Role of nitric oxide after brain ischaemia

Research progress of prodrugs for the treatment of cerebral ischemia

It is well-known that pharmacotherapy plays a pivotal role in the treatment and prevention of cerebral ischemia. Nevertheless, existing drugs, including numerous natural products, encounter various challenges when applied in cerebral ischemia treatment. These challenges comprise poor brain absorption due to low blood-brain barrier (BBB) permeability, limited water solubility, inadequate bioavailability, poor stability, and rapid metabolism. To address these issues, researchers have turned to prodrug strategies, aiming to mitigate or eliminate the adverse properties of parent drug molecules. In vivo metabolism or enzymatic reactions convert prodrugs into active parent drugs, thereby augmenting BBB permeability, improving bioavailability and stability, and reducing toxicity to normal tissues, ultimately aiming to enhance treatment efficacy and safety. This comprehensive review delves into multiple effective prodrug strategies, providing a detailed description of representative prodrugs developed over the past two decades. It underscores the potential of prodrug approaches to improve the therapeutic outcomes of currently available drugs for cerebral ischemia. The publication of this review serves to enrich current research progress on prodrug strategies for the treatment and prevention of cerebral ischemia. Furthermore, it seeks to offer valuable insights for pharmaceutical chemists in this field, offer guidance for the development of drugs for cerebral ischemia, and provide patients with safer and more effective drug treatment options.

Endogenous chemicals guard health through inhibiting ferroptotic cell death

Ferroptosis is a new form of regulated cell death caused by iron-dependent accumulation of lethal polyunsaturated phospholipids peroxidation. It has received considerable attention owing to its putative involvement in a wide range of pathophysiological processes such as organ injury, cardiac ischemia/reperfusion, degenerative disease and its prevalence in plants, invertebrates, yeasts, bacteria, and archaea. To counter ferroptosis, living organisms have evolved a myriad of intrinsic efficient defense systems, such as cyst(e)ine-glutathione-glutathione peroxidase 4 system (cyst(e)ine-GPX4 system), guanosine triphosphate cyclohydrolase 1/tetrahydrobiopterin (BH4) system (GCH1/BH4 system), ferroptosis suppressor protein 1/coenzyme Q10 system (FSP1/CoQ10 system), and so forth. Among these, GPX4 serves as the only enzymatic protection system through the reduction of lipid hydroperoxides, while other defense systems ultimately rely on small compounds to scavenge lipid radicals and prevent ferroptotic cell death. In this article, we systematically summarize the chemical biology of lipid radical trapping process by endogenous chemicals, such as coenzyme Q10 (CoQ10), BH4, hydropersulfides, vitamin K, vitamin E, 7-dehydrocholesterol, with the aim of guiding the discovery of novel ferroptosis inhibitors.

Modelling Cross Talk in the Spatiotemporal System Dynamics of Calcium, IP3 and Nitric Oxide in Neuron Cells

The bioenergetic system of calcium ([Ca2+]), inositol 1, 4, 5-trisphophate (IP3) and nitric oxide (NO) regulate the diverse mechanisms in neurons. The dysregulation in any or all of the calcium, IP3 and nitric oxide dynamics may cause neurotoxicity and cell death. Few studies are noted in the literature on the interactions of two systems like [Ca2+] with IP3 and [Ca2+] with nitric oxide in neuron cells, which gives limited insights into regulatory and dysregulatory processes in neuron cells. But, no study is available on the cross talk in dynamics of three systems [Ca2+], IP3 and NO in neurons. Thus, the cross talk in the system dynamics of [Ca2+], IP3 and NO regulation processes in neurons have been studied using mathematical model. The two-way feedback process between [Ca2+] and IP3 and two-way feedback process between [Ca2+] and NO through cyclic guanosine monophosphate (cGMP) with plasmalemmal [Ca2+]-ATPase (PMCA) have been incorporated in the proposed model. This coupling handles the indirect two-way feedback process between IP3 and nitric oxide in neuronal cells automatically. The numerical outcomes were acquired by employing the finite element method (FEM) with the Crank-Nicholson scheme (CNS). The present model incorporating the sodium-calcium exchanger (NCX) and voltage-gated calcium channel (VGCC) provides novel insights into the various regulatory and dysregulatory processes due to buffer, IP3-receptor, ryanodine receptor, cGMP kinetics through PMCA channel, etc. and their impacts on the interactive spatiotemporal system dynamics of [Ca2+], IP3 and NO in neurons. It is concluded that the behavior of different crucial mechanisms is quite different for interactions of two systems of [Ca2+] and NO and the interactions of three systems of [Ca2+], IP3 and nitric oxide in neuronal cell due to mutual regulatory adjustments. The association of several neurological disorders with the alterations in calcium, IP3 and NO has been explored in neurons.

The effect of acupuncture on oxidative stress in animal models of vascular dementia: a systematic review and meta-analysis

BACKGROUND

Growing evidence showed that acupuncture may improve cognitive function by reducing oxidative stress, key to the pathogenesis in vascular dementia (VaD), but this is yet to be systematically analysed. This study aimed to summarize and evaluate the effect of acupuncture on oxidative stress in animal models of VaD.

METHOD

Eight databases including PubMed, Embase, Web of Science, Cochrane library, CNKI, Wan Fang, CBM, and VIP were searched since their establishment until April 2023, for studies that reported the effect of acupuncture on oxidative stress in VaD animal models. Relevant literature was screened, and information was extracted by two reviewers. The primary outcomes were the levels of oxidative stress indicators. The methodological quality was assessed via the SYRCLE Risk of Bias Tool. Statistical analyses were performed using the RevMan and Stata software.

RESULTS

In total, 22 studies with 747 animals were included. The methodology of most studies had flaws or uncertainties. The meta-analysis indicated that, overall, acupuncture significantly reduced the expression of pro-oxidants including reactive oxygen species (standardized mean differences [SMDs] = -4.29, 95% confidence interval [CI]: -6.26, -2.31), malondialdehyde (SMD = -2.27, 95% CI: -3.07, -1.47), nitric oxide (SMD = -0.85, 95% CI: -1.50, -0.20), and nitric oxide synthase (SMD = -1.01, 95% CI: -1.69, -0.34) and enhanced the levels of anti-oxidants including super oxide dismutase (SMD = 2.80, 95% CI: 1.98, 3.61), glutathione peroxidase (SMD = 1.32, 95% CI: -0.11, 2.76), and catalase (SMD = 1.31, 95% CI: 0.05, 2.58) in VaD animal models. In subgroup analyses, acupuncture showed significant effects on most variables. Only partial modelling methods and treatment duration could interpret the heterogeneity of some outcomes.

CONCLUSION

Acupuncture may inhibit oxidative stress to improve cognitive deficits in animal models of VaD. Nevertheless, the methodological quality is unsatisfactory. More high-quality research with a rigorous design and further experimental researches and clinical trials are needed to confirm these findings.

SYSTEMATIC REVIEW REGISTRATION

This study was registered in PROSPERO (CRD42023411720).

