Involvement of oxidative stress and caspase-3 in cortical infarction after photothrombotic ischemia in mice

Advancing Post-Stroke Depression Research: Insights from Murine Models and Behavioral Analyses

Post-stroke depression (PSD) represents a significant neuropsychiatric complication that affects between 39% and 52% of stroke survivors, leading to impaired recovery, decreased quality of life, and increased mortality. This comprehensive review synthesizes our current knowledge of PSD, encompassing its epidemiology, risk factors, underlying neurochemical mechanisms, and the existing tools for preclinical investigation, including animal models and behavioral analyses. Despite the high prevalence and severe impact of PSD, challenges persist in accurately modeling its complex symptomatology in preclinical settings, underscoring the need for robust and valid animal models to better understand and treat PSD. This review also highlights the multidimensional nature of PSD, where both biological and psychosocial factors interplay to influence its onset and course. Further, we examine the efficacy and limitations of the current animal models in mimicking the human PSD condition, along with behavioral tests used to evaluate depressive-like behaviors in rodents. This review also sets a new precedent by integrating the latest findings across multidisciplinary studies, thereby offering a unique and comprehensive perspective of existing knowledge. Finally, the development of more sophisticated models that closely replicate the clinical features of PSD is crucial in order to advance translational research and facilitate the discovery of future effective therapies.

From static to dynamic: live observation of the support system after ischemic stroke by two photon-excited fluorescence laser-scanning microscopy

Ischemic stroke is one of the most common causes of mortality and disability worldwide. However, treatment efficacy and the progress of research remain unsatisfactory. As the critical support system and essential components in neurovascular units, glial cells and blood vessels (including the blood-brain barrier) together maintain an optimal microenvironment for neuronal function. They provide nutrients, regulate neuronal excitability, and prevent harmful substances from entering brain tissue. The highly dynamic networks of this support system play an essential role in ischemic stroke through processes including brain homeostasis, supporting neuronal function, and reacting to injuries. However, most studies have focused on postmortem animals, which inevitably lack critical information about the dynamic changes that occur after ischemic stroke. Therefore, a high-precision technique for research in living animals is urgently needed. Two-photon fluorescence laser-scanning microscopy is a powerful imaging technique that can facilitate live imaging at high spatiotemporal resolutions. Two-photon fluorescence laser-scanning microscopy can provide images of the whole-cortex vascular 3D structure, information on multicellular component interactions, and provide images of structure and function in the cranial window. This technique shifts the existing research paradigm from static to dynamic, from flat to stereoscopic, and from single-cell function to multicellular intercommunication, thus providing direct and reliable evidence to identify the pathophysiological mechanisms following ischemic stroke in an intact brain. In this review, we discuss exciting findings from research on the support system after ischemic stroke using two-photon fluorescence laser-scanning microscopy, highlighting the importance of dynamic observations of cellular behavior and interactions in the networks of the brain's support systems. We show the excellent application prospects and advantages of two-photon fluorescence laser-scanning microscopy and predict future research developments and directions in the study of ischemic stroke.

Time course of recovery of different motor functions following a reproducible cortical infarction in non-human primates

A major challenge in human stroke research is interpatient variability in the extent of sensorimotor deficits and determining the time course of recovery following stroke. Although the relationship between the extent of the lesion and the degree of sensorimotor deficits is well established, the factors determining the speed of recovery remain uncertain. To test these experimentally, we created a cortical lesion over the motor cortex using a reproducible approach in four common marmosets, and characterized the time course of recovery by systematically applying several behavioral tests before and up to 8 weeks after creation of the lesion. Evaluation of in-cage behavior and reach-to-grasp movement revealed consistent motor impairments across the animals. In particular, performance in reaching and grasping movements continued to deteriorate until 4 weeks after creation of the lesion. We also found consistent time courses of recovery across animals for in-cage and grasping movements. For example, in all animals, the score for in-cage behaviors showed full recovery at 3 weeks after creation of the lesion, and the performance of grasping movement partially recovered from 4 to 8 weeks. In addition, we observed longer time courses of recovery for reaching movement, which may rely more on cortically initiated control in this species. These results suggest that different recovery speeds for each movement could be influenced by what extent the cortical control is required to properly execute each movement.

Beneficial Effect of Methanolic Extract of Frankincense (Boswellia Sacra) on Testis Mediated through Suppression of Oxidative Stress and Apoptosis

Boswellia sacra oleo gum resin (Burseraceae) commonly known as frankincense is traditionally used in many countries for its beneficial effect on male fertility. This study explores its effect on the male reproductive system after a 60-day repeated administration at two different doses to rats (in vivo) and on human Leydig cells (in vitro). The methanolic extract of B. sacra was analyzed for the presence of various constituents by preliminary phytochemical analysis and gas chromatography-mass spectrometry (GC-MS) while quantitative analysis of boswellic acids was done by high-performance liquid chromatography (HPLC). Administration of B. sacra extract to rats elevated the serum testosterone levels with an associated reduction in serum levels of FSH and LH. An increase in the activity of antioxidant enzymes, superoxide dismutase and catalase, was seen. A dose-dependent increase in the sperm count and sperm motility was also observed. The in vivo results were supported by changes in the expression of the Bcl-2 gene and caspase-3 gene in human Leydig cells in vitro. The results of this study support the traditional use of B. sacra to increase male fertility.

Diversity of Reactive Astrogliosis in CNS Pathology: Heterogeneity or Plasticity?

Astrocytes are essential for the development and homeostatic maintenance of the central nervous system (CNS). They are also critical players in the CNS injury response during which they undergo a process referred to as "reactive astrogliosis." Diversity in astrocyte morphology and gene expression, as revealed by transcriptional analysis, is well-recognized and has been reported in several CNS pathologies, including ischemic stroke, CNS demyelination, and traumatic injury. This diversity appears unique to the specific pathology, with significant variance across temporal, topographical, age, and sex-specific variables. Despite this, there is limited functional data corroborating this diversity. Furthermore, as reactive astrocytes display significant environmental-dependent plasticity and fate-mapping data on astrocyte subsets in the adult CNS is limited, it remains unclear whether this diversity represents heterogeneity or plasticity. As astrocytes are important for neuronal survival and CNS function post-injury, establishing to what extent this diversity reflects distinct established heterogeneous astrocyte subpopulations vs. environmentally dependent plasticity within established astrocyte subsets will be critical for guiding therapeutic development. To that end, we review the current state of knowledge on astrocyte diversity in the context of three representative CNS pathologies: ischemic stroke, demyelination, and traumatic injury, with the goal of identifying key limitations in our current knowledge and suggesting future areas of research needed to address them. We suggest that the majority of identified astrocyte diversity in CNS pathologies to date represents plasticity in response to dynamically changing post-injury environments as opposed to heterogeneity, an important consideration for the understanding of disease pathogenesis and the development of therapeutic interventions.

