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

There is an accumulating body of data to suggest that estrogen mediates its cardioprotective effects via cyclooxygenase activation and synthesis of prostaglandins (PG), specifically PGI2. We hypothesized that inhibition of COX-2 would prevent estrogen's cardioprotective effects after myocardial ischemia-reperfusion. Acute treatment with 17beta-estradiol (E2; 20 microg/rabbit) increased COX-2 protein expression and activity in the myocardium. To determine the effects of COX-2 inhibition on infarct size after E2 treatment, New Zealand white rabbits were anesthetized and administered the COX-2 inhibitor nimesulide (5 mg/kg) or vehicle intravenously 30 minutes before an intravenous injection of E2. Thirty minutes after estrogen treatment, the coronary artery was occluded for 30 minutes followed by 4 hours of reperfusion. E2 significantly decreased infarct size as a percent of area at risk when compared to vehicle (18.9 +/- 3.1 versus 47.0 +/- 4.1; P < 0.001). Pretreatment with nimesulide nullified the infarct size sparing effect of E2 (55.8 +/- 5.6). Treatment with the PGI2 receptor antagonist RO3244794 also abolished the protective effects of E2 (45.3 +/- 4.5). The results indicate that estrogen protects the myocardium from ischemia-reperfusion injury through increased production of COX-2-derived PGI2. The data indicate that selective COX-2 inhibitors might counteract the potential cytoprotective effects of estrogen in premenopausal or postmenopausal women.
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PMID:Estrogen protects the heart from ischemia-reperfusion injury via COX-2-derived PGI2. 1880 3

Renal excretion of organic anions such as para-aminohippurate is reduced during severe sepsis and following ischemia/reperfusion injury. In order to better define the pathophysiology of sepsis-associated renal tubular dysfunction we measured the effect of lipopolysaccharide on renocortical organic anion transporter (OAT) expression in the rat. Prostaglandin E2 (PGE2) downregulates OATs in vitro, therefore, we also evaluated the effect of the cyclooxygenase (COX)-2 inhibitor parecoxib on this process. Endotoxemia caused a time- and dose-dependent decrease of OAT1 and OAT3 expression that paralleled increased renocortical COX-2 expression and PGE2 formation. Pretreatment with parecoxib decreased endotoxin-stimulated PGE(2) formation. Parecoxib attenuated OAT1 and OAT3 gene repression in the rat kidney following endotoxin treatment and during ischemia/reperfusion-induced acute renal injury. COX-2 inhibition improved the creatinine clearance in lipopolysaccharide-treated rats but not after ischemia/reperfusion-induced acute renal injury. The decreased clearance of para-aminohippurate in rats following endotoxin- or ischemia/reperfusion-induced renal injury was improved by parecoxib. Our findings show that COX-2 derived prostanoids downregulate OATs during lipopolysaccharide-induced acute renal injury.
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PMID:COX-2 inhibition attenuates endotoxin-induced downregulation of organic anion transporters in the rat renal cortex. 1894 99

The molecular mechanisms of preconditioning-induced ischemic tolerance (PCIT) have yet to be elucidated. We investigated whether minimal expression levels of COX-2 induced by preconditioning trigger HO-1, thereby inducing the synthesis of cytoprotective proteins. We show that both COX-2 and HO-1 are induced in rat brains subjected to preconditioning by middle cerebral artery (MCA) occlusion for 10 min followed by different amounts of reperfusion time (1-24 h). Although preconditioning significantly reduced the brain infarct size against severe ischemia (24 h MCA occlusion), pretreatment with the COX-2-selective inhibitor rofecoxib increased infarct size and abolished PCIT-induced COX-2 and HO-1 expression in vivo. We also found that PGE(2) increased the phosphorylation of Akt, which was significantly inhibited by the PI3 kinase inhibitor LY294002. Taken together, we conclude that the kinetic changes in COX-2 induction during the reperfusion period following preconditioning may be important for ischemic tolerance.
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PMID:The obligatory role of COX-2 expression for induction of HO-1 in ischemic preconditioned rat brain. 1899 13

