Erythropoietin-mediated protection of insect brain neurons involves JAK and STAT but not PI3K transduction pathways

JAK and STAT5B mediate olfactory response of migratory locusts to their own volatiles

Janus kinase (JAK) and signal transducer and activator of transcription (STAT) signaling affect social aggregation, mood and psychiatric disorders, nociceptive and depressive behaviors. Olfactory dysfunction is one of the distinct symptoms of these behaviors, but function and mechanism of JAK and STAT in modulating olfaction remain largely unknown. Migratory locusts show olfactory preference for their own volatiles. We thus use this animal model to explore functions and mechanisms of JAK and STAT5B in mediating olfaction response to their own volatiles. Tissue distribution study shows that JAK and STAT5B express in antennae and brains, especially in antennal lobes and mushroom bodies in locust brains, and knockdown of these two genes by RNA interference (RNAi) in antennae and brains results in the loss of olfactory preference for locust volatiles, including chemical odorants indole and β-ionone. RNA-seq analysis reveals that JAK and STAT5B RNAi knockdown downregulates a functional class of transcripts in nucleoprotein complex, including heterogeneous nuclear ribonucleoprotein C (hnRNPC) and small nuclear ribonucleoprotein polypeptide F (SNRPF). HnRNPC and SNRPF mRNAs and proteins are also expressed in antennae and brains, and RNAi knockdown of these two genes reduces the percentage of locusts preferring volatiles, including chemical odorants indole and β-ionone. Furthermore, RNAi knockdown of dopamine receptor 1 (DopR1) results in the decrease of JAK mRNA level in antennae, and JAK/STAT5B, hnRNPC and SNRPF are required for dopamine receptor 1 (DopR1) to modulate olfactory preference for their own volatiles. This study confirms that JAK/STAT5B signaling modulates olfaction by affecting expression levels of hnRNPC and SNRPF, and this pathway is also required for DopR1 to modulate olfactory preference for their own volatiles. These findings highlight novel roles of JAK and STAT5B in modulating olfactory preference. This study provides novel insights into functional links among JAK/STAT5B signaling, RNA binding proteins and DopR1 underlying the modulation of olfactory behaviors.

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.

The cytokine receptor CRLF3 is a human neuroprotective EV-3 (Epo) receptor

The evolutionary conserved orphan cytokine receptor-like factor 3 (CRLF3) has been implicated in human disease, vertebrate hematopoiesis and insect neuroprotection. While its specific functions are elusive, experimental evidence points toward a general role in cell homeostasis. Erythropoietin (Epo) is a major regulator of vertebrate hematopoiesis and a general cytoprotective cytokine. Erythropoietic functions mediated by classical Epo receptor are understood in great detail whereas Epo-mediated cytoprotective mechanisms are more complex due to involvement of additional Epo receptors and a non-erythropoietic splice variant with selectivity for certain receptors. In the present study, we show that the human CRLF3 mediates neuroprotection upon activation with the natural Epo splice variant EV-3. We generated CRLF3 knock-out iPSC lines and differentiated them toward the neuronal lineage. While apoptotic death of rotenone-challenged wild type iPSC-derived neurons was prevented by EV-3, EV-3-mediated neuroprotection was absent in CRLF3 knock-out neurons. Rotenone-induced apoptosis and EV-3-mediated neuroprotection were associated with differential expression of pro-and anti-apoptotic genes. Our data characterize human CRLF3 as a receptor involved in Epo-mediated neuroprotection and identify CRLF3 as the first known receptor for EV-3.

Protection of insect neurons by erythropoietin/CRLF3-mediated regulation of pro-apoptotic acetylcholinesterase

Cytokine receptor-like factor 3 (CRLF3) is a conserved but largely uncharacterized orphan cytokine receptor of eumetazoan animals. CRLF3-mediated neuroprotection in insects can be stimulated with human erythropoietin. To identify mechanisms of CRLF3-mediated neuroprotection we studied the expression and proapoptotic function of acetylcholinesterase in insect neurons. We exposed primary brain neurons from Tribolium castaneum to apoptogenic stimuli and dsRNA to interfere with acetylcholinesterase gene expression and compared survival and acetylcholinesterase expression in the presence or absence of the CRLF3 ligand erythropoietin. Hypoxia increased apoptotic cell death and expression of both acetylcholinesterase-coding genes ace-1 and ace-2. Both ace genes give rise to single transcripts in normal and apoptogenic conditions. Pharmacological inhibition of acetylcholinesterases and RNAi-mediated knockdown of either ace-1 or ace-2 expression prevented hypoxia-induced apoptosis. Activation of CRLF3 with protective concentrations of erythropoietin prevented the increased expression of acetylcholinesterase with larger impact on ace-1 than on ace-2. In contrast, high concentrations of erythropoietin that cause neuronal death induced ace-1 expression and hence promoted apoptosis. Our study confirms the general proapoptotic function of AChE, assigns a role of both ace-1 and ace-2 in the regulation of apoptotic death and identifies the erythropoietin/CRLF3-mediated prevention of enhanced acetylcholinesterase expression under apoptogenic conditions as neuroprotective mechanism.

