Celastrol is an effective proteasome inhibitor for the chymotrypsin-like activity of a purified 20S proteasome(IC50=2.5 μM) with antioxidant and anti-inflammatory activity.
Inhibition of purified 20S proteasome activity: A purified rabbit 20S proteasome (0.1 μg) is incubated with 40 μM of various fluorogenic peptide substrates in 100 μL assay buffer (20 mM Tris-HCl (pH 7.5)), in the presence of Celastrol at different concentrations or in the solvent DMSO for 2 hours at 37 ℃, followed by measurement of inhibition of each proteasomal activity.
The anti-proliferative effect of celastrol on various human tumor cell lines is determined by the MTT uptake method. Briefly, 5×103 cells are incubated with Celastrol in triplicate in a 96-well plate at 37 ℃. MTT solution is then added to each well. After a 2 hours incubation at 37 ℃, extraction buffer (20% SDS, 50% dimethylformamide) is added, cells are incubated overnight at 37 ℃, and the optical density is then measured at 570 nm using a Tecan plate reader.(Only for Reference)