ATP-linked Respiration Research Articles

Mitochondrial-related effects of pentabromophenol, tetrabromobisphenol A, and triphenyl phosphate on murine BV-2 microglia cells

The predominant reliance on bromated flame retardants (BFRs) is diminishing with expanded use of alternative organophosphate flame retardants. However, exposure related issues for susceptible populations, the developing, infirmed, or aged, remain given environmental persistence and home-environment detection. In this regard, reports of flame retardant (FR)-related effects on the innate immune system suggest process by which a spectrum of adverse health effects could manifest across the life-span. As representative of the nervous system innate immune system, the current study examined changes in microglia following exposure to representative FRs, pentabromophenol (PBP), tetrabromobisphenol A (2,2′,6,6′,-tetrabromo-4,4′-isopropylidine diphenol; TBBPA) and triphenyl phosphate (TPP). Following 18hr exposure of murine BV-2 cells, at dose levels resulting in ≥80% viability (10 and 40 μM), limited alterations in pro-inflammatory responses were observed however, changes were observed in mitochondrial respiration. Basal respiration was altered by PBP; ATP-linked respiration by PBP and TBBPA, and maximum respiration by all three FRs. Basal glycolytic rate was altered by PBP and TBBPA and compensatory glycolysis by all three. Phagocytosis was decreased for PBP and TBBPA. NLRP3 inflammasome activation was assessed using BV-2-ASC (apoptosis-associated speck-like protein containing a CARD) reporter cells to visualize aggregate formation. PBP, showed a direct stimulation of aggregate formation and properties as a NLRP3 inflammasome secondary trigger. TBBPA showed indications of possible secondary triggering activity while no changes were seen with TPP. Thus, the data suggests an effect of all three FRs on mitochondria metabolism yet, different functional outcomes including, phagocytic capability and NLRP3 inflammasome activation.

The effect of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) severity on cellular bioenergetic function.

Myalgic encephalomyelitis/ Chronic fatigue syndrome (ME/CFS) has been associated with abnormalities in mitochondrial function. In this study we have analysed previous bioenergetics data in peripheral blood mononuclear cells (PBMCs) using new techniques in order to further elucidate differences between ME/CFS and healthy control cohorts. We stratified our ME/CFS cohort into two individual cohorts representing moderately and severely affected patients in order to determine if disease severity is associated with bioenergetic function in PBMCs. Both ME/CFS cohorts showed reduced mitochondrial function when compared to a healthy control cohort. This shows that disease severity does not correlate with mitochondrial function and even those with a moderate form of the disease show evidence of mitochondrial dysfunction. Equations devised by another research group have enabled us to calculate ATP-linked respiration rates and glycolytic parameters. Parameters of glycolytic function were calculated by taking into account respiratory acidification. This revealed severely affected ME/CFS patients to have higher rates of respiratory acidification and showed the importance of accounting for respiratory acidification when calculating parameters of glycolytic function. Analysis of previously published glycolysis data, after taking into account respiratory acidification, showed severely affected patients have reduced glycolysis compared to moderately affected patients and healthy controls. Rates of ATP-linked respiration were also calculated and shown to be lower in both ME/CFS cohorts. This study shows that severely affected patients have mitochondrial and glycolytic impairments, which sets them apart from moderately affected patients who only have mitochondrial impairment. This may explain why these patients present with a more severe phenotype.

SLC25A34 regulates bioenergetic metabolism in the murine liver

Background and RationaleLiver regeneration and diseases associated with altered mitochondrial metabolism, including NAFLD, are associated with alterations in ploidy. Many genes that regulate mitochondrial metabolism are also reported to alter hepatic polyploidy. SLC25A34 encodes an uncharacterized inner mitochondrial membrane protein, with a novel role in liver polyploidy. Interestingly, dysregulated Slc25a34 expression has been reported in numerous studies, which are all characterized by metabolic dysfunction, particularly altered glucose metabolism and fatty acid metabolism. We now hypothesize that SLC25A34 regulates various aspects of liver metabolism.ResultsIn the current study, SLC25A34 was over expressed or knocked down in primary hepatocytes harvested from adult C57BL/6 mice and subsequent effects on different metabolic phenotypes were studied. Downregulation of SLC25A34 significantly increased the lipid droplets with a concurrent increase in expression of key players of fatty acid metabolism (Cpt1A, Srebf1, Acly). Maximal mitochondrial respiration and spare respiratory capacity were significantly elevated, possibly attributing to the increased levels of lipid droplets. Also, basal mitochondrial respiration and ATP‐linked mitochondrial respiration were significantly increased, accompanied by increased expression of regulators of mitochondrial biogenesis (PGC‐1 alpha, PGC‐1 beta, Prc and Tfam). In contrast, overexpression of SLC25A34 decreased expression of Cpt1A, Srebf1, Acly, but had no effect on lipid droplets. Unexpectedly, SLC25A34 overexpression also increased maximal mitochondrial respiration and spare respiratory capacity, as well as non‐mitochondrial respiration. Further, effect on energy intermediates (ADP, ATP and their ratio) and hepatocyte proliferation were studied. SLC25A34 depletion raised the ADP/ATP ratio and decreased hepatocyte proliferation, whereas overexpression of SLC25A34 decreased the ADP/ATP ratio and increased proliferation. Furthermore, SLC25A34 manipulation altered fatty acid oxidation and glycolysis functionally in primary hepatocytes as determined using the seahorse extracellular flux analyzer. Preliminary in‐vivo studies utilizing both whole‐body and liver‐specific SLC25A34 knockout mice indicate similar bioenergetic changes upon SLC25A34 deletion.ConclusionThe data suggest that SLC25A34 is a key regulator of bioenergetic metabolism where it is involved in metabolic homeostasis and that modulation of SLC25A34 creates distinct metabolic phenotypes in the primary hepatocytes.Support or Funding InformationThis study is supported by NIDDKR01DK103645 and UPP Academic Foundation awarded to Dr. Andrew Wayne Duncan.

