Focusing and orienting spatial attention differently modulate crowding in central and peripheral vision

The allocation of attentional resources to a particular location or object in space involves two distinct processes: an orienting process and a focusing process. Indeed, it has been demonstrated that performance of different visual tasks can be improved when a cue, such as a dot, anticipates the position of the target (orienting), or when its dimensions (as in the case of a small square) inform about the size of the attentional window (focusing). Here, we examine the role of these two components of visuo-spatial attention (orienting and focusing) in modulating crowding in peripheral (Experiment 1 and Experiment 3a) and foveal (Experiment 2 and Experiment 3b) vision. The task required to discriminate the orientation of a target letter "T,'' close to acuity threshold, presented with left and right "H'' flankers, as a function of target-flanker distance. Three cue types have been used: a red dot, a small square, and a big square. In peripheral vision (Experiment 1 and Experiment 3a), we found a significant improvement with the red dot and no advantage when a small square was used as a cue. In central vision (Experiment 2 and Experiment 3b), only the small square significantly improved participants' performance, reducing the critical distance needed to recover target identification. Taken together, the results indicate a behavioral dissociation of orienting and focusing attention in their capability of modulating crowding. In particular, we confirmed that orientation of attention can modulate crowding in visual periphery, while we found that focal attention can modulate foveal crowdin

DAT atypical inhibitors as novel antipsychotic drugs

Despite its classification as a psychiatric disease, schizophrenia is both a behavioral and a biological disorder resulting in neurocognitive dysfunction. Social and economic costs of schizophrenia are extremely high compared to its incidence and prevalence, however, due to a heterogeneous pattern of brain pathology and symptoms and to an unknown etiology, developing an effective treatment has been really challenging. Among the many neurochemical hypothesis, the dysregulation of dopaminergic neurotransmission has been considered as a central dogma of schizophrenia over the last few decades. In fact, patients with this pathology exhibit increased dopamine (DA) synthesis and release in the striatum which seems to correlate with positive symptoms and moreover, most of the effective antipsychotic drugs (APDs) are D2-receptor antagonists. Unfortunately, chronic treatment with APDs is associated with the induction of extrapyramidal side effects (EPS). In order to identify new possible APDs with a novel mechanism of action and potentially less EPS we tested 3 different compounds generated from the structural modification of vanoxerine (or GBR12909), a known atypical inhibitor of the presynaptic DA transporter (DAT) with cocaine-like activity but cardiotoxic properties that have precluded its clinical use. Preliminary in vitro studies showed that DAhLIs (DAT atypical inhibitors) are able to bind to DAT and inhibit DA reuptake. Additionally, our in vivo results showed that DAhLI i) have putative central effects, ii), unlike vanoxerine, reduce novelty-induced locomotor activity, and iii) counteract cocaine stimulating effects, suggesting that DAhLI may potentiate DA reuptake via DAT. These compounds may provide a way to reduce DA extracellular levels and DA neurotransmission with a selective action on active DA synapses, thus with reduced EPS typical of D2 antagonists, representing a new promising class of presynaptic APDs

Identification of a Thyroid Hormone Derivative as a Pleiotropic Agent for the Treatment of Alzheimer's Disease.

The identification of effective pharmacological tools for Alzheimer's disease (AD) represents one of the main challenges for therapeutic discovery. Due to the variety of pathological processes associated with AD, a promising route for pharmacological intervention involves the development of new chemical entities that can restore cellular homeostasis. To investigate this strategy, we designed and synthetized SG2, a compound related to the thyroid hormone thyroxine, that shares a pleiotropic activity with its endogenous parent compound, including autophagic flux promotion, neuroprotection, and metabolic reprogramming. We demonstrate herein that SG2 acts in a pleiotropic manner to induce recovery in a C. elegans model of AD based on the overexpression of Aβ42 and improves learning abilities in the 5XFAD mouse model of AD. Further, in vitro ADME-Tox profiling and toxicological studies in zebrafish confirmed the low toxicity of this compound, which represents a chemical starting point for AD drug development

PLGA-PEG-ANG-2 Nanoparticles for Blood-Brain Barrier Crossing: Proof-of-Concept Study

The treatment of diseases that affect the central nervous system (CNS) represents a great research challenge due to the restriction imposed by the blood-brain barrier (BBB) to allow the passage of drugs into the brain. However, the use of modified nanomedicines engineered with different ligands that can be recognized by receptors expressed in the BBB offers a favorable alternative for this purpose. In this work, a BBB-penetrating peptide, angiopep-2 (Ang-2), was conjugated to poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles through pre- and post-formulation strategies. Then, their ability to cross the BBB was qualitatively assessed on an animal model. Proof-of-concept studies with fluorescent and confocal microscopy studies highlighted that the brain-targeted PLGA nanoparticles were able to cross the BBB and accumulated in neuronal cells, thus showing a promising brain drug delivery system

