MicroRNA-668 represses MTP18 to preserve mitochondrial dynamics in ischemic acute kidney injury
Qingqing Wei, … , Changlin Mei, Zheng Dong
Qingqing Wei, … , Changlin Mei, Zheng Dong
Published October 16, 2018
Citation Information: J Clin Invest. 2018;128(12):5448-5464. https://doi.org/10.1172/JCI121859.
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Research Article Nephrology

MicroRNA-668 represses MTP18 to preserve mitochondrial dynamics in ischemic acute kidney injury

Abstract

The pathogenesis of ischemic diseases remains unclear. Here we demonstrate the induction of microRNA-668 (miR-668) in ischemic acute kidney injury (AKI) in human patients, mice, and renal tubular cells. The induction was HIF-1 dependent, as HIF-1 deficiency in cells and kidney proximal tubules attenuated miR-668 expression. We further identified a functional HIF-1 binding site in the miR-668 gene promoter. Anti–miR-668 increased apoptosis in renal tubular cells and enhanced ischemic AKI in mice, whereas miR-668 mimic was protective. Mechanistically, anti–miR-668 induced mitochondrial fragmentation, whereas miR-668 blocked mitochondrial fragmentation during hypoxia. We analyzed miR-668 target genes through immunoprecipitation of microRNA-induced silencing complexes followed by RNA deep sequencing and identified 124 protein-coding genes as likely targets of miR-668. Among these genes, only mitochondrial protein 18 kDa (MTP18) has been implicated in mitochondrial dynamics. In renal cells and mouse kidneys, miR-668 mimic suppressed MTP18, whereas anti–miR-668 increased MTP18 expression. Luciferase microRNA target reporter assay further verified MTP18 as a direct target of miR-668. In renal tubular cells, knockdown of MTP18 suppressed mitochondrial fragmentation and apoptosis. Together, the results suggest that miR-668 is induced via HIF-1 in ischemic AKI and that, upon induction, miR-668 represses MTP18 to preserve mitochondrial dynamics for renal tubular cell survival and kidney protection.

Authors

Qingqing Wei, Haipeng Sun, Shuwei Song, Yong Liu, Pengyuan Liu, Man Jiang Livingston, Jianwen Wang, Mingyu Liang, Qing-Sheng Mi, Yuqing Huo, Norris Stanley Nahman, Changlin Mei, Zheng Dong

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Figure 3

miR-668 is antiapoptotic in kidney proximal tubular cells.

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miR-668 is antiapoptotic in kidney proximal tubular cells. (A) Represent...
(A) Representative cell and nuclear images of RPTCs showing the induction of apoptosis by 200 nM anti–miR-668, but not by scrambled-sequence LNAs. Scale bar: 0.2 mm. (B) Percentage of apoptosis in anti–miR-668–treated or scrambled-sequence LNA–treated cells assessed by counting of the cells with typical apoptotic morphologies (n = 6; **P = 0.00316, 2-tailed Student’s t test). (C) Caspase activity showing the induction of caspase activation by anti–miR-668 (n = 4; *P = 0.030, 2-tailed Student’s t test). (D) Representative cell and nuclear images of RPTCs showing the antiapoptotic effect of 200 nM miR-668 mimics (miR-668), but not the negative control (NC) oligonucleotides. The cells were treated with 10 mM azide for 3 hours to induce ATP depletion and then recovered for 2 hours in full culture medium to develop apoptosis (Azide). Scale bars: 0.2 mm. (E) Percentage of apoptosis assessed by counting of the cells with typical apoptotic morphologies (n = 3 for control groups, n = 7 for azide groups; **P = 0.0004, 2-tailed Student’s t test). (F) Caspase activity verifying the antiapoptotic effect of miR-668 (n = 3 for control groups, n = 5 for azide groups; **P = 0.0011, 2-tailed Student’s t test).