Biomedical subjects

Michael Brines

Publications and source records attributed to Michael Brines.

29 records · Page 2Linked to original sources

PubMed2003

Recombinant human erythropoietin protects the myocardium from ischemia-reperfusion injury and promotes beneficial remodeling.

Erythropoietin (EPO), originally identified for its critical hormonal role in promoting erythrocyte survival and differentiation, is a member of the large and diverse cytokine superfamily. Recent studies have identified multiple paracrineautocrine functions of EPO that coordinate local responses to injury by maintaining vascular autoregulation and attenuating both primary (apoptotic) and secondary (inflammatory) causes of cell death. Experimental evidence also supports a role for EPO in repair and regeneration after brain and spinal cord injury, including the recruitment of stem cells into the region of damage. Tissue expression of the EPO receptor is widespread, especially during development, and includes the heart. However, it is currently unknown as to whether EPO plays a physiological function in adult myocardial tissue. We have assessed the potential protective role of EPO in vitro with adult rat cardiomyocytes, and in vivo in a rat model of myocardial infarction with reperfusion. The results show that EPO markedly prevents the apoptosis of cultured adult rat myocardiocytes subjected to 28 h of hypoxia (approximately 3% normal oxygen). Additional studies employing a rat model of coronary ischemia-reperfusion showed that the administration of recombinant human EPO (5,000 units/kg of body weight; i.p. daily for 7 days) reduces cardiomyocyte loss by approximately 50%, an extent sufficient to normalize hemodynamic function within 1 week after reperfusion. These observations not only suggest a potential therapeutic role for recombinant human EPO in the treatment of myocardial ischemia and infarction by preventing apoptosis and attenuating postinfarct deterioration in hemodynamic function, but also predict that EPO is likely a tissue-protective cytokine in other organs as well.

Acidosis↗

PubMed2003

Erythropoietin is a multifunctional tissue-protective cytokine.

Erythropoietin (EPO) was originally identified as a hormone produced by the adult kidney to facilitate optimum delivery of oxygen to tissue beds by adjustment of the circulating erythrocyte mass. The cloning of the EPO gene, subsequent production of recombinant protein, and successful introduction into clinical practice for the treatment of the anemia of renal failure is a triumph of biotechnology. However, molecular biologic studies have established that EPO is a member of the cytokine superfamily, with significant homology to mediators of growth and inflammation. Therefore, it is not surprising that additional biologic functions for this protein have been identified. Results from studies have shown that EPO and its receptor are widely expressed in embryonic and adult tissues, including the central nervous system, gut, kidney, muscle (eg, smooth, skeletal, and heart), uterus, retina, pancreas, gonads, and lung. We review the evidence that EPO and its receptor function as a paracrine/autocrine system to mediate the protection of tissues subjected to metabolic stress.

Animals↗

PubMed2002

Erythropoietin administration protects retinal neurons from acute ischemia-reperfusion injury.

Erythropoietin (EPO) plays an important role in the brain's response to neuronal injury. Systemic administration of recombinant human EPO (rhEPO) protects neurons from injury after middle cerebral artery occlusion, traumatic brain injury, neuroinflammation, and excitotoxicity. Protection is in part mediated by antiapoptotic mechanisms. We conducted parallel studies of rhEPO in a model of transient global retinal ischemia induced by raising intraocular pressure, which is a clinically relevant model for retinal diseases. We observed abundant expression of EPO receptor (EPO-R) throughout the ischemic retina. Neutralization of endogenous EPO with soluble EPO-R exacerbated ischemic injury, which supports a crucial role for an endogenous EPO/EPO-R system in the survival and recovery of neurons after an ischemic insult. Systemic administration of rhEPO before or immediately after retinal ischemia not only reduced histopathological damage but also promoted functional recovery as assessed by electroretinography. Exogenous EPO also significantly diminished terminal deoxynucleotidyltransferase-mediated dUTP end labeling labeling of neurons in the ischemic retina, implying an antiapoptotic mechanism of action. These results further establish EPO as a neuroprotective agent in acute neuronal ischemic injury.

Animals↗

PubMed2002

Recombinant human erythropoietin counteracts secondary injury and markedly enhances neurological recovery from experimental spinal cord trauma.