H3.3A e H3.3B: distribuzione regionale ed espressione cellulare delle isoforme della variante istonica H3.3 in diverse condizioni fisiologiche

Le varianti istoniche svolgono un ruolo fondamentale nel complesso scenario dell’epigenetica e del rimodellamento della cromatina; l’evidenza della loro incorporazione replicazione-indipendente all’interno della cromatina e di un turnover rapido hanno recentemente portato a ipotizzare un loro coinvolgimento nella fisiopatologia e plasticità del sistema nervoso centrale (SNC), ma rimane ancora da chiarire quale parte svolgano in questi processi. La variante istonica H3.3, altamente espressa nel cervello, è codificata da due diversi geni chiamati H3f3a e H3f3b. Sebbene le proteine che ne derivano, rispettivamente H3.3A e H3.3B, siano identiche, inattivando H3f3b si genera un fenotipo più grave rispetto a H3f3a, il che suggerisce la mancanza di una completa sovrapposizione funzionale. Questi diversi fenotipi potrebbero derivare da una diversa espressione cellulo-specifica e distribuzione regionale nel SNC delle due isoforme. Al fine di comprendere il ruolo funzionale dell’espressione della variante H3.3 nel SNC è necessario dunque chiarire la localizzazione e l'espressione cellulare delle due isoforme. Questo consentirà di definire se il turnover di H3.3A e H3.3B, singolarmente o insieme, è alla base di processi neuroplastici e alterazioni funzionali in specifici circuiti neuronali. In questo progetto di tesi sono stati usati topi H3.3A (WT/HA-fH3.3A) e H3.3B (WT/HA-fH3.3B) che esprimono un tag di emoagglutinina (HA) per eseguire un'analisi dettagliata della distribuzione delle isoforme di H3.3, nelle regioni di sostanza bianca e grigia del SNC, tramite immunoistochimica (IHC) semi-quantitativa. È stata inoltre valutata l’espressione cellulo-specifica di queste proteine mediante l’utilizzo di anticorpi diretti contro microglia, astrociti, oligodendrociti e neuroni grazie a tecniche di doppia immunofluorescenza e microscopia confocale ad alta risoluzione. H3.3A e H3.3B hanno una differente distribuzione nel SNC, per entrambe molto diffusa ma eterogenea, e, per quanto riguarda la loro espressione cellulare, sono per la maggior parte, ma non esclusivamente, espresse dai neuroni. Tecniche innovative quali la chiarificazione dei tessuti e la microscopia a foglio di luce hanno permesso di ottenere una visione d’insieme della localizzazione delle isoforme di H3.3 nell’intero cervello. Abbiamo infine studiato i possibili cambiamenti nell’espressione di H3.3 in diverse condizioni fisiologiche, quali l’invecchiamento e l’esposizione ad ambiente arricchito, una procedura che mima gli effetti neurotrofici e neuroprotettivi di un livello elevato di istruzione negli uomini. In quest’ultimo modello, è stato osservato un incremento nell’espressione di H3.3B in specifiche aree cerebrali e specifici tipi cellulari. I nostri risultati descrivono per la prima volta la precisa distribuzione regionale ed espressione cellulare delle due isoforme di H3.3 nel SNC di topo così come i loro cambiamenti in varie condizioni fisiologiche. Questo studio apre la strada alla generazione di topi knock-out condizionali per specifiche popolazioni cellulari al fine di comprendere il contributo delle isoforme di H3.3 in specifici circuiti cerebrali.Histone variants play a fundamental role in the complex scenery of epigenetic dynamics and chromatin remodelling; their replication-independent incorporation into chromatin and rapid turnover have recently suggested their involvement in central nervous system (CNS) pathophysiology and plasticity, though their precise role is still to be elucidated. The H3.3 histone variant, highly expressed in the brain, is encoded by two different intron-containing genes namely H3f3a and H3f3b. Although the coded proteins, H3.3A and H3.3B respectively, are identical, knocking out H3f3b generates a more severe phenotype compared to H3f3a, suggesting the lack of a complete functional overlap. This different impact may derive from a differential cell-type expression and regional distribution in the CNS. In order to investigate the functional role of H3.3 variant expression in the CNS it is therefore necessary to clarify the localization and cellular expression of the two isoforms. This will permit to define whether H3.3A and H3.3B turnover, alone or together, participates to molecular mechanisms that lead to neuroplasticity in specific neuronal circuits and associated functions. In this project, hemagglutinin (HA)-tagged H3.3A (WT/HA-fH3.3A) and HA-tagged H3.3B (WT/HA-fH3.3B) mice were used to perform a detailed analysis of H3.3 isoform distribution in CNS white and grey matter regions, by using semi-quantitative immunohistochemistry (IHC). Moreover, cell-specific expression of these proteins was assessed by using specific antibodies against microglia, astrocytes, oligodendrocytes and neurons through double immunofluorescent (IF) stainings and high-resolution confocal microscopy. H3.3A and H3.3B have a widespread though different region-specific distribution and, as concerns their cellular expression, they are mostly, though not exclusively, expressed by neurons. Innovative techniques such as tissue clearing and lightsheet microscopy allowed us to obtain an overall view of H3.3 isoform distribution in the whole brain. Finally, we investigated the possible changes in H3.3 expression in various physiological conditions, including ageing and exposure to an enriched environment, a procedure that models the neurotrophic and neuroprotective impact of high educational attainment in humans. In this latter model, an increased expression of H3.3B variant in specific brain areas and cell types was observed. Our results demonstrate for the first time a different regional distribution and cellular expression of the two H3.3 isoforms in the mouse CNS as well as their changes in various physiological conditions. This opens up a path to the generation of cell-population specific conditional knock-out mice to elucidate H3.3 isoform contribution to the function of precise cerebral circuits

