The Role of PI3K/AKT and MAPK Signaling Pathways in Erythropoietin Signalization

Erythropoietin (EPO) is a glycoprotein cytokine known for its pleiotropic effects on various types of cells and tissues. EPO and its receptor EPOR trigger signaling cascades JAK2/STAT5, MAPK, and PI3K/AKT that are interconnected and irreplaceable for cell survival. In this article, we describe the role of the MAPK and PI3K/AKT signaling pathways during red blood cell formation as well as in non-hematopoietic tissues and tumor cells. Although the central framework of these pathways is similar for most of cell types, there are some stage-specific, tissue, and cell-lineage differences. We summarize the current state of research in this field, highlight the novel members of EPO-induced PI3K and MAPK signaling, and in this respect also the differences between erythroid and non-erythroid cells.     

Erythropoietin Ameliorates Neonatal Hypoxia-Ischemia-Induced Neurobehavioral Deficits,Neuroinflammation, and Hippocampal Injury in the Juvenile Rat

The hematopoietic growth factor erythropoietin (EPO) has been shown to be neuroprotective against hypoxia-ischemia (HI) in Postnatal Day 7 (P7)–P10 or adult animal models. The current study was aimed to determine whether EPO also provides long-lasting neuroprotection against HI in P5 rats, which is relevant to immature human infants. Sprague-Dawley rats at P5 were subjected to right common carotid artery ligation followed by an exposure to 6% oxygen with balanced nitrogen for 1.5 h. Human recombinant EPO (rEPO, at a dose of 5 units/g) was administered intraperitoneally one hour before or immediately after insult, followed by additional injections at 24 and 48 h post-insult. The control rats were injected with normal saline following HI. Neurobehavioral tests were performed on P8 and P20, and brain injury was examined on P21. HI insult significantly impaired neurobehavioral performance including sensorimotor, locomotor activity and cognitive ability on the P8 and P20 rats. HI insult also resulted in brain inflammation (as indicated by microglia activation) and neuronal death (as indicated by Jade B positive staining) in the white matter, striatum, cortex, and hippocampal areas of the P21 rat. Both pre- and post-treatment with rEPO significantly improved neurobehavioral performance and protected against the HI-induced neuronal death, microglia activation (OX42+) as well as loss of mature oligodendrocytes (APC-CC1+) and hippocampal neurons (Nissl+). The long-lasting protective effects of rEPO in the neonatal rat HI model suggest that to exert neurotrophic activity in the brain might be an effective approach for therapeutic treatment of neonatal brain injury induced by hypoxia-ischemia.     

Mortality risk in hemodialysis patients according to anemia control and erythropoietin dosing

There is no consensus about the toxicity of erythropoiesis‐stimulating agents among hemodialysis patients. We aimed to calculate the risk of death according to anemia control and erythropoietin (EPO) dosing among end‐stage renal disease patients undergoing hemodialysis. We retrospectively studied 156 end‐stage renal disease patients on hemodialysis from a single renal unit during 12 months. Participants were classified according to anemia control into four groups: excellent (A), good (B), moderate (C) and bad (D) control. They were also classified according to EPO dosing into two groups: usual and high EPO dosing. The Cox proportional hazards regression model, adjusted for the difference in age, sex, time on dialysis, comorbidity, albumin, and Kt/V index, was performed to calculate the risk of death according to anemia control and EPO dosing profiles. Multivariate analysis by backward stepwise logistic regression was used to calculate the risk of death according to the variables that differed in the comparison between survivors and nonsurvivors. The hazard ratio of death was not significant according to anemia control profile C/D vs. A/B, but hazard ratio was 2.967 (95% confidence interval [CI] = 1.132–7.777; P = 0.027) for high EPO dosing profile patients. The multivariate analysis showed comorbidity (odds ratio [OR] = 8.958; 95% CI = 2.843–26.223; P < 0.001], high EPO dosing profile (OR = 5.172; 95% CI = 1.663–16,081; P = 0.005), age (OR = 1.056; 95% CI = 1.020–1.094; P = 0.002), and mean hemoglobin (OR = 0.435; 95% CI = 0.267–0.709; P = 0.001) to be predictive of death. Even though we cannot conclude that mortality risk is due to EPO toxicity, hemodialysis patients using high EPO dosing must be seen as at risk.     

乳汁中的促红细胞生成素及其对婴幼儿的生理作用

本文简介乳汁EPO的结构、功能及其测定方法,重点关注母乳EPO影响新生幼仔生理功能的研究进展,这些研究显示:母乳EPO在新生幼仔体内红血球生成、肠道发育、神经营养以及免疫调节等方面均有重要作用。     

Erythropoietin‐stimulating agents in the management of anemia of end‐stage renal disease patients on regular hemodialysis: A prospective randomized comparative study from Qatar

