Recombinant human erythropoietin inhibits iNOS activity and reverts vascular dysfunction in splanchnic artery occlusion shock

Coping with hypoxemia: Could erythropoietin (EPO) be an adjuvant treatment of COVID-19?

A very recent epidemiological study provides preliminary evidence that living in habitats located at 2500 m above sea level (masl) might protect from the development of severe respiratory symptoms following infection with the novel SARS-CoV-2 virus. This epidemiological finding raises the question of whether physiological mechanisms underlying the acclimatization to high altitude identifies therapeutic targets for the effective treatment of severe acute respiratory syndrome pivotal to the reduction of global mortality during the COVID-19 pandemic. This article compares the symptoms of acute mountain sickness (AMS) with those of SARS-CoV-2 infection and explores overlapping patho-physiological mechanisms of the respiratory system including impaired oxygen transport, pulmonary gas exchange and brainstem circuits controlling respiration. In this context, we also discuss the potential impact of SARS-CoV-2 infection on oxygen sensing in the carotid body. Finally, since erythropoietin (EPO) is an effective prophylactic treatment for AMS, this article reviews the potential benefits of implementing FDA-approved erythropoietin-based (EPO) drug therapies to counteract a variety of acute respiratory and non-respiratory (e.g. excessive inflammation of vascular beds) symptoms of SARS-CoV-2 infection.

Evaluation of the effects of erythropoietin and interleukin-6 in rats submitted to acute spinal cord injury

OBJECTIVE

To evaluate the effects of interleukin-6 (IL-6) and erythropoietin (EPO) in experimental acute spinal cord injury (SCI) in rats.

METHODS

Using standardized equipment, namely, a New York University (NYU) Impactor, a SCI was produced in 50 Wistar rats using a 10-g weight drop from a 12.5-mm height. The rats were divided into the following 5 groups of 10 animals each: "Group EPO", treated with erythropoietin only; "Group EPO + IL-6", treated with both substances; "Group IL-6", receiving IL-6 administration only; "Group Placebo", receiving a placebo solution; and "Group Sham", submitted to an incomplete procedure (only laminectomy, without SCI). All drugs and the placebo solution were administered intraperitoneally for three weeks. The animals were followed up for 42 days. Functional motor recovery was monitored by the Basso, Beattie, and Bresnahan (BBB) scale on days 2, 7, 14, 21, 28, 35 and 42. Motor-evoked potential tests were performed on the 42nd day. Histological analysis was performed after euthanasia.

RESULTS

The group receiving EPO exhibited superior functional motor results on the BBB scale. IL-6 administration alone was not superior to the placebo treatment, and the IL-6 combination with EPO yielded worse results than did EPO alone.

CONCLUSIONS

Using EPO after acute SCI in rats yielded benefits in functional recovery. The combination of EPO and IL-6 showed benefits, but with inferior results compared to those of isolated EPO; moreover, isolated use of IL-6 resulted in no benefit.

Erythropoietin attenuates experimental haemorrhagic shock-induced renal damage through an iNOS- dependent mechanism in male Wistar rats

AIM

Erythropoietin (EPO) is shown to exert protective effects on different tissues in haemorrhagic shock (HS) states. Nitric oxide (NO), as a multifunctional signaling molecule, is implicated in diverse physiologic and pathologic processes. In order to understand the exact mechanism of EPO protection, in this study we evaluated the role of different NOS enzymes in the EPO signaling pathway in male rats.

METHODS

Rats were randomized to five groups: 1) Sham, 2) HS 3) EPO 4) L-NAME, a non-specific NOS inhibitor 5) 1400W, a specific iNOS inhibitor. HS was induced by withdrawal of 50% of total blood volume. After 2h, resuscitation was performed with the shed blood and Ringer's lactate. In group 3, rats were treated with EPO (300IU/kg, i.v.) over 10min before HS induction. In the L-NAME and 1400W groups, L-NAME (10mg/kg, i.p.) and 1400W (2mg/kg, i.p.) were administered 30min before EPO injection. Blood and kidney tissue samples were obtained 3h after resuscitation.

RESULTS

EPO increased the survival rate and significantly improved kidney function and histology compared to the HS group. There were less renal oxidative stress, apoptosis and systemic inflammatory responses in the EPO group. EPO increased eNOS and more abundantly iNOS mRNA expressions. L-NAME and 1400W significantly abolished all beneficial effects of EPO.

CONCLUSION

In this in vivo animal model, we showed that EPO administration prior to HS attenuates renal injury and dysfunction in rats. The protective effects of EPO may be mediated by nitric oxide and the expression of different NOS enzymes, especially iNOS isoform.

Mesenteric lymph reperfusion exacerbates spleen injury caused by superior mesenteric artery occlusion shock

The intestinal lymph pathway plays an important role in the pathogenesis of organ injury following superior mesenteric artery occlusion (SMAO) shock. We hypothesized that mesenteric lymph reperfusion (MLR) is a major cause of spleen injury after SMAO shock. To test this hypothesis, SMAO shock was induced in Wistar rats by clamping the superior mesenteric artery (SMA) for 1 h, followed by reperfusion for 2 h. Similarly, MLR was performed by clamping the mesenteric lymph duct (MLD) for 1 h, followed by reperfusion for 2 h. In the MLR+SMAO group rats, both the SMA and MLD were clamped and then released for reperfusion for 2 h. SMAO shock alone elicited: 1) splenic structure injury, 2) increased levels of malondialdehyde, nitric oxide (NO), intercellular adhesion molecule-1, endotoxin, lipopolysaccharide receptor (CD14), lipopolysaccharide-binding protein, and tumor necrosis factor-α, 3) enhanced activities of NO synthase and myeloperoxidase, and 4) decreased activities of superoxide dismutase and ATPase. MLR following SMAO shock further aggravated these deleterious effects. We conclude that MLR exacerbates spleen injury caused by SMAO shock, which itself is associated with oxidative stress, excessive release of NO, recruitment of polymorphonuclear neutrophils, endotoxin translocation, and enhanced inflammatory responses.

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.

Erythropoietin improves neuronal proliferation in dentate gyrus of hippocampal formation in an animal model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a prevalent disorder with severe learning and memory defects. Because it has been demonstrated that erythropoietin (EPO) has positive effects on the central nervous system, the aim of this study was to evaluate the effect of EPO on neuronal proliferation in dentate gyrus of hippocampal formation in a well-defined model for AD.

MATERIALS AND METHODS

A rat model of sporadic dementia of Alzheimer's type was established by a bilateral intracerebroventricular injection of streptozotocin (ICV-STZ). Impairment of learning and memory was confirmed 2 weeks after ICV-STZ injection by passive avoidance learning test and then rats were divided into fourgroups:Control, control-EPO, Alzheimer and Alzheimer-EPO. EPO was injected intraperitoneally every other day with a dose of 5000 IU/kg and, finally, the rats were anesthetized and decapitated for immunohistochemical study and neurogenesis investigation (by Ki67 method) in dentate gyrus of hippocampal formation.

RESULTS

The results driven from the histological study showed that EPO significantly increases neuronal proliferation in dentate gyrus of hippocampus in the Alzheimer-EPO group compared with the control, control-EPO and Alzheimer groups; however, there were no differences between the other groups.

CONCLUSION

Our results show that even though EPO in intact animals doesnot change neurogenesis in dentate gyrus, it can nonetheless significantly increase neurogenesis if there is an underlying disorder like neurodegenerative diseases.

Effects of darbepoetin-α in spinal cord ischemia-reperfusion injury in the rabbit

BACKGROUND

Darbepoetin-alpha (DA) is a novel erythropoiesis-stimulating agent developed for treating anemia. In animal models, recombinant human erythropoietin has been reported to be beneficial for neuroprotection. In this study, we determined whether DA would protect the spinal cord against ischemia-reperfusion injury in a rabbit model.

