Rhodamine 123 as a probe of transmembrane potential in isolated rat-liver mitochondria: spectral and metabolic properties

Study and optimization of the photobiomodulation effects induced on mitochondrial metabolic activity of human cardiomyocytes for different radiometric and spectral conditions

Photobiomodulation (PBM) represents a promising and powerful approach for non-invasive therapeutic interventions. This emerging field of research has gained a considerable attention due to its potential for multiple disciplines, including medicine, neuroscience, and sports medicine. While PBM has shown the ability to stimulate various cellular processes in numerous medical applications, the fine-tuning of treatment parameters, such as wavelength, irradiance, treatment duration, and illumination geometry, remains an ongoing challenge. Furthermore, additional research is necessary to unveil the specific mechanisms of action and establish standardized protocols for diverse clinical applications. Given the widely accepted understanding that mitochondria play a pivotal role in the PBM mechanisms, our study delves into a multitude of PBM illumination parameters while assessing the PBM's effects on the basis of endpoints reflecting the mitochondrial metabolism of human cardiac myocytes (HCM), that are known for their high mitochondrial density. These endpoints include: i) the endogenous production of protoporphyrin IX (PpIX), ii) changes in mitochondrial potential monitored by Rhodamine 123 (Rhod 123), iii) changes in the HCM's oxygen consumption, iv) the fluorescence lifetime of Rhod 123 in mitochondria, and v) alterations of the mitochondrial morphology. The good correlation observed between these different methods to assess PBM effects underscores that monitoring the endogenous PpIX production offers interesting indirect insights into the mitochondrial metabolic activity. This conclusion is important since many approved therapeutics and cancer detection approaches are based on the use of PpIX. Finally, this correlation strongly suggests that the PBM effects mentioned above have a common "fundamental" mechanistic origin.

Ethanolic Extract from Fruits of Pintoa chilensis, a Chilean Extremophile Plant. Assessment of Antioxidant Activity and In Vitro Cytotoxicity

Pintoa chilensis is a shrub with yellow flowers that reach up to two meters high, endemic of the Atacama Region in Chile. This species grows under special environmental conditions such as low altitude, arid areas, and directly sun-exposed habitats. In the present study, ethanolic extract was obtained from fruits of P. chilensis, and then partitioned in solvents of increasing polarity to obtain five fractions: hexane (HF), dichloromethane (DF), ethyl acetate (AF), and the residual water fraction (QF). The antioxidant activity of extracts was evaluated by using the DPPH, ABTS, and FRAP methods. The results show that the antioxidant capacity of P. chilensis is higher than that reported for other plants growing in similar environments. This effect is attributed to the highest content of flavonoids and total phenols found in P. chilensis. On the other hand, the cell viability of a breast cancer cell line (MCF-7) and a non-tumor cell line (MCF-10A) was assessed in the presence of different extract fractions. The results indicate that the hexane fraction (HF) exhibits the highest cytotoxicity on both cell lines (IC50 values equal to 35 and 45 µg/mL), whereas the dichloromethane fraction (DF) is the most selective one. The GC-MS analysis of the dichloromethane fraction (DF) shows the presence of fatty acids, sugars, and polyols as major components.

Distinct concentration-dependent oxidative stress profiles by cadmium in a rat kidney proximal tubule cell line

Levels and chemical species of reactive oxygen/nitrogen species (ROS/RNS) determine oxidative eustress and distress. Abundance of uptake pathways and high oxygen consumption for ATP-dependent transport makes the renal proximal tubule particularly susceptible to cadmium (Cd2+)-induced oxidative stress by targeting ROS/RNS generation or antioxidant defence mechanisms, such as superoxide dismutase (SOD) or H2O2-metabolizing catalase (CAT). Though ROS/RNS are well-evidenced, the role of distinct ROS profiles in Cd2+ concentration-dependent toxicity is not clear. In renal cells, Cd2+ (10-50 µM) oxidized dihydrorhodamine 123, reaching a maximum at 2-3 h. Increases (up to fourfold) in lipid peroxidation by TBARS assay and H2O2 by Amplex Red were evident within 30 min. ROS and loss in cell viability by MTT assay with 50 µM Cd2+ could not be fully reversed by SOD mimetics Tempol and MnTBAP nor by SOD1 overexpression, whereas CAT expression and α-tocopherol were effective. SOD and CAT activities were attenuated below controls only with >6 h 50 µM Cd2+, yet augmented by up to 1.5- and 1.2-fold, respectively, by 10 µM Cd2+. Moreover, 10 µM, but not 25-50 µM Cd2+, caused 1.7-fold increase in superoxide anion (O2•-), detected by dihydroethidium, paralled by loss in cell viability, that was abolished by Tempol, MnTBAP, α-tocopherol and SOD1 or CAT overexpression. H2O2-generating NADPH oxidase 4 (NOX4) was attenuated by ~50% with 10 µM Cd2+ at 3 h compared to upregulation by 50 µM Cd2+ (~1.4-fold, 30 min), which was sustained for 24 h. In summary, O2•- predominates with low-moderate Cd2+, driving an adaptive response, whereas oxidative stress by elevated H2O2 at high Cd2+ triggers cell death signaling pathways.Highlights Different levels of reactive oxygen species are generated, depending on cadmium concentration. Superoxide anion predominates and H2O2 is suppressed with low cadmium representing oxidative eustress. High cadmium fosters H2O2 by inhibiting catalase and increasing NOX4 leading to oxidative distress. Superoxide dismutase mimetics and overexpression were less effective with high versus low cadmium. Oxidative stress profile could dictate downstream signalling pathways.

Novel diarylated tacrine derivatives: Synthesis, characterization, anticancer, antiepileptic, antibacterial, and antifungal activities

In this study, our goal was to synthesize novel aryl tacrine derivatives and assess their potential as anticancer, antibacterial agents, and enzyme inhibitors. We adopted a two-step approach, initiating with the synthesis of dibromotacrine derivatives 3 and 4 through the Friedlander reaction. These intermediates underwent further transformation into diarylated tacrine derivatives 3a-e and 4a-e using a Suzuki-Miyaura cross-coupling reaction. Thorough characterization of these novel diarylated tacrines was achieved using various spectroscopic techniques. Our findings highlighted the potent anticancer effects of these innovative compounds across a range of cancer cell lines, including lung, gynecologic, bone, colon, and breast cancers, while demonstrating low cytotoxicity against normal cells. Notably, these compounds surpassed the control drug, 5-Fluorouracil, in terms of antiproliferative activity in numerous cancer cell lines. Moreover, our investigation included an analysis of the inhibitory properties of these novel compounds against various microorganisms and cytosolic carbonic anhydrase enzymes. The results suggest their potential for further exploration as cancer-specific, enzyme inhibitory, and antibacterial therapeutic agents. Notably, four compounds, namely, 5,7-bis(4-(methylthio)phenyl)tacrine (3d), 5,7-bis(4-(trifluoromethoxy)phenyl)tacrine (3e), 2,4-bis(4-(trifluoromethoxy)phenyl)-7,8,9,10-tetrahydro-6H-cyclohepta[b]quinolin-11-amine (4e), and 6,8-dibromotacrine (3), emerged as the most promising candidates for preclinical studies.

How and when to measure mitochondrial inner membrane potentials

The scientific literature on mitochondria has increased significantly over the years due to findings that these organelles have widespread roles in the onset and progression of pathological conditions such as metabolic disorders, neurodegenerative and cardiovascular diseases, inflammation, and cancer. Researchers have extensively explored how mitochondrial properties and functions are modified in different models, often using fluorescent inner mitochondrial membrane potential (ΔΨm) probes to assess functional mitochondrial aspects such as protonmotive force and oxidative phosphorylation. This review provides an overview of existing techniques to measure ΔpH and ΔΨm, highlighting their advantages, limitations, and applications. It discusses drawbacks of ΔΨm probes, especially when used without calibration, and conditions where alternative methods should replace ΔΨm measurements for the benefit of the specific scientific objectives entailed. Studies investigating mitochondria and their vast biological roles would be significantly advanced by the understanding of the correct applications as well as limitations of protonmotive force measurements and use of fluorescent ΔΨm probes, adopting more precise, artifact-free, sensitive, and quantitative measurements of mitochondrial functionality.

