Publications by authors named "Shlomo Sasson"

41 Publications

Investigation of the Membrane Fluidity Regulation of Fatty Acid Intracellular Distribution by Fluorescence Lifetime Imaging of Novel Polarity Sensitive Fluorescent Derivatives.

Int J Mol Sci 2021 Mar 18;22(6). Epub 2021 Mar 18.

Neuroscience Department, Biophysics Section, Università Cattolica del Sacro Cuore, 00168 Rome, Italy.

Free fatty acids are essential structural components of the cell, and their intracellular distribution and effects on membrane organelles have crucial roles in regulating the metabolism, development, and cell cycle of most cell types. Here we engineered novel fluorescent, polarity-sensitive fatty acid derivatives, with the fatty acid aliphatic chain of increasing length (from 12 to 18 carbons). As in the laurdan probe, the lipophilic acyl tail is connected to the environmentally sensitive dimethylaminonaphthalene moiety. The fluorescence lifetime imaging analysis allowed us to monitor the intracellular distribution of the free fatty acids within the cell, and to simultaneously examine how the fluidity and the microviscosity of the membrane environment influence their localization. Each of these probes can thus be used to investigate the membrane fluidity regulation of the correspondent fatty acid intracellular distribution. We observed that, in PC-12 cells, fluorescent sensitive fatty acid derivatives with increased chain length compartmentalize more preferentially in the fluid regions, characterized by a low microviscosity. Moreover, fatty acid derivatives with the longest chain compartmentalize in lipid droplets and lysosomes with characteristic lifetimes, thus making these probes a promising tool for monitoring lipophagy and related events.
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http://dx.doi.org/10.3390/ijms22063106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8002861PMC
March 2021

Endothelial Cell-Derived Triosephosphate Isomerase Attenuates Insulin Secretion From Pancreatic Beta Cells of Male Rats.

Endocrinology 2021 Mar;162(3)

Institute for Drug Research, Department of Pharmacology, School of Pharmacy, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.

Insulin secretion from pancreatic beta cells is tightly regulated by glucose and paracrine signals within the microenvironment of islets of Langerhans. Extracellular matrix from islet microcapillary endothelial cells (IMEC) affect beta-cell spreading and amplify insulin secretion. This study was aimed at investigating the hypothesis that contact-independent paracrine signals generated from IMEC may also modulate beta-cell insulin secretory functions. For this purpose, conditioned medium (CMp) preparations were prepared from primary cultures of rat IMEC and were used to simulate contact-independent beta cell-endothelial cell communication. Glucose-stimulated insulin secretion (GSIS) assays were then performed on freshly isolated rat islets and the INS-1E insulinoma cell line, followed by fractionation of the CMp, mass spectroscopic identification of the factor, and characterization of the mechanism of action. The IMEC-derived CMp markedly attenuated first- and second-phase GSIS in a time- and dose-dependent manner without altering cellular insulin content and cell viability. Size exclusion fractionation, chromatographic and mass-spectroscopic analyses of the CMp identified the attenuating factor as the enzyme triosephosphate isomerase (TPI). An antibody against TPI abrogated the attenuating activity of the CMp while recombinant human TPI (hTPI) attenuated GSIS from beta cells. This effect was reversed in the presence of tolbutamide in the GSIS assay. In silico docking simulation identified regions on the TPI dimer that were important for potential interactions with the extracellular epitopes of the sulfonylurea receptor in the complex. This study supports the hypothesis that an effective paracrine interaction exists between IMEC and beta cells and modulates glucose-induced insulin secretion via TPI-sulfonylurea receptor-KATP channel (SUR1-Kir6.2) complex attenuating interactions.
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http://dx.doi.org/10.1210/endocr/bqaa234DOI Listing
March 2021

Endothelial Cell-Derived Triosephosphate Isomerase Attenuates Insulin Secretion From Pancreatic Beta Cells of Male Rats.

Endocrinology 2021 Mar;162(3)

Institute for Drug Research, Department of Pharmacology, School of Pharmacy, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.

Insulin secretion from pancreatic beta cells is tightly regulated by glucose and paracrine signals within the microenvironment of islets of Langerhans. Extracellular matrix from islet microcapillary endothelial cells (IMEC) affect beta-cell spreading and amplify insulin secretion. This study was aimed at investigating the hypothesis that contact-independent paracrine signals generated from IMEC may also modulate beta-cell insulin secretory functions. For this purpose, conditioned medium (CMp) preparations were prepared from primary cultures of rat IMEC and were used to simulate contact-independent beta cell-endothelial cell communication. Glucose-stimulated insulin secretion (GSIS) assays were then performed on freshly isolated rat islets and the INS-1E insulinoma cell line, followed by fractionation of the CMp, mass spectroscopic identification of the factor, and characterization of the mechanism of action. The IMEC-derived CMp markedly attenuated first- and second-phase GSIS in a time- and dose-dependent manner without altering cellular insulin content and cell viability. Size exclusion fractionation, chromatographic and mass-spectroscopic analyses of the CMp identified the attenuating factor as the enzyme triosephosphate isomerase (TPI). An antibody against TPI abrogated the attenuating activity of the CMp while recombinant human TPI (hTPI) attenuated GSIS from beta cells. This effect was reversed in the presence of tolbutamide in the GSIS assay. In silico docking simulation identified regions on the TPI dimer that were important for potential interactions with the extracellular epitopes of the sulfonylurea receptor in the complex. This study supports the hypothesis that an effective paracrine interaction exists between IMEC and beta cells and modulates glucose-induced insulin secretion via TPI-sulfonylurea receptor-KATP channel (SUR1-Kir6.2) complex attenuating interactions.
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http://dx.doi.org/10.1210/endocr/bqaa234DOI Listing
March 2021

The Combination of Whole Cell Lipidomics Analysis and Single Cell Confocal Imaging of Fluidity and Micropolarity Provides Insight into Stress-Induced Lipid Turnover in Subcellular Organelles of Pancreatic Beta Cells.

Molecules 2019 Oct 17;24(20). Epub 2019 Oct 17.

Institute for Drug Research, Faculty of Medicine, The Hebrew University, 911210 Jerusalem, Israel.