Targeting Metal Homeostasis as a Therapeutic Strategy for Alzheimer’s Disease

ABSTRACT Trace metals play an important role in the pathophysiology of amyloid precursor protein, amyloid beta, and tau, the key molecules involved in Alzheimer's disease. Altering trace metal concentrations in the brain has been explored as a therapeutic strategy for Alzheimer's disease. It is not only the accumulation of metals that drives amyloid beta aggregation, but also the lack of sufficient trace metals for other biological processes created through sequestration by amyloid beta that affects brain health and function. Thus, balancing metal levels to achieve therapeutic effects is an intricate process. This chapter summarizes the role of trace metals in Alzheimer's disease and highlights the preclinical and clinical studies targeting metal homeostasis in animal models and humans. It further discusses recent developments in pharmacological approaches targeting metals in Alzheimer's disease and provides an outlook on possible future treatments based on current translational research, for example, nanomedicine

S100B dysregulation during brain development affects synaptic SHANK protein networks via alteration of zinc homeostasis

Autism Spectrum Disorders (ASD) are caused by a combination of genetic predisposition and nongenetic factors. Among the nongenetic factors, maternal immune system activation and zinc deficiency have been proposed. Intriguingly, as a genetic factor, copy-number variations in S100B, a pro-inflammatory damage-associated molecular pattern (DAMP), have been associated with ASD, and increased serum S100B has been found in ASD. Interestingly, it has been shown that increased S100B levels affect zinc homeostasis in vitro. Thus, here, we investigated the influence of increased S100B levels in vitro and in vivo during pregnancy in mice regarding zinc availability, the zinc-sensitive SHANK protein networks associated with ASD, and behavioral outcomes. We observed that S100B affects the synaptic SHANK2 and SHANK3 levels in a zinc-dependent manner, especially early in neuronal development. Animals exposed to high S100B levels in utero similarly show reduced levels of free zinc and SHANK2 in the brain. On the behavioral level, these mice display hyperactivity, increased stereotypic and abnormal social behaviors, and cognitive impairment. Pro-inflammatory factors and zinc-signaling alterations converge on the synaptic level revealing a common pathomechanism that may mechanistically explain a large share of ASD cases

Nanomedicine against Aβ aggregation by β–sheet breaker peptide delivery:In vitro evidence

The accumulation of amyloid β (Aβ) triggers a cascade of toxic events in Alzheimer’s disease (AD). The KLVFF peptide can interfere with Aβ aggregation. However, the peptide suffers from poor bioavailability and the inability to cross the blood–brain barrier. In this work, we study the possibility of adopting nanomedicine to overcome KLVFF limits in biodistribution. We produced new engineered polymeric nanoparticles (NPs), and we evaluated the cellular toxicity of these NPs and validated that KVLFF peptides released by NPs show the same promising effects on AD pathology. Our results revealed the successful generation of KVLFF loaded NPs that, without significant effects on cell heath, are even more potent in reversing Aβ-induced pathologies compared to the free peptide. Therefore, NPs will significantly advance KVLFF treatment as a therapeutic option for AD