Association of immune responses and ischemic brain infarction in rat

Investigating the therapeutic effects of nimodipine on vasogenic cerebral edema and blood-brain barrier impairment in an ischemic stroke rat model

Vasogenic brain edema, a potentially life-threatening consequence following an acute ischemic stroke, is a major clinical problem. This research aims to explore the therapeutic benefits of nimodipine, a calcium channel blocker, in mitigating vasogenic cerebral edema and preserving blood-brain barrier (BBB) function in an ischemic stroke rat model. In this research, animals underwent the induction of ischemic stroke via a 60-min blockage of the middle cerebral artery and treated with a nonhypotensive dose of nimodipine (1 mg/kg/day) for a duration of five days. The wet/dry method was employed to identify cerebral edema, and the Evans blue dye extravasation technique was used to assess the permeability of the BBB. Furthermore, immunofluorescence staining was utilized to assess the protein expression levels of matrix metalloproteinase-9 (MMP-9) and intercellular adhesion molecule-1 (ICAM-1). The study also examined mitochondrial function by evaluating mitochondrial swelling, succinate dehydrogenase (SDH) activity, the collapse of mitochondrial membrane potential (MMP), and the generation of reactive oxygen species (ROS). Post-stroke administration of nimodipine led to a significant decrease in cerebral edema and maintained the integrity of the BBB. The protective effects observed were associated with a reduction in cell apoptosis as well as decreased expression of MMP-9 and ICAM-1. Furthermore, nimodipine was observed to reduce mitochondrial swelling and ROS levels while simultaneously restoring MMP and SDH activity. These results suggest that nimodipine may reduce cerebral edema and BBB breakdown caused by ischemia/reperfusion. This effect is potentially mediated through the reduction of MMP-9 and ICAM-1 levels and the enhancement of mitochondrial function.

The cerebroprotection and prospects of FNDC5/irisin in stroke

Stroke, the leading cause of disability and cognitive impairment, is also the second leading cause of death worldwide. The drugs with multi-targeted brain cytoprotective effects are increasingly being advocated for the treatment of stroke. Irisin, a newly discovered myokine produced by cleavage of fibronectin type III domain 5, has been shown to regulate glucose metabolism, mitochondrial energy, and fat browning. A large amount of evidence indicated that irisin could exert anti-inflammatory, anti-apoptotic, and antioxidant properties in a variety of diseases such as myocardial infarction, inflammatory bowel disease, lung injury, and kidney or liver disease. Studies have found that irisin is widely distributed in multiple brain regions and also plays an important regulatory role in the central nervous system. The most common cause of a stroke is a sudden blockage of an artery (ischemic stroke), and in some circumstances, a blood vessel rupture can also result in a stroke (hemorrhagic stroke). After a stroke, complicated pathophysiological processes lead to serious brain injury and neurological dysfunction. According to recent investigations, irisin may protect elements of the neurovascular unit by acting on multiple pathological processes in stroke. This review aims to outline the currently recognized effects of irisin on stroke and propose possible directions for future research.

The effect of calpain inhibitor-I on copper oxide nanoparticle-induced damage and cerebral ischemia-reperfusion in a rat model

This study aimed to investigate the effects of the calpain inhibitor N-Acetyl-Leu-Leu-norleucinal (ALLN) on neuroapoptotic cell damage caused by Copper Oxide Nanoparticles (CuO-NP) and exacerbation of damage through brain ischemia/reperfusion (I/R) in a rat model. Male Wistar Albino rats (n=80) were divided into eight groups: Control, I/R, CuO-NP, CuO-NP+I/R, I/R+ALLN, CuO-NP+ALLN, CuO-NP+I/R+ALLN, and DMSO. Biochemical markers (MBP, S100B, NEFL, NSE, BCL-2, Cyt-C, Calpain, TNF-α, Caspase-3, MDA, and CAT) were measured in serum and brain tissue samples. Histological examinations (H&E staining), DNA fragmentation analysis (TUNEL) were performed, along with Caspase-3 assessment. The ALLN-treated groups exhibited significant improvements in biochemical markers and a remarkable reduction in apoptosis compared to the damaged groups (CuO-NP and I/R). H&E and Caspase-3 staining revealed damage-related morphological changes and reduced apoptosis in the ALLN-treated group. However, no differences were observed among the groups with TUNEL staining. The findings suggest that ALLN, as a calpain inhibitor, has potential implications for anti-apoptotic treatment, specifically in mitigating neuroapoptotic cell damage caused by CuO-NP and I/R.

Timing of Cord Blood Treatment after Experimental Stroke Determines Therapeutic Efficacy

Embolic stroke is thought to cause irreparable damage in the brain immediately adjacent to the region of reduced blood perfusion. Therefore, much of the current research focuses on treatments such as anti-inflammatory, neuroprotective, and cell replacement strategies to minimize behavioral and physiological consequences. In the present study, intravenous delivery of human umbilical cord blood cells (HUCBC) 48 h after a middle cerebral artery occlusion (MCAo) in a rat resulted in both behavioral and physiological recovery. Nissl and TUNEL staining demonstrated that many of the neurons in the core were rescued, indicating that while both necrotic and apoptotic cell death occur in ischemia, it is clear that apoptosis plays a larger role than first anticipated. Further, immunohistochemical and histochemical analysis showed a diminished and/or lack of granulocyte and monocyte infiltration and astrocytic and microglial activation in the parenchyma in animals treated with HUCBC 48 h poststroke. Successful treatment at this time point should offer encouragement to clinicians that a therapy with a broader window of efficacy may soon be available to treat stroke.

Fluoxetine and vitamin C synergistically inhibits blood-spinal cord barrier disruption and improves functional recovery after spinal cord injury

Recently we reported that fluoxetine (10 mg/kg) improves functional recovery by attenuating blood spinal cord barrier (BSCB) disruption after spinal cord injury (SCI). Here we investigated whether a low-dose of fluoxetine (1 mg/kg) and vitamin C (100 mg/kg), separately not possessing any protective effect, prevents BSCB disruption and improves functional recovery when combined. After a moderate contusion injury at T9 in rat, a low-dose of fluoxetine and vitamin C, or the combination of both was administered intraperitoneally immediately after SCI and further treated once a day for 14 d. Co-treatment with fluoxetine and vitamin C significantly attenuated BSCB permeability at 1 d after SCI. When only fluoxetine or vitamin C was treated after injury, however, there was no effect on BSCB disruption. Co-treatment with fluoxetine and vitamin C also significantly inhibited the expression and activation of MMP-9 at 8 h and 1 d after injury, respectively, and the infiltration of neutrophils (at 1 d) and macrophages (at 5 d) and the expression of inflammatory mediators (at 2 h, 6 h, 8 h or 24 h after injury) were significantly inhibited by co-treatment with fluoxetine and vitamin C. Furthermore, the combination of fluoxetine and vitamin C attenuated apoptotic cell death at 1 d and 5 d and improved locomotor function at 5 weeks after SCI. These results demonstrate the synergistic effect combination of low-dose fluoxetine and vitamin C on BSCB disruption after SCI and furthermore support the effectiveness of the combination treatment regimen for the management of acute SCI.

