Koichiro Irie

Involvement of toll-like receptor 2 and 4 in association between dyslipidemia and osteoclast differentiation in apolipoprotein E deficient rat periodontium

BackgroundDyslipidemia increases circulating levels of oxidized low-density lipoprotein (OxLDL) and this may induce alveolar bone loss through toll-like receptor (TLR) 2 and 4. The purpose of this study was to investigate the effects of dyslipidemia on osteoclast differentiation associated with TLR2 and TLR4 in periodontal tissues using a rat dyslipidemia (apolipoprotein E deficient) model.MethodsLevels of plasma OxLDL, and the cholesterol and phospholipid profiles in plasma lipoproteins were compared between apolipoprotein E-deficient rats (16-week-old males) and wild-type (control) rats. In the periodontal tissue, we evaluated the changes in TLR2, TLR4, receptor activator of nuclear factor kappa B ligand (RANKL) and tartrate resistant acid phosphatase (TRAP) expression.ResultsApolipoprotein E-deficient rats showed higher plasma levels of OxLDL than control rats (p<0.05), with higher plasma levels of total cholesterol (p<0.05) and LDL-cholesterol (p<0.05) and lower plasma levels of high-density lipoprotein cholesterol (p<0.05). Their periodontal tissue also exhibited a higher ratio of RANKL-positive cells and a higher number of TRAP-positive osteoclasts than control rats (p<0.05). Furthermore, periodontal gene expression of TLR2, TLR4 and RANKL was higher in apolipoprotein E-deficient rats than in control rats (p<0.05).ConclusionThese findings underscore the important role for TLR2 and TLR4 in mediating the osteoclast differentiation on alveolar bone response to dyslipidemia.

Effects of Ethanol Consumption on Periodontal Inflammation in Rats

Studies suggest a correlation between ethanol consumption and periodontal disease. We hypothesized that elevated levels of blood reactive oxygen species following ethanol consumption may increase inflammation in periodontal tissue. Rats were divided into 4 groups (6–7 rats/group). Two groups were fed an ethanol-containing liquid diet, and 2 groups were fed a pair-fed control diet. In one of each dietary group, periodontitis was ligature-induced, while the other group was left unligated. Chronic ethanol feeding alone decreased the ratio of reduced/oxidized glutathione and increased 8-hydroxydeoxy-guanosine and tumor necrosis factor (TNF)-α levels in the gingiva. Blood hydroperoxides were also increased. In ligature-induced periodontitis lesions, ethanol feeding enhanced polymorpho-nuclear leukocyte infiltration and TNF-α expression. The results suggest that chronic alcohol consumption increased periodontal inflammation, oxidative damage, and TNF-α production and had an additive effect on polymorphonuclear leukocyte infiltration and gingival oxidative damage, increasing the severity of periodontal inflammation in the ligature model.

Effects of vitamin C intake on gingival oxidative stress in rat periodontitis.

Increased levels of oxidative stress due to excessive production of reactive oxygen species are involved in the pathogenesis of periodontitis. Studies suggest a negative association between plasma vitamin C level and the severity of periodontitis. We hypothesized that increases in plasma vitamin C levels after vitamin C intake might clinically reduce gingival oxidative stress in a rat periodontitis model. A ligature was placed around rat mandibular molars for 4 weeks to induce periodontitis, and the rats were then given drinking water with or without 1 g/L vitamin C for 2 weeks after the ligature was removed. The periodontitis-induced rats showed a 149% increase in 8-hydroxydeoxyguanosine level and a 40% decrease in reduced:oxidized glutathione ratio in gingival tissue. Vitamin C intake induced a 175% increase in plasma vitamin C level, resulting in an improvement in the gingival 8-hydroxydeoxyguanosine level (decreased) and in the reduced:oxidized glutathione ratio (increased). Furthermore, in ligature-induced periodontitis lesions, gene expression encoding inflammation, including interleukin-1 alpha and interleukin-1 beta, was more than twofold down-regulated by vitamin C intake. The results suggest that systemic administration of vitamin C could be clinically beneficial in improving periodontitis-induced oxidative stress by down-regulating inflammatory gene expression.

Sex differences in gingivitis relate to interaction of oral health behaviors in young people

BACKGROUND Although many epidemiologic surveys have shown that gingivitis is more prevalent in males than in females, few studies have clearly explained what causes this difference. The objective of the present study is to explain the sex difference in gingivitis based on the interaction between oral health behaviors and related factors, such as knowledge, attitude, and lifestyle, in young people. METHODS The study was comprised of 838 subjects (440 males and 398 females), aged 18 and 19 years. Gingivitis was assessed by the percentage of bleeding on probing (%BOP). Additional information was collected regarding oral hygiene status, oral health behaviors, and related factors. Structural equation modeling was used to test pathways from these factors to %BOP. Multiple-group modeling was also conducted to test for sex differences. RESULTS Females had greater knowledge, a more positive attitude, a healthier lifestyle, and higher level of oral health behaviors than males. There were significant differences in the paths (i.e., from lifestyle, knowledge, and attitude to %BOP) through oral health behaviors and oral health status. CONCLUSIONS Sex-based differences in gingivitis in young people can be explained by oral health behaviors and hygiene status, which are influenced by lifestyle, knowledge, and attitude. To prevent gingivitis, different approaches to males and females may be useful.

