The pleiotropic effects of erythropoietin in the central nervous system

Mast cells and macrophages in duodenal mucosa of mice overexpressing erythropoietin

There is increasing evidence suggesting a wider biological role of erythropoietin (Epo) and Epo receptor (EpoR) not related to erythropoiesis, such as the detection of EpoR in other cells, i.e. polymorphonuclear leukocytes, megakaryocytes, endothelial, myocardial and neural cells. In this study, by using a mouse model (designated tg6) that constitutively overexpresses human Epo in an oxygen-independent manner, we have investigated mast cell and macrophage number and distribution in duodenal mucosa using immunohistochemical, morphometric and image analysis methods. The results showed that tryptase-positive mast cells and BM8-positive macrophages were more numerous in duodenal mucosa specimens of tg6 mice compared with wild-type mice. Moreover, whereas in wild-type specimens both mast cells and macrophages were generally scattered throughout the villus, in tg6 specimens they were aligned along the axis of the villus. Morphometric analysis confirms this observation, and the quantitative analysis of the spatial distribution of the cells in duodenal villi indicated that in both wild-type and tg6 groups the macrophage and mast cell distribution was characterized by significant deviations from randomness. In addition, an increased number of c-kit-positive cells have been identified in the villus axis of tg6 mice, indicating an expanded compartment of mast cell precursors in the intestinal mucosa of these animals. Finally, we have also demonstrated that in tg6 specimens the number of duodenal epithelial cells positive for Epo were significantly higher as compared to wild type. Overall, these data confirm that Epo, acting as a general stimulator of the hemopoietic compartment, is able to induce an expansion of two effectors of the immune response, mast cells and macrophages, in a specific peripheral site, the duodenal mucosa, in the tg6 mouse experimental model.

Safety of epoietin beta-quinine drug combination in children with cerebral malaria in Mali

BACKGROUND

Cerebral malaria carries an unacceptable case fatality rate in children despite timely and adequate chemotherapy. To improve the survival rate, adjunctive therapies previously tested mainly focused on the modulation of the inflammatory response, without definitive effect in humans. In this context, a new adjunctive strategy using a neuroprotective drug: erythropoietin (epoietin-beta, Epo) was proposed.

METHODS

An open-labelled study including cerebral malaria children (Blantyre coma score below 3) was conducted in Mali. The objective was to assess the short-term safety (seven days) of erythropoietin at high doses (1,500 U/kg/day during three days) combined to quinine.

RESULTS

35 patients with unrousable coma were included in the study. None of expected side effects of erythropoietin were observed during the seven days follow-up. No significant increase in the case fatality rate (7/35 patients) was observed compared to other studies with mortality rates ranging from 16 to 22% in similar endemic areas.

CONCLUSION

These data provide the first evidence of the short-term safety of erythropoietin at high doses combined to quinine. A multicentre study is needed to assess the potential of Epo as an adjunctive therapy to increase the survival during cerebral malaria. CLINICAL REGISTRATION NUMBER: ClinicalTrials.gov ID: NCT00697164.

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.

Expression of erythropoietin in the spinal cord of lewis rats with experimental autoimmune encephalomyelitis

Background and Purpose

Erythropoietin (Epo), originally recognized for its central role in erythropoiesis, has been shown to improve the outcomes in patients with various neurological disorders. The aim of this study was to elucidate the Epo expression pattern in the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis (EAE) and to assess the systemic effect of Epo during the course of EAE.

Methods

We used an EAE model induced in Lewis rats by immunization with myelin basic protein. Immunized rats were given recombinant human Epo (rhEpo) intraperitoneally at a dose of 5,000 U/kg for 7 consecutive days, either starting on day 3 post-immunization (five rats) or on the day of clinical symptom onset (score ≥1, five rats). After immunization, the rats were observed daily for clinical signs of EAE. Epo expression was investigated by Western blot analysis and immunohistochemistry.

Results

Western blot analysis showed that, Epo expression was significantly elevated relative to control in the rat spinal cord during the peak stage of EAE (p<0.05), and then decreased thereafter. Immunohistochemistry demonstrated that Epo was expressed in some neurons and glial cells. Epo immunoreactivity was detected in ED1-positive macrophages and astrocytes in EAE lesions. Furthermore, we found that the intraperitoneal administration of rhEpo reduced both the disease severity and duration of paralysis in EAE rats, and reduced macrophage activity and increased Epo activity.

Conclusions

Based on these findings, we postulate that Epo expression begins to increase at the start of EAE and that rhEpo administration leads to functional recovery from EAE paralysis.

Erythropoietin attenuates ischemia-reperfusion induced lung injury by inhibiting tumor necrosis factor-alpha and matrix metalloproteinase-9 expression

Erythropoietin (Epo) was recently defined as an endogenous agent with more than hematopoietic functions. Previously we explored the potential of this agent to ameliorate lung ischemia-reperfusion (I/R) injury. The present study aims to determine the optimal dose and timing of administration for improving lung injury, and to further investigate the mechanisms by which Epo ameliorates lung I/R injury. The left lungs of Sprague-Dawley rats underwent 90 min ischemia and 120 min reperfusion. Firstly, animals in different groups were intraperitoneally injected with various doses of recombined human erythropoietin (rhEpo) 24 h prior to operation, 2 h prior to operation, or after the onset of reperfusion. Pulmonary myeloperoxidase (MPO) activity and malondialdehyde (MDA) content were evaluated. Treatment with 3 KU/kg rhEpo 2 h prior to operation was optimal for attenuating pulmonary MPO activity and MDA content. With such treatment, ultrastructural changes of pneumocytes were observed, and the pneumocyte apoptosis index was also determined by terminal dUTP nick-end labeling method. The plasma concentrations of tumor necrosis factor (TNF)-alpha and matrix metalloproteinase (MMP)-9 were evaluated by enzyme-linked immunosorbent assay, and pulmonary expression by immunohistochemistry. When pretreated with rhEpo, the pneumocyte ultrastructure was predominantly maintained and the pulmonary apoptosis index was markedly reduced. In comparison with untreated animals, in treated animals the plasma concentrations of TNF-alpha and MMP-9 were significantly decreased, and their expression in lung tissue was markedly reduced as well. The results indicated that Epo potently protected against lung I/R injury by inhibiting systemic and local expression of TNF-alpha and MMP-9.

Multiorgan-protective actions of blockers of the renin-angiotensin system, statins and erythropoietin: common pleiotropic effects in reno-, cardio- and neuroprotection

Renal diseases induce nephroprotective measures that may affect the heart, brain and other organs. In addition, many cardiovascular and neurological diseases are accompanied by renal lesions. For these reasons, multiorgan-protective measures, including cardio-, reno- and neuro-protective measures, are necessary to treat these diseases. The drugs used in nephrology are often pleiotropic. Although they usually address a single organ or tissue, many of them have complex actions that may provide multiorgan-protection. The present paper aims to review 3 classes of drugs that are commonly prescribed in nephrological practice: statins, RAS blockers (such as ACEIs and ARBs) and erythropoietin (EPO). This paper highlights the renoprotective actions, as well as those that are protective of the heart, brain and other organs, of these drugs at the cellular and molecular level. Their protective actions are attributable to their main effects and pleiotropic effects. The protective pleiotropic actions of these drugs may be exerted on multiple organs, making them multiorgan-protective. Another objective is to analyse the shared multiorgan-protective pleiotropic effects of RAS blockers (ACEIs and ARBs), statins and erythropoietin. This will allow for the practical association of the main renoprotective drugs with multiorgan protection.

