Cigarette smoke condensate modulates migration of human gingival epithelial cells and their interactions with Porphyromonas gingivalis

Smoking Impacts Alzheimer's Disease Progression Through Oral Microbiota Modulation

Alzheimer's disease (AD) is an important public health challenge with a limited understanding of its pathogenesis. Smoking is a significant modifiable risk factor for AD progression, and its specific mechanism is often interpreted from a toxicological perspective. However, microbial infections also contribute to AD, with oral microbiota playing a crucial role in its progression. Notably, smoking alters the ecological structure and pathogenicity of the oral microbiota. Currently, there is no systematic review or summary of the relationship between these three factors; thus, understanding this association can help in the development of new treatments. This review summarizes the connections between smoking, AD, and oral microbiota from existing research. It also explores how smoking affects the occurrence and development of AD through oral microbiota, and examines treatments for oral microbiota that delay the progression of AD. Furthermore, this review emphasizes the potential of the oral microbiota to act as a biomarker for AD. Finally, it considers the feasibility of probiotics and oral antibacterial therapy to expand treatment methods for AD.

Tobacco-enhanced biofilm formation by Porphyromonas gingivalis and other oral microbes

Microbial biofilms promote pathogenesis by disguising antigens, facilitating immune evasion, providing protection against antibiotics and other antimicrobials and, generally, fostering survival and persistence. Environmental fluxes are known to influence biofilm formation and composition, with recent data suggesting that tobacco and tobacco-derived stimuli are particularly important mediators of biofilm initiation and development in vitro and determinants of polymicrobial communities in vivo. The evidence for tobacco-augmented biofilm formation by oral bacteria, tobacco-induced oral dysbiosis, tobacco-resistance strategies, and bacterial physiology is summarized herein. A general overview is provided alongside specific insights gained through studies of the model and archetypal, anaerobic, Gram-negative oral pathobiont, Porphyromonas gingivalis.

Influence of Smoking on Periodontal and Implant Therapy: A Narrative Review

BACKGROUND

smoking is considered the most modifiable risk factor for periodontal disease.

OBJECTIVE

the aim of this narrative review is to emphasize the effect of smoking on periodontal and implant therapy.

METHODS

The authors reviewed the literature reporting the clinical outcomes of smoking on periodontal surgical and nonsurgical treatment. The impact of smoking on implant therapy and sinus lifting procedures were also reviewed.

RESULTS

Periodontal and implant therapy outcomes are adversely affected by smoking. Smokers respond less favorably to periodontal therapy and periodontal flap procedures as compared to nonsmokers. Clinical outcomes for smokers are 50-75% worse than for nonsmokers. Studies reveal that smokers experience a significantly lower reduction in pocket depth compared to nonsmokers as well as less bone growth after treating infra-bony defects with guided tissue regeneration. The relative risk of implant failure is significantly higher in patients who smoke 20 cigarettes or more per day compared to nonsmokers. Additionally, smoking has also been shown to increase postoperative wound dehiscence and infection rates following sinus floor elevation. Longitudinal studies on smoke cessation have shown a reduction in bone loss and probing depths for periodontitis patients after cessation compared to those who smoke.

CONCLUSION

Smoking cessation can reduce probing depths and improve clinical attachment after nonsurgical periodontal therapy. There is insufficient evidence regarding the effect of smoking on peri-implantitis, as well as the loss of implants in the long-term.

Zoledronic acid affects the process of Porphyromonas gingivalis infecting oral mucosal epithelial barrier: An in-vivo and in-vitro study

