Non-target toxic effects of avermectin on carp spleen involve oxidative stress, inflammation, and apoptosis

Avermectin is one of the most widely used pesticides, but its toxicity to non-target organisms, especially aquatic organisms , has been ignored. Therefore, an acute spleen injury model of avermectin in carp was established to assess the non-target toxicity of avermectin to carp. In this study, 3.005 μg/L and 12.02 μg/L were set as the low and high dose groups of avermectin, respectively, and a four days acute exposure experiment was conducted. Pathological structure observation showed that avermectin damaged spleen tissue structure and produced inflammatory cell infiltration . Biochemical analysis showed that avermectin significantly reduced the activities of antioxidant enzymes CAT, SOD, and GSH-px, but increased the content of MDA, a marker of oxidative damage. Avermectin exposure also significantly increased the transcription levels of inflammatory cytokines such as IL-1β, IL-6, TNF-α, and INOS, and also significantly enhanced the activity of the inflammatory mediator iNOS, but suppressed the transcription levels of anti-inflammatory factors TGF-β1 and IL-10. In addition, TUNEL detected that the apoptosis rate increased significantly with the increase of avermectin dosage, and the transcription levels of apoptosis-related genes BAX, P53, and Caspase 3/9 also increased in a dose-dependent manner. This study is preliminary evidence that avermectin induces spleen injury in carp through oxidative stress , inflammation, and apoptosis, which has important implications for subsequent studies on the effects of avermectin on non-target organisms.