In vivo evidence that erythropoietin has a neuroprotective effect during subarachnoid hemorrhage

Avoiding Complications in Aneurysm Ligation: Operative Tips and Tricks

Preventing possible complications during brain aneurysm surgery is mandatory to ensure a better outcome for patients. Currently, it is possible to rely on some technologic innovations such as motor evoked potential, endoscope-assisted surgery, dye with indocyanine green, and video angiography capable of supporting the surgeon's work. The innovation process has mainly assisted the endovascular technique compared with surgery. The latter, apart from some new technical expedients, always requires anatomic knowledge and optimal technical preparation. A careful patient selection, adequate surgical exposure, use of microsurgical techniques in expert hands, and meticulous postoperative management represent the key to success for the surgical treatment of cerebral aneurysms.

Recent Advances in Stem Cell Research in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a type of hemorrhagic stroke with significant morbidity and mortality, and it often leads to poor clinical outcome. Although great efforts have been made toward animal and clinical studies, optimal therapy of SAH remains a challenge for scientists and clinicians. Increasing evidence suggests that stem-cell-based therapies may provide innovative approaches for treatment of SAH-related disability. In this review, we summarized the recent advances in stem cell research in SAH. Neuroregeneration after SAH could be conducted by the activation of endogenous neural stem cells (NSCs), transplantation of external stem cells, or reprogramming non-neuronal cell to neurons. The potential mechanism and signaling pathways, as well as the efficiency and safety of these stem cell treatments, were discussed in detail. Although lots of challenges remain for translating the laboratory findings and technologies into clinical therapies, these research studies provided the foundation and guidance for using different resources of stem cells as a brain repair strategy after SAH.

Neuroprotective Role of the Nrf2 Pathway in Subarachnoid Haemorrhage and Its Therapeutic Potential

The mechanisms underlying poor outcome following subarachnoid haemorrhage (SAH) are complex and multifactorial. They include early brain injury, spreading depolarisation, inflammation, oxidative stress, macroscopic cerebral vasospasm, and microcirculatory disturbances. Nrf2 is a global promoter of the antioxidant and anti-inflammatory response and has potential protective effects against all of these mechanisms. It has been shown to be upregulated after SAH, and Nrf2 knockout animals have poorer functional and behavioural outcomes after SAH. There are many agents known to activate the Nrf2 pathway. Of these, the actions of sulforaphane, curcumin, astaxanthin, lycopene, tert-butylhydroquinone, dimethyl fumarate, melatonin, and erythropoietin have been studied in SAH models. This review details the different mechanisms of injury after SAH including the contribution of haemoglobin (Hb) and its breakdown products. It then summarises the evidence that the Nrf2 pathway is active and protective after SAH and finally examines the evidence supporting Nrf2 upregulation as a therapy after SAH.

Management of aneurysmal subarachnoid hemorrhage: State of the art and future perspectives

Background:

Aneurysmal subarachnoid hemorrhage (SAH) accounts for 5% of strokes and carries a poor prognosis. It affects around 6 cases per 100,000 patient years occurring at a relatively young age.

Methods:

Common risk factors are the same as for stroke, and only in a minority of the cases, genetic factors can be found. The overall mortality ranges from 32% to 67%, with 10–20% of patients with long-term dependence due to brain damage. An explosive headache is the most common reported symptom, although a wide spectrum of clinical disturbances can be the presenting symptoms. Brain computed tomography (CT) allow the diagnosis of SAH. The subsequent CT angiography (CTA) or digital subtraction angiography (DSA) can detect vascular malformations such as aneurysms. Non-aneurysmal SAH is observed in 10% of the cases. In patients surviving the initial aneurysmal bleeding, re-hemorrhage and acute hydrocephalus can affect the prognosis.

Results:

Although occlusion of an aneurysm by surgical clipping or endovascular procedure effectively prevents rebleeding, cerebral vasospasm and the resulting cerebral ischemia occurring after SAH are still responsible for the considerable morbidity and mortality related to such a pathology. A significant amount of experimental and clinical research has been conducted to find ways in preventing these complications without sound results.

Conclusions:

Even though no single pharmacological agent or treatment protocol has been identified, the main therapeutic interventions remain ineffective and limited to the manipulation of systemic blood pressure, alteration of blood volume or viscosity, and control of arterial dioxide tension.

Erythropoietin for the Treatment of Subarachnoid Hemorrhage: A Feasible Ingredient for a Successful Medical Recipe

Subarachnoid hemorrhage (SAH) following aneurysm bleeding accounts for 6% to 8% of all cerebrovascular accidents. Although an aneurysm can be effectively managed by surgery or endovascular therapy, delayed cerebral ischemia is diagnosed in a high percentage of patients resulting in significant morbidity and mortality. Cerebral vasospasm occurs in more than half of all patients after aneurysm rupture and is recognized as the leading cause of delayed cerebral ischemia after SAH. Hemodynamic strategies and endovascular procedures may be considered for the treatment of cerebral vasospasm. In recent years, the mechanisms contributing to the development of vasospasm, abnormal reactivity of cerebral arteries and cerebral ischemia following SAH, have been investigated intensively. A number of pathological processes have been identified in the pathogenesis of vasospasm, including endothelial injury, smooth muscle cell contraction from spasmogenic substances produced by the subarachnoid blood clots, changes in vascular responsiveness and inflammatory response of the vascular endothelium. To date, the current therapeutic interventions remain ineffective as they are limited to the manipulation of systemic blood pressure, variation of blood volume and viscosity and control of arterial carbon dioxide tension. In this scenario, the hormone erythropoietin (EPO) has been found to exert neuroprotective action during experimental SAH when its recombinant form (rHuEPO) is administered systemically. However, recent translation of experimental data into clinical trials has suggested an unclear role of recombinant human EPO in the setting of SAH. In this context, the aim of the current review is to present current evidence on the potential role of EPO in cerebrovascular dysfunction following aneurysmal subarachnoid hemorrhage.

The single and double blood injection rabbit subarachnoid hemorrhage model

Over the past 30 years, the rabbit subarachnoid hemorrhage model (SAH) has been used for investigating the post-hemorrhage pathology, especially with respect to understanding of the mechanisms of cerebral vasospasm. However, the molecular mechanisms of cerebral vasospasm remain to be elucidated. Furthermore, it is not clear whether the rabbit SAH model is suitable for the investigation of pathological conditions other than cerebral vasospasm, such as early brain injury. Therefore, the properties of the rabbit SAH model need to be validated, and the reasons for using the rabbit should be clarified. This review explores the settings and technical issues of establishing a rabbit cisterna magna single and double blood injection SAH model and discusses the characteristics and feasibilities of the models.

The rabbit shunt model of subarachnoid haemorrhage

Aneurysmal subarachnoid haemorrhage (SAH) is a disease with devastating complications that leads to stroke, permanent neurological deficits and death. Clinical and ex-perimental work has demonstrated the importance of the contribution of delayed cerebral vasospasm (DCVS) indepen-dent early events to mortality, morbidity and functional out-come after SAH. In order to elucidate processes involved in early brain injury (EBI), animal models that reflect acute events of aneurysmal bleeding, such as increase in intracranial pressure (ICP) and decrease in cerebral perfusion pressure, are needed. In the presented arterial shunt model, bleeding is initially driven by the pressure gradient between mean arterial blood pressure and ICP. SAH dynamics (flow rate, volume and duration) depend on physiological reactions and local anatomical intrathecal (cistern) conditions. During SAH, ICP reaches a plateau close to diastolic arterial blood pressure and the blood flow stops. Historical background, anaesthesia, perioperative care and monitoring, SAH induction, technical considerations and advantages and limitations of the rabbit blood shunt SAH model are discussed in detail. Awareness of technical details, physiological characteristics and appropriate monitoring methods guarantees successful implementation of the rabbit blood shunt model and allows the study of both EBI and DCVS after SAH.

