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

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.

Inflammation and immune response in the development of periodontal disease: a narrative review

We present this critical review with the aim of highlighting the current status of periodontal diseases, focusing on the relevance of host modulating agents and immune pathways, in addition to new complementary therapeutic approaches for the treatment of these pathologies. Periodontal diseases are prevalent pathologies worldwide and the main cause of edentulism in the adult population. Their pathogenesis seems to be based on a dysbiosis of the oral microbiota that interacts with the host's immune defenses and is responsible for the inflammatory/immune response, which would be modified by a number of conditions such as individual susceptibility, environmental and sociodemographic factors, certain systemic pathologies and the individual's genetic condition, among others. Numerous studies have reported on the complex web of inflammatory mediators in periodontal disease and their role in tissue destruction as well as in homeostatic imbalance. Precisely, the role of epigenetics as a modifier of the host genetic condition has captured research attention in recent years. Therefore, this mini-review first discusses an updated etiological hypothesis of periodontal disease and the roles of certain cytokines in the immune response. In addition, the latest therapeutic trends with new developments and future perspectives are summarized.

Transcriptomic features of programmed and inflammatory cell death in gingival tissues

The local gingival tissue environment with homeostasis and tissue-destructive events of periodontitis demonstrates major changes in histological features and biology of the oral/sulcular epithelium, fibroblasts, vascular cells, inflammatory cell infiltration, and alveolar bone.

OBJECTIVE

This study used an experimental periodontitis model to detail the gingival transcriptome related to cell death processes of pyroptosis, necroptosis, ferroptosis, and cuproptosis.

MATERIALS AND METHODS

Healthy Macaca mulatta primates stratified by age, ≤3 years (young), 7-12 years (adolescent), 12-15 years (adult), and 17-23 years (aged), provided gingival tissue biopsies for microarray analysis focused on 257 genes representative of the four cell death processes and bacterial plaque samples for 16S rRNA gene analysis.

RESULTS

Age differences in the profiles of gene expression in healthy tissues were noted for cuproptosis, ferroptosis, necroptosis, and pyroptosis. Major differences were then observed with disease initiation, progression, and resolution also related to the age of the animals. Distinct bacterial families/consortia of species were significantly related to the gene expression differences for the cell death pathways.

CONCLUSIONS

These results emphasized age-associated differences in the gingival tissue molecular response to changes in the quality and quantity of bacteria accumulating with the disease process reflected in regulated cell death pathways that are both physiological and pathophysiological.

PANoptosis: a new insight for oral diseases

PANoptosis, a burgeoning area of research, is a unique type of programmed cell death typified by pyroptosis, apoptosis, and necroptosis, yet it defies singular classification by any one mode of death. The assembly and activation of PANoptosomes are pivotal processes in PANoptosis, with several PANoptosomes already identified. Linkages between PANoptosis and the pathophysiology of various systemic illnesses are established, with increasing recognition of its association with oral ailments. This paper aims to deepen understanding by conducting a comprehensive analysis of the molecular pathways driving PANoptosis and exploring its potential implications in oral diseases.

Mitochondrial ROS participates in Porphyromonas gingivalis-induced pyroptosis in cementoblasts

This study aimed to investigate correlation between mitochondrial reactive oxygen species and Porphyromonas gingivalis in the process of cementoblast pyroptosis. Lactate dehydrogenase activity assay, enzyme-linked immunosorbent assay, western blotting and flow cytometry analysis were utilized to explore whether Porphyromonas gingivalis triggered pyroptosis in cementoblasts. Reactive oxygen species and mitochondrial reactive oxygen species were detected using flow cytometry and fluorescence staining. The effect of mitochondrial reactive oxygen species on the Porphyromonas gingivalis-induced pyroptosis of cementoblasts was assessed by Mito-Tempo, mitochondrion-targeted superoxide dismutase mimetic. Phosphorylation levels of p65 were measured by western blotting. SC75741, a nuclear factor-kappa B inhibitor, was added to block the nuclear factor-kappa B in the Porphyromonas gingivalis-infected cementoblasts. Porphyromonas gingivalis triggered pyroptosis of cementoblasts, and an elevation in reactive oxygen species generation in the mitochondria was observed. Inhibition of mitochondrial reactive oxygen species reduced pyroptosis and nuclear factor-kappa B signaling pathway mediated the pyroptotic cell death in Porphyromonas gingivalis-infected cementoblasts. Together, our findings demonstrate that mitochondrial reactive oxygen species increased by Porphyromonas gingivalis participated in the pyroptosis of cementoblasts. Targeting mitochondrial reactive oxygen species may offer therapeutic strategies for root surface remodeling or periodontal regeneration.

