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Alterations in gene expression in Caenorhabditis elegans associated with organophosphate pesticide intoxication and recovery

ABSTRACT: The principal toxicity of acute organophosphate (OP) pesticides poisoning is the disruption of neurotransmission through inhibition of acetylcholinesterase (AChE). However, other mechanisms leading to persistent effects and neurodegeneration remain controversial and difficult to detect. Because Caenorhabditis elegans is relatively resistant to OP lethality—particularly through the inhibition of AChE—studies in this nematode provide an opportunity to observe alterations in global gene expression following OP exposure that cannot be readily observed in less resistant organisms. We exposed cultures of worms in axenic, defined medium to dichlorvos under three exposure protocols. In the first, worms were exposed continuously throughout the experiment. In the second and third, the worms were exposed for either 2 or 8 h, the dichlorvos was washed out of the culture, and the worms were allowed to recover. We then analyzed gene expression using whole genome microarrays from RNA sampled at multiple time points throughout the exposure. The worms showed a time-dependent response that progressively worsened. Early in the exposure, the predominant effect was on metabolic processes, while at later times, an immune-like response and cellular repair mechanisms dominated the expression pattern. Following removal of dichlorvos, the gene expression in the worms appeared to relatively, rapidly return to steady-state levels. The changes in gene expression observed in the worms following exposure to dichlorvos point towards two potential mechanisms of toxicity: inhibition of AChE and mitochondrial disruption.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE41366 | GEO | 2013/10/05

SECONDARY ACCESSION(S): PRJNA176694

REPOSITORIES: GEO

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Project description:The principal toxicity of acute organophosphate (OP) pesticides poisoning is the disruption of neurotransmission through inhibition of acetylcholinesterase (AChE). However, other mechanisms leading to persistent effects and neurodegeneration remain controversial and difficult to detect. Because Caenorhabditis elegans is relatively resistant to OP lethalityM-bM-^@M-^Tparticularly through the inhibition of AChEM-bM-^@M-^Tstudies in this nematode provide an opportunity to observe alterations in global gene expression following OP exposure that cannot be readily observed in less resistant organisms. We exposed cultures of worms in axenic, defined medium to dichlorvos under three exposure protocols. In the first, worms were exposed continuously throughout the experiment. In the second and third, the worms were exposed for either 2 or 8 h, the dichlorvos was washed out of the culture, and the worms were allowed to recover. We then analyzed gene expression using whole genome microarrays from RNA sampled at multiple time points throughout the exposure. The worms showed a time-dependent response that progressively worsened. Early in the exposure, the predominant effect was on metabolic processes, while at later times, an immune-like response and cellular repair mechanisms dominated the expression pattern. Following removal of dichlorvos, the gene expression in the worms appeared to relatively, rapidly return to steady-state levels. The changes in gene expression observed in the worms following exposure to dichlorvos point towards two potential mechanisms of toxicity: inhibition of AChE and mitochondrial disruption. Synchronized cultures of worms at the L3/L4 molt were treated with dichlorvos (0.6 M-BM-5M or 15 M-BM-5M) or maintained as a controls according to one of three protocols. In the first protocol, the set of flasks was incubated without interruption for the duration of the experiment with flasks being harvested at 2, 8, 14, 20, and 26 h. The other two sets were incubated for 2 or 8 h, at which time the worms were centrifuged out of the exposure medium, washed 3 times with a modified CeHR medium (Washout Buffer), resuspended in fresh CeHR medium without dichlorvos, and returned to the incubator. Flasks were harvested at 6 h intervals following the washout through 26 h. Flasks of worms were also harvested prior to beginning the exposure as the 0 h controls. Total RNA was isolated from the frozen harvested worms then analyzed using Affymetrix GeneChips. A total of 148 microarrays were processed (47 per exposure protocol with 4 replicates) however only 146 were included in final analysis as 2 falied to pass QC criteria.