The comparative effects of recombinant human erythropoietin and darbepoetin-alpha on cerebral vasospasm following experimental subarachnoid hemorrhage in the rabbit

BACKGROUND

Darbepoetin alpha is a hypersialylated analogue of erythropoietin effective for activating erythropoietin-receptors. This study investigated the vasodilator and neuroprotective effects of darbepoetin alpha on an experimental subarachnoid hemorrhage model and compared it with erythropoietin.

METHODS

Forty adult male New Zealand white rabbits were randomly divided into four groups of ten rabbits each: group 1 (control), group 2 (subarachnoid hemorrhage), group 3 (erythropoietin), and group 4 (darbepoetin alpha). Recombinant human erythropoietin was administered at a dose of 1,000 U/kg intraperitoneally after the induction of subarachnoid hemorrhage and continued every 8 h up to 72 h. Darbepoetin alpha was administered at a single intraperitoneal dose of 30 μg/kg. Animals were killed 72 h after subarachnoid hemorrhage. Basilar artery cross-sectional areas, arterial wall thicknesses, hippocampal degeneration scores and biochemical analyses were measured in all groups.

RESULTS

Both erythropoietin and darbepoetin alpha treatments were found to attenuate cerebral vasospasm and provide neuroprotection after subarachnoid hemorrhage in rabbits. Darbepoetin alpha revealed better morphometric and histopathological results than erythropoietin among experimental subarachnoid hemorrhage-induced vasospasm.

CONCLUSIONS

Our findings, for the first time, showed that darbepoetin alpha can prevent vasospasm and provides neuroprotection following experimental subarachnoid hemorrhage. Moreover, darbepoetin alpha showed better results when compared with erythropoietin.

Different expression patterns of Ngb and EPOR in the cerebral cortex and hippocampus revealed distinctive therapeutic effects of intranasal delivery of Neuro-EPO for ischemic insults to the gerbil brain

The purpose of this study was to evaluate the neuroprotective effects of intranasally delivered recombinant human neuronal erythropoietin (Neuro-EPO) on brain injury induced by unilateral permanent ischemia in the Mongolian gerbil. Expression of EPO receptor (EPOR) and neuroglobin (Ngb) over 5 weeks after intranasal treatment with Neuro-EPO was determined using immunohistochemistry. Mortality of Neuro-EPO-treated gerbils decreased after surgery, and the sensory and motor function was significantly improved. Histopathological mapping showed that Neuro-EPO significantly reduced delayed neuronal death in the brain. Expression of Ngb was upregulated in the cerebral cortex at most time points (expect for 10 min and 48 hr) and in the hippocampus at 10 min and from 48 hr to 5 weeks, whereas EPOR was almost downregulated or unchanged in the brain (expect for 48 hr). The 10 min and 48 hr seemed to be two time points for the brain to switch the expression of both Ngb and EPOR to early and late recovery phase, respectively. In addition, there were two phases, 10 min to 1 hr and 24 hr to 72 hr, respectively, closing to the "golden hour" of about 60 min and the "silver day" of 1 to 3 days, for the brain to recover from stroke onset with intranasal Neuro-EPO treatment. Therefore, the results suggest that the intranasal administration of Neuro-EPO is effective in the treatment of acute brain ischemia. The different expression patterns of Ngb and EPOR is probably due to ischemic tolerance in the cerebral cortex and ischemic sensitivity in the hippocampus.

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.

Erythropoietin as neuroprotective and neuroregenerative treatment strategy: comprehensive overview of 12 years of preclinical and clinical research

Erythropoietin (EPO), originally discovered as hematopoietic growth factor, has direct effects on cells of the nervous system that make it a highly attractive candidate drug for neuroprotection/neuroregeneration. Hardly any other compound has led to so much preclinical work in the field of translational neuroscience than EPO. Almost all of the >180 preclinical studies performed by many independent research groups from all over the world in the last 12 years have yielded positive results on EPO as a neuroprotective drug. The fact that EPO was approved for the treatment of anemia >20 years ago and found to be well tolerated and safe, facilitated the first steps of translation from preclinical findings to the clinic. On the other hand, the same fact, naturally associated with loss of patent protection, hindered to develop EPO as a highly promising therapeutic strategy for application in human brain disease. Therefore, only few clinical neuroprotection studies have been concluded, all with essentially positive and stimulating results, but no further development towards the clinic has occurred thus far. This article reviews the preclinical and clinical work on EPO for the indications neuroprotection/neuroregeneration and cognition, and hopefully will stimulate new endeavours promoting development of EPO for the treatment of human brain diseases.

Erythropoietin 2nd cerebral protection after acute injuries: a double-edged sword?

Over the past 15 years, a large body of evidence has revealed that the cytokine erythropoietin exhibits non-erythropoietic functions, especially tissue-protective effects. The discovery of EPO and its receptors in the central nervous system and the evidence that EPO is made locally in response to injury as a protective factor in the brain have raised the possibility that recombinant human EPO (rhEPO) could be administered as a cytoprotective agent after acute brain injuries. This review highlights the potential applications of rhEPO as a neuroprotectant in experimental and clinical settings such as ischemia, traumatic brain injury, and subarachnoid and intracerebral hemorrhage. In preclinical studies, EPO prevented apoptosis, inflammation, and oxidative stress induced by injury and exhibited strong neuroprotective and neurorestorative properties. EPO stimulates vascular repair by facilitating endothelial progenitor cell migration into the brain and neovascularisation, and it promotes neurogenesis. In humans, small clinical trials have shown promising results but large prospective randomized studies failed to demonstrate a benefit of EPO for brain protection and showed unwanted side effects, especially thrombotic complications. Recently, regions have been identified within the EPO molecule that mediate tissue protection, allowing the development of non-erythropoietic EPO variants for neuroprotection conceptually devoid of side effects. The efficacy and the safety profile of these new compounds are still to be demonstrated to obtain, in patients, the benefits observed in experimental studies.

Erythropoietin: a multimodal neuroprotective agent

The tissue protective functions of the hematopoietic growth factor erythropoietin (EPO) are independent of its action on erythropoiesis. EPO and its receptors (EPOR) are expressed in multiple brain cells during brain development and upregulated in the adult brain after injury. Peripherally administered EPO crosses the blood-brain barrier and activates in the brain anti-apoptotic, anti-oxidant and anti-inflammatory signaling in neurons, glial and cerebrovascular endothelial cells and stimulates angiogenesis and neurogenesis. These mechanisms underlie its potent tissue protective effects in experimental models of stroke, cerebral hemorrhage, traumatic brain injury, neuroinflammatory and neurodegenerative disease. The preclinical data in support of the use of EPO in brain disease have already been translated to first clinical pilot studies with encouraging results with the use of EPO as a neuroprotective agent.

