Yun-Jung Yoo

In vitro antimicrobial activity of a chitooligosaccharide mixture against Actinobacillus actinomycetemcomitans and Streptococcus mutans

The purpose of this study was to evaluate the in vitro antibacterial activity of a chitooligosaccharide mixture (MW 2000-30000 Da) with a deacetylation degree of 91.5% against two representative oral pathogens, Actinobacillus actinomycetemcomitans and Streptococcus mutans. A 0.1% concentration of the chitooligosaccharides (derived from the exoskeletons of marine crustaceans) was used to estimate antibacterial activity. Approximately 2 logcolony forming units (CFU)/ml of A. actinomycetemcomitans were inactivated by 0.1% chitosan after 30 min, while 120 min exposure inactivated about 4.5 logCFU/ml of this organism. In contrast, the level of inactivation against S. mutans was less than 0.5 logCFU/ml after an exposure of up to 120 min. Electron microscopy showed that the exposure of A. actinomycetemcomitans to the chitooligosaccharides resulted in the disruption of cell membranes and that it could be considered for the treatment of periodontal diseases associated with A. actinomycetemcomitans.

Polymorphism in the CagA EPIYA Motif Impacts Development of Gastric Cancer

ABSTRACT Helicobacter pylori causes diseases ranging from gastritis to peptic ulcer disease to gastric cancer. Geographically, areas with high incidences of H. pylori infection often overlap with areas with high incidences of gastric cancer, which remains one of the leading causes of cancer-related deaths worldwide. Strains of H. pylori that carry the virulence factor cytotoxin-associated gene A (cagA) are much more likely to be associated with the development of gastric cancer. Moreover, particular C-terminal polymorphisms in CagA vary by geography and have been suggested to influence disease development. We conducted a large-scale molecular epidemiologic analysis of South Korean strains and herein report a statistical link between the East Asian CagA EPIYA-ABD genotype and the development of gastric cancer. Characterization of a subset of the Korean isolates showed that all strains from cancer patients expressed and delivered phosphorylatable CagA to host cells, whereas the presence of the cagA gene did not strictly correlate to expression and delivery of CagA in all noncancer strains.

Epidemiological Link between Gastric Disease and Polymorphisms in VacA and CagA

ABSTRACT Gastritis, peptic ulcer disease, and gastric cancer are a few of the diverse disease manifestations that have been shown to be associated with infection by Helicobacter pylori. Why some individuals develop more severe forms of disease remains largely unknown. In this study, 225 South Korean strains were genotyped for vacA and then analyzed to determine if particular genotypes varied across disease state, sex, or cagA allele. Of these strains, 206 strains carried an s1/i1/m1 allele, 11 strains carried an s1/i1/m2 allele, and 8 strains carried an s1/i2/m2 allele. By using Fishers exact test, a statistical association between variations in the cagA and vacA alleles was identified (P = 0.0007), and by using log linear modeling, this variation was shown to affect the severity of disease outcome (P = 0.027). Additionally, we present evidence that variation within the middle region of VacA contributes significantly to the distribution of vacA alleles across gender (P = 0.008) as well as the association with disease outcome (P = 0.011). In this South Korean population, the majority of H. pylori strains carry the vacA s1/i1/m1 allele and the CagA EPIYA-ABD allele. These facts may contribute to the high incidence of gastric maladies, including gastric cancer.

Induction of Osteoclastogenesis and Matrix Metalloproteinase Expression by the Lipooligosaccharide of Treponema denticola

ABSTRACT Alveolar bone destruction is a characteristic feature of periodontitis. Treponema denticola is known to be involved in periodontitis. To elucidate the role of T. denticola in alveolar bone destruction in periodontitis, the effects of lipooligosaccharide (LOS) from T. denticola on osteoclast formation and on expression of osteoclast differentiation factor (ODF) and osteoprotegerin (OPG) mRNAs were examined in a coculture system by using mouse calvaria and bone marrow cells. In addition, the effect of T. denticola LOS on expression of matrix metalloproteinases (MMPs), which are involved in bone resorption, was estimated in mouse calvaria-derived osteoblastic cells. When the mouse calvaria and bone marrow cells were challenged with LOS (0.1 to 10 μg/ml) for 4 days, the number of tartrate-resistant acid phosphatase-positive multinucleated cells increased in a dose-dependent manner. The expression of ODF mRNA increased, while OPG mRNA expression decreased. Polymyxin B changed the effect of LOS (10 μg/ml) on ODF and OPG mRNA expression to the control level. LOS (10 μg/ml) stimulated prostaglandin E2 (PGE2) production in the cocultures. Adding indomethacin, an inhibitor of prostaglandin synthesis, resulted in a reduction in the number of osteoclasts induced by LOS and eliminated the effect of T. denticola LOS on ODF and OPG mRNA expression. T. denticola LOS increased the levels of mRNAs encoding MMP-3, -8, -9, -10, -13, and -14. Expression of one of these mRNAs, MMP-9 mRNA, was significantly induced by T. denticola LOS. These findings suggest that LOS from T. denticola stimulates osteoclastogenesis and MMP expression. Up-regulation of ODF and down-regulation of OPG by a PGE2-dependent mechanism were involved in the osteoclastogenesis induced by T. denticola LOS.

