Pasquale D'Acunzo, United States of America
Nathan S. Kline Institute for Psychiatric Research Center for Dementia ResearchAuthor Of 2 Presentations
MITOCHONDRIAL DYSFUNCTION IN THE BRAIN ALTERS THE HOMEOSTASIS OF A NEWLY IDENTIFIED POPULATION OF MITOCHONDRIA-DERIVED EXTRACELLULAR VESICLES
Abstract
Aims
Mitochondrial damage and oxidative stress are well-established players in the pathophysiology of several neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease, and Down syndrome (DS). Using a novel high-resolution density step-gradient to isolate and fractionate subpopulations of extracellular vesicles (EVs) from the brain parenchyma, we investigated the effect of mitochondrial dysfunction on the number and content of EVs in DS brains.
Methods
We isolated EVs from murine and human DS and diploid control post-mortem brains or from cell media. EVs were analyzed by nanoparticle tracking analysis, cryogenic electron microscopy, Western blotting, mass spectrometry, and qPCR.
Results
We found that the extracellular matrix of the brain contains a newly identified population of metabolically active, double-membrane, electron-dense EVs of mitochondrial origin that we have named ‘mitovesicles’. In vitro study revealed that oxidative stress enhances mitovesicle release in a mitophagy-independent fashion. In wild-type brains, we revealed that mitovesicles are low in number and encapsulate a specialized subset of mitochondrial constituents that reflects only partially the composition of intracellular mitochondria. Conversely, in human and murine DS brains, mitovesicle number is higher when compared to controls. The content is also modified, as the amount of the pro-inflammatory mitochondrial DNA in mitovesicles was higher in DS compared to controls.
Conclusions
Brain mitovesicles are tightly regulated in normal conditions and are modified in DS, suggesting that mitovesicles are a previously unrecognized player in mitochondria quality control and may have a yet undiscovered role in the inter-cellular response to oxidative stress and neuroinflammation.
SEX AND AGING ALTER SECRETION OF BRAIN EXTRACELLULAR VESICLES: A POTENTIAL MECHANISM FOR MAINTAINING BRAIN HOMEOSTASIS
Abstract
Aims
Upon aging, changes occur in the brain, including compromised communication between neurons, changes that are also affected by sex. Moreover, aging is a major risk factor for neurodegenerative diseases, including Alzheimer’s disease, and females and males differ in the incidence of the disease. Extracellular vesicles (EVs) in the normal brain play a role in neuronal homeostasis, by removing intracellular accumulated material and regulating cell-to-cell communication. We investigated age- and sex-dependent differences in EV levels and content in the brain.
Methods
EVs were isolated and fractioned from the right hemibrains of 3, 6, 12, 18, and 24-month-old female and male C57BL/6 mice. Morphometric EV sizes and numbers were investigated by nanoparticle tracking analysis. EV constituents were characterized by Western blotting.
Results
Using biochemical analyses of brain EVs, we investigated the amount of the plasma membrane-derived microvesicles, late endosome-derived exosomes, and mitochondria-derived mitovesicles, recently identified in our laboratory. We found an age-associated increase in the number of microvesicles, exosomes and mitovesicles in the brain of both sexes. The number of these EVs was higher in the brain of females compared to males. Analysis of the EV content of the amyloid β precursor protein and its metabolites (APP-carboxyl-terminal fragments) revealed an increased load of β-CTF in exosomes with age in both sexes.
Conclusions
These findings reveal age-dependent altered generation and secretion of EVs into the brain extracellular space and a difference in exosome generation between females and males, likely a compensation mechanism that impacts successful brain aging and sex-dependent susceptibility to age-related neurodegenerative diseases.
Presenter of 2 Presentations
LIVE DISCUSSION
MITOCHONDRIAL DYSFUNCTION IN THE BRAIN ALTERS THE HOMEOSTASIS OF A NEWLY IDENTIFIED POPULATION OF MITOCHONDRIA-DERIVED EXTRACELLULAR VESICLES
Abstract
Aims
Mitochondrial damage and oxidative stress are well-established players in the pathophysiology of several neurodegenerative diseases, including Parkinson’s disease, Alzheimer’s disease, and Down syndrome (DS). Using a novel high-resolution density step-gradient to isolate and fractionate subpopulations of extracellular vesicles (EVs) from the brain parenchyma, we investigated the effect of mitochondrial dysfunction on the number and content of EVs in DS brains.
Methods
We isolated EVs from murine and human DS and diploid control post-mortem brains or from cell media. EVs were analyzed by nanoparticle tracking analysis, cryogenic electron microscopy, Western blotting, mass spectrometry, and qPCR.
Results
We found that the extracellular matrix of the brain contains a newly identified population of metabolically active, double-membrane, electron-dense EVs of mitochondrial origin that we have named ‘mitovesicles’. In vitro study revealed that oxidative stress enhances mitovesicle release in a mitophagy-independent fashion. In wild-type brains, we revealed that mitovesicles are low in number and encapsulate a specialized subset of mitochondrial constituents that reflects only partially the composition of intracellular mitochondria. Conversely, in human and murine DS brains, mitovesicle number is higher when compared to controls. The content is also modified, as the amount of the pro-inflammatory mitochondrial DNA in mitovesicles was higher in DS compared to controls.
Conclusions
Brain mitovesicles are tightly regulated in normal conditions and are modified in DS, suggesting that mitovesicles are a previously unrecognized player in mitochondria quality control and may have a yet undiscovered role in the inter-cellular response to oxidative stress and neuroinflammation.