Induction of CYP1A1 in rat liver after ingestion of mussels contaminated by Erika fuel oils.

Polycyclic aromatic hydrocarbons (PAH) are known to be specific inducers of CYP1A1 expression in vertebrates. CYP1A1 induction has been widely studied in mammal cell cultures or in vivo, in conditions of exposure to single PAH chemicals. Here, we studied the possible transfer of PAH to rats via the food chain in environmentally-relevant conditions. Rats were fed for 2 days with PAH-contaminated mussels sampled on coasts polluted by the Erika oil-tanker wreck. CYP1A1 expression was investigated by measuring mRNA levels and EROD enzymatic activity over the 84 h following the last ingestion. CYP1A1 expression in treated rats was compared to controls fed with mussels free from PAH contamination. The results showed that ingestion of PAH-contaminated mussels induced CYP1A1 mRNA and EROD activity. Increase of transcriptional level and of EROD activity was transient with a peak within 12 h and a return to basal levels within 36 h.

Insights into the role of the metal binding site in methionine-R-sulfoxide reductases B.

Methionine sulfoxide reductases B (MsrBs) catalyze the reduction of methionine-R-sulfoxide via a three-step chemical mechanism including a reductase step, formation of an intradisulfide bond followed by a thioredoxin recycling process. Fifty percent of the MsrBs, including the Escherichia coli enzyme, possess a metal binding site composed of two CXXC motifs of unknown function. It is located on the opposite side of the active site. The overexpressed E. coli MsrB tightly binds one atom of zinc/iron. Substitution of the cysteines of E. coli MsrB results in complete loss of bound metal and reductase activity, and leads to a low-structured conformation of the protein as shown by CD, fluorescence, and DSC experiments. Introduction of the two CXXC motifs in Neisseria meningitidis MsrB domain leads to a MsrB that tightly binds one atom of zinc/iron, shows a strongly increased thermal stability and displays a reductase activity similar to that of the wild-type but lacking thioredoxin recycling activity. These results demonstrate the stabilizing effect of the metal and the existence of a preformed metal binding site in the nonbound metal MsrB. The data also indicate that metal binding to N. meningitidis MsrB induces subtle structural modifications, which prevent formation of a competent binary complex between oxidized MsrB and reduced thioredoxin but not between reduced MsrB and substrate. The fact that the E. coli and the N. meningitidis MsrBs exhibit a similar thermal stability suggests the existence of other structural factors in the nonbound metal MsrBs that compensate the metal bound stabilizing effect.

DNA damage measured by the single-cell gel electrophoresis (Comet) assay in mammals fed with mussels contaminated by the 'Erika' oil-spill.

This research aimed to estimate potential genotoxicity for consumers resulting from the ingestion of seafood contaminated with polycyclic aromatic hydrocarbons (PAHs) released into the marine environment after the 'Erika' shipwreck along the coasts of south Brittany, in France. Mussels (Mytilus sp.) collected from sites on the Atlantic coast that were affected by the oil slick in various degrees, were used to feed rats daily for 2 and 4 weeks. DNA damage was measured by use of the Comet assay in the liver, bone marrow and blood of rats receiving food contaminated with 312 microg of 16PAHs/kg dry weight (d.w.) equivalent to 33.8 microg TEQs (toxic equivalent quantities to benzo(a)pyrene (BaP))/kg d.w. mussels, 569 microg/kg d.w. (83.6 microg TEQs/kg) and 870 microg/kg d.w. (180.7 microg TEQs/kg). A dose-effect-time relationship was observed between the amount of DNA damage in the liver and bone marrow of the rats and the PAH contamination level of the mussels. Genotoxicity increased during the period between 15 and 30 days in rats that received food at the highest two PAH levels. On the other hand, no significant change in liver and bone marrow of rats fed with mussels containing 33.8 microg TEQs/kg d.w. was recorded at 30 days compared with 15 days, indicating efficient DNA repair capacity at low levels of exposure. No signs of genotoxicity were found in peripheral blood. Globally, the observed effects were rather moderate. These results show that oil-contaminated food caused DNA damage in predators, and underline the bioavailability to consumers of pollutants in mussels contaminated with fuel oil. The usefulness of the Comet assay as a sensitive tool in biomonitoring studies analyzing responses of PAH transfer through food webs was also confirmed.

Genotoxicity related to transfer of oil spill pollutants from mussels to mammals via food.

