Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I

Transcriptomic and bioinformatics analysis of the mechanism by which erythropoietin promotes recovery from traumatic brain injury in mice

Recent studies have found that erythropoietin promotes the recovery of neurological function after traumatic brain injury. However, the precise mechanism of action remains unclear. In this study, we induced moderate traumatic brain injury in mice by intraperitoneal injection of erythropoietin for 3 consecutive days. RNA sequencing detected a total of 4065 differentially expressed RNAs, including 1059 mRNAs, 92 microRNAs, 799 long non-coding RNAs, and 2115 circular RNAs. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analyses revealed that the coding and non-coding RNAs that were differentially expressed after traumatic brain injury and treatment with erythropoietin play roles in the axon guidance pathway, Wnt pathway, and MAPK pathway. Constructing competing endogenous RNA networks showed that regulatory relationship between the differentially expressed non-coding RNAs and mRNAs. Because the axon guidance pathway was repeatedly enriched, the expression of Wnt5a and Ephb6, key factors in the axonal guidance pathway, was assessed. Ephb6 expression decreased and Wnt5a expression increased after traumatic brain injury, and these effects were reversed by treatment with erythropoietin. These findings suggest that erythropoietin can promote recovery of nerve function after traumatic brain injury through the axon guidance pathway.

Synergism of Carbamoylated Erythropoietin and Insulin-like Growth Factor-1 in Immediate Early Gene Expression

Trophic factors are secreted proteins that can modulate neuronal integrity, structure, and function. Previous preclinical studies have shown synergistic effects on decreasing apoptosis and improving behavioral performance after stroke when combining two such trophic factors, erythropoietin (EPO) and insulin-like growth factor-1 (IGF-1). However, EPO can elevate the hematocrit level, which can be life-threatening for non-anemic individuals. A chemically engineered derivative of EPO, carbamoylated EPO (CEPO), does not impact hematological parameters but retains neurotrophic effects similar to EPO. To obtain insight into CEPO and IGF-1 combination signaling, we examined immediate early gene (IEG) expression after treatment with CEPO, IGF-1, or CEPO + IGF-1 in rat pheochromocytoma (PC-12) cells and found that combining CEPO and IGF-1 produced a synergistic increase in IEG expression. An in vivo increase in the protein expression of Npas4 and Nptx2 was also observed in the rat hippocampus. We also examined which kinase signaling pathways might be mediating these effects and found that while AKT inhibition did not alter the pattern of IEG expression, both ERK and JAK2 inhibition significantly decreased IEG expression. These results begin to define the molecular effects of combining CEPO and IGF-1 and indicate the potential for these trophic factors to produce positive, synergistic effects.

Asialo-rhuEPO as a Potential Neuroprotectant for Ischemic Stroke Treatment

Neuroprotective drugs to protect the brain against cerebral ischemia and reperfusion (I/R) injury are urgently needed. Mammalian cell-produced recombinant human erythropoietin (rhuEPOM) has been demonstrated to have excellent neuroprotective functions in preclinical studies, but its neuroprotective properties could not be consistently translated in clinical trials. The clinical failure of rhuEPOM was thought to be mainly due to its erythropoietic activity-associated side effects. To exploit its tissue-protective property, various EPO derivatives with tissue-protective function only have been developed. Among them, asialo-rhuEPO, lacking terminal sialic acid residues, was shown to be neuroprotective but non-erythropoietic. Asialo-rhuEPO can be prepared by enzymatic removal of sialic acid residues from rhuEPOM (asialo-rhuEPOE) or by expressing human EPO gene in glycoengineered transgenic plants (asialo-rhuEPOP). Both types of asialo-rhuEPO, like rhuEPOM, displayed excellent neuroprotective effects by regulating multiple cellular pathways in cerebral I/R animal models. In this review, we describe the structure and properties of EPO and asialo-rhuEPO, summarize the progress on neuroprotective studies of asialo-rhuEPO and rhuEPOM, discuss potential reasons for the clinical failure of rhuEPOM with acute ischemic stroke patients, and advocate future studies needed to develop asialo-rhuEPO as a multimodal neuroprotectant for ischemic stroke treatment.

The Role of PI3K/AKT and MAPK Signaling Pathways in Erythropoietin Signalization

Erythropoietin (EPO) is a glycoprotein cytokine known for its pleiotropic effects on various types of cells and tissues. EPO and its receptor EPOR trigger signaling cascades JAK2/STAT5, MAPK, and PI3K/AKT that are interconnected and irreplaceable for cell survival. In this article, we describe the role of the MAPK and PI3K/AKT signaling pathways during red blood cell formation as well as in non-hematopoietic tissues and tumor cells. Although the central framework of these pathways is similar for most of cell types, there are some stage-specific, tissue, and cell-lineage differences. We summarize the current state of research in this field, highlight the novel members of EPO-induced PI3K and MAPK signaling, and in this respect also the differences between erythroid and non-erythroid cells.

Past and Future Biologics for Otologic Disorders

Biologic therapies have the ability to fundamentally change the management of hearing loss; clinicians need to familiarize themselves with their prospective applications in practice. This article reviews the current application of 4 categories of biological therapeutics-growth factors, apoptosis inhibitors, monoclonal antibodies, and gene therapy-in otology and their potential future directions and applications.

Experimental Study on the Correlation between miRNA-373 and HIF-1α, MMP-9, and VEGF in the Development of HIE

INTRODUCTION

Microribonucleic acids (miRNAs) have short (approximately 18 to 25) nucleotides and are evolutionarily conserved and endogenously expressed RNAs belonging to a family of noncoding RNA molecules. miRNA-373 regulates cell proliferation, migration, apoptosis, invasion, and repairing damaged DNA after hypoxia stress. Neonatal hypoxic-ischemic encephalopathy (HIE) refers to perinatal asphyxia caused by partial or complete hypoxia, reduced or suspended cerebral blood flow, and fetal or neonatal brain damage. We aim to investigate the relationship between miRNA-373 and HIF-1α, between miRNA-373 MMP-9, and between miRNA-373 VEGF in the occurrence and development of HIE.

METHODS

Human (children) samples were divided into four groups (n = 15 in each group) according to HIE severity. The patient group was divided into middle, moderate, and severe HIE groups. The control group included healthy children or children with nonneurological diseases. The expressions of miRNA-373, HIF-1α, MMP-9, and VEGF were assayed in the serum samples.

RESULTS

Our study showed a strong relationship between miRNA-373 and HIF-1α, between miRNA-373 and MMP-9, and between miRNA-373 and VEGF. The expression levels of miRNA-373, HIF-1α, MMP-9, and VEGF in the HIE groups were much higher than those of the control group.

CONCLUSION

The increased change in miRNA-373 expression has a certain diagnostic significance on neonatal HIE. In the occurrence and development of HIE, miRNA-373 is positively correlated with HIF-1α, MMP-9, and VEGF.

Otoprotection to Implanted Cochlea Exposed to Noise Trauma With Dexamethasone Eluting Electrode

Cochlear implantation (CI) is now widely used to provide auditory rehabilitation to individuals having severe to profound sensorineural hearing loss (SNHL). However, CI can lead to electrode insertion trauma (EIT) that can cause damage to sensory cells in the inner ear resulting in loss of residual hearing. Even with soft surgical techniques where there is minimal macroscopic damage, we can still observe the generation of molecular events that may initiate programmed cell death via various mechanisms such as oxidative stress, the release of pro-inflammatory cytokines, and activation of the caspase pathway. In addition, individuals with CI may be exposed to noise trauma (NT) due to occupation and leisure activities that may affect their hearing ability. Recently, there has been an increased interest in the auditory community to determine the efficacy of drug-eluting electrodes for the protection of residual hearing. The objective of this study is to determine the effect of NT on implanted cochlea as well as the otoprotective efficacy of dexamethasone eluting electrode to implanted cochlea exposed to NT in a guinea pig model of CI. Animals were divided into five groups: EIT with dexamethasone eluting electrode exposed to NT; EIT exposed to NT; NT only; EIT only and naïve animals (control group). The hearing thresholds were determined by auditory brainstem recordings (ABRs). The cochlea was harvested and analyzed for transcript levels of inflammation, apoptosis and fibrosis genes. We observed that threshold shifts were significantly higher in EIT, NT or EIT + NT groups compared to naive animals at all the tested frequencies. The dexamethasone eluting electrode led to a significant decrease in hearing threshold shifts in implanted animals exposed to NT. Proapoptotic tumor necrosis factor-α [TNF-α, TNF-α receptor 1a (TNFαR1a)] and pro-fibrotic transforming growth factor β1 (TGFβ) genes were more than two-fold up-regulated following EIT and EIT + NT compared to the control group. The use of dexamethasone releasing electrode significantly decreased the transcript levels of pro-apoptotic and pro-fibrotic genes. The dexamethasone releasing electrode has shown promising results for hearing protection in implanted animals exposed to NT. The results of this study suggest that dexamethasone releasing electrode holds great potential in developing effective treatment modalities for NT in the implanted cochlea.