Erythropoietin (EPO) functions as a tissue-protective cytokine in addition to its crucial hormonal role in red cell production. In the brain, for example, EPO and its receptor are locally produced, are modulated by metabolic stressors, and provide neuroprotective and antiinflammatory functions. We have previously shown that recombinant human EPO (rhEPO) administered within the systemic circulation enters the brain and is neuroprotective. At present, it is unknown whether rhEPO can also improve recovery after traumatic injury of the spinal cord. To evaluate whether rhEPO improves functional outcome if administered after cord injury, two rodent models were evaluated. First, a moderate compression of 0.6 N was produced by application of an aneurysm clip at level T3 for 1 min. RhEPO (1,000 units per kg of body weight i.p.) administered immediately after release of compression was associated with partial recovery of motor function within 12 h after injury, which was nearly complete by 28 days. In contrast, saline-treated animals exhibited only poor recovery. In the second model used, rhEPO administration (5,000 units per kg of body weight i.p. given once 1 h after injury) also produced a superior recovery of function compared with saline-treated controls after a contusion of 1 N at level T9. In this model of more severe spinal cord injury, secondary inflammation was also markedly attenuated by rhEPO administration and associated with reduced cavitation within the cord. These observations suggest that rhEPO provides early recovery of function, especially after spinal cord compression, as well as longer-latency neuroprotective, antiinflammatory and antiapoptotic functions.

Animals↗

PubMed2002

Erythropoietin prevents motor neuron apoptosis and neurologic disability in experimental spinal cord ischemic injury.

The cytokine erythropoietin (EPO) possesses potent neuroprotective activity against a variety of potential brain injuries, including transient ischemia and reperfusion. It is currently unknown whether EPO will also ameliorate spinal cord injury. Immunocytochemistry performed using human spinal cord sections showed abundant EPO receptor immunoreactivity of capillaries, especially in white matter, and motor neurons within the ventral horn. We used a transient global spinal ischemia model in rabbits to test whether exogenous EPO can cross the blood-spinal cord barrier and protect these motor neurons. Spinal cord ischemia was produced in rabbits by occlusion of the abdominal aorta for 20 min, followed by saline or recombinant human (rHu)-EPO (350, 800, or 1,000 units/kg of body weight) administered intravenously immediately after the onset of reperfusion. The functional neurological status of animals was better for rHu-EPO-treated animals 1 h after recovery from anesthesia, and improved dramatically over the next 48 h. In contrast, saline-treated animals exhibited a poorer neurological score at 1 h and did not significantly improve. Histopathological examination of the affected spinal cord revealed widespread motor neuron injury associated with positive terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling in control but not in rHu-EPO-treated animals. These observations suggest both an acute as well as a delayed beneficial action of rHu-EPO in ischemic spinal cord injury. Because rHu-EPO is currently used widely with an excellent safety profile, clinical trials evaluating its potential to prevent motor neuron apoptosis and the neurological deficits that occur as a consequence of ischemic injury are warranted.

Animals↗

PubMed2002

Neuroprotective properties of epoetin alfa.

Erythropoietin and its receptor function as primary mediators of the normal physiological response to hypoxia. Erythropoietin is recognized for its central role in erythropoiesis, but studies in which recombinant human erythropoietin (epoetin alfa) is injected directly into ischaemic rodent brain show that erythropoietin also mediates neuroprotection. Abundant expression of the erythropoietin receptor has been observed at brain capillaries, which could provide a route for circulating erythropoietin to enter the brain. In confirmation of this hypothesis, systemic administration of epoetin alfa before or up to 6 h after focal brain ischaemia reduced injury by 50-75%. Epoetin alfa also limited the extent of concussive brain injury, the immune damage in experimental autoimmune encephalomyelitis and excitotoxicity induced by kainate. Thus, systemically administered epoetin alfa in animal models has neuroprotective effects, demonstrating its potential use after brain injury, trauma and multiple sclerosis. It is evident that erythropoietin has biological activities in addition to increasing red cell mass. Given the excellent safety profile of epoetin alfa, clinical trials evaluating systemically administered epoetin alfa as a general neuroprotective treatment are warranted.

Acute Disease↗

PubMed2002

Recombinant human erythropoietin for neuroprotection: what is the evidence?

Erythropoietin (EPO) is an endogenous cytokine with antiapoptotic, antiinflammatory, and neurotrophic properties. Apart from being produced by the kidney, liver, and spleen in response to hypoxia, EPO is highly expressed in the brain during development and after neuropathological insults. The observation that receptors for EPO are present on brain capillaries and glial capillary end-feet has suggested that circulating (plasma) EPO may be transferred into the brain. This review summarizes the increasing number of studies indicating that peripherally administered recombinant human (rHu) EPO crosses the blood-brain barrier. Moreover, several of these studies have shown that peripherally administered rHuEPO can protect against the damage caused by a diversity of neuropathological conditions such as (a) stroke, (b) head and spinal cord trauma, (c) inflammatory and demyelinating conditions, (d) toxin-induced epileptic seizures, and (e) retinal ischemia. While all these studies are based on experiments in animal models, the effectiveness of rHuEPO in ischemic stroke in human patients has recently been suggested in a proof-of-concept trial, which is also discussed.

Animals↗

PubMed2002

What evidence supports use of erythropoietin as a novel neurotherapeutic?

