Diallyl trisulfide-induced apoptosis of bladder cancer cells is caspase-dependent and regulated by PI3K/Akt and JNK pathways.

Diallyl trisulfide (DATS) is one of the major organosulfur components of garlic (Allium sativum L.), which inhibits the proliferation of various cancer cells, but the exact mechanisms of this action in human bladder cancer cells still remain largely unresolved. In this study, we investigated how DATS induces apoptosis in T24 human bladder cancer cells in vitro. Treatment of T24 cells with DATS resulted in potent anti-proliferative activity. Additionally, some typical apoptotic characteristics, such as chromatin condensation and an increase in the population of sub-G1 hypodiploid cells, were observed. With respect to the mechanism underlying the induction of apoptosis, DATS reduced the expression of anti-apoptotic Bcl-2 and Bcl-xL, and inhibitor of apoptosis protein family proteins, but the expression of pro-apoptotic Bax and death receptor-related proteins was increased compared with the controls. DATS also activated caspase-8 and -9, the respective initiator caspases of the extrinsic and the intrinsic apoptotic pathways. The increase in mitochondrial membrane depolarization was correlated with activation of effector caspase-3 and cleavage of poly-ADP-ribose polymerase, a vital substrate of activated caspase-3. Blockage of caspase activation through treatment with a pan-caspase inhibitor consistently inhibited apoptosis and abrogated growth inhibition in DATS-treated T24 cells. The study further investigated the roles of the phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinases (MAPKs) pathways with respect to the apoptotic effect of DATS, and showed that DATS deactivates Akt. Additionally, DATS activates extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK), but not p38 MAPK, in T24 cells. Unlike ERK, JNK inhibitors reversed DATS-induced apoptosis and growth inhibition; however, inhibition of PI3K/Akt notably enhanced the apoptotic action of DATS. The results suggest that the pro-apoptotic activity of DATS is probably regulated by a caspase-dependent cascade through the activation of both intrinsic and extrinsic signaling pathways, which is mediated through the blocking of PI3K/Akt and the activation of the JNK pathway.

Shin DY ，Kim GY ，Hwang HJ ，Kim WJ ，Choi YH ... -  《-》

Diallyl trisulfide induces apoptosis in human breast cancer cells through ROS-mediated activation of JNK and AP-1.

Multiple lines of evidence support an inverse association between consumption of garlic and the risk of cancer. Chemopreventive effects of garlic have been attributed to its oil-soluble sulfur ingredients, such as diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), but their underlying molecular mechanisms remain largely unresolved. In the present study, we found that DATS showed the most potent anti-proliferative effects in human breast cancer MCF-7 cells. MCF-7 cells treated with DATS underwent apoptotic death as revealed by a progressive increase in the proportion of the sub-G0/G1 cell population and a typical pattern of annexin V/propidium iodide staining. DATS induced phosphorylation of the antiapoptotic Bcl-2 and proteolytic cleavage of poly(ADP-ribose)polymerase (PARP) in MCF-7 cells. DATS treatment activated c-Jun N-terminal kinase (JNK). DATS-induced apoptosis was blunted in MCF-7 cells treated with a specific JNK inhibitor SP600125 or transiently transfected with dominant negative JNK. DATS treatment resulted in accumulation of reactive oxygen species (ROS). DATS-induced apoptosis as well as activation of JNK was abrogated by N-acetyl-l-cysteine (NAC). Furthermore, DATS induced phosphorylation and expression of c-Jun, which were attenuated by NAC. MCF-7 cells treated with DATS also exhibited increased DNA binding activity of AP-1, which was blocked by NAC and the JNK inhibitor. Proteolytic cleavage of PARP induced by DATS was abrogated in the cells transfected with c-jun siRNA. Oral administration of 5μmol/kg DATS to female Balb/c mice inhibited the growth of human MCF-7 cell tumor xenografts. These results suggest that DATS-induced apoptosis is mediated through ROS generation and subsequent activation of JNK and AP-1.

Na HK ，Kim EH ，Choi MA ，Park JM ，Kim DH ，Surh YJ ... -  《-》

Diallyl trisulfide-induced apoptosis in human prostate cancer cells involves c-Jun N-terminal kinase and extracellular-signal regulated kinase-mediated phosphorylation of Bcl-2.

