Mendelian Randomisation Confirms the Role of Y-Chromosome Loss in Alzheimer’s Disease Aetiopathogenesis in Men

Mosaic loss of chromosome Y (mLOY) is a common ageing-related somatic event and has been previously associated with Alzheimer’s disease (AD). However, mLOY estimation from genotype microarray data only reflects the mLOY degree of subjects at the moment of DNA sampling. Therefore, mLOY phenotype associations with AD can be severely age-confounded in the context of genome-wide association studies. Here, we applied Mendelian randomisation to construct an age-independent mLOY polygenic risk score (mloy-PRS) using 114 autosomal variants. The mloy-PRS instrument was associated with an 80% increase in mLOY risk per standard deviation unit (p = 4.22 × 10−20) and was orthogonal with age. We found that a higher genetic risk for mLOY was associated with faster progression to AD in men with mild cognitive impairment (hazard ratio (HR) = 1.23, p = 0.01). Importantly, mloy-PRS had no effect on AD conversion or risk in the female group, suggesting that these associations are caused by the inherent loss of the Y chromosome. Additionally, the blood mLOY phenotype in men was associated with increased cerebrospinal fluid levels of total tau and phosphorylated tau181 in subjects with mild cognitive impairment and dementia. Our results strongly suggest that mLOY is involved in AD pathogenesis.P.G.-G. (Pablo García-González) is supported by CIBERNED employment plan CNV-304-PRF-866. CIBERNED is integrated into ISCIII (Instituto de Salud Carlos III). I.d.R is supported by a national grant from the Instituto de Salud Carlos III FI20/00215. A.C. (Amanda Cano) acknowledges the support of the Spanish Ministry of Science, Innovation, and Universities under the grant Juan de la Cierva (FJC2018-036012-I). M.B. (Mercé Boada) and A.R. (Agustín Ruiz) are also supported by national grants PI13/02434, PI16/01861, PI17/01474, PI19/01240, and PI19/01301. The Genome Research @ Fundació ACE project (GR@ACE) is supported by Grifols SA, Fundación bancaria “La Caixa”, Fundació ACE, and CIBERNED. Acción Estratégica en Salud is integrated into the Spanish National R + D + I Plan and funded by ISCIII (Instituto de Salud Carlos III)—Subdirección General de Evaluación—and the Fondo Europeo de Desarrollo Regional (FEDER—“Una manera de hacer Europa”). Genotyping of the ACE MCI-EADB samples was performed in the context of EADB (European Alzheimer DNA biobank) funded by the JPco-fuND FP-829-029 (ZonMW project number 733051061). This work was supported by a grant (European Alzheimer DNA BioBank, EADB) from the EU Joint Program—Neurodegenerative Disease Research (JPND). Partial funding for open access charge: Universidad de Málag

Activation of PKR Causes Amyloid ß-Peptide Accumulation via De-Repression of BACE1 Expression

BACE1 is a key enzyme involved in the production of amyloid ß-peptide (Aß) in Alzheimer's disease (AD) brains. Normally, its expression is constitutively inhibited due to the presence of the 5′untranslated region (5′UTR) in the BACE1 promoter. BACE1 expression is activated by phosphorylation of the eukaryotic initiation factor (eIF)2-alpha, which reverses the inhibitory effect exerted by BACE1 5′UTR. There are four kinases associated with different types of stress that could phosphorylate eIF2-alpha. Here we focus on the double-stranded (ds) RNA-activated protein kinase (PKR). PKR is activated during viral infection, including that of herpes simplex virus type 1 (HSV1), a virus suggested to be implicated in the development of AD, acting when present in brains of carriers of the type 4 allele of the apolipoprotein E gene. HSV1 is a dsDNA virus but it has genes on both strands of the genome, and from these genes complementary RNA molecules are transcribed. These could activate BACE1 expression by the PKR pathway. Here we demonstrate in HSV1-infected neuroblastoma cells, and in peripheral nervous tissue from HSV1-infected mice, that HSV1 activates PKR. Cloning BACE1 5′UTR upstream of a luciferase (luc) gene confirmed its inhibitory effect, which can be prevented by salubrinal, an inhibitor of the eIF2-alpha phosphatase PP1c. Treatment with the dsRNA analog poly (I∶C) mimicked the stimulatory effect exerted by salubrinal over BACE1 translation in the 5′UTR-luc construct and increased Aß production in HEK-APPsw cells. Summarizing, our data suggest that PKR activated in brain by HSV1 could play an important role in the development of AD

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Presence of activated PKR in human brain tissue.

