In mouse hippocampal CA1 pyramidal neurons, the activity of synaptic small-conductance Ca2+-activated K+ channels type 2 (SK2 channels) provides a negative feedback on N-methyl-d-aspartate receptors (NMDARs), reestablishing Mg2+ block that reduces Ca2+ influx. The well-established role of NMDARs in ischemia-induced excitotoxicity led us to test the neuroprotective effect of modulating SK2 channel activity following cerebral ischemia induced by cardiac arrest and cardiopulmonary resuscitation (CA/CPR). Administration of the SK channel positive modulator, 1-ethyl-benzimidazolinone (1-EBIO), significantly reduced CA1 neuron cell death and improved CA/CPR-induced cognitive outcome. Electrophysiological recordings showed that CA/CPR-induced ischemia caused delayed and sustained reduction of synaptic SK channel activity, and immunoelectron microscopy showed that this is associated with internalization of synaptic SK2 channels, which was prevented by 1-EBIO treatment. These results suggest that increasing SK2 channel activity, or preventing ischemia-induced loss of synaptic SK2 channels, are promising and novel approaches to neuroprotection following cerebral ischemia.

Background and Purpose-Experimental stroke induces a biphasic effect on the immune response that involves early activation of peripheral leukocytes followed by severe immunodepression and atrophy of the spleen and thymus. In tandem, the developing infarct is exacerbated by influx of numerous inflammatory cell types, including T and B lymphocytes. These features of stroke prompted our use of recombinant T cell receptor ligands (RTL), partial major histocompatibility complex Class II molecules covalently bound to myelin peptides. We tested the hypothesis that RTL would improve ischemic outcome in the brain without exacerbating defects in the peripheral immune system function. Methods-Four daily doses of RTL were administered subcutaneously to C57BL/6 mice after middle cerebral artery occlusion, and lesion size and cellular composition were assessed in the brain and cell numbers were assessed in the spleen and thymus. Results-Treatment with RTL551 (I-Ab molecule linked to MOG-35-55 peptide) reduced cortical and total stroke lesion size by approximately 50%, inhibited the accumulation of inflammatory cells, particularly macrophages/activated microglial cells and dendritic cells, and mitigated splenic atrophy. Treatment with RTL1000 (HLA-DR2 moiety linked to human MOG-35-55 peptide) similarly reduced the stroke lesion size in HLA-DR2 transgenic mice. In contrast, control RTL with a nonneuroantigen peptide or a mismatched major histocompatibility complex Class II moiety had no effect on stroke lesion size. Conclusions-These data are the first to demonstrate successful treatment of experimental stroke using a neuroantigen-specific immunomodulatory agent administered after ischemia, suggesting therapeutic potential in human stroke.

Background Severe ischemia induces renal injury less frequently in women than men. In this study, cardiac arrest and cardiopulmonary resuscitation were used to assess whether estradiol is renoprotective via an estrogen receptor (ER)-dependent mechanism. Materials and Methods Male and female C57BL/6 and ER gene-deleted mice underwent 10 min of cardiac arrest followed by cardiopulmonary resuscitation. Serum chemistries and renal stereology were measured 24 h after arrest. Results Estrogen did not affect mean arterial pressure, regional renal cortical blood flow, and arterial blood gases. Hence, female kidneys were protected (mean ± SEM: blood urea nitrogen, 65 ± 21 vs.149 ± 27 mg/dl, P = 0.04; creatinine, 0.14 ± 0.05 vs. 0.73 ± 0.16 mg/dl, P = 0.01; volume of necrotic tubules, 7 ± 1% vs. 10 ± 0%, P = 0.04). Estrogen also reduced renal injury. In intact females (n = 5), ovariectomized/vehicle-treated (n = 8), and ovariectomized/estrogen-treated (n = 8) animals, blood urea nitrogen was 65 ± 21, 166 ± 28, and 50 ± 14 mg/dl (P = 0.002); creatinine was 0.14 ± 0.05, 0.74 ± 0.26, and 0.23 ± 0.27 mg/dl (P = 0.014); necrotic tubules were 2.5 ± 0.25%, 12.0 ± 1.9%, and 5.0 ± 1.6% (P = 0.004), respectively. In ER-α and ER-β gene-deleted mice and controls estradiol-reduced functional injury (blood urea nitrogen: estradiol 117 ± 71, vehicle 167 ± 56, P = 0.007; creatinine: estradiol 0.5 ± 0.5, vehicle 1.0 ± 0.4, P = 0.013), but the effect of estradiol was not different between ER-α or ER-β gene-deleted mice. Adding ICI 182,780 to estradiol did not alter injury. Conclusions In women, kidneys were protected from cardiac arrest through estrogen. Estradiol-mediated renoprotection was not affected by ER deletion or blockade. Estradiol is renoprotective after cardiac arrest. The results indicate that estradiol renoprotection is ER-α and ER-β independent.

Female sex steroids, particularly estrogens, contribute to the sexually dimorphic response observed in cerebral ischemic outcome, with females being relatively protected compared to males. Using a mouse model of cardiac arrest and cardiopulmonary resuscitation (CA/CPR), we previously demonstrated that estrogen neuroprotection is mediated in part by the estrogen receptor β, with no involvement of estrogen receptor α. In this study we examined the neuroprotective effect of the novel estrogen receptor, G-protein coupled estrogen receptor 1 (GPER1/GPR30). Male mice administered the GPR30 agonist G1 exhibited significantly reduced neuronal injury in the hippocampal CA1 region and striatum. The magnitude of neuroprotection observed in G1 treated mice was indistinguishable from estrogen treated mice, implicating GPR30 in estrogen neuroprotection. Real-time quantitative RT-PCR indicates that G1 treatment increases expression of the neuroprotective ion channel, small conductance calcium-activated potassium channel 2. We conclude that GPR30 agonists show promise in reducing brain injury following global cerebral ischemia.

Cardiac arrest (CA) causes hippocampal neuronal death that frequently leads to severe loss of memory function in survivors. No specific treatment is available to reduce neuronal death and improve functional outcome. The brain's inflammatory response to ischemia can exacerbate injury and provides a potential treatment target. We hypothesized that microglia are activated by CA and contribute to neuronal loss. We used a mouse model to determine whether pharmacologic inhibition of the proinflammatory microglial enzyme soluble epoxide hydrolase (sEH) after CA alters microglial activation and neuronal death. The sEH inhibitor 4-phenylchalcone oxide (4-PCO) was administered after successful cardiopulmonary resuscitation (CPR). The 4-PCO treatment significantly reduced neuronal death and improved memory function after CA/CPR. We found early activation of microglia and increased expression of inflammatory tumor necrosis factor (TNF)-α and interleukin (IL)-1β in the hippocampus after CA/CPR, which was unchanged after 4-PCO treatment, while expression of antiinflammatory IL-10 increased significantly. We conclude that sEH inhibition after CA/CPR can alter the transcription profile in activated microglia to selectively induce antiinflammatory and neuroprotective IL-10 and reduce subsequent neuronal death. Switching microglial gene expression toward a neuroprotective phenotype is a promising new therapeutic approach for ischemic brain injury.