Drinking water quality: an in vitro approach for the assessment of cytotoxic and genotoxic load in water sampled along distribution system

An in vitro approach was performed to assess the quality of drinking water collected at two treatment/distribution networks located near the source (Plant #1) and the mouth of River Po (Plant #2). The water was sampled at different points of each distribution network, before (raw water) and after the chlorine dioxide disinfection, and in two points of the pipeline system to evaluate the influence of the distribution system on the amount and quality of the disinfection by-product. Cytotoxicity and genotoxicity of water extracts were evaluated in human peripheral lymphocytes and Hep-G2 cells by the use of the micronucleus (MN) test and Comet assay. Raw water samples of both plants induced cytotoxic effects, but not the increases of MN frequency in Hep-G2 cells and in human lymphocytes. Increases of DNA damage in human leukocytes was detected by Comet assay for raw water of Plant #2 at concentration > or = 0.25 Leq/mL. The disinfection process generally has reduced the toxicity of water samples, even if potential direct DNA-damaging compounds have been detectable in drinking water samples. The proposal approach, if currently used together with chemical analysis, can contribute to improve the monitoring drinking water.

Estrogenic activity of procymidone in primary cultured rainbow trout hepatocytes (Oncorhynchus mykiss)

It has been shown that procymidone, a dicarboximide fungicide, alters sexual differentiation in vivo and in vitro. The aim of this study was to evaluate the estrogenic activity of this fungicide using the synthesis of vitellogenin (Vtg) in rainbow trout hepatocyte as a biological marker. The cells were treated for 24 h with procymidone 150 microM, using 17beta-estradiol 20 microM as a positive control. The doses were chosen on the basis of cell viability (Neutral Red and MTT tests) and solubility. The results show that procymidone leads to a qualitative and quantitative increase in Vtg synthesis. In Western immonoblots, the 170 and 30 kDa bands, which respectively correspond to the monomeric form of Vtg and posvitine, were brighter in cells treated with procymidone and 17beta-estradiol than those corresponding to the negative controls (cells treated for 24 h with DMSO 0.1% alone); ELISA showed that the cells treated with the fungicide and 17beta-estradiol had a 48 and 76%, respectively, higher Vtg concentration than the negative controls (P<0.01). Western blotting also revealed the induction of HSP27 (27 KDa), which further confirms the estrogenic acitivity of procymidone as it is known that the 3' region of HSP27/28 containing the gene mRNAs is induced by estrogen treatment. Procymidone increased also the production of both HSP70 protein (70 KDa) and free oxygen radicals. This last finding is in agreement with the toxic mechanism of dicarboximide fungicides. It can therefore be presumed that the estrogenic activity of procymidone in primary cultured trout hepatocytes is related to oxidative damage which, as many other studies have shown, can increase the levels of estrogens such as 17beta-estradiol, and thus increase Vtg synthesis

Response of rainbow trout (Oncorhynchus mykiss) D-11 cell line to 3-methylcholanthrene (3MC) exposure

The rainbow trout cytochrome P4501A gene subfamily consists of two members, CYP1A1 and CYP1A3, which are induced by polycyclic aromatic hydrocarbons (PAHs). In this study, we investigated the induction of cytochrome P4501A3 in the rainbow trout (Onchorhynchus mykiss) D-11 cell line after 3-methylcholanthrene (3MC) exposure by generating chimeric constructs in which a 2.3 kb fragment or portion of the 5'-flanking region of the trout cytochrome CYP1A3 gene was fused to the firefly luciferase (Luc) gene. The constructs were then transiently transfected into the trout D-11 cells and their transcriptional activity measured by luciferase assay after treatment with different 3MC concentrations. Maximal induction following exposure to 2 microM 3MC was 2.2-fold after 72 h. Deletion of the region specifying the 5' untranslated region (5'UTR) of the mRNA encoding the CYP1A3 gene increased unstimulated luciferase activity but also led to a loss of response to 3MC treatment. This finding suggests that the region specifying the 5'UTR contains a negative element that is also involved in the transcriptional response to 3MC.

