Punicalagin induces apoptotic and autophagic cell death in human U87MG glioma cells.
OBJECTIVE
To investigate the effects of punicalagin, a polyphenol isolated from Punica granatum, on human U87MG glioma cells in vitro.


METHODS
The viability of human U87MG glioma cells was evaluated using MTT assay. Cell cycle was detected with flow cytometry analysis. The levels of Bcl-2, cleaved caspase-9, cleaved poly(ADP-ribose) polymerase (PARP), phosphor-AMPK and phosphor-p27 at Thr198 were measured using immunoblot analyses. Caspase-3 activity was determined with spectrophotometer. To determine autophagy, LC3 cleavage and punctate patterns were examined.


RESULTS
Punicalagin (1-30 μg/mL) dose-dependently inhibited the cell viability in association with increased cyclin E level and decreased cyclin B and cyclin A levels. The treatment also induced apoptosis as shown by the cleavage of PARP, activation of caspase-9, and increase of caspase-3 activity in the cells. However, pretreatment of the cells with the pan-caspase inhibitor z-DEVD-fmk (50 μmol/L) did not completely prevent the cell death. On the other hand, punicalagin treatment increased LC3-II cleavage and caused GFP-LC3-II-stained punctate pattern in the cells. Suppressing autophagy of cells with chloroquine (1-10 μmol/L) dose-dependently alleviated the cell death caused by punicalagin. Punicalagin (1-30 μg/mL) also increased the levels phosphor-AMPK and phosphor-p27 at Thr198 in the cells, which were correlated with the induction of autophagic cell death.


CONCLUSIONS
Punicalagin induces human U87MG glioma cell death through both apoptotic and autophagic pathways.
1] Institute of Pharmaceutical Science and Technology, Central Taiwan University of Science and Technology, Taichung, Taiwan, China [2] Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan, China.
Shyang-guang
SG
Wang
Ming-hung
MH
Huang
Jui-hsiang
JH
Li
Fu-i
FI
Lai
Horng-mo
HM
Lee
Yuan-nian
YN
Hsu
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D005910:Glioma / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D047348:Hydrolyzable Tannins / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D029561:Lythraceae / Q000737:chemistry; D010766:Phosphorylation
D000972:Antineoplastic Agents, Phytogenic; D047348:Hydrolyzable Tannins; C115642:punicalagin; D055372:AMP-Activated Protein Kinases