Effect Of Water Nitrite Nitrogen Stress On Physiology And Key Gene Expression Of GSH/GSTs And HIF-1? Pathways In Liver And Gill Of Bighead Carp,Aristichthys Nobilis

In order to study physiological reponse and molecular regulation mechanism to aquaculture water nitrite nitrogen stress of Aristichthys nobilis,120 healthy individals(initial body weight of 180.05±0.092 g,mean±SEM)were first exposed to water with nitrite nitrogen concentration of 48.634 mg/L for 96 h,and then recovered for 96 h.Blood,liver and gills were sampled at 0 h,6 h,12 h,24 h,48 h,72 h and 96 h,respectively,after nitrite nitrogen stressed and be sampled at 12 h,24 h,48 h,72 h,96 h after recovered,respectively.Blood biochemical indexes,stress hormones and HSP70 mRNA expressions,key genes expressions of GSH/GSTs signal pathway and HIF-la signaling pathway in liver and gill of Aristichthys nobilis were detected.The results were as following:1 Effect of ntrite nitrogen stress on the physiological metabolism and HSP70 expression of Aristichthys nobilisIn the perspective of the stress and recovery process,the results showed serum cortisol and ALT activity significantly increased after being stressed for 6 h(P<0.05).Thereafter,serum GLU presented significantly increased(P<0.05)at 12 h after being stressed.Serum CHOL and TP,TG,T3,AST decreased significantly at 24 h and 48h after being stressed(P<0.05),while serum LDL and HDL decreased significantly at stress 72 h(P<0.05).Aristichthys nobilis have been recovered from nitrite nitrogen stress at 96 h after recovered(P ? 0.05).The HSP70 mRNA expression of different tissues showed,head kidney presented responsing to water nitrite nitrogen stress firstly,while the second was gill,and intestine and spleen were the last(P<0.05).Recovering for 96 h,HSP70 mRNA expression in head kidney,intestine and spleen have return to the normal level(P ^ 0.05).The result suggested that nitrite nitrogen affected the protein metabolism,lipid metabolism and glycometabolism of Aristichthys nobilis,and also influenced the HSP70 mRNA expression in head kidney,gill,intestine and spleen.It showed that Aristichthys nobilis could regulate physiological metabolism,improve protection from stress damage by response to nitrite nitrogen stress(48.634 mg/L)rapidly.2 Effect of nitrite nitrogen stress on antioxidant enzyme activity and genes expression of GSH/GSTs signaling pathways in liver of Aristichthys nobilisCompared with that of 0 h after stressed,CAT activity was significantly increased(P<0.05)at 24 h after stressed.T-SOD activity is significantly reduced(P<0.05)at 96 h after stressed.GSH-Px mRNA expression level and enzyme activity is significantly higher at 6 h and 12 h after being stressed(P<0.05).GSTs,GR and T-AOC mRNA expression level in liver increased significantly at 48 h,72 h and 96 h after being stressed(P<0.05),respectively.The liver cells nuclear presented to be swelling after being stressed for 48 h by HE method,and the populations was growing that covered the whole visionat at 96 h.However,all the indexes and liver cell structure turned to recover to the same level before stress(P ? 0.05).The study suggested that under the nitrite nitrogen stress of 48.634 mg/L,the liver GSH-Px and CAT activity is relatively sensitive to nitrite nitrogen stress of Aristichthys nobilis and GSTs and GR mRNA expression level in the liver and T-AOC activity also increased,subsequently.The liver improved antioxidant capacity,scavenginged free radicals in the early stress,reduce the degree of lipid peroxidation and protect from damage for resistance of environmental stress.3 Effect of nitrite nitrogen stress on oxygen carrying ability and HIF-la signal factor expression regulation in gills of Aristichthys nobilisAs the stress time going,HIF-la and NF-?B in gill responded to nitrite nitrogen stress firstly,which presented mRNA expression significant increased at 6 h(P<0.05),while TLR4 mRNA expression significantly increased at 12 h(P<0.05).HGB and MHBR content in blood decreased significantly at 12 h after being stressed(P<0.05),but MHB content began to rise significantly at 24 h(P<0.05).HE section staining showed that it showed the top of the gill filament swellinged at 48 h,strengthened and be curly at 96 h after being stressed.HIF-la and NF-?B mRNA expression level and the content of HGB and MHB have been recovered to the same with that before stress(P?0.05).This study show that,under the stress of 48.634 mg/L nitrite nitrogen in the water,a large number of HGB changed into MHB which resulted in lack of oxygen of Aristichthys nobilis,which then be alleviateed because of MHBR induced expression.Besides,TLR4/NF-?B signaling pathway in gill was more sensitive to nitrite nitrogen stress and be activated to improve the transcription level of HIF-1?,protect from oxidative damage,and compensate the oxygen deficiency caused by nitrite nitrogen stress.