[Research progress in dual immune regulation of neutrophils in periodontal inflammation].

Periodontitis is a chronic inflammatory condition of the periodontal tissues triggered by bacterial biofilm, leading to manifestations such as gingival bleeding, tooth mobility, and eventual exfoliation. Neutrophils exhibit a dual role throughout the course of periodontitis, both in defense against pathogens and in potentially detrimental effects on periodontal tissues. This article elucidates the intricate mechanisms underlying the dual functions of neutrophils in periodontitis, including respiratory burst, neutrophil extracellular traps (NETs) formation, degranulation, and phagocytosis. By providing a comprehensive understanding of neutrophils involvement in periodontitis, this study aims to empower clinicians with insights into the pathogenesis of periodontitis, thereby fostering novel strategies for its prevention and treatment.

Investigating the Interplay: Periodontal Disease and Type 1 Diabetes Mellitus-A Comprehensive Review of Clinical Studies.

Diabetes mellitus (DM) poses a significant challenge to global health, with its prevalence projected to rise dramatically by 2045. This narrative review explores the bidirectional relationship between periodontitis (PD) and type 1 diabetes mellitus (T1DM), focusing on cellular and molecular mechanisms derived from the interplay between oral microbiota and the host immune response. A comprehensive search of studies published between 2008 and 2023 was conducted to elucidate the association between these two diseases. Preclinical and clinical evidence suggests a bidirectional relationship, with individuals with T1DM exhibiting heightened susceptibility to periodontitis, and vice versa. The review includes recent findings from human clinical studies, revealing variations in oral microbiota composition in T1DM patients, including increases in certain pathogenic species such as Porphyromonas gingivalis, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans, along with shifts in microbial diversity and abundance. Molecular mechanisms underlying this association involve oxidative stress and dysregulated host immune responses, mediated by inflammatory cytokines such as IL-6, IL-8, and MMPs. Furthermore, disruptions in bone turnover markers, such as RANKL and OPG, contribute to periodontal complications in T1DM patients. While preventive measures to manage periodontal complications in T1DM patients may improve overall health outcomes, further research is needed to understand the intricate interactions between oral microbiota, host response, periodontal disease, and systemic health in this population.

Changing behind the scenes.

Th17 cell plasticity is associated with pathogenicity in chronic inflammation. In a model of periodontitis, McClure et al. (https://doi.org/10.1084/jem.20232015) describe location-dependent divergence in Th17 plasticity, with surprisingly limited conversion in inflamed gingiva but emergence of protective exTh17-TfH cells in draining LN that enhance protective antibody.

Modulation of allograft immune responses by Porphyromonas gingivalis lipopolysaccharide administration in a rat model of kidney transplantation.

Periodontitis is a chronic inflammatory disease that affects the periodontal tissues. Although it is associated with various systemic diseases, the impact of periodontitis on kidney transplantation (KT) outcomes, particularly allograft rejection, remains unclear. This study investigated the effect of periodontitis on transplant immunity, specifically examining Porphyromonas gingivalis-derived lipopolysaccharide (LPS-PG). In vitro experiments revealed that LPS-PG increased regulatory T cells (Tregs) in Lewis rat spleen cells. In a mixed lymphocyte reaction assay, concentrations of interferon-γ, indicative of alloreactivity, were lower than in controls when LPS-PG was added to the culture and when LPS-PG-administered Lewis rat spleen cells were used as responders. In a rat KT model, LPS-PG administration to recipients promoted mild tubulitis and low serum creatinine and blood urea nitrogen levels 5 days post-KT compared with PBS-administered controls. Furthermore, LPS-PG-administered recipients had an elevated Treg proportion in their peripheral blood and spleen cells, and increased infiltrating Tregs in kidney allografts, compared with controls. The elevated Treg proportion in peripheral blood and spleen cells had a significant negative correlation with serum creatinine, suggesting elevated Tregs modulated allograft rejection. These findings suggest that periodontitis might modulate alloimmune reactivity through LPS-PG and Tregs, offering insights to refine immunosuppressive strategies for KT recipients.

Periodontal inflammation as a potential driver of HIV low level viremia.