METHODS

Forty rabbits were randomized into five groups of eight animals each: group 1 (sham), group 2 (ischemia), group 3 (vehicle), group 4 (30 mg/kg methylprednisolone), group 5 (30 μg/kg DA). Only laparotomy was performed in the sham group. In all the other groups, the spinal cord ischemia model was created by a 20-min occlusion of the aorta just caudal to renal artery with an aneurysm clip. The drugs were administered immediately after the clamp was removed. The animals were killed 24 h later. Spinal cord segments between L2 and L5 were harvested for analysis. Neurological evaluation was performed with the Tarlov scoring system just before the animals were killed. Level of tissue malondialdehyde was analyzed as a marker of lipid peroxidation and tissue caspase-3 activity as a marker of apoptosis. Also, histopathological evaluation of the tissues was performed.

RESULTS

Both malondialdehyde and caspase-3 levels were significantly decreased by DA administration. Histopathological evaluation of the tissues also demonstrated decrease in neuronal degeneration and infiltration parameters after DA administration. In the DA group, neurological outcome scores were statistically significantly better compared with the ischemia and the vehicle groups.

CONCLUSIONS

Although further studies considering different dose regimens and time intervals are required, DA was shown to be at least as effective as methylprednisolone in spinal cord ischemia/reperfusion model.

Erythropoietin alleviates post-ischemic injury of rat hearts by attenuating nitrosative stress

AIMS

Nitrosative stress caused by ischemia contributes to poor functional recovery in hearts. A previous study showed that recombinant human erythropoietin (EPO) activates the Janus-tyrosine kinase 2/extracellular signal-regulated kinase (Jak2/ERK) pathway to protect myocardium against ischemia/reperfusion (IR) injury. However, it is not clear how pro-survival signals triggered by EPO affect the nitric oxide (NO) system in post-ischemic myocardial tissue.

MAIN METHODS

Isolated rat hearts were subjected to IR injury and changes in protein expression in the myocardium were evaluated by immunostaining.

KEY FINDINGS

Compared with untreated hearts, EPO-treated IR hearts showed significant improvements in contractility and reduced myocardial injury and infarction; this was associated with attenuated caspase-3 activation. Excess formation of NO metabolites and nitrotyrosine, which cause nitrosative stress, was markedly suppressed by EPO. The mechanism underlying EPO-mediated alleviation of nitrosative stress was related to an increase in arginase II expression and to the suppression of heat shock protein 90 (HSP90)-dependent upregulation of endothelial and inducible NO synthase (NOS). Myocardial EPO content was restored after EPO treatment, which in turn recruited signal transducer and activator of transcription (STAT) 3 protein and induced ERK signaling downstream of Jak2, which increased arginase II levels and suppressed HSP90 expression, respectively. Inhibition of STAT3 and ERK specifically reversed the effects of EPO on arginase II and HSP90 expression.

SIGNIFICANCE

These results indicate that EPO triggers the Jak2-STAT3/ERK pathway to restore the balance between arginase and NOS and, thus, reduces nitrosative stress. This may form the basis of myocardial protection following IR.

The nonhematopoietic effects of erythropoietin in skin regeneration and repair: from basic research to clinical use

Erythropoietin (EPO) is the main regulator of red blood cell production but there exists also a variety of nonhematopoietic properties. More recent data show that EPO is also associated with the protection of tissues suffering from ischemia and reperfusion injury as well as with improved regeneration in various organ systems, in particular the skin. This review highlights the mechanisms of EPO in the different stages of wound healing and the reparative processes in the skin emphasizing pathophysiological mechanisms and potential clinical applications. There is clear evidence that EPO effectively influences all wound-healing phases in a dose-dependent manner. This includes inflammation, tissue, and blood vessel formation as well as the remodeling of the wound. The molecular mechanism is predominantly based on an increased expression of the endothelial and inducible nitric oxide (NO) synthase with a consecutive rapid supply of NO as well as an increased content of vascular endothelial growth factor (VEGF) in the wound. The improved understanding of the functions and regulatory mechanisms of EPO in the context of wound-healing problems and ischemia/reperfusion injury, especially during flap surgery, may lead to new considerations of this growth hormone for its regular clinical application in patients.

Erythropoietin improves skeletal muscle microcirculation through the activation of eNOS in a mouse sepsis model

BACKGROUND

Sepsis and septic shock remain the major causes of morbidity and mortality in intensive care units. One mechanism that leads to organ failure is microcirculatory dysfunction. Erythropoietin (EPO) is a glycoprotein produced by the kidney that primarily regulates erythropoiesis, but it also can exert hemodynamic, anti-inflammatory, and tissue protective effects. We previously reported that administration of EPO to septic mice improves mouse skeletal muscle capillary perfusion and tissue bioenergetics. The objective of this study was to explore the potential mechanism(s) involved.

METHODS

Sepsis was induced by intraperitoneal (i.p.) injection of a fecal suspension (12.5 g in 0.5 saline/mouse) in mice. At 18 hours after sepsis induction, a single dose of rHuEPO (400 U/kg) was given to the mice. Mouse capillary perfusion density and nicotinamide adenine dinucleotide (NADH) fluorescence in skeletal muscle were observed using intravital microscopy. Endothelial cells derived from the skeletal muscle were treated with rHuEPO (5 U/mL) and endothelial nitric oxide synthase (eNOS) activation and activity were assessed.

RESULTS

Septic mice had decreased capillary perfusion density and increased tissue NADH fluorescence indicating impaired tissue bioenergetics, whereas animals treated with rHuEPO demonstrated an improvement in capillary perfusion density and decreased skeletal muscle NADH fluorescence. The beneficial effect of rHuEPO did not occur in septic mice treated with l-NAME (an NOS inhibitor, 20 mg/kg) or mice genetically deficient in eNOS. Treatment of endothelial cells with rHuEPO resulted in activation of eNOS as indicated by increased eNOS phosphorylation and NO production.

CONCLUSIONS

Our results suggest that eNOS plays an important role in mediating the beneficial effect of rHuEPO on microcirculation in this septic mouse model.

Protective effects of erythropoietin on myocardial infarction in rats: the role of AMP-activated protein kinase signaling pathway

Erythropoietin (EPO) has protective effects on myocardial infarction (MI). This study was to test whether EPO administrated after MI is as effective as EPO administrated before MI and to determine the role of AMP-activated protein kinase (AMPK) in the cardioprotective effects of EPO. Recombinant human EPO (5000 IU/kg) was intraperitoneally injected 12 hours before MI (pretreatment) or 30 minutes after MI (posttreatment). The levels of serum enzymes were assayed at 24 and 72 hours after MI. The infarct size was determined by nitro blue tetrazolium staining. The microarchitecture damages were evaluated by electron microscopy. EPO receptor messenger RNA and protein levels were determined by RT-PCR and immunohistochemistry, respectively. Activation of AMPK and nuclear factor kappa B was determined by immunoblotting. An AMPK-specific inhibitor, compound C, was used to inhibit AMPK activation in vivo. The authors found that both pretreatment and posttreatment of EPO successfully attenuated the serum enzyme levels, reduced the infarct size and ameliorated the microarchitecture damage. Moreover, both pretreatment and posttreatment of EPO decreased the EPO receptor messenger RNA and protein expressions, which were up-regulated in MI. More importantly, under MI conditions, EPO further increased the phosphorylation of AMPK and suppressed the activation of nuclear factor kappa B. Moreover, when AMPK was blocked by compound C, the cardioprotective effect of EPO was significantly attenuated (P < 0.01). Thus, this study demonstrates that both pretreatment and posttreatment of EPO are cardioprotective in an AMPK-dependent manners, providing the first evidence that the AMPK signaling pathway is involved in the cardioprotective effects of EPO.

