CNS & Neurological Disorders - Drug Targets (Formerly Current Drug Targets - CNS & Neurological Disorders) - Volume 13, Issue 4, 2014

Traumatic brain injury causes progressive neurodegeneration associated with chronic microglial activation. Recent studies show that neurodegeneration and neuroinflammation after traumatic brain injury can be inhibited as late as one month in animals by the activation of the metabotropic glutamate receptor 5 in microglia using (RS)-2-chloro-5- hydroxy-phenylglycine. However, the therapeutic potential of this agonist is limited due to its relatively weak potency and brain permeability. To address such concerns, we evaluated the anti-inflammatory activities of several positive allosteric modulators using various in vitro assays, and found that 3,3’-difluorobenzaldazine, 3-cyano-N-(1,3-diphenyl-1H-pyrazol- 5-yl)benzamide and 4-nitro-N-(1-(2-fluorophenyl)-3-phenyl-1H-pyrazol-5-yl)benzamide showed significantly improved potency which makes them potential lead compounds for further development of positive allosteric modulators for the treatment of traumatic brain injury.

For more than two decades the intensive research effort on the role of NMDA receptors (NMDAR) in traumatic brain injury (TBI) and cerebral ischemia (stroke) was led by the observations that extracellular concentrations of glutamate and aspartate are elevated after the insult and play a major role in brain pathologies. Indeed, NMDAR antagonists were shown to improve post-injury recovery in animal models and subsequently, large scale placebocontrolled clinical trials in TBI and stroke were performed with NMDAR antagonists. However, all these trials have demonstrated either no benefit or even deleterious effects. The discrepancy between the animal and human studies prompted us to investigate the temporal changes of the NMDAR after brain insult in TBI and stroke mouse models. We found that the early hyperactivation of the NMDAR is followed by loss of functional NMDAR which persists for weeks. Such dynamic changes could well explain the discrepancies between the preclinical and clinical experience as well as suggest alternative modes of treatment, namely, activation, rather than blockade of the NMDAR in the sub-acute period after TBI and stroke. Stimulation of the glycine modulatory site of the glycine/NMDAR by the partial agonist Dcycloserine (DCS) when given at least 24 hrs after TBI or stroke was shown to improve recovery of neurobehavioral and cognitive functions. It was also shown to restore impaired hippocampal Long-Term potentiation (LTP) and induce expression of Brain Derived-Neurotrophic Factor (BDNF) in a TBI model and to improve somatosensory and cognitive function in a stroke model. Experiments to optimize the DCS treatment paradigm showed that similar benefits were demonstrated in TBI mice whether the drug was given as a single injection at 24 or 72 hrs post injury, or as double (24 and 48 hrs) or triple (24, 48 and 72 hrs) doses. Interestingly, beneficial effects of DCS were reported in a range of animal models of human diseases as well as in several clinical indications thought to involve disruptions in NMDAR function, such as drug addiction, post-traumatic stress disorder, Parkinson's disease, aging and psychiatric disorders. As DCS has a good safety profile, and is already in use in humans in several different indications, and based on studies with DCS in the mouse TBI model, a multi-center prospective randomized controlled clinical trial, aiming to assess the effect of a single dose of DCS on cognitive outcome in patients with moderate TBI has recently begun.

The role of the 18-kDa Translocator Protein (TSPO) in cell death induced by NH4Cl (1-50 mM) for 24-72 hours to human glioblastoma U118MG cells was investigated. Cell death was already observed after 48 hours of treatment with NH4Cl at 5 mM. Dose and time-responses curves indicated that 15 mM of NH4Cl applied for 72 hours was the optimal condition for our viability assays. For example, 72 hours of 15 mM of NH4Cl caused a 50.3% increase in propidium iodide uptake, and lactate dehydrogenase release was 41.2% of the positive control, indicating significant increases in cell death. Furthermore, compared to vehicle control, these experimental conditions resulted in a significant decrease of 44.9% of the mitochondrial activity, a 62.3% increase in incidence of collapse of mitochondrial membrane potential, and an increase of 49.0% of cardiolipin peroxidation. In addition, a significant 4.3 fold increase in the maximal binding capacity (Bmax) of TSPO was found in NH4Cl-exposed cells. Surprisingly, western blot analysis and real-time PCR did not demonstrate changes in TSPO expression. We also found that neither NH4Cl nor glutamine (a metabolic product of enhanced NH4Cl levels) inhibited binding of the TSPO ligand [3H]PK 11195. Interestingly, we observed a bimodal effect of the TSPO ligands PK 11195, Ro5-4864, and FGIN-1-27 on the toxicity of NH4Cl; such that 1-100 nM concentrations of TSPO ligands were protective, while concentrations above 1 μM enhanced NH4Cl-induced cell death processes. In conclusion, TSPO takes part in a bimodal way in the lethal effects induced by NH4Cl in glial type cells.

