Hee-Don Choi

Enzymatic modification enhances the protective activity of citrus flavonoids against alcohol-induced liver disease.

Alcoholic liver disease (ALD) can be developed by a prolonged or large intake of alcohol in a short period of time. ALD is considered as a leading cause for a liver injury in modern dietary life. This study was aimed to investigate the effects of orally administrated citrus flavonoids (CFs) and their enzymatically modified ones (EM-CFs) to prevent ALD. Hesperidin and narirutin were extracted from peels of Citrus unshiu by ultra-sonication and purified further. These CFs were modified enzymatically through glycosylation and de-rhamnosylation by the actions of cyclodextrin glucanotransferase (CGTase) and hesperidinase, respectively. CFs and EM-CFs were fed to ICR mouse along with ethanol for 8 weeks, and changes in lipid contents, lipid peroxidation, GSH, antioxidant enzymes activity and proinflammatory cytokines in hepatic tissues were observed. Administration of CFs and EM-CFs along with alcohol significantly suppressed increases in prognostic parameters of a hepatocellular injury. Especially, EM-CFs fed groups maintained malondialdehyde, GSH levels and catalase activity in hepatic tissues close to those of the normal diet fed group. Abrupt increases in proinflammatory cytokines such as IκB-α, TNF-α, IL-1β and IL-6 in hepatocytes due to a chronic alcohol uptake were significantly suppressed by co-administration of EM-CFs. These results indicate that although the administration of CFs can alleviate ALD through preventing excessive lipid formation, protecting the antioxidant system and suppressing induction of inflammation in hepatocytes, their effectiveness can be further improved by glycosylation and de-rhamnosylation.

Immunostimulatory effects and characterization of a glycoprotein fraction from rice bran.

Many natural resources obtained from plants have been studied for their utility as host defense potentiators. In the present study, we investigated whether a glycoprotein fraction from rice (Oryza sativa) bran (GFRB) could modulate immune responses such as the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10 in the RAW 264.7 macrophage cell line. GFRB, which contained 65.7% of protein and 7.7% of total sugar, was prepared by treating an aqueous extract of rice bran with 80% (NH4)2SO4 and the extraction yield was 4.9%. GFRB consisted of 5 bands with varying molecular weights by SDS-PAGE and remarkably improved production of NO in RAW 264.7 murine macrophage cells, up to approximately 10-fold compared to the normal control at 100μg/mL concentration. In RAW 264.7 cells treated with 50μg/mL GFRB, released levels of various cytokines such as TNF-α, IL-1β, IL-6, and IL-10 were 2824.4±90.7, 224.5±4.0, 524.3±4.8, and 143.0±9.5pg/mL, respectively, which were higher than the levels in normal controls. Moreover, GFRB exhibited no cytotoxicity. According to the results of region-selective enzyme hydrolysis, the immune responses against GFRB were elicited by the glycans in the GFRB. These results show the potential of GFRB as a functional therapeutic agent with demonstrable immunostimulatory activity.

Oral administration of glucosylceramide ameliorates inflammatory dry-skin condition in chronic oxazolone-induced irritant contact dermatitis in the mouse ear

BACKGROUND Irritant contact dermatitis (ICD) is an inflammatory skin disease triggered by exposure to a chemical that is toxic or irritating to the skin. A major characteristic of chronic ICD is an inflammatory dry-skin condition with associated itching. Although glucosylceramide (GlcCer) is known to improve the skin barrier function, its mechanism of action is unknown. OBJECTIVES Using a mouse model of oxazolone-induced chronic ICD, this study investigated the effects of oral administration of GlcCer on inflammatory dry skin. METHODS Chronic ICD was induced by repeated application of oxazolone in mice. GlcCer was orally administered once daily throughout the elicitation phase. The beneficial efficacy of GlcCer on cutaneous inflammation was evaluated by assessing ear thickness, lymph node weight, histological findings, and mRNA expression of pro-inflammatory cytokines such as IL-1β and IL-6. Additionally, parameters of the itch-associated response, including scratching behavior, water content of the skin, and aquaporin-3 levels in the lesional ear, were measured. RESULTS Oral GlcCer administration significantly suppressed mRNA expression of the pro-inflammatory cytokines IL-1β and IL-6. GlcCer also suppressed ear swelling, lymph node weight gains, and infiltration of leukocytes and mast cells in ICD mice. In oxazolone-induced ICD mice, GlcCer significantly inhibited irritant-related scratching behavior and dehydration of the stratum corneum, and decreased aquaporin-3 expression. CONCLUSIONS Our results indicate that GlcCer suppressed inflammation not only by inhibiting cytokine production but also by repairing the skin barrier function, suggesting a potential beneficial role for GlcCer in the improvement of chronic ICD.

