Bench-to-bedside review: Erythropoietin and its derivatives as therapies in critical care

Iron and erythropoietin to heal and recover after intensive care (ITHRIVE): A pilot randomised clinical trial

Objective

To determine the feasibility of a pivotal randomised clinical trial of intravenous (IV) iron and erythropoietin in adult survivors of critical illness with anaemia requiring treatment in the intensive care unit.

Design

An investigator-initiated, parallel group, placebo-controlled, randomised feasibility trial.

Setting

A tertiary intensive care unit (ICU) in Perth, Western Australia.

Participants

Adults with anaemia (haemoglobin <100 g/L), requiring ICU-level care for more than 48 h, and likely to be ready for ICU discharge within 24 h.

Interventions

A single dose of IV ferric carboxymaltose and Epoetin alfa (active group) or an equal volume of 0.9% saline (placebo group).

Main outcome measures

Study feasibility was considered met if the pilot achieved a recruitment rate of ≥2 participants per site per month, ≥90% of participants received their allocated study treatment, and≥ 90% of participants were followed up for the proposed pivotal trial primary outcome - days alive and at home to day 90 (DAH90).

Results

The 40-participant planned sample size included twenty in each group and was enrolled between 1/9/2021 and 2/3/2022. Participants spent a median of 3.4 days (interquartile range 2.8-5.1) in the ICU prior to enrolment and had a mean baseline haemoglobin of 83.7 g/L (standard deviation 6.7). The recruitment rate was 6.7 participants per month [95% confidence interval (CI) 4.8-9.0], DAH90 follow-up was 100% (95% CI 91.2%-100%), and 39 (97.5%, 95% CI 86.8%-99.9%) participants received the allocated study intervention. No serious adverse events were reported.

Conclusion

The iron and erythropoietin to heal and recover after intensive care (ITHRIVE) pilot demonstrated feasibility based on predefined participant recruitment, study drug administration, and follow-up thresholds.

Asialo-rhuEPO as a Potential Neuroprotectant for Ischemic Stroke Treatment

Neuroprotective drugs to protect the brain against cerebral ischemia and reperfusion (I/R) injury are urgently needed. Mammalian cell-produced recombinant human erythropoietin (rhuEPOM) has been demonstrated to have excellent neuroprotective functions in preclinical studies, but its neuroprotective properties could not be consistently translated in clinical trials. The clinical failure of rhuEPOM was thought to be mainly due to its erythropoietic activity-associated side effects. To exploit its tissue-protective property, various EPO derivatives with tissue-protective function only have been developed. Among them, asialo-rhuEPO, lacking terminal sialic acid residues, was shown to be neuroprotective but non-erythropoietic. Asialo-rhuEPO can be prepared by enzymatic removal of sialic acid residues from rhuEPOM (asialo-rhuEPOE) or by expressing human EPO gene in glycoengineered transgenic plants (asialo-rhuEPOP). Both types of asialo-rhuEPO, like rhuEPOM, displayed excellent neuroprotective effects by regulating multiple cellular pathways in cerebral I/R animal models. In this review, we describe the structure and properties of EPO and asialo-rhuEPO, summarize the progress on neuroprotective studies of asialo-rhuEPO and rhuEPOM, discuss potential reasons for the clinical failure of rhuEPOM with acute ischemic stroke patients, and advocate future studies needed to develop asialo-rhuEPO as a multimodal neuroprotectant for ischemic stroke treatment.

A Novel Plant-Produced Asialo-rhuEPO Protects Brain from Ischemic Damage Without Erythropoietic Action

