Electron Transport Chain Function Research Articles

Receptor for advanced glycation end products modulates oxidative stress and mitochondrial function in the soleus muscle of mice fed a high-fat diet.

Accumulation of advanced glycation end products (AGEs) and activation of the receptor for AGEs (RAGE) are implicated in the progression of pathologies associated with aging, chronic inflammation, diabetes, and cellular stress. RAGE activation is also implicated in cardiovascular complications of type 2 diabetes, such as nephropathy, retinopathy, accelerated vascular diseases, and cardiomyopathy. Studies investigating the effects of AGE/RAGE axis activation on skeletal muscle oxidative stress and metabolism are more limited. We tested whether a high-fat diet (HFD) would alter circulating AGE concentration, skeletal muscle AGE accumulation, and oxidative stress in wild-type and RAGE-deficient mice. The physiological significance of AGE/RAGE axis activation in HFD-fed mice was evaluated in terms of exercise tolerance and mitochondrial respiratory chain complex activity. HFD elicited adiposity, abnormal fat distribution, and oral glucose intolerance. HFD also induced accumulation of Nε-carboxymethyl-l-lysine, increased protein carbonyl levels, and impaired respiratory chain complex activity in soleus muscle. Ablation of RAGE had no effects on weight gain and oral glucose tolerance in HFD-fed mice. Peak aerobic capacity and mitochondrial cytochrome-c oxidase activity were restored in HFD-fed RAGE-/- mice. We concluded that RAGE signaling plays an important role in skeletal muscle homeostasis of mice under metabolic stress. Novelty HFD in mice induces accumulation of AGEs, oxidative stress, and mitochondrial dysfunction in the soleus muscle. RAGE, the multi-ligand receptor for AGEs, modulates oxidative stress and mitochondrial electron transport chain function in the soleus muscle of HFD-fed mice.

Regulation of mitochondrial energy production in the diabetic renal proximal tubule by the β2‐adrenergic receptor agonist formoterol

While diabetic kidney disease is the leading cause of end stage renal disease, the pathophysiology of this disease remains poorly understood. Diabetes causes mitochondrial dysfunction and changes in cellular energy production in renal proximal tubules. Therefore, we examined the effect of formoterol, a β2‐adrenergic receptor (AR) agonist previously demonstrated to induce mitochondrial biogenesis and promote recovery from acute kidney injury, on renal cortical mitochondrial function and energy production in diabetic db/db mice and in renal proximal tubule cells (RPTC) treated with high glucose. Db/db and db/m (control) mice were treated with formoterol or vehicle daily for 3 wks beginning at 10 wks of age. Compared to controls, 13‐wk‐old diabetic mice showed in creased renal cortex expression of electron transport chain (ETC) proteins in complexes I, II, III and V that was reversed to control levels with formoterol treatment. Conversely, we found that renal cortex from db/db mice had lower ATP levels than that from db/m controls and that these levels were restored with formoterol treatment. Similarly, we found that RPTC exposed to 17 mM glucose for 96 hr exhibited increased expression of ETC complex I–V proteins and reduced ATP content vs. cells cultured in in the absence of glucose or osmotic controls. ETC proteins and ATP levels were unaffected by high glucose when cells were co‐treated with formoterol. Additionally, exposure to 17 mM glucose decreased uncoupled oxygen consumption rate in the cells, suggesting that glucose reduced electron transport chain function. Together, these results demonstrate that diabetes and exposure to high glucose alters the mitochondrial bioenergetic profile in proximal tubule cells in vivo and in vitro, and that treatment with formoterol can reverse these effects.

Melatonin for the treatment of sepsis: the scientific rationale.

