The role of excessive versus acute administration of erythropoietin in attenuating hepatic ischemia-reperfusion injury

Effect of erythropoietin on angiogenic potential of dental pulp cells

Erythropoietin (EPO) is a 34-kDa glycoprotein that possesses the potential for angiogenesis, as well as anti-inflammatory and anti-apoptotic properties. The present study aimed to examine the effect of EPO on the angiogenesis of dental pulp cells (DPCs) and to explore the underlying mechanisms of these effects. It was demonstrated that EPO not only promoted DPCs proliferation but also induced angiogenesis of DPCs in a paracrine fashion. EPO enhanced the angiogenic capacity by stimulating DPCs to secrete a series of angiogenic cytokines. ELISA confirmed that high concentrations of EPO increased the production of MMP-3 and angiopoietin-1 but decreased the secretion of IL-6. Furthermore, EPO activated the ERK1/2 and p38 signaling pathways in DPCs, while inhibition of these pathways diminished the angiogenesis capacity of DPCs. The present study suggested that EPO may have an important role in the repair and regeneration of dental pulp.

Pharmacological Benefits and Risk of Using Hormones in Organ Perfusion and Preservation Solutions in the Aspect of Minimizing Hepatic Ischemia-Reperfusion Injury during Storage

For several years, research has been carried out on the effectiveness of solutions for perfusion and preservation of organs, including the liver. There is a search for an optimal pharmacological composition of these solutions, allowing to preserve or improve vital functions of the organ for as long as possible until it is transplanted into a recipient. Hormones due to their properties, often resulting from their pleiotropic effects, may be a valuable component for optimizing the composition of liver perfusion and preservation solutions. The paper presents the current state of knowledge on liver perfusion and preservation solutions modified with hormones. It also shows the characteristics of the hormones evaluated, taking into account their physiological functions in the body.

Placental erythropoietin expression is upregulated in growth-restricted fetuses with abnormal umbilical artery Doppler findings: a case-control study of monochorionic twins

BACKGROUND

We previously reported that fetal plasma erythropoietin (EPO) concentrations are significantly increased in growth-restricted fetuses with abnormal umbilical artery (UA) Doppler. During hypoxia in an ovine model, the primary site of fetal EPO synthesis was switched from the kidneys to the placenta. Therefore, we designed this study to evaluate human placental EPO gene expression and the correlation to fetal serum EPO concentration in growth-restricted fetuses in a monochorionic (MC) twin model.

METHODS

In MC twin pairs, selective intrauterine growth restriction (sIUGR) was defined as the presence of (i) birth weight discordance of > 20% and (ii) a smaller twin with a birth weight less than the 10th percentile. Fetal UA and middle cerebral artery (MCA) Doppler were checked within 1 week before delivery. An abnormal UA Doppler was defined as persistently absent or reverse end-diastolic flow. Cerebroplacental ratio (CPR) was defined as MCA-pulsatility index (PI)/UA-PI. Fetal plasma EPO concentrations were measured in cord blood, and EPO gene expression was assayed in each twin's placental territory. The intertwin plasma EPO ratio was calculated as the cord plasma EPO level of the smaller (or sIUGR) twin divided by the EPO concentration of the larger (or appropriate-for-gestational-age (AGA)) twin, and the intertwin placental EPO gene expression ratio was calculated similarly.

RESULTS

Twenty-six MC twins were analyzed, including normal twins (Group 1, n = 9), twins with sIUGR without UA Doppler abnormalities (Group 2, n = 9), and twins with sIUGR and UA Doppler abnormalities (Group 3, n = 8). The CPRs of smaller (sIUGR) fetuses were significantly decreased in Group 3 MC twins (p < 0.001), but not significantly different between Group 1 and Group 2. The highest fetal plasma EPO ratio and placental EPO gene expression ratio were identified in Group 3 MC twins (p < 0.001). The placental EPO gene expression ratios were significantly correlated with the fetal plasma EPO ratios (Pearson's correlation test, p = 0.004).

CONCLUSION

This study provides evidence of increased placental EPO expression in MC twin fetuses with sIUGR and abnormal UA Doppler. Future studies are needed to confirm the similar role of placental EPO in severe IUGR singletons.

