Influence of different neuroprotective drugs on dopamine neurotoxicity induced by 3,4-methylenedioxymethamphetamine and MPTP in mice

Introduction: Parkinson‟s disease (PD) is characterized by a chronic progressive loss of nigrostriatal dopaminergic neurons that is associated with chronic neuroinflammation. Current treatments for PD can significantly improve symptoms but do not cure the disease or slow its progression. An approach used in existing therapies is based on the inhibition of monoamine oxidase (MAO), enzyme involved in the metabolic degradation of dopamine. Although, preclinical studies showed that MAO-B inhibitors have neuroprotective activity in cellular and animal models of PD, clinical trials did not completely confirm this result. Therefore a large number of new molecules, with more potent MAO-B inhibitory activity and a possible neuroprotective effect, have been proposed to replace the pre-existing MAO-B inhibitors. The profile of the recent MAO inhibitor, SZV558, appears to be particularly interesting because of its pharmacodynamic, favorable for disease-modifying properties and its irreversible MAO-B enzyme bind. The enhancement of adult neurogenesis could be of great clinical interest in the management of neurodegenerative disorders. In line with this, the metformin, a well-known antidiabetic drug, has recently been proposed to promote neurogenesis and to have a neuroprotective effect on the neurodegenerative processes induced by the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in a mice PD model. Although, PD has multiple origins, one hypothesis is that amphetamine-related drugs may be part of the wide array of factors leading to the dopaminergic neuron degeneration that causes the disease. These hypothesis are supported by different results that showed a persistent, long-term dopaminergic toxicity induced by 3,4-methylenedioxymethamphetamine (MDMA) in mice. Moreover, the MDMA, altering the dopaminergic transmission, may affect neurogenesis and synaptogenesis. On these basis, considering that the young brain is particularly sensitive to drug-induced neurotoxicity, the consumption of MDMA during the adolescence might increase the vulnerability of dopaminergic neurons. However, the use of amphetamine-related drugs by adolescent and young people is often combined with caffeinated energy drinks in order to amplify their stimulant actions. Although caffeine use is safe, the combined treatment of caffeine and MDMA increases not only the DA release but also the microglia and astroglia activation. Aims: During my Ph.D. I studied the influence of neuroprotective drugs, such as MAO inhibitors and metformin, or substances, such as caffeine, on the neurodegenerative effects of two dopaminergic toxins, MDMA and MPTP, in mice. 1. In the first phase of my study, I evaluated the neuroprotective activity of the new MAO-B inhibitor SZV558, compared with well-known rasagiline, in a chronic mouse model of MPTP plus probenecid (MPTPp), which induces a progressive loss of nigrostriatal dopaminergic neurons. 2. Previous results showed that when MDMA is associated with caffeine, a more pronounced degeneration in adolescent compared with adult mice was observed. To better clarify the molecular mechanism at the base of the different neurotoxic effect of this drug association at different ages, I evaluated the neuronal nitric oxide synthase (nNOS) expression, which plays a critical role in the integration of dopaminergic and glutamatergic transmissions, in the CPu of adolescent or adult mice treated with MDMA, alone or in combination with caffeine. 3. Finally, I investigated the neuroprotective effect of metformin against dopaminergic neurotoxicity induced by MDMA in the CPu and SNc of adult mice. Conclusions: These results demonstrated that the dopaminergic neurodegenerative process may be induced or conditioned by environment stressors or substances which influence, through different ways, the development of neurodegenerative mechanisms. In the present study I evaluated the effects of 3 substances, known as potentially neuroprotective, in combination with two different neurotoxins that affect the nigrostriatal dopaminergic system. The SZV558 MAO-B inhibitor and the metformin protected the nigrostriatal pathway, usually affected in PD, by MPTP- and MDMA- induced neurotoxicity, respectively. On the other hand, caffeine, administrated with MDMA, showed a neurotoxic potential depending on the age of consumers, confirming the vulnerability of adolescent brain to consumption of drug and substances that affected the dopaminergic system. In conclusion, the study of neurodegenerative processes may be relevant to understand the human pharmacology, the origin and development of neurodegenerative disease and to predict the neurotoxic effect of drug abuse.