The Activation of GABAAR Alleviated Cerebral Ischemic Injury via the Suppression of Oxidative Stress, Autophagy, and Apoptosis Pathways

Ischemic stroke is a devastating disease leading to neurologic impairment. Compounding the issue is the very limited array of available interventions. The activation of a γ-aminobutyric acid (GABA) type A receptor (GABAAR) has been reported to produce neuroprotective properties during cerebral ischemia, but its mechanism of action is not yet fully understood. Here, in a rat model of photochemically induced cerebral ischemia, we found that muscimol, a GABAAR agonist, modulated GABAergic signaling, ameliorated anxiety-like behaviors, and attenuated neuronal damage in rats suffering cerebral ischemia. Moreover, GABAAR activation improved brain antioxidant levels, reducing the accumulation of oxidative products, which was closely associated with the NO/NOS pathway. Notably, the inhibition of autophagy markedly relieved the neuronal insult caused by cerebral ischemia. We further established an oxygen-glucose deprivation (OGD)-induced PC12 cell injury model. Both in vivo and in vitro experiments demonstrated that GABAAR activation obviously suppressed autophagy by regulating the AMPK-mTOR pathway. Additionally, GABAAR activation inhibited apoptosis through inhibiting the Bax/Bcl-2 pathway. These data suggest that GABAAR activation exerts neuroprotective effects during cerebral ischemia through improving oxidative stress and inhibiting autophagy and apoptosis. Our findings indicate that GABAAR serves as a target for treating cerebral ischemia and highlight the GABAAR-mediated autophagy signaling pathway.

Study of disorders in regulatory spatiotemporal neurodynamics of calcium and nitric oxide

Experimental studies have reported the dependence of nitric oxide (NO) on the regulation of neuronal calcium ([Ca2+]) dynamics in neurons. But, there is no model available to estimate the disorders caused by various parameters in their regulatory dynamics leading to various neuronal disorders. A mathematical model to analyze the impacts due to alterations in various parameters like buffer, ryanodine receptor, serca pump, source influx, etc. leading to regulation and dysregulation of the spatiotemporal calcium and NO dynamics in neuron cells is constructed using a system of reaction-diffusion equations. The numerical simulation is performed with the finite element approach. The disturbances in the different constitutive processes of [Ca2+] and nitric oxide including source influx, buffer mechanism, ryanodine receptor, serca pump, IP3 receptor, etc. can be responsible for the dysregulation in the [Ca2+] and NO dynamics in neurons. Also, the results reveal novel information about the magnitude and intensity of disorders in response to a range of alterations in various parameters of this neuronal dynamics, which can cause dysregulation leading to neuronal diseases like Parkinson's, cerebral ischemia, trauma, etc.

Analysis of endothelial gene polymorphisms in Spanish patients with vascular dementia and Alzheimer´s disease

There is increasing evidence for the involvement of blood-brain barrier (BBB) in vascular dementia (VaD) and Alzheimer´s disease (AD) pathogenesis. However, the role of endothelial function-related genes in these disorders remains unclear. We evaluated the association of four single-nucleotide polymorphisms (VEGF, VEGFR2 and NOS3) with diagnosis and rate of cognitive decline in AD and VaD in a Spanish case-control cohort (150 VaD, 147 AD and 150 controls). Participants carrying -604AA genotype in VEGFR2 (rs2071559) were less susceptible to VaD after multiple testing. Further analysis for VaD subtype revealed a significant difference between small-vessel VaD patients and controls, but not for large-vessel VaD patients. In addition, -2578A and -460C alleles in VEGF (rs699947 and rs833061) showed to decrease the risk of AD, whereas NOS3 (rs1799983) influenced disease progression. Our study supports previous findings of a deleterious effect of VEGFR2 reduced expression on small-vessel disease, but not on large-vessel disease; as well as a detrimental effect of down-regulating VEGF and eNOS in AD, affecting vascular permeability and neuronal survival. These data highlight the relevance of endothelial function and, therefore, BBB in both VaD and AD.

mTOR pathway - a potential therapeutic target in stroke

Stroke is ranked as the second leading cause of death worldwide and a major cause of long-term disability. A potential therapeutic target that could offer favorable outcomes in stroke is the mammalian target of rapamycin (mTOR) pathway. mTOR is a serine/threonine kinase that composes two protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), and is regulated by other proteins such as the tuberous sclerosis complex. Through a significant number of signaling pathways, the mTOR pathway can modulate the processes of post-ischemic inflammation and autophagy, both of which play an integral part in the pathophysiological cascade of stroke. Promoting or inhibiting such processes under ischemic conditions can lead to apoptosis or instead sustained viability of neurons. The purpose of this review is to examine the pathophysiological role of mTOR in acute ischemic stroke, while highlighting promising neuroprotective agents such as hamartin for therapeutic modulation of this pathway. The therapeutic potential of mTOR is also discussed, with emphasis on implicated molecules and pathway steps that warrant further elucidation in order for their neuroprotective properties to be efficiently tested in future clinical trials.

Advanced Glycation End-Products and Their Effects on Gut Health

Dietary advanced glycation end-products (AGEs) are a heterogeneous group of compounds formed when reducing sugars are heated with proteins, amino acids, or lipids at high temperatures for a prolonged period. The presence and accumulation of AGEs in numerous cell types and tissues are known to be prevalent in the pathology of many diseases. Modern diets, which contain a high proportion of processed foods and therefore a high level of AGE, cause deleterious effects leading to a multitude of unregulated intracellular and extracellular signalling and inflammatory pathways. Currently, many studies focus on investigating the chemical and structural aspects of AGEs and how they affect the metabolism and the cardiovascular and renal systems. Studies have also shown that AGEs affect the digestive system. However, there is no complete picture of the implication of AGEs in this area. The gastrointestinal tract is not only the first and principal site for the digestion and absorption of dietary AGEs but also one of the most susceptible organs to AGEs, which may exert many local and systemic effects. In this review, we summarise the current evidence of the association between a high-AGE diet and poor health outcomes, with a special focus on the relationship between dietary AGEs and alterations in the gastrointestinal structure, modifications in enteric neurons, and microbiota reshaping.

Advances in Optogenetics Applications for Central Nervous System Injuries

Injuries to the central nervous system (CNS) often lead to severe neurological dysfunction and even death. However, there are still no effective measures to improve functional recovery following CNS injuries. Optogenetics, an ideal method to modulate neural activity, has shown various advantages in controlling neural circuits, promoting neural remapping, and improving cell survival. In particular, the emerging technique of optogenetics has exhibited promising therapeutic methods for CNS injuries. In this review, we introduce the light-sensitive proteins and light stimulation system that are important components of optogenetic technology in detail and summarize the development trends. In addition, we construct a comprehensive picture of the current application of optogenetics in CNS injuries and highlight recent advances for the treatment and functional recovery of neurological deficits. Finally, we discuss the therapeutic challenges and prospective uses of optogenetics therapy by photostimulation/photoinhibition modalities that would be suitable for clinical applications.

Inhibiting Sphingosine 1-Phosphate Receptor Subtype 3 Attenuates Brain Damage During Ischemia-Reperfusion Injury by Regulating nNOS/NO and Oxidative Stress

Background

Ischemic stroke (IS) is a common disease endangering human life and health. Cerebral ischemia triggers a series of complex harmful events, including excitotoxicity, inflammation and cell death, as well as increased nitric oxide production through the activation of nitric oxide synthase (NOS). Oxidative stress plays a major role in cerebral ischemia and reperfusion. Sphingosine 1-phosphate receptor subtype 3 (S1PR3), a member of S1P’s G protein-coupled receptors S1PR1-S1PR5, is involved in a variety of biological effects in the body, and its role in regulating oxidative stress during cerebral ischemia and reperfusion is still unclear.

Methods

Transient middle cerebral artery occlusion (tMCAO) mice were selected as the brain ischemia–reperfusion (I/R) injury model. Male C57/BL6 mice were treated with or without a selective S1PR3 inhibition after tMCAO, and changes in infarct volume, Nissl staining, hematoxylin-eosin (H&E) staining and NOS protein, nitric oxide (NO), superoxide dismutase (SOD), and malondialdehyde (MDA) content after tMCAO were observed.

