Up-regulation of osteolytic mediators in human osteosarcoma cells stimulated with nicotine

Evaluation of the Impact of Smoking on Orthodontic Treatment

Smoking is a prevalent habit known for its detrimental effects on oral health and it affects not only oral health but also various organ systems. The influence of smoking on periodontal health, including gingival inflammation, bone loss and delayed wound healing, poses significant challenges during orthodontic therapy. Orthodontic treatment depends on healthy bone and periodontal remodelling. Smoking reduces blood flow and oxygen to these areas, which can slow tooth movement and complicate treatment. It also increases plaque buildup, leading to potential periodontal diseases and enamel damage. Even after treatment, smoking can affect how well your teeth stay in their new position, increasing the risk of relapse. Quitting smoking can help improve your results and keep your smile healthier in the long run. Therefore, the literature concluded that orthodontists should consider smoking cessation interventions as an integral part of patient management to optimize treatment success and long-term oral health. This review explores the specific implications of smoking on orthodontic treatment outcomes.

Effect of cigarette smoking on alveolar bone thickness and density in patients undergoing leveling and alignment of crowded lower anterior teeth: a controlled clinical trial

OBJECTIVE

To evaluate the effect of cigarette smoking on the alveolar bone thickness and density in patients undergoing leveling and alignment of crowded lower anterior teeth.

METHODS

This controlled clinical trial involved 17 smokers and 17 nonsmokers with mild to moderate crowding of the anterior mandibular teeth. Two cone-beam computed tomography images of the mandible were taken before and after treatment. The length of each tooth root was calculated in each T0 image, and the root was divided into three equal regions. Three lines were drawn parallel to the line of the cementoenamel junction at these three regions of the root, and the previously drawn lines were used to measure bone thickness and bone density.

RESULTS

The mean changes in cortical bone thickness and bone density were significantly smaller in smokers than nonsmokers. Cortical bone thickness and bone density were significantly lower after than before treatment in both smokers and nonsmokers.

CONCLUSION

In addition to all of its known dangers, cigarette smoking may also harm the alveolar bone by decreasing the bone thickness and density during orthodontic treatment in heavy smokers.

Smoking Is Associated with Sex-Specific Effects on Bone Microstructure in Older Men and Women

BACKGROUND

Smoking is a risk factor for fracture, but the mechanism by which smoking increases fracture risk is unclear.

METHODS

Musculoskeletal health was compared with dual energy X-ray absorptiometry (DXA), high resolution peripheral quantitative computed tomography (HR-pQCT), trabecular bone score, and vertebral fracture assessment in current and past smokers and nonsmokers from a multiethnic study of adults ≥ age 65. Skeletal indices were adjusted for age and weight.

RESULTS

Participants (n = 311) were mean age (±SD) 76.1 ± 6.5 years, mostly female (66.0%) and non-white (32.7% black/39.4% mixed race/26.3% white). Mean pack-years was 34.6 ± 20.4. In men (n = 106), weight and BMI were lower (both p < 0.05) in current vs past smokers. Male smokers consumed half the calcium of never and past smokers. BMD by DXA did not differ by smoking status at any skeletal site in either sex. Current male smokers had 13.5%-15.3% lower trabecular bone score vs never and past smokers (both p < 0.05). By HR-pQCT, trabecular volumetric BMD was 26.6%-30.3% lower and trabeculae were fewer, thinner and more widely spaced in male current vs past and never smokers at the radius (all p < 0.05). Cortical indices did not differ. Tibial results were similar, but stiffness was also 17.5%-22.2% lower in male current vs past and never smokers (both p< 0.05). In women, HR-pQCT trabecular indices did not differ, but cortical porosity was almost twice as high in current vs never smokers at the radius and 50% higher at the tibia (both p < 0.05).

CONCLUSIONS

In summary, current smoking is associated with trabecular deterioration at the spine and peripheral skeleton in men, while women have cortical deficits. Smoking may have sex-specific skeletal effects. The consistent association with current, but not past smoking, suggests the effects of tobacco use may be reversible with smoking cessation.

Moderate-to-heavy smoking in women is potentially associated with compromised cortical porosity and stiffness at the distal radius

Though smokers have poor clinical outcomes after treatment for fractures, the skeletal effects of smoking are still debated. Our results showed that female smokers had 33% higher cortical bone porosity. Smoking targets cortical compartment microstructure and mechanics, and micron-scale variables are essential to better understand the specific effects of smoking.

