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Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I.

ABSTRACT: Erythropoietin (EPO) and insulin-like growth factor I (IGF-I) are cytokines that inhibit neuronal apoptosis. However, their maximal antiapoptotic effect, even at high concentrations, is observed only when neurons are pretreated for several hours before insult. Here we show that simultaneous administration of EPO and IGF-I (EPO+IGF-I) eliminates the preincubation period required to prevent N-methyl-D-aspartate (NMDA)-induced apoptosis in cultured rat cerebrocortical neurons. The synergistic effect of EPO+IGF-I was mediated, at least in part, by activation of phosphatidylinositol 3-kinase (PI3-K). EPO+IGF-I synergistically activated Akt (protein kinase B), a downstream target of PI3-K, and prevented dephosphorylation of Akt. Overexpression of a dominant interfering form of Akt (dnAkt) abrogated EPO+IGF-I-mediated neuroprotection. EPO+IGF-I treatment did not prevent initial NMDA-induced caspase-3 activation, which was observed within 6 h of insult; however, EPO+IGF-I-treated neurons survived at least 2 days after NMDA insult. These cytokines prevented neuronal apoptosis downstream of caspase activation by facilitating association between X-linked inhibitor of apoptosis protein, an inhibitor of caspase proteolytic activity, and activated caspase-3. These results imply that EPO+IGF-I exert cooperative actions that afford acute neuroprotection via activation of the PI3-K-Akt pathway.

SUBMITTER: Digicaylioglu M

PROVIDER: S-EPMC470763 | biostudies-literature | 2004 Jun

REPOSITORIES: biostudies-literature

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Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I.

Digicaylioglu Murat M Garden Gwenn G Timberlake Sonia S Fletcher Lauren L Lipton Stuart A SA

Proceedings of the National Academy of Sciences of the United States of America 20040621 26

Erythropoietin (EPO) and insulin-like growth factor I (IGF-I) are cytokines that inhibit neuronal apoptosis. However, their maximal antiapoptotic effect, even at high concentrations, is observed only when neurons are pretreated for several hours before insult. Here we show that simultaneous administration of EPO and IGF-I (EPO+IGF-I) eliminates the preincubation period required to prevent N-methyl-D-aspartate (NMDA)-induced apoptosis in cultured rat cerebrocortical neurons. The synergistic effec ...[more]

