Development of a pattern in biochemical parameters in the core and penumbra during infarct evolution after transient MCAO in rats

Changes in excitatory amino acid transporters in response to remote ischaemic preconditioning and glutamate excitotoxicity

The successful implementation of remote ischaemic conditioning as a clinical neuroprotective strategy requires a thorough understanding of its basic principles, which can be modified for each patient. The mechanisms of glutamate homeostasis appear to be a key component. In the current study, we focused on the brain-to-blood glutamate shift mediated by glutamate transporters (excitatory amino acid transports [EAATs]) and the effect of remote ischaemic preconditioning (RIPC) as a mediator of ischaemic tolerance. We used model mimicking ischaemia-mediated excitotoxicity (intracerebroventricular administration of glutamate) to avoid the indirect effect of ischaemia-triggered mechanisms. We found quantitative changes in EAAT2 and EAAT3 and altered membrane trafficking of EAAT1 on the cells of the choroid plexus. These changes could underlie the beneficial effects of ischaemic tolerance. There was reduced oxidative stress and increased glutathione level after RIPC treatment. Moreover, we determined the stimulus-specific response on EAATs. While glutamate overdose stimulated EAAT2 and EAAT3 overexpression, RIPC induced membrane trafficking of EAAT1 and EAAT2 rather than a change in their expression. Taken together, mechanisms related to glutamate homeostasis, especially EAAT-mediated transport, represents a powerful tool of ischaemic tolerance and allow a certain amount of flexibility based on the stimulus used.

Multi-Echo Complex Quantitative Susceptibility Mapping and Quantitative Blood Oxygen Level-Dependent Magnitude (mcQSM + qBOLD or mcQQ) for Oxygen Extraction Fraction (OEF) Mapping

Oxygen extraction fraction (OEF), the fraction of oxygen that tissue extracts from blood, is an essential biomarker used to directly assess tissue viability and function in neurologic disorders. In ischemic stroke, for example, increased OEF can indicate the presence of penumbra-tissue with low perfusion yet intact cellular integrity-making it a primary therapeutic target. However, practical OEF mapping methods are not currently available in clinical settings, owing to the impractical data acquisitions in positron emission tomography (PET) and the limitations of existing MRI techniques. Recently, a novel MRI-based OEF mapping technique, termed QQ, was proposed. It shows high potential for clinical use by utilizing a routine sequence and removing the need for impractical multiple gas inhalations. However, QQ relies on the assumptions of Gaussian noise in susceptibility and multi-echo gradient echo (mGRE) magnitude signals for OEF estimation. This assumption is unreliable in low signal-to-noise ratio (SNR) regions like disease-related lesions, risking inaccurate OEF estimation and potentially impacting clinical decisions. Addressing this, our study presents a novel multi-echo complex QQ (mcQQ) that models realistic Gaussian noise in mGRE complex signals. We implemented mcQQ using a deep learning framework (mcQQ-NET) and compared it with the existing QQ-NET in simulations, ischemic stroke patients, and healthy subjects, using identical training and testing datasets and schemes. In simulations, mcQQ-NET provided more accurate OEF than QQ-NET. In the subacute stroke patients, mcQQ-NET showed a lower average OEF ratio in lesions relative to unaffected contralateral normal tissue than QQ-NET. In the healthy subjects, mcQQ-NET provided uniform OEF maps, similar to QQ-NET, but without unrealistically high OEF outliers in areas of low SNR, such as SNR ≤ 15 (dB). Therefore, mcQQ-NET improves OEF accuracy by more accurately reflecting realistic Gaussian noise in complex mGRE signals. Its enhanced sensitivity to OEF abnormalities, based on more realistic biophysics modeling, suggests that mcQQ-NET has potential for investigating tissue variability in neurologic disorders.

