Modulation of ethoxyquin genotoxicity by free radical scavengers and DNA damage repair in human lymphocytes.

N-tert-butyl-alpha-phenylnitrone (PBN) and its new derivative N-(Pyridine-4-ylmethylidene)-2-carboxy-tert-butylamine N-oxide (PBNC) were synthesized and used to modulate ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline, EQ) genotoxicity. Ethoxyquin, an antioxidant used mainly as a preservative in animal feeds, was shown to cause DNA breaks in human lymphocytes. The aim of the study was to evaluate the involvement of free radicals in the genotoxicity of EQ and its modulation by cellular repair systems. Human lymphocytes treated with EQ (10-50 microM) and nitrone free radical scavengers (100 microM) were tested with the comet assay. It was shown that both PBN and PBNC reduced the level of EQ-induced DNA damage, but PBN was slightly more effective. The modulation of the level of DNA damage was also observed as a result of DNA repair by cellular repair systems. Moreover, induction of oxidized bases by ethoxyquin was showed; lymphocytes exposed to ethoxyquin and treated with endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (FpG), enzymes recognizing oxidized bases, displayed greater extent of DNA damage than those not treated with the enzymes.

Gibbs monolayers at the air/water interface: surface partitioning and lateral mobility of an electrochemically active surfactant.

Monolayer films of a water-soluble surfactant, 4-octaneamido-2,2,6,6-tetramethyl-1-piperidinyloxy (C8-TEMPO) were investigated at the air/water interface. An electrochemical, horizontal touch method was developed to measure the equilibrium surface concentrations (gamma) of C8TEMPO. The dependence of gamma on the solution concentration followed a Langmuir isotherm and yielded the partition constant K = (2.3+/-0.2) x 10(4) M(-1). These results were verified by surface tension measurements and Brewster angle microscopy. Within experimental error, the same K values were obtained. The lateral diffusion constants vs surface concentration of this molecule were measured by 2D voltammetry. In these experiments, the component of the oxidation current due to C8TEMPO in the bulk of the solution was subtracted from the total measured current to obtain the component due to the lateral surface diffusion. In the ange of mean molecular areas from 120 to 400 A2/molecule, the lateral diffusion constant of C8TEMPO increased from 1.0 x 10(-6) to 1.0 x 10(-5) cm2/s. The latter value is about 2.5 times larger than the C8TEMPO diffusion constant in bulk water. Comparison of the lateral mobilities of C8TEMPO and two longer alkane chain, water-insoluble homologues, C14TEMPO and C18TEMPO, showed no statistically significant differences.