Allergy and Alzheimer disease

Alzheimer disease (AD) is a neurodegenerative disorder characterized by progressive dementia with devastating effects for the patients and their families. The treatments available are purely symptomatic and there is need for treatment strategies aiming at the etiopathogenesis of AD. The effects of systemic inflammation on the development and/or progress of AD are not clarified. Present knowledge points towards both beneficial and detrimental effects of inflammation on AD, depending on both its timing and its nature. Allergy is associated with chronic systemic inflammatory changes, and its effects on the brain are largely unknown. Epidemiological studies have shown that allergic diseases were associated with increased risk for AD. The aim of this thesis was to investigate the effects of allergy on the normal brain and in association with AD-like pathology. In Paper I, we aimed to study whether chronic airway allergy affects the AD-related proteins amyloid precursor protein (APP) and hyperphosphorylated tau (p-tau), and the inflammatory status in the brain of naïve mice. We found that allergy increased p-tau levels in the brain, whereas levels of APP were not modified. Furthermore, the levels of immunoglobulin (Ig) G and E were significantly increased in the brain of allergic mice. The increase was not only confined to blood vessels but broadly in the brain parenchyma. We then aimed to study in Paper II the changes in gene expression induced by chronic airway allergy in the brain using microarray technology. Allergy induced changes in several inflammation-related signaling pathways. We found that the levels of insulin-degrading enzyme (IDE) and phosphorylated insulin receptor (p-IR) were decreased in the brain in response to allergy. In Paper III, we investigated the effects of chronic airway allergy on the brain in the 3xTgAD (Tg) mouse model for AD, and their background strain (Bg). The levels of IgG and IgE were also increased in the brain of Tg mice in response to allergy. Allergy increased the levels of C1q component C and interleukin-1β, decreased p-IR, and impaired the burrowing activity in Bg animals. The Tg mice showed increased levels of brain-derived neurotrophic factor and decay-accelerating factor (complement inhibitor), and decreased levels of phosphorylated p38. In paper IV, we analysed the levels of Igs and cytokines in cerebrospinal fluid (CSF) and serum obtained from patients with subjective cognitive impairment (SCI), mild cognitive impairment (MCI) and AD, with or without allergy. The relation of allergy to CSF biomarkers (p-tau, total (t)-tau, and β-amyloid (Aβ)) and mini-mental statement examination (MMSE) was investigated. We found that the CSF levels of IgG1 ratio, IgA and t-tau were lower in AD cases with allergy compared to those without allergy. The serum interferon γ levels were lower while MMSE scores were higher in MCI cases with allergy. In conclusion, our studies suggest that allergy may have negative effects on the normal brain but seemingly beneficial effects in the presence of AD-like pathology. It is possible that stimulation of immune responses induced by allergy may lead to beneficial effects on AD. So far, little is known regarding the association between AD and allergies and further studies are needed to clarify the impact of allergy on AD pathogenesis and progression

Understanding the mechanisms of food intake and obesity in Down syndrome is supported by behavioral and neurochemical abnormalities

