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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neurogenesis in the brain continues throughout life and is promoted by brain insults including ischemia. There is no critical conclusion, however, about whether proliferated cells acquire neuronal function after ischemia. Transient global ischemia was produced by a four-vessel occlusion procedure in rats (n = 54). To label proliferative cells, rats were administrated with a single dose of 5-bromo-2'-deoxyuridine (BrdU) at 4, 6, 8, 10, 13, or 15 days after ischemia. Increases in BrdU-positive cells were detected in the hippocampal dentate gyrus at 5, 7, and 9 days after ischemia. To determine the phenotype of BrdU-positive cells, BrdU was administrated twice daily for 3 consecutive days during 6 to 8 days after ischemia. A basic helix-loop-helix transcription factor NeuroD at 7 and 14 days and an immature migrating neuronal marker doublecortin at 14 days after ischemia were expressed transiently in proliferative cells. These proliferative cells after ischemia differentiated to the phenotype of neuron at 28 days after ischemia. Furthermore, BrdU-positive neurons showed phosphorylation of extracellular signal-regulated kinase (ERK) by intracerebroventricular injection of N-methyl-D-aspartate (NMDA) at 28 and 56 days after ischemia as seen in surrounding mature neurons. The number of BrdU-positive neurons, which responded to NMDA stimulation, increased with time after ischemia and was greater than that of sham-operated animals. The present study provides evidence for in vivo ERK phosphorylation in response to NMDA stimulation of BrdU-positive neurons in the adult hippocampus after transient forebrain ischemia.
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PMID:Characterization of BrdU-positive neurons induced by transient global ischemia in adult hippocampus. 1512 87

Abstract The dualistic activities of the amyloid beta (Abeta) peptide as a pro-oxidant and ubiquitous constituent of amyloid deposits in Alzheimer's disease plaques and as an antioxidant of purported physiological function has been suggested but the mechanisms are far from being understood. In this report we measure several oxidative stress parameters and signaling cascades in brains of fetal rats subjected to global ischemia in order to evaluate the putative bifunctional properties of the Abeta(1-40) peptide. Intraperitoneal injection of 6 microg Abeta(1-40) into 18-days-old rat fetuses (approximately 3 g body weight) resulted after 24 h in the appearance of the peptide in various fetal organs including brain where it enhanced the levels of glutathione (GSH), glutathione reductase, glutathione peroxidase, and stimulated the levels of pro-survival signaling activities such as Akt serine/threonine kinase, extracellular signal-regulated kinase (ERK) and protein kinase C enzymes. Moreover, pretreatment with Abeta(1-40) reversed the consequences of a transient hypovolemic/hypotensive oxidative stress by restoring GSH levels via its recycling enzymes and by lowering the production of lipid peroxides presumably by activating the aforementioned pro-survival signaling cascades. It also caused a reduction in the number of DAPI-enhanced reactive cells and a decrease in p38 kinase phosphorylation and caspase-9 and -3 activity. These data suggest that pre-exposure to Abeta(1-40) stimulates fetal tolerance to ischemia via regulation of GSH metabolism and as such may be considered as neuroprotective.
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PMID:Amyloid Abeta1-40 preconditions non-apoptotic signals in vivo and protects fetal rat brain from intrauterine ischemic stress. 1552 50

In the hippocampus, extracellular signal-regulated kinase (ERK) and the non-receptor protein proline-rich tyrosine kinase 2 (PYK2) are activated by depolarization and involved in synaptic plasticity. Both are also activated under pathological conditions following ischemia, convulsions, or electroconvulsive shock. Although in non-neuronal cells PYK2 activates ERK through the recruitment of Src-family kinases (SFKs), the link between these pathways in the hippocampus is not known. We addressed this question using K(+)-depolarized rat hippocampal slices. Depolarization increased the phosphorylation of PYK2, SFKs, and ERK. These effects resulted from Ca(2+) influx through voltage-gated Ca(2+) channels and were diminished by GF109203X, a protein kinase C inhibitor. Inhibition of SFKs with PP2 decreased PYK2 tyrosine phosphorylation dramatically, but not its autophosphorylation on Tyr-402. Moreover, PYK2 autophosphorylation and total tyrosine phosphorylation were profoundly altered in fyn-/- mice, revealing an important functional relationship between Fyn and PYK2 in the hippocampus. In contrast, ERK activation was unaltered by PP2, Fyn knock-out, or LY294002, a phosphatidyl-inositol-3-kinase inhibitor. ERK activation was prevented by MEK inhibitors that had no effect on PYK2. Immunofluorescence of hippocampal slices showed that PYK2 and ERK were activated in distinct cellular compartments in somatodendritic regions and nerve terminals, respectively, with virtually no overlap. Activation of ERK was critical for the rephosphorylation of a synaptic vesicle protein, synapsin I, following depolarization, underlining its functional importance in nerve terminals. Thus, in hippocampal slices, in contrast to cell lines, depolarization-induced activation of non-receptor tyrosine kinases and ERK occurs independently in distinct cellular compartments in which they appear to have different functional roles.
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PMID:Depolarization activates ERK and proline-rich tyrosine kinase 2 (PYK2) independently in different cellular compartments in hippocampal slices. 1553 34

