ATM/ATR-related checkpoint signals mediate arsenite-induced G2/M arrest in primary aortic endothelial cells

Epidemiological studies have demonstrated a high association of inorganic arsenic exposure with vascular disease. Our recent in vitro studies have linked this vascular damage to vascular endothelial dysfunction induced by arsenic exposure. However, cell-cycle arrest induced by arsenic and its involvement in vascular dysfunction remain to be clarified. In this study, we employed primary porcine aortic endothelial cells to investigate regulatory mechanisms of G₂/M phase arrest induced by arsenite. Our study revealed that lower concentrations of arsenite (1 and 3 μM) increased cell proliferation, whereas higher concentrations of arsenite (10, 20, and 30 μM) inhibited cell proliferation together with correlated increases in G₂/M phase arrest. We found that this arsenite-induced G₂/M phase arrest was accompanied by accumulation and/or phosphorylation of checkpoint-related molecules, including p53, Cdc25B, Cdc25C, and securin. Inhibition of activations of these checkpoint-related molecules by caffeine significantly attenuated the 30-μM arsenite-induced G₂/M phase arrest by 93%. Our data suggest that the DNA damage responsive kinases ATM (ataxia-telangiectasia mutated) and ATR (ATM and Rad3-related) play critical roles in arsenite-induced G₂/M phase arrest in aortic endothelial cells possibly via regulation of checkpoint-related signaling molecules including p53, Cdc25B, Cdc25C, and securin.     

Cadmium induces cell cycle arrest in rat kidney epithelial cells in G2/M phase

Cadmium (Cd) has been reported to cause cell cycle arrest in various cell types by p53-dependent and -independent mechanisms. This study was designed to investigate cell cycle progression in kidney cells that are the target of chronic Cd toxicity. Rat renal proximal tubular epithelial cells, NRK-52E, were treated with up to 20 microM CdCl2 in DMEM containing 10% calf serum for up to 24 h. Flow cytometric analysis revealed time- and concentration-dependent increases in cells in G2/M phase of the cell cycle. As compared to the control cells, the cells exposed to 20 microM Cd showed a doubling of the number of cells in this phase after 24 h. The cell cycle arrest was associated with a decrease in protein levels of both cyclins A and B. Further investigation into the mechanism revealed that Cd treatment led to down-modulation of cyclin-dependent kinases, Cdk1 and Cdk2, apparently by elevating the expression of cyclin kinase inhibitors, KIP1/p27 and WAF1/p21. Furthermore, the wild-type p53 DNA-binding activity was up-regulated. Based on these observations, it appears that Cd causes G2/M phase arrest in NRK-52E cells via elevation of p53 activity, increasing the expression of cyclin kinase inhibitors p27 and p21, and decreasing the expression of cyclin-dependent kinases Cdk1 and 2, and of cyclins A and B.     

Ligand modulation of a dinuclear platinum compound leads to mechanistic differences in cell cycle progression and arrest

Despite similar structures and DNA binding profiles, two recently synthesized dinuclear platinum compounds are shown to elicit highly divergent effects on cell cycle progression. In colorectal HCT116 cells, BBR3610 shows a classical G₂/M arrest with initial accumulation in S phase, but the derivative compound BBR3610-DACH, formed by introduction of the 1,2-diaminocyclohexane (DACH) as carrier ligand, results in severe G₁/S as well as G₂/M phase arrest, with nearly complete S phase depletion. The origin of this unique effect was studied. Cellular interstrand crosslinking as assayed by comet analysis was similar for both compounds, confirming previous in vitro results obtained on plasmid DNA. Immunoblotting revealed a stabilization of p53 and concomitant transient increases in p21 and p27 proteins after treatment with BBR3610-DACH. Cell viability assays and cytometric analysis of p53 and p21 null cells indicated that BBR3610-DACH-induced cell cycle arrest was p21-dependent and partially p53-dependent. However, an increase in the levels of cyclin E was observed with steady state levels of CDK2 and Cdc25A, suggesting that the G₁ block occurs downstream of CDK/cyclin complex formation. The G₂/M block was corroborated with decreased levels of cyclin A and cyclin B1. Surprisingly, BBR3610-DACH-induced G₁ block was independent of ATM and ATR. Finally, both compounds induced apoptosis, with BBR3610-DACH showing a robust PARP-1 cleavage that was not associated with caspase-3/7 cleavage. In summary, BBR3610-DACH is a DNA binding platinum agent with unique inhibitory effects on cell cycle progression that could be further developed as a chemotherapeutic agent complementary to cisplatin and oxaliplatin.     

