Renoprotective effect of erythropoietin against ischaemia-reperfusion injury in a non-human primate model

Low-Dose Erythropoietin Amplifies Beneficial Effects of Angiotensin II Blockade on Glomerulosclerosis

Exogenous erythropoietin (EPO) is used to treat anemia in patients with chronic kidney disease (CKD). Concerns about the possible adverse effect of EPO on the progression of CKD have been raised owing to nonerythroid cell effects. We investigated the effects of low-dose EPO, independent of correcting anemia, on existing glomerulosclerosis. Adult mice underwent 5/6 nephrectomy and were randomized into the following 4 groups at week 8 after surgery: vehicle (VEH), losartan (angiotensin II type 1 receptor blocker [ARB]), darbepoetin-α (DA), or combination (DA+ARB). Four weeks later, mice were euthanized, followed by evaluation of renal structure and function. Glomerular endothelial cells and podocytes were cultured to evaluate the effects of DA on cell migration, apoptosis, and Akt signaling. ARB reduced blood pressure, albuminuria, and the level of serum creatinine and increased hematocrit compared with VEH, whereas low-dose DA only reduced the level of serum creatinine. Combination treatment showed a trend to increase hematocrit and survival compared with ARB alone. Combination treatment but not ARB alone significantly reduced the progression of glomerulosclerosis compared with VEH. Low-dose DA resulted in more preserved glomerular and peritubular capillary endothelial cells with increased p-Akt and even further endothelial cell preservation in combination with ARB. In cultured glomerular endothelial cells, angiotensin II induced more apoptosis, reduced migration, and decreased p-Flk1, a receptor for the proangiogenic vascular endothelial growth factor. DA counteracted these injuries and increased p-Akt, a key factor in angiogenesis and cell survival. DA also protected cultured podocytes against transforming growth factor β-induced apoptosis and synaptopodin loss. Low-dose EPO directly protects glomerular and peritubular endothelial cells via Akt phosphorylation. Therefore, treatment using a combination of low-dose EPO and ARB results in less progression of glomerulosclerosis in an experimental CKD model.

Novel PHD2/HDACs hybrid inhibitors protect against cisplatin-induced acute kidney injury

Acute kidney injury (AKI) is associated with high morbidity and mortality. Cisplatin is a common chemotherapeutic, but its nephrotoxicity-driven AKI limits its clinical application. Currently, there are no specific and satisfactory therapies in the clinic for AKI. Inhibitors of hypoxia-inducible factor prolyl hydroxylase 2 (HIF-PHD2) or histone deacetylase (HDACs) had shown renoprotective effects against AKI in preclinical studies. This study aimed to develop a novel therapeutic to prevent AKI progression by targeting PHD2 and HDACs simultaneously. We designed and synthesized a series of PHD2/HDACs hybrid inhibitors. The initial drug activity screening identified a candidate compound 31c, which exhibited potent inhibitory activities against PHD2 and HDAC1/2/6. Cellular analyses further showed that 31c did not affect cisplatin's antitumor activity in cancer cells but strongly protected cisplatin-induced toxicity on HK-2 cells. In vivo studies with the cisplatin-induced AKI mouse model demonstrated that 31c remarkably alleviated kidney dysfunction with suppressed plasma BUN/SCr and increased EPO levels. The potent renoprotective effects of 31c on AKI were confirmed by significant improvements in pathological kidney conditions in the mouse model. These results suggest that the novel PHD2/HDACs hybrid inhibitor, 31c, has a clinical potential as the renoprotective agent for the treatment/prevention of cisplatin-induced AKI for various cancers.

Large animal models for translational research in acute kidney injury

While extensive research using animal models has improved the understanding of acute kidney injury (AKI), this knowledge has not been translated into effective treatments. Many promising interventions for AKI identified in mice and rats have not been validated in subsequent clinical trials. As a result, the mortality rate of AKI patients remains high. Inflammation plays a fundamental role in the pathogenesis of AKI, and one reason for the failure to translate promising therapeutics may lie in the profound difference between the immune systems of rodents and humans. The immune systems of large animals such as swine, nonhuman primates, sheep, dogs and cats, more closely resemble the human immune system. Therefore, in the absence of a basic understanding of the pathophysiology of human AKI, large animals are attractive models to test novel interventions. However, there is a lack of reviews on large animal models for AKI in the literature. In this review, we will first highlight differences in innate and adaptive immunities among rodents, large animals, and humans in relation to AKI. After illustrating the potential merits of large animals in testing therapies for AKI, we will summarize the current state of the evidence in terms of what therapeutics have been tested in large animal models. The aim of this review is not to suggest that murine models are not valid to study AKI. Instead, our objective is to demonstrate that large animal models can serve as valuable and complementary tools in translating potential therapeutics into clinical practice.

