Changes in oxidative stress, iNOS activity and neutrophil infiltration in severe transient focal cerebral ischemia in rats

Update on Antioxidant Therapy with Edaravone: Expanding Applications in Neurodegenerative Diseases

The brain is susceptible to oxidative stress, which is associated with various neurological diseases. Edaravone (MCI-186, 3-methyl-1 pheny-2-pyrazolin-5-one), a free radical scavenger, has promising effects by quenching hydroxyl radicals (∙OH) and inhibiting both ∙OH-dependent and ∙OH-independent lipid peroxidation. Edaravone was initially developed in Japan as a neuroprotective agent for acute cerebral infarction and was later applied clinically to treat amyotrophic lateral sclerosis (ALS), a neurodegenerative disease. There is accumulating evidence for the therapeutic effects of edaravone in a wide range of diseases related to oxidative stress, including ischemic stroke, ALS, Alzheimer's disease, and placental ischemia. These neuroprotective effects have expanded the potential applications of edaravone. Data from experimental animal models support its safety for long-term use, implying broader applications in various neurodegenerative diseases. In this review, we explain the unique characteristics of edaravone, summarize recent findings for specific diseases, and discuss its prospects for future therapeutic applications.

Citrate-coated silver nanoparticles loaded with agomelatine provide neuronal therapy in acute cerebral ischemia/reperfusion of rats by inhibiting the oxidative stress, endoplasmic reticulum stress, and P2X7 receptor-mediated inflammasome

Cerebral ischemia and reperfusion are related to various situations like injuries after various traumas, oxidative stress, increased calcium ion, capillary hypoperfusion, microvascular hyperpermeability, leukocyte infiltration, and blood-brain barrier disruption. An antidepressant Agomelatine which is a melatonin receptor (MT1/MT2) agonist and serotonin receptor (5-HT2C) antagonist has been reported by studies to have antioxidant and anti-inflammatory effects. In our study, we aimed to detect the effects of citrate-coated silver nanoparticle-loaded agomelatine application on neurodegeneration, endoplasmic reticulum stress, autophagic and apoptotic cell death, inflammation, and P2X7R expression in the cerebral ischemia-reperfusion model to facilitate the passage of blood-brain barrier. Forty two Sprague-Dawley rats in total were divided into six equal groups (n:7) and applications were performed. Acute cerebral injury in the ischemia-reperfusion model was created 2 h after internal carotid artery ligation in rats and then at the 2nd hour of reperfusion citrate-coated silver nanoparticles loaded with Agomelatine were applied. Twenty four hours later, neurologic analysis on animals in experimental groups was performed, animals were decapitated and GSH, GPx, SOD, CAT, MDA, IL-1β, and TNF-α parameters were examined after taking blood and the cerebral tissue samples. As a result, it was determined that ischemia-reperfusion caused endoplasmic reticulum stress in the cerebral tissues and thus caused cellular injury.

A Review on Neuroinflammatory Pathway Mediating Through Ang-II/AT1 Receptors and a Novel Approach for the Treatment of Cerebral Ischemia in Combination with ARB's and Ceftriaxone

Background

Ischemic stroke is one of the prevalent neurodegenerative disorders; it is generally characterized by sudden abruption of blood flow due to thromboembolism and vascular abnormalities, eventually impairing the supply of oxygen and nutrients to the brain for its metabolic needs. Oxygen-glucose deprived conditions provoke the release of excessive glutamate, which causes excitotoxicity.

Summary

Recent studies suggest that circulatory angiotensin-II (Ang-II) has an imperative role in initiating detrimental events through binding central angiotensin 1 (AT1) receptors. Insufficient energy metabolites and essential ions often lead to oxidative stress during ischemic reperfusion, which leads to the release of proinflammatory mediators such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and cytokines like interleukin-18 (IL-18) and interleukin- 1beta (IL-1β). The transmembrane glutamate transporters, excitatory amino acid transporter-2 (EAAT-2), which express in astroglial cells, have a crucial role in the clearance of glutamate from its releasing site and convert glutamate into glutamine in normal circumstances of brain physiology.

Key Message

During cerebral ischemia, an impairment or dysfunction of EAAT-2 attributes the risk of delayed neuronal cell death. Earlier studies evidencing that angiotensin receptor blockers (ARB) attenuate neuroinflammation by inhibiting the Ang-II/AT1 receptor-mediated inflammatory pathway and that ceftriaxone ameliorates the excitotoxicity-induced neuronal deterioration by enhancing the transcription and expression of EAAT-2 via the nuclear transcriptional factor kappa-B (NF-kB) signaling pathway. The present review will briefly discuss the mechanisms involved in Ang-II/AT1-mediated neuroinflammation, ceftriaxone-induced EAAT-2 expression, and the repurposing hypothesis of the novel combination of ARBs and ceftriaxone for the treatment of cerebral ischemia.

The therapeutic role of Jingchuan tablet on ischaemic cerebral stroke via the HIF-1α/EPO/VEGFA signalling pathway

CONTEXT

Jingchuan tablet (JCT) is a Chinese medicine prescription for treating ischaemic cerebral stroke (ICS). However, its relevant mechanisms remain unclear.

OBJECTIVE

To unravel the intrinsic mechanisms of JCT anti-ICS.

MATERIALS AND METHODS

'Hongjingtian', 'chuanxiong', 'yanhusuo', 'bingpian', 'cerebral infarction', 'cerebral ischemia' or 'stroke' were used as keywords, and then components, targets and underlying mechanisms of JCT anti-ICS were analysed in TCMSP, TTD, DrugBank, STRING and Metascape databases up to June 2020. Male Sprague-Dawley rats under permanent middle cerebral artery occlusion (pMCAO) model, randomly assigned as: model, sham, nimodipine (0.012 g/kg/d) and JCT (0.78, 1.56 and 3.12 g/kg/d) groups, received oral gavage administration for a week. Therapeutic effects were evaluated by detecting the proportion of cerebral infarction, neuronal apoptosis and neurological deficits. Bioactive components were detected by HPLC-MS. Molecular biology and computational docking were used to verify the underlying mechanisms.

RESULTS

Eighty-one components, 166 targets and HIF-1α/EPO/VEGFA pathway contributed to the anti-ICS effect of JCT. JCT treatment effectively reduced the proportion of cerebral infarction (33.13%), apoptosis rate (14.80%) and neurobehavioural score (2.00). JCT increased the protein levels of HIF-1α (0.84), EPO (0.64) and VEGFA (0.69), respectively (p < 0.05). Gallic acid, salidroside, chlorogenic acid, ethyl gallate, ferulic acid and tetrahydropalmatine detected by HPLC-MS showed good interaction and binding with HIF-1α/EPO/VEGFA.

CONCLUSIONS

Our study demonstrated the mechanisms of JCT anti-ICS associated with the activation of the HIF-1α/EPO/VEGFA pathway, which provided a pharmacological basis for expanding the clinical application and some scientific ideas for further research into the material basis JCT anti-ICS.

Chandamarutha Chenduram, an Indian traditional Siddha preparation attenuated the neuronal degeneration in ischemic mice through ameliorating cytokines and oxy-radicals mediated EAAT-2 dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

Chandamarutha Chenduram (CC), an Indian traditional Siddha preparation officially recorded in the Siddha formulary of India and its composition are widely used in the Siddha practice of neurological disorders like stroke/paralysis in India. However, the scientific validation and mechanistic evidence is lacking and yet to be elucidated.

AIM OF THE STUDY

To establish the scientific evidences and to explore the possible neuroprotective mechanism of CC in cerebral ischemia.

MATERIALS AND METHODS

Chemical standardization of the CC was performed using atomic absorption spectroscopy and gravimetric analysis. Acute toxicity study for CC in mice was performed in accordance with OECD 423 guidelines. CC (5 mg/kg) and CC (10 mg/kg) were investigated in bilateral common carotid occlusion (BCCAo) model in mice. After, behavioral assessments, the brain samples were collected and the hippocampus region was micro-dissected for neurotransmitter, neurobiochemicals and inflammatory cytokines estimation. The excitatory amino acid transporter-2 (EAAT-2) expressions was analyzed by RT-PCR to understand the possible molecular mechanism. In addition, hematoxylin and eosin staining of CA1 hippocampal brain region was performed to support the neuroprotective effect of CC in ischemic condition.