[eng] Obesity prevalence is higher in Down syndrome (DS) than in the general population. Beyond metabolic alterations, individuals with DS present increased impulsivity, a trait observed in obese people and in compulsive eaters that may affect their control of food intake. In this Thesis, we used a trisomic DS mouse model (Ts65Dn) to understand the behavioral component of obesity in DS and explore some possible underlying mechanisms. Our meal pattern analysis revealed longer and slowly meals in Ts65Dn mice, leading to reduced eating rate, which may be associated to the mandible hypoplasia described in both human and mice. When exposed to obesogenic environments, Ts65Dn mice showed higher preference for energy-dense food, gained more weight in specific conditions and scored higher in compulsivity and inflexibility tests than WT mice, as measured by binge eating during limited access and persistence of consumption of quine adulteration of energy-dense food. High performance liquid chromatography revealed reduced levels of dopamine in prefrontal cortex in Ts65Dn mice. This could lead to higher reward sensitivity that in turn would facilitate overeating as a compensatory response to restore optimal dopamine levels. Feeding behavior is also regulated by hormones and other circulating signals. We detected higher plasma leptin and glucose levels along with reduced insulin levels in Ts65Dn mice. Upon a glucose challenge, Ts65Dn mice showed reduced glucose-stimulated insulin response both in vivo and in vitro, suggesting a deficient insulin secretion or the reduced pancreatic mass. Indeed, we detected that Ts65Dn mice had altered plasma profile for some markers of inflammation and oxidative damage, in agreement with the high prevalence of autoimmune diseases and diabetes in DS people. We also explored the involvement of the serine/threonine kinase DYRK1A, a candidate DS gene, in obesity and feeding behavior. Dyrk1A overexpression was sufficient to recapitulate some behavioral aspects associated to overeating in DS, but with a distinct profile. We conclude that increased obesity prevalence in DS is explained by both metabolic and behavioral alterations, in part driven by a hypodopaminergic status, and that Dyrk1A overexpression is only involved in specific DS obesity phenotypes.[spa] La prevalencia de obesidad es más alta en el síndrome de Down (SD) que en la población general. Más allá de las alteraciones metabólicas, los individuos con SD tienen mayor impulsividad, rasgo común en personas obesas y en comedores compulsivos, que pueden afectar el control de la ingesta de alimentos. En esta Tesis, se ha utilizado un modelo de ratón trisómico (Ts65Dn) para comprender el componente de comportamiento en el desarrollo de la obesidad en SD. Nuestro análisis del patrón de ingesta mostró que los ratones Ts65Dn comen más lento que los euploides, lo que podría estar asociado con la hipoplasia mandibular descrita en ratones y humanos con SD. Cuando los ratones Ts65Dn son expuestos a ambientes obesogénicos, comen mayores cantidades de dietas hipercalóricas, engordan más en determinadas condiciones y puntúan más alto en pruebas de compulsividad e inflexibilidad que los ratones euploides. La cuantificación de los niveles de monoaminas mediante cromatografía líquida reveló que los ratones Ts65Dn presentan niveles más bajos de dopamina en corteza prefrontal. Dado que las dietas hipercalóricas promueven la liberación del neurotransmisor en el circuito de recompensa, el sobre consumo de las mismas podría indicar un intento de restaurar los niveles óptimos de dopamina. La regulación de la ingesta también depende de otras señales circulantes. Detectamos que los ratones Ts65Dn tienen mayores niveles de leptina y glucosa en plasma y niveles más bajos de insulina que los euploides. La administración exógena de glucosa produjo una menor respuesta secretoria de insulina en los ratones Ts65Dn in vivo e in vitro. Además, diversos marcadores de inflamación y estrés oxidativo son más elevados en los ratones Ts65Dn, en consonancia con la mayor incidencia de enfermedades autoinmunes y diabetes en personas con SD. En esta Tesis también se ha explorado la contribución de la proteína serina / treonina quinasa DYRK1A, un gen candidato para SD en la obesidad e ingesta. La sobreexpresión de Dyrk1A es suficiente para recapitular algunos comportamientos asociados a la ingesta compulsiva, pero con un perfil distinto al observado en el modelo trisómico. Concluimos que la prevalencia de la obesidad en SD se explica por alteraciones tanto metabólicas como conductuales, en parte como consecuencia de un estado de hipodopaminergia, y que la sobreexpresión de Dyrk1A está implicada en fenotipos específicos de la obesidad en SD

Hereditary and sporadic beta-amyloidoses.

