Pharmacological activation of SIRT6 triggers lethal autophagy in human cancer cells

Sirtuin 6 (SIRT6) is a member of the NAD+-dependent class III deacetylase sirtuin family, which plays a key role in cancer by controlling transcription, genome stability, telomere integrity, DNA repair, and autophagy. Here we analyzed the molecular and biological effects of UBCS039, the first synthetic SIRT6 activator. Our data demonstrated that UBCS039 induced a time-dependent activation of autophagy in several human tumor cell lines, as evaluated by increased content of the lipidated form of LC3B by western blot and of autophagosomal puncta by microscopy analysis of GFP-LC3. UBCS039-mediated activation of autophagy was strictly dependent on SIRT6 deacetylating activity since the catalytic mutant H133Y failed to activate autophagy. At the molecular level, SIRT6-mediated autophagy was triggered by an increase of ROS levels, which, in turn, resulted in the activation of the AMPK-ULK1-mTOR signaling pathway. Interestingly, antioxidants were able to completely counteract UBCS039-induced autophagy, suggesting that ROS burst had a key role in upstream events leading to autophagy commitment. Finally, sustained activation of SIRT6 resulted in autophagy-related cell death, a process that was markedly attenuated using either a pan caspases inhibitor (zVAD-fmk) or an autophagy inhibitor (CQ). Overall, our results identified UBCS039 as an efficient SIRT6 activator, thereby providing a proof of principle that modulation of the enzyme can influence therapeutic strategy by enhancing autophagy-dependent cell death

Glutamate Excitotoxicity Linked to Spermine Oxidase Overexpression

Excitotoxic stress has been associated with several different neurological disorders, and it is one of the main causes of neuronal degeneration and death. To identify new potential proteins that could represent key factors in excitotoxic stress and to study the relationship between polyamine catabolism and excitotoxic damage, a novel transgenic mouse line overexpressing spermine oxidase enzyme in the neocortex (Dach-SMOX) has been engineered. These transgenic mice are more susceptible to excitotoxic injury and display a higher oxidative stress, highlighted by 8-Oxo-2′-deoxyguanosine increase and activation of defense mechanisms, as demonstrated by the increase of nuclear factor erythroid 2-related factor 2 (Nrf-2) in the nucleus. In Dach-SMOX astrocytes and neurons, an alteration of the phosphorylated and non-phosphorylated subunits of glutamate receptors increases the kainic acid response in these mice. Moreover, a decrease in excitatory amino acid transporters and an increase in the system xc− transporter, a Nrf-2 target, was observed. Sulfasalazine, a system xc− transporter inhibitor, was shown to revert the increased susceptibility of Dach-SMOX mice treated with kainic acid. We demonstrated that astrocytes play a crucial role in this process: neuronal spermine oxidase overexpression resulted in an alteration of glutamate excitability, in glutamate uptake and efflux in astrocytes involved in the synapse. Considering the involvement of oxidative stress in many neurodegenerative diseases, Dach-SMOX transgenic mouse can be considered as a suitable in vivo genetic model to study the involvement of spermine oxidase in excitotoxicity, which can be considered as a possible therapeutic target

Skeletal Muscle Pathophysiology: The Emerging Role of Spermine Oxidase and Spermidine

Skeletal muscle comprises approximately 40% of the total body mass. Preserving muscle health and function is essential for the entire body in order to counteract chronic diseases such as type II diabetes, cardiovascular diseases, and cancer. Prolonged physical inactivity, particularly among the elderly, causes muscle atrophy, a pathological state with adverse outcomes such as poor quality of life, physical disability, and high mortality. In murine skeletal muscle C2C12 cells, increased expression of the spermine oxidase (SMOX) enzyme has been found during cell differentiation. Notably, SMOX overexpression increases muscle fiber size, while SMOX reduction was enough to induce muscle atrophy in multiple murine models. Of note, the SMOX reaction product spermidine appears to be involved in skeletal muscle atrophy/hypertrophy. It is effective in reactivating autophagy, ameliorating the myopathic defects of collagen VI-null mice. Moreover, spermidine treatment, if combined with exercise, can affect D-gal-induced aging-related skeletal muscle atrophy. This review hypothesizes a role for SMOX during skeletal muscle differentiation and outlines its role and that of spermidine in muscle atrophy. The identification of new molecular pathways involved in the maintenance of skeletal muscle health could be beneficial in developing novel therapeutic lead compounds to treat muscle atrophy

