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Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The brain cyclic AMP generation was studied in rats subjected to 15 min of cardiac arrest. We have used a particulate, synaptoneurosomal fraction to demonstrate the effect of ischemia in vivo on the responsiveness of adenylate cyclase (AC) system. It has been shown that, although there is a slight decrease in AC activity after ischemia, the in vitro fractions produce more cAMP in response to a variety of stimuli, suggesting an indirect, nonadenylate cyclase activation mechanism. For elucidation of this mechanism we have probed phorbol-12,13-dibutyrate (PDBu) as a direct PKC activator, forskolin to activate the catalytic subunit of AC, and cholera toxin (CT) for stabilizing the active, GTP-bound form of stimulatory guanine nucleotide binding protein (Gs). All these postreceptor AC modulators as well as the receptor activators such as adenosine and alpha 1-adrenergic agonists markedly enhanced cAMP production in the rat brain particulate fraction, although the postischemic hyperactive response to these stimuli was still present. However, when AC was stimulated by the combination of CT and PDBu, cAMP responses were identical in both control and postischemic fractions. The data, taken together, support the hypothesis that ischemia increases cAMP accumulation by facilitating the postreceptor AC activation through a PKC-involving pathway and by promoting the stronger coupling of membrane AC receptors with G-protein. Protein kinase C (PKC) activity during cerebral ischemia was also investigated. In contradistinction to our expectation PKC decreased significantly in the ischemic brain to 85% of the control activity in the cytosol and 72% in the membranes. However, in the incubated post-ischemic brain particulate fraction a relative increase in the membrane-bound form of the enzyme, from 30% for control to 53% for ischemia, was observed. This may suggest that ischemia-induced membrane changes could promote the enzyme translocation/activation during recovery, resulting in the sensitization of cAMP producing system.
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PMID:Postreceptor modulation of cAMP accumulation in rat brain particulate fraction after ischemia--involvement of protein kinase C. 135 40

The changes in the levels of protein kinase C [PKC(alpha, beta II, gamma)] were studied in cytosolic and particulate fractions of striatal homogenates from rats subjected to 15 min of cerebral ischemia induced by bilateral occlusion of the common carotid arteries and following 1 h, 6 h, and 48 h of reperfusion. During ischemia the levels of PKC(beta II) and -(gamma) increased in the particulate fraction to 390% and 590% of control levels, respectively, concomitant with a decrease in the cytosolic fraction to 36% and 20% of control, respectively, suggesting that PKC is redistributed from the cytosol to cell membranes. During reperfusion the PKC(beta II) levels in the particulate fraction remained elevated at 1 h postischemia and decreased to below control levels after 48 h reperfusion, whereas PKC(gamma) rapidly decreased to subnormal levels. In the cytosol PKC(beta II) and -(gamma) decreased to 25% and 15% of control levels at 48 h, respectively. The distribution of PKC(alpha) did not change significantly during ischemia and early reperfusion. The PKC activity in the particulate fraction measured in vitro by histone IIIS phosphorylation in the presence of calcium, 4 beta-phorbol 13-myristate 12-acetate, and phosphatidylserine (PS) significantly decreased by 52% during ischemia, and remained depressed over the 48-h reperfusion period. In the cytosolic fraction PKC activity was unchanged at the end of ischemia, and decreased by 47% after 6 h of reperfusion. The appearance of a stable cytosolic 50-kDa PKC-immunoreactive peptide or an increase in the calcium- and PS-independent histone IIIS phosphorylation was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Changes in the activity of protein kinase C and the differential subcellular redistribution of its isozymes in the rat striatum during and following transient forebrain ischemia. 200 38

