Role of neuronal and endothelial nitric oxide synthase in nitric oxide generation in the brain following cerebral ischemia

Vitamin D supplementation as a prophylactic therapy in the management of pre-eclampsia: Focus on VEGF, Ki67, oxidative stress markers in correlation to placental ultra structure

BACKGROUND

Pre-eclampsia (PE) is a progressive hypertension condition that manifests in the second or third trimester of pregnancy and causes significant proteinuria. A lack of vitamin D (Vit. D) is linked to different pregnancy problems, including impaired placental development. Vitamin D has been shown to enhance fetal growth and lower the incidence of PE.

AIM OF THE WORK

To better understand the pathophysiological mechanisms behind the PE disease and the therapeutic approaches used to manage it, this study examines the role of Vit. D in placental ischemia and its regulatory effects in Nitro L-arginine Methyl Ester (L-NAME) animal model of PE.

METHODS

Fifty female rats in the estrus stage were mated with 30 male rats. Thirty female rats were pregnant and divided into three equal groups: control, Preeclampsia group (PE); using L-NAME for induction of PE, and Vit. D group from 7th day then induction by L-NAME at 10th day till end of pregnancy. Mean arterial Bp, proteinuria, oxidative stress markers, histological structure and immunohistochemical expression of Ki67 and VEGF, Morphometric study, and transmission electron microscopy(TEM) were assessed. The results of the current study suggested that, Vit. D supplementation could lower blood pressure, reduce oxidative stress, and restore angiogenic balance through vascular endothelial growth factor (VEGF) and Ki67.

CONCLUSION

For the first time, we conclude that vitamin D supplementation may not only have direct effects on blood pressure regulation and angiogenic hemostasis but also recover placental function, actually contributing to the prevention or management of PE.

Role of nitric oxide in cerebral ischemia/reperfusion injury: A biomolecular overview

Nitric oxide (NO) is a gaseous molecule produced by 3 different NO synthase (NOS) isoforms: Neural/brain NOS (nNOS/bNOS, type 1), endothelial NOS (eNOS, type 3) and inducible NOS (type 2). Type 1 and 3 NOS are constitutively expressed. NO can serve different purposes: As a vasoactive molecule, as a neurotransmitter or as an immunomodulator. It plays a key role in cerebral ischemia/reperfusion injury (CIRI). Hypoxic episodes simulate the production of oxygen free radicals, leading to mitochondrial and phospholipid damage. Upon reperfusion, increased levels of oxygen trigger oxide synthases; whose products are associated with neuronal damage by promoting lipid peroxidation, nitrosylation and excitotoxicity. Molecular pathways in CIRI can be altered by NOS. Neuroprotective effects are observed with eNOS activity. While nNOS interplay is prone to endothelial inflammation, oxidative stress and apoptosis. Therefore, nNOS appears to be detrimental. The interaction between NO and other free radicals develops peroxynitrite; which is a cytotoxic agent. It plays a main role in the likelihood of hemorrhagic events by tissue plasminogen activator (t-PA). Peroxynitrite scavengers are currently being studied as potential targets to prevent hemorrhagic transformation in CIRI.

A Fluorescent Probe for Imaging and Treating S-Nitrosation Stress in OGD/R Cells

Protein S-nitrosation, a redox post-translational modification elicited by nitric oxide (NO), is essential for modulating diverse protein functions and signaling pathways. Dysregulation of S-nitrosation is implicated in various pathological processes, including oxygen-glucose deprivation/reperfusion (OGD/R) injury, a widely used model for ischemia-reperfusion diseases. The dynamic changes in S-nitrosothiols (SNOs) during ischemia-reperfusion highlight the need for theranostic strategies to monitor and modulate SNO levels based on pathological progression. However, to date, no theranostic strategies have been reported for addressing dysregulated SNO in disease models, particularly in OGD/R conditions. Here, we report the development of a selective probe P-EHC, which could specifically react with SNOs to release EHC, not only exhibiting turn-on fluorescence with high quantum yield and good water solubility but also demonstrating macrophage migration inhibitory factor (MIF) inhibitory activity. In an OGD/R model of SH-SY5Y cells, we observed elevated SNO levels by using live-cell confocal imaging. Treatment of P-EHC significantly reduced intracellular reactive oxygen species (ROS), lowered total NOx species, and improved cell viability in the OGD/R model. In summary, the simplicity and versatility of P-EHC suggest its broad applicability for monitoring SNO in various biological models and therapeutic contexts, particularly in ischemia-reperfusion diseases.

Oxidative Stress in Cerebral Ischemia/Reperfusion Injury

Oxidative stress in cerebral ischemia/reperfusion injury (CIRI) involves reactive oxygen and nitrogen species (ROS and RNS). Despite efficient antioxidant pathways in the brain, hypoxia triggers the production of oxygen free radicals and downregulates ATP, which leads to oxidative stress. Sources of free radicals during CIRI include Ca²⁺-dependent enzymes, phospholipid degradation and mitochondrial enlargement. Upon reperfusion, the abrupt increase of oxygen triggers a massive radical production via enzymes like xantin oxidase (XO), phospholipase A2 (PLA2) and oxide synthases (OS). These enzymes play an essential role in neuronal damage by excitotoxicity, lipoperoxidation, nitrosylation, inflammation and programmed cell death (PCD). Endothelial nitric oxide synthase (eNOS) decreases as compared to neuronal nitric oxide synthase (nNOS). This is associated with neuronal damage, endothelial inflammation, apoptosis and oxidative stress. Strategies promoting activation of eNOS while inhibiting nNOS could offer neuroprotective benefits in CIRI. Understanding and targeting these pathways could mitigate brain damage in ischemia/reperfusion events. Clinically, tissue plasminogen activator (t-PA) has been shown to restore cerebral blood flow. However, serious side effects have been described, including hemorrhagic transformation. Different treatments are currently under investigation to avoid I/R injury. Baicalin has been reported as a potential agent that could improve t-PA adverse effects, which have to do with peroxynitrite synthesis and matrix metalloproteinase (MMP) expression. In this review, CIRI and interventions in oxidative stress are addressed. Special attention is paid to efficient antioxidant mechanisms in the brain and the production of free radicals, especially nNOS-derived nitric oxide (NO). The primary purpose is to describe accessible radical pathways with the activity of Ca²⁺-dependent oxidative enzymes, leading to membrane phospholipids and mitochondrial breakdown. <strong>Key</strong><strong>w</strong><strong>ords</strong>Oxidative stress; cerebral ischemia/reperfusion; nitric oxide; reactive oxygen species; nitric oxide synthase

Treatment of Ischemic Stroke by Atorvastatin-Loaded PEGylated Liposome

There is insufficient evidence on the effect of nanoparticles, particularly liposomes loaded with a statin, on acute ischemic stroke. We investigated the impact of atorvastatin-loaded PEG (polyethylene glycol) conjugated liposomes (LipoStatin) on the outcomes in rats with cerebral ischemia-reperfusion. PEGylated liposome loaded with atorvastatin was developed as a nanoparticle to specifically accumulate in an ischemic region and release the drug to ameliorate the harmful effects of the stroke. LipoStatin was administered to rats with transient middle cerebral artery occlusion through the tail vein immediately after reperfusion (LipoStatin group). LipoStatin efficiently accumulated at the cerebral ischemic injury site of the rat. The LipoStatin group showed a significantly reduced infarct volume (p < 0.01) in brain micro-MR imaging and improved neurological function recovery compared to the control group (p < 0.05). In addition, markedly improved brain metabolism using fluorine-18 fluorodeoxyglucose micro-PET/CT imaging was demonstrated in the LipoStatin group compared with the control group (p < 0.01). Mechanistically, as a result of evaluation through IL-1 beta, TNF-alpha, ICAM-1, and Iba-1 mRNA expression levels at 5 days after cerebral ischemia, LipoStatin showed significant anti-inflammatory effects. Protein expression of occludin, JAM-A, Caveolin-1, and eNOS by western blot at 3 days and fluorescent images at 7 days showed considerable recovery of blood-brain barrier breakdown and endothelial dysfunction. PEGylated LipoStatin can be more effectively delivered to the ischemic brain and may have significant neuroprotective effects. Thus, PEGylated LipoStatin can be further developed as a promising targeted therapy for ischemic stroke and other major vascular diseases.