Hsp90 inhibitor BIIB021 enhances triptolide-induced apoptosis of human T-cell acute lymphoblastic leukemia cells in vitro mainly by disrupting p53-MDM2 balance

Aim:

To investigate the effects of BIIB021, an inhibitor of heat shock protein 90 (Hsp90) alone or in combination with triptolide (TPL) on T-cell acute lymphoblastic leukemia (T-ALL) and the mechanisms of action.

Methods:

Human T-ALL cells line Molt-4 was examined. The cell viability was measured using MTT assay. Apoptotic cells were studied with Hoechst 33258 staining. Cell apoptosis and cell cycle were analyzed using flow cytometry with Annexin V/PI staining and PI staining, respectively. The levels of multiple proteins, including Akt, p65, CDK4/6, p18, Bcl-2 family proteins, MDM2, and p53, were examined with Western blotting. The level of MDM2 mRNA was determined using RT-PCR.

Results:

Treatment of Molt-4 cells with BIIB021 (50–800 nmol/L) inhibited the cell growth in a dose-dependent manner (the IC₅₀ value was 384.6 and 301.8 nmol/L, respectively, at 48 and 72 h). BIIB021 dose-dependently induced G₀/G₁ phase arrest, followed by apoptosis of Molt-4 cells. Furthermore, BIIB021 increased the expression of p18, decreased the expression of CDK4/6, and activated the caspase pathway in Molt-4 cells. Moreover, BIIB021 (50–400 nmol/L) dose-dependently decreased the phospho-MDM2 and total MDM2 protein levels, but slightly increased the phospho-p53 and total p53 protein levels, whereas TPL (5–40 nmol/L) dose-dependently enhanced p53 activation without affecting MDM2 levels. Co-treatment with BIIB021 and TPL showed synergic inhibition on Molt-4 cell growth. The co-treatment disrupted p53-MDM2 balance, thus markedly enhanced p53 activation. In addition, the co-treatment increased the expression of Bak and Bim, followed by increased activation of caspase-9.

Conclusion:

The combination of BIIB021 and TPL may provide a novel strategy for treating T-ALL by overcoming multiple mechanisms of apoptosis resistance.     

Antiapoptotic effect of ras in the apoptosis induced by serum deprivation and exposure to actinomycin D

Serum deprivation or exposure of NIH 3T3 cells to actinomycin D (0.25–1.0 mg/ml ; 1 h) was associated with the accumulation of numerous apoptotic cells, as identified by their condensed nuclei and the decrease in cell size. In contrasts, v-H-ras-transformed NIH 3T3 cells were found to be resistant to this apoptosis induction. When v-H-ras-transformed cells were first pretreated for 24 h with 50 μM mevastatin, an agent which is known to be capable to deactivate the ras funcion, cell viability decreased and apoptotic cells became abundant (~60–80%) 72 h after serum deprivation or exposure to actinomycin D. During the serum deprivation of NIH 3T3 cells, appearance of the apoptotic cells was preceded by G₁ phase arrest. Accumulation of cells in the G₁ phase was also observed in v-H-ras-transformed cells 24 h after serum deprivation. At later times (48–72 h), v-H-ras-transformed cells seemed to be capable of breaking through the G₁ arrest and were then found to be distributed normally in the cell cycle. Received: 6 May 1996 / Accepted: 2 September 1996     

Normalizing effect of plant-originated glycoprotein (116 kDa) on G0/G1 arrest in cadmium chloride-induced primary cultured mouse myelocytes

