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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Early olfactory preference learning in rat pups occurs when novel odors are paired with tactile stimulation, for example stroking. cAMP-triggered phosphorylation of cAMP response element binding protein (pCREB) has been implicated as a mediator of learning and memory changes in various animals (Frank and Greenberg 1994). In the present study we investigate whether CREB is phosphorylated in response to conditioned olfactory training as might be predicted given the proposed role of the phosphorylated protein in learning. On postnatal day 6, pups were trained for 10 min using a standard conditioned olfactory learning paradigm in which a conditioned stimulus, Odor, was either used alone or paired with an unconditioned stimulus, Stroking (using a fine brush to stroke the pup). In some instances stroking only was used. The pups were sacrificed at 0, 10, 30, or 60 min after the training. Using Western blot analysis, we observed that the majority of olfactory bulbs in conditioned pups (Odor + Stroking) had a greater increase in pCREB activation at 10 min after training than pups given nonlearning training (Odor only or Stroking only). The phosphorylated protein levels were low at 0 min and at 60 min after training. This is in keeping with the slightly delayed and short-lived activation period for this protein. The localization of pCREB increases within the olfactory bulb as seen by immunocytochemistry. Naive pups were not exposed to odor or training. There was a significantly higher level of label in mitral cell nuclei within the dorsolateral quadrant of the bulb of pups undergoing odor-stroke pairing. No significant differences were observed among nonlearning groups (Naive, Odor only, or Stroking only) or among any training groups in the granule or periglomerular cells of the dorsolateral region. The localized changes in the nuclear protein are consistent with studies showing localized changes in the bulb in response to a learned familiar odor. The present study demonstrates that selective increases in pCREB occur as an early step following pairing procedures that normally lead to the development of long-term olfactory memories in rat pups. These results support the hypothesized link between pCREB and memory formation.
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PMID:pCREB in the neonate rat olfactory bulb is selectively and transiently increased by odor preference-conditioned training. 1064 65

Two relatively well characterised kinase signalling pathways are those involving MAPK/ERK and p38/SAPK2, that are known to be activated in vitro by various factors known to increase following stroke, such as glutamate, IL-1 and TNF. The present study was designed to investigate the activation and cellular distribution of phosphorylated-ERK1/2, -p38 and the transcription factor CREB following focal cerebral ischaemia using phosphospecific antibodies. Up to 24 h following transient MCAO (90 min) and 6 h following permanent MCAO, phospho-ERK1/2 staining was markedly increased within the cytoplasm of neuronal perikarya in 'penumbral-like' regions. In contrast, phospho-p38 immunostaining was markedly increased in cells with astrocyte-like morphology in both 'core' and 'penumbral-like' regions. Phospho-p38 staining was also detected in some neurones within 'penumbral-like' regions up to 24 h following transient MCAO. CREB activation was confined to neurones in 'penumbral-like' regions. Increased phospho-p38 immunoreactivity was detected in astrocyte-like cells present in the subcortical white matter ipsilateral to the occluded MCAO, while phospho-CREB and -ERK1/2 staining was localised to cells with the morphological appearance of oligodendrocytes. This study demonstrates phosphorylation, indicative of activation, of both the MAPK and p38 pathways following transient and permanent MCAO. However, each pathway shows a distinct cellular and spatial distribution within ischaemic tissue. Together these data indicate that neuroprotection offered by agents directed towards the ERK1/2 pathway may act directly through protection of neurones and oligodendrocytes, while those directed towards the p38 pathway kinase signalling pathways may be indirectly via inhibition of cytokines and other mediators involved in the brains response to injury.
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PMID:Differential activation of MAPK/ERK and p38/SAPK in neurones and glia following focal cerebral ischaemia in the rat. 1081 33

