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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Concurrent metabolism of pentose and hexose sugars by the polyextremophile Alicyclobacillus acidocaldarius

Abstract Alicyclobacillus acidocaldarius is a thermoacidophilic bacterium capable of growth on sugars from plant biomass. Carbon catabolite repression (CCR) allows bacteria to focus cellular resources on a sugar that provides efficient growth, but also allows sequential, rather than simultaneous use when more than one sugar is present. The A. acidocaldarius genome encodes all components of CCR, but transporters encoded are multifacilitator superfamily and ATP-binding cassette-type transporters, uncommon for CCR. Therefore, global transcriptome analysis of A. acidocaldarius grown on xylose or fructose was performed in chemostats, followed by attempted induction of CCR with glucose or arabinose. Alicyclobacillus acidocaldarius grew while simultaneously metabolizing xylose and glucose, xylose and arabinose, and fructose and glucose, indicating that CCR did not control carbon metabolism. Microarrays showed down-regulation of genes during growth on one sugar compared to two, and occurred primarily in genes encoding: (1) regulators; (2) enzymes for cell wall synthesis; and (3) sugar transporters.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Preface: special issues on photosystem II

Here, the appearance of oxygenic photosynthesis 3–4 billion years ago is arguably one of the most important evolutionary developments which radically transformed both the biotic and abiotic landscapes of Earth. The presence of molecular oxygen enabled the evolution of complex lifeforms requiring large amounts of chemical energy which could only be produced by aerobic respiration. Additionally, molecular oxygen remodeled the geochemistry of the planet during its transition from a reducing to an oxidizing atmosphere during the Great Oxidation Event. Central to these processes is Photosystem II (PS II), the light energy-driven, water-plastoquinone oxidoreductase which initially evolved in cyanobacteria and subsequently was incorporated, along with Photosystem I (PS I), the cytochrome b 6 f complex and the Ndh complex, into all algae and higher plants by the process of endosymbiosis. This membrane protein complex releases molecular oxygen and protons as the byproducts of water splitting and produces plastoquinol, which provides reducing equivalents that are used sequentially by the cytochrome b 6 /f complex, PS I, and ultimately, as NADPH + H + , by the Calvin–Benson–Bassham cycle. Additionally, the protons released by PS II (and those pumped by the cytochrome b 6 /f complex and the NDH complex (during cyclic electron transfer)) form the proton motive force that drives ATP synthesis via the ATP Synthase, thus providing the chemical energy source for carbon fixation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Molecular level insight into non-bilayer structure formation in thylakoid membranes: a molecular dynamics study

In oxygenic photosynthetic organisms, the light reactions are performed by protein complexes embedded in the lipid bilayer of thylakoid membranes (TMs). The organization of the bulk lipid molecules into bilayer structures provide optimal conditions for the build-up of the proton motive force (pmf) and its utilization for ATP synthesis. However, the lipid composition of TMs is dominated by the non-bilayer lipid species monogalactosyl diacylglycerol (MGDG), and functional plant TMs, besides the bilayer, contain large amounts of non-bilayer lipid phases. Bulk lipids have been shown to be associated with lumenal, stromal-side and marginal-region proteins and proposed to play roles in the self-assembly and photoprotection of the photosynthetic machinery. Furthermore, it has recently been pointed out that the generation and utilization of pmf for ATP synthesis according to the ‘protet’ or protonic charge transfer model Kell (Biochim Biophys Acta Bioenerg 1865(4):149504, 2024), requires high MGDG content Garab (Physiol Plant 177(2):e70230, 2025). In this study, to gain better insight into the structural and functional roles of MGDG, we employed all atom and coarse-grained molecular dynamics simulations to explore how temperature, hydration levels and varying MGDG concentrations affect the structural and dynamic properties of bilayer membranes constituted of plant thylakoid lipids. Our findings reveal that MGDG promotes increased membrane fluidity and dynamic fluctuations in membrane thickness. MGDG-rich stacked bilayers spontaneously formed inverted hexagonal phases; these transitions were enhanced at low hydration levels and at elevated but physiologically relevant temperatures. It can thus be inferred that MGDG plays important roles in heat and drought stress mechanisms.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Dynamic fatigue measurement of human erythrocytes using dielectrophoresis

