Erythropoietin: elucidating new cellular targets that broaden therapeutic strategies

Expression of erythropoietin receptor protein in the mouse hippocampus in response to normobaric hypoxia

Background

Over the past decades, accumulating research on erythropoietin (EPO) and its receptor (EPOR) has revealed various neuroprotective actions and upregulation in hypoxic conditions. To our knowledge, EPOR protein levels in the hippocampus and isocortex have never been measured. Therefore, the aim of this study was to measure EPOR protein in the hippocampus (HPC) and prefrontal cortex (PFC). Further objectives were to examine the effects of exposure to normobaric hypoxia of various degrees and durations on EPOR protein and to explore how long-lasting these effects were.

Method

Adult C57BL/6 mice were randomized into a control group (N = 12) or various hypoxia groups (N = 5-11). Mice were exposed to three different O2 concentrations (10 %, 12 %, or 18 %) for 8 h a day for 5 days and sacrificed immediately after the last exposure. The effect of exposure to 12 % O2 for 1 day and 4 weeks (8 h per day) at this survival time was also examined. Additionally, groups of mice were exposed to 12 % O2 for 1 or 5 days (8 h per day) and euthanized at various times (up to 3 weeks) thereafter to examine the duration of EPOR protein regulation in the HPC and the PFC. EPOR protein was detected with a sandwich-ELISA method.

Results

EPOR protein was present in the HPC and PFC, at 206.64 ± 43.98 pg/mg and 184.25 ± 48.21 pg/mg, respectively. The highest increase in EPOR protein was observed in the HPC after 5 days of 8 h exposure to 12 % O2 and was most pronounced 24 h after last exposure. The effect of hypoxia normalized within one week after the last exposure.

Conclusion

This study successfully measured hippocampal EPOR protein and showed a significant association between normobaric hypoxia and acute EPOR elevation. It is our hope that this study can provide guidance to future research on the neuroprotective effects of EPO.

Probiotic Potential of Bacillus amyloliquefaciens Isolated from Tibetan Yaks

The Tibetan livestock sector is now ailing from many infectious ailments brought on by harmful microorganisms. Therefore, this research aimed to assess the probiotic potential and safety of Bacillus amyloliquefaciens isolated from yaks in the Tibet area to provide upper-edge strain resources for probiotics development. The four strains isolated from the intestine of yaks had been identified as Bacillus amyloliquefaciens after the 16S rRNA sequence. The ethanol, bile salt, and acid tolerance revealed that the isolates had significant tolerance levels. The antibiotics susceptibility assay showed that the strains were sensitive to commonly used antibiotics, while the antibacterial assay prevented the isolates from outperforming five harmful bacteria in terms of antibacterial potency. Moreover, it was evident that strain BA5 had the strongest activity to scavenge hydroxyl radical and reduce power. According to the animal experiment, no apparent pathological change was observed in intestinal tissue sections. Furthermore, the strain had a positive effect on promoting the development of jejunal villi referred to its safety. Therefore, more research is required into the bacteriostatic and antioxidant capabilities of isolates in animal production.

The role and therapeutic potential of nuclear factor κB (NF-κB) in ischemic stroke

Stroke is a prevalent cerebrovascular condition with a global impact, causing significant rates of illness and death. Despite extensive research, the available treatment options for stroke remain restricted. Hence, it is crucial to gain a deeper understanding of the molecular mechanisms associated with the onset and advancement of stroke in order to establish a theoretical foundation for novel preventive and therapeutic approaches. NF-κB, also known as nuclear factor κB, is a transcription factor responsible for controlling the expression of numerous genes and plays a crucial role in diverse physiological processes. NF-κB is triggered and regulates neuroinflammation and other processes after stroke, promoting the generation of cytokine storms and contributing to the advancement of ischemic stroke (IS). Therefore, NF-κB could potentially play a vital role in stroke by regulating diverse pathophysiological processes. This review provides an overview of the functions of NF-κB in stroke and its governing mechanisms. In addition, our attention is directed towards various potential therapies that aim to inhibit the NF-κB signaling pathway in order to offer valuable insights for the advancement of innovative treatment approaches for stroke.

Drug Utilization Evaluation of Erythropoietin at a Referral Teaching Hospital in Iran

Objectives

Drug utilization evaluation (DUE) studies aim to survey the appropriateness of drug use. DUE is an executive approach used to improve the use of medications as well as reduce the cost of treatment, ensure drug adequacy, and improve patient safety. The aim of this study was to evaluate the pattern of erythropoietin use, according to standard guidelines, in patients admitted to Namazi Hospital in Shiraz, Iran.

Methods

In this descriptive, retrospective study, 230 patients were assessed. All patients who were hospitalized in different wards of Namazi Hospital, affiliated to Shiraz University of Medical Sciences, and received at least three doses of erythropoietin from September 2019 to March 2020 participated in this study. The following standard indicators of erythropoietin use were evaluated through reviewing medical charts of the cohort: drug dose, dosing intervals, route of administration, indication, monitoring of laboratory parameters, drug dose adjustment based on the response rate as well as target hemoglobin ≥12 g/dl, attention to major drug interactions, and administration of injectable or oral iron supplementation during treatment.

Results

Most (65.2%) of the participants were male. The mean ± SD age of the patients was 47.55 ± 22.71 years. More than half (51.3%) of the included subjects were hospitalized in the nephrology ward. PDpoetin® and Cinnapoietin® were given to 52.6% and 47.4% of the study participants, respectively. Treatment of anemia due to chronic kidney disease was the most frequent indication of erythropoietin. The time interval of erythropoietin administration was three times a week for 68.3% of the patients. The most frequently administered weekly dose of erythropoietin was 12,000 units. The weekly dose, dose interval, and route of administration of erythropoietin were appropriate in 52.6%, 77.4%, and 100% of the patients, respectively. Dose adjustment based on the response rate, attention to major drug interactions as well as absolute-relative contraindications, and attention to the target hemoglobin ≥12 g/dl to decide whether or not to continue treatment were based on standard guideline in 98.1%, 98.7%, and 93% of the patients, respectively. The sum indexes of erythropoietin use were in line with standard guidelines in 75.84% of the cases.

Conclusion

According to our results, in the setting of erythropoietin use in hospitals, physicians need more attention and education in areas such as selecting the proper dose of medication, correct indication of the drug, temporal arrangement of monitoring laboratory items, and the patient's need for iron supplements.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Therapeutic Effect of Erythropoietin on Alzheimer's Disease by Activating the Serotonin Pathway

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by memory impairment in patients. Erythropoietin (EPO) has been reported to stimulate neurogenesis. This study was conducted to determine the regenerative effects of EPO in an AD model and to assess its underlying mechanism. Recombinant human EPO was intraperitoneally administered to AD mice induced by intracerebroventricular Aβ oligomer injection. Behavioral assessments with novel object recognition test and passive avoidance task showed improvement in memory function of the EPO-treated AD mice compared to that of the saline-treated AD mice (p < 0.0001). An in vivo protein assay for the hippocampus and cortex tissue indicated that EPO treatment modulated neurotransmitters, including dopamine, serotonin, and adrenaline. EPO treatment also restored the activity of serotonin receptors, including 5-HT4R, 5-HT7R, and 5-HT1aR (p < 0.01), at mRNA levels. Furthermore, EPO seemed to exert an anti-inflammatory influence by downregulating TLR4 at mRNA and protein levels (p < 0.05). Finally, an immunohistochemical assay revealed increments of Nestin(+) and NeuN(+) neuronal cells in the CA3 region in the EPO-treated AD mice compared to those in the saline-treated AD mice. The conclusion is that EPO administration might be therapeutic for AD by activating the serotonergic pathway, anti-inflammatory action, and neurogenic characteristics.

