Heat shock induction of a 65 kDa ATP-binding proteinase in rat C6 glioma cells

The 45, 55, 65 and 100 kDa ATP-binding proteinases (ATP-BPases) of the heat-shocked (44 ℃ for 30 min, recovery for 12h) rat C6 glioma cells were purified by DEAE-ionexchange and ATP-affinity chromatography. Their molecular masses, isoelectric points (pI), pH-optima and other properties were analyzed by native proteinase gels.It was shown that the 65 kDa ATP-BPase is specifically induced by heat shock and not detectable in control cells.Its N-terminal 1-9 amino acid sequence was determined by Edman degradation, but no homologies to other proteins in the protein data bases were found. 30 and 31 kDa proteinases can be cleaved from the 45, 55 and 65 kDa proteinases to which they are linked. A possible relationship of the heat-induced 65 kDa ATP-BPase with the ATP-dependent proteinases (ATP-DPases) in prokaryotes and eukaryotes is discussed.

Lipid-albumin nanoassemblies co-loaded with borneol and paclitaxel for intracellular drug delivery to C6 glioma cells with P-gp inhibition and its tumor targeting

Successful chemotherapy with paclitaxel(PTX)is impeded by multidrug resistance(MDR)in tumor cells.In this study,lipid-albumin nanoassemblies co-loaded with borneol and paclitaxel(BOR/PTX LANs)were prepared to circumvent MDR in C6 glioma cells.The physiochemical properties including particle size,encapsulation efficiency and morphology were evaluated in vitro.Quantitative and qualitative investigations of cellular uptake were carried out in C6 glioma cells.The cytotoxicity of the BOR/PTX LANs was determined by MTT assay.After that,the tumor targeting was also evaluated in C6 glioma bearing mice by in vivo imaging analysis.BOR/PTX LANs have a higher entrapment efficiency(90.4±1.2%),small particle size(107.5±3.2 nm),narrow distribution(P.I.=0.171±0.02).The cellular uptake of PTX was significantly increased by BOR/PTX LANs compared with paclitaxel loaded lipidalbumin nanoassemblies(PTX LANs)in quantitative research.The result was further confirmed by confocal laser scanning microscopy qualitatively.The cellular uptake was energy-,timeand concentration-dependent,and clathrin-and endosome/lysosome-associated pathways were involved.The BOR/PTX LANs displayed a higher cytotoxicity agaist C6 glioma cells in comparion with PTX LANs and Taxol.Moreover,the encapsulation of BOR in LANs obviously increased the accumulation of the drug in tumor tissues,demonstrating the tumor targeted ability of BOR/PTX LANs.These results indicated that BOR/PTX LANs could overcome MDR by combination of drug delivery systems and P-gp inhibition,and shown the potential for treatment of gliomas.

Effects of antigliomatin from the scorpion venom of Buthus martensii Karsch on chloride channels on C6 glioma cells

Using whole-cell patch-clamp recordings, the effects of antigliomatin were observed on chloride channels on C6 glioma cells cultured in vitro. Antigliomatin was extracted from the venom of the scorpion Buthus martensii Karsch. Chloride channels are closed under normal osmotic pressure. When osmotic pressure was reduced to 120, 110 and 100 mV, the cell volume enlarged, chloride channels opened, and the chloride channel current increased. Three minutes after antigliomatin treatment, the chloride channel current decreased in a dose-dependent manner. These results show that antigliomatin extracted from the venom of the scorpion Buthus martensii Karsch diminishes chloride channel currents on C6 glioma cells.

Induction of apoptosis and inhibition of proliferation of C6 glioma cells in vitro by tamoxifen

Objective To investigate the anti-tumor effect and mechanism of tamoxifen on rat C6 glioma cells. Methods C6 cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) with 3% fetal calf serum (FCS), and treated with tamoxifen of different concentrations, i.e. group A (1.25μmol/L), group B (2.50 μmol/L), group C (5.00 μmol/L), group D (10.00 μmol/L), group E (20.00 μmol/L) and control group (0.00 μmol/L). Morphological changes, MTT assay and 5-bromo-2’-deoxyuriding labeling ratio were assessed. Apoptosis was observed by flow cytometry. Results C6 cells treated with different doses of tamoxifen for 24, 48, and 72 hours became irregular in shape, while cells treated with vehicle grew normally. MTT assay showed that tamoxifen did not suppress C6 cell growth until 72 hours after treatment. Seventy-two hours after treatment, there were significant differences in cell viable rate between group A versus groups C, D and E; so did group B versus group D as well as group E (P<0.05). BrdU incorporation assay indicated significant difference of BrdU labbled index (BrdU LI) among groups A, C, E and control group 48 hours after treatment (P<0.05). And the BrdU LI decreased with the increased concentration of tamoxifen. Flow cytometry (FCM) showed significant difference between treated group and control group at 24, 48, and 72 hours after treatment (P<0.05). Conclusion Tamoxifen significantly suppresses the growth of C6 glioma cells in a time-and dose-dependent manner. The mechanism of tamoxifen suppressing C6 glioma cells may be inhibiting proliferation and inducing apoptosis. Therefore, tamoxifen can be a candidate as a chemotherapy agent for glioma.