Alzheimer’s disease (AD) is the most common form of dementia occurring in the elderly. Several hypotheses have been proposed to explain the pathophysiology of AD, including amyloidogenesis, disruption of calcium homeostasis, energetic failure, induction of oxidative stress, and hyperphosphorylation of tau protein. This review examines associations between cellular and subcellular injuries, neurodegeneration, and cell death in experimental models, clinical symptoms, and autopsy reports of AD to identify the subcellular events leading to disease onset and progression. The order in which these events occur is discussed. The first injuries reported in AD are subcellular and occur at the Golgi apparatus before any β-amyloid proteins deposit in the Golgi and endosomes. This is followed by lysosomal alterations and the inability of cells to clear β-amyloid. The next stage reveals functional changes and modifications in hippocampal synaptic transmission before structural changes are observed at the cellular level. Subsequently, an extensive intracellular inflammatory process develops in neurons and astrocytes. This inflammatory reaction begins in the nucleus, endoplasmic reticulum, endosomes and mitochondria, and is thought to lead to neurodegeneration and cell death. Finally, the neuroinflammatory response of chronically activated microglia escalates the neurodegeneration and cell death. Identifying the detailed sequence of subcellular events induced by the primum movens defect in AD may lead to the identification of novel drug targets for the treatment of the disease.

Traumatic brain injury (TBI) is still the worldwide, leading cause of mortality and morbidity in young adults. The prognosis of TBI patients is strongly affected by secondary brain damage including mitochondrial dysfunctions. In many basic and clinical studies, mitochondrial dysfunctions, including the opening of mitochondrial permeability transition (mPT) pore, and treatments including cyclosporine A (CsA) have been studied. These evidences suggest an important role for mitochondria as therapeutic targets for neuroprotection after TBI. This review summarizes the data about normal and pathological mitochondrial function after TBI, TBI pathobiology relating to mitochondrial dysfunction and therapeutic strategies including drug treatment. This review also mentioned about glucose, lactate, and pyruvate metabolisms in TBI, including the "astrocyte-neuron lactate shuttle (ANLS)" hypothesis. Mitochondrial pathophysiology in TBI is still unclear. Thus, the pharmacological treatment in TBI patient is still challenging. This review could help further understanding of this topic. Hopefully, this could help further development and innovation for drug therapies in TBI.

Traumatic brain injuries represent the leading cause of death and morbidity in young adults in western countries, and are responsible for a major social and economical burden. For decades, the mainstay of neurotrauma management has been represented by control of post-traumatic edema. With the emergence of a better understanding of the underlying cellular mechanisms responsible for the generation of secondary brain damage, the hope for the "magic bullet" has prompted the development of novel drugs that have repeatedly failed to significantly improve outcome of head-injured patients. During the past decade, mitochondrial functional and structural impairment has emerged as a pivotal event in the pathway of cell to secondary death. Extensive research has identified a vast range of deleterious signals that are generated and integrated at the mitochondrial level resulting in impairment of major mitochondrial functions such as calcium homeostasis, free radicals generation and detoxification, energy production and neurosteroidogenesis. Mitochondria have therefore emerged as a potential therapeutic target. Within the spectrum of major mitochondrial structural components, the 18 kDa translocator protein (TSPO) has shown important and relevant functions such as steroid synthesis and modulation of the mitochondrial permeability transition that may substantially affect the fate of injured cells. This review summarizes the potential therapeutic implications of TSPO modulation in traumatic brain injury in the view of the current knowledge on this intriguing mitochondrial complex.

