In vitro metabolism of naphthalene and its alkylated congeners by human and rat liver microsomes via alkyl side chain or aromatic oxidation
Wang, Danlei ; Bruyneel, Ben ; Kamelia, Lenny ; Wesseling, Sebastiaan ; Rietjens, Ivonne M.C.M. ; Boogaard, Peter J. - \ 2020
Chemico-Biological Interactions 315 (2020). - ISSN 0009-2797
Alkylated naphthalene - Human - Michaelis-menten kinetics - Microsomes - Rat
Mineral oils are wide applied in food production and processing and may contain polycyclic aromatic hydrocarbons (PAHs). The PAHs that may be present in mineral oils are typically alkylated, and have been barely studied. Metabolic oxidation of the aromatic ring is a key step to form DNA-reactive PAH metabolites, but may be less prominent for alkylated PAHs since alkyl substituents would facilitate side chain oxidation as an alternative. The current study investigates this hypothesis of preferential side chain oxidation at the cost of aromatic oxidation using naphthalene and a series of its alkyl substituted analogues as model compounds. The metabolism was assessed by measuring metabolite formation in rat and human liver microsomal incubations using UPLC and GC-MS/MS. The presence of an alkyl side chain markedly reduced aromatic oxidation for all alkyl-substituted naphthalenes that were converted. 1-n-Dodecyl-naphthalene was not metabolized under the experimental conditions applied. With rat liver microsomes for 1-methyl-, 2-methyl-, 1-ethyl-, and 2-ethyl- naphthalene, alkyl side chain oxidation was preferred over aromatic oxidation. With human liver microsomes this was the case for 2-methyl-, and 2-ethyl-naphthalene. It is concluded that addition of an alkyl substituent in naphthalene shifts metabolism in favor of alkyl side chain oxidation at the cost of aromatic ring oxidation. Furthermore, alkyl side chains of 6 or more carbon atoms appeared to seriously hamper and reduce overall metabolism, metabolic conversion being no longer observed with the C12 alkyl side chain. In summary, alkylation of PAHs likely reduces their chances of aromatic oxidation and bioactivation.
Molecular analysis of three Clostridium difficile strain genomes isolated from pig farm-related samples
Martín-Burriel, I. ; Andrés-Lasheras, S. ; Harders, F. ; Mainar-Jaime, R.C. ; Ranera, B. ; Zaragoza, P. ; Falceto, V. ; Bolea, Y. ; Kuijper, E.J. ; Bolea, R. ; Bossers, A. ; Chirino-Trejo, M. - \ 2017
Anaerobe 48 (2017). - ISSN 1075-9964 - p. 224 - 231.
Clostridium difficile - Environment - Genome sequencing - PCR-ribotype 078 - Pig - Rat
Clostridium difficile is an anaerobic spore-forming bacillus that usually causes gastrointestinal disorders in man and other animal species. Most of the strains isolated from animals are toxigenic being the virulent ribotype (RT) 078 predominant in several animal species. Although C. difficile is pathogenic to both humans and animals, there is no direct evidence of zoonosis. Deep genome sequencing provides sufficient resolution to analyse which strains found in animals might be related to human pathogens. So far, there are only a few fully sequenced genomes of C. difficile strains isolated from domestic and wild animals. Using Illumina technology, we have sequenced the genome of three isolates; a strain isolated from the vagina of a sow (5754), one from rat (Rattus spp) intestinal content (RC10) and a third one isolated from environmental rat faeces (RF17). Both, rat and rat faeces were sampled in fattening pig farms. Our study reveals a close genetic relationship of two of these isolates with the virulent strain M120 (RT078) isolated from a human patient. The analysis of the sequences has revealed the presence of antibiotic resistance genes, mobile elements, including the transposon linked with virulence Tn6164, and the similarity of virulence factors between these isolates and human strains. This is the first study focused on the sequencing of C. difficile genomes obtained from wild animals like rats, which can be considered as potential reservoirs for humans and other animal species. This study can help to understand the genome composition and epidemiology of this bacterium species.
Dataset of liver proteins of eu- and hypothyroid rats affected in abundance by any of three factors: in vivo exposure to hexabromocyclododecane (HBCD), thyroid status, gender differences
Miller, I. ; Renaut, J. ; Cambier, S. ; Murk, A.J. ; Gutleb, A.C. ; Serchi, T. - \ 2016
Data in Brief 8 (2016). - ISSN 2352-3409 - p. 1344 - 1347.
