Long noncoding RNA MEG3 silencing protects against hypoxia-induced pheochromocytoma-12 cell injury through inhibition of TIMP2 promoter methylation

Hypoxia is a common pathological process caused by insufficient oxygen. Long noncoding RNAs (lncRNAs) have been proven to participate in this pathology. Hypoxia is reported to significantly reduce the secretion of tissue inhibitor of metalloproteinase 2 (TIMP2) and TIMP2 induces pheochromocytoma-12 (PC12) cell cycle arrest. Thus, our study aimed to explore the mechanism by which lncRNA maternally expressed gene 3 (MEG3) was implicated in hypoxia-induced PC12 cell injury through TIMP2 promoter methylation. To elucidate the potential biological significance of MEG3 and the regulatory mechanism between MEG3 and TIMP2, a hypoxia-induced PC12 cell injury model was generated. The hypoxia-exposed cells were subjected to a series of overexpression plasmids and short hairpin RNAs, followed by the measurement of levels of MEG3, TIMP2, lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), reactive oxygen species (ROS), Bcl-2-associated X protein, B-cell lymphoma-2, and caspase-3, as well as the changes in MMP, cell proliferation, apoptosis, and cell cycle progression. On the basis of the findings, MEG3 was upregulated in hypoxia-injured PC12 cells. MEG3 recruited methylation proteins DNMT3a, DNMT3b, and MBD1 and accelerated TIMP2 promoter methylation, which in turn inhibited its expression. Moreover, PC12 cells following MEG3 silencing and TIMP2 overexpression exhibited significantly decreased levels of LDH, MDA, and ROS along with cell apoptosis, yet increased SOD and MMP levels, as well as cell cycle entry to the S phase and cell proliferation. In conclusion, MEG3 silencing suppresses hypoxia-induced PC12 cell injury by inhibiting TIMP2 promoter methylation. This study may provide novel therapeutic targets for hypoxia-induced injury.