Modern omics techniques reveal molecular structures and cellular networks of tissues and cells in unprecedented detail. Recent advances in single cell analysis have further revolutionized all disciplines in cellular and molecular biology. These methods have also been employed in current investigations on the structure and function of insulin secreting beta cells under normal and pathological conditions that lead to an impaired glucose tolerance and type 2 diabetes. Proteomic and transcriptomic analyses have pointed to significant alterations in protein expression and function in beta cells exposed to diabetes like conditions (e.g., high glucose and/or saturated fatty acids levels). These nutritional overload stressful conditions are often defined as glucolipotoxic due to the progressive damage they cause to the cells. Our recent studies on the rat insulinoma-derived INS-1E beta cell line point to differential effects of such conditions in the phospholipid bilayers in beta cells. This review focuses on confocal microscopy-based detection of these profound alterations in the plasma membrane and membranes of insulin granules and lipid droplets in single beta cells under such nutritional load conditions.
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http://dx.doi.org/10.3390/molecules24203742DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6833103PMC
October 2019

Qualitative analysis of phospholipids and their oxidised derivatives - used techniques and examples of their applications related to lipidomic research and food analysis.

Free Radic Res 2019 5;53(sup1):1068-1100. Epub 2019 Sep 5.

Department of Food Chemistry, Technology and Biotechnology, Faculty of Chemistry, Gdansk University of Technology, Gdańsk, Poland.

Phospholipids (PLs) are important biomolecules that not only constitute structural building blocks and scaffolds of cell and organelle membranes but also play a vital role in cell biochemistry and physiology. Moreover, dietary exogenous PLs are characterised by high nutritional value and other beneficial health effects, which are confirmed by numerous epidemiological studies. For this reason, PLs are of high interest in that targets both the analysis of membrane lipid distribution as well as correlates composition of lipids with their effects on functioning of cells, tissues and organs. Lipidomic assessments follow-up the changes occurring in living organisms, such as free radical attack and oxidative modifications of the polyunsaturated fatty acids (PUFAs) build in PL structures. Oxidised PLs (oxPLs) can be generated exogenously and supplied to organisms with processed food or formed endogenously as a result of oxidative stress. Cellular and tissue oxPLs can be a biomarker predictive of the development of numerous diseases such as atherosclerosis or neuroinflammation. Therefore, suitable high-throughput analytical techniques, which enable comprehensive analysis of PL molecules in terms of the structure of hydrophilic group, fatty acid (FA) composition and oxidative modifications of FAs, have been currently developed. This review addresses all aspects of PL analysis, including lipid isolation, chromatographic separation of PL classes and species, as well as their detection. The bioinformatic tools that enable handling of a large amount of data generated during lipidomic analysis are also discussed. In addition, imaging techniques such as confocal microscopy and mass spectrometry imaging for analysis of cellular lipid maps, including membrane PLs, are presented.
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http://dx.doi.org/10.1080/10715762.2019.1657573DOI Listing
April 2020

Catalyzing Transcriptomics Research in Cardiovascular Disease: The CardioRNA COST Action CA17129.

Noncoding RNA 2019 03 29;5(2). Epub 2019 Mar 29.

Research Unit of Biomedicine, University of Oulu, 90014 Oulu, Finland.

Cardiovascular disease (CVD) remains the leading cause of death worldwide and, despite continuous advances, better diagnostic and prognostic tools, as well as therapy, are needed. The human transcriptome, which is the set of all RNA produced in a cell, is much more complex than previously thought and the lack of dialogue between researchers and industrials and consensus on guidelines to generate data make it harder to compare and reproduce results. This European Cooperation in Science and Technology (COST) Action aims to accelerate the understanding of transcriptomics in CVD and further the translation of experimental data into usable applications to improve personalized medicine in this field by creating an interdisciplinary network. It aims to provide opportunities for collaboration between stakeholders from complementary backgrounds, allowing the functions of different RNAs and their interactions to be more rapidly deciphered in the cardiovascular context for translation into the clinic, thus fostering personalized medicine and meeting a current public health challenge. Thus, this Action will advance studies on cardiovascular transcriptomics, generate innovative projects, and consolidate the leadership of European research groups in the field.COST (European Cooperation in Science and Technology) is a funding organization for research and innovation networks (www.cost.eu).
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http://dx.doi.org/10.3390/ncrna5020031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6630366PMC
March 2019

Impact of apolipoprotein A1- or lecithin:cholesterol acyltransferase-deficiency on white adipose tissue metabolic activity and glucose homeostasis in mice.

Biochim Biophys Acta Mol Basis Dis 2019 06 10;1865(6):1351-1360. Epub 2019 Feb 10.

University of Patras, School of Medicine, Department of Pharmacology, Rio, Achaias, TK. 26500, Greece. Electronic address:

High density lipoprotein (HDL) has attracted the attention of biomedical community due to its well-documented role in atheroprotection. HDL has also been recently implicated in the regulation of islets of Langerhans secretory function and in the etiology of peripheral insulin sensitivity. Indeed, data from numerous studies strongly indicate that the functions of pancreatic β-cells, skeletal muscles and adipose tissue could benefit from improved HDL functionality. To better understand how changes in HDL structure may affect diet-induced obesity and type 2 diabetes we aimed at investigating the impact of Apoa1 or Lcat deficiency, two key proteins of peripheral HDL metabolic pathway, on these pathological conditions in mouse models. We report that universal deletion of apoa1 or lcat expression in mice fed western-type diet results in increased sensitivity to body-weight gain compared to control C57BL/6 group. These changes in mouse genome correlate with discrete effects on white adipose tissue (WAT) metabolic activation and plasma glucose homeostasis. Apoa1-deficiency results in reduced WAT mitochondrial non-shivering thermogenesis. Lcat-deficiency causes a concerted reduction in both WAT oxidative phosphorylation and non-shivering thermogenesis, rendering lcat mice the most sensitive to weight gain out of the three strains tested, followed by apoa1 mice. Nevertheless, only apoa1 mice show disturbed plasma glucose homeostasis due to dysfunctional glucose-stimulated insulin secretion in pancreatic β-islets and insulin resistant skeletal muscles. Our analyses show that both apoa1 and lcat mice fed high-fat diet have no measurable Apoa1 levels in their plasma, suggesting no direct involvement of Apoa1 in the observed phenotypic differences among groups.
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http://dx.doi.org/10.1016/j.bbadis.2019.02.003DOI Listing
June 2019

Development of a novel monoclonal antibody against 4-hydroxy-2E,6Z-dodecadienal (4-HDDE)-protein adducts: Immunochemical application in quantitative and qualitative analyses of lipid peroxidation in vitro and ex vivo.

