO administration, especially to non-neuronal cell populations, and the associated molecular pathways, were investigated. Apoptosis was increased with hypoxia and this was significantly reduced with rhEPO (p < 0.05). The neuronal marker, microtubule-associated protein-2, increased in expression (p < 0.05) when apoptosis was significantly reduced by rhEPO. In addition, compared with hypoxia alone, rhEPO-treated hypoxia had the following significant protein expression increases (p < 0.05): the intermediate filament structural protein nestin; myelin basic protein (oligodendrocytes); and glial fibrillary acidic protein (astrocytes). In conclusion, rhEPO protects the developing brain via anti-apoptotic mechanisms and promotes the health of non-neuronal as well as neuronal cell populations at a time when loss of these cells would have long-lasting effects on brain function.

Erythropoietin prevents vascular inflammation and oxidative stress in subtotal nephrectomized rat aorta beyond haematopoiesis

1. Recombinant human erythropoietin (rHuEPO) has been used for the management of renal anaemia. Recent studies suggest pleiotropic properties of rHuEPO in various tissues. The aim of the present study was to investigate the vasoprotective effects of rHuEPO in renal failure rats. 2. Rats subjected to 5/6 and 17/18 nephrectomy (5/6Nx and 17/18Nx rats, respectively) were treated with rHuEPO (75 U/kg, s.c.) three times a week for 2 weeks. 3. Administration of rHuEPO to 5/6Nx or 17/18Nx rats had no effect on systolic blood pressure or decreased haematocrit. However, rHuEPO treatment normalized proteinuria and creatinine clearance in 5/6Nx, but not in 17/18Nx, rats. 4. Vasodilation in response to acetylcholine in aortic rings was impaired in 5/6Nx and 17/18Nx rats and improved by rHuEPO in both groups. Immunohistochemical analysis revealed that macrophage infiltration into adventitial areas and the expression of osteopontin were enhanced in aortas from 5/6Nx and 17/18Nx rats, but that rHuEPO suppressed these effects. In addition, rHuEPO attenuated medial hyperplasia and NADPH oxidase-derived superoxide production in 5/6Nx and 17/18Nx rats. 5. Activation of the Akt signalling pathway was evident in rHuEPO-treated rats as the increased expression of phosphorylated Akt and glycogen synthase kinase-3β. Treatment with rHuEPO restored the expression of phosphorylated endothelial nitric oxide synthase in the aorta and urinary excretion of NO(x) in nephrectomized rats. 6. These results suggest that a low dose of rHuEPO results in the normalization of endothelial function, vascular inflammation and oxidative stress in rats with renal ablation beyond haematopoiesis. In addition, these vasoprotective effects are observed even in a state of deteriorating renal dysfunction.

Erythropoietin enhances endogenous haem oxygenase-1 and represses immune responses to ameliorate experimental autoimmune encephalomyelitis

Both erythropoietin (EPO) and haem oxygenase-1 (HO-1), an anti-oxidative stress protein, have proven protective roles in experimental autoimmune encephalomyelitis (EAE), a reliable animal model of multiple sclerosis. In this study, EPO delivered intraperitoneally could reduce disease severity in myelin oligodendrocyte glycoprotein (MOG)–EAE mice. To assess the effect of EPO on endogenous HO-1 in EAE, we investigated expression of HO-1 mRNA by real-time polymerase chain reaction (RT–PCR), protein expression centrally and peripherally by Western blot and immunohistochemistry and mean fluorescence intensity of splenic HO-1 by flow cytometry. A significantly higher expression of HO-1 in both the central nervous system (CNS) and spleen was shown in EPO-treated MOG–EAE mice than in controls.We further examined the immunomodulatory effect of EPO in EAE, and via RT–PCR demonstrated significantly lower expression of interferon-γ, interleukin (IL)-23, IL-6 and IL-17 mRNA, and significantly higher expression of IL-4 and IL-10 mRNA in CNS of EPO-treated MOG–EAE mice than in controls. Using flow cytometry, we also observed a significantly decreased ratio of both T helper type 1 (Th1) and Th17 lymphocyte subsets isolated from CNS and a significantly increased ratio of splenic regulatory CD4 T cells in EPO-treated MOG–EAE mice. In addition, we demonstrated that MOG-specific T cell proliferation was lower in the EPO-treated group than in controls and showed amelioration of EAE by adoptive transfer of splenocytes from EPO-treated MOG–EAE mice. Together, our data show that in EAE, EPO induction of endogenous HO-1 and modulation of adaptive immunity both centrally and peripherally may involve the repression of inflammatory responses.