Results

In the cerebral ischemia–reperfusion model, inhibition of S1PR3 improved the infarct volume and neuronal damage in mice after tMCAO. Similarly, inhibition of S1PR3 can reduce the expression of NO synthase subtype neuronal NOS (nNOS) and reduce the production of NO after cerebral ischemia. After cerebral ischemia and reperfusion, the oxidative stress response was enhanced, and after the administration of the S1PR3 inhibitor, the SOD content increased and the MDA content decreased, indicating that S1PR3 plays an important role in regulating oxidative stress response.

Conclusion

Inhibiting S1PR3 attenuates brain damage during I/R injury by regulating nNOS/NO and oxidative stress, which provides a potential new therapeutic target and mechanism for the clinical treatment of IS.

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

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

The Genetic Basis of Moyamoya Disease

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive spontaneous bilateral occlusion of the intracranial internal cerebral arteries (ICA) and their major branches with compensatory capillary collaterals resembling a “puff of smoke” (Japanese: Moyamoya) on cerebral angiography. These pathological alterations of the vessels are called Moyamoya arteriopathy or vasculopathy and a further distinction is made between primary and secondary MMD. Clinical presentation depends on age and population, with hemorrhage and ischemic infarcts in particular leading to severe neurological dysfunction or even death. Although the diagnostic suspicion can be posed by MRA or CTA, cerebral angiography is mandatory for diagnostic confirmation. Since no therapy to limit the stenotic lesions or the development of a collateral network is available, the only treatment established so far is surgical revascularization. The pathophysiology still remains unknown. Due to the early age of onset, familial cases and the variable incidence rate between different ethnic groups, the focus was put on genetic aspects early on. Several genetic risk loci as well as individual risk genes have been reported; however, few of them could be replicated in independent series. Linkage studies revealed linkage to the 17q25 locus. Multiple studies on the association of SNPs and MMD have been conducted, mainly focussing on the endothelium, smooth muscle cells, cytokines and growth factors. A variant of the RNF213 gene was shown to be strongly associated with MMD with a founder effect in the East Asian population. Although it is unknown how mutations in the RNF213 gene, encoding for a ubiquitously expressed 591 kDa cytosolic protein, lead to clinical features of MMD, RNF213 has been confirmed as a susceptibility gene in several studies with a gene dosage-dependent clinical phenotype, allowing preventive screening and possibly the  development of new therapeutic approaches. This review focuses on the genetic basis of primary MMD only.

Brain vulnerability and viability after ischaemia

The susceptibility of the brain to ischaemic injury dramatically limits its viability following interruptions in blood flow. However, data from studies of dissociated cells, tissue specimens, isolated organs and whole bodies have brought into question the temporal limits within which the brain is capable of tolerating prolonged circulatory arrest. This Review assesses cell type-specific mechanisms of global cerebral ischaemia, and examines the circumstances in which the brain exhibits heightened resilience to injury. We suggest strategies for expanding such discoveries to fuel translational research into novel cytoprotective therapies, and describe emerging technologies and experimental concepts. By doing so, we propose a new multimodal framework to investigate brain resuscitation following extended periods of circulatory arrest.

Effect of L-carnitine and atorvastatin on a rat model of ischemia-reperfusion injury of spinal cord

Pro-inflammatory cytokines and reactive oxygen species (ROS) are produced in acute spinal cord injury, leading to myelin breakdown, inflammation, mitochondrial dysfunction, and apoptosis of neurons and glial cells. The aim of the present study was to investigate possible protective effects of L-carnitine (carn) or atorvastatin (ator) on spinal cord ischemia-reperfusion injury (IRI). Rats were randomized into nine equal groups (n = 8): control and control taking carn (100 mg/kg BW), ator (2.5 mg/kg BW) or both, as well as sham-operation, IRI and IRI taking same doses of carn, ator or both. Neurological assessments were done 48 hours after IRI, and serum nitrite/nitrate was measured. Finally, lumbar segments of spinal cord were excised, and part was homogenized and prepared for measuring tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), malondialdehyde (MDA), advanced oxidation protein products (AOPP), reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase. The other part was sectioned for evaluation of histopathological changes and for immunostaining by glial fibrillary acidic protein (GFAP), Bax and Bcl-2. The IRI increased ROS (nitrite/nitrate, MDA, AOPP) and pro-inflammatory cytokines (TNF-α, IL-1β), and decreased antioxidants (GSH, GPx, SOD, catalase) with impaired sensory and motor functions. Astrogliosis was detected by GFAP, and increased apoptosis was demonstrated by increasing Bax and decreasing Bcl-2. Treatment with carn or ator alone decreased TNF-α, IL-1β, nitrite/nitrate, MDA and AOPP, and increased GSH, GPx, SOD, and catalase with improvement of neurological functions and histological studies. Combination of carn and ator improved most of measured IRI-affected parameters better than isolated carn or ator administration.

Nutraceuticals in the Prevention of Neonatal Hypoxia-Ischemia: A Comprehensive Review of their Neuroprotective Properties, Mechanisms of Action and Future Directions

Neonatal hypoxia-ischemia (HI) is a brain injury caused by oxygen deprivation to the brain due to birth asphyxia or reduced cerebral blood perfusion, and it often leads to lifelong limiting sequelae such as cerebral palsy, seizures, or mental retardation. HI remains one of the leading causes of neonatal mortality and morbidity worldwide, and current therapies are limited. Hypothermia has been successful in reducing mortality and some disabilities, but it is only applied to a subset of newborns that meet strict inclusion criteria. Given the unpredictable nature of the obstetric complications that contribute to neonatal HI, prophylactic treatments that prevent, rather than rescue, HI brain injury are emerging as a therapeutic alternative. Nutraceuticals are natural compounds present in the diet or used as dietary supplements that have antioxidant, anti-inflammatory, or antiapoptotic properties. This review summarizes the preclinical in vivo studies, mostly conducted on rodent models, that have investigated the neuroprotective properties of nutraceuticals in preventing and reducing HI-induced brain damage and cognitive impairments. The natural products reviewed include polyphenols, omega-3 fatty acids, vitamins, plant-derived compounds (tanshinones, sulforaphane, and capsaicin), and endogenous compounds (melatonin, carnitine, creatine, and lactate). These nutraceuticals were administered before the damage occurred, either to the mothers as a dietary supplement during pregnancy and/or lactation or to the pups prior to HI induction. To date, very few of these nutritional interventions have been investigated in humans, but we refer to those that have been successful in reducing ischemic stroke in adults. Overall, there is a robust body of preclinical evidence that supports the neuroprotective properties of nutraceuticals, and these may represent a safe and inexpensive nutritional strategy for the prevention of neonatal HI encephalopathy.

Identification and relative quantification of 3-nitrotyrosine residues in fibrinogen nitrated in vitro and fibrinogen from ischemic stroke patient plasma using LC-MS/MS

Ischemic stroke is one of the leading causes of death and disability worldwide. This acute vascular event interferes with blood supply to the brain and induces a burst of free radicals such as nitric oxide and superoxide, producing peroxynitrite, a precursor of strong nitrating agents. Fibrinogen is one of the most abundant plasma proteins; it plays a role in the hemostatic system, mediating clot formation, which can be affected by nitrotyrosine formation. We hypothesized that nitration of fibrinogen by ONOOH and ONOOCO₂^- radical products could be one of the early events of the ischemic stroke, and protein-bound 3-nitrotyrosine could be a potential biomarker for diagnosis and/or prognosis of this condition. A targeted mass spectrometry approach was developed to analyze the nitration of fibrinogen and its association with ischemic stroke. First, a comprehensive mapping of 3-nitrotyrosine locations and their relative quantification was performed by LC-MS/MS, using in vitro nitrated fibrinogen samples. Twenty different 3-nitrotyrosine residues were identified on fibrinogen nitrated in vitro, varying with the peroxynitrite tofibrinogen molar ratio used. Nine tyrosine residues that were consistently modified at different treatment ratios were chosen to perform a targeted LC-MS/MS analysis in clinical samples. Enriched fibrinogen fractions from clinical samples from 24 ischemic stroke and 12 patients with non-inflammatory conditions were analysed with this method. Three of the nine tyrosine residues analysed (βY452, βY475 and γY380) showed a significant difference between the ischemic stroke and non-inflammatory disease groups. ROC curve analysis suggested an association of these residues either individually or in combination with ischemic stroke. Different tyrosine nitration patterns were also observed in fibrinogen modified in vitro and in vivo, suggesting differences in the nitration process in these situations. This is the first study showing a putative association between the nitration profile of specific tyrosine residues in human fibrinogen and ischemic stroke.

