Molybdenum And Cadmium Co-induce Pyroptosis Via Inhibiting Nrf2-mediated Antioxidant Defense Response In The Brain Tissue Of Ducks

To investigate the effects of molybdenum（Mo）and cadmium（Cd）co-exposure on pyroptosis via Nrf2-mediated antioxidant defense response in the brain of ducks.160healthy 8-day-old Shaoxing ducks were selected and randomly assigned to 4 groups（40ducks per group）according to the equal proportion of male and female,and Mo[（NH4）6Mo7O24·4H2O]or/and Cd[Cd SO4·8H2O]were supplemented to the basic diet per kilogram（kg）as follows:the control group（Con group）was fed with basal diet,Mo group（100 mg Mo）,Cd group（4 mg Cd）,Mo+Cd group（100 mg Mo,4 mg Cd）.At the16^th week of the experiment,10 ducks were randomly selected to collect brain tissue samples from each group.HE staining,ELISA,RT-q PCR and western blotting etc.were used to detect the pathological histological changes,the content of trace elements,oxidative stress indicators,and the levels of Nrf2-mediated antioxidative defense response and pyroptosis in brains.The results indicated that:1.HE staining results showed that the number of microglia and the ratio of neuronal pathology（nuclear cleavage,shrinkage）were increased in the Mo or/and Cd groups and were most severe in the Mo+Cd group.In addition,there was a white matter vacuolation phenomenon of brain tissue in the Mo+Cd group.2.Compared to the Con group,Mo and Cd contents were significantly elevated（p<0.001）and iron（Fe）,copper（Cu）,zinc（Zn）and selenium（Se）contents were markedly decreased（p<0.05 or p<0.01 or p<0.001）in the brain tissue of all treatment groups,and the changes of these indicators were more significant in the Mo+Cd group,which indicated that Mo or/and Cd caused a disruption of trace elements in duck brain tissue.3.Compared to the Con group,except for the activity of GSH-Px and MDA content in the Mo group showed no statistical difference（p>0.05）,the activities of T-AOC,T-SOD,GSH-Px and CAT were markedly decreased（p<0.05 or p<0.01 or p<0.001）and MDA content was significantly increased（p<0.05 or p<0.001）in all treatment groups,and the changes of these indicators were more pronounced in the Mo+Cd group.The above results indicated that Mo or/and Cd could cause oxidative stress in duck brain tissue.4.Compared to the Con group,the mRNA levels of Nrf2,CAT,SOD1,GST,HO-1,NQO1,GCLC,GCLM and Nrf2 protein levels were notably decreased in the three treatment groups（p<0.05 or p<0.01 or p<0.001）,and the changes in the above indicators were more pronounced in the Mo+Cd group,which indicated that Mo or/and Cd inhibited Nrf2-mediated antioxidant defense pathway.5.Compared to the Con group,except for IL-1βmRNA level,IL-18 content in the Mo or Cd alone groups and caspase-1,NEK7 mRNA levels,ASC protein level in the Mo group had no significant difference（p>0.05）,the mRNA levels of NLRP3,caspase-1,NEK7,ASC,GSDMA,GSDME,IL-18,IL-1βand IL-1βcontents as well as NLRP3,ASC,caspase-1 p20,GSDMD protein levels showed notably elevated（p<0.05,p<0.01 or p<0.001）in all treatment groups,and these indicators were more significant in the Mo+Cd group,which suggested that Mo or/and Cd induced pyroptosis in duck brain tissue.Conclusion:Mo or/and Cd exposure can lead to pathological damage of brain tissue,imbalance in trace elements homeostasis,oxidative stress,inhibition of the Nrf2 signaling pathway and the development of pyroptosis in the brain tissue.Therefore,the pyroptosis induced by Mo or/and Cd in duck brain tissue are related to the inhibition of Nrf2-mediated antioxidant defense responses.The co-exposure of Mo and Cd can aggravate the toxic damage of brain tissue.