Recombinant human erythropoietin increases survival and reduces neuronal apoptosis in a murine model of cerebral malaria

Background

Cerebral malaria (CM) is an acute encephalopathy with increased pro-inflammatory cytokines, sequestration of parasitized erythrocytes and localized ischaemia. In children CM induces cognitive impairment in about 10% of the survivors. Erythropoietin (Epo) has – besides of its well known haematopoietic properties – significant anti-inflammatory, antioxidant and anti-apoptotic effects in various brain disorders. The neurobiological responses to exogenously injected Epo during murine CM were examined.

Methods

Female C57BL/6j mice (4–6 weeks), infected with Plasmodium berghei ANKA, were treated with recombinant human Epo (rhEpo; 50–5000 U/kg/OD, i.p.) at different time points. The effect on survival was measured. Brain pathology was investigated by TUNEL (Terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-digoxigenin nick end labelling), as a marker of apoptosis. Gene expression in brain tissue was measured by real time PCR.

Results

Treatment with rhEpo increased survival in mice with CM in a dose- and time-dependent manner and reduced apoptotic cell death of neurons as well as the expression of pro-inflammatory cytokines in the brain. This neuroprotective effect appeared to be independent of the haematopoietic effect.

Conclusion

These results and its excellent safety profile in humans makes rhEpo a potential candidate for adjunct treatment of CM.

Erythropoietin in patients with aneurysmal subarachnoid haemorrhage: a double blind randomised clinical trial

BACKGROUND

Erythropoietin (EPO) is neuroprotective in experimental models of stroke and subarachnoid haemorrhage (SAH) and possibly in patients with thromboembolic stroke. We studied the efficacy and safety of EPO in patients with SAH.

METHODS

A larger scale clinical trial was planned but preliminarily terminated because of a lower than expected inclusion rate. However, 73 patients were randomised to treatment with EPO (500 IU/kg/day for three days) or placebo. The primary endpoint was Glasgow Outcome Score at six months. We further studied surrogate measures of secondary ischaemia, i.e. transcranial Doppler (TCD) flow velocity, symptomatic vasospasm, cerebral metabolism (microdialysis) and jugular venous oximetry, biochemical markers of brain damage (S-100beta and neuron specific enolase) and blood-brain barrier integrity.

FINDINGS

The limited sample size precluded our primary hypotheses being verified and refuted. However, data from this study are important for any other study of SAH and as much raw data as possible are presented and can be included in future meta analyses. On admission the proportion of patients in a poor condition was higher in the EPO group compared with the placebo group but the difference was statistically insignificant. In the EPO-treated patients the CSF concentration of EPO increased 600-fold. Except for a higher extracelullar concentration of glycerol in the EPO group probably caused by the poorer clinical condition of these patients, there were no statistically significant group differences in the primary or secondary outcome measures. EPO was well tolerated.

CONCLUSIONS

Beneficial effects of EPO in patients with SAH cannot be excluded or concluded on the basis of this study and larger scale trials are warranted.

Expression of erythropoietin receptor and in vitro functional effects of epoetins in B-cell malignancies

PURPOSE

Erythropoietin (EPO) and EPO receptor (EPO-R) expression have been reported in solid tumors and are claimed to regulate tumor growth; however, no data have been published on this issue in B-cell malignancies or normal lymphoid cells. This report describes genomic/protein EPO-R expression and in vitro effects of recombinant human EPO (epoetin) in B-cell chronic lymphocytic leukemia (B-CLL), mantle-cell lymphoma (MCL), and multiple myeloma (MM).

EXPERIMENTAL DESIGN

Blood samples were obtained from patients with B-CLL, MCL, and healthy volunteers, and bone marrow was obtained from MM patients. EPO-R mRNA was detected by reverse transcription-PCR. EPO-R surface expression was investigated by flow cytometry using digoxigenin-labeled epoetin and polyclonal rabbit anti-EPO-R antibody for intracellular receptor. Tumor cell stimulation was determined in vitro using [(3)H]thymidine incorporation and CD69 expression after exposure to epoetin alpha or beta or darbepoetin alpha.

RESULTS

EPO-R mRNA was detected in mononuclear cells from 32 of 41 (78%) B-CLL and 5 of 7 (71%) MCL patients, and 21 of 21 (100%) MM samples. Expression was also detected in highly purified T cells from six of eight B-CLL patients, four of four MM patients, and normal donor B and T cells. Surface EPO-R protein was not detected. Intracellular EPO-R staining with anti-EPO-R antibodies was unspecific. No tumor-stimulatory effect was observed with high epoetin concentrations.

CONCLUSIONS

EPO-R gene is frequently expressed in lymphoid malignancies and normal B and T cells. However, there was no surface protein expression and no epoetin-induced in vitro stimulation of tumor B cells, indicating that epoetin therapy in vivo is likely to be safe in patients with lymphoid malignancies.

The role of erythropoietin in central and peripheral nerve injury

Erythropoietin (Epo) is a cytokine which controls red cell production. Apart from the red cell surface, erythropoietin's receptor (Epo-R) is also expressed in a large variety of normal tissues. Erythropoietin, as well as its receptor, is present in the central and peripheral nervous system. As erythropoietin having direct and indirect effect on nerve cells, enhances antioxidotic enzyme production, antagonizes glutamate's cytotoxic action, metabolizes free radicals, normalizes cerebral blood flow, affects neurotransmitters release and stimulates neoangiogenesis. After injury of the central as well as the peripheral nervous system, Epo presents an anti-apoptotic action. In combination with its anti-apoptotic effect, Epo, by reducing the inflammatory response plays a crucial role in neuroprotection in many types of injury in the central and the peripheral nervous system. Epo's administration contributes to the recovery of mechanical allodynia and may be effective in peripheral nerve regeneration after neurorrhaphy.

Erythropoietin enhances immune responses in mice

Erythropoietin (Epo) is the main erythropoietic hormone. Recombinant human Epo (rHuEpo) is thus used in clinical practice for the treatment of anemia. Accumulating data reveals that Epo exerts pleiotropic activities. We have previously shown an anti-neoplastic activity of Epo in murine multiple myeloma (MM) models, and in MM patients. Our findings that this anti-neoplastic effect operates via CD8+ T lymphocytes led us to hypothesize that Epo possesses a wider range of immunomodulatory functions. Here we demonstrate the effect of Epo on B lymphocyte responses, focusing on three experimental models: (i) tumor-bearing mice, (5T2 MM mouse); (ii) antigen-injected healthy mice; and (iii) antigen-injected transgenic mice (tg6), overexpressing human Epo. In the MM model, despite bone marrow dysfunction, Epo-treated mice retained higher levels of endogenous polyclonal immunoglobulins, compared to their untreated controls. In both Epo-treated wild type and tg6 mice, Epo effect was manifested in the higher levels of splenocyte proliferative response induced in vitro by lipopolysaccharide. Furthermore, these mice had increased in vivo production of anti-dinitrophenyl (DNP) antibodies following immunization with DNP-keyhole limpet hemocyanin. Epo-treated mice showed an enhanced immune response also to the clinically relevant hepatitis B surface antigen. These findings suggest a potential novel use of rHuEpo as an immunomodulator.

