Recombinant human erythropoietin attenuates hepatic injury induced by ischemia/reperfusion in an isolated mouse liver model

Effects of Recombinant Human Erythropoietin and 2-Mercaptoethane Sulfonate on Liver Ischemia-Reperfusion Injury in Rats

OBJECTIVES

The aim of this study was to determine the effects of recombinant human erythropoietin and 2-merkaptoethane sulfonate, administered in combination, on the biochemical and histopathological changes of ischemia-reperfusion injury.

MATERIALS AND METHODS

Fifty female Wistar Albino rats were used in this study. The animals were randomly divided into 5 groups: a sham group that underwent standard laparotomy only, an ischemia-reperfusion group that was subjected to 30 minutes of hepatic ischemia and 2 hours of reperfusion, a group that intraperitoneally received 1000 IU/kg recombinant human erythropoietin 5 minutes before ischemiareperfusion, a group that intraperitoneally received 150 mg/kg 2-merkaptoethane sulfonate 15 minutes before ischemia-reperfusion, and a combined group that received both drugs intraperitoneally before ischemia-reperfusion. After the reperfusion period, serum aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and malondialdehyde levels were measured. We also evaluated histological changes in rat liver tissues samples.

RESULTS

Serum aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and malondialdehyde levels were high in the control groups, but aspartate and alanine aminotransferase levels were within normal limits, especially in rats that only received recombinant human erythropoietin. In rats that received combined treatment, parenchymal alterations in liver tissue were less severe than in the other groups and necrosis did not occur.

CONCLUSIONS

Recombinant human erythropoietin was clearly more effective than 2-merkaptoethane sulfonate for preventing oxidative injury. When the agents were combined, obvious biochemically and histologically protective effects occurred, providing significant tissue protection in ischemia-reperfusion injury.

Carbon monoxide mechanism of protection against renal ischemia and reperfusion injury

Carbon monoxide is quickly moving past its historic label as a molecule once feared, to a therapeutic drug that modulates inflammation. The development of carbon monoxide releasing molecules and utilization of heme oxygenase-1 inducers have shown carbon monoxide to be a promising therapy in reducing renal ischemia and reperfusion injury and other inflammatory diseases. In this review, we will discuss the developments and application of carbon monoxide releasing molecules in renal ischemia and reperfusion injury, and transplantation. We will review the anti-inflammatory mechanisms of carbon monoxide in respect to mitigating apoptosis, suppressing dendritic cell maturation and signalling, inhibiting toll-like receptor activation, promoting anti-inflammatory responses, and the effects on renal vasculature.

Hypothermic Oxygenated Machine Perfusion Alleviates Donation After Circulatory Death Liver Injury Through Regulating P-selectin-dependent and -independent Pathways in Mice

BACKGROUND

Hypothermic oxygenated machine perfusion (HOPE) has been shown to improve the quality of liver donation after circulatory death (DCD) compared to cold storage (CS). However, the mechanism by which HOPE works is unclear. In this study, a mouse liver HOPE system was developed to characterize the role of P-selectin in the protective effect of HOPE on DCD livers.

METHODS

A warm ischemia model of the liver and an isolated perfused liver system were established to determine a suitable flow rate for HOPE. Perfusate and tissue samples from wild-type and P-selectin knockout (KO) mice were used to determine liver function, apoptosis and necrosis rates, deoxyribonucleic acid injury and oxidative stress levels, leukocyte and endothelial cell activation, and inflammatory reactions.

RESULTS

A mouse liver HOPE system was successfully established. HOPE at flow rates between 0.1 and 0.5 mL/min · g were shown to have a protective effect on the DCD liver. P-selectin KO improved the quality of the DCD liver in the CS group, and reduction of P-selectin expression in the wild-type HOPE group had similar protective effects. Moreover, there was a reduction in the degree of oxidative stress and deoxyribonucleic acid injury in the P-selectin KO HOPE group compared with the P-selectin KO CS group.

CONCLUSIONS

We established a mouse HOPE system and determined its suitable flow. We also proved that P-selectin deficiency alleviated DCD liver injury. HOPE protected the DCD liver through regulating P-selectin-dependent and -independent pathways.

Preoperative erythropoietin treatment improves survival following major hepatic resection in a cirrhotic rat model

AIM

Major hepatic resection of a cirrhotic liver may result in a fatal clinical course. Preoperative erythropoietin (EPO) treatment has been shown to have protective properties and to stimulate liver regeneration. This study aims to investigate the effect of preoperative EPO on survival following major hepatic resection in a cirrhotic rat model.

