Depletes Adenosine Triphosphate Research Articles

Monomethyl Phthalate Causes Early Embryo Development Delay, Apoptosis, and Energy Metabolism Disruptions Through Inducing Redox Imbalance.

Phthalates are a class of environmental endocrine disrupting chemicals which can cause reproductive system damages. However, data about reproductive toxicity spectrum of phthalate metabolites among Chinese women undergoing in vitro fertilization (IVF) treatments are scarce yet. Previous studies regarding underlying embryo toxicities focused on oxidative stress and apoptosis, while energy metabolism abnormality might be another key cause for embryo developmental disruptions. Here, we found that among the measured eight phthalate metabolites, monomethyl phthalate (MMP) had the second highest urinary concentration in women receiving IVF. Compare to the lowest exposure level group, MMP in tertile 3 was associated with fewer counts of oocyte retrieved and good-quality embryos, and MMP in tertile 2 was correlated with reduced good-quality embryo rate. The direct embryo toxicities of MMP were studied using mouse 2-cell embryos. Consistent to results found in human populations, exposure to MMP induced mouse early embryo developmental delay. Furthermore, MMP exposure led to excessive reactive oxygen species production in early embryos, and antioxidant can partially rescue the early embryo development slow down. Embryo apoptosis could also be caused by oxidative stress. To be noted, elevated apoptosis level was not found in live "slow" embryos but dead embryos, which suggested that apoptosis was not related to early embryo developmental delay. Additionally, MMP exposure depleted adenosine triphosphate (ATP) synthesis of early embryos, which could be reversed by antioxidant. In conclusion, MMP, as the newly found embryonic toxicant in Chinese women, resulted in early embryo development delay, apoptosis, and energy metabolism disruptions via inducing redox imbalance.

Pancreatic INS-1 β-Cell Response to Thapsigargin and Rotenone: A Comparative Proteomics Analysis Uncovers Key Pathways of β-Cell Dysfunction.

Insulin-secreting β-cells in the pancreatic islets are exposed to various endogenous and exogenous stressing conditions, which may lead to β-cell dysfunction or apoptosis and ultimately to diabetes mellitus. However, the detailed molecular mechanisms underlying β-cell's inability to survive under severe stresses remain to be explored. This study used two common chemical stressors, thapsigargin and rotenone, to induce endoplasmic reticulum (ER) and mitochondria stress in a rat insuloma INS-1 832/13 β-cell line, mimicking the conditions experienced by dysfunctional β-cells. Proteomic changes of cells upon treatment with stressors at IC50 were profiled with TMT-based quantitative proteomics and further verified using label-free quantitive proteomics. The differentially expressed proteins under stress conditions were selected for in-depth bioinformatic analysis. Thapsigargin treatment specifically perturbed unfolded protein response (UPR) related pathways; in addition, 58 proteins not previously linked to the UPR related pathways were identified with consistent upregulation under stress induced by thapsigargin. Conversely, rotenone treatment resulted in significant proteome changes in key mitochondria regulatory pathways such as fatty acid β-oxidation, cellular respiration, citric acid cycle, and respiratory electron transport. Our data also demonstrated that both stressors increased reactive oxygen species production and depleted adenosine triphosphate synthesis, resulting in significant dysregulation of oxidative phosphorylation signaling pathways. These novel dysregulated proteins may suggest an alternative mechanism of action in β-cell dysfunction and provide potential targets for probing ER- and mitochondria stress-induced β-cell death.

Estrogen-related receptor is critical for testicular mitochondrial homeostasis and sperm motility: a Drosophila-based study

To study the role of estrogen-related receptors (ERRs) in testicular function, with particular emphasis on mitochondrial homeostasis, testicular steroidogenesis, and sperm motility using Drosophila as a model. Experimental study. Academic research laboratory. Wild-type and transgenic strains of Drosophila melanogaster. Using a ribonucleic acid interference-based approach, ERR was knocked down specifically in the testes to generate Drosophila males with reduced ERR levels in their testes. Genetically matched sibling males without the knockdown formed the controls. Analysis of the testicular mitochondrial structure and function in relation to energy production, steroidogenesis, and sperm motility in Drosophila. Depletion of ERR affects mitochondrial homeostasis (biogenesis, fission, fusion, mitophagy, and transport) and oxidative respiration in the testes. Consequently, ERR knockdown testes have significantly reduced mitochondrial size, mass, and depleted adenosine triphosphate levels resulting in testicular oxidative stress. Further, Halloween genes, associated with steroidogenesis in Drosophila, are misregulated in ERR knockdown testes, and knockdown of some of the steroidogenic genes in a testis-specific manner results in significantly reduced fertility. In addition, sperm from ERR knockdown testes have significantly reduced levels of glucose transporter, Na+K+ ATPase, Dynein heavy chain, and adenosine triphosphate-5α synthase essential for sperm function. Corroborating this, sperm from ERR knockdown males are significantly less motile compared with control. The ERR is crucial for meeting the cellular energy requirements of the testes and the generation of normal motile sperm and hormone synthesis/secretion in the testes. To our knowledge, this is the first report implicating ERR in these ultimate functions of the testes. These findings can potentially contribute to the etiologic understanding of asthenozoospermia or infertility at large in men.

