Assay of the redox state of the tumor suppressor PTEN by mobility shift.

PTEN is reversibly oxidized in various cells by exogenous hydrogen peroxide as well as by endogenous hydrogen peroxide generated when cells are stimulated with growth factors, cytokines and hormones. A gel mobility shift assay showed that oxidized PTEN migrated more rapidly than reduced PTEN on a non-reducing SDS-PAGE gel. Oxidized PTEN was reduced when treated with dithiothreitol. Supplementation of N-ethylmaleimide in the cell lysis buffer was critical for the apparent bands of oxidized and reduced PTEN. Formation of oxidized PTEN was abolished when the active site Cys(124) or nearby Cys(71) was replaced with Ser suggesting that Cys(124) and Cys(71) are involved in the formation of an intramolecular disulfide bond. These results show that the mobility shift assay is a convenient method to analyze the redox state of PTEN in cells.

Protective effect of diet supplemented with rice prolamin extract against DNCB-induced atopic dermatitis in BALB/c mice.

BACKGROUND: Rice prolamin has been reported to possess antioxidative, anti-inflammatory and immune-promoting properties. This study is aimed to examine the protective effects of dietary rice prolamin extract (RPE) against dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD)-like skin lesions in mice. METHODS: BALB/c mice were fed diet supplemented with 0-0.1 % RPE for 6 weeks. For the last 2 weeks, 1 % or 0.2 % DNCB was applied repeatedly to the back skin of mice to induce AD-like lesions. Following AD induction, the severity of skin lesions was examined macroscopically and histologically. In addition, the serum levels of IgE, IgG1 and IgG2a were determined by ELISA, and the mRNA expression of IL-4 and IFN-γ in the skin was determined by real-time PCR. RESULTS: Dietary RPE suppressed the clinical symptoms of DNCB-induced dermatitis as well as its associated histopathological changes such as epidermal hyperplasia and infiltration of mast cells and eosinophils in the dermis. RPE treatment also suppressed the DNCB-induced increase in transepidermal water loss. Dietary RPE inhibited the DNCB-induced enhancement of serum IgE and IgG1 levels, whereas it increased the serum IgG2a level in DNCB-treated mice. In addition, dietary RPE upregulated the IFN-γ mRNA expression and downregulated the IL-4 mRNA expression in the skin of DNCB-treated mice. CONCLUSIONS: The above results suggest that dietary RPE exerts a protective effect against DNCB-induced AD in mice via upregulation of Th1 immunity and that RPE may be useful for the treatment of AD.

Redox regulation of the tumor suppressor PTEN by glutaredoxin 5 and Ycp4.

Human PTEN (phosphatase and tensin homolog deleted on chromosome 10; a phosphatidylinositol 3-phosphatase) expressed in Saccharomyces cerevisiae was oxidized in a time- and H(2)O(2)-concentration-dependent manner. Oxidized hPTEN was reduced by cellular reductants as in human cells. The reduction rate of oxidized hPTEN was monitored in S. cerevisiae mutants in which the genes involved in redox homeostasis had been disrupted. Reduction of hPTEN was delayed in each of S. cerevisiae grx5Δ and ycp4Δ mutants. Expression of Grx5 and Ycp4 in each of the mutants rescued the reduction rate of oxidized hPTEN. Furthermore, an in vitro assay revealed that the human Grx5/GSH system efficiently catalyzed the reduction of oxidized hPTEN. These results suggest that the reduction of oxidized hPTEN is regulated by Grx5 and Ycp4.

Black tea extract prevents lipopolysaccharide-induced NF-κB signaling and attenuates dextran sulfate sodium-induced experimental colitis.

