Pixantrone (PIX) Inhibition of Doxorubicinol (DOXOL) Formation in Human Myocardium: Implications for Cardiac Safety in Non-Hodgkin Lymphoma (NHL) Patients with Prior Anthracycline Treatment

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4966-4966
Author(s):  
Emanuela Salvatorelli ◽  
Odalys Gonzalez Paz ◽  
Elvio Covino ◽  
Massimo Chello ◽  
Jack Singer ◽  
...  
Keyword(s):  
Research Funding ◽  
Secondary Alcohol ◽  
Coronary Bypass ◽  
Human Myocardium ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Non Hodgkin Lymphoma ◽  
Cardiac Model ◽  
Inhibition Curve ◽  
Soluble Fractions

Abstract Abstract 4966 Background Doxorubicin (DOX) and related drugs are incompletely cleared from the heart, persist for months to years (Stewart et al Anticancer Res 1993), and slowly transform to longer-lived and more toxic secondary alcohol metabolites (eg, DOXOL) that are associated with an increased lifetime risk of congestive heart failure (Minotti et al J Pharmacol Exp Ther 2010). Anthracycline-related cardiotoxicity can be precipitated by enhanced stress or exposure to drugs that increase DOXOL formation. PIX is a novel aza-anthracenedione that is under development in patients with NHL that relapsed or was refractory after DOX-containing combination therapy. In preclinical models, PIX produced substantially less cardiotoxicity than DOX or MITOX even when animals were pretreated with DOX. Compared to anthracyclines and the anthracenedione analogue, mitoxantrone (MITOX), PIX lacks a hydroquinone moiety that binds iron and facilitates cardiotoxic free radical reactions. To further establish that it is safe in patients with NHL and prior DOX exposure, PIX should also have no effect on or diminish DOXOL formation from the cardiac residues of first-line DOX. Aims To characterize the effects of PIX on DOXOL formation in a translational cardiac model of DOX administration followed by PIX administration. MITOX was used as the comparator. Methods Myocardial samples that were routinely discarded during aorto-coronary bypass grafting were dissected into strips and loaded with 10 μM DOX in plasma. After 30 min the strips were subjected to 2h multiple washouts to simulate post-treatment clearance. The strips were then incubated for 1.5h in fresh anthracycline-free plasma w/wo 1 μM PIX or MITOX. After the experiments, DOX(OL), PIX, and MITOX were extracted from the soluble fractions of the strips and assayed by HPLC. Pharmacometabolic interactions of 10 μM or 50 μM DOX with increasing concentrations of PIX or MITOX were also studied in NADPH-supplemented isolated soluble fractions. Results After sequential DOX loading/clearance and PIX or MITOX administration, PIX:DOX ratios were significantly higher than MITOX:DOX ratios in soluble fractions of human myocardial strips. This correlated with inhibition of DOXOL formation by both PIX and MITOX, but PIX decreased DOXOL levels in a significant manner when compared to MITOX (Table). In isolated soluble fractions, both PIX and MITOX, in a concentration-dependent manner, inhibited the metabolism of 10 μM DOX to DOXOL; however, PIX caused stronger inhibition (Figure). Increasing DOX to 50 μM abated inhibition by MITOX but not by PIX. Discussion PIX inhibited DOXOL formation in a translation model of human heart used to simulate sequential DOX and PIX administration. This finding was obtained under pharmacokinetically relevant conditions that probed DOX and PIX at their clinically documented plasma Cmax values of 10 μM or 1 μM, respectively. Studies with isolated soluble fractions suggest that PIX diminished DOXOL formation by noncompetitive inhibition of NADPH-dependent reductases. MITOX was less effective than PIX at diminishing DOXOL formation, which correlated with the lower MITOX:DOX ratios in treated human myocardial strips and with the competitive mode of action of MITOX. By inhibiting formation of toxic and long-lived DOXOL, PIX potentially is a cardiac tolerable therapeutic agent for patients with NHL that failed or relapsed after DOX treatment. Inhibition of DOXOL formation by PIX and MITOX in isolated soluble fractions of human myocardium incubated with NADPH (0.25 mM) and DOX for 4h. Control DOXOL was 0.15–0.19 nmoles/mg of protein at 10 μM DOX and 0.34–0.84 nmoles/mg of protein at 50 μM DOX. Each inhibition curve is the mean and SE of three experiments. Disclosures: Salvatorelli: Cell Therapeutics, Inc: Research Funding. Gonzalez Paz:Cell Therapeutics, Inc: Research Funding. Singer:Cell Therapeutics, Inc: Employment. Menna:Cell Therapeutics, Inc: Research Funding. Minotti:Cell Therapeutics, Inc: Research Funding.