Zoledronic acid (ZA), one of the commonly used bisphosphonates, is mainly used for bone-metabolic diseases. Studies proved that ZA has adverse effects on oral soft tissues. As the first line of innate immunity, the gingival epithelium could be infected by periodontal pathogens, which is a key process of the initiation of periodontal diseases. Yet, how ZA affects the periodontal pathogens infecting the epithelial barrier remains unclear. This study aimed to investigate the influences of ZA on the process of Porphyromonas gingivalis (P. gingivalis) infecting the gingival epithelial barrier via in-vitro and in-vivo experiments. In the in-vitro experiments, under the condition of different concentrations of ZA (0, 1, 10, and 100 μM), P. gingivalis was used to infect human gingival epithelial cells (HGECs). The infections were detected by transmission electron microscope and confocal laser scanning microscope. Besides, the internalization assay was applied to quantify the P. gingivalis, which infected the HGECs, in the different groups. To evaluate the expression levels of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, and IL-8, by infected HGECs, real-time quantitative reverse transcription-polymerase chain reactions were applied. In the in-vivo experiments, rats were given ZA solution (ZA group) or saline (control group) by tail intravenous injection for 8 weeks. Subsequently, we put ligatures around the maxillary second molars of all the rats and inoculated P. gingivalis to the gingiva every other day from day 1 to day 13. The rats were sacrificed on days 3, 7, and 14 for micro-CT and histological analyses. The in-vitro results manifested that the quantity of P. gingivalis that had infected HGECs increased with the ZA concentrations. Pro-inflammatory cytokines expression by HGECs were significantly increased by 100 μM ZA. In the in-vivo study, compared to the control group, more P. gingivalis was detected in the superficial layer of gingival epithelium in the ZA group. Besides, ZA significantly increased the expression level of IL-1β on day 14 and IL-6 on days 7 and 14 in gingival tissues. These findings suggest that the oral epithelial tissues of patients who receive high-dose ZA treatment may be more susceptible to periodontal infections, resulting in severe inflammatory conditions.

Investigating the Effects of Dehydrated Human Amnion-Chorion Membrane on Periodontal Healing

Each growth factor (GF) has different effects and targets, and plays a critical role in periodontal healing. Dehydrated human amnion-chorion membrane (dHACM) contains various GFs and has been used to enhance wound healing. The purpose of this study was to evaluate the effects of dHACM on periodontal healing, using in vitro and in vivo experimental approaches. Standardized periodontal defects were created in rats. The defects were randomly divided into three groups: Unfilled, filled with hydroxypropyl cellulose (HPC), and dHACM+HPC. At 2 and 4 weeks postoperatively, periodontal healing was analyzed by microcomputed tomography (micro-CT), and histological and immunohistochemical analyses. In vitro, periodontal ligament-derived cells (PDLCs) isolated from rat incisors were incubated with dHACM extract. Cell proliferation and migration were evaluated by WST-1 and wound healing assay. In vivo, micro-CT examination at 2 weeks revealed enhanced formation of new bone in the dHACM+HPC group. At 4 weeks, the proportions of vascular endothelial growth factor (VEGF)-positive cells and α-smooth muscle actin (α-SMA)-positive blood vessels in the dHACM+HPC group were significantly greater than those in the Unfilled group. In vitro, dHACM extracts at 100 µg/mL significantly increased cell proliferation and migration compared with control. These findings suggest that GFs contained in dHACM promote proliferation and migration of PDLCs and angiogenesis, which lead to enhanced periodontal healing.

PINK1 mediated mitophagy attenuates early apoptosis of gingival epithelial cells induced by high glucose

BACKGROUND

Oxidative stress mediated by hyperglycemia damages cell-reparative processes such as mitophagy. Down-regulation of mitophagy is considered to be a susceptible factor for diabetes mellitus (DM) and its complications. However, the role of mitophagy in DM-associated periodontitis has not been fully elucidated. Apoptosis of human gingival epithelial cells (hGECs) is one of the representative events of DM-associated periodontitis. Thus, this study aimed to investigate PTEN-induced putative kinase 1 (PINK1)-mediated mitophagy activated in the process of high glucose (HG)-induced hGECs apoptosis.

METHODS

For dose-response studies, hGECs were incubated in different concentrations of glucose (5.5, 15, 25, and 50 mmol/L) for 48 h. Then, hGECs were challenged with 25 mmol/L glucose for 12 h and 48 h, respectively. Apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL), caspase 9 and mitochondrial membrane potential (MMP). Subsequently, autophagy was evaluated by estimating P62, LC3 II mRNA levels, LC3 fluorescent puncta and LC3-II/I ratio. Meanwhile, the involvement of PINK1-mediated mitophagy was assessed by qRT-PCR, western blotting and immunofluorescence. Finally, hGECs were transfected with shPINK1 and analyzed by MMP, caspase 9 and annexin V-FITC apoptosis.

