Protective Effects Of Baicalin On Oxidative Stress-induced Liver Injury In Tilapia(Oreochromis Niloticus)

In fish,the liver is a key organ for material and energy metabolism,and also an important barrier organ of the body,its detoxification and phagocytosis function exerts protective effect.Liver damage or lesions often lead to metabolic disorders and reduced disease resistance,which can easily cause the outbreak of secondary infectious diseases.In recent years,diseases such as hepatobiliary syndrome,fatty liver,and chemical liver injury occur frequently in a variety of fish,and their causes are complicated,but there is a common point that is severe oxidative stress.Therefore,oxidative stress is considered to be a common pathogenesis of various liver injury.In the aquaculture environment,lots of factors,such as stocking density,temperature,salinity,heavy metals,bacteria,viruses,etc.can induce the formation of reactive oxygen species(ROS)in the body,causing oxidative stress.Under oxidative stress,excessive ROS can attack cytomembrane,protein and DNA,causing tissues damage or cell death,which in turn affects the normal physiological and behavioral activities of fish.Excessive or long-term oxidative stress can lead to decreased immunity,induce multiple diseases and even death,which is not conducive to the healthy development of aquaculture.Therefore,study of the formation,pathogenesis and effective measures of fish liver injury induced by oxidative stress is of great significance on improving the efficiency of aquaculture.In this experiment,hydrogen peroxide(H2O2)was used to construct an oxidative stress injury model(in vivo)in tilapia.Meanwhile the protective effect of baicalin on H2O2-induced liver injury in tilapia was also discussed.The main research contents and results are as follows:1.Establishment of liver injury model:Tilapia were injected with various concentrations of H2O2(0,40 and 300 mM)for 72 h.The blood and liver were collected to assay biochemical parameters and genes expression after 24,48 and 72 h of injection.The results showed that treatments with higher H2O2 levels(300 mM)significantly increased the levels glutamatepyruvate transaminase(GPT),glutamate oxalate transaminase(GOT)and malondialdehyde(MDA),and apparently decreased the levels of total protein(TP),albumin(Alb),superoxide dismutase(SOD),glutathione(GSH),Cata-lase(CAT),Glutathione S-transferase(GST)and total antioxidant capacity(T-AOC)throughout of the 72 h.The gene expression data showed that treatments with 300 mM H2O2 suppressed Nrf2/Keapl pathway and its downstream genes including HO-1,NQO1 and GSTa,activated inflammatory response via enhancing the mRNA levels of TNF-α,IL-1β and IL-8,and attenuated IL-10 mRNA level.Additionally,there was a mild or strong increase in levels of Nrf2 and its subsequent antioxidant genes or enzymes such as HO-1,NQO1,GSTa,CAT and SOD in treatments with lower concentrations of H2O2(40 mM)for 24 and/or 48h.2.The effects of baicalin against oxidative stress in tilapia:The experimental fish were randomly divided into 4 groups,normal control group and three baicalin groups(0.4,0.8 and 1.6 g/kg),and feeding for 60 days.The blood,liver,gill and muscle tissue were collected to assay biochemical parameters.In serum,the baicalin significantly increased the levels of SOD,T-AOC and GSH;in liver,baicalin significantly increased SOD activity and GSH content,and decreased MDA formation;in gills baicalin significantly increased the level of T-AOC.The results indicate that baicalin can increase the antioxidant capacity of tilapia.3.The fish were divided into normal control group,H2O2 group,and three baicalin groups(0.4,0.8 and 1.6 g/kg).After 60 days of feeding,the normal control group was intraperitoneally(i.p.)injected with saline,while the other groups were i.p.injected with H2O2.After 24 h of H2O2 injection,blood and liver tissues were collected to detect biochemical parameters and genes expression.The results showed that pre-treatments with baicalin can effectively decreased the levels of glutamate pyruvate transaminase(GPT),glutamate oxalate transaminase(GOT),alkaline phosphatase(AKP)and higher malondialdehyde(MDA);and increased the levels of total protein(TP),albumin(Alb),superoxide dismutase(SOD),total antioxidant capacity(T-AOC)and glutathione(GSH)in a dose-dependent manner.Meanwhile,baicalin pre-treatments suppressed the activation of nuclear factor kappaB(NF-κB),inflammatory mediators including tumor necrosis factor α(TNF-α)and Interleukin 1β(IL-1β).Taken together,these data suggested baicalin has protective effect against H2O2-induced hepatotoxicity in tilapia.This might be due to its ability to enhance antioxidant capacity,and suppress NF-κB signaling pathway.