Gender-specific effects - HBCD - Hypothyroidism - Liver - Proteomics - Rat
Male Wistar rats with different thyroid status (eu-, hypothyroid) were exposed to 0, 3 or 30 mg/kg body weight of the flame retardant HBCD for 7 days and obtained data compared with a previous study in females, “Hexabromocyclododecane (HBCD) induced changes in the liver proteome of eu- and hypothyroid female rats” (Miller et al., 2016) . Specifically, proteomic investigation of liver protein patterns obtained by 2D-DIGE was performed and differences between animals groups recorded, based on the factors exposure, thyroid status and gender. All proteins with significantly changed abundance in any of these comparisons were identified by mass spectrometry. General, hormone and proteomic data of both the present and the previous studies are discussed in Miller et al. (2016)  and in “Gender specific differences in the liver proteome of rats exposed to hexabromocyclododecane (HBCD)” Miller et al. (2016) .
Prediction of carcinogenic potential of chemicals using repeated-dose (13-week) toxicity data
Woutersen, Ruud A. ; Soffers, Ans E.M.F. ; Kroese, E.D. ; Krul, Cyrille A.M. ; Laan, Jan Willem van der; Benthem, Jan van; Luijten, Mirjam - \ 2016
Regulatory Toxicology and Pharmacology 81 (2016). - ISSN 0273-2300 - p. 242 - 249.
Carcinogenicity - Non-genotoxic carcinogens - Predictivity - Preneoplastic lesions - Rat - Risk assessment - Sub-chronic toxicity - Tumours
Sub-chronic toxicity studies of 163 non-genotoxic chemicals were evaluated in order to predict the tumour outcome of 24-month rat carcinogenicity studies obtained from the EFSA and ToxRef databases. Hundred eleven of the 148 chemicals that did not induce putative preneoplastic lesions in the sub-chronic study also did not induce tumours in the carcinogenicity study (True Negatives). Cellular hypertrophy appeared to be an unreliable predictor of carcinogenicity. The negative predictivity, the measure of the compounds evaluated that did not show any putative preneoplastic lesion in de sub-chronic studies and were negative in the carcinogenicity studies, was 75%, whereas the sensitivity, a measure of the sub-chronic study to predict a positive carcinogenicity outcome was only 5%. The specificity, the accuracy of the sub-chronic study to correctly identify non-carcinogens was 90%. When the chemicals which induced tumours generally considered not relevant for humans (33 out of 37 False Negatives) are classified as True Negatives, the negative predictivity amounts to 97%. Overall, the results of this retrospective study support the concept that chemicals showing no histopathological risk factors for neoplasia in a sub-chronic study in rats may be considered non-carcinogenic and do not require further testing in a carcinogenicity study.
Effects of black hoof medicinal mushroom, phellinus linteus (Agaricomycetes), polysaccharide extract in streptozotocin-induced diabetic rats
Yamaç, Mustafa ; Zeytinoğlu, Melih ; Şentürk, Hakan ; Kartkaya, Kazim ; Kanbak, Göngör ; Bayramoğlu, Gökhan ; Oğlakci, Ayşegül ; Griensven, Leo J.L.D. van - \ 2016
International Journal of Medicinal Mushrooms 18 (2016)4. - ISSN 1521-9437 - p. 301 - 311.
Antidiabetic activity - Medicinal mushrooms - Phellinus linteus - Polysaccharide - Rat
In this article we report the healing effects of a Phellinus linteus fruiting body hot water extract (PLE) in streptozotocin (STZ)–induced diabetic rats. PLE was given before and after STZ. The preprotective, protective, and postprotective effects of PLE on STZ-induced oxidative stress were studied using biochemical (caspase 3 activity, cytosolic-to-lysosomal ratio of cathepsin B and L, DNA fragmentation levels), ordinary histological and immuno-his-tochemical investigation parameters. Following oral administration of PLE after STZ application, the serum glucose concentration significantly decreased up to 41.13% compared with the control group (P <0.05). The hypoglycemic potential of the PLE was further supported by an increase of insulin secretion in the islets of Langerhans. In addition, the number of cells in Langerhans islets increased by 45.89% when PLE was given after STZ application. On the other hand, the use of PLE before oxidative stress could not prevent the onset of diabetes. This is, to our knowledge, the first study of the effect of application time of orally administered Ph. linteus hot water extract on STZ-induced diabetes.