Cadmium chloride is a well-known carcinogenic and immunotoxic metal chemical, which is commonly found in cigarette smoke and industrial effluent and which is able to cause cell cycle arrest in various cell lines. This study demonstrated that glycoprotein (116 kDa) isolated from Ulmus Davidiana Nakai (UDN) is able to normalize cell cycle arrest caused by cadmium chloride (10 μM, for indicated treatment time in the each experiment) in primary cultured mouse myelocytes. To assess cell cycle arrest, the parameters that are related to the cell cycle evaluated included cytotoxicity, production of intracellular reactive oxygen species (ROS), intracellular Ca²⁺ mobilization, the activities of cell cycle-related proteins (p53, p21, and p27), and cyclin D1/cell cyclin-dependent kinase 4 (CDK4) using immunoblot analysis and fluorescence-activated cell sorter analysis. The results in this study showed that UDN glycoprotein (50 μg/ml) inhibits the cytotoxicity, production of intracellular reactive oxygen species (ROS), and intracellular Ca²⁺ mobilization brought about by cadmium chloride. With regard to cell cycle-related proteins, UDN glycoprotein (50 μg/ml) significantly suppressed the expression of p53, p21, and p27, whereas it enhanced activity of cyclin D1/CDK4. Taken together, these findings suggest that UDN glycoprotein (50 μg/ml) significantly normalizes arrest of G₀/G₁ in the cell cycle. Thus, UDN glycoprotein appears to be one compound derived from natural products that is able normalize the calcium chloride-mediated arrest of cell cycle (G₀/G₁) in immune cells.     

Effects of 4′,7-dimethoxyflavanone on cell cycle arrest and apoptosis in human breast cancer MCF-7 cells

The present study was designed to investigate the anticancer activity of 4,7-dimethoxyflavanone in vitro. When human breast cancer MCF-7 cells were treated with 4′,7-dimethoxyflavanone at various concentrations (1–200 μM) for 24 h, antiproliferative effects were first observed at 1 μM and the IC₅₀ was 115.62 μM. Conversely, 4′,7-dimethoxyflavanone was not cytotoxic (measured as lactate dehydrogenase release in CHO-K1 cells) under the same conditions. MCF-7 cells exposed to the 4′,7-dimethoxyflavanone at the IC₅₀ concentration showed cell cycle arrest and apoptosis. Compared to the respective control level, exposure to 4′,7-dimethoxyflavanone resulted in a remarkable increase of small DNA fragments at the sub-G1 phase and an increase in the G2/M phase cell population. Moreover, when 4′,7-dimethoxyflavanone treatment caused G2/M phase arrest, an increase in CDK1 together with an increase in cyclin B was observed. Based on these results, 4′,7-dimethoxyflavanone may be a useful anticancer agent.     

Dimethoxycurcumin-induced cell death in human breast carcinoma MCF7 cells: evidence for pro-oxidant activity,mitochondrial dysfunction,and apoptosis

The factors responsible for the induction of cell death by dimethoxycurcumin (Dimc), a synthetic analog of curcumin, were assessed in human breast carcinoma MCF7 cells. Initial cytotoxic studies with both curcumin and Dimc using MTT assay indicated their comparable effects. Further, the mechanism of action was explored in terms of oxidative stress, mitochondrial dysfunction, and modulation in the expression of proteins involved in cell cycle regulation and apoptosis. Dimc (5–50 μM) caused generation of reactive oxygen species, reduction in glutathione level, and induction of DNA damage. The mitochondrial dysfunction induced by Dimc was evidenced by the reduction in mitochondrial membrane potential and decrease in cellular energy status (ATP/ADP) monitored by HPLC analysis. The observed decrease in ATP was also supported by the significant suppression of different (α, β, γ, and ε) subunits of ATP synthase. The cytotoxic effect of Dimc was further characterized in terms of induction of S-phase cell cycle arrest and apoptosis, and their relative contribution was found to vary with the treatment concentration of Dimc. The S-phase arrest and apoptosis could also be correlated with the changes in the expressions of cell cycle proteins like p53, p21, CDK4, and cyclin-D1 and apoptotic markers like Bax and Bcl-2. Overall, the results demonstrated that Dimc induced cell death in MCF7 cells through S-phase arrest and apoptosis.     

