Inhibition Of Quercetagetin On Heat Stress Injury In Broiler Hearts

Heat stress occurs easily in broilers,which leads to metabolic disorders,production performance and immunity decline,sudden cardiac death,infection of pathogenic microorganisms,etc.,and brings huge economic losses to broiler breeding industry.Flavonoid derivatives can inhibit heat stress in broilers,but there was no report on the inhibition of quercetagetin on oxidative damage of heart caused by heat stress in broilers.Therefore,the effect of quercetagetin on inhibiting heat stress induced cardiac oxidative damage in broilers was investigated in vivo and in vitro,providing a theoretical basis for the development of functional plant products against cardiac damage induced by heat stress.The research results are as follows:First,effect of quercetagetin on heat stress injury of broiler heart.160 7-day-old broilers were randomly divided into 4 groups.The Control group and the HS group were fed with the base diet,the QG group and the QG+HS group were fed with the basic diet+ 500mg/kg QG,pre-feeding for 14 days.The broilers in the HS group and the QG+HS group were exposed to 40±1 °C for 12 h.The results: Compared with HS group,the activity of T-SOD and GSH in serum of broilers in QG+HS group increased significantly,while the content of MDA decreased significantly.The activities of CK,AST and LDH were significantly decreased,and the wavy and irregular myocardial fibers were reduced.It showed that quercetagetin could improve the serum antioxidant capacity of heatstressed broilers and inhibit pathological damage of heat-stressed hearts.Second,the protective effect of quercetagetin on heat stress injury model of broiler cardiomyocytes.The broiler cardiomyocytes were randomly divided into 5 groups.Control group were cultured without any treatment;HS group were cultured in 43 ℃incubator for 2 h to trigger heat stress;The rest three groups were pre-treated with corresponding concentrations of QG for 12 h before heat stress.The results: compared with HS group,along with the increasing of QG concentration,the activities of T-SOD and GSH in cardiomyocytes gradually increased,the content of MDA regularly decreased,and the activity of LDH first decreased and then increased.This indicates that 50 μmol/L QG can inhibit heat stress injury of myocardial cells most obviously.Third,study on the mechanism of quercetagetin inhibiting heat stress injury of broiler heart.The broiler cardiomyocytes were randomly divided into 5 groups.Control group were cultured without any treatment;HS group were placed in 43 ℃ incubator for2 h to trigger heat stress;ML+HS group,QG+ML+HS group and QG+HS group were treated with 2 μmol/L ML385,50 μmol/L QG+2 μmol/L ML385,50 μmol/L QG pretreatment for 12 h.The results: QG could significantly up-regulate the expression of GCLC and NQO1 genes which locate in the downstream of Keap1/Nrf2/ARE signal pathway,and the expression of Nrf2 and HO-1 protein was also significantly increased compared with HS group.Nrf2 inhibitors could block the up-regulation of QG on the antioxidant genes and proteins above.This suggests that quercetagetin may inhibit the heat stress injury of broiler heart through the Keap1/Nrf2/ARE antioxidant signal pathway.In conclusion,quercetagetin may have the effect of inhibiting heat stress induced oxidative damage to broiler hearts by activating the Keap1/Nrf2/ARE signal pathway and increasing the expression level of antioxidant genes and proteins downstream of the pathway.