Mitochondrial Electron Transfer Chain Complexes Research Articles

Placental Bioenergetics and Antioxidant Homeostasis in Maternal Obesity and Gestational Diabetes.

Maternal obesity has been associated with short- and long-term risks of pregnancy-perinatal adverse events, possibly due to alterations of placental mitochondrial bioenergetics. However, several detrimental mechanisms occurring in the placentas of women with obesity still need to be clarified. Here, we analyzed placental mitochondrial features and oxidative environment of 46 pregnancies in relation to pre-pregnancy BMI. Seventeen Caucasian normal-weight (NW) and twenty-nine women who were obese (OB) were enrolled. The protein expression of mitochondrial CypD and electron transfer chain complexes (C) I-V were measured, as well as ATP production and oxygen consumption rates (OCRs). The protein levels of the pro/anti-oxidant enzymes TXNIP, SOD2, and PON2 were also analyzed. Despite no differences in CypD expression, OCRs were significantly lower in OB vs. NW women. Accordingly, ATP synthase (CV) levels and ATP content were decreased in OB women, positively correlating with placental efficiency, suggesting a link between ATP deficiency and placental dysfunction. SOD2 expression negatively correlated with maternal BMI, indicating a possible impairment of antioxidant defenses with increasing BMI. These changes were worsened in 10 OB women presenting with gestational diabetes mellitus. Overall, these results suggest alterations of placental bioenergetics in pregnancies of women with obesity, possibly leading to placental dysfunction and altered fetal development and programming.

AMPK phosphorylation of FNIP1 (S220) controls mitochondrial function and muscle fuel utilization during exercise.

Exercise-induced activation of adenosine monophosphate-activated protein kinase (AMPK) and substrate phosphorylation modulate the metabolic capacity of mitochondria in skeletal muscle. However, the key effector(s) of AMPK and the regulatory mechanisms remain unclear. Here, we showed that AMPK phosphorylation of the folliculin interacting protein 1 (FNIP1) serine-220 (S220) controls mitochondrial function and muscle fuel utilization during exercise. Loss of FNIP1 in skeletal muscle resulted in increased mitochondrial content and augmented metabolic capacity, leading to enhanced exercise endurance in mice. Using skeletal muscle-specific nonphosphorylatable FNIP1 (S220A) and phosphomimic (S220D) transgenic mouse models as well as biochemical analysis in primary skeletal muscle cells, we demonstrated that exercise-induced FNIP1 (S220) phosphorylation by AMPK in muscle regulates mitochondrial electron transfer chain complex assembly, fuel utilization, and exercise performance without affecting mechanistic target of rapamycin complex 1-transcription factor EB signaling. Therefore, FNIP1 is a multifunctional AMPK effector for mitochondrial adaptation to exercise, implicating a mechanism for exercise tolerance in health and disease.

Ginsenoside Rh2 stimulates the production of mitochondrial reactive oxygen species and induces apoptosis of cervical cancer cells by inhibiting mitochondrial electron transfer chain complex.

Ginsenoside Rh2 (G-Rh2) is a monomeric compound that extracted from ginseng and possesses anti-cancer activities both in vitro and in vivo. Previously, we reported that G-Rh2 induces apoptosis in HeLa cervical cancer cells and that the process was related to reactive oxygen species (ROS) accumulation and mitochondrial dysfunction. However, the upstream mechanisms of G-Rh2, along with its cellular targets, remain to be elucidated. In the present study, the Cell Counting Kit-8 assay, flow cytometry and Hoechst staining revealed that G-Rh2 significantly inhibited cell viability and induced apoptosis of cervical cancer cells. However, G-Rh2 was demonstrated to be non-toxic to End1/e6e7 cells. JC-1, rhodamine 123 staining, oxidative phosphorylation and glycolysis capacity assays demonstrated that G-Rh2 exposure caused an immediate decrease in mitochondrial transmembrane potential due to its inhibition of mitochondrial oxidative phosphorylation, as well as glycolysis, both of which reduced cellular ATP production. Western blotting and electron transport chain (ETC) activity assays revealed that G-Rh2 significantly inhibited the activity of ETC complexes I, III and V. Overexpression of ETC complex III partially significantly restored mitochondrial ROS and inhibited the apoptosis of cervical cancer cells induced by G-Rh2. The predicted results of binding energy in molecular docking, confirmed that G-Rh2 was highly likely to induce mitochondrial ROS production and promote cell apoptosis by targeting the ETC complex, especially for ETC complex III. Taken together, the present results revealed the potential anti-cervical cancer activity of G-Rh2 and provide direct evidence for the contribution of impaired ETC complex activity to cervical cancer cell death.

