Browsing by Subject "Mitochondrial dysfunction"

Now showing 1 - 7 of 7
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    68722 Role of ER calcium in beta cell senescence and diabetes pathophysiology
    (Cambridge University Press, 2021) Weaver, Staci A.; Kono, Tatsuyoshi; Syed, Farooq; Bone, Robert; Evans-Molina, Carmella; Biochemistry and Molecular Biology, School of Medicine
    ABSTRACT IMPACT: The proposed study has the potential to inform new paradigms of type 1 diabetes prevention and therapy with the overall goal of improving β cell health during autoimmunity. OBJECTIVES/GOALS: Type 1 diabetes (T1D) results from immune-mediated destruction of pancreatic βcells. Recent data suggest that activation of senescence and acquisition of a senescence associated secretory phenotype (SASP) by βcells may contribute to T1D pathogenesis. However, the molecular mechanisms responsible for this phenotype are not well understood. METHODS/STUDY POPULATION: We hypothesize that loss of endoplasmic reticulum (ER) Ca2+ induces βcell senescence, SASP as well as mitochondrial dysfunction which drive T1D development. The current study utilizes SERCA2 KO INS-1 βcells (S2KO) exhibiting loss of ER Ca2+ and a SERCA2 haploinsufficient mice on a non-obese diabetic background (NOD-S2+/-) to test the role of ER Ca2+ loss during T1D development. Senescence associated βgalactosidase staining (SA-βgal), expression of senescence markers (RT-qPCR), mitochondrial function (Seahorse, TMRM) and mitochondrial copy number (qPCR) were all measured in S2KO versus WT βcells and are currently being measured in the NOD-S2+/- mouse model at 6, 8, 12, 14, and 16wks of age. RESULTS/ANTICIPATED RESULTS: RT-qPCR assays detecting senescence markers cdkn1a and cdkn2a and mitochondrial specific genes cox1 and nd1 were developed and validated in both INS-1 βcells and mouse islets. Mitochondrial function assay (Seahorse) was optimized for use in INS-1 βcells and is currently under development for use in intact mouse islets. S2KO βcells displayed increased SA- βgal staining as well as increased mitochondrial coupling efficiency (p=0.0146) and baseline mitochondrial copy number (p=0.0053) compared to WT βcells, suggesting a senescence phenotype and altered mitochondrial function. NOD-S2+/- mice exhibited increased expression of the senescence marker cdkn2a in the islet at 12wks (p=0.0117) compared to control mice, whereas cdkn1a remained unchanged across all timepoints tested. DISCUSSION/SIGNIFICANCE OF FINDINGS: Our results suggest that loss of SERCA2 and reduced ER Ca2+ alter βcell mitochondrial function and are associated with features of senescence. Future studies will test whether SERCA2 activation and/or senolytic/senomorphic drugs are able to prevent or delay diabetes onset in NOD-S2+/- mice.
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    Chronic Inflammation in Chronic Kidney Disease Progression: Role of Nrf2
    (Elsevier, 2021-05-04) Stenvinkel, Peter; Chertow, Glenn M.; Devarajan, Prasad; Levin, Adeera; Andreoli, Sharon P.; Bangalore, Sripal; Warady, Bradley A.; Pediatrics, School of Medicine
    Despite recent advances in the management of chronic kidney disease (CKD), morbidity and mortality rates in these patients remain high. Although pressure-mediated injury is a well-recognized mechanism of disease progression in CKD, emerging data indicate that an intermediate phenotype involving chronic inflammation, oxidative stress, hypoxia, senescence, and mitochondrial dysfunction plays a key role in the etiology, progression, and pathophysiology of CKD. A variety of factors promote chronic inflammation in CKD, including oxidative stress and the adoption of a proinflammatory phenotype by resident kidney cells. Regulation of proinflammatory and anti-inflammatory factors through NF-κB– and nuclear factor, erythroid 2 like 2 (Nrf2)–mediated gene transcription, respectively, plays a critical role in the glomerular and tubular cell response to kidney injury. Chronic inflammation contributes to the decline in glomerular filtration rate (GFR) in CKD. Whereas the role of chronic inflammation in diabetic kidney disease (DKD) has been well-elucidated, there is now substantial evidence indicating unresolved inflammatory processes lead to fibrosis and eventual end-stage kidney disease (ESKD) in several other diseases, such as Alport syndrome, autosomal-dominant polycystic kidney disease (ADPKD), IgA nephropathy (IgAN), and focal segmental glomerulosclerosis (FSGS). In this review, we aim to clarify the mechanisms of chronic inflammation in the pathophysiology and disease progression across the spectrum of kidney diseases, with a focus on Nrf2.