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.

Local erythropoietin and endothelial progenitor cells improve regional cardiac function in acute myocardial infarction

Background

Expanded endothelial progenitor cells (eEPC) improve global left ventricular function in experimental myocardial infarction (MI). Erythropoietin beta (EPO) applied together with eEPC may improve regional myocardial function even further by anti-apoptotic and cardioprotective effects. Aim of this study was to evaluate intramyocardial application of eEPCs and EPO as compared to eEPCs or EPO alone in experimental MI.

Methods and Results

In vitro experiments revealed that EPO dosed-dependently decreased eEPC and leukocyte apoptosis. Moreover, in the presence of EPO mRNA expression in eEPC of proangiogenic and proinflammatory mediators measured by TaqMan PCR was enhanced. Experimental MI was induced by ligation and reperfusion of the left anterior descending coronary artery of nude rats (n = 8-9). After myocardial transplantation of eEPC and EPO CD68+ leukocyte count and vessel density were enhanced in the border zone of the infarct area. Moreover, apoptosis of transplanted CD31 + TUNEL + eEPC was decreased as compared to transplantation of eEPCs alone. Regional wall motion of the left ventricle was measured using Magnetic Resonance Imaging. After injection of eEPC in the presence of EPO regional wall motion significantly improved as compared to injection of eEPCs or EPO alone.

Conclusion

Intramyocardial transplantation of eEPC in the presence of EPO during experimental MI improves regional wall motion. This was associated with an increased local inflammation, vasculogenesis and survival of the transplanted cells. Local application of EPO in addition to cell therapy may prove beneficial in myocardial remodeling.

Erythropoietin attenuates hyperoxia-induced oxidative stress in the developing rat brain

Oxygen toxicity contributes to the pathogenesis of adverse neurological outcome in survivors of preterm birth in clinical studies. In infant rodent brains, hyperoxia triggers widespread apoptotic neurodegeneration, induces pro-inflammatory cytokines and inhibits growth factor signaling cascades. Since a tissue-protective effect has been observed for recombinant erythropoietin (rEpo), we hypothesized that rEpo would influence hyperoxia-induced oxidative stress in the developing rat brain. The aim of this study was to investigate the level of glutathione (reduced and oxidized), lipid peroxidation and the expression of heme oxygenase-1 (HO-1) and acetylcholinesterase (AChE) after hyperoxia and rEpo treatment. Six-day-old Wistar rats were exposed to 80% oxygen for 2-48 h and received 20,000 IU/kg rEpo intraperitoneally (i.p.). Sex-matched littermates kept under room air and injected with normal saline or rEpo served as controls. Treatment with rEpo significantly reduced hyperoxia-induced upregulation of oxidized glutathione (GSSG) and malondialdehyde, a product of lipid breakdown, whereas reduced glutathione (GSH) was upregulated by rEpo. In parallel, hyperoxia-treated immature rat brains revealed rEpo-suppressible upregulation of synaptic AChE-S as well as of the stress-inducible AChE-R variant, together predicting rEpo-protected cholinergic signaling and restrained inflammatory reactions. Furthermore, treatment with rEpo induced upregulation of HO-1 on mRNA, protein and activity level in the developing rat brain. Our results suggest that rEpo generates its protective effect against oxygen toxicity by a reduction of diverse oxidative stress parameters and by limiting the stressor-inducible changes in both HO-1 and cholinergic functions.