Rectangular method: a modified technique for sampling the ischemic border zone in a rat model of transient middle cerebral artery occlusion

To date, there have been three common methods for sampling the cerebral ischemic border zone in a rat model of transient middle cerebral artery occlusion (tMCAO): the "two o'clock method", the "diagonal method", and the "parallel line method". However, these methods have their own advantages and limitations. Here, we propose a modified technique (the "rectangular method") for sampling the ischemic border zone. A rat tMCAO model was prepared under the support of a compact small animal anesthesia machine. Cerebral blood flow was monitored by high-resolution laser Doppler to control the quality of modeling, and 2,3,5-triphenyl tetrazolium chloride (TTC) staining was used for cerebral infarction location assessment. Superoxide dismutase 2 (SOD2), cysteinyl aspartate specific proteinase (caspase)-3, caspase-9, and heat shock protein 70 (HSP70) were used to verify the reliability and reproducibility of the rectangular method. The expression of biomarkers (SOD2, caspase-3, caspase-9, and HSP70) in the traditional (two o'clock method after TTC staining) and modified (rectangular method) groups were increased. There were no significant differences between the groups. The rectangular method proposed herein is based on a modification of the diagonal method and parallel line method, which could provide a directly observable infarct borderline and a sufficient sampling area for subsequent experimental operations regardless of the cerebral infarct location. The assessed biomarkers (SOD2, caspase-3, caspase-9, and HSP70) demonstrated the reliability and reproducibility of the rectangular method, which may facilitate inter-laboratory comparisons.

PAK1 contributes to cerebral ischemia/reperfusion injury by regulating the blood-brain barrier integrity

Globally, stroke is one of the leading causes of death and significant contributors to disability. Gaining a thorough comprehension of the underlying pathogenic processes is essential for stroke treatment and prevention. In this study, we investigated the role of p21-activated kinase 1 (PAK1) in stroke by using oxygen-glucose deprivation (OGD) and transient middle cerebral artery occlusion and reperfusion (tMCAO/R) models. We reported that focal ischemia and reperfusion affect the PAK1 expression and activity levels. We further demonstrated that PAK1 is responsible for the endothelial hyperpermeability that occurs in the early stages of ischemia and reperfusion. Additionally, inhibition of PAK1 was discovered to alleviate blood-brain barrier disruption and protect against brain injury induced by tMCAO/R. Mechanistically, we provide the evidence that PAK1 regulates the formation of stress fibers and expression of surface junctional proteins. Together, our findings reveal a pathogenic function of PAK1 in stroke.

QQ-NET - using deep learning to solve quantitative susceptibility mapping and quantitative blood oxygen level dependent magnitude (QSM+qBOLD or QQ) based oxygen extraction fraction (OEF) mapping

PURPOSE

To improve accuracy and speed of quantitative susceptibility mapping plus quantitative blood oxygen level-dependent magnitude (QSM+qBOLD or QQ) -based oxygen extraction fraction (OEF) mapping using a deep neural network (QQ-NET).

METHODS

The 3D multi-echo gradient echo images were acquired in 34 ischemic stroke patients and 4 healthy subjects. Arterial spin labeling and diffusion weighted imaging (DWI) were also performed in the patients. NET was developed to solve the QQ model inversion problem based on Unet. QQ-based OEF maps were reconstructed with previously introduced temporal clustering, tissue composition, and total variation (CCTV) and NET. The results were compared in simulation, ischemic stroke patients, and healthy subjects using a two-sample Kolmogorov-Smirnov test.

RESULTS

In the simulation, QQ-NET provided more accurate and precise OEF maps than QQ-CCTV with 150 times faster reconstruction speed. In the subacute stroke patients, OEF from QQ-NET had greater contrast-to-noise ratio (CNR) between DWI-defined lesions and their unaffected contralateral normal tissue than with QQ-CCTV: 1.9 ± 1.3 vs 6.6 ± 10.7 (p = 0.03). In healthy subjects, both QQ-CCTV and QQ-NET provided uniform OEF maps.

CONCLUSION

QQ-NET improves the accuracy of QQ-based OEF with faster reconstruction.

