Programmed cell death in periodontitis: recent advances and future perspectives

Effects of different curcumin concentrations on human periodontal ligament fibroblast adhesion and proliferation on periodontally involved root surfaces: In-vitro study

Introduction

Periodontopathic endotoxins infiltrate root surface and prevent cellular adhesion to tooth surfaces. Naturally occurring curcumin has anti-inflammatory, antioxidant and antibacterial qualities that promote fast wound healing by increasing fibroblast cell proliferation and migration in concentration-dependent manner.

Objectives

This study was conducted to evaluate the effect of 0.12 %, 1 % and 2 % curcumin concentrations on PDL cell adhesion, viability and proliferation to periodontally affected root surfaces.

Materials and methods

20 periodontally affected teeth sectioned into root samples were included. PDL fibroblasts were collected from freshly extracted teeth, cultured and expanded. PDL fibroblast (1 × 105 cells/ml) was seeded on curcumin coated root samples in different concentrations. Study samples were divided into 4 groups: G1 (0.12 % of curcumin paste), G2 (1 % curcumin paste), G3 (2 % curcumin paste) and G4 (control/unconditioned group). All samples were investigated by SEM and MTT assay.

Results

G3 showed highest viability and cell proliferation compared to other groups where well defined multilayered adherent cells covering entire surface with totally flat polyhedral bodies with long cytoplasmic extensions and little or no bacterial colonization.

Conclusion

Curcumin 2 % provides optimal stimulation of cellular attachment, viability, proliferation and antibacterial effects over periodontitis affected root surfaces.

Clinical relevance

Determination of optimal curcumin concentration in this study revealed 2 % concentration produced highest levels of PDL cellular attachment, viability, proliferation and antibacterial action over root surfaces afflicted by periodontitis. Therefore, the use of that optimal curcumin concentration as adjunctive to non-surgical periodontal therapy may modify the periodontal pocket ecology to improve the healing of periodontal tissues.

Investigating the role of necroptosis in the immunological microenvironment of periodontitis

BACKGROUND

Extensive research has delved into the nexus between necroptosis and immunity, yet its impact on the immunological microenvironment of periodontitis remains elusive. Therefore, the study aims to elucidate the role of necroptosis in shaping this particular microenvironment.

RESULTS

We examined the differential expression of necroptosis genes in healthy and periodontitis samples, analyzing their correlations with infiltrating immunocytes, immune responses, and the human leukocyte antigen (HLA) gene. Distinct necroptosis-mediated expression patterns were identified, along with genes associated with the necroptosis phenotype. Notably, 37 necroptosis genes were dysregulated, leading to the development of a seven-necroptosis classifier that accurately distinguished periodontitis from healthy samples. The findings reveal a profound association between necroptosis and the immunological microenvironment, evidenced by the positive correlation between ZBP1 and MLKL expression with plasma cells, the negative correlation between TNFRSF1B and ZBP1 with resting dendritic cells, and the modulation of BCR signaling and TGF family receptor activity by ZBP1 and MLKL. Furthermore, we uncovered a positive correlation between ZBP1 and HLA-C expression and a negative correlation between HSPA4 and HLA-A expression. The analysis identified two distinct necroptosis expression patterns, each characterized by unique immune features. Among the 5272 genes associated with the necroptosis phenotype, 339 genes were linked to immunity, their biological functions centering on immunocyte regulation.

CONCLUSION

This study underscores the significant role of necroptosis in shaping the immunological microenvironment of periodontitis, offering novel insights into the pathogenesis of this condition and paving the way for potential therapeutic strategies for periodontitis and its systemic comorbidities.

Immunologic cell deaths: involvement in the pathogenesis and intervention therapy of periodontitis

Periodontitis is one of the most common diseases and primary causes of tooth loss. The main factor that causes periodontitis is an overactive host immunological response. An in-depth investigation into the molecular pathways that cause periodontitis can aid in creating novel therapeutic approaches for periodontitis and its related systemic disorders. Several immunologic cell death (ICD) pathways have been implicated in advancing periodontitis. Nevertheless, there is still a substantial lack of understanding surrounding the precise molecular mechanisms of ICD in periodontitis. Additionally, the beneficial feature of ICD in periodontitis, which involves its ability to eliminate pathogens, needs further confirmation. According to this, a comprehensive literature search utilizing the Web of Science™, PubMed®, and Scopus® databases was conducted. Only items published in the English language up until October 2024 were taken into account, and finally, 65 relevant papers were selected to be included in this review. In this article, we present a comprehensive analysis of the processes and outcomes of ICD activation in the progression of periodontitis. Lastly, the present difficulties linked to ICDs as a viable treatment option for periodontitis are emphasized.

Sodium butyrate activates the extrinsic and intrinsic apoptotic processes in murine cementoblasts

Background

/purpose: The metabolic by-product butyric acid of Gram-negative anaerobic bacteria can invoke pathological effects on periodontal cells resulting in inflammation and further destruction of periodontium. However, limited researches on the effects of butyric acid on cementoblasts were reported. Therefore, this study aimed to investigate the type of cell death in murine cementoblast (OCCM.30) caused by adding the different concentrations of sodium butyrate to the cell culture.

Materials and methods

OCCM.30 cells were exposed to sodium butyrate (0, 2, 4, 8, 16 mM) for 48 h. Cell viability was determined by microculture tetrazolium assay. Cell cycle distribution and cell death were analyzed by flow cytometry. Caspase-mediated apoptotic cascade was evaluated by Western blot.

Results

The concentrations of sodium butyrate≧4 mM were found to inhibit cell viability of OCCM.30 cells in a dose-dependent manner (P < 0.05). Sodium butyrate elevated sub-G1 cell population which exhibited cell apoptosis in OCCM.30 cells (P < 0.05). In addition, early and later apoptotic cells were found in sodium butyrate-induced cell death. Sodium butyrate significantly stimulated the degradation of procaspases-3, -8, and -9 levels, respectively (P < 0.05). Simultaneously, sodium butyrate corresponded to augment the levels of cleaved forms of caspases-3, -8, and -9, respectively (P < 0.05).

Conclusion

Taken together, sodium butyrate is a cytotoxic agent and can induce apoptosis on cementoblasts. The pathway involved in apoptosis is activated by caspase family signaling pathways. These evidences may provide a new mechanistic insight into the mechanism of damage of cementoblasts during the development and progression of periodontitis.

Novel Insights from Comprehensive Bioinformatics Analysis Utilizing Large-Scale Human Transcriptomes and Experimental Validation: The Role of Autophagy in Periodontitis

Objective

Autophagy plays a crucial role in the pathophysiology of periodontitis, yet its precise involvement in the disease process remains elusive. The aim of the present study was thus to investigate the involvement of autophagy in the pathology of periodontitis. This investigation involved transcriptomic analysis of a broad range of human samples and complemented by in vitro experimentation.

Materials and Methods

We analyzed the transcriptomes of human gingival tissues from individuals with periodontitis and health controls to identify the differential expression of autophagy-related genes (DEARGs) and to investigate their potential interactions and functional pathways. Additionally, protein-protein interaction (PPI) networks were constructed to identify key functional modules and hub genes. Experimental validation of autophagy regulation in periodontitis and identification of key autophagy-regulating genes was accomplished through in vitro cellular experiments. Subsequently, a comprehensive analysis of immune cell infiltrate utilizing the CIBERSORT algorithm was performed. Finally, leveraging the DSigDB database, potential candidate drugs for periodontitis treatment targeting autophagy were predicted.

Results

A total of 79 genes have been identified as DEARGs in periodontitis. An intricate interplay among the DEARGs and their impact on the regulatory mechanisms of autophagy within the context of periodontitis was observed. Subsequently, 10 hub genes were discerned through the establishment of a PPI network. Furthermore, dysregulated autophagic activity in periodontitis was validated, and 9 key genes (APP, KDR, IL1B, CXCL12, CXCR4, IL6, FOS, LCK, and SHC1) were identified through in vitro experiments. Our analysis unveiled an association between these genes and altered immune cell infiltration in periodontitis. Additionally, we predicted potential therapeutic agents such as curcumin, 27-hydroxycholesterol, and Trolox, showing promise in the treatment of periodontitis by modulating the autophagic process.

Conclusion

This study identified nine key genes for autophagy regulation and potential therapeutic agents in periodontitis. These findings not only enhance our comprehension of the pathological mechanisms of periodontitis but also provide substantial evidence for the advancement of novel therapeutic strategies.

Insight into the role of macrophages in periodontitis restoration and development

Periodontitis is one of the chronic diseases that have the greatest impact on human health, and it is associated with several other chronic diseases. Tissue damage associated with periodontitis is often connected with immune response. Immune cells are a crucial component of the human immune system and are directly involved in periodontitis during the inflammatory phase of the disease. Macrophages, as a key component of the immune system, are responsible for defence, antigen presentation and phagocytosis in healthy tissue. They are also closely linked to the development and resolution of periodontitis, through mechanisms such as macrophage polarization, pattern recognition receptors recognition, efferocytosis, and Specialized Pro-resolving Mediators (SPMs) production. Additionally, apoptosis and autophagy are also known to play a role in the recovery of periodontitis. This review aims to investigate the aforementioned mechanisms in more detail and identify novel therapeutic approaches for periodontitis.

Analysis of immunogenic cell death in periodontitis based on scRNA-seq and bulk RNA-seq data

Background

Recent studies have suggested that cell death may be involved in bone loss or the resolution of inflammation in periodontitis. Immunogenic cell death (ICD), a recently identified cell death pathway, may be involved in the development of this disease.