PURPOSE

Smokers have poor outcomes in the clinic after treatment for fractures. However, skeletal effects of smoking are still debated. Inconsistencies in published data are likely due to macro-scale variables used to characterize bone differences due to smoking. Therefore, our goal was to characterize distal radius microstructure and macrostructure differences between smokers and non-smokers, and determine the degree to which smoking is associated with compartment-specific mechanical differences resulting from compromised cortical-trabecular microstructure.

METHODS

Data were acquired from 46 female smokers (35 to 64 years old), and 45 age- and body mass-matched female non-smokers. Distal radius microstructure and mechanical variables were determined from high-resolution peripheral quantitative computed tomography (HR-pQCT) images and multiscale finite element analysis. Distal radius macro-scale variables (bone volume, bone mineral content, volumetric bone mineral density [vBMD]) were determined from low-resolution images.

RESULTS

Age- and body mass index-adjusted results showed that cortical porosity was 33% higher (p < 0.01), and that cortical vBMD and stiffness were 3% and 8% lower, respectively (p < 0.05), among smokers. We also observed unloading of the cortical compartment in smokers. There were no differences in the macro-scale variables. Average HR-pQCT-derived vBMD was 8% lower (p < 0.05) in smokers corresponding to 5 years of postmenopausal loss.

CONCLUSION

Skeletal effects of smoking become evident at the micron level through a structurally and mechanically compromised cortical compartment, which partially explains the inconsistent results observed at the macro-level, and the poor clinical outcomes. Smoking may also compound postmenopausal effects on bone potentially placing women having undergone menopause at a greater risk for fracture.

Nicotine inhibits osteogenic differentiation of human periodontal ligament cells under cyclic tensile stress through canonical Wnt pathway and α7 nicotinic acetylcholine receptor

BACKGROUND AND OBJECTIVES

Nicotine, the main psychoactive component of tobacco, affects cell metabolism, proliferation, adhesion and, importantly, the osteogenic differentiation of fibroblasts. Approximately 15% of all orthodontic patients are adults among who one-fifth are smokers. Hence, it is necessary to have insight into the effects of nicotine on the osteogenic differentiation of hPDLCs during orthodontic tooth movement. This study aimed to investigate the effects and mechanisms of nicotine on the osteogenic differentiation of human periodontal ligament cells (hPDLCs) under the application of cyclic tensile stress.

MATERIAL AND METHODS

hPDLCs were obtained from donor third molars. The hPDLCs were treated with nicotine and/or cyclic tensile stress that was applied with a cell stress plus unit. The effect of nicotine on cell viability was analyzed using the MTT assay. The osteogenic differentiation of hPDLCs was detected by alkaline phosphatase staining, Alizarin Red S staining, quantitative real-time polymerase chain reaction and western blotting.

RESULTS

In combination with cyclic tensile stress, nicotine prevented the tensile stress-induced increase in alkaline phosphatase activity, formation of mineralization nodules and the upregulation of mRNA and protein expression of Runt-related transcription factor 2, transcription factor Sp7 and collagen type I; however, canonical Wnt pathway was activated. Furthermore, the addition of Dickkopf-related protein 1 and α-bungarotoxin counteracted the negative effect of nicotine and rescued the osteogenic differentiation of hPDLCs, respectively.

CONCLUSION

These results indicate that nicotine prevents the increased osteogenic potential of hPDLCs induced by cyclic tensile stress by binding to an α7 nicotinic acetylcholine receptor and activating the canonical Wnt pathway.

Osteoactivin regulates head and neck squamous cell carcinoma invasion by modulating matrix metalloproteases

Nearly 60% of patients with head and neck squamous cell carcinoma (HNSCC) die of metastases or locoregional recurrence. Metastasis is mediated by cancer cell migration and invasion, which are in part dependent on extracellular matrix degradation by matrix metalloproteinases. Osteoactivin (OA) overexpression plays a role in metastases in several malignancies, and has been shown to upregulate matrix metalloproteinase (MMP) expression and activity. To determine how OA modulates MMP expression and activity in HNSCC, and to investigate OA effects on cell invasion, we assessed effects of OA treatment on MMP mRNA and protein expression, as well as gelatinase and caseinolytic activity in HNSCC cell lines. We assessed the effects of OA gene silencing on MMP expression, gelatinase and caseinolytic activity, and cell invasion. OA treatment had differential effects on MMP mRNA expression. OA treatment upregulated MMP-10 expression in UMSCC14a (p = 0.0431) and SCC15 (p < 0.0001) cells, but decreased MMP-9 expression in UMSCC14a cells (p = 0.0002). OA gene silencing decreased MMP-10 expression in UMSCC12 cells (p = 0.0001), and MMP-3 (p = 0.0005) and -9 (p = 0.0036) expression in SCC25 cells. In SCC15 and SCC25 cells, OA treatment increased MMP-2 (p = 0.0408) and MMP-9 gelatinase activity (p < 0.0001), respectively. OA depletion decreased MMP-2 (p = 0.0023) and -9 (p < 0.0001) activity in SCC25 cells. OA treatment increased 70 kDa caseinolytic activity in UMSCC12 cells consistent with tissue type plasminogen activator (p = 0.0078). OA depletion decreased invasive capacity of UMSCC12 cells (p < 0.0001). OA's effects on MMP expression in HNSCC are variable, and may promote cancer cell invasion.

