Erythropoietin improves long-term spatial memory deficits and brain injury following neonatal hypoxia-ischemia in rats

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.

Erythropoietin attenuates brain injury, subventricular zone expansion, and sensorimotor deficits in hypoxic-ischemic neonatal rats

The aim of this study was to investigate the effect of erythropoietin (EPO) on histological brain injury, subventricular zone (SVZ) expansion, and sensorimotor function deficits induced by hypoxia-ischemia (HI) in newborn rat pups. Seven-day-old male rat pups were divided into six groups: normoxia control, normoxia EPO, hypoxia control, hypoxia EPO, HI control, and HI EPO group. Sham surgery or HI was performed in all animals. HI was induced by ligation of the right common carotid artery followed by 90 min of hypoxia with 8% oxygen. Recombinant human EPO 3 U/g or saline was administered intraperitoneally, immediately, at 24- and 48-hr after insult. At two weeks after insult, animals were challenged with cylinder-rearing test for evaluating forelimb asymmetry to determine sensorimotor function. All animals were then sacrificed for volumetric analysis of the cerebral hemispheres and the SVZ. The saline-treated HI rats showed marked asymmetry by preferential use of the non-impaired, ipsilateral paw in the cylinder-rearing test. Volumetric analysis of brains revealed significantly decreased preserved ipsilateral hemispheric volume and increased ipsilateral SVZ volume compared with the sham-operated animals. Treatment of EPO significantly improved forelimb asymmetry and preserved ipsilateral hemispheric volume along with decreased expansion of ipsilateral SVZ following HI compared to the saline-treated HI rats. These results support the use of EPO as a candidate drug for treatment of neonatal hypoxic-ischemic brain damage.

Erythropoietin promotes axonal growth in a model of neuronal polarization

Erythropoietin (EPO) enhances neurogenesis, neuroprotection and regeneration. Here, we examined the effects of EPO on axonal and dendritic growth in a model of neuronal polarization. EPO did not effect survival or the polarized morphology of hippocampal neurons but its effect on neurite outgrowth depended upon the stage of polarization. When added to neurons in the process of establishing polarity (0-2 days in vitro (DIV)), it enhanced axonal and dendritic growth, while EPO added to early polarized cultures at 3-4 DIV promoted the growth of axons but not dendrites. EPO stimulated the phosphorylation of Akt at serine-473 and co-incubation of the Akt/PI-3 kinase pathway inhibitor LY294002 with EPO abolished its effects on Akt phosphorylation and axonal growth. However, while Leukemia Inhibitory Factor (LIF) similarly stimulated phosphorylation of Akt, it had no effect on axonal or dendritic growth, indicating that AKT phosphorylation is necessary but not sufficient for neurite outgrowth in hippocampal neurons.

Neuroprotective properties and mechanisms of erythropoietin in in vitro and in vivo experimental models for hypoxia/ischemia

Besides its established function in erythropoiesis, erythropoietin (EPO) is currently also appreciated for its neuroprotective effects. The detrimental sequelae of prolonged cerebral hypoxia and ischemia have been shown to attenuate by EPO treatment. After binding to the EPO receptor, EPO is capable of initiating a cascade of events which--via different pathways--may lead to neuroprotection. The circumstances that determine which specific signalling route(s) are activated by EPO are largely unknown. We aim to provide the reader with a timely overview on the use of EPO in models of stroke and hypoxia-ischemia and to discuss the molecular events that underlie its neuroprotection.

Protective effects of erythropoietin against acute lung injury in a rat model of acute necrotizing pancreatitis

AIM

To investigate the effect of exogenous erythro-poietin (EPO) administration on acute lung injury (ALI) in an experimental model of sodium taurodeoxycholate- induced acute necrotizing pancreatitis (ANP).

METHODS

Forty-seven male Wistar albino rats were randomly divided into 7 groups: sham group (n = 5), 3 ANP groups (n = 7 each) and 3 EPO groups (n = 7 each). ANP was induced by retrograde infusion of 5% sodium taurodeoxycholate into the common bile duct. Rats in EPO groups received 1000 U/kg intramuscular EPO immediately after induction of ANP. Rats in ANP groups were given 1 mL normal saline instead. All animals were sacrificed at postoperative 24 h, 48 h and 72 h. Serum amilase, IL-2, IL-6 and lung tissue malondialdehyde (MDA) were measured. Pleural effusion volume and lung/body weight (LW/BW) ratios were calculated. Tissue levels of TNF-alpha, IL-2 and IL-6 were screened immunohistochemically. Additionally, ox-LDL accumulation was assessed with immune-fluorescent staining. Histopathological alterations in the lungs were also scored.

RESULTS

The mean pleural effusion volume, calculated LW/BW ratio, serum IL-6 and lung tissue MDA levels were significantly lower in EPO groups than in ANP groups. No statistically significant difference was observed in either serum or tissue values of IL-2 among the groups. The level of tumor necrosis factor-alpha (TNF-alpha) and IL-6 and accumulation of ox-LDL were evident in the lung tissues of ANP groups when compared to EPO groups, particularly at 72 h. Histopathological evaluation confirmed the improvement in lung injury parameters after exogenous EPO administration, particularly at 48 h and 72 h.

CONCLUSION

EPO administration leads to a significant decrease in ALI parameters by inhibiting polymorphonuclear leukocyte (PMNL) accumulation, decreasing the levels of proinflammatory cytokines in circulation, preserving microvascular endothelial cell integrity and reducing oxidative stress-associated lipid peroxidation and therefore, can be regarded as a cytoprotective agent in ANP-induced ALI.

Effects of erythropoietin on posttraumatic place learning in fimbria-fornix transected rats after a 30-day postoperative pause

Human recombinant erythropoietin (EPO) has been shown to exert neuroprotective effects following both vascular and mechanical brain injury. Previously, we showed that behavioral symptoms associated with mechanical lesions of the hippocampus are nearly abolished due to EPO treatment. In these studies, the EPO administration took place simultaneously with the infliction of brain injury and the rehabilitation training started 6-7 days postoperatively. In the present study, we tested whether the therapeutic effect of EPO on the acquisition of an allocentric eight-arm radial maze spatial task also manifests itself if the rehabilitative training is postponed. Postoperatively, the animals were left without any specific stimulation for 30 days. The current results show an improved behavioral performance of the EPO-treated lesioned group relative to the saline-treated lesioned group, and confirm EPO's therapeutic effect even in case of postponed rehabilitation. However, compared to the control group, the EPO-treated lesioned group demonstrated an impaired task acquisition. All subjects eventually recovered functionally. Subsequently, the animals were given behavioral challenges during which the cue constellation in the room was changed. The challenges revealed that, although the EPO-treated lesion group had achieved the same level of task proficiency as the control group, the cognitive mechanisms mediating the task performance in the EPO-treated lesion group (as well as in the saline-treated lesion group) were dissimilar from those mediating the task in the control group. Both the EPO-treated and the saline-treated lesion group demonstrated an increased dependency on the original cue configuration.

