Nitric oxide production during focal cerebral ischemia in rats

Mild traumatic brain injury in Drosophila melanogaster alters reactive oxygen and nitrogen species in a sex-dependent manner

Traumatic brain injury (TBI) is an outside force causing a modification in brain function and/or structural brain pathology that upregulates brain inducible nitric oxide synthase (iNOS), instigating increased levels of nitric oxide activity which is implicated in secondary pathology leading to behavioral deficits (Hall et al., 2012; Garry et al., 2015; Kozlov et al., 2017). In mammals, TBI-induced NO production activates an immune response and potentiates metabolic crisis through mitochondrial dysfunction coupled with vascular dysregulation; however, the direct influence on pathology is complicated by the activation of numerous secondary cascades and activation of other reactive oxygen species. Drosophila TBI models have demonstrated key features of mammalian TBI, including temporary incapacitation, disorientation, motor deficits, activation of innate immunity (inflammation), and autophagy responses observed immediately after injury (Katzenberger et al., 2013; Barekat et al., 2016; Simon et al., 2017; Anderson et al., 2018; Buhlman et al., 2021b). We hypothesized that acute behavioral phenotypes would be associated with deficits in climbing behavior and increased oxidative stress. Because flies lack mammalian-like cardiovascular and adaptive immune systems, we were able to make our observations in the absence of vascular disruption and adaptive immune system interference in a system where highly targeted interventions can be rapidly evaluated. To demonstrate the induction of injury, ten-day-old transgenic flies received an injury of increasing angles from a modified high impact trauma (HIT) device where angle-dependent increases occurred for acute neurological behavior assessments and twenty-four-hour mortality, and survival was significantly decreased. Injury caused sex-dependent effects on climbing activity and measures of oxidative stress. Specifically, after a single 60-degree HIT, female flies exhibited significant impairments in climbing activity beyond that observed in male flies. We also found that several measures of oxidative stress, including Drosophila NOS (dNOS) expression, protein nitration, and hydrogen peroxide production were significantly decreased in female flies. Interestingly, protein nitration was also decreased in males, but surpassed sham levels with a more severe injury. We also observed decreased autophagy demand in vulnerable dopaminergic neurons in female, but not male flies. In addition, mitophagy initiation was decreased in females. Collectively, our data suggest that TBI in flies induces acute behavioral phenotypes and climbing deficits that are analogous to mammalian TBI. We also observed that various indices of oxidative stress, including dNOS expression, protein tyrosine nitration, and hydrogen peroxide levels, as well as basal levels of autophagy, are altered in response to injury, an effect that is more pronounced in female flies.

A comprehensive review of stroke-related signaling pathways and treatment in western medicine and traditional Chinese medicine

This review provides insight into the complex network of signaling pathways and mechanisms involved in stroke pathophysiology. It summarizes the historical progress of stroke-related signaling pathways, identifying potential interactions between them and emphasizing that stroke is a complex network disease. Of particular interest are the Hippo signaling pathway and ferroptosis signaling pathway, which remain understudied areas of research, and are therefore a focus of the review. The involvement of multiple signaling pathways, including Sonic Hedgehog (SHH), nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE), hypoxia-inducible factor-1α (HIF-1α), PI3K/AKT, JAK/STAT, and AMPK in pathophysiological mechanisms such as oxidative stress and apoptosis, highlights the complexity of stroke. The review also delves into the details of traditional Chinese medicine (TCM) therapies such as Rehmanniae and Astragalus, providing an analysis of the recent status of western medicine in the treatment of stroke and the advantages and disadvantages of TCM and western medicine in stroke treatment. The review proposes that since stroke is a network disease, TCM has the potential and advantages of a multi-target and multi-pathway mechanism of action in the treatment of stroke. Therefore, it is suggested that future research should explore more treasures of TCM and develop new therapies from the perspective of stroke as a network disease.

Depletion of iNOS-positive inflammatory cells decelerates neuronal degeneration and alleviates cerebral ischemic damage by suppressing the inflammatory response

Ischemic stroke leads to neuronal damage and severe inflammation that activate iNOS expression in different cell types, especially inflammatory cells in the brain. It is shown that NO released from iNOS contributes to the pathological development of cerebral ischemia. However, the role of these iNOS-expressing inflammatory cells in ischemic stroke has not been fully elucidated. Our purpose is to test if ischemia-induced iNOS⁺ inflammatory cells may exaggerate cerebral inflammation to exacerbate neuronal deficit. We studied the dynamics of iNOS⁺ cells after stroke and found an early and sustained iNOS expression at lesion site. Since iNOS is highly expressed in inflammatory cells after injury, we depleted the iNOS ⁺ inflammatory cells via the selective scavenger GdCl₃, and investigated its effect on stroke outcome, neuronal and vascular deficit, and inflammatory response. After GdCl₃ treatment, half of iNOS⁺ inflammatory cells were depleted, including mainly activated microglia/macrophages and some astrocytes. Selective depletion of iNOS⁺ inflammatory cells resulted in a pronounced reduction in brain damage, resulting in improvement of motor ability. Histologic studies and in vivo two-photon imaging data revealed a slowdown of neuronal degeneration after the depletion of iNOS⁺ inflammatory cells. In contrast to iNOS inhibition alone, depletion of iNOS⁺ inflammatory cells profoundly altered the immune microenvironment profile, in addition to reducing NO production. qRT-PCR analysis showed that depletion of iNOS⁺ inflammatory cells significantly restrained the production of pro-inflammatory cytokines, which moderated the immune microenvironment at the lesion site. Taken together, our data demonstrate that depleting iNOS⁺ inflammatory cells prevents neuronal damage not only by inhibiting NO, but also importantly by suppressing the inflammatory response, which is beneficial to ischemic injury. These results provide evidence that iNOS⁺ inflammatory cells, as a vital source of pro-inflammatory cytokines, contribute to the development of ischemic damage and could be a potential therapeutic target for the treatment of ischemia.

Role of Nitric Oxide and Protein S-Nitrosylation in Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a process in which damage is induced in hypoxic tissue when oxygen supply is resumed after ischemia. During IRI, restoration of reduced nitric oxide (NO) levels may alleviate reperfusion injury in ischemic organs. The protective mechanism of NO is due to anti-inflammatory effects, antioxidant effects, and the regulation of cell signaling pathways. On the other hand, it is generally known that S-nitrosylation (SNO) mediates the detrimental or protective effect of NO depending on the action of the nitrosylated target protein, and this is also applied in the IRI process. In this review, the effect of each change of NO and SNO during the IRI process was investigated.

Overview of therapeutic potentiality of Angelica sinensis for ischemic stroke

BACKGROUND

Ischemic stroke is a common cerebrovascular disease. Due to sudden interruption of blood flow by arterial thrombus, amounts of neurons in ischemic central and penumbral regions occur necrosis and apoptosis resulting in serious injury of neurological function. Chinese medicines have a great advantage in ischemic stroke treatment and recovery, especially Angelica sinensis.

PURPOSE

There are a large number of studies reported that Angelica injection and A. sinensis active compounds. We systematically reviewed the effects and mechanisms of A. sinensis in recent years according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statements, and excavated its therapeutic potentiality for exploring more effective and safe compounds for ischemic stroke precision treatment.

