Erythropoietin: a candidate compound for neuroprotection in schizophrenia

Effects of cognitive training under hypoxia on cognitive proficiency and neuroplasticity in remitted patients with mood disorders and healthy individuals: ALTIBRAIN study protocol for a randomized controlled trial

BACKGROUND

Cognitive impairment is prevalent across neuropsychiatric disorders but there is a lack of treatment strategies with robust, enduring effects. Emerging evidence indicates that altitude-like hypoxia cognition training may induce long-lasting neuroplasticity and improve cognition. We will investigate whether repeated cognition training under normobaric hypoxia can improve cognitive functions in healthy individuals and patients with affective disorders and the neurobiological underpinnings of such effects.

METHODS

In sub-study 1, 120 healthy participants are randomized to one of four treatment arms in a double-blind manner, allowing for examination of separate and combined effects of three-week repeated moderate hypoxia and cognitive training, respectively. In sub-study 2, 60 remitted patients with major depressive disorder or bipolar disorder are randomized to hypoxia with cognition training or treatment as usual. Assessments of cognition, psychosocial functioning, and quality of life are performed at baseline, end-of-treatment, and at 1-month follow-up. Functional magnetic resonance imaging (fMRI) scans are conducted at baseline and 1-month follow-up, and [11C]UCB-J positron emission tomography (PET) scans are performed at end-of-treatment to quantify the synaptic vesicle glycoprotein 2A (SV2A). The primary outcome is a cognitive composite score of attention, verbal memory, and executive functions. Statistical power of ≥ 80% is reached to detect a clinically relevant between-group difference with minimum n = 26 per treatment arm. Behavioral data are analyzed with an intention-to-treat approach using mixed models. fMRI data is analyzed with the FMRIB Software Library, while PET data is quantified using the simplified reference tissue model (SRTM) with centrum semiovale as reference region.

DISCUSSION

The results will provide novel insights into whether repeated hypoxia cognition training increases cognition and brain plasticity, which can aid future treatment development strategies.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT06121206 . Registered on 31 October 2023.

Efficacy of erythropoietin as a neuroprotective agent in CKD-associated cognitive dysfunction: A literature systematic review

Patients with chronic kidney disease (CKD) often experience mild cognitive impairment and other neurocognitive disorders. Studies have shown that erythropoietin (EPO) and its receptor have neuroprotective effects in cell and animal models of nervous system disorders. Recombinant human EPO (rHuEPO), commonly used to treat anemia in CKD patients, could be a neuroprotective agent. In this systematic review, we aimed to assess the published studies investigating the cognitive benefits of rHuEPO treatment in individuals with reduced kidney function. We comprehensively searched Pubmed, Cochrane Library, Scopus, and Web of Science databases from 1990 to 2023. After selection, 24 studies were analyzed, considering study design, sample size, participant characteristics, intervention, and main findings. The collective results of these studies in CKD patients indicated that rHuEPO enhances brain function, improves performance on neuropsychological tests, and positively affects electroencephalography measurements. These findings suggest that rHuEPO could be a promising neuroprotective agent for managing CKD-related cognitive impairment.

Effect of erythropoietin on cognitive side-effects of electroconvulsive therapy in depression: A randomized, double-blind, placebo-controlled trial

Electroconvulsive therapy (ECT) is one of the most effective and rapid-acting treatment for severe depression but is associated with cognitive side-effects. Identification of add-on treatments that counteract these side-effects would be very helpful. This randomized, double-blinded, placebo-controlled, parallel-group study investigated the effects of four add-on erythropoietin (EPO; 40,000 IU/ml) or saline (placebo) infusions over 2.5 weeks of ECT (eight ECT sessions) in severely depressed patients with unipolar or bipolar depression. Neuropsychological assessments were conducted pre-ECT, three days after the eighth ECT (week 4), and at a 3-month follow-up. Further, functional magnetic resonance imaging (fMRI) was conducted after the eighth ECT. The primary outcome was change from pre- to post-ECT in a 'speed of complex cognitive processing' composite. Secondary outcomes were verbal and autobiographical memory. Of sixty randomized patients, one dropped out before baseline. Data were thus analysed for 59 patients (EPO, n = 33; saline, n = 26), of whom 28 had fMRI data. No ECT-related decline occurred in the primary global cognition measure (ps≥0.1), and no effect of EPO versus saline was observed on this outcome (ps≥0.3). However post-ECT, EPO-treated patients exhibited faster autobiographical memory recall than saline-treated patients (p = 0.02), which was accompanied by lower memory-related parietal cortex activity. The absence of global cognition changes with ECT and EPO, coupled with the specific impact of EPO on autobiographical memory recall speed and memory-related parietal cortex activity, suggests that assessing autobiographical memory may provide increased sensitivity in evaluating and potentially preventing cognitive side-effects of ECT. TRIAL REGISTRATIONS: ClinicalTrials.gov: NCT03339596, EudraCT no.: 2016-002326-36.

Pharmacological modulation of HIF-1 in the treatment of neuropsychiatric disorders

Hypoxia-inducible factor 1 has been identified as an important therapeutic target in psychiatric illnesses. Hypoxia is a condition in which tissues do not receive enough oxygen, resulting in less oxidative energy production. HIF-1, the master regulator of molecular response to hypoxia, is destabilized when oxygen levels fall. HIF-1, when activated, increases the gene transcription factors that promote adaptive response and longevity in hypoxia. HIF-regulated genes encode proteins involved in cell survival, energy metabolism, angiogenesis, erythropoiesis, and vasomotor control. Multiple genetic and environmental variables contribute to the pathophysiology of psychiatric disease. This review focuses on the most recent findings indicating the role of oxygen deprivation in CNS damage, with strong attention on HIF-mediated pathways. Several pieces of evidence suggested that, in the case of hypoxia, induction and maintenance of HIF-1 target genes may help reduce nerve damage. Major new insights into the molecular mechanisms that control HIF's sensitivity to oxygen are used to make drugs that can change the way HIF works as a therapeutic target for some CNS diseases.

Latent class analysis of psychotic-affective disorders with data-driven plasma proteomics

Data-driven approaches to subtype transdiagnostic samples are important for understanding heterogeneity within disorders and overlap between disorders. Thus, this study was conducted to determine whether plasma proteomics-based clustering could subtype patients with transdiagnostic psychotic-affective disorder diagnoses. The study population included 504 patients with schizophrenia, bipolar disorder, and major depressive disorder and 160 healthy controls, aged 19 to 65 years. Multiple reaction monitoring was performed using plasma samples from each individual. Pathologic peptides were determined by linear regression between patients and healthy controls. Latent class analysis was conducted in patients after peptide values were stratified by sex and divided into tertile values. Significant demographic and clinical characteristics were determined for the latent clusters. The latent class analysis was repeated when healthy controls were included. Twelve peptides were significantly different between the patients and healthy controls after controlling for significant covariates. Latent class analysis based on these peptides after stratification by sex revealed two distinct classes of patients. The negative symptom factor of the Brief Psychiatric Rating Scale was significantly different between the classes (t = -2.070, p = 0.039). When healthy controls were included, two latent classes were identified, and the negative symptom factor of the Brief Psychiatric Rating Scale was still significant (t = -2.372, p = 0.018). In conclusion, negative symptoms should be considered a significant biological aspect for understanding the heterogeneity and overlap of psychotic-affective disorders.

