Araoz R

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Full name : Araoz Romulo

First name : Romulo

Mail : CNRS Neuro-PSI \/ CEA SIMOPRO Gif sur Yvette 91191

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Country : France

Email : romulo.araoz@cea.fr

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References (14)

Title : Functional characterization of multifunctional ligands targeting acetylcholinesterase and alpha 7 nicotinic acetylcholine receptor - Cieslikiewicz-Bouet_2020_Biochem.Pharmacol__114010
Author(s) : Cieslikiewicz-Bouet M , Naldi M , Bartolini M , Perez B , Servent D , Jean L , Araoz R , Renard PY
Ref : Biochemical Pharmacology , :114010 , 2020
Abstract : Alzheimer's disease (AD) is a neurodegenerative disorder associated with cholinergic dysfunction, provoking memory loss and cognitive dysfunction in elderly patients. The cholinergic hypothesis provided over the years with molecular targets for developing palliative treatments for AD, acting on the cholinergic system, namely, acetylcholinesterase and alpha7 nicotinic acetylcholine receptor (alpha7 nAChR). In our synthetic work, we used "click-chemistry" to synthesize two Multi Target Directed Ligands (MTDLs) MB105 and MB118 carrying tacrine and quinuclidine scaffolds which are known for their anticholinesterase and alpha7 nicotinic acetylcholine receptor agonist activities, respectively. Both, MB105 and MB118, inhibit human acetylcholinesterase and human butyrylcholinesterase in the nanomolar range. Electrophysiological recordings on Xenopus laevis oocytes expressing human alpha7 nAChR showed that MB105 and MB118 acted as partial agonists of the referred nicotinic receptor, albeit, with different potencies despite their similar structure. The different substitution at C-3 on the 2,3-disubtituted quinuclidine scaffold may account for the significantly lower potency of MB118 compared to MB105. Electrophysiological recordings showed that the tacrine precursor MB320 behaved as a competitive antagonist of human alpha7 nAChR, in the micromolar range, while the quinuclidine synthetic precursor MB099 acted as a partial agonist. Taken all together, MB105 behaved as a partial agonist of alpha7 nAChR at concentrations where it completely inhibited human acetylcholinesterase activity paving the way for the design of novel MTDLs for palliative treatment of AD.
ESTHER : Cieslikiewicz-Bouet_2020_Biochem.Pharmacol__114010
PubMedSearch : Cieslikiewicz-Bouet_2020_Biochem.Pharmacol__114010
PubMedID: 32360492

Title : Cyclic imine toxins from dinoflagellates: a growing family of potent antagonists of the nicotinic acetylcholine receptors - Molgo_2017_J.Neurochem_142 Suppl 2_41
Author(s) : Molgo J , Marchot P , Araoz R , Benoit E , Iorga BI , Zakarian A , Taylor P , Bourne Y , Servent D
Ref : Journal of Neurochemistry , 142 Suppl 2 :41 , 2017
Abstract : We present an overview of the toxicological profile of the fast-acting, lipophilic macrocyclic imine toxins, an emerging family of organic compounds associated with algal blooms, shellfish contamination and neurotoxicity. Worldwide, shellfish contamination incidents are expanding; therefore, the significance of these toxins for the shellfish food industry deserves further study. Emphasis is directed to the dinoflagellate species involved in their production, their chemical structures, and their specific mode of interaction with their principal natural molecular targets, the nicotinic acetylcholine receptors, or with the soluble acetylcholine-binding protein, used as a surrogate receptor model. The dinoflagellates Karenia selliformis and Alexandrium ostenfeldii / A. peruvianum have been implicated in the biosynthesis of gymnodimines and spirolides, while Vulcanodinium rugosum is the producer of pinnatoxins and portimine. The cyclic imine toxins are characterized by a macrocyclic skeleton comprising 14-27 carbon atoms, flanked by two conserved moieties, the cyclic imine and the spiroketal ring system. These phycotoxins generally display high affinity and broad specificity for the muscle type and neuronal nicotinic acetylcholine receptors, a feature consistent with their binding site at the receptor subunit interfaces, composed of residues highly conserved among all nAChRs, and explaining the diverse toxicity among animal species. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.
ESTHER : Molgo_2017_J.Neurochem_142 Suppl 2_41
PubMedSearch : Molgo_2017_J.Neurochem_142 Suppl 2_41
PubMedID: 28326551