Sepsis affects 30 million people worldwide, leading to 6 million deaths every year (WHO), and despite decades of research, novel initiatives are drastically needed. According to the current literature, oxidative imbalance and mitochondrial dysfunction are common features of septic patients that can cause multiorgan failure and death. Melatonin, alongside its traditionally accepted role as the master hormonal regulator of the circadian rhythm, is a promising adjunctive drug for sepsis through its anti-inflammatory, antiapoptotic and powerful antioxidant properties. Several animal models of sepsis have demonstrated that melatonin can prevent multiorgan dysfunction and improve survival through restoring mitochondrial electron transport chain (ETC) function, inhibiting nitric oxide synthesis and reducing cytokine production. The purpose of this article is to review the current evidence for the role of melatonin in sepsis, review its pharmacokinetic profile and virtual absence of side effects. While clinical data is limited, we propose the adjunctive use of melatonin is patients with severe sepsis and septic shock.

Inhibition of lipolysis: A novel explanation for the hypothermic actions of acetaminophen in non-febrile rodents

Acetaminophen is both widely used to treat children with fever and is also responsible for thousands being hospitalised annually. Historically the antipyretic actions of acetaminophen were attributed to the inhibition of cyclooxygenase (COX-1/2) enzymes and more recently a novel COX-1 variant (COX-3) located in the brain. However, the evidence for acetaminophen-mediated COX inhibition remains contentious. This study assesses the impact of acetaminophen and other putative COX-3 inhibitors on the release of fatty acids during lipolysis as an alternative mechanism by which antipyretics can reduce body temperature during fever. 3T3-L1 adipocytes, primary brown adipocytes and isolated mitochondria were exposed to COX-3 inhibitors and lipolysis and mitochondrial electron transport chain function assessed. Acetaminophen, aminopyrine and antipyrine at 1–10 mM caused a significant decrease (up to 70%; P < 0.01, from control) in lipolysis within 1, 3 and 24 h without affecting cell viability. The inhibition was observed regardless of where along its signalling pathway lipolysis was stimulated. All three compounds were found to significantly attenuate mitochondrial function by up to 30% for complex I and 40% for complex II (P < 0.01, from control). These novel observations combined with the known limited inhibition of the COX enzymes by acetaminophen suggest both the antipyretic and hypothermia induced by acetaminophen and related compounds could be attributed to the direct inhibition of lipolysis and mitochondrial function, rather than cyclooxygenase inhibition centrally. Further these observations could provide new drug targets for reducing fever with the added bonus of fewer individuals being hospitalized by accidental acetaminophen overdose.

The MAPK Hog1 mediates the response to amphotericin B in Candida albicans

The HOG MAP kinase pathway plays a crucial role in the response to different stresses in the opportunistic pathogen Candida albicans. The polyene amphotericin B (AMB) has been reported to trigger oxidative stress in several pathogenic fungi, including C. albicans. In the present work, we have analyzed the role of the MAPK Hog1 in sensing and survival to AMB treatment. Mutants lacking Hog1 are more susceptible to AMB than their parental strains and Hog1 became phosphorylated in the presence of this polyene. A set of mutated versions of Hog1 revealed that both the kinase activity and phosphorylation of Hog1 are required to cope with AMB treatment. Flow cytometry analysis showed that AMB induced intracellular ROS accumulation in both parental and hog1 null mutant strains. In addition, AMB triggered a Hog1-independent synthesis of trehalose. The addition of rotenone to AMB-treated cells improved cell viability, decreased intracellular ROS and prevented intracellular trehalose accumulation, suggesting that AMB-induced ROS is associated to a functional electron transport chain but the presence of rotenone did not impair Hog1 phosphorylation in AMB-treated cells. Our results indicate that Hog1 is necessary during AMB treatment to increase its survival.