Axonal regeneration stimulated by erythropoietin: An experimental study in rats

The aim of the present study is to evaluate the effects of erythropoietin to the collateral sprouting by using systemically delivered erythropoietin in an end-to-side nerve repair model. Forty-five rats were evaluated in four groups: (A) end-to-side neurorrhaphy only, (B) end-to-side neurorrhaphy and erythropoietin administration, (C) end-to-end neurorrhaphy and (D) nerve stumps buried into neighboring muscles. In all animals, the contralateral healthy side served as control. Functional assessment of nerve regeneration was performed at intervals up to 5 months using the Peroneal Function Index. Evaluation 150 days after surgery included peroneal and tibial nerve morphometric examination, and wet weights of the tibialis anterior muscle. During the first three weeks after surgery, when erythropoietin was regularly administered, functional evaluation showed that erythropoietin may facilitate peripheral nerve regeneration. However, there was rapid deterioration in the functional recovery when erythropoietin's administration was discontinued. As a consequence, at the end of this study, erythropoietin failed to maintain its initial stimulating effect in axonal regeneration. The results of wet muscle weights revealed statistically significant differences between Groups A and C, and Group B. Furthermore, data on axonal counting showed significant difference between Groups A and C, and Group B. Erythropoietin appears to facilitate peripheral nerve regeneration at the initial phase of its administration. Further investigation will be necessary to optimise the conditions (dose, mode of administration) in order to maintain its effects.

Cisplatin-induced peripheral neuropathy: Neuroprotection by erythropoietin without affecting tumour growth

This study examined the dose-dependent efficacy of erythropoietin (EPO) for preventing and/or treating cisplatin (CDDP) induced peripheral neurotoxicity (CINP), and its influence on tumour treatment and growth. Rats received eight intraperitoneal (ip) injections of 2 mg/kg CDDP twice weekly. EPO co-administered (50 or 10 microg/kg ip, three times/week) had a dose-dependent effect, partially preventing CINP, but 0.5 microg/kg ip was not effective. The neuroprotective effect lasted at least 5 weeks after the last dose of EPO and CDDP. In addition, EPO (50 microg/kg ip three times/week) after the last injection of CDDP still induced a significant recovery of CINP. In a separate experiment in rats bearing mammary carcinoma EPO treatment (50 microg/kg ip) given concurrently with CDDP (1.0 and 1.5 mg/kg twice a week for four weeks) was neuroprotective without influencing the effectiveness of the treatment or tumour growth. EPO thus appears to be an effective neuroprotectant that does not interfere with tumour treatment.

Does erythropoietin augment noise induced hearing loss?

Noise-induced hearing loss may result from excessive release of glutamate, nitrogen oxide and reactive oxygen species. The effects of these factors on the inner ear may potentially be prevented or reduced by erythropoietin (EPO), as indicated by previously demonstrated neuro-protective effects of EPO upon damage to the central nervous system and the retina. This paper reports three separate trials, conducted to investigate the hypothesis that noise-induced hearing loss is prevented or reduced by erythropoietin. The trials employed three different modes of drug application, different administration time windows and different rodent species. In trial 1, guinea pigs were exposed to 110dB SPL, 4-20kHz wide band noise (WBN) for 8h. EPO was administered to the round window membrane 24h after noise exposure, either sustained by pump for a week or by single dose middle ear instillation. In trial 2, rats were exposed to 105dB SPL, 4-20kHz WBN for 8h. EPO was administered by single dose middle ear instillation 1 or 14h after noise exposure. In trial 3, rats were exposed to 105dB SPL, 4-20kHz WBN for 8 or 3x8h. EPO was injected intraperitoneally 1h before noise exposure. Oto-acoustic emissions and auditory brainstem responses (at 16kHz) were recorded before and after noise exposure in all trials. The noise exposure induced a hearing loss in all animals. In trial 1, no recovery and no improvement of hearing occurred in any treatment group. In trial 2 and 3, a partial hearing recovery was seen. However, the hearing loss of the EPO treated animals was significantly worse than controls in trial 2. In trial 3, the hearing of the EPO treated animals exposed for 3x8h was significantly worse than controls. Thus, surprisingly, the results from 2 of the 3 present trials indicate that erythropoietin may in fact augment noise-induced hearing loss. This is contradictory to the beneficial effect of EPO reported by the vast majority of studies on stressed neural tissues. EPO administration may alter the blood flow dynamics of the cochlear vascular bed during or after noise exposure, by a potential induction of vasoconstriction. This may be the cause of the surprising findings.

Protective effect of erythropoietin and its carbamylated derivative in experimental Cisplatin peripheral neurotoxicity

PURPOSE

Antineoplastic drugs, such as cisplatin (CDDP), are severely neurotoxic, causing disabling peripheral neuropathies with clinical signs known as chemotherapy-induced peripheral neurotoxicity. Cotreatment with neuroprotective agents and CDDP has been proposed for preventing or reversing the neuropathy. Erythropoietin given systemically has a wide range of neuroprotective actions in animal models of central and peripheral nervous system damage. However, the erythropoietic action is a potential cause of side effects if erythropoietin is used for neuroprotection. We have successfully identified derivatives of erythropoietin, including carbamylated erythropoietin, which do not raise the hematocrit but retain the neuroprotective action exerted by erythropoietin.

EXPERIMENTAL DESIGN

We have developed previously an experimental chemotherapy-induced peripheral neurotoxicity that closely resembles CDDP neurotoxicity in humans. The present study compared the effects of erythropoietin and carbamylated erythropoietin (50 microg/kg/d thrice weekly) on CDDP (2 mg/kg/d i.p. twice weekly for 4 weeks) neurotoxicity in vivo.

RESULTS

CDDP given to Wistar rats significantly lowered their growth rate (P < 0.05), with slower sensory nerve conduction velocity (P < 0.001) and reduced intraepidermal nerve fibers density (P < 0.001 versus controls). Coadministration of CDDP and erythropoietin or carbamylated erythropoietin partially but significantly prevented the sensory nerve conduction velocity reduction. Both molecules preserved intraepidermal nerve fiber density, thus confirming their neuroprotective effect at the pathologic level. The protective effects were not associated with any difference in platinum concentration in dorsal root ganglia, sciatic nerve, or kidney specimens.

CONCLUSIONS

These results widen the spectrum of possible use of erythropoietin and carbamylated erythropoietin as neuroprotectant drugs, strongly supporting their effectiveness.

