Design and Progress of Oral Health Examinations in the Tohoku Medical Megabank Project.

In order to assess the long-term impact of the Great East Japan Earthquake on the oral health of disaster victims and to evaluate gene-environmental interactions in the development of major oral diseases and oral-systemic associations, the oral part of two large-scale genome cohort studies by the Tohoku Medical Megabank Organization (ToMMo), including the Community-based cohort (CommCohort) study and the Birth and Three-Generation cohort (BirThree) study, have been conducted. The study population comprised 32,185 subjects, including 16,886 participants in the CommCohort study and 15,299 participants in the BirThree cohort study, recruited from 2013 to 2017. The oral studies consist of a questionnaire regarding oral hygiene behavior, clinical examinations by dentists, and oral plaque and saliva sampling for microbiome analyses, which were carried out at seven community support centers in Miyagi prefecture. The median age of all participants was 55.0 years, and 66.1% of participants were women. Almost all participants reported that they brushed their teeth more than once a day. The median number of present teeth was 27.0, and the decayed, missing and filled tooth number was 16.0, with a significant difference according to age and sex. The median periodontal pocket and clinical attachment level was 2.48 mm and 4.00 mm, respectively. Periodontal parameters increased significantly according to age, except for the accumulation of dental calculus. The oral part of these extensive cross-sectional studies provides a unique and important platform for future studies on oral health and diseases that elicit through interactions with systemic diseases, lifestyles, life events and genetic backgrounds, and contributes to researches clarifying the long-term effects of disasters on oral health.

Augmentation of Lipopolysaccharide-Induced Production of IL-1α and IL-1ß in Mice Given Intravenous Zoledronate (a Nitrogen-Containing Bisphosphonate) and Its Prevention by Clodronate (a Non-nitrogen-containing Bisphosphonate).

Bisphosphonates (BPs) bind strongly to bone and exhibit long-acting anti-bone-resorptive effects. Among BPs, nitrogen-containing BPs (N-BPs) have far stronger anti-bone-resorptive effects than non-N-BPs. However, N-BPs induce acute inflammatory reactions (fever, arthralgia and myalgia, etc.) after their first injection. The mechanisms underlying these side effects remain unclear. Zoledronate (one of the most potent N-BPs) is given intravenously to patients, and the side-effect incidence is reportedly the highest among N-BPs. Our murine experiments have clarified that (a) intraperitoneally injected N-BPs induce various inflammatory reactions, including a production of interleukin-1 (IL-1) (a typical inflammatory cytokine), and these inflammatory reactions are weak in IL-1-deficient mice, (b) subcutaneously injected N-BPs induce inflammation/necrosis at the injection site, (c) lipopolysaccharide (LPS; a cell-wall component of Gram-negative bacteria) and N-BPs mutually augment their inflammatory/necrotic effects, (d) the non-N-BP clodronate can reduce N-BPs' inflammatory/necrotic effects. However, there are few animal studies on the side effects of intravenously injected N-BPs. Here, we found in mice that (i) intravenous zoledronate exhibited weaker inflammatory effects than intraperitoneal zoledronate, (ii) in mice given intravenous zoledronate, LPS-induced production of IL-1α and IL-1ß was augmented in various tissues, including bone, resulting in them increasing in serum, and (iii) clodronate (given together with zoledronate) prevented such augmentation and enhanced, slightly but significantly, zoledronate's anti-bone-resorptive effect. These results suggest that infection may be a factor promoting the acute inflammatory side effects of N-BPs via augmented production of IL-1 in various tissues (including bone), and that clodronate may be useful to reduce or prevent such side effects.

Possible pathogenic engagement of soluble Semaphorin 4D produced by γδT cells in medication-related osteonecrosis of the jaw (MRONJ).

Prior consensus held that medication-related osteonecrosis of the jaw (MRONJ) lesion was composed of necrotic bone; however, more recent studies have identified inflammatory infiltrates in the lesion. Herein, we report that remarkably elevated infiltrating γδT cells (90% of lymphocytes) express Semaphorin 4D (Sema4D) in human patient with MRONJ lesion, whereas γδT cells only account for 2-5% of lymphocytes in blood. Importantly, Sema4D is implicated in the pathogenesis of T cell-mediated inflammatory diseases, such as rheumatoid arthritis and multiple sclerosis. Indeed, in a mouse model of MRONJ, an elevated number of γδT, but not αßT, cells infiltrating in the MRONJ-like lesion was observed. Both elevated soluble Sema4D (sSema4D) production accompanied by pro-inflammatory cytokines, including TNF-α IFN-γ and IL-1ß, and Sema4D-expressing γδT cells were detected in mouse MRONJ-like lesion. Activated γδT cells produced sSema4D in vitro, which could promote TNF-α production from macrophages. Meanwhile, γδT cell-KO mice were resistant to the induction of MRONJ and, hence, showed no elevation of local productions of Sema4D and TNF-α. Finally, systemic administration of anti-Sema4D neutralizing mAb suppressed the onset of MRONJ in wild-type mice in conjunction with diminished level of TNF-α. These results suggested a critical pathogenic engagement of Sema4D produced by γδT cells in the development of MRONJ.