Targeting mitochondria as an anticancer strategy

Mitochondria are organelles controlling adenosine triphosphate (ATP) generation, redox homeostasis, metabolic signaling, and apoptotic pathways. Although glycolysis was traditionally considered as the major source of energy in cancer cells, in-line with the so-called “Warburg effect”, mitochondria have been recognized to play a key role in oncogenesis [1]. Cancer cells uniquely reprogram their cellular activities to support their rapid proliferation and migration, as well as to counteract metabolic and genotoxic stress during cancer progression [2]. Further, mitochondria can switch their metabolic phenotypes to meet the challenges of high energy demand and macromolecular synthesis [3]. Thus, cancer mitochondria have the ability to flexibly switching between glycolysis and oxidative phosphorylation (OXPHOS) for their survival. The electron transport chain (ETC) function is pivotal for mitochondrial respiration, which is also needed for dihydroorotate dehydrogenase (DHODH) activity that is essential for de novo pyrimidine synthesis [4]. Recent researches have demonstrated that cancer cells devoid of mitochondrial DNA (mtDNA) lack their tumorigenic potential, and they re-gain this ability by acquiring healthy mtDNA from the host stromal cells via horizontal transfer of whole mitochondria [5, 6] for recovery of the respiratory function. Functionally, respiration propels DHODH activity for pyrimidine biosynthesis [7]. Therefore, targeting mitochondria holds great potential for anticancer strategy with high therapeutic opportunities.

DeepETC: A deep convolutional neural network architecture for investigating and classifying electron transport chain's complexes

An electron transport chain is a series of protein complexes embedded in the transport protein, which is an important process to transfer electrons and other macromolecules throughout the cell. It is the primary process to extract energy via redox reactions in the case of oxidation of sugars in cellular respiration. According to the molecular functions, the components of the electron transport chain could be formed with five complexes and with several different electron carriers. The functional loss of a specific molecular function in electron transport chain has been implicated in a variety of human diseases such as diabetes, neurodegenerative disorders, Parkinson, and Alzheimer's disease. Therefore, creating a precise model to identify its functions is pertinent to the understanding of human diseases and designing of drug targets. Previous bioinformatics studies have almost exclusively focused on the electron transport proteins without information on the five complexes. Here we present DeepETC, a deep learning model that uses a two-dimensional convolutional neural network and position-specific scoring matrices profiles to classify electron transport proteins into the five complexes. DeepETC can classify the electron transporters with the independent test accuracy of 99.6%, 99.7%, 99.7%, 99.1% and 99.8% for complex I, II, III, IV, and V, respectively. Our performance results are significantly more accurate than the state-of-the-art traditional neural networks in all typical measurement metrics. Throughout the proposed study, we provide an effective tool for investigating electron transport proteins and our achievement could promote the use of deep learning in bioinformatics and computational biology. DeepETC can be freely accessible via http://www.biologydeep.com/deepetc/.

Validating mitochondrial electron transport chain content in individuals at clinical high risk for psychosis

Altered mitochondrial electron transport chain function has been implicated in the pathophysiology and etiology of schizophrenia. To date, our previously published study (i.e. first cohort) is still the only study to demonstrate that mitochondrial electron transport chain is not altered in white blood cells from individuals at clinical high risk for psychosis. Here, we aimed to replicate our previous findings with an independent set of samples and validate the levels of mitochondrial complex I-V content in individuals at clinical high risk for psychosis. We demonstrated that the second cohort (i.e. validation cohort) expressed similar results as the first cohort. We combined the first cohort study with the second cohort and once more validated a lack of differential levels in mitochondrial complex I-V content between the two groups. In addition, we were able to validate a correlation between complex III content and prodromal negative symptom severity when the two cohorts studies were combined. Additionally, a correlation between complex V content and prodromal disorganization symptom severity was found when the two cohorts were combined. In conclusion, our results showed that dysfunction of the mitochondrial electron transport chain is not detected in peripheral blood mononuclear cells of individuals in the putative prodromal stage of schizophrenia.

Unique, Diverged, and Conserved Mitochondrial Functions Influencing Candida albicans Respiration.