METHODS

Cirrhotic liver was induced by intraperitoneal injection of thioacetamide (200mg/kg/mL) in 72 Lewis rats. Each 36 rats received EPO (1IU/g, every second day, 5 times preoperatively) or saline (control) and major hepatectomy (removal of the left and half of the median lobe) was performed. Biochemical and immunohistochemical parameters, cytokines and overall survival were compared following surgery.

RESULTS

Rats that received preoperative EPO had decreased hepatic aspartate aminotransferase, alanine aminotransferase and interleukin (IL)-1β expression, 48hours following surgery. They had increased hepatocyte growth factor and vascular endothelial growth factor expression at 1hour, increased IL-6 expression at 24, 48 and 120hours and increased Ki-67, 120hours following surgery. Overall, survival was significantly improved among EPO-treated rats (P=0.034).

CONCLUSION

Preoperative EPO treatment has a protective effect and stimulates liver regeneration, leading to improved overall survival following major hepatectomy in a cirrhotic rat model.

Carbon monoxide protects the kidney through the central circadian clock and CD39

Ischemia reperfusion injury (IRI) is the predominant tissue insult associated with organ transplantation. Treatment with carbon monoxide (CO) modulates the innate immune response associated with IRI and accelerates tissue recovery. The mechanism has been primarily descriptive and ascribed to the ability of CO to influence inflammation, cell death, and repair. In a model of bilateral kidney IRI in mice, we elucidate an intricate relationship between CO and purinergic signaling involving increased CD39 ectonucleotidase expression, decreased expression of Adora1, with concomitant increased expression of Adora2a/2b. This response is linked to a >20-fold increase in expression of the circadian rhythm protein Period 2 (Per2) and a fivefold increase in serum erythropoietin (EPO), both of which contribute to abrogation of kidney IRI. CO is ineffective against IRI in Cd39^-/- and Per2^-/- mice or in the presence of a neutralizing antibody to EPO. Collectively, these data elucidate a cellular signaling mechanism whereby CO modulates purinergic responses and circadian rhythm to protect against injury. Moreover, these effects involve CD39- and adenosinergic-dependent stabilization of Per2. As CO also increases serum EPO levels in human volunteers, these findings continue to support therapeutic use of CO to treat IRI in association with organ transplantation, stroke, and myocardial infarction.

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.

Cibinetide dampens innate immune cell functions thus ameliorating the course of experimental colitis

Two distinct forms of the erythropoietin receptor (EPOR) mediate the cellular responses to erythropoietin (EPO) in different tissues. EPOR homodimers signal to promote the maturation of erythroid progenitor cells. In other cell types, including immune cells, EPOR and the ß-common receptor (CD131) form heteromers (the innate repair receptor; IRR), and exert tissue protective effects. We used dextran sulphate sodium (DSS) to induce colitis in C57BL/6 N mice. Once colitis was established, mice were treated with solvent, EPO or the selective IRR agonist cibinetide. We found that both cibinetide and EPO ameliorated the clinical course of experimental colitis in mice, resulting in improved weight gain and survival. Correspondingly, DSS-exposed mice treated with cibinetide or EPO displayed preserved tissue integrity due to reduced infiltration of myeloid cells and diminished production of pro-inflammatory disease mediators including cytokines, chemokines and nitric oxide synthase-2. Experiments using LPS-activated primary macrophages revealed that the anti-inflammatory effects of cibinetide were dependent on CD131 and JAK2 functionality and were mediated via inhibition of NF-κB subunit p65 activity. Cibinetide activation of the IRR exerts potent anti-inflammatory effects, especially within the myeloid population, reduces disease activity and mortality in mice. Cibinetide thus holds promise as novel disease-modifying therapeutic of inflammatory bowel disease.

