Toxic Effects Of Penoxsulam Single And Combined Exposure With AgNPs On Earthworms

Penoxsulam is a new triazolopyrimidine sulfonamide herbicide that has been used on a large scale to remove various broad-leaved weeds in rice fields because of its low quantity of application and high efficiency.With the continuous application of this herbicide,it will inevitably be released into the soil environment and persist,thus affecting non-target organisms.Current studies on the ecotoxicological effects of penoxsulam mainly focus on aquatic organisms,while there is a paucity of studies on its toxicity to soil organisms,especially earthworms,and its toxic effects and mechanisms on earthworms are still unclear.Therefore,the study of the toxicological effects of penoxsulam on earthworms is of great importance for evaluating the ecological risk of this herbicide in the soil environment.Silver nanoparticles(Ag NPs)have been widely used in various fields due to their high efficiency and broad-spectrum antibacterial ability,and they can enter the soil environment through various ways,such as sewage irrigation,sludge backfill,and other ways.As more and more Ag NPs enter the soil environment,there is a risk of co-exposure with penoxsulam.It has been shown that Ag NPs can affect the biotoxicity of other contaminants that co-exist with them,but the effect of Ag NPs on the toxicity of penoxsulam is still unclear.Therefore,this paper further investigates the toxic effects and differences between the combined exposure of penoxsulam and Ag NPs on earthworms based on the study of the toxic effects of penoxsulam on earthworms.The present study used Eisenia fetida as the test organism to investigate the toxic effects and differences of penoxsulam(0.05,0.5,and 2.5 mg/kg)single and co-exposure with Ag NPs(10 mg/kg)after 28 and 56 days.The study assessed physiological related indicators,functional gene expression,and also calculated an integrated biomarker response(IBR)index.In addition,histopathological and transcriptomic techniques were used to explore the tissue damage of earthworms and the molecular mechanism of toxicity.The main results are as follows:(1)At the physiological level,penoxsulam single and co-exposure with Ag NPs all induced the increase of reactive oxygen species(ROS)content,interfered with superoxide dismutase(SOD),catalase(CAT),and glutathione S-transferase(GST)activities,and induced the increase of malondialdehyde(MDA)and 8-hydroxydeoxyguanosine(8-OHd G)contents,thus leading to lipid peroxidation and DNA damage in earthworms.(2)At the genetic level,after 28 and 56 days of different concentrations of penoxsulam single and co-exposure with Ag NPs induced oxidative stress by up-regulating the expression of calreticulin(CRT)and heat shock protein 70(HSP70)genes,induced apoptosis by up-regulating the expression of translationally controlled tumor protein(TCTP)gene and affected the normal growth and development process of the organism,and inhibited the reproductive behavior of the earthworms by down-regulating the expression of annetocin(ANN)gene.(3)The results of IBR on the physiological and genetic levels showed that the comprehensive toxicity of both penoxsulam single and co-exposure with Ag NPs on earthworms increased with increasing concentration and duration of penoxsulam,and that the toxicity of co-exposure was greater than that penoxsulam single exposure.(4)After 56 days of penoxsulam single and co-exposure with Ag NPs,the damage to the epidermis,longitudinal muscle tissue,and intestinal tissues of earthworms were caused to different degrees,and the damage was greater in the combination exposure group.(5)Transcriptomic results showed that multiple pathways related to oxidative stress,inflammation,and regulation of cell processes such as cell proliferation,differentiation,and apoptosis were disrupted in earthworms after 2.5 mg/kg penoxsulam single and co-exposure with Ag NPs.The combined exposure induced more genes to be differentially expressed than the single exposure of penoxsulam.In summary,the toxic mechanisms of penoxsulam single and co-exposure with Ag NPs on Eisenia fetida mainly manifest as oxidative stress,inflammatory response,tissue damage,and regulation of multiple cellular processes.In addition,Ag NPs increased the toxicity of penoxsulam to Eisenia fetida.