脊髓损伤后促红细胞生成素防御保护性机制研究进展

随交通运输的高速化、体育运动的极限化及频发的暴力意外伤害,脊髓损伤(SCI)的发生呈现:高致残率、低死亡率、治疗耗费高等特点,并业已成为全球性医疗棘手问题.促红细胞生成素(EPO)是由肾脏分泌用以调节红细胞生成的糖蛋白激素之一,其与促红细胞生成素受体(EPOR)在中枢神经系统(CNS)中皆有表达[1].动物体内实验和神经元体外培养证实EPO是一种神经保护因子,可通过以下途径发挥神经组织保护作用[2],包括:抗细胞凋亡以促进神经元的生成与存活,诱导神经滋养血管生长,抑制自由基和一氧化氮过量生成,拮抗细胞兴奋性毒性作用,协同神经营养因子发挥作用,减弱脂质过氧化反应.目前国内对EPO在全身各器官系统中的作用机制研究较少,现对EPO应用于脊髓损伤实验和临床治疗的研究现状综述如下.     

促红细胞生成素与缺氧性脑损伤

促红细胞生成素(erythropoietin,EPO)是神经系统的一种神经营养因子和神经保护因子.EPO及其受体(erythro-poietin receptor,EPOR)在神经元、星形胶质细胞、少突胶质细胞、小胶质细胞和血管内皮细胞都可表达.脑组织缺氧缺血性损伤首先激活低氧诱发因子-1(HIF-1).后者促进EPO的分泌和表达,EPO和EPOR结合引发下游信号的级联反应表现出脑保护作用,其脑保护作用体现在抗凋亡、抗氧化、抗炎症等方面.众多动物实验和临床应用都证实重组人红细胞生成素(recombi-nant human erythmpoietin,rhEPO)对脑缺氧缺血性疾病具有脑保护作用.     

促红细胞生成素对急性脊髓损伤后氧自由基和Caspase-3表达变化的干预作用

有研究表明促红细胞生成紊(EPO)及其受体在中枢以及周围神经系统中均有广泛的表达,具有调节中枢神经系统发育、神经营养及神经保护作用.我们通过观察给予EPO治疗后大鼠神经功能行为,自由基以及凋亡的变化,探讨其防止脊髓继发性损伤的机制.     

促红细胞生成素(EPO)对神经细胞的保护作用

促红细胞生成素是一种多功能的营养因子,目前发现EPO对脊髓损伤有良好的神经保护作用.本文回顾了国内外近年来促红细胞生成素(EPO)对脊髓损伤的的研究进展,对EPO可能的神经保护机制作一综述.     

红细胞生成素对单侧输尿管梗阻大鼠肾间质纤维化的保护作用

肾间质纤维化几乎是所有慢性肾脏疾病发展至终末期肾衰竭(ESRD)的共同通路.梗阻性肾病的病理变化主要表现为肾小管萎缩和间质纤维化,而肾小管上皮细胞凋亡是肾小管萎缩和肾实质丧失的主要原因[1,2].红细胞生成素(EPO)能调节红细胞生成以增加组织供氧,除此之外,EPO也是一种抗凋亡因子,介导多种细胞抗凋亡作用.Koury等[3]报道EPO调节红细胞生成的一种主要机制就是防止红系祖细胞凋亡.而EPO对肾间质纤维化的影响及其机制尚未见阐明.本研究旨在观察EPO对肾间质纤维化的影响并初步探讨其可能的作用机制.     

促红细胞生长素对神经保护作用及其机制

促红细胞生长素(erythropoietin,EPO)目前临床上治疗肾性贫血的主要药物。近来研究发现EPO在中枢神经系统内有大量分布及其受体的广泛表达,对中枢神经系统的发育起着重要的调节作用并对各种中枢神经系统损伤有很好的保护作用。本文针对EPO作为一个神经保护剂,对其神经保护作用和其保护机制作简要综述。     