Methylmalonic Acid Compromises Energy Metabolism and Decreases the Expression of Neuronal Differentiation Genes in SH‐SY5Y Human Neuroblastoma Cells

Methylmalonic acidemia is an organic acidemia caused by deficient activity of L‐methylmalonyl‐CoA mutase or its cofactor cyanocobalamin and it is biochemically characterized by an accumulation of methylmalonic acid (MMA) in tissue and body fluids of patients. The main clinical manifestations of this disease are neurological and symptoms during metabolic decompensation commonly appear in newborns. Considering that the mechanisms underlying neurological alterations of this disorder are not fully understood, this study aimed to investigate the toxic effects of MMA in a neuroblastoma cell line presenting neuronal features. Undifferentiated and retinoic acid (RA)‐differentiated human neuroblastoma SH‐SY5Y cells were exposed to MMA (1–10mM) for 24 or 48 hours and cell viability, glucose consumption and mitochondrial metabolic function were analyzed. Additionally, the expression of some molecular markers of neuronal differentiation was also quantified after co‐exposition with 10 μM RA and 1 mM of MMA for 3 and 7 days.MMA significantly reduced cell viability after 48‐hour period exposition in undifferentiated and RA differentiated SH‐SY5Y cells. It was also observed an increase in glucose consumption in cells exposed to MMA. Regarding oxygen consumption, there was an increase in respiratory parameters in RA differentiated SH‐SY5Y cells when compared to undifferentiated cells. MMA significantly reduced basal, ATP‐linked and maximal respiration, as well as the reserve respiratory capacity of cells after 48‐hour exposition in both undifferentiated and RA differentiated SH‐SY5Y cells. Regarding the effects of MMA in the neuronal differentiation process, it was observed that co‐exposition to RA and MMA significantly decreased the expression of enolase 2 (ENO2) and synaptophysin (SYP) genes after 7 days of exposition.In summary, MMA cell viability and oxygen consumption in SH‐SY5Y neuronal cells, suggesting that this organic acid compromises cell respiration, at resting and reserve capacity states, which might influence the cell capacity to meet energetic demands. In addition, glucose uptake was increased after exposition to MMA, corroborating that aerobic metabolism is compromised. The expression of mature neuronal genes was also reduced, suggesting that MMA possibly compromises neuronal differentiation, which can be involved in symptoms presented by affected patients during brain development. Finally, our findings suggest that these effects could be involved in the pathophysiology of neurological dysfunction of this disease.Support or Funding InformationThis study was supported by grants from FAPESP (2015/25541‐0), CAPES and UFABC.

Metabolic Reprograming Due to Deletion of <i>CISH</i> in Human Natural Killer Cells Promotes <i>in vivo</i> Persistence and Enhances Anti-Tumor Activity

Cytokine-inducible SH2-containing protein (CIS, encoded by the gene CISH) is a key negative regulator of IL-15 signaling in natural killer (NK) cells. Here, we developed human CISH knockout (CISH-/-) NK cells using an induced pluripotent stem cell-derived NK cell (iPSC-NK cell) platform. CISH-/- iPSC-derived NK cells demonstrate increased IL-15 mediated JAK-STAT pathway signaling activity. Consequently CISH-/- iPSC-NK cells exhibit improved expansion and increased cytotoxic activity against multiple tumor cell lines when maintained at low cytokine concentration. CISH-/- iPSC-NK cells display significantly increased in vivo persistence and inhibition of tumor progression in a leukemia xenograft model. Mechanistically, CISH-/- iPSC-NK cells display improved metabolic fitness characterized by a significant increase in basal glycolysis, glycolytic capacity, maximal mitochondrial respiration, ATP-linked respiration and spare capacity respiration which are mediated by mTOR signaling and directly contribute to enhanced NK cell function. In addition, we demonstrate that deletion of CISH in human NK cells increases single-cell polyfunctionality by secreting multiple effector cytokines, a profile has been proven to be positively associated with clinical outcome of CAR-T cells. Together, these studies demonstrate CIS plays a key role to regulate human NK cell metabolic activity and deletion of CIS leads to enhanced anti-tumor activity.

