八代 耕児

Salivary peroxidase and myeloperoxidase are known to display antibacterial activity against oral microbes, and previous indications have pointed to the possibility that horseradish peroxidase (HRP) adsorbs onto the membrane of the major oral streptococci, Streptococcus mutans and Streptococcus sanguinis (S. sanguinis). However, the mechanism of interaction between HRP and the bacterial cell wall component is unclear. Dental plaques containing salivary glycoproteins and extracellular microbial products are visualized with 'dental plaque disclosing agent', and are controlled within dental therapy. However, current 'dental plaque disclosing agents' are difficult to evaluate with just dental plaques, since they stain and disclose not only dental plaques but also pellicle formed with salivary glycoproteins on a tooth surface. In this present study, we have demonstrated that HRP interacted with the cell wall component of the major gram-positive bacterial peptidoglycan, but not the major cell wall component of gram-negative bacteria lipopolysaccharide. Furthermore, we observed that the adsorbed HRP labeled with fluorescence was detected on the major oral gram-positive strains S. sanguinis and Streptococcus salivarius (S. salivarius), but not on a gram-negative strain, Escherichia coli (E. coli). Furthermore, we have demonstrated that the combination of HRP and chromogenic substrate clearly disclosed the dental plaques and the biofilm developed by S. sanguinis, S. salivarius and the major gram-postive bacteria Lactobacillus casei on tooth surfaces, and slightly disclosed the biofilm by E. coli. The combination of HRP and chromogenic substrate did not stain either the dental pellicle with the salivary glycoprotein mucin, or naked tooth surfaces. These results have suggested the possibility that the adsorption activity of HRP not only contributes to the evaluation of dental plaque, but that enzymatic activity of HRP may also contribute to improve dental hygiene.

In the present study, we examined the effect of high fructose-induced metabolic syndrome (MetS) on tissue vitamin E and lipid peroxide (LPO) levels in rats. Feeding of a diet containing 60% fructose (HFD) to Wistar rats for 2, 4, and 6 wk caused week-dependent increases in HOMA-IR score and serum insulin, triglyceride, total cholesterol, and free fatty acid concentrations. Each week HFD feeding increased serum vitamin E concentration. Six-week HFD feeding reduced vitamin E status (the serum ratio of vitamin E/triglyceride+total cholesterol). Four- and 6-wk HFD feeding increased serum LPO concentration. Two-week HFD feeding increased liver, heart, kidney, and skeletal muscle (SM) vitamin E contents and decreased white adipose tissue (WAT) vitamin E content. Four- and 6-wk HFD feeding further reduced WAT vitamin E content without affecting the increased kidney and SM vitamin E contents. Six-week HFD feeding reduced the increased liver and heart vitamin E contents below the level of non-HFD feeding. Four-week HFD feeding increased heart and WAT LPO contents. Six-week HFD feeding increased liver LPO content and further increased heart and WAT LPO contents. Kidney and SM LPO contents remained unchanged. These results indicate that HFD-rats with early MetS have increased liver, kidney, heart, and SM vitamin E contents and decreased WAT vitamin E content under unchanged tissue LPO content and vitamin E status, while HFD-fed rats with progressed MetS have both decreased liver, heart, and WAT vitamin E contents under increased tissue LPO content and disrupted vitamin E status.

Four human hydroxysteroid dehydrogenases in the aldo-keto reductase (AKR) superfamily, AKR1C1-AKR1C4, are involved in the metabolism of steroids and other carbonyl compounds including drugs, and altered expression of AKRs (1C1, 1C2 and/or 1C3) is related to the pathogenesis of several extrahepatic cancers. Here, we report that unsaturated fatty acids (FAs) are potent competitive inhibitors of the AKR enzymes. The sensitivities to the FAs were different among the enzymes, especially between AKR1C1 and AKR1C2. The most potent inhibitors for AKR1C1, AKR1C2 and AKR1C4 were docosahexaenoic acid (K-i 0.77 A mu M), palmitoleic acid (K-i 0.41 A mu M) and linoleic acid (K-i 0.33 A mu M), respectively. AKR1C3 was the most sensitive to FA inhibition, showing low K-i values (0.23-0.29 A mu M) for oleic, linoleic, eicosapentaenoic and docosahexaenoic acids. Linoleic and oleic acids also inhibited AKR1C3-mediated metabolism of 9,10-phenanthrenequinone in colon DLD1 cells. Molecular docking and site-directed mutagenesis studies suggested upon FA binding to AKR1C1 and AKR1C3: (i) the carboxyl group of the FA binds to the oxyanion-binding site in the active site; (ii) the difference in FA sensitivity between AKR1C1 and AKR1C2 is due to their residue difference at position 54; (iii) Ser118, Phe306 and Phe311 of AKR1C3 are important for determining the inhibitory potency of FAs.

In the present study, we examined the protective effect of N,N'-dimethylthiourea (DMTU), a scavenger of hydroxyl radical (OH), against water-immersion restraint stress (WIRS)-induced gastric mucosal lesions in rats. When male Wistar rats fasted for 24 h were exposed to WIRS for 3 h, gastric mucosal lesions occurred with increases in the levels of gastric mucosal myeloperoxidase (MPO), an index of tissue neutrophil infiltration, pro-inflammatory cytokines (tumor necrosis factor alpha and interleukin 1beta), lipid peroxide (LPO), and nitrite/nitrate (NOx), an index of nitric oxide synthesis, and decreases in the levels of gastric mucosal nonprotein SH and vitamin C and gastric adherent mucus. DMTU (1, 2.5, or 5 mmol/kg) administered orally at 0.5 h before the onset of WIRS reduced the severity of gastric mucosal lesions with attenuation of the changes in the levels of gastric mucosal MPO, pro-inflammatory cytokines, LPO, NOx, nonprotein SH, and vitamin C and gastric adherent mucus found at 3 h after the onset of WIRS in a dose-dependent manner. Serum levels of corticosterone and glucose, which are indices of stress responses, increased in rats exposed to WIRS for 3 h, but DMTU pre-administered at any dose had no effect on these increases. These results indicate that DMTU protects against WIRS-induced gastric mucosal lesions in rats by exerting its antioxidant action including OH scavenging and its anti-inflammatory action without affecting the stress response.

In this study, we examined whether compound 48/80 (C48/80), a mast cell degranulator, causes hepatic oxidative damage in rats. Serum and liver biochemical parameters were determined 0.5, 3 or 6 h after a single treatment with C48/80 (0.75 mg/kg). Serum histamine and serotonin levels increased 0.5 h after C48/80 treatment but diminished thereafter. Increases in serum vitamin C (VC) and transaminases and hepatic hydrogen peroxide, lipid peroxide, and myeloperoxidase levels and a decrease in hepatic reduced glutathione level occurred 0.5 h after C48/80 treatment and further proceeded at 3 h, but these changes diminished at 6 h. Serum lipid peroxide and hepatic VC levels increased 3 h after C48/80 treatment. Hepatic glycogen level decreased 0.5 h after C48/80 treatment and further decreased at 3 h. Pre-administered ketotifen diminished all these changes found at 3 h after treatment, while pre-administered. NPC 14686 diminished these changes except changes in serum histamine and serotonin levels. Hepatocellular apoptosis observed at 3 h after C48/80 treatment was attenuated by pre-administered ketotifen and NPC 14686. These results indicate that C48/80 causes oxidative damage by enhancing VC synthesis via reduced glutathione depletion-dependent glycogenolysis and lipid peroxidation through neutrophil infiltration following mast cell degranulation in rat livers.