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

The nuclear transcription factor-kappaB (NF-kappaB) and free radicals are known to be involved in apoptosis. We studied the effects of a series of di-aryl-substituted pyrazole NF-kappaB inhibitors including tepoxalin on tumor necrosis factor alpha (TNFalpha)-induced apoptosis in murine fibrosarcoma WEHI 164 cells. We found that potent inhibitors of NF-kappaB were also effective in attenuating apoptosis. WEHI 164 cells that had been dually treated with tepoxalin and the antioxidant pyrrolidine dithiocarbamate (PDTC) were significantly protected from TNFalpha-induced killing. To study the role of free radicals in mediating TNFalpha-induced apoptosis, stable WEHI 164 cells overexpressing Bcl-2, an antioxidant protein, were generated. These cells were protected from TNFalpha-induced apoptosis and neither tepoxalin nor PDTC provided further significant protection. These results suggest that Bcl-2, PDTC, and tepoxalin may attenuate apoptosis in this system by affecting the same signaling pathway or converging pathways. Because tepoxalin suppresses the release of free radicals, PDTC scavenges free radicals and Bcl-2 is an antioxidant protein, free radicals are among the key mediators of this TNF-induced killing event. Tepoxalin and antioxidants may be useful in developing new therapeutics for treating neurodegenerative diseases, autoimmune deficiency syndrome, and ischemia-reperfusion injuries.
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PMID:Tepoxalin enhances the activity of an antioxidant, pyrrolidine dithiocarbamate, in attenuating tumor necrosis factor alpha-induced apoptosis in WEHI 164 cells. 1033 40

Nitric oxide synthesis by inducible nitric oxide synthase (iNOS) has been postulated to contribute to ischemia-reperfusion neurotoxicity. The expression of this enzyme has been demonstrated in cells present in the postischemic brain. The mechanisms of iNOS expression after cerebral ischemia are a subject of current research. We therefore decided to investigate whether glutamate, which is released in ischemia and is implicated in neurotoxicity, might be involved in the mechanisms by which oxygen and glucose deprivation (OGD) leads to the expression of iNOS in rat forebrain slices. In this model, we have shown previously that 20 min of OGD causes the expression of iNOS. We have now found that the NMDA receptor antagonist MK-801 blocks the expression of iNOS, suggesting that the activation of the NMDA subtype of glutamate receptor is implicated in the mechanisms that lead to the expression of this isoform. Moreover, we have found that glutamate alone could trigger the induction process, as shown by the appearance of a Ca(2+)-independent NOS activity and by the detection of iNOS mRNA and protein in slices exposed to glutamate. Glutamate-dependent iNOS expression was concentration-dependent and was blocked by EGTA and by the inhibitors of nuclear factor kappaB (NF-kappaB) activation pyrrolidine dithiocarbamate and MG132. In addition, glutamate induced NF-kappaB translocation to the nucleus, an effect that was inhibited by MG132. Taken together, our data suggest that activation of NMDA receptors by glutamate released in ischemia is involved in the expression of iNOS in rat forebrain slices via a Ca(2+)-dependent activation of the transcription factor NF-kappaB. To our knowledge, this is the first report showing an implication of excitatory amino acids in the expression of iNOS caused by ischemia.
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PMID:Implication of glutamate in the expression of inducible nitric oxide synthase after oxygen and glucose deprivation in rat forebrain slices. 1080 Sep 47

The extracellular glutamate concentration ([glu](o)) rises during cerebral ischemia, reaching levels capable of inducing delayed neuronal death. The mechanisms underlying this glutamate accumulation remain controversial. We used N-methyl-D-aspartate receptors on CA3 pyramidal neurons as a real-time, on-site, glutamate sensor to identify the source of glutamate release in an in vitro model of ischemia. Using glutamate and L-trans-pyrrolidine-2,4-dicarboxylic acid (tPDC) as substrates and DL-threo-beta-benzyloxyaspartate (TBOA) as an inhibitor of glutamate transporters, we demonstrate that energy deprivation decreases net glutamate uptake within 2-3 min and later promotes reverse glutamate transport. This process accounts for up to 50% of the glutamate accumulation during energy deprivation. Enhanced action potential-independent vesicular release also contributes to the increase in [glu](o), by approximately 50%, but only once glutamate uptake is inhibited. These results indicate that a significant rise in [glu](o) already occurs during the first minutes of energy deprivation and is the consequence of reduced uptake and increased vesicular and nonvesicular release of glutamate.
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PMID:Acute decrease in net glutamate uptake during energy deprivation. 1080 15