Erythropoietin promotes M2 macrophage phagocytosis of Schwann cells in peripheral nerve injury

Following acute sciatic nerve crush injury (SNCI), inflammation and the improper phagocytic clearance of dying Schwann cells (SCs) has effects on remodeling that lead to morbidity and incomplete functional recovery. Therapeutic strategies like the use of erythropoietin (EPO) for peripheral nerve trauma may serve to bring immune cell phagocytotic clearance under control to support debris clearance. We evaluated EPO’s effect on SNCI and found EPO treatment increased myelination and sciatic functional index (SFI) and bolstered anti-apoptosis and phagocytosis of myelin debris via CD206⁺ macrophages when compared to saline treatment. EPO enhanced M2 phenotype activity, both in bone marrow-derived macrophages (BMMØs) and peritoneal-derived macrophages (PMØs) in vitro, as well as in PMØs in vivo. EPO increased efferocytosis of apoptotic sciatic nerve derived Schwann cells (SNSCs) in both settings as demonstrated using immunofluorescence (IF) and flow cytometry. EPO treatment significantly attenuated pro-inflammatory genes (IL1β, iNOS, and CD68) and augmented anti-inflammatory genes (IL10 and CD163) and the cell-surface marker CD206. EPO also increased anti-apoptotic (Annexin V/7AAD) effects after lipopolysaccharide (LPS) induction in macrophages. Our data demonstrate EPO promotes the M2 phenotype macrophages to ameliorate apoptosis and efferocytosis of dying SCs and myelin debris and improves SN functional recovery following SNCI.

Erythropoietin Promotes Infection Resolution and Lowers Antibiotic Requirements in E. coli- and S. aureus-Initiated Infections

Endogenous mechanisms underlying bacterial infection resolution are essential for the development of novel therapies for the treatment of inflammation caused by infection without unwanted side effects. Herein, we found that erythropoietin (EPO) promoted the resolution and enhanced antibiotic actions in Escherichia coli (E. coli)- and Staphylococcus aureus (S. aureus)-initiated infections. Levels of peritoneal EPO and macrophage erythropoietin receptor (EPOR) were elevated in self-limited E. coli-initiated peritonitis. Myeloid-specific EPOR-deficient mice exhibited an impaired inflammatory resolution and exogenous EPO enhanced this resolution in self-limited infections. Mechanistically, EPO increased macrophage clearance of bacteria via peroxisome proliferator-activated receptor γ (PPARγ)-induced CD36. Moreover, EPO ameliorated inflammation and increased the actions of ciprofloxacin and vancomycin in resolution-delayed E. coli- and S. aureus-initiated infections. Collectively, macrophage EPO signaling is temporally induced during infections. EPO is anti-phlogistic, increases engulfment, promotes infection resolution, and lowers antibiotic requirements.

Effect of simulated microgravity on metabolism of HGC-27 gastric cancer cells

The understanding into the pathogenesis and treatment of gastric cancer has improved in recent years; however, a number of limitations have delayed the development of effective treatment. Cancer cells can undergo glycolysis and inhibit oxidative phosphorylation in the presence of oxygen (Warburg effect). Previous studies have demonstrated that a rotary cell culture system (RCCS) can induce glycolytic metabolism. In addition, the potential of regulating cancer cells by targeting their metabolites has led to the rapid development of metabolomics. In the present study, human HGC-27 gastric cancer cells were cultured in a RCCS bioreactor, simulating weightlessness. Subsequently, liquid chromatography-mass spectrometry was used to examine the effects of simulated microgravity (SMG) on the metabolism of HGC-27 cells. A total of 67 differentially regulated metabolites were identified, including upregulated and downregulated metabolites. Compared with the normal gravity group, phosphatidyl ethanolamine, phosphatidyl choline, arachidonic acid and sphinganine were significantly upregulated in SMG conditions, whereas sphingomyelin, phosphatidyl serine, phosphatidic acid, L-proline, creatine, pantothenic acid, oxidized glutathione, adenosine diphosphate and adenosine triphosphate were significantly downregulated. The Human Metabolome Database compound analysis revealed that lipids and lipid-like metabolites were primarily affected in an SMG environment in the present study. Overall, the findings of the present study may aid our understanding of gastric cancer by identifying the underlying mechanisms of metabolism of the disease under SMG.

Integration of probabilistic regulatory networks into constraint-based models of metabolism with applications to Alzheimer's disease

Background

Mathematical models of biological networks can provide important predictions and insights into complex disease. Constraint-based models of cellular metabolism and probabilistic models of gene regulatory networks are two distinct areas that have progressed rapidly in parallel over the past decade. In principle, gene regulatory networks and metabolic networks underly the same complex phenotypes and diseases. However, systematic integration of these two model systems remains a fundamental challenge.

Results

In this work, we address this challenge by fusing probabilistic models of gene regulatory networks into constraint-based models of metabolism. The novel approach utilizes probabilistic reasoning in BN models of regulatory networks serves as the “glue” that enables a natural interface between the two systems. Probabilistic reasoning is used to predict and quantify system-wide effects of perturbation to the regulatory network in the form of constraints for flux variability analysis. In this setting, both regulatory and metabolic networks inherently account for uncertainty. Applications leverage constraint-based metabolic models of brain metabolism and gene regulatory networks parameterized by gene expression data from the hippocampus to investigate the role of the HIF-1 pathway in Alzheimer’s disease. Integrated models support HIF-1A as effective target to reduce the effects of hypoxia in Alzheimer’s disease. However, HIF-1A activation is far less effective in shifting metabolism when compared to brain metabolism in healthy controls.

Conclusions

The direct integration of probabilistic regulatory networks into constraint-based models of metabolism provides novel insights into how perturbations in the regulatory network may influence metabolic states. Predictive modeling of enzymatic activity can be facilitated using probabilistic reasoning, thereby extending the predictive capacity of the network. This framework for model integration is generalizable to other systems.

Electronic supplementary material

The online version of this article (10.1186/s12859-019-2872-8) contains supplementary material, which is available to authorized users.

Pharmacological modulation of cell functional activity with valproic acid and erythropoietin

Introduction: Valproic acid (VA) is carboxylic acid with a branched chain, which is used as an antiepileptic drug.

Valproic acid influence on cells in vivo: VA, which is an antiepileptic drug, is also a teratogen, which causes defects of a neural tube and an axial skeleton, although the mechanisms are not yet fully clear.

Valproic acid influence on mesenchymal stem cells (MSC) in vitro: It is shown that valproic acid reduces the intracellular level of oxygen active forms.

Valproic acid effect on tumor cells: VA inhibits tumor growth through several mechanisms, including the cell cycle stop, differentiation induction and inhibition of growth of tumor vessels.

Valproic acid influence on enzymes: It affects mainly GSK-3.

Valproic acid influence on animals’ cells: It is shown that VA can significantly improve an ability to develop in vitro and improve nuclear reprogramming of embryos.

Erythropoietin (EPO): Is an hypoxia-induced hormone and a cytokine, which is necessary for normal erythropoiesis. EPO is widely used in in vitro experiments.

Conclusion: Thus, the influence of VA and EPO on cells can be used in cell technologies.

Potential use of transgenic domestic pigs expressing recombinant human erythropoietin in diabetes translation research

Recently, diabetes mellitus (DM) has shown rapid global increases with about five million deaths annually. Animal models are imperative to understand disease mechanisms and develop diagnostic, preventive, and therapeutic interventions in translational research. Rodent and mini-pig models have been established and widely used for DM research. However, domestic pig models are limited in spite of advantages such as pharmacokinetic and physiopathological availability. This study examines the potential use of domestic pigs expressing recombinant human erythropoietin (rhEPO) as disease and therapeutic response models for DM. We previously generated transgenic pigs (n = 16, EPO Tg) in which rhEPO was expressed and circulated in all organs. Thirty-two pigs, including 16 controls, were fed high fat (HF) diets for 42 weeks. Subsequently, blood samples for chemical and metabolic analysis were collected after fasting for 24 h and glucose loading for oral glucose tolerance tests (OGTTs). We found increased activation of the PI3 K/Akt signaling pathway under hypoxic conditions after rhEPO treatment, and HF diet-inducible-obesity in the EPO Tg and control pigs. OGTTs showed lower fasting glucose levels in the EPO Tg pigs than in controls before and after the HF diet, suggesting that rhEPO may affect glucose concentrations. Insulin and C-peptide concentrations responded slowly to glucose administration and returned to initial levels after 2 h. The blood test results suggest that EPO might affect metabolic and chemical components such as glucose, high-density lipoprotein, glucagon, triglyceride, and free fatty acid. Our findings support the use of rhEPO transgenic domestic pigs as model animals for translational DM research.