Serotonin synthesis, release and reuptake in terminals: a mathematical model.

BACKGROUND: Serotonin is a neurotransmitter that has been linked to a wide variety of behaviors including feeding and body-weight regulation, social hierarchies, aggression and suicidality, obsessive compulsive disorder, alcoholism, anxiety, and affective disorders. Full understanding of serotonergic systems in the central nervous system involves genomics, neurochemistry, electrophysiology, and behavior. Though associations have been found between functions at these different levels, in most cases the causal mechanisms are unknown. The scientific issues are daunting but important for human health because of the use of selective serotonin reuptake inhibitors and other pharmacological agents to treat disorders in the serotonergic signaling system. METHODS: We construct a mathematical model of serotonin synthesis, release, and reuptake in a single serotonergic neuron terminal. The model includes the effects of autoreceptors, the transport of tryptophan into the terminal, and the metabolism of serotonin, as well as the dependence of release on the firing rate. The model is based on real physiology determined experimentally and is compared to experimental data. RESULTS: We compare the variations in serotonin and dopamine synthesis due to meals and find that dopamine synthesis is insensitive to the availability of tyrosine but serotonin synthesis is sensitive to the availability of tryptophan. We conduct in silico experiments on the clearance of extracellular serotonin, normally and in the presence of fluoxetine, and compare to experimental data. We study the effects of various polymorphisms in the genes for the serotonin transporter and for tryptophan hydroxylase on synthesis, release, and reuptake. We find that, because of the homeostatic feedback mechanisms of the autoreceptors, the polymorphisms have smaller effects than one expects. We compute the expected steady concentrations of serotonin transporter knockout mice and compare to experimental data. Finally, we study how the properties of the the serotonin transporter and the autoreceptors give rise to the time courses of extracellular serotonin in various projection regions after a dose of fluoxetine. CONCLUSIONS: Serotonergic systems must respond robustly to important biological signals, while at the same time maintaining homeostasis in the face of normal biological fluctuations in inputs, expression levels, and firing rates. This is accomplished through the cooperative effect of many different homeostatic mechanisms including special properties of the serotonin transporters and the serotonin autoreceptors. Many difficult questions remain in order to fully understand how serotonin biochemistry affects serotonin electrophysiology and vice versa, and how both are changed in the presence of selective serotonin reuptake inhibitors. Mathematical models are useful tools for investigating some of these questions.

Serotonin transporter genotype modulates social reward and punishment in rhesus macaques

Background: Serotonin signaling influences social behavior in both human and nonhuman primates. In humans, variation upstream of the promoter region of the serotonin transporter gene (5-HTTLPR) has recently been shown to influence both behavioral measures of social anxiety and amygdala response to social threats. Here we show that length polymorphisms in 5-HTTLPR predict social reward and punishment in rhesus macaques, a species in which 5-HTTLPR variation is analogous to that of humans. Methodology/Principal Findings: In contrast to monkeys with two copies of the long allele (L/L), monkeys with one copy of the short allele of this gene (S/L) spent less time gazing at face than non-face images, less time looking in the eye region of faces, and had larger pupil diameters when gazing at photos of a high versus low status male macaques. Moreover, in a novel primed gambling task, presentation of photos of high status male macaques promoted risk-aversion in S/L monkeys but promoted risk-seeking in L/L monkeys. Finally, as measured by a "pay-per-view" task, S/L monkeys required juice payment to view photos of high status males, whereas L/L monkeys sacrificed fluid to see the same photos. Conclusions/Significance: These data indicate that genetic variation in serotonin function contributes to social reward and punishment in rhesus macaques, and thus shapes social behavior in humans and rhesus macaques alike. © 2009 Watson et al.

