Does mechanism matter? Unrelated neurotoxicants converge on cell cycle and apoptosis during neurodifferentiation
Theodore A Slotkin1, Frederic J Seidler
1Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC, USA. t.slotkin@duke.edu
Abstract:
Mechanistically unrelated developmental neurotoxicants often produce neural cell loss culminating in similar functional and behavioral outcomes. We compared an organophosphate pesticide (diazinon), an organochlorine pesticide (dieldrin) and a metal (Ni(2+)) for effects on the genes regulating cell cycle and apoptosis in differentiating PC12 cells, an in vitro model of neuronal development. Each agent was introduced at 30μM for 24 or 72h, treatments devoid of cytotoxicity. Using microarrays, we examined the mRNAs encoding nearly 400 genes involved in each of the biological processes. All three agents targeted both the cell cycle and apoptosis pathways, evidenced by significant transcriptional changes in 40-45% of the cell cycle-related genes and 30-40% of the apoptosis-related genes. There was also a high degree of overlap as to which specific genes were affected by the diverse agents, with 80 cell cycle genes and 56 apoptosis genes common to all three. Concordance analysis, which assesses stringent matching of the direction, magnitude and timing of the transcriptional changes, showed highly significant correlations for pairwise comparisons of all the agents, for both cell cycle and apoptosis. Our results show that otherwise disparate developmental neurotoxicants converge on common cellular pathways governing the acquisition and programmed death of neural cells, providing a specific link to cell deficits. Our studies suggest that identifying the initial mechanism of action of a developmental neurotoxicant may be strategically less important than focusing on the pathways that converge on common final outcomes such as cell loss.
Insights
Diverse developmental neurotoxicants, including pesticides and metals, converge on common cellular pathways. These pathways regulate cell cycle and apoptosis, leading to neural cell loss and similar outcomes.
Area of Science:
- Neuroscience
- Toxicology
- Molecular Biology
Background:
- Developmental neurotoxicants can cause neural cell loss with similar functional outcomes despite different mechanisms.
- Understanding the common pathways targeted by these toxicants is crucial for predicting and mitigating neurodevelopmental deficits.
Purpose of the Study:
- To investigate whether mechanistically distinct developmental neurotoxicants converge on common cellular pathways.
- To compare the effects of an organophosphate pesticide (diazinon), an organochlorine pesticide (dieldrin), and a metal (Ni2+) on cell cycle and apoptosis genes in differentiating PC12 cells.
Main Methods:
- Utilized PC12 cells as an in vitro model of neuronal development.
- Applied diazinon, dieldrin, and Ni2+ at 30μM for 24 or 72 hours.
- Employed microarrays to analyze mRNA expression of nearly 400 genes involved in cell cycle and apoptosis pathways.
Main Results:
- All three agents significantly altered gene expression in both cell cycle (40-45%) and apoptosis (30-40%) pathways.
- A substantial overlap was observed, with 80 cell cycle and 56 apoptosis genes commonly affected by all agents.
- Concordance analysis revealed highly significant correlations in the transcriptional changes across all pairwise agent comparisons.
Conclusions:
- Disparate developmental neurotoxicants converge on common cellular pathways regulating neural cell proliferation and programmed death.
- This convergence provides a mechanistic link between diverse toxicants and observed neural cell deficits.
- Focusing on common downstream pathways may be more critical than identifying the initial mechanism of action for developmental neurotoxicants.
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