Protection against ultraviolet B-induced oxidative DNA damage in rabbit corneal-derived cells (SIRC) by 4-coumaric acid.

The exposure of cells to ultraviolet B radiation (UV-B) can induce the production of reactive oxygen species (ROS) which damage cellular components. Free radical scavengers and antioxidants can interfere with the production of ROS. We measured 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, a marker of oxidative DNA damage in rabbit corneal-derived cells (SIRC) exposed to UV-B in the presence of 4-coumaric acid, a natural polyphenol. The levels of 8-OHdG were increased significantly (P<0.01) following irradiation (from 12+/-1.2x10(-6) to 29+/-6.2x10(-6) dG, means+/-SE). When 10 microM 4-coumaric acid was added to the medium, 8-OHdG levels were similar to those of unexposed cells (16.8+/-0.8x10(-6) dG). UV-B irradiation decreased superoxide dismutase (SOD) activity in SIRC cells from 0.29+/-0.6 to 0.15+/-0.04 mU/mg (means+/-SE). The presence of 10 microM 4-coumaric acid prevented the decrease in SOD activity (0.20+/-0.05 mU/mg, P<0.05). On the contrary, SIRC cells exposed to UV-B had higher levels of xanthine oxidase (XO) activity compared with control ones (0.40+/-0.07 and 0.24+/-0.08 mU/mg, means+/-SE, respectively). In the presence of 10 microM 4-coumaric acid, the increase in XO activity was prevented (0.16+/-0.03 mU/mg; mean+/-SE). In conclusion, UV-B-induced oxidative DNA damage in SIRC cells is inhibited by 4-coumaric acid, which, probably through its free radical scavenging activity, stabilizes SOD activity and blocks the increase of XO activity following UV-B irradiation. Thus, the topical use of 4-coumaric acid may prevent free radical damage in the cornea.