Insulin attenuates apoptosis in neuronal cells by an integrin-linked kinase-dependent mechanism

Insulin promotes neuronal survival by activating a phosphatidylinositol 3-kinase (PI 3-kinase)/AKT-dependent signaling pathway and reducing caspase activation. We investigated a role for integrin-linked kinase (ILK) in insulin-mediated cell survival in cultured neurons and differentiated R28 cells. We used a serum and depolarization withdrawal model to induce apoptosis in cerebellar granule neurons and a serum withdrawal model to induce apoptosis in differentiated R28 cells. ILK knock-out decreased insulin-mediated protection as did the addition of pharmacological inhibitors of ILK, KP-392 or QLT-0267. Prosurvival effects of insulin were rescued by Boc-Asp (O-methyl)-CH₂F (BAF), a pancaspase inhibitor, in the presence of KP-392. Insulin and IGF-1 decreased caspase-3 activation, an effect that was inhibited by KP-392 and QLT-0267. Western blot analysis indicates that insulin-induced stimulation of AKT Ser-473 phosphorylation was decreased after the ILK gene was conditionally knocked-out, following overexpression of AKT-DN or in the presence of QLT-0267. Insulin and IGF-1 stimulated ILK kinase activity in primary neurons and this was inhibited following ILK-DN overexpression. Western blot analysis indicates that insulin exposure upregulated the expression of the cellular inhibitor of apoptosis protein c-IAP2 in an extracellular matrix-dependent manner, an effect blocked by KP-392. These results indicate that ILK is an important effector in insulin-mediated neuroprotection.

EPO promotes axonal sprouting via upregulating GDF10

Erythropoietin (EPO) has an exact neuroprotective effect on stroke. However, it remains unknown whether it participates in axonal sprouting after neuron damage. Growth and differentiation factor 10 (GDF10) has been shown to be a trigger of axonal sprouting after stroke. Hence, it was hypothesized that EPO promotes axonal sprouting mainly through GDF10. In the present in vitro experiment, it was found that EPO could promote axonal sprouting and GDF10 expression in a dose-dependent manner. The knockdown of GDF10 using siRNA abolished the effect of EPO-mediated axonal sprouting, indicating that GDF10 is the executor of EPO-mediated axonal sprouting. The treatment of neurons with nuclear factor-kappaB (NF-κB) inhibitor JSH-23 could inhibit the accumulation of NF-κB phospho-p65 (p-p65) in the nucleus, the upregualtion of GDF10 and extending of axonal length. Furthermore, the addition of Janus kinase 2 (JAK2) inhibitor CEP-33779 or phosphoinositide 3-kinase (PI3K) inhibitor LY294002 to the culture medium also blocked the nuclear translocation of p-p65, the expression of GDF10, and axonal sprouting, suggesting that EPO induces axonal sprouting via activating cellular JAK2 and PI3K signaling. Impeding JAK2 signaling with CEP-33779 can suppress the phosphorylation of PI3K, and this confirms that the upstream of PI3K signaling is JAK2. These present results provide a novel insight into the role of EPO and the molecular mechanism of axonal sprouting, which is beneficial for the development of novel approaches for neurological recovery after brain injury, including stroke.

Defining the Inflammatory Microenvironment in the Human Cochlea by Perilymph Analysis: Toward Liquid Biopsy of the Cochlea

The molecular pathomechanisms in the majority of patients suffering from acute or progressive sensorineural hearing loss cannot be determined yet. The size and the complex architecture of the cochlea make biopsy and in-depth histological analyses impossible without severe damage of the organ. Thus, histopathology correlated to inner disease is only possible after death. The establishment of a technique for perilymph sampling during cochlear implantation may enable a liquid biopsy and characterization of the cochlear microenvironment. Inflammatory processes may not only participate in disease onset and progression in the inner ear, but may also control performance of the implant. However, little is known about cytokines and chemokines in the human inner ear as predictive markers for cochlear implant performance. First attempts to use multiplex protein arrays for inflammatory markers were successful for the identification of cytokines, chemokines, and endothelial markers present in the human perilymph. Moreover, unsupervised cluster and principal component analyses were used to group patients by lead cytokines and to correlate certain proteins to clinical data. Endothelial and epithelial factors were detected at higher concentrations than typical pro-inflammatory cytokines such as TNF-a or IL-6. Significant differences in VEGF family members have been observed comparing patients with deafness to patients with residual hearing with significantly reduced VEGF-D levels in patients with deafness. In addition, there is a trend toward higher IGFBP-1 levels in these patients. Hence, endothelial and epithelial factors in combination with cytokines may present robust biomarker candidates and will be investigated in future studies in more detail. Thus, multiplex protein arrays are feasible in very small perilymph samples allowing a qualitative and quantitative analysis of inflammatory markers. More results are required to advance this method for elucidating the development and course of specific inner ear diseases or for perioperative characterization of cochlear implant patients.

Biological therapies in otology

Hearing loss is present in millions of people worldwide. Current treatment for patients with severe to profound hearing loss consists of cochlear implantation. Providing the cochlear nerve is intact, patients generally benefit greatly from this intervention, frequently achieving significant improvements in speech comprehension. There are, however, some cases where current technology does not provide patients with adequate benefit. Ongoing research in cell transplantation and gene therapy promises to lead to new developments that will improve the function of cochlear implants. Translation of these experimental approaches is presently at an early stage. This review focuses on the application of biological therapies in severe hearing loss and discusses some of the barriers to translating basic scientific research into clinical reality. We emphasize the application of these novel therapies to cochlear implantation.

Biological Effects of Tetrahydroxystilbene Glucoside: An Active Component of a Rhizome Extracted from Polygonum multiflorum

Polygonum multiflorum Thunb. (PM), a traditional Chinese medicinal herb, has been widely used in the Orient as a tonic and antiaging agent. 2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside (TSG, C20H22O9, FW = 406.38928) is one of the active components extracted from PM. TSG is an antioxidant agent, which exhibits remarkable antioxidative activities in vivo and in vitro. The antioxidant effect of TSG is achieved by its radical-scavenging effects. TSG can inhibit apoptosis and protect neuronal cells against injury through multifunctional cytoprotective pathways. TSG performs prophylactic and therapeutic activities against Alzheimer's disease, Parkinson's disease, and cerebral ischemia/reperfusion injury. It is also antiatherosclerotic and anti-inflammatory. However, the mechanisms underlying these pharmacological activities are unclear. This study aimed at reviewing experimental studies and describing the effectiveness and possible mechanisms of TSG.

A New Approach to Cerebral Palsy Treatment: Discussion of the Effective Components of Umbilical Cord Blood and its Mechanisms of Action

Cerebral palsy (CP) includes a group of persistent non-progressive disorders affecting movement, muscle tone, and/or posture. The total economic loss during the life-span of an individual with CP places a heavy financial burden on such patients and their families worldwide; however, a complete cure is still lacking. Umbilical cord blood (UCB)-based interventions are emerging as a scientifically plausible treatment and possible cure for CP. Stem cells have been used in many experimental CP animal models and achieved good results. Compared with other types of stem cells, those from UCB have advantages in terms of treatment safety and efficacy, ethics, non-neoplastic proliferation, accessibility, ease of preservation, and regulation of immune responses, based on findings in animal models and clinical trials. Currently, the use of UCB-based interventions for CP is limited as the components of UCB are complex and possess different therapeutic mechanisms. These can be categorized by three aspects: homing and neuroregeneration, trophic factor secretion, and neuroprotective effects. Our review summarizes the features of active components of UCB and their therapeutic mechanism of action. This review highlights current research findings and clinical evidence regarding UCB that contribute to treatment suggestions, inform decision-making for therapeutic interventions, and help to direct future research.

