Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The patterns of expression of the bcl-2, bax, and bci-X genes were examined immunohistochemically in neurons of the adult rat brain before and after 10 min of global ischemia induced by transient cardiac arrest. High levels of the cell death promoting protein Bax and concomitant low levels of the apoptosis-blocking protein Bcl-2 were found in some populations of neurons that are particularly sensitive to cell death induced by transient global ischemia, such as the CA1 sector of the hippocampus and the Purkinje cells of the cerebellum. Moreover, within 0.5 to 3 hr after an ischemic episode, immunostaining for Bax was markedly increased within neurons with morphological features of degeneration in many regions of the brain. Use of a two-color staining method for simultaneous analysis of Bax protein and in situ detection of DNA-strand breaks revealed high levels of Bax immunoreactivity in many neurons undergoing apoptosis. Postischemic elevations in Bax protein levels in the hippocampus, cortex, and cerebellum were also demonstrated by immunoblotting. At early times after transient ischemia, regulation of Bcl-2 and Bcl-x protein levels varied among neuronal subpopulations, but from 3 hr on, those neurons with morphological evidence of degeneration uniformly contained reduced levels of Bci-2 and particularly Bci-X immunoreactivity. The findings suggest that differential expression of some members of the bcl-2 gene family may play an important role in determining the relative sensitivity of neuronal subpopulations to ischemia and that postischemic alterations in the expression of bax, bcl-2, and bcl-x may contribute to the delayed neuronal cell death that occurs during the repurfusion phase after a transient ischemic episode.
 ...
PMID:Upregulation of bax protein levels in neurons following cerebral ischemia. 747 1

Permanent occlusion of the middle cerebral artery in rats was used to assess the effects of focal ischemia on the expression of members of the bcl-2 family which have been implicated in the regulation of programmed cell death. Intraluminal occlusion of one middle cerebral artery for 6 h resulted in histologically detectable brain damage within the ipsilateral caudate putamen, basolateral cortex and parts of the thalamus. In the infarcted basolateral cortex and thalamus fragmentation of DNA was detected in many nuclei using in-situ end-labeling of DNA breaks by terminal transferase, whereas only scattered labeled nuclei were visible in the infarcted caudate putamen. Immunohistochemical analysis revealed activation of c-Fos in the infarcted cortex and thalamus and in the non-infarcted cingulate cortex as has been shown by others. A decrease in immunoreactivity for Bcl-2, and Bcl-X and an increase in immunostaining for Bax was observed exclusively in neurons within the ischemic cortex and thalamus. Within the infarcted caudate putamen, however, protein levels of all bcl-2 family members declined and c-Fos remained absent. By reverse transcription and polymerase chain reaction it was demonstrated that levels of bcl-2 mRNA markedly decreased in the ipsilateral hemisphere, whereas the amount of bax mRNA was elevated. These findings suggest that a shift in the ratio of cell death repressor Bcl-2 to cell death effector Bax and a concomitant activation of c-Fos may contribute to neuronal apoptosis in the infarcted thalamus and cortex.
 ...
PMID:Altered expression of Bcl-2, Bcl-X, Bax, and c-Fos colocalizes with DNA fragmentation and ischemic cell damage following middle cerebral artery occlusion in rats. 887 9

Using in situ hybridization, Northern blotting and RT-PCR we studied the post-ischemic expression of bcl-2, bcl-x, bax and ICE. One day following 5 min or 10 min of global ischemia bcl-2 and bcl-x mRNAs were induced in CA1 hippocampal pyramidal neurons while bax was unchanged. By 72 h after ischemia the expression of bcl-2, bcl-x and bax mRNAs decreased in CA1. The large isoform of bcl-x (bcl-xL), detected using RT-PCR, decreased in whole hippocampus by 24-72 h after ischemia relative to the putative short (bcl-xS) and transmembrane deleted (bcl-x delta TM) forms. Oligonucleotides to interleukin-1 beta convertase (ICE), which detected the expected 2-kb transcript and two lesser 1.5- and 3-kb hybridizing species, demonstrated slight mRNA induction in the CA1 region at 72 h following ischemia. DNA nick end-labeling at 3 days following ischemia showed DNA fragmentation in neurons limited to the CA1 region of hippocampus following 5 min ischemia, while DNA fragmentation was detected in CA1, CA3, dentate gyrus and cortical neurons following 10 min ischemia. The data support the view that hippocampal neurons might undergo an apoptosis-like death after global ischemia. Since global ischemia decreases total protein synthesis especially in the CA1 region, the increases in bcl-2 mRNA levels may not necessarily lead to increased Bcl-2 protein levels. This may explain why the CA1 neurons die despite the prominent induction of the protective bcl-2 gene. The observed decrease by 24 h in the bcl-xL/bcl-xS ratio which preceded DNA fragmentation may participate in the cell death produced by ischemia. However, because of the ischemia-induced decrease in total protein synthesis, the decreased bcl-xL/bcl-xS ratio does not necessarily lead to a changed ratio in the amount of the appropriate proteins. Since ICE-like mRNA was induced at 72 h when the CA1 neurons were dead, the significance of this ICE-like mRNA induction remains unclear.
 ...
PMID:Global ischemia induces apoptosis-associated genes in hippocampus. 891 83

