Flavia Trettel - Academia.edu (original) (raw)

Papers by Flavia Trettel

Journal of Neuroimmunology, 2003

We find that cerebellar granule neurons (CGN) obtained from newborn rats (p3) migrate in response... more We find that cerebellar granule neurons (CGN) obtained from newborn rats (p3) migrate in response to both CXC chemokine ligand-2 (CXCL2) and -12 (CXCL12), while CGN from p7 rats are unresponsive to CXCL2. The expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptor 1 (GluR1) greatly impairs the chemotaxis induced by CXCL2 in CXCR2-expressing HEK cells. By immunoprecipitation, we show that CXCR2 is

The Journal of Physiology, Jun 1, 2011

AbstractAdenosine modulates the function of nicotinic ACh receptors (nAChRs) in a variety of prep... more AbstractAdenosine modulates the function of nicotinic ACh receptors (nAChRs) in a variety of preparations, possibly through pathways involving protein kinase A (PKA), but these phenomena have not yet been investigated in detail. In this work we studied, using the patch clamp technique, the functional modulation of recombinant human α3β4 nAChR by the A2A adenosine receptor, co-expressed in HEK cells. Tonic activation of A2A receptor slowed current decay during prolonged applications of nicotine and accelerated receptor recovery from desensitization. Together, these changes resulted into a more sustained current response upon multiple nicotine or ACh applications. These findings were confirmed in cultured mouse superior cervical ganglion neurones, which express nAChR containing the α3 subunit together with β2 and/or β4 and A2A receptor. Expression of the A2A receptor in HEK cells also increased the apparent potency of nAChR for nicotine, further supporting a general A2A-induced gain of function for nAChR. These effects were dependent on PKA since the direct activation of PKA mimicked, and its inhibition prevented almost completely, the effects of the A2A receptor. Mutations of R385 and S388 in the cytoplasmic loop of the α3 subunit abolished the functional modulation of nAChR induced by activation of A2A receptor, PKA and other Ser/Thr kinases, suggesting that this region constitutes a putative consensus site for these kinases. These data provide conclusive evidence that activation of the A2A receptor determines functional changes of human α3β4 nAChR, through pathways involving PKA.

Journal of Neuroimmunology, Feb 1, 2003

We compared the signal transduction pathways activated by stromal cell-derived factor-1 (CXCL12) ... more We compared the signal transduction pathways activated by stromal cell-derived factor-1 (CXCL12) chemokine in two different cell systems: primary cultures of rat cerebellar granule neurons (CGN) and human neuroepithelioma CHP100 cells. Both cell types express functional CXC chemokine receptor 4 (CXCR4), which is coupled both to extracellular signal-regulated kinase (ERK) and Akt phosphorylation pathways. The activation of ERK shows different dependency on the phosphatidylinositol 3-kinase (PI3-K) pathway and different sensitivity to pertussis toxin (PTX) treatment, indicative of coupling to different G proteins in the two cell systems considered. We demonstrate that the inhibition of either the ERK kinase or the PI3-K pathways blocks the CXCL12 induced-chemotaxis in CHP100 cells; while only PI3-K activity is stringently necessary for CGN migration.

Journal of Neuroimmunology, Jul 1, 2010

, 2nd workshop Recent studies suggest that inflammatory cytokines can induce production of chemok... more , 2nd workshop Recent studies suggest that inflammatory cytokines can induce production of chemokines, which elicit effects on food intake. Considering obesity as an inflammatory state, Dr. Guyon showed that the concentration of the chemokine CCL5 (RANTES) is increased in the serum of obese patients and decreased 3 months after weightloss surgery. Patch-clamp recordings from Melanin Concentrating Hormone (MCH) neurons of lateral hypothalamus showed that CCL5 was consistently able to induce changes in membrane potential, inducing small depolarization in 88% of MHC neurons and hyperpolarization in 12% of MCH neurons. In the larger group of neurons, CCL5 induced a small inward current associated to an increase in membrane conductance and in the frequency of spontaneous synaptic currents, indicating a presynaptic modulation, mediated through

Parkinsonism & Related Disorders, Mar 1, 2020

Co-occurring WARS2 and CHRNA6 mutations in a child with a severe form of infantile parkinsonism

