Potassium channels and their role in glioma: A mini review.

K+ channels regulate a multitude of biological processes and play important roles in a variety of diseases by controlling potassium flow across cell membranes. They are widely expressed in the central and peripheral nervous system. As a malignant tumor derived from nerve epithelium, glioma has the characteristics of high incidence, high recurrence rate, high mortality rate, and low cure rate. Since glioma cells show invasive growth, current surgical methods cannot completely remove tumors. Adjuvant chemotherapy is still needed after surgery. Because the blood-brain barrier and other factors lead to a lower effective concentration of chemotherapeutic drugs in the tumor, the recurrence rate of residual lesions is extremely high. Therefore, new therapeutic methods are needed. Numerous studies have shown that different K+ channel subtypes are differentially expressed in glioma cells and are involved in the regulation of the cell cycle of glioma cells to arrest them at different stages of the cell cycle. Increasing evidence suggests that K+ channels express in glioma cells and regulate glioma cell behaviors such as cell cycle, proliferation and apoptosis. This review article aims to summarize the current knowledge on the function of K+ channels in glioma, suggests K+ channels participating in the development of glioma.

Catalpol inhibits LPS plus IFN-γ-induced inflammatory response in astrocytes primary cultures.

A large body of evidence suggests that the inflammatory reaction plays an important role in the pathogenesis of neurodegenerative diseases. Our previous studies described the neuroprotective effects of catalpol in lipopolysaccharide (LPS)-induced inflammatory models, in which catalpol was shown to prevent mesencephalic neuron death and ameliorate cognitive ability animals. To further investigate the protective effect and underlying mechanism of catalpol, astrocytes were pretreated with low (0.1mM) and high dose (0.5mM) catalpol for 1h prior to LPS plus interferon-γ stimulation. Biochemical analyses showed that NO and ROS production and iNOS activity were significantly reduced by catalpol. Data at transcriptional level also demonstrated that catalpol potently attenuated gene expressions involved in inflammation, such as iNOS, COX-2 and TLR4. In addition, our exploration further revealed that the suppressive action of catalpol on inflammation was mediated via inhibiting nuclear factor-κB (NF-κB) activation. Collectively, these results suggest that catalpol can exert inhibitory effects on the inflammatory reaction in astrocytes and that inactivation of NF-κB could be the major determinant for its anti-inflammatory mechanism. Therefore, catalpol may potentially be a highly effective therapeutic agent in treating neurodegenerative diseases associated with inflammation.

Effects of resibufogenin on voltage-gated sodium channels in cultured rat hippocampal neurons.

Voltage-gated sodium channels (VGSCs) play important roles in maintaining the excitability of hippocampal neurons. The present study investigated the effects of resibufogenin (RBG, a main component of bufadienolides) on voltage-gated sodium channel currents (I(Na)) in rat hippocampal neurons using whole-cell patch clamp recording. According to the results, RBG activated I(Na) in a concentration-dependent manner. RBG at 1 µM concentration could alter some channel kinetics of I(Na), such as activation thresholds, steady-state activation and inactivation curves, time constant of recovery, and activity-dependent attenuation of I(Na). RBG influenced peak amplitude, overshoot and half-width of the evoked single action potential, and simultaneously lessened the firing rate of evoked repetitive firing. These findings suggested that I(Na) is probably a target of RBG, which may explain the mechanisms for the pathological effects of RBG on central nervous system.

Anti-ageing effects of protocatechuic acid from Alpinia on spleen and liver antioxidative system of senescent mice.

The effects of Alpinia protocatechuic acid (PCA) on spleen and liver antioxidant system in aged rats have been studied. Alpinia PCA, a phenolic compound, was first isolated from the dried fruits of Alpinia Oxyphylla Miq. in our laboratory. Young and aged rats were injected intraperitoneally with Alpinia PCA at single doses of 5 mg kg(-1) (low dose) or 10 mg kg(-1) (high dose) per day for 7 days. The activities of endogenous antioxidants and the content of lipid peroxide in spleen and liver were assayed. Compared with young group, aged rats had significantly lower splenic weights, lower activities of glutathione peroxidase (GSH-PX) and catalase (CAT), higher level of malondialdehyde (MDA) in spleen and liver. The results proved that Alpinia PCA significantly elevated the splenic weights, increased the activities of GSH-PX and CAT and decreased the MDA level of aged rats. All these suggested that Alpinia PCA was a potential anti-ageing agent, and its effects on spleen and liver were achieved at least partly by promoting endogenous antioxidant enzymatic activities and normalizing age-associated alterations. It may be therapeutically useful to minimize age-associated disorders where oxidative damage is the major cause.