Prospects for Neurotrophic Factor-Based Early Intervention in Schizophrenia: Lessons Learned from the Effects of Antipsychotic Drugs on Cognition, Neurogenesis, and Neurotrophic Factors

Although reducing psychotic symptoms in schizophrenia has been a major focus of therapeutic interventions for decades, improving cognition is considered a better predictor of functional outcomes. However, the most commonly prescribed antipsychotic drugs (APDs) show only marginal beneficial effects on cognition in patients with schizophrenia. The neural mechanisms underlying cognitive disturbances in schizophrenia remain unknown that making drug development efforts very challenging. Since neurotrophic factors are the primary architects of neurogenesis, synaptic plasticity, learning, and memory, the findings from preclinical and clinical studies that assess changes in neurogenesis and neurotrophic factors and their relationship to cognitive performance in schizophrenia, and how these mechanisms might be impacted by APD treatment, may provide valuable clues in developing therapies to combat cognitive deficit in schizophrenia. Numerous evidence produced over the years suggests a deficit in a wide spectrum of neurotrophic factors in schizophrenia. Since schizophrenia is considered a neurodevelopmental disorder, early intervention with neurotrophic factors may be more effective in ameliorating the cognitive deficits and psychopathological symptoms associated with this pathology. In this context, results from initial clinical trials with neurotrophic factors and their future potential to improve cognition and psychosocial functioning in schizophrenia are discussed.

Association of Endogenous Erythropoietin Levels and Iron Status With Cognitive Functioning in the General Population

Background

Emerging data suggest that erythropoietin (EPO) promotes neural plasticity and that iron homeostasis is needed to maintain normal physiological brain function. Cognitive functioning could therefore be influenced by endogenous EPO levels and disturbances in iron status.

Objective

To determine whether endogenous EPO levels and disturbances in iron status are associated with alterations in cognitive functioning in the general population.

Materials and Methods

Community-dwelling individuals from the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study, a general population-based cohort in Groningen, Netherlands, were surveyed between 2003 and 2006. Additionally, endogenous EPO levels and iron status, consisting of serum iron, transferrin, ferritin, and transferrin saturation were analyzed. Cognitive function was assessed by scores on the Ruff Figural Fluency Test (RFFT), as a reflection of executive function, and the Visual Association Test (VAT), as a reflection of associative memory.

Results

Among 851 participants (57% males; mean age 60 ± 13 years), higher endogenous EPO levels were independently associated with an improved cognitive function, reflected by RFFT scores (ß = 0.09, P = 0.008). In multivariable backward linear regression analysis, EPO levels were among the most important modifiable determinants of RFFT scores (ß = 0.09, P = 0.002), but not of VAT scores. Of the iron status parameters, only serum ferritin levels were inversely associated with cognitive function, reflected by VAT scores, in multivariable logistic regression analysis (odds ratio, 0.77; 95% confidence interval 0.63–0.95; P = 0.02 for high performance on VAT, i.e., ≥11 points). No association between iron status parameters and RFFT scores was identified.

Conclusion

The findings suggest that endogenous EPO levels and serum ferritin levels are associated with specific cognitive functioning tests in the general population. Higher EPO levels are associated with better RFFT scores, implying better executive function. Serum ferritin levels, but not other iron status parameters, were inversely associated with high performance on the VAT score, implying a reduced ability to create new memories and recall recent past. Further research is warranted to unravel underlying mechanisms and possible benefits of therapeutic interventions.

Introducing the brain erythropoietin circle to explain adaptive brain hardware upgrade and improved performance

Executive functions, learning, attention, and processing speed are imperative facets of cognitive performance, affected in neuropsychiatric disorders. In clinical studies on different patient groups, recombinant human (rh) erythropoietin (EPO) lastingly improved higher cognition and reduced brain matter loss. Correspondingly, rhEPO treatment of young rodents or EPO receptor (EPOR) overexpression in pyramidal neurons caused remarkable and enduring cognitive improvement, together with enhanced hippocampal long-term potentiation. The 'brain hardware upgrade', underlying these observations, includes an EPO induced ~20% increase in pyramidal neurons and oligodendrocytes in cornu ammonis hippocampi in the absence of elevated DNA synthesis. In parallel, EPO reduces microglia numbers and dampens their activity and metabolism as prerequisites for undisturbed EPO-driven differentiation of pre-existing local neuronal precursors. These processes depend on neuronal and microglial EPOR. This novel mechanism of powerful postnatal neurogenesis, outside the classical neurogenic niches, and on-demand delivery of new cells, paralleled by dendritic spine increase, let us hypothesize a physiological procognitive role of hypoxia-induced endogenous EPO in brain, which we imitate by rhEPO treatment. Here we delineate the brain EPO circle as working model explaining adaptive 'brain hardware upgrade' and improved performance. In this fundamental regulatory circle, neuronal networks, challenged by motor-cognitive tasks, drift into transient 'functional hypoxia', thereby triggering neuronal EPO/EPOR expression.

Unravelling the potential neuroprotective facets of erythropoietin for the treatment of Alzheimer's disease

During the last three decades, recombinant DNA technology has produced a wide range of hematopoietic and neurotrophic growth factors, including erythropoietin (EPO), which has emerged as a promising protein drug in the treatment of several diseases. Cumulative studies have recently indicated the neuroprotective role of EPO in preclinical models of acute and chronic neurodegenerative disorders, including Alzheimer's disease (AD). AD is one of the most prevalent neurodegenerative illnesses in the elderly, characterized by the accumulation of extracellular amyloid-ß (Aß) plaques and intracellular neurofibrillary tangles (NFTs), which serve as the disease's two hallmarks. Unfortunately, AD lacks a successful treatment strategy due to its multifaceted and complex pathology. Various clinical studies, both in vitro and in vivo, have been conducted to identify the various mechanisms by which erythropoietin exerts its neuroprotective effects. The results of clinical trials in patients with AD are also promising. Herein, it is summarized and reviews all such studies demonstrating erythropoietin's potential therapeutic benefits as a pleiotropic neuroprotective agent in the treatment of Alzheimer's disease.

Addressing the 'hypoxia paradox' in severe COVID-19: literature review and report of four cases treated with erythropoietin analogues

BACKGROUND

Since fall 2019, SARS-CoV-2 spread world-wide, causing a major pandemic with estimated ~ 220 million subjects affected as of September 2021. Severe COVID-19 is associated with multiple organ failure, particularly of lung and kidney, but also grave neuropsychiatric manifestations. Overall mortality reaches > 2%. Vaccine development has thrived in thus far unreached dimensions and will be one prerequisite to terminate the pandemic. Despite intensive research, however, few treatment options for modifying COVID-19 course/outcome have emerged since the pandemic outbreak. Additionally, the substantial threat of serious downstream sequelae, called 'long COVID' and 'neuroCOVID', becomes increasingly evident. Among candidates that were suggested but did not yet receive appropriate funding for clinical trials is recombinant human erythropoietin. Based on accumulating experimental and clinical evidence, erythropoietin is expected to (1) improve respiration/organ function, (2) counteract overshooting inflammation, (3) act sustainably neuroprotective/neuroregenerative. Recent counterintuitive findings of decreased serum erythropoietin levels in severe COVID-19 not only support a relative deficiency of erythropoietin in this condition, which can be therapeutically addressed, but also made us coin the term 'hypoxia paradox'. As we review here, this paradox is likely due to uncoupling of physiological hypoxia signaling circuits, mediated by detrimental gene products of SARS-CoV-2 or unfavorable host responses, including microRNAs or dysfunctional mitochondria. Substitution of erythropoietin might overcome this 'hypoxia paradox' caused by deranged signaling and improve survival/functional status of COVID-19 patients and their long-term outcome. As supporting hints, embedded in this review, we present 4 male patients with severe COVID-19 and unfavorable prognosis, including predicted high lethality, who all profoundly improved upon treatment which included erythropoietin analogues.

SHORT CONCLUSION

Substitution of EPO may-among other beneficial EPO effects in severe COVID-19-circumvent downstream consequences of the 'hypoxia paradox'. A double-blind, placebo-controlled, randomized clinical trial for proof-of-concept is warranted.