Ligustrazine monomer against cerebral ischemia/reperfusion injury

Ligustrazine (2,3,5,6-tetramethylpyrazine) is a major active ingredient of the Szechwan lovage rhizome and is extensively used in treatment of ischemic cerebrovascular disease. The mechanism of action of ligustrazine use against ischemic cerebrovascular diseases remains unclear at present. This study summarizes its protective effect, the optimum time window of administration, and the most effective mode of administration for clinical treatment of cerebral ischemia/reperfusion injury. We examine the effects of ligustrazine on suppressing excitatory amino acid release, promoting migration, differentiation and proliferation of endogenous neural stem cells. We also looked at its effects on angiogenesis and how it inhibits thrombosis, the inflammatory response, and apoptosis after cerebral ischemia. We consider that ligustrazine gives noticeable protection from cerebral ischemia/reperfusion injury. The time window of ligustrazine administration is limited. The protective effect and time window of a series of derivative monomers of ligustrazine such as 2-[(1,1-dimethylethyl)oxidoimino]methyl]-3,5,6-trimethylpyrazine, CXC137 and CXC195 after cerebral ischemia were better than ligustrazine.

Puerarin protects brain tissue against cerebral ischemia/reperfusion injury by inhibiting the inflammatory response

Puerarin, a traditional Chinese medicine, exerts a powerful neuroprotective effect in cerebral ischemia/reperfusion injury, but its mechanism is unknown. Here, we established rat models of middle cerebral artery ischemia/reperfusion injury using the suture method. Puerarin (100 mg/kg) was administered intraperitoneally 30 minutes before middle cerebral artery occlusion and 8 hours after reperfusion. Twenty-four hours after reperfusion, we found that puerarin significantly improved neurological deficit, reduced infarct size and brain water content, and notably diminished the expression of Toll-like receptor-4, myeloid differentiation factor 88, nuclear factor kappa B and tumor necrosis factor-α in the ischemic region. These data indicate that puerarin exerts an anti-inflammatory protective effect on brain tissue with ischemia/reperfusion damage by downregulating the expression of multiple inflammatory factors.

Therapeutic effects of human adipose stem cell-conditioned medium on stroke

Stem cell therapy is a promising approach for stroke. However, low survival rates and potential tumorigenicity of implanted cells could undermine the efficacy of the cell-based treatment. The use of stem cell-conditioned medium (CM) may be a feasible approach to overcome these limitations. Especially, specific stem cell culture condition and continuous infusion of CM into ischemic brains would have better therapeutic results. The CM was prepared by culturing human adipose-derived stem cells in a three-dimensional spheroid form to increase the secretion of angiogenic/neuroprotective factors. Ischemic stroke was induced by standard middle cerebral artery occlusion methods in the brain of 8-week-old Sprague-Dawley rats. Continuous infusion of CM or αMEM media (0.5 μl/hr) into the lateral ventricle was initiated 8 days after the surgery and maintained for 7 days. Alteration in the motor function was monitored by the rotarod test. Infarction volume and the number of microvessels or TUNEL-positive neural cells were analyzed 15 days after the surgery. Compared with αMEM, continuous CM infusion reduced the infarction volume and maintained motor function. The number of CD31-positive microvessels and TUNEL-positive neural cells significantly increased and decreased, respectively, in the penumbra regions. Although the apoptosis of all neural cell types decreased, reduction in the microglial apoptosis and astrogliosis was prominent and significant. In this study, the therapeutic effects of the CM against stroke were confirmed in an animal model. Increased endothelial cell proliferation, reduced neural cell apoptosis, and milder astrogliosis may play important roles in the treatment effects of CM.

The optimal therapeutic timing and mechanism of puerarin treatment of spinal cord ischemia-reperfusion injury in rats

AIM OF THE STUDY

The purpose of this study was to explore the optimal therapeutic timing and mechanism of puerarin treatment of spinal cord ischemia-reperfusion injury.

MATERIALS AND METHODS

The spinal ischemia-reperfusion injury was conducted in male Sprague-Dawley rats, and 50mg/kg of puerarin was injected intraperitoneally at 1, 2, 4 and 6h after the injury. Motor function was measured 48 h after reperfusion started. Thioredoxin expression and apoptosis indices were determined.

RESULTS

Improvement of motor function at 1, 2, and 4h was demonstrated in the animals with puerarin treatment. Ischemia-reperfusion injury resulted in a decrease in the expression of thioredoxin, while puerarin administration elevated the expression of thioredoxin-1/thioredoxin-2 mRNA. Apoptosis indices were significantly reduced by puerarin administration.

CONCLUSIONS

We conclude that administration of puerarin within 4h of spinal ischemia-reperfusion injury reduces ischemic reperfusion damage, and that the neuroprotective effect of puerarin involves an increase in the transcription of thioredoxin and a reduction of apoptosis.

Hydroxysafflor Yellow A suppresses thrombin generation and inflammatory responses following focal cerebral ischemia-reperfusion in rats

Hydroxysafflor Yellow A has been demonstrated to attenuate pressure overloaded hypertrophy in rats and inhibit platelet aggregation. Herein we found that Hydroxysafflor Yellow A prevented cerebral ischemia-reperfusion injury by inhibition of thrombin generation. In addition, treatment with Hydroxysafflor Yellow A significantly inhibited NF-kappaB p65 nuclear translation and p65 binding activity, both mRNA and protein levels of ICAM-1 and the infiltration of neutrophils. Mean while, Hydroxysafflor Yellow A had the capacity to improve neurological deficit scores, increase the number of the surviving hippocampal CA1 pyramidal cells and decrease the plasma angiotensin II level. These results illustrated that anti-cerebral ischemic mechanism of Hydroxysafflor Yellow A may be due to its suppression of thrombin generation and inhibition of thrombin-induced inflammatory responses by reducing angiotensin II content.

Acupuncture-mediated inhibition of inflammation facilitates significant functional recovery after spinal cord injury

Here, we first demonstrated the neuroprotective effect of acupuncture after SCI. Acupuncture applied at two specific acupoints, Shuigou (GV26) and Yanglingquan (GB34) significantly alleviated apoptotic cell death of neurons and oligodendrocytes, thereby leading to improved functional recovery after SCI. Acupuncture also inhibited caspase-3 activation and reduced the size of lesion cavity and extent of loss of axons. We also found that the activation of both p38 mitogen-activated protein kinase and resident microglia after injury are significantly attenuated by acupuncture. In addition, acupuncture significantly reduced the expression or activation of pro-nerve growth factor, proinflammatory factors such as tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, nitric oxide synthase, cycloxygenase-2, and matrix metalloprotease-9 after SCI. Thus, our results suggest that the neuroprotection by acupuncture may be partly mediated via inhibition of inflammation and microglial activation after SCI and acupuncture can be used as a potential therapeutic tool for treating acute spinal injury in human.

Cornel iridoid glycoside inhibits inflammation and apoptosis in brains of rats with focal cerebral ischemia

The capacity of cornel iridoid glycoside (CIG) to suppress the manifestations of ischemic stroke was investigated. CIG was administered to rats by the intragastric route once daily for 7 days. Focal cerebral ischemia was induced by 2 h of middle cerebral artery occlusion followed by 24 h of reperfusion. In non-treated rats large infarct areas were observed within 24 h of reperfusion. Examination of the ischemic cerebral cortex revealed microglia and astrocyte activation, increased interleukin-1beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) concentrations, increased DNA fragmentation in the ischemia penumbra, elevated Bax expression, increased caspase-3 cleavage, and decreased Bcl-2 expression. Pretreatment with CIG decreased the infarct area, DNA fragmentation, IL-1beta and TNF-alpha concentrations, microglia and astrocyte activation, Bax expression, and caspase-3 cleavage while increasing Bcl-2 expression. CIG exerts anti-neuroinflammatory and anti-apoptotic effects which should prove beneficial for prevention or treatment of stroke.

