Polyethylene microplastics affect behavioural, oxidative stress, and molecular responses in the <i>Drosophila</i> model

The escalating presence of microplastic pollution poses a significant environmental threat, with far-reaching implications for both ecosystems and human health. This study investigated the toxicological impact of polyethylene microplastics (PE MPs) using <i>Drosophila melanogaster</i>, fruit flies, as a model organism. <i>Drosophila</i> were exposed to PE MPs orally at concentrations of 1 mg ml^-1 and 10 mg ml^-1 agar food. The study assessed behavioural parameters and biochemical markers including reactive oxygen species (ROS), superoxide dismutase (SOD), and glutathione-<i>S</i>-transferase (GST) activity. The expression levels of key genes (<i>Hsp70Bc</i>, <i>rpr</i>, and <i>p53</i>) were also analysed using the RT-qPCR technique. Results indicated a significant decline in climbing activity among adult flies and crawling behaviour in larvae, indicating potential disruption of motor function. Biochemical analysis revealed elevated ROS levels, indicative of oxidative stress, in both larval and fly stages. Moreover, the antioxidant defence system exhibited decreased SOD activity and a concentration-dependent increase in GST activity indicating the functioning of a quick xenobiotic clearance mechanism. Gene expression analysis demonstrated upregulation of <i>rpr</i>, <i>p53</i>, and <i>Hsp70Bc</i> genes, suggesting activation of cell death pathways and stress response mechanisms. Overall, these findings underline the adverse effects of PE MPs on <i>Drosophila</i>, including behavioural impairment, oxidative stress, and activation of stress response pathways.