RESULTS

Chemical standardization analysis showed that CC has acceptable range of mercury (0.82 ppm) and elemental sulphur (11% w/w). Also, other heavy metal limits were found to be less or not detectable. Toxicity study also evidenced the safety profile of CC. CC has significantly reversed the behavioral dysfunctions (p < 0.001) in global ischemic mice. Treatment with CC has attenuated the excitatory neurotransmitter glutamate, lipid peroxide, nitric oxide, cytokines (IL-1β, TNF-α) (p < 0.001) and increased the antioxidant enzymes (SOD, CAT, GSH) and EAAT-2 expression level (p < 0.001) in ischemic brain. The hematoxylin and eosin staining in CA1 region of hippocampus also evidence the neuroprotective effect exhibited by CC.

CONCLUSIONS

Treatment with CC has exhibited dose dependent effect and CC10 has shown significant protective effect in comparison to CC5 in most of the parameters studied. CC prevented further degeneration of neurons in cerebral ischemic mice through ameliorating inflammatory cytokines and oxy-radicals mediated EAAT-2 dysfunction and subsequent excitotoxicity in neurons.

Effect of Dimethyl Fumarate on the Motor Function and Spatial Arrangement of Primary Motor Cortical Neurons in the Sub-Acute Phase of Stroke in a Rat Model

BACKGROUND

The therapeutic effects of dimethyl fumarate (DMF) in patients with multiple sclerosis and animal models of neurologic disease were reported. The density and the distribution pattern of motor neurons are important in transmitting the signal and controlling the movement-related functions. The present study evaluated the effects of DMF treatment on the neurological functions, infarct volume, and spatial distribution of the neurons in the primary motor cortex after cerebral ischemia.

METHODS

Thirty-three Sprague-Dawley rats were randomly divided into three groups: The sham group underwent surgery without middle cerebral artery occlusion (MCAO) and drug. The vehicle and treatment groups after MCAO received a vehicle or DMF for three consecutive days. Post-stroke neurological and motor functions were assessed. At the end of the third day, the brains were removed, and the cerebral infarct volume was evaluated. We used cresyl violet staining to analyze the density and the spatial arrangement of motor cortical neurons using Voronoi tessellation.

RESULTS

Treatment of the brain ischemia for three days with DMF could not significantly reduce the neurological and motor function deficits and infarct volume. However, it reduced the neuronal area and death and preserved their spatial distribution in the normal regular pattern.

CONCLUSION

Cerebral ischemia decreased the neuronal density of the primary motor cortex and changed their distributions to a random pattern. DMF treatment during sub-acute ischemic stroke did not significantly improve the neurological deficit scores. However, it could prevent neuronal swelling and death and preserved the spatial distribution of the cortical neurons in their normal pattern.

Curcumin Efficacy in a Serum/Glucose Deprivation-Induced Neuronal PC12 Injury Model

BACKGROUND

Glucose/serum deprivation (GSD), has been used for understanding molecular mechanisms of neuronal damage during ischemia. It has been suggested that curcumin may improve neurodegenerative diseases.

AIM

In this study, the protective effects of curcumin and its underlying mechanisms were investigated in PC12 cells upon GSD-induced stress.

METHODS

PC12 cells were cultured in DMEM overnight and then incubated in GSD condition for either 6 or 12h. GSD-treated cells were pretreated with various concentrations of curcumin (10, 20, and 40 μM) for 5h. The cell viability, apoptosis, reactive oxygen species (ROS) level, oxidative stress, expression of apoptosis-related genes, and IL-6 were determined.

RESULTS

Curcumin increased cell viability and caused an anti-apoptotic effect in PC12 cells exposed for 12h to GSD . Curcumin also increased antioxidant enzyme expression, suppressed lipid peroxidation, and decreased interleukin-6 secretion in PC12 cells subjected to GSD. In addition, pretreatment with curcumin down-regulated pro-apoptotic (Bax), and up-regulated antiapoptotic (Bcl2) mediators.

CONCLUSION

Curcumin mitigates many of the adverse effects of ischemia, and therefore, should be considered as an adjunct therapy in ischemic patients.

Induction of inducible nitric oxide synthase expression in activated microglia and astrocytes following pre- and postnatal immune challenge in an animal model of schizophrenia

In the central nervous system, activated microglia and astrocytes produce proinflammatory mediators such as inducible nitric oxide (iNOS) and cytokines. Uncontrolled release of these mediators induced by immune challenge can lead to increased vulnerability to complex brain disorders such as schizophrenia. In this study, BALB/c mice were injected intraperitoneally (i.p) with the viral mimetic polyriboinosinic-polyribocytidilic acid (poly(I:C)) or saline. At postnatal day 30 (PND0), the animals were sacrificed and the hippocampus, corpus callosum, striatum, cortex, fimbria and ventricle were immunostained for Iba-1, a microglial marker, glial fibrillary acidic protein (GFAP), an astrocyte marker, and iNOS, an activation marker for NO. Additionally, serum cytokine profiling (Interleukin-2 (IL-2), IL- 4, IL-6, interferon gamma (IFN-γ), tumour necrosis factor (TNF), IL-17A and IL-10) was determined using serum samples from poly(I:C)-treated and control mice. Our results demonstrated that poly(I:C) induced overactivation of differential proinflammatory responses in microglia and astrocytes, which could be strongly enhanced by a postnatal poly(I:C) administration before PND 30 in one part of the animals investigated. Specifically, there was significant iNOS upregulation in hippocampus, cortex and corpus callosum of poly(I:C)-affected off-springs. These inflammatory alterations were accompanied by increased circulating levels of the proinflammatory cytokines tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). This study provides insight into the role of microglia and astrocytes in an animal model of schizophrenia and an understanding of the regulation of iNOS expression in glial cells and cytokine networks. This knowledge could help identify novel targets for anti-oxidative and anti-inflammatory therapeutic schizophrenia intervention.

The Molecular Signatures of Acute-immobilization-induced Antinociception and Chronic-immobilization-induced Antinociceptive Tolerance

In the present study, the productions of antinociception induced by acute and chronic immobilization stress were compared in several animal pain models. In the acute immobilization stress model (up to 1 hr immobilization), the antinociception was produced in writhing, tail-flick, and formalin-induced pain models. In chronic immobilization stress experiment, the mouse was enforced into immobilization for 1 hr/day for 3, 7, or 14 days, then analgesic tests were performed. The antinociceptive effect was gradually reduced after 3, 7 and 14 days of immobilization stress. To delineate the molecular mechanism involved in the antinociceptive tolerance development in the chronic stress model, the expressions of some signal molecules in dorsal root ganglia (DRG), spinal cord, hippocampus, and the hypothalamus were observed in acute and chronic immobilization models. The COX-2 in DRG, p-JNK, p-AMPKα1, and p-mTOR in the spinal cord, p-P38 in the hippocampus, and p-AMPKα1 in the hypothalamus were elevated in acute immobilization stress, but were reduced gradually after 3, 7 and 14 days of immobilization stress. Our results suggest that the chronic immobilization stress causes development of tolerance to the antinociception induced by acute immobilization stress. In addition, the COX-2 in DRG, p-JNK, p-AMPKα1, and p-mTOR in the spinal cord, p-P38 in the hippocampus, and p-AMPKα1 in the hypothalamus may play important roles in the regulation of antinociception induced by acute immobilization stress and the tolerance development induced by chronic immobilization stress.

Protective effect of Danhong Injection combined with Naoxintong Capsule on cerebral ischemia-reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Danhong Injection (DHI) and Naoxintong Capsule (NXT) are renowned traditional Chinese medicine in China. The drug combination of DHI and NXT is frequently applied for the treatment of cardiovascular and cerebrovascular diseases in clinic. However, there had been no pharmacological experiment studies of interaction between DHI and NXT. Due to the drug interactions, exploring their interaction profile is of great importance.

MATERIAL AND METHODS

In this study, focal cerebral I/R injury in adult male Sprague-Dawley rats were induced by transient middle cerebral artery occlusion (tMCAO) for 1h followed by reperfusion. Rats were divided into 5 groups: sham group, ischemia reperfusion untreated group (IRU), DHI group (DHI 10mL/kg/d), NXT group (NXT 0.5g/kg/d), DHI plus NXT group (DHI-NXT, DHI 10mL/kg/d plus NXT 0.5g/kg/d). All drug-treated groups were respectively successive administrated for 7 days after ischemia/ reperfusion (I/R) injury. The effects on rat neurological function were estimated by neurological defect scores. Brain infarct volumes were determined based on 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Pathological changes in brain tissues were observed using hematoxylin and eosin (H&E) staining and transmission electron microscope (TEM). Levels of nitric oxide (NO), granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in serum were determined with enzyme-linked immunosorbent assay (ELISA). Immunohisto-chemistry and Western blot were used to detect the expressions of basic fibroblast growth factor (bFGF), von Willebrand factor-microvessel vascular density (vWF-MVD), vascular endothelial cell growth factor (VEGF), transforming growth factor-β1 (TGF-β1), angiogenin-1 (Ang-1), angiogenin-2 (Ang-2) and platelet derived growth factor (PDGF) at day 7 after ischemia/reperfusion (I/R) injury.

