Indole phytoalexin derivatives induce mitochondrialmediated apoptosis in human colorectal carcinoma cells

To investigate the mechanism of the antiproliferative effect of synthetic indole phytoalexin derivatives on human colorectal cancer cell lines. METHODSChanges in cell proliferation and the cytotoxic effect of the tested compounds on human colorectal cancer cell lines and human fibroblasts were evaluated using MTS and BrdU assay, allowing us to choose the most potent substance. Cell cycle alterations were analyzed using flow cytometric analysis. The apoptosis-inducing effect of compound K-453 on the HCT116 cell line was examined with annexin V/PI double staining using flow cytometry, as well as acridine orange/propidium iodide (AO/PI) staining. The flow cytometry method also allowed us to measure changes in levels or activation states of other factors associated with apoptosis, such as poly (ADP-ribose) polymerase (PARP), caspase-3 and -9, cytochrome c, Bcl-2 family proteins, and also the integrity of the mitochondrial membrane. To evaluate activity of the transcription factors and proteins involved in signaling pathways we used Western blot analysis together with flow cytometry. RESULTSAmong the ten tested compounds, compound K-453 {(±)-trans-1,2-dimethoxy-2’-(3,5-bis-trifluoromethylphenylamino)spiro{indoline-3,5’[4’,5’]dihydrothiazol} exhibited the most potent activity with IC50 = 32.22 ± 1.14 μmol/L in human colorectal HCT116 cells and was thus selected for further studies. Flow cytometric analysis revealed a K-453-induced increase in the population of cells with sub-G1 DNA content, which is considered as a marker of apoptotic cell death. The apoptosis-inducing effect of compound K453 was also confirmed by annexin V/PI double staining and AO/PI staining. The apoptosis was associated with the loss of mitochondrial membrane potential, PARP cleavage, caspase-3 and caspase-9 activation, release of cytochrome c, as well as changes in the levels of Bcl-2 family members. Moreover, flow cytometry showed that compound K-453 stimulates phosphorylation of p38 MAPK but decreases phosphorylation of Akt and Erk 1/2. Activation of p38 MAPK was also confirmed using Western blot analysis. This analysis also revealed down-regulation of NF-κB1 (p50) and RelA (p65) proteins and the loss of their anti-apoptotic activity. CONCLUSIONIn our study compound K-453 exhibited an antiproliferative effect by induction of intrinsic apoptosis as well as modulation of several signaling pathways.

Anti-proliferation and apoptosis-inducing effects of sodium aescinate on retinoblastoma Y79 cells

AIM:To investigate the anti-proliferation and apoptosisinducing effects of sodium aescinate(SA)on retinoblastoma Y79 cells and its mechanism.METHODS:Y79 cells were cultured at different drug concentrations for different periods of time(24,48,and 72 h).The inhibitory effect of SA on proliferation of Y79 cells was detected by the cell counting kit-8(CCK-8)assay,and the morphology of Y79 cells in each group was observed under an inverted microscope.An IC50 of 48 h was selected for subsequent experiments.After pretreatment with SA for 24 and 48 h,cellular DNA distribution and apoptosis were detected by flow cytometry.Real-time qunatitative polymerase chain reaction(RT-qPCR)and Western blot were used to assess changes in related genes(CDK1,CyclinB1,Bax,Bcl-2,caspase-9,caspase-8,and caspase-3).RESULTS:SA inhibited proliferation and induced apoptosis of Y79 cells in a time-dependent and concentrationdependent manner.Following its intervention in the cell cycle pathway,SA can inhibit the expression of CDK1 and Cyclin B1 at the mRNA and protein levels,and block cells in the G2/M phase.In caspase-related apoptotic pathways,up-regulation of Bax and down-regulation of Bcl-2 caused caspase-9 to self-cleave and further activate caspase-3.What’s more,the caspase-8-mediated extrinsic apoptosis pathway was activated,and the activated caspase-8 was released into the cytoplasm to activate caspase-3,which as a member of the downstream apoptotic effect group,initiates a caspase-cascade reaction that induces cell apoptosis.CONCLUSION:SA inhibits the proliferation of Y79 cells by arresting the cell cycle at the G2/M phase,and induces apoptosis via the caspase-related apoptosis pathway,indicating that SA may have promising potential as a chemotherapeutic drug.

Mitochondrial superoxide anions induced by exogenous oxidative stress determine tumor cell fate: an individual cell-based study

Objective: Reactive oxygen species(ROS) are involved in a variety of biological phenomena and serve both deleterious and beneficial roles. ROS quantification and assessment of reaction networks are desirable but difficult because of their short half-life and high reactivity. Here, we describe a pro-oxidative model in a single human lung carcinoma SPC-A-1 cell that was created by application of extracellular H2O2 stimuli. Methods: Modified microfluidics and imaging techniques were used to determine O2·- levels and construct an O2^·- reaction network. To elucidate the consequences of increased O2^·- input, the mitochondria were given a central role in the oxidative stress mode, by manipulating mitochondria-interrelated cytosolic Ca2+ levels, mitochondrial Ca^2+ uptake, auto-amplification of intracellular ROS and the intrinsic apoptotic pathway. Results and conclusions: Results from a modified microchip demonstrated that 1 mmol/L H·-2 O2 induced a rapid increase in cellular O2 levels(>27 vs.>406 amol in 20 min), leading to increased cellular oxidizing power(evaluated by ROS levels) and decreased reducing power(evaluated by glutathione(GSH) levels). In addition, we examined the dynamics of cytosolic Ca^2+ and mitochondrial Ca^2+ by confocal laser scanning microscopy and confirmed that Ca^2+ stores in the endoplasmic reticulum were the primary source of H2O2-induced cytosolic Ca^2+ bursts. It is clear that mitochondria have pivotal roles in determining how exogenous oxidative stress affects cell fate. The stress response involves the transfer of Ca^2+ signals between organelles,ROS auto-amplification, mitochondrial dysfunction, and a caspase-dependent apoptotic pathway.