Residual Complex I activity and amphidirectional Complex II operation support glutamate catabolism through mtSLP in anoxia

Anoxia halts oxidative phosphorylation (OXPHOS) causing an accumulation of reduced compounds in the mitochondrial matrix which impedes dehydrogenases. By simultaneously measuring oxygen concentration, NADH autofluorescence, mitochondrial membrane potential and ubiquinone reduction extent in isolated mitochondria in real-time, we demonstrate that Complex I utilized endogenous quinones to oxidize NADH under acute anoxia. 13C metabolic tracing or untargeted analysis of metabolites extracted during anoxia in the presence or absence of site-specific inhibitors of the electron transfer system showed that NAD+ regenerated by Complex I is reduced by the 2-oxoglutarate dehydrogenase Complex yielding succinyl-CoA supporting mitochondrial substrate-level phosphorylation (mtSLP), releasing succinate. Complex II operated amphidirectionally during the anoxic event, providing quinones to Complex I and reducing fumarate to succinate. Our results highlight the importance of quinone provision to Complex I oxidizing NADH maintaining glutamate catabolism and mtSLP in the absence of OXPHOS.

Auranofin sensitizes breast cancer cells to paclitaxel chemotherapy by disturbing the cellular redox system

The intrinsic redox status of cancer cells limits the efficacy of chemotherapeutic drugs. Auranofin, a Food and Drug Administration-approved gold-containing compound, documented with effective pharmacokinetics and safety profiles in humans, has recently been repurposed for anticancer activity. This study examined the paclitaxel-sensitizing effect of auranofin by targeting redox balance in the MDA-MB-231 and MCF-7 breast cancer cell lines. Auranofin treatment depletes the activities of superoxide dismutase, catalase, and glutathione peroxidase and alters the redox ratio in the breast cancer cell lines. Furthermore, it has been noticed that auranofin augmented paclitaxel-mediated cytotoxicity in a concentration-dependent manner in both MDA-MB-231 and MCF-7 cell lines. Moreover, auranofin increased the levels of intracellular reactive oxygen species (observed using 2, 7-diacetyl dichlorofluorescein diacetate staining) and subsequently altered the mitochondrial membrane potential (rhodamine-123 staining) in a concentration-dependent manner. Further, the expression of apoptotic marker p21 was found to be higher in auranofin plus paclitaxel-treated breast cancer cells compared to paclitaxel-alone treatment. Thus, the present results illustrate the chemosensitizing property of auranofin in MDA-MB-231 and MCF-7 breast cancer cell lines via oxidative metabolism. Therefore, auranofin could be considered a chemosensitizing agent during cancer chemotherapy.

Enhanced mitochondrial buffering prevents Ca2+ overload in naked mole-rat brain

Deleterious Ca2+ accumulation is central to hypoxic cell death in the brain of most mammals. Conversely, hypoxia-mediated increases in cytosolic Ca2+ are retarded in hypoxia-tolerant naked mole-rat brain. We hypothesized that naked mole-rat brain mitochondria have an enhanced capacity to buffer exogenous Ca2+ and examined Ca2+ handling in naked mole-rat cortical tissue. We report that naked mole-rat brain mitochondria buffer >2-fold more exogenous Ca2+ than mouse brain mitochondria, and that the half-maximal inhibitory concentration (IC50 ) at which Ca2+ inhibits aerobic oxidative phosphorylation is >2-fold higher in naked mole-rat brain. The primary driving force of Ca2+ uptake is the mitochondrial membrane potential (Δψm ), and the IC50 at which Ca2+ decreases Δψm is ∼4-fold higher in naked mole-rat than mouse brain. The ability of naked mole-rat brain mitochondria to safely retain large volumes of Ca2+ may be due to ultrastructural differences that support the uptake and physical storage of Ca2+ in mitochondria. Specifically, and relative to mouse brain, naked mole-rat brain mitochondria are larger and have higher crista density and increased physical interactions between adjacent mitochondrial membranes, all of which are associated with improved energetic homeostasis and Ca2+ management. We propose that excessive Ca2+ influx into naked mole-rat brain is buffered by physical storage in large mitochondria, which would reduce deleterious Ca2+ overload and may thus contribute to the hypoxia and ischaemia-tolerance of naked mole-rat brain. KEY POINTS: Unregulated Ca2+ influx is a hallmark of hypoxic brain death; however, hypoxia-mediated Ca2+ influx into naked mole-rat brain is markedly reduced relative to mice. This is important because naked mole-rat brain is robustly tolerant against in vitro hypoxia, and because Ca2+ is a key driver of hypoxic cell death in brain. We show that in hypoxic naked mole-rat brain, oxidative capacity and mitochondrial membrane integrity are better preserved following exogenous Ca2+ stress. This is due to mitochondrial buffering of exogenous Ca2+ and is driven by a mitochondrial membrane potential-dependant mechanism. The unique ultrastructure of naked mole-rat brain mitochondria, as a large physical storage space, may support increased Ca2+ buffering and thus hypoxia-tolerance.

Synthesis of Tricyclic Pterolobirin H Analogue: Evaluation of Anticancer and Anti-Inflammatory Activities and Molecular Docking Investigations

Pterolobirin H (3), a cassane diterpene isolated from the roots of Pterolobium macropterum, exhibits important anti-inflammatory and anticancer properties. However, its relatively complex tetracyclic structure makes it difficult to obtain by chemical synthesis, thus limiting the studies of its biological activities. Therefore, we present here a short route to obtain a rational simplification of pterolobirin H (3) and some intermediates. The anti-inflammatory activity of these compounds was assayed in LPS-stimulated RAW 264.7 macrophages. All compounds showed potent inhibition of NO production, with percentages between 54 to 100% at sub-cytotoxic concentrations. The highest anti-inflammatory effect was shown for compounds 15 and 16. The simplified analog 16 revealed potential NO inhibition properties, being 2.34 higher than that of natural cassane pterolobirin H (3). On the other hand, hydroxyphenol 15 was also demonstrated to be the strongest NO inhibitor in RAW 264.7 macrophages (IC50 NO = 0.62 ± 0.21 μg/mL), with an IC50NO value 28.3 times lower than that of pterolobirin H (3). Moreover, the anticancer potential of these compounds was evaluated in three cancer cell lines: HT29 colon cancer cells, Hep-G2 hepatoma cells, and B16-F10 murine melanoma cells. Intermediate 15 was the most active against all the selected tumor cell lines. Compound 15 revealed the highest cytotoxic effect with the lowest IC50 value (IC50 = 2.45 ± 0.29 μg/mL in HT29 cells) and displayed an important apoptotic effect through an extrinsic pathway, as evidenced in the flow cytometry analysis. Furthermore, the Hoechst staining assay showed that analog 15 triggered morphological changes, including nuclear fragmentation and chromatin condensation, in treated HT29 cells. Finally, the in silico studies demonstrated that cassane analogs exhibit promising binding affinities and docking performance with iNOS and caspase 8, which confirms the obtained experimental results.

Arf1 coordinates fatty acid metabolism and mitochondrial homeostasis

Lipid mobilization through fatty acid β-oxidation is a central process essential for energy production during nutrient shortage. In yeast, this catabolic process starts in the peroxisome from where β-oxidation products enter mitochondria and fuel the tricarboxylic acid cycle. Little is known about the physical and metabolic cooperation between these organelles. Here we found that expression of fatty acid transporters and of the rate-limiting enzyme involved in β-oxidation is decreased in cells expressing a hyperactive mutant of the small GTPase Arf1, leading to an accumulation of fatty acids in lipid droplets. Consequently, mitochondria became fragmented and ATP synthesis decreased. Genetic and pharmacological depletion of fatty acids phenocopied the arf1 mutant mitochondrial phenotype. Although β-oxidation occurs in both mitochondria and peroxisomes in mammals, Arf1's role in fatty acid metabolism is conserved. Together, our results indicate that Arf1 integrates metabolism into energy production by regulating fatty acid storage and utilization, and presumably organelle contact sites.