Metabolic Capability to Induce the Pasteur Effect Mediates Sensitivity of Human Leukemic Cells to Metformin

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2601-2601
Author(s):  
Sarah Scotland ◽  
Estelle Saland ◽  
Lindsay Peyriga ◽  
Rémi Peyraud ◽  
Elizabeth Micklow ◽  
...  
Keyword(s):  
Cell Lines ◽  
Research Funding ◽  
Leukemic Cell ◽  
Leukemic Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Pasteur Effect ◽  
Cytotoxic Response ◽  
Leukemic Cell Lines

Abstract Abstract 2601 An emerging hallmark of cancer cells is the reprogramming of intermediary and energy metabolism these cells undergo. Several epidemiological studies have shown that metformin, widely used to treat patients with type 2 diabetes, may reduce their risk of cancer. Despite several reports of anti-neoplastic activity of metformin, the mechanisms responsible for this activity have not been fully elucidated in cancer or leukemic cells. We hypothesized that metformin elicits a metabolic reprogramming driven by alterations in mitochondrial function and signaling, which induces apoptosis in leukemic cells, and that metabolic flexibility determines the variation(s) of the cytotoxic response to metformin among different leukemic cell lines. We first demonstrated that metformin markedly decreased oxygen consumption of six leukemic cell lines in a concentration-dependent manner. We also observed that the cytotoxic effect of metformin varies between cell lines reflecting their energetic capacity to compensate for the mitochondrial inhibition induced by metformin (eg. to induce the Pasteur effect). Importantly, metformin-insensitive leukemic cells did not exhibit a Pasteur effect in response to metformin. All leukemic cells exhibited high basal conversion of glucose to lactate (eg. aerobic glycolysis) and specific expression of key metabolic genes as compared to normal mononuclear cells. Despite dependence on glucose catabolism, metformin sensitivity was associated with relative resistance to glucose starvation. Metformin effects in drug-resistant cells were potentiated by the addition of a glycolytic inhibitor, but not by inhibitors of the pentose phosphate pathway or glutaminolysis. Leukemic cells with broad metabolic capacities to utilize other energetic substrates in response to diverse nutrient starvation showed insensitivity to metformin. Metformin induced a significant decrease in metabolites of the upper segment of glycolysis and the oxidative branch of the pentose phosphate pathway as well as a clear increase of PRPP and IMP biosynthesis. Energy charge, the nucleotide phosphate pool and lactate/glucose ratio remained stable after metformin treatment. Furthermore, our results showed that basal glucose uptake/consumption and the activity of the lower segment of the glycolytic pathway are key determinants of a cytotoxic response to metformin. In addition, high glutathione, malate, IMP and orotate content were observed in metformin-insensitive leukemic cells. Moreover, the cytotoxic effect of metformin was independent of AMPK/LKB1 status of the leukemic cells while p53 expression abrogated this effect. The presence of wild-type p53 appears to partially protect tumor cells from glucose starvation and metformin cytotoxicity and prevents the induction of the Pasteur effect. Finally, we demonstrated that metformin increased the cytotoxicity of chemotherapy agent, cytarabine, on all leukemic cell lines in vitro and significantly reduced leukemic colony-forming units (CFU-L) from six primary AML patient samples in a concentration-dependent manner. Additional experiments on metabolic and signaling pathways as well as in vivo studies are in progress to better understand the cytotoxic response of metformin in both AML cell lines and primary AML patient specimens that impact the therapeutic potential of metformin in vivo. Disclosures: Carroll: Agios Pharmaceuticals: Research Funding; TetraLogic Pharmaceuticals: Research Funding; Sanofi Aventis Corporation: Research Funding; Glaxo Smith Kline, Inc.: Research Funding.

