Management of Acute Ischemic Stroke

Akt activation improves microregional oxygen supply/consumption balance after cerebral ischemia-reperfusion

There have been reports that activation of Akt may provide neuroprotection after cerebral ischemia-reperfusion. We tested the hypothesis that activation of Akt would decrease infarct size and improve microregional O₂ supply/consumption balance after cerebral ischemia-reperfusion. This hypothesis was tested in isoflurane-anesthetized rats with middle cerebral artery blockade for 1 h and reperfusion for 2 h with or without SC-79 (Akt activator, 0.05 mg/kg, three doses). Regional cerebral blood flow was determined using a C¹⁴-iodoantipyrine autoradiographic technique. Regional small vessel (20-60 μm diameter) arterial and venous oxygen saturations were determined microspectrophotometrically. Akt phosphorylation was determined by Western blot. There were no significant hemodynamic or blood gas differences between groups. The control ischemic-reperfused cortex had a similar O₂ consumption, but lower blood flow and higher O₂ extraction compared to the contralateral cortex. However, microregional O₂ supply/consumption balance was significantly reduced in the ischemic-reperfused cortex with many areas of low O₂ saturation (42 of 80 veins with O₂ saturation below 50%). SC-79 did not significantly affect cerebral O₂ consumption, but significantly improved O₂ supply/consumption balance in the reperfused area (18 of 80 veins with O₂ saturation below 50%). This was associated with a reduced cortical infarct size (13.3 ± 0.5% control vs 6.7 ± 0.3% SC-79). In control, Akt phosphorylation was elevated at 2 h after ischemia. With SC-79, Akt was activated at 15 min but not at 2 h in the ischemic reperfused area. These results suggest that early Akt activation is important for not only cell survival, but also for the control of local oxygen balance after cerebral ischemia-reperfusion.

Elevated Serum High-Mobility Group Box-1 Protein Level Is Associated with Poor Functional Outcome in Ischemic Stroke

BACKGROUND

In experimental models, inhibition of high-mobility group box-1 (HMGB1) signaling has been reported to protect against the sequelae of ischemic stroke. Here, we determined the clinical significance of serum HMGB1 levels in patients with acute ischemic stroke.

METHODS

We enrolled 183 patients (114 men, 69 women; mean age: 72.7 years) over 6 consecutive months. On admission and day 7, we recorded the National Institutes of Health Stroke Scale scores and measured serum high-sensitivity C-reactive protein (hs-CRP) and HMGB1 levels. Stroke volumes were estimated using diffusion-weighted magnetic resonance imaging performed on admission. One year later, clinical outcome was assessed using the modified Rankin Scale (mRS).

RESULTS

Serum hs-CRP and HMGB1 levels in patients with ischemic stroke were increased relative to healthy controls (both P < .01). On day 7, hs-CRP, but not HMBG1, levels had increased significantly relative to levels at admission (P < .01 and .54, respectively). Higher HMGB1, but not hs-CRP, levels at day 7 correlated with larger stroke volumes (P < .01 and .28, respectively). HMGB1 levels did not significantly differ between stroke subtypes. Multiple logistic regression analysis indicated that a serum HMGB1 level higher than 7.5 ng/mL was an independent risk factor for poor prognosis, defined as a 1-year mRS score of 3-6 (odds ratio, 2.34; 95% confidence interval, 1.02-5.38).

CONCLUSIONS

Acute ischemic stroke is associated with elevated serum HMGB1 levels, and HMGB1 levels at admission independently predict poor outcome at 1 year. These results suggest that HMGB1 quantification provides more accurate prognostic information after ischemic stroke.

Upregulation of neuronal zinc finger protein A20 expression is required for electroacupuncture to attenuate the cerebral inflammatory injury mediated by the nuclear factor-kB signaling pathway in cerebral ischemia/reperfusion rats

Background

Zinc finger protein A20 (tumor necrosis factor alpha-induced protein 3) functions as a potent negative feedback inhibitor of the nuclear factor-kB (NF-kB) signaling. It exerts these effects by interrupting the activation of IkB kinase beta (IKKβ), the most critical kinase in upstream of NF-kB, and thereby controlling inflammatory homeostasis. We reported previously that electroacupuncture (EA) could effectively suppress IKKβ activation. However, the mechanism underlying these effects was unclear. Therefore, the current study further explored the effects of EA on A20 expression in rat brain and investigated the possible mechanism of A20 in anti-neuroinflammation mediated by EA using transient middle cerebral artery occlusion (MCAO) rats.

Methods

Rats were treated with EA at the “Baihui (GV20),” “Hegu (L14),” and “Taichong (Liv3)” acupoints once a day starting 2 h after focal cerebral ischemia. The spatiotemporal expression of A20, neurobehavioral scores, infarction volumes, cytokine levels, glial cell activation, and the NF-kB signaling were assessed at the indicated time points. A20 gene interference (overexpression and silencing) was used to investigate the role of A20 in mediating the neuroprotective effects of EA and in regulating the interaction between neuronal and glial cells by suppressing neuronal NF-kB signaling during cerebral ischemia/reperfusion-induced neuroinflammation.