Title : Poster: Multi-target directed ligands: Electrophysiological characterization of an anticholinesterase inhibitor coupled to an agonist of alpha7 nicotinic acetylcholine receptor -
Author(s) : Araoz R , Bouet m , Bartolini M , Coquelle N , Colletier JP , Servent D , Molgo J , Jean L , Renard PY
Ref : Biochemical Pharmacology , 97 :621 , 2015
PubMedID:

Title : Poster: Cyclic imine toxins: From shellfish poisoning to neuroscience: The case of acyl derivatives -
Author(s) : Araoz R , Hess P , Pelissier F , Benoit E , Servent D , Zakarian A , Molgo J
Ref : Biochemical Pharmacology , 97 :622 , 2015
PubMedID:

Title : Marine Macrocyclic Imines, Pinnatoxins A and G: Structural Determinants and Functional Properties to Distinguish Neuronal alpha7 from Muscle alpha1(2)betagammadelta nAChRs - Bourne_2015_Structure_23_1106
Author(s) : Bourne Y , Sulzenbacher G , Radic Z , Araoz R , Reynaud M , Benoit E , Zakarian A , Servent D , Molgo J , Taylor P , Marchot P
Ref : Structure , 23 :1106 , 2015
Abstract : Pinnatoxins are macrocyclic imine phycotoxins associated with algal blooms and shellfish toxicity. Functional analysis of pinnatoxin A and pinnatoxin G by binding and voltage-clamp electrophysiology on membrane-embedded neuronal alpha7, alpha4beta2, alpha3beta2, and muscle-type alpha12betagammadelta nicotinic acetylcholine receptors (nAChRs) reveals high-affinity binding and potent antagonism for the alpha7 and alpha12betagammadelta subtypes. The toxins also bind to the nAChR surrogate, acetylcholine-binding protein (AChBP), with low Kd values reflecting slow dissociation. Crystal structures of pinnatoxin-AChBP complexes (1.9-2.2 A resolution) show the multiple anchoring points of the hydrophobic portion, the cyclic imine, and the substituted bis-spiroketal and cyclohexene ring systems of the pinnatoxins that dictate tight binding between the opposing loops C and F at the receptor subunit interface, as observed for the 13-desmethyl-spirolide C and gymnodimine A congeners. Uniquely, however, the bulky bridged EF-ketal ring specific to the pinnatoxins extends radially from the interfacial-binding pocket to interact with the sequence-variable loop F and govern nAChR subtype selectivity and central neurotoxicity.
ESTHER : Bourne_2015_Structure_23_1106
PubMedSearch : Bourne_2015_Structure_23_1106
PubMedID: 26004441

Title : Detection of Anatoxin-a and Three Analogs in Anabaena spp. Cultures: New Fluorescence Polarization Assay and Toxin Profile by LC-MS\/MS - Sanchez_2014_Toxins.(Basel)_6_402
Author(s) : Sanchez JA , Otero P , Alfonso A , Ramos V , Vasconcelos V , Araoz R , Molgo J , Vieytes MR , Botana LM
Ref : Toxins (Basel) , 6 :402 , 2014
Abstract : Anatoxin-a (ATX) is a potent neurotoxin produced by several species of Anabaena spp. Cyanobacteria blooms around the world have been increasing in recent years; therefore, it is urgent to develop sensitive techniques that unequivocally confirm the presence of these toxins in fresh water and cyanobacterial samples. In addition, the identification of different ATX analogues is essential to later determine its toxicity. In this paper we designed a fluorescent polarization (FP) method to detect ATXs in water samples. A nicotinic acetylcholine receptor (nAChR) labeled with a fluorescein derivative was used to develop this assay. Data showed a direct relationship between the amount of toxin in a sample and the changes in the polarization degree of the emitted light by the labeled nAChR, indicating an interaction between the two molecules. This method was used to measure the amount of ATX in three Anabaena spp. cultures. Results indicate that it is a good method to show ATXs presence in algal samples. In order to check the toxin profile of Anabaena cultures a LC-MS/MS method was also developed. Within this new method, ATX-a, retention time (RT) 5 min, and three other molecules with a mass m/z 180.1 eluting at 4.14 min, 5.90 min and 7.14 min with MS/MS spectra characteristic of ATX toxin group not previously identified were detected in the Anabaena spp. cultures. These ATX analogues may have an important role in the toxicity of the sample.
ESTHER : Sanchez_2014_Toxins.(Basel)_6_402
PubMedSearch : Sanchez_2014_Toxins.(Basel)_6_402
PubMedID: 24469431