Cytokine Receptor-Like Factor 3 (CRLF3) Contributes to Early Zebrafish Hematopoiesis

Cytokine receptor-like factor 3 (CRLF3) is an ancient protein conserved across metazoans that contains an archetypal cytokine receptor homology domain (CHD). This domain is found in cytokine receptors present in bilateria, including higher vertebrates, that play key roles in a variety of developmental and homeostatic processes, particularly relating to blood and immune cells. However, understanding of CRLF3 itself remains very limited. This study aimed to investigate this evolutionarily significant protein by studying its embryonic expression and function in early development, particularly of blood and immune cells, using zebrafish as a model. Expression of crlf3 was identified in mesoderm-derived tissues in early zebrafish embryos, including the somitic mesoderm and both anterior and posterior lateral plate mesoderm. Later expression was observed in the thymus, brain, retina and exocrine pancreas. Zebrafish crlf3 mutants generated by genome editing technology exhibited a significant reduction in primitive hematopoiesis and early definitive hematopoiesis, with decreased early progenitors impacting on multiple lineages. No other obvious phenotypes were observed in the crlf3 mutants.

Janus Kinase Mediates Faster Recovery From Sevoflurane Anesthesia Than Isoflurane Anesthesia in the Migratory Locusts

Inhalation anesthetics isoflurane and sevoflurane have been widely used in clinical practice for anesthesia. However, the molecular mechanisms underlying the faster recovery from sevoflurane anesthesia than isoflurane anesthesia remain largely undetermined. Herein, we use RNA-seq, RNA interference, quantitative real-time PCR and western blotting to explore the mechanisms of recovery from isoflurane and sevoflurane anesthesia in the migratory locusts. Although the migratory locusts show similar anesthetic responses to these two chemicals in corresponding half-maximal effective concentrations (EC50s), the recovery from sevoflurane anesthesia is significantly faster than that for isoflurane anesthesia after 30 min of anesthetic exposure. Transcriptome analysis shows that those transcripts involved in cytoskeletal components, Janus kinase (JAK) pathway and cuticle protein are differentially expressed in locust brains in response to isoflurane and sevoflurane. RNAi knockdown confirms that Actin, Myosin-like protein 84B (Mlp84B), JAK and cuticle protein NCP56 do not affect anesthetic response of the locusts to these two chemical anesthetics. Moreover, actin, Mlp84B and NCP56 do not affect differential recovery from isoflurane and sevoflurane anesthesia, whereas RNAi knockdown of JAK and its partner STAT5B does not affect anesthetic recovery from isoflurane but elongates recovery duration from sevoflurane anesthesia. Thus, JAK may mediate faster recovery from sevoflurane anesthesia than from isoflurane anesthesia in the migratory locust. This finding provides novel insights into the molecular mechanism underlying faster recovery from sevoflurane anesthesia than isoflurane anesthesia.

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.

EpoR-tdTomato-Cre mice enable identification of EpoR expression in subsets of tissue macrophages and hematopoietic cells

The erythropoietin receptor (EpoR) has traditionally been thought of as an erythroid-specific gene. Notably, accumulating evidence suggests that EpoR is expressed well beyond erythroid cells. However, the expression of EpoR in non-erythroid cells has been controversial. In this study, we generated EpoR-tdTomato-Cre mice and used them to examine the expression of EpoR in tissue macrophages and hematopoietic cells. We show that in marked contrast to the previously available EpoR-eGFPcre mice, in which a very weak eGFP signal was detected in erythroid cells, tdTomato was readily detectable in both fetal liver (FL) and bone marrow (BM) erythroid cells at all developmental stages and exhibited dynamic changes during erythropoiesis. Consistent with our recent finding that erythroblastic island (EBI) macrophages are characterized by the expression of EpoR, tdTomato was readily detected in both FL and BM EBI macrophages. Moreover, tdTomato was also detected in subsets of hematopoietic stem cells, progenitors, megakaryocytes, and B cells in BM as well as in spleen red pulp macrophages and liver Kupffer cells. The expression of EpoR was further shown by the EpoR-tdTomato-Cre-mediated excision of the floxed STOP sequence. Importantly, EPO injection selectively promoted proliferation of the EpoR-expressing cells and induced erythroid lineage bias during hematopoiesis. Our findings imply broad roles for EPO/EpoR in hematopoiesis that warrant further investigation. The EpoR-tdTomato-Cre mouse line provides a powerful tool to facilitate future studies on EpoR expression and regulation in various non-hematopoietic cells and to conditionally manipulate gene expression in EpoR-expressing cells for functional studies.

