Effects of D-Tetramethrin on Zebrafish Development and Immune System

D-tetramethrin is a common insecticide that is important for the control of mosquito-transmitted diseases such as malaria and dengue and, due to its widespread use, it is frequently detected in environmental systems. However, there is currently very little information on the influence of D-tetramethrin on non-target organisms. In this study, zebrafish embryos were exposed to various concentrations of D-tetramethrin (0, 3, 6, and 9 mg/L) from 6 to 72 h past fertilization (hpf) to ascertain the influence of D-tetramethrin on the zebrafish immune system and development. We found that D-tetramethrin exposure led to a significant decrease in heart rate, an increase in the yolk area and tail flick frequency, and a shortening of body length in zebrafish larvae, compared with the control group. The number of macrophages and neutrophils in the experimental group of zebrafish larvae decreased significantly and the oxidative stress levels increased compared with the control group. The malondialdehyde (MDA) content and reactive oxygen species (ROS) content increased significantly, while catalase (CAT) activity increased and superoxide dismutase (SOD) activity decreased in the experimental group. At the same time, apoptosis increased in the zebrafish embryo cells, and the expression of apoptosis-related genes such as p53, Bax, and Bcl-2 was abnormal. Moreover, the pro-inflammatory genes IL-8, IFN-γ, IL-6, and TNF-α were up-regulated, while the anti-inflammatory gene, IL-10, was down-regulated. Therefore, D-tetramethrin significantly affects the immune system and oxidative stress levels in zebrafish, inducing cell apoptosis and negatively affecting embryo development. These results provide novel data for the toxicity of D-tetramethrin and the potential adverse effects of environment residues.