Gamma radiolysis as a tool to study lipoprotein oxidation mechanisms

Role of Anti-Inflammatory, Reactive Oxygen Species Scavenging Activity and Nematicidal Properties of Myrtle Berry Seeds on Helminthiasis Treatment

This study was undertaken to investigate the involvement of the reactive oxygen species (ROS) and proinflammatory cytokine production in the pathogenicity of gastrointestinal nematode Heligmosomoides polygyrus in mice and also the protective effect of myrtle (Myrtus communis L.) berry seeds aqueous extract (MBSAE). With this aim, Swiss Albino mice were divided into four groups of 10 animals each: control, helminthiasis, helminthiasis + MBSAE, and helminthiasis + Albendazole. The animals were infected with infective third larval stage (L3) of H. polygyrus by oral administration. Mice were treated with bidistilled water, MBSAE (100 mg/kg, b.w., p.o.) or Albendazole (100 mg/kg, b.w., p.o.). We have demonstrated that MBSAE (100 mg/kg, b.w., p.o.) significantly reduced the total mean adult worms compared with the infected and nontreated group. Moreover, hematological parameters, intestinal ROS such as hydrogen peroxide (H₂O₂), hydroxyl radical (OH^•), and superoxide anion (O₂^•-), as well as serum cytokines such as interleukin (IL)-1β and IL-6 were analyzed. We have shown that H. polygyrus infection has disrupted all these biochemical parameters and that MBSAE treatment has significantly corrected these disturbances. The effect of plant extract was comparable to the standard drug albendazole. Therefore, MBSAE appeared to be a promising agent for the control of intestinal helminthiasis.

Singlet Oxygen Sensor Green is not a Suitable Probe for 1O2 in the Presence of Ionizing Radiation

A great number of fluorescent probes have been developed for detecting singlet oxygen (¹O₂), which is considered to be one of the most effective reactive oxygen species (ROS), especially in clinical applications. The commercially available fluorescent probe Singlet Oxygen Sensor Green (SOSG) is widely used due to its reported high selectivity to ¹O₂. In this study, we carried out systemic experiments to determine the activation of SOSG in the presence of ionizing radiation. The results show that the SOSG probe exhibits a pronounced fluorescence increase as a function of radiation dose delivered by gamma-rays as well as X-rays, in conditions where the formation of singlet oxygen is not expected. Furthermore, scavenger tests indicate that hydroxyl radicals may be involved directly or indirectly in the activation process of SOSG although the exact mechanism remains unknown.

HPLC/PDA/ESI-MS/MS analysis of chamomile decoction and mechanism of its protective effects on aspirin-induced small bowel injuries

The aim of the present study is to evaluate the effect of chamomile (Matricaria recutitaL.) decoction extract (CDE) on aspirin-induced small bowel injuries.

A dramatic effect of oxygen on protection of human cells against γ-radiation by lycopene

Reducing radiation damage is important and dietary antioxidants that can protect cells from such damage are of value. Dietary lycopene, a carotenoid found in tomatoes, protects human lymphoid cell membranes from damage by γ-radiation. We report that such protective effects are remarkably reduced as the oxygen concentration increases - near zero at 100% oxygen from fivefold protection at 20% oxygen and, dramatically, from 50-fold protection at 0% oxygen. Such huge differences imply that under higher oxygen concentrations lycopene could lead to improved cancer therapy using γ-radiation. The cells are not efficiently protected from the superoxide radical by lycopene. Noncellular studies suggest molecular mechanisms for the oxygen effect.

Study of tryptophan lifetime fluorescence following low-density lipoprotein modification

In this paper we report the effects of the irradiation of low-density lipoprotein (LDL) by ultra-short laser pulses to obtain in vitro alterations mimicking proatherogenic modifications occurring in vivo in LDL. The modifications by metallic ions (copper and iron) and ultra-short laser pulses were studied by fluorescence steady state and time-resolved lifetime measurements. The results demonstrate that the modifications caused by ultra-short laser pulses and by iron affect the tryptophan residues of apolipoprotein B-100 (Apo-B), slightly decreasing fluorescent lifetimes, with almost no modifications in pre-exponential factors, indicating preservation of structural properties around the fluorophore. On the other hand, oxidation by copper strongly affects the Apo-B protein associated with LDL. We describe a fast, inexpensive, and nondestructive fluorescence-based method that is readily accessible to provide the LDL particle characterization.