Guanosine Neuroprotective Action in Hippocampal Slices Subjected to Oxygen and Glucose Deprivation Restores ATP Levels, Lactate Release and Glutamate Uptake Impairment: Involvement of Nitric Oxide

Stroke is a major cause of disability and death worldwide. Oxygen and glucose deprivation (OGD) in brain tissue preparations can reproduce several pathological features induced by stroke providing a valuable ex vivo protocol for studying the mechanism of action of neuroprotective agents. Guanosine, an endogenous guanine nucleoside, promotes neuroprotection in vivo and in vitro models of neurotoxicity. We previously showed that guanosine protective effect was mimicked by inhibition of nitric oxide synthases (NOS) activity. This study was designed to investigate the involvement of nitric oxide (NO) in the mechanisms related to the protective role of guanosine in rat hippocampal slices subjected to OGD followed by reoxygenation (OGD/R). Guanosine (100 μM) and the pan-NOS inhibitor, L-NAME (1 mM) afforded protection to hippocampal slices subjected to OGD/R. The presence of NO donors, DETA-NO (800 μM) or SNP (5 μM) increased reactive species production, and abolished the protective effect of guanosine or L-NAME against OGD/R. Guanosine or L-NAME treatment prevented the impaired ATP production, lactate release, and glutamate uptake following OGD/R. The presence of a NO donor also abolished the beneficial effects of guanosine or L-NAME on bioenergetics and glutamate uptake. These results showed, for the first time, that guanosine may regulate cellular bioenergetics in hippocampal slices subjected to OGD/R injury by a mechanism that involves the modulation of NO levels.

Role of neuronal nitric oxide synthase on cardiovascular functions in physiological and pathophysiological states

This review describes and summarizes the role of neuronal nitric oxide synthase (nNOS) on the central nervous system, particularly on brain regions such as the ventrolateral medulla (VLM) and the periaqueductal gray matter (PAG), and on blood vessels and the heart that are involved in the regulation and control of the cardiovascular system (CVS). Furthermore, we shall also review the functional aspects of nNOS during several physiological, pathophysiological, and clinical conditions such as exercise, pain, cerebral vascular accidents or stroke and hypertension. For example, during stroke, a cascade of molecular, neurochemical, and cellular changes occur that affect the nervous system as elicited by generation of free radicals and nitric oxide (NO) from vulnerable neurons, peroxide formation, superoxides, apoptosis, and the differential activation of three isoforms of nitric oxide synthases (NOSs), and can exert profound effects on the CVS. Neuronal NOS is one of the three isoforms of NOSs, the others being endothelial (eNOS) and inducible (iNOS) enzymes. Neuronal NOS is a critical homeostatic component of the CVS and plays an important role in regulation of different systems and disease process including nociception. The functional and physiological roles of NO and nNOS are described at the beginning of this review. We also elaborate the structure, gene, domain, and regulation of the nNOS protein. Both inhibitory and excitatory role of nNOS on the sympathetic autonomic nervous system (SANS) and parasympathetic autonomic nervous system (PANS) as mediated via different neurotransmitters/signal transduction processes will be explored, particularly its effects on the CVS. Because the VLM plays a crucial function in cardiovascular homeostatic mechanisms, the neuroanatomy and cardiovascular regulation of the VLM will be discussed in conjunction with the actions of nNOS. Thereafter, we shall discuss the up-to-date developments that are related to the interaction between nNOS and cardiovascular diseases such as hypertension and stroke. Finally, we shall focus on the role of nNOS, particularly within the PAG in cardiovascular regulation and neurotransmission during different types of pain stimulus. Overall, this review focuses on our current understanding of the nNOS protein, and provides further insights on how nNOS modulates, regulates, and controls cardiovascular function during both physiological activity such as exercise, and pathophysiological conditions such as stroke and hypertension.

Anaemia at admission is associated with poor clinical outcome in cerebral venous thrombosis

Background and purpose

Anaemia is associated with poor clinical outcome after ischaemic and haemorrhagic stroke. The association between anaemia and outcome in patients with cerebral venous thrombosis (CVT) was examined.

Methods

Consecutive adult patients with CVT were included from seven centres. Anaemia at admission was scored according to World Health Organization definitions. Poor clinical outcome was defined as a modified Rankin Scale score 3–6 at last follow‐up. A multiple imputation procedure was applied for handling missing data in the multivariable analysis. Using binary logistic regression analysis, adjustments were made for age, sex, cancer and centre of recruitment (model 1). In a secondary analysis, adjustments were additionally made for coma, intracerebral haemorrhage, non‐haemorrhagic lesion and deep venous system thrombosis (model 2). In a sensitivity analysis, patients with cancer were excluded.

Results

Data for 952 patients with CVT were included, 22% of whom had anaemia at admission. Patients with anaemia more often had a history of cancer (17% vs. 7%, P < 0.001) than patients without anaemia. Poor clinical outcome (21% vs. 11%, P < 0.001) and mortality (11% vs. 6%, P = 0.07) were more common amongst patients with anaemia. After adjustment, anaemia at admission increased the risk of poor outcome [adjusted odds ratio (aOR) 2.4, 95% confidence interval (CI) 1.5–3.7, model 1]. Model 2 revealed comparable results (aOR 1.9, 95% CI 1.2–3.2), as did the sensitivity analysis excluding patients with cancer (aOR 2.3, 95% CI 1.3–3.8, model 1).

Conclusion

The risk of poor clinical outcome is doubled in CVT patients presenting with anaemia at admission.

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.

GCH1 (rs841) polymorphism in the nitric oxide-forming pathway has protective effects on obstructive sleep apnea

Several studies have recently investigated the contribution of genetic factors in obstructive sleep apnea (OSA). Patients with OSA suffer from a reduction in nitric oxide (NO) serum level. This study investigated rs841, A930G p22phox, and rs1799983 polymorphisms in three critical genes involved in NO formation. A total of 94 patients with OSA and 100 healthy controls were enrolled into the study. Results showed there was no association between rs841, A930G p22phox and rs1799983 polymorphism and the risk of OSA (P = 0.51, P = 0.4 and P = 0.33, respectively). Moreover, rs841 GA genotype had a reverse relationship with the severity of OSA (P = 0.005). On the other hand, rs841 GA and A930G p22phox AA genotypes had a protective effect on daytime sleepiness in OSA patients (P = 0.01and P = 0.02, respectively). Additionally, the combination of rs841 and A930G p22phox (AG/AG and AG/AA) genotypes was significantly associated with a reduction in daytime sleepiness in OSA patients (P = 0.03 and P = 0.03, respectively). According to the results of our study, GA genotype of rs841 and GA/AA genotypes of A930G p22phox polymorphisms significantly reduced the severity of the problem and daytime sleepiness in OSA patients.