Multicomponent Reaction-Assisted Drug Discovery: A Time- and Cost-Effective Green Approach Speeding Up Identification and Optimization of Anticancer Drugs

Multicomponent reactions (MCRs) have emerged as a powerful strategy in synthetic organic chemistry due to their widespread applications in drug discovery and development. MCRs are flexible transformations in which three or more substrates react to form structurally complex products with high atomic efficiency. They are being increasingly appreciated as a highly exploratory and evolutionary tool by the medicinal chemistry community, opening the door to more sustainable, cost-effective and rapid synthesis of biologically active molecules. In recent years, MCR-based synthetic strategies have found extensive application in the field of drug discovery, and several anticancer drugs have been synthesized through MCRs. In this review, we present an overview of representative and recent literature examples documenting different approaches and applications of MCRs in the development of new anticancer drugs

Spectroscopic and calorimetric characterization of spermine oxidase and its association forms

Spermine oxidase (SMOX) is a flavin-containing enzyme that oxidizes spermine to produce spermidine, 3-aminopropanaldehyde and hydrogen peroxide. SMOX has been shown to play key roles in inflammation and carcinogenesis; indeed it is differentially expressed in several human cancer types. Our previous investigation has revealed that SMOX purified after heterologous expression in Escherichia coli actually consists of monomers, covalent homodimers, and other higher-order forms. All association forms oxidise spermine and, after treatment with DTT, revert to SMOX monomer.Here we report a detailed investigation on the thermal denaturation of SMOX and its association forms in native and reducing conditions. By combining spectroscopic methods (circular dichroism, fluorescence) and thermal methods (differential scanning calorimetry) we provide new insights into the structure, the transformation, and the stability of SMOX. While the crystal structure of this protein is not available yet, experimental results are interpreted also on the basis of a novel SMOX structural model, obtained in silico exploiting the recently solved acetylspermine oxidase crystal structure.We conclude that while at least one specific intermolecular disulfide bond links two SMOX molecule to form the homodimer, the thermal denaturation profiles can be justified by the presence of at least one intramolecular disulfide bond, which also plays a critical role in the stabilization of the overall three dimensional SMOX structure, and in particular of its FAD-containing active site

Knowledge of Diagnostic and Therapeutic Aspects of IBD Among Nurses Working in Digestive Endoscopy: A Nationwide Italian Survey

The importance of inflammatory bowel disease (IBD) dedicated nurses in endoscopy services is poorly explored. Non-IBD healthcare professionals who work in endoscopy units may underestimate the discomfort and the secondary psychological distress that endoscopic procedures cause in IBD patients. We performed a nationwide survey to evaluate nurses' level of knowledge working in endoscopy facilities throughout Italy related to IBD patients' needs undergoing endoscopic procedures. A non-validate 45 items questionnaire divided into six sections was assembled by a group of experts and supervised by nurses and IBD physicians as part of the board of IGIBD, ANOTE-ANIGEA, and AGGEI. The questionnaire was sent to 397 nurses of which 335 (84.4%) responded to the questionnaire. The median level of knowledge registered was 29 \ub1 12, corresponding to a medium level of knowledge based on the scores described in the method section. One hundred eighty-three nurses (54.6%) reported a high score, 113 (33.7%) a medium score, and 39 (11.6%) a low score. The majority of nurses worked in high-volume endoscopy centers, where 48% were educated in IBD management. A low level of knowledge was recorded regarding disease severity definition, bowel preparation strategies in severe colitis, and evaluation of perianal fistula. This nationwide survey clearly shows that there is a need for endoscopic nurses to acquire specific knowledge in the IBD field. Dedicated pathways for IBD management in endoscopy, continuous educational programs for nurses, and further studies to improve nurse education are needed