Sfrps Family Invovled in Growth Inhibition of K562 Cells Induced by Artesunate

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 5015-5015
Author(s):  
Wang Ying ◽  
Guo xiao Nan ◽  
Zhang xue Jun ◽  
Ren jin Hai ◽  
Qiao shu Kai ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Research Funding ◽  
Wnt Pathway ◽  
K562 Cells ◽  
Hebei Province ◽  
Control Group ◽  
Dependent Manner ◽  
Inhibition Rate ◽  
Concentration Dependent Manner ◽  
Expression Levels

Abstract Abstract 5015 Introduction: Studies have shown that abnormal activation of wnt signaling pathway is closely related to tumor genesis. Cell surface coil protein (frizzled, fzd) is a specific receptor for wnt pathway to activate its downstream signaling through β-catenin to stimulate the growth of a range of tumor cells. Secreted frizzled related proteins (sfrps) are the main antagonists of wnt pathway. sfrps can inhibit the function of wnt pathway via competing with fzd receptor. Recent studies have found that sfrps family memberes expressed at very low levels in a variety of tumor cells,which was closely related to the methylation of sfrps gene promoters. DNA methyltransferase (dnmts) are the key enzymes involved in DNA methylation, which can promote the methylation of tumor suppressor genes' promoters and inhibit transcription of these genes, and induce tumor genesis. Artesunate, a semi-synthetic derivative of artemisinin, is very effective in antimalaria. Recent studies have shown that artesunate has anti-tumor functions. However, the effect of artesunate on the expression of sfrps- and dnmts- mRNAs and β-catenin protein are not clear. To evaluate the growth inhibition effect of Artesunate (at final concentrations of 0μg/ml, 4μg/ml, 10μg/ml, 20μg/ml and 40μg/ml) on K562 cells and to investigate its potential mechanism by detecting the expression levels of sfrps- and dnmts- mRNAs and β-catenin protein in K562 cells treated with artesunate. Methods: Cell growth inhibition rate and cell cycle distribution of K562 cells induced by artesunate treatment were measured by MTT assay and flow cytometry, respectively. The mRNA expression levels of sfrp1, sfrp2, sfrp4 and dnmt1, dnmt3a, dnmt3b in K562 cells which had been treated with or without artesunate for 48 hours were evaluated with reverse transcription-polymerase chain reaction (RT-PCR). Protein expression level of β-catenin in K562 cells were detected by Western blot. Results: Artesunate treatment significantly induced growth inhibition of K562 cells in a concentration-dependent manner after the cells were treated with artesunate for 48 hours(p < 0.05). The inhibition rate of 4,10,20 and 40(μg/ml)artesunate exposure were 54.29%, 58.03%, 69.33% and 77.98% respectively. Flow cytometry analysis showed that K562 cells were arrested at G0/Gl and G2/M phase in concentration-dependent manner after 48 hours exposure of artesunate (p < 0.05). After treated with artesunate at the final concentrations of 0, 4, 10, 20 and 40μg/ml, the relative expression levels of sfrp1, sfrp2 and sfrp4 mRNA in K562 cells increased, while the expression levels of dnmtl, dnmt3a, dnmt3b mRNA decreased significantly compared with the control group. Results from Western blot showed that β-catenin protein levels decreased in a concentration-dependent manner, when compared with that of the control group (P<0.05). Conclusion: Results from the present study indicated that artesunate could inhibite the mRNA expression of dnmts family and minimize the methylation of sfrps gene promoter. Therefore, sfrps could inhibit the function of wnt pathway through competing with fzd receptors. Meanwhile, artesunate could decrease the expression of β-catenin protein in K562 cells, and could further inhibit the function of wnt pathway. Therefore, data from the present experiment provides a new theoretical basis for clinical application of artesunate in leukemia treatment. Disclosures: Ying: Nature science foundation of Hebei Province: Research Funding. Nan:Nature science foundation of Hebei Province: Research Funding. Jun:Nature science foundation of Hebei Province: Research Funding. Hai:Nature science foundation of Hebei Province: Research Funding. Kai:Nature science foundation of Hebei Province: Research Funding. Xu:Nature science foundation of Hebei Province: Research Funding. Pan:Nature science foundation of Hebei Province: Research Funding.