RESULTS

The number of TUNEL-positive cells and caspase 9 protein were significantly increased in cells challenged with HG (25 mmol/L) for 48 h (HG 48 h). MMP was impaired both at HG 12 h and HG 48 h, but the degree of depolarization was more serious at HG 48 h. The autophagy improved as the amount of LC3 II increased and p62 decreased in HG 12 h. During this process, HG 12 h treatment induced PINK1-mediated mitophagy. PINK1 silencing with HG 12 h resulted in MMP depolarization and cell apoptosis.

CONCLUSIONS

These results suggested that loss of the PINK1 gene may cause mitochondrial dysfunction and increase sensitivity to HG-induced apoptosis of hGECs at the early stage. PINK1 mediated mitophagy attenuates early apoptosis of gingival epithelial cells induced by high glucose.

Cigarette Smoke Stimulates SARS-CoV-2 Internalization by Activating AhR and Increasing ACE2 Expression in Human Gingival Epithelial Cells

A large body of evidence shows the harmful effects of cigarette smoke to oral and systemic health. More recently, a link between smoking and susceptibility to coronavirus disease 2019 (COVID-19) was proposed. COVID-19 is due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which uses the receptor ACE2 and the protease TMPRSS2 for entry into host cells, thereby infecting cells of the respiratory tract and the oral cavity. Here, we examined the effects of cigarette smoke on the expression of SARS-CoV-2 receptors and infection in human gingival epithelial cells (GECs). We found that cigarette smoke condensates (CSC) upregulated ACE2 and TMPRSS2 expression in GECs, and that CSC activated aryl hydrocarbon receptor (AhR) signaling in the oral cells. ACE2 was known to mediate SARS-CoV-2 internalization, and we demonstrate that CSC treatment potentiated the internalization of SARS-CoV-2 pseudovirus in GECs in an AhR-dependent manner. AhR depletion using small interference RNA decreased SARS-CoV-2 pseudovirus internalization in CSC-treated GECs compared with control GECs. Our study reveals that cigarette smoke upregulates SARS-CoV-2 receptor expression and infection in oral cells. Understanding the mechanisms involved in SARS-CoV-2 infection in cells of the oral cavity may suggest therapeutic interventions for preventing viral infection and transmission.

Environmental factors and periodontal microbiome

Periodontal diseases are chronic inflammatory, multifactorial diseases where the major triggering factors for disease onset are bacteria and their toxins, but the major part of tissue destruction occurs as a result of host response towards the periodontal microbiome. Periodontal microbiome consists of a wide range of microorganisms including obligate and facultative anaerobes. In health, there is a dynamic balance between the host, environment, and the microbiome. Environmental factors, mainly tobacco smoking and psychological stress, disrupt the symbiotic relationship. Tobacco smoke and its components alter the bacterial surface and functions such as growth. Psychological stressors and stress hormones may affect the outcome of an infection by changing the virulence factors and/or host response. This review aims to provide currently available data on the effects of the major environmental factors on the periodontal microbiome.

Effect of e-cigarettes on nasal epithelial cell growth, Ki67 expression, and pro-inflammatory cytokine secretion

OBJECTIVE

Upon use, e-cigarette aerosol comes in contact with various mucosal tissues, including the nasal epithelium, which may lead to nasal pathologies. We therefore assessed the effect of e-cigarettes on nasal epithelial cell and tissue behaviours.

METHODS

Human primary nasal epithelial cells and engineered 3D nasal mucosa tissues were exposed or not to either e-cigarette aerosol or standard cigarette smoke. We then evaluated cell viability and lactate dehydrogenase (LDH) activity. With the tissues analysed tissue structure, the expression of Ki67 proliferating marker, and the secretion of pro-inflammatory cytokines by the engineered nasal mucosa.

RESULTS

The nasal epithelial cells exposed to e-cigarettes displayed a larger cell size and a faint nucleus following exposure to e-cigarettes. This is supported by the increased levels of LDH activity following exposure to e-cigarettes, compared to that observed in the control. Tissues exposed to e-cigarette aerosol displayed a structural deregulation, with more large-sized cells, fewer Ki67-positive cells, and a reduced proliferation rate, compared to that observed in the non-exposed tissues. Cytokine measurements showed high levels of IL-6, IL-8, TNFα, and MCP-1, demonstrating that e-cigarettes activated pro-inflammatory cytokine responses.

CONCLUSION

E-cigarette aerosol showed adverse effects on nasal epithelial cells and nasal engineered mucosa tissue. These findings indicate that e-cigarettes could be a threat to nasal tissues and may impair the innate immune function of nasal epithelial cells.