Mitigation of cholestasis-associated hepatic and renal injury by edaravone treatment: Evaluation of its effects on oxidative stress and mitochondrial function

Background and aimThe liver is the primary organ affected by cholestasis, and complications such as renal injury, renal failure, and the need for renal transplantation are associated with cholestatic liver disease. There is substantial evidence indicating that reactive oxygen species (ROS) and mitochondrial impairment are fundamental mechanisms underlying cholestasis-induced hepatic and renal injury. Edaravone (EDV) is a potent radical scavenger and antioxidant that may prevent oxidative stress and improve impaired mitochondrial function in various diseases. This study was performed to evaluate the effects and mechanisms of action of EDV on hepatic and renal injury in an animal model of cholestasis. MethodsRats subjected to bile duct ligation (BDL) were treated with EDV 1 or 10 mg/kg/day intraperitoneally for 14 consecutive days. Biomarkers of oxidative stress and mitochondrial impairment in the liver and kidney were assessed in EDV-treated and untreated rats with cholestasis. ResultsSignificant increases in tissue ROS level, lipid peroxidation, protein carbonylation, and oxidized glutathione level were detected in rats subjected to BDL. Additionally, significant decreases in tissue glutathione level and antioxidant capacity were observed in the hepatic and renal tissues of rats with cholestasis. Markers of mitochondrial impairment, including mitochondrial depolarization, lipid peroxidation, mitochondrial permeabilization, depleted adenosine triphosphate content, and decreased dehydrogenase activity, were also detected in rats subjected to BDL. Furthermore, portal inflammation, necrosis, and tissue fibrosis were detected in the liver and significant tubular atrophy and interstitial inflammation, as well as fibrotic lesions, were detected in the kidneys of rats with cholestasis. EDV treatment significantly mitigated cholestasis-associated hepatic and renal injury. ConclusionsThe antioxidative properties of EDV and its positive effects on the indices of mitochondrial function may be critical factors contributing to protection against cholestasis-associated hepatic and renal injury.

Delta-9-tetrahydrocannabinol disrupts mitochondrial function and attenuates syncytialization in human placental BeWo cells.

The psychoactive component in cannabis, delta‐9‐tetrahydrocannabinol, can restrict fetal growth and development. Delta‐9‐tetrahydrocannabinol has been shown to negatively impact cellular proliferation and target organelles like the mitochondria resulting in reduced cellular respiration. In the placenta, mitochondrial dysfunction leading to oxidative stress prevents proper placental development and function. A key element of placental development is the proliferation and fusion of cytotrophoblasts to form the syncytium that comprises the materno‐fetal interface. The impact of delta‐9‐tetrahydrocannabinol on this process is not well understood. To elucidate the nature of the mitochondrial dysfunction and its consequences on trophoblast fusion, we treated undifferentiated and differentiated BeWo human trophoblast cells, with 20 µM delta‐9‐tetrahydrocannabinol for 48 hr. At this concentration, delta‐9‐tetrahydrocannabinol on BeWo cells reduced the expression of markers involved in syncytialization and mitochondrial dynamics, but had no effect on cell viability. Delta‐9‐tetrahydrocannabinol significantly attenuated the process of syncytialization and induced oxidative stress responses in BeWo cells. Importantly, delta‐9‐tetrahydrocannabinol also caused a reduction in the secretion of human chorionic gonadotropin and the production of human placental lactogen and insulin growth factor 2, three hormones known to be important in facilitating fetal growth. Furthermore, we also demonstrate that delta‐9‐tetrahydrocannabinol attenuated mitochondrial respiration, depleted adenosine triphosphate, and reduced mitochondrial membrane potential. These changes were also associated with an increase in cellular reactive oxygen species, and the expression of stress responsive chaperones, HSP60 and HSP70. These findings have important implications for understanding the role of delta‐9‐tetrahydrocannabinol‐induced mitochondrial injury and the role this might play in compromising human pregnancies.

