Neuroprotective action of tacrolimus (FK506) in focal and global cerebral ischemia in rodents: dose dependency,therapeutic time window and long-term efficacy

Tacrolimus (FK506), a potent immunosuppressive drug, is effective in attenuating brain infarction after cerebral ischemia. However, there has been no report characterizing the neuroprotective action and therapeutic time window of tacrolimus systematically using different types of stroke models and extended observation periods. Therefore, we evaluated the neuroprotective effect of tacrolimus in three different animal models of cerebral ischemia: transient and permanent focal ischemia in rats and transient global ischemia in gerbils. Tacrolimus at doses higher than 0.1 mg/kg (i.v.) produced a statistically significant reduction in ischemic brain damage following permanent and transient focal ischemia in rats when administered immediately after the onset of ischemia. Tacrolimus (1 mg/kg, i.v.) demonstrated similar neuroprotective activity even after delayed administration (2 h after permanent or 1 h after transient focal ischemia). The neuroprotective effect of tacrolimus was still present 2 weeks after transient focal ischemia and 1 week after permanent focal ischemia. After transient global ischemia in gerbils, tacrolimus (1 mg/kg, i.v.) given immediately after reperfusion also produced long-lasting neuroprotective effects with a protective time-window of 1-2 h. Taken together, the results clearly indicate that tacrolimus exerts potent, long-term neuroprotective effects with a favorable therapeutic time-window, regardless of the model of cerebral ischemia. These results strengthen the notion that tacrolimus might be of clinical value for the treatment of acute stroke.     

The effects of selective brain hypothermia on intracerebral hemorrhage in rats

Prolonged hypothermia effectively treats global cerebral ischemic injury in animal models as well as in cardiac arrest victims. Furthermore, clinical trials, based upon encouraging animal findings, are underway to assess efficacy in ischemic stroke. Intracerebral hemorrhage (ICH) is a more devastating stroke, but one that shares mechanisms of injury with ischemia. Accordingly, ICH may be amenable to hypothermia treatment. In this study we tested whether selective brain hypothermia improves outcome after an ICH in rats created by infusing 100 microL of autologous whole blood into the striatum. Striatal hypothermia ( approximately 32 degrees C) was induced with a novel method (implanted cooling coil) that does not cause systemic cooling, thereby providing a safer and potentially more effective treatment for stroke than systemic hypothermia. Edema occurred for 4 days after ICH, but it peaked at 3 days ( approximately 5%). At this time it was significantly reduced (to approximately 2%) by cooling starting 1 h after ICH (3 day duration). Next, we determined whether 1 and 12 h delayed cooling treatments (4 day duration) would lessen functional impairment and lesion size. Untreated (normothermic) ICH resulted in significant forelimb use asymmetry, as well as deficits in walking and skilled reaching. These deficits were unaffected by hypothermia, as was the volume of tissue lost ( approximately 20 mm(3)) at 1 month. Thus, attenuated edema did not result in behavioral or histological benefit. In conclusion, while additional research with alternative cooling protocols and ICH models are required, these findings suggest that while hypothermia lessens edema, it will not be directly neuroprotective after ICH.     

亚低温对大鼠局灶性脑缺血再灌注后多聚腺苷二磷酸核糖聚合酶表达的影响

目的研究亚低温对大鼠局灶性脑缺血再灌注后多聚腺苷二磷酸核糖聚合酶(PARP-1)不同时空表达的影响,进一步探讨亚低温脑保护作用的分子机制。方法线栓法建立大鼠大脑中动脉阻塞再灌注模型,分假手术组、假手术 亚低温组、模型组及模型 亚低温组。应用Western blotting和免疫组化技术分别检测再灌注后不同时相缺血侧皮层PARP-1蛋白的表达与裂解。结果模型组PARP-1蛋白表达量随再灌注时间的延长逐渐增加,至再灌注24h达高峰,然后逐渐减少,再灌注72h时仍高于假手术组的水平;模型组PARP-1蛋白出现裂解,随再灌注时间的延长,裂解逐渐增强。每一相同再灌注时间点,模型 亚低温组PARP-1蛋白表达量和裂解片段含量均低于模型组。结论PARP-1的过度表达和裂解是局灶性脑缺血再灌注神经元死亡的重要分子机制。亚低温可通过抑制PARP-1的过度表达及减少PARP-1的裂解而发挥脑保护作用。     

