Erythropoietin as a tissue-protective cytokine in brain injury: what do we know and where do we go?

Cellular and molecular biomarkers of long COVID: a scoping review

BACKGROUND

Long-COVID (LC) encompasses diverse symptoms lasting months after the initial SARS-CoV-2 infection. Symptoms can be debilitating and affect the quality of life of individuals with LC and their families. Although the symptoms of LC are well described, the aetiology of LC remains unclear, and consequently, patients may be underdiagnosed. Identification of LC specific biomarkers is therefore paramount for the diagnosis and clinical management of the syndrome. This scoping review describes the molecular and cellular biomarkers that have been identified to date with potential use for diagnosis or prediction of LC.

METHODS

This review was conducted using the Joanna Briggs Institute (JBI) Methodology for Scoping Reviews. A search was executed in the MEDLINE and EMBASE databases, as well as in the grey literature for original studies, published until October 5th, 2022, reporting biomarkers identified in participants with LC symptoms (from all ages, ethnicities, and sex), with a previous infection of SARS-CoV-2. Non-English studies, cross-sectional studies, studies without a control group, and pre-prints were excluded. Two reviewers independently evaluated the studies, extracted population data and associated biomarkers.

FINDINGS

23 cohort studies were identified, involving 2163 LC patients [median age 51.8 years, predominantly female sex (61.10%), white (75%), and non-vaccinated (99%)]. A total of 239 candidate biomarkers were identified, consisting mainly of immune cells, immunoglobulins, cytokines, and other plasma proteins. 19 of the 239 candidate biomarkers identified were evaluated by the authors, by means of receiver operating characteristic (ROC) curves.

INTERPRETATION

Diverse cellular and molecular biomarkers for LC have been proposed. Validation of candidate biomarkers in independent samples should be prioritized. Modest reported performance (particularly in larger studies) suggests LC may encompass many distinct aetiologies, which should be explored e.g., by stratifying by symptom clusters and/or sex.

FUNDING

Dr. Tebbutt has received funding from the Canadian Institutes of Health Research (177747) to conduct this work. The funding source was not involved in this scoping review, or in the decision to submit this manuscript for publication.

The Latest Evidence of Erythropoietin in the Treatment of Glaucoma

Erythropoietin (EPO) is a circulating hormone conventionally considered to be responsible for erythropoiesis. In addition to facilitating red blood cell production, EPO has pluripotent potential, such as for cognition improvement, neurogenesis, and anti-fibrotic, anti-apoptotic, anti-oxidative, and anti-inflammatory effects. In human retinal tissues, EPO receptors (EPORs) are expressed in the photoreceptor cells, retinal pigment epithelium, and retinal ganglion cell layer. Studies have suggested its potential therapeutic effects in many neurodegenerative diseases, including glaucoma. In this review, we discuss the correlation between glaucoma and EPO, physiology and potential neuroprotective function of the EPO/EPOR system, and latest evidence for the treatment of glaucoma with EPO.

Topical Erythropoietin for Treatment of Scleral Necrosis

PURPOSE

To investigate the safety and efficacy of topical erythropoietin for the treatment of scleral necrosis.

METHODS

This study enrolled eight consecutive patients with scleral necrosis due to previous ocular surgery, rheumatoid arthritis-associated necrotizing anterior scleritis, and thermal and chemical burns. Conventional treatments failed to heal avascular scleral lesions in all eyes. Patients were treated with topical erythropoietin (3000 IU/mL) four times a day.

RESULTS

The mean patient age was 37.6 ± 15.5 years. The interval between the development of scleral necrosis and initiation of topical erythropoietin was 25.6 ± 12.0 days. The necrotic sclera completely healed within 31.9 ± 16.9 days in all patients. The avascular lesions did not recur, and there was no evidence of side effects during the study.

CONCLUSION

Our results showed that topical erythropoietin could be safely used to manage scleral necrosis. Randomized clinical trials are needed to further explore the efficacy of this intervention in patients with avascular scleral lesions.

Does erythropoietin affect the outcome and complication rates of patient with traumatic brain injury? A pooled-analysis

OBJECTIVE

The aim of this meta-analysis was to review the scientific literature published until April 18, 2021, to summarize existing knowledge on the efficacy and safety of erythropoietin (EPO) for traumatic brain injury (TBI).

METHODS

This systematic review followed PRISMA guidelines. Randomized controlled trials (RCTs) reporting on the efficacy and safety of EPO in the treatment of TBI were systematically searched in relevant electronic databases according to a pre-designed search strategy. The primary outcomes are the mortality; and secondary outcomes are the good functional outcome (GFO) and adverse events (AEs).

RESULTS

A total of 10 RCTs involving 2,402 participants fulfilled the inclusion criteria. The results showed that there is a significant difference in terms of the mortality (RR = 0.67, 95% CI = 0.54-0.84, P = 0.0003) and seizure rate (RR = 0.52, 95% CI = 0.29-0.96, P = 0.04) between the EPO groups compared to those in the control groups. However, compared with the control groups, the GFO in the EPO groups was not statistically significant (RR = 1.18, 95% CI = 0.93-1.48, P = 0.17).

CONCLUSIONS

Findings of the present meta-analysis suggest that the use of EPO could reduce mortality rate in patients with TBI, without increasing the incidence of AEs. EPO has potential research and application value in the treatment of TBI.

The Development of Novel Drug Treatments for Stroke Patients: A Review

Acute ischemic stroke is a critical condition that can result in disability and death. The consequences of this medical condition depend on various factors, including the size of the stroke, affected brain region, treatment onset, and the type of treatment. The primary objective of stroke treatment is to restart ischemic penumbra tissue perfusion and reduce infarct volume by sustaining blood flow. Recent research on the condition’s pathological pathways and processes has significantly improved treatment options beyond restoring perfusion. Many studies have concentrated on limiting injury severity via the manipulation of molecular mechanisms of ischemia, particularly in animal research. This article reviews completed and ongoing research on the development of acute ischemic stroke drugs. This study focuses on three main categories of antithrombotic drugs, thrombolytic drugs, and neuroprotective agents. The paper outlines findings from animal and clinical trials and explores the working mechanisms of these drugs.

Erythropoietin Protects against Diffuse Alveolar Hemorrhage in Mice by Regulating Macrophage Polarization through the EPOR/JAK2/STAT3 Axis

Macrophages play an important role in the pathogenesis of systemic lupus erythematosus-associated diffuse alveolar hemorrhage (DAH). The immunomodulation of macrophage responses might be a potential approach for the prevention and treatment of DAH. Erythropoietin (EPO) could regulate macrophage bioactivities by binding to the EPO receptor expressing on macrophages. This study assessed the effects of EPO on DAH protection using an immune-mediated DAH murine model with macrophages as the major contributor. A DAH murine model was established in female C57BL/6 mice by an i.p. injection of pristane. We found that EPO administration alleviates DAH by reducing pulmonary macrophages recruitment and promoting phenotype switch toward M2 macrophages in vivo. EPO drove macrophages to the anti-inflammatory phenotype in the primary murine bone marrow-derived macrophages and macrophages cell line RAW 264.7 with LPS, IFN-γ, and IL-4 in vitro. Moreover, EPO treatment increases the expression of EPOR and decreases the expression of miR-494-3p, resulting in increased phosphorylation of JAK2 and STAT3. In conclusion, EPO can be a potential therapeutic agent in DAH by reducing cell apoptosis and regulating macrophage polarization through the EPOR/JAK2/STAT3 axis. Further studies are also needed to validate the direct target of miR-494-3p in regulating JAK2/STAT3 signaling transduction.