Mitochondrial Dysfunction as Substrate for Arrhythmogenic Cardiomyopathy: A Search for New Disease Mechanisms.

Arrhythmogenic cardiomyopathy (ACM) is a familial heart disease, associated with ventricular arrhythmias, fibrofatty replacement of the myocardial mass and an increased risk of sudden cardiac death (SCD). Malignant ventricular arrhythmias and SCD largely occur in the pre-clinical phase of the disease, before overt structural changes occur. To prevent or interfere with ACM disease progression, more insight in mechanisms related to electrical instability are needed. Currently, numerous studies are focused on the link between cardiac arrhythmias and metabolic disease. In line with that, a potential role of mitochondrial dysfunction in ACM pathology is unclear and mitochondrial biology in the ACM heart remains understudied. In this review, we explore mitochondrial dysfunction in relation to arrhythmogenesis, and postulate a link to typical hallmarks of ACM. Mitochondrial dysfunction depletes adenosine triphosphate (ATP) production and increases levels of reactive oxygen species in the heart. Both metabolic changes affect cardiac ion channel gating, electrical conduction, intracellular calcium handling, and fibrosis formation; all well-known aspects of ACM pathophysiology. ATP-mediated structural remodeling, apoptosis, and mitochondria-related alterations have already been shown in models of PKP2 dysfunction. Yet, the limited amount of experimental evidence in ACM models makes it difficult to determine whether mitochondrial dysfunction indeed precedes and/or accompanies ACM pathogenesis. Nevertheless, current experimental ACM models can be very useful in unraveling ACM-related mitochondrial biology and in testing potential therapeutic interventions.

Vitamin C induces apoptosis in AGS cells via production of ROS of mitochondria.

It has been demonstrated that vitamin C exhibits anti-cancer activity in various tumor cell lines; however, its specific mechanism of action remains unknown. Although the diagnosis and therapy of cancer patients have markedly improved in recent years, safer and more cost-effective treatments are still required. Therefore, the present study examined the effect of vitamin C on the induction of cell death in gastric cancer and its underlying mechanism of action. It was observed that the cytotoxicity of vitamin C on the human gastric cancer cell line AGS is dependent on the apoptotic pathway, including caspase cascades, but not on the necroptotic pathway. It was demonstrated that the vitamin C-induced calcium influx and ROS generation have critical roles in the induction of apoptosis. Furthermore, vitamin C treatment depleted adenosine triphosphate (ATP) production in AGS cells, and the autophagy pathway may be involved in this process. Taken together, the current study suggests that a high dose of vitamin C may induce gastric cancer cell apoptosis through the dysfunction of mitochondria, including calcium influx, reactive oxygen species generation and ATP depletion.

A novel manganese complex selectively induces malignant glioma cell death by targeting mitochondria.

Despite advances in treatment, malignant glioma commonly exhibits recurrence, subsequently leading to a poor prognosis. As manganese (Mn) compounds can be transported by the transferrin-transferrin receptor system, the present study synthesized and examined the potential use of Adpa-Mn as a novel antitumor agent. Adpa-Mn time and dose-dependently inhibited U251 and C6 cell proliferation; however, it had little effect on normal astrocytes. Apoptosis was significantly elevated following treatment with Adpa-Mn, as detected by chromatin condensation, Annexin V/propidium iodide staining, cytochrome c release from mitochondria to the cytoplasm, and the activation of caspases-9, -7 and -3 and poly (ADP-ribose) polymerase. In addition, Adpa-Mn enhanced fluorescence intensity of monodansylcadaverine and elevated the expression levels of the autophagy-related protein microtubule-associated protein 1 light chain 3. Pretreatment with the autophagy inhibitors 3-methyladenine and chloroquine enhanced Adpa-Mn-induced cell inhibition, thus indicating that autophagy has an essential role in this process. Furthermore, evidence of mitochondrial dysfunction was detected in the Adpa-Mn-treated group, including disrupted membrane potential, elevated levels of reactive oxygen species (ROS) and depleted adenosine triphosphate. Conversely, treatment with the mitochondrial permeability transition inhibitor cyclosporin A reversed Adpa-Mn-induced ROS production, mitochondrial damage and cell apoptosis, thus suggesting that Adpa-Mn may target the mitochondria. Taken together, these data suggested that Adpa-Mn may be considered for use as a novel anti-glioma therapeutic option.