Protective effects of erythropoietin against acute lung injury in a rat model of acute necrotizing pancreatitis

AIM: To investigate the effect of exogenous erythro-poietin (EPO) administration on acute lung injury (ALI) in an experimental model of sodium taurodeoxycholate-induced acute necrotizing pancreatitis (ANP).

METHODS: Forty-seven male Wistar albino rats were randomly divided into 7 groups: sham group (n = 5), 3 ANP groups (n = 7 each) and 3 EPO groups (n = 7 each). ANP was induced by retrograde infusion of 5% sodium taurodeoxycholate into the common bile duct. Rats in EPO groups received 1000 U/kg intramuscular EPO immediately after induction of ANP. Rats in ANP groups were given 1 mL normal saline instead. All animals were sacrificed at postoperative 24 h, 48 h and 72 h. Serum amilase, IL-2, IL-6 and lung tissue malondialdehyde (MDA) were measured. Pleural effusion volume and lung/body weight (LW/BW) ratios were calculated. Tissue levels of TNF-α, IL-2 and IL-6 were screened immunohistochemically. Additionally, ox-LDL accumulation was assessed with immune-fluorescent staining. Histopathological alterations in the lungs were also scored.

RESULTS: The mean pleural effusion volume, calculated LW/BW ratio, serum IL-6 and lung tissue MDA levels were significantly lower in EPO groups than in ANP groups. No statistically significant difference was observed in either serum or tissue values of IL-2 among the groups. The level of tumor necrosis factor-α (TNF-α) and IL-6 and accumulation of ox-LDL were evident in the lung tissues of ANP groups when compared to EPO groups, particularly at 72 h. Histopathological evaluation confirmed the improvement in lung injury parameters after exogenous EPO administration, particularly at 48 h and 72 h.

CONCLUSION: EPO administration leads to a significant decrease in ALI parameters by inhibiting polymorphonuclear leukocyte (PMNL) accumulation, decreasing the levels of proinflammatory cytokines in circulation, preserving microvascular endothelial cell integrity and reducing oxidative stress-associated lipid peroxidation and therefore, can be regarded as a cytoprotective agent in ANP-induced ALI.

Early high-dose erythropoietin therapy and hypothermia after out-of-hospital cardiac arrest: a matched control study

AIM

To test the possible neuroprotective effect of early high-dose erythropoietin-alpha (Epo-alpha) after out-of-hospital cardiac arrest (OHCA).

METHODS

A matched control study. Following resuscitation with mild hypothermia after OHCA, participants received a first dose of Epo-alpha followed by four additional injections within 48 h (40,000 IU intravenously each injection). Plasma Epo-alpha levels were measured at different time points. Outcome and adverse events were assessed up to day 28 and were compared with those of matched-paired controls.

RESULTS

In all 18 participants received Epo-alpha and were compared with 40 matched controls. Pharmacokinetic variables were similar to those previously reported for healthy people or for persons treated with usual dosages of Epo. At day 28, survival rates among the Epo-treated group and the controls (55% versus 47.5%, p=0.17) and rates of full neurological recovery (55% versus 37.5%) did not differ significantly. Incidences of thrombocytosis in the Epo-treated group and controls were 15% and 5%, respectively; an arterial vascular thrombosis was observed in one case (5%) from the Epo-treated cohort.

CONCLUSIONS

Among victims of OHCA treated with Epo-alpha and hypothermia, we observed a high survival rate, with no minor cerebral sequels but potential haematological side effects. Future studies of Epo should pay particular attention to these findings.

Erythropoietin enhances long-term neuroprotection and neurogenesis in neonatal stroke

Neonatal stroke leads to mortality and severe morbidity, but there is no effective treatment currently available. Erythropoietin (EPO) has been shown to promote cytoprotection and neurogenesis and decrease subventricular zone morphologic changes following brain injury. The long-term cellular response to EPO has not been defined, and local changes in cell fate decision may play a role in functional improvement. We performed middle cerebral artery occlusion in P10 rats. EPO treatment (5 U/g i.p.) significantly preserved hemispheric brain volume 6 weeks after injury. Furthermore, EPO increased the percentage of newly generated neurons while decreasing newly generated astrocytes following brain injury, without demonstrating long-term differences in the subventricular zone. These results suggest that EPO may neuroprotect and direct cell fate toward neurogenesis and away from gliogenesis in neonatal stroke.

Hypobaric hypoxia damages the hippocampal pyramidal neurons in the rat brain

Hypobaric hypoxia (HH), a predisposing environmental condition at high altitude (HA), encountered by many mountaineers, jeopardizes their normal physiology like motor coordination and cognitive functions. A large body of evidence shows that HH has deleterious effect on cognitive functions. Among them the hippocampal dependent memory deficit is well known. However, our current understanding of the mechanistic details of cognitive deficits at HA remains largely unclear and hence limits a solution for this problem. Therefore, the present study was designed to investigate the temporal component of the hippocampal pyramidal neuron damage in the rat brain subjected to chronic HH exposure. Three groups (sham HH, 3 days HH and 7 days HH) of rats were exposed to simulated HH equivalent to 6100 m in an animal decompression chamber for 3 or 7 days. Later, the hippocampal (CA1 and CA3) neurons were analysed for the cell morphology, neurodegeneration and DNA fragmentation. The CA1 and CA3 neurons showed HH induced neuronal pyknosis, cell shrinkage, and consequent inter-cellular vacuolization in the CA1 and CA3 areas. In addition, the total neuron (intact) numbers and mean surface area were decreased. The number of dead neurons increased significantly following exposure to HH for 3 or 7 days. The neurodegenerative (Fluoro jade B) and apoptotic (TUNEL) markers were more positive in CA1 and CA3 neurons. The magnitude of morphological changes, neurodegeneration and apoptosis was enhanced in 7 days HH group than 3 days HH group. Our studies indicate that CA3 neurons are more vulnerable to HH than CA1 neurons, and that may destabilize the neural circuits in the hippocampus and thus cause memory dysfunction.

Erythropoietin Promotes Neuronal Replacement Through Revascularization and Neurogenesis After Neonatal Hypoxia/Ischemia in Rats

BACKGROUND AND PURPOSE

Erythropoietin (EPO) has been well characterized and shown to improve functional outcomes after ischemic injury, but EPO may also have unexplored effects on neurovascular remodeling and neuronal replacement in the neonatal ischemic brain. The current study investigates the effects of exogenous administration of EPO on revascularization and neurogenesis, 2 major events thought to contribute to neuronal replacement, in the neonatal brain after hypoxia/ischemia (H/I).