Adenosine A1 receptor delayed preconditioning (PC) against myocardial infarction has been well described; however, there have been limited investigations of the signaling mechanisms that mediate this phenomenon. In addition, there are multiple conflicting reports on the role of inducible nitric oxide synthase (iNOS) in mediating A1 late-phase PC. The purpose of this study was to determine the roles of the p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases (MAPKs) in in vivo delayed A1 receptor PC and whether this protection at the myocyte level is due to upregulation of iNOS. Myocardial infarct size was measured in open-chest anesthetized rats 24 h after treatment with vehicle or the adenosine A1 agonist 2-chloro-N6-cyclopentyladenosine (CCPA; 100 microg/kg ip). Additional rats receiving CCPA were pretreated with the p38 inhibitor SB-203580 (1 mg/kg ip) or the MAPK/ERK kinase (MEK) inhibitor PD-098059 (0.5 mg/kg ip). At 24 h after CCPA administration, a group of animals was given the iNOS inhibitor 1400 W 10 min before ischemia. Treatment with CCPA reduced infarct size from 48 +/- 2 to 28 +/- 2% of the area at risk, an effect that was blocked by both SB-203580 and PD-098059 but not 1400 W. Ventricular myocytes isolated 24 h after CCPA injection exhibited significantly reduced oxidative stress during H2O2 exposure compared with myocytes from vehicle-injected animals, and this effect was not blocked by the iNOS inhibitor 1400 W. Western blot analysis of whole heart and cardiac myocyte protein samples revealed no expression of iNOS 6 or 24 h after CCPA treatment. These results indicate that adenosine A1 receptor delayed PC in rats is mediated by MAPK-dependent mechanisms, but this phenomenon is not associated with the early or late expression of iNOS.
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PMID:Delayed adenosine A1 receptor preconditioning in rat myocardium is MAPK dependent but iNOS independent. 1583 99

Langendorff-perfused rat hearts treated with EPO exhibited significantly improved postischemic recovery of left ventricular developed pressure (LVDP) and reduced infarct size compared with control hearts. Perfusion with the mitogen/extracellular signal-regulated kinase (MEK) inhibitor U0126 just before and concomitant with EPO treatment abolished EPO-induced phosphorylation of the MEK substrate extracellular signal-regulated kinase (ERK) but had no effect of EPO-mediated cardioprotection. EPO treatment of the perfused hearts induced translocation of protein kinase C (PKC) epsilon isoform to the membrane fraction of the hearts and the protective effect of EPO was significantly inhibited by the PKC catalytic inhibitor chelerythrine added before and concomitant with EPO. These data demonstrate that EPO-mediated activation of the PKC signaling pathway before or during ischemia is required for the cardioprotective effect of EPO during ischemia-reperfusion injury. Perfusion with the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin just before and concomitant with EPO treatment attenuated EPO-induced phosphorylation of the PI3K substrate Akt but had no effect on EPO-mediated cardioprotection. However, when wortmannin was added during EPO treatment and continued during reperfusion, EPO-mediated cardioprotection was significantly inhibited. We also show that postischemia EPO treatment at the onset of reperfusion significantly improved recovery of LVDP and reduced infarct size. Postischemia cardioprotection by EPO required the PI3K pathway but was not affected by inhibition of PKC at the time of EPO treatment.
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PMID:Mechanisms of erythropoietin-mediated cardioprotection during ischemia-reperfusion injury: role of protein kinase C and phosphatidylinositol 3-kinase signaling. 1594 93

