Evaluation of in silico tools to predict the skin sensitization potential of chemicals.

Public domain and commercial in silico tools were compared for their performance in predicting the skin sensitization potential of chemicals. The packages were either statistical based (Vega, CASE Ultra) or rule based (OECD Toolbox, Toxtree, Derek Nexus). In practice, several of these in silico tools are used in gap filling and read-across, but here their use was limited to make predictions based on presence/absence of structural features associated to sensitization. The top 400 ranking substances of the ATSDR 2011 Priority List of Hazardous Substances were selected as a starting point. Experimental information was identified for 160 chemically diverse substances (82 positive and 78 negative). The prediction for skin sensitization potential was compared with the experimental data. Rule-based tools perform slightly better, with accuracies ranging from 0.6 (OECD Toolbox) to 0.78 (Derek Nexus), compared with statistical tools that had accuracies ranging from 0.48 (Vega) to 0.73 (CASE Ultra - LLNA weak model). Combining models increased the performance, with positive and negative predictive values up to 80% and 84%, respectively. However, the number of substances that were predicted positive or negative for skin sensitization in both models was low. Adding more substances to the dataset will increase the confidence in the conclusions reached. The insights obtained in this evaluation are incorporated in a web database www.asopus.weebly.com that provides a potential end user context for the scope and performance of different in silico tools with respect to a common dataset of curated skin sensitization data.

Expression analysis of immune-related genes in CD34(+) progenitor-derived dendritic cells after exposure to the chemical contact allergen DNCB.

We studied the changes in gene expression after exposure of human dendritic cells (DCs) to the model allergen dinitrochlorobenzene (DNCB). DCs were derived from CD34(+) progenitor cells of three different donors and exposed to 10 microM DNCB or solvent for several time intervals (3, 6 and 12h). cDNA microarrays were used to assess the transcriptional activity of 11,000 human genes. Compared to control gene expression, changes larger than +/-two-fold were observed for 241 genes after exposure to DNCB. Of these genes, 137 were up-regulated and 104 down-regulated. Twenty of these genes encode proteins that are related to the immune response (cytokines, chemokines, their receptors, cytokine/chemokines-related genes, transcription and signal transduction genes) and are discussed in more detail. Our data indicate that exposure to DNCB does not induce a typical maturation pattern in DCs.

Effect of coexposure to 50 Hz magnetic fields and an aneugen on human lymphocytes, determined by the cytokinesis block micronucleus assay.

Interference of 50 Hz extremely low frequency magnetic fields (ELF-MF) with the known aneugen vinblastine (VBL) on micronucleus formation was tested with the in vitro cytokinesis block micronucleus assay in human lymphocyte cultures. Isolated lymphocyte cultures were prepared from 18 individuals. Three groups of quadruplicate cultures from six unrelated individuals were exposed to 50 Hz ELF-MF of background (bkg), 80 and 800 microT, respectively, during the complete incubation period (72 h). Twenty-four hours after culture initiation, one replicate culture from each individual within each ELF-MF group was exposed to 0, 5, 10, or 15 ng/ml VBL. The isolated lymphocyte cultures were scored for the presence of micronuclei, the nuclear division index (NDI), and apoptosis. As expected, increased VBL concentration resulted in an increased micronucleus and apoptosis frequency and in a decreased NDI. In the presence of VBL, there was a systematic tendency for increased micronucleus and apoptosis frequency in the ELF-MF exposed groups compared to the bkg group. In the absence of VBL, we observed no statistically significant effect of ELF-MF on micronucleus induction or apoptosis frequency, but the NDI was significantly higher in the 800 microT group compared to the other groups, suggesting an effect of ELF-MF on cell proliferation. An interaction between ELF-MF and VBL on NDI was observed. This interaction reflected the drastic decrease in NDI due to coexposure to VBL.

Molecular interpretation of expanded RED products in bipolar disorder by CAG/CTG repeats located at chromosomes 17q and 18q.

Previously we provided evidence that the anticipation observed in bipolar (BP) disorder may be explained by expanded CAG/CTG triplet repeats. Data were generated with the repeat expansion detection (RED) method in a BP case-control sample showing a significant association of BP disorder with expanded CAG/CTG repeats (RED products of 120 bp). In this study we demonstrated that 86% of the RED expansions could be accounted for by the ERDA1 and CTG18.1 CAG/CTG repeats located respectively on chromosomes 17 and 18. Further, significantly different allele distributions were observed for ERDA1, with a larger proportion of BP patients (34.7%) carrying one or two expanded ERDA1 alleles (CAG/CTG repeats >40) than controls (19.2%) (P = 0.032). Also, a negative correlation was observed for ERDA1 between CAG/CTG length and age at onset in affected offspring of eight BP families. Although interesting, these data should be interpreted with caution since the ERDA1 association did not remain significant after correcting for multiple testing. Also, no linkage was observed between BP disorder and expanded ERDA1 alleles in the families.

Genetic refinement and physical mapping of a chromosome 18q candidate region for bipolar disorder.

Recent genetic studies have implicated chromosome 18 in bipolar disorder (BP) with putative loci in the pericentromeric region and on 18q. We reported linkage to chromosome 18q21.33-q23 in a large family. In this study we typed additional markers in the family and were able to reduce the candidate region significantly. All affected family members are sharing alleles for markers spanning a genetic distance of maximal 8.9 cM. Haplotype analysis provided a marker order in agreement with published genetic and physical maps. Using yeast artificial chromosomes, we constructed a contig map that will help to identify positional candidate genes for bipolar disorder.

Association analysis of the 5-HT2C receptor and 5-HT transporter genes in bipolar disorder.

We selected 42 patients with bipolar disorder type I (BPI) and 40 healthy controls for genetic analysis of DNA polymorphisms in the serotonin receptor 2c (5-HTR2c) and serotonin transporter (5-HTT) genes. No significant associations were found in the total patient sample. However, when the individuals were divided according to gender, trends for association with both polymorphisms (P = 0.051 for 5-HTR2c and P = 0.049 for 5-HTT) in female patients were observed. These results suggest that variations in these genes may be responsible for a minor increase in susceptibility for bipolar disorder in women.

Analysis of the tyrosine hydroxylase and dopamine D4 receptor genes in a Croatian sample of bipolar I and unipolar patients.

We selected 83 patients with bipolar disorder type I or unipolar recurrent major depression and 71 healthy controls for genetic analysis of the tyrosine hydroxylase and the dopamine D4 receptor gene. No significant association was found between bipolar disorder type I and unipolar recurrent major depression and the polymorphisms located near these genes. Therefore, the hypothesis that the tyrosine hydroxylase and the dopamine D4 receptor genes may be involved in the etiology of bipolar disorder and unipolar recurrent major depression is not supported in our study.

Positive association between the GABRA5 gene and unipolar recurrent major depression.

The gamma-aminobutyric acid (GABA) neurotransmitter system has been implicated in the pathogenesis of mood disorders. To test this hypothesis we carried out an association study between a dinucleotide repeat polymorphism in the GABAA receptor alpha 5 subunit gene and bipolar and unipolar mood disorders. Our results suggest a possible involvement of this gene in unipolar but not in bipolar disorder.