Erythropoietin enhances Kupffer cell number and activity in the challenged liver

Erythropoietin (EPO) is the main hormone driving mammalian erythropoiesis, with activity mediated via the surface receptor, EPO-R, on erythroid progenitor cells. Recombinant human EPO is currently used clinically for the treatment of anemia in patients with end-stage renal disease, and in certain cancer patients suffering from anemia induced either by the tumor itself or by chemotherapy. EPO-R expression is also detected in non-erythroid cells, including macrophages present in the peritoneum, spleen, and bone marrow (BM). Here we demonstrate that Kupffer cells (KCs) - the liver-resident macrophages - are EPO targets. We show that, in vitro, EPO initiated intracellular signalling and enhanced phagocytosis in a rat KC line (RKC-2) and in sorted KCs. Moreover, continuous EPO administration in mice, resulted in an increased number of KCs, up-regulation of liver EPO-R expression and elevated production of the monocyte chemoattractant CCL2, with corresponding egress of Ly6C^hi monocytes from the BM. In a model of acute acetaminophen-induced liver injury, EPO administration increased the recruitment of Ly6C^hi monocytes and neutrophils to the liver. Taken together, our results reveal a new role for EPO in stimulating KC proliferation and phagocytosis, and in recruiting Ly6C^hi monocytes in response to liver injury.

The Protective Effects of Helix B Surface Peptide on Experimental Acute Liver Injury Induced by Carbon Tetrachloride

BACKGROUND

To investigate the protective effects of helix B surface peptide (HBSP) on acute liver injury induced by carbon tetrachloride (CCl₄).

METHODS

HBSP (8 nmol/kg) was intraperitoneally injected into C57 BL/6 mice 2 h after CCl₄ administration. Serum and liver tissue samples were collected 24 h after injury. Liver function and histological injuries were evaluated. Inflammatory cell infiltration and cytokines were examined and hepatocytes apoptosis was measured. The human liver cell line LO2 and murine primary hepatocytes were stimulated by CCl₄ with and without HBSP treatment and glutathione peroxidase activity, cell survival, and apoptosis were evaluated. In addition, we examined the PI3K/Akt/mTORC1 pathway to elucidate the mechanism underlying HBSP-mediated protection in acute liver injury.

RESULTS

HBSP significantly decreased serum alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and pro-inflammatory cytokines in liver tissues after CCl₄ injection compared with those in the control group. Immunohistochemical staining indicated that the number of CD3-, CD8-, and CD68-positive cells and the expression of cleaved caspase-3 were significantly decreased by HBSP treatment. Additionally, HBSP reduced apoptosis in vivo. In an in vitro study, the glutathione peroxidase activity and survival rate increased, while the total apoptotic rate was reduced in the HBSP-treated group compared with that in the control group after CCl₄ treatment. HBSP activated the PI3K/Akt/mTORC1 pathway, which was confirmed by the PI3K inhibitor LY294002 both in vivo and in vitro. Furthermore, HBSP increased the survival of mice with acute liver injury, and this effect was abolished by LY294002.

CONCLUSIONS

HBSP is a potential therapeutic agent against acute liver injury induced by CCl₄.

Endogenous erythropoietin varies significantly with inflammation-related proteins in extremely premature newborns

INTRODUCTION

Erythropoietin, a pluripotent glycoprotein essential for erythropoiesis, fetal growth, and development, has recently been implicated in innate immune regulation. Data from the ELGAN Study allowed us to evaluate relationships between endogenous erythropoietin and 25 inflammation-related proteins in extremely premature newborns.

METHODS

We measured the concentrations of 25 inflammation-related proteins and of erythropoietin in blood spots collected on postnatal days 1, 7, and 14 from 936 infants born before 28 weeks gestation. We calculated the odds that infants with an inflammation-related protein in the highest quartile for gestational age and collection day had an erythropoietin concentration in the highest or lowest quartile.

RESULTS

The proportion of children with inflammation-associated protein concentrations in the top quartile tended to increase monotonically with increasing quartile of EPO concentrations on 2 of the 3 days assessed. To a large extent, on each of the 3 days assessed, the odds ratios for an erythropoietin concentration in the top quartile were significantly elevated among those with an inflammation-related protein concentration in the top quartile.

CONCLUSIONS

Our findings suggest that in very preterm newborns, circulating levels of endogenous erythropoietin vary significantly with circulating levels of inflammation-related proteins. Elevation of endogenous erythropoietin might not be an epiphenomenon, but instead might contribute to subsequent events, by either promoting or reducing inflammation, or by promoting an anti-injury or repair capability.

