p38 MAPK and ERK1/2 pathways are involved in the pro-apoptotic effect of notoginsenoside Ft1 on human neuroblastoma SH-SY5Y cells

Aims

This study aims to investigate the effect and the mechanisms of notoginsenoside Ft1, a natural compound exclusively found in P. notoginseng, on the proliferation and apoptosis of human neuroblastoma SH-SY5Y cells.

Main methods

CCK-8 assay was used to assess the cell proliferation. Flow cytometry was performed to measure the cell cycle distribution and cell apoptosis. Hoechst 33258 staining was conducted to confirm the morphological changes of apoptotic cells. Protein expression was detected by western blot analysis and caspase 3 activity was measured by colorimetric assay kit.

Key findings

Among the saponins examined, Ft1 showed the best inhibitory effect on cell proliferation of SH-SY5Y cells with IC₅₀ of 45 μM. Ft1 not only arrested the cell cycle at S, G₂/M stages, but also promoted cell apoptosis, which was confirmed by Hoechst 33258 staining. Further studies demonstrated that Ft1 up-regulated the protein expressions of cleaved caspase 3, phospho-p53, p21, and cyclin B1, but down-regulated that of Bcl-2. Moreover, Ft1 enhanced the phosphorylation of ERK1/2, JNK and p38 MAPK. However, the phosphorylation of Jak2 and p85 PI3K was reduced by Ft1. Inhibitors of p38 MAPK and ERK1/2 but not JNK abrogated the up-regulated protein expressions of cleaved caspase 3, p21 and down-regulated protein expression of Bcl-2 as well as elevated caspase 3 activity induced by Ft1.

Significance

Ft1 arrested the proliferation and elicited the apoptosis of SH-SY5Y cells possibly via p38 MAPK and ERK1/2 pathways, which indicates the potential therapeutic effect of it on human neuroblastoma.     

Plagiochin E,an antifungal active macrocyclic bis(bibenzyl), induced apoptosis in Candida albicans through a metacaspase-dependent apoptotic pathway

Background

Plagiochin E (PLE) is an antifungal active macrocyclic bis(bibenzyl) isolated from liverwort Marchantia polymorpha L. To elucidate the mechanism of action, previous studies revealed that the antifungal effect of PLE was associated with the accumulation of ROS, an important regulator of apoptosis in Candida albicans. The present study was designed to find whether PLE caused apoptosis in C. albicans.

Methods

We assayed the cell cycle by flow cytometry using PI staining, observed the ultrastructure by transmission electron microscopy, studied the nuclear fragmentation by DAPI staining, and investigated the exposure of phosphatidylserine at the outer layer of the cytoplasmic membrane by the FITC-annexin V staining. The effect of PLE on expression of CDC28, CLB2, and CLB4 was determined by RT-PCR. Besides, the activity of metacaspase was detected by FITC-VAD-FMK staining, and the release of cytochrome c from mitochondria was also determined. Furthermore, the effect of antioxidant L-cysteine on PLE-induced apoptosis in C. albicans was also investigated.

Results

Cells treated with PLE showed typical markers of apoptosis: G₂/M cell cycle arrest, chromatin condensation, nuclear fragmentation, and phosphatidylserine exposure. The expression of CDC28, CLB2, and CLB4 was down-regulated by PLE, which may contribute to PLE-induced G₂/M cell cycle arrest. Besides, PLE promoted the cytochrome c release and activated the metacaspase, which resulted in the yeast apoptosis. The addition of L-cysteine prevented PLE-induced nuclear fragmentation, phosphatidylserine exposure, and metacaspase activation, indicating the ROS was an important mediator of PLE-induced apoptosis.

Conclusions

PLE induced apoptosis in C. albicans through a metacaspase-dependent apoptotic pathway.

General significance

In this study, we reported for the first time that PLE induced apoptosis in C. albicans through activating the metacaspase. These results would conduce to elucidate its underlying antifungal mechanism.     

Polyunsaturated fatty acids cause apoptosis in C. albicans and C. dubliniensis biofilms

Background

Polyunsaturated fatty acids (PUFAs) have antifungal properties, but the mode by which they induce their action is not always clear. The aim of the study was to investigate apoptosis as a mode of action of antifungal PUFAs (stearidonic acid, eicosapentaenoic acid and docosapentaenoic acid) which are inhibitory towards biofilm formation of C. albicans and C. dubliniensis.

