Browsing by Subject "Bioenergetics"

Now showing 1 - 5 of 5
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    Cardiomyopathy in Duchenne Muscular Dystrophy and the Potential for Mitochondrial Therapeutics to Improve Treatment Response
    (MDPI, 2024-07-09) Gandhi, Shivam; Sweeney, H. Lee; Hart, Cora C.; Han, Renzhi; Perry, Christopher G. R.; Pediatrics, School of Medicine
    Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease caused by mutations to the dystrophin gene, resulting in deficiency of dystrophin protein, loss of myofiber integrity in skeletal and cardiac muscle, and eventual cell death and replacement with fibrotic tissue. Pathologic cardiac manifestations occur in nearly every DMD patient, with the development of cardiomyopathy—the leading cause of death—inevitable by adulthood. As early cardiac abnormalities are difficult to detect, timely diagnosis and appropriate treatment modalities remain a challenge. There is no cure for DMD; treatment is aimed at delaying disease progression and alleviating symptoms. A comprehensive understanding of the pathophysiological mechanisms is crucial to the development of targeted treatments. While established hypotheses of underlying mechanisms include sarcolemmal weakening, upregulation of pro-inflammatory cytokines, and perturbed ion homeostasis, mitochondrial dysfunction is thought to be a potential key contributor. Several experimental compounds targeting the skeletal muscle pathology of DMD are in development, but the effects of such agents on cardiac function remain unclear. The synergistic integration of small molecule- and gene-target-based drugs with metabolic-, immune-, or ion balance-enhancing compounds into a combinatorial therapy offers potential for treating dystrophin deficiency-induced cardiomyopathy, making it crucial to understand the underlying mechanisms driving the disorder.
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    A Computational Study of the Mechanism for F1-ATPase Inhibition by the Epsilon Subunit
    (2013) Thomson, Karen J.; Pu, Jingzhi; Ge, Haibo; Sardar, Rajesh; Long, Eric C. (Eric Charles)
    The multi-protein complex of F0F1 ATP synthase has been of great interest in the fields of microbiology and biochemistry, due to the ubiquitous use of ATP as a biological energy source. Efforts to better understand this complex have been made through structural determination of segments based on NMR and crystallographic data. Some experiments have provided useful data, while others have brought up more questions, especially when structures and functions are compared between bacteria and species with chloroplasts or mitochondria. The epsilon subunit is thought to play a signi cant role in the regulation of ATP synthesis and hydrolysis, yet the exact pathway is unknown due to the experimental difficulty in obtaining data along the transition pathway. Given starting and end point protein crystal structures, the transition pathway of the epsilon subunit was examined through computer simulation.The purpose of this investigation is to determine the likelihood of one such proposed mechanism for the involvement of the epsilon subunit in ATP regulation in bacterial species such as E. coli.
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    Deciphering the Role of Mitochondrial Dysfunction in Pulmonary Arterial Hypertension
    (2024-06) Balachandar, Srimmitha; Aldred, Micheala A.; Graham, Brett H.; Zhang, Jie; Geraci, Mark W.; Machado, Roberto F.
    Pulmonary arterial hypertension (PAH) is a life-threatening vasculopathy caused by remodeling of pulmonary arterioles. It is unknown as to why some people are at more risk of developing PAH compared to others. Notably, while germline pathogenic variants in PAH genes are a strong driver of disease susceptibility, less than half of mutation carriers actually develop the disease, suggesting the need for additional triggers. Our previous studies have shown increased DNA damage and total reactive oxygen species (ROS) in cells from PAH patients and unaffected relatives, indicating a potential genetic component, leading to our hypothesis: Mitochondrial dysfunction is an independent genetically determined modifier of PAH susceptibility. Untargeted metabolomics (Metabolon) revealed abnormalities in the antioxidants, glutamate, urea, amino acid, galactose, and phospholipid metabolism pathways in the PAH Lymphoblastoid cells (LCLs) compared to controls. Intriguingly, the healthy relatives also had altered phospholipids, suggesting that it occurs independent of the disease. ROS analysis on LCLs from patients, their relatives and unrelated controls showed that the PAH LCLs had significantly higher levels of all ROS species compared to controls, with the highest in heritable PAH cells. LCLs from relatives clustered into two groups, one with increased mitochondrial (mt) ROS and hydrogen peroxide, the other comparable to controls. Seahorse assays showed that the LCLs with increased mtROS had reduced spare respiratory capacity indicative of dysfunctional electron transport chain (ETC); but no glycolytic switch. Cybrid models generated using the high and low ROS LCLs (H and L-donors) on a 143B nuclear background showed that the H-donors had mt respiration similar to L-donors, suggesting a functional ETC. However, these cells had significantly elevated mtROS, with reduced SOD2 protein (potentially a consequence of increased degradation), passed on from the parental LCLs to the recipient cybrids. PAH is a complex disease, and mutation status alone doesn’t determine disease susceptibility. LCLs from patients recapitulate some of the metabolomic abnormalities in lung vascular cells. Oxidative stress in LCLs extends to some unaffected relatives, suggesting this is an independent genetic trait that modifies PAH risk. Our study highlights the importance of identifying potential modifiers and the second hits in the pathogenesis of PAH.
