Mitochondrial Cholesterol Loading Exacerbates Amyloid Peptide-Induced Inflammation and Neurotoxicity
ABSTRACT The role of cholesterol in Alzheimer's disease (AD) has been linked to the generation of toxic amyloid beta peptides (Abeta). Using genetic mouse models of cholesterol loading, we examined whether mitochondrial cholesterol regulates Abeta neurotoxicity and AD pathology. Isolated mitochondria from brain or cortical neurons of transgenic mice overexpressing SREBP-2 (sterol regulatory element binding protein 2) or NPC1 (Niemann-Pick type C1) knock-out mice exhibited mitochondrial cholesterol accumulation, mitochondrial glutathione (mGSH) depletion and increased susceptibility to Abeta1-42-induced oxidative stress and release of apoptogenic proteins. Similar findings were observed in pharmacologically GSH-restricted rat brain mitochondria, while selective mGSH depletion sensitized human neuronal and glial cell lines to Abeta1-42-mediated cell death. Intracerebroventricular human Abeta delivery colocalized with mitochondria resulting in oxidative stress, neuroinflammation and neuronal damage that were enhanced in Tg-SREBP-2 mice and prevented upon mGSH recovery by GSH ethyl ester coinfusion, with a similar protection observed by intraperitoneal administration of GSH ethyl ester. Finally, APP/PS1 (amyloid precursor protein/presenilin 1) mice, a transgenic AD mouse model, exhibited mitochondrial cholesterol loading and mGSH depletion. Thus, mitochondrial cholesterol accumulation emerges as a novel pathogenic factor in AD by modulating Abeta toxicity via mGSH regulation; strategies boosting the particular pool of mGSH may be of relevance to slow down disease progression.
- SourceAvailable from: Jan Albrecht
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- "Mitochondria isolated from cortical neurons of mice with enhanced cholesterol accumulation obtained by genetic manipulations: overexpression of SREBP-2, a sterol regulatory element binding protein 2 or Niemann–Pick type C1 knockout, showed a decrease in mGSH content and high susceptibility to Aβ-induced oxidative stress (Fernandez et al., 2009). In turn, selective mGSH depletion sensitized human neuronal and glial cell lines to Aβ-mediated cell death (Fernandez et al., 2009). Mitochondrial GSH depletion in SREBP-2-overexpressing APP/PS1 mice, an AD model, was shown to be subsequent to early mitochondrial cholesterol loading (Barbero-Camps et al., 2013). "
ABSTRACT: Oxidative and nitrosative stress (ONS) contributes to the pathogenesis of most brain maladies, and the magnitude of ONS is related to the ability of cellular antioxidants to neutralize the accumulating reactive oxygen and nitrogen species (ROS/RNS). While the major ROS/RNS scavengers and regenerators of bio-oxidized molecules: superoxide dysmutases (SODs), glutathione (GSH), thioredoxin (Trx) and peroxiredoxin (Prx) are distributed in all cellular compartments. This review specifically focuses on the role of the systems operating in mitochondria. There is a growing consensus that the mitochondrial SOD isoform - SOD2 and GSH are critical for the cellular antioxidant defense. Variable changes of the expression or activities of one or more of the mitochondrial antioxidant systems have been documented in the brains derived from human patients and/or in animal models of neurodegenerative diseases (Alzheimer's disease, Parkinson's disease), cerebral ischemia, toxic brain cell damage associated with overexposure to mercury or excitotoxins, or hepatic encephalopathy. In many cases, ambiguity of the responses of the different antioxidant systems in one and the same disease need to be more conclusively evaluated before the balance of the changes in viewed as beneficial or detrimental. Modulation of the mitochondrial antioxidant systems may in the future become a target of antioxidant therapy. Copyright © 2014. Published by Elsevier Ltd.Neurochemistry International 01/2015; 88. DOI:10.1016/j.neuint.2014.12.012 · 3.09 Impact Factor
