Apoptosis in cerebral ischemia: executional and regulatory signaling mechanisms

Epigallocatechin gallate restores the reduction of protein phosphatase 2 A subunit B caused by middle cerebral artery occlusion

BACKGROUND

Epigallocatechin gallate (EGCG) is a flavonoid compound commonly found in green tea. It exhibits antioxidant, anti-inflammatory, and neuroprotective effects in cerebral ischemia. Protein phosphatase 2 A (PP2A) is an important serine/threonine phosphatase enzyme involved in various cellular activities. PP2A subunit B is present abundantly in the brain and plays an important role in the nervous system. We investigated the effect of EGCG on the expression level of PP2A subunit B in cerebral ischemia caused by middle cerebral artery occlusion (MCAO). EGCG (50 mg/kg) or vehicle was injected into the peritoneal cavity prior to MCAO surgery. Neurological behavior tests were performed 24 h after MCAO, and right cerebral cortex tissue was collected. Cerebral ischemia caused serious neurological abnormalities, which were alleviated by EGCG administration. We screened the expression of PP2A subunits containing A, B, and C using reverse-transcription PCR. We confirmed that PP2A subunit B exhibited significant changes in MCAO animals compared to subunits A and C. We continuously examined the expression of PP2A subunit B protein in MCAO animals using Western blot analysis.

RESULTS

EGCG alleviated the reduction of PP2A subunit B protein by MCAO damage. In addition, immunohistochemistry demonstrated a decrease in the number of PP2A subunit B-positive cells in the cerebral cortex, and EGCG attenuated this decrease. Maintenance of PP2A subunit B is important for normal brain function.

CONCLUSION

Therefore, our findings suggest that EGCG exerts neuroprotective effects against cerebral ischemia through modulation of PP2A subunit B expression.

Biological Effects and Mechanisms of Caspases in Early Brain Injury after Subarachnoid Hemorrhage

Caspases are an evolutionarily conserved family of proteases responsible for mediating and initiating cell death signals. In the past, the dysregulated activation of caspases was reported to play diverse but equally essential roles in neurodegenerative diseases, such as brain injury and neuroinflammatory diseases. A subarachnoid hemorrhage (SAH) is a traumatic event that is either immediately lethal or induces a high risk of stroke and neurological deficits. Currently, the prognosis of SAH after treatment is not ideal. Early brain injury (EBI) is considered one of the main factors contributing to the poor prognosis of SAH. The mechanisms of EBI are complex and associated with oxidative stress, neuroinflammation, blood-brain barrier disruption, and cell death. Based on mounting evidence, caspases are involved in neuronal apoptosis or death, endothelial cell apoptosis, and increased inflammatory cytokine-induced by apoptosis, pyroptosis, and necroptosis in the initial stages after SAH. Caspases can simultaneously mediate multiple death modes and regulate each other. Caspase inhibitors (including XIAP, VX-765, and Z-VAD-FMK) play an essential role in ameliorating EBI after SAH. In this review, we explore the related pathways mediated by caspases and their reciprocal regulation patterns after SAH. Furthermore, we focus on the extensive crosstalk of caspases as a potential area of research on therapeutic strategies for treating EBI after SAH.

Gualou Guizhi Granule Suppresses LPS-Induced Inflammatory Response of Microglia and Protects against Microglia-Mediated Neurotoxicity in HT-22 via Akt/NF-κB Signaling Pathways

Neuroinflammation plays a crucial part in the commencement and advancement of ischemic stroke. Gualou Guizhi granule (GLGZG) is known to well exhibit neuroprotective effect, but it is not known whether GLGZG can regulate the inflammatory process at the cellular level in BV2 microglia cells and protect against microglia-mediated neurotoxicity in neurons. Herein, we aimed to investigate the anti-inflammatory effects of GLGZG on BV2 microglia cells and protection against microglia-mediated neurotoxicity in neurons. Methods. The cell model of neuroinflammation was constructed by lipopolysaccharide (LPS) to observe the effect of GLGZG in the presence or absence of GLGZG. The production of nitric oxide (NO), inflammatory mediators, was detected. Moreover, potential mechanisms associated with the anti-inflammatory effect, such as inhibition of microglial activation and nuclear factor kappa B (NF-κB), were also investigated. In addition, to prove whether GLGZG protects against microglia-mediated neurotoxicity, neuronal HT-22 cells were cultured in the conditioned medium. And cell survivability and neuronal apoptosis of HT-22 were evaluated. Results. It was found that a main regulator of inflammation, NO, is suppressed by GLGZG in BV2 microglial cells. Moreover, GLGZG dose dependently decreased the mRNA and protein levels of inducible NO synthase (iNOS) in LPS-stimulated BV2 cells. Additionally, GLGZG inhibited the expression and secretion of proinflammatory cytokines in BV2 microglial cells. Also, GLGZG inhibited LPS-activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in BV2 microglial cells at the intracellular level. GLGZG significantly affected Akt phosphorylation: phosphorylated forms of Akt increased. To check whether GLGZG protects against microglia-mediated neurotoxicity, neuronal HT-22 cells were incubated in the conditioned medium. GLGZG showed a neuroprotective effect by promoting cell survivability and suppressing neuronal apoptosis. Conclusions. GLGZG exerted its potential effects on suppressing inflammatory responses in LPS-induced BV2 cells by regulating NF-κB and Akt pathways. In addition, GLGZG could protect against microglia-mediated neurotoxicity in HT-22.

Emerging promise of sulforaphane-mediated Nrf2 signaling cascade against neurological disorders

Neurological disorders represent a great challenge and are the leading cause of death and disability globally. Although numerous complicated mechanisms are involved in the progressions of chronic and acute neurodegenerative disorders, most of the diseases share mutual pathogenic features such as oxidative stress, mitochondrial dysfunction, neuroinflammation, protein misfolding, excitotoxicity, and neuronal damage, all of these are the common targets of nuclear factor erythroid 2 related factor 2 (Nrf2) signaling cascade. No cure has yet been discovered to tackle these disorders, so, intervention approaches targeting phytochemicals have been recommended as an alternative form of treatment. Sulforaphane is a sulfur-rich dietary phytochemical which has several activities such as antioxidant, anti-inflammatory, and anti-tumor via multiple targets and various mechanisms. Given its numerous actions, sulforaphane has drawn considerable attention for neurological disorders in recent years. Nrf2 is one of the most crucial targets of sulforaphane which has potential in regulating the series of cytoprotective enzyme expressions that have neuroprotective, antioxidative, and detoxification actions. Neurological disorders are auspicious candidates for Nrf2-targeted treatment strategy. Sulforaphane protects various neurological disorders by regulating the Nrf2 pathway. In this article, we recapitulate current studies of sulforaphane-mediated Nrf2 activation in the treatment of various neurological disorders.

