Yong Hwan Han

Gallic acid inhibits the growth of HeLa cervical cancer cells via apoptosis and/or necrosis

Gallic acid (GA) is widely distributed in various plants and foods, and its various biological effects have been reported. Here, we evaluated the effects of GA on HeLa cells in relation to cell growth inhibition and death. HeLa cell growth was diminished with an IC(50) of approximately 80 microM GA at 24h whereas an IC(50) of GA in human umbilical vein endothelial cells (HUVEC) was approximately 400 microM. GA-induced apoptosis and/or necrosis in HeLa cells and HUVEC, which was accompanied by the loss of mitochondrial membrane potential (MMP; DeltaPsi(m)). The percentages of MMP (DeltaPsi(m)) loss cells and death cells were lower in HUVEC than HeLa cells. All the tested caspase inhibitors (pan-caspase, caspase-3, -8 or -9 inhibitor) significantly rescued HeLa cells from GA-induced cell death. GA increased reactive oxygen species (ROS) level and GSH (glutathione) depleted cell number in HeLa cells. Caspase inhibitors reduced GSH depleted cell number but not ROS level in GA-treated HeLa cells. In conclusion, GA inhibited the growth of HeLa cells and HUVEC via apoptosis and/or necrosis. The susceptibility of HeLa cells to GA was higher than that of HUVEC. GA-induced HeLa cell death was accompanied by ROS increase and GSH depletion.

Arsenic trioxide inhibits the growth of Calu-6 cells via inducing a G2 arrest of the cell cycle and apoptosis accompanied with the depletion of GSH

Arsenic trioxide (ATO) can regulate many biological functions such as apoptosis and differentiation in various cells. We evaluated the effects of ATO on the viability, cell cycle and apoptosis of human pulmonary adenocarcinoma, Calu-6 and A549 cells. ATO reduced the viability of Calu-6 cells with an IC50 of approximately 3 or 4 microM. However, A549 cells were very resistant to ATO. Calu-6 cells treated with 1, 3 or 5 microM ATO showed a G2 phase arrest of the cell cycle at 72 h. The G2 phase arrest was accompanied with the down-regulation of cdc2 protein. Treatment with ATO-induced apoptosis in Calu-6 cells. The apoptotic process was accompanied by the down-regulation of Bcl-2 protein, the activation of caspase-3, and the loss of the mitochondrial membrane potential (Delta Psi m). All of the caspase inhibitors, especially pan-caspase inhibitor (Z-VAD), markedly rescued Calu-6 cells from ATO-induced cell death. Caspase inhibitors also prevented the loss of mitochondrial membrane potential (Delta Psi m). The inhibitors significantly increased the number of G2 phase cells in 10 microM ATO-treated cells. In addition, the levels of O2- were significantly increased in 10 microM ATO-treated cells. However, the changes of ROS by 10 microM ATO are not correlated with apoptosis in Calu-6 cells. Treatment with 10 microM ATO depleted GSH content in Calu-6 cells and caspase inhibitors significantly prevented the GSH depletion in these cells. In conclusion, we have demonstrated that ATO inhibits the growth of Calu-6 cells by inducing a G2 arrest of the cell cycle and by triggering apoptosis accompanied with the depletion of GSH.

2,4-dinitrophenol induces G1 phase arrest and apoptosis in human pulmonary adenocarcinoma Calu-6 cells.

2,4-dinitrophenol (DNP) is an uncoupler of oxidative phosphorylation in the mitochondria. Here, we investigated the effect of DNP on the growth of Calu-6 lung cancer cells in view of cell cycle, apoptosis, ROS production and GSH content. DNP dose-dependently decreased cell viability at 72 h (EC50 of about 200 microM) as measured by a MTT assay. The lower doses of DNP induced a G1 arrest of the cell cycle in Calu-6 cells. Analysis of the cell cycle regulatory proteins demonstrated that DNP decreased the steady-state levels of cyclin proteins and cyclin dependent kinase (CDK), but increased the protein levels of cyclin dependent kinase inhibitor (CDKI) p27. DNP also caused a marked increase in apoptosis, as evidenced by DNA fragmentation (sub-G1 DNA content), DAPI staining, the loss of mitochondrial membrane potential (DeltaPsim), externalization of phosphatidylserine (PS). In addition, DNP-treated cells significantly increased the intracellular H2O2 and O2.- levels. All of caspase inhibitors could markedly rescue Calu-6 cells from DNP-induced cell death and only pan-caspase inhibitor, Z-VAD-FMK, could slightly prevent the loss of mitochondrial membrane potential (DeltaPsim). However, none of the caspase inhibitors reduced the increased H2O2 levels, but the increased O2.- levels was slightly attenuated by pan-caspase inhibitor. In addition, the depletion of GSH content in DNP-treated cells was prevented by all of caspase inhibitors. In conclusion, DNP, which induced ROS and reduced GSH content, inhibited the growth of Calu-6 cells via cell cycle arrest at G1 phase and apoptosis.

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) as an O2(*-) generator induces apoptosis via the depletion of intracellular GSH contents in Calu-6 cells.