Could erythropoietin reduce the ovarian damage of cisplatin in female rats?

The aim of this study is to investigate whether erythropoietin (EPO) can reduce the ovarian damage of cisplatin or not. Thirty, female, Wistar-Albino rats were used in the study. Control group (N = 10): Intraperitoneal saline infusion, Cisplatin group (N = 10): Intraperitoneal 7 mg/kg cisplatin, Cisplatin + EPO group (N = 10): Intraperitoneal 7 mg/kg cisplatin and subcutaneous 200 IU/kg/day EPO. Serum AMH concentrations were measured by enzyme-linked immunosorbent assay kit of AMH. Follicular counts were evaluated according to mean diameter of the follicles. Ovarian damage; including follicular cell degeneration, vascular congestion, hemorrhage, and inflammation was scored histologically using a graduated scale. Posttreatment AMH levels of cisplatin group were significantly lower than control and cisplatin + EPO groups. In cisplatin group, there was a significant decrement in posttreatment AMH level compared to pretreatment AMH level. The total damage score of cisplatin group was significantly higher than scores of control and cisplatin + EPO groups. The mean primordial follicle counts of control and cisplatin + EPO groups were significantly higher than that of cisplatin group (p = .007 and p = .003). The results of this study revealed that EPO administration to cisplatin chemotherapy could ameliorate the ovarian damage. Erythropoietin administration to chemotherapeutic agents might suggest to protect ovarian failure and infertility.

Erythropoietin and mTOR: A "One-Two Punch" for Aging-Related Disorders Accompanied by Enhanced Life Expectancy

Life expectancy continues to increase throughout the world, but is accompanied by a rise in the incidence of non-communicable diseases. As a result, the benefits of an increased lifespan can be limited by aging-related disorders that necessitate new directives for the development of effective and safe treatment modalities. With this objective, the mechanistic target of rapamycin (mTOR), a 289-kDa serine/threonine protein, and its related pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), proline rich Akt substrate 40 kDa (PRAS40), AMP activated protein kinase (AMPK), Wnt signaling, and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), have generated significant excitement for furthering novel therapies applicable to multiple systems of the body. Yet, the biological and clinical outcome of these pathways can be complex especially with oversight of cell death mechanisms that involve apoptosis and autophagy. Growth factors, and in particular erythropoietin (EPO), are one avenue under consideration to implement control over cell death pathways since EPO can offer potential treatment for multiple disease entities and is intimately dependent upon mTOR signaling. In experimental and clinical studies, EPO appears to have significant efficacy in treating several disorders including those involving the developing brain. However, in mature populations that are affected by aging-related disorders, the direction for the use of EPO to treat clinical disease is less clear that may be dependent upon a number of factors including the understanding of mTOR signaling. Continued focus upon the regulatory elements that control EPO and mTOR signaling could generate critical insights for targeting a broad range of clinical maladies.

FOXO Signaling Pathways as Therapeutic Targets in Cancer

Many transcription factors play a key role in cellular differentiation and the delineation of cell phenotype. Transcription factors are regulated by phosphorylation, ubiquitination, acetylation/deacetylation and interactions between two or more proteins controlling multiple signaling pathways. These pathways regulate different physiological processes and pathological events, such as cancer and other diseases. The Forkhead box O (FOXO) is one subfamily of the fork head transcription factor family with important roles in cell fate decisions and this subfamily is also suggested to play a pivotal functional role as a tumor suppressor in a wide range of cancers. During apoptosis, FOXOs are involved in mitochondria-dependent and -independent processes triggering the expression of death receptor ligands like Fas ligand, TNF apoptosis ligand and Bcl‑X_L, bNIP3, Bim from Bcl-2 family members. Different types of growth factors like insulin play a vital role in the regulation of FOXOs. The most important pathway interacting with FOXO in different types of cancers is the PI3K/AKT pathway. Some other important pathways such as the Ras-MEK-ERK, IKK and AMPK pathways are also associated with FOXOs in tumorigenesis. Therapeutically targeting the FOXO signaling pathway(s) could lead to the discovery and development of efficacious agents against some cancers, but this requires an enhanced understanding and knowledge of FOXO transcription factors and their regulation and functioning. This review focused on the current understanding of cell biology of FOXO transcription factors which relates to their potential role as targets for the treatment and prevention of human cancers. We also discuss drugs which are currently being used for cancer treatment along with their target pathways and also point out some potential drawbacks of those drugs, which further signifies the need for development of new drug strategies in the field of cancer treatment.

Age-associated expression of erythropoietin and its receptor in rat spiral ganglion neurons and its association with neuronal apoptosis and hearing alterations

The present study aimed to determine the expression of erythropoietin (EPO) and the EPO receptor (EPOR) in spiral ganglion neurons (SGNs) in the inner ear of rats of various ages, and the associated neuronal apoptosis and hearing alterations. A total of 15 healthy rats (n=30 ears), were divided into three groups: i) A nominated infant group at post-natal day (PND) 12–14, ii) an adult group at PND 60 and iii) a 3-year postnatal aged group. Auditory brainstem response (ABR) measurements were performed on all rats. EPO and EPOR expression in the inner ear was detected by immunohistochemistry. In situ terminal deoxynucleotidyl transferase dUTP nick end labeling assays were performed to detect the apoptosis of SGNs. The average hearing thresholds of the ABR (decibels above normal hearing level) were 5.625±4.955 in the infant, 15.000±8.498 in the adult and 23.500±13.134 in the aged groups. Hearing thresholds for aged and adult rats increased significantly compared with infant rats. However, the difference in latencies of peak I was not significant (P>0.05). EPO in SGNs was detected during different developmental periods without significant alterations, but were reduced compared with Corti's organ or the stria vascularis. EPOR expression increased significantly from infant to adult stage, and this increased expression was maintained in the aged group. An age-associated increase in the apoptosis of SGNs was detected in all three groups (P=0.0347). The potential neuroprotective effects of EPO in SGNs may not be revealed during the aging process under natural conditions, and may be associated with spontaneous neuronal apoptosis and consequently, hearing diminution. However, the age-associated increase in EPOR in SGNs may exert a role in neuroprotection when necessary, for example in presbycusis.

Phagocyte respiratory burst activates macrophage erythropoietin signalling to promote acute inflammation resolution

Inflammation resolution is an active process, the failure of which causes uncontrolled inflammation which underlies many chronic diseases. Therefore, endogenous pathways that regulate inflammation resolution are fundamental and of wide interest. Here, we demonstrate that phagocyte respiratory burst-induced hypoxia activates macrophage erythropoietin signalling to promote acute inflammation resolution. This signalling is activated following acute but not chronic inflammation. Pharmacological or genetical inhibition of the respiratory burst suppresses hypoxia and macrophage erythropoietin signalling. Macrophage-specific erythropoietin receptor-deficient mice and chronic granulomatous disease (CGD) mice, which lack the capacity for respiratory burst, display impaired inflammation resolution, and exogenous erythropoietin enhances this resolution in WT and CGD mice. Mechanistically, erythropoietin increases macrophage engulfment of apoptotic neutrophils via PPARγ, promotes macrophage removal of debris and enhances macrophage migration to draining lymph nodes. Together, our results provide evidences of an endogenous pathway that regulates inflammation resolution, with important implications for treating inflammatory conditions.