Acetoacetate enhances oxidative metabolism and response to toxicants of cultured kidney cells

Cultured kidney cells maintained in conventional growth media with high glucose levels exhibit increased glycolytic activity compared to the cells in vivo. In contrast, renal proximal tubules utilize substrates such as ketone bodies and rely on mitochondrial oxidative phosphorylation. LLC-PK1 cells maintain many features of the proximal tubule but are exposed to glucose concentrations ranging from 17 to 25 mM. This may impact their reliability in predicting mitochondrial toxicity. This study is designed to test the impact of the ketone body acetoacetate on metabolic characteristics of LLC-PK1 cells. Basal respiration, maximal respiration, spare respiratory capacity and ATP-linked respiration were significantly increased in cells grown in growth medium supplemented with 5 mM acetoacetate. In contrast, glycolytic capacity, as well as glycolytic reserve were significantly reduced in the acetoacetate group. There was an increased expression in biomarkers of mitochondrial biogenesis, and an increase in mitochondrial protein expression. Cells grown in medium complemented with acetoacetate displayed a significantly lower LC50 when treated with clotrimazole and diclofenac. There was a marked increase in uncoupled respiration in the presence of diclofenac, while clotrimazole and ciprofibrate significantly decreased respiration in the acetoacetate. The results indicate that acetoacetate complemented media can alter cellular metabolism and increase sensitization to toxicants.

Toxic effects of arsenic trioxide on spermatogonia are associated with oxidative stress, mitochondrial dysfunction, autophagy and metabolomic alterations.

Arsenic is a toxic metalloid that can cause male reproductive malfunctions and is widely distributed in the environment. The aim of this study was to investigate the cytotoxicity of arsenic trioxide (ATO) induced GC-1 spermatogonial (spg) cells. Our results found that ATO increased the levels of catalase (CAT) and malonaldehyde (MDA) and reactive oxygen species (ROS), while decreasing glutathione (GSH) and the total antioxidant capacity (T-AOC). Therefore, ATO triggered oxidative stress in GC-1 spg cells. In addition, ATO also caused severe mitochondrial dysfunction that included an increase in residual oxygen consumption (ROX), and decreased the routine respiration, maximal and ATP-linked respiration (ATP-L-R), as well as spare respiratory capacity (SRC), and respiratory control rate (RCR); ATO also damaged the mitochondrial structure, including mitochondrial cristae disordered and dissolved, mitochondrial vacuolar degeneration. Moreover, degradation of p62, LC3 conversion, increasing the number of acidic vesicle organelles (AVOs) and autophagosomes and autolysosomes are demonstrated that the cytotoxicity of ATO may be associated with autophagy. Meanwhile, the metabolomics analysis results showed that 20 metabolites (10 increased and 10 decreased) were significantly altered with the ATO exposure, suggesting that maybe there are the perturbations in amino acid metabolism, lipid metabolism, glycan biosynthesis and metabolism, metabolism of cofactors and vitamins. We concluded that ATO was toxic to GC-1 spg cells via inducing oxidative stress, mitochondrial dysfunction and autophagy as well as the disruption of normal metabolism. This study will aid our understanding of the mechanisms behind ATO-induced spermatogenic toxicity.

Deletion of CISH in Human Pluripotent Stem Cell-Derived Natural Killer Cells Enhances Anti-Tumor Activity Via Metabolic Reprogramming