Retinopathies are major causes of visual impairment. We used a model of ischemic retinopathy to examine the role of CD40 in the pathogenesis of retinal injury. Retinal inflammation, loss of ganglion cells, and capillary degeneration were markedly attenuated in ischemic retinas of CD40(-/-) mice. Up-regulation of NOS2 and COX2 after retinal ischemia were blunted in CD40(-/-) mice. NOS2-COX-2 up-regulation in ischemic retinas from wild-type mice was at least in part explained by recruitment of NOS2(+)COX-2(+) leukocytes. Up-regulation of KC/CXCL1 and ICAM-1 also required CD40. Retinal endothelial and Muller cells expressed CD40. Stimulation of these cells through CD40 caused ICAM-1 up-regulation and KC/CXCL1 production. Bone marrow transplant experiments revealed that leukocyte infiltration, ganglion cell loss, and up-regulation of proinflammatory molecules after retinal ischemia were dependent on CD40 expression in the retina and not peripheral blood leukocytes. These studies identified CD40 as a regulator of retinal inflammation and neurovascular degeneration. They support a model in which CD40 stimulation of endothelial and Muller cells triggers adhesion molecule up-regulation and chemokine production, promoting the recruitment of leukocytes that express NOS2/COX-2, molecules linked to neurovascular degeneration.
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PMID:CD40 mediates retinal inflammation and neurovascular degeneration. 1905 Feb 92

Different lines of evidence suggest that inhibition of COX-2 activity exacerbates reperfusion injury, but direct data showing beneficial effects of increased COX-2 activity are lacking. The aim of this study was to determine the effect of constitutive expression of COX-2 on cardiomyocyte tolerance to ischemia-reperfusion injury. We generated a transgenic mouse (B6D2-Tg (MHC-PTGS2)17Upme) that constitutively expresses functional human COX-2 in cardiomyocytes under the control of alpha-myosin heavy chain promoter. COX-2 expression was confirmed by immunoblotting and by increased levels of PGE(2) and PGI(2) in myocardium. Histological and echocardiographic analysis revealed no differences in the phenotype of transgenic mice (TgCOX-2) with respect to wild type (Wt) mice. Tolerance to ischemia-reperfusion injury was analysed in a Langendorff system. Reperfused TgCOX-2 hearts after 40 min of ischemia improved functional recovery (32.9+/-6.2% vs. 9.45+/-4.4%, P=0.004) and reduced cell death assessed by LDH release (43% of reduction, P<0.001) and triphenyltetrazolium staining (41% of reduction, P=0.002). Cardioprotection was not further increased by ischemic preconditioning. Pretreatment of mice with the COX-2 inhibitor DFU attenuated cardioprotection with a correlation between myocardial PGE(2) levels and the extent of cell death. NMR spectroscopy showed a marked reduction in arachidonic acid (AA) content in TgCOX-2 hearts. Both, DFU pretreatment and perfusion of TgCOX-2 hearts with AA increased myocardial AA to values similar to those measured in Wt hearts and reversed cardioprotection. We conclude that constitutive expression of COX-2 in cardiomyocytes confers a permanent cardioprotective state against reperfusion injury. Increased PGE(2) synthesis and reduced AA content could explain this effect.
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PMID:Constitutive COX-2 activity in cardiomyocytes confers permanent cardioprotection Constitutive COX-2 expression and cardioprotection. 1908 34