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

Charting a course for erythropoietin in traumatic brain injury

Traumatic brain injury (TBI) is a severe public health problem that impacts more than four million individuals in the United States alone and is increasing in incidence on a global scale. Importantly, TBI can result in acute as well as chronic impairments for the nervous system leaving individuals with chronic disability and in instances of severe trauma, death becomes the ultimate outcome. In light of the significant negative health consequences of TBI, multiple therapeutic strategies are under investigation, but those focusing upon the cytokine and growth factor erythropoietin (EPO) have generated a great degree of enthusiasm. EPO can control cell death pathways tied to apoptosis and autophagy as well oversees processes that affect cellular longevity and aging. In vitro studies and experimental animal models of TBI have shown that EPO can restore axonal integrity, promote cellular proliferation, reduce brain edema, and preserve cellular energy homeostasis and mitochondrial function. Clinical studies for neurodegenerative disorders that involve loss of cognition or developmental brain injury support a positive role for EPO to prevent or reduce injury in the nervous system. However, recent clinical trials with EPO and TBI have not produced such clear conclusions. Further clinical studies are warranted to address the potential efficacy of EPO during TBI, the concerns with the onset, extent, and duration of EPO therapeutic strategies, and to focus upon the specific downstream pathways controlled by EPO such as protein kinase B (Akt), mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), sirtuins, wingless pathways, and forkhead transcription factors for improved precision against the detrimental effects of TBI.

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.

FoxO proteins in the nervous system

Acute as well as chronic disorders of the nervous system lead to significant morbidity and mortality for millions of individuals globally. Given the ability to govern stem cell proliferation and differentiated cell survival, mammalian forkhead transcription factors of the forkhead box class O (FoxO) are increasingly being identified as potential targets for disorders of the nervous system, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and auditory neuronal disease. FoxO proteins are present throughout the body, but they are selectively expressed in the nervous system and have diverse biological functions. The forkhead O class transcription factors interface with an array of signal transduction pathways that include protein kinase B (Akt), serum- and glucocorticoid-inducible protein kinase (SgK), IκB kinase (IKK), silent mating type information regulation 2 homolog 1 (S. cerevisiae) (SIRT1), growth factors, and Wnt signaling that can determine the activity and integrity of FoxO proteins. Ultimately, there exists a complex interplay between FoxO proteins and their signal transduction pathways that can significantly impact programmed cell death pathways of apoptosis and autophagy as well as the development of clinical strategies for the treatment of neurodegenerative disorders.

Novel applications of trophic factors, Wnt and WISP for neuronal repair and regeneration in metabolic disease

Diabetes mellitus affects almost 350 million individuals throughout the globe resulting in significant morbidity and mortality. Of further concern is the growing population of individuals that remain undiagnosed but are susceptible to the detrimental outcomes of this disorder. Diabetes mellitus leads to multiple complications in the central and peripheral nervous systems that include cognitive impairment, retinal disease, neuropsychiatric disease, cerebral ischemia, and peripheral nerve degeneration. Although multiple strategies are being considered, novel targeting of trophic factors, Wnt signaling, Wnt1 inducible signaling pathway protein 1, and stem cell tissue regeneration are considered to be exciting prospects to overcome the cellular mechanisms that lead to neuronal injury in diabetes mellitus involving oxidative stress, apoptosis, and autophagy. Pathways that involve insulin-like growth factor-1, fibroblast growth factor, epidermal growth factor, and erythropoietin can govern glucose homeostasis and are intimately tied to Wnt signaling that involves Wnt1 and Wnt1 inducible signaling pathway protein 1 (CCN4) to foster control over stem cell proliferation, wound repair, cognitive decline, β-cell proliferation, vascular regeneration, and programmed cell death. Ultimately, cellular metabolism through Wnt signaling is driven by primary metabolic pathways of the mechanistic target of rapamycin and AMP activated protein kinase. These pathways offer precise biological control of cellular metabolism, but are exquisitely sensitive to the different components of Wnt signaling. As a result, unexpected clinical outcomes can ensue and therefore demand careful translation of the mechanisms that govern neural repair and regeneration in diabetes mellitus.

Erythropoietin attenuates advanced glycation endproducts-induced toxicity of Schwann cells in vitro

Advanced glycation endproducts (AGEs)-induced cytotoxicity is regarded as one of the main mechanisms responsible for neurological disorders. Although erythropoietin (EPO) is demonstrated to have neuroprotective effects in neurodegenerative diseases, the effects of EPO on AGEs-induced toxicity of Schwann cells (SCs) remain open for investigation. Primary cultured SCs isolated from 4 day-old Wistar rats were exposed to AGEs with or without EPO treatment for 5 days. AGEs decreased cell viability, increased apoptotic rate, elevated intracellular reactive oxygen species levels, and reduced total glutathione levels of SCs. The AGEs-induced toxic effects on SCs were partially blocked by AGER siRNA or AGER inhibitor FPS-ZM1. SCs exposed to AGEs exhibited higher mRNA and protein levels of receptor for AGEs (AGER), EPO, and EPO receptor (EPOR). Exogenous EPO treatment attenuated AGEs-induced oxidative stress and apoptosis probably by reducing the mRNA and protein expression of AGER. The protective effect of EPO against AGEs-induced toxicity was blocked by EPOR siRNA. The data of the present study gives, for the first time, evidence of the protective effects of EPO on SCs with AGEs-induced oxidative stress and apoptosis. These results imply that EPO might be a novel valuable agent for treating AGEs-induced toxicity.

Programming apoptosis and autophagy with novel approaches for diabetes mellitus

According to the World Health Organization, diabetes mellitus (DM) in the year 2030 will be ranked the seventh leading cause of death in the world. DM impacts all systems of the body with oxidant stress controlling cell fate through endoplasmic reticulum stress, mitochondrial dysfunction, alterations in uncoupling proteins, and the induction of apoptosis and autophagy. Multiple treatment approaches are being entertained for DM with Wnt1 inducible signaling pathway protein 1 (WISP1), mechanistic target of rapamycin (mTOR), and silent mating type information regulation 2 homolog) 1 (S. cerevisiae) (SIRT1) generating significant interest as target pathways that can address maintenance of glucose homeostasis as well as prevention of cellular pathology by controlling insulin resistance, stem cell proliferation, and the programmed cell death pathways of apoptosis and autophagy. WISP1, mTOR, and SIRT1 can rely upon similar pathways such as AMP activated protein kinase as well as govern cellular metabolism through cytokines such as EPO and oral hypoglycemics such as metformin. Yet, these pathways require precise biological control to exclude potentially detrimental clinical outcomes. Further elucidation of the ability to translate the roles of WISP1, mTOR, and SIRT1 into effective clinical avenues offers compelling prospects for new therapies against DM that can benefit hundreds of millions of individuals throughout the globe.

Systemic and Cerebral Vascular Endothelial Growth Factor Levels Increase in Murine Cerebral Malaria along with Increased Calpain and Caspase Activity and Can be Reduced by Erythropoietin Treatment

The pathogenesis of cerebral malaria (CM) includes compromised microvascular perfusion, increased inflammation, cytoadhesion, and endothelial activation. These events cause blood-brain barrier disruption and neuropathology and associations with the vascular endothelial growth factor (VEGF) signaling pathway have been shown. We studied this pathway in mice infected with Plasmodium berghei ANKA causing murine CM with or without the use of erythropoietin (EPO) as adjunct therapy. ELISA and western blotting was used for quantification of VEGF and relevant proteins in brain and plasma. CM increased levels of VEGF in brain and plasma and decreased plasma levels of soluble VEGF receptor 2. EPO treatment normalized VEGF receptor 2 levels and reduced brain VEGF levels. Hypoxia-inducible factor (HIF)-1α was significantly upregulated whereas cerebral HIF-2α and EPO levels remained unchanged. Furthermore, we noticed increased caspase-3 and calpain activity in terminally ill mice, as measured by protease-specific cleavage of α-spectrin and p35. In conclusion, we detected increased cerebral and systemic VEGF as well as HIF-1α, which in the brain were reduced to normal in EPO-treated mice. Also caspase and calpain activity was reduced markedly in EPO-treated mice.

