Yh Wang

Melatonin ameliorates neural function by promoting endogenous neurogenesis through the MT2 melatonin receptor in ischemic-stroke mice

Melatonin has many protective effects against ischemic stroke, but the underlying neuroprotective mechanisms are not fully understood. Our aim was to explore the relationship between melatonins neuroprotective effects and activation of the MT2 melatonin receptor in a murine ischemic-stroke model. Male ICR mice were subjected to a transient middle cerebral ischemic/reperfusional injury, and melatonin (5 and 10 mg/kg, ip) was administrated once daily starting 2 h after ischemia. More than 80% of the mice died within 5 days after stroke without treatment. Melatonin treatment significantly improved the survival rates and neural functioning with modestly prolonged life span of the stroke mice by preserving blood-brain barrier (BBB) integrity via a reduction in the enormous amount of stroke-induced free radical production and significant gp91(phox) cell infiltration. These protective effects of melatonin were reversed by pretreatment with MT2 melatonin receptor antagonists (4-phenyl-2-propionamidotetralin (4P-PDOT) and luzindole). Moreover, treatment with melatonin after stroke dramatically enhanced endogenous neurogenesis (doublecortin positive) and cell proliferation (ki67 positive) in the peri-infarct regions. Most ki67-positive cells were nestin-positive and NG2-positive neural stem/progenitor cells that coexpressed two neurodevelopmental proteins (adam11 and adamts20) and the MT2 melatonin receptor. RT-PCR revealed that the gene expression levels of doublecortin, ki67, adamts20, and adam11 are markedly reduced by stroke, but are restored by melatonin treatment; furthermore, pretreatment with 4P-PDOT and luzindole antagonized melatonins restorative effect. Our results support the hypothesis that melatonin is able to protect mice against stroke by activating MT2 melatonin receptors, which reduces oxidative/inflammatory stress. This results in the preservation of BBB integrity and enhances endogenous neurogenesis by upregulating neurodevelopmental gene/protein expression.

Preventive effect of silymarin in cerebral ischemia-reperfusion-induced brain injury in rats possibly through impairing NF-κB and STAT-1 activation.

Silymarin and silibinin are bioactive components isolated from Silybum marianum. They have been reported to exhibit anti-oxidative and anti-inflammatory effects. Many studies revealed that drugs with potent anti-inflammatory potential can protect animals against inflammation-associated neurodegenerative disease, e.g., stroke. In this current work we established an animal model of acute ischemic stroke injury by inducing cerebral ischemic/reperfusion (CI/R) in rats to elucidate whether silymarin or silibinin can protect animals from CI/R injury. Pretreatment with silymarin, but not silibinin, dose-dependently (1-10μg/kg, i.v.) reduced CI/R-induced brain infarction by 16-40% and improved neurological deficits in rats with a stroke. Elevated pathophysiological biomarkers for CI/R-induced brain injury, including lipid peroxidation, protein nitrosylation, and oxidative stress, were all reduced by silymarin. In addition, expression of inflammation-associated proteins (e.g., inducible nitric oxide synthase, cyclooxygenase-2 and myeloperoxidase), and transcriptional factors (e.g., nuclear factor (NF)-kappa B and signal transducer and activator of transcription (STAT)-1), as well as production of proinflammatory cytokine (e.g., interleukin-1β and tumor necrosis factor-α) was all significantly prevented by silymarin. Furthermore, an in vitro study on microglial BV2 cells showed that silymarin could inhibit nitric oxide and superoxide anion production, possibly by interfering with NF-κB nuclear translocation/activation. Likewise, silymarin pretreatment also inhibited IκB-α degradation and NF-κB nuclear translocation in brain tissues of ischemic rats. Our results reveal that silymarin, but not its active component silibinin, protected rats against CI/R-induced stroke injury by amelioration of the oxidative and nitrosative stresses and inflammation-mediated tissue injury through impeding the activation of proinflammatory transcription factors (e.g., NF-κB and STAT-1) in the upregulation of proinflammatory proteins and cytokines in stroke-damaged sites. In conclusion, silymarin displays beneficial effects of preventing inflammation-related neurodegenerative disease, e.g., stroke, which needs further investigation and clinical evidences.