Decreases in fetal blood pressure stimulate homeostatic stress responses that help return blood pressure to normal levels. Fetal hypothalamus-pituitary-adrenal (HPA) axis responses to hypotension are mediated by chemoreceptor and baroreceptor reflexes and ischemia of the fetal central nervous system. Indomethacin, a nonselective inhibitor of prostaglandin endoperoxide synthase (PGHS)-1 and -2, attenuates the HPA response to hypotension in the fetus. The present study was designed to test the hypothesis that selective inhibition of PGHS-2 also inhibits the HPA response to cerebral hypoperfusion. We studied 13 chronically catheterized fetal sheep (126-136 days gestation). Five fetal sheep were subjected to intracerebroventricular infusion of nimesulide (0.01 mg/day), a specific inhibitor of PGHS-2, and eight were treated with vehicle (DMSO in water) for 5 days. Each fetus was subjected to a 10-min period of brachiocephalic occlusion, which decreased carotid arterial pressure approximately 75% and reflexively increased fetal plasma concentrations of ACTH, POMC, cortisol, and femoral arterial pressure, and decreased fetal heart rate. Nimesulide significantly inhibited the ACTH response to the BCO, while significantly augmenting the reflex cardiovascular response and altering fetal heart rate variability consistent with increased sympathetic nervous system activity. The results of this study demonstrate that the activity of PGHS-2 in the brain is a necessary component of the fetal HPA response to cerebral hypoperfusion in the late-gestation fetal sheep. These results are consistent with those of recent study, in which we demonstrated that the preparturient increase in fetal ACTH secretion depends upon PGHS-2 activity within the fetal brain.
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PMID:Blockade of PGHS-2 inhibits the hypothalamus-pituitary-adrenal axis response to cerebral hypoperfusion in the sheep fetus. 1929 37

The roots of Panax notoginseng (PN) are commonly used as a therapeutic agent to stop hemorrhage and as a tonic to promote health in traditional Korean medicine. Stroke triggers an inflammatory response that not only plays a central role in the pathogenesis of cerebral ischemia, but also induces secondary damage. This study was designed to investigate the neuroprotective effects of the methanol extract of PN on the infarct volume induced by middle cerebral artery occlusion (MCAO) (90-min occlusion and 24-h reperfusion) in rat brains. The PN extract (50 mg/kg, i.p.) was administered 2 h after the onset of MCAO. The PN-treated groups had a reduction in infarct volume by 23.82 +/- 8.9%. In the PN extract-treated groups, the microglial density was significantly decreased in the peri-infarct region; the underlying mechanism was inhibition of inflammatory mediators, such as inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, via blocking of the NF-kappaB pathway. Furthermore, in vitro studies showed that the PN extract significantly reduced the production of iNOS-derived NO and COX-2-derived prostaglandin E(2) through the regulation of gene transcription levels in primary microglia and BV-2 cells. These results suggest that anti-inflammatory and microglial activation inhibitory effects of the PN extract may contribute to its neuroprotective effects in brain ischemia.
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PMID:Panax notoginseng Attenuates the Infarct Volume in Rat Ischemic Brain and the Inflammatory Response of Microglia. 1930 21

Although some of the COX-2 metabolites and prostaglandins have been implicated in stroke and excitotoxicity, the role of prostaglandin F(2alpha) (PGF(2alpha)) and its FP receptor have not been elucidated in the pathogenesis of ischemic-reperfusion (I/R) brain injury. Here we investigated the FP receptor's contribution in a unilateral middle cerebral artery (MCA) occlusion model of focal cerebral ischemia in mice. The MCA in wild type (WT) and FP knockout (FP(-/-)) C57BL/6 male mice was transiently occluded with a monofilament for 90 min. After 96 h of reperfusion, the FP(-/-) mice had 25.3% less neurological deficit (P < 0.05) and 34.4% smaller infarct volumes (P < 0.05) than those of the WT mice. In a separate cohort, physiological parameters were monitored before, during, and after ischemia, and the results revealed no differences between the groups. Because excitotoxicity is an acute mediator of stroke outcome, the effect of acute NMDA-induced neurotoxicity was also tested. Forty-eight hours after unilateral intrastriatal NMDA injection, excitotoxic brain damage was 20.8% less extensive in the FP(-/-) mice (P < 0.05) than in the WT counterparts, further supporting the toxic contribution of the FP receptor in I/R injury. Additionally, we investigated the effect of post-treatment with the FP agonist latanoprost in mice subjected to MCA occlusion; such treatment resulted in an increase in neurological deficit and infarct size in WT mice (P < 0.05), though no effects were observed in the latanoprost-treated FP(-/-) mice. Together, the results suggest that the PGF(2alpha) FP receptor significantly enhances cerebral ischemic and excitotoxic brain injury and that these results are of importance when planning for potential development of therapeutic drugs to treat stroke and its acute and/or long term consequences.
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PMID:PGF(2alpha) FP receptor contributes to brain damage following transient focal brain ischemia. 1938 89

