Unveiling the integrated toxicological effects and underlying mechanisms of bisphenol A and cadmium, two hormesis-type endocrine disruptors, on Chromochloris zofingiensis.

Bisphenol A (BPA) and cadmium (Cd2 +) are typical endocrine-disrupting compounds (EDCs) that often coexist in aquatic environments and disrupt hormonal pathways, causing adverse effects on organisms. This study showed that both BPA and Cd2+ exhibited hormesis effects on Chromochloris zofingiensis, with promoting concentrations of 0.1 mg L-1 and 0.05 mg L-1, while inhibiting concentrations of 10 mg L-1 and 2.5 mg L-1, respectively. The combination of inhibiting concentrations of BPA and Cd2+ significantly elevated intracellular reactive oxygen species level, which resulted in more severe growth inhibition and storage substances accumulation. Additionally, the presence of Cd2+ significantly enhanced the degradation rate of BPA by a minimum of 11.8 %, simultaneously shifting the degradation pathway from glycosylation to hydroxylation products. Notably, co-exposure to 0.1 mg L-1 BPA alleviated the inhibitory effects caused by 2.5 mg L-1 Cd2+, while weakened the promotion effects caused by 0.05 mg L-1 Cd2+. Comparative transcriptome analysis revealed that 0.1 mg L-1 BPA attenuated Cd2+ inhibitory effects by upregulating the expression of the DNA mismatch repair ATPase MLH1 gene involved in mismatch repair. This study provides insights into toxic mechanisms of BPA and Cd2+ to microalgae together with their biodegradation patterns, which offers a theoretical basis for the assessment of the risks of coexisted EDCs in the aquatic ecosystems.