Chronic Corticosterone Exposure Suppresses Copper Transport through GR-Mediated Intestinal CTR1 Pathway in Mice

SIMPLE SUMMARY: Copper (Cu) is a redox active metal and an essential trace element for human health, which is required as a cofactor for enzymes involved in numerous important cellular functions and pathways. Chronic stress is a common environmental issue, which induces nutritional or metabolic disorders and leads to a significant adverse health consequence. In this study, corticosterone drinking water was used to simulate chronic stress to explore the effects of stress on the disorder of copper metabolism and its regulatory mechanism in mice. It was proved that corticosterone impairs copper transport by down-regulating intestinal CTR1 expression via GR-mediated transcriptional inhibition in vivo and in vitro. This study provides the theoretical basis for regulating the copper homeostasis under chronic stress. ABSTRACT: Numerous studies have discovered that chronic stress induces metabolic disorders by affecting iron and zinc metabolism, but the relationship between chronic stress and copper metabolism remains unclear. Here, we explore the influence of chronic corticosterone (CORT) exposure on copper metabolism and its regulatory mechanism in mice. Mice were treated with 100 μg/mL CORT in drinking water for a 4-week trial. We found that CORT treatment resulted in a significant decrease in plasma copper level, plasma ceruloplasmin activity, plasma and liver Cu/Zn-SOD activity, hepatic copper content, and liver metallothionein content in mice. CORT treatment led to the reduction in duodenal expression of copper transporter 1 (CTR1), duodenal cytochrome b (DCYTB), and ATPase copper-transporting alpha (ATP7A) at the mRNA and protein level in mice. CORT treatment activated nuclear glucocorticoid receptor (GR) and down-regulated CRT1 expression in Caco-2 cells, whereas these phenotypes were reversible by an antagonist of GR, RU486. Chromatin immunoprecipitation analysis revealed that GR bound to the Ctr1 promoter in Caco-2 cells. Transient transfection assays in Caco-2 cells demonstrated that the Ctr1 promoter was responsive to the CORT-activated glucocorticoid receptor, whereas mutation/deletion of the glucocorticoid receptor element (GRE) markedly impaired activation of the Ctr1 promoter. In addition, CORT-induced downregulation of Ctr1 promoter activity was markedly attenuated in Caco-2 cells when RU486 was added. These findings present a novel molecular target for CORT that down-regulates intestinal CTR1 expression via GR-mediated trans-repression in mice.