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.

Brain↗

PubMed2002

Erythropoietin therapy for acute stroke is both safe and beneficial.

BACKGROUND: Erythropoietin (EPO) and its receptor play a major role in embryonic brain, are weakly expressed in normal postnatal/adult brain and up-regulated upon metabolic stress. EPO protects neurons from hypoxic/ ischemic injury. The objective of this trial is to study the safety and efficacy of recombinant human EPO (rhEPO) for treatment of ischemic stroke in man. MATERIALS AND METHODS: The trial consisted of a safety part and an efficacy part. In the safety study, 13 patients received rhEPO intravenously (3.3 X 10(4) IU/50 ml/30 min) once daily for the first 3 days after stroke. In the double-blind randomized proof-of-concept trial, 40 patients received either rhEPO or saline. Inclusion criteria were age <80 years, ischemic stroke within the middle cerebral artery territory confirmed by diffusion-weighted MRI, symptom onset <8 hr before drug administration, and deficits on stroke scales. The study endpoints were functional outcome at day 30 (Barthel Index, modified Rankin scale), NIH and Scandinavian stroke scales, evolution of infarct size (sequential MRI evaluation using diffusion-weighted [DWI] and fluid-attenuated inversion recovery sequences [FLAIR]) and the damage marker S100ss. RESULTS: No safety concerns were identified. Cerebrospinal fluid EPO increased to 60-100 times that of nontreated patients, proving that intravenously administered rhEPO reaches the brain. In the efficacy trial, patients received rhEPO within 5 hr of onset of symptoms (median, range 2:40-7:55). Admission neurologic scores and serum S100beta concentrations were strong predictors ofoutcome. Analysis of covariance controlled for these two variables indicated that rhEPO treatment was associated with an improvement in follow-up and outcome scales. A strong trend for reduction in infarct size in rhEPO patients as compared to controls was observed by MRI. CONCLUSION: Intravenous high-dose rhEPO is well tolerated in acute ischemic stroke and associated with an improvement in clinical outcome at 1 month. A larger scale clinical trial is warranted.

Blood Platelets↗

PubMedDate not supplied

Carbamylated erythropoietin reduces radiosurgically-induced brain injury.

Gamma knife radiosurgery is an attractive noninvasive treatment of brain tumors and vascular malformations that minimizes collateral tissue damage. However, exposure of normal tissue to even low-dose radiation triggers a cascade of acute and chronic injury and potentially significant morbidity and mortality. Because many irradiated patients now survive for years, identifying methods to prevent radiotherapy-induced collateral tissue damage is a major focus of current research. Erythropoietin (EPO), a cytokine produced locally by many tissues in response to injury, antagonizes apoptosis, reduces inflammation, and promotes healing. Systemic administration of recombinant EPO, widely used for treatment of anemia, provides robust protection from numerous insults in a variety of tissues, including the brain. Although irradiation injury is likely sensitive to EPO, the hematopoietic activity of EPO is undesirable in this setting, increasing erythrocyte number and predisposing to thrombosis. To avoid these potential adverse effects, we developed carbamylated EPO (CEPO) which does not stimulate the bone marrow. In this study, we show that CEPO (50 microg kg(-1) intraperitoneally) improves functional outcome when administered to adult rats just before, and then once daily for 10 d after, a necrotizing dose of radiation (100 Gy) to the right striatum. Immediately following irradiation, use and reflex movements of the contralateral forelimb to vibrissae stimulation were abnormal but rapidly improved in animals receiving CEPO. Moreover, histological examination revealed that the extent of brain necrosis after 90 days was reduced by approximately 50%. These findings further extend the kinds of injury for which administration of a tissue-protective cytokine provides benefit.

Animals↗

PubMedDate not supplied

Nonhematopoietic erythropoietin derivatives prevent motoneuron degeneration in vitro and in vivo.

Chronic treatment with asialo erythropoietin (ASIALO-EPO) or carbamylated erythropoietin (CEPO) improved motor behavior and reduced motoneuron loss and astrocyte and microglia activation in the cervical spinal cord of wobbler mice, an animal model of amyotrophic lateral sclerosis, but had no effect on hematocrit values. ASIALO-EPO and CEPO, like the parent compound EPO, protected primary motoneuron cultures from kainate-induced death in vitro. Both EPO receptor and the common CD131 beta chain were expressed in cultured motoneurons and in the anterior horn of wobbler mice spinal cord. Our results strongly support a role for the common beta chain CD131 in the protective effect of EPO derivatives on motoneuron degeneration. Thus CEPO, which does not bind to the classical homodimeric EPO receptor and is devoid of hematopoietic activity, could be effective in chronic treatment aimed at reducing motoneuron degeneration.

Animals↗