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Environ Sci Technol. 2012 Jan 17;46(2):1223-32. doi: 10.1021/es203642e. Epub 2012 Jan 6.

Gene expression analysis of CL-20-induced reversible neurotoxicity reveals GABA(A) receptors as potential targets in the earthworm Eisenia fetida.

Author information

1
Environmental Services, SpecPro Inc., San Antonio, Texas 78216, United States. ping.gong@usace.army.mil

Abstract

The earthworm Eisenia fetida is one of the most used species in standardized soil ecotoxicity tests. End points such as survival, growth, and reproduction are eco-toxicologically relevant but provide little mechanistic insight into toxicity pathways, especially at the molecular level. Here we apply a toxicogenomic approach to investigate the mode of action underlying the reversible neurotoxicity of hexanitrohexaazaisowurtzitane (CL-20), a cyclic nitroamine explosives compound. We developed an E. fetida-specific shotgun microarray targeting 15119 unique E. fetida transcripts. Using this array we profiled gene expression in E. fetida in response to exposure to CL-20. Eighteen earthworms were exposed for 6 days to 0.2 μg/cm(2) of CL-20 on filter paper, half of which were allowed to recover in a clean environment for 7 days. Nine vehicle control earthworms were sacrificed at days 6 and 13, separately. Electrophysiological measurements indicated that the conduction velocity of earthworm medial giant nerve fiber decreased significantly after 6-day exposure to CL-20, but was restored after 7 days of recovery. Total RNA was isolated from the four treatment groups including 6-day control, 6-day exposed, 13-day control, and 13-day exposed (i.e., 6-day exposure followed by 7-day recovery), and was hybridized to the 15K shotgun oligo array. Statistical and bioinformatic analyses suggest that CL-20 initiated neurotoxicity by noncompetitively blocking the ligand-gated GABA(A) receptor ion channel, leading to altered expression of genes involved in GABAergic, cholinergic, and Agrin-MuSK pathways. In the recovery phase, expression of affected genes returned to normality, possibly as a result of autophagy and CL-20 dissociation/metabolism. This study provides significant insights into potential mechanisms of CL-20-induced neurotoxicity and the recovery of earthworms from transient neurotoxicity stress.

PMID:
22191394
PMCID:
PMC3332050
DOI:
10.1021/es203642e
[Indexed for MEDLINE]
Free PMC Article

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