Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In its hormonal role, erythropoietin is produced by the kidney in response to hypoxic stress and signals the bone marrow to increase the number of circulating erythrocytes. It has become clear in recentyears, however, that erythropoietin and its receptor are members of a cytokine superfamily that mediates diverse functions in nonhematopoietic tissues. Nonhormonal erythropoietin actions include a critical role in the development, maintenance, protection, and repair of the central nervous system (CNS). Our group has found serendipitously that recombinant human erythropoietin administered into the systemic circulation is not strictly excluded from the brain. Human recombinant erythropoietin appears within the cerebrospinal fluid in neuroprotective concentrations, probably by translocation initiated by binding to the erythropoietin receptor on the luminal surface of the endothelium. This observation suggested that recombinant human erythropoietin could be therapeutic for CNS diseases, a possibility further supported by positive findings in a model of ischemic stroke. Recombinant human erythropoietin administered systemically either in advance of, or up to 3 hours after, a cerebral arterial occlusion in rats prevents apoptosis of neurons within the ischemic penumbra and reduces infarction volume by 75%. Erythropoietin also dramatically reduces postinfarct inflammation in this model. Other brain and spinal cord injuries such as mechanical trauma, experimental autoimmune encephalitis or subarachnoid hemorrhage also respond favorably to erythropoietin administered within a similar window of time. In addition to ameliorating neuronal injury, erythropoietic therapy also directly modulates neuronal excitability and acts as a trophic factor for neurons in vivo and in vitro. Erythropoietin may therefore provide benefit in epileptic or degenerative neurologic diseases. Given the outstanding safety record for recombinant human erythropoietin after more than a decade in widespread clinical use, the results of multiple preclinical investigations suggest that this cytokine or its derivatives may be useful for treatment of a variety of nervous system diseases.
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PMID:What evidence supports use of erythropoietin as a novel neurotherapeutic? 1238 Sep 58

In many types of cardiovascular pathophysiology such as hypercholesterolemia and atherosclerosis, diabetes, cigarette smoking, or hypertension (with its sequelae stroke and heart failure) the expression of endothelial NO synthase (eNOS) is altered. Both up- and downregulation of eNOS have been observed, depending on the underlying disease. When eNOS is upregulated, the upregulation is often futile and goes along with a reduction in bioactive NO. This is due to an increased production of superoxide generated by NAD(P)H oxidase and by an uncoupled eNOS. A number of drugs with favorable effects on cardiovascular disease upregulate eNOS expression. The resulting increase in vascular NO production may contribute to their beneficial effects. These compounds include statins, angiotensin-converting enzyme inhibitors, AT1 receptor antagonists, calcium channel blockers, and some antioxidants. Other drugs such as glucocorticoids, whose administration is associated with cardiovascular side effects, downregulate eNOS expression. Stills others such as the immunosuppressants cyclosporine A and FK506/tacrolimus or erythropoietin have inconsistent effects on eNOS. Thus regulation of eNOS expression and activity contributes to the overall action of several classes of drugs, and the development of compounds that specifically upregulate this protective enzyme appears as a desirable target for drug development.
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PMID:Regulation of endothelial-type NO synthase expression in pathophysiology and in response to drugs. 1238 13

Currently, intravenous recombinant tissue plasminogen activator is the only US Food and Drug Administration-approved therapy for acute ischemic stroke. Although efficacious, its usefulness is limited, mainly because of the very limited time window for its administration. Neuroprotective treatments are therapies that block the cellular, biochemical, and metabolic elaboration of injury during or after exposure to ischemia, and have a potential role in ameliorating brain injury in patients with acute ischemic stroke. More than 50 neuroprotective agents have reached randomized human clinical trials in focal ischemic stroke, but none has been unequivocally proven efficacious, despite successful preceding animal studies. The failed neuroprotective trials of the past have greatly increased understanding of the fundamental biology of ischemic brain injury and have laid a strong foundation for future advance. Moreover, the recent favorable results of human clinical trials of hypothermia in human cardiac arrest and global brain ischemia have validated the general concept of neuroprotection for ischemic brain injury. Recent innovations in strategies of preclinical drug development and clinical trial design that rectify past defects hold great promise for neuroprotective investigation, including novel approaches to accelerating time to initiation of experimental treatment, use of outcome measures sensitive to treatment effects, and trial testing of combination therapies rather than single agents alone. Although no neuroprotective agent is of proven benefit for focal ischemic stroke, several currently available interventions have shown promising results in preliminary trials and may be considered for cautious, off-label use in acute stroke, including hypothermia, magnesium sulfate, citicoline, albumin, and erythropoietin. Overall, the prospects for safe and effective neuroprotective therapies to improve stroke outcome remain promising.
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PMID:Potential Role of Neuroprotective Agents in the Treatment of Patients with Acute Ischemic Stroke. 1289 99

