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Contact allergies are complex diseases, and one of the important challenges for public health and immunology. The German ‘Federal Institute for Risk Assessment’ hosted an ‘International Workshop on Contact Dermatitis’. The scope of the workshop was to discuss new discoveries and developments in the field of contact dermatitis. This included the epidemiology and molecular biology of contact allergy, as well as the development of new in vitro methods. Furthermore, it considered regulatory aspects aiming to reduce exposure to contact sensitisers. An estimated 15–20% of the general population suffers from contact allergy. Workplace exposure, age, sex, use of consumer products and genetic predispositions were identified as the most important risk factors. Research highlights included: advances in understanding of immune responses to contact sensitisers, the importance of autoxidation or enzyme-mediated oxidation for the activation of chemicals, the mechanisms through which hapten-protein conjugates are formed and the development of novel in vitro strategies for the identification of skin-sensitising chemicals. Dendritic cell cultures and structure-activity relationships are being developed to identify potential contact allergens. However, the local lymph node assay (LLNA) presently remains the validated method of choice for hazard identification and characterisation. At the workshop the use of the LLNA for regulatory purposes and for quantitative risk assessment was also discussed.

Summary The recent advent of microphysiological systems – microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro – is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-five experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale.

SummaryLysR-type transcriptional regulators (LTTRs) constitute the largest family of regulators in prokaryotes. The full-length structures of the LTTR TsaR from Comamonas testosteroni T-2 and its complex with the natural inducer para-toluensulfonate have been characterized by X-ray diffraction. Both ligand-free and complexed forms reveal a dramatically different quaternary structure from that of CbnR from Ralstonia eutropha, or a putative LysR-type regulator from Pseudomonas aeruginosa, the only other determined full-length structures of tetrameric LTTRs. Although all three show a head-to-head tetrameric ring, TsaR displays an open conformation, whereas CbnR and PA01-PR present additional contacts in opposing C-terminal domains that close the ring. Such large differences may be due to a broader structural versatility than previously assumed or either, reflect the intrinsic flexibility of tetrameric LTTRs. On the grounds of the sliding dimer hypothesis of LTTR activation, we propose a structural model in which the closed structures could reflect the conformation of a ligand-free LTTR, whereas inducer binding would bring about local changes to disrupt the interface linking the two compact C-terminal domains. This could lead to a TsaR-like, open structure, where the pairs of recognition helices are closer to each other by more than 10 Å.

SummaryModels of the outer epithelia of the human body -namely the skin, the intestine and the lung -have found valid applications in both research and industrial settings as attractive alternatives to animal testing. A variety of approaches to model these barriers are currently employed in such fields, ranging from the utilization of ex vivo tissue to reconstructed in vitro models, and further to chip-based technologies, synthetic membrane systems and, of increasing current interest, in silico modeling approaches. An international group of experts in the field of epithelial barriers was convened from academia, industry and regulatory bodies to present both the current state of the art of non-animal models of the skin, intestinal and pulmonary barriers in their various fields of application, and to discuss research-based, industry-driven and regulatory-relevant future directions for both the development of new models and the refinement of existing test methods. Issues of model relevance and preference, validation and standardization, acceptance, and the need for simplicity versus complexity were focal themes of the discussions. The outcomes of workshop presentations and discussions, in relation to both current status and future directions in the utilization and development of epithelial barrier models, are presented by the attending experts in the current report.

Pseudomonas aeruginosa is an opportunistic pathogen that causes a number of infections in humans, but is best known for its association with cystic fibrosis. It is able to use a wide range of sulfur compounds as sources of sulfur for growth. Gene expression in response to changes in sulfur supply was studied in P. aeruginosa E601, a cystic fibrosis isolate that displays mucin sulfatase activity, and in P. aeruginosa PAO1. A large family of genes was found to be upregulated by sulfate limitation in both isolates, encoding sulfatases and sulfonatases, transport systems, oxidative stress proteins, and a sulfate-regulated TonB/ExbBD complex. These genes were localized in five distinct islands on the genome and encoded proteins with a significantly reduced content of cysteine and methionine. Growth of P. aeruginosa E601 with mucin as the sulfur source led not only to a sulfate starvation response but also to induction of genes involved with type III secretion systems.

Polycyclic aromatic hydrocarbons (PAHs) are some of the most widespread xenobiotic pollutants, with the potentially carcinogenic high-molecular-weight representatives being of particular interest. However, while in eukaryotes, the cytochrome P450 (CYP)-mediated activation of benzo[a]pyrene (B[a]P) has become a model for metabolism-mediated carcinogenesis, the oxidative degradation of B[a]P by microorganisms is less well studied. This should be reason for concern as the human organ most exposed to environmental PAHs is the skin, which at the same time is habitat to a most diverse population of microbial commensals. Yet, nothing is known about the skin's microbiome potential to metabolise B[a]P. This study now reports on the isolation of 21 B[a]P-degrading microorganisms from human skin, 10 of which were characterised further. All isolates were able to degrade B[a]P as sole source of carbon and energy, and degradation was found to be complete in at least four isolates. Substrate metabolism involved two transcripts that encode a putative DszA/NtaA-like monooxygenase and a NifH-like reductase, respectively. Analysis of the 16S-rRNA genes showed that the B[a]P-degrading isolates comprise Gram(+) as well as Gram(-) skin commensals, with Micrococci being predominant. Moreover, microbial B[a]P-degradation was detected on all volunteers probed, indicating it to be a universal feature of the skin's microbiome.

Prevailing knowledge gaps in linking specific molecular changes to apical outcomes and methodological uncertainties in the generation, storage, processing, and interpretation of ‘omics data limit the application of ‘omics technologies in regulatory toxicology. Against this background, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) convened a workshop Applying ‘omics technologies in chemicals risk assessment that is reported herein. Ahead of the workshop, multi-expert teams drafted frameworks on best practices for (i) a Good-Laboratory Practice-like context for collecting, storing and curating ‘omics data; (ii) the processing of ‘omics data; and (iii) weight-of-evidence approaches for integrating ‘omics data. The workshop participants confirmed the relevance of these Frameworks to facilitate the regulatory applicability and use of ‘omics data, and the workshop discussions provided input for their further elaboration. Additionally, the key objective (iv) to establish approaches to connect ‘omics perturbations to phenotypic alterations was addressed. Generally, it was considered promising to strive to link gene expression changes and pathway perturbations to the phenotype by mapping them to specific adverse outcome pathways. While further work is necessary before gene expression changes can be used to establish safe levels of substance exposure, the ECETOC workshop provided important incentives towards achieving this goal.