Neuroprotective effects of minocycline on focal cerebral ischemia injury: a systematic review

To review the neuroprotective effects of minocycline in focal cerebral ischemia in animal models.By searching in the databases of PubMed,ScienceDirect,and Scopus,and considering the inclusion and exclusion criteria of the study.Studies were included if focal cerebral ischemia model was performed in mammals and including a control group that has been compared with a minocycline group.Written in languages other than English;duplicate data;in vitro studies and combination of minocycline with other neuroprotective agents were excluded.Neurological function of patients was assessed by National Institute of Health Stroke Scale,modified Rankin Scale,and modified Barthel Index.Neuroprotective effects were assessed by detecting the expression of inflammatory cytokines.We examined 35 papers concerning the protective effects of minocycline in focal cerebral ischemia in animal models and 6 clinical trials which had evaluated the neuroprotective effects of minocycline in ischemic stroke.These studies revealed that minocycline increases the viability of neurons and decreases the infarct volume following cerebral ischemia.The mechanisms that were reported in these studies included anti-inflammatory,antioxidant,as well as anti-apoptotic effects.Minocycline also increases the neuronal regeneration following cerebral ischemia.Minocycline has considerable neuroprotective effects against cerebral ischemia-induced neuronal damages.However,larger clinical trials may be required before using minocycline as a neuroprotective drug in ischemic stroke.     

Therapeutic hypothermia for acute ischemic stroke: ready to start large randomized trials?

Therapeutic hypothermia is a means of neuroprotection well established in the management of acute ischemic brain injuries such as anoxic encephalopathy after cardiac arrest and perinatal asphyxia. As such, it is the only neuroprotective strategy for which there is robust evidence for efficacy. Although there is overwhelming evidence from animal studies that cooling also improves outcome after focal cerebral ischemia, this has not been adequately tested in patients with acute ischemic stroke. There are still some uncertainties about crucial factors relating to the delivery of hypothermia, and the resolution of these would allow improvements in the design of phase III studies in these patients and improvements in the prospects for successful translation. In this study, we discuss critical issues relating first to the targets for therapy including the optimal depth and duration of cooling, second to practical issues including the methods of cooling and the management of shivering, and finally, of factors relating to the design of clinical trials. Consideration of these factors should inform the development of strategies to establish beyond doubt the place of hypothermia in the management of acute ischemic stroke.     

Current status and perspectives of neuroprotection in ischemic stroke treatment

In developed countries, ischemic stroke is one of the leading causes of death and neurological impairment. The two most important therapeutic approaches in patients with acute cerebral ischemia consist of improving cerebral blood flow and blocking the biochemical and metabolic changes at the ischemic cascade level. The significant advances made in the past decade in the knowledge of the physiopathological mechanisms of cerebral ischemia, and the development of new drugs have given rise to true expectations regarding treatment and the rejection of nihilist attitudes. In the past 15 years, based on the excellent results obtained in experimental models of ischemia, many clinical trials have been conducted with different neuroprotective drugs. The results obtained in most studies have been negative, or the studies were terminated early owing to side effects. However, some drugs (citicoline, clomethiazole, piracetam and ebselen) have shown a certain degree of clinical efficacy, limited to subgroups of patients, and with a narrow therapeutic window, longer-lasting in the case of citicoline. The design of new clinical trials with neuroprotective drugs requires adequate preclinical assessment and the use of the new magnetic resonance techniques for the selection of patients and the assessment of the efficacy of treatment. The new trends in neuroprotection in focal cerebral ischemia and the results of the clinical trials published to date are reviewed.     

Neuroprotective therapy for the treatment of acute ischemic stroke]

Following cerebral ischemia, various biochemical reactions are provoked in a stepwise manner leading neuronal cells to ischemic death. The prevention of these biochemical reactions may exert neuroprotective actions and consequently reduce the magnitude of ischemic cerebral injury. On the basis of such a view, numerous neuroprotective drugs have been developed during the last decade. Quite a few drugs were found effective in reducing the infarct volume in experimental studies, and more than 15 of them were subjected to clinical phase III trials to see a therapeutic effectiveness. However, the results of phase III trials were disappointing in the majority drugs. Only three drugs, nicaravene, ebselen and edaravone, all radical scavengers, were judged effective by small-sized trials with a wide therapeutic window, 48-72 hours after stroke, in Japan. The fact suggests that a one-point prevention of biochemical reactions by single drug is unable to rescue ischemic neuronal cells. Ischemic insult causes damages of vascular wall including the endothelium which play an important role in the development of hemorrhagic changes or cerebral edema. Vascular protection is considered as important as neuroprotection in treatment of clinical stroke. Mild hypothermia has neuroprotective and vascular protective actions and hence may be more effective than neuroprotective drugs for the treatment of stroke. The prevention of fever, which often occurs in severe stroke, may exert the similar effect as hypothermia in neuroprotection. Neuroprotective therapy in the future should proceed toward the simultaneous protections of neurons and vessels using combination of multiple drugs.     