Protective effects of lycopene on mitochondrial oxidative injury and dysfunction in the liver of aflatoxin B1-exposed broilers

This study was conducted to investigate the effects of lycopene (LYC) on mitochondrial oxidative injury and dysfunction in the liver of aflatoxin B1 (AFB1)-exposed broilers. A total of 192 healthy 1-day-old male broilers were randomly divided into 3 groups with 8 replicates of 8 birds each. Birds in the 3 groups were fed basal diet (control), basal diet with 100 µg/kg AFB1, and basal diet with 100 µg/kg AFB1 and 200 mg/kg LYC, respectively. The experiment lasted 42 d. The results showed that AFB1 decreased average daily body weight gain (ADG), average daily feed intake, and gain to feed ratio (G :F) compared to the control group, the LYC supplementation increased ADG and G/F compared to AFB1 group (P < 0.05). Broilers in the AFB1 group had lower mitochondrial glutathione (mGSH) concentration and glutathione peroxidase (GSH-Px), manganese superoxide dismutase (MnSOD), and thioredoxin reductase activities, and higher hydrogen peroxide (H2O2) and reactive oxygen species (ROS) concentrations than the control group (P < 0.05). The LYC increased mGSH concentration and GSH-Px and MnSOD activities, and decreased H2O2 and ROS concentrations compared to AFB1 group (P < 0.05). Broilers fed the AFB1 diet showed increased mitochondrial swelling and decreased adenosine triphosphate concentration than the control group, and LYC had opposite effects (P < 0.05). The AFB1 decreased the activities of mitochondrial electron transfer chain (ETC) complexes I, II, III, and V, downregulated the mRNA expression levels of hepatic MnSOD, thioredoxin 2, thioredoxin reductase, peroxiredoxin-3, peroxisome proliferator-activated receptor γ coactivator 1α, nuclear respiratory factor 1, and mitochondrial transcription factor A compared with the control group (P < 0.05), and LYC increased activities of mitochondrial ETC complexes III and V, and upregulated mRNA expression levels of these genes in comparison to AFB1 group (P < 0.05). In conclusion, the LYC protected broilers from AFB1-induced liver mitochondrial oxidative injury and dysfunction by stimulating mitochondrial antioxidant capacity and maintaining mitochondrial biogenesis.

The Energy Status of Astrocytes Is the Achilles' Heel of eIF2B-Leukodystrophy.

Translation initiation factor 2B (eIF2B) is a master regulator of global protein synthesis in all cell types. The mild genetic Eif2b5(R132H) mutation causes a slight reduction in eIF2B enzymatic activity which leads to abnormal composition of mitochondrial electron transfer chain complexes and impaired oxidative phosphorylation. Previous work using primary fibroblasts isolated from Eif2b5(R132H/R132H) mice revealed that owing to increased mitochondrial biogenesis they exhibit normal cellular ATP level. In contrast to fibroblasts, here we show that primary astrocytes isolated from Eif2b5(R132H/R132H) mice are unable to compensate for their metabolic impairment and exhibit chronic state of low ATP level regardless of extensive adaptation efforts. Mutant astrocytes are hypersensitive to oxidative stress and to further energy stress. Moreover, they show migration deficit upon exposure to glucose starvation. The mutation in Eif2b5 prompts reactive oxygen species (ROS)-mediated inferior ability to stimulate the AMP-activated protein kinase (AMPK) axis, due to a requirement to increase the mammalian target of rapamycin complex-1 (mTORC1) signalling in order to enable oxidative glycolysis and generation of specific subclass of ROS-regulating proteins, similar to cancer cells. The data disclose the robust impact of eIF2B on metabolic and redox homeostasis programs in astrocytes and point at their hyper-sensitivity to mutated eIF2B. Thereby, it illuminates the central involvement of astrocytes in Vanishing White Matter Disease (VWMD), a genetic neurodegenerative leukodystrophy caused by homozygous hypomorphic mutations in genes encoding any of the 5 subunits of eIF2B.