Renal Protective Effects of Erythropoietin on Ischemic Reperfusion Injury

While the problem of organ shortage has not yet been solved, the number of patients who need to be treated with dialysis due to end-stage renal disease (ESRD) is increasing each year. With the aim of eliminating dialytic therapy as much as possible, the opportunities for organ donation from expansive criteria donor (ECD) or marginal donors due to cardiac death have been increasing. With the purpose of extracting organs in a state in which the function is preserved as much as possible, we reexamined the conditions of tissue disorders resulting from temporary ischemia of the organs as well as changes in tissue function and the effects on the preservation of renal function over time by using rat models in order to clinically utilize erythropoietin, which has inhibitory effects on ischemia-reperfusion disorder, as has been conventionally reported. With 8- to 9-week-old Wister male rats, after the right kidney had been resected under general anesthesia, the left renal artery was clamped to inhibit the blood flow for 45 min. At 30 min before inhibiting the blood flow and after releasing the inhibited blood flow, 100 U/kg of recombinant human erythropoietin (rhEPO) was administered via the inferior vena cava and the abdominal cavity, and then the tissues and blood samples were extracted at 6 and 24 h after the release. The renal tissue specimens were evaluated using H&E staining and TUNEL staining in order to observe differences in the expression of apoptosis as well as the renal function and changes in the emergence of active oxygen were investigated by using samples that had been obtained from drawn blood. Moreover, we examined the degree of renal dysfunction by means of neutrophil gelatinase-associated lipocalin (NGAL) in the spot urine samples. The changes in renal function, which were observed according to the serum creatinine level, showed that the renal function was preserved with a significant difference in the rhEPO administration group. The liver deviation enzymes, which had also shown increases in the serum as well as the occurrence of renal dysfunction, showed clear decreases in the serum, even though changes with a significant difference were not observed in the rhEPO administration group. The active oxygen did not show changes before and after ischemia-reperfusion nor changes due to the rhEPO administration. When examining the status of apoptosis in the tissues, apoptosis was shown to be inhibited due to the rhEPO administration. It is believed that the main preservation effects of rhEPO are the elimination of cytopathy/cell death, as derived from the resulting ischemic condition that extends to the target organ before ischemia occurs. In this examination, no direct effects of rhEPO administration on the emergence of active oxygen were observed. It is therefore suggested that there is a possibility of preserving the renal function in marginal donors with a longer agonal stage by effectively using rhEPO.

Epoetin delta reduces oxidative stress in primary human renal tubular cells

Erythropoietin (EPO) exerts (renal) tissue protective effects. Since it is unclear whether this is a direct effect of EPO on the kidney or not, we investigated whether EPO is able to protect human renal tubular epithelial cells (hTECs) from oxidative stress and if so which pathways are involved. EPO (epoetin delta) could protect hTECs against oxidative stress by a dose-dependent inhibition of reactive oxygen species formation. This protective effect is possibly related to the membranous expression of the EPO receptor (EPOR) since our data point to the membranous EPOR expression as a prerequisite for this protective effect. Oxidative stress reduction went along with the upregulation of renoprotective genes. Whilst three of these, heme oxygenase-1 (HO-1), aquaporin-1 (AQP-1), and B-cell CLL/lymphoma 2 (Bcl-2) have already been associated with EPO-induced renoprotection, this study for the first time suggests carboxypeptidase M (CPM), dipeptidyl peptidase IV (DPPIV), and cytoglobin (Cygb) to play a role in this process.

Impact of anti-apoptotic and anti-oxidative effects of bone marrow mesenchymal stem cells with transient overexpression of heme oxygenase-1 on myocardial ischemia

Although mesenchymal stem cells (MSCs) have therapeutic potential for tissue injury, intolerance and poor cell viability limit their reparative capability. Therefore, we examined the impact of bone marrow-derived MSCs, in which heme oxygenase-1 (HO-1) was transiently overexpressed, on the repair of an ischemic myocardial injury. When MSCs and HO-1-overexpressed MSCs (MSCHO-1) were exposed to serum deprivation/hypoxia or H2O2-induced oxidative stress, MSCHO-1 exhibited increased resistance to cell apoptosis compared with MSCs (17 ± 1 vs. 30 ± 2%, P < 0.05) and were markedly resistant to cell death (2 ± 1 vs. 32 ± 2%, P < 0.05). Under these conditions, vascular endothelial growth factor (VEGF) production was 2.1-fold greater in MSCHO-1 than in MSCs. Pretreatment of MSCs and MSCHO-1 with phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt) pathway inhibitors such as LY-294002 (50 μM) or wortmannin (100 nM) significantly decreased VEGF production. In a rat infarction model with MSCs or MSCHO-1 (5 × 106 ± 0.1 × 106 cells/rat) transplantation, the number of TdT-mediated dUTP nick end-labeling-positive cells was significantly lower in the MSCHO-1 group than in the MSC group (12.1 ± 1.0 cells/field vs. 26.5 ± 2.6, P < 0.05) on the 4th day after cell transplantation. On the 28th day, increased capillary density associated with decreased infarction size was observed in the MSCHO-1 group (1,415 ± 47/mm2 with 21.6 ± 2.3%) compared with those in the MSCs group (1,215 ± 43/mm2 with 28.2 ± 2.3%, P < 0.05), although infarction size relative to area at risk was not different in each group at 24 h after transplantation. These results demonstrate that MSCHO-1 exhibit markedly enhanced anti-apoptotic and anti-oxidative capabilities compared with MSCs, thus contributing to improved repair of ischemic myocardial injury through cell survival and VEGF production associated with the PI 3-kinase/Akt pathway.