Methods

Candida biofilms were grown in the absence or presence of 1 mM PUFAs (linoleic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid) for 48 h at 37 °C. The effect of these PUFAs on the membrane fatty acid profile and unsaturation index, oxidative stress, mitochondrial transmembrane potential and apoptosis was evaluated.

Results

When biofilms of C. albicans and C. dubliniensis were exposed to certain PUFAs there was an increase in unsaturation index of the cellular membranes and accumulation of intracellular reactive oxygen species (ROS). This resulted in apoptosis, evidenced by reduced mitochondrial membrane potential and nuclear condensation and fragmentation. The most effective PUFA was stearidonic acid.

Conclusions

The resultant cell death of both C. albicans and C. dubliniensis is due to apoptosis.

General significance

Due to the increase in drug resistance, alternative antifungal drugs are needed. A group of natural antifungal compounds is PUFAs. However, understanding their mechanisms of action is important for further use and development of these compounds as antifungal drugs. This paper provides insight into a possible mode of action of antifungal PUFAs.     

Powerful tumor cell growth-inhibiting activity of a synthetic derivative of atractyligenin: Involvement of PI3K/Akt pathway and thioredoxin system

Background

The semi-synthetic ent-kaurane 15-ketoatractyligenin methyl ester (SC2017) has been previously reported to possess high antiproliferative activity against several solid tumor-derived cell lines. Our study was aimed at investigating SC2017 tumor growth-inhibiting activity and the underlying mechanisms in Jurkat cells (T-cell leukemia) and xenograft tumor models.

Methods

Cell viability was evaluated by MTT assay. Cell cycle progression, reactive oxygen species (ROS) elevation and apoptotic hallmarks were monitored by flow cytometry. Inhibition of thioredoxin reductase (TrxR) by biochemical assays. Levels and/or activation status of signaling proteins were assessed by western blotting. Xenograft tumors were generated with HCT 116 colon carcinoma cells.

Results

SC2017 displayed cell growth-inhibiting activity against Jurkat cells (half maximal inhibitory concentration values (IC50) < 2 μM), but low cell-killing potential in human peripheral blood mononuclear cells (PBMC). The primary response of Jurkat cells to SC2017 was an arrest in G₂ phase followed by caspase-dependent apoptosis. Inhibition of PI3K/Akt pathway and TrxR activity by SC2017 was demonstrated by biochemical and pharmacological approaches. At least, SC2017 was found to inhibit xenograft tumor growth.

Conclusions

Our results demonstrate that SC2017 inhibits tumor cell growth in in vitro and in vivo models, but displays moderate toxicity against PBMC. We also demonstrate that SC2017 promotes caspase-dependent apoptosis in Jurkat cells by affecting Akt activation status and TrxR functionality.

General significance

Our observations suggest the semi-synthetic ent-kaurane SC2017 as a promising chemotherapeutic compound. SC2017 has, indeed, shown to possess tumor growth inhibiting activity and be able to counteract PI3K/Akt and Trx system survival signaling.     

Plagiochin E,an antifungal bis(bibenzyl), exerts its antifungal activity through mitochondrial dysfunction-induced reactive oxygen species accumulation in Candida albicans

Background

Plagiochin E (PLE) is an antifungal macrocyclic bis(bibenzyl) isolated from liverwort Marchantia polymorpha L. Its antifungal mechanism is unknown. To elucidate the mechanism of action, its effect on mitochondria function in Candida albicans was studied.

Methods

We assayed the mitochondrial membrane potential (mtΔψ) using rhodamine 123, measured ATP level in mitochondria by HPLC, and detected the activities of mitochondrial F₀F₁-ATPase and dehydrogenases. Besides, the mitochondrial dysfunction-induced reactive oxygen species (ROS) production was determined by a fluorometric assay, and the effects of antioxidant L-cysteine on PLE-induced ROS production and the antifungal effect of PLE on C. albicans were also investigated.

Results

Exposure to PLE resulted in an elevation of mtΔψ, and a decrease of ATP level in mitochondria. The ATP depletion owed to PLE-induced enhancement of mitochondrial F₀F₁-ATPase and inhibition of the mitochondrial dehydrogenases. These dysfunctions of mitochondria caused ROS accumulation in C. albicans, and this increase in the level of ROS production and PLE-induced decrease in cell viability were prevented by addition of L-cysteine, indicating that ROS was an important mediator of the antifungal action of PLE.

