A Novel and Selective Dopamine Transporter Inhibitor, (S)-MK-26, Promotes Hippocampal Synaptic Plasticity and Restores Effort-Related Motivational Dysfunctions

Dopamine (DA), the most abundant human brain catecholaminergic neurotransmitter, modulates key behavioral and neurological processes in young and senescent brains, including motricity, sleep, attention, emotion, learning and memory, and social and reward-seeking behaviors. The DA transporter (DAT) regulates transsynaptic DA levels, influencing all these processes. Compounds targeting DAT (e.g., cocaine and amphetamines) were historically used to shape mood and cognition, but these substances typically lead to severe negative side effects (tolerance, abuse, addiction, and dependence). DA/DAT signaling dysfunctions are associated with neuropsychiatric and progressive brain disorders, including Parkinson's and Alzheimer diseases, drug addiction and dementia, resulting in devastating personal and familial concerns and high socioeconomic costs worldwide. The development of low-side-effect, new/selective medicaments with reduced abuse-liability and which ameliorate DA/DAT-related dysfunctions is therefore crucial in the fields of medicine and healthcare. Using the rat as experimental animal model, the present work describes the synthesis and pharmacological profile of (S)-MK-26, a new modafinil analogue with markedly improved potency and selectivity for DAT over parent drug. Ex vivo electrophysiology revealed significantly augmented hippocampal long-term synaptic potentiation upon acute, intraperitoneally delivered (S)-MK-26 treatment, whereas in vivo experiments in the hole-board test showed only lesser effects on reference memory performance in aged rats. However, in effort-related FR5/chow and PROG/chow feeding choice experiments, (S)-MK-26 treatment reversed the depression-like behavior induced by the dopamine-depleting drug tetrabenazine (TBZ) and increased the selection of high-effort alternatives. Moreover, in in vivo microdialysis experiments, (S)-MK-26 significantly increased extracellular DA levels in the prefrontal cortex and in nucleus accumbens core and shell. These studies highlight (S)-MK-26 as a potent enhancer of transsynaptic DA and promoter of synaptic plasticity, with predominant beneficial effects on effort-related behaviors, thus proposing therapeutic potentials for (S)-MK-26 in the treatment of low-effort exertion and motivational dysfunctions characteristic of depression and aging-related disorders

Mutagenesis and Functional Studies with Succinate Dehydrogenase Inhibitors in the Wheat Pathogen Mycosphaerella graminicola

A range of novel carboxamide fungicides, inhibitors of the succinate dehydrogenase enzyme (SDH, EC 1.3.5.1) is currently being introduced to the crop protection market. The aim of this study was to explore the impact of structurally distinct carboxamides on target site resistance development and to assess possible impact on fitness

Frühe Sprachbildung in sprachlich heterogenen Spielgruppen: Kurzbericht zum Forschungsprojekt «Mehrsprachige Praktiken von Kindern und Fachpersonen in Spielgruppen» (MePraS)

Ce rapport court s’adresse aux responsables et chef∧f∧s de projet dans le domaine de l’éducation préscolaire et au public intéressé. Nous renvoyons les lectrices et lecteurs des milieux académiques à l’ouvrage Gespräche im Kindergarten als Erwerbskontexte sprachlicher Fähigkeiten, qui sera publié par Beltz Juventa en 2021 et présentera le projet et ses résultats en détail.This general summary is directed towards policymakers and government officials, managers and project leaders in the area of preschool education, and other interested readers. For German-speaking academic staff, we recommend the forthcoming book Gespräche im Kindergarten als Erwerbskontexte sprachlicher Fähigkeiten, which provides a detailed description of the project and its outcomes; the book will be published by Beltz Juventa in 2021.Dieser Kurzbericht richtet sich an Akteurinnen und Akteure in Politik und Administration, an Führungs- und Projektverantwortliche im Bereich der frühen Bildung und an die interessierte Öffentlichkeit. Leserinnen und Leser aus der Wissenschaft verweisen wir auf die Buchpublikation Gespräche im Kindergarten als Erwerbskontexte sprachlicher Fähigkeiten, welche 2021 bei Beltz Juventa erscheinen wird und das Projekt und seine Ergebnisse ausführlich darstellt

Comparison of the resistance phenotypes displayed by transformants of the SDHB or SDHC subunits.

