Inhibition of class-3 aldehyde dehydrogenase and cell growth by restored lipid peroxidation in hepatoma cell lines.

Hepatoma cells have a below-normal content of polyunsaturated fatty acids; this reduces lipid peroxidation and the production of cytotoxic and cytostatic aldehydes within the cells. In proportion to the degree of deviation, hepatoma cells also show an increase in the activity of Class-3 aldehyde dehydrogenase, an enzyme important in the metabolism of lipid peroxidation products and also in that of several drugs. When hepatoma cells with different degrees of deviation were enriched with arachidonic acid and stimulated to peroxidize by ascorbate/iron sulphate, their growth rate was reduced in proportion to the quantity of aldehydes produced and to the activity of aldehyde dehydrogenase. Therefore, 7777 cells, less deviated and with low Class-3 aldehyde dehydrogenase activity, were more susceptible to lipid peroxidation products than JM2 cells. It is noteworthy that repeated treatments with prooxidant also caused a decrease in mRNA and activity of Class-3 aldehyde dehydrogenase, contributing to the decreased growth and viability. Thus, Class-3 aldehyde dehydrogenase could be considered relevant for the growth of hepatoma cells, since it defends them against cell growth inhibiting aldehydes derived from lipid peroxidation.

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.

Genotoxic effects of alpha-hexachlorocyclohexane in primary cultures of rodent and human hepatocytes.

The genotoxicity of alpha-hexachlorocyclohexane (alpha-HCH) was evaluated in primary cultures of mouse, rat and human hepatocytes. DNA fragmentation was measured by the alkaline elution technique and DNA repair synthesis by quantitative autoradiography. A 20 h exposure to subtoxic concentrations ranging from 0.056 to 0.32 mM produced a dose-dependent frequency of DNA breaks in rat hepatocytes and in hepatocytes from four of five human donors, but not in mouse hepatocytes, DNA repair induction was absent in hepatocytes from all three species. The reduction in the frequency of DNA breaks observed in rat hepatocytes simultaneously exposed to metyrapone suggests that alpha-HCH is transformed into reactive species by a cytochrome P450-dependent reaction. The detection of DNA fragmentation but not of DNA repair synthesis may be tentatively explained by assuming that alpha-HCH behaves as a chemical eliciting short patch DNA repair, which is more easily revealed as genotoxic by the occurrence of DNA single-strand breaks.

The changing managed care market.

A continuum of managed care options has evolved reflecting differing health care market characteristics. Alternative health plans are increasing, outdistancing the "gold standard" staff model HMOs. A dizzying array of options, however, has led to considerable confusion. Direct contracting has evolved as a way for employers to understand what they are paying for and to managed costs. Increases in managed care, and a degree of financial distress, will encourage the development of integrated networks. National reform is unlikely to convert today's loosely structured system to a fully integrated system overnight, but will stimulate managed care in markets sooner than otherwise expected.