Acetylcholinesterase promotes apoptosis in insect neurons

Apoptosis plays a major role in development, tissue renewal and the progression of degenerative diseases. Studies on various types of mammalian cells reported a pro-apoptotic function of acetylcholinesterase (AChE), particularly in the formation of the apoptosome and the degradation of nuclear DNA. While three AChE splice variants are present in mammals, invertebrates typically express two ache genes that code for a synaptically located protein and a protein with non-synaptic functions respectively. In order to investigate a potential contribution of AChE to apoptosis in insects, we selected the migratory locust Locusta migratoria. We established primary neuronal cultures of locust brains and characterized apoptosis progression in vitro. Dying neurons displayed typical characteristics of apoptosis, including caspase-activation, nuclear condensation and DNA fragmentation visualized by TUNEL staining. Addition of the AChE inhibitors neostigmine and territrem B reduced apoptotic cell death under normal culture conditions. Moreover, both inhibitors completely suppressed hypoxia-induced neuronal cell death. Exposure of live animals to severe hypoxia moderately increased the expression of ace-1 in locust brains in vivo. Our results indicate a previously unreported role of AChE in insect apoptosis that parallels the pro-apoptotic role in mammalian cells. This similarity adds to the list of apoptotic mechanisms shared by mammals and insects, supporting the hypothesized existence of an ancient, complex apoptosis regulatory network present in common ancestors of vertebrates and insects.

Locust Hemolymph Conveys Erythropoietin-Like Cytoprotection via Activation of the Cytokine Receptor CRLF3

The cytokine receptor-like factor 3 (CRLF3) is an evolutionary conserved class 1 cytokine receptor present in all major eumetazoan groups. Endogenous CRLF3 ligands have not been identified and the physiological responses mediated by mammalian CRLF3 are poorly characterized. Insect CRLF3 is activated by erythropoietin (Epo) and several related molecules that protect mammalian neurons from stress-induced apoptosis. However, insects neither express Epo nor “classical” Epo receptor. Cell-protective effects of insect hemolymph have been described for several species. In this study, we explored the possibility that the endogenous CRLF3 ligand is contained in locust hemolymph. PCR analyses confirmed expression of crfl3-transcripts in neurons and hemocytes of Locusta migratoria and Tribolium castaneum. Survival of locust hemocytes in primary cultures was significantly increased by supplementation of culture medium with locust hemolymph serum. Locust primary neuron cultures were also protected by locust hemolymph, though preceding exposure to fetal bovine serum changed the hemolymph dose-dependency of neuroprotection. Direct comparison of 10% hemolymph serum with recombinant human Epo in its optimal neuroprotective concentration revealed equivalent anti-apoptotic effects on hypoxia-exposed locust neurons. The same concentration of locust hemolymph serum also protected hypoxia-exposed T. castaneum neurons. This indicates that the neuroprotective factor in locust hemolymph is sufficiently conserved in insects to allow activation of neuroprotective receptors in different species. Locust hemolymph-induced neuroprotection in both L. migratoria and T. castaneum was abolished after RNAi-mediated suppression of crlf3-expression. In summary, we report the presence of a conserved endogenous cytokine in locust hemolymph that activates CRLF3 and connected anti-apoptotic processes in hemocytes and neurons. Identification and characterization of the CRLF3 ligand will promote knowledge about cytokine evolution and may unravel cell-protective agents with potential clinical application.

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.

The Orphan Cytokine Receptor CRLF3 Emerged With the Origin of the Nervous System and Is a Neuroprotective Erythropoietin Receptor in Locusts