RESULTS

Compared with IRU group and mono-therapy group (DHI group or NXT group), Danhong Injection combined with Naoxintong Capsule (DHI-NXT) group significantly ameliorated neurological deficits scores, infarct volume and pathological change, significantly decreased the overexpression of NO and the level of Ang-1, significantly increased the expressions of VEGF, Ang-2, G-CSF, GM-CSF, bFGF, PDGF, vWF, TGF-β1.

CONCLUSION

The protective benefits on rat brain against I/R injury were clearly produced when DHI and NXT were used in combination, which provided rational guidance for clinical combined application of DHI and NXT, and this protection maybe associated with the up-regulation expressions of the related chemokines and growth factors of angiogenesis.

Superior Microvascular Perfusion of Infused Liposome-Encapsulated Hemoglobin Prior to Reductions in Infarctions after Transient Focal Cerebral Ischemia

BACKGROUND

The development of cerebral infarction after transient ischemia is attributed to postischemic delayed hypoperfusion in the microvascular region. In the present study, we assessed the microvascular perfusion capacity of infused liposome-encapsulated hemoglobin (LEH) in a therapeutic approach for transient middle cerebral artery occlusion (tMCAO).

METHODS

Two-hour middle cerebral artery occlusion rats were immediately subjected to intra-arterial infusion of LEH (LEH group) or saline (vehicle group) or no treatment (control group), and then to recanalization. Neurological findings, infarct and edema progression, microvascular endothelial dysfunction, and inflammatory reactions were compared between the 3 groups after 24 hours of reperfusion. Microvascular perfusion in the early phase of reperfusion was evaluated by hemoglobin immunohistochemistry and transmission electron microscopy.

RESULTS

The LEH group achieved significantly better results in all items evaluated than the other groups. Hemoglobin immunohistochemistry revealed that the number of hemoglobin-positive microvessels was significantly greater in the LEH group than in the other groups (P < .01), with microvascular perfusion being more likely in narrow microvessels (≤5 µm in diameter). An electron microscopic examination revealed that microvessels in the control group were compressed and narrowed by swollen astrocyte end-feet, whereas those in the LEH group had a less deformed appearance and contained LEH particles and erythrocytes.

CONCLUSION

The results of the present study demonstrated that the infusion of LEH reduced infarctions after tMCAO with more hemoglobin-positive and less deformed microvessels at the early phase of reperfusion, suggesting that the superiority of the microvascular perfusion of LEH mediates its neuroprotective effects.

Treatment Effects of Ischemic Stroke by Berberine, Baicalin, and Jasminoidin from Huang-Lian-Jie-Du-Decoction (HLJDD) Explored by an Integrated Metabolomics Approach

Berberine, baicalin, and jasminoidin were major active ingredients of Huang-Lian-Jie-Du-Decoction (HLJDD), a famous prescription of traditional Chinese medicine (TCM), which has been used for the treatment of ischemic stroke. The aim of the present study was to classify their roles in the treatment effects of ischemic stroke. A rat model of middle cerebral artery occlusion (MCAO) was constructed to mimic ischemic stroke and treatment effects of berberine, baicalin, and jasminoidin, and HLJDD was assessed by neurologic deficit scoring, infarct volume, histopathology, immunohistochemistry, biochemistry, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting. In addition, the ¹H NMR metabolomics approach was used to assess the metabolic profiles, which combined with correlation network analysis successfully revealed metabolic disorders in ischemic stroke concerning the treatment of the three principal compounds from HLJDD for the first time. The combined results suggested that berberine, baicalin, and jasminoidin are responsible for the effectiveness of HLJDD on the treatment of ischemic stroke by amelioration of abnormal metabolism and regulation of oxidative stress, neuron autophagy, and inflammatory response. This integrated metabolomics approach showed its potential in understanding the function of complex formulae and clarifying the role of its components in the overall treatment effects.

Anti-Inflammatory and Neuroprotective Effects of Co-UltraPEALut in a Mouse Model of Vascular Dementia

Vascular dementia (VaD), the second most common cause of cognitive impairment in the population, is a disease that results from reduction in regional cerebral blood flow and involves oxidative stress and inflammation. Co-ultramicronized PEALut (co-ultra PEALut) is a new compound with beneficial effects, which include anti-inflammatory and antioxidant properties. Recently, co-ultraPEALut has been shown to exhibit neuroprotective effects in models of Parkinson’s disease, cerebral ischemia and Alzheimer’s disease. However, its effects on VaD remain unknown. Therefore, the purpose of the present study was to highlight the potential neuroprotective actions of co-ultraPEALut containing N-palmitoylethanolamine (PEA) and the antioxidant flavonoid luteolin (Lut) (10:1 by mass) in a mouse model of VaD induced by bilateral carotid arteries occlusion. At 24 h after VaD induction, mice were orally treated with 1 mg/kg co-ultraPEALut daily for 15 days. On the 15th day, brain tissues were processed for histological, immunohistochemical, Western blot, and immunofluorescent analysis. Our results clearly demonstrate that co-ultraPEALut improved learning, memory ability, locomotor activity, and the reciprocal social interaction. In addition, the mice subjected to VaD and treated with the co-ultraPEALut showed a reorganization of CA1 and CA3 regions of the hippocampus and restored the number of hippocampal neurons as evidenced by NeuN expression, a specific marker of neurons. Furthermore following carotid arteries ligation, mice treated with co-ultraPEALut showed a modification of proinflammatory, proapoptotic proteins and of oxidative stress as evidenced by the expression of IκB-α, NF-κB p65, Bax, Bcl-2, inducible nitric oxide synthase, and cyclooxygenase-2. In order, co-ultraPEALut treatment restored VaD-induced loss of brain-derived neurotrophic factor and neurotrophins 3 (NT-3) expression in mice. These results confirmed that the neuroprotective effects of co-ultraPEALut were associated with its anti-inflammatory and antioxidant properties.

High oxidative stress adversely affects NFκB mediated induction of inducible nitric oxide synthase in human neutrophils: Implications in chronic myeloid leukemia

Increasing evidence support bimodal action of nitric oxide (NO) both as a promoter and as an impeder of oxygen free radicals in neutrophils (PMNs), however impact of high oxidative stress on NO generation is less explored. In the present study, we comprehensively investigated the effect of high oxidative stress on inducible nitric oxide synthase (iNOS) expression and NO generation in human PMNs. Our findings suggest that PMA or diamide induced oxidative stress in PMNs from healthy volunteers, and high endogenous ROS in PMNs of chronic myeloid leukemia (CML) patients attenuate basal as well as LPS/cytokines induced NO generation and iNOS expression in human PMNs. Mechanistically, we found that under high oxidative stress condition, S-glutathionylation of NFκB (p50 and p65 subunits) severely limits iNOS expression due to its reduced binding to iNOS promoter, which was reversed in presence of DTT. Furthermore, by using pharmacological inhibitors, scavengers and molecular approaches, we identified that enhanced ROS generation via NOX2 and mitochondria, reduced Grx1/2 expression and GSH level associated with NFκB S-glutathionylation in PMNs from CML patients. Altogether data obtained suggest that oxidative status act as an important regulator of NO generation/iNOS expression, and under enhanced oxidative stress condition, NOX2-mtROS-NFκB S-glutathionylation is a feed forward loop, which attenuate NO generation and iNOS expression in human PMNs.

Inhibition of myeloperoxidase oxidant production by N-acetyl lysyltyrosylcysteine amide reduces brain damage in a murine model of stroke

BACKGROUND

Oxidative stress plays an important and causal role in the mechanisms by which ischemia/reperfusion (I/R) injury increases brain damage after stroke. Accordingly, reducing oxidative stress has been proposed as a therapeutic strategy for limiting damage in the brain after stroke. Myeloperoxidase (MPO) is a highly potent oxidative enzyme that is capable of inducing both oxidative and nitrosative stress in vivo.