Hippocampal CA1 neurons are highly susceptible to short periods of transient global ischemia. We have previously reported in a rat model of transient forebrain global ischemia that activation and nuclear localization of NF-kB occurs in the CA1 neurons at 24 and 72 h post reperfusion. Events following NF-kB activation would ultimately determine whether damaged cells will undergo programmed cell death. We have selected bcl-x gene expression for study because there is increasing evidence that proteins encoded by the bcl-2 gene family (bcl-2, bcl-x, bax etc) play a role in the regulation of programmed cell death. We have observed that the bcl-x gene promoter contains a putative consensus sequence for NF-kB/CS4 responsive activation. We also can show that other members of the bcl-2 multigene family contain the NF-kB/CS4 sequence in their five prime regulatory regions. In this study, we show that NF-kB p50 and NF-kB p65 act in synergy to transactivate the bcl-x promoter in co-transfected 293 cells. We also report that following ischemia and NF-kB activation, bcl-x messenger RNA levels increase in the CA1 hippocampal region. As a result of this transcriptional increase, surprisingly, it is bcl-xs, the apoptotic form of bcl-x, that is elevated. These results suggest that activation of NF-kB can lead to increased expression of bcl-x as manifested by the increase in the short form of bcl-x.
 ...
PMID:Bcl-Xshort is elevated following severe global ischemia in rat brains. 943 16

This study was performed to examine the involvement of apoptosis and the expression of bcl-2 family genes in ischemia-induced retinal injury. Retinal ischemia was induced in adult rats by raising the intraocular pressure to 130 mmHg for 45 min. Selective damage to the inner retina was observed 7 days after ischemia. No terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) positive cells were observed in the normal retina, but there was a significant number of TUNEL positive cells 6-48 h after transient ischemia followed by a decrease at 96 and 168 h. The number of TUNEL positive cells reached a maximum at 24 h after ischemia. DNA laddering was observed on agarose gel electrophoresis with the retinas 24 and 48 h after ischemia but not in the normal retina. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that bax gene expression did not change immediately after cessation of ischemia, but gradually increased as early as 6 h, reached a peak at 24 h, then decreased to near baseline levels at 168 h. On the other hand, bcl-2 gene expression showed no obvious changes at any time after transient ischemia. Moreover, intense Bax protein immunoreactivity was detected in the retinal sections at 24 h after ischemia although little immunoreactivity was present in the normal sections. These results suggest that apoptosis associated with the expression of Bax is involved in retinal cell loss after ischemic insult.
 ...
PMID:Apoptotic DNA fragmentation and upregulation of Bax induced by transient ischemia of the rat retina. 997 17