10-O-(N N-Dimethylaminoethyl)-Ginkgolide B Methane-Sulfonate (XQ-1H) Ameliorates Cerebral Ischemia Via Suppressing Neuronal Apoptosis

OBJECTIVES

The 10-O-(N N-dimethylaminoethyl)-ginkgolide B methane-sulfonate (XQ-1H) is an effective novel drug for the treatment of ischemic cerebrovascular disease derived from Ginkgolide B, a traditional Chinese medicine, has been widely used in the treatment of cardiovascular and cerebrovascular diseases. However, whether XQ-1H exerts neuroprotective effect via regulating neuronal apoptosis and the underlying mechanism remain to be elucidated.

MATERIALS AND METHODS

This study was aimed to investigate the neuroprotective effect of XQ-1H in rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R) and the oxygen glucose deprivation/reoxygenation (OGD/R) induced neuronal apoptosis on pheochromocytoma (PC-12) cells.

RESULTS

The results showed that administration of XQ-1H at different dosage (7.8, 15.6, 31.2 mg/kg) reduced the brain infarct and edema, attenuated the neuro-behavioral dysfunction, and improved cell morphology in brain tissue after MCAO/R in rats. Moreover, incubation with XQ-1H (1 µM, 3 µM, 10 µM, 50 µM, 100 µM) could increase the cell viability, and showed no toxic effect to PC-12 cells. XQ-1H at following 1 µM, 10 µM, 100 µM decreased the lactate dehydrogenase (LDH) activity and suppressed the cell apoptosis in PC-12 cells exposed to OGD/R. In addition, XQ-1H treatment could significantly inhibit caspase-3 activation both in vivo and in vitro, reciprocally modulate the expression of apoptosis related proteins, bcl-2, and bax via activating PI3K/Akt signaling pathway. For mechanism verification, LY294002, the inhibitor of PI3K/Akt pathway was introduced the expressions of bcl-2 and phosphorylated Akt were down-regulated, the expression of bax was up-regulated, indicating that XQ-1H could alleviate the cell apoptosis through activating the PI3K/Akt pathway.

CONCLUSIONS

Our findings demonstrated that XQ-1H treatment could provide a neuroprotective effect against ischemic stroke induced by cerebral ischemia/reperfusion injury in vivo and in vitro through regulating neuronal survival and inhibiting apoptosis. The findings of the study confirmed that XQ-1H could be develop as a potential drug for treatment of cerebral ischemic stroke.

Oxiracetam Mediates Neuroprotection Through the Regulation of Microglia Under Hypoxia-Ischemia Neonatal Brain Injury in Mice

In neonatal hypoxic-ischemic brain damage (HIBD), in addition to damage caused by hypoxia and ischemia, over-activation of inflammation leads to further deterioration of the condition, thus greatly shortening the optimal treatment time window. Ischemic penumbra, the edematous area encompassing the infarct core, is characterized by typical activation of microglia and overt inflammation, and prone to incorporate into the infarct core gradually after ischemia onset. If treated in time, the cells located in the penumbra can survive, thereby impeding the expansion of the infarction. We demonstrated for the first time that in the acute phase of HIBD in neonatal mice, treatment of Oxiracetam (ORC) significantly curtailed the size of ischemic penumbra together with drastic reduction of infarction. By staining various cellular markers, we found that the penumbra was defined and concentrated with activated microglia. We also analyzed transmission electron microscopy and Luminex assay results to elucidate the mechanisms involved. We further confirmed that ORC switched polarization of microglia from the inflammatory towards the alternatively activated phenotype, thus promoting microglia from being neurotoxic into neuroprotective. Meanwhile, ORC decreased proliferation of microglia; however, their functions of phagocytosis and autophagy were otherwise enhanced. Last, we clarified that ORC promoted autophagy through the AMPK/mTOR pathway, which further induced the transition of the inflammatory to the alternatively activated phenotype in microglia. The pro-inflammatory factors secretion was inhibited as well, thereby reducing the progression of the infarction. Taken together, it is concluded that Oxiracetam reduced the expansion of ischemic infarction in part via regulating the interplay between microglia activation and autophagy, which would delay the progression of HIBD and effectively prolong the time window for the clinical treatment of HIBD.