METHODS

To determine if and the extent to which MPO-generated oxidants contribute to brain I/R injury, we treated mice subjected to middle cerebral artery occlusion (MCAO) with N-acetyl lysyltyrosylcysteine amide (KYC), a novel, specific and non-toxic inhibitor of MPO. Behavioral testing, ischemic damage, blood-brain-barrier disruption, apoptosis, neutrophils infiltration, microglia/macrophage activation, and MPO oxidation were analyzed within a 7-day period after MCAO.

RESULTS

Our studies show that KYC treatment significantly reduces neurological severity scores, infarct size, IgG extravasation, neutrophil infiltration, loss of neurons, apoptosis, and microglia/macrophage activation in the brains of MCAO mice. Immunofluorescence studies show that KYC treatment reduces the formation of chlorotyrosine (ClTyr), a fingerprint biomarker of MPO oxidation, nitrotyrosine (NO2Tyr), and 4-hydroxynonenal (4HNE) in MCAO mice. All oxidative products colocalized with MPO in the infarcted brains, suggesting that MPO-generated oxidants are involved in forming the oxidative products.

CONCLUSIONS

MPO-generated oxidants play detrimental roles in causing brain damage after stroke which is effectively reduced by KYC.

Co-ultramicronized Palmitoylethanolamide/Luteolin in the Treatment of Cerebral Ischemia: from Rodent to Man

Acute ischemic stroke, the most frequent cause of permanent disability in adults worldwide, results from transient or permanent reduction in regional cerebral blood flow and involves oxidative stress and inflammation. Despite the success of experimental animal models of stroke in identifying anti-inflammatory/neuroprotective compounds, translation of these putative neuroprotectants to human clinical trials has failed to produce a positive outcome. Tissue injury and stress activate endogenous mechanisms which function to restore homeostatic balance and prevent further damage by upregulating the synthesis of lipid signaling molecules, including N-palmitoylethanolamine (PEA or palmitoylethanolamide). PEA exerts neuroprotection and reduces inflammatory secondary events associated with brain ischemia reperfusion injury (middle cerebral artery occlusion (MCAo)). Here, we examined the neuroprotective potential of a co-ultramicronized composite containing PEA and the antioxidant flavonoid luteolin (10:1 by mass), nominated co-ultraPEALut. The study consisted of two arms. In the first, rats subjected to MCAo and treated with co-ultraPEALut post-ischemia showed reduced edema and brain infract volume, improved neurobehavioral functions, and reduced expression of pro-inflammatory markers and astrocyte markers. In the second arm, a cohort of 250 stroke patients undergoing neurorehabilitation on either an inpatient or outpatient basis were treated for 60 days with a pharmaceutical preparation of co-ultraPEALut (Glialia). At baseline and after 30 days of treatment, all patients underwent a battery of evaluations to assess neurological status, impairment of cognitive abilities, the degree of spasticity, pain, and independence in daily living activities. All indices showed statistically significant gains at study end. Despite its observational nature, this represents the first description of co-ultraPEALut administration to human stroke patients and clinical improvement not otherwise expected from spontaneous recovery. Further, controlled trials are warranted to confirm the utility of co-ultraPEALut to improve clinical outcome in human stroke.

Role of nitric oxide and related molecules in schizophrenia pathogenesis: biochemical, genetic and clinical aspects

Currently, schizophrenia is considered a multifactorial disease. Over the past 50 years, many investigators have considered the role of toxic free radicals in the etiology of schizophrenia. This is an area of active research which is still evolving. Here, we review the recent data and current concepts on the roles of nitric oxide (NO) and related molecules in the pathogenesis of schizophrenia. NO is involved in storage, uptake and release of mediators and neurotransmitters, including glutamate, acetylcholine, noradrenaline, GABA, taurine and glycine. In addition, NO diffuses across cell membranes and activates its own extrasynaptic receptors. Further, NO is involved in peroxidation and reactive oxidative stress. Investigations reveal significant disturbances in NO levels in the brain structures (cerebellum, hypothalamus, hippocampus, striatum) and fluids of subjects with schizophrenia. Given the roles of NO in central nervous system development, these changes may result in neurodevelopmental changes associated with schizophrenia. We describe here the recent literature on NOS gene polymorphisms on schizophrenia, which all point to consistent results. We also discuss how NO may be a new target for the therapy of mental disorders. Currently there have been 2 randomized double-blind placebo-controlled trials of L-lysine as an NOS inhibitor in the CNS.

12/15-Lipoxygenase metabolites of arachidonic acid activate PPARγ: a possible neuroprotective effect in ischemic brain

The enzyme 12/15-lipoxygenase (LOX) oxidizes various free fatty acids, including arachidonic acid (AA). In the brain, the principal 12/15-LOX metabolites of AA are 12(S)-HETE and 15(S)-HETE. PPARγ is a nuclear receptor whose activation is neuroprotective through its anti-inflammatory properties. In this study, we investigate the involvement of 12(S)- and 15(S)-HETE in the regulation of PPARγ following cerebral ischemia and their effects on ischemia-induced inflammatory response. We show here the increased expression of 12/15-LOX, predominantly in neurons, and elevated production of 12(S)-HETE and 15(S)-HETE in ischemic brain. The exogenous 12(S)- and 15(S)-HETE increase PPARγ protein level, nuclear translocation, and DNA-binding activity in ischemic rats, suggesting the activation of PPARγ. This effect was further confirmed by showing the increased PPARγ transcriptional activity in primary cortical neurons when incubated with 12(S)- or 15(S)-HETE. Moreover, both 12(S)- and 15(S)-HETE potently inhibited the induction of nuclear factor-κB, inducible NO synthase, and cyclooxygenase-2 in ischemic rats, and elicited neuroprotection. The reversal of the effects of 12(S)- and 15(S)-HETE on pro-inflammatory factors by PPARγ antagonist GW9662 indicated their actions were mediated via PPARγ. Thus, the induction of 12(S)- and 15(S)-HETE during brain ischemia suggests that endogenous signals of neuroprotection may be generated.

SOD1 aggregation in astrocytes following ischemia/reperfusion injury: a role of NO-mediated S-nitrosylation of protein disulfide isomerase (PDI)

Background

Ubiquitinated-protein aggregates are implicated in cerebral ischemia/reperfusion injury. The very presence of these ubiquitinated-protein aggregates is abnormal and seems to be disease-related. However, it is not clear what leads to aggregate formation and whether the aggregations represent a reaction to aggregate-mediated neurodegeneration.

Methods

To study the nitrosative stress-induced protein aggregation in cerebral ischemia/reperfusion injury, we used primary astrocyte cultures as a cell model, and systematically examined their iNOS expression and consequent NO generation following oxygen glucose deprivation and reperfusion. The expression of protein disulfide isomerase (PDI) and copper-zinc superoxide dismutase (SOD1) were also examined, and the biochemical interaction between PDI and SOD1 was determined by immunoprecipitation. In addition, the levels of S-nitrosylated PDI in cultured astrocytes after oxygen glucose deprivation and reperfusion treatment were measured using the biotin-switch assay. The formation of ubiquitinated-protein aggregates was detected by immunoblot and immunofluorescence staining.

Results

Our data showed that the up-regulation of iNOS expression after oxygen glucose deprivation and reperfusion treatment led to excessive NO generation. Up-regulation of PDI and SOD1 was also identified in cultured astrocytes following oxygen glucose deprivation and reperfusion, and these two proteins were found to bind to each other. Furthermore, the increased nitrosative stress due to ischemia/reperfusion injury was highly associated with NO-induced S-nitrosylation of PDI, and this S-nitrosylation of PDI was correlated with the formation of ubiquitinated-protein aggregates; the levels of S-nitrosylated PDI increased in parallel with the formation of aggregates. When NO generation was pharmacologically inhibited by iNOS specific inhibitor 1400W, S-nitrosylation of PDI was significantly blocked. In addition, the formation of ubiquitinated-protein aggregates in cultured astrocytes following oxygen glucose deprivation and reperfusion was also suppressed by 1400W. Interestingly, these aggregates were colocalized with SOD1, which was found to co-immunoprecipitate with PDI.

Conclusions

NO-mediated S-nitrosylation of PDI may be involved in the formation of the SOD1-linked ubiquitinated-protein aggregates in cerebral ischemia/reperfusion injury.

Antioxidant and Anti-Inflammatory Properties of Longan (Dimocarpus longan Lour.) Pericarp

This study examined the antioxidant and anti-inflammatory activities of the water extract of longan pericarp (WLP). The results showed that WLP exhibited radical scavenging, reducing activity and liposome protection activity. In addition, WLP also inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in macrophages. Further, administration of WLP, in the range of 100-400 mg/kg, showed a concentration-dependent inhibition on paw edema development following carrageenan (Carr) treatment in mice. The anti-inflammatory effects of WLP may be related to NO and tumor necrosis factor (TNF-α) suppression and associated with the increase in the activities of antioxidant enzymes, including catalase, superoxide dismutase, and glutathione peroxidase. Overall, the results showed that WLP might serve as a natural antioxidant and inflammatory inhibitor.

