Biology subjects

Picard, M.

Publications and source records attributed to Picard, M..

46 records · Page 3Linked to original sources

bioRxiv2021

Cross-species metabolomic analysis of DDT and Alzheimer's disease-associated tau toxicity

BackgroundThe formation of hyperphosphorylated tau (p-tau) protein tangles in neurons is a pathological marker of Alzheimers disease (AD). Exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) has been associated with increased risk of AD. ObjectivesTo determine if there was a connection between DDT exposure and tau toxicity we investigated whether exposure to DDT can exacerbate tau protein toxicity in C. elegans. In addition, we examined the association between p-tau protein and metabolism in a human population study and in a transgenic C. elegans strain neuronally expressing a mutant tau protein fragment that is prone to aggregation. MethodsIn the human population study, we used a metabolome-wide association framework to determine the association between p-tau measured in the cerebrospinal fluid (CSF) and metabolomic features measured in both plasma (n = 142) and CSF (n = 78) using high-resolution metabolomics (HRM). Using the same HRM method, we determined changes in metabolomic features in the transgenic C. elegans strain compared to its control strain. Metabolites associated with p-tau in both species were analyzed for overlap. We also examined the effect of DDT and aggregating tau protein on growth, swim behavior, mitochondrial function, metabolism, learning, and lifespan in C. elegans. ResultsPlasma and CSF-derived features associated with p-tau level were related to drug, amino acid, fatty acid and mitochondrial metabolism pathways. Five metabolites overlapped between plasma and C. elegans, and 4 between CSF and C. elegans. DDT exacerbated the inhibitory effect of aggregating tau protein on growth and basal respiration. In the presence of aggregating tau protein, DDT induced more curling and was associated with reduced levels of amino acids but increased levels of uric acid and adenosylselenohomocysteine. Developmental exposure to DDT blunted the lifespan reduction caused by aggregating tau protein. ConclusionThe model organism C. elegans can complement human studies by providing a means to study mechanisms of environmental toxicants. Specifically, our C. elegans data show that DDT exposure and tau protein aggregation both inhibit mitochondrial function and DDT exposure can exacerbate the mitochondrial inhibitory effects of tau protein aggregation providing a plausible explanation for the observed human associations.

pharmacology and toxicology↗

bioRxiv2021

Mouse brain-wide mitochondrial connectivity anchored in gene, brain and behavior

The brain and behavior are under energetic constraints, limited by mitochondrial energy transformation capacity. However, the mitochondria-behavior relationship has not been systematically studied on a brain-wide scale. Here we examined the association between multiple features of mitochondrial respiratory chain capacity and stress-related behaviors in mice with diverse behavioral phenotypes. Miniaturized assays of mitochondrial respiratory chain enzyme activities and mitochondrial DNA (mtDNA) content were deployed on 571 samples across 17 brain areas, defining specific patterns of mito-behavior associations. By applying multi-slice network analysis to our brain-wide mitochondrial dataset, we identified three large-scale networks of brain areas with shared mitochondrial signatures. A major network composed of cortico-striatal areas exhibited the strongest mitochondria-behavior correlations, accounting for up to 50% of animal-to-animal behavioral differences, suggesting that this mito-based network is functionally significant. The mito-based brain networks also overlapped with regional gene expression and structural connectivity and quantitatively diverged in their molecular mitochondrial phenotype signatures. Therefore, this work provides convergent multimodal evidence anchored in enzyme activities, gene expression, and animal behavior that distinct, behaviorally-relevant mitochondrial phenotypes exist across the mouse brain.

neuroscience↗

bioRxiv2021

3D Neuronal Mitochondrial Morphology in Axons, Dendrites, and Somata of the Aging Mouse Hippocampus

The brains ability to process complex informations relies on the constant supply of energy through aerobic respiration by mitochondria. Neurons contain three anatomically distinct compartments - the soma, dendrites, and projecting axons - which have different energetic and biochemical requirements, as well as different mitochondrial morphologies in cultured systems. Here we apply a quantitative three-dimensional electron microscopy approach to map mitochondrial network morphology and complexity in the mouse brain. We examine three neuronal sub-compartments - the soma, dendrites, myelinated axons - in the dentate gyrus and CA1 of the mouse hippocampus, two subregions with distinct principal cell types and functions. We also establish compartment-specific differences in mitochondrial morphology across these cell types between young and old mice, highlighting differences in age-related morphological recalibrations. Overall, these data define the nature of the neuronal mitochondrial network in the mouse hippocampus, providing a foundation to examine the role of mitochondrial morpho-function in the aging brain.

