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Published on: April 10, 2018
Long Non-Coding RNA MALAT1 Protects Human Osteoblasts from Dexamethasone-Induced Injury via Activation of PPM1E-AMPK
Jian-Bo Fan1,2, Yingzi Zhang3, Wei Liu1
1Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong, China.
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.
Insights
Long non-coding RNA MALAT1 protects human osteoblasts from dexamethasone-induced injury. Upregulating Lnc-MALAT1 activates Ppm1e-AMPK signaling, reducing cell death and oxidative stress.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Dexamethasone (Dex) is known to induce injuries in human osteoblasts.
- The role of long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (Lnc-MALAT1) in this process requires investigation.
Purpose of the Study:
- To investigate the role of Lnc-MALAT1 in dexamethasone-induced human osteoblast injury.
- To elucidate the underlying molecular mechanisms involving Ppm1e and AMP-activated protein kinase (AMPK) signaling.
Main Methods:
- Human osteoblastic cell lines (OB-6, hFOB1.19) and primary osteoblasts were treated with dexamethasone.
- Lnc-MALAT1 expression was quantified using qRT-PCR.
- Cell viability, apoptosis, and death were assessed using MTT, histone-DNA, and trypan blue assays.
- AMPK signaling, Ppm1e expression, and reactive oxygen species (ROS) production were evaluated.
Main Results:
- Dexamethasone downregulated Lnc-MALAT1 expression in osteoblasts and in necrotic femoral head tissues.
- Overexpression of Lnc-MALAT1 protected osteoblasts against dexamethasone-induced cytotoxicity, reduced apoptosis, and inhibited ROS production.
- Lnc-MALAT1 activated Ppm1e-AMPK signaling and Nrf2 signaling pathways, mitigating dexamethasone-induced damage.
Conclusions:
- Lnc-MALAT1 plays a protective role against dexamethasone-induced injuries in human osteoblasts.
- This protection is mediated through the activation of the Ppm1e-AMPK signaling pathway.
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