RESULTS

A. sinensis extracts and active compounds, such as Z-ligustilide, 3-n-Butylphthalide, and ferulic acid have significant effects of anti-inflammation, anti-oxidative stress, angiogenesis, neurogenesis, anti-platelet aggregation, anti-atherosclerosis, protection of vessels, which contributes to improvement of neurological function on ischemic stroke.

CONCLUSION

A. sinensis is a key agent for ischemic stroke treatment, and worth deeply excavating its therapeutic potentiality with the aid of pharmacological network, computer-aided drug design, artificial intelligence, big data and multi-scale modelling techniques.

Nitric oxide and the brain. Part 2: Effects following neonatal brain injury-friend or foe?

Nitric oxide (NO) has critical roles in a wide variety of key biologic functions and has intricate transport mechanisms for delivery to key distal tissues under normal conditions. However, NO also plays important roles during disease processes, such as hypoxia-ischemia, asphyxia, neuro-inflammation, and retinopathy of prematurity. The effects of exogenous NO on the developing neonatal brain remain controversial. Inhaled NO (iNO) can be neuroprotective or toxic depending on a variety of factors, including cellular redox state, underlying disease processes, duration of treatment, and dose. This review identifies key gaps in knowledge that should prompt further investigation into the possible role of iNO as a therapeutic agent after injury to the brain. IMPACT: NO is a key signal mediator in the neonatal brain with neuroprotective and neurotoxic properties. iNO, a commonly used medication, has significant effects on the neonatal brain. Dosing, duration, and timing of administration of iNO can affect the developing brain. This review article summarizes the roles of NO in association with various disease processes that impact neonates, such as brain hypoxia-ischemia, asphyxia, retinopathy of prematurity, and neuroinflammation. The impact of this review is that it clearly describes gaps in knowledge, and makes the case for further, targeted studies in each of the identified areas.

Role of the Platelets and Nitric Oxide Biotransformation in Ischemic Stroke: A Translative Review from Bench to Bedside

Ischemic stroke remains the fifth cause of death, as reported worldwide annually. Endothelial dysfunction (ED) manifesting with lower nitric oxide (NO) bioavailability leads to increased vascular tone, inflammation, and platelet activation and remains among the major contributors to cardiovascular diseases (CVD). Moreover, temporal fluctuations in the NO bioavailability during ischemic stroke point to its key role in the cerebral blood flow (CBF) regulation, and some data suggest that they may be responsible for the maintenance of CBF within the ischemic penumbra in order to reduce infarct size. Several years ago, the inhibitory role of the platelet NO production on a thrombus formation has been discovered, which initiated the era of extensive studies on the platelet-derived nitric oxide (PDNO) as a platelet negative feedback regulator. Very recently, Radziwon-Balicka et al. discovered two subpopulations of human platelets, based on the expression of the endothelial nitric oxide synthase (eNOS-positive or eNOS-negative platelets, respectively). The e-NOS-negative ones fail to produce NO, which attenuates their cyclic guanosine monophosphate (cGMP) signaling pathway and-as result-promotes adhesion and aggregation while the e-NOS-positive ones limit thrombus formation. Asymmetric dimethylarginine (ADMA), a competitive NOS inhibitor, is an independent cardiovascular risk factor, and its expression alongside with the enzymes responsible for its synthesis and degradation was recently shown also in platelets. Overproduction of ADMA in this compartment may increase platelet activation and cause endothelial damage, additionally to that induced by its plasma pool. All the recent discoveries of diverse eNOS expression in platelets and its role in regulation of thrombus formation together with studies on the NOS inhibitors have opened a new chapter in translational medicine investigating the onset of acute cardiovascular events of ischemic origin. This translative review briefly summarizes the role of platelets and NO biotransformation in the pathogenesis and clinical course of ischemic stroke.

Endogenous BMP-4/ROS/COX-2 Mediated IPC and Resveratrol Alleviated Brain Damage

The objective of the study was to examine the therapeutic role of combined ischemic preconditioning (IPC) and resveratrol (RES) on brain ischemia/reperfusion injury (BI/RI) by modulating endogenous bone morphogenetic protein-4 (BMP-4)/reactive oxygen species (ROS)/cyclooxygenase-2 (COX-2) in rats. Sprague Dawley (SD) rats were pretreated with 20 mg/kg RES (20 mg/kg RES was administered once a day via intraperitoneal injection 7 days prior to the I/R procedure) and IPC (equal volumes of saline were administered once a day by intraperitoneal injection over 7 days, and the bilateral common carotid arteries were separated for clamp 5 minutes followed by 5 minutes of reperfusion prior to the I/R procedure), and then subjected to 2 hours of ischemia and 22 hours of reperfusion. Blood and cerebral tissues were collected, cerebral pathological injuries and infarct sizes were investigated, serum interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels were measured, the activities of superoxide dismutase (SOD) and ROS were calculated, the contents of methane dicarboxylic aldehyde (MDA), IL-6, TNF-α and hemodynamic change were estimated, and expression levels of b-cell lymphoma-2 (Bcl-2), bcl-2-associated x (Bax), BMP-4 and COX-2 were assessed in cerebral tissues. IPC, RES and a combination of IPC and RES preconditioning ameliorated the pathological damage and infarct sizes, reduced cerebral oxidative stress damage, alleviated inflammatory damage, restrained apoptosis, and downregulated the expression levels of BMP-4 and COX-2 compared with those of the ischemia/reperfusion (I/R) group. This study suggested a combined strategy that could enhance protection against BI/RI in clinical brain disease.

Transdermal delivery of glyceryl trinitrate: clinical applications in acute stroke

Introduction: Glyceryl trinitrate (GTN), a nitric oxide donor, is a candidate treatment for the management of acute stroke with hemodynamic and potential reperfusion and neuroprotective effects.Areas covered: Here we discuss the evidence to date from clinical trials and present and future possibilities for the clinical application of transdermal GTN in acute stroke. When administered as a transdermal patch during the acute and subacute phases after stroke, GTN was safe, lowered blood pressure, maintained cerebral blood flow, and did not induce cerebral steal or alter functional outcome. However, when given within the hyperacute phase (<6 h of stroke onset), GTN reduced death and dependency, death, disability, cognitive impairment, and mood disturbance, and improved quality of life. However, in a large prehospital trial with treatment within 4 h, GTN did not influence clinical outcomes.Expert opinion: Transdermal GTN is an easy to administer BP-lowering therapy, which is safe when given after 2 h of stroke onset, may improve outcome when initiated within 2-6 h, but should be avoided (outside of a clinical trial) in the ultra-acute period within 2 h of stroke onset. Further research needs to investigate the mechanisms of benefit or harm in ultra/hyperacute stroke patients.

Effects of Edaravone on Nitric Oxide, Hydroxyl Radicals and Neuronal Nitric Oxide Synthase During Cerebral Ischemia and Reperfusion in Mice

BACKGROUND

The purpose of this study was to investigate the effects of edaravone on nitric oxide (NO) production, hydroxyl radical (OH^-) metabolism, and neuronal nitric oxide synthase (nNOS) expression during cerebral ischemia and reperfusion.

METHODS

Edaravone (3 mg/kg) was administered intravenously to 14 C57BL/6 mice just before reperfusion. Eleven additional mice received saline (controls). NO production and OH^- metabolism were continuously monitored using bilateral striatal in vivo microdialysis. OH^- formation was monitored using the salicylate trapping method. Forebrain ischemia was produced in all mice by bilateral occlusion of the common carotid artery for 10 minutes. Levels of NO metabolites, nitrite (NO₂^-) and nitrate (NO₃^-), were determined using the Griess reaction. Brain sections were immunostained with an anti-nNOS antibody and the fractional area density of nNOS-immunoreactive pixels to total pixels determined.

