Effects of toluene, acrolein and vinyl chloride on motor activity of Drosophila melanogaster

Motor dysfunction in Drosophila melanogaster as a biomarker for developmental neurotoxicity

Adequate alternatives to conventional animal testing are needed to study developmental neurotoxicity (DNT). Here, we used kinematic analysis to assess DNT of known (toluene (TOL) and chlorpyrifos (CPS)) and putative (β-N-methylamino-L-alanine (BMAA)) neurotoxic compounds. Drosophila melanogaster was exposed to these compounds during development and evaluated for survival and adult kinematic parameters using the FlyWalker system, a kinematics evaluation method. At concentrations that do not induce general toxicity, the solvent DMSO had a significant effect on kinematic parameters. Moreover, while TOL did not significantly induce lethality or kinematic dysfunction, CPS not only induced developmental lethality but also significantly impaired coordination in comparison to DMSO. Interestingly, BMAA, which was not lethal during development, induced motor decay in young adult animals, phenotypically resembling aged flies, an effect later attenuated upon aging. Furthermore, BMAA induced abnormal development of leg motor neuron projections. Our results suggest that our kinematic approach can assess potential DNT of chemical compounds.

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Alternatives to mammalian testing are needed to detect developmental neurotoxicity

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The pesticide chlorpyrifos causes partial lethality and motor dysfunction

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Non-lethal levels of BMAA induce motor dysfunction in a dose-dependent manner

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Kinematic profiling of adult Drosophila can identify developmental neurotoxicity

Effects of long-term and low-concentration exposures of benzene and formaldehyde on mortality of Drosophila melanogaster

Single-chemical thresholds cannot comprehensively evaluate the risk of chemical mixture exposure in indoor air. Moreover, a large number of researches have focused on short-term and high-concentration co-exposure scenarios related to different species, based on diverse endpoints, which hampers the application and improvement of existing risk evaluation models of chemical mixture exposures. More importantly, current risk evaluation models are not user-friendly for construction practitioners who do not have sufficient toxicological knowledge. Therefore, in this study, an inhalation experiment system and a hazard index (HI) were developed to investigate the risks associated with low-concentration and long-term inhalation exposure scenarios of formaldehyde and benzene, individually and combined, based on Drosophila melanogaster mortality. The results showed that the system exhibited good reproducibility in providing stable exposure concentrations during D. melanogaster life cycle. Furthermore, in a range of experimental concentrations, the interaction between formaldehyde and benzene was additive or synergistic, which was concentration- and ratio-dependent. This study is of great significance in harmonising and providing toxicity data under long-term and low-concentration exposure scenarios, which is beneficial for establishing a new user-friendly risk evaluation model for indoor chemical mixture exposures. It should be noted that the proposed HI value could indicate the hazard degrees of long-term inhalation exposures of formaldehyde and benzene, individually and combined, to D. melanogaster. However, the applicability of this index requires further experiments to evaluate the exposure risks of other volatile organic compounds (VOCs) to D. melanogaster.

Inhalation toxicity of indoor air pollutants in Drosophila melanogaster using integrated transcriptomics and computational behavior analyses

We conducted an inhalation toxicity test on the alternative animal model, Drosophila melanogaster, to investigate potential hazards of indoor air pollution. The inhalation toxicity of toluene and formaldehyde was investigated using comprehensive transcriptomics and computational behavior analyses. The ingenuity pathway analysis (IPA) based on microarray data suggests the involvement of pathways related to immune response, stress response, and metabolism in formaldehyde and toluene exposure based on hub molecules. We conducted a toxicity test using mutants of the representative genes in these pathways to explore the toxicological consequences of alterations of these pathways. Furthermore, extensive computational behavior analysis showed that exposure to either toluene or formaldehyde reduced most of the behavioral parameters of both wild-type and mutants. Interestingly, behavioral alteration caused by toluene or formaldehyde exposure was most severe in the p38b mutant, suggesting that the defects in the p38 pathway underlie behavioral alteration. Overall, the results indicate that exposure to toluene and formaldehyde via inhalation causes severe toxicity in Drosophila, by inducing significant alterations in gene expression and behavior, suggesting that Drosophila can be used as a potential alternative model in inhalation toxicity screening.

Editor's Highlight: Genetic Targets of Acute Toluene Inhalation in Drosophila melanogaster

Interpretation and use of data from high-throughput assays for chemical toxicity require links between effects at molecular targets and adverse outcomes in whole animals. The well-characterized genome of Drosophila melanogaster provides a potential model system by which phenotypic responses to chemicals can be mapped to genes associated with those responses, which may in turn suggest adverse outcome pathways associated with those genes. To determine the utility of this approach, we used the Drosophila Genetics Reference Panel (DGRP), a collection of ∼200 homozygous lines of fruit flies whose genomes have been sequenced. We quantified toluene-induced suppression of motor activity in 123 lines of these flies during exposure to toluene, a volatile organic compound known to induce narcosis in mammals via its effects on neuronal ion channels. We then applied genome-wide association analyses on this effect of toluene using the DGRP web portal (http://dgrp2.gnets.ncsu.edu), which identified polymorphisms in candidate genes associated with the variation in response to toluene exposure. We tested ∼2 million variants and found 82 polymorphisms located in or near 66 candidate genes that were associated with phenotypic variation for sensitivity to toluene at P < 5 × 10-5, and human orthologs for 52 of these candidate Drosophila genes. None of these orthologs are known to be involved in canonical pathways for mammalian neuronal ion channels, including GABA, glutamate, dopamine, glycine, serotonin, and voltage sensitive calcium channels. Thus this analysis did not reveal a genetic signature consistent with processes previously shown to be involved in toluene-induced narcosis in mammals. The list of the human orthologs included Gene Ontology terms associated with signaling, nervous system development and embryonic morphogenesis; these orthologs may provide insight into potential new pathways that could mediate the narcotic effects of toluene.

Intersection of toxicogenomics and high throughput screening in the Tox21 program: an NIEHS perspective

Humans are exposed to thousands of chemicals with inadequate toxicological data. Advances in computational toxicology, robotic high throughput screening (HTS), and genome-wide expression have been integrated into the Tox21 program to better predict the toxicological effects of chemicals. Tox21 is a collaboration among US government agencies initiated in 2008 that aims to shift chemical hazard assessment from traditional animal toxicology to target-specific, mechanism-based, biological observations using in vitro assays and lower organism models. HTS uses biocomputational methods for probing thousands of chemicals in in vitro assays for gene-pathway response patterns predictive of adverse human health outcomes. In 1999, NIEHS began exploring the application of toxicogenomics to toxicology and recent advances in NextGen sequencing should greatly enhance the biological content obtained from HTS platforms. We foresee an intersection of new technologies in toxicogenomics and HTS as an innovative development in Tox21. Tox21 goals, priorities, progress, and challenges will be reviewed.