RNA interference affects tumorigenicity and expression of insulin-like growth factor-1,insulin-like growth factor-1 receptor,and basic fibroblast growth factor-2 in rat C6 glioma cells

BACKGROUND： Human gliomas are more likely to express basic fibroblast growth factor-2 （FGF-2） insulin-like growth factor-1（IGF-1）, and IGF-1 receptor （IGF-1R） than normal brain tissue. These factors activate signal transduction systems of Ras/MAPK and PI3K/Akl, which promote glioma growth. OBJECTIVE： To utilize RNA interference （RNAi） technique to down-regulate FGF-2, IGF-1, and IGF-1R gene expression, and to investigate the effects of these genes on rat C6 glioma cells, as well as the feasibility of RNAi for treating glioma. DESIGN, TIME AND SETTING： This neurooncological, randomized, controlled, in vivo and in vitro experiment, which used RNAi methodology, was performed at the Laboratory of Molecular Biology, Institute of Biochemistry, Chinese Academy of Sciences between August 2005 and February 2008. MATERIALS： Rat C6 cell lines were purchased from Shanghai Institute of Cellular Biology Affiliated to Chinese Academy of Sciences. Small interfering RNA （siRNA） was synthesized by Shanghai GenePharma. Anti-IGF-1, anti-IGF-1R, anti-FGF-2, anti-mouse and anti-rabbit IgG G1-HRP antibodies were provided by Santa Cruz Biotechnology, USA. Four to six week-old BALB/c nude mice were purchased from the Laboratory Animal Center, Chinese Academy of Sciences. METHODS： C6 glioma cells were transfected with siRNA, which was chemically synthesized in vitro to correspond to endogenous FGF-2, IGF-1, and IGF-1R genes. The inhibition ratio of targeting mRNA expression was detected by semiquantitative RT-PCR, and protein expression was determined by Western blot analysis. C6 glioma cell proliferation was observed using a growth curve C6 glioma cell apoptosis rate and cell cycle were detected by flow cytometry. C6 glioma cell growth regression was observed by transwell migration assay. In addition, nude mouse subcutaneous tumor models were used in this study. For studying the anti-tumor effects of IGF-1 and IGF-1R siRNA, two blank control groups, with six mice each, were set up： A （2.5 μg siRNA was injected one week after C6 cells were inoculated, Le., when tumor volume reached 8 mm × 8 mm） and B （siRNA was injected at the same time with C6 cells were inoculated. To study the effects of FGF-2 siRNA, the groups consisted of a blank control group, negative control group, 2.6 μg siRNA group, 4 μg siRNA group, and 5.3 μg siRNA group, with six mice each. MAIN OUTCOME MEASURES： mRNA and protein inhibition ratio of FGF-2, IGF-1, and IGF-1 R; C6 glioma cell proliferation, apoptosis, and cycle growth arrest; C6 glioma cell growth regression and subcutaneous tumorigenicity rates. RESULTS： All siRNA constructs proved to be effective. After 48 hours, transfection of 200 nmol/L siRNA resulted in a FGF-2 or IGF-1R gene inhibition ratio 〉 80% and an IGF-1 gene inhibition ratio of approximately 70%. Protein expression levels for FGF-2, IGF-1, and IGF-1R decreased in a dose-dependent manner following siRNA transfection, with an inhibition rate 〉 85%, 60%, and 50%, respectively. C6 glioma cell proliferation and apoptosis rates increased in proportion to siRNA. The apoptosis rate of C6 glioma cells induced by FGF-2, IGF-1, and IGF-1R siRNA was 39.96%, 15.07% and 22.47%, respectively （P 〈 0.01）. Transfection of 200 nmol/L IGF or IGF-1R siRNA for 48 hours suppressed C6 glioma cell migration. At 30 days after intratumoral injection of 2.6, 4, and 5.3 tJg FGF-2 siRNA, tumor growth regression rate of FGF-2 siRNA was 56%, 67%, and 86%, respectively. The tumor growth regression rate was 71.88% and 45.71%, respectively, when IGF-1 or IGF-1R siRNA was intratumorally injected 1 week after C6 glioma cell transplantation. When IGF-1 or IGF-1 R siRNA was intratumorally injected during C6 glioma cell transplantation, the tumor growth regression rate was 78.13% and 74.29%, respectively. CONCLUSION： siRNA transfection downregulated gene expression of FGF-2, IGF-1, and IGF-1R In addition, siRNA treatment markedly suppressed glioma cell proliferation, growth, and migration, and concomitantly reduced subcutaneous tumorigenicity.

