Background and objective: Membranous nephropathy (MN) is an autoimmune disease. The up-regulation of the long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (Neat1) has been found in MN but the mechanism is still unclear. Here, we explored the effect and the underlying mechanism of lncRNA Neat1 on the apoptosis of renal tubular epithelial cells in MN.
Methods: Albumin-stimulated E11 podocytes and proximal tubular epithelial cells in vitro and the cationic-bovine serum albumin-induced MN mouse model in vivo were established. The expression of Neat1 in E11 podocytes, renal tubular epithelial cells, and renal tubules and the mRNA expression of BH3-only (the Bcl-2 homology 3-only) proteins were determined by quantitative reverse transcription-polymerase chain reaction. Levels of Cleaved Caspase 3, 6, 7, and Noxa were examined by western blotting. The number of apoptotic cells was detected by flow cytometry. Cellular proliferation was determined by 5-Ethynyl-2'-deoxyuridine and Cell Counting Kit-8 assay. Interactions between BH3-only protein Noxa and Bcl-2 as well as Bcl-xL were evaluated with co-immunoprecipitation.
Results: The expression of lncRNA Neat1 was unchanged in albumin-stimulated E11 podocytes, but it was up-regulated in albumin-stimulated renal tubular epithelial cells and MN renal tubule tissues and there was a time-dependent increase in vivo. In the albumin-stimulated proximal tubular epithelial cells, overexpression of Neat1 could increase apoptosis and decrease proliferation. In turn, interference with Neat1 reduced apoptosis and increased proliferation accordingly. The mRNA expression levels of BH3-only proteins (Bad, Bim, Bid, Puma, Noxa) were detected with qRT-PCR, the results indicated that after overexpression of Neat1, mRNA and protein levels of Noxa were significantly increased, and the interference with BH3-only protein Noxa alleviated apoptosis of renal tubular epithelial cells in vitro.
Conclusion: In our study, we proved that lncRNA Neat1 promoted the development of MN by inducing apoptosis and this effect may be exerted by inhibiting the anti-apoptotic protein activity mediated by Noxa.
Keywords: BH3-only protein; apoptosis; lncRNA Neat1; membranous nephropathy.