Effects of early high-dose erythropoietin on acute kidney injury following cardiac arrest: exploratory post hoc analyses from an open-label randomized trial

BACKGROUND

Acute kidney injury (AKI) is frequent in patients resuscitated from cardiac arrest (CA) and may worsen outcome. Experimental data suggest a renoprotective effect by treating these patients with a high dose of erythropoietin (Epo) analogues. We aimed to evaluate the efficacy of epoetin alpha treatment on renal outcome after CA.

METHODS

We did a post hoc analysis of the Epo-ACR-02 trial, which randomized patients with a persistent coma after a witnessed out-of-hospital CA. Only patients admitted in one intensive care unit were analysed. In the intervention group, patients received five intravenous injections of Epo spaced 12 h apart during the first 48 h, started as soon as possible after resuscitation. In the control group, patients received standard care without Epo. The main endpoint was the proportion of patients with persistent AKI defined by Kidney Disease: Improving Global Outcomes criteria at Day 2. Secondary endpoints included the occurrence of AKI through Day 7, estimated glomerular filtration rate (eGFR) at Day 28, haematological indices and adverse events.

RESULTS

A total of 162 patients were included in the primary analysis (74 in the Epo group, 88 in the control group). Baseline characteristics were similar in the two groups. At Day 2, 52.8% of the patients (38/72) in the intervention group had an AKI, as compared with 54.4% of the patients (46/83) in the control group (P = 0.74). There was no significant difference between the two groups regarding the proportion of patients with AKI through Day 7. Among patients with persistent AKI at Day 2, 33% (4/12) in the intervention group had an eGFR <75 mL/min/1.73 m2 compared with 25% (3/12) in the control group at Day 28 (P = 0.99). We found no significant differences in haematological indices or adverse events.

CONCLUSION

After CA, early administration of Epo did not confer any renal protective effect as compared with standard therapy.

Renoprotective potential of exogen erythropoietin on experimental ruptured abdominal aortic aneurysm model: An animal study

Objective(s):

The aim of this study is to investigate the renoprotective effect of erythropoietin (EPO) on hypovolemic shock and ischemia/reperfusion (IR) injury on kidneys as end-organs in an experimentally-created ruptured abdominal aortic aneurysm (rAAA) model.

Materials and Methods:

Thirty anesthetized Sprague-Dawley male rats were randomized to sham ((Sh n:6) (Sh+EPO n:6)) or shock and I/R groups ((S/IR n:9) (S/IR+EPO n:9)). Additional surgical procedure except aortic exploration was not performed on Sh and Sh+EPO groups. 60 min of shock, 60 min of ischemia, and 120 min of reperfusion were applied on S/IR and S/IR+EPO groups. In the S/IR and S/IR+EPO groups, hemorrhagic shock, lower torso ischemia, and reperfusion were created. At the end of the shock period, saline solutions were separately and equally administered to Sh and S/IR groups, whereas 2000 U/kg EPO was intraperitoneally administered to Sh+EPO and S/IR+EPO groups. At the end of the experimental study, some biochemical and histological parameters were studied in serum and kidney tissues.

Results:

Biochemical parameters were all significantly increased in the S/IR group compared with the Sh group. These parameters were not statistically significantly different between S/IR+EPO and Sh+EPO groups. In histopathologic examination, EPO prevented high-grade injury.

Conclusion:

Our data indicate that EPO may have a renoprotective effect and reduce the systemic inflammatory response that resulted from shock and I/R in an experimental model of rAAA.

Renal Procurement: Techniques for Optimizing the Quality of the Graft in the Cadaveric Setting

PURPOSE OF REVIEW

Kidney transplantation is the best treatment for end-stage renal disease. However, due to organ shortage, suboptimal grafts are increasingly being used.