Methods

By analyzing single-cell RNA sequencing (scRNA-seq) for periodontitis and scoring gene set activity, we identified cell populations associated with ICD, which were further verified by qPCR, enzyme linked immunosorbent assay (ELISA) and immunofluorescence (IF) staining. By combining the bulk transcriptome and applying machine learning methods, we identified several potential ICD-related hub genes, which were then used to build diagnostic models. Subsequently, consensus clustering analysis was performed to identify ICD-associated subtypes, and multiple bioinformatics algorithms were used to investigate differences in immune cells and pathways between subtypes. Finally, qPCR and immunohistochemical staining were performed to validate the accuracy of the models.

Results

Single-cell gene set activity analysis found that in non-immune cells, fibroblasts had a higher ICD activity score, and KEGG results showed that fibroblasts were enriched in a variety of ICD-related pathways. qPCR, Elisa and IF further verified the accuracy of the results. From the bulk transcriptome, we identified 11 differentially expressed genes (DEGs) associated with ICD, and machine learning methods further identified 5 hub genes associated with ICD. Consensus cluster analysis based on these 5 genes showed that there were differences in immune cells and immune functions among subtypes associated with ICD. Finally, qPCR and immunohistochemistry confirmed the ability of these five genes as biomarkers for the diagnosis of periodontitis.

Conclusion

Fibroblasts may be the main cell source of ICD in periodontitis. Adaptive immune responses driven by ICD may be one of the pathogenesis of periodontitis. Five key genes associated with ICD (ENTPD1, TLR4, LY96, PRF1 and P2RX7) may be diagnostic biomarkers of periodontitis and future therapeutic targets.

Local Application of a New Chalconic Derivative (Chalcone T4) Reduces Inflammation and Oxidative Stress in a Periodontitis Model in Rats

Chalcones are phenolic compounds with biological properties. This study had the aim to evaluate the effects of topical administration of a new synthetic chalcone, Chalcone T4, in an animal model of periodontitis induced by ligature. Forty rats were distributed in the following experimental groups: negative control (without periodontitis and topical application of distilled water), positive control (periodontitis and topical application of distilled water), chalcone I and II (periodontitis and topical application of 0.6 mg/mL and 1.8 mg/mL, respectively). Chalcone or distilled water was administered into the gingival sulcus of the first molars daily for 10 days, starting with the ligature installation. The following outcomes were evaluated: alveolar bone loss (µCT and methylene blue dye staining), quantification of osteoclasts (histomorphometry), cell infiltrate and collagen content (stereometry), gene expression of mediators (Nfact11, Tnf-α, Mmp-13, iNos, Sod and Nrf2) by (RT-qPCR); expression of BCL-2 and Caspase-1 (immunohistochemistry). Chalcone T4 inhibited bone resorption and prevented collagen matrix degradation. Reduction in the expression of inflammatory markers (Nfact11, Tnf-α, Mmp-13, and Caspase-1), attenuation of oxidative stress (iNOS reduction, and increase in Sod), and pro-apoptotic effect of the compound (BCL-2 reduction), were associated its effects on periodontal tissues. Topical application of Chalcone T4 prevented bone resorption and inflammation, demonstrating potential in the adjunctive treatment of periodontitis.

Identification of disulfidptosis- and ferroptosis-related transcripts in periodontitis by bioinformatics analysis and experimental validation

Background

Disulfidptosis and ferroptosis are forms of programmed cell death that may be associated with the pathogenesis of periodontitis. Our study developed periodontitis-associated biomarkers combining disulfidptosis and ferroptosis, which provides a new perspective on the pathogenesis of periodontitis.

Methods

Firstly, we obtained the periodontitis dataset from public databases and found disulfidptosis- and ferroptosis-related differentially expressed transcripts based on the disulfidptosis and ferroptosis transcript sets. After that, transcripts that are tissue biomarkers for periodontitis were found using three machine learning methods. We also generated transcript subclusters from two periodontitis microarray datasets: GSE16134 and GSE23586. Furthermore, three transcripts with the best classification efficiency were further screened. Their expression and classification efficacy were validated using qRT-PCR. Finally, periodontal clinical indicators of 32 clinical patients were collected, and the correlation between three transcripts above and periodontal clinical indicators was analyzed.

Results

We identified six transcripts that are tissue biomarkers for periodontitis, the top three transcripts with the best classification, and delineated two expression patterns in periodontitis.

Conclusions

Our study found that disulfidptosis and ferroptosis were associated with immune responses and may involve periodontitis genesis.

Exploring the molecular mechanisms of ferroptosis-related genes in periodontitis: a multi-dataset analysis

PURPOSE

This study aims to elucidate the biological functions of ferroptosis-related genes in periodontitis, along with their correlation to tumor microenvironment (TME) features such as immune infiltration. It aims to provide potential diagnostic markers of ferroptosis for clinical management of periodontitis.

METHODS

Utilizing the periodontitis-related microarray dataset GSE16134 from the Gene Expression Omnibus (GEO) and a set of 528 ferroptosis-related genes identified in prior studies, this research unveils differentially expressed ferroptosis-related genes in periodontitis. Subsequently, a protein-protein interaction network was constructed. Subtyping of periodontitis was explored, followed by validation through immune cell infiltration and gene set enrichment analyses. Two algorithms, randomForest and SVM(Support Vector Machine), were employed to reveal potential ferroptosis diagnostic markers for periodontitis. The diagnostic efficacy, immune correlation, and potential transcriptional regulatory networks of these markers were further assessed. Finally, potential targeted drugs for differentially expressed ferroptosis markers in periodontitis were predicted.

RESULTS

A total of 36 ferroptosis-related genes (30 upregulated, 6 downregulated) were identified from 829 differentially expressed genes between 9 periodontitis samples and the control group. Subsequent machine learning algorithm screening highlighted 4 key genes: SLC1A5(Solute Carrier Family 1 Member 5), SLC2A14(Solute Carrier Family 1 Member 14), LURAP1L(Leucine Rich Adaptor Protein 1 Like), and HERPUD1(Homocysteine Inducible ER Protein With Ubiquitin Like Domain 1). Exploration of these 4 key genes, supported by time-correlated ROC analysis, demonstrated reliability, while immune infiltration results indicated a strong correlation between key genes and immune factors. Furthermore, Gene Set Enrichment Analysis (GSEA) was conducted for the four key genes, revealing enrichment in GO/KEGG pathways that have a significant impact on periodontitis. Finally, the study predicted potential transcriptional regulatory networks and targeted drugs associated with these key genes in periodontitis.

CONCLUSIONS

The ferroptosis-related genes identified in this study, including SLC1A5, SLC2A14, LURAP1L, and HERPUD1, may serve as novel diagnostic and therapeutic targets for periodontitis. They are likely involved in the occurrence and development of periodontitis through mechanisms such as immune infiltration, cellular metabolism, and inflammatory chemotaxis, potentially linking the ferroptosis pathway to the progression of periodontitis. Targeted drugs such as flurofamide, L-733060, memantine, tetrabenazine, and WAY-213613 hold promise for potential therapeutic interventions in periodontitis associated with these ferroptosis-related genes.

Mechanisms of mechanical force aggravating periodontitis: A review

Periodontitis is a widespread oral disease accompanied by uncontrolled inflammation-related tissue destruction. Periodontitis is related to various factors. Among them, occlusal trauma can aggravate the severity of periodontitis and has been attracting a great deal of attention. We systematically searched PubMed and Web of Science databases for related articles. Keywords for the search were "mechanical force", "mechanical stress", "occlusal trauma" and "periodontitis". This review focuses on the effect of mechanical forces on periodontitis and discusses the possible pivotal targets participating in this process. We elucidated and summarized 21 articles that reported on our topic. Several biological processes and pathways that participate in enhancing the inflammatory response to mechanical stress have been studied, including the regulation of osteogenesis and osteoclastic resorption balance, Yes-associated protein signaling, induction of collagen destruction, and regulation of programmed cell death. Mechanical force enhances the process of periodontitis in multiple ways. However, currently, no studies have further examined its underlying mechanism. Understanding the specific roles of mechanical forces may assist in the treatment of periodontitis with traumatic occlusal trauma.

Effects and mechanisms of Porphyromonas gingivalis outer membrane vesicles induced cardiovascular injury

BACKGROUND

The outer membrane vesicles (OMVs) derived from Porphyromonas gingivalis (P. gingivalis) have long been acknowledged for their crucial role in the initiation of periodontitis. However, the implications of P. gingivalis OMVs in the context of cardiovascular disease (CVD) remain incompletely understood. This study aimed to clarify both the impact and the underlying mechanisms through which P. gingivalis OMVs contribute to the propagation of distal cardiovascular inflammation and trauma.

METHODS

In this study, various concentrations (0, 1.25, 2.5, and 4.5 µg/µL) of P. gingivalis OMVs were microinjected into the common cardinal vein of zebrafish larvae at 48 h post-fertilization (hpf) to assess changes in cardiovascular injury and inflammatory response. Zebrafish larvae from both the PBS and the 2.5 µg/µL injection cohorts were harvested at 30 h post-injection (hpi) for transcriptional analysis. Real-time quantitative PCR (RT-qPCR) was employed to evaluate relative gene expression.

RESULTS

These findings demonstrated that P. gingivalis OMVs induced pericardial enlargement in zebrafish larvae, caused vascular damage, increased neutrophil counts, and activated inflammatory pathways. Transcriptomic analysis further revealed the involvement of the immune response and the extracellular matrix (ECM)-receptor interaction signaling pathway in this process.