[Evaluation of the effects following low doses of inorganic mercury from environmental and occupational exposures]

AIMS

This paper reviews the studies, both in vivo and in vitro, carried out for the project on low-dose effects of inorganic mercury, financed by the Italian Ministry of Universities and Scientific and Technological Research.

RESULTS, COMMENTS AND PROPOSAL

The results offer both innovative aspects and potential practical applications. Particular attention is drawn to the reliability of biomarkers of exposure [mercury in urine (HgU) and blood (HgB), possibility of speciation] as well as to the availability of guidance values for risk assessment (reference value, action level, biological threshold value). In the general population, HgU and HgB levels are significantly related to the presence of dental amalgams and to fish consumption; nevertheless, such exposure levels do not elicit adverse health effects on renal, immune and nervous functions, according to the markers evaluated in the studies. The present biological threshold values for occupational exposure appear adequate to prevent health effects, considering the immune system, kidney and central nervous system as the target organs. However, possible effects of low doses of mercury on immune and neuroendocrine functions should be further examined; moreover, consideration should be given to the risk of consuming fish species with high Hg content, particularly concerning the renal and central nervous system effects. Finally, further studies should be planned on other potentially important effects, that could not be considered in this study, such as those on prenatal development, the cardiovascular system and the thyroid gland.

Effect of iprodione, a dicarboximide fungicide, on primary cultured rainbow trout (Oncorhynchus mykiss) hepatocytes

As is known from literature, iprodione, a dicarboximide fungicide, has a highly specific action, with a capacity to cause oxidative damage through production of free oxygen radicals (ROS), but it does not appear to be species selective. Since this substance is able to diffuse in water, evaluation of its capacity to induce oxidative damage in an aquatic organism such as the rainbow trout (Oncorhynchus mykiss) was considered of particular interest. A study was, therefore, undertaken to investigate the effect of iprodione on free radicals (ROS) and malondialdehyde (MDA) production, reduced glutathione (GSH) content and catalase activity (CAT), in primary cultured trout hepatocytes, following treatment with 0.2, 0.3 and 0.4 mM concentrations for a 24-h period. The iprodione 0.3 and 0.4 mM concentrations increased both ROS and MDA production and decreased GSH content and CAT activity. These results suggest that iprodione is able to produce oxidative damage in primary cultured fish hepatocytes, thus confirming that its action is specific, but not species selective. It is also well known that ROS production in fungi is due to interaction with the flavin enzyme NADPH cytochrome c reductase to the extent that the normal electron flow from NADPH to cytochrome c is blocked. In contrast, we observed that, in primary cultured trout hepatocytes, iprodione appears to have no effect on NADPH cytochrome c reductase activity. It is, therefore, possible to presume that the mechanism of oxidative damage in trout hepatocytes differs from that observed in fungi. Moreover, our experiments also demonstrate that iprodione is able to induce "in vitro" CYP1A1, leading to the conclusion that the production of ROS is due to this phenomenon.

Stimulation of in vitro rat hepatocyte proliferation by conditioned medium obtained from an immortalized macrophage cell line

The hepatomitogenic effect of conditioned medium (CDM), obtained from the N-11 mouse macrophage cell line was analysed in rat hepatocyte primary cultures. CDM concentrations from 0.01% to 100% were used and the stimulating action in terms of mitotic index (MI) was evaluated. A clear mitogenic effect was observed only with concentrations higher than 10% with peak effects around 60%. Further increase in CDM concentrations resulted in an MI decrease, and at 100% CDM the effect was totally abolished. Tests addressed to identify the presence of hepatocyte growth factor (HGF) yielded negative results. In order to identify the mitogenic factor(s) involved, we tested CDM obtained after lipopolysaccharide (LPS) stimulation of N-11 cells. Comparison of the results obtained with untreated or LPS stimulated CDMs suggested that macrophage activation does not affect the release of hepatomitogenic activity. To further characterize this macrophage-derived activity, we checked whether CDM could interact with the mitogenic effects of epidermal growth factor (EGF). CDM (10 or 50%) showed no stimulatory effect to hepatocytes cultured in the presence of a maximally stimulatory concentration of EGF. Conversely, both CDM concentrations were able to increase the MI of hepatocyte cultures treated with a suboptimal dose of EGF. These results suggest that macrophages release factor(s) which interact, in hepatocytes, with the EGF signal transduction mechanisms, or with the EGF receptor itself.