METHODS

Seven-day-old rat pups were treated with recombinant human EPO or vehicle 20 minutes after H/I and again on postischemic days 2, 4, and 6. Rats were euthanized 7 or 28 days after H/I for evaluation of infarct volume, revascularization, neurogenesis, and neuronal replacement using bromodeoxyuridine incorporation, immunohistochemistry, and lectin labeling. Neurological function was assessed progressively for 28 days after H/I by gait testing, righting reflex and foot fault testing.

RESULTS

We demonstrate that exogenous EPO-enhanced revascularization in the ischemic hemisphere correlated with decreased infarct volume and improved neurological outcomes after H/I. In addition to vascular effects, EPO increased both neurogenesis in the subventricular zone and migration of neuronal progenitors into the ischemic cortex and striatum. A significant number of newly synthesized cells in the ischemic boundary expressed neuronal nuclei after EPO treatment, indicating that exogenous EPO led to neuronal replacement.

CONCLUSIONS

Our data suggest that treatment with EPO contributes to neurovascular remodeling after H/I by promoting tissue protection, revascularization, and neurogenesis in neonatal H/I-injured brain, leading to improved neurobehavioral outcomes.

Neuroprotection by erythropoietin administration after experimental traumatic brain injury

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

Recent trends in erythropoietin-mediated neuroprotection

Fifteen years of evidence have established that the cytokine erythropoietin offers promise as a treatment for brain injury. In particular, neonatal brain injury may be reduced or prevented by early treatment with recombinant erythropoietin. Extreme prematurity and perinatal asphyxia are common conditions associated with poor neurodevelopmental outcomes including cerebral palsy, mental retardation, hearing or visual impairment, and attention deficit hyperactivity disorder. When high doses of erythropoietin are administered systemically, a small proportion crosses the blood-brain barrier and can protect against hypoxic-ischemic brain injury. In addition to other protective effects, erythropoietin can specifically protect dopaminergic neurons. Since reduced dopamine neurotransmission contributes to attention deficit hyperactivity disorder, this condition may be amenable to erythropoietin treatment. This review focuses on the potential application of erythropoietin as a neuroprotectant with regard to neurologic complications of extreme prematurity, including attention deficit hyperactivity disorder. Recent concerns that early erythropoietin might exacerbate the pathologic neovascularization associated with retinopathy of prematurity are addressed.

Epo and other hematopoietic factors

The growth factors erythropoietin and granulocyte-colony stimulating factor have hematopoietic and non-hematopoietic functions. Both are used clinically in their recombinant forms. Both also have interesting tissue-protective effects in other organs, which are unrelated to their hematopoietic functions. They have clinical hematopoietic uses in neonatal populations and in experimental non-hematopoietic research, and clinical potential as neuroprotective or tissue-protective agents.

Effect of erythropoietin on brain tissue after experimental head trauma in rats

BACKGROUND

The purpose of this study was to investigate the effect of EPO on LPO, on ultrastructural findings, and on antiapoptotic bcl-2 and survivin gene expressions after TBI. The authors also compared the activity of EPO with that of MPSS.

METHODS

Wistar rats were divided into 6 groups: sham-operated, control, moderate TBI-alone (300 g/cm), TBI + EPO-treated (1000 IU/kg), TBI + MPSS-treated (30 mg/kg), and TBI + vehicle-treated (0.4 mL albumin solution) groups.

RESULTS

Compared with the levels in control and sham-operated animals, LPO was significantly elevated in rats in the trauma-alone group. The administration of EPO and MPSS significantly decreased the LPO levels (P < .05). Trauma also increases the antiapoptotic bcl-2 gene expression significantly at 24 hours postinjury (P < .05), but it has no effect on survivin expression. The EPO and MPSS treatments caused significant elevation in both gene expressions (P < .05). It is also showed that MPSS has more protective effect than EPO on brain ultrastructure, especially on the structure of small- (P < .05) and medium-sized myelinated axons, after TBI.

CONCLUSIONS

EPO has protective effects after moderate TBI, and this effect seems better than MPSS on antiapoptotic gene expression and LPO. The protection of cerebral subcellular organelles after traumatic injury is more prominent in MPSS-treated animals than EPO-treated animals quantitatively. This experimental study indicates that the benefits of EPO in the management of TBI have promising results and prompts further studies on the difference between EPO and MPSS in histopathological findings at the subcellular level.

Effects of a single dose of erythropoietin on subsequent seizure susceptibility in rats exposed to acute hypoxia at P10

PURPOSE

To determine if posthypoxia treatment with erythropoietin (EPO) has protective effects against subsequent susceptibility to seizure related neuronal injury in rat pups subjected to acute hypoxia at P10.

METHODS

Four groups of rats were manipulated at P10, as described below, then all received kainic acid (KA) (10 mg/kg i.p.) at P29: Hypoxia-NS-KA group (n = 11): subjected to acute hypoxia (down to 4% O2), and then immediately received saline i.p. Hypoxia-EPO-KA group (n = 10): subjected to acute hypoxia and then immediately received EPO (1,000 U/Kg i.p.). Normoxia-NS-KA group (n = 11): sham manipulated and injected with saline. Normoxia-EPO-KA group (n = 10): sham manipulated then immediately injected with EPO (1000 U/Kg i.p.). After receiving KA at P29, all rats were monitored using videotape techniques, and were sacrificed at P31. TUNEL and Hoechst stains to assess for apoptosis, and regular histology for hippocampal cell counts were performed.

RESULTS

Administration of the single dose of erythropoietin directly after an acute hypoxic event at P10 resulted at P29 in increased latency to forelimb clonus seizures, reduced duration of these seizures, protection against hippocampal cell loss, and decreased hippocampal apoptosis in the Hypoxia-EPO-KA group as compared to the Hypoxia-NS-KA group.

CONCLUSION

These data support the presence of favorable protective effects of erythropoietin against the long-term consequences of acute hypoxia in the developing brain and raise the possibility of its investigation as a potential neuroprotective agent after human neonatal hypoxic encephalopathy.

Auditory processing and learning/memory following erythropoietin administration in neonatally hypoxic–ischemic injured rats

BACKGROUND

Hypoxia-ischemia (HI) is a common injury arising from prematurity/complications at birth and is associated with later language, auditory, and learning impairments.

OBJECTIVE

To investigate the efficacy of two doses (300 or 1000 U/kg) of Erythropoietin (Epo) in protecting against neuropathological and behavioral impairments associated with HI injury in rats.

METHODS

HI injury (right carotid artery cauterization and 120 min of 8% O(2)) was induced on postnatal day 7 (P7) and Epo or saline was administered i.p. immediately following the procedure. Auditory processing and learning/memory were assessed throughout development.

RESULTS

Both doses of Epo provided behavioral protection following HI injury. Rats given 300 or 1000 U/kg of Epo performed significantly better than HI animals on a short duration complex auditory processing procedure, on a spatial Morris water maze assessing spatial learning/reference memory, and a non-spatial water maze assessing associative learning/reference memory.

