CNS & Neurological Disorders - Drug Targets - Volume 14, Issue 8, 2015

Disturbances in the circadian rhythms have long been associated with depression and mania. Animal models of mania and depression exhibit differential effects upon the intrinsic circadian period and the same occurs with antidepressants and mood stabilizers treatment. The intrinsic circadian period is expressed when there are no time clues or when the light/dark cycle length is beyond the capacity of synchronization. In summary, while there is no clear association between the circadian period and mania, depressive-like behaviour is generally associated either with lengthening of the circadian period or with arrythmicity, and the improvement of depressive-like behaviour is associated with shortening of the circadian period. Thus, this review is an attempt to summarize data regarding these correlations and find a putative role of the circadian intrinsic period in mood regulation, particularly concerning the switch from depression to mania.

Since most patients with schizophrenia do not respond properly to treatment, scientific effort has been driven to the development of new compounds acting on pharmacological targets beyond the dopaminergic system. Therefore, the aim is to review basic and clinical research findings from studies evaluating the effects of cannabidiol (CBD), an inhibitor of the reuptake and metabolism of anandamide and several other effects on nervous system, and sodium nitroprusside, a nitric oxide donor, on the prevention and treatment of psychosis. Animal and human research supports that CBD and sodium nitroprusside might be effective in the prevention and treatment of psychosis in general and especially in schizophrenia. The evidence available to date shows that CBD and sodium nitroprusside act in pathways associated with psychotic symptoms and that they may be important agents in the management of prodromal psychotic states and psychosis. This underscores the relevance of further research on the effects of these agents and others that mediate the activity of the cannabinoid system and of nitric oxide, as well as comparative studies of their antipsychotic effects and those of other antipsychotic drugs currently used to treat schizophrenia.

Nitric oxide is a gaseous neuromodulator that displays a core role in several neuronal processes. Beyond regulating the release of neurotransmitters, nitric oxide also plays a role in cell differentiation and maturation in the central nervous system. Although the mode of action of nitric oxide is not fully understood, it involves the activation of soluble guanylate cyclase as well as the nitration and S-nitrosylation of specific amino acid residues in other proteins. Brain-derived neurotrophic factor is a member of neurotrophic factor family and, acting through its receptor tropomyosinrelated kinase B, increases the production of nitric oxide, modulates neuronal differentiation and survival, and plays a crucial role in synaptic plasticity, such as long-term potentiation. Furthermore, nitric oxide is an important regulator of the production of these factors. The aim of the present review is to present a condensed view of the evidence related to the interaction between nitric oxide and brain-derived neurotrophic factor. Additionally, we conducted bioinformatics analysis based on the amino acid sequences of brain-derived neurotrophic factor and tropomyosin-related kinase receptors, and proposed that nitric oxide might nitrate/S-nitrosylate these proteins. Thus, we suggest a putative direct mode of action between these molecules to be further explored.

The dorsal periaqueductal gray (DPAG) has long been implicated in the pathophysiology of anxiety, particularly in panic disorder (PD). Evidence obtained with animal models indicates that different neurotransmitters/neuromodulators in this midbrain area are involved in the regulation of anxiety- (e.g. inhibitory avoidance) and panic- (e.g. escape) associated defensive behaviors. Earlier findings showed that activation of serotonin (5-HT) 1A and 2A receptors in the DPAG inhibits escape expression, a panicolytic-like effect. Recently gathered evidence shows that different classes of antipanic drugs, such as the selective serotonin reuptake inhibitor antidepressant fluoxetine or the benzodiazepine alprazolam, enhance the inhibitory action of 5-HT upon these receptors. They also show that opioidergic mechanisms, through the activation of μ-receptors, contribute to this process. As with 5-HT, activation of GABAA or GABAB receptors, or cannabinoid type 1receptors as well as the tropomyosin-related kinase B receptors by brain-derived neurotrophic factor in the DPAG also inhibits escape expression. There is evidence that chronic antidepressant treatment, besides facilitating 5-HT/opioid neurotransmission, also increases brain-derived neurotrophic factor levels in this area with an impact on its panicolytic effect. On the other hand, facilitation of corticotrophin releasing factor- or cholecystokinin-mediated neurotransmission in the DPAG, via CRF1 and CCK2 receptors, respectively, causes panicogenic-like effects with implications for the pathogenesis of PD. A better understanding of the neurochemical control of defense in the DPAG may foster the development of new strategies for pharmacological treatment of PD.