Conclusions

PLE exerts its antifungal activity through mitochondrial dysfunction-induced ROS accumulation in C. albicans.

General significance

The effect of PLE on the mitochondria function in C. albicans was assayed for the first time. These results would conduce to elucidate its underlying antifungal mechanism.     

VP2118 has major roles in Vibrio parahaemolyticus response to oxidative stress

Background

Reactive oxygen species (ROS), including superoxide anion radical, induce chronic risk of oxidative damage to many cellular macromolecules resulting in damage to cells. Superoxide dismutases (SODs) catalyze the dismutation of superoxide to oxygen and hydrogen peroxide and are a primary defense against ROS. Vibrio parahaemolyticus, a marine bacterium that causes acute gastroenteritis following consumption of raw or undercooked seafood, can survive ROS generated by intestinal inflammatory cells. However, there is little information concerning SODs in V. parahaemolyticus. This study aims to clarify the role of V. parahaemolyticus SODs against ROS.

Methods

V. parahaemolyticus SOD gene promoter activities were measured by a GFP reporter assay. Mutants of V. parahaemolyticus SOD genes were constructed and their SOD activity and resistance to oxidative stresses were measured.

Results

Bioinformatic analysis showed that V. parahaemolyticus SODs were distinguished by their metal cofactors, FeSOD (VP2118), MnSOD (VP2860), and CuZnSOD (VPA1514). VP2118 gene promoter activity was significantly higher than the other SOD genes. In a VP2118 gene deletion mutant, SOD activity was significantly decreased and could be recovered by VP2118 gene complementation. The absence of VP2118 resulted in significantly lowered resistance to ROS generated by hydrogen peroxide, hypoxanthine–xanthine oxidase, or Paraquat. Furthermore, both the N- and C-terminal SOD domains of VP2118 were necessary for ROS resistance.

Conclusion

VP2118 is the primary V. parahaemolyticus SOD and is vital for anti-oxidative stress responses.

General significance

The V. parahaemolyticus FeSOD VP2118 may enhance ROS resistance and could promote its survival in the intestinal tract to facilitate host tissue infection.     

Induction of apoptosis by Polygonatum odoratum lectin and its molecular mechanisms in murine fibrosarcoma L929 cells

Background

The Galanthus nivalis agglutinin (GNA)-related lectins have been reported to bear antiproliferative and apoptosis-inducing activities in cancer cells; however, the precise mechanisms by which GNA-related lectins induce cell death are still only rudimentarily understood.

Methods

In the present study, Polygonatum odoratum lectin (designated POL), a mannose-binding specific GNA-related lectin, possessed a remarkable antiproliferative activity toward murine fibrosarcoma L929 cells. And, this lectin induced L929 cell apoptosis in a caspase-dependent manner. In addition, POL treatment increased the levels of FasL and Fas-Associated protein with Death Domain (FADD) proteins and resulted in caspase-8 activation. Also, POL treatment caused mitochondrial transmembrane potential collapse and cytochrome c release, leading to activations of caspase-9 and caspase-3. Moreover, POL treatment enhanced tumor necrosis factor α (TNFα)-induced L929 cell apoptosis.

Results

Our data demonstrate for the first time that this lectin induces apoptosis through both death-receptor and mitochondrial pathways, as well as amplifies TNFα-induced L929 cell apoptosis.

General significance

These inspiring findings would provide new molecular basis for further understanding cell death mechanisms of the Galanthus nivalis agglutinin (GNA)-related lectins in future cancer investigations.     

AD-1, a novel ginsenoside derivative,shows anti-lung cancer activity via activation of p38 MAPK pathway and generation of reactive oxygen species

Background

Ginseng is a traditional Chinese herb that has been used for thousands of years. In the present study, effects and mechanisms of AD-1 were evaluated for its development as a novel anti-lung cancer drug.

Methods

The cytotoxic activity was evaluated by MTT assay. Flow cytometry was employed to detect cell cycle, apoptosis and ROS. Western blot and immunohistochemistry were used to analyze signaling pathways. Lung cancer xenograft models were established by subcutaneous implantation of A549 or H292 cells into nude mice.