Induction of heme oxygenase-1 protects mouse liver from apoptotic ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is the main cause of primary graft dysfunction of liver allografts. Cobalt-protoporphyrin (CoPP)-dependent induction of heme oxygenase (HO)-1 has been shown to protect the liver from I/R injury. This study analyzes the apoptotic mechanisms of HO-1-mediated cytoprotection in mouse liver exposed to I/R injury. HO-1 induction was achieved by the administration of CoPP (1.5 mg/kg body weight i.p.). Mice were studied in in vivo model of hepatic segmental (70 %) ischemia for 60 min and reperfusion injury. Mice were randomly allocated to four main experimental groups (n = 10 each): (1) A control group undergoing sham operation. (2) Similar to group 1 but with the administration of CoPP 72 h before the operation. (3) Mice undergoing in vivo hepatic I/R. (4) Similar to group 3 but with the administration of CoPP 72 h before ischemia induction. When compared with the I/R mice group, in the I/R+CoPP mice group, the increased hepatic expression of HO-1 was associated with a significant reduction in liver enzyme levels, fewer apoptotic hepatocytes cells were identified by morphological criteria and by immunohistochemistry for caspase-3, there was a decreased mean number of proliferating cells (positively stained for Ki67), and a reduced hepatic expression of: C/EBP homologous protein (an index of endoplasmic reticulum stress), the NF-κB's regulated genes (CIAP2, MCP-1 and IL-6), and increased hepatic expression of IκBa (the inhibitory protein of NF-κB). HO-1 over-expression plays a pivotal role in reducing the hepatic apoptotic IR injury. HO-1 may serve as a potential target for therapeutic intervention in hepatic I/R injury during liver transplantation.

Hepatic ischemia and reperfusion injury: effects on the liver sinusoidal milieu

Ischemia-reperfusion injury is an important cause of liver damage occurring during surgical procedures including hepatic resection and liver transplantation, and represents the main underlying cause of graft dysfunction post-transplantation. Cellular and biochemical processes occurring during hepatic ischemia-reperfusion are diverse and complex, and include the deregulation of the healthy phenotype of all liver cellular components. Nevertheless, a significant part of these processes are still unknown or unclear. The present review aims at summarizing the current knowledge in liver ischemia-reperfusion, but specifically focusing on liver cell phenotype and paracrine interaction deregulations. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field will be described. Finally, the importance of considering the subclinical situation of liver grafts when translating basic knowledge to the bedside is discussed.

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 increases survival and attenuates fulminant hepatic failure injury induced by D-galactosamine/lipopolysaccharide in mice

BACKGROUND

Liver transplantation is the only therapy of proven benefit in fulminant hepatic failure (FHF). Lipopolysaccharide (LPS), d-galactosamine (GalN)-induced FHF is a well-established model of liver injury in mice. Erythropoietin has a powerful tissue-protective effect in animal models. The aim of this study was to investigate the effect and mechanism of recombinant human erythropoietin (rhEPO) administration in FHF mice.

METHODS

C57BL/6 (n=42) mice were studied in vivo in a fulminant model induced by GalN/LPS. rhEPO was administered 30 min after the induction of FHF. Serum liver enzymes and hepatic tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels were determined. Histologic analysis was performed, and apoptotic cells were identified by immunohistochemistry for caspase-3. Nuclear factor (NF)-κB and c-Jun-N-terminal kinase (JNK) activation were studied using Western blot analysis.

RESULTS

After the induction of FHF, all control mice died within 12 hr of GalN/LPS administration. However, 83% of mice that were administered rhEPO were alive 2 weeks later, and overall survival improved (Kaplan-Meier, P<0.001). The serum liver enzymes, hepatic TNF-α and IL-1β levels, liver histologic injury, and apoptotic hepatocytes were significantly reduced in FHF mice that were administered rhEPO compared with untreated mice. A significant decrease in hepatic NF-κB and JNK activation was noted in FHF rhEPO-treated mice compared with FHF untreated mice.

CONCLUSIONS

The administration of rhEPO brought about increased survival and attenuation of the hepatic injury. This was associated with decreased hepatic NF-κB and JNK activation and thus TNF-α and IL-1β levels. These findings have important implications for the potential use of rhEPO in FHF.

Proteomic analysis to display the effect of low doses of erythropoietin on rat liver regeneration

AIMS

Several groups found different impact of erythropoietin (EPO) on liver regeneration. Both pro-proliferative as well as anti-proliferative and non-proliferative activities have been reported using high dosage of EPO. Systemic administration of high doses of this cytokine is a clinical concern due to risk of thrombosis. Herein, we applied EPO in low dosages and investigated whether it can stimulate liver regeneration after liver resection.