Neurological and neurobehavioral assessment of experimental subarachnoid hemorrhage

About 50% of humans with aneurysmal subarachnoid hemorrhage (SAH) die and many survivors have neurological and neurobehavioral dysfunction. Animal studies usually focused on cerebral vasospasm and sometimes neuronal injury. The difference in endpoints may contribute to lack of translation of treatments effective in animals to humans. We reviewed prior animal studies of SAH to determine what neurological and neurobehavioral endpoints had been used, whether they differentiated between appropriate controls and animals with SAH, whether treatment effects were reported and whether they correlated with vasospasm. Only a few studies in rats examined learning and memory. It is concluded that more studies are needed to fully characterize neurobehavioral performance in animals with SAH and assess effects of treatment.

Erythropoietin Stimulates Wound Healing and Angiogenesis in Mice

Erythropoietin exerts hematopoietic effects by stimulating proliferation of early erythroid precursors. Nonhematopoietic effects of erythropoietin have also been shown. It may act as a new angiogenic factor in wound healing. This study aimed to investigate the effect of systemic administration of recombinant human erythropoietin on wound healing in mice. Dorsal incisional wounds were performed in mice, which were then divided into two groups; a group treated for 7 days with recombinant human erythropoietin, and a control group. Sacrificing animals on day 7, the wound tissues were collected for analysis of wound breaking strength, malondialdehyde, a marker of lipid peroxidation, hydroxyproline, an index of reparative collagen deposition, reduced glutathione levels, and for histological evaluation. The immunohistochemical determination of vascular endothelial growth factor (VEGF) which is believed to be the most prevalent angiogenic factor throughout the skin repair process, was also studied. The treatment significantly increased wound breaking strength by decreasing malondialdehyde and increasing hydroxyproline levels on day 7 after wounding. No statistically meaningful change was observed in reduced glutathione content. VEGF was immunostained significantly more on wound tissue of treated animals compared to the control group. Recombinant human erythropoietin treatment may be effective in wound healing due to inhibition of lipid peroxidation, deposition of collagen, and VEGF expression in wound area.

Effects of recombinant human erythropoietin (rhEPO) on JAK2/STAT3 pathway and endothelial apoptosis in the rabbit basilar artery after subarachnoid hemorrhage

Previous studies have shown that recombinant human erythropoietin (rhEPO) can attenuate the degree of cerebral vasospasm following experimental subarachnoid hemorrhage (SAH). However, the mechanisms for this beneficial effect are still poorly understood. SAH-induced endothelial apoptosis may trigger, aggravate, and maintain cerebral vasospasm. We, therefore, tried to analyze whether rhEPO administration influenced the endothelial cell apoptosis in the basilar artery after SAH. Another aim of the current study was to investigate the modulation of rhEPO on the activity of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), which played an important role in the signaling of apoptosis. A total of 48 rabbits were randomly divided into four groups; control group, SAH group, SAH+vehicle group, and SAH+rhEPO group. All SAH animals were subjected to injection of autologous blood into cisterna magna twice on day 0 and day 2. The rhEPO was administered i.p. starting 5 min after the induction of SAH on day 0 and repeated every 8 h for 120 h. The basilar arteries were extracted on day 5 after SAH. As a result, we found that administration of rhEPO could activate JAK2 and STAT3 in the basilar artery and decrease the apoptosis index of endothelial cells following SAH. Moreover, the anti-apoptotic genes such as bcl-2 and bcl-xL were up-regulated after the injections of rhEPO. In conclusion, the therapeutic effect of rhEPO on the subsequent vasospasm after SAH may relate to its inhibition on the endothelial apoptosis in the cerebral arteries, which may be mediated in part by JAK2/STAT3 signaling pathway.

Hemodynamic effects of recombinant human erythropoietin on the central nervous system after subarachnoid hemorrhage: reduction of microcirculatory impairment and functional deficits in a rabbit model

OBJECT

The authors investigated the hemodynamic effects of recombinant human erythropoietin (rhEPO) after subarachnoid hemorrhage (SAH) in rabbits.

METHODS

The authors used male New Zealand White rabbits in this study divided into the following groups: SAH plus saline (16 rabbits), SAH plus low-dose rhEPO (16 rabbits; 1500 IU/kg on Day 0 and 500 IU/kg on Days 2 and 4), SAH plus high-dose rhEPO (10 rabbits; 1500 IU/kg on Days 0, 2, 4, and 6), and sham (6 rabbits). Computed tomography perfusion studies and CT angiography were performed for 1 hour after SAH on Day 0, and once each on Days 2, 4, 7, 9, and 16 after SAH. Assessments of neurological function and tissue histology were also performed.

RESULTS

The mortality rate was significantly lower after rhEPO treatment (12%) than after saline treatment (44%) (p < 0.05). Neurological outcomes in the low-dose and high-dose rhEPO groups were better than in the saline group after SAH (p < 0.05), and the cerebral blood flow in the high-dose rhEPO group was greater than that in the saline group (p < 0.05). The mean transit time was significantly lower on Days 2 and 4 in the low-dose and high-dose rhEPO groups than in the saline group, but increased significantly on Day 7 in both groups (p < 0.05). The hematocrit increased significantly from baseline values in the high-dose and low-dose rhEPO groups on Days 4 and 7, respectively (p < 0.05).

CONCLUSIONS

Treatment with rhEPO after experimental SAH is associated with improved cerebral blood flow and microcirculatory flow as reflected by lower mean transit times. Improved tissue perfusion correlated with reduced mortality and improved neurological outcomes. Further investigation of the impact of increasing hematocrit on hemodynamic changes is needed.

Neuroprotective effects of erythropoietin on acute metabolic and pathological changes in experimentally induced neurotrauma

OBJECT

Head trauma is a dynamic process characterized by a cascade of metabolic and molecular events. Erythropoietin (EPO) has been shown to have neuroprotective effects in animal models of traumatic brain injury (TBI). Acute in vivo mechanisms and pathological changes associated with EPO following TBI are unknown. In this study the authors compare acute metabolic and pathological changes following TBI with and without systemically administered EPO.

METHODS

Right frontal lobe microdialysis cannulae and right parietal lobe percussion hubs were inserted into 16 Sprague-Dawley rats. After a 4- to 5-day recovery, TBI was induced via a DragonFly fluid-percussion device at 2.5-2.8 atm. Rats were randomized into 2 groups, which received 5000 U/kg EPO or normal saline intraperitoneally 30 minutes after TBI. Microdialysis samples for glucose, lactate, pyruvate, and glutamate were obtained every 25 minutes for 10 hours. Rats were killed, their brains processed for light microscopy, and sections stained with H & E.

RESULTS

Erythropoietin administered 30 minutes after TBI directly affects acute brain metabolism. Brains treated with EPO maintain higher levels of glucose 4-10 hours after TBI (p<0.01), lower levels of lactate 6-10 hours after TBI (p<0.01), and lower levels of pyruvate 7.5-10 hours after TBI (p<0.01) compared with saline-treated controls. Erythropoietin maintains aerobic metabolism after TBI. Systemic EPO administration reduces acute TBI-induced lesion volume (p<0.05).

