Reproductive Toxicity of Diazinon on Caenorhabditis elegans
Worldwide, pesticide usage is on the rise. From 2006-2007, the global market saw a 1% increase in overall pesticide usage (Environmental Protection Agency 2012), a small percentage until you consider that one percent represents 14 million pounds of chemicals being introduced to our soil, food, and water sources (Environmental Protection Agency 2012). One widely used class of pesticides, the organophosphates, acts through the nervous system of their target organism to inhibit the enzyme Acetylcholinesterase. Without this enzyme, buildup of the neurotransmitter acetylcholine occurs in nerve synapses and the nerve is no longer able to regulate signal transmission. While an effective means of controlling agricultural pests, human exposure to these chemicals can result in severe acute and long term symptoms, sometimes with lethal consequences. The effects of these chemicals are not just experienced by those who utilize them in their professional environment. Often, these pesticides adhere to the clothing of workers who then go home and expose their families to the chemicals. Studies have shown higher than normal pesticide and metabolite levels not only in the field workers themselves, but also in their spouses. There is a growing body of research concerned with the impact of these chronic, low-level exposures in such individuals. This type of occupational exposure represents a serious problem given the reproductive damage that can result from chronic exposure to organophosphates. C. elegans makes an ideal model organism for this type of study due to its short life cycle and ease of maintenance. Each adult hermaphrodite produces a large brood size and its small, transparent body allows for easy visualization of internal structures. C. elegans was the first organism to have its genome mapped, making it an ideal candidate for gene expression analysis and it possesses a neurotransmitter system very similar to that of humans. Using Caenorhabditis elegans as a model system, experiments were carried out to determine the effects of diazinon on reproductive success, germ cell apoptosis, and gene expression patterns. Reproductive effects were based upon the average progeny number, defined as total larvae+eggs produced, measured at 24-hour intervals over the course of 5 days. No significant differences were found between the control and low or high-dose treatment groups at any time point. There was no difference in overall progeny counts among treated groups; however it was noted that overall offspring totals appeared to decrease in a linear fashion with increasing pesticide concentrations. In determining the effect of diazinon exposure on germline apoptosis, it was found that exposure to both low and high-doses resulted in significant increases in the number of apoptotic germ cells per gonad. Analysis of gene expression showed a significant up-regulation of the novel nicotinic acetylcholine receptor (nAChR) lev-8 in response to low and high-doses of diazinon. These results suggest that moderate doses of the organophosphate diazinon may have a negative impact on reproductive success through its interaction with nervous system. The impact of nominal concentrations on developing germ cells is also of concern and warrants further study. Finally, the increased expression of lev-8 in response to diazinon exposure, though it did not show an effect on reproduction, could potentially be used as a biomarker of exposure.
Cobb, Juliana. (July 2017). Reproductive Toxicity of Diazinon on Caenorhabditis elegans (Master's Thesis, East Carolina University). Retrieved from the Scholarship. (http://hdl.handle.net/10342/6384.)
Cobb, Juliana. Reproductive Toxicity of Diazinon on Caenorhabditis elegans. Master's Thesis. East Carolina University, July 2017. The Scholarship. http://hdl.handle.net/10342/6384. September 23, 2020.
Cobb, Juliana, “Reproductive Toxicity of Diazinon on Caenorhabditis elegans” (Master's Thesis., East Carolina University, July 2017).
Cobb, Juliana. Reproductive Toxicity of Diazinon on Caenorhabditis elegans [Master's Thesis]. Greenville, NC: East Carolina University; July 2017.
East Carolina University