Candida albicans is an opportunistic fungal pathogen of major clinical concern. The virulence of this pathogen is intimately intertwined with its metabolism. Mitochondria, which have a central metabolic role, have undergone many lineage-specific adaptations in association with their eukaryotic host. A screen for lineage-specific genes identified seven such genes specific to the CTG clade of fungi, of which C. albicans is a member. Each is required for respiratory growth and is integral to expression of complex I, III, or IV of the electron transport chain. Two genes, NUO3 and NUO4, encode supernumerary subunits of complex I, whereas NUE1 and NUE2 have nonstructural roles in expression of complex I. Similarly, the other three genes have nonstructural roles in expression of complex III (QCE1) or complex IV (COE1 and COE2). In addition to these novel additions, an alternative functional assignment was found for the mitochondrial protein encoded by MNE1MNE1 was required for complex I expression in C. albicans, whereas the distantly related Saccharomyces cerevisiae ortholog participates in expression of complex III. Phenotypic analysis of deletion mutants showed that fermentative metabolism is unable to support optimal growth rates or yields of C. albicans However, yeast-hypha morphogenesis, an important virulence attribute, did not require respiratory metabolism under hypoxic conditions. The inability to respire also resulted in hypersensitivity to the antifungal fluconazole and in attenuated virulence in a Galleria mellonella infection model. The results show that lineage-specific adaptations have occurred in C. albicans mitochondria and highlight the significance of respiratory metabolism in the pathobiology of C. albicansIMPORTANCECandida albicans is an opportunistic fungal pathogen of major clinical concern. The virulence of this pathogen is intimately intertwined with its metabolic behavior, and mitochondria have a central role in that metabolism. Mitochondria have undergone many evolutionary changes, which include lineage-specific adaptations in association with their eukaryotic host. Seven lineage-specific genes required for electron transport chain function were identified in the CTG clade of fungi, of which C. albicans is a member. Additionally, examination of several highly diverged orthologs encoding mitochondrial proteins demonstrated functional reassignment for one of these. Deficits imparted by deletion of these genes revealed the critical role of respiration in virulence attributes of the fungus and highlight important evolutionary adaptations in C. albicans metabolism.

Ovarian Cancer Risk in Laying Hens Is Reduced by Dietary Polyunsaturated Fatty Acids: A Case for Redox Homeostasis and Reprogrammed Mitochondrial Metabolism in Ovarian Tumors (OR04-05-19)

ObjectivesIn 2012, ovarian cancer accounted for 239,000 new cancer cases and 152,000 cancer-related deaths worldwide. Epidemiological studies around the world suggest that high dietary consumption of polyunsaturated fatty acids (PUFAs) reduces a woman’s odds of developing ovarian cancer. We hypothesize that PUFA-enriched diets will decrease ovarian cancer risk in White Leghorn laying hens. MethodsThe specific aim of our research was to investigate ovarian cancer risk and molecular events in ovarian tumors of White Leghorn laying hens consuming PUFA-enriched diets. We exposed laying hens to long-term (46-week) dietary PUFA treatment, using Whole Flaxseed (WFX), Flaxseed Oil (FXO), Fish Oil (FHO), Corn Oil (CNO), and a low-PUFA diet, Defatted Flaxseed (DFX). At the end of the dietary treatment we collected 88 ovarian tumors and conducted qPCR analysis for gene expression. ResultsIn comparison to a control diet lacking a PUFA supplement, the odds ratios of hens developing ovarian cancer decreased with PUFA enrichment (Odd Ratios: DFX = 0.74, WFX = 0.69, FXO = 0.61, FHO = 0.57, CNO = 0.57), corroborating human epidemiological observations of ovarian cancer risk. Gene expression analysis from hen ovarian tumors suggests that PUFA-rich diets (ie WFX, FXO, FHO, and CNO) improve mitochondrial electron transport chain function by upregulating Cytochrome B (Complex 3) and Cyctochrome C Oxidases 1, 2, and 3 (Complex 4), and likely reduce superoxide emission from Complex 1 as evidenced by the downregulation of NADH Dehydrogenase 2. PUFA enrichment also reduced the expression of enzymes associated with reactive oxygen species (ROS), reactive nitrogen species (RNS), and lipid peroxides, suggesting overall major improvement in the redox state of tumors from PUFA-enriched diets. The FXO diet was uniquely distinguished by increasing the expression of ATP5B1 (catalytic subunit of ATP Synthase) and the ADP/ATP Translocase (ANT1), suggesting increased mitochondrial cristae space and improved oxidative phosphorylation capacity in FXO-enriched ovarian tumors. ConclusionsDietary PUFA enrichment (omega-3 or omega-6) reduces end point risk for ovarian cancer in laying hens. The underlying etiology appears to center on decreasing oxidative stress and increasing mitochondrial function in ovarian tumors. Funding SourcesNational Institutes of Health.