CONCLUSIONS

Following TBI, neuron use initially increases, with subsequent depletion of extracellular glucose, resulting in increased levels of extracellular lactate and pyruvate. This energy requirement can result in cell death due to increased metabolic demands. These data suggest that the neuroprotective effect of EPO may be partially due to improved energy metabolism in the acute phase in this rat model of TBI.

Erythropoietin-mediated tissue protection: reducing collateral damage from the primary injury response

In its classic hormonal role, erythropoietin (EPO) is produced by the kidney and regulates the number of erythrocytes within the circulation to provide adequate tissue oxygenation. EPO also mediates other effects directed towards optimizing oxygen delivery to tissues, e.g. modulating regional blood flow and reducing blood loss by promoting thrombosis within damaged vessels. Over the past 15 years, many unexpected nonhaematopoietic functions of EPO have been identified. In these more recently appreciated nonhormonal roles, locally-produced EPO signals through a different receptor isoform and is a major molecular component of the injury response, in which it counteracts the effects of pro-inflammatory cytokines. Acutely, EPO prevents programmed cell death and reduces the development of secondary, pro-inflammatory cytokine-induced injury. Within a longer time frame, EPO provides trophic support to enable regeneration and healing. As the region immediately surrounding damage is typically relatively deficient in endogenous EPO, administration of recombinant EPO can provide increased tissue protection. However, effective use of EPO as therapy for tissue injury requires higher doses than for haematopoiesis, potentially triggering serious adverse effects. The identification of a tissue-protective receptor isoform has facilitated the engineering of nonhaematopoietic, tissue-protective EPO derivatives, e.g. carbamyl EPO, that avoid these complications. Recently, regions within the EPO molecule mediating tissue protection have been identified and this has enabled the development of potent tissue-protective peptides, including some mimicking EPO's tertiary structure but unrelated in primary sequence.

Erythropoietin improves spatial delayed alternation in a T-maze in rats subjected to ablation of the prefrontal cortex

Systemically administered human recombinant erythropoietin (EPO) may have the potential to reduce the cognitive and behavioural symptoms of mechanical brain injury. In a series of studies we address this possibility. Previously, we studied the effects of EPO given to fimbria-fornix transected rats at the moment of injury. We have found that such treatment improves substantially the posttraumatic acquisition of allocentric place learning tasks administered in a water maze and in an 8-arm radial maze as well as a spatial delayed alternation task administered in a T-maze. It is, however, essential also to evaluate this clinically important ability of EPO after other types of mechanical brain injury. Consequently, we presently studied the effects of similarly administered EPO in rats subjected to bilateral subpial aspiration of the anteromedial prefrontal cortex as well as control operated rats, respectively. We evaluated the posttraumatic behavioural/cognitive abilities of these animals in a spatial delayed alternation task performed in a T-maze. Administration of EPO to the prefrontally ablated rats was associated with a reduction of the lesion-associated behavioural impairment--while such an impairment was clearly seen in the saline injected prefrontally ablated group. In sham operated rats administration of EPO did not influence the task acquisition significantly. The results of the present study confirm our previous demonstrations that EPO is able to reduce the behavioural/cognitive consequences of mechanical brain injury. This ability is emphasized by its relative independence on the type of lesion as well as the neural structure affected.

The erythropoietin receptor in normal and cancer tissues

The hormone erythropoietin (EPO) is essential for the survival, proliferation and differentiation of the erythrocytic progenitors. The EPO receptor (EPO-R) of erythrocytic cells belongs to the cytokine class I receptor family and signals through various protein kinases and STAT transcription factors. The EPO-R is also expressed in many organs outside the bone marrow, suggesting that EPO is a pleiotropic anti-apoptotic factor. The controversial issue as to whether the EPO-R is functional in tumor tissue is critically reviewed. Importantly, most studies of EPO-R detection in tumor tissue have provided falsely positive results because of the lack of EPO-R specific antibodies. However, endogenous EPO appears to be necessary to maintain the viability of endothelial cells and to promote tumor angiogenesis. Although there is no clinical proof that the administration of erythropoiesis stimulating agents (ESAs) promotes tumor growth and mortality, present recommendations are that (i) ESAs should be administered at the lowest dose sufficient to avoid the need for red blood cell transfusions, (ii) ESAs should not be used in patients with active malignant disease not receiving chemotherapy or radiotherapy, (iii) ESAs should be discontinued following the completion of a chemotherapy course, (iv) the target Hb should be 12 g/dL and not higher and (v) the risks of shortened survival and tumor progression have not been excluded when ESAs are dosed to target Hb <12 g/dL.

New insights into the causes and therapy of cerebral vasospasm following subarachnoid hemorrhage

Cerebral vasospasm lingers as the leading preventable cause of death and disability in patients who experience aneurysmal subarachnoid hemorrhage. Despite the potentially devastating consequences of cerebral vasospasm, the mechanisms behind it are incompletely understood. Nitric oxide, endothelin-1, bilirubin oxidation products and inflammation appear to figure prominently in its pathogenesis. Therapies directed at many of these mechanisms are currently under investigation and hold significant promise for an ultimate solution to this substantial problem.

Higher hemoglobin is associated with improved outcome after subarachnoid hemorrhage

OBJECTIVE

There are few data regarding anemia and transfusion after subarachnoid hemorrhage (SAH). We addressed the hypothesis that higher hemoglobin (HGB) levels are associated with less death and disability after SAH.

DESIGN

Prospective registry with automated data retrieval.

PATIENTS

Six hundred eleven patients enrolled in the Columbia University SAH Outcomes Project between August 1996 and June 2002.

SETTING

Neurologic intensive care unit.

INTERVENTIONS

Patients were treated according to standard management protocols.

MEASUREMENTS AND MAIN RESULTS

We electronically retrieved all HGB readings during the acute hospital stay for 611 consecutively admitted SAH patients. Outcomes were measured with the modified Rankin Scale at 14 days or discharge, and at 3 months. Patients who were independent (modified Rankin Scale, 0-3) at discharge or 14 days had higher mean (11.7 +/- 1.5 vs. 10.9 +/- 1.2, p < .001) and nadir (9.9 +/- 2.1 vs. 8.6 +/- 1.8, p < .001) HGB, and had higher HGB values every day in the hospital. There were similar results when patients were stratified by mortality. Higher HGB was associated with reduced risk of poor outcome (modified Rankin Scale, 4-6) at 14 days/discharge and 3 months after correcting for Hunt and Hess grade, age, history of diabetes, and cerebral infarction. Length of stay and HGB interacted such that lower HGB has a more pronounced effect with length of stay > 14 days.

CONCLUSIONS

Higher HGB values are associated with improved outcomes after SAH at 14 days/discharge and 3 months. In contrast to general critical care patients, SAH patients may benefit from higher HGB. Determination of the optimal goal HGB after SAH will require separate prospective research.

Erythropoietin in patients with aneurysmal subarachnoid haemorrhage: a double blind randomised clinical trial

BACKGROUND

Erythropoietin (EPO) is neuroprotective in experimental models of stroke and subarachnoid haemorrhage (SAH) and possibly in patients with thromboembolic stroke. We studied the efficacy and safety of EPO in patients with SAH.