Emerging signal regulating potential of small molecule biflavonoids to combat neuropathological insults of Alzheimer's disease

Alzheimer's disease (AD) is a progressive, chronic and severe neurodegenerative disorder linked with cognitive and memory impairment that eventually lead to death. There are several processes which can cause AD, including mitochondrial dysfunction-mediated oxidative stress (OS), intracellular buildup of hyper-phosphorylated tau as neurofibrillary tangles (NFTs) and excessive buildup of extracellular amyloid beta (Aβ) plaques, and/or genetic as well as the environmental factors. Existing treatments can only provide symptomatic relief via providing temporary palliative therapy which can weaken the rate of AD-associated cognitive decline. Plants are the fundamental building blocks for the environment and produce various secondary metabolites. Biflavonoids are one among such secondary metabolite that possesses the potential to mediate noticeable change in the aggregation of tau, Aβ and also efficiently can decrease the toxic effects of Aβ oligomers in comparison with the monoflavonoid moieties. Nevertheless, the molecular processes remain to be exposed, flavonoids are found to cause a change in the Aβ and tau aggregation pathway to generate non-toxic aggregates. In this review, we discuss the neuroprotective action of small molecule biflavonoid to reduce the neurodegenerative events of AD. Furthermore, this appraisal advances our knowledge to develop potential new targets for the treatment of AD.

Involvement of PARP-1/AIF Signaling Pathway in Protective Effects of Gualou Guizhi Decoction Against Ischemia-Reperfusion Injury-Induced Apoptosis

Cerebral ischemia-reperfusion injury is a complex pathophysiological process. Poly(ADP-ribose) (PAR) polymerase-1 (PARP-1)/apoptosis-inducing factor (AIF) signaling pathway-mediated apoptosis is one of the non-caspase-dependent cell death programs that are widely present in neurological diseases such as stroke. In our study, we aimed to conduct further research on the effects of Gualou Guizhi decoction (GLGZD) on the PARP-1/AIF signaling pathway in cell apoptosis after ischemia-reperfusion injury caused by middle cerebral artery occlusion (MCAO). The results showed that GLGZD administration for 7 days significantly ameliorated MCAO-induced neurological damage, limb paralysis and the pathological state of the ischemic cortex. GLGZD exerted its effects by significantly reducing the volume of ischemic cerebral infarction, increasing the number of Nissl-positive cells, and reducing neuronal apoptosis. Furthermore, Western blot analysis showed that GLGZD significantly inhibited the total protein expression of PARP-1, PAR, AIF and endonuclease G (Endo G) in the ischemic cortex and significantly increased the total protein expression of heat-shock protein 70 (Hsp70). On the one hand, the expression of PARP-1, AIF and Endo G protein in the nucleus significantly decreased while the expression of PAR nucleoprotein significantly upregulated. On the other hand, compared with the MCAO model group, the GLGZD-treated group showed a significantly reduced protein expression of PAR in mitochondria and significantly increased protein expression of mitochondrial AIF and Endo G. It was concluded that GLGZD had good therapeutic effects in MCAO model rats. These effects were closely related to GLGZD-mediated inhibition of ischemia-induced neuronal apoptosis by regulation of protein expression and translocation in the PARP-1/AIF signaling pathway.

ALDH2 and Stroke: A Systematic Review of the Evidence

Cerebral stroke is one of the leading causes of mortality and disability worldwide. The prevalence of cerebral stroke is the result of the synergistic effect of genetic susceptibility and numerous vascular risk factors, including hypertension, diabetes, excessive alcohol intake, obesity, and dyslipidemia. Mitochondrial aldehyde dehydrogenase (ALDH2) is a vital enzyme metabolizing various acetaldehyde and toxic aldehydes. The ALDH2 enzymatic activity is severely decreased in the individuals with ALDH2*2 gene mutation, especially in East Asians. Increasing epidemiological surveys have revealed that ALDH2 genetic polymorphism is closely associated with the increasing incidence of cardiovascular risk factors and cerebral stroke. Evidence from experimental studies has also suggested that ALDH2 facilitates the clearance of reactive aldehydes and reduces the size of cerebral infarct. Therefore, targeting ALDH2 may represent a promising avenue for protection against stroke injury. This review will mainly focus on clinical and epidemiological evidence and the underlying molecular mechanisms involved in the protective effect of ALDH2 in stroke-related injury.

Estrogens as neuroprotectants: Estrogenic actions in the context of cognitive aging and brain injury

There is ample empirical evidence to support the notion that the biological impacts of estrogen extend beyond the gonads to other bodily systems, including the brain and behavior. Converging preclinical findings have indicated a neuroprotective role for estrogen in a variety of experimental models of cognitive function and brain insult. However, the surprising null or even detrimental findings of several large clinical trials evaluating the ability of estrogen-containing hormone treatments to protect against age-related brain changes and insults, including cognitive aging and brain injury, led to hesitation by both clinicians and patients in the use of exogenous estrogenic treatments for nervous system outcomes. That estrogen-containing therapies are used by tens of millions of women for a variety of health-related applications across the lifespan has made identifying conditions under which benefits with estrogen treatment will be realized an important public health issue. Here we provide a summary of the biological actions of estrogen and estrogen-containing formulations in the context of aging, cognition, stroke, and traumatic brain injury. We have devoted special attention to highlighting the notion that estrogen appears to be a conditional neuroprotectant whose efficacy is modulated by several interacting factors. By developing criteria standards for desired beneficial peripheral and neuroprotective outcomes among unique patient populations, we can optimize estrogen treatments for attenuating the consequences of, and perhaps even preventing, cognitive aging and brain injury.