Erythrocytes must undergo severe deformation to pass through narrow capillaries and submicronic splenic slits for several hundred thousand times in their normal lifespan. Studies of erythrocyte biomechanics have been mainly focused on cell deformability and rheology measured from a single application of stress and mostly under a static or quasi-static state using classical biomechanical techniques, such as optical tweezers and micropipette aspiration. Dynamic behavior of erythrocytes in response to cyclic stresses that contributes to the membrane failure in blood circulation is not fully understood. This article presents a new experimental method for dynamic fatigue analysis of erythrocytes, using amplitude modulated electrokinetic force field in a microfluidic platform. Here, we demonstrate the capability of this new technique using a low cycle fatigue analysis of normal human erythrocytes and ATP-depleted erythrocytes. Cyclic tensile stresses are generated to induce repeated uniaxial stretching and extensional recovery of single erythrocytes. Results of morphological and biomechanical parameters of individually tracked erythrocytes show strong correlations with the number of the loading cycles. Under a same strength of electric field, after 180 stress cycles, for normal erythrocytes, maximum stretch ratio decreases from 3.80 to 2.86, characteristic time of cellular extensional recovery increases from 0.16 s to 0.37 s, membrane shear viscosity increases from 1.0 (µN/m) s to 1.6 (µN/m) s. Membrane deformation in a small number of erythrocytes becomes irreversible after large deformation for about 200 cyclic loads. ATP-depleted cells show similar trends in decreased deformation and increased characteristic time with the loading cycles. Lastly, these results show proof of concept of the new microfluidics technique for dynamic fatigue analysis of human erythrocytes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Carbon monoxide stimulates astrocytic mitochondrial biogenesis via L-type Ca{sup 2+} channel-mediated PGC-1α/ERRα activation

Carbon monoxide (CO), derived by the enzymatic reaction of heme oxygenase (HO), is a cellular regulator of energy metabolism and cytoprotection; however, its underlying mechanism has not been clearly elucidated. Astrocytes pre-exposed to the CO-releasing compound CORM-2 increased mitochondrial biogenesis, mitochondrial electron transport components (cytochrome c, Cyt c; cytochrome c oxidase subunit 2, COX2), and ATP synthesis. The increased mitochondrial function was correlated with activation of AMP-activated protein kinase α and upregulation of HO-1, peroxisome proliferators-activated receptor γ-coactivator-1α (PGC-1α), and estrogen-related receptor α (ERRα). These events elicited by CORM-2 were suppressed by Ca{sup 2+} chelators, a HO inhibitor, and an L-type Ca{sup 2+} channel blocker, but not other Ca{sup 2+} channel inhibitors. Among the HO byproducts, combined CORM-2 and bilirubin treatment effectively increased PGC-1α, Cyt c and COX2 expression, mitochondrial biogenesis, and ATP synthesis, and these increases were blocked by Ca{sup 2+} chelators. Moreover, cerebral ischemia significantly increased HO-1, PGC-1α, and ERRα levels, subsequently increasing Cyt c and COX2 expression, in wild-type mice, compared with HO-1{sup +/−} mice. These results suggest that HO-1-derived CO enhances mitochondrial biogenesis in astrocytes by activating L-type Ca{sup 2+} channel-mediated PGC-1α/ERRα axis, leading to maintenance of astrocyte function and neuroprotection/recovery against damage of brain function. - Highlights: • CORM-pretreated astrocytes induces mitochondrial biogenesis by activating L-type Ca{sup 2+} channel-mediated PGC-1α stabilization. • Cerebral ischemia increased electron transport chain proteins (e.g. Cyt c and COX2), in WT mice, compared with HO-1{sup +/−} mice. • CO/HO-1 pathway increases astrocytic mitochondrial functions via a PGC-1α/ERRα axis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Co-crystal structures of PTK6: With Dasatinib at 2.24 Å, with novel imidazo[1,2-a]pyrazin-8-amine derivative inhibitor at 1.70 Å resolution