Results

EA treatment increased A20 expression with an earlier peak and longer lasting upregulation. The upregulated A20 protein was predominantly located in neurons in the cortical zone of the ischemia/reperfusion. Furthermore, neuronal A20 cell counts were positively correlated with neurobehavioral scores but negatively correlated with infarct volume, the accumulation of pro-inflammatory cytokines, and glial cell activation. Moreover, the effects of EA on improving the neurological outcome and suppressing neuroinflammation in the brain were reversed by A20 silencing. Finally, A20 silencing also suppressed the ability of EA to inhibit neuronal NF-kB signaling pathway.

Conclusions

Ischemia/reperfusion cortical neurons in MCAO rats are the main cell types that express A20, and there is a correlation between A20 expression and the suppression of neuroinflammation and the resulting neuroprotective effects. EA upregulated neuronal A20 expression, which played an essential role in the anti-inflammatory effects of EA by suppressing the neuronal NF-kB signaling pathway in the brains of MCAO rats.

Inductive and Deductive Approaches to Acute Cell Injury

Many clinically relevant forms of acute injury, such as stroke, traumatic brain injury, and myocardial infarction, have resisted treatments to prevent cell death following injury. The clinical failures can be linked to the currently used inductive models based on biological specifics of the injury system. Here we contrast the application of inductive and deductive models of acute cell injury. Using brain ischemia as a case study, we discuss limitations in inductive inferences, including the inability to unambiguously assign cell death causality and the lack of a systematic quantitative framework. These limitations follow from an overemphasis on qualitative molecular pathways specific to the injured system. Our recently developed nonlinear dynamical theory of cell injury provides a generic, systematic approach to cell injury in which attractor states and system parameters are used to quantitatively characterize acute injury systems. The theoretical, empirical, and therapeutic implications of shifting to a deductive framework are discussed. We illustrate how a deductive mathematical framework offers tangible advantages over qualitative inductive models for the development of therapeutics of acutely injured biological systems.

Different dynamics of aquaporin 4 and glutamate transporter-1 distribution in the perineuronal and perivascular compartments during ischemic stroke

Aquaporin-4 (AQP4) and glutamate transporter-1 (GLT-1) represent the major water and glutamate astrocyte buffering gateways in the brain. Utilizing perilesional ischemic human cortices, we have performed here for the first time an integrative assessment on both AQP4 and GLT-1, and on their proximity to blood vessels and neurons. Counting the relative number of AQP4±/GLT-1±/glial fibrillary acidic protein± cells showed that double-positive variants were overall most frequent, and their number tended to decrease from organized and recent perilesional cortices to controls. AQP4/GLT-1 colocalization showed higher coefficients for the perilesional cortices compared with controls, suggesting an increased water/glutamate-buffering capability. Distance frequency analysis of AQP4/GLT-1 in relationship to neurons showed that both markers were concentrated at 20-40 μm around the perikarya; with AQP4 being more abundant in close proximity, these differences were not being driven by changes in neuropil density alone. Our study suggests a dual, simultaneous astrocytic function depending on the relative distance to neurons and vessels, with increased water and glutamate-buffering capability in the mid perineuronal space, and an increased water-buffering capability in the immediate perineuronal space, even higher than around vessels. Thus, adding specific AQP4/GLT-1 modulator agents selectively depending on the acute/chronic phase of stroke might increase the efficacy of existing treatments.

The effect of Ginkgo biloba on functional outcome of patients with acute ischemic stroke: a double-blind, placebo-controlled, randomized clinical trial

BACKGROUND

Acute ischemic stroke is a major cerebrovascular disease with potential morbidity and mortality. Despite the availability of thrombolytic therapy in some centers, risk factor modification and rehabilitation therapy are the mainstays of stroke management. There is supporting evidence that Ginkgo biloba may afford neuroprotection and improve the outcomes of patients with acute ischemic stroke.

METHODS

In a double-blind, placebo-controlled, randomized controlled trial, we assessed the efficacy of G biloba on functional outcome in patients with acute stroke. The National Institutes of Heath Stroke Scale (NIHSS) was used to measure functional outcome. A total of 102 patients with acute ischemic stroke were studied. All patients received either G biloba or placebo tablets for 4 months. This trial was registered to the Iranian Registry of Clinical Trials (www.irct.ir; trial IRCT138804212150N1).

RESULTS

There were 52 patients who received G biloba and 50 patients who were in the placebo group. Age, sex distribution, previous medical condition, and laboratory data did not have any significant difference between the 2 groups (P>.05). The mean difference of 4-month follow-up NIHSS scores and NIHSS scores at admission was 4.7±2.7 and 4.1±3.0 in the G biloba and placebo groups, respectively (P>.05). The primary outcome-a 50% reduction in the 4-month follow-up NIHSS score compared to the baseline NIHSS score-was reached in 17 patients (58.6%) and 5 patients (18.5%) in the G biloba and placebo groups, respectively (P<.05). The risk ratio and number needed to treat were 3.16 (confidence interval 1.35-7.39) and 2.50 (confidence interval 1.58-5.90), respectively. In addition, multivariate regression adjusted for age and sex revealed a significant NIHSS decline in the G biloba group compared to the placebo group (P<.05).

CONCLUSIONS

Our data suggest that G biloba may have protective effects in ischemic stroke. Therefore, the administration of G biloba is recommended after acute ischemic stroke.