Phytochemicals targeting nitric oxide signaling in neurodegenerative diseases

Neurodegenerative diseases are a set of diseases in which slow and progressive neuronal loss occurs. Nitric oxide (NO) as a neurotransmitter performs key roles in the stimulation and blockade of various inflammatory processes. Although physiological NO is necessary for protection against a variety of pathogens, reactive oxygen species-mediated oxidative stress induces inflammatory cascades and apoptosis. Activation of glial cells particularly astrocytes and microglia induce overproduction of NO, resulting in neuroinflammation and neurodegenerative disorders. Hence, inhibiting the overproduction of NO is a beneficial therapeutic approach for numerous neuroinflammatory conditions. Several compounds have been explored for the management of neurodegenerative disorders, but they have minor symptomatic benefits and several adverse effects. Phytochemicals have currently gained more consideration owing to their ability to reduce the overproduction of NO in neurodegenerative disorders. Furthermore, phytochemicals are generally considered to be safe and beneficial. The mechanisms of NO generation and their implications in neurodegenerative disorders are explored in this review article, as well as several newly discovered phytochemicals that might have NO inhibitory activity. The current review could aid in the discovery of new anti-neuroinflammatory drugs that can suppress NO generation, particularly during neuroinflammatory and neurodegenerative conditions.

Standardized root extract of Withania somnifera and Withanolide A exert moderate vasorelaxant effect in the rat aortic rings by enhancing nitric oxide generation

ETHNO-PHARMACOLOGICAL RELEVANCE

Withania somnifera (L.) Dunal, commonly known as Ashwagandha, belongs to the family Solanaceae. In Ayurveda, Ashwagandha has been defined as one of the most important herb and is considered to be the best adaptogen. It is also an excellent rejuvenator, a general health tonic and cure for various disorders such as cerebrovascular, insomnia, asthma, ulcers, etc. Steroidal lactones (Withanolides: Withanolide A, Withaferin A, Withanolide D, Withanone, etc) isolated from this plant, possess promising medicinal properties such as anti-inflammatory, immune-stimulatory etc. Standardized root extract of the plant NMITLI-118R (NM) was prepared at CSIR-CIMAP, and was investigated for various biological activities at CSIR-CDRI. Among the notable medicinal properties, NM exhibited excellent neuroprotective activity in the middle cerebral artery occlusion (MCAO) rat model.

AIM OF THE STUDY

Endothelial dysfunction is the primary event in the cerebrovascular or cardiovascular disorders, present study was thus undertaken to evaluate vasoprotective potential of NM and its biomarker compound Withanolide A (WA) using rat aortic rings and EA.hy926 endothelial cells.

MATERIAL AND METHODS

Transverse aortic rings of 10 weeks old Wistar rats were used to evaluate effect of NM and WA on the vasoreactivity. While, mechanism of NM and WA mediated vasorelaxant was investigated in Ea.hy926 cell line by measuring NO generation, nitrite content, Serine 1177 phosphorylation of eNOS, reduced/oxidized biopterin levels and expression of endothelial nitric oxide synthase (eNOS) mRNA and protein.

RESULTS

Fingerprinting of NM using HPLC identified presence of WA in the extract. NM as well as WA exerted moderate vasorelaxant effect in the endothelium intact rat aortic rings which was lesser than acetylcholine (ACh). NM and WA augmented ACh induced relaxation in the rat aortic rings. NM and WA dependent vasorelaxation was blocked by N-nitro-L-arginine methyl ester (L-NAME) or 1H-[1,2,4] oxadiazolo [4,3,-a]quinoxalin-1-one (ODQ), indicating role of NO/cGMP. Further Ea.hy926 cells treated with NM and WA showed accumulation of nitrite content, enhanced NO levels, eNOS expression and eNOS phosphorylation (Serine 1177).

CONCLUSION

Altogether NM and WA dependent improvement in the NO availability seems to be mediated by the enhanced eNOS phosphorylation. WA, seems to be one of the active constituent of NM, and presence of other vasoactive substances cannot be ruled out. The data obtained imply that the vasorelaxant property of NM is beneficial for its neuroprotective potential.

MicroRNA-137-3p Protects PC12 Cells Against Oxidative Stress by Downregulation of Calpain-2 and nNOS

The imbalance between excess reactive oxygen species (ROS) generation and insufficient antioxidant defenses contribute to a range of neurodegenerative diseases. High ROS levels damage cellular macromolecules such as DNA, proteins and lipids, leading to neuron vulnerability and eventual death. However, the underlying molecular mechanism of the ROS regulation is not fully elucidated. Recently, an increasing number of studies suggest that microRNAs (miRNAs) emerge as the targets in regulating oxidative stress. We recently reported the neuroprotective effect of miR-137-3p for brachial plexus avulsion-induced motoneuron death. The present study is sought to investigate whether miR-137-3p also could protect PC12 cells against hydrogen peroxide (H2O2) induced neurotoxicity. By using cell viability assay, ROS assay, gene and protein expression assay, we found that PC-12 cells exposed to H2O2 exhibited decreased cell viability, increased expression levels of calpain-2 and neuronal nitric oxide synthase (nNOS), whereas a decreased miR-137-3p expression. Importantly, restoring the miR-137-3p levels in H2O2 exposure robustly inhibited the elevated nNOS, calpain-2 and ROS expression levels, which subsequently improved the cell viability. Furthermore, the suppressive effect of miR-137-3p on the elevated ROS level under oxidative stress was considerably blunted when we mutated the binding site of calpain-2 targted by miR-137-3p, suggesting the critical role of calpain-2 involving the neuroprotective effect of miR-137-3p. Collectively, these findings highlight the neuroprotective role of miR-137-3p through down-regulating calpain and NOS activity, suggesting its potential role for combating oxidative stress insults in the neurodegenerative diseases.

Nitric Oxide-Dependent Pathways as Critical Factors in the Consequences and Recovery after Brain Ischemic Hypoxia

Brain ischemia is one of the leading causes of disability and mortality worldwide. Nitric oxide (NO^•), a molecule that is involved in the regulation of proper blood flow, vasodilation, neuronal and glial activity constitutes the crucial factor that contributes to the development of pathological changes after stroke. One of the early consequences of a sudden interruption in the cerebral blood flow is the massive production of reactive oxygen and nitrogen species (ROS/RNS) in neurons due to NO^• synthase uncoupling, which leads to neurotoxicity. Progression of apoptotic or necrotic neuronal damage activates reactive astrocytes and attracts microglia or lymphocytes to migrate to place of inflammation. Those inflammatory cells start to produce large amounts of inflammatory proteins, including pathological, inducible form of NOS (iNOS), which generates nitrosative stress that further contributes to brain tissue damage, forming vicious circle of detrimental processes in the late stage of ischemia. S-nitrosylation, hypoxia-inducible factor 1α (HIF-1α) and HIF-1α-dependent genes activated in reactive astrocytes play essential roles in this process. The review summarizes the roles of NO^•-dependent pathways in the early and late aftermath of stroke and treatments based on the stimulation or inhibition of particular NO^• synthases and the stabilization of HIF-1α activity.

Molecular Changes in Circulating microRNAs' Expression and Oxidative Stress in Adults with Mild Cognitive Impairment: A Biochemical and Molecular Study

BACKGROUND

The release of miRNAs in tissue fluids significantly recommends its use as non-invasive diagnostic biomarkers for the progression and pathogenesis of mild cognitive impairment (MCI) in aged patients.

OBJECTIVE

The potential role of circulated miRNAs in the pathogenesis of MCI and its association with cellular oxidative stress, apoptosis, and circulated BDNF, Sirtuin 1 (SIRT1), and dipeptidyl peptidase-4 (DPP4) were evaluated in older adults with MCI.

METHODS

A total of 150 subjects aged 65.4±3.7 years were recruited in this study. The participants were classified into two groups: healthy normal (n=80) and MCI (n=70). Real-time PCR analysis was performed to estimate the relative expression of miRNAs; miR-124a, miR-483-5p, miR-142-3p, and miR-125b, and apoptotic-related genes Bax, Bcl-2, and caspase-3 in the sera of MCI and control subjects. In addition, oxidative stress parameters; MDA, NO, SOD, and CAT; as well as plasma DPP4 activity, BDNF, SIRT1 levels were colorimetrically estimated.

RESULTS

The levels of miR-124a and miR-483-5p significantly increased and miR-142-3p and miR-125b significantly reduced in the serum of MCI patients compared to controls. The expressed miRNAs significantly correlated with severe cognitive decline, measured by MMSE, MoCA, ADL, and memory scores. The expression of Bax, and caspase-3 apoptotic inducing genes significantly increased and Bcl-2 antiapoptotic gene significantly reduced in MCI subjects compared to controls. In addition, the plasma levels of MDA, NO, and DPP4 activity significantly increased, and the levels of SOD, CAT, BDNF, and SIRT1 significantly reduced in MCI subjects compared to controls. The expressed miRNAs correlated positively with NO, MDA, DPP4 activity, BDNF, and SIRT-1, and negatively with the levels of CAT, SOD, Bcl-2, Bax, and caspase-3 genes.