Disrupting Mitochondrial Electron Transfer Chain Complex I Decreases Immune Checkpoints in Murine and Human Acute Myeloid Leukemic Cells.

Simple SummaryDespite all of the advancements made in recent years in the treatment of acute myeloid leukemia (AML), long-term survival is achieved by only 30–40% of AML patients. Thus, new therapeutic strategies are strongly needed. This work confirms the increase in oxidative phosphorylation upon cytarabine resistance in AML murine cells, reinforcing the interest of targeting it. In addition, it identifies a new role of the first complex of the electron transport chain (ETCI) in the regulation of the immune checkpoints PD-L1 and CD39 in murine and human leukemic cells. Thus, this work opens the door to the evaluation of ETCI inhibitors in combination with immunotherapy.Oxidative metabolism is crucial for leukemic stem cell (LSC) function and drug resistance in acute myeloid leukemia (AML). Mitochondrial metabolism also affects the immune system and therefore the anti-tumor response. The modulation of oxidative phosphorylation (OxPHOS) has emerged as a promising approach to improve the therapy outcome for AML patients. However, the effect of mitochondrial inhibitors on the immune compartment in the context of AML is yet to be explored. Immune checkpoints such as ectonucleotidase CD39 and programmed dead ligand 1 (PD-L1) have been reported to be expressed in AML and linked to chemo-resistance and a poor prognosis. In the present study, we first demonstrated that a novel selective electron transfer chain complex (ETC) I inhibitor, EVT-701, decreased the OxPHOS metabolism of murine and human cytarabine (AraC)-resistant leukemic cell lines. Furthermore, we showed that while AraC induced an immune response regulation by increasing CD39 expression and by reinforcing the interferon-γ/PD-L1 axis, EVT-701 reduced CD39 and PD-L1 expression in vitro in a panel of both murine and human AML cell lines, especially upon AraC treatment. Altogether, this work uncovers a non-canonical function of ETCI in controlling CD39 and PD-L1 immune checkpoints, thereby improving the anti-tumor response in AML.

ZFHX3 knockdown dysregulates mitochondrial adaptations to tachypacing in atrial myocytes through enhanced oxidative stress and calcium overload.

To investigate the role of zinc finger homeobox 3 gene (ZFHX3) in tachypacing-induced mitochondrial dysfunction and explore its molecular mechanisms and potential as a therapeutic target in atrial fibrillation (AF). Through a bioluminescent assay, a patch clamp, confocal fluorescence and fluorescence microscopy, microplate enzyme activity assays and Western blotting, we studied ATP and ADP production, mitochondrial electron transfer chain complex activities, ATP-sensitive potassium channels (IKATP ), mitochondrial oxidative stress, Ca2+ content, and protein expression in control and ZFHX3 knockdown (KD) HL-1 cells subjected to 1 and 5-Hz pacing for 24hours. Compared with 1-Hz pacing, 5-Hz pacing increased ATP and ADP production, IKATP , phosphorylated adenosine monophosphate-activated protein kinase and inositol 1,4,5-triphosphate (IP3 ) receptor (IP3 R) protein expression. Tachypacing induced mitochondrial oxidative stress and Ca2+ overload in both cell types. Furthermore, under 1- and 5-Hz pacing, ZFHX3 KD cells showed higher IKATP , ATP and ADP production, mitochondrial oxidative stress and Ca2+ content than control cells. Under 5-Hz pacing, 2-aminoethoxydiphenyl borate (2-APB; 3μmol/L, an IP3 R inhibitor) and MitoTEMPO (10µmol/L, a mitochondria-targeted antioxidant) reduced ADP and increased ATP production in both cell types; however, only 2-APB significantly reduced mitochondrial Ca2+ overload in control cells. Under 5-Hz pacing, mitochondrial oxidative stress was significantly reduced by both MitoTEMPO and 2-APB and only by 2-APB in control and ZFHX3 KD cells respectively. ZFHX3 KD cells modulate mitochondrial adaptations to tachypacing in HL-1 cardiomyocytes through Ca2+ overload, oxidative stress and metabolic disorder. Targeting IP3 R signalling or oxidative stress could reduce AF.