Erythropoietin attenuates oxidative stress and apoptosis in Schwann cells isolated from streptozotocin-induced diabetic rats

OBJECTIVES

High glucose-evoked oxidative stress and apoptosis within Schwann cells (SCs) are mechanisms facilitating the procession of diabetic peripheral neuropathy (DPN). Although erythropoietin (EPO) was demonstrated to have neuroprotective effects in neurodegenerative diseases, the effects of EPO on glucose-evoked oxidative stress and apoptosis of SCs remain unknown.

METHODS

Primary cultured SCs isolated from streptozotocin (STZ)-induced diabetic peripheral neuropathic rats and normal control rats were exposed to high or normal glucose condition with or without EPO incubation for 72 h. Cell viability, apoptotic rate, cellular reactive oxygen species (ROS) level, total glutathione (GSH) level, EPO mRNA and erythropoietin receptor (EPOR) mRNA levels were assayed.

KEY FINDINGS

SCs from diabetic rats showed a lower cell viability and a higher apoptotic rate. High glucose culture condition elevated ROS level and diminished total GSH level of SCs. EPO improved cell viability and decreased cell apoptotic rate of SCs. EPO also elevated total GSH level and decreased intracellular ROS level. SCs from diabetic rats exhibited higher EPO mRNA and EPOR mRNA levels than SCs from normal control rats.

CONCLUSIONS

The data of this study offered fresh viewpoints for interpreting the pathogenesis of DPN and novel pharmacological principles implicit in the therapeutic effect of EPO.

Erythropoietin-derived nonerythropoietic peptide ameliorates experimental autoimmune neuritis by inflammation suppression and tissue protection

Experimental autoimmune neuritis (EAN) is an autoantigen-specific T-cell-mediated disease model for human demyelinating inflammatory disease of the peripheral nervous system. Erythropoietin (EPO) has been known to promote EAN recovery but its haematopoiesis stimulating effects may limit its clinic application. Here we investigated the effects and potential mechanisms of an EPO-derived nonerythropoietic peptide, ARA 290, in EAN. Exogenous ARA 290 intervention greatly improved EAN recovery, improved nerve regeneration and remyelination, and suppressed nerve inflammation. Furthermore, haematopoiesis was not induced by ARA 290 during EAN treatment. ARA 290 intervention suppressed lymphocyte proliferation and altered helper T cell differentiation by inducing increase of Foxp3+/CD4+ regulatory T cells and IL-4+/CD4+ Th2 cells and decrease of IFN-γ+/CD4+ Th1 cells in EAN. In addition, ARA 290 inhibited inflammatory macrophage activation and promoted its phagocytic activity. In vitro, ARA 290 was shown to promote Schwann cell proliferation and inhibit its inflammatory activation. In summary, our data demonstrated that ARA 290 could effectively suppress EAN by attenuating inflammation and exerting direct cell protection, indicating that ARA 290 could be a potent candidate for treatment of autoimmune neuropathies.

High-dose erythropoietin in acute ST-segment elevation myocardial infarction: a meta-analysis of randomized controlled trials

OBJECTIVE

We sought to perform a meta-analysis to evaluate the potential influence of high-dose erythropoietin (EPO) on cardiac function parameters in patients with acute ST-segment elevation myocardial infarction (STEMI).

METHODS AND RESULTS

By searching PubMed, EMBASE, and the Cochrane Library (up to December 2012), seven randomized controlled trials (RCTs) reporting cardiac functional parameters with a total of 1,250 acute STEMI patients were identified. When applied to patients with acute STEMI, high-dose EPO was relatively safe and no increase in all-caused death and severe adverse effects were indicated. Estimates were pooled from fixed or random effects models. Compared with controls, high-dose EPO resulted in a slight but significant improvement in left ventricular ejection fraction of 1.02 % [95 % confidence interval (CI) 0.17-1.88, P = 0.019, I (2) = 0 %] and an improvement in left ventricular end-systolic volume of -4.61 ml (95 % CI -7.64 to -1.58, P = 0.003, I (2) = 27.7 %).

CONCLUSIONS

Available evidence suggested that high-dose EPO has limited cardio-protective effects in patients with STEMI. However, considering the relatively short follow-up durations and small patient populations in the current RCTs, the effects of high-dose EPO on clinical outcomes in patients with STEMI need to be evaluated in larger prospective RCTs of longer duration.

Intranasal formulation of erythropoietin (EPO) showed potent protective activity against amyloid toxicity in the Aβ₂₅₋₃₅ non-transgenic mouse model of Alzheimer's disease

Erythropoietin (EPO) promotes neurogenesis and neuroprotection. We here compared the protection induced by two EPO formulations in a rodent model of Alzheimer's disease (AD): rHu-EPO and a low sialic form, Neuro-EPO. We used the intracerebroventricular administration of aggregated Aβ₂₅₋₃₅ peptide, a non-transgenic AD model. rHu-EPO was tested at 125-500 µg/kg intraperitoneally and Neuro-EPO at 62-250 µg/kg intranasally (IN). Behavioural procedures included spontaneous alternation, passive avoidance, water-maze and object recognition, to address spatial and non-spatial, short- and long-term memories. Biochemical markers of Aβ₂₅₋₃₅ toxicity in the mouse hippocampus were examined and cell loss in the CA1 layer was determined. rHu-EPO and Neuro-EPO led to a significant prevention of Aβ₂₅₋₃₅-induced learning deficits. Both EPO formulations prevented the induction of lipid peroxidation in the hippocampus, showing an antioxidant activity. rHu-EPO (250 µg/kg) or Neuro-EPO (125 µg/kg) prevented the Aβ₂₅₋₃₅-induced increase in Bax level, TNFα and IL-1β production and decrease in Akt activation. A significant prevention of the Aβ₂₅₋₃₅-induced cell loss in CA1 was also observed. EPO is neuroprotective in the Aβ₂₅₋₃₅ AD model, confirming its potential as an endogenous neuroprotection system that could be boosted for therapeutic efficacy. We here identified a new IN formulation of EPO showing high neuroprotective activity. Considering its efficacy, ease and safety, IN Neuro-EPO is a new promising therapeutic agent in AD.

The AKT/mTOR pathway mediates neuronal protective effects of erythropoietin in sepsis

Sepsis is one of the most common causes of mortality in intensive care units. Although sepsis-associated encephalopathy (SAE) is reported to be a leading manifestation of sepsis, its pathogenesis remains to be elucidated. In this study, we investigated whether exogenous recombinant human erythropoietin (rhEPO) could protect brain from neuronal apoptosis in the model of SAE. We showed that application of rhEPO enhanced Bcl-2, decreased Bad in lipopolysaccharide treated neuronal cultures, and improved neuronal apoptosis in hippocampus of cecal ligation and peroration rats. We also found that rhEPO increased the expression of phosphorylated AKT, and the antiapoptotic role of rhEPO could be abolished by phosphoinositide 3-kinase (PI3K)/AKT inhibitor LY294002 or SH-5. In addition, systemic sepsis inhibited the hippocampal-phosphorylated mammalian target of rapamycin (mTOR) and p70S6K (downstream substrates of PKB/AKT signaling), which were restored by administration of exogenous rhEPO. Moreover, treatment with mTOR-signaling inhibitor rapamycin or transfection of mTOR siRNA reversed the neuronal protective effects of rhEPO. Finally, exogenous rhEPO rescued the emotional and spatial cognitive defects without any influence on locomotive activity. These results illustrated that exogenous rhEPO improves brain dysfunction by reducing neuronal apoptosis, and AKT/mTOR signaling is likely to be involved in this process. Application of rhEPO may serve as a potential therapy for the treatment of SAE.

