CNS & Neurological Disorders - Drug Targets (Formerly Current Drug Targets - CNS & Neurological Disorders) - Volume 13, Issue 9, 2014

Parkinson’s disease (PD) is a neurodegenerative disorder, which results from the loss of specific population of neurons, namely the pigmented dopamine secreting neurons of the substnatia nigra pars compatica (SNPc) of midbrain. The exact cause leading to nigrostriatal cell death is not yet known. In recent years, accumulating evidence from the identified molecular events in familial forms of PD contributed much to unraveling the mechanisms by which dopaminergic neurons die in PD and which hopefully would lead to the development of therapeutic interventions. Several major disease causing pathways were identified so far. These are possibly interconnected and some genes share a common pathway e.g., (i) defects in ubiquitin-proteasome pathway and protein misfolding and aggregation caused by α-synuclein and Parkin gene defects; (ii) defects in mitochondrial morphology and function in PINK1/Parkin and DJ-1 mutations; (iii) increased susceptibility to cellular oxidative stress which appear to underlie defects in α-synuclein, Parkin and DJ-1 genes. The aim of this review is to shed light on the molecular mechanisms by which mutations in familial-linked genes cause PD.

Schistosomiasis is a neglected tropical disease which is associated with neuropsychiatric and neuropathological disorders. Herein, the main goal of the presented work is to investigate the effect of Morus alba leaves extract in mice brain infected with Schistosoma mansoni. Since, the resistance of Schistosomes to antischistosomal drug (praziquantel) has been examined, schistosomiasis induced brain oxidative stress as evidenced by the decrease of glutathione level, total antioxidant capacity and the activity of catalase significantly, while a significant elevation in the levels of nitrite/nitrate and malondialdhyde. In addition, the infection resulted in neurochemical disturbances, the main inhibitory amino acid, γ- aminobutyric acid level was decreased. In contrast, the level of chloride ions and acetylcholine esterase activity were significantly increased. Moreover, the histopathological section showed some impairments in the brain. The treatment with Morus alba leaves extract ameliorated the induced disturbances in schistosome-infected mice where the levels of non-enzymatic and enzymatic antioxidants were elevated. On the other hand, the levels of nitrite/nitrate and malondialdhyde were significantly reduced. Likewise, treatment of mice with Morus alba leaves extract improved the altered levels of γ- aminobutyric acid level and chloride ion. Also, it improved the recorded impairments of the histopathological section in the brain of schistosome infected mice.

There is an increasing number of evidence showing analgesic properties of the kynurenic acid (KYNA), and also some studies demonstrate that kynurenine might interact with the opioid system. Therefore in this study, for the first time we investigated the direct binding affinity of KYNA and its structural analog KYNA-1 towards mu, kappa and delta opioid receptor in competition binding experiments applying opioid receptor specific radioligands. The binding affinity measurements were performed in Chinese hamster ovary cell lines overexpressing the corresponding opioid receptor (mu and kappa opioid receptor were rat, delta opioid receptor were mouse sequence). Additionally we also examined the chronic effect of these compounds on mu, kappa and delta opioid receptor and also nociceptin peptide receptor mediated G-protein activity in [35S]GTPγS binding assays performed in mouse cortex and striatum membranes. Our results showed that KYNA and KYNA-1 had no affinity towards any of the three classic opioid receptors. On the other hand the compounds significantly decreased opioid and nociceptin receptor mediated G-protein activity or in some cases enhanced the potency of the activating ligand. Moreover, the alterations were receptor and brain region specific. Accordingly, we conclude that KYNA and KYNA-1 do not interact directly with the opioid receptors, but more likely alter the receptor functions intracellularly.