CONCLUSIONS

Given Epo's extant clinical use (FDA approved for pediatric patients with anemia secondary to prematurity), the current results add to a growing body of literature supporting the use of Epo as a potential protective agent for neurological and behavioral impairments following early HI injury in infants.

Safety of high-dose recombinant erythropoietin in a neonatal rat model

BACKGROUND

High-dose recombinant erythropoietin (rEpo) is neuroprotective in neonatal animal models of brain injury, but the long-term consequences of neonatal exposure have not been studied.

OBJECTIVES

We hypothesized that multiple injections of high-dose rEpo during the neonatal period would be safe, and would improve neurologic outcomes after exposure to neonatal hypoxia or hypoxic-ischemic injury.

METHODS

Three experimental groups of Sprague-Dawley rats were assessed: (1) normoxia, (2) hypoxia and (3) hypoxia-ischemia. Groups 1 and 2 were given 0, 2,500 or 5,000 U/kg rEpo subcutaneously for the first 5 days of life (P1-P5). Group 2 animals also underwent 2 h of hypoxia (8% O(2)) daily from P1-P3. Group 3 animals underwent right carotid artery ligation followed by hypoxia (8% O(2) x 90 min) on P7, followed by either vehicle or rEpo (2,500 U/kg subcutaneously QD x3). We evaluated short- and long-term physiologic and behavioral outcomes. Major organs were evaluated grossly and histologically.

RESULTS

rEpo treatment transiently raised hematocrit, prevented hypoxia-induced delays in geotaxis and growth, improved forelimb strength, promoted liver growth in males, lowered the adult platelet count, but did not alter other CBC indices or histology. rEpo prevented hypoxia-ischemia-induced learning impairment and substantia nigra neuron loss.

CONCLUSIONS

Repeated treatment of newborn rats with high-dose rEpo was safe under all conditions tested. rEpo treatment improved the development of hypoxia-exposed newborns and prevented the learning impairment and dopamine neuron loss due to unilateral hypoxic-ischemic brain injury.

Erythropoietin attenuates lipopolysaccharide-induced white matter injury in the neonatal rat brain

Periventricular leukomalacia (PVL), a common neonatal brain white matter (WM) lesion, is frequently associated with cerebral palsy. Growing evidence has indicated that in addition to ischemia/reperfusion injury, cytokine-induced brain injury associated with maternal or fetal infection may also play an important role in the pathogenesis of PVL. Recent studies have shown that administration of lipopolysaccharide (LPS) to pregnant rats causes enhanced expression of the cytokines, i.e., IL-1 beta, TNF-alpha, and IL-6, in fetal brains. In recent years, it has been shown that erythropoietin (EPO) has a critical role in the development, maintenance, protection and repair of the nervous system. In the present study we investigated the effect of EPO on LPS-induced WM injury in Sprague-Dawley rats. LPS (500 microg/kg) suspension in pyrogen-free saline was administered intraperitoneally to pregnant rats at 18 and 19 days of gestation. The control group was treated with pyrogen-free saline. They were given 5,000 U/kg recombinant human EPO. Seven-day-old Sprague-Dawley rat pups were divided into four groups: control group, LPS-treated group, prenatal maternal EPO-treated group (5,000 U/kg, intraperitoneally given to pregnant rats at 18 and 19 days of gestation), and postnatal EPO-treated group (5,000 U/kg, intraperitoneally given to 1-day-old rat pups). Cytokine induction in the postnatal 7-day-old (P7) rat brain after maternal administration of LPS was determined by the ELISA method. The proinflammatory cytokine levels (IL-1 beta, TNF-alpha, and IL-6) in P7 rat pup brains were significantly increased in the LPS-treated group as compared with the control group. Prenatal maternal EPO treatment significantly reduced the concentration of TNF-alpha and IL-6 in the newborn rat brain following LPS injection. The concentration of IL-1 beta was decreased in the intrauterine EPO treatment group. Postnatal EPO treatment significantly decreased only the IL-6 concentration in the newborn rat brain following LPS injection. The concentration of cytokines, IL-1 beta and TNF-alpha, was reduced in the postnatal EPO treatment group. We demonstrated here that LPS administration in pregnant rats at gestational day 18 and 19 induced WM injury in P7 progeny characterized by apoptosis. Prenatal maternal and postnatal EPO treatment significantly reduced the number of apoptotic cells in the periventricular WM. Using immunohistochemistry techniques, we investigated the effects of maternal administration of LPS on myelin basic protein (MBP) staining, as a marker of myelination in the periventricular area in the neonatal rat brain. MBP staining was significantly less and weaker in the brains of the LPS-treated group as compared with the prenatal maternal EPO-treated group. However, the postnatal EPO treatment did not prevent LPS-stimulated loss of MBP-positive staining. In conclusion, especially prenatal maternal EPO treatment attenuates LPS-induced injury by reducing the expression of inflammatory cytokines and sparing MBP in the neonatal rat brain. While the postnatal EPO treatment prevented LPS-induced brain injury this effect was partial. To our knowledge, this is the first study that demonstrates a protective effect of EPO on LPS-induced WM injury in the developing brain. Regarding the wide use of EPO in premature newborns, this agent maybe potentially beneficial in treating LPS-induced brain injury in the perinatal period.

Intermittent hypoxia impairs performance of adult mice in the two-way shuttle box but not in the Morris water maze

We have previously found that neonatal intermittent hypobaric hypoxia exposure enhanced mouse spatial, but impaired associative, cognition. This study sought to investigate the effects of hypobaric hypoxia on adult mice cognition. Mice were exposed to 2, 5, 10, 15, or 25 days of intermittent hypoxia (IH; 4 hr/day) at 2 km (16.0% O2) or 5 km (10.8% O2) altitudes in a hypobaric chamber for the Morris water maze (MWM) test and exposed to IH for 2, 10, or 25 days for the shuttle-box test. Amino acid dynamics in vivo in the hippocampus and amygdala of mice exposed to 2 km hypoxia were analyzed by high-pressure liquid chromatography. The results in MWM task showed that IH-2d to -25d at 2 km or 5 km did not change the escape latencies of mice in the training test or the retention of platform in the probe test. In the shuttle-box task, however, IH-10d at 5 km significantly reduced mouse avoidances in the acquisition test on day 4, and IH-10d at 2 km reduced avoidances in the retention test; IH-25d at 5 km significantly reduced avoidances of mice throughout the acquisition days. Glutamate in the amygdala persisted in declining to 69% of baseline at 8 hr posthypoxia (P = 0.040 vs. GLU released during 30 min before hypoxia) during the posthypoxia stage. These results suggest that adult hypobaric IH impairs the hippocampal-independent, but not the hippocampal-dependent, task in mice. The different GLU releases in the hippocampus and amygdala in response to hypoxia are involved in the different behaviors.