Evaluation of intranasal delivery route of drug administration for brain targeting

The acute or chronic drug treatments for different neurodegenerative and psychiatric disorders are challenging from several aspects. The low bioavailability and limited brain exposure of oral drugs, the rapid metabolism, elimination, the unwanted side effects and also the high dose to be added mean both inconvenience for the patients and high costs for the patients, their family and the society. The reason of low brain penetration of the compounds is that they have to overcome the blood-brain barrier which protects the brain against xenobiotics. Intranasal drug administration is one of the promising options to bypass blood-brain barrier, to reduce the systemic adverse effects of the drugs and to lower the doses to be administered. Furthermore, the drugs administered using nasal route have usually higher bioavailability, less side effects and result in higher brain exposure at similar dosage than the oral drugs. In this review the focus is on giving an overview on the anatomical and cellular structure of nasal cavity and absorption surface. It presents some possibilities to enhance the drug penetration through the nasal barrier and summarizes some in vitro, ex vivo and in vivo technologies to test the drug delivery across the nasal epithelium into the brain. Finally, the authors give a critical evaluation of the nasal route of administration showing its main advantages and limitations of this delivery route for CNS drug targeting.

Leukemia inhibitory factor inhibits erythropoietin-induced myelin gene expression in oligodendrocytes

Background

The pro-myelinating effects of leukemia inhibitory factor (LIF) and other cytokines of the gp130 family, including oncostatin M (OSM) and ciliary neurotrophic factor (CNTF), have long been known, but controversial results have also been reported. We recently overexpressed erythropoietin receptor (EPOR) in rat central glia-4 (CG4) oligodendrocyte progenitor cells (OPCs) to study the mechanisms mediating the pro-myelinating effects of erythropoietin (EPO). In this study, we investigated the effect of co-treatment with EPO and LIF.

Methods

Gene expression in undifferentiated and differentiating CG4 cells in response to EPO and LIF was analysed by DNA microarrays and by RT-qPCR. Experiments were performed in biological replicates of N ≥ 4. Functional annotation and biological term enrichment was performed using DAVID (Database for Annotation, Visualization and Integrated Discovery). The gene-gene interaction network was visualised using STRING (Search Tool for the Retrieval of Interacting Genes).

Results

In CG4 cells treated with 10 ng/ml of EPO and 10 ng/ml of LIF, EPO-induced myelin oligodendrocyte glycoprotein (MOG) expression, measured at day 3 of differentiation, was inhibited ≥4-fold (N = 5, P < 0.001). Inhibition of EPO-induced MOG was also observed with OSM and CNTF. Analysis of the gene expression profile of CG4 differentiating cells treated for 20 h with EPO and LIF revealed LIF inhibition of EPO-induced genes involved in lipid transport and metabolism, previously identified as positive regulators of myelination in this system. In addition, among the genes induced by LIF, and not by differentiation or by EPO, the role of suppressor of cytokine signaling 3 (SOCS3) and toll like receptor 2 (TLR2) as negative regulators of myelination was further explored. LIF-induced SOCS3 was associated with MOG inhibition; Pam3, an agonist of TLR2, inhibited EPO-induced MOG expression, suggesting that TLR2 is functional and its activation decreases myelination.

Conclusions

Cytokines of the gp130 family may have negative effects on myelination, depending on the cytokine environment.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0052-3) contains supplementary material, which is available to authorized users.

Synergistic Reduction of Apoptosis With Diazoxide and Erythropoietin in Spinal Cord Ischemic Injury

BACKGROUND

Paraplegia remains a devastating complication of thoracoabdominal aortic intervention. Metabolic stress induces expression of beta common receptor subunit of erythropoietin (EPO) receptor (βcR) to exert a neuroprotective effect in spinal cord ischemia reperfusion injury (SCIR). Diazoxide (DZ) has been shown to induce ischemic tolerance. We previously reported that DZ upregulated βcR expression and enhanced the neuroprotective effects of EPO through the upregulation of βcR. We hypothesize that βcR expression induced by DZ before ischemia amplifies the antiapoptotic effects of EPO in a murine model of SCIR.

METHODS

Experimental groups included phosphate-buffered saline (PBS) pretreatment + PBS immediately before the operation, PBS+EPO, DZ+PBS, DZ+EPO, and sham. Spinal cord ischemia was induced by a 4-minute thoracic aortic cross-clamp. Functional scoring (Basso Mouse Score) was done at 12-hour intervals for 48 hours. Spinal cords were harvested for histologic analysis, and antiapoptotic factors (caspase 3, 8, and 9, B-cell lymphoma-2, and neuroglobin) were evaluated by Western blot analysis.

RESULTS

The motor function of DZ+EPO group was significantly preserved compared with all other groups. The levels of cleaved caspase 8 and 3 in DZ+EPO were significantly lower than in the other groups. Mice treated with DZ+EPO had significantly fewer terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling-positive cells than other groups.

CONCLUSIONS

Optimized upregulation of βcR by DZ can increase the extrinsic antiapoptotic effects of EPO. Better understanding of this synergetic mechanism may serve to help prevent ischemic complications caused by aortic intervention.

[Biological therapies in otology. German version]

Millions of people worldwide suffer from hearing loss. Current treatment for patients with severe to profound hearing loss consists of cochlear implants. Providing the cochlear nerve is intact, patients generally benefit enormously from this intervention, frequently achieving significant improvements in speech comprehension. There are, however, some cases where current technology does not provide patients with adequate benefit. New therapeutic concepts based on cell transplantation and gene therapy are developing rapidly, at least in the research sector. Compared to the wealth of basic research available in this area, translation of these new experimental approaches into clinical application is presently at a very early stage. The current review focuses on translatable treatment concepts and discusses the barriers that need to be overcome in order to translate basic scientific research into clinical reality. Furthermore, the first examples of clinical application of biological therapies in severe hearing loss are presented, particularly in connection with cochlear implants.

Oxaloacetate and adipose stromal cells-conditional medium synergistically protected potassium/serum deprivation-induced neuronal apoptosis

Adipose stromal cells conditioned media (ASC-CM) protect neurons in a variety of neuronal death models including potassium/serum deprivation-induced neuronal apoptosis. In this study, we found that ASC-CM contained glutamate oxaloacetate transaminase and its substrate, oxaloacetate (OAA) directly protected cerebellar granule neurons (CGN) from apoptosis induced by serum and potassium deprivation. Additionally, OAA inhibited serum and potassium deprivation-induced caspase 3 activation. ASC-CM and OAA in combination had a synergistic neuroprotective effect. Clearly, different from ASC-CM-induced neuroprotection, OAA-induced neuroprotection was Akt- independent but JNK-dependent. These data establish a mechanistic basis supporting that the application of ASC-CM for neuroprotective treatments could be significantly enhanced by addition of OAA.

The therapeutic potential of insulin-like growth factor-1 in central nervous system disorders

Central nervous system (CNS) development is a finely tuned process that relies on multiple factors and intricate pathways to ensure proper neuronal differentiation, maturation, and connectivity. Disruption of this process can cause significant impairments in CNS functioning and lead to debilitating disorders that impact motor and language skills, behavior, and cognitive functioning. Recent studies focused on understanding the underlying cellular mechanisms of neurodevelopmental disorders have identified a crucial role for insulin-like growth factor-1 (IGF-1) in normal CNS development. Work in model systems has demonstrated rescue of pathophysiological and behavioral abnormalities when IGF-1 is administered, and several clinical studies have shown promise of efficacy in disorders of the CNS, including autism spectrum disorder (ASD). In this review, we explore the molecular pathways and downstream effects of IGF-1 and summarize the results of completed and ongoing pre-clinical and clinical trials using IGF-1 as a pharmacologic intervention in various CNS disorders. This aim of this review is to provide evidence for the potential of IGF-1 as a treatment for neurodevelopmental disorders and ASD.

