Prevention and treatment: Effects on pathological alterations in transgenic Alzheimer’s disease mouse models

Alzheimer’s disease (AD) is a neurodegenerative disorder representing the most common form of dementia worldwide. To date, no successful therapeutic approach to treat AD has been developed, hence preventive strategies started to become a major research focus. In this work, the effects of pharmacological treatment strategies such as chronic memantine, caffeine or riluzole supplementation, as well as the effect of a stimulating environmental living condition on the pathological alterations have been examined in Tg4-42hom and 5xFAD mice, representing two different AD mouse models. The Tg4-42 model overexpresses only the Aβ4-42 peptide mainly in the hippocampus, lacking any mutations linked to the familial form of the disease. Although this mouse model does not present overt extracellular Aβ plaques, Aβ4-42 forms neurotoxic aggregates that well correlate with the age- and dose-dependent pyramidal neuron loss in the CA1 region of the hippocampus as well as with robust learning and memory deficits. It could be shown that long-term oral treatment with either memantine, caffeine or riluzole completely rescued behavioural deficits in 6-month-old Tg4-42hom mice. Interestingly, these beneficial effects on learning and memory were accompanied by a significant amelioration of neuronal loss and a robust increase in neurogenesis. The present study presents evidence that long-term oral treatment with these drugs prevents behavioural decline as well as neuron loss and impaired neurogenesis in a mouse model reflecting the sporadic form of AD. Recently, epidemiological data revealed a potential protective role of physical exercise and cognitive stimulation on AD risk. Hence, it could be demonstrated in Tg4-42hom mice that living in a stimulating environment not only improves general behaviour but also ameliorates sensory-motor deficits. We have shown that the housing condition exerts a strong beneficial effect on a typical floating phenotype in Tg4-42hom mice, since none of the animals housed in an enriched environment presented that characteristic.The 5xFAD model is a well-characterized and commonly studied AD mouse model, reflecting first and foremost the familial form of the disease. In the present work, it could be demonstrated that, despite of an amelioration of memory deficits, chronic caffeine intake has no major influence on the typical pathophysiological alterations in the 5xFAD model, since neither changes with regard to Aβ plaque deposition, neuroinflammation, Aβ1-42 levels or APP processing were observed. These results suggest that a therapeutic intervention, such as chronic caffeine administration, might have a crucial impact on cognition without influencing the aggressive AD pathology observed in 5xFAD mice after onset of pathology.2022-05-1

Coinvolgimento del recettore microgliale RAGE nella disfunzione neuronale della corteccia entorinale in un modello murino di malattia di Alzheimer.

