Cell Death Mechanism and Protective Effect of Erythropoietin after Focal Ischemia in the Whisker-Barrel Cortex of Neonatal Rats

Extrasynaptic NMDA receptors in acute and chronic excitotoxicity: implications for preventive treatments of ischemic stroke and late-onset Alzheimer's disease

Stroke and late-onset Alzheimer's disease (AD) are risk factors for each other; the comorbidity of these brain disorders in aging individuals represents a significant challenge in basic research and clinical practice. The similarities and differences between stroke and AD in terms of pathogenesis and pathophysiology, however, have rarely been comparably reviewed. Here, we discuss the research background and recent progresses that are important and informative for the comorbidity of stroke and late-onset AD and related dementia (ADRD). Glutamatergic NMDA receptor (NMDAR) activity and NMDAR-mediated Ca²⁺ influx are essential for neuronal function and cell survival. An ischemic insult, however, can cause rapid increases in glutamate concentration and excessive activation of NMDARs, leading to swift Ca²⁺ overload in neuronal cells and acute excitotoxicity within hours and days. On the other hand, mild upregulation of NMDAR activity, commonly seen in AD animal models and patients, is not immediately cytotoxic. Sustained NMDAR hyperactivity and Ca²⁺ dysregulation lasting from months to years, nevertheless, can be pathogenic for slowly evolving events, i.e. degenerative excitotoxicity, in the development of AD/ADRD. Specifically, Ca²⁺ influx mediated by extrasynaptic NMDARs (eNMDARs) and a downstream pathway mediated by transient receptor potential cation channel subfamily M member (TRPM) are primarily responsible for excitotoxicity. On the other hand, the NMDAR subunit GluN3A plays a "gatekeeper" role in NMDAR activity and a neuroprotective role against both acute and chronic excitotoxicity. Thus, ischemic stroke and AD share an NMDAR- and Ca²⁺-mediated pathogenic mechanism that provides a common receptor target for preventive and possibly disease-modifying therapies. Memantine (MEM) preferentially blocks eNMDARs and was approved by the Federal Drug Administration (FDA) for symptomatic treatment of moderate-to-severe AD with variable efficacy. According to the pathogenic role of eNMDARs, it is conceivable that MEM and other eNMDAR antagonists should be administered much earlier, preferably during the presymptomatic phases of AD/ADRD. This anti-AD treatment could simultaneously serve as a preconditioning strategy against stroke that attacks ≥ 50% of AD patients. Future research on the regulation of NMDARs, enduring control of eNMDARs, Ca²⁺ homeostasis, and downstream events will provide a promising opportunity to understand and treat the comorbidity of AD/ADRD and stroke.

Pathogenesis of sporadic Alzheimer's disease by deficiency of NMDA receptor subunit GluN3A

The Ca²⁺ hypothesis for Alzheimer's disease (AD) conceives Ca²⁺ dyshomeostasis as a common mechanism of AD; the cause of Ca²⁺ dysregulation, however, is obscure. Meanwhile, hyperactivities of N-Methyl-D-aspartate receptors (NMDARs), the primary mediator of Ca²⁺ influx, are reported in AD. GluN3A (NR3A) is an NMDAR inhibitory subunit. We hypothesize that GluN3A is critical for sustained Ca²⁺ homeostasis and its deficiency is pathogenic for AD. Cellular, molecular, and functional changes were examined in adult/aging GluN3A knockout (KO) mice. The GluN3A KO mouse brain displayed age-dependent moderate but persistent neuronal hyperactivity, elevated intracellular Ca²⁺ , neuroinflammation, impaired synaptic integrity/plasticity, and neuronal loss. GluN3A KO mice developed olfactory dysfunction followed by psychological/cognitive deficits prior to amyloid-β/tau pathology. Memantine at preclinical stage prevented/attenuated AD syndromes. AD patients' brains show reduced GluN3A expression. We propose that chronic "degenerative excitotoxicity" leads to sporadic AD, while GluN3A represents a primary pathogenic factor, an early biomarker, and an amyloid-independent therapeutic target.

Systematic Review of Erythropoietin (EPO) for Neuroprotection in Human Studies

Erythropoietin (EPO) is an exciting neurotherapeutic option. Despite its potential, concerns exist regarding the potential for thrombosis and adverse events with EPO administration in normonemic adults. Systematic review of literature using PRISMA guidelines to examine the application and risks of EPO as a treatment option for neuroprotection in normonemic adults. Independent, systematic searches were performed in July 2019. PubMed (1960-2019) and the Cochrane Controlled Trials Register (1960-2019) were screened. Search terms included erythropoietin, neuroprotection, and humans. The PubMed search resulted in the following search strategy: ("erythropoietin" [MeSH Terms] OR "erythropoietin" [All Fields] OR "epoetin alfa" [MeSH Terms] OR ("epoetin" [All Fields] AND "alfa" [All Fields]) OR "epoetin alfa" [All Fields]) AND ("neuroprotection" [MeSH Terms] OR "neuroprotection" [All Fields]) AND "humans" [MeSH Terms]. PubMed, Cochrane Controlled Trials Register, and articles based on prior searches yielded 388 citations. 50 studies were included, comprising of 4351 patients. There were 13 studies that noted adverse effects from EPO. Three attributed serious adverse effects to EPO and complications were statistically significant. Two of these studies related the adverse events to the co-administration of EPO with tPA. Minor adverse effects associated with the EPO group included nausea, pyrexia, headache, generalized weakness and superficial phlebitis. Most published studies focus on spinal cord injury, peri-surgical outcomes and central effects of EPO. We found no studies to date evaluating the role of EPO in post-operative pain. Future trials could evaluate this application in persistent post-surgical pain and in the peri-operative period.

Differential temporal and spatial post-injury alterations in cerebral cell morphology and viability

Combination of ischemia and β-amyloid (Aβ) toxicity has been shown to simultaneously increase neuro-inflammation, endogenous Aβ deposition, and neurodegeneration. However, studies on the evolution of infarct and panorama of cellular degeneration as a synergistic or overlapping mechanism between ischemia and Aβ toxicity are lacking. Here, we compared fluorojade B (FJB) and hematoxylin and eosin (H&E) stains primarily to examine the chronology of infarct, and the viability and morphological changes in neuroglia and neurons located in different brain regions on d1, d7, and d28 post Aβ toxicity and endothelin-1 induced ischemia (ET1) in rats. We demonstrated a regional difference in cellular degeneration between cortex, corpus callosum, striatum, globus pallidus, and thalamus after cerebral injury. Glial cells in the cortex and corpus callosum underwent delayed FJB staining from d7 to d28, but neurons in cortex disappeared within the first week of cerebral injury. Striatal lesion core and globus pallidus of Aβ + ET1 rats showed extensive degeneration of neuronal cells compared with ET1 rats alone starting from d1. Differential and exacerbated expressions of cyclooxygenase-2 might be the cause of excessive neuronal demise in the striatum of Aβ + ET1 rats. Such an investigation may improve our understanding to identify and manipulate a critical therapeutic window post comorbid injury.