Endogenous erythropoietin signaling regulates migration and laminar positioning of upper-layer neurons in the developing neocortex

Erythropoietin (EPO), the hypoxia-inducible hematopoietic hormone, has well-established neuroprotective/neurotrophic roles in the developing central nervous system and the therapeutic potential of EPO has been widely explored in clinical studies for the treatment of perinatal hypoxic brain lesion, as well as prematurity. Here, we reveal that both EPO and Epo receptor (EPOR) are expressed in the developing rat somatosensory cortex during radial migration and laminar positioning of granular and supragranular neurons. Experimental deregulation of EPO signaling using genetic approaches results in aberrant migration, as well as permanent neuronal misplacement leading to abnormal network activity and protracted sensory behavioral deficits. We identify ERK as the downstream effector of the EPO signaling pathway for neuronal migration. These findings reveal a crucial role for endogenous EPO signaling in neuronal migration, and offer important insights for understanding how the temporary deregulation of EPO could result in migration defects that lead to abnormal behavior in the adult.

PEGylated Erythropoietin Protects against Brain Injury in the MCAO-Induced Stroke Model by Blocking NF-κB Activation

Cerebral ischemia exhibits a multiplicity of pathophysiological mechanisms. During ischemic stroke, the reactive oxygen species (ROS) concentration rises to a peak during reperfusion, possibly underlying neuronal death. Recombinant human erythropoietin (EPO) supplementation is one method of treating neurodegenerative disease by reducing the generation of ROS. We investigated the therapeutic effect of PEGylated EPO (P-EPO) on ischemic stroke. Mice were administered P-EPO (5,000 U/kg) via intravenous injection, and middle cerebral artery occlusion (MCAO) followed by reperfusion was performed to induce in vivo ischemic stroke. P-EPO ameliorated MCAO-induced neurological deficit and reduced behavioral disorder and the infarct area. Moreover, lipid peroxidation, expression of inflammatory proteins (cyclooxygenase-2 and inducible nitric oxide synthase), and cytokine levels in blood were reduced by the P-EPO treatment. In addition, higher activation of nuclear factor kappa B (NF-κB) was found in the brain after MCAO, but NF-κB activation was reduced in the P-EPO-injected group. Treatment with the NF-κB inhibitor PS-1145 (5 mg/kg) abolished the P-EPO-induced reduction of infarct volume, neuronal death, neuroinflammation, and oxidative stress. Moreover, P-EPO was more effective than EPO (5,000 U/kg) and similar to a tissue plasminogen activator (10 mg/kg). An in vitro study revealed that P-EPO (25, 50, and 100 U/mL) treatment protected against rotenone (100 nM)-induced neuronal loss, neuroinflammation, oxidative stress, and NF-κB activity. These results indicate that the administration of P-EPO exerted neuroprotective effects on cerebral ischemia damage through anti-oxidant and anti-inflammatory properties by inhibiting NF-κB activation.

Role of Erythropoietin in Cerebral Glioma: An Innovative Target in Neuro-Oncology

BACKGROUND

Erythropoietin (EPO) is a cytokine primarily involved in the regulation of erythropoiesis. In response to hypoxia-ischemia, hypoxia-inducible factor 1 induces EPO production, which, in turn, inhibits apoptosis of erythroid progenitor cells. By the same mechanism and acting through other signaling pathways, EPO exerts neuroprotective effects. Increased resistance to hypoxia and decreased apoptosis are thought to be important mechanisms for tumor progression, including malignant glioma. Because recent studies have demonstrated that EPO and its receptor (EPOR) are expressed in several tumors and can promote tumor growth, in the present study, we investigated EPO and EPOR expression in human glioma and the effect of EPO administration in a rat model of glioma implantation.

METHODS

Using Western blotting and immunohistochemical analysis, we examined the expression of EPO, EPOR, platelet endothelial cell adhesion molecule, and Ki-67 in human glioma specimens and experimentally induced glioma in rats. In the experimental setting, a daily dose of recombinant human EPO (rHuEPO) or saline solution were administered for 21 days in Fischer rats subjected to 9L cell line implantation.

RESULTS

In both human and animal specimens, we found an increase in EPOR expression as long as the lesion presented with an increasing malignant pattern. A significant direct correlation was found between the expression of EPOR and Ki-67 and EPOR and platelet endothelial cell adhesion molecule in low- and high-grade gliomas. The rats treated with rHuEPO presented with significantly larger tumor spread compared with the saline-treated rats.

CONCLUSIONS

The results of our study have shown that the EPO/EPOR complex might play a significant role in the aggressive behavior of high-grade gliomas. The larger tumor spread in rHuEPO-treated rats suggests a feasible role for EPO in the aggressiveness and progression of malignant glioma.

The Recombinant Human Erythropoietin Administered in Neonatal Rats After Excitotoxic Damage Induces Molecular Changes in the Hippocampus

In vitro and in vivo experimental evidence has contributed important knowledge regarding the antiapoptotic effect mediated by EPO signaling in the damaged brain, particularly through different models with a hypoxic component. However, little emphasis has been placed on the effectiveness of rhEPO administration against cellular alterations caused by in vivo excitotoxicity or on the molecular mechanism that regulates this effect. In this study, we investigated the effects of a single dose of rhEPO on hippocampal damage induced by subcutaneous application of monosodium glutamate (MSG) on postnatal days 1, 3, 5 and 7 in neonatal rats. We found that a dose of 1000 IU/kg of b.w. administered 24 h after MSG had the greatest protective effect. In addition, we analyzed changes in gene expression, particularly in 3 key molecules involved in EPO-mediated signaling (EPO, EPOR and βcR). We observed that the expression of EPO and EPOR was differentially modified at both the mRNA and protein levels under the evaluated conditions, while the expression of the βcR gene was substantially increased. Our data suggest that a low dose of rhEPO is sufficient to induce cellular protection under these experimental conditions and that the molecular changes could be a positive feedback mechanism, mediated by reactive astrocytes in association with in vivo neuroprotective mechanisms.

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

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

Erythropoietin and Nonhematopoietic Effects

Erythropoietin (EPO) is the main regulator of red blood cell production. Since the 1990s, EPO has been used for the treatment of anemia associated with end-stage renal failure and chemotherapy. The erythropoietin receptors were found on other organs such as the brain, spinal cord, heart and skin. In addition, it has been shown that many tissues produce and locally release EPO in response to hypoxic, biochemical and physical stress. In cellular, animal and clinical studies, EPO protects tissues from ischemia and reperfusion injury, has antiapoptotic effects and improves regeneration after injury. In this article, we mainly review the nonhematopoietic effects and new possible clinical indications for EPO.

