Apoptotic neuronal death following cerebral ischaemia

Baseline Cerebral Ischemic Core Quantified by Different Automatic Software and Its Predictive Value for Clinical Outcome

Purpose

This study aims to investigate the agreement of three software packages in measuring baseline ischemic core volume (ICV) and penumbra volume (PV), and determine their predictive values for unfavorable clinical outcome in patients with endovascular thrombectomy (EVT).

Methods

Patients with acute ischemic stroke who underwent computed tomographic perfusion (CTP) were recruited. Baseline CTP measurements including ICV and PV were calculated by three software packages of IntelliSpace Portal (ISP), Rapid Processing of Perfusion and Diffusion (RAPID), and fast-processing of ischemic stroke (F-STROKE). All patients received EVT, and the modified Rankin scale (mRS) at 90 days after EVT was assessed to determine the clinical outcomes (favorable: mRS = 0-2; unfavorable: mRS = 3-6). The agreement of CTP measurements among three software packages was determined using intraclass correlation coefficient (ICC). The associations between CTP measurements and unfavorable clinical outcome were analyzed using logistic regression. Receiver operating characteristic curves were conducted to calculate the area under the curve (AUC) of CTP measurements in predicting unfavorable clinical outcome.

Results

Of 223 recruited patients (68.2 ± 11.3 years old; 145 males), 17.0% had unfavorable clinical outcome after EVT. Excellent agreement between F-STROKE and RAPID was found in measuring ICV (ICC 0.965; 95% CI 0.956-0.973) and PV (ICC 0.966; 95% CI 0.956-0.973). ICVs measured by three software packages were significantly associated with unfavorable clinical outcome before (odds ratios 1.012-1.018, all P < 0.01) and after (odds ratios 1.003-1.014, all P < 0.05) adjusted for confounding factors (age, gender, TOAST classification, and NIHSS on admission). In predicting unfavorable clinical outcome, ICV measured by F-STROKE showed similar performance to that measured by RAPID (AUC 0.701 vs. 0.717) but higher performance than that measured by ISP (AUC 0.629).

Conclusions

The software of F-STROKE has excellent agreement with the widely used analysis tool of RAPID in measuring ICV and PV. The ischemic core volume measured by both F-STROKE and RAPID is a stronger predictor for unfavorable clinical outcome after EVT compared to ISP.

IL-17A Neutralization Improves the Neurological Outcome of Mice With Ischemic Stroke and Inhibits Caspase-12-Dependent Apoptosis

We previously reported that the levels of astrocyte-derived interleukin-17A (IL-17A) increased both in the peri-infarct region and cerebrospinal fluid (CSF) of mice with 1-h middle cerebral artery (MCA) occlusion/12-h reperfusion (1-h MCAO/R 12 h)-induced ischemic stroke. However, the effects of IL-17A neutralization on the neurological outcome of mice with ischemic stroke and its underlying molecular mechanism are unclear. In this study, we found that the intracerebroventricular injection of IL-17A-neutralizing monoclonal antibody (mAb; 2.0 μg) could reduce the infarct volume, alleviate neuron loss, and improve the neurological outcomes of mice with 1-h MCAO/R 24-h- or 3-day-induced ischemic-stroke mice. The IL-17A neutralization could also significantly inhibit the increase of pro-caspase-3 cleavage through caspase-12-dependent cell apoptosis, as well as preventing the decrease of antiapoptotic factor B-cell lymphoma 2 (Bcl-2) and the increase of proapoptotic Bcl-2-associated X protein (Bax) in the peri-infarct region of mice following ischemic stroke. In addition, we confirmed that the recombinant mouse (rm) IL-17A could significantly aggravate 1-h oxygen–glucose deprivation/24-h reoxygenation (1-h OGD/R 24 h)-induced ischemic injuries in cortical neurons in a dose-dependent manner, and the rmIL-17A could also exacerbate neuronal apoptosis through caspase-12 (not caspase-8 or caspase-9)-dependent pathway. These results suggest that IL-17A neutralization could improve the neurological outcome of mice with ischemic stroke through inhibiting caspase-12-dependent neuronal apoptosis.

Detection of neuroinflammation before selective neuronal loss appearance after mild focal ischemia using [18F]DPA-714 imaging

Background

Translocator protein (TSPO) imaging can be used to detect neuroinflammation (including microglial activation) after acute cerebral infarction. However, longitudinal changes of TSPO binding after mild ischemia that induces selective neuronal loss (SNL) without acute infarction are not well understood. Here, we performed TSPO imaging with [¹⁸F]DPA-714 to determine the time course of neuroinflammation and SNL after mild focal ischemia.

Results

Mild focal ischemia was induced by middle cerebral artery occlusion (MCAO) for 20 min. In MCAO rats without acute infarction investigated by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, in vitro ARG revealed a significant increase of [¹⁸F]DPA-714 binding in the ipsilateral striatum compared with that in the contralateral side at 1, 2, 3, and 7 days after MCAO. Increased [¹⁸F]DPA-714 binding was observed in the cerebral cortex penumbra, reaching maximal values at 7 days after MCAO. Activation of striatal microglia and astrocytes was observed with immunohistochemistry of ionized calcium binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) at 2, 3, and 7 days after MCAO. SNL was investigated with Nissl staining and neuronal nuclei (NeuN) immunostaining and observed in the ischemic core region of the striatum on days 3 and 7 after MCAO. We confirmed that total distribution volume of [¹⁸F]DPA-714 in the ipsilateral striatum was significantly increased at 2 and 7 days after MCAO using positron emission tomography (PET).