Multiwalled carbon nanotubes inhibit cell migration and invasion by destroying actin cytoskeleton via mitochondrial dysfunction in ovarian cancer cells.

Objective: This study aimed to investigate the effects of multiwalled carbon nanotubes (MWCNTs) on cytotoxicity and tumor metastasis in ovarian cancer cells, and further explored its mechanism.Results: MWCNTs significantly inhibited cell viability and the clone number, increased the cell number of S phage, promoted cell apoptosis, as well as suppressed cell migration and invasion, and damaged the structure of actin cytoskeleton in a dose-dependent manner in SKOV3. Moreover, MWCNTs treatment obviously damaged the structure of actin cytoskeleton of SKOV3, and inhibited the activities of mitochondrial electron transfer chain complexes I-V.Conclusions: MWCNTs might influence the assembly of actin cytoskeleton by disrupting mitochondrial function, thereby inhibiting migration and invasion of SKOV3.Methods: The characterization of MWCNTs was analyzed by UV visible light absorption spectroscopy and transmission electron microscopy. SKOV3 cells were exposed to different doses of MWCNTs. Then, in vitro cytotoxicity of MWCNTs was evaluated by MTT assay, colony-forming assay, cell cycle, and cell apoptosis assay. Moreover, the effects of MWCNTs on cell migration and invasion as well as actin cytoskeleton were explored in SKOV3 cells. Furthermore, the mitochondrial membrane potential and the activities of mitochondrial electron transfer chain complexes I-V were measured.

Histone deacetylase 6 inhibitor ACY1215 ameliorates mitochondrial dynamic and function injury in hepatocytes by activating AMPK signaling pathway in acute liver failure mice.

Acute liver failure (ALF) is often accompanied by dynamic and functional disorders of mitochondria in hepatocytes. The histone deacetylase 6 inhibitor Rocilinostat (ACY1215) has a hepatoprotective effect. However, its protective effect on mitochondria of hepatocytes and its related mechanisms in ALF remain unknown. The purpose of the present study was to elucidate the protective effect of ACY1215 on mitochondrial of hepatocytes in ALF by regulating AMPK signaling pathway. LPS and D-Gal were used to induce ALF model in C57BL/6 mice. D-Gal and TNF-α were applied in L02 cells as model group. ACY1215 was administered to the mice or culture cells before the model' s establishment as ACY1215 group. The normal group in mice and L02 cells was not given any drug intervention. ACY1215 improves liver histological and functional changes in ALF model mice. Compared with normal group, the expression of p-AMPK and p-ACC proteins was decreased in model group. ACY1215 activated the AMPK signaling pathway with an increase of p-AMPK and p-ACC proteins level in model group. ACY1215 treatment decreased levels of mitochondrial fission proteins DRP1 and FIS1, and enhanced levels of mitochondrial fusion proteins MFN1, MFN2 and OPA1 in models. MtDNA copies in model group was decreased compared with normal group, but ACY1215 elevated the mtDNA copies in models. Mitochondrial respiratory electron transfer chain Complex I-III and citrate synthase (CS) activities in model group were decreased compared with normal group, but ACY1215 treatment enhanced these activities in model group. ACY1215 protects against dynamic disorders and dysfunction of mitochondria in hepatocytes in ALF by activating AMPK signaling pathway.