Title : Colorimetric microtiter plate receptor-binding assay for the detection of freshwater and marine neurotoxins targeting the nicotinic acetylcholine receptors - Rubio_2014_Toxicon_91_45
Author(s) : Rubio F , Kamp L , Carpino J , Faltin E , Loftin K , Molgo J , Araoz R
Ref : Toxicon , 91 :45 , 2014
Abstract : Anatoxin-a and homoanatoxin-a, produced by cyanobacteria, are agonists of nicotinic acetylcholine receptors (nAChRs). Pinnatoxins, spirolides, and gymnodimines, produced by dinoflagellates, are antagonists of nAChRs. In this study we describe the development and validation of a competitive colorimetric, high throughput functional assay based on the mechanism of action of freshwater and marine toxins against nAChRs. Torpedo electrocyte membranes (rich in muscle-type nAChR) were immobilized and stabilized on the surface of 96-well microtiter plates. Biotinylated alpha-bungarotoxin (the tracer) and streptavidin-horseradish peroxidase (the detector) enabled the detection and quantitation of anatoxin-a in surface waters and cyclic imine toxins in shellfish extracts that were obtained from different locations across the US. The method compares favorably to LC/MS/MS and provides accurate results for anatoxin-a and cyclic imine toxins monitoring. Study of common constituents at the concentrations normally found in drinking and environmental waters, as well as the tolerance to pH, salt, solvents, organic and inorganic compounds did not significantly affect toxin detection. The assay allowed the simultaneous analysis of up to 25 samples within 3.5 h and it is well suited for on-site or laboratory monitoring of low levels of toxins in drinking, surface, and ground water as well as in shellfish extracts.
ESTHER : Rubio_2014_Toxicon_91_45
PubMedSearch : Rubio_2014_Toxicon_91_45
PubMedID: 25260255

Title : Pinnatoxin G is responsible for atypical toxicity in mussels (Mytilus galloprovincialis) and clams (Venerupis decussata) from Ingril, a French Mediterranean lagoon - Hess_2013_Toxicon_75_16
Author(s) : Hess P , Abadie E , Herve F , Berteaux T , Sechet V , Araoz R , Molgo J , Zakarian A , Sibat M , Rundberget T , Miles CO , Amzil Z
Ref : Toxicon , 75 :16 , 2013
Abstract : Following a review of official control data on shellfish in France, Ingril Lagoon had been identified as a site where positive mouse bioassays for lipophilic toxins had been repeatedly observed. These unexplained mouse bioassays, also called atypical toxicity, coincided with an absence of regulated toxins and rapid death times in mice observed in the assay. The present study describes pinnatoxin G as the main compound responsible for the toxicity observed using the mouse bioassay for lipophilic toxins. Using a well-characterised standard for pinnatoxin G, LC-MS/MS analysis of mussel samples collected from 2009 to 2012 revealed regular occurrences of pinnatoxin G at levels sufficient to account for the toxicity in the mouse bioassays. Baseline levels of pinnatoxin G from May to October usually exceeded 40 mug kg(-1) in whole flesh, with a maximum in September 2010 of around 1200 mug kg(-1). These concentrations were much greater than those at the other 10 sites selected for vigilance testing, where concentrations did not exceed 10 mug kg(-1) in a 3-month survey from April to July 2010, and where rapid mouse deaths were not typically observed. Mussels were always more contaminated than clams, confirming that mussel is a good sentinel species for pinnatoxins. Profiles in mussels and clams were similar, with the concentration of pinnatoxin A less than 2% that of pinnatoxin G, and pteriatoxins were only present in non-quantifiable traces. Esters of pinnatoxin G could not be detected by analysis of extracts before and after alkaline hydrolysis. Analysis with a receptor-binding assay showed that natural pinnatoxin G was similarly active on the nicotinic acetylcholine receptor as chemically synthesized pinnatoxin G. Culture of Vulcanodinium rugosum, previously isolated from Ingril lagoon, confirmed that this alga is a pinnatoxin G producer (4.7 pg cell(-1)). Absence of this organism from the water column during prolonged periods of shellfish contamination and the dominance of non-motile life stages of V. rugosum both suggest that further studies will be required to fully describe the ecology of this organism and the accumulation of pinnatoxins in shellfish.
ESTHER : Hess_2013_Toxicon_75_16
PubMedSearch : Hess_2013_Toxicon_75_16
PubMedID: 23726853