Gastrodin pretreatment alleviates rat brain injury caused by cerebral ischemic-reperfusion

Brain damage, including blood-brain barrier (BBB) dysfunction, neurological behavior deficit, cerebral infarction and inflammation, is commonly caused by ischemic-reperfusion (I/R) injury. Prevention of the above biological process defects is considered beneficial for patient recovery after I/R injury. This study was aimed to assess the neuroprotective effect of Gastrodin (GAS), an herbal agent, in experimentally induced cerebral ischemia. Sprague-Dawley adult rats were randomly divided into six groups: Sham-operated control group (Sham), middle cerebral artery occlusion (MCAO) group, GAS (50, 100, and 200 mg/kg) pretreatment + MCAO groups (GAS) and Nimodipine (NIM) + MCAO, namely, the NIM group. Additionally, an OGD/R model using BV-2 microglia was established in vitro to simulate I/R injury. We showed here that the neurological scores of rats in the GAS groups were significantly improved compared with the MCAO group. Moreover, the area of cerebral infarction in the GAS pretreatment groups and the NIM group was significantly reduced. Furthermore, Evans blue leakage volume was significantly reduced with GAS pretreatment notably at dose 100 mg/kg. Expression of matrix metalloproteinase 2 (MMP2) and MMP9 in GAS groups was markedly decreased when compared with MCAO group. In BV-2 microglia exposed to OGD/R given GAS pretreatment, MMP2 and MMP9 positive cells were reduced in numbers. The present results have shown that GAS pretreatment significantly compensated for neurological behavior defects in rats with I/R-induced injury, reduced brain infarction size, reversed BBB impairment, and attenuated inflammation. It is suggested that pretreatment with GAS before surgery is beneficial during recovery from I/R injury.

Neuroimaging in former preterm children who received erythropoiesis stimulating agents

BackgroundIn premature children, erythropoiesis-stimulating agents (ESAs) may improve developmental outcome. It is not clear which of the several potential mechanisms are responsible for this improvement. High-resolution MRI and diffusion tensor imaging characterize brain structure and white matter organization, offering possible insight into the long-term effect of ESAs on brain development.MethodsMRI scans were performed at 3.5-4 years of age on former preterm infants treated with ESAs or placebo, and on healthy term controls. Mean cortical thickness, surface area, and fractional anisotropy (FA) were compared across study groups, and were correlated with general IQ measures.ResultsUnivariate analysis found no significant effect of ESAs on cortical thickness (P=0.366), surface area (P=0.940), or FA (P=0.150); however, there was a greater increase in FA among ESA-treated girls. Group analysis found significant correlations between FA and Full-Scale IQ (P=0.044) and Verbal IQ (P=0.036), although there was no significant relationship between Full-Scale IQ and FA among just the preterm children.ConclusionESA treatment may have a preferential effect on white matter development in girls, although factors other than just whole-brain FA are involved in mediating cognitive outcome.

Neuroprotective effects of erythropoietin on neurodegenerative and ischemic brain diseases: the role of erythropoietin receptor

Erythropoietin (Epo) is a fundamental hormone in the regulation of hematopoiesis, and other secondary roles mediated by the binding of the hormone to its specific receptor (EpoR), which leads to an activation of key signaling pathways that induce an increase in cell differentiation, apoptosis control and neuroprotection. It has been suggested that their function depends on final conformation of glycosylations, related with affinity to the receptor and its half-life. The presence of EpoR has been reported in different tissues including central nervous system, where it has been demonstrated to exert a neuroprotective function against oxidative stress conditions, such as ischemic injury and neurodegenerative diseases. There is also evidence of an increase in EpoR expression in brain cell lysates of Alzheimer's patients with respect to healthy patients. These results are related with extensive in vitro experimental data of neuroprotection obtained from cell lines, primary cell cultures and hippocampal slices. Additionally, this data is correlated with in vivo experiments (water maze test) in mouse models of Alzheimer's disease where Epo treatment improved cognitive function. These studies support the idea that receptor activation induces a neuroprotective effect in neurodegenerative disorders including dementias, and especially Alzheimer's disease. Taken together, available evidence suggests that Epo appears to be a central element for EpoR activation and neuroprotective properties in the central nervous system. In this review, we will describe the mechanisms associated with neuroprotection and its relation with the activation of EpoR in order with identify new targets to develop pharmacological strategies.

Effects of Hydroxyurea Exposure on the Rat Cerebellar Neuroepithelium: an Immunohistochemical and Electron Microscopic Study Along the Anteroposterior and Mediolateral Axes

We present a histological study of the cell death of cerebellar neuroepithelial neuroblasts following treatment with the cytotoxic agent hydroxyurea (HU) during the embryonic life. Pregnant rats were treated with a single dose of HU (300 mg/kg) at embryonic days 13, 14, or 15 of gestation, and their fetuses were studied from 5 to 35 h after treatment to elucidate the mechanisms of HU-induced fetotoxicity. Quantification of several parameters such as the density of pyknotic, mitotic, and PCNA-immunoreactive cells indicated that HU compromises the survival of the cerebellar neuroepithelium neuroblasts. On the other hand, our light and electron microscopic investigations during the course of prenatal development indicated that HU leads to two types of cell death: apoptosis and cells presenting cytoplasmic vacuolization, altered organelles, and a recognizable cell nucleus. Both modalities of cell death resulted in a substantial loss of cerebellar neuroepithelium cells. Current results suggest that HU exposure during gestation is toxic to the cerebellar neuroepithelium. Moreover, they allow to examine the mechanisms of HU-induced toxicity during the early development of the central nervous system. Our data also suggest that it is essential to avoid underestimating the adverse effects of HU when administered during early prenatal life.

Erythropoietin and Brain Magnetic Resonance Imaging Findings in Hypoxic-Ischemic Encephalopathy: Volume of Acute Brain Injury and 1-Year Neurodevelopmental Outcome

In the Neonatal Erythropoietin and Therapeutic Hypothermia Outcomes study, 9/20 erythropoietin-treated vs 12/24 placebo-treated infants with hypoxic-ischemic encephalopathy had acute brain injury. Among infants with acute brain injury, the injury volume was lower in the erythropoietin than the placebo group (P = .004). Higher injury volume correlated with lower 12-month neurodevelopmental scores.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01913340.

Prospective clinical biomarkers of caspase-mediated apoptosis associated with neuronal and neurovascular damage following stroke and other severe brain injuries: Implications for chronic neurodegeneration

Acute brain injuries, including ischemic and hemorrhagic stroke, as well as traumatic brain injury (TBI), are major worldwide health concerns with very limited options for effective diagnosis and treatment. Stroke and TBI pose an increased risk for the development of chronic neurodegenerative diseases, notably chronic traumatic encephalopathy, Alzheimer's disease, and Parkinson's disease. The existence of premorbid neurodegenerative diseases can exacerbate the severity and prognosis of acute brain injuries. Apoptosis involving caspase-3 is one of the most common mechanisms involved in the etiopathology of both acute and chronic neurological and neurodegenerative diseases, suggesting a relationship between these disorders. Over the past two decades, several clinical biomarkers of apoptosis have been identified in cerebrospinal fluid and peripheral blood following ischemic stroke, intracerebral and subarachnoid hemorrhage, and TBI. These biomarkers include selected caspases, notably caspase-3 and its specific cleavage products such as caspase-cleaved cytokeratin-18, caspase-cleaved tau, and a caspase-specific 120 kDa αII-spectrin breakdown product. The levels of these biomarkers might be a valuable tool for the identification of pathological pathways such as apoptosis and inflammation involved in injury progression, assessment of injury severity, and prediction of clinical outcomes. This review focuses on clinical studies involving biomarkers of caspase-3-mediated pathways, following stroke and TBI. The review further examines their prospective diagnostic utility, as well as clinical utility for improved personalized treatment of stroke and TBI patients and the development of prophylactic treatment chronic neurodegenerative disease.

