Trichlorfon exposure in common carp (Cyprinus carpio L.) leads to oxidative stress, neurotoxicity, and immune responses

Abstract

Organophosphorus insecticides, which are widely used to control parasitic infections, could accumulat in the environment and organisms, and their potential toxicity is a great concern. In this study, common carp (Cyprinus carpio L.) was exposed to different concentrations of trichlorfon (0, 0.1, 0.5, and 1.0 mg/L) for 28 days. The oxidative stress in brain and liver, the neurotransmitter contents in brain, and immune responses were investigated. Results revealed more severe oxidative stress effects in liver than in brain, including significant suppressive activities of superoxide dismutase, glutathione peroxidase, and total antioxidant capacity (T-AOC); reduced glutathione content; and increased reactive oxygen species and malondialdehyde contents in liver. Meanwhile, only the T-AOC activity decreased in the brain of trichlorfon-exposed groups. For neurotransmitters, the contents of 5-hydroxyindoleacetic acid, choline, and acetylcholine were all reduced after trichlorfon exposure. In the immune responses, alkaline phosphatase activity significantly decreased, while the lysozyme content significantly increased upon exposure to trichlorfon. Meanwhile, trichlorfon significantly increased the contents of inflammatory cytokines, namely, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-12, and transforming growth factor β, and significantly decreased the IL-10 content. Moreover, histological observations showed increased numbers of melano-macrophage centers in the head kidney and spleen of exposed common carp. Taken together, the results demonstrated that trichlorfon induced more severe oxidative stresses in liver than in brain, with the presence of neurotoxicity. Trichlorfon could also affect the immune responses in common carp.