Effect of erythropoietin on Fas/FasL expression in brain tissues of neonatal rats with hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD) occurs due to intrauterine hypoxia ischemia influencing the energy supply for fetal brain cells, which affects the metabolism of the brain to make the brain suffer a severe damage. Erythropoietin (EPO), which regulates hemacytopoiesis, is a kind of cytokine. EPO is sensitive to hypoxia ischemia. In this study, we aimed to investigate the effect of EPO on the expression of Fas/FasL in brain tissues of neonatal rats with HIBD. Neonatal rats were assigned randomly to sham, HIBD, and EPO groups. Five time points for observation were 6, 12, 24, 48, and 72 h after the HIBD rat model had been established, respectively. In the HIBD group, Fas/FasL expression began to rise at 6 h, reached the peak at 12–24 h, and dropped from 24 h. In the EPO group, the expression of Fas/FasL was lower than those in HIBD group at 12, 24, and 48 h (P<0.05). Our findings suggest that EPO may reduce cell apoptosis after hypoxic-ischemic damage through reduction of the expression of Fas and FasL, and that optimal therapeutic time window is 6–24 h after HIBD.

Effect of pioglitazone and simvastatin in lipopolysaccharide-induced amyloidogenesis and cognitive impairment in mice: possible role of glutamatergic pathway and oxidative stress

Neuroinflammation and β-amyloid (Aβ) deposition in the brain are well known characteristics of neurodegeneration. Diabetes and hypercholesterolemia are the main risk factors leading to memory loss and cognitive impairment. Recently, it was found that statins and thiazolidinediones have promising anti-inflammatory and neuroprotective effects that could delay neurodegeneration and neuronal loss in diabetic and hypercholesterolemic patients. The aim of the present study was to investigate the protective effect of simvastatin, pioglitazone, and their combination in lipopolysaccharide (LPS)-induced neuroinflammation and amyloidogenesis. Mice were divided into five groups: group 1 received 0.9% saline, group 2 received LPS (0.8 mg/kg in saline), group 3 received LPS (0.8 mgl kg)+simvastatin (5 mg/kg in saline), group 4 received LPS (0.8 mg/kg)+pioglitazone (20 mg/kg in saline), group 5 receiving LPS (0.8 mg/kg)+simvastatin (5 mg/kg)+pioglitazone (20 mg/kg). Y-maze and novel object recognition were used to assess the spatial and nonspatial behavioral changes. Nitric oxide levels and glutamate levels were measured to elucidate the anti-glutamatergic and anti-inflammatory effects of the tested drugs. Immunohistochemistry was performed to detect the presence of Aβ1-42 in the mice brain. LPS impaired memory, and increased Aβ deposition, nitric oxide, and glutamate brain levels. Both drugs produced a significant improvement in all parameters. We conclude that simvastatin and pioglitazone may have a protective effect against cognitive impairment induced by LPS, through targeting the glutamatergic and inflammatory pathways, especially in patients having hypercholesterolemia and diabetes.

Changes in L-arginine metabolism by Sema4D deficiency induce promotion of microglial proliferation in ischemic cortex

Cerebral ischemia induces neuroinflammation and microglial activation, in which activated microglia upregulate their proliferative activity and change their metabolic states. In activated microglia, l-arginine is metabolized competitively by inducible nitric oxide synthase (iNOS) and arginase (Arg), which then synthesize NO or polyamines, respectively. Our previous study demonstrated that Sema4D deficiency inhibits iNOS expression and promotes proliferation of ionized calcium-binding adaptor molecule 1 (Iba1)-positive (Iba1+) microglia in the ischemic cortex, although the underlying mechanisms were unclear. Using middle cerebral artery occlusion, we tested the hypothesis that Sema4D deficiency alters the balance of l-arginine metabolism between iNOS and Arg, leading to an increase in the production of polyamines, which are an essential factor for cell proliferation. In the peri-ischemic cortex, almost all iNOS+ and/or Arg1+ cells were Iba1+ microglia. In the peri-ischemic cortex of Sema4D-deficient (Sema4D^-/-) mice, the number of iNOS+ Arg1- Iba1+ microglia was smaller and that of iNOS- Arg1+ Iba1+ microglia was greater than those of wild-type (WT) mice. In addition, urea and polyamine levels in the ischemic cortex of Sema4D^-/- mice were higher than those of WT mice; furthermore, the presence of Sema4D inhibited polyamine production in primary microglia obtained from Sema4D^-/- mice. Finally, microglia cultured under polyamine putrescine-supplemented conditions demonstrated increased proliferation rates over non-supplemented controls. These findings indicate that Sema4D regulates microglial proliferation at least in part by regulating the competitive balance of l-arginine metabolism.

The interaction between CSE/H2S and the iNOS/NO-mediated resveratrol/poly(ethylene glycol)-poly(phenylalanine) complex alleviates intestinal ischemia/reperfusion injuries in diabetic rats

INTRODUCTION

The purpose of the experiment was to survey the therapeutic function of resveratrol (RES)-loaded poly(ethylene glycol)-poly(phenylalanine) (PEG-PPhe) on intestinal ischemia/reperfusion injury (II/RI) via the interaction between CSE/H₂S and iNOS/NO compared to free RES in diabetic rats.

METHODS

Diabetic rats were pretreated with 20 mg/kg of RES or the RES/PEG-PPhe complex and then subjected to 1 h of ischemia and 3 h of reperfusion. Blood and intestines were collected, intestinal pathological injury was estimated, and the contents of body weight, weights of different tissues, blood glucose, serum insulin, HOMA index, serum nitric oxide (NO) and serum sulfureted hydrogen (H₂S) were observed. The dry/wet intestine ratios, the activity of superoxide dismutase (SOD); the contents of methane dicarboxylic aldehyde (MDA), glutathione (GSH), H₂S, and NO; and the concentrations of inducible nitric oxide synthase (iNOS) and cystathionine-γ-lyase (CSE) were observed in the intestinal tissues.

RESULTS

A significant reduction of weights of different tissues, blood glucose, pathological damage, dry/wet ratios, MDA, NO, iNOS expression and a significant increasement of body weight, serum insulin, HOMA index, SOD, GSH, H₂S, CSE expression were observed in both treatment groups. However, a greater reduction of weights of different tissues, blood glucose (7.49-13.49 mmol/L for 72 h vs. the control) and pathological damage, iNOS expression, dry/wet ratios (6.14 ± 0.29 vs. 8.51 ± 0.42), MDA (5.01 ± 0.71 nmol vs. 9.98 ± 0.67 nmol), NO (0.52 ± 0.09 μmol vs. 0.99 ± 0.08 μmol in intestinal tissue; 19.29 ± 0.89 μmol vs. 45.23 ± 1.17 μmol in serum) was observed in the RES/PEG-PPhe group relative to the I/R (P < 0.01 for all); a greater increasement of body weight, serum insulin, HOMA index, SOD (39.79±1.78 U vs. 11.84 ± 1.02 U), GSH (31.25 ± 1.19 mg vs. 10.13 ± 0.64 mg), H₂S (39.52 ± 1.32 nmol vs. 13.02 ± 1.03 nmol in intestinal tissue; 9.78 ± 0.79 μmol vs. 3.11 ± 0.85 μmol in serum), CSE expression was observed in the RES/PEG-PPhe group relative to the I/R (P < 0.01 for all). In addition, aminoguanidine (AMI, iNOS inhibitor) reduced I/R injury, and dl-propargylglycine (PAG, CSE inhibitor) increased I/R injury.

CONCLUSIONS

The interaction between CSE/H2S and the iNOS/NO-mediated resveratrol/poly(ethylene glycol)-poly(phenylalanine) complex alleviates intestinal ischemia/reperfusion injuries in diabetic rats.