MAIN METHODS

Parameters of liver regeneration were assessed 3 days after 70% hepatectomy by means of immunochemistry and proteomics. EPO was given twice in low dosages (200 and 600 IU/kg BW).

KEY FINDINGS

We showed that EPO facilitated hepatic regeneration in rats. Enhanced hepatocyte proliferation (Ki67, BrdU-positive cells) was observed in all EPO-treated groups. By performing Differential Proteomic analysis, we identified two proteins which resulted sensitive to EPO treatment after hepatectomy: Peroxiredoxin-1 and glutathione S-transferase Mu 1.

SIGNIFICANCE

Based on our results, low doses of rhEPO increase the hepatic regenerative capacity after partial hepatectomy in rats by enhancing hepatocyte proliferation and acting on antioxidant enzymes. Both proteins identified by proteomic analysis have not previously been associated with liver regeneration and will aid in the understanding of EPO's regenerative response having clinical implications to treat liver failure.

Emerging technologies in the delivery of erythropoietin for therapeutics

Deciphering the function of proteins and their roles in signaling pathways is one of the main goals of biomedical research, especially from the perspective of uncovering pathways that may ultimately be exploited for therapeutic benefit. Over the last half century, a greatly expanded understanding of the biology of the glycoprotein hormone erythropoietin (Epo) has emerged from regulator of the circulating erythrocyte mass to a widely used therapeutic agent. Originally viewed as the renal hormone responsible for erythropoiesis, recent in vivo studies in animal models and clinical trials demonstrate that many other tissues locally produce Epo independent of its effects on red blood cell mass. Thus, not only its hematopoietic activity but also the recently discovered nonerythropoietic actions in addition to new drug delivery systems are being thoroughly investigated in order to fulfill the specific Epo release requirements for each therapeutic approach. The present review focuses on updating the information previously provided by similar reviews and recent experimental approaches are presented to describe the advances in Epo drug delivery achieved in the last few years and future perspectives.

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.

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

Ischemia-reperfusion injury (I/R) is the main cause of primary graft nonfunction. Our aim was to evaluate the effect of excessive versus acute administration of erythropoietin (EPO) in attenuating the hepatic injury induced by I/R in mice. The effect of segmental (70%) hepatic ischemia was evaluated in a transgenic mouse line with constitutive overexpression of human EPO cDNA and in wild-type (WT) mice. Mice were randomly allocated to 5 main experimental groups: (i) WT-sham, (ii) WT ischemia, (iii) WT ischemia + recombinant human erythropoietin (rhEPO), (iv) transgenic-sham, and (v) transgenic ischemia. The EPO-pretreated mice showed a significant reduction in liver enzyme levels and intrahepatic caspase-3 activity and fewer apoptotic hepatocytes (p < 0.05 for all) compared with the WT untreated I/R group. EPO decreased c-Jun N-terminal kinase (JNK) phosphorylation and nuclear factor-κB (NF-κB) expression during I/R. In transgenic I/R livers, baseline histology showed diffused hepatic injury, and no significant beneficial effect was noted between the WT untreated and the transgenic I/R mice. In conclusion, acute pretreatment with EPO in WT mice attenuated in vivo I/R liver injury. However, in excessive EPO overexpression, the initial liver injury abolished the beneficial effect of EPO. These findings have important implications for the potential use of acute EPO in I/R injury during liver transplantation.

Darbepoetin-α inhibits the perpetuation of necro-inflammation and delays the progression of cholestatic fibrosis in mice

Biliary obstruction and cholestasis result in hepatocellular necro-inflammation and lead to the development of liver fibrosis. The objective of this study was to analyze whether the multiple tissue-protective properties of erythropoietin are salutary in an experimental model of liver fibrosis. For this purpose, C57BL/6J mice underwent common bile duct ligation (BDL) and were treated with either darbepoetin-α (10 μg/kg i.p.) or physiological saline every third day, beginning 24 h after BDL. Mice were killed at 2, 5, 14, and 28 days after BDL. Beside hematological parameters, markers of inflammation and fibrosis were assessed histomorphometrically and immunohistochemically as well as by quantitative real-time PCR. In addition, a 7-week survival study was performed. BDL provoked cholestatic hepatitis characterized by biliary infarcts with accumulation of macrophages followed by marked collagen deposition and increased expression of profibrotic gene transcripts. Darbepoetin-α treatment significantly diminished the area of focal necrosis, reduced the infiltration of macrophages, decreased levels of profibrotic genes, and lowered collagen deposition. Moreover, darbepoetin-α significantly reduced systemic anemia caused by BDL. Finally, darbepoetin-α treatment significantly prolonged the survival time after BDL. This study suggests that darbepoetin-α, which is a clinically well-established substance, might be used as an efficient therapeutic option for patients with chronic cholestatic liver disease.

