As QUER and QU-CAP have been related to mechanisms against
oxidative stress, we then addressed the question whether these
substances have an effect on the main secondary anti-oxidant
mechanism of the cell, the proteasome. Young HFL-1 cells were
treated with 2 μg/ml QUER, 0.5, 2 and 5 μg/ml QU-CAP or the diluents
(0.1% DMSO or 0.1% CAP) for 24 h and the CT-L proteasome activity
was measured. As shown in Fig. 6A, the activity was significantly
induced following cell treatment with either of the substances. CT-L
activity was increased from ~1.5 (for QU-CAP) to ~2.4 folds (for
QUER). Moreover we have also detected enhanced protein expression
levels of representative proteasome subunits in the same cells and
experimental conditions (Fig. 6B), thus further verifying proteasome
activation by QUER and QU-CAP.