Gender differences in long-term beneficial effects of erythropoietin given after neonatal stroke in postnatal day-7 rats

Recently, we reported that erythropoietin attenuates neonatal brain injury caused by focal cerebral ischemia. The long-term effects of erythropoietin on focal cerebral ischemia-induced injury to the developing brain and the potential gender differences in these long-term effects have not been studied in detail. The current study demonstrated a similarity in the mean infarct volume in both the vehicle-treated male and female rats at 6 and 12 weeks after focal cerebral ischemia. On the other hand, erythropoietin treatment (1000 U/kg x three doses after focal cerebral ischemia) caused a significant reduction in the mean infarct volume in both males and females at 6 weeks after focal cerebral ischemia when compared with the corresponding vehicle-treated animals (males: 141.4+/-48.2 mm3 vs. 194.0+/-59.2 mm3, P<0.05; females: 85.4+/-31.6 mm3 vs. 183.4+/-46.3 mm3, P<0.05). Interestingly, the reduction in the mean infarct volume in the erythropoietin-treated males was significantly less than that in the erythropoietin-treated females at 6 weeks after focal cerebral ischemia (141.4+/-48.2 mm3 vs. 85.4+/-31.6 mm3, P<0.05). At 12 weeks after focal cerebral ischemia, the mean infarct volume in the erythropoietin-treated males significantly increased to 181.0+/-50.4 mm3 (P<0.05). In contrast, the mean infarct volume in the erythropoietin-treated females remained stable (87.0+/-41.7 mm3). Additionally, erythropoietin treatment significantly improved sensorimotor function recovery with a misstep number similar to the sham-operation group at 6 and 12 weeks after focal cerebral ischemia. Moreover, the mean number of missteps in the erythropoietin-treated females was less than that in males at 6 (13.5+/-2.0 vs. 24.5+/-2.5, P<0.05) and 12 (12.5+/-2.0 vs. 20.0+/-2.0, P<0.05) weeks after focal cerebral ischemia. These results indicate that erythropoietin administration after focal cerebral ischemia produces a significant long-term neuroprotective benefit on the developing brain, and that this effect is more beneficial in the female rats.

Erythropoietin enhances neurogenesis and restores spatial memory in rats after traumatic brain injury

Erythropoietin (EPO) is neuroprotective in models of stroke and traumatic brain injury (TBI) when administered prior to or within the first few hours after injury. We seek to demonstrate that EPO also has neurorestorative effects when administered late (i.e., 1 day) after TBI in the rat. Twelve rats were subjected to TBI. Six rats were treated with EPO daily for 14 days starting 1 day after injury, and an additional six rats were treated with saline. Bromodeoxyuridine (BrdU) was administered daily for 14 days. Memory tests using a Morris Water Maze were performed prior to and after injury and treatment. Animals were sacrificed at 15 days after TBI, and their brains were prepared for histological analysis of damage to the dentate gyrus (DG) and for evaluation of newly formed neurons using double labeling of BrdU and MAP-2. The data revealed a significant improvement in spatial memory and significant increase in the number of newly formed neurons with EPO treatment compared with control animals. These data suggest that EPO treatment initiated 1 day after TBI is neurorestorative by enhancing neurogenesis, as well as neuroprotective.

Beyond anaemia management: evolving role of erythropoietin therapy in neurological disorders, multiple myeloma and tumour hypoxia models

Recombinant human erythropoietin (epoetin) has become the standard of care in the treatment of anaemia resulting from cancer and its treatment, and chronic kidney disease. The discovery that erythropoietin and its receptor are located in regions outside the erythropoietic system has led to interest in the potential role of epoetin in other tissues, such as the central nervous system. Animal studies have shown that systemically applied epoetin can cross the blood-brain barrier, where it reduces tissue injury associated with stroke, blunt trauma and experimental autoimmune encephalomyelitis. Pilot studies in humans have shown that epoetin treatment given within 8 h of stroke reduces infarct size and results in a significantly better outcome when compared with placebo treatment. Studies also suggest that epoetin has the potential to improve cognitive impairment associated with adjuvant chemotherapy in patients with cancer. Anaemia is a major factor causing tumour hypoxia, a condition that can promote changes within neoplastic cells that further tumour survival and malignant progression and also reduces the effectiveness of several anticancer therapies including radiotherapy and oxygen-dependent cytotoxic agents. Use of epoetin to prevent or correct anaemia has the potential to reduce tumour hypoxia and improve treatment outcome. Several therapeutic studies in anaemic animals with experimental tumours have shown a beneficial effect of epoetin on delaying tumour growth. Furthermore, clinical observations in patients with multiple myeloma and animal studies have suggested that epoetin has an antimyeloma effect, mediated via the immune system through activation of CD8+ T cells. Therefore, the role of epoetin may go well beyond that of increasing haemoglobin levels in anaemic patients, although additional studies are required to confirm these promising results.

Anemia, tumor hypoxemia, and the cancer patient

PURPOSE

To review the impact of anemia/tumor hypoxemia on the quality of life and survival in cancer patients, and to assess the problems associated with the correction of this difficulty.

METHODS

MEDLINE searches were performed to find relevant literature regarding anemia and/or tumor hypoxia in cancer patients. Articles were evaluated in order to assess the epidemiology, adverse patient effects, anemia correction guidelines, and mechanisms of hypoxia-induced cancer cell growth and/or therapeutic resistance. Past and current clinical studies of radiosensitization via tumor oxygenation/hypoxic cell sensitization were reviewed. All clinical studies using multi-variate analysis were analyzed to show whether or not anemia and/or tumor hypoxemia affected tumor control and patient survival. Articles dealing with the correction of anemia via transfusion and/or erythropoietin were reviewed in order to show the impact of the rectification on the quality of life and survival of cancer patients.

RESULTS

Approximately 40-64% of patients presenting for cancer therapy are anemic. The rate of anemia rises with the use of chemotherapy, radiotherapy, and hormonal therapy for prostate cancer. Anemia is associated with reductions both in quality of life and survival. Tumor hypoxemia has been hypothesized to lead to tumor growth and resistance to therapy because it leads to angiogenesis, genetic mutations, resistance to apoptosis, and a resistance to free radicals from chemotherapy and radiotherapy. Nineteen clinical studies of anemia and eight clinical studies of tumor hypoxemia were found that used multi-variate analysis to determine the effect of these conditions on the local control and/or survival of cancer patients. Despite differing definitions of anemia and hypoxemia, all studies have shown a correlation between low hemoglobin levels and/or higher amounts of tumor hypoxia with poorer prognosis. Radiosensitization through improvements in tumor oxygenation/hypoxic cell sensitization has met with limited success via the use of hyperbaric oxygen, electron-affinic radiosensitizers, and mitomycin. Improvements in tumor oxygenation via the use of carbogen and nicotinamide, RSR13, and tirapazamine have shown promising clinical results and are all currently being tested in Phase III trials. The National Comprehensive Cancer Network (NCCN) guidelines recommend transfusion or erythropoietin for symptomatic patients with a hemoglobin of 10-11 g/dl and state that erythropoietin should strongly be considered if hemoglobin falls to less than 10 g/dl. These recommendations were based on studies that revealed an improvement in the quality of life of cancer patients, but not patient survival with anemia correction. Phase III studies evaluating the correction of anemia via erythropoietin have shown mixed results with some studies reporting a decrease in patient survival despite an improvement in hemoglobin levels. Diverse functions of erythropoietin are reviewed, including its potential to inhibit apoptosis via the JAK2/STAT5/BCL-X pathway. Correction of anemia by the use of blood transfusions has also shown a decrement in patient survival, possibly through inflammatory and/or immunosuppressive pathways.