Erythropoietin and Non-Erythropoietic Derivatives in Cognition

Cognitive deficits are widespread in psychiatric disorders, including major depression and schizophrenia. These deficits are known to contribute significantly to the accompanying functional impairment. Progress in the development of targeted treatments of cognitive deficits has been limited and there exists a major unmet need to develop more efficacious treatments. Erythropoietin (Epo) has shown promising procognitive effects in psychiatric disorders, providing support for a neurotrophic drug development approach. Several preclinical studies with non-erythropoietic derivatives have demonstrated that the modulation of behavior is independent of erythropoiesis. In this review, we examine the molecular, cellular and cognitive actions of Epo and non-erythropoietic molecular derivatives by focusing on their neurotrophic, synaptic, myelin plasticity, anti-inflammatory and neurogenic mechanisms in the brain. We also discuss the role of receptor signaling in Epo and non-erythropoietic EPO-mimetic molecules in their procognitive effects.

Brain erythropoietin fine-tunes a counterbalance between neurodifferentiation and microglia in the adult hippocampus

In adult cornu ammonis hippocampi, erythropoietin (EPO) expression drives the differentiation of new neurons, independent of DNA synthesis, and increases dendritic spine density. This substantial brain hardware upgrade is part of a regulatory circle: during motor-cognitive challenge, neurons experience "functional" hypoxia, triggering neuronal EPO production, which in turn promotes improved performance. Here, we show an unexpected involvement of resident microglia. During EPO upregulation and stimulated neurodifferentiation, either by functional or inspiratory hypoxia, microglia numbers decrease. Treating mice with recombinant human (rh)EPO or exposure to hypoxia recapitulates these changes and reveals the involvement of neuronally expressed IL-34 and microglial CSF1R. Surprisingly, EPO affects microglia in phases, initially by inducing apoptosis, later by reducing proliferation, and overall dampens microglia activity and metabolism, as verified by selective genetic targeting of either the microglial or pyramidal neuronal EPO receptor. We suggest that during accelerating neuronal differentiation, EPO acts as regulator of the CSF1R-dependent microglia.

Current Evidence on the Protective Effects of Recombinant Human Erythropoietin and Its Molecular Variants against Pathological Hallmarks of Alzheimer's Disease

Substantial evidence in the literature demonstrates the pleiotropic effects of the administration of recombinant human erythropoietin (rhEPO) and its molecular variants in different tissues and organs, including the brain. Some of these reports suggest that the chemical properties of this molecule by itself or in combination with other agents (e.g., growth factors) could provide the necessary pharmacological characteristics to be considered a potential protective agent in neurological disorders such as Alzheimer’s disease (AD). AD is a degenerative disorder of the brain, characterized by an aberrant accumulation of amyloid β (Aβ) and hyperphosphorylated tau (tau-p) proteins in the extracellular and intracellular space, respectively, leading to inflammation, oxidative stress, excitotoxicity, and other neuronal alterations that compromise cell viability, causing neurodegeneration in the hippocampus and the cerebral cortex. Unfortunately, to date, it lacks an effective therapeutic strategy for its treatment. Therefore, in this review, we analyze the evidence regarding the effects of exogenous EPOs (rhEPO and its molecular variants) in several in vivo and in vitro Aβ and tau-p models of AD-type neurodegeneration, to be considered as an alternative protective treatment to this condition. Particularly, we focus on analyzing the differential effect of molecular variants of rhEPO when changes in doses, route of administration, duration of treatment or application times, are evaluated for the improved cellular alterations generated in this disease. This narrative review shows the evidence of the effectiveness of the exogenous EPOs as potential therapeutic molecules, focused on the mechanisms that establish cellular damage and clinical manifestation in the AD.

Recent advances on innate immune pathways related to host-parasite cross-talk in cystic and alveolar echinococcosis

Cystic echinococcosis (CE) and alveolar echinococcosis (AE) are life-threatening parasitic infections worldwide caused by Echinococcus granulosus (sensu lato) and E. multilocularis, respectively. Very little is known about the factors affecting innate susceptibility and resistance to infection with Echinococcus spp. Although benzimidazolic drugs against CE and AE have definitively improved the treatment of these cestodes; however, the lack of successful control campaigns, including the EG95 vaccine, at a continental level indicates the importance of generating novel therapies. This review represents an update on the latest developments in the regulatory functions of innate immune pathways such as apoptosis, toll-like receptors (TLRs), and inflammasomes against CE and AE. We suggest that apoptosis can reciprocally play a bi-functional role among the host-Echinococcus metabolite relationships in suppressive and survival mechanisms of CE. Based on the available information, further studies are needed to determine whether the orchestrated in silico strategy for designing inhibitors and interfering RNA against anti-apoptotic proteins and TLRs would be effective to improve new treatments as well as therapeutic vaccines against the E. granulosus and E. multilocularis.

The effect of erythropoietin on electroconvulsive stimulation induced cognitive impairment in rats

Electroconvulsive therapy (ECT) is the most effective and fast-acting treatment for severe depression but associated with troublesome cognitive side-effects. Systemically administered erythropoietin (EPO) crosses the blood-brain-barrier and is a promising treatment for cognitive dysfunction in a wide array of neuropsychiatric and neurological disorders. In this study we trained rats to locate a submerged platform in a water maze and then subjected them to electroconvulsive stimulations (ECS, the rodent equivalent to ECT) and EPO treatment. We then analysed their ability to remember and relearn the location of the platform. In addition, we examined "wall-clinging" (thigmotaxis), a behavioural indicator of stress. ECS caused significant deficit in a probe trial administered after three weeks (nine stimulations) as well as one week (six stimulations) of treatment, indicative of induction of retrograde amnesia. ECS had no effect on relearning of the water maze task or performance in a subsequent probe trial. EPO treatment did not ameliorate the ECS-induced retrograde amnesia, but after nine ECS stimulations the animals that had received EPO relearned the position of the hidden platform faster than the animals that had not. We also found EPO to decrease "wall-clinging" behaviour, suggesting an effect of EPO on the stress response in rats. Thus, we establish the Morris Water Maze as a suitable model for ECS-induced memory loss in rats and provide some evidence for potential beneficial effects of EPO.

Sex-specific brain erythropoietin regulation of mouse metabolism and hypothalamic inflammation

The blood hormone erythropoietin (EPO), upon binding to its receptor (EpoR), modulates high-fat diet-induced (HFD-induced) obesity in mice, improves glucose tolerance, and prevents white adipose tissue inflammation. Transgenic mice with constitutive overexpression of human EPO solely in the brain (Tg21) were used to assess the neuroendocrine EPO effect without increasing the hematocrit. Male Tg21 mice resisted HFD-induced weight gain; showed lower serum adrenocorticotropic hormone, corticosterone, and C-reactive protein levels; and prevented myeloid cell recruitment to the hypothalamus compared with WT male mice. HFD-induced hypothalamic inflammation (HI) and microglial activation were higher in male mice, and Tg21 male mice exhibited a lower increase in HI than WT male mice. Physiological EPO function in the brain also showed sexual dimorphism in regulating HFD response. Female estrogen production blocked reduced weight gain and HI. Targeted deletion of EpoR gene expression in neuronal cells worsened HFD-induced glucose intolerance in both male and female mice but increased weight gain and HI in the hypothalamus in male mice only. Both male and female Tg21 mice kept on normal chow and HFD showed significantly improved glycemic control. Our data indicate that cerebral EPO regulates weight gain and HI in a sex-dependent response, distinct from EPO regulation of glycemic control, and independent of erythropoietic EPO response.

Updates on Novel Erythropoiesis-Stimulating Agents: Clinical and Molecular Approach

Erythropoietin (EPO) is an important hormone responsible for the stimulation of hematopoiesis which is impaired in a variety of diseases, such as chronic kidney disease, cancer chemotherapy, and the use of some anti-HIV drugs. Difficulties in the purification of endogenous EPO due to problems such as technical limitations, heterogeneity of target cells, inadequate amount and immunogenicity of the resultant product, had limited the entry of endogenous EPO in the clinical applications. The integration of medical biotechnology and hematology has introduced novel procedures for the production of human recombinant erythropoietin (rHuEPO), and other erythropoiesis-stimulating agents (ESAs). To investigate and produce rHuEPO, the first step is to recognize the molecular biology and functional pathways, structure, metabolism, and basic physiology of EPO. In this review, all clinical indications, side effects, challenges and notable points regarding EPO, rHuEPO, and other ESAs have also been addressed along with its molecular characterization, such as the modifications needed to optimize their rHuEPO biosynthesis.