A review of experimental models of focal cerebral ischemia focusing on the middle cerebral artery occlusion model

Cerebral ischemic stroke is a leading cause of death and disability, but current pharmacological therapies are limited in their utility and effectiveness. In vitro and in vivo models of ischemic stroke have been developed which allow us to further elucidate the pathophysiological mechanisms of injury and investigate potential drug targets. In vitro models permit mechanistic investigation of the biochemical and molecular mechanisms of injury but are reductionist and do not mimic the complexity of clinical stroke. In vivo models of ischemic stroke directly replicate the reduction in blood flow and the resulting impact on nervous tissue. The most frequently used in vivo model of ischemic stroke is the intraluminal suture middle cerebral artery occlusion (iMCAO) model, which has been fundamental in revealing various aspects of stroke pathology. However, the iMCAO model produces lesion volumes with large standard deviations even though rigid surgical and data collection protocols are followed. There is a need to refine the MCAO model to reduce variability in the standard outcome measure of lesion volume. The typical approach to produce vessel occlusion is to induce an obstruction at the origin of the middle cerebral artery and reperfusion is reliant on the Circle of Willis (CoW). However, in rodents the CoW is anatomically highly variable which could account for variations in lesion volume. Thus, we developed a refined approach whereby reliance on the CoW for reperfusion was removed. This approach improved reperfusion to the ischemic hemisphere, reduced variability in lesion volume by 30%, and reduced group sizes required to determine an effective treatment response by almost 40%. This refinement involves a methodological adaptation of the original surgical approach which we have shared with the scientific community via publication of a visualised methods article and providing hands-on training to other experimental stroke researchers.

Sickle cell disease mice have cerebral oxidative stress and vascular and white matter abnormalities

Strokes are feared complications of sickle cell disease (SCD) and yield significant neurologic and neurocognitive deficits. However, even without detectable strokes, SCD patients have significant neurocognitive deficits in domains of learning and memory, processing speed and executive function. In these cases, mechanisms unrelated to major cerebrovascular abnormalities likely underlie these deficits. While oxidative stress and stress-related signaling pathways play a role in SCD pathophysiology, their role in cerebral injury remains unknown. We have shown that Townes and BERK SCD mice, while not having strokes, recapitulate neurocognitive deficits reported in humans. We hypothesized that cognitive deficits in SCD mice are associated with cerebral oxidative stress. We showed that SCD mice have increased levels of reactive oxygen species, protein carbonylation, and lipid peroxidation in hippocampus and cortex, thus suggesting increased cerebral oxidative stress. Further, cerebral oxidative stress was associated with caspase-3 activity alterations and vascular endothelial abnormalities, white matter changes, and disruption of the blood brain barrier, similar to those reported after ischemic/oxidative injury. Additionally, after repeated hypoxia/reoxygenation exposure, homozygous Townes had enhanced microglia activation. Our findings indicate that oxidative stress and stress-induced tissue damage is increased in susceptible brain regions, which may, in turn, contribute to neurocognitive deficits in SCD mice.

Environmental enrichment combined with fasudil promotes motor function recovery and axonal regeneration after stroke

Fasudil, a Rho-associated protein kinase (ROCK) inhibitor, has a protective effect on the central nervous system. In addition, environmental enrichment is a promising technique for inducing the recovery of motor impairments in ischemic stroke models. The present study aimed to explore whether environmental enrichment combined with fasudil can facilitate motor function recovery and induce cortical axonal regeneration after stroke. First, a mouse model of ischemic cerebral stroke was established by photochemical embolization of the left sensorimotor cortex. Fasudil solution (10 mg/kg per day) was injected intraperitoneally for 21 days after the photothrombotic stroke. An environmental enrichment intervention was performed on days 7–21 after the photothrombotic stroke. The results revealed that environmental enrichment combined with fasudil improved motor function, increased growth-associated protein 43 expression in the infarcted cerebral cortex, promoted axonal regeneration on the contralateral side, and downregulated ROCK, p-LIM domain kinase (LIMK)1, and p-cofilin expression. The combined intervention was superior to monotherapy. These findings suggest that environmental enrichment combined with fasudil treatment promotes motor recovery after stroke, at least partly by stimulating axonal regeneration. The underlying mechanism might involve ROCK/LIMK1/cofilin pathway regulation. This study was approved by the Institutional Animal Care and Use Committee of Fudan University, China (approval No. 20160858A232) on February 24, 2016.

Filling the gaps on stroke research: Focus on inflammation and immunity

For the last two decades, researchers have placed hopes in a new era in which a combination of reperfusion and neuroprotection would revolutionize the treatment of stroke. Nevertheless, despite the thousands of papers available in the literature showing positive results in preclinical stroke models, randomized clinical trials have failed to show efficacy. It seems clear now that the existing data obtained in preclinical research have depicted an incomplete picture of stroke pathophysiology. In order to ameliorate bench-to-bed translation, in this review we first describe the main actors on stroke inflammatory and immune responses based on the available preclinical data, highlighting the fact that the link between leukocyte infiltration, lesion volume and neurological outcome remains unclear. We then describe what is known on neuroinflammation and immune responses in stroke patients, and summarize the results of the clinical trials on immunomodulatory drugs. In order to understand the gap between clinical trials and preclinical results on stroke, we discuss in detail the experimental results that served as the basis for the summarized clinical trials on immunomodulatory drugs, focusing on (i) experimental stroke models, (ii) the timing and selection of outcome measuring, (iii) alternative entry routes for leukocytes into the ischemic region, and (iv) factors affecting stroke outcome such as gender differences, ageing, comorbidities like hypertension and diabetes, obesity, tobacco, alcohol consumption and previous infections like Covid-19. We can do better for stroke treatment, especially when targeting inflammation following stroke. We need to re-think the design of stroke experimental setups, notably by (i) using clinically relevant models of stroke, (ii) including both radiological and neurological outcomes, (iii) performing long-term follow-up studies, (iv) conducting large-scale preclinical stroke trials, and (v) including stroke comorbidities in preclinical research.

Microcirculatory Changes in Experimental Models of Stroke and CNS-Injury Induced Immunodepression

Stroke is the second-leading cause of death globally and the leading cause of disability in adults. Medical complications after stroke, especially infections such as pneumonia, are the leading cause of death in stroke survivors. Systemic immunodepression is considered to contribute to increased susceptibility to infections after stroke. Different experimental models have contributed significantly to the current knowledge of stroke pathophysiology and its consequences. Each model causes different changes in the cerebral microcirculation and local inflammatory responses after ischemia. The vast majority of studies which focused on the peripheral immune response to stroke employed the middle cerebral artery occlusion method. We review various experimental stroke models with regard to microcirculatory changes and discuss the impact on local and peripheral immune response for studies of CNS-injury (central nervous system injury) induced immunodepression.

Edaravone-Encapsulated Agonistic Micelles Rescue Ischemic Brain Tissue by Tuning Blood-Brain Barrier Permeability

Thrombolysis has been a standard treatment for ischemic stroke. However, only 2-7% patients benefit from it because the thrombolytic agent has to be injected within 4.5 h after the onset of symptoms to avoid the increasing risk of intracerebral hemorrhage. As the only clinically approved neuroprotective drug, edaravone (EDV) rescues ischemic brain tissues by eradicating over-produced reactive oxygen species (ROS) without the limitation of therapeutic time-window. However, EDV's short circulation half-life and inadequate cerebral uptake attenuate its therapeutic efficacy. Here we developed an EDV-encapsulated agonistic micelle (EDV-AM) to specifically deliver EDV into brain ischemia by actively tuning blood-brain barrier (BBB) permeability. The EDV-AM actively up-regulated endothelial monolayer permeability in vitro. HPLC studies showed that EDV-AM delivered more EDV into brain ischemia than free EDV after intravenous injection. Magnetic resonance imaging also demonstrated that EDV-AM more rapidly salvaged ischemic tissue than free EDV. Diffusion tensor imaging indicated the highest efficiency of EDV-AM in accelerating axonal remodeling in the ipsilesional white matter and improving functional behaviors of ischemic stroke models. The agonistic micelle holds promise to improve the therapeutic efficiency of ischemic stroke patients who miss the thrombolytic treatment.