Functional and pharmacological analysis of agmatine administration in different cerebral ischemia animal models

Agmatine (AgM, 100 mg/kg i.p.) effect was tested in parallel at two animal models of cerebral ischemia - rat MCAO model (60'/24 h, 60'/48 h, 90'/24 h, 90'/48 h) and gerbil global ischemia (10') model, administrated 5 min after reperfusion. Aim was to evaluate AgM effect on functional outcome 24 and 48 h after MCAO on neurological and sensor-motor function, and coordination in rats. AgM administration significantly reduced infarct volume, improved neurological score and improved post-ischemic oxidative status. Results of behavioral tests (cylinder test, beam walking test, and adhesive removal test) have shown very effective functional recovery after AgM administration. Efficiency of AgM administration in gerbils was observed in forebrain cortex, striatum, hippocampus, and cerebellum at the level of each examined oxidative stress parameter (nitric oxide level, superoxide production, superoxide dismutase activity, and index of lipid peroxidation) measured in four different time points starting at 3 h up to 48 h after reperfusion. The highest levels were obtained 6 h after the insult. The most sensitive oxidative stress parameter to AgM was nitric oxide. Additionally, we performed pharmacological analysis of AgM on rat isolated common carotid arteries. The findings imply that mixed population of potassium channels located on the smooth muscle cells was involved in common carotid artery response to AgM, with predominance of inward rectifying K⁺ channels. In our comparative experimental approach, judged by behavioral, biochemical, as well as pharmacological data, the AgM administration showed an effective reduction of ischemic neurological damage and oxidative stress, hence indicating a direction towards improving post-stroke recovery.

Therapeutic Hypothermia and Neuroprotection in Acute Neurological Disease

Therapeutic hypothermia has consistently been shown to be a robust neuroprotectant in many labs studying different models of neurological disease. Although this therapy has shown great promise, there are still challenges at the clinical level that limit the ability to apply this routinely to each pathological condition. In order to overcome issues involved in hypothermia therapy, understanding of this attractive therapy is needed. We review methodological concerns surrounding therapeutic hypothermia, introduce the current status of therapeutic cooling in various acute brain insults, and review the literature surrounding the many underlying molecular mechanisms of hypothermic neuroprotection. Because recent work has shown that body temperature can be safely lowered using pharmacological approaches, this method may be an especially attractive option for many clinical applications. Since hypothermia can affect multiple aspects of brain pathophysiology, therapeutic hypothermia could also be considered a neuroprotection model in basic research, which would be used to identify potential therapeutic targets. We discuss how research in this area carries the potential to improve outcome from various acute neurological disorders.

Biochemical Characterization of the Brain Hippocampal Areas after Cerebral Ischemia-Reperfusion Using Raman Spectroscopy

Cerebral ischemic stroke is one of the most common neurodegenerative conditions characterized by cerebral infarction, death of the brain tissue, and loss of brain function. Cerebral ischemia-reperfusion injury is the tissue damage caused when blood supply begins to the tissue after a period of ischemia or poor oxygen supply. In this study, we preliminarily investigated the biochemical changes in the brain hippocampal area, CA1, resulting from ischemia reperfusion and neuronal nitric oxide synthase (nNOS) inhibitor treatment in rats using Raman spectroscopy. A drastic spectral change was observed in the ischemia-reperfusion brain tissue; a strong dependency between the intensity of certain Raman bands was observed at the amide positions of 1276 and 1658 cm^-1 and at the lipid positions of 1300 and 1438 cm^-1. The spectrum of nNOS inhibitor-treated brain tissue was similar to that of the normal brain tissue, indicating that the nNOS inhibitor could protect the brain against excessive production of NO and biochemical processes dependent on it. Principal component analysis (PCA) precisely identified three classes of tissues: normal; ischemic; and nNOS inhibitor-treated. Therefore, we suggest that quantitative analysis of the changes in the brain tissue by using Raman spectroscopy with multivariate statistical technique could be effective for evaluating neuronal injury and drug effects.

Increased BBB Permeability Enhances Activation of Microglia and Exacerbates Loss of Dendritic Spines After Transient Global Cerebral Ischemia

Ischemic stroke can induce rapid disruption of blood-brain barrier (BBB). It has been suggested that increased BBB permeability can affect the pathological progression of ischemic tissue. However, the impact of increased BBB permeability on microglial activation and synaptic structures following reperfusion after ischemia remains unclear. In this study, we investigated microglial activation, dendritic damage and plasticity of dendritic spines after increasing BBB permeability following transient global cerebral ischemia in the somatosensory cortices in mice. Bilateral common carotid artery ligation (BCAL) was used to induce transient global cerebral ischemia. Mannitol was used to increase the BBB permeability. Intravital two-photon imaging was performed to image the dendritic structures and BBB extravasation. Microglial morphology was quantitated using a skeletonization analysis method. To evaluate inflammation of cerebral cortex, the mRNA expression levels of integrin alpha M (CD11b), CD68, chemokine (C-X-C motif) ligand 10 (IP10) and tumor necrosis factor alpha (TNF-α) were measured by fluorescent quantitative PCR. Intravital two-photon imaging revealed that mannitol caused a drastic increase in BBB extravasation during reperfusion after transient global ischemia. Increased BBB permeability induced by mannitol had no significant effect on inflammation and dendritic spines in healthy mice but triggered a marked de-ramification of microglia; importantly, in ischemic animals, mannitol accelerated de-ramification of microglia and aggravated inflammation at 3 h but not at 3 days following reperfusion after ischemia. Although mannitol did not cause significant change in the percentage of blebbed dendrites and did not affect the reversible recovery of the dendritic structures, excessive extravasation was accompanied with significant decrease in spine formation and increase in spine elimination during reperfusion in ischemic mice. These findings suggest that increased BBB permeability induced by mannitol can lead to acute activation of microglia and cause excessive loss of dendritic spines after transient global cerebral ischemia.

Differential behavioral and glial responses induced by dopaminergic mechanisms in the iNOS knockout mice

The interaction between distinctive nitric oxide synthase (NOS) isoforms and the dopamine system provides new avenues to the development of pharmacological tools for the pathophysiological conditions of the dopaminergic system. Our aim was to investigate the influences of dopamine-induced effects in inducible NOS knockout (iNOS KO) mice. In order to characterize iNOS KO mice phenotype, the animals were submitted to the basal analyses of motor, sensorimotor and sensorial abilities. Pharmacological challenging of the dopaminergic system included the investigation of amphetamine-induced prepulse inhibition (PPI) disruption, haloperidol-induced catalepsy, reserpine-induced oral involuntary movements and hyperlocomotion induced by amphetamine in reserpine treated mice. The iNOS KO mice showed significant reduction of spontaneous motor activity, but there was no significant difference in sensorimotor or sensorial responses of iNOS KO mice compared to wild type (WT). Regarding the dopaminergic system, iNOS KO mice showed a significant increase of haloperidol-induced catalepsy. This effect was confirmed through an iNOS pharmacological inhibitor (1400 W) in WT mice. In addition, iNOS KO reserpine treated mice showed reduced oral involuntary movements and amphetamine-induced hyperlocomotion. Knowing that iNOS is mainly expressed in glial cells we analyzed the immunoreactivity (ir) for GFAP (astrocyte marker) and IBA-1 (microglial marker) in the striatum, an area enrolled in motor planning among other functions. iNOS KO presented reduced GFAP-ir and IBA-1-ir compared with WT. Reserpine treatment increased GFAP-ir in both WT and iNOS KO. However, these effects were slighter in iNOS KO. Activated state of microglia was increased by reserpine only in WT mice. Our results further demonstrated that the absence of iNOS interfered with dopamine-mediated behavioral and molecular responses. These results increase the understanding of the dopamine and NO system interaction, which is useful for the management of the dopamine-related pathologies.