Estimation of noncanonical pyroptosis biomarkers gasdermin D and caspase 4 in gingiva of periodontitis and diabetes patients: An observational cross-sectional study

Background

Periodontitis and diabetes are chronic diseases where inflammation plays a central role, with each condition exacerbating the other. Pyroptosis, an inflammatory form of programmed cell death, is implicated in periodontitis and diabetes. The activation of gasdermin D (GSDMD), a key mediator of pyroptosis, promotes cytokine release and perpetuates tissue destruction in both. However, the role of the noncanonical pyroptosis pathway mediated by caspase 4 (CASP4) remains less understood. The study aimed to determine the gene expression of noncanonical pyroptosis biomarkers CASP4 and GSDMD in periodontitis and diabetes individuals and correlate with the periodontal and diabetic parameters.

Materials and Methods

Sixty individuals were recruited and divided into four groups: Group 1 (healthy), Group 2 (periodontitis), Group 3 (diabetes), and Group 4 (periodontitis with diabetes). Gingival tissue samples were collected from all groups, and the relative mRNA expression levels of CASP4 and GSDMD were determined using reverse transcription polymerase chain reaction. The correlation between CASP4 and GSDMD expression and periodontal parameters - plaque index (PI), gingival index (GI), probing pocket depth (PPD), and clinical attachment loss (CAL), as well as diabetic parameters - fasting blood sugar and glycated hemoglobin (HbA1C) was analyzed.

Results

The relative mRNA expression of CASP4 and GSDMD was highest in Group 4 and lowest in Group 1. Statistical significance was observed between the groups (P ≤ 0.05) for CASP4 and GSDMD. A significant positive correlation was found between CASP4 and GSDMD expression and periodontal parameters (PI, GI, PPD, and CAL), as well as the diabetic parameter HbA1C (P ≤ 0.01).

Conclusions

High expression of CASP4 and GSDMD was present in the gingiva of periodontitis and diabetes individuals and correlated with the diabetic and periodontal clinical parameters. This suggests that noncanonical pyroptosis contributes to periodontitis and diabetes pathogenesis through the CASP4/GSDMD axis. The inhibition of GSDMD offers a promising therapeutic approach in managing periodontitis and diabetes.

Activation of receptor-interacting protein 3-mediated necroptosis accelerates periodontitis in mice

OBJECTIVE

To investigate the involvement and role of receptor-interacting protein 3 (RIP3)-mediated necroptosis in periodontitis.

METHODS

A periodontitis murine model was established by oral infection with Porphyromonas gingivalis, and activation of necroptosis pathway was identified by immunohistochemistry. Adeno-associated virus was used to knock down Rip3 and the effect of Rip3 knockdown on periodontal inflammation was examined by Micro-CT, qRT-PCR and histological staining. In vitro, P. gingivalis-LPS was used to infect fibroblast cell line L929 and siRNA was used to knock down Rip3. Necroptosis pathway signalling and inflammation in cells were detected by cell viability and death assay, Western Blot, qRT-PCR and immunofluorescence analysis.

RESULTS

Phosphorylation of RIP3 and mixed lineage kinase domain-like protein (MLKL) was increased in the periodontal ligament of mice infected with P. gingivalis. RIP3 knockdown reduced osteoclastogenesis and inflammatory cytokines in the periodontal area, and alleviated alveolar bone loss in vivo. In vitro, P. gingivalis-LPS-induced RIP3-mediated necroptosis in L929 cells, and knockdown of RIP3 by siRNA decreased the expression of inflammatory cytokines.

CONCLUSION

RIP3-mediated necroptosis is activated in periodontitis and blocking necroptosis alleviates disease progression, indicating that RIP3 may be a potential target for periodontitis treatment.