Neuroprotective Effect of Erythropoietin on Phenylhydrazine-Induced Hemolytic Hyperbilirubinemia in Neonatal Rats

Neonatal unconjugated hyperbilirubinemia might cause severe bilirubin neurotoxicity in especially hemolytic conditions. The study aimed to elucidate the potential neuroprotective effects of erythropoietin (EPO) in hemolysis-induced hyperbilirubinemia. In newborn rats, hyperbilirubinemia secondary to hemolysis was induced by injecting with phenylhydrazine hydrochloride (PHZ) and rats were injected with either vehicle or EPO. At 54th hour of the PHZ injection, rats were decapitated. Serum levels of TNF-α, IL-1β, IL-10, brain-derived neurotrophic factor (BDNF) and S100-B and brain malondialdehyde, glutathione levels and myeloperoxidase activities were measured. TUNEL staining and NF-κB expression were evaluated. As compared to control pups, in vehicle-treated PHZ group, TNF-α and IL-1β levels, malondialdehyde level and myeloperoxidase activity were increased with concomitant decreases in IL-10 and glutathione. All EPO regimens reversed PHZ-induced alterations in IL-10, TNF-α, malondialdehyde and glutathione levels. Three-day-treatment abolished increases in myeloperoxidase activity and IL-1β levels, while BDNF and S100-B were elevated. Increased TUNEL (+) cells and NF-κB expressions in the brain of PHZ group were reduced in the 3-day-treated group. EPO exerted anti-inflammatory effects on PHZ-induced neural damage in newborn rats, while the neuroprotection was more obvious when the treatments were repeated successively. The results suggest that EPO treatment may have a therapeutic potential in supporting neuroplasticity in the hyperbilirubinemic neonates.

Long-term survival and regeneration of neuronal and vasculature cells inside the core region after ischemic stroke in adult mice

Focal cerebral ischemia results in an ischemic core surrounded by the peri-infarct region (penumbra). Most research attention has been focused on penumbra while the pattern of cell fates inside the ischemic core is poorly defined. In the present investigation, we tested the hypothesis that, inside the ischemic core, some neuronal and vascular cells could survive the initial ischemic insult while regenerative niches might exist many days after stroke in the adult brain. Adult mice were subjected to focal cerebral ischemia induced by permanent occlusion of distal branches of the middle cerebral artery (MCA) plus transient ligations of bilateral common carotid artery (CCA). The ischemic insult uniformly reduced the local cerebral blood flow (LCBF) by 90%. Massive cell death occurred due to multiple mechanisms and a significant infarction was cultivated in the ischemic cortex 24 h later. Nevertheless, normal or even higher levels of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) persistently remained in the core tissue, some NeuN-positive and Glut-1/College IV-positive cells with intact ultrastructural features resided in the core 7-14 days post stroke. BrdU-positive but TUNEL-negative neuronal and endothelial cells were detected in the core where extensive extracellular matrix infrastructure developed. Meanwhile, GFAP-positive astrocytes accumulated in the penumbra and Iba-1-positive microglial/macrophages invaded the core several days after stroke. The long term survival of neuronal and vascular cells inside the ischemic core was also seen after a severe ischemic stroke induced by permanent embolic occlusion of the MCA. We demonstrate that a therapeutic intervention of pharmacological hypothermia could save neurons/endothelial cells inside the core. These data suggest that the ischemic core is an actively regulated brain region with residual and newly formed viable neuronal and vascular cells acutely and chronically after at least some types of ischemic strokes.

Erythropoietin Pathway: A Potential Target for the Treatment of Depression

During the past decade, accumulating evidence from both clinical and experimental studies has indicated that erythropoietin may have antidepressant effects. In addition to the kidney and liver, many organs have been identified as secretory tissues for erythropoietin, including the brain. Its receptor is expressed in cerebral and spinal cord neurons, the hypothalamus, hippocampus, neocortex, dorsal root ganglia, nerve axons, and Schwann cells. These findings may highlight new functions for erythropoietin, which was originally considered to play a crucial role in the progress of erythroid differentiation. Erythropoietin and its receptor signaling through JAK2 activate multiple downstream signaling pathways including STAT5, PI3K/Akt, NF-κB, and MAPK. These factors may play an important role in inflammation and neuroprogression in the nervous system. This is particularly true for the hippocampus, which is possibly related to learning, memory, neurocognitive deficits and mood alterations. Thus, the influence of erythropoietin on the downstream pathways known to be involved in the treatment of depression makes the erythropoietin-related pathway an attractive target for the development of new therapeutic approaches. Focusing on erythropoietin may help us understand the pathogenic mechanisms of depression and the molecular basis of its treatment.

Cell death and neurodegeneration in the postnatal development of cerebellar vermis in normal and Reeler mice

Programmed cell death (PCD) was demonstrated in neurons and glia in normal brain development, plasticity, and aging, but also in neurodegeneration. (Macro)autophagy, characterized by cytoplasmic vacuolization and activation of lysosomal hydrolases, and apoptosis, typically entailing cell shrinkage, chromatin and nuclear condensation, are the two more common forms of PCD. Their underlying intracellular pathways are partly shared and neurons can die following both modalities, according to the type of death-triggering stimulus. Reelin is an extracellular protein necessary for proper neuronal migration and brain lamination. In the mutant Reeler mouse, its absence causes neuronal mispositioning, with a notable degree of cerebellar hypoplasia that was tentatively related to an increase in PCD. We have carried out an ultrastructural analysis on the occurrence and type of postnatal PCD affecting the cerebellar neurons in normal and Reeler mice. In the forming cerebellar cortex, PCD took the form of apoptosis or autophagy and mainly affected the cerebellar granule cells (CGCs). Densities of apoptotic CGCs were comparable in both mouse strains at P0-P10, while, in mutants, they increased to become significantly higher at P15. In WT mice the density of autophagic neurons did not display statistically significant differences in the time interval examined in this study, whereas it was reduced in Reeler in the P0-P10 interval, but increased at P15. Besides CGCs, the Purkinje neurons also displayed autophagic features in both WT and Reeler mice. Therefore, cerebellar neurons undergo different types of PCD and a Reelin deficiency affects the type and degree of neuronal death during postnatal development of the cerebellum.

iPSC Transplantation increases regeneration and functional recovery after ischemic stroke in neonatal rats

Limited treatments are available for perinatal/neonatal stroke. Induced pluripotent stem cells (iPSCs) hold therapeutic promise for stroke treatment, but the benefits of iPSC transplantation in neonates are relatively unknown. We hypothesized that transplanted iPSC-derived neural progenitor cells (iPSC-NPCs) would increase regeneration after stroke. Mouse pluripotent iPSCs were differentiated into neural progenitors using a retinoic acid protocol. Differentiated neural cells were characterized by using multiple criteria and assessments. Ischemic stroke was induced in postnatal day 7 (P7) rats by occluding the right middle cerebral artery and right common carotid artery. iPSC-NPCs (400,000 in 4 µl) were transplanted into the penumbra via intracranial injection 7 days after stroke. Trophic factor expression in the peri-infarct tissue was measured using Western blot analysis. Animals received daily bromodeoxyuridine (BrdU) injections and were sacrificed 21 days after stroke for immunohistochemistry. The vibrissae-elicited forelimb placement test was used to evaluate functional recovery. Differentiated iPSCs expressed mature neuronal markers, functional sodium and potassium channels, and fired action potentials. Several angiogenic and neurogenic trophic factors were identified in iPSC-NPCs. Animals that received iPSC-NPC transplantation had greater expression of stromal cell-derived factor 1-α (SDF-1α) and vascular endothelial growth factor (VEGF) in the peri-infarct region. iPSC-NPCs stained positive for neuronal nuclei (NeuN) or glial fibrillary acidic protein (GFAP) 14 days after transplantation. iPSC-NPC-transplanted animals showed greater numbers of BrdU/NeuN and BrdU/Collagen IV colabeled cells in the peri-infarct area compared with stroke controls and performed better in a sensorimotor functional test after stroke. iPSC-NPC therapy may play multiple therapeutic roles after stroke by providing trophic factors, increasing angiogenesis and neurogenesis, and providing new cells for tissue repair.

