Ang II/AT1R介导的肾小管上皮细胞氧化应激在肾结石形成中的作用

The pathogenesis of kidney stones is still unclear. Oxidative stress mediated by crystal-cell interaction has become a hot topic in the study of stone etiology. Recent studies have shown that the level of oxidative stress in patients with kidney stones was significantly increased. After exposure of renal tubular cells to calcium oxalate crystals, ROS production increased significantly, and the NFκB pathway was activated to induce the increased expression of stone-related proteins, which promoted the formation of kidney stones. Furthermore Ang II/AT1R and endoplasmic reticulum calcium release may be involved in activating cellular oxidative stress. Our preliminary studies have found that the level of Ang II/AT1R in hypercalciuria rats was increased, the production of ROS and the expression of NADPH oxidase were increased, and the NF B pathway was activated. Concentration of IP3 and cytoplasmic Ca2+ in renal tubular cells were significantly increased under calcium oxalate crystal treatment. Based on the above evidence we could make this assumption: calcium oxalate crystals induce Ang II/AT1R activation in renal tubular cells and activate oxidative stress and NFκB pathway through endoplasmic reticulum calcium release, resulting in increased expression of stone-related proteins, promoting crystal adhesion and formation of kidney stones. This research program is intended to elucidation the role and mechanism of Ang II/ AT1R mediated oxidative stress in renal tubular cells in the formation of calcium oxalate kidney stones at human, animal and cell levels, and provide new ideas for the study on the causes of kidney stones.

肾结石发病机制尚不清楚。晶体-细胞相互作用介导的氧化应激成为结石病因研究热点。研究发现，肾结石患者体内氧化应激水平明显升高，肾小管上皮细胞暴露于草酸钙晶体后，ROS产生明显增多，激活NFκB通路诱导成石相关蛋白表达增加，促进肾结石形成。而Ang II/AT1R及内质网钙释放可能参与激活细胞氧化应激。我们研究发现高钙尿大鼠体内Ang II/AT1R水平升高，肾脏内ROS产生增多且NADPH氧化酶表达增加，NFκB通路处于激活状态；草酸钙晶体处理导致肾小管上皮细胞内IP3及胞浆Ca2+浓度明显升高。藉此推测：草酸钙晶体诱导肾小管上皮细胞Ang II/AT1R活化并通过内质网钙释放激活氧化应激及NFκB通路，导致成石相关蛋白表达增加，促进晶体的黏附及肾结石的形成。本课题拟从人体、动物、细胞水平阐释Ang II/Ca2+/ROS/NFκB通路在肾结石形成中的作用及机制，为肾结石成因研究提供新思路。

肾结石的发病机制尚未被完全阐明，而草酸钙晶体-细胞相互作用介导的氧化应激在肾结石的发生发展过程中发挥重要作用。研究表明AngⅡ/AT1R通过诱导氧化应激参与多种疾病发生，但其在肾结石中的具体作用尚不清楚。在本项研究中，我们发现肾小管上皮细胞在草酸钙晶体刺激下AngⅡ/AT1R表达增加，进而促进IP3的表达，而IP3作用于内质网表面受体IP3R后促进Ca2+释放到细胞质。胞浆Ca2+增加能够激活NADPH氧化酶，促进活性氧的产生，诱导氧化应激，进一步激活NF-κB通路，导致成石相关蛋白表达增加，促进晶体的黏附及肾结石的形成。AT1R抑制剂losartan，IP3R抑制剂2-APB，以及下调AT1R表达能够在体内外水平显著抑制草酸钙晶体介导的上述效应，减缓肾结石的形成。此外，我们还发现肾素-血管紧张素系统中的Ang-(1-7)/MAS1够能拮抗AngⅡ/AT1R的效应，在肾结石形成中发挥保护性作用。本研究首次揭示AngⅡ/AT1R在草酸钙晶体-细胞相互作用介导的氧化应激的具体作用，为肾结石的病因研究和防治提供新的理论基础。