Protective Effects of Erythropoietin in Cardiac Ischemia

Inhibition the ubiquitination of ENaC and Na,K-ATPase with erythropoietin promotes alveolar fluid clearance in sepsis-induced acute respiratory distress syndrome

Sepsis-induced acute respiratory distress syndrome (ARDS) causes significant fatalities worldwide and lacks pharmacological intervention. Alveolar fluid clearance (AFC) plays a pivotal role in the remission of ARDS and is markedly impaired in the pathogenesis of ARDS. Here, we demonstrated that erythropoietin could effectively ameliorate lung injury manifestations and lethality, restore lung function and promote AFC in a rat model of lipopolysaccharide (LPS)-induced ARDS. Moreover, it was proven that EPO-induced restoration of AFC occurs through triggering the total protein expression of ENaC and Na,K-ATPase channels, enhancing their protein abundance in the membrane, and suppressing their ubiquitination for degeneration. Mechanistically, the data indicated the possible involvement of EPOR/JAK2/STAT3/SGK1/Nedd4-2 signaling in this process, and the pharmacological inhibition of the pathway markedly eliminated the stimulating effects of EPO on ENaC and Na,K-ATPase, and subsequently reversed the augmentation of AFC by EPO. Consistently, in vitro studies of alveolar epithelial cells paralleled with that EPO upregulated the expression of ENaC and Na,K-ATPase, and patch-clamp studies further demonstrated that EPO substantially strengthened sodium ion currents. Collectively, EPO could effectively promote AFC by improving ENaC and Na,K-ATPase protein expression and abundance in the membrane, dependent on inhibition of ENaC and Na,K-ATPase ubiquitination, and resulting in diminishing LPS-associated lung injuries.

Cardiomyocyte Atrophy, an Underestimated Contributor in Doxorubicin-Induced Cardiotoxicity

Left ventricular (LV) mass loss is prevalent in doxorubicin (DOX)-induced cardiotoxicity and is responsible for the progressive decline of cardiac function. Comparing with the well-studied role of cell death, the part of cardiomyocyte atrophy (CMA) playing in the LV mass loss is underestimated and the knowledge of the underlying mechanism is still limited. In this review, we summarized the recent advances in the DOX-induced CMA. We found that the CMA caused by DOX is associated with the upregulation of FOXOs and “atrogenes,” the activation of transient receptor potential canonical 3-NADPH oxidase 2 (TRPC3-Nox2) axis, and the suppression of IGF-1-PI3K signaling pathway. The imbalance of anabolic and catabolic process may be the common final pathway of these mechanisms. At last, we provided some strategies that have been demonstrated to alleviate the DOX-induced CMA in animal models.

Erythropoietin alleviates acute lung injury induced by ischemia-reperfusion through blocking p38 MAPK signaling

Erythropoietin (EPO) has antiapoptotic, antioxidative, and anti-inflammatory effects on ischemia tissues and protects against acute lung injury (ALI) induced by ischemia-reperfusion (I/R). p38 mitogen-activated protein kinases (p38 MAPK) signaling is involved in the processes of I/R-induced ALI. However, the interaction of EPO with p38 MAPK signaling in I/R-induced ALI has not been reported. To explore this issue, we constructed an I/R-induced ALI model in vivo and in vitro using Sprague Dawley rats and BEAS-2B cells. Some I/R rats and hypoxia-reoxygenation (H/R)-induced cells were treated with EPO, and the others were used as control groups. The injuries of lung tissues and cells were respectively assessed by inflammatory cytokine, morphologic changes, cell viability, apoptosis, and oxidative damage-related factors. Western blot determined key proteins in the p38 MAPK signaling. Results indicated that I/R induced the increase of inflammatory factors, lung weight, filtration coefficient, bronchoalveolar lavage fluid protein content, apoptosis, neutrophil, and lung peroxidation, and H/R caused cell growth inhibition, apoptosis, and oxidative damage-related factors' release. EPO attenuated I/R-induced injury in vivo and in vitro. Furthermore, the increase of p-p38, p-JNK, and p-ERK1/2 in lung tissues and cells induced by I/R was downregulated by EPO. Moreover, both EPO and an inhibitor of p38 MAPK (SB203580) alleviated H/R-induced cell injury. Erythropoietin along with SB203580 had more obvious protection effects than EPO alone. Collectively, EPO alleviated I/R-induced ALI by blocking p38 MAPK signaling. The interaction mechanism of EPO with p38 MAPK signaling contributes to understanding the processes of I/R-induced ALI and provides new insights for the disease treatment.

Anemia in Cardiovascular Disease: Marker of Disease Severity or Disease-modifying Therapeutic Target?

PURPOSE OF THE REVIEW

In this review paper, we examine the latest evidence regarding the use of iron supplementation, erythropoiesis-stimulating agents (ESAs), and blood transfusions as therapeutic targets for anemia to mitigate morbidity and mortality in patients with cardiovascular disease.

RECENT FINDINGS

Intravenous ferric carboxymaltose (FC) injections in heart failure (HF) have resulted in improved self-reported patient symptoms; higher exercise capacity, as measured by 6-min walk test distance in anemic patients; and lower re-hospitalization rates in iron deficient patients. Darbepoetin alfa has shown evidence of improved Kansas City Cardiomyopathy Questionnaire scores. No mortality benefits have been noted thus far with FC injections or darbepoetin in HF, with an increase in adverse events with darbepoetin. Aggressive transfusions (Hg < 10 g/dL) are not associated with improved outcomes in cardiovascular disease. Quality of life metrics, rather than mortality, appear to improve with IV FC and ESA use in HF. More studies are required to see if these treatments have a role in coronary artery disease. Current evidence suggests that anemia is a marker of underlying disease severity, with a limited role in disease modification. Further studies are required to solidify our understanding of this topic.

Erythropoietin in Lupus: Unanticipated Immune Modulating Effects of a Kidney Hormone

Systemic lupus erythematosus (SLE) is a multiorgan autoimmune disease with variable clinical presentation, typically characterized by a relapsing-remitting course. SLE has a multifactorial pathogenesis including genetic, environmental, and hormonal factors that lead to loss of tolerance against self-antigens and autoantibody production. Mortality in SLE patients remains significantly higher than in the general population, in part because of the limited efficacy of available treatments and the associated toxicities. Therefore, novel targeted therapies are urgently needed to improve the outcomes of affected individuals. Erythropoietin (EPO), a kidney-produced hormone that promotes red blood cell production in response to hypoxia, has lately been shown to also possess non-erythropoietic properties, including immunomodulatory effects. In various models of autoimmune diseases, EPO limits cell apoptosis and favors cell clearance, while reducing proinflammatory cytokines and promoting the induction of regulatory T cells. Notably, EPO has been shown to reduce autoimmune response and decrease disease severity in mouse models of SLE. Herein, we review EPO's non-erythropoietic effects, with a special focus on immune modulating effects in SLE and its potential clinical utility.