Disassembly of ETC Complexes Drives Macrophage Inflammatory Responses by Reprogramming Cellular Metabolism and Translation

Metabolic switch from oxidative phosphorylation (OxPhos) to glycolysis is a key feature of inflammatory macrophages, but how the switch occurs and contributes to macrophage function is obscure. Here we show that stimulation of macrophages through Toll-like receptors (TLR) disrupts the assembly of mitochondrial electron transfer chain (ETC)complexes I-V, leading to the metabolic switch by inhibiting OxPhos and inducing glycolysis through HIF-1α. Disassembly of ETC complexes also rewires the macrophage transcriptome to induce translational reprogramming via mTORC1 and ATF4, promoting global translation, cell growth, and production of inflammatory cytokines independent of glycolysis. Inhibition of OxPhos via myeloid-specific knockout of OPA1, which stimulates ETC complex assembly, exacerbates sepsis in mice while inhibition of mTORC1 reverses this effect. These findings reveal that disassembly of ETC complexes underlies macrophage metabolic switch and inflammatory responses and may be a conserved pathway to reprogram cellular anabolism and function.

Limited Oxidative Stress Favors Resistance to Skeletal Muscle Atrophy in Hibernating Brown Bears (Ursus Arctos).

Oxidative stress, which is believed to promote muscle atrophy, has been reported to occur in a few hibernators. However, hibernating bears exhibit efficient energy savings and muscle protein sparing, despite long-term physical inactivity and fasting. We hypothesized that the regulation of the oxidant/antioxidant balance and oxidative stress could favor skeletal muscle maintenance in hibernating brown bears. We showed that increased expressions of cold-inducible proteins CIRBP and RBM3 could favor muscle mass maintenance and alleviate oxidative stress during hibernation. Downregulation of the subunits of the mitochondrial electron transfer chain complexes I, II, and III, and antioxidant enzymes, possibly due to the reduced mitochondrial content, indicated a possible reduction of the production of reactive oxygen species in the hibernating muscle. Concomitantly, the upregulation of cytosolic antioxidant systems, under the control of the transcription factor NRF2, and the maintenance of the GSH/GSSG ratio suggested that bear skeletal muscle is not under a significant oxidative insult during hibernation. Accordingly, lower levels of oxidative damage were recorded in hibernating bear skeletal muscles. These results identify mechanisms by which limited oxidative stress may underlie the resistance to skeletal muscle atrophy in hibernating brown bears. They may constitute therapeutic targets for the treatment of human muscle atrophy.

Ataxia-Telangiectasia Mutated is located in cardiac mitochondria and impacts oxidative phosphorylation

The absence of Ataxia-Telangiectasia mutated protein kinase (ATM) is associated with neurological, metabolic and cardiovascular defects. The protein has been associated with mitochondria and its absence results in mitochondrial dysfunction. Furthermore, it can be activated in the cytosol by mitochondrial oxidative stress and mediates a cellular anti-oxidant response through the pentose phosphate pathway (PPP). However, the precise location and function of ATM within mitochondria and its role in oxidative phosphorylation is still unknown. We show that ATM is found endogenously within cardiac myocyte mitochondria under normoxic conditions and is consistently associated with the inner mitochondrial membrane. Acute ex vivo inhibition of ATM protein kinase significantly decreased mitochondrial electron transfer chain complex I-mediated oxidative phosphorylation rate but did not decrease coupling efficiency or oxygen consumption rate during β-oxidation. Chemical inhibition of ATM in rat cardiomyoblast cells (H9c2) significantly decreased the excited-state autofluorescence lifetime of enzyme-bound reduced NADH and its phosphorylated form, NADPH (NAD(P)H; 2.77 ± 0.26 ns compared to 2.57 ± 0.14 ns in KU60019-treated cells). This suggests an interaction between ATM and the electron transfer chain in the mitochondria, and hence may have an important role in oxidative phosphorylation in terminally differentiated cells such as cardiomyocytes.

