Multiple doses of erythropoietin impair liver regeneration by increasing TNF-alpha, the Bax to Bcl-xL ratio and apoptotic cell death

Recombinant Human erythropoietin reduces viability of MCF-7 breast cancer cells from 3D culture without caspase activation

Recombinant human erythropoietin (rHuEPO) is the erythropoiesis-stimulating hormone that is being used concurrently with chemotherapeutic drugs in the treatment of anemia of cancer. The effect of rHuEPO on cancer cells in 3-dimensional (3D) cultures is not known. The objective of the study was to determine the effect of rHuEPO on the viability of MCF-7 breast cancer cells from 2-dimensional (2D) and 3D cell cultures. The monolayer MCF-7 cells from 2D culture and MCF-7 cell from 3D culture generated by ultra-low adhesive microplate technique, were treated with 0, 0.1, 10, 100 or 200 IU/mL rHuEPO for 24, 48 or 72 h. The effects of rHuEPO on MCF-7 cell viability and proliferation were determined using the (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay (MTT), neutral red retention time (NRRT), trypan blue exclusion assay (TBE), DNA fragmentation, acridine orange/propidium iodide staining (AO/PI) assays. The MCF-7 cells for 3D culture were also subjected to caspase assays and cell cycle analysis using flow cytometry. rHuEPO appeared to have greater effect at lowering the viability of MCF-7 cells from 3D than 2D cultures. rHuEPO significantly (p < 0.05) decreased viability and down-regulated the caspase activities of 3D MCF-7 cells in dose- and time-dependent manner. The cell cycle analysis showed that rHuEPO caused MCF-7 cells to enter the subG0/G1 phase. Thus, the study suggests that rHuEPO has a cytostatic effect on the MCF-7 breast cancer cells from 3D culture.

Hepatic erythropoietin response in cirrhosis. A contemporary review

The main function of erythropoietin (EPO) is to maintain red blood cell mass, but in recent years, increasing evidence has suggested a wider biological role not solely related to erythropoiesis, e.g. angiogenesis and tissue protection. EPO is produced in the liver during fetal life, but the main production shifts to the kidney after birth. The liver maintains a production capacity of up to 10% of the total EPO synthesis in healthy controls, but can be up-regulated to 90-100%. However, the hepatic EPO synthesis has been shown not to be adequate for correction of anemia in the absence of renal-derived EPO. Elevated circulating EPO has been reported in a number of diseases, but data from cirrhotic patients are sparse and the level of plasma EPO in patients with cirrhosis is controversial. Cirrhosis is characterized by liver fibrosis, hepatic dysfunction and the release of proinflammatory cytokines, which lead to arterial hypotension, hepatic nephropathy and anemia. An increase in EPO due to renal hypoperfusion, hypoxia and anemia or an EPO-mediated hepato-protective and regenerative mechanism is plausible. However, poor hepatic synthesis capacity, a decreasing co-factor level and inflammatory feedback mechanisms may explain a potential insufficient EPO response in end-stage cirrhosis. Finally, the question remains as to whether a potential increase in EPO production in certain stages of cirrhosis originates from the kidney or liver. This paper aims to review contemporary aspects of EPO relating to chronic liver disease.

Darbepoetin-α Promotes Cell Proliferation in Established Extrahepatic Colorectal Tumors after Major Hepatectomy

BACKGROUND

The glycoprotein hormone erythropoietin and its analogue darbepoetin-α (DPO) have been shown to reduce the risk of acute liver failure after major hepatectomy. However, previous experimental studies have also shown that DPO significantly enhances neovascularization and tumor cell proliferation in established colorectal liver metastasis in hepatectomized and nonhepatectomized mice. The present study now analyzes whether DPO influences cell proliferation and migration as well as vascularization and growth of established colorectal metastasis at extrahepatic sites after major hepatectomy.

METHODS

GFP-transfected CT26.WT colorectal cancer cells were implanted into dorsal skinfold chambers of syngeneic BALB/c mice. Five days after tumor cell implantation, the animals received a single dose of DPO (10 µg/kg body weight) or phosphate-buffered saline solution (PBS) intravenously. Additional animals received a 70% hepatectomy and DPO or PBS treatment. Tumor vascularization and growth as well as tumor cell migration, proliferation and apoptosis were studied repetitively over 14 days using intravital fluorescence microscopy, histology and immunohistochemistry.

RESULTS

DPO did not influence tumor cell migration and apoptosis. In addition, DPO did not stimulate tumor cell infiltration or vascularization; however, significantly increased tumor cell proliferation was detected in hepatectomized animals.