Morphological characteristics of eosinophilic neuronal death after transient unilateral forebrain ischemia in Mongolian gerbils

Various types of eosinophilic neurons (ENs) are found in the post-ischemic brain. The aim of the present study was to elucidate the temporal and spatial profile of ENs, the expression of TUNEL staining and ultrastructural characteristics in the core and peripheral regions of the cortex post-ischemia. Unilateral forebrain ischemia was induced in Mongolian gerbils by transient common carotid artery occlusions, and the brains from 3 h to 2 weeks post-ischemia were prepared for morphometric, electron microscopy (EM) and TUNEL staining of the ENs. Light microscopy showed that ENs with minimally abnormal nuclei and swollen cell bodies appeared at 3 h in the ischemic core and at 12 h in the periphery. Thereafter, ENs with pyknosis and irregular atrophic cytoplasm peaked at 12 h, pyknosis with scant cytoplasm peaked at 4 days, and TUNEL-positive staining was observed in the ischemic core. In the ischemic periphery, ENs had slightly atrophic cytoplasm and sequentially developed pyknosis, karyorrhexis and karyolysis over 1 week. These cells were also positive for TUNEL. In EM, severe organelle dilation and vacuolization preceded chromatin fragmentation in the ischemic core, while chromatin fragmentation and homogenization were the vital characteristics in the ischemic periphery. There might be two region-dependent pathways for EN changes in the post-ischemic brain: pyknosis with cytoplasmic shrinkage in the core and nuclear disintegration with slightly atrophic cytoplasm in the periphery. These pathways were comparable to necrosis and proceeded from non-classical apoptosis to necrosis, respectively.

Behavioral assessment of cell transplantation after focal cerebral ischemia in rats

We induced middle cerebral artery occlusion (MCAO) in rats using silicone-coated vascular embolus. We transplanted mouse embryonic stem (mES) cells after MCAO. Rats were tested behaviorally using motor and sensory function with neurological assessment. Functional effectiveness of the transplanted mES cells gradually improved the function of sensory and motor neurons. This study demonstrated that the transplanted cells have synaptic connection in the recipient brain. We suggest that stem cell transplantation can have a positive effect on behavioral recovery and reduction of infarct size in focal ischemic rats. Cell transplantation may induce certain functional recovery of the brain tissue by endogenous cell mediated effect. Our study suggests that intracerebrally injected mES cells survived and migrated into the infarct area from inoculation site and neuroglially differentiated in the ischemic brain area of adult rats. Therefore, mES cells may be a useful tool for the treatment in neurological diseases. In conclusion, cell transplantation therapy represents a novel approach that may enhance the efficacy and effectiveness of stem cell transplantation after ischemic stroke.

Erythropoietin: a novel therapy for hypoxic-ischaemic encephalopathy?

Perinatal hypoxic-ischaemic encephalopathy (HIE) occurs in 1 to 3 per 1000 term births. HIE is not preventable in most cases, and therapies are limited. Hypothermia improves outcomes and is the current standard of care. Yet, clinical trials suggest that 44-53% of infants who receive hypothermia will die or suffer moderate to severe neurological disability. In this article, we review the preclinical and clinical evidence for erythropoietin (EPO) as a potential novel neuroprotective agent for the treatment of HIE. EPO is a novel neuroprotective agent, with remarkable neuroprotective and neuroregenerative effects in animals. Rodent and primate models of neonatal brain injury support the safety and efficacy of multiple EPO doses for improving histological and functional outcomes after hypoxia-ischaemia. Small clinical trials of EPO in neonates with HIE have also provided evidence supporting safety and preliminary efficacy in humans. There is currently insufficient evidence to support the use of high-dose EPO in newborns with HIE. However, several on-going trials will provide much needed data regarding the safety and efficacy of this potential new therapy when given in conjunction with hypothermia for HIE. Novel neuroprotective therapies are needed to further reduce the rate and severity of neurodevelopmental disabilities resulting from HIE. High-dose EPO is a promising therapy that can be administered in conjunction with hypothermia. However, additional data are needed to determine the safety and efficacy of this adjuvant therapy for HIE.

Intranasal Delivery of Bone Marrow Mesenchymal Stem Cells Improved Neurovascular Regeneration and Rescued Neuropsychiatric Deficits after Neonatal Stroke in Rats

Neonatal stroke is a major cause of mortality and long-term morbidity in infants and children. Currently, very limited therapeutic strategies are available to protect the developing brain against ischemic damage and promote brain repairs for pediatric patients. Moreover, children who experienced neonatal stroke often have developmental social behavior problems. Cellular therapy using bone marrow mesenchymal stem cells (BMSCs) has emerged as a regenerative therapy after stroke. In the present investigation, neonatal stroke of postnatal day 7 (P7) rat pups was treated with noninvasive and brain-specific intranasal delivery of BMSCs at 6 h and 3 days after stroke (1 × 106cells/animal). Prior to transplantation, BMSCs were subjected to hypoxic preconditioning to enhance their tolerance and regenerative properties. The effects on regenerative activities and stroke-induced sensorimotor and social behavioral deficits were specifically examined at P24 of juvenile age. The BMSC treatment significantly reduced infarct size and blood-brain barrier disruption, promoted angiogenesis, neurogenesis, neurovascular repair, and improved local cerebral blood flow in the ischemic cortex. BMSC-treated rats showed better sensorimotor and olfactory functional recovery than saline-treated animals, measured by the adhesive removal test and buried food finding test. In social behavioral tests, we observed functional and social behavioral deficits in P24 rats subjected to stroke at P7, while the BMSC treatment significantly improved the performance of stroke animals. Overall, intranasal BMSC transplantation after neonatal stroke shows neuroprotection and great potential as a regenerative therapy to enhance neurovascular regeneration and improve functional recovery observed at the juvenile stage of development.

Erythropoietin and hypothermia for hypoxic-ischemic encephalopathy

BACKGROUND

Erythropoietin is neuroprotective in animal models of neonatal hypoxic-ischemic encephalopathy. We previously reported a phase I safety and pharmacokinetic study of erythropoietin in neonates. This article presents the neurodevelopmental follow-up of infants who were enrolled in the phase I clinical trial.

METHODS

We enrolled 24 newborns with hypoxic-ischemic encephalopathy in a dose-escalation study. Patients received up to six doses of erythropoietin in addition to hypothermia. All infants underwent neonatal brain magnetic resonance imaging (MRI) reviewed by a single neuroradiologist. Moderate-to-severe neurodevelopmental disability was defined as cerebral palsy with Gross Motor Function Classification System levels III-V or cognitive impairment based on Bayley Scales of Infant Development II mental developmental index or Bayley III cognitive composite score.

RESULTS

Outcomes were available for 22 of 24 infants, at mean age 22 months (range, 8-34 months). There were no deaths. Eight (36%) had moderate-to-severe brain injury on neonatal MRI. Moderate-to-severe disability occurred in one child (4.5%), in the setting of moderate-to-severe basal ganglia and/or thalamic injury. Seven infants with moderate-to-severe watershed injury exhibited the following outcomes: normal (three), mild language delay (two), mild hemiplegic cerebral palsy (one), and epilepsy (one). All 11 patients with a normal brain MRI had a normal outcome.

CONCLUSIONS

This study is the first to describe neurodevelopmental outcomes in infants who received high doses of erythropoietin and hypothermia during the neonatal period. The findings suggest that future studies are warranted to assess the efficacy of this new potential neuroprotective therapy.

Erythropoietin protects newborn rat against sevoflurane-induced neurotoxicity

INTRODUCTION

Recent data on newborn animals exposed to anesthetics have raised safety concerns regarding anesthesia practices in young children. Indeed, studies on rodents have demonstrated a widespread increase in brain apoptosis shortly after exposure to sevoflurane, followed by long-term neurologic impairment. In this context, we aimed to evaluate the protective effect of rh-EPO, a potent neuroprotective agent, in rat pups exposed to sevoflurane.

