Evaluating The Interaction Between Oxidative Stress Management And Insecticide Resistance In Chironomus dilutus

Open Access
- Author:
- Oishi, Grant
- Area of Honors:
- Biology (Behrend)
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Adam Martin Simpson, Thesis Supervisor
Michael A Campbell, Thesis Honors Advisor
Samuel Anthony Nutile, Faculty Reader - Keywords:
- Oxidative stress
Insecticide resistance
Metabolism
Glutathione-S-Transferase
Neonicotinoid
Imidacloprid
Metabolic resistance
Paraquat
Cadmium - Abstract:
- In the environment, organisms encounter both natural and synthetic stressors. Exposure to these stressors may or may not cause acute toxicity; regardless, the metabolism of toxins/toxicants often creates reactive oxygen species, which can induce oxidative stress. Oxidative stress alters a variety of physiological processes, which in turn may impact an organism’s susceptibility to other environmental stressors. Although oxidative stress is known to induce the activity of enzymes that are involved in xenobiotic metabolism, the direct influence of this process on insecticide susceptibility is unknown. This study explores the relationship between oxidative stress and susceptibility to a common-use neonicotinoid insecticide, imidacloprid. Using lab cultures of Chironomus dilutus, the in vitro activity of glutathione-S-transferase (GST) was quantified before and after the induction of oxidative stress via an organic inducer, paraquat, and an inorganic inducer, cadmium (Cd). Paraquat exposure in second-instar C. dilutus resulted in reduced GST activity from 2.655 (± 0.372) mmol/min/mg to 2.053 (± 0.142) mmol/min/mg. In fourth-instar C. dilutus, GST activity was increased following paraquat exposure from 2.182 (± 0.362) mmol/min/mg to 2.456 (± 0.085) mmol/min/mg. Imidacloprid and imidacloprid+paraquat toxicity tests of second-instar C. dilutus yielded median lethal concentrations (LC50) of 1.58 and 1.33 ng/mL, respectively. The synergistic ratio of 1.19 indicates that co-exposure to paraquat increases the toxicity of imidacloprid. Exposure to a range of Cd concentrations in fourth-instar C. dilutus did not show a dose-response GST activity. The information gathered from this thesis has emphasized the complexity of the metabolic responses involved in multiple-stressor exposure scenarios.