Neuroprotective effect of the peptides ADNF-9 and NAP on hypoxic-ischemic brain injury in neonatal rats

Perinatal asphyxia is an important cause of neonatal mortality and subsequent serious sequelae such as motor and cognitive deficits and seizures. Recent studies have demonstrated that short peptides derived from activity-dependent neurotrophic factor (ADNF) and activity-dependent neuroprotective protein (ADNP) are neuroprotective at femtomolar concentrations. However, the effect of these peptides on the hypoxic-ischemic brain injury model is unknown. The aim of this study is to investigate the effects of the peptides ADNF-9 and NAP on neurodegeneration and cerebral nitric oxide (NO) production in a neonatal rat model of hypoxic-ischemic brain injury. Seven-day-old Wistar Albino rat pups have been used in the study (n=42). Experimental groups in the study were: sham-operated group, ADNF-9-treated hypoxia-ischemia group, NAP-treated hypoxia-ischemia group, ADNF-9+NAP-treated hypoxia-ischemia group, and vehicle-treated group. In hypoxia-ischemia groups, left common carotid artery was ligated permanently on the seventh postnatal day. Two hours after the procedure, hypoxia (92% nitrogen and 8% oxygen) was applied for 2.5 h. ADNF-9, NAP, and ADNF-9+NAP were injected (intraperitoneally; i.p.) as a single dose immediately after the hypoxia period. Brain nitrite levels, neuronal cell death, and apoptosis were evaluated in both hemispheres (carotid ligated or nonligated) 72 h after the hypoxic-ischemic insult. Histopathological evaluation demonstrated that ADNF-9 and NAP significantly diminished number of "apoptotic cells" in the hippocampal CA1, CA2, CA3, and gyrus dentatus regions in both hemispheres (ligated and nonligated). When compared with vehicle-treated group, combination treatment with ADNF-9+NAP did not significantly reduce "apoptotic cell death" in any of the hemispheres. ADNF-9 and NAP, when administered separately, significantly preserved the number of neurons CA1, CA2, CA3, and dentate gyrus regions of the hippocampus, when compared with vehicle-treated group. The density of the CA1, CA2, and dentate gyrus neurons was significantly higher when combination therapy with ADNF-9+NAP was used in the carotid ligated hemispheres. In the nonligated hemispheres, combination therapy preserved the number of neurons only in the CA1 and dentate gyrus regions. Brain nitrite levels were evaluated by Griess reagent and showed that hypoxic-ischemic injury caused a significant increase in NO production. Brain nitrite levels in ADNF-9+NAP-treated animals were not different in carotid ligated or nonligated hemispheres. The peptides ADNF-9 and NAP significantly decreased NO overproduction in the hypoxic-ischemic hemisphere, whereas no significant change appeared in hypoxia alone and also in the sham-operated group. These results suggest the beneficial neuroprotective effect of ADNF-9 and NAP in this model of neonatal hypoxic-ischemic brain injury. To our knowledge, this is the first study that demonstrates a protective effect of these peptides against hypoxia-ischemia in the developing brain.

Transplantation of cryopreserved human bone marrow-derived multipotent adult progenitor cells for neonatal hypoxic-ischemic injury: targeting the hippocampus

There is currently no treatment for neonatal hypoxic-ischemic (HI) injury. Although limited clinical trials of stem cell therapy have been initiated in a number of neurological disorders, the preclinical evidence of a cell-based therapy for neonatal HI injury remains in its infancy. Stem cell therapy, via stimulation of endogenous stem cells or transplantation of exogenous stem cells, has targeted neurogenic sites, such as the hippocampus, for brain protection and repair. The hippocampus has also been shown to secrete growth factors, especially during the postnatal period, suggesting that this brain region presents a highly conducive microenvironment for cell survival. Based on its neurogenic and neurotrophic factor-secreting features, the hippocampus stands as an appealing target for stem cell therapy. In the present study, we investigated the efficacy of intrahippocampal transplantation of multipotent adult progenitor cells (MAPCs), which are pluripotent progenitor cells with the ability to differentiate into a neuronal lineage. Seven-day old Sprague-Dawley rats were initially subjected to unilateral HI injury, that involved permanent ligation of the right common carotid artery and subsequent exposure to hypoxic environment. At day 7 after HI

The brain erythropoietin system and its potential for therapeutic exploitation in brain disease

The discovery of the broad neuroprotective potential of erythropoietin (EPO), an endogenous hematopoietic growth factor, has opened new therapeutic avenues in the treatment of brain diseases. EPO expression in the brain is induced by hypoxia. Practically all brain cells are capable of production and release of EPO and expression of its receptor. EPO exerts multifaceted protective effects on brain cells. It protects neuronal cells from noxious stimuli such as hypoxia, excess glutamate, serum deprivation or kainic acid exposure in vitro by targeting a variety of mechanisms and involves neuronal, glial and endothelial cell functions. In rodent models of ischemic stroke, EPO reduces infarct volume and improves functional outcome, but beneficial effects have also been observed in animal models of subarachnoid hemorrhage, intracerebral hemorrhage, traumatic brain injury, and spinal cord injury. EPO has a convenient therapeutic window upon ischemic stroke and favorable pharmacokinetics. Results from first therapeutic trials in humans are promising, but will need to be validated in larger trials. The safety profile and effectiveness of EPO in a wide variety of neurologic disease models make EPO a candidate compound for a potential first-line therapeutic for neurologic emergencies.

The effects of erythropoietin on auditory processing following neonatal hypoxic-ischemic injury

Neonatal hypoxia-ischemia (HI) is a common cause of brain damage and subsequent behavioral deficits in premature/term infants. Rapid auditory processing deficits have been suggested to play a role in later language impairments in this population. We have previously shown auditory deficits in rats with neonatal HI injury and now report novel effects of behavioral sparing and neuroprotection following treatment with a low dose of Erythropoietin using this HI injury model.