Neuroscience, Jul 1, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Human Molecular Genetics, Jul 23, 2009

Sporadic amyotrophic lateral sclerosis (SALS) is a motor neuron degenerative disease of unknown e... more Sporadic amyotrophic lateral sclerosis (SALS) is a motor neuron degenerative disease of unknown etiology. Current thinking on SALS is that multiple genetic and environmental factors contribute to disease liability. Since neuronal acetylcholine receptors (nAChRs) are part of the glutamatergic pathway, we searched for sequence variants in CHRNA3, CHRNA4 and CHRNB4 genes, encoding neuronal nicotinic AChR subunits, in 245 SALS patients and in 450 controls. We characterized missense variants by in vitro mutagenesis, cell transfection and electrophysiology. Sequencing the regions encoding the intracellular loop of AChRs subunits disclosed 15 missense variants (6.1%) in 14 patients compared with only six variants (1.3%) in controls (P 5 0.001; OR 4.48, 95% CI 1.7-11.8). The frequency of variants in exons encoding extracellular and transmembrane domains and in intronic regions did not differ. NAChRs formed by mutant a3 and a4 and wild-type (WT) b4 subunits exhibited altered affinity for nicotine (Nic), reduced use-dependent rundown of Nic-activated currents (I Nic) and reduced desensitization leading to sustained intracellular Ca 21 concentration, in comparison with WT-nAChR. The cellular loop has a crucial importance for receptor trafficking and regulating ion channel properties. Missense variants in this domain are significantly over-represented in SALS patients and alter functional properties of nAChR in vitro, resulting in increased Ca 21 entry into the cells. We suggest that these gain-offunction variants might contribute to disease liability in a subset of SALS because Ca 21 signals mediate nAChR's neuromodulatory effects, including regulation of glutamate release and control of cell survival.

Neuropsychopharmacology, Mar 3, 2010

Fractalkine/CX3CL1 is a neuron-associated chemokine, which modulates microglia-induced neurotoxic... more Fractalkine/CX3CL1 is a neuron-associated chemokine, which modulates microglia-induced neurotoxicity activating the specific and unique receptor CX3CR1. CX3CL1/CX3CR1 interaction modulates the release of cytokines from microglia, reducing the level of tumor necrosis factor-a, interleukin-1-b, and nitric oxide and induces the production of neurotrophic substances, both in vivo and in vitro. We have recently shown that blocking adenosine A 1 receptors (A 1 R) with the specific antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) abolishes CX3CL1-mediated rescue of neuronal excitotoxic death and that CX3CL1 induces the release of adenosine from microglia. In this study, we show that the presence of extracellular adenosine is mandatory for the neurotrophic effect of CX3CL1 as reducing adenosine levels in hippocampal cultures, by adenosine deaminase treatment, strongly impairs CX3CL1-mediated neuroprotection. Furthermore, we confirm the predominant role of microglia in mediating the neuronal effects of CX3CL1, because the selective depletion of microglia from hippocampal cultures treated with clodronate-filled liposomes causes the complete loss of effect of CX3CL1. We also show that hippocampal neurons obtained from A 1 R À/À mice are not protected by CX3CL1 whereas A 2A R À/À neurons are. The requirement of functional A 1 R for neuroprotection is not unique for CX3CL1 as A 1 R À/À hippocampal neurons are not rescued from Glu-induced cell death by other neurotrophins such as brain-derived neurotrophic factor and erythropoietin, which are fully active on wt neurons.

Journal of Neuroimmunology, Jul 1, 2008

Chemokines and their receptors are well-known regulators of leukocyte trafficking and are implica... more Chemokines and their receptors are well-known regulators of leukocyte trafficking and are implicated in other functions such as angiogenesis, tumor growth and metastasis. In the nervous system, these molecules have been reported to act as inflammatory mediators playing a central role in CNS diseases such as multiple sclerosis, stroke and others. Only recently has it become evident that chemokines and chemokine receptors are physiologically expressed in CNS (Table 1), both in neuronal and glial cells, suggesting that these molecules play specific roles in brain development, neurogenesis, neuromodulation, neuron–glia communication, and neurotrophic effects (de Haas et al., 2007). The two-day symposium “Chemokines and Chemokine Receptors in the Nervous System” was organised by Cristina Limatola, Fabrizio Eusebi and Davide Ragozzino in Rome in October 2007. The symposium was divided in four sections: i) chemokines and signal transduction; ii) chemokine neurophysiology: neuromodulation and development; iii) chemokines as mediators of neuron–glial communication; iv) chemokines in neuropathologies. The principal aim of the meeting was to highlight the roles of chemokines and chemokine receptors as a new class of major players in the homeostasis of the CNS.