Remote liver ischemic preconditioning attenuates myocardial ischemia/reperfusion injury in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) exhibits a higher sensitivity to myocardial ischemia/reperfusion (I/R) injury and may compromise the effectiveness of cardioprotective interventions, including ischemic preconditioning. We previously found that liver ischemic preconditioning (RLIPC) could limit infarct size post I/R in non-diabetic rat hearts and further exerted anti-arrhythmic effects in diabetic or non-diabetic rats after myocardial I/R, however, little is known regarding the effect of RLIPC on infarct-sparing in diabetic hearts. In this study, we evaluated the protective effects of RLIPC on I/R injury in streptozotocin-induced type 1 diabetic rats. Type 1 diabetes mellitus was induced by one-time intraperitoneal injection of streptozotocin in Sprague-Dawley rats. Rats were exposed to 45 min of left anterior descend in (LAD) coronary artery occlusion, followed by 3 h of reperfusion. For liver ischemic preconditioning, four cycles of 5 min of liver I/R stimuli were performed before LAD occlusion. The cardioprotective effect of RLIPC was determined in diabetic rats. Compared to non-RLIPC treated DM rats, RLIPC treatment significantly reduced infarct size and cardiac tissue damage, inhibited apoptosis in diabetic hearts post I/R. RLIPC also improved cardiac functions including LVESP, LVEDP, dp/dtmax, and - dp/dtmax. In addition, RLIPC preserved cardiac morphology by reducing the pathological score post I/R in diabetic hearts. Finally, Westernblotting showed that RLIPC stimulated phosphorylation of ventricular GSK-3β and STAT-5, which are key components of RISK and SAFE signaling pathways. Our study showed that liver ischemic preconditioning retains strong cardioprotective properties in diabetic hearts against myocardial I/R injury via GSK-3β/STAT5 signaling pathway.

EPO and EPO-Receptor System as Potential Actionable Mechanism for the Protection of Brain and Heart in Refractory Epilepsy and SUDEP

The most important activity of erythropoietin (EPO) is the regulation of erythrocyte production by activation of the erythropoietin receptor (EPO-R), which triggers the activation of anti-apoptotic and proliferative responses of erythroid progenitor cells. Additionally, to erythropoietic EPO activity, an antiapoptotic effect has been described in a wide spectrum of tissues. EPO low levels are found in the central nervous system (CNS), while EPO-R is expressed in most CNS cell types. In spite of EPO-R high levels expressed during the hypoxicischemic brain, insufficient production of endogenous cerebral EPO could be the cause of determined circuit alterations that lead to the loss of specific neuronal populations. In the heart, high EPO-R expression in cardiac progenitor cells appears to contribute to myocardial regeneration under EPO stimulation. Several lines of evidence have linked EPO to an antiapoptotic role in CNS and in heart tissue. In this review, an antiapoptotic role of EPO/EPO-R system in both brain and heart under hypoxic conditions, such as epilepsy and sudden death (SUDEP) has been resumed. Additionally, their protective effects could be a new field of research and a novel therapeutic strategy for the early treatment of these conditions and avoid SUDEP.

Application of Erythropoietin in Chronic Heart Failure Treatment

Heart Failure (HF) is recognized as an important public health concern worldwide, especially in developed countries, due to its high rate of morbidity and mortality. Although new pharmacological and non-pharmacological agents have improved the clinical sequelae of HF in patients, its mortality remains high, especially among the elderly. Erythropoietin (EPO), a glycoprotein, besides its traditional role in promoting erythropoiesis and production of erythroid progenitors, its beneficial role in reducing infarct area and improving heart function through EPO-induced antiapoptotic and antioxidant effects have been increasingly recognized. This review gathers the evidence to date about the effectiveness of EPO in HF patients. In addition to the growing evidence of EPO in the treatment of HF in the animal studies for improving cardiac function and infarct size, more clinical studies are needed to assess the role of EPO treatment in the management of HF.

EPO enhances the protective effects of MSCs in experimental hyperoxia-induced neonatal mice by promoting angiogenesis

Bronchopulmonary dysplasia (BPD) is the most common type of chronic lung disease in infancy; however, there is no effective treatment for it. In the present study, a neonatal mouse BPD model was established by continuous exposure to high oxygen (HO) levels. Mice were divided randomly into 5 groups: control, BPD, EPO, MSCs, and MSCs+EPO. At 2 weeks post-treatment, vessel density and the expression levels of endothelial growth factor (VEGF), stromal cell-derived factor-1 (SDF-1), and its receptor C-X-C chemokine receptor type 4 (CXCR4) were significantly increased in the MSC+EPO group compared with the EPO or MSCs group alone; moreover, EPO significantly enhanced MSCs proliferation, migration, and anti-apoptosis ability in vitro. Furthermore, the MSCs could differentiate into cells that were positive for the type II alveolar epithelial cell (AECII)-specific marker surfactant protein-C, but not positive for the AECI-specific marker aquaporin 5. Our present results suggested that MSCs in combination with EPO could significantly attenuate lung injury in a neonatal mouse model of BPD. The mechanism may be by the indirect promotion of angiogenesis, which may involve the SDF-1/CXCR4 axis.

Suppression of NLRP3 Inflammasome by Erythropoietin via the EPOR/JAK2/STAT3 Pathway Contributes to Attenuation of Acute Lung Injury in Mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. An excessive inflammatory response results in the progression of ALI/ARDS, and the NLRP3 inflammasome is a key participant in inflammation. Erythropoietin (EPO), which is clinically used for anemia, reportedly exerts pleiotropic effects in ALI. However, whether EPO could protect against lipopolysaccharide (LPS)-induced ALI by regulating the NLRP3 inflammasome and its underlying mechanisms remain poorly elucidated. This study aimed to explore whether the therapeutic effects of EPO rely on the suppression of the NLRP3 inflammasome and the specific mechanisms in an LPS-induced ALI mouse model. ALI was induced in C57BL/6 mice by intraperitoneal (i.p.) injection of LPS (15 mg/kg). EPO was administered intraperitoneally at 5 U/g after LPS challenge. The mice were sacrificed 8 h later. Our findings indicated that application of EPO markedly diminished LPS-induced lung injury by restoring histopathological changes, lessened lung wet/dry (W/D) ratio, protein concentrations in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) levels. Meanwhile, EPO evidently decreased interleukin-1β (IL-1β) and interleukin-18 (IL-18) secretion, the expression of NLRP3 inflammasome components including pro-IL-1β, NLRP3, and cleaved caspase-1 as well as phosphorylation of nuclear factor-κB (NF-κB) p65, which may be associated with activation of EPO receptor (EPOR), phosphorylation of Janus-tyrosine kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). However, all the beneficial effects of EPO on ALI and modulation NLRP3 inflammasome were remarkably abrogated by the inhibition of EPOR/JAK2/STAT3 pathway and knockout (KO) of NLRP3 gene. Taken together, this study indicates that EPO can effectively attenuate LPS-induced lung injury in mice by suppressing the NLRP3 inflammasome, which is dependent upon activation of EPOR/JAK2/STAT3 signaling and inhibition of the NF-κB pathway.