Cytotoxicity of sphingoid marine compound analogs in mono- and multilayered solid tumor cell cultures

Summary A subset of four synthetic sphingoid marine compound analogs was chosen from a preliminary in vitro cytotoxicity study for further analysis. The selected analogs were initially screened in monolayer cultures for their anticancer potential against a panel of eight human tumor cell lines, ovarian, colon and lung cancer, squamous cell carcinoma and leukemia producing IC₅₀ values ranging from 1.5 to 6.9 μM. In a secondary screening, the sphingoid analogs were evaluated against multilayered postconfluent cultures of A2780 ovarian cancer and WiDr colon cancer cells. In this model, compounds 5 and 8 were the most active derivatives showing EC₅₀ values in the range 25–32 μM. The performance of 5 and 8 against both cell lines was not dependent on the cell culture model as shown with resistance factor values in the range 8–12. Cell cycle studies in HL60 leukemia cells showed an arrest in G ₀/G ₁ at a low drug concentration (3 μM) but accumulation in S phase at a high drug concentration (9 μM). It can be concluded that the analogs showed a cell line independent activity, with an apparent selectivity against cells grown in more physiological three-dimensional condition compared to standard anticancer drugs.     

Berberine protects renal tubular cells against hypoxia/reoxygenation injury via the Sirt1/p53 pathway

Berberine (BBR) has been demonstrated to protect against renal ischemia/reperfusion injury; however, the underlying molecular mechanism is largely unknown. In the present study, we examined the role of silent information regulator 1 (Sirt1)/p53 in the protective effect of BBR on hypoxia/reoxygenation (H/R)-mediated mitochondrial dysfunction in rat renal tubular epithelial cells (NRK-52E cells). NRK-52E cells were preconditioned with small interfering RNA targeting Sirt1 (Sirt1-siRNA) and BBR before subjected to H/R. Cell damage was assessed by CCK8 assay and detection of oxidative parameters. The apoptotic rate was determined by flow cytometry and Hoechst 33258 staining. The expression of apoptotic markers, Sirt1, p53 and the translocation of p53 were examined by Western blotting assay. Nuclear p53 deacetylation by Sirt1 was detected using immunoprecipitation. Compared with the H/R group, BBR pretreatment increased cell viability and inhibited mitochondrial oxidative stress and apoptosis. Protein expression of Sirt1 was also enhanced along with a reduction of p53. Furthermore, both nuclear translocation of p53 and its acetylation were inhibited in NRK-52E cells pretreated with BBR. However, the knockdown of Sirt1 counteracted the renoprotection of BBR. BBR preconditioning protects rat renal tubular epithelial cells against H/R-induced mitochondrial dysfunction via regulating the Sirt1/p53 pathway.     

Celecoxib in combination with retinoid CD437 inhibits melanoma A375 cell in vitro

This study aimed to investigate the effects of celecoxib, synthetic retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylicacid (CD437) and the combination of the two on cell proliferation, apoptosis, and cycle arrest of human malignant melanoma A375 cells. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assay (MTT assay) was applied to determine the anti-proliferative effects of the drugs on human malignant melanoma A375 cells. Flow cytometry was performed to investigate the influence of the drugs on cell cycle and cell apoptosis. Both celecoxib and CD437 could inhibit the growth of human malignant melanoma A375 cells in a dose-dependent manner. Celecoxib at 80 μmol/L inhibited proliferation, induced apoptosis and G₂/M cell cycle arrest of human malignant melanoma A375 cells after treatment for 24 h [proliferation inhibiting rate: (50.2 ± 2.51)%, apoptosis rate: (35.91 ± 1.80)%]. CD437 at 10 μmol/L inhibited proliferation, induced apoptosis and G₀/G₁ cell cycle arrest of human malignant melanoma A375 cells after treatment for 24 h [proliferation inhibiting rate: (58.6 ± 2.38)%, apoptosis rate: (28.03 ± 0.77)%]. Celecoxib in combination with CD437 could significantly enhance the effects of inhibiting proliferation and inducing apoptosis of human malignant melanoma A375 cells 24 h after treatment compared with the drug alone [proliferation inhibiting rate: (68.92 ± 1.72)%, apoptosis rate: (42.09 ± 1.05)%, both P<0.05] and decrease the proportion of the S phase in the cell cycle. Celecoxib could inhibit the growth of human malignant melanoma A375 cells by inducing apoptosis and G₂/M cycle arrest. CD437 could inhibit the growth of human malignant melanoma A375 cells by inducing apoptosis and G₀/G₁ cycle arrest. Celecoxib exhibited additive effects with CD437 on retarding the growth and inducing apoptosis of human malignant melanoma A375 cells. Celecoxib in combination with CD437 may become an effective method for prevention and treatment of human melanoma.     

