BACKGROUND

Radiocontrast nephropathy (RCN) is a major complication after radiographic examination. The precise mechanisms underlying RCN are not well understood. Renal tubular cell apoptosis is a feature of RCN, but hyperosmolality cannot fully explain the cytotoxicity of contrast media. There is accumulating evidence that reactive oxygen species (ROS) is involved in the pathophysiology of RCN, whereas the correlation between oxidative stress and contrast media-induced cell apoptosis is not clear. We hypothesized that ROS mediated apoptosis in renal tubular cells exposed to contrast media. Irbesartan, a selective AT(1) receptor antagonist has been demonstrated an antioxidative effect. The present study was designed to determine whether irbesartan attenuated the contrast media-induced renal tubular cell apoptosis.

METHODS

NRK-52E cells were exposed to increasing concentration (25, 50, 100, 150 mgiodinemL(-1), 335, 384, 420, 521 mOsmkg(-1)) of ioversol (a non-ionic contrast media) for 1h or incubated in ioversol (100 mgiodinemL(-1), 420 mOsmkg(-1)) for 15 min, 30 min, 60 min, 120 min, 240 min, respectively. Mannitol with the same osmolality as ioversol (420 mOsmkg(-1)) also treated NRK-52E cells for 1h. In separate experiment, irbesartan (0.01, 0.1, 1 mmolL(-1)) was added 1h before incubation with ioversol (100 mgiodinemL(-1), 420 mOsmkg(-1)) for 1h. Apoptosis was determined by Hoechst staining and flow cytometry with annexinV-FITC and propidium iodide. The intracellular formation of ROS was detected by confocal microscopy with fluorescent probe CM-H2DCFDA. Bax and bcl-2 mRNA expression were determined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Ioversol induced NRK-52E cells apoptosis in a concentration- and time-dependent manner. The intracellular ROS generation was greatly increased following ioversol stimulus. Furthermore, ioversol induced a decrease in the expression for bcl-2 mRNA and an increase for bax mRNA. Irbesartan attenuated the ioversol-induced apoptosis in NRK-52E cells in a dose-dependent manner, in which the protective effect of irbesartan was dependent on decreasing intracellular ROS formation. In addition, irbesartan reversed the ioversol-induced increase in bax mRNA and decrease in bcl-2 mRNA.

CONCLUSION

Ioversol induced NRK-52E cells apoptosis in a concentration- and time-dependant manner via an increase in oxidative stress and subsequent to the increase in mRNA expression for bax and reduction in bcl-2 mRNA. Irbesartan attenuated the ioversol-induced apoptosis in NRK-52E cells by reducing oxidative stress and reversing the enhancement of bax mRNA and the reduction in bcl-2 mRNA.