Gender differences in long-term beneficial effects of erythropoietin given after neonatal stroke in postnatal day-7 rats

Recently, we reported that erythropoietin attenuates neonatal brain injury caused by focal cerebral ischemia. The long-term effects of erythropoietin on focal cerebral ischemia-induced injury to the developing brain and the potential gender differences in these long-term effects have not been studied in detail. The current study demonstrated a similarity in the mean infarct volume in both the vehicle-treated male and female rats at 6 and 12 weeks after focal cerebral ischemia. On the other hand, erythropoietin treatment (1000 U/kg x three doses after focal cerebral ischemia) caused a significant reduction in the mean infarct volume in both males and females at 6 weeks after focal cerebral ischemia when compared with the corresponding vehicle-treated animals (males: 141.4+/-48.2 mm3 vs. 194.0+/-59.2 mm3, P<0.05; females: 85.4+/-31.6 mm3 vs. 183.4+/-46.3 mm3, P<0.05). Interestingly, the reduction in the mean infarct volume in the erythropoietin-treated males was significantly less than that in the erythropoietin-treated females at 6 weeks after focal cerebral ischemia (141.4+/-48.2 mm3 vs. 85.4+/-31.6 mm3, P<0.05). At 12 weeks after focal cerebral ischemia, the mean infarct volume in the erythropoietin-treated males significantly increased to 181.0+/-50.4 mm3 (P<0.05). In contrast, the mean infarct volume in the erythropoietin-treated females remained stable (87.0+/-41.7 mm3). Additionally, erythropoietin treatment significantly improved sensorimotor function recovery with a misstep number similar to the sham-operation group at 6 and 12 weeks after focal cerebral ischemia. Moreover, the mean number of missteps in the erythropoietin-treated females was less than that in males at 6 (13.5+/-2.0 vs. 24.5+/-2.5, P<0.05) and 12 (12.5+/-2.0 vs. 20.0+/-2.0, P<0.05) weeks after focal cerebral ischemia. These results indicate that erythropoietin administration after focal cerebral ischemia produces a significant long-term neuroprotective benefit on the developing brain, and that this effect is more beneficial in the female rats.

Protective effects of erythropoietin against ethanol-induced apoptotic neurodegenaration and oxidative stress in the developing C57BL/6 mouse brain

The developing central nervous system is extremely sensitive to ethanol, with well-defined temporal periods of vulnerability. Recent studies have shown that administration of ethanol to infant rats during the synaptogenesis period triggers extensive apoptotic neurodegeneration throughout many regions of the developing brain. Furthermore, acute ethanol administration produces lipid peroxidation in the brain as an indicator of oxidative stress. In recent years, it has been shown that erythropoietin (EPO) has a critical role in the development, maintenance, protection, and repair of the nervous system. In the present study, we investigated the effect of EPO against ethanol-induced neurodegeneration and oxidative stress in the developing C57BL/6 mouse brain. Seven-day-old C57BL/6 mice were divided into three groups: control group, saline-treated group, EPO-treated group. Ethanol was administered to mice at a dosage of 2.5 g/kg for two times with a 2-h interval. Recombinant human EPO (rhEPO) was given 1000 U/kg. Twenty-four hours after the first dose of ethanol, all the animals were killed. Neuronal cell death, apoptosis, thiobarbituric acid substance (TBARS) levels, superoxide dismutase (SOD), and glutathione peroxidase (Gpx) enzymes activities were evaluated. Histopathological evaluation demonstrated that EPO significantly diminished apoptosis in the cerebellum, prefrontal cortex, and hippocampus and also spared hippocampal CA1, CA2, and CA3 neurons. Simultaneous administration of EPO along with ethanol attenuated the lipid peroxidation process and restored the levels of antioxidants. Regarding the wide use of erythropoietin in premature newborns, this agent may be potentially beneficial in treating ethanol-induced brain injury in the perinatal period.

Protecting Neurons

Brain injury evolves over time, often taking days or even weeks to fully develop. It is a dynamic process that involves immediate oxidative stress and excitotoxicity followed by inflammation and preprogrammed cell death. This article presents a brief overview of mechanisms of neuroprotection in the developing brain. Although the focus is on ischemic injury, the conclusions drawn apply to any type of brain insult-epileptic seizures, trauma, or ischemia. Strategies of neuroprotection include salvaging neurons through the use of targeted pharmacotherapies, protecting neurons through preconditioning, and repairing neurons by enhancing neurogenesis. Drug therapies that dampen the impact of immediate and downstream postinjury events are only modestly effective in protecting the brain from ischemic injury. In experimental models, complete or true protection can be achieved only through preconditioning, a process during which an animal develops tolerance to an otherwise lethal stressor. Although of no clinical use, preconditioning models have provided valuable insight into how repair systems work in the brain. Cumulative evidence indicates that the same genes that are upregulated during preconditioning, those mediating true protection, are also upregulated during injury and repair. Specifically, hypoxic preconditioning and hypoxic-ischemic insult have been shown to induce hypoxia inducible factor-1 (HIF-1) and its target survival genes, vascular endothelial growth factor (VEGF), and erythropoietin (Epo) in rodents. Of particular interest is the upregulation of Epo, a growth factor that may have therapeutic potential in the treatment of ischemic stroke. At this time, however, the postinjury enhancement of neurogenesis appears to offer the best hope for long-lasting functional recovery following brain injury.

Erythropoietin prevents long-term sensorimotor deficits and brain injury following neonatal hypoxia-ischemia in rats

Perinatal asphyxia accounts for behavioral dysfunctions that often manifest as sensorimotor, learning or memory disabilities throughout development and into maturity. Erythropoietin (Epo) has been shown to exert neuroprotective effects in different models of brain injury including experimental models of perinatal asphyxia. However, the effect of Epo on functional abilities following cerebral hypoxia-ischemia (HI) in neonatal rats is not known. The aim of the present study is to investigate the effect of Epo on sensorimotor deficits and brain injury induced by hypoxia-ischemia. Seven-day-old rats underwent unilateral, permanent carotid artery ligation followed by 1 h of hypoxia. Epo was administered as a single dose immediately after the hypoxic insult (2000 U/kg). The neuroprotective effect of Epo was evaluated at postnatal day 42 by using a battery of behavioral tests and histological analysis. The results of the present study suggest that Epo treatment immediately after HI insult significantly facilitated recovery of sensorimotor function. Consistently, histopathological evaluation demonstrated that Epo significantly attenuated brain injury and preserved the integrity of cerebral cortex. These findings indicate that long-term neuroprotective effect of Epo on neonatal HI-induced brain injury might be associated with the preservation of sensorimotor functions.

Erythropoietin is neuroprotective, improves functional recovery, and reduces neuronal apoptosis and inflammation in a rodent model of experimental closed head injury

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in young people in industrialized countries. Although various anti-inflammatory and antiapoptotic modalities have shown neuroprotective effects in experimental models of TBI, to date, no specific pharmacological agent aimed at blocking the progression of secondary brain damage has been approved for clinical use. Erythropoietin (Epo) belongs to the cytokine superfamily and has traditionally been viewed as a hematopoiesis-regulating hormone. The newly discovered neuroprotective properties of Epo lead us to investigate its effect in TBI in a mouse model of closed head injury. Recombinant human erythropoietin (rhEpo) was injected at 1 and 24 h after TBI, and the effect on recovery of motor and cognitive functions, tissue inflammation, axonal degeneration, and apoptosis was evaluated up to 14 days. Motor deficits were lower, cognitive function was restored faster, and less apoptotic neurons and caspase-3 expression were found in rhEpo-treated as compared with vehicle-treated animals (P<0.05). Axons at the trauma area in rhEpo-treated mice were relatively well preserved compared with controls (shown by their density; P<0.01). Immunohistochemical analysis revealed a reduced activation of glial cells by staining for GFAP and complement receptor type 3 (CD11b/CD18) in the injured hemisphere of Epo- vs. vehicle-treated animals. We propose that further studies on Epo in TBI should be conducted in order to consider it as a novel therapy for TBI.