Mammalian cell-produced recombinant human erythropoietin (rhuEPO^M) has been shown to be a multimodal neuroprotectant targeting an array of key pathological mechanisms in experimental stroke models. However, the rhuEPO^M clinical trials were terminated due to increased risk of thrombosis, largely ascribed to its erythropoietic function. We recently took advantage of a plant-based expression system lacking sialylation capacity to produce asialo-rhuEPO^P, a rhuEPO derivative without sialic acid residues. In the present study, we proved that asialo-rhuEPO^P is non-erythropoietic by repeated intravenous injection (44 μg/kg bw) in mice showing no increase in hemoglobin levels and red blood cell counts, and confirmed that it is non-immunogenic by measuring humoral response after immunizing the mice. We demonstrate that it is neuroprotective in a cerebral ischemia and reperfusion (I/R) mouse model, exhibiting ~ 50% reduction in cerebral infarct volume and edema, and significant improvement in neurological deficits and histopathological outcome. Our studies further revealed that asialo-rhuEPO^P, like rhuEPO^M, displays pleiotropic neuroprotective effects, including restoring I/R-interrupted mitochondrial fission and fusion proteins, preventing I/R injury-induced increase in mitophagy and autophagy markers, and inhibiting apoptosis to benefit nerve cell survival. Most importantly, asialo-rhuEPO^P lacking erythropoietic activity and immunogenicity holds great translational potential as a multimodal neuroprotectant for stroke treatment.

Lentiviral delivery of human erythropoietin attenuates hippocampal atrophy and improves cognition in the R6/2 mouse model of Huntington's disease

Huntington's disease (HD) is an incurable neurodegenerative disorder caused by a trinucleotide (CAG) repeat expansion in the huntingtin gene (HTT). The R6/2 transgenic mouse model of HD expresses exon 1 of the human HTT gene with approximately 150 CAG repeats. R6/2 mice develop progressive behavioural abnormalities, impaired neurogenesis, and atrophy of several brain regions. In recent years, erythropoietin (EPO) has been shown to confer neuroprotection and enhance neurogenesis, rendering it a promising molecule to attenuate HD symptoms. In this study, the therapeutic potential of EPO was evaluated in female R6/2 transgenic mice. A single bilateral injection of a lentivirus encoding human EPO (LV-hEPO) was performed into the lateral ventricles of R6/2 mice at disease onset (8 weeks of age). Control groups were either untreated or injected with a lentivirus encoding green fluorescent protein (LV-GFP). Thirty days after virus administration, hEPO mRNA and protein were present in injected R6/2 brains. Compared to control R6/2 mice, LV-hEPO-treated R6/2 mice exhibited reduced hippocampal atrophy, increased neuroblast branching towards the dentate granular cell layer, and improved spatial cognition. Our results suggest that LV-hEPO administration may be a promising strategy to reduce cognitive impairment in HD.

MEPO promotes neurogenesis and angiogenesis but suppresses gliogenesis in mice with acute ischemic stroke

Previously study has proved the non-erythropoietic mutant erythropoietin (MEPO) exerted neuroprotective effects against ischemic cerebral injury, with an efficacy similar to that of wild-type EPO. This study investigates its effects on neurogenesis, angiogenesis, and gliogenesis in cerebral ischemic mice. Male C57BL/6 mice were subjected to middle cerebral artery occlusion (MCAO) and reperfusion. EPO (5000 U/kg), MEPO (5000 U/kg) or equal volume of normal saline was injected intraperitoneally. Neurological function was evaluated by Rota-rod test, Neurological severity scores (NSS) and Adhesive removal test. After ischemia and reperfusion (I/R), the survival rate, brain tissue loss, neurogenesis, angiogenesis and gliogenesis were detected by Nissl staining, Immunofluorescence and Western blot, respectively. The results shown that MEPO significantly increased survival rate, reduced brain tissue loss, and improved neurological function after MCAO (P < 0.05). Furthermore, MEPO obviously enhanced the proliferation of neuronal precursors (DCX) and promoted its differentiation into mature neurons (NeuN) (P < 0.05). In addition, compared to normal saline treatment mice, MEPO increased the number of BrdU-positive cells in the cerebral vasculature (P < 0.05). Whereas, MEPO treatment also reduced the numbers of newly generated astrocytes (GFAP) and microglia (Iba1) (P < 0.05). Among all the tests in this study, there was no significant difference between EPO group and MEPO group. Taken together, MEPO promoted the regeneration of neurons and blood vessels in peripheral area of infarction, and suppressed the gliogenesis, thus promoting neurogenesis, improving neurological function and survival rate. Our findings suggest that the MEPO may be a therapeutic drug for ischemic stroke intervention.

