Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyclooxygenases COX-1 and COX-2 catalyze the first committed step of prostaglandin synthesis from arachidonic acid. Previous studies in rodent stroke models have shown that the inducible COX-2 isoform promotes neuronal injury, and the administration of COX-2 inhibitors reduces infarct volume. We investigated the function of PGE2, a principal prostaglandin product of COX-2 enzymatic activity, in neuronal survival in cerebral ischemia. PGE2 exerts its downstream effects by signaling through a class of four distinct G-protein-coupled EP receptors (for E-prostanoid: EP1, EP2, EP3, and EP4) that have divergent effects on cAMP and phosphoinositol turnover and different anatomical distributions in brain. The EP2 receptor subtype is abundantly expressed in cerebral cortex, striatum, and hippocampus, and is positively coupled to cAMP production. In vitro studies of dispersed neurons and organotypic hippocampal cultures demonstrated that activation of the EP2 receptor was neuroprotective in paradigms of NMDA toxicity and oxygen glucose deprivation. Pharmacologic blockade of EP2 signaling by inhibition of protein kinase A activation reversed this protective effect, suggesting that EP2-mediated neuroprotection is dependent on cAMP signaling. In the middle cerebral artery occlusion-reperfusion model of transient forebrain ischemia, genetic deletion of the EP2 receptor significantly increased cerebral infarction in cerebral cortex and subcortical structures. These studies indicate that activation of the PGE2 EP2 receptor can protect against excitotoxic and anoxic injury in a cAMP-dependent manner. Taken together, these data suggest a novel mechanism of neuroprotection mediated by a dominant PGE2 receptor subtype in brain that may provide a target for therapeutic intervention.
 ...
PMID:Neuroprotective function of the PGE2 EP2 receptor in cerebral ischemia. 1471 58

The activation of glutamate receptors, particularly N-methyl-D-aspartate (NMDA) receptors, initiates ischemic cascade in the early stages of cerebral ischemia. Postischemia, cerebral ischemia is also associated with an inflammatory reaction that contributes to tissue damage. The up-regulation of neuronal cyclooxygenase-2 (COX-2) and elevation of prostaglandin E2 (PGE2) have been reported to occur after cerebral ischemic insult. We therefore studied whether the COX-2 reaction product PGE2 affects glutamate receptor-mediated cell death in cultured rat cortical cells. PGE2 was found to augment NMDA-mediated cell death. The transcription of EP1, EP2, EP3 and EP4 PGE2 receptor genes was investigated using reverse transcriptase-polymerase chain reaction (RT-PCR). EP1, EP2 and EP3 receptor genes were found in cortical cells. Butaprost (an EP2 agonist) markedly enhanced NMDA-mediated cell death, whereas 17-phenyl trinor-PGE2 (an EP1 agonist) and sulprostone (an EP3 agonist) had little effect. Both PGE2 and butaprost elevated cAMP intracellular levels in the cortical cells; moreover, forskolin, an activator of adenylate cyclase, enhanced NMDA-mediated cell death. These results suggest that PGE2, acting via EP2 receptors, aggravates excitotoxic neurodegeneration by a cAMP-dependent mechanism.
 ...
PMID:Prostaglandin E2 deteriorates N-methyl-D-aspartate receptor-mediated cytotoxicity possibly by activating EP2 receptors in cultured cortical neurons. 1630 9

We investigated the distribution and time course of expression of two subtypes of prostaglandin E(2) (PGE(2)) receptors, EP2 and EP4, in a rat model of cerebral ischemia and ischemic tolerance. Adult male Sprague-Dawley rats were subjected to either lethal global ischemia (10 min) with or without sublethal ischemic preconditioning (3 min), or ischemia only (3 min). A short 3-min cerebral ischemia and a 3-min ischemia followed by a second lethal ischemia enhanced the expression of EP2 and EP4 receptors in CA1 pyramidal neurons of the hippocampus. In tolerance-acquired CA1 neurons, the immunoreactivities of EP2 and EP4 were upregulated after 4 h and 12 h, respectively. The immunoreactivities were most prominent at 3 days and were sustained for at least 14 days, consistent with results of immunoblotting experiments. However, immunoreactivities for these PGE(2) receptors increased in reactive glial cells in the vulnerable CA1 and hilar regions of rats subjected to lethal ischemia without ischemic preconditioning. Most of the EP2 immunoreactivity occurred in microglial cells and some astrocytes, whereas increased immunoreactivity for EP4 was found only in astrocytes. These data suggest that ischemia and the induction of ischemia tolerance have different regulatory effects on the expression of EP2 and EP4 receptors. Moreover, PGE(2) may exert its unique pathophysiological functions in relation to delayed neuronal death and ischemic tolerance induction in the rat hippocampus via specific PGE(2) receptors.
 ...
PMID:Expression of prostaglandin E2 receptor subtypes, EP2 and EP4, in the rat hippocampus after cerebral ischemia and ischemic tolerance. 1643 7