BACKGROUND: Black tea has been shown to elicit anti-oxidant, anti-carcinogenic, anti-inflammatory and anti-mutagenic properties. In this study, we investigated the impact of black tea extract (BTE) on lipopolysaccharide (LPS)-induced NF-κB signaling in bone marrow derived-macrophages (BMM) and determined the therapeutic efficacy of this extract on colon inflammation. METHODS: The effect of BTE on LPS-induced NF-κB signaling and pro-inflammatory gene expression was evaluated by RT-PCR, Western blotting, immunofluorescence and electrophoretic mobility shift assay (EMSA). The in vivo efficacy of BTE was assessed in mice with 3% dextran sulfate sodium (DSS)-induced colitis. The severity of colitis was measured by weight loss, colon length and histologic scores. RESULTS: LPS-induced IL-12p40, IL-23p19, IL-6 and IL-1ß mRNA expressions were inhibited by BTE. LPS-induced IκBα phosphorylation/degradation and nuclear translocation of NF-κB/p65 were blocked by BTE. BTE treatment blocked LPS-induced DNA-binding activity of NF-κB. BTE-fed, DSS-exposed mice showed the less weight loss, longer colon length and lower histologic score compared to control diet-fed, DSS-exposed mice. DSS-induced IκBα phosphorylation/degradation and phosphorylation of NF-κB/p65 were blocked by BTE. An increase of cleaved caspase-3 and poly (ADP-ribose) polymerase (PARP) in DSS-exposed mice was blocked by BTE. CONCLUSIONS: These results indicate that BTE attenuates colon inflammation through the blockage of NF-κB signaling and apoptosis in DSS-induced experimental colitis model.

Lysophosphatidic acid promotes cell invasion by up-regulating the urokinase-type plasminogen activator receptor in human gastric cancer cells.

There is a strong correlation between the overexpression of urokinase-type plasminogen activator receptor (uPAR) and gastric cancer invasion. This study examined the effect of phospholipid lysophosphatidic acid (LPA) on uPAR expression in human gastric cancer AGS cells and the underlying signal transduction pathways. Treating human gastric AGS cells with LPA induced the expression of uPAR mRNA and promoter activity in both a time- and dose-dependent manner. Small interfering RNA targeting for LPA receptors, dominant negative Rho-family GTPase (RhoA, Rac1, and Cdc42) and an expression vector encoding a mutated c-jun (TAM67) partially blocked the LPA-induced uPAR expression. Site-directed mutagenesis and electrophoretic mobility shift studies showed that the transcription factors activation protein-1 (AP-1) and nuclear factor (NF)-kappaB are essential for the LPA-induced uPAR transcription. In addition, AGS cells treated with LPA showed enhanced invasion, which was partially abrogated by the uPAR-neutralizing antibodies and inhibitors of Rho kinase, JNK, and NF-kappaB. This suggests that LPA induces uPAR expression through the LPA receptors, Rho-family GTPase, JNK, AP-1 and NF-kappaB signaling pathways, which in turn stimulates the cell invasiveness of human gastric cancer AGS cells.

Gastroprotective Effects of Glutinous Rice Extract against Ethanol-, Indomethacin-, and Stress-induced Ulcers in Rats.

This study was designed to evaluate the efficacy of an orally administered aqueous extract of glutinous rice (GRE) to protect against acute gastric mucosal lesions induced by ethanol, indomethacin, and water immersion restraint stress in rats and to characterize the active substances responsible for the protection. GRE was shown to dose-dependently prevent the gastric lesions induced by the above ulcerogenic treatments at doses of 30 to 300 mg/kg. GRE treatment increased the gastric mucin content and partially blocked the ethanol-induced depletion of the gastric mucus layer. Also, it increased the nonprotein sulfhydryl concentration in the gastric mucosa. The gastroprotective action of GRE was markedly enhanced by co-treatment with 4-8 mg/kg tea extracts. The activity of GRE was completely lost by heat treatment at 80℃ for 3 min or treatment with 0.01% pepsin at 37℃ for 1 h. Protein extraction studies indicated that prolamins are involved in the gastroprotective activity of GRE. Our results suggest that glutinous rice proteins are useful for the prevention and treatment of gastritis and peptic ulcer.

Alterations in the activity and expression of endothelial NO synthase in aged human endothelial cells.