Schizophrenia is a severe psychiatric disorder with a complex presentation comprising positive symptoms (e.g.: hallucinations and delusions), negative symptoms (e.g.: social withdrawal, blunted affect) and pervasive cognitive deficits that have been associated with functional decline. The pathophysiology of the disorder is equally complex, with abnormalities known to occur in the molecular, cellular, neurophysiological, and neuroanatomical domains. Despite significant progress in the comprehension of the various manifestations of schizophrenia, the full picture of its etiology remains unknown. As a result, currently available pharmacological treatments have limited efficacy and little has improved since the discovery of the first antipsychotics back in the 1950s. In addition, these medications have significant adverse effects. Differently from other medical areas, the diagnosis of schizophrenia is essentially clinical and dependent on subjective elements. In an attempt to change this, efforts have been directed to find biomarkers of the disorder that could improve diagnostic accuracy and validity, predict treatment response, enable the early identification of individuals at risk of developing schizophrenia and indicate new targets for the development of drugs with better selective, safety, and efficacy profiles. In this article we describe the main potential schizophrenia markers currently under study and suggest avenues for future research in the field. Key Points: − No reliable markers exist for schizophrenia to date. − The identification of schizophrenia markers could increase diagnostic accuracy and treatment efficacy. − The main research lines in the current search for biomarkers are described.

Since the first report that the mechanism of action of antidepressants involves the facilitation of monoaminergic neurotransmission in the brain in the 1960s, the leading hypothesis about the neurobiology of depression has been the so called “monoaminergic hypothesis”. However, a growing body of evidence from the last two decades also supports important involvement of non-monoaminergic mechanisms in the neurobiology of depression and antidepressant action. The discovery of nitric oxide (NO) and endocannabinoid signaling in the brain during the 1990s challenged the wellestablished criteria of classical neurotransmission. These transmitters are synthesized and released on demand by the postsynaptic neurons, and may act as a retrograde messenger on the presynaptic terminal, modulating neurotransmitter release. These unconventional signaling mechanisms and the important role as neural messengers have classified NO and endocannabinoids as atypical neurotransmitters. They are able to modulate neural signaling mediated by the main conventional neurotransmitters systems in the brain, including the monoaminergic, glutamatergic and GABAergic signaling systems. This review aims at discussing the fundamental aspects of NO- and endocannabinoid-mediated signaling in the brain, and how they can be related to the neurobiology of depression. Both preclinical and clinical evidence supporting the involvement of these atypical neurotransmitters in the neurobiology of depression, and in the antidepressant effects are presented here. The evidence is discussed on basis of their ability to modulate different neurotransmitter systems in the brain, including monoaminergic and glutamatergic ones. A better comprehension of NO and endocannabinoid signaling mechanisms in the neurobiology depression could provide new avenues for the development of novel non-monoamine based antidepressants.

Preclinical studies have shown that phosphodiesterase inhibitors (PDE-Is) represent a potential pharmacological strategy for the treatment of brain ischemia sequelea. PDE-Is 3, 4 and 5 have been tested in several brain ischemia models. All the three PDE-Is after acute or chronic treatment decreased the degree of neurodegeneration and most of them improved functional recovery after brain injury by specific cellular and molecular mechanisms mainly involving an anti-inflammatory and/or neuroprotection action. In contrast to the large number of investigations using PDE-Is in experimental brain ischemia research, the number of clinical studies is still limited. The purpose of this review is to summarize the data currently available on the effects of PDE-Is in experimental models of cerebral ischemia.

Mutations in mitochondrial genes, oxidative insults, imbalance in redox mechanisms and dysregulated mitophagy are some of the leading causes for mitochondrial dysfunction and subsequent neurodegeneration in Parkinson’s disease. Targeting mitochondrial dysfunction and prolonging neuronal survival could potentially prove to be useful neuroprotective strategies. In some recent investigations, peroxisome proliferator activated receptor gamma coactivator 1 alpha mediated mitochondrial biogenesis and its ability to restore reactive oxygen species-detoxifying enzymes have been observed in preclinical studies. In this review, we discuss about physiological importance of peroxisome proliferator activated receptor gamma coactivator 1 alpha along with a list of its activators that could prove useful as possible neuroprotectants in Parkinson’s disease.