Accumulation of α-synuclein is key to the pathogenesis of Parkinson's disease (PD), though the exact mechanisms involved in its toxicity are still subject to debate. Increased α-synuclein expression or reduced degradation may play a role in the proteotoxicity observed in PD. Here we review the mechanisms of α-synuclein ubiquitination by different E3 ubiquitin-ligases, and its degradation via the proteasome, autophagy and lysosomes. Activators of α- synuclein ubiquitination and degradation pathways represent a plausible strategy to decrease α-synuclein burden in the disease. Nevertheless, since proteasomes and autophagy might be impaired in the disease, and because proteolytic impairment causes the accumulation of monoubiquitinated α-synuclein and the formation of toxic inclusions, compounds that promote α-synuclein monoubiquitination should be used in concert with compounds that boost these proteolytic pathways. This combined approach may therefore ease the accumulation of α-synuclein in PD and may represent a promising new avenue for the development of novel treatments for the disease.

The primary aimed of this study was to investigate the potential protective effects of methanolic extract of citrus peel (MECP) on acute cyanide (KCN) poisoning-induced seizures and oxidative stress in rats. The intraperitoneal LD50 value of KCN (6.3 mg/Kg bwt), based on 24 hrs mortality, was significantly increased by 9, 52 or 113% by oral administration of MECP (500 mg/Kg bwt) pre-administered for 1, 2 and 3 days, respectively, in rats in a time-dependent manner. Intraperitoneal injection of the sublethal dose of KCN (3 mg/Kg bwt) into rats increased, 24 hrs later, lipid peroxidation (LPO), nitric oxide (NO), glutamate levels and acetylcholinesterase (AChE) activity in hippocampus, striatum and cerebral cortex. KCN also decreased brain glutathione (GSH) level and superoxide dismutase (SOD) and catalase (CAT) activities in these animals. Pre-treatment of rats with MECP inhibited KCN-induced increases in LPO, NO, and glutamate levels and AChE activity as well as decreases in brain GSH level and SOD and CAT activities. In addition, KCN significantly decreased norepinephrine, dopamine and serotonin levels in different brain regions which were resolved by MECP. From the present results, it can be concluded that the neuroprotective effects of MECP against KCN-induced seizures and oxidative stress may be due to the inhibition of oxidative stress overproduction and maintenance of antioxidant defense mechanisms.

Glatiramer acetate (GA) is one of the most widely used disease-modifying drugs for the treatment of relapsingremitting multiple sclerosis; is assumed to have inductor effects on neurotrophic factor expression. One of these neurotrophic factor systems is the brain-derived neurotrophic factor (BDNF)/receptor tyrosine kinase B (TrkB) pathway. Peripheral blood is thought to contain soluble BDNF, and some blood cells express TrkB. We attempted to determine whether GA treatment leads to changes in plasma BDNF levels and TrkB activation. Such a phenomenon are relapsingremitting multiple sclerosis patients is significantly reduced; GA treatment is not influencing peripheral BDNF levels, after one year of sustained therapy, not from the point of view of total free BDNF nor the phosphorylated TrkB.

The systematical associations between stroke and coronary heart disease (CHD) remain controversial and uncertain. Network construction and modularized analysis have become powerful tools in the field of systems biology research, which can help us to mine the multidimensional characters of correlation between the two diseases in depth. A total of 218 stroke-related and 204 CHD-related genes were identified via the Online Mendelian Inheritance in Man database; text searching engine (Agilent Literature Search 2.71) and MCODE software were employed for network construction and module division, respectively. Finally, 67, 21, 7, and 196 overlapping genes, hubs, modules and modular functions were identified between stroke and CHD, respectively. The overlapping genes, which should be responsible for the similar phenotypes, highlighted the molecular signatures of the two linked diseases. Additionally, the analysis of modules and their functional annotations showed potential dependent and independent risk factors, such as atherosclerosis, cholesterol homeostasis, plasma lipoprotein particle remodeling and response to oxidative stress, etc. Moreover, the potential mechanisms by which the same biological process activating pathological cascade or risk component-based shared pathway between stroke and CHD were uncovered, which may provide useful insights for further drug development and cost saving.