HIV can be successfully suppressed to undetectable levels by antiretroviral therapy (ART) in most people with HIV (PWH). However, a small proportion continues to have persistent low-level viremia (LLV) during ART. A presumed source of LLV is production or replication from viral reservoirs, which are maintained in the presence of ART. It is unknown whether the oral cavity can be considered an HIV reservoir. As periodontal inflammation is a common problem in PWH, we hypothesize that periodontal inflammation in the oral cavity activates (latently) infected cells and thus might be associated with LLV. We included 11 individuals with HIV LLV, and compared HIV-RNA levels in saliva and plasma at baseline and at week 24 after switch of ART. We compared the LLV-group at baseline with 11 age-matched controls with suppressed viremia. To investigate the severity of periodontitis we used Periodontal Inflamed Surface Areas (PISA) by measuring probing depth, gingival recession, bleeding on probing and clinical attachment level. Severity of periodontitis was classified according to the CDC-AAP case definition. Additional insights in periodontal inflammation were obtained by comparing immune activation markers and the presence of periodontal pathogens. In four individuals of the LLV group, residual levels of HIV-RNA were detected in saliva at baseline (N = 1) or at week 24 (N = 2) or both (N = 1). Of the four individuals with LLV, three had residual levels of HIV-RNA in saliva. All 22 individuals had moderate to severe periodontitis. PISA was not significantly different between cases with LLV and controls. Similarly, periodontal pathogens were frequently observed in both groups. Total activated HLA-DR+CD38+ CD4+ cells and CD8+ cells were significantly higher in the LLV group than in the control group (p = <0.01). No immune markers were associated with LLV. In conclusion, periodontal inflammation is an unlikely driver of HIV LLV compared to HIV suppressed individuals.

Single-cell and spatially resolved interactomics of tooth-associated keratinocytes in periodontitis.

Periodontitis affects billions of people worldwide. To address relationships of periodontal niche cell types and microbes in periodontitis, we generated an integrated single-cell RNA sequencing (scRNAseq) atlas of human periodontium (34-sample, 105918-cell), including sulcular and junctional keratinocytes (SK/JKs). SK/JKs displayed altered differentiation states and were enriched for effector cytokines in periodontitis. Single-cell metagenomics revealed 37 bacterial species with cell-specific tropism. Fluorescence in situ hybridization detected intracellular 16 S and mRNA signals of multiple species and correlated with SK/JK proinflammatory phenotypes in situ. Cell-cell communication analysis predicted keratinocyte-specific innate and adaptive immune interactions. Highly multiplexed immunofluorescence (33-antibody) revealed peri-epithelial immune foci, with innate cells often spatially constrained around JKs. Spatial phenotyping revealed immunosuppressed JK-microniches and SK-localized tertiary lymphoid structures in periodontitis. Here, we demonstrate impacts on and predicted interactomics of SK and JK cells in health and periodontitis, which requires further investigation to support precision periodontal interventions in states of chronic inflammation.

An update on periodontal inflammation and bone loss.

Periodontal disease is a chronic inflammatory condition that affects the supporting structures of the teeth, including the periodontal ligament and alveolar bone. Periodontal disease is due to an immune response that stimulates gingivitis and periodontitis, and its systemic consequences. This immune response is triggered by bacteria and may be modulated by environmental conditions such as smoking or systemic disease. Recent advances in single cell RNA-seq (scRNA-seq) and in vivo animal studies have provided new insight into the immune response triggered by bacteria that causes periodontitis and gingivitis. Dysbiosis, which constitutes a change in the bacterial composition of the microbiome, is a key factor in the initiation and progression of periodontitis. The host immune response to dysbiosis involves the activation of various cell types, including keratinocytes, stromal cells, neutrophils, monocytes/macrophages, dendritic cells and several lymphocyte subsets, which release pro-inflammatory cytokines and chemokines. Periodontal disease has been implicated in contributing to the pathogenesis of several systemic conditions, including diabetes, rheumatoid arthritis, cardiovascular disease and Alzheimer's disease. Understanding the complex interplay between the oral microbiome and the host immune response is critical for the development of new therapeutic strategies for the prevention and treatment of periodontitis and its systemic consequences.

Toll-like receptor 4 deficiency affects the balance of osteoclastogenesis and osteoblastogenesis in periodontitis.