Despite extensive use, to the best of our knowledge, no trial has simultaneously compared the three currently used erythropoietin‐stimulating agents (ESAs) in a prospective manner in the treatment of anemia of end‐stage renal disease patients. All hemodialysis patients in Qatar who were treated with short‐acting epoetin alfa or beta have been screened. Eligible patients had been prospectively randomized, either to continue on the previous regimen of epoetin or to receive darbepoetin alfa or continuous erythropoietin receptor activator (CERA) for a total period of 40 weeks. All groups were assessed at the end of the study for safety and efficacy parameters. A total of 327 eligible patients were randomized. Mean hemoglobin concentration remained constant within the recommended target range (11–12 g/dL) throughout the study in the three studied groups. The percentage of patients who reached the target range was constantly above 50% in the second half of the study among CERA group patients who also had significantly lower mean number of dose adjustments as compared with the other two groups (P = 0.001). Similarly, the number of discontinuations of ESA among epoetin, darbepoetin, and CERA groups was 17, 19, and 9, respectively (P = 0.042). The frequencies of adverse events were similar in all groups. This study has specifically compared the effect of ESA type on the variability of serum hemoglobin levels in hemodialysis patients. Furthermore, it confirmed the efficacy and safety of once monthly CERA for maintaining tight hemoglobin control within recommended target ranges.     

Therapeutic Effect of Erythropoietin on Alzheimer’s Disease by Activating the Serotonin Pathway

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by memory impairment in patients. Erythropoietin (EPO) has been reported to stimulate neurogenesis. This study was conducted to determine the regenerative effects of EPO in an AD model and to assess its underlying mechanism. Recombinant human EPO was intraperitoneally administered to AD mice induced by intracerebroventricular Aβ oligomer injection. Behavioral assessments with novel object recognition test and passive avoidance task showed improvement in memory function of the EPO-treated AD mice compared to that of the saline-treated AD mice (p < 0.0001). An in vivo protein assay for the hippocampus and cortex tissue indicated that EPO treatment modulated neurotransmitters, including dopamine, serotonin, and adrenaline. EPO treatment also restored the activity of serotonin receptors, including 5-HT4R, 5-HT7R, and 5-HT1aR (p < 0.01), at mRNA levels. Furthermore, EPO seemed to exert an anti-inflammatory influence by downregulating TLR4 at mRNA and protein levels (p < 0.05). Finally, an immunohistochemical assay revealed increments of Nestin(+) and NeuN(+) neuronal cells in the CA3 region in the EPO-treated AD mice compared to those in the saline-treated AD mice. The conclusion is that EPO administration might be therapeutic for AD by activating the serotonergic pathway, anti-inflammatory action, and neurogenic characteristics.     

Comparison of affinity membrane adsorbers for the purification of recombinant human erythropoietin (rhEPO)

In this work affinity membrane adsorbers were investigated for the chromatographic purification of recombinant human erythropoietin (rhEPO) produced in mammalian cells. Cibacron Blue (CB), IDA‐Cu⁺², wheat germ agglutinin (WGA), concanavalin A (ConA) and an anti‐EPO monoclonal antibody (MAb) were tested as affinity ligands, attached to microporous Sartobind^® membranes. In experiments carried out with cell culture supernatant, the best results were obtained with Sartobind–CB, Sartobind–WGA and Sartobind–MAb membranes. The thermodynamic parameters were determined by adsorption isotherms of rhEPO onto the membranes. Sartobind–ConA presented the lowest affinity for rhEPO, as evidenced by a lower association constant. For Sartobind–CB, Sartobind–IDA‐Cu⁺² and Sartobind–MAb K_A was in the order of 10⁵ L mol^?1, whereas for Sartobind–WGA it was 10⁶ L mol^?1. Sartobind–CB eluates were also investigated by RP‐HPLC. The purity level achieved in this one‐step purification strategy was 55%, indicating that the Sartobind–CB membrane is a promising affinity membrane for rhEPO purification. Copyright © 2007 Society of Chemical Industry     

Effect of improvement in anemia on electroneurophysiological markers (P300) of cognitive dysfunction in chronic kidney disease

Our aim is to study the effect of improvement in anemia on event-related potentials (ERPs; P300) as markers of cognitive dysfunction in predialysis and dialysis patients of chronic kidney disease (CKD). Thirty anemic patients of CKD (hemoglobin [Hb] < 9 g%), 15 in the predialysis group (Group A), and 15 patients on biweekly hemodialysis (Group B) were recruited for the study. Patients of uremic encephalopathy, dyselectrolytemia, and those with hearing problems were excluded. Both groups were given recombinant human erythropoietin (rhuEPO) 100 IU/kg biweekly for 6 weeks by the subcutaneous route. No intervention was performed in the third control group (Group C), which consisted of 30 normal healthy volunteers. The improvement in Hb was assessed every 2 weeks, and the amplitude and latency of the P300 component of the ERPs were studied before initiating treatment and after 6 weeks of rhuEPO administration. There was a significant increase in Hb in both the study groups without any significant alteration in kidney functions. A significant reduction in P300 latency was noted in both the study groups after intervention. Similarly, the amplitude of P300 also increased in both study groups, but attained statistical significance for the dialysis group only. No significant changes were observed in the control group. Administration of EPO in patients of anemia with CKD resulted in a significant improvement in the electrophysiological markers of cognitive function in the form of increased amplitudes and decreased latencies of P300 in both predialysis and dialysis patients.