<p>The presence of activated PKR -autophosphorylated at Thr446- was studied in human brain sections (temporal lobe) from one non-demented control and one AD patient by immunohistochemistry (A). Colocalization of BACE1 and p-PKR(T446) in neurons from an AD patient. All brain sections analysed were positive for HSV1 infection as previously reported <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021456#pone.0021456-Wozniak3" target="_blank">[39]</a> (B).</p

HSV1 infection activates PKR.

<p>SH-SY5Y cells were infected with HSV1 (1 pfu/cell, 24 h) or were not infected (controls). Immunocytochemistry analysis was carried with the following Abs: anti-p-PKR, anti-p-eIF2-alpha and anti-BACE1 (A). Protein extracts of SH-SY5Y cells infected with HSV1 (3 pfu/cell, 24 h) and uninfected cells (controls) were analysed by Western blotting using the following Abs: anti-BACE1, anti-p-PKR, anti-PKR, anti-p-eIF2-alpha, anti- eIF2-alpha and anti-tubulin. Bands were quantified by densitometric analysis. Results are expressed as the mean ± SEM of 3–4 independent experiments. * p<0.05, ** p<0.01, *** p<0.0005 by Student's <i>t</i> test (B). Sections from mouse dorsal ganglion root (DRG) were obtained from HSV1-infected mice. Contralateral uninfected ganglia were used as controls. Immunohistochemistry analysis was carried out to detect p-PKR (C).</p

Poly (I∶C) induces BACE1 translation in a mechanism depending on PKR-catalysed eIF2-alpha phosphorylation.

<p>BACE1 5′UTR fragment was inserted into the HindIII site of a luciferase reporter construct (5′UTR-luc). The plasmids bear the strong cytomegalovirus promoter (CMV), which allows sufficient reporter gene expression for luciferase determinations. HeLa cells were transfected with 5′UTR-luc or empty plasmids (named as CMV) for luciferase reporter studies (A). 5′UTR-luc repressed translation in comparison with the empty 5′UTR-free luciferase construct (B). Inhibition of eIF2-alpha phosphatase PP1c by Sal003 de-repressed the reporter signal elicited by 5′UTR-luc (C). Stimulation (3 h) with poly (I∶C) also de-repressed the reporter signal yielded by 5′UTR-luc. This effect was abolished when cells were preincubated with a specific and potent PKR inhibitor that acts via the PKR ATP-binding site. Data are mean ± SEM of 3 independent experiments performed in triplicate. *p<0.05 by Student's <i>t</i> test (D). Incubation with the specific PKR inhibitor -in the presence/absence of poly (I∶C)- did not result in a decrease in cell viability as shown by an MTT assay. Data are mean ± SEM of 3 independent experiments performed in triplicate (Inset in panel D).</p

Biochemical pathway linking HSV1 infection and AD.

<p>Despite the viral ability to circumvent host defensive mechanisms, including PKR activation, HSV1 activates PKR <i>in vitro</i> and <i>in vivo</i>. Activated PKR increases eIF2-alpha phosphorylation levels, leading to BACE1 translation de-repression, BACE1 protein up-regulation and Aß production (left track; continuous line). In the right track (dotted line) we present the pharmacological and biological tools that we used to study this pathway: poly (I∶C), to mimic the effect of viral dsRNA; a specific imidazolo-oxindole compound that acts as a potent PKR inhibitor; and a 5′UTR-luc reporter construct used for the evaluation of the translational effect exerted by the PKR-eIF2-alpha pathway over BACE1 5′UTR. Also, we have utilized the PP1c inhibitor salubrinal, which prevents the dephosphorylation of eIF2-alpha.</p

The amyloid imaging for the prevention of Alzheimer's disease consortium: A European collaboration with global impact