CONCLUSION

DPO increases cell proliferation in established extrahepatic colorectal metastases after major hepatectomy. Thus, DPO may not be recommended to stimulate regeneration of the remnant liver after major hepatectomy for colorectal liver metastasis.

Green tea polyphenols protect spinal cord neurons against hydrogen peroxide-induced oxidative stress

Green tea polyphenols are strong antioxidants and can reduce free radical damage. To investigate their neuroprotective potential, we induced oxidative damage in spinal cord neurons using hydrogen peroxide, and applied different concentrations (50–200 μg/mL) of green tea polyphenol to the cell medium for 24 hours. Measurements of superoxide dismutase activity, malondialdehyde content, and expression of apoptosis-related genes and proteins revealed that green tea polyphenol effectively alleviated oxidative stress. Our results indicate that green tea polyphenols play a protective role in spinal cord neurons under oxidative stress.

Multiple low doses of erythropoietin delay the proliferation of hepatocytes but promote liver function in a rat model of subtotal hepatectomy

PURPOSE

The impact of various doses of erythropoietin (EPO) on liver regeneration after partial hepatectomy (PH) in different animal models is still under debate. We investigated the impact of low doses of EPO on liver regeneration in a rat model of subtotal hepatectomy.

METHODS

We established a 90 % PH rat model with perioperative injections of low-dose EPO (1,000 IU/kg). We analyzed survival and hepatocyte proliferation in animals treated with or without EPO and assessed liver function by blood ammonia measurement and the indocyanine green 15-min retention test.

RESULTS

Low doses of EPO treatment improved the survival of rats after 90 % PH. Unexpectedly, during the first 24 h after the operation, liver regeneration in the EPO-treated rats was inhibited. DNA synthesis, cell proliferation, and the expression of cyclins and p-STAT3 peaked 48 h after PH, which was delayed by about 24 h vs. the control rats. Furthermore, EPO treatment increased the serum level of IL-6 and protected the hepatocytes from apoptosis.

CONCLUSION

Low doses of EPO do not stimulate early hepatocyte proliferation in the regenerating liver, but contribute to liver protection by inducing IL-6 and inhibiting apoptosis.

A three-component signalling system fine-tunes expression kinetics of HPPK responsible for folate synthesis by positive feedback loop during stress response of Xanthomonas campestris

During adaptation to environments, bacteria employ two-component signal transduction systems, which contain histidine kinases and response regulators, to sense and respond to exogenous and cellular stimuli in an accurate spatio-temporal manner. Although the protein phosphorylation process between histidine kinase and response regulator has been well documented, the molecular mechanism fine-tuning phosphorylation levels of response regulators is comparatively less studied. Here we combined genetic and biochemical approaches to reveal that a hybrid histidine kinase, SreS, is involved in the SreK-SreR phosphotransfer process to control salt stress response in the bacterium Xanthomonas campestris. The N-terminal receiver domain of SreS acts as a phosphate sink by competing with the response regulator SreR to accept the phosphoryl group from the latter's cognate histidine kinase SreK. This regulatory process is critical for bacterial survival because the dephosphorylated SreR protein participates in activating one of the tandem promoters (P2) at the 5' end of the sreK-sreR-sreS-hppK operon, and then modulates a transcriptional surge of the stress-responsive gene hppK, which is required for folic acid synthesis. Therefore, our study dissects the biochemical process of a positive feedback loop in which a 'three-component' signalling system fine-tunes expression kinetics of downstream genes.

Darbepoetin inhibits proliferation of hepatic cancer cells in the presence of TGF-β

Darbepoetin (DPO), an erythropoietin (EPO) derivative, was licensed in 2002 to treat patients with solid tumors suffering from chemotherapy-dependent anemia, although various tumors express EPO to improve vascularization, thus favoring tumor growth and spreading. Therefore, we wanted to investigate direct effects of DPO on the liver tumor cell lines HepG2, SkHep1, Huh-7, AKN1, HCC-T and HCC-M, as well as on primary human hepatocytes (hHeps). DPO (0-40 ng/ml) did not affect viability of hHeps, HepG2, SkHep1, AKN1, HCC-T and HCC-M cells, as determined by Resazurin conversion. However, Huh-7 cells' viability dose-dependently decreased from 5 ng/ml DPO on. Lack of LDH release into culture medium and negative DNA laddering excluded apoptosis or necrosis as the cause for the reduced Resazurin conversion. In Huh-7 cells, DPO increased the expression of p53. Interestingly, Huh-7 cells showed the highest basal TGF-β1 expression as compared to the other cell lines. Upon inhibition of TGF-β1 signaling, DPO no longer reduced viability in Huh-7 cells. On the contrary, co-incubation with TGF-β1 made the other cell lines responsive to DPO. Summarizing our data, we show that DPO reduces the growth of Huh-7 cells by up-regulation of the tumor-suppressor gene p53. This mechanism seems to be dependent on a strong TGF-β expression and corresponding signaling in these cells, as other cell lines became responsive to DPO with TGF-β1 supplementation. The knowledge of this mechanism offers great perspectives for the understanding and treatment of solid liver tumors.

