Regulatory role of monoamine neurotransmitters in astrocytic NT‐3 synthesis

The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise

Amino acid neurotransmitters, including glutamate, phenylalanine, tyrosine, alanine, and glycine, underlie the majority of the excitatory and inhibitory neurotransmission in the nervous system, and acute exercise has been shown to modulate their concentrations. We aimed to determine whether any correlation exists between the above-mentioned amino acid blood concentrations and the neuropsychological performance after an acute exercise intervention. Sixty basketball players were randomly assigned to one of two experimental conditions: exercise or inactive resting. All participants underwent a comprehensive neuropsychological assessment and blood samples were taken on a Guthrie card before and after the end of the experimental conditions. Amino acid blood concentrations were significantly elevated and cognitive performance significantly improved post-exercise on specific neuropsychological assessments. Significant intervention × group interaction effects were apparent for Trail Making Test part-B [F(1,58) = 20.46, p < .0001, η2 = .26] and Digit Span Backwards [F(1,58) = 15.47, p < .0001, η2 = .21] neuropsychological assessments. Additionally, regression analysis indicated that tyrosine accounted for 38.0% of the variance in the Trail Making Test part-A test. These results suggest that elevated blood concentrations of neurotransmission-related amino acids are associated with improved neuropsychological performance after a single bout of high-intensity exercise.

Experiences and Perspectives of GC-MS Application for the Search of Low Molecular Weight Discriminants of Schizophrenia

Schizophrenia is one of the most severe chronic mental disorders that is currently diagnosed and categorized through subjective clinical assessment of complex symptoms. At present, there is a recognized need for an objective, unbiased clinical test for schizophrenia diagnosis at an early stage and categorization of the disease. This can be achieved by assaying low-molecular-weight biomarkers of the disease. Here we give an overview of previously conducted research on the discovery of biomarkers of schizophrenia and focus on the studies implemented with the use of GC-MS and the least invasiveness of biological samples acquisition. The presented data demonstrate that GC-MS is a powerful instrumental platform for investigating dysregulated biochemical pathways implicated in schizophrenia pathogenesis. With this platform, different research groups suggested a number of low molecular weight biomarkers of schizophrenia. However, we recognize an inconsistency between the biomarkers or biomarkers patterns revealed by different groups even in the same matrix. Moreover, despite the importance of the problem, the number of relevant studies is limited. The intensification of the research, as well as the harmonization of the analytical procedures to overcome the observed inconsistencies, can be indicated as future directions in the schizophrenia bio-markers quest.

Vav3-Deficient Astrocytes Enhance the Dendritic Development of Hippocampal Neurons in an Indirect Co-culture System

Vav proteins belong to the class of guanine nucleotide exchange factors (GEFs) that catalyze the exchange of guanosine diphosphate (GDP) by guanosine triphosphate (GTP) on their target proteins. Here, especially the members of the small GTPase family, Ras homolog family member A (RhoA), Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 homolog (Cdc42) can be brought into an activated state by the catalytic activity of Vav-GEFs. In the central nervous system (CNS) of rodents Vav3 shows the strongest expression pattern in comparison to Vav2 and Vav1, which is restricted to the hematopoietic system. Several studies revealed an important role of Vav3 for the elongation and branching of neurites. However, little is known about the function of Vav3 for other cell types of the CNS, like astrocytes. Therefore, the following study analyzed the effects of a Vav3 knockout on several astrocytic parameters as well as the influence of Vav3-deficient astrocytes on the dendritic development of cultured neurons. For this purpose, an indirect co-culture system of native hippocampal neurons and Vav3-deficient cortical astrocytes was used. Interestingly, neurons cultured in an indirect contact with Vav3-deficient astrocytes showed a significant increase in the dendritic complexity and length after 12 and 17 days in vitro (DIV). Furthermore, Vav3-deficient astrocytes showed an enhanced regeneration in the scratch wound heal assay as well as an altered profile of released cytokines with a complete lack of CXCL11, reduced levels of IL-6 and an increased release of CCL5. Based on these observations, we suppose that Vav3 plays an important role for the development of dendrites by regulating the expression and the release of neurotrophic factors and cytokines in astrocytes.

