Herpes Simplex Virus type-1 infection induces synaptic dysfunction in cultured cortical neurons via GSK-3 activation and intraneuronal amyloid-β protein accumulation

Increasing evidence suggests that recurrent Herpes Simplex Virus type 1 (HSV-1) infection spreading to the CNS is a risk factor for Alzheimer's Disease (AD) but the underlying mechanisms have not been fully elucidated yet. Here we demonstrate that in cultured mouse cortical neurons HSV-1 induced Ca 2+ -dependent activation of glycogen synthase kinase (GSK)-3. This event was critical for the HSV-1-dependent phosphorylation of amyloid precursor protein (APP) at Thr668 and the following intraneuronal accumulation of amyloid-β protein (Aβ). HSV-1-infected neurons also exhibited: i) significantly reduced expression of the presynaptic proteins synapsin-1 and synaptophysin; ii) depressed synaptic transmission. These effects depended on GSK-3 activation and intraneuronal accumulation of Aβ. In fact, either the selective GSK-3 inhibitor, SB216763, or a specific antibody recognizing Aβ (4G8) significantly counteracted the effects induced by HSV-1 at the synaptic level. Moreover, in neurons derived from APP KO mice and infected with HSV-1 Aβ accumulation was not found and synaptic protein expression was only slightly reduced when compared to wild-type infected neurons. These data further support our contention that HSV-1 infections spreading to the CNS may contribute to AD phenotype

APP Processing Induced by Herpes Simplex Virus Type 1 (HSV-1) Yields Several APP Fragments in Human and Rat Neuronal Cells

Lifelong latent infections of the trigeminal ganglion by the neurotropic herpes simplex virus type 1 (HSV-1) are characterized by periodic reactivation. During these episodes, newly produced virions may also reach the central nervous system (CNS), causing productive but generally asymptomatic infections. Epidemiological and experimental findings suggest that HSV-1 might contribute to the pathogenesis of Alzheimer's disease (AD). This multifactorial neurodegenerative disorder is related to an overproduction of amyloid beta (Aβ) and other neurotoxic peptides, which occurs during amyloidogenic endoproteolytic processing of the transmembrane amyloid precursor protein (APP). The aim of our study was to identify the effects of productive HSV-1 infection on APP processing in neuronal cells. We found that infection of SH-SY5Y human neuroblastoma cells and rat cortical neurons is followed by multiple cleavages of APP, which result in the intra- and/or extra-cellular accumulation of various neurotoxic species. These include: i) APP fragments (APP-Fs) of 35 and 45 kDa (APP-F35 and APP-F45) that comprise portions of Aβ; ii) N-terminal APP-Fs that are secreted; iii) intracellular C-terminal APP-Fs; and iv) Aβ1-40 and Aβ1-42. Western blot analysis of infected-cell lysates treated with formic acid suggests that APP-F35 may be an Aβ oligomer. The multiple cleavages of APP that occur in infected cells are produced in part by known components of the amyloidogenic APP processing pathway, i.e., host-cell β-secretase, γ-secretase, and caspase-3-like enzymes. These findings demonstrate that HSV-1 infection of neuronal cells can generate multiple APP fragments with well-documented neurotoxic potentials. It is tempting to speculate that intra- and extracellular accumulation of these species in the CNS resulting from repeated HSV-1 reactivation could, in the presence of other risk factors, play a co-factorial role in the development of AD

APP processing induced by herpes simplex virus type 1 (HSV-1) results in the production of several APP fragments and Aβ accumulation in human and rat neuronal cells

Background: HSV-1 is a neurotropic virus that, following primary infection, usually establishes a lifelong latent infection in the trigeminal ganglion. Following periodic reactivations, the newly produced viral particles may be transported to the central nervous system (CNS), resulting in productive but usually asymptomatic infections. Possible links between recurrent HSV-1 infections and Alzheimer's disease (AD) have emerged from epidemiological studies and experimental findings. We have recently found that HSV-1 produces marked changes in neuronal excitability and intracellular Ca2+ signalling which affect the phosphorylation of amyloid precursor protein (APP) and result in intracellular accumulation of amyloid-β peptide (Aβ)

