The Effects of Quercetin on Paraquatinduced cell Damage

Kim, Hoon; Lee, Suk Woo

Abstract

PURPOSE: Paraquat (1,1-dimethy-4,4-bipyridinium dichloride, PQ) is a very effective and widely used herbicide which was introduced commercially in 1962. However, its toxic effects are often fatal to humans and animals through accidental or suicidal poisoning. Quercetin belongs to an extensive class of polyphenolic flavonoid compounds almost ubiquitous in plants and plant food sources. Quercetin is known as a strong free radical scavenger and an inhibitor of reactive oxygen species production. However, the effects of quercetin on paraquat-induced oxidative cell damage have not been investigated.
METHODS
This experiment was conducted in vitro using the HeLa Human cervival carcinoma cell line. The free radical scavenging activity of quercetin was assayed in cell free systems using a stable free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH). Cytotoxicity was studied using the MTT method. Optical density was measured at 540 nm using an ELISA reader. We examined morphological changes in cells after drug treatment using an inverted microscope, and quercetin-induced apoptosis was investigated using an apoptotic DNA fragmentation assay and a caspase-3 activity assay.
RESULTS
Results of anti-DPPH radical assay indicated that quercetin inhibited the production of DPPH radicals in vitro and that its radical scavenging activity was superior to the activities of both ascorbic acid and N-acetylcysteine. Incubation of HeLa cells with quercetin protected HeLa cells from paraquat-induced cytotoxicity according to the MTT assay. In the DNA fragmentation and caspase-3 activity assays, DNA ladders and caspase-3 concentrations characteristic of apoptosis appeared in quercetin-treated HeLa cells.
CONCLUSION
The results of this study suggest that quercetin at less than a concentration of 100uM exhibits an inhibitory effect on paraquat-induced cell death, but that at concentrations of over 100 uM, the protective effects against paraquat-induced cell damage were reduced due to its apoptotic effects.