Analysis of MT-ATP8 gene variants reported in patients by modeling in silico and in yeast model organism

Defects in ATP synthase functioning due to the substitutions in its two mitochondrially encoded subunits a and 8 lead to untreatable mitochondrial diseases. Defining the character of variants in genes encoding these subunits is challenging due to their low frequency, heteroplasmy of mitochondrial DNA in patients' cells and polymorphisms of mitochondrial genome. We successfully used yeast S. cerevisiae as a model to study the effects of variants in MT-ATP6 gene and our research led to understand how eight amino acid residues substitutions impact the proton translocation through the channel formed by subunit a and c-ring of ATP synthase at the molecular level. Here we applied this approach to study the effects of the m.8403T>C variant in MT-ATP8 gene. The biochemical data from yeast mitochondria indicate that equivalent mutation is not detrimental for the yeast enzyme functioning. The structural analysis of substitutions in subunit 8 introduced by m.8403T>C and five other variants in MT-ATP8 provides indications about the role of subunit 8 in the membrane domain of ATP synthase and potential structural consequences of substitutions in this subunit.

Full-Quantum Treatment of Molecular Systems Confirms Novel Supracence Photonic Properties

Our understanding of molecules has stagnated at a single quantum system, with atoms as Newtonian particles and electrons as quantum particles. Here, however, we reveal that both atoms and electrons in a molecule are quantum particles, and their quantum-quantum interactions create a previously unknown, newfangled molecular property-supracence. Molecular supracence is a phenomenon in which the molecule transfers its potential energy from quantum atoms to photo-excited electrons so that the emitted photon has more energy than that of the absorbed one. Importantly, experiments reveal such quantum energy exchanges are independent of temperature. When quantum fluctuation results in absorbing low-energy photons, yet still emitting high-energy photons, supracence occurs. This report, therefore, reveals novel principles governing molecular supracence via experiments that were rationalized by full quantum (FQ) theory. This advancement in understanding predicts the super-spectral resolution of supracence, and molecular imaging confirms such innovative forecasts using closely emitting rhodamine 123 and rhodamine B in living cell imaging of mitochondria and endosomes.

Overexpression of a Short Sulfonylurea Splice Variant Increases Cardiac Glucose Uptake and Uncouples Mitochondria by Regulating ROMK Activity

The mitochondrial splice variant of the sulfonylurea receptor (SUR2A-55) is associated with protection from myocardial ischemia-reperfusion (IR) injury, increased mitochondrial ATP sensitive K+ channel activity (mitoKATP) and altered glucose metabolism. While mitoKATP channels composed of CCDC51 and ABCB8 exist, the mitochondrial K+ pore regulated by SUR2A-55 is unknown. We explored whether SUR2A-55 regulates ROMK to form an alternate mitoKATP. We assessed glucose uptake in mice overexpressing SUR2A-55 (TGSUR2A-55) compared with WT mice during IR injury. We then examined the expression level of ROMK and the effect of ROMK modulation on mitochondrial membrane potential (Δψm) in WT and TGSUR2A-55 mice. TGSUR2A-55 had increased glucose uptake compared to WT mice during IR injury. The expression of ROMK was similar in WT compared to TGSUR2A-55 mice. ROMK inhibition hyperpolarized resting cardiomyocyte Δψm from TGSUR2A-55 mice but not from WT mice. In addition, TGSUR2A-55 and ROMK inhibitor treated WT isolated cardiomyocytes had enhanced mitochondrial uncoupling. ROMK inhibition blocked diazoxide induced Δψm depolarization and prevented preservation of Δψm from FCCP perfusion in WT and to a lesser degree TGSUR2A-55 mice. In conclusion, cardio-protection from SUR2A-55 is associated with ROMK regulation, enhanced mitochondrial uncoupling and increased glucose uptake.

Probing the pathogenicity of patient-derived variants of MT-ATP6 in yeast

The list of mitochondrial DNA (mtDNA) variants detected in individuals with neurodegenerative diseases is constantly growing. Evaluating their functional consequences and pathogenicity is not easy, especially when they are found in only a limited number of patients together with wild-type mtDNA (heteroplasmy). Owing to its amenability to mitochondrial genetic transformation and incapacity to stably maintain heteroplasmy, and the strong evolutionary conservation of the proteins encoded in mitochondria, Saccharomyces cerevisiae provides a convenient model to investigate the functional consequences of human mtDNA variants. We herein report the construction and energy-transducing properties of yeast models of eight MT-ATP6 gene variants identified in patients with various disorders: m.8843T>C, m.8950G>A, m.9016A>G, m.9025G>A, m.9029A>G, m.9058A>G, m.9139G>A and m.9160T>C. Significant defect in growth dependent on respiration and deficits in ATP production were observed in yeast models of m.8950G>A, m.9025G>A and m.9029A>G, providing evidence of pathogenicity for these variants. Yeast models of the five other variants showed very mild, if any, effect on mitochondrial function, suggesting that the variants do not have, at least alone, the potential to compromise human health.

Mitochondrial H2O2 metabolism as central event of heart complex I syndrome in early diabetes

Hydrogen peroxide is the main metabolite effective in redox regulation and it is considered an insulinomimetic agent, with insulin signalling being essential for normal mitochondrial function in cardiomyocytes. Therefore, the aim of this work was to deeply analyse the heart mitochondrial H₂O₂ metabolism, in the early stage of type 1 diabetes. Diabetes was induced by Streptozotocin (STZ, single dose, 60 mg × kg^-1, ip.) in male Wistar rats and the animals were sacrificed 10 days after injection. Mitochondrial membrane potential and ATP production, using malate-glutamate as substrates, in the heart of diabetic animals were like the ones observed in control group. Mn-SOD activity was lower (15%) in the heart of diabetic rats even though its expression was increased (29%). The increment in heart mitochondrial H₂O₂ production (117%) in diabetic animals was accompanied by an enhancement in the activities and expressions of glutathione peroxidase (26% and 42%) and of catalase (200% and 133%), with no changes in the peroxiredoxin activity, leading to [H₂O₂]_ss ∼40 nM. Heart mitochondrial lipid peroxidation and protein nitration were higher in STZ-injected animals (45% and 42%) than in control group. The mitochondrial membrane potential and ATP production preservation suggest the absence of irreversible damage at this early stage of diabetes 1. The increase in mitochondrial [H₂O₂]_ss above the physiological range, but still below supraphysiological concentration (∼100 nM) seems to be part of the adaptive response triggered in cardiomyocytes due to the absence of insulin. The signs of mitochondrial dysfunction observed in this very early stage of diabetes are consistent with the mitochondrial entity called ″complex I syndrome″.

Pre-Exposure of Foodborne Staphylococcus aureus Isolates to Organic Acids Induces Cross-Adaptation to Mild Heat

Staphylococcus aureus is a typical enterotoxin-producing bacterium that causes food poisoning. In the food industry, pasteurization is the most widely used technique for food decontamination. However, pre-exposure to an acidic environment might make bacteria more resistant to heat treatment, which could compromise the bactericidal effect of heat treatment and endanger food safety. In this work, the organic acid-induced cross-adaptation of S. aureus isolates to heat and the associated mechanisms were investigated. Cross-adaptation area analysis indicated that pre-exposure to organic acids induced cross-adaptation of S. aureus to heat in a strain-dependent manner. Compared with other strains, S. aureus strain J15 showed extremely high heat resistance after being stressed by acetic acid, citric acid, and lactic acid. S. aureus strains J19, J9, and J17 were found to be unable to develop cross-adaptation to heat with pre-exposure to acetic acid, citric acid, and lactic acid, respectively. Analysis of the phenotypic characteristics of the cell membrane demonstrated that the acid-heat-cross-adapted strain J15 retained cell membrane integrity and functions through enhanced Na+K+-ATPase and FoF1-ATPase activities. Cell membrane fatty acid analysis revealed that the ratio of anteiso to iso branched-chain fatty acids in the acid-heat-cross-adapted strain J15 decreased and the content of straight-chain fatty acids exhibited a 2.9 to 4.4% increase, contributing to the reduction in membrane fluidity. At the molecular level, fabH was overexpressed with preconditioning by organic acid, and its expression was further enhanced with subsequent heat exposure. Organic acids activated the GroESL system, which participated in the heat shock response of S. aureus to the subsequent heat stress. IMPORTANCE Cross-adaptation is one of the most important phenotypes in foodborne pathogens and poses a potential risk to food safety and human health. In this work, we found that pretreatment with acetic acid, citric acid, and lactic acid could induce subsequent heat tolerance development in S. aureus. Various S. aureus strains exhibited different acid-heat cross-adaptation areas. The acid-induced cross-adaptation to heat might be attributable to membrane integrity maintenance, stabilization of the charge equilibrium to achieve a normal internal pH, and membrane fluidity reduction achieved by decreasing the ratios of anteiso to iso fatty acids. The fabH gene, which is involved in fatty acid biosynthesis, and groES/groEL, which are related to heat shock response, contributed to the development of the acid-heat cross-adaptation phenomenon in S. aureus. The investigations of the stress cross-adaptation phenomenon in foodborne pathogens could help optimize food processing to better control S. aureus.

