Neuronal Cholesterol Accumulation Induced by Cyp46a1 Down-Regulation in Mouse Hippocampus Disrupts Brain Lipid Homeostasis

Impairment in cholesterol metabolism is associated with many neurodegenerative disorders including Alzheimer's disease (AD). However, the lipid alterations underlying neurodegeneration and the connection between altered cholesterol levels and AD remains not fully understood. We recently showed that cholesterol accumulation in hippocampal neurons, induced by silencing Cyp46a1 gene expression, leads to neurodegeneration with a progressive neuronal loss associated with AD-like phenotype in wild-type mice. We used a targeted and non-targeted lipidomics approach by liquid chromatography coupled to high-resolution mass spectrometry to further characterize lipid modifications associated to neurodegeneration and cholesterol accumulation induced by CYP46A1 inhibition. Hippocampus lipidome of normal mice was profiled 4 weeks after cholesterol accumulation due to Cyp46a1 gene expression down-regulation at the onset of neurodegeneration. We showed that major membrane lipids, sphingolipids and specific enzymes involved in phosphatidylcholine and sphingolipid metabolism, were rapidly increased in the hippocampus of AAV-shCYP46A1 injected mice. This lipid accumulation was associated with alterations in the lysosomal cargoe, accumulation of phagolysosomes and impairment of endosome-lysosome trafficking. Altogether, we demonstrated that inhibition of cholesterol 24-hydroxylase, key enzyme of cholesterol metabolism leads to a complex dysregulation of lipid homeostasis. Our results contribute to dissect the potential role of lipids in severe neurodegenerative diseases like AD

Synthesis of <i>S</i>-mono- and <i>S,O</i>-bis-1,2,3-triazole linked 1,5-benzodiazepine conjugates and evaluation of their cytotoxic, anti-tyrosinase, and anti-cholinesterase activities

<p>A series of <i>S</i>-mono and <i>S,O</i>-bis-1,2,3-triazole linked 1,5-benzodiazepines (BZD) conjugates <b>6a-j</b> and <b>7a-j</b> were synthesized employing “click chemistry” under microwave irradiation. The synthesized derivatives have been evaluated for their cytotoxic (MCF-7, HeLa, A549 cell lines), anti-tyrosinase and anti-cholinesterase activities. These molecules exhibited moderate to good biological activity.</p

Ceramides and sphingomyelinases in senile plaques

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Resveratrol metabolism in a non-human primate, the grey mouse lemur (Microcebus murinus), using ultra-high-performance liquid chromatography-quadrupole time of flight.

The grey mouse lemur (Microcebus murinus) is a non-human primate used to study the ageing process. Resveratrol is a polyphenol that may increase lifespan by delaying age-associated pathologies. However, no information about resveratrol absorption and metabolism is available for this primate. Resveratrol and its metabolites were qualitatively and quantitatively analyzed in male mouse-lemur plasma (after 200 mg.kg-1 of oral resveratrol) by ultra-high performance liquid chromatography (UHPLC), coupled to a quadrupole-time-of-flight (Q-TOF) mass spectrometer used in full-scan mode. Data analyses showed, in MSE mode, an ion common to resveratrol and all its metabolites: m/z 227.072, and an ion common to dihydro-resveratrol metabolites: m/z 229.08. A semi-targeted study enabled us to identify six hydrophilic resveratrol metabolites (one diglucurono-conjugated, two monoglucurono-conjugated, one monosulfo-conjugated and two both sulfo- and glucurono-conjugated derivatives) and three hydrophilic metabolites of dihydro-resveratrol (one monoglucurono-conjugated, one monosulfo-conjugated, and one both sulfo- and glucurono-conjugated derivatives). The presence of such metabolites has been already detected in the mouse, rat, pig, and humans. Free resveratrol was measurable for several hours in mouse-lemur plasma, and its two main metabolites were trans-resveratrol-3-O-glucuronide and trans-resveratrol-3-sulfate. Free dihydro-resveratrol was not measurable whatever the time of plasma collection, while its hydrophilic metabolites were present at 24 h after intake. These data will help us interpret the effect of resveratrol in mouse lemurs and provide further information on the inter-species characteristics of resveratrol metabolism

Neuronal Cholesterol Accumulation Induced by Cyp46a1 Down-Regulation in Mouse Hippocampus Disrupts Brain Lipid Homeostasis

International audienc

Low- and high-collision energy spectra of ions specific to resveratrol-glucuronide, <i>m/z</i> 403.102.

<p>Low- and high-collision energy spectra of ions specific to resveratrol-glucuronide, <i>m/z</i> 403.102.</p

Concentrations of <i>trans</i>-resveratrol and its hydrophilic metabolites and hydrophilic metabolites of dihydro-resveratrol (DHR).

<p>Mean values in µmol.L⁻¹. Values expressed as “<i>trans</i>-resveratrol-4′-O-ß-glucuronide equivalent” for <i>trans</i>-resveratrol glucuronide sulfate and DHR-glucuronide sulfate; as “<i>trans</i>-resveratrol-3-O-ß-glucuronide equivalent” for the DHR-glucuronide and as “<i>trans</i>-resveratrol-3-sulfate equivalent” for the DHR-sulfate. CV% between mouse lemurs (round brackets), range [square brackets]. There were three determinations for each concentration. <i>n</i>: sample size.</p><p>LLOQ: lower limit of quantification.</p