γ-Tocotrienol inhibits oxidative phosphorylation and triggers apoptosis by inhibiting mitochondrial complex I subunit NDUFB8 and complex II subunit SDHB

Tocotrienols (T3s) are a subgroup of vitamin E and they have been widely tested to inhibit cell growth in various tumor types. Previous studies have shown that T3s inhibit cancer cell growth by targeting multiple signaling transduction and cellular processes. However, the role of T3s in the regulation of cellular bioenergetic processes remains unclear. In this study, we found that γ-T3 interacts with mitochondrial electron transfer chain NDUFB8 (a subunit of complex I) and SDHB (a subunit of complex II) and inhibits oxidative phosphorylation (OXPHOS), and triggers the production of reactive oxygen species (ROS). In addition, we observed that γ-T3 upregulates the glycolytic capacity in cells, but it did not compensate for cellular ATP generation and decreased the ATP levels in cells. Furthermore, we performed western blots and RT-PCR to measure the mRNA and protein levels of mitochondrial electron transfer chain (ETC) proteins and complex V (ATP synthase), where the results indicated that γ-T3 specifically inhibited the levels of NDUFB8 and SDHB, whereas it had little effect on UQCRC2 (a subunit of complex III), COX4I1 (a subunit of complex IV), and ATP5F1A (a subunit of complex V). The inhibition of NDUFB8 and SDHB by γ-T3 led to the overproduction of ROS and the depletion of ATP, which may be responsible for inducing apoptosis in cancer cells. Our results suggest that mitochondrial respiration may be an effective target for anticancer treatments based on γ-T3.

Increased energetic demand supported by mitochondrial electron transfer chain and astrocyte assistance is essential to maintain the compensatory ability of the dopaminergic neurons in an animal model of early Parkinson's disease

Partial degeneration of dopaminergic neurons in the substantia nigra (SN), induces locomotor disability in animals but with time it is spontaneously compensated for by neurons surviving in the tissue by increasing their functional efficiency. Such compensation probably increases energy requirements and astrocyte support could be essential for this ability.We studied the effect of degeneration of dopaminergic neurons induced by the selective toxin 6-hydroxydopamine and/or death of 30% of astrocytes induced by chronic infusion of the glial toxin fluorocitrate on functioning of the mitochondrial electron transfer chain (ETC) complexes (Cxs) I, II, IV and their higher assembled forms, supercomplexes in the rat SN.Astrocyte death decreased Cx I and IV performance, while significantly increased the amount of Cx II protein SDHA, indicating system adaptation.After death of 50% of dopaminergic neurons in the SN, we observed increased mitochondrial Cxs performing, especially Cx I and IV in the remaining cells. It corresponded with reduction of behavioural deficits. Those results support the hypothesis that the compensatory ability of surviving neurons requires meeting their higher energetic demand by ETC.When astrocytes were defective, the neurons remaining after partial lesion were not able to enhance their functioning anymore and compensate for deficits. It proves in vivo that astrocytic support is important for compensatory potential of neurons in the SN. Neuro-glia cooperation is fundamental for compensation for early deficits in the nigrostriatal system.

Energy crisis precedes global metabolic failure in a novel Caenorhabditis elegans Alzheimer Disease model.

Alzheimer Disease (AD) is a progressive neurological disorder characterized by the deposition of amyloid beta (Aβ), predominantly the Aβ1–42 form, in the brain. Mitochondrial dysfunction and impaired energy metabolism are important components of AD pathogenesis. However, the causal and temporal relationships between them and AD pathology remain unclear. Using a novel C. elegans AD strain with constitutive neuronal Aβ1–42 expression that displays neuromuscular defects and age-dependent behavioural dysfunction reminiscent of AD, we have shown that mitochondrial bioenergetic deficit is an early event in AD pathogenesis, preceding dysfunction of mitochondrial electron transfer chain (ETC) complexes and the onset of global metabolic failure. These results are consistent with an emerging view that AD may be a metabolic neurodegenerative disease, and also confirm that Aβ-driven metabolic and mitochondrial effects can be reproduced in organisms separated by large evolutionary distances.

Synergistic anticancer properties of docosahexaenoic acid and 5-fluorouracil through interference with energy metabolism and cell cycle arrest in human gastric cancer cell line AGS cells.