This study was to investigate factors underlying the age-related decrease in NO production in vascular endothelial cells. The age-related changes in NO production, the activity and expression level of eNOS, and eNOS binding proteins, were studied in HUVECs. NO production in HUVECs significantly decreased in an age-dependent manner. The potentiation of NO production by L-Arg was significantly suppressed by L-NIO (eNOS-specific inhibitor) in young HUVECs and was suppressed by 1400W (iNOS-specific inhibitor) in aged HUVECs. The aged HUVECs had lower eNOS protein levels than young cells. eNOS phosphorylation at Ser-1177 (active) decreased gradually from PDL 23 through 40, and eNOS phosphorylation at Thr-495 (inactive) increased in aged cells. Changes of intracellular eNOS binding proteins, such as caveolin-1, pAkt, and Hsp90, as well as interaction between eNOS and eNOS binding proteins, indicated decreasing enzyme activity in aged HUVECs. Aging might decrease the activity as well as expression level of eNOS in HUVECs. And the decrease in eNOS activity probably implicated to the alterations in the regulatory binding proteins. For further study, it needs to be confirmed that the age-related change in the intracellular distribution of eNOS and the relative contribution of eNOS and iNOS on vascular dysfunction in aged endothelial cells.

Redox regulation of the tumor suppressor PTEN by glutathione.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expressed in Saccharomyces cerevisiae was reversibly oxidized by hydrogen peroxide and reduced by cellular reductants. Reduction of hPTEN was delayed in each of S. cerevisiae gsh1Delta and gsh2Delta mutants. Expression of gamma-glutamylcysteine synthetase Gsh1 in the gsh1Delta mutant rescued regeneration rate of hPTEN. Oxidized hPTEN was reduced by glutathione in a concentration- and time-dependent manner. Glutathionylated PTEN was detected. Incubation of 293T cells with BSO and knockdown expression of GCLc in HeLa cells by siRNA resulted in the delay of reduction of oxidized PTEN. Also, in HeLa cells transfected with GCLc siRNA, stimulation with epidermal growth factor resulted in the increase of oxidized PTEN and phosphorylation of Akt. These results suggest that the reduction of oxidized hPTEN is mediated by glutathione.

Induction of apoptosis by the licochalcone E in endothelial cells via modulation of NF-kappaB and Bcl-2 Family.

Licochalcones have a variety of biological properties including anti-tumor, anti-parasitic and anti-bacterial activities. Recently, a new retrochalcone (licochalcone E, Lico-E) was isolated from the roots of Glycyrrhiza inflata (Chem. Pharm. Bull., 53, 2005, Yoon et al.) by cytotoxicity-guided fractionation. This study examined whether or not Lico-E-induced endothelial cell death occurs through apoptosis, and investigated molecular mechanisms involved in this process. Lico-E was found to suppress ECV304 cell growth and induce apoptosis. The induction of apoptosis by Lico-E was confirmed by the ladder-patterned DNA fragmentation, the presence of cleaved and condensed nuclear chromatin and the increased number of annexin V-positive cells. Lico-E could effectively inhibit the constitutive NF-kappaB activation, as revealed by the electrophoretic mobility shift assay and NF-kappaB-dependent luciferase reporter study. In addition, the Lico-E treatment caused a change in the Bax/Bcl-2 ratio that favored apoptosis. These results suggest that Lico-E induces endothelial cell apoptosis by modulating NF-kappaB and the Bcl-2 family.

Total peroxyl radical-trapping ability and anti-oxidant vitamins of the umbilical venous plasma and the placenta in pre-eclampsia.

