Impact on zebrafish cells of cadmium and polystyrene microplastics co-exposure: an in vitro approach.

Environmental pollution has been a central topic in public discussions for several years due to its potential harmful effects on ecosystems and human health. The accumulation of plastic in the environment has become a growing threat to marine organisms’ health, as plastic breaks down into smaller fragments like microplastics (MP) and nanoplastics (NP), which can infiltrate any part of the body of exposed organisms with harmful effects. Though the mechanism of action remains unclear, it is known that these substances can create an inflammatory-oxidative environment that triggers the formation of oxidant species capable of inducing apoptosis. Recent studies also suggest that microplastics can act as vectors for other toxic substances, leading to synergistic toxic effects. Among the most widespread environmental contaminants are heavy metals, with cadmium (Cd2+) being one of the most prevalent. Exposure to Cd2+ and its accumulation through the food chain pose a significant threat to all organisms. This study aimed to evaluate the cytotoxic and genotoxic effects of PS-MPs and Cd2+ in vitro, both individually and in combination, on Danio rerio blood cells. The cells were exposed to 70 μg/mL of PS-MPs and 0,1 μg/L of Cd2+ for 30, 60, and 90 min. Cytotoxicity was assessed using the eosin viability test, revealing a significant reduction in cell viability due to PS-MP and Cd2+ exposure. To evaluate genotoxicity, the NitroBlue tetrazolium chloride (NBT) test was used to detect oxidative stress and the production of ROS. Results showed a significant increase in ROS after exposure to both PS-MP and Cd2+, either alone or combined. Additionally, RAPD-PCR was conducted to assess genomic template stability (GTS), revealing genotoxic effects. We can be deduced that PS- MP and Cd2+ have cytotoxic and genotoxic activity capable of causing DNA damage in zebrafish through the production of ROS, reducing cell viability, which, in turn, induce oxidative stress with consequent activation of the apoptotic pathway. However, the co- exposure to Cd2+ and PS-MPs induced a lower cytotoxic and geno- toxic response compared to single exposures, suggesting a poten- tial interaction between the substances that modulates their reactivity.