Biomedical subjects

Eugene V Mosharov

Publications and source records attributed to Eugene V Mosharov.

6 recordsLinked to original sources

PubMed2026

Individualised mapping of living human brain mitochondria by MRI reveals signatures of bioenergetic defects.

Mitochondria support the bioenergetic processes that enable brain function and cognition, but we have lacked a label-free, non-invasive approach to explore how brain mitochondria are linked to ageing, disease, and cognition in humans. A recently introduced MitoBrainMap neuroimaging framework predicts mitochondrial features from magnetic resonance data alone, potentially bridging cellular biology with macroscale brain organization. Here, we tested whether this framework captures meaningful age- and pathology-related mitochondrial variation. Consistent with existing literature, we find that MR-predicted mitochondrial density and tissue respiratory capacity consistently declined with age, whereas mitochondrial respiratory capacity-an index of mitochondrial quality-was relatively preserved across the lifespan. Moreover, the relations among specific mitochondrial features predicted from our algorithm were consistent with their biological organization, supporting preliminary construct validity for MR-predicted mitochondrial features. In patients with rare mitochondrial diseases, predicted maps revealed region-specific alterations in mitochondrial density and respiratory chain components, particularly the expected compensatory upregulation of complex II, but not of other mitochondrial genome-encoded components. Finally, the MR-based mitochondrial features were associated with the energetic stress marker GDF15 measured in blood, as well as with cognitive performance measures, linking the novel predictions of brain mitochondria to systemic stress and behavior. These findings introduce a first-generation, label-free, neuroimaging-based mitochondrial mapping as a non-invasive window into living human brain mitochondria.

Journal Article↗

PubMed2006

Alpha-synuclein overexpression increases cytosolic catecholamine concentration.

Dysregulation of dopamine homeostasis and elevation of the cytosolic level of the transmitter have been suggested to underlie the vulnerability of catecholaminergic neurons in Parkinson's disease. Because several known mutations in alpha-synuclein or overexpression of the wild-type (WT) protein causes familial forms of Parkinson's disease, we investigated possible links between alpha-synuclein pathogenesis and dopamine homeostasis. Chromaffin cells isolated from transgenic mice that overexpress A30P alpha-synuclein displayed significantly increased cytosolic catecholamine levels as measured by intracellular patch electrochemistry, whereas cells overexpressing the WT protein and those from knock-out animals were not different from controls. Likewise, catechol concentrations were higher in L-DOPA-treated PC12 cells overexpressing A30P or A53T compared with those expressing WT alpha-synuclein, although the ability of cells to maintain a low cytosolic dopamine level after L-DOPA challenge was markedly inhibited by either protein. We also found that incubation with low-micromolar concentrations of WT, A30P, or A53T alpha-synuclein inhibited ATP-dependent maintenance of pH gradients in isolated chromaffin vesicles and that the WT protein was significantly less potent in inducing the proton leakage. In summary, we demonstrate that overexpression of different types of alpha-synuclein disrupts vesicular pH and leads to a marked increase in the levels of cytosolic catechol species, an effect that may in turn trigger cellular oxyradical damage. Although multiple molecular mechanisms may be responsible for the perturbation of cytosolic catecholamine homeostasis, this study provides critical evidence about how alpha-synuclein might exert its cytotoxicity and selectively damage catecholaminergic cells.

Animals↗

PubMed2005

SNAREs can promote complete fusion and hemifusion as alternative outcomes.

Using a cell fusion assay, we show here that in addition to complete fusion SNAREs also promote hemifusion as an alternative outcome. Approximately 65% of events resulted in full fusion, and the remaining 35% in hemifusion; of those, approximately two thirds were permanent and approximately one third were reversible. We predict that this relatively close balance among outcomes could be tipped by binding of regulatory proteins to the SNAREs, allowing for dynamic physiological regulation between full fusion and reversible kiss-and-run-like events.

3T3 Cells↗

PubMed2005

Analysis of exocytotic events recorded by amperometry.

Amperometry is widely used to study exocytosis of neurotransmitters and hormones in various cell types. Analysis of the shape of the amperometric spikes that originate from the oxidation of monoamine molecules released during the fusion of individual secretory vesicles provides information about molecular steps involved in stimulation-dependent transmitter release. Here we present an overview of the methodology of amperometric signal processing, including (i) amperometric signal acquisition and filtering, (ii) detection of exocytotic events and determining spike shape characteristics, and (iii) data manipulation and statistical analysis. The purpose of this review is to provide practical guidelines for performing amperometric recordings of exocytotic activity and interpreting the results based on shape characteristics of individual release events.

Algorithms↗

PubMed2004

Dopamine neurons release transmitter via a flickering fusion pore.

A key question in understanding mechanisms of neurotransmitter release is whether the fusion pore of a synaptic vesicle regulates the amount of transmitter released during exocytosis. We measured dopamine release from small synaptic vesicles of rat cultured ventral midbrain neurons using carbon fiber amperometry. Our data indicate that small synaptic vesicle fusion pores flicker either once or multiple times in rapid succession, with each flicker releasing approximately 25-30% of vesicular dopamine. The incidence of events with multiple flickers was reciprocally regulated by phorbol esters and staurosporine. Thus, dopamine neurons regulate the amount of neurotransmitter released by small synaptic vesicles by controlling the number of fusion pore flickers per exocytotic event. This mode of exocytosis is a potential mechanism whereby neurons can rapidly reuse vesicles without undergoing the comparatively slow process of recycling.

Animals↗

PubMed2003

Intracellular patch electrochemistry: regulation of cytosolic catecholamines in chromaffin cells.

Alterations in the cytosolic pool directly affect neurotransmitter synthesis and release and are suggested to be key factors in various neurodegenerative disorders. Although this cytosolic pool is the most metabolically active, it is miniscule compared with the amount of vesicular transmitter and has never been quantified separately. Here, we introduce intracellular patch electrochemistry (IPE), a technique that for the first time provides direct measurements of cytosolic oxidizable molecules in single mammalian cells. In amperometric mode, IPE detects total catechols, whereas in cyclic voltammetric mode, it preferentially measures catecholamines. In cultured chromaffin cells, the total cytosolic catechol concentration was 50-500 microm, of which approximately 10% were catecholamines. Reserpine, a vesicular monoamine transporter inhibitor, had no effect on the catecholamine pool but increased total catechols by fourfold to fivefold. Combined with pargyline, a monoamine oxidase inhibitor, reserpine increased catecholamine levels in the cytosol by approximately sixfold. Amphetamine induced a transient approximately fivefold accumulation of cytosolic catecholamines and a slow increase of total catechols. In cells incubated with 3,4-dihydroxy-L-phenylalanine (L-DOPA), catecholamines increased by approximately 2.5-fold and total catechols increased by approximately fourfold. Cytosolic catecholamines returned to control levels <or=10 min after L-DOPA withdrawal, whereas total catechols remained approximately twofold elevated even after a 1.5 hr incubation in L-DOPA-free media. Our data indicate that cytosolic catecholamines are strictly maintained at a defined level, and drug-induced increases in their concentrations lead to the accumulation of other catecholamine derivatives, such as DOPAC and 3,4-dihydroxyphenylethyleneglycol. These derivatives reside in the cytosol for hours after treatment and may be an underlying cause of drug-related cytotoxicity.

Adrenergic Uptake Inhibitors↗