Erythropoietin in heart and vessels: focus on transcription and signalling pathways

Flavonoids from Lycium barbarum Leaves Exhibit Anti-Aging Effects through the Redox-Modulation

Lycium barbarum leaves are a kind of vegetable, and modern nutrition studies have found that they have an anti-aging function. Our study aims to investigate the anti-aging effects of Lycium barbarum leaf flavonoid (LBLF) extracts and its underlying molecular mechanism. LBLFs were purified using D101 and polyamide resin, characterized by ultraperformance liquid chromatography coupled with mass spectrometry, and administered to hydrogen peroxide (H₂O₂)-treated human umbilical vein endothelial cells (HUVECs) and Caenorhabditis elegans. Appropriate enrichment conditions were optimized through dynamic adsorption and desorption experiments, the content of flavonoids reached 909.84 mg/g, rutin and kaempferol being the main ones. LBLFs attenuated H₂O₂-induced HUVEC apoptosis, decreased reactive oxygen species and malondialdehyde production levels, increased superoxide dismutase, glutathione peroxidase and catalase activities. Furthermore, pre-treatment with LBLF increased mRNA expression of erythropoietin (EPO) and heme oxygenase-1 (HO-1) via the mitogen-activated protein kinase (MAPK) signaling pathway in HUVECs. Compared with 100 µM rutin monomer, LBLF prolonged the lifespan of Caenorhabditis elegans, enhanced their mobility in middle life stages and upregulated expression of sod-2, gcs-1 and skn-1 genes, which indicated that the anti-aging effects of LBLF were due to its redox-modulation.

Perinatal Hyperoxia and Developmental Consequences on the Lung-Brain Axis

Approximately 11.1% of all newborns worldwide are born preterm. Improved neonatal intensive care significantly increased survival rates over the last decades but failed to reduce the risk for the development of chronic lung disease (i.e., bronchopulmonary dysplasia (BPD)) and impaired neurodevelopment (i.e., encephalopathy of prematurity (EoP)), two major long-term sequelae of prematurity. Premature infants are exposed to relative hyperoxia, when compared to physiological in-utero conditions and, if needed to additional therapeutic oxygen supplementation. Both are associated with an increased risk for impaired organ development. Since the detrimental effects of hyperoxia on the immature retina are known for many years, lung and brain have come into focus in the last decade. Hyperoxia-induced excessive production of reactive oxygen species leading to oxidative stress and inflammation contribute to pulmonary growth restriction and abnormal neurodevelopment, including myelination deficits. Despite a large body of studies, which unraveled important pathophysiological mechanisms for both organs at risk, the majority focused exclusively either on lung or on brain injury. However, considering that preterm infants suffering from BPD are at higher risk for poor neurodevelopmental outcome, an interaction between both organs seems plausible. This review summarizes recent findings regarding mechanisms of hyperoxia-induced neonatal lung and brain injury. We will discuss common pathophysiological pathways, which potentially link both injured organ systems. Furthermore, promises and needs of currently suggested therapies, including pharmacological and regenerative cell-based treatments for BPD and EoP, will be emphasized. Limited therapeutic approaches highlight the urgent need for a better understanding of the mechanisms underlying detrimental effects of hyperoxia on the lung-brain axis in order to pave the way for the development of novel multimodal therapies, ideally targeting both severe preterm birth-associated complications.

Tibetan Medicine Duoxuekang Capsule Ameliorates High-Altitude Polycythemia Accompanied by Brain Injury

Objective: Duoxuekang (DXK) capsule is an empirical prescription for Tibetan medicine in the treatment of hypobaric hypoxia (HH)-induced brain injury in the plateau. This study aimed to investigate the protective effects and underlying molecular mechanisms of DXK on HH-induced brain injury.

Methods: UPLC–Q-TOF/MS was performed for chemical composition analysis of DXK. The anti-hypoxia and anti-fatigue effects of DXK were evaluated by the normobaric hypoxia test, sodium nitrite toxicosis test, and weight-loaded swimming test in mice. Simultaneously, SD rats were used for the chronic hypobaric hypoxia (CHH) test. RBC, HGB, HCT, and the whole blood viscosity were evaluated. The activities of SOD and MDA in the brain, and EPO and LDH levels in the kidney were detected using ELISA. H&E staining was employed to observe the pathological morphology in the hippocampus and cortex of rats. Furthermore, immunofluorescence and Western blot were carried out to detect the protein expressions of Mapk10, RASGRF1, RASA3, Ras, and IGF-IR in the brain of rats. Besides, BALB/c mice were used for acute hypobaric hypoxia (AHH) test, and Western blot was employed to detect the protein expression of p-ERK/ERK, p-JNK/JNK, and p-p38/p38 in the cerebral cortex of mice.

Results: 23 different chemical compositions of DXK were identified by UPLC–Q-TOF/MS. The anti-hypoxia test verified that DXK can prolong the survival time of mice. The anti-fatigue test confirmed that DXK can prolong the swimming time of mice, decrease the level of LDH, and increase the hepatic glycogen level. Synchronously, DXK can decrease the levels of RBC, HGB, HCT, and the whole blood viscosity under the CHH condition. Besides, DXK can ameliorate CHH-induced brain injury, decrease the levels of EPO and LDH in the kidney, reduce MDA, and increase SOD in the hippocampus. Furthermore, DXK can converse HH-induced marked increase of Mapk10, RASGRF1, and RASA3, and decrease of Ras and IGF-IR. In addition, DXK can suppress the ratio of p-ERK/ERK, p-JNK/JNK, and p-p38/p38 under the HH condition.

Conclusion: Together, the cerebral protection elicited by DXK was due to the decrease of hematological index, suppressing EPO, by affecting the MAPK signaling pathway in oxidative damage, and regulating the RAS signaling pathway.

AMPK-KLF2 signaling pathway mediates the proangiogenic effect of erythropoietin in endothelial colony-forming cells

Endothelial colony-forming cells (ECFCs) were proved to take part in postnatal vasculogenesis and injury repair. The angiogenic properties of ECFCs could be influenced by various cytokines, chemokines, and growth factors. Erythropoietin (EPO) is a promising cytokine participating in angiogenesis. However, the mechanisms for EPO's proangiogenic effect still remain largely elusive. Here, we investigated the role of the AMP-activated protein kinase (AMPK)-Krüppel-like factor 2 (KLF2) signaling pathway in the proangiogenic effect of EPO in ECFCs. Human ECFCs were isolated from cord blood and cultured. EPO significantly enhanced the migration and tube formation capacities of ECFCs and markedly increased the expression of endothelial markers and vascular endothelial growth factor (VEGF). Further, EPO caused the phosphorylation of AMPK and endothelial nitric oxide synthase, a process in which KLF2 was also upregulated on both mRNA and protein levels. The upregulation of KLF2 was blocked by inhibiting AMPK with Compound C or Ad-AMPK-DN, a recombinant adenovirus that encoded a dominant-negative mutant of AMPK. Furthermore, knockdown of KLF2 showed no effect on AMPK but abolished the EPO-enhanced migration and tube formation capacities of ECFCs. Of note, knockdown of KLF2 also diminished the EPO-induced expression of endothelial markers and VEGF; overexpression of KLF2 promoted the expression of endothelial markers and VEGF and enhanced the migration and tube formation capacities of ECFCs. These data suggest that upregulation of KLF2 by AMPK plays an essential role in EPO-induced angiogenesis.

