Jean-Claude Debouzy

Carbon nanotubes induce inflammation but decrease the production of reactive oxygen species in lung

With the rapid spread of carbon nanotubes (CNTs) applications, the respiratory toxicity of these compounds has attracted the attention of many scientists. Several studies have reported that after lung administration, CNTs could induce granuloma, fibrosis, or inflammation. By comparison with the mechanisms involved with other toxic particles such as asbestos, this effect could be attributed to an increase of oxidative stress. The aim of the present work was to test this hypothesis in vivo. Mice were intranasally instilled with 1.5mg/kg of double walled carbon nanotubes (DWCNTs). Six, 24, or 48h after administration, inflammation and localisation of DWCNTs in lungs were microscopically observed. Local oxidative perturbations were investigated using ESR spin trapping experiments, and systemic inflammation was assessed by measuring the plasma concentration of cytokines TNF-alpha, IL-1alpha, IL-1beta, IL-6, IGF-1, Leptin, G-CSF, and VEGF. Examination of lungs and the elevation of proinflammatory cytokines in the plasma (Leptin and IL-6 at 6h) confirmed the induction of an inflammatory reaction. This inflammatory reaction was accompanied by a decrease in the local oxidative stress. This effect could be attributed to the scavenger capability of pure CNTs.

Hydrophobic double walled carbon nanotubes interaction with phopholipidic model membranes: 1H-, 2H-, 31P NMR and ESR study

The interactions of carbon nanotubes synthesized by catalytic chemical vapour deposition with phospholipidic bilayers, mimicking biological membranes, have been investigated using solid state (31)P- and (2)H NMR, (1)H- and (31)P NMR in liquids and ESR studies. It was found that carbon nanotubes can integrate the bilayer, depending on the overall cohesion of the membrane used. Whereas no direct interaction can be observed in small unilamellar vesicles or directly in the presence of short-chained phospholipids, carbon nanotubes incorporate into the membrane of multibilayers. The result is a significant 2-3K lowering of the transition temperature in multibilayers of dimyristoyl lecithins, which is more markedly associated with increased fluidity in the most superficial part of the membrane below the transition temperature (292-300K range). However, no ionophoric property was found on large unilamellar vesicles.

Pulsed electromagnetic field at 9.71 GHz increase free radical production in yeast (Saccharomyces cerevisiae).

Potential human health hazards have been reported after exposure to electromagnetic fields at low power density. Increased oxidative stress has been suggested as a potential mechanism involved in long-term effect of such exposure. In the present work, yeast cultures were exposed for 20 min to a 9.71 GHz pulsed electromagnetic field at specific absorption rates (SAR) from 0.5 W/kg to 16 W/kg. Oxidative perturbations were investigated using ESR spin trapping experiments and their impacts on membrane fluidity were assessed using spin label five nitroxide stearate. The experiments using the water-soluble spin trap alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone and the lipid-soluble N-tert-butyl-alpha-phenylnitrone showed an increase of spin adduct production both in low power density exposure (SAR<4 W/kg) and in thermal conditions (SAR>4 W/kg). The membrane fluidity diminutions after exposure in all the conditions were consistent with lipid peroxidation. The overall results suggest an increase of the free radical production in the intra cellular compartment; however no effect on the yeast vitality was found.

Effects of high and low inspired fractions of oxygen on horse erythrocyte membrane properties, blood viscosity and muscle oxygenation during anaesthesia

OBJECTIVES To evaluate whether a period of hyperoxia or after a period of hypoxia produced changes attributable to reactive oxygen species in anaesthetized horses. STUDY DESIGN Prospective randomized experimental study. ANIMALS Six healthy (ASA I) geldings, aged 4.5-9.5 years and weighing 510-640 kg(-1). METHODS After 30 minutes breathing air as carrier gas for isoflurane, horses were assigned randomly to breathe air as carrier gas (CG0.21) or oxygen as carrier gas (CG1.00) for a further 90 minutes. After an interval of 1 month each horse was re-anaesthetized with the other carrier gas for the 90 minute test period. Ventilation was controlled throughout anaesthesia. Arterial blood was sampled to measure gas tensions, lactate, cholesterol, vitamin E, 4-hydroxy-alkenals, 8-epi-PGF(2 alpha), half haemolysis time, half erythrolysis time, and erythrocyte membrane fluidity. Muscle blood flow and oxygenation were evaluated by near infrared spectroscopy and coloured Doppler. RESULTS After the first 30 minutes horses were hypoxemic. Subsequently the CG1.00 group became hyperoxaemic (PaO(2) approximately 240 mmHg) whereas the CG0.21 group remained hypoxaemic (PaO(2) approximately 60 mmHg) and had increased lactate concentration. No significant changes in vitamin E, 4-hydroxy-alkenals, or 8-epi-PGF(2 alpha) concentrations were detected. During the 90 minute test period the CG0.21 group had increased resistance to free-radical-mediated lysis in erythrocytes, whereas the CG1.00 group had slightly decreased resistance of whole blood to haemolysis. CG0.21 induced a progressive muscle deoxygenation whereas CG1.00 induced an increase in muscle oxygen saturation followed by progressive deoxygenation towards baseline. CONCLUSIONS and clinical relevance During isoflurane anaesthesia in horses, the hyperoxia induced by changing from air to oxygen induced minimal damage from reactive oxygen species. Using air as the carrier gas decreased skeletal muscle oxygenation compared with using oxygen.

Effets des ondes hyperfréquences des téléphones mobiles et des radars sur l’œil

The increasing applications of microwaves, mainly in mobile phones and radar, induce a higher rate of exposed people, sometimes cause of worry. Eyeballs are hotspots of radiofrequency field radiation because of their anatomy and composition. We propose a review of the various effects on the eye. The studies are hardly comparable because the exposure systems, power densities and dosimetries are different. While the thermal effects on the eye are well known including cataracts, corneal edema, endothelial cell loss and retinal degeneration, the non-thermal effects are still controversial. Cell cycle abnormalities, early apoptosis were reported in experimental conditions likely due to oxidative stress, but the studies could not show any significant effect on human eyes when exposed to long-term and low-dose radiation. Next studies need to be closer to human exposure.

In vitro effects of oxygen on physico-chemical properties of horse erythrocyte membrane

Whether direct exposure to different concentrations (0%, 13%, 100%) of oxygen may affect horse erythrocyte membrane fluidity (EMF) and fatty acid (FA) composition was studied during 1 (T60) and 2h (T120) exposure. EMF was investigated at the head group level and hydrophobic core thanks to phosphorus nucleus 31 ((31)P) nuclear magnetic resonance ((31)P NMR) and electronic paramagnetic resonance (EPR) using two spin probes: 5-nitroxydestearic acid and 16-doxylstearic acid. Lipid structure of the membranes was studied by gas liquid chromatography. 4-Hydroxy-2E-nonenal was also analyzed as a marker of lipid peroxidation. It increased at T120 13% and 100% oxygen whereas there were no significant changes in membrane dynamic or structure. Correlation was demonstrated between EMF and partial pressure of oxygen in the blood ( [Formula: see text] ). In vitro high rate of oxygenation was efficient to induce lipid peroxidation but did not change membrane dynamics. This may be due to a low free radical production in vitro or to the high red blood cells antioxidant properties.