Er:YAG laser suppresses pro-inflammatory cytokines expression and inflammasome in human periodontal ligament fibroblasts with Porphyromonas gingivalis-lipopolysaccharide stimulation

Background/purpose

Periodontitis is an inflammatory condition of the tooth-supporting structures triggered by the host's immune response towards the bacterial deposits around the teeth. It is well acknowledged that pro-inflammatory interleukin (IL)-6, IL-8, MCP-1 as well as the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, are the key modulators in the activation of this response. Erbium-doped yttrium-aluminium-garnet (Er:YAG) laser, a solid-state crystal laser have been commonly used in the treatment of periodontal diseases. However, little is understood about the molecular mechanism of the Er:YAG laser, especially in targeting the host immune response brought on by periodontal pathogens. Hence, the current study focused on the protective effects of Er:YAG laser on periodontitis in-vitro in terms of pro-inflammatory cytokines, chemokines and NLRP3 inflammasome expressions.

Materials and methods

Human periodontal ligament fibroblast (PDLFs) were first stimulated with lipopolysaccharides (LPS) from P. gingivalis (Pg-LPS) to simulate periodontitis. Cells were then irradiated with Er:YAG laser of ascending energy densities (3.6-6.3 J/cm2), followed by cell proliferation and wound healing assay. Next, the effects of Er:YAG laser on the expressions of IL-6, IL-8, MCP-1, NLRP3, and cleaved GSDMD were examined.

Results

Pg-LPS was found to reduce cell's proliferation rate and wound healing ability in PDLFs and these were rescued by Er:YAG laser irradiation. In addition, LPS stimuli resulted in a marked upregulation in the secretion of IL-6, IL-8 and MCP-1 as well as the mRNA and protein expression of NLRP3 and cleaved-GSDMD protein whereas Er:YAG laser suppressed the elicited phenomena.

Conclusion

To our knowledge, this is the first study to look into the laser's implication on the NLRP3 inflammasome in periodontitis models. Our study reveals a crucial role of Er:YAG laser in ameliorating periodontitis in-vitro through the modulation of IL-6, IL-8, MCP-1 and the NLRP3 inflammasome and highlights that the control of the NLRP3 inflammasome may become a potential approach for periodontitis.

Casp11 Deficiency Alters Subgingival Microbiota and Attenuates Periodontitis

Periodontitis (PD) is the primary cause of tooth loss in adults. Porphyromonas gingivalis (P.g), a keystone pathogen, has been identified as a crucial contributor to this process. Pyroptosis activation in PD is acknowledged, with accumulating evidence underscoring the crucial role of Caspase-11 (described as Caspase-4/5 in humans)-mediated noncanonical pyroptosis. However, the mechanism behind its impact on PD remains unclear. In this study, we delved into the interplay between the Caspase-11-mediated noncanonical pyroptosis, subgingival microbiota alteration, and macrophage polarization. Clinical samples from PD patients revealed heightened expression of Caspase-4, gasdermin-D, and their active fragments, pointing to the activation of the noncanonical pyroptosis. Single-cell sequencing analysis linked Caspase-4 with gingival macrophages, emphasizing their involvement in PD. In vitro cell experiments confirmed that P.g-induced pyroptosis was activated in macrophages, with Casp11 deficiency attenuating these effects. In an experimental PD mouse model, Casp11 deficiency led to an alteration in subgingival microbiota composition and reduced alveolar bone resorption. Casp11-/- mice cohousing with wild-type mice confirmed the alteration of the subgingival microbiota and aggravated the alveolar bone resorption. Notably, Casp11 deficiency led to decreased M1-polarized macrophages, corresponding with reduced alveolar bone resorption, uncovering a connection between subgingival microbiota alteration, macrophage M1 polarization, and alveolar bone resorption. Taken together, we showed that Caspase-11 fulfilled a crucial role in the noncanonical pyroptosis in PD, potentially influencing the subgingival microbiota and linking to M1 polarization, which was associated with alveolar bone resorption. These findings underscored the pivotal role of the Caspase-11-mediated noncanonical pyroptosis in PD pathogenesis and may provide critical insights into potential therapeutic avenues for mitigating PD.