Initial Experience of Challenge-Free MRI-Based Oxygen Extraction Fraction Mapping of Ischemic Stroke at Various Stages: Comparison With Perfusion and Diffusion Mapping

MRI-based oxygen extraction fraction imaging has a great potential benefit in the selection of clinical strategies for ischemic stroke patients. This study aimed to evaluate the performance of a challenge-free oxygen extraction fraction (OEF) mapping in a cohort of acute and subacute ischemic stroke patients. Consecutive ischemic stroke patients (a total of 30 with 5 in the acute stage, 19 in the early subacute stage, and 6 in the late subacute stage) were recruited. All subjects underwent MRI including multi-echo gradient echo (mGRE), diffusion weighted imaging (DWI), and 3D-arterial spin labeling (ASL). OEF maps were generated from mGRE phase + magnitude data, which were processed using quantitative susceptibility mapping (QSM) + quantitative blood oxygen level-dependent (qBOLD) imaging with cluster analysis of time evolution. Cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) maps were reconstructed from 3D-ASL and DWI, respectively. Further, cerebral metabolic rate of oxygen (CMRO2) was calculated as the product of CBF and OEF. OEF, CMRO2, CBF, and ADC values in the ischemic cores (absolute values) and their contrasts to the contralateral regions (relative values) were evaluated. One-way analysis of variance (ANOVA) was used to compare OEF, CMRO2, CBF, and ADC values and their relative values among different stroke stages. The OEF value of infarct core showed a trend of decrease from acute, to early subacute, and to late subacute stages of ischemic stroke. Significant differences among the three stroke stages were only observed in the absolute OEF (F = 6.046, p = 0.005) and relative OEF (F = 5.699, p = 0.009) values of the ischemic core, but not in other measurements (absolute and relative CMRO2, CBF, ADC values, all values of p > 0.05). In conclusion, the challenge-free QSM + qBOLD-generated OEF mapping can be performed on stroke patients. It can provide more information on tissue viability that was not available with CBF and ADC and, thus, may help to better manage ischemic stroke patients.

Brain ischemic insult induces cofilin rod formation leading to synaptic dysfunction in neurons

Ischemic stroke not only induces neuron death in the infarct area but also structural and functional damage of the surviving neurons in the surrounding peri-infarct area. In the present study, we first identified cofilin rod, a pathological rod-like aggregation, formed in neurons of in vivo ischemic stroke animal model and induced neuronal impairment. Cofilin rods formed only on the ipsilateral side of the middle cerebral artery occlusion and reperfusion (MCAO-R) rat brain and showed the highest density in peri-infarct area. Our real-time live cell imaging, immunostaining and patch clamp studies showed that cofilin rod formation in neurons led to dendritic mitochondrial transportation failure, as well as impairment of synaptic structure and functions. Overexpression of LIM kinase or activation of its upstream regulator Rho, suppressed ischemia-induced cofilin rod formation and showed protective effect on synaptic function and structure impairment in both cultured neurons and MCAO-R rat model. In summary, our results demonstrate a novel mechanism of ischemic stroke-induced neuron injury in peri-infarct area and provide a potential target for the protection of neuronal structure and function against brain ischemia insult.

Oxidative Status in Different Areas of the Cerebral Cortex of Wistar Rats during Focal Ischemia and Its Modulation with Carnosine

Oxidative status was assessed in different areas of the cerebral cortex of male Wistar rats under normal condition and during permanent 24-h focal ischemia. In intact animals, the level of lipid hydroperoxides in the frontal lobes of both hemispheres was by 36% higher than in other cortical areas, while total antioxidant activity was by 25% higher than in other areas. During ischemia, changes in oxidative status were localized only in the ischemic focus and penumbra zone and did not involve other cortical areas. We demonstrated for the first time a neuroprotective effect of therapeutic administration of carnosine in low doses (50 mg/kg) on parameters of the oxidative status under conditions of focal ischemia comparable to its effect of high doses (500 mg/kg) as well as its local effect in the penumbra zone. A dose-dependent effect of carnosine on antioxidant activity in the penumbra zone during ischemia was also demonstrated. These findings confirm effectiveness of not only preventive carnosine administration, but also its application in the postischemic period of the stroke.