Tetra-linoleoyl cardiolipin depletion plays a major role in the pathogenesis of sarcopenia

Sarcopenia, the progressive loss of muscle mass, strength, and physical performance that occurs during aging, is highly prevalent among the elderly. Sarcopenia increases the risk of falls, disability, and death. The biological basis for sarcopenia is not well understood. There are no specific preventive or therapeutic strategies for sarcopenia except exercise. The elucidation of biological pathways and identification of therapeutic targets for treating or preventing sarcopenia remain a high priority in aging research. Mitochondria play a critical role in skeletal muscle by providing energy in the form of ATP, regulation of signaling, calcium homeostasis, autophagy, and other functions. Cardiolipin, a unique dimeric phospholipid specific to mitochondria and an essential component of mitochondrial membranes, is involved in mitochondrial protein transport, maintaining structural organization of mitochondrial membranes, cellular signaling, regulating enzymes involved in β-oxidation of fatty acids, and facilitating normal electron transport chain (ETC) function and generation of ATP. The fatty acid species composition of cardiolipin is critical to mitochondrial bioenergetics, as cardiolipin affects membrane biophysical properties, binds and stabilizes ETC protein complexes, and shapes the curvature of the mitochondrial cristae. Tetra-linoleoyl cardiolipin (18:2)4 comprises ∼80% of cardiolipin in mitochondria in normal human skeletal and cardiac muscle and is optimal for effective ETC function and ATP generation. Aging is associated with a decrease in cardiolipin content, decrease in tetra-linoleoyl cardiolipin (18:2)4 and replacement of linoleic acid (18:2) with other fatty acids in cardiolipin composition, decline of ETC function, and increased generation of reactive oxygen species in muscle. Together, these findings from the literature prompt the hypothesis that depletion of the cardiolipin (18:2)4 species may be at the root of mitochondrial dysfunction with aging, in turn leading to sarcopenia. Corroboration of the tetra-linoleoyl cardiolipin depletion hypothesis suggests new leads for the prevention and treatment of sarcopenia by enhancing the biosynthesis, accretion, and integrity of tetra-linoleoyl cardiolipin.

Mitochondrial Dysfunction in Astrocytes Impairs the Generation of Reactive Astrocytes and Enhances Neuronal Cell Death in the Cortex Upon Photothrombotic Lesion.

Mitochondria are key organelles in regulating the metabolic state of a cell. In the brain, mitochondrial oxidative metabolism is the prevailing mechanism for neurons to generate ATP. While it is firmly established that neuronal function is highly dependent on mitochondrial metabolism, it is less well-understood how astrocytes function rely on mitochondria. In this study, we investigate if astrocytes require a functional mitochondrial electron transport chain (ETC) and oxidative phosphorylation (oxPhos) under physiological and injury conditions. By immunohistochemistry we show that astrocytes expressed components of the ETC and oxPhos complexes in vivo. Genetic inhibition of mitochondrial transcription by conditional deletion of mitochondrial transcription factor A (Tfam) led to dysfunctional ETC and oxPhos activity, as indicated by aberrant mitochondrial swelling in astrocytes. Mitochondrial dysfunction did not impair survival of astrocytes, but caused a reactive gliosis in the cortex under physiological conditions. Photochemically initiated thrombosis induced ischemic stroke led to formation of hyperfused mitochondrial networks in reactive astrocytes of the perilesional area. Importantly, mitochondrial dysfunction significantly reduced the generation of new astrocytes and increased neuronal cell death in the perilesional area. These results indicate that astrocytes require a functional ETC and oxPhos machinery for proliferation and neuroprotection under injury conditions.

