miR‑21 attenuates contrast‑induced renal cell apoptosis by targeting PDCD4

Contrast medium (CM) is widely used in cardiac catheterization; however, it may induce acute kidney injury or renal failure, although the underlying mechanism remains to be elucidated. MicroRNA‑21 (miR‑21) is involved in renal disease and has been indicated to regulate cellular apoptosis and fibrosis, although its role in CM‑induced renal cell injury is unknown. The present study examined the expression and potential targets of miR‑21 in human renal proximal tubular epithelial (HK‑2) cells following CM treatment. CM induced renal cell apoptosis and decreased miR‑21 expression. The expression level of the apoptosis regulator protein, B‑cell lymphoma 2 (Bcl‑2) was upregulated, whereas that of the apoptosis regulator, Bcl‑2‑associated X protein (Bax) was downregulated upon transfection of miR‑21 mimics; miR‑21 overexpression additionally directly inhibited the expression of programmed cell death protein 4 (PDCD4), as determined by a dual luciferase reporter assay, and PDCD4 silencing reduced the rate of HK‑2 cell apoptosis. The results of the present study indicated that miR‑21 protected renal cells against CM‑induced apoptosis by regulating PDCD4 expression.