Resveratrol preconditioning modulates inflammatory response in the rat hippocampus following global cerebral ischemia

Considerable evidence has been accumulated to suggests that blocking the inflammatory reaction promotes neuroprotection and shows therapeutic potential for clinical treatment of ischemic brain injury. Consequently, anti-inflammatory therapies are being explored for prevention and treatment of these diseases. Induction of brain tolerance against ischemia by pretreatment with resveratrol has been found to influence expression of different molecules. It remains unclear, however, whether and how resveratrol preconditioning changes expression of inflammatory mediators after subsequent global cerebral ischemia/reperfusion (I/R). Therefore, we investigated the effect of resveratrol pretreatment on NF-κB inflammatory cascade, COX-2, iNOS and JNK levels in experimental I/R. Adult male rats were subjected to 10 min of four-vessel occlusion and sacrificed at selected post-ischemic time points. Resveratrol (30 mg/kg) pretreatment was injected intraperitoneally 7 days prior to I/R induction. We found that resveratrol treatment before insult remarkably reduced astroglial and microglial activation at 7 days after I/R. It greatly attenuated I/R-induced NF-κB and JNK activation with decreased COX-2 and iNOS production. In conclusion, the neuroprotection of resveratrol preconditioning may be due in part to the suppression of the inflammatory response via regulation of NF-κB, COX-2 and iNOS induced by I/R. JNK was also suggested to play a protective role through in neuroprotection of resveratrol, which may also be contributing to reduction in neuroinflammation. The study adds to a growing literature that resveratrol can have important anti-inflammatory actions in the brain.

Effect of amiloride: An Na / H exchange inhibitor in the middle cerebral artery occlusion model of focal cerebral ischemia in rats

PURPOSE

The effect of pretreatment with amiloride (AML), an Na(+) / H(+) exchange inhibitor was studied in the middle cerebral artery occlusion (MCAO) model of focal cerebral ischemia in rats.

MATERIALS AND METHODS

Male wistar rats were subjected to 2 hr of MCAO followed by 22-hr reperfusion. Grip strength, locomotor activity, and spontaneous alternation performance were assessed after 24 hr. Immediately after behavioral activities, animals were sacrificed and the oxidative stress markers were estimated in brains.

RESULTS

An elevation of thiobarbituric acid reactive substances (TBARS), reduction in glutathione, and antioxidant enzymes activities, namely glutathione-S-transferase, glutathione peroxidase (GPx), glutathione reductase (GR), and superoxide dismutase (SOD) were observed following MCA occluded rats. Pretreatment with AML (0.91 and 1.82 mg/kg p.o) significantly reversed the MCAO-induced elevation in TBARS but could not reverse the other parameters. Paradoxically, AML further reduced the levels of GPx, GR, and SOD, but no significant changes were observed in the catalase activity, grip strength, and spontaneous alternation behavior of rats. Locomotor activity was reduced slightly but reversed on pretreatment with AML.

CONCLUSIONS

Although pretreatment with single dose of AML showed reduction in oxidative stress markers, further multiple doses of AML as pre- and post-treatments are required to establish its potential to be used in cerebral ischemia.

A novel molecular mechanism for nitrated {alpha}-synuclein-induced cell death

Although previous studies have demonstrated the involvement of nitrated α-synuclein in neurodegenerative disorders (synucleinopathies), the effects of nitrated α-synuclein and the molecular mechanisms underlying its toxicity are still unclear. In the present study, nitrated α-synuclein with four 3-nitrotyrosines (Tyr(39), Tyr(125), Tyr(133), and Tyr(136)) was obtained non-enzymatically by incubation with nitrite. The nitrated protein existed as a mixture of monomers, dimers, and polymers in solution. The nitrated α-synuclein could induce cell death in a time- and concentration-dependent manner when SH-SY5Y cells (a human neuroblastoma cell line) were incubated with the dimers and polymers. Treatment with anti-integrin α5β1 antibody partially rescued the SH-SY5Y cells from the cell death. Dot blotting and immunoprecipitation revealed that the nitrated protein bound to integrin on the cell membranes. Level of nitric oxide (NO) and calcium-independent inducible NO synthase (iNOS) activity increased during the initial stages of the treatment. The expression of phosphorylated focal adhesion kinase (FAK) decreased in the cells. Subsequently, an increase in caspase 3 activity was observed in SH-SY5Y cells. Our results demonstrate that activation of iNOS and inhibition of FAK may both be responsible for the cell death induced by nitrated α-synuclein. These data suggest that the cytotoxicity of nitrated α-synuclein is mediated via an integrin-iNOS/-FAK signaling pathway, and that the nitration of α-synuclein plays a role in neuronal degeneration.

Decreased myeloperoxidase expressing cells in the aged rat brain after excitotoxic damage

Brain aging is associated to several morphological and functional alterations that influence the evolution and outcome of CNS damage. Acute brain injury such as an excitotoxic insult induces initial tissue damage followed by associated inflammation and oxidative stress, partly attributed to neutrophil recruitment and the expression of oxidative enzymes such as myeloperoxidase (MPO), among others. However, to date, very few studies have focused on how age can influence neutrophil infiltration after acute brain damage. Therefore, to evaluate the age-dependent pattern of neutrophil cell infiltration following an excitotoxic injury, intrastriatal injection of N-methyl-d-aspartate was performed in young and aged male Wistar rats. Animals were sacrificed at different times between 12h post-lesion (hpl) to 14 days post-lesion (dpl). Cryostat sections were processed for myeloperoxidase (MPO) immunohistochemistry, and double labeling for either neuronal cells (NeuN), astrocytes (GFAP), perivascular macrophages (ED-2), or microglia/macrophages (tomato lectin histochemistry). Our observations showed that MPO + cells were observed in the injured striatum from 12 hpl (when maximum values were found) until 7 dpl, when cell density was strongly diminished. However, at all survival times analyzed, the overall density of MPO + cells was lower in the aged versus the adult injured striatum. MPO + cells were mainly identified as neutrophils (especially at 12 hpl and 1 dpl), but it should be noted that MPO + neurons and microglia/macrophages were also found. MPO + neurons were most commonly observed at 12 hpl and reduced in the aged. MPO + microglia/macrophages were the main population expressing MPO from 3 dpl, when density was also reduced in aged subjects. These results point to neutrophil infiltration as another important factor contributing to the different responses of the adult and aged brain to damage, highlighting the need of using aged animals for the study of acute age-related brain insults.

Investigating the effects of adult neural stem cell transplantation by lumbar puncture in transient cerebral ischemia

Stem cells have the ability to self renew and are therefore a good source for cell therapy following ischemia. In this study, we transplanted adult rat neural stem cells (NSCs) by lumbar puncture (LP) to investigate whether these cells can migrate and differentiate into neurons or glial cells, thereby improving functional outcome in cerebral ischemia. Transient ischemia was induced in adult rats (n=16) for 1h. Three days after the induction of ischemia, NSCs obtained from the subventricular zone of adult rats were injected into ischemic animals (n=8) by LP at the level of L6-S1. Improved recovery of the coordination of movement on the 1st, 7th, 14th, 21st and 28th days after the injury was examined by the Rotarod test and compared with non-transplanted ischemic animals (n=8). The presence of NSCs in the brain tissue of the animals was examined by immunohistofluorscence and immunohistochemical techniques. The coordination of movement in ischemic animals that received neural stem cells was improved significantly (P<0.05) compared with untreated ischemic animals. Cells labeled with PKH26 were observed in the ischemic area of brain tissue sections. The alkaline phosphatase test and immunohistochemical techniques demonstrated a gathering of NSCs in the lateral ventricle. A number of cells which expressed neuronal and astrocytic cell markers had migrated from the lateral ventricle to the subjacent brain parenchyma. NSCs injected by LP were able to migrate to the ischemic tissue and differentiate into neural-like cells. These differentiated cells may have improved the coordination in movement in the ischemic animals injected with NSCs.