Action of SN 28049, a new DNA binding topoisomerase II-directed antitumour drug: comparison with doxorubicin and etoposide

Aim: We have examined the cellular action of SN 28049 (N-[2-(dimethylamino)ethyl]-2,6-dimethyl-1-oxo-1,2-dihydrobenzo[b]-1,6-naphthyridine-4-carboxamide), a DNA binding drug with curative activity against the Colon 38 transplantable murine carcinoma, on human tumour cells. Its action has been compared with that of two topoisomerase II-targetted drugs, etoposide and doxorubicin. Methods: The NZM3 melanoma and HCT116 colon carcinoma cell lines, each expressing wild-type p53, were cultured and responses were compared by flow cytometry, electrophoresis, microscopy, and growth of tumour xenografts. Results: Responses of NZM3 cells to all three drugs, as measured by histone H2AX γ-phosphorylation, induction of the p53 pathway and cell cycle arrest, were comparable and typical of those of topoisomerase II poisons. Xenografts of NZM3 cells responded to SN 28049 with a tumour growth delay of 16 days. In contrast, HCT116 cells had an attenuated DNA damage response to the drugs and SN 28049 had no in vivo activity, consistent with low topoisomerase II activity. However, SN 28049 inhibited HCT116 cell growth in vitro and activated the p53 pathway to induce a state with G₂/M-phase DNA content, low mitotic index and a high proportion of binucleate cells. Treated cells expressed cyclin E and the senescence marker β-galactosidase but showed low expression of cyclin B and survivin. In comparison, etoposide caused little p53 expression or cycle arrest, and doxorubicin had an intermediate effect. Conclusion: The action of SN 28049 in NZM3 cells is typical of a topoisomerase II poison, but the low topoisomerase IIα activity of HCT116 cells allowed the detection of a second antiproliferative action of SN 28049 in which cells undergo post-mitotic cycle arrest and induction of p53.     

Cadmium toxicity is caused by accumulation of p53 through the down-regulation of Ube2d family genes in vitro and in vivo

Cadmium (Cd) causes renal dysfunction with damage to kidney proximal tubule cells; however, the precise mechanisms of the toxicity remain unclear. Previously, we found that the expression of Ube2d4 gene, which is a member of the ubiquitin-conjugating enzyme Ube2d family, is suppressed by Cd in NRK-52E rat renal tubular epithelial cells. To investigate the mechanisms of Cd-induced renal toxicity, we examined the effects of Cd on the ubiquitin-proteasome system, particularly the expression and function of Ube2d family members in the NRK-52E cells and mice. Cd markedly decreased the expression of Ube2d1, Ube2d2, Ube2d3 and Ube2d4 prior to the appearance of cytotoxicity in the NRK-52E cells. Cd also dramatically increased p53 protein levels in the cells, without stimulation of p53 gene expression or inhibition of proteasome activity. In addition, Cd induced phosphorylation of p53 and caused apoptosis in the NRK-52E cells. In vivo, we examined the effect of orally administrated Cd for 12 months on the expression of Ube2d genes and accumulation of p53 in the mouse kidney. Chronic Cd exposure also caused suppression of Ube2d genes expression and accumulation of p53. Cd did not induce severe kidney injury, but caused apoptosis in the renal tubules. These results suggest that the Cd-induced accumulation of p53 may be due to inhibition of p53 degradation through the down-regulation of Ube2d family genes, and that Cd induces p53-dependent apoptosis in renal tubular cells. Moreover, Ube2d family members may be one of the critical targets of renal toxicity caused by Cd.     