Dimemorfan protects rats against ischemic stroke through activation of sigma‐1 receptor‐mediated mechanisms by decreasing glutamate accumulation

Dimemorfan, an antitussive and a sigma‐1 (σ1) receptor agonist, has been reported to display neuroprotective properties. We set up an animal model of ischemic stroke injury by inducing cerebral ischemia (for 1 h) followed by reperfusion (for 24 h) (CI/R) in rats to examine the protective effects and action mechanisms of dimemorfan against stroke‐induced damage. Treatment with dimemorfan (1.0 μg/kg and 10 μg/kg, i.v.) either 15 min before ischemia or at the time of reperfusion, like the putative σ1 receptor agonist, PRE084 (10 μg/kg, i.v.), ameliorated the size of the infarct zone by 67–72% or 51–52%, respectively, which was reversed by pre‐treatment with the selective σ1 receptor antagonist, BD1047 (20 μg/kg, i.v.). Major pathological mechanisms leading to CI/R injury including excitotoxicity, oxidative/nitrosative stress, inflammation, and apoptosis are all downstream events initiated by excessive accumulation of extracellular glutamate. Dimemorfan treatment (10 μg/kg, i.v., at the time of reperfusion) inhibited the expressions of monocyte chemoattractant protein‐1 and interleukin‐1β, which occurred in parallel with decreases in neutrophil infiltration, activation of inflammation‐related signals (p38 mitogen‐activated protein kinase, nuclear factor‐κB, and signal transducer and activator of transcription‐1), expression of neuronal and inducible nitric oxide synthase, oxidative/nitrosative tissue damage (lipid peroxidation, protein nitrosylation, and 8‐hydroxy‐guanine formation), and apoptosis in the ipsilateral cortex after CI/R injury. Dimemorfan treatment at the time of reperfusion, although did not prevent an early rise of glutamate level, significantly prevented subsequent glutamate accumulation after reperfusion. This inhibitory effect was lasted for more than 4 h and was reversed by pre‐treatment with BD1047. These results suggest that dimemorfan activates the σ1 receptor to reduce glutamate accumulation and then suppresses initiation of inflammation‐related events and signals as well as induction of oxidative and nitrosative stresses, leading to reductions in tissue damage and cell death. In conclusion, our results demonstrate for the first time that dimemorfan exhibits protective effects against ischemic stroke in CI/R rats probably through modulation of σ1 receptor‐dependent signals to prevent subsequent glutamate accumulation and its downstream pathologic events.

Deciphering the neuroprotective mechanisms of Bu-yang Huan-wu decoction by an integrative neurofunctional and genomic approach in ischemic stroke mice.

ETHNOPHARMACOLOGICAL RELEVANCE Bu-yang Huan-wu decoction (BHD) is a famous traditional Chinese medicine formula that has been used clinically in Asia to treat stroke-induced disability for centuries, but the underlying neuroprotective mechanisms are not fully understood. AIM OF THE STUDY In this study, we aim to investigate the mechanisms of action using an integrative neurofunctional and broad genomics approach. MATERIALS AND METHODS Male ICR mice were subjected to an acute ischemic stroke by inducing a middle cerebral ischemic/reperfusion (CI/R) injury. To examine whether BHD could extend the lifespan of mice with a stroke, we used oral administration of BHD (0.5 and 1.0g/kg) twice daily starting from 2h after ischemia and compared this with vehicle control treatments, recombinant tissue-type plasminogen activator (rt-PA, 10mg/kg, i.v.), and MK-801 (0.2mg/kg, i.p.). An integrative neurofunctional and genomic approach was performed to elucidate the underlying molecular mechanisms of BHD. RESULTS More than 80% of the mice died within 2 days after stroke induction in the vehicle control treatment group. However, the survival rates and life-spans of mice treated with BHD, rt-PA and MK-801 were significantly enhanced as compared to the vehicle-treated CI/R group in all three cases. Mice treated with BHD (1.0g/kg) showed the greatest protective effect across all groups. BHD successfully restored brain function, ameliorated the cerebral infarction, and significantly improved the neurological deficits of the mice with a stroke. BHD also reduced inflammation, oxidative stress, and apoptosis, as well as improved neurogenesis. The molecular impacts of BHD were assessed by genome-wide transcriptome analysis using brains from the CI/R mice. The results showed a total of 377 ischemia-induced probe-sets that were significantly influenced by BHD including 93 probe-sets that were commonly more abundant in BHD-treated and sham mice, and another 284 ischemia-induced probe sets that were suppressed by BHD. Mining the functional modules and genetic networks of these 377 genes revealed a significant upregulation of neuroprotective genes associated with neurogenesis (6 genes) and nervous system development (9 genes), and a significant down-regulation of destructive genes associated with the induction of inflammation (14 genes), apoptosis (15 genes), angiogenesis (11 genes) and blood coagulation (7 genes) by BHD. CONCLUSIONS Our results suggested that BHD is able to protect mice against stroke and extend lifespan primarily through a significant down-regulation of genes involved in inflammation, apoptosis, angiogenesis and blood coagulation, as well as an up-regulation of genes mediating neurogenesis and nervous system development. The changes in expression after treatment with BHD are beneficial after ischemic stroke.