Toll-like receptor 4 (TLR4) acts as a double-edged sword in the occurrence and development of periodontitis. While the activation of TLR4 in macrophages aids in clearing local pathogens, it can also disrupt innate immune responses, upsetting microecological balance and accelerating the destruction of periodontal bone tissues. To date, the effects of TLR4 on osteogenesis and osteoclastogenesis in periodontitis have not been comprehensively studied. In this study, we investigated the development of periodontitis in the Tlr4-/- mice by ligating their second molars with silk threads. Compared to wild-type (WT) mice, Tlr4-/- mice demonstrated increased resistance to periodontitis-associated bone destruction, as evidenced by decreased bone resorption and enhanced bone regeneration. Mechanistically, the deletion of Tlr4 not only inhibited osteoclast formation by reducing the expression of NFATc1, CTSK and TRAP, but also enhanced osteogenic abilities through increased expression of OCN, OPN and RUNX2. In conclusion, TLR4 tips the balance of osteoclastogenesis and osteogenesis, thereby promoting periodontal bone destruction in periodontitis.

Neural epidermal growth factor-like 1 protein (Nell-1) alleviates periodontal tissue destruction in periodontitis by regulating the ratio of M2/M1 macrophage phenotypes.

BACKGROUND: Periodontitis is a common oral disease with high prevalence worldwide. Neural epidermal growth factor-like 1 protein (Nell-1) has recently been reported to have anti-inflammation effects and may be a drug candidate for osteoarthritis. However, its immunotherapeutic effects in periodontitis remain unknown. Therefore, this study aimed to investigate the effects of Nell-1 on periodontitis in terms of macrophage polarization and analyze its possible underlying mechanism. METHODS: A rat ligation-induced experimental periodontitis model was established and locally injected with Nell-1 (n = 6/group). Periodontal tissue destruction and macrophage polarization in vivo were analyzed using micro-CT, histology analysis, and western blot. Enzyme-linked immunosorbent assay was used to evaluate serum inflammatory cytokines. Then, the RAW 264.7 macrophage cells were treated with lipopolysaccharide (LPS), Nell-1, and the c-Jun N-terminal kinases (JNK) inhibitor (SP600125). RT-PCR, western blot, and flow cytometry were performed to further analyze the effect of Nell-1 on macrophage polarization and the underlying mechanism in vitro. RESULTS: Local treatment with Nell-1 significantly alleviated the destruction of alveolar bone and fibers in periodontitis, and upregulated the ratio of M2/M1 macrophages in periodontal tissues (P < 0.05). In vitro, Nell-1 at the concentrations of 200 and 500 ng/mL could significantly inhibit the expression of M1-related inflammatory factors in LPS-stimulated macrophages, and increase the expression of M2-related markers, regulating the macrophage phenotype switch into M2 (P < 0.05). The mRNA of JNK and relative protein level of phospho-JNK/JNK were also upregulated by Nell-1 (P < 0.05). Additionally, the JNK inhibitor (SP600125) could reverse the effect of Nell-1 on macrophage polarization (P < 0.05). CONCLUSIONS: Nell-1 could modulate the ratio of M2/M1 macrophages possibly through the JNK/MAPK signaling pathway, subsequently attenuating the inflammation and destruction of periodontal tissues caused by periodontitis.

Bioinformatics investigation of adaptive immune-related genes in peri-implantitis and periodontitis: Characteristics and diagnostic values.

BACKGROUND: Peri-implantitis and periodontitis have similar immunological bioprocesses and inflammatory phenotypes. In the inflammatory process, the adaptive immune cells can drive the development of disease. This research investigated the differences and diagnostic significance of peri-implantitis and periodontitis in adaptive immune responses. METHODS: We acquired four GEO datasets of gene expressions in surrounding tissues in healthy person, healthy implant, periodontitis, and peri-implantitis patients. The structural characteristics and enrichment analyses of differential expression genes were examined. The adaptive immune landscapes in peri-implantitis and periodontitis were then evaluated using single sample gene set enrichment analysis. The STRING database and Cytoscape were used to identify adaptive hub genes, and the ROC curve was used to verify them. Finally, qRT-PCR method was used to verify the expression level of Hub gene in activated T cells on the titanium-containing or titanium-free culture plates. RESULTS: At the transcriptome level, the data of healthy implant, peri-implantitis and periodontitis were highly dissimilar. The peri-implantitis and periodontitis both exhibited adaptive immune response. Except for the activated CD4+T cells, there was no significant difference in other adaptive immune cells between peri-implantitis and periodontitis. In addition, correlation analysis showed that CD53, CYBB, and PLEK were significantly positively linked with activated CD4+T cells in the immune microenvironment of peri-implantitis, making them effective biomarkers to differentiate it from periodontitis. CONCLUSIONS: Peri-implantitis has a uniquely immunogenomic landscape that differs from periodontitis. This study provides new insights and ideas into the activated CD4+T cells and hub genes that underpin the immunological bioprocess of peri-implantitis.

