MDL 74,180 reduces cerebral infarction and free radical concentrations in rats subjected to ischaemia and reperfusion

Effect of a novel NSAID derivative with antioxidant moiety on oxidative damage caused by liver and cerebral ischaemia-reperfusion in rats

Tissue ischaemia-reperfusion evokes toxic and harmful biochemical processes such as oxidative stress and inflammation. The aim of this study is to investigate the indices of tissue damage in rat liver and brain after ischaemia-reperfusion injury of these organs, and to study prospective cytoprotection of molecules such as the novel anti-inflammatory N-(2-thiolethyl)-2-(2-[N'-(2,6-dichlorophenyl)amino] phenyl)acetamide (compound 1) and alpha-tocopherol. Two experimental models were studied: firstly, 30 min liver ischaemia via hepatoduodenal ligament clamping followed by 60 min reperfusion; and secondly, 45 min cerebral ischaemia via bilateral common carotid artery occlusion followed by 90 min reperfusion. Compound 1 and alpha-tocopherol were administered intraperitoneally before induction of ischaemia. We hereby report that compound 1, a molecule that combines potent in-vitro antioxidant and in-vivo anti-inflammatory activity with low gastrointestinal toxicity, offered protection in-vivo against liver or brain ischaemia-reperfusion-induced damage. Both compound 1 and alpha-tocopherol prevented changes in lipid peroxidation in the rat liver and brain tissue and in tumour necrosis factor (TNF-alpha) levels in brain. Also compound 1 attenuated glutathione depletion, evoked by ischaemia-reperfusion, in the rat brain but not in the liver. These results could be explained on the basis of the antioxidant/anti-inflammatory properties of compound 1 and suggest its beneficial effect and potential therapeutic use in post-ischaemic injury.

Role of spin trapping and P2Y receptor antagonism in the neuroprotective effects of 2,2'-pyridylisatogen tosylate and related compounds

2,2'-Pyridylisatogen tosylate (PIT) is both an allosteric modulator of P2Y receptors, and an immine oxide, acting as a spin trap for free radicals. PIT (10 mg kg(-1), i.p.) was found to be a powerful neuroprotective agent in protecting against the lesions induced by 15 micro g S-bromo-willardiine injected into the cortex or white matter of 5-day-old mice pups. As the multiple effects of PIT may induce both beneficial and deleterious effects, a reanalysis of the structure-activity relationship was undertaken. PIT (50 micro M) and 2,3'-pyridylisatogen were potent antagonists of responses to ATP in the taenia preparation of the guinea-pig caecum, but 2,3'-nitrophenylisatogen was not. The reactive immine oxide group could be substituted by a keto moiety (N-(2'-pyridyl)phthalide) while maintaining antagonism of responses to ATP, equivalent to PIT. Thus, antagonism of P2Y receptors was not restricted to the isatogen nucleus. Other spin traps did not antagonise P2Y receptors, although dimethyl-pyrroline-N-oxide (DMPO) increased the sensitivity of responses to ATP. Both N-(2'-pyridyl)phthalide and 2,3'-nitrophenylisatogen was less neuroprotective than PIT (10 mg kg(-1), i.p.) in protecting against the S-bromo-willardiine-induced lesions in mice, implying that both antagonism of P2Y receptors and the immine oxide moiety may be important for the neuroprotective effects of PIT. However, the usefulness of the neuroprotection was limited because, in motoneurones obtained from rat embryos, PIT (10-100 micro M) exacerbated cell death.

A novel MCA occlusion model of photothrombotic ischemia with cyclic flow reductions: development of cerebral hemorrhage induced by heparin

Intracerebral hemorrhage is the major complication associated with antithrombotic and thrombolytic therapy. Despite efforts directed toward achieving hemorrhagic infarction, an ideal animal model of cerebral hemorrhage has not yet to be established. Using the photothrombotic technique in rabbits, we developed a model of cerebral hemorrhage by inducing cyclic flow reductions in the middle cerebral artery (MCA). Furthermore, the hemorrhage increased 4-fold after infusion of heparin at a dose prolonging activated partial thromboplastin time by about three times that of control animals. The photothrombotic occlusion of the MCA is based on a thrombosis induced by endothelial injury through singlet oxygen produced by Rose Bengal injection and green light irradiation (Acta Neuropathol. 72 (1987) 315; Acta Neuropathol. 72 (1987) 326; J. Pharmacol. Toxicol. Methods. 29 (1993) 165). Using a pulse Doppler flowmeter, spontaneous reperfusion of the MCA after the thrombotic occlusion following cyclic flow reductions was observed within 2 h in the majority of animals. This model is unusual with respect to the development of clinical stroke, because of the MCA cyclic flow reductions. Thus it is different from permanent or ischemia/reperfusion MCA occlusion in rodents and may be suitable for studying hemorrhagic risks associated with the use of antithrombotic agents.

The neuroprotective activity of 8-alkylamino-1,4-benzoxazine antioxidants

Antioxidant 8-alkylamino-1,4-benzoxazines, (R,S)-(3-tert-butyl-8-phenylethylamino-3,4-dihydro-2H-1,4-benzoxazin-5-yl) (phenyl) methanone (S 24429) and (R,S)-(3-cyclopentyl-8-benzylamino-3,4-dihydro-2H-1,4-benzoxazin-5-yl) (phenyl) methanone (S 24718), were prepared according to a two-step one-pot electrochemical procedure. These compounds had been selected from a previous study of structure/activity. Both compounds (1-100 microM) prevented the fall in ATP levels caused by 24 h of hypoxia in astrocytes. Both compounds (1 and 10 mg/kg i.p.) were powerful neuroprotective agents in protecting against the lesions induced by 15 microg S-bromo-willardiine injected into the cortex or white matter of 5-day old mice pups. In contrast, exifone, an antioxidant compound, was inactive at these doses. S 24429 and S 24718 appear to be novel neuroprotective agents, which are effective in a model of brain damage mimicking the lesions underlying cerebral palsy.

Inhibition of iron-dependent and ischemia-induced brain damage by the alpha-tocopherol analogue MDL 74,722

Free radical-induced lipid peroxidation is an important factor in the pathogenesis of ischemic brain damage. We studied the effects of the alpha-tocopherol analogue MDL 74,722 on iron-dependent lipid peroxidation and infarct volume after transient focal cerebral ischemia. The effects of MDL 74,722 on iron-induced lipid peroxidation were tested in cerebellar granule cell cultures by means of a thiobarbituric acid reactive substances (TBARS) assay. The absorbance resulting from mitochondrial reduction of 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) was taken as a measure of cell viability. Besides, in male Wistar rats the left middle cerebral artery (MCA) was occluded for 3 h by means of an intraluminal filament. Rats were treated with vehicle (n = 19) or MDL 74,722 (n = 17), administered intravenously for 3 h in a dose of 2 mg/(kg.h), starting 105 min after MCA occlusion. Infarct volume was measured in coronal brain sections stained with hematoxylin and eosin. In cerebellar granule cell cultures, MDL 74,722 resulted in a dose-dependent inhibition of TBARS formation and prevention of cell toxicity. The compound reduced infarct volume after transient occlusion of the MCA in rats by 49%. It is concluded that MDL 74,722 is a potent inhibitor of lipid peroxidation and reduces infarct volume by about one half, even when treatment is delayed. This contributes to its potential clinical usefulness.