Figure 7.

Resveratrol Inhibited the Stimulatory Effect of an Acute TPA Treatment on Transglutaminase Activity, as well as TPA-induced PKD Activation and PKC Substrate Serine Phosphorylation, in Epidermal Keratinocytes. (A) Near-confluent keratinocytes were treated for 6 hours with or without 100 nM TPA in the presence and absence of 100 µM resveratrol. The cells were then harvested and transglutaminase activity measured as in [15]. Values are expressed relative to the control and represent the means ± SEM of 4 independent experiments performed in duplicate; *p<0.001 versus the control; †p<0.001 versus TPA alone. (B and C) Keratinocytes were pretreated for 2 hours with vehicle (DMSO, 0.1%) or 100 µM resveratrol prior to stimulation for 15 minutes with or without 100 nM TPA as indicated. [Note that a shorter preincubation of 30 minutes produced lesser inhibitory effects (data not shown), suggesting a time dependence to resveratrol’s inhibitory action.] Cells were harvested and subjected to western analysis as described in Methods. Panel (B) shows a representative blot. (C) Values represent the means ± SEM of 3 separate experiments and are expressed as the percent of the control with all values normalized to actin; *p<0.05, **p<0.001 versus the control value; †p<0.05 versus TPA alone.