The biological actions of alpha hederin on cancer cells
Many saponins are known to induce apoptosis in cancer cells like alpha hederin [1, 2]. Some of these molecules interact also with biological membranes [3,4]. We want to establish a link between these different actions. For this purpose, we tested alpha hederin on U937 cells and liposomes.
Apoptosis has been evaluated by DAPI and acridine orange staining. Cytotoxicity was tested by LDH, trypan blue exclusion and ethidium bromide staining. Calcein release of liposomes was followed by the measure of fluorescence.
Apoptosis reached 35% for 20µM of alpha hederin. The cytotoxicity increased at higher concentrations while apoptosis decreased. The incidence of apoptosis induced by 20µM alpha hederin was reduced to 9% when depleting the cells of cholesterol with methyl-beta cyclodextrin.
30µM of alpha hederin induced a 100% release of calcein from liposomes (LUV) which contained cholesterol. We observed no release of calcein from liposomes where cholesterol was absent.
Induction of apoptosis by alpha hederin could be correlated to membrane cholesterol levels. Depletion of membrane cholesterol has reduced the capacity of alpha hederin to induce apoptosis so it seems that cholesterol is necessary for apoptotic cell death induced by alpha hederin.
References: 1. Muthu, S. et al. (2003) Mol Cell Biol 245:127–139. 2. Park, HJ. et al. (2001) Planta Med. 67:118–121 3. Armah, CN. et al. (1999) Biophys. J. 76:281–290 4. Nandi, B. et al. (2004) Phytother Res. 18:191–194