Multidrug resistance mediated by over-expression of P-glycoprotein (P-gp) in brain is an important mechanism accounting for the drug-therapy failure in epilepsy. Over-expression of P-gp in epilepsy rat brain may be regulated by inflammation and nuclear factor-kappa B (NF-κB) activation. Inhibitory κ B kinase subunit β (IKKβ) is an up-stream molecular controlling NF-κB activation. With the small interfering RNA (siRNA) technique and kainic acid (KA)-induced rat epileptic seizure model, the present study was aimed to further evaluate the role of NF-κB inhibition, via blocking IKKβ gene transcription, in the epileptic brain P-gp over-expression, seizure susceptibility, and post-seizure brain damage. siRNA targeting IKKβ was administered to rats via intracerebroventricular injection before seizure induction by KA microinjection; scrambled siRNA was used as control. Brain mRNA and protein levels of IKKβ and P-gp were detected by RT-PCR and immunohistochemistry. NF-κB activity was measured by electrophoretic mobility shift assay. Latency to grade III or V seizure onset was recorded, brain damage was evaluated by neuronal cell counting and epileptiform activity was monitored by electroencephalography. IKKβ siRNA pre-treatment inhibited NF-κB activation and abolished P-gp over-expression in KA-induced epileptic rat brain, accompanied by decreased seizure susceptibility. These findings suggested that epileptogenic-induced P-gp over-expression could be regulated by IKKβ through the NF-κB pathway.

Depressive disorders have, for a sizeable extent, proven resilient to pharmacotherapy. Established drugs such as selective serotonin reuptake inhibitors (SSRIs) or serotonin-noradrenaline reuptake inhibitors (SNRIs) often provide inadequate symptom relief and sometimes fail altogether. Recently, interest in antidepressant effects of scopolamine, a non-selective muscarinic acetylcholine receptor (mAChR) antagonist, has arisen. Initial evidence suggests that scopolamine provides relatively rapid and long-lasting symptom alleviation for unipolar and bipolar depressed patients. At the same time, side effects of medical dosages appear mild and transient in nature. The aim of the present review is to tentatively discuss the antidepressant potential of scopolamine and to outline putative neurobiological pathways. Clearly, mAChR antagonism provides an intriguing novel therapeutical approach for treating depressive disorders.

The purpose of the study was to evaluate the potential effects of Citrus reticulate (mandarin) peel methanolic extract (MPME) on memory dysfunction in rats. Memory impairment was produced by scopolamine (1.4 mg/kg, intraperitoneally injected). Brain acetylcholinesterase enzyme (AChE) activity was measured to assess the central cholinergic activity. This study also investigated the effect of scopolamine on norepinephrine, dopamine and serotonin content in rat hippocampus, striatum and cerebral cortex. In addition, the levels of brain lipid peroxidation (LPO), nitric oxide (NO) and glutathione (GSH) were estimated to assess the degree of oxidative stress. Scopolamine administration induced a significant impairment of central cholinergic activity in rats, as indicated by a marked increase in AChE activity. The impairment of the cholinergic system was associated with a significant alternation in brain monoamines. Scopolamine administration also caused oxidant damage (elevation in LPO and NO and reduction in GSH levels). Pretreatment of MPME (250 mg/kg, orally administered) significantly reduced scopolamine-induced alternation in brain monoamines with an attenuation of scopolamine-induced rise in brain AChE activity and brain oxidative stress. It is concluded that administration of mandarin peel extract, demonstrating antioxidant activity, may be of value for dementia exhibiting elevated brain oxidative status.

Alzheimer’s disease (AD) represents a neurological disorder, which is caused by enzymatic degradation of an amyloid precursor protein into short peptide fragments that undergo association to form insoluble plaques. Preliminary studies suggest that cyanobacterial extracts, especially the light-harvesting protein phycocyanin, may provide a means to control the progression of the disease. However, the molecular mechanism of disease control remains elusive. In the present study, intact hexameric phycocyanin was isolated and crystallized from the cyanobacterium Leptolyngbya sp. N62DM, and the structure was solved to a resolution of 2.6 A. Molecular docking studies show that the phycocyanin αβ- dimer interacts with the enzyme β-secretase, which catalyzes the proteolysis of the amyloid precursor protein to form plaques. The molecular docking studies suggest that the interaction between phycocyanin and β-secretase is energetically more favorable than previously reported inhibitor-β-secretase interactions. Transgenic Caenorhabditis elegans worms, with a genotype to serve as an AD-model, were significantly protected by phycocyanin. Therefore, the present study provides a novel structure-based molecular mechanism of phycocyanin-mediated therapy against AD.