Erythropoietin and the heart: facts and perspectives

EPO (erythropoietin) has long been identified as a primary regulator of erythropoiesis. Subsequently, EPO has been recognized as playing a role in a broad variety of processes in cardiovascular pathophysiology. In particular, the tight interactions of EPO with the nitric oxide pathway, apoptosis, ischaemia, cell proliferation and platelet activation appear of great interest. Although enhanced EPO synthesis is viewed as an appropriate compensatory mechanism in the cardio-renal syndrome, which features CHF (congestive heart failure) and CRF (chronic renal failure), maladaptative excessive EPO synthesis in the advanced stages of these diseases appears to be predictive of higher mortality. Clinical trials based on the use of EPO in both heart and renal failure have so far produced contradictory results, whereas treatment targeted to restore low Hb levels appears rational and is supported by regulatory authorities. New areas for therapeutic use of EPO, such as acute coronary syndromes, are under investigation, and they are discussed in the present review together with other clinical applications in cardiovascular diseases. The revisited concept of a potential use of endogenous EPO levels as a predictor of CHF severity, as well as in the monitoring of responses to treatment, deserves appropriate investigation, as this may identify EPO as a useful biomarker in the clinical management of cardiovascular diseases.

Dose-dependent ultrastructural and morphometric alterations after erythropoietin treatment in rat femoral artery vasospasm model

PURPOSE

Cerebral vasospasm is the common cause of poor outcome after aneurysmal subarachnoid hemorrhage (aSAH). Although many agents are experimentally and clinicaly used to protect or recover from vasospasm, an effective neurotherapeutic drug is still missing. Erythropoietin (EPO) is recently a promising candidate. The aim of this study is to investigate the dose-dependent effects of recombinant human EPO (rhEPO) on arterial wall in a rat femoral artery vasospasm model.

METHODS

Thirty two animals were divided into four groups: vasospasm without any treatment (group A), vasospasm +250 IU/kg rhEPO group (group B), vasospasm +500 IU/kg rhEPO group (group C), and control group (group D). Rat femoral artery vasospasm model was used. For groups B and C, 7 days of 250 IU/kg and 500 IU/kg intraperitoneal rhEPO in 0.3 ml saline were administered respectively; and for groups A and D, 0.3 ml saline were administered intraperitoneally without any treatment. After 7 days, histological and morphometric analyses were carried out.

RESULTS

Vasospasm alone group demonstrated the highest vessel wall thicknesses, comparing to other groups (p < 0.001). While for groups B and C, vessel wall thickness values were significantly higher than the control group (p < 0.001), between these two groups, there was no significant difference achieved (p > 0.05).

CONCLUSION

In our study, there was no significant difference between the two rhEPO treatment groups, but rhEPO treatment was shown to be histologically and morphometrically effective in vasospasm. However, if dosage of EPO treatment is augmented, successful results may be achieved.

The effect of erythropoietin on microcirculation perfusion and tissue bioenergetics of the small intestine in a hemorrhagic shock and resuscitation rat model

BACKGROUND

Erythropoietin (EPO) can exert acute hemodynamic and anti-inflammatory effects in addition to erythropoiesis. We tested the hypothesis that EPO given at resuscitation with saline will improve capillary perfusion and tissue oxygenation in the gut using a hemorrhagic shock model.

METHODS

Sprague-Dawley rats were bled 30 mL/kg to maintain a mean arterial blood pressure of 40 mm Hg for 50 minutes and then randomized to one of four resuscitation groups (n = 6 per group): blood, blood + recombinant human EPO (rHuEPO), saline, and saline + rHuEPO. Intravenous rHuEPO (1,000 U/kg) was given at the start of resuscitation. Intravital microscopy was used to measure perfused capillary density, flow motion of red blood cell (RBC), and tissue NADH fluorescence 60 minutes after resuscitation. Venous oxygenation saturation (Svo2) was also measured in a second experiment.

RESULTS

In the blood +/- rHuEPO resuscitation group, the perfused capillary density, RBC flow motion scores, and NADH fluorescence returned to near normal values. The saline + rHuEPO group compared with the saline group demonstrated an increased RBC flow motion score (2.32 vs. 1.60; p < 0.01); however, the perfused capillary density was not significantly increased (23.03 Cap/mm vs. 21.61 Cap/mm; p = 0.40). The saline + rHuEPO group also demonstrated statistically significant lower NADH fluorescence than the saline group after shock following resuscitation (110% +/- 3.64% vs. 122% +/- 4.26%; p < 0.05) suggesting decreased tissue dysoxia. The Svo2 in the saline + rHuEPO group was higher when compared with the saline group (45% vs. 38% by continuous oximetry; 38% vs. 29% by co-oximetry; p < 0.05).

CONCLUSION

Our results suggest that the addition of rHuEPO at the time of saline resuscitation may have beneficial effects in hemorrhagic shock by improving tissue perfusion and decreasing dysoxia in the gut.

Erythropoietin (EPO) influences colonic anastomotic healing in a rat model by modulating collagen metabolism

INTRODUCTION

Anastomotic failure is one of the most frequent complications in abdominal surgery. During anastomotic healing. the strength of the intestinal tissue nearby is closely related to the accumulation of collagen in interlinked scar tissue. This in turn is influenced, among other things, by single groups of matrixmetalloproteinases, especially collagenases (MMP-1, -8, and -13) and gelatinases (MMP-2 and -9). EPO is known to induce the expression of tissue-inhibitor-of-matrixmetalloproteinases-1 (TIMP-1) and thereby to down-regulate MMPs.

MATERIALS AND METHODS

We used a rat as an experimental model and applied a high dose of EPO (5U/g BW s.c.), one dose 24 h before operation (as pre-conditioning) and one dose directly after performing a colonic anastomosis. After 3 and after 5 d, respectively, immunohistochemical stainings for MMP-2, -8, and -9 as well as TIMP-1 were carried out and evaluated semiquantitatively for each layer of the colonic wall. Sirius-red staining and cross-polarization microscopy were evaluated and the collagen I/III ratio calculated. Anastomotic and colonic tissue distal to the anastomosis were used to determine collagen content.

RESULTS

We found increased bursting pressure 5 d post-surgery after applying erythropoietin. It was thus shown that EPO influences collagen metabolism and changes the collagen I/III ratio in the colon distal to the anastomosis. The evaluation of immunohistochemistry did not show the expected ubiquitous up-regulation of TIMP-1 and down-regulation of MMPs. Nevertheless, correlations between TIMP-1, MMP-8, and collagen I/III ratio could only be established after the application of EPO.

CONCLUSION

Contrary to our hypothesis, the picture of TIMP-1 and of the regulation of the MMPs after the application of EPO is not as clear as expected. EPO improves anastomotic bursting strength and the correlation of TIMP-1, MMP-8, and collagen type I/III ratio can only be seen after the application of EPO.

A transient inflammatory reaction in the lung after experimental hemorrhagic shock and resuscitation with a hemoglobin-vesicles solution compared with rat RBC transfusion

Transfusion for hemorrhagic shock can improve oxygenation, but immunoreactions may induce inflammation. Artificial oxygen carriers have been developed to address clinical concerns of infection and stability, but whether an artificial oxygen carrier might induce inflammation is not well known. To address this question, we compared inflammatory reactions after resuscitation with hemoglobin vesicles (HbVs) or red blood cells (RBCs) in a hemorrhagic shock rat model. Both HbVs and the stored and irradiated rat RBCs deprived of buffy coat were suspended in recombinant human serum albumin [(Hb) = 8.6 g/dL]. Under anesthesia, hemorrhagic shock was induced for 30 min, followed by resuscitation by 20 min transfusion of HbVs or rat RBCs in a volume equivalent to the volume of withdrawn blood. Lungs were excised 2 or 24 h after resuscitation, and mRNA levels of tumor necrosis factor alpha (TNF-alpha), intercellular adhesion molecule-1 (ICAM-1), nitric oxide synthase 2 (iNOS), nitric oxide synthase 3, hypoxia-inducible factor 1 alpha, and heme oxygenase 1 (HO-1) were measured. In rats resuscitated with HbVs, mRNA levels of TNF-alpha and HO-1 2 h after resuscitation were significantly higher than those in the rat RBC group, but the levels at 24 h were similar in both groups. The expression of iNOS and ICAM-1, second messengers of inflammation, was not affected, and inflammatory levels after 24 h with HbVs are similar to rat RBC transfusion. The rat RBC group did not show an expected inflammatory reaction related to a transfusion-induced lung injury, and a clinical relevance concerning this level of transient inflammatory reaction induced by HbVs is not known; however, attention to the early stage of resuscitation in ongoing studies of HbV is required.