Experimental Cell Research, Jul 1, 2005

We examined the role of cysteine (Cys) residues present in chemokine receptor CXCR2 for proper su... more We examined the role of cysteine (Cys) residues present in chemokine receptor CXCR2 for proper surface expression, dimerization, signaling, and chemotaxis. To address this issue, serine or leucine residues were substituted for Cys, generating nine CXCR2 mutants transiently expressed in HEK cells. Single substitution of Cys residues present in the three extracellular loops (C119L, C196L, C286S) or in the seventh-transmembrane (TM) domain (C308L) abolished CXCL8 agonist binding, while no Cys substitution abolished surface receptor expression. We have previously demonstrated that CXCR2 dimerizes under reducing conditions, due to hydrophobic interactions that involve TM3 regions, and here we show that the dimer/monomer CXCR2 ratio drastically increases when analyzed under non-reducing conditions. We report that none of the Cys-deficient CXCR2 mutants abolishes receptor dimerization, demonstrating that Cys-Cys bonds are not the exclusive determinant of CXCR2 dimerization. Furthermore, both wt- and Cys-mutated CXCR2 dimers are expressed at the cell surface, indicating that receptor dimers are efficiently transferred at the plasma membrane. We also show that every Cys substitution in CXCR2, including those that still bind CXCL8, results in an impairment of receptor activity, analyzed as cell chemotaxis and intracellular signaling, suggesting that some structural requirement is likely fulfilled by Cys presence.

Frontiers research topics, 2015

Virtually involved in all pathologies that present an inflammatory component, it is now evident t... more Virtually involved in all pathologies that present an inflammatory component, it is now evident that, in the central nervous system, chemokines and chemokine receptors possess pleiotropic properties beyond chemotaxis: costitutive brain expression of chemokines and their receptors on endothelial cells, but also on neurons and glia, suggests a role for such molecules in mediating homeostatic cross-talk between cells of the brain perenchyma. Cross-talk between neurons and glia is determinant to the establishment and maintenance of a brain enviroment that ensure normal function, and in particular glial cells are active players that respond to enviromental changes and act for the survival, growth, differentiation and repair of the nervous tissue: in this regard brain endogenous chemokines represent key molecules that play a role in brain development, neurogenesis, neurotransmission and neuroprotection. As important regulators of peripheral immune response, chemokines are molecules of the immune system that play a central role in coordinating communication between the nervous and the immune systems, in the context of infections and brain injury. Indeed, in phatological processes resulting from infections, brain trauma, ischemia and chronic neurodegenerative diseases, chemokines represent important neuroinflammatory mediators that drive leucocytes trafficking into the central nervous system, facilitating an immune response by targeting cells of the innate and adaptive immune system. The third edition of the international conference "Chemokines and Chemokine Receptors in the Nervous System", hold in Rome in October 2013, represented an exciting platform to promote discussion among researchers in different disciplines to understand the role of chemokines in brain homoestasis. This Frontiers Research Topic arises from this conference, and wants to be an opportunity to further discuss and highlight the importance of brain chemokines as key molecules that, not only grant the interplay between the immune and the nervous systems, but in addition drive modulatory functions on brain homeoastasis orchestrating neurons, microglia, and astrocytes communication