Results

AD-1 concentration-dependently reduces lung cancer cell viability without affecting normal human lung epithelial cell viability. In A549 and H292 lung cancer cells, AD-1 induces G₀/G₁ cell cycle arrest, apoptosis and ROS production. The apoptosis can be attenuated by a ROS scavenger — N-acetylcysteine (NAC). In addition, AD-1 up-regulates the expression of p38 and ERK phosphorylation. Addition of a p38 inhibitor SB203580, suppresses the AD-1-induced decrease in cell viability. Furthermore, genetic silencing of p38 attenuates the expression of p38 and decreases the AD-1-induced apoptosis. Treatment with NAC reduces AD-1-induced p38 phosphorylation, which indicates that ROS generation is involved in the AD-1-induced p38 activation. In mice, oral administration of AD-1 (10–40 mg/kg) dose-dependently inhibited the growth of xenograft tumors without affecting body weight and decreases the expression of VEGF, MMP-9 and CD34 in tumor tissue. TUNEL staining confirms that the tumors from AD-1 treated mice exhibit a markedly higher apoptotic index.

Conclusions and general significance

These data support development of AD-1 as a potential agent for lung cancer therapy.     

Stimulation of autophagic activity in human glioma cells by anti-proliferative ardipusilloside I isolated from Ardisia pusilla

Aims

Ardipusilloside I (ADS-I), a triterpenoid saponin isolated from Ardisia pusilla A.DC (Myrsinaceae), has been recently tested for cancer treatment including brain cancer. However, the mechanism of its action remains elusive. The present study was to investigate the role of autophagy activation in the anti-tumor activities of ADS-I in human glioma cells.

Main methods

The tetrazolium dye (MTT) colorimetric assay was used for the measurement of cell proliferation in cultured glioma cells, transmission electron microscopy (TEM) for the examination of autophagic activity, flow cytometric analysis for the determination of cell cycle and apoptotic cells, and immunocytochemistry and Western blot for protein expression of microtubule-associated protein light-chain 3 (LC3) and Beclin 1.

Key findings

ADS-I significantly inhibited the proliferation of both U373 and T98G glioma cells in cultures in a dose-dependent manner. The cytotoxic activity of ADS-I against glioma cell growth was associated not only with the induction of cell cycle arrest at G₂/M phase and cell apoptosis in flow cytometric analysis, but also with the activation of autophagy, indicated by the formation of autophagosomes and up-regulated expression of both autophagic protein Beclin 1 and LC3 in glioma cells. Additionally, the treatment with chloroquine, an autophagy inhibitor, reduced ADS-1-mediated cell death.

Significance

These data suggest that the anti-proliferative activity of ADS-I in human glioma cells is associated with the activation of autophagy in addition to cell cycle arrest and apoptosis, and the antagonistic effect of chloroquine suggests an important role of autophagy in ADS-I-mediated cell death against tumor growth.     

Selenoprotein W serves as an antioxidant in chicken myoblasts

Background

Selenoprotein W (SelW) was thought to play an antioxidant role in mammals. Because chicken SelW has no cysteine (Cys) at the residue 37 (Cys37) that is required for the presumed antioxidant function in mammals, this study was conducted to determine whether chicken SelW possessed the same function.

Methods

Small interfering RNAs (siRNAs) technology was applied to suppress the SelW expression in chicken embryonic myoblasts. Thereafter, these myoblasts were treated with different concentrations of H₂O₂ and assayed for cell viability, apoptosis rate, reactive oxygen species (ROS) status, and expression levels of apoptosis-related genes and proteins (Bax, Bcl-2, and caspase-3).

Results

Silencing of the myoblast SelW gene decreased their cell viability, and increased their apoptosis rate and susceptibility to H₂O₂. While the knockout down of SelW up-regulated Bax and caspase-3 and down-regulated Bcl-2, the induced oxidative injuries were alleviated by treatment with a ROS scavenger, N-acetyl-l-cysteine (NAC).

Conclusion

Chicken SelW protected embryonic myoblasts against cell apoptosis mediated by endogenous and exogenous H₂O₂.

General significance

Chicken SelW possesses antioxidant function similar to the mammalian homologues despite the lack of Cys37 in the peptide.     