Is neurotrophin-3 (NT-3): a potential therapeutic target for depression and anxiety?

Introduction: Neurotrophin-3 (NT-3) is thought to play a role in the neurobiological processes implicated in mood and anxiety disorders. NT-3 is a potential pharmacological target for mood disorders because of its effects on monoamine neurotransmitters, regulation of synaptic plasticity and neurogenesis, brain-derived neurotrophic factor (BDNF) signaling boosting, and modulation of the hypothalamic-pituitary-adrenal (HPA) axis. The mechanisms underlying NT-3 anxiolytic properties are less clear and require further exploration and definition. Areas covered: The evidence that supports NT-3 as a pharmacological target for anxiety and mood disorders is presented and this is followed by a reflection on the quandaries, stumbling blocks, and future perspectives for this novel target. Expert opinion: There is evidence for miRNAs being key post-transcriptional regulators of neurotrophin-3 receptor gene (NTRK3) in anxiety disorders; however, the anxiolytic properties of NT-3 need further examination and delineation. Moreover, NT-3 expression by non-neuronal cells and its role in brain circuits that participate in anxiety and mood disorders require further scrutiny. Further work is vital before progression into clinical trials can be realized.

Neuropathic Pain Causes a Decrease in the Dendritic Tree Complexity of Hippocampal CA3 Pyramidal Neurons

The International Pain Association defines neuropathic pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.” Recent studies show that chronic neuropathic pain causes both morphological and functional changes within brain structures. Due to the impact of supraspinal centers on pain signal processing, patients with chronic pain often suffer from depression, anxiety, memory impairment, and learning disabilities. Changes in hippocampal neuronal and glial plasticity can play a substantial role in the development of these symptoms. Given the special role of the CA3 hippocampal area in chronic stress reactions, we suggested that this region may undergo significant morphological changes as a result of persistent pain. Since the CA3 area is involved in the implementation of hippocampus-dependent memory, changes in the neuronal morphology can cause cognitive impairment observed in chronic neuropathic pain. This study aimed to elucidate the structural and plastic changes within the hippocampus associated with dendritic tree atrophy of CA3 pyramidal neurons in mice with chronic sciatic nerve constriction. Behavioral testing revealed impaired working and long-term memory in mice with a chronic constriction injury. Using the Golgi-Cox method, we revealed a decrease in the number of branches and dendritic length of CA3 pyramidal neurons. The dendritic spine number was decreased, predominantly due to a reduction in mushroom spines. An ­immunohistochemical study showed changes in astro- and microglial activity, which could affect the morphology of neurons both directly and indirectly via the regulation of neurotrophic factor synthesis. Using ELISA, we found a decrease in brain-derived neurotrophic factor production and an increase in neurotrophin-3 production. Morphological and biochemical changes in the CA3 area are accompanied by impaired working and long-term memory of animals. Thus, we can conclude that morphological and biochemical changes within the CA3 hippocampal area may underlie the cognitive impairment in neuropathic pain.

The Astrocytic cAMP Pathway in Health and Disease

Astrocytes are major glial cells that play critical roles in brain homeostasis. Abnormalities in astrocytic functions can lead to brain disorders. Astrocytes also respond to injury and disease through gliosis and immune activation, which can be both protective and detrimental. Thus, it is essential to elucidate the function of astrocytes in order to understand the physiology of the brain to develop therapeutic strategies against brain diseases. Cyclic adenosine monophosphate (cAMP) is a major second messenger that triggers various downstream cellular machinery in a wide variety of cells. The functions of astrocytes have also been suggested as being regulated by cAMP. Here, we summarize the possible roles of cAMP signaling in regulating the functions of astrocytes. Specifically, we introduce the ways in which cAMP pathways are involved in astrocyte functions, including (1) energy supply, (2) maintenance of the extracellular environment, (3) immune response, and (4) a potential role as a provider of trophic factors, and we discuss how these cAMP-regulated processes can affect brain functions in health and disease.

