3-Chloro-1,2-propanediol (3-MCPD) and its fatty acid esters (FE) are present as contaminants in different pro-cessed foods. Based on the available toxicological data the potential risk of 3-MCPD and its FE to human health was assessed by risk assessment authorities, including the European Food Safety Authority (EFSA). Considering the available data, EFSA concluded that 3-MCPD is a non-genotoxic compound exhibiting secondary carcino-genic effects in rodents. A tolerable daily intake of 2 mu g/kg body weight and day was derived by EFSA for free and ester-bound 3-MCPD in 2018. However, there are still different pending issues that have remained unclear until now. Here, we summarize the current knowledge regarding 3-MCPD and its FE with a focus on pending issues regarding exposure assessment via biomarkers as well as the identification of (toxic) metabolites formed after exposure to FE of 3-MCPD and their modes of action.

Alkenylbenzenes are naturally occurring secondary plant metabolites. While some of them are proven genotoxic carcinogens, other derivatives need further evaluation to clarify their toxicological properties. Furthermore, data on the occurrence of various alkenylbenzenes in plants, and especially in food products, are still limited. In this review, we tempt to give an overview of the occurrence of potentially toxic alkenylbenzenes in essential oils and extracts from plants used for flavoring purposes of foods. A focus is layed on widely known genotoxic alkenylbenzenes, such as safrole, methyleugenol, and estragole. However, essential oils and extracts that contain other alkenylbenzenes and are also often used for flavoring purposes are considered. This review may re-raise awareness of the need for quantitative occurrence data for alkenylbenzenes in certain plants but especially in final plant food supplements, processed foods, and flavored beverages as the basis for a more reliable exposure assessment of alkenylbenzenes in the future.

Alkenylbenzenes represent a group of naturally occurring substances that are synthesized as secondary metabolites in various plants, including nutmeg and basil. Many of the alkenylbenzene-containing plants are common spice plants and preparations thereof are used for flavoring purposes. However, many alkenylbenzenes are known toxicants. For example, safrole and methyleugenol were classified as genotoxic carcinogens based on extensive toxicological evidence. In contrast, reliable toxicological data, in particular regarding genotoxicity, carcinogenicity, and reproductive toxicity is missing for several other structurally closely related alkenylbenzenes, such as myristicin and elemicin. Moreover, existing data on the occurrence of these substances in various foods suffer from several limitations. Together, the existing data gaps regarding exposure and toxicity cause difficulty in evaluating health risks for humans. This review gives an overview on available occurrence data of myristicin, elemicin, and other selected alkenylbenzenes in certain foods. Moreover, the current knowledge on the toxicity of myristicin and elemicin in comparison to their structurally related and well-characterized derivatives safrole and methyleugenol, especially with respect to their genotoxic and carcinogenic potential, is discussed. Finally, this article focuses on existing data gaps regarding exposure and toxicity currently impeding the evaluation of adverse health effects potentially caused by myristicin and elemicin.

Alkenylbenzenes are naturally occurring secondary plant metabolites, primarily present in different herbs and spices, such as basil or fennel seeds. Thus, alkenylbenzenes, such as safrole, methyleugenol, and estragole, can be found in different foods, whenever these herbs and spices (or extracts thereof) are used for food production. In particular, essential oils or other food products derived from the aforementioned herbs and spices, such as basil-containing pesto or plant food supplements, are often characterized by a high content of alkenylbenzenes. While safrole or methyleugenol are known to be genotoxic and carcinogenic, the toxicological relevance of other alkenylbenzenes (e.g., apiol) regarding human health remains widely unclear. In this review, we will briefly summarize and discuss the current knowledge and the uncertainties impeding a conclusive evaluation of adverse effects to human health possibly resulting from consumption of foods containing alkenylbenzenes, especially focusing on the genotoxic compounds, safrole, methyleugenol, and estragole.

