CXCR4-mediated neutrophil dynamics in periodontitis.

BACKGROUND AND OBJECTIVE: Periodontitis is a common oral disease closely related to immune response and this study is aimed to identify the key immune-related pathogenic genes and analyze the infiltration and function of immune cells in the disease using bioinformatics methods. METHODS: Transcriptome datasets and single-cell RNA sequencing (scRNA-seq) datasets were downloaded from the GEO database. We utilized weighted correlation network analysis and least absolute selection and shrinkage operator, protein-protein interaction network construction to screen out key pathogenic genes as well as conducted the cell-type identification by estimating relative subsets of RNA transcripts algorithm to analyze and characterize immune cell types in periodontal tissues. In addition to bioinformatics validations, clinical and cell samples were collected and mouse periodontitis models were constructed to validate the important role of key genes in periodontitis. RESULTS: Bioinformatics analysis pointed out the positive correlation between CXCR4 expression and periodontitis, and revealed the increased infiltration of neutrophils in periodontal inflammatory. Similar results were obtained from clinical samples and animal models. In addition, the clustering and functional enrichment results based on CXCR4 expression levels included activation of immune response and cell migration, implying the possible function of CXCR4 on regulating neutrophil dynamics, which might contribute to periodontitis. Subsequent validation experiments confirmed that the increased expression of CXCR4 in neutrophils under periodontitis, where cell migration-related pathways also were activated. CONCLUSION: CXCR4 could be the key pathogenic gene of periodontitis and CXCR4/CXCL12 signal axial might contribute to the development of periodontitis by mediating neutrophil dynamics, suggesting that CXCR4 could be a potential target to help identify novel strategies for the clinical diagnosis and treatment of periodontitis.

Autoinducer-2 produced by oral microbial flora and alveolar bone loss in periodontitis.

OBJECTIVE: The aim of this study was to investigate the association between autoinducer-2 (AI-2) of oral microbial flora and the alveolar bone destruction in periodontitis to determine if AI-2 may have the potential that monitor periodontitis and predict bone loss. BACKGROUND: Plaque biofilm was the initiating factor of periodontitis and the essential factor of periodontal tissue destruction. The formation of biofilms depended on the complex regulation of the quorum sensing (QS) system, in which bacteria could sense changes in surrounding bacterial density by secreting the autoinducer (AI) to regulate the corresponding physiological function. Most oral bacteria also communicated with each other to form biofilms administrating the QS system, which implied that the QS system of periodontal pathogens was related to periodontitis, but the specific relationship was unknown. METHOD: We collected the gingival crevicular fluid (GCF) samples and measured the concentration of AI-2 in samples using the Vibrio harveyi BB180 bioluminescent-reporter system. To explore the interaction between AI-2 and bone metabolism, we utilized AI-2 purified from Fusobacterium nucleatum to investigate the impact of F. nucleatum AI-2 on osteoclast differentiation. Moreover, we constructed murine periodontitis models and multi-species biofilm models to study the association between AI-2 and periodontal disease progression. RESULTS: The AI-2 concentration in GCF samples increased along with periodontal disease progression (p < .0001). F. nucleatum AI-2 promoted osteoclast differentiation in a dose-dependent manner. In the periodontitis mice model, the CEJ-ABC distance in the F. nucleatum AI-2 treatment group was higher than that in the simple ligation group (p < .01), and the maxilla of the mice in the group exhibited significantly lower BMD and BV/TV values (p < .05). CONCLUSIONS: We demonstrated that the AI-2 concentration varied with the alveolar bone destruction in periodontitis, and it may have the potential for screening periodontitis. F. nucleatum AI-2 promoted osteoclast differentiation in a dose-dependent manner and aggravated bone loss.

Sequestered SQSTM1/p62 crosstalk with Keap1/NRF2 axis in hPDLCs promotes oxidative stress injury induced by periodontitis.