Stability of spermine oxidase to thermal and chemical denaturation: comparison with bovine serum amine oxidase

Spermine oxidase (SMOX) is a flavin-containing enzyme that specifically oxidizes spermine to produce spermidine, 3-aminopropanaldehyde and hydrogen peroxide. While no crystal structure is available for any mammalian SMOX, X-ray crystallography showed that the yeast Fms1 polyamine oxidase has a dimeric structure. Based on this scenario, we have investigated the quaternary structure of the SMOX protein by native gel electrophoresis, which revealed a composite gel band pattern, suggesting the formation of protein complexes. All high-order protein complexes are sensitive to reducing conditions, showing that disulfide bonds were responsible for protein complexes formation. The major gel band other than the SMOX monomer is the covalent SMOX homodimer, which was disassembled by increasing the reducing conditions, while being resistant to other denaturing conditions. Homodimeric and monomeric SMOXs are catalytically active, as revealed after gel staining for enzymatic activity. An engineered SMOX mutant deprived of all but two cysteine residues was prepared and characterized experimentally, resulting in a monomeric species. High-sensitivity differential scanning calorimetry of SMOX was compared with that of bovine serum amine oxidase, to analyse their thermal stability. Furthermore, enzymatic activity assays and fluorescence spectroscopy were used to gain insight into the unfolding process

Targeting angiogenesis with poly(ADP-ribose) polymerase inhibitors

The process of angiogenesis is mediated by a wide range of factors, including pro-inflammatory cytokines. On the basis of the involvement of inflammation in tumor development and of the dual role of PARP inhibitor as enhancer of chemotherapy or as anti-inflammatory agent we have investigated the ability of PARP inhibitors to affect endothelial functions and vessel formation. To this end the influence of PARP inhibition on endothelial cell proliferation, migration, in vitro tube formation and on in vivo angiogenesis, using a matrigel plug assay, was investigated. For the in vitro studies we used an immortalized human endothelial cell line (HUV-ST), which displays all major endothelial phenotypic markers and is capable of organizing into tubule-like networks in response to appropriate stimuli. The results indicated that the PARP inhibitor GPI 15427, at concentrations devoid of antiproliferative or cytotoxic effects, abrogated migration in response to vascular endothelial growth factor (VEGF) or Placental growth factor (PlGF) and only slightly inhibited endothelial chemotaxis triggered by other stimuli like Epidermal growth factor (EGF) and basic Fibroblast growth factor (bFGF). Moreover, GPI 15427 significantly reduced the ability of HUV-ST cells to form tube and capillary-like structures in a dose-dependent manner. The in vivo angiogenesis studies using subcutaneous implantation of matrigel gel sponges containing angiogenic factors confirmed the anti-angiogenic effects of the PARP inhibitor. Taken together these results provide evidences for a role of PARP on endothelial functions important during the angiogenetic process and for the anti-angiogenic properties of PARP inhibitors, encouraging further studies on the potential mechanisms underlying this effect. Supported by: PRIN 2004 to GG and PRIN 2005 to LT

Chitosan-based polyelectrolyte complexes for doxorubicin and zoledronic acid combined therapy to overcome multidrug resistance

This study aimed to develop nanovectors co-encapsulating doxorubicin (Doxo) and zoledronic acid (Zol) for a combined therapy against Doxo-resistant tumors. Chitosan (CHI)-based polyelectrolyte complexes (PECs) prepared by ionotropic gelation technique were proposed. The influence of some experimental parameters was evaluated in order to optimize the PECs in terms of size and polydispersity index (PI). PEC stability was studied by monitoring size and zeta potential over time. In vitro studies were carried out on wild-type and Doxo-resistant cell lines, to assess both the synergism between Doxo and Zol, as well as the restoring of Doxo sensitivity. Polymer concentration, incubation time, and use of a surfactant were found to be crucial to achieving small size and monodisperse PECs. Doxo and Zol, only when encapsulated in PECs, showed a synergistic antiproliferative effect in all the tested cell lines. Importantly, the incubation of Doxo-resistant cell lines with Doxo/Zol co-encapsulating PECs resulted in the restoration of Doxo sensitivity