Signaling pathways of cell proliferation are involved in the differential effect of erythropoietin and its carbamylated derivative

It is now recognized that in addition to its activity upon erythroid progenitor cells, erythropoietin (Epo) is capable of stimulating survival of different non-erythroid cells. Since stimulation of erythropoiesis is unwanted for neuroprotection, Epo-like compounds with a more selective action are under investigation. Although the carbamylated derivative of erythropoietin (cEpo) has demonstrated non-hematopoietic tissue protection without erythropoietic effect, little is known about differential mechanisms between Epo and cEpo. Therefore, we investigated signaling pathways which play a key role in Epo-induced proliferation. Here we show that cEpo blocked FOXO3a phosphorylation, allowing expression of downstream target p27(kip1) in UT-7 and TF-1 cells capable of erythroid differentiation. This is consistent with the involvement of cEpo in slowing down G1-to-S-phase progression compared with the effect of Epo upon cell cycle. In contrast, similar antiapoptotic actions of cEpo and Epo were observed in neuronal SH-SY5Y cells. Inhibition and competition assays suggest that Epo may act through both, the homodimeric (EpoR/EpoR) and the heterodimeric (EpoR/βcR) receptors in neuronal SH-SY5Y cells and probably in the TF-1 cell type as well. Results also indicate that cEpo needs both the EpoR and βcR subunits to prevent apoptosis of neuronal cells. Based on evidence suggesting that cell proliferation pathways were involved in the differential effect of Epo and cEpo, we went forward to studying downstream signals. Here we provide the first evidence that unlike Epo, cEpo failed to induce FOXO3a inactivation and subsequent p27(kip1) downregulation, which is clearly shown in the incapacity of cEpo to induce erythroid cell growth.

Targeting erythropoietin for chronic neurodegenerative diseases

INTRODUCTION

Since erythropoietin (EPO) and EPO receptor (EPOR) are expressed in the central nervous system (CNS) beyond hematopoietic system, EPO illustrates a robust biological function in maintaining neuronal survival and regulating neurogenesis and may play a crucial role in neurodegenerative diseases.

AREAS COVERED

EPO is capable of modulating multiple cellular signal transduction pathways to promote neuronal survival and enhance the proliferation and differentiation of neuronal progenitor cells. Initially, EPO binds to EPOR to activate the Janus-tyrosine kinase 2 (Jak2) protein followed by modulation of protein kinase B (Akt), mammalian target of rapamycin, signal transducer and activators of transcription 5, mitogen-activated protein kinases, protein tyrosine phosphatases, Wnt1 and nuclear factor κB. As a result, EPO may actively prevent the progression of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, epilepsy, multiple sclerosis and motor neuron diseases.

EXPERT OPINION

Novel knowledge of the cell signaling pathways regulated by EPO in the CNS will allow us to establish the foundation for the development of therapeutic strategies against neurodegenerative diseases. Further investigation of the role of EPO in neurodegenerative diseases can not only formulate EPO as a therapeutic candidate, but also further identify novel therapeutic targets for these disorders.

Recombinant human erythropoietin preconditioning attenuates liver ischemia reperfusion injury through the phosphatidylinositol-3 kinase/AKT/endothelial nitric oxide synthase pathway

BACKGROUND

The exact mechanism by which erythropoietin protects the liver from ischemia reperfusion (I/R) injury is not yet known. In the present study, we examined the role of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in the protective effect of recombinant human erythropoietin (rHuEPO) on I/R injury of the liver.

MATERIALS AND METHODS

We used a liver in situ I/R model. One hundred twenty adult male Sprague-Dawley rats were divided randomly into six groups. rHuEPO and (or) LY294002 were injected in the tail vein before the operation, and its effect was assessed by measuring the serum levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, nitric oxide (NO), and endothelin-1 (ET-1) and by histologic analysis. The expression of erythropoietin receptor (EPOR) and eNOS was measured by real-time polymerase chain reaction. Total AKT and eNOS and phosphorylated AKT and eNOS were examined by western blot.

RESULTS

rHuEPO dramatically attenuated the functional and morphologic injuries. The serum levels of alanine aminotransferase and lactate dehydrogenase were significantly decreased, but the amount of NO in the serum was increased in the I/R + rHuEPO group. Accordingly, rHuEPO administration significantly ameliorated the histologic damages at 6 h after reperfusion. rHuEPO significantly stimulated the phosphorylation of AKT and eNOS in the rats after liver I/R.

CONCLUSIONS

The protective effect of rHuEPO in I/R injury is mediated via the activation of the phosphatidylinositol-3 kinase/AKT/eNOS signaling pathway, at least in part, by increasing p-AKT and p-eNOS and leads to the maintenance of an elevated level of NO.

Otoprotective effects of erythropoietin on Cdh23erl/erl mice

The Cdh23(erl/erl) mice are a novel mouse model for DFNB12 and are characterized by progressive hearing loss. In this study, erythropoietin (EPO) was given to the Cdh23(erl/erl) mice by intraperitoneal injection every other day from P7 for 7 weeks. Phosphate-buffered saline-treated or untreated Cdh23(erl/erl) mice were used as controls. Auditory-evoked brainstem response (ABR) thresholds and distortion product oto-acoustic emission (DPOAE) were measured in the mouse groups at the age of 4, 6 and 8 weeks. The results show that EPO can significantly decrease the ABR thresholds in the Cdh23(erl/erl) mice as compared with those of the untreated mice at stimulus frequencies of click, 8-, 16- and 32-kHz at three time points. Meanwhile, DPOAE amplitudes in the EPO-treated Cdh23(erl/erl) mouse group were significantly higher than those of the untreated groups at f2 frequency of 15383 Hz at the three time points. Furthermore, the mean percentage of outer hair cell loss at middle through basal turns of cochleae was significantly lower in EPO-treated Cdh23(erl/erl) mice than in the untreated mice (P<0.05). This is the first report that EPO acts as an otoprotectant in a DFNB12 mouse model with progressive hearing loss.

Generation of biologically active multi-sialylated recombinant human EPOFc in plants

Hyperglycosylated proteins are more stable, show increased serum half-life and less sensitivity to proteolysis compared to non-sialylated forms. This applies particularly to recombinant human erythropoietin (rhEPO). Recent progress in N-glycoengineering of non-mammalian expression hosts resulted in in vivo protein sialylation at great homogeneity. However the synthesis of multi-sialylated N-glycans is so far restricted to mammalian cells. Here we used a plant based expression system to accomplish multi-antennary protein sialylation. A human erythropoietin fusion protein (EPOFc) was transiently expressed in Nicotiana benthamiana ΔXTFT, a glycosylation mutant that lacks plant specific N-glycan residues. cDNA of the hormone was co-delivered into plants with the necessary genes for (i) branching (ii) β1,4-galactosylation as well as for the (iii) synthesis, transport and transfer of sialic acid. This resulted in the production of recombinant EPOFc carrying bi- tri- and tetra-sialylated complex N-glycans. The formation of this highly complex oligosaccharide structure required the coordinated expression of 11 human proteins acting in different subcellular compartments at different stages of the glycosylation pathway. In vitro receptor binding assays demonstrate the generation of biologically active molecules. We demonstrate the in planta synthesis of one of the most complex mammalian glycoforms pointing to an outstanding high degree of tolerance to changes in the glycosylation pathway in plants.

Standardized environmental enrichment supports enhanced brain plasticity in healthy rats and prevents cognitive impairment in epileptic rats

Environmental enrichment of laboratory animals influences brain plasticity, stimulates neurogenesis, increases neurotrophic factor expression, and protects against the effects of brain insult. However, these positive effects are not constantly observed, probably because standardized procedures of environmental enrichment are lacking. Therefore, we engineered an enriched cage (the Marlau™ cage), which offers: (1) minimally stressful social interactions; (2) increased voluntary exercise; (3) multiple entertaining activities; (4) cognitive stimulation (maze exploration), and (5) novelty (maze configuration changed three times a week). The maze, which separates food pellet and water bottle compartments, guarantees cognitive stimulation for all animals. Compared to rats raised in groups in conventional cages, rats housed in Marlau™ cages exhibited increased cortical thickness, hippocampal neurogenesis and hippocampal levels of transcripts encoding various genes involved in tissue plasticity and remodeling. In addition, rats housed in Marlau™ cages exhibited better performances in learning and memory, decreased anxiety-associated behaviors, and better recovery of basal plasma corticosterone level after acute restraint stress. Marlau™ cages also insure inter-experiment reproducibility in spatial learning and brain gene expression assays. Finally, housing rats in Marlau™ cages after severe status epilepticus at weaning prevents the cognitive impairment observed in rats subjected to the same insult and then housed in conventional cages. By providing a standardized enriched environment for rodents during housing, the Marlau™ cage should facilitate the uniformity of environmental enrichment across laboratories.