The orphan cytokine receptor-like factor 3 (CRLF3) was identified as a neuroprotective erythropoietin receptor in locust neurons and emerged with the evolution of the eumetazoan nervous system. Human CRLF3 belongs to class I helical cytokine receptors that mediate pleiotropic cellular reactions to injury and diverse physiological challenges. It is expressed in various tissues including the central nervous system but its ligand remains unidentified. A CRLF3 ortholog in the holometabolous beetle Tribolium castaneum was recently shown to induce anti-apoptotic mechanisms upon stimulation with human recombinant erythropoietin. To test the hypothesis that CRLF3 represents an ancient cell-protective receptor for erythropoietin-like cytokines, we investigated its presence across metazoan species. Furthermore, we examined CRLF3 expression and function in the hemimetabolous insect Locusta migratoria. Phylogenetic analysis of CRLF3 sequences indicated that CRLF3 is absent in Porifera, Placozoa and Ctenophora, all lacking the traditional nervous system. However, it is present in all major eumetazoan groups ranging from cnidarians over protostomians to mammals. The CRLF3 sequence is highly conserved and abundant amongst vertebrates. In contrast, relatively few invertebrates express CRLF3 and these sequences show greater variability, suggesting frequent loss due to low functional importance. In L. migratoria, we identified the transcript Lm-crlf3 by RACE-PCR and detected its expression in locust brain, skeletal muscle and hemocytes. These findings correspond to the ubiquitous expression of crlf3 in mammalian tissues. We demonstrate that the sole addition of double-stranded RNA to the culture medium (called soaking RNA interference) specifically interferes with protein expression in locust primary brain cell cultures. This technique was used to knock down Lm-crlf3 expression and to abolish its physiological function. We confirmed that recombinant human erythropoietin rescues locust brain neurons from hypoxia-induced apoptosis and showed that this neuroprotective effect is absent after knocking down Lm-crlf3. Our results affirm the erythropoietin-induced neuroprotective function of CRLF3 in a second insect species from a different taxonomic group. They suggest that the phylogenetically conserved CRLF3 receptor may function as a cell protective receptor for erythropoietin or a structurally related cytokine also in other animals including vertebrate and mammalian species.

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.

Developmental expression patterns of erythropoietin and its receptor in mouse brainstem respiratory regions

Erythropoietin (EPO) is a hypoxia-inducible hormone, classically known to enhance red blood cell production upon binding its receptor (EPOR) present on the surface of the erythroid progenitor cells. EPO and its receptor are also expressed in the central nervous system (CNS), exerting several non-hematopoietic actions. EPO also plays an important role in the control of breathing. In this review, we summarize the known physiological actions of EPO in the neural control of ventilation during postnatal development and at adulthood in rodents under normoxic and hypoxic conditions. Furthermore, we present the developmental expression patterns of EPO and EPORs in the brainstem, and with the use of in situ hybridization (ISH) and immunofluorescence techniques we provide original data showing that EPOR is abundantly present in specific brainstem nuclei associated with central chemosensitivity and control of ventilation in the ventrolateral medulla, mainly on somatostatin negative cells. Thus, we conclude that EPO signaling may act through glutamatergic neuron populations that are the primary source of rhythmic inspiratory excitatory drive. This work underlies the importance of EPO signaling in the central control of ventilation across development and adulthood and provides new insights on the expression of EPOR at the cellular level.

Beetles as Model Organisms in Physiological, Biomedical and Environmental Studies - A Review

Model organisms are often used in biological, medical and environmental research. Among insects, Drosophila melanogaster, Galleria mellonella, Apis mellifera, Bombyx mori, Periplaneta americana, and Locusta migratoria are often used. However, new model organisms still appear. In recent years, an increasing number of insect species has been suggested as model organisms in life sciences research due to their worldwide distribution and environmental significance, the possibility of extrapolating research studies to vertebrates and the relatively low cost of rearing. Beetles are the largest insect order, with their representative - Tribolium castaneum - being the first species with a completely sequenced genome, and seem to be emerging as new potential candidates for model organisms in various studies. Apart from T. castaneum, additional species representing various Coleoptera families, such as Nicrophorus vespilloides, Leptinotarsa decemlineata, Coccinella septempunctata, Poecilus cupreus, Tenebrio molitor and many others, have been used. They are increasingly often included in two major research aspects: biomedical and environmental studies. Biomedical studies focus mainly on unraveling mechanisms of basic life processes, such as feeding, neurotransmission or activity of the immune system, as well as on elucidating the mechanism of different diseases (neurodegenerative, cardiovascular, metabolic, or immunological) using beetles as models. Furthermore, pharmacological bioassays for testing novel biologically active substances in beetles have also been developed. It should be emphasized that beetles are a source of compounds with potential antimicrobial and anticancer activity. Environmental-based studies focus mainly on the development and testing of new potential pesticides of both chemical and natural origin. Additionally, beetles are used as food or for their valuable supplements. Different beetle families are also used as bioindicators. Another important research area using beetles as models is behavioral ecology studies, for instance, parental care. In this paper, we review the current knowledge regarding beetles as model organisms and their practical application in various fields of life science.

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.

Therapeutic time window for the effects of erythropoietin on astrogliosis and neurite outgrowth in an in vitro model of spinal cord injury

BACKGROUND

The objective of this study was to investigate the underlying molecular mechanisms and the therapeutic time window for preventing astrogliosis with erythropoietin (EPO) treatment after in vitro modeled spinal cord injury (SCI).

