Role of Aggregatibacter actinomycetemcomitans in glutathione catabolism

Efficacy of chlorine dioxide mouthwash in reducing oral malodor: A 2-week randomized, double-blind, crossover study

The aim of this clinical trial was to assess the inhibitory effects of a mouthwash containing 0.1% ClO2 used for 2 weeks on oral malodor, periodontal and salivary parameters, tongue coating, and Gram-negative and Gram-positive bacteria in saliva. Thirty-nine subjects with oral malodor were randomly assigned into two groups. In the first stage, one group was instructed to rinse with the experimental mouthwash (containing 0.1% ClO2), whereas the other group was instructed to rinse with the control mouthwash (sodium chloride 0.9%) for 2 weeks. After 4 weeks of washing out, in the second stage, each group then used the other mouthwash for 2 weeks. Oral malodor, periodontal status, tongue coating, salivary pH and flow rate, and the amounts of the salivary bacteria Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, Solobacterium moorei, Streptococcus salivarius, Treponema denticola, and Tannerella forsythia were evaluated at baseline and after 2 weeks of mouthwash use. After 12 hr and after 2 weeks, organoleptic scores and the levels of H2S and CH3SH were significantly lower in the experimental group compared with those in the control group. After 2 weeks, the experimental mouthwash appeared significantly effective in reducing plaque index, tongue-coating score, and the amounts of F. nucleatum, S. moorei, T. denticola, and T. forsythia in the whole saliva, compared with those at baseline. Mouthwash containing 0.1% ClO2 is effective in reducing oral malodor, dental plaque, tongue-coating accumulation, and the amounts of F. nucleatum, S. moorei, T. denticola, and T. forsythia in saliva.

γ-Glutamyltranspeptidase is an endogenous activator of Toll-like receptor 4-mediated osteoclastogenesis

Chronic inflammation-associated bone destruction, which is observed in rheumatoid arthritis (RA) and periodontitis, is mediated by excessive osteoclastogenesis. We showed previously that γ-glutamyltranspeptidase (GGT), an enzyme involved in glutathione metabolism, acts as an endogenous activator of such pathological osteoclastogenesis, independent of its enzymatic activity. GGT accumulation is clinically observed in the joints of RA patients, and, in animals, the administration of recombinant GGT to the gingival sulcus as an in vivo periodontitis model induces an increase in the number of osteoclasts. However, the underlying mechanisms of this process remain unclear. Here, we report that Toll-like receptor 4 (TLR4) recognizes GGT to activate inflammation-associated osteoclastogenesis. Unlike lipopolysaccharide, GGT is sensitive to proteinase K treatment and insensitive to polymyxin B treatment. TLR4 deficiency abrogates GGT-induced osteoclastogenesis and activation of NF-κB and MAPK signaling in precursor cells. Additionally, GGT does not induce osteoclastogenesis in cells lacking the signaling adaptor MyD88. The administration of GGT to the gingival sulcus induces increased osteoclastogenesis in wild-type mice, but does not induce it in TLR4-deficient mice. Our findings elucidate a novel mechanism of inflammation-associated osteoclastogenesis, which involves TLR4 recognition of GGT and subsequent activation of MyD88-dependent signaling.