Besides their well-established actions on reproductive functions, estrogens exert a variety of actions on many regions of the nervous system that influence higher cognitive function, pain mechanisms, fine motor skills, mood, and susceptibility to seizures; they also appear to have neuroprotective actions in relation to stroke damage and Alzheimer's disease. Estrogen actions are now recognized to occur via two different intracellular estrogen receptors, ER-alpha and ER-beta, that reside in the cell nuclei of some nerve cells, as well as by some less well-characterized mechanisms. In the hippocampus, such nerve cells are sparse in number and yet appear to exert a powerful influence on synapse formation by neurons that do not have high levels of nuclear estrogen receptors. However, we also find nonnuclear estrogen receptors outside of the cell nuclei in dendrites, presynaptic terminals, and glial cells, where estrogen receptors may couple to second messenger systems to regulate a variety of cellular events and signal to the nuclear via transcriptional regulators such as CREB. Sex differences exist in many of the actions of estrogens in the brain, and the process of sexual differentiation appears to affect many brain regions outside of the traditional brain areas involved in reproductive functions. Finally, the aging brain is responsive to actions of estrogens, which have neuroprotective effects both in vivo and in vitro. However, in an animal model, the actions of estrogens on the hippocampus appear to be somewhat attenuated with age. In the future, estrogen actions over puberty and in pregnancy and lactation should be further explored and should be studied in both the hypothalamus and the extrahypothalamic regions.
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PMID:Invited review: Estrogens effects on the brain: multiple sites and molecular mechanisms. 1171 47

Here we report that synaptic and extrasynaptic NMDA (N-methyl-D-aspartate) receptors have opposite effects on CREB (cAMP response element binding protein) function, gene regulation and neuron survival. Calcium entry through synaptic NMDA receptors induced CREB activity and brain-derived neurotrophic factor (BDNF) gene expression as strongly as did stimulation of L-type calcium channels. In contrast, calcium entry through extrasynaptic NMDA receptors, triggered by bath glutamate exposure or hypoxic/ischemic conditions, activated a general and dominant CREB shut-off pathway that blocked induction of BDNF expression. Synaptic NMDA receptors have anti-apoptotic activity, whereas stimulation of extrasynaptic NMDA receptors caused loss of mitochondrial membrane potential (an early marker for glutamate-induced neuronal damage) and cell death. Specific blockade of extrasynaptic NMDA receptors may effectively prevent neuron loss following stroke and other neuropathological conditions associated with glutamate toxicity.
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PMID:Extrasynaptic NMDARs oppose synaptic NMDARs by triggering CREB shut-off and cell death pathways. 1197 96

In the acute phase of cerebral infarction, many experimental data suggest that free radicals including superoxide, hydroxy radical and nitric oxide are one of the most important factors to cause brain damage. We have clearly detected nitrotyrosine (a marker of endogenous production of peroxynitrite, which is readily produced from superoxide and nitric oxide) in neurons and intraparenchymal vascular walls during post-ischemic reperfusion. Free radical scavengers thus seem to be very promising tools of treatment, and one of them (edaravone) has recently been approved for clinical use in Japan. CREB (cyclic AMP response element binding protein) is a DNA-binding transcription factor, and its function is activated by phosphorylation of Ser133 residue. CREB plays important roles in neuronal development, synaptic plasticity and regeneration. We have found that phosphorylation of CREB is significantly and persistently increased in surviving neurons and oligodendrocytes in post-ischemic brain, while this phosphorylation is only transiently increased in neurons and oligodendrocytes which eventually die. These data suggest that CREB phosphorylation plays an important role in protection of ischemic brain tissue. Oligodendrocyte progenitor cells (OPC) remain abundant throughout the adult brain, and retain their ability to become not only mature oligodendrocytes, but also neurons. We have recently found that OPC are significantly activated and proliferate in the peri-infarct area at 1-2 weeks after ischemia, suggesting that OPC may be involved in the repair mechanisms of ischemic brain. Future targets of stroke treatment should include enhancement of intrinsic protection mechanisms such as CREB phosphorylation and activation of progenitors cells.
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PMID:[Targets of treatment in the acute phase of cerebral infarction]. 1223 93