During neuropathological states associated with inflammation, the levels of cytokines such as interleukin-1beta (IL-1beta) are increased. Several studies have suggested that the neuronal damage observed in pathogenesis implicating IL-1beta are caused by an alteration in the neurochemical interactions between neurons and astrocytes. We report here that treating striatal astrocytes in primary culture with IL-1beta for 22-24 hr enhances the ATP-evoked release of arachidonic acid (AA) with no effect on the ATP-induced accumulation of inositol phosphates. The molecular mechanism responsible for this effect involves the expression of P2Y2 receptors (a subtype of purinoceptor activated by ATP) and cytosolic phospholipase A2 (cPLA2, an enzyme that mediates AA release). Indeed, P2Y2 antisense oligonucleotides reduce the ATP-evoked release of AA only from IL-1beta-treated astrocytes. Further, both the amount of cPLA2 (as assessed by Western blotting) and the release of AA resulting from direct activation of cPLA2 increased fourfold in cells treated with IL-1beta. We also report evidence indicating that the coupling of newly expressed P2Y2 receptors to cPLA2 is dependent on PKC activity. These results suggest that during inflammatory conditions, IL-1beta reveals a functional P2Y2 signaling pathway in astrocytes that results in a dramatic increase in the levels of free AA. This pathway may thus contribute to the neuronal loss associated with cerebral ischemia or traumatic brain injury.
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PMID:Interleukin-1 enhances the ATP-evoked release of arachidonic acid from mouse astrocytes. 909 30

Cerebral ischemia is known to modify the expression of genetic information in the brain. To complement this knowledge, in the present study we have estimated the expression of calcium- and phospholipid-dependent (classical) protein kinase C (c PKC) isoform mRNAs (alpha, beta1 and gamma) at different time following ischemia. Forebrain cerebral ischemia was performed on Mongolian gerbils by 5 minutes bilateral occlusion of common carotid arteries. At the pointed time the cytoplasmic RNA was extracted from hippocampus and the expression of PKC mRNA quantified by RT PCR technique using GAPDH expression as an internal standard. Results indicate that only one gamma isoform of cPKC mRNA expression becomes significantly modified in postischemic hippocampus. A transient increase up to 145% of control within the first 3 h was followed by its decline to 60-65% at a longer recirculation period. This lowered levels returned back to control at 72 h postischemic recovery. This result indicates that gamma PKC could be particularly sensitive to ischemic insult and would react in accordance with the other early signals determining ischemic outcome.
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PMID:Expression of Ca2+-dependent (classical) PKC mRNA isoforms after transient cerebral ischemia in gerbil hippocampus. 947 87

Experimental evidence suggests that the massive release of glutamate during experimental brain ischemia both directly and indirectly regulates downstream mechanisms of cell suicide. Cerebral ischemia was produced by distal, permanent occlusion of the middle cerebral artery (MCAO) in the rat. Sets of three animals and one sham-operated for each time-point were kept alive for 0-30 min, 1, 4, 12, 24, and 48 h, and 4 days. Additional animals were treated by local administration of a 10 microM (in 10 microl) cocktail of caspase inhibitors (YVAD-cmk, DEVD-fmk, IETD). Immunohistochemistry was performed on free-floating tissue sections with goat polyclonal antibodies to procaspase-1, -2, -3, -6, and -8. Some sections were processed for double-labeling procaspase immunohistochemistry and in situ end-labeling of nuclear DNA fragmentation (TUNEL method). Both immunohistochemistry and double-labeling procaspase immunohistochemistry and TUNEL method were carried out on formalin-fixed sections. For gel electrophoresis and Western blotting, we used antibodies to poly (ADP-ribose) polymerase (PARP), lamin B, and PKC-delta, as specific cleavage substrates of caspases. There was increased immunoreactivity ipsilaterally in the areas corresponding to the infarct and surrounding penumbra with the peak of immunoreactivity between 12 and 24 h for most of the procaspases. Procaspases were present early in the infarcted tissue neurones and their dendrites and axons. Additional procaspase expression occurred in astrocytes and microglial cells at different times following ischemia. Cells with positive in situ end-labeling of nuclear DNA fragmentation appeared in high number predominantly in the infarcted areas and at the edge of the infarction and colocalized with enhanced procaspase expression. These findings suggest increased procaspase expression in dying cells at the edge of the infarction. A major product of PARP degradation of about 89 kDa was found in the samples taken from the infarcted and penumbra areas. There was no difference in the intensity of the bands corresponding to lamin B or PKC-delta. Injection of procaspase inhibitors reduced the levels of major PARP products of 89 kDa and decreased the number of TUNEL-positive cells at 12 h post-MCAO. In conclusion, these results give support to further research on the use of caspase inhibitors as add-on therapeutic agents for the treatment of ischemia.
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PMID:Expression of caspases and their substrates in the rat model of focal cerebral ischemia. 1096 5