<p>Two types of transformants were created, (i) Tr strains where the genes encoding either SDHB or SDHC subunits were ectopically inserted under the control of a GPDA promoter, (ii) HR strains where the WT gene was replaced by a mutated version in its original genomic context. A: SDH inhibition displayed by mitochondrial extracts as measured with the succinate: Q₀/DCPIP reduction test in the presence of varying concentrations of Boscalid. Fitted curve is monophasic with the ectopic transformant containing the WT SDHB expression cassette (black dots) and with the homologous recombinant strain carrying the SDHB_H267L mutation (HR B_H267L, black triangles). Inhibition is biphasic with the ectopic transformant containing the SDHB_H267L expression cassette (Tr B_H267L, black squares). B: Southern blot of genomic DNA extracted from (left to right), the WT (IPO323), one ectopic transformant carrying the WT_SDHB expression cassette, one ectopic transformant carrying the SDHB_H267L expression cassette and signal obtained with one SDHB_H267L homologous recombinant. Boscalid (C) and Fluopyram (D) resistance phenotypes displayed by ectopic and homologous recombinants transformants. In both cases when additional WT SDHB (Tr_WT_SDHB) and SDHC (Tr_WT_SDHC) were inserted ectopically, no significant increase in resistance was observed. When an additional mutated copy of SDHB (Tr_SDHB_H267L) or of SDHC (Tr_SDHC_A84V) was inserted ectopically, significant resistance to the compounds was observed, clearly indicating a dominant effect of the mutated alleles. However, in the homologous recombinant strains where only the mutated subunit SDHB (HR_SDHB_H267L) or SDHC (HR_SDHC_A84_V) was present a further increase in resistance is observed. Whiskers represent minimum and maximum RFs obtained, boxes represent 95% confidence interval and bars value of the median. The data presented correspond to average values of duplicated tests with four independent events of each kind.</p

Tridimensional model of the <i>M. graminicola</i> SDH with Qp site docked carboxamides and interactions to substituted residues.

<p>A: Superposition of all complex II crystal structures with a resolution higher than 3 Å. Only amino acids that are in a 5 Å radius to the bound ligands in the quinone binding site are shown. Amino acids and the heme are represented in lines, the ligands in sticks and water molecules as non bonded spheres. The color code is presented according to atom types. Amino acid and heme carbons are colored in green, ligands carbons in salmon. B: putative binding mode of carboxin in a tridimensional model of <i>M.graminicola</i> SDH. The heme carbons are represented in cyan sticks, the carboxin carbon atoms in salmon. Amino acids that are involved in resistance after mutation are colored in dark blue, amino acids that make key interactions are shown in green and amino acids that are in close proximity to the ligand but which were not found substituted in this study are colored in grey. Hydrogen bonds are shown as yellow dotted lines. C: Putative binding mode of Boscalid in <i>M.graminicola</i> SDH. D: Putative binding mode of Fluopyram in <i>M. graminicola</i> SDH. E: Putative binding mode of Isopyrazam in <i>M. graminicola</i> SDH. F: Model of <i>M. graminicola</i> SDH where SDHB histidine 267 is mutated into a tyrosine. The putative binding mode of the mutated enzyme with Carboxin is shown.</p

Mutagenesis experiments overview.

<p>Mutagenesis experiments overview.</p

Scatter plot presenting <i>in vivo</i> LogIC₅₀ (nM) versus <i>in vitro</i> LogIC₅₀ (nM) adjusted (B) or not (A) for enzyme efficiency.

<p>All data extracted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035429#pone-0035429-t003" target="_blank">table 3</a> and adjusted for amount of enzyme used in the sensitivity test in panel B. Adjustment was performed using enzyme efficiency data extracted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035429#pone-0035429-t004" target="_blank">table 4</a> following a simple equation: if percent efficiency is denoted by E then the efficiency adjusted IC₅₀ = observed IC₅₀×E/100. Following this adjustment the correlation was improved for all compounds.</p

<i>In vivo</i> and <i>in vitro</i> IC50s and resistance factors overview.

<p>Upper panel: <i>In vivo</i> and <i>in vitro</i> IC50 values obtained for the WT (IPO323) ±S.E. (triplicate). Lower panel: resistance factors (RFs) based on IC50 assessment for a selected subset of representative strains. Presented values are based on the ratio of the means of three individual determinations for the <i>in vivo</i> values and based on the ratio of a single determination for the <i>in vitro</i> values. Presented <i>in vitro</i> values were obtained by calibrating mitochondrial dilutions to obtain similar initial velocity (see<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035429#s4" target="_blank"> material and methods</a>). Cbx strains were originally obtained on Carboxin selection media, Flu on Fluopyram, Bos on Boscalid, Izm on Isopyrazam, Ol on pyrrole compound A. nd*: IC₅₀ could not be determined because fitted curves were not tending to 100% inhibition at infinite AI concentration. FR** (full resistance), no sufficient inhibition detected at highest inhibitor concentration tested.</p