Expression dynamics of microRNA-223/Ras-associated binding protein 12 axis in Stage III/Grade B periodontal disease: A case-control analysis

Background

The intricate interplay between periodontal polymicrobial flora and an altered immune response is the central cause of periodontal disease. Multiple cell death methods and their interactions, along with the associated signaling pathways, significantly impact the initiation and advancement of periodontitis. Our speculation revolves around the role of the miR-223/Ras-associated binding protein (RAB12) signaling axis in regulating autophagy-induced pyroptosis, contributing to the pathophysiology of periodontitis. Thus, this study aimed to investigate miR-223 and RAB12 expression patterns in Stage III/Grade B periodontal disease.

Materials and Methods

The study included 50 healthy individuals and 50 patients diagnosed with Stage III/Grade B periodontal disease. Clinical parameters were cataloged for each participant. miRNA-223 underwent an in silico analysis to identify its potential target genes. Gingival crevicular fluid (GCF) samples were collected from the subjects for real-time polymerase chain reaction to evaluate the expression of both miR-223 and the RAB12 gene.

Results

The miRTargetLink2.0 analysis highlighted the RAB12 gene as a prime target for miR-223. In periodontal disease patients, miR-223 and RAB12 gene expressions significantly increased (15.21 and 34.70-fold changes, respectively; P < 0.05). Receiver operating characteristic analysis suggested that miR-223 is a potential biomarker for periodontal disease, with 76% diagnostic accuracy and an area under the curve of 0.777 (P < 0.01).

Conclusion

MicroRNA-223 and its target gene RAB12 exhibit high expression levels in GCF samples from individuals with periodontal disease. This suggests modulation of autophagy and the signaling mechanism for pyroptotic cell death in periodontal tissues during pathogenesis. Consequently, the miR-223/RAB12 axis might represent a plausible link for periodontal disease.

DAMPs and alarmin gene expression patterns in aging healthy and diseased mucosal tissues

Introduction

Periodontitis is delineated by a dysbiotic microbiome at sites of lesions accompanied by a dysregulated persistent inflammatory response that undermines the integrity of the periodontium. The interplay of the altered microbial ecology and warning signals from host cells would be a critical feature for maintaining or re-establishing homeostasis in these tissues.

Methods

This study used a nonhuman primate model (Macaca mulatta) with naturally-occurring periodontitis (n = 34) and experimental ligature-induced periodontitis (n = 36) to describe the features of gene expression for an array of damage-associate molecular patterns (DAMPs) or alarmins within the gingival tissues. The animals were age stratified into: ≤3 years (Young), 7-12 years (Adolescent), 12-15 years (Adult) and 17-23 years (Aged). Gingival tissue biopsies were examined via microarray. The analysis focused on 51 genes representative of the DAMPs/alarmins family of host cell warning factors and 18 genes associated with tissue destructive processed in the gingival tissues. Bacterial plaque samples were collected by curette sampling and 16S rRNA gene sequences used to describe the oral microbiome.

Results

A subset of DAMPs/alarmins were expressed in healthy and naturally-occurring periodontitis tissues in the animals and suggested local effects on gingival tissues leading to altered levels of DAMPs/alarmins related to age and disease. Significant differences from adult healthy levels were most frequently observed in the young and adolescent animals with few representatives in this gene array altered in the healthy aged gingival tissues. Of the 51 target genes, only approximately ⅓ were altered by ≥1.5-fold in any of the age groups of animals during disease, with those increases observed during disease initiation. Distinctive positive and negative correlations were noted with the DAMP/alarmin gene levels and comparative expression changes of tissue destructive molecules during disease across the age groups. Finally, specific correlations of DAMP/alarmin genes and relative abundance of particular microbes were observed in health and resolution samples in younger animals, while increased correlations during disease in the older groups were noted.

Conclusions

Thus, using this human-like preclinical model of induced periodontitis, we demonstrated the dynamics of the activation of the DAMP/alarmin warning system in the gingival tissues that showed some specific differences based on age.