红细胞生成素在脊髓损伤中抑制细胞凋亡的作用

红细胞生成素(erythropoietin;EPO)是细胞因子超家族的成员之一,除具有促进祖红细胞的增生、分化和成熟的功能外,还具有抗血管痉挛、抗凋亡和抗炎等多种功能。EPO及其受体不仅存在于造血系统中,还存在于中枢和周围神经系统中,EPO除对多种原因引起的脑损伤具有保护作用外,对急性脊髓损伤及其继发性损伤也具有保护作用。近期研究发现其中最主要的保护机制是抑制细胞的凋亡。目前研究认为,抑制神经元细胞凋亡是EPO短期神经保护作用的基础,而EPO的神经营养作用则具有长期保护效果。但其抑制细胞凋亡的细胞内信号传导途径、对神经细胞的营养作用需要进一步的研究。     

促红细胞生长素对神经保护作用及其机制

促红细胞生长素（erythropoietin,EPO)目前临床上治疗肾性贫血的主要药物。近年研究发现EPO在中枢神经系统内在大量分布及其受体的广泛表达，对中枢神经系统的发育起着重要的调节作用并对各种中枢神经系统损伤有很好的保护作用。本文针对EPO作为一个神经保护剂，对其神经保护作用和其保护机制作简要综述。     

促红细胞生成素对缺血/再灌注心肌保护作用的研究进展

背景 促红细胞生成素(erythropoietin,EPO)是一种造血刺激因子,过去20多年中用于临床多种原因所致的贫血.随着对EPO及其受体在心血管方面作用的认识,增加了EPO在生理和病理生理方面作用的理解. 目的 将心肌缺血/再灌注损伤(ischemia/reperfusion injury,I/RI)减轻到最低限度. 内容 研究EPO在心脏中的表达及其在心肌保护中所涉及的传导机制,EPO在动物心血管疾病实验模型中起到心肌保护作用及目前EPO心肌保护作用的临床相关研究. 趋向 近年来,EPO心肌保护作用临床研究的报道逐渐增多,为临床心肌保护提供了新的方向,但需要更深入研究EPO的心肌保护作用.     

促红细胞生成素对脊髓缺血再灌注损伤保护作用及其机理的实验研究

目的:探讨促红细胞生成素(EPO)处理对脊髓缺血再灌注损伤的保护作用及其可能的作用机理.方法:建立兔脊髓缺血再灌注损伤模型,通过动物神经运动功能评分和组织学染色评价神经损伤程度;采用免疫组织化学染色测量bcl-2和bax蛋白表达情况;TUNEL法检测脊髓细胞凋亡情况.结果:EPO处理组能明显改善动物的神经运动功能并减轻脊髓由于缺血再灌注所引起的病理性损害:EPO组与对照组相比,脊髓前角细胞的凋亡指数明显下降(P＜0.05),脊髓内bcl-2表达增高(P＜0.01),而bax蛋白表达下降(P＜0.01).结论:EPO对脊髓由于缺血而引起的神经运动功能损害具有保护作用,此种保护作用与EPO能够上调bcl-2和下调bax蛋白表达有关.     

The brain erythropoietin system and its potential for therapeutic exploitation in brain disease

The discovery of the broad neuroprotective potential of erythropoietin (EPO), an endogenous hematopoietic growth factor, has opened new therapeutic avenues in the treatment of brain diseases. EPO expression in the brain is induced by hypoxia. Practically all brain cells are capable of production and release of EPO and expression of its receptor. EPO exerts multifaceted protective effects on brain cells. It protects neuronal cells from noxious stimuli such as hypoxia, excess glutamate, serum deprivation or kainic acid exposure in vitro by targeting a variety of mechanisms and involves neuronal, glial and endothelial cell functions. In rodent models of ischemic stroke, EPO reduces infarct volume and improves functional outcome, but beneficial effects have also been observed in animal models of subarachnoid hemorrhage, intracerebral hemorrhage, traumatic brain injury, and spinal cord injury. EPO has a convenient therapeutic window upon ischemic stroke and favorable pharmacokinetics. Results from first therapeutic trials in humans are promising, but will need to be validated in larger trials. The safety profile and effectiveness of EPO in a wide variety of neurologic disease models make EPO a candidate compound for a potential first-line therapeutic for neurologic emergencies.     