Protective role of recombinant human erythropoietin in kidney and lung injury following renal bilateral ischemia-reperfusion in rat model

BACKGROUND

Acute kidney injury (AKI) has been recognized as one of the most complex clinical complications in modern medicine, and ischemia/reperfusion (I/R) injury is well-known as a main reason of AKI. In addition, AKI leads to important systemic consequences such as acute lung injury. This study was designed to investigate the role of erythropoietin (EPO) on kidney function makers and tissue damage; and lung endothelial permeability and lung water content (LWC) in bilateral renal I/R injury model in rats.

METHODS

Male Wistar rats were randomly divided into three groups of sham, I/R, and I/R treated with EPO (I/R + EPO) groups. The I/R and I/R + EPO groups were subjected to bilateral renal I/R injury; however, only the I/R + EPO group received EPO (500 IU/kg, i.p.) 2 h before ischemia surgery, and the same dose was continued once a day for 3 days after ischemia. The sham group underwent a surgical procedure without ischemia process.

RESULTS

The blood urea nitrogen (BUN) and serum creatinine (Cr) levels, kidney tissue damage score (KTDS), and kidney weight (KW) per 100 g body weight significantly increased in I/R group (P < 0.05). EPO administration decreased levels of BUN and Cr significantly (P < 0.05), and KTDS and KW insignificantly (P = 0.1). No significant differences in kidney and serum levels of malondialdehyde, and lung vascular permeability and LWC were observed between the groups. The serum and kidney levels of nitrite were not significantly different between I/R and sham groups; however, administration of EPO increased the renal level of nitrite (P < 0.05).

CONCLUSIONS

EPO protected the kidney against I/R injury; however, it may not protect the lung tissue from the damage induced by renal I/R injury in rats.

Alternative erythropoietin-mediated signaling prevents secondary microvascular thrombosis and inflammation within cutaneous burns

Alternate erythropoietin (EPO)-mediated signaling via the heteromeric receptor composed of the EPO receptor and the β-common receptor (CD131) exerts the tissue-protective actions of EPO in various types of injuries. Herein we investigated the effects of the EPO derivative helix beta surface peptide (synonym: ARA290), which specifically triggers alternate EPO-mediated signaling, but does not bind the erythropoietic EPO receptor homodimer, on the progression of secondary tissue damage following cutaneous burns. For this purpose, a deep partial thickness cutaneous burn injury was applied on the back of mice, followed by systemic administration of vehicle or ARA290 at 1, 12, and 24 h postburn. With vehicle-only treatment, wounds exhibited secondary microvascular thrombosis within 24 h postburn, and subsequent necrosis of the surrounding tissue, thus converting to a full-thickness injury within 48 h. On the other hand, when ARA290 was systemically administered, patency of the microvasculature was maintained. Furthermore, ARA290 mitigated the innate inflammatory response, most notably tumor necrosis factor-alpha-mediated signaling. These findings correlated with long-term recovery of initially injured yet viable tissue components. In conclusion, ARA290 may be a promising therapeutic approach to prevent the conversion of partial- to full-thickness burn injuries. In a clinical setting, the decrease in burn depth and area would likely reduce the necessity for extensive surgical debridement as well as secondary wound closure by means of skin grafting. This use of ARA290 is consistent with its tissue-protective properties previously reported in other models of injury, such as myocardial infarction and hemorrhagic shock.

Deficiency of the oxygen sensor PHD1 augments liver regeneration after partial hepatectomy

PURPOSE

Liver regeneration after partial hepatectomy (PH) occurs in conditions of reduced oxygen supply. HIF prolyl hydroxylase enzymes (PHD1, PHD2, and PHD3) are oxygen sensors involved in adaptive response to hypoxia. Specific functions of these PHD enzymes in liver regeneration have, however, remained enigmatic. Here, we investigated the significance of PHD1 in liver regeneration following hepatectomy.