Erythropoietin and Friedreich Ataxia: Time for a Reappraisal?

Friedreich ataxia (FRDA) is a rare neurological disorder due to deficiency of the mitochondrial protein frataxin. Frataxin deficiency results in impaired mitochondrial function and iron deposition in affected tissues. Erythropoietin (EPO) is a cytokine which was mostly known as a key regulator of erythropoiesis until cumulative evidence showed additional neurotrophic and neuroprotective properties. These features offered the rationale for advancement of EPO in clinical trials in different neurological disorders in the past years, including FRDA. Several mechanisms of action of EPO may be beneficial in FRDA. First of all, EPO exposure results in frataxin upregulation in vitro and in vivo. By promoting erythropoiesis, EPO influences iron metabolism and induces shifts in iron pool which may ameliorate conditions of free iron excess and iron accumulation. Furthermore, EPO signaling is crucial for mitochondrial gene activation and mitochondrial biogenesis. Up to date nine clinical trials investigated the effects of EPO and derivatives in FRDA. The majority of these studies had a proof-of-concept design. Considering the natural history of FRDA, all of them were too short in duration and not powered for clinical changes. However, these studies addressed significant issues in the treatment with EPO, such as (1) the challenge of the dose finding, (2) stability of frataxin up-regulation, (3) continuous versus intermittent stimulation with EPO/regimen, or (4) tissue changes after EPO exposure in humans in vivo (muscle biopsy, brain imaging). Despite several clinical trials in the past, no treatment is available for the treatment of FRDA. Current lines of research focus on gene therapy, frataxin replacement strategies and on regulation of key metabolic checkpoints such as NrF2. Due to potential crosstalk with all these mechanisms, interventions on the EPO pathway still represent a valuable research field. The recent development of small EPO mimetics which maintain cytoprotective properties without erythropoietic action may open a new era in EPO research for the treatment of FRDA.

Neuroprotective effects of EpoL against oxidative stress induced by soluble oligomers of Aβ peptide

Erythropoietin is a glycoproteic hormone that regulates hematopoiesis by acting on its specific receptor (EpoR). The expression of EpoR in the central nervous system (CNS) suggests a role for this hormone in the brain. Recently, we developed a new Epo variant without hematopoietic activity called EpoL, which showed marked neuroprotective effects against oxidative stress in brain ischemia related models. In this study, we have evaluated the neuroprotective effects of EpoL against oxidative stress induced by chronic treatment with Aβ. Our results show that EpoL was neuroprotective against Aβ-induced toxicity by a mechanism that implicates EpoR, reduction in reactive oxygen species, and reduction in astrogliosis. Furthermore, EpoL treatment improved calcium handling and SV2 levels. Interestingly, the neuroprotective effect of EpoL against oxidative stress induced by chronic Aβ treatment was achieved at a concentration 10 times lower than that of Epo. In conclusion, EpoL, a new variant of Epo without hematopoietic activity, is of potential interest for the treatment of diseases related to oxidative stress in the CNS such as Alzheimer disease.

The Recombinant Human Erythropoietin Administered in Neonatal Rats After Excitotoxic Damage Induces Molecular Changes in the Hippocampus

In vitro and in vivo experimental evidence has contributed important knowledge regarding the antiapoptotic effect mediated by EPO signaling in the damaged brain, particularly through different models with a hypoxic component. However, little emphasis has been placed on the effectiveness of rhEPO administration against cellular alterations caused by in vivo excitotoxicity or on the molecular mechanism that regulates this effect. In this study, we investigated the effects of a single dose of rhEPO on hippocampal damage induced by subcutaneous application of monosodium glutamate (MSG) on postnatal days 1, 3, 5 and 7 in neonatal rats. We found that a dose of 1000 IU/kg of b.w. administered 24 h after MSG had the greatest protective effect. In addition, we analyzed changes in gene expression, particularly in 3 key molecules involved in EPO-mediated signaling (EPO, EPOR and βcR). We observed that the expression of EPO and EPOR was differentially modified at both the mRNA and protein levels under the evaluated conditions, while the expression of the βcR gene was substantially increased. Our data suggest that a low dose of rhEPO is sufficient to induce cellular protection under these experimental conditions and that the molecular changes could be a positive feedback mechanism, mediated by reactive astrocytes in association with in vivo neuroprotective mechanisms.

The past and future of novel, non-dopamine-2 receptor therapeutics for schizophrenia: A critical and comprehensive review

Since the discovery of chlorpromazine in the 1950's, antipsychotic drugs have been the cornerstone of treatment of schizophrenia, and all attenuate dopamine transmission at the dopamine-2 receptor. Drug development for schizophrenia since that time has led to improvements in side effects and tolerability, and limited improvements in efficacy, with the exception of clozapine. However, the reasons for clozapine's greater efficacy remain unclear, despite the great efforts and resources invested therewith. We performed a comprehensive review of the literature to determine the fate of previously tested, non-dopamine-2 receptor experimental treatments. Overall we included 250 studies in the review from the period 1970 to 2017 including treatments with glutamatergic, serotonergic, cholinergic, neuropeptidergic, hormone-based, dopaminergic, metabolic, vitamin/naturopathic, histaminergic, infection/inflammation-based, and miscellaneous mechanisms. Despite there being several promising targets, such as allosteric modulation of the NMDA and α7 nicotinic receptors, we cannot confidently state that any of the mechanistically novel experimental treatments covered in this review are definitely effective for the treatment of schizophrenia and ready for clinical use. We discuss potential reasons for the relative lack of progress in developing non-dopamine-2 receptor treatments for schizophrenia and provide recommendations for future efforts pursuing novel drug development for schizophrenia.

Effects of recombinant human erythropoietin on cognition and neural activity in remitted patients with mood disorders and first-degree relatives of patients with psychiatric disorders: a study protocol for a randomized controlled trial

Background

Bipolar disorder (BD) and unipolar disorder (UD) are associated with cognitive deficits and abnormal neural activity in a “cognitive control network.” There is an increased prevalence of cognitive dysfunction in psychiatric patients’ first-degree relatives, which constitutes a risk factor for psychiatric illness onset. However, there is no treatment with enduring pro-cognitive efficacy. We found preliminary evidence for beneficial effects of eight weekly doses of recombinant human erythropoietin (EPO) on cognition in BD in a recent randomized controlled trial (RCT). The present RCT consists of two sub-studies that extend our previous work by investigating important novel aspects: (1) the effects of 12 weekly doses of EPO on cognition in first-degree relatives of patients with BD, UD, or schizophrenia; and (2) the effects of extending the treatment schedule from 8 to 12 weeks in remitted patients with BD or UD; and (3) assessment of early treatment-associated neural activity changes that may predict cognitive improvement.

Methods

The trial comprises two parallel sub-studies with randomized, controlled, double-blinded, parallel group designs. First-degree relatives (sub-study 1; n = 52) and partially or fully remitted patients with BD or UD (sub-study 2; n = 52) with objectively verified cognitive dysfunction are randomized to receive weekly high-dose EPO (40,000 IU/mL) or placebo (saline) infusions for 12 weeks. Assessments of cognition and mood are conducted at baseline, after two weeks of treatment, after treatment completion, and at six-month follow-up. Functional magnetic resonance imaging (fMRI) is conducted at baseline and after two weeks of treatment. Psychosocial function is assessed at baseline, after treatment completion and six-month follow-up. The primary outcome is change in a cognitive composite score of attention, verbal memory, and executive functions. Statistical power of ≥ 80% is reached to detect a clinically relevant between-group difference by including 52 first-degree relatives and 52 patients with BD or UD, respectively. Behavioral data are analyzed with an intention-to-treat approach using mixed models. fMRI data are analyzed with the FMRIB Software Library.