Thymoquinone Attenuates Cardiomyopathy in Streptozotocin-Treated Diabetic Rats

Diabetic cardiomyopathy is a diabetic complication due to oxidative stress injuries. This study examined the protecting influence of thymoquinone (TQ) on diabetes-caused cardiac complications. The intracellular means by which TQ works against diabetes-caused cardiac myopathy in rats is not completely understood. In this study, Wistar male rats (n = 60) were assigned into four groups: control, diabetic (diabetes induced by IP infusion of streptozotocin, 65 mg/kg), diabetic + TQ (diabetic rats given TQ (50 mg/kg) administered once per day by stomach gavage), and TQ (50 mg/kg) for 12 weeks. TQ supplementation appreciably recovered the cardiac parameters alongside significant declines in plasma nitric oxide concentrations and total superoxide dismutase (T.SOD) activities. Importantly, TQ downgraded expression of cardiac-inducible nitric oxide synthase in addition to significantly upregulating vascular endothelial growth factor and erythropoietin genes and nuclear factor-erythroid-2-related factor 2 (Nrf2) protein. TQ normalized plasma triacylglycerol and low-density lipoprotein-cholesterol and significantly improved the high-density lipoprotein-cholesterol levels. Additionally, TQ administration improved the antioxidant ability of cardiac tissue via significantly increased cardiac T.SOD and decreased cardiac malondialdehyde levels. Oral supplementation with TQ prevented diabetic-induced cardiomyopathy via its inhibitory effect on the E-selectin level, C-reactive protein, and interleukin-6. The TQ protecting effect on the heart tissue was shown by normalization of the plasma cardiac markers troponin I and creatine kinase. This experiment shows the aptitude of TQ to protect cardiac muscles against diabetic oxidative stress, mainly through upregulation of Nrf2, which defeated oxidative damage by improvement of the antioxidant power of cardiac muscle that consequently protected the cardiac muscles and alleviated the inflammatory process.

Angiogenic growth factors in myocardial infarction: a critical appraisal

In the recent past, substantial advances have been made in the treatment of myocardial infarction (MI). Despite the impact of these positive developments, MI remains to be a leading cause of morbidity as well as mortality. An interesting hypothesis is that the development of new blood vessels (angiogenesis) or the remodeling of preexisting collaterals may form natural bypasses that could compensate for the occlusion of an epicardial coronary artery. A number of angiogenic factors are proven to be elicited during MI. Exogenous supplementation of these growth factors either in the form of recombinant protein or gene would enhance the collateral vessel formation and thereby improve the outcome after MI. The aim of this review is to describe the nature and potentials of different angiogenic factors, their expression, their efficacy in animal studies, and clinical trials pertaining to MI.

The Role of Endothelial Progenitors in the Repair of Vascular Damage in Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease characterized by a complex pathological process where the main scenario is represented by progressive loss of microvascular bed, with the consequent progressive fibrotic changes in involved organ and tissues. Although most aspects of vascular injury in scleroderma are poorly understood, recent data suggest that the scleroderma impairment of neovascularization could be related to both angiogenesis and vasculogenesis failure. Particularly, compensatory angiogenesis does not occur normally in spite of an important increase in many angiogenic factors either in SSc skin or serum. Besides insufficient angiogenesis, the contribution of defective vasculogenesis to SSc vasculopathy has been extensively studied. Over the last decades, our understanding of the processes responsible for the formation of new vessels after tissue ischemia has increased. In the past, adult neovascularization was thought to depend mainly on angiogenesis (a process by which new vessels are formed by the proliferation and migration of mature endothelial cells). More recently, increased evidence suggests that stem cells mobilize from the bone marrow into the peripheral blood (PB), differentiate in circulating endothelial progenitors (EPCs), and home to site of ischemia to contribute to de novo vessel formation. Significant advances have been made in understanding the biology of EPCs, and molecular mechanisms regulating EPC function. Autologous EPCs now are becoming a novel treatment option for therapeutic vascularization and vascular repair, mainly in ischemic diseases. However, different diseases, such as cardiovascular diseases, diabetes, and peripheral artery ischemia are related to EPC dysfunction. Several studies have shown that EPCs can be detected in the PB of patients with SSc and are impaired in their function. Based on an online literature search (PubMed, EMBASE, and Web of Science, last updated December 2017) using keywords related to “endothelial progenitor cells” and “Systemic Sclerosis,” “scleroderma vasculopathy,” “angiogenesis,” “vasculogenesis,” this review gives an overview on the large body of data of current research in this issue, including controversies over the identity and functions of EPCs, their meaning as biomarker of SSc microangiopathy and their clinical potency.

Histopathological study of erythropoietin protective effect on carbon monoxide-induced cardiotoxicity in rat

Objective(s):

Cardiotoxicity is one of the major consequences in carbon monoxide poisoning. Following our previous work, in this study we aimed to define the myocardium changes induced by carbon monoxide (CO) intoxication and evaluate erythropoietin (EPO) effect on CO cardiotoxicity in rat.

Materials and Methods:

Severe carbon monoxide toxicity induced by 3000 ppm CO in Wistar rat. EPO was administrated (5000 IU/Kg, intraperitoneal injection) at the end of CO exposure and then the animals were re-oxygenated with the ambient air. Subsequently heart was removed and assessed by histopathology and electron microscopy examinations.

Results:

3000 ppm CO induced significant myocardium injury; multiple foci of necrosis and lymphocyte infiltration compare with the control (P<0.05). Electron microscopy examination showed myofibril lysis and mitochondrial swelling in myocardium due to 3000 ppm CO poisoning. However EPO administration after CO exposure resulted in significant reduction in cardiomyocytes injury (P<0.05).

Conclusion:

Our results represented protective effect of EPO on cardiac injury induced by CO intoxication in rat.