In vitro and in vivo activity of gallic acid and Toona sinensis leaf extracts against HL-60 human premyelocytic leukemia

Toona sinensis is one of the most popular vegetarian cuisines in Taiwan and it has been shown to induce apoptosis in cultured human premyelocytic leukemia (HL-60) cells. In the present study, we examined the effects of T. sinensis leaf extracts (TS extracts) on tumor regression using in vitro cell culture and an in vivo athymic nude mice model. We found that TS extracts (10–75 μg/mL) arrested HL-60 cells at the G₁-S transition phase through the reductions of Cyclin D1, CDK4, Cyclin E, CDK2, and Cyclin A, and induction of CDK inhibitor p27^KIP levels. Furthermore, VEGF expression and release was significantly inhibited by TS extracts. Notably, TS extracts treatment was effective in terms of delaying tumor incidence in the nude mice inoculated with HL-60 cells as well as reducing the tumor burden. Histological analysis confirmed that TS extracts significantly modulated tumor progression in xenograft tumor. Furthermore, a similar pattern of results were observed from gallic acid (5 and 10 μg/mL), a major compound in TS, caused G₁ arrest through regulations of cell-cycle regulatory proteins. Our data suggest that T. sinensis exerts antiproliferative effects on HL-60 cells in vitro and in vivo due mainly to the presence of gallic acid.     

Genotoxicity of short single-wall and multi-wall carbon nanotubes in human bronchial epithelial and mesothelial cells in vitro

Although some types of carbon nanotubes (CNTs) have been described to induce mesothelioma in rodents and genotoxic effects in various cell systems, there are few previous studies on the genotoxicity of CNTs in mesothelial cells. Here, we examined in vitro DNA damage induction by short multi-wall CNTs (MWCNTs; 10–30 nm × 1–2 μm) and single-wall CNTs (SWCNTs; >50% SWCNTs, ∼40% other CNTs; <2 nm × 1–5 μm) in human mesothelial (MeT-5A) cells and bronchial epithelial (BEAS 2B) cells, using the single cell gel electrophoresis (comet) assay and the immunoslot blot assay for the detection of malondialdehyde (M₁dG) DNA adducts. In BEAS 2B cells, we also studied the induction of micronuclei (MN) by the CNTs using the cytokinesis-block method. The cells were exposed to the CNTs (5–200 μg/cm², corresponding to 19–760 μg/ml) for 24 and 48 h in the comet assay and for 48 and 72 h in the MN and M₁dG assays. Transmission electron microscopy (TEM) showed more MWCNT fibres and SWCNT clusters in BEAS 2B than MeT-5A cells, but no significant differences were seen in intracellular dose expressed as area of SWCNT clusters between TEM sections of the cell lines. In MeT-5A cells, both CNTs caused a dose-dependent induction of DNA damage (% DNA in comet tail) in the 48-h treatment and SWCNTs additionally in the 24-h treatment, with a statistically significant increase at 40 μg/cm² of SWCNTs and (after 48 h) 80 μg/cm² of both CNTs. SWCNTs also elevated the level of M₁dG DNA adducts at 1, 5, 10 and 40 μg/cm² after the 48-h treatment, but both CNTs decreased M₁dG adduct level at several doses after the 72-h treatment. In BEAS 2B cells, SWCNTs induced a statistically significant increase in DNA damage at 80 and 120 μg/cm² after the 24-h treatment and in M₁dG adduct level at 5 μg/cm² after 48 h and 10 and 40 μg/cm² after 72 h; MWCNTs did not affect the level of DNA damage but produced a decrease in M₁dG adducts in the 72-h treatment. The CNTs did not affect the level of MN. In conclusion, MWCNTs and SWCNTs induced DNA damage in MeT-5A cells but showed a lower (SWCNTs) or no (MWCNTs) effect in BEAS 2B cells, suggesting that MeT-5A cells were more sensitive to the DNA-damaging effect of CNTs than BEAS 2B cells, despite the fact that more CNT fibres or clusters were seen in BEAS 2B than MeT-5A cells. M1dG DNA adducts were induced by SWCNTs but decreased after a 3-day exposure to MWCNTs and (in MeT-5A cells) SWCNTs, indicating that CNTs may lead to alterations in oxidative effects within the cells. Neither of the CNTs was able to produce chromosomal damage (MN).     