RESULTS

Blood pressure and regional cerebral blood flow were not significantly different between the edaravone and control groups. The levels of NO₂^- did not differ significantly between the 2 groups. The level of NO₃^- was significantly higher in the edaravone group compared with the control group after reperfusion. 2,3-dihydroxybenzoic acid levels were lower in the edaravone group compared with those in the control group after reperfusion. Immunohistochemistry showed nNOS expression in the edaravone group to be significantly lower than that in the control group 96 hours after reperfusion.

CONCLUSIONS

These in vivo data indicate that edaravone may have a neuroprotective effect by reducing levels of OH^- metabolites, increasing NO production and decreasing nNOS expression in brain cells.

Nitrite Protects Neurons Against Hypoxic Damage Through S-nitrosylation of Caspase-6

Aims: The coordination of neurons to execute brain functions requires plenty of oxygen. Thus, it is not surprising that the chronic hypoxia resulting from chronic obstructive pulmonary diseases (COPD) can cause neuronal damage. Injury in the cortex can give rise to anxiety and cognitive dysfunction. This study investigated what causes hypoxia-induced neuronal injury and what strategies might be used to protect neurons against such damage. Results: This study found that hypoxia in primary cortical neurons caused neurite retraction, a caspase-6-dependent process. The hypoxic stress activated caspase-6 within the neurite, leading to microtubule disassembly and neurite retraction. The effect of hypoxia on caspase-6 activation, microtubule disassembly, and neurite retraction was alleviated by nitrite treatment. The protective role of nitrite was further supported by the observation that the active-site Cys146 of caspase-6 was S-nitrosylated in hypoxic neuro-2a cells treated with nitrite. We further validated the beneficial effect of nitrite on neuronal function against hypoxic stress in vivo. Using the wild-type or Apo E^-/- mice exposed to chronic hypoxia as a model, we demonstrated that supplementing drinking water with nitrite suppressed active caspase-6 in the cortex of the brain, concomitant with the prevention of hypoxia-induced anxiety in the animals. Innovation: These results are the first evidence of a new pathway for the activation of caspase-6 and the first to indicate that nitrite can protect neurons against chronic hypoxic insult. Conclusion: Our findings suggest that nitrite holds great potential for the treatment of diseases such as COPD associated with hypoxia-induced neuronal injury.

Correlation of Serum Nitric Oxide (NO) with Glasgow Coma Scale (GCS) in Acute Ischemic Stroke Patient: A Study in North India

Nitric oxide (NO) is one of the key players in the pathogenesis of ischemic stroke. Limited reports are available about the serum level of NO and their correlation with Glasgow Coma Scale (GCS) score in acute (<24 h) ischemic stroke (AIS) patients. A hospital based, cross sectional study was done in North Indian population to find out correlation of serum NO and GCS in AIS patients. 50 patients of AIS and 25 healthy controls were chosen for the study. Serum NO level was measured by ELISA and GCS scores were assessed by a neurologist. Pearson correlation coefficients were analyzed to look for the relationship between NO and GCS. Statistically highly significant elevation in mean serum NO level was observed in cases as compared to controls (p < 0.01). A negative correlation of NO levels with neurological score of GCS r (48) = -0.144, p > 0.05 was seen. This indicates oxidative stress in acute ischemic stroke may be the result of imbalance in oxidant/antioxidant homeostasis.

Protection of Anthocyanin from Myrica rubra against Cerebral Ischemia-Reperfusion Injury via Modulation of the TLR4/NF-κB and NLRP3 Pathways

Myrica rubra (MR) is rich in anthocyanins, and it has good anti-cancer, anti-aging, antioxidant, and antiviral effects. The proportion of disability and death caused by ischemic stroke gradually increased, becoming a major disease that is harmful to human health. However, research on effects of anthocyanin from MR on cerebral ischemia-reperfusion (I/R) injury is rare. In this study, we prepared eight purified anthocyanin extracts (PAEs) from different types of MR, and examined the amounts of total anthocyanin (TA) and cyanidin-3-O-glucoside (C-3-G). After one week of PAE treatment, the cerebral infarction volume, disease damage, and contents of nitric oxide and malondialdehyde were reduced, while the level of superoxide dismutase was increased in I/R mice. Altogether, our results show that Boqi¹ MR contained the most TA (22.07%) and C-3-G (21.28%), and that PAE isolated from Dongkui MR can protect the brain from I/R injury in mice, with the mechanism possibly related to the Toll-like receptor 4 (TLR4)/ nuclear factor-κB (NF-κB) and NOD-like receptor pyrin domain-containing 3 protein (NLRP3) pathways.

Arctic ground squirrel resist peroxynitrite-mediated cell death in response to oxygen glucose deprivation

Cerebral ischemia-reperfusion (I/R) injury initiates a cascade of events, generating nitric oxide (NO) and superoxide(O₂^•-) to form peroxynitrite (ONOO^-), a potent oxidant. Arctic ground squirrels (AGS; Urocitellus parryii) show high tolerance to I/R injury. However, the underlying mechanism remains elusive. We hypothesize that tolerance to I/R modeled in an acute hippocampal slice preparation in AGS is modulated by reduced oxidative and nitrative stress. Hippocampal slices (400µm) from rat and AGS were subjected to oxygen glucose deprivation (OGD) using a novel microperfusion technique. Slices were exposed to NO, O₂^.- donors with and without OGD; pretreatment with inhibitors of NO, O₂^.- and ONOO^- followed by OGD. Perfusates collected every 15min were analyzed for LDH release, a marker of cell death. 3-nitrotyrosine (3NT) and 4-hydroxynonenal (4HNE) were measured to assess oxidative and nitrative stress. Results show that NO/O₂^.- alone is not sufficient to cause ischemic-like cell death, but with OGD enhances cell death more in rat than in AGS. A NOS inhibitor, SOD mimetic and ONOO^- inhibitor attenuates OGD injury in rat but has no effect in AGS. Rats also show a higher level of 3NT and 4HNE with OGD than AGS suggesting the greater level of injury in rat is via formation of ONOO^-.

Neurological and neuropsychological consequences of electrical and lightning shock: review and theories of causation

Injuries from lightning and electrical injuries involve multiple systems of the body, however neurological symptoms are very widely reported. A disabling neuropsychological syndrome is also noted. This paper presents a comprehensive review of neurological and neuropsychological symptoms. Partial theories of causation for these injuries have been advanced, however, there is no convincing explanation for both delay in onset of symptoms and also the genesis of the neuropsychological syndrome. A theory of causation is proposed which satisfies both these constraints. This theory suggests circulating hormones such as cortisol, together with nitric oxide and oxidant free radicals from glutamatergic hyper-stimulation, act on tissues remote from the injury path including the hippocampus. This theory opens a research path to explore treatment options.

Nitric oxide donors (nitrates), L-arginine, or nitric oxide synthase inhibitors for acute stroke

BACKGROUND

Nitric oxide (NO) has multiple effects that may be beneficial in acute stroke, including lowering blood pressure, and promoting reperfusion and cytoprotection. Some forms of nitric oxide synthase inhibition (NOS-I) may also be beneficial. However, high concentrations of NO are likely to be toxic to brain tissue. This is an update of a Cochrane review first published in 1998, and last updated in 2002.