Treatment with the noradrenaline re-uptake inhibitor atomoxetine alone and in combination with the α2-adrenoceptor antagonist idazoxan attenuates loss of dopamine and associated motor deficits in the LPS inflammatory rat model of Parkinson's disease

The impact of treatment with the noradrenaline (NA) re-uptake inhibitor atomoxetine and the α₂-adrenoceptor (AR) antagonist idazoxan in an animal model of Parkinson's disease (PD) was assessed. Concurrent systemic treatment with atomoxetine and idazoxan, a combination which serves to enhance the extra-synaptic availability of NA, exerts anti-inflammatory and neuroprotective effects following delivery of an inflammatory stimulus, the bacterial endotoxin, lipopolysaccharide (LPS) into the substantia nigra. Lesion-induced deficits in motor function (akinesia, forelimb-use asymmetry) and striatal dopamine (DA) loss were rescued to varying degrees depending on the treatment. Treatment with atomoxetine following LPS-induced lesion to the substantia nigra, yielded a robust anti-inflammatory effect, suppressing microglial activation and expression of the pro-inflammatory cytokine TNF-α whilst increasing the expression of neurotrophic factors. Furthermore atomoxetine treatment prevented loss of tyrosine hydroxylase (TH) positive nigral dopaminergic neurons and resulted in functional improvements in motor behaviours. Atomoxetine alone was sufficient to achieve most of the observed effects. In combination with idazoxan, an additional improvement in the impairment of contralateral limb use 7 days post lesion and a reduction in amphetamine-mediated rotational asymmetry 14 days post-lesion was observed, compared to atomoxetine or idazoxan treatments alone. The results indicate that increases in central NA tone has the propensity to regulate the neuroinflammatory phenotype in vivo and may act as an endogenous neuroprotective mechanism where inflammation contributes to the progression of DA loss. In accordance with this, the clinical use of agents such as NA re-uptake inhibitors and α₂-AR antagonists may prove useful in enhancing the endogenous neuroimmunomodulatory potential of NA in conditions associated with brain inflammation.

Noradrenergic antagonists mitigate amphetamine-induced recovery

Brain injury, including that due to stroke, leaves individuals with cognitive deficits that can disrupt daily aspect of living. As of now there are few treatments that shown limited amounts of success in improving functional outcome. The use of stimulants such as amphetamine have shown some success in improving outcome following brain injury. While the pharmacological mechanisms for amphetamine are known; the specific processes responsible for improving behavioral outcome following injury remain unknown. Understanding these mechanisms can help to refine the use of amphetamine as a potential treatment or lead to the use of other methods that share the same pharmacological properties. One proposed mechanism is amphetamine's impact upon noradrenaline (NA). In the current, study noradrenergic antagonists were administered prior to amphetamine to pharmacologically block α- and β-adrenergic receptors. The results demonstrated that the blockade of these receptors disrupted amphetamines ability to induce recovery from hemispatial neglect using an established aspiration lesion model. This suggests that amphetamine's ability to ameliorate neglect deficits may be due in part to noradrenaline. These results further support the role of noradrenaline in functional recovery. Finally, the development of polytherapies and combined therapeutics, while promising, may need to consider the possibility that drug interactions can negate the effectiveness of treatment.

Matrine promotes NT3 expression in CNS cells in experimental autoimmune encephalomyelitis

Neurotrophin 3 (NT3) is a potent neurotrophic factor for promoting remyelination and recovery of neuronal function; upregulation of its expression in the central nervous system (CNS) is thus of major therapeutic importance for neurological deficits. Matrine (MAT), a quinolizidine alkaloid derived from the herb Radix Sophorae Flavescent, has been recently reported to effectively ameliorate clinical signs in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), by secreting antiinflammatory cytokines. In the present study, our goal was to investigate whether MAT could affect NT3 expression of glial cells in the CNS, the major cell populations in the CNS foci of MS/EAE. We found that MAT markedly upregulated NT3 expression in the CNS not only by microglia/macrophages and astrocytes, but also by oligodendrocyte precursor cells, indicative of both paracrine and autocrine effects on myelinating cells. While MAT treatment reduced the numbers of iNOS⁺ M1, but increased Arg1⁺ M2 microglia/macrophage phenotypes, NT3 expression was upregulated in both phenotypes. These results indicate that MAT therapy for EAE acts, at least in part, by stimulating local production of NT3 by glial cells in the CNS, which protects neural cells from CNS inflammation-induced tissue damage.