Muscarinic acetylcholine receptors are stimulated by the neurotransmitter acetylcholine and are involved in various functions across the human body. These receptors have surfaced for their potential use as targets in treatment of Alzheimer’s disease. Muscarinic receptors have been reported to show binding interaction with various mamba toxins, such as dendrotoxins and muscarinic toxins that act as antagonists of these receptors. Therefore, in our study we have focused on the binding analysis of these mamba toxins with the M4 and M2 muscarinic acetylcholine autoreceptors for their potential use as targets in treating cognitive symptoms associated with Alzheimer’s disease. A ligand dataset was developed that consisted of dendrotoxins and muscarinic toxins originating from various mamba species. Receptor dataset consisted of M4 and M2 muscarinic acetylcholine autoreceptors. Docking studies were performed using AutoDock 4.2 between these ligands with each receptor and further analysis was done using various computational tools. Docking experiments were performed and analyzed to check the binding compatibilities between mamba toxins and muscarinic acetylcholine autoreceptors. Detail analysis revealed that these ligands bind to active site residues of both receptors. Therefore by these in silico results, we suggest that the mamba toxins can be potential antagonists of the M4 and M2 muscarinic acetylcholine autoreceptors.

A dyshomeostasis of zinc ions has been reported for many psychiatric and neurodegenerative disorders including schizophrenia, attention deficit hyperactivity disorder, depression, autism, Parkinson’s and Alzheimer’s disease. Furthermore, alterations in zinc-levels have been associated with seizures and traumatic brain injury. Thus, altering zinclevels within the brain is emerging as a new target for the prevention and treatment of psychiatric and neurological diseases. However, given the restriction of zinc uptake into the brain by the blood-brain barrier, methods for controlled regulation and manipulation of zinc concentrations within the brain are rare. Here, we performed in vivo studies investigating the possibility of brain targeted zinc delivery using zinc-loaded nanoparticles which are able to cross the blood-brain barrier. After injecting these nanoparticles, we analyzed the regional and time-dependent distribution of zinc and nanoparticles within the brain. Moreover, we evaluated whether the presence of zinc-loaded nanoparticles alters the expression of zinc sensitive genes and proteins such as metallothioneins and zinc transporters and quantified possible toxic effects. Our results show that zinc loaded g7 nanoparticles offer a promising approach as a novel non - invasive method to selectively enrich zinc in the brain within a small amount of time.

The aggregation of α-synuclein (Syn or S) to form insoluble fibrils is important in the pathogenesis of Parkinson’s disease, but key risk factors remain ill-defined. We have developed Fluorescence Resonance Energy Transfer (FRET)-based assays for α-synuclein aggregation, using Green Fluorescent Protein variants Cerulean (C) or Venus (V), fused to each other (CV, VC) or to human synuclein (SC, SV etc). Bacterially expressed proteins were purified to homogeneity, and C-terminal fusions SC and SV largely retained their ability to aggregate in vitro. FRET signals from mixtures of SC and SV were used to monitor aggregation. These fusion genes were linked to the C. elegans unc-54 myosin promoter to generate integrated transgenic strains. Increased FRET signals, indicative of S aggregation, were observed following treatment of unc-54::SC + unc-54::SV double transgenic worms with low concentrations of mercury or chlorpyrifos, or with RNAi against hsp-70 and hip-1. Opposite changes in Yellow Fluorescent Protein (YFP) fluorescence in an unc-54::SV strain (NL5901) are likely to reflect FRET from Yellow Fluorescent Protein to aggregates of Syn fusion protein. This could provide the basis for a high throughput screening assay, which could be used for studying the effects of toxic chemicals and environmental pollutants on the aggregation of proteins such as Syn in vivo.

Nerve growth factor (NGF) expression is augmented during neuroinflammation. However, its function in the dorsal root ganglia (DRG) and spinal cord (SC) during experimental autoimmune encephalomyelitis (EAE), the inflammatory model of Multiple Sclerosis, is indistinct. Thus, the role of antigenically induced NGF in Lewis rats under a state of EAE was considered. NGF mRNA and protein expression were highly increased in DRG and SC tissues in animals with EAE. Between 18 and 24 days post induction (dpi), NGF mRNA and protein were elevated in the DRG, correlating with neurological recovery. In the SC, an increase in NGF protein at 12 dpi was, in contrast, preceded by neurological recovery. NGF mRNA expression became elevated in the SC at 15 dpi at the onset of neurological improvement and amelioration of EAE. This study revealed that antigenic induction of the 25 kDa pro-NGF isoform is associated with the disease course of EAE. Our findings suggest the induction of NGF represents an adaptive response against immune-mediated neuroinflammation in the DRG and SC that likely contributes to the EAE attenuation.