CONCLUSIONS

Anemia is a prevalent condition associated with cancer and its therapies. Proper Phase III trials are necessary to find the best way to correct anemia for specific patients. Future studies of erythropoietin must evaluate the possible anti-apoptotic effects by directly assessing the tumor for erythropoietin receptors or the presence of the JAK2/STAT5/BCL-X pathway. Due to the ability of transfusions to cause immunosuppression, most probably through inflammatory pathways, it may be best to study the effects of transfusion with the prolonged use of anti-inflammatory medications.

Expression of erythropoietin and its receptor in the brain of late-gestation fetal sheep, and responses to asphyxia caused by umbilical cord occlusion

Asphyxia and hypoxia are common threats faced by the fetus in utero. In late-gestation fetal sheep, asphyxia produced by umbilical cord occlusion (UCO) results in widespread lipid peroxidation and apoptosis. Adaptive mechanisms that might limit fetal brain damage include induction of the hemopoietic cytokine, erythropoietin (EPO). In unanesthetized fetal sheep, we investigated if 1 or 2 bouts of brief asphyxia (UCO for 10 min) induced EPO and EPO type I receptor (EPO-R) expressions, with the second UCO repeated 48 h after the first. Fetal brains were recovered 48 h after either sham, 1 x or 2 x UCO at 129-133 (term approximately 147) days of gestation and prepared for immunocytochemistry. In age-matched control brain, low levels of EPO and EPO-R proteins were present in oligodendrocytes (OLs), periventricular and cortical white matter (WM), with no EPO and very low EPO-R expression in neurons. After 1 x UCO, EPO and EPO-R expressions were increased in astrocytes (periventricular and cortical WM, striatum, corpus callosum), choroid plexus epithelial cells, scattered neurons in cortical layers IV-VI, hippocampal CA1 neurons, and in the molecular and granule layers of the cerebellum. After 2 x UCO, higher levels of EPO and EPO-R occurred in the periventricular and cortical WM, corpus callosum, hippocampal CA1, and in neurons of all cortical layers. Paradoxically, EPO and EPO-R were now lower in hippocampal CA1 neurons and cerebellar molecular and granule cell layers. Few OLs expressed EPO or EPO-R after 1 x or 2 x UCO. Thus, brief asphyxia induces EPO and EPO-R in fetal astrocytes, but only after repeated asphyxial insult in neurons. Whether this is a response to increased injury, or represents an adaptive response that limits further cell death and brain damage awaits further investigation.

Erythropoietin protects dopaminergic neurons and improves neurobehavioral outcomes in juvenile rats after neonatal hypoxia-ischemia

Brain injury as a result of hypoxia-ischemia remains a common cause of morbidity and mortality in neonates. No effective therapy is currently available. The hematopoietic cytokine erythropoietin (Epo) provides neuroprotection in many adult models of brain injury and is currently being investigated as a therapeutic agent for human stroke and spinal cord injury. We tested the hypothesis that recombinant Epo (rEpo) would improve neurobehavioral outcomes after neonatal hypoxic-ischemic brain injury. Postnatal day 7 rats underwent right common carotid artery occlusion followed by a 90-min exposure to 8% oxygen. Rats were subsequently treated with rEpo or placebo. Sensory neglect and apomorphine-induced rotation were measured at P27 and P28. Rats were killed at P30, blood was drawn, and the brains were perfusion-fixed for histology and immunohistochemistry. No differences in gross brain injury between rEpo and placebo-treated rats were found. Neonatal rEpo treatment protected dopamine neurons as indicated by the preservation of tyrosine hydroxylase-positive cells in the substantia nigra pars compacta and ventral tegmental area. rEpo treatment also improved functional outcomes by reducing sensory neglect and preventing the rotational asymmetry seen in control animals. No differences in hematocrit, white blood cell counts, neutrophil counts, or platelet counts were measured. We observed that rEpo treatment protected mesencephalic dopamine neurons and reduced the degree of behavioral asymmetries at 4 wk of life. On the basis of these findings, we conclude that further studies investigating the safety and efficacy of high-dose rEpo as a neuroprotective strategy are indicated in neonatal models of hypoxic-ischemic brain injury.

Recombinant erythropoietin down-regulates IL-6 and CXCR4 genes in TNF-alpha-treated primary cultures of human microvascular endothelial cells: implications for multiple sclerosis

In multiple sclerosis (MS), disruption of the blood-brain barrier might lead to new gadolinium-enhanced lesion formation in the brain and cause acute relapses. Current therapeutic options for acute relapses in MS are limited. The effect of recombinant erythropoietin (rEPO) on cytokine gene expression in TNF-alpha-treated human brain microvascular endothelial cells was studied. The cells were controls (untreated), exposed for either 6 or 24 h to TNF-alpha or TNF-alpha/rEPO. Of the 96 genes studied, interleukin-6 (IL-6), IL-1beta, CXCR4, and IL-1alpha genes were down-regulated when treated with TNF-alpha/rEPO for 6 h as compared with TNF-alpha alone. At 24 h, IL-6 and CXCR4 gene expression was 4.24 and 2.98, respectively. Quantitative RT-PCR analysis showed down-regulation by 3.86 and 1.9 for IL-6 and CXCR4 genes, respectively. Our findings suggest that further studies are warranted to evaluate the use of EPO in minimizing acute relapses in MS.

Brain and cancer: the protective role of erythropoietin

Erythropoietin (Epo) is a pleiotropic agent, that is to say, it can act on several cell types in different ways. An independent system Epo/Epo receptor (EpoR) was detected in brain, leading to the hypothesis that this hormone could be involved in cerebral functions. Epo/EpoR expression changes during ontogenesis, thus indicating the importance of this system in neurodevelopment. Moreover, the hypoxia-induced production of Epo in the adult brain suggests that it could exert a neurotrophic and neuroprotective effect in case of brain injury. Epo could also influence neurotransmission, inducing neurotransmitters (NT) release. Epo therapy in anemic cancer patients is still a controversial issue, because of its possible action as a growth and an angiogenic factor. In our speculative hypothesis Epo could be involved in a "two steps process" that, after a neovascularization phase, leads to its down regulation. Moreover, Epo-activated signaling pathways could be modulated as possible targets to interfere in neoplastic cells cycle. In conclusion, treatment with rHuEpo could change therapeutical perspectives in different pathological conditions, such as central nervous system (CNS) diseases, but further studies are needed to clarify its physiopathological activities in different clinical fields.

Erythropoietin and erythropoietin receptor expression in the guinea pig inner ear

The erythropoietin receptor (EPOR) is expressed in the brain and erythropoietin (EPO) has been shown to have neurotrophic and neuroprotective functions in the central nervous system and in the retina. These findings may be applied to the inner ear, pending EPO receptor presence. Accordingly, this study determines expression of EPO and EPOR in the inner ear of the guinea pig. Normal guinea pig inner ears were processed for immunohistochemistry, using poly-clonal antibodies against EPO and the EPO receptor. EPO expression was exclusively found in most, but not all spiral ganglion neurons. Expression of the EPO receptor was found in the cytoplasm of the inner and outer phalangeal cells (Deiters' cells), as well as the inner sulcus cells and the supporting cells of the organ of Corti (Hensen, Claudius and some Boettcher cells). Some spiral ganglion neurons or glial cells expressed the receptor, as did spiral ligament fibrocytes, some intermediate cells of stria vascularis and the endothelial cells of some modiolar vessels. No parts of the vestibular system stained positive for either antibody. We conclude, that EPO is expressed by spiral ganglion neurons and that the EPO receptor is widely expressed by several cell types within the guinea pig cochlea. We hypothesize on the existence of a local paracrine system and that EPO treatment may be feasible following inner ear damage.