Hyperbaric oxygen increases plasma exudation in rat trachea: involvement of nitric oxide

This study investigates the microvascular permeability changes in tracheal tissue of rats exposed to hyperbaric oxygen (HBO). Rats, following exposure to HBO or ambient air (control animals) for 1.5, 3 and 6 h, were prepared for recording of nitric oxide exhaled (FENO) in air using a chemiluminescence analyser. The level of FENO was not statistically different in the two groups. Plasma exudation, evaluated by measuring the leakage of Evans blue (EB) dye into the tracheal tissue, was significantly elevated (48, 86 and 105% at 1.5, 3 and 6 h, respectively) in HBO-treated rats. Plasma exudation in the trachea of control rats was significantly increased (42%, P<0.05) by NG-nitro-L-arginine methyl ester (L-NAME), whereas it was significantly reduced (31%, P<0.05) in rats exposed to HBO for 3 h. N-acetylcysteine (NAC) and flunisolide significantly prevented the increase in plasma leakage in HBO-treated rats. In contrast, indomethacin was devoid of anti-exudative activity in these experiments. Western immunoblot showed a significant increase in the level of inducible nitric oxide synthase (iNOS) protein in the tracheal homogenates of HBO-treated rats, as compared to basal levels. These results indicate that nitric oxide (NO) is involved in the maintenance of microvascular permeability in tracheal tissue of rats. The protective effect observed with the steroid seems to support this hypothesis. Furthermore, the beneficial action of NAC underlines that reactive oxygen species participate in the microvascular permeability changes observed in tracheal tissue of rats exposed to HBO.

Adaptation to oxidative stress: effects of vinclozolin and iprodione on the HepG2 cell line

It is well known that the dicarboximide fungicides, vinclozolin and iprodione, induce lipid peroxidation by means of oxygen activation in fungi, but their action on mammalian cells is not yet clear. We therefore investigated the effect of 1- and 24-h treatments with vinclozolin at concentrations of 25, 50, 100 microg/ml and iprodione at concentration of 62.5, 125, 250 microg/ml on malonaldehyde and free radical production and on reduced glutathione levels in the human HepG2 hepatoma cell line. The concentrations were chosen on the basis of neutral red cytotoxicity assays. One-hour treatment with the different concentrations of either vinclozolin or iprodione increased both malonaldehyde and free radical content, and decreased reduced glutathione levels, whereas 24-h treatment decreased malonaldehyde content and free radical production, and increased reduced glutathione concentration. These results suggest that the mammalian cells respond to the initial oxidative damage caused by the two dicarboximide fungicides by means of a characteristic adaptative phenomenon within 24 h. This hypothesis is supported by the antagonized effects caused by treatment with the two dicarboximide fungicides and buthionine sulfoximine 0.5 mM, a specific and irreversible inhibitor of reduced glutathione synthesis. The data confirm that the two dicarboximide fungicides maintain their specific action in mammalian cells, although this action is masked by adaptation.

Carbendazim and n-butylisocyanate: metabolites responsible for benomyl double action on cytochrome P450 in HepG2 cells

Changes in the cytochrome P450 monooxygenase system were investigated in HepG2 cells treated for 24 h with 1.25, 2.5, 5, 10 and 20 microg/ml of carbendazim (MBC) and n-butylisocyanate (BIC), the principal benomyl metabolites. The results show that n-butylisocyanate leads to a decrease in both ethoxyresorufin deethylase (P4501A1) (EROD) and ethoxycoumarin deethylase (P4502B) (ECOD), whereas MBC has no effect on EROD and increases ECOD. The decrease in ECOD and EROD activities after BIC treatment can be attributed to the detrimental action of this substance. The MBC-induced increase in ethoxycoumarin can be considered an enzyme-specific inductive phenomenon. This hypothesis was confirmed by Western immunoblot analysis and treatment with actinomycin D 8 x 10(-4) microM: the first showed an increase in P4502B isoenzyme content and the second evidence of a partial block of the increase in ECOD activity induced by MBC. Given these results, MBC and BIC seem to be the metabolites responsible for the double opposite action of their parent compound benomyl. Data deriving from an equimolar mixture of the two metabolites suggest that benomyl activity on some cytochrome P450 isoenzymes is the result of a balance between the action of the single metabolites (Radice et al., 1996).