METHODS

A larger scale clinical trial was planned but preliminarily terminated because of a lower than expected inclusion rate. However, 73 patients were randomised to treatment with EPO (500 IU/kg/day for three days) or placebo. The primary endpoint was Glasgow Outcome Score at six months. We further studied surrogate measures of secondary ischaemia, i.e. transcranial Doppler (TCD) flow velocity, symptomatic vasospasm, cerebral metabolism (microdialysis) and jugular venous oximetry, biochemical markers of brain damage (S-100beta and neuron specific enolase) and blood-brain barrier integrity.

FINDINGS

The limited sample size precluded our primary hypotheses being verified and refuted. However, data from this study are important for any other study of SAH and as much raw data as possible are presented and can be included in future meta analyses. On admission the proportion of patients in a poor condition was higher in the EPO group compared with the placebo group but the difference was statistically insignificant. In the EPO-treated patients the CSF concentration of EPO increased 600-fold. Except for a higher extracelullar concentration of glycerol in the EPO group probably caused by the poorer clinical condition of these patients, there were no statistically significant group differences in the primary or secondary outcome measures. EPO was well tolerated.

CONCLUSIONS

Beneficial effects of EPO in patients with SAH cannot be excluded or concluded on the basis of this study and larger scale trials are warranted.

Recombinant human erythropoietin decreases myeloperoxidase and caspase-3 activity and improves early functional results after spinal cord injury in rats

Inflammatory response and apoptosis have been proposed as mechanisms of secondary injury of the spinal cord after primary insult. Recent studies have shown that erythropoietin (EPO) has neuroprotective properties. In this study, we assessed the efficacy of recombinant human erythropoietin (r-Hu-EPO) in the treatment of acute spinal cord injury (SCI) in rats. Rats were divided into five groups of eight rats each. Controls (Group 1) received laminectomy only. The trauma-only group (Group 2) underwent 40 g/cm contusion injury and had no medication. In group 3, 30 mg/kg of methylprednisolone (MPSS) was administered. Group 4 received 1000 IU/kg body weight of r-Hu-EPO. The vehicle group (Group 5) received a vehicle solution containing human serum albumin, which is the solvent for r-Hu-EPO. Twenty-four hours after trauma, animals were functionally evaluated and a spinal cord samples were obtained for the assessment of caspase-3 and myeloperoxidase (MPO) activities. The results showed that MPO and caspase-3 activities increased to statistically significant higher levels in the spinal cord after contusion injury comparing to the control group. MPO and caspase-3 enzyme activity levels were significantly reduced in animals treated either with r-Hu-EPO or MPSS. In addition, we observed significant early functional recovery in EPO-treated rats. EPO has anti-apoptotic and anti-inflammatory effects, and improves early clinical results after SCI.

Erythropoietin and cerebral vascular protection: role of nitric oxide

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is a major clinical problem causing cerebral ischemia and infarction. The pathogenesis of vasospasm is related to a number of pathological processes including endothelial damage and alterations in vasomotor function leading to narrowing of arterial diameter and a subsequent decrease in cerebral blood flow. Discovery of the tissue protective effects of erythropoietin (EPO) stimulated the search for therapeutic application of EPO for the prevention and treatment of cerebrovascular disease. Recent studies have identified the role of EPO in vascular protection mediated by the preservation of endothelial cell integrity and stimulation of angiogenesis. In this review, we discuss the EPO-induced activation of endothelial nitric oxide (NO) synthase and its contribution to the prevention of cerebral vasospasm.

Association between higher cumulative doses of recombinant erythropoietin and risk for retinopathy of prematurity

BACKGROUND

Retinopathy of prematurity is a complication of premature birth that varies in its severity. The incidence and severity of retinopathy of prematurity at our perinatal center in a regional referral hospital changed substantially during 1995 to 1998 and presented us with an opportunity to examine whether there was a protective effect on risk of retinopathy associated with exposure to recombinant erythropoietin.

METHODS

We undertook a retrospective cohort study. From January 1995 through December 1998, charts of infants weighing<1500 g, who were 30 weeks' gestation or less, and who were admitted and survived to the first eye examination at 6 weeks were reviewed. Primary and secondary risk factors were recorded from the first 6 weeks of life. Of the eligible infants, 327 of 390 (84%) had complete records and retinal examinations. The probability for progression of retinopathy was estimated by logistic regression multivariate analysis using the continuation-ratio model.

RESULTS

The overall incidence of retinopathy of prematurity was 36%. Recombinant erythropoietin exposure, as total 6-week dose, was independently associated with an increased risk for progression of retinopathy, OR=1.27 per 500 units/kg (95%CI=1.04, 1.55, P=0.02). Postnatal day of recombinant erythropoietin initiation also was associated with retinopathy risk but did not reach conventional statistical significance, OR=1.07 (CI=1.00, 1.14, P=0.07).

CONCLUSIONS

These findings identify an association between cumulative recombinant erythropoietin exposure, used to reduce blood transfusions in premature infants, and an increased risk for retinopathy of prematurity. The nonhematopoietic properties of erythropoietin may account for the above findings, however further evaluation with confirmation is required.

Role of endothelial NO synthase phosphorylation in cerebrovascular protective effect of recombinant erythropoietin during subarachnoid hemorrhage-induced cerebral vasospasm

BACKGROUND AND PURPOSE

In the present study, the effect of subarachnoid hemorrhage (SAH) on the phosphorylation of endothelial NO synthase (eNOS) and the ability of recombinant erythropoietin (Epo) to augment this vasodilator mechanism in the spastic arteries were studied.

METHODS

Recombinant adenoviral vectors (10(9) plaque-forming units per animal) encoding genes for human Epo (AdEpo), and beta-galactosidase were injected immediately after injection of autologous arterial blood into the cisterna magna (day 0) of rabbits. Cerebral angiography was performed on day 0 and day 2, and basilar arteries were harvested for Western blots, measurement of cGMP levels, and analysis of vasomotor functions.

RESULTS

Injection of autologous arterial blood into cisterna magna resulted in significant vasospasm of the basilar arteries. Despite the narrowing of arterial diameter and reduced expression of eNOS, expressions of phosphorylated protein kinase B (Akt) and phosphorylated eNOS were significantly increased in spastic arteries. Gene transfer of AdEpo reversed the vasospasm. AdEpo-transduced basilar arteries demonstrated significant augmentation of the endothelium-dependent relaxations to acetylcholine, whereas the relaxations to an NO donor, 2-(N,N-diethylamino)diazenolate-2-oxide sodium salt, were not affected. Transduction with AdEpo further increased the expression of phosphorylated Akt and eNOS and elevated basal levels of cGMP in the spastic arteries.

CONCLUSIONS

Phosphorylation of eNOS appears to be an adaptive mechanism activated during development of vasospasm. The vascular protective effect of Epo against cerebral vasospasm induced by SAH may be mediated in part by phosphorylation of Akt/eNOS.

Neuroprotective effects and intracellular signaling pathways of erythropoietin in a rat model of multiple sclerosis

In multiple sclerosis (MS), long-term disability is primarily caused by axonal and neuronal damage. We demonstrated in a previous study that neuronal apoptosis occurs early during experimental autoimmune encephalomyelitis, a common animal model of MS. In the present study, we show that, in rats suffering from myelin oligodendrocyte glycoprotein (MOG)-induced optic neuritis, systemic application of erythropoietin (Epo) significantly increased survival and function of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve. We identified three independent intracellular signaling pathways involved in Epo-induced neuroprotection in vivo: Protein levels of phospho-Akt, phospho-MAPK 1 and 2, and Bcl-2 were increased under Epo application. Using a combined treatment of Epo together with a selective inhibitor of phosphatidylinositol 3-kinase (PI3-K) prevented upregulation of phospho-Akt and consecutive RGC rescue. We conclude that in MOG-EAE the PI3-K/Akt pathway has an important influence on RGC survival under systemic treatment with Epo.

