Effect of the olive oil phenol hydroxytyrosol on human hepatoma HepG2 cells: Protection against oxidative stress induced by tert-butylhydroperoxide

Eur J Nutr (2007) 46:7078 DOI 10.1007/s00394-006-0633-8

ORIGINAL CONTRIBUTION

Luis Goya Raquel Mateos Laura Bravo

Effect of the olive oil phenol hydroxytyrosol on human hepatoma HepG2 cells

Protection against oxidative stress induced by tert-butylhydroperoxide

Received: 24 July 2006 Accepted: 21 November 2006 Published online: 2 January 2007

j Abstract Background Scientic evidence suggests that olive oils benecial effects are related to the high level of antioxidants, including phenolic compounds such as hydroxytyrosol. In vivo studies have shown that olive oil HTy is bioavailable and its biological activities, similar to those reported for other natural antioxidants such as quercetin, include prevention of LDL oxidation. Previous studies from our laboratory have shown that HTy and other phenolics in olive oil are absorbed and metabolized by cultured human hepatoma HepG2 cells where glucuronidated and methylated conjugates were the main derivatives formed, resembling the metabolic prole of olive oil phenols observed in human plasma and urine. Aim of the study The effect of olive oil phenol (HTy) on cell viability and redox status of cultured HepG2 cells, and the protective effect of HTy against an oxidative stress induced by tertbutylhydroperoxide (t-BOOH) were investigated. Methods Lac-tate dehydrogenase activity as marker for cell integrity, concentration of reduced glutathione (GSH), generation of reactive oxygen species (ROS) and activity of the antioxidant enzyme glu-

tathione peroxidase (GPx) as markers of redox status and determination of malondialdehyde (MDA) as marker of lipid peroxidation were measured. Results No changes in cell integrity or intrinsic antioxidant status resulted from a direct treatment with 1040 lM HTy. Pre-treatment of HepG2 with 1040 lM HTy for 2 or 20 h completely prevented cell damage as well as the decrease of reduced glutathione and increase of malondialdehyde evoked by t-BOOH in HepG2 cells. Reactive oxygen species generation and the signicant increase of glutathione peroxidase activity induced by t-BOOH were greatly reduced when cells were pretreated with HTy. Conclusion The results clearly show that treatment of HepG2 cells with the olive oil phenolic HTy may positively affect their antioxidant defense system, favoring cell integrity and resistance to cope with a stressful situation.

j Key words bioactive compounds dietary antioxidants olive oil phenolics liver cell culture antioxidant defenses biomarkers for oxidative stress

This work was supported by grants AGL2000-1314 and AGL2004-00302...