Long-term survival and regeneration of neuronal and vasculature cells inside the core region after ischemic stroke in adult mice

Focal cerebral ischemia results in an ischemic core surrounded by the peri-infarct region (penumbra). Most research attention has been focused on penumbra while the pattern of cell fates inside the ischemic core is poorly defined. In the present investigation, we tested the hypothesis that, inside the ischemic core, some neuronal and vascular cells could survive the initial ischemic insult while regenerative niches might exist many days after stroke in the adult brain. Adult mice were subjected to focal cerebral ischemia induced by permanent occlusion of distal branches of the middle cerebral artery (MCA) plus transient ligations of bilateral common carotid artery (CCA). The ischemic insult uniformly reduced the local cerebral blood flow (LCBF) by 90%. Massive cell death occurred due to multiple mechanisms and a significant infarction was cultivated in the ischemic cortex 24 h later. Nevertheless, normal or even higher levels of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) persistently remained in the core tissue, some NeuN-positive and Glut-1/College IV-positive cells with intact ultrastructural features resided in the core 7-14 days post stroke. BrdU-positive but TUNEL-negative neuronal and endothelial cells were detected in the core where extensive extracellular matrix infrastructure developed. Meanwhile, GFAP-positive astrocytes accumulated in the penumbra and Iba-1-positive microglial/macrophages invaded the core several days after stroke. The long term survival of neuronal and vascular cells inside the ischemic core was also seen after a severe ischemic stroke induced by permanent embolic occlusion of the MCA. We demonstrate that a therapeutic intervention of pharmacological hypothermia could save neurons/endothelial cells inside the core. These data suggest that the ischemic core is an actively regulated brain region with residual and newly formed viable neuronal and vascular cells acutely and chronically after at least some types of ischemic strokes.

The Effects of Methylene Blue on Autophagy and Apoptosis in MRI-Defined Normal Tissue, Ischemic Penumbra and Ischemic Core

Methylene blue (MB) USP, which has energy-enhancing and antioxidant properties, is currently used to treat methemoglobinemia and cyanide poisoning in humans. We recently showed that MB administration reduces infarct volume and behavioral deficits in rat models of ischemic stroke and traumatic brain injury. This study reports the underlying molecular mechanisms of MB neuroprotection following transient ischemic stroke in rats. Rats were subjected to transient (60-mins) ischemic stroke. Multimodal MRI during the acute phase and at 24 hrs were used to define three regions of interest (ROIs): i) the perfusion-diffusion mismatch salvaged by reperfusion, ii) the perfusion-diffusion mismatch not salvaged by reperfusion, and iii) the ischemic core. The tissues from these ROIs were extracted for western blot analyses of autophagic and apoptotic markers. The major findings were: 1) MB treatment reduced infarct volume and behavioral deficits, 2) MB improved cerebral blood flow to the perfusion-diffusion mismatch tissue after reperfusion and minimized harmful hyperperfusion 24 hrs after stroke, 3) MB inhibited apoptosis and enhanced autophagy in the perfusion-diffusion mismatch, 4) MB inhibited apoptotic signaling cascades (p53-Bax-Bcl2-Caspase3), and 5) MB enhanced autophagic signaling cascades (p53-AMPK-TSC2-mTOR). MB induced neuroprotection, at least in part, by enhancing autophagy and reducing apoptosis in the perfusion-diffusion mismatch tissue following ischemic stroke.

Scheme of Ischaemia-triggered Agents during Brain Infarct Evolution in a Rat Model of Permanent Focal Ischaemia

The impact of therapeutic intervention in stroke depends on its appropriate timing during infarct evolution. We have studied markers of brain tissue damage initiated by permanent occlusion of the middle cerebral artery (MCAO) at three time points during which the infarct spread (1, 3 and 6 h). Based on Evans Blue extravasation and immunohistochemical detection of neurons, we confirmed continuous disruption of blood-brain barrier and loss of neurons in the ischaemic hemisphere that peaked at the sixth hour, especially in the core. Glutamate content started to rise dramatically in the entire hemisphere during the first 3 h; the highest level was determined in the core 6 h after MCAO (141 % increase). Moreover, the enzyme antioxidant defence grew by about 42 % since the first hour in the ipsilateral penumbra. Enzymes of the apoptotic pathway as well as mitochondrial enzyme release were detected since the third hour of MCAO in the ischaemic hemisphere; all achieved their maxima in the penumbra during both time periods (except cytochrome C). In conclusion, the preserved integrity of mitochondrial membrane and incompletely developed process of apoptosis may contribute to the better therapeutic outcome after ischaemic attack; however, a whole brain response should not be omitted.