Inhibitory Effects of Corydalis saxicola Bunting Total Alkaloids on Macrophage Pyroptosis

This study investigated the effect of Corydalis saxicola Bunting total alkaloids (CSBTA) on pyroptosis in macrophages (Mϕ). In the Mϕ pyroptosis model, an inverted fluorescence microscope was used to assess cell pyroptosis, while a scanning electron microscope was used to observe morphological changes in Mϕ. NLR family pyrin domain-containing 3 (NLRP3), caspase-1, and gasdermin D (GSDMD) expression levels were detected by polymerase chain reaction and western blotting, whereas interleukin-1 (IL-1) and interleukin-18 (IL-18) expression levels were measured by an enzyme-linked immunosorbent assay. After pretreatment with CSBTA or the caspase-1 inhibitor, acetyl-tyrosyl-valyl-alanyl-aspartyl-chloromethylketone (Ac-YVAD-cmk), it was discovered that NLRP3, caspase-1, and GSDMD expressions were significantly reduced at both the mRNA and protein levels, as were IL-1 and IL-18 levels. The inhibitory effects of CSBTA and Ac-YVAD-cmk did not differ significantly. These findings indicate that CSBTA blocks Porphyromonas gingivalis-lipopolysaccharide-induced Mϕ pyroptosis.

Glycolytic reprogramming controls periodontitis-associated macrophage pyroptosis via AMPK/SIRT1/NF-κB signaling pathway

Glycolysis has been demonstrated as a crucial metabolic process in bacteria infected diseases via modulating the activity of pyroptosis. Macrophages are the most abundant immune cells that infiltrated in the infected periodontal tissues, which significantly influence the outcome of periodontitis (PD). However, the effect of glycolysis in regulating macrophage pyroptosis during PD development remains unknown. This study aimed to explore the role of glycolysis in PD-associated macrophage pyroptosis and periodontal degeneration. Clinical specimens were used to determine the emergence of macrophage pyroptosis and glycolysis in periodontal tissues by immunohistochemical analysis and western blot. For an in-depth understanding of the regulatory effect of glycolysis in the progression of macrophage pyroptosis associated periodontitis, both in vivo PD model and in vitro PD model were treated with 2-DG (2-Deoxy-d-glucose), a glycolysis inhibitor. The data showed that the blockade of glycolysis could significantly suppress the lipopolysaccharide (LPS) induced macrophage pyroptosis, resulting in an attenuation of the inflammatory response and bone resorption in periodontal lesions. Furthermore, we revealed that the regulatory effect of glycolysis on macrophage pyroptosis can be mediated via AMPK/SIRT1/NF-κB signaling pathway. Our study unveiled that suppressed glycolysis restrains the activity of PD-associated macrophage pyroptosis, osteoclastogenesis, and subsequent periodontal tissue destruction. These findings extend our knowledge of glycolysis in regulating PD-associated macrophage pyroptosis and provide a potential novel target for PD therapy.

Porphyromonas gingivalis regulates atherosclerosis through an immune pathway

Atherosclerosis (AS) is a chronic inflammatory disease, involving a pathological process of endothelial dysfunction, lipid deposition, plaque rupture, and arterial occlusion, and is one of the leading causes of death in the world population. The progression of AS is closely associated with several inflammatory diseases, among which periodontitis has been shown to increase the risk of AS. Porphyromonas gingivalis (P. gingivalis), presenting in large numbers in subgingival plaque biofilms, is the “dominant flora” in periodontitis, and its multiple virulence factors are important in stimulating host immunity. Therefore, it is significant to elucidate the potential mechanism and association between P. gingivalis and AS to prevent and treat AS. By summarizing the existing studies, we found that P. gingivalis promotes the progression of AS through multiple immune pathways. P. gingivalis can escape host immune clearance and, in various forms, circulate with blood and lymph and colonize arterial vessel walls, directly inducing local inflammation in blood vessels. It also induces the production of systemic inflammatory mediators and autoimmune antibodies, disrupts the serum lipid profile, and thus promotes the progression of AS. In this paper, we summarize the recent evidence (including clinical studies and animal studies) on the correlation between P. gingivalis and AS, and describe the specific immune mechanisms by which P. gingivalis promotes AS progression from three aspects (immune escape, blood circulation, and lymphatic circulation), providing new insights into the prevention and treatment of AS by suppressing periodontal pathogenic bacteria.