Effect of erythropoietin therapy on polyneuropathy in predialytic patients

BACKGROUND: Peripheral neuropathy commonly develops in patients with advanced chronic renal failure. The uremic neuropathy is often subclinical and detectable only by electrophysiological studies. Receptors to erythropoietin (EPO) have been described on non-hematopoietic cells including neuronal cells. METHODS: In order to evaluate the effect of five months' EPO therapy on polyneuropathy in predialytic patients, nerve conduction studies (NCS) were done in 46 anemic predialytic patients without neurological complaints. In 22 (twelve non-diabetic and ten diabetic) neuropathy was detected and these patients were included in the study. After five months of subcutaneous EPO therapy NCSs were repeated. RESULTS: Hemoglobin increased significantly (p=0.0001) with no significant increase in plasma creatinine. Motor nerve conduction velocity (MNCV) and compound muscle action potentials (CMAP) of the ulnar nerve were normal before EPO therapy and at the end of the study. MNCV of the median, peroneal and tibial nerves improved significantly (p<0.05). CMAP of the median nerve rose significantly, to the normal range (p=0.01). Sensory nerve conduction velocity (SNCV ) and sensory nerve action potentials (SNAP) were reduced in all sensory nerves and did not improve. The improvement in non-diabetic patients was better than in diabetic patients. No significant correlation was found between the increase in hemoglobin and the improvement in MNCV. CONCLUSIONS: Subcutaneous EPO therapy improved motor polyneuropathy in uremic patients, especially non-diabetic individuals. The improvement in MNCV may reflect remyelination. This non-hematopoietic effect may be related to some direct action through EPO receptors on peripheral neuronal cells.     

Erythropoietin promotes the recovery of erectile function following cavernous nerve injury

PURPOSE: We investigated the effects of recombinant human (rh) erythropoietin (EPO) on erectile function recovery in a rat model of cavernous nerve (CN) injury. MATERIALS AND METHODS: Male rats underwent unilateral CN transection and excision of a 5 mm segment of the contralateral CN. One group received rhEPO (5,000 U/kg) subcutaneously daily for 14 days, while another received rhEPO 1 day and 1 hour prior to nerve injury. An additional group of animals was pretreated with 1 dose of darbepoetin (25 microg/kg). At 14 days following CN injury rats underwent erection physiology studies. Axonal regeneration was evaluated by electron microscopy. EPO receptor expression in the penis and major pelvic ganglion was evaluated immunohistochemically and by real-time polymerase chain reaction. RESULTS: Daily rhEPO effectively recovered erections after CN injury compared with saline treatment. Maximal intracavernous pressure area under the curve normalized to mean arterial pressure was significantly greater in EPO treated vs saline treated animals (p < 0.05). rhEPO and darbepoetin pretreatment was as effective as continuous 14-day therapy. EPO receptor expression was localized to neuronal cell bodies of the major pelvic ganglion, penile nerves and endothelial cells in the penis. Electron microscopy revealed significant improvement in axonal regeneration in rhEPO treated animals 14 days following injury compared to controls. CONCLUSIONS: EPO receptors are expressed in local neuronal and vascular tissues. Exogenous administration of rhEPO or darbepoetin in the setting of CN injury promotes erectile function recovery. This occurs through axonal regeneration of the injured nerve and possible penile protection.     

Erythropoietin receptor expression in the human urogenital tract: immunolocalization in the prostate, neurovascular bundle and penis

OBJECTIVE: To investigate whether the erythropoietin (EPO) receptor is expressed in human periprostatic (including the neurovascular bundles) and penile tissues, and define its distribution in these tissues, as the administration of exogenous EPO in cavernous nerve injury promoted the recovery of erectile function in a rat model. MATERIALS AND METHODS: Human prostate (six samples) and penile (two) tissue were collected and paraffin-embedded. Tissue was sectioned and processed for immunohistochemical studies using an antibody for the EPO receptor; immunolocalization was assessed using light microscopy. RESULTS: There was prominent staining for the EPO receptor in neuronal cell bodies of the periprostatic neurovascular bundles, and in the axons emanating from these ganglia. The glandular epithelium of the prostate also had weak staining. There was EPO receptor immunoreactivity in the penile specimens in the penile dorsal nerves, sinusoidal endothelium of the corpus cavernosum, and endothelial cells lining the dorsal veins and arteries. All slides processed with no primary antibody or blocking peptide showed no staining. CONCLUSIONS: EPO receptor expression was identified and localized in human penile tissues and in the periprostatic neurovascular bundles responsible for erectile function. This suggests a likely role for endogenous EPO within these tissues, and provides the rationale for its clinical use as a protective agent locally.     

