Terpinen-4-ol induces autophagic and apoptotic cell death in human leukemic HL-60 cells.
BACKGROUND
Terpinen-4-ol, a monoterpene, is found as the main component of essential oil extracts from many plants. In this study apoptotic and autophagic types of cell death induced by terpinen-4-ol and associated mechanisms were investigated in human leukemic HL-60 cells.


METHODS
The cytotoxicity of human leukemic U937 and HL-60 cells was determined by MTT assay. Cytochrome c release, expression of Bax, Bcl-2, Bcl-xl and cleaved Bid were determined by Western blotting. Cell morphology was examined under a transmission electron microscope. LC3-I/II, ATG5 and Beclin-1 levels were detected by immunoblotting.


RESULTS
Terpinen-4-ol exhibited cytotoxicity to human leukemic HL-60 but not U937 cells. The apoptotic response to terpinen-4-ol in HL-60 cells was due to induction of cytochrome c release from mitochondria and cleavage of Bid protein after the stimulation of caspase-8. There was a slightly decrease of Bcl-xl protein level. The characteristic cell morphology of autophagic cell death was demonstrated with multiple autophagosomes in the cytoplasm. At the molecular level, the results from Western blot analysis showed that terpinen-4-ol significantly induced accumulation of LC3-I/II, ATG5 and Beclin-1, regulatory proteins required for autophagy in mammalian cells.


CONCLUSIONS
Terpinen-4-ol induced-human leukemic HL-60 cell death was via both autophagy and apoptosis.
Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand E-mail : ratana.b@cmu.ac.th.
Ratana
R
Banjerdpongchai
Patompong
P
Khaw-On
D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D015153:Blotting, Western; D053181:Caspase 8 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D007938:Leukemia / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
D051023:BH3 Interacting Domain Death Agonist Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013729:Terpenes; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C034019:terpinenol-4; D045304:Cytochromes c; D053181:Caspase 8