A Pilot Study of Darbepoetin Alfa for Prophylactic Neuroprotection in Aortic Surgery

Erythropoietin and derivatives: Potential beneficial effects on the brain

Erythropoietin (Epo), the main erythropoiesis-stimulating factor widely prescribed to overcome anemia, is also known nowadays for its cytoprotective action on non-hematopoietic tissues. In this context, Epo showed not only its ability to cross the blood-brain barrier, but also its expression in the brain of mammals. In clinical trials, recombinant Epo treatment has been shown to stimulate neurogenesis; improve cognition; and activate antiapoptotic, antioxidant, and anti-inflammatory signaling pathways. These mechanisms, proposed to characterize a neuroprotective property, opened new perspectives on the Epo pharmacological potencies. However, many questions arise about a possible physiological role of Epo in the central nervous system (CNS) and the factors or environmental conditions that induce its expression. Although Epo may be considered a strong candidate to be used against neuronal damage, long-term treatments, particularly when high Epo doses are needed, may induce thromboembolic complications associated with increases in hematocrit and blood viscosity. To avoid these adverse effects, different Epo analogs without erythropoietic activity but maintaining neuroprotection ability are currently being investigated. Carbamylated erythropoietin, as well as alternative molecules like Epo fusion proteins and partial peptides of Epo, seems to match this profile. This review will focus on the discussion of experimental evidence reported in recent years linking erythropoietin and CNS function through investigations aimed at finding benefits in the treatment of neurodegenerative diseases. In addition, it will review the proposed mechanisms for novel derivatives which may clarify and, eventually, improve the neuroprotective action of Epo.

Anti-inflammatory and Neuroprotective Agents in Clinical Trials for CNS Disease and Injury: Where Do We Go From Here?

Neurological disorders are major contributors to death and disability worldwide. The pathology of injuries and disease processes includes a cascade of events that often involve molecular and cellular components of the immune system and their interaction with cells and structures within the central nervous system. Because of this, there has been great interest in developing neuroprotective therapeutic approaches that target neuroinflammatory pathways. Several neuroprotective anti-inflammatory agents have been investigated in clinical trials for a variety of neurological diseases and injuries, but to date the results from the great majority of these trials has been disappointing. There nevertheless remains great interest in the development of neuroprotective strategies in this arena. With this in mind, the complement system is being increasingly discussed as an attractive therapeutic target for treating brain injury and neurodegenerative conditions, due to emerging data supporting a pivotal role for complement in promoting multiple downstream activities that promote neuroinflammation and degeneration. As we move forward in testing additional neuroprotective and immune-modulating agents, we believe it will be useful to review past trials and discuss potential factors that may have contributed to failure, which will assist with future agent selection and trial design, including for complement inhibitors. In this context, we also discuss inhibition of the complement system as a potential neuroprotective strategy for neuropathologies of the central nervous system.

Erythropoietin's Beta Common Receptor Mediates Neuroprotection in Spinal Cord Neurons

BACKGROUND

Paraplegia from spinal cord ischemia-reperfusion (SCIR) remains an elusive and devastating complication of complex aortic operations. Erythropoietin (EPO) attenuates this injury in models of SCIR. Upregulation of the EPO beta common receptor (βcR) is associated with reduced damage in models of neural injury. The purpose of this study was to examine whether EPO-mediated neuroprotection was dependent on βcR expression. We hypothesized that spinal cord neurons subjected to oxygen-glucose deprivation would mimic SCIR injury in aortic surgery and EPO treatment attenuates this injury in a βcR-dependent fashion.

METHODS

Lentiviral vectors with βcR knockdown sequences were tested on neuron cell cultures. The virus with greatest βcR knockdown was selected. Spinal cord neurons from perinatal wild-type mice were harvested and cultured to maturity. They were treated with knockdown or nonsense virus and transduced cells were selected. Three groups (βcR knockdown virus, nonsense control virus, no virus control; n = 8 each) were subjected to 1 hour of oxygen-glucose deprivation. Viability was assessed. βcR expression was quantified by immunoblot.

RESULTS

EPO preserved neuronal viability after oxygen-glucose deprivation (0.82 ± 0.04 versus 0.61 ± 0.01; p < 0.01). Additionally, EPO-mediated neuron preservation was similar in the nonsense virus and control mice (0.82 ± 0.04 versus 0.80 ± 0.05; p = 0.77). EPO neuron preservation was lost in βcR knockdown mice compared with nonsense control mice (0.46 ± 0.03 versus 0.80 ± 0.05; p < 0.01).

CONCLUSIONS

EPO attenuates neuronal loss after oxygen-glucose deprivation in a βcR-dependent fashion. This receptor holds immense clinical promise as a target for pharmacotherapies treating spinal cord ischemic injury.

Erythropoietin and Nonhematopoietic Effects

Erythropoietin (EPO) is the main regulator of red blood cell production. Since the 1990s, EPO has been used for the treatment of anemia associated with end-stage renal failure and chemotherapy. The erythropoietin receptors were found on other organs such as the brain, spinal cord, heart and skin. In addition, it has been shown that many tissues produce and locally release EPO in response to hypoxic, biochemical and physical stress. In cellular, animal and clinical studies, EPO protects tissues from ischemia and reperfusion injury, has antiapoptotic effects and improves regeneration after injury. In this article, we mainly review the nonhematopoietic effects and new possible clinical indications for EPO.