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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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    Increased Steroidogenic Acute Regulatory Protein Contributes to Cholesterol-induced β-Cell Dysfunction
    (Oxford University Press, 2025) Akter, Rehana; Hogan, Meghan F.; Esser, Nathalie; Barrow, Breanne M.; Castillo, Joseph J.; Boyko, Edward J.; Templin, Andrew T.; Hull, Rebecca L.; Zraika, Sakeneh; Kahn, Steven E.; Medicine, School of Medicine
    Hypercholesterolemia is often observed in individuals with type 2 diabetes. Cholesterol accumulation in subcellular compartments within islet β-cells can result in insulin secretory dysfunction, which is a key pathological feature of diabetes. Previously, we demonstrated that expression of the mitochondrial cholesterol transport protein, steroidogenic acute regulatory protein (StAR), is induced in islets under conditions of β-cell dysfunction. However, whether it contributes to mitochondrial cholesterol accumulation in β-cells and cholesterol-induced β-cell dysfunction has not been determined. Thus, we sought to examine the role of StAR in isolated mouse islets under conditions of excess exogenous cholesterol. Cholesterol treatment of islets upregulated StAR expression, which was associated with cholesterol accumulation in mitochondria, decreased mitochondrial membrane potential and impaired mitochondrial oxidative phosphorylation. Impaired insulin secretion and reduced islet insulin content were also observed in cholesterol-laden islets. To determine the impact of StAR overexpression in β-cells per se, a lentivirus was used to increase StAR expression in INS-1 cells. Under these conditions, StAR overexpression was sufficient to increase mitochondrial cholesterol content, impair mitochondrial oxidative phosphorylation, and reduce insulin secretion. These findings suggest that elevated cholesterol in diabetes may contribute to β-cell dysfunction via increases in StAR-mediated mitochondrial cholesterol transport and accumulation.
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    Plasma and Fecal Metabolite Profiles in Autism Spectrum Disorder
    (Elsevier, 2021) Needham, Brittany D.; Adame, Mark D.; Serena, Gloria; Rose, Destanie R.; Preston, Gregory M.; Conrad, Mary C.; Campbell, A. Stewart; Donabedian, David H.; Fasano, Alessio; Ashwood, Paul; Mazmanian, Sarkis K.; Anatomy, Cell Biology and Physiology, School of Medicine
    Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with hallmark behavioral manifestations including impaired social communication and restricted repetitive behavior. In addition, many affected individuals display metabolic imbalances, immune dysregulation, gastrointestinal dysfunction, and altered gut microbiome compositions. Methods: We sought to better understand nonbehavioral features of ASD by determining molecular signatures in peripheral tissues through mass spectrometry methods (ultrahigh performance liquid chromatography-tandem mass spectrometry) with broad panels of identified metabolites. Herein, we compared the global metabolome of 231 plasma and 97 fecal samples from a large cohort of children with ASD and typically developing control children. Results: Differences in amino acid, lipid, and xenobiotic metabolism distinguished ASD and typically developing samples. Our results implicated oxidative stress and mitochondrial dysfunction, hormone level elevations, lipid profile changes, and altered levels of phenolic microbial metabolites. We also revealed correlations between specific metabolite profiles and clinical behavior scores. Furthermore, a summary of metabolites modestly associated with gastrointestinal dysfunction in ASD is provided, and a pilot study of metabolites that can be transferred via fecal microbial transplant into mice is identified. Conclusions: These findings support a connection between metabolism, gastrointestinal physiology, and complex behavioral traits and may advance discovery and development of molecular biomarkers for ASD.