CONCLUSION

This study illuminated potential mechanisms through which P. gingivalis OMVs contribute to CVD. It accentuated their involvement in distal cardiovascular inflammation and emphasizes the need for further research to comprehensively grasp the connection between periodontitis and CVD.

Sirtuin6 and Lipoxin A4 levels are decreased in severe periodontitis

OBJECTIVE

Sirtuin6 plays an important role in the regulation of inflammation, homeostasis, and apoptosis, and it has anti-inflammatory effects on several diseases. Lipoxin A4 is a pro-resolving lipid mediator of inflammation and inhibits hypoxia-induced apoptosis and oxidative stress. Considering that Lipoxin A4 and Sirtuin6 have protective effects on inflammatory diseases, the aim of this study is to determine the possible roles of these molecules on periodontitis inflammation in saliva and serum and to reveal the relationship of these data with clinical periodontal parameters.

MATERIAL AND METHODS

A total of 20 stage III/grade B periodontitis and 20 periodontally healthy subjects were included in this cross-sectional study (all never smokers and systemically healthy). Clinical periodontal parameters (plaque index, probing pocket depth, bleeding on probing, clinical attachment loss) were recorded. Saliva and serum levels of Sirtuin6 and Lipoxin A4 were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Serum Sirtuin6 and saliva Lipoxin A4 levels were significantly lower in the periodontitis group than the control group (respectively, p = 0.0098, p = 0.0008). There were negative correlations between all periodontal clinical parameters and saliva Lipoxin A4 level (p < 0.05) and between probing pocket depth, clinical attachment loss, and serum and saliva Sirtuin6 levels (respectively, r =  - 0.465 and r =  - 0.473, p < 0.05).

CONCLUSIONS

Decreased levels of serum Sirtuin6 and saliva Lipoxin A4 in periodontitis patients and their correlation with clinical periodontal parameters suggest that serum Sirtuin6 and saliva Lipoxin A4 may be related with periodontal inflammation.

CLINICAL RELEVANCE

Scientific rationale for the study: Sirtuin6 is one of seven members of the family of NAD + dependent protein that played an important role in the regulation of inflammation, energy metabolism, homeostasis, and apoptosis. Sirtuin6 is associated with the pathogenesis of several diseases. Lipoxin A4 is a lipid mediator that inhibits hypoxia-induced apoptosis and oxidative stress, and it has an active role in the resolution of periodontal inflammation. No studies that investigated the potential role Sirtuin6 and its relationship with inflammation resolution and apoptosis mechanisms in severe periodontitis patients.

PRINCIPAL FINDINGS

the serum Sirtuin6 and saliva Lipoxin A4 levels were significantly lower and negatively correlated with clinical periodontal parameters in the patients with periodontitis than the healthy controls.

PRACTICAL IMPLICATIONS

this study shows that serum Sirtuin6 and saliva Lipoxin A4 may be candidate biomarkers related with periodontal inflammation and estimating to periodontal status.

CLINICAL TRIAL REGISTRATION

NCT05417061.

Correlation of Serum and Gingival Crevicular Fluid Levels of Caspase-3 and Milk Fat Globule-Epidermal Growth Factor 8 on Gingival Health

AIM

This study aimed to estimate and correlate the serum and gingival crevicular fluid (GCF) levels of caspase-3 and milk fat globule-epidermal growth factor 8 (MFG-E8) in healthy, gingivitis and generalised chronic periodontitis subjects.

MATERIALS AND METHODS

A total of 24 subjects were selected and divided into three groups. After recording the periodontal parameters (plaque index (PI), modified gingival index (MGI), probing depth (PD) and clinical attachment level (CAL)), the serum and GCF samples were collected and the levels of caspase-3 and MFG-E8 were estimated using enzyme-linked immunoassay (ELISA).

RESULTS

The mean values of PI, MGI, PD and CALs were significantly higher in group III when compared to group II and group I. The mean value of serum and GCF caspase-3 increased with increasing disease severity, whereas the mean serum and GCF values of MFG-E8 decreased with increasing severity of disease. Spearman's correlation showed a strong positive correlation between the serum and GCF levels of caspase-3 and periodontal parameters, whereas serum and GCF levels of MFG-E8 showed a strong negative correlation with the periodontal parameters.

CONCLUSION

The findings of this study are suggestive that the serum and GCF levels of caspase-3 and MFG-E8 could serve as a potential biomarker for the role of apoptosis in periodontal disease. However, further studies are required to explore the mechanism and understand the relationship between these apoptotic markers and periodontitis.

The role of mitochondrial dysfunction in periodontitis: From mechanisms to therapeutic strategy

Periodontitis is an inflammatory and destructive disease of tooth-supporting tissue and has become the leading cause of adult tooth loss. The most central pathological features of periodontitis are tissue damage and inflammatory reaction. As the energy metabolism center of eukaryotic cells, mitochondrion plays a notable role in various processes, such as cell function and inflammatory response. When the intracellular homeostasis of mitochondrion is disrupted, it can lead to mitochondrial dysfunction and inability to generate adequate energy to maintain basic cellular biochemical reactions. Recent studies have revealed that mitochondrial dysfunction is closely related to the initiation and development of periodontitis. The excessive production of mitochondrial reactive oxygen species, imbalance of mitochondrial biogenesis and dynamics, mitophagy and mitochondrial DNA damage can all affect the development and progression of periodontitis. Thus, targeted mitochondrial therapy is potentially promising in periodontitis treatment. In this review, we summarize the above mitochondrial mechanism in the pathogenesis of periodontitis and discuss some potential approaches that can exert therapeutic effects on periodontitis by modulating mitochondrial activity. The understanding and summary of mitochondrial dysfunction in periodontitis might provide new research directions for pathological intervention or treatment of periodontitis.

Necroptosis has a crucial role in the development of chronic periodontitis

Background and aim

Periodontitis is a non-communicable chronic inflammatory disease that affects the entire periodontium and its severe types cause irreparable destruction. The purpose of this study was to determine the type of cell death in chronic periodontitis (CP) with the expression of receptor-interacting protein kinase (RIPK) type1 and RIPK3 genes.

Materials and methods

This cross-sectional study was carried out from September 2019 to 2020. The samples (38 participants) were divided into two groups: 20 recently diagnosed CP patients and 18 healthy individuals. Participants' data was collected in the periodontology Department, Dental school, Mashhad University of Medical Sciences and sent to the Immunology Lab for assessment of RIPK1 and RIPK3 expressions using quantitative real time-PCR.

Results

The study sample consisted of 30 females (78.9%) and 8 males (21.1%) with a mean age of 34 ± 5 years. The expression of the genes of interest in CPs exhibited an opposite pattern. Although, RIPK3 gene expression was significantly greater in CP patients compared to the control group (P = 0.024), the expression of RIPK1 decreased (p < 0.001). Moreover, no significant correlation was observed between age and gender with these molecules in CPs.

Conclusion

The RIPK3 selectively contributes to necroptosis, therefore, it seems that RIPK3-mediated necroptosis is involved in chronic periodontitis. RIPK1 also participates in necroptosis, but mostly in apoptosis. Therefore, necroptosis as an unprogrammed inflammatory cell death induced by pathogenic damages seems to be another mechanism complicated in periodontitis and could be used as a novel target for CP therapy.

Development of a classification model and an immune-related network based on ferroptosis in periodontitis

BACKGROUND AND OBJECTIVES

Periodontitis is an immunoinflammatory disease characterized by irreversible periodontal attachment loss and bone destruction. Ferroptosis is a kind of immunogenic cell death that depends on the participation of iron ions and is involved in various inflammatory and immune processes. However, information regarding the relationship between ferroptosis and immunomodulation processes in periodontitis is extremely limited. The purpose of this study was to investigate the correlation between ferroptosis and immune responses in periodontitis.

METHODS

Gene expression profiles of gingivae were collected from the Gene Expression Omnibus data portal. After detecting differentially expressed ferroptosis-related genes (FRGs), we used univariate logistic regression analysis followed by logistic least absolute shrinkage and selection operator (LASSO) regression to establish a ferroptosis-related classification model in an attempt to accurately distinguish periodontitis gingival tissues from healthy samples. The infiltration level of immunocytes in periodontitis was then assessed through single-sample gene-set enrichment analysis. Subsequently, we screened out immune-related genes by weighted correlation network analysis and protein-protein interaction (PPI) analysis and constructed an immune-related network based on FRGs and immune-related genes.

RESULTS

A total of 24 differentially expressed FRGs were detected, and an 8-FRG combined signature constituted the classification model. The established model showed outstanding discriminating ability according to the results of receiver operating characteristic (ROC) curve analysis. In addition, the periodontitis samples had a higher degree of immunocyte infiltration. Activated B cells had the strongest positive correlation while macrophages had a strong negative correlation with certain FRGs, and we found that XBP1, ALOX5 and their interacting genes might be crucial genes in the immune-related network.

CONCLUSIONS

The FRG-based classification model had a satisfactory determination ability, which could bring new insights into the pathogenesis of periodontitis. Those genes in the immune-related network, especially hub genes along with XBP1 and ALOX5, would have the potential to serve as promising targets of immunomodulatory treatments for periodontitis.