The Impact of Smoking on Subgingival Microflora: From Periodontal Health to Disease

Periodontal disease is one of the most common diseases of the oral cavity affecting up to 90% of the worldwide population. Smoking has been identified as a major risk factor in the development and progression of periodontal disease. It is essential to assess the influence of smoking on subgingival microflora that is the principal etiological factor of the disease to clarify the contribution of smoking to periodontal disease. Therefore, this article reviews the current research findings regarding the impact of smoking on subgingival microflora and discusses several potential mechanisms. Cultivation-based and targeted molecular approaches yield controversial results in determining the presence or absence of smoking-induced differences in the prevalence or levels of certain periodontal pathogens, such as the “red complex.” However, substantial changes in the subgingival microflora of smokers, regardless of their periodontal condition (clinical health, gingivitis, or periodontitis), have been demonstrated in recent microbiome studies. Available literature suggests that smoking facilitates early acquisition and colonization of periodontal pathogens, resulting in an “at-risk-for-harm” subgingival microbial community in the healthy periodontium. In periodontal diseases, the subgingival microflora in smokers is characterized by a pathogen-enriched community with lower resilience compared to that in non-smokers, which increases the difficulty of treatment. Biological changes in key pathogens, such as Porphyromonas gingivalis, together with the ineffective host immune response for clearance, might contribute to alterations in the subgingival microflora in smokers. Nonetheless, further studies are necessary to provide solid evidence for the underlying mechanisms.

Protein carbonylation in human bronchial epithelial cells exposed to cigarette smoke extract

Cigarette smoke is a well-established exogenous risk factor containing toxic reactive molecules able to induce oxidative stress, which in turn contributes to smoking-related diseases, including cardiovascular, pulmonary, and oral cavity diseases. We investigated the effects of cigarette smoke extract on human bronchial epithelial cells. Cells were exposed to various concentrations (2.5-5-10-20%) of cigarette smoke extract for 1, 3, and 24 h. Carbonylation was assessed by 2,4-dinitrophenylhydrazine using both immunocytochemical and Western immunoblotting assays. Cigarette smoke induced increasing protein carbonylation in a concentration-dependent manner. The main carbonylated proteins were identified by means of two-dimensional electrophoresis coupled to MALDI-TOF mass spectrometry analysis and database search (redox proteomics). We demonstrated that exposure of bronchial cells to cigarette smoke extract induces carbonylation of a large number of proteins distributed throughout the cell. Proteins undergoing carbonylation are involved in primary metabolic processes, such as protein and lipid metabolism and metabolite and energy production as well as in fundamental cellular processes, such as cell cycle and chromosome segregation, thus confirming that reactive carbonyl species contained in cigarette smoke markedly alter cell homeostasis and functions.

Effect of tobacco on periodontal disease and oral cancer

INTRODUCTION

Periodontal disease and oral cancer are common health hazards. Epidemiological investigations show that smoking, periodontal disease and oral cancer are closely related. Tobacco is one of the major risk factors for periodontitis and oral cancer.

METHODS

A systematic literature review was performed. To identify relevant studies, the following online databases were searched using specific keywords: PubMed, Web of Science and CNKI.

RESULTS

Tobacco not only possesses an addictive effect, but it aggravates periodontal disease by promoting the invasion of pathogenic bacteria, inhibiting autoimmune defense, aggravating the inflammatory reaction, and aggravating the loss of alveolar bone. According to current evidence, tobacco significantly aggravates the development and progression of periodontal disease and oral cancer, and periodontal disease may be related to the prevalence of oral cancer.

CONCLUSIONS

Clinicians should strongly recommend that smokers undertake a strategy to stop smoking to avoid the exacerbation of nicotine-related periodontal disease and to reduce the incidence of oral cancer.