Hydrodynamics-based transfection of plasmid encoding receptor activator for nuclear factor kappa B-Fc protects against hepatic ischemia/reperfusion injury in mice

Hepatic ischemia/reperfusion (I/R) injury is very important in transplant surgery. To study the mechanism of receptor activator for nuclear factor kappa B-Fc (RANK-Fc) in protection against I/R injury, 90 male BALB/c mice were randomly divided into 3 groups: a phosphate-buffered saline (PBS) (sham) group, a pLNCX2-IRES-eGFP+I/R (Negative-control) group (where IRES means internal ribosome entry site and eGFP means enhanced green fluorescent protein), and a pLNCX2-RANK-Fc-IRES-eGFP+I/R (RANK-Fc) group. All mice were injected with 2.5 mL of PBS (with or without plasmids) within 6 seconds via the tail vein. After 3 days, hepatic I/R was induced under warm conditions by partial occlusion of the left and median lobes for 90 minutes followed by various periods of reperfusion. Hepatic injury was assessed by the levels of liver aminotransferases and histopathology. Tumor necrosis factor alpha, interleukin 6, and interleukin 1beta were measured by enzyme-linked immunosorbent assay, whereas RANK-Fc, phospho-c-Jun, c-Jun N-terminal kinase (JNK), hypoxia inducible factor 1 alpha (HIF-1alpha), nuclear p65, and total p65 were assessed with western blotting. Apoptosis was identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. RANK-Fc was efficiently expressed in the liver. In comparison with the negative-control group, RANK-Fc reduced nuclear factor kappa B (NF-kappaB) p65 nuclear translocation, JNK phosphorylation, and HIF-1alpha expression during I/R. RANK-Fc effectively suppressed proinflammatory cytokine expression. The results indicated that RANK-Fc could protect against hepatic I/R injury in mice at least in part via the inhibition of the proinflammatory NF-kappaB pathway as well as proapoptotic JNK and HIF-1alpha pathway activation.

Dual effect of erythropoietin on liver protection and regeneration after subtotal hepatectomy in rats

The only currently offered curative option for many patients with primary or secondary liver tumors is the resection of hepatic tumors. The aim of this study was to evaluate the role of recombinant human erythropoietin (rhEPO) in liver protection and regeneration after subtotal hepatectomy in rats. Rats undergoing 70% hepatectomy received an intraperitoneal injection of saline (control) or rhEPO (4 U/g) 30 minutes prior to resection. Liver function was assessed by the measurement of the international normalized ratio (INR) levels, and hepatic injury was assessed by serum alanine aminotransferase and aspartate aminotransferase levels. Hepatic apoptosis was assessed by intrahepatic caspase-3 activity and morphological criteria. The regeneration capacity of remnant livers was assessed over 7 days with the regenerated liver/body weight ratio, immunohistochemistry markers of cell proliferation (Ki-67) and angiogenesis (von Willebrand factor), and phosphorylated extracellular signal-regulated kinase signaling. Two and 4 days after subtotal hepatectomy, the regenerated liver/body weight ratio was significantly higher in animals treated with rhEPO versus the control group (P < 0.005). Serum liver enzymes and INR levels on days 2 and 4 post-hepatectomy were significantly lower in animals pretreated with rhEPO in comparison with the control group (P < 0.005). No statistically significant difference was noted in intrahepatic hepatic caspase-3 activity, immunohistochemistry for caspase-3, or a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay between the hepatectomized groups. In the rhEPO-pretreated group, the mitotic index, Ki-67 and von Willebrand factor expression, and extracellular signal-regulated kinase activity were significantly higher on day 2 post-hepatectomy (P < 0.05) in comparison with the control group. In conclusion, rhEPO treatment may offer a unique beneficial dual-function strategy for hepatic protection and regeneration immediately after subtotal hepatectomy in rats.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Preconditioning against hepatic ischemia-reperfusion injury: recent advances

Hepatic ischemia-reperfusion injury (I/R) is a major clinical problem that impedes the development of liver surgery. Recently, intensive research has improved our understanding of the mechanisms involved in I/R liver injury. Here, we will briefly review the most promising preconditioning approaches against I/R injury and discuss the mechanisms involved in their therapeutic effects.