Discussion

If this trial reveals pro-cognitive effects of EPO, this may influence future treatment of mood disorders and/or preventive strategies in at-risk populations. The fMRI analyses may unravel key neurobiological targets for pro-cognitive treatment.

Trial registration

ClinicalTrials.gov, NCT03315897. Registered on 20 October 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2995-7) contains supplementary material, which is available to authorized users.

Erythropoietin as an add-on treatment for cognitive side effects of electroconvulsive therapy: a study protocol for a randomized controlled trial

Background

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression, but its use is impeded by its cognitive side effects. Novel treatments that can counteract these side effects may therefore improve current treatment strategies for depression. The present randomized trial investigates (1) whether short-term add-on treatment with erythropoietin (EPO) can reduce the cognitive side -effects of ECT and (2) whether such effects are long-lasting. Further, structural and functional magnetic resonance imaging (MRI) will be used to explore the neural underpinnings of such beneficial effects of EPO. Finally, the trial examines whether potential protective effects of EPO on cognition are accompanied by changes in markers of oxidative stress, inflammation, and neuroplasticity.

Methods/design

The trial has a double-blind, randomized, placebo-controlled, parallel group design. Patients with unipolar or bipolar disorder with current moderate to severe depression referred to ECT (N = 52) are randomized to receive four high-dose infusions of EPO (40,000 IU/ml) or placebo (saline). The first EPO/saline infusion is administered within 24 h before the first ECT. The following three infusions are administered at weekly intervals immediately after ECT sessions 1, 4, and 7. Cognition assessments are conducted at baseline, after the final EPO/saline infusion (3 days after eight ECT sessions), and at a 3 months follow-up after ECT treatment completion. The neuronal substrates for potential cognitive benefits of EPO are investigated with structural and functional MRI after the final EPO/saline infusion. The primary outcome is change from baseline to after EPO treatment (3 days after eight ECT sessions) in a cognitive composite score spanning attention, psychomotor speed, and executive functions. With a sample size of N = 52 (n = 26 per group), we have ≥ 80% power to detect a clinically relevant between-group difference in the primary outcome measure at an alpha level of 5% (two-sided test). Behavioral, mood, and blood-biomarker data will be analyzed using repeated measures analysis of covariance. Functional MRI data will be preprocessed and analyzed using the FMRIB Software Library.

Discussion

If EPO is found to reduce the cognitive side effects of ECT, this could have important implications for future treatment strategies for depression and for the scientific understanding of the neurobiological etiology of cognitive dysfunction in patients treated with ECT.

Trial registration

ClinicalTrials.gov, NCT03339596. Registered on 10 November 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2627-2) contains supplementary material, which is available to authorized users.

Cognitive, emotional and social phenotyping of mice in an observer-independent setting

Based on the intellicage paradigm, we have developed a novel cognitive, emotional and social phenotyping battery that permits comprehensive standardized behavioral characterization of mice in an experimenter-independent social setting. Evaluation of this battery in a large number of male and female C57BL/6 wildtype mice, tested in >20 independent cohorts, revealed high reproducibility of the behavioral readouts and may serve as future reference tool. We noticed robust sex-specific differences in general activity, cognitive and emotional behavior, but not regarding preference for social pheromones. Specifically, female mice revealed higher activity, decreased sucrose preference, impaired reversal and place-time-reward learning. Furthermore, female mice reacted more sensitively than males to reward-withdrawal showing a negative emotional contrast/Crespi-effect. In a series of validation experiments, we tested mice with different pathologies, including neuroligin-3 deficient mice (male Nlgn3^y/- and female Nlgn3^+/-) for autistic behavior, oligodendrocyte-specific erythropoietin receptor knockout (oEpoR^-/-) mice for cognitive impairment, as well as mouse models of renal failure (unilateral ureteral obstruction and 5/6 nephrectomy) and of type 2 diabetes (ApoE^-/-) - for delineating potentially confounding effects of motivational factors (thirst, glucose-craving) on learning and memory assessments. As prominent features, we saw in Nlgn3 mutants reduced preference for social pheromones, whereas oEpoR^-/- mice showed learning deficits in place or reversal learning tasks. Renal failure led to increased water intake, and diabetic metabolism to enhanced glucose preference, limiting interpretation of hereon based learning and memory performance in these mice. The phenotyping battery presented here may be well-suited as high-throughput multifaceted diagnostic instrument for translational neuropsychiatry and behavioral genetics.

Optimized induction of beta common receptor enhances the neuroprotective function of erythropoietin in spinal cord ischemic injury

BACKGROUND

Paraplegia remains the most feared complication of complex thoracoabdominal aortic intervention. Although erythropoietin (EPO) has demonstrated neuroprotective effects in spinal cord ischemia, it does not work until expression of the beta common receptor subunit of the EPO receptor (βcR) is induced by ischemia. We hypothesized that the βcR can be induced by diazoxide (DZ), amplifying the neuroprotective effects of EPO in spinal cord ischemia-reperfusion injury.

METHODS

For the DZ time trial, adult male C57/BL6 mice received DZ (20 mg/kg) by oral gavage. Spinal cords were harvested after 0, 12, 24, 36, and 48 hours of administration. To evaluate optimal dosing, DZ was administered at 0, 5, 10, 20, and 40 mg/kg. The expression of βcR was assessed by Western blot analysis. Five groups were studied: PBS (pretreatment)+PBS (immediately before), PBS+EPO, DZ+PBS, DZ+EPO, and sham (without cross-clamping). Spinal cord ischemia was induced by 4 minutes of thoracic aortic cross-clamping. Functional scoring (Basso Mouse Score) was done at 12-hour intervals for 48 hours, and spinal cords were harvested for histological analysis.

RESULTS

Western blot analysis demonstrated that optimal βcR up-regulation occurred at 36 hours after DZ administration, and the optimal DZ dosage for βcR induction was 20 mg/kg. Motor function at 48 hours after treatment was significantly better preserved in the DZ+EPO group compared with all other groups, and was significantly better preserved in the DZ only and EPO only groups compared with control (PBS+PBS).

CONCLUSIONS

Pharmacologic up-regulation of βcR with DZ can increase the efficacy of EPO in preventing spinal cord ischemia and reperfusion injury. Improved understanding of this synergetic mechanism may serve to further prevent ischemic complications for high-risk aortic intervention.

Effects of erythropoietin on astrocytes and brain endothelial cells in primary culture during anoxia depend on simultaneous signaling by other cytokines and on duration of anoxia

Studies on animals revealed neuroprotective effects of exogenously applied erythropoietin (EPO) during cerebral ischemia/hypoxia. Yet, application of exogenous EPO in stroke patients often lead to haemorrhagic transformation. To clarify potential mechanism of this adverse effect we explored effects of EPO on viabilities of astrocytes and brain endothelial cells (BECs) in primary culture during anoxia of various durations, in the presence or absence of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1), which are cytokines that are also released from the neurovascular unit during hypoxia. Anoxia (2-48 h) exerted marginal effects on BECs' viability and significant reductions in viability of astrocytes. Astrocyte-conditioned medium did not exert effects and exerted detrimental effects on BECs during 2 h and 24 h anoxia, respectively. This was partially reversed by inhibition of Janus kinase (Jak)2/signal transducer and activator of transcription (STAT)5 activation. Addition of rat recombinant EPO (rrEPO) during 2 h-6h anoxia was protective for astrocytes, but had no effect on BECs. Addition of rrEPO significantly reduced viability of BECs and astrocytes after 48 h anoxia and after 24 h-48 h anoxia, respectively, which was attenuated by inhibition of Jak2/STAT5 activation. Simultaneous addition of rrEPO and VEGFA (1-165) caused marginal effects on BECs, but a highly significant protective effects on astrocytes during 24-48 h anoxia, which were attenuated by inhibition of Jak2/STAT5 activation. Simultaneous addition of EPO, VEGFA 1-165 and Ang1 exerted protective effects on BECs during 24 h-48 h anoxia, which were attenuated by addition of soluble Tie2 receptor. These data revealed that EPO could exert protective, but also injurious effects on BECs and astrocytes during anoxia, which depended on the duration of anoxia and on simultaneous signaling by VEGF and Ang1. If these injurious effects occur in stroke patients, they could enhance vascular damage and haemorrhagic transformation.