Phosphonocarboxylates Can Protect Mice against the Inflammatory and Necrotic Side Effects of Nitrogen-Containing Bisphosphonates by Inhibiting Their Entry into Cells via Phosphate Transporters.

Bisphosphonates (BPs) are used against diseases involving increased bone-resorption. Among BPs, nitrogen-containing BPs (N-BPs) have much stronger anti-bone-resorptive effects than non-nitrogen-containing BPs (non-N-BPs). However, N-BPs carry the risk of inflammatory/necrotic effects, including osteonecrosis of jawbones. When injected into mouse ear-pinnas, N-BPs induce inflammatory/necrotic effects within the ear-pinna. We previously found that (a) the non-N-BPs clodronate and etidronate can reduce such side effects of N-BPs, and (b) phosphonoformate (an inhibitor of the phosphate transporters SLC20 and SLC34) can reduce the inflammatory/necrotic effects of zoledronate (the N-BP with the highest reported risk of side effects). However, it is not clear (i) whether phosphonoformate can reduce the side effects of other N-BPs, too, and (ii) whether other phosphonocarboxylates have such inhibitory effects. Here, using the mouse ear-pinna model, we compared the effects of etidronate, clodronate, and four phosphonocarboxylates on the inflammatory/necrotic effects of N-BPs of the alkyl type (alendronate) or cyclic type (zoledronate and minodronate). Like phosphonoformate, the other three phosphonocarboxylates protected against the inflammatory/necrotic effects of all the N-BPs. The protective potencies were clodronate>etidronate>phosphonoacetate>phosphonoformate>phosphonopropionate>phosphonobutyrate. With a similar order of potencies, these agents reduced the amount of (3)H-alendronate retained within the ear-pinna after its injection therein. The mRNAs of SLC20 and SLC34 were detected in untreated ear-pinnas. These findings suggest that the inhibition of phosphate transporters by phosphonocarboxylates, as well as by etidronate and clodronate, might be a useful preventive strategy against the side effects of both alkyl- and cyclic-type N-BPs.

Inhibition of phosphate transporters ameliorates the inflammatory and necrotic side effects of the nitrogen-containing bisphosphonate zoledronate in mice.

Bisphosphonates (BPs) are pyrophosphate analogs. They are widely used against enhanced bone-resorption in various diseases. Nitrogen-containing BPs (N-BPs) exhibit strong anti-bone-resorptive effects but have inflammatory and necrotic side effects. The non-nitrogen-containing BPs (non-N-BPs) etidronate and clodronate lack such side effects, but their anti-bone-resorptive effects are weak. In mice, etidronate and clodronate reduce the inflammatory/necrotic effects of N-BPs, even those of zoledronate, the N-BP with the strongest anti-bone-resorptive effect yet reported and the highest risk of inflammation/necrosis. Here, to explore the mechanisms underlying this protection, we used a mouse model in which a single reagent or a mixture of two reagents was injected subcutaneously into ear-pinnas. These reagents included zoledronate, four non-N-BPs, pyrophosphate, and inhibitors of various organic-anion-transporters. Pyrophosphate and two of the four non-N-BPs (not etidronate or clodronate) had inflammatory/necrotic effects. These effects were reduced by etidronate and clodronate, but not by phosphonoformate, an inhibitor of two of the three known phosphate-transporter families. Phosphonoformate reduced the inflammatory/necrotic effects of zoledronate, but not those of pyrophosphate or of non-N-BPs. Conversely, pyrophosphate, at non-inflammatory/necrotic concentrations, reduced the inflammatory/necrotic effects of non-N-BPs, but not those of zoledronate. The efficacies of the protective effects against the inflammatory/necrotic effects of zoledronate were clodronate > etidronate > phosphonoformate. These findings suggest that (i) the N-BP zoledronate may enter soft-tissue cells via phosphonoformate-inhibitable phosphate-transporters, (ii) other phosphate-transporters may carry pyrophosphate and inflammatory/necrotic non-N-BPs into such cells, and (iii) etidronate and clodronate inhibit all these transporters, and they ameliorate the side effects of zoledronate by inhibiting phosphonoformate-inhibitable phosphate-transporters.

Inflammatory and necrotic effects of minodronate, a nitrogen-containing bisphosphonate, in mice.