Thrombopoietin limits IL-6 release but fails to attenuate liver injury in two hepatic stress models

OBJECTIVE

Various pleiotropic substances have been suggested as candidates that directly reduce the severity of liver injury after hepatic ischemia/reperfusion (I/R) and upon acute liver failure (ALF). Herein, we studied whether thrombopoietin (TPO), the main regulator of megakaryopoiesis and thrombopoiesis, showed hepatoprotective effects and might mediate an antiapoptotic function in liver tissue under stress.

METHODS/RESULTS

In livers with ALF or undergoing warm hepatic I/R, injury was quantified by intravital fluorescence microscopy, chemical, and immunohistochemical analysis as well as western immunoblot. Induction of both ALF and I/R injury led to hepatocellular expression of c-mpl, the receptor of TPO. Exogenous application of recombinant TPO in a low (12.5 microg/kg) as well as a high (75 microg/kg) dose, however, did not ameliorate postischemic perfusion and leukocyte endothelial cell interaction, but slightly aggravated transaminase release upon I/R. Similarly, TPO was unable to dampen hepatic microcirculatory deteriorations after the induction of ALF, but caused an increase of leukocyte accumulation and transaminase activity when applied in high dose. Low dose of TPO did not influence the amount of hepatocellular apoptosis, whereas high-dose TPO slightly diminished the activation of caspase 3. Interestingly, exogenous TPO application completely reversed the stress-induced increase of plasma IL-6 levels, suggesting a negative feedback of TPO on IL-6 release.

CONCLUSION

Although the existence of the TPO-receptor on target liver cells TPO plays only a minor role in mediating hepatocyte apoptosis and does not provide protection against hepatic injury, contrasting the efficacy of the related hematopoietic growth factor erythropoietin.

Acute kidney injury in the intensive care unit

Acute kidney injury (AKI) is common among critically ill patients and results in increased mortality in this population. This review focuses on the diagnosis and management of AKI. The authors first explore new aspects of diagnosis, including new criteria that take into account even modest changes in renal function, and the development of novel biomarkers to allow earlier identification and better differential diagnosis of AKI. The authors also explore the available data on choice of dialysis modality and dialysis dose for the treatment of AKI, as well as the breakthrough development of the bioartificial kidney. Last, the authors review co-interventions that may have relevance to prognosis of AKI, such as intensive insulin therapy and the use of erythropoietin.

Uridine-5'-triphosphate protects against hepatic- ischemic/reperfusion injury in mice

BACKGROUND AND AIM

Mitochondrial calcium overload triggers apoptosis and also regulates ATP production. ATP and uridine-5'-triphosphate (UTP) depletion from hepatic tissue after ischemia causes cell death. ATP and UTP binds to cell membranes of the hepatocytes through P2Y receptors. Our aim was to investigate the role of UTP on the hepatic injury induced by ischemia.

METHODS

Isolated mouse livers were randomly divided into five groups: (1) control group; (2) ischemic group (90 min); (3) as group 2, but with the administration of UTP; (4) as group 2, but with the administration of suramin, a P2Y antagonist; and (5) as group 3, but with the simultaneous administration of suramin and UTP.

RESULTS

There was a postischemic significant reduction in the release of liver enzymes in the animals pretreated with UTP, the intrahepatic caspase-3 activity was significantly decreased, and the intrahepatic ATP content increased compared with group 2 (ischemic untreated). UTP prevented intracellular Ca overload after hypoxia in hepatocyte cultures. In the UTP-treated groups, significantly fewer apoptotic hepatocyte cells were noted by weaker activation of caspase-3 and by the transferase-mediated dUTP nick end labeling assay. The administration of suramin prevented the beneficial effect of endogenous ATP. UTP treatment attenuated the degradation of IkappaBalpha (nuclear factor-kappaB inhibitor) by 80% during reperfusion with no effect on c-Jun N terminal kinase phosphorylation.

CONCLUSION

The administration of UTP before induction of ischemia-reperfusion can attenuate hepatic injury. UTP administration decreased cytosolic Ca overload in hypoxic conditions. UTP-mediated protective effects may be regulated through nuclear factor- kappaB inactivation. These findings have important implications for the potential use of UTP in ischemic hepatic injury.

