Fucoidan reduces oxidative stress by regulating the gene expression of HO­1 and SOD­1 through the Nrf2/ERK signaling pathway in HaCaT cells.

Fucoidan, a sulfated polysaccharide, is found in edible brown algae. In the present study, the molecular mechanisms of fucoidan against mild oxidative stress in human keratinocytes were investigated. The current study indicated that fucoidan significantly augmented the antioxidants heme oxygenase­1 (HO­1) and superoxide dismutase­1 (SOD­1) via the upregulation of nuclear factor erythroid 2­related factor 2 (Nrf2) and markedly reduced the cytoplasmic stability of kelch­like ECH­associated protein 1. The upregulation of HO­1 and SOD­1 detected in the fucoidan­treated cells may be responsible for the increased resistance to mild oxidative stress, indicating that fucoidan may augment the activities of antioxidant enzymes via stimulating Nrf2. This is the first report, to the best of our knowledge, to demonstrate that fucoidan attenuates oxidative stress by regulating the gene expression of SOD­1 and HO­1 via the Nrf2/extracellular signal­regulated kinase signaling pathway.

[10]-Gingerol induces mitochondrial apoptosis through activation of MAPK pathway in HCT116 human colon cancer cells.

The present study was designed to investigate the molecular mechanisms of [10]-gingerol activity against HCT116 human colon cancer cells. [10]-Gingerol inhibited the proliferation of HCT116 cells by 50% at a concentration of 30 µM, and this inhibition was dose-dependent accompanied by the morphological changes indicative of apoptosis. Furthermore, flow cytometric analysis showed that [10]-gingerol increased DNA in the sub-G1 phase of the cell cycle, and the extent of apoptosis was confirmed by Annexin V and PI double staining. Analysis of the mechanism of these events indicated that [10]-gingerol-treated cells exhibited an increased ratio of Bax/Bcl-2, resulting in the activation of caspase-9, caspase-3, and poly-ADP-ribose polymerase in a dose-dependent manner, which are hallmarks of apoptosis. Moreover, [10]-gingerol-induced apoptosis was accompanied by phosphorylation of the mitogen-activated protein kinase (MAPKs) family, c-Jun N-terminal kinase (JNK), p38 MAPK (p38), and extracellular signal-regulated kinase (ERK). This is the first report to demonstrate the cytotoxic effect of [10]-gingerol on human colon cancer cells, as well as the first to describe its possible chemotherapeutic potentials.

Triphlorethol-A from Ecklonia cava up-regulates the oxidant sensitive 8-oxoguanine DNA glycosylase 1.

This study investigated the protective mechanisms of triphlorethol-A, isolated from Ecklonia cava, against oxidative stress-induced DNA base damage, especially 8-oxoguanine (8-oxoG), in Chinese hamster lung fibroblast V79-4 cells. 8-Oxoguanine DNA glycosylase-1 (OGG1) plays an important role in the removal of 8-oxoG during the cellular response to DNA base damage. Triphlorethol-A significantly decreased the levels of 8-oxoG induced by H2O2, and this correlated with increases in OGG1 mRNA and OGG1 protein levels. Furthermore, siOGG1-transfected cell attenuated the protective effect of triphlorethol-A against H2O2 treatment. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor for OGG1, and Nrf2 combines with small Maf proteins in the nucleus to bind to antioxidant response elements (ARE) in the upstream promoter region of the OGG1 gene. Triphlorethol-A restored the expression of nuclear Nrf2, small Maf protein, and the Nrf2-Maf complex, all of which were reduced by oxidative stress. Furthermore, triphlorethol-A increased Nrf2 binding to ARE sequences and the resulting OGG1 promoter activity, both of which were also reduced by oxidative stress. The levels of the phosphorylated forms of Akt kinase, downstream of phosphatidylinositol 3-kinase (PI3K), and Erk, which are regulators of OGG1, were sharply decreased by oxidative stress, but these decreases were prevented by triphlorethol-A. Specific PI3K, Akt, and Erk inhibitors abolished the cytoprotective effects of triphlorethol-A, suggesting that OGG1 induction by triphlorethol-A involves the PI3K/Akt and Erk pathways. Taken together, these data indicate that by activating the DNA repair system, triphlorethol-A exerts protective effects against DNA base damage induced by oxidative stress.

Effect of silica coating on bond strength between a gold alloy and metal bracket bonded with chemically cured resin.