Induction of COX-2 activity in cerebral ischemia results in increased neuronal injury and infarct size. Recent studies investigating neurotoxic mechanisms of COX-2 demonstrate both toxic and paradoxically protective effects of downstream prostaglandin receptor signaling pathways. We tested whether misoprostol, a PGE(2) receptor agonist that is utilized clinically as an anti-ulcer agent and signals through the protective PGE(2) EP2, EP3, and EP4 receptors, would reduce brain injury in the murine middle cerebral artery occlusion-reperfusion (MCAO-RP) model. Administration of misoprostol, at the time of MCAO or 2h after MCAO, resulted in significant rescue of infarct volume at 24 and 72h. Immunocytochemistry demonstrated dynamic regulation of the EP2 and EP4 receptors during reperfusion in neurons and endothelial cells of cerebral cortex and striatum, with limited expression of EP3 receptor. EP3-/- mice had no significant changes in infarct volume compared to control littermates. Moreover, administration of misoprostol to EP3+/+ and EP3-/- mice showed similar levels of infarct rescue, indicating that misoprostol protection was not mediated through the EP3 receptor. Taken together, these findings suggest a novel function for misoprostol as a protective agent in cerebral ischemia acting via the PGE(2) EP2 and/or EP4 receptors.
 ...
PMID:Misoprostol, an anti-ulcer agent and PGE2 receptor agonist, protects against cerebral ischemia. 1847 36

Cyclooxygenase-2 (COX-2) is a neuronal immediate early gene that is regulated by N-methyl d aspartate (NMDA) receptor activity. COX-2 enzymatic activity catalyzes the first committed step in prostaglandin synthesis. Recent studies demonstrate an emerging role for the downstream PGE(2) EP2 receptor in diverse models of activity-dependent synaptic plasticity and a significant function in models of neurological disease including cerebral ischemia, Familial Alzheimer's disease, and Familial amyotrophic lateral sclerosis. Little is known, however, about the normal function of the EP2 receptor in behavior and cognition. Here we report that deletion of the EP2 receptor leads to significant cognitive deficits in standard tests of fear and social memory. EP2-/- mice also demonstrated impaired prepulse inhibition (PPI) and heightened anxiety, but normal startle reactivity, exploratory behavior, and spatial reference memory. This complex behavioral phenotype of EP2-/- mice was associated with a deficit in long-term depression (LTD) in hippocampus. Our findings suggest that PGE(2) signaling via the EP2 receptors plays an important role in cognitive and emotional behaviors that recapitulate some aspects of human psychopathology related to schizophrenia.
 ...
PMID:Impaired cognition, sensorimotor gating, and hippocampal long-term depression in mice lacking the prostaglandin E2 EP2 receptor. 1941 71

This review presents an overview of the emerging field of prostaglandin signaling in neurological diseases, focusing on PGE(2) signaling through its four E-prostanoid (EP) receptors. A large number of studies have demonstrated a neurotoxic function of the inducible cyclooxygenase COX-2 in a broad spectrum of neurological disease models in the central nervous system (CNS), from models of cerebral ischemia to models of neurodegeneration and inflammation. Since COX-1 and COX-2 catalyze the first committed step in prostaglandin synthesis, an effort is underway to identify the downstream prostaglandin signaling pathways that mediate the toxic effect of COX-2. Recent epidemiologic studies demonstrate that chronic COX-2 inhibition can produce adverse cerebrovascular and cardiovascular effects, indicating that some prostaglandin signaling pathways are beneficial. Consistent with this concept, recent studies demonstrate that in the CNS, specific prostaglandin receptor signaling pathways mediate toxic effects in brain but a larger number appear to mediate paradoxically protective effects. Further complexity is emerging, as exemplified by the PGE(2) EP2 receptor, where cerebroprotective or toxic effects of a particular prostaglandin signaling pathway can differ depending on the context of cerebral injury, for example, in excitotoxicity/hypoxia paradigms versus inflammatory-mediated secondary neurotoxicity. The divergent effects of prostaglandin receptor signaling will likely depend on distinct patterns and dynamics of receptor expression in neurons, endothelial cells, and glia and the specific ways in which these cell types participate in particular models of neurological injury.
 ...
PMID:Emerging roles of PGE2 receptors in models of neurological disease. 2280 72

Neonatal hypoxic-ischemic encephalopathy (HIE) is a leading cause of severe and permanent neurologic disability after birth. The inducible cyclooxygenase COX-2, which along with COX-1 catalyzes the first committed step in prostaglandin (PG) synthesis, elicits significant brain injury in models of cerebral ischemia; however its downstream PG receptor pathways trigger both toxic and paradoxically protective effects. Here, we investigated the function of PGE(2) E-prostanoid (EP) receptors in the acute outcome of hypoxic-ischemic (HI) injury in the neonatal rat. We determined the temporal and cellular expression patterns of the EP1-4 receptors before and after HIE and tested whether modulation of EP1-4 receptor function could protect against cerebral injury acutely after HIE. All four EP receptors were expressed in forebrain neurons and were induced in endothelial cells after HIE. Inhibition of EP1 signaling with the selective antagonist SC-51089 or co-activation of EP2-4 receptors with the agonist misoprostol significantly reduced HIE cerebral injury 24 h after injury. These receptor ligands also protected brain endothelial cells subjected to oxygen glucose deprivation, suggesting that activation of EP receptor signaling is directly cytoprotective. These data indicate that the G-protein coupled EP receptors may be amenable to pharmacologic targeting in the acute setting of neonatal HIE.
 ...
PMID:Function of prostaglandin E2 EP receptors in the acute outcome of rodent hypoxic ischemic encephalopathy. 2193 36