Cerebral amyloidoses are chronic, progressive neurodegenerative diseases that are caused by the aggregation and deposition of misfolded proteins in the central nervous system, and lead to cognitive deficits, stroke, and focal neurological dysfunction including cerebellar and extrapyramidal signs. Among them, beta-amyloidoses are a heterogenous set of conditions characterised by the deposition of beta-amyloid protein in brain parenchyma and/or vessel walls that lead to the development of two main clinico-pathological entities: Alzheimer's disease and cerebral amyloid angiopathy, which may be sporadic or familial, and may also co-exist in the same patient. The aim of this review is to describe the most important differences in the pathways leading to parenchymal and cerebrovascular beta-amyloidoses, and the main clinical, neuropathological and biochemical characteristics of the two conditions. It also discusses the phenotypes associated with a series of familial and sporadic beta-amyloidoses in more detail in order to highlight the clinical and neuropathological features that may help to distinguish the different forms of disease

From Misfolded Recombinant Proteins in vitro to Pathological Agents in vivo

The pathogenesis of a disease involves a stochastic refolding of the etiologic protein into a misfolded infectious state known as prion. Recently, there has been renewed interest in the possibility that proteins causing neurodegeneration are all prions. The \u3b2-sheet rich pathological \u3b1-synuclein (\u3b1-syn) can cross from the neurons of transplanted patients into the grafted cells, and induce a change in the structure of \u3b1-syn in Parkinson\u2019s disease (PD) is an example. The convergence of studies showing the presence of prions in the pathogenesis of common neurodegenerative maladies has since been remarkable. Studies on synthetic prions showed that recombinant (rec) prion protein (PrP) is refolded into infectious conformations in vitro. This synthetic prion protein stimulates the conversion of cellular PrP into nascent pathological PrP and induces the accumulation of the isoform that causes neurodegeneration in vivo. Using defined biophysical and biochemical conditions in vitro, we developed methods for the pathological conversion of recPrP into PrPSc, and we established whether synthetic pathological agents of rec human \u3b1-syn amyloids can be infectious, as Legname et al. showed for the first time in production of mammalian synthetic prions. The pathological conversion process of both PrP and \u3b1-syn required only purified recombinant proteins and common chemicals. We generated putative infectious materials that possess different conformational structures. Moreover, we designed a novel build-in screening methodology for amyloid preparations to achieve putative infectious materials using amyloid-infected-cell culture assay. At fifth cell passage after single infection, prion amyloid fibrils from different preparations induced endogenous PrPC to convert into PrPSc in both non-infected mouse hypothalamic GT1 and mouse neuroblastoma N2a cell lines. Moreover, these variant synthetic proteinaceous infectious agents can replicate and be detected by protein misfolding cyclic amplification (PMCA). Through this methodology that was used to obtain synthetic mammalian prions, we also tested whether recombinant human \u3b1-syn amyloids can infect neuronal cell lines in vitro, and wild-type mice in vivo. A single exposure to amyloid fibrils of human \u3b1-syn was sufficient to induce aggregation of endogenous \u3b1-syn in human neuroblastoma SH-SY5Y cells, mouse hypothalamic GT1 cells and mouse brains. Interestingly, we found pathological phosphorylated \u3b1-syn in amyloid-infected cells and in neurons and neurites of mice. These results suggest that recombinant human \u3b1-syn amyloids can promote endogenous \u3b1-syn aggregation and pathological post-translational modification. Upon subsequent passages, mice inoculated with either human \u3b1-syn amyloid or diseased mouse brain homogenates showed marked neurological symptoms resembling those of PD, as well as neuropathological \u3b1-syn inclusions in neurons

Cytokine genetics and expression : implications of an immunogenetic pathogenesis in autism spectrum disorders.