Cellular metabolism is now recognized to play a key role in regulating function and differentiation of immune cells. Immune cells undergo dynamic metabolic shifts to support their activity. Recent studies have shown the importance of metabolism to regulate NK cell function under different conditions. IL-15 can regulate NK cell metabolism in a dose- and time- dependent manner. However, whether improving metabolic fitness of NK cells can lead to improved anti-tumor activity is largely unknown. Here, we deleted CIS (encoded by the CISH gene in human induced pluripotent stem cells (iPSC)-derived NK cells (CISH-/- iPSC-NK) using CRISPR/Cas9 technology. CIS is known to function as a critical negative regulator of IL-15 signaling and a potent inhibitory checkpoint in NK cell-mediated anti-tumor activity. Surprisingly, more than 3000 differentially expressed genes were identified in CISH-/- iPSC-NK cells through RNA sequencing analysis. Gene ontology (GO) enrichment analysis showed that the top 2 up-regulated signaling pathways were associated with leukocyte differentiation and activation. Notably, more than 50 genes that involved in positive regulation of lymphocyte activation including genes associated with NK cell effector functions were significantly up-regulated in CISH-/- iPSC-NK cells compared with unmodified iPSC-NK cells. As expected, CISH-/- iPSC-NK cells exhibited increased sensitivity to IL-15 stimulation. Specifically, IL-15 stimulated JAK1 tyrosine phosphorylation, STAT3 and STAT5 phosphorylation were all dramatically increased in CISH-/- iPSC-NK cells, compared with unmodified iPSC-NK cells. In addition, when incubated with low concentrations of IL-15 (5 ng/ml), a concentration that does not support the growth and functions of unmodified iPSC-NK cells, CISH-/- iPSC-NK cells maintained significantly better expansion with >10 fold expansion for CISH-/- iPSC-NK cells in 3 weeks, whereas most of WT iPSC-NK cells died under these conditions (p<0.001). These CISH-/- iPSC-NK cells exhibited improved cytotoxic against acute myeloid leukemia (AML) cell lines K562 and Molm-13. More importantly, in an AML (MOLM-13) xenograft model, CISH-/- iPSC-NK cells displayed significantly increased in vivo persistence thus lead to significantly better control of tumor progression. To further understand the underling mechanisms contributing to the increased functionality in CISH-/- iPSC-NK cells, we then analyzed the metabolic profiles of these cells using Agilent Seahorse assays. After treatment with low concentration IL-15 for 7 days, CISH-/- iPSC-NK cells displayed both increased glucose metabolism and increased mitochondrial respiration profiles when compared with unmodified iPSC-NK cells. Increased glucose metabolism include a significant increase in basal glycolysis (p=0.0003, 84.5 ± 1.0 vs 61.1 ± 1.8 mpH/min, n=6), and glycolytic capacity (p=0.0049, 15.2±0.4 vs 11.7±0.5 mpH/min, n=6). And increased mitochondrial respiration profile is characterized by an increase in the spare respiratory capacity (p=0.0009, 16.3±1.9 vs 6.9±0.5 pmol/min, n=6), maximal respiration (p<0.0001, 31.6±1.9 vs 15.7±0.8 pmol/min, n=6) and ATP-linked respiration (p<0.0001, 11.5 ± 0.4 vs 7.0±0.3 pmol/min, n=6). Interestingly, limiting the increase of glucose metabolism and mitochondrial respiration via utilization of an mTOR inhibitor (rapamycin) attenuated the increased functionality in CISH-/- iPSC-NK cells. The findings presented here show that deletion of CISH in iPSC-NK cells enhance anti-tumor activity, at least in part via metabolic reprogramming. These findings suggest that improving NK cell functions for cancer immunotherapy through metabolic reprogramming provides a promising therapeutic strategy. Disclosures Guan: OncoImmune: Equity Ownership. Kaufman:FATE Therapeutics: Consultancy, Research Funding.

Osteocalcin Regulates Arterial Calcification Via Altered Wnt Signaling and Glucose Metabolism.

Arterial calcification is an important hallmark of cardiovascular disease and shares many similarities with skeletal mineralization. The bone-specific protein osteocalcin (OCN) is an established marker of vascular smooth muscle cell (VSMC) osteochondrogenic transdifferentiation and a known regulator of glucose metabolism. However, the role of OCN in controlling arterial calcification is unclear. We hypothesized that OCN regulates calcification in VSMCs and sought to identify the underpinning signaling pathways. Immunohistochemistry revealed OCN co-localization with VSMC calcification in human calcified carotid artery plaques. Additionally, 3 mM phosphate treatment stimulated OCN mRNA expression in cultured VSMCs (1.72-fold, p < 0.001). Phosphate-induced calcification was blunted in VSMCs derived from OCN null mice (Ocn -/- ) compared with cells derived from wild-type (WT) mice (0.37-fold, p < 0.001). Ocn -/- VSMCs showed reduced mRNA expression of the osteogenic marker Runx2 (0.51-fold, p < 0.01) and the sodium-dependent phosphate transporter, PiT1 (0.70-fold, p < 0.001), with an increase in the calcification inhibitor Mgp (1.42-fold, p < 0.05) compared with WT. Ocn -/- VSMCs also showed reduced mRNA expression of Axin2 (0.13-fold, p < 0.001) and Cyclin D (0.71 fold, p < 0.01), markers of Wnt signaling. CHIR99021 (GSK3β inhibitor) treatment increased calcium deposition in WT and Ocn -/- VSMCs (1 μM, p < 0.001). Ocn -/- VSMCs, however, calcified less than WT cells (1 μM; 0.27-fold, p < 0.001). Ocn -/- VSMCs showed reduced mRNA expression of Glut1 (0.78-fold, p < 0.001), Hex1 (0.77-fold, p < 0.01), and Pdk4 (0.47-fold, p < 0.001). This was accompanied by reduced glucose uptake (0.38-fold, p < 0.05). Subsequent mitochondrial function assessment revealed increased ATP-linked respiration (1.29-fold, p < 0.05), spare respiratory capacity (1.59-fold, p < 0.01), and maximal respiration (1.52-fold, p < 0.001) in Ocn -/- versus WT VSMCs. Together these data suggest that OCN plays a crucial role in arterial calcification mediated by Wnt/β-catenin signaling through reduced maximal respiration. Mitochondrial dynamics may therefore represent a novel therapeutic target for clinical intervention. © 2019 American Society for Bone and Mineral Research.