Title : The non-competitive acetylcholinesterase inhibitor APS12-2 is a potent antagonist of skeletal muscle nicotinic acetylcholine receptors - Grandic_2012_Toxicol.Appl.Pharmacol_265_221
Author(s) : Grandic M , Araoz R , Molgo J , Turk T , Sepcic K , Benoit E , Frangez R
Ref : Toxicol Appl Pharmacol , 265 :221 , 2012
Abstract : APS12-2, a non-competitive acetylcholinesterase inhibitor, is one of the synthetic analogs of polymeric alkylpyridinium salts (poly-APS) isolated from the marine sponge Reniera sarai. In the present work the effects of APS12-2 were studied on isolated mouse phrenic nerve-hemidiaphragm muscle preparations, using twitch tension measurements and electrophysiological recordings. APS12-2 in a concentration-dependent manner blocked nerve-evoked isometric muscle contraction (IC(50)=0.74muM), without affecting directly-elicited twitch tension up to 2.72muM. The compound (0.007-3.40muM) decreased the amplitude of miniature endplate potentials until a complete block by concentrations higher than 0.68muM, without affecting their frequency. Full size endplate potentials, recorded after blocking voltage-gated muscle sodium channels, were inhibited by APS12-2 in a concentration-dependent manner (IC(50)=0.36muM) without significant change in the resting membrane potential of the muscle fibers up to 3.40muM. The compound also blocked acetylcholine-evoked inward currents in Xenopus oocytes in which Torpedo (alpha1(2)beta1gammadelta) muscle-type nicotinic acetylcholine receptors (nAChRs) have been incorporated (IC(50)=0.0005muM), indicating a higher affinity of the compound for Torpedo (alpha1(2)beta1gammadelta) than for the mouse (alpha1(2)beta1gammaepsilon) nAChR. Our data show for the first time that APS12-2 blocks neuromuscular transmission by a non-depolarizing mechanism through an action on postsynaptic nAChRs of the skeletal neuromuscular junction.
ESTHER : Grandic_2012_Toxicol.Appl.Pharmacol_265_221
PubMedSearch : Grandic_2012_Toxicol.Appl.Pharmacol_265_221
PubMedID: 23046821

Title : Total synthesis of pinnatoxins A and G and revision of the mode of action of pinnatoxin A - Araoz_2011_J.Am.Chem.Soc_133_10499
Author(s) : Araoz R , Servent D , Molgo J , Iorga BI , Fruchart-Gaillard C , Benoit E , Gu Z , Stivala C , Zakarian A
Ref : Journal of the American Chemical Society , 133 :10499 , 2011
Abstract : Pinnatoxins belong to an emerging class of potent marine toxins of the cyclic imine group. Detailed studies of their biological effects have been impeded by unavailability of the complex natural product from natural sources. This work describes the development of a robust, scalable synthetic sequence relying on a convergent strategy that delivered a sufficient amount of the toxin for detailed biological studies and its commercialization for use by other research groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland-Claisen rearrangement of a complex alpha,alpha-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive evidence for its mode of action as a potent inhibitor of nicotinic acetylcholine receptors selective for the human neuronal alpha7 subtype. The comprehensive electrophysiological, biochemical, and computational studies support the view that the spiroimine subunit of pinnatoxins is critical for blocking nicotinic acetylcholine receptor subtypes, as evidenced by analyzing the effect of a synthetic analogue of pinnatoxin A containing an open form of the imine ring. Our studies have paved the way for the production of certified standards to be used for mass-spectrometric determination of these toxins in marine matrices and for the development of tests to detect these toxins in contaminated shellfish.
ESTHER : Araoz_2011_J.Am.Chem.Soc_133_10499
PubMedSearch : Araoz_2011_J.Am.Chem.Soc_133_10499
PubMedID: 21644584

