Biofactors - Volume 26, issue 4

Authors: Chiu, Po Yee | Ko, Kam Ming

Article Type: Research Article

Abstract: To define the relative role of reduced glutathione (GSH) synthesis and regeneration in schisandrin B (Sch B)-induced increase in cellular GSH level and the associated cytoprotection against oxidative challenge, the effects of L-buthionine-[S,R]-sulfoximine (BSO, a specific inhibitor of γ-glutamate cysteine ligase (GCL)) and 1,3-bis(2-chloroethyl)-1-nitrourea (BCNU, a specific inhibitor of glutathione reductase (GR)) treatments or their combined treatment were examined in control and Sch B-treated AML12 and H9c2 cells, without and/or with menadione …intoxication. Both BSO and BCNU treatments reduced cellular GSH level in AML12 and H9c2 cells, with the effect of BSO being more prominent. The GSH-enhancing effect of Sch B was also suppressed by BSO and BCNU treatments, with the effect of the combined treatment with BSO and BCNU being semi-additive. While Sch B treatment increased the GR but not GCL activity in AML12 and H9c2 cells, it increased the cellular cysteine level. BSO treatment also suppressed the Sch B-induced increase in GR activity. BSO or BCNU treatment per se did not cause any detectable cytotoxic effect, as assessed by lactate dehydrogenase leakage, but the combined treatment with BSO and BCNU was cytotoxic, particularly in H9c2 cells. The cytotoxic effect of BSO and BCNU became more apparent following the menadione challenge. The cytoprotection afforded by Sch B pretreatment was partly suppressed by BSO or BCNU treatment, or completely abrogated by the combined treatment with BSO and BCNU. In conclusion, the results indicate that the cytoprotective action of Sch B is causally related to the increase in cellular GSH level, which is likely mediated by the enhancement of GSH synthesis and regeneration. Show more

Keywords: Schisandrin B, glutathione, cysteine, γ-glutamate cysteine ligase, glutathione reductase, AML12, H9c2, menadione

Citation: BioFactors, vol. 26, no. 4, pp. 221-230, 2006

Authors: Kwon, Daejoong | Yoon, Sun | Carter, Orianna | Bailey, George S. | Dashwood, Roderick H.

Article Type: Research Article

Abstract: Epidemiological studies indicate that consumption of green-yellow vegetables rich in chlorophyll, vitamin C, vitamin E, and carotenoids reduce the risk of cancer. We sought to examine the antigenotoxic and antioxidant properties of chlorophyll-rich methanol extracts of Angelica keiskei, Oenanthe javanica, and Brassica oleracea (kale). In the Salmonella mutagenicity assay, A. keiskei caused dose-dependent inhibition against three heterocyclic amine mutagens in the presence of S9, O. javanica was antimutagenic only at …the highest concentration in the assay (2 mg/plate), and B. oleracea showed no consistent inhibitory activity at non-toxic levels. None of the extracts were effective against three direct-acting mutagens in the absence of S9. Extracts of A. keiskei and, to a lesser extent O. javanica, inhibited two of the major enzymes that play a role in the metabolic activation of heterocyclic amines, based on ethoxyresorufin-O-deethylase and methoxyresorufin-O-demethylase assays in vitro. All three plant extracts were highly effective in assays which measured ferric reducing/antioxidant power, oxygen radical absorbance capacity, and Fe^{2+} /H_{2} O_{2} -mediated DNA nicking. Finally, using the 'comet' assay, all three plant extracts protected against H_{2} O_{2} -induced genotoxic damage in human HCT116 colon cancer cells. These findings provide support for the antigenotoxic and antioxidant properties of chlorophyll-rich extracts of A. keiskei, O. javanica, and B. oleracea, through mechanisms that include inhibition of carcinogen activation and scavenging of reactive oxygen species. Show more

Keywords: Antimutagen, antioxidant, heterocyclic amines, phytochemical, comet assay, DNA breaks

Citation: BioFactors, vol. 26, no. 4, pp. 231-244, 2006

Authors: Kwon, Dae Young | Jang, Jin Sun | Lee, Ji Eun | Kim, Yong-Suk | Shin, Dong-Hwa | Park, Sunmin

Article Type: Research Article

Abstract: We investigated anti-diabetic candidates and their mechanisms from the fractions of Chungkookjang (CKJ), a traditional fermented unsalted soybean, by investigating insulin signaling, peroxisome proliferator-activated receptor (PPAR)-γ activity and glucose-stimulated insulin secretion, in vitro. Cooked soybeans (CSB) and CKJ, fermented predominantly with Bacillus subtilis, were extracted by 70% EtOH followed by an XAD-4 column chromatography with a serial mixture of solvents comprised of MeOH and water. During fermentation, the contents of isoflavonoid …aglycones were elevated, and the fractions enriched with aglycones enhanced insulin-stimulated glucose uptake in 3T3-L1 adipocytes. This increase in glucose uptake resulted from stimulating a translocation of the glucose transporter (GLUT)-4 into the plasma membrane through the phosphorylation of insulin receptor substrate (IRS)-1 and Akt. Especially, daidzein enriched fractions elevated insulin-stimulated glucose uptake by acting as PPAR-γ agonist up to levels exhibited when 10 nM insulin is administered. Fractions containing small peptides with low polarity in CKJ slightly increased glucose-stimulated insulin secretion. The data suggest that an increase in isoflavonoid aglycones in CKJ, in comparison to CSB, enhances glucose utilization via activating insulin signaling and stimulates PPAR-γ activity in adipocytes. In addition, CKJ contains small peptides improving glucose-stimulated insulin secretion in insulinoma cells. Overall, CKJ is superior to CSB in anti-diabetic action. Show more