Effects of selective cyclooxygenase-2 inhibitor on C6 glioma cell proliferation and apoptosis

BACKGROUND： Studies have shown that cyclooxygenase-2 is associated with proliferation and apoptosis of glioma cells. OBJECTIVE： To investigate the effects of selective cyclooxygenase-2 inhibitor celecoxib on proliferation and apoptosis of C6 glioma cells in vitro. DESIGN, TIME AND SETTING： A cellular, molecular, controlled study was performed at the Central Laboratory and Room of Electron Microscope, Medical School, Xi＇an Jiaotong University, China from March 2007 to March 2008. MATERIALS： C6 glioma cells during in vitro log phase were assigned to control and experimental groups. Celecoxib （Pfizer, USA）, dimethyl sulfoxide （Sigma, USA）, and MTT （Sigma, USA） were used for this study. METHODS： The control group was subdivided into blank control and dimethyl sulfoxide control groups. C6 glioma cells in the blank control and dimethyl sulfoxide control groups were incubated in Dulbecco＇s modified Eagle＇s medium supplemented with 10% calf serum and 0.3% dimethyl sulfoxide respectively. C6 glioma cells in the experimental group were separately treated with 60, 80 and 100 μmol/L celecoxib. MAIN OUTCOME MEASURES： Activity of C6 glioma cells was examined by MTT assay. C6 glioma cell cycle and apoptosis were determined by annexin V-fluorescein isothiocyanate/propidium iodide double-staining, followed by flow cytometry. Morphology and ultrastructure of C6 glioma cells were observed with an inverted microscope and a transmission electron microscope, respectively. RESULTS： Compared with the blank control group, cell density was reduced, adherence ability weakened, and irregular nuclei were visible, with the presence of chromatin condensation, margination, and some apoptotic bodies in the experimental group. Activity of C6 glioma cells was significantly decreased （P 〈 0.05）, cell number was reduced during S phase, cell number was significantly increased during G2/M phase （P 〈 0.01 ）, and the apoptotic rate was significantly increased （P 〈 0.05） in the experimental group. These results were displayed in a dose- and time-dependent fashion. The outcomes were obvious in the 100 IJmol/L celecoxib group following 72 hours of treatment. CONCLUSION： Celecoxib blocked proliferation and induced apoptosis of C6 glioma cells in a dose- and time-dependent fashion.

Inhibitory effects of Pseudomonas aeruginosa mannose-sensitive hemagglutinin on rat C6 glioma cell proliferation

BACKGROUND： Pseudomonas aeruginosa mannose-sensitive hemagglutinin （PA-MSHA） parenteral injection is used as a broad-spectrum immunomodulator. It remains unclear whether PA-MSHA exhibits inhibitory effects on tumor cell growth. OBJECTIVE： To investigate inhibitory mechanisms of PA-MSHA-induced proliferation in rat C6 glioma cells in vitro. DESIGN, TIME AND SETTING： Comparative observation and in vitro experiments were performed at the Key Laboratory of Natural Medicine, Kunming Medical College, China from July 2008 to April 2009. MATERIALS： Rat C6 glioma cell line （Shanghai Institute of Cell Biology, Chinese Academy of Sciences, China） and PA-MSHA parenteral injection （Beijing Wanteer Bio-Pharmaceutical, China） were used in the present study. METHODS： Rat C6 glioma cells in logarithmic growth phase were harvested in vitro. Adherent monolayer cells were respectively treated with PA-MSHA at final colony-forming units （cfu） of 1 ×10^8 cfu/mL, 2 × 10^8 cfu/mL, 4 × 10^8 cfu/mL, 6 × 10^8 cfu/mL, and 8 ×10^8 cfu/mL following 24 hours of conventional culture. MAIN OUTCOME MEASURES： MTT colorimetric assay was utilized to determine the inhibitory rate of C6 glioma cells following treatment with various concentrations of PA-MSHA at different times. Cell apoptosis was detected by fluorescent microscopy following Hoechst 33258 staining. Flow cytometry was used to measure PA-MSHA effects on C6 cell cycle. RESULTS： Inhibitory rate of C6 glioma cells increased with prolonged time and increased dose. Hoechst 33258 staining revealed obvious morphological changes in apoptotic C6 glioma cells. Flow cytometry revealed hypodiploid peaks, Le., apoptotic peak, and the apoptotic rate in cells during S-phase significantly increased with increased concentrations in the experimental groups. CONCLUSION： With in vitro experiments, PA-MSHA preparations inhibited C6 glioma cell proliferation in a time- and dose-dependent manner. These mechanisms are likely associated with cell apoptosis induction and inhibition of the S phase.