Ischemic brain injury resulting from stroke arises from primary neuronal losses and by inflammatory responses. Previous studies suggest that erythropoietin (EPO) attenuates both processes. Although EPO is clearly antiapoptotic for neurons after experimental stroke, it is unknown whether EPO also directly modulates EPO receptor (EPO-R)-expressing glia, microglia, and other inflammatory cells. In these experiments, we show that recombinant human EPO (rhEPO; 5,000 U/kg body weight, i.p.) markedly reduces astrocyte activation and the recruitment of leukocytes and microglia into an infarction produced by middle cerebral artery occlusion in rats. In addition, ischemia-induced production of the proinflammatory cytokines tumor necrosis factor, interleukin 6, and monocyte chemoattractant protein 1 concentration is reduced by >50% after rhEPO administration. Similar results were also observed in mixed neuronal-glial cocultures exposed to the neuronal-selective toxin trimethyl tin. In contrast, rhEPO did not inhibit cytokine production by astrocyte cultures exposed to neuronal homogenates or modulate the response of human peripheral blood mononuclear cells, rat glial cells, or the brain to lipopolysaccharide. These findings suggest that rhEPO attenuates ischemia-induced inflammation by reducing neuronal death rather than by direct effects upon EPO-R-expressing inflammatory cells.
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PMID:Erythropoietin selectively attenuates cytokine production and inflammation in cerebral ischemia by targeting neuronal apoptosis. 1297 60

Currently, intravenous recombinant tissue plasminogen activator is the only US Food and Drug Administration-approved therapy for acute ischemic stroke. Although efficacious, its usefulness is limited, mainly because of the very limited time window for its administration. Neuroprotective treatments are therapies that block the cellular, biochemical, and metabolic elaboration of injury during or after exposure to ischemia, and have a potential role in ameliorating brain injury in patients with acute ischemic stroke. More than 50 neuroprotective agents have reached randomized human clinical trials in focal ischemic stroke, but none have been unequivocally proven efficacious, despite successful preceding animal studies. The failed neuroprotective trials of the past have greatly increased understanding of the fundamental biology of ischemic brain injury and have laid a strong foundation for future advance. Moreover, the recent favorable results of human clinical trials of hypothermia in human cardiac arrest and global brain ischemia have validated the general concept of neuroprotection for ischemic brain injury. Recent innovations in strategies of preclinical drug development and clinical trial design that rectify past defects hold great promise for neuroprotective investigation, including novel approaches to accelerating time to initiation of experimental treatment, use of outcome measures sensitive to treatment effects, and trial testing of combination therapies rather than single agents alone. Although no neuroprotective agent is of proven benefit for focal ischemic stroke, several currently available interventions have shown promising results in preliminary trials and may be considered for cautious, off-label use in acute stroke, including hypothermia, magnesium sulfate, citicoline, albumin, and erythropoietin. Overall, the prospects for safe and effective neuroprotective therapies to improve stroke outcome remain promising.
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PMID:Potential Role of Neuroprotective Agents in the Treatment of Patients with Acute Ischemic Stroke. 1457 21

Recombinant human erythropoietin (epoetin alfa) has proven beneficial for the treatment of various anemias. The mechanism of action of endogenous erythropoietin and the therapeutic use of epoetin alfa to stimulate red blood cell production and improve the quality of life in cancer patients are reviewed here. Epoetin alfa may also attenuate the cognitive dysfunction associated with cancer therapy. Interestingly, functional endogenous erythropoietin receptor signaling pathways have been demonstrated in numerous nonerythropoietic tissues. Of particular importance, epoetin alfa confers neurotrophic and neuroprotective effects in cultured neurons and in several animal models for neurologic disease. In one clinical trial, epoetin alfa appeared to limit functional and histologic damage in patients with stroke. Therefore, in cancer patients receiving chemotherapy, the beneficial effects of epoetin alfa could be mediated not only through enhanced erythrocyte production but also via direct effects on the nervous system. Further investigation into the nonerythropoietic effects of epoetin alfa could broaden its clinical utility for patients with cancer and also provide new therapies for various neurologic disorders.
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PMID:New insights into erythropoietin and epoetin alfa: mechanisms of action, target tissues, and clinical applications. 1467 Dec 25

