Showing papers by "Michael Aviram published in 2003"

Mouse Macrophage Paraoxonase 2 Activity Is Increased Whereas Cellular Paraoxonase 3 Activity Is Decreased Under Oxidative Stress

Abstract: Objective— To determine whether paraoxonases (PONs) are expressed in macrophages and to analyze the oxidative stress effect on their expression and activities. Methods and Results— We demonstrated ...

Human Serum Paraoxonase 1 Decreases Macrophage Cholesterol Biosynthesis: Possible Role for Its Phospholipase-A2–Like Activity and Lysophosphatidylcholine Formation

Abstract: Objective— Human serum paraoxonase 1 (PON1) activity is inversely related to the risk of developing an atherosclerotic lesion, which contains cholesterol-loaded macrophage foam cells. To assess a possible mechanism for this relationship, we analyzed the effect of PON1 on cellular cholesterol biosynthesis. Methods and Results— Mouse peritoneal macrophages (MPMs) were harvested from PON1-deficient mice (PON1° and PON1°/E° mice on the genetic background of C57BL/6J and E° mice, respectively). PON1°/E° mice exhibited a significantly 51% increased atherosclerotic lesion area and 35% increased macrophage cholesterol content compared with control E° mice. In parallel, macrophage cholesterol biosynthesis rates were increased in PON1-deficient mice MPMs by 50% compared with their controls. Incubation of macrophages with human PON1 revealed a dose-dependent inhibitory effect (up to 84%) on macrophage cholesterol biosynthesis. We demonstrated a PON1 phospholipase-A 2 –like activity on MPMs, evidenced by release of polyunsaturated fatty acids and formation of lysophosphatidylcholine. On incubation of macrophages with lysophosphatidylcholine, a dose-dependent inhibition (up to 40%) of cellular cholesterol biosynthesis was noted. The inhibitory effect of PON1 on macrophage cholesterol biosynthesis was shown to be downstream to mevalonate, probably at the lanosterol metabolic point. Conclusions— PON1 inhibits macrophage cholesterol biosynthesis and atherogenesis probably through its phospholipase-A 2 –like activity.

Effect of eplerenone, a selective aldosterone blocker, on blood pressure, serum and macrophage oxidative stress, and atherosclerosis in apolipoprotein E-deficient mice.

Abstract: Oxidative stress is involved in the pathogenesis of atherosclerosis, and angiotensin II (AT-II) induces oxidative stress and enhances atherogenesis. Aldosterone, which has an important role in the pathology of heart failure, has recently been implicated as a mediator of AT-II biologic activities. In this study, we analyzed whether administration of the selective aldosterone blocker eplerenone to atherosclerotic apolipoprotein E-deficient (E0) mice would affect their oxidative status and atherogenesis. Apolipoprotein E-deficient mice were administered chow containing eplerenone (200 mg/kg/day) for 3 months. Blood pressure, serum and macrophage oxidative status, and aortic atherosclerotic lesion area were evaluated in mice treated with eplerenone compared with untreated mice. Eplerenone administration significantly decreased systolic and diastolic blood pressure by 12% and 11%, respectively, compared with untreated mice. Serum susceptibility to lipid peroxidation decreased by as much as 26%, and serum paraoxonase activity increased by 28% in eplerenone-treated mice compared with untreated mice. Peritoneal macrophages from eplerenone-treated mice contained reduced levels of lipid peroxides, and their macrophage oxidation of low-density lipoprotein (LDL) and superoxide ion release were significantly reduced (by 17% and 43%, respectively), compared to untreated mice. Daily injections of AT-II (0.1 mL, 10(-)7M) during the final 3 weeks of the study in eplerenone-treated mice substantially attenuated the eplerenone-mediated reduction in macrophage superoxide release and LDL oxidation. Finally, the atherosclerotic lesion area in aortas of eplerenone-treated mice was significantly reduced (by 35%) versus untreated mice, and this effect was reversed by AT-II. Administration of the selective aldosterone blocker eplerenone significantly reduced oxidative stress and atherosclerosis progression in E0 mice. These data suggest that aldosterone could have a significant pro-oxidative role in the pathogenesis of atherosclerosis.