Background: Amyloid-β (Aβ) accumulation is considered the earliest pathological change in Alzheimer's disease (AD). The Amyloid Imaging to Prevent Alzheimer's Disease (AMYPAD) consortium is a collaborative European framework across European Federation of Pharmaceutical Industries Associations (EFPIA), academic, and 'Small and Medium-sized enterprises' (SME) partners aiming to provide evidence on the clinical utility and cost-effectiveness of Positron Emission Tomography (PET) imaging in diagnostic work-up of AD and to support clinical trial design by developing optimal quantitative methodology in an early AD population. The amypad studies: In the Diagnostic and Patient Management Study (DPMS), 844 participants from eight centres across three clinical subgroups (245 subjective cognitive decline, 342 mild cognitive impairment, and 258 dementia) were included. The Prognostic and Natural History Study (PNHS) recruited pre-dementia subjects across 11 European parent cohorts (PCs). Approximately 1600 unique subjects with historical and prospective data were collected within this study. PET acquisition with [18F]flutemetamol or [18F]florbetaben radiotracers was performed and quantified using the Centiloid (CL) method. Results: AMYPAD has significantly contributed to the AD field by furthering our understanding of amyloid deposition in the brain and the optimal methodology to measure this process. Main contributions so far include the validation of the dual-time window acquisition protocol to derive the fully quantitative non-displaceable binding potential (BP ND ), assess the value of this metric in the context of clinical trials, improve PET-sensitivity to emerging Aβ burden and utilize its available regional information, establish the quantitative accuracy of the Centiloid method across tracers and support implementation of quantitative amyloid-PET measures in the clinical routine. Future steps: The AMYPAD consortium has succeeded in recruiting and following a large number of prospective subjects and setting up a collaborative framework to integrate data across European PCs. Efforts are currently ongoing in collaboration with ARIDHIA and ADDI to harmonize, integrate, and curate all available clinical data from the PNHS PCs, which will become openly accessible to the wider scientific community

Mendelian Randomisation Confirms the Role of Y-Chromosome Loss in Alzheimer’s Disease Aetiopathogenesis in Men

Mosaic loss of chromosome Y (mLOY) is a common ageing-related somatic event and has been previously associated with Alzheimer’s disease (AD). However, mLOY estimation from genotype microarray data only reflects the mLOY degree of subjects at the moment of DNA sampling. Therefore, mLOY phenotype associations with AD can be severely age-confounded in the context of genome-wide association studies. Here, we applied Mendelian randomisation to construct an age-independent mLOY polygenic risk score (mloy-PRS) using 114 autosomal variants. The mloy-PRS instrument was associated with an 80% increase in mLOY risk per standard deviation unit (p = 4.22 × 10−20) and was orthogonal with age. We found that a higher genetic risk for mLOY was associated with faster progression to AD in men with mild cognitive impairment (hazard ratio (HR) = 1.23, p = 0.01). Importantly, mloy-PRS had no effect on AD conversion or risk in the female group, suggesting that these associations are caused by the inherent loss of the Y chromosome. Additionally, the blood mLOY phenotype in men was associated with increased cerebrospinal fluid levels of total tau and phosphorylated tau181 in subjects with mild cognitive impairment and dementia. Our results strongly suggest that mLOY is involved in AD pathogenesis

Intermittent Hypoxia Is Associated With High Hypoxia Inducible Factor-1α but Not High Vascular Endothelial Growth Factor Cell Expression in Tumors of Cutaneous Melanoma Patients

Epidemiological associations linking between obstructive sleep apnea and poorer solid malignant tumor outcomes have recently emerged. Putative pathways proposed to explain that these associations have included enhanced hypoxia inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) cell expression in the tumor and altered immune functions via intermittent hypoxia (IH). Here, we examined relationships between HIF-1α and VEGF expression and nocturnal IH in cutaneous melanoma (CM) tumor samples. Prospectively recruited patients with CM tumor samples were included and underwent overnight polygraphy. General clinical features, apnea–hypopnea index (AHI), desaturation index (DI4%), and CM characteristics were recorded. Histochemical assessments of VEGF and HIF-1α were performed, and the percentage of positive cells (0, &lt;25, 25–50, 51–75, &gt;75%) was blindly tabulated for VEGF expression, and as 0, 0–5.9, 6.0–10.0, &gt;10.0% for HIF-1α expression, respectively. Cases with HIF-1α expression &gt;6% (high expression) were compared with those &lt;6%, and VEGF expression &gt;75% of cells was compared with those with &lt;75%. 376 patients were included. High expression of VEGF and HIF-1α were seen in 88.8 and 4.2% of samples, respectively. High expression of VEGF was only associated with increasing age. However, high expression of HIF-1α was significantly associated with age, Breslow index, AHI, and DI4%. Logistic regression showed that DI4% [OR 1.03 (95% CI: 1.01–1.06)] and Breslow index [OR 1.28 (95% CI: 1.18–1.46)], but not AHI, remained independently associated with the presence of high HIF-1α expression. Thus, IH emerges as an independent risk factor for higher HIF-1α expression in CM tumors and is inferentially linked to worse clinical CM prognostic indicators