Erythropoietin reduces necrosis in critically ischemic myocutaneous tissue by protecting nutritive perfusion in a dose-dependent manner

BACKGROUND

Erythropoietin (Epo), the primary regulator of erythropoiesis, has recently been shown to exert antiinflammatory and antiapoptotic properties in neuronal and myocardial tissue. We herein studied whether Epo pretreatment can reduce cell death and ischemic necrosis in a chronic in vivo model.

METHODS

C57BL/6 mice were treated daily for 3 consecutive days with either 500 IU EPO/kg body weight (bw) (group Epo 500, n = 8) or 5000 IU EPO/kg bw (group Epo 5000, n = 8) administered intraperitoneally 24 hours before surgery. Thereafter, a random pattern myocutaneous flap subjected to acute persistent ischemia was elevated and fixed into a dorsal skinfold chamber. Flap elevation in animals receiving the water-soluble vitamin E analog Trolox (6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid) served as a nonspecific antiinflammatory agent control group (Tro); untreated control animals (Con) received saline only. Capillary perfusion, leukocyte-endothelial cell interaction, apoptotic cell death, and tissue necrosis were determined over a 10-day observation period using intravital multifluorescence microscopy.

RESULTS

Epo 5000 (44 +/- 26 cm/cm(2)) but, more noticeably, Epo 500 (116 +/- 32 cm/cm(2)) improved capillary perfusion compared with the two control groups, particularly the Con group (9 +/- 7 cm/cm(2); P < .05). The ischemia-associated leukocytic inflammation was found drastically attenuated in both Epo-pretreatment groups. Epo 500 further decreased apoptotic cell death and was effective in significantly reducing tissue necrosis (16% +/- 4% vs Tro: 48% +/- 7% and Con: 52% +/- 4%; P < .001). No angiogenic blood vessel formation could be observed in either of the Epo groups. Of interest, Epo 5000-but not Epo 500-increased systemic hematocrit.

CONCLUSION

Despite the lack of neovascularization, Epo pretreatment was capable of reducing ischemic tissue necrosis by protecting capillary perfusion, ie, nutrition of the tissue. Low-dose pretreatment was more effective, a result that was most likely due to the better perfusion conditions without an increase of the hematocrit values. Thus, low-dose Epo pretreatment might represent a promising strategy to protect critically perfused ischemic tissue.

No evidence for protective erythropoietin alpha signalling in rat hepatocytes

BACKGROUND

Recombinant human erythropoietin alpha (rHu-EPO) has been reported to protect the liver of rats and mice from ischemia-reperfusion injury. However, direct protective effects of rHu-EPO on hepatocytes and the responsible signalling pathways have not yet been described. The aim of the present work was to study the protective effect of rHu-EPO on warm hypoxia-reoxygenation and cold-induced injury to hepatocytes and the rHu-EPO-dependent signalling involved.

METHODS

Loss of viability of isolated rat hepatocytes subjected to hypoxia/reoxygenation or incubated at 4 degrees C followed by rewarming was determined from released lactate dehydrogenase activity in the absence and presence of rHu-EPO (0.2-100 U/ml). Apoptotic nuclear morphology was assessed by fluorescence microscopy using the nuclear fluorophores H33342 and propidium iodide. Erythropoietin receptor (EPOR), EPO and Bcl-2 mRNAs were quantified by real time PCR. Activation of JAK-2, STAT-3 and STAT-5 in hepatocytes and rat livers perfused in situ was assessed by Western blotting.

RESULTS

In contrast to previous in vivo studies on ischemia-reperfusion injury to the liver, rHu-EPO was without any protective effect on hypoxic injury, hypoxia-reoxygenation injury and cold-induced apoptosis to isolated cultured rat hepatocytes. EPOR mRNA was identified in these cells but specific detection of the EPO receptor protein was not possible due to the lack of antibody specificity. Both, in the cultured rat hepatocytes (10 U/ml for 15 minutes) and in the rat liver perfused in situ with rHu-EPO (8.9 U/ml for 15 minutes) no evidence for EPO-dependent signalling was found as indicated by missing effects of rHu-EPO on phosphorylation of JAK-2, STAT-3 and STAT-5 and on the induction of Bcl-2 mRNA.

CONCLUSION

Together, these results indicate the absence of any protective EPO signalling in rat hepatocytes. This implies that the protection provided by rHu-EPO in vivo against ischemia-reperfusion and other causes of liver injury is most likely indirect and does not result from a direct effect on hepatocytes.