Effects of Gualou Guizhi Decoction Aqueous Extract on Axonal Regeneration in Organotypic Cortical Slice Culture after Oxygen-Glucose Deprivation

Gualou Guizhi decoction (GLGZD) is effective for the clinical treatment of limb spasms caused by ischemic stroke, but its underlying mechanism is unclear. Propidium iodide (PI) fluorescence staining, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), immunohistochemistry, western blot, and real-time qPCR were used to observe the axonal regeneration and neuroprotective effects of GLGZD aqueous extract on organotypic cortical slices exposed to oxygen-glucose deprivation (OGD) and further elucidate the potential mechanisms. Compared with the OGD group, the GLGZD aqueous extract decreased the red PI fluorescence intensity; inhibited neuronal apoptosis; improved the growth of slice axons; upregulated the protein expression of tau and growth-associated protein-43; and decreased protein and mRNA expression of neurite outgrowth inhibitor protein-A (Nogo-A), Nogo receptor 1 (NgR1), ras homolog gene family A (RhoA), rho-associated coiled-coil-containing protein kinase (ROCK), and phosphorylation of collapsin response mediator protein 2 (CRMP2). Our study found that GLGZD had a strong neuroprotective effect on brain slices after OGD injury. GLGZD plays a vital role in promoting axonal remodeling and functional remodeling, which may be related to regulation of the expression of Nogo-A and its receptor NgR1, near the injured axons, inhibition of the Rho-ROCK pathway, and reduction of CRMP2 phosphorylation.

Paeoniflorin exerts neuroprotective effects against glutamate‑induced PC12 cellular cytotoxicity by inhibiting apoptosis

Paeoniflorin (PF) is an active ingredient of Radix Paeoniae, which is known to exert neuroprotective effects. However, the mechanims behind the neuroprotective effects of PF are not yet fully understood. The apoptosis of neurons plays an important role in the cerebral ischemia-induced cascade response. This study aimed to investigate neuroprotective effects of PF against glutamate‑induced PC12 cellular cytotoxicity and to determine whether these effects are mediated via the inhibition of apoptosis in vitro and the activity of mitochondrial apoptosis-associated proteins in PC12 cells. Exposure of the PC12 cells to glutamate induced cell morphological changes, significantly decreased cell viability and induced apoptosis, with similar results being observed from the Hoechst 33342 staining and Annexin V/PI staining experiments. Glutamate also increased the lactate dehydrogenase release by the PC12 cells. However, treatment with PF prevented these effects. Furthermore, PF inhibited Bax and Bad expression and increased Bcl-2 and Bcl-xL expression; it also decreased the levels of downstream protein (caspase-3 and caspase-9). Collectively, our results indicate that PF protects PC12 cells against glutamate-induced neurotoxicity possibly through the inhibition of the expression of mitochondrial apoptosis-associated proteins.

Brain caspase-3 and intestinal FABP responses in preterm and term rats submitted to birth asphyxia

Neonatal asphyxia can cause irreversible injury of multiple organs resulting in hypoxic-ischemic encephalopathy and necrotizing enterocolitis (NEC). This injury is dependent on time, severity, and gestational age, once the preterm babies need ventilator support. Our aim was to assess the different brain and intestinal effects of ischemia and reperfusion in neonate rats after birth anoxia and mechanical ventilation. Preterm and term neonates were divided into 8 subgroups (n=12/group): 1) preterm control (PTC), 2) preterm ventilated (PTV), 3) preterm asphyxiated (PTA), 4) preterm asphyxiated and ventilated (PTAV), 5) term control (TC), 6) term ventilated (TV), 7) term asphyxiated (TA), and 8) term asphyxiated and ventilated (TAV). We measured body, brain, and intestine weights and respective ratios [(BW), (BrW), (IW), (BrW/BW) and (IW/BW)]. Histology analysis and damage grading were performed in the brain (cortex/hippocampus) and intestine (jejunum/ileum) tissues, as well as immunohistochemistry analysis for caspase-3 and intestinal fatty acid-binding protein (I-FABP). IW was lower in the TA than in the other terms (P<0.05), and the IW/BW ratio was lower in the TA than in the TAV (P<0.005). PTA, PTAV and TA presented high levels of brain damage. In histological intestinal analysis, PTAV and TAV had higher scores than the other groups. Caspase-3 was higher in PTAV (cortex) and TA (cortex/hippocampus) (P<0.005). I-FABP was higher in PTAV (P<0.005) and TA (ileum) (P<0.05). I-FABP expression was increased in PTAV subgroup (P<0.0001). Brain and intestinal responses in neonatal rats caused by neonatal asphyxia, with or without mechanical ventilation, varied with gestational age, with increased expression of caspase-3 and I-FABP biomarkers.

Sulforaphane Protects against Brain Diseases: Roles of Cytoprotective Enzymes

Sulforaphane (SFN) is a kind of isothiocyanate derived from broccoli and other cruciferous vegetables. Because of its roles of antioxidant, anti-inflammatory, and anti-tumor through multiple targets and various mechanisms, SFN has drawn broad attention of the researchers. One of the most important target of SFN is nuclear factor erythroid 2 related factor 2 (Nrf2), wildly known for its ability to regulate the expression of a series of cytoprotective enzymes with antioxidative, prosurvival, and detoxification effects. Multiple researches have shown that SFN protects against central nervous system diseases through Nrf2pathway. In this article, we list SFN contents in common cruciferous vegetables, and summarize recent advances in the protective effects of SFN against acute brain injuries and neurodegenerative diseases through activating Nrf2 signaling pathway.

Shengmai injection attenuates the cerebral ischemia/reperfusion induced autophagy via modulation of the AMPK, mTOR and JNK pathways

Context Shengmai injection (SMI) is a patented Chinese medicine originated from the ancient Chinese herbal compound Shengmai san, which is used extensively for the treatment of cardiovascular and cerebrovascular disease in the clinic. Objective To determine the neuroprotective effect of SMI, we investigated the effect of SMI on cerebral ischemia/reperfusion (I/R) injury in mice as well as the mechanisms underlying this effect. Materials and methods Right middle cerebral artery was occluded by inserting a thread through internal carotid artery for 1 h, and then reperfused for 24 h in mice. The neuroprotective effects were determined using transmission electron microscopic examination, the evaluation of infarct volume, neurological deficits and water brain content. Related mechanisms were evaluated by immunofluorescence staining and western blotting. SMI was injected intraperitoneally after 1 h of ischemia at doses of 1.42, 2.84 and 5.68 g/kg. The control group received saline as the SMI vehicle. Results Results showed that SMI (1.42, 2.84 and 5.68 g/kg) could significantly reduce the infarct volume, SMI (5.68 g/kg) could also significantly improve the neurological deficits, decreased brain water content, as well as the neuronal morphological changes. SMI (5.68g/kg) could significantly inhibit the expression of autophagy-related proteins: Beclin1 and LC3. It also reduced the increase in LC3-positive cells. SMI (5.68 g/kg) remarkably inhibited the phosphorylation of adenosine monophosphate activated protein kinase (AMPK), and down-regulated the phosphorylation of mammalian target of rapamycin (mTOR) and Jun N-terminal kinase (JNK) after 24 h of reperfusion. Discussion and conclusion The results indicate that SMI provides remarkable protection against cerebral ischemia/reperfusion injury, which may be partly due to the inhibition of autophagy and related signalling pathways.