Erythropoietin after focal cerebral ischemia activates the Janus kinase-signal transducer and activator of transcription signaling pathway and improves brain injury in postnatal day 7 rats

Erythropoietin (Epo) plays a central role in erythropoiesis but also has neuroprotective properties. Recently, Epo-related neuroprotective studies used a hypoxic-ischemic neonatal model, which is different from focal stroke, a frequent cause of neonatal brain injury. We report on the effects of Epo treatment given after focal stroke and its potential neuroprotective mechanisms in postnatal day 7 rats with focal cerebral ischemia (FCI) achieved by occlusion of the middle cerebral artery. The experimental groups included sham operation, FCI plus vehicle, and FCI plus Epo. In the Epo-treated group, pups received a single intraperitoneal injection of 1000 U/kg 15 min after FCI or three injections of 100, 1000, or 5000 U/kg, starting at 15 min and repeated at 1 and 2 d after FCI. Epo treatment produced significant reductions in the mean infarct area and volume at 1 and 3 d after FCI, demonstrated by 2,3,5-triphenyltetrazolium chloride staining. Terminal deoxynucleotidyltransferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL) staining showed a markedly reduced number of TUNEL-positive cells in the Epo-treated group when compared with the vehicle control 3 d after FCI (p<0.01). The most effective dose after FCI was 1000 U/kg for 3 d. Immunoanalyses showed that Epo induced a significant increase in phosphorylated Janus kinase 2 and signal transducer and activator of transcription-5 expressions at 1 and 3 d and up-regulated Bcl-xL expression by 24 h after FCI but did not affect Epo receptor or NF-kappaB expression. In conclusion, Epo given after FCI in neonatal rats provides significant neuroprotection, mediated possibly by activation of the Janus kinase-signal transducer and activator of transcription-Bcl-xL signaling pathways.

[Erythropoietin and cancer-related anaemia. Light and shade]

The use of recombinant human erythropoietin (r-HuEPO) in cancer patients improves hemoglobin levels and quality of life. This fact, already well known, made oncologists expect a positive outcome in radio and chemotherapy results, as well as in survival. However, new clinical trials show a preliminary evidence of impaired, instead of improved, survival when these agents are prescribed. Erythropoietin (EPO) is becoming a more complex hormone than it was expected. Its non-erythropoietic effects include, among others, angiogenesis and proliferation of certain types of cancer cells. In this work, we review erythropoietin as a natural hormone, as well as the different types of r-HuEPO, focusing on the confusing situation with regard to their use in oncology. We conclude that extreme care must be taken when EPO is prescribed to cancer patients, and we suggest to limit its use to symptomatic anemia, just to achieve moderate hemoglobin levels.

Beneficial effect of erythropoietin on experimental allergic encephalomyelitis

We have known for a long time that erythropoietin signaling plays a key role in bone marrow erythrocyte proliferation. However, recent studies have indicated that erythropoietin also may have protective effects on the nervous system. This unexpected role remains incompletely characterized. To investigate the potential neuroprotective role of erythropoietin in the central nervous system, we assessed its effects on a well-characterized autoimmune demyelinating model of multiple sclerosis-myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) in the mouse. We found that erythropoietin administered intravenously for 14 days after the onset of symptoms reduced both disease severity and duration of maximum impairment at dose levels as low as 50U/kg (p < 0.001). We assessed the neuropathology of diseased spinal cords and found that erythropoietin-treated EAE animals had reduced axonal damage, inflammatory cell infiltration and demyelination, and diminished blood-brain barrier leakage when compared with saline-treated EAE controls. Moreover, the pronounced upregulation of spinal cord major histocompatibility complex (MHC) class II expression found in saline-treated EAE was significantly reduced in erythropoietin-treated animals, a finding we replicated in vitro, using microglial cultures. The notion that short-term erythropoietin therapy might be of clinical benefit in human autoimmune demyelinating diseases needs investigation.

Erythropoietin and erythropoietin receptor system in a large uterine myoma of a patient with myomatous erythrocytosis syndrome: possible relationship with the pathogenesis of unusual tumor size

The rare condition of women with erythrocytosis and a concurrent myomatous uterus has been classified as "myomatous erythrocytosis syndrome". Substantial myoma size has been noted as a common denominator in this condition in which recent evidence have confirmed erythropoietin (Epo) production by myoma tissues themselves. Apart from its primary endocrine role in controlling erythropoiesis, Epo has been demonstrated to mediate several cellular processes such as angiogenesis, mitogenesis, and inhibition of apoptosis by autocrine and paracrine mechanisms. Recently, Epo and its receptor (Epo-R) have been shown to be involved in the growth, viability, and angiogenesis of several malignant tumors including human female reproductive organ malignancies. In this paper, we researched on Epo and, as a first in the literature, Epo-R immunoexpression in a large uterine myoma of a term pregnant patient suffering from the myomatous erythrocytosis syndrome. Eight nongravidic leiomyomas and 8 gravidic leiomyomas were used as control group samples. Apart from confirming Epo production by myoma smooth muscle cells in the myomatous erythrocytosis syndrome, we reveal in this pathologic condition a characteristic strong Epo-R expression in myoma endothelial cells and a weak and sporadic Epo-R expression in myoma smooth muscle cells. The striking presence of Epo-R within myoma tissues in the case of the myomatous erythrocytosis syndrome allows us to speculate that myoma Epo production, besides determining erythrocytosis through systemic effects, may contribute, acting by autocrine and paracrine mechanisms, in determining the large myoma size almost always observed in this condition. Finally, we confirm a less but specific immunostaining for Epo in uterine myomas of patients without erythrocytosis and, as a first in the literature, we prove a weak and sporadic Epo-R expression in these lesions. These last results may contribute to knowledge of the yet unclear etiopathogenesis of the most common human gynecologic neoplasm.

Hypoxia-ischemia affects erythropoietin and erythropoietin receptor expression pattern in the neonatal rat brain

Erythropoietin (EPO), known for its role in erythroid differentiation, has been suggested to have non-hematopoietic functions in the brain, especially during development. In the present study, we investigated the expression of erythropoietin and erythropoietin receptor (EPOR) in the developing rat brain following hypoxia-ischemia. Seven-day-old rats underwent unilateral, permanent carotid artery ligation followed by 1 h of hypoxia, and their brains were examined immediately, 24 h or 4 days after hypoxia-ischemia. RT-PCR and Western blot analysis revealed that hypoxia-ischemia only marginally affected EPO expression. Immunohistochemical study of brains 4 days after hypoxia showed that 60 min of hypoxia (resulting in cortical infarction and severe neuronal loss in other regions) led to the increased EPO immunoreactivity, especially in the boundaries of the damaged cerebral cortex, associated with astrocytosis. In contrast, EPOR was dramatically upregulated within 24 h after hypoxia-ischemia. These results suggest that there is a rapid response of EPOR to the hypoxic-ischemic stimulus, which seems to precede that of EPO, leading to the hypothesis that the EPO/EPOR system is implicated in the processes of neuroprotection from hypoxia-ischemia.