RIASSUNTO La malattia di Alzheimer (AD) è una patologia neurodegenerativa cronica con meccanismi fisiopatologici ben definiti; inizialmente colpisce le strutture mediali del lobo temporale, quali l'ippocampo e la corteccia entorinale (EC) per poi diffondersi alle altre strutture corticali. Le principali caratteristiche istopatologiche della malattia sono rappresentate dalle placche neuritiche e dai grovigli neurofibrillari, che sono, rispettivamente, correlate all'accumulo extracellulare del peptide β-amiloide (Aβ) e ai cambiamenti del citoscheletro derivanti dall’iperfosforilazione della proteina associata ai microtubuli Tau. Il nostro studio è stato incentrato sulla EC, una regione paraippocampale coinvolta nell'apprendimento e nella memoria e che mostra un alto grado di plasticità neuronale. Studi recenti condotti nel modello murino che esprime mutazioni umane del gene della proteina precursore dell'amiloide (mhAPPJ20), hanno evidenziato una disfunzione specifica del circuito cortico-ippocampampale. In particolare è stato dimostrato come la neurodegenerazione si diffonda attraverso le connessioni tra EC ed ippocampo. Il nostro obiettivo è stato quello di descrivere l'andamento temporale delle alterazioni della EC, nei topi mhAPPJ20 a diverse stadi di neurodegenerazione. A questo scopo abbiamo registrato potenziali di campo extracellulare nella circuiteria intrinseca dello strato superficiale della EC, utilizzando il preparato in vitro di fettine cerebrali. Inoltre, utilizzando dei test di memoria che si basano sul riconoscimento di oggetti quali novel object recognition task, novel object place recognition task e novel object place context recognition task (ORT, OPRT e OPCRT), abbiamo valutato se i deficit di plasticità sinaptica fossero associati a deficit comportamentali. I nostri studi precedenti hanno dimostrato come la somministrazione esogena di Aβ sia in grado di inibire la plasticità sinaptica dello strato superficiale della EC. Inoltre, abbiamo dimostrato che questo effetto è mediato dal recettore RAGE che interagendo con la Aβ attiva vie di trasduzione del segnale legate allo stress. In particolare RAGE espresso nelle cellule microgliali è in grado, una volta stimolato dalla Aβ, di attivare un processo pro-infiammatorio che contribuisce alla sviluppo delle alterazioni della funzione sinaptica nella EC. Nel presente lavoro abbiamo studiato il ruolo di RAGE utilizzando topi transgenici ottenuti incrociando la linea mhAPPJ20 con topi che esprimono, in modo selettivo nella microglia, una forma dominante negativa del recettore (DNMSR). I nostri risultati dimostrano come la plasticità sinaptica, in particolare l'espressione di potenziamento a lungo termine (LTP), sia compromessa nello strato superficiale dell’EC di topi mhAPP-J20 già ad uno stadio precoce di neurodegenerazione, corrispondente a 2 mesi di età. Tuttavia a questa età non si osservano nelle fettine ottenute da topi mhAPP-J20 variazioni significative, rispetto ai controlli non transgenici, sia nella trasmissione sinaptica di base che nell'espressione dell'altra principale forma di plasticità sinaptica, la depressione a lungo termine (LTD). Ad uno stadio successivo di neurodegenerazione, ovvero a 6 mesi di età, la funzione sinaptica nella EC dei topi mhAPP-J20 risulta ulteriormente compromessa, come evidenziato da una riduzione della forza nella trasmissione sinaptica di base e dall’assenza della espressione di LTD. L’analisi comportamentale eseguita utilizzando l’OPRT e l’OPCRT, due test di memoria associativa dipendenti dalla integrità funzionale della EC, ha inoltre dimostrato che le alterazioni elettrofisiologiche sono associate a un deficit comportamentale nei topi mhAPP-J20 di 2 mesi di età. Mentre, con il progredire della neurodegenerazione, il deficit di memoria si aggrava ed è evidenziabile anche nel test non-associativo (ORT). Al contrario, i dati ottenuti utilizzando i topi doppi transgenici (mhAPPJ20xDNMSR) dimostrano che i deficit sinaptici e comportamentali osservati nei singoli transgenici mhAPPJ20 possono essere recuperati sia a 2 mesi che a 6 mesi di età attraverso l’inibizione selettiva di RAGE nella microglia. Inoltre, i risultati ottenuti in singoli topi transgenici DNMSR dimostrano che l'inibizione selettiva di RAGE nella microglia non è in grado di alterare la funzione sinaptica e il comportamento dipendente dalla EC. Nel loro insieme i nostri risultati confermano un preciso ordine cronologico nel coinvolgimento della EC durante il progressivo accumulo di Aβ ed evidenziano il contributo del recettore pro-infiammatorio RAGE in una fase iniziale della neurodegenerazione nel modello murino mhAPPJ20. ABSTRACT Alzheimer’s disease (AD) is a chronic neurodegenerative disorder with well-defined pathophysiological mechanisms, which is initially restricted to the medial temporal lobe structures, such as hippocampus and entorhinal cortex (EC) and then spreading to other neocortical areas. Neuritic plaques and neurofibrillary tangles represent the major histopathological hallmarks of the disease, and are respectively related to the extracellular accumulation of the amyloid-beta peptide (Aβ), and to cytoskeletal changes resulting from the hyperphosphorylation of microtubule-associated protein Tau. We focused our study on the EC, a parahippocampal brain region involved in learning and memory and exhibiting a high degree of plasticity. In particular cortico hippocampal network dysfunction has been reported in a mouse model expressing human mutations of the amyloid precursor protein gene (mhAPPJ20), suggesting a spreading of neuronal dysfunction within the EC/hippocampal connections. Our aim was to investigate the time course of EC dysfunction in mhAPPJ20 mice in relation to the progressive accumulation of Aβ, corresponding to different stages of neurodegeneration. To this aim we record extracellular field potential in the intrinsic circuitry of EC superficial layer using in vitro brain slices. Moreover, using an associative memory task based on object recognition we evaluated whether synaptic plasticity deficits where associated with a behavioral impairment. Our previous studies demonstrated that exogenously applied Aβ affects synaptic plasticity of superficial layer of the EC. More importantly we demonstrated that this effect are mediated by cell surface receptor RAGE interacting with Aβ and activating specific signal transduction pathways. In particular RAGE expressed in microglial cell has a prominent role in the activation of a proinfiammatory pathway contributing to Aβ dependent EC synaptic dysfunction. In the present work we investigated the role of RAGE using double transgenic mice obtained crossing mhAPPJ20 with mice expressing a dominant negative form of the receptor that was targeted to microglia (DNMSR). Our results show that synaptic plasticity, in particular the expression of long-term potentiation (LTP), is impaired in the EC superficial layer of hAPP-J20 mice, at an early stage of neurodegeneration, i.e. 2 months of age. LTP was specifically altered as basic synaptic transmission and the expression of the other main form of synaptic plasticity, the long-term depression (LTD), were not affected. Moreover, al later stage of neurodegeneration, i.e. 6 months, we observed more complex synaptic deficit, involving LTD impairment and a reduced strength in basic synaptic transmission. These electrophysiological evidences were associated with behavioural deficit as assessed using the OPRT and OPCRT . The results obtained in single transgenic DNMSR mice demonstrate that selective inhibition of RAGE in microglia did not affect either synaptic function or EC-dependent behaviour . More importantly a complete rescue of synaptic and behavioural deficits were observed either at 2 months or 6 months of age in the double transgenic (mhAPPJ20xDNMSR) mice compared to age-matched single mhAPPJ20 mice. Thus, EC dysfunction induced by overexpression of Aβ is an early sign of neurodegeneration that can be prevented by functional suppression of RAGE in microglia. Our findings support the hypothesis of a precise hierarchical order of involvement of different circuitries during the progressive accumulation of Aβ and highlight the contribution of RAGE-dependent inflammatory pathway at an early stage of neurodegeneration in the mhAPPJ20 mouse model

