Activation of caspase-3 protease during the process of ursolic acid and its derivative-induced apoptosis.
The apoptosis-inducing effect of the triterpene saponins, namely, ursolic acid and its natural derivative, methyl-ursolate beta-D-glucoside on A431 human epidermoid carcinoma cells was studied. The cells treated with 5-50 microg/ml of ursolic acid resulted in a dose- and time-dependent decrease in cell number, due to an increase of apoptotic cells as evidenced by MTT assay together with morphological changes. The highest dose (50 microg/ml) of ursolic acid resulted in approximately 90% inhibition in tumor cell growth after 96 hours of treatment and 60% of apoptosis after 48 hours. To the contrary, when the same treatment was carried out with methyl-ursolate beta-D-glucoside, after 96 hours of treatment the percentage of cell growth inhibition was found to be only 30% at the dose of 50 microg/ml and the value of apoptosis did not exceed 10%. Similarly to these results, ursolic acid effectively induced proteolytic activation of caspase-3 protease in a dose-dependent manner while its derivative showed only weak activity in this enzyme assay. The addition of DEVD-CHO prior to ursolic acid and methyl-ursolate beta-D-glucoside treatment effectively prevented the loss of triterpenes-induced viability. In summary, the triterpene saponins investigated contain an apoptotic-inducing activity in A431 cells and in the case of ursolic acid it is associated with proteolytic activation of caspase-3 and/or other similar caspases. Our results also indicated that methylation of COOH-28 together with the glycosylation of C3 of ursolic acid have a strong impact on its antitumor activity.
Hollósy
F
F
Hungarian Academy of Sciences, Peptidbiochemical Research Group in Semmelweis University Budapest. fhollosy@puskin.sote.hu
Idei
M
M
Csorba
G
G
Szabó
E
E
Bökönyi
G
G
Seprödi
A
A
Mészáros
G
G
Szende
B
B
Kéri
G
G
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D006027:Glycosides / Q000494:pharmacology; D006801:Humans; D014315:Triterpenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D000097245:Ursolic Acid
D053148:Caspase 3; D020169:Caspases; D006027:Glycosides; D014315:Triterpenes; D000097245:Ursolic Acid; C449059:methylursolate glycoside; C505407:CASP3 protein, human