Recombinant human erythropoietin prevents lipopolysaccharide-induced vascular hyporeactivity in the rat

Erythropoietin (EPO) is a hypoxia-inducible hormone that is essential for normal erythropoiesis in the bone marrow. Administration of recombinant human-EPO is currently being used for the therapy of anemia associated with chronic renal failure and cancer. Moreover, EPO reduces organ injury in experimental hemorrhagic as well as in splanchnic artery occlusion shock and preserves cardiac function after experimental cardiac I/R. Erythropoietin receptors are widely distributed in the cardiovascular system, including endothelial, smooth muscle, cardiac, and other cell types, and nonhematopoietic effects of EPO are increasingly recognized. Thus, the vasculature may be a biological target of EPO. Therefore, the aim of our study was to investigate whether EPO exerts a protective effect in septic shock by modulating vascular dysfunction and hyporeactivity. Rats received EPO (300 U/kg, i.v.) or vehicle 30 min before and 1 and 3 h after LPS (8 x 10 U/kg, i.v.). In vivo and ex vivo (aortic rings) experiments were performed to evaluate the vascular response to contracting and vasodilating agents. The expression of iNOS, intercellular adhesion molecule 1, poly(ADP)ribose polymerase, Bcl-xl, and Bcl-2 was evaluated by Western blot analysis in the rat aorta. We demonstrate that EPO significantly prevents LPS-induced vascular hyporeactivity and endothelial dysfunction. Interestingly, EPO inhibits the increase in iNOS, poly(ADP)ribose polymerase, and intercellular adhesion molecule 1 expression in the aorta of endotoxemic rats and attenuated the decline in the expression of both Bcl-xl and Bcl-2 caused by LPS. In conclusion, our data support the view that EPO has important nonerythropoietic effects protecting organ and tissue against injury and indicate that EPO may be useful in the therapy of patients with septic shock.

Therapeutic effects of erythropoietin in murine models of endotoxin shock

OBJECTIVE

Erythropoietin has recently emerged as a cytoprotective cytokine, which possesses the ability to protect many tissues, including the brain, heart, and kidneys, against ischemia or traumatic injury. We investigated the therapeutic effects of erythropoietin in a murine model of endotoxin shock.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Male BALB/c mice.

INTERVENTIONS

Mice intraperitoneally received either lipopolysaccharide (LPS) from Escherichia coli or vehicle. Erythropoietin was administered at a dose of 1000 IU/kg subcutaneously at different time points after LPS administration. We also investigated the effect of erythropoietin on the development of septic shock caused by cecal perforation.

MEASUREMENTS AND MAIN RESULTS

Treatment of mice with erythropoietin, within 2 hours after LPS administration, improved the mortality rate. Treatment of cecal perforated mice with erythropoietin extended survival by 12 hours, but all animals died by 72 hours in both groups. Erythropoietin attenuated apoptosis in the lungs, liver, small intestine, thymus, and spleen, as assessed by terminal deoxynucleotidyl transferase-mediated nucleotide nick-end labeling staining, active caspase-3 immunostaining and immunoblotting, and measurements of caspase-3/7 activity. Erythropoietin also reduced inducible nitric oxide synthase expression, nitric oxide production, peroxynitrite formation, and tissue hypoxia. In contrast, erythropoietin did not affect the degree of LPS-induced inflammation, as assessed by measurements of blood levels of interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, growth-related oncogene/keratinocyte-derived cytokine, and high mobility group box 1, the phosphorylation levels of nuclear factor kappaB, and the number of neutrophils infiltrating the lungs and the liver.

CONCLUSIONS

The results of the study demonstrate that administration of a large dose of erythropoietin after induction of experimental endotoxemia improved survival and that the beneficial effects of erythropoietin were associated with inhibition of apoptosis, nitric oxide production, and tissue hypoxia, without alterations in inflammatory responses.

Erythropoietin attenuates ischemia-reperfusion induced lung injury by inhibiting tumor necrosis factor-alpha and matrix metalloproteinase-9 expression

Erythropoietin (Epo) was recently defined as an endogenous agent with more than hematopoietic functions. Previously we explored the potential of this agent to ameliorate lung ischemia-reperfusion (I/R) injury. The present study aims to determine the optimal dose and timing of administration for improving lung injury, and to further investigate the mechanisms by which Epo ameliorates lung I/R injury. The left lungs of Sprague-Dawley rats underwent 90 min ischemia and 120 min reperfusion. Firstly, animals in different groups were intraperitoneally injected with various doses of recombined human erythropoietin (rhEpo) 24 h prior to operation, 2 h prior to operation, or after the onset of reperfusion. Pulmonary myeloperoxidase (MPO) activity and malondialdehyde (MDA) content were evaluated. Treatment with 3 KU/kg rhEpo 2 h prior to operation was optimal for attenuating pulmonary MPO activity and MDA content. With such treatment, ultrastructural changes of pneumocytes were observed, and the pneumocyte apoptosis index was also determined by terminal dUTP nick-end labeling method. The plasma concentrations of tumor necrosis factor (TNF)-alpha and matrix metalloproteinase (MMP)-9 were evaluated by enzyme-linked immunosorbent assay, and pulmonary expression by immunohistochemistry. When pretreated with rhEpo, the pneumocyte ultrastructure was predominantly maintained and the pulmonary apoptosis index was markedly reduced. In comparison with untreated animals, in treated animals the plasma concentrations of TNF-alpha and MMP-9 were significantly decreased, and their expression in lung tissue was markedly reduced as well. The results indicated that Epo potently protected against lung I/R injury by inhibiting systemic and local expression of TNF-alpha and MMP-9.

Erythropoietin attenuates lung injury in lipopolysaccharide treated rats

BACKGROUND

Erythropoietin (EPO) elicits protective effects in lung ischemia-reperfusion, hyperoxia, acute necrotizing pancreatitis, and some other tissues. In the present study, we investigated the possible protective roles of EPO in the lipopolysaccharide (LPS) induced lung injury.

MATERIALS AND METHODS

Male Sprague-Dawley rats were treated with EPO (3000 U/kg, i.p.) or vehicle (saline), 30 min prior to LPS administration (6 mg/kg, i.v.). Four h following LPS injection, samples of pulmonary tissue were collected. Optical microscopy was performed to examine pathological changes in lungs. Validated methods were used to measure wet/dry ratios (W/D), myeloperoxidase (MPO) activity, malondialdehyde (MDA) concentrations, and nitrite/nitrate (NO(2)(-)/NO(3)(-)) levels in lungs. Western blotting was performed to study the pulmonary expression of inducible nitric oxide synthase (iNOS) and nitrotyrosine protein.

RESULTS

Pretreatment with EPO led to (1) significant attenuation of endotoxemia induced evident lung histologic injury and edema; (2) inhibition of LPS mediated induction in MPO activity and MDA concentration; (3) inhibition of LPS mediated overproduction of pulmonary NO(2)(-)/NO(3)(-) levels; and (4) marked suppression in endotoxin induced expression of iNOS and nitrotyrosine.

CONCLUSIONS

This study provides considerable evidence that EPO has an ability to significantly attenuate endotoxin-induced acute lung injury in rats.

Erythropoietin improves skeletal muscle microcirculation and tissue bioenergetics in a mouse sepsis model

Introduction

The relationship between oxygen delivery and consumption in sepsis is impaired, suggesting a microcirculatory perfusion defect. Recombinant human erythropoietin (rHuEPO) regulates erythropoiesis and also exerts complex actions promoting the maintenance of homeostasis of the organism under stress. The objective of this study was to test the hypothesis that rHuEPO could improve skeletal muscle capillary perfusion and tissue oxygenation in sepsis.

Methods

Septic mice in three experiments received rHu-EPO 400 U/kg subcutaneously 18 hours after cecal ligation and perforation (CLP). The first experiment measured the acute effects of rHuEPO on hemodynamics, blood counts, and arterial lactate level. The next two sets of experiments used intravital microscopy to observe capillary perfusion and nicotinamide adenine dinucleotide (NADH) fluorescence post-CLP after treatment with rHuEPO every 10 minutes for 40 minutes and at 6 hours. Perfused capillary density during a three-minute observation period and NADH fluorescence were measured.