Human Protein tyrosine kinase 6 (PTK6)(EC:2.7.10.2), also known as the breast tumor kinase (BRK), is an intracellular non-receptor Src-related tyrosine kinase expressed five-fold or more in human breast tumors and breast cancer cell lines but its expression being low or completely absent from normal mammary gland. There is a recent interest in targeting PTK6-positive breast cancer by developing small molecule inhibitor against PTK6. Novel imidazo[1,2-a]pyrazin-8-amines (IPA) derivative compounds and FDA approved drug, Dasatinib are reported to inhibit PTK6 kinase activity with IC{sub 50} in nM range. To understand binding mode of these compounds and key interactions that drive the potency against PTK6, one of the IPA compounds and Dasatinib were chosen to study through X-ray crystallography. The recombinant PTK6 kinase domain was purified and co-crystallized at room temperature by the sitting-drop vapor diffusion method, collected X-ray diffraction data at in-house and resolved co-crystal structure of PTK6-KD with Dasatinib at 2.24 Å and with IPA compound at 1.70 Å resolution. Both these structures are in DFG-in & αC-helix-out conformation with unambiguous electron density for Dasatinib or IPA compound bound at the ATP-binding pocket. Relative difference in potency between Dasatinib and IPA compound is delineated through the additional interactions derived from the occupation of additional pocket by Dasatinib at gatekeeper area. Refined crystallographic coordinates for the kinase domain of PTK6 in complex with IPA compound and Dasatinib have been submitted to Protein Data Bank under the accession number (5DA3) and (5H2U) respectively. - Highlights: • We report first co-crystal structures of human PTK6 with potent inhibitors bound at the ATP binding pocket. • Relative difference in potency between FDA approved drug, Dasatinib and an inhibitor is delineated at the molecular level. • These co-crystal structures of PTK6-KD are in DFG-in and αC-helix-out conformation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

A new fluorescence-based method to monitor the pH in the thylakoid lumen using GFP variants

The ΔpH-dependent/Tat pathway is unique for using only the proton motive force for driving proteins transport across the thylakoid membrane in chloroplasts. 9-aminoacridine fluorescence quenching is widely used to monitor the ΔpH developed across the thylakoid membrane in the light. However, this method suffers from limited sensitivity to low ΔpH values and to spurious fluorescence signals due to membrane binding. In order to develop a more sensitive method for monitoring the real pH of the thylakoid lumen without these problems we transformed Arabidopsis thaliana with a ratiometric pH-sensitive GFP variant (termed pHluorin) targeted to the lumen by the prOE17 transit peptide. Positive transgenic plants displayed localization of pHluorin in the chloroplast by confocal microscopy, and fractionation experiments revealed that it is in the lumen. The pHluorin signal was the strongest in very young plants and diminished as the plants matured. The pHluorin released from the lumen displayed the expected fluorescence intensity changes in response to pH titration. The fluorescence signal in isolated chloroplasts responded to illumination in a manner consistent with light-dependent lumen acidification. Future experiments will exploit the use of this new pH-indicating probe of the thylakoid lumen to examine the influence of the thylakoid ΔpH on ATP synthesis and protein transport.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

High-density lipoprotein and apolipoprotein A-I inhibit palmitate-induced translocation of toll-like receptor 4 into lipid rafts and inflammatory cytokines in 3T3-L1 adipocytes