Nanosized titanium dioxide (TiO2) is one of the most interesting and valuable nanomaterials for the construction industry but also in health care applications, food, and consumer goods, e.g., cosmetics. Therefore, the properties associated with this material are described in detail. Despite its widespread use, the analytical determination and characterization of nanosized metal oxides is not as straightforward as the comparatively easy-to-detect metallic nanoparticles (e.g., silver or gold). This study presents the method development and the results of the determination of tissue titanium (Ti) levels after treatment of rats with the nanosized TiO2. Total Ti levels were chosen to evaluate the presence and distribution of TiO2 nanoparticles. A procedure consisting of incubation with a mixture of nitric acid (HNO3) and hydrofluoric acid (HF), and heating was developed to digest tissues and TiO2 nanomaterials in order to determine the total Ti content by inductively coupled plasma mass spectrometry (ICPMS). For the inter-laboratory comparison, altogether four laboratories analyzed the same samples upon digestion using the available ICPMS equipment. A major premise for any toxicokinetic study is the possibility to detect the chemical under investigation in biological samples (tissues). So, the study has to be performed with a dose high enough to allow for subsequent tissue level measurement of the chemical under investigation. On the other hand, dose of the chemical applied should not induce over toxicity in the animal as this may affect its absorption, distribution, metabolism, and excretion. To determine a non-toxic TiO2 dosage, an acute toxicity study in rats was performed, and the organs obtained were evaluated for the presence of Ti by ICPMS. Despite the differences in methodology and independent of the sample preparation and the ICPMS equipment used, the results obtained for samples with Ti concentrations >4 μg Ti/g tissue agreed well.

Silver nanoparticles (SNP) are the subject of worldwide commercialization because of their antimicrobial effects. Yet only little data on their mode of action exist. Further, only few techniques allow for visualization and quantification of unlabeled nanoparticles inside cells. To study SNP of different sizes and coatings within human macrophages, we introduce a novel laser postionization secondary neutral mass spectrometry (Laser-SNMS) approach and prove this method superior to the widely applied confocal Raman and transmission electron microscopy. With time-of-flight secondary ion mass spectrometry (TOF-SIMS) we further demonstrate characteristic fingerprints in the lipid pattern of the cellular membrane indicative of oxidative stress and membrane fluidity changes. Increases of protein carbonyl and heme oxygenase-1 levels in treated cells confirm the presence of oxidative stress biochemically. Intriguingly, affected phagocytosis reveals as highly sensitive end point of SNP-mediated adversity in macrophages. The cellular responses monitored are hierarchically linked, but follow individual kinetics and are partially reversible.

IL-6 gene expression is controlled by a promoter region containing multiple regulatory elements such as NF-κB, NF-IL6, CRE, GRE, and TRE. In this study, we demonstrated that TRE, found within the IL-6 promoter, is embedded in a functional antioxidant response element (ARE) matching an entire ARE consensus sequence. Further, point mutations of the ARE consensus sequence in the IL-6 promoter construct selectively eliminate ARE but not TRE activity. Nrf2 is a redox-sensitive transcription factor which provides cytoprotection against electrophilic and oxidative stress and is the most potent activator of ARE-dependent transcription. Using Nrf2 knock-out mice we demonstrate that Nrf2 is a potent activator of IL-6 gene transcription in vivo. Moreover, we show evidence that Nrf2 is the transcription factor that activates IL6 expression in a cholestatic hepatitis mouse model. Our findings suggest a possible role of IL-6 in oxidative stress defense and also give indication about an important function for Nrf2 in the regulation of hematopoietic and inflammatory processes.

In 2007, 2.7 million vertebrates were used for animal experiments and other scientific purposes in Germany alone. Since 1998 there has been an increase in the number of animals used for research purposes, which is partly attributable to the growing use of transgenic animals. These animals are, for instance, used as in vivo models to mimic human diseases like diabetes, cancer or Alzheimer's disease. Here, transgenic model organisms serve as valuable tools, being instrumental in facilitating the analysis of the molecular mechanisms underlying human diseases, and might contribute to the development of novel therapeutic approaches. Due to variable and, sometimes low, efficiency (depending on the species used), however, the generation of such animals often requires a large number of embryo donors and recipients. The experts evaluated methods that could possibly be utilised to reduce, refine or even replace experiments with transgenic vertebrates in the mid-term future. Among the promising alternative model organisms available at the moment are the fruit fly Drosophila melanogaster and the roundworm Caenorhabditis elegans. Specific cell culture experiments or three-dimensional (3D) tissue models also offer valuable opportunities to replace experiments with transgenic animals or reduce the number of laboratory animals required by assisting in decision-making processes. Furthermore, at the workshop an in vitro technique was presented which permits the production of complete human antibodies without using genetically modified ("humanised") animals. Up to now, genetically modified mice are widely used for this purpose. Improved breeding protocols, enhanced efficiency of mutagenesis as well as training of laboratory personnel and animal keepers can also help to reduce the numbers of laboratory animals. Well-trained staff in particular can help to minimise the pain, suffering and discomfort of animals and, at the same time, improve the quality of data obtained from animal experiments. This, in turn, can lead to a reduction in the numbers of animals needed for each experiment. The experts also came to the conclusion that the numbers of laboratory animals can be reduced by open access to a central database that provides detailed documentation of completed experiments involving transgenic animals. This documentation should not be restricted to experiments with substantial scientific results that warrant publication, but should also include those with "negative" outcome, which are usually not published. Capturing all kinds of results within such a database provides added value to the respective scientists and the scientific community as a whole; it could also help to stimulate collaborations and to ensure funding for future research. An important aspect to be considered in the generation of this kind of database is the quality and standardisation of the information provided on existing in vitro models and the respective opportunities for their use. The experts felt that the greatest potential for reducing the numbers of laboratory animals in the near future realistically might not be offered by the complete replacement of transgenic animal models but by opportunities to examine specific questions to a greater degree using in vitro models, such as cell and tissue cultures including organotypic models. The use of these models would considerably reduce the number of in vivo experiments using transgenic animals. However, the overall number of experimental animals may still be increasing or remain unaffected, e.g. when transgenic animals continue to serve as the source of primary cells and organs/tissues for in vitro experiments.