ATP synthase interactome analysis identifies a new subunit l as a modulator of permeability transition pore in yeast

The mitochondrial ATP synthase, an enzyme that synthesizes ATP and is involved in the formation of the mitochondrial mega-channel and permeability transition, is a multi-subunit complex. In S. cerevisiae, the uncharacterized protein Mco10 was previously found to be associated with ATP synthase and referred as a new 'subunit l'. However, recent cryo-EM structures could not ascertain Mco10 with the enzyme making questionable its role as a structural subunit. The N-terminal part of Mco10 is very similar to k/Atp19 subunit, which along with subunits g/Atp20 and e/Atp21 plays a major role in stabilization of the ATP synthase dimers. In our effort to confidently define the small protein interactome of ATP synthase we found Mco10. We herein investigate the impact of Mco10 on ATP synthase functioning. Biochemical analysis reveal in spite of similarity in sequence and evolutionary lineage, that Mco10 and Atp19 differ significantly in function. The Mco10 is an auxiliary ATP synthase subunit that only functions in permeability transition.

Subcellular analysis of blood-brain barrier function by micro-impalement of vessels in acute brain slices

The blood-brain barrier (BBB) is a tightly and actively regulated vascular barrier. Answering fundamental biological and translational questions about the BBB with currently available approaches is hampered by a trade-off between accessibility and biological validity. We report an approach combining micropipette-based local perfusion of capillaries in acute brain slices with multiphoton microscopy. Micro-perfusion offers control over the luminal solution and allows application of molecules and drug delivery systems, whereas the bath solution defines the extracellular milieu in the brain parenchyma. Here we show, that this combination allows monitoring of BBB transport at the cellular level, visualization of BBB permeation of cells and molecules in real-time and resolves subcellular details of the neurovascular unit. In combination with electrophysiology, it permits comparison of drug effects on neuronal activity following luminal versus parenchymal application. We further apply micro-perfusion to the human and mouse BBB of epileptic hippocampi highlighting its utility for translational research and analysis of therapeutic strategies.

Inverse Lansing Effect: Maternal Age and Provisioning Affecting Daughters' Longevity and Male Offspring Production

AbstractMaternal age effects on offspring life history are known in a variety of organisms, with offspring of older mothers typically having lower life expectancy (the Lansing effect). However, there is no consensus on the generality and mechanisms of this pattern. We tested predictions of the Lansing effect in several Daphnia magna clones and observed clone-specific magnitude and direction of the maternal age effect on offspring longevity. We also report ambidirectional, genotype-specific effects of maternal age on the propensity of daughters to produce male offspring. Focusing on two clones with contrasting life histories, we demonstrate that maternal age effects can be explained by lipid provisioning of embryos by mothers of different ages. Individuals from a single-generation maternal age reversal treatment showed intermediate life span and intermediate lipid content at birth. In the clone characterized by the "inverse Lansing effect," neonates produced by older mothers showed higher mitochondrial membrane potential in neural tissues than their counterparts born to younger mothers. We conclude that an inverse Lansing effect is possible and hypothesize that it may be caused by age-specific maternal lipid provisioning creating a calorically restricted environment during embryonic development, which in turn reduces fecundity and increases life span in offspring.

Semisynthesis and Evaluation of Anti-Inflammatory Activity of the Cassane-Type Diterpenoid Taepeenin F and of Some Synthetic Intermediates

A new strategy for the semisynthesis of the aromatic cassane-type diterpene taepeenin F (6) is reported. The introduction of the methyl group at C-14, characteristic of the target compound, was achieved via dienone 13, easily prepared from abietic acid (10), the major compound in renewable rosin. Biological assays of selected compounds are reported. The antiproliferative activity against HT29, B16-F10, and HepG2 tumor cell lines has been investigated. Salicylaldehyde 21 was the most active compound (IC₅₀ = 7.72 μM). Products 16 and 21 displayed apoptotic effects in B16-F10 cells, with total apoptosis rates of 46 and 38.4%, respectively. This apoptotic process involves a significant arrest of the B16-F10 cell cycle, blocking the G0/G1 phase. Dienone 16 did not cause any loss of the mitochondrial membrane potential (MMP), while salicylaldehyde 21 caused a partial loss of the MMP. The anti-inflammatory activity of the selected compounds was investigated with the LPS-stimulated RAW 264.7 macrophages. All compounds showed potent NO inhibition, with percentages between 80 and 99% at subcytotoxic concentrations. Dienone 16 inhibited LPS-induced differentiation of RAW 264.7 cells, by increasing the proportion of cells in the S phase. In addition, salicylaldehyde 21 had effects on the cell cycle, recovering the cells from the G0/G1 full arrest produced in response to LPS action.

Proline Oxidation Supports Mitochondrial ATP Production When Complex I Is Inhibited

The oxidation of proline to pyrroline-5-carboxylate (P5C) leads to the transfer of electrons to ubiquinone in mitochondria that express proline dehydrogenase (ProDH). This electron transfer supports Complexes CIII and CIV, thus generating the protonmotive force. Further catabolism of P5C forms glutamate, which fuels the citric acid cycle that yields the reducing equivalents that sustain oxidative phosphorylation. However, P5C and glutamate catabolism depend on CI activity due to NAD⁺ requirements. NextGen-O2k (Oroboros Instruments) was used to measure proline oxidation in isolated mitochondria of various mouse tissues. Simultaneous measurements of oxygen consumption, membrane potential, NADH, and the ubiquinone redox state were correlated to ProDH activity and F₁F_O-ATPase directionality. Proline catabolism generated a sufficiently high membrane potential that was able to maintain the F₁F_O-ATPase operation in the forward mode. This was observed in CI-inhibited mouse liver and kidney mitochondria that exhibited high levels of proline oxidation and ProDH activity. This action was not observed under anoxia or when either CIII or CIV were inhibited. The duroquinone fueling of CIII and CIV partially reproduced the effects of proline. Excess glutamate, however, could not reproduce the proline effect, suggesting that processes upstream of the glutamate conversion from proline were involved. The ProDH inhibitors tetrahydro-2-furoic acid and, to a lesser extent, S-5-oxo-2-tetrahydrofurancarboxylic acid abolished all proline effects. The data show that ProDH-directed proline catabolism could generate sufficient CIII and CIV proton pumping, thus supporting ATP production by the F₁F_O-ATPase even under CI inhibition.

Reductive stress triggers ANAC017-mediated retrograde signaling to safeguard the endoplasmic reticulum by boosting mitochondrial respiratory capacity

Redox processes are at the heart of universal life processes, such as metabolism, signaling, or folding of secreted proteins. Redox landscapes differ between cell compartments and are strictly controlled to tolerate changing conditions and to avoid cell dysfunction. While a sophisticated antioxidant network counteracts oxidative stress, our understanding of reductive stress responses remains fragmentary. Here, we observed root growth impairment in Arabidopsis thaliana mutants of mitochondrial alternative oxidase 1a (aox1a) in response to the model thiol reductant dithiothreitol (DTT). Mutants of mitochondrial uncoupling protein 1 (ucp1) displayed a similar phenotype indicating that impaired respiratory flexibility led to hypersensitivity. Endoplasmic reticulum (ER) stress was enhanced in the mitochondrial mutants and limiting ER oxidoreductin capacity in the aox1a background led to synergistic root growth impairment by DTT, indicating that mitochondrial respiration alleviates reductive ER stress. The observations that DTT triggered nicotinamide adenine dinucleotide (NAD) reduction in vivo and that the presence of thiols led to electron transport chain activity in isolated mitochondria offer a biochemical framework of mitochondrion-mediated alleviation of thiol-mediated reductive stress. Ablation of transcription factor Arabidopsis NAC domain-containing protein17 (ANAC017) impaired the induction of AOX1a expression by DTT and led to DTT hypersensitivity, revealing that reductive stress tolerance is achieved by adjusting mitochondrial respiratory capacity via retrograde signaling. Our data reveal an unexpected role for mitochondrial respiratory flexibility and retrograde signaling in reductive stress tolerance involving inter-organelle redox crosstalk.