EPOR2/βcR2-independendent effects of low-dose epoetin-α in porcine liver transplantation

Ischemia–reperfusion injury (IRI) remains a key component of graft damage during transplantation. Erythropoietin (EPO) induces anti-inflammatory and anti-apoptotic effects via the EPOR₂/βcR₂ complex, with a potential risk of thrombosis. Previous work indicates that EPO has EPOR₂/βcR₂-independent protective effects via direct effects on the endothelium. As the EPOR₂/βcR₂ receptor has a very low affinity for EPO, we aimed to test the hypothesis that EPO doses below the level that stimulate this receptor elicit cytoprotective effects via endothelial stimulation in a porcine liver transplantation model. Landrace pigs underwent allogenic liver transplantation (follow-up: 6 h) with a portojugular shunt. Animals were divided into two groups: donor and recipient treatment with low-dose EPO (65 IU/kg) or vehicle, administered 6 h before cold perfusion and 30 min after warm reperfusion. Fourteen of 17 animals (82.4%) fulfilled the inclusion criteria. No differences were noted in operative values between the groups including hemoglobin, cold or warm ischemic time. EPO-treated animals showed a significantly lower histopathology score, reduced apoptosis, oxidative stress, and most important a significant up-regulation of endothelial nitric oxide (NO) synthase (eNOS). Donor and recipient treatment with low-dose EPO reduces the hepatic IRI via EPOR₂/βcR₂-independent cytoprotective mechanisms and represents a clinically applicable way to reduce IRI.

Erythropoietin pretreatment exerts anti-inflammatory effects in hepatic ischemia/reperfusion-injured rats via suppression of the TLR2/NF-κB pathway

INTRODUCTION

The inflammatory response plays an important role in liver dysfunction after hepatic ischemia/reperfusion (I/R), which is tightly regulated by the Toll-like receptor 2 (TLR2)/nuclear factor (NF)-κB pathway; suppression of TLR2/NF-κB signaling has therefore become a promising target for anti-inflammatory treatment in hepatic I/R injury. Erythropoietin (EPO) is a glycoprotein cytokine produced primarily by the kidney that has anti-inflammatory activities. The purpose of the present study was to investigate the effect of EPO preconditioning, if any, against hepatic I/R injury in rats and its underlying mechanisms.

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to partial (70%) hepatic ischemia for 45 minutes after pretreatment with either saline or EPO followed by 24-hour reperfusion. Hepatic injury was evaluated according to biochemical and histopathologic examinations. The expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) were measured by using enzyme-linked immunosorbent assay and real-time polymerase chain reaction. The expression of nuclear translocation and phosphorylation of NF-κB p65, EPOR receptor (EPOR), p-EPOR, p-IκB-α, IκB-α, and TLR2 were determined by using Western blot analysis.

RESULTS

EPO treatment significantly improved hepatic function and histology, as indicated by reduced transaminase levels and pathologic changes. The expression of TNF-α, IL-1β, IL-6, p-IκB-α, and TLR2 was significantly decreased with up-regulation of p-EPOR by EPO. Moreover, EPO pretreatment also reduced I/R-induced the phosphorylation and nuclear translocation of NF-κB p65 subunits in liver tissue, but EPO had no influence on the expression of p65 and IκB-α.

CONCLUSIONS

These results suggest that EPO pretreatment ameliorates hepatic I/R injury, which is involved in suppressing TLR2/NF-κB-mediated inflammation.

Erythropoietin inhibits gluconeogenesis and inflammation in the liver and improves glucose intolerance in high-fat diet-fed mice

Erythropoietin (EPO) has multiple biological functions, including the modulation of glucose metabolism. However, the mechanisms underlying the action of EPO are still obscure. This study is aimed at investigating the potential mechanisms by which EPO improves glucose tolerance in an animal model of type 2 diabetes. Male C57BL/6 mice were fed with high-fat diet (HFD) for 12 weeks and then treated with EPO (HFD-EPO) or vehicle saline (HFD-Con) for two week. The levels of fasting blood glucose, serum insulin and glucose tolerance were measured and the relative levels of insulin-related phosphatidylinositol 3-kinase (PI3K)/Akt, insulin receptor (IR) and IR substrate 1 (IRS1) phosphorylation were determined. The levels of phosphoenolpyruvate carboxykinase (PEPCK), glucose-6- phosphatase (G6Pase), toll like receptor 4 (TLR4), tumor necrosis factor (TNF)-α and IL-6 expression and nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK), extracellular-signal-regulated kinase (ERK) and p38 MAPK activation in the liver were examined. EPO treatment significantly reduced the body weights and the levels of fasting blood glucose and serum insulin and improved the HFD-induced glucose intolerance in mice. EPO treatment significantly enhanced the levels of Akt, but not IR and IRS1, phosphorylation, accompanied by inhibiting the PEPCK and G6Pase expression in the liver. Furthermore, EPO treatment mitigated the HFD-induced inflammatory TNF-α and IL-6 production, TLR4 expression, NF-κB and JNK, but not ERK and p38 MAPK, phosphorylation in the liver. Therefore, our data indicated that EPO treatment improved glucose intolerance by inhibiting gluconeogenesis and inflammation in the livers of HFD-fed mice.