Heavy fuel oils containing high levels of polycyclic aromatic hydrocarbons (PAHs) were released into the marine environment after the Erika oil spill on the Atlantic coast. As highly condensed PAH pollutants can bioaccumulate in invertebrates, their transfer to vertebrates through the food chain was of concern. This study aimed to estimate potential genotoxic effects in rats fed for 2 or 4 weeks with the marine mussel Mytilus edulis contaminated by oil pollutants. Two levels of PAH contamination were studied, around 100 and 500 microg of total PAHs/kg dry weight (d.w.) in mussels. Genotoxic damage in rats was investigated by single-cell gel electrophoresis (Comet assay) and micronucleus assays in liver, bone marrow, and peripheral blood. DNA damage was observed in the liver of rats fed with the most contaminated mussels (500 microg PAHs/kg d.w.).DNA damage also was observed in the bone marrow but less than that in the liver. A small increase in micronuclei frequency was registered as well. This work underlines the bioavailability of pollutants in fuel-oil-contaminated mussels to consumers and the usefulness of the Comet assay as a sensitive tool in biomonitoring to analyze responses to PAH transfer in food. The occurrence of substituted PAHs and related compounds such as benzothiophenes in addition to nonsubstituted PAHs in fuel oils and mussels raised the question of whether they were implicated in the genotoxic effects registered in rats.

Comparative in situ study of the intestinal absorption of aluminum, manganese, nickel, and lead in rats.

This comparative study of the intestinal absorption of four toxic metals (aluminum, manganese, nickel, and lead) carried out in rats using the in situ intestinal perfusion technique was able to measure the partition of each metal between the intestine (intestinal retention), the blood circulation, and target tissues after 1 h. The perfused metal solutions were at concentrations likely to occur during oral intoxication. It was found that aluminum (48 and 64 mM), even as a citrate complex, crossed the brush border with difficulty (0.4% of the perfused amount); about 60% of this was retained in the intestine and the remainder was found in target tissues (about 36%). Conversely, lead (4.8-48 microM) penetrated the intestine more easily (about 35% of the perfused amount), was slightly retained (about 12% of the input), and was soon found in the tissues (about 58% of the input) and to a lesser degree in circulation (about 29%). Within the same concentration range, nickel and manganese showed certain similarities, such as a reduced crossing of the brush border proportional to the increase in the concentration perfused (0.17-9.5 mM). There was similar intestinal retention and absorption (about 80% and 20% of the input, respectively). Manganese crossed the brush border more easily and was diffused more rapidly into tissues. Finally, the addition of equimolar amounts of iron (4.7 mM) produced opposite effects on the absorption of the two elements, inhibiting manganese and showing a trend to increase in nickel absorption. This could be the result of competition between Fe2+ and Mn2+ for the same transcellular transporters and the slight predominance of paracellular mechanism in the event of "Fe2+-Ni2+" association.

Environmental boron exposure and activity of delta-aminolevulinic acid dehydratase (ALA-D) in a newborn population.

Following boron intake, multiple effects have been observed in animal experiments. However, human data is lacking, and no data is available on the ability of boron to accumulate in fetal tissues. Positive responses in animal species suggest that developmental toxicity may be an area of concern in humans, following exposure to boron. Two hypotheses have seemed to account for the multiple effects described in scientific findings. One hypothesis is that boron is a negative regulator that influences a number of metabolic pathways by competitively inhibiting some key enzyme reactions. The other hypothesis is that boron has a role in ionic membrane transport regulations. To better understand boron potential toxicity, the present study examined the relationship between boron exposure and some key enzymes, well-known for their affinity for mineral elements, such as delta-aminolevulinic acid dehydratase (ALA-D), and two fundamental enzymes having a role in ionic membrane transport regulations (Ca-pump and Na(+)K(+)-ATPase). We investigated the potential effects of an environmental boron exposure on the activity of these enzymes in an urban population of 197 "normal" newborns. Environmental boron exposure was assessed in placental tissue. Because of the well-known inhibiting effect of lead on these enzymes, cord blood and placental lead were also analyzed. After adjustment for potential confounders, including lead, placental boron levels were negatively significantly correlated to ALA-D activity while Ca-pump and Na(+)K(+)-ATPase activities did not seem to be affected by the level of boron exposure. Given boron's ability, as a Lewis acid, to complex with hydroxyl groups, we suggest that such a mechanism would explain the inhibiting effect of boron on ALA-D.

In vitro and in vivo studies of lead immobilization by synthetic hydroxyapatite.

Apatite appears a useful compound for removing lead from water, due to its ability to immobilize the metal by precipitation. In dilute solution, dissolved hydroxyapatite [HA, Ca1O(P04)6(OH)2] provided phosphates that were reactive with aqueous lead (molar ratio HA/Pb= 1/10) forming precipitates at around pH 6. These dissolved at a more acidic pH (3). Solid HA in contact with Pb2+ions, led to the formation of pyromorphite [Pblo(P04)6(OH)2], identified by X-ray diffraction and insoluble at pH tested (3-8). The amount of pyromorphite increased with the weight ratio of HA/Pb. When this one increased from 1 to 1000, lead precipitated as pyromorphite rose from 19 to 99%. In vivo experiments on rats confirmed the in vitro results. In fact, lead bioavailability assessed by intestinal perfusion was unchanged in the presence of dissolved HA, whereas it was significantly lower in the presence of solid HA, evaluated by gastric intubation, at a weight ratio equal to 10 (amount of lead absorbed decreased by 60%). Apatite could bean effective means of immobilizing lead in drinking or sewage, since accidental pyromorphite ingestion does not yield bioavailable lead.