METHODS

Cultured rat spinal cord astrocytes were treated with kainate and scratching to generate an in vitro model of SCI. EPO (100U/mL or 300U/mL) was added immediately or 2, 4, or 8 hours after injury. Some cultures were also treated with AG490, an inhibitor of the EPO-EPO receptor (EpoR) pathway mediator Janus kinase 2 (JAK2). To evaluate neurite extension, rat embryonic spinal cord neurons were seeded onto astrocyte cultures and treated with EPO immediately after injury in the presence or absence of anti-EpoR antibody.

RESULTS

EPO treatment at up to 8 hours after injury reduced the expression of axonal growth inhibiting molecules (glial fibrillary acidic protein, vimentin, and chondroitin sulfate proteoglycan), cytoskeletal regulatory proteins (Rho-associated protein kinase and ephephrin A4), and proinflammatory cytokines (tumor necrosis factor-alpha, transforming growth factor-beta, and phosphorylated-Smad3) in a dosedependent manner (P < .001). Most effects peaked with EPO treatment 2-4hours after injury. Additionally, EPO treatment up to 4 hours after injury promoted expression of the EpoR (>2-fold) and JAK2 (>3-fold) in a dose-dependent manner (P < .001), whereas co-treatment with AG490 precluded these effects (P < .001). EPO treatment up to 4hours after injury also enhanced axonal b-III tubulin-immunoreactivity (>12-fold), and this effect was precluded by co-treatment with an anti-EpoR antibody (P < .001).

CONCLUSIONS

EPO treatment within 8 hours after injury reduced astrogliosis, and EPO treatment within 4 hours promoted neurite outgrowth. EPO therapy immediately after spinal cord injury may regulate glia to generate an environment permissive of axonal regeneration.

Alternative Erythropoietin Receptors in the Nervous System

In addition to its regulatory function in the formation of red blood cells (erythropoiesis) in vertebrates, Erythropoietin (Epo) contributes to beneficial functions in a variety of non-hematopoietic tissues including the nervous system. Epo protects cells from apoptosis, reduces inflammatory responses and supports re-establishment of compromised functions by stimulating proliferation, migration and differentiation to compensate for lost or injured cells. Similar neuroprotective and regenerative functions of Epo have been described in the nervous systems of both vertebrates and invertebrates, indicating that tissue-protective Epo-like signaling has evolved prior to its erythropoietic function in the vertebrate lineage. Epo mediates its erythropoietic function through a homodimeric Epo receptor (EpoR) that is also widely expressed in the nervous system. However, identification of neuroprotective but non-erythropoietic Epo splice variants and Epo derivatives indicated the existence of other types of Epo receptors. In this review, we summarize evidence for potential Epo receptors that might mediate Epo's tissue-protective function in non-hematopoietic tissue, with focus on the nervous system. In particular, besides EpoR, we discuss three other potential neuroprotective Epo receptors: (1) a heteroreceptor consisting of EpoR and common beta receptor (βcR), (2) the Ephrin (Eph) B4 receptor and (3) the human orphan cytokine receptor-like factor 3 (CRLF3).

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

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

Effects of erythropoietin and methylprednisolone on AQP4 expression in astrocytes

Methylprednisolone sodium succinate (MPSS) has been suggested as a treatment for spinal cord injury (SCI), but its use has been limited due to its adverse effects. Erythropoietin (EPO) has been suggested as a promising candidate for limiting SCI in mammals. The aim of the present study was to investigate the effects of EPO in combination with MPSS on astrocytes following ischemic injury in vitro. Astrocytes were isolated from the cerebral cortex of postnatal day 3 Sprague-Dawley rats and cultured in vitro. Astrocyte ischemic injury was induced by oxygen and glucose deprivation for 4 h, and reperfusion was simulated by subsequent culture under normoxic conditions. The effects of EPO and MPSS on the expression of aquaporin-4 (AQP4) were investigated. Ischemic astrocytes were treated with EPO (10 U/ml), MPSS (10 µg/ml), or EPO (10 U/ml) in combination with MPSS (10 µg/ml) during reperfusion. The cell viability of astrocytes was assessed using an MTT assay. The mRNA and protein expression levels of AQP4 were determined using reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. The role of the protein kinase C (PKC) signaling pathway in the molecular mechanisms underlying the effects of EPO and MPSS was also investigated. The present results demonstrated that following treatment with EPO and MPSS, the mRNA expression levels of AQP4 were upregulated and cell viability was enhanced. EPO and MPSS effectively inhibited the oxygen and glucose deprivation-mediated downregulation of AQP4 following reperfusion. In addition, the combined treatment with EPO and MPSS exhibited higher AQP4 expression levels and cell viability compared with each treatment alone. Finally, the effects of EPO and MPSS on AQP4 expression were partially reversed by pretreatment with the PKC inhibitor Ro 31–8220. The present study indicated that EPO and MPSS had a synergistic effect on AQP4 expression following reperfusion, and suggest that they may be combined in the treatment of SCI.