Toll-like receptor 4-mediated myeloid differentiation factor 88-dependent signaling pathway is activated by cerebral ischemia-reperfusion in hippocampal CA1 region in mice

The Toll-like receptor 4 (TLR4)-mediated myeloid differentiation factor 88 (MyD88)-dependent signaling pathway plays an essential role in inflammation resulting from invading microbes. However, whether the signaling pathway is activated in the inflammatory reaction of cerebral ischemia-reperfusion and its mechanism is still unclear. In this experiment mice were randomly divided into sham group, ischemia/reperfusion group and TLR4-blocked group with different time points of reperfusion at 12, 24, 48 and 72 h . Mice cerebral ischemia was induced by occlusion of common carotid arteries (CCA) bilaterally. TLR4 signaling pathway was inhibited using specific anti-TLR4 binding protein to prevent TLR4 from interacting with its receptors. We determined the result of TLR4 antibodies-blocking and mice cerebral ischemia-reperfusion injuries by Western blot, and evaluated neuronal damage in the hippocampus. We also determined expression of TLR4 mRNA and MyD88 mRNA by in situ hybridization (ISH), activation of nuclear factor (NF)-kappaB by electrophoretic mobility-shift analysis (EMSA), and expression of interrleukin (IL)-1beta protein by Western blot. The results demonstrated that TLR4-mediated MyD88-dependent signaling pathway activated by ischemia-reperfusion may be involved in the mechanism of ischemia-reperfusion through upregulation of NF-kappaB, IL-1beta.

Graptopetalum paraguayense E. Walther Leaf Extracts Protect Against Brain Injury in Ischemic Rats

As practice in folk medicine, Graptopetalum paraguayense E. Walther possesses several biological/pharmacological activities including hepatoprotective, anti-oxidant, and anti-inflammatory. We investigated the neuroprotective potential of Graptopetalum paraguayense E. Walther leaf extracts on inflammation-mediated ischemic brain injury. Water (GWE), 50% alcohol (GE50) extracts of Graptopetalum paraguayense E. Walther, and extracts obtained from further extraction of GE50 with ethyl acetate (GEE) were used. Oral administration of GEE, but not GWE or GE50, for 2 weeks protected animals against cerebral ischemia/reperfusion brain injury. The neuroprotective effect of GEE was accompanied by reductions in brain infarction, neurological deficits, caspase-3 activity, malondialdehyde content, microglia activation, and inducible nitric oxide synthase (iNOS) expression. Since microglia-mediated inflammation plays critical roles in ischemic brain injury, anti-inflammatory potential of Graptopetalum paraguayense E. Walther leaf extracts was further investigated on lipopolysaccharide (LPS)/interferon-γ (IFN-γ-activated BV-2 microglial cells. GEE decreased H2O2 - and LPS/IFN-γ-induced free radical generation and LPS/IFN-γ-induced iNOS expression. Mechanistic study revealed that the neuroactive effects of GEE were markedly associated with anti-oxidative potential, activation of serine/threonine and tyrosine phosphatases, and down-regulation of extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38, Akt, Src, Janus kinase-1, Tyk2, signal transducer and activator of transcription-1, and NF-κB and might be attributed to the presence of polyphenolic compounds such as gallic acid, genistin, daidzin, and quercetin. Together, our findings point out its potential therapeutic strategies that target microglia activation, oxidative stress, and iNOS expression to reduce ischemic brain injury and suggest that Graptopetalum paraguayense E. Walther leaf extracts represent a valuable source for the development of neuroprotective agents.

Elucidating novel mechanisms of brain injury following subarachnoid hemorrhage: an emerging role for neuroproteomics

Subarachnoid hemorrhage (SAH) is a devastating neurological injury associated with significant patient morbidity and death. Since the first demonstration of cerebral vasospasm nearly 60 years ago, the preponderance of research has focused on strategies to limit arterial narrowing and delayed cerebral ischemia following SAH. However, recent clinical and preclinical data indicate a functional dissociation between cerebral vasospasm and neurological outcome, signaling the need for a paradigm shift in the study of brain injury following SAH. Early brain injury may contribute to poor outcome and early death following SAH. However, elucidation of the complex cellular mechanisms underlying early brain injury remains a major challenge. The advent of modern neuroproteomics has rapidly advanced scientific discovery by allowing proteome-wide screening in an objective, nonbiased manner, providing novel mechanisms of brain physiology and injury. In the context of neurosurgery, proteomic analysis of patient-derived CSF will permit the identification of biomarkers and/or novel drug targets that may not be intuitively linked with any particular disease. In the present report, the authors discuss the utility of neuroproteomics with a focus on the roles for this technology in understanding SAH. The authors also provide data from our laboratory that identifies high-mobility group box protein-1 as a potential biomarker of neurological outcome following SAH in humans.

Human Umbilical Cord Blood Cell Grafts for Brain Ischemia

Irreversible and permanent damage develop immediately adjacent to the region of reduced cerebral blood perfusion in stroke patients. Currently, the proven thrombolytic treatment for stroke, tissue plasminogen activator, is only effective when administered within 3 h after stroke. These disease characteristics should be taken under consideration in developing any therapeutic intervention designed to widen the narrow therapeutic range, especially cell-based therapy. Over the past several years, our group and others have characterized the therapeutic potential of human umbilical cord blood cells for stroke and other neurological disorders using in vitro and vivo models focusing on the cells' ability to differentiate into nonhematopoietic cells including neural lineage, as well as their ability to produce several neurotrophic factors and modulate immune and inflammatory reaction. Rather than the conventional cell replacement mechanism, we advance alternative pathways of graft-mediated brain repair involving neurotrophic effects resulting from release of various growth factors that afford cell survival, angiogenesis, and anti-inflammation. Eventually, these multiple protective and restorative effects from umbilical cord blood cell grafts may be interdependent and act in harmony in promoting therapeutic benefits for stroke.

Neuroprotective effect of Scutellaria baicalensis on spinal cord injury in rats

Inflammation has been known to play an important role in the pathogenesis after spinal cord injury (SCI). Microglia are activated after injury and produce a variety of proinflammatory factors such as tumor necrosis factor-alpha, interleukin-1beta, cyclooxygenase-2, and reactive oxygen species leading to apoptosis of neurons and oligodendrocytes. In this study, we examined the neuroprotective effects of total ethanol extract of Scutellaria baicalensis (EESB), after SCI. Using primary microglial cultures, EESB treatment significantly inhibited lipopolysaccharide-induced expression of such inflammatory mediators as tumor necrosis factor-alpha, IL-1beta, IL-6, cyclooxygenase-2, and inducible nitric oxide synthase. Furthermore, reactive oxygen species and nitric oxide production were significantly attenuated by EESB treatment. For in vivo study, rats that had received a moderate spinal cord contusion injury at T9 received EESB orally at a dose of 100 mg/kg. EESB inhibited expression of proinflammatory factors and protein carbonylation and nitration after SCI. EESB also inhibited microglial activation at 4 h after injury. Furthermore, EESB significantly inhibited apoptotic cell death of neurons and oligodendrocytes and improved functional recovery after SCI. Lesion cavity and myelin loss were also reduced following EESB treatment. Thus, our data suggest that EESB significantly improve functional recovery by inhibiting inflammation and oxidative stress after injury.

