No abstract

Xanthohumol (XN) is a hop flavonoid contained in beers and soft drinks. In vitro and animal studies indicated that XN has DNA and cancer protective properties. To find out if it causes DNA protective effects in humans, an intervention trial was conducted in which the participants (n = 22) consumed a XN containing drink (12 mg XN/P/d). We monitored prevention of DNA damage induced by representatives of major groups of dietary carcinogens [i.e., nitrosodimethylamine (NDMA) benzo(a)pyrene (B(a)P) and the heterocyclic aromatic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)]. Lymphocytes were collected before, during, and after the intervention and incubated with the carcinogens and with human liver homogenate (S9). We found substantial reduction of B(a)P and IQ (P < 0.001 for both substances) induced DNA damage after consumption of the beverage; also, with the nitrosamine a moderate, but significant protective effect was found. The results of a follow-up trial (n = 10) with XN pills showed that the effects are caused by the flavonoid and were confirmed in γH2AX experiments. To elucidate the underlying mechanisms we measured several parameters of glutathione related detoxification. We found clear induction of α-GST (by 42.8%, P < 0.05), but no alteration of π-GST. This observation provides a partial explanation for the DNA protective effects and indicates that the flavonoid also protects against other carcinogens that are detoxified by α-GST. Taken together, our findings support the assumption that XN has anticarcinogenic properties in humans. Cancer Prev Res; 10(2); 153-60. ©2016 AACR.

Cell lines which are currently used in genotoxicity tests lack enzymes which activate/detoxify mutagens. Therefore, rodent-derived liver preparations are used which reflect their metabolism in humans only partly; as a consequence misleading results are often obtained. Previous findings suggest that certain liver cell lines express phase I/II enzymes and detect promutagens without activation; however, their use is hampered by different shortcomings. The aim of this study was the identification of a suitable cell line. The sensitivity of twelve hepatic cell lines was investigated in single cell gel electrophoresis assays. Furthermore, characteristics of these lines were studied which are relevant for their use in genotoxicity assays (mitotic activity, p53 status, chromosome number, and stability). Three lines (HuH6, HCC1.2, and HepG2) detected representatives of five classes of promutagens, namely, IQ and PhIP (HAAs), B(a)P (PAH), NDMA (nitrosamine), and AFB1 (aflatoxin), and were sensitive towards reactive oxygen species (ROS). In contrast, the commercially available line HepaRG, postulated to be a surrogate for hepatocytes and an ideal tool for mutagenicity tests, did not detect IQ and was relatively insensitive towards ROS. All other lines failed to detect two or more compounds. HCC1.2 cells have a high and unstable chromosome number and mutated p53, these features distract from its use in routine screening. HepG2 was frequently employed in earlier studies, but pronounced inter-laboratory variations were observed. HuH6 was never used in genotoxicity experiments and is highly promising, it has a stable karyotype and we demonstrated that the results of genotoxicity experiments are reproducible.Electronic supplementary materialThe online version of this article (10.1007/s00204-017-2109-4) contains supplementary material, which is available to authorized users.

The marine bristle worm Platynereis dumerilii is a useful functional model system for the study of the circadian clock and its interplay with others, e.g., circalunar clocks. The focus has so far been on the worm’s head. However, behavioral and physiological cycles in other animals typically arise from the coordination of circadian clocks located in the brain and in peripheral tissues. Here, we focus on peripheral circadian rhythms and clocks, revisit and expand classical circadian work on the worm’s chromatophores, investigate locomotion as read-out and include molecular analyses. We establish that different pieces of the trunk exhibit synchronized, robust oscillations of core circadian clock genes. These circadian core clock transcripts are under strong control of the light-dark cycle, quickly losing synchronized oscillation under constant darkness, irrespective of the absence or presence of heads. Different wavelengths are differently effective in controlling the peripheral molecular synchronization. We have previously shown that locomotor activity is under circadian clock control. Here, we show that upon decapitation worms exhibit strongly reduced activity levels. While still following the light-dark cycle, locomotor rhythmicity under constant darkness is less clear. We also observe the rhythmicity of pigments in the worm’s individual chromatophores, confirming their circadian pattern. These size changes continue under constant darkness, but cannot be re-entrained by light upon decapitation. Our works thus provides the first basic characterization of the peripheral circadian clock of P. dumerilii . In the absence of the head, light is essential as a major synchronization cue for peripheral molecular and locomotor circadian rhythms, while circadian changes in chromatophore size can continue for several days in the absence of light/dark changes and the head. Thus, in Platynereis the dependence on the head depends on the type of peripheral rhythm studied. These data show that peripheral circadian rhythms and clocks should also be considered in “non-conventional” molecular model systems, i.e., outside Drosophila melanogaster , Danio rerio , and Mus musculus , and build a basic foundation for future investigations of interactions of clocks with different period lengths in marine organisms.