Protective Effect of D-Limonene against Oxidative Stress-Induced Cell Damage in Human Lens Epithelial Cells via the p38 Pathway

Oxidative stress, as mediated by ROS, is a significant factor in initiating the development of age-associated cataracts; D-limonene is a common natural terpene with powerful antioxidative properties which occurs naturally in a wide variety of living organisms. It has been shown to have antioxidant effect; we found that D-limonene can effectively prevent the oxidative damage caused by H(2)O(2) and propose that the main mechanism underlying the inhibitory effects of D-limonene is the inhibition of HLECs apoptosis. In the present study, we used confocal-fluorescence microscopy, flow cytometry analysis, Hoechst staining, H(2)DCFDA staining, transmission electron microscopy, and immunoblot analysis; the results revealed that slightly higher concentrations of D-limonene (125–1800 μM) reduced the H(2)O(2)-induced ROS generation and inhibited the H(2)O(2)-induced caspase-3 and caspase-9 activation and decreased the Bcl-2/Bax ratio. Furthermore, it inhibited H(2)O(2)-induced p38 MAPK phosphorylation. Thus, we conclude that D-limonene could effectively protect HLECs from H(2)O(2)-induced oxidative stress and that its antioxidative effect is significant, thereby increasing the cell survival rate.