Metformin Prevents Glucose-Induced Protein Kinase C-β2 Activation in Human Umbilical Vein Endothelial Cells Through an Antioxidant Mechanism

Hyperglycemia determines the vascular complications of diabetes through different mechanisms: one of these is excessive activation of the isoform β2 of protein kinase C (PKC-β2). Metformin, a widely used antidiabetic agent, is associated with decreased cardiovascular mortality in obese type 2 diabetic patients. Therefore, we assessed the role of metformin in glucose-induced activation of PKC-β2 and determined the mechanism of its effect in human umbilical venous endothelial cells grown to either normo- (5 mmol/l) or hyperglycemia (10 mmol/l) and moderately and acutely exposed to 25 mmol/l glucose. We studied PKC-β2 activation by developing adenovirally expressed chimeras encoding fusion protein between green fluorescent protein (GFP) and conventional β2 isoform (PKC-β2–GFP). Glucose (25 mmol/l) induced the translocation of PKC-β2–GFP from the cytosol to the membrane in cells grown to hyperglycemia but not in those grown in normal glucose medium. Metformin (20 μmol/l) prevented hyperglycemia-induced PKC-β2–GFP translocation. We also assessed oxidative stress under the same conditions with a 4-((9-acridine-carbonyl)amino)-2,2,6,6-tetramethylpiperidin-oxyl,free radical (TEMPO-9-AC) fluorescent probe. We observed significantly increased radical oxygen species production in cells grown in hyperglycemia medium, and this effect was abolished by metformin. We show that in endothelial cells, metformin inhibits hyperglycemia-induced PKC-β2 translocation because of a direct antioxidant effect. Our data substantiate the findings of previous large intervention studies on the beneficial effect of this drug in type 2 diabetic patients

INFN Camera demonstrator for the Cherenkov Telescope Array

The Cherenkov Telescope Array is a world-wide project for a new generation of ground-based Cherenkov telescopes of the Imaging class with the aim of exploring the highest energy region of the electromagnetic spectrum. With two planned arrays, one for each hemisphere, it will guarantee a good sky coverage in the energy range from a few tens of GeV to hundreds of TeV, with improved angular resolution and a sensitivity in the TeV energy region better by one order of magnitude than the currently operating arrays. In order to cover this wide energy range, three different telescope types are envisaged, with different mirror sizes and focal plane features. In particular, for the highest energies a possible design is a dual-mirror Schwarzschild-Couder optical scheme, with a compact focal plane. A silicon photomultiplier (SiPM) based camera is being proposed as a solution to match the dimensions of the pixel (angular size of ~ 0.17 degrees). INFN is developing a camera demonstrator made by 9 Photo Sensor Modules (PSMs, 64 pixels each, with total coverage 1/4 of the focal plane) equipped with FBK (Fondazione Bruno Kessler, Italy) Near UltraViolet High Fill factor SiPMs and Front-End Electronics (FEE) based on a Target 7 ASIC, a 16 channels fast sampler (up to 2GS/s) with deep buffer, self-trigger and on-demand digitization capabilities specifically developed for this purpose. The pixel dimensions of $6\times6$ mm$^2$ lead to a very compact design with challenging problems of thermal dissipation. A modular structure, made by copper frames hosting one PSM and the corresponding FEE, has been conceived, with a water cooling system to keep the required working temperature. The actual design, the adopted technical solutions and the achieved results for this demonstrator are presented and discussed.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

Inactivation of pathogenic microorganisms by photodynamic techniques: mechanistic aspects and perspective applications.

The worldwide rise in antibiotic resistance by microorganisms has stimulated intensive research toward the development of alternative therapeutic strategies. Photodynamic therapy (PDT) is emerging as a promising modality for the treatment of localized microbial infections. Studies on the relationship between the chemical structure of photosensitising agents and their phototoxicity against microbial pathogens led to the identification of a selected number of compounds with optimal cytocidal effects. These include phenothiazine, porphyrin and phthalocyanine derivatives, whose molecule has been engineered to introduce the following features: (a) presence of cationic moieties, preferably due to quaternarized amino groups; (b) introduction of at least one N-alkyl group having a relatively long hydrocarbon chain; (c) overall amphiphilic character to promote the partitioning in the plasma membrane. Studies on cell cultures indicate that PDT is endowed with favourable properties to act as an antimicrobial modality: (a) broad spectrum of action, since one irradiation protocol can be used to obtain the inactivation of different groups of pathogens, such as Gram-positive and Gram-negative bacteria, yeasts, mycoplasmas and protozoa in both vegetative and cystic stages; (b) fast association with microbial cells, which allows irradiations to be performed after incubation times as short as 5-10 min., thereby guaranteeing a high selectivity as compared with host tissues; (d) high photoinactivation efficiency, since a 5-6 log decrease in microbial population is obtained by irradiation under mild conditions; (e) photosensitising activity independent of the antibiotic-resistance spectrum of the given pathogen; (f) lack of selection of photoresistant strains upon repeated treatment and minimal risk to induce the onset of mutagenic processes