Increased inflammatory markers in brain and blood of rats subjected to acute homocysteine administration

Hyperhomocysteinemia plays an etiologic role in the pathogenesis of disorders, including homocystinuria and neurodegenerative and cardiovascular diseases. In the present study, we studied the effect of acute administration of homocysteine, similar to that found in homocystinuria, on parameters of inflammation such as cytokines (TNF-alpha, IL-1beta and IL-6), chemokine CCL2 (MCP-1), nitrite and acute phase-proteins (C-reactive protein and alpha(1)-Acid glycoprotein) levels in brain and blood of rats. In addition, a differential count of blood leukocytes was performed. Wistar rats, aged 29 days, received a single subcutaneous injection of saline (control) or homocysteine (0.6 micromol/g body weight). Fifteen minutes, 1 h, 6 h or 12 h after the injection, the rats were sacrificed and serum, hippocampus and cerebral cortex were used. Results showed that homocysteine significantly increased proinflammatory cytokines (TNF-alpha, IL-1beta and IL-6) and chemokine CCL2 (MCP-1) in serum, hippocampus and cerebral cortex. Nitrite levels also increased in hippocampus and cerebral cortex at 15 min, 1 h and 6 h, but not 12 h after homocysteine administration. Acute phase-protein levels were not altered by homocysteine. The percentage of neutrophils and monocytes significantly increased in blood at 15 min and 1 h, but not at 6 h and 12 h after acute hyperhomocysteinemia, when compared to the control group. Our results showed that acute administration of homocysteine increased inflammatory parameters, suggesting that inflammation might be associated, at least in part, with the neuronal and cardiovascular dysfunctions observed in homocystinuric patients.

Ascorbate sustains neutrophil NOS expression, catalysis, and oxidative burst

Previous studies from this lab have demonstrated that in vitro ascorbate augments neutrophil nitric oxide (NO) generation and oxidative burst. The present study was therefore undertaken in guinea pigs to further assess the implication of ascorbate deficiency in vivo on neutrophil ascorbate and tetrahydrobiopterin content, NOS expression/activity, phagocytosis, and respiratory burst. Ascorbate deficiency significantly reduced ascorbate and tetrahydrobiopterin amounts, NOS expression/activity, and NO as well as free radical generation in neutrophils from scorbutics. Ascorbate and tetrahydrobiopterin supplementation in vitro, though, significantly enhanced NOS catalysis in neutrophil lysates and NO generation in live cells, but could not restore them to control levels. Although phagocytic activity remained unaffected, scorbutic neutrophils were compromised in free radical generation. Ascorbate-induced free radical generation was NO dependent and prevented by NOS and NADPH oxidase inhibitors. Augmentation of oxidative burst with dehydroascorbate (DHA) was counteracted in the presence of glucose (DHA uptake inhibitor) and iodoacetamide (glutaredoxin inhibitor), suggesting the importance of ascorbate recycling in neutrophils. Ascorbate uptake was, however, unaffected among scorbutic neutrophils. These observations thus convincingly demonstrate a novel role for ascorbate in augmenting both NOS expression and activity in vivo, thereby reinforcing oxidative microbicidal actions of neutrophils.

Effect of thioperamide on oxidative stress markers in middle cerebral artery occlusion model of focal cerebral ischemia in rats

In view of the recent evidence for the involvement of histamine in cerebral ischemia, the present study evaluated the effect of thioperamide (THP), a selective histamine H3-receptor antagonist, on middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia in rats. The rats were subjected to 2 h of MCAO followed by 22 h reperfusion after which the grip strength, locomotor activity and spontaneous alternation performance were assessed. Animals were then killed and oxidative stress markers were estimated in the whole brain. An elevation of thiobarbituric acid reactive substance (TBARS) and a reduction in glutathione (GSH) and antioxidant enzymes, such as glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase (SOD), was observed following MCAO, the last two being statistically insignificant. Pretreatment with THP (5.5 mg/kg i.p. and 11 mg/kg i.p.) significantly reversed the MCAO-induced increase in TBARS, but could not reverse the other parameters. Paradoxically, it further reduced the levels of GPx, GR and SOD. No significant changes were observed in the catalase levels and in the grip strength and spontaneous alternation behavior of rats. Locomotor activity was reduced slightly, but reversed on pretreatment with THP. The dual effect of THP on oxidative stress requires further investigation and raises doubts on its possible use in cerebral ischemia.

Temporary pretreatment with the angiotensin II type 1 receptor blocker, valsartan, prevents ischemic brain damage through an increase in capillary density

BACKGROUND AND PURPOSE

We investigated the effect of temporary treatment with a nonhypotensive dose of valsartan on ischemic brain damage in C57BL/6 mice.

METHODS

We separated the mice into 3 groups of valsartan treatment before middle cerebral artery (MCA) occlusion: (1) for 4 weeks: Val (2W, 2W); (2) for 2 weeks followed by its cessation for 2 weeks: Val (2W, -); and (3) no treatment for 4 weeks: Val (-, -).

RESULTS

Ischemic volume, DNA damage, superoxide production, and mRNA levels of monocyte chemoattractant protein-1 and tumor necrosis factor-alpha on the ipsilateral side after 24 hours of MCA occlusion were significantly reduced in both Val (2W, 2W) and Val (2W, -) mice compared with those in Val (-, -) mice, whereas these parameters were larger in Val (2W, -) mice than in Val (2W, 2W) mice. Moreover, mice in both the Val (2W, 2W) and Val (2W, -) groups exhibited an increase in cerebral blood flow in the peripheral territory of the MCA 1 hour after MCA occlusion, with increases in endothelial nitric oxide synthase activation and nitric oxide production. Before MCA occlusion, treatment with valsartan did not influence superoxide production or mRNA levels of monocyte chemoattractant protein-1 and tumor necrosis factor-alpha in the brain. However, the capillary density in the brain in both Val (2W, 2W) and Val (2W, -) mice was increased before MCA occlusion.

CONCLUSIONS

Our results suggest that temporary valsartan treatment could protect against ischemic brain damage even after its cessation, at least in part due to an increase in capillary density.

Reperfusion enhances nitrotyrosine formation in rat focal cerebral ischemia

The widespread benefit of thrombolysis has been emphasized, but relatively little is known about reperfusion injury. The purpose of this study is to evaluate the difference in nitrotyrosine formation and infarct volume between permanent and transient focal ischemia in rats. Permanent (n = 14) or transient (n = 12) focal ischemia was induced by permanent or 2-hour occlusion of the middle cerebral artery, respectively, with the permanent ligation of the bilateral common carotid arteries in Sprague-Dawley rats. In both models all animals were killed 24 hours after the start of occlusion. The ratio of nitrotyrosine in the peri-infarct and core-of-infarct regions in transient focal ischemia was significantly higher than in permanent focal ischemia (P < .01). Infarct volume in the cortex, but not caudoputamen or whole brain, was significantly larger in transient ischemia than in permanent ischemia (P < .05), with a significant expansion of brain swelling. These results may reflect the higher production of superoxide and nitric oxide owing to reperfusion, and suggest the need to administer neuroprotective drugs such as anti-oxidants as well as thrombolytic agents in the treatment of acute ischemic cerebral damage.

Nitric oxide, ischaemia and brain inflammation

Cerebral ischaemia results in the activation of three isoforms of NOS (nitric oxide synthase) that contribute to the development of and recovery from stroke pathology. This review discusses, in particular, the role of the transcriptionally activated NOS-2 (inducible NOS) isoform and summarizes the outcomes of experimental stroke studies with regard to the therapeutic utility of nitric oxide donors and NOS inhibitors.

Reduced HO-1 protein expression is associated with more severe neurodegeneration after transient ischemia induced by cortical compression in diabetic Goto-Kakizaki rats

Pronounced hyperglycemia provoked by extradural compression (EC) of the sensorimotor cortex was recently described in the non-insulin dependent Goto-Kakizaki (GK) diabetic rat. Compared with control Wistar rats, GK rats exhibited more extensive brain damage after cortical ischemia at 48 h of reperfusion (Moreira et al, 2007). We hypothesized that the enhanced brain injury in GK rats could be caused by differential regulation of the heme degrading enzyme heme oxygenase (HO)-1, known to interact with the expression of other target genes implicated in antioxidant defense, inflammation and neurodegeneration, such as superoxide dismutase (SOD)-1, -2, inducible nitric oxide synthase (iNOS), and tumor necrosis factor-alpha (TNFalpha). At 48 h after ischemia, relative mRNA expression of such target genes was compared between ipsilateral (compressed) and contralateral (uncompressed) hemispheres of GK rats, along with baseline comparison of sham, uncompressed GK and Wistar rats. Immunohistochemistry was performed to detect cellular and regional localization of HO-1 at this time point. Baseline expression of HO-1, iNOS, and TNFalpha mRNA was increased in the cortex of sham GK rats. GK rats showed pronounced hyperglycemia during EC and transient attenuation of regional cerebral blood flow recovery. At 48 h after reperfusion, HO-1 mRNA expression was 7- to 8-fold higher in the ischemic cortex of both strains, being the most upregulated gene under study. Heme oxygenase-1 protein expression was significantly reduced in diabetic rats and was found in perilesional astrocytes and rare microglial cells, in both strains. The reduced HO-1 protein expression in GK rats at 48 h after reperfusion combined with more extensive neurodegeneration induced by EC, provides further in vivo evidence for a neuroprotective role of HO after brain ischemia.

