Objective To examine whether glyburide inhibits bone destruction caused by traumatic occlusion in a rat occlusal trauma model. Background Excessive mechanical stress, such as traumatic occlusion, induces expression of IL‐1β and may be involved in bone resorption. NLRP3 inflammasomes have been linked to IL‐1β expression, but it is currently unclear whether glyburide, the inhibiter of NLRP3 inflammasome, suppresses occlusal trauma in rats. Methods Male SD rats aged 7 weeks were used. In the trauma group, the occlusal surface of the maxillary first right molar was raised by attaching a metal wire to apply occlusal trauma to the mandibular first right molar. In the trauma + glyburide group, the NLRP3 inhibitor glyburide was administered orally every 24 hours from 1 day before induction of occlusal trauma. Rats were euthanized after 5 or 10 days, and the maxillary first molars were harvested with the adjacent tissues for histopathological investigation. Immunohistochemical expression of IL‐1β, NLRP3, and RANKL was also assessed. Results On day 5, bone resorption was significantly greater in the trauma group compared with the control group or the trauma + glyburide group, and there were significantly higher numbers of osteoclasts and cells positive for IL‐1β, NLRP3, and RANKL in the trauma group. Conclusion In this study, glyburide inhibits bone resorption by traumatic occlusion in rats. It suggests that the NLRP3/IL‐1β pathway might be associated with bone resorption induced by traumatic occlusion.

Citrullination is likely a protein modification that plays an important role in maintaining the structure and function of oral cornified mucosa in a way that is distinctly different from that of the skin.

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Background: Epithelial cells expressed in different regions exhibit marked differences in their differentiation capacity to provide a suitable protective barrier. Peptidylarginine deiminase (PAD) is known to change the structure of filaggrin (FLG) and keratins, by converting arginine residues into neutral citrulline residues in the stratifying epithelium of skin. The role of PAD in modifying stratification of oral mucosa has not yet been defined. Methods: We aimed to clarify the role of PAD in stratification of epithelium in the rat palate, buccal mucosa and skin and to examine the effects of compounds that alter PAD activity in immunofluorescence, immunoblotting and PAD activity assays. We developed a 3-dimensional mucosal model derived from epithelial cells and fibroblasts isolated from the rat palate. Results: PAD1 expression was highest in the palate, whereas PAD2 and PAD3 expression was highest in the skin. Immunoblotting showed that the FLG monomer, as well as its degradation products and precursor (proFLG), were abundantly expressed in the skin but had lower expression in the palate, whereas only faint expression was detected in the buccal mucosa. FLG and keratin 1 (K1) were co-localized with PAD1 and were citrullinated in the cornified layers of the skin, but not on the palatal surface. Instead, granular expression of PAD1 and citrullinated proFLG were found in the palate. Next, in the mucosal model, Cl-amidine, a pan-PAD inhibitor reduced the breakdown of FLG, increased its association with K1 together with epithelial compaction, and decreased dye permeability. Conversely, acefylline, a PAD activator increased the breakdown of FLG, decreased the K1 association, and increased the dye permeability. Conclusions: These results suggest that localization of PAD and its protein modification are different in palate, buccal mucosa and skin, and that modification of citrullination is likely to alter the structure and function of stratifying oral epithelia.