Free Radic Biol Med 2018 08 25;124:12-20. Epub 2018 May 25.

Institute for Drug Research, Faculty of Medicine, Hebrew University, Jerusalem 9112001, Israel. Electronic address:

Non-enzymatic peroxidation of polyunsaturated fatty acids (PUFA) results in the formation of various α,β-unsaturated aldehydes, of which 4-hydroxyalkenals are abundant. The propensity of n-6 PUFA, such as linoleic acid, γ-linolenic acid and arachidonic acid, to undergo radical-induced peroxidation and generate 4-hydroxy-2E-nonenal (4-HNE) has been widely demonstrated. The ability of the latter to form covalent adducts with macromolecules and modify cellular functions has been linked to numerous pathological processes. Concomitantly, evidence has accumulated on specific signaling properties of low concentrations of 4-HNE that may induce hormetic and protective responses to peroxidation stress in cells. It has long been known that peroxidation of PUFA, and particularly arachidonic acid, also give rise to 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), which is more chemically reactive than 4-HNE. Few studies on 4-HDDE revealed its ability to avidly interact covalently with electronegative moieties in macromolecules and to its ability to selectively activate the transcriptional regulator Peroxisome Proliferator-Activated Receptor (PPAR)-β/δ. The research on 4-HDDE has been impeded due to the lack of available pure 4-HDDE and antibodies that recognize 4-HDDE-modified epitopes in proteins. The purpose of this study was to employ an established procedure to synthesize 4-HDDE and use it to create and characterize a monoclonal antibody against 4-HDDE-modified proteins and establish its application for ELISA and immunohistochemical analysis of cells and tissues and further expand lipid peroxidation research.
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http://dx.doi.org/10.1016/j.freeradbiomed.2018.05.079DOI Listing
August 2018

Real time quantitative analysis of lipid storage and lipolysis pathways by confocal spectral imaging of intracellular micropolarity.

Biochim Biophys Acta Mol Cell Biol Lipids 2018 07 11;1863(7):783-793. Epub 2018 Apr 11.

Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 9112001, Israel.

Organisms store fatty acids in triacylglycerols in the form of lipid droplets, or hydrolyze triacylglycerols in response to energetic demands via activation of lipolytic or storage pathways. These pathways are complex sets of sequential reactions that are finely regulated in different cell types. Here we present a high spatial and temporal resolution-based method for the quantification of the turnover of fatty acids into triglycerides in live cells without introducing sample preparation artifacts. We performed confocal spectral imaging of intracellular micropolarity in cultured insulin secreting beta cells to detect micropolarity variations as they occur in time and at different pixels of microscope images. Acquired data are then analyzed in the framework of the spectral phasors technique. The method furnishes a metabolic parameter, which quantitatively assesses fatty acids - triacylglycerols turnover and the activation of lipolysis and storage pathways. Moreover, it provides a polarity profile, which represents the contribution of hyperpolar, polar and non-polar classes of lipids. These three different classes can be visualized on the image at a submicrometer resolution, revealing the spatial localization of lipids in cells under physiological and pathological settings. This new method allows for a fine-tuned, real-time visualization of the turnover of fatty acids into triglycerides in live cells with submicrometric resolution. It also detects imbalances between lipid storage and usage, which may lead to metabolic disorders within living cells and organisms.
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http://dx.doi.org/10.1016/j.bbalip.2018.04.004DOI Listing
July 2018

A Novel Phenylchromane Derivative Increases the Rate of Glucose Uptake in L6 Myotubes and Augments Insulin Secretion from Pancreatic Beta-Cells by Activating AMPK.

Pharm Res 2017 Dec 5;34(12):2873-2890. Epub 2017 Oct 5.

Division of Medicinal Chemistry, Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, 52900, Ramat-Gan, Israel.

Purpose: A series of novel polycyclic aromatic compounds that augment the rate of glucose uptake in L6 myotubes and increase glucose-stimulated insulin secretion from beta-cells were synthesized. Designing these molecules, we have aimed at the two main pathogenic mechanisms of T2D, deficient insulin secretion and diminished glucose clearance. The ultimate purpose of this work was to create a novel antidiabetic drug candidate with bi-functional mode of action.

Methods: All presented compounds were synthesized, and characterized in house. INS-1E cells and L6 myoblasts were used for the experiments. The rate of glucose uptake, mechanism of action, level of insulin secretion and the druggability of the lead compound were studied.

Results: The lead compound (6-(1,3-dithiepan-2-yl)-2-phenylchromane), dose- and time-dependently at the low μM range increased the rate of glucose uptake in L6 myotubes and insulin secretion in INS-1E cells. The compound exerted its effects through the activation of the LKB1 (Liver Kinase B1)-AMPK pathway. In vitro metabolic parameters of this lead compound exhibited good druggability.

Conclusions: We anticipate that bi-functionality (increased rate of glucose uptake and augmented insulin secretion) will allow the lead compound to be a starting point for the development of a novel class of antidiabetic drugs.
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http://dx.doi.org/10.1007/s11095-017-2271-7DOI Listing
December 2017

Supportive data on the regulation of GLUT4 activity by 3-O-methyl-D-glucose.

Data Brief 2017 Oct 28;14:329-336. Epub 2017 Jul 28.

The Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel.

The data presented in this article are related to the research article entitled "Regulation of GLUT4 activity in myotubes by 3-O-methyl-D-glucose" (Shamni et al., 2017) [1]. These data show that the experimental procedures used to analyze the effects of 3-O-methyl-D-glucose (MeGlc) on the rate of hexose transport into myotubes were valid and controlled. The stimulatory effect of MeGlc was limited to glucose transporter 4 (GLUT4) and was independent of ambient glucose and protein synthesis. Cornish-Bowden kinetic analysis of uptake data revealed that MeGlc attenuated indinavir-induced inhibition of hexose transport in a competitive manner.
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http://dx.doi.org/10.1016/j.dib.2017.07.069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5547241PMC
October 2017

Regulation of GLUT4 activity in myotubes by 3-O-methyl-d-glucose.