Susceptibility of mice strains to oxidative stress and neurotransmitter activity induced by Plasmodium berghei

This study investigated the susceptibility of female C57Bl/6 and Swiss Albino mice to oxidative stress and neurotransmitters activity induced by Plasmodium berghei. On day 9 p.i. with P. berghei infected erythrocytes, the mice reduced in weight. This weight loss was markedly higher in SW mice and reached about −14%. Also, the infection was able to cause oxidative damage to the brain tissue. Catalase activity as well as glutathione, malondialdehyde and nitric oxide levels were different in the two mice strains. Moreover, the brain content of neurotransmitters, epinephrine, norepinephrine, dopamine and serotonin in mice brain was higher in SW mice than B6 mice. We concluded that, the strain of mice is one factor that could alter the response of mice to P. berghei infection.

Hyperbaric oxygen preserves neurotrophic activity of carbon monoxide-exposed astrocytes

In astrocytes, carbon monoxide (CO) poisoning causes oxidative stress and mitochondrial dysfunction accompanied by caspase and calpain activation. Impairment in astrocyte function can be time-dependently reduced by hyperbaric (3bar) oxygen (HBO). Due to the central role of astrocytes in maintaining neuronal function by offering neurotrophic support we investigated the hypothesis that HBO therapy may exert beneficial effect on acute CO poisoning-induced impairment in intrinsic neurotrophic activity. Exposure to 3000ppm CO in air followed by 24-72h of normoxia caused a progressive decline of gene expression, synthesis and secretion of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) to different extent. 1h treatment with 100% oxygen disclosed a pressure- and time-dependent efficacy in preserving astrocytic neurotrophic support. The beneficial effect was most evident when the astrocytes were exposed to HBO 1-5h after exposure to CO. The results further support an active role of hyperbaric, not normobaric, oxygenation in reducing dysfunction of astrocytes after acute CO poisoning. By preserving endogenous neurotrophic activity HBO therapy might promote neuronal protection and thus prevent the occurrence of late neuropsychological sequelae.

Noradrenergic regulation of glial activation: molecular mechanisms and therapeutic implications

It has been known for many years that the endogenous neurotransmitter noradrenaline (NA) exerts anti-inflammatory and neuroprotective effects both in vitro and in vivo. In many cases the site of action of NA are beta-adrenergic receptors (βARs), causing an increase in intracellular levels of cAMP which initiates a broad cascade of events including suppression of inflammatory transcription factor activities, alterations in nuclear localization of proteins, and induction of patterns of gene expression mediated through activity of the CREB transcription factor. These changes lead not only to reduced inflammatory events, but also contribute to neuroprotective actions of NA by increasing expression of neurotrophic substances including BDNF, GDNF, and NGF. These properties have prompted studies to determine if treatments with drugs to raise CNS NA levels could provide benefit in various neurological conditions and diseases having an inflammatory component. Moreover, increasing evidence shows that disruptions in endogenous NA levels occurs in several diseases and conditions including Alzheimer's disease (AD), Parkinson's disease (PD), Down's syndrome, posttraumatic stress disorder (PTSD), and multiple sclerosis (MS), suggesting that damage to NA producing neurons is a common factor that contributes to the initiation or progression of neuropathology. Methods to increase NA levels, or to reduce damage to noradrenergic neurons, therefore represent potential preventative as well as therapeutic approaches to disease.

Graphene and its nanocomposite material based electrochemical sensor platform for dopamine

In this review, the recent progress in the electrochemical sensing of dopamine with various graphene and their nanocomposite materials modified electrodes are presented.

''70th Birthday Professor Riederer'' induction of glial cell line-derived and brain-derived neurotrophic factors by rasagiline and (-)deprenyl: a way to a disease-modifying therapy?