Blocking poly(ADP-ribosyl)ation of nuclear proteins protects the heart from ischemia-reperfusion injury. In addition, activation of Akt and mitogen-activated protein kinase (MAPK) cascades also plays a pivotal role in the survival of cardiomyocytes during ischemia-reperfusion; however, the potential interplay between these pathways is yet to be elucidated. We therefore tested the hypothesis whether poly(ADP-ribose) polymerase (PARP) inhibition can modulate Akt and MAPK signaling of ischemic-reperfused rat hearts. A novel PARP inhibitor, L-2286 [2-[(2-piperidin-1-yletil)thio]quinazolin-4(3H)-one] was administered during ischemia-reperfusion in Langendorff perfused rat hearts and in isoproterenol-induced myocardial infarction. Thereafter, the cardiac energy metabolism, oxidative damage, and the phosphorylation state of Akt and MAPK cascades were monitored. L-2286 exerted significant protective effect against ischemia-reperfusion-induced myocardial injury in both experimental models. More importantly, L-2286 facilitated the ischemia-reperfusion-induced activation of Akt, extracellular signal-regulated kinase, and p38-MAPK in both isolated hearts and in vivo cardiac injury. By contrast, isoproterenol-induced rapid c-Jun N-termainal kinase activation was repressed by L-2286. Here, we provide evidence for the first time that PARP inhibition beneficially modulates the cardiac Akt and MAPK signaling in ex vivo and in vivo ischemia-reperfusion models. We therefore propose that this novel mechanism may contribute to the cardioprotective properties of PARP inhibitors.
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PMID:The role of Akt and mitogen-activated protein kinase systems in the protective effect of poly(ADP-ribose) polymerase inhibition in Langendorff perfused and in isoproterenol-damaged rat hearts. 1595

Reactive oxygen species (ROS) are implicated in tissue damage causing primary hepatic dysfunction following ischemia/reperfusion injury and during inflammatory liver diseases. A potential role of extracellular signal-regulated kinase (ERK) as a mediator of survival signals during oxidative stress was investigated in primary cultures of hepatocytes exposed to ROS. Hydrogen peroxide (H(2)O(2)) induced a dose-dependent activation of ERK, which was dependent on MEK activation. The ERK activation pattern was transient compared with the ERK activation seen after stimulation with epidermal growth factor (EGF). Nuclear accumulation of ERK was found after EGF stimulation, but not after H(2)O(2) exposure. A slow import/rapid export mechanism was excluded through the use of leptomycin B, an inhibitor of nuclear export sequence-dependent nuclear export. Reduced survival of hepatocytes during ROS exposure was observed when ERK activation was inhibited. Ribosomal S6 kinase (RSK), a cytoplasmic ERK substrate involved in cell survival, was activated and located in the nucleus of H(2)O(2)-exposed hepatocytes. The activation was abolished when ERK was inhibited with U0126. In conclusion, our results indicate that activity of ERK in the cytoplasm is important for survival during oxidative stress in hepatocytes and that RSK is activated downstream of ERK. Supplementary material for this article can be found on the HEPATOLOGY website (http://www.interscience.wiley.com/jpages/0270-9139/suppmat/index.html).
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PMID:Cytoplasmic retention of peroxide-activated ERK provides survival in primary cultures of rat hepatocytes. 1596 31

In vivo, pathological conditions such as ischemia and ischemia/reperfusion are known to damage the blood-brain barrier (BBB) leading to the development of vasogenic brain edema. Using an in vitro model of the BBB, consisting of brain-derived microvascular endothelial cells (BMEC), it was demonstrated that hypoxia-induced paracellular permeability was strongly aggravated by reoxygenation (H/R), which was prevented by catalase suggesting that H2O2 is the main mediator of the reoxygenation effect. Therefore, mechanisms leading to H2O2-induced hyperpermeability were investigated. N-acetylcysteine and suramin and furthermore usage of a G protein antagonist inhibited H202 effects suggesting that activation of cell surface receptors coupled to G proteins may mediate signal initiation by H2O2. Further, H2O2 activated phospholipase C (PLC) and increased the intracellular Ca2+ release because U73122, TMB-8, and the calmodulin antagonist W7 inhibited H2O2-induced hyperpermeability. H2O2 did not activate protein kinase C (PKC), nitric-oxide synthase (NOS), and phosphatidyl-inositol-3 kinase (PI3-K/Akt). Inhibition of the extracellular signal-regulated kinase (ERK1/ERK2 or p44/42 MAPK), but not of the p38 and of the c-jun NH2-terminal kinase (JNK), inhibited hyperpermeability by H2O2 and H/R completely. Corresponding to H2O2- and H/R-induced permeability changes the phosphorylation of the p44/42 MAP kinase was inhibited by the specific MAP kinase inhibitor PD98059 and by TMB-8 and W7. Paracellular permeability changes by H2O2 correlated to changes of the localization of the tight junction (TJ) proteins occludin, zonula occludens 1 (ZO-1), and zonula occludens 2 (ZO-2) which were prevented by blocking the p44/p42 MAP kinase activation. Results suggest that H2O2 is the main inducer of H/R-induced permeability changes. The hyperpermeability is caused by activation of PLC via receptor activation leading to the intracellular release of Ca2+ followed by activation of the p44/42 MAP kinase and paracellular permeability changes mediated by changes of the localization of TJ proteins.
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PMID:H2O2 induces paracellular permeability of porcine brain-derived microvascular endothelial cells by activation of the p44/42 MAP kinase pathway. 1610 12