MicroRNA-106b inhibits osteoclastogenesis and osteolysis by targeting RANKL in giant cell tumor of bone

Giant cell tumor (GCT) of bone consists of three major cell types: giant cells, monocytic cells, and stromal cells. From microarray analysis, we found that miR-106b was down-regulated in GCT clinical samples and further determined by fluorescence in situ hybridization. In addition, the expression of novel potential target of miR-106b, RANKL, was elevated in GCT along with previously determined targets in other tumors such as IL-8, MMP2 and TWIST. In a RANKL 3′UTR luciferase reporter assays, agomiR-106b repressed the luciferase activity and the effect was eliminated when the targeting site in the reporter was mutated, suggesting a direct regulation of miR-106b on RANKL mRNA. Moreover, overexpression of miR-106b in GCTSCs through TALEN-mediated site-specific knockin clearly inhibited osteoclastogenesis and osteolysis. By grafting the GCT onto the chick CAM, we confirmed the inhibitory effect of miR-106b on RANKL expression and giant cell formation. Furthermore, in an OVX mouse model, silencing of miR-106b increased RANKL protein expression and promoted bone resorption, while up-regulation of miR-106b inhibited bone resorption. These results suggest that miR-106b is a novel suppressor of osteolysis by targeting RANKL and some other cytokines, which indicates that miR-106b may be a potential therapeutic target for the treatment of GCT.

Short-term effects of nicotine on orthodontically induced root resorption in rats

Objective: 

To investigate the effect of nicotine exposure on root resorption in an in vivo rat model of orthodontic tooth movement (OTM), and its association with odontoclastogenesis and receptor activator of nuclear factor-kappa B ligand (RANKL) expression.

Materials and Methods: 

Forty-eight 10-week-old male Wistar rats were divided into three groups. The negative control group was untreated. The left maxillary first molars in the nicotine-treated group and the positive control group received OTM with an initial force of 0.6 N in the mesial direction. Also, the nicotine-treated group received intraperitoneal injection of nicotine at 7 mg/kg per day. After 21 days, the rats were humanely killed. Eight rats from each group were randomly chosen for crater volume analysis by micro-computed tomography. For the remaining eight rats in each group, specimen slices were generated for histologic examination to determine the odontoclast number and the mean optical density value of RANKL.

Results: 

The resorption volumes in the nicotine-treated group were significantly larger than those in the control groups. Also, the nicotine-treated group displayed significantly higher number of odontoclasts and elevated RANKL expression compared to the control groups.

Conclusions: 

In an in vivo rat model, nicotine exposure promotes odontoclastogenesis and RANKL expression, evoking aggravated root resorption during OTM.

The in vitro and in vivo effects of nicotine on bone, bone cells and fracture repair

INTRODUCTION

Cigarette smoke has negative effects on bone metabolism and fracture repair. However, no study has reviewed effects of nicotine on bone and fracture repair independent of other constituents of cigarette smoke. The authors review the existing evidence of the effect of nicotine on 'bone' and 'bone cells' and fracture repair, drawing conclusions relevant to clinical practice and future research.

AREAS COVERED

A literature review was conducted using PRISMA guidelines and PubMed, Cochrane, MEDLINE/OVID, EMBASE, NHS Evidence and Google scholar databases. Articles were included if they specifically investigated the effects of nicotine on 'bone' or fracture repair in animal or human models or in vitro effects on 'bone cells'. A total of 64 papers were included in this review, of which 15 were human in vitro studies and 49 animal studies wherein 9 were in vitro and 40 in vivo. In vivo studies of the effects of nicotine in animals demonstrated widespread effects on bone including osteoneogenesis, osseointegration, steady-state skeletal bone and genes and cytokines relevant to bone cell physiology and bone homeostasis. In these studies, nicotine's effects are predominately negative, inhibiting bone cell metabolism and fracture repair, whereas most in vitro studies reported biphasic responses in all bone cells except osteoclastic cells.

