Down‐regulation of heat‐shock protein 27–induced resistance to photodynamic therapy in oral cancer cells

Photodynamic therapy (PDT) of cells is a new treatment modality involving selective delivery of a photosensitive dye into target cells, followed by visible light irradiation. PDT induces cell death by excessive ROS generation. The effects of multiple photosensitizers were owing to the difference in cell types involving sensitizer‐specific protein changes linked to resistance. HSP27 is regulated in response to stress and is associated with apoptotic process. The effects of HSP27 on PDT resistance are controversial and unclear. The purpose of this study was to investigate the role of HSP27 down‐regulation in the PDT‐induced cells and HSP27 regulation in the resistance to PDT. KB cells transfected with HSP27 siRNA were exposed to hematoporphyrin (HP) followed by irradiation at 635 nm at an energy density of 4.5 mW/cm². After irradiation, the effects on HSP27 down‐regulation were assessed by MTT assay, flow cytometry, confocal analysis, Western blotting and caspase activity. The results of this study showed that down‐regulation of HSP27 restored cell survival in HP‐PDT‐induced apoptotic KB cells. HSP27 down‐regulation attenuated PDT‐induced apoptosis through caspase‐mediated pathway in KB cells. Also, HSP27 silencing regulated Bax, Bcl‐2, and PARP protein expression in PDT‐induced cells. Therefore, HSP27 down‐regulation confers resistance to PDT through interruption of apoptotic protein activity in PDT‐induced cell death. HSP27 might contribute to regulating PDT‐induced apoptosis in PDT‐resistant cells.     

Mechanism of action of tin‐containing fluoride solutions as anti‐erosive agents in dentine – an in vitro tin‐uptake,tissue loss,and scanning electron microscopy study

Ganss C, Hardt M, Lussi A, Cocks A‐K, Klimek J, Schlueter N. Mechanism of action of tin‐containing fluoride solutions as anti‐erosive agents in dentine – an in vitro tin‐uptake, tissue loss, and scanning electron microscopy study. Eur J Oral Sci 2010; 118: 376–384. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci Solutions containing tin and fluoride exhibit remarkable anti‐erosive properties with tin ions as a major agent. To elucidate its mechanism of action in dentine, the tin uptake on and in the tissue was investigated and related to histological findings and substance loss. Samples were treated twice daily, each treatment lasting for 2 min, with fluoride solutions [pH 4.5; 1,500 parts per million (p.p.m.) F] containing 2,100, 1,400, or 400 p.p.m. Sn as SnCl₂. In experiments 1 and 2, samples were eroded with citric acid (pH 2.3) six times each day, each treatment lasting for 5 min; in experiment 2, the demineralized organic matrix was continuously digested by collagenase; in experiment 3, no erosive challenges were performed. Sample surfaces and cross‐sections were investigated using energy dispersive X‐ray spectroscopy, scanning electron microscopy, and profilometry. Surface retention of tin was found in almost all treatment groups and was highest in experiment 2. On cross‐sections, tin was retained within the organic matrix; in mineralized areas, tin was found mainly within a depth of 10 μm. Test solutions inhibited substance loss significantly; in experiment 2, the effect was dose‐dependent. Erosion inhibition seemed to depend mainly on the incorporation of tin in the mineralized dentine when the organic portion was preserved, but on surface precipitation when the organic portion was continuously digested.     

18β‐Glycyrrhetinic acid inhibits periodontitis via glucocorticoid‐independent nuclear factor‐κB inactivation in interleukin‐10‐deficient mice

Sasaki H, Suzuki N, AlShwaimi E, Xu Y, Battaglino R, Morse L, Stashenko P. 18β‐Glycyrrhetinic acid inhibits periodontitis via glucocorticoid‐independent nuclear factor‐κB inactivation in interleukin‐10‐deficient mice. J Periodont Res 2010; 45: 757–763. © 2010 John Wiley & Sons A/S Background and Objective: 18β‐Glycyrrhetinic acid (GA) is a natural anti‐inflammatory compound derived from licorice root extract (Glycyrrhiza glabra). The effect of GA on experimental periodontitis and its mechanism of action were determined in the present study. Material and Methods: Periodontitis was induced by oral infection with Porphyromonas gingivalis W83 in interleukin‐10‐deficient mice. The effect of GA, which was delivered by subcutaneous injections in either prophylactic or therapeutic regimens, on alveolar bone loss and gingival gene expressions was determined on day 42 after initial infection. The effect of GA on lipopolysaccharide (LPS)‐stimulated macrophages, T cell proliferation and osteoclastogenesis was also examined in vitro. Results: 18β‐Glycyrrhetinic acid administered either prophylactically or therapeutically resulted in a dramatic reduction of infection‐induced bone loss in interleukin‐10‐deficient mice, which are highly disease susceptible. Although GA has been reported to exert its anti‐inflammatory activity via downregulation of 11β‐hydroxysteroid dehydrogenase‐2 (HSD2), which converts active glucocorticoids to their inactive forms, GA did not reduce HSD2 gene expression in gingival tissue. Rather, in glucocorticoid‐free conditions, GA potently inhibited LPS‐stimulated proinflammatory cytokine production and RANKL‐stimulated osteoclastogenesis, both of which are dependent on nuclear factor‐κB. Furthermore, GA suppressed LPS‐ and RANKL‐stimulated phosphorylation of nuclear factor‐κB p105 in vitro. Conclusion: These findings indicate that GA inhibits periodontitis by inactivation of nuclear factor‐κB in an interleukin‐10‐ and glucocorticoid‐independent fashion.     