Results

rHuEPO did not have any effects on blood pressure, lactate level, or blood cell numbers. CLP mice demonstrated a 22% decrease in perfused capillary density compared to the sham group (28.5 versus 36.6 capillaries per millimeter; p < 0.001). Treatment of CLP mice with rHuEPO resulted in an immediate and significant increase in perfused capillaries in the CLP group at all time points compared to baseline from 28.5 to 33.6 capillaries per millimeter at 40 minutes; p < 0.001. A significant increase in baseline NADH, suggesting tissue hypoxia, was noted in the CLP mice compared to the sham group (48.3 versus 43.9 fluorescence units [FU]; p = 0.03) and improved with rHuEPO from 48.3 to 44.4 FU at 40 minutes (p = 0.02). Six hours after treatment with rHuEPO, CLP mice demonstrated a higher mean perfused capillary density (39.4 versus 31.7 capillaries per millimeter; p < 0.001) and a lower mean NADH fluorescence as compared to CLP+normal saline mice (49.4 versus 52.7 FU; p = 0.03).

Conclusion

rHuEPO produced an immediate increase in capillary perfusion and decrease in NADH fluorescence in skeletal muscle. Thus, it appears that rHuEPO improves tissue bioenergetics, which is sustained for at least six hours in this murine sepsis model.

The protective effect of darbepoetin alfa on experimental testicular torsion and detorsion injury

AIM

Testicular torsion is a serious urological emergency, usually involving newborns, children, and adolescents which can lead to subfertility and infertility. Prevention of testicular damage caused by torsion is still a clinical and experimental problem. So far many chemicals and drugs have been investigated for decreasing ischemia/reperfusion (I/R) injury in experimental animals. The possible protective effect of darbepoetin alfa, a novel erythropoietic protein, on testicular tissue after I/R injury was examined in this study.

METHODS

Thirty rats were divided into three groups: sham operation, torsion/detorsion, and torsion/detorsion plus darbepoetin alfa groups. After torsion (2 hours) and detorsion (4 hours), bilateral orchiectomy was performed. Malondialdehyde, nitric oxide and glutathione levels were determined in testicular tissue.

RESULTS

Administration of darbepoetin alfa caused a decrease of malondialdehyde and nitric oxide levels and an increase in glutathione levels compared with the torsion/detorsion group. In addition, histological injury scores were significantly decreased in the treatment group more than the torsion/detorsion group.

CONCLUSION

The results suggest that darbepoetin alfa may be a potential protective agent for preventing testicular injury caused by testis torsion.

Friedreich's ataxia: clinical pilot trial with recombinant human erythropoietin

To determine the role of recombinant human erythropoietin as a possible treatment option in Friedreich's ataxia, we performed an open-label clinical pilot study. Primary outcome measure was the change of frataxin levels at week 8 versus baseline. Twelve Friedreich's ataxia patients received 5,000 units recombinant human erythropoietin three times weekly subcutaneously. Frataxin levels were measured in isolated lymphocytes by enzyme-linked immunosorbent assay. In addition, urinary 8-hydroxydeoxyguanosine and serum peroxides, were measured. Treatment with recombinant human erythropoietin showed a persistent and significant increase in frataxin levels after 8 weeks (p < 0.01). All patients showed a reduction of oxidative stress markers.

Neuroprotection by erythropoietin administration after experimental traumatic brain injury

A large body of evidence indicates that the hormone erythropoietin (EPO) exerts beneficial effects in the central nervous system (CNS). To date, EPO's effect has been assessed in several experimental models of brain and spinal cord injury. This study was conducted to validate whether treatment with recombinant human EPO (rHuEPO) would limit the extent of injury following experimental TBI. Experimental TBI was induced in rats by a cryogenic injury model. rHuEPO or placebo was injected intraperitoneally immediately after the injury and then every 8 h until 2 or 14 days. Forty-eight hours after injury brain water content, an indicator of brain edema, was measured with the wet-dry method and blood-brain barrier (BBB) breakdown was evaluated by assay of Evans blue extravasation. Furthermore, extent of cerebral damage was assessed. Administration of rHuEPO markedly improved recovery from motor dysfunction compared with placebo group (P<0.05). Brain edema was significantly reduced in the cortex of the EPO-treated group relative to that in the placebo-treated group (80.6+/-0.3% versus 91.8%+/-0.8% respectively, P<0.05). BBB breakdown was significantly lower in EPO-treated group than in the placebo-treated group (66.2+/-18.7 mug/g versus 181.3+/-21 mug/g, respectively, P<0.05). EPO treatment reduced injury volume significantly compared with placebo group (17.4+/-5.4 mm3 versus 37.1+/-5.3 mm3, P<0.05). EPO, administered in its recombinant form, affords significant neuroprotection in experimental TBI model and may hold promise for future clinical applications.

Protective Effects of Erythropoietin in Cardiac Ischemia

Erythropoietin (EPO) is a hypoxia-induced hormone produced in the kidneys that stimulates hematopoiesis in the bone marrow. However, recent studies have also shown important nonhematopoietic effects of EPO. A functional EPO receptor is found in the cardiovascular system, including endothelial cells and cardiomyocytes. In animal studies, treatment with EPO during ischemia/reperfusion in the heart has been shown to limit the infarct size and the extent of apoptosis. In the longer term, EPO may promote ischemia-induced neovascularization, either by stimulating endothelial cells in situ or by mobilizing endothelial progenitor cells from bone marrow. The effects of EPO in the ischemic heart support the concept of EPO as a pleiotropic, tissue-protective agent for other organs expressing the EPO receptor. We recently performed a first randomized clinical study showing the safety and feasibility of EPO administration in patients with acute myocardial infarction. Future clinical studies are warranted to translate the beneficial effects of EPO from basic experiments to cardiac patients.

Recombinant human erythropoietin protects the liver from hepatic ischemia-reperfusion injury in the rat

Recently, erythropoietin was shown to have both hematopoietic as well as tissue-protective properties. Erythropoietin (EPO) had a protective effect in animal models of cerebral ischemia, mechanical trauma of the nervous system, myocardial infarction, and ischemia-reperfusion (I/R) injury of the kidney. It is not known whether EPO protects the liver against I/R injury. Using a rat model of liver I/R injury, we aimed to determine the effect of the administration of human recombinant erythropoietin (rhEPO) on liver injury. Rats were subjected to 30 min of liver ischemia followed by 2 h of reperfusion. When compared with the sham-operated rats, I/R resulted in significant rises in the serum levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, gamma-glutamyl transferase, tissue lipid peroxidation, caspase-3 activity and altered histology. Administration of rhEPO 5 min before ischemia was able to reduce the biochemical evidence of liver injury; however, this protection was not evident when rhEPO was administered 5 min before reperfusion. Mechanistically, early administration of rhEPO was able to reduce the oxidative stress and caspase-3 activation, suggesting the subsequent reduction of apoptosis. This study provides the first evidence that rhEPO causes a substantial reduction of the liver injury induced by I/R in the rat.