Identification of beta-adrenergic receptors in human lymphocytes by (-) (3H) alprenolol binding.

Human lymphocytes are known to posessess a catecholamine-responsive adenylate cyclase which has typical beta-adrenergic specificity. To identify directly and to quantitate these beta-adenergic receptors in human lymphocytes, (-) [3H] alprenolol, a potent beta-adrenergic antagonist, was used to label binding sites in homogenates of human mononuclear leukocytes. Binding of (-) [3H] alprenolol to these sites demonstrated the kinetics, affinity, and stereospecificity expected of binding to adenylate cyclase-coupled beta-adrenergic receptors. Binding was rapid (t1/2 less than 30 s) and rapidly reversible (t1/2 less than 3 min) at 37 degrees C. Binding was a saturable process with 75 +/- 12 fmol (-) [3H] alprenolol bound/mg protein (mean +/- SEM) at saturation, corresponding to about 2,000 sites/cell. Half-maximal saturation occurred at 10 nM (-) [3H] alprenolol, which provides an estimate of the dissociation constant of (-) [3H] alprenolol for the beta-adrenergic receptor. The beta-adrenergic antagonist, (-) propranolol, potently competed for the binding sites, causing half-maximal inhibition of binding at 9 nM. beta-Adrenergic agonists also competed for the binding sites. The order of potency was (-) isoproterenol greater than (-) epinephrine greater than (-)-norepinephrine which agreed with the order of potency of these agents in stimulating leukocyte adenylate cyclase. Dissociation constants computed from binding experiments were virtually identical to those obtained from adenylate cyclase activation studies. Marked stereospecificity was observed for both binding and activation of adenylate cyclase. (-)Stereoisomers of beta-adrenergic agonists and antagonists were 9- to 300-fold more potent than their corresponding (+) stereoisomers. Structurally related compounds devoid of beta-adrenergic activity such as dopamine, dihydroxymandelic acid, normetanephrine, pyrocatechol, and phentolamine did not effectively compete for the binding sites. (-) [3H] alprenolol binding to human mononuclear leukocyte preparations was almost entirely accounted for by binding to small lymphocytes, the predominant cell type in the preparations. No binding was detectable to human erythrocytes. These results demonstrate the feasibility of using direct binding methods to study beta-adrenergic receptors in a human tissue. They also provide an experimental approach to the study of states of altered sensitivity to catecholamines at the receptor level in man.

Antidepressant specificity of serotonin transporter suggested by three LeuT-SSRI structures.

Sertraline and fluoxetine are selective serotonin re-uptake inhibitors (SSRIs) that are widely prescribed to treat depression. They exert their effects by inhibiting the presynaptic plasma membrane serotonin transporter (SERT). All SSRIs possess halogen atoms at specific positions, which are key determinants for the drugs' specificity for SERT. For the SERT protein, however, the structural basis of its specificity for SSRIs is poorly understood. Here we report the crystal structures of LeuT, a bacterial SERT homolog, in complex with sertraline, R-fluoxetine or S-fluoxetine. The SSRI halogens all bind to exactly the same pocket within LeuT. Mutation at this halogen-binding pocket (HBP) in SERT markedly reduces the transporter's affinity for SSRIs but not for tricyclic antidepressants. Conversely, when the only nonconserved HBP residue in both norepinephrine and dopamine transporters is mutated into that found in SERT, their affinities for all the three SSRIs increase uniformly. Thus, the specificity of SERT for SSRIs is dependent largely on interaction of the drug halogens with the protein's HBP.