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) is an uncoupler of mitochondrial oxidative phosphorylation in eukaryotic cells. Here, we investigated an involvement of O(2)(*-) and GSH in FCCP-induced Calu-6 cell death and examined whether ROS scavengers rescue cells from FCCP-induced cell death. Levels of intracellular O(2)(*-) were markedly increased depending on the concentrations (5-100 microM) of FCCP. A depletion of intracellular GSH content was also observed after exposing cells to FCCP. Stable SOD mimetics, Tempol and Tiron did not change the levels of intracellular O(2)(*-), apoptosis and the loss of mitochondrial membrane potential (DeltaPsi(m)). Treatment with thiol antioxidants, NAC and DTT, showed the recovery of GSH depletion and the reduction of O(2)(*-) levels in FCCP-treated cells, which were accompanied by the inhibition of apoptosis. In contrast, BSO, a well-known inhibitor of GSH synthesis, aggravated GSH depletion, oxidative stress of O(2)(*-) and cell death in FCCP-treated cells. Taken together, our data suggested that FCCP as an O(2)(*-) generator, induces apoptosis via the depletion of intracellular GSH contents in Calu-6 cells.

Growth inhibition in antimycin A treated-lung cancer Calu-6 cells via inducing a G1 phase arrest and apoptosis

Antimycin A (AMA) inhibits mitochondrial electron transport between cytochrome b and c. We evaluated the effects of AMA on the growth of human lung cancer cell line, Calu-6. AMA inhibited the growth of Calu-6 cells. AMA induced a G1 phase arrest of the cell cycle in these cells at 72h. AMA increased a cyclin-dependent kinase inhibitor (CDKI), p27 and decreased CDK2, CDK4, and CDK6, as well as cyclin D1 and cyclin E in Calu-6 cells. AMA also induced apoptosis in Calu-6 cells. The apoptotic process in AMA-treated Calu-6 cells was accompanied by the up-regulation of Bax, the loss of mitochondrial membrane potential (DeltaPsi(m)), and the activation of caspase-3 and -8. All of the tested caspase inhibitors, especially pan-caspase inhibitor (Z-VAD), markedly rescued Calu-6 cells from AMA-induced Calu-6 cell death. Inhibitors of pan-caspase and caspase-8 also prevented the loss of mitochondrial membrane potential (DeltaPsi(m)). AMA decreased the intracellular ROS levels but increased the O(2)(*-) levels in Calu-6 cells. In conclusion, AMA as a mitochondrial electron transport inhibitor decreased the growth of lung cancer Calu-6 cell via inducing a G1 arrest of the cell cycle and apoptosis.

Apoptosis in arsenic trioxide‐treated Calu‐6 lung cells is correlated with the depletion of GSH levels rather than the changes of ROS levels

Arsenic trioxide (ATO) can regulate many biological functions such as apoptosis and differentiation in various cells. We investigated an involvement of ROS such as H2O2 and O  2.− , and GSH in ATO‐treated Calu‐6 cell death. The levels of intracellular H2O2 were decreased in ATO‐treated Calu‐6 cells at 72 h. However, the levels of O  2.− were significantly increased. ATO reduced the intracellular GSH content. Many of the cells having depleted GSH contents were dead, as evidenced by the propidium iodine staining. The activity of CuZn‐SOD was strongly down‐regulated by ATO at 72 h while the activity of Mn‐SOD was weakly up‐regulated. The activity of catalase was decreased by ATO. ROS scavengers, Tiron and Trimetazidine did not reduce levels of apoptosis and intracellular O  2.− in ATO‐treated Calu‐6 cells. Tempol showing a decrease in intracellular O  2.− levels reduced the loss of mitochondrial transmembrane potential (ΔΨm). Treatment with NAC showing the recovery of GSH depletion and the decreased effect on O  2.− levels in ATO‐treated cells significantly inhibited apoptosis. In addition, BSO significantly increased the depletion of GSH content and apoptosis in ATO‐treated cells. Treatment with SOD and catalase significantly reduced the levels of O  2.− levels in ATO‐treated cells, but did not inhibit apoptosis along with non‐effect on the recovery of GSH depletion. Taken together, our results suggest that ATO induces apoptosis in Calu‐6 cells via the depletion of the intracellular GSH contents rather than the changes of ROS levels. J. Cell. Biochem. 104: 862–878, 2008.

Antimycin A as a mitochondria damage agent induces an S phase arrest of the cell cycle in HeLa cells

Antimycin A (AMA), an electron transport chain inhibitor in mitochondria can produce reactive oxygen species (ROS) in cells. It has been reported that ROS may have roles in cell cycle progression via regulating cell cycle-related proteins. In the present study, we investigated the changes of the cell cycle distribution in AMA-treated HeLa cells in relation to cell cycle-related proteins. DNA flow cytometric analysis indicated that treatment with AMA significantly induced an S phase arrest of the cell cycle at 72 h. AMA decreased the expression of cyclin-dependent kinase inhibitor (CDKI), p21 and p27, CDK4, and cdc2 proteins. The expression of CDK6, cyclin D1, cyclin E, cyclin A, and cyclin B proteins was increased by 0.5 microM AMA, but was decreased by 2 and 10 microM AMA. The phosphorylation of Rb on the Ser (780) residue was increased by 0.5 microM AMA. Furthermore, treatment with AMA caused the accumulation of cells expressing cyclin A, B, and D1 proteins at the S phase of the cell cycle. However, treatment with 100 microM AMA nonspecifically extended all phases of the cell cycle. In conclusion, treatment with AMA (2, 10 and 50 microM) induced an S phase arrest of the cell cycle. An S phase arrest was accompanied by the alteration of other cell cycle-regulated proteins as well as S phase-related proteins.