Alzheimer’s disease (AD) is the most common neurodegenerative disorder. Its neuropathological hallmarks include deposition of beta amyloid (Aβ) fibrils in senile plaques. Numerous biochemical events, leading to Aβ neurotoxicity in AD, have been proposed and it seems that neuroinflammation plays a prominent role among these. Thus, since inflammatory processes and oxidative stress are considered to play an important role in neuroinflammatory disorders and in AD pathology, in the present work we decided to test a new composite, which is a formulation constituted of an anti-inflammatory compound such as palmitoylethanolamide (PEA) and the well recognized antioxidant flavonoid luteolin (Lut), subjected to an ultra-micronization process, here designated co-ultraPEALut. We investigated the effect of co-ultraPEALut in both an in vitro and ex vivo organotypic model of AD. For the in vitro model, we used human neuronal cells, obtained by differentiating SH-SY5Y neuroblastoma cells into sustainable neuronal morphology. These welldifferentiated cells express features specific to mature neurons, such as synaptic structures and functional axonal vesicle transport, making this new concept for in vitro differentiation valuable for many neuroscientific research areas, including AD. Differentiated SH-SY5Y cells were pre-treated with co-ultraPEALut (reference concentrations: 27, 2.7 and 0.27 µM PEA) for 2 h. AD features were induced by Aβ1-42 stimulation (1 µM). Twenty-four hours later cell vitality was evaluated by the colorimetric MTT assay, whereas the neuroinflammation underling AD was observed by Western blot analysis for IΚBα degradation and nuclear factor-ΚB traslocation, as well as glial fibrillary acidic protein expression. For the organotypic model of AD, hippocampal slice cultures were prepared from mice at postnatal day 6 and after 21 days of culturing the slices were pre-treated with co-ultraPEALut (reference concentrations: 27, 2.7 and 0.27 µM PEA) for 2 h and then incubated with Aβ1-42 (1 µg/ml) for 24 h. Pre-treatment with co-ultraPEALut significantly reduced inducible nitric oxide synthase and glial fibrillary acidic protein expression, restored neuronal nitric oxide synthase and brainderived neurotrophic factor and reduced the apoptosis. Taken together our results clearly showed that co-ultraPEALut is able to blunt Aβ-induced astrocyte activation and to exert a marked protective effect on glial cells. These findings suggest that the association of co-ultraPEALut may provide an effective strategy for AD.

Alzheimer’s disease (AD) is a neurodegenerative disorder mainly characterized by amyloid-β (Aβ) plaques, neurofibrillary tangles, loss of synapses and neurons and chronic neuroinflammation. Emerging data highlight the involvement of innate immunity, that has been shown to play opposing roles during the AD progression. Activated microglia and reactive astrocytes exert neuroprotection mediated through Aβphagocytosis in the early stage, whereas, as the disease progresses, they fail in Aβclearance and exert detrimental effects, including neuroinflammation and neurodegeneration. Specific toll-like receptors (TLRs) and coreceptors can directly or indirectly be activated to induce Aβ uptake or inflammatory responses, depending on the disease stage. Fibrillar Aβcan directly interact with TLR2, TLR4, and CD14 to induce microglial Aβphagocytosis in the beginning stages, and neuroinflammatory responses in the late stages. Early TLR3-mediated signal enhances neuronal Aβautophagy, although it increases neuronal apoptosis in the late AD stage. Similarly, TLR7, TLR8 and TLR9 can enhance microglial Aβuptake in the early stage, but over time they contribute to neuroinflammation. Therefore, TLRs, and in particular TLR2 and TLR4, represent a suitable target for therapeutic intervention within the disease progression and targeting them carefully could increase Aβ autophagy and phagocytosis or reduce inflammatory responses. Several modulators with selective TLR agonist or antagonist activity have been developed, and many of them could have a therapeutic benefit in AD patients. This paper outlines the role of specific TLRs in AD, also focusing on TLR-targeted compounds yet indicated for the treatment of other inflammatory diseases, that could be used to treat the different stages of the disease.