Mitofusins modulate the increase in mitochondrial length, bioenergetics and secretory phenotype in therapy-induced senescent melanoma cells.

Cellular senescence is an endpoint of chemotherapy, and targeted therapies in melanoma and the senescence-associated secretory phenotype (SASP) can affect tumor growth and microenvironment, influencing treatment outcomes. Metabolic interventions can modulate the SASP, and an enhanced mitochondrial energy metabolism supports resistance to therapy in melanoma cells. Herein, we assessed the mitochondrial function of therapy-induced senescent melanoma cells obtained after exposing the cells to temozolomide (TMZ), a methylating chemotherapeutic agent. Senescence induction in melanoma was accompanied by a substantial increase in mitochondrial basal, ATP-linked, and maximum respiration rates and in coupling efficiency, spare respiratory capacity, and respiratory control ratio. Further examinations revealed an increase in mitochondrial mass and length. Alterations in mitochondrial function and morphology were confirmed in isolated senescent cells, obtained by cell-size sorting. An increase in mitofusin 1 and 2 (MFN1 and 2) expression and levels was observed in senescent cells, pointing to alterations in mitochondrial fusion. Silencing mitofusin expression with short hairpin RNA (shRNA) prevented the increase in mitochondrial length, oxygen consumption rate and secretion of interleukin 6 (IL-6), a component of the SASP, in melanoma senescent cells. Our results represent the first in-depth study of mitochondrial function in therapy-induced senescence in melanoma. They indicate that senescence increases mitochondrial mass, length and energy metabolism; and highlight mitochondria as potential pharmacological targets to modulate senescence and the SASP.

Abstract P2007: Muscadine Grape Extract Prevents Cardiac Cell Cytotoxicity Due to Oxidative Stress by Enhancing Mitochondrial Function

Mitochondrial health is critical for the physiological function of tissues and responses to stress. During oxidative stress, failure to maintain mitochondrial respiration can ultimately lead to cell death and thus cardiac dysfunction. Agents that preserve mitochondrial integrity and maintain or increase mitochondrial respiratory capacity may prevent cardiac tissue damage due to oxidative stress. Muscadine grapes are rich in polyphenols, which are natural antioxidants, and are known to reduce cardiac damage. We treated cardiac cells with a proprietary muscadine grape extract (MGE), to prevent cardiac myoblast death due to reactive oxygen species (ROS) in the presence of the redox cycling agent 2,3 dimethoxynaphthoquinone (DMNQ), which generates both superoxide and hydrogen peroxide intracellularly, thus mimicking pathologies of elevated ROS. DMNQ increased cardiac cell cytotoxicity, as measured by LDH release, which was prevented by doses of MGE equivalent to 60 μg/mL of total phenolics (1.3 ± 0.023 DMNQ vs. 0.90 ± 0.030, n=3, *p&lt;0.01). Moreover, cell respirometry measurements indicated that, while DMNQ reduced the oxygen consumption rate (OCR) by 50% (*p&lt;0.05, n=3), treatment with MGE prevented this reduction, suggesting that the protective effect may be mediated by preservation of mitochondrial function. Furthermore, MGE treatment prevented the decrease in ATP-linked respiration (18.8 ±. 2.6 DMNQ vs. 34.0±.4.7 DMNQ + MGE, n=3, *p&lt;0.01) and maximal respiratory capacity (31.6 ± 8.2 DMNQ vs. 48.91 ± 6.54 DMNQ + MGE, n=3, *p&lt;0.01) observed with DMNQ treatment. Furthermore, the basal extracellular acidification rate (ECAR) was increased 2-fold with MGE pretreatment when compared to DMNQ alone (13.6 ± 2.3 DMNQ + MGE vs. 6.8 ±.0.88 DMNQ, n=3, *p&lt;0.01), suggesting that MGE treatment may also increase glycolysis as a response to stress. These data suggest that MGE enhances mitochondrial function and cellular bioenergetics in cardiomyoblast cells during stress and thus may be used as a strategy to prevent tissue damage from oxidative stress observed in acute and chronic cardiac pathologies.

Mitochondrial bioenergetic changes during development as an indicator of C. elegans health-span.