The combination of insulin-like growth factor 1 and erythropoietin protects against ischemic spinal cord injury in rabbits

INTRODUCTION

Insulin-like growth factor 1 (IGF-1) and erythropoietin (EPO) have been reported to independently protect against ischemic spinal cord injury in rabbits. In the present study, we investigated whether the combination of IGF-1 and EPO protects against ischemic spinal cord injury in rabbits.

METHODS

Animals were assigned to 1 of 4 groups (n = 6 in each): a control group (saline), an IGF-1 group (IGF-1 0.3 mg/kg), an EPO group (EPO 800 U/kg), or an IGF-1 + EPO group (IGF-1 0.3 mg/kg + EPO 800 U/kg). Spinal cord ischemia was produced by occluding the abdominal aorta for 15 min. Saline, IGF-1, and EPO were administered intravenously just after the start of reperfusion. Hindlimb motor function was assessed daily for 7 days, after which histopathological evaluation was performed. To analyze phosphorylation of signal transduction molecules, animals were assigned to 1 of the 4 groups (n = 8 in each). Spinal cord ischemia and the treatment were the same as those described above. The spinal cords were removed at 15 or 30 min after reperfusion and used to analyze phosphorylation of signal transduction molecules. Four animals served as the preischemic control, and the spinal cord was removed just before the start of ischemia.

RESULTS

In the IGF-1 + EPO group, both neurological and histopathological outcomes were significantly improved as compared to the control group, which was consistent with the increase of Janus kinase-2 (JAK2) phosphorylation.

CONCLUSIONS

The combination of IGF-1 and EPO protects against ischemic spinal cord injury in rabbits. JAK2 might contribute to the protective effect.

Activity increase in EpoR and Epo expression by intranasal recombinant human erythropoietin (rhEpo) administration in ischemic hippocampi of adult rats

Erythropoietin in the nervous system is a potential neuroprotective factor for cerebral ischemic damage due to specific-binding to the erythropoietin receptor, which is associated with survival mechanisms. However, the role of its receptor is unclear. Thus, this work assessed whether a low dose (500UI/Kg) of intranasal recombinant human erythropoietin administered 3h after ischemia induced changes in the activation of its receptor at the Tyr456-phosphorylated site in ischemic hippocampi in rats. The results showed that recombinant human erythropoietin after injury maintained cell survival and was associated with an increase in receptor phosphorylation at the Tyr456 site as an initial signaling step, which correlated with a neuroprotective effect.

Propofol anesthesia induces proapoptotic tumor necrosis factor-α and pro-nerve growth factor signaling and prosurvival Akt and XIAP expression in neonatal rat brain

Previously we observed that prolonged exposure to propofol anesthesia causes caspase-3- and calpain-mediated neuronal death in the developing brain. The present study examines the effects of propofol anesthesia on the expression of tumor necrosis factor-α (TNFα), pro-nerve growth factor (NGF), and their receptors in the cortex and the thalamus. We also investigated how propofol influences the expression of Akt and X-linked inhibitor of apoptosis (XIAP) expression, proteins that promote prosurvival pathways. Seven-day-old rats (P7) were exposed to propofol anesthesia lasting 2, 4, or 6 hr and killed 0, 4, 16, or 24 hr after anesthesia termination. The relative levels of mRNA and protein expression were estimated by RT-PCR and Western blot analysis, respectively. The treatments caused marked activation of TNFα and its receptor TNFR-1 and pro-NGF and p75(NTR) receptor expression. In parallel with the induction of these prodeath signals, we established that propofol anesthesia promotes increased expression of the prosurvival molecules pAkt and XIAP during the 24-hr postanesthesia period. These results show that different brain structures respond to propofol anesthesia with a time- and duration of exposure-dependent increase in proapoptotic signaling and with concomitant increases in activities of prosurvival proteins. We hypothesized that the fine balance between these opposing processes sustains homeostasis in the immature rat brain and prevents unnecessary damage after exposure to an injurious stimulus. The existence of this highly regulated process provides a time frame for potential therapeutic intervention directed toward suppressing the deleterious component of propofol anesthesia.

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.

Definition of a Family of Tissue-Protective Cytokines Using Functional Cluster Analysis: A Proof-of-Concept Study

The discovery of the tissue-protective activities of erythropoietin (EPO) has underlined the importance of some cytokines in tissue-protection, repair, and remodeling. As such activities have been reported for other cytokines, we asked whether we could define a class of tissue-protective cytokines. We therefore explored a novel approach based on functional clustering. In this pilot study, we started by analyzing a small number of cytokines (30). We functionally classified the 30 cytokines according to their interactions by using the bioinformatics tool STRING (Search Tool for the Retrieval of Interacting Genes), followed by hierarchical cluster analysis. The results of this functional clustering were different from those obtained by clustering cytokines simply according to their sequence. We previously reported that the protective activity of EPO in a model of cerebral ischemia was paralleled by an upregulation of synaptic plasticity genes, particularly early growth response 2 (EGR2). To assess the predictivity of functional clustering, we tested some of the cytokines clustering close to EPO (interleukin-11, IL-11; kit ligand, KITLG; leukemia inhibitory factor, LIF; thrombopoietin, THPO) in an in vitro model of human neuronal cells for their ability to induce EGR2. Two of these, LIF and IL-11, induced EGR2 expression. Although these data would need to be extended to a larger number of cytokines and the biological validation should be done using more robust in vivo models, rather then just one cell line, this study shows the feasibility of this approach. This type of functional cluster analysis could be extended to other fields of cytokine research and help design biological experiments.

Autonomic neuropathy in experimental models of diabetes mellitus

Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.

Spatial distribution of insulin-like growth factor binding protein-2 following hypoxic-ischemic injury

BACKGROUND

Insulin-like growth factor binding protein-2 (IGFBP-2) regulates the bioavailability, transportation, and localization of insulin-like growth factor-I (IGF-I), an effective neuroprotectant in animal stroke models especially when administered intranasally. Therefore, determining IGFBP-2's endogenous distribution in the normal and ischemic brain is essential in maximizing the neuroprotective potential of the intranasal IGF-I treatment approach. However, current data on IGFBP-2 is limited to mRNA and in situ hybridization studies. The purpose of this study was to determine if there are any changes in IGFBP-2 protein levels and distribution in ischemic brain and also to determine if IGFBPs play a role in the transportation of intranasally administered IGF-I into the brain.

RESULTS

Using an in vitro approach, we show that ischemia causes changes in the distribution of IGFBP-2 in primary cortical neurons and astrocytes. In addition, we show using the transient middle cerebral artery occlusion (MCAO) model in mice that there is a significant increase in IGFBP-2 levels in the stroke penumbra and core after 72 h. This correlated with an overall increase in IGF-I after stroke, with the highest levels of IGF-I in the stroke core after 72 h. Brain sections from stroke mice indicate that neurons and astrocytes located in the penumbra both have increased expression of IGFBP-2, however, IGFBP-2 was not detected in microglia. We used binding competition studies to show that intranasally administered exogenous IGF-I uptake into the brain is not receptor mediated and is likely facilitated by IGFBPs.

CONCLUSIONS

The change in protein levels indicates that IGFBP-2 plays an IGF-I-dependent and -independent role in the brain's acute (neuroprotection) and chronic (tissue remodeling) response to hypoxic-ischemic injury. Competition studies indicate that IGFBPs may have a role in rapid transportation of exogenous IGF-I from the nasal tissue to the site of injury.

Erythropoietin signaling promotes oligodendrocyte development following prenatal systemic hypoxic-ischemic brain injury

BACKGROUND

Brain injury from preterm birth causes white matter injury (WMI), and it leads to chronic neurological deficits including cerebral palsy, epilepsy, cognitive, and behavioral delay. Immature O4+ oligodendrocytes are particularly vulnerable to WMI. Understanding how the developing brain recovers after injury is essential to finding more effective therapeutic strategies. Erythropoietin (EPO) promotes neuronal recovery after injury; however, its role in enhancing oligodendroglial lineage recovery is unclear. Previously, we found that recombinant EPO (rEPO) treatment enhances myelin basic protein (MBP) expression and functional recovery in adult rats after prenatal transient systemic hypoxia-ischemia (TSHI). We hypothesized that after injury, rEPO would enhance oligodendroglial lineage cell genesis, survival, maturation, and myelination.