Erythropoietin protects dopaminergic neurons and improves neurobehavioral outcomes in juvenile rats after neonatal hypoxia-ischemia

Brain injury as a result of hypoxia-ischemia remains a common cause of morbidity and mortality in neonates. No effective therapy is currently available. The hematopoietic cytokine erythropoietin (Epo) provides neuroprotection in many adult models of brain injury and is currently being investigated as a therapeutic agent for human stroke and spinal cord injury. We tested the hypothesis that recombinant Epo (rEpo) would improve neurobehavioral outcomes after neonatal hypoxic-ischemic brain injury. Postnatal day 7 rats underwent right common carotid artery occlusion followed by a 90-min exposure to 8% oxygen. Rats were subsequently treated with rEpo or placebo. Sensory neglect and apomorphine-induced rotation were measured at P27 and P28. Rats were killed at P30, blood was drawn, and the brains were perfusion-fixed for histology and immunohistochemistry. No differences in gross brain injury between rEpo and placebo-treated rats were found. Neonatal rEpo treatment protected dopamine neurons as indicated by the preservation of tyrosine hydroxylase-positive cells in the substantia nigra pars compacta and ventral tegmental area. rEpo treatment also improved functional outcomes by reducing sensory neglect and preventing the rotational asymmetry seen in control animals. No differences in hematocrit, white blood cell counts, neutrophil counts, or platelet counts were measured. We observed that rEpo treatment protected mesencephalic dopamine neurons and reduced the degree of behavioral asymmetries at 4 wk of life. On the basis of these findings, we conclude that further studies investigating the safety and efficacy of high-dose rEpo as a neuroprotective strategy are indicated in neonatal models of hypoxic-ischemic brain injury.

Neonatal Hypoxia/Ischemia Is Associated With Decreased Inflammatory Mediators After Erythropoietin Administration

Background and Purpose— Erythropoietin (EPO), a hematopoietic growth factor, has been shown to be neuroprotective when administered as either a pretreatment or posttreatment. This study tested the hypothesis that one of the mechanisms of protection afforded by posttreatment with recombinant human EPO (rh-EPO) is an anti-inflammatory effect via inhibition of interleukin (IL)-1β.

Methods— Seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 90 minutes of hypoxia (8% O 2 at 37°C). Pups were divided into the following groups: control, hypoxia/ischemia, and hypoxia/ischemia plus rh-EPO. In the rh-EPO–treated pups, rh-EPO (5 U/g body weight IP) was administered starting 24 hours after the insult and then for 2 additional days. Samples were collected at 3, 7, 14, and 21 days after the insult. IL-1β mRNA and protein levels were determined by quantitative real-time reverse transcription–polymerase chain reaction and ELISA. Tumor necrosis factor (TNF)-α mRNA levels were determined by colorimetric microplate assay.

Results— rhEPO attenuated brain injury, as assessed by brain weight, and attenuated both the hypoxia/ischemia–induced increases in IL-1β mRNA and protein levels. TNF-α mRNA levels did not increase at 3 to 14 days after the hypoxic/ischemic insult.

Conclusions— Administration of exogenous rh-EPO starting 24 hours after a hypoxic/ischemic insult is neuroprotective in the neonatal rat. This neuroprotective activity prevented the secondary, delayed rise in IL-1β and attenuated the infiltration of leukocytes into the ipsilateral hemisphere.

Erythropoietin improves functional and histological outcome in neonatal stroke

Neonatal stroke is a condition that leads to disability in later life, and as yet there is no effective treatment. Recently, erythropoietin (EPO) has been shown to be cytoprotective following brain injury and may promote neurogenesis. However, the effect of EPO on functional outcome and on morphologic changes in neonatal subventricular zone (SVZ) following experimental neonatal stroke has not been described. We used a transient focal model of neonatal stroke in P10 rat. Injury was documented by diffusion weighted MRI during occlusion. Immediately upon reperfusion, either EPO (5U/gm) or vehicle was administered intraperitoneally and animals were allowed to grow for 2 wk. Sensorimotor function was assessed using the cylinder rearing test and then brains were processed for volumetric analysis of the SVZ. Stroke induced SVZ expansion proportional to hemispheric volume loss. EPO treatment markedly preserved hemispheric volume and decreased the expansion of SVZ unilaterally. Furthermore, EPO treatment significantly improved the asymmetry of forelimb use following neonatal stroke. This functional improvement directly correlated with the amount of preserved hemispheric volume. These results suggest EPO may be a candidate in the treatment of neonatal stroke.

Potential for protection and repair following injury to the developing brain: a role for erythropoietin?

Perinatal brain injury is a major contributor to perinatal morbidity and mortality, and a considerable number of these children will develop long term neurodevelopmental disabilities. Despite the severe clinical and socio-economic significance and the advances in neonatal care over the past twenty years, no therapy yet exists that effectively prevents or ameliorates detrimental neurodevelopmental effects in cases of perinatal/neonatal brain injury. Our objective is to review recent evidence in relation to the pervading hypothesis for targeting time-dependent molecular and cellular repair mechanisms in the developing brain. In addition we review several potential neuroprotective strategies specific to the developing nervous system, with a focus on erythropoietin (Epo) because of its potential role in protection as well as repair.

Oxidative stress in the brain: novel cellular targets that govern survival during neurodegenerative disease

Despite our present knowledge of some of the cellular pathways that modulate central nervous system injury, complete therapeutic prevention or reversal of acute or chronic neuronal injury has not been achieved. The cellular mechanisms that precipitate these diseases are more involved than initially believed. As a result, identification of novel therapeutic targets for the treatment of cellular injury would be extremely beneficial to reduce or eliminate disability from nervous system disorders. Current studies have begun to focus on pathways of oxidative stress that involve a variety of cellular pathways. Here we discuss novel pathways that involve the generation of reactive oxygen species and oxidative stress, apoptotic injury that leads to nuclear degradation in both neuronal and vascular populations, and the early loss of cellular membrane asymmetry that mitigates inflammation and vascular occlusion. Current work has identified exciting pathways, such as the Wnt pathway and the serine-threonine kinase Akt, as central modulators that oversee cellular apoptosis and their downstream substrates that include Forkhead transcription factors, glycogen synthase kinase-3beta, mitochondrial dysfunction, Bad, and Bcl-x(L). Other closely integrated pathways control microglial activation, release of inflammatory cytokines, and caspase and calpain activation. New therapeutic avenues that are just open to exploration, such as with brain temperature regulation, nicotinamide adenine dinucleotide modulation, metabotropic glutamate system modulation, and erythropoietin targeted expression, may provide both attractive and viable alternatives to treat a variety of disorders that include stroke, Alzheimer's disease, and traumatic brain injury.