neuroscience↗

bioRxiv2021

Ovarian Tumor Mitochondria Exhibit Abnormal Phenotypes and Blunted Associations with Biobehavioral Factors

Tumor cells exhibit mitochondrial alterations and are also influenced by biobehavioral processes, but the intersection of biobehavioral factors and tumor mitochondria remains unexplored. Here we examined multiple biochemical and molecular markers of mitochondrial content and function in benign and cancerous ovarian tissue in parallel with exploratory analyses of biobehavioral factors. First, analysis of a publicly-available database (n=1,435) showed that gene expression of specific mitochondrial proteins in ovarian tumors is associated with survival. Quantifying multiple biochemical and molecular markers of mitochondrial content and function in 51 benign and 128 high-grade epithelial ovarian tumors revealed that compared to benign tissue, tumors exhibit 3.3-8.4-fold higher mitochondrial content and respiratory chain enzymatic activities (P<0.001) but similar mitochondrial DNA levels (-3.1%), documenting abnormal mitochondrial phenotypes in tumors. Mitochondrial respiratory chain activity was also associated with interleukin-6 (IL-6) levels in ascites. In benign tissue, negative biobehavioral factors were inversely correlated with mitochondrial content and respiratory chain activities, whereas positive biobehavioral factors tended to be positively correlated with mitochondrial measures, although effect sizes were small to medium (r=-0.43 to 0.47). In contrast, serous tumors showed less pronounced biobehavioral-mitochondrial correlations. These results document abnormal mitochondrial functional phenotypes in ovarian tumors and warrant further research on the link between biobehavioral factors and mitochondria in cancer.

cancer biology↗

bioRxiv2020

Mitochondrial profiling reveals dynamic, sex- and age-specific mitochondrial phenotypes in human immune cell subtypes

Using a high-throughput mitochondrial phenotyping platform to quantify multiple mitochondrial features among molecularly-defined immune cell subtypes, we quantify the natural variation in citrate synthase, mitochondrial DNA copy number (mtDNAcn), and respiratory chain enzymatic activities in human neutrophils, monocytes, B cells, and naive and memory T lymphocyte subtypes. In mixed peripheral blood mononuclear cells (PBMCs) from the same individuals, we show to what extent mitochondrial measures are confounded by both cell type distributions and contaminating platelets. Cell subtype-specific measures among women and men spanning 4 decades of life indicate potential age- and sex-related differences, including an age-related elevation in mtDNAcn, which are masked or blunted in mixed PBMCs. Finally, a proof-of-concept, repeated-measures study in a single individual validates cell type differences and also reveals week-to-week changes in mitochondrial activities. Larger studies are required to validate and mechanistically extend these findings. These mitochondrial phenotyping data build upon established immunometabolic differences among leukocyte sub-populations, and provide foundational quantitative knowledge to develop interpretable blood-based assays of mitochondrial health.

cell biology↗

bioRxiv2020

An automated, high throughput methodology optimized for quantitative cell-free mitochondrial and nuclear DNA isolation from plasma

Circulating, cell-free mitochondrial DNA (ccf-mtDNA) and nuclear DNA (ccf-nDNA) are under investigation as biomarkers for various diseases. Optimal ccf-mtDNA isolation parameters, like those outlined for ccf-nDNA, have not been established. Here, we optimized a protocol for both ccf-mtDNA and ccf-nDNA recovery using a magnetic bead-based isolation process on an automated 96-well platform. Using the optimized protocol, our data show 6-fold improved yields of ccf-mtDNA when compared to the starting protocol. Digestion conditions, liquid handling characteristics, and magnetic particle processor programming all contributed to increased recovery and improved reproducibility. To our knowledge, this is the first high-throughput approach optimized for mtDNA and nDNA recovery and serves as an important starting point for clinical studies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=191 HEIGHT=200 SRC="FIGDIR/small/206987v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@13ab547org.highwire.dtl.DTLVardef@1535020org.highwire.dtl.DTLVardef@b191aaorg.highwire.dtl.DTLVardef@1d23fa4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2020

Quantum dot probes for the quantitative study of drug transport by the MacAB TolC efflux pump in lipid scaffolds

ABC tripartite efflux pumps are macromolecular membrane protein machineries that expel a large variety of drugs and export virulence factors from Gram negative bacteria. Using a lipid scaffold mimicking the two-membrane environment of the transporter and designing spectroscopic conditions allowing the monitoring of both ATP hydrolysis and substrate transport in real time, we show that MacAB-TolC accommodates transport and energy consumption with high coupling efficiency.

biochemistry↗

bioRxiv2020

Human Hair Graying is Naturally Reversible and Linked to Stress

Hair graying is a universal hallmark of aging believed to be linked to psychological stress. Here we develop a novel approach to quantitatively profile natural graying events along individual human hair shafts, resulting in a quantifiable physical timescale of hair pigmentation patterns (HPPs). Using this approach, we quantify rare events of white/gray hairs that naturally regain pigmentation within days to weeks, thereby quantitatively defining the reversibility of graying in healthy, unmedicated individuals. Proteomic analysis shows that graying is marked by the upregulation of proteins related to energy metabolism, mitochondria, and antioxidant defenses. Combining hair pigmentation profiling and proteomics at the single hair level, we also report hair graying and its reversal occurring in parallel with behavioral and psychological stressors. A computational simulation suggests a threshold-based mechanism for the temporary reversibility of graying. Quantitatively mapping HPPs in humans provides an opportunity to longitudinally examine the influence of life exposures on biological aging.

cell biology↗

bioRxiv2019

Human Aging DNA Methylation Signatures are Conserved but Accelerated in Cultured Fibroblasts

Aging is associated with progressive and site-specific changes in DNA methylation (DNAm). These global changes are captured by DNAm clocks that accurately predict chronological age in humans but relatively little is known about how clocks perform in vitro. Here we culture primary human fibroblasts across the cellular lifespan ([~]6 months) and use four different DNAm clocks to show that age-related DNAm signatures are conserved and accelerated in vitro. The Skin & Blood clock shows the best linear correlation with chronological time (r=0.90), including during replicative senescence. Although similar in nature, the rate of epigenetic aging is approximately 62x times faster in cultured cells than in the human body. Consistent with in vivo data, cells aged under hyperglycemic conditions exhibit an approximately three years elevation in baseline DNAm age. Moreover, candidate gene-based analyses further corroborate the conserved but accelerated biological aging process in cultured fibroblasts. Fibroblasts mirror the established DNAm topology of the age-related ELOVL2 gene in human blood and the rapid hypermethylation of its promoter cg16867657, which correlates with a linear decrease in ELOVL2 mRNA levels across the lifespan. Using generalized additive modeling on twelve timepoints across the lifespan, we also show how single CpGs exhibit loci-specific, linear and nonlinear trajectories that reach rates up to -47% (hypomethylation) to +23% (hypermethylation) per month. Together, these high temporal resolution global, gene-specific, and single CpG data highlight the conserved and accelerated nature of epigenetic aging in cultured fibroblasts, which may constitute a system to evaluate age-modifying interventions across the lifespan.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC=\"FIGDIR/small/605295_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (60K):\norg.highwire.dtl.DTLVardef@101e4f2org.highwire.dtl.DTLVardef@15df049org.highwire.dtl.DTLVardef@4a704dorg.highwire.dtl.DTLVardef@112f970_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract\n\nC_FIG

cell biology↗

bioRxiv2018

Acute Psychological Stress Triggers Circulating Cell-Free Mitochondrial DNA

Intrinsic biological mechanisms transduce psychological stress into physiological adaptation, but the role of mitochondria and mitochondrial DNA (mtDNA) in this process has not been defined in humans. Here, we show that similar to physical injury, psychological stress triggers elevation in circulating cell- free mtDNA (ccf-mtDNA). Healthy midlife adults exposed on two separate occasions to a brief psychological challenge exhibit a 2-3-fold increase in ccf-mtDNA, with no change in nuclear DNA levels, establishing the magnitude and specificity to ccf-mtDNA. In cell-based studies, we show that glucocorticoid signaling - a consequence of psychological stress in humans - is sufficient to induce mtDNA extrusion in a time frame consistent with human psychophysiology. Collectively, these findings provide the first evidence that psychological stress induces ccf-mtDNA and implicate glucocorticoid signaling as a trigger for ccf-mtDNA release. Further work is needed to examine the functional significance of psychological stress-induced ccf-mtDNA as a mitokine in humans.

molecular biology↗