Optimizing the host substrate environment for cardiac angiogenesis, arteriogenesis, and myogenesis

INTRODUCTION

The diseased host milieu, such as endothelial dysfunction (ED), decreased NO bioavailability, and ischemic/inflammatory post-MI environment, hamper the clinical success of existing cardiac regenerative therapies. Area covered: In this article, current strategies including pharmacological and nonpharmacological approaches for improving the diseased host milieu are reviewed. Specifically, the authors provide focus on: i) the mechanism of ED in patients with cardiovascular diseases, ii) the current results of ED improving strategies in pre-clinical and clinical studies, and iii) the use of biomaterials as a novel modulator in damaged post-MI environment. Expert opinion: Adjunct therapies which improve host endothelial function have demonstrated promising outcomes, potentially overcoming disappointing results of cell therapy in human studies. In the future, elucidation of the interactions between the host tissue and therapeutic agents, as well as downstream signaling pathways, will be the next challenges in enhancing regenerative therapy. More careful investigations are also required to establish these agents' safety and efficacy for wide usage in humans.

Erythropoietin and Nonhematopoietic Effects

Erythropoietin (EPO) is the main regulator of red blood cell production. Since the 1990s, EPO has been used for the treatment of anemia associated with end-stage renal failure and chemotherapy. The erythropoietin receptors were found on other organs such as the brain, spinal cord, heart and skin. In addition, it has been shown that many tissues produce and locally release EPO in response to hypoxic, biochemical and physical stress. In cellular, animal and clinical studies, EPO protects tissues from ischemia and reperfusion injury, has antiapoptotic effects and improves regeneration after injury. In this article, we mainly review the nonhematopoietic effects and new possible clinical indications for EPO.

Erythropoietin and a nonerythropoietic peptide analog promote aortic endothelial cell repair under hypoxic conditions: role of nitric oxide

The cytoprotective effects of erythropoietin (EPO) and an EPO-related nonerythropoietic analog, pyroglutamate helix B surface peptide (pHBSP), were investigated in an in vitro model of bovine aortic endothelial cell injury under normoxic (21% O₂) and hypoxic (1% O₂) conditions. The potential molecular mechanisms of these effects were also explored. Using a model of endothelial injury (the scratch assay), we found that, under hypoxic conditions, EPO and pHBSP enhanced scratch closure by promoting cell migration and proliferation, but did not show any effect under normoxic conditions. Furthermore, EPO protected bovine aortic endothelial cells from staurosporine-induced apoptosis under hypoxic conditions. The priming effect of hypoxia was associated with stabilization of hypoxia inducible factor-1α, EPO receptor upregulation, and decreased Ser-1177 phosphorylation of endothelial nitric oxide synthase (NOS); the effect of hypoxia on the latter was rescued by EPO. Hypoxia was associated with a reduction in nitric oxide (NO) production as assessed by its oxidation products, nitrite and nitrate, consistent with the oxygen requirement for endogenous production of NO by endothelial NOS. However, while EPO did not affect NO formation in normoxia, it markedly increased NO production, in a manner sensitive to NOS inhibition, under hypoxic conditions. These data are consistent with the notion that the tissue-protective actions of EPO-related cytokines in pathophysiological settings associated with poor oxygenation are mediated by NO. These findings may be particularly relevant to atherogenesis and postangioplasty restenosis.

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.

Erythropoietin and the use of a transgenic model of erythropoietin-deficient mice

Despite its well-known role in red blood cell production, it is now accepted that erythropoietin (Epo) has other physiological functions. Epo and its receptors are expressed in many tissues, such as the brain and heart. The presence of Epo/Epo receptors in these organs suggests other roles than those usually assigned to this protein. Thus, the aim of this review is to describe the effects of Epo deficiency on adaptation to normoxic and hypoxic environments and to suggest a key role of Epo on main physiological adaptive functions. Our original model of Epo-deficient (Epo-TAg^h) mice allowed us to improve our knowledge of the possible role of Epo in O₂ homeostasis. The use of anemic transgenic mice revealed Epo as a crucial component of adaptation to hypoxia. Epo-TAg^h mice survive well in hypoxic conditions despite low hematocrit. Furthermore, Epo plays a key role in neural control of ventilatory acclimatization and response to hypoxia, in deformability of red blood cells, in cerebral and cardiac angiogenesis, and in neuro- and cardioprotection.

Erythropoietin Decreases the Occurrence of Myocardial Fibrosis by Inhibiting the NADPH-ERK-NF-x03BA;B Pathway

OBJECTIVES

The aim of this study was to investigate the protective role of erythropoietin (EPO) against myocardial fibrosis (MF).

METHODS

Pressure-overloaded rats were established by abdominal aortic constriction, the rats were randomly divided in a double-blind manner into 3 groups (n = 12 for each group): sham-operated rats (sham), operated rats receiving physiological saline (vehicle) and operated rats receiving 4,000 U/kg rhEPO (EPO group). The vehicle and drugs were administered to rats by intraperitoneal injection. In addition, cultured adult rat cardiac fibroblasts (CFs) were utilized to investigate the role of EPO in CF proliferation and collagen secretion.

RESULTS

After 4 weeks, besides an increase in blood pressure, myocardial hypertrophy, collagen deposition in the myocardium and decreased cardiac function were observed in the pressure-overloaded rats. The expression of NADPH oxidase (Nox2 and Nox4) and inflammatory cytokines (CD45, F4/80 and MCP-1) was also significantly increased. All these alterations were prevented by EPO. TGF-β promoted CF proliferation, collagen secretion, ROS production and Nox2/Nox4 expression, which was inhibited by EPO. In addition, the TGF-β-induced increase of ERK1/2 phosphorylation and NF-x03BA;B expression were attenuated by EPO.

CONCLUSION

EPO inhibited rat MF induced by pressure overload and improved myocardial function by decreasing CF proliferation and differentiation via inhibition of the NADPH-ERK-NF-x03BA;B pathway.

Pathogenesis of Myeloproliferative Neoplasms: Role and Mechanisms of Chronic Inflammation

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal diseases characterized by the excessive and chronic production of mature cells from one or several of the myeloid lineages. Recent advances in the biology of MPNs have greatly facilitated their molecular diagnosis since most patients present with mutation(s) in the JAK2, MPL, or CALR genes. Yet the roles played by these mutations in the pathogenesis and main complications of the different subtypes of MPNs are not fully elucidated. Importantly, chronic inflammation has long been associated with MPN disease and some of the symptoms and complications can be linked to inflammation. Moreover, the JAK inhibitor clinical trials showed that the reduction of symptoms linked to inflammation was beneficial to patients even in the absence of significant decrease in the JAK2-V617F mutant load. These observations suggested that part of the inflammation observed in patients with JAK2-mutated MPNs may not be the consequence of JAK2 mutation. The aim of this paper is to review the different aspects of inflammation in MPNs, the molecular mechanisms involved, the role of specific genetic defects, and the evidence that increased production of certain cytokines depends or not on MPN-associated mutations, and to discuss possible nongenetic causes of inflammation.