Transient global ischemia results in selective neuronal damage of hippocampal CA1 neurons. Five minutes of bilateral common carotid artery occlusion, in the Mongolian gerbil, effectively restricts forebrain blood flow, resulting in a delayed neuronal death of CA1 pyramidal cells. While there is a delay of approximately 72 h in the appearance of cell death, markers related to the mechanism of ischemic death become apparent well before neurons die. Ischemia-induced increases in the cell-death-promoting protein, bax, may disrupt the bcl-2/bax ratio necessary for normal neuronal functioning and thus promote transient ischemic death. In order to locally maintain this critical bcl-2/bax ratio and thus protect CA1 neurons from delayed neuronal death, a herpes simplex viral (HSV) vector was used to selectively introduce human bcl-2, under the control of the herpes IE 4/5 promoter, into the CA1 region of the gerbil hippocampus. Twenty-four hours prior to ischemia surgery, 1 microl of HSVbcl-2 was infused unilaterally into the CA1 region at a rate of 2 nl/min. Seventy-two hours after ischemia the animals were sacrificed and processed using Nissl, silver degeneration, and immunohistochemical (anti-human bcl-2) staining. Immunohistochemistry demonstrated both glial and neuronal bcl-2 expression around the HSVbcl-2 infusion site. The evaluation following silver degeneration staining indicated a further degeneration of CA1 neurons in the immediate area of the viral vector infusion. This damage seems to be the result of cellular debris associated with the processing of the viral amplicons. Silver degeneration staining is not present in the areas that demonstrate bcl-2 staining. These neurons appear to have been rescued from ischemic damage. This result was confirmed using the Nissl staining. Therefore, by altering the local ratio of bcl-2/bax using the HSVbcl-2 vector one may protect CA1 pyramidal cell from the delayed neuronal death of transient global ischemia.
 ...
PMID:BCL-2 transduction, using a herpes simplex virus amplicon, protects hippocampal neurons from transient global ischemia. 1019 84

We have shown that physiological levels of estradiol exert profound protective effects on the cerebral cortex in ischemia induced by permanent middle cerebral artery occlusion. The major goal of this study was to begin to elucidate potential mechanisms of estradiol action in injury. Bcl-2 is a proto-oncogene that promotes cell survival in a variety of tissues including the brain. Because estradiol is known to promote cell survival via Bcl-2 in non-neural tissues, we tested the hypothesis that estradiol decreases cell death by influencing bcl-2 expression in ischemic brain injury. Furthermore, because estradiol may protect the brain through estrogen receptor-mediated mechanisms, we examined expression of both receptor subtypes ERalpha and ERbeta in the normal and injured brain. We analyzed gene expression by RT-PCR in microdissected regions of the cerebral cortex obtained from injured and sham female rats treated with estradiol or oil. We found that estradiol prevented the injury-induced downregulation of bcl-2 expression. This effect was specific to bcl-2, as expression of other members of the bcl-2 family (bax, bcl-x(L), bcl-x(S), and bad) was unaffected by estradiol treatment. We also found that estrogen receptors were differentially modulated in injury, with ERbeta expression paralleling bcl-2 expression. Finally, we provide the first evidence of functional ERbeta protein that is capable of binding ligand within the region of the cortex where estradiol-mediated neuroprotection was observed in cerebral ischemia. These findings indicate that estradiol modulates the expression of bcl-2 in ischemic injury. Furthermore, our data suggest that estrogen receptors may be involved in hormone-mediated neuroprotection.
 ...
PMID:Estradiol modulates bcl-2 in cerebral ischemia: a potential role for estrogen receptors. 1041 67

Neuronal death following ischemic insults has been thought to reflect necrosis. However, recent evidence from several labs suggests that programmed cell death, leading to apoptosis, might additionally contribute to this death. We have used both in vitro and in vivo models to study the role of apoptosis in ischemic cell death. Some features of apoptosis (TUNEL staining, internucleosomal DNA fragmentation, sensitivity to cycloheximide) were observed following transient focal ischemia in rats. Brief transient focal ischemia was followed by delayed infarction more than 3 days later; this delayed infarction was sensitive to cycloheximide. A cycloheximide-sensitive component of neuronal cell death was also observed in cultured murine neocortical neurons deprived of oxygen-glucose in the presence of glutamate receptor antagonists. This presumed ischemic apoptosis was attenuated by caspase inhibitors, or by homozygous deletion of the bax gene. Neurons may undergo both apoptosis and necrosis after ischemic insults, and thus it may be therapeutically desirable to block both processes.
 ...
PMID:Apoptosis and necrosis in cerebrovascular disease. 1067 41