Conclusions

[¹⁸F]DPA-714 binding measured with in vitro ARG was increased before SNL appeared, and this change was detected by in vivo PET. These findings suggest that TSPO PET imaging might be useful for detection of neuroinflammation leading to SNL after focal ischemia.

Betulinic acid protects against cerebral ischemia/reperfusion injury by activating the PI3K/Akt signaling pathway

Betulinic acid (BA), a naturally occurring pentacyclic lupane group triterpenoid, has been demonstrated to protect against ischemia/reperfusion-induced renal damage. However, the effects of BA on cerebral ischemia/reperfusion (I/R) injury remain unclear. Hence, this study was to investigate the effects of BA on oxygen and glucose deprivation/reperfusion (OGD/R) induced neuronal injury in rat hippocampal neurons. Our results showed that BA pretreatment greatly attenuated OGD/R-induced neuronal injury. BA also inhibited OGD/R-induced intracellular ROS production and MDA level in rat hippocampal neurons. Furthermore, the down-regulation of Bcl-2, up-regulation of Bax and the consequent activation of caspase-3 induced by OGD/R were reversed by BA pretreatment. Mechanistic studies demonstrated that BA pretreatment up-regulated the expression levels of p-PI3K and p-Akt in hippocampal neurons induced by OGD/R. Taken together, these data suggested that BA inhibits OGD/R-induced neuronal injury in rat hippocampal neurons through the activation of PI3K/Akt signaling pathway.

Evaluation of preconditioning treatments to protect near-pure cortical neuronal cultures from in vitro ischemia induced acute and delayed neuronal death

We evaluated the efficacy of cycloheximide, heat stress, NMDA receptor blockade (MK801/AP-5), oxygen--glucose deprivation, hypoxia, hypothermia and TNFalpha preconditioning to protect cortical neurons from in vitro ischemic insults that result in acute necrotic and delayed apoptotic neuronal death. Preconditioning treatments were performed 22--24 h before in vitro ischemia. In vitro ischemia was carried out in 96-well microtitre strip-plates by washing neuronal cultures with a balanced salt solution containing 25 mM 2-deoxy-D-glucose and incubating in an anaerobic chamber. Glutamate receptor blockers were present during in vitro ischemia to induce delayed neuronal death. Cycloheximide, heat stress, MK801 and oxygen--glucose deprivation preconditioning were neuroprotective in both acute and delayed in vitro ischemic neuronal death models. AP-5 preconditioning and a 12 h post-MK801 preconditioning interval protected neurons from acute ischemic neuronal death only. Hypoxia, TNFalpha and hypothermic preconditioning provided no neuronal protection in the in vitro ischemia models. This study has confirmed for the first time that several preconditioning treatments can protect neurons from in vitro ischemia induced acute necrotic and delayed apoptotic neuronal death. In addition, a unique feature of this study is the finding that preconditioning could be induced in near-pure primary cortical neuronal cultures, thus confirming that ischemic tolerance is an intrinsic property of neurons and provides a simplified culture system for identifying neuroprotective proteins.

Establishment of neuronal in vitro models of ischemia in 96-well microtiter strip-plates that result in acute, progressive and delayed neuronal death

Using 96-well microtiter strip-plates we established in vitro ischemia models with acute, progressive and delayed neuronal death onset. In vitro ischemia was induced by washing neuronal cultures with a balanced salt solution with (acute/delayed models) or without (progressive model) 25 mM 2-deoxy-D-glucose and incubating in an anaerobic chamber. Reperfusion was performed by removing cultures from the anaerobic chamber and washing and/or adding Dulbecco's modified Eagle medium containing N2 supplement. Acute neuronal death resulted in cell swelling during in vitro ischemic incubation with the majority of neurons appearing swollen and necrotic within 3 h post-insult. Progressive neuronal death was characterized by cell shrinkage during and immediately following in vitro ischemia with increasing neuronal degeneration resembling both necrosis and apoptosis over a 24-h period post-in vitro ischemia. Delayed neuronal death was induced by glutamate-receptor blockade during in vitro ischemia. Neurons appeared morphologically normal immediately following and up to 6 h after in vitro ischemia and then started to degenerate over the next 42 h by a process resembling apoptosis. We monitored oxygen consumption during in vitro ischemia and found it to be similar for the three models and have shown that plastic culture wells store oxygen. The establishment of acute, progressive and delayed in vitro models of ischemia using 96-well microtiter strip-plates will provide useful tools to further investigate ischemic neuronal death/survival mechanisms and provide a high-throughput system to evaluate potential neuroprotective agents. Oxygen storage in plastic culture wells is likely to contribute to the extended oxygen- and oxygen-glucose-deprivation times required to induce significant neuronal injury in vitro.