Acute exposure to a glyphosate-containing herbicide formulation inhibits Complex II and increases hydrogen peroxide in the model organism Caenorhabditis elegans

Glyphosate-based herbicides, such as Touchdown (TD) and Roundup, are among the most heavily-used herbicides in the world. While the active ingredient is generally considered non-toxic, the toxicity resulting from exposure to commercially-sold formulations is less clear. In many cases, cell cultures or various model organisms exposed to glyphosate formulations show toxicity and, in some cases, lethality. Using Caenorhabditis elegans, we assessed potential toxic mechanisms through which a highly-concentrated commercial formulation of TD promotes neurodegeneration. Following a 30-min treatment, we assayed mitochondrial electron transport chain function and reactive oxygen species (ROS) production. Initial oxygen consumption studies indicated general mitochondrial inhibition compared to controls (*p < 0.05). When Complex II activity was further assessed, inhibition was observed in all TD-treated groups (*p < 0.05). Complex IV activity, however, was not adversely affected by TD. This electron transport chain inhibition also resulted in reduced ATP levels (*p < 0.05). Furthermore, hydrogen peroxide levels, but not other ROS, were increased (*p < 0.05). Taken together, these data indicate that commercially-available formulations of TD may exert neurotoxicity through Complex II (succinate dehydrogenase) inhibition, decreased ATP levels, and increased hydrogen peroxide production.

Global Proteome Remodeling during ER Stress Involves Hac1-Driven Expression of Long Undecoded Transcript Isoforms

Cellular stress responses often require transcription-based activation of gene expression to promote cellular adaptation. Whether general mechanisms exist for stress-responsive gene downregulation is less clear. A recently defined mechanism enables both up- and downregulation of protein levels for distinct gene sets by the same transcription factor via coordinated induction of canonical mRNAs andlong undecoded transcript isoforms (LUTIs). Weanalyzed parallel gene expression datasets to determine whether this mechanism contributes to the conserved Hac1-driven branch of the unfolded protein response (UPRER), indeed observing Hac1-dependent protein downregulation accompanying the upregulation of ER-related proteins that typifies UPRER activation. Proteins downregulated by Hac1-driven LUTIs include those with electron transport chain (ETC) function. Abrogated ETC function improves the fitness of UPRER-activated cells, suggesting functional importance to this regulation. We conclude that the UPRER drives large-scale proteome remodeling, including coordinated up- and downregulation of distinct protein classes, which is partly mediated by Hac1-induced LUTIs.

Abstract 3530: Coenzyme Q10 (BPM31510-IV in clinical trials) increases mitochondrial Q-pool and modulates electron transport chain function to elicit cell death in pancreatic cancer cells