To explore the synergistic effect of docosahexaenoic acid (DHA)/5-fluorouracil (5-FU) on the human gastric cancer cell line AGS and examine the underlying mechanism. AGS cells were cultured and treated with a series of concentrations of DHA and 5-FU alone or in combination for 24 and 48 h. To investigate the synergistic effect of DHA and 5-FU on AGS cells, the inhibition of cell proliferation was determined by MTT assay and cell morphology. Flow cytometric analysis was also used to assess cell cycle distribution, and the expression of mitochondrial electron transfer chain complexes (METCs) I, II and V in AGS cells was further determined by Western blot analysis. DHA and 5-FU alone or in combination could markedly suppress the proliferation of AGS cells in a significant time and dose-dependent manner. DHA markedly strengthened the antiproliferative effect of 5-FU, decreasing the IC50 by 3.56-2.15-fold in an apparent synergy. The morphological changes of the cells were characterized by shrinkage, cell membrane blebbing and decreased adherence. Cell cycle analysis showed a shift of cells into the G0/G1 phase from the S phase following treatment with DHA or 5-FU (G0/G1 phase: 30.04% ± 1.54% vs 49.05% ± 6.41% and 63.39% ± 6.83%, respectively, P < 0.05; S phase: 56.76% ± 3.14% vs 34.75% ± 2.35% and 25.63% ± 2.21%, respectively, P < 0.05). Combination treatment of DHA and 5-FU resulted in a significantly larger shift toward the G0/G1 phase and subsequent reduction in S phase (G0/G1 phase: 69.06% ± 2.63% vs 49.05% ± 6.41% and 63.39% ± 6.83%, respectively, P < 0.05; S phase: 19.80% ± 4.30% vs 34.75% ± 2.35% and 25.63% ± 2.21%, respectively, P < 0.05). This synergy was also reflected in the significant downregulation of the expression of METCs in AGS cells. Synergistic anticancer properties of DHA and 5-FU may involve interference with energy production of AGS cells via downregulation of METCs and cell cycle arrest.

Proteomics annotate therapeutic properties of a traditonal Tibetan medicine – Tsantan Sumtang targeting and regulating multiple perturbed pathways

Ethnopharmacological relevanceTsantan Sumtang is a traditional Tibetan medicine, which has been traditionally used as medicine for the treatment of cardiopyretic disease which is similar to angina. However, the precise and comprehensive mechanism of it pretreatment remain elusive, so in this study, we used proteomics to systematically analyse the therapeutic mechanism of it. Materal and methodsRats were divided into three groups (n=6): Tsantan Sumtang group (2g/kg), the model group, the control group (distilled water, 10ml/kg). Drugs were treated once a day for 20 days. After the last administration of drug, left anterior descending coronary artery ligation in vivo was performed. 5 days latter, the hearts were harvested and we applied HPLC- MS/MS using an isobaric TMTs proteomics technology to analyse the differentially expressed proteins among groups. ResultsWe comfirmed from the data that 752 proteins were differentially expressed in model group when compared with the control group, 314 proteins showed the recovery of the values by Tsantan Sumtang treatment. The differential proteins were analysed by gene ontology, cellular pathways and clustering analyses, most of them were metabolic enzymes. These included glycolytic enzymes, enzymes implicated in fatty acids oxidation and the tricarboxylic acid cycle, various subunits of different mitochondrial electron transfer chain complexes, as well as enzymes involved in antioxidation system. ConclusionTsantan Sumtang can target and regulate multiple metabolic perturbed pathways, especially it can partially inhibite fatty acid β-oxidation, stimulate glucose metabolism, oxidative phosphorylation and ATP utilization to protect the injured heart. This helped us to understand the molecular therapeutic mechanisms of Tsantan Sumtang on mycardial ischemia.

Xanthohumol induces generation of reactive oxygen species and triggers apoptosis through inhibition of mitochondrial electron transfer chain complex I