Biochim Biophys Acta Biomembr 2017 Oct 23;1859(10):1900-1910. Epub 2017 Jun 23.

Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel. Electronic address:

The rate of glucose influx to skeletal muscles is determined primarily by the number of functional units of glucose transporter-4 (GLUT4) in the myotube plasma membrane. The abundance of GLUT4 in the plasma membrane is tightly regulated by insulin or contractile activity, which employ distinct pathways to translocate GLUT4-rich vesicles from intracellular compartments. Various studies have indicated that GLUT4 intrinsic activity is also regulated by conformational changes and/or interactions with membrane components and intracellular proteins in the vicinity of the plasma membrane. Here we show that the non-metabolizable glucose analog 3-O-methyl-d-glucose (MeGlc) augmented the rate of hexose transport into myotubes by increasing GLUT4 intrinsic activity without altering the content of the transporter in the plasma membrane. This effect was not a consequence of ATP depletion or hyperosmolar stress and did not involve Akt/PKB or AMPK signal transduction pathways. MeGlc reduced the inhibitory potency (increased K) of indinavir, a selective inhibitor of GLUT4, in a dose-dependent manner. Kinetic analyses indicate that MeGlc induced changes in GLUT4 or GLUT4 complexes within the plasma membrane, which enhanced the hexose transport activity and reduced the potency of indinavir inhibition. Finally, we present a simple kinetic analysis for screening and discovering low molecular weight compounds that augment GLUT4 activity.
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http://dx.doi.org/10.1016/j.bbamem.2017.06.013DOI Listing
October 2017

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS).

Redox Biol 2017 10 18;13:94-162. Epub 2017 May 18.

Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, Portugal; Faculdade de Ciências da Saúde, Universidade da Beira Interior, Covilhã, Portugal.

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.
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http://dx.doi.org/10.1016/j.redox.2017.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5458069PMC
October 2017

4-Hydroxyalkenal-activated PPARδ mediates hormetic interactions in diabetes.

Authors:
Shlomo Sasson

Biochimie 2017 May 18;136:85-89. Epub 2016 Oct 18.

Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Hebrew University Faculty of Medicine, Jerusalem, 9112001, Israel. Electronic address:

Activated peroxisome proliferator-activated receptor-δ (PPARδ) induces the expression of genes encoding enzymes that metabolize fatty acids and carbohydrate. Attempts to identify cellular activators of PPARδ produced large lists of various fatty acids and their metabolic derivatives; however, there is no consensus on specific and selective binding interactions of natural ligands with PPARδ. Most models on binding interactions within the ligand binding domain (LBD) of PPARδ have been derived from analyses of PPARδ-LBD crystals formed with synthetic low molecular weight ligands. Nonetheless, crystals of the whole receptor with natural ligands or of its heterodimer with its cognate retinoid X receptor (RXR) are not yet available for analysis. We have found that 4-hydroxyalkenals, non-enzymatic peroxidation products of polyunsaturated fatty acids (PUFA), namely, 4-hydroxy-2E,6Z-dodecadienal (4-HDDE) and 4-hydroxy-2E-nonenal (4-HNE), activate PPARδ in vascular endothelial cells and insulin-secreting beta cells, respectively. In both cases activated PPARδ induced adaptive responses that allowed the cells to adjust to ambient stressful metabolic conditions. This review article addresses the interactions of 4-hydroxyalkenals with PPARδ and the resulting hormetic interactions in cells exposed to nutrient overload conditions.
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http://dx.doi.org/10.1016/j.biochi.2016.10.007DOI Listing
May 2017

Nutrient overload, lipid peroxidation and pancreatic beta cell function.

Authors:
Shlomo Sasson

Free Radic Biol Med 2017 10 4;111:102-109. Epub 2016 Sep 4.

Institute for Drug Research, Section of Pharmacology, Diabetes Research Unit, Hebrew University Faculty of Medicine, Jerusalem 9112001, Israel. Electronic address:

Since the landmark discovery of α,β-unsaturated 4-hydroxyalkenals by Esterbauer and colleagues most studies have addressed the consequences of the tendency of these lipid peroxidation products to form covalent adducts with macromolecules and modify cellular functions. Many studies describe detrimental and cytotoxic effects of 4-hydroxy-2E-nonenal (4-HNE) in myriad tissues and organs and many pathologies. Other studies similarly assigned unfavorable effects to 4-hydroxy-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE). Nutrient overload (e.g., hyperglycemia, hyperlipidemia) modifies lipid metabolism in cells and promotes lipid peroxidation and the generation of α,β-unsaturated 4-hydroxyalkenals. Advances glycation- and lipoxidation end products (AGEs and ALEs) have been associated with the development of insulin resistance and pancreatic beta cell dysfunction and the etiology of type 2 diabetes and its peripheral complications. Less acknowledged are genuine signaling properties of 4-hydroxyalkenals in hormetic processes that provide defense against the consequences of nutrient overload. This review addresses recent findings on such lipohormetic mechanisms that are associated with lipid peroxidation in pancreatic beta cells. This article is part of a Special Issue entitled SI: LIPID OXIDATION PRODUCTS, edited by Giuseppe Poli.
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http://dx.doi.org/10.1016/j.freeradbiomed.2016.09.003DOI Listing
October 2017

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells.

Mol Aspects Med 2016 06 21;49:49-77. Epub 2016 Mar 21.

Department of Pharmacology, Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel. Electronic address:

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.
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http://dx.doi.org/10.1016/j.mam.2016.03.001DOI Listing
June 2016

Deficiency in apolipoprotein A-I ablates the pharmacological effects of metformin on plasma glucose homeostasis and hepatic lipid deposition.

Eur J Pharmacol 2015 Nov 28;766:76-85. Epub 2015 Sep 28.