脊髓损伤后促红细胞生成素对bcl-2的影响

目的 探讨促红细胞生成素（EPO）对大鼠脊髓损伤后伤区脊髓细胞凋亡和神经功能恢复的影响。方法 Wistar大鼠210只，随机分为4组：假手术组、脊髓损伤组、脊髓损伤加重组人EPO治疗组、脊髓损伤加生理盐水治疗组。采用原位末端脱氧核糖核苷酸转移酶介导dUTP标记（TUNEL标记法）检测神经元和少突胶质细胞凋亡，Western blot免疫印迹法和免疫组化染色检测bcl-2表达，免疫组化染色和图像分析方法观察对白质内神经纤维（NF-200染色）的保护作用，通过感觉诱发电位（SSEP）、运动诱发电位（MEP）和大鼠BBB后肢运动功能评分，观察损伤脊髓传导功能的恢复。结果 EPO保护组bcl-2在各时相点的表达明显增高，8h和7d时神经元和少突胶质细胞的TUNEL阳性细胞数明显减少；在7d时白质中NF-200阳性神经纤维明显增多；SSEP和MEP的平均潜伏期和波幅以及BBB功能评分明显提高，与损伤组和生理盐水治疗相比，差异有统计学意义（P〈0．01）。结论 EPO通过上调bcl-2的表达，在抑制脊髓损伤后神经元和少突胶质细胞的凋亡中起到神经保护作用。     

Recombinant human erythropoietin (rHuEPO): more than just the correction of uremic anemia

Hematopoiesis is controlled by numerous interdependent humoral and endocrine factors. Erythropoietin (EPO), a hydrophobic sialoglycoproteic hormone, plays a crucial role in the regulation of hematopoiesis, and induces proliferation, maturation and differentiation of the erythroid cell line precursors. Thanks to recombinant DNA techniques, different recombinant hormones can now be produced at low cost and in large amounts. This has led to greater understanding of the pathophysiological factors regulating hematopoiesis. This in turn, hasprompted the search for new therapeutic approaches. EPO might also be used to treat patients with different types of anemia: uremics, newborns, patients with anemia from cancer or myeloproliferative disease, thalassemia, bone marrow transplants, chronic infectious diseases. Besides erythroid cells, EPO affects other blood cell lines, such as myeloid cells, lymphocytes and megakaryocytes. It can also enhance polymorphonuclear cell phagocytosis and reduce macrophage activation, thus modulating the inflammatory process. Hematopoietic and endothelial cells probably have the same origin, and the discovery of eyrthropoietin receptors also on mesangial, myocardial and smooth muscle cells has prompted research into the non-erythropoietic function of the hormone. EPO has an important, direct, hemodynamic and vasoactive effect, which does not depend only on an increase in hematocrit and viscosity. Moreover, EPO and its receptors have been found in the brain, suggesting a role in preventing neuronal death. Finally, the recently discovered interaction between EPO and vascular endothelial growth factor (VEGF), and the ability of EPO to stimulate endothelial cell mitosis and motility may be of importance in neovascularization and wound healing.     

Mechanisms of Disease: erythropoietin resistance in patients with both heart and kidney failure

Anemia is common in patients who have both heart failure and chronic kidney disease, and there is an association between anemia and progression of both diseases. The main causes of anemia are deficient production of erythropoietin (EPO), iron deficiency, and chronic disease with endogenous EPO resistance. EPO has been successfully used for over a decade to treat anemia in patients with chronic kidney disease. Less obvious are the safety and efficacy of EPO treatment in patients with both heart failure and renal disease. Up to 10% of patients receiving EPO are hyporesponsive to therapy and require large doses of the agent. Several mechanisms could explain resistance to endogenous and exogenous EPO. Proinflammatory cytokines antagonize the action of EPO by exerting an inhibitory effect on erythroid progenitor cells and by disrupting iron metabolism (a process in which hepcidin has a central role). EPO resistance might also be caused by inflammation, which has a negative effect on EPO receptors. Furthermore, neocytolysis could have a role. As resistance to exogenous EPO is associated with an increased risk of death, it is important to understand how cardiorenal failure affects EPO production and function.     