Intermittent hypobaric hypoxia induces neuroprotection in kainate-induced oxidative stress in rats

Severe hypoxia induces oxidative stress, which can lead to brain injury. In this study, we wanted to determine whether intermittent hypobaric hypoxia induces oxidative stress in the brain. In adult rats exposed to 380 mmHg in a hypobaric chamber for 3 h/day for 6 days, we determined the levels of malondialdehyde and nitric oxide derivatives in the brain, which indicated that there was no oxidative stress. The levels of N-acetylaspartate indicated that there was no neuronal loss or mitochondrial dysfunction and finally because apoptotic proteins such as caspase-3 and nuclear factor-kappa B (NF-κB) were not activated, apoptosis was probably not induced. The increase in the expression of erythropoietin (EPO) in the brain of rats exposed to hypoxia confirms the efficacy of the method used to induce hypoxia in the brain. Because EPO have antioxidant effects on the brain, the results suggest that intermittent hypoxia can increase the antioxidant capacity of the brain. This effect of intermittent hypoxia was studied using the systemic administration of kainate, as a model of brain oxidative stress. Kainate treatment induces oxidative stress in the brain, which is measured by an increase in lipid peroxidation and nitric oxide. Furthermore, in rats treated with kainate, both caspase-3 and NF-κB activity increased. However, in rats previously exposed to intermittent hypobaric hypoxia, 3 h per day for 6 days, the effect of kainate treatment resulted in the reduction of both oxidative stress and apoptotic activity. This study demonstrates that intermittent hypobaric hypoxia can increase brain antioxidant capacity in rats and induces neuroprotection in kainate-induced oxidative injury.

Evidence of synergistic/additive effects of sildenafil and erythropoietin in enhancing survival and migration of hypoxic endothelial cells

Endothelial cell dysfunction is a common event to several pathologies including pulmonary hypertension, which is often associated with hypoxia. As the endothelium plays an essential role in regulating the dynamic interaction between pulmonary vasodilatation and vasoconstriction, this cell type is fundamental in the development of vascular remodeling and increased vascular resistance. We investigated the protective effects of sildenafil, a phosphodiesterase type 5 inhibitor, given in combination with erythropoietin (Epo), as it has been demonstrated that both drugs have antiapoptotic effects on several cell types. Specifically, we examined the viability and angiogenic properties of rat pulmonary artery endothelial cells upon exposure to either 21% or 1% oxygen, in presence of sildenafil (1 and 100 nM) and Epo (5 and 20 U/ml) alone or in combination (1 nM and 20 U/ml). Cell proliferation and viability were analyzed by Trypan blue staining, MTT assay, and Annexin V/propidium iodide stainings. In all assays, the ability of the combination treatment in improving cell viability was superior to that of either drug alone. The angiogenic properties were studied using a migration and a 3D collagen assay, and the results revealed increases in the migration potential of endothelial cells as well as the ability to form tube-like structures in response to sildenafil and the combination treatment. We therefore conclude that both drugs exert protective effects on endothelial cells on hypoxia and that sildenafil enhances the migratory and angiogenic properties, especially in hypoxic conditions. Furthermore, we present evidence of possible additive or synergistic effects of both drugs.

Shedding new light on neurodegenerative diseases through the mammalian target of rapamycin

Neurodegenerative disorders affect a significant portion of the world's population leading to either disability or death for almost 30 million individuals worldwide. One novel therapeutic target that may offer promise for multiple disease entities that involve Alzheimer's disease, Parkinson's disease, epilepsy, trauma, stroke, and tumors of the nervous system is the mammalian target of rapamycin (mTOR). mTOR signaling is dependent upon the mTORC1 and mTORC2 complexes that are composed of mTOR and several regulatory proteins including the tuberous sclerosis complex (TSC1, hamartin/TSC2, tuberin). Through a number of integrated cell signaling pathways that involve those of mTORC1 and mTORC2 as well as more novel signaling tied to cytokines, Wnt, and forkhead, mTOR can foster stem cellular proliferation, tissue repair and longevity, and synaptic growth by modulating mechanisms that foster both apoptosis and autophagy. Yet, mTOR through its proliferative capacity may sometimes be detrimental to central nervous system recovery and even promote tumorigenesis. Further knowledge of mTOR and the critical pathways governed by this serine/threonine protein kinase can bring new light for neurodegeneration and other related diseases that currently require new and robust treatments.

Oxidant stress and signal transduction in the nervous system with the PI 3-K, Akt, and mTOR cascade

Oxidative stress impacts multiple systems of the body and can lead to some of the most devastating consequences in the nervous system especially during aging. Both acute and chronic neurodegenerative disorders such as diabetes mellitus, cerebral ischemia, trauma, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and tuberous sclerosis through programmed cell death pathways of apoptosis and autophagy can be the result of oxidant stress. Novel therapeutic avenues that focus upon the phosphoinositide 3-kinase (PI 3-K), Akt (protein kinase B), and the mammalian target of rapamycin (mTOR) cascade and related pathways offer exciting prospects to address the onset and potential reversal of neurodegenerative disorders. Effective clinical translation of these pathways into robust therapeutic strategies requires intimate knowledge of the complexity of these pathways and the ability of this cascade to influence biological outcome that can vary among disorders of the nervous system.

Novel directions for diabetes mellitus drug discovery

INTRODUCTION

Diabetes mellitus impacts almost 200 million individuals worldwide and leads to debilitating complications. New avenues of drug discovery must target the underlying cellular processes of oxidative stress, apoptosis, autophagy, and inflammation that can mediate multi-system pathology during diabetes mellitus.

AREAS COVERED

The authors examine the novel directions for drug discovery that involve: the β-nicotinamide adenine dinucleotide (NAD(+)) precursor nicotinamide, the cytokine erythropoietin, the NAD(+)-dependent protein histone deacetylase SIRT1, the serine/threonine-protein kinase mammalian target of rapamycin (mTOR), and the wingless pathway. Furthermore, the authors present the implications for the targeting of these pathways that oversee gluconeogenic genes, insulin signaling and resistance, fatty acid beta-oxidation, inflammation, and cellular survival.

EXPERT OPINION

Nicotinamide, erythropoietin, and the downstream pathways of SIRT1, mTOR, forkhead transcription factors, and wingless signaling offer exciting prospects for novel directions of drug discovery for the treatment of metabolic disorders. Future investigations must dissect the complex relationship and fine modulation of these pathways for the successful translation of robust reparative and regenerative strategies against diabetes mellitus and the complications of this disorder.

Antagonizing effects of soybean isoflavones on β-amyloid peptide-induced oxidative damage in neuron mitochondria of rats

Soybean isoflavone (SIF) has been demonstrated to have neuroprotective effects induced by β-amyloid peptides (Aβ) through suppressing oxidative stress; however, the explicit mechanisms still remain uncovered. In the present study, 32 Wistar rats were randomly divided into four groups: an Aβ1-42-treated group, a SIF + Aβ1-42 group, a SIF-treated group and a control group. We measured the protein content of 8-hydroxydeoxyguanosine (8-OhdG) and mRNA expression of 8-oxoguanine DNA glycosylase (OGG1). The protein expression of OGG1, Bcl-xl, Bad, beta subunit of ATP synthase (ATPB) and pyruvate dehydrogenase (PDH) in brain was also measured. The results showed that the level of 8-OHdG in both SIF groups was significantly decreased compared to the Aβ1-42-treated group (p < 0.05), while the mRNA and protein expression of OGG1 in the SIF + Aβ1-42 groups were up-regulated compared with the Aβ1-42-treated groups (p < 0.05). The expression of Bcl-xl was up-regulated in the SIF-treated group compared with the Aβ1-42-treated groups (p < 0.05), while the expression of Bad was down-regulated in the two SIF-treated groups (p < 0.05). Aβ1-42 significantly down-regulated the expression of ATPase and PDH proteins compared with the control group (p < 0.05). SIF reversed the down-regulation effects on the mitochondrial energy metabolic enzymes induced by Aβ1-42 (p < 0.05) in the rats. These results suggest that SIF alleviate the oxidative stress in neurons and mitochondria of rat brains mediated by Aβ1-42, and these protective effects might be associated with the regulation of OGG1, Bad, Bcl-xl, ATPB and PDH.