Blood as the carrier of ischemic tolerance in rat brain

This study provides clear evidence that the factor inducing tolerance to ischemia is transmitted via the circulating blood. By using the remote ischemia and the cross-circulation model, the tolerance to ischemia was transmitted from donor to recipient. For this study, the following experimental groups were designed: I, sham control group; II, group of tolerant hindlimb tourniquet-treated rats; III, positive control group; IV, control for cross-circulation influence; preconditioned animals: V, tolerant animals subjected to middle cerebral artery occlusion (MCAO); VI, tolerant animals cross-circulated with SHC, followed by MCAO; VII, SHC animals cross-circulated with tolerant animals and subsequently subjected to MCAO; VIII, tolerant animals cross-circulated with ischemic rats, followed by MCAO; IX, SHC animals cross-circulated with ischemic animals and subjected to MCAO; postconditioned animals: X, ischemic animals treated with a remote limb tourniquet; XI, ischemic animals cross-circulated with SHC control rats; and XII, ischemic animals cross-circulated with tolerant rats. Results confirmed that remote ischemia induced reduction of infarct volume in the preconditioned (V, 60%) as well as in the postconditioned group (X, 52%). Significant diminution was also observed in group XII (56.6%). In the preconditioned group, decreased infarct volume was detected in groups VI and VII (about 65%) and in group IX (about 50%). The greatest infarct reduction (84%) was induced by the presence of ischemic blood in a tolerant rat before ischemia induction. In summary, the factor inducing tolerance to ischemia is generated by remote ischemia and by ischemia itself; from the site of origin to the rest of the body, it is transported by the systemic blood circulation and can be transferred from animal to animal. The effect of conditioning with two different ischemic events (brain and hindlimb ischemia) led to a cumulative, stronger tolerance response.

Study on integrated pharmacokinetics of gardenia acid and geniposide: time-antioxidant efficacy after oral administration of Huanglian-Zhizi couplet medicine from Huang-Lian-Jie-Du-Tang in MCAO rats

Huanglian-Zhizi couplet medicine comes from classical prescription Huang-Lian-Jie-Du-Tang (HLJDT), which has been proven by previous researches to be an effective compound for cerebral ischemia. This paper explores the integrated pharmacokinetics of gardenia acid and geniposide-time-antioxidant efficacy after the oral administration of Huanglian-Zhizi couplet medicine from HLJDT in rats with middle cerebral artery occlusion (MCAO). To investigate the differences in pharmacokinetics and antioxidant effect of Huanglian-Zhizi and HLJDT in MCAO rats, which have been scarcely reported, an oral dose, 24 crud drug g/kg, of Huanglian-Zhizi and 40 crud drug/kg of HLJDT were administered in two groups of normal rats and two groups of Sprague-Dawley (SD) MCAO rats, respectively. At different time points, concentrations of gardenia acid and geniposide were determined by high performance liquid chromatography (HPLC), and levels of superoxide dismutase (SOD) were calculated by ELIASA. Pharmacokinetic parameters including AUC, MRT, t1/2, T max , C max were estimated by statistical moment analysis using a data analysis system (DAS) 2.0. An AUC based on weighting approach was used for integrating gardenia acid and geniposide. Finally, the concentration-time efficacy profiles were obtained. The integrated pharmacokinetics profiles of index components could reveal the pharmacokinetics behavior of Huanglian-Zhizi and HLJDT, corresponding to the antioxidant efficacy.