Low Oxygen Tension Primes Aortic Endothelial Cells to the Reparative Effect of Tissue-Protective Cytokines

Erythropoietin (EPO) has both erythropoietic and tissue-protective properties. The EPO analogues carbamylated EPO (CEPO) and pyroglutamate helix B surface peptide (pHBSP) lack the erythropoietic activity of EPO but retain the tissue-protective properties that are mediated by a heterocomplex of EPO receptor (EPOR) and the β common receptor (βCR). We studied the action of EPO and its analogues in a model of wound healing where a bovine aortic endothelial cells (BAECs) monolayer was scratched and the scratch closure was assessed over 24 h under different oxygen concentrations. We related the effects of EPO and its analogues on repair to their effect on BAECs proliferation and migration (evaluated using a micro-Boyden chamber). EPO, CEPO and pHBSP enhanced scratch closure only at lower oxygen (5%), while their effect at atmospheric oxygen (21%) was not significant. The mRNA expression of EPOR was doubled in 5% compared with 21% oxygen, and this was associated with increased EPOR assessed by immunofluorescence and Western blot. By contrast, βCR mRNA levels were similar in 5% and 21% oxygen. EPO and its analogues increased both BAECs proliferation and migration, suggesting that both may be involved in the reparative process. The priming effect of low oxygen tension on the action of tissue-protective cytokines may be of relevance to vascular disease, including atherogenesis and restenosis.

Erythropoietin as a new therapeutic opportunity in brain inflammation and neurodegenerative diseases

Highly expressed Erythropoietin Receptor (EPO-R) has been detected in several nonhematopoietic hypoxic cells, including cells from different brain areas in response to many different types of cell injury. In brain, hypoxia-ischemia (HI) can induce a wide spectrum of biologic responses, where inflammation and apoptosis are the main protagonists. Inflammation, as a primary brain insult, can induce a chronic hypoxic condition, producing the continuous cycle of inflammation-hypoxia that increases the apoptotic-cell number. It has also been demonstrated that administration of erythropoietin (EPO) prevented the neuronal death induced by HI, as well as the induction of lipid peroxidation in the hippocampus in a rodent model of Alzheimer's disease. Anti-apoptotic, anti-inflammatory, anti-oxidant, and/or cell-proliferative effects of EPO, have been observed in all type of cells expressing EPO-R, resulting in a potential tool for neuroprotection, neuroreparation, or neurogenesis of brain damaged areas. The nasal route is an alternative way of drugs administration that has been successfully exploited for bypassing the blood brain barrier, and subsequently delivering EPO and other molecules to central nervous system. Intranasal administration of EPO could be a new therapeutic opportunity in several brain damages that includes hypoxia, inflammation, neurodegenerative process, and apoptosis.

Neuroprotection with erythropoietin in preterm and/or low birth weight infants

Neonatal brain injury caused by extreme prematurity remains a great challenge for prevention. Erythropoietin (EPO) has shown neuroprotective effects in a series of neonatal experimental models and recent clinical trials of premature infants. In this meta-analysis of seven clinical trials, EPO was associated with a highly reproducible reduction in the risk of neurodevelopmental disability in preterm infants. However, there was no difference in the risk for morbidity, cerebral palsy, visual deficit, severe hearing deficit, necrotizing enterocolitis, intracranial hemorrhage and patent ductus arteriosus. The use of EPO, to some extent, is associated with reduction in neurodevelopmental disability in preterm infants. More double blind randomized controlled trials are needed to establish the best therapeutic approach for neuroprotection in preterm infants.

Antioxidant and antigenotoxic role of recombinant human erythropoeitin against alkylating agents: Cisplatin and mitomycin C in cultured Vero cells

Cisplatin (CDDP) and mitomycin C (MMC), two alkylating agents used against various solid tumours, are a common source of acute kidney injury. Thus, strategies for minimizing CDDP and MMC toxicity are of a clinical interest. In this study, we aimed to investigate the protective role of recombinant human erythropoietin (rhEPO) against oxidative stress and genotoxicity induced by CDDP and MMC in cultured Vero cells. Three types of treatments were performed: (i) cells were treated with rhEPO 24 h before exposure to CDDP/MMC (pre-treatment), (ii) cells were treated with rhEPO and CDDP/MMC simultaneously (co-treatment), (iii) cells were treated with rhEPO 24 h after exposure to CDDP/MMC (post-treatment). Our results showed that rhEPO decreased the reactive oxygen species levels, the malondialdehyde levels and ameliorated glutathione (reduced and oxidized glutathione) modulation induced by CDDP and MMC in cultured Vero cells. Furthermore, rhEPO administration prevented alkylating agents-induced DNA damage accessed by comet test. Altogether, our results suggested a protective role of rhEPO, against CDDP- and MMC-induced oxidative stress and genotoxicity, especially in pre-treatment condition.

Only repeated administration of the serotonergic agonist 8-OH-DPAT improves place learning of rats subjected to fimbria-fornix transection

Serotonergic agonists may act neuroprotectively against brain injury. This study addressed the therapeutic potential of 8-hydroxy-2-di-n-propylamino-tetralin (8-OH-DPAT), a selective 5-HT1A/7 receptor agonist, after mechanical brain injury, and evaluated its effects in terms of acquisition of an allocentric place learning task in a water maze. Rats were divided into 6 experimental groups, three of which were subjected to bilateral transection of fimbria-fornix (FF), while three groups were given control surgery (Sham). After surgery, within both the lesioned, and sham-operated animals, respectively, one group was administered a single dose of saline, one group was given a single dose (0.5 mg/kg/b.w.) of 8-OH-DPAT, and one group was treated with daily administration of 8-OH-DPAT (0.5 mg/kg/b.w.) for eight days. The acquisition of the water maze based place learning task started on the 8th day post-surgery and continued for 20 days. The results show that the lesioned group subjected to repeated administration of 8-OH-DPAT demonstrated a significantly improved acquisition of the place learning task compared to the vehicle injected lesion group. In contrast, the lesioned group treated with a single administration displayed impaired performance compared to the baseline lesion group. There were no significant effects of the 8-OH-DPAT administration in the sham control groups. We conclude that only the repeated stimulation of the 5-HT1A/7 system was associated with beneficial, recovery enhancing effects.

Epo and non-hematopoietic cells: what do we know?