OBJECTIVES

To assess the safety and efficacy of NO donors, L-arginine, and NOS-I in people with acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (last searched 6 February 2017), MEDLINE (1966 to June 2016), Embase (1980 to June 2016), ISI Science Citation Indexes (1981 to June 2016), Stroke Trials Registry (searched June 2016), International Standard Randomised Controlled Trial Number (ISRCTN) (searched June 2016), Clinical Trials registry (searched June 2016), and International Clinical Trials Registry Platform (ICTRP) (searched June 2016). Previously, we had contacted drug companies and researchers in the field.

SELECTION CRITERIA

Randomised controlled trials comparing nitric oxide donors, L-arginine, or NOS-I versus placebo or open control in people within one week of onset of confirmed stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria, assessed trial quality and risk of bias, and extracted data. The review authors cross-checked data and resolved issues through discussion. We obtained published and unpublished data, as available. Data were reported as mean difference (MD) or odds ratio (OR) with 95% confidence intervals (CI).

MAIN RESULTS

We included five completed trials, involving 4197 participants; all tested transdermal glyceryl trinitrate (GTN), an NO donor. The assessed risk of bias was low across the included studies; one study was double-blind, one open-label and three were single-blind. All included studies had blinded outcome assessment. Overall, GTN did not improve the primary outcome of death or dependency at the end of trial (modified Rankin Scale (mRS) > 2, OR 0.97, 95% CI 0.86 to 1.10, 4195 participants, high-quality evidence). GTN did not improve secondary outcomes, including death (OR 0.78, 95% CI 0.40 to 1.50) and quality of life (MD -0.01, 95% CI -0.17 to 0.15) at the end of trial overall (high-quality evidence). Systolic/diastolic blood pressure (BP) was lower in people treated with GTN (MD -7.2 mmHg (95% CI -8.6 to -5.9) and MD -3.3 (95% CI -4.2 to -2.5) respectively) and heart rate was higher (MD 2.0 beats per minute (95% CI 1.1 to 2.9)). Headache was more common in those randomised to GTN (OR 2.37, 95% CI 1.55 to 3.62). We did not find any trials assessing other nitrates, L-arginine, or NOS-I.

AUTHORS' CONCLUSIONS

There is currently insufficient evidence to recommend the use of NO donors, L-arginine or NOS-I in acute stroke, and only one drug (GTN) has been assessed. In people with acute stroke, GTN reduces blood pressure, increases heart rate and headache, but does not alter clinical outcome (all based on high-quality evidence).

Therapeutic Potential of Transdermal Glyceryl Trinitrate in the Management of Acute Stroke

The nitric oxide donor, glyceryl trinitrate (GTN), is a candidate treatment for the management of acute stroke with haemodynamic and potential reperfusion and neuroprotective effects. When administered as a transdermal patch during the acute and subacute phases after stroke, GTN was safe, lowered blood pressure, maintained cerebral blood flow, and did not induce cerebral steal or alter functional outcome. However, when given within 6 h of stroke onset, GTN reduced death and dependency (odds ratio 0.52; 95% confidence interval 0.34-0.78), death, disability, cognitive impairment and mood disturbance, and improved quality of life (data from two trials, n = 312). In a pooled analysis of four studies (n = 186), GTN reduced between-visit systolic blood pressure variability over days 1-7 compared with no GTN (mean difference -2.09; 95% confidence interval -3.83 to -0.35; p = 0.019). The efficacy of GTN given in the ultra-acute/pre-hospital setting is currently being assessed and, if found to be beneficial, the implications for hyperacute stroke practice are significant. Here, we discuss the evidence to date, potential mechanisms of action and future possibilities, including unanswered questions, for the therapeutic potential of GTN in acute stroke.

Adaptation of the cerebrocortical circulation to carotid artery occlusion involves blood flow redistribution between cortical regions and is independent of eNOS

Cerebral circulation is secured by feed-forward and feed-back control pathways to maintain and eventually reestablish the optimal oxygen and nutrient supply of neurons in case of disturbances of the cardiovascular system. Using the high temporal and spatial resolution of laser-speckle imaging we aimed to analyze the pattern of cerebrocortical blood flow (CoBF) changes after unilateral (left) carotid artery occlusion (CAO) in anesthetized mice to evaluate the contribution of macrovascular (circle of Willis) vs. pial collateral vessels as well as that of endothelial nitric oxide synthase (eNOS) to the cerebrovascular adaptation to CAO. In wild-type mice CoBF reduction in the left temporal cortex started immediately after CAO, reaching its maximum (-26%) at 5-10 s. Thereafter, CoBF recovered close to the preocclusion level within 30 s indicating the activation of feed-back pathway(s). Interestingly, the frontoparietal cerebrocortical regions also showed CoBF reduction in the left (-17-19%) but not in the right hemisphere, although these brain areas receive their blood supply from the common azygos anterior cerebral artery in mice. In eNOS-deficient animals the acute CoBF reduction after CAO was unaltered, and the recovery was even accelerated compared with controls. These results indicate that 1) the Willis circle alone is not sufficient to provide an immediate compensation for the loss of one carotid artery, 2) pial collaterals attenuate the ischemia of the temporal cortex ipsilateral to CAO at the expense of the blood supply of the frontoparietal region, and 3) eNOS, surprisingly, does not play an important role in this CoBF redistribution.

Hydroxyl Radical Production in the Cortex and Striatum in a Rat Model of Focal Cerebral Ischemia

Background:

Increases in hydroxyl radical production have been used as evidence of oxidative stress in cerebral ischemia/ reperfusion. Ischemia can also induce increased dopamine release from the striatum that may contribute to hydroxyl radical formation. We have compared hydroxyl radical production in the cortex and striatum as an index of oxidative stress in a rat model of focal cerebral ischemia with cortical infarction.

Methods:

Using a three vessel occlusion model of focal cerebral ischemia combined with bilateral microdialysis, hydroxylation of 4-hydroxybenzoate (4HB) was continuously monitored in both hemispheres in either the lateral striatum or frontoparietal cortex. The ischemia protocol consisted of one hour equilibration, 30 min of three vessel occlusion, then release of the contralateral common carotid artery (CCA) for 2.5 h.

Results:

Induction of ischemia resulted in a 30-fold increase in dopamine release in the lateral striatum. Compared to the nonischemic striatum, the ratio of the hydroxylation product 3,4-dihydroxybenzoate (34DHB) to 4HB (trapping agent) in the ipsilateral striatum increased significantly 30 min after ischemia induction. In contrast, during the 30 min of three vessel occlusion there was no increase in the ratio in the cortex. Following the release of the contralateral CCA, the ratio from the ischemic cortex increased significantly compared to sham-operated animals. However, under all circumstances, the 34DHB/4HB ratio was greater in the striatum than in the cortex.

Conclusion:

The increase in the 34DHB/4HB ratio in the lateral striatum coincides with the increased dopamine release suggesting a role for dopamine oxidation in the increased production of hydroxyl radicals. The significant increase in the ratio from the ischemic cortex compared to that from the sham-operated animals is consistent with increased oxidative stress induced by ischemia. However, the lower 34DHB/4HB ratio in the cortex whichdoes not receive dopaminergic innervation compared to the striatum suggests a different mechanism for hydroxyl radical production. Such an alternate mechanism may represent a more toxic oxidative insult that contributes to infarction.