TLR4-mediated MyD88-dependent signaling pathway is activated by cerebral ischemia-reperfusion in cortex in mice

To study whether the signaling pathway is activated in the inflammatory reaction of cerebral ischemia-reperfusion and its mechanism. The mice were randomly divided into sham group, ischemia-reperfusion group and TLR4-blocked group with different time points of reperfusion 12h, 24h, 48h and 72h group. We observed the different expression of TLR4 mRNA and MyD88 mRNA, activation of NF-kappaB and the TNF-alpha and IL-1beta protein levels in each group at different time point after ischemia-reperfusion. Mice cerebral ischemia was induced by occlusion of common carotid arteries (CCA) bilaterally. TLR4 signaling pathway could be inhibited by specific anti-TLR4 binding protein to prevent TLR4 from interacting with its receptors. We determined the result of TLR4 antibodies-blocking and mice cerebral ischemia-reperfusion injuries by Western blot, and evaluated neuronal damage in cortex. We also determined the expression of TLR4 mRNA and MyD88 mRNA by in situ hybridization (ISH), the activation of NF-kappaB by EMSA, and the expression of TNF-alpha protein by Western blot. Anti-TLR4 binding TLR4 receptors before reperfusion was effective; There was distinct difference among each group respecting neuronal damage; The expression of TLR4 mRNA and MyD88 mRNA, the activation of NF-kappaB, and the expression of TNF-alpha protein showed clear difference as well. LR4-mediated MyD88-dependent signaling pathway activated by ischemia-reperfusion may be involved in the mechanism of ischemia-reperfusion through upregulation of NF-kappaB and TNF-alpha.

Tumor necrosis factor alpha-mediated nitric oxide production enhances manganese superoxide dismutase nitration and mitochondrial dysfunction in primary neurons: an insight into the role of glial cells

Tumor necrosis factor-alpha (TNF-alpha), a ubiquitous pro-inflammatory cytokine, is an important mediator in the immune-neuroendocrine system that affects the CNS. The present study demonstrates that treatment with TNF-alpha activates microglia to increase TNF-alpha production in primary cultures of glial cells isolated from wild-type (WT) mice and mice deficient in the inducible form of nitric oxide synthase (iNOSKO). However, mitochondrial dysfunction in WT neurons occurs at lower concentrations of TNF-alpha when neurons are directly treated with TNF-alpha or co-cultured with TNF-alpha-treated microglia than iNOSKO neurons similarly treated. Immunofluorescent staining of primary neurons co-cultured with TNF-alpha-treated microglia reveals that the antioxidant enzyme in mitochondria, manganese superoxide dismutase (MnSOD), is co-localized with nitrotyrosine in WT but not in iNOSKO primary neuronal cells. Importantly, the percentage of surviving neurons is significantly reduced in WT neurons compared with iNOSKO neurons under identical treatment conditions. Together, the results suggest that TNF-alpha activates microglia to produce high levels of TNF-alpha and that production of nitric oxide (NO) in neurons is an important factor affecting MnSOD nitration and subsequent mitochondrial dysfunction.

Activation of Toll-like receptor 4 signaling contributes to hippocampal neuronal death following global cerebral ischemia/reperfusion

Toll-like receptors (TLRs) play a critical role in the induction of innate immune responses which have been implicated in neuronal death induced by global cerebral ischemia/reperfusion (GCI/R). The present study investigated the role and mechanisms-of-action of TLR4 signaling in ischemia-induced hippocampal neuronal death. Neuronal damage, activation of the TLR4 signaling pathway, expression of pro-inflammatory cytokines and activation of the PI3K/Akt signaling pathway in the hippocampal formation (HF) were assessed in wild type (WT) mice and TLR4 knockout (TLR4(-/-)) mice after GCI/R. GCI/R increased expression of TLR4 protein in the hippocampal formation (HF) and other brain structures in WT mice. Phosphorylation of the inhibitor of kappa B (p-IkappaB) as well as activation of nuclear factor kappa B (NFkappaB) increased in the HF of WT mice. In contrast, there were lower levels of p-IkappaB and NFkappaB binding activity in TLR4(-/-) mice subjected to GCI/R. Pro-inflammatory cytokine expression was also decreased, while phosphorylation of Akt and GSK3beta were increased in the HF of TLR4(-/-) mice after GCI/R. These changes correlated with decreased neuronal death/apoptosis in TLR4(-/-) mice following GCI/R. These data suggest that activation of TLR4 signaling contributes to ischemia-induced hippocampal neuronal death. In addition, these data suggest that modulation of TLR4 signaling may attenuate ischemic injury in hippocampal neurons.

Effects of tissue plasminogen activator on cerebral microvessels of rats during focal cerebral ischemia and reperfusion

The time window in the treatment of ischemic stroke with tissue plasminogen activator (tPA) is narrow, arbitrarily within 3 hours after the onset of symptom. Hemorrhagic transformation resulting from cerebral ischemia may be related to damage of the microvascular basal lamina of the brain, which may in turn cause microvascular fibrin deposition and aggravate cerebral ischemia. Here, we investigated the effect of tPA on the microvascular tissue changes during cerebral ischemia/reperfusion. Sprague-Dawley rats were subjected to focal cerebral ischemia by ligation of the right middle cerebral artery and bilateral common carotid arteries for 90 minutes. Sixty minutes after the onset of ischemia, escalated dosages of tPA from 2.5 to 10 mg/kg or saline were intravenously infused for 60 minutes. Twenty-four hours after reperfusion, the animals were allowed to be killed for examination. Low dosage of tPA (2.5-7.5 mg/kg) reduced post-ischemic brain infarction, suppressed metalloproteinase 2 (MMP-2) activity and restored blood-brain barrier (BBB) integrity. In contrast, high dose of tPA (10 mg/kg) aggravated brain infarction, increased MMP-2 activity and exacerbated BBB disruption. Cerebral ischemia/reperfusion decreased the immunoreactivity of both collagen type IV- and laminin-positive microvessels, whereas the low dosage of tPA (2.5-7.5 mg/kg) attenuated the reduction. When these molecules in whole cortical tissues were analysed, tPA dosage-dependently decreased the total content of collagen type IV, laminin and fibronectin. Although the detailed mechanisms regarding the action of tPA are yet to be investigated, our findings demonstrate that the detrimental effect of tPA was mediated, at least in part, through the destruction of the basal lamina in the cerebral microvessels by activating MMP-2.

Suppression of inflammatory cell recruitment by histamine receptor stimulation in ischemic rat brains

Inflammation is a crucial factor in the development of ischemia-induced brain injury. Since facilitation of central histaminergic activity ameliorates reperfusion injury, effects of postischemic administration of L-histidine, a precursor of histamine, and thioperamide, a histamine H3 receptor antagonist, on inflammatory cell infiltration were evaluated in a rat model of transient occlusion of the middle cerebral artery. After reperfusion for 12, 24, or 72 h following 2 h of occlusion, brain slices were immunohistochemically stained with antibodies against myeloperoxidase and CD68, which were markers of polymorphonuclear leukocytes and macrophages/microglia, respectively. After reperfusion for 12-24 h, the number of neutrophils on the ischemic side increased markedly, whereas the increase was not observed on the contralateral side. Administration of L-histidine (1000 mg/kg x 2, i.p.), immediately and 6 h after reperfusion, reduced the number of neutrophils to 52%. Simultaneous administration of thioperamide (5 mg/kg, s.c.) further decreased the number of neutrophils to 32%. Likewise, the ischemia induced increase in the number of CD68-positive cells after 24 h was suppressed by L-histidine injections. The L-histidine administration decreased the number of CD4+ T lymphocytes on both ischemic and contralateral sides after 12 h, and concurrent administration of thioperamide prolonged the effect. Although administration of mepyramine (3 nmol, i.c.v.) did not affect suppression of leukocyte infiltration, ranitidine tended to reverse the effect of L-histidine. These data suggest that enhancement of central histaminergic activity suppresses inflammatory cell recruitment after ischemic events through histamine H2 receptors, which may be a mechanism underlying the protective effect of L-histidine.