Mild suppression of mitochondrial activity has beneficial effects across species. The nematode Caenorhabditis elegans is a versatile, genetically tractable model organism widely employed for aging studies, which has led to the identification of many of the known evolutionarily conserved mechanisms regulating lifespan. In C. elegans the pro-longevity effect of reducing mitochondrial function, for example by RNA interference, is only achieved if mitochondrial stress is applied during larval development. Surprisingly, a careful analysis of changes in mitochondrial functions resulting from such treatments during the developmental windows in which pro-longevity signals are programmed has never been carried out. Thus, although the powerful C. elegans genetics have led to the identification of different molecular mechanisms causally involved in mitochondrial stress control of longevity, specific functional mitochondrial biomarkers indicative or predictive of lifespan remain to be identified. To fill this gap, we systematically characterized multiple mitochondrial functional parameters at an early developmental stage in animals that are long-lived due to mild knockdown of twelve different mitochondrial proteins and correlated these parameters with animals’ lifespan. We found that basal oxygen consumption rate and ATP-linked respiration positively correlate with lifespan extension and propose the testable hypothesis that the Bioenergetic Health Index can be used as a proxy to predict health-span outcomes.

E6 Oncoproteins from High-Risk Human Papillomavirus Induce Mitochondrial Metabolism in a Head and Neck Squamous Cell Carcinoma Model

Head and neck squamous cell carcinoma (HNSCC) cells that are positive for human papillomavirus (HPV+) favor mitochondrial metabolism rather than glucose metabolism. However, the involvement of mitochondrial metabolism in HNSCC HPV+ cells is still unknown. The aim of this work was to evaluate the role of E6 oncoproteins from HPV16 and HPV18 in the mitochondrial metabolism in an HNSCC model. We found that E6 from both viral types abates the phosphorylation of protein kinase B-serine 473 (pAkt), which is associated with a shift in mitochondrial metabolism. E6 oncoproteins increased the levels of protein subunits of mitochondrial complexes (I to IV), as well as the ATP synthase and the protein levels of the voltage dependent anion channel (VDAC). Although E6 proteins increased the basal and leak respiration, the ATP-linked respiration was not affected, which resulted in mitochondrial decoupling. This increase in leak respiration was associated to the induction of oxidative stress (OS) in cells expressing E6, as it was observed by the fall in the glutathione/glutathione disulfide (GSH/GSSG) rate and the increase in reactive oxygen species (ROS), carbonylated proteins, and DNA damage. Taken together, our results suggest that E6 oncoproteins from HPV16 and HPV18 are inducers of mitochondrial metabolism.

Platelet bioenergetics correlate with muscle energetics and are altered in older adults.

Physical function decreases with age, and though bioenergetic alterations contribute to this decline, the mechanisms by which mitochondrial function changes with age remains unclear. This is partially because human mitochondrial studies require highly invasive procedures, such as muscle biopsies, to obtain live tissue with functional mitochondria. However, recent studies demonstrate that circulating blood cells are potentially informative in identifying systemic bioenergetic changes. Here, we hypothesize that human platelet bioenergetics reflect bioenergetics measured in muscle biopsies. We demonstrate that maximal and ATP-linked respiratory rate measured in isolated platelets from older adults (86-93 years) correlates significantly with maximal respiration (r = 0.595; P = 0.003) measured by muscle biopsy respirometry and maximal ATP production (r = 0.643; P = 0.004) measured by 31P-MRS respectively, in the same individuals. Comparison of platelet bioenergetics in this aged cohort to platelets from younger adults (18-35 years) shows aged adults demonstrate lower basal and ATP-linked respiration. Platelets from older adults also show enhanced proton leak, which is likely due to increased protein levels of uncoupling protein 2, and correlates with increased gate speed in this cohort (r = 0.58; P = 0.0019). While no significant difference in glycolysis was observed in older adults compared to younger adults, platelet glycolytic rate correlated with fatigability (r = 0.44; P = 0.016). These data advance the mechanistic understanding of age-related changes in mitochondrial function. Further, they suggest that measuring platelet bioenergetics provides a potential supplement or surrogate for muscle biopsy measurement and may be a valuable tool to study mitochondrial involvement in age-related decline of physical function.

1945-P: The Mitochondrial Protein DRP1 Is Required for Endogenous Fatty Acid Oxidation