Erythropoietin and the hypoxic brain

Normal tissue function in mammals depends on adequate supply of oxygen through blood vessels. A discrepancy between oxygen supply and consumption (hypoxia) induces a variety of specific adaptation mechanisms at the cellular, local and systemic level. These mechanisms are in part governed by the activation of hypoxia-inducible transcription factors (HIF-1, HIF-2), which in turn modulate expression of hypoxically regulated genes such as those encoding vascular endothelial growth factor (VEGF) and erythropoietin (EPO). EPO is a glycoprotein that is produced mainly by interstitial fibroblasts in the kidneys of the adult and in hepatocytes in the foetus. Released into the circulation, EPO makes its way to the bone marrow, where it regulates red cell production by preventing apoptosis of erythroid progenitor cells. Recently, EPO has emerged as a multifunctional growth factor that plays a significant role in the nervous system. Both EPO and its receptor are expressed throughout the brain in glial cells, neurones and endothelial cells. Hypoxia and ischaemia have been recognised as important driving forces of EPO expression in the brain. EPO has potent neuroprotective properties in vivo and in vitro and appears to act in a dual way by directly protecting neurones from ischaemic damage and by stimulating endothelial cells and thus supporting the angiogenic effect of VEGF in the nervous system. Thus, hypoxia-induced gene products such as VEGF and EPO might be part of a self-regulated physiological protection mechanism to prevent neuronal injury, especially under conditions of chronically reduced blood flow (chronic ischaemia). In this review, I will briefly summarize the recent findings on the molecular mechanisms of hypoxia-regulated EPO expression in general and give an overview of its expression in the central nervous system, its action as a growth factor with non-haematopoietic functions and its potential clinical relevance in various brain pathologies.

The erythropoietin-receptor pathway modulates survival of cancer cells

Anemia in cancer patients is associated with reduced quality of life and local failure after radiation treatment. However, the use of erythropoietin to correct cancer anemia and to improve radiation efficacy was disappointing. Erythropoietin-receptor signaling mainly acts via activation of STAT 5, but also crossactivates the antiapoptotic transcription factor NF-kappaB. This causes neuroprotection against oxidative stress and implies radioprotection. In order to investigate possible radioprotective effects of erythropoietin-receptor signaling, we used an in vitro model system employing HeLa TetOff cells, stably transfected with an expression vector for the erythropoietin-receptor gene. Using electrophoretic mobility shift assays, we could demonstrate strong activation of NF-kappaB by erythropoietin-receptor signaling in HeLa cells. Activation of NF-kappaB did not require degradation of IkappaBalpha and was not prevented by proteasome inhibition. Furthermore, stimulation with erythropoietin resulted in a 50% increased clonogenicity of erythropoietin-receptor-expressing cells but did not alter radiation sensitivity itself. As most human tumors express erythropoietin receptor, we advocate a restricted use erythropoietin to patients suffering from erythropoietin-receptor-expressing cancers.

Treatment of cancer-related anemia with epoetin alfa: a review

Erythropoietin (EPO) is a hematopoietic growth hormone that regulates survival, proliferation, and differentiation of erythroid progenitor cells. A reduction in tissue oxygenation stimulates EPO production, through a complex feedback mechanism. Patients with cancer-related anemia have an inadequate EPO response that is further impaired by cancer treatments such as chemotherapy. Cancer-related anemia substantially impairs patient functioning and may contribute to poor treatment outcomes. A significant number of studies demonstrates that treatment of anemia in cancer patients using recombinant human EPO (rHuEPO, epoetin alfa) significantly increases haemoglobin (Hb) levels, reduces transfusion requirements, and improves quality of life, particularly by relieving fatigue. Recent data also show that epoetin alfa therapy may improve cognitive function in patients receiving chemotherapy. In addition, the correction of anemia may prolong survival by enhancing tumor oxygenation, thus increasing tumor sensitivity to chemotherapy or radiation. The indicated dose of epoetin alfa is 150-300 IU/kg three times per week, but it is commonly dosed at 40,000-60,000 IU once weekly based on trial data and extensive clinical use. Determining the timing of initiation of epoetin alfa is a clinical judgement; however, data suggest that patient functioning declines and the risk of transfusion increases when the Hb level falls under 12 g/dL.

Beneficial and ominous aspects of the pleiotropic action of erythropoietin

The primary function of the glycoprotein hormone erythropoietin (Epo) is to promote red cell production by inhibiting apoptosis of erythrocytic progenitors in hemopoietic tissues. However, functional Epo receptors (Epo-R) have recently been demonstrated in various nonhemopoietic tissues indicating that Epo is a more pleiotropic viability and growth factor. Herein, in vitro and in vivo effects of Epo in the brain and the cardiovascular system are reviewed. In addition, the therapeutic impact of Epo in oncology is considered, including the question of whether Epo might promote tumor growth. Convincing evidence is available that Epo acts as a neurotrophic and neuroprotective factor in the brain. Epo prevents neuronal cells from hypoxia-induced and glutamate-induced cell death. Epo-R is expressed by neurons and glia cells in specific regions of the brain. Epo supports the survival of neurons in the ischemic brain. The neuroprotective potential of Epo has already been confirmed in a clinical trial on patients with acute stroke. With respect to the vasculature, Epo acts on both endothelial and smooth muscle cells. Epo promotes angiogenesis and stimulates the production of endothelin and other vasoactive mediators. In addition, Epo-R is expressed by cardiomyocytes. The role of Epo as a myocardial protectant is at the focus of present research. Epo therapy in tumor patients is practiced primarily to maintain the hemoglobin concentration above the transfusion trigger and to reduce fatigue. In addition, increased tumor oxygenation may improve the efficacy of chemotherapy and radiotherapy. However, tumor cells often express Epo-R. Therefore, careful studies are required to fully exclude that recombinant human Epo (rHuEpo) promotes tumor growth.

Age-related changes in erythropoietin immunoreactivity in the cerebral cortex and hippocampus of rats

Although oxidative stress may influence the fluid properties of blood, resulting in a potential decrement in blood flow and oxygen delivery to the brain during aging, very little is known about age-related changes in Epo expression. Therefore, we examined age-related changes in Epo expression in the cerebral cortex and hippocampus with an immunohistochemical technique. In aged rats, there was a significant decrease in Epo immunoreactivity in the pyramidal cells in the cortical regions. In the hippocampus of adult rats, a distinct immunoreactivity pattern was observed in the CA1-3 areas and dentate gyrus. In aged hippocampus, Epo immunoreactivity was significantly deceased in the pyramidal layer of CA1 regions, and the granule cell layer of dentate gyrus. It was noted that there was distinct pattern of Epo immunoreactivity in the pyramidal layer of CA2-CA3 region of aged rats. Epo immunoreactivity was relatively strong, but was observed only in the periphery of the cytoplasm. The first demonstration of age-related decreases in Epo expression in the cerebral cortex and hippocampus may provide useful data for investigating the pathogenesis of age-related neurodegenerative diseases, suggesting that age-related decreases in Epo may contribute to degenerative events following age-related decreases in brain flow and oxygen supply.