Oxymatrine attenuated hypoxic-ischemic brain damage in neonatal rats via improving antioxidant enzyme activities and inhibiting cell death

Oxymatrine (OMT), an active constituent of Chinese herb Sophora flavescens Ait, has been proved to possess anti-tumor, anti-oxidant, anti-inflammatory, and anti-apoptotic activities. Previous study has demonstrated that OMT had protective roles on multiple in vitro and in vivo brain injury models including regulation of apoptosis-related proteins caspase-3, Bax and Bcl-2. In this study, we investigated whether this protective effect could apply to neonatal hypoxic-ischemic brain damage. Seven-day-old Sprague-Dawley rats were treated with the left carotid artery ligation followed by exposure to 8% oxygen (balanced with nitrogen) for 2.5 h at 37 °C. In sham group rats, neither ligation nor hypoxia was performed. After two successive days intraperitoneal injection with OMT (30, 60 and 120 mg/kg), Nimodipine (1 mg/kg), and saline, brain infarct volume was estimated, histomorphology changes were performed by hematoxylin-eosin (HE) staining as well as electron microscopy. In addition, the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and total antioxidant capacity (T-AOC), as well as production of malondialdehyde (MDA) were assayed in ipsilateral hemisphere homogenates to evaluate the redox status after hypoxic-ischemic. Expression of apoptosis-related proteins Caspase-3, Bax and Bcl-2 in brain were analyzed by western-blot analysis and immunofluorescence. Administration of OMT significantly decreased brain infarct volume and the percentage of injured cells, and ameliorated histopathology and morphological injury as well. Furthermore, OMT obviously increased the activities of SOD, GSH-Px, CAT and T-AOC, and decreased MDA content. Western-blot analysis showed a marked decrease in Caspase-3 expression and increase in the ratio of Bcl-2/Bax after OMT (120 mg/kg) post-treatment as compared with hypoxic-ischemic group. These results suggest that OMT exerts a neuroprotective effect against hypoxic-ischemic brain damage in neonatal rats, which is likely to be mediated through increasing anti-oxidant enzyme activities and inhibiting cell death.

Matrine attenuates focal cerebral ischemic injury by improving antioxidant activity and inhibiting apoptosis in mice

Matrine, an active constituent of the Chinese herb, Sophora flavescens Ait., and it is known for its antioxidant, anti-inflammatory and antitumor activities. It has been demonstrated that matrine exerts protective effects against heart failure by decreasing the expression of caspase-3 and Bax, and increasing Bcl-2 levels. In this study, we aimed to determine whether these protective effects of matrine can be applied to cerebral ischemia. Following 7 successive days of treatment with matrine (7.5, 15 and 30 mg/kg) and nimodipine (1 mg/kg) by intraperitoneal injection, male Institute of Cancer Research (ICR) mice were subjected to middle cerebral artery occlusion (MCAO). Following reperfusion, the neurobehavioral score and brain infarct volume were estimated, and morphological changes were analyzed by hematoxylin and eosin (H&E) staining and electron microscopy. The percentage of apoptotic neurons was determined by flow cytometry. The levels of oxidative stress were assessed by measuring the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), and the total antioxidant capacity (T-AOC). Western blot analysis and immunofluorescence staining were used to examine the expression of the apoptosis-related proteins, caspase-3, Bax and Bcl-2. Our results revealed that pre-treatment with matrine significantly decreased the infarct volume and improved the neurological scores. Matrine also reduced the percentage of apoptotic neurons and relieved neuronal morphological damage. Furthermore, matrine markedly decreased the MDA levels, and increased SOD, GSH-Px and CAT activity, and T-AOC. Western blot analysis and immunofluorescence staining revealed a marked decrease in caspase-3 expression and an increase in the Bcl-2/Bax ratio in the group pre-treated with matrine (30 mg/kg) as compared with the vehicle-treated group. The findings of the present study demonstrate that matrine exerts neuroprotective effects against cerebral ischemic injury and that these effects are associated with its antioxidant and anti-apoptotic properties.

The effect of concentration and duration of normobaric oxygen in reducing caspase-3 and -9 expression in a rat-model of focal cerebral ischaemia

The aim of this study was to determine the effect of different concentrations of normobaric oxygen (NBO) on neurological function and the expression of caspase-3 and -9 in a rat model of acute cerebral ischaemia. Sprague-Dawley rats (n=120) were randomly divided into four groups (n=30 per group), including 3 groups given NBO at concentrations of 33%, 45% or 61% and one control group given air (21% oxygen). After 2h of ischaemic occlusion, each group was further subdivided into six subgroups (n=5) during reperfusion according to the duration (3, 6, 12, 24, 48 or 72h) and concentration of NBO (33%, 45% or 61%) or air treatment. The Fluorescence Quantitative polymerase chain reaction (PCR) and immunohistochemistry were used to detect caspase-3 and -9 mRNA and protein relative expression respectively. The Neurologic Impairment Score (NIS) was significantly lower in rats given 61% NBO ≥3h after reperfusion when compared to the control group (P<0.05, Mann-Whitney U). NBO significantly reduced caspase-3 and -9 mRNA and protein expression when compared to the control group at all NBO concentrations and time points (P<0.05, ANOVA). The expression of caspase-3 and -9 was lower in the group given 61% NBO compared any other group, and this difference was statistically significant when compared to the group given 33% NBO for ≥48h and the control group (both P<0.05, ANOVA). These findings indicate that NBO may inhibit the apoptotic pathway by reducing caspase-3 and -9 expression, thereby promoting neurological functional recovery after stroke.