Identification of ferroptosis, necroptosis, and pyroptosis-associated genes in periodontitis-affected human periodontal tissue using integrated bioinformatic analysis

Introduction: Periodontitis is a chronic inflammatory oral disease that destroys soft and hard periodontal support tissues. Multiple cell death modes including apoptosis, necroptosis, pyroptosis, and ferroptosis play a crucial role in the pathogenicity of inflammatory diseases. This study aimed to identify genes associated with ferroptosis, necroptosis, and pyroptosis in different cells present in the periodontium of periodontitis patients. Methods: Gingival tissues' mRNA sequencing dataset GSE173078 of 12 healthy control and 12 periodontitis patients' and the microarray dataset GSE10334 of 63 healthy controls and 64 periodontitis patients' were obtained from Gene Expression Omnibus (GEO) database. A total of 910 differentially expressed genes (DEGs) obtained in GSE173078 were intersected with necroptosis, pyroptosis, and ferroptosis-related genes to obtain the differential genes associated with cell death (DCDEGs), and the expression levels of 21 differential genes associated with cell death were verified with dataset GSE10334. Results: Bioinformatic analysis revealed 21 differential genes associated with cell death attributed to ferroptosis, pyroptosis, and necroptosis in periodontitis patients compared with healthy controls. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that 21 differential genes associated with cell death were related to various cellular and immunological pathways including inflammatory responses, necroptosis, and osteoclast differentiation. Additionally, the single-cell RNA (scRNA) sequencing data GSE171213 of 4 healthy controls and 5 periodontitis patients' periodontal tissue was analyzed to obtain cell clustering and cell types attributed to differential genes associated with cell death. We found that among 21 DCDEGs, SLC2A3, FPR2, TREM1, and IL1B were mainly upregulated in neutrophils present in the periodontium of periodontitis patients. Gene overlapping analysis revealed that IL-1B is related to necroptosis and pyroptosis, TREM1 and FPR2 are related to pyroptosis, and SLC2A3 is related to ferroptosis. Finally, we utilized the CIBERSORT algorithm to assess the association between DCDEGs and immune infiltration phenotypes, based on the gene expression profile of GSE10334. The results revealed that the upregulated SLC2A3, FPR2, TREM1, and IL1B were positively correlated with neutrophil infiltration in the periodontium. Discussion: The findings provide upregulated SLC2A3, FPR2, TREM1, and IL1B in neutrophils as a future research direction on the mode and mechanism of cell death in periodontitis and their role in disease pathogenicity.

Canonical and noncanonical pyroptosis are both activated in periodontal inflammation and bone resorption

BACKGROUND AND OBJECTIVE

Pyroptosis has both a caspase-1-dependent canonical pathway and a caspase-4/-5/-11-dependent noncanonical pathway. They play an important role in inflammatory damage and related diseases. Canonical pyroptosis was reported to be involved in periodontitis. However, knowledge of caspase-4/-5/-11-dependent noncanonical pathway involvement remains limited. The aim of this study was to investigate the outcomes of pyroptosis inhibition on periodontitis as well as the possible mechanism, in order to provide a potential target for alleviating periodontitis.

METHODS

Human and rat periodontitis tissues were collected for immunohistochemistry (IHC). Micro-computed tomography was used to assess alveolar bone loss in experimental periodontitis model. Pyroptosis-related proteins were tested by western blot. propidium iodide staining and lactate dehydrogenase release were used to verify pyroptosis activation. RNA sequencing was applied to investigate the preliminary mechanism of the reduced periodontal inflammation induced by YVAD-CHO.

RESULTS

Both canonical- and noncanonical-related proteins were detected in human and rat periodontitis tissue. The pyroptosis-inhibited group demonstrated less inflammatory response and bone absorption. In vitro, pyroptosis was activated by lipopolysaccharide and inhibited by YVAD-CHO. RNA sequencing demonstrated that the expression of A20 and IκB-ζ was increased and verified by western blot in vitro and IHC in vivo.

CONCLUSION

These results suggest that inhibition of pyroptosis-reduced inflammation and alveolar bone resorption in periodontitis.

The neutrophil elastase-upregulated placenta growth factor promotes the pathogenesis and progression of periodontal disease

BACKGROUND

Periodontal disease is a chronic inflammatory disease. Given its high prevalence, especially in aging population, the detailed mechanisms about pathogenesis of periodontal disease are important issues for study. Neutrophil firstly infiltrates to periodontal disease-associated pathogen loci and amplifies the inflammatory response for host defense. However, excessive neutrophil-secreted neutrophil elastase (NE) damages the affected gingival. In lung and esophageal epithelium, NE had been proved to upregulate several growth factors including placenta growth factor (PGF). PGF is an angiogenic factor with proinflammatory properties, which mediates the progression of inflammatory disease. Therefore, we hypothesize excessive NE upregulates PGF and participates in the pathogenesis and progression of periodontal disease.

METHODS

In gingival epithelial cells (GEC), growth factors array demonstrated NE-increased growth factors and further be corroborated by Western blot assay and ELISA. The GEC inflammation was evaluated by ELISA. In mice, the immunohistochemistry results demonstrated ligature implantation-induced neutrophil infiltration and growth factor upregulation. By multiplex assay, the ligature-induced proinflammatory cytokines level in gingival crevicular fluid (GCF) were evaluated. Finally, alveolar bone absorption was analyzed by micro-CT images and H &amp; E staining.

RESULTS

NE upregulated PGF expression and secretion in GEC. PGF promoted GEC to secret IL-1β, IL-6, and TNF-α in GCF In periodontal disease animal model, ligature implantation triggered NE infiltration and PGF expression. Blockade of PGF attenuated the ligature implantation-induced IL-1β, IL-6, TNF-α and MIP-2 secretion and ameliorated the alveolar bone loss in mice.

CONCLUSION

In conclusion, the NE-induced PGF triggers gingival epithelium inflammation and promotes the pathogenesis and progression of periodontal disease.

Enterococcus faecalis-Induced Macrophage Necroptosis Promotes Refractory Apical Periodontitis

The persistence of residual bacteria, particularly Enterococcus faecalis, contributes to refractory periapical periodontitis, which still lacks effective therapy. The role of receptor-interacting protein kinase 3 (RIPK3)- and mixed lineage kinase domain-like protein (MLKL)-mediated necroptosis, a highly proinflammatory form of regulated cell death, has recently drawn much attention. However, the role of necroptosis in the pathogenesis of refractory periapical periodontitis remains unclear. We investigated whether the RIPK3/MLKL signaling pathway was activated in periapical lesion specimens obtained from patients diagnosed with refractory periapical periodontitis. RIPK3-deficient mice were then used to determine the role of necroptosis under this condition in vivo. We found that the phosphorylation levels of RIPK3 and MLKL were elevated in periapical lesion specimens of patients with refractory periapical periodontitis. In addition, necroptosis was induced in an E. faecalis-infected refractory periapical periodontitis mouse model, in which inhibition of necroptosis by RIPK3 deficiency could markedly alleviate inflammation and bone destruction. Moreover, double-labeling immunofluorescence suggested that macrophage necroptosis may be involved in the development of refractory periapical periodontitis. Then, we established an in vitro macrophage infection model with E. faecalis. E. faecalis infection was found to induce necroptotic cell death in macrophages through the RIPK3/MLKL signaling pathway, which was markedly alleviated by the RIPK3- or MLKL-specific inhibitor. Our study revealed that RIPK3/MLKL-mediated macrophage necroptosis contributes to the development of refractory periapical periodontitis and suggests that inhibitors or treatments targeting necroptosis represent a plausible strategy for the management of refractory periapical periodontitis. IMPORTANCE Oral infectious diseases represent a major neglected global population health challenge, imposing an increasing burden on public health and economy. Refractory apical periodontitis (RAP), mainly caused by Enterococcus faecalis, is a representative oral infectious disease with considerable therapeutic challenges. The interplay between E. faecalis and the host often leads to the activation of programmed cell death. This study identifies an important role of macrophage necroptosis induced by E. faecalis in the pathogenesis of RAP. Manipulating RIPK3/MLKL-mediated necroptosis may represent novel therapeutic targets, not only for RAP but also for other E. faecalis-associated infectious diseases.

The role of endoplasmic reticulum stress in the pathophysiology of periodontal disease

The endoplasmic reticulum (ER) is a principal organelle for folding, post-translational modifications and transport of secretory, luminal, and membrane proteins. ER stress is a condition induced by the accumulation of unfolded or misfolded proteins owing to a variety of physiological and pathological phenomena. To overcome the deleterious effects of ER stress, unfolded protein response (UPR) is initiated to translocate and remove the misfolded and accumulated proteins. Plenty of evidence shows the correlation between ER stress/UPR and the pathology of inflammatory disease. Periodontal disease is a chronic inflammatory disease characterized by the irreversible destruction of periodontal tissues, which associates with the onset and progress of several systemic diseases. Periodontopathic bacterium and pro-inflammatory mediators play a pivotal role in the progress of periodontal disease. Besides, cigarette smoke has long been associated with periodontal disease. As an inflammatory disorder of the periodontium, periodontal disease is highly related to ER stress. In this review, we provide an overview of the pathophysiological effect of ER stress on periodontal disease through five aspects as follow: ER stress and periodontal tissue remodeling, including both soft tissue and hard tissue; ER stress and the inflammation; ER stress and systematic effect during the periodontal disease; last but not least, ER stress and the autophagic apoptosis in cells.

Identification of Key Pyroptosis-Related Genes and Distinct Pyroptosis-Related Clusters in Periodontitis

Aim

This study aims to identify pyroptosis-related genes (PRGs), their functional immune characteristics, and distinct pyroptosis-related clusters in periodontitis.

Methods

Differentially expressed (DE)-PRGs were determined by merging the expression profiles of GSE10334, GSE16134, and PRGs obtained from previous literatures and Molecular Signatures Database (MSigDB). Least absolute shrinkage and selection operator (LASSO) regression was applied to screen the prognostic PRGs and develop a prognostic model. Consensus clustering was applied to determine the pyroptosis-related clusters. Functional analysis and single-sample gene set enrichment analysis (ssGSEA) were performed to explore the biological characteristics and immune activities of the clusters. The hub pyroptosis-related modules were defined using weighted correlation network analysis (WGCNA).