Brain and cancer: the protective role of erythropoietin

Erythropoietin (Epo) is a pleiotropic agent, that is to say, it can act on several cell types in different ways. An independent system Epo/Epo receptor (EpoR) was detected in brain, leading to the hypothesis that this hormone could be involved in cerebral functions. Epo/EpoR expression changes during ontogenesis, thus indicating the importance of this system in neurodevelopment. Moreover, the hypoxia-induced production of Epo in the adult brain suggests that it could exert a neurotrophic and neuroprotective effect in case of brain injury. Epo could also influence neurotransmission, inducing neurotransmitters (NT) release. Epo therapy in anemic cancer patients is still a controversial issue, because of its possible action as a growth and an angiogenic factor. In our speculative hypothesis Epo could be involved in a "two steps process" that, after a neovascularization phase, leads to its down regulation. Moreover, Epo-activated signaling pathways could be modulated as possible targets to interfere in neoplastic cells cycle. In conclusion, treatment with rHuEpo could change therapeutical perspectives in different pathological conditions, such as central nervous system (CNS) diseases, but further studies are needed to clarify its physiopathological activities in different clinical fields.

Erythropoietin and Erythropoietin Receptor Expression after Experimental Spinal Cord Injury Encourages Therapy by Exogenous Erythropoietin

OBJECTIVE

Erythropoietin (EPO) is a pleiotropic cytokine originally identified for its role in erythropoiesis. Recent studies have demonstrated that EPO and its receptor (EPO-R) are expressed in the central nervous system, where EPO exerts neuroprotective functions. Because the expression of the EPO and EPO-R network is poorly investigated in the central nervous system, the aim of the present study was to investigate whether the resident EPO and EPO-R network is activated in the injured nervous system.

METHODS

A well-standardized model of compressive spinal cord injury in rats was used. EPO and EPO-R expression was determined by immunohistochemical analysis at 8 hours and at 2, 8, and 14 days in the spinal cord of injured and noninjured rats.

RESULTS

In noninjured spinal cord, weak immunohistochemical expression of EPO and EPO-R was observed in neuronal and glial cells as well as in endothelial and ependymal cells. In injured rats, a marked increase of expression of EPO and EPO-R was observed in neurons, vascular endothelium, and glial cells at 8 hours after injury, peaking at 8 days, after which it gradually decreased. Two weeks after injury, EPO immunoreactivity was scarcely detected in neurons, whereas glial cells and vascular endothelium expressed strong EPO-R immunoreactivity.

CONCLUSION

These observations suggest that the local EPO and EPO-R system is markedly engaged in the early stages after nervous tissue injury. The reduction in EPO immunoexpression and the increase in EPO-R staining strongly support the possible usefulness of a therapeutic approach based on exogenous EPO administration.

Cytoprotection by darbepoetin/epoetin alfa in pig tubular and mouse mesangial cells

BACKGROUND

Erythropoietin has recently been found to have cytoprotective effects in the central nervous system (CNS) and retina. The purpose of this study was to determine if darbepoetin alfa (DA) has cytoprotective properties in renal tissues.

METHODS

DA was studied in LLC/PK1 and mesangial cells. Renal cellular injury was induced in different experiments by prostaglandin D2 synthase (PGDS), camptothecin, hydrogen peroxide, and hypoxia. Cellular proliferation and apoptosis were measured [apoptosis by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL) assay or by caspase-3 activity]. In a separate experiment, an inactive form of erythropoietin alfa was used to study receptor effects.

RESULTS

DA protected against the antiproliferative effects of PGDS. In both LLC/PK1 (TUNEL and caspase-3) and mesangial cells (TUNEL), DA reduced the apoptotic stimulus of PGDS. Epoetin alfa was also found to reduce apoptosis. In LLC/PK1 cells, DA reduced apoptosis induced by camptothecin, but not hydrogen peroxide. DA reduced LLC/PK1 apoptosis induced by hypoxia when added 24 hours before hypoxia, but not when given concurrent with the hypoxic stimulus. Erythropoietin inactive did not protect against PGDS-induced apoptosis.

CONCLUSION

DA has renal antiapoptotic effects for both toxic and hypoxic stimuli. The effect may be mediated via the Erythropoietin receptor.

Beneficial and ominous aspects of the pleiotropic action of erythropoietin

The primary function of the glycoprotein hormone erythropoietin (Epo) is to promote red cell production by inhibiting apoptosis of erythrocytic progenitors in hemopoietic tissues. However, functional Epo receptors (Epo-R) have recently been demonstrated in various nonhemopoietic tissues indicating that Epo is a more pleiotropic viability and growth factor. Herein, in vitro and in vivo effects of Epo in the brain and the cardiovascular system are reviewed. In addition, the therapeutic impact of Epo in oncology is considered, including the question of whether Epo might promote tumor growth. Convincing evidence is available that Epo acts as a neurotrophic and neuroprotective factor in the brain. Epo prevents neuronal cells from hypoxia-induced and glutamate-induced cell death. Epo-R is expressed by neurons and glia cells in specific regions of the brain. Epo supports the survival of neurons in the ischemic brain. The neuroprotective potential of Epo has already been confirmed in a clinical trial on patients with acute stroke. With respect to the vasculature, Epo acts on both endothelial and smooth muscle cells. Epo promotes angiogenesis and stimulates the production of endothelin and other vasoactive mediators. In addition, Epo-R is expressed by cardiomyocytes. The role of Epo as a myocardial protectant is at the focus of present research. Epo therapy in tumor patients is practiced primarily to maintain the hemoglobin concentration above the transfusion trigger and to reduce fatigue. In addition, increased tumor oxygenation may improve the efficacy of chemotherapy and radiotherapy. However, tumor cells often express Epo-R. Therefore, careful studies are required to fully exclude that recombinant human Epo (rHuEpo) promotes tumor growth.

Erythropoietin (epoetin) as a protective factor for the brain

Erythropoietin (EPO) has been viewed traditionally as a hematopoietic cytokine. Emerging evidence now exists supporting a physiologic role for EPO within the nervous system. EPO is expressed in the developing central nervous system and is capable of regulating the production of neuronal progenitor cells. There are numerous preclinical studies demonstrating a neuroprotective potential for EPO in a variety of disorders of both the central and peripheral nervous systems. A small pilot study in patients with acute ischemic stroke has recently been completed and the results are encouraging. Its mechanism of action is multifactorial but probably related to its ability to act as an antiapoptotic agent. Its widespread use clinically for the treatment of anemias has given us the experience and knowledge of its safety and pharmacokinetics. EPO is thus an ideal compound to study for the potential treatment of a variety of neurologic disorders.