Influence of acetylcysteine on aggravation of ischemic damage in ex vivo hearts of rats exposed to hyperbaric oxygen

Rats were exposed to hyperbaric oxygen (HBO = 100% oxygen; 2.5 atmospheres absolute pressure) for 6 h. Isovolumic left heart preparations from these animals were subjected to global low flow-ischemia (perfusion rate from 12 ml/min to 2 ml/min for 40 min) and reperfusion. Hearts from rats not exposed to HBO underwent the same ischemic-reperfusion procedure (controls). As compared to control, HBO treatment caused in ex vivo hearts a significant aggravation of cardiac ischemic picture as indicated by a marked increase in left ventricular end diastolic pressure (LVEDP) and reduced post ischemic left ventricular developed pressure (LVDP). At the end of the ischemic and reperfusion periods LVEDP values were 6.8 (p < 0.001) and 8 (p < 0.001) times higher than the corresponding control values. Moreover, LVDP and coronary perfusion pressure (CPP) values were decreased (2.8 times; p < 0.001) and increased (56%; p < 0.001), respectively, as compared to control preparations. These events were also associated with a considerable impairment of the cardiac tissue to generate 6-keto-PGF1 alpha. Treatments of rats with different doses of acetylcysteine (N-acetylcysteine, CAS 616-91-1, NAC; 0.25-0.5-1 g/kg p.o.) before HBO displayed a clear-cut and dose-related protective activity in hearts subjected to ischemia-reperfusion. Also the generating capacity of 6-keto-PGF1 alpha from these hearts were restored according to the dose of NAC employed. When aortic rings from rats exposed to HBO were considered, they showed a reduced capacity to release 6-keto-PGF1 alpha and an increased sensitivity to endothelin-1. At the same time, the relaxant activity of acetylcholine in these tissues was almost lost. Again, NAC treatment of the animals before HBO restored in a dose-dependent way the capacity of the aortic rings to generate 6-keto-PGF1 alpha. This event was paralleled by normalized responses of the preparations to endothelin-1 and acetylcholine. Taken together these results clearly indicate that acute HBO treatment of the rats markedly aggravates the ischemic-reperfusion damage in ex vivo hearts. This event is coupled with a compromised integrity of cardiac and extracardiac endothelial cell functions. The protective activity of NAC observed in this study once more emphasises its therapeutic role in increasing antioxidant defence mechanisms.

Hyperbaric oxygen worsens myocardial low flow ischemia-reperfusion injury in isolated rat heart

In these experiments rats were exposed to hyperbaric oxygen (100% oxygen; 2.5 atmospheres absolute pressure) for 1, 3 or 6 h. At the end of these periods the hearts were removed and subjected to low flow ischemia (perfusion rate from 12 ml/min to 2 ml/min for 40 min) and reperfusion. Hearts excised from control rats were subjected to the same procedure of ischemia and reperfusion. The data obtained from these experiments clearly indicate that the ischemic picture observed in control hearts is worsened in hearts obtained from hyperbaric oxygen-exposed animals. In fact, after ventricular standstill of the ischemic phase, the left ventricular end-diastolic pressure increased significantly and proportionally according to the time of hyperbaric oxygen exposure. The vasopressor activity of angiotensin II on coronary perfusion pressure was significantly changed, as compared to that in the control preparation: these alterations, well correlated to the time of hyperbaric oxygen exposure, seem to suggest impairment of the vascular endothelium-dependent relaxant function. Furthermore N-acetylcysteine and defibrotide, given orally to the rats before hyperbaric oxygen exposure, prevented the aggravation of the ischemic damage induced in ex vivo hearts.

Benomyl affects the microtubule cytoskeleton and the glutathione level of mammalian primary cultured hepatocytes

Rat primary hepatocyte cultures have been used to study the effect of Benomyl alone or in combination with Pirimiphos-methyl. The results presented demonstrate that Benomyl alone is responsible for the microtubular disorganization in both a time- and dose-dependent manner, that the effect is reversible after the agent is removed, and that Benomyl is a potent glutathione-depleting agent. Pirimiphos-methyl, alone or combined with Benomyl had no effect on microtubule organization, but reinforced the decrease in glutathione.

