Department of Biochemistry, Centre for Excellence in Genomics Science, School of Biological Sciences, Madurai Kamaraj University, Madurai, 625 021, India.
Department of Oral Biology, School of Dental Medicine, University at Buffalo, Buffalo, NY, USA.
J Physiol Biochem. 2017 Nov;73(4):561-573. doi: 10.1007/s13105-017-0587-8. Epub 2017 Sep 5.
Oxalate, a non-essential end product of metabolism, causes hyperoxaluria and eventually calcium oxalate (CaOx) stone disease. Kidney cells exposed to oxalate stress results in generation of reactive oxygen species (ROS) and progression of stone formation. Perturbations in endoplasmic reticulum (ER) result in accumulation of misfolded proteins and Ca ions homeostasis imbalance and serve as a common pathway for various diseases, including kidney disorders. ER stress induces up-regulation of pro-survival protein glucose-regulated protein 78 (GRP78) and pro-apoptotic signaling protein C/EBP homologous protein (CHOP). Since the association of oxalate toxicity and ER stress on renal cell damage is uncertain, the present study is an attempt to elucidate the interaction of GRP78 with oxalate by computational analysis and study the role of ER stress in oxalate-mediated apoptosis in vitro and in vivo. Molecular docking results showed that GRP78-oxalate/CaOx interaction takes place. Oxalate stress significantly up-regulated expression of ER stress markers GRP78 and CHOP both in vitro and in vivo. Exposure of oxalate increased ROS generation and altered antioxidant enzyme activities. N-Acetyl cysteine treatment significantly ameliorated oxalate-mediated oxidative stress and moderately attenuated ER stress marker expression. The result indicates oxalate toxicity initiated oxidative stress-induced ER stress and also activating ER stress mediated apoptosis directly. In addition, the up-regulation of transforming growth factor β- revealed oxalate may induce kidney fibrosis through ER stress-mediated mechanisms. The present study provide insights into the pathogenic role of oxidative and ER stress by oxalate exposure in the formation of calcium oxalate stone.
草酸盐是代谢的非必需终产物，可导致高草酸尿症，并最终导致草酸钙（CaOx）结石病。暴露于草酸盐应激下的肾细胞会导致活性氧（ROS）的产生和结石形成的进展。内质网（ER）的紊乱会导致错误折叠的蛋白质积累和钙离子动态平衡失衡，并成为包括肾脏疾病在内的各种疾病的共同途径。ER 应激诱导细胞存活蛋白葡萄糖调节蛋白 78（GRP78）和促凋亡信号蛋白 C/EBP 同源蛋白（CHOP）的上调。由于草酸毒性和 ER 应激对肾细胞损伤的关联尚不确定，因此本研究试图通过计算分析阐明 GRP78 与草酸的相互作用，并研究 ER 应激在草酸介导的体外和体内细胞凋亡中的作用。分子对接结果表明，GRP78-草酸/CaOx 相互作用发生。草酸应激显著上调了体外和体内 ER 应激标志物 GRP78 和 CHOP 的表达。暴露于草酸会增加 ROS 的产生并改变抗氧化酶的活性。N-乙酰半胱氨酸处理可显著改善草酸介导的氧化应激，并适度减轻 ER 应激标志物的表达。结果表明，草酸毒性通过诱导氧化应激，直接激活 ER 应激介导的细胞凋亡。此外，转化生长因子β的上调表明，草酸可能通过 ER 应激介导的机制诱导肾脏纤维化。本研究为草酸暴露在草酸钙结石形成过程中诱导氧化应激和 ER 应激的致病作用提供了新的见解。
