bims-cytox1 2018-06-10 papers

Issue of 2018–06–10
four papers selected by
Gavin McStay, Staffordshire University

Carcinogenesis. 2018 May 31.

Curcumin Induces a Fatal Energetic Impairment in Tumor Cells in Vitro and in Vivo by Inhibiting ATP-synthase Activity.

Giovanna Bianchi, Silvia Ravera, Chiara Traverso, Adriana Amaro, Francesca Piaggio, Laura Emionite, Tiziana Bachetti, Ulrich Pfeffer, Lizzia Raffaghello.

Curcumin has been reported to inhibit inflammation, tumor growth, angiogenesis and metastasis by decreasing cell growth and by inducing apoptosis mainly through the inhibition of nuclear factor kappa-B (NFκB), a master regulator of inflammation. Recent reports also indicate potential metabolic effects of the polyphenol, therefore we analyzed whether and how it affects the energy metabolism of tumor cells. We show that curcumin (10µM) inhibits the activity of ATP-synthase in isolated mitochondrial membranes leading to a dramatic drop of ATP and a reduction of oxygen consumption in in vitro and in vivo tumor models. The effects of curcumin on ATP-synthase are independent of the inhibition of NFκB since the IκB Kinase inhibitor, SC-514, does not affect ATP-synthase. The activities of the glycolytic enzymes hexokinase, phosphofructokinase, pyruvate kinase and lactate dehydrogenase are only slightly affected in a cell type specific manner. The energy impairment translates into decreased tumor cell viability. Moreover, curcumin induced apoptosis by promoting the generation of reactive oxygen species (ROS) and malondialdehyde (MDA), a marker of lipid oxidation, and autophagy at least in part due to the activation of the AMP-activated protein kinase (AMPK). According to the in vitro anti-tumor effect, curcumin (30mg/kg body weight) significantly delayed in vivo cancer growth likely due to an energy impairment but also through the reduction of tumor angiogenesis. These results establish the ATP-synthase, a central enzyme of the cellular energy metabolism, as a target of the anti-tumoral polyphenol leading to inhibition of cancer cell growth and a general reprogramming of tumor metabolism.

DOI: https://doi.org/10.1093/carcin/bgy076

Toxicology. 2018 May 30. pii: S0300-483X(18)30107-0. [Epub ahead of print]

Neuroprotective effect of zolpidem against glutamate-induced toxicity is mediated via the PI3K/Akt pathway and inhibited by PK11195.

Maja Jazvinšćak Jembrek, Vedrana Radovanović, Josipa Vlainić, Lidija Vuković, Nikolina Hanžić.

Excitotoxicity is a pathological process in which neuronal dysfunction and death are induced by excessive glutamate stimulation, the major fast excitatory neurotransmitter in the mammalian brain. Excitotoxicity-induced neurodegeneration is a contributing factor in ischemia-induced brain damage, traumatic brain injury, and various neurodegenerative diseases. It is triggered by calcium overload due to prolonged over-activation of ionotropic N-methyl-D-aspartate (NMDA) receptors. Enhanced Ca2+ release results in neuronal vulnerability through several intertwined mechanisms, including activation of proteolytic enzymes, increased production of reactive oxygen species (ROS), mitochondrial dysfunction and modulation of intracellular signalling pathways. We investigated the neuroprotective effect of hypnotic zolpidem, a drug that exerts its central effects at the GABAA receptor complex, against glutamate-induced toxicity in P19 neurons. Zolpidem prevented death of P19 neurons exposed to glutamate, and abolished the glutamate-induced increase in ROS production, p53 and Bax expression, and caspase-3/7 activity. Zolpidem effects were mediated by marked over-activation of Akt kinase. The pro-survival effect, as well as the pAkt induction, were prevented in the presence of wortmannin, an inhibitor of phosphatidylinositol-3-kinase (PI3K) that functions upstream of Akt. The beneficial effect of zolpidem on neuronal survival was not prevented by flumazenil, a GABAA receptor antagonist. PK11195, a drug that modulates the mitochondrial translocator protein 18 kDa (TSPO) and F0F1-ATPase, prevented the beneficial effect of zolpidem, indicating that the mechanism of zolpidem action involves preservation of mitochondrial function and integrity. Zolpidem effects were further mediated by prevention of glutamate-induced increase in the expression of the NR2B subunit of NMDA receptor. The obtained results suggest the promising therapeutic potential of zolpidem against excitotoxic insults and highlight the importance of mitochondria and the Akt pathway as valuable targets for therapeutic interventions in glutamate-mediated neuropathological conditions.