The Insect Ortholog of the Human Orphan Cytokine Receptor CRLF3 Is a Neuroprotective Erythropoietin Receptor

The cytokine erythropoietin (Epo) mediates various cell homeostatic responses to environmental challenges and pathological insults. While stimulation of vertebrate erythrocyte production is mediated by homodimeric “classical” Epo receptors, alternative receptors are involved in neuroprotection. However, their identity remains enigmatic due to complex cytokine ligand and receptor interactions and conflicting experimental results. Besides the classical Epo receptor, the family of type I cytokine receptors also includes the poorly characterized orphan cytokine receptor-like factor 3 (CRLF3) present in vertebrates including human and various insect species. By making use of the more simple genetic makeup of insect model systems, we studied whether CRLF3 is a neuroprotective Epo receptor in animals. We identified a single ortholog of CRLF3 in the beetle Tribolium castaneum, and established protocols for primary neuronal cell cultures from Tribolium brains and efficient in vitro RNA interference. Recombinant human Epo as well as the non-erythropoietic Epo splice variant EV-3 increased the survival of serum-deprived brain neurons, confirming the previously described neuroprotective effect of Epo in insects. Moreover, Epo completely prevented hypoxia-induced apoptotic cell death of primary neuronal cultures. Knockdown of CRLF3 expression by RNA interference with two different double stranded RNA (dsRNA) fragments abolished the neuroprotective effect of Epo, indicating that CRLF3 is a crucial component of the insect Epo-responsive receptor. This suggests that a common urbilaterian ancestor of the orphan human and insect cytokine receptor CRLF3 served as a neuroprotective receptor for an Epo-like cytokine. Our work also suggests that vertebrate CRLF3, like its insect ortholog, might represent a tissue protection-mediating receptor.

Neuroprotective effects of erythropoietin against hypoxic injury via modulation of the mitogen-activated protein kinase pathway and apoptosis

Purpose

Hypoxic-ischemic encephalopathy is a significant cause of neonatal morbidity and mortality. Erythropoietin (EPO) is emerging as a therapeutic candidate for neuroprotection. Therefore, this study was designed to determine the neuroprotective role of recombinant human EPO (rHuEPO) and the possible mechanisms by which mitogen-activated protein kinase (MAPK) signaling pathway including extracellular signal-regulated kinase (ERK1/2), JNK, and p38 MAPK is modulated in cultured cortical neuronal cells and astrocytes.

Methods

Primary neuronal cells and astrocytes were prepared from cortices of ICR mouse embryos and divided into the normoxic, hypoxia (H), and hypoxia-pretreated with EPO (H+EPO) groups. The phosphorylation of MAPK pathway was quantified using western blot, and the apoptosis was assessed by caspase-3 measurement and terminal deoxynucleotidyl transferase dUTP nick end labeling assay.

Results

All MAPK pathway signals were activated by hypoxia in the neuronal cells and astrocytes (P<0.05). In the neuronal cells, phosphorylation of ERK-1/-2 and apoptosis were significantly decreased in the H+EPO group at 15 hours after hypoxia (P<0.05). In the astrocytes, phosphorylation of ERK-1/-2, p38 MAPK, and apoptosis was reduced in the H+EPO group at 15 hours after hypoxia (P<0.05).

Conclusion

Pretreatment with rHuEPO exerts neuroprotective effects against hypoxic injury reducing apoptosis by caspase-dependent mechanisms. Pathologic, persistent ERK activation after hypoxic injury may be attenuateed by pretreatment with EPO supporting that EPO may regulate apoptosis by affecting ERK pathways.

Erythropoietin-Mediated Regulation of Central Respiratory Command

Erythropoietin (Epo) is a cytokine expressed throughout the body, including in the central nervous system where it can act as a breathing modulator in the central respiratory network. In vitro, Epo allows maintaining the activity of respiratory neurons during acute hypoxia, resulting in inhibition of the hypoxia-induced rhythm depression. In vivo, Epo action on the central respiratory command results in enhancement of the acute hypoxic ventilatory response, allowing a better oxygenation of the body by improvement of gases exchanges in the lungs. Importantly, this effect of Epo is age-dependent, being observed at adulthood and at both early and late postnatal ages, but not at middle postnatal ages, when an important setup of the central respiratory command occurs. Epo regulation of the central respiratory command involves at least two intracellular signaling pathways, PI3K-Akt and MEK-ERK pathways. However, the exact mechanism underlying the action of Epo on the central respiratory control remains to be deciphered, as well as the exact cell types and nuclei involved in this control. Epo-mediated effect on the central respiratory command is regulated by several factors, including hypoxia, sex hormones, and an endogen antagonist. Although more knowledge is needed before reaching the clinical trial step, Epo seems to be a promising therapeutic treatment, notably against newborn breathing disorders.