Diseases involving enhanced bone-resorption (e.g., osteoporosis) are widely treated with bisphosphonates (BPs). BPs are of two types: the nitrogen-containing BPs (N-BPs) and the non-nitrogen-containing BPs (non-N-BPs). N-BPs have much stronger anti-bone-resorptive effects than non-N-BPs, and N-BPs can exert inflammatory and necrotic effects, including osteonecrosis of jawbones. Minodronate, an N-BP, was approved in 2009 in Japan for osteoporosis. Its anti-bone-resorptive effect is comparable to that of zoledronate, the N-BP with the strongest anti- bone-resorptive effect and the highest risk of side effects yet reported. Unlike other N-BPs, minodronate has an analgesic effect, and no serious side effects have been documented. Here, to examine whether minodronate lacks inflammatory and/or necrotic effects, we used mice (since the N-BPs tested so far induce such effects in mice with potencies that parallel those reported in humans). To facilitate comparison with previous studies, we gave a single systemic (intraperitoneal) or local (ear pinna) injection of minodronate (or another N-BP). We measured the systemic responses (weight of thoracic exudate, number of inflammatory cells in the peritoneal cavity, and spleen weight) or local responses (area of inflamed skin and incidence of necrosis). Anti-bone-resorptive effects were evaluated by X-ray analysis of tibias following intraperitoneal injection. Minodronate's anti-bone-resorptive effect and its inflammatory and necrotic effects were as great as, or greater than those of zoledronate. Moreover, in cultured human periodontal ligament cells, the cytotoxicity of minodronate was significantly greater than that of zoledronate. These results suggest that caution may be needed with minodronate in clinical use, as with other N-BPs.

Interleukin-6 maintains glucose homeostasis to support strenuous masseter muscle activity in mice.

The cytokine interleukin-6 (IL-6) is released from working skeletal muscles and reportedly plays key roles in their glucose homeostasis. However, it is unclear whether IL-6 plays such roles in the masseter muscle (MM), which is important in normal and pathological chewing behaviors, such as bruxism and/or prolonged clenching. When restrained (R+) in a narrow cylinder blocked at the front end with a thin plastic strip, a mouse gnaws away (G+) the strip to escape. The absolute weight of plastic gnawed away serves as an index of MM activity. Using this model, we examined the roles of IL-6 in MM with the following results. R+G+ increased the expression levels of IL-6 and glucose transporter 4 (Glut4) mRNAs in MM and the serum level of IL-6 protein. IL-6-deficient mice exhibited about 60% less gnawing activity than wild-type mice at 3-4 h after the start of R+G+, slower recovery of glycogen levels (indicating poorer glucose supply) in MM after R+G+, and no significant change in Glut4 mRNA in MM upon R+G+. During an R+G+ test conducted after "training" (repeated R+G+ sessions), wild-type mice exhibited greater gnawing activity than untrained controls, but no increase in IL-6 mRNA in MM. IL-6 mRNA increased in MM when hard food was eaten by mice raised on soft food for 3 weeks from weaning, but not in those raised on (accustomed to) hard food. Thus, IL-6 may maintain glucose homeostasis in MM in support of unusually strenuous activity, but not of accustomed activity levels.

[Basic Studies on the Mechanism, Prevention, and Treatment of Osteonecrosis of the Jaw Induced by Bisphosphonates].

Since the first report in 2003, bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been increasing, without effective clinical strategies. Osteoporosis is common in elderly women, and bisphosphonates (BPs) are typical and widely used anti-osteoporotic or anti-bone-resorptive drugs. BRONJ is now a serious concern in dentistry. As BPs are pyrophosphate analogues and bind strongly to bone hydroxyapatite, and the P-C-P structure of BPs is non-hydrolysable, they accumulate in bones upon repeated administration. During bone-resorption, BPs are taken into osteoclasts and exhibit cytotoxicity, producing a long-lasting anti-bone-resorptive effect. BPs are divided into nitrogen-containing BPs (N-BPs) and non-nitrogen-containing BPs (non-N-BPs). N-BPs have far stronger anti-bone-resorptive effects than non-N-BPs, and BRONJ is caused by N-BPs. Our murine experiments have revealed the following. N-BPs, but not non-N-BPs, exhibit direct and potent inflammatory/necrotic effects on soft-tissues. These effects are augmented by lipopolysaccharide (the inflammatory component of bacterial cell-walls) and the accumulation of N-BPs in jawbones is augmented by inflammation. N-BPs are taken into soft-tissue cells via phosphate-transporters, while the non-N-BPs etidronate and clodronate inhibit this transportation. Etidronate, but not clodronate, has the effect of expelling N-BPs that have accumulated in bones. Moreover, etidronate and clodronate each have an analgesic effect, while clodronate has an anti-inflammatory effect via inhibition of phosphate-transporters. These findings suggest that BRONJ may be induced by phosphate-transporter-mediated and infection-promoted mechanisms, and that etidronate and clodronate may be useful for preventing and treating BRONJ. Our clinical trials support etidronate being useful for treating BRONJ, although additional clinical trials of etidronate and clodronate are needed.