Increase of micronucleus frequency in cultured rat hepatocytes treated in vitro with benomyl and pirimiphos-methyl separately and in mixture

The pesticides benomyl, a benzimidazole fungicide, and pirimiphos-methyl, an organophosphorus insecticide, were tested separately and in combination at a ratio of 6:1, a mixture frequently found in foodstuffs by residual analysis, to determine their possible genotoxic action. The effect was measured by the micronucleus test carried out on cultured rat hepatocytes stimulated to proliferate by epidermal growth factor (EGF). Adult rat hepatocytes were exposed in vitro for 48 h to the substances at increasing non-cytotoxic doses, chosen on the basis of cytotoxicity tests such as LDH and Neutral red assays. Benomyl induced a significant dose-related increase in micronucleus frequency; in contrast, pirimiphos-methyl was not genotoxic at any dose tested. When the hepatocytes were exposed to the two pesticides together at increasing doses, an enhancement in micronucleus frequency similar to that of benomyl alone was found, indicating that at this ratio and non-cytotoxic doses (up to 25 micrograms/ml benomyl + 4.2 micrograms/ml pirimiphos-methyl) no interaction occurs.

Genotoxicity assay of five pesticides and their mixtures in Saccharomyces cerevisiae D7

Four organophosphorus pesticides (azinphos-methyl, diazinone, dimethoate, and pirimiphos-methyl), and one carbamate (benomyl) were tested for cytotoxicity, reverse mutation and gene conversion in Saccharomyces cerevisiae D7, with and without the S9 metabolic system. Furthermore, two mixtures of the above compounds, namely benomyl + pirimiphos-methyl (6/1 ratio) and dimethoate + diazinone + azinphos-methyl (10/4/6 ratio) were tested in the same experimental model. Azinphos-methyl, benomyl, and pirimiphos-methyl alone did not induce any genotoxic effect, whereas azinphos-methyl and diazinone were active in inducing reversion and gene conversion. The benomyl + pirimiphos-methyl mixture did not show any genotoxic activity. The dimethoate + diazinone + azimphos-methyl mixture was genotoxic, although an antagonistic effect between the components was observed. The addition of S9 post-mitochondrial liver fraction decreased the activity of both single and mixed genotoxic agents.

Intraocular and plasma kinetics of tenoxicam in rabbits

Non-steroidal anti-inflammatory drugs (NSAID) represent potentially useful agents in the treatment of a number of ocular pathologies, but their intraocular penetration and distribution have not yet been reported. With the aim of clarifying this point, we evaluated the concentrations of the well known NSAID, tenoxicam, in the aqueous and vitreous humors of rabbits treated i.m. with the drug (7 mg/kg). The tenoxicam kinetics in these ocular fluids followed that in plasma with the time-to-peak shifted to higher values in the vitreous (1 h) as compared to that in the aqueous and plasma (40 min). AUC was also higher in the vitreous (10.4 micrograms.h/ml) than in the aqueous humor (2.8 micrograms.h/ml).

Tolerance to some behavioural effects of lisuride, a dopamine receptor agonist, and reverse tolerance to others, after repeated administration

To investigate whether prolonged pretreatment with the dopamine (DA) agonist lisuride would result in modification of some of its behavioural effects, food intake, locomotor activity, body temperature or stereotyped and mounting behaviour were evaluated after acute injections of different doses of lisuride into rats, pretreated daily for four weeks with either saline or lisuride. Rats pretreated with lisuride developed tolerance to its anorexigenic and hypothermic effects, and reverse tolerance to its effects on locomotor activity, stereotyped and mounting behaviour. Pretreatment with lisuride did not modify the activity of drug-metabolizing enzymes in the liver. These results, in addition to revealing the pattern of the changes in the behavioural effects of a DA agonist drug, after repeated administration, may be taken as evidence for the existence of different DA receptor systems in different areas of the brain, that mediate different behavioural effects, and that differ markedly in their reactions to prolonged stimulation with an agonist drug.

