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Statins exhibit anti-leukemic properties due to suppression of the mevalonate pathway by the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase, and subsequent depletion of cholesterol, farnesylpyrophosphate, and geranylgeranylpyrophosphate. We investigated the role of autophagy, a controlled intracellular self-digestion, in the anti-leukemic action of statins. Treatment with low concentrations (≤6 µM) of statins, cholesterol depletion, and specific inhibition of cholesterol synthesis and protein farnesylation or geranylgeranylation, all inhibited proliferation of leukemic cell lines and primary leukemic cells without inducing overt cell death. Statins and agents that selectively reduce intracellular cholesterol levels, but not the inhibition of protein farnesylation or geranylgeranylation, induced autophagy in leukemic cells. The observed autophagic response was associated with the reduction of phosphorylated Akt levels in the lipid rafts, accompanied by a decrease in the activation of the main autophagy suppressor mammalian target of rapamycin (mTOR) and its substrate ribosomal p70S6 kinase (p70S6K). No significant autophagy induction and downregulation of mTOR/p70S6K activation were observed in normal leukocytes. Autophagy suppression by bafilomycin A1 or RNA interference-mediated knockdown of beclin-1 and microtubule-associated protein 1 light chain 3B induced apoptotic death in statin-treated leukemic cells, an effect attenuated by the addition of mevalonate or squalene, but not farnesylpyrophosphate or geranylgeranylpyrophosphate. Therefore, while the inhibition of cholesterol synthesis, protein farnesylation, and geranylgeranylation all contributed to anti-leukemic effects of statins, the inhibition of cholesterol synthesis was solely responsible for the induction of cytoprotective autophagy. These data indicate that combined treatment with statins and autophagy inhibitors might be potentially useful in anti-leukemic therapy.

We investigated the cytotoxicity of recently synthesized (S,S)-ethyleridiamine-N,N'-di-2-(3-cyclohexyl)propanoic acid esters toward human leukemic cell lines and healthy blood mononuclear cells. Cell viability was assessed by acid phosphatase assay, apoptosis, and differentiation were analyzed by flow cytometry and electron microscopy, while intracellular localization of apoptosis-inducing factor (AIF) was determined by immunoblotting. It was demonstrated that methyl, ethyl, and n-propyl esters were toxic to HL-60, REH, MOLT-4, KG-1, JVM-2, and K-562 leukemic cell lines, while the nonesterified parental compound and n-butyl ester were devoid of cytotoxic action. The ethyl ester exhibited the highest cytotoxic activity (IC50 10.7 mu M-45.4 mu M), which was comparable to that of the prototypical anticancer drug cisplatin. The observed cytotoxic effect in HL-60 cells was associated with an increase in superoxide production and mitochondrial membrane depolarization, leading to apoptotic cell death characterized by phosphatidylserine externalization and DNA fragmentation in the absence of autophagic response. DNA fragmentation preceded caspase activation and followed AIF translocation from mitochondria to nucleus, which was indicative of caspase-independent apoptotic cell death. HL-60 cells treated with subtoxic concentration of the compound displayed morphological signs of granulocytic differentiation (nuclear indentations and presence of cytoplasmic primary granules), as well as an increased expression of differentiation markers CD11b and CD15. The cyclohexyl analogues of ethylenediamine dipropanoic acid were also toxic to peripheral blood mononuclear cells of both healthy controls and leukemic patients, the latter being more sensitive. Our data demonstrate that the toxicity of the investigated cyclohexyl compounds against leukemic cell lines is mediated by caspase-independent apoptosis associated with oxidative stress, mitochondrial dysfunction, and AIF translocation.

The role of autophagy, a process in which the cell self-digests its own components, was investigated in glioma cell death induced by the hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase-inhibiting drug simvastatin. Induction of autophagy and activation of autophagy-regulating signalling pathways were analyzed by immunoblotting. Flow cytometry/fluorescent microscopy was used to assess autophagy-associated intracellular acidification and apoptotic markers (phosphatidylserine exposure, DNA fragmentation and caspase activation). Cell viability was determined by crystal violet, MTT or LDH release assay. Simvastatin treatment of U251 and C6 glioma cell lines caused the appearance of autophagolysosome-like intracytoplasmic acidic vesicles. The induction of autophagy in U251 cells was confirmed by the upregulation of autophagosome-associated LC3-II and pro-autophagic beclin-1, as well as by the downregulation of the selective autophagic target p62. Simvastatin induced the activation of AMP-activated protein kinase (AMPK) and its target Raptor, while simultaneously downregulating activation of Akt. Mammalian target of rapamycin (mTOR), a major AMPK/Akt downstream target and a major negative autophagy regulator, and its substrate p70 S6 kinase 1 were also inhibited by simvastatin. Mevalonate, the product of HMG-CoA reductase enzymatic activity, AMPK siRNA or pharmacological inactivation of AMPK with compound C suppressed, while the inhibitors of Akt (10-DEBC hydrochloride) and mTOR (rapamycin) mimicked autophagy induction by simvastatin. Inhibition of autophagy with bafilomycin A1, 3-methyladenine and LC3β shRNA, as well as AMPK inhibition with compound C or AMPK siRNA, markedly increased apoptotic death of simvastatin-treated U251 cells. These data suggest that inhibition of AMPK-dependent autophagic response might sensitize glioma cells to statin-induced apoptotic death.