Results

Of the 26 periodontitis-related DE-PRGs, the highest positive relevance was for High-Mobility Group Box 1 (HMGB1) and SR-Related CTD Associated Factor 11 (SCAF11). A 14-PRG-based signature was developed through the LASSO model. In addition, three pyroptosis-related clusters were obtained based on the 14 prognostic PRGs. Caspase 3 (CASP3), Granzyme B (GZMB), Interleukin 1 Alpha (IL1A), IL1Beta (B), IL6, Phospholipase C Gamma 1 (PLCG1) and PYD And CARD Domain Containing (PYCARD) were dysregulated in the three clusters. Distinct biological functions and immune activities, including human leukocyte antigen (HLA) gene expression, immune cell infiltration, and immune pathway activities, were identified in the three pyroptosis-related clusters of periodontitis. Furthermore, the pink module associated with endoplasmic stress-related functions was found to be correlated with cluster 2 and was suggested as the hub pyroptosis-related module.

Conclusion

The study identified 14 key pyroptosis-related genes, three distinct pyroptosis-related clusters, and one pyroptosis-related gene module describing several molecular aspects of pyroptosis in the pathogenesis and immune micro-environment regulation of periodontitis and also highlighted functional heterogeneity in pyroptosis-related mechanisms.

Pentraxin-3 promotes LPS-induced pyroptosis in human periodontal ligament stem cells

The aim of this study was to explore the function of Pentraxin-3 (PTX3) in cell viability, pyroptosis, inflammation, osteogenic differentiation and oxidative stress of lipopolysaccharide (LPS)-stimulated human periodontal ligament stem cells (hPDLSCs). In the study, hPDLSCs were stimulated by LPS from Porphyromonas gingivalis to establish an in vitro inflammatory cellular model. Protein expression was measured using western blotting. Messenger RNA (mRNA) levels were evaluated by real-time polymerase chain reaction (qRT-PCR). Cell viability, inflammatory cytokine production and caspase-1 activity was measured with commercially available kits. Oxidative stress was assessed by examining reactive oxygen species and nitric oxide production. We found that PTX3 was upregulated in LPS-stimulated hPDLSCs. PTX3 overexpression aggravated LPS-induced cell viability loss, inflammatory cytokine production and oxidative stress, as well as suppressed the osteogenic differentiation in hPDLSCs, while silencing PTX3 had the opposite effects. Further, PTX3 overexpression promoted NOD-like receptor family, pyrin domain containing protein 3 (NLRP3) inflammasome overactivation and pyroptosis, evidenced by increased protein levels of NLRP3, cleaved-caspase-1, apoptosis-associated speck-like protein (ASC) and N-terminal gasdermin D (GSDMD-N). Inhibition of NLRP3 inflammasome and/or caspase-1 partially attenuated the effects of PTX3 on LPS-stimulated hPDLSCs. This study indicated that PTX3 promotes LPS-induced pyroptosis and inflammation in hPDLSCs through activation of the caspase-1-dependent NLRP3 inflammasome.

Mixed lineage kinase domain-like pseudokinase-mediated necroptosis aggravates periodontitis progression

Necroptosis is a form of cell death that is reportedly involved in the pathogenesis of periodontitis. The role of Mlkl-involved necroptosis remains unclear. Herein, this project aimed to explore the role of MLKL-mediated necroptosis in periodontitis in vitro and in vivo. Expression of RIPK3, MLKL, and phosphorylated MLKL was observed in gingival tissues obtained from healthy subjects or patients with periodontitis. The cell viability of Porphyromonas gingivalis lipopolysaccharide (LPS-Pg)-treated cells was detected. In wild type or Mlkl deficiency mice with ligature-induced periodontitis, alveolar bone loss and osteoclast activation were assessed. mRNA levels of inflammatory cytokines in bone marrow-derived macrophages were tested by qRT-PCR. Increased expression of RIPK3, MLKL, and phosphorylated MLKL was observed in gingival tissues obtained from patients with periodontitis. Porphyromonas gingivalis lipopolysaccharide (LPS-Pg)-treated cells developed necroptosis after caspase inhibition and negatively regulated the NF-κB signaling pathway. In mice with ligature-induced periodontitis, Mlkl deficiency reduced alveolar bone loss and weakened osteoclast activation. Furthermore, genetic ablation of Mlkl in LPS-Pg-treated bone marrow-derived macrophages increased the mRNA levels of tumor necrosis factor-α, interleukin (Il)-1β, Il-6, cyclooxygenase 2, matrix metalloproteinase 9, and receptor activator of nuclear factor kappa-B ligand. Our data indicated that MLKL-mediated necroptosis aggravates the development of periodontitis in a Mlkl-deficient mouse. This will provide a new sight for the understanding of etiology and therapies of periodontitis. KEY MESSAGES: MLKL expression was up-regulated in inflamed human gingival tissue. Mlkl deficiency affected the progression of periodontitis. Necroptosis played a major role in mice periodontitis model. Knockout of Mlkl had a significant effect on inflammatory responses.

NLRP3 Inflammasome Expression in Gingival Crevicular Fluid of Patients with Periodontitis and Chronic Hepatitis C

The study is aimed at assessing the impact that periodontal disease and chronic hepatitis C could have on gingival crevicular fluid levels of the NLRP3 inflammasome, caspase-1 (CASP-1), and interleukin-18 (IL-18) and at evaluating whether the increased local inflammatory reaction with clinical periodontal consequences is correlated to their upregulation. Patients were divided into four groups, according to their periodontal status and previously diagnosed hepatitis C, as follows: (i) CHC group, chronic hepatitis C patients; (ii) P group, periodontal disease patients, systemically healthy; (iii) CHC + P group, patients suffering from both conditions; and (iv) H group, systemically and periodontally healthy controls. Gingival crevicular samples were collected for quantitative analysis of the NLRP3 inflammasome, CASP-1, and IL-18. CHC + P patients expressed the worse periodontal status and the highest NLRP3, CASP-1, and IL-18 levels, the difference being statistically significant (p < 0.05). The P group patients also expressed significantly more elevated NLRP3, CASP-1, and IL-18 levels, as compared to nonperiodontal patients (CHC and H groups). Chronic hepatitis C and periodontal disease could have a significant influence on the upregulation of NLRP3 inflammasome and its components, possibly contributing to an increased local inflammatory reaction and clinical periodontal consequences.

Inflammasomes in Alveolar Bone Loss

Bone remodeling is tightly controlled by osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Fine tuning of the osteoclast-osteoblast balance results in strict synchronization of bone resorption and formation, which maintains structural integrity and bone tissue homeostasis; in contrast, dysregulated bone remodeling may cause pathological osteolysis, in which inflammation plays a vital role in promoting bone destruction. The alveolar bone presents high turnover rate, complex associations with the tooth and periodontium, and susceptibility to oral pathogenic insults and mechanical stress, which enhance its complexity in host defense and bone remodeling. Alveolar bone loss is also involved in systemic bone destruction and is affected by medication or systemic pathological factors. Therefore, it is essential to investigate the osteoimmunological mechanisms involved in the dysregulation of alveolar bone remodeling. The inflammasome is a supramolecular protein complex assembled in response to pattern recognition receptors and damage-associated molecular patterns, leading to the maturation and secretion of pro-inflammatory cytokines and activation of inflammatory responses. Pyroptosis downstream of inflammasome activation also facilitates the clearance of intracellular pathogens and irritants. However, inadequate or excessive activity of the inflammasome may allow for persistent infection and infection spreading or uncontrolled destruction of the alveolar bone, as commonly observed in periodontitis, periapical periodontitis, peri-implantitis, orthodontic tooth movement, medication-related osteonecrosis of the jaw, nonsterile or sterile osteomyelitis of the jaw, and osteoporosis. In this review, we present a framework for understanding the role and mechanism of canonical and noncanonical inflammasomes in the pathogenesis and development of etiologically diverse diseases associated with alveolar bone loss. Inappropriate inflammasome activation may drive alveolar osteolysis by regulating cellular players, including osteoclasts, osteoblasts, osteocytes, periodontal ligament cells, macrophages, monocytes, neutrophils, and adaptive immune cells, such as T helper 17 cells, causing increased osteoclast activity, decreased osteoblast activity, and enhanced periodontium inflammation by creating a pro-inflammatory milieu in a context- and cell type-dependent manner. We also discuss promising therapeutic strategies targeting inappropriate inflammasome activity in the treatment of alveolar bone loss. Novel strategies for inhibiting inflammasome signaling may facilitate the development of versatile drugs that carefully balance the beneficial contributions of inflammasomes to host defense.

The Effect of Porphyromonas gingivalis Lipopolysaccharide on the Pyroptosis of Gingival Fibroblasts

Periodontitis is a chronic inflammatory disease induced by Porphyromonas gingivalis (P. gingivalis) and other pathogens. P. gingivalis release various virulence factors including lipopolysaccharide (LPS). However, whether P. gingivalis-LPS inducing pyroptosis in human gingival fibroblasts (HGFs) remains unknown. In present study, P. gingivalis-LPS decreased the membrane integrity of HGFs, and pyroptosis-associated cytokines were upregulated at the mRNA level. In addition, pyroptosis proteins were highly expressed in gingival tissues of periodontitis. P. gingivalis-LPS induced gingivitis in the rat model, and the expression level of pyroptosis-associated proteins increased. Together, P. gingivalis-LPS can activate the pyroptosis reaction, which may be a pro-pyroptosis status in a relative low concentration.