Erythropoietin: new directions for the nervous system

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

Targeting cardiovascular disease with novel SIRT1 pathways

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

EPO relies upon novel signaling of Wnt1 that requires Akt1, FoxO3a, GSK-3β, and β-catenin to foster vascular integrity during experimental diabetes

Multiple complications can ensue in the cardiovascular, renal, and nervous systems during diabetes mellitus (DM). Given that endothelial cells (ECs) are susceptible targets to elevated serum D-glucose, identification of novel cellular mechanisms that can protect ECs may foster the development of unique strategies for the prevention and treatment of DM complications. Erythropoietin (EPO) represents one of these novel strategies but the dependence of EPO upon Wnt1 and its downstream signaling in a clinically relevant model of DM with elevated D-glucose has not been elucidated. Here we show that EPO can not only maintain the integrity of EC membranes, but also prevent apoptotic nuclear DNA degradation and the externalization of membrane phosphatidylserine (PS) residues during elevated D-glucose over a 48-hour period. EPO modulates the expression of Wnt1 and utilizes Wnt1 to confer EC protection during elevated D-glucose exposure, since application of a Wnt1 neutralizing antibody, treatment with the Wnt1 antagonist DKK-1, or gene silencing of Wnt1 with Wnt1 siRNA transfection abrogates the protective capability of EPO. EPO through a novel Wnt1 dependent mechanism controls the post-translational phosphorylation of the "pro-apoptotic" forkhead member FoxO3a and blocks the trafficking of FoxO3a to the cell nucleus to prevent apoptotic demise. EPO also employs the activation of protein kinase B (Akt1) to foster phosphorylation of GSK-3β that appears required for EPO vascular protection. Through this inhibition of GSK-3β, EPO maintains β-catenin activity, allows the translocation of β-catenin from the EC cytoplasm to the nucleus through a Wnt1 pathway, and requires β-catenin for protection against elevated D-glucose since gene silencing of β-catenin eliminates the ability of EPO as well as Wnt1 to increase EC survival. Subsequently, we show that EPO requires modulation of both Wnt1 and FoxO3a to oversee mitochondrial membrane depolarization, cytochrome c release, and caspase activation during elevated D-glucose. Our studies identify critical elements of the protective cascade for EPO that rely upon modulation of Wnt1, Akt1, FoxO3a, GSK-3β, β-catenin, and mitochondrial apoptotic pathways for the development of new strategies against DM vascular complications.

Liver graft injury induced by ischemia and reperfusion secondary to retrograde reperfusion

AIM: To evaluate the influence of retrograde reperfusion on ischemia/reperfusion injury in a rat model of liver transplantation.

METHODS: Thirty-six male Sprague-Dawley rats undergoing orthoptic liver transplantation were divided into three groups (n = 12 for each group): group 1, antegrade reperfusion via the portal vein; group 2, antegrade reperfusion simultaneously via the portal vein and hepatic artery; group 3: retrograde reperfusion via the vena cava. Serum parameters were determined 1, 6 and 24 h after operation. Liver samples were taken for histological assessment. Cell apoptotic index was determined.

RESULTS: Rats of group 3 showed significantly lower serum level of aspartate aminotransferase compared to groups 1 and 2 (968.4 U/L ± 221.5 U/L vs 1 801.6 U/L ± 324.5 U/L, 2 564.1 U/L ± 410.3 U/L, P = 0.003, 0.000). Serum level of aspartate aminotransferase was significantly lower in group 1 than in group 2. The liver of rats of group 3 showed significantly less leukocytic infiltrates compared to groups 1 and group 2. The apoptotic index was lower in group 3 than in group 1 and 2.

CONCLUSION: Retrograde reperfusion leads to a lower level of ischemia/reperfusion injury than antegrade reperfusion in rats undergoing liver transplantation.