Astrocytes, therapeutic targets for neuroprotection and neurorestoration in ischemic stroke

Astrocytes are the most abundant cell type within the central nervous system. They play essential roles in maintaining normal brain function, as they are a critical structural and functional part of the tripartite synapses and the neurovascular unit, and communicate with neurons, oligodendrocytes and endothelial cells. After an ischemic stroke, astrocytes perform multiple functions both detrimental and beneficial, for neuronal survival during the acute phase. Aspects of the astrocytic inflammatory response to stroke may aggravate the ischemic lesion, but astrocytes also provide benefit for neuroprotection, by limiting lesion extension via anti-excitotoxicity effects and releasing neurotrophins. Similarly, during the late recovery phase after stroke, the glial scar may obstruct axonal regeneration and subsequently reduce the functional outcome; however, astrocytes also contribute to angiogenesis, neurogenesis, synaptogenesis, and axonal remodeling, and thereby promote neurological recovery. Thus, the pivotal involvement of astrocytes in normal brain function and responses to an ischemic lesion designates them as excellent therapeutic targets to improve functional outcome following stroke. In this review, we will focus on functions of astrocytes and astrocyte-mediated events during stroke and recovery. We will provide an overview of approaches on how to reduce the detrimental effects and amplify the beneficial effects of astrocytes on neuroprotection and on neurorestoration post stroke, which may lead to novel and clinically relevant therapies for stroke.

Stretch and/or oxygen glucose deprivation (OGD) in an in vitro traumatic brain injury (TBI) model induces calcium alteration and inflammatory cascade

The blood-brain barrier (BBB), made up of endothelial cells of capillaries in the brain, maintains the microenvironment of the central nervous system. During ischemia and traumatic brain injury (TBI), cellular disruption leading to mechanical insult results to the BBB being compromised. Oxygen glucose deprivation (OGD) is the most commonly used in vitro model for ischemia. On the other hand, stretch injury is currently being used to model TBI in vitro. In this paper, the two methods are used alone or in combination, to assess their effects on cerebrovascular endothelial cells cEND in the presence or absence of astrocytic factors. Applying severe stretch and/or OGD to cEND cells in our experiments resulted to cell swelling and distortion. Damage to the cells induced release of lactate dehydrogenase enzyme (LDH) and nitric oxide (NO) into the cell culture medium. In addition, mRNA expression of inflammatory markers interleukin (I L)-6, IL-1α, chemokine (C-C motif) ligand 2 (CCL2) and tumor necrosis factor (TNF)-α also increased. These events could lead to the opening of calcium ion channels resulting to excitotoxicity. This could be demonstrated by increased calcium level in OGD-subjected cEND cells incubated with astrocyte-conditioned medium. Furthermore, reduction of cell membrane integrity decreased tight junction proteins claudin-5 and occludin expression. In addition, permeability of the endothelial cell monolayer increased. Also, since cell damage requires an increased uptake of glucose, expression of glucose transporter glut1 was found to increase at the mRNA level after OGD. Overall, the effects of OGD on cEND cells appear to be more prominent than that of stretch with regards to TJ proteins, NO, glut1 expression, and calcium level. Astrocytes potentiate these effects on calcium level in cEND cells. Combining both methods to model TBI in vitro shows a promising improvement to currently available models.

Hypoxia/ischemia a key player in early post stroke seizures: modulation by opioidergic and nitrergic systems

Stroke is a leading cause of death, disability, and socioeconomic loss worldwide. All attempts at pharmacological reduction of the complications of stroke (e.g. post-stroke seizure, and brain׳s vulnerability to hypoxic/ischemic injury) have failed. Endogenous opioids and nitric oxide (NO) overproduction has been documented in brain hypoxia/ischemia (H/I), which can exert pro-convulsive effects. In this study, we aimed to examine the possible involvement of opioidergic and nitrergic pathways in the pathogenesis of post-stroke seizure. H/I was induced by right common carotid ligation and sham-operated mice served as controls. We demonstrated that right common carotid ligation decreases the threshold for clonic seizures induced by pentylenetetrazole (PTZ), a GABA antagonist. Furthermore, pro-convulsive effect of H/I following right common carotid ligation was blocked by naltrexone (NTX) (3mg/kg), NG-Nitro-l-arginine methyl ester (l-NAME) (10mg/kg), and aminoguanidine (AG) (100mg/kg) administration (P<0.001). Interestingly, co-administration of non-effective doses of NTX and l-NAME (1 and 0.5mg/kg, respectively) reverses epileptogenesis of H/I (P<0.001). In the same way, co-administration of non-effective doses of NTX and AG (1 and 5mg/kg, respectively), reverses epileptogenesis of H/I (P<0.001). Indeed, the histological studies performed on mice exposed to H/I confirmed our previous data. These findings suggest hyper-susceptibility to PTZ induced seizure following H/I is mediated by interaction of opioidergic, and iNOS/NO pathways. Therefore, our results identify new pharmacological targets and provide the rationale for a novel strategy to promote recovery after stroke and possibly other brain injuries.

Blood-letting punctures at twelve Jing-Well points of the hand can treat cerebral ischemia in a similar manner to mannitol

A rat model of middle cerebral artery permanent occlusion was established using the modified Longa method. Successfully established model animals were treated by blood-letting puncture at twelve Jing-Well points of the hand, and/or by injecting mannitol into the caudal vein twice daily. Brain tissue was collected at 24, 48 and 72 hours after modeling, and blood was collected through the retinal vein before Evans blue was injected, approximately 1 hour prior to harvesting of brain tissue. Results showed that Evans blue leakage into brain tissue and serum nitric oxide synthase activity were significantly increased in model rats. Treatment with blood-letting punctures at twelve Jing-Well points of the hand and/or injection of mannitol into the caudal vein reduced the amount of Evans blue leakage into the brain tissue and serum nitric oxide synthase activity to varying degrees. There was no significant difference between single treatment and combined treatment. Experimental findings indicate that blood-letting punctures at twelve Jing-Well points of the hand can decrease blood-brain barrier permeability and serum nitric oxide synthase activity in rats following middle cerebral artery occlusion, and its effect is similar to that of mannitol injection alone and Jing-Well points plus mannitol injection.

S-nitrosylation-mediated redox transcriptional switch modulates neurogenesis and neuronal cell death

Redox-mediated posttranslational modifications represent a molecular switch that controls major mechanisms of cell function. Nitric oxide (NO) can mediate redox reactions via S-nitrosylation, representing transfer of an NO group to a critical protein thiol. NO is known to modulate neurogenesis and neuronal survival in various brain regions in disparate neurodegenerative conditions. However, a unifying molecular mechanism linking these phenomena remains unknown. Here, we report that S-nitrosylation of myocyte enhancer factor 2 (MEF2) transcription factors acts as a redox switch to inhibit both neurogenesis and neuronal survival. Structure-based analysis reveals that MEF2 dimerization creates a pocket, facilitating S-nitrosylation at an evolutionally conserved cysteine residue in the DNA binding domain. S-Nitrosylation disrupts MEF2-DNA binding and transcriptional activity, leading to impaired neurogenesis and survival in vitro and in vivo. Our data define a molecular switch whereby redox-mediated posttranslational modification controls both neurogenesis and neurodegeneration via a single transcriptional signaling cascade.

