Munc18-1 相互作用蛋白 3 通过保护肾小管上皮细胞免于凋亡来减轻肾纤维化。
Munc18-1-interacting protein 3 mitigates renal fibrosis through protection of tubular epithelial cells from apoptosis.
机构信息
Division of Nephrology and Endocrinology, University of Tokyo, Tokyo, Japan.
Department of Nephrology and Rheumatology, Kyorin University School of Medicine, Tokyo, Japan.
出版信息
Nephrol Dial Transplant. 2020 Apr 1;35(4):576-586. doi: 10.1093/ndt/gfz177.
BACKGROUND
Tubulointerstitial fibrosis is a hallmark of chronic kidney disease (CKD), and is initiated by tubular epithelial cell (TEC) injury. Hypoxia promotes tubular cell death, fibrosis and CKD progression. Munc18-1-interacting protein 3 (Mint3) is a molecule that activates hypoxia-inducible factors (HIFs) by binding and suppressing factor inhibiting HIF-1 (FIH). However, the role of Mint3 in tubulointerstitial fibrosis remains unknown.
METHODS
We induced fibrosis of the kidney after unilateral ischemia-reperfusion injury (uIRI) in Mint3-knockout and littermate wild-type mice. The duration of ischemia was 23 min and the kidneys were harvested at 24 h and 7 days after ischemia-reperfusion. The function of Mint3 was further investigated by using mouse cortical tubular (MCT) cells, which were treated with Mint3 and/or FIH small interfering RNA and exposed to normoxia or hypoxia.
RESULTS
Knockout of Mint3 did not affect the acute injury induced by uIRI, but exacerbated the tubulointerstitial fibrosis, accompanied by an increase in TEC apoptosis. Consistently, hypoxia-induced apoptosis of MCT cells was aggravated by Mint3 knockdown. Unexpectedly, the additional knockdown of FIH did not suppress the increase in apoptosis by Mint3 knockdown, demonstrating the irrelevance of the FIH/HIF pathway. Therefore, we next focused on nuclear factor (NF)-κB, which has an anti-apoptotic role. Indeed, not only the expression of the inhibitory NF-κB p50 but also the DNA-binding activity of p50/p50 homodimer was increased by knockdown of Mint3 in the TECs, along with the decreased expressions of the NF-κB-targeted anti-apoptotic genes. An increase in NF-κB p50 was also confirmed in Mint3-knockout kidneys.
CONCLUSIONS
Mint3 in epithelial cells protects the cells from apoptosis by up-regulating anti-apoptotic effects of NF-κB, leading to fibrosis suppression. This new pathophysiology of tubulointerstitial fibrosis could be a target of future therapy for CKD.
背景
肾小管间质纤维化是慢性肾脏病（CKD）的一个标志，由肾小管上皮细胞（TEC）损伤引发。缺氧可促进肾小管细胞死亡、纤维化和 CKD 进展。Munc18-1 相互作用蛋白 3（Mint3）是一种通过与抑制低氧诱导因子-1（FIH）的因子结合并抑制其功能来激活低氧诱导因子（HIF）的分子。然而，Mint3 在肾小管间质纤维化中的作用尚不清楚。
方法
我们通过在 Mint3 敲除和同窝野生型小鼠的单侧缺血再灌注损伤（uIRI）后诱导肾脏纤维化，来研究 Mint3 的作用。缺血时间为 23 分钟，在缺血再灌注后 24 小时和 7 天采集肾脏。我们使用鼠皮质肾小管（MCT）细胞进一步研究了 Mint3 的功能，这些细胞用 Mint3 和/或 FIH 小干扰 RNA 处理，并暴露于常氧或缺氧环境中。
结果
Mint3 敲除不影响 uIRI 引起的急性损伤，但加重了肾小管间质纤维化，同时增加了 TEC 细胞凋亡。一致的是，Mint3 敲低加剧了缺氧诱导的 MCT 细胞凋亡。出乎意料的是，FIH 的额外敲低并没有抑制 Mint3 敲低引起的凋亡增加，表明 FIH/HIF 途径与 Mint3 无关。因此，我们接下来专注于具有抗凋亡作用的核因子（NF）-κB。事实上，Mint3 敲低不仅增加了 TEC 中抑制性 NF-κB p50 的表达，还增加了 p50/p50 同源二聚体的 DNA 结合活性，同时 NF-κB 靶向抗凋亡基因的表达减少。在 Mint3 敲除的肾脏中也证实了 NF-κB p50 的增加。
结论
上皮细胞中的 Mint3 通过上调 NF-κB 的抗凋亡作用来保护细胞免于凋亡，从而抑制纤维化。这种肾小管间质纤维化的新病理生理学可能成为未来 CKD 治疗的靶点。
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