Heat indicators of oxidative stress, inflammation and metal transport show dependence of cadmium pollution history in the liver of female zebrafish

Highlights: • Experimental fish had been exposed to 0, 2.5 and 5 μg/L Cd for 10 weeks. • Effects of heat on stress responses were examined in three groups of fish. • Indicators including mRNA, activity and protein levels of genes were analyzed. • Responses to heat depended on Cd pollution history. - Abstract: Environmental stressors such as high temperature and metal exposure may occur sequentially, simultaneously, previously in aquatic ecosystems. However, information about whether responses to high temperature depend on Cd exposure history is still unknown in fish. Zebrafish were exposed to 0 (group 1), 2.5 (group 2) and 5 μg/L (group 3) cadmium (Cd) for 10 weeks, and then each group was subjected to Cd-free water maintained at 26 °C and 32 °C for 7 days respectively. 26 indicators were used to compare differences between 26 °C and 32 °C in the liver of female zebrafish, including 5 biochemical indicators (activity of Cu/Zn-SOD, CAT and iNOS; LPO; MT protein), 8 molecular indicators of oxidative stress (mRNA levels of Nrf2, Cu/Zn-SOD, CAT, HSF1, HSF2, HSP70, MTF-1 and MT), 5 molecular indicators of inflammation (mRNA levels of IL-6, IL-1β, TNF-α, iNOS and NF-κB), 8 molecular indicators of metal transport (mRNA levels of, ZnT1, ZnT5, ZIP8, ZIP10, ATP7A, ATP7 B and CTR1). All biochemical indicators were unchanged in group 1 and changed in group 2 and 3. Contrarily, differences were observed in almost all of molecular indicators of inflammation and metal transport in group 1, about half in group 2, and few in group 3. We also found that all molecular indicators of oxidative stress in group 2 and fewer in group 1 and 3 were significantly affected by heat. Our data indicated that heat indicators of oxidative stress, inflammation and metal transport showed dependence of previous cadmium exposure in the liver of zebrafish, emphasizing metal pollution history should be carefully considered when evaluating heat stress in fish.