Low Oxygen Tension Primes Aortic Endothelial Cells to the Reparative Effect of Tissue-Protective Cytokines

Erythropoietin (EPO) has both erythropoietic and tissue-protective properties. The EPO analogues carbamylated EPO (CEPO) and pyroglutamate helix B surface peptide (pHBSP) lack the erythropoietic activity of EPO but retain the tissue-protective properties that are mediated by a heterocomplex of EPO receptor (EPOR) and the β common receptor (βCR). We studied the action of EPO and its analogues in a model of wound healing where a bovine aortic endothelial cells (BAECs) monolayer was scratched and the scratch closure was assessed over 24 h under different oxygen concentrations. We related the effects of EPO and its analogues on repair to their effect on BAECs proliferation and migration (evaluated using a micro-Boyden chamber). EPO, CEPO and pHBSP enhanced scratch closure only at lower oxygen (5%), while their effect at atmospheric oxygen (21%) was not significant. The mRNA expression of EPOR was doubled in 5% compared with 21% oxygen, and this was associated with increased EPOR assessed by immunofluorescence and Western blot. By contrast, βCR mRNA levels were similar in 5% and 21% oxygen. EPO and its analogues increased both BAECs proliferation and migration, suggesting that both may be involved in the reparative process. The priming effect of low oxygen tension on the action of tissue-protective cytokines may be of relevance to vascular disease, including atherogenesis and restenosis.

Interleukin-27 Protects Cardiomyocyte-Like H9c2 Cells against Metabolic Syndrome: Role of STAT3 Signaling

The present results demonstrated that high glucose (G), salt (S), and cholesterol C (either alone or in combination), as mimicking extracellular changes in metabolic syndrome, damage cardiomyocyte-like H9c2 cells and reduce their viability in a time-dependent manner. However, the effects were greatest when cells were exposed to all three agents (GSC). The mRNA of glycoprotein (gp) 130 and WSX-1, both components of the interleukin (IL)-27 receptor, were present in H9c2 cells. Although mRNA expression was not affected by exogenous treatment with IL-27, the expression of gp130 mRNA (but not that of WSX-1 mRNA) was attenuated by GSC. Treatment of IL-27 to H9c2 cells increased activation of signal transducer and activator of transcription 3 (STAT3) and protected cells from GSC-induced cytochrome c release and cell damage. The protective effects of IL-27 were abrogated by the STAT3 inhibitor, stattic. The results of the present study clearly demonstrate that the STAT3 pathway triggered by anti-inflammatory IL-27 plays a role in protecting cardiomyocytes against GSC-mediated damage.

Novel perspectives on the PHD-HIF oxygen sensing pathway in cardioprotection mediated by IPC and RIPC

Reperfusion of ischemic cardiac tissue is the standard treatment for improving clinical outcome following myocardial infarction but is inevitably associated with ischemia-reperfusion injury (IRI). Ischemic myocardial injury can be alleviated by exposing the heart to brief episodes of sublethal ischemia-reperfusion prior to the ischemic insult, a phenomenon that has been termed ischemic preconditioning (IPC). Similarly, remote IPC (RIPC) is defined as transient episodes of ischemia at a distant site before a subsequent prolonged injury of the target organ. In this setting, adaptive responses to hypoxia/ischemia in peripheral tissues include the release of soluble factors that have the potential to protect cardiomyocytes remotely. Oxygen fluctuations is a hallmark of insufficient tissue perfusion and ischemic episodes. Emerging evidence indicates that prolyl hydroxylase oxygen sensors (PHDs) and hypoxia-inducible transcription factors (HIFs) are critical regulators of IPC and RIPC. In this review, we discuss recent findings concerning the role of the PHD-HIF axis in IPC and RIPC-mediated cardioprotection and examine molecular pathways and cell types that might be involved. We also appraise the therapeutic value of targeting the PHD-HIF axis to enhance cardiac tolerance against IRI.

Endothelial nitric oxide synthase mediates the cerebrovascular effects of erythropoietin in traumatic brain injury

Background: Erythropoietin (Epo) improves post-traumatic cerebral blood flow (CBF), pressure autoregulation, and vascular reactivity to l-arginine. This study examines the dependence of these cerebral hemodynamic effects of Epo on nitric oxide generated by endothelial nitric oxide synthase (eNOS).

Methods: Using laser Doppler flow imaging, CBF was monitored in wild-type (WT) and eNOS-deficient mice undergoing controlled cortical impact followed by administration of Epo (5000 U/kg) or normal saline.

Results: Cerebral blood flow decreased in all groups post-injury with the greatest reductions occurring at the impact site. Epo administration resulted in significantly higher CBF in the peri-contusional sites in the WT mice [70.2 ± 3.35% in Epo-treated compared to 53 ± 3.3% of baseline in saline-treated mice (p < 0.0001)], but no effect was seen in the eNOS-deficient mice. No CBF differences were found at the core impact site where CBF dropped to 20–25% of baseline in all groups.

Conclusion: These differences between eNOS-deficient and WT mice indicate that the Epo mediated improvement in CBF in traumatic brain injury is eNOS dependent.

Systemic administration of erythropoietin inhibits retinopathy in RCS rats

Objective

Royal College of Surgeons (RCS) rats develop vasculopathy as photoreceptors degenerate. The aim of this study was to examine the effect of erythropoietin (EPO) on retinopathy in RCS rats.

Methods

Fluorescein angiography was used to monitor retinal vascular changes over time. Changes in retinal glia and vasculature were studied by immunostaining. To study the effects of EPO on retinal pathology, EPO (5000 IU/kg) was injected intraperitoneally in 14 week old normal and RCS rats twice a week for 4 weeks. Changes in the retinal vasculature, glia and microglia, photoreceptor apoptosis, differential expression of p75 neurotrophin receptor (p75^NTR), pro-neurotrophin 3 (pro-NT3), tumour necrosis factor-α (TNFα), pigment epithelium derived factor (PEDF) and vascular endothelial growth factor-A (VEGF-A), the production of CD34⁺ cells and mobilization of CD34⁺/VEGF-R2⁺ cells as well as recruitment of CD34⁺ cells into the retina were examined after EPO treatment.

Results

RCS rats developed progressive capillary dropout and subretinal neovascularization which were accompanied by retinal gliosis. Systemic administration of EPO stabilized the retinal vasculature and inhibited the development of focal vascular lesions. Further studies showed that EPO modulated retinal gliosis, attenuated photoreceptor apoptosis and p75^NTR and pro-NT3 upregulation, promoted the infiltration of ramified microglia and stimulated VEGF-A expression but had little effect on TNFα and PEDF expression. EPO stimulated the production of red and white blood cells and CD34⁺ cells along with effective mobilization of CD34⁺/VEGF-R2⁺ cells. Immunofluorescence study demonstrated that EPO enhanced the recruitment of CD34⁺ cells into the retina.

Conclusions

Our results suggest that EPO has therapeutic potentials in treatment of neuronal and vascular pathology in retinal disease. The protective effects of EPO on photoreceptors and the retinal vasculature may involve multiple mechanisms including regulation of retinal glia and microglia, inhibition of p75^NTR-pro-NT3 signaling together with stimulation of production and mobilization of bone marrow derived cells.

Molecular and functional characterization of erythropoietin receptor of the goldfish (Carassius auratus L.)