Antiepileptic drugs as a possible neuroprotective strategy in brain ischemia

Several new antiepileptic drugs (AEDs) have been introduced for clinical use recently. These new AEDs, as did the classic AEDs, target multiple cellular sites both pre- and postsynaptically. The major common goal of the pharmacological treatment using AEDs is to counteract abnormal brain excitability by either decreasing excitatory transmission or enhancing neuronal inhibition. Interestingly, an excessive release of excitatory amino acids and a reduced neuronal inhibition also occur in brain ischemia. Thus, recently, the use of AEDs as a possible neuroprotective strategy in brain ischemia is receiving increasing attention, and many AEDs have been tested in animal models of stroke, providing encouraging results. Experimental studies utilizing global or focal ischemia in rodents have provided insights into the possible neuroprotective action of the various AEDs. However, the implication of these studies in the treatment of acute stroke in humans is not always direct. In fact, various clinical studies with drugs targeting the same voltage- and ligand-gated channels modulated by most of the AEDs failed to show neuroprotection. The differential mechanisms that underlie the development of focal ischemic injury in experimental animal models versus human stroke require further investigation to open a new therapeutic perspective for neuroprotection that might be applicable in the future.     

Relevance of experimental ischemia in cats for stroke management: a comparative reevaluation

Repeat studies in animal models of acute focal ischemia can be compared to incidental studies in the course of ischemic stroke in order to shed light on the development of changes causing ischemic infarcts or recovery of critically perfused tissue. Positron emission tomography (PET) studies of regional cerebral blood flow, cerebral metabolic rate for oxygen, oxygen extraction fraction (OEF), cerebral metabolic rate of glucose and flumazenil (FMZ) binding in the cat middle cerebral artery occlusion (MCAO) model and in patients with acute ischemic hemispheric stroke were reviewed. After permanent MCAO, the development of "misery-perfused" penumbral tissue and its centrifugal conversion into necrosis could be demonstrated, resembling focal pathophysiological changes in patients with ischemic attacks. In the experimental model and in vascular insults in humans, a chance of recovery existed if collateral perfusion developed spontaneously within the first hours. In transient MCAO, reperfusion was only effective in preventing infarction when it was initiated as long as misery perfusion persisted; in these cases tissue was salvaged and large infarcts did not develop. In the other instances when oxygen metabolism broke down, and an increased OEF was no longer seen, reperfusion even at levels above preocclusion had no effect, and large space-occupying infarcts developed. These experimental findings are comparable to the variable outcome after thrombolytic therapy; if reperfusion is achieved within the therapeutic window of tissue viability, large infarcts are prevented and complete or partial recovery can be achieved. In the experimental model of focal ischemia and in human stroke, FMZ can be utilized as a marker of neuronal integrity. If FMZ binding in the cortex is decreased below 4 times the mean value of white matter in the acute stage, permanent infarcts were observed on late CT/MRI; this irreversible damage could not be prevented by thrombolytic therapy. These results demonstrated that PET studies in suitable ischemia models in cats can help to explain various courses and diverging outcomes of acute ischemic stroke. Comparable findings from experimental ischemia and human stroke may affect the selection of appropriate therapeutic strategies.     