CONCLUSION

Circulating miR-124a, miR-483-5p, miR-142-3p, and miR-125b significantly associated with severe cognitive decline, cellular oxidative stress, and apoptosis in patients with MCI. Thus, it could be potential non-invasive biomarkers for the diagnosis of MCI with high diagnostic performance.

Role of Nitric Oxide in Neurodegeneration: Function, Regulation, and Inhibition

Reactive nitrogen species (RNS) and reactive oxygen species (ROS), collectively known as reactive oxygen and nitrogen species (RONS), are the products of normal cellular metabolism and interact with several vital biomolecules including nucleic acid, proteins, and membrane lipids and alter their function in an irreversible manner which can lead to cell death. There is an imperative role for oxidative stress in the pathogenesis of cognitive impairments and the development and progression of neural injury. Elevated production of higher amounts of nitric oxide (NO) takes place in numerous pathological conditions, such as neurodegenerative diseases, inflammation, and ischemia, which occur concurrently with elevated nitrosative/oxidative stress. The enzyme nitric oxide synthase (NOS) is responsible for the generation of NO in different cells by conversion of L-arginine (Arg) to L-citrulline. Therefore, the NO signaling pathway represents a viable therapeutic target. Naturally occurring polyphenols targeting the NO signaling pathway can be of major importance in the field of neurodegeneration and related complications. Here, we comprehensively review the importance of NO and its production in the human body and afterwards highlight the importance of various natural products along with their mechanisms against various neurodegenerative diseases involving their effect on NO production.

Modulation of peroxynitrite produced via mitochondrial nitric oxide synthesis during Ca2+ and succinate-induced oxidative stress in cardiac isolated mitochondria

We hypothesized that NO^• is generated in isolated cardiac mitochondria as the source for ONOO^- production during oxidative stress. We monitored generation of ONOO^- from guinea pig isolated cardiac mitochondria subjected to excess Ca²⁺ uptake before adding succinate and determined if ONOO^- production was dependent on a nitric oxide synthase (NOS) located in cardiac mitochondria (mtNOS). Mitochondria were suspended in experimental buffer at pH 7.15, and treated with CaCl₂ and then the complex II substrate Na-succinate, followed by menadione, a quinone redox cycler, to generate O₂^•-. L-tyrosine was added to the mitochondrial suspension where it is oxidized by ONOO^- to form dityrosine (diTyr) in proportion to the ONOO^- present. We found that exposing mitochondria to excess CaCl₂ before succinate resulted in an increase in diTyr and amplex red fluorescence (H₂O₂) signals, indicating that mitochondrial oxidant stress, induced by elevated mtCa²⁺ and succinate, increased mitochondrial ONOO^- production via NO^• and O₂^•-. Changes in mitochondrial ONOO^- production dependent on NOS were evidenced by using NOS inhibitors L-NAME/L-NNA, TEMPOL, a superoxide dismutase (SOD) mimetic, and PTIO, a potent global NO^• scavenger. L-NAME and L-NNA decreased succinate and menadione-mediated ONOO^- production, PTIO decreased production of ONOO^-, and TEMPOL decreased ONOO^- levels by converting more O₂^•- to H₂O₂. Electron microscopy showed immuno-gold labeled iNOS and nNOS in mitochondria isolated from cardiomyocytes and heart tissue. Western blots demonstrated iNOS and nNOS bands in total heart tissue, bands for both iNOS and nNOS in β-tubulin-free non-purified (crude) mitochondrial preparations, and a prominent iNOS band, but no nNOS band, in purified (Golgi and ER-free) mitochondria. Prior treatment of guinea pigs with lipopolysacharride (LPS) enhanced expression of iNOS in liver mitochondria but not in heart mitochondria. Our results indicate that release of ONOO^- into the buffer is dependent both on O₂^•- released from mitochondria and NO^• derived from a mtCa²⁺-inducible nNOS isoform, possibly attached to mitochondria, and a mtNOS isoform like iNOS that is non-inducible.

Progesterone Protects Prefrontal Cortex in Rat Model of Permanent Bilateral Common Carotid Occlusion via Progesterone Receptors and Akt/Erk/eNOS

Sustained activation of pro-apoptotic signaling due to a sudden and prolonged disturbance of cerebral blood circulation governs the neurodegenerative processes in prefrontal cortex (PFC) of rats whose common carotid arteries are permanently occluded. The adequate neuroprotective therapy should minimize the activation of toxicity pathways and increase the activity of endogenous protective mechanisms. Several neuroprotectants have been proposed, including progesterone (P4). However, the underlying mechanism of its action in PFC following permanent bilateral occlusion of common carotid arteries is not completely investigated. We, thus herein, tested the impact of post-ischemic P4 treatment (1.7 mg/kg for seven consecutive days) on previously reported aberrant neuronal morphology and amount of DNA fragmentation, as well as the expression of progesterone receptors along with the key elements of Akt/Erk/eNOS signal transduction pathway (Bax, Bcl-2, cytochrome C, caspase 3, PARP, and the level of nitric oxide). The obtained results indicate that potential amelioration of histological changes in PFC might be associated with the absence of activation of Bax/caspase 3 signaling cascade and the decline of DNA fragmentation. The study also provides the evidence that P4 treatment in repeated regiment of administration might be effective in neuronal protection against ischemic insult due to re-establishment of the compromised action of Akt/Erk/eNOS-mediated signaling pathway and the upregulation of progesterone receptors.

S-Nitrosoglutathione Mimics the Beneficial Activity of Endothelial Nitric Oxide Synthase-Derived Nitric Oxide in a Mouse Model of Stroke

BACKGROUND

The nitric oxide (NO)-producing activity of endothelial nitric oxide synthase (eNOS) plays a significant role in maintaining endothelial function and protecting against the stroke injury. However, the activity of the eNOS enzyme and the metabolism of major NO metabolite S-nitrosoglutathione (GSNO) are dysregulated after stroke, causing endothelial dysfunction. We investigated whether an administration of exogenous of GSNO or enhancing the level of endogenous GSNO protects against neurovascular injury in wild-type (WT) and eNOS-null (endothelial dysfunction) mouse models of cerebral ischemia-reperfusion (IR).

METHODS

Transient cerebral ischemic injury was induced by middle cerebral artery occlusion (MCAO) for 60 minutes in male adult WT and eNOS null mice. GSNO (0.1 mg/kg body weight, intravenously) or N6022 (GSNO reductase inhibitor, 5.0 mg/kg body weight, intravenously) was administered 30 minutes before MCAO in preinjury and at the reperfusion in postinjury studies. Brain infarctions, edema, and neurobehavioral functions were evaluated at 24 hours after the reperfusion.

RESULTS

eNOS-null mice had a higher degree (P< .05) of injury than WT. Pre- or postinjury treatment with either GSNO or N6022 significantly reduced infarct volume, improved neurological and sensorimotor function in both WT and eNOS-null mice.

CONCLUSION

Reduced brain infarctions and edema, and improved neurobehavioral functions by pre- or postinjury GSNO treatment of eNOS knock out mice indicate that GSNO can attenuate IR injury, likely by mimicking the eNOS-derived NO-dependent anti-ischemic and anti-inflammatory functions. Neurovascular protection by GSNO/N6022 in both pre- and postischemic injury groups support GSNO as a promising drug candidate for the prevention and treatment of stroke injury.

Antioxidant enzymes expression in lymphocytes of patients undergoing carotid endarterectomy

To remedy carotid artery stenosis and prevent stroke surgical intervention is commonly used, and the gold standard being carotid endarterectomy (CEA). During CEA cerebrovascular hemoglobin oxygen saturation decreases and when this decrease reaches critical levels it leads to cerebral hypoxia that causes neuronal damage. One of the proposed mechanism that affects changes during CEA and contribute to acute brain ischemia (ABI) is oxidative stress. The increased production of reactive oxygen species and reactive nitrogen species during ABI may cause an unregulated inflammatory response and further lead to structural and functional injury of neurons. Antioxidant activity are involved in the protection against neuronal damage after cerebral ischemia. We hypothesized that neuronal injury and poor outcomes in patients undergoing CEA may be results of oxidative stress that disturbed function of antioxidant enzymes and contributed to the DNA damage in lymphocytes.

Aerobic exercise repairs neurological function after cerebral ischaemia by regulating the nitric oxide

To investigate the mechanism of different exercise patterns on neurological function after focal cerebral ischaemia in rats. Rats with focal cerebral cerebral ischaemia were randomly divided into an aerobic exercise group, an exhaustive exercise group and a control group, with 8 rats in each group. A score for nerve function in each group was calculated, and the ultrastructure of nerve cells was observed. Levels of NO and NOS in the brain motor area of the ​​rats were measured in each group. The aerobic exercise group had lower nerve function scores than the exhaustive exercise group and higher scores than the control group (P<0.05). Under transmission electron microscopy, irregular shapes and organs were observed in nerve cells in the control group, while regular cell shapes and organs were observed in the aerobic exercise group. The aerobic exercise group and exhaustive exercise group had higher measures of NO content, NOS activity and eNOS, nNOS and iNOS gene expression than the control group, but eNOS expression in the aerobic exercise group and iNOS expression in the exhaustive exercise group were clearly higher according to RT-PCR (P<0.05). Aerobic exercise can promote the expression of NOS, mainly in eNOS, which can promote nerve repair.

