Many chemicals can induce allergic contact dermatitis. Because evaluation of skin sensitizing potential by animal testing is prohibited for cosmetics, and screening of many chemicals is required within Registration, Evaluation, Authorisation and Restriction of Chemicals, urgent need exists for predictive in vitro assays to identify contact allergens. Keratinocytes (KC) are the first cells encountered when chemicals land on the skin. Therefore, KC form an important site of haptenization and their metabolism is likely to be important. Moreover, KC secrete mediators that affect processing and presentation of haptenized proteins by dendritic cells. To develop a KC-based in vitro assay to predict sensitizing potential of chemicals, in vitro exposure effects of eight contact sensitizers and six irritants on the KC cell line HaCaT were examined by gene profiling. Classifiers predictive of the class sensitizers or irritants were calculated, based on support vector machine (SVM) and random forest (RF) algorithms. Classifiers using high-ranking genes were 70% (SVM) and 62% (RF) accurate, based on three (SVM) and two to five (RF) features. Classifiers using oxidative stress pathway gene sets were 68–73% (SVM) and 69–71% (RF) accurate. Cross-validation showed that the top-3 of most discriminating genes added up to 13 genes and included oxidative stress gene HMOX1 irrespective of the chemical left out. Moreover, HMOX1 was the most significantly regulated gene. Gene Set Enrichment Analysis showed upregulation of “Keap1 dependent” and “oxidative stress” gene lists. In conclusion, KC expression profiling can identify contact sensitizers, providing opportunities for nonanimal testing for sensitizing potential. Moreover, our data suggest that contact sensitizers induce the oxidative stress pathway in KC.

1 We examined the effects of plant-feeding nematodes on competition between Holcus lanatus and Anthoxanthum odoratum. In the Drentse A nature reserve, the Netherlands, a relatively productive grassland, represented by H. lanatus, has gradually been replaced by a less-productive community, represented by A. odoratum, after the application of fertiliser was stopped. Stressed plants are generally considered to be more sensitive to herbivory. 2 We hypothesized that plant-feeding nematodes would exacerbate the competitive disadvantage of H. lanatus resulting from nutrient limitation. We compared performance in an adjusted De Wit replacement series with monocultures, grown in soil that was either treated or untreated with nematicides at both low and high nutrient supply. 3 The biomass production of both plant species was negatively affected by intra- and interspecific competition. Although H. lanatus was a stronger competitor than A. odoratum in mixed cultures, it was more sensitive to plant-feeding nematodes and nutrient limitation. Nematodes and nutrient stress therefore reduced the competitive suppression of A. odoratum by H. lanatus. Low nutrient availability did not enhance the effect of plant-feeding nematodes on plant growth and competition, indicating additive rather than synergistic effects on plant performance. 4 We conclude that plant-feeding nematodes may contribute to species replacements in grasslands after fertilization has been stopped, albeit to a lesser extent than reduced nutrient availability. Plant species-specific differences in tolerance to plant-feeding nematodes in general, rather than host specificity of nematodes, are responsible for any effects.

The zebrafish embryotoxicity test (ZET) is considered a promising alternative model in predictive toxicology. Currently, morphological assessment of the embryo is the main readout for this assay. However, implementation of transcriptomics may help to detect more subtle effects, which may increase the sensitivity and predictability of the test. In this study, we tested a concentration response of flusilazole in the ZET. After exposure for 24 h postfertilization, microarray analysis revealed a number of processes to be regulated in a concentration-dependent way. We identified development related processes, retinol metabolism and transcription, as well as processes corresponding to the antifungal mechanism of action, steroid biosynthesis, and fatty acid metabolism, to be differentially regulated. Retinol metabolism and transcription were already significantly altered at concentrations that were not inducing morphological effects. Differential expression of genes related to steroid biosynthesis and fatty acid metabolism showed a concentration response similar to morphological response. An increase in concentration was also positively associated with an increase in magnitude of expression for individual genes within functional processes. Our study shows that transcriptomics analysis in the ZET is a more sensitive readout of compound-induced effects than morphological assessment. However, the interpretation of differential gene expression in terms of predicting morphological effects is not straightforward and requires further study.