PMID: 15210945

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Project description:Hypoxic-ischemic (HI) injury in the developing brain is a common cause of disability in children, and there are no effective treatments at this time. Erythropoietin (EPO) has recently gained interest as a neuroprotective drug, and EPO and its receptor are expressed within the central nervous system. We have recently shown that pretreatment with EPO markedly reduced brain injury caused by unilateral hypoxic-ischemic insult in 7 day old mice. EPO did not reduce early signs of neuronal injury at 6 hours, but significantly protected the neonatal brain when assessed 24 hours and 7 days after HI. The mechanism of this delayed protection is unclear, but is thought to involve transcription of neuroprotective genes, possibly subsequent to activation of NFkB. By comparing gene expression in EPO- and vehicle- (VEH) treated mice after HI, we should gain insight into the mechanisms underlying the neuroprotective effects of EPO and may identify additional targets for therapeutic interventions. We will compare gene expression patterns in 7-day old mouse forebrain after 1) VEH pretreatment plus sham surgery, 2) VEH pretreatment plus HI, and 3) EPO pretreatment plus HI. We will thus identify genes induced by HI in the developing brain and characterize changes in gene expression caused by EPO pretreatment. We will use the model of neonatal hypoxic-ischemic injury and EPO treatment parameters that were used in our prior studies demonstrating neuroprotection. Based on the time-course of neuroprotection defined in our prior study and the pharmacokinetic profile of EPO, we will examine gene expression 18 hours after HI. We hypothesize that changes in gene expression after EPO pretreatment underlie the neuroprotective effects of this cytokine after neonatal hypoxic ischemic injury. We will examine gene expression in 3 groups: 1) 1) VEH pretreatment + sham surgery, 2) VEH pretreatment + HI, and 3) EPO pretreatment + HI. EPO (5U/g, i.p.) or VEH was injected in 7 day old mice, drawn from 4 litters, with 3 to 4 pups per treatment group in each litter. One hour later, the right common carotid artery was ligated under isoflurane anesthesia, animals were allowed to recover for 90 min and were then placed in hypoxic chambers (10% oxygen, balance nitrogen) for 50 min. The animals subjected to sham surgery received isoflurane anesthesia for a comparable period, incision and dissection to visualize the common carotid artery, but no ligation and no hypoxia. Eighteen hrs later, animals were anesthetized with isoflurane and the right hemisphere was rapidly dissected and placed in RNA Later (Qiagen) at 4C. Total RNA was isolated using an RNeasy lipid tissue mini kit (QIAzol lysis and RNeasy purification, Qiagen). RNA concentrations were determined spectrophotometrically and an aliquot of each sample was examined by gel electrophoresis to screen for degradation. Samples were stored at -80C. After quality control screening, we selected 5 male and 5 female samples per treatment group (extra samples were reserved). We plan to pool 1 male and 1 female for each microarray sample and we plan to run 5 microarrays from each treatment group, for a total of 15 microarrays. We would like to have Agilent Bioanalyzer quality control assays on the individual samples carried out by the consortium before pooling. We will send 10 micrograms of each sample for Agilent QC and subsequent pooling of equimolar amounts. We would like to use Affymetrix mouse gene chips (please advise which specific chips are available; are you using the GeneChip Mouse Expression array 430A or the GeneChip Mouse Genome 430 2.0 Array?). Keywords: dose response

Project description:IntroductionNeuroendocrine deficiencies may affect recovery after aneurysmal subarachnoid hemorrhage (aSAH). Insulin like growth factor-I (IGF-I) regulates neuronal growth and apoptosis in ischemic stroke. Our study was designed to a) characterize the behavior of serum IGF-I and growth hormone (GH) in the acute and late phases after aSAH reflecting possible pituitary gland function and b) evaluate the association between IGF-I and morbidity assessed by Glasgow outcome scale (GOS) and health related quality of life (HRQoL) in patients with aSAH.MethodsIn this prospective cohort study, patients with aSAH (n = 30) were compared to patients who underwent elective aneurysm surgery (n = 16). Serum GH and IGF-I concentrations were measured daily for five (controls) or seven (aSAH) days and at three months. GOS and 15d HRQoL was measured at three months. A mixed models method was used for testing between the groups. For factors possibly affecting HRQoL in aSAH patients, we constructed a Bayesian predicting model using a P-course Bayesian classifier.ResultsThe mean IGF-I concentrations for days one to five were 8.1 +/- 3.5 nmol/l in patients with aSAH and 11.2 +/- 3.1 in the control group (P = 0.01). No corresponding difference was found at three months. Serum GH concentrations were similar in both patient groups. Severity of the aSAH did not affect serum IGF-I concentrations. Patients with GOS <or= 4 had lower IGF-I concentrations and lower HRQoL than patients with GOS 5 (P = 0.02 and 0.003 respectively). The 15d HRQoL was 0.81 +/- 0.16 in patients with aSAH and 0.86 +/- 0.09 in control patients (P = 0.24). In the Bayesian model, the use of statins prior to aSAH, hyponatremia, high maximal sequential organ specific score (SOFAmax), and low cumulative IGF-I concentrations on days one to seven were associated with poor HRQoL (accuracy 89%, sensitivity 86%, and specificity 93%).ConclusionsIGF-I concentrations are low during acute aSAH, which may have an impact on morbidity.Trial registrationClinicalTrials.gov Identifier NCT00614887.

Dataset Information

Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I.

Publications

Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I.

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