Tumour necrosis factor-alpha (TNF-alpha) is a major immunomodulatory and proinflammatory cytokine which is shed in its soluble form by a membrane-anchored zinc protease, identified as a disintegrin and metalloproteinase (ADAM) called TNF-alpha convertase (TACE; ADAM17). The role of this protease in the adult nervous system remains poorly understood. During cerebral ischemia and subsequent reperfusion, expression and release of TNF-alpha have been shown. We have investigated the expression and activity of TACE in an in vitro model of brain ischemia consisting of rat forebrain slices exposed to oxygen-glucose deprivation (OGD). OGD caused the release of TNF-alpha, an effect which was inhibited by a hydroxamate-based metalloprotease inhibitor, BB-3103, with an IC(50) of 0.1 microM, suggesting that TNF-alpha release results selectively from TACE activity. Assay of TACE enzymatic activity on a fluorescein-labelled peptide spanning the cleavage site in pro-TNF-alpha, as well as Western blot and RT-PCR analyses showed that TACE is present in control forebrain and, more interestingly, that TACE expression is increased in OGD-exposed tissue. TACE enzymatic activity from OGD-exposed slices was significantly inhibited by cycloheximide, suggesting that de novo synthesis of TACE contributes to TNF-alpha release after ischaemia. Moreover, it was also inhibited by bisindolylmaleimide I, indicating that TACE activity is regulated by PKC. These findings posed the question of what was its function therein. Among other actions, TNF-alpha has been described to be involved in the expression of inducible nitric oxide synthase (iNOS), a high-output NOS isoform associated to cellular damage, but the link between TNF-alpha release after brain ischaemia and iNOS expression in this condition has not been shown. We have now found that iNOS expression in OGD-subjected brain slices is inhibited by BB-3103 at concentrations below 1 microM, indicating that shedding of TNF-alpha by TACE plays a necessary part in the induction of this NOS isoenzyme after OGD. Taken together, these data demonstrate that (1) TACE/ADAM17 activity accounts for the majority of TNF-alpha shedding after OGD in rat forebrain slices, (2) an increase in TACE expression contributes, at least in part, to the rise in TNF-alpha after OGD and (3) iNOS expression in OGD-subjected brain slices results from TACE activity and subsequent increase in TNF-alpha levels.
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PMID:Up-regulation of TNF-alpha convertase (TACE/ADAM17) after oxygen-glucose deprivation in rat forebrain slices. 1140 1

Mild cerebral anoxic/ischemic/stress insults promote 'tolerance' and thereby protect the brain from subsequent 'lethal' anoxic/ischemic insults. We examined whether specific activation of PKC alpha, delta, epsilon, or zeta isoforms is associated with ischemic preconditioning (IPC) in rat brain. IPC was produced by a 2-minute global cerebral ischemia. Membrane and cytosolic fractions of the hippocampi were immunoblotted using specific antibodies for PKCalpha, delta, epsilon, and zeta. PKCalpha showed a significant translocation to the membrane fraction from 30 min to 4 h and PKCdelta at 4 h following IPC. In contrast, the membrane/cytosol ratio of PKCepsilon showed a tendency to decrease at 30 min and 8 h, and the membrane/cytosol ratio of PKCzeta was significantly decreased from 30 min to 24 h following IPC. These findings indicate PKC isoform-specific membrane translocations in the hippocampus after brief global brain ischemia and suggest that activation of PKCalpha and PKCdelta may be associated with IPC-induced tolerance in the rat hippocampus.
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PMID:Isoform-specific membrane translocation of protein kinase C after ischemic preconditioning. 1170 Sep 56