Abstract Mitochondria play a multifaceted role in tumorigenesis through regulation of energy production, biomass, redox state, and engagement of cell death pathways. The mitochondrial Q (coenzyme Q10)-pool facilitates electron transport from Complexes I and II to III and is essential for regulating these activities. Therefore, altering mitochondrial Q-pool homeostasis represents a potential therapeutic strategy in cancer. BPM 31510 is a Coenzyme Q10 containing lipid nanodispersion currently in clinical trials for pancreatic cancer. Here, we used BPM 31510 to assess how modulation of mitochondrial Q-pool homeostasis impacts mitochondrial electron transport chain function to activate regulated cell death. Pancreatic cancer cell lines (MIA PaCa-2 and Panc-1) represent models with sensitivity to BPM 31510 both in vitro and in vivo. Treatment with BPM 31510 (EC50 dose, 24 h) resulted in significant mitochondrial enrichment of CoQ10 compared to other subcellular compartments, and quantitatively, CoQ10 levels were 100 times higher in mitochondria isolated from BPM 31510 treated cells over untreated controls (MIA PaCa-2 untreated, 0.31 nmol/mg; treated, 39.4 nmol/mg; Panc1 untreated, 0.21 nmol/mg; treated, 29.3 nmol/mg). Alterations in mitochondrial respiration characterized by dose-dependent decreases in succinate- or glycerol-3-phosphate-fueled respiration were observed in cells treated with BPM 31510, while pyruvate or TMPD/ascorbate-fueled respiration was only modestly affected, suggesting that BPM31510 specifically impairs respiratory responses dependent on Complexes II/III. Moreover, in the presence of multiple mitochondrial substrates, total respiratory capacity was decreased and reliance on pyruvate (Complex I)-fueled respiration was increased with BPM 31510 treatment, indicative of bioenergetic remodeling. Concomitantly to BPM 31510-dependent changes in mitochondrial respiratory responses, BPM 31510 exposure increased oxidation of the reactive oxygen species (ROS) probes, CellROX Green and DCF-DA, increased oxidized glutathione, and decreased levels of the cellular reducing equivalent NADPH. Importantly, BPM 31510-induced death could be partially rescued by agents which alleviate electron transport chain impairment linking respiratory function to the anti-cancer mechanism of action of BPM 31510. Together, these data indicate that BPM31510 directly impairs the mitochondrial Q-pool and respiratory function resulting in oxidative stress and consequential cell death and thus provide mechanistic understanding of the anti-cancer activity of BPM31510. Citation Format: Pallavi Awate, Tulin Dadali, Ryan Ng, Saie Mogre, Anne R. Diers, Hannah Rockwell, Justice McDaniel, Emily Chen, Fei Gao, Michael Kiebish, Stephane Gesta, Vivek Vishnudas, Niven R. Narain, Rangaprasad Sarangarajan. Coenzyme Q10 (BPM31510-IV in clinical trials) increases mitochondrial Q-pool and modulates electron transport chain function to elicit cell death in pancreatic cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3530.

Metabolism-Associated Markers and Childhood Autism Rating Scales (CARS) as a Measure of Autism Severity.

Autism spectrum disorder (ASD) is a neuro-behavioral syndrome with a broad spectrum of different mechanisms and etiologies that are caused by abnormal brain development. To date, no highly reliable and effective diagnostic biomarker to assess ASD is available so far. The present study investigated the predictivity potential of some suggested markers in ASD diagnosis focusing onto the relative ratios of several plasma biomarkers of electron transport chain function, and mitochondrial metabolism in 41 patients with ASD evaluated for behavior deficits measured using Childhood Autism Rating Scales (CARS). The control matched for further 41 healthy subjects. The relation of these relative ratios to ASD severity was also examined, as well as their ability to distinguish ASD children from neurotypical children. All predictive ratios were found to be markedly altered and correlated in ASD patients. However, no ratio was connected with autism severity. Interestingly, MRCC-I/caspase-7, GSH/GST, and MRCC-I/COQ10 were the most distinctive relative ratios between neurotypical controls and ASD patients and may thereby be useful biomarkers for early diagnosis of ASD. Overall, this investigation proves that relative ratios of numerous mitochondrial biomarkers might be predictive and efficient to differentiate between neurotypical children and ASD.

Gene expression to mitochondrial metabolism: Variability among cultured Trypanosoma cruzi strains.