Fibroblast growth factor 14 (FGF14) is a member of the intracellular FGF (iFGFs) family and a functionally relevant component of the neuronal voltage-gated Na+ (Nav) channel complex. Through a monomeric interaction with the intracellular C-terminus of neuronal Nav channels, FGF14 modulates Na+ currents in an Nav isoform-specific manner serving as a fine-tuning regulator of excitability. Previous studies based on the highly homologous FGF13 homodimer crystal structure have proposed a conserved protein:protein interaction (PPI) interface common to both Nav channel binding and iFGF homodimer formation. This interface could provide a novel target for drug design against neuronal Nav channels. Here, we provide the first in-cell reconstitution of the FGF14:FGF14 protein complex and measure the dimer interaction using the split-luciferase complementation assay (LCA). Based on the FGF14 dimer structure generated in silico, we designed short peptide fragments against the FGF14 dimer interface. One of these fragments, FLPK aligns with the pocket defined by the β12-strand and β8-β9 loop, reducing the FGF14:FGF14 dimer interaction by 25% as measured by LCA. We further compared the relative interaction strength of FGF14 wild type homodimers with FGF14 hetero- and homodimers carrying double N mutations at the Y153 and V155 residues, located at the β8-β9 loop. The Y153N/V155N double mutation counteracts the FLPK effect by increasing the strength of the dimer interaction. These data suggest that the β12 strand of FGF14 might serve as scaffold for drug design against neuronal FGF14 dimers and Nav channels.

Autophagy is a cellular process that mediates selective degradation of cellular components in lysosomes. Autophagy may protect against neuronal apoptosis, which is induced in a number of neurodegenerative diseases. Thus, compounds that modulate autophagy could be beneficial to treat neurological disorders characterized by apoptosis such as Parkinson’s and Alzheimer’s diseases, as well as human-immunodeficiency virus-dementia complex. In this paper, we review new and old evidence on the role of autophagy in neuronal cell survival and we present evidence that humanimmunodeficiency virus may have adapted strategies to alter autophagic pathways in neurons. Moreover, we discuss the usefulness of drugs that facilitate autophagic clearance of proteins that are associated with neurodegeneration.

Parkinson’s disease (PD) is a chronic neurodegenerative disease with major impacts on patients’ lives and on society as a whole. It is one of the most common neurodegenerative diseases in the world, second only to Alzheimer’s disease. Low levels of production of dopamine (DA) are associated with PD. This is caused by a progressive loss of neurons in the midbrain’s substantia nigra, resulting in changes in neural conduction within the nigrostriatum. Research into PD has been going on since 1960, still there is no cure although the symptoms can be effectively controlled and the severity of the affliction can be reduced. The main obstacle in the development of neuroprotective therapy is a limited understanding of the key molecular events that provoke neurodegeneration. A misfolding of proteins and dysfunction of the ubiquitin–proteasome pathway are the critical factors in the pathogenesis of PD. Neurotoxic models (particularly 1- methyl-4-phenyl-1,2,3,6-tetrahydropyridine) have been very useful in elucidating the molecular cascade of cell death in dopaminergic neurons. They are also of use in efforts to limit the progression of the disease and to prevent the long-term functional and pathological outcome in PD. The establishment of animal and cellular models of mutations in LRRK2 and α-synuclein, and mutations in parkin, DJ-1 and PINK1, has been of use in elucidating the molecular mechanisms of this disorder, and research using these models is providing new ideas about the pathogenesis of PD. Several researchers are synthesizing and screening novel derivatives for their antiparkinsonian potential using different animal models. In this work we describe different animal models used in assessing the antiparkinson activity of novel therapeutic treatments.

Anesthetic agents induce cellular stress that may affect blood-brain barrier (BBB) permeability permeability in the developing brain causing brain dysfunction. In this investigation, effects of Propofol on cellualr stress using inducible heat shock protein (HSP72) and BBB breakdown employing albumin immunoreactivity in the mouse brain were examined. Propofol was administered to in mice on the postnatal day 10 once (10 mg/kg or 60 mg/kg subcutaneously). On the 75th day, HSP72 and albumin immunostaining were examined on 3-µm thick paraffin sections in the midbrain areas using standard protocol. Saline-treated and age-matched mice served as controls. Propofol dose-dependently produced a significant increase in the number of HSP72 and albumin-positive cells in cortex, hippocampus, thalamus and hypothalamus, a feature not seen in the saline-treated group. HSP72 and albumin activity in the propofol-treated group was largely confined to neurons and often localized to their cell cytoplasm and/or nucleus. HSP72 and albumin expression was the most prominent in cerebral cortex and in hippocampus, followed by hypothalamus and thalamus. These novel observations suggest that anesthetic agents, by inducing cellular stress in the developing brain may disrupt the BBB permeability that may have long lasting effects on adult brain function.