Exclusion of linkage between schizophrenia and the D2 dopamine receptor gene region of chromosome 11q in 112 Irish multiplex families

A leading theory hypothesizes that schizophrenia arises from dysregulation of the dopamine system in certain brain regions. As this dysregulation could arise from abnormal expression of D2 dopamine receptors, the D2 receptor gene (DRD2) on chromosome 11q is a candidate locus for schizophrenia. We tested whether allelic variation at DRD2 and five surrounding loci cosegregated with schizophrenia in 112 small- to moderate-size Irish families containing two or more members affected with schizophrenia or schizoaffective disorder, defined by DSM-III-R. Evidence of linkage was assessed using varying definitions of illness and modes of transmission. Assuming genetic homogeneity, linkage between schizophrenia and large regions of 11q around DRD2 could be strongly excluded. Assuming genetic heterogeneity, variation at the DRD2 locus could be rejected as a major risk factor for schizophrenia in more than 50% of these families for all models tested and in as few as 25% of the families for certain models. The DRD2 linkage in fewer than 25% of these families could not be excluded under any of the models tested. Our results suggest that the major component of genetic susceptibility to schizophrenia is not due to allelic variation at the DRD2 locus or other genes in the surrounding chromosomal region.

A single-component multidrug transporter of the major facilitator superfamily is part of a network that protects Escherichia coli from bile salt stress

Resistance to high concentrations of bile salts in the human intestinal tract is vital for the survival of enteric bacteria such as Escherichia coli. Although the tripartite AcrAB-TolC efflux system plays a significant role in this resistance, it is purported that other efflux pumps must also be involved. We provide evidence from a comprehensive suite of experiments performed at two different pH values (7.2 and 6.0) that reflect pH conditions that E. coli may encounter in human gut that MdtM, a single-component multidrug resistance transporter of the major facilitator superfamily, functions in bile salt resistance in E. coli by catalysing secondary active transport of bile salts out of the cell cytoplasm. Furthermore, assays performed on a chromosomal ΔacrB mutant transformed with multicopy plasmid encoding MdtM suggested a functional synergism between the single-component MdtM transporter and the tripartite AcrAB-TolC system that results in a multiplicative effect on resistance. Substrate binding experiments performed on purified MdtM demonstrated that the transporter binds to cholate and deoxycholate with micromolar affinity, and transport assays performed on inverted vesicles confirmed the capacity of MdtM to catalyse electrogenic bile salt/H(+) antiport.

Expression of transketolase-like 1 protein (TKTL1) in human endometrial cancer

Malignant tumors metabolize glucose to lactate even in the presence of oxygen (aerobic glycolysis). The metabolic switch from oxidative glycolysis to non-oxidative fermentation of glucose and proteins performed by the tumor cells seems to be associated with TKTL1 and pAkt overexpression. Therefore the aim of the present study was to investigate the expression of TKTL1 and pAkt in human specimens of endometrial cancer as compared to benign endometrium. Additionally, expression of the glucose transporter GLUT1 was also investigated as aerobic glycolysis is associated with an increased need for glucose.

Multidrug transporter proteins of the major facilitator superfamily: not only for drug efflux

Multidrug resistance in prokaryotes is due primarily to efflux of offending antimicrobials from the cell by representatives of several different families of integral membrane transporter proteins. Clearly, in evolutionary terms, these proteins did not arise specifically to pump human-made antimicrobials out of the cell and thereby confer resistance. Despite this, often only their role in antibiotic resistance is characterised and highlighted.
In recent years, however, a transition from the traditional anthropocentric perception of antibiotic resistance mechanisms in microorganisms has occurred, with naturally produced antimicrobials now generally regarded as physiologically important signalling molecules or sources of nutrition for bacteria rather than antimicrobial agents, and bacterial multidrug efflux proteins not merely as a defensive response to antimicrobials but as important players in fundamental physiological processes such as cellular homeostasis.
This emerging perspective supports the notion that a better understanding of the complexities of infection and multidrug resistance in bacteria can be achieved via a more detailed understanding of those physiological processes. In this chapter, we review the ‘true’ physiological roles of multidrug efflux proteins of the largest non-ATP-hydrolysing family of membrane transporters, the major facilitator superfamily, and explore the evidence for their function in processes such as pH and metal homeostasis, import and export of metabolites and biofilm formation