Ischemic stroke: experimental models and reality

The vast majority of cerebral stroke cases are caused by transient or permanent occlusion of a cerebral blood vessel (“ischemic stroke”) eventually leading to brain infarction. The final infarct size and the neurological outcome depend on a multitude of factors such as the duration and severity of ischemia, the existence of collateral systems and an adequate systemic blood pressure, etiology and localization of the infarct, but also on age, sex, comorbidities with the respective multimedication and genetic background. Thus, ischemic stroke is a highly complex and heterogeneous disorder. It is immediately obvious that experimental models of stroke can cover only individual specific aspects of this multifaceted disease. A basic understanding of the principal molecular pathways induced by ischemia-like conditions comes already from in vitro studies. One of the most frequently used in vivo models in stroke research is the endovascular suture or filament model in rodents with occlusion of the middle cerebral artery (MCA), which causes reproducible infarcts in the MCA territory. It does not require craniectomy and allows reperfusion by withdrawal of the occluding filament. Although promptly restored blood flow is far from the pathophysiology of spontaneous human stroke, it more closely mimics the therapeutic situation of mechanical thrombectomy which is expected to be increasingly applied to stroke patients. Direct transient or permanent occlusion of cerebral arteries represents an alternative approach but requires craniectomy. Application of endothelin-1, a potent vasoconstrictor, allows induction of transient focal ischemia in nearly any brain region and is frequently used to model lacunar stroke. Circumscribed and highly reproducible cortical lesions are characteristic of photothrombotic stroke where infarcts are induced by photoactivation of a systemically given dye through the intact skull. The major shortcoming of this model is near complete lack of a penumbra. The two models mimicking human stroke most closely are various embolic stroke models and spontaneous stroke models. Closeness to reality has its price and goes along with higher variability of infarct size and location as well as unpredictable stroke onset in spontaneous models versus unpredictable reperfusion in embolic clot models.

Synthesis and Evaluation of Neuroprotective Selenoflavanones

The physicochemical properties and antioxidant activity of a molecule could be improved by the substitution of an oxygen atom in a molecule with selenium. We synthesized selenoflavanones and flavanones to evaluate their neuroprotective effects. The selenoflavanones showed improved physicochemical properties, suggestive of the ability to pass through the blood-brain barrier (BBB). They showed in vitro antioxidant effects against hydrogen peroxide, and did not result in severe cytotoxicity. Moreover, infarction volumes in a transient ischemia mouse model were significantly reduced by the selenoflavanone treatments.

Salvaging brain ischemia by increasing neuroprotectant uptake via nanoagonist mediated blood brain barrier permeability enhancement

Ischemic stroke is a leading cause of adult disability and cognitive impairment worldwide. Neuroprotective therapy aims to save neurons by impeding the deleterious ischemic insults. However, the low efficiency of the neuroprotectants crossing blood brain barrier (BBB) prevents their clinical translation. In this work, a nanoagonist (NA) was developed to enhance neuroprotectant uptake by specifically increasing BBB permeability in brain ischemia. This NA first targeted ischemic brain vasculatures, temporarily opened local BBB by activating adenosine 2A receptors, and up-regulated the neuroprotectant uptake in brain ischemia. This NA significantly increased the delivery of superoxide dismutase (SOD), a free radical scavenger, into mouse brain ischemia. The combined treatment of NA/SOD achieved a five-fold ischemic volume reduction rate compared to the animal models treated with SOD alone. Non-invasive magnetic resonance imaging (MRI) confirmed the ischemia targeted BBB opening, increased brain drug delivery efficiency and up-regulated therapeutic response during the combined NA/SOD treatment. Since the inefficient brain drug delivery is a general problem for the treatment of central nervous system (CNS) diseases, this work provides a novel strategy to deliver therapeutics by crossing BBB with high efficiency and targeting specificity.

Oxygen therapy does not increase production and damage induced by reactive oxygen species in focal cerebral ischemia

Oxygen therapy with hyperbaric oxygen (HBO) or normobaric hyperoxia (NBO) improves outcome in experimental cerebral ischemia. However, an increased formation of reactive oxygen species (ROS) may be an undesirable side effect of oxygen therapy. We investigated the effect of both oxygen therapies on ROS production and adverse effects in murine focal ischemia. 25 min after 90 min filament-induced middle cerebral artery occlusion (MCAO), mice breathed either air, 100% O2 (NBO), or 100% O2 at 3 ata (HBO) for 60 min. ROS were depicted on tissue sections after preischemic injection of hydroethidine, a marker of in vivo superoxide production. Moreover, infarct sizes were quantified in experiments using peroxybutinitrite (PBN) in mice treated with HBO. Effects of oxygen therapy were also tested in superoxide 2 knock-out mice. Both NBO and HBO significantly reduced superoxide radicals compared to air. Application of PBN had no additional protective effect when combined with HBO. Infarct volumes did not differ among SOD2 knock-out mice receiving air (34.0 ± 19.6mm(3)), NBO (35.4 ± 14.3mm(3)) or HBO (33.4 ± 12.2mm(3)). In conclusion, brief episodes of oxygen therapy do not appear to promote damage inflicted by ROS in experimental stroke.

Electrophysiological and metabolic effects of CHF5074 in the hippocampus: protection against in vitro ischemia

CHF5074 is a non-steroidal anti-inflammatory derivative holding disease-modifying potential for the treatment of Alzheimer's disease. The aim of the present study was to characterize the electrophysiological and metabolic profile of CHF5074 in the hippocampus. Electrophysiological recordings show that CHF5074 inhibits in a dose-dependent manner the current-evoked repetitive firing discharge in CA1 pyramidal neurons. This result is paralleled by a dose-dependent reduction of field excitatory post-synaptic potentials with no effect on the paired-pulse ratio. The effects of CHF5074 were not mediated by AMPA or NMDA receptors, since the inward currents induced by local applications of AMPA and NMDA remained constant in the presence of this compound. We also suggest a possible activity of CHF5074 on ASIC1a receptor since ASIC1a-mediated current, evoked by application of a pH 5.5 solution, is reduced by pretreatment with this compound. Moreover, we demonstrate that CHF5074 treatment is able to counteract in hippocampal slices the OGD-induced increase in alanine, lactate and acetate levels. Finally, CHF5074 significantly reduced the apoptosis in hippocampal neurons exposed to OGD, as revealed by cleaved-caspase-3 immunoreactivity and TUNEL staining. Overall, the present work identifies novel mechanisms for CHF5074 in reducing metabolic acidosis, rendering this compound potentially useful also in conditions of brain ischemia.

In vivo diagnostic imaging using micro-CT: sequential and comparative evaluation of rodent models for hepatic/brain ischemia and stroke

Background

There is an increasing need for animal disease models for pathophysiological research and efficient drug screening. However, one of the technical barriers to the effective use of the models is the difficulty of non-invasive and sequential monitoring of the same animals. Micro-CT is a powerful tool for serial diagnostic imaging of animal models. However, soft tissue contrast resolution, particularly in the brain, is insufficient for detailed analysis, unlike the current applications of CT in the clinical arena. We address the soft tissue contrast resolution issue in this report.