Xanthohumol is a prenylflavonoid extracted from hops (Humulus lupulus). It possesses anti-cancer and anti-inflammatory activities in vitro and in vivo, and offers therapeutic benefits for treatment of metabolic syndromes. However, the precise mechanisms underlying its pharmacological effects remain to be elucidated, together with its cellular target. Here, we provide evidence that xanthohumol directly interacts with the mitochondrial electron transfer chain complex I (NADH dehydrogenase), inhibits the oxidative phosphorylation, triggers the production of reactive oxygen species, and induces apoptosis. In addition, we show that as a result of the inhibition of the mitochondrial oxidative phosphorylation, xanthohumol exposure causes a rapid decrease of mitochondrial transmembrane potential. Furthermore, we showed that xanthohumol up-regulates the glycolytic capacity in cells, and thus compensates cellular ATP generation. Dissection of the multiple steps of aerobic respiration by extracellular flux assays revealed that xanthohumol specifically inhibits the activity of mitochondrial complex I, but had little effect on that of complex II, III and IV. Inhibition of complex I by xanthohumol caused the overproduction of reactive oxygen species, which are responsible for the induction of apoptosis in cancer cells. We also found that isoxanthohumol, the structural isomer of xanthohumol, is inactive to cells, suggesting that the reactive 2-hydroxyl group of xanthohumol is crucial for its targeting to the mitochondrial complex I. Together, the remodeling of cell metabolism revealed here has therapeutic potential for the use of xanthohumol.

Mitochondrial electron transfer chain complexes inhibition by different organochalcogens

Mitochondrial dysfunction plays a pivotal role in the cell toxicology and death decision. The aim of the present study was to investigate the effect of three organocompounds (ebselen [Ebs], diphenyl diselenide [(PhSe)2] and diphenyl ditelluride [(PhTe)2]) on mitochondrial complexes (I, II, I–III, II–III and IV) activity from rat liver and kidney to determine their potential role as molecular targets of organochalcogens. All studied organochalcogens caused a statistically significant inhibition of the mitochondrial complex I activity. Ebs and (PhTe)2 caused a statistically significant inhibition of the mitochondrial complex II activity in both hepatic and renal membranes. Hepatic mitochondrial complex II activity was practically unchanged by (PhSe)2, whereas it significantly inhibited renal complex II activity. Mitochondrial complex IV activity was practically unchanged by the organochalcogens. Furthermore, organochalcogens inhibited the mitochondrial respiration supported by complex I or complex II substrates. The inhibitory effect of Ebs, (PhSe)2 and (PhTe)2 on mitochondrial complex I was prevented by NADH, but it was not prevented by catalase (CAT) and/or superoxide dismutase (SOD). Additionally, the organochalcogens-induced inhibition of complex I and II was completely reversed by reduced glutathione (GSH). In conclusion, Ebs, (PhSe)2 and (PhTe)2 were more effective inhibitors of renal and hepatic mitochondrial complex I than complex II, whereas complexes III and IV were little modified by these compounds. Taking into account the presented results, we suggest that organochalcogen-induced mitochondrial complexes I and II inhibition can be mediated by their thiol oxidation activity, i.e., Ebs, (PhSe)2 and (PhTe)2 can oxidize critical thiol groups from mitochondrial complexes I and II. So, mitochondrial dysfunction can be considered an important factor in the toxicity of Ebs, (PhSe)2 and (PhTe)2.

Mitochondrial mutation impairs cytoplasmic male sterility rice in response to H2O2 stress

Cytoplasmic male sterility (CMS) is a phenomenon widely observed in various plant species characterized with disrupted anther development caused by mitochondrial mutation. CMS is becoming a model system for the investigations of nucleus–cytoplasmic interaction. To reveal the possible effects of CMS genes on plant growth in adverse environment, plant development and biochemical characters of mitochondria from Honglian (HL)-CMS line Yuetai A and maintainer Yuetai B treated with H2O2 were analyzed. Results showed that 40–60mM H2O2 significantly inhibits rice seedling development and growth. When treated with H2O2, ATP content and mitochondrial membrane potential in Yuetai A decreased significantly faster than those of Yuetai B. These biochemical changes were accompanied by the severe nuclear DNA fragmentation and the release of mitochondrial cytochrome c in the leaf cells of Yuetai A. In addition, the antioxidative enzyme activities and mitochondrial electron transfer chain complexes were significantly down-regulated. Disturbance of the biochemical indexes indicate that HL-CMS line is more susceptible to H2O2 stress than the maintainer line, the deleterious effects caused by the CMS-related ORFH79 peptide compromises the adaptability of HL-CMS line to the adverse environment.