Données nouvelles sur l’innervation à dopamine du striatum et son co-phénotype glutamatergique

Une sous-population des neurones à dopamine (DA) du mésencéphale ventral du rat et de la souris étant connue pour exprimer l'ARN messager du transporteur vésiculaire 2 du glutamate (VGLUT2), nous avons eu recours à l'immunocytochimie en microscopie électronique, après simple ou double marquage de l'enzyme de synthèse tyrosine hydroxylase (TH) et de VGLUT2, pour déterminer la présence de l'une et/ou l'autre protéine dans les terminaisons (varicosités) axonales de ces neurones et caractériser leur morphologie ultrastructurale dans diverses conditions expérimentales. Dans un premier temps, des rats jeunes (P15) ou adultes (P90), ainsi que des rats des deux âges soumis à l'administration intraventriculaire cérébrale de la cytotoxine 6-hydroxydopamine (6-OHDA) dans les jours suivant la naissance, ont été examinés, afin d'étayer l'hypothèse d'un rôle de VGLUT2 au sein des neurones DA, au cours du développement normal ou pathologique de ces neurones. Chez le jeune rat, ces études ont montré: i) la présence de VGLUT2 dans une fraction importante des varicosités axonales TH immunoréactives du coeur du noyau accumbens ainsi que du néostriatum; ii) une augmentation de la proportion de ces terminaisons doublement marquées dans le noyau accumbens par suite de la lésion 6-OHDA néonatale; iii) le double marquage fréquent des varicosités axonales appartenant à l'innervation DA aberrante (néoinnervation), qui se développe dans la substance noire, par suite de la lésion 6-OHDA néonatale. Des différences significatives ont aussi été notées quant à la dimension des terminaisons axonales marquées pour la TH seulement, VGLUT2 seulement ou TH et VGLUT2. Enfin, à cet âge (P15), toutes les terminaisons doublement marquées sont apparues dotées d'une spécialisation membranaire synaptique, contrairement aux terminaisons marquées pour la TH ou pour VGLUT2 seulement. Dans un deuxième temps, nous avons voulu déterminer le devenir du double phénotype chez le rat adulte (P90) soumis ou non à la lésion 6-OHDA néonatale. Contrairement aux observations recueillies chez le jeune rat, nous avons alors constaté: i) l'absence complète de terminaisons doublement marquées dans le coeur du noyau accumbens et le néostriatum d'animaux intacts, de même que dans les restes de la substance noire des animaux 6-OHDA lésés; ii) une très forte baisse de leurnombre dans le coeur du noyau accumbens des animaux 6-OHDA lésés. Ces observations, suggérant une régression du double phénotype TH/VGLUT2 avec l'âge, sont venues renforcer l'hypothèse d'un rôle particulier d'une co-libération de glutamate par les neurones mésencéphaliques DA au cours du développement. Dans ces conditions, il est apparu des plus intéressants d'examiner l'innervation DA méso-striatale chez deux lignées de souris dont le gène Vglut2 avait été sélectivement invalidé dans les neurones DA du cerveau, ainsi que leurs témoins et des souris sauvages. D'autant que malgré l'utilisation croissante de la souris en neurobiologie, cette innervation DA n'avait jamais fait l'objet d’une caractérisation systématique en microscopie électronique. En raison de possibles différences entre le coeur et la coque du noyau accumbens, l'étude a donc porté sur les deux parties de ce noyau ainsi que le néostriatum et des souris jeunes (P15) et adultes (P70-90) de chaque lignée, préparées pour l'immunocytochimie de la TH, mais aussi pour le double marquage TH et VGLUT2, selon le protocole précédemment utilisé chez le rat. Les résultats ont surpris. Aux deux âges et quel que soit le génotype, les terminaisons axonales TH immunoréactives des trois régions sont apparues comparables quant à leur taille, leur contenu vésiculaire, le pourcentage contenant une mitochondrie et une très faible incidence synaptique (5% des varicosités, en moyenne). Ainsi, chez la souris, la régression du double phénotype pourrait être encore plus précoce que chez le rat, à moins que les deux protéines ne soient très tôt ségréguées dans des varicosités axonales distinctes des mêmes neurones DA. Ces données renforcent aussi l’hypothèse d’une transmission diffuse (volumique) et d’un niveau ambiant de DA comme élément déterminant du fonctionnement du système mésostriatal DA chez la souris comme chez le rat.