Delayed administration of darbepoetin or erythropoietin protects against ischemic acute renal injury and failure

Administration of human recombinant erythropoietin (EPO) at time of acute ischemic renal injury (IRI) inhibits apoptosis, enhances tubular epithelial regeneration, and promotes renal functional recovery. The present study aimed to determine whether darbepoetin-alfa (DPO) exhibits comparable renoprotection to that afforded by EPO, whether pro or antiapoptotic Bcl-2 proteins are involved, and whether delayed administration of EPO or DPO 6 h following IRI ameliorates renal dysfunction. The model of IRI involved bilateral renal artery occlusion for 45 min in rats (N = 4 per group), followed by reperfusion for 1-7 days. Controls were sham-operated. Rats were treated at time of ischemia or sham operation (T0), or post-treated (6 h after the onset of reperfusion, T6) with EPO (5000 IU/kg), DPO (25 mug/kg), or appropriate vehicle by intraperitoneal injection. Renal function, structure, and immunohistochemistry for Bcl-2, Bcl-XL, and Bax were analyzed. DPO or EPO at T0 significantly abrogated renal dysfunction in IRI animals (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.08 +/- 0.03 mmol/l vs EPO-IRI 0.04 +/- 0.01 mmol/l, P = 0.01). Delayed administration of DPO or EPO (T6) also significantly abrogated subsequent renal dysfunction (serum creatinine for IRI 0.17 +/- 0.05 mmol/l vs DPO-IRI 0.06 +/- 0.01 mmol/l vs EPO-IRI 0.03 +/- 0.03 mmol/l, P = 0.01). There was also significantly decreased tissue injury (apoptosis, P < 0.05), decreased proapoptotic Bax, and increased regenerative capacity, especially in the outer stripe of the outer medulla, with DPO or EPO at T0 or T6. These results reaffirm the potential clinical application of DPO and EPO as novel renoprotective agents for patients at risk of ischemic acute renal failure or after having sustained an ischemic renal insult.

Therapeutic Effectiveness of a Single vs Multiple Doses of Erythropoietin After Experimental Myocardial Infarction in Rats

BACKGROUND

Systemic application of recombinant human erythropoietin (rhEPO) greatly limits cardiac tissue damage and attenuates left ventricular (LV) remodeling after experimentally induced myocardial infarction (MI). However, multiple injections of rhEPO stimulate red blood cell production and elevate the hematocrit (Htc), which might negatively affect the outcome of acute MI. We compared the outcome of experimental MI in rats treated with a single or multiple doses of rhEPO.

MATERIALS AND METHODS

Sprague-Dawley male rats were subjected to a permanent ligation of the left descending coronary artery (CL) or sham operation. Immediately after CL animals received either a single i.v. injection of 3,000 IU/kg of rhEPO, or a single injection plus additional injections of the same dose of rhEPO repeated daily for six more days. Echocardiography and blood collection for measurement of Htc were performed prior to, and at 2 and 4 weeks after CL; MI size was measured histologically 4 weeks after CL.

RESULTS

A single injection of rhEPO elevated Htc by 11% (p < 0.05) 1 week after CL, but after multiple rhEPO injections Htc increased by 40%. In untreated rats a 140 and 340% expansion in end-diastolic and end-systolic LV volumes, respectively, and 55% decline in ejection fraction (EF) occurred during the 4 week period following CL. A single rhEPO dose attenuated the LV remodeling and EF reduction by 50%. Repeated rhEPO injections did not elicit any additional benefits in respect to LV remodeling. Moreover, at the end of 4 weeks, MI size was significantly reduced (by 40%) by a single injection, while after repeated rhEPO injections the reduction of MI size was not statistically significant.

CONCLUSION

The results of this study indicate that multiple dosing of rhEPO after induced myocardial infarction in rats has no added therapeutic benefits over those achieved by a single dose.

Activation of the cholinergic anti-inflammatory pathway reduces NF-kappab activation, blunts TNF-alpha production, and protects againts splanchic artery occlusion shock

The cholinergic anti-inflammatory pathway has not yet been studied in splanchnic artery occlusion (SAO) shock. We investigated whether electrical stimulation (STIM) of efferent vagus nerves suppresses the inflammatory cascade in SAO shock. Animals were subjected to clamping of the splanchnic arteries for 45 min, followed by reperfusion. This surgical procedure resulted in an irreversible state of shock (SAO shock). Sham-operated animals were used as controls. Two minutes before the start of reperfusion, rats were subjected to bilateral cervical vagotomy (VGX) or sham surgical procedures. Application of constant voltage pulses to the caudal vagus ends (STIM: 5 V, 2 ms, 6 Hz for 15 min, 5 min after the beginning of reperfusion) increased survival rate (VGX + SAO + Sham STIM = 0% at 4 h of reperfusion; VGX + SAO + STIM = 90% at 4 h of reperfusion), reverted the marked hypotension, inhibited IkappaBalpha liver loss, blunted the augmented nuclear factor-kappaB activity, decreased hepatic tumor necrosis factor (TNF)-alpha mRNA (VGX + SAO + Sham STIM = 1.0 +/- 1.9 TNF-alpha/glyceraldehyde-3-phosphate dehydrogenase ratio; VGX + SAO + STIM = 0.3 +/- 0.2 TNF-alpha/glyceraldehyde-3-phosphate dehydrogenase ratio), reduced plasma TNF-alpha (VGX + SAO + Sham STIM = 118 +/- 19 pg/mL; VGX + SAO + STIM = 39 +/- 8 pg/mL), ameliorated leukopenia, and decreased leukocyte accumulation, as revealed by means of myeloperoxidase activity in the ileum (VGX + SAO + Sham STIM = 7.9 +/- 1 U/g tissue; VGX + SAO + STIM = 3.1 +/- 0.7 U/g tissue) and in the lung (VGX + SAO + Sham STIM = 8.0 +/- 1.0 U/g tissue; VGX + SAO + STIM = 3.2 +/- 0.6 U/g tissue). Chlorisondamine, a nicotinic receptor antagonist, abated the effects of vagal stimulation. Our results show a parasympathetic inhibition of nuclear factor-kappaB and TNF-alpha in SAO shock.

Amelioration of spinal cord compressive injury by pharmacological preconditioning with erythropoietin and a nonerythropoietic erythropoietin derivative

OBJECT

Spinal cord injury (SCI) is a devastating clinical syndrome for which no truly efficacious therapy has yet been identified. In preclinical studies, erythropoietin (EPO) and its nonerythropoietic derivatives asialoEPO and carbamylated EPO have markedly improved functional outcome when administered after compressive SCI. However, an optimum treatment paradigm is currently unknown. Because the uninjured spinal cord expresses a high density of EPO receptor (EPOR) in the basal state, signaling through these existing receptors in advance of injury (pharmacological preconditioning) might confer neuroprotection and therefore be potentially useful in situations of anticipated damage.

METHODS

The authors compared asialoEPO, a molecule that binds to the EPOR with high affinity but with a brief serum half-life (t1/2 < 2 minutes), to EPO to determine whether a single dose (10 microg/kg of body weight) administered by intravenous injection 24 hours before 1 minute of spinal cord compression provides benefit as determined by a 6-week assessment of neurological outcome and by histopathological analysis. Rats pretreated with asialoEPO or EPO and then subjected to a compressive injury exhibited improved motor function over 42 days, compared with animals treated with saline solution. However, pretreatment efficacy was substantially poorer than efficacy of treatment initiated at the time of injury. Serum samples drawn immediately before compression confirmed that no detectable asialoEPO remained within the systemic circulation. Western blot and immunohistochemical analyses performed using uninjured spinal cord 24 hours after a dose of asialoEPO exhibited a marked increase in glial fibrillary acidic protein, suggesting a glial response to EPO administration.

CONCLUSIONS

These results demonstrate that EPO and its analog do not need to be present at the time of injury to provide tissue protection and that tissue protection is markedly effective when either agent is administered immediately after injury. Furthermore, the findings suggest that asialoEPO is a useful reagent with which to study the dynamics of EPO-mediated neuroprotection. In addition, the findings support the concept of using a nonerythropoietic EPO derivative to provide tissue protection without activating the undesirable effects of EPO.

Erythropoietin reduces the development of nonseptic shock induced by zymosan in mice*

OBJECTIVE

Erythropoietin is a potent stimulator of erythroid progenitor cells, and its expression is enhanced by hypoxia. In the present study, we investigated the effects of erythropoietin (1000 IU/kg subcutaneously) on the development of nonseptic shock caused by zymosan.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Male CD mice.

INTERVENTIONS

Mice received either intraperitoneally zymosan (500 mg/kg, administered intraperitoneally as a suspension in saline) or vehicle (0.25 mL/mouse saline). Erythropoietin was administered at the dose of 1000 IU/kg subcutaneously, 1 and 6 hrs after zymosan administration. Organ failure and systemic inflammation in mice was assessed 18 hrs after administration of zymosan and/or erythropoietin.