Interactions between Rhodamine Dyes and Model Membrane Systems—Insights from Molecular Dynamics Simulations

Background: rhodamines are dyes widely used as fluorescent tags in cell imaging, probing of mitochondrial membrane potential, and as P-glycoprotein model substrates. In all these applications, detailed understanding of the interaction between rhodamines and biomembranes is fundamental. Methods: we combined atomistic molecular dynamics (MD) simulations and fluorescence spectroscopy to characterize the interaction between rhodamines 123 and B (Rh123 and RhB, respectively) and POPC bilayers. Results: while the xanthene moiety orients roughly parallel to the membrane plane in unrestrained MD simulations, variations on the relative position of the benzoic ring (below the xanthene for Rh123, above it for RhB) were observed, and related to the structure of the two dyes and their interactions with water and lipids. Subtle distinctions were found among different ionization forms of the probes. Experimentally, RhB displayed a lipid/water partition coefficient more than two orders of magnitude higher than Rh123, in agreement with free energy profiles obtained from umbrella sampling MD. Conclusions: this work provided detailed insights on the similarities and differences in the behavior of bilayer-inserted Rh123 and RhB, related to the structure of the probes. The much higher affinity of RhB for the membranes increases the local concentration and explains its higher apparent affinity for P-glycoprotein reconstituted in model membranes.

Comprehensive understanding of multiple actions of anticancer drug tamoxifen in isolated mitochondria

Tamoxifen has been widely used in the treatment of estrogen receptor (ER)-positive breast cancer, whereas it also exhibits ER-independent anticancer effects in various cancer cell types. As one of the convincing mechanisms underlying the ER-independent effects, induction of apoptosis through mitochondrial dysfunction has been advocated. However, the mechanism of action of tamoxifen even at the isolated mitochondrial level is not fully understood and remains controversial. Here, we attempted to comprehensively understand tamoxifen's multiple actions in isolated rat liver mitochondria through not only revisiting the actions hitherto reported but also conducting originally designed experiments. Using submitochondrial particles, we found that tamoxifen has potential as an inhibitor of both respiratory complex I and ATP synthase. However, these inhibitory effects were not elicited in intact mitochondria, likely because penetration of tamoxifen across the inner mitochondrial membrane is highly restricted owing to its localized positive charge (-N⁺H(CH₃)₂). This restricted penetration may also explain why tamoxifen is unable to function as a protonophore-type uncoupler in mitochondria. Moreover, tamoxifen suppressed opening of the mitochondrial permeability transition pore induced by Ca²⁺ overload through enhancing phosphate uptake into the matrix. The photoaffinity labeling experiments using a photolabile tamoxifen derivative (pTAM1) indicated that pTAM1 specifically binds to voltage-dependent anion channels (VDACs) 1 and 3, which regulate transport of various substances into mitochondria. The binding of tamoxifen to VDAC1 and/or VDAC3 could be responsible for the enhancement of phosphate uptake. Taking all the results together, we consider the principal impairment of mitochondrial functions caused by tamoxifen.

Creation of Yeast Models for Evaluating the Pathogenicity of Mutations in the Human Mitochondrial Gene MT-ATP6 and Discovering Therapeutic Molecules

Numerous diseases in humans have been associated with mutations of the mitochondrial genome (mtDNA). This genome encodes 13 protein subunits of complexes involved in oxidative phosphorylation (OXPHOS), a process that provides aerobic eukaryotes with the energy-rich adenosine triphosphate molecule (ATP). Mutations of the mtDNA may therefore have dramatic consequences especially in tissues and organs with high energy demand. Evaluating the pathogenicity of these mutations may be difficult because they often affect only a fraction of the numerous copies of the mitochondrial genome (up to several thousands in a single cell), which is referred to as heteroplasmy. Furthermore, due to its exposure to reactive oxygen species (ROS) produced in mitochondria, the mtDNA is prone to mutations, and some may be simply neutral polymorphisms with no detrimental consequences on human health. Another difficulty is the absence of methods for genetically transforming human mitochondria. Face to these complexities, the yeast Saccharomyces cerevisiae provides a convenient model for investigating the consequences of human mtDNA mutations in a defined genetic background. Owing to its good fermentation capacity, it can survive the loss of OXPHOS, its mitochondrial genome can be manipulated, and genetic heterogeneity in its mitochondria is unstable. Taking advantage of these unique attributes, we herein describe a method we have developed for creating yeast models of mitochondrial ATP6 gene mutations detected in patients, to determine how they impact OXPHOS. Additionally, we describe how these models can be used to discover molecules with therapeutic potential.

Fluorescence and Photoacoustic Spectroscopy-Based Assessment of Mitochondrial Dysfunction in Oral Cancer Together with Machine Learning: A Pilot Study

The current study reports an integrated approach of machine learning and tryptophan fluorescence and photoacoustic spectral properties to assess the mitochondrial status under oral pathological conditions. The mitochondria in the study were isolated from oral cancer tissues and adjacent normal counterparts, and the corresponding fluorescence and photoacoustic spectra of tryptophan were recorded at 281 nm pulsed laser excitations. A set of features were selected from the pre-processed spectra and were used to classify the data using support vector machine (SVM) learning in the MATLAB platform. SVM analysis demonstrated clear differentiation between mitochondria isolated from normal and cancer tissues for fluorescence (sensitivity, 86.6%; specificity, 90%) and photoacoustic (sensitivity, 86.6%; specificity, 96.6%) measurements. Further investigation into the influence of change in protein conformation on the nature of tryptophan spectral properties was evaluated by 8-anilino-1-naphthalene sulfonic acid (ANS) fluorescence assay. The impact of protein structural changes on the mitochondrial functions was also estimated by mitochondrial membrane potential (MMP), reactive oxygen species (ROS), and cytochrome c oxidase (COX) assays, suggesting an altered mitochondrial function. The findings indicate that tryptophan fluorescence and photoacoustic spectral properties together with machine learning algorithms may delineate the mitochondrial functional status in vitro, indicating its translational potential.

5,6-diiodo-1H-benzotriazole: new TBBt analogue that minutely affects mitochondrial activity

4,5,6,7-Tetrabromo-1H-benzotriazole is widely used as the reference ATP-competitive inhibitor of protein kinase CK2. Herein, we study its new analogs: 5,6-diiodo- and 5,6-diiodo-4,7-dibromo-1H-benzotriazole. We used biophysical (MST, ITC) and biochemical (enzymatic assay) methods to describe the interactions of halogenated benzotriazoles with the catalytic subunit of human protein kinase CK2 (hCK2α). To trace the biological activity, we measured their cytotoxicity against four reference cancer cell lines and the effect on the mitochondrial inner membrane potential. The results obtained lead to the conclusion that iodinated compounds are an attractive alternative to brominated ones. One of them retains the cytotoxicity against selected cancer cell lines of the reference TBBt with a smaller side effect on mitochondrial activity. Both iodinated compounds are candidate leaders in the further development of CK2 inhibitors.

Chronic GPER activation prevents ischemia/reperfusion injury in ovariectomized rats

During menopause women are exposed to an increase in cardiovascular risk. G protein-coupled estrogen receptor (GPER) is known to mediate several of the protective effects of such hormones. G1 was described as a selective and synthetic agonist for GPER. The aim of the present research is to evaluate the effect of a chronic treatment with G1 in ovariectomized (OVX) rats exposed to ischemia/reperfusion (I/R). Considering the hypothesis that an impaired mitochondrial state could be involved in the alterations produced in OVX rats, other objective of this study was to investigate it in an isolated preparation. Three months old rats were assigned to undergo either bilateral ovariectomy or sham operation. The OVX rats were randomly treated during one month with either G1 or vehicle. Cardiac mitochondria from OVX rats showed a depolarized membrane potential and a decreased calcium retention capacity in comparison with Sham rats, which were prevented by chronic G1 treatment. I/R caused a higher decrease of left ventricular developed pressure and a higher increase of left ventricular end diastolic pressure in OVX compared to Sham hearts. These altered mechanical parameters were prevented by G1. The induced infarct size was significantly higher in OVX, which was reduced by G1 treatment. These results indicate that the mitochondrial state in OVX rats is impaired, accompanied by an altered mechanical response after ischemia and reperfusion injury, which was effectively prevented with chronic treatment with G1. The present study may provide further insights for the potential development of a therapy based on the GPER modulation.

