miR-135b expression downregulates Ppm1e to activate AMPK signaling and protect osteoblastic cells from dexamethasone

Oncotarget. 2016 Oct 25;7(43):70613-70622. doi: 10.18632/oncotarget.12138.

Abstract

Activation of AMP-activated protein kinase (AMPK) could potently protect osteoblasts/osteoblastic cells from dexamethasone (Dex). We aim to induce AMPK activation via microRNA ("miRNA") downregulation of its phosphatase Ppm1e. We discovered that microRNA-135b ("miR-135b") targets the 3' untranslated regions (UTRs) of Ppm1e. In human osteoblasticOB-6 cells and hFOB1.19 cells, forced-expression of miR-135b downregulated Ppm1e and activated AMPK signaling. miR-135b also protected osteoblastic cells from Dex. shRNA-induced knockdown of Ppm1e similarly activated AMPK and inhibited Dex-induced damages. Intriguingly, in the Ppm1e-silenced osteoblastic cells, miR-135b expression failed to offer further cytoprotection against Dex. Notably, AMPK knockdown (via shRNA) or dominant negative mutation abolished miR-135b-induced AMPK activation and cytoprotection against Dex. Molecularly, miR-135b, via activating AMPK, increased nicotinamide adenine dinucleotide phosphate (NADPH) activity and inhibited Dex-induced oxidative stress. At last, we found that miR-135b level was increased in human necrotic femoral head tissues, which was correlated with Ppm1e downregulation and AMPK activation. There results suggest that miR-135b expression downregulates Ppm1e to activate AMPK signaling, which protects osteoblastic cells from Dex.

Keywords: AMP-activated protein kinase (AMPK); dexamethasone (Dex); microRNA-135b; osteoblastic cells; phosphatase 1E (Ppm1e).

MeSH terms

  • 3' Untranslated Regions / genetics
  • AMP-Activated Protein Kinases / genetics*
  • AMP-Activated Protein Kinases / metabolism
  • Cytoprotection / genetics
  • Dexamethasone / pharmacology
  • Down-Regulation
  • Gene Expression Regulation*
  • Glucocorticoids / pharmacology
  • Humans
  • MicroRNAs / genetics*
  • Osteoblasts / drug effects
  • Osteoblasts / metabolism*
  • Osteonecrosis / genetics
  • Osteonecrosis / metabolism
  • Protein Phosphatase 2C / genetics*
  • Protein Phosphatase 2C / metabolism
  • RNA Interference
  • Signal Transduction / genetics

Substances

  • 3' Untranslated Regions
  • Glucocorticoids
  • MIRN135 microRNA, human
  • MicroRNAs
  • Dexamethasone
  • AMP-Activated Protein Kinases
  • PPM1E protein, human
  • Protein Phosphatase 2C