Tissue Angiotensin-Converting-Enzyme (ACE) Deficiency Leads to a Reduction in Oxidative Stress and in Atherosclerosis. Studies in ACE-Knockout Mice Type 2

Abstract: Background— Angiotensin II, produced by angiotensin-converting-enzyme (ACE), enhances oxidative stress and atherogenesis. In this study, we analyzed whether tissue ACE deficiency in ACE-knockout mice type-2 would affect their oxidative status. Moreover, by crossbreeding the ACE-knockout mice with atherosclerotic apolipoprotein E (apo E)–deficient (E 0 ) mice, we questioned whether tissue ACE deficiency affects atherogenesis. Methods and Results— ACE-deficient mice type-2 (ACE +/− ) exhibited reduced serum lipid peroxidation compared with ACE +/+ mice. Peritoneal macrophages from ACE +/− mice demonstrated lower oxidative status, as exhibited by decreases of 47%, 33% 56%, and 51%, in their lipid peroxides, superoxide release, dichlorofluorescein fluorescence, and LDL oxidation, respectively, compared with ACE +/+ mice. ACE +/− mice crossbred with E 0 mice, resulting in atherosclerotic mice heterozygous for ACE (ACE +/− /E 0 mice), exhibited reduced lipid peroxidation, increased paraoxonase activity, and lower macrophage LDL oxidation compared with E 0 and ACE +/+ /E 0 mice. ACE +/− /E 0 mice also exhibited reduced NADPH-induced aortic superoxide ion production by 52% and a reduction of 43% in their atherosclerotic lesion size compared with E 0 mice. Finally, 2 animals genotyped as homozygous-knockout for both ACE and APOE genes (ACE − / − /E 0 ), exhibited a striking reduction of 86% in their atherosclerotic lesion area compared with E 0 mice. Conclusions— Reduction of tissue ACE with the ACE-knockout mouse type-2 model inhibited oxidative stress and atherogenesis.

Cholesterol, linoleic acid or/and tyrosine yield different spectra of products when oxidized alone or in a mixture: studies in various oxidative systems.

Abstract: Identification of reliable biomarkers for oxidative stress for the prediction of the early development of pathological conditions is essential. The detection of biomarkers for oxidative stress such as degradation products of polyunsaturated fatty acid (PUFA), oxysterols, and oxidized proteins, as indicators of oxidative stress are in use, but suffers from insufficient specificity, accuracy and reliability. The overall aim of the present study was to develop new markers which will not only provide information about the presence and level of oxidative stress in biological systems but also on the type of reactive oxygen species (ROS) involved and their metabolic consequences. In the first stage of the study, we compared the level and type of oxidized products formed when different ROS were applied onto three major biomolecules, i.e. cholesterol, linoleic acid (LH) and tyrosine, representing sterols, PUFA and protein, when each compounds was exposed alone or in a mixture to the ROS [copper ions, 2,2-azobis(2-...

Lipid peroxidation and atherosclerosis: the importance of selected patient group analysis.