Erythropoietin receptor (EPOR) is a member of the class I cytokine receptor superfamily and signaling through this receptor is important for the proliferation, differentiation and survival of erythrocyte progenitor cells. This study reports on the molecular and functional characterization of goldfish EPOR. The identified goldfish EPOR sequence possesses the conserved EPOR ligand binding domain, the fibronectin domain, the class I cytokine receptor superfamily motif (WSXWS) as well as several intracellular signaling motifs characteristic of other vertebrate EPORs. The expression of epor mRNA in goldfish tissues, cell populations and cells treated with recombinant goldfish EPO (rgEPO) were evaluated by quantitative PCR revealing that goldfish epor mRNA is transcribed in both erythropoietic tissues (blood, kidney and spleen) and non-hematopoietic tissues (brain, heart and gill), as well as in immature erythrocytes. Recombinant goldfish EPOR (rgEPOR), consisting of its extracellular domain, dose-dependently inhibited proliferation of progenitor cells induced by rgEPO. In vitro binding studies indicated that rgEPO exists as monomer, dimer and/or trimmer and that rgEPOR exists as monomer and/or homodimer, and when incubated together, formed a ligand-receptor complex. Our results demonstrate that goldfish EPO/EPOR signaling has been highly conserved throughout vertebrate evolution as a required mechanism for erythrocyte development.

STAT transcription in the ischemic heart

All seven STAT proteins are expressed in the heart, and in this review we will focus on their contribution to cardiac physiology and to ischemic heart disease and its consequences. A substantial literature has focused on the roles of STAT1 and STAT3 in ischemic heart disease, where, at least in the acute phase, they appear to have a yin-yang relationship. STAT1 contributes to the loss of irreplaceable cardiac myocytes both by increasing apoptosis and by reducing cardioprotective autophagy. In contrast, STAT3 is cardioprotective, since STAT3-deficient mice have larger infarcts following ischemic injury, and a number of cardioprotective agents have been shown to act, at least partly, through STAT3 activation. STAT3 is also absolutely required for preconditioning—a process where periods of brief ischemia protect against a subsequent or previous prolonged ischemic episode. Prolonged activation of STAT3, however, is strongly implicated in the post-infarction remodeling of the heart which leads to heart failure, where, possibly together with STAT5, it augments activation of the renin-angiotensin system.

Expression of hypoxia-inducible factor-1α, endothelin-1 and adrenomedullin in newborn rats with hypoxia-induced pulmonary hypertension

Hypoxia-inducible factor (HIF)-1α is associated with hypoxia-induced pulmonary hypertension (HPH) in adults. In the present study, the expression levels of HIF-1α, endothelin (ET)-1 and adrenomedullin (ADM) were analyzed during HPH in neonates. In total, 96 newborn rats were subjected to hypoxia or normoxia for 3, 5, 7, 10, 14 or 21 days (n=8 per subgroup). HIF-1α, ET-1 and ADM expression levels were measured by quantitative polymerase chain reaction. In addition, the intima-media thickness/external diameter ratio (MT%) and medial wall cross-sectional area/vessel total cross-sectional area ratio (MA%) were calculated to evaluate pulmonary vascular remodeling. The mean pulmonary arterial pressure (mPAP) increased with exposure to hypoxia. Furthermore, the expression levels of HIF-1α, ET-1 and ADM in the lungs were shown to increase after three and five days of hypoxia, while the MT% and MA% increased after seven days of hypoxia, as compared with the controls (P<0.05). Therefore, the expression of HIF-1α, ET-1 and ADM is upregulated in the lungs of newborn rats during early HPH. At later stages, the mPAP increases, vascular remodeling occurs and HIF-1α, ET-1 and ADM expression levels restore to normal levels.

Genistein attenuates hypoxic pulmonary hypertension via enhanced nitric oxide signaling and the erythropoietin system

Upregulation of the erythropoietin (EPO)/EPO receptor (EPOR) system plays a protective role against chronic hypoxia-induced pulmonary hypertension (hypoxic PH) through enhancement of endothelial nitric oxide (NO)-mediated signaling. Genistein (Gen), a phytoestrogen, is considered to ameliorate NO-mediated signaling. We hypothesized that Gen attenuates and prevents hypoxic PH. In vivo, Sprague-Dawley rats raised in a hypobaric chamber were treated with Gen (60 mkg/kg) for 21 days. Pulmonary hemodynamics and vascular remodeling were ameliorated in Gen-treated hypoxic PH rats. Gen also restored cGMP levels and phosphorylated endothelial NO synthase (p-eNOS) at Ser(1177) and p-Akt at Ser(473) expression in the lungs. Additionally, Gen potentiated plasma EPO concentration and EPOR-positive endothelial cell counts. In experiments with hypoxic PH rats' isolated perfused lungs, Gen caused NO- and phosphatidylinositol 3-kinase (PI3K)/Akt-dependent vasodilation that reversed abnormal vasoconstriction. In vitro, a combination of EPO and Gen increased the p-eNOS and the EPOR expression in human umbilical vein endothelial cells under a hypoxic environment. Moreover, Gen potentiated the hypoxic increase in EPO production from human hepatoma cells. We conclude that Gen may be effective for the prevention of hypoxic PH through the improvement of PI3K/Akt-dependent, NO-mediated signaling in association with enhancement of the EPO/EPOR system.

Co-delivery of G-CSF and EPO released from fibrin gel for therapeutic neovascularization in rat hindlimb ischemia model

OBJECTIVE

G-CSF and EPO have shown a notable capability in neovascularization. However, their use is limited because of untoward leucocytosis, erythrogenesis, and short half-life in the plasma. Herein, we examined whether G-CSF and EPO released from fibrin gel injected into ischemic tissues would synergistically promote neovascularization with limited systematic effects in a rat hindlimb ischemic model.

METHODS AND RESULTS

In vivo study, group Gel received an intramuscular injection of fibrin gel; group Gel+G-CSF received fibrin gel containing human G-CSF; group Gel+EPO received fibrin gel containing human EPO; group Gel+G-CSF&EPO received fibrin gel containing G-CSF and EPO; group G-CSF&EPO received G-CSF and EPO. Through promoting the expression of SDF-1, local high concentration of EPO could traffic CXCR4+ cells mobilized by G-CSF to enhance neovascularization in ischemic muscle. The treatment with Gel+G-CSF&EPO was superior to the other treatments on blood flow reperfusion, capillary density, and α smooth muscle actin-positive vessel density. And this treatment induced a modest WBC count increase in peripheral blood.

CONCLUSIONS

G-CSF and EPO released from fibrin gel had a combined effect on postischemia neovascularization. This treatment may be a novel therapeutic modality for ischemic peripheral artery disease.

Erythropoietin has a restorative effect on the contractility of arteries following experimental hypoxia

INTRODUCTION

The aim of this study was to investigate the effect of erythropoietin on vascular contractility using an in vitro model of hypoxia replicating the hypoxic environment of blood vessels and surrounding adipose tissue in obesity.

METHODS AND RESULTS

Pharmacological in vitro studies were carried out on small mesenteric arterial segments from male Wistar rats with and without perivascular fat and endothelium. Contractile responses were investigated by wire myography under normoxia, experimental hypoxia ± erythropoietin and l-NNA. Perivascular fat exerted an anticontractile effect which was lost following the induction of experimental hypoxia. Erythropoietin prevented the loss of the anticontractile capacity when vessels were incubated for one hour before the induction of hypoxia or throughout the period of hypoxia; this was found to be independent of the function of perivascular fat, as fat denuded arteries had a similar reduction in contractility (artery no fat + hypoxia vs. artery no fat + hypoxia + erythropoietin). The mechanism by which erythropoietin was exerting its effect was found to be partially endothelium dependent and associated with an increase of nitric oxide bioavailability as nitric oxide synthase inhibition prevented the effect.

CONCLUSIONS

Whilst erythropoietin is working downstream from perivascular fat, it is possible that it may be therapeutically useful in obesity when hypoxia and inflammation reduce the normal activity of perivascular fat.

