The Immunotoxicity Of Three Pyrethroid Pesticides On Chinese Rare Minnow (Gobiocypris Rarus)

As one of the great inventions of mankind,pesticides has significantly improved human production and life.With the development of society and industrial progress,people pay increasing attention to the pesticides safety,leading to the prohibition or replacement of high-toxic or high-permanence pesticides.Pyrethroid insecticides,a type of broad-spectrum and high-efficiency biomimetic pesticides,are widely used from land to aquatic and developed as third-generation pesticides due to their low acute toxicity and fast degradation.Therefore,they have been frequently detected in the aquatic environment.Although pyrethroid insecticides have pass the assessments of environmental safety through evaluating the acute toxicity to non-target biological fish prior to the marketing,the chronic toxicity,especially immunotoxicity to fish,is not clear until now.To better protect fish in aquaculture and fish health in natural waters,cypermethrin,deltamethrin and fenvalerate were used to study their immunotoxicity and toxicological effects on Chinese rare minnows in this study.We performed the pyrethroid insecticides exposure test and subsequent host resistance challenge test.Finally,the immunotoxicity and the mechanisms of three pyrethroids were illustrated by many endpoints,such as physiological and biochemical levels,histopathology,gene expression and disease resistance of Chinese rare minnow.The main results in the present study were as follows:1.Cypermethrin,deltamethrin and fenvalerate had reduced the levels of immune molecules,disrupted the TLR signaling pathway and caused structural damage to the liver,intestine and gill of Chinese rare minnows.2.Host resistance test results showed that the three pyrethroid insecticides had reduced the disease resistance of Chinese rare minnow,resulting in increased sensitivity of the fish to Pseudomonas fluorescens(P.fluorescens).The mortalities of fish that exposed to cypermethrin,deltamethrin and fenvalerate were increased when challenged with P.fluorescen,and showed a dose-effect relationship with the increase of the concentration of three pyrethroid insecticides.3.Exposure to three pyrethroid insecticides inhibited the immune response of fish immune molecules(Immunoglobulin M,lysozyme,complement C3,C-reactive protein)and disturbed the TLR signaling pathway to P.fluorescens,leading to the suppression in levels of immune molecules and the expression of TLR signaling pathway related-genes.Taken together,the three pyrethroid insecticides induced immunotoxicity in fish,might destroy the immune system,and inhibit the innate immune response of fish by inhibiting the production of immune molecules and disturbing the TLR signaling pathways.This could weaken the ability of the immune system to recognize and clear pathogens in fish,which rendered them vulnerable to pathogens and subsequently caused death.These results can provide evidence for systematic assessment of the ecological risks of pyrethroid insecticides and are important for the protection of aquatic living resources.