scholarly journals The Effects of Antiplatelet Agents on Endocytosis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1058-1058
Author(s):  
Harvey G. Roweth ◽  
Michael Malloy ◽  
Jodi A. Forward ◽  
Julia Ceglowski ◽  
Robert C. Flaumenhaft ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Research Funding ◽  
Platelet Rich Plasma ◽  
Antiplatelet Agents ◽  
Small Gtpases ◽  
Dependent Manner ◽  
Liquid Biopsies ◽  
Concentration Dependent Manner ◽  
Receptor Mediated Endocytosis ◽  
Angiogenic Proteins

Almost every platelet-derived protein originates from either megakaryocytes (MKs), or the endocytosis of factors within blood circulation. These endocytosed factors can be locally released upon platelet activation to regulate hemostasis, or to promote the growth and neovascularization of solid tumors. Although platelet endocytosis has long been recognized, our mechanistic understanding remains largely confined to receptor-mediated endocytosis of fibrinogen via integrin αIIbβ3. Whether antiplatelet therapy and/or different disease states influence platelet endocytosis remain understudied areas of investigation. In this project, we examined how various antiplatelet agents affect the endocytosis of vascular endothelial growth factor (VEGF) and endostatin, which are broad pro-angiogenic and anti-angiogenic regulators, respectively. For our initial experiments, human platelets in platelet-rich plasma were exposed to either recombinant VEGF or endostatin for 1 hour, then washed to remove residual/unbound protein. Platelets were then lysed and changes in VEGF or endostatin concentration determined by ELISA. Using this approach, we demonstrated that platelets endocytose VEGF and endostatin in a concentration-dependent manner. We next established that following platelet activation, lysate concentrations of endocytosed VEGF and endostatin decreased and supernatant concentrations increased. This finding implies that endocytosed VEGF and endostatin are packaged into platelet alpha granules and are released following their activation, which we aim to confirm by measuring co-localization with endosomal and alpha granule markers. We have also developed two assays to track endocytosis into platelets, one where proteins are conjugated to pH-sensitive dyes that increase their fluorescence upon endosomal compartmentalization, and another utilizing fluorophore-targeting antibodies to quench eternal fluorescence of labeled factors. We next assessed if antiplatelet agents modulated endocytosis into platelets. We found that pre-treating platelets with aspirin, vorapaxar or ticagrelor resulted in dose-dependent inhibition of VEGF and fibrinogen but not endostatin endocytosis. This finding suggests that antiplatelet agents selectively inhibit the uptake of pro-angiogenic regulators, a statement we aim to support by measuring the endocytosis of additional angiogenic proteins. Our observations also affirm previous studies, claiming that fibrinogen and VEGF are differentially packaged into a subset of alpha granules distinct from endostatin. Experiments are ongoing to measure platelet levels of VEGF and endostatin in human subjects before and after aspirin intervention, to assess if our findings hold physiological relevance. The fact that several antiplatelet agents impaired VEGF endocytosis suggests a common inhibitory mechanism linked to suppressing basal levels of platelet activation. We tested this hypothesis by either simulating platelets with low-dose adenosine diphosphate or by chelating intracellular calcium to prevent basal activation. Neither of these processes influenced VEGF or endostatin endocytosis, suggesting that the process is not associated with basal platelet activation. We are currently investigating if antiplatelet agents alter the activity of small GTPases Arf6 and Dynamin-2, which have been shown to regulate receptor-mediated endocytosis of fibrinogen by platelets. Future experiments will aim to elucidate the mechanism by which antiplatelet agents inhibit protein uptake. It has previously been shown that platelets endocytose tumor-derived factors and RNA that may promote disease progression or act as biomarkers for liquid biopsies. We are currently studying if the daily administration of aspirin prevents the endocytosis of tumor-derived factors in a mouse model of tumor generation. In summary, our data show platelets endocytose and release key angiogenic regulators, a process which can be blocked through pre-treatment with various antiplatelet agents. Given the important role of platelets to tumor neovascularization, preventing the endocytosis of pro-angiogenic mediators could represent a novel mechanism that contributes to the inhibitory effects of antiplatelet agents on tumor growth and metastasis. Disclosures Flaumenhaft: Relay Therapeutics: Consultancy; PlateletDiagnostics: Consultancy, Other: Founder. Italiano:Platelet Biogenesis: Employment, Equity Ownership; Ionis Research Funding: Research Funding.