We studied the early pathophysiological response of lenticulostriate arterioles in rats in three models of human conditions associated with stroke: (a) chronic angiotensin II-hypertension; (b) chronic nicotine administration; (c) oxidative endothelial injury. In all three models, quantitative patch clamp analysis of freshly isolated vascular smooth muscle cells from lenticulostriate arterioles and posterior cerebral arteries showed significant increases in activity of functional L-type calcium channels that were due to an increase in open channel probability, with no change in other biophysical properties or in channel expression. In addition, all three models showed evidence of endothelial dysfunction, but of a different nature in the three. With chronic angiotensin II-hypertension, but not in the other two models, endothelial nitric oxide synthase (eNOS) was dysfunctional, was mislocalized away from its normal abluminal location, and was accumulated in peri-nuclear Golgi. By contrast, the other two models showed no mislocalization of eNOS, but instead showed evidence of oxidative stress in endothelium, with up-regulation of superoxide dismutase and hexose kinase. All three models showed significant up-regulation of expression of proliferative cell nuclear antigen (PCNA) (PCNA index, 70-80%) in arterioles in situ, which is associated with increased activation of the nuclear transcription factor, phospho-cAMP response element binding protein (phospho-CREB). In addition, calmodulin-dependent protein (CaM) kinase II was activated, in concert with the activation of L-type calcium channels. Furthermore, blockers of either L-type calcium channels (amlodipine) or of CaM kinase II (KN-93) completely prevented the activation of CREB and the up-regulation of PCNA in arterioles. Our findings demonstrate that abnormal regulation of L-type calcium channels is directly responsible for abnormal proliferative responses in vascular smooth muscle in various forms of cerebral arteriolar injury associated with endothelial dysfunction.
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PMID:Early pathophysiological changes in cerebral vessels predisposing to stroke. 1472 53

Programmed cell death (PCD) is major concept in neurobiology and transcription factors are pivotal in switching on the nerve cell death program. More recently, the transcriptional control of programmed cell life (PCL) is beginning to be understood. This work began in studies of the activation of the CREB transcription factor in stroke models where it was shown that CREB is phosphorylated (and presumably activated) in neurons that survive this insult. In this review I will describe this data and also discuss the up-stream and down-stream pathways in this CREB neuroprotective transcriptional cassette. Finally, I will discuss studies showing that this CREB survival pathway may be inactivated by neurotoxins and genes involved in neurodegenerative disorders.
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PMID:CREB and neurodegeneration. 1476 49

Cilostazol was developed as a selective inhibitor of cyclic nucleotide phosphodiesterase 3 (PDE3). The anti-platelet and vasodilator properties of cilostazol have been extensively characterized and considered to contribute to the variety of clinical effects such as intermittent claudication and recurrent stroke. In this review, the novel action mechanism (s) of cilostazol are overviewed with the focus on the action of cilostazol in in vitro and in vivo studies as a maxi-K channel opener targeting anti-apoptotic signaling pathways. Under treatment with cilostazol (10 mg/kg intravenously or 30 mg/kg orally), a significant reduction in cerebral infarct area was evident in rats subjected to ischemia/reperfusion. Increase in cyclic AMP and decrease in TNF-alpha levels were identified in the ipsilateral cortex under treatment with cilostazol accompanied by decreased Bax formation and cytochrome c release with increased Bcl-2 production in the penumbral area as well as in the in vitro human umbilical endothelial cells. Cilostazol suppressed TNF-alpha-induced decrease in viability of SK-N-SH (human neuroblastoma) cells and HCN-1A (human cortical neuron) cells in association with decrease in PTEN phosphorylation and increase in Akt/CREB phosphorylation with suppression of DNA fragmentation, all of which were antagonized by iberiotoxin, a maxi-K(+) channel blocker. Further, cilostazol prevented TNF-alpha-induced PTEN phosphorylation and apoptotic cell death via increased CK2 phosphorylation in the SK-N-SH cells. Cilostazol increased K(+) current in SK-N-SH cells by opening the maxi-K channels. Thus, it was suggested that the action of cilostazol to promote cell survival was ascribed to the maxi-K channel opening-coupled upregulation of CK2 phosphorylation and downregulation of PTEN phosphorylation with resultant increased phosphorylation of Akt and CREB. These in vitro data were confirmed in the in vivo results of rats subjected to focal transient ischemic damage.
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PMID:Cilostazol: therapeutic potential against focal cerebral ischemic damage. 1647 48