Pharmacology Department, University of Patras Medical School, Rio, Achaias TK 26500, Greece. Electronic address:

Recently, we showed that deficiency in apolipoprotein A-I (ApoA-I) sensitizes mice to diet-induced obesity, glucose intolerance and NAFLD. Here we investigated the potential involvement of ApoA-I in the pharmacological effects of metformin on glucose intolerance and NAFLD development. Groups of apoa1-deficient (apoa1(-/-)) and C57BL/6 mice fed western-type diet were either treated with a daily dose of 300 mg/kg metformin for 18 weeks or left untreated for the same period. Then, histological and biochemical analyses were performed. Metformin treatment led to a comparable reduction in plasma insulin levels in both C57BL/6 and apoa1(-/-) mice following intraperitoneal glucose tolerance test. However, only metformin-treated C57BL/6 mice maintained sufficient peripheral insulin sensitivity to effectively clear glucose following the challenge, as indicated by a [(3)H]-2-deoxy-D-glucose uptake assay in isolated soleus muscle. Similarly, deficiency in ApoA-I ablated the effect of metformin on hepatic lipid deposition and NAFLD development. Gene expression analysis indicated that the effects of ApoA-I on metformin treatment may be independent of adenosine monophosphate-activated protein kinase (AMPK) activation and de novo lipogenesis. Interestingly, metformin treatment reduced mitochondrial oxidative phosphorylation function only in apoa1(-/-) mice. Our data show that the role of ApoA-I in diabetes extends to the modulation of the pharmacological actions of metformin, a common drug for the treatment of type 2 diabetes.
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http://dx.doi.org/10.1016/j.ejphar.2015.09.040DOI Listing
November 2015

Hyperlipidemia-induced hepatic and small intestine ER stress and decreased paraoxonase 1 expression and activity is associated with HDL dysfunction in Syrian hamsters.

Mol Nutr Food Res 2015 Nov 13;59(11):2293-302. Epub 2015 Sep 13.

Department of Lipidomics, Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, Bucharest, Romania.

Scope: We aimed at investigating the mechanisms linking hyperlipidemia (HL) with dysfunctional HDL and its main antioxidant enzyme, paraoxonase1 (PON1). PON1 expression and activity was determined in the small intestine, liver, and sera of normal and HL hamsters and associated with the ER stress (ERS) and the development of aortic valve lesions.

Methods And Results: Male Golden Syrian hamsters were fed standard chow (N) or standard diet with 3% cholesterol and 15% butter for 16 weeks. All hamsters on fat diet developed HL, 50% also hyperglycemia (HLHG) and a fourfold increased homeostasis model assessment of insuline resistance. PON1 expression was reduced in the small intestine and liver (N > HL > HLHG) along with the increased extent of ERS, oxidized lipids, and decreased expression of liver X receptors beta (LXRβ) in the small intestine, peroxisome proliferator-activated receptor-γ (PPARγ) in the liver, and of the glucose transporter 4 in the myocardium. Serum PON1 levels decreased along with the increase of oxidized LDL and lesion areas of the aortic valves (N > HL > HLHG).

Conclusion: The fat diet activates the ERS and oxidative stress, decreases LXRβ, PPARγ, and PON1 in the small intestine, liver, and sera of all HL animals, in parallel with the appearance of atherosclerotic lesions in the aortic valves.
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http://dx.doi.org/10.1002/mnfr.201500422DOI Listing
November 2015

Regulation of Nox enzymes expression in vascular pathophysiology: Focusing on transcription factors and epigenetic mechanisms.

Redox Biol 2015 Aug 25;5:358-366. Epub 2015 Jun 25.

Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, 8, B.P. Hasdeu Street, 050568 Bucharest, Romania. Electronic address:

NADPH oxidases (Nox) represent a family of hetero-oligomeric enzymes whose exclusive biological function is the generation of reactive oxygen species (ROS). Nox-derived ROS are essential modulators of signal transduction pathways that control key physiological activities such as cell growth, proliferation, migration, differentiation, and apoptosis, immune responses, and biochemical pathways. Enhanced formation of Nox-derived ROS, which is generally associated with the up-regulation of different Nox subtypes, has been established in various pathologies, namely cardiovascular diseases, diabetes, obesity, cancer, and neurodegeneration. The detrimental effects of Nox-derived ROS are related to alterations in cell signalling and/or direct irreversible oxidative damage of nucleic acids, proteins, carbohydrates, and lipids. Thus, understanding of transcriptional regulation mechanisms of Nox enzymes have been extensively investigated in an attempt to find ways to counteract the excessive formation of Nox-derived ROS in various pathological states. Despite the numerous existing data, the molecular pathways responsible for Nox up-regulation are not completely understood. This review article summarizes some of the recent advances and concepts related to the regulation of Nox expression in the vascular pathophysiology. It highlights the role of transcription factors and epigenetic mechanisms in this process. Identification of the signalling molecules involved in Nox up-regulation, which is associated with the onset and development of cardiovascular dysfunction may contribute to the development of novel strategies for the treatment of cardiovascular diseases.
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http://dx.doi.org/10.1016/j.redox.2015.06.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4501559PMC
August 2015

Beta cell response to nutrient overload involves phospholipid remodelling and lipid peroxidation.

Diabetologia 2015 Jun 26;58(6):1333-43. Epub 2015 Mar 26.

Department of Pharmacology, Institute for Drug Research, Faculty of Medicine, The Hebrew University, Jerusalem, 9112102, Israel.

Aims/hypothesis: Membrane phospholipids are the major intracellular source for fatty acid-derived mediators, which regulate myriad cell functions. We showed previously that high glucose levels triggered the hydrolysis of polyunsaturated fatty acids from beta cell phospholipids. These fatty acids were subjected to free radical-catalysed peroxidation to generate the bioactive aldehyde 4-hydroxy-2E-nonenal (4-HNE). The latter activated the nuclear peroxisome proliferator-activated receptor-δ (PPARδ), which in turn augmented glucose-stimulated insulin secretion. The present study aimed at investigating the combined effects of glucose and fatty acid overload on phospholipid turnover and the subsequent generation of lipid mediators, which affect insulin secretion and beta cell viability.

Methods: INS-1E cells were incubated with increasing glucose concentrations (5-25 mmol/l) without or with palmitic acid (PA; 50-500 μmol/l) and taken for fatty acid-based lipidomic analysis and functional assays. Rat isolated islets of Langerhans were used similarly.