Smoking and periodontal microorganisms

Resolution of dysbiosis following treatment for periodontal disease and tobacco dependence has been reported in longitudinal intervention studies. In the present report, we evaluated the biological findings regarding the effect of smoking on the periodontal microbiome. A standardized electronic search was conducted using MEDLINE; overall, 1099 papers were extracted. Studies that addressed the relationship between tobacco and periodontal pathogens were included. Finally, 42 papers were deemed appropriate for the present review. Functional changes in periodontal pathogens exposed to nicotine and cigarette smoke extract support the clinical findings regarding dysbiosis of the subgingival microbiome. Dysbiosis of the periodontal microbiome was presented in smokers regardless of their periodontal condition (healthy, gingivitis, or periodontitis) and remained significant only in smokers even after the resolution of experimentally-induced gingivitis and following reduction of clinical signs of periodontitis with non-surgical periodontal treatment and over 3 months post-therapy. Based on these findings, smoking cessation in periodontitis patients is beneficial for promoting a health-compatible subgingival microbial community. To maximize the benefits of these interventions in dental settings, further studies on periodontal microbiome are needed to elucidate the impact of tobacco intervention on preventing recurrence of periodontal destruction in the susceptible subjects.

NFE2L2/NRF2, OGG1, and cytokine responses of human gingival keratinocytes against oxidative insults of various origin

OBJECTIVE

Bacterial or tobacco-related insults induce oxidative stress in gingival keratinocytes. The aim of this study was to investigate anti-oxidative and cytokine responses of human gingival keratinocytes (HMK cells) against Porphyromonas gingivalis lipopolysaccharide (Pg LPS), nicotine, and 4-nitroquinoline N-oxide (4-NQO).

MATERIALS AND METHODS

HMK cells were incubated with Pg LPS (1 µl/ml), nicotine (1.54 mM), and 4-NQO (1 µM) for 24 h. Intracellular and extracellular levels of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1Ra), IL-8, monocyte chemoattractant protein (MCP)-1, and vascular endothelial growth factor (VEGF) were measured with the Luminex® xMAP™ technique, and nuclear factor, erythroid 2 like 2 (NFE2L2/NRF2) and 8-oxoguanine DNA glycosylase (OGG1) with Western blots. Data were statistically analyzed by two-way ANOVA with Bonferroni correction.

RESULTS

All tested oxidative stress inducers increased intracellular OGG1 levels, whereas only nicotine and 4-NQO induced NFE2L2/NRF2 levels. Nicotine, 4-NQO, and their combinational applications with Pg LPS induced the secretions of IL-1β and IL-1Ra, while that of IL-8 was inhibited by the presence of Pg LPS. MCP-1 secretion was suppressed by nicotine, alone and together with Pg LPS, while 4-NQO activated its secretion. Treatment of HMK cells with Pg LPS, nicotine, 4-NQO, or their combinations did not affect VEGF levels.

CONCLUSION

Pg LPS, nicotine, and 4-NQO induce oxidative stress and regulate anti-oxidative response and cytokine expressions in human gingival keratinocytes differently. These results may indicate that bacterial and tobacco-related insults regulate distinct pathways.

The Porphyromonas gingivalis/Host Interactome Shows Enrichment in GWASdb Genes Related to Alzheimer's Disease, Diabetes and Cardiovascular Diseases

Periodontal disease is of established etiology in which polymicrobial synergistic ecology has become dysbiotic under the influence of Porphyromonas gingivalis. Following breakdown of the host's protective oral tissue barriers, P. gingivalis migrates to developing inflammatory pathologies that associate with Alzheimer's disease (AD). Periodontal disease is a risk factor for cardiovascular disorders (CVD), type II diabetes mellitus (T2DM), AD and other chronic diseases, whilst T2DM exacerbates periodontitis. This study analyzed the relationship between the P. gingivalis/host interactome and the genes identified in genome-wide association studies (GWAS) for the aforementioned conditions using data from GWASdb (P < 1E-03) and, in some cases, from the NCBI/EBI GWAS database (P < 1E-05). Gene expression data from periodontitis or P. gingivalis microarray was compared to microarray datasets from the AD hippocampus and/or from carotid artery plaques. The results demonstrated that the host genes of the P. gingivalis interactome were significantly enriched in genes deposited in GWASdb genes related to cognitive disorders, AD and dementia, and its co-morbid conditions T2DM, obesity, and CVD. The P. gingivalis/host interactome was also enriched in GWAS genes from the more stringent NCBI-EBI database for AD, atherosclerosis and T2DM. The misregulated genes in periodontitis tissue or P. gingivalis infected macrophages also matched those in the AD hippocampus or atherosclerotic plaques. Together, these data suggest important gene/environment interactions between P. gingivalis and susceptibility genes or gene expression changes in conditions where periodontal disease is a contributory factor.