MATERIAL AND METHODS

At postnatal day 7, 75 rat pups were allocated into three groups: SEVO + EPO (n = 27) exposed to sevoflurane 2 vol% (0.5 MAC) for 6 h in an air/O2 mixture (60/40) + 5000 UI.kg(-1) rh-EPO IP; SEVO (n = 27) exposed to sevoflurane + vehicle IP; and CONTROL (n = 21) exposed to the mixture without sevoflurane + vehicle IP. Three days after anesthesia (D10), apoptosis was quantified on brain extract with TUNEL method and caspase 3. NGF and BDNF expression was determined by Western blotting. Rats reaching adulthood were evaluated in terms of exploration capacities (object exploration duration) together with spatial and object learning (water maze and novel object test).

RESULTS

Sevoflurane exposure impaired normal behavior in adult rats by reducing the exploratory capacities during the novel object test and impaired both spatial and object learning capacities in adult rats (water maze, ratio time to find platform 3rd trial/1st trial: 1.1 ± 0.2 vs 0.4 ± 0.1; n = 9, SEVO vs CONTROL; P = 0.01). Rh-EPO reduced sevoflurane-induced behavior and learning abnormalities in adult rats (water maze, ratio time to find platform 3rd trial/1st trial: 0.3 ± 0.1 vs 1.1 ± 0.2; n = 9, SEVO + EPO vs SEVO; P = 0.01). Three days after anesthesia, rh-EPO prevented sevoflurane-induced brain apoptosis (5 ± 3 vs 35 ± 6 apoptotic cells·mm(-2) ; n = 6, SEVO + EPO vs SEVO; P = 0.01) and elevation of caspase three level and significantly increased the brain expression of BDNF and NGF (n = 6, SEVO + EPO vs SEVO; P = 0.01).

CONCLUSION

Six hours of sevoflurane anesthesia in newborn rats induces significant long-term cognitive impairment. A single administration of rh-EPO immediately after postnatal exposure to sevoflurane reduces both early activation of apoptotic phenomenon and late onset of neurologic disorders.

Erythropoietin improves neurobehavior by reducing dopaminergic neuron loss in a 6‑hydroxydopamine‑induced rat model

The purpose of this study was to determine the effectiveness of the systemic administration of high dose erythropoietin (EPO) in a 6-hydroxydopamine (6-OHDA)- induced rat model. Rats were divided into 7 groups. Groups 1–4 were administered daily EPO doses of 0; 2,500; 5,000 and 10,000 U/kg via intraperitoneal injection (i.p.) for 5 days. The EPO concentration in cerebrospinal fluid (CSF) was determined by enzyme-linked immunosorbent assay (ELISA) and western blot analysis. The dose of 10,000 U/kg was then selected for subsequent experiments. In group 5, rats received saline via medial forebrain bundle (MFB). In group 6, rats received 6-OHDA via MFB. In group 7, an EPO concentration of 10,000 U/kg was constantly administered i.p. for 5 days to rats prior to 6-OHDA injection via MFB. Behavioral analysis was performed for groups 5–7 by rat rotation tests. The number of tyrosine hydroxylase (TH)-immunopositive cells in the substantia nigra (SN) was measured by immunocytochemistry. The activation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinases (MAPKs) and caspase-3 signaling in rats were analyzed using western blotting. The results showed that there was a significant increase in EPO levels in the CSF in 10,000 U/kg group compared with the 2,500 and 5,000 U/kg groups (P<0.01). Significantly fewer rotational counts were obtained in rats that were pretreated with EPO compared with saline-pretreated 6-OHDA-lesioned rats (P<0.001). The dopaminergic neurons in the 6-OHDA-lesioned SN were also increased in the EPO-pretreated rats when compared with control rats (P<0.01). Western blot analysis revealed that EPO inhibited the 6-OHDA-induced activation of JNK, ERK, p38 MAPK and caspase-3 signaling in the rat model. In conclusion, systemic administration of a high dose of EPO exerted neuroprotective effects in reversing behavioral deficits associated with Parkinson’s disease and prevented loss of the dopaminergic neurons through the MAPK pathway.

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.

High-dose phenobarbital or erythropoietin for the treatment of perinatal asphyxia in term newborns

BACKGROUND

The aim of this study was to compare two neuroprotective strategies to supportive care in the treatment of perinatal asphyxia.

METHODS

A total of 67 term newborns with perinatal asphyxia were included and randomized into three groups: one group received supportive treatment; another group received a single dose of 40 mg/kg phenobarbital; and the third received three daily doses of 1000 IU/kg erythropoietin. The following parameters were analyzed: gestational age, birthweight, Apgar scores, cord blood pH, total serum antioxidant status (TAS), superoxide dismutase (SOD), glutathione peroxidase (GPx) and malondialdehyde (MDA). The newborns were included in the follow-up program and examined up to 18 months of age.

RESULTS

TAS was higher in the erythropoietin group than in the other groups. SOD and GPx were lower for infants treated with phenobarbital or erythropoietin compared to control infants. MDA was lower in the erythropoietin group compared to the other groups, although the difference was not statistically significant (P > 0.05). The mortality rate was lower in the phenobarbital and erythropoietin groups (both 4.6%) than in the control group (17.4%). Long-term neurologic follow up showed a high incidence of sequelae in the control group compared to the phenobarbital and erythropoietin groups. Follow-up results were better in the phenobarbital group than in the erythropoietin group for motor and cognitive function at 3 and 6 months and worse for expressive language. At 18 months, however, the differences between these two groups were not significant.

CONCLUSION

High-dose phenobarbital or erythropoietin along with supportive treatment has a positive influence on the outcome of newborns with perinatal asphyxia. Phenobarbital has the advantage of low cost and simplicity.

Constitutive excessive erythrocytosis causes inflammation and increased vascular permeability in aged mouse brain

Excessive erythrocytosis results in severely increased blood viscosity that may compromise the vascular endothelium. Using our transgenic mouse model of excessive erythrocytosis we previously showed that despite altered brain endothelial cell morphology and an activated vasculature, brain vascular integrity was largely maintained up to 4-5 months of age. We now present data showing that persistent long-term damage of the vascular wall during the later stages of adulthood (9-12 months) results in a chronic detrimental inflammatory phenotype and increased vessel permeability that likely contributes to the reduced life span of our erythropoietin overexpressing transgenic mouse. In aged transgenic animals inflammatory cells were detected in brain tissue and elevated RNA and protein levels of inflammatory markers such as IL-6 and TNFα were observed in both brain tissue and blood plasma. Additionally, increased expression of p53 and other pro-apoptotic markers, as well as decreased Bcl-xL expression in the brain vasculature, indicated ongoing cell death within the vascular compartment. Finally, abnormally elevated vascular permeability in all organs was detected in correlation with decreased expression of the tight junction protein occludin and the adherens junction protein β-catenin in brain. Thus chronic erythrocytosis results in sustained activation of inflammatory pathways, vascular dysfunction and blood-brain barrier disruption.

The involvement of autophagy pathway in exaggerated ischemic brain damage in diabetic mice

BACKGROUND

Patients with Diabetes are at greater risk for ischemic stroke and usually suffer more severe ischemic brain damage than nondiabetic patients. However, the underlying mechanism of the exaggerated injury is not well defined.

AIMS

Macroautophagy (hereafter called autophagy in this report) plays a key role in cellular homeostasis and may contribute to cell death as well. Our aim was to determine whether autophagy was involved in the enhanced susceptibility of diabetic brain cells to ischemic injury and explore it as a possible target for the treatment of stroke in a diabetic condition.