RECENT FINDINGS

We carried out a review on the methods and techniques of organ optimization in the cadaveric setting. Donor care is the first link in a chain of care. Right after brain death, there is a set of changes, of which hormonal and hemodynamic changes are the most relevant. Several studies have been conducted to determine which drugs to administer, although in most cases, the results are not definitive. The main goal seems rather achieve a set of biochemical and hemodynamic objectives. The ischemia-reperfusion injury is a critical factor for kidney damage in transplantation. One of the ways found to deal with this type of injury is preconditioning. Local and remote ischemic preconditioning has been studied for various organs, but studies on the kidney are scarce. A new promising area is pharmacological preconditioning, which is taking its first steps. Main surgical techniques were established in the late twentieth century. Some minor new features have been introduced to deal with anatomical variations or the emergence of donation after circulatory death. Finally, after harvesting, it is necessary to ensure the best conditions for the kidneys until the time of transplantation. Much has evolved since static cold preservation, but the best preservation conditions are yet to be determined. Conservation in the cold has come to be questioned, and great results have appeared at temperatures closer to physiological.

Mitochondria-targeted antioxidant MitoQ reduced renal damage caused by ischemia-reperfusion injury in rodent kidneys: Longitudinal observations of T2 -weighted imaging and dynamic contrast-enhanced MRI

Purpose

To investigate the effect of mitochondria‐targeted antioxidant MitoQ in reducing the severity of renal ischemia‐reperfusion injury (IRI) in rats using T₂‐weighted imaging and dynamic contrast‐enhanced MRI (DCE‐MRI).

Methods

Ischemia‐reperfusion injury was induced by temporarily clamping the left renal artery. Rats were pretreated with MitoQ or saline. The MRI examination was performed before and after IRI (days 2, 5, 7, and 14). The T₂‐weighted standardized signal intensity of the outer stripe of the outer medulla (OSOM) was measured. The unilateral renal clearance rate k_cl was derived from DCE‐MRI. Histopathology was evaluated after the final MRI examination.

Results

The standardized signal intensity of the OSOM on IRI kidneys with MitoQ were lower than those with saline on days 5 and 7 (P = 0.004, P < 0.001, respectively). K_cl values of IRI kidneys with MitoQ were higher than those with saline at all time points (P = 0.002, P < 0.001, P = 0.001, P < 0.001). Histopathology showed that renal damage was the most predominant on the OSOM of IRI kidneys with saline, which was less obvious with MitoQ (P < 0.001).

Conclusions

These findings demonstrate that MitoQ can reduce the severity of renal damage in rodent IRI models using T₂‐weighted imaging and DCE‐MRI. Magn Reson Med 79:1559–1667, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

The Protective Effects of Helix B Surface Peptide on Experimental Acute Liver Injury Induced by Carbon Tetrachloride

BACKGROUND

To investigate the protective effects of helix B surface peptide (HBSP) on acute liver injury induced by carbon tetrachloride (CCl₄).

METHODS

HBSP (8 nmol/kg) was intraperitoneally injected into C57 BL/6 mice 2 h after CCl₄ administration. Serum and liver tissue samples were collected 24 h after injury. Liver function and histological injuries were evaluated. Inflammatory cell infiltration and cytokines were examined and hepatocytes apoptosis was measured. The human liver cell line LO2 and murine primary hepatocytes were stimulated by CCl₄ with and without HBSP treatment and glutathione peroxidase activity, cell survival, and apoptosis were evaluated. In addition, we examined the PI3K/Akt/mTORC1 pathway to elucidate the mechanism underlying HBSP-mediated protection in acute liver injury.

RESULTS

HBSP significantly decreased serum alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and pro-inflammatory cytokines in liver tissues after CCl₄ injection compared with those in the control group. Immunohistochemical staining indicated that the number of CD3-, CD8-, and CD68-positive cells and the expression of cleaved caspase-3 were significantly decreased by HBSP treatment. Additionally, HBSP reduced apoptosis in vivo. In an in vitro study, the glutathione peroxidase activity and survival rate increased, while the total apoptotic rate was reduced in the HBSP-treated group compared with that in the control group after CCl₄ treatment. HBSP activated the PI3K/Akt/mTORC1 pathway, which was confirmed by the PI3K inhibitor LY294002 both in vivo and in vitro. Furthermore, HBSP increased the survival of mice with acute liver injury, and this effect was abolished by LY294002.

CONCLUSIONS

HBSP is a potential therapeutic agent against acute liver injury induced by CCl₄.