Hypothesis related to the regulation of inducible nitric oxide synthase during carotid endarterectomy

Sudden occlusion of an artery caused by a thrombus or emboli is the most frequent cause of acute brain ischemia (ABI). Carotid endarterectomy (CEA) represents the gold standard for preventing strokes of carotid origin. However, neuronal damage caused by ischemia and/or reperfusion may contribute to a poor clinical outcome after CEA. In response to shear stress caused by hypoxic-ischemic conditions in patients undergoing CEA, stimulation of the hypothalamic-pituitaryadrenal axis leads to biological responses known as hypermetabolic stress, characterized by hemodynamic, metabolic, inflammatory and immunological changes. These changes maintain homeostasis and assist recovery, but an unregulated inflammatory response could lead to further tissue damage and death of neurons. Nitric oxide (NO) is an important signaling molecule involved in several physiological and pathological processes, including ABI. However, an excess of NO could have detrimental effects. We hypothesized that the hypoxic-ischemic state induced by carotid clamping leads to overexpression of inducible NO synthase and that uncontrolled production of NO could adversely affect outcome after CEA.

The dual role of KCNQ/M channels upon OGD or OGD/R insults in cultured cortical neurons of mice: Timing is crucial in targeting M-channels against ischemic injur ies

KCNQ/M potassium channels play a vital role in neuronal excitability; however, it is required to explore their pharmacological modulation on N-Methyl- d-aspartic acid receptors (NMDARs)-mediated glutamatergic transmission of neurons upon ischemic insults. In the current study, both presynaptic glutamatergic release and activities of NMDARs were measured by NMDAR-induced miniature excitatory postsynaptic currents (mEPSCs) in cultured cortical neurons of C57 mice undergoing oxygen and glucose deprivation (OGD) or OGD/reperfusion (OGD/R). The KCNQ/M-channel opener, retigabine (RTG), suppressed the overactivation of postsynaptic NMDARs induced by OGD and then NO transient; RTG also decreased OGD-induced neuronal death measured with MTT assay, suggesting the beneficial role of KCNQ/M-channels for the neurons exposed to ischemic insults. However, when the neurons exposed to the subsequent reperfusion, KCNQ/M-channels played a differential role from its protective effect. OGD/R increased presynaptic glutamatergic release, which was further augmented by RTG or decreased by KCNQ/M-channel blocker, XE991. Reactive oxygen species (ROS) were produced partly in a NO-dependent manner. In addition, XE991 decreased neuronal injuries upon reperfusion measured with DCF and PI staining. Meanwhile, the addition of RTG upon OGD or XE991 upon reperfusion can reverse OGD or OGD/R-reduced mitochondrial membrane potential. Our present study indicates the dual role of KCNQ/M-channels in OGD and OGD/R, which will decide the fate of neurons. Provided that activation of KCNQ/M-channels has differential effects on neuronal injuries during OGD or OGD/R, we propose that therapy targeting KCNQ/M-channels may be effective for ischemic injuries but the proper timing is so crucial for the corresponding treatment.

Development of a reactive oxygen species-sensitive nitric oxide synthase inhibitor for the treatment of ischemic stroke

Ischemic stroke is caused by a blockage of cerebral blood flow resulting in neuronal and glial hypoxia leading to inflammatory and reactive oxygen species (ROS)-mediated cell death. Nitric oxide (NO) formed by NO synthase (NOS) is known to be protective in ischemic stroke, however NOS has been shown to 'uncouple' under oxidative conditions to instead produce ROS. Nitrones are antioxidant molecules that are shown to trap ROS to then decompose and release NO. In this study, the nitrone 5 was designed such that its decomposition product is a NOS inhibitor, 6, effectively leading to NOS inhibition specifically at the site of ROS production. The ability of 5 to spin-trap radicals and decompose to 6 was observed using EPR and LC-MS/MS. The pro-drug concept was tested in vitro by measuring cell viability and 6 formation in SH-SY5Y cells subjected to oxygen glucose deprivation (OGD). 5 was found to be more efficacious and more potent than PBN, and was able to increase phospho-Akt while reducing nitrotyrosine and cleaved caspase-3 levels. 6 treatment, but not 5, was found to decrease NO production in LPS-stimulated microglia. Doppler flowmetry on anesthetized mice showed increased cerebral blood flow upon intravenous administration of 1mg/kg of 5, but a return to baseline upon administration of 10mg/kg, likely due to its dual nature of antioxidant/NO-donor and NOS-inhibition. Mice treated with 5 after permanent ischemia exhibited a >30% reduction in infarct volume, and higher formation of 6 in ischemic tissue resulting in region specific effects limited to the infarct area.

Free Radical Damage in Ischemia-Reperfusion Injury: An Obstacle in Acute Ischemic Stroke after Revascularization Therapy

Acute ischemic stroke is a common cause of morbidity and mortality worldwide. Thrombolysis with recombinant tissue plasminogen activator and endovascular thrombectomy are the main revascularization therapies for acute ischemic stroke. However, ischemia-reperfusion injury after revascularization therapy can result in worsening outcomes. Among all possible pathological mechanisms of ischemia-reperfusion injury, free radical damage (mainly oxidative/nitrosative stress injury) has been found to play a key role in the process. Free radicals lead to protein dysfunction, DNA damage, and lipid peroxidation, resulting in cell death. Additionally, free radical damage has a strong connection with inducing hemorrhagic transformation and cerebral edema, which are the major complications of revascularization therapy, and mainly influencing neurological outcomes due to the disruption of the blood-brain barrier. In order to get a better clinical prognosis, more and more studies focus on the pharmaceutical and nonpharmaceutical neuroprotective therapies against free radical damage. This review discusses the pathological mechanisms of free radicals in ischemia-reperfusion injury and adjunctive neuroprotective therapies combined with revascularization therapy against free radical damage.

The role of nitric oxide in stroke

Stroke is considered to be an acute cerebrovascular disease, including ischemic stroke and hemorrhagic stroke. The high incidence and poor prognosis of stroke suggest that it is a highly disabling and highly lethal disease which can pose a serious threat to human health. Nitric oxide (NO), a common gas in nature, which is often thought as a toxic gas, because of its intimate relationship with the pathological processes of many diseases, especially in the regulation of blood flow and cell inflammation. However, recent years have witnessed an increased interest that NO plays a significant and positive role in stroke as an essential gas signal molecule. In view of the fact that the neuroprotective effect of NO is closely related to its concentration, cell type and time, only in the appropriate circumstances can NO play a protective effect. The purpose of this review is to summarize the roles of NO in ischemic stroke and hemorrhagic stroke.

Neuroprotective Effects of Inhibiting Fyn S-Nitrosylation on Cerebral Ischemia/Reperfusion-Induced Damage to CA1 Hippocampal Neurons

Nitric oxide (NO) can regulate signaling pathways via S-nitrosylation. Fyn can be post-translationally modified in many biological processes. In the present study, using a rat four-vessel-occlusion ischemic model, we aimed to assess whether Fyn could be S-nitrosylated and to evaluate the effects of Fyn S-nitrosylation on brain damage. In vitro, Fyn could be S-nitrosylated by S-nitrosoglutathione (GSNO, an exogenous NO donor), and in vivo, endogenous NO synthesized by NO synthases (NOS) could enhance Fyn S-nitrosylation. Application of GSNO, 7-nitroindazole (7-NI, an inhibitor of neuronal NOS) and hydrogen maleate (MK-801, the N-methyl-d-aspartate receptor (NMDAR) antagonist) could decrease the S-nitrosylation and phosphorylation of Fyn induced by cerebral ischemia/reperfusion (I/R). Cresyl violet staining validated that these compounds exerted neuroprotective effects against the cerebral I/R-induced damage to hippocampal CA1 neurons. Taken together, in this study, we demonstrated that Fyn can be S-nitrosylated both in vitro and in vivo and that inhibiting S-nitrosylation can exert neuroprotective effects against cerebral I/R injury, potentially via NMDAR-mediated mechanisms. These findings may lead to a new field of inquiry to investigate the underlying pathogenesis of stroke and the development of novel treatment strategies.

