MDM2 mediates fibroblast activation and renal tubulointerstitial fibrosis via a p53-independent pathway
MDM2 mediates fibroblast activation and renal tubulointerstitial fibrosis via a p53-independent pathway
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MDM2 通过 p53 独立途径介导成纤维细胞活化和肾小管间质纤维化。
DOI：
10.1152/ajprenal.00528.2016
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发表时间：
2017-04-01
影响因子：
4.2
通讯作者：
Su, Hua
中科院分区：
文献类型：
--
作者：
Ye, Chen;Tang, Hui;Su, Hua
众所周知，小鼠双微体基因2（MDM 2）在肿瘤发生过程中的细胞增殖和炎症过程中起关键作用。还报道MDM 2在肾小球中表达并参与足细胞损伤。然而，MDM 2是否与肾纤维化有关仍不清楚。在这里，我们研究了MDM 2在肾小管间质纤维化（TIF）中的作用。通过免疫组织化学染色和Western blotting，我们证实了MDM 2在TIF患者和单侧尿道梗阻（UUO）小鼠的肾小管间质室中上调，其主要来源于肌成纤维细胞。一致地，体外MDM 2在TGF-β 1处理的成纤维细胞中增加，所述成纤维细胞是TIF期间产生胶原的肌成纤维细胞的主要来源之一，沿着成纤维细胞活化。重要的是，MDM 2的基因缺失显著减弱成纤维细胞活化。然后，我们分析了成纤维细胞活化过程中MDM 2可能的下游信号传导。p53依赖性通路是MDM 2的经典下游信号传导途径，Nutlin-3是MDM 2-p53相互作用的小分子抑制剂。令人惊讶的是，Nutlin-3不能改善体外成纤维细胞活化和UUO小鼠的TIF。然而，我们发现Notch 1信号在成纤维细胞活化过程中减弱，这可以通过MDM 2敲低而显着挽救。通过质粒过表达Notch 1胞内区（NICD）可明显抑制TGF-β 1诱导的成纤维细胞活化。此外，NICD的降解被泛素失活酶E1的抑制剂PYR-41和蛋白酶体抑制剂MG 132显著抑制。总而言之，我们的研究结果提供了第一个证据表明MDM 2参与成纤维细胞活化和TIF，而TIF与Notch 1遍在蛋白化和蛋白酶体降解相关。
It is well recognized that murine double minute gene 2 (MDM2) plays a critical role in cell proliferation and inflammatory processes during tumorigenesis. It is also reported that MDM2 is expressed in glomeruli and involved in podocyte injury. However, whether MDM2 is implicated in renal fibrosis remains unclear. Here we investigated the role of MDM2 in tubulointerstitial fibrosis (TIF). By immunohistochemical staining and Western blotting we confirmed that MDM2 is upregulated in the tubulointerstitial compartment in patients with TIF and unilateral urethral obstruction (UUO) mice, which mainly originates from myofibroblasts. Consistently, in vitro MDM2 is increased in TGF-beta 1-treated fibroblasts, one of the major sources of collagen-producing myofibroblasts during TIF, along with fibroblast activation. Importantly, genetic deletion of MDM2 significantly attenuates fibroblast activation. We then analyzed the possible downstream signaling of MDM2 during fibroblast activation. p53-dependent pathway is the classic downstream signaling of MDM2, and Nutlin-3 is a small molecular inhibitor of MDM2-p53 interaction. To our surprise, Nutlin-3 could not ameliorate fibroblast activation in vitro and TIF in UUO mice. However, we found that Notch1 signaling is attenuated during fibroblast activation, which could be markedly rescued by MDM2 knockdown. Overexpression of intracellular domain of Notch1 (NICD) by plasmid could obviously minimize fibroblast activation induced by TGF-beta 1. In addition, the degradation of NICD is strikingly suppressed by PYR-41, an inhibitor of ubiquitinactivating enzyme E1, and proteasome inhibitor MG132. Taken together, our findings provide the first evidence that MDM2 is involved in fibroblast activation and TIF, which associates with Notch1 ubiquitination and proteasome degradation.