Background and Purpose-Ischemia/hypoxia induces de novo expression of the sulfonylurea receptor 1-regulated NC(Ca-ATP) channel. In rodent models of ischemic stroke, early postevent administration of the sulfonylurea, glibenclamide, is highly effective in reducing edema, mortality, and lesion volume, and in patients with diabetes presenting with ischemic stroke, pre-event plus postevent use of sulfonylureas is associated with better neurological outcome. However, the therapeutic window for treatment with glibenclamide has not been studied. Methods-We examined the effect of low-dose (nonhypoglycemogenic) glibenclamide in 3 rat models of ischemic stroke, all involving proximal middle cerebral artery occlusion (MCAo): a thromboembolic model, a permanent suture occlusion model, and a temporary suture occlusion model with reperfusion (105 minutes occlusion, 2-day reperfusion). Treatment was started at various times up to 6 hours post-MCAo. Lesion volumes were measured 48 hours post-MCAo using 2,3,5-triphenyltetrazolium chloride. Results-Glibenclamide reduced total lesion volume by 53% in the thromboembolic MCAo model at 6 hours, reduced corrected cortical lesion volume by 51% in the permanent MCAo model at 4 hours, and reduced corrected cortical lesion volume by 41% in the temporary MCAo model at 5.75 hours (PϽ0.05 for all 3). Analysis of pooled data from the permanent MCAo and temporary MCAo series indicated a sigmoidal relationship between hemispheric swelling and corrected cortical lesion volume with the half-maximum cortical lesion volume being observed with 10% hemispheric swelling. Conclusions-Low-dose glibenclamide has a strong beneficial effect on lesion volume and has a highly favorable therapeutic window in several models of ischemic stroke.
Background and Purpose-Treating patients with malignant cerebral infarctions remains a major unsolved problem in medicine. Decompressive craniectomy (DC) improves the bleak outlook but is suboptimal. Using a rat model of severe ischemia/reperfusion with very high mortality due to malignant cerebral edema, we tested the hypothesis that blocking of sulfonylurea receptor 1-regulated NC Ca-ATP channels with glibenclamide would compare favorably to DC when reperfusion and treatment were begun 6 hours after onset of ischemia. Methods-Male Wistar rats underwent filament occlusion of the middle cerebral artery to reduce laser Doppler flowmetry perfusion signals by Ͼ75%, with filament removal plus treatment 6 hours later. In rats treated with vehicle versus glibenclamide (10 g/kg IP plus 200 ng/h SC), we compared mortality, neurologic function, and brain swelling at 24 hours. In rats treated with DC versus glibenclamide, we compared neurologic function for 2 weeks and histologic outcomes. Results-Compared with vehicle, glibenclamide treatment reduced 24-hour mortality from 67% to 5% and reduced hemispheric swelling at 24 hours from 21% to 8%. DC eliminated 24-hour mortality, but neurologic function during the next 2 weeks was significantly better with glibenclamide compared with DC. Watershed cortex and deep white matter were significantly better preserved with glibenclamide compared with DC. Conclusions-In a rat model of severe ischemia/reperfusion, with reperfusion and treatment beginning 6 hours after onset of ischemia, glibenclamide is as effective as DC in preventing death from malignant cerebral edema but is superior to DC in preserving neurologic function and the integrity of watershed cortex and deep white matter. (Stroke. 2010;41:531-537.)
Glibenclamide improves outcomes in rat models of stroke, with treatment as late as 6 h after onset of ischemia shown to be beneficial. Because the molecular target of glibenclamide, the sulfonylurea receptor 1 (Sur1)-regulated NC Ca-ATP channel, is upregulated de novo by a complex transcriptional mechanism, and the principal pathophysiological target, brain swelling, requires hours to develop, we hypothesized that the treatment window would exceed 6 h. We studied a clinically relevant rat model of stroke in which middle cerebral artery occlusion (75% < reduction in LDF signal ≤90%) was produced using an intra-arterial occluder.
In animal models of stroke, spinal cord injury, and subarachnoid hemorrhage, transient receptor potential melastatin 4 (Trpm4), a non-selective monovalent cation channel, is transcriptionally upregulated in neural and vascular cells. In these contexts, Trpm4 has been shown to co-associate with sulfonylurea receptor 1 (Sur1) to form Sur1-Trpm4 channels, which play a critical role in cytotoxic edema, accidental necrotic (oncotic) cell death, blood-brain barrier (BBB) breakdown and formation of vasogenic edema. To date, the expression and molecular interactions of Trpm4 within human cerebral infarcts have not been systematically evaluated. In this study, we examined Trpm4 expression in postmortem specimens obtained from 15 patients within the first 31 days after onset of focal cerebral ischemia. Significant upregulation of Trpm4 protein was found in all cases, relative to controls. De novo transcriptional upregulation of Trpm4 protein was confirmed using in situ hybridization for Trpm4 mRNA. Trpm4 co-localized and co-associated with Sur1 within ischemic endothelial cells and neurons which exhibited membrane thickening and irregularities characteristic of necrotic cell death. Sur1 and Trpm4 co-expression in abnormal endothelial cells also was associated with vasogenic edema, as evidenced by upregulated perivascular TNFα, perivascular extravasation of serum immunoglobulin G and associated inflammation. Upregulated Trpm4 protein persisted up to one month post onset of cerebral ischemia. Furthermore, pharmacological channel blockade by glibenclamide, a selective inhibitor of sulfonylurea receptor, was found to mitigate perivascular TNFα labeling in a rat middle cerebral artery occlusion (MCAo) stroke model. We conclude that the Sur1-Trpm4 channel is upregulated and associated with BBB disruption and cerebral edema formation in human cerebral infarcts. These data suggest that pharmacological targeting of this channel may represent a promising therapeutic strategy for clinical management of ischemic stroke.
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