The hematopoietic growth factor erythropoietin (Epo) circulates in plasma and controls the oxygen carrying capacity of the blood (Fisher. Exp Biol Med (Maywood) 228:1-14, 2003). Epo is produced primarily in the adult kidney and fetal liver and was originally believed to play a role restricted to stimulation of early erythroid precursor proliferation, inhibition of apoptosis, and differentiation of the erythroid lineage. Early studies showed that mice with targeted deletion of Epo or the Epo receptor (EpoR) show impaired erythropoiesis, lack mature erythrocytes, and die in utero around embryonic day 13.5 (Wu et al. Cell 83:59-67, 1995; Lin et al. Genes Dev. 10:154-164, 1996). These animals also exhibited heart defects, abnormal vascular development as well as increased apoptosis in the brain suggesting additional functions for Epo signaling in normal development of the central nervous system and heart. Now, in addition to its well-known role in erythropoiesis, a diverse array of cells have been identified that produce Epo and/or express the Epo-R including endothelial cells, smooth muscle cells, and cells of the central nervous system (Masuda et al. J Biol Chem. 269:19488-19493, 1994; Marti et al. Eur J Neurosci. 8:666-676, 1996; Bernaudin et al. J Cereb Blood Flow Metab. 19:643-651, 1999; Li et al. Neurochem Res. 32:2132-2141, 2007). Endogenously produced Epo and/or expression of the EpoR gives rise to autocrine and paracrine signaling in different organs particularly during hypoxia, toxicity, and injury conditions. Epo has been shown to regulate a variety of cell functions such as calcium flux (Korbel et al. J Comp Physiol B. 174:121-128, 2004) neurotransmitter synthesis and cell survival (Velly et al. Pharmacol Ther. 128:445-459, 2010; Vogel et al. Blood. 102:2278-2284, 2003). Furthermore Epo has neurotrophic effects (Grimm et al. Nat Med. 8:718-724, 2002; Junk et al. Proc Natl Acad Sci U S A. 99:10659-10664, 2002), can induce an angiogenic phenotype in cultured endothelial cells and is a potent angiogenic factor in vivo (Ribatti et al. Eur J Clin Invest. 33:891-896, 2003) and might enhance ventilation in hypoxic conditions (Soliz et al. J Physiol. 568:559-571, 2005; Soliz et al. J Physiol. 583, 329-336, 2007). Thus multiple functions have been identified breathing new life and exciting possibilities into what is really an old growth factor.This review will address the function of Epo in non-hematopoietic tissues with significant emphasis on the brain and heart.

Erythropoietin stimulation decreases hepcidin expression through hematopoietic activity on bone marrow cells in mice

Erythropoiesis-stimulating agents (ESA) are now central to the treatment of renal anemia and are associated with improved clinical outcomes. It is well known that erythropoietin (EPO) is a key regulator of erythropoiesis through its promotion of red blood cell production. In order to investigate the role of ESA on iron metabolism, we analyzed the regulation of the iron regulatory hormone hepcidin by ESA treatment in a bone marrow transplant model in mouse. After treating C57BL/6 mice with continuous erythropoietin receptor activator (C.E.R.A.), recombinant human epoetin-β (rhEPO), or recombinant human carbamylated epoetin-β (rhCEPO), we investigated serum hepcidin concentrations and parameters of erythropoiesis. Serum hepcidin concentrations after rhEPO treatment were analyzed in mice subjected to total body irradiation followed by bone marrow transplantation. C.E.R.A. administration caused long-term downregulation of serum hepcidin levels. Serum hepcidin levels in rhEPO-treated mice decreased significantly, whereas there was no change in rhCEPO-treated mice. The reduction in circulating hepcidin levels after rhEPO administration was not observed in irradiated mice. Finally, bone marrow transplantation recovered the response to rhEPO administration that downregulates hepcidin concentration in irradiated mice. These results indicate that ESA treatment downregulates serum hepcidin concentrations, mainly by indirect mechanisms affecting hematopoietic activity in bone marrow cells.

Erythropoietin mediated bone formation is regulated by mTOR signaling

The role of erythropoietin (Epo) and Epo/Epo receptor (EpoR) signaling pathways for production of red blood cells are well established. However, little is known about Epo/EpoR signaling in non-hematopoietic cells. Recently, we demonstrated that Epo activates JAK/STAT signaling in hematopoietic stem cells (HSCs), leading to the production of bone morphogenetic protein 2 (BMP2) and bone formation and that Epo also directly activates mesenchymal cells to form osteoblasts in vitro. In this study, we investigated the effects of mTOR signaling on Epo-mediated osteoblastogenesis and osteoclastogenesis. We found that mTOR inhibition by rapamycin blocks Epo-dependent and -independent osteoblastic phenotypes in human bone marrow stromal cells (hBMSCs) and ST2 cells, respectively. Furthermore, we found that rapamycin inhibits Epo-dependent and -independent osteoclastogenesis in mouse bone marrow mononuclear cells and Raw264.7 cells. Finally, we demonstrated that Epo increases NFATc1 expression and decreases cathepsin K expression in an mTOR-independent manner, resulting in an increase of osteoclast numbers and a decrease in resorption activity. Taken together, these results strongly indicate that mTOR signaling plays an important role in Epo-mediated bone homeostasis.

Molecular and cellular mechanisms underlying the role of blood vessels in spinal cord injury and repair

Spinal cord injury causes immediate damage of nervous tissue accompanied by the loss of motor and sensory function. The limited self-repair ability of damaged nervous tissue underlies the need for reparative interventions to restore function after spinal cord injury. Blood vessels play a crucial role in spinal cord injury and repair. Injury-induced loss of local blood vessels and a compromised blood-brain barrier contribute to inflammation and ischemia and thus to the overall damage to the nervous tissue of the spinal cord. Lack of vasculature and leaking blood vessels impede endogenous tissue repair and limit prospective repair approaches. A reduction of blood vessel loss and the restoration of blood vessels so that they no longer leak might support recovery from spinal cord injury. The promotion of new blood vessel formation (i.e., angio- and vasculogenesis) might aid repair but also incorporates the danger of exacerbating tissue loss and thus functional impairment. The delicate interplay between cells and molecules that govern blood vessel repair and formation determines the extent of damage and the success of reparative interventions. This review deals with the cellular and molecular mechanisms underlying the role of blood vessels in spinal cord injury and repair.

Protective effect of recombinant human erythropoietin against cisplatin-induced oxidative stress and nephrotoxicity in rat kidney

Cisplatin (Cisp) is one of the most widely used chemotherapeutic agents for the treatment of several human malignancies. The efficacy of Cisp is dose dependent and at higher doses serious kidney injury may occur. Recombinant human erythropoietin (rhEPO) has recently been shown to exert an important cytoprotective effect in experimental brain injury and ischemic acute renal failure. The aim of the present study was to explore whether rhEPO administration is protective against Cisp-induced oxidative damage and renal injury. Our results showed that Cisp induced a marked oxidative stress and renal failure. Administration of rhEPO (pre-, co- or postadministration with regard to Cisp) decreased oxidative damage induced by Cisp. Recombinant human EPO reduced malondialdehyde and protein carbonyl levels. Recombinant human EPO also prevented glutathione depletion and ameliorated the increased catalase activity induced by Cisp treatment. Furthermore, rhEPO restored creatinine and blood urea nitrogen levels increased by Cisp. We concluded that rhEPO administration especially in pretreatment condition protected rats against Cisp-induced renal oxidative stress and nephrotoxicity.