Human CD133+ Renal Progenitor Cells Induce Erythropoietin Production and Limit Fibrosis After Acute Tubular Injury

Persistent alterations of the renal tissue due to maladaptive repair characterize the outcome of acute kidney injury (AKI), despite a clinical recovery. Acute damage may also limit the renal production of erythropoietin, with impairment of the hemopoietic response to ischemia and possible lack of its reno-protective action. We aimed to evaluate the effect of a cell therapy using human CD133⁺ renal progenitor cells on maladaptive repair and fibrosis following AKI in a model of glycerol-induced rhabdomyolysis. In parallel, we evaluated the effect of CD133⁺ cells on erythropoietin production. Administration of CD133⁺ cells promoted the restoration of the renal tissue, limiting the presence of markers of injury and pro-inflammatory molecules. In addition, it promoted angiogenesis and protected against fibrosis up to day 60. No effect of dermal fibroblasts was observed. Treatment with CD133⁺ cells, but not with PBS or fibroblasts, limited anemia and increased erythropoietin levels both in renal tissue and in circulation. Finally, CD133⁺ cells contributed to the local production of erythropoietin, as observed by detection of circulating human erythropoietin. CD133⁺ cells appear therefore an effective source for cell repair, able to restore renal functions, including erythropoietin release, and to limit long term maldifferentiation and fibrosis.

Bridging translation for acute kidney injury with better preclinical modeling of human disease

The current lack of effective therapeutics for patients with acute kidney injury (AKI) represents an important and unmet medical need. Given the importance of the clinical problem, it is time for us to take a few steps back and reexamine current practices. The focus of this review is to explore the extent to which failure of therapeutic translation from animal studies to human studies stems from deficiencies in the preclinical models of AKI. We will evaluate whether the preclinical models of AKI that are commonly used recapitulate the known pathophysiologies of AKI that are being modeled in humans, focusing on four common scenarios that are studied in clinical therapeutic intervention trials: cardiac surgery-induced AKI; contrast-induced AKI; cisplatin-induced AKI; and sepsis associated AKI. Based on our observations, we have identified a number of common limitations in current preclinical modeling of AKI that could be addressed. In the long term, we suggest that progress in developing better preclinical models of AKI will depend on developing a better understanding of human AKI. To this this end, we suggest that there is a need to develop greater in-depth molecular analyses of kidney biopsy tissues coupled with improved clinical and molecular classification of patients with AKI.

Improving the outcome of kidney transplantation by ameliorating renal ischemia reperfusion injury: lost in translation?

Kidney transplantation is the treatment of choice in patients with end stage renal disease. During kidney transplantation ischemia reperfusion injury (IRI) occurs, which is a risk factor for acute kidney injury, delayed graft function and acute and chronic rejection. Kidneys from living donors show a superior short- and long-term graft survival compared with deceased donors. However, the shortage of donor kidneys has resulted in expansion of the donor pool by using not only living- and brain death donors but also kidneys from donation after circulatory death and from extended criteria donors. These grafts are associated with an increased sensitivity to IRI and decreased graft outcome due to prolonged ischemia and donor comorbidity. Therefore, preventing or ameliorating IRI may improve graft survival. Animal experiments focus on understanding the mechanism behind IRI and try to find methods to minimize IRI either before, during or after ischemia. This review evaluates the different experimental strategies that have been investigated to prevent or ameliorate renal IRI. In addition, we review the current state of translation to the clinical setting. Experimental research has contributed to the development of strategies to prevent or ameliorate IRI, but promising results in animal studies have not yet been successfully translated to clinical use.

Bridging Translation by Improving Preclinical Study Design in AKI

Despite extensive research, no therapeutic interventions have been shown to prevent AKI, accelerate recovery of AKI, or reduce progression of AKI to CKD in patients. This failure in translation has led investigators to speculate that the animal models being used do not predict therapeutic responses in humans. Although this issue continues to be debated, an important concern that has not been addressed is whether improvements in preclinical study design can be identified that might also increase the likelihood of translating basic AKI research into clinical practice using the current models. In this review, we have taken an evidence-based approach to identify common weaknesses in study design and reporting in preclinical AKI research that may contribute to the poor translatability of the findings. We focused on use of N-acetylcysteine or sodium bicarbonate for the prevention of contrast-induced AKI and use of erythropoietin for the prevention of AKI, two therapeutic approaches that have been extensively studied in clinical trials. On the basis of our findings, we identified five areas for improvement in preclinical study design and reporting. These suggested and preliminary guidelines may help improve the quality of preclinical research for AKI drug development.