Results: PA was incorporated into membrane phospholipids in a concentration- and time-dependent manner; incorporation was highest at 25 mmol/l glucose. This was coupled to a rapid exchange with saturated, mono-unsaturated and polyunsaturated fatty acids. Importantly, released arachidonic acid and linoleic acid were subjected to peroxidation, resulting in the generation of 4-HNE, which further augmented insulin secretion by activating PPARδ in beta cells. However, this adaptive increase in insulin secretion was abolished at high glucose and PA levels, which induced endoplasmic reticulum stress, apoptosis and cell death.

Conclusions/interpretation: These findings highlight a key role for phospholipid remodelling and fatty acid peroxidation in mediating adaptive and cytotoxic interactions induced by nutrient overload in beta cells.
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http://dx.doi.org/10.1007/s00125-015-3566-zDOI Listing
June 2015

Foam cell-derived 4-hydroxynonenal induces endothelial cell senescence in a TXNIP-dependent manner.

J Cell Mol Med 2015 Aug 5;19(8):1887-99. Epub 2015 Mar 5.

Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.

Vascular endothelial cell (VEC) senescence is considered an early event in the development of atherosclerotic lesions. Stressful stimuli, in particular oxidative stress, have been linked to premature senescence in the vasculature. Foam cells are a major source of reactive oxygen species and may play a role in the induction of VEC senescence; hence, we investigated their involvement in the induction of VEC senescence in a co-culture transwell system. Primary bovine aortic endothelial cells, exposed to the secretome of THP-1 monocyte-derived foam cells, were analysed for the induction of senescence. Senescence associated β-galactosidase activity and the expression of p16 and p21 were increased, whereas phosphorylated retinoblastoma protein was reduced. This senescent phenotype was mediated by 4-hydroxnonenal (4-HNE), a lipid peroxidation product secreted from foam cells; scavenging of 4-HNE in the co-culture medium blunted this effect. Furthermore, both foam cells and 4-HNE increased the expression of the pro-oxidant thioredoxin-interacting protein (TXNIP). Molecular manipulation of TXNIP expression confirmed its involvement in foam cell-induced senescence. Previous studies showed that peroxisome proliferator-activated receptor (PPAR)δ was activated by 4-hydroalkenals, such as 4-HNE. Pharmacological interventions supported the involvement of the 4-HNE-PPARδ axis in the induction of TXNIP and VEC senescence. The association of TXNIP with VEC senescence was further supported by immunofluorescent staining of human carotid plaques in which the expression of both TXNIP and p21 was augmented in endothelial cells. Collectively, these findings suggest that foam cell-released 4-HNE activates PPARδ in VEC, leading to increased TXNIP expression and consequently to senescence.
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http://dx.doi.org/10.1111/jcmm.12561DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4549039PMC
August 2015

High-glucose-increased expression and activation of NADPH oxidase in human vascular smooth muscle cells is mediated by 4-hydroxynonenal-activated PPARα and PPARβ/δ.

Cell Tissue Res 2015 Aug 27;361(2):593-604. Epub 2015 Feb 27.

Institute of Cellular Biology and Pathology "Nicolae Simionescu" of the Romanian Academy, 8 B.P. Hasdeu Street, 050568, Bucharest, Romania,

High glucose induces vascular smooth muscle cell (SMC) dysfunction by generating oxidative stress attributable, in part, to the up-regulated NADPH oxidases (Nox). We have attempted to elucidate the high-glucose-generated molecular signals that mediate this effect and hypothesize that products of high-glucose-induced lipid peroxidation regulate Nox by activating peroxisome proliferator-activated receptors (PPARs). Human aortic SMCs were exposed to glucose (5.5-25 mM) or 4-hydroxynonenal (1-25 μM, 4-HNE). Lucigenin assay, real-time polymerase chain reaction, western blot, and promoter analyses were employed to investigate Nox. We found that high glucose generated an increase in Nox activity and expression. It also promoted oxidative stress that consequently induced lipid peroxidation, which resulted in the production of 4-HNE. Pharmacological inhibition of Nox activity significantly reduced the formation of high-glucose-induced 4-HNE. Exposure of SMCs to non-cytotoxic concentrations (1-10 μM) of 4-HNE alone mimicked the effect of high glucose incubation, whereas scavenging of 4-HNE by N-acetyl L-cysteine completely abolished both the effects of high glucose and 4-HNE. The latter exerted its effect by activating PPARα and PPARβ/δ, but not PPARγ, as assessed pharmacologically by the inhibitory effect of selective antagonists and following the silencing of the expression of these receptors. These new data indicate that 4-HNE, generated following Nox activation, functions as an endogenous activator of PPARα and PPARβ/δ. The newly discovered "lipid peroxidation products-PPARs-Nox axis" represents a novel mechanism of Nox regulation and an additional therapeutic target for oxidative stress in diabetes.
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http://dx.doi.org/10.1007/s00441-015-2120-0DOI Listing
August 2015

Activation of PPARδ: from computer modelling to biological effects.

Br J Pharmacol 2015 Feb 15;172(3):754-70. Epub 2014 Dec 15.

Division of Medicinal Chemistry, Department of Chemistry, Faculty of Exact Sciences, Bar-Ilan University, Ramat-Gan, Israel.

PPARδ is a ligand-activated receptor that dimerizes with another nuclear receptor of the retinoic acid receptor family. The dimers interact with other co-activator proteins and form active complexes that bind to PPAR response elements and promote transcription of genes involved in lipid metabolism. It appears that various natural fatty acids and their metabolites serve as endogenous activators of PPARδ; however, there is no consensus in the literature on the nature of the prime activators of the receptor. In vitro and cell-based assays of PPARδ activation by fatty acids and their derivatives often produce conflicting results. The search for synthetic and selective PPARδ agonists, which may be pharmacologically useful, is intense. Current rational modelling used to obtain such compounds relies mostly on crystal structures of synthetic PPARδ ligands with the recombinant ligand binding domain (LBD) of the receptor. Here, we introduce an original computational prediction model for ligand binding to PPARδ LBD. The model was built based on EC50 data of 16 ligands with available crystal structures and validated by calculating binding probabilities of 82 different natural and synthetic compounds from the literature. These compounds were independently tested in cell-free and cell-based assays for their capacity to bind or activate PPARδ, leading to prediction accuracy of between 70% and 93% (depending on ligand type). This new computational tool could therefore be used in the search for natural and synthetic agonists of the receptor.
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http://dx.doi.org/10.1111/bph.12950DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4301687PMC
February 2015

Signaling properties of 4-hydroxyalkenals formed by lipid peroxidation in diabetes.

