AMPK Mediates Glucocorticoids Stress-Induced Downregulation of the Glucocorticoid Receptor in Cultured Rat Prefrontal Cortical Astrocytes

PLoS One. 2016 Aug 11;11(8):e0159513. doi: 10.1371/journal.pone.0159513. eCollection 2016.

Abstract

Chronic stress induces altered energy metabolism and plays important roles in the etiology of depression, in which the glucocorticoid negative feedback is disrupted due to imbalanced glucocorticoid receptor (GR) functions. The mechanism underlying the dysregulation of GR by chronic stress remains elusive. In this study, we investigated the role of AMP-activated protein kinase (AMPK), the key enzyme regulating cellular energy metabolism, and related signaling pathways in chronic stress-induced GR dysregulation. In cultured rat cortical astrocytes, glucocorticoid treatment decreased the level, which was accompanied by the decreased expression of liver kinase B1 (LKB1) and reduced phosphorylation of AMPK. Glucocorticoid-induced effects were attenuated by glucocorticoid-inducible kinase 1 (SGK1) inhibitor GSK650394, which also inhibited glucocorticoid induced phosphorylation of Forkhead box O3a (FOXO3a). Furthermore, glucocorticoid-induced down-regulation of GR was mimicked by the inhibition of AMPK and abolished by the AMPK activators or the histone deacetylase 5 (HDAC5) inhibitors. In line with the role of AMPK in GR expression, AMPK activator metformin reversed glucocorticoid-induced reduction of AMPK phosphorylation and GR expression as well as behavioral alteration of rats. Taken together, these results suggest that chronic stress activates SGK1 and suppresses the expression of LKB1 via inhibitory phosphorylation of FOXO3a. Downregulated LKB1 contributes to reduced activation of AMPK, leading to the dephosphorylation of HDAC5 and the suppression of transcription of GR.

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Animals
  • Animals, Newborn
  • Astrocytes / cytology
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Cells, Cultured
  • Forkhead Box Protein O3 / metabolism
  • Gene Expression Regulation / drug effects*
  • Glucocorticoids / pharmacology*
  • Immediate-Early Proteins / metabolism
  • Male
  • Phosphorylation / drug effects
  • Prefrontal Cortex / cytology
  • Prefrontal Cortex / drug effects
  • Prefrontal Cortex / metabolism*
  • Protein Serine-Threonine Kinases / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Glucocorticoid / antagonists & inhibitors*
  • Receptors, Glucocorticoid / metabolism
  • Signal Transduction / drug effects
  • Stress, Physiological*

Substances

  • FOXO3 protein, rat
  • Forkhead Box Protein O3
  • Glucocorticoids
  • Immediate-Early Proteins
  • Receptors, Glucocorticoid
  • Protein Serine-Threonine Kinases
  • serum-glucocorticoid regulated kinase
  • AMP-Activated Protein Kinases

Grants and funding

This work was supported by grants from the National Basic Research Program of China (973 Program, No. 2013CB531303 to J.-G. Chen, No. 2014CB744601 to F. Wang). It was supported by the National Natural Science Foundation of China (No. 81101003) and the Chenguang Plan of Wuhan Municipal Science and Technology Bureau to J. Liu (No. 2014070404010226). It was also supported by National Major Scientific Instrument and Equipment Development Projects (No. 2013YQ03092306) and PCSIRT (No. IRT13016) to J.G.C.