SIRT3-FoxO3信号通路在草酸钙肾结石形成中的作用和分子机制

The incidence of kidney stones is as high as 6.06%, of which the underlying mechanisms are still unknown. Renal tubular epithelial cell injury is thought to be the key link of stone formation. Our previous study found that stimulation of calcium oxalate crystals inhibited mitochondrial autophagy, and further promoted apoptosis and injury of renal tubular epithelial cells. As a deacetylase in mitochondria, SIRT3 plays an important role in preventing cells from oxidative damage. Further study showed that stimulation of calcium oxalate crystals to renal tubular epithelial cells led to downregulation of SIRT3. Overexpression of SIRT3 increased deacetylation of transcription factor FoxO3, and downregulated phosphorylation and ubiquitination status, thereby reducing the generation of reactive oxygen species and apoptosis. Based on previous study, we speculate that SIRT3 regulates FoxO3 post-translational modification on autophagy and apoptosis after calcium oxalate crystals stimulation. Our research is to explore the interaction between autophagy and apoptosis stimulated by calcium oxalate crystals, to illustrate the influence of epigenetic regulation of SIRT3 to FoxO3 on apoptosis and autophagy in the stone formation model, and to provide novel approach to prevent calcium oxalate stone formation.

肾结石的患病率高达6.06%，其具体发病机制仍不明。目前研究认为肾小管上皮细胞损伤是导致结石形成的中心环节。我们前期研究发现草酸钙晶体刺激下调了肾小管上皮细胞的自噬，同时促进其损伤和凋亡。SIRT3是线粒体中最重要的去乙酰化蛋白酶，在对抗氧化应激损伤细胞中发挥重要作用。进一步研究发现，草酸钙晶体刺激肾小管上皮细胞后SIRT3表达下调；过表达SIRT3能够增加转录因子FoxO3的去乙酰化，进而下调FoxO3的磷酸化和泛素化，从而降低活性氧的产生，使细胞凋亡减少。据此我们推测，SIRT3通过对FoxO3翻译后修饰调控草酸钙晶体诱导的肾小管上皮细胞自噬和凋亡。本研究拟进一步探究草酸钙晶体刺激下肾小管上皮细胞自噬和凋亡的相互作用，阐明SIRT3对FoxO3的表观调控在结石形成模型中对肾小管上皮细胞凋亡和自噬的影响，解析FoxO3调控肾小管上皮细胞自噬的分子机制，为探索草酸钙肾结石的预防提供新思路。

草酸钙（CaOx）晶体诱导的肾小管上皮细胞损伤促进结晶黏附和聚集，在肾结石中起关键作用，而其具体机制尚待深入阐明。我们前期前期研究发现草酸钙晶体刺激下调了肾小管上皮细胞的自噬，同时促进其损伤和凋亡。草酸钙晶体刺激肾小管上皮细胞后SIRT3 表达下调；过表达SIRT3 能够增加FoxO3的去乙酰化，进而下调FoxO3的磷酸化和泛素化，从而降低活性氧的产生，使细胞凋亡减少。Sirt3/FoxO3a信号通路上调肾小管上皮细胞的自噬水平，自噬增加可减少肾小管上皮细胞的损伤。发现Foxo3a与LC3B的启动子区域相互作用并增加其表达，增强肾小管上皮细胞自噬并抑制细胞凋亡和坏死。总之，我们的研究结果表明MAPK / Sirt3 / FoxO3a途径调节肾小管上皮细胞损伤中的肾TEC死亡和自噬。