Simvastatin blocks soluble SSAO/VAP-1 release in experimental models of cerebral ischemia: Possible benefits for stroke-induced inflammation control

Beyond cholesterol reduction, statins mediate their beneficial effects on stroke patients through pleiotropic actions. They have shown anti-inflammatory properties by a number of different mechanisms, including the inhibition of NF-κB transcriptional activity and the consequent increase and release of adhesion molecules. We have studied simvastatin's effects on the vascular enzyme semicarbazide-sensitive amine oxidase/vascular adhesion protein 1 (SSAO/VAP-1), which is involved in stroke-mediated brain injury. SSAO/VAP-1 has leukocyte-binding capacity and mediates the expression of other adhesion proteins through signaling molecules generated by its catalytic activity. Our results indicate that soluble SSAO/VAP-1 is released into the bloodstream after an ischemic stimulus, in parallel with an increase in E-selectin and VCAM-1 and correlating with infarct volume. Simvastatin blocks soluble SSAO/VAP-1 release and prevents E-selectin and VCAM-1 overexpression as well. Simvastatin also effectively blocks SSAO/VAP-1-mediated leukocyte adhesion, although it is not an enzymatic inhibitor of SSAO in vitro. In addition, simvastatin-induced changes in adhesion molecules are greater in human brain endothelial cell cultures expressing SSAO/VAP-1, compared to those not expressing it, indicating some synergic effect with SSAO/VAP-1. We think that part of the beneficial effect of simvastatin in stroke is mediated by the attenuation of the SSAO/VAP-1-dependent inflammatory response.

The importance of controlling in vitro oxygen tension to accurately model in vivo neurophysiology

The majority of in vitro studies modeling in vivo conditions are performed on the lab bench in atmospheric air. However, the oxygen tension (pO₂) present in atmospheric air (160mm Hg, ∼21% O₂) is in great excess to the pO₂ that permeates tissues within the brain (5-45mm Hg, ∼1-6% O₂). This review will discuss the differentiation between pO₂ in the in vivo environment and the pO₂ commonly used during in vitro experiments, and how this could affect assay outcomes. Also highlighted are studies linking changes in pO₂ to changes in cellular function, particularly the role of pO₂ in mitochondrial function, reactive oxygen species production, and cellular growth and differentiation. The role of hypoxia inducible factor 1 and oxygen sensing is also presented. Finally, emerging literature exploring sex differences in tissue oxygenation is discussed.

Minocycline Has Anti-inflammatory Effects and Reduces Cytotoxicity in an Ex Vivo Spinal Cord Slice Culture Model of West Nile Virus Infection

West Nile virus (WNV) is a neurotropic flavivirus that can cause significant neurological disease. Mouse models of WNV infection demonstrate that a proinflammatory environment is induced within the central nervous system (CNS) after WNV infection, leading to entry of activated peripheral immune cells. We utilized ex vivo spinal cord slice cultures (SCSC) to demonstrate that anti-inflammatory mechanisms may also play a role in WNV-induced pathology and/or recovery. Microglia are a type of macrophage that function as resident CNS immune cells. Similar to mouse models, infection of SCSC with WNV induces the upregulation of proinflammatory genes and proteins that are associated with microglial activation, including the microglial activation marker Iba1 and CC motif chemokines CCL2, CCL3, and CCL5. This suggests that microglia assume a proinflammatory phenotype in response to WNV infection similar to the proinflammatory (M1) activation that can be displayed by other macrophages. We now show that the WNV-induced expression of these and other proinflammatory genes was significantly decreased in the presence of minocycline, which has antineuroinflammatory properties, including the ability to inhibit proinflammatory microglial responses. Minocycline also caused a significant increase in the expression of anti-inflammatory genes associated with alternative anti-inflammatory (M2) macrophage activation, including interleukin 4 (IL-4), IL-13, and FIZZ1. Minocycline-dependent alterations to M1/M2 gene expression were associated with a significant increase in survival of neurons, microglia, and astrocytes in WNV-infected slices and markedly decreased levels of inducible nitric oxide synthase (iNOS). These results demonstrate that an anti-inflammatory environment induced by minocycline reduces viral cytotoxicity during WNV infection in ex vivo CNS tissue.IMPORTANCE West Nile virus (WNV) causes substantial morbidity and mortality, with no specific therapeutic treatments available. Antiviral inflammatory responses are a crucial component of WNV pathology, and understanding how they are regulated is important for tailoring effective treatments. Proinflammatory responses during WNV infection have been extensively studied, but anti-inflammatory responses (and their potential protective and reparative capabilities) following WNV infection have not been investigated. Minocycline induced the expression of genes associated with the anti-inflammatory (M2) activation of CNS macrophages (microglia) in WNV-infected SCSC while inhibiting the expression of genes associated with proinflammatory (M1) macrophage activation and was protective for multiple CNS cell types, indicating its potential use as a therapeutic reagent. This ex vivo culture system can uniquely address the ability of CNS parenchymal cells (neurons, astrocytes, and microglia) to respond to minocycline and to modulate the inflammatory environment and cytotoxicity in response to WNV infection without peripheral immune cell involvement.

Genistein: mechanisms of action for a pleiotropic neuroprotective agent in stroke

Genistein is a plant estrogen promoted as an alternative to post-menopausal hormone therapy because of a good safety profile and its promotion as a natural product. Several preclinical studies of cerebral ischemia and other models of brain injury support a beneficial role for genistein in protecting the brain from injury whether administered chronically or acutely. Like estrogen, genistein is a pleiotropic molecule that engages several different mechanisms to enhance brain health, including reduction of oxidative stress, promotion of growth factor signaling, and immune suppression. These actions occur in endothelial, glial, and neuronal cells to provide a coordinated beneficial action to ischemic challenge. Though many of these protective actions are associated with estrogen-like actions of genistein, additional activities on other receptors and intracellular targets suggest that genistein is more than a mere estrogen-mimic. Importantly, genistein lacks some of the detrimental effects associated with post-menopausal estrogen treatment and may provide an alternative to hormone therapy in those patients at risk for ischemic events.

ALA16VAL-MnSOD gene polymorphism and stroke: Association with dyslipidemia and glucose levels

Stroke risk has been associated to the progression of carotid plaques due to high glucose levels and lipid accumulation, which are greatly associated to cerebral injury, brain oxidative stress, and apoptosis. The ALA16VAL-MnSOD gene single nucleotide polymorphism (SNP) has shown to modulate risk factors of several metabolic and vascular diseases, such as blood glucose (GLU) and lipid levels. However, the association of these factors in stroke patients has not been studied to date. Thus, we evaluated the influence of the Ala16Val-MnSOD SNP on lipid profile, GLU levels, oxidative and DNA damage of 44 patients in a late phase of stroke (>6months). The statistical analysis showed a greater proportion of VV carries in stroke patients. The results also indicated that stroke patients had higher cholesterol (CHO) and GLU levels when compared to healthy counterparts. Interestingly, V allele carriers with stroke showed higher levels of CHO and GLU when compared to AA stroke and healthy counterparts. Our findings suggest that oxidative stress markers are still increased even after 6 months of cerebral injury. Furthermore, we propose that the Ala16Val-MnSOD SNPs may contribute to hypercholesterolemia and higher GLU levels, increasing the risk to neurovascular events that may lead to stroke.