OBJECTIVE: The purpose of this study was to evaluate the effects of three different surface conditioning methods on the shear bond strength (SBS) of metal brackets bonded directly to gold alloy with chemically cured resin. METHODS: Two hundred ten type III gold alloy specimens were randomly divided into six groups according to the combination of three different surface conditioning methods (aluminum oxide sandblasting only, application of a metal primer after aluminum oxide sandblasting, silica coating and silanation) and thermocycling (with thermocycling, without thermocycling). After performing surface conditioning of specimens in accordance with each experimental condition, metal brackets were bonded to all specimens using a chemically cured resin. The SBS was measured at the moment of bracket debonding, and the resin remnants on the specimen surface were evaluated using the adhesive remnant index. RESULTS: Application of metal primer after aluminum oxide sandblasting yielded a higher bond strength than that with aluminum oxide sandblasting alone (p < 0.001), and silica coating and silanation yielded a higher bond strength than that with metal primer after aluminum oxide sandblasting (p < 0.001). There was no significant change in SBS after thermocycling in all groups. CONCLUSIONS: With silica coating and silanation, clinically satisfactory bond strength can be attained when metal brackets are directly bonded to gold alloys using a chemically cured resin.

Effect of 7, 8-dihydroxyflavone on the up-regulation of Nrf2-mediated heme oxygenase-1 expression in hamster lung fibroblasts.

The cytoprotective mechanism of 7, 8-dihydroxyflavone (DHF) against oxidative stress-induced cell damage with respect to its stimulatory effect on the expression of heme oxygenase-1 (HO-1), a potent antioxidant enzyme, was investigated in the present study. Up-regulation of HO-1 expression by DHF was both dose and time dependent in lung fibroblast V79-4 cells. DHF also increased the protein expression level of the transcription factor nuclear factor erythroid-2-related factor 2 (Nrf2), and induced the translocation of Nrf2 from the cytosol into the nucleus, leading to elevated HO-1 expression. The siNrf2 RNA-transfection attenuated HO-1 expression induced by DHF treatment. In addition, DHF induced the activation of extracellular signal-regulated kinase (ERK), while U0126 (a specific pharmacological inhibitor of ERK kinase) abrogated DHF-activated Nrf2 and HO-1 expression. This suggests that DHF increased the levels of Nrf2 and HO-1 via ERK-dependent pathways. Furthermore, DHF significantly prevented the reduction of cell viability in response to oxidative stress; however, U0126 attenuated the protective effect of DHF. Taken together, these results demonstrate that DHF protected cells from oxidative stress via the activation of an ERK/Nrf2/HO-1 signaling pathway.

7,8-Dihydroxyflavone protects human keratinocytes against oxidative stress-induced cell damage via the ERK and PI3K/Akt-mediated Nrf2/HO-1 signaling pathways.

This study investigated the effect of 7,8-dihydroxyflavone (DHF) on the expression and activity of heme oxygenase-1 (HO-1), an enzyme with potent antioxidant properties, as well as the molecular mechanisms involved. DHF markedly upregulated HO-1 mRNA and protein expression in human keratinocytes (HaCaT cells), resulting in increased HO-1 activity. DHF also increased the protein level of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates HO-1 expression by binding to the antioxidant response element (ARE) within the HO-1 gene promoter, in a time-dependent manner. Moreover, DHF decreased the expression of Kelch-like ECH-associated protein 1, a repressor of Nrf2 activity, and induced the translocation of Nrf2 from the cytosol into the nucleus, thereby allowing its association with the ARE site. DHF activated extracellular-regulated kinase (ERK) and protein kinase B (PKB, Akt) in keratinocytes, while the ERK and Akt inhibitors attenuated DHF-enhanced Nrf2 and HO-1 expression. DHF also protected the keratinocytes against hydrogen peroxide- and ultraviolet B-induced oxidative damage, while HO-1, ERK and Akt inhibitors markedly suppressed DHF-mediated cytoprotection. Taken together, the results suggested that DHF activates ERK- and Akt-Nrf2 signaling cascades in HaCaT cells, leading to the upregulation of HO-1 and cytoprotection against oxidative stress.

The green algae Ulva fasciata Delile extract induces apoptotic cell death in human colon cancer cells.

This study investigated the mechanisms underlying the cytotoxicity of the green algae Ulva fasciata Delile. U. fasciata extract (UFE) inhibited the growth of HCT 116 human colon cancer cells by 50% at a concentration of 200 µg/ml. In addition, UFE stimulated the production of intracellular reactive oxygen species, an effect that was abolished by pretreatment with N-acetyl cysteine, which also inhibited the cytotoxic effects of UFE. UFE also induced morphological changes indicative of apoptosis, such as the formation of apoptotic bodies, DNA fragmentation, an increase in the population of apoptotic sub-G(1) phase cells, and mitochondrial membrane depolarization. Concomitant activation of the mitochondria-dependent apoptotic pathway occurred via modulation of Bax and Bcl-2 expression, resulting in disruption of the mitochondrial membrane potential and activation of caspase-9 and caspase-3. This is the first report to demonstrate the cytotoxic effect of U. fasciata on human colon cancer cells and to provide a possible mechanism for this activity.