Introduction: Mitochondria are organelles that routinely undergo fission and fusion in a process known as mitochondrial dynamics. Increased mitochondrial fission is implicated in the pathogenesis of obesity, type 2 diabetes, and metabolic disease. DRP1 has been identified as a key regulator of mitochondrial fission. We and others have demonstrated that loss of DRP1 is associated with improvements in glucose homeostasis, however, the role of DRP1 in mitochondrial fatty acid oxidation is unknown. The purpose of this study was to measure endogenous fatty acid oxidation in DRP1-deficient skeletal muscle cells. Methods: C2C12 myoblasts were stably transfected with DRP1 shRNA (KO) or a scrambled control (CT). Myoblasts were then cultured in a substrate-limited DMEM (0.5mM glucose, 0.5mM carnitine, 1mM glutamine, and 1% FBS) overnight. 15 minutes prior to assay, etomoxir was added to inhibit endogenous fatty acid oxidation (FAO). Cells were then challenged with either bovine serum albumin (BSA) or palmitate (PA) and assessed for mitochondrial function using whole cell respirometry (Agilent XFe24). Additionally, cells were treated with 14C-labeled PA in the absence and presence of increasing glucose concentrations to assess metabolic flexibility and fatty acid oxidation. Results: Basal whole cell (P&amp;lt;0.05) and endogenous fatty acid (P&amp;lt;0.05) oxygen consumption were reduced in KO cells relative to CT (P&amp;lt;0.05). Furthermore, ATP linked fatty acid oxidation was blunted in the KO cells (P&amp;lt;0.05). Conclusion: Here, we show that DRP1 is required for FAO. After inhibition of FAO with etomoxir, basal and ATP-linked respiration were ablated in DRP1-deficient cells. These findings suggest that loss of DRP1 ablates the ability of cells to use endogenous fatty acids as substrate when carbohydrate is not available. These data suggest that impaired lipid metabolism, rather than inhibition of mitochondrial fission, may explain improvements in glucose homeostasis with the loss of DRP1. Disclosure W.T. King: None. C.L. Axelrod: None. G. Davuluri: None. R.C. Noland: None. J.P. Kirwan: None. Funding National Institutes of Health (R01DK108089, U54GM104940, R01DK103860)

Dynamic bioenergetic alterations in colorectal adenomatous polyps and adenocarcinomas

BackgroundEnergy metabolism in carcinogenesis is poorly understood. It is widely accepted the majority of colorectal cancers (CRCs) arise from adenomatous polyps (APs). We aimed to characterize the bioenergetic alterations in APs and CRCs. MethodsFifty-six APs, 93 CRCs and adjacent normal mucosae were tested. Oxygen consumption rate (OCR) was measured representing mitochondrial oxidative phosphorylation (OxPhos), and extracellular acidification rate (ECAR)was measured representing glycolysis. Mitochondrial DNA (mtDNA) variants and mutations were studied. Over-expressed metabolic genes in APs were identified by microarray and validated by qRT-PCR, Western blots and immunohistochemistry. Identified genes were knocked down in WiDr and colo205 CRC cell lines, and their expression was analyzed in APs/CRCs with enhanced glycolysis. FindingsECAR, not OCR, was significantly increased in APs. While no difference of ECAR was found between CRCs and normal mucosae, OCR was significantly reduced in CRCs. OCR/ECAR ratio was decreased in APs over 1 cm, APs with a villous component and CRCs, indicating their glycolytic tendencies. The number of mtDNA mutations was increased in APs and CRCs, but not correlated with metabolic profiles. Two metabolic genes ALDOB and SLC16A4 were up-regulated in APs. Both ALDOB-knockdown and SLC16A4-knockdown CRC cell lines showed increased basal motichondrial OxPhos and decreased basal glycolysis. Moreover, the increase of mitochondrial ATP-linked respiration and the decrease of glycolytic capacity were showed in SLC16A4-knockdown cells. Finally, APs/CRCs with enhanced glycolysis had increased SLC16A4 expression. InterpretationATP production shifts from OxPhos to glycolysis in the process of AP enlargement and villous transformation. OxPhos defects are present in CRCs but not in APs. APs and CRCs tend to accumulate mtDNA mutations, but these are not correlated with bioenergetic profiles. Finally, the ALDOB and SLC16A4 may contribute to the glycolytic shift in APs/CRCs.

Alterations in Mitochondrial Function in Blood Cells Obtained From Patients With Sepsis Presenting to an Emergency Department.

Mitochondrial dysfunction has been implicated as a key cellular event leading to organ dysfunction in sepsis. Our objective is to measure changes in mitochondrial bioenergetics in subjects with early presentation of sepsis to provide insight into the incompletely understood pathophysiology of the dysregulated host response in sepsis. Prospective observational study. Single site tertiary academic emergency department. We enrolled a total of 48 subjects in the study, 10 with sepsis or septic shock, 10 with infection without sepsis, 14 older and 14 younger healthy controls. Peripheral blood mononuclear cells were measured with high-resolution respirometry (OROBOROS O2K). The median age in patients with sepsis, infection only, older control and younger controls were 63, 34, 61, and 29 years old, respectively. In the Sepsis group, the median 1st 24-h SOFA score was 8, and the initial median lactate was 4.2 mmol/dL, compared with 1.1 in the Infection Group. The 30-day mortality of the sepsis/septic shock group was 50%, with a median length of stay of 7-days. The Sepsis Group had significantly lower routine and Max respiration when compared with the other groups as well as uncoupled Complex I respiration. There was also a significant decrease in ATP-linked respiration along with the Spare Reserve Capacity in the Sepsis Group when compared with the other group. There were no age-related differences in respiration between the Older and Younger control group. Bedside measurement of mitochondrial respiration can be minimally invasive and performed in a timely manner. Mitochondrial dysfunction, detected by decreased oxygen consumption utilized for energy production and depleted cellular bioenergetics reserve.