Revisiting Cerebral Postischemic Reperfusion Injury: New Insights in Understanding Reperfusion Failure, Hemorrhage, and Edema

Cerebral postischemic reperfusion injury is defined as deterioration of ischemic brain tissue that parallels and antagonizes the benefits of restoring cerebral circulation after therapeutic thrombolysis for acute ischemic stroke. To understand the paradox of injury caused by treatment, we first emphasize the phenomenon in which recanalization of an occluded artery does not lead to tissue reperfusion. Additionally, no-reflow after recanalization may be due to injury of the neurovascular unit, distal microthrombosis, or both, and certainly worsens outcome. We examine the mechanism of molecular and sub-cellular damage in the neurovascular unit, notably oxidative stress, mitochondrial dysfunction, and apoptosis. At the level of the neurovascular unit, which mediates crosstalk between the damaged brain and systemic responses in blood, we summarize emerging evidence demonstrating that individual cell components play unique and cumulative roles that lead to damage of the blood–brain barrier and neurons. Furthermore, we review the latest developments in establishing a link between the immune system and microvascular dysfunction during ischemic reperfusion. Progress in assessing reperfusion injury has also been made, and we review imaging studies using various magnetic resonance imaging modalities. Lastly, we explore potential treatment approaches, including ischemic preconditioning, postconditioning, pharmacologic agents, and hypothermia.

The Role of NMDA Receptors in the Development of Brain Resistance through Pre- and Postconditioning

Brain tolerance or resistance can be achieved by interventions before and after injury through potential toxic agents used in low stimulus or dose. For brain diseases, the neuroprotection paradigm desires an attenuation of the resulting motor, cognitive, emotional, or memory deficits following the insult. Preconditioning is a well-established experimental and clinical translational strategy with great beneficial effects, but limited applications. NMDA receptors have been reported as protagonists in the adjacent cellular mechanisms contributing to the development of brain tolerance. Postconditioning has recently emerged as a new neuroprotective strategy, which has shown interesting results when applied immediately, i.e. several hours to days, after a stroke event. Investigations using chemical postconditioning are still incipient, but nevertheless represent an interesting and promising clinical strategy. In the present review pre- and postconditioning are discussed as neuroprotective paradigms and the focus of our attention lies on the participation of NMDA receptors proteins in the processes related to neuroprotection.

Temporal regulation of apoptotic and anti-apoptotic molecules after middle cerebral artery occlusion followed by reperfusion

A tremendous effort has been expended to elucidate the role of apoptotic molecules in ischemia. However, many agents that target apoptosis, despite their proven efficacy in animal models, have failed to translate that efficacy and specificity in clinical settings. Therefore, comprehensive knowledge of apoptotic mechanisms involving key apoptotic regulatory molecules and the temporal expression profiles of various apoptotic molecules after cerebral ischemia may provide insight for the development of better therapeutic strategies aimed at cerebral ischemia. The present study investigates the extent of apoptosis and the regulation of apoptotic molecules both at mRNA and protein levels at various time points after focal cerebral ischemia in a rat model of middle cerebral artery occlusion. In this study, we performed various techniques, such as TTC (2,3,5-triphenyltetrazolium chloride), H&E (hematoxylin and eosin), and TUNEL (terminal deoxy nucleotidyl transferase-mediated nick-end labeling) staining, along with polymerase chain reaction (PCR) microarray, antibody microarray, reverse transcription (RT)-PCR, immunofluorescence, and immunoblot analyses. Our research provided a large list of pro-apoptotic and anti-apoptotic molecules and their temporal expression profiles both at the mRNA and protein levels. This information could be very useful for designing future stroke therapies and aid in targeting the right molecules at critical time to obtain maximum therapeutic benefit.

The rationale of targeting mammalian target of rapamycin for ischemic stroke

Given the current limitation of therapeutic approach for ischemic stroke, a leading cause of disability and mortality in the developed countries, to develop new therapeutic strategies for this devastating disease is urgently necessary. As a serine/threonine kinase, mammalian target of rapamycin (mTOR) activation can mediate broad biological activities that include protein synthesis, cytoskeleton organization, and cell survival. mTOR functions through mTORC1 and mTORC2 complexes and their multiple downstream substrates, such as eukaryotic initiation factor 4E-binding protein 1, p70 ribosomal S6 kinase, sterol regulatory element-binding protein 1, hypoxia inducible factor-1, and signal transducer and activator transcription 3, Yin Ying 1, Akt, protein kinase c-alpha, Rho GTPase, serum-and gucocorticoid-induced protein kinase 1, etc. Specially, the role of mTOR in the central nervous system has been attracting considerable attention. Based on the ability of mTOR to prevent neuronal apoptosis, inhibit autophagic cell death, promote neurogenesis, and improve angiogenesis, mTOR may acquire the capability of limiting the ischemic neuronal death and promoting the neurological recovery. Consequently, to regulate the activity of mTOR holds a potential as a novel therapeutic strategy for ischemic stroke.

Interference of apoptosis in the pathophysiology of subarachnoid hemorrhage

Programmed cell death is crucial for the correct development of the organism and the clearance of harmful cells like tumor cells or autoreactive immune cells. Apoptosis is initiated by the activation of cell death receptors and in most cases it is associated with the activation of the cysteine proteases, which lead to apoptotic cell death. Cells shrink, chromatin clumps and forms a large, sharply demarcated, crescent-shaped or round mass; the nucleus condenses, apoptotic bodies are formed and eventually dead cells are engulfed by a neighboring cell or cleared by phagocytosis. The authors have summarized the most important data concerning apoptosis in subarachnoid hemorrhage that have been issued in the medical literature in the last 20 years.

Neuroprotective effect of calycosin on cerebral ischemia and reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Astragali has been commonly used as traditional herbal medicine in China for reinforcing vital energy, strengthening superficial resistance and promoting the discharge of pus and the growth of new tissue.

AIM OF THE STUDY

The present study was to investigate the neuroprotective effect of calycosin isolated from the roots of Radix Astragali on cerebral ischemic/reperfusion injury.

MATERIALS AND METHODS

After 24h of reperfusion following ischemia for 2h induced by middle cerebral artery occlusion (MCAO), Sprague-Dawley rats were intragastrically administered different doses of calycosin (7.5, 15, 30 mg/kg, respectively). Neurological deficit, infarct volume, histopathology changes and some oxidative stress markers were evaluated after 24h of reperfusion.