Transient expression of minimum linear gene cassettes in onion epidermal cells via direct transformation.

A new method without any special devices for direct transformation of linear gene cassettes was developed. Its feasibility was verified through 5'-fluorescent dye (fluorescein isothiocyanate, FITC)-labeled fluorescent tracing and transient expression of a gus reporter gene. Minimal linear gene cassettes, containing necessary regulation elements and a gus reporter gene, was prepared by polymerase chain reaction and dissolved in transformation buffer solution to 100 ng/mL. The basic transformation solution used was Murashige and Skoog basal salt mixture (MS) liquid medium. Hypertonic pretreatment of explants and transformation cofactors, including Ca(2+), surfactant assistants, Agrobacterium LBA4404 cell culture on transformation efficiency were evaluated. Prior to the incubation of the explants and target linear cassette in each designed transformation solution for 3 h, the onion low epidermal explants were pre-cultured in darkness at 27 degrees C for 48 h and then transferred to MS solid media for 72 h. FITC-labeled linear DNA was used to trace the delivery of DNA entry into the cell and the nuclei. By GUS staining and flow-cytometry-mediated fluorescent detection, a significant increase of the ratios of fluorescent nuclei as well as expression of the gus reporter gene was observed by each designed transformation solution. This potent and feasible method showed prospective applications in plant transgenic research.

Catalpol protects rat pheochromocytoma cells against oxygen and glucose deprivation-induced injury.

OBJECTIVES: Catalpol has been identified to have neuroprotective effect on gerbils subjected to transient global cerebral ischemia. However, the mechanism that catalpol prevents ischemia is still unclear. In the present study, PC12 cells, exposed to oxygen and glucose deprivation (OGD) followed by reperfusion, were used as an in vitro model of ischemia. The protective effects of catalpol were investigated in ischemic-induced apoptosis in PC12 cells. METHODS: After OGD for 3 hours and reoxygenation for 18 hours, cell survival was quantified by the reduction of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were determined using commercially available kits. Caspase-3 assay was performed using caspase-3 assay kit. Microplate reader was used to detect the intensities of rhodamine123 (Rh123) and reactive oxygen species (ROS). The level of Bcl-2 protein was measured by flow cytometry. RESULTS: Catalpol attenuated ischemia-induced apoptotic death via preventing the decrease in the level of Bcl-2 protein and the activities of SOD and GSH-PX, inhibiting the reduction of mitochondrial membrane potential and suppressing activation of caspase-3. DISCUSSION: The results suggest that the catalpol has the potential to prevent ischemic-induced apoptosis.

Benzobijuglone, a novel cytotoxic compound from Juglans mandshurica, induced apoptosis in HeLa cervical cancer cells.

A new quinone compound, p-hydroxymethoxybenzobijuglone (HMBBJ), isolated from Juglans mandshurica by bioassay-guided fractionation, showed cytotoxic activity against HeLa cell line. Its chemical structure was determined by NMR and HREIMS spectra. In this paper, its ability to induce apoptosis in HeLa cells was studied for the first time. After treated with HMBBJ, the growth of HeLa cells was inhibited and cells displayed typical morphological apoptotic characteristics. Data from flow cytometry analysis showed that the HeLa cell cycle was arrested in the G2/M phase by HMBBJ, and the apoptotic rate of HeLa cells increased in a dose-dependent manner. Meanwhile, HMBBJ increased the expression of caspase-8, -3 and Bax, decreased the expression of Bcl-2, and lowered the DeltaPsi(m). These findings reveal that HMBBJ could efficiently induce HeLa cells apoptosis through mitochondria dependent pathway and activation of the caspase cascade, and it may be a potential chemotherapeutic candidate for the treatment of cancer.

Catalpol increases hippocampal neuroplasticity and up-regulates PKC and BDNF in the aged rats.

