Department of Nephrology, Shengjing Hospital of China Medical University, 110022, Shenyang, Liaoning, China.
Cell Death Dis. 2021 Feb 18;12(2):191. doi: 10.1038/s41419-021-03466-5.
Ischemia-reperfusion injury (IRI)-induced acute kidney injury (AKI) is a life-threatening disease. The activation of mitophagy was previously identified to play an important role in IRI. Maternally expressed 3 (MEG3) can promote cerebral IRI and hepatic IRI. The present study was designed to study the role of MEG3 in renal IRI. Renal IRI mice models were established, and HK-2 cells were used to construct the in vitro models of IRI. Hematoxylin-eosin staining assay was applied to reveal IRI-triggered tubular injury. MitoTracker Green FM staining and an ALP kit were employed for detection of mitophagy. TdT-mediated dUTP-biotin nick-end labeling assay was used to reveal cell apoptosis. The results showed that renal cortex of IRI mice contained higher expression of MEG3 than that of sham mice. MEG3 expression was also elevated in HK-2 cells following IRI, suggesting that MEG3 might participate in the development of IRI. Moreover, downregulation of MEG3 inhibited the apoptosis of HK-2 cells after IRI. Mitophagy was activated by IRI, and the inhibition of MEG3 can restore mitophagy activity in IRI-treated HK-2 cells. Mechanistically, we found that MEG3 can bind with miR-145-5p in IRI-treated cells. In addition, rhotekin (RTKN) was verified to serve as a target of miR-145-5p. MEG3 upregulated RTKN expression by binding with miR-145-5p. Further, MEG3 activated the Wnt/β-catenin pathway by upregulation of RTKN. The downstream effector of Wnt/β-catenin pathway, c-MYC, served as the transcription factor to activate MEG3. In conclusion, the positive feedback loop of MEG3/miR-145-5p/RTKN/Wnt/β-catenin/c-MYC promotes renal IRI by activating mitophagy and inducing apoptosis, which might offer a new insight into the therapeutic methods for renal IRI in the future.
缺血再灌注损伤（IRI）诱导的急性肾损伤（AKI）是一种危及生命的疾病。先前的研究表明，自噬的激活在 IRI 中发挥着重要作用。母系表达基因 3（MEG3）可促进脑 IRI 和肝 IRI。本研究旨在研究 MEG3 在肾 IRI 中的作用。建立肾 IRI 小鼠模型，并使用 HK-2 细胞构建 IRI 体外模型。苏木精-伊红（HE）染色法用于揭示 IRI 引起的肾小管损伤。使用 MitoTracker Green FM 染色和碱性磷酸酶（ALP）试剂盒检测自噬。末端转移酶介导的 dUTP 缺口末端标记法（TUNEL）用于检测细胞凋亡。结果显示，与假手术组相比，IRI 小鼠的肾皮质中 MEG3 的表达水平更高。在 IRI 后 HK-2 细胞中也观察到 MEG3 表达上调，表明 MEG3 可能参与了 IRI 的发生发展。此外，下调 MEG3 抑制了 IRI 后 HK-2 细胞的凋亡。IRI 激活了自噬，而抑制 MEG3 可以恢复 IRI 处理的 HK-2 细胞中的自噬活性。在机制上，我们发现 MEG3 可以在 IRI 处理的细胞中与 miR-145-5p 结合。此外，Rhotekin（RTKN）被验证为 miR-145-5p 的靶基因。MEG3 通过与 miR-145-5p 结合而上调 RTKN 表达。进一步研究发现，MEG3 通过上调 RTKN 激活 Wnt/β-catenin 通路。Wnt/β-catenin 通路的下游效应因子 c-MYC 作为转录因子激活 MEG3。综上所述，MEG3/miR-145-5p/RTKN/Wnt/β-catenin/c-MYC 的正反馈环通过激活自噬和诱导细胞凋亡促进肾 IRI，这可能为未来肾 IRI 的治疗方法提供新的思路。