Gene expression profiles of mitochondria-endoplasmic reticulum tethering in human gingival fibroblasts in response to periodontal pathogens

OBJECTIVE

The current study aimed to elucidate the potential involvement of mitochondria-endoplasmic reticulum contact genes in the pathogenesis of periodontal disease by monitoring levels of contact associated genes including Mitofusion 1 (MFN1) and MFN2, inositol 1,4,5-trisphosphate receptor (IP3R), chaperone glucose-regulated protein 75 (GRP75), sigma non-opioid intracellular receptor 1 (SIGMAR1) and phosphate and tensin homolog induced putative kinase 1 (PINK1) in human gingival fibroblasts in response to periodontal pathogens Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis) in vitro.

DESIGN

Primary human gingival fibroblasts were exposed to live cultures of P. gingivalis (W83; ATCC BAA-308) and F. nucleatum (subsp. Polymorphum; ATCC 10953) alone or in combination for 4 h at a 50 or 200 multiplicity of infection. Escherichia coli lipopolysaccharide (10 μg/mL) exposure was used as a positive control. Gene expression levels of contact genes (MFN1, MFN2, IP3R, GRP75, SIGMAR1 and PINK1) as well as a proinflammatory cytokine, Tumor necrosis factor-α (TNF-α), and the apoptosis associated gene, Immediate early response 3 (IER3), were evaluated by reverse transcription polymerase chain reaction analysis.

RESULTS

MFN1, GRP75, IP3R and PINK1 were significantly upregulated by P. gingivalis with or without F. nucleatum. Only P. gingivalis with F. nucleatum caused a significant upregulation of SIGMAR1. TNF-α and IER3 gene expression positively correlated with the contact-associated gene expression changes.

CONCLUSION

F. nucleatum and P. gingivalis alone or in combination may differentially dysregulate the gene expression levels of contact-associated genes in human gingival fibroblasts. These host-microbiome interactions may mechanistically be important in the pathogenesis of periodontal disease.

Dec2 attenuates autophagy in inflamed periodontal tissues

INTRODUCTION

Transcriptional regulation of autophagy depends on the transcription factors coordinated inflammatory feedback mechanism. Here, we provide a comprehensive functional characterization of periodontal ligament fibroblasts (PDLFs) treated with Porphyromonas gingivalis lipopolysaccharide (LPS), aiming to reveal previously unappreciated biological changes and to investigate how a transcription factor differentiated embryonic chondrocytes 2 (Dec2)-deficient environment influences the function of autophagy in nflamed human PDLFs.

METHODS

A Dec2-deficient (Dec2KO) experimental periodontal inflammation mouse model and treatment with P. gingivalis LPS were employed to examine the role of autophagy in PDLFs using hematoxylin and eosin staining and immunohistochemistry in vivo. A Dec2 small interfering RNA (siRNA) was used to modulate autophagy, and the effect of autophagy on the Dec2 pathway was explored using real-time polymerase chain reaction and western blot analysis in vitro.

RESULTS

LPS-treated human PDLFs (HPDLFs) induced autophagy, as demonstrated by the enhanced levels of microtubule-associated protein 1 light chain 3-II (LC3-II) and the induction of ATG5, Beclin1, and Dec2. Compared with a scrambled siRNA, a Dec2 siRNA triggered the detrimental influences of LPS and markedly enhanced autophagy expression in inflamed HPDLFs. The expression of phosphorylated ERK was increased and levels of phosphorylated mammalian target of rapamycin (mTOR) were decreased after exposure to LPS in Dec2 siRNA transfected HPDLFs. The Dec2KO model exhibited that P. gingivalis in Dec2 deficient conditions increases the inflammation of PDLFs by regulating autophagy.

CONCLUSIONS

These results demonstrate that a Dec2 deficiency can alleviate LPS-induced inflammation via the ERK/mTOR signaling pathway by regulating autophagy, conceivably delivering a novel approach for the detection of periodontal treatments.

Regulation of Anti-Apoptotic SOD2 and BIRC3 in Periodontal Cells and Tissues

The aim of the study was to clarify whether orthodontic forces and periodontitis interact with respect to the anti-apoptotic molecules superoxide dismutase 2 (SOD2) and baculoviral IAP repeat-containing protein 3 (BIRC3). SOD2, BIRC3, and the apoptotic markers caspases 3 (CASP3) and 9 (CASP9) were analyzed in gingiva from periodontally healthy and periodontitis subjects by real-time PCR and immunohistochemistry. SOD2 and BIRC3 were also studied in gingiva from rats with experimental periodontitis and/or orthodontic tooth movement. Additionally, SOD2 and BIRC3 levels were examined in human periodontal fibroblasts incubated with Fusobacterium nucleatum and/or subjected to mechanical forces. Gingiva from periodontitis patients showed significantly higher SOD2, BIRC3, CASP3, and CASP9 levels than periodontally healthy gingiva. SOD2 and BIRC3 expressions were also significantly increased in the gingiva from rats with experimental periodontitis, but the upregulation of both molecules was significantly diminished in the concomitant presence of orthodontic tooth movement. In vitro, SOD2 and BIRC3 levels were significantly increased by F. nucleatum, but this stimulatory effect was also significantly inhibited by mechanical forces. Our study suggests that SOD2 and BIRC3 are produced in periodontal infection as a protective mechanism against exaggerated apoptosis. In the concomitant presence of orthodontic forces, this protective anti-apoptotic mechanism may get lost.

Inflammasome dysregulation in human gingival fibroblasts in response to periodontal pathogens

OBJECTIVE

Uncontrolled production of Interleukin-1β (IL-1β), a major proinflammatory cytokine, is associated with tissue destruction in periodontal disease. IL-1β production is controlled by inflammasomes which are multiprotein regulatory complexes. The current study aimed to elucidate potential regulatory pathways by monitoring the effects of periodontal pathogens Fusobacterium nucleatum (Fn) and Porphyromonas gingivalis (Pg) on inflammasomes and their regulators in human gingival fibroblasts (HGFs) in vitro.

METHODS

HGFs were exposed to Fn and Pg alone or in combination for 24 hr at a multiplicity of infection of 100, ±30 min exposure with 5 mM adenosine triphosphate (ATP) incubation. Gene expression of NLRP3 and AIM2, inflammasome regulatory proteins POP1, CARD16 and TRIM16, and inflammasome components ASC and CASPASE 1, and IL-1β, were evaluated by RT-PCR. Pro- and mature IL-1β levels were monitored intracellularly by immunocytochemistry and extracellularly by ELISA.

RESULTS

Fn + ATP significantly upregulated NLRP3, AIM2, IL-1β, ASC, and CASPASE 1; however, it downregulated POP1 and TRIM16. Pg + ATP downregulated NLRP3, ASC, POP1, but upregulated IL-1β and CARD16. Pg + Fn+ATP significantly upregulated AIM2, IL-1β and CARD16, and downregulated POP1, TRIM16, and CASPASE 1. Pg + ATP exposure significantly increased pro- and mature IL-1β production.

CONCLUSION

Bacterial exposure with ATP may deregulate IL-1β by dysregulating inflammasomes and their regulators in HGFs.

CXXC5 orchestrates Stat3/Erk/Akt signaling networks to modulate P. gingivalis-elicited autophagy in cementoblasts

The keystone pathogen Porphyromonas gingivalis (P. gingivalis) elicits inflammation and autophagy in periodontal tissues. Transcription factor CXXC-type zinc finger protein 5 (CXXC5) and various signals are sensitive to P. gingivalis invasion. Herein, we investigated the P. gingivalis-elicited autophagy activity, the contribution of CXXC5, and the involvement of signals in cementoblasts, tooth root surface cells crucial in periodontal and periapical regions. After coculture with P. gingivalis, cementoblasts exhibited inflammatory cytokine increase, light chain 3(LC3)-I/II conversion, autophagosome activation, and CXXC5 reduction. Cementoblasts with loss and gain of CXXC5 were developed. CXXC5 silencing suppressed autophagy and inflammation, thereby partially compensating for the effects of P. gingivalis, and vice versa. We then screened potential signals and verified the positive participation of Stat3/Akt/Erk networks through specific inhibitor employment. P. gingivalis and CXXC5 induced autophagy through Beclin1 and Atg5 activation. Intriguingly, Annexin V/PI assay and EdU detection revealed that P. gingivalis promoted apoptosis and repressed cell proliferation. In sum, coculture with P. gingivalis enhanced autophagy activity in cementoblasts, which was partially suppressed by CXXC5 downregulation and mediated by Jak/Stat3, PI3K-Akt, and Erk1/2 signaling. This process probably influenced cell apoptosis and proliferation.

Periodontitis-level butyrate-induced ferroptosis in periodontal ligament fibroblasts by activation of ferritinophagy

Loss of periodontal ligament fibroblasts (PDLFs) is one critical issue for regenerating lost periodontal tissues. A wide variety of regulated cell death pathways, such as apoptosis, pyroptosis, and necroptosis have been proposed in the periodontitis development. The aim of the present study was to explore whether long-term periodontitis-level butyrate may trigger ferroptosis, a newly characterized iron-dependent regulated cell death in PDLFs. Here, we showed that long-term treatment of butyrate, an important short-chain fatty acid in the periodontal pocket, induces the cargo receptor nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy and ferroptosis in PDLFs. Butyrate-induced iron accumulation, reactive oxygen species (ROS) generation, glutathione depletion and lipid peroxidation in PDLFs, and the butyrate-induced ferroptosis can be blocked by the lipid peroxide scavenger ferrostatin-1. The NCOA4-mediated ferritinophagy is dependent on p38/hypoxia inducible factor-1α (HIF-1α) pathway activation as well as Bromodomain-containing protein (BRD) 4 and cyclin-dependent kinase 9 (CDK9) coordination. These lines of evidence provide a new mechanistic insight into the mechanism of loss of PDLFs during periodontitis development, showing that periodontitis-level butyrate disrupted iron homeostasis by activation of NCOA4-mediated ferritinophagy, leading to ferroptosis in PDLFs.

