Background and Purpose-Brain edema is detrimental in ischemic stroke and its treatment options are limited. Kinins are proinflammatory peptides that are released during tissue injury.

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Rodent models of focal cerebral ischemia are essential tools in experimental stroke research. They have added tremendously to our understanding of injury mechanisms in stroke and have helped to identify potential therapeutic targets. A plethora of substances, however, in particular an overwhelming number of putative neuroprotective agents, have been shown to be effective in preclinical stroke research, but have failed in clinical trials. A lot of factors may have contributed to this failure of translation from bench to bedside. Often, deficits in the quality of experimental stroke research seem to be involved. In this article, we review the commonest rodent models of focal cerebral ischemia - middle cerebral artery occlusion, photothrombosis, and embolic stroke models - with their respective advantages and problems, and we address the issue of quality in preclinical stroke modeling as well as potential reasons for translational failure.

Magnetic resonance imaging (MRI) is a powerful tool to assess brain lesions, but currently available contrast agents are limited in the assessment of cellular and functional alterations. By use of the novel MRI contrast agent gadofluorine M (Gf) we report on imaging of transient and widespread changes of blood-brain barrier (BBB) properties as a consequence of focal photothrombotic brain lesions in rats. After i.v. application, Gf led to bright contrast in the lesions, but also the entire ipsilateral cortex on T1-weighted MRI. In contrast, enhancement after application of gadolinium diethylenetriamine-pentaacetic acid (Gd-DTPA), a common clinical indicator of BBB leakage was restricted to the lesions. Remote Gf enhancement was restricted in time to the first 24 h after photothrombosis and corresponded to a transient breakdown of the BBB as revealed by extravasation of the dye Evans blue. In conclusion, our study shows that Gf can visualize subtle disturbances of the BBB in three dimensions not detectable by Gd-DTPA. Upon entry into the central nervous system Gf most likely is locally trapped by interactions with extracellular matrix proteins. The unique properties of Gf hold promise as a more sensitive contrast agent for monitoring BBB disturbances in neurologic disorders, which appear more widespread than anticipated previously.

Oxygen depletion (O2) and a decrease in pH are initial pathophysiological events in stroke development, but secondary mechanisms of ischemic cell death are incompletely understood. By patch-clamp recordings of brain slice preparations we show that TASK1 and TASK3 channels are inhibited by pH-reduction (42 ± 2%) and O2 deprivation (36 ± 5%) leading to membrane depolarization, increased input resistance and a switch in action potential generation under ischemic conditions. In vivo TASK blockade by anandamide significantly increased infarct volumes at 24h in mice undergoing 30 min of transient middle cerebral artery occlusion (tMCAO). Moreover, blockade of TASK channels accelerated stroke development. Supporting these findings TASK1−/− mice developed significantly larger infarct volumes after tMCAO accompanied by worse outcome in functional neurological tests compared to wild type mice. In conclusion, our data provide evidence for an important role of functional TASK channels in limiting tissue damage during cerebral ischemia.

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Background and Purpose-Models of photochemically-induced thrombosis are widely used in cerebrovascular research. Photothrombotic brain infarctions can be induced by systemic application of photosensitizing dyes followed by focal illumination of the cerebral cortex. Although the ensuing activation of platelets is well established, their contribution for thrombosis and tissue damage has not formally been proved. Methods-Infarction to the cerebral cortex was induced in mice by Rose Bengal and a cold light source. To assess the functional role of platelets, animals were platelet-depleted by anti-GPIb␣ antibodies or treated with GPIIb/IIIa-blocking F(ab) 2 fragments. The significance of the plasmatic coagulation cascade was determined by using blood coagulation factor XII (FXII)-deficient mice or heparin. Infarct development and infarct volumes were determined by serial MRI and conventional and electron microscopy. Results-There was no difference in development and final size of photothrombotic infarctions in mice with impaired platelet function. Moreover, deficiency of FXII, which initiates the intrinsic pathway of coagulation and is essential for thrombus formation, or blockade of FXa, the key protease during the waterfall cascade of plasmatic coagulation, by heparin likewise did not affect lesion development. Conclusions-Our data demonstrate that platelet activation, factor XII-driven thrombus formation, and plasmatic coagulation pathways downstream of FX are not a prerequisite for ensuing tissue damage in models of photothrombotic vessel injury indicating that other pathomechanisms are involved. We suggest that this widely used model does not depend on platelet-or plasmatic coagulation-derived thrombosis. (Stroke. 2008;39:1262-1268.)

The purpose of this study was to investigate the potential effects of 2-methoxyestradiol, a natural mammalian steroid, in glioma cells, since antiproliferative effects of this compound had been shown earlier in several leukemia and carcinoma cell lines. The effects of 0.2, 2 and 20 microM concentrations of 2-methoxyestradiol were measured in three malignant human glioma cell lines (U87MG, U138MG, LN405) and one malignant rat glioma cell line (RG-2) using a microtiter-tetrazolium (MTT) assay. In all cell lines, a significant reduction of the viable cell number by more then 75% occurred ( P < 0.05) for concentrations of 2 and 20 microM 2-methoxyestradiol after 6 days. A concentration of 0.2 microM had smaller effects (10-40% cell reduction), which were significant in two of the cell lines tested. The apoptotic nature of cell death was further analyzed in U87MG and RG-2 cells. Caspase-3 activity was significantly induced to levels between 3.4- and 23-fold after 4 days for the two higher 2-methoxyestradiol concentrations (P < 0.05). In the cell line RG-2 nuclear fragmentation was visible in many nuclei, following stains with Hoechst H33258. A round cell morphology occurred in most treated cells, which was not accompanied by a complete destruction of the microtubule network, as it can be observed with other microtubule targeting drugs.