Pathogenic DNM1L variant (1085G>A) linked to infantile progressive neurological disorder: Evidence of maternal transmission by germline mosaicism and influence of a contemporary in cis variant (1535T>C)

Mitochondria are dynamic organelles undergoing continuous fusion and fission with Drp1, encoded by the DNM1L gene, required for mitochondrial fragmentation. DNM1L dominant pathogenic variants lead to progressive neurological disorders with early exitus. Herein we report on the case of a boy affected by epileptic encephalopathy carrying two heterozygous variants (in cis) of the DNM1L gene: a pathogenic variant (PV) c.1085G>A (p.Gly362Asp) accompanied with a variant of unknown significance (VUS) c.1535T>C (p.Ile512Thr). Amplicon sequencing of the mother’s DNA revealed the presence of the PV and VUS in 5% of cells, with the remaining cells presenting only VUS. Functional investigations performed on the patient and his mother’s cells unveiled altered mitochondrial respiratory chain activities, network architecture and Ca2+ homeostasis as compared with healthy unrelated subjects’ samples. Modelling Drp1 harbouring the two variants, separately or in combination, resulted in structural changes as compared with Wt protein. Considering the clinical history of the mother, PV transmission by a maternal germline mosaicism mechanism is proposed. Altered Drp1 function leads to changes in the mitochondrial structure and bioenergetics as well as in Ca2+ homeostasis. The novel VUS might be a modifier that synergistically worsens the phenotype when associated with the PV

Herpes Simplex Virus type 1 (HSV-1) increases the excitability of rat neocortical neurons and triggers amyloid precursor protein (APP) processing.

Introduction: HSV-1 infection may spread within the central nervous system and cause neurological disorders including encephalitis and epileptic seizures. Recurrent HSV-1 infections have also been proposed to play a co-factorial role in the pathogenesis of Alzheimer\u2019s disease. Objective: Aim of our study was to determine the effects of HSV-1 on electrophysiological properties of cortical neurons, and the pathophysiological impact of virally induced changes. Methods: Patch-clamp, immunofluorescence and Western blot experiments were performed on rat cultured cortical neurons either soon after challenge with HSV-1 or 12 24 hours post-infection (hpi). Results: Cell exposure to HSV-1 induced membrane depolarization (11.8\ub10.7 mV) that triggered action potentials and increased the discharge rate of spontaneously firing neurons (from 0.1\ub10.1 to 1.1\ub10.3 Hz). This effect depended on viral binding to neuronal membrane. In fact, when cells were challenged with HSV-1 pretreated with heparin (which prevents the binding of viral glicoproteins to membrane receptors) no depolarization was observed whereas when we applied UV-inactivated HSV-1 (that binds to membrane but is unable to replicate) the observed responses were similar to those produced by active virus. In most neurons, membrane depolarization started soon after HSV-1 application and steady-state was reached after 2 10 s. This effect was due to both inhibition of leak K+ currents and increase of persistent Na+ currents (+53% at 20 mV). Neither transient Na+ currents nor Ca2+ currents were affected. Similar effects were observed 12 hpi. The HSV-1-induced neuronal hyperexcitability triggered intracellular Ca2+ signals promoting APP processing and intracellular and extracellular accumulation of amyloid-b peptide and several neurotoxic APP fragments. Conclusions: Changes in neuronal electrophysiological properties induced by HSV-1 may play a role in the pathophysiology of epileptic seizures and neurodegeneration

HSV-1 and CNS: the long term effects of a lasting affair

Starting from the pioneering studies showing evidence of herpes simplex virus type-1 (HSV-1) genome in Alzheimer’s disease (AD) brains, different epidemiological and experimental reports have proposed a possible connection between AD risk and HSV-1 recurrent infections. The main hypothesis is that, beyond massive HSV-1 entry in the brain, resulting in rare, but severe form of herpetic encephalitis, milder cerebral infection may also occur, followed by latency and virus reactivations, whose damages, may accumulate over life and result in pathologic outcomes in the elderly. This paper provides a review of literature supporting HSV-1 as a risk factor for neurodegeneration and showing the possible mechanisms involve