Platycodi radix is used as a folk remedy for several conditions. In this study, we investigated the neuroprotective effects of five major extracts; deapioplatycoside E (DPE), platycoside E (PE), platyconic acid A (PA), platycodin D (PD) and 2''-o-acetyl-polygalacin D2 (PD2) isolated from the P.radix in the hippocampal CA1 region (CA1) 4 or 10 days after ischemia/reperfusion (I/R). Each extract was administered into gerbils with intraperitoneal injection (5 mg/kg/day) 10 days before ischemic surgery and the gerbils were sacrificed 4 or 10 days after I/R. Fluoro-Jade B (F-J B, a marker for neurodegeneration) positive ((+)) neurons increased significantly in the stratum pyramidale of the CA1 region in the vehicle-treated group after I/R. A similar pattern was observed in the DPE-, PE- and PA-treated groups; however, in the PD- and PD2-treated groups, F-J B(+) neurons were small in number. We also observed that activations of astrocytes and microglia in the CA1 region after I/R were blocked by the PD- and PD2 treatments. In addition, we found that Cu,Zn-superoxide dismutase (SOD1) immunoreactivity in the pyramidal layer of the PD- and PD2-treated groups was similar to that of the sham group and COX-2(+) and NF-kappaB(+) cells were significantly lower in the PD- and PD2-treated group than those in the vehicle-treated group after I/R. These results suggest that PD and PD2 rescue neurons in the CA1 region from an ischemic damage.
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PMID:Platycodin D and 2''-O-acetyl-polygalacin D2 isolated from Platycodon grandiflorum protect ischemia/reperfusion injury in the gerbil hippocampus. 1943 75

The post-treatment effects of the selective cyclooxygenase (COX)-2 inhibitor, valdecoxib, were investigated in a rat model of temporary focal ischemia. Valdecoxib reduced basal brain prostaglandin E(2) concentrations at dosages that did not affect serum thromboxane B(2), consistent with a selective COX-2 effect. Temporary focal cerebral ischemia was produced in rats by middle cerebral artery occlusion for 90 min. There was increased expression of COX-2 protein detected by Western blot and immunocytochemistry within neurons in the ischemic cortex at 4 and 24 h after ischemia. Rats were treated with vehicle or valdecoxib 15 min before or 1.5, 3 and 6 h after cerebral ischemia. Rats were sacrificed and brain infarction volume determined 24 h after ischemia. Valdecoxib treatment was associated with a decrease in infarction volume when administered 15 min before, and 1.5 or 3 h but not 6 h after cerebral ischemia. There were no differences in physiological parameters during the procedure. Valdecoxib administered at 1.5 h after ischemia significantly reduced the concentrations of prostaglandin E(2) in ischemic penumbral cortex as compared to the vehicle-treated group and contralateral non-ischemic cortex. These results suggest that COX-2 inhibition with valdecoxib is effective when initiated both before and after middle cerebral artery occlusion.
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PMID:Prolonged opportunity for neuroprotection in experimental stroke with selective blockade of cyclooxygenase-2 activity. 1944 33


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