Periodontitis is a recognized multifactorial inflammatory chronic disease, however, the exact role of oxidative stress in the pathogenesis of periodontitis is undefined. This study aims to imply the mechanism of NRF2-regulated oxidative stress and inflammatory responses under periodontitis and explored the novelty therapeutic targets. We first demonstrate that redox imbalance caused by inhibited NRF2 signaling pathway is induced in periodontium during hypoxia and bacterial events. Then we propose that LPS from P. gingivalis and hypoxia stimuli could inhibit hPDLCs proliferation and GSH level, promote ROS production, lipid peroxidation level, and pro-inflammatory cytokines such as IL-6, TNF-α, and IL-17 level caused by the inhibited PI3K/AKT/mTOR pathway and sequential sequestered crosstalk between selective autophagy SQSTM1/p62 and Keap1/NRF2 axis accompanied by the reinforced NRF2 ubiquitination degradation and inactivated NRF2 nuclear translocation. Overexpression of NRF2 and SQSTM1 can protect hPDLCs from oxidative stress and inflammation exacerbation because of enhanced NRF2 activity. Further, the antioxidant and anti-inflammation potential of puerarin is verified in vitro and in experimental periodontitis in mice through diminishing above negative feedback loop mechanically. Altogether, we speculate that NRF2-mediated redox homeostasis is a profound candidate for one of the prominent roles in periodontitis pathogenesis and suggest puerarin as a promising therapeutic target.

A20 inhibits periodontal bone resorption and NLRP3-mediated M1 macrophage polarization.

A20 is involved in inflammation and bone metabolism in periodontitis. Regulation of macrophage polarization may be an effective target for periodontitis treatment, and A20 has a regulatory role in macrophage polarization. This study aimed to explore the effects of A20 on macrophage polarization in periodontitis and the underlying mechanism. Adeno-associated virus (AAV) targeting A20 was exploited to achieve A20 knockdown or overexpression in periodontal tissues of mice with experimental periodontitis. The (AAV-A20-RNAi) +P group showed increased alveolar bone resorption when compared with PBS + P and CON305 + P groups. However, the degree of bone destruction was reduced in the (AAV-A20) +P group relative to PBS + P and CON299 + P groups. A20 knockdown resulted in enhanced inducible nitric oxide synthase (iNOS) expression and decreased CD206 expression in mice periodontal tissues. In addition, higher levels of M1 macrophage polarization markers (iNOS, CD86, TNF-α) and lower CD206 expression were found in THP-1 cells treated with lipopolysaccharide (LPS) from Porphyromonas gingivalis (P. gingivalis) (Pg. LPS) and interferon-γ (IFN-γ) when A20 was silenced. A20 overexpression showed opposite effects on macrophage polarization in vivo and in vitro. Knockdown of A20 was correlated with upregulation of the NLRP3 inflammasome pathway in mice periodontal tissues or THP-1 cells. On the contrary, A20 overexpression inhibited the NLRP3 inflammasome pathway. MCC950 suppressed M1 macrophage polarization aggravated through A20 knockdown in Pg. LPS and IFN-γ stimulated cells. Our data suggested that A20 inhibits periodontal bone resorption and NLRP3-mediated M1 macrophage polarization; A20 is expected to be a novel target for the treatment of periodontitis.

Lactate inhibits osteogenic differentiation of human periodontal ligament stem cells via autophagy through the MCT1-mTOR signaling pathway.