Autism Spectrum Disorder (ASD) is an idiopathic pervasive neurodevelopmental disorder associated with various neuropathologies and immunological dysfunctions. Cytokines are regulatory proteins that facilitate communication between the immune and central nervous systems and mediate inflammation, immunity, and hemopoiesis. Previous literature demonstrates that cytokine expression is altered systemically and in the central nervous system of individuals diagnosed with ASD when compared to matched neurotypical controls. Here it is proposed that cytokines are crucial mediators in autism pathogenesis. The central hypothesis of this research posits that an underlying genetic susceptibility in cytokine genes is triggered by environmental exigencies (e.g., stress, infection, ultrasound, hypoxia, pollutant or chemical exposure) during prenatal development. This hypothesis proposes that the convergence of these scenarios during vulnerable periods of neurodevelopment ultimately culminates in the autism phenotype. To test whether cytokines are crucial mediators in autism pathogenesis, the DNA sequences of 22 single nucleotide polymorphisms (SNPs) within 13 cytokine genes were genotyped in a cohort of autistic patients and controls. Three SNP frequencies for both pro-inflammatory [IL1R(+1970)] and anti-inflammatory [IL4(-590) and IL4(-33)] cytokine genes were found to be significantly associated with autism incidence. Next, cytokine mRNA profiles were investigated in post-mortem cortical tissue of eight autistic subjects and eight matched controls. Transcriptional profiling of cytokine genes in five post-mortem cortical regions corresponding to Brodmann Areas 4, 9, 17, 22 and 46 indicated heterogeneous expression of cytokine (TNF-a, IL-6, TGFß-l, IL-1ß) and chemokine (IL-8) transcripts in autistic subjects, but these alterations did not reach statistical significance or reflect values of cortical cytokine translational patterns established in previous literature. Finally, it was shown that systemic cytokine translational expression in the blood plasma of children diagnosed with autism disorder was not modulated with intravenous glutathione administration. These findings indicate that cytokines play an important role in ASD pathogenesis and reveal possible molecular mechanisms that warrant future investigation in etiological research. They also show that the antioxidant agent glutathione, which ostensibly alters cytokine expression at the intracellular level, does not affect systemic cytokine expression or ameliorate behavioral outcome when administered exogenously

Understanding Mechanistic Details of Neuroinflammatory Pathways Stimulated by the Alzheimer\u27s Disease Amyloid-Beta Protein

Alzheimer’s disease (AD) is characterized by neuroinflammation. Senile plaques composed of aggregated amyloid-β protein (Aβ) are found in AD patients’ brains. The Aβ is formed by the proteolytic cleavage of the amyloid precursor protein (APP) resulting in Aβ fragments that are 39-42 amino acids in length. The two most common peptides are Aβ(1-40) and Aβ(1-42), which differ by two amino acids, isoleucine and alanine. Within the brain of AD patients, Aβ monomer self-assembles to form several aggregate morphologies, including oligomers, protofibrils, and fibrils. Activated microglial cells and associated secreted proinflammatory cytokines surround these plaques producing a localized inflammatory environment in the brain. Several innate-immune pathways, including Toll-like receptors (TLRs) and the NLRP3 inflammasome, have been implicated in AD inflammation. Aβ plays a primary role in activating these pathways likely contributing to the progressive neurodegeneration in AD. In order to better understand the complexities of this interaction, I investigated the inflammatory response of microglia to Aβ(1-42) and Aβ(1-42)/Aβ(1-40) protofibrils, along with additional biophysical properties. Increased understanding of these pathological events will expand the current model of Aβ neuroinflammatory pathways and help identify new therapeutic targets for AD. My research has demonstrated that the Aβ(1-42) protofibrils triggered a time- and TLR/MyD88-dependent process that produced inflammatory cytokines tumor necrosis factor alpha (TNFα) and interleukin-1β (IL-1β) mRNA and intracellular pro and mature forms of IL-1β protein. Despite previous reports suggesting that NLRP3 activation requires two signals from two distinct molecules, my research indicated that Aβ(1-42) protofibrils alone could efficiently prime (TLR-dependent pro-IL-1β production) and activate (cleavage of pro-IL-1β to mature-IL-1β) the NLRP3 inflammasome. However, the increased intracellular mature-IL-1β did not translate into greater IL-1β secretion. Instead, we found that Aβ was able to elicit a very rapid, unsustainable, yet re-inducible quantized burst of secreted IL-1β, which occurred prior to Aβ priming of the microglia. These findings suggested a basal level of either pro- or mature-IL-1β in the cultured primary microglia yet revealed multiple sites of IL-1β regulation by Aβ(1-42) protofibrils. These sites, which are potential therapeutic targets, include TLR/MyD88-mediated priming, NLRP3 inflammasome activation, and modulation of the IL-1β secretory process