Mental retardation (MR)/ intellectual disability (ID) is a neuro-developmental disorder characterized by a low intellectual quotient (IQ) and deficits in adaptive behavior related to everyday life tasks such as delayed language acquisition, social skills or self-help skills with onset before age 18. To date, a few genes (PRSS12, CRBN, CC2D1A, GRIK2, TUSC3, TRAPPC9, TECR, ST3GAL3, MED23, MAN1B1, NSUN1) for autosomal-recessive forms of non syndromic MR (NS-ARMR) have been identified and established in various families with ID. The recently reported candidate gene TRAPPC9 was selected for computational analysis to explore its potentially important role in pathology as it is the only gene for ID reported in more than five different familial cases worldwide. YASARA (12.4.1) was utilized to generate three dimensional structures of the candidate gene TRAPPC9. Hybrid structure prediction was employed. Crystal Structure of a Conserved Metalloprotein From Bacillus Cereus (3D19-C) was selected as best suitable template using position-specific iteration-BLAST. Template (3D19-C) parameters were based on E-value, Z-score and resolution and quality score of 0.32, -1.152, 2.30°A and 0.684 respectively. Model reliability showed 93.1% residues placed in the most favored region with 96.684 quality factor, and overall 0.20 G-factor (dihedrals 0.06 and covalent 0.39 respectively). Protein-Protein docking analysis demonstrated that TRAPPC9 showed strong interactions of the amino acid residues S253, S251, Y256, G243, D131 with R105, Q425, W226, N225, S233, its functional partner 1KBKB. Protein-protein interacting residues could facilitate the exploration of structural and functional outcomes of wild type and mutated TRAPCC9 protein. Actively involved residues can be used to elucidate the binding properties of the protein, and to develop drug therapy for NS-ARMR patients.

Introduction: Parkinson’s disease (PD) is one of the most common neurodegenerative diseases, and PD patients can present a variety of comorbidities that increase with age. Among them, cardiovascular and cerebrovascular diseases are the most prominent. Aim: To assess the cardiovascular and cerebrovascular profiles of PD patients. Patients and Methods: The cardiovascular risk factors of 126 PD patients were assessed according to laboratory tests (fasting blood sugar, serum cholesterol, triglycerides, and total lipids), Doppler ultrasound examinations and personal histories of cerebrovascular disease (ischemic/hemorrhagic), cardiovascular disease (myocardial infarct or angina confirmed by electrocardiogram), hypertension and diabetes. All patients underwent cerebral structural imaging procedures: computed tomography or magnetic resonance imaging. Results: 58.73% of the patients presented with hypertension, with a slight predominance of female patients (65.38% vs 47.92%, P = 0.05). Carotid or vertebral atheromatosis was present in 39 (30.95%) and 28 (22.22%) of patients, respectively, and was statistically correlated with the presence of ischemic lesions on cerebral imaging. Regarding the computed tomography findings, 33 patients (28.21%) presented with cortical atrophy that was not correlated with any of the investigated cardiovascular factors. Conclusions: Our findings indicate that risk factors for cardiovascular and cerebrovascular diseases are common in PD patients, possibly due to their older age. The presence of atherosclerosis and its complications can be detected in cerebral imaging studies.

Prolonged exposure to volatile anesthetics alone may be detrimental to the brain. However, volatile anesthetics, such as isoflurane, can provide neuroprotection against various damaging insults. Application of isoflurane after focal brain ischemia reduces ischemic brain injury. We determined whether this isoflurane postconditioning-induced neuroprotection requires inhibition of brain ischemia-induced Notch signaling activation. Here, we showed that TUNELpositive staining cell density and active caspase 3 expression were increased in the ischemic penumbral brain tissues of male rats after a 90-min middle cerebral arterial occlusion (MCAO). This increase was inhibited by isoflurane postconditioning and a Notch inhibitor. Isoflurane postconditioning and the Notch inhibitor also inhibited brain ischemiainduced Notch activation and proinflammatory cytokine production. Most cells expressing active Notch also were positive for CD11b, a microglial and white blood cell marker. Isoflurane postconditioning and the Notch inhibitor inhibited 1 ng/ml lipopolysaccharide- and oxygen-glucose deprivation-induced Notch activation and proinflammatory cytokine production from microglial cultures. The inhibition of cytokine production by isoflurane postconditioning, but not by a high concentration of the Notch inhibitor, disappeared in the presence of 10 ng/ml lipopolysaccharide. Our results suggest that Notch activation in microglia contributes to the cell apoptosis in the ischemic brain tissues. Inhibiting this Notch activation may participate in isoflurane postconditioning-induced neuroprotection against transient focal brain ischemia in male rats.