BACKGROUND: Periodontal ligament stem cells (PDLSCs) play a crucial role in periodontal bone regeneration. Lactate used to be considered a waste product of glucose metabolism. In recent years, a few pieces of evidence revealed its roles in regulating the osteogenic differentiation of stem cells, but the standpoints were controversial. This study aims to investigate the effects and the mechanisms of lactate on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs). METHODS: The hPDLSCs were treated with different concentrations of lactic acid and lactate to differentiate the effects of the acidic PH and ion lactate. Proliferation and cytotoxicity were measured by Cell Counting Kit-8 (CCK8) assay and Live/Dead assay. The osteogenic differentiation of hPDLSCs was analyzed by alizarin red staining, alkaline phosphatase (ALP) staining, and then osteogenic proteins and genes were measured by western blot and reverse transcription-quantitative PCR (qRT-PCR). To investigate the potential signaling pathways, MCT1 inhibitor, G-protein inhibitors, and rapamycin were used, and then autophagy-related proteins and osteogenic proteins were measured by western blot. RESULTS: The inhibition of lactic acid on the osteogenic differentiation of hPDLSCs was more significant than lactate at the same concentration. Lactate inhibited the expression of ALP which can be rescued by Gα inhibitor. Alizarin red staining, the protein expression levels of osteocalcin (OCN), osteoprotegerin (OPN), osterix (OSX), and beclin1, LC3-II/LC3-I were decreased by lactate and partly rescued by MCT1 inhibitor. Rapamycin restored the protein expression levels of beclin1, LC3-II/LC3-I and OCN, OPN, OSX under the high lactate conditions. CONCLUSIONS: Lactate inhibits the expression of ALP via Gα subunit signaling, and inhibits mineralized nodules formation and the expression of osteogenic-related proteins via reducing autophagy through the MCT1-mTOR signaling pathway.

Effects of lactate in immunosuppression and inflammation: Progress and prospects.

Lactate used to be considered as a waste product of glucose metabolism. However, accumulating evidence has revealed its crucial role in regulating various biological and pathological processes. Hypoxia, inflammation, viral infection, and tumor promote the production of lactate. Then lactate activates G protein-coupled receptor 81 (GPR81) or shuttles across membranes by monocarboxylate-transporters (MCTs) to execute its intricate effects. Many studies highlighted the function of lactate in regulating dendritic cells, monocytes, natural killer cells, mast cells, T cells, tumor cells, fibroblasts, macrophages polarization, and the differentiation of Th1, Th17, MDSCs, Tregs; all of which play a role in maintaining the immune homeostasis of the host when challenged with the noxious stimuli. In this review, we summarized the influence of lactate in diverse tissue-specific cells, and discuss their effects on viral infection, acute inflammation, chronic inflammation, sepsis, and tumor immunosuppression. The goal of this review is to expose that lactate has a double-edged effect on host immunity and accompanying inflammatory reactions, which could be a potentially effective target for treating the tumor and multiple infectious diseases.

Microcirculation and somatosensory profiling of patients with periodontitis: a preliminary case control report.

OBJECTIVES: The purpose of this preliminary study was to explore blood microcirculation and somatosensory profiles in periodontitis patients before and after non-surgical periodontal therapy. MATERIALS AND METHODS: Twenty patients (10 men and 10 women, 20 to 30 years old) and 20 age- and gender-matched healthy controls were included. Non-surgical periodontal therapy was performed for all patients. Clinical examination including pocket probing depth (PPD), clinical attachment loss (CAL), and bleeding on probing (BOP) were performed at baseline (BL), 1 week (1W), and 4 weeks (4W) after non-surgical periodontal therapy on 6 sites of tooth 32 and 42. Laser Doppler flowmetry (LDF) and quantitative sensory testing (QST) were applied at the attached gingiva of tooth 32 and 42 at BL, 1W, and 4W after non-surgical periodontal therapy. Data were analyzed with a two-way mixed-model of ANOVA. RESULTS: The PPD, CAL and BOP significantly improved after non-surgical periodontal therapy (p < 0.001). Periodontitis patients demonstrated a higher tissue microvascular blood cell concentration (p = 0.015) and a significant gain in thermal (p = 0.037) and mechanical (p = 0.003) somatosensory function compared to controls. After non-surgical periodontal therapy, the flux (p = 0.002) and speed (p = 0.008) of blood flow decreased significantly and thermal (p = 0.029) and mechanical (p < 0.001) somatosensory function were reversed. CONCLUSION: Gingival microcirculation and somatosensory function seem impaired in patients with periodontitis and are reversed following non-surgical periodontal therapy. CLINICAL RELEVANCE: LDF and QST may be appropriate tools to further characterize gingival inflammation and treatment responses in periodontitis.