Saturated fatty acids (SFAs) activate toll-like receptor 4 (TLR4) signal transduction in macrophages and are involved in the chronic inflammation accompanying obesity. High-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) produce anti-inflammatory effects via reverse cholesterol transport. However, the underlying mechanisms by which HDL and apoA-I inhibit inflammatory responses in adipocytes remain to be determined. Here we examined whether palmitate increases the translocation of TLR4 into lipid rafts and whether HDL and apoA-I inhibit inflammation in adipocytes. Palmitate exposure (250 μM, 24 h) increased interleukin-6 and tumor necrosis factor-α gene expressions and translocation of TLR4 into lipid rafts in 3T3-L1 adipocytes. Pretreatment with HDL and apoA-I (50 μg/mL, 6 h) suppressed palmitate-induced inflammatory cytokine expression and TLR4 translocation into lipid rafts. Moreover, HDL and apoA-I inhibited palmitate-induced phosphorylation of nuclear factor-kappa B. HDL showed an anti-inflammatory effect via ATP-binding cassette transporter G1 and scavenger receptor class B, member 1, whereas apoA-I showed an effect via ATP-binding cassette transporter A1. These results demonstrated that HDL and apoA-I reduced palmitate-potentiated TLR4 trafficking into lipid rafts and its related inflammation in adipocytes via these specific transporters. - Highlights: • Palmitate induces TLR4 translocation into lipid rafts in 3T3-L1 adipocytes. • Raft disruption by MβCD inhibits lipid raft formation. • HDL and apoA-I inhibit palmitate-induced translocation of TLR4 into lipid rafts. • Anti-inflammatory effects of HDL and apoA-I occur via specific transporters.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

3-(Naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride attenuates NLRP3 inflammasome-mediated signaling pathway in lipopolysaccharide-stimulated BV2 microglial cells

Highlights: • KHG26792 attenuated LPS-induced TNF-α, IL-1β, and IL-6 level in BV2 cells. • KHG26792 attenuated LPS-induced ROS and nitrotyrosine level. • KHG26792 attenuated LPS-induced damage in mitochondrial potential. • KHG26792 attenuated LPS-induced expression of NLRP3, activated caspase-1, and ASC. • KHG26792 attenuated LPS-induced ATP level through P2X7 receptor. The nucleotide-binding and oligomerization domain-like receptor containing a pyrin domain 3 (NLRP3) inflammasome is a multiprotein complex with a role in innate immune responses. NLRP3 inflammasome dysfunction is a common feature of chronic inflammatory diseases. Microglia activation is also associated with neuroinflammatory pathologies. We previously reported that 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792) reduced hypoxia-induced toxicity by modulating inflammation. However, no studies have elucidated the precise mechanisms for the anti-inflammatory action of KHG26792, in particular via inflammasome mediation. This study investigated the effects of KHG26792 on the inflammasome-mediated signaling pathway in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. KHG26792 significantly attenuated several inflammatory responses including tumor necrosis factor-α, interleukin-1β, interleukin-6, reactive oxygen species, and mitochondrial potential in these cells. KHG26792 also suppressed LPS-induced increase NLRP3, activated caspase-1, and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) levels. Furthermore, KHG26792 successfully blocked LPS-activated adenosine triphosphate (ATP) level, likely through the purinergic receptor P2X ligand-gated ion channel 7 (P2X7) receptor. Our results suggest that the anti-inflammatory functions of KHG26792 may be, at least in part, due to regulation of the P2X7R/NLRP3-mediated signaling pathway during microglial activation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Rv2477c is an antibiotic-sensitive manganese-dependent ABC-F ATPase in Mycobacterium tuberculosis