A central role for nuclear factor-kappaB (NF-kappaB) in the induction of lung inflammatory injury is emerging. We hypothesized that NF-kappaB is a critical early regulator of the inflammatory response in lung ischemia-reperfusion injury, and inhibition of NF-kappaB activation reduces this injury and improves pulmonary graft function. With use of a porcine transplantation model, left lungs were harvested and stored in cold Euro-Collins preservation solution for 6 h before transplantation. Activation of NF-kappaB occurred 30 min and 1 h after transplant and declined to near baseline levels after 4 h. Pyrrolidine dithiocarbamate (PDTC), a potent inhibitor of NF-kappaB, given to the lung graft during organ preservation (40 mmol/l) effectively inhibited NF-kappaB activation and significantly improved lung function. Compared with control lungs 4 h after transplant, PDTC-treated lungs displayed significantly higher oxygenation, lower PCO(2), reduced mean pulmonary arterial pressure, and reduced edema and cellular infiltration. These results demonstrate that NF-kappaB is rapidly activated and is associated with poor pulmonary graft function in transplant reperfusion injury, and targeting of NF-kappaB may be a promising therapy to reduce this injury and improve lung function.
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PMID:Attenuation of lung reperfusion injury after transplantation using an inhibitor of nuclear factor-kappaB. 1095 28

The effect of diethylmaleate administration on ascorbic acid release following cerebral ischemia was investigated in anesthetized rat brain cortex. Cerebral ischemia, induced by ligating bilateral common carotid arteries and unilateral middle cerebral artery, significantly increased the extracellular ascorbic acid levels. Diethylmaleate (4 mmoles/kg, i.p.), which has been shown in earlier studies to decrease the ischemia-induced glutamate release, significantly reduced the ischemia-induced ascorbic acid release. The ischemia-induced ascorbic acid release was unaffected by perfusing NMDA receptor antagonist MK 801 (75 microM). Additionally, elevated extracellular glutamate levels, achieved by either externally applied glutamate solutions or by perfusing L-trans-pyrrolidine-2,4-dicarboxylate (PDC) (31.4 mM and 15.7 mM) to inhibit the glutamate uptake transporter, also significantly increased the extracellular ascorbic acid levels. These results suggested that ascorbic acid release in cerebral ischemia might be related to the elevated extracellular glutamate levels, which occurs following cerebral ischemia.
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PMID:Diethylmaleate decreased ascorbic acid release induced by cerebral ischemia in cerebral cortex of the anesthetized rat. 1099 93

The novel phosphorylated pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH) was evaluated as a (31)P NMR probe of the pH changes associated with ischemia/reperfusion of rat isolated hearts and livers. In vitro titration curves indicated that DEPMPH exhibited a 4-fold larger amplitude of chemical shift variation than inorganic phosphate yielding an enhanced NMR sensitivity in the pH range of 5.0-7.5 that allowed us to assess pH variations of less than 0.1 pH units. At the non-toxic concentration of 5 mm, DEPMPH distributed into external and cytosolic compartments in both normoxic organs, as assessed by the appearance of two resonance peaks. An additional peak was observed in normoxic and ischemic livers, assigned to DEPMPH in acidic vesicles (pH 5.3-5.6). During severe myocardial ischemia, a third peak corresponding to DEPMPH located in ventricular and atrial cavities appeared (pH 6.9). Mass spectrometry and NMR analyses of perchloric extracts showed that no significant metabolism of DEPMPH occurred in the ischemic liver. Reperfusion with plain buffer resulted in a rapid washout of DEPMPH from both organs. It was concluded that the highly pH-sensitive DEPMPH could be of great interest in noninvasive ex vivo studies of pH gradients that may be involved in many pathological processes.
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PMID:Use of diethyl(2-methylpyrrolidin-2-yl)phosphonate as a highly sensitive extra- and intracellular 31P NMR pH indicator in isolated organs. Direct NMR evidence of acidic compartments in the ischemic and reperfused rat liver. 1101 64