Vector-mediated expression of erythropoietin improves functional outcome after cervical spinal cord contusion injury

We evaluated the therapeutic effect of erythropoietin (EPO) delivered by direct injection of a nonreplicating herpes simplex virus (HSV)-based vector coding for EPO (vEPO) in a model of cervical hemicord contusion at C7. At 1 h after spinal cord injury (SCI), either vEPO or control vector carrying a reporter gene (vC) was injected into the cord above and below the lesion. Animals injected with vEPO showed a statistically significant improvement in the ipsilateral forelimb function, as measured by open-field evaluation of motor performance, forelimb reaching in the cylinder test and misplacement in grid walk. This correlated with preservation of gray matter in the area of the lesion. There was also mild but significant improvement of hindlimb motor function measured by Basso-Beattie-Bresnahan score and computerized gait analysis in vEPO compared with control vector-injected animals. Microtubule-associated protein tau, phosphorylated and nonphosphorylated neurofilament protein and the synaptic proteins synaptophysin and PSD-95 were all significantly increased in the spinal cord of vEPO-treated animals compared with control vector-injected animals. These data suggest that gene transfer of EPO after cervical SCI by minimizing the injury size and enhancing tissue sparing preserves large-caliber axons and promotes synaptogenesis.

Protective effect of recombinant human erythropoeitin against cisplatin cytotoxicity and genotoxicity in cultured Vero cells

Cisplatin is an effective agent against various solid tumors. Despite its effectiveness, the dose of cisplatin that can be administered is limited by its nephrotoxicity. Therefore, strategies for minimising the toxicity of cisplatin are of a clinical interest. The aim of this study was to investigate the protective effect of recombinant human erythropoietin (rhEPO) against the cytotoxicity and apoptosis induced by cisplatin in cultured Vero cells. Three types of treatments were performed: (i) cells were treated with rhEPO 24 h before exposure to cisplatin (pre-treatment), (ii) cells were treated with rhEPO and cisplatin simultaneously (co-treatment), (iii) cells were treated with rhEPO 24 h after exposure to cisplatin (post-treatment). Our results showed that rhEPO reduced cisplatin-induced cell mortality. Besides, rhEPO administration prevented cisplatin-induced DNA damage. Furthermore, rhEPO decreased the caspase-3 activity and pro-apoptotic factors levels (p53 and Bax) induced by cisplatin. It increased also the expression of the anti-apoptotic factor Bcl2 in Vero cells. Altogether, our results suggest a protective action of rhEPO against cisplatin cytotoxicity and genotoxicity via an anti-apoptotic process. The most protective effect was observed with rhEPO when it was administrated 24 h before cisplatin treatment.

Dose-dependent neurorestorative effects of delayed treatment of traumatic brain injury with recombinant human erythropoietin in rats

OBJECT

Delayed (24 hours postinjury) treatment with erythropoietin (EPO) improves functional recovery following experimental traumatic brain injury (TBI). In this study, the authors tested whether therapeutic effects of delayed EPO treatment for TBI are dose dependent in an attempt to establish an optimal dose paradigm for the delayed EPO treatment.

METHODS

Experimental TBI was performed in anesthetized young adult male Wistar rats using a controlled cortical impact device. Sham animals underwent the same surgical procedure without injury. The animals (8 rats/group) received 3 intraperitoneal injections of EPO (0, 1000, 3000, 5000, or 7000 U/kg body weight, at 24, 48, and 72 hours) after TBI. Sensorimotor and cognitive functions were assessed using a modified neurological severity score and foot fault test, and Morris water maze tests, respectively. Animals were killed 35 days after injury, and the brain sections were stained for immunohistochemical analyses.

RESULTS

Compared with the saline treatment, EPO treatment at doses from 1000 to 7000 U/kg did not alter lesion volume but significantly reduced hippocampal neuron loss, enhanced angiogenesis and neurogenesis in the injured cortex and hippocampus, and significantly improved sensorimotor function and spatial learning. The animals receiving the medium dose of 5000 U/kg exhibited a significant improvement in histological and functional outcomes compared with the lower or higher EPO dose groups.

CONCLUSIONS

These data demonstrate that delayed (24 hours postinjury) treatment with EPO provides dose-dependent neurorestoration, which may contribute to improved functional recovery after TBI, implying that application of an optimal dose of EPO is likely to increase successful preclinical and clinical trials for treatment of TBI.

Erythropoietin prevents vascular inflammation and oxidative stress in subtotal nephrectomized rat aorta beyond haematopoiesis

1. Recombinant human erythropoietin (rHuEPO) has been used for the management of renal anaemia. Recent studies suggest pleiotropic properties of rHuEPO in various tissues. The aim of the present study was to investigate the vasoprotective effects of rHuEPO in renal failure rats. 2. Rats subjected to 5/6 and 17/18 nephrectomy (5/6Nx and 17/18Nx rats, respectively) were treated with rHuEPO (75 U/kg, s.c.) three times a week for 2 weeks. 3. Administration of rHuEPO to 5/6Nx or 17/18Nx rats had no effect on systolic blood pressure or decreased haematocrit. However, rHuEPO treatment normalized proteinuria and creatinine clearance in 5/6Nx, but not in 17/18Nx, rats. 4. Vasodilation in response to acetylcholine in aortic rings was impaired in 5/6Nx and 17/18Nx rats and improved by rHuEPO in both groups. Immunohistochemical analysis revealed that macrophage infiltration into adventitial areas and the expression of osteopontin were enhanced in aortas from 5/6Nx and 17/18Nx rats, but that rHuEPO suppressed these effects. In addition, rHuEPO attenuated medial hyperplasia and NADPH oxidase-derived superoxide production in 5/6Nx and 17/18Nx rats. 5. Activation of the Akt signalling pathway was evident in rHuEPO-treated rats as the increased expression of phosphorylated Akt and glycogen synthase kinase-3β. Treatment with rHuEPO restored the expression of phosphorylated endothelial nitric oxide synthase in the aorta and urinary excretion of NO(x) in nephrectomized rats. 6. These results suggest that a low dose of rHuEPO results in the normalization of endothelial function, vascular inflammation and oxidative stress in rats with renal ablation beyond haematopoiesis. In addition, these vasoprotective effects are observed even in a state of deteriorating renal dysfunction.

Erythropoietin promotes neurovascular remodeling and long-term functional recovery in rats following traumatic brain injury

Erythropoietin (EPO) improves functional recovery after traumatic brain injury (TBI). This study was designed to investigate long-term (3 months) effects of EPO on brain remodeling and functional recovery in rats after TBI. Young male Wistar rats were subjected to unilateral controlled cortical impact injury. TBI rats were divided into the following groups: (1) saline group (n=7); (2) EPO-6h group (n=8); and (3) EPO-24h group (n=8). EPO (5000 U/kg in saline) was administered intraperitoneally at 6h, and 1 and 2 days (EPO-6h group) or at 1, 2, and 3 days (EPO-24h group) postinjury. Neurological function was assessed using a modified neurological severity score, footfault and Morris water maze tests. Animals were sacrificed at 3 months after injury and brain sections were stained for immunohistochemical analyses. Compared to the saline, EPO-6h treatment significantly reduced cortical lesion volume, while EPO-24h therapy did not affect the lesion volume (P<0.05). Both the EPO-6h and EPO-24h treatments significantly reduced hippocampal cell loss (P<0.05), promoted angiogenesis (P<0.05) and increased endogenous cellular proliferation (BrdU-positive cells) in the injury boundary zone and hippocampus (P<0.05) compared to saline controls. Significantly enhanced neurogenesis (BrdU/NeuN-positive cells) was seen in the dentate gyrus of both EPO groups compared to the saline group. Both EPO treatments significantly improved long-term sensorimotor and cognitive functional recovery after TBI. In conclusion, the beneficial effects of posttraumatic EPO treatment on injured brain persisted for at least 3 months. The long-term improvement in functional outcome may in part be related to the neurovascular remodeling induced by EPO.