Nardostachys chinensis induces granulocytic differentiation with the suppression of cell growth through p27Kip1 protein-related G0/G1 phase arrest in human promyelocytic leukemic cells

Abstract

Context: Nardostachys chinensis Batalin (Valerianaceae) has been used in Korean traditional medicine to elicit stomachic and sedative effects. However, the anti-leukemic activities of N. chinensis have not been well examined.

Objective: To investigate the effect of N. chinensis on differentiation and proliferation in the human promyelocytic leukemic HL-60 cells.

Materials and methods: The dried roots and stems of N. chiensis are extracted using hot water and then freeze-dried. The yield of extract was 12.82% (w/w). The HL-60 cells were treated with 25–200?μg/ml of N. chinensis for 72?h or 100?μg/ml of N. chinensis for 24–72?h.

Results: Nardostachys chinensis significantly inhibited cell viability dose dependently with an IC₅₀ of 100?μg/ml in HL-60 cells. Nardostachys chinensis induced differentiation of the cells as measured by reduction activity of NBT and expression of CD11b but not of CD14 as analyzed by flow cytometry, which indicates a differentiation toward the granulocytic lineage. Nardostachys chinensis also induced growth inhibition through G₀/G₁ phase arrest in the cell cycle of HL-60 cells. Among the G₀/G₁ phase in the cell cycle-related protein, the expression of cyclin-dependent kinase (CDK) inhibitor p27^Kip1 was increased in N. chinensis-treated HL-60 cells, whereas the expression levels of CDK2, CDK4, CDK6, cyclin D1, cyclin D3, cyclin E, and cyclin A were decreased. Interestingly, N. chinensis markedly enhanced the binding of p27^Kip1 with CDK2 and CDK6.

Discussion and conclusion: This study demonstrated that N. chinensis is capable of inducing cellular differentiation and growth inhibition through p27^Kip1 protein-related G₀/G₁ phase arrest in HL-60 cells.     

Induction of G<Subscript>1</Subscript>/S phase arrest and apoptosis by quercetin in human osteosarcoma cells

Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is a polyphenolic flavonoid compound and is found in a variety of plants. Potential biological activities including antioxidant and anticarcinogenesis have been reported. The antiproliferative effect and apoptosis inducing effect of quercetin in human osteosarcoma cells was evaluated in this study. The IC₅₀ values were 290 μM and 160 μM at 24 h and 48 h incubation, respectively. Antiproliferative action of quercetin appeared to be linked to apoptotic cell death based on increase in the sub-G₁ apoptotic cell population analyzed by flow cytometric analysis. Prior to apoptosis induction, quercetin caused cell cycle arrest at G₁/S phase. The G₁/S phase arrest was accompanied by down regulation of cyclin D1, one of the cyclins required for advance from G₁ to S. Subsequent apoptosis was induced by the gradual activation of caspase-3 and the cleavage of PARP.     

