Introduction: In Alzheimer's Disease (AD) brains, three pathological characteristics are observed: extracellular insoluble senile plaques formed by amyloid-β (Aβ) peptide, apoE, and its corresponding cholesterol that co-localize with Aβ plaques (Lazar 2013) and intraneuronal neurofibrillary tangles (NFT) formed by tau protein (Kumar 2015). Recent findings suggest a possible implication of HHV-6A in AD (Eimer 2018; Readhead 2018), and we showed the ability of HHV-6A to induce the expression of apoE, a risk factor for AD onset (Rizzo 2019). The control of viral infections in the brain involves the activation of microglial cells, the macrophages of the brain that are constantly surveying the central nervous system and, in response to small variations, they rapidly change their morphology, become activated, secrete pro- and anti-inflammatory molecules, and phagocytose foreign material that can alter the equilibrium of the brain (Ransohoff 2016). We evaluated the effect of HHV-6A infection on microglial cells expression of the common risk factor for AD development: apoE, Aβ, and tau. Materials and Methods: We have infected microglial cells (HMC3, ATCC®CRL-3304), in monolayer and spheroid 3D model, with HHV-6A (strain U1102) cell-free virus inocula with 100 genome equivalents per 1 cell. We collected the cells 1, 3, 7 and 14 days post infection (d.p.i.) and analyzed them for viral DNA and RNA, apoE, Aβ (1-40, 1-42), tau and phospho-tau (Threonine 181) by Real Time, immunofluorescence and immunoenzymatic assay. Results: We observed a productive infection by HHV-6A. The expression of apoE increased at 3 d.p.i. and Aβ 1-40 expression increased from 7 d.p.i., while no significant induction was observed for Aβ 1-42 expression. The secretion of Tau started from 7 d.p.i., with an increasing percentage of the phosphorylated form. Conclusions: Microglial cells are permissive to HHV-6A infection, that induces the expression of the common risk factor for AD development: apoE, Aβ, and tau. Interesting, there is a temporal induction of these molecules: apoE is induced from 3 d.p.i. followed by Aβ 1-40 from 7 d.p.i. and by phospho-tau from 14 d.p.i.
HHV-6A infection of microglial cells induces the expression of Alzheimer’s disease risk factors
D. Bortolotti;V. Gentili;E. Caselli;A. Rotola;D. Di Luca;R. Rizzo
2019
Abstract
Introduction: In Alzheimer's Disease (AD) brains, three pathological characteristics are observed: extracellular insoluble senile plaques formed by amyloid-β (Aβ) peptide, apoE, and its corresponding cholesterol that co-localize with Aβ plaques (Lazar 2013) and intraneuronal neurofibrillary tangles (NFT) formed by tau protein (Kumar 2015). Recent findings suggest a possible implication of HHV-6A in AD (Eimer 2018; Readhead 2018), and we showed the ability of HHV-6A to induce the expression of apoE, a risk factor for AD onset (Rizzo 2019). The control of viral infections in the brain involves the activation of microglial cells, the macrophages of the brain that are constantly surveying the central nervous system and, in response to small variations, they rapidly change their morphology, become activated, secrete pro- and anti-inflammatory molecules, and phagocytose foreign material that can alter the equilibrium of the brain (Ransohoff 2016). We evaluated the effect of HHV-6A infection on microglial cells expression of the common risk factor for AD development: apoE, Aβ, and tau. Materials and Methods: We have infected microglial cells (HMC3, ATCC®CRL-3304), in monolayer and spheroid 3D model, with HHV-6A (strain U1102) cell-free virus inocula with 100 genome equivalents per 1 cell. We collected the cells 1, 3, 7 and 14 days post infection (d.p.i.) and analyzed them for viral DNA and RNA, apoE, Aβ (1-40, 1-42), tau and phospho-tau (Threonine 181) by Real Time, immunofluorescence and immunoenzymatic assay. Results: We observed a productive infection by HHV-6A. The expression of apoE increased at 3 d.p.i. and Aβ 1-40 expression increased from 7 d.p.i., while no significant induction was observed for Aβ 1-42 expression. The secretion of Tau started from 7 d.p.i., with an increasing percentage of the phosphorylated form. Conclusions: Microglial cells are permissive to HHV-6A infection, that induces the expression of the common risk factor for AD development: apoE, Aβ, and tau. Interesting, there is a temporal induction of these molecules: apoE is induced from 3 d.p.i. followed by Aβ 1-40 from 7 d.p.i. and by phospho-tau from 14 d.p.i.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