Garlic-derived organosulfides (OSCs) including diallyl trisulfide (DATS) are highly effective in affording protection against chemically induced cancer in animals. Evidence is also mounting to indicate that some naturally occurring OSCs can suppress proliferation of cancer cells by causing apoptosis, but the sequence of events leading to proapoptotic effect of OSCs is poorly defined. Using PC-3 and DU145 human prostate cancer cells as a model, we now demonstrate that DATS is a significantly more potent apoptosis inducer than diallyl sulfide (DAS) or diallyl disulfide (DADS). DATS-induced apoptosis in PC-3 cells was associated with phosphorylation of Bcl-2, reduced Bcl-2 : Bax interaction, and cleavage of procaspase-9 and -3. Bcl-2 overexpressing PC-3 cells were significantly more resistant to apoptosis induction by DATS compared with vector-transfected control cells. DATS treatment resulted in activation of extracellular-signal regulated kinase 1/2 (ERK1/2) and c-jun N-terminal kinase 1 (JNK1) and/or JNK2, but not p38 mitogen-activated protein kinase. Phosphorylation of Bcl-2 in DATS-treated PC-3 cells was fully blocked in the presence of JNK-specific inhibitor SP600125. Moreover, JNK inhibitor afforded significant protection against DATS-induced apoptosis in both cells. DATS-induced Bcl-2 phosphorylation and apoptosis were partially attenuated by pharmacological inhibition of ERK1/2 using PD98059 or U0126. Overexpression of catalase inhibited DATS-mediated activation of JNK1/2, but not ERK1/2, and apoptosis induction in DU145 cells suggesting involvement of hydrogen peroxide as a second messenger in DATS-induced apoptosis. In conclusion, our data point towards important roles for Bcl-2, JNK and ERK in DATS-induced apoptosis in human prostate cancer cells.

Xiao D ，Choi S ，Johnson DE ，Vogel VG ，Johnson CS ，Trump DL ，Lee YJ ，Singh SV ... -  《ONCOGENE》

Antioxidant effects of diallyl trisulfide on high glucose-induced apoptosis are mediated by the PI3K/Akt-dependent activation of Nrf2 in cardiomyocytes.

Hyperglycemia-induced reactive oxygen species (ROS) generation contributes to development of diabetic cardiomyopathy. Nuclear factor E2-related factor 2 (Nrf2), a redox-sensing transcription factor, induces the antioxidant enzyme expressions. Diallyl trisulfide (DATS) is the most powerful antioxidant among the sulfur-containing compounds in garlic oil. We investigated whether DATS inhibits hyperglycemia-induced ROS production via Nrf2-mediated activation of antioxidant enzymes in cardiac cells exposed to high glucose (HG). Treatment of H9c2 cells with HG resulted in an increase in intracellular ROS level and caspase-3 activity, which were markedly reduced by the administration of DATS (10 μM). DATS treatment significantly increased Nrf2 protein stability and nuclear translocation, upregulated downstream gene HO-1, and suppressed its repressor Keap1. However, apoptosis was not inhibited by DATS in cells transfected with Nrf2-specific siRNA. Inhibition of PI3K/Akt signaling by LY294002 (PI3K inhibitor) or PI3K-specific siRNA not only decreased the level of DATS-induced Nrf2-mediated HO-1 expression, but also diminished the protective effects of DATS. Similar results were also observed in high glucose-exposed neonatal primary cardiomyocytes and streptozotocin-treated diabetic rats fed DATS at a dose of 40 mg/kg BW. Our findings indicate that DATS protects against hyperglycemia-induced ROS-mediated apoptosis by upregulating the PI3K/Akt/Nrf2 pathway, which further activates Nrf2-regulated antioxidant enzymes in cardiomyocytes exposed to HG.

Tsai CY ，Wang CC ，Lai TY ，Tsu HN ，Wang CH ，Liang HY ，Kuo WW ... -  《-》

Diallyl trisulfide inhibits angiogenic features of human umbilical vein endothelial cells by causing Akt inactivation and down-regulation of VEGF and VEGF-R2.

Xiao D ，Li M ，Herman-Antosiewicz A ，Antosiewicz J ，Xiao H ，Lew KL ，Zeng Y ，Marynowski SW ，Singh SV ... -  《NUTRITION AND CANCER-AN INTERNATIONAL JOURNAL》