The Effect of Metformin on Alveolar Bone in Ligature-Induced Periodontitis in Rats: A Pilot Study

BACKGROUND The use of metformin, an antidiabetic agent, is associated with a reduced risk of fractures in patients with diabetes, suggesting that metformin exerts a beneficial effect on bone tissues. The objective of this study was to assess the effect of metformin on alveolar bone loss in ligature-induced periodontitis and osteoblast, osteoclast, and adipocyte differentiation. METHODS Periodontitis was induced by a ligature around the mandibular first molar of each rat. The rats were divided into two groups: 1) rats with ligature receiving a vehicle (n = 5), and 2) rats with ligature receiving metformin (n = 5). On day 10, after the induction of periodontitis, the alveolar bone volume between the first and second molar was determined via microcomputed tomography. The effect of metformin on osteoblast, osteoclast, and adipocyte differentiation was assessed using MC3T3-E1, cocultures of mouse bone marrow cells and calvaria-derived osteoblasts, and 3T3-L1/C3H10T1/2 cells, respectively. Osteoblast, osteoclast, and adipocyte differentiation was estimated by the degree of mineralization, the formation of tartrate-resistant acid phosphatase-positive multinucleated cells, and the accumulation of triglycerides, respectively. RESULTS In ligature-induced periodontitis, the metformin treatment of rats induced a significant reduction in alveolar bone loss compared to vehicle-treated rats. With regard to osteoblast differentiation, metformin augmented the mineralization of MC3T3-E1 cells approximately two-fold over the non-treated cells. However, metformin was shown to exert no effects on osteoclast formation induced by 1,25-dihydroxyvitamin D(3), lipopolysaccharide, and prostaglandin E(2). Moreover, metformin exerted no effect on adipocyte differentiation. CONCLUSION Our findings suggest that metformin may exert a beneficial effect on alveolar bone in periodontitis by increasing osteoblast differentiation.

Licochalcone E has an antidiabetic effect

Licochalcone E (lico E) is a retrochalcone isolated from the root of Glycyrrhiza inflata. Retrochalcone compounds evidence a variety of pharmacological profiles, including anticancer, antiparasitic, antibacterial, antioxidative and superoxide-scavenging properties. In this study, we evaluated the biological effects of lico E on adipocyte differentiation in vitro and obesity-related diabetes in vivo. We employed 3T3-L1 preadipocyte and C3H10T1/2 stem cells for in vitro adipocyte differentiation study and diet-induced diabetic mice for in vivo study. The presence of lico E during adipogenesis induced adipocyte differentiation to a significant degree, particularly at the early induction stage. Licochalcone E evidenced weak, but significant, peroxisome proliferator-activated receptor gamma (PPARγ) ligand-binding activity. Two weeks of lico E treatment lowered blood glucose levels and serum triglyceride levels in the diabetic mice. Additionally, treatment with lico E resulted in marked reductions in adipocyte size and increases in the mRNA expression levels of PPARγ in white adipose tissue (WAT). Licochalcone E was also shown to significantly stimulate Akt signaling in epididymal WAT. In conclusion, lico E increases the levels of PPARγ expression, at least in part, via the stimulation of Akt signals and functions as a PPARγ partial agonist, and this increased PPARγ expression enhances adipocyte differentiation and increases the population of small adipocytes, resulting in improvements in hyperglycemia and hyperlipidemia under diabetic conditions.

The inhibitory effect of alendronate and taurine on osteoclast differentiation mediated by Porphyromonas gingivalis sonicates in vitro.

The objective of this study was to investigate the ability of alendronate and taurine in inhibiting in vitro osteoclast differentiation induced by bacteria. Whole cell sonicates of Porphyromonas gingivalis were used as an osteoclast-stimulating factor in a mouse coculture system and differentiated osteoclasts were confirmed by tartrate-resistant acid phosphatase (TRAP) staining. Alendronate at the concentrations of 10(-7) M, 10(-6) M, and 10(-5) M and taurine at the concentrations of 4 mM, 8 mM, and 12 mM were used. The cytotoxic effects of alendronate and taurine were examined using methylthiazole-tetrazolium bromide (MTT) assay. The amounts of interleukin-6 (IL-6) in culture supernatants were also measured using ELISA. The sonicates of P. gingivalis at the concentration of 0.01-0.1 microg/ml significantly stimulated the formation of osteoclasts (p < 0.05). Alendronate (10(-5) M) and taurine (12 mM) significantly suppressed the sonicate-stimulated osteoclast formation. In MTT assay, no cytotoxic effects were evident in all concentrations of alendronate and taurine. Alendronate and taurine did not affect the amount of IL-6 induced by P. gingivalis sonicates. These data indicate that alendronate and taurine have inhibitory effects on bacteria-stimulated osteoclast formation in vitro and that this inhibitory mechanism is not related to the blocking of IL-6 production.

