Damage and immunosuppression to Mytilus galloprovincialis hemocytes caused by chronic tris(chloropropyl)phosphate exposure

Tris(chloropropyl)phosphate (TCPP), a pervasive aquatic contaminant, poses risks to ecologically important bivalves, including Mytilus galloprovincialis. However, its toxicity at environmentally related levels to M. galloprovincialis hemocytes remains poorly understood. In this study, the toxic effects and mechanisms of TCPP at 10 and 100 nmol/L (3.276 and 32.76 μg/L) were explored through multiple biomarkers and proteomic profiling, respectively. Biomarker assays revealed that, especially at a high-dose, TCPP led to hemocyte damage (reduced mitochondrial membrane potential and lysosome membrane stability, and induced DNA damage), immunosuppression (suppressed viability, phagocytic activity, and lysozyme activity), and oxidative stress (reactive oxygen species (ROS) and malondialdehyde elevation). Proteomic analysis identified differentially expressed proteins (DEPs) related to these toxic effects: down-regulated lysosomal H⁺ -ATPase subunit and digestive enzymes, oxidative phosphorylation proteins, and DNA repair proteins might collectively cause hemocyte damage; up-regulated pro-apoptotic and down-regulated phagosome-forming and antimicrobial proteins might result in immunosuppression; and up-regulated ROS-generating enzymes with incompletely induced antioxidase might trigger oxidative stress. Protein association analysis identified DEPs implicated in ROS homeostasis and glycometabolism as central network hubs. Taken together, disrupted ROS homeostasis and inhibited glycometabolism played critical roles in the induction of the hemocyte damage and immunosuppression. These findings provided new insights into TCPP toxicities to mussel hemocytes and the underlying mechanisms, offering clues for mechanisms causing shellfish population declines under organic pollutant stress and establishing foundational data for ecological risk assessments in aquatic ecosystems.