In vitro protection of adipose tissue-derived mesenchymal stem cells by erythropoietin

Mobilization of stem cells and their differentiation into cardiomyocytes are known to have protective effects after myocardial infarction. The integrity of transplanted mesenchymal stem cells for cardiac regeneration is dependent on cell-cell or cell-matrix interaction, which is adversely affected by reactive oxygen species in an ischemic environment. Treatment with erythropoietin was shown to protect human adipose tissue derived mesenchymal stem cells in an ischemic injury in vitro model. The analyses indicated that expression of erythropoietin receptors played a pivotal role in erythropoietin mediated cell survival. In this study, the anti-apoptotic effect of erythropoietin on stem cells was analyzed in apoptosis-induced human mesenchymal stem cells. Apoptosis was induced in cultured adult human adipose tissue derived mesenchymal stem cells by hydrogen peroxide. A group of cultured cells was also treated with recombinant human erythropoietin in a concentration of 50 ng mL(-1). The degree of apoptosis was analyzed by flow-cytometry and immunohistochemical staining for Caspase 3. The average percentages of apoptotic cells were significantly higher in H2O2-induced stem cells than in cells co-cultured with erythropoietin (63.03 ± 4.96% vs 29 ± 3.41%, p<0.01). We conclude that preconditioning with erythropoietin suppresses apoptosis of mesenchymal stem cells and enhances their survival.

Hypoxia preconditioning increases survival and decreases expression of Toll-like receptor 4 in pulmonary artery endothelial cells exposed to lipopolysaccharide

Abstract Pulmonary or systemic infections and hypoxemic respiratory failure are among the leading causes of admission to intensive care units, and these conditions frequently exist in sequence or in tandem. Inflammatory responses to infections are reproduced by lipopolysaccharide (LPS) engaging Toll-like receptor 4 (TLR4). Apoptosis is a hallmark of lung injury in sepsis. This study was conducted to determine whether preexposure to LPS or hypoxia modulated the survival of pulmonary artery endothelial cells (PAECs). We also investigated the role TLR4 receptor expression plays in apoptosis due to these conditions. Bovine PAECs were cultured in hypoxic or normoxic environments and treated with LPS. TLR4 antagonist TAK-242 was used to probe the role played by TLR4 receptors in cell survival. Cell apoptosis and survival were measured by caspase 3 activity and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) incorporation. TLR4 expression and tumor necrosis factor α (TNF-α) production were also determined. LPS increased caspase 3 activity in a TAK-242-sensitive manner and decreased MTT incorporation. Apoptosis was decreased in PAECs preconditioned with hypoxia prior to LPS exposure. LPS increased TNF-α production, and hypoxic preconditioning blunted it. Hypoxic preconditioning reduced LPS-induced TLR4 messenger RNA and TLR4 protein. TAK-242 decreased to baseline the LPS-stimulated expression of TLR4 messenger RNA regardless of environmental conditions. In contrast, LPS followed by hypoxia substantially increased apoptosis and cell death. In conclusion, protection from LPS-stimulated PAEC apoptosis by hypoxic preconditioning is attributable in part to reduction in TLR4 expression. If these signaling pathways apply to septic patients, they may account for differing sensitivities of individuals to acute lung injury depending on oxygen tensions in PAECs in vivo.

Whole body metabolic effects of prolonged endurance training in combination with erythropoietin treatment in humans: a randomized placebo controlled trial

Erythropoietin (Epo) administration improves aerobic exercise capacity and insulin sensitivity in renal patients and also increases resting energy expenditure (REE). Similar effects are observed in response to endurance training. The aim was to compare the effects of endurance training with erythropoiesis-stimulating agent (ESA) treatment in healthy humans. Thirty-six healthy untrained men were randomized to 10 wk of either: 1) placebo (n = 9), 2) ESA (n = 9), 3) endurance training (n = 10), or 4) ESA and endurance training (n = 8). In a single-blinded design, ESA/placebo was injected one time weekly. Training consisted of biking for 1 h at 65% of wattmax three times per week. Measurements performed before and after the intervention were as follows: body composition, maximal oxygen uptake, insulin sensitivity, REE, and palmitate turnover. Uncoupling protein 2 (UCP2) mRNA levels were assessed in skeletal muscle. Fat mass decreased after training (P = 0.003), whereas ESA induced a small but significant increase in intrahepatic fat (P = 0.025). Serum free fatty acid (FFA) levels and palmitate turnover decreased significantly in response to training, whereas the opposite pattern was found after ESA. REE corrected for lean body mass increased in response to ESA and training, and muscle UCP2 mRNA levels increased after ESA (P = 0.035). Insulin sensitivity increased only after training (P = 0.011).

IN CONCLUSION

1) insulin sensitivity is not improved after ESA treatment despite improved exercise capacity, 2) the calorigenic effects of ESA may be related to increased UCP2 gene expression in skeletal muscle, and 3) training and ESA exert opposite effects on lipolysis under basal conditions, increased FFA levels and liver fat fraction was observed after ESA treatment.

STAT5 fits the RISK profile for cardioprotection

How wonderful would it be if there were a simple, cheap, safe, non-invasive treatment that could be administered to a patient to protect their organs from ischemia and reperfusion? Such a treatment might be used to protect the organs during temporary loss of blood flow, as occurs for example during a heart attack or stroke. As unlikely as this may sound, such a treatment has indeed been discovered, although research into the mechanism is only just beginning. A recent paper by Heusch et al. in Circulation Research has taken the first step in this direction, as explained below.

Experimental acute myocardial infarction in rats: HIF-1α, caspase-3, erythropoietin and erythropoietin receptor expression and the cardioprotective effects of two different erythropoietin doses

The cardioprotective effects of two different doses of erythropoietin administration were analyzed in rats with experimental myocardial infarction. None, saline, standard-dose (5000Ukg(-1)) and high-dose (10,000Ukg(-1)) of human recombinant erythropoietin alpha were administered intraperitoneally in Wistar rats with myocardial infarction induced by coronary artery ligation. Infarct sizes measured after triphenyltetrazolium chloride staining, levels of biochemical markers, histopathology examined by light and electron microscopy, and immunohistochemical expressions of erythropoietin, erythropoietin receptor, hypoxia inducible factor-1α and caspase-3, were analyzed. Lower scores of infarction and hemorrhage, lower number of macrophages and higher score of vascularization surrounding the infarct area were observed in the erythropoietin administered groups (p<0.05). Erythropoietin administration after myocardial infarction reduced the area of infarction and hemorrhage. There were hypoxia inducible factor-1α and caspase-3 expressions in the marginal area, and erythropoietin and erythropoietin receptor expression in both marginal and normal areas (p<0.001). Vascularization, erythropoietin expression in the normal area and vascular erythropoietin expression were positively correlated with human erythropoietin levels. The cardioprotective effects of erythropoietin treatment were independent of endogenous erythropoietin/erythropoietin receptor activity. Moreover exogenous erythropoietin treatment did not suppress endogenous erythropoietin. Erythropoietin administration after myocardial infarction reduced caspase 3 expression (apoptotic activity) and induced neovascularization around the infarct area. Higher erythropoietin administration did not provide an additional benefit over the standard-dose in myocardial protection.