METHODS

In vitro assays were used to define how rEPO contributes to specific stages of oligodendrocyte development and recovery after TSHI.

RESULTS

After prenatal TSHI injury, rEPO promotes genesis of oligodendrocyte progenitors from oligodendrospheres, survival of oligodendrocyte precursor cells (OPCs) and O4+ immature oligodendrocytes, O4+ cell process extension, and MBP expression. rEPO did not alter OPC proliferation.

CONCLUSION

Together, these studies demonstrate that EPO signaling promotes critical stages of oligodendroglial lineage development and recovery after prenatal TSHI injury. EPO treatment may be beneficial to preterm and other infant patient populations with developmental brain injury hallmarked by WMI.

Potential role of erythropoietin receptors and ligands in attenuating apoptosis and inflammation in critical limb ischemia

OBJECTIVE

Managing critical limb ischemia (CLI) is challenging. Furthermore, ischemic myopathy prevents good functional outcome after revascularization. Hence, we have focused on limiting the tissue damage rather than angiogenesis, which has traditionally been the motivation to develop nonsurgical treatments for CLI. Erythropoietin (EPO) protects ischemic tissue, and this property may also benefit CLI. The objective of this study was to examine the expression of the tissue-protective EPO receptor complex (EPOR-CD131 [β-chain of interleukin (IL)-3/IL-5/granulocyte macrophage colony-stimulating factor receptor]) in skeletal muscle obtained from humans with CLI. Because native EPO is thrombogenic, the antiapoptotic and anti-inflammatory effects of a nonhematopoietic helix-B peptide of EPO (ARA 290) were investigated on ischemic myotubes in vitro.

METHODS

Tissue was obtained from gastrocnemius muscle of 12 patients undergoing amputation for CLI and from 12 patients without limb ischemia. The expression of EPOR and CD131 was demonstrated by immunohistochemistry and Western blot. A validated in vitro model of myotube ischemia was used in which mature C2C12 myotubes were cultured 6 to 12 hours in a depleted media and gas mixture (20% CO2 and 80% N2). The myotubes were pretreated with EPO or ARA 290 before exposure to simulated ischemia. Apoptosis and cell death were determined by cleaved caspase-3 assay and lactate dehydrogenase release assay. Enzyme-linked immunosorbent assay measured the inflammatory cytokines.

RESULTS

EPOR and CD131 were expressed and significantly upregulated in CLI (average optical density [OD] in Western blot [control vs CLI] EPOR, 0.05 U vs 0.1 U; CD131, 0.10 U vs 0.22 U; P < .01). There was colocalization of EPOR and CD131 in the sarcolemma (cell membrane) of the skeletal myofiber. There was no difference in the distribution of colocalization between the CLI and the normal muscle. The ischemic myotubes treated by ARA 290 in vitro had a significantly decreased number of apoptotic cells (ischemia vs ischemia plus ARA 290: 71.1% vs 55.1%; P < .01), cleaved caspase-3 (OD of ischemia vs ischemia plus ARA 290: 0.15 U vs 0.02 U; P < .01), lactate dehydrogenase release (ischemia vs ischemia plus ARA 290: 32.5 U/L vs 21.3 U/L; P < .01), and IL-6 release (OD at 450 nm, ischemia vs ischemia plus ARA 290: 0.18 vs 0.13; P < .01).

CONCLUSIONS

This study demonstrates the expression and the upregulation of EPOR and CD131 in CLI and also shows that EPOR and CDI are colocalized in the cell membrane of both ischemic and control muscle fiber. The in vitro experiments demonstrate that ARA 290 decreases inflammation and apoptosis of ischemic myotubes. ARA 290 may potentially be used as adjunctive treatment for CLI.

Neuroprotective effect of insulin-like growth factor-1: effects on tyrosine kinase receptor (Trk) expression in dorsal root ganglion neurons with glutamate-induced excitotoxicity in vitro

Insulin-like growth factor-1 (IGF-1) may play an important role in regulating the expression of distinct tyrosine kinase receptor (Trk) in primary sensory dorsal root ganglion (DRG) neurons. Glutamate (Glu) is the main excitatory neurotransmitter and induces neuronal excitotoxicity for primary sensory neurons. It is not known whether IGF-1 influences expression of TrkA, TrkB, and TrkC in DRG neurons with excitotoxicity induced by Glu. In the present study, primary cultured DRG neurons with Glu-induced excitotoxicity were used to determine the effects of IGF-1 on TrkA, TrkB, and TrkC expression. The results showed that IGF-1 increased the expression of TrkA and TrkB and their mRNAs, but not TrkC and its mRNA, in primary cultured DRG neurons with excitotoxicity induced by Glu. Interestingly, neither the extracellular signal-regulated protein kinase (ERK1/2) inhibitor PD98059 nor the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 blocked the effect of IGF-1, but both inhibitors together were effective. IGF-1 may play an important role in regulating different Trk receptor expression in DRG neurons through ERK1/2 and PI3K/Akt signaling pathways. The contribution of distinct Trk receptors might be one of the mechanisms that IGF-1 rescues dying neurons from Glu excitotoxic injury. These data imply that IGF-1 signaling might be a potential target on modifying distinct Trk receptor-mediated biological effects of primary sensory neurons with excitotoxicity.

Chronic treadmill exercise in rats delicately alters the Purkinje cell structure to improve motor performance and toxin resistance in the cerebellum

Although exercise usually improves motor performance, the underlying cellular changes in the cerebellum remain to be elucidated. This study aimed to investigate whether and how chronic treadmill exercise in young rats induced Purkinje cell changes to improve motor performance and rendered the cerebellum less vulnerable to toxin insults. After 1-wk familiarization of treadmill running, 6-wk-old male Wistar rats were divided into exercise and sedentary groups. The exercise group was then subjected to 8 wk of exercise training at moderate intensity. The rotarod test was carried out to evaluate motor performance. Purkinje cells in cerebellar slices were visualized by lucifer yellow labeling in single neurons and by calbindin immunostaining in groups of neurons. Compared with sedentary control rats, exercised rats not only performed better in the rotarod task, but also showed finer Purkinje cell structure (higher dendritic volume and spine density with the same dendritic field). The exercise-improved cerebellar functions were further evaluated by monitoring the long-lasting effects of intraventricular application of OX7-saporin. In the sedentary group, OX7-saporin treatment retarded the rotarod performance and induced ∼60% Purkinje cell loss in 3 wk. As a comparison, the exercise group showed much milder injuries in the cerebellum by the same toxin treatment. In conclusion, exercise training in young rats increased the dendritic density of Purkinje cells, which might play an important role in improving the motor performance. Furthermore, as Purkinje cells in the exercise group were relatively toxin resistant, the exercised rats showed good motor performance, even under toxin-treated conditions.

Isobaric tagging-based quantification by mass spectrometry of differentially regulated proteins in synaptosomes of HIV/gp120 transgenic mice: implications for HIV-associated neurodegeneration

HIV/gp120 transgenic mice manifest neuropathological features similar to HIV-associated neurocognitive disorders (HAND) in humans, including astrogliosis, microglia activation, and decreased neuronal synapses. Here, proteomic screening of synaptosomes from HIV/gp120 transgenic mice was conducted to determine potential neuronal markers and drug targets associated with HAND. Synaptosomes from 13 month-old wild-type (wt) and HIV/gp120 transgenic mouse cortex were subjected to tandem mass tag (TMT) labeling and subsequent analysis using an LTQ-Orbitrap mass spectrometer in pulsed-Q dissociation (PQD) mode for tandem mass spectrometry (MS/MS). A total of 1301 proteins were identified in both wt and HIV/gp120 transgenic mice. Three of the most differentially-regulated proteins were validated by immunoblotting. To elucidate putative pathways associated with the proteomic profile, 107 proteins manifesting a ≥1.5 fold change in expression were analyzed using a bioinformatics pathway analysis tool. This analysis revealed direct or indirect involvement of the phosphotidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway, a well-known neuronal survival pathway. Immunoblots confirmed a lower phospho (p)Akt/Akt ratio in synaptosomes from HIV/gp120 transgenic animals compared to wt, suggesting that this neuroprotective pathway was inactivated in the HIV/gp120 transgenic brain. Based on this information, we then compared immunoblots of pAkt/Akt in the forebrains of these mice as well as in human postmortem brain. We observed a significant decrease in the pAkt/Akt ratio in synaptosomes and forebrain of HIV/gp120 transgenic compared to wt mice, and a similar decrease in human forebrain from HAND patients compared to neurologically unimpaired HIV+ and HIV- controls. Moreover, mechanistic insight into an additional pathway for decreased Akt activity in HIV/gp120 mouse brains and human HAND brains was shown to occur via S-nitrosylation of Akt protein, a posttranslational modification known to inhibit Akt activity and contribute to neuronal cell injury and death. Thus, MS proteomic profiling in the HIV/gp120 transgenic mouse predicted dysregulation of the PI3K/Akt pathway observed in human brains with HAND, providing evidence that this mouse is a useful disease model and that the Akt pathway may provide multiple drug targets for the treatment of HIV-related dementias.