The erythropoietin-derived peptide MK-X and erythropoietin have neuroprotective effects against ischemic brain damage

Erythropoietin (EPO) has been well known as a hematopoietic cytokine over the past decades. However, recent reports have demonstrated that EPO plays a neuroprotective role in the central nervous system, and EPO has been considered as a therapeutic target in neurodegenerative diseases such as ischemic stroke. Despite the neuroprotective effect of EPO, clinical trials have shown its unexpected side effects, including undesirable proliferative effects such as erythropoiesis and tumor growth. Therefore, the development of EPO analogs that would confer neuroprotection without adverse effects has been attempted. In this study, we examined the potential of a novel EPO-based short peptide, MK-X, as a novel drug for stroke treatment in comparison with EPO. We found that MK-X administration with reperfusion dramatically reduced brain injury in an in vivo mouse model of ischemic stroke induced by middle cerebral artery occlusion, whereas EPO had little effect. Similar to EPO, MK-X efficiently ameliorated mitochondrial dysfunction followed by neuronal death caused by glutamate-induced oxidative stress in cultured neurons. Consistent with this effect, MK-X significantly decreased caspase-3 cleavage and nuclear translocation of apoptosis-inducing factor induced by glutamate. MK-X completely mimicked the effect of EPO on multiple activation of JAK2 and its downstream PI3K/AKT and ERK1/2 signaling pathways, and this signaling process was involved in the neuroprotective effect of MK-X. Furthermore, MK-X and EPO induced similar changes in the gene expression patterns under glutamate-induced excitotoxicity. Interestingly, the most significant difference between MK-X and EPO was that MK-X better penetrated into the brain across the brain–blood barrier than did EPO. In conclusion, we suggest that MK-X might be used as a novel drug for protection from brain injury caused by ischemic stroke, which penetrates into the brain faster in comparison with EPO, even though MK-X and EPO have similar protective effects against excitotoxicity.

Context-Dependent Skeletal Effects of Erythropoietin

Erythropoietin (Epo) is the main hormone that regulates the production of red blood cells (hematopoiesis), by stimulating their progenitors. Beyond this vital function, several emerging roles have been noted for Epo in other tissues, including neurons, heart, and retina. The skeletal system is also affected by Epo; however, its actions on bone are, as yet, controversial. Here, we review the seemingly contradicting evidence regarding Epo effects on bone remodeling. We also discuss the evidence pointing to a direct vs indirect effect of Epo on the osteoblastic and osteoclastic cell lineages. The current controversy may derive from a context-dependent mode of function of Epo, namely, opposite skeletal actions during bone regeneration and steady-state bone remodeling. Differences in conclusions deriving from the published in vitro studies may thus relate to the different experimental conditions. Taken together, the current state-of-the-art indicates definite Epo effects on bone cells and points to the complexity of the mode of function.

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.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Novel, selective EPO receptor ligands lacking erythropoietic activity reduce infarct size in acute myocardial infarction in rats

Erythropoietin (EPO) has been shown to protect the heart against acute myocardial infarction in pre-clinical studies, however, EPO failed to reduce infarct size in clinical trials and showed significant safety problems. Here, we investigated cardioprotective effects of two selective non-erythropoietic EPO receptor ligand dimeric peptides (AF41676 and AF43136) lacking erythropoietic activity, EPO, and the prolonged half-life EPO analogue, darbepoetin in acute myocardial infarction (AMI) in rats. In a pilot study, EPO at 100U/mL significantly decreased cell death compared to vehicle (33.8±2.3% vs. 40.3±1.5%, p<0.05) in rat neonatal cardiomyocytes subjected to simulated ischemia/reperfusion. In further studies (studies 1-4), in vivo AMI was induced by 30min coronary occlusion and 120min reperfusion in male Wistar rats. Test compounds and positive controls for model validation (B-type natriuretic peptide, BNP or cyclosporine A, CsA) were administered iv. before the onset of reperfusion. Infarct size (IS) was measured by standard TTC staining. In study 1, 5000U/kg EPO reduced infarct size significantly compared to vehicle (45.3±4.8% vs. 59.8±4.5%, p<0.05). In study 2, darbepoetin showed a U-shaped dose-response curve with maximal infarct size-reducing effect at 5μg/kg compared to the vehicle (44.4±5.7% vs. 65.9±2.7%, p<0.01). In study 3, AF41676 showed a U-shaped dose-response curve, where 3mg/kg was the most effective dose compared to the vehicle (24.1±3.9% vs. 44.3±2.5%, p<0.001). The positive control BNP significantly decreased infarct size in studies 1-3 by approximately 35%. In study 4, AF43136 at 10mg/kg decreased infarct size, similarly to the positive control CsA compared to the appropriate vehicle (39.4±5.9% vs. 58.1±5.4% and 45.9±2.4% vs. 63.8±4.1%, p<0.05, respectively). This is the first demonstration that selective, non-erythropoietic EPO receptor ligand dimeric peptides AF41676 and AF43136 administered before reperfusion are able to reduce infarct size in a rat model of AMI. Therefore, non-erythropoietic EPO receptor peptide ligands may be promising cardioprotective agents.

Protective effects of BMSCs in combination with erythropoietin in bronchopulmonary dysplasia-induced lung injury

Bronchopulmonary dysplasia (BPD) is the most common type of chronic lung disease in infancy, for which no effective therapy is currently available. The aim of the present study was to investigate the effect of treatment with bone marrow mesenchymal stem cells (BMSCs) in combination with recombinant human erythropoietin (rHuEPO) on BPD‑induced mouse lung injury, and discuss the underlying mechanism. The BPD model was established by the exposure of neonatal mice to continuous high oxygen exposure for 14 days, following which 1x106 BMSCs and 5,000 U/kg rHuEPO were injected into the mice 1 h prior to and 7 days following exposure to hyperoxia. The animals received four treatments in total (n=10 in each group). After 14 days, the body weights, airway structure, and levels of matrix metalloproteinase‑9 (MMP‑9) and vascular endothelial growth factor (VEGF) were detected using histological and immunohistochemical analyses. The effect on cell differentiation was observed by examining the presence of platelet endothelial cell adhesion molecule (PECAM) and VEGF using immunofluorescence. Compared with the administration of BMSCs alone, the body weight, airway structure, and the levels of MMP‑9 and VEGF were significantly improved in the BMSCs/rHuEPO group. The results of the present study demonstrated that the intravenous injection of BMSCs significantly improved lung damage in the hyperoxia‑exposed neonatal mouse model. Furthermore, the injection of BMSCs in combination with intraperitoneal injection of rHuEPO had a more marked effect, compared with BMSCs alone, and the mechanism may be mediated by the promoting effects of BMSCs and EPO. The results of the present study provided information, which may assist in future clinical trials.

Erythropoietin Reduces Post-PCI Arrhythmias in Patients With ST-elevation Myocardial Infarction

BACKGROUND

Arrhythmia is the foremost cause of sudden death after myocardial infarction (MI). Animal models have recently shown that erythropoietin (EPO) can reduce the incidence of arrhythmia after MI.

METHODS

We investigated the effects of administrating 33,000 IU EPO on the occurrence of post-MI arrhythmia in 40 patients with ST-elevation MI who were randomly assigned in either EPO or placebo groups. Arrhythmias were blindly documented using full 12-lead configuration during 24 hours after percutaneous coronary intervention (PCI) by a cardiologist. Afterward, CK-MB, hematologic, and hemodynamic data were examined within 2 weeks after MI.

RESULTS

A comparison made between the 2 groups showed significant differences in the incidence of arrhythmias (20% in EPO group and 35% in placebo group, P = 0.043). However, no significant differences in type of arrhythmias were observed between the groups. There was no significant difference between levels of CK-MB in the 2 groups during 24 hours (P = 0.186). Hematologic and hemodynamic data showed no significant changes 2 weeks after PCI.