RESULTS

A type II diabetic mouse model generated by combined administration of streptozotocin and nicotinamide showed enlarged infarct volume, increased cell death and excessive blood-brain barrier (BBB) disruption compared with nondiabetic stroke mice. After ischemic stroke, both diabetic and nondiabetic mice showed enhanced autophagosome formation and autophagic flux as demonstrated by increased expression of autophagy signals Beclin 1, microtubule-associated protein light-chain II (LC3-II), and decreased autophagy-specific substrate p62. The increased autophagic activity was significantly higher in diabetic stroke mice than that in nondiabetic stroke mice. The autophagy inhibitor 3-methyladenine (3-MA) attenuated the exaggerated brain injury and improved functional recovery.

CONCLUSIONS

These data suggest that autophagy contributes to exacerbated brain injury in diabetic condition, and autophagy-mediated cell death may be a therapeutic target in diabetic stroke.

The switches.ELM resource: a compendium of conditional regulatory interaction interfaces

Short linear motifs (SLiMs) are protein interaction sites that play an important role in cell regulation by controlling protein activity, localization, and local abundance. The functionality of a SLiM can be modulated in a context-dependent manner to induce a gain, loss, or exchange of binding partners, which will affect the function of the SLiM-containing protein. As such, these conditional interactions underlie molecular decision-making in cell signaling. We identified multiple types of pre- and posttranslational switch mechanisms that can regulate the function of a SLiM and thereby control its interactions. The collected examples of experimentally characterized SLiM-based switch mechanisms were curated in the freely accessible switches.ELM resource (http://switches.elm.eu.org). On the basis of these examples, we defined and integrated rules to analyze SLiMs for putative regulatory switch mechanisms. We applied these rules to known validated SLiMs, providing evidence that more than half of these are likely to be pre- or posttranslationally regulated. In addition, we showed that posttranslationally modified sites are enriched around SLiMs, which enables cooperative and integrative regulation of protein interaction interfaces. We foresee switches.ELM complementing available resources to extend our knowledge of the molecular mechanisms underlying cell signaling.

The regulatory role of NF-κB in autophagy-like cell death after focal cerebral ischemia in mice

Autophagy may contribute to ischemia-induced cell death in the brain, but the regulation of autophagic cell death is largely unknown. Nuclear factor kappa B (NF-κB) is a regulator of apoptosis in cerebral ischemia. We examined the hypothesis that autophagy-like cell death could contribute to ischemia-induced brain damage and the process was regulated by NF-κB. In adult wild-type (WT) and NF-κB p50 knockout (p50(-/-)) mice, focal ischemia in the barrel cortex was induced by ligation of distal branches of the middle cerebral artery. Twelve to 24h later, autophagic activity increased as indicated by enhanced expression of Beclin-1 and LC3 in the ischemic core and/or penumbra regions. This increased autophagy contributed to cell injury, evidenced by terminal deoxynucleotidyltransferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) co-staining and a protective effect achieved by the autophagy inhibitor 3-methyladenine. The number of Beclin-1/TUNEL-positive cells was significantly more in p50(-/-) mice than in WT mice. Neuronal and vascular cell death, as determined by TUNEL-positive cells co-staining with NeuN or Collagen IV, was more abundant in p50(-/-) mice. Immunostaining of the endothelial cell tight junction marker occludin revealed more damage to the blood-brain barrier in p50(-/-) mice. Western blotting of the peri-infarct tissue showed a reduction of Akt-the mammalian target of rapamycin (mTOR) signaling in p50(-/-) mice after ischemia. These findings provide the first evidence that cerebral ischemia induced autophagy-like injury is regulated by the NF-κB pathway, which may suggest potential treatments for ischemic stroke.

Neuroprotective therapies after perinatal hypoxic-ischemic brain injury

Hypoxic-ischemic (HI) brain injury is one of the main causes of disabilities in term-born infants. It is the result of a deprivation of oxygen and glucose in the neural tissue. As one of the most important causes of brain damage in the newborn period, the neonatal HI event is a devastating condition that can lead to long-term neurological deficits or even death. The pattern of this injury occurs in two phases, the first one is a primary energy failure related to the HI event and the second phase is an energy failure that takes place some hours later. Injuries that occur in response to these events are often manifested as severe cognitive and motor disturbances over time. Due to difficulties regarding the early diagnosis and treatment of HI injury, there is an increasing need to find effective therapies as new opportunities for the reduction of brain damage and its long term effects. Some of these therapies are focused on prevention of the production of reactive oxygen species, anti-inflammatory effects, anti-apoptotic interventions and in a later stage, the stimulation of neurotrophic properties in the neonatal brain which could be targeted to promote neuronal and oligodendrocyte regeneration.

Outcomes of extremely low birth weight infants given early high-dose erythropoietin

OBJECTIVE

To evaluate long-term outcomes of 60 extremely low birth weight (ELBW) infants treated with or without three injections of high-dose erythropoietin (Epo).

STUDY DESIGN

A retrospective analysis of anthropometric and neurodevelopmental outcome data comparing 30 ELBW infants enrolled in a phase I/II study examining the pharmacokinetics of high-dose Epo (500, 1000 and 2500 U/kg × 3 doses) administered to 30 concurrent controls.

RESULT

Birth characteristics and growth from 4 to 36 months were similar for untreated and Epo-treated patients. Multiple linear regression analysis of neurodevelopmental follow-up scores from 17/25 Epo-treated and 18/26 control infants identified that Epo correlated with improvement of cognitive (R=0.22, P=0.044) and motor (R=0.15, P=0.026) scores. No negative long-term effects of Epo treatment were evident.

CONCLUSION

Retrospective analysis of the only available long-term follow-up data from ELBW infants given high-dose Epo treatment suggests that Epo treatment is safe and correlates with modest improvement of neurodevelopmental outcomes.

The neuroprotective and neurorescue effects of carbamylated erythropoietin Fc fusion protein (CEPO-Fc) in a rat model of Parkinson's disease

Parkinson's disease is characterized by progressive degeneration of dopaminergic neurons. Thus the development of therapeutic neuroprotection and neurorescue strategies to mitigate disease progression is important. In this study we evaluated the neuroprotective/rescue effects of erythropoietin Fc fusion protein (EPO-Fc) and carbamylated erythropoietin Fc fusion protein (CEPO-Fc) in a rat model of Parkinson's disease. Adult female Sprague-Dawley rats received intraperitoneal injection of EPO-Fc, CEPO-Fc or PBS. Behavioral evaluations consisted of rota-rod, cylinder and amphetamine-induced rotation tests. In the neuroprotection experiment, the CEPO-Fc group demonstrated significant improvement compared with the EPO-Fc group on the amphetamine-induced rotation test throughout the four-week follow-up period. Histologically, significantly more tyrosine hydroxylase (TH)-positive neurons were recognized in the substantia nigra (SN) pars compacta in the CEPO-Fc group than in the PBS and EPO-Fc groups. In the neurorescue experiment, rats receiving CEPO-Fc showed significantly better behavioural scores than those receiving PBS. The histological data concerning striatum also showed that the CEPO-Fc group had significantly better preservation of TH-positive fibers compared to the PBS and EPO-Fc groups. Importantly, there were no increases in hematocrit or hemoglobin levels in the CEPO-Fc group in either the neuroprotection or the neurorescue experiments. In conclusion, the newly developed CEPO-Fc might confer neuroprotective and neurorescue benefits in a rat model of Parkinson's disease without the side effects associated with polycythemia. CEPO-Fc might be a therapeutic tool for patients with Parkinson's disease.