Methodology

We performed contrast-enhanced CT (CECT) on mouse models of experimental cerebral infarction and hepatic ischemia. Pathological changes in each lesion were quantified for two weeks by measuring the lesion volume or the ratio of high attenuation area (%HAA), indicative of increased vascular permeability. We also compared brain images of stroke rats and ischemic mice acquired with micro-CT to those acquired with 11.7-T micro-MRI. Histopathological analysis was performed to confirm the diagnosis by CECT.

Principal Findings

In the models of cerebral infarction, vascular permeability was increased from three days through one week after surgical initiation, which was also confirmed by Evans blue dye leakage. Measurement of volume and %HAA of the liver lesions demonstrated differences in the recovery process between mice with distinct genetic backgrounds. Comparison of CT and MR images acquired from the same stroke rats or ischemic mice indicated that accuracy of volumetric measurement, as well as spatial and contrast resolutions of CT images, was comparable to that obtained with MRI. The imaging results were also consistent with the histological data.

Conclusions

This study demonstrates that the CECT scanning method is useful in rodents for both quantitative and qualitative evaluations of pathologic lesions in tissues/organs including the brain, and is also suitable for longitudinal observation of the same animals.

Oxidative stress and its role in the pathogenesis of ischaemic stroke

Stroke is one of the leading causes of mortality and morbidity, with astronomical financial repercussions on health systems worldwide. Ischaemic stroke accounts for approximately 80-85% of all cases and is characterised by the disruption of cerebral blood flow and lack of oxygen to the affected area. Oxidative stress culminates due to an imbalance between pro-oxidants and antioxidants and consequent excessive production of reactive oxygen species. Reactive oxygen species are biphasic, playing a role in normal physiological processes and are also implicated in a number of disease processes, whereby they mediate damage to cell structures, including lipids, membranes, proteins, and DNA. The cerebral vasculature is a major target of oxidative stress playing a critical role in the pathogenesis of ischaemic brain injury following a cerebrovascular attack. Superoxide, the primary reactive oxygen species, and its derivatives have been shown to cause vasodilatation via the opening of potassium channels and altered vascular reactivity, breakdown of the blood-brain barrier and focal destructive lesions in animal models of ischaemic stroke. However, reactive oxygen species are involved in normal physiological processes including cell signalling, induction of mitogenesis, and immune defence. Primarily, this review will focus on the cellular and vascular aspects of reactive oxygen and nitrogen species generation and their role in the pathogenesis of ischaemia-reperfusion phenomena. Secondly, the proposed mechanisms of oxidative stress-related neuronal death will be reflected upon and in summation specific targeted neuroprotective therapies targetting oxidative stress and their role in the pathogenesis of stroke will be discussed.

The adenoviral vector-mediated increase in apurinic/apyrimidinic endonuclease inhibits the induction of neuronal cell death after transient ischemic stroke in mice

Despite the correlation between changes in the levels of apurinic/apyrimidinic endonuclease and ischemic neuronal damage, no studies have addressed the question of whether increased APE/Ref-1 can prevent ischemic neuronal cell death in vivo. Using an adenoviral vector, we investigated whether increased APE/Ref-1 can inhibit the loss of APE/Ref-1 and thereby prevent oxidative DNA damage after transient focal cerebral ischemia. Mice were subjected to intraluminal suture occlusion of the middle cerebral artery for 1 h, followed by reperfusion. Pre-ischemic treatment of the adenoviral vector was introduced intracerebrally. An adenoviral vector harboring the entire APE/Ref-1 gene sequence or a control virus without the APE/Ref-1 sequence was introduced 3 days before ischemia/reperfusion (I/R). The reduction of APE/Ref-1 occurred before DNA fragmentation, which was shown by temporal and spatial analysis. Increased APE/Ref-1 significantly decreased DNA damage and infarct volume after I/R. In conclusion, increased APE/Ref-1 enhanced DNA repair and inhibited the induction of ischemic oxidative DNA damage and cerebral infarction after I/R.

Methazolamide and melatonin inhibit mitochondrial cytochrome C release and are neuroprotective in experimental models of ischemic injury

BACKGROUND AND PURPOSE

The identification of a neuroprotective drug for stroke remains elusive. Given that mitochondria play a key role both in maintaining cellular energetic homeostasis and in triggering the activation of cell death pathways, we evaluated the efficacy of newly identified inhibitors of cytochrome c release in hypoxia/ischemia induced cell death. We demonstrate that methazolamide and melatonin are protective in cellular and in vivo models of neuronal hypoxia.

METHODS

The effects of methazolamide and melatonin were tested in oxygen/glucose deprivation-induced death of primary cerebrocortical neurons. Mitochondrial membrane potential, release of apoptogenic mitochondrial factors, pro-IL-1beta processing, and activation of caspase -1 and -3 were evaluated. Methazolamide and melatonin were also studied in a middle cerebral artery occlusion mouse model. Infarct volume, neurological function, and biochemical events were examined in the absence or presence of the 2 drugs.

RESULTS

Methazolamide and melatonin inhibit oxygen/glucose deprivation-induced cell death, loss of mitochondrial membrane potential, release of mitochondrial factors, pro-IL-1beta processing, and activation of caspase-1 and -3 in primary cerebrocortical neurons. Furthermore, they decrease infarct size and improve neurological scores after middle cerebral artery occlusion in mice.

CONCLUSIONS

We demonstrate that methazolamide and melatonin are neuroprotective against cerebral ischemia and provide evidence of the effectiveness of a mitochondrial-based drug screen in identifying neuroprotective drugs. Given the proven human safety of melatonin and methazolamide, and their ability to cross the blood-brain-barrier, these drugs are attractive as potential novel therapies for ischemic injury.

Molecular mechanism for neuro-protective effect of prosaposin against oxidative stress: its regulation of dimeric transcription factor formation

Prosaposin triggers G-protein-coupled receptor (GPCR)-mediated protein kinase B (Akt)/extracellular signal-regulated kinase (ERK) phosphorylation cascades to exert its neurotrophic and myelinotrophic activity capable of preventing neural cell death and promoting neural proliferation and glial differentiation. In the present study, we investigated the down-stream neurotrophic signaling mechanism of prosaposin by which rat pheochromocytoma (PC-12) cells are protected from cell death induced by oxidative stress. When PC-12 cells were exposed to H2O2, the cells underwent abrupt shrinkage followed by apoptosis. Prosaposin treatment at as low as 1 nM protected PC-12 cells from cell death by the oxidative stress with the activation of an ERK phosphorylation cascade. Simultaneously, prosaposin blocked the oxidative stress induced-Akt phosphorylation that acts on the down-stream of caspase-3 activation. A MEK inhibitor, PD98059, or a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, abolished the survival effect of prosaposin on the oxidative stress-induced cell death. Furthermore, prosaposin blocked the oxidative stress-induced phosphorylations of c-Jun N-terminal kinase (JNK) and p38 stress-activated protein kinase. We further investigated the effect of prosaposin treatment on the phosphorylation of activating protein-1 (AP-1) complex components, c-Jun and activating transcription factor (ATF)-3. Western blot analysis demonstrated that prosaposin treatment at 100 ng/ml decreased the levels of c-Jun and ATF-3 induced by H2O2 stimulation. Our results suggest that prosaposin aids survival of PC-12 cells from oxidative stress not only by reducing the phosphorylation levels of JNK and p38, but also by regulating the c-Jun/AP-1 pathway.