Predicting defibrillation success in sudden cardiac arrest patients

Although the importance of quality cardiopulmonary resuscitation (CPR) and its link to survival is still emphasized, there has been recent debate about the balance between CPR and defibrillation, particularly for long response times. Defibrillation shocks for ventricular fibrillation (VF) of recently perfused hearts have high success for the return of spontaneous circulation (ROSC), but hearts with depleted adenosine triphosphate (ATP) stores have low recovery rates. Since quality CPR has been shown to both slow the degradation process and restore cardiac viability, a measurement of patient condition to optimize the timing of defibrillation shocks may improve outcomes compared to time-based protocols. Researchers have proposed numerous predictive features of VF and shockable ventricular tachycardia (VT) which can be computed from the electrocardiogram (ECG) signal to distinguish between the rhythms which convert to spontaneous circulation and those which do not. We looked at the shock-success prediction performance of thirteen of these features on a single evaluation database including the recordings from 116 out-of-hospital cardiac arrest patients which were collected for a separate study using defibrillators in ambulances and medical centers in 4 European regions and the US between March 2002 and September 2004. A total of 469 shocks preceded by VF or shockable VT rhythm episodes were identified in the recordings. Based on the experts' annotation for the post-shock rhythm, the shocks were categorized to result in either pulsatile (ROSC) or non-pulsatile (no-ROSC) rhythm. The features were calculated on a 4-second ECG segment prior to the shock delivery. These features examined were: Mean Amplitude, Average Peak-Peak Amplitude, Amplitude Range, Amplitude Spectrum Analysis (AMSA), Peak Frequency, Centroid Frequency, Spectral Flatness Measure (SFM), Energy, Max Power, Centroid Power, Power Spectrum Analysis (PSA), Mean Slope, and Median Slope. Statistical hypothesis tests (two-tailed t-test and Wilcoxon with 5% significance level) were applied to determine if the means and medians of these features were significantly different between the ROSC and no-ROSC groups. The ROC curve was computed for each feature, and Area Under the Curve (AUC) was calculated. Specificity (Sp) with Sensitivity (Se) held at 90% as well as Se with Sp held at 90% was also computed. All features showed statistically different mean and median values between the ROSC and no-ROSC groups with all p-values less than 0.0001. The AUC was >76% for all features. For Sp = 90%, the Se range was 33–45%; for Se = 90%, the Sp range was 49–63%. The features showed good shock-success prediction performance. We believe that a defibrillator employing a clinical decision tool based on these features has the potential to improve overall survival from cardiac arrest.

Glucose deprivation increases hydrogen peroxide level in immunostimulated rat primary astrocytes.

Activated astrocytes produce a large amount of bioactive molecules, including reactive oxygen and nitrogen species. Astrocytes are in general resistant to those reactive species. However, we previously reported that immunostimulated astrocytes became highly vulnerable to metabolic insults, such as glucose deprivation. In this study, we investigated whether H(2)O(2) production was associated with the increased vulnerability. Glucose deprivation for up to 8 hr did not change the intracellular level of H(2)O(2) in astrocytes. Treatment with lipopolysaccharide plus interferon-gamma for 48 hr evoked astroglial H(2)O(2) production; however, no apparent death or injury was observed in immunostimulated astrocytes. Glucose deprivation after 48 hr of immunostimulation markedly increased H(2)O(2) level, depleted adenosine triphosphate (ATP), and enhanced lactate dehydrogenase (LDH) release. The ATP depletion and LDH release were in part prevented by catalase, mannitol, and N-acetyl-L-cysteine. The enhanced level of H(2)O(2) in glucose-deprived immunostimulated astrocytes appeared to be secondary to the depletion of reduced glutathione. 4-(2-Aminoethyl)bebzenesulfonyl fluoride (AEBSF), an inhibitor of NADPH oxidase, reduced H(2)O(2) level and LDH release in glucose-deprived immunostimulated astrocytes. H(2)O(2), either endogenously produced or exogenously added, depolarized mitochondrial transmembrane potential in glucose-deprived astrocytes, leading to their ATP depletion and death. The present results strongly indicate that glucose deprivation causes deterioration of immunostimulated astrocytes by increasing the intracellular concentration of H(2)O(2).

Oxidant injury in neonatal erythrocytes during the perinatal period.

