Early-life long-term exposure to di(2-ethylhexyl) phthalate (DEHP) impairs pathogenic avoidance behavior associated with dopaminergic pathway in Caenorhabditis elegans

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is frequently detected at high environmental concentrations in the environment. Bacillus thuringiensis (Bt), used for insect control, and the soil nematode Caenorhabditis elegans (C. elegans) likely coexist in soil ecosystems. Avoidance behavior is essential for organisms to evade potential hazards and optimize survival in fluctuating environments; however, research regarding the pathogenic avoidance behavior of C. elegans against Bt is still limited. This study investigated whether DEHP exposure impairs Bt avoidance in C. elegans and the mechanisms involved. Results show that Bt adversely affects the growth and survival of C. elegans. In addition, exposure to 5 mg/L of DEHP for 5 days interferes with the avoidance behavior towards Bt, yet it does not impact the food preference between Bt and its food source Escherichia coli OP50. Furthermore, the impaired avoidance behavior correlates with the downregulation of tyrosine hydroxylase homolog cat-2 and dopamine D1 receptor homolog dop-1. Moreover, molecular docking analysis reveals that DEHP exhibits a stronger binding affinity with the dopamine D1 receptor than dopamine. As DEHP is a ubiquitous environmental contaminant, the observed impairment in avoidance behavior, a crucial survival mechanism for C. elegans, highlights the potential environmental risks of DEHP exposure to the ecosystems.