Systemic inflammatory impact of periodontitis on cognitive impairment.

OBJECTIVES: The role in dementia of systemic inflammation derived from periodontal disease is not fully elucidated. The objective of our study was to examine the impact of inflammation on the relationship between periodontitis and cognitive impairment. METHODS: We have designed a case (n = 171) and control (n = 131) study to determine the periodontal health status, grade of cognitive impairment/dementia and systemic inflammation level, the last being measured by analysis of 29 inflammatory biomarkers using multiplex techniques. RESULTS: At the time of sampling, 11 of the 29 inflammatory biomarkers were associated with cognitive impairment in patients with more severe periodontitis. However, the inflammatory response to severe periodontitis was more reduced (lower biomarker concentrations) in cases (with cognitive impairment or dementia) than in (cognitively healthy) controls, an unexpected finding. CONCLUSIONS: Based on these results, we cannot confirm that systemic inflammation derived from periodontal disease plays a relevant role in the aetiology of cognitive impairment.

Preclinical safety and immunological efficacy of Alternaria alternata polymerized extracts.

INTRODUCTION: Alternaria alternata is a widespread fungi whose allergy is a risk factor for asthma development. The use of a polymerized allergen extract (allergoid) may be safer than native extract based treatments while maintaining efficacy. The objective of this study was to characterize biochemically and immunochemically a new Alternaria alternata allergoid. METHODS: Characterization of native and allergoid extracts was performed by determination of protein content, protein and allergenic profile, biological potency, identification of Alternaria allergens, and Alt a 1 quantification. Safety was evaluated in toxicological assays (Ames test, limit test, and fish embryo acute toxicity test in zebrafish, and maximum tolerated dose and Dose-range finding study in rats). Efficacy was evaluated as the capacity to induce IgG antibodies that block IgE-binding to the allergen and cytokine induction (IFN-γ, IL-4, IL-6, IL-10, and TNF-α) in PBMC from atopic donors. RESULTS: Protein and antigenic profiles showed significant modification of the depigmented allergoid with respect to the native extract, inducing a lower IgE binding capacity. Alt a 1, Alt a 3, Alt a 6, and Alt a 8 allergen sequences were identified in the polymer. No toxicological nor genotoxicity effects were observed. The polymer induced IgG antibodies that blocked human IgE binding epitopes, and it induced higher IL-10 levels and similar levels of the other cytokines than native extract in PBMC. CONCLUSIONS: This new A. alternata allergoid could be an effective immunotherapy treatment leading to cytokine stimulation and inducing synthesis of IgG antibodies able to block IgE binding to the allergen. In addition, no toxicological effect was observed, and it may be safer than native extract due to its lower IgE binding capacity and cytokine induction that suggest tolerance induction via T cell shift to Treg (IL-10).

Association Between Periodontitis and Amyloid ß Peptide in Elderly People With and Without Cognitive Impairment.

BACKGROUND: Evidence that periodontal disease is a possible risk factor for cognitive impairment may be explained by the inflammatory hypothesis. The aim of this study is to determine whether periodontitis is related to the amyloid ß (Aß) load in blood and the role of any such relationship in the association between Aß and cognitive impairment. METHODS: A case-control study was performed in elderly people diagnosed with cognitive impairment with or without dementia (cases group) and cognitively healthy elderly people (control group); data were collected on the medical and dental history of participants, and blood samples were drawn to determine Aß levels using enzyme-linked immunosorbent assay. RESULTS: The study included 166 patients and 122 control participants. Higher blood Aß1-42 levels (P = 0.01) and higher Aß42:40 ratio (P = 0.06) were observed in participants with severe attachment loss than in other participants. Periodontitis was a significant interaction variable, given that the association between Aß1-42 and Aß1-40 and cognitive impairment was only observed in patients with severe periodontitis. According to these data, periodontitis may be a modulating variable of the association between Aß and cognitive impairment. CONCLUSIONS: Plasma Aß1-42 levels are higher in individuals who have severe periodontal disease. The presence of periodontitis may modify the association between Aß and cognitive impairment.

2-Methyl-6-(phenylethynyl)pyridine Hydrochloride Modulates Metabotropic Glutamate 5 Receptors Endogenously Expressed in Zebrafish Brain.