Effect of recombinant human erythropoietin on mitomycin C-induced oxidative stress and genotoxicity in rat kidney and heart tissues

Mitomycin C (MMC) is an antineoplastic agent used for the treatment of several human malignancies. Nevertheless, the prolonged use of the drug may result in a serious heart and kidney injuries. Recombinant human erythropoietin (rhEPO) has recently been shown to exert an important cytoprotective effect in experimental brain injury and ischemic acute renal failure. The aim of the present work is to investigate the cardioprotective and renoprotective effects of rhEPO against MMC-induced oxidative damage and genotoxicity. Our results showed that MMC induced oxidative stress and DNA damage. rhEPO administration in any treatment conditions decreased oxidative damage induced by MMC. It reduced malondialdehyde and protein carbonyl levels. rhEPO ameliorated reduced glutathione plus oxidized glutathione modulation and the increased catalase activity after MMC treatment. Furthermore, rhEPO restored DNA damage caused by MMC. We concluded that rhEPO administration especially in pretreatment condition protected rats against MMC-induced heart and renal oxidative stress and genotoxicity.

rhErythropoietin-b as a tissue protective agent in kidney transplantation: a pilot randomized controlled trial

BACKGROUND

Extended criteria donor (ECD) and donation after circulatory death (DCD) kidneys are at increased risk of delayed graft function (DGF). Experimental evidence suggests that erythropoietin (EPO) attenuates renal damage in acute kidney injury. This study piloted the administration of high dose recombinant human EPO-beta at implantation of ECD and DCD kidneys, and evaluated biomarkers of kidney injury post-transplant.

METHODS

Forty patients were randomly assigned to receive either rhEPO-b (100,000 iu) (n = 19 in the intervention group, as 1 patient was un-transplantable post randomisation), or placebo (n = 20) in this, double blind, placebo-controlled trial at Manchester Royal Infirmary from August 2007 to June 2009. Participants received either an ECD (n = 17) or DCD (n = 22) kidney. Adverse events, renal function, haematopoietic markers, and rejections were recorded out to 90 days post-transplant. Biomarkers of kidney injury (neutrophil gelatinase-associated lipocalin, Kidney Injury Molecule-1 and IL-18) were measured in blood and urine during the first post-operative week.

RESULTS

The incidence of DGF (53% vs 55%) (RR = 1.0; CI = 0.5-1.6; p = 0.93) and slow graft function (SGF) (32% vs 25%) (RR = 1.1; CI = 0.5-1.9; p = 0.73) respectively, serum creatinine, eGFR, haemoglobin and haematocrit, blood pressure, and acute rejection were similar in the 2 study arms. High dose rhEPO-b had little effect on the temporal profiles of the biomarkers.

CONCLUSIONS

High dose rhEPO-b appears to be safe and well tolerated in the early post- transplant period in this study, but has little effect on delayed or slow graft function in recipients of kidneys from DCD and ECD donors. Comparing the profiles of biomarkers of kidney injury (NGAL, IL-18 and KIM-1) showed little difference between the rhEPO-b treated and placebo groups. A meta-analysis of five trials yielded an overall estimate of the RR for DGF of 0.89 (CI = 0.73; 1.07), a modest effect favouring EPO but not a significant difference. A definitive trial based on this estimate would require 1000-2500 patients per arm for populations with base DGF rates of 50-30% and 90% power. Such a trial is clearly unfeasible.

TRIAL REGISTRATION

EudraCT Number 2006-005373-22 ISRCTN ISRCTN85447324 registered 19/08/09.

Recombinant human erythropoietin pretreatment attenuates acute renal tubular injury against ischemia-reperfusion by restoring transient receptor potential channel-6 expression and function in collecting ducts

OBJECTIVE

Acute renal tubular injury is a serious complication in the postoperative period, which is associated with high mortality and increased ICU stay. We aimed to demonstrate the protective effect of rhEPO against acute tubular injury induced by ischemia-reperfusion and to explore the mechanism of canonical transient receptor potential channel-6.

DESIGN

Randomized laboratory animal study.

SETTINGS

Animal research laboratory.

INTERVENTIONS

Male Sprague-Dawley rats were randomly divided into three groups: the sham group, the control group, and the rhEPO group. Experimental acute tubular injury was established in rats by bilateral renal arterial occlusion for 30 minutes followed by reperfusion.