An overview of new pharmacological treatments for cerebrovascular dysfunction after experimental subarachnoid hemorrhage

Cerebral vasospasm and the resulting cerebral ischemia occurring after subarachnoid hemorrhage (SAH) are still responsible for the considerable morbidity and mortality in patients affected by cerebral aneurysms. Mechanisms contributing to the development of vasospasm, abnormal reactivity of cerebral arteries and cerebral ischemia after SAH have been intensively investigated in recent years. It has been suggested that the pathogenesis of vasospasm is related to a number of pathological processes, including endothelial damage, smooth muscle cell contraction resulting from spasmogenic substances generated during lyses of subarachnoid blood clots, changes in vascular responsiveness and inflammatory or immunological reactions of the vascular wall. A great deal of experimental and clinical research has been conducted in an effort to find ways to prevent these complications. However, to date, the main therapeutic interventions remain elusive and are limited to the manipulation of systemic blood pressure, alteration of blood volume or viscosity, and control of arterial dioxide tension. Even though no single pharmacological agent or treatment protocol has been identified which could prevent or reverse these deadly complications, a number of promising drugs have been investigated. Among these is the hormone erythropoietin (EPO), the main regulator of erythropoiesis. It has recently been found that EPO produces a neuroprotective action during experimental SAH when its recombinant form (rHuEPO) is systemically administered. This topic review collects the relevant literature on the main investigative therapies for cerebrovascular dysfunction after aneurysmal SAH. In addition, it points out rHuEPO, which may hold promise in future clinical trials to prevent the occurrence of vasospasm and cerebral ischemia after SAH.

Erythropoietin exerts neuroprotection after acute spinal cord injury in rats: effect on lipid peroxidation and early ultrastructural findings

Lipid peroxidation has been reported to play an important role in spinal cord injury (SCI). Erythropoietin (EPO) is a hematopoietic growth factor that stimulates proliferation and differentiation of erythroid precursor cells and is also known to exert neurotrophic activity in the central nervous system. The purpose of this study was to investigate the effectiveness of recombinant human EPO in attenuating the severity of experimental SCI. Rats were divided into seven groups. Controls (1) received only laminectomy. The trauma-only group (2) underwent 50-g/cm contusion injury and had no medication. In group 3, 30 mg/kg of methylprednisolone was introduced. The vehicle group (4) received vehicle solution containing human serum albumin, which is a solvent of EPO. Groups 5, 6, and 7 received 100 IU/kg, 1,000 IU/kg, and 5,000 IU/kg of EPO, respectively. All treatments were given as single doses, intraperitoneally, immediately after injury. Thiobarbituric acid-reactive substances were estimated to demonstrate lipid peroxidation, and ultrastructure was evaluated by electron microscopy. The results showed that lipid peroxidation by-products increased after injury. Administration of EPO and methylprednisolone sodium succinate (MPSS) reduced thiobarbituric acid-reactive substances after trauma. The best biochemical results were obtained with 5,000 IU/kg of EPO. Electron microscopic findings showed that EPO protected the spinal cord from injury. Although 1,000 IU/kg and 5,000 IU/kg of EPO inhibited lipid peroxidation better than MPSS, ultrastructural neuroprotection was similar.

Erythropoietin improves place learning in fimbria–fornix-transected rats and modifies the search pattern of normal rats

The acquisition of a water-maze-based allocentric place learning task was studied in four groups of rats: two groups subjected to bilateral transections of the fimbria-fornix and two groups undergoing a sham control operation. At the moment of surgery all animals were given one systemic (intraperitoneal) injection of either human recombinant erythropoietin (EPO) (at a dosage of 5000 IU/kg body weight), given to one of the fimbria-fornix-transected groups and one of the sham-operated groups, or vehicle (saline), given to the two remaining groups. The 25-day task acquisition period (one session/day) began 6 or 7 days after the day of surgery. The fimbria-fornix-transected and saline-injected group exhibited a pronounced and long-lasting impairment of task acquisition. In contrast, the fimbria-fornix-transected and EPO-treated group demonstrated a less pronounced and more transient lesion-associated impairment. The two sham-operated groups did not differ with respect to the proficiency of task acquisition. But administration of EPO to intact animals caused a significant modification of swim patterns-apparently reflecting a somewhat modified strategy of task solution. It is concluded that systemic administration of EPO significantly improves the posttraumatic functional recovery of the presently studied place learning task after transections of the fimbria-fornix. Additionally, administration of EPO influences the strategy, although not quality, of task solution in normal (sham-operated) rats.

Erythropoietin in the cerebrospinal fluid of patients with aneurysmal subarachnoid haemorrhage originates from the brain

Recent years' research has revealed a specific, neuroprotective erythropoietin (EPO) system in the central nervous system (CNS) that is upregulated by hypoxia. The presence and dynamics of EPO in the cerebrospinal fluid (CSF) of patients with subarachnoid haemorrhage (SAH) has not been investigated. We collected a total of 83 corresponding serum and CSF samples from 18 patients with aneurysmal SAH and compared the concentrations of EPO with those of blood-derived markers of blood-brain barrier function (albumin, transferrin, alpha(2)-macroglobulin) and with those of proteins with well-known CNS synthesis (prealbumin, apolipoprotein E). The EPO concentration in CSF was 0.93 (0.82) mU/ml (median and inter-quartile range). Nine patients presented CSF-EPO values above 1 mU/ml. CSF levels did not correlate with serum concentrations and were independent of blood-brain barrier integrity suggesting a synthesis in CNS rather than a blood-derived origin. Furthermore, the median CSF:serum ratio (Q(protein)) of EPO was similar to those of prealbumin and apolipoprotein E, and much higher than those of albumin, transferrin and alpha(2)-macroglobulin. When the Q(protein) of all proteins were plotted against Q(albumin), EPO showed dynamics similar to CNS-derived proteins. Our data indicate that EPO in the CSF of patients with aneurysmal SAH originates mainly from the CNS.

The pleiotropic effects of erythropoietin in the central nervous system

Erythropoietin (Epo) is a hydrophobic sialoglycoproteic hormone produced by the kidney and responsible for the proliferation, maturation, and differentiation of the precursors of the erythroid cell line. Human recombinant erythropoietin (rHuEpo) is used to treat different types of anemia, not only in uremic patients but also in newborns with anemia of prematurity, in patients with cancer-related anemia or myeloproliferative disease, thalassemias, bone marrow transplants, or those with chronic infectious diseases. The pleiotropic functions of Epo are well known. It has been shown that this hormone can modulate the inflammatory and immune response, has direct hemodynamic and vasoactive effects, could be considered a proangiogenic factor because of its interaction with vascular endothelial growth factor, and its ability to stimulate mitosis and motility of endothelial cells. The multifunctional role of Epo has further been confirmed by the discovery in the central nervous system of a specific Epo/Epo receptor (EpoR) system. Both Epo and EpoR are expressed by astrocytes and neurons and Epo is present in the cerebrospinal fluid (CSF). Therefore, novel functions of Epo, tissue-specific regulation, and the mechanisms of action have been investigated. In this review we have tried to summarize the current data on the role of Epo on brain function. We discuss the different sites of cerebral expression and mechanisms of regulation of Epo and its receptor and its role in the development and maturation of the brain. Second, we discuss the neurotrophic and neuroprotective function of Epo in different conditions of neuronal damage, such as hypoxia, cerebral ischemia, and subarachnoid hemorrhage, and the consequent possibility that rHuEpo therapy could soon be used in clinical practice to limit neuronal damage induced by these diseases.