Electron flow into cytochrome c coupled with reactive oxygen species from the electron transport chain converts cytochrome c to a cardiolipin peroxidase: role during ischemia–reperfusion

Background

Cytochrome c (Cyt c) is a mobile component of the electron transport chain (ETC.) which contains a tightly coordinated heme iron. In pathologic settings, a key ligand of the cyt c's heme iron, methionine (Met₈₀), is oxidized allowing cyt c to participate in reactions as a peroxidase with cardiolipin as a target. Myocardial ischemia (ISC) results in ETC. blockade and increased production of reactive oxygen species (ROS). We hypothesized that during ischemia–reperfusion (ISC-REP); ROS generation coupled with electron flow into cyt c would oxidize Met₈₀ and contribute to mitochondrial-mediated ETC. damage.

Methods

Mitochondria were incubated with specific substrates and inhibitors to test the contributions of ROS and electron flow into cyt c. Subsequently, cyt c and cardiolipin were analyzed. To test the pathophysiologic relevance, mouse hearts that underwent ISC-REP were tested for methionine oxidation in cyt c.

Results

The combination of substrate/inhibitor showed that ROS production and electron flux through cyt c are essential for the oxidation of methionine residues that lead to cardiolipin depletion. The content of cyt c methionine oxidation increases following ISC-REP in the intact heart.

Conclusions

Increase in intra-mitochondrial ROS coupled with electron flow into cyt c, oxidizes cyt c followed by depletion of cardiolipin. ISC-REP increases methionine oxidation, supporting that cyt c peroxidase activity can form in the intact heart.

General significance

This study identifies a new site in the ETC. that is damaged during cardiac ISC-REP. Generation of a neoperoxidase activity of cyt c favors the formation of a defective ETC. that activates signaling for cell death.     

Importance of cytochrome c redox state for ceramide-induced apoptosis of human mammary adenocarcinoma cells

Background

Ceramides are intracellular lipid mediator implicated in various cellular responses, including oxidative stress and programmed cell death. Studies demonstrated strong links between ceramide and the mitochondria in the regulation of apoptosis. However, the mechanism of apoptosis induced by ceramides is not fully understood. The present study delineates importance of the redox state of cytochrome c for release of cytochrome c and apoptosis of human mammary adenocarcinoma MCF-7 and MDA-MB-231 cells induced by ceramides.

Methods

The study uses MCF-7 and MDA-MB-231 cells, isolated mitochondria, submitochondrial particles, and oxidized and reduced cytochrome c. Methods used include flow cytometry, immunoblotting, spectroscopy, and respirometry.

Results

We show that ceramides induce mitochondrial oxidative stress and release of cytochrome c from the mitochondria of these cells. Our findings show that ceramides react with oxidized cytochrome c whereas reduced cytochrome c does not react with ceramides. We also show that oxidized cytochrome c reacted with ceramides exerts lower reducibility and function to support mitochondrial respiration. Furthermore, our data show that glutathione protects cytochrome c of reacting with ceramides by increasing the reduced state of cytochrome c.

Conclusions

Ceramides induce oxidative stress and apoptosis in human mammary adenocarcinoma cells by interacting with oxidized cytochrome c leading to the release of cytochrome c from the mitochondria. Our findings suggest a novel mechanism for protective role of glutathione.

General significance

Our study suggests that the redox state of cytochrome c is important in oxidative stress and apoptosis induced by ceramides.     

Alternative cell death of Apaf1-deficient neural progenitor cells induced by withdrawal of EGF or insulin

Background

Various forms of cell death, such as apoptotic, autophagic and non-lysosomal types, are implicated in normal physiological processes. Apoptotic protease activating factor 1 (Apaf1) is an important component of the intrinsic apoptotic pathway. Deficiency of Apaf1 results in an accumulation of neural progenitor cells (NPCs) in the developing central nervous system and thus, in perinatal lethality. A small percentage of the mutant mice, however, are viable and grow to maturity. The occurrence of such normal mutants implicates alternative cell death pathways during neurogenesis.

Methods

NPCs prepared from wild-type or Apaf1-deficient embryos were cultured in growth factor-deprived medium and examined for cell death, caspase activation and morphological alterations. Generation of reactive oxygen species (ROS) and the effects of antioxidants were examined.

Results

Wild-type NPCs underwent apoptosis within 24 hours of withdrawal of epidermal growth factor (EGF) or insulin, whereas Apaf1-deficient NPCs underwent cell death but showed no signs of apoptosis. Autophagy was not necessarily accompanied by cell death. Cell death of the Apaf1-deficient NPCs resembled necroptosis—necrosis-like programmed cell death. The necroptosis inhibitor necrostatin-1, however, failed to inhibit the cell death. ROS accumulation was detected in NPCs deprived of growth factors, and an antioxidant partially suppressed the non-apoptotic cell death of Apaf1-deficient NPCs.