Due to phylogenetic proximity to the human, zebrafish has been recognized as a reliable model to study Alzheimer's disease (AD) and other central nervous system disorders. Furthermore, metabotropic glutamate receptors have been previously reported to be impaired in brain from AD patients. Metabotropic glutamate 5 (mGlu5) receptors are G-protein coupled receptors proposed as potential targets for therapy of different neurodegenerative disorders. Thus, MPEP (2-methyl-6-(phenylethynyl)pyridine hydrochloride), a selective noncompetitive mGlu5 receptor antagonist, has been suggested for pharmacological treatment of AD. The aim of the present work was to quantify mGlu5 receptors in brain from zebrafish and to study the possible modulation of these receptors by MPEP treatment. To this end, radioligand binding assay and open field test were used. Results showed a slightly higher presence of mGlu5 receptors in brain from male than in that from female zebrafish. However, a significant increase of mGlu5 receptor in male without variation in female was observed after MPEP treatment. This gender specific response was also observed in locomotor behavior, being significantly decreased only in male zebrafish. These results confirm the presence of mGlu5 receptors in brain from zebrafish and their gender specific modulation by selective antagonist treatment and suggest a role of these receptors on locomotor activity, which is affected in many disorders. In addition, our data point to zebrafish as a useful model to study mGlu receptor function in both healthy and pathological conditions.

Herpes simplex virus type 2 infection induces AD-like neurodegeneration markers in human neuroblastoma cells.

Herpes simplex virus (HSV) types 1 and 2 are neurotropic viruses that establish lifelong latent infections in neurons. Mounting evidence suggests that HSV-1 infection is involved in the pathogenesis of Alzheimer's disease (AD). The relationships between other herpesvirus infections and events associated with neurodegeneration have not, however, been extensively studied. The present work reports that HSV-2 infection leads to the strong accumulation of hyperphosphorylated tau and the amyloid-ß peptides Aß40 and Aß42 (all major pathological hallmarks of AD) in human SK-N-MC neuroblastoma cells. Infection is also associated with a marked reduction in the amount of Aß40 secreted and in the proteolytic fragments of the amyloid-ß precursor protein (APP) (secreted APPα and the α-C-terminal fragment). These results indicate that HSV-2 infection inhibits the nonamyloidogenic pathway of APP processing and impairs Aß secretion in these cells. In addition, HSV-2 induces the accumulation of intracellular autophagic compartments containing Aß due to a failure in the late stages of autophagy. To our knowledge, this is the first report to show that HSV-2 infection strongly alters the tau phosphorylation state, APP processing, and autophagic process in human neuroblastoma cells, leading to the appearance of AD-like neurodegeneration markers.

Oxidative stress enhances neurodegeneration markers induced by herpes simplex virus type 1 infection in human neuroblastoma cells.

Mounting evidence suggests that Herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of Alzheimer's disease (AD). Previous work from our laboratory has shown HSV-1 infection to induce the most important pathological hallmarks of AD brains. Oxidative damage is one of the earliest events of AD and is thought to play a crucial role in the onset and development of the disease. Indeed, many studies show the biomarkers of oxidative stress to be elevated in AD brains. In the present work the combined effects of HSV-1 infection and oxidative stress on Aß levels and autophagy (neurodegeneration markers characteristic of AD) were investigated. Oxidative stress significantly potentiated the accumulation of intracellular Aß mediated by HSV-1 infection, and further inhibited its secretion to the extracellular medium. It also triggered the accumulation of autophagic compartments without increasing the degradation of long-lived proteins, and enhanced the inhibition of the autophagic flux induced by HSV-1. These effects of oxidative stress were not due to enhanced virus replication. Together, these results suggest that HSV-1 infection and oxidative damage interact to promote the neurodegeneration events seen in AD.

Herpes simplex virus type I induces an incomplete autophagic response in human neuroblastoma cells.