Project description:Chlorpyrifos oxon (CPO), the toxic metabolite of the organophosphorus (OP) insecticide chlorpyrifos, causes developmental neurotoxicity in humans and rodents. CPO is hydrolyzed by paraoxonase-1 (PON1), with protection determined by PON1 levels and the human Q192R polymorphism. To examine how the Q192R polymorphism influences fetal toxicity associated with gestational CPO exposure, we measured biomarker inhibition and fetal-brain gene expression in wild-type (PON1+/+), PON1-knockout (PON1-/-), and tgHuPON1R192 and tgHuPON1Q192 transgenic mice. Pregnant mice exposed dermally to 0, 0.50, 0.75 or 0.85 mg/kg/d CPO from gestational days (GD) 6 through 17 were sacrificed on GD18. Biomarkers of CPO exposure inhibited in maternal tissues included brain acetylcholinesterase (AChE), RBC acylpeptide hydrolase (APH), plasma butyrylcholinesterase (BChE) and carboxylesterase (CES). Fetal plasma BChE was inhibited in PON1-/- and tgHuPON1Q192, but not PON1+/+ or tgHuPON1R192 mice. Fetal brain AChE and plasma CES were inhibited in PON1-/- mice, but not in other genotypes. Pregnant mice (wild type (WT), PON1-knockout (KO), tgHuPON1R192 (R-tg) and tgHuPON1Q192 (Q-tg)) were exposed to various amounts of CPO (0, 0.5, 0.75 and 0.85 mg/kg/d) for 12 days (gestational days 6-17). On gestational day 18, dams were sacrificed and fetal brains were collected. A total of 264 fetal brains from 80 dams were processed to extract total RNA using TRIZOL and the QIAamp Tissue kit from QIAGEN. Microarray analysis was performed using the fetuses of 5 dams per experimental group (total RNA was pooled from individual fetal brains from each dam). The dams used for fetal-brain microarray analysis were selected using a random-number generator, after first eliminating dams with brain AChE activities > 1.5 SD compared to the mean for their treatment group. RNA samples isolated from individual fetal brains from each dam were combined, then labeled and hybridized to Affymetrix Mouse Gene 1.0 ST microarrays.

Project description:Contamination of the environment with endocrine disrupting chemicals (EDCs) has raised concerns about potential health hazards for humans and wildlife. P-tert-octylphenol (OP) is one such ubiquitous chemical reported to bind to the estrogen receptor (ER) and alter expression of estrogen-responsive genes. Human and wildlife exposure to OP are likely, due to its persistence in the environment and its presence in food, water and items of daily use. Detrimental effects of OP exposures on the reproductive system have been observed in some, but not all, in vivo experiments. This study compared estrogenic effects of OP in vitro with those in vivo in adult female rats, attempting to better mimic real-life exposures in adults. In vitro, OP bound to human ER weakly and accelerated proliferation of MCF-7 cells. Adult Sprague-Dawley rats were given OP by gavage either once (125 mg/kg OP) or daily for 35 days (25, 50, 125 mg/kg). Body and organ weights and ovarian follicle populations were unaltered in OP-exposed adult rats after either time point, despite detectable levels of OP in reproductive organs. Toxicity of OP was demonstrated by a slightly reduced growth rate and slightly altered estrous cycle, but there were no significant estrogen-like changes in histomorphology or microarray analyses of gene expression of uterine tissue. Prepubertal rats exposed by gavage to 125 or 250 mg/kg OP for three days failed to show any uterotrophic effects, although E2 caused a 3-fold increase in uterine weight. These results do not support a dose-dependent, estrogenic mode of action for OP. Keywords: treatment vs control Individual uterine RNA samples from 4 female 35-day old rats per treatment (4 OP and 4 vehicle) sacrificed on the second day of diestrus after 35 days of exposure to OP (125 mg/kg/day in propylene glycol) or solvent (propylene glycol, PG) by gavage were compared with liver RNA pooled from all 8 rats (as reference, combined OP and solvent treatment groups). Comparisons were made between treatments. Liver cDNA was always marked with Cy5 and uterine cDNA was always marked with Cy3.

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Alterations in gene expression in Caenorhabditis elegans associated with organophosphate pesticide intoxication and recovery

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