Inhibition of tumor growth in vitro and in vivo by fucoxanthin against melanoma B16F10 cells

The present study was designed to evaluate the molecular mechanisms of fucoxanthin against melanoma cell lines (B16F10 cells). Fucoxanthin reduced the proliferation of B16F10 cells in a dose-dependent manner accompanied by the induction of cell cycle arrest during the G₀/G₁ phase and apoptosis. Fucoxanthin-induced G₀/G₁ arrest was associated with a marked decrease in the protein expressions of phosphorylated-Rb (retinoblastoma protein), cyclin D (1 and 2) and cyclin-dependent kinase (CDK) 4 and up-regulation of the protein levels of p15^INK4B and p27^Kip1. Fucoxanthin-induced apoptosis was accompanied with the down-regulation of the protein levels of Bcl-xL, an inhibitor of apoptosis proteins (IAPs), resulting in a sequential activation of caspase-9, caspase-3, and PARP. Furthermore, the anti-tumor effect of fucoxanthin was assessed in vivo in Balb/c mice. Intraperitoneal administration of fucoxanthin significantly inhibited the growth of tumor mass in B16F10 cells implanted mice.     

Physical properties of single-wall carbon nanotubes in cell culture and their dispersal due to alveolar epithelial cell response

Abstract

Concern over the influence of carbon nanotubes (CNTs) on human health has arisen due to advances; however, little is known about the potential toxicity of CNTs. In this study, impurity-free single-wall carbon nanotubes (SWCNTs), with different physical properties in cell culture medium, were prepared by a novel dispersion procedure. SWCNTs with small bundles (short linear shape) and SWCNTs with large bundles (long linear shape) did not cause a significant inhibition of cell proliferation, induction of apoptosis or arrest of cell cycle progression in A549 alveolar epithelial cells. Expression of many genes involved in the inflammatory response, apoptosis, response to oxidative stress and degradation of the extracellular matrix were not markedly upregulated or downregulated. However, SWCNTs with relatively large bundles significantly increased the level of intracellular reactive oxygen species (ROS) in a dose-dependent manner, and the levels of these ROS were higher than those of SWCNTs with relatively small bundles or commercial SWCNTs with residual metals. Transmission electron microscopy (TEM) revealed that impurity-free SWCNTs were observed in the cytoplasm and vacuoles of cells after 24?h. These results suggested that the physical properties, especially the size and length of the bundles of the SWCNTs dispersed in cell culture medium, contributed to a change in intracellular ROS generation, even for the same bulk SWCNTs. Additionally, the residual metals associated with the manufacturing of SWCNTs may not be a definitive parameter for intracellular ROS generation in A549 cells.     

Anti-tumor activity of CrTX in human lung adenocarcinoma cell line A549

Aim:

To assess the cytotoxic effect of crotoxin (CrTX), a potent neurotoxin extracted from the venom of the pit viper Crotalus durissus terrificus, in human lung adenocarcinoma A549 cells and investigated the underlying mechanisms.

Methods:

A549 cells were treated with gradient concentrations of CrTX, and the cell cycle and apoptosis were analyzed using a flow cytometric assay. The changes of cellular effectors p53, caspase-3 and cleaved caspase-3, total P38MAPK and pP38MAPK were investigated using Western blot assays. A549 xenograft model was used to examine the inhibition of CrTX on tumor growth in vivo.

Results:

Treatment of A549 cells with CrTX (25–200 μg/mL) for 48 h significantly inhibited the cell growth in a dose-dependent manner (IC₅₀=78 μg/mL). Treatment with CrTX (25 μg/mL) for 24 h caused G1 arrest and induced cell apoptosis. CrTX (25 μg/mL) significantly increased the expression of wt p53, cleaved caspase-3 and phospho-P38MAPK. Pretreatment with the specific P38MAPK inhibitor SB203580 (5 μmol/L) significantly reduced CrTX-induced apoptosis and cleaved caspase-3 level, but G₁ arrest remained unchanged and highly expressed p53 sustained. Intraperitoneal injection of CrTX (10 μg/kg, twice a week for 4 weeks) significantly inhibited A549 tumor xenograft growth, and decreased MVD and VEGF levels.

Conclusion:

CrTX produced significant anti-tumor effects by inducing cell apoptosis probably due to activation of P38MAPK and caspase-3, and by cell cycle arrest mediated by increased wt p53 expression. In addition, CrTX displayed anti-angiogenic effects in vivo.