Influence of polystyrene nanoplastics on the toxicity of haloperidol to amphibians: An in vivo and in vitro approach

Chemical pollution is a major driver for the current worldwide crisis of amphibian decline. The present study aimed to assess the influence of polystyrene nanoplastics (PS-NPLs) on the toxicity of haloperidol to aquatic life stages of amphibians, by using in vivo (tadpoles of Xenopus laevis and Pelophylax perezi) and in vitro (A6 and XTC-2 cell lines of X. laevis) biological models. Tadpoles of both species were exposed, for 96 h, to haloperidol: 0.404 to 2.05 mg l^-1 (X. laevis) or 0.404 to 3.07 mg L^-1 (P. perezi). The most sensitive species to haloperidol (X. laevis) was exposed to haloperidol's LC_50,96h combined with two PS-NPLs concentrations (0.01 mg L^-1 or 10 mg L^-1); the following endpoints were monitored: mortality, malformations, body lengths and weight. In vitro cytotoxicity was assessed by exposing the two cell lines, for 72 h, to: haloperidol (0.195 to 100 mg L^-1) alone and combined with 0.01 mg L^-1 or 10 mg L^-1 of PS-NPLs. Xenopus laevis tadpoles revealed a higher lethal and sublethal sensitivity to haloperidol than those of P. perezi, with LC_50,96h of 1.45 and 2.20 mg L^-1. In vitro assays revealed that A6 cell line is more sensitive haloperidol than XTC-2: LC_50,72h of 13.2 mg L^-1 and 5.92 mg L^-1, respectively. Results also suggested a higher sensitivity of in vivo models when compared to in vitro biological. Overall, PS-NPLs did not influence haloperidol's toxicity for in vivo and in vitro biological models, except for a reduction on the incidence of malformations while increasing the lethal toxicity (at the lowest concentration) in tadpoles. These opposite interaction patterns highlight the need for a deeper comprehension of NPLs and pharmaceuticals interactions. Results suggest a low risk of haloperidol for anuran tadpoles, though in the presence of PS-NPLs the risk may be increased.