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- "One possibility is that impaired mitophagy leads to the accumulation of dysfunctional mitochondria that produce more ROS . Several groups, including ours, have also shown that cholesterol trafficking defects in NPC1-deficient cells can lead to an increase of cholesterol in mitochondria, which in turn may affect their function –. An upregulation of glycolysis in Npc1-/- neurons and/or decreased ME1 activity may further increase oxidative stress by decreasing NADPH synthesis for glutathione regeneration . "
ABSTRACT: Niemann-Pick Type C (NPC) disease is an autosomal recessive neurodegenerative disorder caused in most cases by mutations in the NPC1 gene. NPC1-deficiency is characterized by late endosomal accumulation of cholesterol, impaired cholesterol homeostasis, and a broad range of other cellular abnormalities. Although neuronal abnormalities and glial activation are observed in nearly all areas of the brain, the most severe consequence of NPC1-deficiency is a near complete loss of Purkinje neurons in the cerebellum. The link between cholesterol trafficking and NPC pathogenesis is not yet clear; however, increased oxidative stress in symptomatic NPC disease, increases in mitochondrial cholesterol, and alterations in autophagy/mitophagy suggest that mitochondria play a role in NPC disease pathology. Alterations in mitochondrial function affect energy and neurotransmitter metabolism, and are particularly harmful to the central nervous system. To investigate early metabolic alterations that could affect NPC disease progression, we performed metabolomics analyses of different brain regions from age-matched wildtype and Npc1 (-/-) mice at pre-symptomatic, early symptomatic and late stage disease by (1)H-NMR spectroscopy. Metabolic profiling revealed markedly increased lactate and decreased acetate/acetyl-CoA levels in Npc1 (-/-) cerebellum and cerebral cortex at all ages. Protein and gene expression analyses indicated a pre-symptomatic deficiency in the oxidative decarboxylation of pyruvate to acetyl-CoA, and an upregulation of glycolytic gene expression at the early symptomatic stage. We also observed a pre-symptomatic increase in several indicators of oxidative stress and antioxidant response systems in Npc1 (-/-) cerebellum. Our findings suggest that energy metabolism and oxidative stress may present additional therapeutic targets in NPC disease, especially if intervention can be started at an early stage of the disease.PLoS ONE 12/2013; 8(12):e82685. DOI:10.1371/journal.pone.0082685 · 3.23 Impact Factor
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- "However, few studies to date have investigated the direct impact of LA on SCD-1 activity. SCD-1 plays an important role in maintaining the balance between SFA and UFA in the cell.38 We have examined SCD-1 mRNA expression by RT-PCR. "
ABSTRACT: BACKGROUNDAIMS: It is suggested that the hepatic lipid composition is more important than lipid quantity in the pathogenesis of non-alcoholic steatohepatitis. We examined whether lipoic acid (LA) could alter intrahepatic lipid composition and free cholesterol distribution. HepG2 cells were cultured with palmitic acid (PA) with and without LA. Apoptosis, changes of the mitochondrial structure, intracellular lipid partitioning, and reactive oxygen species (ROS) activity were measured. Free fatty acid (FA) increased apoptosis, and LA co-treatment prevented this lipotoxicity (apoptosis in controls vs PA vs PA+LA, 0.5% vs 19.5% vs 1.6%, p<0.05). LA also restored the intracellular mitochondrial DNA copy number (553±33.8 copies vs 291±14.55 copies vs 421±21.05 copies, p<0.05) and reversed the morphological changes induced by PA. In addition, ROS was increased in response to PA and was decreased in response to LA co-treatment (41,382 relative fluorescence unit [RFU] vs 43,646 RFU vs 41,935 RFU, p<0.05). LA co-treatment increased the monounsaturated and polyunsaturated FA concentrations and decreased the total saturated FA fraction. It also prevented the movement of intracellular free cholesterol from the cell membrane to the cytoplasm. LA opposes free FA-generated lipotoxicity by altering the intracellular lipid composition and free cholesterol distribution.Gut and liver 03/2013; 7(2):221-7. DOI:10.5009/gnl.2013.7.2.221 · 1.81 Impact Factor