EXPERT OPINION

The review suggests that nicotine has effects on osteoneogenesis, osseointegration and steady-state skeletal bone in animal in vivo models, as well as effects on all 'bone cells', via several mechanisms in both animal and human cell in vitro studies. The effect of nicotine is dose-dependent, with higher concentrations having predominantly negative effects, whereas at low concentrations a stimulatory effect is seen. Stimulatory effects on certain cells may indicate a possible, limited therapeutic role; advice regarding smoking cessation perioperatively should remain due to the other harmful components of cigarette smoke, but there may be scope for allowing the use of nicotine patches instead of complete abstention. Further research into clinical outcomes is required before the exact response of bone and fracture repair in humans to nicotine is known.

TNFRSF11A and TNFSF11 are associated with age at menarche and natural menopause in white women

OBJECTIVE

Menarche and menopause mark the lower and upper limits of the female reproductive period. The timing of these events influences women's health in later life. The onsets of menarche and menopause have a strong genetic basis. We tested two genes, TNFRSF11A (RANK) and TNFSF11 (RANKL), for their association with age at menarche (AM) and age at natural menopause (ANM).

METHODS

Nineteen single nucleotide polymorphisms (SNPs) of TNFRSF11A and 12 SNPs of TNFSF11 were genotyped in a random sample of 306 unrelated white women. This sample was analyzed for the association of the SNPs and common haplotypes with AM. Then, a subsample of 211 women with natural menopause was analyzed for the association of both genes with ANM. Smoking, alcohol intake, and duration of lactation were applied as covariates in the association analyses.

RESULTS

Three polymorphisms of TNFSF11 were associated with AM: rs2200287 (P = 0.005), rs9525641 (P = 0.039), and rs1054016 (P = 0.047). Two SNPs of this gene, rs346578 and rs9525641, showed an association with ANM (P = 0.007 and P = 0.011, respectively). Two SNPs of TNFRSF11A were associated with AM (rs3826620; P = 0.022) and ANM (rs8086340; P = 0.015). Multiple SNP-SNP and SNP-environment interaction effects on AM and ANM were detected for both genes. One polymorphism of TNFRSF11A, rs4436867, was not directly associated with either trait but indicated significant interactions with four TNFSF11 polymorphisms on ANM. Two other TNFRSF11A polymorphisms, rs4941125 and rs7235803, showed interaction effects with several TNFSF11 polymorphisms on AM. Both genes manifested significant interaction with the duration of breast-feeding in their effect on ANM.

CONCLUSIONS

The TNFRSF11A and TNFSF11 genes are associated with the onset of AM and ANM in white women.

Antibodies to porphyromonas gingivalis are associated with anticitrullinated protein antibodies in patients with rheumatoid arthritis and their relatives

OBJECTIVE

Anticitrullinated protein antibodies (ACPA) are relatively specific for rheumatoid arthritis (RA), and predate disease. The oral pathogen Porphyromonas gingivalis may play a role in breaking immune tolerance to citrullinated antigens. We studied a cohort of patients with RA and their relatives looking for associations between anti-P. gingivalis antibodies and ACPA.

METHODS

Patients with RA (n = 82) and their relatives (n = 205) from a North American Native (NAN) population were studied, along with 47 NAN and 60 non-NAN controls. IgM and IgA rheumatoid factor (RF) were tested by nephelometry and ELISA. Second-generation anticyclic citrullinated peptide (anti-CCP2) isotypes and IgG anti-P. gingivalis lipopolysaccharides were tested by ELISA. HLA-DRB1 typing was performed by sequencing. Oral hygiene and smoking habits were assessed by questionnaires.

RESULTS

Autoantibody frequency in patients with RA and relatives: ACPA 91% vs 19%, respectively; IgM RF 82% vs 17%; IgA RF 48% vs 22%. Anti-P. gingivalis levels were higher in patients with RA compared to relatives and controls (p = 0.005) and higher in ACPA-positive patients with RA than in ACPA-negative patients with RA (p = 0.04) and relatives (p < 0.001), but comparable in RF-positive and RF-negative patients and relatives. Poor oral hygiene and smoking were prevalent, but with no clear association with autoantibodies. Relatives with 2 shared-epitope alleles were more likely to be ACPA-positive (OR 2.5, p = 0.02).

CONCLUSION

In a genetically predisposed population of NAN patients with RA and their relatives, anti-P. gingivalis antibodies were associated with ACPA. These findings suggest that immune responses to P. gingivalis may be involved in breaking immune tolerance to citrullinated antigens.