Erythropoietin Enhanced Recovery After Traumatic Nerve Injury: Myelination and Localized Effects

PURPOSE

We previously found that administration of erythropoietin (EPO) shortens the course of recovery after experimental crush injury to the mouse sciatic nerve. The course of recovery was more rapid than would be expected if EPO's effects were caused by axonal regeneration, which raised the question of whether recovery was instead the result of promoting remyelination and/or preserving myelin on injured neurons. This study tested the hypothesis that EPO has a direct and local effect on myelination in vivo and in vitro.

METHODS

Animals were treated with EPO after standard calibrated sciatic nerve crush injury; immunohistochemical analysis was performed to assay for myelinated axons. Combined in vitro neuron-Schwann cell co-cultures were performed to assess EPO-mediated effects directly on myelination and putative protective effects against oxidative stress. In vivo local administration of EPO in a fibrin glue carrier was used to demonstrate early local effects of EPO treatment well in advance of possible neuroregenerative effects.

RESULTS

Systemic Administration of EPO maintained more in vivo myelinated axons at the site of nerve crush injury. In vitro, EPO treatment promoted myelin formation and protected myelin from the effects of nitric oxide exposure in co-cultures of Schwann cells and dorsal root ganglion neurons. In a novel, surgically applicable local treatment using Food and Drug Administration-approved fibrin glue as a vehicle, EPO was as effective as systemic EPO administration at time points earlier than those explainable using standard models of neuroregeneration.

CONCLUSIONS

In nerve crush injury, EPO may be exerting a primary influence on myelin status to promote functional recovery.

CLINICAL RELEVANCE

Mixed injury to myelin and axons may allow the opportunity for the repurposing of EPO for use as a myeloprotective agent in which injuries spare a requisite number of axons to allow early functional recovery.

Erythropoietin reduces acute lung injury and multiple organ failure/dysfunction associated to a scald-burn inflammatory injury in the rat

Erythropoietin (EPO) is an endogenous regulator of erythropoiesis and is given exogenously as a replacement therapy for selected red blood cell disorders. In the past years, EPO has been emerging as a multifunctional, cytoprotective cytokine with anti-apoptotic, anti-inflammatory, and immunomodulatory properties. We aimed to evaluate the cytoprotective effect of rhEPO (recombinant human EPO) treatment on a rat model of multiorgan dysfunction induced by thermal injury. rhEPO was administered at 1000 U/kg (i.v.) 5 min prior to induction of injury and significantly reduced multiorgan dysfunction markers (liver, kidney, lung, serum cytokine levels). In the lung, rhEPO reduced: histological signs of tissue injury, inflammatory/injury markers on the bronchoalveolar fluid, neutrophil chemotaxis/infiltration, GSK-3β activation, and apoptosis. Our study showed that erythropoietin has the potential to exhibit pleiotropic cytoprotective effects and that it might be an interesting pharmacological strategy in the modulation of acute lung injury, such as the one associated to severe burn.

Expression of erythropoietin and its receptor in kidneys from normal and cyclosporine-treated rats

Long-term treatment with cyclosporine A (CsA) is associated with various types of complications; however, CsA-induced anemia has not been reported. The present study examined the impact of CsA on hematopoietic parameters and intrarenal expression of erythropoietin (EPO) and the EPO receptor (EPOR) in a rat model of chronic CsA nephrotoxicity. Sprague-Dawley rats were fed a low-salt diet (0.05% sodium) and were treated daily for 4 weeks with vehicle (olive oil 1 mL/kg subcutaneously) or CsA (15 mg/kg subcutaneously). The expression of EPO and EPOR was evaluated by immunohistochemistry and immunoblotting, and hematopoietic parameters were assessed by measuring blood hemoglobin and hematocrit levels, and these variables were compared between treatment groups. Renal function, oxidative stress, histopathology (tubulointerstitial fibrosis), apoptotic cell death, and expression of transforming growth factor β-inducible gene-h3 (βig-h3) were also compared between treatment groups. In kidneys from vehicle-treated rats, endogenous EPO and EPOR protein were expressed constitutively in the outer stripe of the outer medulla and the cortex. EPO protein expression decreased significantly in kidneys from CsA-treated rats. By contrast, EPOR expression was higher in kidneys from CsA-treated rats than in vehicle-treated rats. These changes were accompanied by decreases in serum hemoglobin and hematocrit levels and correlated with the number of cells positive for terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (r = -0.769, P = .003) and βig-h3 protein expression (r = -0.910, P < .001). Long-term treatment with CsA suppresses renal endogenous EPO expression, resulting in anemia. Increases in apoptotic cell death and βig-h3 expression are closely associated with inhibition of EPO expression in chronic CsA nephrotoxicity.