Free Radic Biol Med 2013 Dec 20;65:978-987. Epub 2013 Aug 20.

Department of Pharmacology, Institute for Drug Research, Faculty of Medicine, The Hebrew University, Jerusalem Israel. Electronic address:

Peroxidation of polyunsaturated fatty acids is intensified in cells subjected to oxidative stress and results in the generation of various bioactive compounds, of which 4-hydroxyalkenals are prominent. During the progression of type 2 diabetes mellitus, the ensuing hyperglycemia promotes the generation of reactive oxygen species (ROS) that contribute to the development of diabetic complications. It has been suggested that ROS-induced lipid peroxidation and the resulting 4-hydroxyalkenals markedly contribute to the development and progression of these pathologies. Recent findings, however, also suggest that noncytotoxic levels of 4-hydroxyalkenals play important signaling functions in the early phase of diabetes and act as hormetic factors to induce adaptive and protective responses in cells, enabling them to function in the hyperglycemic milieu. Our studies and others' have proposed such regulatory functions for 4-hydroxynonenal and 4-hydroxydodecadienal in insulin secreting β-cells and vascular endothelial cells, respectively. This review presents and discusses the mechanisms regulating the generation of 4-hydroxyalkenals under high glucose conditions and the molecular interactions underlying the reciprocal transition from hormetic to cytotoxic agents.
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http://dx.doi.org/10.1016/j.freeradbiomed.2013.08.163DOI Listing
December 2013

Synthesis and mechanism of hypoglycemic activity of benzothiazole derivatives.

J Med Chem 2013 Jul 26;56(13):5335-50. Epub 2013 Jun 26.

Division of Medicinal Chemistry, Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University , Ramat Gan, 5290002, Israel.

Adenosine 5'-monophosphate activated protein kinase (AMPK) has emerged as a major potential target for novel antidiabetic drugs. We studied the structure of 2-chloro-5-((Z)-((E)-5-((5-(4,5-dimethyl-2-nitrophenyl)furan-2-yl)methylene)-4-oxothiazolidin-2-ylidene)amino)benzoic acid (PT-1), which attenuates the autoinhibition of the enzyme AMPK, for the design and synthesis of different benzothiazoles with potential antidiabetic activity. We synthesized several structurally related benzothiazole derivatives that increased the rate of glucose uptake in L6 myotubes in an AMPK-dependent manner. One compound, 2-(benzo[d]thiazol-2-ylmethylthio)-6-ethoxybenzo[d]thiazole (34), augmented the rate of glucose uptake up to 2.5-fold compared with vehicle-treated cells and up to 1.1-fold compared to PT-1. Concomitantly, it elevated the abundance of GLUT4 in the plasma membrane of the myotubes and activated AMPK. Subcutaneous administration of 34 to hyperglycemic Kuo Kondo rats carrying the Ay-yellow obese gene (KKAy) mice lowered blood glucose levels toward the normoglycemic range. In accord with its activity, compound 34 showed a high fit value to a pharmacophore model derived from the PT-1.
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http://dx.doi.org/10.1021/jm4001488DOI Listing
July 2013

Endothelial Cells Derived from the Blood-Brain Barrier and Islets of Langerhans Differ in their Response to the Effects of Bilirubin on Oxidative Stress Under Hyperglycemic Conditions.

Front Pharmacol 2012 13;3:131. Epub 2012 Jul 13.

Department of Pharmacology, Institute of Drug Research, School of Pharmacy, The Hebrew University of Jerusalem Jerusalem, Israel.

Unconjugated bilirubin (UCB) is a neurotoxic degradation product of heme. Its toxic effects include induction of apoptosis, and ultimately neuronal cell death. However, at low concentrations, UCB is a potent antioxidant that may protect cells and tissues against oxidative stress by neutralizing toxic metabolites such as reactive oxygen species (ROS). High glucose levels (hyperglycemia) generate reactive metabolites. Endothelial cell dysfunction, an early vascular complication in diabetes, has been associated with hyperglycemia-induced oxidative stress. Both glucose and UCB are substrates for transport proteins in microvascular endothelial cells of the blood-brain barrier (BBB). In the current study we show that UCB (1-40 μM) induces apoptosis and reduces survival of bEnd3 cells, a mouse brain endothelial cell line which serves as an in vitro model of the BBB. These deleterious effects of UCB were enhanced in the presence of high glucose (25 mM) levels. Interestingly, the bEnd3 cells exhibited an increased sensitivity to the apoptotic effects of UCB when compared to the MS1 microcapillary endothelial cell line. MS1 cells originate from murine pancreatic islets of Langerhans, and are devoid of the barrier characteristics of BBB-derived endothelial cells. ROS production was increased in both bEnd3 and MS1 cells exposed to high glucose, as compared with cells exposed to normal (5.5 mM) glucose levels. While UCB (0.1-40 μM) did not alter ROS production in cells exposed to normal glucose, relatively low ("physiological") UCB concentrations (0.1-5 μM) attenuated ROS generation in both cell lines exposed to high glucose levels. Most strikingly, higher UCB concentrations (20-40 μM) increased ROS generation in bEnd3 cells exposed to high glucose, but not in similarly treated MS1 cells. These results may be of critical importance for understanding the vulnerability of the BBB endothelium upon exposure to increasing UCB levels under hyperglycemic conditions.
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http://dx.doi.org/10.3389/fphar.2012.00131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3396126PMC
October 2012

Role of lipid peroxidation and PPAR-δ in amplifying glucose-stimulated insulin secretion.

Diabetes 2011 Nov 6;60(11):2830-42. Epub 2011 Sep 6.

Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Institute for Drug Research, Hebrew University, Jerusalem, Israel.