Embryonic stem cells inhibit expression of erythropoietin in the injured spinal cord

Recent observations have demonstrated neuroprotective role of erythropoietin (Epo) and Epo receptor in the central nervous system. Here we examined Epo function in the murine spinal cord after transplantation of pluripotent mouse embryonic stem (ES) cells pre-differentiated towards neuronal type following spinal cord injury. Expression of Epo was measured at both mRNA and protein levels in the ES cells as well as in the spinal cords after 1 and 7 days. Our data demonstrated that expression of Epo mRNA, as well as its protein content, in ES cells was significantly decreased after differentiation procedure. In the spinal cords, analysis showed that Epo mRNA level was significantly decreased after 1 day of ES cell injections in comparison to media-injected control. Epo protein level detected by Western blot was diminished as well. Examination of Epo production in the injured spinal cords after media or ES cells injections by indirect immunofluorescence showed increased Epo-immunopositive staining after media injections 1 day after injection. In contrast, ES cell transplantation did not induce Epo expression. Seven days after ES cell injections, Epo-immunopositive cells' distribution in the ipsilateral side was not changed, while the intensity of immunostaining on the contralateral side was increased, approaching levels in control media-injected tissues. Our data let us to presume that previously described immediate positive effects of ES cells injected into the injured zone of spinal cord are not based on Epo, but on other factors or hormones, which should be elucidated further.

The neuroprotective effect of recombinant human erythropoietin via an antiapoptotic mechanism on hypoxic-ischemic brain injury in neonatal rats

PURPOSE

The neuroprotective effects of erythropoietin (EPO) have been recently shown in many animal models of brain injury, including hypoxic-ischemic (HI) encephalopathy, trauma, and excitotoxicity; however, limited data are available for such effects during the neonatal periods. Therefore, we investigated whether recombinant human EPO (rHuEPO) can protect against perinatal HI brain injury via an antiapoptotic mechanism.

METHODS

The left carotid artery was ligated in 7-day-old Sprague-Dawley (SD) rat pups (in vivo model). The animals were divided into 6 groups: normoxia control (NC), normoxia sham-operated (NS), hypoxia only (H), hypoxia+vehicle (HV), hypoxia+rHuEPO before a hypoxic insult (HE-B), and hypoxia+rHuEPO after a hypoxic insult (HE-A). Embryonic cortical neuronal cell culture of SD rats at 18 days gestation (in vitro model) was performed. The cultured cells were divided into 5 groups: normoxia (N), hypoxia (H), and 1, 10, and 100 IU/mL rHuEPO-treated groups.

RESULTS

In the in vivo model, Bcl-2 expressions in the H and HV groups were lower than those in the NC and NS groups, whereas those in the HE-A and HE-B groups were greater than those of the H and HV groups. The expressions of Bax and caspase-3 and the ratio of Bax/Bcl-2 were in contrast to those of Bcl-2. In the in vitro model, the patterns of Bcl-2, Bax, and caspase-3 expression and Bax/Bcl-2 ratio were similar to the results obtained in the in vivo model.

CONCLUSION

rHuEPO exerts neuroprotective effect against perinatal HI brain injury via an antiapoptotic mechanism.

Transport of epidermal growth factor in the stroke-injured brain

Stroke is a neurological disorder that currently has no cure. Intrathecal delivery of growth factors, specifically recombinant human epidermal growth factor (rhEGF), stimulates endogenous neural precursor cells in the subventricular zone (SVZ) and promotes tissue regeneration in animal models of stroke. In this model, rhEGF is delivered with an invasive minipump/catheter system, which causes trauma to the brain. A less invasive strategy is to deliver rhEGF from the brain cortex; however, this requires the protein to diffuse through the brain, from the site of injection to the SVZ. Although this method of delivery has great potential, diffusion is limited by rapid removal from the extracellular space and hence for successful translation into the clinic strategies are needed to increase the diffusion distance. Using integrative optical imaging we investigate diffusion of rhEGF vs. poly(ethylene glycol)-modified rhEGF (PEG-rhEGF) in brain slices of both uninjured and stroke-injured animals. For the first time, we quantitatively show that PEG modification reduces the rate of growth factor elimination by over an order of magnitude. For rhEGF this corresponds to a two to threefold increase in predicted brain penetration distance, which we confirm with in vivo data.

Cerebral malaria: mechanisms of brain injury and strategies for improved neurocognitive outcome

Cerebral malaria is the most severe neurological complication of infection with Plasmodium falciparum. With >575,000 cases annually, children in sub-Saharan Africa are the most affected. Surviving patients have an increased risk of neurological and cognitive deficits, behavioral difficulties, and epilepsy making cerebral malaria a leading cause of childhood neurodisability in the region. The pathogenesis of neurocognitive sequelae is poorly understood: coma develops through multiple mechanisms and there may be several mechanisms of brain injury. It is unclear how an intravascular parasite causes such brain injury. Understanding these mechanisms is important to develop appropriate neuroprotective interventions. This article examines possible mechanisms of brain injury in cerebral malaria, relating this to the pathogenesis of the disease, and explores prospects for improved neurocognitive outcome.

Erythropoietin improves histological and functional outcomes after traumatic brain injury in mice in the absence of the neural erythropoietin receptor

Erythropoietin (EPO), essential for erythropoiesis, provides neuroprotection. The EPO receptor (EPOR) is expressed in both neural and non-neural cells in the brain. This study was designed to test the hypothesis that EPO provides beneficial therapeutic effects, even in the absence of the neural EPOR. In this study, EPOR-null mice were rescued with selective EpoR expression driven by the endogenous EpoR promoter in hematopoietic tissue, but not in the neural cells. Anesthetized young adult female EPOR-null and wild-type mice were subjected to traumatic brain injury (TBI) induced by controlled cortical impact. EPO (5000 U/kg) or saline was intraperitoneally administered at 6 h and 3 and 7 days post-injury. Sensorimotor and spatial learning functions were assessed. Expression of EPOR and its downstream signal proteins were evaluated by Western blot analysis. Our data demonstrated that EPO treatment significantly reduced cortical tissue damage and hippocampal cell loss, and improved spatial learning following TBI in both the wild-type and EPOR-null mice. EPO treatment significantly improved sensorimotor functional recovery, with better outcomes in the wild-type mice. EPO treatment upregulated anti-apoptotic proteins (p-Akt and Bcl-XL) in the ipsilateral hippocampus and cortex of the injured wild-type and EPOR-null mice. These data demonstrate that EPO significantly provides neuroprotection following TBI, even in the absence of EPOR in the neural cells, suggesting that its therapeutic benefits may be mediated through vascular protection.