Tamoxifen neuroprotection in cerebral ischemia involves attenuation of kinase activation and superoxide production and potentiation of mitochondrial superoxide dismutase

The purpose of this study was to enhance our understanding of the mechanisms of neuronal death after focal cerebral ischemia and the neuroprotective effects of tamoxifen (TMX). The phosphorylation state of 31 protein kinases/signaling proteins and superoxide anion (O(2)(-)) production in the contralateral and ipsilateral cortex was measured after permanent middle cerebral artery occlusion (pMCAO) in ovariectomized rats treated with placebo or TMX. The study revealed that pMCAO modulated the phosphorylation of a number of kinases/proteins in the penumbra at 2 h after pMCAO. Of significant interest, phospho-ERK1/2 (pERK1/2) was elevated significantly after pMCAO. TMX attenuated the elevation of pERK1/2, an effect correlated with reduced infarct size. In situ detection of O(2)(-) production showed a significant elevation at 1-2 h after pMCAO in the ischemic cortex with enhanced oxidative damage detected at 24 h. ERK activation may be downstream of free radicals, a suggestion supported by the findings that cells positive for O(2)(-) had high pERK activation and that a superoxide dismutase (SOD) mimetic, tempol, significantly attenuated pERK activation after MCAO. TMX treatment significantly reduced the MCAO-induced elevation of O(2)(-) production, oxidative damage, and proapoptotic caspase-3 activation. Additionally, pMCAO induced a significant reduction in the levels of manganese SOD (MnSOD), which scavenge O(2)(-), an effect largely prevented by TMX treatment, thus providing a potential mechanistic basis for the antioxidant effects of TMX. As a whole, these studies suggest that TMX neuroprotection may be achieved via an antioxidant mechanism that involves enhancement of primarily MnSOD levels, with a corresponding reduction of O(2)(-) production, and downstream kinase and caspase-3 activation.

Effects of leptin on stress-induced changes of caspases in rat gastric mucosa

BACKGROUND

In this study, we investigated the effect of leptin on caspase-3, caspase-8, and caspase-9 immunoreactivity and lipid peroxidation in the stomachs of rats exposed to cold-restraint stress.

METHODS

Thirty-two male Wistar Albino rats were used. Rats pretreated with leptin (10 microg/kg per day for 7 days) were restrained in a wire cage for 4 h at 4 degrees C. Spectrophotometric techniques were used for detection of malondialdehyde (MDA) and glutathione (GSH) levels, and immunoreactivity of caspases was investigated by immunohistochemistry.

RESULTS

While the stomach MDA level of the cold-restraint stress group was increased significantly, the level of GSH was decreased when compared with the control group. Caspase-9 and caspase-3 immunoreactivities of the stress group were not changed, while caspase-8 immunoreactivity was decreased. Leptin administration prevented the increase in the MDA level and the decrease in the GSH content of the gastric mucosa in animals subjected to stress. Leptin administration produced no significant change in caspase-8 immunoreactivity but caused a decrease in caspase-3 immunoreactivity.

CONCLUSIONS

Cold-restraint stress decreases the antioxidant capacity of stomach tissue while activating oxidants, and induces apoptosis by an increase in caspase immunoreactivity. The presence of leptin reverses these mechanisms and suppresses the apoptosis.

NEUROPROTECTIVE EFFECTS OF DAURICINE AGAINST APOPTOSIS INDUCED BY TRANSIENT FOCAL CEREBRAL ISCHAEMIA IN RATS VIA A MITOCHONDRIAL PATHWAY

1. Previous experimental studies have shown that dauricine can protect the brain against ischaemic damage, but the underlying mechanisms remain unknown. In the present study, we examined whether dauricine inhibits neuronal apoptosis in the penumbra in a rat model of transient focal cerebral ischaemia. 2. Male Wistar rats underwent a 90 min temporary occlusion of the middle cerebral artery. Dauricine (21, 42 and 84 mg/kg) was administered by intragastric gavage twice a day for 3 days before ischaemia. Rats were killed and brain samples were collected 24 h after ischaemia. Histopathological outcome was evaluated by haematoxylin-eosin staining. Apoptotic changes were evaluated by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) for DNA fragmentation. The mitochondrial pathway was explored using immunohistochemistry for cytochrome c release, caspase 9 and caspase 3 activation, as well as by reverse transcription-polymerase chain reaction for determination of caspase 9 and caspase 3 mRNA expression. 3. Cytochrome c release, activation of caspase 9 and caspase 3 and DNA fragmentation were detected 24 h after ischaemia. Dauricine (42 and 84 mg/kg) pretreatment improved histopathological recovery, diminished DNA fragmentation and reduced cytochrome c release and activation of caspase 9 and caspase 3 in the penumbra at 24 h. 4. These findings suggest that dauricine attenuates apoptosis in the penumbra after transient focal cerebral ischaemia. The infarct-reducing effects of dauricine may be due, in part, to the inhibition of apoptotic cell death via a mitochondrial pathway in the penumbra.

THE SPECIFIC FREE RADICAL SCAVENGER EDARAVONE SUPPRESSES BLEOMYCIN-INDUCED ACUTE PULMONARY INJURY IN RABBITS

1. Intratracheal instillation of bleomycin induces a condition in rabbits that serves as a useful model of human pulmonary fibrosis. Bleomycin-induced production of reactive oxygen species leads to acute lung inflammation and induction of apoptosis, which is followed by pulmonary fibrosis at a later chronic stage. In the present study, we tested whether edaravone, a free radical scavenger, would suppress bleomycin-induced acute pulmonary inflammation. 2. Rabbits were divided into three groups (n = 10 in each): (i) a bleomycin-treated group, which received intratracheal instillation of 2 mg/kg bleomycin; (ii) a bleomycin + edaravone group, which received a 10 day regimen of daily intravenous injections of edaravone (3 mg/kg per day) beginning 3 days before bleomycin instillation; and (iii) a saline control group. Rabbits were killed for analysis 7 days after bleomycin administration. 3. In lung tissues from the bleomycin-treated group, marked infiltration of inflammatory cells, consisting mainly of lymphocytes, neutrophils and eosinophils, was observed. In addition, significantly increased numbers of TUNEL-positive (apoptotic) and transforming growth factor-beta-positive cells were seen. All these effects were significantly attenuated by treatment with edaravone. 4. The findings of the present study suggest that edaravone may be useful in the prevention of acute lung injury resulting from the production of reactive oxygen species.