Effects of three γ‐alkylidene‐γ‐lactams on the formation of multispecies biofilms

This study evaluated the inhibitory effects of lactams on Streptococcus mutans, Enterococcus faecalis, and Candida glabrata multispecies biofilm formation. γ‐Alkylidene‐γ‐lactams 1, 2, and 3 [solubilized in 3.5% dimethyl sulfoxide (DMSO)] were tested. Glass coverslips were conditioned with either the lactams or 3.5% DMSO (control) for 1 h, inoculated with microbial cultures, and incubated for 48 h. To assess the effect of the lactams on biofilm formation, the following parameters were determined: the biofilm biomass (by both crystal violet staining and protein determination); the amount of insoluble polysaccharides of the extracellular matrix; and the number of viable and total cells [by both colony‐forming unit counting and quantitative real‐time PCR (qPCR)]. Data were analysed using one‐way anova and post‐hoc Tukey tests. Lactams 1, 2, and 3 promoted a statistically significant reduction in the amount of biofilm biomass, but only lactam 3 resulted in a statistically significant reduction in the number of attached viable E. faecalis. Both total protein content and the amount of extracellular polysaccharides decreased significantly. The effects of γ‐alkylidene‐γ‐lactams 1, 2, and 3 on the inhibition of multispecies biofilm formation were evident by their ability to reduce the amount of protein and extracellular polysaccharides.     

Role of the NH2‐terminal fragment of dentin sialophosphoprotein in dentinogenesis

Dentin sialophosphoprotein (DSPP) is a large precursor protein that is proteolytically processed into a NH₂‐terminal fragment [composed of dentin sialoprotein (DSP) and a proteoglycan form (DSP‐PG)] and a COOH‐terminal fragment [dentin phosphoprotein (DPP)]. In vitro studies indicate that DPP is a strong initiator and regulator of hydroxyapatite crystal formation and growth, but the role(s) of the NH₂‐terminal fragment of DSPP (i.e. DSP and DSP‐PG) in dentinogenesis remain unclear. This study focuses on the function of the NH₂‐terminal fragment of DSPP in dentinogenesis. Here, transgenic (Tg) mouse lines expressing the NH₂‐terminal fragment of DSPP driven by a 3.6‐kb type I collagen promoter (Col 1a1) were generated and cross‐bred with Dspp null mice to obtain mice that express the transgene but lack the endogenous Dspp (Dspp KO/DSP Tg). We found that dentin from the Dspp KO/DSP Tg mice was much thinner, more poorly mineralized, and remarkably disorganized compared with dentin from the Dspp KO mice. The fact that Dspp KO/DSP Tg mice exhibited more severe dentin defects than did the Dspp null mice indicates that the NH₂‐terminal fragment of DSPP may inhibit dentin mineralization or may serve as an antagonist against the accelerating action of DPP and serve to prevent predentin from being mineralized too rapidly during dentinogenesis.     

Insulin‐like growth factor‐binding protein‐2 and ‐3 in gingival crevicular fluid

Takenouchi Y, Ohshima M, Yamaguchi Y, Nishida T, Senda N, Idesawa M, Otsuka K, Ito K. Insulin‐like growth factor‐binding protein‐2 and ‐3 in gingival crevicular fluid. J Periodont Res 2010; 45: 803–808. © 2010 John Wiley & Sons A/S Background and Objective: Insulin‐like growth factor‐binding proteins (IGFBPs) are crucial regulators of insulin‐like growth factor (IGF). They enhance or inhibit IGF functions, but also exhibit IGF‐independent effects. In a previous study, we detected, qualitatively, IGFBP‐2 and ‐3 in gingival crevicular fluid using a cytokine antibody array. Here we extended these results using an ELISA to determine the concentrations of IGFBP‐2 and ‐3 in gingival crevicular fluid. In addition, we explored whether the expression of IGFBP‐2 and IGFBP‐3 correlates with periodontal disease severity. Material and Methods: Gingival crevicular fluid samples from 92 sites of 12 patients affected with periodontal disease and from 100 sites of 19 healthy volunteers, were collected, divided into two groups and analyzed by ELISA for IGFBP‐2 and ‐3 expression. The potential correlation among probing depth, gingival index and the concentrations of IGFBP‐2 and ‐3 was analyzed. Results: Positive correlations were observed between the concentration of IGFBP‐2 and probing depth and gingival index, but not for IGFBP‐3. The IGFBP‐2 concentrations at bleeding on probing‐positive sites and at sites with a probing depth of ≥ 4 mm were higher than at bleeding on probing‐negative sites and at sites with a probing depth of ≤ 3 mm. Conclusion: These results indicate that IGFBP‐2 is a potential novel marker for periodontal disease progression. As IGFBP‐2 modulates bone metabolism and cell migration, IGFBP‐2 in the gingival crevicular fluid may reflect periodontal disease activity.     

Preservation of Hypermobile Teeth by Establishing Posterior Occlusal Support Using Implant Prostheses: A 5‐Year Follow‐Up

For patients with periodontally compromised, hypermobile teeth, implant‐supported fixed dental prostheses (FDPs) or removable dentures are often used after extracting mobile teeth. The loss of native teeth may carry social consequences, depending upon the patient's age, state of health, and degree of social functioning. This report represents successful stabilization and preservation of questionable, hypermobile teeth that have been damaged by traumatic occlusion due to the loss of posterior support with a cross‐arch splinted FDP, as well as the implementation of posterior support using implant‐supported prostheses.