Protective effect of catalpol on nicotine‑induced injury of alveolar bone and associated underlying mechanisms

Smoking is an important factor that causes periodontitis, which manifests as alveolar bone injury and absorption, and has a high incidence and unfavorable treatment efficacy. Nicotine causes ischemia and inflammation of the periodontium and inhibits the mineralization of alveolar bones. Previous studies have revealed the anti‑tumor biological activities of catalpol, in addition to neuroprotection and anti‑inflammation. The present study therefore investigated the underlying protective mechanism of catalpol in alveolar bone injury. A total of 24 Wistar rats were infused with nicotine (0.7 mg/kg for 30 days), followed by subcutaneous injection of catalpol (2 µg/kg for 14 days). The loss of alveolar bone was examined, and bone alkaline phosphatase (AP) and osteocalcin levels were examined by ELISA. The expression of tumor necrosis factor (TNF)‑α and cyclooxygenase‑2 (COX‑2) was quantified by reverse transcription‑quantitative polymerase chain reaction analysis and western blotting. Treatment with nicotine decreased AP and osteocalcin levels, increased TNF‑α and COX‑2 expression levels, and led to alveolar bone loss compared with the control group. Catalpol decreased bone loss, increased AP and osteocalcin, and decreased TNF‑α and COX‑2 expression compared with the nicotine treatment group. Catalpol may alleviate nicotine‑induced injury and alveolar bone loss via inhibition of inflammatory factors, and facilitate the mineralization of alveolar bones.

E-Cigarette Vapor Induces an Apoptotic Response in Human Gingival Epithelial Cells Through the Caspase-3 Pathway

Electronic cigarettes represent an increasingly significant proportion of today's consumable tobacco products. E-cigarettes contain several chemicals which may promote oral diseases. The aim of this study was to investigate the effect of e-cigarette vapor on human gingival epithelial cells. Results show that e-cigarette vapor altered the morphology of cells from small cuboidal form to large undefined shapes. Both single and multiple exposures to e-cigarette vapor led to a bulky morphology with large faint nuclei and an enlarged cytoplasm. E-cigarette vapor also increased L-lactate dehydrogenase (LDH) activity in the targeted cells. This activity was greater with repeated exposures. Furthermore, e-cigarette vapor increased apoptotic/necrotic epithelial cell percentages compared to that observed in the control. Epithelial cell apoptosis was confirmed by TUNEL assay showing that exposure to e-cigarette vapor increased apoptotic cell numbers, particularly after two and three exposures. This negative effect involved the caspase-3 pathway, the activity of which was greater with repeated exposure and which decreased following the use of caspase-3 inhibitor. The adverse effects of e-cigarette vapor on gingival epithelial cells may lead to dysregulated gingival cell function and result in oral disease. J. Cell. Physiol. 232: 1539-1547, 2017. © 2016 Wiley Periodicals, Inc.

Role of mitogen-activated protein kinase pathways in migration of gingival epithelial cells in response to stimulation by cigarette smoke condensate and infection by Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Previous studies have shown that cigarette smoke (CS) and periodontal pathogens could alter wound healing responses of gingival epithelial cells. To elucidate molecular mechanisms leading to these epithelial changes, we studied the signaling pathway involved in the modulation of cell migration by CS condensate (CSC) and the infection by a prominent periodontal pathogen, Porphyromonas gingivalis.

MATERIAL AND METHODS

Human gingival epithelial cells (Ca9-22) were treated with CSC or vehicle control for 24 h. Activation of mitogen-activated protein kinases (MAPK) in cells with or without infection by P. gingivalis was assessed by polymerase chain reaction array and immunoblotting using phospho-specific antibodies. Cell migration was assessed using in vitro wound closure model, and specific pharmacologic inhibitors of MAPK pathways were used to characterize further the extent of involvement of the MAPK pathways.