Oxidative stress is believed to play an important role in neuronal cell death associated with several neurodegenerative diseases (e.g., Alzheimer disease, Parkinson disease, and cerebral ischemia). Neuronal cell death might be one of the crucial mediators of these diseases. The transcription factor NF-kappaB is well-known for its roles in preventing apoptotic cell death. Data indicated that NF-kappaB activation by pre-conditioning is part of a general brain tolerance program. Here we show that pre-conditioning leading to NF-kappaB activation also protects against oxidative insults generated by Fe2+ ions. Protection was accompanied by a long-lasting (more than 24 h) NF-kappaB activation. Using this paradigm of oxidative insult, we analyzed the effect of hypericin, one of the active principles of St. John's Wort. Hypericin alone was able to induce short-time activation of NF-kappaB, which declined to basal levels after 24 h. Cell death was induced by hypericin at a concentration of 10 microM. A profound synergistic action in inducing apoptosis was detected in co-treatment of hypericin together with FeSO4. In contrast, hypericin in low concentrations was able to partly prevent cell death induced by amyloid-beta-peptide (Abeta). Hypericin (10 microM) synergistically enhanced Abeta neurotoxicity. Since hypericin is a described inhibitor of protein kinase C, we compared its action to staurosporine, another natural neuronal death-promoting PKC inhibitor. Staurosporine induced cell death and activates NF-kappaB. Molecular inhibition of NF-kappaB activation with a transdominant negative IkappaB-alpha protected against staurosporine-induced cell death. In summary, the data describe NF-kappaB in the same primary neuronal culture as stimulus-dependent, anti-apoptotic, or pro-apoptotic factor.
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PMID:Stimulus-dependent activation of NF-kappaB specifies apoptosis or neuroprotection in cerebellar granule cells. 1262 8

To explore biochemical basis for cerebroprotective effect of immunosuppressant FK506, we studied changes in subcellular distribution of protein kinase C gamma (PKC gamma) as well as calcium/calmodulin-dependent protein kinase II (CaMKII) after ischemia. Male Mongolian gerbils were subjected to 5 min forebrain ischemia. FK506 (1 or 3 mg kg-1) was administered at 1 min after recirculation, which was confirmed to be cerebroprotective by histological examination at seven days after ischemia. At the designated time points (before ischemia, 5 min ischemia, 1 and 24 h recovery), heads were frozen and samples were taken from CA1 subfield of hippocampus. Western blot analysis was carried out. Persistent translocations of PKC gamma and CaMKII to synaptosomal P2 fraction were observed in vehicle-treated group. FK506 significantly decreased levels of PKC gamma and CaMKII in P2 fraction at 24 h of recovery. The present results suggest FK506 downregulates translocated PKC gamma and CaMKII, which may contribute to its survival promoting effect after cerebral ischemia.
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PMID:Effects of FK506 on the translocation of protein kinase C and CaM kinase II in the gerbil hippocampal CA1 neurons. 1286 2

Cerebral ischemia induces rapid efflux of glutamate into the extracellular space contributing to excessive activation of glutamate receptors in postsynaptic cells, particularly N-methyl-D-aspartate (NMDA) receptors, which triggers the neuron lesion through calcium overload. Our studies indicated that cerebral ischemia stimulated the rapid activation of nonreceptor tyrosine kinases proline-rich tyrosine kinase 2 (Pyk2) and Src and the binding to Pyk2 activated the latter. Pyk2 activation significantly depends on the increase of the intracellular calcium level; blockage of both calcium ion channel NMDA receptors and L-type voltage-gated Ca2+ channel (L-VGCC), respectively, could effectively inhibit phosphorylation of Pyk2 in early ischemia episodes. Moreover, pretreatment with the protein kinase C inhibitor (chelerythrine chloride) reduced the ischemia-induced activation of Pyk2. Noticeably, CaMKII, a family of calcium/calmodulin-dependent kinases, also may be involved in the regulation of Pyk2 activity because its inhibitor KN62 attenuated Pyk2 phosphorylation during ischemia. Together with previous studies, these results indicate that calcium influx elicited by active NMDA receptors and L-VGCC triggers the Pyk2-Src signaling pathway mediated by PKC, which aggravates cerebral ischemia lesions through up-regulating the function of NMDA receptors after the onset of ischemia, and also could be regulated partly by CaM-dependent kinases like CaMKII.
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PMID:N-methyl-D-aspartate receptor and L-type voltage-gated Ca2+ channel activation mediate proline-rich tyrosine kinase 2 phosphorylation during cerebral ischemia in rats. 1473 60


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