Andrographolide Inhibits PI3K/AKT-Dependent NOX2 and iNOS Expression Protecting Mice against Hypoxia/Ischemia-Induced Oxidative Brain Injury

This study aimed to explore the mechanisms by which andrographolide protects against hypoxia-induced oxidative/nitrosative brain injury provoked by cerebral ischemic/reperfusion (CI/R) injury in mice. Hypoxia IN VITRO was modeled using oxygen-glucose deprivation (OGD) followed by reoxygenation of BV-2 microglial cells. Our results showed that treatment of mice that have undergone CI/R injury with andrographolide (10-100 µg/kg, i. v.) at 1 h after hypoxia ameliorated CI/R-induced oxidative/nitrosative stress, brain infarction, and neurological deficits in the mice, and enhanced their survival rate. CI/R induced a remarkable production in the mouse brains of reactive oxygen species (ROS) and a significant increase in protein nitrosylation; this primarily resulted from enhanced expression of NADPH oxidase 2 (NOX2), inducible nitric oxide synthase (iNOS), and the infiltration of CD11b cells due to activation of nuclear factor-kappa B (NF- κB) and hypoxia-inducible factor 1-alpha (HIF-1 α). All these changes were significantly diminished by andrographolide. In BV-2 cells, OGD induced ROS and nitric oxide production by upregulating NOX2 and iNOS via the phosphatidylinositol-3-kinase (PI3K)/AKT-dependent NF- κB and HIF-1 α pathways, and these changes were suppressed by andrographolide and LY294002. Our results indicate that andrographolide reduces NOX2 and iNOS expression possibly by impairing PI3K/AKT-dependent NF- κB and HIF-1 α activation. This compromises microglial activation, which then, in turn, mediates andrographolides protective effect in the CI/R mice.

Anti-inflammatory effects of dimemorfan on inflammatory cells and LPS-induced endotoxin shock in mice

Dimemorfan (a σ1 receptor agonist) showed neuroprotective properties in animal models of inflammation‐mediated neurodegenerative conditions, but its effects on inflammatory cells and systemic inflammation remain unclear.

2-Methoxystypandrone ameliorates brain function through preserving BBB integrity and promoting neurogenesis in mice with acute ischemic stroke

2-Methoxystypandrone (2-MS), a naphthoquinone, has been shown to display an immunomodulatory effect in a cellular model. To explore whether 2-MS could protect mice against cerebral ischemic/reperfusion (I/R)-induced brain injury, we evaluated 2-MSs protective effects on an acute ischemic stroke by inducing a middle cerebral artery occlusion/reperfusion (MCAO) injury in murine model. Treatment of mice that have undergone I/R injury with 2-MS (10-100 μg/kg, i.v.) at 2 h after MCAO enhanced survival rate and ameliorated neurological deficits, brain infarction, neural dysfunction and massive oxidative stress, due to an enormous production of free radicals and breakdown of blood-brain barrier (BBB) by I/R injury; this primarily occurred with extensive infiltration of CD11b-positive inflammatory cells and upexpression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 and p65 nuclear factor-kappa B (NF-κB). All of these pathological changes were diminished by 2-MS; 2-MS also intensively limited cortical infarction and promoted upexpression of neurodevelopmental genes near peri-infarct cortex and endogenous neurogenesis near subgranular zone of hippocampal dentate gyrus and the subventricular zone, most possibly by inactivation of GSK3β which in turn upregulating β-catenin, Bcl-2 adam11 and adamts20. We conclude that 2-MS blocks inflammatory responses by impairing NF-κB signaling to limit the inflammation and oxidative stress for preservation of BBB integrity; 2-MS also concomitantly promotes neurodevelopmental protein expression and endogenous neurogenesis through inactivation of GSK3β to enhance β-catenin signaling for upexpression of neuroprotective genes and proteins.

Prodigiosin inhibits gp91(phox) and iNOS expression to protect mice against the oxidative/nitrosative brain injury induced by hypoxia-ischemia.