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    S-Adenosylmethionine Negatively Regulates the Mitochondrial Respiratory Chain Repressor MCJ in the Liver
    (Ivyspring, 2024-01-27) Barbier-Torres, Lucía; Chhimwal, Jyoti; Kim, So Yeon; Ramani, Komal; Robinson, Aaron; Yang, Heping; Van Eyk, Jenny; Liangpunsakul, Suthat; Seki, Ekihiro; Mato, José M.; Lu, Shelly C.; Biochemistry and Molecular Biology, School of Medicine
    MCJ (Methylation-Controlled J protein), an endogenous repressor of the mitochondrial respiratory chain, is upregulated in multiple liver diseases but little is known about how it is regulated. S-adenosylmethionine (SAMe), the biological methyl donor, is frequently depleted in chronic liver diseases. Here, we show that SAMe negatively regulates MCJ in the liver. While deficiency in methionine adenosyltransferase alpha 1 (MATα1), enzyme that catalyzes SAMe biosynthesis, leads to hepatic MCJ upregulation, MAT1A overexpression and SAMe treatment reduced MCJ expression. We found that MCJ is methylated at lysine residues and that it interacts with MATα1 in liver mitochondria, likely to facilitate its methylation. Lastly, we observed that MCJ is upregulated in alcohol-associated liver disease, a condition characterized by reduced MAT1A expression and SAMe levels along with mitochondrial injury. MCJ silencing protected against alcohol-induced mitochondrial dysfunction and lipid accumulation. Our study demonstrates a new role of MATα1 and SAMe in reducing hepatic MCJ expression.
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    Serum Humanin in Pediatric Septic Shock Associated Multiple Organ Dysfunction Syndrome
    (Wolters Kluwer, 2024) Atreya, Mihir R.; Piraino, Giovanna; Cvijanovich, Natalie Z.; Fitzgerald, Julie C.; Weiss, Scott L.; Bigham, Michael T.; Jain, Parag N.; Schwarz, Adam J.; Lutfi, Riad; Nowak, Jeffrey; Thomas, Neal J.; Baines, Torrey; Haileselassie, Bereketeab; Zingarelli, Basilia; Pediatrics, School of Medicine
    Background: Multiple organ dysfunction syndrome (MODS) disproportionately contributes to pediatric sepsis morbidity. Humanin (HN) is a small peptide encoded by mitochondrial DNA and thought to exert cytoprotective effects in endothelial cells and platelets. We sought to test the association between serum HN (sHN) concentrations and MODS in a prospectively enrolled cohort of pediatric septic shock. Methods: Human MT-RNR2 ELISA was used to determine sHN concentrations on day 1 and 3. The primary outcome was thrombocytopenia associated multi-organ failure (TAMOF). Secondary outcomes included individual organ dysfunctions on day 7. Associations across pediatric sepsis biomarker (PERSEVERE) based mortality risk strata and correlation with platelet and markers endothelial activation were tested. Results: 140 subjects were included in this cohort, of whom 39 had TAMOF. The concentration of sHN was higher on day 1 relative to day 3, and among those with TAMOF phenotype in comparison to those without. However, the association between sHN and TAMOF phenotype was not significant after adjusting for age and illness severity in multivariate models. In secondary analyses, sHN was associated with presence of day 7 sepsis-associated acute kidney injury (SA-AKI) (p=0.049). Further, sHN was higher among those with high PERSEVERE-mortality risk strata and correlated with platelet counts and several markers of endothelial activation. Conclusion: Future investigation is necessary to validate the association between sHN and SA-AKI among children with septic shock. Further, mechanistic studies that elucidate the role of humanin may lead to therapies that promote organ recovery through restoration of mitochondrial homeostasis among those critically ill.