MEASUREMENTS AND MAIN RESULTS

Blood samples were obtained for cystatin-C and neutrophil gelatinase-associated lipocalin measurements by enzyme-linked immunosorbance assays. Seventy-two hours after reperfusion, urine samples were collected for osmolality and fractional excretion of sodium (%) assays on a chemistry analyzer. Kidneys were harvested at 24, 48, and 72 hours after reperfusion. Transient receptor potential channel-6, aquaporin-2, and Na,K-ATPase expression in collecting ducts were studied by immunofluorescence and Western blot. Coimmunoprecipitations were also performed to identify the possible signalplex relation between transient receptor potential channel-6 and aquaporin-2 or Na,K-ATPase channels. RhEPO pretreatment significantly inhibited serum cystatin-C (2 hr: 453 ± 64 μg/L vs 337 ± 28 μg/L, p < 0.01), serum neutrophil gelatinase-associated lipocalin (72 hr: 1,175 ± 107 ng/L vs 1,737 ± 402 ng/L, p < 0.05), and urinary fractional excretion of sodium (%) increase (0.9 ± 0.1 vs 2.2 ± 0.8, p < 0.05) and alleviated the decrease of urinary osmolality (1,293 ± 101 mosmol/kg H2O vs 767 ± 91 mosmol/kg H2O, p < 0.05) induced by ischemia-reperfusion injury. Meanwhile, recombinant human erythropoietin greatly improved the ischemia-reperfusion-induced attenuation of transient receptor potential channel-6 expression (48 hr: 42% ± 2% vs 67% ± 2% and 72 hr: 55% ± 2% vs 66% ± 2%), as well as aquaporin-2 and Na,K-ATPase expression in collecting ducts. Transient receptor potential channel-6 functionally interacted with Na,K-ATPase but not aquaporin-2.

CONCLUSIONS

Recombinant human erythropoietin pretreatment at the dose of 5,000 IU/kg potently prevented ischemia-reperfusion-induced acute tubular injury, which might be partly attributed to the restoring the effect of transient receptor potential channel-6 expression and collecting duct function.

Effect of high-dose erythropoietin on graft function after kidney transplantation: a meta-analysis of randomized controlled trials

PURPOSE

Current evidence suggests that preconditioning with erythropoietin (EPO) can protect against ischemia reperfusion injury in rodents. However, randomized controlled trials (RCTs) assessing the efficacy and safety of high-dose EPO in kidney transplantation have yielded inconclusive results. Herein, we performed a meta-analysis of RCTs to assess whether the administration of high-dose EPO can improve graft function and the potential adverse events.

METHODS

Relevant RCT studies that investigated high-dose EPO on graft function after kidney transplantation were comprehensively searched in Pubmed, Embase, and Cochrane Library until July 10, 2014. All statistical analyses were performed using Review Manager 5.0 and STATA 12.0.

RESULTS

A total of 4 RCTs involving 356 patients were identified. Comprehensively, a trend of reduction in the incidence of delayed graft function could be observed in the EPO group (EPO vs. placebo groups: RR=0.88); however, the result did not reach the significance level (95% CI, 0.72-1.08; P=0.21). Furthermore, no significant difference in the incidences of adverse events was observed between the two groups.

CONCLUSIONS

The current meta-analysis indicates that the administration of high-dose EPO is, to some extent, prone to protect kidney function without increasing the susceptibility to adverse events.

Erythropoietin: powerful protection of ischemic and post-ischemic brain

Ischemic brain injury inflicted by stroke and cardiac arrest ranks among the leading causes of death and long-term disability in the United States. The brain consumes large amounts of metabolic substrates and oxygen to sustain its energy requirements. Consequently, the brain is exquisitely sensitive to interruptions in its blood supply, and suffers irreversible damage after 10-15 min of severe ischemia. Effective treatments to protect the brain from stroke and cardiac arrest have proven elusive, due to the complexities of the injury cascades ignited by ischemia and reperfusion. Although recombinant tissue plasminogen activator and therapeutic hypothermia have proven efficacious for stroke and cardiac arrest, respectively, these treatments are constrained by narrow therapeutic windows, potentially detrimental side-effects and the limited availability of hypothermia equipment. Mounting evidence demonstrates the cytokine hormone erythropoietin (EPO) to be a powerful neuroprotective agent and a potential adjuvant to established therapies. Classically, EPO originating primarily in the kidneys promotes erythrocyte production by suppressing apoptosis of proerythroid progenitors in bone marrow. However, the brain is capable of producing EPO, and EPO's membrane receptors and signaling components also are expressed in neurons and astrocytes. EPO activates signaling cascades that increase the brain's resistance to ischemia-reperfusion stress by stabilizing mitochondrial membranes, limiting formation of reactive oxygen and nitrogen intermediates, and suppressing pro-inflammatory cytokine production and neutrophil infiltration. Collectively, these mechanisms preserve functional brain tissue and, thus, improve neurocognitive recovery from brain ischemia. This article reviews the mechanisms mediating EPO-induced brain protection, critiques the clinical utility of exogenous EPO to preserve brain threatened by ischemic stroke and cardiac arrest, and discusses the prospects for induction of EPO production within the brain by the intermediary metabolite, pyruvate.