Autophagy is a homeostatic process involved in the turnover or elimination of cytoplasmic components, damaged organelles, and protein aggregates via a lysosomal degradation mechanism. Autophagy also provides a mechanism of innate immunity, known as xenophagy, designed to protect cells from intracellular pathogens, but it may unfortunately be subverted to act as a pro-viral pathway facilitating the replication of certain viruses. Herpes simplex virus type I (HSV-1) is a neurotropic virus that remains latent in host neurons; it is the most common cause of sporadic viral encephalitis. Moreover, HSV-1 has been related to the pathogenesis of Alzheimer's disease. HSV-1 can modulate the autophagic process through a mechanism mediated by the viral protein ICP34.5. Here we report that HSV-1 induces a strong increase in GFP-LC3 and endogenous LC3 lipidation, and triggers the accumulation of intracellular autophagic compartments (mainly autophagosomes) without enhancing autophagic long-lived protein degradation in the late stages of infection. Autophagy inhibition mediated by ATG5 gene silencing had no effect on viral growth. The present results suggest that HSV-1 infection activates the host autophagic machinery and strongly controls the autophagic process, blocking the fusion of autophagosomes with lysosomes. These events might be important in the neurodegenerative process associated with HSV-1 infection.

Herpes simplex virus type 1 induces nuclear accumulation of hyperphosphorylated tau in neuronal cells.

Herpes simplex virus type 1 (HSV-1) is a neurotropic virus that remains latent in host neurons. Viral DNA replication is a highly structured process in which the redistribution of nuclear proteins plays an important role. Although tau is most widely known as a microtubule-associated protein found in a hyperphosphorylated state in the brains of patients with Alzheimer's disease (AD), this protein has also been detected at other sites such as the nucleolus. Here, we establish that HSV-1 infection gives rise to an increase in tau phosphorylation and that hyperphosphorylated tau accumulates in the nucleus, forming defined structures in HSV-1-infected neuronal cells reminiscent of the common sites of viral DNA replication. When tau expression in human neuroblastoma cells was specifically inhibited using an adenoviral vector expressing a short hairpin RNA to tau, viral DNA replication was not affected, indicating that tau is not required for HSV-1 growth in neuronal cells. Given that HSV-1 is considered a risk factor for AD, our results suggest a new way in which to understand the relationships between HSV-1 infection and the pathogenic mechanisms leading to AD.

Can zebrafish be used as animal model to study Alzheimer's disease?

Zebrafish is rapidly emerging as a promising model organism to study various central nervous system (CNS) disorders, including Alzheimer's disease (AD). AD is the main cause of dementia in the human population and there is an urgency to understand the causes of this neurodegenerative disease. In this respect, the development of new animal models to study the underlying neurodegenerative mechanisms of AD is an urgent need. In this review we analyze the current situation in the use of zebrafish as a model for AD, discussing the reasons to use this experimental paradigm in CNS investigation and analyzing the several strategies adopted to induce an AD-like pathology in zebrafish. We discuss the strategies of performing interventions to cause damage in the zebrafish brain by altering the major neurotransmitter systems (such as cholinergic, glutamatergic or GABAergic circuits). We also analyze the several transgenic zebrafish constructed for the AD study, discussing both the familial-AD models based on APP processing pathway (APP and presenilins) and in the TAU hyperphosphorylation, together with the genes involved in sporadic-AD, as apolipoprotein E. We conclude that zebrafish is in a preliminary stage of development in the AD field, and that the transgenic animals must be improved to use this fish as an optimal model for AD research. Furthermore, a deeper knowledge of the zebrafish brain and a better characterization of the injury caused by alterations in the major neurotransmitter systems are needed.

Herpes simplex virus type I induces the accumulation of intracellular ß-amyloid in autophagic compartments and the inhibition of the non-amyloidogenic pathway in human neuroblastoma cells.

Mounting evidence suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of Alzheimer's disease (AD). Epidemiological analyses have shown that HSV-1 is a risk factor for AD in people with at least 1 type 4 allele of the apolipoprotein E gene. Recent studies have also suggested that HSV-1 contributes to the appearance of the biochemical anomalies characteristic of AD brains. In addition, autophagic activity appears to be reduced with aging, and the final stages of autophagy in neurodegenerative process appear to be impaired. The present work reports that HSV-1 provokes the strong intracellular accumulation of both the main species of ß-amyloid (Aß) in the autophagic compartments and that it is associated with a marked inhibition of Aß secretion. Autophagosomes containing Aß failed to fuse with lysosomes in HSV-1-infected cells, indicating the impaired degradation of Aß localized in the autophagic vesicles. In addition, HSV-1 infection was associated with the inhibition of the nonamyloidogenic pathway of amyloid precursor protein (APP) processing without significantly affecting the activity of the secretases involved in the amyloidogenic pathway. Taken together, these data suggest that HSV-1 infection modulates autophagy and amyloid precursor protein processing, contributing to the accumulation of Aß characteristic of AD.