A comparison of protective effects between l-histidine and hypothermia against ischemia-induced neuronal damage in gerbil hippocampus

An increase in the histamine concentration in the brain has been demonstrated to provide protective effects against ischemia/reperfusion brain injury. Since hypothermia and barbiturates are also regarded to protect ischemic brains, effects of postischemic treatments were compared in gerbils between mild hypothermia and intraperitoneal administration of L-histidine, a precursor of histamine. Furthermore, effects of thioperamide, a histamine H(3) receptor antagonist, were evaluated in histidine-treated gerbils after 60 days. Transient forebrain ischemia for 4 min at 37 degrees C provoked severe neuronal damage in the hippocampal CA1 pyramidal cells after 7 days. Postischemic hypothermia (33 degrees C) for 3 h under pentobarbital anesthesia alleviated neuronal death, and the number of preserved neurons was 77+/-56/mm (mean+/-S.D., n=14). The effect of L-histidine injected three times, immediately, 6 h, and 24 h after reperfusion (1,000 mg/kg, i.p., each), was more prominent than that of hypothermia, and the number of preserved neurons was 142+/-55/mm (n=14). When the histologic outcome was evaluated after 60 days, most neurons were damaged in both the hypothermic and histidine groups. The improvement of the histologic outcome was observed even after 60 days in animals injected with thioperamide, immediately and 6 h after reperfusion (5 mg/kg, s.c., each), with three injections of l-histidine. The number of preserved neurons was 133+/-88/mm (n=10), while that in the hypothermic group was 7+/-15 (n=10). Activation of the central histaminergic system provides beneficial effects against cerebral ischemia.

Manganese modulates pro-inflammatory gene expression in activated glia

Redox-active metals are of paramount importance for biological functions. Their impact and cellular activities participate in the physiological and pathophysiological processes of the central nervous system (CNS), including inflammatory responses. Manganese is an essential trace element and it is required for normal biological activities and ubiquitous enzymatic reactions. However, excessive chronic exposure to manganese results in neurobehavioral deficits. Recent evidence suggests that manganese neurotoxicity involves activation of microglia or astrocytes, representative CNS immune cells. In this study, we assessed the molecular basis of the effects of manganese on the modulation of pro-inflammatory cytokines and nitric oxide (NO) production in primary rat cortical glial cells. Cultured glial cells consisted of 85% of astrocytes and 15% of microglia. Within the assayed concentrations, manganese was unable to induce tumor necrosis factor alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS) expression, whereas it potentiated iNOS and TNF-alpha gene expression by lipopolysaccharide/interferon-gamma-activated glial cells. The enhancement was accompanied by elevation of free manganese, generation of oxidative stress, activation of mitogen-activated protein kinases, and increased NF-kappaB and AP-1 binding activities. The potentiated degradation of inhibitory molecule IkappaB-alpha was one of underlying mechanisms for the increased activation of NF-kappaB by manganese. However, manganese decreased iNOS enzymatic activity possibly through the depletion of cofactor since exogenous tetrahydrobiopterin reversed manganese's action. These data indicate that manganese could modulate glial inflammation through variable strategies.

Neuroprotection by tetramethylpyrazine against ischemic brain injury in rats

In traditional Chinese medicine, Ligusticum wallichii Franchat (Chuan Xiong) and its active ingredient tetramethylpyrazine (TMP) have been used to treat cardiovascular diseases and to relieve various neurological symptoms such as ischemic deficits. However, scientific evidence related to their effectiveness or precise modes of neuroprotective action is largely unclear. In the current study, we elicited the neuroprotective mechanisms of TMP after focal cerebral ischemic/reperfusion (I/R) by common carotid arteries and middle cerebral artery occlusion model in rats. TMP was administrated 60 min before occlusion via intraperitoneal injection. TMP concentration-dependently exhibited significant neuroprotective effect against ischemic deficits by reduction of behavioral disturbance. Neuronal loss and brain infarction in the ischemic side of rats were markedly lowered by treatment with TMP. Cerebral I/R-induced internucleosomal DNA fragmentation, caspase-8, caspase-9, and caspase-3 activation, and cytochrome c release were reduced by TMP treatment. Western blot analysis revealed the down-regulation of Bcl-2 and Bcl-xL and the up-regulation of Bax and Bad by cerebral I/R insult. Among them, only the alteration in Bcl-xL expression was reversed by TMP treatment. Moreover, the activation of microglia and/or recruitment of inflammatory cells within the ischemic side and the consequent production of monocyte chemoattractant protein 1 (MCP-1) were suppressed by TMP pre-treatment. Our findings suggest that TMP might provide neuroprotection against ischemic brain injury, in part, through suppression of inflammatory reaction, reduction of neuronal apoptosis, and prevention of neuronal loss.

Progress in the identification of stroke-related genes: emerging new possibilities to develop concepts in stroke therapy

Stroke is a very complex disease influenced by many risk factors: genetic, environmental and comorbidities, such as hypertension, diabetes mellitus, obesity and having had a previous stroke. Neuroprotective therapies that have been found to be successful in laboratory animals have failed to produce the same benefits in clinical trials. Currently, a re-analysis of the clinical trial failures is underway and new therapeutic approaches using the growing knowledge from neurogenesis and neuroinflammation studies, combined with the information from gene expression studies, are taking place. This review focuses on possible ways to identify therapeutic targets using the new discoveries in neuroinflammation and intrinsic regenerative mechanisms of the brain. Molecular events associated with ischaemia trigger an environment for inflammation. Within the ischaemic region and its penumbra, a battery of chemokines and cytokines are released, which have both detrimental and beneficial effects, depending on the specific timepoint after injury and the current activation status of microglia/macrophages. Preventive therapies and treatments for stroke may be established by identifying the genes that are responsible for the induction of those phenotypic changes of microglia/macrophages that switch them to become players in tissue repair and regeneration processes. To aid in the establishment of new target sources for novel therapeutic agents, animal stroke models should closely mimic stroke in humans. To do so, these models should take into account the various risk factors for stroke. For example, hypertensive animals have a more vulnerable blood-brain barrier that in turn may trigger a greater degree of damage after stroke. Furthermore, in aged animals an accelerated astrocytic and microglial reaction has been observed and the regenerative capacity of aged brains is not as high as young brains. Improvements in animal models may also help to ensure better success rates of potential therapies in clinical studies. Inflammation in the brain is a double-edged sword--characterised by the deleterious effect of nerve cell damage and nerve cell death, as well as the beneficial influence on regeneration. The major challenge to develop successful stroke therapies is to broaden the knowledge regarding the underlying pathologic processes and the intrinsic mechanisms of the brain to drive regenerative and plasticity-related changes. On this basis, new concepts can be created leading to better stroke therapy.