Ischemia/reperfusion injury increases the expression of bioactive heparin-binding epidermal growth factor-like growth factor (HB-EGF) in the rat kidney, suggesting that oxidant stress or cell injury related to oxidant stress might affect HB-EGF expression in the injured renal parenchyma. We utilized a nontransformed rat renal epithelial cell line (NRK-52E cells) to investigate whether reactive oxygen species induced transcriptional activation of HB-EGF mRNA. Hypoxia/reoxygenation increased HB-EGF expression in NRK-52E cells, and at concentrations that induced sublethal cell injury, hydrogen peroxide (H(2)O(2)) increased HB-EGF mRNA expression 4.7-fold. The free radical scavengers, dimethylthiourea and N-acetylcysteine inhibited HB-EGF mRNA induction. In contrast, another free radical scavenger, pyrrolidine thiocarbamate (PDTC), augmented H(2)O(2)-mediated HB-EGF expression. Since PDTC has been reported to augment AP-1-mediated transcriptional activation, we utilized an electrophoretic mobility shift assay to confirm that H(2)O(2) administration to NRK-52E cells did increase nuclear extract DNA-binding activity to a consensus AP-1 sequence. Using a CAT reporter assay coupled to the proximal 2,000 bp of the human HB-EGF 5'-untranslated region, we determined that H(2)O(2) administration increased CAT activity 5.5-fold. Truncation or deletion mutations of a putative AP-1-binding site reduced the H(2)O(2)-stimulated activity by >60%, and there was increased DNA binding of nuclear extracts from H(2)O(2)-treated cells to a 24-bp oligonucleotide containing this putative AP-1 site. Anti-fos and jun antibodies inhibited this binding, and there was no binding to an oligonucleotide in which the putative AP-1 site was mutated. The site of the residual activation was found to exist in the most proximal 5'-untranslated region (-121 to +60), which contains two putative SP1 sites. Timing and localization of AP-1-binding activity from nuclear extracts from the post-ischemic tissue correlated with HB-EGF mRNA expression. Therefore, in renal epithelial cells, oxidant stress increases HB-EGF expression, which appears to be mediated in part by an increase in AP-1 binding. This activation may play an important role in the induction of HB-EGF mRNA in response to tissue injury and may regulate early stages of recovery following ischemic damage.
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PMID:Oxidant stress activates AP-1 and heparin-binding epidermal growth factor-like growth factor transcription in renal epithelial cells. 1105 78

Increased levels of extracellular excitatory amino acids and failure of energy metabolism are two conditions associated with brain ischemia. In the present study we have combined the simultaneous inhibition of glutamate uptake and mitochondrial electron transport chain to simulate neuronal damage associated with brain ischemia. Results show that cerebellar granule neurons are not vulnerable to transient glutamate uptake inhibition by L-trans-pyrrolidine-2,4-dicarboxylate (PDC) despite the increase in the extracellular concentration of glutamate, unless they are simultaneously exposed to the mitochondrial toxins 3-nitropropionic acid (3-NP) or sodium azide. Cell damage was assessed by light microscopy observation, by reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and by the fluorescent markers for live and dead cells, calcein and ethidium homodimer, respectively. The protective effect of alternative energy substrates, such as pyruvate, acetoacetate, and beta-hydroxybutyrate against PDC-induced neuronal death during 3-NP exposure was studied and compared to the effects of the antioxidant vitamin E, the spin trapper alpha-phenyl-N-tert-butylnitrone (PBN), voltage-dependent calcium channel antagonists, and glutamate receptor antagonists. Results show that neuronal damage can be efficiently prevented in the presence of pyruvate and the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801, whereas the non-NMDA receptor antagonist NBQX, acetoacetate, vitamin E, and PBN showed partial protection. In contrast, beta-hydroxybutyrate and voltage-dependent calcium channels blockers did not show any protective effect at the concentrations tested.
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PMID:Strategies for neuroprotection against L-trans-2,4-pyrrolidine dicarboxylate-induced neuronal damage during energy impairment in vitro. 1134 Jun 49