Neuroprotection has been proposed in neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases, to delay or halt disease progression or reverse neuronal deterioration. The inhibitors of type B monoamine oxidase (MAO), rasagiline and (-)deprenyl, prevent neuronal loss in cellular and animal models of neurodegenerative disorders by intervening in the death signal pathway in mitochondria. In addition, rasagiline and (-)deprenyl increase the expression of anti-apoptotic Bcl-2 protein family and neurotrophic factors. Neurotrophic factors, especially glial cell line-derived neurotrophic factor (GDNF) and brain-derived derived neurotrophic factor (BDNF), are required not only for growth and maintenance of developing neurons, but also for function and plasticity of distinct population of adult neurons. GDNF and BDNF have been reported to reduce Parkinson and Alzheimer's diseases, respectively. GDNF protects the nigra-striatal dopamine neurons in animal models of Parkinson's disease, and its administration has been tried as a disease-modifying therapy for parkinsonian patients. However, the results of clinical trials have not been fully conclusive and more practical ways to enhance GDNF levels in the targeted neurons are essentially required for future clinical application. Rasagiline and (-)deprenyl induced preferentially GDNF and BDNF in cellular and non-human primate experiments, and (-)deprenyl increased BDNF level in the cerebrospinal fluid of parkinsonian patients. In this paper, we review the induction of GDNF and BDNF by these MAO inhibitors as a strategy of neuroprotective therapy. The induction of prosurvival genes is discussed in relation to a possible disease-modifying therapy with MAO inhibitors in neurodegenerative disorders.

Vascular endothelial growth factor is upregulated by L-dopa in the parkinsonian brain: implications for the development of dyskinesia

Angiogenesis and increased permeability of the blood-brain barrier have been reported to occur in animal models of Parkinson's disease and l-dopa-induced dyskinesia, but the significance of these phenomena has remained unclear. Using a validated rat model of l-dopa-induced dyskinesia, this study demonstrates that chronic treatment with l-dopa dose dependently induces the expression of vascular endothelial growth factor in the basal ganglia nuclei. Vascular endothelial growth factor was abundantly expressed in astrocytes and astrocytic processes in the proximity of blood vessels. When co-administered with l-dopa, a small molecule inhibitor of vascular endothelial growth factor signalling significantly attenuated the development of dyskinesia and completely blocked the angiogenic response and associated increase in blood-brain barrier permeability induced by the treatment. The occurrence of angiogenesis and vascular endothelial growth factor upregulation was verified in post-mortem basal ganglia tissue from patients with Parkinson's disease with a history of dyskinesia, who exhibited increased microvascular density, microvascular nestin expression and an upregulation of vascular endothelial growth factor messenger ribonucleic acid. These congruent findings in the rat model and human patients indicate that vascular endothelial growth factor is implicated in the pathophysiology of l-dopa-induced dyskinesia and emphasize an involvement of the microvascular compartment in the adverse effects of l-dopa pharmacotherapy in Parkinson's disease.

Curcumin prevents corticosterone-induced neurotoxicity and abnormalities of neuroplasticity via 5-HT receptor pathway

Curcumin, a major active component of Curcuma longa, possesses antioxidant and neuroprotective activities. The present study explores the mechanisms underlying the neuroprotective effect of curcumin against corticosterone and its relation to 5-hydroxy tryptamine (5-HT) receptors. Exposure of cortical neurons to corticosterone results in decreased mRNA levels for three 5-HT receptor subtypes, 5-HT(1A), 5-HT(2A) and 5-HT(4), but 5-HT(1B,) 5-HT(2B), 5-HT(2C), 5-HT(6) and 5-HT(7) receptors remain unchanged. Pre-treatment with curcumin reversed this effect on mRNA for the 5-HT(1A) and 5-HT(4) receptors, but not for the 5-HT(2A) receptor. Moreover, curcumin exerted a neuroprotective effect against corticosterone-induced neuronal death. This observed effect of curcumin was partially blocked by either 5-HT(1A) receptor antagonist p-MPPI or 5-HT(4) receptor antagonist RS 39604 alone; whereas, the simultaneous application of both antagonists completely reversed the effect. Curcumin was also found to regulate corticosterone-induced morphological changes such as increases in soma size, dendritic branching and dendritic spine density, as well as elevate synaptophysin expression in cortical neurons. p-MPPI and RS 39604 reversed the effect of curcumin-induced change in neuronal morphology and synaptophysin expression of corticosterone-treated neurons. In addition, an increase in cyclic adenosine monophosphate (cAMP) level was observed after curcumin treatment, which was further prevented by RS 39604, but not by p-MPPI. However, curcumin-induced elevation in protein kinase A activity and phosphorylation of cAMP response element-binding protein levels were inhibited by both p-MPPI and RS 39604. These findings suggest that the neuroprotection and modulation of neuroplasticity exhibited by curcumin might be mediated, at least in part, via the 5-HT receptor-cAMP-PKA-CREB signal pathway.