The influence that the mode of dialysis has on the prognosis of patients with renal disease is controversial. The controversy arises at least in part because of the heterogeneity of patient populations, who may be receiving either continuous ambulatory peritoneal dialysis (CAPD) or hemodialysis (HD). In the absence of randomized trials, epidemiologic investigations present the best method for studying the problem. To determine the influence of the mode of dialysis on prognosis and on the cardiovascular system, erythropoiesis, and calcium metabolism, we selected 36 patients undergoing CAPD and 36 patients undergoing HD for a 3-year follow-up study. Patients were matched for age, sex, and cause of renal disease. Among the HD patients, 8 deaths occurred from congestive heart failure, 1 death from cerebrovascular accident, and 2 deaths from severe infection. In the HD group, the average age was 63 +/- 3 years. Among the CAPD patients, 6 were transferred to HD because of recurrent peritonitis or elevation of serum creatinine. Patients on CAPD had lower blood pressures, and patients on HD had lower total cholesterol levels. Other parameters were not significantly different between the two groups, including dose of erythropoietin and calcium supplements administered. Our study provides evidence that clinical outcome in renal failure may depend to some extent on the mode of dialysis. Our results suggest that blood pressure level and serum cholesterol should be taken into account for patients treated with either CAPD or HD. Blood pressure and cholesterol level are both likely to be important contributors to mortality and morbidity in renal patients.
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PMID:Peritoneal dialysis versus hemodialysis: a five-year comparison of survival and effects on the cardiovascular system, erythropoiesis, and calcium metabolism. 1476 52

Glutamate excitotoxicity, oxidative stress, and acidosis are primary mediators of neuronal death during ischemia and reperfusion. Astrocytes influence these processes in several ways. Glutamate uptake by astrocytes normally prevents excitotoxic glutamate elevations in brain extracellular space, and this process appears to be a critical determinant of neuronal survival in the ischemic penumbra. Conversely, glutamate efflux from astrocytes by reversal of glutamate uptake, volume sensitive organic ion channels, and other routes may contribute to extracellular glutamate elevations. Glutamate activation of neuronal N-methyl-D-aspartate (NMDA) receptors is modulated by glycine and D-serine: both of these neuromodulators are transported by astrocytes, and D-serine production is localized exclusively to astrocytes. Astrocytes influence neuronal antioxidant status through release of ascorbate and uptake of its oxidized form, dehydroascorbate, and by indirectly supporting neuronal glutathione metabolism. In addition, glutathione in astrocytes can serve as a sink for nitric oxide and thereby reduce neuronal oxidant stress during ischemia. Astrocytes probably also influence neuronal survival in the post-ischemic period. Reactive astrocytes secrete nitric oxide, TNFalpha, matrix metalloproteinases, and other factors that can contribute to delayed neuronal death, and facilitate brain edema via aquaporin-4 channels localized to the astrocyte endfoot-endothelial interface. On the other hand erythropoietin, a paracrine messenger in brain, is produced by astrocytes and upregulated after ischemia. Erythropoietin stimulates the Janus kinase-2 (JAK-2) and nuclear factor-kappaB (NF-kB) signaling pathways in neurons to prevent programmed cell death after ischemic or excitotoxic stress. Astrocytes also secrete several angiogenic and neurotrophic factors that are important for vascular and neuronal regeneration after stroke.
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PMID:Astrocyte influences on ischemic neuronal death. 1503 13

Exogenous erythropoietin (EPO) is a potent neurotrophic factor in vivo, protective against neuronal death in animal models of brain ischemia and human stroke. To date, reports on the distribution of EPO receptor in brain suggest that it is expressed mostly on capillaries. This receptor pattern suggests an indirect effect of EPO on neurons. In these studies, we show that EPO receptor is abundantly expressed on adult dopaminergic neurons, suggesting a direct effect of EPO on neurons. Furthermore, we show that EPO mediates the classic neurotrophic effects of proliferation, differentiation and maintenance in a dopaminergic cell line. The biology of therapeutically administered EPO in brain is a function of its receptor distribution, and the neuronal expression of EPO receptor on adult CNS neurons is consistent with EPO's potent neurotrophic function in vivo.
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PMID:Erythropoietin receptor is expressed on adult rat dopaminergic neurons and erythropoietin is neurotrophic in cultured dopaminergic neuroblasts. 1505 Jul 26

Most drugs with central nervous system (CNS) activity enter the brain either by diffusing across the membranes which comprise the blood-brain barrier (BBB) or by being transported by carrier systems across those membranes. Substances which cannot cross the BBB by one of these mechanisms, like serum albumin, are virtually excluded from the CNS. However, this exclusion is not absolute. Cerebrospinal fluid (CSF) levels of albumin, for example, are about 0.5% those of serum levels. Albumin enters the CNS through a variety of pathways collectively termed the extracellular pathways. Any circulating substance can, in theory, use these pathways to enter the CNS. But, traditional drug development has ignored this pathway. To approach even the CSF/serum ratio of 0.5%, a candidate therapeutic would need to meet several criterion: long half-life in blood, small volume of distribution, high potency in the CNS, and absence of brain-to-blood efflux. Two emerging therapeutics which are likely exerting their CNS effects by way of the extracellular pathways are antibodies directed against amyloid beta protein (ABP) and erythropoietin (Epo) used in the treatment of stroke. These examples suggest that the extracellular pathways are an option for the delivery of certain therapeutics to the brain.
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PMID:Are the extracellular [correction of extracelluar] pathways a conduit for the delivery of therapeutics to the brain? 1513 87


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