Abstract: It is widely accepted that lipid peroxidation plays a central role in the development of cardiovascular diseases, and that low density lipoprotein oxidation is considered to be the hallmark of early atherosclerosis [1,2]. Oxidized LDL is atherogenic ± it causes arterial cell death, accumulation of inflammatory cells in the arterial wall, and stimulation of growth factors and cytokine release. In addition, Ox-LDL contributes to platelet aggregation, smooth muscle cell proliferation and thrombotic and inflammatory processes. Increased susceptibility of LDL to oxidation was shown in patients with hypercholesterolemia, hypertension, diabetes mellitus, chronic renal failure, and in smokers [3]. Upon specific treatment with statins, angiotensin-converting inhibitors, b-carotene or selenium respectively, LDL oxidizability in these patients returned to normal levels [3]. Patients on hemodialysis do not have a significantly increased LDL oxidation rate [4,5]. In the present issue of IMAJ, Boaz et al. [6] present a study on copper ion-induced lipid oxidation kinetics in unfractionated serum from hemodialysis patients. Selecting males with a history of myocardial infarction, and comparing them to a matched group of dialysis patients (age, diabetes mellitus and smoking status) with no cardiovascular disease revealed a significant increased oxidative stress in the dialysis patients with CVD vs. those with no CVD. Tmax, the oxidation kinetic parameter defined as the time at which the rate of absorbing lipid peroxidation products accumulation was maximal, was significantly shorter in dialyzed patients with a history of MI than in those without CVD. Similarly, serum levels of thiobarbituric acid reactive substances (measured as malondialdehyde equivalents) were increased in dialysis patients with MI, in comparison to dialysis patients with no CVD. Tmax and MDA were negatively correlated to one another. Unlike Tmax values, OD max or Vmax (absorbance and rate of conjugated dienes formation) was not significantly different between the two hemodialysis patient groups, probably because these measurements are not good predictors of oxidative stress in vivo. Oxidation of LDL is a free radical-driven lipid peroxidation process. Oxidative stress is defined as a disturbance in the balance between the production of reactive oxygen and/or nitrogen species and the antioxidant defense. Oxidative stress includes ROS/RNS endogenous sources (mitochondria, peroxisomes, inflammatory cells) and exogenous sources (radiation, ozone, xenobiotics). On the other hand, the defense against oxidative stress includes enzymatic systems (superoxide dismutase, catalase, glutathione peroxidase, paraoxonase) and non-enzymatic systems (vitamin E, vitamin C, glutathione, flavonoids). In biological systems, ROS/RNS include: superoxide anion, hydrogen peroxide, hydroxyl radical, nitrogen oxide, peroxynitrite, and hypochlorous acid, which are all formed under normal metabolism, taking part in the signaling cascade, and involved in cellular functions such as proliferation, inflammation and adhesion processes. Oxidative stress can be assessed [7] by indirect measurements like conjugated dienes formation and the accumulation of oxidized degradation products of polyunsaturated fatty acids. The kinetic analysis of serum lipid peroxidation allows for a dynamic quantification of conjugated dienes formed as a result of the conversion of the C=C double bond in polyunsaturated fatty acids into the conjugated double bond (-C-C=C-C=C-), which is characterized by a strong ultraviolet absorption at 245 nm. During lipoprotein oxidation, peroxides are formed, with a subsequent formation of peroxyl radicals, followed by a decomposition phase to yield aldehydes such as hexanal, MDA and 4hydroxynonenal. The assay is based on the detection of a stable product, which is formed between aldehydes and thiobarbituric acid in the aqueous phase. Oxidation is also determined as endproducts of lipid peroxidation, like isoprostanes, linoleic acid and cholesteryl linoleate hydroxide/hydroperoxides, oxysterols, protein oxidation products and DNA oxidation products [7]. Some of the detection methods are non-specific, measuring products that are not necessarily a result of oxidative stress, and their application is questionable (e.g., conjugated dienes, peroxide values, thiobarbituric acid reactive substances). Some of the measures are confounded by diet [7,8]. Other markers are indeed produced in vivo (oxysterols, isoprostans, ketoproteins), but their accumulation under increased oxidative stress is not certain, and they do not provide information on the types and sources of the stress [7,8]. For the above reasons, until a reliable method for in vivo LDL = low density lipoprotein Ox-LDL = oxidized LDL CVD = cardiovascular disease MI = myocardial infarction MDA = malondialdehyde ROS/RNS = reactive oxygen and/or nitrogen species