Glucosylceramide attenuates the inflammatory mediator expression in lipopolysaccharide-stimulated RAW264.7 cells ☆,☆☆

The positive effect of glucosylceramide (GlcCer) on skin conditions is well known. Recently, there has been increasing interest in the potential antiinflammatory effects of GlcCer due to its efficacy in relieving atopic skin symptoms. However, the role of GlcCer in inflammation has not been investigated completely. Thus, we hypothesized that GlcCer might exhibit the antiinflammatory effects through the inhibition of nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling. To test this hypothesis, the antiinflammatory effects and signaling mechanisms of GlcCer were investigated in lipopolysaccharide (LPS)-induced RAW 264.7 cells. We report that GlcCer inhibited messenger RNA and protein expression of tissue necrosis factor α and interleukin 1β without cytotoxicity. However, it did not affect interleukin 6 production in LPS-stimulated RAW 264.7 macrophages. Glucosylceramide also suppressed prostaglandin E2 but not nitric oxide production, consistent with its inhibition of cyclooxygenase 2 but not of inducible nitric oxide synthase expression. The molecular mechanism of GlcCer-mediated inhibition of LPS-induced inflammation in RAW 264.7 cells is closely related to suppression of NF-κB p65 subunit nuclear translocation as well as to phosphorylation of extracellular signal-regulated kinase and, in particular, p38 MAPK. In addition, GlcCer did not affect c-Jun N-terminal kinase phosphorylation. In conclusion, GlcCer inhibits LPS-induced inflammation by blocking the nuclear translocation of NF-κB and inhibiting the phosphorylation of extracellular signal-regulated kinase/p38 MAPK pathways in macrophages, suggesting that it might be a promising potential drug candidate for various inflammatory diseases.

Cleavage of the terminal N-acetylglucosamine of egg-white ovalbumin N-glycans significantly reduces IgE production and Th2 cytokine secretion.

Ovalbumin (OA) is one of the most abundant of the glycoprotein allergens, and induces a T-helper type 2 immune response that results in an IgE-mediated hypersensitivity. In this study, the terminal carbohydrates of N-glycans from intact OA were cleaved with the exoglycosidases galactosidase, mannosidase, and N-acetylglucosaminidase to generate degalactosylated-OA, demannosylated-OA, and de-N-acetylglucosaminylated-OA, respectively, in order to evaluate their role in allergenicity. The exoglycosidase digestion procedure did not result in either degradation or contamination of the three deglycosylated sample, and the digestion efficiency was confirmed by comparing the results of glycan analysis of the three exoglycosidase-treated OAs with that of glycans of intact OA. Mice were immunized with either intact or exoglycosidase-treated OAs, and their respective allergic reactions were compared. IgE production in the de-N-acetylglucosaminylated-OA group was reduced to 58.8% of that in the intact OA group. In addition, the production levels of the cytokines interleukin-4 and interleukin-5 were significantly reduced in the de-N-acetylglucosaminylated-OA group to 53.4% and 45.8% of the levels in the intact OA group, respectively. However, there were almost no changes (or only slight reductions) in the degalactosylated-OA and demannosylated-OA groups, respectively. These results indicate that cleavage of the terminal carbohydrate, and particularly N-acetylglucosamine, reduces the allergenicity of OA. This is the first report of the effect of cleavage of the terminal carbohydrate on glycoprotein allergenicity.

Quality characteristics of vacuum-fried snacks prepared from various sweet potato cultivars

The effects of vacuum frying and atmospheric frying on the physicochemical properties and quality characteristics of the deep-fat-fried snacks were compared in manufacturing snacks using general, yellow-fleshed, and purple-fleshed sweet potatoes. Regarding the moisture and lipid content of snacks, vacuum-fried snacks showed about 50% lower values compared to atmospheric-fried snacks, while for the colors, vacuum-fried snacks showed higher L and b values and a slightly lower a value, with almost no difference in the texture, compared to atmospheric-fried snacks. The total carotenoid and anthocyanin contents of snacks were decreased greatly compared to fresh sweet potatoes, and was considerably higher in vacuum-fried snacks compared to atmospheric-fried snacks. For the sensory evaluation of snacks, the acceptability for color and flavor was higher in the vacuum-fried snacks, while the acceptability for texture was higher in atmospheric-fried snacks due to a higher degree of crispiness. In conclusion, it is considered that the vacuum frying in manufacturing sweet potato snacks, compared to the atmospheric frying, is the appropriate deep-fat frying method for modern people who take excessive fats and oils from foods and are highly interested in health and high quality products.

