Calcifying nanoparticles induce cytotoxicity mediated by ROS-JNK signaling pathways
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Calcifying nanoparticles (CNPs) play an important role in kidney stone formation, but the mechanism(s) are unclear. CNPs were isolated and cultured from midstream urine of patients with kidney stones. CNP morphology and characteristics were examined by electron microscopy and electrophoresis analysis. Chemical composition was analyzed using energy-dispersive X-ray microanalysis and Western blotting. Human renal proximal convoluted tubule cell (HK-2) cultures were exposed to CNPs for 0, 12 and 72 h, and production of reactive oxygen species (ROS), mitochondrial membrane potential and apoptosis levels were evaluated. CNPs isolated from patients showed classical morphology, the size range of CNPs were 15–500 nm and negative charge; they were found to contain fetuin-A. Exposure of HK-2 cells to CNPs induced ROS production, decreased mitochondrial membrane potential and decreased cell viability. Transmission electron microscopy showed that CNPs can enter the cell by phagocytosis, and micrographs revealed signs of apoptosis and autophagy. CNPs increased the proportion of apoptotic cells, down-regulated Bcl-2 expression and up-regulated Bax expression. CNPs also up-regulated expression of LC3-B, Beclin-1and p-JNK.CNPs are phagocytosed by HK-2 cells, leading to autophagy, apoptosis and ROS production, in part through activation of JNK signaling pathways. ROS and JNK pathways may contribute to CNP-induced cell injury and kidney stone formation.
KeywordsCalcifying nanoparticles Cytotoxicity HK-2 cells Kidney stone ROS
This work was supported by grants from the National Natural Science Foundation of China (No. 81760127, 81360113, 30860280 and 30960455), the Guangxi Natural Science Foundation (No. 2017GXNSFAA198070). We are grateful to the members of the Electron Microscopy Group in the Department of Life Science at Guangxi Medical University, Guangxi, and People’s Republic of China.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no any conflict of interests.
The study protocol was approved by the Ethics Committee of Guangxi Medical University (Guangxi, China).
Informed consent was obtained from all individual participants included in the study.
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