Erythropoietin-Mediated Neuroprotection in Insects Suggests a Prevertebrate Evolution of Erythropoietin-Like Signaling

The cytokine erythropoietin (Epo) mediates protective and regenerative functions in mammalian nervous systems via activation of poorly characterized receptors that differ from the "classical" homodimeric Epo receptor expressed on erythroid progenitor cells. Epo genes have been identified in vertebrate species ranging from human to fish, suggesting that Epo signaling evolved earlier than the vertebrate lineage. Studies on insects (Locusta migratoria, Chorthippus biguttulus, Tribolium castaneum) revealed Epo-mediated neuroprotection and neuroregeneration. Recombinant human Epo (rhEpo) prevents apoptosis by binding to a janus kinase-associated receptor, stimulation of STAT transcription factors, and generation of factors that prevent the activation of proapoptotic caspases. Insect neurons were also protected by a neuroprotective but nonerythropoietic Epo splice variant, suggesting similarity with mammalian neuroprotective but not with homodimeric "classical" Epo receptors. Additionally, rhEpo promotes the regeneration of neurites in primary cultured insect brain neurons and after nerve crush in an in vivo preparation. In contrast to neuroprotective and regenerative effects shared with mammalian species, no evidence for a role of Epo signaling in the regulation of neuro- or gliogenesis was found in insects. Similar structural and functional characteristics of the Epo binding receptors, partly shared transduction pathways that prevent apoptosis and the functional implication in neuroprotective and neuroregenerative processes in both mammalian and insect species, suggest that Epo-like signaling was already established in their last common ancestor. Originally functioning as a tissue-protective response to unfavorable physiological situations, cell injury, and pathogen invasion, Epo was later adapted as a humoral regulator of erythropoiesis in the vertebrate lineage.

Erythropoietin Pretreatment Attenuates Seawater Aspiration-Induced Acute Lung Injury in Rats

Seawater drowning-induced acute lung injury (ALI) is a serious clinical condition characterized by increased alveolar-capillary permeability, excessive inflammatory responses, and refractory hypoxemia. However, current therapeutic options are largely supportive; thus, it is of great interest to search for alternative agents to treat seawater aspiration-induced ALI. Erythropoietin (EPO) is a multifunctional agent with antiinflammatory, antioxidative, and antiapoptotic properties. However, the effects of EPO on seawater aspiration-induced ALI remain unclear. In the present study, male rats were randomly assigned to the naive group, normal saline group, seawater group, or seawater + EPO group. EPO was administered intraperitoneally at 48 and 24 h before seawater aspiration. Arterial blood gas analysis was performed with a gas analyzer at baseline, 30 min, 1 h, 4 h, and 24 h after seawater aspiration, respectively. Histological scores, computed tomography scan, nuclear factor kappa B p65, inducible nitric oxide synthase, caspase-3, tumor necrosis factor-alpha, interleukin (IL)-1β, IL-6, IL-10, wet-to-dry weight ratio, myeloperoxidase activity, malondialdehyde, and superoxide dismutase in the lung were determined 30 min after seawater aspiration. Our results showed that EPO pretreatment alleviated seawater aspiration-induced ALI, as indicated by increased arterial partial oxygen tension and decreased lung histological scores. Furthermore, EPO pretreatment attenuated seawater aspiration-induced increase in the expressions of pulmonary nuclear factor kappa B p65, inducible nitric oxide synthase, caspase-3, tumor necrosis factor-alpha, IL-1β, myeloperoxidase activity, and malondialdehyde when compared with the seawater group. Collectively, our study suggested that EPO pretreatment attenuates seawater aspiration-induced ALI by down-regulation of pulmonary pro-inflammatory cytokines, oxidative stress, and apoptosis.

Erythropoietin Pathway: A Potential Target for the Treatment of Depression

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

Analysis of the erythropoietin of a Tibetan Plateau schizothoracine fish (Gymnocypris dobula) reveals enhanced cytoprotection function in hypoxic environments

BACKGROUND

Erythropoietin (EPO) is a glycoprotein hormone that plays a principal regulatory role in erythropoiesis and initiates cell homeostatic responses to environmental challenges. The Qinghai-Tibet Plateau is a natural laboratory for hypoxia adaptation. Gymnocypris dobula is a highly specialized plateau schizothoracine fish that is restricted to > 4500 m high-altitude freshwater rivers and ponds in the Qinghai-Tibet Plateau. The role of EPO in the adaptation of schizothoracine fish to hypoxia is unknown.