Pyroptosis in bone loss

Pyroptosis could be responsible for the bone loss from bone metabolic diseases, leading to the negative impact on people's health and life. It has been shown that osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells may be involved in bone loss linked with pyroptosis. So far, the involved mechanisms have not been fully elucidated. In this review, we introduced the related cells involved in the pyroptosis associated with bone loss and summarized the role of these cells in the bone metabolism during the process of pyroptosis. We also discuss the clinical potential of targeting mechanisms in the osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells touched upon pyroptosis to treat bone loss from bone metabolic diseases as well as the challenges of avoiding potential side effects and producing efficient treatment methods.

Pyroptosis in inflammatory bone diseases: Molecular insights and targeting strategies

Inflammatory bone diseases include osteoarthritis (OA) and rheumatoid arthritis (RA), which can cause severe bone damage in a chronic inflammation state, putting tremendous pressure on the patients' families and government agencies regarding medical costs. In addition, the complexity of osteoimmunology makes research on these diseases difficult. Hence, it is urgent to determine the potential mechanisms and find effective drugs to target inflammatory bone diseases to reduce the negative effects of these diseases. Recently, pyroptosis, a gasdermin-induced necrotic cell death featuring secretion of pro-inflammatory cytokines and lysis, has become widely known. Based on the effect of pyroptosis on immunity, this process has gradually emerged as a vital component in the etiopathogenesis of inflammatory bone diseases. Herein, we review the characteristics and mechanisms of pyroptosis and then focus on its clinical significance in inflammatory bone diseases. In addition, we summarize the current research progress of drugs targeting pyroptosis to enhance the therapeutic efficacy of inflammatory bone diseases and provide new insights for future directions.

Functionalized Prussian Blue Nanozyme as Dual-Responsive Drug Therapeutic Nanoplatform Against Maxillofacial Infection via Macrophage Polarization

Purpose

Maxillofacial infection is a common disease in stomatology and is difficult to treat owing to its high potential to spread to vital anatomical structures. Excessive levels of reactive oxygen species (ROS) in infected tissues lead to cellular damage and impede tissue regeneration. However, uncontrollable strategies to remove ROS have limited therapeutic efficacy. Nanoparticle systems for scavenging ROS and remodeling the inflammatory microenvironment offer much promise in the treatment of maxillofacial inflammation.

Methods

Here, a novel microenvironment-stimuli-responsive drug delivery nanoplatform (HMPB@Cur@PDA) based on a polydopamine (PDA)-functionalized hollow mesoporous Prussian blue (HMPB) nanozyme was developed for the delivery of curcumin (Cur) in the treatment of maxillofacial infection. Low pH and excess ROS in the inflammatory microenvironment cause degradation of the outer PDA layer of the nanocomplex, exposing the HMPB nanozyme and loaded Cur, which synergistically act as a ROS scavenger and anti-inflammatory agent, respectively, and induce macrophage polarization from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype.

Results

Experiments in vitro provided strong evidence for the application of novel nanocomplexes in scavenging multiple ROS and inhibiting lipopolysaccharide-induced inflammation. In addition, in vivo results obtained using a mouse maxillofacial infection model demonstrated that HMPB@Cur@PDA had excellent biocompatibility, significantly attenuated the inflammatory response in periodontal tissue, and improved the repair of damaged tissue.

Conclusion

Our results indicate that HMPB@Cur@PDA nanocomposites have great potential for ROS regulation as well as having anti-inflammatory effects, providing new insights for the development of dual-response maxillofacial infection treatments.