TGF-beta superfamily member activin A acts with BDNF and erythropoietin to improve survival of spiral ganglion neurons in vitro

Activins are regulators of embryogenesis, osteogenesis, hormones and neuronal survival. Even though activin receptor type II has been detected in spiral ganglion neurons (SGN), little is known about the role of activins in the inner ear. An activin-mediated neuroprotection is of considerable clinical interest since SGN are targets of electrical stimulation with cochlear implants in hearing impaired patients. Thus, the presence of activin type-I and type-II receptors was demonstrated immunocytochemically and the individual and combined effects of activin A, erythropoietin (EPO) and brain-derived neurotrophic factor (BDNF) on SGN were examined in vitro. SGN isolated from neonatal rats (P 3-5) were cultured in serum-free medium supplemented with activin A, BDNF and EPO. Compared to the negative control, survival rates of SGN were significantly improved when cultivated individually with activin A (p<0.001) and in combination with BDNF (p<0.001). Neither neurite outgrowth nor neuronal survival was influenced by the addition of EPO to activin A-treated neurons. However, when all three factors were added, a significantly (p<0.001) improved neuronal survival was observed (61.2±3.6%) compared to activin A (25.4±2.1%), BDNF (22.8±3.3%) and BDNF+EPO (19.2±1.5%). Under the influence of the EPO-inhibitors, this increase in neuronal survival was blocked. Acting with BDNF and EPO to promote neuronal survival in vitro, activin A presents an interesting factor for pharmacological intervention in the inner ear. The present study demonstrates a synergetic effect of a combined therapy with several trophic factors.

MAPK and PI3K pathways regulate hypoxia-induced atrial natriuretic peptide secretion by controlling HIF-1 alpha expression in beating rabbit atria

Mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways are pivotal and intensively studied signaling pathways in hypoxic conditions. However, the roles of MAPK and PI3K in the regulation of hypoxia-induced atrial natriuretic peptide (ANP) secretion are not well understood. The purpose of the present study was to investigate the mechanism by which the MAPK/ERK (extracellular signal-regulated kinase) and PI3K signaling pathways regulate the acute hypoxia-induced ANP secretion in isolated beating rabbit atria. An acute hypoxic perfused beating rabbit atrial model was used. The ANP levels in the atrial perfusates were measured by radioimmunoassay, and the hypoxia-inducible factor-1α (HIF-1α) mRNA and protein levels in the atrial tissue were determined by RT-PCR and Western blot. Acute hypoxia significantly increased ANP secretion and HIF-1α mRNA and protein levels. Hypoxia-induced ANP secretion was markedly attenuated by the HIF-1α inhibitors, rotenone (0.5μmol/L) and CAY10585 (10μmol/L), concomitantly with downregulation of the hypoxia-induced HIF-1α mRNA and protein levels. PD098059 (30μmol/L) and LY294002 (30μmol/L), inhibitors of MAPK and PI3K, markedly abolished the hypoxia-induced ANP secretion and atrial HIF-1α mRNA and protein levels. The hypoxia-suppressed atrial dynamics were significantly attenuated by PD098059 and LY294002. Acute hypoxia in isolated perfused beating rabbit atria, markedly increased ANP secretion through HIF-1α upregulation, which was regulated by the MAPK/ERK and PI3K pathways. ANP appears to be part of the protective program regulated by HIF-1α in the response to acute hypoxic conditions.

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.

Regulation of Erythropoietin Receptor Activity in Endothelial Cells by Different Erythropoietin (EPO) Derivatives: An in Vitro Study

In endothelial cells, erythropoietin receptors (EPORs) mediate the protective, proliferative and angiogenic effects of EPO and its analogues, which act as EPOR agonists. Because hormonal receptors undergo functional changes upon chronic exposure to agonists and because erythropoiesis-stimulating agents (ESAs) are used for the long-term treatment of anemia, it is critical to determine the mechanism by which EPOR responsiveness is regulated at the vascular level after prolonged exposure to ESAs. Here, we investigated EPOR desensitization/resensitization in human umbilical vein endothelial cells (HUVECs) upon exposure to three ESAs with different pharmacokinetic profiles, epoetin alpha (EPOα), darbepoetin alpha (DarbEPO) and continuous EPOR activator (CERA). These agonists all induced activation of the transcription factor STAT-5, which is a component of the intracellular pathway associated with EPORs. STAT-5 activation occurred with either monophasic or biphasic kinetics for EPOα/DarbEPO and CERA, respectively. ESAs, likely through activation of the STAT-5 pathway, induced endothelial cell proliferation and stimulated angiogenesis in vitro, demonstrating a functional role for epoetins on endothelial cells. All epoetins induced EPOR desensitization with more rapid kinetics for CERA compared to EPOα and DarbEPO. However, the recovery of receptor responsiveness was strictly dependent on the type of epoetin, the agonist concentration and the time of exposure to the agonist. EPOR resensitization occurred with more rapid kinetics after exposure to low epoetin concentrations for a short period of desensitization. When the highest concentration of agonists was tested, the recovery of receptor responsiveness was more rapid with CERA compared to EPOα and was completely absent with DarbEPO. Our results demonstrate that these three ESAs regulate EPOR resensitization by very different mechanisms and that both the type of molecule and the length of EPOR stimulation are factors that are critical for the control of EPOR functioning in endothelial cells. The differences observed in receptor resensitization after stimulation with the structurally different ESAs are most likely due different control mechanisms of receptor turnover at the intracellular level.

Dual functions of the C5a receptor as a connector for the K562 erythroblast-like cell-THP-1 macrophage-like cell island and as a sensor for the differentiation of the K562 erythroblast-like cell during haemin-induced erythropoiesis

The transcriptional nuclear factor binding to the Y box of human leukocyte antigen genes (NF-Y) for the C5a receptor (C5aR) gene is active in erythroblasts. However, the roles of the C5aR in erythropoiesis are unclear. We have previously demonstrated that apoptotic cell-derived ribosomal protein S19 (RP S19) oligomers exhibit extraribosomal functions in promoting monocyte chemotaxis and proapoptosis via the C5aR without receptor internalisation. In contrast to the extraribosomal functions of the RP S19, a proapoptotic signal in pro-EBs, which is caused by mutations in the RP S19 gene, is associated with the inherited erythroblastopenia, Diamond-Blackfan anaemia. In this study, we detected C5aR expression and RP S19 oligomer generation in human erythroleukemia K562 cells during haemin-induced erythropoiesis. Under monocell culture conditions, the differentiation into K562 erythrocyte-like cells was enhanced following the overexpression of Wild-type RP S19. Conversely, the differentiation was repressed following the overexpression of mutant RP S19. An RP S19 oligomer inhibitor and a C5aR inhibitor blocked the association of the K562 basophilic EB-like cells and the THP-1 macrophage-like cells under coculture conditions. When bound to RP S19 oligomers, the C5aR may exhibit dual functions as a connector for the EB-macrophage island and as a sensor for EB differentiation in the bone marrow.

Erythropoietin acutely decreases airway resistance in the rat

While some experimental data suggest that erythropoietin (EPO) influences respiratory mechanics, reports on scientific trials are lacking. In the present work, respiratory mechanics were measured using the end-inflation occlusion method in control and EPO treated anaesthetised and positive-pressure ventilated rats. Causing an abrupt inspiratory flow arrest, the end-inflation occlusion method makes it possible to measure the ohmic airway resistance and the respiratory system elastance. It was found that EPO induces a significant decrement in the ohmic airway resistance, not noted in control animals, 20 and 30 min after intraperitoneal EPO injection. The elastic characteristics of the respiratory system did not vary. Hypotheses about the mechanism (s) explaining these results were addressed. In particular, additional experiments have indicated that the decrement in airway resistance could be related to an increase in nitric oxide production induced by EPO. Spontaneous increments in plasmatic erythropoietin levels, such as those that take place in association with hypoxia and/or blood loss, appear to be related to the decrement in airway resistance, allowing pulmonary ventilation to increase without altering respiratory mechanics leading to deleterious increments in energy dissipation during breathing.

