Biology subjects

Stuppard, R.

Publications and source records attributed to Stuppard, R..

4 recordsLinked to original sources

bioRxiv2025

Mitochondrial Dysfunction Drives Age-Related Degeneration of the Thoracic Aorta

This study investigated the role of mitochondrial function in aortic aging. As the aorta ages, it becomes stiffer and less compliant, increasing the risk of aneurysmal disease, hypertension, and diastolic dysfunction. Given the role of mitochondrial dysfunction in non-age related aortopathies and as a hallmark of aging, we investigated its contribution to the aging aorta. Both male and female young (5-6 month) and aged (24-25 month) C57Bl/6J mice received mitochondrial-targeted peptide elamipretide (ELAM; SS-31) for 8 weeks. ELAM restored complex II-linked respiration in aged mice to values seen in young mice, while also improving relative phosphorylative flux. ELAM treatment also reduced inflammatory MMP9 expression and elastin breaks in aged mice. Bulk RNAseq analysis revealed that ELAM treatment significantly affected the aortic transcriptome in an age-dependent manner, reducing the expression of senescent and associated pro-inflammatory genes. Mitochondrial dysfunction thus drives aortic aging and is a potential therapeutic target for future study. TeaserLoss of mitochondrial function with age drives degeneration of the aging aorta, and thus is a potential target for therapy.

cell biology↗

bioRxiv2024

Inducible and reversible SOD2 knockdown in mouse skeletal muscle drives impaired pyruvate oxidation and reduced metabolic flexibility

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/614547v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@e71637org.highwire.dtl.DTLVardef@1638df6org.highwire.dtl.DTLVardef@fd1b6borg.highwire.dtl.DTLVardef@11345b3_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG HighlightsO_LISOD2 knockdown and recovery is achieved in skeletal muscle by using a shRNA targeted to SOD2 mRNA controlled by a tetracycline Response Element and reverse tetracycline transactivator protein C_LIO_LISOD2 KD is induced by administering doxycycline in the drinking water C_LIO_LIMitochondrial functional decline and recovery follows the time course of SOD2 protein decline and recovery C_LIO_LISustained SOD2 KD precipitates reduced metabolic flexibility in skeletal muscle mitochondria characterized by impaired pyruvate respiration in the presence of other substrates C_LI IntroductionSkeletal muscle mitochondrial dysfunction is a key characteristic of aging muscle and contributes to age related diseases such as sarcopenia, frailty, and type 2 diabetes. Mitochondrial oxidative distress has been implicated as a driving factor in these age-related diseases, however whether it is a cause, or a consequence of mitochondrial dysfunction remains to be determined. The development of more flexible genetic models is an important tool to test the mechanistic role of mitochondrial oxidative stress on skeletal muscle metabolic dysfunction. We characterize a new model of inducible and reversible mitochondrial redox stress using a tetracycline controlled skeletal muscle specific short hairpin RNA targeted to superoxide dismutase 2 (iSOD2). MethodsiSOD2 KD and control (CON) animals were administered doxycycline for 3-or 12-weeks and followed for up to 24 weeks and mitochondrial respiration and muscle contraction were measured to define the time course of SOD2 KD and muscle functional changes and recovery. ResultsMaximum knockdown of SOD2 protein occurred by 6 weeks and recovered by 24 weeks after DOX treatment. Mitochondrial aconitase activity and maximum mitochondrial respiration declined in KD muscle by 12 weeks and recovered by 24 weeks. There were minimal changes in gene expression between KD and CON muscle. Twelve-week KD showed a small, but significant decrease in muscle fatigue resistance. The primary phenotype was reduced metabolic flexibility characterized by impaired pyruvate driven respiration when other substrates are present. The pyruvate dehydrogenase kinase inhibitor dichloroacetate partially restored pyruvate driven respiration, while the thiol reductant DTT did not. ConclusionWe use a model of inducible and reversible skeletal muscle SOD2 knockdown to demonstrate that elevated matrix superoxide reversibly impairs mitochondrial substrate flexibility characterized by impaired pyruvate oxidation. Despite the bioenergetic effect, the limited change in gene expression suggests that the elevated redox stress in this model is confined to the mitochondrial matrix.

physiology↗

bioRxiv2022

Mitochondrial interactome remodeling in aging mouse skeletal muscle associated with functional decline.

Genomic, transcriptomic, and proteomic approaches have been employed to gain insight into molecular underpinnings of aging in laboratory animals and in humans. However, protein function in biological systems is under complex regulation and includes factors in addition to abundance levels, such as modifications, localization, conformation, and protein-protein interactions. We have applied new robust quantitative chemical cross-linking technologies to uncover changes muscle mitochondrial interactome contributing to functional decline in aging. Statistically significant age-related changes in protein cross-link levels relating to assembly of electron transport system complexes I and IV, activity of glutamate dehydrogenase, and coenzyme-A binding in fatty acid beta-oxidation and TCA enzymes were observed. These changes showed remarkable correlation with measured CI based respiration differences within the same young-old animal pairs, indicating these cross-link levels offer new molecular insight on commonly observed age-related phenotypic differences. Overall, these system-wide quantitative mitochondrial interactome data provide the first molecular-level insight on ETS complex and substrate utilization enzyme remodeling that occur during age-related mitochondrial dysfunction. Each observed cross-link can serve as a protein conformational or protein-protein interaction probe in future studies making this dataset a unique resource for many additional in-depth molecular studies that are needed to better understand complex molecular changes that occur with aging.

systems biology↗

bioRxiv2019

Mitochondrial protein interaction landscape of SS-31

Mitochondrial dysfunction underlies the etiology of a broad spectrum of diseases including heart disease, cancer, neurodegenerative diseases, and the general aging process. Therapeutics that restore healthy mitochondrial function hold promise for treatment of these conditions. The synthetic tetrapeptide, elamipretide (SS-31), improves mitochondrial function, but mechanistic details of its pharmacological effects are unknown. Reportedly, SS-31 primarily interacts with the phospholipid cardiolipin in the inner mitochondrial membrane. Here we utilize chemical cross-linking with mass spectrometry to identify protein interactors of SS-31 in mitochondria. The SS-31-interacting proteins, all known cardiolipin binders, fall into two groups, those involved in ATP production through the oxidative phosphorylation pathway and those involved in 2-oxoglutarate metabolic processes. Residues cross-linked with SS-31 reveal binding regions that in many cases, are proximal to cardiolipin-protein interacting regions. These results offer the first glimpse of the protein interaction landscape of SS-31 and provide new mechanistic insight relevant to SS-31 mitochondrial therapy. Significance StatementSS-31 is a synthetic peptide that improves mitochondrial function and is currently undergoing clinical trials for treatments of heart failure, primary mitochondrial myopathy, and other mitochondrial diseases. SS-31 interacts with cardiolipin which is abundant in the inner mitochondrial membrane, but mechanistic details of its pharmacological effects are unknown. Here we apply a novel chemical cross-linking/mass spectrometry method to provide the first direct evidence for specific interactions between SS-31 and mitochondrial proteins. The identified SS-31 interactors are functional components in ATP production and 2-oxoglutarate metabolism and signaling, consistent with improved mitochondrial function resultant from SS-31 treatment. These results offer the first glimpse of the protein interaction landscape of SS-31 and provide new mechanistic insight relevant to SS-31 mitochondrial therapy.

systems biology↗