Myocardial and mitochondrial effects of the anhydrase carbonic inhibitor ethoxzolamide in ischemia-reperfusion

We have previously demonstrated that inhibition of extracellularly oriented carbonic anhydrase (CA) isoforms protects the myocardium against ischemia-reperfusion injury. In this study, our aim was to assess the possible further contribution of CA intracellular isoforms examining the actions of the highly diffusible cell membrane permeant inhibitor of CA, ethoxzolamide (ETZ). Isolated rat hearts, after 20 min of stabilization, were assigned to the following groups: (1) Nonischemic control: 90 min of perfusion; (2) Ischemic control: 30 min of global ischemia and 60 min of reperfusion (R); and (3) ETZ: ETZ at a concentration of 100 μM was administered for 10 min before the onset of ischemia and then during the first 10 min of reperfusion. In additional groups, ETZ was administered in the presence of SB202190 (SB, a p38MAPK inhibitor) or chelerythrine (Chel, a protein kinase C [PKC] inhibitor). Infarct size, myocardial function, and the expression of phosphorylated forms of p38MAPK, PKCε, HSP27, and Drp1, and calcineurin Aβ content were assessed. In isolated mitochondria, the Ca2+ response, Ca2+ retention capacity, and membrane potential were measured. ETZ decreased infarct size by 60%, improved postischemic recovery of myocardial contractile and diastolic relaxation increased P-p38MAPK, P-PKCε, P-HSP27, and P-Drp1 expression, decreased calcineurin content, and normalized calcium and membrane potential parameters measured in isolated mitochondria. These effects were significantly attenuated when ETZ was administered in the presence of SB or Chel. These data show that ETZ protects the myocardium and mitochondria against ischemia-reperfusion injury through p38MAPK- and PKCε-dependent pathways and reinforces the role of CA as a possible target in the management of acute cardiac ischemic diseases.

Effects of stem cell-derived exosomes on neuronal apoptosis and inflammatory cytokines in rats with cerebral ischemia-reperfusion injury via PI3K/AKT pathway-mediated mitochondrial apoptosis

OBJECTIVE

This study aimed to investigate the effects of stem cell-derived exosomes (SC-Exos) on learning, memory, and neuronal apoptosis in rats with cerebral ischemia-reperfusion injury and to determine whether SC-Exos exert their effects via phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathway-mediated mitochondrial pathways of apoptosis.

MATERIALS AND METHODS

Eighty rats were randomly allocated to control, model, SC-Exos, and PI3K inhibitor groups. A model of focal cerebral ischemia-reperfusion was established using the improved Longa method. Expression of interleukin-1α (IL-1α), interleukin-2 (IL-2), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) were compared in the brains and serum of each group. The expressions of Bcl-2, Bax, cleaved-caspase-3, cleaved-caspase-9, cytochrome C (CytC), PI3K, and AKT-related genes and proteins were evaluated by real-time quantitative polymerase chain reaction and western blotting.

RESULTS

The SC-Exos-group exhibited more novel entries, less latency for the novel arm, and fewer entries into the starting arm and other arms than the model group (p<.05). Lower expression of the inflammatory cytokines IL-1α, IL-2, and TNF-α and higher expression of IFN-γ were observed in the SC-Exos group than in the model group. TdT-mediated dUTP nick end labeling (TUNEL) assay showed that lower neural cell apoptosis rate and expression of Bax, cleaved-caspase-3, cleaved-caspase-9, CytC, PI3K, and AKT mRNA and proteins and higher expression of Bcl-2 mRNA and protein were observed in the SC-Exos group than in the model group (p<.05).

CONCLUSIONS

SC-Exos can significantly ameliorate brain injury caused by cerebral ischemia-reperfusion. The mechanism may be a novel therapeutic target for ischemia-reperfusion injury.

Selective delivery of remarkably high levels of gadolinium to tumour cells using an arsonium salt

The use of a triphenylarsonium vector for tumour cell-targeting leads to a dramatic increase in Gd³⁺ uptake in human glioblastoma multiforme cells by up to an order of magnitude over the isosteric triarylphosphonium analogue, with significant implications for 'theranostic' applications involving delivery of this important lanthanoid metal ion to tumour cells.

A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation

Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.

Applications of flow cytometry sorting in the pharmaceutical industry: A review

The article reviews applications of flow cytometry sorting in manufacturing of pharmaceuticals. Flow cytometry sorting is an extremely powerful tool for monitoring, screening and separating single cells based on any property that can be measured by flow cytometry. Different applications of flow cytometry sorting are classified into groups and discussed in separate sections as follows: (a) isolation of cell types, (b) high throughput screening, (c) cell surface display, (d) droplet fluorescent-activated cell sorting (FACS). Future opportunities are identified including: (a) sorting of particular fractions of the cell population based on a property of interest for generating inoculum that will result in improved outcomes of cell cultures and (b) the use of population balance models in combination with FACS to design and optimize cell cultures.

Breaking free from thermodynamic constraints: thermal acclimation and metabolic compensation in a freshwater zooplankton species

Respiration rates of ectothermic organisms are affected by environmental temperatures, and sustainable metabolism at high temperatures sometimes limits heat tolerance. Organisms are hypothesized to exhibit acclimatory metabolic compensation effects, decelerating their metabolic processes below Arrhenius expectations based on temperature alone. We tested the hypothesis that either heritable or plastic heat tolerance differences can be explained by metabolic compensation in the eurythermal freshwater zooplankton crustacean Daphnia magna We measured respiration rates in a ramp-up experiment over a range of assay temperatures (5-37°C) in eight genotypes of D. magna representing a range of previously reported acute heat tolerances and, at a narrower range of temperatures (10-35°C), in D. magna with different acclimation history (either 10 or 25°C). We discovered no difference in temperature-specific respiration rates between heat-tolerant and heat-sensitive genotypes. In contrast, we observed acclimation-specific compensatory differences in respiration rates at both extremes of the temperature range studied. Notably, there was a deceleration of oxygen consumption at higher temperature in 25°C-acclimated D. magna relative to their 10°C-acclimated counterparts, observed in active animals, a pattern corroborated by similar changes in filtering rate and, partly, by changes in mitochondrial membrane potential. A recovery experiment indicated that the reduction of respiration was not caused by irreversible damage during exposure to a sublethal temperature. Response time necessary to acquire the respiratory adjustment to high temperature was lower than for low temperature, indicating that metabolic compensation at lower temperatures requires slower, possibly structural changes.

The pathogenic m.8993 T > G mutation in mitochondrial ATP6 gene prevents proton release from the subunit c-ring rotor of ATP synthase

The human ATP synthase is an assembly of 29 subunits of 18 different types, of which only two (a and 8) are encoded in the mitochondrial genome. Subunit a, together with an oligomeric ring of c-subunit (c-ring), forms the proton pathway responsible for the transport of protons through the mitochondrial inner membrane, coupled to rotation of the c-ring and ATP synthesis. Neuromuscular diseases have been associated to a number of mutations in the gene encoding subunit a, ATP6. The most common, m.8993 T > G, leads to replacement of a strictly conserved leucine residue with arginine (aL156R). We previously showed that the equivalent mutation (aL173R) dramatically compromises respiratory growth of Saccharomyces cerevisiae and causes a 90% drop in the rate of mitochondrial ATP synthesis. Here, we isolated revertants from the aL173R strain that show improved respiratory growth. Four first-site reversions at codon 173 (aL173M, aL173S, aL173K and aL173W) and five second-site reversions at another codon (aR169M, aR169S, aA170P, aA170G and aI216S) were identified. Based on the atomic structures of yeast ATP synthase and the biochemical properties of the revertant strains, we propose that the aL173R mutation is responsible for unfavorable electrostatic interactions that prevent the release of protons from the c-ring into a channel from which protons move from the c-ring to the mitochondrial matrix. The results provide further evidence that yeast aL173 (and thus human aL156) optimizes the exit of protons from ATP synthase, but is not essential despite its strict evolutionary conservation.