Supplementation of green tea catechins in dentifrices suppresses gingival oxidative stress and periodontal inflammation

OBJECTIVE this study examined the effects of a dentifrice containing green tea catechins on gingival oxidative stress and periodontal inflammation using a rat model. DESIGN twenty-four male Wister rats were randomly divided into four groups. The first group (Control group) received no treatment for 8 weeks. Periodontal inflammation was induced in the second group for 8 weeks. Periodontal inflammation was induced in the last two groups for 8 weeks and dentifrices with or without green tea catechins were topically applied to the gingival sulcus daily for 4 weeks prior to the end of the experimental period. RESULTS rats that had experimental periodontal inflammation showed apical migration of the junctional epithelium, alveolar bone loss and inflammatory cell infiltration in the connective tissue subjacent to the junctional epithelium at 8 weeks, whilst the control group showed no pathologic changes. Topical application of a green tea catechin-containing dentifrice reduced inflammatory cell infiltration in the periodontal lesions to a greater degree than the control dentifrice at 8 weeks. The gingiva in which green tea catechin-containing dentifrice was applied also showed a lower level of expression of hexanoyl-lysine (a marker of lipid peroxidation), nitrotyrosine (a marker of oxidative protein damage), and tumour necrosis factor-α (an indicator of pro-inflammatory cytokines) at 8 weeks compared to gingiva in which the control dentifrice was applied. CONCLUSIONS adding green tea catechins to a dentifrice may contribute to prevention of periodontal inflammation by decreasing gingival oxidative stress and expression of pro-inflammatory cytokines.

Preventive effects of a cocoa-enriched diet on gingival oxidative stress in experimental periodontitis.

BACKGROUND Oxidative stress affects the progression of periodontitis. Cocoa is a rich source of flavonoids with antioxidant properties, which could suppress gingival oxidative stress in periodontal lesions. The purpose of the present study was to investigate the effects of a cocoa-enriched diet on gingival oxidative stress in a rat-periodontitis model. METHODS In this 4-week study, rats were divided into three groups (n = 8/group): a control group (fed a regular diet) and two periodontitis groups (fed a regular diet or cocoa-enriched diet [10% of food intake]). Periodontitis was induced by ligature placement around the mandibular first molars. Serum levels for reactive oxygen metabolites were measured at baseline and 2 and 4 weeks. At 4 weeks, the levels of 8-hydroxydeoxyguanosine and reduced/oxidized glutathione ratio were determined to evaluate gingival oxidative damage and antioxidant status, respectively. RESULTS Rats with experimental periodontitis that were fed a regular diet showed an increase in the level of serum reactive oxygen metabolites in a time-dependent manner. These rats also had an increased 8-hydroxydeoxyguanosine level and decreased reduced/oxidized glutathione ratio in the gingival tissue, inducing alveolar bone loss and polymorphonuclear leukocyte infiltration. Although experimental periodontitis was induced in the rats fed a cocoa-enriched diet, they did not show impairments in serum reactive oxygen metabolite level and gingival levels for 8-hydroxydeoxyguanosine and reduced/oxidized glutathione ratio. Alveolar bone loss and polymorphonuclear leukocyte infiltration after ligature placement were also inhibited by cocoa intake. CONCLUSION Consuming a cocoa-enriched diet could diminish periodontitis-induced oxidative stress, which, in turn, might suppress the progression of periodontitis.

Experimental Periodontitis Induces Gene Expression of Proinflammatory Cytokines in Liver and White Adipose Tissues in Obesity

BACKGROUND Recent studies indicated that periodontitis induces systemic low-grade inflammation. The increase in systemic low-grade inflammation induced by periodontitis may alter the effects of obesity on the production of inflammatory molecules, including C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor-alpha (TNF-alpha), in the liver and white adipose tissue (WAT). The purpose of the present study is to investigate the effects of periodontitis on the expression of proinflammatory cytokines in the liver and WAT in obese Zucker rats. METHODS Obese Zucker rats and their lean litter mates were divided into four groups of six rats each: lean Zucker rats without periodontitis (control group), lean Zucker rats with periodontitis (periodontitis group), obese Zucker rats without periodontitis (obesity group), and obese Zucker rats with periodontitis (combination group). Periodontitis was ligature induced for 4 weeks in the periodontitis and combination groups, whereas the other groups were left unligated. RESULTS At 4 weeks, the gene expression for CRP, IL-6, and TNF-alpha in the liver and CRP and IL-6 in the WAT of combination groups was significantly higher than in each of the three groups. Serum TNF-alpha in the periodontitis and obesity groups was significantly higher than in the control group. Serum CRP and TNF-alpha in the combination group was significantly higher than in each of the three groups. CONCLUSION Systemic low-grade inflammation after experimental periodontitis was associated with increased gene expression for hepatic levels of TNF-alpha and CRP and adipose tissue levels of IL-6 and CRP in the obese-rat model.