The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

2014 ◽  
Vol 84 (1-2) ◽  
pp. 79-91 ◽  
Author(s):  
Amin F. Majdalawieh ◽  
Hyo-Sung Ro
Keyword(s):  
Cholesterol Efflux ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Foam Cell ◽  
Mapk Signaling ◽  
Luciferase Reporter ◽  
Foam Cell Formation ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamin’s anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

Trimucytin: A Collagen-Like Aggregating Inducer Isolated from Trimeresurus mucrosquamatus Snake Venom

1993 ◽  
Vol 69 (03) ◽  
pp. 286-292 ◽  
Author(s):  
Che-Ming Teng ◽  
Feng-Nien Ko ◽  
Inn-Ho Tsai ◽  
Man-Ling Hung ◽  
Tur-Fu Huang
Keyword(s):  
Platelet Aggregation ◽  
Snake Venom ◽  
Inositol Phosphate ◽  
Shape Change ◽  
Platelet Activating Factor ◽  
Atp Release ◽  
Platelet Membrane ◽  
Thromboxane B2 ◽  
Dependent Manner ◽  
Concentration Dependent Manner

SummaryTrimucytin is a potent platelet aggregation inducer isolated from Trimeresurus mucrosquamatus snake venom. Similar to collagen, trimucytin has a run of (Gly-Pro-X) repeats at the N-terminal amino acids sequence. It induced platelet aggregation, ATP release and thromboxane formation in rabbit platelets in a concentration-dependent manner. The aggregation was not due to released ADP since it was not suppressed by creatine phosphate/creatine phosphokinase. It was not either due to thromboxane A2 formation because indomethacin and BW755C did not have any effect on the aggregation even thromboxane B2 formation was completely abolished by indomethacin. Platelet-activating factor (PAF) was not involved in the aggregation since a PAF antagonist, kadsurenone, did not affect. However, RGD-containing peptide triflavin inhibited the aggregation, but not the release of ATP, of platelets induced by trimucytin. Indomethacin, mepacrine, prostaglandin E1 and tetracaine inhibited the thromboxane B2 formation of platelets caused by collagen and trimucytin. Forskolin and sodium nitroprusside inhibited both platelet aggregation and ATP release, but not the shape change induced by trimucytin. In quin-2 loaded platelets, the rise of intracellular calcium concentration caused by trimucytin was decreased by 12-O-tetradecanoyl phorbol-13 acetate, imipramine, TMB-8 and indomethacin. In the absence of extracellular calcium, both collagen and trimucytin caused no thromboxane B2 formation, but still induced ATP release which was completely blocked by R 59022. Inositol phosphate formation in platelets was markedly enhanced by trimucytin and collagen. MAB1988, an antibody against platelet membrane glycoprotein Ia, inhibited trimucytinand collagen-induced platelet aggregation and ATP release. However, trimucytin did not replace the binding of 125I-labeled MAB1988 to platelets. Platelets pre-exposed to trimucytin were resistant to the second challenge with trimucytin itself or collagen. It is concluded that trimucytin may activate collagen receptors on platelet membrane, and cause aggregation and release mainly through phospholipase C-phosphoinositide pathway.