Chemokine expression is associated with reperfusion of infarcted myocardium in the setting of tissue necrosis, intense inflammation, and inflammatory cytokine release. The specific synthesis of monocyte chemotactic protein (MCP)-1 mRNA by cardiac venules in reperfused infarcts corresponded to the region where leukocytes normally localize. MCP-1 could be induced by exogenous tumor necrosis factor (TNF)-alpha or by postischemic cardiac lymph containing TNF-alpha. However, the release of TNF-alpha during early reperfusion did not explain the venular localization of MCP-1 induction. To better understand the factors mediating MCP-1 induction, we examined the role of ischemia/reperfusion in a model of brief coronary occlusion in which no necrosis or inflammatory response is seen. Adult mongrel dogs were subjected to 15 minutes of coronary occlusion and 5 hours of reperfusion. Ribonuclease protection assay revealed up-regulation of MCP-1 mRNA only in ischemic segments of reperfused canine myocardium. Pretreatment with the reactive oxygen scavenger N-(2-mercaptopropionyl)-glycine completely inhibited MCP-1 induction. In situ hybridization localized MCP-1 message to small venular endothelium in ischemic areas without myocyte necrosis. Gel shift analysis of nuclear extracts from the ischemic area showed enhanced DNA binding of the transcription factors AP-1 and nuclear factor (NF)-kappaB, crucial for MCP-1 expression, in ischemic myocardial regions. Immunohistochemical staining demonstrated reperfusion-dependent nuclear translocation of c-Jun and NF-kappaB (p65) in small venular endothelium, only in the ischemic regions of the myocardium, that was inhibited by N-(2-mercaptopropionyl)-glycine. In vitro, treatment of cultured canine jugular vein endothelial cells with the reactive oxygen intermediate H2O2 induced a concentration-dependent increase in MCP-1 mRNA levels, which was inhibited by the antioxidant N-acetyl-L-cysteine, a precursor of glutathione, but not pyrrolidine dithiocarbamate, an inhibitor of NF-kappaB and activator of AP-1. In contrast to our studies with infarction, incubation of canine jugular vein endothelial cells with postischemic cardiac lymph did not induce MCP-1 mRNA expression suggesting the absence of cytokine-mediated MCP-1 induction after a sublethal ischemic period. These results suggest that reactive oxygen intermediate generation, after a brief ischemic episode, is capable of inducing MCP-1 expression in venular endothelium through AP-1 and NF-kappaB. Short periods of ischemia/reperfusion, insufficient to produce a myocardial infarction, induce MCP-1 expression, potentially mediating angiogenesis in the ischemic noninfarcted heart.
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PMID:Reactive oxygen intermediates induce monocyte chemotactic protein-1 in vascular endothelium after brief ischemia. 1158 58

Production of reactive oxygen species (ROS) by ischemic tissue after ischemia-reperfusion (I/RP) is an important factor that contributes to tissue injury. The small GTPase Rac1 mediates the oxidative burst, and ROS act on signaling pathways involved in expression of inflammatory genes. Because there is evidence implicating monocytes in the pathogenesis of I/RP injury, our objective was to determine the molecular mechanisms that regulate adhesive interactions between monocytes and hypoxia-reoxygenation (H/RO)-exposed cultured endothelial cells (ECs). When U937 cells were perfused over human umbilical vein ECs at 1 dyn/cm2, H (1 h at 1% O2)/RO (13 h) significantly increased the fluxes of rolling and stably adherent U937 cells. Either EC treatment with the antioxidant pyrrolidine dithiocarbamate (PDTC) or infection with AdRac1N17, which results in expression of the dominant-negative form of Rac1, abolished H/RO-induced ROS production, attenuated rolling, and abolished stable adhesion of U937 cells to H/RO-exposed ECs. Infection with AdRac1N17 also abolished H/RO-induced upregulation of vascular cell adhesion molecule (VCAM)-1. In turn, blocking VCAM-1 abolished U937 cell stable adhesion and slightly increased rolling. We concluded that the Rac1-dependent ROS partially regulate rolling and exclusively regulate stable adhesion of monocytic cells to ECs after H/RO and that stable adhesion, but not rolling, is mediated by ROS-induced expression of VCAM-1.
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PMID:Adhesion of flowing monocytes to hypoxia-reoxygenation-exposed endothelial cells: role of Rac1, ROS, and VCAM-1. 1205 77


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