It has been known for many decades that oxidative stress leads to oxidation of hemoglobin and damage to the erythrocyte membrane. More recently, the factors involved in denaturating of membrane proteins and lipid peroxidation have been investigated in detail, as well as the mechanism of reactive oxygen species formation in red cells. Oxidative stress depletes adenosine triphosphate (ATP) and adenine nucleotides, whereas adenosine monophosphate (AMP) deaminase seems to depress energy metabolism by blocking the salvage pathway of purine nucleotides. Depletion of ATP and activation of AMP deaminase are related to calcium ion concentrations. Denaturating of membrane proteins generally precedes lipid peroxidation and consequent phagocytosis due to caspase activation. Extensive investigations demonstrated the key role of oxidative stress and iron release in a reactive form causing membrane protein damage via the Fenton reaction and hydroxyl radical production. In the absence of efficient protection by antioxidant factors and other molecules such as flavonoids, oxidative stress is responsible for the release of iron in reactive form, predisposing red cells to hemolysis through the formation of senescence antigen. Other well-known sources of oxidative stress in red cells are free radical production outside the red cell by activated phagocytes, endothelial metabolism, hyperoxia, ischemia-reperfusion and the arachidonic acid cascade. The recent insight into the mechanism of oxidative injury of red cells and evidence of relationships between erythrocyte oxidative stress and hypoxia suggest that increased hemolysis is induced by severe hypoxia and acidosis in the fetus as well as the newborn.

Hyperthermia depletes adenosine triphosphate and decreases glutamate uptake in rat hippocampal slices.

The central nervous system is especially vulnerable to hyperthermia-induced dysfunction, yet the mechanism for this susceptibility is poorly understood. High levels of adenosine triphosphate are necessary to maintain normal re-uptake of glutamate and aspartate, the major excitatory amino acids, by excitatory amino acid co-transporters. We hypothesized that excitotoxic neurotransmitters accumulate extracellularly when hyperthermia depletes adenosine triphosphate, leading to decreased uptake or release of excitatory amino acids by these co-transporters. Incubation of hippocampal slices at 42 degrees C, a temperature that results in coma in vivo, reduced adenosine triphosphate to 70% of control values and decreased uptake of the transportable excitatory amino acid analogue, D,L threo-beta-hydroxyaspartate, to 50% of control values. The degree of adenosine triphosphate depletion induced by hyperthermia was highly correlated with decreases in excitatory amino acid uptake. Severe adenosine triphosphate depletion (< or = 20% of control) induced by hyperthermia in combination with metabolic insults was highly correlated with the release of endogenous glutamate and aspartate. Preloading slices with excitatory amino acid analogues potentiated hyperthermia-induced alterations of excitatory amino acid transport, strongly suggesting that the hyperthermia-induced changes were largely due to altered excitatory amino acid co-transporter activity. Immunocytochemical studies suggested glutamate-like immunoreactivity was lost from axonal terminals during hyperthermia in a similar manner to losses induced by metabolic toxins. Hyperthermia due to infectious diseases or heat stroke my induce disorientation and coma. These dysfunctions may be due, in part, to altered excitatory amino acid transport induced by adenosine triphosphate depletion.

Mechanisms of endothelial cell killing by H 2O 2 or products of activated neutrophils

Interactions between rat pulmonary artery endothelial cells and hydrogen peroxide or toxic oxygen products from phorbol ester-activated human neutrophils result in endothelial cell killing defined by 51Cr release. It has been shown that this cytotoxic reaction can be blocked by the presence of catalase, iron chelators, or scavengers of the hydroxyl radical. Evidence shows that products from xanthine oxidase of endothelial cells are necessary for the toxic effects of hydrogen peroxide or phorbol ester-activated neutrophils. Addition of xanthine oxidase inhibitors protects against phorbol ester-mediated injury of endothelial cells. Preloading of endothelial cells with superoxide dismutase attenuates injury caused either by hydrogen peroxide or phorbol ester-activated neutrophils. Conversion of xanthine dehydrogenase to xanthine oxidase in endothelial cells occurs during contact of endothelial cells by activated neutrophils. This conversion is not related to oxygen products of neutrophils. Conversion of xanthine dehydrogenase to xanthine oxidase in endothelial cells is also induced by endothelial cell contact with C5a, N′-formyl-methionyl-leucyl-phenylalanine (fMLP), or tumor necrosis factor alpha (TNFα). Interaction of hydrogen peroxide with endothelial cells rapidly depletes adenosine triphosphate (ATP) and causes the extracellular appearance of xanthine and hypoxanthine. Agents that protect endothelial cells from the toxic effects of hydrogen peroxide do not prevent falls in cellular ATP caused by hydrogen peroxide, indicating that ATP levels do not necessarily correlate with cytotoxic events. A synergy between hydrogen peroxide and proteases in endothelial cell killing has been demonstrated. TNFα causes alterations in endothelial cells, the result of which is increased susceptibility to killing by PMA-activated neutrophils.