Abstract: Objective Previous study showed that plasma urotensin II (UⅡ) increased in contrast induced nephropathy. However, its pathogenesis is unclear. The aim of this study is to observe the roles of UⅡ in the injury of human renal tubular epithelial cell induced by contrast medium. Methods Human renal tubular
epithelial cell (HK-2) was exposed in different concentration of UⅡ, contrast medium (Iopromide), and U Ⅱ combined with iopromide for 2～24 hours. Apoptosis rate by annexin V method, malondialdehyde (MDA) level in the supernatant, and autophgy markers including light chain 3-Ⅱ (LC3Ⅱ) and Beclin-1 by western
blot were measured. Results ① Both UⅡ 10- 5 mol/L～10- 8 mol/L and iopromide 50 gI/L could increase MDA level in supernatant. MDA in supernatant was 152.65±18.72 nmol/ml, 149.19±1.17 nmol/ml, 151.12± 3.05 nmol/ml and 116.81±6.85 nmol/ml, respectively from the cell treated with UⅡ10- 5 mol/L～10- 8 mol/L, and was 99.44±12.00 nmol/ml from the cells treated with iopromide 50 gI/L, significantly higher than that from normal control cells (20.32±3.00 nmol/ml, F=41.863, P=0.000). MDA in supernatant was lower from the cells treated with UⅡ10-6 mol/l + iopromide 200gI/l (5.95±1.63 nmol/ml) than from those treated with iopromide 200gI/l (41.70±8.46 nmol/ml; P=0.033, 95% CI -66.688～-4.798 by post hoc test Dunnett T3)； ② Both UⅡ and iopromide could induce apoptosis in Hk-2 cells. The rate of late apoptosis was 9.33±0.23%, 8.63±2.10%, 9.93±2.35%, 10.10±1.97%, respectively in cells treated with UⅡ10- 5～10- 8 mol/L, was 8.20±1.21% in cells treated with iopromide 50gI/L, and was 15.03±0.55% in cells treated with iopromide 200gI/L, significantly higher than that in normal control cells (3.65±1.17%; F=28.322, P=0.000 by ANOVA). The rateof late apoptosis was higher in cells treated with UⅡ10- 6 mol/L + iopromide 50gI/L (15.16±2.27%) than in those treated with iopromide 50gI/L (8.20±1.21%, P=0.031, 95% CI 0.681～12.404). However, the rate of late apoptosis was lower in cells treated with UⅡ10-6 mol/L+iopromide 200 gI/L (10.27±0.61%) than in those treated with iopromide 200 gI/L (15.03±0.55%; P=0.000, 95% CI -6.481～-3.041 by post hoc test Dunnett T3). ③ LC3Ⅱ expression was lower in Hk-2 cell treated with UⅡ10-8 mol/L (LC3Ⅱ/actin = 0.029±0.009) than in untreated Hk-2 cells (LC3Ⅱ/actin=0.05±0.01; t=-2.892, P=0.031), but was higher in Hk-2 cells treated with iopromide 50 gI/L (LC3II/actin = 0.40±0.02) than in untreated Hk-2 cells (0.09±0.02, t=4.989, P=0.000). Conclusions Contrast medium can induce oxidative stress, apoptosis and autophagy renal tubular epithelial cell. UII can also induce oxidative stress and apoptosis but inhibit autophagy in renal tubular epithelial cell. U Ⅱ prevents HK-2 cell from apoptosis induced by high dose of contrast medium. The dual roles of UⅡ in the contrast induced nephropathy need to be further studied.

Key words: Contrast induced nephropathy, Urotensin Ⅱ, Oxidative stress, Apoptosis, Autophagy