A Comparison of ToxCast Test Results with In Vivo and Other In Vitro Endpoints for Neuro, Endocrine, and Developmental Toxicities: A Case Study Using Endosulfan and Methidathion

INTRODUCTION

The U.S. Environmental Protection Agency's (EPA's) Toxicity Forecaster (ToxCast) is a potential tool for chemical prioritization, hazard identification, and risk assessment. We conducted a case study to compare ToxCast data with endpoints from other in vitro and in vivo studies for two data-rich pesticides: endosulfan and methidathion.

METHODS

ToxCast assays for endocrine disruption, development (zebrafish), and neurotoxicity were qualitatively compared to traditional neurotoxicity, developmental and reproductive toxicity findings. We also used in vitro-in vivo extrapolation to convert half-maximal activity concentrations in active ToxCast assays to rat oral equivalent doses, and quantitatively compared these to the lowest observable effect level (LOEL) from in vivo studies.

RESULTS

Endosulfan was inactive for GABAA R, unlike in vivo; but active with dopamine transporter assays and was neurotoxic in zebrafish as expected. Methidathion was not active for these endpoints in vivo or in vitro. Acetylcholinesterase inhibition was ToxCast-inactive, although both pesticides are inhibitors in vivo. ToxCast results were generally inactive for endosulfan estrogen receptor agonism and androgen receptor antagonism unlike in vivo. Calculated oral equivalent doses for estrogen receptor and androgen receptor pathways and for zebrafish assays for both compounds were generally consistent with in vivo LOELs. Endosulfan showed neurotoxicity and both pesticides showed developmental effects in the zebrafish assays, although methidathion is not developmentally toxic in vivo.

CONCLUSIONS

ToxCast's predictions showed concordance on some endpoints and nonconcordance, consisting mainly of false inactives, in several critical endpoints, likely due to a lack of metabolic activation and limitations in assay design. Zebrafish assays were good predictors of developmental toxicity and neurotoxicity for endosulfan.

Bak apoptotic pores involve a flexible C-terminal region and juxtaposition of the C-terminal transmembrane domains

Bak and Bax mediate apoptotic cell death by oligomerizing and forming a pore in the mitochondrial outer membrane. Both proteins anchor to the outer membrane via a C-terminal transmembrane domain, although its topology within the apoptotic pore is not known. Cysteine-scanning mutagenesis and hydrophilic labeling confirmed that in healthy mitochondria the Bak α9 segment traverses the outer membrane, with 11 central residues shielded from labeling. After pore formation those residues remained shielded, indicating that α9 does not line a pore. Bak (and Bax) activation allowed linkage of α9 to neighboring α9 segments, identifying an α9:α9 interface in Bak (and Bax) oligomers. Although the linkage pattern along α9 indicated a preferred packing surface, there was no evidence of a dimerization motif. Rather, the interface was invoked in part by Bak conformation change and in part by BH3:groove dimerization. The α9:α9 interaction may constitute a secondary interface in Bak oligomers, as it could link BH3:groove dimers to high-order oligomers. Moreover, as high-order oligomers were generated when α9:α9 linkage in the membrane was combined with α6:α6 linkage on the membrane surface, the α6-α9 region in oligomerized Bak is flexible. These findings provide the first view of Bak carboxy terminus (C terminus) membrane topology within the apoptotic pore.

Pre-clinical efficacy of combined therapy with novel β-catenin antagonist BC2059 and histone deacetylase inhibitor against AML cells

The canonical WNT-β-catenin pathway is essential for self-renewal, growth and survival of AML stem/blast progenitor cells (BPCs). Deregulated WNT signaling inhibits degradation of β-catenin, causing increased nuclear translocation and co-factor activity of β-catenin with the transcriptional regulator TCF4/LEF1 in AML BPCs. Here, we determined the pre-clinical anti-AML activity of the anthraquinone oxime-analog BC2059 (BC), known to attenuate β-catenin levels. BC treatment disrupted the binding of β-catenin with the scaffold protein TBL1 (transducin β-like 1) and proteasomal degradation and decline in the nuclear levels of β-catenin. This was associated with reduced transcriptional activity of TCF4 and expression of its target genes, cyclin D1, c-MYC and survivin. BC treatment dose-dependently induced apoptosis of cultured and primary AML BPCs. Treatment with BC also significantly improved the median survival of immune-depleted mice engrafted with either cultured or primary AML BPCs exhibiting nuclear expression of β-catenin. Co-treatment with the pan-histone deacetylase inhibitor panobinostat and BC synergistically induced apoptosis of cultured and primary AML BPCs, including those expressing FLT3-ITD, as well as further significantly improved the survival of immune-depleted mice engrafted with primary AML BPCs. These findings underscore the promising pre-clinical activity and warrant further testing of BC against human AML, especially those expressing FLT3-ITD.

