Methylene chloride fraction of Scutellaria barbata induces apoptosis in human U937 leukemia cells via the mitochondrial signaling pathway.
BACKGROUND
Scutellaria barbata D.Don has been applied to treat cancers, inflammation and urinary disease. However, its antitumor mechanism still remains unclear.


METHODS
With methylene chloride fraction of Herba Scutellariae barbatae (MCSB), apoptosis-related experiments were carried out on human U937 leukemia cells by (a) 2,3-bis[2-4-nitro-5-sulphophenyl]2H-tetrazolium-5-carboxanilide (XTT) assay for cytotoxicity; (b) terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) assay for morphological changes; (c) cell cycle analysis; (d) Western blot analysis of poly(ADP-ribose) polymerase (PARP), caspase-8, caspase-9, caspase-3 and Bax, Bcl-2 and cytochrome c expressions for apoptosis signaling pathway.


RESULTS
MCSB inhibited the proliferation of human U937 leukemia cells in a dose-dependent manner (IC50 = approximately 10 microg/ml). MCSB dose-dependently increased the sub-G1 DNA contents by cell cycle analysis. DNA fragments indicating induction of apoptosis were observed in MCSB-treated U937 cells by TUNEL assay. Caspase-9 and caspase-3 were activated while caspase-8 was intact by MCSB. Similarly, MCSB effectively cleaved PARP, increased the ratio of Bax/Bcl-2 and released the cytochrome c from mitochondria during apoptosis in U937 cells.


CONCLUSIONS
Our results suggest that MCSB can induce apoptosis via the mitochondria-mediated signaling pathway.
Cha
Yun-Yi
YY
Graduate School of East-West Medical Science, KyungHee University, Yoingin 449-701, South Korea.
Lee
Eun-Ok
EO
Lee
Hyo-Jeong
HJ
Park
Young-Doo
YD
Ko
Seong-Gyu
SG
Kim
Dong-Hee
DH
Kim
Hyung-Min
HM
Kang
In-Cheol
IC
Kim
Sung-Hoon
SH
D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D006801:Humans; D020287:In Situ Nick-End Labeling; D008752:Methylene Chloride; D008928:Mitochondria / Q000502:physiology*; D010936:Plant Extracts / Q000494:pharmacology; D031363:Scutellaria; D015398:Signal Transduction; D012997:Solvents; D020298:U937 Cells
D010936:Plant Extracts; D012997:Solvents; D008752:Methylene Chloride