Pyroptosisin periodontitis: From the intricate interaction with apoptosis, NETosis, and necroptosis to the therapeutic prospects

Periodontitis is highly prevalent worldwide. It is characterized by periodontal attachment and alveolar bone destruction, which not only leads to tooth loss but also results in the exacerbation of systematic diseases. As such, periodontitis has a significant negative impact on the daily lives of patients. Detailed exploration of the molecular mechanisms underlying the physiopathology of periodontitis may contribute to the development of new therapeutic strategies for periodontitis and the associated systematic diseases. Pyroptosis, as one of the inflammatory programmed cell death pathways, is implicated in the pathogenesis of periodontitis. Progress in the field of pyroptosis has greatly enhanced our understanding of its role in inflammatory diseases. This review first summarizes the mechanisms underlying the activation of pyroptosis in periodontitis and the pathological role of pyroptosis in the progression of periodontitis. Then, the crosstalk between pyroptosis with apoptosis, necroptosis, and NETosis in periodontitis is discussed. Moreover, pyroptosis, as a novel link that connects periodontitis with systemic disease, is also reviewed. Finally, the current challenges associated with pyroptosis as a potential therapeutic target for periodontitis are highlighted.

D-aspartic acid protects against gingival fibroblasts inflammation by suppressing pyroptosis

BACKGROUND

Peri-implantitis is the main cause of dental implant failure, which is associated with pyroptosis. The roles of D-aspartic acid (D-Asp) on pyroptosis and the mechanism of the protective effect of D-Asp on human gingival fibroblasts (HGFs) remain unknown. This study investigated the effects of D-Asp on the pyroptosis of HGFs induced by high mobility group box 1 protein (HMGB1).

METHODS

The cytotoxic effects of D-Asp on HGFs was detected by Cell Counting Kit-8 assay, the membrane permeability was investigated by propidium iodide/ Hoechst 33,342 double staining, flow cytometry analysis, and lactate dehydrogenase releasing, The gene and protein expression levels were detected by real-time quantitative PCR, enzyme-linked immunosorbent assay, and Western blot, respectively.

RESULTS

Cell viability analysis showed that D-Asp ≤ 30 mM had no cytotoxicity to HGFs. HMGB1 drastically raised the membrane permeability of HGFs, while 1/10/30 mM D-Asp suppressed the permeability and remained the integrity of the membrane. HMGB1 promoted the mRNA expression of NLRP3, caspase-1, GSDMD, IL-1β, and IL-18, and the protein expression of IL-1β, IL-18, caspase-1, GSDMD, and NLRP3.

CONCLUSIONS

With the pretreatment of HGFs with D-Asp of 1/10/30 mM for 24 h, the cell membrane permeability was reduced and the expression of NLRP3, caspase-1, GSDMD, IL-1β, and IL-18 was significantly decreased compared with the HMGB1 group, indicating the competitive antagonism of D-Asp against HMGB1 on the binding with toll-like receptors. Hence, this study may provide a novel insight into preventing pyroptosis and propose a new strategy for the treatment of peri-implantitis.

PANoptosis: A New Insight Into Oral Infectious Diseases

The oral microbiome, one of the most complex and intensive microbial ecosystems in the human body, comprises bacteria, archaea, fungi, protozoa, and viruses. Dysbiosis of the oral microbiome is the initiating factor that leads to oral infectious diseases. Infection is a sophisticated biological process involving interplay between the pathogen and the host, which often leads to activation of programmed cell death. Studies suggest that pyroptosis, apoptosis, and necroptosis are involved in multiple oral infectious diseases. Further understanding of crosstalk between cell death pathways has led to pyroptosis, apoptosis, and necroptosis being integrated into a single term: PANoptosis. PANoptosis is a multifaceted agent of the immune response that has important pathophysiological relevance to infectious diseases, autoimmunity, and cancer. As such, it plays an important role in innate immune cells that detect and eliminate intracellular pathogens. In addition to the classical model of influenza virus-infected and Yersinia-infected macrophages, other studies have expanded the scope of PANoptosis to include other microorganisms, as well as potential roles in cell types other than macrophages. In this review, we will summarize the pathophysiological mechanisms underlying inflammation and tissue destruction caused by oral pathogens. We present an overview of different pathogens that may induce activation of PANoptosis, along with the functional consequences of PANoptosis in the context of oral infectious diseases. To advance our understanding of immunology, we also explore the strategies used by microbes that enable immune evasion and replication within host cells. Improved understanding of the interplay between the host and pathogen through PANoptosis will direct development of therapeutic strategies that target oral infectious diseases.

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.