Pretreatment with eplerenone reduces stroke volume in mouse middle cerebral artery occlusion model

Eplerenone, a mineralocorticoid receptor antagonist, is reported to be effective to prevent end-stage cardiovascular damage induced by aldosterone. However, the effect of eplerenone on brain damage is not fully understood. Here, we investigated whether pretreatment with eplerenone attenuates stroke size in mice subjected to middle cerebral artery occlusion. Middle cerebral artery occlusion with a microfilament technique induced focal ischemia, to approximately 25% of the total area in a coronal section of the brain. Treatment with eplerenone at a dose of 1.67 mg/g chow significantly reduced the ischemic area, ischemic volume, and neurological deficit, without a blood pressure-lowering effect. Laser-Doppler flowmetry analysis showed a decrease in surface cerebral blood flow in the peripheral region after 1 h of middle cerebral artery occlusion. This decrease was smaller in mice treated with eplerenone. Superoxide production evaluated by staining with dihydroethidium was attenuated in the ischemic area of the brain in eplerenone-treated mice. Taken together, our findings suggest that eplerenone has a protective effect on ischemic brain damage, at least partly due to improvement of cerebral blood flow in the penumbra and reduction of oxidative stress.

Can albumin administration relieve lung injury in trauma/hemorrhagic shock?

AIM: To study the effect of albumin administration on lung injury in trauma/hemorrhagic shock (T/HS).

METHODS: Sixty experimental animals were randomly divided into three groups: rats undergoing laparotomy without shock (T/SS); rats with T/HS and resuscitation with blood plus twice the volume of shed blood as Ringer’s lactate (RL), and rats with T/HS and resuscitation with blood plus additional 3 mL of 50 g/L human albumin. Expression of polymorphonuclear neutrophil (PMN) CD11b/CD18, intercellular adhesion molecule-1 (ICAM-1) of jugular vein blood and the severity of lung injuries [determined mainly by measuring activity of lung tissue myeloperoxidase (MPO) and lung injury score (LIS)] were measured after a 3-h recovery period.

RESULTS: All three groups showed a significant difference in the expressions of CD11b/CD18, ICAM-1, and severity of lung injury. The expressions of CD11b/CD18 in T/SS group, T/HS + RL group, T/HS + albumin group were 17.76% ± 2.11%, 31.25% ± 3.48%, 20.36% ± 3.21%, respectively (F = 6.25, P < 0.05). The expressions of ICAM-1 (U/mL) in T/SS group, T/HS + RL group, T/HS + albumin group were 258.76 ± 98.23, 356.23 ± 65.6, 301.01 ± 63.21, respectively (F = 5.86, P < 0.05). The expressions of MPO (U/g) in T/SS group, T/HS + RL group, T/HS + albumin group were 2.53 ± 0.11, 4.63 ± 1.31, 4.26 ± 1.12, respectively (F = 6.26, P < 0.05). Moreover, LIS in T/HS + RL group, T/HS + albumin group was 2.62 ± 0.23, 1.25 ± 0.24, respectively. The expressions of CD11b/CD18, ICAM-1 and MPO in T/HS + RL group were significantly increased compared to T/SS group (P = 0.025, P = 0.036, P = 0.028, respectively). However, administration of 3 mL of 50 g/L albumin significantly down-regulated the expressions of CD11b/CD18, ICAM-1 and lung injury index (MPO and LIS) when compared with the T/HS + RL rats (P = 0.035, P = 0.046, P = 0.038, P = 0.012, respectively).

CONCLUSION: The infusion of albumin during resuscitation period can protect lung from injury and decrease the expressions of CD11b/CD18, ICAM-1 in T/HS rats.

Carotid artery intima-media thickness and reactive oxygen species formation by monocytes in hypertensive patients

Carotid artery intima-media thickness (IMT) is a widely accepted index for assessing atherosclerosis, and is known to be a risk indicator for cardiovascular and cerebrovascular events. Oxidative stress and inflammation are also known to play critical roles in the pathogenesis of vascular events. We studied the association between IMT and inflammatory markers, such as oxidative stress in polymorphonuclear leukocytes (PMNs) and mononuclear cells (MNCs) in 156 patients with essential hypertension. Reactive oxygen species (ROS) formation by PMNs and MNCs was measured by gated flow cytometry. CRP and traditional risk factors, such as age, gender, body mass index, hemoglobin A(1c), and total cholesterol were also measured. The subjects were divided into a plaque group (max-IMT>or=1.1 mm, n=40), and a nonplaque group (max-IMT<1.1 mm, n=116). ROS formation by MNCs was significantly increased in the plaque group when compared with the nonplaque group (P<0.0001). Multiple regression analysis revealed a significant correlation between IMT and ROS formation by MNCs (r=0.407, P<0.0001), or CRP (r=0.216, P=0.0029) or hemoglobinA1c (r=0.158, P=0.0270) or age (r=0.157, P=0.0447). No significant correlation was observed between IMT and ROS formation by PMNs. These results suggest that carotid artery IMT may be affected by increased ROS formation by MNCs, and that increased ROS formation by MNCs may be related to the development of atherosclerosis. We propose that ROS formation by MNCs is a marker for prediction of carotid atherosclerosis.

Baicalein attenuates methamphetamine-induced loss of dopamine transporter in mouse striatum

Methamphetamine (METH) has been shown to cause dopaminergic neurotoxicity. By using the loss of dopamine transporter (DAT) as a marker of neurotoxicity, this study was aimed to investigate the neuroprotective effect of baicalein against METH-induced striatal damages in mice. Results from Western blotting showed that repeated METH administration (5 mg/kg, i.p., four injections at 2-h interval) caused 40% decrease of DAT level in mouse striatum measured at 72h after the last injection. Despite of the ineffectiveness at high dose (3.0 mg/kg, i.p.), pretreatment with lower doses of baicalein (0.3-1.0 mg/kg, i.p.) significantly attenuated the METH-induced striatal DAT loss in a dose-dependent manner. Furthermore, baicalein diminished METH-induced increase in striatal malondialdehyde content and myeloperoxidase activity, markers for lipid peroxidation and neutrophil increase, respectively. In addition, the present study also revealed that baicalein effectively diminished the ROS production by leukocytes stimulated with METH or PMA, a phorbol ester used as a positive control of stimulant. Surprisingly, we found that METH-induced nNOS overexpression was further increased by the pretreatment with baicalein while the level of nNOS was not altered significantly by baicalein treatment alone. These results suggested that baicalein may attenuate methamphetamine-induced DAT loss by inhibiting the neutrophil increase and the lipid peroxidation caused by neutrophil-derived reactive oxygen species in striatum.

Cyclopentenone isoprostanes are novel bioactive products of lipid oxidation which enhance neurodegeneration

Oxidative stress and subsequent lipid peroxidation are involved in the pathogenesis of numerous neurodegenerative conditions, including stroke. Cyclopentenone isoprostanes (IsoPs) are novel electrophilic lipid peroxidation products formed under conditions of oxidative stress via the isoprostane pathway. These cyclopentenone IsoPs are isomeric to highly bioactive cyclopentenone prostaglandins, yet it has not been determined if these products are biologically active or are formed in the brain. Here we demonstrate that the major cyclopentenone IsoP isomer 15-A2t-IsoP potently induces apoptosis in neuronal cultures at submicromolar concentrations. We present a model in which 15-A2t-IsoP induced neuronal apoptosis involves initial depletion of glutathione and enhanced production of reactive oxygen species, followed by 12-lipoxygenase activation and phosphorylation of extracellular signal-regulated kinase 1/2 and the redox sensitive adaptor protein p66shc, which results in caspase-3 cleavage. 15-A2t-IsoP application also dramatically potentiates oxidative glutamate toxicity at concentrations as low as 100 nm, demonstrating the functional importance of these molecules in neurodegeneration. Finally, we employ novel mass spectrometric methods to show that cyclopentenone IsoPs are formed abundantly in brain tissue under conditions of oxidative stress. Together these findings suggest that cyclopentenone IsoPs may contribute to neuronal death caused by oxidative insults, and that their activity should perhaps be addressed when designing neuroprotective therapies.