Coenzyme Q10 Alleviates Chronic Nucleoside Reverse Transcriptase Inhibitor-Induced Premature Endothelial Senescence.

Human immunodeficiency virus (HIV)-infected patients undergoing antiretroviral therapy are afforded an increased lifespan but also exhibit an elevated incidence of cardiovascular disease. HIV therapy uses a combination drug approach, and nucleoside reverse transcriptase inhibitors (NRTI) are a backbone of this therapy. Endothelial dysfunction is an initiating event in cardiovascular disease etiology, and in our prior studies, NRTIs induced an endothelial dysfunction that was dependent upon mitochondrial oxidative stress. Moreover, short-term NRTI administration induced a mitophagy-associated endothelial toxicity and increased reactive oxygen species (ROS) production that was rescued by coenzyme Q10 (Q10) or overexpression of a mitochondrial antioxidant enzyme. Thus, our objective was to examine mitochondrial toxicity in endothelial cells after chronic NRTI treatment and evaluate Q10 as a potential adjunct therapy for preventing NRTI-induced mitochondrial toxicity. Human aortic endothelial cells (HAEC) were exposed to chronic NRTI treatment, with or without Q10. ROS production, cell proliferation rate, levels of senescence, and mitochondrial bioenergetic function were determined. Chronic NRTI increased ROS production but decreased population doubling. In addition, NRTI increased the accumulation of β-galactosidase, indicative of an accelerated rate of senescence. Moreover, ATP-linked respiration was diminished. Co-treatment with Q10 delayed the onset of NRTI-induced senescence, decreased ROS production and rescued the cells' mitochondrial respiration rate. Thus, our findings may suggest antioxidant enrichment approaches for reducing the cardiovascular side effects of NRTI therapy.

Oxidative stress-induced senescence markedly increases disc cell bioenergetics

Cellular senescence is a phenotype characterized by irreversible growth arrest, chronic elevated secretion of proinflammatory cytokines and matrix proteases, a phenomenon known as senescence-associated secretory phenotype (SASP). Biomarkers of cellular senescence have been shown to increase with age and degeneration of human disc tissue. Senescent disc cells in culture recapitulate features associated with age-related disc degeneration, including increased secretion of proinflammatory cytokines, matrix proteases, and fragmentation of matrix proteins. However, little is known of the metabolic changes that underlie the senescent phenotype of disc cells. To assess the metabolic changes, we performed a bioenergetic analysis of in vitro oxidative stress-induced senescent (SIS) human disc cells. SIS disc cells acquire SASP and exhibit significantly elevated mitochondrial content and mitochondrial ATP-linked respiration. The metabolic changes appear to be driven by the upregulated protein secretion in SIS cells as abrogation of protein synthesis using cycloheximide decreased mitochondrial ATP-linked respiration. Taken together, the results of the study suggest that the increased energy generation state supports the secretion of senescent associated proteins in SIS disc cells.

Statin‐dependent modulation of mitochondrial metabolism in cancer cells is independent of cholesterol content

Statins, widely used to treat hypercholesterolemia, inhibit the 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the rate-limiting enzyme of de novo cholesterol (Chol) synthesis. Statins have been also reported to slow tumor progression. In cancer cells, ATP is generated both by glycolysis and oxidative phosphorylation. Mitochondrial membrane potential (ΔΨ), a readout of mitochondrial metabolism, is sustained by the oxidation of respiratory substrates in the Krebs cycle to generate NADH and flavin adenine dinucleotide, which are further oxidized by the respiratory chain. Here, we studied the short-term effects of statins (3-24 h) on mitochondrial metabolism on cancer cells. Lovastatin (LOV) and simvastatin (SIM) increased ΔΨ in HepG2 and Huh7 human hepatocarcinoma cells and HCC4006 human lung adenocarcinoma cells. Mitochondrial hyperpolarization after LOV and SIM was dose and time dependent. Maximal increase in ΔΨ occurred at 10 µM and 24 h for both statins. The structurally unrelated atorvastatin also hyperpolarized mitochondria in HepG2 cells. Cellular and mitochondrial Chol remained unchanged after SIM. Both LOV and SIM decreased basal respiration, ATP-linked respiration, and ATP production. LOV and SIM did not change the rate of lactic acid production. In summary, statins modulate mitochondrial metabolism in cancer cells independently of the Chol content in cellular membranes without affecting glycolysis.-Christie, C. F., Fang, D., Hunt, E. G., Morris, M. E., Rovini, A., Heslop, K. A., Beeson, G. C., Beeson, C. C., Maldonado, E. N. Statin-dependent modulation of mitochondrial metabolism in cancer cells is independent of cholesterol content.