Biochemical and morphological comparison of microsomal preparations from rat, quail, trout, mussel, and water flea

Differential centrifugation methods already in use were applied to purify rat, quail, and trout liver microsomes and modified as necessary to purify microsomes from mussel digestive gland and whole water flea. All these microsomal preparations were comparatively characterized with respect to protein and RNA content, levels of markers of subcellular contaminants, ultrastructural morphology, differential spectra of cytochromes P-450 and b5, monoxygenase activity, and in vitro metabolism of p-dichlorobenzene. Yields of microsomal proteins of the tested organisms differed widely, with mussel showing the lowest yield. Very low levels of nuclear and mitochondrial contaminants were detected in all microsomal preparations, but cell membrane contaminants were clearly present in most preparations. Daphnia microsomes were significantly contaminated by plasma membranes, and hepatopancreas microsomes contained significant amounts of partially disrupted secretory granules and plasma membrane. From a qualitative standpoint differential spectra of cytochrome b5 were very similar for all the preparations, whereas cytochrome P-450 spectra were largely dependent on the microsomal preparation as well as on the assay method used. The content of cytochrome P-450 was highest for rat liver microsomes and very low or absent in Daphnia and mussel preparations; the range of cytochrome b5 contents was much narrower. Significant differences were observed among monoxygenase activities of the different preparations. In Daphnia and mussel microsomes, aniline hydroxylase was absent and benzo[a]pyrene hydroxylase activity was much lower than in rat and quail microsomes. Benzo[a]pyrene hydroxylase activity of trout liver microsomes was similar to that of rat and quail microsomes, whereas hydroxylation of substrates which in rat liver are preferentially metabolized by phenobarbital-inducible forms of cytochrome P-450 was much lower in trout microsomes.

Interaction of acrylonitrile with the liver mixed function oxidases

The effect on the liver mixed function oxidases of acrylonitrile revealed an inhibition of the benzo(a)pyrene hydroxylase and of the epoxide hydrase whereas aniline hydroxylase is unaffected. These findings exclude the possibility that the inhibitory effect of certain hydroxylation activities of the liver microsomes can be secondary to a direct effect of acrylonitrile on cytochrome P-450 but suggest the hypothesis that the inhibition is mediated by the cyanide released during acrylonitrile metabolism.

Chromosome damage in heroin-marijuana and marijuana addicts

The aim of this study was to determine the frequency of chromosome damage in heroin-marijuana addicts and marijuana addicts. A group of 45 subjects, aged between 19 and 21 years, was divided into 15 controls, 15 heroin-marijuana addicts and 15 marijuana addicts. These patients were examined for the presence of chromosome aberrations in their peripheral lymphocytes. The findings indicate that the incidence of chromosome anomalies in heroin-marijuana addicts is approximately 21.3 times greater than in the controls and approximately 7.9 times greater than in marijuana addicts.

NADH-dependent aryl hydrocarbon hydroxylase in rat liver mitochondrial outer membrane

NADH-dependent 3,4-benzpyrene hydroxylase activity was detected in the purified mitochondrial outer membrane fraction from the livers of rats treated with 3-methylcholanthrene. The specific activity in the outer membrane fraction is nearly equal to that of microsomes, a level too high to be accounted for only by the microsomal contamination. On the other hand, the NADPH-dependent 3,4-benzpyrene hydroxylase activity in the outer membrane fraction is about 50% of that of microsomes. The ratio of the specific activity of NADPH- to NADH-dependent 3,4-benzpyrene hydroxylase in microsomal fraction was about 3.5, while that of the outer membrane fraction was about 1.5. Moreover, it was found that NADH-dependent 3,4-benzpyrene hydroxylase activity in mitochondrial outer membrane from control rat liver was cyanide-insensitive, while that in microsomes was cyanide-sensitive. These results suggest the presence in the mitochondrial outer membrane fraction of aryl hydrocarbon hydroxylase activity which uses as electron donor NADH nearly to the same extent as NADPH. The hydroxylase system is composed of cyanide-insensitive cytochrome P-450 and is inducible markedly by 3-methylcholanthrene treatment. The probable electron transfer pathways in the mitochondrial outer membrane cytochrome P-450 oxidase system are discussed.