Highlights: • ATP-binding cassette (ABC) subfamily F ATPase in Mycobacterium tuberculosis. • ATPase activity of Rv2477c is maximal at pH 5.2 in the presence of Mn{sup 2+}. • Walker B motif glutamate residues are critical for ATPase activity. • Tetracycline and erythromycin inhibit the ATPase activity of Rv2477c. The Rv2477c protein of Mycobacterium tuberculosis (Mtb) belongs to the ATP-binding cassette (ABC) subfamily F that contains proteins with tandem nucleotide-binding domains but lacking transmembrane domains. ABC-F subfamily proteins have been implicated in diverse cellular processes such as translation, antibiotic resistance, cell growth and nutrient sensing. In order to investigate the biochemical characteristics of Rv2477c, we expressed it in Escherichia coli, purified it and characterized its enzymatic functions. We show that Rv2477c displays strong ATPase activity (V{sub max} = 45.5 nmol/mg/min; K{sub m} = 90.5 μM) that is sensitive to orthovanadate. The ATPase activity was maximal in the presence of Mn{sup 2+} at pH 5.2. The Rv2477c protein was also able to hydrolyze GTP, TTP and CTP but at lower rates. Glutamate to glutamine substitutions at amino acid residues 185 and 468 in the two Walker B motifs of Rv2477c severely inhibited its ATPase activity. The antibiotics tetracycline and erythromycin, which target protein translation, were able to inhibit the ATPase activity of Rv2477c. We postulate that Rv2477c could be involved in mycobacterial protein translation and in resistance to tetracyclines and macrolides. This is the first report of the biochemical characterization of an ABC-F subfamily protein in Mtb.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Inhibition of the NLRP3 inflammasome attenuates foam cell formation of THP-1 macrophages by suppressing ox-LDL uptake and promoting cholesterol efflux

Highlights: • NLRP3 inflammasome inhibition attenuates foam cell formation of THP-1 macrophages. • NLRP3 inflammasome inhibition diminishes ox-LDL uptake in THP-1 macrophages. • NLRP3 inflammasome inhibition promotes cholesterol efflux from THP-1 macrophages. • NLRP3 inflammasome inhibition downregulates CD36 expression. • NLRP3 inflammasome inhibition upregulates ABCA1 and SR-BI expression. The NOD-like receptor family, pyrin domain–containing protein 3 (NLRP3) inflammasome plays an important role in the development of atherosclerosis. The activated NLRP3 inflammasome has been reported to promote macrophage foam cell formation, but not all studies have obtained the same result, and how NLRP3 inflammasome is involved in the formation of foam cells remains elusive. We used selective NLRP3 inflammasome inhibitors and NLRP3-deficient THP-1 cells to assess the effect of NLRP3 inflammasome inhibition on macrophage foam cell formation, oxidized low-density lipoprotein (ox-LDL) uptake, esterification, and cholesterol efflux, as well as the expression of associated proteins. Inhibition of the NLRP3 inflammasome attenuated foam cell formation, diminished ox-LDL uptake, and promoted cholesterol efflux from THP-1 macrophages. Moreover, it downregulated CD36, acyl coenzyme A: cholesterol acyltransferase-1 and neutral cholesterol ester hydrolase expression; upregulated ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI) expression; but had no effect on the expression of scavenger receptor class A and ATP-binding cassette transporter G1. Collectively, our findings show that inhibition of the NLRP3 inflammasome decreases foam cell formation of THP-1 macrophages via suppression of ox-LDL uptake and enhancement of cholesterol efflux, which may be due to downregulation of CD36 expression and upregulation of ABCA1 and SR-BI expression, respectively.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Guanine and inosine nucleotides/nucleosides suppress murine T cell activation