Neurotransmitter Functional Role in Neurodegenerative Diseases: human Health

Neuroscience is the study of'tbe ne rvous system , including the i - ; . in, spinal cord and peripheral nerves . Neurons are the basic cells of the brain and nervous system which exerts its functional role through various neurotransmitters and receptor systems . The activity of a nen ren depends on the balance between the number of excitatory and inhibito r y processes affecting it, both processes occurring individually and sin ,tlte-' ,ieously. The functional bal,ince of different neurotransmitters such as Acct >>lcholine (Ach), Dopamine (DA), Serotonin (5-1-17), Nor epinepbri,te (N.1 j, Epinephrine (LPI), Glutamate and Gamma amino butyric acid (GA BA) regulates the growth , division and other vital functions ofa normal cell / organisin (Sudha, 1 998). The micro-environ ; nertt of the cell is controlled / the macro-environment that surrounds the individual. Any change in the cell environment causes imbalance in cell homeostasis and f,ntction. Pollution is a significant cause of imbalance caused iii the inacYcenvironment. Interaction with polluted environments can have an adverse impact on the health of humans. The alarming rise in enviromilmieil cont.iniin :rtion has been linked to rises in levels of pesticides, ndltstr al effluents, domestic Waste, car exhausts and other anthropogenic activities. Persistent exposures to contaminant cause a negative imp,-, on brain health and development . Pollution also causes a change in the neurotransmitters and their receptor function leading to earl.;' recurrence of neurodcge,terative disorders such as flypoxia , Alzbeimers's and Huntington 's disease early in life.

Over Expression of the CMP-sialic Acid Transporter in Chinese Hamster Ovary Cells Leads to Increased Sialylation

Most glyco-engineering approaches used to improve quality of recombinant glycoproteins involve the manipulation of glycosyltransferase and/or glycosidase expression. We investigated whether the over expression of nucleotide sugar transporters, particularly the CMP-sialic acid transporter (CMP-SAT), would be a means to improve the sialylation process in CHO cells. We hypothesized that increasing the expression of the CMP-SAT in the cells would increase the transport of the CMP-sialic acid in the Golgi lumen, hence increasing the intra-lumenal CMP-sialic acid pool, and resulting in a possible increase in sialylation extent of proteins being produced. We report the construction of a CMP-SAT expression vector which was used for transfection into CHO-IFNγ, a CHO cell line producing human IFNγ. This resulted in approximately 2 to 5 times increase in total CMP-SAT expression in some of the positive clones as compared to untransfected CHO-IFNγ, as determined using real-time PCR analysis. This in turn concurred with a 9.6% to 16.3% percent increase in site sialylation. This engineering approach has thus been identified as a novel means of improving sialylation in recombinant glycoprotein therapeutics. This strategy can be utilized feasibly on its own, or in combination with existing sialylation improvement strategies. It is believed that such multi-prong approaches are required to effectively manipulate the complex sialylation process, so as to bring us closer to the goal of producing recombinant glycoproteins of high and consistent sialylation from mammalian cells.