A Combination of Caffeine Supplementation and Enriched Environment in an Alzheimer’s Disease Mouse Model

A variety of factors has been associated with healthy brain aging, and epidemiological studies suggest that physical activity and nutritional supplements such as caffeine may reduce the risk of developing dementia and, in particular, Alzheimer’s disease (AD) in later life. Caffeine is known to act as a cognitive enhancer but has been also shown to positively affect exercise performance in endurance activities. We have previously observed that chronic oral caffeine supplementation and a treatment paradigm encompassing physical and cognitive stimulation by enriched environment (EE) housing can improve learning and memory performance and ameliorate hippocampal neuron loss in the Tg4-42 mouse model of AD. Here, we investigated whether these effects were synergistic. To that end, previous findings on individual treatments were complemented with unpublished, additional data and analyzed in depth by ANOVA followed by Bonferroni multiple comparison post tests. We further evaluated whether plasma neurofilament light chain levels reflect neuropathological and behavioral changes observed in the experimental groups. While a treatment combining physical activity and caffeine supplementation significantly improved learning and memory function compared to standard-housed vehicle-treated Tg4-42 in tasks such as the Morris water maze, no major additive effect outperforming the effects of the single interventions was observed

A Combination of Caffeine Supplementation and Enriched Environment in an Alzheimer’s Disease Mouse Model

