Quercetin-3-O-(2"-galloyl)-α-l-rhamnopyranoside prevents TRAIL-induced apoptosis in human keratinocytes by suppressing the caspase-8- and Bid-pathways and the mitochondrial pathway.

Quercetin and its derivatives have antioxidant and anti-inflammatory effects. Nevertheless, in human keratinocytes, compared to the reports on other toxic insults, researches on the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis that may be involved in skin diseases are rare. Furthermore, the effect of quercetin-3-O-(2"-galloyl)-α-l-rhamnopyranoside (QGR), a new quercetin derivative, on TRAIL-induced apoptosis in keratinocytes has not been studied. In this respect, we investigated the effect of QGR on TRAIL-induced apoptosis in human keratinocytes. TRAIL triggers apoptosis by inducing a decrease in Bid, Bcl-2, Bcl-xL and survivin protein levels, increase in Bax and VDAC1 levels, loss of the mitochondrial transmembrane potential, release of cytochrome c, activation of caspases (-8, -9 and -3), cleavage of PARP-1, and an increase in the tumor suppressor p53 levels. Treatment with QGR prevented TRAIL-induced apoptosis-related protein activation, formation of reactive oxygen species, nuclear damage, and cell death. In contrast, quercetin induces cytotoxicity and had an additive effect on TRAIL-induced apoptosis-related protein activation and cell death. These results suggest that the QGR, unlike quercetin, may reduce TRAIL-induced apoptosis in human keratinocytes by suppressing the activation of the caspase-8- and Bid-pathways and the mitochondria-mediated cell death pathway, which is associated with the formation of reactive oxygen species. These data suggest that QGR could be effective in the prevention of TRAIL-induced apoptosis-mediated skin diseases.