Erythropoietin Attenuates Postoperative Cognitive Dysfunction by Shifting Macrophage Activation toward the M2 Phenotype

Postoperative cognitive dysfunction (POCD) may be driven by transference of the innate immune response to the brain after aseptic surgical damage. Macrophages are key mediators of innate immunity that can display a pro-inflammatory M1 phenotype or an anti-inflammatory M2 phenotype. Erythropoietin (EPO) is a hematopoietic hormone that exerts anti-inflammatory effects by influencing macrophage function. We hypothesized that EPO would prevent POCD by promoting macrophage phenotype switching to the M2 phenotype post-surgery. To evaluate the effects of EPO on POCD and macrophage polarization post-surgery, we administered EPO (5,000 U/kg) with or without an arginase inhibitor (amino-6-boronohexanoic acid, 10 mg/kg) to ICR mice before and after abdominal surgery. Forty-eight hours post-surgery, we assessed memory, synapse function, and macrophage/microglial phenotypes in the spleen and hippocampus. We also investigated M1/M2 phenotypes in RAW264.7 and BV2 cells stimulated with lipopolysaccharide and interferon-γ (M1 inducers) in the presence or absence of EPO. EPO prevented POCD, decreased surgery-related synaptic dysfunction, and attenuated pro-inflammatory cytokine generation in the hippocampus. Moreover, EPO suppressed M1-related genes expression and promoted M2 genes expression in the spleen and hippocampus post-surgery. Furthermore, EPO decreased the proportions of macrophages/microglia expressing an M1 surface marker (CD40) and increased those expressing an M2 surface marker (CD206). Arginase inhibition abolished the beneficial effects of EPO on POCD. In vitro, EPO treatment promoted switching of RAW264.7 and BV2 cells stimulated with M1 inducers to an M2 phenotype. In conclusion, EPO prevents POCD by promoting macrophage phenotype switching toward the M2 phenotype.

Concordance of Several Subcellular Interactions Initiates Alzheimer's Dementia: Their Reversal Requires Combination Treatment

The pathogenesis of Alzheimer's disease involves multiple pathways that, at the macrolevel, include decreased proliferation plus increased loss affecting neurons, astrocytes, and capillaries and, at the subcellular level, involve several elements: amyloid/amyloid precursor protein, presenilins, the unfolded protein response, the ubiquitin/proteasome system, the Wnt/catenin system, the Notch signaling system, mitochondria, mitophagy, calcium, and tau. Data presented show the intimate, anatomical interactions between neurons, astrocytes, and capillaries; the interactions between the several subcellular factors affecting those cells; and the treatments that are currently available and that might correct dysfunctions in the subcellular factors. Available treatments include lithium, valproate, pioglitazone, erythropoietin, and prazosin. Since the subcellular pathogenesis involves multiple interacting elements, combination treatment would be more effective than administration of a single drug directed at only 1 element. The overall purpose of this presentation is to describe the pathogenesis in detail and to explain the proposed treatments.

Revisiting adult neurogenesis and the role of erythropoietin for neuronal and oligodendroglial differentiation in the hippocampus

Recombinant human erythropoietin (EPO) improves cognitive performance in neuropsychiatric diseases ranging from schizophrenia and multiple sclerosis to major depression and bipolar disease. This consistent EPO effect on cognition is independent of its role in hematopoiesis. The cellular mechanisms of action in brain, however, have remained unclear. Here we studied healthy young mice and observed that 3-week EPO administration was associated with an increased number of pyramidal neurons and oligodendrocytes in the hippocampus of ~20%. Under constant cognitive challenge, neuron numbers remained elevated until >6 months of age. Surprisingly, this increase occurred in absence of altered cell proliferation or apoptosis. After feeding a ¹⁵N-leucine diet, we used nanoscopic secondary ion mass spectrometry, and found that in EPO-treated mice, an equivalent number of neurons was defined by elevated ¹⁵N-leucine incorporation. In EPO-treated NG2-Cre-ERT2 mice, we confirmed enhanced differentiation of preexisting oligodendrocyte precursors in the absence of elevated DNA synthesis. A corresponding analysis of the neuronal lineage awaits the identification of suitable neuronal markers. In cultured neurospheres, EPO reduced Sox9 and stimulated miR124, associated with advanced neuronal differentiation. We are discussing a resulting working model in which EPO drives the differentiation of non-dividing precursors in both (NG2+) oligodendroglial and neuronal lineages. As endogenous EPO expression is induced by brain injury, such a mechanism of adult neurogenesis may be relevant for central nervous system regeneration.

Prolyl-4-hydroxylase 2 and 3 coregulate murine erythropoietin in brain pericytes

A classic response to systemic hypoxia is the increased production of red blood cells due to hypoxia-inducible factor (HIF)-mediated induction of erythropoietin (EPO). EPO is a glycoprotein hormone that is essential for normal erythropoiesis and is predominantly synthesized by peritubular renal interstitial fibroblast-like cells, which express cellular markers characteristic of neuronal cells and pericytes. To investigate whether the ability to synthesize EPO is a general functional feature of pericytes, we used conditional gene targeting to examine the von Hippel-Lindau/prolyl-4-hydroxylase domain (PHD)/HIF axis in cell-expressing neural glial antigen 2, a known molecular marker of pericytes in multiple organs. We found that pericytes in the brain synthesized EPO in mice with genetic HIF activation and were capable of responding to systemic hypoxia with the induction of Epo. Using high-resolution multiplex in situ hybridization, we determined that brain pericytes represent an important cellular source of Epo in the hypoxic brain (up to 70% of all Epo-expressing cells). We furthermore determined that Epo transcription in brain pericytes was HIF-2 dependent and cocontrolled by PHD2 and PHD3, oxygen- and 2-oxoglutarate-dependent prolyl-4-hydroxylases that regulate HIF activity. In summary, our studies provide experimental evidence that pericytes in the brain have the ability to function as oxygen sensors and respond to hypoxia with EPO synthesis. Our findings furthermore suggest that the ability to synthesize EPO may represent a functional feature of pericytes in the brain and kidney.

Perioperative erythropoietin protects the CNS against ischemic lesions in patients after open heart surgery

AIM

The aim of this study was to establish erythropoietin as a protective factor against brain ischemia during open heart surgery.

METHODS

A total of 36 consecutive patients scheduled for revascularization heart surgery were included in the study. Of the patients 18 received 3 intravenous doses of recombinant human erythropoietin (rHuEpo, 24,000 IU) and 18 patients received a placebo. Magnetic resonance imaging (MRI) to detect new brain ischemic lesions was performed. Additionally, S100A, S100B, neuron-specific enolase A and B (NSE-A and B) and the concentration of antibodies against N‑methyl-D-aspartate receptors (NMDAR) to identify new neurological complications were determined.

RESULTS

Patients who received rHuEpo showed no postoperative ischemic changes in the brain on MRI images. In the control group 5 (27.8 %) new ischemic lesions were found. The NMDAR antibody concentration, S100A, S100B and NSE showed no significant differences between the groups for new cerebral ischemia. High levels of lactate before and after external aortic compression (p = 0.022 and p = 0.048, respectively) and duration of operation could predict new ischemic lesions (p = 0.009).

CONCLUSIONS

The addition of rHuEpo reduced the formation of lesions detectable by MRI in the brain and could be used clinically as neuroprotection in cardiac surgery.

