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

Leukotrienes are powerful metabolites of arachidonic acid which are known to increase the permeability of peripheral blood vessels. These substances are found in brain tissue in association with cerebral ischemia, and in brain tumors. Therefore, it has been proposed that leukotrienes have a mediator function in brain edema. This hypothesis was subjected to further experimental analysis in this study, in which the authors investigated whether: 1) superfusion of the exposed brain surface with leukotrienes increases the permeability of extraparenchymal blood vessels in vivo; 2) intraparenchymal infusion of leukotrienes induces brain edema; and 3) pharmacological inhibition of leukotriene formation by BW755C, an inhibitor of leukotriene synthesis, reduces formation of brain edema from a standardized traumatic insult. The pial vessels of the parietal cortex of cats were examined by fluorescence microscopy during cerebral superfusion with the leukotrienes C4 (LTC4), D4 (LTD4), or E4 (LTE4) by using an open cranial window preparation. Intravenous Na(+)-fluorescein served as an in vivo blood-brain barrier (BBB) indicator. Superfusion of the pia with leukotrienes (up to 2 microM) did not open the barrier to fluorescein, but was associated with a significant constriction (up to 25%) of arterial and venous vessels. In experiments with slow infusion of leukotriene B4 (LTB4) or LTC4 into the white matter of feline brain, the tissue water content was subsequently determined in serial brain slices using the specific gravity method. Tissue water profiles obtained after a 15-microM infusion of either LTB4 or LTC4 were virtually identical with those of control animals infused with mock cerebrospinal fluid. Thus, neither LTB4 nor LTC4 led to an augmentation of infusion-induced brain edema. In a final series, a cold lesion of the left parietal cortex was induced in rabbits. Twenty-four hours later, swelling of the exposed hemisphere was quantified by gravimetrical comparison of its weight with that of the contralateral nontraumatized hemisphere. Eight animals received BW755C intravenously prior to and after trauma to inhibit formation of leukotrienes. Seven rabbits were infused with an equivalent volume of saline as a control study. The resulting hemispheric swelling was 7.7% +/- 0.6% (mean +/- standard error of the mean) 24 hours later in animals receiving BW755C and 7.8% +/- 1.2% in the control group, indicating that inhibition of leukotrienes was ineffective in preventing formation of vasogenic brain edema. The findings demonstrate that leukotrienes administered to the brain in concentrations occurring under pathological conditions do not open the BBB nor do they induce brain edema.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Evidence against leukotrienes as mediators of brain edema. 173 Sep 68

Leukotrienes accumulate in brain tissue after cerebral ischemia and in brain tumors. Thus, their release might contribute to the blood-brain barrier damage observed under these conditions and, hence, brain edema. The effect of these substances on the permeability of pial vessels and whether inhibition of LT synthesis reduces cold injury brain edema were studied. The pial vasculature of cats was studied by fluorescence microscopy. The cortex was superfused with LTC4, LTD4, or LTE4 via a cranial window. Na(+)-fluorescein was intravenously administered as blood-brain barrier indicator. LT concentrations up to 2 microM did not induce any leakage of the blood-brain barrier indicator into the parenchyma. However, all LTs tested constricted pial arteries and veins. Brain edema formation was studied in rabbits with cold injury. BW755C, an inhibitor of cyclooxygenase and lipoxygenase preventing formation of LTs, was given before and after trauma. Control animals received saline only. BW755C was ineffective in attenuating cold injury edema. Hemispheric swelling in control animals was 7.8 +/- 1.1%, and 7.7 +/- 0.4% in animals with treatment. LTs, even when administered to the brain in concentrations exceeding levels occurring under pathological conditions, did not induce barrier damage, nor did inhibition of LT synthesis attenuate formation of vasogenic edema. The results provide further evidence against LTs as mediator compounds of this process.
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PMID:Role of leukotrienes as mediator compounds in brain edema. 211 15

Human plasma leukotriene C4 (LTC4) levels of cerebral infarcted patients showed a significant increase and plasma vitamin A (VA) levels showed a significant decrease compared to the normal plasma obtained from age-matched control. Therefore, the effect of VA on leukotriene (LT) levels and the progress of cerebral edema were investigated in VA deficient Wistar rat brains. Incomplete global cerebral ischemia was induced by occluding the bilateral common carotid arteries (BLCO) with clips. Wistar rats were made VA deficient by feeding them a vitamin A deficient diet for 5 weeks on a specific pathogen free status. After 3 hours of BLCO the blood was reperfused by removing the clips. After each period of reperfusion, the rat brain was fixed by freezing in situ and used for assaying leukotrienes, vitamin A, and water content. Slow reacting substance of anaphylaxis (LTC4 + LTD4 + LTE4) levels showed an increase at the end of BLCO in the VA deficient group and the high levels persisted for 30 min and then decreased to the control level. Brain water contents were elevated significantly at the 30 min phase of reperfusion. With VA administration, the water contents tended to be lower than in the VA deficient group at any phase. Histologically, after ischemia and reperfusion, evans blue extravasation and marked spongioid formations around small vessels were observed in the VA deficient rats only. These facts indicate that VA functions to stabilize cell membranes and suppress ischemic cerebral damage.
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PMID:[The effect of vitamin A on leukotriene production in the ischemic rat brain]. 260 50

In the ischemic brain, leukotrienes (LTs) are increased and their receptor antagonists protect neurons. However, it has not yet been sufficiently clarified how antagonists for LT receptors exhibit neuroprotective effects. In the present study, we evaluated protective effects of receptor antagonists for LTB4 (LY293111) and cysteinyl LTs (ONO-1078) in the primary culture of rat cortical neurons. The group IB secretory phospholipase A2 (sPLA2-IB)-induced neuronal cell death had been established as the in vitro model for cerebral ischemia. sPLA2-IB triggered the influx of Ca(2+) into neurons via L-type voltage-dependent calcium channel (L-VDCC). Subsequently, the enzyme produced eicosanoids including LTB4 before neuronal cell death. Neither administration of LTB4 nor cysteinyl LTs such as LTC4, LTD4 and LTE4 killed neurons. However, both LY293111 and ONO-1078 significantly prevented neurons from the neurotoxicity of sPLA2-IB, suggesting that the two LT receptor blockers protected neurons through alternative pathways beside LT receptors. An L-VDCC blocker does not only inhibit the influx of Ca(2+) into neurons but also rescues neurons from the sPLA2-IB-induced neuronal cell death. The two LT receptor antagonists also blocked the sPLA2-IB-induced Ca(2+) influx significantly. Thus, LTs exhibited no neurotoxicity, but their receptor antagonists protected neurons directly in the in vitro ischemic model. Furthermore, the suppression of L-VDCC appeared to be involved in the neuroprotective effects of LY293111 and ONO-1078 independent of blocking their receptors.
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PMID:Leukotriene receptor antagonists, LY293111 and ONO-1078, protect neurons from the sPLA2-IB-induced neuronal cell death independently of blocking their receptors. 2379 23