Induction by xenobiotics of phase I and phase II enzyme activities in the human keratinocyte cell line NCTC 2544.

This study analyses the expression and induction of several drug-metabolising enzyme activities involved in either phase I or phase II biotransformations in NCTC 2544 human keratinocytes. The phase I activities 7-ethoxycoumarin O-deethylase (ECOD), 7-ethoxyresorufin O-deethylase (EROD) and 7-pentoxyresorufin O-depenthylase (PROD) were easily detectable in basal conditions. During incubations lasting up to 144 h in the presence of the classical cytochrome P450 inducers beta-naphthoflavone (BNF), 3-methylcholanthrene (MC) and phenobarbital (PB), a considerable and significant increase in all the three activities was observed. PROD activity was induced up to 4.5-fold after 96 h in the presence of PB. The MC-induced ECOD and EROD activities were also dose-dependently inhibited by alpha-naphothflavone, which was given to the cells during the incubation with CYP 1A1 inducers. Also the PB-induced PROD activity was decreased by the simultaneous addition of the CYP 2B inhibitor metyrapone. Both cytochrome P450 inhibitors were used at non-cytotoxic concentrations. The phase II enzymes glutathione S-transferase, aldehyde dehydrogenase and quinone reductase were all highly expressed and inducible by MC. The exposure (24 h) of the cells to four hair dyes used in cosmetic formulations resulted in a marked increase in ECOD activity. All data give sustained evidence for the suitability of NCTC 2544 cell line to skin toxicology studies.

An "in vitro" approach to water pollution monitoring.

Pollutants of River Lambro, a tributary River Po, were monitored by their potential to induce 1A1 isoform of cytochrome P450 in the FaO hepatoma cell line. Extracts of water samples taken during different months over about one year were fractionated by reverse phase HPLC technique. Six fractions of decreasing polarity were collected, concentrated, freeze-dried and suspended in DMSO for the treatment of the cells. Aliquots of such suspensions were dissolved in the growth medium and left for 48 h in contact with FaO cells, that were maintained in 24-well plates. Cellular monolayers were also exposed to a mixture of the six fractions, to evaluate the effects of all the pollutants mixed together in the original water sample. The CYP1A1-dependent ethoxyresorufin-O-deethylase (EROD) activity was fluorimetrically detected as a measure of inducing potential, and total protein content was evaluated as cytotoxicity end-point. The results showed significant increases of EROD activity over the controls in nearly all the fractions with marked reduction of viability only in two of the mixed samples. The effects of the mixtures were not simply additive, thus suggesting both synergistic and antagonistic interactions. The potential utility of this simple and fast bioassay in environmental risk/hazard assessment is clearly apparent.

Esters of 1,3,3,-trimethyl-2-oxabicyclo [2.2.2]octan-6-ols: synthesis, odour evaluation and in vitro preliminary toxicity assays.

Synopsis The synthesis of a series of alkyl and arylesters of 1,3,3,-trimethyl-2-oxabicyclo[2.2.2]octan-6-ols (2-cineolylols) is described. All cineole esters obtained were tested for their olfactive character; the esters derived from aryl acyl chlorides were odourless, while aliphatic esters showed interesting multipurpose aromas. Some of these compounds exhibited fruity, woody, green, pine oil and violet-like notes and some showed aromas interesting for foodstuffs. In vitro toxicity tests were carried out on the cyclopropyl ester of 2-cineolylols, the most promising of these compounds as a potential perfume ingredient. In this study, cultured mouse fibroblast L-929 and human keratinocyte NCTC 2544 cell lines were used. The results obtained with the evaluation of three different physiological end points showed that the tested compound possess much lower cytotoxicity than sodium dodecylsulphate (SDS) used as positive control.

Lack of DNA alterations induced by orotic acid in rat liver as evaluated with two DNA unwinding methods.

One percent orotic acid supplemented diet is a promoting treatment in the rat model of liver carcinogenesis. After treatment with this type of diet, DNA alterations were observed using alkaline sucrose gradients and alkaline elution methods. In this work we have utilized two unwinding methods for the detection of DNA fragmentation. One method is a viscosimetric method in which the rate of increase in DNA viscosity with time is related to the rate of alkaline DNA unwinding. The second method measures fluorimetrically the amount of renatured and denatured DNA after different times allowed for alkaline DNA unwinding. These two methods are very sensitive in detecting DNA breaks induced by typical alkylating agents, X-rays and H2O2. The two unwinding methods were clearly negative for the orotic acid supplemented diet. We suggest that the DNA alterations detected with alkaline sucrose gradients and alkaline elution methods, after promoting treatment with orotic acid, are probably different from the DNA breaks induced by typical alkylating agents, X-rays and H2O2.