Changes in the antigenicity and allergenicity of ovalbumin in chicken egg white by N-acetylglucosaminidase

Ovalbumin (OVA), an (hen) egg allergen, is one of the most abundant glycoprotein allergens associated with IgE-mediated hypersensitivity through the T-helper type 2 immune response. The effect of deglycosylation of the N-terminal glycan in OVA on allergenicity and antigenicity after N-acetylglucosaminidase treatment was studied. N-acetylglucosaminidase-treated OVA (N-OVA) evaluated using an enzyme-linked immunosorbent assay, respectively. N-OVA significantly (p<0.05) OVA-specific IgE and histamine levels. In addition, N-OVA decreased the antigenicity of OVA 1000-fold. These results suggest that the degree of allergenicity and antigenicity reduced with deglycosylation of N-terminal glycan in OVA.

Immunomodulatory Effects of Nontoxic Glycoprotein Fraction Isolated from Rice Bran

Rice bran, a by-product of brown rice milling, is a rich source of dietary fiber and protein, and its usage as a functional food is expected to increase. In this study, immunomodulatory effects of glycoprotein obtained from rice bran were studied in normal mice and mouse models of cyclophosphamide-induced immunosuppression. We prepared glycoprotein from rice bran by using ammonium precipitation and anion chromatography techniques. Different doses of glycoprotein from rice bran (10, 25, and 50 mg/kg) were administered orally for 28 days. On day 21, cyclophosphamide at a dose of 100 mg/kg was administered intraperitoneally. Glycoprotein from rice bran showed a significant dose-dependent restoration of the spleen index and white blood cell count in the immunocompromised mice. Glycoprotein from rice bran affected the immunomodulatory function by inducing the proliferation of splenic lymphocytes, which produce potential T and B cells. Moreover, it prevented cyclophosphamide-induced damage of Th1-type immunomodulatory function through enhanced secretion of Th1-type cytokines (interferon-γ and interleukin-12). These results indicate that glycoprotein from rice bran significantly recovered cyclophosphamide-induced immunosuppression. Based on these data, it was concluded that glycoprotein from rice bran is a potent immunomodulator and can be developed to recover the immunity of immunocompromised individuals.

Immuno-enhancing Effect of Seed Extracts on a RAW 264.7 Macrophage Cell Line

In this study, the immuno-enhancing activity of seed extracts were studied on the macrophage cell lines. We examined the effect of nine seed extracts on nitric oxide (NO) production in RAW 264.7 cells and selected four highly-effective seed candidates (Fagopyrum esculentum, Taraxacum platycarpum, Impatiens balsamina, Helianthus annuus) for further immune-related studies. The effects of the four seed extracts on the production of immune-related cytokines in the RAW 264.7 macrophage cell line and proliferation of Molt-4 as a T cell line were investigated. The secretion of NO from the RAW 264.7 cells was increased up to 39 by adding the seed extracts (25 ) compared to the control. Also, the secretion of tumor necrosis factor-alpha (TNF-) was also increased up to 32 times by adding the seed extracts (25 ). Secretion of cytokines such as interleukin-1 beta (IL-), interleukin-6 (IL-6), and interleukin-10 (IL-10) was also increased and induced the proliferation of T cells compared to the control. In conclusion, these results suggest that four seed extracts provide beneficial immuno-enhancing effects for human health.

Physicochemical Properties of Taro Flours with Different Drying, Roasting and Steaming Conditions

To evaluate the processing adaptability of taro flours, the physicochemical properties of taro flour with different drying, roasting and steaming conditions were investigated. The moisture content and total dietary fiber were decreased as temperature increased with hot-air drying. Freeze-dried taro flours showed the highest vitamin C contents. Taro flours made by freeze-drying and hot-air drying showed significantly higher total dietary fiber content than those with roasting and steaming process. Steamed taro flours had the highest water absorption index, while hot-air dried and freeze dried taro flours had the highest water solubility index. No differences were displayed in the differential scanning calorimetry (DSC) thermal characteristics among hot-air dried and freeze dried taro flours. Roasted taro displayed decreased onset temperature and peak temperature as roasting temperature increased. Using a rapid visco-analyzer, the peak viscosity, through viscosity, and final viscosity of dried and steamed taro flours were higher than roasted taro flours, whereas the set back value, which is a prediction of retrogradation, decreased with steaming processing. From those results, it could be concluded that hotair dried taro flours, which have high gelatinization viscosity, are beneficial in imparting viscosity to dough products and hot-air drying after steaming taro flours, which retard retrogradation, is good for porridge and flake base products.