This study aimed to explore the mechanisms by which prodigiosin protects against hypoxia-induced oxidative/nitrosative brain injury induced by middle cerebral artery occlusion/reperfusion (MCAo/r) injury in mice. Hypoxia in vitro was modeled using oxygen-glucose deprivation (OGD) followed by reoxygenation of BV-2 microglial cells. Our results showed that treatment of mice that have undergone MCAo/r injury with prodigiosin (10 and 100μg/kg, i.v.) at 1h after hypoxia ameliorated MCAo/r-induced oxidative/nitrosative stress, brain infarction, and neurological deficits in the mice, and enhanced their survival rate. MCAo/r induced a remarkable production in the mouse brains of reactive oxygen species (ROS) and a significant increase in protein nitrosylation; this primarily resulted from enhanced expression of NADPH oxidase 2 (gp91(phox)), inducible nitric oxide synthase (iNOS), and the infiltration of CD11b leukocytes due to breakdown of blood-brain barrier (BBB) by activation of nuclear factor-kappa B (NF-κB). All these changes were significantly diminished by prodigiosin. In BV-2 cells, OGD induced ROS and nitric oxide production by up-regulating gp91(phox) and iNOS via activation of the NF-κB pathway, and these changes were suppressed by prodigiosin. In conclusion, our results indicate that prodigiosin reduces gp91(phox) and iNOS expression possibly by impairing NF-κB activation. This compromises the activation of microglial and/or inflammatory cells, which then, in turn, mediates prodigiosins protective effect in the MCAo/r mice.

Common and unique mechanisms of Chinese herbal remedies on ischemic stroke mice revealed by transcriptome analyses

ETHNOPHARMACOLOGICAL RELEVANCE Four traditional Chinese herbal remedies (CHR) including Buyang Huanwu decoction (BHD), Xuefu Zhuyu decoction (XZD), Tianma Gouteng decoction (TGD) and Shengyu decoction (SYD) are popular used in treating brain-related dysfunction clinically with different syndrome/pattern based on traditional Chinese medicine (TCM) principles, yet their neuroprotective mechanisms are still unclear. MATERIALS AND METHODS Mice were subjected to an acute ischemic stroke to examine the efficacy and molecular mechanisms of action underlying these CHR. RESULTS CHR treatment significantly enhanced the survival rate of stroke mice, with BHD being the most effective CHR. All CHR were superior to recombinant tissue-type plasminogen activator (rt-PA) treatment in successfully ameliorating brain function, infarction, and neurological deficits in stroke mice that also paralleled to improvements in blood-brain barrier damage, inflammation, apoptosis, and neurogenesis. Transcriptome analyses reveals that a total of 774 ischemia-induced probe sets were significantly modulated by four CHR, including 52 commonly upregulated genes and 54 commonly downregulated ones. Among them, activation of neurogenesis-associated signaling pathways and down-regulating inflammation and apoptosis pathways are key common mechanisms in ischemic stroke protection by all CHR. Besides, levels of plasma CX3CL1 and S100a9 in patients could be used as biomarkers for therapeutic evaluation before functional recovery could be observed. CONCLUSION Our results suggest that using CHR, a combinatory cocktail therapy, is a better way than rt-PA for treating cerebral ischemic-associated diseases through modulating a common as well as a specific group of genes/pathways that may partially explain the syndrome differentiation and treatment principle in TCM.

Preventive Effect of Baicalein on Methamphetamine-Induced Amnesia in the Passive Avoidance Test in Mice

Background/Aims: Methamphetamine abuse may produce cognitive impairment. Baicalein, a bioactive flavonoid, has antioxidative, anti-inflammatory and neuroprotective effects. This study examined the effects of baicalein pretreatment on memory performance in the passive avoidance test after either one dose or an acute binge of methamphetamine in Institute of Cancer Research (ICR) mice. Methods: Methamphetamine was administered by intraperitoneal (i.p.) injection of either one dose (3 mg/kg) or an acute binge (3 mg/kg, 4 i.p. injections at 2-hour intervals). The effects of baicalein pretreatment (1 mg/kg, i.p.) on methamphetamine-induced changes of locomotor activity and memory performance were compared with those of eticlopride, a selective dopamine D2 receptor antagonist. The effects of baicalein on acute binge methamphetamine-induced oxidative stress (malondialdehyde- and nitrotyrosine-modified protein production) in the mouse hippocampus were also examined. Results: One-dose methamphetamine treatment (i.p., 30 min before or immediately after the training trial) induced hyperlocomotion and amnesia in mice, which were blocked by eticlopride but not by baicalein pretreatment. The memory performance in mice was impaired 5 days after acute binge methamphetamine, which was significantly attenuated by baicalein but not by eticlopride pretreatment. Baicalein pretreatment also attenuated acute binge methamphetamine-induced oxidative stress in the mouse hippocampus. Conclusions: Baicalein exhibits antioxidative and neuroprotective effects in attenuating acute binge methamphetamine-induced memory deficits and oxidative hippocampal damage.