Impact of implant location on the prevalence of peri-implantitis: A systematic review and meta- analysis.

OBJECTIVES: To evaluate scientific evidence about the impact of implant location on the prevalence of peri-implantitis at implant level. SOURCE: Databases (PubMed, Embase and Cochrane) were searched until March 2020without limitations on language or publication year. Hand searches and gray literature were also included. STUDY SELECTION: Clinical studies reporting data on prevalence of peri-implantitis in anterior and posterior regions at implant level, and evaluations of implants with at least 1 year of function were selected. DATA: Ten studies with a low risk of bias were included. Meta-analysis was performed to estimate the pooled risk ratio. A significantly higher prevalence of peri-implantitis in anterior region compared to posterior region was found (Risk ratio: 1.34; 95 % CI: [1.07, 1.69]; p = 0.01). Meta-regression was performed to analyze the potential influence of confounding factors by calculating p-value of the coefficient. Subjects (p = 0.827), implants (p = 0.859) and age (p = 0.656) did not significantly influence the outcome. Subgroup analysis by jaw revealed significantly higher prevalence of peri-implantitis in maxillary anterior (Risk ratio: 1.37; 95 % CI: [1.10, 1.71]; p = 0.005) and mandibular anterior (Risk ratio: 1.76; 95 % CI: [1.29, 2.42]; p = 0.0004) regions compared to maxillary posterior region. No significant difference was found between maxillary anterior and mandibular posterior (Risk ratio: 1.15; 95 % CI: [0.75, 1.75]; p = 0.53) regions. A meta-analysis was precluded between mandibular anterior and mandibular posterior regions due to high statistical heterogeneity (I 2 = 76 %). CONCLUSIONS: Implants in the maxillary anterior and mandibular anterior regions had a higher prevalence of peri-implantitis compared to the maxillary posterior region. CLINICAL SIGNIFICANCE: Practitioners should strictly grasp the indications for patients missing anterior teeth and make comprehensive treatment planning.

Adjunctive effects of laser therapy on somatosensory function and vasomotor regulation of periodontal tissues in patients with periodontitis: A randomized controlled clinical trial.

BACKGROUND: The purpose of this prospective study was to compare the changes in periodontal somatosensory function and microcirculation in patients with periodontitis following initial treatment with scaling and root planing (SRP) with or without adjuvant laser therapy. METHODS: Twenty-four patients suffering from periodontitis were recruited and randomly allocated into a split-mouth design to either SRP combined laser therapy side (test side) or SRP only side (control side). All treatments were performed by the same investigator at a single visit. Laser Doppler Flowmetry (LDF) and Quantitative Sensory Testing (QST) were performed at baseline (W0), 1 week (1W), 2 weeks (2W), and 4 weeks (4W) after treatment on both sides of the attached gingiva of the maxillary lateral incisor. Clinical examination including probing depth (PD) and bleeding on probing (BOP) was performed at W0, 2W, and 4W on both sides. Data were analyzed with two-way analysis of variance. RESULTS: PD and BOP significantly improved after treatment (P <0.001). LDF values were significantly decreased on both sides at all follow-up time points (P <0.001), temperature was increased only on the test side (P = 0.017) whereas there was no significant change on the control side (P = 0.792). Significantly less sensitivity was observed for all QST parameters (P <0.030) except for warmth detection after treatment. CONCLUSION: Adjunctive use of laser therapy did not provide any significant clinical advantage or additional effects on the recovery of periodontal somatosensory function or gingival microcirculation in the present study.