Autophagy is activated to protect renal tubular epithelial cells against iodinated contrast media-induced cytotoxicity

With the steady increase in the use of various contrast-related technologies in recent years, contrast-induced nephropathy has received significant attention from clinicians and researchers. The present study aimed to determine the potential role of autophagy in iodinated contrast media (CM)-induced cell injury and apoptosis in human proximal renal tubular epithelial HK-2 cells. The present study used the iodinated CM iohexol (200 mg iodine/ml) to treat HK-2 cells for 6 h, in order to establish a damaged cell model. The autophagy inhibitor 3-methyladenine (3-MA; 10 mM) was used to inhibit the formation of autophagosomes. Immunofluorescence assay and transmission electron microscopy (TEM) were used to observe the formation of autophagosomes in the cytoplasm. The protein expression levels of microtubule-associated protein 1A/1B-light chain 3 (LC3)-II and autophagy-related protein 7 (Atg7) were detected by western blotting. The cytotoxicity of CM was evaluated by MTT assay and lactate dehydrogenase release, and cell apoptosis was detected by flow cytometry. Increased formation of autophagosomes and autophagic vesicles was observed under TEM in HK-2 cells following iohexol treatment for 6 h. Immunofluorescence assay demonstrated that iohexol increased LC3-II expression in HK-2 cells. Furthermore, the expression levels of LC3-II and Atg7 in HK-2 cells were significantly upregulated by iohexol administration; however, LC3-II and Atg7 expression was decreased by 3-MA treatment. These results provided evidence to suggest that autophagy is activated in response to iohexol-induced cell injury and apoptosis, and may exert a renoprotective role in HK-2 cells.