Targeting the nNOS/peroxynitrite/calpain system to confer neuroprotection and aid functional recovery in a mouse model of TBI

Traumatic brain injury (TBI) derails nitric oxide (NO)-based anti-inflammatory and anti-excitotoxicity mechanisms. NO is consumed by superoxide to form peroxynitrite, leading to decreased NO bioavailability for S-nitrosoglutathione (GSNO) synthesis and regulation of neuroprotective pathways. Neuronal peroxynitrite is implicated in neuronal loss and functional deficits following TBI. Using a contusion mouse model of TBI, we investigated mechanisms for the opposed roles of GSNO versus peroxynitrite for neuroprotection and functional recovery. TBI was induced by controlled cortical impact (CCI) in adult male mice. GSNO treatment at 2h after CCI decreased the expression levels of phospho neuronal nitric oxide synthase (pnNOS), alpha II spectrin degraded products, and 3-NT, while also decreasing the activities of nNOS and calpains. Treatment of TBI with FeTPPS, a peroxynitrite scavenger, had effects similar to GSNO treatment. GSNO treatment of TBI also reduced neuronal degeneration and improved neurobehavioral function in a two-week TBI study. In a cell free system, SIN-1 (a peroxynitrite donor and 3-nitrotyrosinating agent) increased whereas GSNO (an S-nitrosylating agent) decreased calpain activity, and these activities were reversed by, respectively, FeTPPS and mercuric chloride, a cysteine-NO bond cleaving agent. These data indicate that peroxynitrite-mediated activation and GSNO-mediated inhibition of the deleterious nNOS/calpain system play critical roles in the pathobiology of neuronal protection and functional recovery in TBI disease. Given GSNO׳s safety record in other diseases, its neuroprotective efficacy and promotion of functional recovery in this TBI study make low-dose GSNO a potential candidate for preclinical evaluation.

Blocking a vicious cycle nNOS/peroxynitrite/AMPK by S-nitrosoglutathione: implication for stroke therapy

BACKGROUND

Stroke immediately sets into motion sustained excitotoxicity and calcium dysregulation, causing aberrant activity in neuronal nitric oxide synthase (nNOS) and an imbalance in the levels of nitric oxide (NO). Drugs targeting nNOS-originated toxicity may therefore reduce stroke-induced damage. Recently, we observed that a redox-modulating agent of the NO metabolome, S-nitrosoglutathione (GSNO), confers neurovascular protection by reducing the levels of peroxynitrite, a product of aberrant NOS activity. We therefore investigated whether GSNO-mediated neuroprotection and improved neurological functions depend on blocking nNOS/peroxynitrite-associated injurious mechanisms using a rat model of cerebral ischemia reperfusion (IR).

RESULTS

IR increased the activity of nNOS, the levels of neuronal peroxynitrite and phosphorylation at Ser(1412) of nNOS. GSNO treatment of IR animals decreased IR-activated nNOS activity and neuronal peroxynitrite levels by reducing nNOS phosphorylation at Ser(1412). The Ser(1412) phosphorylation is associated with increased nNOS activity. Supporting the notion that nNOS activity and peroxynitrite are deleterious following IR, inhibition of nNOS by its inhibitor 7-nitroindazole or reducing peroxynitrite by its scavenger FeTPPS decreased IR injury. GSNO also decreased the activation of AMP Kinase (AMPK) and its upstream kinase LKB1, both of which were activated in IR brain. AMPK has been implicated in nNOS activation via Ser(1412) phosphorylation. To determine whether AMPK activation is deleterious in the acute phase of IR, we treated animals after IR with AICAR (an AMPK activator) and compound c (an AMPK inhibitor). While AICAR potentiated, compound c reduced the IR injury.

CONCLUSIONS

Taken together, these results indicate an injurious nNOS/peroxynitrite/AMPK cycle following stroke, and GSNO treatment of IR inhibits this vicious cycle, resulting in neuroprotection and improved neurological function. GSNO is a natural component of the human body, and its exogenous administration to humans is not associated with any known side effects. Currently, the FDA-approved thrombolytic therapy suffers from a lack of neuronal protective activity. Because GSNO provides neuroprotection by ameliorating stroke's initial and causative injuries, it is a candidate of translational value for stroke therapy.

Altered endothelial nitric oxide synthesis in preterm and small for gestational age infants

BACKGROUND

Preterm infants are often exposed to neuronal and endothelial damage. The aim of the present study was to investigate the correlation between endothelial dysfunction and neuronal injury in preterm infants.

METHODS

We compared serum nitric oxide (NO), endothelial nitric oxide synthase (eNOS) and neuron-specific enolase (NSE) concentrations in 33 moderate preterm (MP) and 47 late preterm (LP) infants using standard ELISA. Each group was classified as appropriate for gestational age (AGA) or small for gestational age (SGA).

RESULTS

Compared to the AGA infants, the SGA infants had higher NO on day 1 (MP: mean, 72.3 ng/mL, range, 50.9-99.5 ng/mL vs 52.2 ng/mL, range, 28.1-68.2 ng/mL, P < 0.05; LP: mean, 58.4 ng/mL, range, 25.7-66.4 ng/mL vs 43.7 ng/mL, range, 21.2-60.6 ng/mL, P < 0.05), lower eNOS concentration on day 3 in the MP group (mean, 5.8 IU/mL, range, 1.2-7.9 IU/mL vs 8.9 IU/mL, range, 4.2-14.6 IU/mL, P < 0.05), and on day 1 in the LP group (mean, 5.5 IU/mL, range, 1.5-8.1 IU/mL vs 7.7 IU/mL, range, 4.4-13.8 IU/mL, P < 0.05). The NO/eNOS ratio was higher in SGA infants compared with the AGA subgroups (MP: mean, 13.8, range, 9.9-20.2 vs mean, 9.9, range, 4.7-13.1, P < 0.05; LP: mean, 12.2, range, 9.2-19.9 vs mean, 9.9, range, 5.4-14.4, P < 0.05). AGA infants had lower NSE concentration compared with the SGA infants on day 1 in the LP group (mean, 27.4 ng/mL, range, 20-43 ng/mL vs mean, 40.89 ng/mL, range, 34-51 ng/mL, P < 0.05). A positive correlation was found between NO/eNOS ratio and NSE concentration (r = 0.75, P < 0.05 and r = 0.64, P < 0.05 on days 1 and 3, respectively).

CONCLUSION

High NO concentration in the context of low eNOS activity suggests a possible role of NO in the development of neuronal injury in SGA infants.

Cooling for cerebral protection during brain surgery

BACKGROUND

Patients undergoing neurosurgery are at risk of cerebral ischaemia with resultant cerebral hypoxia and neuronal cell death. This can increase both the risk of mortality and long term neurological disability. Induced hypothermia has been shown to reduce the risk of cerebral ischaemic damage in both animal studies and in humans who have been resuscitated following cardiac arrest. This had lead to an increasing interest in its neuroprotective potential in neurosurgical patients. This review was originally published in 2011 and did not find any evidence of either effectiveness or harm in these patients. This updated review was designed to capture current evidence to readdress these issues.

OBJECTIVES

To evaluate the effectiveness and safety profile of induced hypothermia versus normothermia for neuroprotection in patients undergoing brain surgery. Effectiveness was to be measured in terms of short and long term mortality and functional neurological outcomes. Safety was to be assessed in terms of the rate of the adverse events infection, myocardial infarction, ischaemic stroke, congestive cardiac failure and any other adverse events reported by the authors of the included studies.

SEARCH METHODS

For the original review, the authors searched the databases Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OvidSP), EMBASE (OvidSP) and LILACS to November 2010. For the updated review all these databases were re-searched from November 2010 to May 2014.For both the original and updated versions, grey literature was sought by searching reference lists of identified studies and relevant review articles, and conference proceedings. No language restrictions were applied.

SELECTION CRITERIA

As in the original review, we included randomized controlled trials (RCTs) of induced hypothermia versus normothermia for neuroprotection in patients of any age and gender undergoing brain surgery, which addressed mortality, neurological morbidity or adverse event outcomes.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data and two independently assessed the risk of bias of the included studies. Any discrepancies were resolved by discussion between authors.

