Long Non-Coding RNA MALAT1 Protects Human Osteoblasts from Dexamethasone-Induced Injury via Activation of PPM1E-AMPK Signaling

Cell Physiol Biochem. 2018;51(1):31-45. doi: 10.1159/000495159. Epub 2018 Nov 15.

Abstract

Background/aims: Dexamethasone (Dex) induces injuries to human osteoblasts. In this study, we tested the potential role of the long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (Lnc-MALAT1) in this process.

Materials: Two established human osteoblastic cell lines (OB-6 and hFOB1.19) and primary human osteoblasts were treated with Dex. Lnc-MALAT1 expression was analyzed by quantitative real-time polymerase chain reaction assay. Cell viability, apoptosis, and death were tested by the MTT assay, histone-DNA assay, and trypan blue staining assay, respectively. AMP-activated protein kinase (AMPK) signaling was evaluated by western blotting and AMPK activity assay.

Results: Lnc-MALAT1 expression was downregulated by Dex treatment in the established osteoblastic cell lines (OB-6 and hFOB1.19) and primary human osteoblasts. The level of Lnc-MALAT1 was decreased in the necrotic femoral head tissues of Dex-administered patients. In osteoblastic cells and primary human osteoblasts, forced overexpression of Lnc-MALAT1 using a lentiviral vector (LV-MALAT1) inhibited Dex-induced cell viability reduction, cell death, and apoptosis. Conversely, transfection with Lnc-MALAT1 small interfering RNA aggravated Dex-induced cytotoxicity. Transfection with LV-MALAT1 downregulated Ppm1e (protein phosphatase, Mg2+/ Mn2+-dependent 1e) expression to activate AMPK signaling. Treatment of osteoblasts with AMPKα1 short hairpin RNA or dominant negative mutation (T172A) abolished LV-MALAT1-induced protection against Dex-induced cytotoxicity. Furthermore, LV-MALAT1 induced an increase in nicotinamide adenine dinucleotide phosphate activity and activation of Nrf2 signaling. Dex-induced reactive oxygen species production was significantly attenuated by LV-MALAT1 transfection in osteoblastic cells and primary osteoblasts.

Conclusion: Lnc-MALAT1 protects human osteoblasts from Dex-induced injuries, possibly via activation of Ppm1e-AMPK signaling.

Keywords: Dexamethasone; LncRNA MALAT1; Nrf2; Osteoblasts.

MeSH terms

  • AMP-Activated Protein Kinases / antagonists & inhibitors
  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism
  • Apoptosis / drug effects
  • Cells, Cultured
  • Dexamethasone / pharmacology*
  • Dexamethasone / therapeutic use
  • Down-Regulation / drug effects
  • Femur Head Necrosis / drug therapy
  • Femur Head Necrosis / metabolism
  • Femur Head Necrosis / pathology
  • Humans
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • NF-E2-Related Factor 2 / metabolism
  • Osteoblasts / cytology
  • Osteoblasts / drug effects
  • Osteoblasts / metabolism
  • Protein Phosphatase 2C / metabolism
  • RNA Interference
  • RNA, Long Noncoding / antagonists & inhibitors
  • RNA, Long Noncoding / genetics
  • RNA, Long Noncoding / metabolism*
  • RNA, Small Interfering / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / drug effects*

Substances

  • MALAT1 long non-coding RNA, human
  • NF-E2-Related Factor 2
  • NFE2L2 protein, human
  • RNA, Long Noncoding
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • Dexamethasone
  • AMP-Activated Protein Kinases
  • PPM1E protein, human
  • Protein Phosphatase 2C