Oxidative stress by peripheral blood mononuclear cells is increased in hypertensives with an extreme-dipper pattern and/or morning surge in blood pressure

Because oxidative stress and inflammation are known to play important roles in the pathogenesis of cardiovascular events that occur most frequently in the morning, we studied the association between reactive oxygen species (ROS) formation by polymorphonuclear leukocytes (PMNs) or mononuclear cells (MNCs) and morning blood pressure (BP) rhythm. A total of 31 hypertensives in whom ambulatory BP monitoring was performed participated in this study. They were first divided into three groups according to their nocturnal BP rhythm (non-dippers, dippers and extreme dippers), and then into two groups according to their morning BP change (surge-type and sustained-type). ROS formation by PMNs and MNCs was measured by gated flow cytometry. C-reactive protein and traditional risk factors such as age, gender, body mass index, hemoglobin A1c, and total cholesterol were also measured. ROS formation by MNCs was significantly increased in extreme dippers (vs. dippers, p<0.05, n=11) and in morning BP surge-type hypertensives (vs. sustained-type, p<0.05, n=13). In patients who were both extreme dippers and morning BP surge-types, ROS formation by MNCs was significantly higher than that in other groups. These results suggest that both extreme dippers and morning BP surge-type hypertensives may suffer increased ROS formation by MNCs, and that increased ROS formation by MNCs may underlie morning strokes.

Nitric oxide down-regulates caveolin-1 expression in rat brains during focal cerebral ischemia and reperfusion injury

As a signalling molecule of the integral membrane protein family, caveolin participates in cellular signal transduction via interaction with other signalling molecules. The nature of interaction between nitric oxide (NO) and caveolin in the brain, however, remains largely unknown. In this study we investigated the role(s) of NO in regulating caveolin-1 expression in rat ischemic brains with middle cerebral artery occlusion (MCAO). Exposure to 1 h ischemia induced the increases in neuronal nitric oxide synthase (nNOS) and NO concentration with concurrent down-regulation of caveolin-1 expression in the ischemic core of rat brains. Subsequent 24 h or more reperfusion time led to an increase in inducible NOS (iNOS) expression and NO production, as well as a decline of caveolin-1 protein at the core and penumbra of the ischemic brain. Afterwards, NOS inhibitors and an NO donor were utilized to clarify the link between NO production and caveolin-1 expression in the rats with 1 h ischemia plus 24 h reperfusion. N(G)-nitro-l-arginine methyl ester (L-NAME, a non-selective NOS inhibitor), N(6)-(1-iminoethyl)-lysine (NIL, an iNOS inhibitor), and 7-nitroindazole (7-NI, a nNOS inhibitor) prevented the loss of caveolin-1 in the core and penumbra of the ischemic brain, whereas l-N(5)-(1-iminoethyl)-ornithine (L-NIO, an endothelial NOS inhibitor) showed less effect than the other NOS inhibitors. S-Nitroso-N-acetylpenicillamine (SNAP, a NO donor) down-regulated the expression of caveolin-1 protein in normal and ischemic brains. These results, when taken together, suggest that NO modulates the expression of caveolin-1 in the brain and that the loss of caveolin-1 is associated with NO production in the ischemic brain.

Modulation of the oxidative stress and inflammatory response by PPAR-γ agonists in the hippocampus of rats exposed to cerebral ischemia/reperfusion

Agonists of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) exert protective effects in several models of ischemia/reperfusion injury, but their role in stroke is less clear. The study investigates the effects of two PPAR-gamma agonists, rosiglitazone and pioglitazone, on oxidative stress and inflammatory response induced by ischemia/reperfusion in the rat hippocampus. Common carotid artery occlusion for 30 min followed by 1 h reperfusion resulted in a significant increase in the generation of reactive oxygen species, nitric oxide and the end products of lipid peroxidation as well as markedly reduced endogenous antioxidant glutathione levels and up-regulated superoxide dismutase activity. Western blot analysis showed that ischemia/reperfusion lead to an increase in cyclooxygenase-2 (COX-2) expression, as well activating p38 and p42/44 mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB). Pre-treatment with either rosiglitazone or pioglitazone significantly reduced oxidative stress, COX-2 protein expression and activation of MAPKs and NF-kappaB. Taken together, the results provide convincing evidence that PPAR-gamma agonists exert protective effects in a rat model of mild forebrain ischemia/reperfusion injury by inhibiting oxidative stress and excessive inflammatory response.

Inhibition of brain GTP cyclohydrolase I and tetrahydrobiopterin attenuates cerebral infarction via reducing inducible NO synthase and peroxynitrite in ischemic stroke

BACKGROUND

Inducible NO synthase (NOS)-derived peroxynitrite (ONOO-) during ischemia/reperfusion contributes to ischemic brain injury. However, inducible NOS (iNOS) regulation in ischemic stroke remains unknown. Tetrahydrobiopterin (BH4) is an essential cofactor for NOS activity. The present study tested the hypothesis that inhibition of endogenous BH4 rate-limiting enzyme GTP cyclohydrolase I (GTPCH I), and thus BH4 synthesis, reduces cerebral infarction via inhibiting iNOS and ONOO- in transient focal ischemia.

METHODS

Focal ischemia (2 hours) was created in adult male Sprague-Dawley rats (250 to 300 g) by middle cerebral artery occlusion (MCAO). Rats were treated 12 hours before MCAO with vehicle or diamino-6-hydroxypyrimidine (DAHP; 0.5 g/kg IP), a selective GTPCH I inhibitor. Brains were harvested 24 hours after reperfusion for assays of infarct volume, blood-brain barrier (BBB) permeability, GTPCH I activity, BH4 levels, GTPCH I and NOS mRNA, protein expression, and superoxide anion (O2*-) and ONOO- levels.

RESULTS

Endogenous GTPCH I activity, BH4 levels, iNOS activity, and (O2*- and ONOO- levels were all augmented after ischemia/reperfusion. DAHP treatment significantly reduced GTPCH I activity, resulting in decreased BH4 levels, iNOS activity, and ONOO- levels. Consequently, DAHP treatment significantly reduced the infarct size compared with the nontreated group (22.3+/-5.6 versus 38.3+/-7.4%; n=6; P<0.05). Similarly, BBB permeability was significantly reduced after DAHP pretreatment compared with the control group (4.11+/-0.22 versus 7.78+/-0.44 microg/g tissue; n=5; P<0.05).

CONCLUSIONS

These results demonstrate that blockade of endogenous brain BH4 synthesis attenuates cerebral infarction via inhibiting iNOS and ONOO-, which may provide a mechanistic basis of novel therapeutic strategies for ischemic stroke.

Taxifolin ameliorates cerebral ischemia-reperfusion injury in rats through its anti-oxidative effect and modulation of NF-kappa B activation

Infarction in adult rat brain was induced by middle cerebral arterial occlusion (MCAO) followed by reperfusion to examine whether taxifolin could reduce cerebral ischemic reperfusion (CI/R) injury. Taxifolin administration (0.1 and 1.0 microg/kg, i.v.) 60 min after MCAO ameliorated infarction (by 42%+/-7% and 62%+/-6%, respectively), which was accompanied by a dramatic reduction in malondialdehyde and nitrotyrosine adduct formation, two markers for oxidative tissue damage. Overproduction of reactive oxygen species (ROS) and nitric oxide (NO) via oxidative enzymes (e.g., COX-2 and iNOS) was responsible for this oxidative damage. Taxifolin inhibited leukocyte infiltration, and COX-2 and iNOS expressions in CI/R-injured brain. Taxifolin also prevented Mac-1 and ICAM-1 expression, two key counter-receptors involved in firm adhesion/transmigration of leukocytes to the endothelium, which partially accounted for the limited leukocyte infiltration. ROS, generated by leukocytes and microglial cells, activated nuclear factor-kappa B (NF-kappaB) that in turn signaled up-regulation of inflammatory proteins. NF-kappaB activity in CI/R was enhanced 2.5-fold over that of sham group and was inhibited by taxifolin. Production of both ROS and NO by leukocytes and microglial cells was significantly antagonized by taxifolin. These data suggest that amelioration of CI/R injury by taxifolin may be attributed to its anti-oxidative effect, which in turn modulates NF-kappaB activation that mediates CI/R injury.