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Pro-apoptotic role of AMP-activated protein kinase under oxidative conditions linked to bioenergetic impairment: implications for cancer treatment and neurodegeneration
No full textLo squilibrio tra produzione di ROS e loro eliminazione porta a stress ossidativo, una condizione implicata nella patogenesi di molti disordini cellulari come la neurodegenerazione e il cancro.
In questi constesti, condizioni pro-ossidanti attivano molte proteine redox-sensibili coinvolte nella regolazione del programma apoptotico. Tra di questi, p53 e le MAPK sono implicate nella patogenesi dei disordini neurodegenerativi e in molte strategie chemioterapeutiche finalizzate alla eliminazione di cellule cancerose dal pool replicativo. Recentemente AMPK è stata identificata come un componente della cascata di segnalazione capace di percepire stress bioenergetici e ossidativi. Inoltre la sua capacità di indurre apoptosi attivando p53 o taluni membri della famiglia delle MAPK (ad es. p38MAPK), la rende implicata sia nelle malattie neurodegnerative che nel trattamento del cancro. Sulla base di queste conoscenze, questa tesi di dottorato è finalizzata ad elucidare le prpoprietà pro-apoptotiche di AMPK nella linea neuronale SH-SY5Y in risposta a condizioni pro-ossidanti di AMPK associate a stress bioenergetico. La ricerca è stata realizzata usando 3 composti noti influenzare l'omeosatsi redox:Bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl)pyridine-N,N’]copper(II) perchlorate (Cu(isaepy)2), tetrahydrobiopterin (BH4) and sodium nitroprusside (SNP).The imbalance between ROS production and clearance leads to oxidative stress, a condition implicated in the pathogenesis of several cell disorders such as neurodegeneration and cancer. In these settings, pro-oxidant conditions activate many redox-sensitive proteins involved in the regulation of the apoptotic program. Among them, the tumor suppressor p53 and the mitogen-activated protein kinases (MAPK) are implicated both in the pathogenesis of neurodegenerative disorders and in many chemotherapeutic strategies aimed to the elimination of cancer-prone cells from the replicative pool. Recently, AMP-activated protein kinase (AMPK) has been identified as a component of the signaling cascade able to sense bioenergetic and oxidative challenges. Moreover, its capability to trigger apoptosis by activating p53 or some members of the MAPK family (e.g. p38MAPK), makes it a putative player both in neurodegenerative disease and in cancer management.
On the basis of this knowledge, this PhD thesis is aimed to elucidate the pro-apoptotic properties of AMPK in SH-SY5Y neuronal cell line under pro-oxidant conditions associated to bioenergetic impairment. This research has been performed by using three compounds known to affect cellular redox homeostas: Bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl)pyridine-N,N’]copper(II) perchlorate (Cu(isaepy)2), tetrahydrobiopterin (BH4) and sodium nitroprusside (SNP). Our experiments demonstrated that Cu(isaepy)2, by acting as a DLC-like molecule, was able to induce cell death by activating the AMPK/ p38MAPK/p53 signaling axis, in response to a mitochondrial impairment. The cross-talk between these proteins was found to be operative also in SH-SY5Y cell death induced by BH4, an obligatory cofactor for tyrosine hydroxylase in dopamine synthesis, and to be sensitive to the alteration of glycolytic metabolism. Finally the observation that the iron-nytrosil complex SNP was unable to affect cellular energetics, explains on the one hand the uneffectivenes of AMPK in mediating SNP-induced apoptosis and, on the other, suggests a possible role for this energy-responsive kinase in apoptosis engagement only under condition of bioenergetic stress
Deprive to kill: glutamine closes the gate to anticancer monocarboxylic drugs
No full textKilling properties of antitumor drugs can be enhanced by strategies targeting biochemical adaptations of cancer cells. Recently, we reported that depriving cancer cells of glutamine is a feasible approach to enhance antitumor effects of the alkylating analog of pyruvic acid, 3-bromopyruvate, which rely on the induction of autophagic cell death by metabolic-oxidative stress. 3-bromopyruvate chemopotentiation is the result of its increased intracellular uptake mediated by the monocarboxylate transporter 1, whose expression is post-transcriptionally increased upon glutamine withdrawal. Overall, our results identified the metabolic condition able to increase the selectivity of 3-bromopyruvate targets in neoplastic tissues, thereby providing a stage for its use in clinical settings for targeting malignancies and represent a proof of principle that modulation of glutamine availability can influence the delivery of monocarboxylic drugs into tumors
Redox implications of AMPK-mediated signal transduction beyond energetic clues
Get PDFSince the discovery of AMP-dependent protein kinase (AMPK), its fundamental role in regulating metabolic pathways and the molecular mechanism underlying the regulation of its activity by adenine nucleotides has been widely studied. AMPK is not only an energy-responsive enzyme, but it also senses redox signals. This review aims at recapitulating the recent lines of evidence that demonstrate the responsiveness of this kinase to metabolic and nitroxidative imbalance, thus providing new insights into the intimate networks of redox-based signals upstream of AMPK. In particular, we discuss its well-recognized activation downstream of mitochondrial dysfunction, debate the recent findings that AMPK is directly targeted by pro-oxidant species, and question alternative redox pathways that allow AMPK to be included into the large class of redox-sensing proteins. The possible therapeutic implications of the role of AMPK in redox-associated pathologies, such as cancer and neurodegeneration, are also discussed in light of recent advances that suggest a role for AMPK in the tuning of redox-dependent processes, such as apoptosis and autophagy
TCA Cycle Defects and Cancer: When Metabolism Tunes Redox State
Get PDFInborn defects of the tricarboxylic acid (TCA) cycle enzymes have been known for more than twenty years. Until recently, only recessive mutations were described which, although resulted in severe multisystem syndromes, did not predispose to cancer onset. In the last ten years, a causal role in carcinogenesis has been documented for inherited and acquired alterations in three TCA cycle enzymes, succinate dehydrogenase (SDH), fumarate hydratase (FH), and isocitrate dehydrogenase (IDH), pointing towards metabolic alterations as the underlying hallmark of cancer. This paper summarizes the neoplastic alterations of the TCA cycle enzymes focusing on the generation of pseudohypoxic phenotype and the alteration of epigenetic homeostasis as the main tumor-promoting effects of the TCA cycle affecting defects. Moreover, we debate on the ability of these mutations to affect cellular redox state and to promote carcinogenesis by impacting on redox biology
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Targeting aerobic glycolysis: 3-bromopyruvate as a promising anticancer drug
No full textThe Warburg effect refers to the phenomenon whereby cancer cells avidly take up glucose and produce lactic acid under aerobic conditions. Although the molecular mechanisms underlying tumor reliance on glycolysis remains not completely clear, its inhibition opens feasible therapeutic windows for cancer treatment. Indeed, several small molecules have emerged by combinatorial studies exhibiting promising anticancer activity both in vitro and in vivo, as a single agent or in combination with other therapeutic modalities. Therefore, besides reviewing the alterations of glycolysis that occur with malignant transformation, this manuscript aims at recapitulating the most effective pharmacological therapeutics of its targeting. In particular, we describe the principal mechanisms of action and the main targets of 3-bromopyruvate, an alkylating agent with impressive antitumor effects in several models of animal tumors. Moreover, we discuss the chemo-potentiating strategies that would make unparalleled the putative therapeutic efficacy of its use in clinical settings
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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