Unveiling the link between NADPH oxidase 2 activation and mitochondrial superoxide formation in leukemic cell killing induced by arsenic trioxide.

This study focused on the interplay between NADPH oxidase 2 (NOX 2) activation and mitochondrial superoxide (mitoO) formation induced by clinically relevant concentrations of arsenic trioxide (ATO; AsO) in acute promyelocytic leukemia (APL) cells. Carefully controlled inhibitor studies and small interfering RNA mediated downregulation of p47 (a component of the NOX 2 complex) expression demonstrated that, in an APL cell line, ATO promotes upstream NOX 2 activation critically connected with the formation of mitoO and with the ensuing mitochondrial permeability transition (MPT)-dependent apoptosis. Instead, acute myeloid leukemia (AML) cell lines respond to ATO with low NOX 2 activation, resulting in a state that is non-permissive for mitoO formation.

Clozapine suppresses NADPH oxidase activation, counteracts cytosolic HO, and triggers early onset mitochondrial dysfunction during adipogenesis of human liposarcoma SW872 cells.

Long-term treatment of schizophrenia with clozapine (CLZ), an atypical antipsychotic drug, is associated with an increased incidence of metabolic disorders mediated by poorly understood mechanisms. We herein report that CLZ, while slowing down the morphological changes and lipid accumulation occurring during SW872 cell adipogenesis, also causes an early (day 3) inhibition of the expression/nuclear translocation of CAAT/enhancer-binding protein β and peroxisome proliferator-activated receptor γ. Under the same conditions, CLZ blunts NADPH oxidase-derived reactive oxygen species (ROS) by a dual mechanism involving enzyme inhibition and ROS scavenging.

ERO1α primes the ryanodine receptor to respond to arsenite with concentration dependent Ca release sequentially triggering two different mechanisms of ROS formation.

A 6 h exposure of U937 cells to 2.5 μM arsenite stimulates low Ca release from the inositol 1, 4, 5-triphosphate receptor (IPR), causing a cascade of causally connected events, i.e.

Nrf2-Mediated Pathway Activated by L. (Rosaceae) Fruit Extract: Bioinformatics Analyses and Experimental Validation.

In our previous studies, fruit (PSF) ethanol extract was showed to exert antioxidant, antimicrobial, anti-inflammatory and wound healing activities. In the present study, an integrated bioinformatics analysis combined with experimental validation was carried out to investigate the biological mechanism(s) that are responsible for the reported PSF beneficial effects as an antioxidant during a pro-inflammatory TLR4 insult. Bioinformatics analysis using miRNet 2.

Arsenite enhances ERO1α expression via ryanodine receptor dependent and independent mechanisms.

Arsenite is a potent carcinogen and toxic compound inducing an array of deleterious effects via different mechanisms, which include the Ca-dependent formation of reactive oxygen species. The mechanism whereby the metalloid affects Ca homeostasis involves an initial stimulation of the inositol 1, 4, 5-triphosphate receptor, an event associated with an endoplasmic reticulum (ER) stress leading to increased ERO1α expression, and ERO1α dependent activation of the ryanodine receptor (RyR). Ca release from the RyR is then critically connected with the mitochondrial accumulation of Ca.

Loss-of-rescue of Ryr1-related pathology by the genetic inhibition of the ER stress response mediator CHOP.

RYR1 is the gene encoding the ryanodine receptor 1, a calcium release channel of the endo/sarcoplasmic reticulum. I4898T in RYR1 is one of the most common mutations that give rise to central core disease (CCD), with a variable phenotype ranging from mild to severe myopathy to lethal early-onset core-rod myopathy. Mice with the corresponding I4895T mutation in Ryr1 present mild myopathy when the mutation is heterozygous while I4895T homozygous is perinatal-lethal.

Inhibition of activity/expression, or genetic deletion, of ERO1α blunts arsenite geno- and cyto-toxicity.

