Nano‑titanium dioxide alters carbamazepine accumulation and aggravates gonadal toxicity and transcriptomic disruption in thick shell mussel Mytilus coruscus.

Abstract

Nanoparticles and pharmaceuticals co-occur in marine environments, potentially altering pollutant exposure and increasing reproductive risks in marine organisms. This study investigated the combined effects of nano‑titanium dioxide (Nano-TiO₂) and carbamazepine (CBZ) on the gonads of the thick shell mussel Mytilus coruscus after 14-day exposure. Integrated analyses included pollutant bioaccumulation, gonadal histopathology, reactive oxygen species (ROS) levels, apoptosis, and transcriptomics. The results showed that Nano-TiO₂ aggregated in seawater and adsorbed CBZ. Compared with single exposure, combined exposure significantly increased Ti and CBZ accumulation in the gonads and caused more pronounced structural damage in the ovaries and testes, including follicular rupture, gamete abnormalities, and interfollicular fibrosis, together with abnormal increases in oocyte diameter, elevated ROS levels, and enhanced cell apoptosis. Transcriptomic analysis showed that sex was an important factor affecting baseline expression in mussel gonads. The numbers of differentially expressed genes and enriched pathways were generally higher under single exposure than under combined exposure, whereas the transcriptomic response under combined exposure was mainly concentrated in damage-handling processes, including apoptosis, lysosome, phagocytosis, and regulation of the actin cytoskeleton. These results indicate that Nano-TiO₂ can alter the internal exposure pattern of CBZ in the gonads of the thick shell mussel and aggravate reproduction-related organ and cellular damage, providing experimental evidence for ecological risk assessment of pharmaceutical-nanomaterial combined pollution in coastal waters.