Anna Pittaluga

Background/Objectives: The neurotransmitter glycine is involved in several physiological and pathological conditions in the Central Nervous System. Different biological structures, including glycine receptors and transporters, are under study as targets for potential drugs acting against serious neurological and psychiatric disorders. The regulation of glycine release from nerve terminals is only partially understood. We report here preliminary evidence of the modulation of glycine release through presynaptic metabotropic glutamate receptors 1 (mGlu1) from glycinergic nerve terminals in mouse hippocampi. Methods: Purified mouse hippocampal synaptosomes labeled with [³H]glycine were used to study glycine release under superfusion conditions. Results: The group I metabotropic glutamate receptor agonist 3,5-DHPG potentiated depolarization-evoked [³H]glycine release from hippocampal synaptosomes, an effect strongly counteracted by the selective mGlu1 antagonist LY 367385. 3,5-DHPG failed to increase [³H]glycine release in Grm1^crv4/crv4 mice, a mouse model lacking mGlu1. Although further research is needed to clarify these mechanisms, data suggest that glycine-releasing hippocampal nerve terminals are endowed with presynaptic mGlu1 receptors whose activation potentiates glycine release. Conclusions: Considering that in the hippocampus, glycine is relevant as a co-agonist of glutamate at NMDA receptors and that mGlu1 receptor ligands are under study as potential drugs, we propose that the possible effects of these agents on the release of glycine should be considered when studying these compounds.

Ongoing global research actions seek to comprehensively understand the adverse impact of stress and anxiety on the physical and mental health of both human beings and animals. Niaprazine (NIA) is a chemical compound that belongs to the class of piperazine derivatives. This compound has recently gained renewed attention due to its potential therapeutic properties for treating certain conditions such as anxiety. Despite its potential benefits, the behavioral effects of NIA have not been thoroughly investigated. This study aimed to examine NIA’s potential as an anti-anxiety and anti-stress agent. After administering either vehicle or NIA in their drinking water to mice for 14 days, we conducted behavioral analyses using the Marble Burying Test and the Elevated Plus Maze test. NIA-treated mice spend more time in the open arms and bury fewer marbles. Moreover, a stability study confirmed the linear relationship between NIA concentration and its response across concentrations encompassing the NIA mother solution and the NIA solutions administered to mice. Also, a preliminary synaptic toxicity analysis showed no direct damage to cortical nerve endings. Here, we show that NIA can modulate anxiety-related behaviors without significantly impacting exploratory activity or adverse effects. Our work describes new findings that contribute to the research on safer and more tolerable anxiety management options.

Background and Purpose: To deepen our knowledge of the role of complement in synaptic impairment in experimental autoimmune encephalomyelitis (EAE) mice, we investigated the distribution of C1q and C3 proteins and the role of complement as a promoter of glutamate release in purified nerve endings (synaptosomes) and astrocytic processes (gliosomes) isolated from the cortex of EAE mice at the acute stage of the disease (21 ± 1 day post‐immunization).Experimental Approach: EAE cortical synaptosomes and gliosomes were analysed for glutamate release efficiency (measured as release of preloaded [³H]D‐aspartate ([³H]D‐ASP)), C1q and C3 protein density, and for viability and ongoing apoptosis.Key Results: In healthy mice, complement releases [³H]D‐ASP from gliosomes more efficiently than from synaptosomes. The releasing activity occurs in a dilution‐dependent manner and involves the reversal of the excitatory amino acid transporters (EAATs). In EAE mice, the complement‐induced releasing activity is significantly reduced in cortical synaptosomes but amplified in cortical gliosomes. These adaptations are paralleled by decreased density of the EAAT2 protein in synaptosomes and increased EAAT1 staining in gliosomes. Concomitantly, PSD95, GFAP, and CD11b, but not SNAP25, proteins are overexpressed in the cortex of the EAE mice. Similarly, C1q and C3 protein immunostaining is increased in EAE cortical synaptosomes and gliosomes, although signs of ongoing apoptosis or altered viability are not detectable.Conclusion and Implications: Our results unveil a new noncanonical role of complement in the CNS of EAE mice relevant to disease progression and central synaptopathy that suggests new therapeutic targets for the management of MS.

Background: Glymphatic system (GS) is a glial‐dependent perivascular network that under circadian regulation (Hablitz et al, 2020) controls the clearance of waste products in the central nervous system during the sleep (Xie et al, 2013) and its function is suppressed in several neurodegenerative diseases. Our aim is to investigate whether alteration in the circadian‐controlled dynamics of the GS may be the linker between the periphery and the brain. Our hypothesis is that the disruption of the gut‐brain dialogue, due to peripheral colonic inflammation, alters the circadian clockwork both in periphery and CNS, thereby impacting on the circadian‐regulated GS flux in the brain.Method: The peripheral inflammation was obtained using an acute dextran sulfate sodium (DSS) mouse model of colitis. Alterations in GS dynamics and in the relative concentrations of selected metabolites in the brain have been evaluated by MRI and MRS, respectively. Aquaporin‐4, α‐syntropin, Connexin‐43 as well as clock genes expression have been assessed in colon, and in different brain areas, by real‐time PCR. AQP4 mis‐location has been evaluated by transmission electron microscopy.Result: Our data demonstrate that, in DSS‐driven acute colitis model, the inflammatory hit strongly impacts on the circadian clockwork both at peripheric and central level, by altering the expression of the core clock components. Such alteration in the clock components expression pattern correlates with changes in GS dynamics in the brain. In particular, colonic inflammation impacts on the expression of astrocyte aquaporin‐4, as well as of α‐syntropin and Connexin‐43, in both cerebellum and cortex, thus suggesting a potential molecular derangement in the regulation of glymphatic influx. Alterations in GS dynamics have also been detected in the relative concentrations of specific metabolites in selective brain areas by MRS. As a consequence of brain changes in GS dynamics, we observed an increased phospho‐tau deposition in the hippocampus of DSS mice.Conclusion: The characterization of the cascade of events and the relationship among gut inflammation, glymphatic influx alteration and brain waste product deposition has a novel significance since it will allow understanding how a persistent peripheral enteric hit may disorganize a central hierarchy thus triggering a self‐sustaining process prodromal of neurodegeneration.

Autoantibodies against NMDA and AMPA receptors have been identified in the central nervous system of patients suffering from brain disorders characterized by neurological and psychiatric symptoms. It has been demonstrated that these autoantibodies can affect the functions and/or the expression of the targeted receptors, altering synaptic communication. The importance to clarify, in preclinical models, the molecular mechanisms involved in the autoantibody-mediated effects has emerged in order to understand their pathogenic role in central disorders, but also to propose new therapeutic approaches for preventing the deleterious central consequences. In this review, we describe some of the available preclinical literature concerning the impact of antibodies recognizing NMDA and AMPA receptors in neurons. This review discusses the cellular events that would support the detrimental roles of the autoantibodies, also illustrating some contrasting findings that in our opinion deserve attention and further investigations before translating the preclinical observations to clinic.