RESULTS

The EPO and EPO receptor genes from G. dobula and four other schizothoracine fish from various altitudinal habitats were characterized. Schizothoracine EPOs are predicted to possess 2-3 N-glycosylation (NGS) sites, 4-5 casein kinase II phosphorylation (CK2) sites, 1-2 protein kinase C (PKC) phosphorylation sites, and four conserved cysteine residues within four helical domains, with variations in the numbers of NGS and CK2 sites in G. dobula. PAML analysis indicated a d N/d S value (ω) = 1.112 in the G. dobula lineage, and a few amino acids potentially under lineage-specific positive selection were detected within the G. dobula EPO. Similarly, EPO receptors of the two high-altitude schizothoracines (G. dobula and Ptychobarbus kaznakovi), were found to be statistically on the border of positive selection using the branch-site model (P-value = 0.096), and some amino acids located in the ligand-binding domain and the fibronectin type III domain were identified as potentially positive selection sites. Tissue EPO expression profiling based on transcriptome sequencing of three schizothoracines (G. dobula, Schizothorax nukiangensis Tsao, and Schizothorax prenanti) showed significant upregulation of EPO expression in the brain and less significantly in the gill of G. dobula. The elevated expression together with the rapid evolution of the EPO gene in G. dobula suggested a possible role for EPO in adaptation to hypoxia. To test this hypothesis, Gd-EPO and Sp-EPO were cloned into an expression vector and transfected into the cultured cell line 293 T. Significantly higher cell viability was observed in cells transfected with Gd-EPO than cells harboring Sp-EPO when challenged by hypoxia.

CONCLUSION

The deduced EPO proteins of the schizothoracine fish contain characteristic structures and important domains similar to EPOs from other taxa. The presence of potentially positive selection sites in both EPO and EPOR in G. dobula suggest possible adaptive evolution in the ligand-receptor binding activity of the EPO signaling cascade in G. dobula. Functional study indicated that the EPO from high-altitude schizothoracine species demonstrated features of hypoxic adaptation by reducing toxic effects or improving cell survival when expressed in cultured cells, providing evidence of molecular adaptation to hypoxic conditions in the Qinghai-Tibet Plateau.

Regeneration in the nervous system with erythropoietin

Globally, greater than 30 million individuals are afflicted with disorders of the nervous system accompanied by tens of thousands of new cases annually with limited, if any, treatment options. Erythropoietin (EPO) offers an exciting and novel therapeutic strategy to address both acute and chronic neurodegenerative disorders. EPO governs a number of critical protective and regenerative mechanisms that can impact apoptotic and autophagic programmed cell death pathways through protein kinase B (Akt), sirtuins, mammalian forkhead transcription factors, and wingless signaling. Translation of the cytoprotective pathways of EPO into clinically effective treatments for some neurodegenerative disorders has been promising, but additional work is necessary. In particular, development of new treatments with erythropoiesis-stimulating agents such as EPO brings several important challenges that involve detrimental vascular outcomes and tumorigenesis. Future work that can effectively and safely harness the complexity of the signaling pathways of EPO will be vital for the fruitful treatment of disorders of the nervous system.

Expression of the erythropoietin receptor by germline-derived cells - further support for a potential developmental link between the germline and hematopoiesis

BACKGROUND

Expressing several markers of migrating primordial germ cells (PGCs), the rare population of quiescent, bone marrow (BM)-residing very small embryonic-like stem cells (VSELs) can be specified like PGCs into hematopoietic stem/progenitor cells (HSPCs). These two properties of VSELs support the possibility of a developmental origin of HSPCs from migrating PGCs.

METHODS

To address a potential link between VSELs and germ line cells we analyzed by RT-PCR and FACS expression of erythropoietin receptor (EpoR) on murine bone marrow- and human umbilical cord blood-derived VSELs, murine and human teratocarcinoma cell lines and human ovarian cancer cells. A proper gating strategy and immunostaining excluded from FACS analysis potential contamination by erythroblasts. Furthermore, the transwell chemotaxis assays as well as adhesion and signaling studies were performed to demonstrate functionality of erythropoietin - EpoR axes on these cells.

RESULTS

We report here that murine and human VSELs as well as murine and human teratocarcinoma cell lines and ovarian cancer cell lines share a functional EpoR.

CONCLUSIONS

Our data provide more evidence of a potential developmental link between germline cells, VSELs, and HSCs and sheds more light on the developmental hierarchy of the stem cell compartment in adult tissues.