Dataset of liver proteins changed in eu- and hypothyroid female rats upon in vivo exposure to hexabromocyclododecane (HBCD)
Miller, I. ; Serchi, T. ; Cambier, S. ; Diepenbroek, C. ; Renaut, J. ; Berg, J.H.J. van den; Kwadijk, C. ; Gutleb, A.C. ; Rijntjes, E. ; Murk, A.J. - \ 2016
Data in Brief (2016). - ISSN 2352-3409 - p. 386 - 392.
HBCD - Hypothyroidism - Lipid metabolism - Liver - Proteomics - Rat
Female Wistar rats with different thyroid status (eu-, hypothyroid) were exposed to 0, 3 or 30 mg/kg body weight of the flame retardant HBCD for 7 days. Changes in protein patterns obtained by 2D-DIGE were evaluated, and different animal groups compared taking into account their exposure and thyroid status. Proteins significantly altered in abundance in any of these comparisons were identified by mass spectrometry. These data, together with hormone data of the animals, are discussed in "Hexa-bromocyclododecane (HBCD) induced changes in the liver proteome of eu- and hypothyroid female rats" (Miller et al., 2016) .
Hexabromocyclododecane (HBCD) induced changes in the liver proteome of eu- and hypothyroid female rats
Miller, I. ; Serchi, T. ; Cambier, S. ; Diepenbroek, C. ; Renaut, J. ; Berg, J.H.J. Van der; Kwadijk, C. ; Gutleb, A.C. ; Rijntjes, E. ; Murk, A.J. - \ 2016
Toxicology Letters 245 (2016). - ISSN 0378-4274 - p. 40 - 51.
HBCD - Hypothyroidism - Lipid metabolism - Liver - Proteomics - Rat
Hexabromocyclododecane (HBCD) is a brominated flame retardant known for its low acute toxicity as observed in animal experiments. However, HBCD exposure can affect liver functioning and thyroid hormone (TH) status. As exact mechanisms are unknown and only limited toxicological data exists, a gel-based proteomic approach was undertaken. In a eu- and hypothyroid female rat model, rats were exposed to 3 and 30 mg/kg. bw/day HBCD for 7 days via their diet, and exposure was related to a range of canonical endpoints (hormone status, body weight) available for these animals. Alterations in the liver proteome under HBCD exposure were determined in comparison with patterns of control animals, for both thyroid states. This revealed significantly changed abundance of proteins involved in metabolic processes (gluconeogenesis/glycolysis, amino acid metabolism, lipid metabolism), but also in oxidative stress responses, in both euthyroid and hypothyroid rats. The results provide a more detailed picture on the mechanisms involved in these alterations, e.g. at the protein level changes of the proposed influence of HBCD on the lipid metabolism. Present results show that proteomic approaches can provide further mechanistic insights in toxicological studies.
Postprandial oxidative losses of dietary leucine depend on the time interval between consecutive meals : A model study with rats
Myszkowska-Ryciak, J. ; Keller, J.S. ; Bujko, J. ; Stankiewicz-Ciupa, J. ; Koopmanschap, R.E. ; Schreurs, V.V.A.M. - \ 2015
Journal of Animal and Feed Sciences 24 (2015)1. - ISSN 1230-1388 - p. 71 - 79.
Breath test - Consecutive meals - Rat - Time intervals - [1-<sup>13</sup>C]-leucine oxidation
Postprandial oxidative losses of egg white-bound [1-13C]-leucine were studied as 13C recovery in the breath of rats in relation to different time intervals between two meals. Male Wistar rats (n = 48; 68.3 ±5.9 g) divided into 4 groups (n = 12) were fed two meals a day (9:00 and 16:30; interval 7 h) of a 13.2% egg white-based diet for 30 min. After 14 days, 3 out of the 4 groups received the 2nd meal at shorter time intervals of 3, 1, and 0 h. Two [13CO2] breath tests (BT) were performed on days 19 and 40. The breath samples were analyzed for 13C Atom % (At %) enrichment by IRMS, and the results were expressed as the rate of 13C At % excess and cumulative recovery (% of dose). The 7 h interval group showed higher 13C cumulative recovery after the 2nd meal during both the BT and after the 1st meal on the day 40 BT compared with the 3, 1, and 0 h intervals. In groups with the 3, 1, and 0 h intervals, the cumulative recovery of 13C after the 2nd meal was lower compared with the 1st meal due to interaction between meals, which probably caused dilution of the tracer in the larger volume of feed in the rat's stomach. On day 40, all cumulative recovery values were higher than on day 19. An important finding of this study is that despite the differences in postprandial Leu oxidation among interval groups, the weight gain of all rats was similar.