Transplantation of mouse embryonic stem cell after middle cerebral artery occlusion

PURPOSE

Stem cell transplantation has been extensively studied as individual therapies for ischemic stroke. The present investigation is an initial effort to combine these methods to achieve increased therapeutic effects after brain ischemia. Cell transplantation may recover massive neuronal loss by replacing damaged brain cells.

METHODS

Undifferentiated mouse embryonic stem (mES) cells were used to induce differentiation in vitro into neuron-like cells with good cell viability for use a graft. In this study, middle cerebral artery occlusion (MCAO) was induced in rats using intra-luminal vascular occlusion, and infused mES cells after MCAO. The animals were examined behaviorally using motor and sensory test with neurological assessment.

RESULTS

Motor function of the recipients was gradually improved, whereas little improvement was observed in control rats. This result may suggest that the grafted cells have synaptic connection in the recipient brain. Our study revealed that stem cell transplantation can have a positive effect on behavioral recovery and reduction of infarct size in focal ischemic rats. Consequently after euthanasia, rats were histochemically investigated to explore graft survival with green fluorescent protein (GFP).

CONCLUSION

The mouse embryonic stem cells may have advantage for use as a donor source in various neurological disorders including motor dysfunction.

HIF-prolyl hydroxylases and cardiovascular diseases

Prolyl hydroxylases belong to the family of iron- and 2-oxoglutamate-dependent dioxygenase enzyme. Several distinct prolyl hydroxylases have been identified. The hypoxia-inducible factor (HIF) prolyl hydroxylase termed prolyl hydroxylase domain (PHD) enzymes play an important role in oxygen regulation in the physiological network. There are three isoforms that have been identified: PHD1, PHD2 and PHD3. Deletion of PHD enzymes result in stabilization of HIFs and offers potential treatment options for many ischemic disorders such as peripheral arterial occlusive disease, myocardial infarction, and stroke. All three isoforms are oxygen sensors that regulate the stability of HIFs. The degradation of HIF-1α is regulated by hydroxylation of the 402/504 proline residue by PHDs. Under hypoxic conditions, lack of oxygen causes hydroxylation to cease HIF-1α stabilization and subsequent translocation to the nucleus where it heterodimerizes with the constitutively expressed β subunit. Binding of the HIF-heterodimer to specific DNA sequences, named hypoxia-responsive elements, triggers the transactivation of target genes. PHD regulation of HIF-1α-mediated cardioprotection has resulted in considerable interest in these molecules as potential therapeutic targets in cardiovascular and ischemic diseases. In recent years, attention has been directed towards identifying small molecule inhibitors of PHD. It is postulated that such inhibition might lead to a clinically useful strategy for protecting the myocardium against ischemia and reperfusion injury. Recently, it has been reported that the orally absorbed PHD inhibitor GSK360A can modulate HIF-1α signaling and protect the failing heart following myocardial infarction. Furthermore, PHD1 deletion has been found to have beneficial effects through an increase in tolerance to hypoxia of skeletal muscle by reprogramming basal metabolism. In the mouse liver, such deletion has resulted in protection against ischemia and reperfusion. As a result of these preliminary findings, PHDs is attracting increasing interest as potential therapeutic targets in a wide range of diseases.

Erythropoietin neuroprotection with traumatic brain injury

Numerous experimental studies in recent years have suggested that erythropoietin (EPO) is an endogenous mediator of neuroprotection in various central nervous system disorders, including TBI. Many characteristics of EPO neuroprotection that have been defined in TBI experimental models suggest that it is an attractive candidate for a new treatment of TBI. EPO targets multiple mechanisms known to cause secondary injury after TBI, including anti-excitotoxic, antioxidant, anti-edematous, and anti-inflammatory mechanisms. EPO crosses the blood-brain barrier. EPO has a known dose response and time window for neuroprotection and neurorestoration that would be practical in the clinical setting. However, EPO also stimulates erythropoiesis, which can result in thromboembolic complications. Derivatives of EPO which do not bind to the classical EPO receptor (carbamylated EPO) or that have such a brief half-life in the circulation that they do not stimulate erythropoiesis (asialo EPO and neuro EPO) have the neuroprotective activities of EPO without these potential thromboembolic adverse effects associated with EPO administration. Likewise, a peptide based on the structure of the Helix B segment of the EPO molecule that does not bind to the EPO receptor (pyroglutamate Helix B surface peptide) has promise as another alternative to EPO that may provide neuroprotection without stimulating erythropoiesis.

Visualizing cell death in experimental focal cerebral ischemia: promises, problems, and perspectives

One of the hallmarks of stroke pathophysiology is the widespread death of many different types of brain cells. As our understanding of the complex disease that is stroke has grown, it is now generally accepted that various different mechanisms can result in cell damage and eventual death. A plethora of techniques is available to identify various pathological features of cell death in stroke; each has its own drawbacks and pitfalls, and most are unable to distinguish between different types of cell death, which partially explains the widespread misuse of many terms. The purpose of this review is to summarize the standard histopathological and immunohistochemical techniques used to identify various pathological features of stroke. We then discuss how these methods should be properly interpreted on the basis of what they are showing, as well as advantages and disadvantages that require consideration. As there is much interest in the visualization of stroke using noninvasive imaging strategies, we also specifically discuss how these techniques can be interpreted within the context of cell death.

Cerebral tissue repair and atrophy after embolic stroke in rat: a magnetic resonance imaging study of erythropoietin therapy

Using magnetic resonance imaging (MRI) protocols of T(2)-, T(2)*-, diffusion- and susceptibility-weighted imaging (T2WI, T2*WI, DWI, and SWI, respectively) with a 7T system, we tested the hypothesis that treatment of embolic stroke with erythropoietin (EPO) initiated at 24 hr and administered daily for 7 days after stroke onset has benefit in repairing ischemic cerebral tissue. Adult Wistar rats were subjected to embolic stroke by means of middle cerebral artery occlusion (MCAO) and were randomly assigned to a treatment (n = 11) or a control (n = 11) group. The treated group was given EPO intraperitoneally at a dose of 5,000 IU/kg daily for 7 days starting 24 hr after MCAO. Controls were given an equal volume of saline. MRI was performed at 24 hr and then weekly for 6 weeks. MRI and histological measurements were compared between groups. Serial T2WI demonstrated that expansion of the ipsilateral ventricle was significantly reduced in the EPO-treated rats. The volume ratio of ipsilateral parenchymal tissue relative to the contralateral hemisphere was significantly increased after EPO treatment compared with control animals, indicating that EPO significantly reduces atrophy of the ipsilateral hemisphere, although no significant differences in ischemic lesion volume were observed between the two groups. Angiogenesis and white matter remodeling were significantly increased and occurred earlier in EPO-treated animals than in the controls, as evident from T2*WI and diffusion anisotropy maps, respectively. These data indicate that EPO treatment initiated 24 hr poststroke promotes angiogenesis and axonal remodeling in the ischemic boundary, which may potentially reduce atrophy of the ipsilateral hemisphere.

Neuroprotective potential of erythropoietin and its derivative carbamylated erythropoietin in periventricular leukomalacia

Periventricular leukomalacia (PVL) is the predominant pathology in premature infants, characterized by prominent cerebral white matter injury, and commonly caused by hypoxia-ischemia and inflammation. Activated microglia trigger white matter damage and play a major role in the development of PVL. Erythropoietin (EPO) and its derivative carbamylated erythropoietin (CEPO) have been shown to be neuroprotective in several brain disease models. Here we investigated whether EPO and CEPO could provide protection in mouse models of PVL induced by hypoxia-ischemia or hypoxia-ischemia-inflammation. We administered EPO or CEPO to mice with PVL, and found that both EPO and CEPO treatments decreased microglia activation, oligodendrocyte damage and myelin depletion. We also noted improved performance in neurological function assays. Inhibited disease progression in PVL mice by EPO or CEPO treatment was associated with decreased poly-(ADP-ribose) polymerase-1 (PARP-1) activity. PARP-1 activity was increased dramatically in activated microglia in untreated mice with PVL. Furthermore, we demonstrated that the neuroprotective properties of EPO and CEPO were diminished after PARP-1 gene depletion. The therapeutic doses of EPO and CEPO used in this study did not interfere with normal oligodendrocyte maturation and myelination. Together, our data demonstrate that EPO and CEPO are neuroprotective in cerebral white matter injury via a novel microglial PARP-1 dependent mechanism, and hold promise as a future treatment for PVL and other hypoxic-ischemic/inflammatory white matter diseases.