Dual anti-ischemic effects of rosmarinic acid n-butyl ester via alleviation of DAPK-p53-mediated neuronal damage and microglial inflammation

The discovery of efficacious anti-ischemic drugs remains a challenge. Recently we have found that rosmarinic acid n-butyl ester (RABE), a derivative of rosmarinic acid, significantly protects SH-SY5Y cells against oxygen glucose deprivation (OGD)-induced cell death. In the present study we simultaneously investigated the effects of RABE on the two key players in the pathophysiology of cerebral ischemia, ischemic neuronal damage and microglial inflammation. Pretreatment with RABE (1, 10 μmol/L) dose-dependently attenuated OGD- or H2O2-induced reduction of the viability of SH-SY5Y neuroblastoma cells. RABE pretreatment concurrently reduced the apoptotic cell rate, down-regulated the expression of the pro-apoptotic proteins Bax and p53, and up-regulated the expression of the anti-apoptotic protein phosphorylated death-associated protein kinase (DAPK). Furthermore, pretreatment with RABE (3 μmol/L) markedly inhibited lipopolysaccharide (LPS)-induced increases in the release of TNF-α, IL-1β, NO and PGE2, and the expression levels of iNOS, and COX-2 in cultured rat microglial cells. In conclusion, these results reveal for the first time the potential anti-ischemic effects of RABE on neuronal and glial cells and elucidate the molecular mechanisms involved in its dual beneficial profiles in vitro. RABE may be a promising drug lead/candidate for the treatment of ischemic stroke.

Homology analysis detects topological changes of Iba1 localization accompanied by microglial activation

The state of microglial activation provides important information about the central nervous system. However, a reliable index of microglial activation in histological samples has yet to be established. Here, we show that microglial activation induces topological changes of Iba1 localization that can be detected by analysis based on homology theory. Analysis of homology was applied to images of Iba1-stained tissue sections, and the 0-dimentional Betti number (b0: the number of solid components) and the 1-dimentional Betti number (b1: the number of windows surrounded by solid components) were obtained. We defined b1/b0 as the Homology Value (HV), and investigated its validity as an index of microglial activation using cerebral ischemia model mice. Microglial activation was accompanied by changes to Iba1 localization and morphology of microglial processes. In single microglial cells, the change of Iba1 localization increased b1. Conversely, thickening or retraction of microglial processes decreased b0. Consequently, microglial activation increased the HV. The HV of a tissue area increased with proximity to the ischemic core and showed a high degree of concordance with the number of microglia expressing activation makers. Furthermore, the HV of human metastatic brain tumor tissue also increased with proximity to the tumor. These results suggest that our index, based on homology theory, can be used to correctly evaluate microglial activation in various tissue images.

The Association between NOS3 Gene Polymorphisms and Hypoxic-Ischemic Encephalopathy Susceptibility and Symptoms in Chinese Han Population

Endothelial NOS (NOS3) has a potential role in the prevention of neuronal injury in hypoxic-ischemic encephalopathy (HIE). Thus, we aimed to explore the association between NOS3 gene polymorphisms and HIE susceptibility and symptoms in a Chinese Han population. Three single nucleotide polymorphisms (SNPs) in the NOS3 gene, rs1800783, rs1800779, and rs2070744, were detected in 226 children with HIE and 212 healthy children in a Chinese Han population. Apgar scores and magnetic resonance image scans were used to estimate the symptoms and brain damage. The association analyses were conducted by using SNPStats and SPSS 18.0 software. The genotype and allele distributions of rs1800779 and rs1799983 displayed no significant differences between the patients and the controls, while the rs2070744 allele distribution was significantly different (corrected P = 0.009). For clinical characteristics, the rs2070744 genotype distribution was significantly different in patients with different Apgar scores (≤5, TT/TC/CC = 6/7/5; 6~7, TT/TC/CC = 17/0/0; 8~9, TT/TC/CC = 6/2/0; 10, TT/TC/CC = 7/1/0; corrected P = 0.006) in the 1001 to 1449 g birth weight subgroup. The haplotype test did not show any associations with the risk and clinical characteristics of HIE. The results suggest that NOS3 gene SNP rs2070744 was significantly associated with HIE susceptibility and symptom expression in Chinese Han population.

Hemoglobin extravasation in the brain of rats exchange-transfused with hemoglobin-based oxygen carriers

Haemoglobin (Hb)-based oxygen carriers are under consideration as oxygen therapeutics. Their effect on apoptosis is critical, because the onset of pro-apoptotic pathways may lead to tissue damage. MP4OX, a polyethylene glycol-conjugated human Hb preserves the baseline level of neuron apoptosis with respect to sham. Here we develop a method for measuring Hb extravasation in brain. We exchange transfused rats by haemorrhaging 50% of their blood with simultaneous, isovolemic replacement with Hextend (negative control), MP4OX, or αα-cross-linked Hb. Animals were sacrificed 2 h after transfusion, brain tissue was harvested and processed for double-staining immunofluorescence, whereby Hb ? chain and NeuN (a neuron protein) were stained and quantitated. Whereas Hextend did not induce Hb extravasation, in both MP4OX and ??Hb brains Hb molecules were detected outside neurons. The level of extravasated Hb chains was > 3-fold higher in Hb compared to MP4OX. Western blot analysis revealed that the expression levels of protein related to redox imbalance (e.g., Nrf2, iNOS and ERK phosphorylation) were higher in ααHb than MP4OX. In conclusions, higher Hb extravasation in ααHb than MP4OX induces redox imbalance, which causes higher anti-oxidant response. Whereas Nrf2 response may be considered protective, iNOS response appears damaging.

Neuroprotective Effects of Bone Marrow Mesenchymal Stem Cells on Bilateral Common Carotid Arteries Occlusion Model of Cerebral Ischemia in Rat

Cell therapy is the most advanced treatment of the cerebral ischemia, nowadays. Herein, we discuss the neuroprotective effects of bone marrow mesenchymal stem cells (BMSCs) on rat hippocampal cells following intravenous injection of these cells in an ischemia-reperfusion model. Adult male Wistar rats were divided into 5 groups: control, sham (surgery without blockage of common carotid arteries), ischemia (common carotid arteries were blocked for 30 min prior to reperfusion), vehicle (7 days after ischemia PBS was injected via the tail vein), and treatment (injections of BMSC into the tail veins 7 days after ischemia). We performed neuromuscular and vestibulomotor function tests to assess behavioral function and, finally, brains were subjected to hematoxylin and eosin (H&E), anti-Brdu immunohistochemistry, and TUNEL staining. The ischemia group had severe apoptosis. The group treated with BMSCs had a lower mortality rate and also had significant improvement in functional recovery (P < 0.001). Ischemia-reperfusion for 30 min causes damage and extensive neuronal death in the hippocampus, especially in CA1 and CA3 regions, leading to several functional and neurological deficits. In conclusion, intravenous injection of BMSCs can significantly decrease the number of apoptotic neurons and significantly improve functional recovery, which may be a beneficial treatment method for ischemic injuries.

Direct Measurement of Free Radical Levels in the Brain After Cortical Ischemia Induced by Photothrombosis

Tissue ischemia is connected with the production of free radicals (FR). This study was designed to directly measure of the amount of FR in rat brains related to a photothrombotic ischemic event shortly after establishing the lesion. A model of left hemisphere photothrombosis ischemia was used in the experiment. Brains of animals from the experimental group were removed and placed in liquid N2 for 60 min after the green laser exposure, the control group brains, exposed to the photosensitive dye Rose Bengal (RB), were placed in liquid N2 for 80 min after RB application, naïve control brains were also briefly stored in liquid N2. Spectroscopy of electron paramagnetic (spin) resonance was used to directly measure FR (hydroxyl (OH●) and nitroxyl (NO●). Compared to naïve controls, both the ischemia and RB groups had significantly higher levels of OH●, however, there were no differences between them. Comparison of hemispheres, i.e. with and without ischemia, in the experimental group did not show any significant difference in OH●. NO● were elevated in the ischemia and RB groups compare to naïve controls. Higher levels of NO● were found in hemispheres with ischemia compared to unexposed hemispheres. Increases in OH● were probably associated with the action of RB itself in this model of ischemia. Increases in NO● were closely related to the pathogenesis of photothrombotic ischemia and could be related to the activity of nitric oxide synthases.