Interrupting reperfusion as a stroke therapy: ischemic postconditioning reduces infarct size after focal ischemia in rats

Cerebral ischemic preconditioning protects against stroke, but is clinically feasible only when the occurrence of stroke is predictable. Reperfusion plays a critical role in cerebral injury after stroke; we tested the hypothesis that interrupting reperfusion lessens ischemic injury. We found for the first time that such postconditioning with a series of mechanical interruptions of reperfusion significantly reduces ischemic damage. Focal ischemia was generated by permanent distal middle cerebral artery (MCA) occlusion plus transient bilateral common carotid artery (CCA) occlusion. After 30 secs of CCA reperfusion, ischemic postconditioning was performed by occluding CCAs for 10 secs, and then allowing for another two cycles of 30 secs of reperfusion and 10 secs of CCA occlusion. Infarct size was measured 2 days later. Cerebral blood flow (CBF) was measured in animals subjected to permanent MCA occlusion plus 15 mins of bilateral CCA occlusion, which demonstrates that postconditioning disturbed the early hyperemia immediately after reperfusion. Postconditioning dose dependently reduced infarct size in animals subjected to permanent MCA occlusion combined with 15, 30, and 60 mins of bilateral CCA occlusion, by reducing infarct size approximately 80%, 51%, and 17%, respectively. In addition, postconditioning blocked terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling-positive staining, a marker of apoptosis, in the penumbra 2 days after stroke. Furthermore, in situ superoxide detection using hydroethidine suggested that postconditioning attenuated superoxide products during early reperfusion after stroke. In conclusion, postconditioning reduced infarct size, most plausibly by blocking apoptosis and free radical generation. With further study it may eventually be clinically applicable for stroke treatment.

Rodent models of focal stroke: size, mechanism, and purpose

Rodent stroke models provide the experimental backbone for the in vivo determination of the mechanisms of cell death and neural repair, and for the initial testing of neuroprotective compounds. Less than 10 rodent models of focal stroke are routinely used in experimental study. These vary widely in their ability to model the human disease, and in their application to the study of cell death or neural repair. Many rodent focal stroke models produce large infarcts that more closely resemble malignant and fatal human infarction than the average sized human stroke. This review focuses on the mechanisms of ischemic damage in rat and mouse stroke models, the relative size of stroke generated in each model, and the purpose with which focal stroke models are applied to the study of ischemic cell death and to neural repair after stroke.

Apoptotic cell death progression after photothrombotic focal cerebral ischaemia: effects of the lipophilic iron chelator 2,2'-dipyridyl

Two different forms of cell death have been distinguished morphologically following cerebral ischaemia: necrotic and apoptotic cell death. The aim of this study was to investigate the contribution of apoptosis to ischaemic damage by carefully depicting the temporal and spatial neuronal death following focal ischaemia. For this purpose, rats were subjected to chemical photothrombosis, and histological and biochemical analyses were performed over a period of 24 h after the onset of ischaemia. In addition, the effects of the lipophilic antioxidant iron chelator 2,2'-dipyridyl (DP) were evaluated 24 h after photothrombosis when the lesion volume was maximal. Our results showed two separate waves of neuronal death. In the first wave, shrunken dark neurons were massively present as early as 2 h after photothrombosis in the infarct core. From this initial neuronal abnormal population, progressive and time-dependent changes of both necrotic and apoptotic cell death were observed, leading to ghost neurons and apoptotic bodies after 24 h. The extension of the lesion coincided with a second wave of cell death. Massive and rapid neuronal loss occurred at the infarct border, which appeared as a sharply demarcated pale region. Procaspase and poly(ADP-ribose) polymerase-1 (PARP-1) cleavages were also detected in the infarct core and surrounding damaged tissue. DP treatment markedly blocked the enlargement of the lesion, the infarct border being rescued from infarction. Furthermore, a large decrease of apoptotic bodies was associated with a significant drop of caspase and PARP-1 cleavages, suggesting that the protective effect of DP closely correlates with limitation of apoptosis expansion.

Anti-apoptotic and neuroprotective effects of edaravone following transient focal ischemia in rats

To investigate the effect of an antioxidant edaravone on the apoptotic process, we examined Bax and Bcl-2 immunohistochemical expression and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) reactivity. Rat focal ischemia models were prepared by 2 h transient middle cerebral artery occlusion. Edaravone or physiological saline was intravenously administered after reperfusion. After 24 h of reperfusion, infarction volume assessments, Bax and Bcl-2 immunohistochemistry and TUNEL staining were performed as well as neurological evaluation. Cortical cerebral blood flow was not statistically different between the treatment-groups. Edaravone-treated animals showed significantly improved neurological outcome. Total and cortical infarct volumes in the edaravone group significantly decreased. In addition, edaravone-treatment provided a significant reduction in the number of TUNEL-positive apoptotic cells, a decrease in Bax immunoreactivity and an increase in Bcl-2 expression within the peri-infarct area. Edaravone shows an excellent neuroprotective effect against ischemia/reperfusion brain injury through a Bax/Bcl-2 dependent anti-apoptotic mechanism.

Krypton laser-induced photothrombotic distal middle cerebral artery occlusion without craniectomy in mice

Recent advances in genetical engineering of the mouse have highlighted the importance of reproducible and less invasive models of cerebral ischemia in mice. In this paper, we developed minimally invasive and reproducible model of distal middle cerebral artery (MCA) occlusion in mice using krypton (Kr) laser-induced photothrombosis. C57BL/6 or BALB mice (n=8 each) were anesthetized with halothane. The skin was cut, the temporal muscle was retracted, and the right distal MCA was observed through the skull. A Kr laser beam of wavelength 568 nm was focused onto the MCA over the intact skull. Upon laser irradiation, intravenous administration of a rose bengal solution was begun. After 4 min of irradiation, the laser beam was refocused on the MCA just proximal to the first spot, and another 4-min irradiation was performed. Then, the right common carotid artery (CCA) was ligated. Three days later, the brain was removed, and infarct volume was determined. Infarction confined almost solely to the cortical area was produced in each mouse. Mean infarct volume in C57BL/6 mice was 25.2+/-13.7 mm3. The BALB mice group showed significantly larger and more reproducible infarction (44.1+/-5.2 mm3; the coefficient of variation was 12%) than did C57BL/6 mice (P<0.005). Our photothrombosis model of stroke in mice can be performed without craniectomy, and its reproducibility is satisfactory when using BALB mice.

Cytoprotective Efficacy and Mechanisms of the Liposoluble Iron Chelator 2,2′-Dipyridyl in the Rat Photothrombotic Ischemic Stroke Model

We examined the efficacy of the liposoluble iron chelator 2,2'-dipyridyl (DP) in reducing histological damage in rats submitted to cerebral ischemia and the mechanisms involved in the potential cytoprotection. For this purpose, DP (20 mg/kg, i.p.) was administered 15 min before and 1 h after induction of cortical photothrombotic vascular occlusion in rat. Histological studies were performed to assess infarct volume (at days 1 and 3 postischemia) and astromicroglial activation (at day 3 postischemia). Damage to endothelial and neuronal cells was evaluated at day 1 postischemia by quantitative measurements of Evans Blue extravasation and N-acetylaspartate levels, respectively. Cerebral blood flow was recorded in the ischemic core by laser-Doppler flowmetry within the 15 min to 2 h period after photothrombosis. At 4-h postischemia, radical oxygen species (ROS) production was evaluated by measuring brain glutathione concentrations. The cortical expression of the proteins heme oxygenase-1 (HO-1) and hypoxia-inducible factor-1alpha (HIF-1alpha) was analyzed by Western blotting at day 1 postischemia. Infarct volume and ischemic damage to endothelial and neuronal cells were significantly reduced by DP treatment. This cytoprotection was associated with a reduction in ROS production, perfusion deficits, and astrocytic activation. DP treatment also resulted in significant changes in HO-1 (+100%) and HIF-1alpha (-50%) protein expression at the level of the ischemic core. These results report the efficacy of the liposoluble iron chelator DP in reducing histological damage induced by permanent focal ischemia.