Objective: Previous studies show that polyunsaturated fatty acids (PUFAs) increase the insulin secretory capacity of pancreatic β-cells. We aimed at identifying PUFA-derived mediators and their cellular targets that are involved in the amplification of insulin release from β-cells preexposed to high glucose levels.

Research Design And Methods: The content of fatty acids in phospholipids of INS-1E β-cells was determined by lipidomics analysis. High-performance liquid chromatography was used to identify peroxidation products in β-cell cultures. Static and dynamic glucose-stimulated insulin secretion (GSIS) assays were performed on isolated rat islets and/or INS-1E cells. The function of peroxisome proliferator-activated receptor-δ (PPAR-δ) in regulating insulin secretion was investigated using pharmacological agents and gene expression manipulations.

Results: High glucose activated cPLA(2) and, subsequently, the hydrolysis of arachidonic and linoleic acid (AA and LA, respectively) from phospholipids in INS-1E cells. Glucose also increased the level of reactive oxygen species, which promoted the peroxidation of these PUFAs to generate 4-hydroxy-2E-nonenal (4-HNE). The latter mimicked the GSIS-amplifying effect of high glucose preexposure and of the PPAR-δ agonist GW501516 in INS-1E cells and isolated rat islets. These effects were blocked with GSK0660, a selective PPAR-δ antagonist, and the antioxidant N-acetylcysteine or by silencing PPAR-δ expression. High glucose, 4-HNE, and GW501516 also induced luciferase expression in a PPAR-δ-mediated transactivation assay. Cytotoxic effects of 4-HNE were observed only above the physiologically effective concentration range.

Conclusions: Elevated glucose levels augment the release of AA and LA from phospholipids and their peroxidation to 4-HNE in β-cells. This molecule is an endogenous ligand for PPAR-δ, which amplifies insulin secretion in β-cells.
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http://dx.doi.org/10.2337/db11-0347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3198069PMC
November 2011

Antihyperglycaemic activity of 2,4:3,5-dibenzylidene-D-xylose-diethyl dithioacetal in diabetic mice.

J Cell Mol Med 2012 Mar;16(3):594-604

Department of Pharmacology, Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel.

We have recently generated lipophilic D-xylose derivatives that increase the rate of glucose uptake in cultured skeletal muscle cells in an AMP-activated protein kinase (AMPK)-dependent manner. The derivative 2,4:3,5-dibenzylidene-D-xylose-diethyl dithioacetal (EH-36) stimulated the rate of glucose transport by increasing the abundance of glucose transporter-4 in the plasma membrane of cultured myotubes. The present study aimed at investigating potential antihyperglycaemic effects of EH-36 in animal models of diabetes. Two animal models were treated subcutaneously with EH-36: streptozotocin-induced diabetes in C57BL/6 mice (a model of insulin-deficient type 1 diabetes), and spontaneously diabetic KKAy mice (Kuo Kondo rats carrying the A(y) yellow obese gene; insulin-resistant type 2 diabetes). The in vivo biodistribution of glucose in control and treated mice was followed with the glucose analogue 2-deoxy-2-[(18) F]-D-glucose; the rate of glucose uptake in excised soleus muscles was measured with [(3) H]-2-deoxy-D-glucose. Pharmacokinetic parameters were determined by non-compartmental analysis of the in vivo data. The effective blood EH-36 concentration in treated animals was 2 μM. It reduced significantly the blood glucose levels in both types of diabetic mice and also corrected the typical compensatory hyperinsulinaemia of KKAy mice. EH-36 markedly increased glucose transport in vivo into skeletal muscle and heart, but not to adipose tissue. This stimulatory effect was mediated by Thr(172) -phosphorylation in AMPK. Biochemical tests in treated animals and acute toxicological examinations showed that EH-36 was well tolerated and not toxic to the mice. These findings indicate that EH-36 is a promising prototype molecule for the development of novel antidiabetic drugs.
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http://dx.doi.org/10.1111/j.1582-4934.2011.01340.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3822934PMC
March 2012

Signaling and cytotoxic functions of 4-hydroxyalkenals.

Am J Physiol Endocrinol Metab 2010 Dec 21;299(6):E879-86. Epub 2010 Sep 21.

Dept. of Pharmacology, The Hebrew Univ. Jerusalem 91120, Israel.

The peroxidation of n-3 and n-6 polyunsaturated fatty acids (PUFAs) and of their hydroperoxy metabolites is a complex process. It is initiated by free oxygen radical-induced abstraction of a hydrogen atom from the lipid molecule followed by a series of nonenzymatic reactions that ultimately generate the reactive aldehyde species 4-hydroxyalkenals. The molecule 4-hydroxy-2E-hexenal (4-HHE) is generated by peroxidation of n-3 PUFAs, such as linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid. The aldehyde product 4-hydroxy-2E-nonenal (4-HNE) is the peroxidation product of n-6 PUFAs, such as arachidonic and linoleic acids and their 15-lipoxygenase metabolites, namely 15-hydroperoxyeicosatetraenoic acid (15-HpETE) and 13-hydroperoxyoctadecadienoic acid (13-HpODE). Another reactive peroxidation product is 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), which is derived from 12-hydroperoxyeicosatetraenoic acid (12-HpETE), the 12-lipoxygenase metabolite of arachidonic acid. Hydroxyalkenals, notably 4-HNE, have been implicated in various pathophysiological interactions due to their chemical reactivity and the formation of covalent adducts with macromolecules. The progressive accumulation of these adducts alters normal cell functions that can lead to cell death. The lipophilicity of these aldehydes positively correlates to their chemical reactivity. Nonetheless, at low and noncytotoxic concentrations, these molecules may function as signaling molecules in cells. This has been shown mostly for 4-HNE and to some extent for 4-HHE. The capacity of 4-HDDE to generate such "mixed signals" in cells has received less attention. This review addresses the origin and cellular functions of 4-hydroxyalkernals.
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http://dx.doi.org/10.1152/ajpendo.00508.2010DOI Listing
December 2010

Pathological aspects of lipid peroxidation.

Free Radic Res 2010 Oct;44(10):1125-71

INSERM I2MR-858, IFR-150, Avenue J Poulhès, BP 84225, Toulouse, France.

Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.
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http://dx.doi.org/10.3109/10715762.2010.498478DOI Listing
October 2010