Background/Aims: Contrast induced-acute kidney injury (CI-AKI) is one of the most common causes of acute kidney injury (AKI) in hospitalized patients. Mitophagy, the selective elimination of mitochondria via autophagy, is an important mechanism of mitochondrial quality control in physiological and pathological conditions. In this study, we aimed to determine effects of iohexol and iodixanol on mitochondrial reactive oxygen species (ROS), mitophagy and the potential role of mitophagy in CI-AKI cell models. Methods: Cell viability was measured by cell counting kit-8. Cell apoptosis, mitochondrial ROS and mitochondrial membrane potential were detected by western blot, MitoSOX fluorescence and TMRE staining respectively. Mitophagy was detected by the colocalization of LC3-FITC with MitoTracker Red, western blot and electronic microscope. Results: The results showed that mitophagy was induced in human renal tubular cells (HK-2 cells) under different concentrations of iodinated contrast media. Mitochondrial ROS displayed increased expression after the treatment. Rapamycin (Rap) enhanced mitophagy and alleviated contrast media induced HK-2 cells injury. In contrast, autophagy inhibitor 3-methyladenine (3-MA) down-regulated mitophagy and aggravated cells injury. Conclusions: Together, our finding indicates that iohexol and iodixanol contribute to the generation of mitochondrial ROS and mitophagy. The enhancement of mitophagy can effectively protect the kidney from iodinated contrast (iohexol)-induced renal tubular epithelial cells injury.

Recent progress in angiography and interventional therapy has revived interest in comparison of nephrotoxicity of low-or iso-osmolar contrast media, but detailed mechanisms and effective treatments of contrast-induced acute kidney injury (CI-AKI) remain elusive. We established a new model of CI-AKI and compared the nephrotoxicity of iohexol and iodixanol with a focus on renal oxidative stress, mitochondrial damage and mitophagy. Our results showed that 48-h dehydration plus furosemide injection before iohexol administration successfully induced CI-AKI in rats. Compared with iodixanol, iohexol induced a greater decrease in renal function, more severe morphological damage and mitochondrial ultrastructural changes, an increased number of apoptotic cells, decreased antioxidative enzymes with activation of NLRP3 inflammasome in renal tissue. Renal contrast media kinetics showed the immediate excretion of iohexol and the transient renal accumulation of iodixanol. Plasma mtDNA Tc numbers were positively correlated with markers of renal mitochondrial disruption but negatively correlated with the level of serum creatinine and the score of tubular injury. Of note, iodixanol appeared to induce a stronger activation of mitophagy than iohexol, evidenced by greater protein levels of LC3II and PINK1/Parkin in the renal tissue of iodixanol-treated rats. Taken together, our results indicate that iohexol induced more severe nephrotoxicity than iodixanol in vivo due to apoptosis, destruction of antioxidative defense machinery, activation of NLRP3 inflammasome, mitochondrial damage and mitophagy. Plasma mtDNA may serve as a biological marker for renal mitochondrial disruption and damage in CI-AKI. Antioxidative defense and mitophagy are involved in the process of CI-AKI and may be promising targets of therapies.

Contrast-induced acute kidney injury (CI-AKI) is a severe complication of intravascular applied radial contrast media, and recent progress in interventional therapy and angiography has revived interest in explaining detailed mechanisms and developing effective treatment. Recent studies have indicated a potential link between CI-AKI and microRNA (miRNA). However, the potential non-coding RNA-associated-competing endogenous RNA (ceRNA) pairs involved in CI-AKI still remain unclear. In this study, we systematically explored the circRNA or lncRNA-associated-ceRNA mechanism in a new rat model of CI-AKI through deep RNA sequencing. The results revealed that the expression of 38 circRNAs, 12 lncRNAs, 13 miRNAs and 127 mRNAs were significantly dysregulated. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses for mRNAs with significantly different expression and then constructed comprehensive circRNA or lncRNA-associated ceRNA networks in kidney of CI-AKI rats. Thereafter, two constructed ceRNA regulatory pathways in this CI-AKI rat model—novel_circ_0004153/rno-miR-144-3p/Gpnmb or Naglu and LNC_000343/rno-miR-1956-5p/KCP—were validated by real-time qPCR. This study is the first one to provide a systematic dissection of non-coding RNA-associated ceRNA profiling in kidney of CI-AKI rats. The selected non-coding RNA-associated ceRNA networks provide new insight for the underlying mechanism and may profoundly affect the diagnosis and therapy of CI-AKI.