MEASUREMENTS AND MAIN RESULTS

Treatment of mice with erythropoietin (1000 IU/kg subcutaneously, 1 and 6 hrs after zymosan administration) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan. Erythropoietin also attenuated the lung, liver, and pancreatic injury and renal dysfunction caused by zymosan as well as the increase in myeloperoxidase activity caused by zymosan in the lung and intestine. Immunohistochemical analysis for nitrotyrosine and poly(ADP-ribose) revealed positive staining in lung and intestine tissues obtained from zymosan-treated mice. The degree of staining for nitrotyrosine and poly(ADP-ribose) was markedly reduced in tissue sections obtained from zymosan-treated mice, which received erythropoietin. In addition, administration of zymosan caused severe illness in the mice characterized by a systemic toxicity, significant loss of body weight, and a 70% mortality rate at the end of observation period (7 days). Treatment with erythropoietin significantly reduced the development of systemic toxicity, the loss in body weight, and the mortality caused by zymosan.

CONCLUSIONS

This study provides evidence, for the first time, that erythropoietin attenuates the degree of zymosan-induced nonseptic shock in mice.

The effects of systemically administered methylprednisolone and recombinant human erythropoietin after acute spinal cord compressive injury in rats

The study design was to decrease the damage of spinal cord on the experimentally induced acute spinal cord injury in rats. The objective of this study was to evaluate whether recombinant human erythropoietin (rHu-EPO) and methylprednisolone (MPSS) improve neurological function and histopathological changes if systemically administered after traumatic spinal cord injury. This study included 48 rats that underwent experimental SCI. Forty-eight animals were randomly divided into six groups. Animals constituted a moderate compression of 0.6 N that was produced by application of an aneurysm clip at level T3 for 1 min. rHu-EPO (1,000 and 3,000 U (Unit) per kg of body weight i.p.) and MPSS (30 mg/kg) were administered 5 min after injury, and control group was saline treated. (1) Control group (n=8), (2) MPSS group (n=8), (3) rHu-EPO 1,000 U group (n=8), (4) MPSS + rHu-EPO 1,000 U group (n=8), (5) rHu-EPO 3,000 U group (n=8), and (6) MPSS + rHu-EPO 3,000 U group (n=8). The neurological function and histopathology were evaluated at 24 and 72 h. According to the neurological functional test scores significant improvements between the control group and the other groups that had taken medical treatment were observed (P<0.001). Histopathologically severe ischemic findings were observed in the control group. A significant decrease in ischemic damage was detected in MPSS + rHu-EPO 3,000 U group (P<0.001). The most significant neurological functional and histopathological improvements were observed after systemical administration of MPSS + rHu-EPO 3,000 U and rHu-EPO 3,000 U. Furthermore, the MPSS + rHu-EPO 3,000 U group provides the most improved neurological functional and histopathological recovery.

Methylprednisolone neutralizes the beneficial effects of erythropoietin in experimental spinal cord injury

Inflammation plays a major pathological role in spinal cord injury (SCI). Although antiinflammatory treatment using the glucocorticoid methyprednisolone sodium succinate (MPSS) improved outcomes in several multicenter clinical trials, additional clinical experience suggests that MPSS is only modestly beneficial in SCI and poses a risk for serious complications. Recent work has shown that erythropoietin (EPO) moderates CNS tissue injury, in part by reducing inflammation, limiting neuronal apoptosis, and restoring vascular autoregulation. We determined whether EPO and MPSS act synergistically in SCI. Using a rat model of contusive SCI, we compared the effects of EPO [500-5,000 units/kg of body weight (kg-bw)] with MPSS (30 mg/kg-bw) for proinflammatory cytokine production, histological damage, and motor function at 1 month after a compression injury. Although high-dose EPO and MPSS suppressed proinflammatory cytokines within the injured spinal cord, only EPO was associated with reduced microglial infiltration, attenuated scar formation, and sustained neurological improvement. Unexpectedly, coadministration of MPSS antagonized the protective effects of EPO, even though the EPO receptor was up-regulated normally after injury. These data illustrate that the suppression of proinflammatory cytokines alone does not necessarily prevent secondary injury and suggest that glucocorticoids should not be coadministered in clinical trials evaluating the use of EPO for treatment of SCI.

Brain-derived erythropoietin protects from focal cerebral ischemia by dual activation of ERK-1/-2 and Akt pathways

Apart from its hematopoietic function, erythropoietin (Epo) exerts neuroprotective functions in brain hypoxia and ischemia. To examine the mechanisms mediating Epo's neuroprotective activity in vivo, we made use of our transgenic mouse line tg21 that constitutively expresses human Epo in brain without inducing excessive erythrocytosis. We show that human Epo is expressed in tg21 brains and that cortical and striatal neurons carry the Epo receptor. After middle cerebral artery occlusion, human Epo potently protected brains of tg21 mice against ischemic injury, both when severe (90 min) and mild (30 min) ischemia was imposed. Histochemical studies revealed that Epo induced an activation of JAK-2, ERK-1/-2, and Akt pathways in the ischemic brain. This activation was associated with elevated Bcl-XL and decreased NO synthase-1 and -2 levels in neurons. Intracerebroventricular injections of selective inhibitors of ERK-1/-2 (PD98059) or Akt (wortmannin) pathways revealed that both ERK-1/-2 and Akt were required for Epo's neuroprotective function, antagonization of either pathway completely abolishing tissue protection. On the other hand, ERK-1/-2 and Akt blockade did not reverse the neuronal NO synthase-1/-2 inhibition, indicating that Epo down-regulates these NO synthases in an ERK-1/-2 and Akt independent manner. On the basis of our data, the dual activation of ERK-1/-2 and Akt is crucial for Epo's neuroprotective activity.

Pleiotropic renal actions of erythropoietin

CONTEXT

Erythropoietin (EPO), which is used clinically as recombinant human EPO (rHuEPO) for anaemia associated with end-stage renal failure and cancer chemotherapy, also has pleiotropic properties. Although EPO and its receptor are primary mediators of the normal physiological response to hypoxia, rHuEPO can provide impressive protection against acute ischaemic injury in several organs and tissues. The longer-acting hyperglycosylated derivative of EPO, darbepoetin-alpha, is also used for anaemia and has pleiotropic properties. However, the ability of EPO or its analogues to act directly to reduce the severity of renal injury associated with chronic renal failure is not known.

STARTING POINT

Ferdinand Bahlmann and colleagues (Circulation 2004; 110: 1006-12) investigated whether low-dose subcutaneous darbepoetin-alpha could protect against renal dysfunction and injury in rats with induced chronic renal failure. Given once weekly, the drug improved renal function and reduced histological evidence of renal injury. Treated rats also had greater weight gain than controls, with no change in systemic blood pressure. The drug did not increase packed-cell volume and it improved survival. WHERE NEXT?: Although the pleiotropic actions of rHuEPO can ameliorate ischaemic and nephrotoxic acute renal failure, Bahlmann's work is the first evidence that darbepoetin-alpha reduces the renal dysfunction and injury of chronic renal failure. Thus rHuEPO and its analogues might have a use in patients with different types of renal failure. These pleiotropic actions, seen at lower doses, must be separated from the haemopoietic properties that occur at clinical doses and which, at the highest doses, might lead to unwanted effects. Novel analogues of EPO are devoid of haemopoietic activity but still possess protective properties. Their ability to reduce renal injury and dysfunction awaits investigation.

Pretreatment with EPO reduces the injury and dysfunction caused by ischemia/reperfusion in the mouse kidney in vivo

BACKGROUND

Erythropoietin (EPO) is a potent stimulator of erythroid progenitor cells and is known to be up-regulated during states of hypoxia. Here we investigate the effects of renal ischemia/reperfusion (I/R) on the degree of renal dysfunction and injury with recombinant human EPO in mice when given as either a 3-day pretreatment, or upon reperfusion of the kidney.

