A Novel Redox-Based Approach to Myelodysplastic Syndrome (MDS) Therapy

minor or lack both activities. Different classes of redox-active compounds that have shown beneficial effects in vivo were explored: Mn(III) porphyrins, Mn(III) salens, cyclic polyamines, nitrones and nitroxides. Among them, cationic Mn(III) pyridylporphyrins (MnPs) have the highest catalase activity, which, though, presents only 0.0004% of enzyme activity. Catalase activity is highly dependent on the reduction potential of Mn center (E1/2 of MnIIIP/MnIIP) as well as on the metal-ligand stability. Herein we explored the same compounds on their glutathione peroxidase (GPx) activity. 25 compounds were tested on their ability to catalyze H2O2 reduction in a GPx-like fashion. Again cationic MnPs exhibited the highest GPx activity. The GSH oxidation rates, followed spectrophotometrically via NADPH oxidation, are in the range of 2.6 ± 14.2 μM GSH/min per μM of catalyst. The highest GPx activity accounts for ~0.4% of enzymatic activity. As is the case with their SOD and catalase activities, GPx activity depends on E1/2; compounds with E1/2 ~+200mV vs NHE have the highest rate of GSH oxidation. Electrochemical studies revealed near complete suppression of H2O2 dismutation in a catalase-like fashion in the presence of GSH ± no O2 generation was recorded under anaerobic conditions. In contrast, pH-dependent O2 consumption and formation of GSƔ radical were demonstrated during MnPcatalyzed GSH-mediated H2O2 reduction under aerobic condition. The GSƔ is involved in S-glutathionylation of protein thiols, which presents one of major mechanisms of MnPs therapeutic actions. Interestingly, Fe porphyrins with the highest catalase activity (~0.05% of enzyme) exhibit only 0.09% of GPx enzyme activity. In vivo, given the mM intracellular GSH levels and the lack of O2 generation, GPx activity of Fe porphyrins will predominate over their catalase activity. Well-known GPx mimic, ebselen, with 0.2% of GPx activity, is less potent than most MnPs. Mn(III) salen, EUK-8, was the only other compound that possesses fairly high activity of 0.1% of that of GPx. Both the formation of GS Ɣ radicals and reduction of O2Ɣ- in vivo, reveal the involvement of prooxidative actions in MnPs therapeutic effects. Our data show that kinetics and thermodynamics, resulting in high SOD activity, give rise to the high GPx activity also, and in turn control MnPs therapeutic effects. Support: 1R03-NS082704-01, CNPq/CAPES

doi: xxxxx doi: 10.1016/j.freeradbiomed.2015.10.227 184 $1RYHO5HGR[%DVHG$SSURDFKWR0\HORG\VSODVWLF 6\QGURPH0'6 7KHUDS\

Dustin Carroll1, Yanming Zhao1, Ines Batinic-Haberle2, and Daret St. Clair1 1 University of Kentucky, USA, 2Duke University, USA Malignant cells depend on elevated levels of intracellular redox state to proliferate and self-renew. Thus, treatment with compounds traditionally considered to be antioxidants, but which are capable of redox cycling, may act as prooxidants. This may be accomplished by compounds that can mimic the activity of endogenous enzymes. Here, we investigated the therapeutic effect of a mitochondrial- targeted, MnSOD mimetic, Mn(III) mesotetrakis (N-n-butoxyethylpyridinium-2yl) porphyrin, MnBuOE (MnP) in the hematopoietic disorder myelodysplastic syndrome (MDS). We show that MnP has a significant killing effect in patient- derived MDS (MDSL) cells at concentrations that we have previously shown to be non-toxic to normal hematopoietic stem cells (HSC), and to increase HSC function. In air, (21% O2) treatment with MnP at 10 or 20 ɊM reduces MDSL cell viability by 40% (p=3.1 E-6) and 49% (p=2.0 E-6), respectively. Under physiological conditions, (5% O2) 20 or 30 μM MnP treatment

reduces MDSL cell viability by 28% (p=4.0 E-4) and 45% (p=5.1 E), respectively. In contrast, similar treatment of normal mononuclear blood cells increases cell viability by 8% (p=0.005). Using quantitative LC-MS/MS analysis of the GSH/GSSG cellular redox pair, we found that MnP treatment of MDSL cells results in DGHFUHDVHLQWKHFHOOXODUUHGXFWLRQSRWHQWLDO¨ P9 7KLV mild prooxidant condition activates the antioxidant transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2) in normal HSCs but activates the activator protein 1 (AP-1) in MDSL cells. The finding that MnP can exert oxygen- dependent selective killing of MDS cells via preferential activation of a pro-apoptosis pathway will galvanize further developments of redox-based therapeutics for clinical applications and will have a groundbreaking impact on future drug design.

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Ana Paula Ribeiro Barcelos Castro1, Rosangela Maria Neves Bezerra1, and Diogo Thimoteo Cunha1 1 UNICAMP, Brazil Obesity is a critical public health issue and it is strictly related with chronic non-communicable diseases that influence the health status of Brazilian population. This research aims to verify the effects of beetroot leaf and stalk flour supplementation on biochemical, anthropometric and dietetic parameters of volunteers from the Specialties Medic Ambulatory (Ambulatório Médico de Especialidades (AME-Limeira)), which were overweight or obese people and shown some serum lipid alteration (dyslipidemia). 36 volunteers were randomly divided in two groups. The control group received nutritional orientation and the other group was suggested to consume the flour supplement for a month. Both groups were submitted to a diagnostic evaluation and received the same nutritional instructions. Data was measured from biochemical and anthropometric exams. In addition, food assessment as the 24 hour food recall and the Food Frequency Questionnaire, applied before and after the intervention. Results between both groups were similar. Body weight and BMI were significantly reduced in both groups. However, the supplemented group suffered a significantly higher decrease in LDL levels when compared with control group. This study suggest that beetroot leaf and stalk flour supplementation could act as a complement in the dyslipidemia control in obese patients.

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Ying Chen1,2, Surendra Singh2, Akiko Matsumoto2, Soumen Manna3, Mohamed Abdelmegeed4, Srujana Golla4, Robert Murphy2, Hongbin Dong1,2, Byoung-Joon Song4, Frank Gonzalez3, David C. Thompson2, and Vasilis Vasiliou1,2 1 Yale University, USA, 2University of Colorado, USA, 3National Cancer Institute, USA, 4National Institutes of Health, USA Alcohol abuse induces liver steatosis, which can progress to

SFRBM 2015

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