Transplantation of bone marrow stromal cells improves animal neurological functional recovery after stroke. Astrocytes are known to provide structural, trophic and metabolic support for neurons. Thus astrocytes are critical for neural survival during post-ischemia. However, information on the effects of bone marrow stromal cells on astrocytic survival post-ischemia is unavailable. We investigated the influence of rat bone marrow stromal cells on rat astrocytic apoptosis and survival post-ischemia employing an anaerobic chamber. Our data indicate that rat bone marrow stromal cells reduce cell death and apoptosis, and increase the DNA proliferation rate in astrocytes post-ischemia. Mitogen-activated protein kinase kinase/extracellular signal regulated kinase and phosphoinositide 3-kinase/threonine protein kinase pathways are involved in cell survival. Western blot showed that rat bone marrow stromal cells activate these two pathways in astrocytes post-ischemia, and upregulate total extracellular signal regulated kinase 1/2 and threonine protein kinase. Since astrocytes produce various neurotrophic factors, we performed reverse transcription polymerase chain reaction to investigate rat bone marrow stromal cells' effect on astrocyte growth factor gene expression post-ischemia. We observed that brain-derived neurotrophic factor, vascular endothelial growth factor and basic fibroblast growth factor gene expression was enhanced by rat bone marrow stromal cell coculture. These data suggest that bone marrow stromal cells increase astrocytic survival post-ischemic injury. This protective function might involve the activation of mitogen-activated protein kinase kinase/extracellular signal-regulated kinase and phosphoinositide 3-kinase/threonine protein kinase pathways. Upregulation of brain-derived neurotrophic factor, vascular endothelial growth factor and basic fibroblast growth factor may also contribute to astrocyte survival.
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PMID:Bone marrow stromal cells increase astrocyte survival via upregulation of phosphoinositide 3-kinase/threonine protein kinase and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathways and stimulate astrocyte trophic factor gene expression after anaerobic insult. 1619 97

It has been shown that dietary red palm oil (RPO) supplementation improves reperfusion function. However, no exact protective cellular mechanisms have been established. To determine a potential mechanism for functional improvement, we examined the regulation of both mitogen-activated protein kinases (MAPKs) and PKB/Akt in the presence and absence of dietary RPO supplementation in ischemia/reperfusion-induced injury. Wistar rats were fed a control diet or control diet plus 7 g RPO/kg diet for 6 weeks. Hearts were excised and mounted on an isolated working heart perfusion apparatus. Cardiac function was measured before and after hearts were subjected to 25 min of total global ischemia. Hearts subjected to the same conditions were freeze clamped and used to characterize the degree of phosphorylation of extracellular signal-regulated kinase, p38, c-Jun NH(2)-terminal protein kinase (JNK) and PKB/Akt. Dietary RPO supplementation significantly improved aortic output recovery (72.1 +/- 3.2% vs. 54.0 +/- 3.2%, P < .05). This improved aortic output recovery was associated with significant increases in p38 and PKB/Akt phosphorylation during reperfusion when compared with control hearts. Furthermore, a significant decrease in JNK phosphorylation and attenuation of poly(ADP-ribose) polymerase cleavage occurred in the RPO-supplemented group during reperfusion. Our results suggest that dietary RPO supplementation caused differential phosphorylation of the MAPKs and PKB/Akt during ischemia/reperfusion-induced injury. These changes in phosphorylation were associated with improved functional recovery and reduced cleavage of an apoptotic marker, arguing that dietary RPO supplementation may confer protection via the MAPK and PKB/Akt signaling pathways during ischemia/reperfusion-induced injury.
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PMID:p38-MAPK and PKB/Akt, possible role players in red palm oil-induced protection of the isolated perfused rat heart? 1622 99


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