Minocycline and neurodegenerative diseases

Minocycline is a semi-synthetic, second-generation tetracycline analog which is effectively crossing the blood-brain barrier, effective against gram-positive and -negative infections. In addition to its own antimicrobacterial properties, minocycline has been reported to exert neuroprotective effects over various experimental models such as cerebral ischemia, traumatic brain injury, amyotrophic lateral sclerosis, Parkinson's disease, kainic acid treatment, Huntington' disease and multiple sclerosis. Minocycline has been focused as a neuroprotective agent over neurodegenerative disease since it has been first reported that minocycline has neuroprotective effects in animal models of ischemic injury [Yrjanheikki J, Keinanen R, Pellikka M, Hokfelt T, Koisinaho J. Tetracyclines inhibit microglial activation and are neuroprotective in global brain ischemia. Proc Natl Acad Sci USA 1998;95:15769-74; Yrjanheikki J, Tikka T, Keinanen R, Goldsteins G, Chan PH, Koistinaho J. A tetracycline derivative, minocycline, reduces inflammation and protects against focal cerebral ischemia with a wide therapeutic window. Proc Natl Acad Sci USA 1999;96:13496-500]. Recently, the effect of minocycline on Alzheimer's disease has been also reported. Although its precise primary target is not clear, the action mechanisms of minocycline for neuroprotection reported so far are; via; the inhibition of mitochondrial permeability-transition mediated cytochrome c release from mitochondria, the inhibition of caspase-1 and -3 expressions, and the suppression of microglial activation, involvement in some signaling pathways, metalloprotease activity inhibition. Because of the high tolerance and the excellent penetration into the brain, minocycline has been clinically tried for some neurodegenerative diseases such as stroke, multiple sclerosis, spinal cord injury, amyotropic lateral sclerosis, Hungtington's disease and Parkinson's disease. This review will briefly summarize the effects and action mechanisms of minocycline on neurodegenerative diseases.     

Clomethiazole is neuroprotective in models of global and focal cerebral ischemia when infused at doses producing clinically relevant plasma concentrations

We investigated the neuroprotective effect of infusing various doses of clomethiazole in models of global and focal cerebral ischemia. In a model of global ischemia, gerbils were infused with clomethiazole (intravenous), attaining steady state plasma concentrations of between 1 and 13 microM for 24 h. In a transient middle cerebral artery occlusion model in rats, clomethiazole was administered subcutaneously over 22.75 h using osmotic minipumps producing steady state plasma concentrations of between 1 and 13 microM. Clomethiazole was protective in these models at plasma concentrations of respectively 6.1 microM and above and 3.5 microM and above. Clomethiazole is thus neuroprotective in both global and focal ischemia at plasma concentrations known to be well tolerated in stroke patients.     

Neuroprotective agents for the treatment of acute ischemic stroke

Neuroprotective treatments are therapies designed to interrupt the cellular, biochemical, and metabolic elaboration of injury during or following exposure to ischemia; they encompass a rapidly expanding array of pharmacologic interventions. Various classes of neuroprotective agents have reached phase III efficacy trials in focal ischemic stroke, but none has proven effective, despite successful preceding animal studies. This notwithstanding, recent favorable results of hypothermia in human cardiac arrest trials have validated the general concept of neuroprotection. In addition, the promise of neuroprotective therapy for focal acute ischemic stroke has been renewed by innovations in strategies of preclinical drug development and clinical trial design that rectify past defects, including trial testing of combination therapies rather than single agents and novel approaches to accelerating time to initiation of experimental treatment.     

Reperfusion plus Selective Intra-arterial Cooling (SI-AC) Improve Recovery in a Nonhuman Primate Model of Stroke

Early reperfusion is increasingly prioritized in ischemic stroke care, but outcomes remain suboptimal. Therefore, there is an urgent need to find neuroprotective approaches that can be combined with reperfusion to maximize efficacy. Here, the neuroprotective mechanisms behind therapeutic hypothermia were evaluated in a monkey model of ischemic stroke. Focal ischemia was induced in adult rhesus monkeys by placing autologous clots in the middle cerebral artery. Monkeys were treated with tissue plasminogen activator (t-PA) alone or t-PA plus selective intra-arterial cooling (SI-AC). Serial MRI scans and functional deficit were evaluated after ischemia. Histopathology and immunohistochemistry analysis were performed after the final MRI scan. t-PA plus SI-AC treatment led to a higher rate of MRI tissue rescue, and significantly improved neurologic deficits and daily activity scores compared with t-PA alone. In peri-infarct areas, higher fractional anisotropy values and greater fiber numbers were observed in models receiving t-PA plus SI-AC. Histological findings indicated that myelin damage, spheroids, and spongiosis were significantly ameliorated in models receiving SI-AC treatment. White matter integrity was also improved by SI-AC based on immunochemical staining. Our study demonstrates that SI-AC can be effectively combined with t-PA to improve both structural and functional recovery in a monkey model of focal ischemia. These findings provide proof-of-concept that it may be feasible to add neuroprotective agents as adjunctive treatments to reperfusion therapy for stroke.Electronic supplementary materialThe online version of this article (10.1007/s13311-020-00895-6) contains supplementary material, which is available to authorized users.Key Words: Stroke, recovery, hypothermia, white matter, diffusion tensor imaging, rhesus monkey     