Pflügers Archiv: European Journal of Physiology, Nov 25, 2010

Recently identified mutations in the genes encoding the neuronal nicotinic ACh receptor (nAChR) s... more Recently identified mutations in the genes encoding the neuronal nicotinic ACh receptor (nAChR) subunits in patients affected by sporadic amyotrophic lateral sclerosis (sALS) may represent a factor which enhances disease susceptibility, in particular in association with ambient causes such as cigarette smoking. In this work, we characterize the functional properties of nAChRs containing the β4R349C subunit, the mutation most frequently encountered in sALS patients. The mutation was coexpressed with wild-type α3 or α4 subunits or with mutant α4R487Q subunit, which has been detected in one patient together with β4R349C mutation. None of the functional parameters examined showed differences between α4β4 and α4R487Qβ4 nAChRs. By contrast, β4R349C mutation, independent of the companion α subunit, caused the reduction in potency of both ACh and nicotine, decreased the density of whole-cell current evoked by maximal transmitter concentrations, and altered the kinetics of ACh-evoked whole-cell currents. These data confirm that sALS-associated mutations in nicotinic subunits may markedly perturb cholinergic transmission in individuals bearing the mutations.

Frontiers in Cellular Neuroscience, Oct 12, 2015

Adenosine is a widespread neuromodulator within the CNS and its extracellular level is increased ... more Adenosine is a widespread neuromodulator within the CNS and its extracellular level is increased during hypoxia or intense synaptic activity, modulating pre-and postsynaptic sites. We studied the neuromodulatory action of adenosine on glutamatergic currents in the hippocampus, showing that activation of multiple adenosine receptors (ARs) by basal adenosine impacts postsynaptic site. Specifically, the stimulation of both A 1 R and A 3 R reduces AMPA currents, while A 2A R has an opposite potentiating effect. The effect of ARs stimulation on glutamatergic currents in hippocampal cultures was investigated using pharmacological and genetic approaches. A 3 R inhibition by MRS1523 increased GluR1-Ser845 phosphorylation and potentiated AMPA current amplitude, increasing the apparent affinity for the agonist. A similar effect was observed blocking A 1 R with DPCPX or by genetic deletion of either A 3 R or A 1 R. Conversely, impairment of A 2A R reduced AMPA currents, and decreased agonist sensitivity. Consistently, in hippocampal slices, ARs activation by AR agonist NECA modulated glutamatergic current amplitude evoked by AMPA application or afferent fiber stimulation. Opposite effects of AR subtypes stimulation are likely associated to changes in GluR1 phosphorylation and represent a novel mechanism of physiological modulation of glutamatergic transmission by adenosine, likely acting in normal conditions in the brain, depending on the level of extracellular adenosine and the distribution of AR subtypes.

The Journal of Neuroscience, Mar 14, 2017

Oleandrin is a glycoside that inhibits the ubiquitous enzyme Na ϩ /K ϩ-ATPase. In addition to its... more Oleandrin is a glycoside that inhibits the ubiquitous enzyme Na ϩ /K ϩ-ATPase. In addition to its known effects on cardiac muscle, recent in vitro and in vivo evidence highlighted its potential for anticancer properties. Here, we evaluated for the first time the effect of oleandrin on brain tumors. To this aim, mice were transplanted with human or murine glioma and analyzed for tumor progression upon oleandrin treatment. In both systems, oleandrin impaired glioma development, reduced tumor size, and inhibited cell proliferation. We demonstrated that oleandrin does the following: (1) enhances the brain-derived neurotrophic factor (BDNF) level in the brain; (2) reduces both microglia/macrophage infiltration and CD68 immunoreactivity in the tumor mass; (3) decreases astrogliosis in peritumoral area; and (4) reduces glioma cell infiltration in healthy parenchyma. In BDNF-deficient mice (bdnftm1Jae/J) and in glioma cells silenced for TrkB receptor expression, oleandrin was not effective, indicating a crucial role for BDNF in oleandrin's protective and antitumor functions. In addition, we found that oleandrin increases survival of temozolomide-treated mice. These results encourage the development of oleandrin as possible coadjuvant agent in clinical trials of glioma treatment.