Potential of Novel EPO Derivatives in Limb Ischemia

Erythropoietin (EPO) has tissue-protective properties, but it increases the risk of thromboembolism by raising the haemoglobin concentration. New generation of EPO derivatives is tissue protective without the haematopoietic side effects. Preclinical studies have demonstrated their effectiveness and safety. This paper summarizes the development in EPO derivatives with emphasis on their potential use in critical limb ischaemia.

Upregulated miR-29b promotes neuronal cell death by inhibiting Bcl2L2 after ischemic brain injury

It is increasingly clear that microRNAs (miRNAs) play an important role in controlling cell survival. However, the functional significance of miRNAs in ischemic brain injury remains poorly understood. In the present study, we assayed the expression levels of miR-29b after ischemic brain injury, and defined the target genes and biological functions of miR-29b. We found that the miR-29b levels were significantly increased in rat brain after transient middle cerebral artery occlusion and neurons after oxygen-glucose deprivation. Moreover, ectopic expression of miR-29b promoted neuronal cell death, whereas its repression decreased cell death. Furthermore, we verified that miR-29b directly targeted and inhibited Bcl2L2 gene expression, and then increased neuronal cell death. Importantly, Bcl2L2 overexpression rescued neuronal cell death induced by miR-29b. These results suggest an important role of miR-29b in regulating neuronal cell death, thus offering a new target for the development of therapeutic agents against ischemic brain injury.

From oxygen to erythropoietin: relevance of hypoxia for retinal development, health and disease

Photoreceptors and other cells of the retina consume large quantities of energy to efficiently convert light information into a neuronal signal understandable by the brain. The necessary energy is mainly provided by the oxygen-dependent generation of ATP in the numerous mitochondria of retinal cells. To secure the availability of sufficient oxygen for this process, the retina requires constant blood flow through the vasculature of the retina and the choroid. Inefficient supply of oxygen and nutrients, as it may occur in conditions of disturbed hemodynamics or vascular defects, results in tissue ischemia or hypoxia. This has profound consequences on retinal function and cell survival, requiring an adaptational response by cells to cope with the reduced oxygen tension. Central to this response are hypoxia inducible factors, transcription factors that accumulate under hypoxic conditions and drive the expression of a large variety of target genes involved in angiogenesis, cell survival and metabolism. Prominent among these factors are vascular endothelial growth factor and erythropoietin, which may contribute to normal angiogenesis during development, but may also cause neovascularization and vascular leakage under pathologically reduced oxygen levels. Since ischemia and hypoxia may have a role in various retinal diseases such as diabetic retinopathy and retinopathy of prematurity, studying the cellular and molecular response to reduced tissue oxygenation is of high relevance. In addition, the concept of preconditioning with ischemia or hypoxia demonstrates the capacity of the retina to activate endogenous survival mechanisms, which may protect cells against a following noxious insult. Part of these mechanisms is the local production of protective factors such as erythropoietin. Due to its plethora of effects in the retina including neuro- and vaso-protective activities, erythropoietin has gained strong interest as potential therapeutic factor for retinal degenerative diseases.

PINK1 enhances insulin-like growth factor-1-dependent Akt signaling and protection against apoptosis

Mutations in the PARK6 gene coding for PTEN-induced kinase 1 (PINK1) cause recessive early-onset Parkinsonism. Although PINK1 and Parkin promote the degradation of depolarized mitochondria in cultured cells, little is known about changes in signaling pathways that may additionally contribute to dopamine neuron loss in recessive Parkinsonism. Accumulating evidence implicates impaired Akt cell survival signaling in sporadic and familial PD (PD). IGF-1/Akt signaling inhibits dopamine neuron loss in several animal models of PD and both IGF-1 and insulin are neuroprotective in various settings. Here, we tested whether PINK1 is required for insulin-like growth factor 1 (IGF-1) and insulin dependent phosphorylation of Akt and the regulation of downstream Akt target proteins. Our results show that embryonic fibroblasts from PINK1-deficient mice display significantly reduced Akt phosphorylation in response to both IGF-1 and insulin. Moreover, phosphorylation of glycogen synthase kinase-3β (GSK-3β) and nuclear exclusion of FoxO1 are decreased in IGF-1 treated PINK1-deficient cells. In addition, phosphorylation of ribosomal protein S6 is reduced indicating decreased activity of mitochondrial target of rapamycin (mTOR) in IGF-1 treated PINK1(-/-) cells. Importantly, the protection afforded by IGF-1 against staurosporine-induced metabolic dysfunction and apoptosis is abrogated in PINK1-deficient cells. Moreover, IGF-1-induced Akt phosphorylation is impaired in primary cortical neurons from PINK1-deficient mice. Inhibition of cellular Ser/Thr phosphatases did not increase the amount of phosphorylated Akt in PINK1(-/-) cells, suggesting that components upstream of Akt phosphorylation are compromised in PINK1-deficient cells. Our studies show that PINK1 is required for optimal IGF-1 and insulin dependent Akt signal transduction, and raise the possibility that impaired IGF-1/Akt signaling is involved in PINK1-related Parkinsonism by increasing the vulnerability of dopaminergic neurons to stress-induced cell death.

Activation of ERK1/2 and PI3K/Akt by IGF-1 on GAP-43 expression in DRG neurons with excitotoxicity induced by glutamate in vitro

Insulin-like growth factor-1 (IGF-1) is a neurotrophic factor and plays an important role in promoting axonal growth from dorsal root ganglion (DRG) neurons. Whether IGF-1 influences growth-associated protein 43 (GAP-43) expression and activates the extracellular signal-regulated protein kinase (ERK1/2) and the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways in DRG neurons with excitotoxicity induced by glutamate (Glu) remains unknown. In this study, embryonic 15-day-old rat DRG explants were cultured for 48 h and then exposed to IGF-1, Glu, Glu + IGF-1, Glu + IGF-1 + PD98059, Glu + IGF-1 + LY294002, Glu + IGF-1 + PD98059 + LY294002 for additional 12 h. The DRG explants were continuously exposed to growth media as control. The levels of GAP-43 mRNA were detected by real time-PCR analysis. The protein levels of GAP-43, phosphorylated ERK1/2, phosphorylated Akt, total ERK1/2, and total Akt were detected by Western blot assay. GAP-43 expression in situ was determined by immunofluorescent labeling. Apoptotic cell death was monitored by Hoechst 33342 staining. IGF-1 alone increased GAP-43 and its mRNA levels in the absence of Glu. The decreased GAP-43 and its mRNA levels caused by Glu could be partially reversed by the presence of IGF-1. IGF-1 rescued neuronal cell death caused by Glu. Neither the ERK1/2 inhibitor PD98059 nor the PI3K inhibitor LY294002 blocked the effect of IGF-1, but both inhibitors together were effective. To validate the impact of GAP-43 expression by IGF-1, GAP-43 induction was blocked by administration of dexamethasone (DEX). IGF-1 partially rescued the decrease of GAP-43 and its mRNA levels induced by DEX. DEX induced an increase of cell apoptosis. IGF-1 may play an important role in neuroprotective effects on DRG neurons through regulating GAP-43 expression with excitotoxicity induced by Glu and the process was involved in both ERK1/2 and PI3K/Akt signaling pathways.