Vitamin C intake attenuates the degree of experimental atherosclerosis induced by periodontitis in the rat by decreasing oxidative stress.

OBJECTIVE Periodontitis has been causally linked to cardiovascular disease, which is mediated through the oxidative stress induced by periodontitis. Since vitamin C has been suggested to limit oxidative damage, we hypothesized that vitamin C intake may reduce endothelial oxidative stress induced by periodontitis in the aorta. The aim of this study was to investigate the effects of vitamin C intake on the initiation of atherosclerosis in a ligature-induced rat periodontitis model. DESIGN Eighteen 8-week-old-male Wistar rats were divided into three groups of six rats and all rats received daily fresh water and powdered food through out the 6-week study. In the vitamin C and periodontitis groups, periodontitis was ligature-induced for the first 4 weeks. In the vitamin C group, rats were given distilled water containing 1 g/L vitamin C for the 2 weeks after removing the ligature. RESULTS In the periodontitis group, there was lipid deposition in the descending aorta and significant increases of serum level of hexanoyl-lysine (HEL), and aortic levels of nitrotyrosine expression, HEL expression and 8-hydroxydeoxyguanosine (8-OHdG) compared to the control group. Vitamin C intake significantly increased plasma vitamin C level and GSH:GSSG ratio (178% and 123%, respectively), and decreased level of serum HEL and aortic levels of nitrotyrosine, HEL and 8-OHdG (23%, 87%, 84%, and 38%, respectively). CONCLUSIONS These results suggest that vitamin C intake attenuates the degree of experimental atherosclerosis induced by periodontitis in the rat by decreasing oxidative stress.

Periodontitis‐induced lipid peroxidation in rat descending aorta is involved in the initiation of atherosclerosis

BACKGROUND AND OBJECTIVE Periodontitis is a risk factor for the development of atherosclerosis. Recent studies indicate that oxidative mechanisms, including lipid peroxidation, are involved not only in periodontitis but also in atherosclerosis. Lipid peroxidation may play an important role in the pathogenesis of atherosclerosis, particularly during its earliest stages. The purpose of this study was to investigate the relationship between lipid peroxidation induced by periodontitis and the initiation of atherosclerosis. MATERIAL AND METHODS Sixteen rats were randomly divided into two groups of eight rats each. Periodontitis was ligature-induced for 4 wk in the experimental group, whereas the control group was left untreated. After the experimental period, the mandibular first molar regions were resected and then subjected to histological analysis and measurement of hexanoyl-lysine expression as an indicator of lipid peroxidation. Descending aorta was used for measuring the levels of hexanoyl-lysine, reactive oxygen species and lipid deposits, and for real-time polymerase chain reaction microarray analysis. The level of hexanoyl-lysine was also measured in serum. RESULTS In the experimental group, the levels of hexanoyl-lysine in periodontal tissue and serum increased. Only aorta samples in the experimental group showed lipid accumulation, with increased expression of hexanoyl-lysine, reactive oxygen species and oxidative stress-related genes (including nitric oxide synthases 2 and 3), whereas the superoxide dismutase 1 gene level was down-regulated. CONCLUSION In a ligature-induced periodontitis rat model, increased lipid peroxidation was found in serum and aorta as well as in periodontal tissue. Atherosclerosis-related gene expression and histological changes were also stimulated. Periodontitis-induced lipid peroxidation in the aorta may be involved in the early stage of atherosclerosis.

Oxidative damage of rat liver induced by ligature-induced periodontitis and chronic ethanol consumption

OBJECTIVE Oxidative stress plays a central role in the initiation and progression of liver disease. Chronic ethanol consumption induces oxidative damage of the liver. Using a rat model, we previously showed that chronic administration of lipopolysaccharide and proteases to gingival sulcus induced both periodontal inflammation and liver injury. Periodontitis and ethanol consumption may have an additional effect on hepatic oxidative damage. The present study investigated the effects of periodontitis on ethanol-induced oxidative damage of the liver using a rat model. DESIGN Male Wistar rats were divided into four groups (six rats/group). During the experimental period of eight weeks, two groups were fed an ethanol-containing liquid diet, and two groups were on a pair-fed control diet. Four weeks prior to the end of the experimental period, one group from each dietary treatment was ligated to induce periodontitis, while the other group was left unligated. In order to evaluate hepatic oxidative damage, the level of hexanoyl-lysine and the ratio of reduced form glutathione/oxidized form glutathione (GSH/GSSG) was determined. The concentration of blood hexanoyl-lysine was also measured as an index of circulating lipid peroxide. RESULTS Ligature-induced periodontitis increased plasma levels of hexanoyl-lysine. In the liver, periodontitis decreased the GSH/GSSG ratio, and the combination of periodontitis and ethanol consumption induced a significant increase in hexanoyl-lysine level compared to ethanol consumption alone. CONCLUSION In the rat model, ligature-induced periodontitis increased plasma lipid peroxide, decreased the hepatic GSH/GSSG ratio and augmented ethanol-induced lipid peroxidation in the liver.