Renoprotective capacities of non-erythropoietic EPO derivative, ARA290, following renal ischemia/reperfusion injury

Background

ARA290 is a non-erythropoietic EPO derivative which only binds to the cytoprotective receptor complex (EPOR₂-βcR₂) consisting of two EPO-receptors (EPOR) and two β common receptors (βcR). ARA290 is renoprotective in renal ischemia/reperfusion (I/R). In a renal I/R model we focussed on timing of post-reperfusional administration of ARA290. Furthermore, we investigated the anti-inflammatory properties of ARA290.

Methods

Twenty-six male Lewis/HanHsd rats were exposed to unilateral ischemia for 30 minutes, with subsequent removal of the contralateral kidney. Post-reperfusion, ARA290 was administered early (one hour), late (four hours) or repetitive (one and four hours). Saline was used as vehicle treatment. Rats were sacrificed after three days.

Results

Early ARA290 treatment improved renal function. Late- or repetitive treatment tended to improve clinical markers. Furthermore, early ARA290 treatment reduced renal inflammation and acute kidney injury at three days post-reperfusion. Late- or repetitive treatment did not affect inflammation or acute kidney injury.

Conclusions

ARA290 attenuated renal ischemia/reperfusion injury. This study showed the anti-inflammatory effect of ARA290 and suggests early administration in the post-reperfusional phase is most effective. ARA290 is a candidate drug for protection against ischemic injury following renal transplantation.

Erythropoietin-mediated protection in kidney transplantation: nonerythropoietic EPO derivatives improve function without increasing risk of cardiovascular events

The protective, nonerythropoietic effects of erythropoietin (EPO) have become evident in preclinical models in renal ischaemia/reperfusion injury and kidney transplantation. However, four recently published clinical trials using high-dose EPO treatment following renal transplantation did not reveal any protective effect for short-term renal function and even reported an increased risk of thrombosis. This review focusses on the current status of protective pathways mediated by EPO, the safety concerns using high EPO dosage and discusses the discrepancies between pre-clinical and clinical studies. The protective effects are mediated by binding of EPO to a heteromeric receptor complex consisting of two β-common receptors and two EPO receptors. An important role for the activation of endothelial nitric oxide synthase is proposed. EPO-mediated cytoprotection still has enormous potential. However, only nonerythropoietic EPO derivatives may induce protection without increasing the risk of cardiovascular events. In preclinical models, nonerythropoietic EPO derivatives, such as carbamoylated EPO and ARA290, have been tested. These EPO derivatives improve renal function and do not affect erythropoiesis. Therefore, nonerythropoietic EPO derivatives may be able to render EPO-mediated cytoprotection useful and beneficial for clinical transplantation.

Helix B surface peptide administered after insult of ischemia reperfusion improved renal function, structure and apoptosis through beta common receptor/erythropoietin receptor and PI3K/Akt pathway in a murine model

Erythropoietin (EPO) has been well recognized as a tissue protective agent by inhibiting apoptosis and inflammation. The tissue protective effect of EPO, however, only occurs at a high dosage, which may elicit severe side-effects at the meantime. Helix B surface peptide (HBSP), a novel peptide derived from the non-erythropoietic helix B of EPO, plays a specific role in tissue protection. We investigated effects of HBSP and the expression of its heterodimeric receptor, beta common receptor (βcR)/EPO receptor ( ), in a murine renal ischemia reperfusion (IR) injury model. HBSP significantly ameliorated renal dysfunction and tissue damage, decreased apoptotic cells in the kidney and reduced activation of caspase-9 and -3. The βcR/EPOR in the kidney was up-regulated by IR, but down-regulated by HBSP. Further investigation revealed that the expression and phosphorylation of Akt was dramatically enhanced by HBSP, but strongly reversed by wortmannin, the PI3K inhibitor. Wortmannin intervention improved βcR/EPOR expression, promoted caspase-9 and -3 activation, and increased active caspase-3 positive cells, while renal function and structure, and apoptotic cell counts scarcely changed. This result indicates a significant contribution of PI3K/Akt signaling pathway in the renoprotection of HBSP. The therapeutic effects of HBSP in this study suggest that HBSP could be a better candidate for renal protection.