Melatonin protects PLPC liposomes and LDL towards radical-induced oxidation

This study investigated the in vitro protective effects of melatonin against oxidation of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC) liposomes [(PLPC) = 250 μm] and low-density lipoproteins (LDL, 3 g/L total concentration) by hydroxyl radicals produced by water gamma radiolysis. Conjugated dienes (CD) and hydroperoxides from cholesteryl esters (CEOOH) and phospholipids (PCOOH) were measured as indices of lipid peroxidation. Protein (apoB) oxidation in LDL was assessed by carbonyl groups. Two LDL antioxidants (vitamin E and β-carotene) were monitored as a function of the radiation dose. Three concentrations of melatonin were studied in PLPC liposomes, i.e., 20, 50 and 100 μm, and one in LDL, i.e., 100 μm. Melatonin consumption was also followed up in both lipid models upon irradiation, together with the residual PLPC concentration in liposomes. In PLPC liposomes, scavenging of lipid-derived peroxyl radicals was not the only phenomenon to explain the protective properties of melatonin towards lipid peroxidation. Indeed, melatonin also reacted with hydroxyl radicals generated in aqueous phase, which led us to suggest that hydroxyl radicals reacted relatively slowly with PLPC. Melatonin was efficient in lowering lipid peroxidation in LDL, as shown by the decrease in the formation of CDs and in hydroperoxides. Moreover, melatonin clearly slowed radio-induced apolipoprotein B carbonylation and protected α-tocopherol and β-carotene in LDL.

A new insight into resveratrol as an atheroprotective compound: inhibition of lipid peroxidation and enhancement of cholesterol efflux

Resveratrol, a polyphenolic constituent of red wine, is known for its anti-atherogenic properties and is thought to be beneficial in reducing the incidence of cardiovascular diseases (CVD). However, the mechanism of action by which it exerts its anti-atherogenic effect remains unclear. In this study, we investigated the relationship between the antioxidant effects of resveratrol and its ability to promote cholesterol efflux. We measured the formation of conjugated dienes and the rate of lipid peroxidation, and observed that resveratrol inhibited copper- and irradiation-induced LDL and HDL oxidation as observed by a reduction in oxidation rate and an increase in the lag phase (p<0.05). We used DPPH screening to measure free radical scavenging activity and observed that resveratrol (0-50microM) significantly reduced the content of free radicals (p<0.001). Respect to its effect on cholesterol homeostasis, resveratrol also enhanced apoA-1-mediated cholesterol efflux (r(2)=0.907, p<0.05, linear regression) by up-regulating ABCA-1 receptors, and reduced cholesterol influx or uptake in J774 macrophages (r(2)=0.89, p<0.05, linear regression). Incubation of macrophages (J774, THP-1 and MPM) with Fe/ascorbate ion, attenuated apoA-1 and HDL(3)-mediated cholesterol efflux whereas resveratrol (0-25microM) significantly redressed this attenuation in a dose-dependent manner (p<0.001). Resveratrol thus appears to be a natural antioxidant that enhances cholesterol efflux. These properties make it a potential natural antioxidant that could be used to prevent and treat CVD.

Ionizing radiation induces a Yap1-dependent peroxide stress response in yeast

Repair of DNA damage is fundamental for cellular tolerance to ionizing radiation (IR) and many IR-induced DNA lesions are thought to occur as a result of oxidative stress. We investigated the physiological effects of IR in Saccharomyces cerevisiae by performing protein expression profiles in cells exposed to electron pulse irradiation. Transient induction of several antioxidant enzymes in wild-type cells, but not in cells lacking the oxidative stress regulator Yap1, indicated that IR exposure causes cellular oxidative stress. Yap1 activation involved oxidation to the intramolecular disulfide bond, a signature of activation by peroxide, and was dependent on the Yap1 peroxide sensor Orp1/Gpx3. H(2)O(2) was produced in the culture medium of irradiated cells and was both necessary and sufficient for IR-induced Yap1 activation. When IR was performed in the presence of N(2)O, obviating H(2)O(2) production and increasing hydroxyl radical ((*)OH) production, the Yap1 response was lost, indicating that Yap1 was unable to respond to (*)OH or (*)OH-induced damage. However, the Yap1 response to IR did not seem to be a primary determinant of cellular IR tolerance. Altogether, these data provide a molecular demonstration that cells experience in vivo peroxide stress during IR and indicate that the H(2)O(2) produced cannot account for IR toxicity.

Aspects physico-chimiques des espèces réactives de l’oxygène

Reactive Oxygen Species (ROS), namely hydroxyl (*OH) and superoxide (O2*-) free radicals and hydrogen peroxide (H2O2), are involved in all oxidative stress phenomena. These latter occur in numerous pathological disorders such as, for example, cardiovascular diseases, diabetes or neurodegenerative diseases. Knowledge of thermodynamic (reduction potentials) and kinetic (rate constants) properties of ROS allows to draw up a rigorous overview of the chemical reactivity of these species. Hydroxyl free radicals (*OH) are powerful oxidants (very toxic species) which attack all the biomolecular targets (DNA, proteins, lipids...), giving other free radicals localized on the targets. Superoxide free radicals (O2*-) have a more graduated reactivity, since they don't directly react with biological molecules. However, some toxicity would be attributed to them via secondary radicular reactions. Other free radicals (of peroxyl RO2* and alkoxyl RO* types), belonging also to the ROS family, contribute by enhancement to oxidative stress.