Potential neuroprotective benefits of erythropoietin during experimental hypothermic circulatory arrest

OBJECTIVE

Recent studies have shown that erythropoietin protects neurons from glutamate toxicity and ischemia. This study was performed to evaluate the potential neuroprotective effect of erythropoietin during experimental hypothermic circulatory arrest.

METHODS

Twenty pigs were randomized to receive intravenously either 500 IU/kg recombinant human erythropoietin or saline before a 75-minute period of hypothermic circulatory arrest at an intracerebral temperature of 18 degrees C.

RESULTS

After the administration of erythropoietin, its concentration in the cerebrospinal fluid increased 4.5-fold 8 hours after the start of rewarming, whereas it did not increase in control animals. The 7-day survival rate was 60% in the erythropoietin group and 70% in the control group (P = 1.0). No significant differences were observed between the study groups in terms of electroencephalography, behavioral score, and histopathologic score. The erythropoietin group had higher vascular resistance and mean arterial pressure values, lower intracerebral concentrations of glutamate and glycerol, higher brain tissue oxygen tension, and lower apoptotic index.

CONCLUSIONS

Administration of 500 IU/kg erythropoietin intravenously before hypothermic circulatory arrest was followed by an increased erythropoietin concentration in the cerebrospinal fluid. Although previous studies have demonstrated neuroprotective effects of erythropoietin during brain ischemia, the present study, using a chronic porcine model, failed to show any significant benefit after administration of erythropoietin in terms of mortality or brain histopathology. Lower intracerebral concentrations of glutamate and glycerol, higher brain tissue oxygen tension, and lower apoptotic index observed in the erythropoietin group, however, suggest that a distinct neuroprotective effect of erythropoietin might be achieved at different dosages and timing of administration.

Beneficial effects of systemic administration of recombinant human erythropoietin in rabbits subjected to subarachnoid hemorrhage

Cerebral vasospasm and ischemic damage are important causes of mortality and morbidity in patients affected by aneurysmal subarachnoid hemorrhage (SAH). Recently, i.p. administration of recombinant human erythropoietin (r-Hu-EPO) has been shown to exert a neuroprotective effect during experimental SAH. The present study was conducted to evaluate further the effect of r-Hu-EPO administration after SAH in rabbits on neurological outcome, degree of basilar artery spasm, and magnitude of neuronal ischemic damage. Experimental animals were divided into six groups: group 1 (n = 8), control; group 2 (n = 8), control plus placebo; group 3 (n = 8), control plus r-Hu-EPO; group 4 (n = 8), SAH; group 5 (n = 8), SAH plus placebo; group 6 (n = 8), SAH plus r-Hu-EPO. r-Hu-EPO, at a dose of 1,000 units/kg, and placebo were injected i.p. starting 5 min after inducing SAH and followed by clinical and pathological assessment 72 h later. Systemic administration of r-Hu-EPO produced significant increases in cerebrospinal fluid EPO concentrations (P < 0.001), and reduced vasoconstriction of the basilar artery (P < 0.05), ischemic neuronal damage (P < 0.001), and subsequent neurological deterioration (P < 0.05). These observations suggest that r-Hu-EPO may provide an effective treatment to reduce the post-SAH morbidity.

Does administration of recombinant human erythropoietin attenuate the increase of S-100 protein observed in cerebrospinal fluid after experimental subarachnoid hemorrhage?

OBJECT

Results of recent studies indicate that erythropoietin (EPO) produces a neuroprotective effect on experimental subarachnoid hemorrhage (SAH). It has been reported that S-100 protein levels increase in cerebrospinal fluid (CSF) after SAH, providing a highly prognostic indication of unfavorable outcome. This study was conducted to validate further the findings of S-100 protein as an index of brain damage and to assess whether treatment with recombinant human EPO (rhEPO) would limit the increase of S-100 protein level in CSF following experimental SAH.

METHODS

Thirty-two rabbits were each assigned to one of four groups: Group 1, control; Group 2, SAH; Group 3, SAH plus placebo; and Group 4, SAH plus rhEPO (each group consisted of eight rabbits). The rhEPO and placebo were administered to the rabbits after SAH had been induced, and S-100 protein levels in the CSF of these animals were measured at 24, 48, and 72 hours after the experimental procedure. In each group of animals levels of S-100 protein were compared with the mortality rate, neurological outcome, and neuronal ischemic damage. High S-100 protein levels were found in rabbits in Groups 2 and 3, which exhibited poor neurological status and harbored a high number of damaged cortical neurons. Favorable neurological outcome and significant reductions in total numbers of damaged neurons were observed in animals in Group 4 in which there were significantly lower S-100 protein concentrations compared with animals in Groups 2 and 3 (p < 0.001).

CONCLUSIONS

The results of this study support the concept that determination of the S-100 protein level in CSF has prognostic value after SAH. The findings also confirm that rhEPO acts as a neuroprotective agent during experimental SAH.

Erythropoietin prevents cognition impairment induced by transient brain ischemia in gerbils

Erythropoietin has recently been studied for its role in the central nervous system (CNS). It has been shown to exert neuroprotective effects in different models of brain injury. We studied whether neuroprotective effects assessed from the reduction of neuronal loss after transient brain ischemia are associated to the preservation of learning ability. Recombinant human erythropoietin (0.5-25 U) was injected in the lateral cerebral ventricle of gerbils that are subjected to temporary (3 min) bilateral carotid occlusion. Post-ischemic histological evaluation of CA1 area neuronal loss and passive avoidance test were performed. Treatment with recombinant human erythropoietin significantly reduced delayed neuronal death in the CA1 area of the hippocampus and prevented cognition impairment in the passive avoidance test. These data indicate that recombinant human erythropoietin neuroprotective effects in brain ischemia are associated with the preservation of learning function.

Erythropoietin prevents motor neuron apoptosis and neurologic disability in experimental spinal cord ischemic injury

The cytokine erythropoietin (EPO) possesses potent neuroprotective activity against a variety of potential brain injuries, including transient ischemia and reperfusion. It is currently unknown whether EPO will also ameliorate spinal cord injury. Immunocytochemistry performed using human spinal cord sections showed abundant EPO receptor immunoreactivity of capillaries, especially in white matter, and motor neurons within the ventral horn. We used a transient global spinal ischemia model in rabbits to test whether exogenous EPO can cross the blood-spinal cord barrier and protect these motor neurons. Spinal cord ischemia was produced in rabbits by occlusion of the abdominal aorta for 20 min, followed by saline or recombinant human (rHu)-EPO (350, 800, or 1,000 units/kg of body weight) administered intravenously immediately after the onset of reperfusion. The functional neurological status of animals was better for rHu-EPO-treated animals 1 h after recovery from anesthesia, and improved dramatically over the next 48 h. In contrast, saline-treated animals exhibited a poorer neurological score at 1 h and did not significantly improve. Histopathological examination of the affected spinal cord revealed widespread motor neuron injury associated with positive terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling in control but not in rHu-EPO-treated animals. These observations suggest both an acute as well as a delayed beneficial action of rHu-EPO in ischemic spinal cord injury. Because rHu-EPO is currently used widely with an excellent safety profile, clinical trials evaluating its potential to prevent motor neuron apoptosis and the neurological deficits that occur as a consequence of ischemic injury are warranted.