Rehmannia, a traditional Chinese medical herb, has a long history in age-related disease therapy. Previous work has indicated that catalpol is a main active ingredient performing neuroprotective effect in rehmannia, while the mechanism underlying the effect remains poorly understood. In this study, we attempt to investigate the effect of catalpol on presynaptic proteins and explore a potential mechanism. The hippocampal levels of GAP-43 and synaptophysin in 3 groups of 4 months (young group), 22-24 months (aged group) and catalpol-treated 22-24 months (catalpol-treated group) rats were evaluated by western blotting. Results clearly showed a significant decrease in synaptophysin (46.6%) and GAP-43 (61.4%) levels in the aged group against the young animals and an increase (45.0% and 31.8% respectively) in the catalpol-treated aged rats in comparison with the untreated aged group. In particular, synaptophysin immunoreactivity (OD) in the dentate granule layer of the hippocampus was increased 0.0251 in the catalpol-treated group as compared with the aged group. The study also revealed a catalpol-associated increase of PKC and BDNF in the hippocampus of the catalpol-treated group in comparison with the aged rats and highly correlated with synaptophysin and GAP-43. Such positive correlations between presynaptic proteins and signaling molecules also existed in the young group. These results suggested that catalpol could increase presynaptic proteins and up-regulate relative signaling molecules in the hippocampus of the aged rats. Consequently, it seemed to indicate that catalpol might ameliorate age-related neuroplasticity loss by "normalizing" presynaptic proteins and their relative signaling pathways in the aged rats.

Catalpol modulates the expressions of Bcl-2 and Bax and attenuates apoptosis in gerbils after ischemic injury.

Our previous study described the neuroprotective effects of catalpol in gerbil ischemic model, in which catalpol was shown to prevent hippocampal neurons from death and ameliorate the cognitive ability of the animals. In the study, we focused on investigating the neuroprotective mechanism of catalpol. Animals were randomly assigned three groups as sham-operated, ischemia-treated with saline and ischemia-treated with catalpol. Transient global ischemia was produced by a 5 min occlusion of the bilateral common carotid arteries. Catalpol was intraperitoneally injected at the dose of 5 mg/kg immediately after reperfusion and repeatedly at 12, 24, 48 and 72 h. Histology as well as immunohistochemistry and TUNEL (the terminal deoxynucleotidyl transferase-mediated UTP nick end label) analysis were performed on serial slices through the dorsal hippocampus after gerbils were sacrificed. The results showed that 5 min transient global ischemia followed by 4 days reperfusion caused significant increases in TUNEL-positive and Bax-positive cells in hippocampal CA1 subfield. Catalpol not only significantly reduced TUNEL-positive and Bax-positive cells but also significantly increased Bcl-2-positive cells. All these suggested that catalpol could effectively inhibit apoptosis by modulating the expressions of Bcl-2 and Bax genes.

Alpinia protocatechuic acid protects against oxidative damage in vitro and reduces oxidative stress in vivo.

In this study, the neuroprotective effects of Alpinia protocatechuic acid (PCA), a phenolic compound isolated from the dried fruits of Alpinia Oxyphylla Miq. was found. The protective effect of Alpinia PCA against H2O2-induced oxidative damage on PC12 cells was investigated by measuring cell viability via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Rats were injected intraperitoneally with Alpinia PCA at a dose of 5mg/kg per day for 7 days, behavioral testing was performed in Y-maze. In order to make clear the neuroprotective mechanism of Alpinia PCA, the activities of endogenous antioxidants and the content of lipid peroxide in brain were assayed. The results proved that Alpinia PCA significantly prevented the H2O2-induced reduction in cell survival, improved the cognition of aged rats, reduced the content of lipid peroxide, increased the activity of glutathione peroxidase and superoxide dismutase. All these suggested that Alpinia PCA was a potential neuroprotective agent and its neuroprotective effects were achieved at least partly by promoting endogenous antioxidant enzymatic activities and inhibiting free radical generation.

Protective effect of protocatechuic acid from Alpinia oxyphylla on hydrogen peroxide-induced oxidative PC12 cell death.

The neuroprotective effects of protocatechuic acid (PCA), a phenolic compound isolated from the kernels of Alpinia oxyphylla, on hydrogen peroxide (H(2)O(2))-induced apoptosis and oxidative stress in cultured PC12 cells were investigated. Exposure of PC12 cells to 0.4 mM H(2)O(2) induced a leakage of lactate dehydrogenase (LDH) and decreased cell viability denoted by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. PCA increased PC12 cellular viability and markedly attenuated H(2)O(2)-induced apoptotic cell death in a dose-dependent manner. By flow cytometric analysis, PCA showed its significant effect on protecting PC12 cells against H(2)O(2)-induced apoptosis. In these cells, the levels of glutathione (GSH) and activity of catalase were augmented, while glutathione peroxidase activity remained unchanged. In addition, PCA also protected against cell damage induced by H(2)O(2) and Fe(2+), which generated hydroxyl radicals (OH) by the Fenton reaction. These results suggest that PCA may be a candidate chemical for the treatment of oxidative stress-induced neurodegenerative disease.

[The protect effect of flavonoids from Cuscuta chinensis in PC12 cells from damage induced by H2O2].