RESULTS

Treatment with calycosin significantly ameliorated neurologic deficit and infarct volume after cerebral ischemia reperfusion. Calycosin also reduced the content of malondialdehyde (MDA), protein carbonyl and reactive oxygen species (ROS), and up-regulated the activities of superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px) in a dose-dependent manner. Moreover, calycosin can also inhibit the expression of 4-Hydroxy-2-nonenal (4-HNE).

CONCLUSION

These results suggest that calycosin has a neuroprotective effect against cerebral ischemia/reperfusion injury. The mechanism might be attributed to its antioxidant effects.

Lipid peroxidation dysregulation in ischemic stroke: plasma 4-HNE as a potential biomarker?

4-hydroxynonenal (4-HNE) is a major aldehyde produced during the lipid peroxidation of ω-6 polyunsaturated fatty acids. Recently, 4-HNE has been reported to contribute to the pathogenesis of neuronal diseases such as Alzheimer's disease. However, the role of 4-HNE in ischemic stroke is unclear yet. In this study, we found that plasma 4-HNE concentrations were higher in the genetic stroke-prone rats (stroke-prone spontaneously hypertensive rats) and experimental stroke rats with middle cerebral artery occlusion (MCAO). Moreover, administration of 4-HNE via intravenous injection before MCAO surgery not only enlarged cerebral ischemia-induced infarct area, but also increased oxidative stress in brain tissue, which was evidenced by the enhanced ROS/MPA levels, and the reduced GSH/GSSG ratio and MnSOD levels. Overexpression of aldehyde dehydrogenasesbcl-2 (ALDH2), an enzyme catalyses 4-HNE, rescued neuronal survival against 4-HNE treatment in PC12 cells. The plasma 4-HNE concentrations in patients with ischemic stroke were higher than those in control subjects. In a small sample population (N=60), the plasma 4-HNE concentration was positively correlated with the plasma homocysteine concentration, a risk factor for ischemic stroke. Taken together, our study suggests that the plasma 4-HNE level is a potential biomarker for ischemic stroke.

Protective effects and mechanisms of sirtuins in the nervous system

Silent information regulator two proteins (sirtuins or SIRTs) are a group of histone deacetylases whose activities are dependent on and regulated by nicotinamide adenine dinucleotide (NAD(+)). They suppress genome-wide transcription, yet upregulate a select set of proteins related to energy metabolism and pro-survival mechanisms, and therefore play a key role in the longevity effects elicited by calorie restriction. Recently, a neuroprotective effect of sirtuins has been reported for both acute and chronic neurological diseases. The focus of this review is to summarize the latest progress regarding the protective effects of sirtuins, with a focus on SIRT1. We first introduce the distribution of sirtuins in the brain and how their expression and activity are regulated. We then highlight their protective effects against common neurological disorders, such as cerebral ischemia, axonal injury, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. Finally, we analyze the mechanisms underlying sirtuin-mediated neuroprotection, centering on their non-histone substrates such as DNA repair enzymes, protein kinases, transcription factors, and coactivators. Collectively, the information compiled here will serve as a comprehensive reference for the actions of sirtuins in the nervous system to date, and will hopefully help to design further experimental research and expand sirtuins as therapeutic targets in the future.

Mechanisms of estrogens' dose-dependent neuroprotective and neurodamaging effects in experimental models of cerebral ischemia

Ever since the hypothesis was put forward that estrogens could protect against cerebral ischemia, numerous studies have investigated the mechanisms of their effects. Despite initial studies showing ameliorating effects, later trials in both humans and animals have yielded contrasting results regarding the fundamental issue of whether estrogens are neuroprotective or neurodamaging. Therefore, investigations of the possible mechanisms of estrogen actions in brain ischemia have been difficult to assess. A recently published systematic review from our laboratory indicates that the dichotomy in experimental rat studies may be caused by the use of insufficiently validated estrogen administration methods resulting in serum hormone concentrations far from those intended, and that physiological estrogen concentrations are neuroprotective while supraphysiological concentrations augment the damage from cerebral ischemia. This evidence offers a new perspective on the mechanisms of estrogens’ actions in cerebral ischemia, and also has a direct bearing on the hormone replacement therapy debate. Estrogens affect their target organs by several different pathways and receptors, and the mechanisms proposed for their effects on stroke probably prevail in different concentration ranges. In the current article, previously suggested neuroprotective and neurodamaging mechanisms are reviewed in a hormone concentration perspective in an effort to provide a mechanistic framework for the dose-dependent paradoxical effects of estrogens in stroke. It is concluded that five protective mechanisms, namely decreased apoptosis, growth factor regulation, vascular modulation, indirect antioxidant properties and decreased inflammation, and the proposed damaging mechanism of increased inflammation, are currently supported by experiments performed in optimal biological settings.

Apoptotic mechanisms for neuronal cells in early brain injury after subarachnoid hemorrhage

OBJECTS

The major causes of death and disability in subarachnoid hemorrhage (SAH) may be early brain injury (EBI) and cerebral vasospasm. Although cerebral vasospasm has been studied and treated by a lot of drugs, the outcome is not improved even if vasospasm is reversed. Based on these data, EBI is considered a primary target for future research, and apoptosis may be involved in EBI after experimental SAH.

METHODS

We reviewed the published literature about the relationship between SAH induced EBI and apoptosis in PubMed.

RESULT

Most available information can be obtained from the endovascular filament perforation animal model. After onset of SAH, intracranial pressure is increased and then cerebral blood flow is reduced. Many factors are involved in the mechanism of apoptotic cell death in EBI after SAH. In the neuronal cells, both intrinsic and extrinsic pathways of apoptosis can occur. Some antiapoptotic drugs were studied and demonstrated a protective effect against EBI after SAH. However, apoptosis in EBI after SAH has been little studied and further studies will provide us more beneficial findings.

CONCLUSIONS

The study of apoptosis in EBI after experimental SAH may give us new therapies for SAH.