CONCLUSION

High-dose administration of EPO in patients with ST-elevation MI who have been treated by primary PCI and standard antiplatelet therapy reduces the occurrence of arrhythmias. For clinical interpretation of the results, further well-designed trials are required.

Protective effect of erythropoietin on myocardial apoptosis in rats exposed to carbon monoxide

AIMS

Cardiac complications are common in carbon monoxide (CO) poisoning and associated with high morbidity and mortality. We have previously shown that erythropoietin (EPO) could reduce CO-induced cardiac ischemia in rat. In the current study, the anti-apoptotic effect of EPO during CO cardiotoxicity was investigated in order to elucidate the mechanism of EPO anti-ischemic action.

MAIN METHODS

Wistar rats were exposed to CO (250, 1000 and 3000ppm). EPO (5000IU/kg) was administered to all groups by intraperitoneal injection at the end of CO exposure period. TUNEL and caspase-3 activity levels were assessed to investigate the effects of CO exposure and subsequent EPO administration on myocardial apoptosis. The changes of mitochondrial membrane potential (MMP) were also assessed with sensitive lipophilic dye JC-1 by flow cytometry. The roles of Bcl2 and Bax in EPO protective effect were investigated by Western blotting.

KEY FINDINGS

Myocardial apoptosis was observed following CO exposure. Moreover, mitochondrial membrane depolarization and significant reduction in Bcl2/Bax ratio were shown following CO poisoning especially at 3000ppm. On the other hand, EPO administration could effectively suppress apoptosis in myocardial cells. Also, EPO significantly prevented the CO-induced depolarization of MMP (p<0.001) and preserved Bcl2/Bax ratio (p<0.01).

SIGNIFICANCE

EPO reduces myocardial injury due to CO intoxication. Thus EPO could be suggested as a possible candidate for the management of CO cardiotoxicity with clinical applications.

Erythropoietin in bone - Controversies and consensus

Erythropoietin (Epo) is the main hormone that regulates the production of red blood cells (hematopoiesis), by stimulating their progenitors. Beyond this vital function, several emerging roles have been noted for Epo in other tissues, including neurons, heart and retina. The skeletal system is also affected by Epo, however, its actions on bone are, as yet, controversial. Here, we review the seemingly contradicting evidence regarding Epo effects on bone remodeling. We also discuss the evidence pointing to a direct versus indirect effect of Epo on the osteoblastic and osteoclastic cell lineages. The current controversy may derive from a context-dependent mode of action of Epo, namely opposite skeletal actions during bone regeneration and steady-state bone remodeling. Differences in conclusions from the published in-vitro studies may thus relate to the different experimental conditions. Taken together, these studies indicate a complexity of Epo functions in bone cells.

Cardioprotective effect of erythropoietin on sepsis-induced myocardial injury in rats

BACKGROUND:

Sepsis-induced myocardial injury is one of the major predictors of morbidity and mortality of sepsis. The cytoprotective function of erythropoietin (EPO) has been discovered and extensively studied. However, the cardioprotective effects of EPO on sepsis-induced myocardial injury in the rat sepsis model has not been reported.

METHODS:

The rat models of sepsis were produced by cecal ligation and perforation (CLP) surgery. Rats were randomly (random number) assigned to one of three groups (n=8 for each group): sham group, CLP group and EPO group (1000 IU/kg erythropoietin). Arterial blood was withdrawn at 3, 6, 12, and 24 hours after CLP. cTnI, BNP, CK-MB, LDH, AST, TNF-α, IL-6, IL-10, and CRP were tested by the ELISA assay. Changes of hemodynamic parameters were recorded at 3, 6, 12, 24 hours after the surgery. Histological diagnosis was made by hematoxylin and eosin. Flow cytometry was performed to examine cell apoptosis, myocardium mitochondrial inner membrane potential, and NF-κB (p65). Survival rate at 7 days after CLP was recorded.

RESULTS:

In the CLP group, myocardial enzyme index and inflammatory index increased at 3, 6, 12 and 24 hours after CLP compared with the sham group, and EPO significantly blocked the increase. Compared with the CLP group, EPO significantly improved LVSP, LV +dp/dt_max, LV −dp/dt_min, and decreased LVEDP at different time. EPO blocked the reduction of mitochondrial transmembrane potential, suppressed the cardiomyocyte apoptosis, inhibited the activation of NF-κB, and reduced the production of proinflmmatory cytokines. No difference in the survival rate at 7 days was observed between the CLP group and the EPO group.

CONCLUSION:

Exogenous EPO has cardioprotective effects on sepsis-induced myocardial injury.

Safety and clinical outcome of erythropoiesis-stimulating agents in patients with ST-elevation myocardial infarction: a meta-analysis of individual patient data

BACKGROUND

Erythropoiesis-stimulating agents (ESAs) have been investigated in small studies in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). Erythropoiesis-stimulating agents did not show a clear effect on left ventricular function or clinical outcome, but some studies suggested an increased risk of thromboembolic events.

METHODS

A systematic literature search in MEDLINE was performed, until December 2012. We included randomized clinical trials investigating the effect of ESAs in STEMI patients undergoing primary PCI, with ≥30 days of follow-up. The primary end point was a composite of all-cause mortality, myocardial infarction, and stent thrombosis after PCI. Secondary end point was all-cause mortality.

RESULTS

Individual patient data were obtained from 10 of 11 trials, including 97.3% (1,242/1,277) of all patients randomized to control (n = 600) or to ESAs (n = 642). Baseline characteristics were well balanced between the treatment allocations. Mean follow-up time was 248 (±131) days. The primary end point occurred in 3.5% (20/577) in the control group and in 2.1% (13/610) in the ESA group (hazard ratio for ESAs, 0.63; 95% CI [0.31-1.27]; P = .20). Mortality occurred in 13 (2.3%) in the control group and 5 (0.8%) in the ESA group (hazard ratio for ESAs, 0.38; 95% CI [0.13-1.06]; P = .06).

CONCLUSIONS

Erythropoiesis-stimulating agent administration does not result in an increased risk of adverse cardiac events in STEMI patients undergoing primary PCI. Results of ongoing studies may provide further insight to the potential beneficial clinical effects of ESAs in STEMI patients.

Functional polymers of gene delivery for treatment of myocardial infarct

Ischemic heart disease is rapidly growing as the common cause of death in the world. It is a disease that occurs as a result of coronary artery stenosis and is caused by the lack of oxygen within cardiac muscles due to an imbalance between oxygen supply and demand. The conventional medical therapy is focused on the use of drug eluting stents, coronary-artery bypass graft surgery and anti-thrombosis. Gene therapy provides great opportunities for treatment of cardiovascular disease. In order for gene therapy to be successful, the development of proper gene delivery systems and hypoxia-regulated gene expression vectors is the most important factors. Several non-viral gene transfer methods have been developed to overcome the safety problems of viral transduction. Some of which include plasmids that regulate gene expression that is controlled by environment specific promoters in the transcriptional or the translational level. This review explores polymeric gene carriers that target the myocardium and hypoxia-inducible vectors, which regulate gene expression in response to hypoxia, and their application in animal myocardial infarction models.