Detecting tissue deterioration after brain injury: regional blood flow level versus capacity to raise blood flow

Regional cerebral blood flow (rCBF) is spatially and temporally adjusted to local energy needs. This coupling involves dilation of vessels both at the site of metabolite exchange and upstream of the activated region. Deficits in upstream blood supply limit the 'capacity to raise rCBF' in response to functional activation and therefore compromise brain function. We here demonstrate in rats that the 'capacity to raise rCBF' can be determined from real-time measurements of rCBF using laser speckle imaging during an energy challenge induced by cortical spreading depolarizations (CSDs). Cortical spreading depolarizations (CSDs) occur with high incidence in stroke and various other brain injuries and cause large metabolic changes. Various conditions of cerebral perfusion were induced, either by modifying microvascular tone, or by altering upstream blood supply independently. The increase in rCBF per unit of time in response to CSD was linearly correlated to the upstream blood supply. In an experimental model of stroke, we found that this marker of the capacity to raise rCBF which, in pathologic tissue may be additionally limited by impaired vasoactive signaling, was a better indicator of the functional status of cerebral tissue than local rCBF levels.

Reduced inflammatory phenotype in microglia derived from neonatal rat spinal cord versus brain

Microglia are the primary immune cells of the central nervous system (CNS). Membrane bound sensors on their processes monitor the extracellular environment and respond to perturbations of the CNS such as injury or infection. Once activated, microglia play a crucial role in determining neuronal survival. Recent studies suggest that microglial functional response properties vary across different regions of the CNS. However, the activation profiles of microglia derived from the spinal cord have not been evaluated against brain microglia in vitro. Here, we studied the morphological properties and secretion of inflammatory and trophic effectors by microglia derived from the brain or spinal cord of neonatal rats under basal culture conditions and after activation with lipopolysaccharide (LPS). Our results demonstrate that spinal microglia assume a less inflammatory phenotype after LPS activation, with reduced release of the inflammatory effectors tumor necrosis factor alpha, interleukin-1 beta, and nitric oxide, a less amoeboid morphology, and reduced phagocytosis relative to brain-derived microglia. Phenotypic differences between brain and spinal microglia are an important consideration when evaluating anti-inflammatory or immunomodulatory therapies for brain versus spinal injury.

PTEN degradation after ischemic stroke: a double-edged sword

Tumor suppressor phosphatase and tensin homolog (PTEN) is highly expressed in neurons and PTEN inhibition has been reported to be neuroprotective against ischemic stroke in experimental models. On the other hand, PTEN deletion has been shown to lead to cognitive impairment. In the current study, we examined the expression and functions of PTEN in an ischemic stroke rodent model. We found rapid S-nitrosylation and degradation of PTEN after cerebral ischemia/reperfusion injury. PTEN degradation leads to activation of Akt. PTEN partial deletion or PTEN inhibition increased the expression of GABAA receptor (GABAAR) γ2 subunit and enhanced GABAA receptor current. After cerebral ischemia, increased expression of GABAAR γ2 subunit was observed in the ischemia region and the penumbra area. We also observed PTEN loss in astrocytes after cerebral ischemia. Astrocytic PTEN partial knockout increased astrocyte activation and exacerbated ischemic damage. We speculated that ischemic stroke induced neuronal PTEN degradation, hence enhanced GABAA receptor-medicated neuronal activity inhibition which could attenuate excitotoxicity and provide neuroprotection during the acute phase after stroke, while inhibiting long-term functional recovery and contributing to vascular cognitive impairment after stroke. On the other hand, ischemic stroke induced astrocytic PTEN loss and enhanced ischemic damage and astrogliosis. Taken together, our study indicates that ischemic stroke induces rapid PTEN degradation in both neurons and astrocytes which play both protective and detrimental action in a spatiotemporal- and cell-type-dependent manner. Our study provides critical insight for targeting PTEN signaling pathway for stroke treatment.

The dynamic detection of NO during the ischemic postconditioning against global cerebral ischemia/reperfusion injury

Little is known about role of Nitric Oxide (NO) of ischemic postconditioning in global cerebral ischemia and reperfusion (I/R) injury. In this study, we detected the dynamic change of NO during the ischemic postconditioning against global cerebral I/R in vivo, and compared the effects of six postconditioning conditions with different numbers of cycles and periods for reperfusion/occlusion. The animals underwent postconditioning consisting of 3 or 10 cycles of 15-s reperfusion, followed by 15-s occlusion (post-3-15/15, post-10-15/15), or 3 or 10 cycles of 30-s reperfusion/30-s occlusion (post-3-30/30, post-10-30/30), or 3 or 10 cycles of 60-s reperfusion/15-s occlusion (post-3-60/15, post-10-60/15). The results showed that four groups increased NO concentration, while all groups improved CBF significantly. Different postconditioning groups had different effects on NO and CBF. Post-3-30/30 had the strongest effect on both. Also it reduced infarct size from 33.0% to 24.29%, and downregulated the cell death ratio from 6.71% to 1.04%, showing the strongest protective effect among tested conditions. And we found that post-3-30/30 was an optional method in ischemic postconditioning, which obviously induced a large amount of NO synthesis with a slow speed, increased CBF and reduced the brain injuries. Therefore we concluded that NO is a reliable candidate in mediating ischemic postconditioning neuroprotection.

Aquaporin-4 inhibition mediates piroxicam-induced neuroprotection against focal cerebral ischemia/reperfusion injury in rodents

BACKGROUND AND PURPOSE

Aquaporin-4(AQP4) is an abundant water channel protein in brain that regulates water transport to maintain homeostasis. Cerebral edema resulting from AQP4 over expression is considered to be one of the major determinants for progressive neuronal insult during cerebral ischemia. Although, both upregulation and downregulation of AQP4 expression is associated with brain pathology, over expression of AQP4 is one of the chief contributors of water imbalance in brain during ischemic pathology. We have found that Piroxicam binds to AQP4 with optimal binding energy value. Thus, we hypothesized that Piroxicam is neuroprotective in the rodent cerebral ischemic model by mitigating cerebral edema via AQP4 regulation.

METHODS

Rats were treated with Piroxicam OR placebo at 30 min prior, 2 h post and 4 h post 60 minutes of MCAO followed by 24 hour reperfusion. Rats were evaluated for neurological deficits and motor function just before sacrifice. Brains were harvested for infarct size estimation, water content measurement, biochemical analysis, RT-PCR and western blot experiments.

RESULTS

Piroxicam pretreatment thirty minutes prior to ischemia and four hour post reperfusion afforded neuroprotection as evident through significant reduction in cerebral infarct volume, improvement in motor behavior, neurological deficit and reduction in brain edema. Furthermore, ischemia induced surge in levels of nitrite and malondialdehyde were also found to be significantly reduced in ischemic brain regions in treated animals. This neuroprotection was found to be associated with inhibition of acid mediated rise in intracellular calcium levels and also downregulated AQP4 expression.

CONCLUSIONS

Findings of the present study provide significant evidence that Piroxicam acts as a potent AQP4 regulator and renders neuroprotection in focal cerebral ischemia. Piroxicam could be clinically exploited for the treatment of brain stroke along with other anti-stroke therapeutics in future.

Exogenous nitric oxide negatively regulates the S-nitrosylation p38 mitogen-activated protein kinase activation during cerebral ischaemia and reperfusion

AIMS

A number of studies have suggested that nitric oxide (NO) plays an important role in the reactive phosphorylation of p38MAPKα (p38). However, whether S-nitrosylation of p38 is activated by NO and the details remain unclear. The aim of the present work was to assess the activation of p38, the S-nitrosylation site and the p38 signalling pathway in rat hippocampus and in HEK293 cell induced by exogenous NO.

