Affiliation:
1. Clinical College of Orthopedics, Tianjin Medical University
2. Department of Nephrology, Tianjin Hospital of Tianjin University
3. Department of Nephrology, Renmin Hospital of Wuhan University
4. Tianjin Key Laboratory of Biomedical Materials, Institute of Biomedical Engineering, Chinese Academy of Medical Science & Peking Union Medical College
Abstract
Abstract
Background
Contrast-induced acute kidney injury (CI-AKI) is the acute onset of renal failure occurring 24–48 hours after intravascular injection of contrast medium (CM), which is a common cause of hospital-acquired acute kidney injury. Previous researches on CI-AKI have demonstrated that cytoplasmic Ca2+ overload and mitochondrial damage were strongly associated with CI-AKI, but the precise pathogenesis remains elusive. Therefore, we aimed to identify the role of mitochondrial calcium uniporter (MCU), the most important Ca2+ unidirectional channel of mitochondria, in CM-induced tubular epithelial cell injury and explore the molecular conformation of MCU interacting with iohexol.
Methods
Human renal proximal tubular epithelial (HK-2) cells were incubated with 100 mg I/ml iohexol. Cell injury and apoptosis were detected by Cell Counting Kit-8 and flow cytometry. The mitochondrial Ca2+ level was evaluated by Rhod-2 fluorescence. Mitochondrial damage was assessed by transmission electron microscopy, fluorescence of mitotracker, and JC-1. Protein expression of dynamin-related protein 1 (DRP1) and optic atrophy 1 (OPA1) was assessed by Western Blot.
Results
Iohexol administration successfully induced HK-2 cell injury and apoptosis. Moreover, there is an interaction between Iohexol and MCU. We also demonstrated that iohexol could lead to increase of mitochondrial Ca2+ concentration, upregulation of MCU expression, mitochondrial injury, and mitochondrial dynamics imbalance (excessive mitochondrial fission and loss of mitochondrial fusion) in HK-2 cells. Of note, inhibiting MCU by Ru360 efficiently maintaining mitochondrial function by reducing mitochondrial Ca2+ influx and improving impaired mitochondrial dynamics, thereby protecting HK-2 cells from CM-induced injury and apoptosis. On the contrary, the activation of MCU by spermine aggravated cell injury under the same mechanisms.
Conclusions
The present study illustrated a novel molecular mechanism of CI-AKI involving MCU-mediated mitochondrial dynamics imbalance, and suppression of MCU exhibited a cytoprotective effect on CM-treated renal tubular cells.
Publisher
Research Square Platform LLC