Long term effects of epoetin alfa in patients with ST- elevation myocardial infarction

PURPOSE

The HEBE III trial showed that epoetin alfa administration in patients with a first ST-elevation myocardial infarction (STEMI) did not improve left ventricular function at 6 weeks after primary percutaneous coronary intervention (PCI). The long term effects of erythropoiesis- stimulating agents on cardiovascular morbidity and mortality are unknown, therefore we evaluated clinical events at 1 year after PCI.

METHODS

A total of 529 patients with a first STEMI and successful primary PCI were randomized to standard optimal medical treatment (N = 266) or an additional bolus of 60,000 IU epoetin alfa administered intravenously (N = 263) within 3 h after PCI. Analyses were performed by intention to treat.

RESULTS

At 1 year after STEMI, 485 patients had complete follow-up. The rate of the composite end point of all-cause mortality, re-infarction, target vessel revascularization, stroke and/or heart failure was 6.4 % (N = 15) in the epoetin alfa group and 9.6 % (N = 24) in the control group (p = 0.18). Thromboembolic events were present in 1.3 % (N = 3) of patients in the epoetin alfa group and 2.4 % (N = 6) in the control group. There was no evidence of benefit from epoetin alfa administration in subgroups of patients.

CONCLUSIONS

Administration of a single bolus of epoetin alfa in patients with STEMI does not result in a reduction of cardiovascular events at 1 year after primary PCI. There was a comparable incidence of thromboembolic complications in both treatment groups, suggesting that epoetin alfa administration is safe at long term.

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.

Erythropoietin and the heart: physiological effects and the therapeutic perspective

Erythropoietin (Epo) has been thought to act exclusively on erythroid progenitor cells. The identification of Epo receptor (EpoR) in non-haematopoietic cells and tissues including neurons, astrocytes, microglia, immune cells, cancer cell lines, endothelial cells, bone marrow stromal cells, as well as cells of myocardium, reproductive system, gastrointestinal tract, kidney, pancreas and skeletal muscle indicates that Epo has pleiotropic actions. Epo shows signals through protein kinases, anti-apoptotic proteins and transcription factors. In light of interest of administering recombinant human erythropoietin (rhEpo) and its analogues for limiting infarct size and left ventricular (LV) remodelling after acute myocardial infarction (AMI) in humans, the foremost studies utilising rhEpo are reviewed. The putative mechanisms involved in Epo-induced cardioprotection are related to the antiapoptotic, anti-inflammatory and angiogenic effects of Epo. Thus, cardioprotective potentials of rhEpo are reviewed in this article by focusing on clinical applicability. An overview of non-haematopoietic Epo analogues, which are a reliable alternative to the classic EpoR agonists and may prevent undesired side effects, is also provided.

Cardiac regeneration: current therapies-future concepts

Cardiovascular disease (CVD) continues to be one of the main causes of death in the western world. A high burden of disease and the high costs for the healthcare systems claim for novel therapeutic strategies besides current conventional medical care. One decade ago first clinical trials addressed stem cell based therapies as a potential alternative therapeutic strategy for myocardial regeneration and repair. Besides bone marrow derived stem cells (BMCs), adult stem cells from adipose or cardiac tissue have been used in current clinical studies with inconsistent results. Although outcomes in terms of safety and feasibility are generally encouraging, functional improvements were mostly disappointingly low and have failed to reach expectations. In the future, new concepts for myocardial regeneration, especially concerning recovery of cardiomyocyte loss, have to be developed. Transplantation of novel stem or progenitor cell populations with "true" regenerative potential, direct reprogramming of scar tissue into functional myocardium, tissue engineering or stimulation of endogenous cardiac repair by pharmacological agents are conceivable. This review summarizes current evidence of stem cell based regenerative therapies and discusses future strategies to improve functional outcomes.

Protein engineering for cardiovascular therapeutics: untapped potential for cardiac repair

A number of new and innovative approaches for repairing damaged myocardium are currently undergoing investigation, with several encouraging results. In addition to the progression of stem cell-based approaches and gene therapy/silencing methods, evidence continues to emerge that protein therapeutics may be used to directly promote cardiac repair and even regeneration. However, proteins are often limited in their therapeutic potential by short local half-lives and insufficient bioavailability and bioactivity, and many academic laboratories studying cardiovascular diseases are more comfortable with molecular and cellular biology than with protein biochemistry. Protein engineering has been used broadly to overcome weaknesses traditionally associated with protein therapeutics and has the potential to specifically enhance the efficacy of molecules for cardiac repair. However, protein engineering as a strategy has not yet been used in the development of cardiovascular therapeutics to the degree that it has been used in other fields. In this review, we discuss the role of engineered proteins in cardiovascular therapies to date. Further, we address the promise of applying emerging protein engineering technologies to cardiovascular medicine and the barriers that must be overcome to enable the ultimate success of this approach.

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.

Cardiac antiapoptotic and proproliferative effect of recombinant human erythropoietin in a moderate stage of chronic renal failure in the rat

Objective:

Recombinant human erythropoietin (rhEPO) therapy under circumstances of moderate chronic renal failure (CRF), with yet lower kidney and heart lesion, may have a protective cardiac effect beyond the correction of anemia, whose mechanism deserves better elucidation, namely by clarifying the impact on gene expression profile of markers of apoptosis, inflammation, proliferation, angiogenesis, and lesion/stress in the heart.

Materials and Methods:

Four groups of rats were studied over a period of 15 weeks (n=7 each): control—without surgery and without drug treatment; rhEPO—treated with 50 IU/kg/week of rhEPO—beta; CRF—submitted to partial nephrectomy (3/4); CRF + rhEPO—CRF with rhEPO treatment after the 3rd week of surgery. The heart was collected in order to evaluate the gene expression, by real-time qPCR, of markers of apoptotic machinery, inflammation/immunology, proliferation/angiogenesis, and lesion/stress.

Results:

The main findings obtained were (a) CRF rats have demonstrated overexpression of EPO-R in the heart without changes on EPO expression, together with overexpression of Bax/Bcl2 ratio, PCNA, and IL-2; (b) rhEPO therapy on the heart of the rats with CRF induced by partial 3/4 nephrectomy promoted nonhematopoietic protection, demonstrated by the apoptosis prevention, viewed by the Bax/Bcl2 balance, by the promotion of proliferation, due to PCNA increment, and by the immunomodulatory action, expressed by a trend to prevent the IL-2 increment.