Impact of erythropoietin on intensive care unit patients

Anemia is common in intensive care unit (ICU) patients. Red blood cell (RBC) transfusions are mainstays of their treatment and can be life-saving. Allogeneic blood components inherently bear risks of infection and immune reactions. Although these risks are rare in developed countries, recombinant human erythropoietin (rhEpo) and other erythropoiesis-stimulating agents (ESAs) have been considered alternative anti-anemia treatment options. As summarized herein, however, most of the clinical studies suggest that ESAs are not usually advisable in ICU patients unless approved indications exist (e.g., renal disease). First, ESAs act in a delayed way, inducing an increase in reticulocytes only after a lag of 3-4 days. Second, many critically ill patients present with ESA resistance as inflammatory mediators impair erythropoietic cell proliferation and iron availability. Third, the ESA doses used for treatment of ICU patients are very high. Fourth, ESAs are not legally approved for general use in ICU patients. Solely in distinct cases, such as Jehovah's Witnesses who refuse allogeneic blood transfusions due to religious beliefs, ESAs may be considered an exceptional therapy.

Post-ischemic continuous infusion of erythropoeitin enhances recovery of lost memory function after global cerebral ischemia in the rat

Background

Erythropoietin (EPO) and its covalently modified analogs are neuroprotective in various models of brain damage and disease. We investigated the effect on brain damage and memory performance, of a continuous 3-day intravenous infusion of EPO, starting 20 min after a transient 10 minute period of global cerebral ischemia in the rat.

Results

We found no effect on selective neuronal damage in the CA1 region of the hippocampus, neocortical damage and damage to the striatum assessed at 7 days after ischemia. Also, no differences were observed in sensori-motor scores between EPO treated and saline treated ischemic animals. In contrast, memory performance was significantly improved in the EPO treated group. Saline treated injured animals (n = 7) failed in a test assessing recovery of spatial memory (6/6 and 5/6), while EPO treated animals had few and none failures (0/7 and 1/7).

Conclusion

We conclude that although post-ischemic treatment with EPO is not neuroprotective in a model of cardiac arrest brain ischemia, its markedly positive effect on brain plasticity and recovery of memory function warrants consideration as treatment of cardiac arrest patients.

Erythropoietin and autoimmune neuroinflammation: lessons from experimental autoimmune encephalomyelitis and experimental autoimmune neuritis

Erythropoietin (EPO) is known to have numerous biological functions. While its primary function is during haematopoiesis, recent studies have shown that EPO plays important role in cytoprotection, immunomodulation, and antiapoptosis. These secondary functions of EPO are integral to tissue protection following hypoxic injury, ischemia-reperfusion injury, and spinal cord injury in the central nervous system. This review focuses on experimental evidence documenting the neuroprotective effects of EPO in organ-specific autoimmune nervous system disorders such as experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune neuritis (EAN). In addition, the immunomodulatory role of EPO in the pathogenesis of EAE and EAN animal models of human multiple sclerosis and Guillain-Barré syndrome, respectively, will be discussed.

Erythropoietin in the critically ill: do we ask the right questions?

There is a plethora of experimental data on the potential therapeutic benefits of recombinant human erythropoietin (rhEPO) and its synthetic derivatives in critical care medicine, in particular in ischemia/reperfusion injury. Most of the recent clinical trials have not shown clear benefits, and, in some patients, EPO-aggravated morbidity and mortality was even reported. Treatment with rhEPO has been successfully used in patients with anemia resulting from chronic kidney disease, but even a subset of this patient population does not adequately respond to rhEPO therapy. The following viewpoint uses rhEPO as an example to highlight the possible pitfalls in current practice using young healthy animals for the evaluation of therapies to treat patients of variable age and underlying chronic co-morbidity.