The rostral migratory stream plays a key role in intranasal delivery of drugs into the CNS

Background

The blood brain barrier (BBB) is impermeable to most drugs, impeding the establishment of novel neuroprotective therapies and strategies for many neurological diseases. Intranasal administration offers an alternative path for efficient drug delivery into the CNS. So far, the anatomical structures discussed to be involved in the transport of intranasally administered drugs into the CNS include the trigeminal nerve, olfactory nerve and the rostral migratory stream (RMS), but the relative contributions are debated.

Methods and Findings

In the present study we demonstrate that surgical transection, and the resulting structural disruption of the RMS, in mice effectively obstructs the uptake of intranasally administered radioligands into the CNS. Furthermore, using a fluorescent cell tracer, we demonstrate that intranasal administration in mice allows agents to be distributed throughout the entire brain, including olfactory bulb, hippocampus, cortex and cerebellum.

Conclusions

This study provides evidence of the vital role the RMS has in the CNS delivery of intranasally administered agents. The identification of the RMS as the major access path for intranasally administered drugs into the CNS may contribute to the development of treatments that are tailored for efficient transport within this structure. Research into the RMS needs to continue to elucidate its limitations, capabilities, mechanisms of transport and potential hazards before we are able to advance this technique into human research.

Early and sustained increase in the expression of hippocampal IGF-1, but not EPO, in a developmental rodent model of traumatic brain injury

Pediatric traumatic brain injury (pTBI) is the leading cause of traumatic death and disability in children in the United States. Impaired learning and memory in these young survivors imposes a heavy toll on society. In adult TBI (aTBI) models, cognitive outcome improved after administration of erythropoietin (EPO) or insulin-like growth factor-1 (IGF-1). Little is known about the production of these agents in the hippocampus, a brain region critical for learning and memory, after pTBI. Our objective was to describe hippocampal expression of EPO and IGF-1, together with their receptors (EPOR and IGF-1R, respectively), over time after pTBI in 17-day-old rats. We used the controlled cortical impact (CCI) model and measured hippocampal mRNA levels of EPO, IGF-1, EPOR, IGF-1R, and markers of caspase-dependent apoptosis (bcl2, bax, and p53) at post-injury days (PID) 1, 2, 3, 7, and 14. CCI rats performed poorly on Morris water maze testing of spatial working memory, a hippocampally-based cognitive function. Apoptotic markers were present early and persisted for the duration of the study. EPO in our pTBI model increased much later (PID7) than in aTBI models (12 h), while EPOR and IGF-1 increased at PID1 and PID2, respectively, similar to data from aTBI models. Our data indicate that EPO expression showed a delayed upregulation post-pTBI, while EPOR increased early. We speculate that administration of EPO in the first 1-2 days after pTBI would increase hippocampal neuronal survival and function.

Effects of erythropoietin on intracellular calcium concentration of rat primary cortical neurons

Erythropoietin (Epo) has been shown to afford neuroprotection in many experimental models. Although the cytosolic Ca(2+) concentration ([Ca(2+)](i)) is an important factor regulating cell survival, the effects of Epo on [Ca(2+)](i) in neurons are not fully elucidated. We studied the effects of human recombinant Epo on [Ca(2+)](i) of rat primary cortical neurons in normal and excitotoxic conditions. Changes in [Ca(2+)](i) were measured using fura-2 microfluorometry in rat primary cortical cultures. In the control condition with 2mM Mg(2+) in the bath solution, Epo at 4 u/ml significantly increased the fluorescence ratio, but the Epo-induced increase in the fluorescence ratio was abolished by omission of Ca(2+) from the bath solution and by the addition of cadmium. Omission of Mg(2+) and supplementation with glycine resulted in basal and periodic increases in the fluorescence ratio, due to sustained activation of N-methyl-d-asparate (NMDA) receptors. Epo at 0.4 and 4 u/ml significantly decreased the fluorescence ratio in this condition, and this effect was attenuated by the phosphoinositide 3-kinase (PI3K) inhibitors, LY 294002 and wortmannin, and the Ca-activated K channel blocker, iberiotoxin. In the presence of Mg(2+) and exogenous glutamate, 4 but not 0.4 u/ml Epo slightly but significantly reduced the [Ca(2+)](i) elevation. These results suggest that Epo increased [Ca(2+)](i) in cortical neurons by inducing Ca(2+) entry in the control condition but decreased [Ca(2+)](i) in the Mg(2+)-free excitotoxic condition, at least in part via PI3K-dependent activation of Ca-activated K channels. Reduction of [Ca(2+)](i) by Epo in the excitotoxic condition may contribute to neuroprotection.

Temporal differences in microRNA expression patterns in astrocytes and neurons after ischemic injury

MicroRNAs (miRNAs) are small, non-protein-coding RNA molecules that modulate gene translation. Their expression is altered in many central nervous system (CNS) injuries suggesting a role in the cellular response to stress. Current studies in brain tissue have not yet described the cell-specific temporal miRNA expression patterns following ischemic injury. In this study, we analyzed the expression alterations of a set of miRNAs in neurons and astrocytes subjected to 60 minutes of ischemia and collected at different time-points following this injury. To mimic ischemic conditions and reperfusion in vitro, cortical primary neuronal and astrocytic cultures prepared from fetal rats were first placed in oxygen and glucose deprived (OGD) medium for 60 minutes, followed by their transfer into normoxic pre-conditioned medium. Total RNA was extracted at different time-points after the termination of the ischemic insult and the expression levels of miRNAs were measured. In neurons exposed to OGD, expression of miR-29b was upregulated 2-fold within 6 h and up to 4-fold at 24 h post-OGD, whereas induction of miR-21 was upregulated 2-fold after 24 h when compared to expression in neurons under normoxic conditions. In contrast, in astrocytes, miR-29b and miR-21 were upregulated only after 12 h. MiR-30b, 107, and 137 showed expression alteration in astrocytes, but not in neurons. Furthermore, we show that expression of miR-29b was significantly decreased in neurons exposed to Insulin-Like Growth Factor I (IGF-I), a well documented neuroprotectant in ischemic models. Our study indicates that miRNAs expression is altered in neurons and astrocytes after ischemic injury. Furthermore, we found that following OGD, specific miRNAs have unique cell-specific temporal expression patterns in CNS. Therefore the specific role of each miRNA in different intracellular processes in ischemic brain and the relevance of their temporal and spatial expression patterns warrant further investigation that may lead to novel strategies for therapeutic interventions.

Insulin-like growth factor 2 receptor is an IFNgamma-inducible microglial protein that facilitates intracellular HIV replication: implications for HIV-induced neurocognitive disorders

Insulin-like growth factor 2 receptor (IGF2R), also known as cation-independent mannose 6-phosphate (M6P) receptor, is a transmembrane glycoprotein localized in the trans-Golgi region and is involved in targeting both M6P-bearing enzymes and IGF2 to the lysosomal compartment. During development, IGF2R plays a crucial role in removing excess growth factors from both tissue and blood. Due to the perinatal lethality of the global Igf2r knockout, the function of IGF2R in adults, particularly in the CNS, is not known. We made a novel observation that IGF2R is highly expressed in microglial nodules in human brains with HIV encephalitis. In vitro, microglial IGF2R expression was uniquely enhanced by IFNγ among the several cytokines and TLR ligands examined. Furthermore, in several in vitro models of HIV infection, including human and murine microglia, macrophages, and nonmacrophage cells, IGF2R is repeatedly shown to be a positive regulator of HIV infection. IGF2R RNAi also down-regulated the production of the IP-10 chemokine in HIV-infected human microglia. Injection of VSVg env HIV into mouse brain induced HIV p24 expression in neurons, the only cell type normally expressing IGF2R in the adult brain. Our results demonstrate a novel role for IGF2R as an inducible microglial protein involved in regulation of HIV and chemokine expression. Mice with the Csf1r- driven Igf2r knockout should be useful for the investigation of macrophage-specific IGF2R function.