Conclusion:

In this model of moderate CRF, rhEPO treatment showed important cardiac nonhematopoietic effects, expressed mainly by the antiapoptotic and the proproliferative action, suggesting that early rhEPO therapy in moderate stages of CRF might have further therapeutic benefits.

Use of high-dose erythropoietin for repair after injury: A comparison of outcomes in heart and kidney

CONTEXT

There is a need to define the exact benefits and contraindications of use of high-dose recombinant human erythropoietin (EPO) for its non-hematopoietic function as a cytokine that enhances tissue repair after injury. This review compares the outcomes from use of EPO in the injured heart and kidney, two organs that are thought, traditionally, to have intrinsically-different repair mechanisms.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

Ongoing work by us on EPO protection of ischemia-reperfusion-injured kidneys indicated, first, that EPO acutely enhanced kidney repair via anti-apoptotic, pro-regenerative mechanisms, and second, that EPO may promote chronic fibrosis in the long term. Work by others on the ischaemia-injured heart has also indicated that EPO promotes repair. Although myocardial infarcts are made up mostly of necrotic tissue, many publications state EPO is anti-apoptotic in the heart, as well as promoting healing via cell differentiation and stimulation of granulation tissue. In the case of the heart, promotion of fibrosis may be advantageous where an infarct has destroyed a zone of cardiomyocytes, but if EPO stimulates progressive fibrosis in the heart, this may promote cardiac failure.

CONCLUSIONS

A major concern in relation to the use of EPO in a cytoprotective role is its stimulation of long-term inflammation and fibrosis. EPO usage for cytoprotection is undoubtedly advantageous, but it may need to be offset with an anti-inflammatory agent in some organs, like kidney and heart, where progression to chronic fibrosis after acute injury is often recorded.

Human erythropoietin gene delivery for cardiac remodeling of myocardial infarction in rats

Considerable efforts have been made to exploit cardioprotective drugs and gene delivery systems for myocardial infarction (MI). The promising cardioprotective effects of recombinant human erythropoietin (rHuEPO) protein in animal experiments have not been consistently reproduced in clinical human trials of acute MI; however, the mechanisms underlying the inconsistent discrepancies are not yet fully understood. We hypothesized that the plasmid human erythropoietin gene (phEPO) delivered by our bioreducible polymer might produce cardioprotective effects on post-infarct cardiac remodeling. We demonstrated that intramyocardial delivery of phEPO by an arginine-grafted poly(disulfide amine) (ABP) polymer in infarcted rats preserves cardiac geometry and systolic function. The reduced infarct size of phEPO/ABP delivery was followed by decrease in fibrosis, protection from cardiomyocyte loss, and down-regulation of apoptotic activity. In addition, the increased angiogenesis and decreased myofibroblast density in the border zone of the infarct support the beneficial effects of phEPO/ABP administration. Furthermore, phEPO/ABP delivery induced prominent suppression on Ang II and TGF-β activity in all subdivisions of cardiac tissues except for the central zone of infarct. These results of phEPO gene therapy delivered by a bioreducible ABP polymer provide insight into the lack of phEPO gene therapy translation in the treatment of acute MI to human trials.

Serum erythropoietin: a useful biomarker for coronary collateral development and potential target for therapeutic angiogenesis among the patients with coronary chronic total occlusion

The study was to investigate the association of endogenous erythropoietin (EPO) and coronary collateral development. Forty-nine patients (31 with chronic total occlusion (CTO), 18 with normal coronary artery) were consecutively enrolled. The serum EPO was positively related with Rentrop class. Increased serum EPO was one of the independent predictors of good collateral development (odds ratio 1.31; p = 0.025). A significantly positive correlation was seen between serum EPO and vascular endothelial growth factor (VEGF) levels (r = 0.96, p < 0.001). Circulatory EPO may be a useful biomarker for coronary collateral development and potential target for therapeutic angiogenesis in patients with CTO.

Chronic administration of small nonerythropoietic peptide sequence of erythropoietin effectively ameliorates the progression of postmyocardial infarction-dilated cardiomyopathy

The cardioprotective properties of erythropoietin (EPO) in preclinical studies are well documented, but erythropoietic and prothrombotic properties of EPO preclude its use in chronic heart failure (CHF). We tested the effect of long-term treatment with a small peptide sequence within the EPO molecule, helix B surface peptide (HBSP), that possesses tissue-protective, but not erythropoietic properties of EPO, on mortality and cardiac remodeling in postmyocardial infarction-dilated cardiomyopathy in rats. Starting 2 weeks after permanent left coronary artery ligation, rats received i.p. injections of HBSP (60 µg/kg) or saline two times per week for 10 months. Treatment did not elicit an immune response, and did not affect the hematocrit. Compared with untreated rats, HBSP treatment reduced mortality by 50% (P < 0.05). Repeated echocardiography demonstrated remarkable attenuation of left ventricular dilatation (end-diastolic volume: 41 versus 86%; end-systolic volume: 44 versus 135%; P < 0.05), left ventricle functional deterioration (ejection fraction: -4 versus -63%; P < 0.05), and myocardial infarction (MI) expansion (3 versus 38%; P < 0.05). A hemodynamic assessment at study termination demonstrated normal preload independent stroke work (63 ± 5 versus 40 ± 4; P < 0.05) and arterioventricular coupling (1.2 ± 0.2 versus 2.7 ± 0.7; P < 0.05). Histologic analysis revealed reduced apoptosis (P < 0.05) and fibrosis (P < 0.05), increased cardiomyocyte density (P < 0.05), and increased number of cardiomyocytes in myocardium among HBSP-treated rats. The results indicate that HBSP effectively reduces mortality, ameliorates the MI expansion and CHF progression, and preserves systolic reserve in the rat post-MI model. There is also a possibility that HBSP promoted the increase of the myocytes number in the myocardial wall remote from the infarct. Thus, HBSP peptide merits consideration for clinical testing.

Myocardial infarction: cardioprotection by erythropoietin

Extensive research during the last decade demonstrated that a single systemic administration of -erythropoietin (EPO) lead to significant attenuation of myocardial infarction (MI) induced in animals, mostly small rodents, either by a myocardial ischemia followed by reperfusion or by a permanent ligation of a coronary artery. Both methods are critically reviewed with the aim of helping the reader in appreciating key issues in the translation of experimental results to the clinic. Results of several clinical trials in patients with acute MI completed to date failed to demonstrate beneficial effects of EPO, and thus put into question the validity of results obtained in animal models. Comprehensive review of design and results of animal experiments and clinical trials presented here allowed authors to postulate that therapeutic window for EPO during developing MI is very narrow and was possibly missed in negative clinical trials. This point was illustrated by the negative outcome of experiment in the rat model of MI in which timing of EPO administration was similar to that in clinical trials. The design of future clinical trials should allow for a narrow therapeutic window of EPO. Given current standards for onset-to-door and door-to-balloon time the optimal time for EPO administration should be just prior to PCI.