Induction of nitric oxide by erythropoietin is mediated by the β common receptor and requires interaction with VEGF receptor 2

Vascular endothelial growth factor (VEGF) and erythropoietin (EPO) have profound effects on the endothelium and endothelial progenitor cells (EPCs), which originate from the bone marrow and differentiate into endothelial cells. Both EPO and VEGF have demonstrated an ability to increase the number and performance properties of EPCs. EPC behavior is highly dependent on nitric oxide (NO), and both VEGF and EPO can stimulate intracellular NO. EPO can bind to the homodimeric EPO receptor (EPO-R) and the heterodimeric receptor, EPO-R and the common β receptor (βC-R). Although VEGF has several receptors, VEGF-R2 appears most critical to EPC function. We demonstrate that EPO induction of NO is dependent on the βC-R and VEGF-R2, that VEGF induction of NO is dependent on the expression of the βC-R, and that the βC-R and VEGF-R2 interact. This is the first definitive functional and structural evidence of an interaction between the 2 receptors and has implications for the side effects of EPO.

Cardiovascular effects of erythropoietin an update

Erythropoietin (EPO) is a therapeutic product of recombinant DNA technology and it has been in clinical use as stimulator of erythropoiesis over the last two decades. Identification of EPO and its receptor (EPOR) in the cardiovascular system expanded understanding of physiological and pathophysiological role of EPO. In experimental models of cardiovascular and cerebrovascular disorders, EPO exerts protection either by preventing apoptosis of cardiac myocytes, smooth muscle cells, and endothelial cells, or by increasing endothelial production of nitric oxide. In addition, EPO stimulates mobilization of progenitor cells from bone marrow thereby accelerating repair of injured endothelium and neovascularization. A novel signal transduction pathway involving EPOR--β-common heteroreceptor is postulated to enhance EPO-mediated tissue protection. A better understanding of the role of β-common receptor signaling as well as development of novel analogs of EPO with enhanced nonhematopoietic protective effects may expand clinical application of EPO in prevention and treatment of cardiovascular and cerebrovascular disorders.

The erythropoietin and regenerative medicine: a lesson from fish

BACKGROUND

Erythropoietin (EPO), the main haematopoietic growth factor for the proliferation and differentiation of erythroid progenitor cells, is also known for its angiogenic and regenerative properties.

MATERIALS AND METHODS

In this study, we aimed to test the regenerative effects of EPO administration in an experimental model of Sea bass (Dicentrarchus labrax) subjected to amputation of the caudal fin.

RESULTS

Erythropoietin-treated fishes (3000 UI of human recombinant EPO-alpha immediately after cutting and after 15 days) showed an increased growth rate of their fins compared with those untreated (anova variance: P: 0.01 vs. P: 0.04). By analysing fin length at established times (15 and 30 days after cut), EPO-treated fishes always showed an increased length compared with untreated ones (T-15: 1.1 +/- 0.2 vs. 0.7 +/- 0.2 cm, P: 0.03; T-30: 1.9 +/- 0.3 vs. 1.2 +/- 0.2 cm, P: 0.01). Moreover, exogenous EPO administration induced an enormous increase in EPO-blood levels at each observation time (T-15: 2240 +/- 210 vs. 16.7 +/- 1.8 mU mL(-1), P < 0.001; T-30: 2340 +/- 190 vs. 17.1 +/- 1.9 mU mL(-1), P < 0.001), whereas these levels remained quite unmodified in untreated fishes. Immunochemical analyses performed by confocal laser scanning microscopic observations showed an increased expression of EPO-receptors and PECAM-1 (an endothelial surface marker of vessels sprout) in the regenerating tissue, whereas no signs of inflammation or fibrosis were recognisable.

CONCLUSIONS

All these findings confirm EPO as a new factor involved in regenerative processes, also suggesting a potential, future utility for new therapeutical applications in the field of human regenerative medicine.

Therapeutic effects of erythropoietin on histological and functional outcomes following traumatic brain injury in rats are independent of hematocrit

Erythropoietin (EPO) provides neuroprotection and neurorestoration after traumatic brain injury (TBI). The EPO doses used for treatment of TBI significantly increase hematocrit, which may affect the efficacy of EPO therapy for TBI. The aim of this study was to investigate whether normalization of hematocrit would affect EPO efficacy for treatment of TBI. Young adult male Wistar rats were randomly divided into four groups: (1) Sham group (n=6); (2) TBI+ saline group (n=6); (3) TBI+ EPO group (n=6); and (4) TBI+ EPO+ hemodilution group (n=7). TBI was induced by controlled cortical impact over the left parietal cortex. EPO (5,000 U/kg) or saline was administered intraperitoneally at days 1, 2, and 3 postinjury. Neurological function was assessed using a modified neurological severity score (mNSS), footfault and the Morris water maze (MWM) tests. Animals were sacrificed 35 days after injury, and brain sections were stained for immunohistochemistry. Compared to the saline treatment, EPO treatment significantly reduced hippocampal cell loss, enhanced angiogenesis and neurogenesis in the injured cortex and hippocampus, and significantly improved sensorimotor functional outcome (lowered mNSS and foot faults) and spatial learning (MWM test). Normovolemic hemodilution effectively normalized the hematocrit and did not significantly affect the histological and functional outcome of EPO therapy for TBI. These data for the first time demonstrate that increased hematocrit does not affect therapeutic effects of EPO on histological and long-term functional outcomes in rats after TBI and also suggest that neuroprotection and neurorestoration of EPO treatment are independent of hematocrit.

Emerging treatments for traumatic brain injury

BACKGROUND

This review summarizes promising approaches for the treatment of traumatic brain injury (TBI) that are in either preclinical or clinical trials.

OBJECTIVE

The pathophysiology underlying neurological deficits after TBI is described. An overview of select therapies for TBI with neuroprotective and neurorestorative effects is presented.

METHODS

A literature review of preclinical TBI studies and clinical TBI trials related to neuroprotective and neurorestorative therapeutic approaches is provided.

RESULTS/CONCLUSION

Nearly all Phase II/III clinical trials in neuroprotection have failed to show any consistent improvement in outcome for TBI patients. The next decade will witness an increasing number of clinical trials that seek to translate preclinical research discoveries to the clinic. Promising drug- or cell-based therapeutic approaches include erythropoietin and its carbamylated form, statins, bone marrow stromal cells, stem cells singularly or in combination or with biomaterials to reduce brain injury via neuroprotection and promote brain remodeling via angiogenesis, neurogenesis, and synaptogenesis with a final goal to improve functional outcome of TBI patients. In addition, enriched environment and voluntary physical exercise show promise in promoting functional outcome after TBI, and should be evaluated alone or in combination with other treatments as therapeutic approaches for TBI.