METHODS

Liver regeneration was studied in PHD1-deficient (PHD1(-/-)) and wild type (WT) mice subjected to 80% hepatectomy. For in vitro analyses, hepatocytes were isolated from PHD1(-/-) and WT livers. Cell cycle progression was studied via FACS-based analysis of nuclear DNA profile. Transcription factor binding assays, qRT-PCR, and immunoblotting were applied to study the relevance of PHD1 downstream effectors during liver regeneration.

RESULTS

Liver regeneration was significantly enhanced in PHD1(-/-) mice compared to WT littermates. This effect was due to enhanced proliferation rather than to hypertrophy of liver cells. Cell cycle progression was significantly enhanced, and transcriptional activity of the cell cycle regulator c-Myc was increased in PHD1-deficient hepatocytes. These changes coincided with increased expression of cyclin D2, a cell cycle-promoting c-Myc target, and decreased expression of the cell cycle-delaying c-Myc target p21.

CONCLUSIONS

Loss of PHD1 enhances liver regeneration by boosting hepatocyte proliferation in a c-Myc-dependent fashion. PHD1 might, therefore, represent a potential target to facilitate liver regeneration after surgical resection.

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.

The combined effect of erythropoietin and granulocyte macrophage colony stimulating factor on liver regeneration after major hepatectomy in rats

Background

The liver presents a remarkable capacity for regeneration after hepatectomy but the exact mechanisms and mediators involved are not yet fully clarified. Erythropoietin (EPO) and Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) have been shown to promote liver regeneration after major hepatectomy.

Aim of this experimental study is to compare the impact of exogenous administration of EPO, GM-CSF, as well as their combination on the promotion of liver regeneration after major hepatectomy.

Methods

Wistar rats were submitted to 70% major hepatectomy. The animals were assigned to 4 experimental groups: a control group (n = 21) that received normal saline, an EPO group (n = 21), that received EPO 500 IU/kg, a GM-CSF group (n = 21) that received 20 mcg/kg of GM-CSF and a EPO+GMCSF group (n = 21) which received a combination of the above. Seven animals of each group were killed on the 1st, 3rd and 7th postoperative day and their remnant liver was removed to evaluate liver regeneration by immunochemistry for PCNA and Ki 67.

Results

Our data suggest that EPO and GM-CSF increases liver regeneration following major hepatectomy when administered perioperatively. EPO has a more significant effect than GM-CSF (p < 0.01). When administering both, the effect of EPO seems to fade as EPO and GM-CSF treated rats have decreased regeneration compared to EPO administration alone (p < 0.01).

Conclusion

EPO, GM-CSF and their combination enhance liver regeneration after hepatectomy in rats when administered perioperatively. However their combination has a weaker effect on liver regeneration compared to EPO alone. Further investigation is needed to assess the exact mechanisms that mediate this finding.

Erythropoietin and sonic hedgehog mediate the neuroprotective effects of brain-derived neurotrophic factor against mitochondrial inhibition

Brain-derived neurotrophic factor (BDNF) deficiency and mitochondrial dysfunction have been implicated in the pathogenesis of Huntington's disease (HD). 3-Nitropropionic acid (3-NP) is a mitochondrial inhibitor commonly used as a pharmacological model mimicking HD. We have recently reported that preconditioning of primary rat cortical cultures with BDNF induces sonic hedgehog (SHH), which contributes to the protective effects of BDNF against 3-NP neurotoxicity. Because carbamylated erythropoietin (EPO) may induce SHH, we investigated whether BDNF-dependent SHH expression and 3-NP resistance require prior induction of EPO. We found that BDNF induced EPO expression at both mRNA and protein levels. BDNF-mediated SHH induction and 3-NP resistance were abolished by the soluble EPO receptor (sEPO-R), an EPO inhibitor. Recombinant rat EPO (rEPO) induced SHH and attenuated 3-NP neurotoxicity. The rEPO-dependent neuroprotection was suppressed by the SHH inhibitor cyclopamine (CPM); however, sEPO-R failed to affect SHH neuroprotection. Furthermore, the rEPO-dependent neuroprotection was not suppressed by the BDNF neutralizing antibody, which completely abolished BDNF-mediated 3-NP resistance at the same dosage. Overall, our results demonstrate that BDNF-dependent SHH expression and 3-NP resistance require prior induction of EPO, thus establishing a signaling cascade of "BDNF-->EPO-->SHH-->3-NP resistance" in rat cortical neurons.