Permanent focal cerebral ischemia activates erythropoietin receptor in the neonatal rat brain

Erythropoietin (Epo) has been shown to act as a neurotrophic and neuroprotective factor via binding to its receptor (EpoR) which is activated in adult brains following hypoxia and ischemia. However, no evidence suggests that cerebral ischemia can activate EpoR in the neonatal brain. In the present study, the changes in EpoR expression were investigated using a modified model of permanent focal cerebral ischemia (FCI) in 7-day-old rat pups. Western blot analysis with an anti-rabbit EpoR antibody revealed a significant increase in the EpoR protein in the ischemic areas, starting from 6 to 12 h after FCI. Moreover, many EpoR-positive cells were detected in the ischemic areas from 12 h after FCI, and the positive cells were identified as neurons and microglia/macrophage but not astrocytes 24 h after FCI. Additionally, double staining with a red in situ apoptosis detection kit and the EpoR antibody indicated that EpoR-positive cells were in apoptotic cell death in the ischemic area. Therefore, these results suggest that EpoR is activated in the ischemic areas of neonatal rats and plays an important role in brain injury during development.

Recombinant erythropoietin as a neuroprotective treatment: in vitro and in vivo models

The biologic effects of erythropoietin in the central and peripheral nervous system involve the activation of its specific cell surface receptor and corresponding signal transduction pathways. This article reviews the neuroprotective effects of erythropoietin in brain, emphasizing the progress made using in vitro and in vivo research models.

Mechanisms of erythropoietin-induced brain protection in neonatal hypoxia-ischemia rat model

Erythropoietin, a hemotopoietic growth factor, has brain protective actions. This study investigated the mechanisms of Recombinant Human EPO (rhEPO)-induced brain protection in neonates. An established rat hypoxia-ischemia model was used by ligation of the right common carotid artery of 7-day-old pups, followed by 90 minute of hypoxia (8% 02 and 92% N2) at 37 degrees C. Animals were divided into three groups: control, hypoxia-ischemia, and hypoxia-ischemia plus rhEPO treatment. In rhEPO treated pups, 300 units rhEPO was administered intraperitoneally 24 hours before hypoxia. rhEPO treatment (300 units) was administered daily for an additional 2 days. ELISA and immunohistochemistry examined the expression of EPO and EPOR. Brain weight, morphology, TUNEL assay, and DNA laddering evaluated brain protection. rhEPO abolished mortality (from 19% to 0%) during hypoxia insult, increased brain weight from 52% to 88%, reduced DNA fragmentation, and decreased TUNEL-positive cells. Real-time RT-PCR, Western blot, and immunohistochemistry revealed an enhanced expression of heat shock protein 27 (HSP27) in ischemic brain hemisphere. Double labeling of TUNEL with HSP27 showed most HSP27 positive cells were negative to TUNEL staining. rhEPO reduces brain injury, especially apoptotic cell death after neonatal hypoxia-ischemia, partially mediated by the activation of HSP27.

New Insights Into Erythropoietin and Epoetin Alfa: Mechanisms of Action, Target Tissues, and Clinical Applications

Recombinant human erythropoietin (epoetin alfa) has proven beneficial for the treatment of various anemias. The mechanism of action of endogenous erythropoietin and the therapeutic use of epoetin alfa to stimulate red blood cell production and improve the quality of life in cancer patients are reviewed here. Epoetin alfa may also attenuate the cognitive dysfunction associated with cancer therapy. Interestingly, functional endogenous erythropoietin receptor signaling pathways have been demonstrated in numerous nonerythropoietic tissues. Of particular importance, epoetin alfa confers neurotrophic and neuroprotective effects in cultured neurons and in several animal models for neurologic disease. In one clinical trial, epoetin alfa appeared to limit functional and histologic damage in patients with stroke. Therefore, in cancer patients receiving chemotherapy, the beneficial effects of epoetin alfa could be mediated not only through enhanced erythrocyte production but also via direct effects on the nervous system. Further investigation into the nonerythropoietic effects of epoetin alfa could broaden its clinical utility for patients with cancer and also provide new therapies for various neurologic disorders.

Plasma angiopoietin-1, angiopoietin-2 and Tie-2 in breast and prostate cancer: a comparison with VEGF and Flt-1

BACKGROUND

Angiogenesis is essential for tumour growth and metastasis, and is coordinated by several classes of growth factors mediating their effect through receptors linked, in turn, to tyrosine kinase. These growth factors include angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF), which act through receptors Flt-1 and Tie-2.

MATERIALS AND METHODS

In order to further determine abnormalities in levels of Ang-1, Ang-2, Tie-2, sFlt-1 and VEGF in human cancer (and their interrelationships), these molecules were measured in plasma from 30 patients with breast cancer, 30 patients with prostate cancer and 12 healthy controls per cancer group.

RESULTS

In breast cancer, levels of Ang-1 (P=0.0005), Ang-2 (P=0.0173), Tie-2 (P=0.0001), and VEGF (P=0.0001) were all significantly raised, and plasma levels of sFlt-1 (P=0.045) were significantly reduced compared with controls. However, in prostate cancer, only levels of VEGF and Tie-2 were significantly higher (both P=0.001). There were no significant differences between levels of any molecule between the two groups of cancer. The only difference between the healthy control groups was lower Ang-1 in the women compared with men. Significant correlations were found between levels of Ang-1 and Tie-2 both in breast (r=0.498, P=0.005) and prostate cancer (r=0.643, P=<0.001). Angiopoietin-1 was also positively correlated with Ang-2 in both breast (r=0.422, P=0.02) and prostate cancer (r=0.543, P=0.002).

CONCLUSIONS

Abnormal levels of Ang-1, Ang-2 and their receptor, Tie-2, are present in breast and prostate cancer, and their interrelationships may be important in the pathophysiology of these conditions.

Erythropoietin as an angiogenic factor

Erythropoietin (Epo) is produced by the fetal liver and adult kidney and is an essential stimulator of erythropoiesis. It has, however, been shown to modulate host cellular signal transduction pathway to perform many other functions. New sites of Epo production have been found, such as the female reproductive organs and central nervous system. This review summarizes the involvement of Epo in the regulation of angiogenesis in both normal and pathological conditions.

Intracerebroventricular injection of erythropoietin enhances sleep in the rat

Systemic injection of erythropoietin (EPO) over several days reduces sleep fragmentation in patients with periodic limb movements in sleep (PLMS). However, there are no studies concerning the effects of EPO on spontaneous sleep. In this study, we determined the effects of intracerebroventricular (i.c.v.) administration of EPO on spontaneous rat sleep. Three doses of EPO (25, 75, and 125 ng) were injected i.c.v. at the onset of the dark period. All doses of EPO increased non-rapid eye movement sleep (NREMS). In addition, high and low doses of EPO (125 and 25 ng) increased rapid eye movement sleep (REMS), but the medium dose of EPO (75 ng) inhibited REMS. Electroencephalogram slow-wave activity during NREMS also increased following the two higher doses of EPO. In contrast, EPO injection during the light period failed to affect sleep. Brain temperature (Tbr) was not affected by any dose of EPO. These results suggest that EPO could be part of the cytokine network involved in sleep regulation.