Highlights: • We investigated T-cell activation by guanine and inosine nucleotides/nucleosides. • They dose-dependently suppressed IL-2 production via T-cell receptor stimulation. • GTP, ITP, guanosine and inosine suppressed ConA-induced IL-2/IL-6 production. • They did not affect CD25 expression or ERK1/2 activation during T cell activation. • These nucleotides/nucleosides are candidate agents to treat inflammatory diseases. Damaged tissues and cells release intracellular purine nucleotides, which serve as intercellular signaling factors. We previously showed that exogenously added adenine nucleotide (250 μM ATP) suppressed the activation of murine splenic T lymphocytes. Here, we examined the effects of other purine nucleotides/nucleosides on mouse T cell activation. First, we found that pretreatment of mouse spleen T cells with 250 μM GTP, GDP, GMP, guanosine, ITP, IDP, IMP or inosine significantly reduced the release of stimulus-inducible cytokine IL-2. This suppression of IL-2 release was not caused by induction of cell death. Further studies with GTP, ITP, guanosine and inosine showed that pretreatment with these nucleotides/nucleosides also suppressed release of IL-6. However, these nucleotides/nucleosides did not suppress stimulus-induced phosphorylation of ERK1/2, suggesting that the suppression of the release of inflammatory cytokines does not involve inhibition of ERK1/2 signaling. In contrast to ATP pretreatment at the same concentration, guanine or inosine nucleotides/nucleosides did not attenuate the expression of CD25. Our findings indicate that exogenous guanine or inosine nucleotides/nucleosides can suppress inflammatory cytokine release from T cells, and may be promising candidates for use as supplementary agents in the treatment of T cell-mediated immune diseases.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Interleukin-enhanced binding factor 2 interacts with NLRP3 to inhibit the NLRP3 inflammasome activation

Highlights: • The NLRP3 inflammasome activation is attenuated by PSMD10, BCL2L10, CTSS, and ILF2. • ILF2 represses inflammasome activation, pro-Casp-1 cleavege, and pro-IL-1β maturation. • ILF2 interacts with NLRP3 to inhibit the inflammasome activation in the cytoplasm. • ILF2 represses ATP-induced activation of endogenous NLRP3 inflammasome in macrophages. The activation of the NLRP3 inflammasome is a key process of host immune response that establishes the first line of defense against pathogen infections and cellular stresses, whereas excessive inflammasome activation may damage the hosts, and thus it must be precisely controlled. However, the mechanism underlying the repression of the NLRP3 inflammasome activation remains largely unknown. In this study, by establishing and using a reconstructed NLRP3 inflammasome activation system, we reveal that the NLRP3 inflammasome activation, pro-caspase-1 cleavage, and pro-interleukin-1β (pro-IL-1β) activation are repressed by the interleukin-enhanced binding factor 2 (ILF2). Further studies demonstrate that ILF2 represses the activation of NLRP3 inflammasome through interacting with the NACHT-associated domain (NAD) of NLRP3 and co-localized with NLRP3 in the cytoplasm of HEK293T cells. Finally, by generating a THP-1 cell line stably expressing ILF2 protein using the lentivirus infection system, we demonstrate that ILF2 represses ATP-induced activation of endogenous NLRP3 inflammasome in macrophages. Therefore, this study identifies a new role of ILF2 in the regulation of the NLRP3 inflammasome, and reveals a unique mechanism underlying the repression of the NLRP3 inflammasome activation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Sennoside A protects mitochondrial structure and function to improve high-fat diet-induced hepatic steatosis by targeting VDAC1

