Monocrotophos-Induced Oxidative Stress Disrupts Locomotion and Metabolic Function in Drosophila melanogaster

The study unveils potential toxic effects of a widespread organophosphate pesticide, monocrotophos, in a non-target model organism Drosophila melanogaster. Monocrotophos has been used in cotton, sugarcane, and paddy fields for many decades. Hence, a wide range of non-target organisms are get exposed to this pesticide. For the present study, five sub-lethal concentrations of monocrotophos were selected for chronic toxicity testing, which are below the determined LC₅₀ value (0.68 µg/mL). Drosophila larvae were exposed to different sub-lethal concentrations of monocrotophos through food media from their 1st instar stage to 3rd instar stage. The present study aims to explore the reactive oxygen species generation by thioredoxin reductase activity, glutathione content, along with H₂-DCFDA staining, which shows a significant amount of oxidative stress generation in both quantitative and qualitative means. MTT assay has been performed in brain tissue, which reflected a lower number of viable brain cells in treated larvae. Moreover, nuclear fragmentation in brain tissue by DAPI staining indicates the genotoxic potential of the test chemical. Acetylcholinesterase activity was found to be significantly decreased in the treated ones. Meanwhile, chronic sub-lethal exposure significantly reduced the metabolic activity, which was evident in cytosolic glucose content, glucose 6 phosphate dehydrogenase enzyme activity, and malate dehydrogenase enzyme activity. As both enzymes are closely linked with glucose metabolism, so decreased glucose level and both enzyme activity indicate altered metabolic status in cells. Poor brain health and altered metabolism status in monocrotophos-exposed larvae manifested impairment in crawling, phototaxic and embedding behavior in Drosophila. The overall study indicates monocrotophos mediated redox-imbalance, deficiency in metabolism, and compromised brain health untimely visible in poor behavioral responses. As this pesticide is able to contaminate different environmental compartments thus these hazardous effects will inevitably impact many non-target organisms. Observations of the present study can also be extrapolated to other non-target organisms as D. melanogaster shares significant homology with higher vertebrates.