Perturbation of cytochrome P450, generation of oxidative stress and induction of DNA damage in Cyprinus carpio exposed in situ to potable surface water

Abstract

Epidemiological evidence suggests a link between consumption of chlorinated drinking water and various cancers. Chlorination of water rich in organic chemicals produces carcinogenic organochlorine by-products (OBPs) such as trihalomethanes and haloacetic acids. Since the discovery of the first OBP in the 1970s, there have been several investigations designed to determine the biological effects of single chemicals or small artificial OBP combinations. However, there is still insufficient information regarding the general biological response to these compounds, and further studies are still needed to evaluate their potential genotoxic effects. In the current study, we evaluated the effect of three drinking water disinfectants on the activity of cytochrome P450 (CYP)-linked metabolizing enzymes and on the generation of oxidative stress in the livers of male and female Cyprinus carpio fish (carp). The fish were exposed in situ for up 20 days to surface water obtained from the Trasmene lake in Italy. The water was treated with 1-2 mg/L of either sodium hypochlorite (NaClO) or chlorine dioxide (ClO 2 ) as traditional disinfectants or with a relatively new disinfectant product, peracetic acid (PAA). Micronucleus (MN) frequencies in circulating erythrocytes from the fish were also analysed as a biomarker of genotoxic effect. In the CYP-linked enzyme assays, a significant induction (up to a 57-fold increase in the deethylation of ethoxyresorufin with PAA treatment) and a notable inactivation (up to almost a 90% loss in hydroxylation of p-nitrophenol with all disinfectants, and of testosterone 2␤-hydroxylation with NaClO) was observed in subcellular liver preparations from exposed fish. Using the electron paramagnetic resonance (EPR) spectroscopy radical-probe technique, we also observed that CYP-modulation was associated with the production of reactive oxygen species (ROS). In addition, we found a significant increase in MN frequency in circulating erythrocytes after 10 days of exposure of fish to water treated with ClO 2 , while a non-significant six-fold increase in MN frequency was observed with NaClO, but not with PAA. Our data suggest that the use of ClO 2 and NaClO to disinfect drinking water could generate harmful OBP mixtures that are able to perturb CYP-mediated reactions, generate oxidative stress and induce Abbreviations: NaClO, sodium hypochlorite; ClO 2 , chlorine dioxide; PAA, peracetic acid; CYP, cytochrome P450; MN, micronuclei; OBPs, organochlorine by-products; ROS, reactive oxygen species * Corresponding author. . Sapone et al. / Mutation Research 626 (2007) 143-154 genetic damage. These data may provide a mechanistic explanation for epidemiological studies linking consumption of chlorinated drinking water to increased risk of urinary, gastrointestinal and bladder cancers.

Modulation of cytochrome P450 and induction of DNA damage in Cyprinus carpio exposed in situ to surface water treated with chlorine or alternative disinfectants in different seasons

“…The positive mutagenic effect here detected by the MN induction in fish erythrocytes confirms those previously presented by Sapone et al [32]. They are also in agreement with results obtained from the longitudinal study on the genotoxic effect (Comet assay and MN test) induced by disinfectants in fish erythrocytes of C. carpio [54] which showed a clear genotoxic effect mainly induced by NaClO and to a lesser extent by ClO 2 , as opposed to the negative results obtained from PAA.…”

“…A similar heterogeneous pattern of induction/suppression of phase I MFO modulation was also shown in a previous pilot experiment carried out in autumn (October) [32]. It was reported that the most induced CYP isoforms were CYP1A1 and CYP2B1, in particular with PAA and NaClO disinfectants after 10 days' treatment while the most notable inactivation regarded CYP2E1 activity by ClO 2 in both time periods.…”

“…To better characterize and mimic real human exposure, the effects of two traditional chlorinated disinfectants (NaClO and ClO 2 ) and an alternative disinfectant (PAA) were investigated on the modulation of liver CYP-linked monooxygenases of Cyprinus carpio fish, exposed in situ (up to 20 days) to treated surface waters from Lake Trasimene near Perugia, Italy. As CYP induction is linked to an overproduction of free radical and mutagenic metabolites (co-mutagens), these endpoints are regarded as possible epigenetic mechanisms for DBP carcinogenesis [28][29][30][31][32], which are totally ignored in most works. A parallel estimation of the genotoxic effect of the three disinfectants was also carried out through the micronucleus (MN) test in circulating erythrocytes of the same C. carpio fish populations.…”

Evidence of Bioactivation of Halomethanes and its Relation to Oxidative Stress Response in Chirostoma riojai, an Endangered Fish from a Polluted Lake in Mexico

“…These findings were confirmed by the areas obtained in IBR star plots. In contrast to these results, depletion of CYP 2E1-like activity has been reported to occur in common carp (Cyprinus carpio) exposed to HM precursors, such as NaClO and ClO 2 (Sapone et al 2007). These differences are probably explained by oxidative damage induced by residual chlorine, although some part of the content of these chemicals may have formed HMs depending on temperature, pH, and the presence of organic carbon.…”

“…There is little information regarding toxicity in fish induced by HMs and haloacids, which are potentially carcinogenic compounds (Teuschler et al 2000;Sapone et al 2007). In the present study, formaldehyde, a major metabolite of chlorinated or chlorobrominated HMs, was detected in both organ tissues, but its levels were greater in liver.…”