Preparation, Release-control and Cell Apoptosis of C_6 Glioma Cells in PEG-PLGA-Rg3 Nanoparticles

With biodegradable material poly（ethylene glycol）-poly（lactide-co-glycolide） （PEG-PLGA） as substrate, the size distribution of Rg3-NPs was approved by the scanning electron microscopy. MTT assay was used to detect the effects of Rg3-NPs on the growth rate of C6 cells at various concentrations and flow cytometry（FCM） was applied to assay the cell cycle and cell apoptosis of C6 glioma cells. Western blot analysis was used to measure the protein level of PCNA. The results show that Rg3-NPs are slick and uniformity, the average diameter of the nanoparticles is about 75-90 nm, entrapment efficiency is （89.7±1.7）%. MTT assay shows the growth of C6 Glioma Cells can be significantly inhibited by Rg3-NPs in a dose-dependence manner. FCM and Western blot analysis show Rg3 can be released from the conjugated nanoparticles to function in the cell nuclei so as to lead to the changes in the growth cycle of the cells, which results in the arrest of G0-G1 cell cycle and induces the apoptosis of C6 cells. Therefore, Rg3-NPs may be used for the auxiliary therapy of brain glioma.

Apoptosis in glioma-bearing rats after neural stem cell transplantation

Abnormal activation of the Ras/Raf/Mek/Erk signaling cascade plays an important role in glioma. Inhibition of this aberrant activity could effectively hinder glioma cell proliferation and promote cell apoptosis. To investigate the mechanism of gJioblastoma treatment by neural stem ceiJ trans- plantation with respect to the Ras/Raf/Mek/Erk pathway, C6 glioma cells were prepared in sus- pension and then infused into the rat brain to establish a glioblastoma model. Neural stem cells isolated from fetal rats were then injected into the brain of this glioblastoma model. Results showed that Raf-1, Erk and Bcl-2 protein expression significantly increased, while Caspase-3 protein expression decreased. After transplantation of neural stem cells, Raf-1, Erk and Bcl-2 protein expression significantly decreased, while Caspase-3 protein expression significantly in-creased. Our findings indicate that transplantation of neural stem cells may promote apoptosis of glioma cells by inhibiting Ras/Raf/Mek/Erk signaling, and thus may represent a novel treatment approach for glioblastoma.

Ethanol Extract of Lycopodium serratum Thunb. Attenuates Lipopolysaccharide-Induced C6 Glioma Cells Migration via Matrix Metalloproteinase-9 Expression

Objectives： To elucidate how ethanol extract of L. serratum（ELS） could exert anti-migratory effects on glioma with the suppression of nuclear factor kappa B（NF-κB） downstream pathway. Methods： Cell viability of ELS on C6 glioma was detected by 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide（MTT） assay. Nitric oxide（NO） assay and 2＇,7＇-dichlorofluorescin diacetate（DCFH-DA） assay were applied to measure NO production and reactive oxygen species（ROS） generation on lipopolysaccharide（LPS）-induced C6 glioma cells. NF-κB, mitogen-activated protein kinase（MAPK）, inducible nictric oxide synthase（i NOS） and cyclooxygenase-2（COX-2） protein were determined by Western blot. Wound healing assay was used to investigate the inhibitory effect of ELS on fetal bovine serum（FBS）-induced migration and matrix metalloproteinase（MMP）-9 and-2 activity was examined by zymography. Results： ELS suppressed LPS-induced phosphorylation of extracellular signal-regulated kinase（ERK）, c-Jun N-terminal kinase（JNK）, and p38 through inhibiting the expression of chemokine CCL2（or monocyte chemoattractant protein-1, MCP-1）. In addition, ELS inhibited the expression of i NOS, COX-2, and the production of NO by LPS in C6 glioma cells. ELS also significantly decreased serum-induced migration of C6 glioma cells in scratch wound healing in a dose-dependent manner（P〈0.01）. The activity of MMP-9 and-2 were also significantly attenuated by ELS with LPS treatment（P〈0.01）. Conclusion： Our results suggest that downregulation of MMP-9 gene expression might be involved in the anti-migration effect of ELS against LPS-induced C6 glioma cells.