Keywords: Akt signalling; NR2B subunit of NMDA receptor; PK11195; excitotoxicity; p53; zolpidem

DOI: https://doi.org/10.1016/j.tox.2018.05.014

Biochim Biophys Acta. 2018 May 31. pii: S0005-2728(18)30135-X. [Epub ahead of print]

Mitochondrial uncoupling, ROS generation and cardioprotection.

Susana Cadenas.

Mitochondrial oxidative phosphorylation is incompletely coupled, since protons translocated to the intermembrane space by specific respiratory complexes of the electron transport chain can return to the mitochondrial matrix independently of the ATP synthase -a process known as proton leak- generating heat instead of ATP. Proton leak across the inner mitochondrial membrane increases the respiration rate and decreases the electrochemical proton gradient (Δp), and is an important mechanism for energy dissipation that accounts for up to 25% of the basal metabolic rate. It is well established that mitochondrial superoxide production is steeply dependent on Δp in isolated mitochondria and, correspondingly, mitochondrial uncoupling has been identified as a cytoprotective strategy under conditions of oxidative stress, including diabetes, drug-resistance in tumor cells, ischemia-reperfusion (IR) injury or aging. Mitochondrial uncoupling proteins (UCPs) are able to lower the efficiency of oxidative phosphorylation and are involved in the control of mitochondrial reactive oxygen species (ROS) production. There is strong evidence that UCP2 and UCP3, the UCP1 homologues expressed in the heart, protect against mitochondrial oxidative damage by reducing the production of ROS. This review first analyzes the relationship between mitochondrial proton leak and ROS generation, and then focuses on the cardioprotective role of chemical uncoupling and uncoupling mediated by UCPs. This includes their protective effects against cardiac IR, a condition known to increase ROS production, and their roles in modulating cardiovascular risk factors such as obesity, diabetes and atherosclerosis.

Keywords: Cardioprotection; Ischemia-reperfusion; Mitochondrial uncoupling; Proton leak; Reactive oxygen species (ROS); Uncoupling proteins (UCPs)

DOI: https://doi.org/10.1016/j.bbabio.2018.05.019

Geroscience. 2018 Jun 02.

Measurement of respiratory function in isolated cardiac mitochondria using Seahorse XFe24 Analyzer: applications for aging research.

Siva S V P Sakamuri, Jared A Sperling, Venkata N Sure, Monica H Dholakia, Nicholas R Peterson, Ibolya Rutkai, Padmini S Mahalingam, Ryosuke Satou, Prasad V G Katakam.

Mitochondria play a critical role in the cardiomyocyte physiology by generating majority of the ATP required for the contraction/relaxation through oxidative phosphorylation (OXPHOS). Aging is a major risk factor for cardiovascular diseases (CVD) and mitochondrial dysfunction has been proposed as potential cause of aging. Recent technological innovations in Seahorse XFe24 Analyzer enhanced the detection sensitivity of oxygen consumption rate and proton flux to advance our ability study mitochondrial function. Studies of the respiratory function tests in the isolated mitochondria have the advantages to detect specific defects in the mitochondrial protein function and evaluate the direct mitochondrial effects of therapeutic/pharmacological agents. Here, we provide the protocols for studying the respiratory function of isolated murine cardiac mitochondria by measuring oxygen consumption rate using Seahorse XFe24 Analyzer. In addition, we provide details about experimental design, measurement of various respiratory parameters along with interpretation and analysis of data.

Keywords: Cardiac mitochondria; Oxygen consumption rate; Respiratory control ratio

DOI: https://doi.org/10.1007/s11357-018-0021-3