Sex differences in cerebral injury after severe haemorrhage and ventricular fibrillation in pigs

BACKGROUND

Experimental studies of haemorrhagic shock have documented a superior haemodynamic response and a better outcome in female animals as compared with male controls. Such sexual dimorphism has, nevertheless, not been reported after circulatory arrest that follows exsanguination and shock. We aimed to study differences in cerebral injury markers after exsanguination cardiac arrest in pre-pubertal piglets. The hypothesis was that cerebral injury is less extensive in female animals, and that this difference is independent of sexual hormones or choice of resuscitative fluid.

METHODS

Thirty-two sexually immature piglets (14 males and 18 females) were subjected to 5 min of haemorrhagic shock followed by 2 min of ventricular fibrillation and 8 min of cardiopulmonary resuscitation, using three resuscitation fluid regimens (whole blood, hypertonic saline and dextran, or acetated Ringers' solution plus whole blood and methylene blue). Haemodynamic values, cellular markers of brain injury and brain histology were studied.

RESULTS

After successful resuscitation, female piglets had significantly greater cerebral cortical blood flow, tended to have lower S-100beta values and a lower cerebral oxygen extraction ratio. Besides, in female animals, systemic and cerebral venous acidosis were mitigated. Female piglets exhibited a significantly smaller increase in neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) expression in their cerebral cortex, smaller blood-brain-barrier (BBB) disruption and significantly smaller neuronal injury.

CONCLUSION

After resuscitation from haemorrhagic circulatory arrest, cerebral reperfusion is greater, and BBB permeability and neuronal injury is smaller in female piglets. An increased cerebral cortical iNOS and nNOS expression in males implies a mechanistic relationship with post-resuscitation neuronal injury and warrants further investigation.

Ionic storm in hypoxic/ischemic stress: can opioid receptors subside it?

Neurons in the mammalian central nervous system are extremely vulnerable to oxygen deprivation and blood supply insufficiency. Indeed, hypoxic/ischemic stress triggers multiple pathophysiological changes in the brain, forming the basis of hypoxic/ischemic encephalopathy. One of the initial and crucial events induced by hypoxia/ischemia is the disruption of ionic homeostasis characterized by enhanced K(+) efflux and Na(+)-, Ca(2+)- and Cl(-)-influx, which causes neuronal injury or even death. Recent data from our laboratory and those of others have shown that activation of opioid receptors, particularly delta-opioid receptors (DOR), is neuroprotective against hypoxic/ischemic insult. This protective mechanism may be one of the key factors that determine neuronal survival under hypoxic/ischemic condition. An important aspect of the DOR-mediated neuroprotection is its action against hypoxic/ischemic disruption of ionic homeostasis. Specially, DOR signal inhibits Na(+) influx through the membrane and reduces the increase in intracellular Ca(2+), thus decreasing the excessive leakage of intracellular K(+). Such protection is dependent on a PKC-dependent and PKA-independent signaling pathway. Furthermore, our novel exploration shows that DOR attenuates hypoxic/ischemic disruption of ionic homeostasis through the inhibitory regulation of Na(+) channels. In this review, we will first update current information regarding the process and features of hypoxic/ischemic disruption of ionic homeostasis and then discuss the opioid-mediated regulation of ionic homeostasis, especially in hypoxic/ischemic condition, and the underlying mechanisms.

The molecular mechanisms of cell death in the course of transient ischemia are differentiated in evolutionary distinguished brain structures

There is large body of evidence suggesting distinct susceptibility to ischemia in various brain regions. However, the reason for this remains unexplained. Comparative studies of programmed cell death (PCD) pathways indicate their differentiated evolutional origin. The caspase-independent pathway is regarded as an older, whereas the caspase-dependent--as more advanced. In our study we address the question of whether there are any characteristic differences in the activation and course of PCD in phylogenetically and morphologically distinguished brain structures after transient focal ischemia. Using Western blot, we studied changes in expression of caspases: 3, 8, 9, and AIF in the frontoparietal neocortex, archicortex (CA1 and CA2 sectors of the hippocampus) and striatum, during reperfusion after 1 h occlusion of the middle cerebral artery. The caspase and AIF expression were differentiated between the studied structures. The activation of only the caspase-dependent pathway was observed in the neocortex. In the archicortex and striatum both caspase-dependent and caspase-independent pathways were activated, although in the latter the extrinsic apoptotic pathway was not activated. In summary, it is conceivable that structures of different evolutionary origin undergo cell-death processes with the participation of phylogenetically distinguished mechanisms. The previously reported unequal susceptibility to ischemia may co-exist with activation of different cell death pathways.

Estradiol is a potent protective, restorative, and trophic factor after brain injury

Estrogens are a group of pleiotropic steroid hormones that exhibit diverse mechanisms of action in multiple physiologic systems. Over the past 30 years, biomedical science has begun to appreciate that endogenous estrogens and their receptors display important roles beyond the reproductive system. Our growing appreciation of novel, nonreproductive functions for estrogens has fundamentally contributed to our knowledge of their role in human health and disease. Recent findings from the Women's Health Initiative have caused clinicians and scientists to question whether estrogens are protective factors or risk factors. In light of the dichotomy between basic science and clinical studies, this review will attempt to reconcile differences between them. We will focus on studies from our laboratory and others highlighting the beneficial properties of the most abundant endogenous estrogen, 17beta-estradiol, using in vivo and in vitro models of cerebral ischemia and neuronal injury. These studies demonstrate that 17beta-estradiol powerfully protects the brain using multiple molecular mechanisms that promote: (1) decreased cell death, (2) increased neurogenesis, (3) an enhancement of neurotrophic support, and (4) the suppression of proinflammatory pathways.

Possible mechanisms of Cyclosporin A ameliorated the ischemic microenvironment and inhibited mitochondria stress in tree shrews' hippocampus

OBJECTIVE

The ischemic brain damage is always accompanied by the significant accumulation of glutamate and calcium ions (Ca(2+)). Our objectives were to observe the effects of glutamate and Ca(2+) overloading in tree shrew's hippocampal microenvironment on mitochondrial stress resulting in cytochrome C release and caspase apoptotic gene activation, and to explore the possible mechanism of Cyclosporin A (CsA) inhibiting mitochondrial stress.