MAIN RESULTS

In this updated review, one new ongoing study was found but no new eligible completed studies were identified. This update was therefore conducted using the same four studies included in the original review. These studies included a total of 1219 participants, mean age 40 to 54 years. All included studies were reported as RCTs. Two were multicentred, together including a total of 1114 patients who underwent cerebral aneurysm clipping, and were judged to have an overall low risk of bias. The other two studies were single centred. One included 80 patients who had a craniotomy following severe traumatic brain injury and was judged to have an unclear or low risk of bias. The other study included 25 patients who underwent hemicranicectomy to relieve oedema following cerebral infarction and was judged to have an unclear or high risk of bias. All studies assessed hypothermia versus normothermia. Overall 608 participants received hypothermia with target temperatures ranging from 32.5 °C to 35 °C, and 611 were assigned to normothermia with the actual temperatures recorded in this group ranging form 36.5 °C to 38 °C. For those who were cooled, 556 had cooling commenced immediately after induction of anaesthesia that was continued until the surgical objective of aneurysm clipping was achieved, and 52 had cooling commenced immediately after surgery and continued for 48 to 96 hours.Pooled estimates of effect were calculated for the outcomes mortality during treatment or follow-up (ranging from in-hospital to one year); neurological outcome measured in terms of the Glasgow Outcome Score (GOS) of 3 or less; and adverse events of infections, myocardial infarction, ischaemic stroke and congestive cardiac failure. With regards to mortality, the risk of dying if allocated to hypothermia compared to normothermia was not statistically significantly different (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.59 to 1.27, P = 0.47). There was no indication that the time at which cooling was started affected the risk of dying (RR with intraoperative cooling 0.95, 95% CI 0.60 to 1.51, P = 0.83; RR for cooling postoperatively 0.67, 95% CI 0.34 to 1.35, P = 0.26). For the neurological outcome, the risk of having a poor outcome with a GOS of 3 or less was not statistically different in those who received hypothermia versus normothermia (RR 0.80, 95% CI 0.61 to 1.04, P = 0.09). Again there was no indication that the time at which cooling was started affected this result. Regarding adverse events, there was no statistically significant difference in the incidence in those allocated to hypothermia versus normothermia for risk of surgical infection (RR 1.20, 95% CI 0.73 to 1.97, P = 0.48), myocardial infarction (RR 1.86, 95% CI 0.69 to 4.98, P = 0.22), ischaemic stroke (RR 0.93, 95% CI 0.82 to 1.05, P = 0.24) or congestive heart failure (RR 0.85, 95% CI 0.60 to 1.21, P = 0.38). In contrast to other outcomes, where time of application of cooling did not change the statistical significance of the effect estimates, there was a weak statistically significant increased risk of infection in those who were cooled postoperatively versus those who were not cooled (RR 1.77, 95% CI 1.05 to 2.98, P = 0.03). Overall, as in the original review, no evidence was found that the use of induced hypothermia was either beneficial or harmful in patients undergoing neurosurgery.

AUTHORS' CONCLUSIONS

We found no evidence that the use of induced hypothermia was associated with a significant reduction in mortality or severe neurological disability, or an increase in harm in patients undergoing neurosurgery.

A fast and selective near-infrared fluorescent sensor for multicolor imaging of biological nitroxyl (HNO)

The first near-infrared fluorescent turn-on sensor for the detection of nitroxyl (HNO), the one-electron reduced form of nitric oxide (NO), is reported. The new copper-based probe, CuDHX1, contains a dihydroxanthene (DHX) fluorophore and a cyclam derivative as a Cu(II) binding site. Upon reaction with HNO, CuDHX1 displays a five-fold fluorescence turn-on in cuvettes and is selective for HNO over thiols and reactive nitrogen and oxygen species. CuDHX1 can detect exogenously applied HNO in live mammalian cells and in conjunction with the zinc-specific, green-fluorescent sensor ZP1 can perform multicolor/multianalyte microscopic imaging. These studies reveal that HNO treatment elicits an increase in the concentration of intracellular mobile zinc.

Mechanisms of hypothermic neuroprotection

Prolonged, moderate cerebral hypothermia initiated within a few hours after severe hypoxia-ischemia and continued until resolution of the acute phase of delayed cell death can reduce acute brain injury and improve long-term behavioral recovery in term infants and in adults after cardiac arrest. The specific mechanisms of hypothermic neuroprotection remain unclear, in part because hypothermia suppresses a broad range of potential injurious factors. This article examines proposed mechanisms in relation to the known window of opportunity for effective protection with hypothermia. Knowledge of the mechanisms of hypothermia will help guide the rational development of future combination treatments to augment neuroprotection with hypothermia and identify those most likely to benefit.

Continuous monitoring of changes in plasma nitrite following cerebral ischemia in a rabbit embolic stroke model

In this proof-of-concept study, we investigated direct, continuous monitoring of plasma nitrite as an indicator of cerebral ischemia following clot embolization of rabbits via an indwelling carotid catheter. Two groups of rabbits were studied to compare the effects of embolization on nitrite levels. In the control group, blood was continuously obtained from a jugular venous catheter. The blood was immediately passed through an ultrafiltration filter; the filtrate was chemically reduced to convert free nitrite to nitric oxide (NO) and then measured using a NO-specific electrode. In the embolized group, after a baseline nitrite level was achieved, blood clots were injected into the brain via the carotid artery catheter, and then nitrite levels were continuously measured from jugular venous blood. The stroke group showed a significantly greater increase in nitrite as compared to controls (p=0.017). Using the area-under-the-curve (AUC) method, results reached statistical significance (p<0.05) within 3 min of embolization. In embolized rabbits, NO(2) levels increased 424±256% compared to baseline. This study shows that nitrite can be measured immediately following a stroke and that our system measures nitrite independent of the extent of the stroke. This study provides evidence for the feasibility of using nitrite as a marker of ischemic stroke.

Link between oxidative stress and acute brain ischemia

The pathogenesis of acute brain ischemia (ABI) is highly complex and involves multiple mechanisms including free radical generation. Imbalance between the cellular production of free radicals and the ability of cells to defend against them is referred to as oxidative stress. Oxidative stress is one of the mechanisms contributing to neuronal damage, potentially induced through the ABI. Through interactions with a large number of molecules, reactive oxygen species may irreversibly destroy or alter the function of the cellular lipids, proteins, and nucleic acids and initiate cell signaling pathways after cerebral ischemia. Future investigations should focus on the understanding of oxidative stress mechanisms and neuroprotection in order to discover new treatment targets.

Partial neuroprotection by nNOS inhibition during profound asphyxia in preterm fetal sheep

Preterm brain injury is partly associated with hypoxia-ischemia starting before birth. Excessive nitric oxide production during HI may cause nitrosative stress, leading to cell membrane and mitochondrial damage. We therefore tested the hypothesis that therapy with a new, selective neuronal nitric oxide synthase (nNOS) inhibitor, JI-10 (0.022mg/kg bolus, n=8), given 30min before 25min of complete umbilical cord occlusion was protective in preterm fetal sheep at 101-104day gestation (term is 147days), compared to saline (n=8). JI-10 had no effect on fetal blood pressure, heart rate, carotid and femoral blood flow, total EEG power, nuchal activity, temperature or intracerebral oxygenation on near-infrared spectroscopy during or after occlusion. JI-10 was associated with later onset of post-asphyxial seizures compared with saline (p<0.05), and attenuation of the subsequent progressive loss of cytochrome oxidase (p<0.05). After 7days recovery, JI-10 was associated with improved neuronal survival in the caudate nucleus (p<0.05), but not the putamen or hippocampus, and more CNPase positive oligodendrocytes in the periventricular white matter (p<0.05). In conclusion, prophylactic nNOS inhibition before profound asphyxia was associated with delayed onset of seizures, slower decline of cytochrome oxidase and partial white and gray matter protection, consistent with protection of mitochondrial function.

Long-term remodeling of rat pial microcirculation after transient middle cerebral artery occlusion and reperfusion

OBJECTIVE

The aim of this study was to assess the in vivo structural and functional remodeling of pial arteriolar networks in the ischemic area of rats submitted to transient middle cerebral artery occlusion (MCAO) and different time intervals of reperfusion.

METHODS AND RESULTS

Two closed cranial windows were implanted above the left and right parietal cortex to observe pial microcirculation by fluorescence microscopy. The geometric characteristics of pial arteriolar networks, permeability increase, leukocyte adhesion and capillary density were analyzed after 1 h or 1, 7, 14 or 28 days of reperfusion. MCAO and 1-hour reperfusion caused marked microvascular changes in pial networks. The necrotic core was devoid of vessels, while the penumbra area presented a few arterioles, capillaries and venules with severe neuronal damage. Penumbra microvascular permeability and leukocyte adhesion were pronounced. At 7 days of reperfusion, new pial arterioles were organized in anastomotic vessels, overlapping the ischemic core and in penetrating pial arterioles. Vascular remodeling caused different arteriolar rearrangement up to 28 days of reperfusion and animals gradually regained their motor and sensory functions.

CONCLUSIONS

Transient MCAO-induced pial-network remodeling is characterized by arteriolar anastomotic arcades. Remodeling mechanisms appear to be accompanied by an increased expression of nitric oxide synthases.

