Corticosterone increases intracellular Zn2+ release in hippocampal HT-22 cells

The previous studies suggested that the hippocampal zinc dyshomeostasis and high glucocorticoid level might hurt hippocampal function. However, the effect of corticosterone (CORT) on hippocampus zinc homeostasis is not fully characterized. In this study, we investigated the intracellular Zn2+ concentration in hippocampal HT-22 cells after CORT treatment. The cells were incubated with 10 μM CORT for 0 h-24 h, 0 μM-50 μM CORT for 6 h and 2.5 μM glucocorticoid receptor antagonist RU486 administered 30 min before CORT application. The results showed that 10 μM CORT increased the intracellular Zn2+ level after 6 h, which was diminished by 2.5 μM RU486. Co-treatment of ZnSO4 and CORT augmented the increase in Zn2+ level. TPEN, a membrane-permeable chelator for intracellular Zn2+ greatly attenuated the Zn2+ increase by CORT, while DTPA, a chelator for extracellular Zn2+, had no same effects. CCK-8 tests demonstrated that 10 μM CORT treatment for 6 h had no inhibition effect on cells. However, intracellular reactive oxygen species (ROS) production increased and adenosine triphosphate (ATP) level decreased significantly after same CORT treatment, which was corrected by TPEN and aggravated by ZnSO4. It could be suggested that the increased intracellular Zn2+ by CORT was greatly dependent on intracellular Zn2+ release, but not extracellular Zn2+ intake. Meanwhile, our results demonstrated that increased intracellular Zn2+ by CORT resulted in ROS generation and decreased ATP level in cells, which have possible roles in the hippocampal function disorder induced by stress.