Our recent studies suggest that arsenite stimulates the crosstalk between the inositol 1, 4, 5-triphosphate receptor (IPR) and the ryanodine receptor (RyR) via a mechanism dependent on endoplasmic reticulum (ER) oxidoreductin1α (ERO1α) up-regulation. Under these conditions, the fraction of Ca released by the RyR via an ERO1α-dependent mechanism was promptly cleared by the mitochondria and critically mediated O formation, responsible for the triggering of time-dependent events associated with strand scission of genomic DNA and delayed mitochondrial apoptosis. We herein report that, in differentiated C2C12 cells, this sequence of events can be intercepted by genetic deletion of ERO1α as well as by EN460, an inhibitor of ERO1α activity.

Mitochondrial ROS, ER Stress, and Nrf2 Crosstalk in the Regulation of Mitochondrial Apoptosis Induced by Arsenite.

Long-term ingestion of arsenicals, a heterogeneous group of toxic compounds, has been associated with a wide spectrum of human pathologies, which include various malignancies. Although their mechanism of toxicity remains largely unknown, it is generally believed that arsenicals mainly produce their effects via direct binding to protein thiols and ROS formation in different subcellular compartments. The generality of these mechanisms most probably accounts for the different effects mediated by different forms of the metalloid in a variety of cells and tissues.

Crosstalk between ERO1α and ryanodine receptor in arsenite-dependent mitochondrial ROS formation.

Arsenite, a well-established human carcinogen and toxic compound, promotes the formation of mitochondrial superoxide (mitoO) via a Ca-dependent mechanism, in which an initial stimulation of the inositol 1, 4, 5-trisphosphate receptor (IPR) is followed by the activation of the ryanodine receptor (RyR), critical for providing Ca to the mitochondria. We now report that, under the same conditions, arsenite triggers endoplasmic reticulum (ER) stress and a threefold increase in ER oxidoreductin 1α (ERO1 α) levels in proliferating U937 cells. EN460, an inhibitor of ERO1 α, recapitulated all the effects associated with RyR inhibition or downregulation, including prevention of RyR-induced Ca accumulation in mitochondria and the resulting O formation.

Functional organization of the endoplasmic reticulum dictates the susceptibility of target cells to arsenite-induced mitochondrial superoxide formation, mitochondrial dysfunction and apoptosis.

Arsenite induces many critical effects associated with the formation of reactive oxygen species (ROS) through different mechanisms. We focused on Ca-dependent mitochondrial superoxide (mitoO) formation and addressed questions on the effects of low concentrations of arsenite on the mobilization of the cation from the endoplasmic reticulum and the resulting mitochondrial accumulation. Using various differentiated and undifferentiated cell types uniquely expressing the inositol-1, 4, 5-triphosphate receptor (IPR), or both the IPR and the ryanodine receptor (RyR), we determined that expression of this second Ca channel is an absolute requirement for mitoO formation and for the ensuing mitochondrial dysfunction and downstream apoptosis.

Temporal correlation of morphological and biochemical changes with the recruitment of different mechanisms of reactive oxygen species formation during human SW872 cell adipogenic differentiation.

Human SW872 preadipocyte conversion to mature adipocytes is associated with time-dependent changes in differentiation markers' expression and with morphological changes accompanied by the accumulation of lipid droplets (LDs) as well as by increased mitochondriogenesis and mitochondrial membrane potential. Under identical conditions, the formation of reactive oxygen species (ROS) revealed with a general probe was significant at days 3 and 10 of differentiation and bearly detectable at day 6. NADPH oxidase (NOX)-2 activity determined with an immunocytochemical approach followed a very similar pattern.

Arsenite impinges on endoplasmic reticulum-mitochondria crosstalk to elicit mitochondrial ROS formation and downstream toxicity.

Arsenite is an important carcinogen and toxic compound, causing various deleterious effects through multiple mechanisms. In this review, we focused on mitochondrial ROS (mitoROS) and discussed on the mechanisms mediating their formation. The metalloid promotes direct effects in mitochondria, resulting in superoxide formation only under conditions of increased mitochondrial Ca concentration ([Ca]).

