Successful pregnancy relies on dynamic control of cell signaling to achieve uterine receptivity and the necessary biological changes required for endometrial decidualization, embryo implantation, and fetal development. Glucocorticoids are master regulators of intracellular signaling and can directly regulate embryo implantation and endometrial remodeling during murine pregnancy. In immortalized human uterine cells, we have shown that glucocorticoids and estradiol (E2) coregulate thousands of genes. Recently, glucocorticoids and E2 were shown to coregulate the expression of Left-right determination factor 1 (LEFTY1), previously implicated in the regulation of decidualization. To elucidate the molecular mechanism by which glucocorticoids and E2 regulate the expression of LEFTY1, immortalized and primary human endometrial cells were evaluated for gene expression and receptor recruitment to regulatory regions of the LEFTY1 gene. Glucocorticoid administration induced expression of LEFTY1 messenger RNA and protein and recruitment of the glucocorticoid receptor (GR) and activated polymerase 2 to the promoter of LEFTY1. Glucocorticoid-mediated recruitment of GR was dependent on pioneer factors FOXA1 and FOXA2. E2 was found to antagonize glucocorticoid-mediated induction of LEFTY1 by reducing recruitment of GR, FOXA1, FOXA2, and activated polymerase 2 to the LEFTY1 promoter. Gene expression analysis identified several genes whose glucocorticoid-dependent induction required FOXA1 and FOXA2 in endometrial cells. These results suggest a molecular mechanism by which E2 antagonizes GR-dependent induction of specific genes by preventing the recruitment of the pioneer factors FOXA1 and FOXA2 in a physiologically relevant model.
Exogenous glucocorticoid administration results in hyperglycemia, insulin resistance, hepatic dyslipidemia, and hypertension, a constellation of findings known as Cushing's syndrome. These effects are mediated by the glucocorticoid receptor (GR). Because GR activation in liver and adipose has been implicated in metabolic syndrome (MS), we wanted to determine the role of GR in these tissues in the development of MS. Because GR knockout (KO) mice (whole-body KO) exhibit perinatal lethality due to respiratory failure, we generated tissue-specific (liver or adipose) GRKO mice using cre-lox technology. Real-time PCR analysis of liver mRNA from dexamethasone-treated wildtype (WT) and liver GRKO mice indicated that hepatic GR regulates the expression of key genes involved in gluconeogenesis and glycogen metabolism. Interestingly, we have observed that liver-specific deletion of GR resulted in a significant increase in mRNA expression of key genes involved in gluconeogenesis and glycogen metabolism in kidney tissue, indicating a compensatory mechanism to maintain glucose homeostasis. We have also observed that GR plays an important role in regulating the mRNA expression of key genes involved in lipid metabolism. Liver GRKO mice demonstrated decreased fat mass and liver glycogen content compared with WT mice administered dexamethasone for 2 weeks. Adipose-specific deletion of GR did not alter glucose tolerance or insulin sensitivity of adipose GRKO mice compared with WT mice administrated dexamethasone. This indicates that liver GR might be more important in development of MS in dexamethasone-treated mice, whereas adipose GR plays a little role in these paradigms.
Chronic stress is known to precipitate and exacerbate neuropsychiatric symptoms, and exposure to stress is particularly pathological in individuals with certain genetic predispositions. Recent genome wide association studies have identified single nucleotide polymorphisms (SNPs) in the gene CACNA1C, which codes for the Cav1.2 subunit of the L-type calcium channel (LTCC), as a common risk variant for multiple neuropsychiatric conditions. Cav1.2 channels mediate experience-dependent changes in gene expression and long-term synaptic plasticity through activation of downstream calcium signaling pathways. Previous studies have found an association between stress and altered Cav1.2 expression in the brain, however the contribution of Cav1.2 channels to chronic stress-induced behaviors, and the precise Cav1.2 signaling mechanisms activated are currently unknown. Here we report that chronic stress leads to a delayed increase in Cav1.2 expression selectively within the prefrontal cortex (PFC), but not in other stress-sensitive brain regions such as the hippocampus or amygdala. Further, we demonstrate that while Cav1.2 heterozygous (Cav1.2+/-) mice show chronic stress-induced depressive-like behavior, anxiety-like behavior, and deficits in working memory 1-2 days following stress, they are resilient to the effects of chronic stress when tested 5-7 days later. Lastly, molecular studies find a delayed upregulation of the p25/Cdk5-glucocorticoid receptor (GR) pathway in the PFC when examined 8 days post-stress that is absent in Cav1.2+/- mice. Our findings reveal a novel Cav1.2-mediated molecular mechanism associated with the persistent behavioral effects of chronic stress and provide new insight into potential Cav1.2 channel mechanisms that may contribute to CACNA1C-linked neuropsychiatric phenotypes.