The role of aquaporin-4 polymorphisms in the development of brain edema after middle cerebral artery occlusion.

BACKGROUND AND PURPOSE: Some patients develop severe brain edema after complete middle cerebral artery occlusion, whereas others do not. Aquaporin-4 (AQP4) is the main water channel in the brain and has been shown to be critical for the development of brain edema after ischemia. We asked whether genetic variation in the AQP4 gene is related to the severity of brain edema after middle cerebral artery occlusion. METHODS: We genotyped 10 single nucleotide polymorphisms distributed across the AQP4 gene in 41 patients with middle cerebral artery occlusion with and without severe brain edema and assessed single marker association as well as the linkage dysequilibrium structure across AQP4. RESULTS: One single nucleotide polymorphism (rs9951307) at the 3' end of AQP4 was associated with severe brain edema (dominant model, P=0.01; OR, 0.10; 95% CI, 0.02 to 0.49 for the protective G-allele). Linkage dysequilibrium across AQP4 was low; no clear haplotype blocks could be identified for the assessment of haplotype association. CONCLUSIONS: This explorative study shows that genetic variation in AQP4 might contribute to brain edema formation after middle cerebral artery occlusion and warrants further investigation.

Neuroprotection by hyperbaric oxygenation after experimental focal cerebral ischemia monitored by MRI.

BACKGROUND: Hyperbaric oxygenation (HBO) after focal cerebral ischemia reduces infarct size and improves outcome when applied early after stroke. Here, we evaluated effects of HBO on permanent focal cerebral ischemia and applied magnetic resonance imaging (MRI) monitoring to study lesion evolution. METHODS: Rats underwent permanent middle cerebral artery occlusion (MCAO). Two hours later, animals were treated with HBO (100% O(2)/2 atm; n=17) for 1 hour or treated with room air (n=17). Animals underwent serial MRI studies (DWI, PI, T2) beginning 90 minutes after MCAO. Neuroscore was assessed (5-point rating scale). Animals were euthanized and brains were 2,3,5-triphenyltetrazolium chloride (TTC)-stained for infarct volume calculation 120 hours after MCAO. Immunohistochemistry was performed with antibodies against c-FOS and 4-hydroxy-2-nonenal-modified proteins (HNE) to check for effects of oxidative stress caused by HBO treatment. RESULTS: HBO reduced infarct volume by 38% (P<0.001). As shown by MRI, neuroprotection began 5 hours after ischemia and remained effective for 5 days. The relative regional cerebral blood flow was not different between groups at 3.5 and 5 hours after occlusion. There was less neurological deficit in HBO-treated animals compared with controls (P<0.05). Lipid peroxidation of cerebral vessels after HBO treatment as measured by HNE staining and pattern of c-FOS induction were not significantly different between groups at 3.5 and 8 hours after ischemia. CONCLUSIONS: As monitored by MRI HBO treatment reversed ischemic lesion size between 3 and 5 hours after ischemia and achieved a long-lasting neuroprotective effect without significant oxidative damage.

High-dose aspirin is neuroprotective in a rat focal ischemia model.

Acetylsalicylic acid (ASA) is neuroprotective through various pharmacological action sites. We used a temporary middle cerebral artery occlusion (tMCAO) model in 56 Wistar rats to assess whether repeated ASA injections at 30 min, 6 h, 1, 2, 3, and 4 days after stroke onset are neuroprotective. Animals were sacrificed 5 days after MCAO; infarct size was analyzed with 2,3,5-triphenyltetrazolium chloride staining. As compared to saline (164+/-13 mm(3), n=14), only repeated injections of 40 mg/kg ASA (79+/-18 mm(3), n=14, P=0.0029), but not of 20 mg/kg ASA (129+/-19 mm(3), n=15), reduced infarct volume significantly. No significant change was noted with 40 mg/kg ASA injected only once at 30 min after MCAO (117+/-16 mm(3), n=13).

Decompressive craniectomy in acute cerebral ischemia in rats. Is there any benefit in smaller thromboembolic infarcts?

Early craniectomy has shown to reduce infarction size in experimental large MCA infarction probably due to improved leptomeningeal perfusion. Based on the hypothesis that craniectomy may also be beneficial in smaller MCA infarction we evaluated the effects of craniectomy on infarction size in small thromboembolic cerebral infarction in rats. Therefore, thromboembolic cerebral ischemia was induced in 40 rats by endovascular injection of autologous, fibrin-rich emboli. Twenty-one animals with a diffusion-weighted MR imaging (DWI)-derived infarction size of 50-100 mm3 (involving one- to two-third of the MCA territory) at 1 h after injection were randomly assigned to two groups. Eleven animals of group 1 immediately underwent craniectomy, ten animals of group 2 (controls) were not treated. Serial DWI was performed at 4 and 24 h. Infarction size was assessed by TTC-staining at 48 h after emboli injection. As result, prior to treatment, at 1 h after emboli injection, infarction size in groups 1 and 2 was 65.9 +/- 16.0 mm3 and 67.9 +/- 17.8 mm3, respectively. At 4 and 24 h, infarction size in group 1 was 73.5 +/- 22.1 mm3 and 85.2 +/- 24.7 mm3, and 76.3 +/- 21.0 mm3 and 83.4 +/- 22.9 mm3 in group 2, respectively. TTC-derived infarction size was 84.0 +/- 23.3 mm3 and 82.7 +/- 21.5 mm3, respectively. There was no significant difference between the two groups (P > 0.79). In conclusion, our results demonstrate that for small thromboembolic MCA infarction early craniectomy is not beneficial.

Massive accumulation of N-acylethanolamines after stroke. Cell signalling in acute cerebral ischemia?

We investigated levels and compositions of N-acylethanolamines (NAEs) and their precursors, N-acyl phosphatidylethanolamines (N-acyl PEs), in a rat stroke model applying striatal microdialysis for glutamate assay. Rats (n = 18) were treated with either intravenous saline (control), NMDA receptor antagonist MK801 (1 mg/kg), or CB1 receptor antagonist SR141716A (1 mg/kg) 30 min after permanent middle cerebral artery occlusion (MCAO). MK801 significantly attenuated the release of glutamate in the infarcted striatum (79 +/- 22 micromol/L) as compared with controls (322 +/- 104 micromol/L). The administration of CB1 antagonist SR141716A had no statistically significant effect on glutamate release (340 +/- 89 micromol/L), but reduced infarct volume at 5 h after MCAO significantly by approximately 40%, whereas MK801 treatment resulted in a non-significant (18%) reduction of infarct volume. In controls, striatal and cortical NAE concentrations were about 30-fold higher in the infarcted than in the non-infarcted hemisphere, whereas ipsilateral N-acyl phosphatidylethanolamine (N-acyl PE) levels exceeded contralateral levels by only a factor of two to three. Treatment with MK801 or SR141716A, or glutamate release in the infarcted tissue, had no significant effect on these levels. NAE accumulation during acute stroke may be due to increased synthesis as well as decreased degradation, possibly by inhibition of fatty acid amide hydrolase (FAAH).