Protective effects of erythropoietin on cirrhotic cardiomyopathy in rats

INTRODUCTION

Erythropoietin exerts cardioprotective effects. The present study aimed to investigate the therapeutic effects of erythropoietin on cirrhotic cardiomyopathy.

MATERIALS AND METHODS

Rats were divided into 5 groups: sham control; sham+ erythropoietin; bile duct ligation; bile duct ligation+erythropoietin; bile duct ligation+erythropoietin+anti-tumour necrosis factor alpha (TNFα) antibody and were studied 4 wk after surgery. Erythropoietin was administrated for 10 days before the study date. TNFα, erythropoietin receptor-1 expression and oxidative stress-related parameters were measured. In separate groups, isolated cardiomyocytes were subjected to contractile and relaxation studies. Cardiomyocyte cell line was used to test the direct effect of erythropoietin on nuclear factor (erythroid-derived 2)-like 2(Nrf2).

RESULTS

Erythropoietin receptor-1, TNFα and oxidative modified proteins were significantly increased (p<0.01), and the antioxidant regulator Nrf2 transcription decreased in cirrhotic hearts (p<0.01). Erythropoietin reversed these parameters. Maximal cardiac contractile and relaxation velocity was significantly decreased in cirrhotic cardiomyocytes. Erythropoietin significantly reversed these inhibitions. Anti-TNFα antibody significantly decreased cardiac TNFα content but did not further increase contractility.

CONCLUSIONS

TNFα and oxidative stress are involved in cardiac dysfunction in the cirrhotic heart. Erythropoietin significantly decreased TNFα and oxidative stress and reversed the impaired cardiac function.

Acute hemodynamic effects of erythropoietin do not mediate its cardioprotective properties

Activation of nitric oxide (NO) signaling is considered, at list partially, a mechanistic basis for EPO-induced cardioprotection. Surprisingly, hemodynamic response subsequent to NO activation after EPO administration has never been reported. The objectives of this study were to evaluate the acute hemodynamic and cardiovascular responses to EPO administration, to confirm their NO genesis, and to test the hypothesis that EPO-induced cardioprotection is mediated through cardiovascular changes related to NO activation. In Experiment 1, after 3000 U/kg of rhEPO was administered intravenously to Wistar rats, arterial blood pressure, monitored via indwelling catheter, progressively declined almost immediately until it leveled off 90 minutes after injection at 20% below control level. In Experiment 2 the 25% reduction of mean blood pressure, compared to control group, was observed 2 hours after intravenous injection of either 3000 or 150 U/kg of rhEPO. Detailed pressure–volume loop analyses of cardiac performance (Experiment 3) 2 hours after intravenous injection of human or rat recombinant EPO (3000 U/kg) revealed a significant reduction of systolic function (PRSW was 33% less than control). Reduction of arterial blood pressure and systolic cardiac function in response to rhEPO were blocked in rats pretreated with a non-selective inhibitor of nitric oxide synthase (L-NAME). In Experiment 4, 24 hours after a permanent ligation of a coronary artery, myocardial infarction (MI) measured 26±3.5% of left ventricle in untreated rats. MI in rats treated with 3000 U/kg of rhEPO immediately after coronary ligation was 56% smaller. Pretreatment with L-NAME did not attenuate the beneficial effect of rhEPO on MI size, while MI size in rats treated with L-NAME alone did not differ from control. Therefore, a single injection of rhEPO resulted in a significant, NO-mediated reduction of systemic blood pressure and corresponding reduction of cardiac systolic function. However, EPO-induced protection of myocardium from ischemic damage is not associated with NO activation or NO-mediated hemodynamic responses.

Erythropoietin attenuates cardiac dysfunction by increasing myocardial angiogenesis and inhibiting interstitial fibrosis in diabetic rats

Background

Recent studies revealed that erythropoietin (EPO) has tissue-protective effects in the heart by increasing vascular endothelial growth factor (VEGF) expression and attenuating myocardial fibrosis in ischemia models. In this study, we investigated the effect of EPO on ventricular remodeling and blood vessel growth in diabetic rats.

Methods

Male SD rats were randomly divided into 3 groups: control rats, streptozotocin (STZ)-induced diabetic rats, and diabetic rats treated with 1000 U/kg EPO by subcutaneous injection once per week. Twelve weeks later, echocardiography was conducted, and blood samples were collected for counting of peripheral blood endothelial progenitor cells (EPCs). Myocardial tissues were collected, quantitative real-time PCR (RT-PCR) was used to detect the mRNA expression of VEGF and EPO-receptor (EPOR), and Western blotting was used to detect the protein expression of VEGF and EPOR. VEGF, EPOR, transforming growth factor beta (TGF-β), and CD31 levels in the myocardium were determined by immunohistochemistry. To detect cardiac hypertrophy, immunohistochemistry of collagen type I, collagen type III, and Picrosirius Red staining were performed, and cardiomyocyte cross-sectional area was measured.

Results

After 12 weeks STZ injection, blood glucose increased significantly and remained consistently elevated. EPO treatment significantly improved cardiac contractility and reduced diastolic dysfunction. Rats receiving the EPO injection showed a significant increase in circulating EPCs (27.85 ± 3.43%, P < 0.01) compared with diabetic untreated animals. EPO injection significantly increased capillary density as well as EPOR and VEGF expression in left ventricular myocardial tissue from diabetic rats. Moreover, EPO inhibited interstitial collagen deposition and reduced TGF-β expression.

Conclusions

Treatment with EPO protects cardiac tissue in diabetic animals by increasing VEGF and EPOR expression levels, leading to improved revascularization and the inhibition of cardiac fibrosis.

Early sustained injections of erythropoietin improve angiogenesis and restoration of perfusion in the ischemic mouse hindlimb

This study was conducted to investigate the effects of erythropoietin (Epo) on both acute and chronic limb ischemia (ALI and CLI) and to evaluate the differences in mechanisms according to the method of Epo administration. Hindlimb ischemia was made in BALB/c mice with femoral artery ligation. The mice were divided into four groups: Group 1 (control, no treatment), Group 2 (ALI, early multiple doses), Group 3 (ALI, early single high dose), Group 4 (CLI, late multiple doses). Blood flow ratio significantly increased in Group 2 in 4 weeks. Expression of pAkt and Erythropoietin receptor were significantly higher in Group 2 on postoperative day (POD) 7. The number of CD31- and vascular endothelial growth factor-positive cells were significantly higher in Group 2 on POD 7 and 56. Group 3 and 4 showed a tendency of higher cell counts than the control. The early sustained Epo was effective in improving blood flow through angiogenesis. In chronic phase, weekly multiple dosing of Epo induced angiogenesis, however, the blood flow ratio did not increase significantly. The results of this study suggest that Epo administration during the acute phase followed by maintenance for several days may be important for increasing blood flow and angiogenesis.