Naofumi Tamaki

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.

Resveratrol improves oxidative stress and prevents the progression of periodontitis via the activation of the Sirt1/AMPK and the Nrf2/antioxidant defense pathways in a rat periodontitis model

Oxidative stress is a key factor regulating the systemic pathophysiological effects associated with periodontitis. Resveratrol is a phytochemical with antioxidant and anti-inflammatory properties that can reduce oxidative stress and inflammation. We hypothesized that resveratrol may prevent the progression of periodontitis and reduce systemic oxidative stress through the activation of the sirtuin 1 (Sirt1)/AMP-activated protein kinase (AMPK) and the nuclear factor E2-related factor 2 (Nrf2)/antioxidant defense pathways. Three groups of male Wistar rats (periodontitis treated with melinjo resveratrol, periodontitis without resveratrol, and control rats with no periodontitis or resveratrol treatment) were examined. A ligature was placed around the maxillary molars for 3 weeks to induce periodontitis, and the rats were then given drinking water with or without melinjo resveratrol. In rats with periodontitis, ligature placement induced alveolar bone resorption, quantified using three-dimensional images taken by micro-CT, and increased proinflammatory cytokine levels in gingival tissue. Melinjo resveratrol intake relieved alveolar bone resorption and activated the Sirt1/AMPK and the Nrf2/antioxidant defense pathways in inflamed gingival tissues. Further, melinjo resveratrol improved the systemic levels of 8-hydroxydeoxyguanosine, dityrosine, nitric oxide metabolism, nitrotyrosine, and proinflammatory cytokines. We conclude that oral administration of melinjo resveratrol may prevent the progression of ligature-induced periodontitis and improve systemic oxidative and nitrosative stress.

Hydrogen-rich water prevents progression of nonalcoholic steatohepatitis and accompanying hepatocarcinogenesis in mice.

Oxidative stress is a strong contributor to the progression from simple fatty liver to nonalcoholic steatohepatitis (NASH). Molecular hydrogen is an effective antioxidant that reduces cytotoxic reactive oxygen species. In this study, we investigated the effects of hydrogen‐rich water and the drug pioglitazone on the progression of NASH in mouse models. A methionine‐choline–deficient (MCD) diet mouse model was prepared. Mice were divided into three experimental groups and fed for 8 weeks as follows: (1) MCD diet + control water (CW group); (2) MCD diet + hydrogen‐rich water (HW group); and (3) MCD diet mixed with pioglitazone (PGZ group). Plasma alanine aminotransferase levels, hepatic expression of tumor necrosis factor‐α, interleukin‐6, fatty acid synthesis–related genes, oxidative stress biomarker 8‐hydroxydeoxyguanosine (8‐OHdG), and apoptosis marker terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick‐end labeling (TUNEL)–positive cells in the liver were decreased in the HW and PGZ groups. The HW group showed a smaller decrease in hepatic cholesterol; however, stronger antioxidative effects in serum and lower peroxisome proliferator‐activated receptor‐α expression in the liver were seen in comparison with the PGZ group. We then investigated the effects of hydrogen in the prevention of hepatocarcinogenesis in STAM mice, known as the NASH‐related hepatocarcinogenesis model. Eight‐week‐old male STAM mice were divided into three experimental groups as follows: (1) control water (CW‐STAM); (2) hydrogen‐rich water (HW‐STAM); and (3) pioglitazone (PGZ‐STAM). After 8 weeks, hepatic tumors were evaluated. The number of tumors was significantly lower in the HW‐STAM and PGZ‐STAM groups than in the CW‐STAM group. The maximum tumor size was smaller in the HW‐STAM group than in the other groups. Conclusion: Consumption of hydrogen‐rich water may be an effective treatment for NASH by reducing hepatic oxidative stress, apoptosis, inflammation, and hepatocarcinogenesis. (HEPATOLOGY 2012;56:912–921)

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.

Oxidative damage of periodontal tissue in the rat periodontitis model: effects of a high-cholesterol diet.

Studies suggest an association between consumption of a high‐cholesterol diet and periodontitis. We addressed the mechanism by which high dietary cholesterol could be detrimental to periodontal health in a rat model. Feeding a high‐cholesterol diet augmented the effects of bacterial pathogens and their products (e.g., lipopolysaccharide and proteases) on production of pro‐inflammatory cytokines in fibroblasts. High dietary cholesterol also increased mitochondrial 8‐hydroxydeoxyguanosine in the periodontal tissues. These results suggest that excessive tissue oxidative damage induced by high dietary cholesterol could potentiate pro‐inflammatory cytokine production by fibroblasts stimulated with bacterial pathogens.

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.

Short-Term Effects of Non-Surgical Periodontal Treatment on Plasma Level of Reactive Oxygen Metabolites in Patients With Chronic Periodontitis

BACKGROUND Elevated levels of blood reactive oxygen species (ROS) are associated with the severity of periodontitis. Therefore, improvement of periodontitis may result in a decrease in blood ROS. However, it is unclear how periodontal treatment affects blood ROS. Recently, reactive oxygen metabolites (ROMs) were recognized as a useful measure of blood ROS. The aim of this longitudinal study was to investigate the effect of non-surgical periodontal treatment on plasma ROMs in patients with chronic periodontitis. METHODS Nineteen subjects with chronic periodontitis (mean age: 46.8 years) were monitored at baseline (prior to scaling and root planing) and 1 and 2 months after therapy. Dental health parameters were evaluated, and plasma was obtained at these time points from patients and controls (19 subjects without periodontitis; mean age: 45.3 years). The plasma ROM level was determined using a spectrophotometric technique. RESULTS At baseline, patients with chronic periodontitis had higher plasma ROM level (441.8 +/- 71.1 Carratelli units) than the control subjects (324.4 +/- 34.0 Carratelli units; P <0.01). Probing depth, clinical attachment level, and bleeding on probing in patients with chronic periodontitis showed a significant improvement 2 months after non-surgical periodontal treatment, and this was accompanied by a significant reduction in plasma ROM level (P <0.01). CONCLUSIONS In patients with chronic periodontitis, non-surgical periodontal treatment was effective at improving clinical parameters and reducing plasma ROMs. The improvement in chronic periodontitis by non-surgical periodontal treatment might offer clinical benefits by decreasing blood ROS.

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.