Neuroprotection for ischemic stroke using hypothermia

The development of animal models of acute stroke has allowed the evaluation of mild and moderate hypothermia as a therapeutic modality in this clinical setting. Studies have demonstrated that animals subjected to hypothermia up to 3 hours after the primary central nervous system insult have reduced mortality and neuronal injury, and improved neurological outcome. These results warranted the evaluation of hypothermia in clinical trials. Even though hypothermia has potent neuroprotective effects in animal models of ischemic stroke, there are only a few clinical studies of therapeutic hypothermia in humans. Because of the small number of patients in the studies and the absence of matched controls, clinical studies are considered pilot studies for feasibility and safety. Thus, therapeutic hypothermia for ischemic stroke remains a promising but fiercely debated therapeutic modality.     

病变侧亚低温对局部脑缺血再灌流损伤有关因素的影响

目的　研究病变侧脑亚低温对脑缺血再灌流损伤梗塞体积、 Ｎ Ｏ 的影响确定病变侧亚低温的疗效, 探讨机理。方法　应用可反馈控温半导体致冷块对大鼠局灶脑缺血模型病变侧降温至３２ ～３３ ℃研究持续缺血及再灌流损伤的保护作用及有关因素的影响。结果　持续缺血１０ 分钟低温组及缺血４０ 分钟再灌流并低温组梗塞体积均小于常温对照组。亚低温组 Ｎ Ｏ 含量明显低于常温对照组。结论　病变侧亚低温对脑缺血再灌流损伤在一定时间窗内有明显保护作用, 而亚低温使 Ｎ Ｏ 产生减少可能是其脑保护作用的部分机制。     

Mild hypothermia effects on intercellular adhesion molecule-1 and serum interleukin-6 expression in brain tissues of a rat focal ischemia model

BACKGROUND： Previous studies have confirmed the neuroprotective effect of mild hypothermia on ischemic brain injury. OBJECTIVE： To investigate the effects of mild hypothermia on intercellular adhesion molecule-1 expression and serum interleukin-6 levels in ischemic brain tissues of focal brain ischemia rats, and to explore the neuroprotective effects of mild hypothermia on ischemic brain injury. DESIGN, TIME AND SETTING： A randomized, controlled, neurobiological experiment was performed at the Central Laboratory, First Affiliated Hospital, Xinxiang Medical College, China from February to July 2006. MATERIALS： Thirty healthy, adult, Sprague Dawley rats were used to establish middle cerebral artery occlusion models using the suture method, The immunohistochemistry （streptavidin-biotin-peroxidase complex method） kit was purchased from Boster, China. Interleukin-6 radioimmunoassay was supplied by Institute of Radioimmunity, Technology Development Center, General Hospital of Chinese PLA. METHODS： The rats were equally and randomly assigned into mild hypothermia and control groups, and middle cerebral artery occlusion models were established. The rectal temperature was maintained at （37 ±0.5）℃ in the control group. In the mild hypothermia group, the rectal temperature was maintained at （33±1）℃. MAIN OUTCOME MEASURES： At 12 hours after model establishment, the ischemic brain hemispheres were coronally sliced at the level of the optic chiasm. The number of intercellular adhesion molecule-1-positive vessels per high-power field was observed with an optical microscope. Serum interleukin-6 levels were measured by radioimmunoassay. RESULTS： Compared with the control group, intercellular adhesion molecule-1 and serum interleukin-6 expressions were significantly decreased in ischemic brain tissues of the mild hypothermia group （P 〈 0.01）. CONCLUSION： Mild hypothermia exhibits a neuroprotective effect by reducing serum interleukin-6 and intercellular adhesion molecule-1 expression followi     

Pathophysiology and Neuroprotection of Global and Focal Perinatal Brain Injury: Lessons From Animal Models