Lidocaine attenuates apoptosis in the ischemic penumbra and reduces infarct size after transient focal cerebral ischemia in rats

Lidocaine is a local anesthetic and antiarrhythmic agent. Although clinical and experimental studies have shown that an antiarrhythmic dose of lidocaine can protect the brain from ischemic damage, the underlying mechanisms are unknown. In the present study, we examined whether lidocaine inhibits neuronal apoptosis in the penumbra in a rat model of transient focal cerebral ischemia. Male Wistar rats underwent a 90-min temporary occlusion of middle cerebral artery. Lidocaine was given as an i.v. bolus (1.5 mg/kg) followed by an i.v. infusion (2 mg/kg/h) for 180 min, starting 30 min before ischemia. Rats were killed and brain samples were collected at 4 and 24 h after ischemia. Apoptotic changes were evaluated by immunohistochemistry for cytochrome c release and caspase-3 activation and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) for DNA fragmentation. Cytochrome c release and caspase-3 activation were detected at 4 and 24 h after ischemia and DNA fragmentation was detected at 24 h. Double-labeling with NeuN, a neuronal marker, demonstrated that cytochrome c, caspase-3, and TUNEL were confined to neurons. Lidocaine reduced cytochrome c release and caspase-3 activation in the penumbra at 4 h and diminished DNA fragmentation in the penumbra at 24 h. Lidocaine treatment improved early electrophysiological recovery and reduced the size of the cortical infarct at 24 h, but had no significant effect on cerebral blood flow in either the penumbra or core during ischemia. These findings suggest that lidocaine attenuates apoptosis in the penumbra after transient focal cerebral ischemia. The infarct-reducing effects of lidocaine may be due, in part, to the inhibition of apoptotic cell death in the penumbra.

Neurodegeneration in striatum induced by the mitochondrial toxin 3-nitropropionic acid: role of matrix metalloproteinase-9 in early blood-brain barrier disruption?

Blood-brain barrier (BBB) dysfunction is a potential mechanism involved in progressive striatal damage induced by the mitochondrial excitotoxin, 3-nitropropionic acid (3-NP). After activation by proteases and free radicals, matrix metalloproteinases (MMPs), particularly MMP-9 and -2, can digest the endothelial basal lamina leading to BBB opening. Using CD-1 mice, we show that MMP-9 expression by zymography is increased in the injured striatum compared with the contralateral striatum 2 hr after 3-NP injection [133.50 +/- 57.17 vs 50.25 +/- 13.56; mean +/- SD of optical densities in arbitrary units (A.U.); p < 0.005] and remains elevated until 24 hr (179.33 +/- 78.24 A.U.). After 4 hr, MMP-9 expression and activation are accompanied by an increase in BBB permeability. MMP inhibition attenuates BBB disruption, swelling, and lesion volume compared with vehicle-treated controls. There is a clear spatial relationship between MMP-9 expression and oxidized hydroethidine, indicating reactive oxygen species (ROS) production. Furthermore, transgenic mice that overexpress copper/zinc-superoxide dismutase (SOD1) show decreased lesion size and edema along with decreased immunoreactivity for MMP-9, compared with wild-type littermates (lesion: 38.8 +/- 15.1 and 53.3 +/- 10.3, respectively, p < or = 0.05; edema: 21.8 +/- 11.2 and 35.28 +/- 11, respectively, p < or = 0.05; MMP-9-positive cells: 352 +/- 57 and 510 +/- 45, respectively, p < or = 0.005), whereas knock-out mice deficient in SOD1 display significantly greater swelling (48.65 +/- 17; p < or = 0.05). We conclude that early expression and activation of MMP-9 by ROS may be involved in early BBB disruption and progressive striatal damage after 3-NP treatment.

Overexpression of SOD1 protects vulnerable motor neurons after spinal cord injury by attenuating mitochondrial cytochrome c release

Defective Cu,Zn-superoxide dismutase (SOD1) is responsible for some types of amyotrophic lateral sclerosis, and ventral horn motor neurons (VMN) have been shown to die through a mitochondria-dependent apoptotic pathway after chronic exposure to high levels of reactive oxygen species (ROS). VMN are also selectively vulnerable to mild spinal cord injury (SCI); however, the involvement of SOD1, ROS, and apoptosis in their death has not been clarified. Mild compression SCI was induced in SOD1-overexpressing transgenic rats and wild-type littermates. Superoxide production, mitochondrial release of cytochrome c, and activation of caspase-9 were examined, and apoptotic DNA injury was also characterized. In the wild-type animals, increased superoxide production, mitochondrial release of cytochrome c, and cleaved caspase-9 were observed exclusively in VMN after SCI. Subsequently, a majority of VMN (75%) selectively underwent delayed apoptotic cell death. Transgenic animals showed less superoxide production, mitochondrial cytochrome c release, and caspase-9 activation, resulting in death of only 45% of the VMN. These results suggest that the ROS-initiated mitochondrial signaling pathway possibly plays a pivotal role in apoptotic VMN death after SCI and that increased levels of SOD1 in VMN reduce oxidative stress, thereby attenuating the activation of the pathway and delayed cell death.

Analysis of mitochondrial free radical generation in animal models of neuronal disease

Mitochondria, the power plant of all eukaryotic cells, produce cellular energy in the form of ATP via electron transport and oxidative phosphorylation. However, the mitochondria leak electrons that can act as major sources of oxidative stress, and their dysfunction, have been proposed as causative events underlying neurodegeneration in stroke and neurodegenerative diseases. We examined whether MitoTracker Red CM-H(2)XRos, a rosamine derivative used to detect mitochondrial free radicals in vitro, would be applied to analyze the mitochondrial free radicals in various models of neurological diseases in vivo. The injections of MitoTracker Red CM-H(2)XRos revealed generation of mitochondrial free radicals primarily in vulnerable neurons following focal cerebral ischemia as well as administration of Fe(2+) or 3-nitropropionic acid. MitoTracker Red CM-H(2)XRos was retained after fixation, compatible with immunocytochemistry or nuclear staining, and can be applied to study roles of mitochondrial free radicals in the process of neurodegeneration in vivo.

Involvement of superoxide in excitotoxicity and DNA fragmentation in striatal vulnerability in mice after treatment with the mitochondrial toxin, 3-nitropropionic acid

Oxidative stress and excitotoxicity have been implicated in selective striatal vulnerability caused by the mitochondrial toxin, 3-nitropropionic acid (3-NP), which may simulate Huntington's disease in animals and humans. The detailed mechanism of the role of superoxide in striatal vulnerability induced by 3-NP is still unknown. The authors investigated oxidative cellular injury and DNA fragmentation after systemic 3-NP injection in wild-type (Wt) mice and mutant mice with a deficiency in manganese superoxide dismutase (MnSOD; Sod2 -/+). Furthermore, they investigated the effects of decortication after 3-NP treatment in Sod2 -/+ mice, and copper/zinc SOD (CuZnSOD) treatment in recently developed Sod2 -/+ mice that overexpress CuZnSOD (SOD1 +/- / Sod2 -/+ mice). Oxidized hydroethidine, 8-hydroxyguanosine immunoreactivity, and nitrotyrosine immunoreactivity were increased in the Sod2 -/+ mice compared with the Wt mice after 3-NP treatment (P < 0.001). Decortication completely abolished oxidative striatal damage after 3-NP treatment in the Sod2 -/+ mice. Increased CuZnSOD attenuated DNA fragmentation and striatal lesion volume after 3-NP treatment in the Sod2 -/+ mice (P < 0.001). These data suggest that production of superoxide may be a critical step to excitotoxicity and subsequent DNA fragmentation in selective striatal vulnerability after 3-NP treatment.