Title : Parazoanthoxanthin A blocks Torpedo nicotinic acetylcholine receptors - Rozman_2010_Chem.Biol.Interact_187_384
Author(s) : Rozman KB , Araoz R , Sepcic K , Molgo J , Suput D
Ref : Chemico-Biological Interactions , 187 :384 , 2010
Abstract : Nicotinic acetylcholine receptors are implicated in different nervous system-related disorders, and their modulation could improve existing therapy of these diseases. Parazoanthoxanthin A (ParaA) is a fluorescent pigment of the group of zoanthoxanthins. Since it is a potent acetylcholinesterase inhibitor, it may also bind to nicotinic acetylcholine receptors (nAChRs). For this reason its effect on Torpedo nAChR (alpha1(2)betagammadelta) transplanted to Xenopus laevis oocytes was evaluated, using the voltage-clamp technique. ParaA dose-dependently reduced the acetylcholine-induced currents. This effect was fully reversible only at lower concentrations. ParaA also reduced the Hill coefficient and the time to peak current, indicating a channel blocking mode of action. On the other hand, the combined effect of ParaA and d-tubocurarine (d-TC) on acetylcholine-induced currents exhibited only partial additivity, assuming a competitive mode of action of ParaA on nAChR. These results indicate a dual mode of action of ParaA on the Torpedo AChR.
ESTHER : Rozman_2010_Chem.Biol.Interact_187_384
PubMedSearch : Rozman_2010_Chem.Biol.Interact_187_384
PubMedID: 20230806

Title : Structural determinants in phycotoxins and AChBP conferring high affinity binding and nicotinic AChR antagonism - Bourne_2010_Proc.Natl.Acad.Sci.U.S.A_107_6076
Author(s) : Bourne Y , Radic Z , Araoz R , Talley TT , Benoit E , Servent D , Taylor P , Molgo J , Marchot P
Ref : Proc Natl Acad Sci U S A , 107 :6076 , 2010
Abstract : Spirolide and gymnodimine macrocyclic imine phycotoxins belong to an emerging class of chemical agents associated with marine algal blooms and shellfish toxicity. Analysis of 13-desmethyl spirolide C and gymnodimine A by binding and voltage-clamp recordings on muscle-type alpha1(2)betagammadelta and neuronal alpha3beta2 and alpha4beta2 nicotinic acetylcholine receptors reveals subnanomolar affinities, potent antagonism, and limited subtype selectivity. Their binding to acetylcholine-binding proteins (AChBP), as soluble receptor surrogates, exhibits picomolar affinities governed by diffusion-limited association and slow dissociation, accounting for apparent irreversibility. Crystal structures of the phycotoxins bound to Aplysia-AChBP ( approximately 2.4A) show toxins neatly imbedded within the nest of ar-omatic side chains contributed by loops C and F on opposing faces of the subunit interface, and which in physiological conditions accommodates acetylcholine. The structures also point to three major features: (i) the sequence-conserved loop C envelops the bound toxins to maximize surface complementarity; (ii) hydrogen bonding of the protonated imine nitrogen in the toxins with the carbonyl oxygen of loop C Trp147 tethers the toxin core centered within the pocket; and (iii) the spirolide bis-spiroacetal or gymnodimine tetrahydrofuran and their common cyclohexene-butyrolactone further anchor the toxins in apical and membrane directions, along the subunit interface. In contrast, the se-quence-variable loop F only sparingly contributes contact points to preserve the broad receptor subtype recognition unique to phycotoxins compared with other nicotinic antagonists. These data offer unique means for detecting spiroimine toxins in shellfish and identify distinctive ligands, functional determinants and binding regions for the design of new drugs able to target several receptor subtypes with high affinity.
ESTHER : Bourne_2010_Proc.Natl.Acad.Sci.U.S.A_107_6076
PubMedSearch : Bourne_2010_Proc.Natl.Acad.Sci.U.S.A_107_6076
PubMedID: 20224036