Genistein attenuates ischemic oxidative damage and behavioral deficits via eNOS/Nrf2/HO-1 signaling

Global cerebral ischemia, such as occurs following cardiac arrest, can lead to oxidative stress, hippocampal neuronal cell death, and cognitive defects. The current study examined the potential beneficial effect and underlying mechanisms of post-treatment with the naturally occurring isoflavonic phytoestrogen, genistein, which has been implicated to attenuate oxidative stress. Genistein (1 mg kg(-1)) was administered i.v. 5 min after reperfusion in rats subjected to four-vessel global cerebral ischemia (GCI). The results revealed that genistein exerted significant neuroprotection of hippocampal CA1 neurons following GCI, as evidenced by an increase in NeuN-positive neurons and the decrease in TUNEL-positive neurons. Furthermore, genistein treatment also resulted in significantly improved spatial learning and memory as compared to vehicle control animals. The beneficial effects of genistein appear to be mediated by an increase of phosphorylation/activation of eNOS, with subsequent activation of the antioxidant/detoxification Nrf2/Keap1 transcription system. Along these lines, genistein increased keap1 S-nitrosylation, with a corresponding nuclear accumulation and enhanced DNA binding activity of Nrf2. Genistein also enhanced levels of the Nrf2 downstream antioxidant protein, heme oxygenase (HO)-1, as compared to vehicle control groups. In accordance with its induction of Nrf2 activation, genistein exerted a robust attenuation of oxidative DNA damage and lipid peroxidative damage in hippocampal CA1 neurons after GCI, as measured by immunofluorescence staining of the oxidative stress markers, 8-hydroxy-2-deoxyguanosine (8-OHdG) and 4-Hydroxynonenal (4-HNE). Interestingly, the aforementioned effects of genistein were abolished by pretreatment with L-NAME, an inhibitor of eNOS activation. In conclusion, the results of the study demonstrate that low dose genistein can exert significant antioxidant, neuroprotective, and cognitive-enhancing effects in the hippocampal CA1 region following GCI. Mechanistically, the beneficial effects of genistein appear to be mediated by enhanced eNOS phosphorylation/activation and nitric oxide (NO)-mediated thiol modification of Keap1, with subsequent upregulation of the Nrf2/HO-1 antioxidative signaling pathway and a resultant attenuation of oxidative stress.

Nitric oxide donors as neuroprotective agents after an ischemic stroke-related inflammatory reaction

Cerebral ischemia initiates a cascade of detrimental events including glutamate-associated excitotoxicity, intracellular calcium accumulation, formation of Reactive oxygen species (ROS), membrane lipid degradation, and DNA damage, which lead to the disruption of cellular homeostasis and structural damage of ischemic brain tissue. Cerebral ischemia also triggers acute inflammation, which exacerbates primary brain damage. Therefore, reducing oxidative stress (OS) and downregulating the inflammatory response are options that merit consideration as potential therapeutic targets for ischemic stroke. Consequently, agents capable of modulating both elements will constitute promising therapeutic solutions because clinically effective neuroprotectants have not yet been discovered and no specific therapy for stroke is available to date. Because of their ability to modulate both oxidative stress and the inflammatory response, much attention has been focused on the role of nitric oxide donors (NOD) as neuroprotective agents in the pathophysiology of cerebral ischemia-reperfusion injury. Given their short therapeutic window, NOD appears to be appropriate for use during neurosurgical procedures involving transient arterial occlusions, or in very early treatment of acute ischemic stroke, and also possibly as complementary treatment for neurodegenerative diseases such as Parkinson or Alzheimer, where oxidative stress is an important promoter of damage. In the present paper, we focus on the role of NOD as possible neuroprotective therapeutic agents for ischemia/reperfusion treatment.

Early ischaemic preconditioning requires Akt- and PKA-mediated activation of eNOS via serine1176 phosphorylation

AIMS

The role of endothelial nitric oxide synthase (eNOS)/NO signalling is well documented in late ischaemic preconditioning (IPC); however, the role of eNOS and its activation in early IPC remains controversial. This study investigates the role of eNOS in early IPC and the signalling pathways and molecular interactions that regulate eNOS activation during early IPC.

METHODS AND RESULTS

Rat hearts were subjected to 30-min global ischaemia and reperfusion (I/R) with or without IPC (three cycles 5-min I and 5-min R) in the presence or absence of the NOS inhibitor l-NAME, phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (LY), and protein kinase A (PKA) inhibitor H89 during IPC induction or prior endothelial permeablization. IPC improved post-ischaemic contractile function and reduced infarction compared with I/R with this being abrogated by l-NAME or endothelial permeablization. eNOS(Ser1176), Akt(Ser473), and PKA(Thr197) phosphorylation was increased following IPC. I/R decreased eNOS(Ser1176) phosphorylation, whereas IPC increased it. Mass spectroscopy confirmed eNOS(Ser1176) phosphorylation and quantitative Western blots showed ∼24% modification of eNOS(Ser1176) following IPC. Immunoprecipitation demonstrated eNOS, Akt, and PKA complexation. Immunohistology showed IPC-induced Akt and PKA phosphorylation in cardiomyocytes and endothelium. With eNOS activation, IPC increased NO production as measured by electron paramagnetic resonance spin trapping and fluorescence microscopy. LY or H89 not only decreased Akt(Ser473) or PKA(Thr197) phosphorylation, respectively, but also abolished IPC-induced preservation of eNOS and eNOS(Ser1176) phosphorylation as well as cardioprotection.

CONCLUSION

Thus, Akt- and PKA-mediated eNOS activation, with phosphorylation near the C-terminus, is critical for early IPC-induced cardioprotection, with eNOS-derived NO from the endothelium serving a critical role.

Discovery of a potent, orally bioavailable and highly selective human neuronal nitric oxide synthase (nNOS) inhibitor, N-(1-(piperidin-4-yl)indolin-5-yl)thiophene-2-carboximidamide as a pre-clinical development candidate for the treatment of migraine

We recently reported a series of 1,6-disubstituted indoline-based thiophene amidine compounds (5) as selective neuronal nitric oxide synthase (nNOS) inhibitors to mitigate the cardiovascular liabilities associated with hERG K(+) channel inhibition (IC(50) = 4.7 μM) with previously reported tetrahydroquinoline-based selective nNOS inhibitors (4). The extended structure-activity relationship studies within the indoline core led to the identification of 43 as a selection candidate for further evaluations. The in vivo activity in two different pain (spinal nerve ligation and migraine pain) models, the excellent physicochemical and pharmacokinetic properties, oral bioavailability (F(po) = 91%), and the in vitro safety profile disclosed in this report make 43 an ideal candidate for further evaluation in clinical applications related to migraine pain.

Co-expression of endothelial and neuronal nitric oxide synthases in the developing vasculatures of the human fetal eye

BACKGROUND

Nitric oxide (NO) is a multifunctional gaseous molecule that regulates various physiological functions in both neuronal and non-neuronal cells. NO is synthesized by nitric oxide synthases (NOSs), of which three isoforms have been identified. Neuronal NOS (nNOS) and endothelial NOS (eNOS) constitutively produce low levels of NO as a cell-signaling molecule in response to an increase in intracellular calcium concentration. Recent data have revealed a predominant role of eNOS in both angiogenesis and vasculogenesis.

METHODS

The immunohistochemical localization of nNOS and eNOS was investigated during embryonic and fetal ocular vascular development from 7 to 21 weeks gestation (WG) on sections of cryopreserved tissue.

RESULTS

eNOS was confined to endothelial cells of developing vessels at all ages studied. nNOS was prominent in nuclei of vascular endothelial and smooth muscle cells in the fetal vasculature of vitreous and choriocapillaris. nNOS was also prominent in the nuclei of CXCR4(+) progenitors in the inner retina and inner neuroblastic layer.

CONCLUSIONS

These findings demonstrate co-expression of n- and eNOS isoforms in different compartments of vasoformative cells during development. Nuclear nNOS was present in vascular and nonvascular progenitors as well as endothelial cells and pericytes. This suggests that nNOS may play a role in the transcription regulatory systems in endothelial cells and pericytes during ocular hemo-vasculogenesis, vasculogenesis, and angiogenesis.

Decreased production of neuronal NOS-derived hydrogen peroxide contributes to endothelial dysfunction in atherosclerosis

BACKGROUND AND PURPOSE

Reduced NO availability has been described as a key mechanism responsible for endothelial dysfunction in atherosclerosis. We previously reported that neuronal NOS (nNOS)-derived H(2)O(2) is an important endothelium-derived relaxant factor in the mouse aorta. The role of H(2)O(2) and nNOS in endothelial dysfunction in atherosclerosis remains undetermined. We hypothesized that a decrease in nNOS-derived H(2)O(2) contributes to the impaired vasodilatation in apolipoprotein E-deficient mice (ApoE(-/-)).

EXPERIMENTAL APPROACH

Changes in isometric tension were recorded on a myograph; simultaneously, NO and H(2)O(2) were measured using carbon microsensors. Antisense oligodeoxynucleotides were used to knockdown eNOS and nNOS in vivo. Western blot and confocal microscopy were used to analyse the expression and localization of NOS isoforms.