METHODS

Primary hippocampal cultures, HEK293 cells and rat model of cerebral ischaemia/reperfusion (brain ischaemia was induced by four-vessel occlusion procedure) were used in this study. Biotin-switch method and immunoblotting were performed to study the S-nitrosylation and phosphorylation of p38, and neuronal loss was observed by histology.

RESULTS

Endogenous NO increased p38 phosphorylation and S-nitrosylation, and the activation of p38 was dependent on the S-nitrosylation of Cys-211, which was critical for the NO-mediated activation of p38. The exogenous NO donor sodium nitroprusside, S-nitrosoglutathione, 7-nitroindazole, the inhibitor of the neuronal nitric oxide synthase, inhibited the activation of p38 signal pathway induced by cerebral ischaemia/reperfusion and attenuated the damage in rat hippocampal neurones. Moreover, the N-methyl-D-aspartate receptor (NMDAR) is probably involved in the p38 activation process of S-nitrosylation and phosphorylation.

CONCLUSION

Endogenous NO induces the S-nitrosylation and phosphorylation of p38 and mediates p38 signalling pathway by NMDAR, and as exogenous NO inhibits this process and is neuroprotective in rat cerebral ischaemia/reperfusion, it may make a contribution to stroke therapy.

Mechanisms of acute brain injury after subarachnoid hemorrhage

Brain injury after subarachnoid hemorrhage (SAH) is a biphasic event with an acute ischemic insult at the time of the initial bleed and secondary events such as cerebral vasospasm 3 to 7 days later. Although much has been learned about the delayed effects of SAH, less is known about the mechanisms of acute SAH-induced injury. Distribution of blood in the subarachnoid space, elevation of intracranial pressure, reduced cerebral perfusion and cerebral blood flow (CBF) initiates the acute injury cascade. Together they lead to direct microvascular injury, plugging of vessels and release of vasoactive substances by platelet aggregates, alterations in the nitric oxide (NO)/nitric oxide synthase (NOS) pathways and lipid peroxidation. This review will summarize some of these mechanisms that contribute to acute cerebral injury after SAH.

Pathophysiology of an hypoxic–ischemic insult during the perinatal period

Hypoxia-ischemia is a leading cause of morbidity and mortality in the perinatal period with an incidence of 1/4000 live births. Biochemical events such as energy failure, membrane depolarization, brain edema, an increase of neurotransmitter release and inhibition of uptake, an increase of intracellular Ca(2+), production of oxygen-free radicals, lipid peroxidation, and a decrease of blood flow are triggered by hypoxia-ischemia and may lead to brain dysfunction and neuronal death. These abnormalities can result in mental impairments, seizures, and permanent motor deficits, such as cerebral palsy. The physical and emotional strain that is placed on the children affected and their families is enormous. The care that these individuals need is not only confined to childhood, but rather extends throughout their entire life span, so it is very important to understand the pathophysiology that follows a hypoxic-ischemic insult. This review will highlight many of the mechanisms that lead to neuronal death and include the emerging area of white matter injury as well as the role of inflammation and will provide a summary of therapeutic strategies. Hypothermia and oxygen will also be discussed as treatments that currently lack a specific target in the hypoxic/ischemic cascade.

Transient focal cerebral ischemia induces long-term cognitive function deficit in an experimental ischemic stroke model

Vascular dementia ranks as the second leading cause of dementia in the United States. However, its underlying pathophysiological mechanism is not fully understood and no effective treatment is available. The purpose of the current study was to evaluate long-term cognitive deficits induced by transient middle cerebral artery occlusion (tMCAO) in rats and to investigate the underlying mechanism. Sprague-Dawley rats were subjected to tMCAO or sham surgery. Behavior tests for locomotor activity and cognitive function were conducted at 7 or 30days after stroke. Hippocampal long term potentiation (LTP) and involvement of GABAergic neurotransmission were evaluated at 30days after sham surgery or stroke. Immunohistochemistry and Western blot analyses were conducted to determine the effect of tMCAO on cell signaling in the hippocampus. Transient MCAO induced a progressive deficiency in spatial performance. At 30days after stroke, no neuron loss or synaptic marker change in the hippocampus were observed. LTP in both hippocampi was reduced at 30days after stroke. This LTP impairment was prevented by blocking GABAA receptors. In addition, ERK activity was significantly reduced in both hippocampi. In summary, we identified a progressive decline in spatial learning and memory after ischemic stroke that correlates with suppression of hippocampal LTP, elevation of GABAergic neurotransmission, and inhibition of ERK activation. Our results indicate that the attenuation of GABAergic activity or enhancement of ERK/MAPK activation in the hippocampus might be potential therapeutic approaches to prevent or attenuate cognitive impairment after ischemic stroke.

Novel multiple agents loaded PLGA nanoparticles for brain delivery via inner ear administration: in vitro and in vivo evaluation

The aim of this study was to develop novel multiple agents loaded poly (D,L-lactide-co-glycolide acid) (PLGA) nanoparticles (NPs) and evaluate their potential for brain delivery via inner ear administration. PLGA NPs loaded with salvianolic acid B (Sal B), tanshinone IIA (TS IIA) and panax notoginsenoside (PNS) were prepared by double emulsion/solvent evaporation method. It was observed that optimized NPs displayed satisfactory encapsulation efficiency and desired sustained-release characteristics. NPs following intratympanic administration (IT) in guinea pigs greatly improved drug distribution within the inner ear, cerebrospinal fluid (CSF) and brain tissues compared with intravenous administration (IV). Pharmacodynamic studies demonstrated that NPs following IT markedly inhibited oxidizing reactions and protected the brain from cerebral ischemia reperfusion (I/R) injury by upregulating superoxide dismutase (SOD) activity both in serum and brain tissues, simultaneously significantly reducing the levels of malondialdehyde (MDA) and nitric oxide synthase (NOS). Moreover intratympanic delivery did not cause injury of cochlear function by preliminary study on the toxicity. These findings suggested that PLGA NPs-based delivery system via inner ear administration was a promising candidate to brain delivery for the treatment of brain diseases.

Targeting reactive nitrogen species: a promising therapeutic strategy for cerebral ischemia-reperfusion injury

Ischemic stroke accounts for nearly 80% of stroke cases. Recanalization with thrombolysis is a currently crucial therapeutic strategy for re-building blood supply, but the thrombolytic therapy often companies with cerebral ischemia-reperfusion injury, which are mediated by free radicals. As an important component of free radicals, reactive nitrogen species (RNS), including nitric oxide (NO) and peroxynitrite (ONOO(-)), play important roles in the process of cerebral ischemia-reperfusion injury. Ischemia-reperfusion results in the production of nitric oxide (NO) and peroxynitrite (ONOO(-)) in ischemic brain, which trigger numerous molecular cascades and lead to disruption of the blood brain barrier and exacerbate brain damage. There are few therapeutic strategies available for saving ischemic brains and preventing the subsequent brain damage. Recent evidence suggests that RNS could be a therapeutic target for the treatment of cerebral ischemia-reperfusion injury. Herein, we reviewed the recent progress regarding the roles of RNS in the process of cerebral ischemic-reperfusion injury and discussed the potentials of drug development that target NO and ONOO(-) to treat ischemic stroke. We conclude that modulation for RNS level could be an important therapeutic strategy for preventing cerebral ischemia-reperfusion injury.