Highlights: • SA inhibited VDAC1 expression in livers of HFD-induced hepatic steatosis mice. • SA suppressed the ATP surplus by inhibiting mitochondrial complex I in livers of HFD-induced hepatic steatosis mice. • SA protected mitochondrial function and structure in livers of HFD-induced hepatic steatosis mice. • SA improved HFD-induced hepatic steatosis and hepatomegaly. Mitochondrial dysfunction is mainly associated with high-fat-diet (HFD)-induced hepatic steatosis. Sennoside A (SA), a commonly used clinical stimulant laxative, is reported to improve energy metabolism and insulin resistance. However, the effect and mechanism of SA on HFD-induced hepatic steatosis remain largely unknown. The aim of this study was to determine the effect and mechanism of SA on HFD-induced hepatic steatosis in mice. We examined the liver and body weight of mice to evaluate the physical changes in the liver. Hematoxylin and eosin (H&E) and oil red O staining were used to detect the lipid accumulation. The mitochondrial structure and function were tested by transmission electron microscopy and the Seahorse XF24 Analyzer. Furthermore, mitochondrial complexes I, II, and IV and voltage-dependent anion channel 1 (VDAC1) protein activity were detected to understand the mechanism of the protective effect on mitochondria. As a result, damage to the structure and function in the hepatic mitochondria of HFD-induced hepatic steatosis was observed in mice. The structural damage was in the form of loss of cristae, mitochondrial swelling, vacuolization and even rupturing of the outer mitochondrial membrane (OMM). Functional alterations were found by activation of complex I and deficiency in complexes II and IV. The VDAC1 activity and the total ATP in the liver tissue was increased under hepatic steatosis conditions. The above effects were reversed by SA. These data suggest that inhibition of VDAC1 may be an underlying mechanism of SA for protecting mitochondria in HFD-induced hepatic steatosis in mice. Thus, VDAC1 may be a promising target for treating fatty liver disease.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Analysis of metastasis associated signal regulatory network in colorectal cancer

Metastasis is a key factor that affects the survival and prognosis of colorectal cancer patients. To elucidate molecular mechanism associated with the metastasis of colorectal cancer, genes related to the metastasis time of colorectal cancer were screened. Then, a network was constructed with this genes. Data was obtained from colorectal cancer expression profile. Molecular mechanism elucidated the time of tumor metastasis and the expression of genes related to colorectal cancer. We found that metastasis-promoting and metastasis-inhibiting networks included protein hubs of high connectivity. These protein hubs were components of organelles. Some ribosomal proteins promoted the metastasis of colorectal cancer. In some components of organelles, such as proteasomes, mitochondrial ribosome, ATP synthase, and splicing factors, the metastasis of colorectal cancer was inhibited by some sections of these organelles. After performing survival analysis of proteins in organelles, joint survival curve of proteins was constructed in ribosomal network. This joint survival curve showed metastasis was promoted in patients with colorectal cancer (P = 0.0022939). Joint survival curve of proteins was plotted against proteasomes (P = 7 e–07), mitochondrial ribosome (P = 0.0001157), ATP synthase (P = 0.0001936), and splicing factors (P = 1.35e–05). These curves indicate that metastasis of colorectal cancer can be inhibited. After analyzing proteins that bind with organelle components, we also found that some proteins were associated with the time of colorectal cancer metastasis. Hence, different cellular components play different roles in the metastasis of colorectal cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Activation of TGR5 promotes mitochondrial biogenesis in human aortic endothelial cells

Highlights: • Activation of TGR5 increases the expression of PGC-1α, NRF1 and TFAM. • Activation of TGR5 promotes mitochondrial biogenesis. • Activation of TGR5 leads to a functional gain of mitochondria. • The effect of TGR5 on mitochondrial biogenesis is mediated by CREB. Impairment of mitochondrial biogenesis has been associated with vascular pathophysiology. The G-protein–coupled receptor (TGR5) is an important mediator of bile acid signaling and glucose metabolism. However, the effects of TGR5 on mitochondrial biogenesis in endothelial cells remain elusive. In this study, we found that activation of TGR5 using its specific agonist taurolithocholic acid (TLCA) promoted the expression of PGC-1α, a master regulator of mitochondrial biogenesis in human aortic endothelial cells (HAECs). Additionally, activation of TGR5 increased the expression of PGC-1α target genes, such as NRF1 and TFAM. Indeed, we found that TLCA treatment promoted mitochondrial biogenesis by increasing mitochondrial mass, mitochondrial-to-nuclear DNA (mtDNA/nDNA), COX-Ⅰ expression, and cytochrome c oxidase activity in HAECs. Notably, our results displayed that activation of TGR5 resulted in a functional gain in mitochondria by increasing the rate of respiration and ATP production. Mechanistically, we found that TLCA treatment activated the transcriptional factor CREB by inducing the phosphorylation of CREB at Ser133. Using the PKA/CREB inhibitor H89 abolished the effects of TLCA on PGC-1α, NRF1 and TFAM expression as well as the increase in mtDNA/nDNA and ATP production. These findings suggest that activation of TGR5 promoted mitochondrial biogenesis in endothelial cells, which is mediated by the CREB/PGC-1α signaling pathway.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