We investigated the effects of centrally administered orexigenic hormone ghrelin on energy imbalance-induced inflammation. Rats were subjected for four weeks to three different dietary regimes: normal (standard food), high-fat (standard food with 30% lard) or food-restricted (70%, 50%, 40% and 40% of the expected food intake in 1st, 2nd, 3rd and 4th week, respectively). Compared to normal-weight controls, starved, but not obese rats had significantly higher levels of proinflammatory cytokines (TNF, IL-1 beta, IFN-gamma) in the blood. When compared to normally fed animals, the hearts of starved and obese animals expressed higher levels of mRNAs encoding proinflammatory mediators (TNF, IL-1 beta, IL-6, IFN-gamma, IL-17, IL-12, iNOS), while mRNA levels of the anti-inflammatory TGF-beta remained unchanged. Intracerebroventricular (ICV) injection of ghrelin (1 mu g/day) for five consecutive days significantly reduced TNF, IL-1 beta and IFN-gamma levels in the blood of starved rats, as well as TNF, IL-17 and IL-12p40 mRNA expression in the hearts of obese rats. Conversely, ICV ghrelin increased the levels of 1FN-gamma, IL-17,1L-12p35 and IL-12p40 mRNA in the heart tissue of food-restricted animals. This was associated with an increase of immunosuppressive ACTH/corticosterone production in starved animals and a decrease of the immunostimulatory adipokine leptin both in food-restricted and high-fat groups. Ghrelin activated the energy sensor AMP-activated protein kinase (AMPK) in the hypothalamus and inhibited extracellular signal-regulated kinase (ERK) in the hearts of obese, but not starved rats. Therefore, central ghrelin may play a complex role in energy imbalance-induced inflammation by modulating HPA axis, leptin and AMPK/ERK signaling pathways. (C) 2011 Elsevier Inc. All rights reserved.

In the present study, we report that compound C, an inhibitor of a key intracellular energy sensor AMP-activated protein kinase (AMPK), can induce autophagy in cancer cells. The induction of autophagy in U251 human glioma cell line was demonstrated by acridine orange staining of intracellular acidic vesicles, Beclin 1 induction, p62 decrease and conversion of LC3-I to autophagosome-associated LC3-II in the presence of proteolysis inhibitors. The presence of autophagosome-like vesicles was confirmed by transmission electron microscopy. Compound C-mediated inhibition of AMPK and raptor in U251 cells was associated with paradoxical decrease in phosphorylation of AMPK/raptor-repressed mTOR, a major negative regulator of autophagy, and its downstream target p70S6K. The phosphorylation of an mTOR activator Akt and the PI3K-activating kinase Src was also impaired in compound C-treated cells. The siRNA-mediated AMPK silencing did not reduce the activity of the Akt/mTOR/p70S6K pathway and AMPK activators metformin and AICAR failed to block compound C-induced autophagy. Autophagy inhibitors bafilomycin and chloroquine significantly increased the cytotoxicity of compound C towards U251 cells, as confirmed by increase in lactate dehydrogenase release, DNA fragmentation and caspase-3 activation. Similar effects of compound C were also observed in C6 rat glioma, L929 mouse fibrosarcoma and B16 mouse melanoma cell lines. Since compound C has previously been reported to suppress AMPK-dependent autophagy in different cell types, our findings suggest that the effects of compound C on autophagy might be dose-, cell type- and/or context-dependent. By demonstrating the ability of compound C to induce autophagic response in cancer cells via AMPK inhibition-independent downregulation of Akt/mTOR pathway, our results warrant caution when using compound C to inhibit AMPK-dependent cellular responses, but also support further exploration of compound C and related molecules as potential anticancer agents. Ministry of Science and Technological Development of the Republic of Serbia [145073, 145058]

