Heparin interacts with candidalysin and neutralizes its cytotoxicity to oral epithelial cells.

OBJECTIVES: Candidalysin is a peptide toxin produced by Candida albicans that causes damage to epithelial cells by destabilizing the plasma membrane. This study aimed to evaluate heparin's ability to neutralize candidalysin and protect epithelial cells from lysis. METHODS: The study was conducted using a human oral epithelial cell line and synthetic candidalysin. Cell damage was assessed by measuring lactate dehydrogenase release. Enzyme-linked immunosorbent assay and immunoblotting were used to determine cytokine concentrations and assess activation of intracellular signaling molecules and transcription factors, respectively. Flow cytometry was used to measure cell-bound candidalysin. RESULTS: Heparin diminished the cell-lytic activity of candidalysin and subsequent epithelial responses. Additionally, heparin inhibited the interaction between candidalysin and epithelial cells. Furthermore, polyacrylic acid, a synthetic polymer, mimicked the neutralizing effects of candidalysin. CONCLUSION: Our findings suggest that negatively charged polymers could be a potential therapeutic option for preventing the damage caused by candidalysin. Further research is needed to explore the effectiveness of other anionic polymers and their potential clinical applications.

Knockdown of sphingomyelin synthase 2 inhibits osteoclastogenesis by decreasing RANKL expression in mouse primary osteoblasts.

Sphingomyelin is a major lipid of the plasma membrane and is enriched in microdomains of the plasma membrane that are critical for signal transduction. However, the function of sphingomyelin in the cell membrane of osteoblasts has not been clarified. Therefore, we examined how sphingomyelin synthase 2 (SMS2) affects osteoclast differentiation by osteoblasts. We knocked down the expression of SMS2 with siRNA targeting the Sgms2 gene in mouse primary osteoblasts. The effects of SMS2 knockdown in osteoblasts were examined using polymerase chain reaction and western blotting. The knockdown of SMS2 suppressed the formation of TRAP-positive multinucleated cells by co-culture of osteoblasts and bone marrow cells compared to the control. We found that receptor activator of nuclear factor κB ligand (RANKL) mRNA expression was significantly reduced by 1,25(OH)2D3 stimulation in SMS2 siRNA osteoblasts. The knockdown of SMS2 repressed the expression of retinoid-X-receptor-α (RXRα) regardless of 1,25(OH)2D3 stimulation. TRAP-positive multinucleated cell formation was significantly reduced by RXRα siRNA in osteoblasts in a co-culture system. These results suggest that SMS2 regulates osteoclast differentiation by inducing RANKL expression via RXRα.

RNA interference-mediated knockdown of Smad1 inhibits receptor activator of nuclear factor κB ligand expression induced by BMP-2 in primary osteoblasts.

OBJECTIVE: BMP-2 induces osteoblast differentiation and activates osteoclast formation. Here, we investigated the role of Smad1, a molecule that signals downstream of BMP-2, in mediating the effects of BMP-2 on osteoclast differentiation induced by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in osteoblasts. DESIGN: The effects of 1,25(OH)2D3 and BMP-2 in osteoclasts were examined using polymerase chain reaction and Western blotting to measure changes in target gene and protein expression. Immunostaining was carried out to investigate the localization of the vitamin D receptor (VDR) in the nucleus in response to BMP-2. RESULTS: Stimulation with both 1,25(OH)2D3 and BMP-2 resulted in significantly greater osteoclast formation and receptor activator of nuclear factor κB ligand (RANKL) mRNA expression compared to stimulation with 1,25(OH)2D3 alone. In addition, expression of the VDR protein was increased, enhancing the activity of 1,25(OH)2D3. Interestingly, knockdown of Smad1 resulted in reduced osteoclast formation, RANKL mRNA expression, and VDR protein expression compared with control cells. Costimulation with 1,25(OH)2D3 and BMP-2 enhanced VDR localization in the nucleus. CONCLUSIONS: We found that BMP-2 induced Smad1 activation, thereby influencing the localization of VDR in the nucleus in the presence of 1,25(OH)2D3 and resulting in increased RANKL mRNA expression. These effects ultimately resulted in enhanced osteoclast differentiation.

Assessment of alveolar bone mineral density as a predictor of lumbar fracture probability.

INTRODUCTION: Osteoporosis and tooth loss have been linked with advancing age, but no clear relationship between these conditions has been proven. Several studies of bone mineral density measurements of the jaw and spine have shown similarities in their rate of age-related deterioration. Thus, measurements of jawbone density may predict lumbar vertebral bone density. Using jawbone density as a proxy marker would circumvent the need for lumbar bone measurements and facilitate prediction of osteoporotic spinal fracture susceptibility at dental clinics. We aimed to characterize the correlation between bone density in the jaw and spine and the incidence of osteoporotic spinal fractures. METHODS: We used computerized radiogrammetry to measure alveolar bone mineral density (al-BMD) and dual-energy X-ray absorptiometry to measure lumbar bone mineral density (L-BMD). L-BMD and al-BMD in 30 female patients (average age: 59 ± 5 years) were correlated with various patient attributes. Statistical analysis included area under the curve (AUC) and probability of asymptomatic significance (PAS) in a receiver operating characteristic curve. The predictive strength of L-BMD T-scores (L-BMD[T]) and al-BMD measurements for fracture occurrence was then compared using multivariate analysis with category weight scoring. RESULTS: L-BMD and al-BMD were significantly correlated with age, years since menopause, and alveolar bone thickness. Both were also negatively correlated with fracture incidence. Category weight scores were -0.275 for a L-BMD(T) <80%; +0.183 for a L-BMD(T) ≥ 80%; -0.860 for al-BMD <84.9 (brightness); and +0.860 for al-BMD ≥ 84.9. AUC and PAS analyses suggested that al-BMD had a higher association with fracture occurrence than L-BMD. CONCLUSIONS: Our results suggest the possible association between al-BMD and vertebral fracture risk. Assessment of alveolar bone density may be useful in patients receiving routine dental exams to monitor the clinical picture and the potential course of osteoporosis in patients who may be at a higher risk of developing osteoporosis.

[Osteoporosis and oral biology].

Estrogen deficiency in post-menopausal osteoporosis not only causes decreased bone mass in mandibular bone, but also affect cartilaginous ossification in mandibular condyle. Although the mechanisms of action are not entirely clear, estrogen is thought to promote the programmed cell death of osteoclasts and hence reduce their period of activity. Treatment with estrogen or some agents prevent bone loss in alveolar bone through blocking production of cytokines in osteoblasts and promoting osteoclast apoptosis. It's necessary to address basic principles and current concepts in bone remodeling, mediators of bone resorption and their clinical relevance.