Chronic migraine (CM) is a disabling painful condition that is associated with dementia and thrombotic disease. It has been proposed that carbon monoxide (CO) and iron may play a role in CM, and CO and iron are products of the heme oxygenase system which is widespread within the brain. Further, CO and iron enhance plasmatic coagulation in part via a fibrinogen-dependent mechanism. Thus, our goal was to determine whether patients with CM had experienced carboxyhemefibrinogen formation, iron bound fibrinogen formation and plasmatic hypercoagulability. Nonsmokers with CM were recruited after informed, written consent. Blood was collected, anticoagulated with sodium citrate, and then centrifuged with plasma stored at -80ºC. Carboxyhemefibrinogen formation, iron bound fibrinogen formation and coagulation kinetics were determined via thrombelastographic methods. Patient results were compared with laboratory values generated from normal control plasmas. Incidence (95% confidence intervals) of the various parameters was determined using the Clopper-Pearson method. Twenty-six CM patients (24 female) were recruited; they were 46±12 years old. With regard to fibrinogen modification, 88.5% (69.8%-97.6%) of CM patients had formation of carboxyhemefibrinogen, iron bound fibrinogen, or both. With regard to coagulation, 42.3% (23.4%-63.1%) of patients had abnormally decreased time to clot initiation, 80.8% (60.6%-93.4%) had abnormally large velocity of clot formation, and 46.2% (26.6%-66.7%) had abnormally strong clot strength. Patients with CM have a large incidence of carboxyhemefibrinogen and iron bound fibrinogen formation and hypercoagulability. Confirmatory and potential therapeutic clinical trials targeting CO and iron modified hypercoagulation as a source of pain and vascular disease in CM patients are indicated.

Schizophrenia is a neuropsychiatric disorder in which abnormalities in the prefrontal cortex lead to impaired synthesis of dopamine. It is associated with hallucination, psychosis and hearing impairments. Many susceptible genes have been identified in schizophrenia such as catechol-O-methyltransferase (COMT) and serine/threonine kinase (AKT1). Single nucleotide polymorphisms (SNPs) in these genes have not been identified in Pakistan. Therefore, we investigated the allelic and genotypic frequencies in COMT and AKT1 genes in the Pakistani population. Polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP) and DNA sequencing were used to identify SNPs in the genes. The present study shows that COMT Val and COMT Met allelic frequencies for the controls were p=0.52, q=0.48 and for the schizophrenic cases they were p=0.34, q=0.66 respectively. The distribution of polymorphism in COMT Val158Met genotype by Hardy-Weinberg equilibrium (HWE) was P=0.61 for controls and P=0.005 for cases. The data reveal that SNP rs1130214 T allele mutation was found neither in patients nor in controls in the 5’ untranslated region (UTR). This proves that no association of AKT1 and positive association of COMT with schizophrenia exist in the population of Pakistan. Moreover, a study based on a single family showed COMT Met allele inheritance in schizophrenic offspring. This suggested that COMT allele alteration influences susceptibility to at least some forms of psychosis in the Pakistani population. Interestingly, according to our socio-economical survey, COMT genotype has no association with cannabis but it is strongly associated with tobacco. The Pakistani population with Val158Met SNP showed more susceptibility towards developing schizophrenia. This study highlights the genetic differences between Pakistani and other Caucasian populations.

Recently, microRNAs (miRNAs) are emerging as new regulators in the pathogenesis of temporal lobe epilepsy (TLE) and playing a major role in the inflammatory and immune processes. The aim of the present study was to evaluate the dynamic expression of brain-specific miR-183 and miR-135a, brain-enriched miR-125b and miR-128 and inflammation-related miR-30c and miR-27a. Status epilepticus evoked by pilocarpine administeration was used to induce epilepsy in rats. Quantitative polymerase chain reaction was performed on rat hippocampus 2 hours, 3 weeks and 2 months following pilocarpine-induced status epilepticus, representing the acute, latent, and chronic phases, respectively. Expression levels were also measured in hippocampus obtained from TLE patients and normal controls. In the rat model, miR-183, miR-135a and miR-125b were detected upregulated during the acute and chronic phases compared to controls, but not during the latent phase. miR-30c and miR-27a were upregulated in the acute and chronic phases of TLE, while in the latent phase miR-30c was downregulated and miR-27a was upregulated. On the other hand, miR-128 showed significantly downregulated in all phases of TLE development. In TLE patients, miR-183, miR- 135a, miR-125b, miR-30c and miR-27a were upregulated, whereas miR-128 was downregulated. Our study revealed upregulation of miR-183, miR-135a and miR-125b in the seizure-related phases and TLE patients, suggesting that all may provide a potential therapeutic approach for the treatment of TLE, whereas the dysregulation of miR-128, miR-30c and miR-27a may suggest different functions during the process of TLE development.