Conclusions

These data indicate that after withdrawal EGF or insulin withdrawal, the Apaf1-deficient cells underwent non-apoptotic cell death. ROS generation may partially participate in the cell death.

General Significance

Non-apoptotic cell death in NPCs may be a compensatory mechanism in the developing CNS of Apaf1-deficient embryos.     

Characterization of O-GlcNAc cycling and proteomic identification of differentially O-GlcNAcylated proteins during G1/S transition

Background

DNA replication represents a critical step of the cell cycle which requires highly controlled and ordered regulatory mechanisms to ensure the integrity of genome duplication. Among a plethora of elements, post-translational modifications (PTMs) ensure the spatiotemporal regulation of pivotal proteins orchestrating cell division. Despite increasing evidences showing that O-GlcNAcylation regulates mitotic events, the impact of this PTM in the early steps of the cell cycle remains poorly understood.

Methods and results

Quiescent MCF7 cells were stimulated by serum mitogens and cell cycle progression was determined by flow cytometry. The levels of O-GlcNAc modified proteins, O-GlcNAc Transferase (OGT) and O-GlcNAcase (OGA) were examined by Western blotting and OGA activity was measured during the progression of cells towards S phase. A global decrease in O-GlcNAcylation was observed at S phase entry, concomitantly to an increase in the activity of OGA. A combination of two-dimensional electrophoresis, Western blotting and mass spectrometry was then used to detect and identify cell cycle-dependent putative O-GlcNAcylated proteins. 58 cytoplasmic and nuclear proteins differentially O-GlcNAcylated through G1/S transition were identified and the O-GlcNAc variations of Cytokeratin 8, hnRNP K, Caprin-1, Minichromosome Maintenance proteins MCM3, MCM6 and MCM7 were validated by immunoprecipitation.

Conclusions

The dynamics of O-GlcNAc is regulated during G1/S transition and observed on key proteins involved in the cytoskeleton networks, mRNA processing, translation, protein folding and DNA replication.

General significance

Our results led us to propose that O-GlcNAcylation joins the PTMs that take part in the regulation of DNA replication initiation.     

Bioinformatics analysis reveals disturbance mechanism of MAPK signaling pathway and cell cycle in Glioblastoma multiforme

Background & objectives

To analyze the reversal gene pairs and identify featured reversal genes related to mitogen-activated protein kinases (MAPK) signaling pathway and cell cycle in Glioblastoma multiforme (GBM) to reveal its pathogenetic mechanism.

Methods

We downloaded the gene expression profile GSE4290 from the Gene Expression Omnibus database, including 81 gene chips of GBM and 23 gene chips of controls. The t test was used to analyze the DEGs (differentially expressed genes) between 23 normal and 81 GBM samples. Then some perturbing metabolic pathways, including MAPK (mitogen-activated protein kinases) and cell cycle signaling pathway, were extracted from KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway database. Cancer genes were obtained from the database of Cancer Gene Census. The reversal gene pairs between DEGs and cancer genes were further analyzed in MAPK and cell cycle signaling pathway.

Results

A total 8523 DEGs were obtained including 4090 up-regulated and 4433 down-regulated genes. Among them, ras-related protein rab-13(RAB13), neuroblastoma breakpoint family member 10 (NBPF10) and disks large homologue 4 (DLG4) were found to be involved in GBM for the first time. We obtained MAPK and cell cycle signaling pathways from KEGG database. By analyzing perturbing mechanism in these two pathways, we identified several reversal gene pairs, including NRAS (neuroblastoma RAS) and CDK2 (cyclin-dependent kinase 2), CCND1 (cyclin D1) and FGFR (fibroblast growth factor receptor). Further analysis showed that NRAS and CDK2 were positively related with GBM. However, FGFR2 and CCND1 were negatively related with GBM.

Interpretation & conclusions

These findings suggest that newly identified DEGs and featured reversal gene pairs participated in MAPK and cell cycle signaling pathway may provide a new therapeutic line of approach to GBM.     