Anticonvulsant Activity of Extracts of Plectranthus barbatus Leaves in Mice

Plectranthus barbatus is a medicinal plant used to treat a wide range of disorders including seizure. However, the anticonvulsant activity of this plant has not been studied in depth. We therefore sought to evaluate the anticonvulsant activity of a hydroalcoholic extract of P. barbatus leaves on seizures induced by strychnine sulphate (2.0 mg/kg) and pilocarpine (600 mg/kg) in mice. The extract was administered orally at 1, 10, 30, and 100 mg/kg. We report that the P. barbatus extract had marked anticonvulsant activity against strychnine-induced convulsions, but was quite ineffective against pilocarpine-induced convulsions. Further experiments will be required to identify the active molecules(s) and their mechanism(s) of action.

Comparison of canine umbilical cord blood-derived mesenchymal stem cell transplantation times: involvement of astrogliosis, inflammation, intracellular actin cytoskeleton pathways, and neurotrophin-3

Canine mesenchymal stem cells (cMSCs) derived from umbilical cord blood represent a potentially useful source of stem cells for therapy. The aim of this study was to compare the effects of different transplantation times of cMSCs after spinal cord injury (SCI). A total of 21 dogs were subjected to SCI by balloon-induced compression of the first lumbar vertebrae for 12 h. Of the 21 dogs, 12 were divided into four groups of three according to the time of stem cell (1 × 10(6)) transplantation at the injury site: control no treatment, 12 h, 1 week, and 2 weeks. The remaining 9 animals were negative harvest (HA) time controls for each treatment group (n = 3). Olby and Tarlov scores were used to evaluate functional recovery of the hindlimbs. Markers for neuronal regeneration (Tuj-1, nestin, MAP2, and NF-M), astrogliosis (GALC, GFAP, and pSTAT3), signal molecules for actin cytoskeleton (RhoA, Cdc42, and Rac1), inflammation (COX-2), and neurotrophins (NT-3) were evaluated by Western blot analysis. Scores of the 1-week transplantation group showed significant improvement compared to controls. Hematoxylin and eosin (H&E) staining revealed less fibrosis at the injury site in the 1-week transplantation group compared to other groups and immunohistochemistry showed increased expression of neuronal markers. Furthermore, in both 1-week and 2-week transplantation groups, Tuj-1, nestin, MAP2, NF-M, NT-3, and GFAP increased, but pSTAT3, GALC, and COX2 decreased. RhoA decreased and Rac1 and Cdc42 increased in the 1-week transplantation group. In conclusion, transplantation of cMSCs 1 week after SCI was more effective in improving clinical signs and neuronal regeneration and reducing fibrosis formation compared to the other transplantation times evaluated. Subsequently, these data may contribute to the optimization of timing for MSC transplantation used as a therapeutic modality.

Type A monoamine oxidase regulates life and death of neurons in neurodegeneration and neuroprotection

In Parkinson's disease, type B monoamine oxidase (MAO-B) is proposed to play an important role in the pathogenesis through production of reactive oxygen species and neurotoxins from protoxicants, such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. In addition, inhibitors of MAO-B protect neurons in the cellular and animal models of Parkinson's and Alzheimer's diseases. However, the role of type A MAO (MAO-A) in neuronal death and neuroprotection by MAO-B inhibitors has been scarcely elucidated. This chapter presents our recent results on the involvement of MAO-A in the activation of mitochondrial death signal pathway and in the induction of prosurvival genes to prevent cell death with MAO-B inhibitors. The roles of MAO-A in the regulation of neuronal survival and death are discussed in concern to find a novel strategy to protect neurons in age-associated neurodegenerative disorders and depression.