A variety of factors has been associated with healthy brain aging, and epidemiological studies suggest that physical activity and nutritional supplements such as caffeine may reduce the risk of developing dementia and, in particular, Alzheimer’s disease (AD) in later life. Caffeine is known to act as a cognitive enhancer but has been also shown to positively affect exercise performance in endurance activities. We have previously observed that chronic oral caffeine supplementation and a treatment paradigm encompassing physical and cognitive stimulation by enriched environment (EE) housing can improve learning and memory performance and ameliorate hippocampal neuron loss in the Tg4-42 mouse model of AD. Here, we investigated whether these effects were synergistic. To that end, previous findings on individual treatments were complemented with unpublished, additional data and analyzed in depth by ANOVA followed by Bonferroni multiple comparison post tests. We further evaluated whether plasma neurofilament light chain levels reflect neuropathological and behavioral changes observed in the experimental groups. While a treatment combining physical activity and caffeine supplementation significantly improved learning and memory function compared to standard-housed vehicle-treated Tg4-42 in tasks such as the Morris water maze, no major additive effect outperforming the effects of the single interventions was observed

A new Montanide™ Seppic IMS1313-adjuvanted autogenous vaccine as a useful emergency tool to resolve a Salmonella enterica subsp. ,i>enterica serovar abortus equi abortion outbreak in mares

Background: In Italy, an autogenous registered vaccine, adjuvanted with aluminum hydroxide, can be administrated to contrast Salmonella enterica subsp. enterica serovar abortus equi infection, coupled to a specific antimicrobial treatment.Case Description: Here, we report the case of an abortion outbreak by Salmonella abortus equi in Central Italy where mares were vaccinated but immediately developed a strong local reaction, maybe due to the adjuvant. Promptly, another autogenous vaccine, substituting the aluminum hydroxide with a new generation adjuvant (Montanide™ Seppic IMS1313), was produced and administrated. The new formulated vaccine did not cause any adverse outcome and conferred high protection titers against the infection. To the best of our knowledge, this is the first reported case of immunization by a vaccine adjuvanted with Montanide™ Seppic IMS1313 in horses.Conclusion: This approach may be used as a preventive strategy for further outbreaks in association with the application of recommended biosafety principles

Identification of Resistance Genes and Response to Arsenic in Rhodococcus aetherivorans BCP1

Arsenic (As) ranks among the priority metal(loid)s that are of public health concern. In the environment, arsenic is present in different forms, organic or inorganic, featured by various toxicity levels. Bacteria have developed different strategies to deal with this toxicity involving different resistance genetic determinants. Bacterial strains of Rhodococcus genus, and more in general Actinobacteria phylum, have the ability to cope with high concentrations of toxic metalloids, although little is known on the molecular and genetic bases of these metabolic features. Here we show that Rhodococcus aetherivorans BCP1, an extremophilic actinobacterial strain able to tolerate high concentrations of organic solvents and toxic metalloids, can grow in the presence of high concentrations of As(V) (up to 240 mM) under aerobic growth conditions using glucose as sole carbon and energy source. Notably, BCP1 cells improved their growth performance as well as their capacity of reducing As(V) into As(III) when the concentration of As(V) is within 30–100 mM As(V). Genomic analysis of BCP1 compared to other actinobacterial strains revealed the presence of three gene clusters responsible for organic and inorganic arsenic resistance. In particular, two adjacent and divergently oriented ars gene clusters include three arsenate reductase genes (arsC1/2/3) involved in resistance mechanisms against As(V). A sequence similarity network (SSN) and phylogenetic analysis of these arsenate reductase genes indicated that two of them (ArsC2/3) are functionally related to thioredoxin (Trx)/thioredoxin reductase (TrxR)-dependent class and one of them (ArsC1) to the mycothiol (MSH)/mycoredoxin (Mrx)-dependent class. A targeted transcriptomic analysis performed by RT-qPCR indicated that the arsenate reductase genes as well as other genes included in the ars gene cluster (possible regulator gene, arsR, and arsenite extrusion genes, arsA, acr3, and arsD) are transcriptionally induced when BCP1 cells were exposed to As(V) supplied at two different sub-lethal concentrations. This work provides for the first time insights into the arsenic resistance mechanisms of a Rhodococcus strain, revealing some of the unique metabolic requirements for the environmental persistence of this bacterial genus and its possible use in bioremediation procedures of toxic metal contaminated sites