SVCT2-Dependent plasma and mitochondrial membrane transport of ascorbic acid in differentiating myoblasts.

The Na-dependent Vitamin C transporter 2 (SVCT2) is expressed in the plasma and mitochondrial membranes of various cell types. This notion was also established in proliferating C2C12 myoblasts (Mb), in which the transporter was characterised by a high and low affinity in the plasma and mitochondrial membranes, respectively. In addition, the mitochondrial expression of SVCT2 appeared particularly elevated and, consistently, a brief pre-exposure to low concentrations of Ascorbic Acid (AA) abolished mitochondrial superoxide formation selectively induced by the cocktail arsenite/ATP.

Mitochondrial reactive oxygen species: the effects of mitochondrial ascorbic acid vs untargeted and mitochondria-targeted antioxidants.

Premise: Mitochondria represent critical sites for reactive oxygen species (ROS) production, which dependent on concentration is responsible for the regulation of both physiological and pathological processes.

Purpose: Antioxidants in mitochondria regulate the redox balance, prevent mitochondrial damage and dysfunction and maintain a physiological ROS-dependent signaling. The aim of the present review is to provide critical elements for addressing this issue in the context of various pharmacological approaches using antioxidants targeted or non-targeted to mitochondria.

Arsenite-Induced Mitochondrial Superoxide Formation: Time and Concentration Requirements for the Effects of the Metalloid on the Endoplasmic Reticulum and Mitochondria.

The present study used human myeloid leukemia U937 cells, a versatile promonocytic cellular system that, based on its endoplasmic reticulum (ER)/mitochondria functional relationships, responds to low micromolar concentrations of arsenite with a single, defined mechanism of superoxide (O ) formation. Under these conditions, we observe an initial Ca mobilization from the ER associated with the mitochondrial accumulation of the cation, which is followed by Ca-dependent mitochondrial O (mitoO ) formation. These events, which were barely detectable after 3 hours, were better appreciated at 6 hours.

The compartmentalised nature of the mechanisms governing superoxide formation and scavenging in cells exposed to arsenite.

In this study, respiration-proficient (RP) and -deficient (RD) cells were exposed to 2.5 or 10 μM arsenite to generate superoxide (O) respectively in the mitochondrial respiratory chain or via NADPH oxidase activation. These treatments, while causing similar, although mitochondrial permeability transition-dependent (RP-cells) or independent (RD-cells), delayed apoptosis, surprisingly generated identical kinetics and levels of dihydrorhodamine oxidation, indicative of O formation.

Prostaglandin E Signals Through E Prostanoid Receptor 2 to Inhibit Mitochondrial Superoxide Formation and the Ensuing Downstream Cytotoxic and Genotoxic Effects Induced by Arsenite.

We investigated the effects of prostaglandin E (PGE), an important inflammatory lipid mediator, on the cytotoxicity-genotoxicity induced by arsenite. With the use of a toxicity paradigm in which the metalloid uniquely induces mitochondrial superoxide (mitoO ) formation, PGE promoted conditions favoring the cytosolic accumulation of Bad and Bax and abolished mitochondrial permeability transition (MPT) and the ensuing lethal response through an E prostanoid receptor 2/adenylyl cyclase/protein kinase A (PKA) dependent signaling. It was, however, interesting to observe that, under the same conditions, PGE also abolished the DNA-damaging effects of arsenite and that this response was associated with an unexpected suppression of mitoO formation.

Calcium signals between the ryanodine receptor- and mitochondria critically regulate the effects of arsenite on mitochondrial superoxide formation and on the ensuing survival vs apoptotic signaling.

A low concentration of arsenite (6 h), selectively stimulating the intraluminal crosstalk between the inositol-1, 4, 5-triphosphate receptor and the ryanodine receptor (RyR), increased the mitochondrial transport of RyR-derived Ca through the mitochondrial Ca uniporter. This event was characterized in intact and permeabilized cells, and was shown to be critical for mitochondrial superoxide (mitoO) formation. Inhibition of mitochondrial Ca accumulation therefore prevented the effects of arsenite, in both the mitochondrial (e.