The anti-malarial atovaquone selectively increases chemosensitivity in retinoblastoma via mitochondrial dysfunction-dependent oxidative damage and Akt/AMPK/mTOR inhibition

Highlights: • Anti-malarial atovaquone exhibits preferential toxicity to retinoblastoma cells. • Atovaquone increases chemosensitivity in retinoblastoma. • Retinoblastoma cells have higher mitochondrial biogenesis than normal retinal cells. • Atovaquone targets Akt/AMPK/mTOR signaling via inducing mitochondrial dysfunction. • Mitochondrial respiration inhibition is required for atovaquone's action. Mitochondria has been identified as a promising target in several cancers. However, little is known on the effects of targeting mitochondria in retinoblastoma. In this work, we show that anti-malarial atovaquone, at clinically achievable concentration, demonstrates inhibitory effects to retinoblastoma cells, to a more extent than in normal retinal cells. Atovaquone also significantly increases chemosensitivity in retinoblastoma. Importantly, we show that retinoblastoma cells have higher level of mitochondrial respiration, membrane potential, mass and ATP compared to normal retinal cells. Although atovaquone significantly inhibits mitochondrial respiration and decrease ATP level in both malignant and normal retinal cells in a similar manner, atovaquone induces much more oxidative stress and damage in retinoblastoma than normal retinal cells. These suggest that normal retinal cells are more tolerable to mitochondrial dysfunctions than retinoblastoma cells. We further demonstrate that atovaquone targets Akt/AMPK/mTOR signaling via inducing mitochondrial dysfunction. Our pre-clinical work demonstrates the translational potential of atovaquone as an addition to the treatment armamentarium for retinoblastoma. Our work also demonstrates the differences of mitochondrial biogenesis and function in malignant versus normal retinal cells which are important for the targeted therapy in retinoblastoma.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Resistin destroys mitochondrial biogenesis by inhibiting the PGC-1α/ NRF1/TFAM signaling pathway

Highlights: • Resistin caused impairment of mitochondrial biogenesis in neuronal cells. • Resistin induced loss of mitochondrial function by reducing respiration rate and ATP. • Resistin inhibited the PGC-1α/NRF1/TFAM pathway. • PGC-1α abolished the inhibitory effects of resistin in mitochondrial biogenesis. Mitochondrial biogenesis deficits in neuronal cells are associated with the pathological progression of neurodegenerative diseases. Resistin, a secretory adipocytokine, possesses multiple physiological functions in diverse cells and tissues. However, the effects of resistin on mitochondrial biogenesis in neuronal cells are still elusive. In the current study, we found that resistin caused a sustainable decrease in mitochondrial contents, including mitochondrial DNA/nuclear DNA ratio (mtDNA/nDNA), mitochondrial mass, cytochrome b protein expression, and cytochrome c oxidase activity, which were correlated with “loss of mitochondrial function” including reduced mitochondrial respiration rate and ATP production in human SH-SY5Y neuronal cells. Indeed, resistin treatment destroyed the expression of peroxisome proliferator activator receptor gamma-coactivator 1α (PGC-1α), a master regulator of mitochondrial biogenesis, as well as its downstream target genes including nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM). Notably, overexpression of PGC-1α could completely rescue mitochondrial biogenesis and mitochondrial deficits induced by resistin. Mechanistically, inhibition of 5′-adenosine monophosphate-activated protein kinase (AMPK) was shown to mediate the inhibitory effects of resistin on mitochondrial biogenesis.

60 APPLIED LIFE SCIENCES↗