PRAS40 is an integral regulatory component of erythropoietin mTOR signaling and cytoprotection

Emerging strategies that center upon the mammalian target of rapamycin (mTOR) signaling for neurodegenerative disorders may bring effective treatment for a number of difficult disease entities. Here we show that erythropoietin (EPO), a novel agent for nervous system disorders, prevents apoptotic SH-SY5Y cell injury in an oxidative stress model of oxygen-glucose deprivation through phosphatidylinositol-3-kinase (PI 3-K)/protein kinase B (Akt) dependent activation of mTOR signaling and phosphorylation of the downstream pathways of p70 ribosomal S6 kinase (p70S6K), eukaryotic initiation factor 4E-binding protein 1 (4EBP1), and proline rich Akt substrate 40 kDa (PRAS40). PRAS40 is an important regulatory component either alone or in conjunction with EPO signal transduction that can determine cell survival through apoptotic caspase 3 activation. EPO and the PI 3-K/Akt pathways control cell survival and mTOR activity through the inhibitory post-translational phosphorylation of PRAS40 that leads to subcellular binding of PRAS40 to the cytoplasmic docking protein 14-3-3. However, modulation and phosphorylation of PRAS40 is independent of other protective pathways of EPO that involve extracellular signal related kinase (ERK 1/2) and signal transducer and activator of transcription (STAT5). Our studies highlight EPO and PRAS40 signaling in the mTOR pathway as potential therapeutic strategies for development against degenerative disorders that lead to cell demise.

Erythropoietin: new directions for the nervous system

New treatment strategies with erythropoietin (EPO) offer exciting opportunities to prevent the onset and progression of neurodegenerative disorders that currently lack effective therapy and can progress to devastating disability in patients. EPO and its receptor are present in multiple systems of the body and can impact disease progression in the nervous, vascular, and immune systems that ultimately affect disorders such as Alzheimer's disease, Parkinson's disease, retinal injury, stroke, and demyelinating disease. EPO relies upon wingless signaling with Wnt1 and an intimate relationship with the pathways of phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), and mammalian target of rapamycin (mTOR). Modulation of these pathways by EPO can govern the apoptotic cascade to control β-catenin, glycogen synthase kinase-3β, mitochondrial permeability, cytochrome c release, and caspase activation. Yet, EPO and each of these downstream pathways require precise biological modulation to avert complications associated with the vascular system, tumorigenesis, and progression of nervous system disorders. Further understanding of the intimate and complex relationship of EPO and the signaling pathways of Wnt, PI 3-K, Akt, and mTOR are critical for the effective clinical translation of these cell pathways into robust treatments for neurodegenerative disorders.

Priming of late endothelial progenitor cells with erythropoietin before transplantation requires the CD131 receptor subunit and enhances their angiogenic potential

BACKGROUND

 Endothelial colony-forming cells (ECFCs) are promising candidates for cell therapy of ischemic diseases. Erythropoietin (EPO) is a cytokine that promotes angiogenesis after ischemic injury. EPO receptors (EPORs) classically include two EPOR subunits, but may also associate with the β-common chain (CD131) in a newly identified receptor involved in EPO cytoprotective effects.

OBJECTIVE

The aim was to take advantage of the proangiogenic properties of EPO to enhance ECFC graft efficiency. We postulated that priming ECFCs by adding epoietin α in culture medium prior to experiments might increase their angiogenic properties. We also explored the role of the CD131 subunit in EPO priming of ECFCs.

METHODS AND RESULTS

By western blotting on cord blood ECFC lysates, we showed that EPOR and CD131 expression increased significantly after EPO priming. These proteins coimmunoprecipitated and colocalized, suggesting that they are covalently bound in ECFCs. EPO at 5 IU mL(-1) significantly stimulated proliferation, wound healing, migration and tube formation of ECFCs. EPO priming also increased ECFC resistance to H2 O2-induced apoptosis and survival in vivo. Similarly, in vivo studies showed that, as compared with non-primed ECFC injection, 5 IU mL(-1) EPO-primed ECFCs, injected intravenously 24 h after hindlimb ischemia in athymic nude mice, increased the ischemic/non-ischemic ratios of hindlimb blood flow and capillary density. These effects were all prevented by CD131 small interfering RNA transfection, and involved the phosphoinositide 3-kinase-Akt pathway.

CONCLUSION

These results highlight the potential role of EPO-primed ECFCs for cell-based therapy in hindlimb ischemia, and underline the critical role of CD131 as an EPO coreceptor.

Prevention of β-amyloid degeneration of microglia by erythropoietin depends on Wnt1, the PI 3-K/mTOR pathway, Bad, and Bcl-xL

Central nervous system microglia promote neuronal regeneration and sequester toxic β-amyloid (Aβ) deposition during Alzheimer's disease. We show that the cytokine erythropoietin (EPO) decreases the toxic effect of Aβ on microgliain vitro. EPO up-regulates the cysteine-rich glycosylated wingless protein Wnt1 and activates the PI 3-K/Akt1/mTOR/ p70S6K pathway. This in turn increases phosphorylation and cytosol trafficking of Bad, reduces the Bad/Bcl-x_L complex and increases the Bcl-x_L/Bax complex, thus preventing caspase 1 and caspase 3 activation and apoptosis. Our data may foster development of novel strategies to use cytoprotectants such as EPO for Alzheimer's disease and other degenerative disorders.

Treating patients with schizophrenia deficit with erythropoietin?

This systematic review summarizes and critically appraises the literature on the effect of erythropoietin (EPO) in schizophrenia patients and the pathophysiological mechanisms that may explain the potential of its use in this disease. EPO is mainly known for its regulatory activity in the synthesis of erythrocytes and is frequently used in treatment of chronic anemia. This cytokine, however, has many other properties, some of which may improve the symptoms of psychiatric illness. The review follows the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement guidelines. Three databases (Medline, Web of Science, and Cochrane) were searched combining the search terms 'erythropoietin AND (psychotic disorders OR schizophrenia)'. Seventy-eight studies were included in qualitative synthesis, a meta-analytic approach being prohibited. The findings suggest that several EPO cerebral potential properties may be relevant for schizophrenia treatment, such as neurotransmission regulation, neuroprotection, modulation of inflammation, effects on blood-brain barrier permeability, effects on oxidative stress and neurogenesis. Several potentially detrimental side-effects of EPO therapy, such as increased risk of thrombosis, cancer, increased metabolic rate and mean arterial blood pressure leading to cerebral ischemia could severely limit or halt the use of EPO. Overall, because the available data are inconclusive, further efforts in this field are warranted.

Targeting cardiovascular disease with novel SIRT1 pathways

Sirtuin (the mammalian homolog of silent information regulation 2 of yeast Saccharomyces cerevisiae) 1 (SIRT1), a NAD-dependent histone deacetylase, has emerged as a critical regulator in response to oxidative stress. Through antagonism of oxidative stress-induced cell injury and through the maintenance of metabolic homeostasis in the body, SIRT1 can block vascular system injury. SIRT1 targets multiple cellular proteins, such as peroxisome proliferator-activated receptor-γ and its coactivator-1α, forkhead transcriptional factors, AMP-activated protein kinase, NF-κB and protein tyrosine phosphatase to modulate intricate cellular pathways of multiple diseases. In the cardiovascular system, activation of SIRT1 can not only protect against oxidative stress at the cellular level, but can also offer increased survival at the systemic level to limit coronary heart disease and cerebrovascular disease. Future knowledge regarding SIRT1 and its novel pathways will open new directions for the treatment of cardiovascular disease as well as offer the potential to limit disability from several related disorders.