The Neuregulin 1 (NRG1) gene has been associated with schizophrenia in several populations, and all four types of NRG1 genes are linked with neurotransmitters activities. In this study for the first time we have demonstrated an association between NRG1 mutation and schizophrenia in Pakistani population. We examined the relationship of three genetic variants SNPs: rs3924999, rs2954041 and rs35753505 of NRG1 gene with the onset of disease. Genomic DNA samples were obtained from the blood of 100 patients and 80 matched controls. All three NRG1 SNPs were genotyped by polymerase chain reaction-restriction fragment length polymorphism method and further confirmed by DNA sequencing. The SNPs frequencies were estimated by Hardy-Weinberg equilibrium and Chi-square tests. Our study established a significant association of rs35753505 with schizophrenia but no association with rs3924999 and rs2954041. The frequency of risk allele C was significantly higher (62.5%) in rs35753505 patients when compared to controls (28.13%). Genotype frequency by Hardy-Weinberg equilibrium for SNPrs3924999 in patients was GG 77.4%, GA 21.12% and AA 1.44% and showed no association with the disease. Similarly, no genotype association was observed in rs2954041: GG 92.98%, GT 6.89%, TT 0.13% of NRG1. However, one unexpected G allele, 100% guanine (G) with no adenine (A) was found to be present in SNP rs35753505 in both patients and controls. This is an interesting finding that both cohorts display only allele G peak but no peak for allele A in the electropherogram for this SNP. Our results suggest that SNP rs35753505 of NRG1 plays an important role in conferring susceptibility to the schizophrenia in a Pakistani population.

Recently, it has been proposed that the receptor for advanced glycation end-products (RAGE) plays a crucial role in damaging cellular processes, such as neuroinflammation, neurodegeneration, excitotoxicity and oxidative stress. RAGE is a multiligand receptor belonging to the immunoglobulin superfamily of cell surface molecules acting as a counter-receptor for diverse molecules. Engagement of RAGE converts a brief pulse of cellular activation into sustained cellular dysfunction and tissue damage. Indeed, the involvement of RAGE in physiopathological processes has been demonstrated for several neurodegenerative diseases. It is the full-length form of RAGE the one constituting the cellular receptor which is able to activate intracellular signals. After the binding of ligands to RAGE, oxidative stress is increased; then, over-expression of RAGE produces vicious cycles that perpetuate oxidative stress and contribute to neuroinflammation by nuclear factor-kB (NF-kB) up-regulation. The NF-kB activation promotes the expression of proinflammatory cytokines, including RAGE expression, to induce a prolonged activation and promotion of signaling mechanisms for cell damage. Because inflammatory and oxidative events have been demonstrated to concertedly interact during neurodegenerative events, this review is aimed to discuss the role of RAGE as mediator of an interaction between inflammation and oxidative stress through NF-kB signaling pathway.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by selective neuron loss, amyloid plaques, and neurofibrillary tangles. Oxidative stress plays an essential role in the progression of AD. As the carotenoid crocetin has been shown to possess anti-oxidative effects in previous studies, now we have investigated the neuroprotective effects and potential molecular mechanism of crocetin action against Aβ1-42 induced toxicity in mouse hippocampal-derived Ht22 cells. Our results showed that there was a significant reduction in Ht22 cell viability when exposed to Aβ1-42 (0.5 µM) for 24 hours. Furthermore, increased reactive oxygen species production, reduced mitochondrial membrane potential and phosphorylation of extracellular signal-regulated kinase were observed in the cells. However, when pre-incubated with crocetin (1 and 5 µM) for 24 hours followed by Aβ1-42 (0.5 µM) challenge, there was a marked increase in cell viability, reduced in reactive oxygen species formation, and increased mitochondrial membrane potential. Pre-treatment with crocetin (5 µM) also activated extracellular signal-regulated kinase 1/2 phosphorylation. These data demonstrate that crocetin has neuroprotective effects on Aβ1-42-induced Ht22 cell injury which may result from its anti-oxidative role. This finding may provide a potential therapeutic candidate for the treatment of AD.