The influence of G protein subtype on agonist action at D-2 dopamine receptors

In previous studies, we have shown that agonists influence the ability of D-2 dopamine receptors to couple to G proteins and here we extend this work. The human D-2Short dopamine receptor and a natural polymorphism of this D-2Short(Ser(311)Cys), have been studied by co-expressing the receptors in insect cells with Gbeta(1)gamma(2) and either Galpha(o), Galpha(i1), Galpha(i2) or Galpha(i3) G protein subunits. These preparations have been used to study the G protein coupling profiles of the two receptors and the influence of agonists. Receptor/G protein coupling was analysed in dopamine/[H-3]spiperone competition binding experiments and through stimulation of [S-35]GTPgammaS binding. Although the Ser(311)Cys polymorphism itself had no appreciable effect on the G protein coupling specificity of the D-2 receptor, agonist stimulation of [S-35]GTPgammaS binding, revealed that both dopamine and (+)-3PPP showed a clear preference for Galpha(o) compared to the Galpha(i) subtypes, but quinpirole did not. These results indicate that agonists are able to stabilise different receptor conformations with different abilities to couple to G proteins. (C) 2004 Elsevier Ltd. All rights reserved.

Interaction of the D-2short dopamine receptor with G proteins: analysis of receptor G protein selectivity

The human D-2short (D-2S) dopamine receptor has been expressed together with the G proteins Gi2 and Go in insect cells using the baculovirus system. Levels of receptor were determined using [H-3]spiperone binding. Levels of G protein heterotrimer were determined using quantitative Western blot and using [S-35]GTPgammaS saturation binding experiments. Levels of the receptor and G protein and the receptor/G protein ratio were similar in the two preparations. Stimulation of [S-35]GTPgammaS binding by a range of agonists occurred with higher relative efficacy and in some cases higher potency in the preparation expressing Go, indicating that interaction of the D-2S receptor is more efficient with this G protein. The effects of various G protein-selective agents on 10,11-dihydroxy-N-n-propylnorapomorphine ([H-3]NPA) binding were used to examine the receptor/G protein complex in the two preparations. Suramin inhibited [H-3]NPA binding with slightly higher potency in the Gi2 preparation, whereas GppNHp inhibited [H-3]NPA binding with greater potency (similar to6-fold) in the Go preparation. This may imply that the G protein is more readily activated in the D-2S/Go preparation. [H-3]Spiperone binding occurred with an increased B-max in the presence of suramin in the Go preparation but not in the Gi2 preparation, suggesting a higher affinity interaction between the free receptor and this G protein. It is concluded that the higher efficiency activation of Go by the D-2S receptor may be a function of higher affinity receptor/G protein interaction as well as a greater ability to activate the G protein. (C) 2003 Elsevier Science Inc. All rights reserved.

MicroRNA expression is differentially altered by xenobiotic drugs in different human cell lines

Several noncoding microRNAs (miR or miRNA) have been shown to regulate the expression of drug-metabolizing enzymes and transporters. Xenobiotic drug-induced changes in enzyme and transporter expression may be associated with the alteration of miRNA expression. Therefore, this study investigated the impact of 19 xenobiotic drugs (e. g. dexamethasone, vinblastine, bilobalide and cocaine) on the expression of ten miRNAs (miR-18a, -27a, -27b, -124a, -148a, -324-3p, -328, -451, -519c and -1291) in MCF-7, Caco-2, SH-SY5Y and BE(2)-M17 cell systems. The data revealed that miRNAs were differentially expressed in human cell lines and the change in miRNA expression was dependent on the drug, as well as the type of cells investigated. Notably, treatment with bilobalide led to a 10-fold increase of miR-27a and a 2-fold decrease of miR-148a in Caco-2 cells, but no change of miR-27a and a 2-fold increase of miR-148a in MCF-7 cells. Neuronal miR-124a was generally down-regulated by psychoactive drugs (e. g. cocaine, methadone and fluoxetine) in BE(2)-M17 and SH-SY5Y cells. Dexamethasone and vinblastine, inducers of drug-metabolizing enzymes and transporters, suppressed the expression of miR-27b, -148a and -451 that down-regulate the enzymes and transporters. These findings should provide increased understanding of the altered gene expression underlying drug disposition, multidrug resistance, drug-drug interactions and neuroplasticity. Copyright (C) 2011 John Wiley & Sons, Ltd.