Erythropoietin: a possible cytoprotective cytokine in acute necrotizing pancreatitis

BACKGROUND/PURPOSE

Despite decades of research and clinical trials, a specific therapeutic treatment for acute pancreatitis (AP) has yet to be developed. The aim of the present study was to investigate the effects of erythropoietin on the severity of taurocolic acid-induced acute necrotizing pancreatitis.

METHODS

Forty-seven male Wistar albino rats were randomized into seven experimental groups. In group I, animals were sham-operated (n = 5). In groups II, III, IV, IIepo, IIIepo, and IVepo, AP was induced by sodium taurodeoxycholate treatment (n = 7). In groups II, III, and IV, 1 ml normal saline and in groups IIepo, IIIepo, and IVepo, 1000 U/kg body weight erythropoietin (EPO) was administered intramuscularly immediately after the induction of AP. Animals were killed at 24, 48, and 72 h postoperatively. Histopathological and biochemical evaluations were performed.

RESULTS

The serum levels of interleukin-6 (IL-6) and tissue levels of malondialdehyde were found to be significantly lower in EPO-administered groups when compared with the levels in groups without EPO treatment. The severity of pancreatic edema, acinar necrosis, inflammation, and perivascular infiltrate were reduced in all the EPO groups compared with the no-treatment groups.

CONCLUSIONS

Our findings may reflect the possible cytoprotective effect of EPO in acute necrotizing pancreatitis.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Erythropoietin improves brain mitochondrial function in rats after traumatic brain injury

Mitochondria play a central role in cellular energetics, calcium homeostasis and apoptosis. Our previous study demonstrates traumatic brain injury induces brain mitochondrial dysfunction after injury. Preservation and/or restoration of mitochondrial function may be one of the strategies for neuroprotection. Erythropoietin, a hormone for erythropoiesis, also provides tissue protection against traumatic brain injury and stroke. The present study was undertaken to evaluate the effect of erythropoietin on traumatic brain injury-induced brain mitochondrial dysfunction. Traumatic brain injury decreased rates of respiration at the active state (state 3), increased that at the resting state (state 4) and consequently decreased respiratory control index (state 3/state 4 ratio) and the efficiency of ATP synthesis (the amount of ADP phosphorylated by inorganic phosphate divided by the amount of oxygen consumed during state 3 respiration). Erythropoietin administered intraperitoneally 30 minutes post-injury at 1000 U/kg partially improved mitochondrial function at day 1 post-injury. However, erythropoietin-induced improvement was not sustained at day 7 post-injury. Erythropoietin at 2000 or 5000 U/kg restored states 3 and 4 examined at day 1 post-injury to the sham levels. Consequently, the energy coupling capacities, such as respiratory control index and/or the efficiency of ATP synthesis, were also improved. The beneficial effect of erythropoietin at these doses persisted for at least 7 days post-injury. The beneficial effect of erythropoietin on brain mitochondrial function was observed with a wide therapeutic window from 5 minutes to 6 hours post-injury. Our data, for the first time, demonstrate that erythropoietin treatment restores brain mitochondrial function after traumatic brain injury, which will enhance cellular energy generation and reduce oxidative stress, strongly supporting erythropoietin as a promising agent for the therapeutic treatment of traumatic brain injury.

Can erythropoietin be used to prevent brain damage in cerebral malaria?

Erythropoietin (Epo) modulates the survival of developing erythroid cells and the production of new erythrocytes in the bone marrow and is a key molecule in the adaptation to hypoxia and anaemia. Epo receptors have been found to be widely expressed on non-haematopoietic cells, and Epo has been shown to have diverse actions (in particular, preventing ischaemic damage to tissues of the central nervous system). Recently, Epo has been shown to improve the outcome in a murine model of malaria, and high plasma levels of Epo in children with cerebral malaria were associated with a better outcome. Here, we review the biological importance of Epo, its mechanisms of action and the rationale for the proposed use of Epo as an adjunct treatment in cerebral malaria.

The cytokine basis of cachexia and its treatment: are they ready for prime time?

Cachexia is a hypercatabolic condition that is often associated with the terminal stages of many diseases, in which the patient's resting metabolic rate is high and loss of muscle and fat tissue mass occur at an alarming rate. The patient also usually has concurrent anorexia, amplifying the wasting syndrome that is cachexia. The greater the extent of cachexia (regardless of underlying disease), the worse the prognosis. Efforts to treat cachexia over the years have fallen short of satisfactorily reversing the wasting syndrome. This article reviews the pathophysiology of cachexia, enumerating the different pro-inflammatory cytokines that contribute to the syndrome and attempting to illustrate their interwoven pathways. We also review the different treatments that have been explored, as well as the recent literature addressing the use of anti-cytokine therapy to treat cachexia.

Erythropoietin promotes hepatic regeneration after extended liver resection in rats

BACKGROUND AND AIM

It has been proven in various animal studies that recombinant human erythropoietin (rHuEPO) protects renal, cardiac and neuronal, as well as hepatic, tissue from ischemia, and promotes regeneration of adult central nervous system neurons. To date, no data are available as to whether rHuEPO has the ability to stimulate liver regeneration after liver resection.

METHODS

Rats undergoing 70% or 90% hepatectomy received an intraportalvenous administration (i.p.) of rHuEPO prior to resection or a subcutaneous injection (s.c.) for 3 days postoperatively, control animals were treated with surgery and saline injection only. Regeneration capacity of remnant livers was studied over 7 days by histology and immunohistochemistry (Ki-67, proliferating cell nuclear antigen [PCNA]). Polymerase chain reaction was carried out to measure transforming growth factor beta (TGF-beta), hypoxia induced factor (HIF), signal transducing activator 3 and vascular endothelial growth factor.

RESULTS

Ten-day survival in rats undergoing 90% hepatectomy significantly increased in i.p.-pretreated animals. After 70% hepatectomy the mitotic index was significantly increased in both rHuEPO-treated groups. These data were confirmed by PCNA and Ki-67 expression, which was significantly increased in the treated groups 24 h and 2 days after liver resection. TGF-beta and HIF mRNA both were upregulated in control animals 3 h after surgery.

CONCLUSION

rHuEPO effectively increased liver regeneration in rats after 70% liver resection and enhanced survival after 90% hepatectomy. Thus, rHuEPO may increase the regenerative capacity after major hepatectomy.

Cytokines and Brain Injury: Invited Review

The brain reacts to injury or disease by cascades of cellular and molecular responses. Evidence suggests that immune-inflammatory processes are key elements in the physiopathological processes associated with brain injury or damage. Cytokines are among major mediators implicated in these processes. Cytokine responses in the initial phase of brain injury might have a role in aggravating brain damage. However, in later stages, these molecular mediators might contribute to recovery or repair. Hemodynamic stabilization and optimalization of oxygen delivery to the brain remain cornerstones in the management of acute brain injury. New approaches might use anticytokine therapy to limit progression and halt or attenuate secondary brain damage. Progress toward such novel neuroprotection strategies, however, awaits better understanding of the optimal timing and dosing of those neuromodulatory therapies and better knowledge of the numerous interactions of those mediators. This also requires understanding of how and when precisely immune mechanisms shift from noxious to protective or restorative actions.