KEY RESULTS

Aortas from ApoE(-/-) mice showed impaired vasodilatation paralleled by decreased NO and H(2)O(2) production. Inhibition of nNOS with L-Arg(NO2) -L-Dbu, knockdown of nNOS and catalase, which decomposes H(2)O(2) into oxygen and water, decreased ACh-induced relaxation by half, produced a small diminution of NO production and abolished H(2)O(2) in wild-type animals, but had no effect in ApoE(-/-) mice. Confocal microscopy showed increased nNOS immunostaining in endothelial cells of ApoE(-/-) mice. However, ACh stimulation of vessels resulted in less phosphorylation on Ser852 in ApoE(-/-) mice.

CONCLUSIONS AND IMPLICATIONS

Our data show that endothelial nNOS-derived H(2)O(2) production is impaired and contributes to endothelial dysfunction in ApoE(-/-) aorta. The present study provides a new mechanism for endothelial dysfunction in atherosclerosis and may represent a novel target to elaborate the therapeutic strategy for vascular atherosclerosis.

Nitric oxide contributes to hypoxia-reoxygenation-induced P-glycoprotein expression in rat brain endothelial cells

Ischemia-reperfusion leads to increased levels at the blood-brain barrier of the multidrug efflux transporter, P-glycoprotein that provides protection to the brain by limiting access of unwanted substances. This is coincident with the production of nitric oxide. This present study using immortalized rat brain endothelial cells (GPNTs) examines whether following hypoxia-reoxygenation, nitric oxide contributes to the alterations in P-glycoprotein levels. After 6 h of hypoxia, both nitric oxide and reactive oxygen species, detected intracellularly using fluorescent monitoring dyes, were produced in the subsequent reoxygenation phase coincident with increased P-glycoprotein. The evidence that nitric oxide can directly affect P-glycoprotein expression was sought by applying S-nitroso-N-acetyl-DL: -penicillamine that as shown increased the nitric oxide generation. Sodium nitroprusside, though more effective at increasing P-glycoprotein expression, appeared to produce different reactive species. Real time RT-PCR analysis revealed the predominant form of nitric oxide synthase in these cells to be endothelial, inhibition of which partially prevented the increase in P-glycoprotein during reoxygenation. These data indicate that the production of nitric oxide by endothelial nitric oxide synthase during reoxygenation can influence P-glycoprotein expression in cells of the blood-rat brain barrier, highlighting another route by which nitric oxide may protect the brain.

Effects of lead exposure on nitric oxide-associated gene expression in the olfactory bulb of mice

Lead (Pb) is known to have toxic effects on the brain; however, data regarding its specific toxic effects on the olfactory bulb are lacking. Therefore, we investigated the relationship between acute Pb exposure and alterations in gene expression associated with the nitric oxide signaling pathway in the olfactory bulb of mice. After administration of Pb (intraperitoneal injections of 1 or 10 mg/kg Pb(CH(3)CO(2))(2) · 3H(2)O once per day for 4 days), body weight, motor activity, and gene expression in the olfactory bulb of mice were examined. High doses of Pb resulted in significant decreases in body weight, but motor coordination was not significantly altered until 11 days after the end of Pb treatment. The expression patterns of dimethylarginine dimethylaminohydrolase 1 (Ddah1), superoxide dismutase 1 (Sod1), and superoxide dismutase (Ccs) were increased, whereas expression of the Stratifin (Sfn) gene was significantly decreased following treatment with 10 mg/kg Pb. The expression patterns of nitric oxide synthases at the mRNA and protein levels, however, were not significantly altered by treatment with 10 mg/kg Pb. These findings indicate that Pb-induced neurotoxicity may be modulated in part by the expression of Ddah1, Sod1, Ccs, and Sfn in the olfactory bulb.

Correlation between cognitive functions and nitric oxide levels in patients with dementia

Dementia is defined as a clinical syndrome characterized by acquired loss of cognitive and emotional abilities, severe enough to interfere with daily functioning and quality of life. Event related potentials (ERP) are sensitive to task variables that relate to cognitive behavior. They might be altered in patients with disorders of cognition such as dementia. Application of the P300 ERP component to the study of cognitive disorders provides a means of quantifying the level of mental impairment. At high levels, nitric oxide (NO), which is produced by microglia due to induction of nitric oxide synthase (NOS), is neurotoxic and may play a role in neurodegeneration. In our study an attempt has been made to record ERP in patients of mild and moderate dementia and to correlate their findings with nitric oxide levels in CSF and serum. Twenty patients with dementia were selected as cases and 20 subjects as controls, which were further subdivided according to the age groups. Both dementia cases and controls were assessed by minimental state examination (MMSE) and clinical dementia rating scale (CDRS) for evaluating the degree of dementia. It was observed that the MMSE score was reduced in demented cases. P300 latency was significantly delayed in mild and moderate cases of dementia. However, no change was seen in NO levels of cerebrospinal fluid (CSF) and serum in dementia cases and controls. A negative correlation was found between MMSE and P300 latency. Hence we conclude that cognitive impairment in demented patients is reflected in P300 latency but not in NO levels in CSF and serum.

Neuronal nitric oxide synthase inhibition prevents cerebral palsy following hypoxia-ischemia in fetal rabbits: comparison between JI-8 and 7-nitroindazole

Cerebral palsy and death are serious consequences of perinatal hypoxia-ischemia (HI). Important concepts can now be tested using an animal model of cerebral palsy. We have previously shown that reactive oxygen and nitrogen species are produced in antenatal HI. A novel class of neuronal nitric oxide synthase (nNOS) inhibitors have been designed, and they ameliorate postnatal motor deficits when administered prior to the hypoxic-ischemic insult. This study asks how the new class of inhibitors, using JI-8 (K(i) for nNOS: 0.014 μM) as a representative, compare with the frequently used nNOS inhibitor 7-nitroindazole (7-NI; K(i): 0.09 ± 0.024 μM). A theoretical dose equivalent to 75 K(i) of JI-8 or equimolar 7-NI was administered to pregnant rabbit dams 30 min prior to and immediately after 40 min of uterine ischemia at 22 days gestation (70% term). JI-8 treatment resulted in a significant decrease in NOS activity (39%) in fetal brain homogenates acutely after HI, without affecting maternal blood pressure and heart rate. JI-8 treatment resulted in 33 normal kits, 2 moderately and 13 severely affected kits and 5 stillbirths, compared with 8 normal, 3 moderately affected and 5 severely affected kits and 10 stillbirths in the 7-NI group. In terms of neurobehavioral outcome, 7-NI was not different from saline treatment, while JI-8 was superior to saline and 7-NI in its protective effect (p < 0.05). In the surviving kits, JI-8 significantly improved the locomotion score over both saline and 7-NI scores. JI-8 was also significantly superior to saline in preserving smell, muscle tone and righting reflex function, but 7-NI did not show significant improvement. Furthermore, a 100-fold increase in the dose (15.75 μmol/kg) of 7-NI significantly decreased systolic blood pressure in the dam, while JI-8 did not. The new class of inhibitors such as JI-8 shows promise in the prevention of cerebral palsy and is superior to the previously more commonly used nNOS inhibitor.

Beneficial effect of Sparassis crispa on stroke through activation of Akt/eNOS pathway in brain of SHRSP

Sparassis crispa (S. crispa) is a mushroom used as a natural medicine that recently became cultivatable in Japan. In this study, we investigated not only the preventive effects of S. crispa against stroke and hypertension in stroke-prone spontaneously hypertensive rats (SHRSP) but also the mechanism involved by using studies of the cerebral cortex at a young age. Six-week-old male SHRSP were divided into 2 groups, a control group and an S. crispa group administered 1.5% S. crispa in feed, and we then observed their survival. In addition, rats of the same age were treated with 1.5% S. crispa for 4 weeks and we measured body weight, blood pressure, blood flow from the tail, NO_x production, and the levels of expression of several proteins in the cerebral cortex by western blot analysis. Our results showed that the S. crispa group had a delayed incidence of stroke and death and significantly decreased blood pressure and increased blood flow after the administration. Moreover, the quantity of urinary excretion and the nitrate/nitrite concentration in cerebral tissue were higher than those of control SHRSP rats. In the cerebral cortex, phosphor-eNOS (Ser1177) and phosphor-Akt (Ser473) in S. crispa-treated SHRSP were increased compared with those of control SHRSP rats. In conclusion, S. crispa could ameliorate cerebrovascular endothelial dysfunction by promoting recovery of Akt-dependent eNOS phosphorylation and increasing NO production in the cerebral cortex. S. crispa may be useful for preventing stroke and hypertension.