Allergic contact dermatitis is an unpleasant, sometimes even painful disease of great clinical relevance. Contact sensitizers are low molecular weight compounds that activate antigen-presenting dendritic cells (DCs) in the skin (so-called Langerhans cells, LCs) and thus a delayed-type immune response can occur. Our approach was to identify putative biomarkers of high predictive value in separating contact allergens from irritants and in reflecting their allergenic potency. As recently shown some of these compounds can induce activation of the Keap1-Nrf2-ARE signaling pathway, one major cytoprotective pathway in cells stressed by chemicals or oxidants. In our studies we used the well characterized monocytic THP-1 cell line as surrogate for LCs. Through immunoblotting we were able to confirm that known contact allergens such as cinnamic aldehyde (CA) and 1-chloro-2,4-dinitrobenzene (DNCB), but no irritants such as Sodium Dodecyl Sulfate (SDS), triggered the activation of Nrf2 and subsequent expression of its target genes in THP-1 cells. We found a time- and dose-dependent upregulation of heme oxygenase-1 (HO-1). Importantly, moderate doses of CA (i.e. 20 iM) caused only a temporal increase in HO-1 protein levels, while higher oncentrations (i.e. 40 iM) that still lacked significant cytotoxicity, led to a steadily increasing HO-1 protein expression level over a 24 h period. Applying a proteomics based strategy we were able to identify several proteins that are significantly upregulated after treatment with CA, some of them known to be regulated through Nrf2. Currently we evaluate the significance of our results by analyzing cellular signaling pathways in primary human monocyte-derived LCs.

One hallmark of Alzheimer's disease is the accumulation of amyloid beta-peptide (AP), which can initiate a cascade of oxidative events that may result in neuronal death. Because nuclear factor erythroid 2-related factor 2 (Nrf2) is the major regulator for a battery of genes encoding detoxifying and antioxidative enzymes via binding to the antioxidant response element (ARE), it is of great interest to find nontoxic activators of Nrf2 rendering neuronal cells more resistant to AP toxicity. Using ARE-luciferase assay and Western blot, we provide evidence that the kavalactones methysticin, kavain, and yangonin activate Nrf2 time- and dose-dependently in neural PC-12 and astroglial C6 cells and thereby up-regulate cytoprotective genes. Viability and cytotoxicity assays demonstrate that Nrf2 activation is able to protect neural cells from amyloid beta-(1-42) induced neurotoxicity. Down-regulation of Nrf2 by small hairpin RNA as well as extracellular signal-regulated kinase 1/2 inhibition abolishes cytoprotection. We further give evidence that kavalactone-mediated Nrf2 activation is not dependent on oxidative stress production. Our results demonstrate that kavalactones attenuate amyloid beta-peptide toxicity by inducing protective gene expression mediated by Nrf2 activation in vitro. These findings indicate that the use of purified kavalactones might be considered as an adjunct therapeutic strategy to combat neural demise in Alzheimer disease and other oxidative stress-related diseases.

Reactive oxygen and nitrogen species (ROS and RNS) are known to contribute as pathogenic factors to the development of chronic progressive diseases at various stages. The present review discusses the role of oxidative stress in chemically induced cancer development and progression. Reactive species are capable of inducing DNA damage that eventually may contribute to cell transformation and tumor initiation. ROS and RNS are also associated with tumor promotion and progression. Both endogenous processes and redox-cycling of xenobiotic compounds have been shown to result in oxidative DNA damage. In addition, several exocyclic DNA adducts represent secondary DNA damage caused by products of lipid peroxidation in the course of oxidative cellular stress. Due to their intrinsic ability to catalyze redox reactions, transition metals, and quinones from various classes of xenobiotics or endogenous compounds are important mediators of oxidative stress and thus likely of being involved in DNA damage, lipid peroxidation, cell transformation, and tumor development.