Reduction in brain infarction by augmentation of central histaminergic activity in rats

Inflammation is a factor in the aggravation of reperfusion injury after cerebral ischemia. Since histamine H(2) receptor stimulation suppresses inflammatory reactions, effects of the central histaminergic activation on brain infarction were examined in rats. Focal cerebral ischemia for 2 h was provoked by transient occlusion of the right middle cerebral artery, and the infarct size was determined by 2,3,5-triphenyltetrazolium chloride stain after 24 h. Effects of postischemic administration of thioperamide, an H(3) antagonist, and metoprine, an inhibitor of histamine-N-methyltransferase, were evaluated in rats treated with l-histidine, a precursor of histamine. Furthermore, effects of these agents on changes in the striatal histamine level were examined by a microdialysis procedure. Focal ischemia provoked marked damage in rats treated with l-histidine (1000 mg/kg) alone. Administration of l-histidine (1000 mg/kg) with either thioperamide (5 mg/kg) or metoprine (10 mg/kg) alleviated brain infarction. The size of brain infarction was 27% and 10% of that in animals treated solely with l-histidine, respectively. The combination treatment with thioperamide and metoprine decreased the size of brain infarction in rats given l-histidine (500 mg/kg), although protective effects were not clear without l-histidine. A marked increase in the histamine concentration was observed in the histidine plus metoprine group, the value being 363% of that in the saline-injected group after 2-3 h. The histamine concentrations in the histidine group and histidine plus thioperamide group were 188% and 248%, respectively. These findings indicate that facilitation of central histaminergic activity reduced the brain infarction.

Cerebral ischemia and brain histamine

Cerebral ischemia induces excess release of glutamate and an increase in the intracellular Ca(2+) concentration in neurons, which provokes enzymatic process leading to irreversible neuronal injury. Histamine plays a role as a neurotransmitter in the mammalian brain, and histamine release from nerve endings is enhanced in ischemia by facilitation of histaminergic activity. Dissimilar to ischemia-induced release of glutamate, histamine release is gradual and long lasting. The enhancement may contribute to neuroprotection against ischemic damage, because suppression of histaminergic activity aggravates the histologic outcome caused by ischemia. Preischemic administration of histamine (i.c.v.) suppresses ischemic release of glutamate and ameliorates neuronal damage, whereas blockade of central histamine H(2) receptors aggravates ischemic injury. These suggest that histamine provides beneficial effects against ischemic damage through histamine H(2) receptors, when administered before induction of ischemia. Postischemic loading with histidine, a precursor of histamine, alleviates both brain infarction and delayed neuronal death. Since the alleviation is abolished by blockade of central histamine H(2) receptors, facilitation of central histamine H(2) action caused by histidine may prevent reperfusion injury after ischemic events. Because the ischemia-induced increase in the glutamate level rapidly resumes after reperfusion of cerebral blood flow, beneficial effects caused by postischemic loading with histidine may be due to other mechanisms besides suppression of excitatory neurotransmitter release. Anti-inflammatory action by histamine H(2) receptor stimulation is a likely mechanism responsible for the improvement.

Prevention of brain infarction by postischemic administration of histidine in rats

Focal cerebral ischemia for 2 h by occlusion of the right middle cerebral artery provoked severe brain infarction in the rat brain after 24 h. Intraperitoneal administration of histidine, a precursor of histamine, immediately and 6 h after reperfusion, alleviated brain infarction. The infarct size in the histidine (200 mg/kg, 500 mg/kg, and 1000 mg/kg, each time) groups was 71%, 39%, and 7% of that in the control group, respectively. Although intracerebroventricular administration of mepyramine (3 nmol), an H1 antagonist, did not affect the morphologic outcome in histidine-treated rats, ranitidine (30 nmol), an H2 antagonist, completely abolished the alleviation caused by histidine. These findings indicate that postischemic administration of histidine prevents development of brain infarction by stimulating central histamine H2 receptors.

Tetramethylpyrazine reduces ischemic brain injury in rats

Tetramethylpyrazine (TMP), which is widely used in the treatment of ischemic stroke by Chinese herbalists, is one of the most important active ingredients of the traditional Chinese herbal medicine, Ligusticum wallichii Franchat (Chung Xiong). However, the mechanism by which TMP protects the brain is still not clear. We examined neuroprotective effects of TMP after transient focal cerebral ischemia using common carotid artery and middle cerebral artery occlusion model in rats and evaluated the involvement of anti-inflammation. TMP administrated intraperitoneally significantly protected the brain against ischemic insult as evidenced by the reduction in infarction volume, preservation of neurons, and decrease in brain edema. TMP markedly reduced cerebral ischemia/reperfusion-induced inflammatory cell activation and proinflammatory mediator production. Moreover, TMP suppressed lipopolysaccharide/interferon-gamma-induced inflammation and prostaglandin E(2) production in cultured glial cells. Our findings suggest that one of neuroprotective effects of TMP against ischemic brain injury might involve its anti-inflammatory potential.

Temporal changes in cerebral antioxidant enzyme activities after ischemia and reperfusion in a rat focal brain ischemia model: effect of dietary fish oil

This study investigated the neuroprotective effects of dietary supplementation of fish oil on both brain infarction and the activities of antioxidant enzymes. Male Sprague-Dawley rats (4-weeks old) were divided into two groups and received either a regular diet (RD) or a fish-oil-supplemented diet (FOD) for 6 weeks prior to middle cerebral artery (MCA) occlusion. The infarction volume of the brain was calculated using image analysis after staining. Antioxidant enzymes were measured before ischemia (BI), after 2 h of ischemia (AI) and after 24 h (24hR), 48 h (48hR) and after 7 days (7dR) of reperfusion. The infarction volume of the brain was significantly smaller in the FOD group than in the RD group after 24 h of reperfusion (p<0.05). Before ischemia, the levels of lipid peroxide and the glutathione peroxidase (GPx) activity were higher in the FOD group than in the RD group. During reperfusion, the catalase (CAT) activity in the FOD group remained at the preischemia level until after 48 h of reperfusion, while those in the RD group did not. The Mn-superoxide dismutase (SOD) activity and GPx activity were higher in the FOD group than in the RD group only after 2 h of ischemia. In the fatty acid analysis, the ratio of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were higher in the FOD group than in the RD group (p<0.05). Our results demonstrate that supplementing the diet with fish oil could decrease the cerebral infarction volume following ischemia and reperfusion (I/R) partly by working directly as an antioxidant and partly by modulating antioxidant enzyme activities.

Transient focal ischemia in rat brain differentially regulates mRNA expression of protease-activated receptors 1 to 4

Degeneration or survival of cerebral tissue after ischemic injury depends on the source, intensity, and duration of the insult. In the model of focal ischemia, reduced blood flow results in a cascade of pathophysiologic events, including inflammation, excitotoxicity, and platelet activation at the site of injury. One serine protease that is associated closely with and produced in response to central nervous system (CNS) injury is thrombin. Thrombin enters the injury cascade in brain either via a compromised blood-brain barrier or possibly from endogenous prothrombin. Thrombin mediates its action through the protease-activated receptor family (PAR-1, -3, and -4). PARs belong to the superfamily of G protein-coupled receptors with a 7-transmembrane domain structure and are activated by proteolytic cleavage of their N-terminus. We showed that thrombin can be neuroprotective or deleterious when present at different concentrations before and during oxygen-glucose deprivation, an in vitro model of ischemia. We examined the change in mRNA expression levels of PAR-1 to 4 as a result of transient focal ischemia in rat brain, induced by microinjection of endothelin near the middle cerebral artery. Using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis, after ischemic insult on the ipsilesional side, PAR-1 was found to be downregulated significantly, whereas PAR-2 mRNA levels decreased only moderately. PAR-3 was upregulated transiently and then downregulated, and PAR-4 mRNA levels showed the most striking (2.5-fold) increase 12 hr after ischemia, in the injured side. In the contralateral hemisphere, mRNA expression was also affected, where decreased mRNA levels were observed for PAR-1, -2, and -3, whereas PAR-4 levels were reduced only after 7 days. Taken together, these data suggest involvement of the thrombin receptors PAR-1, PAR-3, and PAR-4 in the pathophysiology of brain ischemia.