CaMKII-dependent ryanodine receptor phosphorylation mediates sepsis-induced cardiomyocyte apoptosis

Sepsis is associated with cardiac dysfunction, which is at least in part due to cardiomyocyte apoptosis. However, the underlying mechanisms are far from being understood. Using the colon ascendens stent peritonitis mouse model of sepsis (CASP), we examined the subcellular mechanisms that mediate sepsis‐induced apoptosis. Wild‐type (WT) CASP mice hearts showed an increase in apoptosis respect to WT‐Sham. CASP transgenic mice expressing a CaMKII inhibitory peptide (AC3‐I) were protected against sepsis‐induced apoptosis. Dantrolene, used to reduce ryanodine receptor (RyR) diastolic sarcoplasmic reticulum (SR) Ca²⁺ release, prevented apoptosis in WT‐CASP. To examine whether CaMKII‐dependent RyR2 phosphorylation mediates diastolic Ca²⁺ release and apoptosis in sepsis, we evaluated apoptosis in mutant mice hearts that have the CaMKII phosphorylation site of RyR2 (Serine 2814) mutated to Alanine (S2814A). S2814A CASP mice did not show increased apoptosis. Consistent with RyR2 phosphorylation‐dependent enhancement in diastolic SR Ca²⁺ release leading to mitochondrial Ca²⁺ overload, mitochondrial Ca²⁺ retention capacity was reduced in mitochondria isolated from WT‐CASP compared to Sham and this reduction was absent in mitochondria from CASP S2814A or dantrolene‐treated mice. We conclude that in sepsis, CaMKII‐dependent RyR2 phosphorylation results in diastolic Ca²⁺ release from SR which leads to mitochondrial Ca²⁺ overload and apoptosis.

Organelle membrane-specific chemical labeling and dynamic imaging in living cells

Lipids play crucial roles as structural elements, signaling molecules and material transporters in cells. However, the functions and dynamics of lipids within cells remain unclear because of a lack of methods to selectively label lipids in specific organelles and trace their movement by live-cell imaging. We describe here a technology for the selective labeling and fluorescence imaging (microscopic or nanoscopic) of phosphatidylcholine in target organelles. This approach involves the metabolic incorporation of azido-choline, followed by a spatially limited bioorthogonal reaction that enables the visualization and quantitative analysis of interorganelle lipid transport in live cells. More importantly, with live-cell imaging, we obtained direct evidence that the autophagosomal membrane originates from the endoplasmic reticulum. This method is simple and robust and is thus powerful for real-time tracing of interorganelle lipid trafficking.

Exposure to copper nanoparticles impairs ion uptake, and acid and ammonia excretion by ionocytes in zebrafish embryos

The potential toxicity of copper nanoparticles (CuNPs) to early stages of fishes is not fully understood, and little is known about their effects on ionocytes and associated functions. This study used zebrafish embryos as a model to investigate the toxic effects of CuNPs on two subtypes of ionocytes. Zebrafish embryos were exposed to 0.1, 1, and 3 mg L^-1 CuNPs for 96 h. After exposure, whole-body Na⁺ and Ca²⁺ contents were significantly reduced at ≥0.1 mg L^-1, while the K⁺ content had decreased at ≥1 mg L^-1. H⁺ and NH₄⁺ excretion by the skin significantly decreased at ≥1 mg L^-1. The number of living ionocytes labeled with rhodamine-123 had significantly decreased with ≥0.1 mg L^-1 CuNPs. The ionocyte subtypes of H⁺-ATPase-rich (HR) and Na⁺/K⁺-ATPase-rich (NaR) cells were labeled by immunostaining and had decreased with ≥1 mg L^-1. Shrinkage of the apical opening of ionocytes was revealed by scanning electronic microscopy. Functional impairment was also reflected by changes in gene expressions, including ion transporters/channels and Ca²⁺-regulatory hormones. This study shows that CuNP exposure can impair two subtypes of ionocytes and their associated functions, including Na⁺/Ca²⁺ uptake and H⁺/NH₄⁺ excretion in zebrafish embryos.

Molecular Supracence Resolving Eight Colors in 300-nm Width: Unprecedented Spectral Resolution

Monitoring multiple molecular probes simultaneously establishes their correlations and reveals the holistic mechanism. Current fluorescence imaging, however, is limited to about four colors because of typically circa 100-nm spectral width. Herein, we show that molecular supracence imparts superior spectral resolution, resolving eight colors in 300-nm width, about 37.5-nm per color. A recently discovered light-molecule interacting phenomenon, supracence only measures molecular emission above its excitation energy due to entanglement between atomic quantum system and electronic quantum system. As such, supracence takes advantage of sharp spectral edge of a single pathway and excitation specificity to produce narrow bands, whereas fluorescence has to deal with multiple pathways spilling out low-energy long tail, that causes poor resolution. Thus, supracence enables myriad innovative molecular spectroscopy and microscopic imaging with profound impact broadly.

The mechanism of BAF60c in myocardial metabolism through the PGC1α/PPARα/mTOR signaling pathway in rats with heart failure

BRM-associated factor (BAF) 60c promotes muscle glycolysis and improves glucose homeostasis. This study explored the mechanism of BAF60c in heart failure (HF). Fetal/adult rat models of HF were established, and the levels of cardiac contractile proteins and energy metabolism-, oxidative metabolism- and glycolysis-related factors were detected. Overexpression/siRNA BAF60c plasmids were injected into adult HF rats to estimate myocardial glucose uptake, high-energy phosphate contents, mitochondrial function, and cell proliferation and apoptosis. The overexpression/siRNA BAF60c plasmids were transfected into cardiac hypertrophic H9C2 cells to explore the in vitro effects. The interaction of BAF60c and PGC1α was detected. The results suggested that adult HF rats presented increased levels of fetal proteins (ssTnI and fTnT), BAF60c and glycolysis-related factors, and reduced levels of cardiac contractile proteins, PGC1α, PPARα, and oxidative metabolism-related factors. BAF60c knockdown improved glucose uptake, maintained the oxidative metabolism/glycolysis balance, promoted H9C2 cell proliferation, and inhibited apoptosis. PGC1α interacted with BAF60c. Knocking down BAF60c also activated the PGC1α/PPARα/mTOR pathway. Overexpression of PGC1α decreased the damage to H9C2 cells caused by BAF60c. Altogether, BAF60c downregulation activated the PGC1α/PPARα/mTOR pathway, maintained the oxidative metabolism/glycolysis balance and improved mitochondrial function in rat models of HF. This study may offer novel insights into HF treatment.

Diabetic Encephalopathy Affecting Mitochondria and Axonal Transport Proteins

Introduction

Diabetic encephalopathy is described as any cognitive and memory impairments associated with hippocampal degenerative changes, including the neurodegenerative process and decreased number of living cells. Mitochondrial diabetes (MD) appears following activation of mutant mitochondrial DNA and is a combination of diabetes and cognitive deficit. In this research, we showed the correlation of diabetic encephalopathy, dysfunctional mitochondria, and changes in the expression of axonal transport proteins (KIF5b, Dynein).

Methods

Twenty-four male Wistar rats were divided into three groups: (n=8 in each group):1. Control + saline; 2. Diabetic, and 3. Diabetic + insulin. Before starting the experiments, the animals with blood sugar lower than 150 mg/dL entered the study. Diabetes induction was carried out by Intraperitoneal (IP) Streptozotocin (STZ) administration. Fasting Blood Sugar (FBS) and body weight was checked after the first week and at the end of the eighth week. Then, behavioral studies (elevated plus maze, Y-maze, and passive avoidance learning) were performed. After behavioral studies, blood samples were taken to measure serum insulin level and HgbA1c. Next, fresh hippocampal tissue was collected. Gene expression of motor proteins was assessed by real-time PCR and mitochondrial membrane potential by rhodamine123.

Results

Our results showed the impairment of HgbA1c, serum insulin, FBS, and weight in the diabetic group (P<0.05). Behavioral tests revealed different degrees of impairment in diabetic rats (P<0.05). KIF5b mRNA expression increased in the hippocampus (P<0.05) with no change in dynein gene expression. These changes were associated with abnormal mitochondrial membrane potential (P<0.05).

Conclusion

KIF5b mRNA up-regulation in hippocampal neurons of STZ-diabetic rats is a factor that can be involved in abnormal axonal transport and decreased MMP, leading to impairment of mitochondrial function. These manifestations showed mitochondrial dysfunction in diabetes and resulted in abnormal behavioral tests and diabetic encephalopathy.