Brain penetrating IgG-erythropoietin fusion protein is neuroprotective following intravenous treatment in Parkinson's disease in the mouse

Parkinson's disease (PD) is caused by oxidative stress, and erythropoietin (EPO) reduces oxidative stress in the brain. However, EPO cannot be developed as a treatment for PD, because EPO does not cross the blood-brain barrier (BBB). A brain penetrating form of human EPO has been developed wherein EPO is fused to a chimeric monoclonal antibody (MAb) against the mouse transferrin receptor (TfR), which is designated as the cTfRMAb-EPO fusion protein. The TfRMAb acts as a molecular Trojan horse to transport the fused EPO into brain via transport on the BBB TfR. Experimental PD was induced in adult mice by the intra-striatal injection of 6-hydroxydopamine, and PD mice were treated with 1mg/kg of the cTfRMAb-EPO fusion protein intravenously (IV) every other day starting 1 h after toxin injection. Following 3weeks of treatment mice were euthanized for measurement of striatal tyrosine hydroxylase (TH) enzyme activity. Mice treated with the cTfRMAb-EPO fusion protein showed a 306% increase in striatal TH enzyme activity, which correlated with improvement in three assays of neurobehavior. The blood hematocrit increased 10% at 2weeks, with no further changes at 3weeks of treatment. A sandwich ELISA showed the immune reaction against the cTfRMAb-EPO fusion protein was variable and low titer. In conclusion, the present study demonstrates that a brain penetrating form of EPO is neuroprotective in PD following IV administration with minimal effects on erythropoiesis.

Erythropoietin attenuates inflammatory factors and cell death in neonatal rats with intracerebral hemorrhage

Stroke affects infants at a rate of 26/100,000 live births each year. Of these strokes, approximately 6.7 are hemorrhagic strokes. Erythropoietin (EPO) is an anti-apoptotic and neuroprotective hormone. In adult rodents, EPO attenuates inflammatory factor expression and blood-brain barrier damage after intracerebral hemorrhage (ICH). However, the effect of EPO in neonatal ICH stroke remains unexplored. This investigation aimed to elucidate the underpinnings of inflammation after ICH in postnatal day 7 (P7) rats and the effect of human recombinant EPO (hrEPO) treatment on ICH-induced inflammation. The P7 rat pups were pretreated with hrEPO (5,000 U/kg i.p.) or saline vehicle 4 h prior to the induction of ICH by blood injection into the right cerebral cortex and basal ganglia. Supplemental half doses of hrEPO treatment or saline injections were subsequently given 16 h after ICH induction. Real-time PCR done 24 h after ICH showed reductions in interleukin1-β (IL1-β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNFα) mRNA expression in the basal ganglia of the hrEPO-treated rats compared to saline-treated rats. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining indicated fewer dying cells in the hrEPO-treated brain. Our data suggest that hrEPO has an anti-inflammatory action in neonates after ICH. The suppression of inflammatory cascades likely contributes to hrEPO's neuroprotective effect, which may be explored as a therapeutic treatment for ICH.

Erythropoietin prevents nitric oxide and cathepsin-mediated neuronal death in focal brain ischemia

We examined the preventive effect of human recombinant erythropoietin (HrEPO) on nitric oxide (NO)-mediated toxicity to neurons and cysteine protease release into cytoplasm, which is attributed to neuronal death in brain ischemia. Focal cerebral ischemia was induced by permanent occlusion of middle cerebral artery in two sets of rat. The first set was used to monitor NO concentration and cathepsin activity, while the second was used for histological examination with hematoxylin and eosin, and TUNEL staining. A group in both set was administered human recombinant erythropoietin (HrEPO). NO content, cathepsins B and L activity increased significantly in the post-ischemic cerebral tissue (p<0.05). HrEPO treatment reduced NO concentration and cathepsin activity to control level (p>0.05). A significant increase in the number of necrotic and apoptotic neurons was observed in the post-ischemic cerebral cortex (p<0.05). HrEPO treatment was markedly lowered both of these (p<0.05). It is concluded that HrEPO prevents neuronal death by protecting neuronal liposomes from NO-mediated toxicity and suppressing the release of cathepsins.

Neuroprotection in experimental stroke in the rat with an IgG-erythropoietin fusion protein

Erythropoietin (EPO) is a potent neuroprotective agent that could be developed as a new treatment for stroke. However, the blood-brain barrier (BBB) is intact in the early hours after stroke when neuroprotection is still possible, and EPO does not cross the intact BBB. To enable BBB transport, human EPO was re-engineered as an IgG-EPO fusion protein, wherein the IgG part is a monoclonal antibody (MAb) against the human insulin receptor (HIR). The HIRMAb acts as a BBB molecular Trojan horse to ferry the fused EPO across the BBB via transport on the BBB insulin receptor. The HIRMAb part of the HIRMAb-EPO fusion protein does not recognize the rat insulin receptor. However, the EPO part of the fusion protein does recognize the rat EPO receptor. Therefore, the neuroprotective properties of the HIRMAb-EPO fusion protein were investigated with a permanent middle cerebral artery occlusion model in the rat. The HIRMAb-EPO fusion protein was injected into the ipsilateral brain under stereotaxic guidance. High doses of the HIRMAb-EPO fusion protein (61pmol) completely eliminated both cortical and sub-cortical infarction. Lower doses of the fusion protein (4.5pmol) eliminated the cortical infarct with no significant effect on sub-cortical infarct. The neurologic deficit was reduced by 35% and 90%, respectively, by the 4.5 and 61pmol doses of the HIRMAb-EPO fusion protein. In conclusion, these studies demonstrate the biological activity of the HIRMAb-EPO fusion protein in the brain in vivo, and that EPO retains neuroprotective properties following fusion to the HIRMAb BBB Trojan horse.

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.

Donor pretreatment with carbamylated erythropoietin in a brain death model reduces inflammation more effectively than erythropoietin while preserving renal function

OBJECTIVE

We hypothesized that donor treatment of deceased brain dead donors would lead to a decrease in inflammatory responses seen in brain death and lead to a restoration of kidney function.

DESIGN

A standardized slow-induction rat brain death model followed by evaluation of kidney function in an isolated perfused kidney model.

SETTINGS

Surgery Research Laboratory, University Medical Center Groningen, the Netherlands.

SUBJECTS

Male Fisher rats.

INTERVENTIONS

Donor treatment with erythropoietin, carbamylated erythropoietin, which lacks erythropoietic activity, or vehicle.

MEASUREMENTS AND MAIN RESULTS

In brain death, carbamylated erythropoietin and, to a lesser extent, erythropoietin were able to decrease the expression of several proinflammatory genes and to decrease the infiltration of polymorphonuclear cells in the kidney. No effect on tubular injury parameters was seen. Kidney function decreased almost by 50% after brain death but was fully restored after treatment with both carbamylated erythropoietin and erythropoietin.

CONCLUSIONS

Carbamylated erythropoietin can inhibit the inflammatory response caused by brain death more effectively than erythropoietin, whereas both substances can restore kidney function after brain death.