Recent studies of transient focal ischemia have focused interest on apoptotic mechanisms of neuronal cell death involving constitutive pro-apoptotic proteins. The finding of specific patterns of novel gene expression might indicate the activation of pro-apoptotic genes in previously ischemic areas. Thus, we investigated gene expression for the pro-apoptotic regulators, Bax and caspase-3, after transient focal brain ischemia, together with the p53-regulated cell cycle inhibitor, p21/WAF1/CIP1. Reversible occlusion of the middle cerebral artery for 2 h was carried out in halothane-anesthetized rats using the poly-L-lysine coated filament method. In situ hybridization was performed at 0, 1, 3, 6 h and 1, 3 and 7 d of recirculation and in sham controls. Radioactive antisense probes served for detection of bax, p21 and caspase-3 mRNAs on brain sections, and quantitative film autoradiography was combined with image-averaging techniques. Bax mRNA tended to decline after focal brain ischemia within 1 d. p21 mRNA was upregulated with a perifocal pattern at 3 h and 1 d after ischemia whereas the ischemic regions themselves failed to show significant upregulation. Caspase-3 mRNA was elevated in the resistant dorsomedial cortex at 1 d. A pro-apoptotic pattern of novel gene expression, involving Bax and caspase-3, was not observed after transient focal brain ischemia. Rather, the perifocal expression of p21 and caspase-3 mRNAs observed at 1 d after ischemia points to reactive changes in resistant brain areas.
 ...
PMID:Differential changes of bax, caspase-3 and p21 mRNA expression after transient focal brain ischemia in the rat. 1092 46

Many studies have reported ischemia protection using various preconditioning techniques, including single dose 3-nitropropionic acid (3-NPA), a mitochondrial toxin. However, the cellular signal transduction cascades resulting in ischemic tolerance and the mechanisms involved in neuronal survival in the tolerant state still remain unclear. The current study investigated the mRNA and protein expression of the antiapoptotic bcl-2 and the proapoptotic bax. two antagonistic members of the bcl-2 gene family, in response to a single dose of 3-NPA, to global cerebral ischemia-reperfusion. and to the combination of both 3-NPA-pretreatment and subsequent global cerebral ischemia-reperfusion. Brain homogenates of adult Wistar rats (n = 25) were analyzed for bcl-2 and bax mRNA expression using a new highly sensitive and quantitative polymerase chain reaction (PCR) technique that allows real-time fluorescence measurements of the PCR product (LightCycler; Roche Diagnostics, Mannheim, Germany). Animals for mRNA analysis received 3-NPA (20 mg/kg, intraperitoneal; "chemical preconditioning") or vehicle (normal saline), and were either observed for 24 plus 3 hours or were subjected to 15 minutes of global cerebral ischemia 24 hours after the pretreatment and observed for 3 hours of reperfusion. Immunohistochemistry was applied to serial brain sections of additional rats (n = 68) to determine amount and localization of the respective Bcl-2 and Bax protein expression in various brain areas. One set of animals was injected with 3-NPA and observed for 3, 12, 24, and 96 hours; a second set was exposed to 15 minutes global cerebral ischemia, 3, 12, and 24 hours reperfusion; and a third set was pretreated with 3-NPA or saline 24 hours before the ischemic brain insult and observed for 96 hours of reperfusion. The authors found single dose 3-NPA treatment to be associated with an elevated bcl-2:bax ratio (increased bcl-2 expression, decreased bax expression), both on the transcriptional (mRNA) and the translational (protein) level. The differential influence of 3-NPA was maintained during early recovery from global cerebral ischemia (3 hours), when 3-NPA pretreated animals showed higher bcl-2 and lower bax mRNA levels compared with rats with saline treatment. Respective changes in protein expression were localized predominately in neurons vulnerable to ischemic damage. Compared with baseline, Bcl-2 protein was significantly higher in surviving neurons at 96 hours after the insult, whereas Bax protein remained unchanged. However, at this late time of postischemic recovery (96 hours), the protein expression pattern of surviving neurons was not different between animals with and without 3-NPA pretreatment. To the authors' knowledge, the current study is the first report on the differential expression of pro- and antiapoptotic genes after a single, nonlethal dose of 3-NPA. The current results suggest alterations in the balance between pro- and antiapoptotic proteins as a potential explanation for the reported protection provided by chemical preconditioning using 3-NPA in rats.
 ...
PMID:Tolerance-Inducing dose of 3-nitropropionic acid modulates bcl-2 and bax balance in the rat brain: a potential mechanism of chemical preconditioning. 1104 5


1 2 3 4 5 6 Next >>