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    Tumor Lymphatic Interactions Induce CXCR2-CXCL5 Axis and Alter Cellular Metabolism and Lymphangiogenic Pathways to Promote Cholangiocarcinoma
    (MDPI, 2021-11-09) Roy, Sukanya; Kumaravel, Subhashree; Banerjee, Priyanka; White, Tori K.; O’Brien, April; Seelig, Catherine; Chauhan, Rahul; Ekser, Burcin; Bayless, Kayla J.; Alpini, Gianfranco; Glaser, Shannon S.; Chakraborty, Sanjukta; Surgery, School of Medicine
    Cholangiocarcinoma (CCA), or cancer of bile duct epithelial cells, is a very aggressive malignancy characterized by early lymphangiogenesis in the tumor microenvironment (TME) and lymph node (LN) metastasis which correlate with adverse patient outcome. However, the specific roles of lymphatic endothelial cells (LECs) that promote LN metastasis remains unexplored. Here we aimed to identify the dynamic molecular crosstalk between LECs and CCA cells that activate tumor-promoting pathways and enhances lymphangiogenic mechanisms. Our studies show that inflamed LECs produced high levels of chemokine CXCL5 that signals through its receptor CXCR2 on CCA cells. The CXCR2-CXCL5 signaling axis in turn activates EMT (epithelial-mesenchymal transition) inducing MMP (matrix metalloproteinase) genes such as GLI, PTCHD, and MMP2 in CCA cells that promote CCA migration and invasion. Further, rate of mitochondrial respiration and glycolysis of CCA cells was significantly upregulated by inflamed LECs and CXCL5 activation, indicating metabolic reprogramming. CXCL5 also induced lactate production, glucose uptake, and mitoROS. CXCL5 also induced LEC tube formation and increased metabolic gene expression in LECs. In vivo studies using CCA orthotopic models confirmed several of these mechanisms. Our data points to a key finding that LECs upregulate critical tumor-promoting pathways in CCA via CXCR2-CXCL5 axis, which further augments CCA metastasis.
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    Uric acid formation is driven by crosstalk between skeletal muscle and other cell types
    (American Society for Clinical Investigation, 2024-01-23) Miller, Spencer G.; Matias, Catalina; Hafen, Paul S.; Law, Andrew S.; Witczak, Carol A.; Brault, Jeffrey J.; Anatomy, Cell Biology and Physiology, School of Medicine
    Hyperuricemia is implicated in numerous pathologies, but the mechanisms underlying uric acid production are poorly understood. Using a combination of mouse studies, cell culture studies, and human serum samples, we sought to determine the cellular source of uric acid. In mice, fasting and glucocorticoid treatment increased serum uric acid and uric acid release from ex vivo-incubated skeletal muscle. In vitro, glucocorticoids and the transcription factor FoxO3 increased purine nucleotide degradation and purine release from differentiated muscle cells, which coincided with the transcriptional upregulation of AMP deaminase 3, a rate-limiting enzyme in adenine nucleotide degradation. Heavy isotope tracing during coculture experiments revealed that oxidation of muscle purines to uric acid required their transfer from muscle cells to a cell type that expresses xanthine oxidoreductase, such as endothelial cells. Last, in healthy women, matched for age and body composition, serum uric acid was greater in individuals scoring below average on standard physical function assessments. Together, these studies reveal skeletal muscle purine degradation is an underlying driver of uric acid production, with the final step of uric acid production occurring primarily in a nonmuscle cell type. This suggests that skeletal muscle fiber purine degradation may represent a therapeutic target to reduce serum uric acid and treat numerous pathologies.