The insect-transmitted protozoan parasite Trypanosoma cruzi experiences changes in nutrient availability and rate of flux through different metabolic pathways across its life cycle. The species encompasses much genetic diversity of both the nuclear and mitochondrial genomes among isolated strains. The genetic or expression variation of both genomes are likely to impact metabolic responses to environmental stimuli, and even steady state metabolic function, among strains. To begin formal characterization these differences, we compared aspects of metabolism between genetically similar strains CL Brener and Tulahuen with less similar Esmeraldo and Sylvio X10 strains in a culture environment. Epimastigotes of all strains took up glucose at similar rates. However, the degree of medium acidification that could be observed when glucose was absent from the medium varied by strain, indicating potential differences in excreted metabolic byproducts. Our main focus was differences related to electron transport chain function. We observed differences in ATP-coupled respiration and maximal respiratory capacity, mitochondrial membrane potential, and mitochondrial morphology between strains, despite the fact that abundances of two nuclear-encoded proteins of the electron transport chain are similar between strains. RNA sequencing reveals strain-specific differences in abundances of mRNAs encoding proteins of the respiratory chain but also other metabolic processes. From these differences in metabolism and mitochondrial phenotypes we have generated tentative models for the differential metabolic fluxes or differences in gene expression that may underlie these results.

Generation of two isogenic human induced pluripotent stem cell lines from a 15 year-old female patient with MERRF syndrome and A8344G mutation of mitochondrial DNA

MERRF syndrome is predominantly caused by A8344G mutation in the mitochondrial DNA (mtDNA), affecting MT-TK gene, which impairs the mitochondrial electron transport chain function. Here, we report the generation of two isogenic induced pluripotent stem cell (iPSC) lines, TVGH-iPSC-MRF-Mlow and TVGH-iPSC-MRF-Mhigh, from the skin fibroblasts of a female MERRF patient harboring mtDNA A8344G mutation by using retrovirus transduction system. Both cell lines share the same genetic background except containing different proportions of mtDNA with the A8344G mutation. Both cell lines exhibited the pluripotency and capacity to differentiate into three germ layers.

P-115 - Functional electron transport chain is necessary for stress resistance in quiescent cells

Mitochondria are organelles central to energy metabolism and cell death. In the present work we investigated the role of functional electron transfer chain (ETC) in cell's adaptation to the quiescent state, using ETC-deficient (ρ0 cells) endothelial cell line EA.hy926 as a model. Preliminary results showed an increase in glucose consumption and lactate production in ETC-deficient quiescent cells compared to their proliferative counterparts. Unlike control cells, quiescent cells lacking the ETC were highly susceptible to reactive oxygen species (ROS) inducers such as phenethyl isothicyanate (PEITC). This was surprising, as the ETC-deficient quiescent cells, similar to ETC-functional counterparts, showed elevated activity of mitochondrial antioxidant defense. Interestingly, we observed a reduced autophagic flux in quiescent ρ0 cells. Moreover, pharmacological interference with autophagy or the knock down of ATG5, a protein essential for autophagy, not only reduced autophagic flux but also increased sensitivity to ROS and the ROS-induced cell death in quiescent cells with functional ETC, recapitulating the ETC-deficient phenotype. This suggest that quiescent ETC-deficient cells are metabolically stressed, leading to compromised autophagic flux and limited protection from ROS.

Effects of exogenous phenolic acids on photosystem functions and photosynthetic electron transport rate in strawberry leaves

Our study investigated the physiological and biochemical basis for the effects of exogenous phenolic acids on the function of the photosynthetic apparatus and photosynthetic electron transport rate in strawberry seedlings. Potted seedlings of the strawberry (Fragaria × ananassa Duch.) were used. Syringic acid inhibited net photosynthetic rate and water-use efficiency decreased. Additionally, primary quinone electron acceptor of the PSII reaction centre, the PSII reaction centre and the oxygen evolving complex were also impaired. Both the maximum quantum yield of the PSII primary photochemistry and the performance index on absorption basis were depressed, resulting in reduced function of the photosynthetic electron transport chain. Otherwise, low phthalic acid concentrations enhanced photosynthetic capacity, while high concentrations showed opposite effects. Syringic acid exhibited a higher toxic effect than that of phthalic acid which was more evident at higher concentrations.