Pharmacologic Inhibition of Autophagy Sensitizes Human Acute Leukemia Jurkat T Cells to Acacetin-Induced Apoptosis.
Exposure of Jurkat T cell clone (J/Neo cells) to acacetin (5,7-dihydroxy-4'-methoxyflavone), which is present in barnyard millet (Echinochloa esculenta(A. Braun)) grains, caused cytotoxicity, enhancement of apoptotic sub-G1rate, Bak activation, loss of mitochondrial membrane potential (Δψ), activation of caspase-9 and caspase-3, degradation of poly(ADP-ribose) polymerase, and FITC-Annexin V-stainable phosphatidylserine exposure on the external surface of the cytoplasmic membrane without accompanying necrosis. These apoptotic responses were abrogated in Jurkat T cell clone (J/Bcl-xL) overexpressing Bcl-xL. Under the same conditions, cellular autophagic responses, including suppression of the Akt-mTOR pathway and p62/SQSTM1 down-regulation, were commonly detected in J/Neo and J/Bcl-xL cells; however, formation of acridine orange-stainable acidic vascular organelles, LC3-I/II conversion, and Beclin-1 phosphorylation (Ser-15) were detected only in J/Neo cells. Correspondingly, concomitant treatment with the autophagy inhibitor (3-methyladenine or LY294002) appeared to enhance acacetin-induced apoptotic responses, such as Bak activation, Δψ loss, activation of caspase-9 and caspase-3, and apoptotic sub-G1accumulation. This indicated that acacetin could induce apoptosis and cytoprotective autophagy in Jurkat T cells simultaneously. Together, these results demonstrate that acacetin induces not only apoptotic cell death via activation of Bak, loss of Δψ, and activation of the mitochondrial caspase cascade, but also cytoprotective autophagy resulting from suppression of the Akt-mTOR pathway. Furthermore, pharmacologic inhibition of the autophagy pathway augments the activation of Bak and resultant mitochondrial damage-mediated apoptosis in Jurkat T cells.
Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
Ji Young
JY
Lee
Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
Do Youn
DY
Jun
Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
Ki Yun
KY
Kim
Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
Eun Ji
EJ
Ha
College of Pharmacy, Catholic University of Daegu, Gyeongsan 38430, Republic of Korea.
Mi Hee
MH
Woo
Upland Crop Breeding Research Division, Department of Southern Area Crop Science, RDA, Miryang 50424, Republic of Korea.
Jee Youn
JY
Ko
Upland Crop Breeding Research Division, Department of Southern Area Crop Science, RDA, Miryang 50424, Republic of Korea.
Young Ho
YH
Yun
Upland Crop Breeding Research Division, Department of Southern Area Crop Science, RDA, Miryang 50424, Republic of Korea.
In-Seok
IS
Oh
Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
Young Ho
YH
Kim
Acacetin; Bak activation; Echinochloa esculenta (A. Braun); Jurkat T cells; cytoprotective autophagy; mitochondria-dependent apoptosis