Erythropoietin plus insulin-like growth factor-I protects against neuronal damage in a murine model of human immunodeficiency virus-associated neurocognitive disorders

OBJECTIVE

Prolonged human immunodeficiency virus-1 (HIV-1) infection leads to neurological debilitation, including motor dysfunction and frank dementia. Although pharmacological control of HIV infection is now possible, HIV-associated neurocognitive disorders (HAND) remain intractable. Here, we report that chronic treatment with erythropoietin (EPO) and insulin-like growth factor-I (IGF-I) protects against HIV/gp120-mediated neuronal damage in culture and in vivo.

METHODS

Initially, we tested the neuroprotective effects of various concentrations of EPO, IGF-I, or EPO+IGF-I from gp120-induced damage in vitro. To assess the chronic effects of EPO+IGF-I administration in vivo, we treated HIV/gp120-transgenic or wild-type mice transnasally once a week for 4 months and subsequently conducted immunohistochemical analyses.

RESULTS

Low concentrations of EPO+IGF-I provided neuroprotection from gp120 in vitro in a synergistic fashion. In vivo, EPO+IGF-I treatment prevented gp120-mediated neuronal loss, but did not alter microgliosis or astrocytosis. Strikingly, in the brains of both humans with HAND and gp120-transgenic mice, we found evidence for hyperphosphorylated tau protein (paired helical filament-I tau), which has been associated with neuronal damage and loss. In the mouse brain following transnasal treatment with EPO+IGF-I, in addition to neuroprotection we observed increased phosphorylation/activation of Akt (protein kinase B) and increased phosphorylation/inhibition of glycogen synthase kinase (GSK)-3beta, dramatically decreasing downstream hyperphosphorylation of tau. These results indicate that the peptides affected their cognate signaling pathways within the brain parenchyma.

INTERPRETATION

Our findings suggest that chronic combination therapy with EPO+IGF-I provides neuroprotection in a mouse model of HAND, in part, through cooperative activation of phosphatidylinositol 3-kinase/Akt/GSK-3beta signaling. This combination peptide therapy should therefore be tested in humans with HAND.

Postnatal erythropoietin treatment mitigates neural cell loss after systemic prenatal hypoxic-ischemic injury

OBJECT

Brain injury from preterm birth predisposes children to cerebral palsy, epilepsy, cognitive delay, and behavioral abnormalities. The CNS injury often begins before the early birth, which hinders diagnosis and concurrent treatment. Safe, effective postnatal interventions are urgently needed to minimize these chronic neurological deficits. Erythropoietin (EPO) is a pleiotropic neuroprotective cytokine, but the biological basis of its efficacy in the damaged developing brain remains unclear. Coordinated expression of EPO ligand and receptor expression occurs during CNS development to promote neural cell survival. The authors propose that prenatal third trimester global hypoxia-ischemia disrupts the developmentally regulated expression of neural cell EPO signaling, and predisposes neural cells to death. Furthermore, the authors suggest that neonatal exogenous recombinant human EPO (rhEPO) administration can restore the mismatch of EPO ligand and receptor levels, and enhance neural cell survival.

METHODS

Transient systemic hypoxia-ischemia (TSHI) on embryonic Day 18 in rats mimics human early-third trimester placental insufficiency. This model was used to test the authors' hypothesis using a novel clinically relevant paradigm of prenatal injury on embryonic Day 18, neonatal systemic rhEPO administration initiated 4 days after injury on postnatal Day 1, and histological, biochemical, and functional analyses in neonatal, juvenile, and adult rats.

RESULTS

The results showed that prenatal TSHI upregulates brain EPO receptors, but not EPO ligand. Sustained EPO receptor upregulation was pronounced on oligodendroglial lineage cells and neurons, neural cell populations particularly prone to loss from CNS injury due to preterm birth. Postnatal rhEPO administration after prenatal TSHI minimized histological damage and rescued oligodendrocytes and gamma-aminobutyric acidergic interneurons. Myelin basic protein expression in adult rats after insult was reduced compared with sham controls, but could be restored to near normal levels by neonatal rhEPO treatment. Erythropoietin-treated TSHI rats performed significantly better than their saline-treated peers as adults in motor skills tests, and showed significant seizure threshold restoration using a pentylenetetrazole increasing-dose paradigm.

CONCLUSIONS

These data demonstrate that neonatal rhEPO administration in a novel clinically relevant paradigm initiated 4 days after a global prenatal hypoxic-ischemic insult in rats rescues neural cells, and induces lasting histological and functional improvement in adult rats.

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

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

Erythropoietin in stroke: quo vadis

IMPORTANCE OF THE FIELD

Recombinant erythropoietin (rEPO) failed in a recent clinical study to protect from damages induced by ischemic stroke. The lack of acute treatments in ischemic stroke and the promising outcome in numerous preclinical studies in vivo demands a more critical evaluation of the future use of EPO as an acute treatment.

AREAS COVERED IN THIS REVIEW

The current use and administration of rhEPO and its analogs in animal models and the future use of this cytokine in the treatment of ischemic stroke.

WHAT THE READER WILL GAIN

In this review the potential reasons for the failure of EPO in the clinical trial are analysed and whether the preclinical trials sufficiently evaluated the true potential of recombinant EPO and its analogs is assessed. Alternative methods for administration of EPO to enhance its potential as a neuroprotective drug in ischemic stroke are discussed.

TAKE HOME MESSAGE

Failure in clinical trial does not necessarily indicate the lack of therapeutic potential of EPO. This review encourages further investigation of the true potential of EPO as a candidate drug for the treatment of ischemic stroke by improved preclinical experimental design and utilization of alternative administration methods.

Intranasal delivery of neurotrophic factors BDNF, CNTF, EPO, and NT-4 to the CNS

Injury to the central nervous system (CNS) generally results in significant neuronal death and functional loss. In vitro experiments have demonstrated that neurotrophic factors such as brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), and neurotrophin-4/5 (NT-4/5) can promote neuronal survival. However, delivery to the injured CNS is difficult as these large protein molecules do not efficiently cross the blood-brain barrier. Intranasal delivery of 70 microg [(125)I]-radiolabeled BDNF, CNTF, NT-4, or erythropoietin (EPO) resulted in 0.1-1.0 nM neurotrophin concentrations within 25 min in brain parenchyma. In addition, not only did these neurotrophic factors reach the CNS, they were present in sufficient concentrations to activate the prosurvival PI3Kinase/Akt pathway, even where lower levels of neurotrophic factors were measured. Currently traumatic, ischemic and compressive injuries to the CNS have no effective treatment. There is potential clinical relevancy of this method for rescuing injured CNS tissues in order to maintain CNS function in affected patients. The intranasal delivery method has great clinical potential due to (1) simplicity of administration, (2) noninvasive drug administration, (3) relatively rapid CNS delivery, (4) ability to repeat dosing easily, (5) no requirement for drug modification, and (6) minimal systemic exposure.

Erythropoietin for infants with hypoxic-ischemic encephalopathy

PURPOSE OF REVIEW

Perinatal asphyxia, intraventricular hemorrhage and stroke are common causes of neonatal brain injury, with hypoxia-ischemia as the final common pathway of injury. Erythropoietin (Epo) has potential to lessen neurologic sequelae due to hypoxia-ischemia. The purpose of this review is to highlight new clinical trials and experimental evidence that expand our understanding of Epo as a potential treatment for perinatal brain injury.

RECENT FINDINGS

Several trials of Epo treatment are reviewed: two phase I/II trials of high-dose Epo given to preterm infants established pharmacokinetic and safety profiles, and a trial of Epo treatment for term infants with moderate hypoxic-ischemic encephalopathy found reduced disability. Potential risks and benefits of high-dose Epo are discussed. New evidence related to Epo receptor expression, signal transduction pathways, and mechanisms of neuroprotection are reviewed.

SUMMARY

Cautious optimism is warranted regarding the use of high-dose Epo as a treatment option for neonatal brain injury. To date, Epo has been well tolerated to use in neonatal populations and now studies of neuroprotective efficacy are underway.

Oxidative stress: Biomarkers and novel therapeutic pathways

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO) and members of the mammalian forkhead transcription factors of the O class (FoxOs) may offer the greatest promise for new treatment regimens since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. However, biological outcome with EPO and FoxOs may sometimes be both unexpected and undesirable that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as complicated role EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.