Erythropoietin-activated mesenchymal stem cells promote healing ulcers by improving microenvironment

BACKGROUND

Mesenchymal stem cell (MSC) transplantation is an effective treatment therapy for ischemic ulcers. However, in high-glucose microenvironment, the original inflammation-inhibiting function of MSCs leads to turns into secreting large amounts of inflammatory mediators, such as tumor necrosis factor alpha, for example, which decreases their capacity and becomes poor quality stem cells over inflammation cells for diabetic foot ulcers repair in the healing of diabetic foot ulcers. Erythropoietin (EPO) is an anti-inflammatory, proangiogenic cytokine. It is unclear whether EPO-activated MSCs with biomaterials can promote the effective healing of diabetic foot ulcers.

METHODS

Cultivated MSCs in MSC-L, MSC-H, EPO-G, Akt-G, and mTOR-G, then separated the supernatant-conditioned medium of these groups to stimulate human umbilical vein endothelial cells on proliferation and migration experiments; a new type of biomaterial planted with the EPO-activated MSCs was applied to the diabetic foot ulcers of the C57 mice.

RESULTS

In vitro experiments showed that EPO could stimulate MSCs to secrete vascular endothelial growth factor in high-glucose microenvironment. More importantly, EPO could reduce the damage to MSCs by high-glucose microenvironment, promote their proliferation and migration functions, and inhibit the high-glucose-induced MSCs from secreting the inflammatory mediator tumor necrosis factor alpha. In vivo experiments showed greater angiogenesis in EPO-MSC group than in control group, ulcer healing in EPO-MSC group was significantly better than that in control group, and MSCs partially differentiated into endothelial cells. EPO-activated MSCs could inhibit the monocyte invasion of localized diabetic foot ulcers.

CONCLUSIONS

Our results indicate that EPO-activated MSCs can promote the effective healing of diabetic foot ulcers. The mechanism is that EPO can change stem cells from excessive inflammation into general inflammation and improved diabetic foot ulcers inflammatory microenvironment.

Carbamylated erythropoietin enhances mice ventilatory responses to changes in O2 but not CO2 levels

Erythropoietin (EPO) has beneficial tissue-protective effects in several diseases but erythrocytosis may cause deleterious effects in EPO-treated patients. Thus carbamylated-EPO (C-EPO) and other derivatives retaining tissue-protective but lacking bone marrow-stimulating actions have been developed. Although EPO modulates ventilatory responses, the effects of C-EPO on ventilation have not been investigated. Here, basal breathing and respiratory chemoreflexes were measured by plethysmography after acute and chronic treatments with recombinant human C-EPO (rhC-EPO; 15,000 IU/kg during 5days) or saline (control group). Hematocrit, plasma and brainstem rhC-EPO levels were also quantified. Chronic rhC-EPO significantly elevated tissue rhC-EPO levels but not hematocrit. None of the drug regimen altered basal ventilation (normoxia). Chronic but not acute rhC-EPO enhanced hyperoxic ventilatory depression, and sustained the hypoxic ventilatory response mainly via a reduction of the roll-off phase. By contrast, rhC-EPO did not blunt the ventilatory response to hypercapnia. Thus, chronic C-EPO may be a promising therapy to improve breathing during hypoxia while minimizing adverse effects on cardiovascular function.

Neural correlates of improved executive function following erythropoietin treatment in mood disorders

BACKGROUND

Cognitive dysfunction in depression and bipolar disorder (BD) is insufficiently targeted by available treatments. Erythropoietin (EPO) increases neuroplasticity and may improve cognition in mood disorders, but the neuronal mechanisms of these effects are unknown. This functional magnetic resonance imaging (fMRI) study investigated the effects of EPO on neural circuitry activity during working memory (WM) performance.

METHOD

Patients with treatment-resistant major depression, who were moderately depressed, or with BD in partial remission, were randomized to eight weekly infusions of EPO (40 000 IU) (N = 30) or saline (N = 26) in a double-blind, parallel-group design. Patients underwent fMRI, mood ratings and blood tests at baseline and week 14. During fMRI patients performed an n-back WM task.

RESULTS

EPO improved WM accuracy compared with saline (p = 0.045). Whole-brain analyses revealed that EPO increased WM load-related activity in the right superior frontal gyrus (SFG) compared with saline (p = 0.01). There was also enhanced WM load-related deactivation of the left hippocampus in EPO-treated compared to saline-treated patients (p = 0.03). Across the entire sample, baseline to follow-up changes in WM performance correlated positively with changes in WM-related SFG activity and negatively with hippocampal response (r = 0.28-0.30, p < 0.05). The effects of EPO were not associated with changes in mood or red blood cells (p ⩾0.08).

CONCLUSIONS

The present findings associate changes in WM-load related activity in the right SFG and left hippocampus with improved executive function in EPO-treated patients.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov: NCT00916552.

Polycythemia and high levels of erythropoietin in blood and brain blunt the hypercapnic ventilatory response in adult mice

Changes in arterial Po2, Pco2, and pH are the strongest stimuli sensed by peripheral and central chemoreceptors to adjust ventilation to the metabolic demand. Erythropoietin (Epo), the main regulator of red blood cell production, increases the hypoxic ventilatory response, an effect attributed to the presence of Epo receptors in both carotid bodies and key brainstem structures involved in integration of peripheral inputs and control of breathing. However, it is not known whether Epo also has an effect on the hypercapnic chemoreflex. In a first attempt to answer this question, we tested the hypothesis that Epo alters the ventilatory response to increased CO2 levels. Basal ventilation and hypercapnic ventilatory response (HCVR) were recorded from control mice and from two transgenic mouse lines constitutively expressing high levels of human Epo in brain only (Tg21) or in brain and plasma (Tg6), the latter leading to polycythemia. To tease apart the potential effects of polycythemia and levels of plasma Epo in the HCVR, control animals were injected with an Epo analog (Aranesp), and Tg6 mice were treated with the hemolytic agent phenylhydrazine after splenectomy. Ventilatory parameters measured by plethysmography in conscious mice were consistent with data from electrophysiological recordings in anesthetized animals and revealed a blunted HCVR in Tg6 mice. Polycythemia alone and increased levels of plasma Epo blunt the HCVR. In addition, Tg21 mice with an augmented level of cerebral Epo also had a decreased HCVR. We discuss the potential implications of these findings in several physiopathological conditions.

Widespread Expression of Erythropoietin Receptor in Brain and Its Induction by Injury

Erythropoietin (EPO) exerts potent neuroprotective, neuroregenerative and procognitive functions. However, unequivocal demonstration of erythropoietin receptor (EPOR) expression in brain cells has remained difficult since previously available anti-EPOR antibodies (EPOR-AB) were unspecific. We report here a new, highly specific, polyclonal rabbit EPOR-AB directed against different epitopes in the cytoplasmic tail of human and murine EPOR and its characterization by mass spectrometric analysis of immuno-precipitated endogenous EPOR, Western blotting, immunostaining and flow cytometry. Among others, we applied genetic strategies including overexpression, Lentivirus-mediated conditional knockout of EpoR and tagged proteins, both on cultured cells and tissue sections, as well as intracortical implantation of EPOR-transduced cells to verify specificity. We show examples of EPOR expression in neurons, oligodendroglia, astrocytes and microglia. Employing this new EPOR-AB with double-labeling strategies, we demonstrate membrane expression of EPOR as well as its localization in intracellular compartments such as the Golgi apparatus. Moreover, we show injury-induced expression of EPOR. In mice, a stereotactically applied stab wound to the motor cortex leads to distinct EpoR expression by reactive GFAP-expressing cells in the lesion vicinity. In a patient suffering from epilepsy, neurons and oligodendrocytes of the hippocampus strongly express EPOR. To conclude, this new analytical tool will allow neuroscientists to pinpoint EPOR expression in cells of the nervous system and to better understand its role in healthy conditions, including brain development, as well as under pathological circumstances, such as upregulation upon distress and injury.