Knockout of NRAGE promotes autophagy-related gene expression and the periodontitis process in mice

BACKGROUND AND OBJECTIVE

Neurotrophin receptor-interacting MAGE homologue (NRAGE) plays a crucial role in the regulation of bone metabolism. The present study investigated the regulation role of NRAGE on autophagy activation and periodontitis process during experimental periodontitis.

MATERIALS AND METHODS

Six-week-old wild-type (WT) and NRAGE-/- mice were randomly divided into three time points in the periodontitis groups (0, 2, and 4 weeks). Histopathological changes were determined using the tooth mobility, hematoxylin and eosin (H&E) staining, and micro-computed tomography (micro-CT). Osteoclasts activation and number were investigated using tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemistry, and real-time quantitative PCR (RT-PCR). The level of autophagy-related gene expression was measured using immunohistochemistry, immunofluorescence, and RT-PCR.

RESULTS

H&E staining and Micro-CT showed that the destruction of the alveolar bone was considerably more severe in the NRAGE-/- group than the WT group after ligation. Tooth mobility in the NRAGE-/- group was obviously higher than that in the WT group. The activation and number of osteoclasts and the level of autophagy-related gene expression in NRAGE-/- group were significantly higher than that in WT group.

CONCLUSIONS

The present study showed that knockout of NRAGE induced autophagy-related gene expression and accelerated the process of periodontitis disease via increasing the activity and differentiation of osteoclast.

Nec-1 attenuates inflammation and cytotoxicity induced by high glucose on THP-1 derived macrophages through RIP1

OBJECTIVES

This research aimed to study whether necrostain-1 (Nec-1) could alleviate inflammatory injury induced by high glucose upon THP-1 derived macrophages through RIP1.

DESIGN

Firstly, THP-1 derived macrophages were incubated with 5.5 mM glucose (normal glucose, NG), 25 mM glucose (high glucose, HG), and mannitol as the high osmotic pressure group (5.5 mM glucose+19.5 mM mannitol) for 24, 48, and 72 h respectively. TNF-α, IL-1β, IL-6, and IL-8 levels were measured by ELISA. Secondly, macrophages were exposed to NG, HG, or HG plus 5 μM necrostatin-1 (Nec-1) for 72 h. mRNA expression of inflammatory cytokine was measured by RT-PCR, and protein levels of inflammatory cytokines and LDH leakage were determined by ELISA. RIP1 expression was determined by RT-PCR and WB. Thirdly, macrophages were transfected with si-RIP1 or negative control (si-NC). Wild type and RIP1-silenced macrophages were incubated with NG or HG, and TNF-α, IL-1β, IL-6, IL-8, and LDH levels were measured again by ELISA.

RESULTS

1) TNF-α, IL-1β, IL-6, and IL-8 levels were elevated in the HG group, as compared with that the NG group. Inflammation remained unchanged in the mannitol group. 2) Inflammatory response and LDH levels in the HG plus Nec-1 group were remarkably lower than in the HG group. 3) Inflammatory injury in the si-NC group was more severe than in the si-RIP1 group.

CONCLUSIONS

Current results indicated that Nec-1 could alleviate HG-caused inflammatory injury on THP-1 derived macrophages by regulating RIP1. These findings could help cast light on the relationships between diabetes and periodontitis.

Inflammasomes and their regulation in periodontal disease: A review

Interleukin-1β (IL-1β), which is secreted by host tissues leading to periodontal tissue inflammation, is a major pro-inflammatory cytokine in the pathogenesis of periodontal disease. The conversion of pro-IL-1β into its biologically active form is controlled by multiprotein complexes named as inflammasomes, which are key regulator of host defense mechanisms and inflammasome involved diseases, including the periodontal diseases. Inflammasomes are regulated by different proteins and processes, including pyrin domain (PYD)-only proteins (POPs), CARD-only proteins (COPs), tripartite motif family proteins (TRIMs), autophagy, and interferons. A review of in vitro, in vivo, and clinical data from these publications revealed that several inflammasomes including (NOD)-like receptor (NLR) pyrin domain-containing 3 (NLRP3) and absent in melanoma 2 (AIM2) have been found to be involved in periodontal disease pathogenesis. To the best of our knowledge, the current article provides the first review of the literature focusing on studies that evaluated both inflammasomes and their regulators in periodontal disease. An upregulation for inflammasomes and a downregulation of inflammasome regulator proteins including POPs, COPs, and TRIMs have been reported in periodontal disease. Although interferons (types I and II) and autophagy have been found to be involved in periodontal disease, their possible role in inflammasome activation has not evaluated yet. Modulating the excessive inflammatory response by the use of inflammasome regulators may have potential in the management of periodontal disease.

Effects of colchicine on gingival inflammation, apoptosis, and alveolar bone loss in experimental periodontitis

BACKGROUND

The aim of the study was to investigate the effects of colchicine on cytokine production, apoptosis, alveolar bone loss, and oxidative stress in an experimental model of periodontitis in rats.

METHODS

Forty-eight rats were divided equally into four groups: healthy (H); periodontitis (P); periodontitis+colchicine low dose (CL, 30 μg/kg/day), and periodontitis+colchicine high dose (CH, 100 μg/kg/day). After 11 days, interleukin (IL) -1β, IL-8, and IL-10 were analyzed in gingival samples using Enzyme-Linked ImmunoSorbent Assay. Receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), total oxidative stress (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) were measured in gingiva and serum. Alveolar bone volume was evaluated via micro-CT. Apoptotic cells were detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay in histological sections.

RESULTS

Colchicine treatment significantly reduced IL-1β, IL-8, RANKL, RANKL/OPG, TOS, OSI, and bone volume ratio levels, and increased TAS levels compared to group P (p < 0.05). High dose colchicine treatment (CH) significantly decreased TUNEL+ cell counts compared to group P (p < 0.05).

CONCLUSIONS

These finding suggest that colchicine has a prophylactic potential for the prevention of periodontal tissue destruction through anti-inflammatory, anti-oxidative, anti-apoptotic, and bone-protective effects.

[Role of autophagy in the pathogenesis of periodontitis]

Periodontitis is a chronic inflammatory disease of periodontal tissues initiated by oral biofilm. Cellular autophagy is an effective weapon against bacterial infection. Recent studies have shown that autophagy not only promotes the removal of bacteria and toxins from infected cells, but also helps to suppress the inflammatory response to maintain the homeostasis of intracellular environment, which is closely related to the development of periodontitis. Here, we reviewed the relationship between autophagy and periodontitis from three aspects: the interactions between autophagy and periodontal pathogen infection, the regulation of autophagy and immune inflammatory responses, and the relationship between autophagy and alveolar bone metabolism. We aim to provide ideas for further study on the mechanisms of autophagy and periodontitis, and ultimately contribute to a better prevention and treatment of periodontitis.

Anti-apoptotic traits in gingival tissue from patients with severe generalized chronic periodontitis

AIM

In the present study, we aimed to evaluate the cytosolic and nuclear-mitochondrial expression of pro-apoptotic and anti-apoptotic markers in gingival tissue from patients with severe generalized chronic periodontitis (sGCP).

METHODS

Twenty-four patients participated in the study: 15 (54.3 + 8.3 years) with sGCP and nine (38.2 + 5.4 years) with gingivitis alone. Gingival tissue was collected using a 1.5-mm diameter punch and homogenized using a cell disruptor. The supernatants were analyzed for the cytosolic and nuclear-mitochondrial fractions of caspase-3, Bax, Bak, Smac, lamin B, Bad, Bim, survivin, Bcl-xL, Mcl-1, and of the dimers Bcl-2/Bax, Bcl-xL/Bak and Mcl-1/Bak using a multiplex immunoassay.

RESULTS

Significantly higher levels of cytosolic Bcl-xL/Bak, nuclear-mitochondrial Mcl-1/Bak, and cytosolic Bcl-xL were observed in gingival tissues from periodontitis patients compared to controls (P = 0.03, 0.03, and 0.05, respectively). The patients with gingivitis presented significantly increased levels of nuclear-mitochondrial Bad, cytosolic and nuclear-mitochondrial Bcl-2/Bax, and cytosolic Bim compared to the patients with periodontitis (P < 0.001, 0.03, 0.05, and 0.04, respectively).

CONCLUSION

Significantly higher levels of anti-apoptotic markers, such as Bcl-xL/Bak, Mcl-1/Bak, and Bcl-xL, and lower levels of pro-apoptotic markers Bad and Bim in inflamed tissues indicate an anti-apoptotic trait in patients with sGCP.