Nuclear phospholipase C β1 signaling, epigenetics and treatments in MDS

Myelodysplastic syndromes (MDS), clonal hematopoietic stem-cell disorders mainly affecting older adult patients, show ineffective hematopoiesis in one or more of the lineages of the bone marrow. Most MDS are characterized by anemia, and a number of cases progresses to acute myeloid leukemia (AML). Indeed, the molecular mechanisms underlying the MDS evolution to AML are still unclear, even though the nuclear signaling elicited by PI-PLCβ1 has been demonstrated to play an important role in the control of the balance between cell cycle progression and apoptosis in MDS cells. Here we review both the role of epigenetic therapy on PI-PLCβ1 promoter and the changes in PI-PLCβ1 expression in MDS patients treated for anemia.

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.

Activation of nuclear inositide signalling pathways during erythropoietin therapy in low-risk MDS patients

Inositide signaling pathways can have a role in the Myelodysplastic Syndromes (MDS) progression to acute myeloid leukemia. Erythropoietin (EPO) is currently used in low-risk MDS, where it successfully corrects anemia in 50-70% of patients. However, some MDS patients are refractory to this treatment and little is known about the exact molecular mechanisms underlying the effect of EPO in these subjects. Here, we investigated the role of inositide pathways in low-risk MDS treated with EPO, mainly focusing on the Akt/PI-PLC (Phosphoinositide-Phospholipase C) gamma1 axis, which is activated by the EPO receptor, and PI-PLCbeta1/Cyclin D3 signaling, as Cyclin D3 is associated with hematopoietic proliferation and differentiation. Interestingly, EPO responder patients showed a specific activation of both the Akt/PI-PLCgamma1 pathway and beta-Globin gene expression, while nonresponders displayed an increase in PI-PLCbeta1 signaling. Moreover, in normal CD34+ cells induced to erythroid differentiation, PI-PLCbeta1 overexpression abrogated both EPO-induced Akt phosphorylation and beta-Globin expression. Overall, these findings suggest that PI-PLCbeta1 can act as a negative regulator of erythroid differentiation and confirm the involvement of Akt/PI-PLCgamma1 pathway in EPO signaling, therefore contributing to the comprehension of the effect of EPO in low-risk MDS and possibly paving the way to the identification of MDS patients at higher risk of refractoriness to EPO treatment.

Evaluation of functional erythropoietin receptor status in skeletal muscle in vivo: acute and prolonged studies in healthy human subjects

BACKGROUND

Erythropoietin receptors have been identified in human skeletal muscle tissue, but downstream signal transduction has not been investigated. We therefore studied in vivo effects of systemic erythropoietin exposure in human skeletal muscle.

METHODOLOGY/PRINCIPAL FINDINGS

The protocols involved 1) acute effects of a single bolus injection of erythropoietin followed by consecutive muscle biopsies for 1-10 hours, and 2) a separate study with prolonged administration for 16 days with biopsies obtained before and after. The presence of erythropoietin receptors in muscle tissue as well as activation of Epo signalling pathways (STAT5, MAPK, Akt, IKK) were analysed by western blotting. Changes in muscle protein profiles after prolonged erythropoietin treatment were evaluated by 2D gel-electrophoresis and mass spectrometry. The presence of the erythropoietin receptor in skeletal muscle was confirmed, by the M20 but not the C20 antibody. However, no significant changes in phosphorylation of the Epo-R, STAT5, MAPK, Akt, Lyn, IKK, and p70S6K after erythropoietin administration were detected. The level of 8 protein spots were significantly altered after 16 days of rHuEpo treatment; one isoform of myosin light chain 3 and one of desmin/actin were decreased, while three isoforms of creatine kinase and two of glyceraldehyd-3-phosphate dehydrogenase were increased.

CONCLUSIONS/SIGNIFICANCE

Acute exposure to recombinant human erythropoietin is not associated by detectable activation of the Epo-R or downstream signalling targets in human skeletal muscle in the resting situation, whereas more prolonged exposure induces significant changes in the skeletal muscle proteome. The absence of functional Epo receptor activity in human skeletal muscle indicates that the long-term effects are indirect and probably related to an increased oxidative capacity in this tissue.

Vascular incompetence in dialysis patients--protein-bound uremic toxins and endothelial dysfunction

Patients with chronic kidney disease (CKD) have a much higher risk of cardiovascular diseases than the general population. Endothelial dysfunction, which participates in accelerated atherosclerosis, is a hallmark of CKD. Patients with CKD display impaired endothelium-dependent vasodilatation, elevated soluble biomarkers of endothelial dysfunction, and increased oxidative stress. They also present an imbalance between circulating endothelial populations reflecting endothelial injury (endothelial microparticles and circulating endothelial cells) and repair (endothelial progenitor cells). Endothelial damage induced by a uremic environment suggests an involvement of uremia-specific factors. Several uremic toxins, mostly protein-bound, have been shown to have specific endothelial toxicity: ADMA, homocysteine, AGEs, and more recently, p-cresyl sulfate and indoxyl sulfate. These toxins, all poorly removed by hemodialysis therapies, share mechanisms of endothelial toxicity: they promote pro-oxidant and pro-inflammatory response and inhibit endothelial repair. This article (i) reviews the evidence for endothelial dysfunction in CKD, (ii) specifies the involvement of protein-bound uremic toxins in this dysfunction, and (iii) discusses therapeutic strategies for lowering uremic toxin concentrations or for countering the effects of uremic toxins on the endothelium.

Endogenous serum erythropoietin and no-reflow in patients with ST-elevation myocardial infarction

BACKGROUND

In models of acute ischaemia, erythropoietin (EPO) administration has been found to attenuate vascular injury largely through reduced apoptosis, suppressed inflammation and increased nitric oxide availability. We studied the association between circulating endogenous EPO and no-reflow in patients with first ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI).

METHODS

Blood sampling was performed before PPCI. Consecutive patients with (n = 24) or without (n = 24) evidence of angiographic no-reflow after PPCI were enrolled. Angiographic no-reflow was defined as Thrombolysis in Myocardial Infarction (TIMI) flow ≤ 2 or as TIMI flow = 3 but with myocardial blush grade < 2. We also assessed electrocardiographic (ECG) no-reflow as ≤ 50% resolution of maximal ST elevation 60 min after PPCI.

RESULTS

Baseline characteristics did not correlate significantly with EPO concentrations. In contrast, both angiographic and ECG no-reflow correlated with lower EPO levels at univariate analysis [median (interquartile): 4·2 (0·6-9·5) vs. 12·2 (5·2-20·3) mIU mL(-1), P = 0·001, and 4·0 (0·6-7·1) vs. 9·3 (1·0-12·6) mIU mL(-1), P = 0·01, respectively]. At multivariable analysis, decreasing EPO tertiles and left anterior descending as the infarct-related artery were the only factors that predicted both angiographic and ECG no-reflow (P = 0·017 and P = 0·02 for EPO; P < 0·005 and P > 0·05 for left anterior descending artery, respectively).