Title : Neurotoxic cyanobacterial toxins - Araoz_2010_Toxicon_56_813
Author(s) : Araoz R , Molgo J , Tandeau de Marsac N
Ref : Toxicon , 56 :813 , 2010
Abstract : Worldwide development of cyanobacterial blooms has significantly increased in marine and continental waters in the last century due to water eutrophication. This phenomenon is favoured by the ability of planktonic cyanobacteria to synthesize gas vesicles that allow them to float in the water column. Besides, benthic cyanobacteria that proliferate at the bottom of lakes, rivers and costal waters form dense mats near the shore. Cyanobacterial massive proliferation is of public concern regarding the capacity of certain cyanobacterial strains to produce hepatotoxic and neurotoxic compounds that can affect public health, human activities and wild and stock animals. The cholinergic synapses and voltage-gated sodium channels constitute the targets of choice of cyanobacterial neurotoxins. Anatoxin-a and homoanatoxin-a are agonists of nicotinic acetylcholine receptors. Anatoxin-a(s) is an irreversible inhibitor of acetylcholinesterase. Saxitoxin, kalkitoxin and jamaicamide are blockers of voltage-gated sodium channels, whereas antillatoxin is an activator of such channels. Moreover the neurotoxic amino acid l-beta-N-methylamino-l-alanine was shown to be produced by diverse cyanobacterial taxa. Although controversial, increasing in vivo and in vitro evidence suggest a link between the ingestion of l-beta-N-methylamino-l-alanine and the development of amyotrophic lateral sclerosis/Parkinsonism-dementia complex, a neurodegenerative disease. This paper reviews the occurrence of cyanobacterial neurotoxins, their chemical properties, mode of action and biosynthetic pathways.
ESTHER : Araoz_2010_Toxicon_56_813
PubMedSearch : Araoz_2010_Toxicon_56_813
PubMedID: 19660486

Title : Fluorescent agonists for the Torpedo nicotinic acetylcholine receptor - Krieger_2008_Chembiochem_9_1146
Author(s) : Krieger F , Mourot A , Araoz R , Kotzyba-Hibert F , Molgo J , Bamberg E , Goeldner M
Ref : Chembiochem , 9 :1146 , 2008
Abstract : We have synthesized a series of fluorescent acylcholine derivatives carrying different linkers that vary in length and structure and connect the acylcholine unit to the environment-sensitive fluorophores 7-(diethylamino)coumarin-3-carbonyl (DEAC) or N-(7-nitrobenz-2-oxa-1,3-diazol-yl) (NBD). The pharmacological properties of the fluorescent analogues were investigated on heterologously expressed nicotinic acetylcholine receptor (nAChR) from Torpedo californica and on oocytes transplanted with nAChR-rich Torpedo marmorata membranes. Agonist action strongly depends on the length and the structure of the linker. One particular analogue, DEAC-Gly-C6-choline, showed partial agonist behavior with about half of the maximum response of acetylcholine, which is at least 20 times higher than those observed with previously described fluorescent dansyl- and NBD-acylcholine analogues. Binding of DEAC-Gly-C6-choline to Torpedo nAChR induces a strong enhancement of fluorescence intensity. Association and displacement kinetic experiments revealed dissociation constants of 0.5 nM for the alphadelta-binding site and 15.0 nM for the alphagamma-binding site. Both the pharmacological and the spectroscopic properties of this agonist show great promise for characterizing the allosteric mechanism behind the function of the Torpedo nAChR, as well as for drug-screening studies.
ESTHER : Krieger_2008_Chembiochem_9_1146
PubMedSearch : Krieger_2008_Chembiochem_9_1146
PubMedID: 18386276