Safety assessment of rhamnogalacturonan-enriched carrot pectin fraction: 90-Day oral toxicity study in rats and in vitro genotoxicity studies.

The dietary fibre product examined is a pectic polysaccharide extract from carrot (Daucus carota), enriched for pectin fragments comprising mainly rhamnogalacturonan-I (RG-I) (abbreviated product name cRG-I). To assess the safety of cRG-I for use as food ingredient, repeated-dose oral toxicity and in vitro genotoxicity studies were conducted. In the subchronic toxicity study (OECD test guideline 408), Wistar Hannover rats received cRG-I at dietary levels (w/w) of 0%, 2.5%, 5% and 10% for 13 weeks. cRG-I induced no adverse effects in this study. The NOAEL was 10% in the diet (equivalent to 6.9 and 7.8 g cRG-I/kg body weight/day in male and female rats, respectively). A package of three in vitro genotoxicity tests (Ames, mouse lymphoma and micronucleus assay in human peripheral blood lymphocytes) was negative for induction of point mutation and chromosome damage. An initial Ames test showed a weak positive response in Salmonella typhimurium strain (TA1537). This response was non-reproducible and attributed to microbial contamination as subsequent tests with an irradiated batch of cRG-I including a repeat Ames test were negative. cRG-I was therefore considered to be non-mutagenic.

Transcriptomics analysis of interactive effects of benzene, trichloroethylene and methyl mercury within binary and ternary mixtures on the liver and kidney following subchronic exposure in the rat.

The present research aimed to study the interaction of three chemicals, methyl mercury, benzene and trichloroethylene, on mRNA expression alterations in rat liver and kidney measured by microarray analysis. These compounds were selected based on presumed different modes of action. The chemicals were administered daily for 14 days at the Lowest-Observed-Adverse-Effect-Level (LOAEL) or at a two- or threefold lower concentration individually or in binary or ternary mixtures. The compounds had strong antagonistic effects on each other's gene expression changes, which included several genes encoding Phase I and II metabolizing enzymes. On the other hand, the mixtures affected the expression of "novel" genes that were not or little affected by the individual compounds. The three compounds exhibited a synergistic interaction on gene expression changes at the LOAEL in the liver and both at the sub-LOAEL and LOAEL in the kidney. Many of the genes induced by mixtures but not by single compounds, such as Id2, Nr2f6, Tnfrsf1a, Ccng1, Mdm2 and Nfkb1 in the liver, are known to affect cellular proliferation, apoptosis and tissue-specific function. This indicates a shift from compound specific response on exposure to individual compounds to a more generic stress response to mixtures. Most of the effects on cell viability as concluded from transcriptomics were not detected by classical toxicological endpoints illustrating the benefit of increased sensitivity of assessing gene expression profiling. These results emphasize the benefit of applying toxicogenomics in mixture interaction studies, which yields biomarkers for joint toxicity and eventually can result in an interaction model for most known toxicants.

Toxicogenomic analysis of gene expression changes in rat liver after a 28-day oral benzene exposure.

Benzene is an industrial chemical, component of automobile exhaust and cigarette smoke. After hepatic bioactivation benzene induces bone marrow, blood and hepatic toxicity. Using a toxicogenomics approach this study analysed the effects of benzene at three dose levels on gene expression in the liver after 28 daily doses. NMR based metabolomics was used to assess benzene exposure by identification of characteristic benzene metabolite profiles in urine. The 28-day oral exposure to 200 and 800 mg/kg/day but not 10 mg/kg/day benzene-induced hematotoxicity in male Fisher rats. Additionally these upper dose levels slightly reduced body weight and increased relative liver weights. Changes in hepatic gene expression were identified with oligonucleotide microarrays at all dose levels including the 10 mg/kg/day dose level where no toxicity was detected by other methods. The benzene-induced gene expression changes were related to pathways of biotransformation, glutathione synthesis, fatty acid and cholesterol metabolism and others. Some of the effects on gene expression observed here have previously been observed after induction of acute hepatic necrosis with bromobenzene and acetaminophen. In conclusion, changes in hepatic gene expression were found after treatment with benzene both at the toxic and non-toxic doses. The results from this study show that toxicogenomics identified hepatic effects of benzene exposure possibly related to toxicity. The findings aid to interpret the relevance of hepatic gene expression changes in response to exposure to xenobiotics. In addition, the results have the potential to inform on the mechanisms of response to benzene exposure.

Repeated dose oral toxicological evaluation of concentrated barley beta-glucan in CD-1 mice including a recovery phase.

The cholesterol-lowering effect observed following consumption of oats and barley is attributable to the beta-glucan component of the soluble fiber fraction of these cereal grains. beta-Glucan has also been reported to modulate immune activity, however, few studies have evaluated the hematological effects of beta-glucan following oral exposure. In the current study, a concentrated beta-glucan (64%) preparation from barley (Barley Betafiber) was blended into mouse feed at concentrations of 1, 5, or 10% (corresponding to approximately 0.7, 3.5, and 7% beta-glucan) and evaluated in CD-1 mice. Plasma was collected for clinical chemistry and hematological measurements at the initiation of the study and again following 14 and 28 days of exposure. Plasma was also collected from animals that consumed the same diets for 28-days but were switched to control diet (containing no supplemental beta-glucan) for an additional 14-day period to evaluate reversibility or delayed occurrence of treatment-related changes. Half of the animals were sacrificed for histopathologic analysis following the 28-day exposure period and the other half were evaluated following the recovery period. Histopathologic analysis focused on primary lymphoid organs and lymph nodes proximal and distal to the route of exposure. An additional group of untreated animals (nai;ve) was bled and sacrificed at day 0, 14, 27 and 41 for comparison of the hematology parameters with those of the control group because it was not known if multiple blood draws would affect hematology parameters. Compared to animals consuming the control diet, no treatment-related adverse effects were observed in hematological or clinical chemistry measurements or in organ weights and immunopathology in either sex following consumption of concentrated barley beta-glucan for 28-days or following the recovery period. Likewise, no differences were observed between the nai;ve and control groups. Results from this study showed that consumption of concentrated barley beta-glucan did not cause treatment-related inflammatory or other adverse effects in CD-1 mice.