Keywords: Fermented soybeans, insulin sensitizing, glucose-stimulated insulin secretion, PPAR-γ agonist

Citation: BioFactors, vol. 26, no. 4, pp. 245-258, 2006

Authors: Ghoshal, Srabasti | Sengupta, Tanusree | Sen, Parimal C.

Article Type: Research Article

Abstract: The goat sperm microsomal membranes have been found to contain an Mg^{2+} -independent Ca^{2+} -ATPase, a low affinity but highly active enzyme sharing similarities with the SERCA family of ATPases. The present study reports the identification and characterization of a 14 kilodalton cytosolic protein from bovine brain which can act as an endogenous stimulator of the enzyme with an S_{50} (concentration producing 50% stimulation) of 0.8 μ molar. Kinetic analysis …suggests that the stimulation is noncompetitive with respect to the substrate, and the binding site(s) of the stimulator and substrate are distinct. Binding of the stimulator to the enzyme is reversible. The stimulator increases the affinity of the enzyme for calcium as evident from a decrease in K_{0.5} of the enzyme for calcium in presence of the stimulator. Radioactive labeling of the enzyme with [γ-^{32} P]-ATP suggests that the stimulator enhances the rate of dephosphorylation of the phosphoenzyme intermediate without altering the phosphorylation reaction step. The stimulatory effect of the protein has been observed only for the Mg^{2+} -independent form of the enzyme, the Mg^{2+} -dependent form being unaffected. Show more

Keywords: Stimulator protein, Ca^{2+}-ATPase, phosphorylation-dephosphorylation, bovine brain

Citation: BioFactors, vol. 26, no. 4, pp. 259-271, 2006

Authors: Choi, Inwook | Park, Yongkon | Choi, Heedon | Lee, Eunjoo H.

Article Type: Research Article

Abstract: Polyphenolic compounds were examined for their effects on suppressing adipocyte differentiation in 3T3-L1 cells. Most polyphenolic compounds inhibited adipocyte development from 3T3-L1 cells to some extent. Among them, rutin was the most effective in suppressing adipocyte differentiation in a dosage dependant manner. Activity of glycerol-3-phosphate dehydrogenase (GPDH), which has a central position in lipogenesis in adipose cells, was also decreased by rutin addition at the induction stage. RT-PCR results demonstrated that mRNA …expression of adipogenic transcription factors such as peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer binding protein-α (C/EBPα) in 3T3-L1 cells were remarkably down regulated by rutin treatment. For further investigation on anti-adipogenic activities of rutin, it was orally administered (25 and 50 mg/kg b.w/daily) with high-fat diet (64.4% of total calories as fat) to C57BL/6 mice. Body weight gains were less in high-fat diet + rutin fed groups (HFR) than high-fat diet alone fed group (HF) after 4 weeks. Total cholesterol contents in blood were significantly lower in HFR groups. When mRNA expressions of PPARγ and C/EBPα in hepatocytes were compared between the control HF and HFR groups, their expressions in hepatocytes of HFR groups were significantly suppressed. These results indicate that rutin inhibits adipogenic development in pre-adipocytes and hepatocytes by down regulating expressions of key adipogenic transcription factors. Show more

Keywords: Rutin, adipogenesis, PPARγ, C/EBPα, liver steatosis

Citation: BioFactors, vol. 26, no. 4, pp. 273-281, 2006

Authors: Krjukov, Alexei A. | Semenkova, Galina N. | Cherenkevich, Sergei N. | Gerein, Valentin

Article Type: Research Article

Abstract: In this work the influence of H_{2} O_{2} on the ability of human blood monocytes to generate ROS upon stimulation of cells by adhesion to glass surface and fMLP was studied using the luminol-dependent chemiluminescence (LDCL) method. Pretreatment of cells with H_{2} O_{2} increased the adhesiveness of monocytes and ROS generation. Superoxide generation by cells in response to fMLP depended on the duration of pretreatment and …the concentration of H_{2} O_{2} . The stimulatory effect on fMLP-induced LDCL of cells further depended on the Ca^{2+} concentration in the medium and on the activities of phospholipase A_{2} , cyclooxygenases, and Mek1/2. Show more

Keywords: Monocytes, chemiluminescence, reactive oxygen species, hydrogen peroxide, adhesiveness

Citation: BioFactors, vol. 26, no. 4, pp. 283-292, 2006