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-G1 rate, 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-G1 accumulation. 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.

Isolation of Lignan and Fatty Acid Derivatives from the Grains of Echinochloa utilis and Their Inhibition of Lipopolysaccharide-Induced Nitric Oxide Production in RAW 264.7 Cells.

Two new fatty acid derivatives, echinochlorins A (8) and B (9) and a racemic lignan, (±)-anti-1-(4-hydroxy-3-methoxyphenyl)-2-{4-[(E)-3-acetoxypropen-1-yl]-2-methoxyphenoxy}propan-1,3-diol 3-acetate (1), were isolated from Echinochloa utilis grains, along with six known lignans (2-7) and two fatty acid derivatives (10, 11). Their structures were established by spectroscopic data analyses (IR, UV, HR-FABMS, GC-MS, and 1D and 2D NMR). The configuration of 1 was determined by Mosher's method. Compound 5 displayed potential inhibitory activity on lipopolysaccharide-induced NO production in macrophage RAW 264.7 cells with an IC50 value of 4.8 ± 0.5 µM. These isolated compounds in crude EtOH extract were also quantitated by HPLC.

Kaempferol Activates G2-Checkpoint of the Cell Cycle Resulting in G2-Arrest and Mitochondria-Dependent Apoptosis in Human Acute Leukemia Jurkat T Cells.

The effect of kaempferol (3,5,7,4-tetrahydroxyflavone), a flavonoid compound that was identified in barnyard millet (Echinochloa crus-galli var. frumentacea) grains, on G2-checkpoint and apoptotic pathways was investigated in human acute leukemia Jurkat T cell clones stably transfected with an empty vector (J/Neo) or a Bcl-xL expression vector (J/Bcl-xL). Exposure of J/Neo cells to kaempeferol caused cytotoxicity and activation of the ATM/ATR-Chk1/Chk2 pathway, activating the phosphorylation of p53 (Ser-15), inhibitory phosphorylation of Cdc25C (Ser-216), and inactivation of cyclin-dependent kinase 1 (Cdk1), with resultant G2- arrest of the cell cycle. Under these conditions, apoptotic events, including upregulation of Bak and PUMA levels, Bak activation, mitochondrial membrane potential (Δψm) loss, activation of caspase-9, -8, and -3, anti-poly (ADP-ribose) polymerase (PARP) cleavage, and accumulation of apoptotic sub-G1 cells, were induced without accompanying necrosis. However, these apoptotic events, except for upregulation of Bak and PUMA levels, were completely abrogated in J/Bcl-xL cells overexpressing Bcl-xL, suggesting that the G2-arrest and the Bcl-xL-sensitive mitochondrial apoptotic events were induced, in parallel, as downstream events of the DNA-damage-mediated G2-checkpoint activation. Together these results demonstrate that kaempferol-mediated antitumor activity toward Jurkat T cells was attributable to G2-checkpoint activation, which caused not only G2-arrest of the cell cycle but also activating phosphorylation of p53 (Ser-15) and subsequent induction of mitochondriadependent apoptotic events, including Bak and PUMA upregulation, Bak activation, Δpsim loss, and caspase cascade activation.