Paper Title
Anti-Oxidativeand Anti-Inflammatory Effects Of Hydroquinone

Abstract
Hydroquinone (HQ) and its derivatives are present in many dermatological cream (2-10%), paints, motor fuels, air, microorganisms and plant products like wheat bread, fruit, coffee, red wine. The effect of HQ on humans is not fully clear. In this study, we evaluated the anti-oxidant and anti-inflammatory effect of HQ using cell culture model. Dental pulp cells were exposed to IL-1 with/without pretreatment and co-incubation by various concentrations of HQ. 8-isoprostane, PGE2 and IL-8 production of dental pulp cells were studied by enzyme linked immunosorbant (ELISA) assay. Cyclooxygenase-2 (COX-2) and IL-8 protein expression of dental pulp cells were evaluated by western blotting. We found that IL-1(0.5-10 ng/ml) stimulated 8-isoprostane, PGE2 and IL-8 production of dental pulp cells. HQ at non-toxic concentrations of 50 and 100 M was effective to prevent the IL-1-induced 8-isoprostane (an oxidative stress marker), and PGE2(inflammatory mediator) production, but not IL-8 production of pulp cells. On the other hand, HQ was not able to attenuate the IL-1-induced COX-2 and IL-8 protein expression of pulp cells as analyzed by western blotting. These results indicate that IL-1 is involved in the inflammatory and repair response of dental pulp via stimulation of 8-isoprostane, PGE2 and IL-8. HQ has anti-oxidative and anti-inflammatory effects via inhibition of 8-isoprostane and PGE2 production, and possible inhibition of COX. Exposure and consumption of HQ-containing products, such as food or drugs may have potential anti-oxidative and anti-inflammatory effects. These results can be useful for understanding of HQ on health and its clinical application. More studies are necessary to evaluate the beneficial and harmful effects of HQ on human health. (This study is supported by grants from Ministry of Science and Technology, Taiwan, ROC; and National Taiwan University Hospital, NTUH, Taipei, Taiwan).