HSV-1 and CNS: the long term effects of a lasting affair

Starting from the pioneering studies showing evidence of herpes simplex virus type-1 (HSV-1) genome in Alzheimer’s disease (AD) brains, different epidemiological and experimental reports have proposed a possible connection between AD risk and HSV-1 recurrent infections. The main hypothesis is that, beyond massive HSV-1 entry in the brain, resulting in rare, but severe form of herpetic encephalitis, milder cerebral infection may also occur, followed by latency and virus reactivations, whose damages, may accumulate over life and result in pathologic outcomes in the elderly. This paper provides a review of literature supporting HSV-1 as a risk factor for neurodegeneration and showing the possible mechanisms involve

Prevalence of the bullying phenomenon in a schools sample of Palermo, Sicily: A pre-post intervention observational study among teachers

Background and aim of the work: Bullying involves a significant percentage of school-age children. According to the latest available surveillance data, in Sicily, the estimated prevalence among 11-15 years old children is 14%. This study aimed to estimate a prevalence of the bullying phenomenon, observed by teachers, in a sample of secondary schools of Palermo, Sicily. Moreover, after the conduction of preventive interventions among teachers, aimed to evaluate any modification in bullying prevalence. Methods: A cluster sampling selection according to socio-economic level of the school neighborhood was carried out. Two anonymous online questionnaires, pre and post-intervention, were administered to the 63 teaching staff, belonging to second and third year classes of ten secondary schools enrolled. Preventive interventions were conducted among teachers by experienced researchers. Results: Prevalence of bullying reported decreased significantly from 44.4% to 19.0% (p-value 0.001), comparing pre and post-intervention questionnaires. A reduction in the prevalence of verbal and physical bullying and a concomitant slight increase of indirect bullying were also observed. All the characteristics, reported by the teaching staff, for describing bullies, victims and observers of bullying have been categorized under three different content domains (affective-relational discomfort, sociocultural context, and character/natural disposition). Conclusions: The present study estimated the prevalence and the characteristics of bullying phenomenon in a sample of secondary schools of Palermo, evaluating the reduction of bullying episodes among students, after a preventive interventions conducted among teaching staff. Data obtained confirmed the effectiveness of this approach and suggested an extension of the project at Regional Level

Prevalence of smoking habits, attitudes and knowledge on counteractive strategies among a sample of healthcare employees: results of the smoking-free health environments project in the province of Palermo, Italy

Introduction: Tobacco use is responsible for over 7 million deaths annually, making smoking the leading cause of preventable mortality globally. Over the last two decades in Italy, the prevalence of smoking among physicians has consistently decreased, while it remains higher and is gradually decreasing among non-physician healthcare workers. The aim of this study was to investigate the Prevalence of smoking habits, attitudes, and knowledge on counteractive strategies among employees in the Primary Healthcare Facilities in the Province of Palermo, Italy.Methods: A cross-sectional survey was conducted between June 2020 and December 2020 through a previously validated anonymous questionnaire structured in four sections including 34 items. Data were analyzed using Stata/MP 12.1 statistical software.Results: Overall, 2,645 participants answered the questionnaire. The prevalence of either current or former smokers was 18.6%. Based on the multivariable analysis conducted, a significantly higher frequency of current smokers was observed among male participants (AdjOR: 1.29; CI95%: 1.02-1.64) and those belonging to the Surgical Unit (AdjOR: 1.92; CI95%: 1.27-2.90). Conversely, the prevalence of current smokers was significantly lower among those with at least one child (AdjOR: 0.67; CI95%: 0.49-0.91), with an educational qualification equal to or greater than a graduation degree (AdjOR: 0.56; CI95%: 0.43-0.73), those who considered second-hand smoke harmful (AdjOR: 0.06; CI95%: 0.008-0.60), those who had observed smoking or detected the smell of smoke in their workplace (AdjOR: 0.64; CI95%: 0.45-0.91). Furthermore, the prevalence of current smokers was significantly lower among participants who believed that healthcare professionals could play a crucial role in influencing their patients' lifestyles (AdjOR: 0.67; CI95%: 0.50-0.90) and among those who recommend their patients to quit smoking (AdjOR: 0.35; CI95%: 0.24-0.51).Discussion: The results of the current research demonstrate that, despite the decline in smoking prevalence among physicians, the rate of smokers among healthcare facility employees remains unacceptably high. This underscores the need to re-evaluate current anti-tobacco strategies in the workplace