Induction of IL-8 in periodontal ligament cells by H(2)O (2).

Periodontitis is an inflammatory disease caused by bacteria. In periodontitis, reactive oxygen species (ROS) are released from inflammatory cells in response to bacteria. Interleukin (IL)-8 is one of pro-inflammatory cytokines. To investigate the role of ROS in pathogenesis of periodontitis, we estimated the effect of H2O2, one of ROS, on the expression of IL-8 in human periodontal ligament (PDL) cells. PDL cells were treated with H2O2. IL-8 expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38) and c-jun NH2-terminal kinase (JNK) was estimated by Western blotting. Treatment with H2O2 at concentration of up to 250 μM increased IL-8 mRNA expression and production in a concentration-dependent manner. However, treatment with 500 μM H2O2 did not increase IL-8 production. Catalase, an inhibitor of H2O2, down-regulated the production of IL-8 induced by H2O2. H2O2 increased the phosphorylation of ERK, p38, and JNK. Pretreatment with PD98059 (ERK inhibitor), SB203580 (p38 inhibitor), or SP600125 (JNK inhibitor) decreased the IL-8 production induced by H2O2. These results indicate that H2O2 acts as an inducer of IL-8 secretion via activation of ERK, p38, and JNK in PDL cells. H2O2 deposited in periodontal tissue during inflammation against bacteria may accelerate tissue destruction via induction of IL-8 in PDL cells.

Wogonin ameliorates hyperglycemia and dyslipidemia via PPARα activation in db/db mice

BACKGROUND & AIMS Wogonin is a flavonoid extracted from the root of Scutellaria baicalensis Gerogi. We evaluated the therapeutic effects of wogonin using db/db mice. METHODS Mice received wogonin or vehicle by oral gavage for 2 weeks. Blood glucose, insulin, and cholesterol levels were measured, and liver morphology was observed with histopathological analysis. The mRNA expression levels of PPARα, PPARγ, and adiponectin in the liver and white adipose tissue (WAT) were determined by real-time PCR. Immunoblotting for AMPK and PPARγ, and adipocyte differentiation were investigated in vitro using 3T3-L1 cells. A luciferase assay was used to measure PPARα and PPARγ binding activity. RESULTS The wogonin group showed decreased weight gain without a change in food intake and improved glucose tolerance. Serum insulin and cholesterol levels in the wogonin group were significantly decreased compared to those in the control group. The wogonin group also showed less accumulation of lipid droplets and glycogen in the liver. PPARα and PPARγ expression levels in the liver and WAT and adiponectin expression level in WAT in the wogonin group were higher than those in the control group. In 3T3-L1 cells, wogonin was shown to stimulate AMPK activation in a dose-dependent manner. The presence of wogonin did not affect adipocyte differentiation or PPARγ protein level during adipogenesis. Notably, wogonin enhanced PPARα but not PPARγ transactivation. CONCLUSIONS These indicate that wogonin may have beneficial effects on glucose and lipid metabolism related to enhanced PPARα and adiponectin expression via AMPK activation. Importantly, wogonin did not cause deleterious effects, such as weight gain and fatty liver. Wogonin might be a useful therapeutic agent to treat type 2 diabetes.

Genetic analysis of Helicobacter pylori clinical isolates suggests resistance to metronidazole can occur without the loss of functional rdxA.

Resistance to metronidazole (MTZ) in Helicobacter pylori is associated with mutations in rdxA, encoding an oxygen-insensitive NADPH nitroreductase, and mutations in frxA, encoding a NAD(P)H-flavin oxidoreductase. Despite this association, the strict correlation of MTZ resistance with mutations in rdxA or frxA is still controversial. In this study, rdxA allelic replacement was used to distinguish resistance-associated nucleotide mutations from the natural genetic diversity of H. pylori. Replacement with truncated rdxA resulted in MTZ resistance, whereas replacement with missense-mutated rdxA from resistant clinical isolates failed to yield MTZ resistance. Thus, although truncation of rdxA confers MTZ resistance in G27 H. pylori, MTZ resistance found in other clinical isolates is not due to the identified amino-acid substitutions. Three of our MTZ-resistant clinical isolates expressed functional rdxA and two of these also encoded full-length frxA. Therefore, MTZ resistance can arise in H. pylori possessing functional rdxA, suggesting that other factors are involved in MTZ resistance.