Manganese superoxide dismutase deficiency exacerbates cerebral infarction after focal cerebral ischemia/reperfusion in mice: implications for the production and role of superoxide radicals

BACKGROUND AND PURPOSE

Superoxide anion radicals (O2*-) are implicated in ischemia/reperfusion injury, although a direct relationship has not been elucidated. Recently, a specific method of hydroethidine (HEt) oxidation by O2*- was developed to detect O2*- production in a variety of experimental brain injury models. To clarify the role of O2*- in the mechanism of ischemia/reperfusion, we investigated O2*- production after ischemia/reperfusion and ischemia/reperfusion injury in mutant mice deficient in mitochondrial manganese superoxide dismutase (MnSOD) and in wild-type littermates.

METHODS

Ischemia/reperfusion was performed for 60 minutes using intraluminal suture blockade of the middle cerebral artery in the mutant or wild-type mice. We evaluated fluorescent kinetics of HEt or ethidium, the oxidized form of HEt, in brains after an intravenous injection of HEt, followed by measurement of cellular O2*- production using specific HEt oxidation by O2*- before and after ischemia/reperfusion. Furthermore, we compared O2*- production and subsequent infarct volume in the mice using triphenyltetrazolium chloride after ischemia/reperfusion.

RESULTS

HEt oxidation to ethidium is primarily a result of mitochondrially produced O2*- under physiological conditions. Cerebral ischemia/reperfusion produced O2*- prominently in neurons shortly after reperfusion, followed by a delayed increase in endothelial cells. A deficiency in MnSOD in mutant mice increased mitochondrial O2*- production and exacerbated cerebral infarction, worsening neurological deficits after ischemia/reperfusion.

CONCLUSION

These results suggest that mitochondrial O2*- production may be a critical step underlying the mechanism of ischemia/reperfusion injury and that MnSOD may protect against ongoing oxidative cell death after ischemia/reperfusion.

The cytosolic antioxidant, copper/zinc superoxide dismutase, attenuates blood-brain barrier disruption and oxidative cellular injury after photothrombotic cortical ischemia in mice

Oxidative stress has been associated with the development of blood-brain barrier disruption and cellular injury after ischemia. The cytosolic antioxidant, copper/zinc superoxide dismutase, has been shown to protect against blood-brain barrier disruption and infarction after cerebral ischemia-reperfusion. However, it is not clear whether copper/zinc superoxide dismutase can protect against evolving ischemic lesions after thromboembolic cortical ischemia. In this study, the photothrombotic ischemia model, which is physiologically similar to thromboembolic stroke, was used to develop cortical ischemia. Blood-brain barrier disruption and oxidative cellular damage were investigated in transgenic mice that overexpress copper/zinc superoxide dismutase and in littermate wild-type mice after photothrombotic ischemia, which was induced by both injection of erythrosin B (30 mg/kg) and irradiation using a helium neon laser for 3 min. Free radical production, particularly superoxide, was increased in the lesioned cortex as early as 4 h after ischemia using hydroethidine in situ detection. The transgenic mice showed a prominent decrease in oxidative stress compared with the wild-type mice. Blood-brain barrier disruption, evidenced by quantitation of Evans Blue leakage, occurred 1 h after ischemia and gradually increased up to 24 h. Compared with the wild-type mice, the transgenic mice showed less blood-brain barrier disruption, a decrease in oxidative DNA damage using 8-hydroxyguanosine immunohistochemistry, a subsequent decrease in DNA fragmentation using the in situ nick-end labeling technique, and decreased infarct volume after ischemia. From these results we suggest that superoxide anion radical is an important factor in blood-brain barrier disruption and oxidative cellular injury, and that copper/zinc superoxide dismutase could protect against the evolving infarction after thromboembolic cortical ischemia.

Generation of a constitutively active fragment of PKN in microglia/macrophages after middle cerebral artery occlusion in rats

PKN is a fatty acid- and Rho-activated serine/threonine kinase, which has a catalytic domain highly homologous to that of protein kinase C (PKC). Recent studies have demonstrated that PKN is proteolytically cleaved after apoptotic stimulation and then a constitutively active 55-kDa fragment is generated. However, the role of the 55-kDa fragment are poorly understood. Adult Sprague-Dawley (SD) rats underwent middle cerebral artery occlusion (MCAO), and the temporal and spatial changes in the fragmentation of PKN and of PKC delta were examined by immunoblotting. No proteolytic fragment of PKC delta (about 40 kDa) was detected. The 55-kDa fragment of PKN appeared transiently from 3 days after MCAO at the ipsilateral normal cortex. At the boundary zone of infarction, the 55-kDa fragment was markedly induced from day 5 then peaked on day 21 and persisted until day 28. Analysis of anti-phosphoserine immunoprecipitates with an anti-PKN antibody revealed phosphorylation of the 55-kDa band. Double staining for PKN and Ox42 was used to examine the source of the 55-kDa fragment. PKN immunoreactivity was significantly increased in Ox42-positive cells (microglia/hematogenous macrophages). No DNA laddering and only a few terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells were observed on day 14 in despite of the high level appearance of the 55-kDa band. These results suggest that the constitutively active 55-kDa fragment of PKN does not contribute to apoptosis, but may contribute to a function of microglia/macrophages.

Ebselen reduces cytochrome c release from mitochondria and subsequent DNA fragmentation after transient focal cerebral ischemia in mice

BACKGROUND AND PURPOSE

The seleno-organic compound ebselen has both antioxidant and anti-inflammatory properties. Although ebselen has been shown to protect the brain against stroke, it is unclear how ebselen provides neuroprotection. In the present study the authors examined whether ebselen inhibits neuronal apoptosis resulting from transient focal cerebral ischemia in mice. The cytochrome c release and DNA fragmentation, both of which are biochemical markers of apoptosis, were compared between vehicle- and ebselen-treated mice.

METHODS

Cerebral ischemia was induced by transient middle cerebral artery occlusion for 30 minutes in ICR mice under halothane anesthesia. Ebselen (10 mg/kg) was given orally twice, 30 minutes before ischemia and 12 hours after reperfusion. By Western blot analysis, we examined release of mitochondrial cytochrome c. To evaluate brain damage, the brain sections were treated for terminal deoxynucleotidyl transferase-mediated DNA nick-end labeling (TUNEL) and Nissl staining. Prolonged neuroprotective efficacy of ebselen was determined by counting neuronal nuclei (NeuN) immunopositive cells at 21 days after ischemia.

RESULTS

- Cytochrome c release was detected in the ischemic hemisphere at 3 to 24 hours after ischemia. Ebselen treatment diminished the cytochrome c release at 12 and 24 hours. In addition, ebselen decreased both DNA fragmentation determined by TUNEL and brain damage volume at 3 days after ischemia. Furthermore, ebselen increased the number of NeuN immunopositive cells at 21 days after ischemia.

CONCLUSIONS

These results indicate that ebselen attenuates ischemic neuronal apoptosis by inhibiting cytochrome c release. Ebselen may be a potential compound in stroke therapy.