Discovery of a master regulator of injury and healing: tipping the outcome from damage toward repair

Disease processes provoke a balancing act between tissue damage and repair. In the 1980s, the discovery that tumor necrosis factor (TNF)-α is a general mediator of disease-related injury led to the development of novel therapeutics to neutralize its activity. In contrast, identification of potential mediator(s) of tissue repair remained elusive. Studies performed over the last 15 years have documented that the type 1 cytokine erythropoietin (EPO), produced by cells within surrounding regions subjected to injury, acts as a master regulator, controlling both damage and repair. The transducer of these activities is the previously unrecognized innate repair receptor (IRR), which is comprised of the EPO receptor and β common receptor subunits. Notably, although proinflammatory cytokines upregulate the IRR, EPO and proinflammatory cytokines inhibit each other's production, resulting in a relative underproduction of EPO. Although exogenous EPO attenuates disease activity in many preclinical models, its clinical utility is limited by serious hematopoietic and thrombotic adverse effects. To circumvent this problem, novel compounds engineered from the structure of EPO have been developed as selective ligands of the IRR. These compounds possess no hematopoietic activity, yet are fully tissue-protective and reparative. The lead molecule of this development effort (the 11-amino acid peptide ARA290) tips the balance toward healing in diverse preclinical models of disease and is currently under evaluation in advanced clinical trials as a disease-modifying agent in painful neuropathy and diabetes.

In-vivo detection of the erythropoietin receptor in tumours using positron emission tomography

OBJECTIVE

Recombinant human erythropoietin (rhuEpo) is used clinically to treat anaemia. However, rhuEpo-treated cancer patients show decreased survival rates and erythropoietin receptor (EpoR) expression has been found in patient tumour tissue. Thus, rhuEpo application might promote EpoR(+) tumour progression. We therefore developed the positron emission tomography (PET)-probe (68)Ga-DOTA-rhuEpo and evaluated its performance in EpoR(+) A549 non-small-cell lung cancer (NSCLC) xenografts.

METHODS

(68)Ga-DOTA-rhuEpo was generated by coupling DOTA-hydrazide to carbohydrate side-chains of rhuEpo. Biodistribution was determined in tumour-bearing mice 0.5, 3, 6, and 9 h after probe injection. Competition experiments were performed by co-injecting (68)Ga-DOTA-rhuEpo and rhuEpo in five-fold excess. Probe specificity was further evaluated histologically using Epo-Cy5.5 stainings.

RESULTS

The blood half-life of (68)Ga-DOTA-rhuEpo was 2.6 h and the unbound fraction was cleared by the liver and kidney. After 6 h, the highest tumour to muscle ratio was reached. The highest (68)Ga-DOTA-rhuEpo accumulation was found in liver (10.06 ± 6.26%ID/ml), followed by bone marrow (1.87 ± 0.53%ID/ml), kidney (1.58 ± 0.39%ID/ml), and tumour (0.99 ± 0.16%ID/ml). EpoR presence in these organs was histologically confirmed. Competition experiments showed significantly (p < 0.05) lower PET-signals in tumour and bone marrow at 3 and 6 h.

CONCLUSION

(68)Ga-DOTA-rhuEpo shows favourable pharmacokinetic properties and detects EpoR specifically. Therefore, it might become a valuable radiotracer to monitor EpoR status in tumours and support decision-making in anaemia therapy.

KEY POINTS

• PET-probe (68) Ga-DOTA-rhuEpo was administered to assess the EpoR status in vivo • (68) Ga-DOTA-rhuEpo binds specifically to EpoR positive organs in vivo • Tumour EpoR status determination might enable decision-making in anaemia therapy with rhuEpo.

Enhancement of ventricular-subventricular zone-derived neurogenesis and oligodendrogenesis by erythropoietin and its derivatives

In the postnatal mammalian brain, stem cells in the ventricular-subventricular zone (V-SVZ) continuously generate neuronal and glial cells throughout life. Genetic labeling of cells of specific lineages have demonstrated that the V-SVZ is an important source of the neuroblasts and/or oligodendrocyte progenitor cells (OPCs) that migrate toward injured brain areas in response to several types of insult, including ischemia and demyelinating diseases. However, this spontaneous regeneration is insufficient for complete structural and functional restoration of the injured brain, so interventions to enhance these processes are sought for clinical applications. Erythropoietin (EPO), a clinically applied erythropoietic factor, is reported to have cytoprotective effects in various kinds of insult in the central nervous system. Moreover, recent studies suggest that EPO promotes the V-SVZ-derived neurogenesis and oligodendrogenesis. EPO increases the proliferation of progenitors in the V-SVZ and/or the migration and differentiation of their progenies in and around injured areas, depending on the dosage, timing, and duration of treatment, as well as the type of animal model used. On the other hand, EPO has undesirable side effects, including thrombotic complications. We recently demonstrated that a 2-week treatment with the EPO derivative asialo-EPO promotes the differentiation of V-SVZ-derived OPCs into myelin-forming mature oligodendrocytes in the injured white matter of neonatal mice without causing erythropoiesis. Here we present an overview of the multifaceted effects of EPO and its derivatives in the V-SVZ and discuss the possible applications of these molecules in regenerative medicine.

Putative neuroprotective agents in neuropsychiatric disorders

In many individuals with major neuropsychiatric disorders including depression, bipolar disorder and schizophrenia, their disease characteristics are consistent with a neuroprogressive illness. This includes progressive structural brain changes, cognitive and functional decline, poorer treatment response and an increasing vulnerability to relapse with chronicity. The underlying molecular mechanisms of neuroprogression are thought to include neurotrophins and regulation of neurogenesis and apoptosis, neurotransmitters, inflammatory, oxidative and nitrosative stress, mitochondrial dysfunction, cortisol and the hypothalamic-pituitary-adrenal axis, and epigenetic influences. Knowledge of the involvement of each of these pathways implies that specific agents that act on some or multiple of these pathways may thus block this cascade and have neuroprotective properties. This paper reviews the potential of the most promising of these agents, including lithium and other known psychotropics, aspirin, minocycline, statins, N-acetylcysteine, leptin and melatonin. These agents are putative neuroprotective agents for schizophrenia and mood disorders.

Alternative pharmacologic targets for the treatment of schizophrenia: results from phase I and II trials

PURPOSE OF REVIEW

The current article provides a brief review of the clinical efficacy and safety outcomes from selected phase I and II clinical trials of compounds in development acting on targets beyond the dopamine D2 receptor in patients with schizophrenia.

RECENT FINDINGS

A number of experimental pharmacological targets have been studied in clinical trials. Among those, glutamatergic and nicotinergic pathways have received most attention. Glycine transporter 1 inhibitors used adjunctively with antipsychotics suggest efficacy for negative symptoms of schizophrenia. Adjunctive alpha7 nicotinic acetylcholine receptor agonists and minocycline may improve negative symptoms and cognitive deficits. Adjunctive oxytocin may benefit psychotic symptoms and social cognitive deficits. Adjunctive erythropoietin may improve cognitive function.

SUMMARY

Experimental therapeutic research for schizophrenia is rapidly expanding and a number of compounds with novel mechanisms of action are demonstrating encouraging evidence for efficacy across a range of symptoms. However, much work still needs to be conducted before these new agents can be considered for routine clinical treatment. In particular, further assessment of efficacy and longer term safety and tolerability monitoring are required.

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

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

Evaluating effects of EPO in rodent behavioral assays related to depression

The cytokine erythropoietin (EPO) is an important regulator of hematopoesis and has well-known tissue protective properties. Neurotrophic action is implicated as mechanistically important in the treatment of depression, and neurotrophic actions of EPO suggest potential therapeutic utility of an EPO-like mechanism in depressive disorder. Rodent behavioral models that are responsive to clinically used antidepressants as well as to neurotrophic compounds can be used to assess potential antidepressant properties of EPO and EPO-like compounds. Rodent models described here are the forced-swim test (FST), a hyponeophagia test and the novel object recognition test. Each of these models provides different information and relevance to depression and each can be tested with EPO and similar compounds.