Melatonin protects hippocampal HT22 cells from the effects of serum deprivation specifically targeting mitochondria.

Neurons contain a high number of mitochondria, these neuronal cells produce elevated levels of oxidative stress and live for a long time without proliferation; therefore, mitochondrial homeostasis is crucial to their health. Investigations have recently focused on mitochondrial dynamics revealing the ability of these organelles to change their distribution and morphology. It is known that mitochondrial fission is necessary for the transmission of mitochondria to daughter cells during mitosis and mitochondrial fragmentation has been used as an indicator of cell death and mitochondrial dysfunction.

The Activity of L. Essential Oil on Inflammation.

The use of herbs with medicinal value and biomedical effects has increased tremendously in the last years. However, inadequate basic knowledge of their mode of action is the main issue related to phytotherapy, although they have shown promising potential. To provide insights into these important issues, we tested here on appropriate models the efficacy of essential oil (Aa-EO) for anti-inflammatory properties.

Low Concentrations of Arsenite Target the Intraluminal Inositol 1, 4, 5-Trisphosphate Receptor/Ryanodine Receptor Crosstalk to Significantly Elevate Intracellular Ca.

Arsenite is an established human carcinogen that induces cytotoxic and genotoxic effects through poorly defined mechanisms involving the formation of reactive oxygen species (ROS) and deregulated Ca homeostasis. We used variants of the U937 cell line to address the central issue of the mechanism whereby arsenite affects Ca homeostasis. We found that 6-hour exposure to the metalloid (2.

Differentiation of Promonocytic U937 Cells to Monocytes Is Associated with Reduced Mitochondrial Transport of Ascorbic Acid.

Growth of promonocytic U937 cells in the presence of DMSO promotes their differentiation to monocytes. After 4 days of culture in differentiating medium, these cells ceased to proliferate, displayed downregulated ryanodine receptor expression, and responded to specific stimuli with enhanced NADPH-oxidase-derived superoxide formation or cytosolic phospholipase A-dependent arachidonic acid release. We found that the 4-day differentiation process is also associated with downregulated SVCT2 mRNA expression, in the absence of apparent changes in SVCT2 protein expression and transport rate of ascorbic acid (AA).

The dual role of mitochondrial superoxide in arsenite toxicity: Signaling at the boundary between apoptotic commitment and cytoprotection.

Arsenite toxicity is in numerous cellular systems dependent on the formation of reactive oxygen and or nitrogen species. This is also true in U937 cells in which the metalloid selectively promotes the formation of mitochondrial superoxide (mitoO) rapidly converted to diffusible HO. We tested the hypothesis that, under the same conditions, mitoO also mediates the triggering of a parallel survival signaling.

Intramitochondrial Ascorbic Acid Enhances the Formation of Mitochondrial Superoxide Induced by Peroxynitrite via a Ca-Independent Mechanism.

Exposure of U937 cells to peroxynitrite promotes mitochondrial superoxide formation via a mechanism dependent on both inhibition of complex III and increased mitochondrial Ca accumulation. Otherwise inactive concentrations of the oxidant produced the same maximal effects in the presence of either complex III inhibitors or agents mobilizing Ca from the ryanodine receptor and enforcing its mitochondrial accumulation. l-Ascorbic acid (AA) produced similar enhancing effects in terms of superoxide formation, DNA strand scission and cytotoxicity.

Arsenite induces DNA damage via mitochondrial ROS and induction of mitochondrial permeability transition.

Arsenite is an established DNA-damaging agent and human carcinogen. We initially selected conditions in which the metalloid causes DNA strand scission in the absence of detectable apoptotic DNA degradation in U937 cells. This response was suppressed by catalase and by treatments (rotenone and ascorbic acid), or manipulations (respiration-deficient phenotype), preventing the mitochondrial formation of O2-.