Evaluation of milk fat globule-epidermal growth factor-factor VIII and IL-1β levels in gingival crevicular fluid and saliva in periodontal disease and health

The aim of this study is to determine the levels of MFG-E8 and interleukin (IL)-1β in saliva and gingival crevicular fluid (GCF) associated with periodontal health and disease. Whole saliva and GCF samples were obtained from systemically healthy participants who were either periodontally healthy (n = 24) or suffered from gingivitis (n = 25) or chronic periodontitis (n = 25). Full-mouth clinical periodontal measurements, including bleeding on probing, probing depth, gingival index, plaque index, and clinical attachment level were also recorded. Enzyme-linked immunosorbent assay was used to estimate MFG-E8 and IL-1β levels in the samples. Analysis of variance, Kruskal-Wallis tests, and Pearson correlation tests were used to analyse the data statistically. The total level of MFG-E8 in GCF was significantly higher in the healthy group than in the other two groups (P = 0.01). Salivary MFG-E8 levels did not differ significantly among the groups. There were negative correlations between the level of MFG-E8 in GCF and probing depth (P = 0.03), bleeding on probing (P = 0.001), plaque index (P = 0.003), and gingival index (P = 0.003). The total level of IL-1β in GCF was significantly lower in the healthy group than in the groups with gingivitis and chronic periodontitis (P < 0.001). Salivary IL-1β levels showed significant differences across all three groups (P < 0.001). The level of MFG-E8 in GCF was higher in the healthy group than in the periodontal disease groups. Furthermore, there was no difference between gingivitis and periodontitis groups. The relationship between MFG-E8 and periodontal status should be further investigated.

Treatment With a Flavonoid-Rich Fraction of Bergamot Juice Improved Lipopolysaccharide-Induced Periodontitis in Rats

Objective: In this study, we investigated the effects of a flavonoid-rich fraction of Bergamot juice (BJe) in rats subjected to experimental periodontitis induced by a single intragingival injection of lipopolysaccharides (LPS).

Main Methods: Periodontitis was induced by a single intragingival injection of 1 μl LPS (10 μg/μl) derived from Salmonella typhimurium in sterile saline solution. The injection was made in the mesolateral side at the interdental papilla between the first and the second molar. Fourteen days after LPS injection, we performed radiographic analyses and then we surgically removed the gingivomucosal tissue surrounding the mandibular first molar for histological, immunohistochemical and molecular analysis.

Results: LPS significantly induced oedema, tissue damage and increased neutrophil infiltration. At molecular level, we found increased NF-κB translocation as well as raised both TNF-α and IL-1β expression, other than modulation of apoptosis-associated proteins. Moreover, the increased myeloperoxidase activity was associated with up-regulation of adhesion molecules. Immunohistochemical analysis for nitrotyrosine and poly ADP-ribose displayed an intense staining in the gingivomucosal tissue. Oral administration of BJe for 14 consecutive days reduced tissue injury and several markers of gingival inflammation including nuclear NF-κB translocation, cytokines expression, myeloperoxidase activity and the expression of some adhesion molecules such as ICAM and P-selectin. BJe also decreased both nitrosative stress and PARP positive staining. Moreover, it caused down-regulation of Bax and up-regulation of Bcl-2 expression.

Conclusion: Our findings demonstrate that BJe improves LPS-induced periodontitis in rats by reducing the typical markers of inflammation, thus suggesting its potential in the treatment of periodontal diseases.

The role of caspase-8, caspase-9, and apoptosis inducing factor in periodontal disease

BACKGROUND

Caspases are key mediators of apoptosis. Caspase-8 mediates extrinsic, and caspase-9 initiates the intrinsic pathway of apoptosis. Apoptosis Inducing Factor (AIF), a mitochondrial proapoptotic protein, mediates cell death by a caspase-independent process. Because apoptosis is involved in periodontal disease, this study evaluated caspase-8, -9, and AIF in periodontal disease.

METHODS

Twenty periodontally healthy volunteers (Group Healthy), 20 patients with generalized aggressive periodontitis (Group AgP), and 20 patients with generalized chronic periodontitis (Group CP) were included in this study. Levels of caspase-8, -9, and AIF were evaluated in gingival crevicular fluid (GCF) of all participants via enzyme-linked immunosorbent assays.

RESULTS

AIF was significantly higher in the AgP (P = 0.07) and CP groups (P = 0.01) than the Healthy group, and similar to the CP and AgP groups (P > 0.05). Caspase-8 was significantly higher in the CP and Healthy groups than the AgP group (P = 0.00), and similar between Healthy and CP groups (P > 0.05). Caspase-9 was significantly higher in the AgP group than the Healthy group (P = 0.01), and similar between Healthy and CP groups (P > 0.05).

CONCLUSIONS

The mitochondrial-centered intrinsic pathway involving caspase-9 and AIF, and the extrinsic pathway involving caspase-8 are significant for aggressive periodontitis. The intrinsic pathway involving caspase-independent AIF is also significant for chronic periodontitis.

Salidroside promotes human periodontal ligament cell proliferation and osteocalcin secretion via ERK1/2 and PI3K/Akt signaling pathways

Salidroside modulates cell proliferation and serves as an anti-inflammatory and anti-apoptotic agent with efficacy against various diseases. The objective of the present study was to investigate the efficacy of salidroside in enhancing the proliferation of human periodontal ligament cells (hPDLCs). hPDLCs were isolated and the effects of salidroside on cell viability, soluble osteocalcin levels and activation of proliferation-associated signaling pathways were determined using a CCK-8 assay, ELISA and Western blotting, respectively. The results indicated that salidroside induced proliferation of hPDLCs, increased secretion of soluble osteocalcin and enhanced activation of extracellular signal-regulated kinase (ERK)1/2 and phosphoinositide-3 kinase (PI3K)/Akt signaling pathways. These factors were upregulated by salidroside in a dose-dependent manner. The results of the present study suggested that salidroside mediated hPDLC proliferation via the ERK1/2 and PI3K/Akt signaling pathways, as well as osteocalcin secretion. Salidroside may therefore be used as a novel therapeutic agent in the treatment of the tooth-supporting apparatus, progressive tooth destruction or periodontitis.

Calcitonin gene‑related peptide reduces Porphyromonas gingivalis LPS‑induced TNF‑α release and apoptosis in osteoblasts

Periodontal diseases comprise mixed bacterial infections mainly caused by Gram‑negative anaerobic bacteria. Lipopolysaccharides (LPS) are important virulence factors and periodontal pathogens, which change local cytokine levels and promote osteoblast apoptosis, thereby leading to an imbalance in bone remodeling mechanisms and accelerating bone loss. Calcitonin gene‑related peptide (CGRP) is a vasoactive neuropeptide that is released from sensory nerves and has a positive effect on osteoblast proliferation and differentiation. In addition, this small molecule peptide is an important immune regulator in the inflammatory response. The aim of the present study was to assess the in vitro effects of CGRP on Porphyromonas gingivalis (Pg)LPS‑induced osteoblast apoptosis. Osteoblast cultures were stimulated either with various concentrations of PgLPS (0, 25, 50, 100, 500 and 1,000 ng/ml) for 48 h or with 500 ng/ml PgLPS for various lengths of time (0, 6, 12, 24, 48 and 72 h). The PgLPS‑stimulated cells were pretreated with different concentrations of CGRP (0, 1, 10, 100 and 1,000 nM) and cell viability and apoptotic rates were measured by Cell Counting kit‑8 assays and flow cytometry, respectively. CGRP, cleaved (c)‑Caspase‑8 and c‑Caspase‑3 protein expression levels were analyzed by western blotting. Changes in cytokine expression levels, which included tumor necrosis factor (TNF)‑α, interleukin (IL)‑1β, IL‑6, monocyte chemotactic protein (MCP)‑1 and MCP‑2, were measured by ELISA. PgLPS was demonstrated to inhibit osteoblast viability and promote apoptosis in a time‑ and concentration‑dependent manner. CGRP expression was revealed to reduce PgLPS‑induced cytostatic activity and apoptosis in osteoblasts. CGRP also suppressed the PgLPS‑induced release of TNF‑α and inhibited the activation of c‑Caspase‑3 and c‑Caspase‑8, thus preventing apoptosis in osteoblasts. CGRP may be an important neuropeptide in bone remodeling and may reduce osteoblast apoptosis in inflammatory conditions. These results may provide a solid foundation for CGRP to serve as a new target for the treatment of periodontitis.

Porphyromonas gingivalis Differentially Modulates Apoptosome Apoptotic Peptidase Activating Factor 1 in Epithelial Cells and Fibroblasts

Porphyromonas gingivalis is able to invade and modulate host-immune response to promote its survival. This bacterium modulates the cell cycle and programed cell death, contributing to periodontal lesion worsening. Several molecular pathways have been identified as key triggers of apoptosis, including apoptosome apoptotic peptidase activating factor 1 (APAF-1). Apaf-1 and X-linked inhibitor of apoptosis protein (Xiap) mRNA were differentially expressed between gingival samples harvested from human healthy and chronic periodontitis tissues (Apaf-1, 19.2-fold; caspase-9, 14.5-fold; caspase-3, 6.8-fold; Xiap: 2.5-fold in chronic periodontitis) (P < 0.05), highlighting their potential role in periodontitis. An increased proteic expression of APAF-1 was also observed in a murine experimental periodontitis model induced by P. gingivalis-soaked ligatures. In vitro, it was observed that P. gingivalis targets APAF-1, XIAP, caspase-3, and caspase-9, to inhibit epithelial cell death at both mRNA and protein levels. Opposite effect was observed in fibroblasts in which P. gingivalis increased cell death and apoptosis. To assess if the observed effects were associated to APAF-1, epithelial cells and fibroblasts were transfected with siRNA targeting Apaf-1. Herein, we confirmed that APAF-1 is targeted by P. gingivalis in both cell types. This study identified APAF-1 apoptosome and XIAP as intracellular targets of P. gingivalis, contributing to the deterioration of periodontal lesion through an increased persistence of the bacteria within tissues and the subversion of host-immune response.