Activation of migration of endogenous stem cells by erythropoietin as potential rescue for neurodegenerative diseases

Neurodegenerative disorders such as Alzheimer's disease (AD) are characterized by progressive cognitive dysfunction and memory loss. There is deposition of amyloid plaques in the brain and subsequent neuronal loss. Neuroinflammation plays a key role in the pathogenesis of AD. There is still no effective curative therapy for these patients. One promising strategy involves the stimulation of endogenous stem cells. This study investigated the therapeutic effect of erythropoietin (EPO) in neurogenesis, and proved its manipulation of the endogenous mesenchymal stem cells in model of lipopolysaccharide (LPS)-induced neuroinflammation.

METHODS

Forty five adult male mice were divided equally into 3 groups: Group I (control), group II (LPS untreated group): mice were injected with single dose of lipopolysaccharide (LPS) 0.8 mg/kg intraperitoneally (ip) to induce neuroinflammation, group III (EPO treated group): in addition to (LPS) mice were further injected with EPO in dose of 40 μg/kg of body weight three times weekly for 5 consecutive weeks. Groups were tested for their locomotor activity and memory using open field test and Y-maze. Cerebral specimens were subjected to histological and morphometric studies. Glial fibrillary acidic protein (GFAP) and mesenchymal stem cell marker CD44 were assessed using immunostaining. Gene expression of brain derived neurotrophic factor (BDNF) was examined in brain tissue.

RESULTS

LPS decreased locomotor activity and percentage of correct choices in Y-maze test. Cerebral sections of LPS treated mice showed increased percentage area of dark nuclei and amyloid plaques. Multiple GFAP positive astrocytes were detected in affected cerebral sections. In addition, decrease BDNF gene expression was noted. On the other hand, EPO treated group, showed improvement in locomotor and cognitive function. Examination of the cerebral sections showed multiple neurons exhibiting less dark nuclei and less amyloid plaques in comparison to the untreated group. GFAP positive astrocytes were also reduced. Cerebral sections of the EPO treated group showed multiple branched and spindle CD44 positive cells inside and around blood vessels more than in LPS group. This immunostaining was negative in the control group. EPO administration increased BDNF gene expression.

CONCLUSION

This study proved that EPO provides excellent neuroprotective and neurotrophic effects in vivo model of LPS induced neuroinflammation. It enhances brain tissue regeneration via stimulation of endogenous mesenchymal stem cells proliferation and their migration to the site of inflammation. EPO also up regulates cerebral BDNF expression and production, which might contributes to EPO mediated neurogenesis. It also attenuates reactive gliosis thus reduces neuroinflammation. These encouraging results obtained with the use of EPO proved that it may be a promising candidate for future clinical application and treatment of neurodegenerative diseases.

Neuroprotective Effect of Erythropoietin in Postoperation Cervical Spinal Cord Injury: Case Report and Review

INTRODUCTION

New research shows shown that erythropoietin has neuro-protective effects. In preclinical trial and human clinical trials, it was demonstrated that erythropoietin is effective treatment for spinal cord injury. Early administration of medications after injury increases the hope of attenuating secondary damage and maximizing an improved outcome.

CASE PRESENTATION

A 42-year-old female patient presented with gait instability and progressive weakness in her right leg over a 6-year period. She was diagnosed as myelomalacia and was candidate for cervical discectomy. After surgery, she suffered from right hemiplegia due to spinal cord injury that did not respond well to routine treatment. Darbepoetin alpha (Aranesp) 100 mcg, subcutaneous daily for three days, was added to the patient's treatment seven days after trauma and resulted in rapid improvement. The patient recovered progressively and was discharged from the hospital ten days after erythropoietin therapy.

CONCLUSIONS

This case report supports the beneficial role of erythropoietin in function, maintenance, and recovery of neurons. Erythropoietin is a double-edge sword, as long-term erythropoietin therapy has some complications, like thromboembolism and stroke. Recent studies suggested that erythropoietin should be given as single high dose to exert a rapid neuro-protective effect with minimal hematopoietic side effects. We believe that the effects and other adverse consequences of erythropoietin and its non-erythropoietic derivatives should be evaluated in clinical trials.

Darbepoetin Administration in Term and Preterm Neonates

Erythropoiesis-stimulating agents (ESAs) such as erythropoietin have been studied as red cell growth factors in preterm and term infants for more than 20 years. Recent studies have evaluated darbepoetin (Darbe, a long-acting ESA) for both erythropoietic effects and potential neuroprotection. We review clinical trials of Darbe in term and preterm infants, which have reported significant erythropoietic uses and neuroprotective effects. ESAs show great promise in decreasing or eliminating transfusions, and in preventing and treating brain injury in term and preterm infants.

Neuroprotective effects of erythropoiesis-stimulating agents in term and preterm neonates

PURPOSE OF REVIEW

The use of erythropoiesis-stimulating agents (ESAs) such as erythropoietin and darbepoetin in preterm and term infants has been studied for over 20 years. Recent investigations have explored the potential neuroprotective effects of ESAs. We review the recent clinical trials and experimental animal models that provide evidence in support of using ESA to improve the neurodevelopmental outcomes in term and preterm infants.

RECENT FINDINGS

Continued work using animal models have confirmed the neuroprotective properties of ESAs, including promotion of oligodendrocyte development in the face of neuronal injury. Clinical studies in term and preterm infants have reported the neuroprotective effects following ESA administration, and improved neurodevelopmental outcomes have been reported in the studies of preterm infants.

SUMMARY

ESAs show great promise in preventing and treating brain injury in term and preterm infants.