BackgroundArterial ischemic stroke occurs more frequently in term newborns than in the elderly, and brain immaturity affects mechanisms of ischemic injury and recovery. The susceptibility to injury of the brain was assumed to be lower in the perinatal period as compared with childhood. This concept was recently challenged by clinical studies showing marked motor disabilities after stroke in neonates, with the severity of motor and cortical sensory deficits similar in both perinatal and childhood ischemic stroke. Our understanding of the triggers and the pathophysiological mechanisms of perinatal stroke has greatly improved in recent years, but many factors remain incompletely understood.MethodsIn this review, we focus on the pathophysiology of perinatal stroke and on therapeutic strategies that can protect the immature brain from the consequences of stroke by targeting inflammation and brain microenvironment.ResultsStudies in neonatal rodent models of cerebral ischemia have suggested a potential role for soluble inflammatory molecules as important modulators of injury and recovery. A great effort is underway to investigate neuroprotective molecules based on our increasing understanding of the pathophysiology.ConclusionIn this review, we provide a comprehensive summary of new insights concerning pathophysiology of focal and global perinatal brain injury and their implications for new therapeutic approaches.     

亚低温对大鼠局灶性脑缺血ICAM-1和TNF-α表达的影响

目的:脑缺血后ICAM-1和TNF-α的表达增加。降低ICAM-1和TNF-α的表达和亚低温对缺血性脑卒中具有神经保护作用。本研究的目的在于观察亚低温对大鼠局灶性脑缺血ICAM-1和TNF-α表达的影响,并探讨亚低温对脑缺血性损害的神经保护作用机制。方法:采用栓线法阻断大鼠一侧大脑中动脉制作局灶性脑缺血动物模型,设实验组和对照组,分别置于冰毯机上和常温操作台上,使其肛温分别保持在34℃±0.5℃和37℃±0.5℃。12h后断头取脑,采用免疫组化方法检测缺血区ICAM-1阳性血管数目和采用双抗夹心酶联免疫吸附法(ELISA)测定血清TNF-α水平。结果:实验组ICAM-1和TNF-α的表达较对照组下降。结论:亚低温可降低大鼠局灶性脑缺血的ICAM-1和TNF-α的表达,推测亚低温降低ICAM-1和TNF-α的表达为亚低温减轻脑缺血性损害的神经保护作用机制之一。     

亚低温对大鼠短暂全脑缺血后神经元凋亡的影响

目的 探讨亚低温对大鼠脑缺血后神经元凋亡的影响，揭示亚低温的部分神经保护机制。方法 采用“双侧颈总动脉阻断＋全身低血压”方法来建立大鼠短暂性全脑缺血模型。用神经元尼氏体亚甲兰特殊染色法观察大鼠脑缺血后海马CA1区神经元损害情况；原位细胞凋亡检测法（TUNEL染色）及电镜观察脑缺血后CA1区神经元凋亡情况。结果 与假手术组、低温缺血组相比，常温缺血组海马CA1区神经元缺失明显（P＜0．01）。常温及低温缺血组海马CA1区均存在神经元凋亡，但低温缺血组海马CA1区凋亡神经元数明显少于缺血组（P＜0．01）。结论 经“双侧颈总动脉阻断＋全身低血压”方法建立的大鼠短暂全脑缺血模型证实了亚低温的脑保护作用。全脑缺血后的迟发性神经元死亡很可能经由凋亡途径，而亚低温可通过抑制缺血性神经元凋亡而发挥一定的神经保护作用。     

Neuronal death/survival signaling pathways in cerebral ischemia

Cumulative evidence suggests that apoptosis plays a pivotal role in cell deathin vitro after hypoxia. Apoptotic cell death pathways have also been implicated in ischemic cerebral injury inin vivo ischemia models. Experimental ischemia and reperfusion models, such as transient focal/global ischemia in rodents, have been thoroughly studied and the numerous reports suggest the involvement of cell survival/death signaling pathways in the pathogenesis of apoptotic cell death in ischemic lesions. In these models, reoxygenation during reperfusion provides a substrate for numerous enzymatic oxidation reactions. Oxygen radicals damage cellular lipids, proteins and nucleic acids, and initiate cell signaling pathways after cerebral ischemia. Genetic manipulation of intrinsic antioxidants and factors in the signaling pathways has provided substantial understanding of the mechanisms involved in cell death/survival signaling pathways and the role of oxygen radicals in ischemic cerebral injury. Future studies of these pathways may provide novel therapeutic strategies in clinical stroke.