OBJECTIVE: To study the protective effects of flavonoids from Cuscuta chinensis (CF) on oxidative stress in cultured PC12 cells and investigate the mechanism of the effects. METHODS: The cell viability was analyzed by MTT method and the radical scavenging activity of CF was examined by DPPH (1, 1-diphenyl-2-picrylhydrazyl). The morphological changes were observed by Hoechst 33258 staining assay, and the apoptosis rate of PC12 cells was detected by propidium iodide stain flow cytometry (FCM). RESULTS: Application with 0.3-0.5 mM H2O2 induced a dose and time dependent viability loss in PC12 cells; Treatment with 0.5 mM H2O2 for 24 h was shown to cause nearly 50% viabliity loss and apoptosis in PC12 cells; Pretreatment with different concentrations of CF for 0.5 h increased the survival rate of PC12 cells, inhibited apoptosis induced by H2O2; CF had the activity of scavenging free radicals generated by DPPH in a dose-dependent manner. CONCLUSION: CF can protect PC12 cells against oxidative stress. The mechanism of it may be the ability of scavenging ROS and increasing the activity of antioxidant enzyme.

Studies of chemical constituents and their antioxidant activities from Astragalus mongholicus Bunge.

OBJECTIVE: To evaluate the antioxidant activities of different chemical constituents from Astragalus mongholicus Bunge and their protection against xanthine (XA)/xanthine oxidase (XO)-induced toxicity in PC12 cells. METHODS: The compounds of Astragalus mongholicus Bunge were isolated by chromatography and the structures were elucidated on the basis of spectral data interpretation. Their antioxidant activities were detected by 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities in a cell-free system. Meanwhile, the effects against XA/XO-induced toxicity were assessed using MTT assay in PC12 cells. RESULTS: Ten principal constituents were isolated and identified as formononetin (I), ononin (II), calycosin (III), calycosin-7-O-beta-D-glucoside (IV), 9,10-dimethoxypterocarpan-3-O-beta-D-glucoside (V), adenosine (VI), pinitol (VII), daucosterol (VIII), beta-sitoster (IX) and saccharose (X) from Astragalus mongholicus Bunge. The compounds I, III, and IV scavenged DPPH free radicals in vitro. Formononetin and calycosin were found to inhibit XA/XO-induced cell injury significantly, with an estimated EC50 of 50 ng/mL. CONCLUSION: Compound II, VI, and VII are first reported in this plant. Calycosin exhibits the most potent antioxidant activity both in the cell-free system and in the cell system.

Protein amino acid composition of plasma membranes affects membrane fluidity and thereby ethanol tolerance in a self-flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae.

A combination of three amino acids including 1.0 g/L isoleucine, 0.5 g/L methionine and 2.0 g/L phenylalanine was found to enhance ethanol tolerance of a self-flocculating fusant of Schizosaccharomyces pombe and Saccharomyces cerevisiae. When subjected to 20% (V/V) ethanol for 9 h at 30 degrees C, all cells died whereas 57% remained viable for the cells grown in the presence of the three amino acids. Based on the analysis of protein amino acid composition of plasma membranes and the determination of plasma membrane fluidity by measuring fluorescence anisotropy using diphenylhexatriene as a probe, it was found that the significantly increased ethanol tolerance of cells grown with the three amino acids was due to the incorporation of the supplementary amino acids into the plasma membranes, thus resulting in enhanced ability of the plasma membranes to efficiently counteract the fluidizing effect of ethanol when subjected to ethanol stress. This is the first time to report that plasma membrane fluidity can be influenced by protein amino acid composition of plasma membranes.

Codonopsis pilosula (Franch) Nannf total alkaloids potentiate neurite outgrowth induced by nerve growth factor in PC12 cells.

AIM: To explore the effect of Codonopsis pilosula (Franch) Nannf total alkaloids (DSA) on differentiation induced by nerve growth factor (NGF) in PC12 cells. METHODS: After culturing PC12 cells with DSA in the presence or absence of NGF, neurite outgrowth in PC12 cells and correlated protein kinases were assayed. RESULTS: DSA alone did not exhibit neuritogenic activity, but caused a significant enhancement of NGF (2 microg/L)-induced neurite outgrowth in PC12 cells, and increased the phosphorylation of mitogen-activated protein kinase (MAPK). Furthermore, this enhancing effect was completely blocked by a specific MAPK kinase inhibitor, PD98059. CONCLUSION: DSA enhanced the NGF-induced neurite outgrowth in PC12 cells by amplifying an up-stream step of the MAPK-dependent signaling pathway.