Inhibition of lncRNA MEG3 protects renal tubular from hypoxia-induced kidney injury in acute renal allografts by regulating miR-181b/TNF-α signaling pathway

Early damage to transplanted organs initiates excess inflammation that deteriorates existing injury, which is a leading cause of graft loss. Long noncoding RNAs (lncRNAs) are recently thought to play a significant role in cellular homeostasis during pathological process of kidney diseases. The aim of this study was to assess the function and mechanism of lncRNA, maternally expressed gene 3 (MEG3), on early renal allografts pathogenesis. Real-time polymerase chain reaction (RT-PCR) analysis found that the levels of MEG3 and miR-181b-5p were increased and decreased respectively in grafted kidney. The Western blot assay showed that TNF-alpha was upregulated in the kidney and in HK-2 cells. Administering MEG3-specific small interfering RNA (siRNA) in mice silenced MEG3 expression and protected kidney renal allograft from injury. Bioinformatical analysis and luciferase assay indicated that MEG3 is a target of miR-181b-5p. MEG3 inhibition and overexpression promoted and suppressed miR-181b-5p levels respectively. In addition, Western blot and immunohistochemical staining suggested that decreased TNF-alpha expression was observed in the kidney. In contrary to MEG3, miR181b overexpression attenuated hypoxia-induced HK-2 cell apoptosis, as well as suppressed hypoxia-induced TNF-alpha upregulation. In luciferase reporter assay, we confirmed that miR-181b directly bound to the 3 '-untranslated region (3 '-UTR) of TNF-alpha, thereby negatively regulating the TNF-alpha expression. Our data suggested that MEG3 functions as a competing endogenous RNA for miR-181b to regulate the TNF-alpha expression in hypoxia-induced kidney injury in acute renal allografts.