Erythropoietin after focal cerebral ischemia activates the Janus kinase-signal transducer and activator of transcription signaling pathway and improves brain injury in postnatal day 7 rats

Erythropoietin (Epo) plays a central role in erythropoiesis but also has neuroprotective properties. Recently, Epo-related neuroprotective studies used a hypoxic-ischemic neonatal model, which is different from focal stroke, a frequent cause of neonatal brain injury. We report on the effects of Epo treatment given after focal stroke and its potential neuroprotective mechanisms in postnatal day 7 rats with focal cerebral ischemia (FCI) achieved by occlusion of the middle cerebral artery. The experimental groups included sham operation, FCI plus vehicle, and FCI plus Epo. In the Epo-treated group, pups received a single intraperitoneal injection of 1000 U/kg 15 min after FCI or three injections of 100, 1000, or 5000 U/kg, starting at 15 min and repeated at 1 and 2 d after FCI. Epo treatment produced significant reductions in the mean infarct area and volume at 1 and 3 d after FCI, demonstrated by 2,3,5-triphenyltetrazolium chloride staining. Terminal deoxynucleotidyltransferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL) staining showed a markedly reduced number of TUNEL-positive cells in the Epo-treated group when compared with the vehicle control 3 d after FCI (p<0.01). The most effective dose after FCI was 1000 U/kg for 3 d. Immunoanalyses showed that Epo induced a significant increase in phosphorylated Janus kinase 2 and signal transducer and activator of transcription-5 expressions at 1 and 3 d and up-regulated Bcl-xL expression by 24 h after FCI but did not affect Epo receptor or NF-kappaB expression. In conclusion, Epo given after FCI in neonatal rats provides significant neuroprotection, mediated possibly by activation of the Janus kinase-signal transducer and activator of transcription-Bcl-xL signaling pathways.

Erythropoietin on a tightrope: balancing neuronal and vascular protection between intrinsic and extrinsic pathways

Enthusiasm for erythropoietin (EPO) as a broad cytoprotective agent continues to increase at an almost exponential rate. The premise that EPO was required only for erythropoiesis was eventually shed by recent work demonstrating the existence of EPO and its receptor in other organs and tissues outside of the liver and the kidney, such as the brain and heart. As a result, EPO has been identified as a possible candidate in the formulation of therapeutic strategies for both cardiac and nervous system diseases. EPO has been shown to mediate an array of vital cellular functions that involve progenitor stem cell development, cellular protection, angiogenesis, DNA repair, and cellular longevity. An important requirement to achieve the goal of preventing or even reducing cellular injury by any cytoprotective agent is the ability to uncover the cellular pathways that ultimately drive a cell to its demise. We present for consideration several critical cellular pathways modulated by EPO that involve Janus kinase 2 (Jak2), the serine-threonine kinase Akt, forkhead transcription factors, glycogen synthase kinase-3beta (GSK-3beta), cellular calcium, protein kinase C, caspases, as well as the control of inflammatory microglial activation. As we continue to gain new insight into these pathways, EPO should emerge as a critical agent for the development, maturation, and survival of cells throughout the body.

Auditory processing deficits in rats with neonatal hypoxic-ischemic injury

Hypoxia-ischemia (HI) refers to reduced blood oxygenation and/or a diminished amount of blood perfusing the brain, and is associated with premature birth/very low birth weight (VLBW). HI represents a common cause of injury to the perinatal brain. Indeed, a significant number of premature/VLBW infants go on to demonstrate cognitive/behavioral deficits, with particularly high incidence of disruptions in language development. Auditory processing deficits, in turn, have been suggested to play a causal role in the development of language impairments. Specifically, the inability to identify fast elements in speech is purported to exert cascading detrimental effects on phonological discrimination, processing, and identification. Based on this convergent evidence, the current studies address auditory processing evaluation in a rodent model of HI injury induced on postnatal days 1, 7, or 10 (which in turn is well accepted as modeling HI-related injury to the perinatal human). Induced injuries were followed by a battery of auditory testing, and a spatial maze assessment, performed both during juvenile and adult periods. Results indicate that rats suffering from these early HI insults performed significantly worse than shams on tasks requiring rapid auditory processing, and on a test of spatial learning (Morris water maze (MWM)), although these effects were not seen on simpler versions of auditory tasks or on a water escape assessment (thus ruling out hearing/motor impairments). Correlations were found between performance on rapid auditory and spatial behavioral tasks and neuroanatomical measures for HI animals such as: the volume of the hippocampus, cerebral cortex, ventricles, and/or the area of the corpus callosum. Cumulative findings suggest that perinatal HI injury in the rat may lead to neurodevelopmental damage associated, in turn, with auditory processing and/or learning and memory impairments. As such, the current model may have critical implications for the study of neurophysiological underpinnings of cognitive deficits in premature/VLBW infants.

New avenues of exploration for erythropoietin

Discovery that the hormone erythropoietin (EPO) and its receptor play a significant biological role in tissues outside of the hematopoietic system has fueled significant interest in EPO as a novel cytoprotective agent in both neuronal and vascular systems. Erythropoietin is now considered to have applicability in a variety of disorders that include cerebral ischemia, myocardial infarction, and chronic congestive heart failure. Erythropoietin modulates a broad array of cellular processes that include progenitor stem cell development, cellular integrity, and angiogenesis. As a result, cellular protection by EPO is robust and EPO inhibits the apoptotic mechanisms of injury, including the preservation of cellular membrane asymmetry to prevent inflammation. As the investigation into clinical applications for EPO that maximize efficacy and minimize toxicity progresses, a deeper appreciation for the novel roles that EPO plays in the brain and heart and throughout the entire body should be acquired.

Have no fear, erythropoietin is here: erythropoietin protects fear conditioning performances after functional inactivation of the amygdala

This study investigated the capacity of erythropoietin (EPO) to protect fear conditioning performances against functional inactivation of the amygdala. We infused an excitotoxic dose of glutamate in the lateral nucleus of the amygdala (LA) of adult rats in order to block the output projections to brainstem areas controlling the expression of conditioned fear responses. Subsequently, animals with excitotoxic lesions in the LA displayed altered short and long-term fear conditioned responses, but the integrity of their general emotional reactivity was preserved, as indicated by their open-field behavior. EPO infused immediately after glutamate succeeded to protect the conditioned fear performances of rats. This effect was reliably represented on both short, and long-term memory tests of conditioned fear. This and other studies have supported the potent neuroprotective activity of EPO, discriminable both morphologically, and behaviorally.