METHODS

The thrombotic focal cerebral ischemia was induced by photochemical reaction in tree shrews. The extracellular contents of amino acidic neurotransmitters and Ca(2+) were determined, respectively, with high performance liquid chromatography (HPLC) and atomic absorption spectrophotometry at 4, 24 and 72h after cerebral ischemia. The glutamate-calcium chloride solutions were microperfused into hippocampus by a kind of single-pumped push-pull perfusion (SPPP) system under three-dimensional orientation instrument in tree shrews. At 24h, the expression of cytochrome C was observed in perfused lateral hippocampus by immunochemistry. Also, the hippocampus was removed, then mitochondria and cytoplasmic fragment were divided by low temperature centrifugation and the distribution of cytochrome C was assessed through Western blot. Real time fluorescence polymerase chain reaction was used to evaluate the relative amounts of caspase-3 and caspase-9 mRNA. In the treated group, CsA (40mg/kg) was intravenously injected at 6h after the microperfuse or cerebral ischemia. The glutamate-calcium solutions were perfused into the hippocampus and inspected the above-mentioned items at 24h. Data were compared between the two groups (ischemia group vs. sham group, or ischemia group vs. CsA group).

RESULTS

Thrombotic cerebral ischemia led to significant increase in extracellular glutamate and Ca(2+) level of hippocampus (P<0.01). The cerebral ischemia group and the microperfusion group, which cytochrome C immunoreactivity increased and Western blot analysis demonstrated that the cytochrome C content in the mitochondria of hippocampal cells decreased (P<0.01), but the cytochrome C in the cytosol increased (P<0.01). When CsA was intravenously injected at 6h after the microperfusion or cerebral ischemia, the cytochrome C expression weakened and its release was diminished to a lesser extent. By real time PCR, in relation to the control group, the caspase-3 and caspase-9 mRNA was higher in the glutamate-calcium chloride solution perfused group. CsA treatment cut down the contents of caspase-3 mRNA and caspase-9 mRNA (P<0.01).

CONCLUSIONS

It is a primary factor that glutamate and Ca(2+) accumulate in hippocampal microenvironment, which results in proapoptotic protein cytochrome C release from mitochondria into cytoplasm and caspase cascade activation, and finally mitochondria stress and neuronal secondary injury appear. The neuroprotection of CsA is in relation to inhibiting glutamate receptor overactivation and reducing the Ca(2+) influx, which can decrease cytochrome C release and caspase mRNA transition.

Leptin neuroprotection in the CNS: mechanisms and therapeutic potentials

Leptin is well known as a hormone important in the central control of appetitive behaviors via receptor-mediated actions in the hypothalamus, where leptin adjusts food intake to maintain homeostasis with the body's energy stores. Recent evidence has shown that leptin and its receptors are widespread in the CNS and may provide neuronal survival signals. This review summarizes our current knowledge of how leptin functions in the brain and then focuses on the ability of leptin to mitigate neuronal damage in experimental models of human neurological disorders. Damage to the brain by acute events such as stroke, or long-term loss of neurons associated with neurodegenerative diseases, including Parkinson's and Alzheimer's disease, may be amenable to treatment using leptin to limit death of susceptible cells. Leptin-mediated pro-survival signaling is now known to prevent the death of neurons in these models. The signaling cascades that leptin generates are shared by other neuroprotective molecules including insulin and erythropoietin, and are thus a component of the neurotrophic effects mediated by endogenous hormones. Coupled with evidence that leptin dysregulation in human disease also results in enhanced neuronal susceptibility to damage, development of leptin as a therapeutic methodology is an attractive and viable possibility.

Leptin protects hippocampal CA1 neurons against ischemic injury

Leptin is an adipose hormone with well characterized roles in regulating food intake and energy balance. A novel neuroprotective role for leptin has recently been discovered; however, the underlying mechanisms are not clearly defined. The purpose of this study was to determine whether leptin protects against delayed neuronal cell death in hippocampal CA1 following transient global cerebral ischemia in rats and to study the signaling mechanism responsible for the neuroprotective effects of leptin. Leptin receptor antagonist, protein kinase inhibitors and western blots were used to assess the molecular signaling events that were altered by leptin after ischemia. The results revealed that intracerebral ventricle infusion of leptin markedly increased the numbers of survival CA1 neurons in a dose-dependent manner. Infusion of a specific leptin antagonist 10 min prior to transient global ischemia abolished the pro-survival effects of leptin, indicating the essential role of leptin receptors in mediating this neuroprotection. Both the Akt and extracellular signal-related kinase 1/2 (ERK1/2) signaling pathways appear to play a critical role in leptin neuroprotection, as leptin infusion increased the phosphorylation of Akt and ERK1/2 in CA1. Furthermore, pharmacological inhibition of either pathway compromised the neuroprotective effects of leptin. Taken together, the results suggest that leptin protects against delayed ischemic neuronal death in the hippocampal CA1 by maintaining the pro-survival states of Akt and ERK1/2 MAPK signaling pathways.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.

Caspase activation in fetal rat brain following experimental intrauterine inflammation

Intrauterine inflammation has been implicated in developmental brain injuries, including the development of periventricular leukomalacia (PVL) and cerebral palsy (CP). Previous studies in our rat model of intrauterine inflammation demonstrated apoptotic cell death in fetal brains within the first 5 days after lipopolysaccharide (LPS) administration to mothers and eventual dysmyelination. Cysteine-containing, aspartate-specific proteases, or caspases, are proteins involved with apoptosis through both intracellular (intrinsic pathway) and extracellular (extrinsic pathway) mechanisms. We hypothesized that cell death in our model would occur mainly via activation of the extrinsic pathway. We further hypothesized that Fas, a member of the tumor necrosis factor receptor (TNFR) superfamily, would be increased and the death inducing signaling complex (DISC) would be detectable. Pregnant rats were injected intracervically with LPS at E15 and immunoblotting, immunohistochemical and immunoprecipitation analyses were performed. The presence of the activated form of the effector caspase (caspase-3) was observed 24 h after LPS administration. Caspase activity assays demonstrated rapid increases in (i) caspases-9 and -10 within 1 h, (ii) caspase-8 at 2 h and (iii) caspase-3 at 4 h. At 24 h after LPS, activated caspase-3(+)/Fas(+) cells were observed within the developing white matter. Lastly, the DISC complex (caspase-8, Fas and Fas-associated death domain (FADD)) was observed within 30 min by immunoprecipitation. Apoptosis in our model occurs via both extrinsic and intrinsic pathways, and activation of Fas may play a role. Understanding the mechanisms of cell death in models of intrauterine inflammation may affect development of future strategies to mitigate these injuries in children.