Perinatal phencyclidine (PCP) administration to rodents represents one of the more compelling animal models of schizophrenia. There is evidence that decreased glutathione (GSH) levels and oxidative stress mediated through free radicals in the central nervous system are involved in the pathophysiology of this disease. Limited data are available on the role of free radicals in neurotoxicity induced by NMDA-receptor antagonists. The aim of this study was to elucidate the long-term effects of perinatal phencyclidine administration on superoxide dismutase (SOD), catalase (CAT), gamma-glutamyl cisteine ligase (gamma-GCL), glutathione peroxidase (GPx), glutathione reductase (GR) and levels of lipid peroxides as well as GSH content. The Wistar rats were treated on the 2nd, 6th, 9th and 12th postnatal (PN) days with either phencyclidine (10mg/kg) or saline and sacrificed on PN70. The activities of antioxidant enzymes and level of lipid peroxides and GSH were determined in dorsolateral frontal cortex (dlFC), hippocampus, thalamus and caudate nucleus. Expression of SOD1 and SOD2 was determined by immunoblot. Region-specific changes of the measured parameters were observed. Decreased content of reduced GSH and altered activities of GR, GPx and SOD were determined in dlFC. In hippocampus, reduced GSH content and decreased activities of GPx and GR were accompanied with increased activity of gamma-GCL and increased level of lipid peroxides. gamma-GCL and GSH content were also decreased in caudate nucleus, while in thalamus major findings are increased levels of lipid peroxides and GR activity and decreased gamma-GCL activity. It can be concluded that perinatal PCP administration produces long-term alteration of antioxidant defense. Further studies are necessary in order to clarify role of redox dysregulation in the pathogenetic mechanism of schizophrenia.

The role of autophagy in cisplatin anticancer action was investigated using human U251 glioma, rat C6 glioma and mouse L929 fibrosarcoma cell lines. A dose- and time-dependent induction of autophagy was observed in tumour cells following cisplatin treatment, as demonstrated by up-regulation of autophagy-inducing protein beclin-1 and subsequent appearance of acridine orange-stained acidic autophagic vesicles. The presence of autophagosomes in cisplatin-treated cells was also confirmed by electron microscopy. Inhibition of autophagy with lysosomal inhibitors bafilomycin A1 and chloroquine, or a PI3 kinase inhibitor wortmannin, markedly augmented cisplatin-triggered oxidative stress and caspase activation, leading to an increase in DNA fragmentation and apoptotic cell death. The mechanisms underlying the protective effect of autophagy apparently involved the interference with cisplatin-induced modulation of Bcl-2 family proteins, as inhibition of autophagy potentiated cisplatin-mediated up-regulation of proapoptotic Bax and down-regulation of anti-apoptotic Bcl-2. Autophagy induction in cisplatin-treated cells was preceded by activation of adenosine monophosphate-activated protein kinase (AMPK) and concomitant down-regulation of mammalian target of rapamycin (mTOR)-mediated phosphorylation of p70S6 kinase. The ability of cisplatin to trigger autophagy was reduced by small interfering RNA (siRNA)-mediated AMPK silencing, while transfection with mTOR siRNA was sufficient to trigger autophagy in tumour cells. Finally, siRNA-mediated AMPK down-regulation and AMPK inhibitor compound C increased cisplatin-induced tumour cell death, while mTOR siRNA and AMPK activator metformin protected tumour cells from cisplatin. Taken together, these data suggest that cisplatin-triggered activation of AMPK and subsequent suppression of mTOR activity can induce an autophagic response that protects tumour cells from cisplatin-mediated apoptotic death.

Metformin is an antidiabetic drug with anticancer properties, which mainly acts through induction of AMP-activated protein kinase (AMPK). In the present study we investigated the influence of metformin on the in vitro anticancer activity of the well-known chemotherapeutic agent cisplatin. Cell viability was determined by MTT and LDH release assay, oxidative stress and apoptosis (caspase activation, DNA fragmentation, and phosphatidylserine exposure) were assessed by flow cytometry, while activation of AMPK and Akt was analyzed by immunoblotting. Although metformin reduced the number of tumour cells when applied alone, it surprisingly antagonized the cytotoxicity of cisplatin towards U251 human glioma, C6 rat glioma, SHSY5Y human neuroblastoma, L929 mouse fibrosarcoma and HL-60 human leukemia cell lines. Only in B16 mouse melanoma cells metformin augmented the cytotoxicity of cisplatin. In U251 glioma cells metformin suppressed cisplatin-induced apoptotic cell death through inhibition of oxidative stress and caspase activation. The observed cytoprotection was apparently AMPK-independent, as metformin did not further increase cisplatin-induced AMPK activation in U251 cells and other pharmacological AMPK activators failed to block cisplatin-mediated apoptosis. On the other hand, metformin induced Akt activation in cisplatin-treated cells and Akt inhibitor 10-DEBC hydrochloride or phosphoinositide 3-kinase/Akt inhibitor LY294002 abolished metformin-mediated antioxidant and antiapoptotic effects. In conclusion, the antidiabetic drug metformin reduces cisplatin in vitro anticancer activity through AMPK-independent upregulation of Akt survival pathway. These data warrant caution when considering metformin for treatment of diabetic cancer patients receiving cisplatin or as a potential adjuvant in cisplatin-based chemotherapeutic regimens. (c) 2010 Published by Elsevier B.V.