Influence of Brain Gangliosides on the Formation and Properties of Supported Lipid Bilayers for Binding Kinetics Studies

2018 ◽  
Author(s):  
Luke Jordan ◽  
Nathan Wittenberg
Keyword(s):  
Lipid Bilayers ◽  
Binding Kinetics ◽  
Supported Lipid Bilayers ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Supported Lipid Bilayer ◽  
Head Groups ◽  
Lipid Diffusion ◽  
Kinetics Of ◽  
Brain Gangliosides

This is a comprehensive study of the effects of the four major brain gangliosides (GM1, GD1b, GD1a, and GT1b) on the adsorption and rupture of phospholipid vesicles on SiO2 surfaces for the formation of supported lipid bilayer (SLB) membranes. Using quartz crystal microbalance with dissipation monitoring (QCM-D) we show that gangliosides GD1a and GT1b significantly slow the SLB formation process, whereas GM1 and GD1b have smaller effects. This is likely due to the net ganglioside charge as well as the positions of acidic sugar groups on ganglioside glycan head groups. Data is included that shows calcium can accelerate the formation of ganglioside-rich SLBs. Using fluorescence recovery after photobleaching (FRAP) we also show that the presence of gangliosides significantly reduces lipid diffusion coefficients in SLBs in a concentration-dependent manner. Finally, using QCM-D and GD1a-rich SLB membranes we measure the binding kinetics of an anti-GD1a antibody that has similarities to a monoclonal antibody that is a hallmark of a variant of Guillain-Barre syndrome.

Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

1998 ◽  
Vol 38 (6) ◽  
pp. 147-154 ◽  
Author(s):  
Hideo Utsumi ◽  
Sang-Kuk Han ◽  
Kazuhiro Ichikawa
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Spin Trapping ◽  
Active Species ◽  
Generation Rate ◽  
Peak Height Ratio ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Phenol Derivatives ◽  
Semiquinone Radicals

Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

Chickpea (Cicer arietinum L.) Lectin Exhibit Inhibition of ACE-I, α-amylase and α-glucosidase Activity

2019 ◽  
Vol 26 (7) ◽  
pp. 494-501 ◽  
Author(s):  
Sameer Suresh Bhagyawant ◽  
Dakshita Tanaji Narvekar ◽  
Neha Gupta ◽  
Amita Bhadkaria ◽  
Ajay Kumar Gautam ◽  
...  
Keyword(s):  
Biological Effects ◽  
Exchange Chromatography ◽  
Health Concern ◽  
Carbohydrate Binding ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ic50 Values ◽  
Chickpea Lectin

Background: Diabetes and hypertension are the major health concern and alleged to be of epidemic proportions. This has made it a numero uno subject at various levels of investigation. Glucosidase inhibitor provides the reasonable option in treatment of Diabetes Mellitus (DM) as it specifically targets post prandial hyperglycemia. The Angiotensin Converting Enzyme (ACE) plays an important role in hypertension. Therefore, inhibition of ACE in treatment of elevated blood pressure attracts special interest of the scientific community. Chickpea is a food legume and seeds contain carbohydrate binding protein- a lectin. Some of the biological properties of this lectin hitherto been elucidated. Methods: Purified by ion exchange chromatography, chickpea lectin was tested for its in vitro antioxidant, ACE-I inhibitory and anti-diabetic characteristic. Results: Lectin shows a characteristic improvement over the synthetic drugs like acarbose (oral anti-diabetic drug) and captopril (standard antihypertensive drug) when, their IC50 values are compared. Lectin significantly inhibited α-glucosidase and α-amylase in a concentration dependent manner with IC50 values of 85.41 ± 1.21 ҝg/ml and 65.05 ± 1.2 µg/ml compared to acarbose having IC50 70.20 ± 0.47 value of µg/ml and 50.52 ± 1.01 µg/ml respectively. β-Carotene bleaching assay showed antioxidant activity of lectin (72.3%) to be as active as Butylated Hydroxylanisole (BHA). In addition, lectin demonstrated inhibition against ACE-I with IC50 value of 57.43 ± 1.20 µg/ml compared to captopril. Conclusion: Lectin demonstrated its antioxidant character, ACE-I inhibition and significantly inhibitory for α-glucosidase and α-amylase seems to qualify as an anti-hyperglycemic therapeutic molecule. The biological effects of chickpea lectin display potential for reducing the parameters of medically debilitating conditions. These characteristics however needs to be established under in vivo systems too viz. animals through to humans.

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