Protective effect of quercetin against arsenite-induced COX-2 expression by targeting PI3K in rat liver epithelial cells

J Agric Food Chem. 2010 May 12;58(9):5815-20. doi: 10.1021/jf903698s.


Abnormal expression of cyclooxygenase-2 (COX-2) and prostaglandin (PG)E(2) is an important mediator in inflammation and tumor promotion. Arsenite is a well-known metalloid carcinogen that is strongly associated with increased risk of liver cancer, but the underlying mechanism remains to be clarified. The present study demonstrates that COX-2 expression and PGE(2) secretion are up-regulated by arsenite in rat liver epithelial (RLE) cells. The possible inhibitory effect of quercetin, a naturally occurring dietary flavonol, on arsenite-induced COX-2 expression and PGE(2) production was investigated. Pretreatment with quercetin resulted in the reduction of arsenite-induced expression of COX-2 and production of PGE(2). The arsenite-induced phosphorylation of Akt, p70S6K, and extracellular signal-regulated protein kinases (ERKs), but not p38, was inhibited by quercetin treatment. An ex vivo kinase assay revealed that quercetin suppressed arsenite-induced phosphoinositide 3-kinase (PI3K) activity upstream of Akt in RLE cell lysates. Ex vivo pull-down assays demonstrated that quercetin directly bound with PI3K to inhibit PI3K activity. Moreover, LY294002 (a PI3K inhibitor) significantly attenuated COX-2 expression and PGE(2) production in arsenite-treated RLE cells. These results suggest that quercetin suppresses arsenite-induced COX-2 expression mainly by blocking the activation of the PI3K signaling pathway, which may contribute to its chemopreventive potential.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arsenites / toxicity*
  • Cyclooxygenase 2 / metabolism*
  • Liver Neoplasms, Experimental / chemically induced
  • Liver Neoplasms, Experimental / enzymology
  • Liver Neoplasms, Experimental / prevention & control*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Quercetin / pharmacology*
  • Rats
  • Tumor Cells, Cultured


  • Arsenites
  • Quercetin
  • Cyclooxygenase 2
  • Phosphatidylinositol 3-Kinases
  • arsenite