RESULTS

Polymerase chain reaction array showed that gene expression of several members of the MAPK, particularly p38 and JNK, was upregulated more than twofold in Ca9-22 cells stimulated with 10 μg/mL CSC. Coincubation with P. gingivalis induced a different pattern of gene expression for MAPK pathways, but it did not suppress the MAPK-related genes upregulated by CSC. A significant phosphorylation of ERK1/2 and p38 was observed in cells stimulated with 10 μg/mL CSC (p < 0.05), whereas coincubation with a higher concentration of CSC (250 μg/mL) evoked no such activation. P. gingivalis infection resulted in a tendency to reduce the phosphorylation of ERK1/2 and p38, which had been enhanced by stimulation with 10 μg/mL CSC. Incubation with ERK1/2 and p38 inhibitors significantly reduced the wound closure of CSC-stimulated cells, by approximately 43% and 46%, respectively (p < 0.05).

CONCLUSION

CSC exerts effects on the migration of human gingival epithelial cells through the activation of the MAPK ERK1/2 and p38 signaling pathways. P. gingivalis infection attenuates the CSC-induced migration at least partly by suppressing the phosphorylation of ERK1/2 and p38, but other pathways are likely to be involved in this modulatory process.

Repeated exposure to whole cigarette smoke promotes primary human gingival epithelial cell growth and modulates keratin expression

BACKGROUND AND OBJECTIVE

The gingiva is the first oral tissue directly exposed to cigarette smoke (CS). Exposure to CS compromises the structure and function of gingival tissue. Damaging or altering the gingival epithelium leads to a compromised protective barrier of the periodontium, resulting in several diseases. The aim of this study was to assess the effect of repeated exposure to CS on gingival epithelial cell growth and on expression of apoptotic protein and keratin.

MATERIAL AND METHODS

Primary human gingival epithelial cells were seeded on a collagen scaffold for 5 d to allow growth and stratification. The cells were then exposed for 5 min to whole CS for 3, 6 and 9 d. At the end of each exposure period, cell proliferation [using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) (MTT) and 5-bromo-2'-deoxyuridine (BrdU) assays], gene expression [by quantitative reverse transcription polymerase chain reaction (qRT-PCR)] and protein production (by western blot analysis) were investigated.

RESULTS

Higher metabolic activity was found in the CS-exposed cells than in the nonexposed cells, specifically after 3 and 6 d of exposure to CS. At 9 d there was no significant difference between CS-exposed and nonexposed cells. Metabolic activity was supported by the BrdU cell-proliferation analyses, which showed increased cell growth at 3 d compared with the control. However, at 6 and 9 d, cell proliferation in the CS-exposed culture was comparable to that in the nonexposed culture. Interestingly, the Bax/Bcl-2 protein ratios decreased with increased CS exposure, suggesting cell resistance. Moreover, protein analyses showed that CS decreased expression of keratin(K) 5 at 3, 6 and 9 d, and increased expression of K14 at 6 and 9 d. Finally, mRNA analyses showed significant decreases of K1, K6, K10 and K16 in CS-exposed cultures, correlating, at times, with a decrease of protein production.

CONCLUSION

CS was shown to increase epithelial cell proliferation, which may involve cell resistance to apoptosis. This is supported by the modulation of expression of different keratin genes and proteins. Altogether, these data may explain the hyperplasia reported in gingival tissue, as well as periodontal disease, in smokers.

In vitro Effect of Mouthrinse Containing Essential Oils on Proliferation and Migration of Gingival Epithelial Cells

We aimed to investigate in vitro the effects of mouthrinses containing essential oils (EOs) on proliferation and migration of gingival epithelial cells. Human gingival epithelial cells were treated with predetermined dilutions of commercially available EO mouthrinses with or without ethanol and a mouthrinse containing cetyl pyridinium chloride (CPC) for 60 s. Cell proliferation was evaluated using WST-1 assay. Cell migration was assessed using a wound closure model. Within 10 s of exposure to EO mouthrinse without ethanol, the epithelial cells became aberrant and shrank. No statistically significant difference in cell migration or proliferation was observed among cells pretreated by the EO mouthrinse with ethanol, CPC mouthrinse and control (phosphate buffered saline). In contrast, the EO mouthrinse without ethanol significantly reduced cell proliferation (p < 0.001) to approximately 20% relative to control. As for the EO mouthrinse without ethanol, it was not possible to assess its effect on cell migration using this model, because treated cells could be easily detached from the culture plate upon scratch, possibly because of the surfactant ingredient in the formulation. Within the limitations of the study, the EO mouthrinse with ethanol exerted no inhibitory effect on proliferation and migration of the gingival epithelial cells. Copyright © 2016 John Wiley & Sons, Ltd.