Endogenous nitric oxide induces activation of apoptosis signal-regulating kinase 1 via S-nitrosylation in rat hippocampus during cerebral ischemia-reperfusion

Apoptosis signal-regulating kinase 1 (ASK1) is a general mediator of cell death in response to a variety of stimuli, including reactive oxygen species, tumor necrosis factor α, lipopolysaccharide, endoplasmic reticulum stress, calcium influx and ischemia. Here we reported ASK1 was activated by nitric oxide (NO) through S-nitrosylation during cerebral ischemia-reperfusion. The reagents that abrogate neuronal nitric oxide synthase (nNOS) activity such as nNOS inhibitor 7NI and N-methyl-D-aspartate receptor antagonist MK801 prevented ASK1 activation via decreasing ASK1 S-nitrosylation. In HEK293 cells, over-expressed ASK1 could be S-nitrosylated by both exogenous and endogenous NO and Cys869 was identified as the site of ASK1 S-nitrosylation. S-nitrosylation increased the level of ASK1 phosphorylation at Thr845, which represents ASK1 activation. Our results further confirmed that S-nitrosylation led to the increment of ASK1 dimerization. S-nitrosylation of ASK1 also activated the downstream JNK signaling and JNK-mediated nucleic pathway. The exogenous NO (SNP and GSNO) reversed the effect of endogenous NO by suppressing S-nitrosylation of ASK1 and exerted neuroprotection during ischemia-reperfusion. These results suggest that inhibiting ASK1 S-nitrosylation may be a novel approach for stroke therapy.

Effect of Treatment with Cyanidin-3-O-β-D-Glucoside on Rat Ischemic/Reperfusion Brain Damage

This study investigated the effect of cyanidin-3-O-β-glucoside on an experimental model of partial/transient cerebral ischemia in the rats in order to verify the effectiveness of both pre- and posttreatments. Cyanidin-3-O-β-glucoside-pretreated rats were injected with 10 mg/Kg i.p. 1 h before the induction of cerebral ischemia; in posttreated rats, the same dosage was injected during reperfusion (30 min after restoring blood flow). Cerebral ischemia was induced by bilateral clamping of common carotid arteries for 20 min. Ischemic rats were sacrificed immediately after 20 min ischemia; postischemic reperfused animals were sacrificed after 3 or 24 h of restoring blood flow. Results showed that treatment with cyanidin increased the levels of nonproteic thiol groups after 24 h of postischemic reperfusion, significantly reduced the lipid hydroperoxides, and increased the expression of heme oxygenase and γ-glutamyl cysteine synthase; a significant reduction in the expression of neuronal and inducible nitric oxide synthases and the equally significant increase in the endothelial isoform were observed. Significant modifications were also detected in enzymes involved in metabolism of endogenous inhibitors of nitric oxide. Most of the effects were observed with both pre- and posttreatments with cyanidin-3-O-β-glucoside suggesting a role of anthocyanin in both prevention and treatment of postischemic reperfusion brain damage.

Nitric oxide: considerations for the treatment of ischemic stroke

Some 40 years ago it was recognized by Furchgott and colleagues that the endothelium releases a vasodilator, endothelium-derived relaxing factor (EDRF). Later on, several groups identified EDRF to be a gas, nitric oxide (NO). Since then, NO was identified as one of the most versatile and unique molecules in animal and human biology. Nitric oxide mediates a plethora of physiological functions, for example, maintenance of vascular tone and inflammation. Apart from these physiological functions, NO is also involved in the pathophysiology of various disorders, specifically those in which regulation of blood flow and inflammation has a key role. The aim of the current review is to summarize the role of NO in cerebral ischemia, the most common cause of stroke.

Astrocytes: targets for neuroprotection in stroke

In the past two decades, over 1000 clinical trials have failed to demonstrate a benefit in treating stroke, with the exception of thrombolytics. Although many targets have been pursued, including antioxidants, calcium channel blockers, glutamate receptor blockers, and neurotrophic factors, often the focus has been on neuronal mechanisms of injury. Broader attention to loss and dysfunction of non-neuronal cell types is now required to increase the chance of success. Of the several glial cell types, this review will focus on astrocytes. Astrocytes are the most abundant cell type in the higher mammalian nervous system, and they play key roles in normal CNS physiology and in central nervous system injury and pathology. In the setting of ischemia astrocytes perform multiple functions, some beneficial and some potentially detrimental, making them excellent candidates as therapeutic targets to improve outcome following stroke and in other central nervous system injuries. The older neurocentric view of the central nervous system has changed radically with the growing understanding of the many essential functions of astrocytes. These include K+ buffering, glutamate clearance, brain antioxidant defense, close metabolic coupling with neurons, and modulation of neuronal excitability. In this review, we will focus on those functions of astrocytes that can both protect and endanger neurons, and discuss how manipulating these functions provides a novel and important strategy to enhance neuronal survival and improve outcome following cerebral ischemia.

Quercetin in hypoxia-induced oxidative stress: novel target for neuroprotection

Oxidative stress in the central nervous system is one of the key players for neurodegeneration. Thus, antioxidants could play important roles in treating several neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and aging-related brain disorders. This review is focused on the new developments in oxidative stress-induced neurodegeneration. Further, based on our own investigations, new roles of quercetin, an antioxidant compound in hypoxia and ischemia induced neuroprotection in relation to suppression of oxidative stress, improvement in behavioral function, reduction in infarct volume, brain swelling, and cellular injury in both in vivo and in vitro models are discussed. Our new findings clearly suggest that antioxidant compounds have potential role in therapeutic strategies to treat neurodegenerative diseases in clinical settings.

WITHDRAWN: Glutamate Attenuates IGF-1 Receptor Signaling via NR2B containing NMDA Receptors 3 and neuronal Nitric Oxide Synthase

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Protective effects of alkaloid extract from Leonurus heterophyllus on cerebral ischemia reperfusion injury by middle cerebral ischemic injury (MCAO) in rats

The neuronal damage following cerebral ischemia is a serious risk to stroke patients. The aim of this study was to investigate the neuroprotective effects of alkaloid extract from Leonurus heterophyllus (LHAE) on cerebral ischemic injury. After 24 h of reperfusion following ischemia for 2 h induced by middle cerebral artery occlusion (MCAO), some rats were intraperitoneally administered different doses of LHAE (3.6, 7.2, 14.4 mg/kg, respectively). Neurological examination was measured in all animals. Infarct volume, myeloperoxidase (MPO) activity, levels of nitrate/nitrite metabolite (NO) and apoptosis ratio of nerve fiber in brain were determined. The results showed that LHAE at 7.2 mg/kg or 14.4 mg/kg exerted significantly decreasing neurological deficit scores and reducing the infarct volume on rats with focal cerebral ischemic injury (p<0.05). At those dose, the MPO content were significantly decreased in ischemic brain as compared with model group (p<0.05). LHAE at 14.4 mg/kg significantly decreased the NO level compared with the model group (p<0.05). In addition, LHAE significantly decreased the apoptosis ratio of nerve fiber compared with the model group (p<0.05). This study suggests that LHAE may be used for treatment of ischemic stroke as a neuroprotective agent. Further studies are warranted to assess the efficacy and safety of LHAE in patients.