es203642e_si_003.zip (474.13 kB)
Gene Expression Analysis of CL-20-Induced Reversible Neurotoxicity Reveals GABAA Receptors as Potential Targets in the Earthworm Eisenia fetida
dataset
posted on 2012-01-17, 00:00 authored by Ping Gong, Xin Guan, Mehdi Pirooznia, Chun Liang, Edward
J. PerkinsThe 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/cm2 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 GABAA 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.