Eupalinin A isolated from Eupatorium chinense L. induces autophagocytosis in human leukemia HL60 cells.
Eupalinin A, a natural phytoalexin included in Eupatorium chinense L., exhibited a marked inhibitory effect on cell growth in HL60 cells. The morphological aspects of eupalinin A-treated cells evaluated by Hoechst 33342 nuclear staining indicated cell death, only a small part of which showed a typical apoptosis with nuclear fragmentation and condensation. To determine what type of cell death is caused by eupalinin A, we examined the contribution of caspases, Bcl-2 family proteins, MAP kinase, and PI3K/Akt, and mitochondrial membrane potential to this cell death. As a result, most part of the cell death was not associated with apoptosis because of caspase independence and no death factor released from mitochondria. Electron microscopic study indicated a characteristic finding of autophagy such as the formation of autophagosomes. Furthermore, the level of microctubule-associated-protein light chain 3 (LC3) II protein and monodancylcanaverin (MDC) incorporation were gradually increased with reduction of mitochondrial membrane potential by the accumulation of intracellular ROS after eupalinin A treatment. From these results, we can conclude that eupalinin A-induced cell death was mainly due to autophagy, which was initiated by increased ROS, resulting in the perturbation of mitochondrial membrane potential. Since the class III PI3K inhibitor such as 3-MA or LY294002 did not inhibit the eupalinin A-induced type II programmed cell death (PCD II), it was suggested that the PCD II was executed by Beclin-1 independent pathway of damage-induced mitochondrial autophagy (mitophagy).
Itoh
Tomohiro
T
Gifu International Institute of Biotechnology, 1-1 Naka-Fudogaoka, Kakamigahara, Gifu 504-0838, Japan. titoh@giib.or.jp
Ito
Yuko
Y
Ohguchi
Kenji
K
Ohyama
Masayoshi
M
Iinuma
Munekazu
M
Otsuki
Yoshinori
Y
Nozawa
Yoshinori
Y
Akao
Yukihiro
Y
D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D036602:Eupatorium / Q000737:chemistry*; D018922:HL-60 Cells; D006801:Humans; D007783:Lactones / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry*; D012717:Sesquiterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D013729:Terpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D000094162:Phytoalexins
D007783:Lactones; D012717:Sesquiterpenes; D013729:Terpenes; C526410:eupalinin A; D000094162:Phytoalexins