Pyrogallol inhibits the growth of lung cancer Calu-6 cells via caspase-dependent apoptosis

Pyrogallol (PG) is a polyphenol compound and a known O2- generator. We evaluated the effects of PG on the growth and apoptosis of human pulmonary adenocarcinoma Calu-6 cells. PG decreased the viability of Calu-6 cells in a dose- and time-dependent manner. The induction of apoptosis by PG was accompanied by the loss of mitochondrial membrane potential (DeltaPsi(m)), cytochrome c release from mitochondria and activation of caspase-3 and caspase-8. All tested caspase inhibitors, especially the pan-caspase inhibitor (Z-VAD), markedly rescued Calu-6 cells from PG-induced cell death. Rescue was accompanied by inhibition of caspase-3 activation and PARP cleavage. Treatment with Z-VAD also prevented the loss of mitochondrial membrane potential (DeltaPsi(m)). In conclusion, PG inhibits the growth of Calu-6 cells via caspase-dependent apoptosis.

Effects of carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone on the growth inhibition in human pulmonary adenocarcinoma Calu-6 cells.

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) is an uncoupler of mitochondrial oxidative phosphorylation in eukaryotic cells. Here, we evaluated the in vitro effects of FCCP on the growth of Calu-6 lung cancer cells. FCCP inhibited the growth of Calu-6 cells with an IC(50) of approximately 6.64+/-1.84 microM at 72 h, as shown by MTT. DNA flow cytometric analysis indicated that FCCP induced G1 phase arrest below 20 microM of FCCP. Treatment with FCCP decreased the level of CDKs and cyclines in relation to G1 phase. In addition, FCCP not only increased the p27 level but also enhanced its binding with CDK4, which was associated with hypophosphorylation of Rb protein. While transfection of p27 siRNA inhibited G1 phase arrest in FCCP-treated cells, it did not enhance Rb phosphorylation. FCCP also efficiently induced apoptosis. The apoptotic process was accompanied with an increase in sub-G1 cells, annexin V staining cells, mitochondria membrane potential (MMP) loss and cleavage of PARP protein. All of the caspase inhibitors (caspase-3, -8, -9 and pan-caspase inhibitor) markedly rescued the Calu-6 cells from FCCP-induced cell death. However, knock down of p27 protein intensified FCCP-induced cell death. Moreover, FCCP induced the depletion of GSH content in Calu-6 cells, which was prevented by all of the caspase inhibitors. In summary, our results demonstrated that FCCP inhibits the growth of Calu-6 cells in vitro. The growth inhibitory effect of FCCP might be mediated by cell cycle arrest and apoptosis via decrease of CDKs and caspase activation, respectively. These findings now provide a better elucidation of the mechanisms involved in FCCP-induced growth inhibition in lung cancer.

Intracellular GSH level is a factor in As4.1 juxtaglomerular cell death by arsenic trioxide.

Arsenic trioxide has been known to regulate many biological functions such as cell proliferation, apoptosis, differentiation, and angiogenesis in various cell lines. We investigated the involvement of GSH and ROS such as H2O2 and O  2.− in the death of As4.1 cells by arsenic trioxide. The intracellular ROS levels were changed depending on the concentration and length of incubation with arsenic trioxide. The intracellular O  2.− level was significantly increased at all the concentrations tested. Arsenic trioxide reduced the intracellular GSH content. Treatment of Tiron, ROS scavenger decreased the levels of ROS in 10 µM arsenic trioxide‐treated cells. Another ROS scavenger, Tempol did not decrease ROS levels in arsenic trioxide‐treated cells, but slightly recovered the depleted GSH content and reduced the level of apoptosis in these cells. Exogenous SOD and catalase did not reduce the level of ROS, but did decrease the level of O  2.− . Both of them inhibited GSH depletion and apoptosis in arsenic trioxide‐treated cells. In addition, ROS scavengers, SOD and catalase did not alter the accumulation of cells in the S phase induced by arsenic trioxide. Furthermore, JNK inhibitor rescued some cells from arsenic trioxide‐induced apoptosis, and this inhibitor decreased the levels of O  2.− and reduced the GSH depletion in these cells. In summary, we have demonstrated that arsenic trioxide potently generates ROS, especially O  2.− , in As4.1 juxtaglomerular cells, and Tempol, SOD, catalase, and JNK inhibitor partially rescued cells from arsenic trioxide‐induced apoptosis through the up‐regulation of intracellular GSH levels. J. Cell. Biochem. 104: 995–1009, 2008.