METHODS

Mice were treated with EPO (1000 IU/kg/day subcutaneously) for 3 days, or treated with EPO (1000 IU/kg subcutaneously) upon reperfusion, and subsequently subjected to bilateral renal artery occlusion (30 minutes) and reperfusion (24 hours). At the end of experiments, the following indicators and markers of renal injury and dysfunction were measured: plasma urea, creatinine, and aspartate aminotransferase (AST), tissue myeloperoxidase (MPO) activity [for polymorphonuclear leukocyte (PMN) infiltration], and tissue malonaldehyde (MDA) levels (for tissue lipid peroxidation). Kidneys were used for histologic evaluation of renal injury.

RESULTS

EPO was able to significantly attenuate the renal dysfunction and injury associated with I/R, as well as the tissue injury. The increase in renal MPO activity and, hence, the degree of PMN infiltration were also significantly reduced in EPO-treated mice. In addition, lipid peroxidation as a result of renal I/R injury was also attenuated in EPO-treated mice.

CONCLUSION

The protection afforded by the pretreatment regime of EPO was greater than that of administering EPO as a single bolus upon reperfusion. We propose that different mechanisms underlie the protective effects seen with EPO when given as either a daily pretreatment or as a single bolus, which need to be further investigated.

Erythropoietin reduces the development of experimental inflammatory bowel disease

Inflammatory bowel disease is characterized by oxidative and nitrosative stress, leukocyte infiltration, and up-regulation of the expression of intercellular adhesion molecule-1 (ICAM-1) in the colon. Erythropoietin (EPO) is a potent stimulator of erythroid progenitor cells, and its expression is enhanced by hypoxia. Here we investigate the effects EPO has on the development of experimental colitis. To address this question, we used an experimental model of colitis induced by dinitrobenzene sulfonic acid (DNBS). When compared with DNBS-treated mice, EPO (1000 IU/kg day s.c.)-treated mice subjected to DNBS-induced colitis experienced significantly lower rates in the extent and severity of the histological signs of colon injury. DNBS-treated mice experienced diarrhea and weight loss. At 4 days after administration of DNBS, the mucosa of the colon exhibited large areas of necrosis. Neutrophil infiltration (determined by histology as well as an increase in myeloperoxidase activity in the mucosa) was associated with up-regulation of ICAM-1. Immunohistochemistry for nitrotyrosine and poly(ADP-ribose) showed an intense staining in the inflamed colon. On the contrary, the treatment of DNBS-treated mice with EPO significantly reduced the degree of diarrhea and weight loss caused by administration of DNBS. EPO also caused a substantial reduction of the degree of colon injury, the rise in myeloperoxidase activity (mucosa), and the increase in staining (immunohistochemistry) for nitrotyrosine as well as the up-regulation of ICAM-1 caused by DNBS in the colon. Thus, treatment of rat with EPO reduces the degree of colitis caused by DNBS. We propose that EPO may be useful in the treatment of inflammatory bowel disease.

Science review: recombinant human erythropoietin in critical illness: a role beyond anemia?

Erythropoiesis usually fails during severe illness because of a blunting of the kidney-erythropoietin (EPO)-bone marrow axis. In this setting, clinical studies have shown that recombinant human erythropoietin (rhEPO), administered in pharmacological amounts, significantly reduces the need for blood transfusions. In addition to the kidney, however, EPO is also produced locally by other tissues in a paracrine-autocrine manner. Here, similar to its role in the bone marrow, EPO rescues cells from apoptosis. Additionally, EPO reduces inflammatory responses, restores vascular autoregulation, and promotes healing. The results of many studies (including a phase II clinical trial in ischemic stroke) demonstrate that rhEPO protects the brain, spinal cord, retina, heart, and kidney from ischemic and other types of injury. Although rhEPO is efficacious in the treatment of EPO-deficient anemia during illness, inadequate effort has been devoted to determining whether direct tissue protection might also result from its administration. Here, we speculate on the potential utility of EPO as a protective cytokine in the context of acute critical illness and suggest key parameters required for a proof-of-concept clinical study.

Erythropoietin reduces myocardial infarction and left ventricular functional decline after coronary artery ligation in rats

Erythropoietin (EPO), well known for its role in stimulation of erythropoiesis, has recently been shown to have a dramatic neuroprotective effect in animal models of cerebral ischemia, mechanical trauma of the nervous system, and excitotoxins, mainly by reducing apoptosis. We studied the effect of single systemic administration of recombinant human EPO (rhEPO) on left ventricular (LV) size and function in rats during 8 weeks after the induction of a myocardial infarction (MI) by permanent ligation of the left descending coronary artery. We found that an i.p. injection of 3,000 units/kg of rhEPO immediately after the coronary artery ligation resulted, 24 h later, in a 50% reduction of apoptosis in the myocardial area at risk. Eight weeks after the induction of MI, rats treated with rhEPO had an infarct size 15-25% of the size of that in untreated animals. The reduction in myocardial damage was accompanied by reductions in LV size and functional decline as measured by repeated echocardiography. Thus, a single dose of rhEPO administered around the time of acute, sustained coronary insufficiency merits consideration with respect to its therapeutic potential to limit the extent of resultant MI and contractile dysfunction.

Asialoerythropoietin is a nonerythropoietic cytokine with broad neuroprotective activity in vivo

Erythropoietin (EPO) is a tissue-protective cytokine preventing vascular spasm, apoptosis, and inflammatory responses. Although best known for its role in hematopoietic lineages, EPO also affects other tissues, including those of the nervous system. Enthusiasm for recombinant human erythropoietin (rhEPO) as a potential neuroprotective therapeutic must be tempered, however, by the knowledge it also enlarges circulating red cell mass and increases platelet aggregability. Here we examined whether erythropoietic and tissue-protective activities of rhEPO might be dissociated by a variation of the molecule. We demonstrate that asialoerythropoietin (asialoEPO), generated by total enzymatic desialylation of rhEPO, possesses a very short plasma half-life and is fully neuroprotective. In marked contrast with rhEPO, this molecule at doses and frequencies at which rhEPO exhibited erythropoiesis, did not increase the hematocrit of mice or rats. AsialoEPO appeared promptly within the cerebrospinal fluid after i.v. administration; intravenously administered radioiodine-labeled asialoEPO bound to neurons within the hippocampus and cortex in a pattern corresponding to the distribution of the EPO receptor. Most importantly, asialoEPO exhibits a broad spectrum of neuroprotective activities, as demonstrated in models of cerebral ischemia, spinal cord compression, and sciatic nerve crush. These data suggest that nonerythropoietic variants of rhEPO can cross the blood-brain barrier and provide neuroprotection.

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

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

Recombinant human erythropoietin counteracts secondary injury and markedly enhances neurological recovery from experimental spinal cord trauma

Erythropoietin (EPO) functions as a tissue-protective cytokine in addition to its crucial hormonal role in red cell production. In the brain, for example, EPO and its receptor are locally produced, are modulated by metabolic stressors, and provide neuroprotective and antiinflammatory functions. We have previously shown that recombinant human EPO (rhEPO) administered within the systemic circulation enters the brain and is neuroprotective. At present, it is unknown whether rhEPO can also improve recovery after traumatic injury of the spinal cord. To evaluate whether rhEPO improves functional outcome if administered after cord injury, two rodent models were evaluated. First, a moderate compression of 0.6 N was produced by application of an aneurysm clip at level T3 for 1 min. RhEPO (1,000 units per kg of body weight i.p.) administered immediately after release of compression was associated with partial recovery of motor function within 12 h after injury, which was nearly complete by 28 days. In contrast, saline-treated animals exhibited only poor recovery. In the second model used, rhEPO administration (5,000 units per kg of body weight i.p. given once 1 h after injury) also produced a superior recovery of function compared with saline-treated controls after a contusion of 1 N at level T9. In this model of more severe spinal cord injury, secondary inflammation was also markedly attenuated by rhEPO administration and associated with reduced cavitation within the cord. These observations suggest that rhEPO provides early recovery of function, especially after spinal cord compression, as well as longer-latency neuroprotective, antiinflammatory and antiapoptotic functions.