The Effects of a Polyacrylonitrile Membrane and a Membrane Made of Regenerated Cellulose on the Plasma Concentrations of Erythropoietin During Hemodialysis

In vitro studies have shown that some dialysis membranes significantly adsorb erythropoietin (EPO), a fact that might have an effect on anemia in long-term hemodialysis (HD) patients and on anemia treatment with recombinant human EPO. The purpose of the study was to determine whether the ability of adsorption demonstrated in vitro also has an effect on EPO concentrations in vivo. In a crossover study, the plasma concentrations of EPO were examined in 11 patients on chronic HD during HD using a polyacrylonitrile (AN69) membrane (high in vitro adsorption) plus EPO administered subcutaneously after the HD session, HD using a Cuprophan membrane (low in vitro adsorption) plus EPO administered subcutaneously after the HD session, HD using an AN69 membrane plus EPO administered subcutaneously after the HD session plus EPO administered intravenously immediately before HD, or HD using a Cuprophan membrane plus EPO administered subcutaneously after the HD session plus EPO intravenously immediately before HD. The intradialysis plasma concentrations of EPO (not detectable in the dialysate) determined at the dialyzer inlet and outlet at Minutes 5 and 240 of the procedure did not differ significantly after its subcutaneous administration from its predialysis concentrations with either the Cuprophan or AN69 membrane. A comparison of EPO concentrations between AN69 and Cuprophan did not reveal marked differences either. The course of concentrations after additional EPO intravenous administration was similar with no statistically demonstrable difference between the 2 membranes. In conclusion, under clinical conditions, AN69 and Cuprophan membranes do not differ in their effects on plasma EPO concentrations. The differences in EPO adsorption between AN69 and Cuprophan, demonstrated in vitro, do not seem to be of clinical importance.     

Erythropoietin‐mediated protection in kidney transplantation: nonerythropoietic EPO derivatives improve function without increasing risk of cardiovascular events

The protective, nonerythropoietic effects of erythropoietin (EPO) have become evident in preclinical models in renal ischaemia/reperfusion injury and kidney transplantation. However, four recently published clinical trials using high‐dose EPO treatment following renal transplantation did not reveal any protective effect for short‐term renal function and even reported an increased risk of thrombosis. This review focusses on the current status of protective pathways mediated by EPO, the safety concerns using high EPO dosage and discusses the discrepancies between pre‐clinical and clinical studies. The protective effects are mediated by binding of EPO to a heteromeric receptor complex consisting of two β‐common receptors and two EPO receptors. An important role for the activation of endothelial nitric oxide synthase is proposed. EPO‐mediated cytoprotection still has enormous potential. However, only nonerythropoietic EPO derivatives may induce protection without increasing the risk of cardiovascular events. In preclinical models, nonerythropoietic EPO derivatives, such as carbamoylated EPO and ARA290, have been tested. These EPO derivatives improve renal function and do not affect erythropoiesis. Therefore, nonerythropoietic EPO derivatives may be able to render EPO‐mediated cytoprotection useful and beneficial for clinical transplantation.     

Response to Cyclosporine A in a Patient with Pure Red Cell Aplasia Due to Antierythropoietin-α Antibodies

Reported cases of pure red cell aplasia (PRCA) from the administration of erythropoietin (EPO)‐α molecule in the United States are rare, and the optimal treatment is still unknown. We present a patient with end‐stage renal disease (ESRD) who became hyporesponsive and later unresponsive to EPO‐α treatment a few months after initiation of hemodialysis. A comprehensive anemia examination was negative while the patient became transfusion dependent. The diagnosis of EPO‐α‐induced PRCA was confirmed by bone marrow biopsy, by undetectable serum EPO levels following the administration of a large dose of EPO‐α, and by documenting the presence of EPO‐neutralizing antibodies. Administration of cyclosporine A in addition to prednisone enabled the patient to become transfusion and EPO independent. This case further documents the possible occurrence of PRCA with EPO‐α administration in the United States and reaffirms the potential beneficial effect of cyclosporine A.