AIM: Our purpose was to investigate lipid peroxide levels, total peroxyl radical-trapping anti-oxidative parameter (TRAP) values, and anti-oxidant vitamin levels in umbilical venous plasma and placental tissues, and to evaluate their roles in the pathophysiology of pre-eclampsia. METHODS: Samples of umbilical venous plasma and placental tissue homogenates were obtained from 23 normal and 18 pre-eclamptic women at between 33 and 40 weeks' gestation. The enzyme-linked immunosorbent assay method was used to assay alpha-tumor necrosis factor (TNF-alpha), and lipid peroxide levels were measured by thiobarbituric acid reaction. The TRAP values were measured using the modified Wayner's method. Ascorbic acid, retinol alpha-tocopherol and gamma-tocopherol were measured by high performance liquid chromatography. RESULTS: Levels of TNF-alpha in placental tissue homogenates of women with pre-eclampsia were significantly higher than those of women with normal pregnancy (21.4 +/- 3.39 v. 10.3 +/- 1.06 pg/mL, P < 0.05). Lipid peroxide levels in umbilical venous plasma and placental tissue homogenates of women with pre-eclampsia were significantly higher than those of women with normal pregnancy (10.3 +/- 1.1 v. 5.85 +/- 0.53, P < 0.01, 5.14 +/- 0.40 v. 3.99 +/- 0.33 nmol/mg protein, P < 0.05, respectively). The TRAP values in umbilical venous plasma and placental tissue homogenates of women with pre-eclampsia were significantly lower than those of women with normal pregnancy (0.39 +/- 0.02 v. 0.45 +/- 0.02, P < 0.05, 0.27 +/- 0.02 v. 0.34 +/- 0.03 mM, P < 0.05, respectively). Ascorbic acid levels in umbilical venous plasma and placental tissue homogenates of women with pre-eclampsia were significantly lower than those of women with normal pregnancy (325.4 +/- 50.4 v. 543 +/- 73.8, P < 0.05, 219.0 +/- 21.0 v. 333.3 +/- 32.6 nmol/mL, P < 0.05, respectively). CONCLUSIONS: The above results suggest that increased oxidative stress in the placenta is involved in the pathophysiology of pre-eclampsia, and ascorbic acid may act as an important preventative factor in the development of pre-eclampsia.

Effect of drinking green tea on age-associated accumulation of Maillard-type fluorescence and carbonyl groups in rat aortic and skin collagen.

Tea catechins and other flavonoids have been shown to potentially protect against chronic cardiovascular diseases such as coronary heart disease and atherosclerosis. In this study, 6-month-old female Sprague-Dawley rats were fed green tea extract (50 mg/100 ml in drinking water) up to the age of 22 months, and the age-associated changes in Maillard-type fluorescence and carbonyl groups in the aortic and skin collagen were compared with those occurring in the water-fed control animals. Collagen-linked Maillard-type fluorescence was found to increase in both the aortic and skin tissues as animals aged. The age-associated increase in the fluorescence in the aortic collagen was remarkably inhibited by the green tea extract treatment, while that occurring in the skin collagen was not significantly inhibited by the treatment. The collagen carbonyl content also increased in both the aortic and skin tissues as animals aged. In contrast with the case of Maillard-type fluorescence, however, the age-associated increase in the carbonyl content was not inhibited by the green tea extract treatment either in the aortic or skin collagen. These results suggest that the inhibition of AGE formation in collagen is an important mechanism for the protective effects of tea catechins against cardiovascular diseases.

SB203580, a P38 MAPK Inhibitor, Blocks in vitro Invasion by Human Gastric SNU-638 Cells.

PURPOSE: The role of P38 mitogen-activated protein kinase (MAPK) in gastric cancer invasion has not yet been determined. In this study, we examined the effects of SB203580, a specific P38 MAPK inhibitor, on the in vitro invasion of gastric cancer and upon the molecules involved in this process. MATERIALS AND METHODS: Human gastric cancer SNU-638 cells were maintained in RPMI 1640 supplemented with 10% FBS. BIOCOAT matrigel invasion chambers were used to examine in vitro invasiveness, zymography for gelatinase activity, CAT assay for uPA promoter activity and Western and Northern blotting to determine protein and mRNA levels, respectively. RESULTS: Treatment of SNU-638 cells with SB203580, a specific P38 MAPK inhibitor, reduced in vitro invasiveness, dose-dependently. SB203580 treatment was found to decrease both mRNA expression and uPA promoter activity in gastric SNU-638 cells. In vitro invasion of SNU-638 cells was partially abrogated by uPA-neutralizing antibodies. The activities of MMPs were not significantly altered by SB203580. CONCLUSION: Our results suggest that P38 MAPK is a potential therapeutic target for inhibiting uPA-dependent gastric tumor invasiveness and metastasis.