Ethanol attenuates ischemic and hypoxic injury in rat brain and cultured neurons

Reactive oxygen species play a critical role in ischemic injury and oxidative stress induces apoptosis and triggers inflammation in neural cells. The effect of ethanol on ischemic brain injury was examined. Ethanol attenuated ischemia/reperfusion-induced brain infarction and elevation of inflammatory mediators, including tumor necrosis factor-alpha (TNF-alpha) expression, metalloproteinase-9, and neutrophil-associated myeloperoxidase activities. In cultured neurons, ethanol suppressed combined oxygen and glucose deprivation (COGD)/reoxygenation-induced oxidative stress and neuronal apoptosis. Furthermore, ethanol suppressed COGD/reoxygenation-induced activation of NF-kappaB, a free-radical-sensitive regulator, leading to the attenuation of TNF-alpha expression in glial cultures. We propose that scavenging of free radicals and attenuation of free-radical-induced alterations might account for ethanol's beneficial action against ischemic brain injury.

Inhibition of inducible nitric oxide synthase expression by baicalein in endotoxin/cytokine-stimulated microglia

Excessive production of nitric oxide (NO) in the central nervous system (CNS) mediated by activation of microglia has been implicated in neurotoxicity after stresses such as ischemia. Baicalein, a polyphenolic flavonoid antioxidant, is known to have anti-inflammatory, anticarcinogenic, and neuroprotective effects. In the present study, we report the inhibitory effect of baicalein on endotoxin/cytokine-induced NO production and inducible nitric oxide synthase (iNOS) gene expression in microglia. Baicalein abolished the endotoxin/cytokine-induced expression of iNOS protein, iNOS mRNA, and iNOS promoter activity in a parallel concentration-dependent manner. The suppression of iNOS expression was not mediated through the down-regulation of tumor necrosis factor-alpha (TNF-alpha) by baicalein because TNF-alpha failed to enhance endotoxin/cytokine-induced NO production in microglia. From the electrophoretic mobility shift assay (EMSA), we found that baicalein exerted a distinct inhibitory effect on the DNA binding activity of transcription factors, and this was significantly greater in nuclear factor IL-6 (NF-IL6) than in nuclear factor kappa B (NF-kappaB) and activated protein 1 (AP-1). Although extracellular signal-regulated kinase (ERK) is critical to iNOS expression, endotoxin/cytokine-stimulated phosphorylation of ERK1/2 was not significantly inhibited by baicalein. These results indicate that NF-IL6 inactivation could be the major determinant for the suppression of NO production by baicalein in microglia. Furthermore, it suggests that the inhibitory effect of baicalein on microglia activation and neurotoxic factor production is responsible for its neuroprotective action.

Alleviation of ischemic neuronal damage by postischemic loading with histidine in the rat striatum

Inflammatory reactions play an important role in ischemia-reperfusion injury in the brain. Since histamine H(2) action suppresses inflammatory reactions, effects of postischemic loading with histidine, a precursor of histamine, were examined. Focal cerebral ischemia for 15 min was provoked by transient occlusion of the right middle cerebral artery in rats, and delayed neuronal death were evaluated in striatal neurons after 7 days. Histidine was administered four times, immediately, 6, 24, and 48 h after reperfusion of blood flow (1000 mg/kg, i.p., each time). To examine the role of histaminergic action on changes in histologic outcome, effects of mepyramine (3 nmol, i.c.v.), an H(1) antagonist, and ranitidine (30 nmol, i.c.v.), an H(2) antagonist, were evaluated in histidine-treated rats. Transient ischemia for 15 min provoked severe neuronal damage in the saline-injected control group, and the number of striatal neurons decreased to 21% of that on the contralateral side. Administration of histidine alleviated ischemic neuronal damage, and the number of preserved neurons was 76% of that on the contralateral side. Simultaneous administration of mepyramine with histidine did not affect the histologic outcome. However, administration of ranitidine abolished the alleviation by histidine. These findings indicate that the elevation of histamine H(2) receptor stimulation by massive administration of histidine suppresses reperfusion injury in the brain.

Minocycline reduces cell death and improves functional recovery after traumatic spinal cord injury in the rat

We examined the effects of minocycline, an anti-inflammatory drug, on functional recovery following spinal cord injury (SCI). Rats received a mild, weight-drop contusion injury to the spinal cord and were treated with the vehicle or minocycline at a dose of 90 mg/kg immediately after SCI and then twice at a dose of 45 mg/kg every 12 h. Injecting minocycline after SCI improved hind limb motor function as determined by the Basso-Beattie-Bresnahan (BBB) locomotor open field behavioral rating test. Twenty four to 38 days after SCI, BBB scores were significantly higher in minocycline-treated rats as compared with those in vehicle-treated rats. Morphological analysis showed that lesion size increased progressively in both vehicle-treated and minocycline-treated spinal cords. However, in response to treatment with minocycline, the lesion size was significantly reduced at 21-38 days after SCI when compared to the vehicle control. Minocycline treatment significantly reduced the number of terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL)-positive cells 24 h after SCI as compared to that of the vehicle control. DNA gel electrophoresis also revealed a marked decrease in DNA laddering in response to treatment with minocycline. In addition, minocycline treatment significantly reduced the specific caspase-3 activity after SCI as compared to that of vehicle control. Furthermore, RT-PCR analyses revealed that minocycline treatment increased expression of interleukin-10 mRNA but decreased tumor necrosis factor-alpha expression. These data suggest that, after SCI, minocycline treatment modulated expression of cytokines, attenuated cell death and the size of lesions, and improved functional recovery in the injured rat. This approach may provide a therapeutic intervention enabling us to reduce cell death and improve functional recovery after SCI.

Alleviation of ischemic neuronal damage by histamine H2 receptor stimulation in the rat striatum

Transient ischemia was produced for 15 min by occlusion of the middle cerebral artery in halothane-anesthetized rats, and changes in the extracellular concentrations of neurotransmitter monoamines and amino acids were examined in the striatum. The occlusion produced marked increases in the extracellular concentrations of both dopamine and glutamate in the striatum in the saline-injected control group, the peak values being 148 and 5.2 times those before ischemia, respectively. Preischemic administration of histamine (200 nmol, i.c.v.) suppressed the increase in dopamine and glutamate levels during ischemia, the peak values being 38% and 40% of those in the control group, respectively. Neither the dopamine nor glutamate level was affected by 6-[2-(4-imidazolyl)ethylamino]-N-(trifluoromethylphenyl)heptanecarboxamide (HTMT), an H(1) agonist (100 nmol, i.c.v.). However, dimaprit, an H(2) agonist (100 nmol, i.c.v.) suppressed the peak values to 42% and 32%, respectively. Most neurons were degenerated 7 days after ischemia in control animals. Histologic outcome was alleviated by either histamine or dimaprit treatment, whereas HTMT did not affect the outcome. Although postischemic administration of mepyramine, an H(1) antagonist (5 nmol, i.c.v.), did not affect the histologic alleviation caused by preischemic treatment with histamine, ranitidine, an H(2) antagonist (30 nmol, i.c.v.), partly abolished the improvement caused by histamine. These results suggest that suppression of ischemic release of excitatory neurotransmitters by histamine H(2) action is a contributing factor in alleviation of histologic outcome.