N-truncated Aβ4–x peptides in sporadic Alzheimer’s disease cases and transgenic Alzheimer mouse models

Abstract Background The deposition of neurotoxic amyloid-β (Aβ) peptides in plaques in the brain parenchyma and in cerebral blood vessels is considered to be a key event in Alzheimer’s disease (AD) pathogenesis. Although the presence and impact of full-length Aβ peptides such as Aβ1–40 and Aβ1–42 have been analyzed extensively, the deposition of N-terminally truncated Aβ peptide species has received much less attention, largely because of the lack of specific antibodies. Methods This paper describes the generation and characterization of novel antibodies selective for Aβ4–x peptides and provides immunohistochemical evidence of Aβ4–x in the human brain and its distribution in the APP/PS1KI and 5XFAD transgenic mouse models. Results The Aβ4–x staining pattern was restricted mainly to amyloid plaque cores and cerebral amyloid angiopathy in AD and Down syndrome cases and in both AD mouse models. In contrast, diffuse amyloid deposits were largely negative for Aβ4–x immunoreactivity. No overt intraneuronal staining was observed. Conclusions The findings of this study are consistent with previous reports demonstrating a high aggregation propensity of Aβ4–x peptides and suggest an important role of these N-truncated Aβ species in the process of amyloidogenesis and plaque core formation

Additional file 3: Figure S3. of N-truncated Aβ4–x peptides in sporadic Alzheimer’s disease cases and transgenic Alzheimer mouse models

Predominant plaque core staining using 029-2 in a patient with sporadic AD. (PDF 183 kb

Incidence of Pneumothorax and Pneumomediastinum in 497 COVID-19 Patients with Moderate–Severe ARDS over a Year of the Pandemic: An Observational Study in an Italian Third Level COVID-19 Hospital

Background: COVID-19 is a novel cause of acute respiratory distress syndrome (ARDS). Indeed, with the increase of ARDS cases due to the COVID-19 pandemic, there has also been an increase in the incidence of cases with pneumothorax (PNX) and pneumomediastinum (PNM). However, the incidence and the predictors of PNX/PMN in these patients are currently unclear and even conflicting. (2) Methods: The present observational study analyzed the incidence of barotrauma (PNX/PNM) in COVID-19 patients with moderate–severe ARDS hospitalized in a year of the pandemic, also focusing on the three waves occurring during the year, and treated with positive-pressure ventilation (PPV). We collected demographic and clinical data. (3) Results: During this period, 40 patients developed PNX/PNM. The overall incidence of barotrauma in all COVID-19 patients hospitalized in a year was 1.6%, and in those with moderate–severe ARDS in PPV was 7.2% and 3.8 events per 1000 positive-pressure ventilator days. The incidence of barotrauma in moderate–severe ARDS COVID-19 patients during the three waves was 7.8%, 7.4%, and 8.7%, respectively. Treatment with noninvasive respiratory support alone was associated with an incidence of barotrauma of 9.1% and 2.6 events per 1000 noninvasive ventilator days, of which 95% were admitted to the ICU after the event, due to a worsening of respiratory parameters. The incidence of barotrauma of ICU COVID-19 patients in invasive ventilation over a year was 5.8% and 2.7 events per 1000 invasive ventilator days. There was no significant difference in demographics and clinical features between the barotrauma and non-barotrauma group. The mortality was higher in the barotrauma group (17 patients died, 47.2%) than in the non-barotrauma group (170 patients died, 37%), although this difference was not statistically significant (p = 0.429). (4) Conclusions: The incidence of PNX/PNM in moderate–severe ARDS COVID-19 patients did not differ significantly between the three waves over a year, and does not appear to be very different from that in ARDS patients in the pre-COVID era. The barotrauma does not appear to significantly increase mortality in COVID-19 patients with moderate–severe ARDS if protective ventilation strategies are applied. Attention should be paid to the risk of barotrauma in COVID-19 patients in noninvasive ventilation because the event increases the probability of admission to the intensive care unit (ICU) and intubation