Proceedings of the National Academy of Sciences of the United States of America, Oct 30, 2002

Poly(A ؉) RNA was extracted from the temporal lobe (TL) of medically intractable epileptic patien... more Poly(A ؉) RNA was extracted from the temporal lobe (TL) of medically intractable epileptic patients which underwent surgical TL resection. Injection of this mRNA into Xenopus oocytes led to the expression of ionotropic receptors for ␥-aminobutyric acid (GABA), kainate (KAI) and ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Membrane currents elicited by GABA inverted polarity at ؊15 mV, close to the oocyte's chloride equilibrium potential, were inhibited by bicuculline, and were potentiated by pentobarbital and flunitrazepam. These basic characteristics were also displayed by GABA currents elicited in oocytes injected with mRNAs isolated from human TL glioma (TLG) or from mouse TL. However, the GABA receptors expressed by the epileptic TL mRNA exhibited some unusual properties, consisting in a rapid current run-down after repetitive GABA applications and a large EC 50 (125 M). AMPA alone evoked very small or nil currents, whereas KAI induced larger currents. Nevertheless, upon cyclothiazide treatment, AMPA elicited substantial currents that, like the KAI currents, were inhibited by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Furthermore, the glutamate receptor 5 (GluR5) agonist, ATPA, failed to evoke an obvious current although both RT-PCR and Western blot analyses showed GluR5 expression in the epileptic TL. Oocytes injected with mouse TL or human TLG mRNAs generated KAI and AMPA currents similar to those evoked in oocytes injected with epileptic TL mRNA but, in contrast to these, the mouse TL and human TLG oocytes were also responsive to ATPA. Our findings are in accord with the concept that both a depression of GABA inhibition and a dysfunction of the KAI-receptor system maintain a high neuronal excitability that results in epileptic seizures.

Journal of Immunology, Dec 1, 2006

Fractalkine/CX3CL1 and its specific receptor CX3CR1 are constitutively expressed in several regio... more Fractalkine/CX3CL1 and its specific receptor CX3CR1 are constitutively expressed in several regions of the CNS and are reported to mediate neuron-microglial interaction, synaptic transmission, and neuronal protection from toxic insults. CX3CL1 is released both by neuronal and astrocytic cells, whereas CX3CR1 is mainly expressed by microglial cells and neurons. Microglial cells efficiently migrate in response to CX3CL1, whereas no evidence is reported to date on CX3CL1-induced neuronal migration. For this reason, we have investigated in vitro the effects of CX3CL1 on basal migration of neurons and of the microglial and astrocytic populations, all these cells being obtained from the hippocampus and the cerebellum of newborn rats. We report that CX3CL1 stimulates microglial cell migration but efficiently reduces basal neuronal movement, regardless of the brain source. The effect of CX3CL1 is pertussis toxin (PTX) sensitive and PI3K dependent on hippocampal neurons, while it is PTX sensitive, PI3K dependent, and ERK dependent on cerebellar granules. Interestingly, CX3CL1 also increases neuron adhesion to the extracellular matrix component laminin, with mechanisms dependent on PTX-sensitive G proteins, and on the ERK and PI3K pathways. Both the reduction of migration and the increase of neuron adhesion require the activation of the ␤ 1 and ␣ 6 integrin subunits with the exception of cerebellar neuron migration, which is only dependent on the ␤ 1 subunit. More importantly, in neurons, CX3CL1/ CXCL12 cotreatment abolished the effect mediated by a single chemokine on chemotaxis and adhesion. In conclusion, our findings indicate that CX3CL1 reduces neuronal migration by increasing cell adhesion through integrin-dependent mechanisms in hippocampal and cerebellar neurons.

$Research paper thumbnail of LTP impairment by fractalkine/CX3CL1 in mouse hippocampus is mediated through the activity of adenosine receptor type 3 (A3R)$

Journal of Neuroimmunology, Oct 30, 2009

We have examined how the chemokine fractalkine/CX(3)CL1 influences long-term potentiation (LTP) i... more We have examined how the chemokine fractalkine/CX(3)CL1 influences long-term potentiation (LTP) in CA1 mouse hippocampal slices. Field potentials (fEPSPs) were recorded upon electrical stimulation of Schaffer collaterals. It was found that application of CX(3)CL1 inhibits LTP when present during the critical induction period. LTP impairment (i) failed to occur in CX(3)CR1 deficient mice (CX(3)CR1(GFP/GFP)) and in the presence of okadaic acid (OA); (ii) required the activation of adenosine receptor 3 (A(3)R), since it was prevented in A(3)R-deficient mice or by MRS1523, a selective A(3)R antagonist. Together, these findings indicate that CX(3)CL1 inhibits hippocampal LTP through A(3)R activity.

Proceedings of the National Academy of Sciences of the United States of America, Sep 17, 2002