LF 16-0687 Ms, a bradykinin B2 receptor antagonist, reduces ischemic brain injury in a murine model of transient focal cerebral ischemia

1. Bradykinin promotes neuronal damage and brain edema through the activation of the B(2) receptor. The neuroprotective effect of LF 16-0687 Ms, a B(2) receptor antagonist, has been described when given prior to induction of transient focal cerebral ischemia in rat, but there are no data regarding the consequence of a treatment when given after injury. Therefore, in a murine model of transient middle cerebral artery occlusion (MCAO), we evaluated the effect of LF 16-0687 Ms given prior to and/or after the onset of ischemia on neurological deficit, infarct volume and inflammatory responses including cerebral edema, blood-brain barrier (BBB) disruption and neutrophil accumulation. 2. LF 16-0687 Ms (1, 2 and 4 mg kg(-1)) administered 0.5 h before and, 1.25 and 6 h after MCAO, decreased the infarct volume by a maximum of 33% and significantly improved the neurological recovery. 3. When given at 0.25 and 6.25 h after MCAO, LF 16-0687 Ms (1.5, 3 and 6 mg kg(-1)) decreased the infarct volume by a maximum of 25% and improved the neurological score. 4. Post-treatment with LF 16-0687 Ms (1.5 mg kg(-1)) significantly decreased brain edema (-28%), BBB disruption (-60%) and neutrophil accumulation (-65%) induced by ischemia. Physiological parameters were not modified by LF 16-0687 Ms. 5. These data emphasize the role of bradykinin B(2) receptor in the development of infarct lesion, neurological deficit and inflammatory responses resulting from transient focal cerebral ischemia. Therefore, B(2) receptor antagonist might represent a new therapeutic approach in the pharmacological treatment of stroke.

Neuroprotective effects of (S)-N-[4-[4-[(3,4-Dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)carbonyl]-1-piperazinyl]phenyl]-2-thiophenecarboximid-amide (BN 80933), an inhibitor of neuronal nitric-oxide synthase and an antioxidant, in model of transient focal cerebral ischemia in mice

Nitric oxide (NO) and reactive oxygen species are both implicated in neuronal death due to cerebral ischemia. BN 80933, an original compound associating an inhibitor of neuronal NO synthase with an antioxidant, has been shown to reduce functional and histological damage in rat submitted to cerebral ischemia. The aim of the present study was to confirm these results in mice and to further examine the effects of BN 80933 on inflammatory response, including blood-brain barrier (BBB) disruption, brain edema, and neutrophil infiltration after transient middle cerebral artery occlusion (MCAO). Intravenous administration of BN 80933 at 3 and 10 mg/kg 3 h after MCAO significantly reduced by 26 to 36% the infarct volume evaluated 24 and 48 h after ischemia, and improved the neurological score. Furthermore, BN 80933 at both dosages decreased by 42 to 75% the extravasation of Evans blue in brain parenchyma observed 24 h after ischemia. This reduction in BBB disruption was associated with decreased brain edema as demonstrated by the 37% reduction in brain water content induced by BN 80933 at 3 mg/kg 24 h after MCAO. Neutrophil infiltration in brain parenchyma, evaluated by the myeloperoxidase activity, was also reduced by 45 to 56% in animals treated with BN 80933 at 3 and 10 mg/kg. Together, these results extend the protective capacity of BN 80933 against brain ischemic injury and confirm that BN 80933 represents a promising treatment for stroke.

Inflammatory mechanisms after ischemia and stroke

Inflammation has been implicated as a secondary injury mechanism following ischemia and stroke. A variety of experimental models, including thromboembolic stroke, focal and global ischemia, have been used to evaluate the importance of inflammation. The vasculature endothelium promotes inflammation through the upregulation of adhesion molecules such as ICAM, E-selectin, and P-selectin that bind to circulating leukocytes and facilitate their migration into the CNS. Once in the CNS, the production of cytotoxic molecules may facilitate cell death. The macrophage and microglial response to injury may either be beneficial by scavenging necrotic debris or detrimental by facilitating cell death in neurons that would otherwise recover. While many studies have tested these hypotheses, the importance of inflammation in these models is inconclusive. This review summarizes data regarding the role of the vasculature, leukocytes, blood-brain barrier, macrophages, and microglia after experimental and clinical stroke.

Estrogen attenuates tumor necrosis factor-alpha expression to provide ischemic neuroprotection in female rats

Proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) plays an important role in the pathogenesis of neurodegenerative diseases including ischemia. Circulating estrogen is positively associated with neuroprotection against ischemia in female rats. In the present study, we examined whether endogenous estrogen levels affect ischemia-induced TNF-alpha expression in normal cycling female rats. An elevated concentration of TNF-alpha was toxic to neurons. A high level of expression of TNF-alpha accompanied the decline in circulating estrogen levels in normal cycling female rats. Estrogen administration attenuated endotoxin-induced TNF-alpha expression and neuronal injury, indicating that the down-regulation of TNF-alpha expression plays a role in ischemic neuroprotection by estrogen. Therefore, we propose that one mechanism by which estrogen protects females from ischemic damage is through the regulation of TNF-alpha production.

Hwangryun-Hae-Dok-tang (Huanglian-Jie-Du-Tang) extract and its constituents reduce ischemia-reperfusion brain injury and neutrophil infiltration in rats

The preventive effect of Hwangryun-Hae-Dok-tang (HHDT, Huanglian-Jie-Du-Tang), a Chinese herbal medicine, and its ingredients on ischemia/reperfusion-induced brain injury was evaluated in the rat brain. HHDT consists of four herbs, namely, Coptidis rhizoma, Scutellariae radix, Phellodendri cortex, and Gardeniae fructus. Ischemia was induced by intraluminal occlusion of the right middle cerebral artery for 120 min and reperfusion was continued for 22 h. HHDT (200 mg/kg), Coptidis rhizoma (100 mg/kg), Scutellariae radix (100 mg/kg), Phellodendri cortex (100 mg/kg), and Gardeniae fructus (100 mg/kg) were orally administered, promptly prior to reperfusion and 2 h after reperfusion. Baicalein, a component of Scutellariae radix, was also examined at a dosage of 50 mg/kg given 2 h apart, promptly prior to and 2 h after reperfusion. Total infarction volume in the ipsilateral hemisphere of ischemia/reperfusion rats was significantly lowered by treatment with HHDT, Scutellariae radix, and balicalein. However, the other ingredient of HHDT did not show any ameliorating effects on total infarction volume. The inhibiting effect of Scutellariae radix on total infarction volume was much higher than that of the others. In addition, HHDT, Scutellariae radix, and baicalein significantly inhibited myeloperoxidase (MPO) activity, an index of neutrophil infiltration in ischemic brain tissue at about the same rate (30%). There was marked mismatch between total infarction volume and MPO activity in the Scutellariae radix-treated rats but not in the HHDT- and baicalein-treated groups. Our findings suggest that Scutellariae radix as an ingredient of HHDT plays a crucial protective role in ischemia-induced brain injury. In addition, it is apparent that the effect of Scutellariae radix is the result, in part, of baicalein, a compound contained in Scutellariae radix.