CONCLUSIONS

We found an independent, graded, inverse relation between endogenous EPO levels and angiographic and ECG no-reflow following PPCI. In animal models of ischaemia, EPO has been found to be protective. In humans, endogenous EPO may contribute to offset the mechanisms responsible for no-reflow.

Erythropoietin ameliorates renal ischemia and reperfusion injury via inhibiting tubulointerstitial inflammation

BACKGROUND

Tubulointerstitial inflammation is the characteristics of renal ischemia reperfusion injury (IRI) that is inevitable in kidney transplantation. Erythropoietin (EPO) has recently been shown to have protective effects on renal IRI by anti-apoptosis and anti-oxidation. Here, the effect and mechanism of EPO on renal IRI were further investigated, with a focus on tubulointerstitial inflammation.

MATERIALS AND METHODS

Male Sprague-Dawley rats were administrated with saline or EPO prior to IRI induced by bilateral renal pedicle clamping. Twenty-four hours following reperfusion, the effects of EPO on renal IRI were assessed by renal function and structure, tubulointerstitial myeloperoxidase (MPO) positive neutrophils, and proinflammatory mediator gene expression. The translocation and activity of NF-κB in renal tissues were also evaluated.

RESULTS

Compared with control groups, the EPO treated group exhibited lower serum urea and creatinine levels, limited tubular necrosis with a lower score of renal histological lesion. MPO positive cells in the tubulointerstitial area were greatly increased by IRI, but significantly reduced by the treatment of EPO. The gene expression of proinflammatory cytokines (IL-1β, IL-6, IL-10, and TNF-α) and chemokine (MCP-1) was also significantly decreased by EPO. In addition, less activation and nuclear-translocation of NF-κB was observed in the kidney treated by EPO as well.

CONCLUSION

EPO improved renal function and structure in IRI rats via reducing neutrophils in the tubulointerstitium, the production of proinflammatory cytokines and chemokine, as well as the activation and nuclear-translocation of NF-κB. EPO may have potential clinical applications as an anti-inflammation agent clinically for a wide range of injury.

Long-term treatment with suberythropoietic Epo is vaso- and neuroprotective in experimental diabetic retinopathy

BACKGROUND/AIMS

Diabetic retinopathy is characterized by pericyte loss and vasoregression both in the clinic and in animal models. A mild neurodegeneration with loss of ganglion cells is also described in the diabetic retina. Like VEGF-A, Epo is angioprotective and, in high doses, neuroprotective, however, without affecting vessel permeability. This study was to investigate the effect of a long-term suberythropoietic dose of Epo on vascular damage and neurodegeneration in a rat model of diabetic retinopathy.

METHODS

We administered Epo 3x256 IU/kg body weight/week to streptozotocin-diabetic Wistar rats for up to 6 months. Leukostasis was analyzed by quantitation of CD45 positive cells adherent to the retinal microvasculature. VEGF-A levels were assessed by Elisa at 3 months of treatment. Vasoregression was quantified in retinal digest preparations after 6 months of Epo treatment. Neurodegeneration was analyzed from PAS stained retinal paraffin preparations.

RESULTS

Leukostasis was unaffected by treatment with Epo which significantly inhibited the loss of pericyte and the formation of acellular capillaries. Neurodegeneration in the diabetic retina was significantly reduced by Epo treatment. Increased VEGF-A levels in the diabetic retina were normalized by Epo treatment.

CONCLUSIONS

Suberythropoietic Epo is effective to protect microvascular and neuronal damage in the experimental diabetic retina.

Hypoxia and fetal heart development

Fetal hearts show a remarkable ability to develop under hypoxic conditions. The metabolic flexibility of fetal hearts allows sustained development under low oxygen conditions. In fact, hypoxia is critical for proper myocardial formation. Particularly, hypoxia inducible factor 1 (HIF-1) and vascular endothelial growth factor play central roles in hypoxia-dependent signaling in fetal heart formation, impacting embryonic outflow track remodeling and coronary vessel growth. Although HIF is not the only gene involved in adaptation to hypoxia, its role places it as a central figure in orchestrating events needed for adaptation to hypoxic stress. Although "normal" hypoxia (lower oxygen tension in the fetus as compared with the adult) is essential in heart formation, further abnormal hypoxia in utero adversely affects cardiogenesis. Prenatal hypoxia alters myocardial structure and causes a decline in cardiac performance. Not only are the effects of hypoxia apparent during the perinatal period, but prolonged hypoxia in utero also causes fetal programming of abnormality in the heart's development. The altered expression pattern of cardioprotective genes such as protein kinase c epsilon, heat shock protein 70, and endothelial nitric oxide synthase, likely predispose the developing heart to increased vulnerability to ischemia and reperfusion injury later in life. The events underlying the long-term changes in gene expression are not clear, but likely involve variation in epigenetic regulation.

Erythropoietin and the heart: facts and perspectives

EPO (erythropoietin) has long been identified as a primary regulator of erythropoiesis. Subsequently, EPO has been recognized as playing a role in a broad variety of processes in cardiovascular pathophysiology. In particular, the tight interactions of EPO with the nitric oxide pathway, apoptosis, ischaemia, cell proliferation and platelet activation appear of great interest. Although enhanced EPO synthesis is viewed as an appropriate compensatory mechanism in the cardio-renal syndrome, which features CHF (congestive heart failure) and CRF (chronic renal failure), maladaptative excessive EPO synthesis in the advanced stages of these diseases appears to be predictive of higher mortality. Clinical trials based on the use of EPO in both heart and renal failure have so far produced contradictory results, whereas treatment targeted to restore low Hb levels appears rational and is supported by regulatory authorities. New areas for therapeutic use of EPO, such as acute coronary syndromes, are under investigation, and they are discussed in the present review together with other clinical applications in cardiovascular diseases. The revisited concept of a potential use of endogenous EPO levels as a predictor of CHF severity, as well as in the monitoring of responses to treatment, deserves appropriate investigation, as this may identify EPO as a useful biomarker in the clinical management of cardiovascular diseases.

Design and rationale of the Reduction of Infarct Expansion and Ventricular Remodeling with Erythropoietin after Large Myocardial Infarction (REVEAL) trial

BACKGROUND

Acute myocardial infarction (MI) remains a leading cause of death despite advances in pharmacologic and percutaneous therapies. Animal models of ischemia/reperfusion have demonstrated that single-dose erythropoietin may reduce infarct size, decrease apoptosis, and increase neovascularization, possibly through mobilization of endothelial progenitor cells.

STUDY DESIGN

REVEAL is a randomized, double-blind, placebo-controlled, multicenter trial evaluating the effects of epoetin α on infarct size and left ventricular remodeling in patients with large MIs. The trial comprises a dose-escalation safety phase and a single-dose efficacy phase using the highest acceptable epoetin α dose up to 60,000 IU. Up to 250 ST-segment elevation myocardial infarction patients undergoing primary or rescue percutaneous coronary intervention will be randomized to intravenous epoetin α or placebo within 4 hours of successful reperfusion. The primary study end point is infarct size expressed as a percentage of left ventricular mass, as measured by cardiac magnetic resonance imaging 2 to 6 days post study medication administration. Secondary end points will assess changes in endothelial progenitor cell numbers and changes in indices of ventricular remodeling.

CONCLUSION

The REVEAL trial will evaluate the safety and efficacy of the highest tolerated single dose of epoetin α in patients who have undergone successful rescue or primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction.