Biology subjects

Darley-Usmar, V.

Publications and source records attributed to Darley-Usmar, V..

8 recordsLinked to original sources

bioRxiv2026

ROCK inhibitor Ripasudil reduces Alzheimer pathological proteins and enhances cellular bioenergetics

Rho-associated kinase (ROCK) inhibitors have been explored as an Alzheimer Disease (AD) therapeutic agent. In this study, we aim to determine the efficacy of a potent ROCK inhibitor, ripasudil, in impacting AD pathological protein tau in mice. The time-course study showed that ripasudil rapidly penetrated mouse brains, reaching maximal concentration half an hour post-injection. To determine the efficacy of ripasudil, we injected AppNL-G-F knock-in mice with ripasudil at 30 mg/kg and sacrificed them after three hours. We used Tandem Mass Tag labels and compared the proteomic profiles of mouse brains exposed to ripasudil to those exposed to saline. We also treated AD-patient-derived Neural Stem Cells (NSCs) with ripasudil and performed a Seahorse Mito Stress Test to evaluate their impact on mitochondrial activity. Bioinformatics analysis of the proteomic profiles revealed differentially enriched components of chromosome. The Mito Stress Test of NSCs revealed significant increases in basal oxygen consumption, ATP-linked respiration, maximal respiration, and reserve capacity oxygen consumption compared to untreated NSCs. Importantly, we found a significant reduction of Tau and pTau 396 in brains of mice treated with ripasudil. Overall, our findings highlight the feasibility and promise of ROCK inhibitor ripasudil as an AD therapeutic agent.

neuroscience↗

bioRxiv2024

Sex-specific decline in prefrontal cortex mitochondrial bioenergetics in aging baboons correlates with walking speed

Mitochondria play a crucial role in brain aging due to their involvement in bioenergetics, neuroinflammation and brain steroid synthesis. Mitochondrial dysfunction is linked to age-related neurodegenerative diseases, including Alzheimers disease and Parkinsons disease. We investigated changes in the activities of the electron transport chain (ETC) complexes in normally aging baboon brains and determined how these changes relate to donor sex, morning cortisol levels, and walking speed. Using a novel approach, we assessed mitochondrial bioenergetics from frozen prefrontal cortex (PFC) tissues from a large cohort (60 individuals) of well-characterized aging baboons (6.6-22.8 years, approximately equivalent to 26.4-91.2 human years). Aging was associated with a decline in mitochondrial ETC complexes in the PFC, which was more pronounced when activities were normalized for citrate synthase activity, suggesting that the decline in respiration is predominantly driven by changes in the specific activity of individual complexes rather than changes in mitochondrial number. Moreover, when donor sex was used as a covariate, we found that mitochondrial respiration was preserved with age in females, whereas males showed significant loss of ETC activity with age. Males had higher activities of each individual ETC complex and greater lactate dehydrogenase activity relative to females. Circulating cortisol levels correlated only with complex II-linked respiration in males. We also observed a robust positive predictive relationship between walking speed and respiration linked to complexes I, III, and IV in males but not in females. This data reveals a previously unknown link between aging and bioenergetics across multiple tissues linking frailty and bioenergetic function. This study highlights a potential molecular mechanism for sexual dimorphism in brain resilience and suggests that in males changes in PFC bioenergetics contribute to reduced motor function with age.

physiology↗

bioRxiv2024

Impact of O-GlcNAcylation elevation on mitophagy and glia in the dentate gyrus

O-GlcNAcylation is a dynamic and reversible protein post-translational modification of serine or threonine residues which modulates the activity of transcriptional and signaling pathways and controls cellular responses to metabolic and inflammatory stressors. We and others have shown that O-GlcNAcylation has the potential to regulate autophagy and mitophagy to play a critical role in mitochondrial quality control, but this has not been assessed in vivo in the brain. This is important since mitochondrial dysfunction contributes to the development of neurodegenerative disease. We used mito-QC reporter mice to assess mitophagy in diverse cells in the dentate gyrus in response to pharmacological inhibition of OGA with thiamet G which leads to elevation of protein O-GlcNAcylation. We demonstrate that mitophagy occurs predominantly in the GFAP positive astrocytes and is significantly decreased in response to elevated O-GlcNAcylation. Furthermore, with increased O-GlcNAcylation, the levels of astrocyte makers GFAP and S100B, and microglial cell marker IBA1 were decreased in the dentate gyrus, while the levels of microglial cell marker TMEM119 were increased, indicating significant changes in glia homeostasis. These results provide strong evidence of the regulation of mitophagy and glia signatures by the O-GlcNAc pathway.

neuroscience↗

bioRxiv2024

Alpha-synuclein preformed fibril-induced aggregation and dopaminergic cell death in cathepsin D overexpression and ZKSCAN3 knockout mice

-synuclein accumulation is recognized as a prominent feature in the majority of Parkinsons disease cases and also occurs in a broad range of neurodegenerative disorders including Alzheimers disease. It has been shown that -synuclein can spread from a donor cell to neighboring cells and thus propagate cellular damage, antagonizing the effectiveness of therapies such as transplantation of fetal or iPSC derived dopaminergic cells. As we and others previously have shown, insufficient lysosomal function due to genetic mutations or targeted disruption of cathepsin D can cause -synuclein accumulation. We here investigated whether overexpression of cathepsin D or knockout (KO) of the transcriptional suppressor of lysosomal biogenesis ZKSCAN3 can attenuate propagation of -synuclein aggregation and cell death. We examined dopaminergic neurodegeneration in the substantia nigra using stereology of tyrosine hydroxylase-immunoreactive cells 4 months and 6 months after intrastriatal injection of -synuclein preformed fibrils or monomeric -synuclein control in control, central nervous system (CNS)-cathepsin D overexpressing and CNS-specific ZKSCAN3 KO mice. We also examined pS129--synuclein aggregates in the substantia nigra, cortex, amygdala and striatum. The extent of dopaminergic neurodegeneration and pS129--synuclein aggregation in the brains of CNS-specific ZKSCAN3 knockout mice and CNS-cathepsin D overexpressing mice was similar to that observed in wild-type mice. Our results indicate that neither enhancing cathepsin D expression nor disrupting ZKSCAN3 in the CNS is sufficient to attenuate pS129--synuclein aggregate accumulation or dopaminergic neurodegeneration.

neuroscience↗

bioRxiv2021

Metabolic Derangement in Polycystic Kidney Disease Mouse Models Is Ameliorated by Mitochondrial-Targeted Antioxidants

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressively enlarging cysts. Here we elucidate the interplay between oxidative stress, mitochondrial dysfunction, and metabolic derangement using two mouse models of PKD1 mutation, PKD1RC/null and PKD1RC/RC. Mouse kidneys with PKD1 mutation have decreased mitochondrial complexes activity. Targeted proteomics analysis shows a significant decrease in proteins involved in the TCA cycle, fatty acid oxidation (FAO), respiratory complexes, and endogenous antioxidants. Overexpressing mitochondrial-targeted catalase (mCAT) using adeno-associated virus reduces mitochondrial ROS, oxidative damage, ameliorates the progression of PKD and partially restores expression of proteins involved in FAO and the TCA cycle. In human ADPKD cells, inducing mitochondrial ROS increased ERK1/2 phosphorylation and decreased AMPK phosphorylation, whereas the converse was observed with increased scavenging of ROS in the mitochondria. Treatment with the mitochondrial protective peptide, SS31, recapitulates the beneficial effects of mCAT, supporting its potential application as a novel therapeutic for ADPKD.

pathology↗

bioRxiv2021

Mesenchymal Stromal Cell Aging Impairs the Self-Organizing Capacity of Lung Alveolar Epithelial Stem Cells

Multicellular organisms maintain structure and function of tissues/organs through emergent, self-organizing behavior. In this report, we demonstrate a critical role for lung mesenchymal stromal cell (L-MSC) aging in determining the capacity to form 3-dimentional organoids or "alveolospheres " with type 2 alveolar epithelial cells (AEC2s). In contrast to L-MSCs from aged mice, young L-MSCs support the efficient formation of alveolospheres when co-cultured with young or aged AEC2s. Aged L-MSCs demonstrated features of cellular senescence, altered bioenergetics, and a senescence-associated secretory profile (SASP). The reactive oxygen species generating enzyme, NADPH oxidase 4 (Nox4), was highly activated in aged L-MSCs and Nox4 downregulation was sufficient to, at least partially, reverse this age-related energy deficit, while restoring the self-organizing capacity of alveolospheres. Together, these data indicate a critical role for cellular bioenergetics and redox homeostasis in an organoid model of self-organization, and supports the concept of thermodynamic entropy in aging biology.

cell biology↗

bioRxiv2020

Oxylipin metabolism is controlled by mitochondrial b-oxidation during bacterial inflammation.

Oxylipins are potent biological mediators requiring strict control, but how they are removed en masse during infection and inflammation is unknown. Here we show that lipopolysaccharide (LPS) dynamically enhances oxylipin removal via mitochondrial {beta}-oxidation. Specifically, genetic or pharmacological targeting of carnitine palmitoyl transferase 1 (CPT1), a mitochondrial importer of fatty acids, reveal that many oxylipins are removed by this protein during inflammation in vitro and in vivo. Using stable isotope-tracing lipidomics, we find secretion-reuptake recycling for 12-HETE and its intermediate metabolites. Meanwhile, oxylipin {beta}-oxidation is uncoupled from oxidative phosphorylation, thus not contributing to energy generation. Testing for genetic control checkpoints, transcriptional interrogation of human neonatal sepsis finds upregulation of many genes involved in mitochondrial removal of long-chain fatty acyls, such as ACSL1,3,4, ACADVL, CPT1B, CPT2 and HADHB. Also, ACSL1/Acsl1 upregulation is consistently observed following the treatment of human/murine macrophages with LPS and IFN-{gamma}. Last, dampening oxylipin levels by {beta}-oxidation is suggested to impact on their regulation of leukocyte functions. In summary, we propose mitochondrial {beta}-oxidation as a regulatory metabolic checkpoint for oxylipins during inflammation.

biochemistry↗

bioRxiv2019

Mito-SinCe2 Approach to Quantify Relationships between Mitochondrial Dynamics and Energetics status

Mitochondrial dynamics primarily refers to the opposing fission and fusion events between individual mitochondria, which maintains steady-state mitochondrial morphology in cells. The details of the bidirectional relationship between mitochondrial dynamics and energetics are unclear as the methods to integrate these mitochondrial aspects are lacking. To study the quantitative relationship between mitochondrial dynamics (fission, fusion, matrix continuity and diameter) and energetics (ATP and redox), we have developed and validated an analytical approach, mito-SinCe2. Application of this approach led to the hypothesis that mitochondria-dependent ovarian tumor initiating cells interconvert between 3 states with distinct relationships between mitochondrial energetics and dynamics. Interestingly, fusion and ATP increase linearly with each other only once a certain level of fusion is attained. Moreover, mitochondrial dynamics status changes linearly either with ATP or with redox, but not simultaneously with both. Furthermore, mito-SinCe2 analyses can potentially predict new quantitative features of the opposing fission vs. fusion relationship and classify cells into functional classes based on their mito-SinCe2 states.

cell biology↗