Exercise increases brain-derived neurotrophic factor (BDNF), phosphorylated cAMP response-element binding protein (pCREB), insulin-like growth factor (IGF-I) and synapsin-I, each of which has been implicated in neuroplastic processes underlying recovery from ischemia. In this study we examined the temporal profile (0, 30, 60 and 120 min following exercise) of these proteins in the hippocampus and sensorimotor cortex following both motorized (60 min) and voluntary (12 h) running, 2 weeks after focal ischemia. Our goal was to identify the optimal training paradigms (intensity, duration and frequency) needed to integrate endurance exercise in stroke rehabilitation. Therefore we utilized telemetry to measure changes in heart rate with both exercise methods. Our findings show that although the more intense, motorized running exercise induced a rapid increase in BDNF, the elevation was more short-lived than with voluntary running. Motorized running was also associated with higher levels of synapsin-I in several brain regions but simultaneously, a more pronounced increase in the stress hormone, corticosterone. Furthermore, both forms of exercise resulted in decreased phosphorylation of CREB and downregulation of synapsin-I in hippocampus beginning 30 to 60 min after the exercise bout. This phenomenon was more robust after motorized running, the method that generated higher heart rate and serum corticosterone levels. This immediate stress response is likely specific to acute exercise and may diminish with repeated exercise exposure. The present data illustrate a complex interaction between different forms of exercise and proteins implicated in neuroplasticity. For clinical application, frequent lower intensity exercise episodes (as in voluntary running wheels), which may be safer to provide to patients with stroke, has a delayed but sustained effect on BDNF that may support brain remodeling after stroke.
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PMID:Exercise intensity influences the temporal profile of growth factors involved in neuronal plasticity following focal ischemia. 1738 14

The acute neuronal degeneration in the ischemic core upon stroke is followed by a second wave of cell demise in the ischemic penumbra and neuroanatomically connected sites. This temporally delayed deleterious event of programmed cell death ('secondary degeneration') often exceeds the initial damage of stroke and, thus, contributes pivotally to significant losses in neurological functions. In fact, it is the injured neurons in these regions around the ischemic core zone that neuropharmacological prevention is targeting to preserve. Clinical and pre-clinical studies have focussed on neuroprotective interventions with caspase inhibitors, but it remains ambiguous whether diminishing or even silencing these aspartate-specific cysteine proteases are in sum beneficial for the clinical outcome. It is often ignored that caspase inhibitors are able to antagonize calpain and cathepsins, thereby protecting the cytoskeleton from damage. Moreover, there is a point of no return, beyond which interfering with caspases cannot rescue the cell, but spoil the obligate and necessary suicide program such that the cellular environment suffers from by-products of necrosis and secondary inflammation. Here we discuss novel alternative strategies to abrogate the death cascade at the level of the genomic response (transcription factors, NF-kappaB, CREB, ICER, HIF), of mitochondrial effectors (cytochrome c, Bcl-2, Smac/DIABLO, HtrA2), and of inhibitor of apoptosis proteins (IAPs). IAPs are the only known endogenous proteins that inhibit specifically and with high affinity the activity of both initiator and effector caspases. Based on compelling biochemical evidence, we argue that patronizing the neuronal endogenous anti-apoptotic machinery could be superior to the pharmacological inhibition of caspases at various levels, with regard to specificity, side effects, and the 'therapeutic window of opportunity'.
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PMID:Exploiting endogenous anti-apoptotic proteins for novel therapeutic strategies in cerebral ischemia. 1851 Nov 72


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