Pre-treatment with the synthetic antioxidant T-butyl bisphenol protects cerebral tissues from experimental ischemia reperfusion injury

Treatments to inhibit or repair neuronal cell damage sustained during focal ischemia/reperfusion injury in stroke are largely unavailable. We demonstrate that dietary supplementation with the antioxidant di-tert-butyl-bisphenol (BP) before injury decreases infarction and vascular complications in experimental stroke in an animal model. We confirm that BP, a synthetic polyphenol with superior radical-scavenging activity than vitamin E, crosses the blood-brain barrier and accumulates in rat brain. Supplementation with BP did not affect blood pressure or endogenous vitamin E levels in plasma or cerebral tissue. Pre-treatment with BP significantly lowered lipid, protein and thiol oxidation and decreased infarct size in animals subjected to middle cerebral artery occlusion (2 h) and reperfusion (24 h) injury. This neuroprotective action was accompanied by down-regulation of hypoxia inducible factor-1α and glucose transporter-1 mRNA levels, maintenance of neuronal tissue ATP concentration and inhibition of pro-apoptotic factors that together enhanced cerebral tissue viability after injury. That pre-treatment with BP ameliorates oxidative damage and preserves cerebral tissue during focal ischemic insult indicates that oxidative stress plays at least some causal role in promoting tissue damage in experimental stroke. The data strongly suggest that inhibition of oxidative stress through BP scavenging free radicals in vivo contributes significantly to neuroprotection. We demonstrate that pre-treatment with ditert-butyl bisphenol(Di-t-Bu-BP) inhibits lipid, protein, and total thiol oxidation and decreases caspase activation and infarct size in rats subjected to middle cerebral artery occlusion (2 h) and reperfusion (24 h) injury. These data suggest that inhibition of oxidative stress contributes significantly to neuroprotection.

Antioxidant and protective mechanisms against hypoxia and hypoglycaemia in cortical neurons in vitro

In the present work, we have studied whether cell death could be induced in cortical neurons from rats subjected to different period of O₂ deprivation and low glucose (ODLG). This “in vitro” model is designed to emulate the penumbra area under ischemia. In these conditions, cortical neurons displayed loss of mitochondrial respiratory ability however, nor necrosis neither apoptosis occurred despite ROS production. The absence of cellular death could be a consequence of increased antioxidant responses such as superoxide dismutase-1 (SOD1) and GPX3. In addition, the levels of reduced glutathione were augmented and HIF-1/3α overexpressed. After long periods of ODLG (12–24 h) cortical neurons showed cellular and mitochondrial membrane alterations and did not recuperate cellular viability during reperfusion. This could mean that therapies directed toward prevention of cellular and mitochondrial membrane imbalance or cell death through mechanisms other than necrosis or apoptosis, like authophagy, may be a way to prevent ODLG damage.

Delayed post-conditioning reduces post-ischemic glutamate level and improves protein synthesis in brain

In the clinic delayed post-conditioning would represent an attractive strategy for the survival of vulnerable neurons after an ischemic event. In this paper we studied the impact of ischemia and delayed post-conditioning on blood and brain tissue concentrations of glutamate and protein synthesis. We designed two groups of animals for analysis of brain tissues and blood after global ischemia and post-conditioning, and one for analysis of blood glutamate after transient focal ischemia. Our results showed elevated blood glutamate in two models of transient brain ischemia and decreases in blood glutamate to control in the first 20min of post-conditioning recirculation followed by a consecutive drop of about 20.5% on the first day. Similarly, we recorded reduced protein synthesis in hippocampus and cortex 2 and 3days after ischemia. However, increased glutamate was registered only in the hippocampus. Post-conditioning improves protein synthesis in CA1 and dentate gyrus and, surprisingly, leads to 50% reduction in glutamate in whole hippocampus and cortex. In conclusion, ischemia leads to meaningful elevation of blood and tissue glutamate. Post-conditioning activates mechanisms resulting in rapid elimination of glutamate from brain tissue and/or in the circulatory system that could otherwise impede brain-to-blood glutamate efflux mechanisms. Moreover, post-conditioning induces protein synthesis renewing in ischemia affected tissues that could also contribute to elimination of excitotoxicity. In addition, the potential of glutamate for monitoring the progress of ischemia and efficacy of therapy was shown.