Studyon Intervention Effects And Mechanisms Of Taraxasterol On Liver Injury Induced By AFB1 In Broilers

AFB1 is the main form of aflatoxin in feed and the most harmful toxin.Feed contaminated by AFB1 can affect the growth performance of livestock and poultry,reduce or even lose immunity,cause obvious liver damage,do great harm to livestock and poultry,and cause huge economic losses to livestock and poultry industry.Taraxacum is a kind of perennial Chinese herbal medicine in compositae.It is rich in nutrients such as minerals,proteins and vitamins,as well as active substances such as polysaccharides,polyphenols,flavonoids and terpenes.As one of the main active components of Taraxacum,taraxasterol has many pharmacological effects,such as anti-inflammatory,anti-tumor,antioxidant and so on.Our laboratory had shown that taraxasterol has good effects on drug-induced liver injury,immune liver injury and alcoholic liver injury.However,whether taraxasterol can control or alleviate the hepatotoxicity of AFB1 is still unclear.Therefore,taraxasterol was used as the research object in this experiment,the model of AFB1-induced liver injury was established in broilers to explore the intervention effects and mechanisms of taraxasterol on AFB1 liver injury.In this experiment,blank group,model group,low,medium and high dose groups of taraxasterol(25 mg/kg,50 mg/kg,100 mg/kg)and positive group(300 mg/kg silybin)were set up.The blank group was fed with basic diet,and the other groups were fed with diet containing0.5 mg/kg AFB1 for 21 days.During this period,the corresponding concentration of drugs was given to the drinking water every day.At the end of the experimental period,the weight and feed weight ratio of broilers in each group were counted.The contents of serum aspartate aminotransferase(AST),alanine aminotransferase(ALT),γ-the contents of glutamyltransferase(GGT),total bilirubin(TBIL)and alkaline phosphatase(ALP)in broilers were detected by related kits.The mRNA expressions of liver CYP1A1 and CYP2A6 in broilers were measured by RT-qPCR.The liver tissues of broilers were analyzed by ocular and pathological sections.The activities of reactive oxygen species(ROS),malondialdehyde(MDA),superoxide dismutase(SOD),catalase(CAT)and glutathione(GSH)in liver of broilers were detected by related kits.The mRNA and protein expressions of nuclear factor E2 related factor 2(Nrf2),kelch like ECH associated protein 1(Keap1),heme oxygenase 1(HO-1),NAD(P)H:quinone oxidoreductase 1(NQO1)in liver of broilers were measured by RT-qPCR and Western blot,respectively.The apoptosis and autophagy of hepatocytes were observed by transmission electron microscope.The expressions of phosphatidylinositol 3-kinase K(PI3K),protein kinase B(AKT),mammalian rapamycin target protein(mTOR),b-lymphoma-2(Bcl-2),Bax and caspase 3(caspase 3)mRNA in liver of broilers were measured by RT-qPCR.The results showed that taraxasterol could increase the body weight of broilers induced by AFB1 and reduce the feed weight ratio.Taraxasterol improved the activity of serum AST,ALT,GGT,TBIL,ALP and liver histopathological changes in broilers induced by AFB1.Taraxasterol sterol could down-regulate the mRNA expression of CYP1A1 and CYP2A6 in broiler liver induced by AFB1.Taraxasterol could inhibit the activities of ROS and MDA and increase the activities of CAT,SOD,and GSH in broiler liver induced by AFB1.Taraxasterol could up-regulate the expression levels of Nrf2,NQO1 and HO-1 mRNA and protein,and down-regulate the expression levels of Keap1 mRNA and protein in broiler liver induced by AFB1.Taraxasterol inhibited hepatocyte apoptosis induced by AFB1,up-regulated the expression of Bcl-2 mRNA and down-regulated the expression of Bax and caspase3 mRNA.Taraxasterol could restore the autophagy of hepatocytes induced by AFB1 and down-regulate the mRNA expression of PI3 K,AKT and mTOR.In conclusion,the intervention of taraxasterol could improve the growth performance of broilers induced by AFB1,improve the indexes of liver function,liver pathological changes and oxidative stress,and inhibit the expression of CYP2A6 and CYP1A1 mRNA in the liver,indicating that taraxasterol has a certain protective effect on the liver injury of broilers induced by AFB1.The intervention mechanism of taraxasterol on AFB1 induced liver injury may be to exert its antioxidant effect by regulating Nrf2/Keap1 signal pathway,improve the anti-apoptotic ability of broiler liver by regulating the expression of apoptotic factors,and effectively restore the autophagy ability of broiler hepatocytes caused by AFB1 by regulating PI3K/AKT/mTOR signal pathway.It provides a theoretical basis for the research and development of taraxasterol as a drug for the prevention and treatment of chicken AFB1 induced liver injury,and has also certain strategic significance for the development and utilization of Taraxacum wild resources in Changbai Mountains area.