Extracellular ATP induces cell death in human intestinal epithelial cells

Background

Extracellular ATP is an endogenous signaling molecule released by various cell types and under different stimuli. High concentrations of ATP released into the extracellular medium activate the P2X7 receptor in most inflammatory conditions. Here, we seek to characterize the effects of ATP in human intestinal epithelial cells and to evaluate morphological changes in these cells in the presence of ATP.

Methods

We treated human intestinal epithelial cells with ATP and evaluated the effects of this nucleotide by scanning and transmission electron microscopy analysis and calcium measurements. We used flow cytometry to evaluate apoptosis. We collected human intestinal explants for immunohistochemistry, apoptosis by the TUNEL approach and caspase-3 activity using flow cytometry analyses. We also evaluated the ROS production by flow cytometry and NO secretion by the Griess technique.

Results

ATP treatment induced changes characteristic of cell death by apoptosis and autophagy but not necrosis in the HCT8 cell line. ATP induced apoptosis in human intestinal explants that showed TUNEL-positive cells in the epithelium and in the lamina propria. The explants exhibited a significant increase of caspase-3 activity when the colonic epithelial cells were incubated with IFN-gamma followed by ATP as compared to control cells. In addition, it was found that antioxidants were able to inhibit both the ROS production and the apoptosis induced by ATP in epithelial cells.

General significance

The activation of P2X7 receptors by ATP induces apoptosis and autophagy in human epithelial cells, possibly via ROS production, and this effect might have implications for gut inflammatory conditions.     

MicroRNA-34a induces apoptosis in the human glioma cell line,A172, through enhanced ROS production and NOX2 expression

Background

MicroRNA is a type of non-coding small RNA involved in regulating genes and signaling pathways through incomplete complementation with target genes. Recent research supports key roles of miRNA in the formation and development of human glioma.

Methods

The relative quantity of miR-34a was initially determined in human glioma A172 cells and glioma tissues. Next, we analyzed the impact of miR-34a on A172 cell viability with the MTT assay. The effects of miR-34a overexpression on apoptosis were confirmed with flow cytometry and Hoechst staining experiments. We further defined the target genes of miR-34a using immunofluorescence and Western blot.

Results

MiR-34a expression was significantly reduced in human glioma A172 cells and glioma tissue, compared with normal glial cells and tissue samples. Our MTT data suggest that up-regulation of miR-34a inhibits cell viability while suppression of miR-34a enhances cell viability. Flow cytometry and Hoechst staining results revealed increased rates of apoptosis in A172 human glioma cells overexpressing miR-34a. Using immunofluorescence and Western blot analyses, we identified NOX2 as a target of miR-34a in A172 cells.

Conclusion

MiR-34a serves as a tumor suppressor in human glioma mainly by decreasing NOX2 expression.     

5′-Nitro-indirubinoxime induces G1 cell cycle arrest and apoptosis in salivary gland adenocarcinoma cells through the inhibition of Notch-1 signaling

Background

5′-Nitro-indirubinoxime (5′-NIO) is a new derivative of indirubin that exhibits anti-cancer activity in a variety of human cancer cells. However, its mechanism has not been fully clarified.

Methods

Human salivary gland adenocarcinoma (SGT) cells were used in this study. Western blot and RT-PCR analyses were performed to determine cellular Notch levels. The cell cycle stage and level of apoptosis were analyzed using flow cytometry analysis.

Results

5′-NIO significantly inhibited the mRNA levels of Notch-1 and Notch-3 and their ligands (Delta1, 2, 3, and Jagged-2) in SGT cells. Immunocytochemistry analysis showed that 5′-NIO specifically decreased the level of Notch-1 in the nucleus. In addition, 5′-NIO induced G1 cell cycle arrest by reducing levels of CDK4 and CDK6 in SGT cells. Using flow cytometry and immunoblotting analysis, we found that 5′-NIO induces apoptosis following the secretion of cytochrome c and the activation of caspase-3 and caspase-7. Intracellular Notch-1 overexpression led to a decrease in G1 phase arrest and an inhibition of 5′-NIO-induced apoptosis.

Conclusion

These observations suggest that 5′-NIO induces cell cycle arrest and apoptosis by down-regulating Notch-1 signaling.

General significance

This study identifies a new mechanism of 5′-NIO-mediated anti-tumor properties. Thus, 5′-NIO could be used as a candidate for salivary gland adenocarcinoma therapeutics.