Carbamylated erythropoietin-FC fusion protein and recombinant human erythropoietin during porcine kidney ischemia/reperfusion injury

PURPOSE

To test the hypothesis that a carbamylated EPO-FC fusion protein (cEPO-FC) or recombinant human erythropoietin (rhEPO) would protect against kidney ischemia/reperfusion (I/R) injury in pigs with atherosclerosis.

METHODS

Anesthetized and mechanically ventilated animals received cEPO-FC (50 μg kg(-1)), rhEPO (5,000 IU kg(-1)), or vehicle (n = 9 per group) prior to 120 min of aortic occlusion and over 4 h of reperfusion. During aortic occlusion, mean arterial pressure (MAP) was maintained at 80-120 % of baseline values by esmolol, nitroglycerin, and ATP. During reperfusion, noradrenaline was titrated to keep MAP at pre-ischemic levels. Blood creatinine and neutrophil gelatinase-associated lipocalin (NGAL) levels, creatinine clearance, fractional Na(+) excretion, and HE and PAS staining were used to assess kidney function and histological damage. Plasma interleukin-6, tumor necrosis factor-α, nitrate + nitrite and 8-isoprostane levels were measured to assess systemic inflammation, and nitrosative and oxidative stress.

RESULTS

I/R caused acute kidney injury with reduced creatinine clearance, increased fractional Na(+) excretion and NGAL levels, moderate to severe glomerular and tubular damage and apoptosis, systemic inflammation and oxidative and nitrosative stress, but there were no differences between the treatment groups. Pre-ischemia nitrate + nitrite and 8-isoprostanes levels were lower and higher, respectively, than in healthy animals of a previous study, and immune histochemistry showed higher endothelial nitric oxide synthase and lower EPO receptor expression in pre-ischemia kidney biopsies than in biopsies from healthy animals.

CONCLUSIONS

In swine with atherosclerosis, rhEPO and cEPO-FC failed to attenuate prolonged ischemia-induced kidney injury within an 8-h reperfusion period, possibly due to reduced EPO receptor expression resulting from pre-existing oxidative stress and/or reduced NO release.

Erythropoietin in the critically ill: do we ask the right questions?

There is a plethora of experimental data on the potential therapeutic benefits of recombinant human erythropoietin (rhEPO) and its synthetic derivatives in critical care medicine, in particular in ischemia/reperfusion injury. Most of the recent clinical trials have not shown clear benefits, and, in some patients, EPO-aggravated morbidity and mortality was even reported. Treatment with rhEPO has been successfully used in patients with anemia resulting from chronic kidney disease, but even a subset of this patient population does not adequately respond to rhEPO therapy. The following viewpoint uses rhEPO as an example to highlight the possible pitfalls in current practice using young healthy animals for the evaluation of therapies to treat patients of variable age and underlying chronic co-morbidity.

Erythropoietin in the intensive care unit: beyond treatment of anemia

Erythropoietin (EPO) is the major hormone stimulating the production and differentiation of red blood cells. EPO is used widely for treating anemia of critical illness or anemia induced by chemotherapy. EPO at pharmacological doses is used in this setting to raise hemoglobin levels (by preventing the apoptosis of erythroid progenitor cells) and is designed to reduce patient exposure to allogenic blood through transfusions. Stroke, heart failure, and acute kidney injury are a frequently encountered clinical problem. Unfortunately, in the intensive care unit advances in supportive interventions have done little to reduce the high mortality associated with these conditions. Tissue protection with EPO at high, nonpharmacological doses after injury has been found in the brain, heart, and kidney of several animal models. It is now well known that EPO has anti-apoptotic effects in cells other than erythroid progenitor cells, which is considered to be independent of EPOs erythropoietic activities. This review article summarizes what is known in preclinical models of critical illness and discusses why this does not correlate with randomized, controlled clinical trials.