Molecular Basis of the Pathogenic Mechanism Induced by the m.9191T>C Mutation in Mitochondrial ATP6 Gene

Probing the pathogenicity and functional consequences of mitochondrial DNA (mtDNA) mutations from patient’s cells and tissues is difficult due to genetic heteroplasmy (co-existence of wild type and mutated mtDNA in cells), occurrence of numerous mtDNA polymorphisms, and absence of methods for genetically transforming human mitochondria. Owing to its good fermenting capacity that enables survival to loss-of-function mtDNA mutations, its amenability to mitochondrial genome manipulation, and lack of heteroplasmy, Saccharomyces cerevisiae is an excellent model for studying and resolving the molecular bases of human diseases linked to mtDNA in a controlled genetic background. Using this model, we previously showed that a pathogenic mutation in mitochondrial ATP6 gene (m.9191T>C), that converts a highly conserved leucine residue into proline in human ATP synthase subunit a (aL222P), severely compromises the assembly of yeast ATP synthase and reduces by 90% the rate of mitochondrial ATP synthesis. Herein, we report the isolation of intragenic suppressors of this mutation. In light of recently described high resolution structures of ATP synthase, the results indicate that the m.9191T>C mutation disrupts a four α-helix bundle in subunit a and that the leucine residue it targets indirectly optimizes proton conduction through the membrane domain of ATP synthase.

Deregulating mitochondrial metabolite and ion transport has beneficial effects in yeast and human cellular models for NARP syndrome

The m.8993T>G mutation of the mitochondrial MT-ATP6 gene has been associated with numerous cases of neuropathy, ataxia and retinitis pigmentosa and maternally inherited Leigh syndrome, which are diseases known to result from abnormalities affecting mitochondrial energy transduction. We previously reported that an equivalent point mutation severely compromised proton transport through the ATP synthase membrane domain (FO) in Saccharomyces cerevisiae and reduced the content of cytochrome c oxidase (Complex IV or COX) by 80%. Herein, we report that overexpression of the mitochondrial oxodicarboxylate carrier (Odc1p) considerably increases Complex IV abundance and tricarboxylic acid-mediated substrate-level phosphorylation of ADP coupled to conversion of α-ketoglutarate into succinate in m.8993T>G yeast. Consistently in m.8993T>G yeast cells, the retrograde signaling pathway was found to be strongly induced in order to preserve α-ketoglutarate production; when Odc1p was overexpressed, this stress pathway returned to an almost basal activity. Similar beneficial effects were induced by a partial uncoupling of the mitochondrial membrane with the proton ionophore, cyanide m-chlorophenyl hydrazone. This chemical considerably improved the glutamine-based, respiration-dependent growth of human cytoplasmic hybrid cells that are homoplasmic for the m.8993T>G mutation. These findings shed light on the interdependence between ATP synthase and Complex IV biogenesis, which could lay the groundwork for the creation of nutritional or metabolic interventions for attenuating the effects of mtDNA mutations.

Effect of dipole moment on amphiphile solubility and partition into liquid ordered and liquid disordered phases in lipid bilayers

Association of amphiphiles with biomembranes is important for their availability at specific locations in organisms and cells, being critical for their biological function. A prominent role is usually attributed to the hydrophobic effect, and to electrostatic interactions between charged amphiphiles and lipids. This work explores a closely related and complementary aspect, namely the contribution made by dipole moments to the strength of the interactions established. Two xanthene amphiphiles with opposite relative orientations of their dipole and amphiphilic moments have been selected (Rhodamine-C₁₄ and Carboxyfluorescein-C₁₄). The membranes studied have distinct lipid compositions, representing typical cell membrane pools, ranging from internal membranes to the outer and inner leaflet of the plasma membrane. A comprehensive study is reported, including the affinity of the amphiphiles for the different membranes, the stability of the amphiphiles as monomers and their tendency to form small clusters, as well as their transverse location in the membrane. The orientation of the amphiphile dipole moment, which determines whether its interaction with the membrane dipole potential is repulsive or attractive, is found to exert a large influence on the association of the amphiphile with ordered lipid membranes. These interactions are also responsible for the formation of small clusters or stabilization of amphiphile monomers in the membrane. The results obtained allow understanding the prevalence of protein lipidation at the N-terminal for efficient targeting to the plasma membrane, as well as the tendency of GPI-anchored proteins (usually lipidated at the C-terminal) to form small clusters in the membrane ordered domains.

Elucidation of the Chemopreventive Role of Stigmasterol Against Jab1 in Gall Bladder Carcinoma

BACKGROUND

Plant sterols have proven a potent anti-proliferative and apoptosis inducing agent against several carcinomas including breast and prostate cancers. Jab1 has been reported to be involved in the progression of numerous carcinomas. However, antiproliferative effects of sterols against Jab1 in gall bladder cancer have not been explored yet.

OBJECTIVE

In the current study, we elucidated the mechanism of action of stigmasterol regarding apoptosis induction mediated via downregulation of Jab1 protein in human gall bladder cancer cells.

METHODS

In our study, we performed MTT and Trypan blue assay to assess the effect of stigmasterol on cell proliferation. In addition, RT-PCR and western blotting were performed to identify the effect of stigmasterol on Jab1 and p27 expression in human gall bladder cancer cells. We further performed cell cycle, Caspase-3, Hoechst and FITC-Annexin V analysis, to confirm the apoptosis induction in stigmasterol treated human gall bladder cancer cells.

RESULTS

Our results clearly indicated that stigmasterol has up-regulated the p27 expression and down-regulated Jab1 gene. These modulations of genes might occur via mitochondrial apoptosis signaling pathway. Caspase-3 gets activated with the apoptotic induction. Increase in apoptotic cells and DNA were confirmed through annexin V staining, Hoechst staining, and cell cycle analysis.

CONCLUSION

Thus, these results strongly suggest that stigmasterol has the potential to be considered as an anticancerous therapeutic agent against Jab1 in gall bladder cancer.

Measurement of Energy States of the Trypanosomatid Mitochondrion

The evaluation of mitochondrial functionality is critical to interpret most biological data at the (eukaryotic) cellular level. For example, metabolism, cell cycle, epigenetic regulation, cell death mechanisms, autophagy, differentiation, and response redox imbalance are dependent on the mitochondrial state. In case of parasitic organisms, such as trypanosomatids, it is very often important to have information on mitochondrial functionality in order to assess the mechanisms of actions of drugs being proposed for therapy. In this chapter we present a set of methods that together allow to evaluate with some precision the mitochondrial functionality in Trypanosoma cruzi and Trypanosoma brucei. We discuss how to determine O2 consumption, mitochondrial inner membrane potential, ATP production, and the endogenous production of reactive oxygen species.

Crude Cell-Free Extract From Deinococcus radiodurans Exhibit Anticancer Activity by Inducing Apoptosis in Triple-Negative Breast Cancer Cells

Extremophilic organisms have the potential to tolerate extremely challenging environments of nature. This property can be accredited to its production of novel secondary metabolites that possess anticancer and other pharmaceutical values. The present study was aimed to investigate the anticancer activity of crude secondary metabolite extract (CSME) obtained from the radiation-tolerant bacterium Deinococcus radiodurans in triple-negative human breast carcinoma (MDA-MB-231) cells. The 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay showed the antiproliferative potential of CSME in MDA-MB-231 cells (IC₅₀ = 25 μg/ml) and MCF-7 cells (IC₅₀ = 10 μg/ml). Further, the CSME treatment led to the production of intracellular reactive oxygen species (ROS) and nuclear membrane alterations with the formation of apoptotic bodies in MDA-MB-231 cells. Considerable DNA damage and low antioxidant status were observed in CSME-treated MDA-MB-231 cells. The results also showed that the CSME treatment induced apoptotic markers expression in MDA-MB-231 cells. Western blot results illustrated significant upregulation of p53, caspase-3, and caspase-9 proteins expression. Then, we analyzed the presence of secondary metabolites which may be linked with antiproliferative potential of CSME by gas chromatography-mass spectrometry (GC-MS). The results illustrated the presence of 23 bioactive compounds some of which are already reported to possess anticancer properties. The study indicates that the CSME of D. radiodurans possess anticancer properties and exhibit the potential to be used as an anticancer agent.