The management of animal bites in the United kingdom

OBJECTIVE

Animal bites represent a significant global health issue. The evidence in the literature regarding their management in many areas is conflicting and unclear. This project attempts to identify current evidence in the literature on the management of animal bites and assess if current practice in the United Kingdom is evidence based.

MATERIALS AND METHODS

A literature review on the management of animal bites was performed, and a national UK survey was contacted using a questionnaire based on the available evidence in the literature.

RESULTS

The results from this survey show that 98% of plastic surgery units routinely use prophylactic antibiotics in all animal bite wounds; 58% close low-risk injuries primarily after initial washout, and there are conflicting opinions regarding the management of associated fractures and soft tissue injuries. The available data in the literature suggest that appropriate wound management is the most important factor for prevention of infection in animal bites. Antibiotic prophylaxis should only be given in high-risk wounds and primary closure should be performed in low-risk wounds.

CONCLUSIONS

The management protocols of many plastic surgery units often diverge from the available evidence within the literature. On the basis of a thorough literature review, a guideline for the management of animal bites is presented. Future studies should investigate the management of associated fractures and soft tissue injuries.

Abstract P3-04-08: Expression of hormone-responsive genes in benign breast tissue varies with menstrual cycle phase and menopausal status

Background: The expression of many genes is known to be regulated by ambient hormone levels. In a preliminary study of random fine-needle aspirate (rFNA) samples from benign breast tissue, we found several genes that were highly correlated with the serum levels of progesterone (P4) and estradiol (E2). We now present data to further validate these genes as markers of menstrual cycle phase (MCP) and menopausal status (MPS) in benign breast tissue which may allow retrospective classification of archived breast samples with respect to MCP and MPS at the time of sampling.

Methods: 240 rFNA samples from healthy women with recorded hormonal data at the time of sampling were analyzed. We divided these subjects by menstrual cycle phase (MCP) and menopausal status (MPS): 41 early follicular: (low circulating E2 and P4); 48 mid-cycle (high E2 and low P4); 31 luteal (moderate E2 and high P4). 120 post-menopausal (low E2 and low P4). 100 ng of RNA from rFNA samples of the breast was reverse transcribed. Amplicons of interest were linearly amplified to 14 cycles for 35 genes related to hormone responsiveness. qPCR reactions were carried out using the TaqMan OpenArray (Applied Biosystems). For each gene of interest, expression levels were normalized to the average expression of GAPDH. Gene expression difference between groups were conducted using the Mann-Whitney Test. P-values from gene expression difference were adjusted via the Benjamini-Hochberg (1995) approach.

Results: The mean value of TNFSF11 expression level was 13.19 fold higher in luteal phase subjects than in post-menopausal subjects (p = 0.0003) where there was also the biggest difference of serum P4 level between groups. The expression of DIO2 and MYBPC1 was also significantly higher in luteal phase group than in the post-menopausal group (p = 0.005, p = 0.02, respectively). These 3 genes also demonstrated a higher expression pattern in luteal phase than mid-cycle and follicular phase but analysis is still ongoing. All comparisons between these groups will be presented at the meeting.

Conclusion: The expression levels of TNFSF11, DIO2 and MYBPC1 vary with MCP and MPS. These hormone-responsive genes are candidate MCP classifiers which could be applied to archived breast samples to assess whether biomarkers of breast cancer risk are stable across the menstrual cycle, since MCP and MPS variation is likely an important source of biological noise in studies of archived breast biopsy material.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-04-08.