Photobiomodulation of Gingival Cells Challenged with Viable Oral Microbes.

The oral cavity, a unique ecosystem harboring diverse microorganisms, maintains health through a balanced microflora. Disruption may lead to disease, emphasizing the protective role of gingival epithelial cells (GECs) in preventing harm from pathogenic oral microbes. Shifting GECs' response from proinflammatory to antimicrobial could be a novel strategy for periodontitis. Photobiomodulation therapy (PBMT), a nonpharmacologic host modulatory approach, is considered an alternative to drugs. While the host cell response induced by a single type of pathogen-associated molecular patterns (PAMPs) was widely studied, this model does not address the cellular response to intact microbes that exhibit multiple PAMPs that might modulate the response. Inspired by this, we developed an in vitro model that simulates direct interactions between host cells and intact pathogens and evaluated the effect of PBMT on the response of human gingival keratinocytes (HGKs) to challenge viable oral microbes at both the cellular and molecular levels. Our data demonstrated that LED pretreatment on microbially challenged HGKs with specific continuous wavelengths (red: 615 nm; near-infrared: 880 nm) induced the production of various antimicrobial peptides, enhanced cell viability and proliferation, promoted reactive oxygen species scavenging, and down-modulated proinflammatory activity. The data also suggest a potential explanation regarding the superior efficacy of near-infrared light treatment compared with red light in enhancing antimicrobial activity and reducing cellular inflammation of HGKs. Taken together, the findings suggest that PBMT enhances the overall barrier function of gingival epithelium while minimizing inflammation-mediated breakdown of the underlying structures.

Active targeting microemulsion-based thermosensitive hydrogel against periodontitis by reconstructing Th17/Treg homeostasis via regulating ROS-macrophages polarization cascade.

Periodontitis is a multifactorial inflammatory disease characterized by severe alveolar bone damage and attachment loss. The imbalance of T help 17 (Th17) / regulatory T cells (Treg) induces excessive interleukin (IL)-17, which leads to alveolar bone damage and aggravates the development of periodontitis. Therefore, we proposed a therapeutic strategy to restore Th17/Treg homeostasis by interfering reactive oxygen species (ROS)-macrophage polarization cascade using active targeting microemulsions-based thermosensitive hydrogel. Folic acid-modified quercetin-loaded microemulsions (FA-Qu-MEs) were dispersed in poloxamer 407 and poly(N-isopropylacrylamide) matrix of hydrogel (FA-Qu-MEs@Gel). FA-Qu-MEs@Gel could be locally injected into the periodontal pocket and sustainedly release drugs. FA-Qu-MEs exhibited excellent ROS scavenging potency by targeting macrophages, resulting M1 phenotype macrophage from to M2 phenotype macrophage. Subsequently, the phenotypic changes of macrophages lead to decreased expression of IL-6 and tumor necrosis factor-α, which inhibited activated Th17, while IL-10 secreted by M2 macrophages promoted Treg differentiation. Finally, the restored Th17/Treg homeostasis reduced the level of IL-17 to accelerate alveolar bone regeneration. This study deigns a novel system that promote alveolar bone regeneration by remodeling Th17/Treg homeostasis via regulating ROS-macrophages polarization cascade for periodontitis treatment.

Salivary interleukin-17A and interleukin-18 levels in patients with celiac disease and periodontitis.

Background: An increased level of interleukin-17A and interleukin-18 in the serum and intestinal mucosa of celiac disease patients reflecting the severity of villous atrophy and inflammation was documented. Thus, the objective of this study was to evaluate the concentrations of salivary-17A, interleukin-1 beta, and interleukin-18 in patients with celiac disease who are on a gluten-free diet, both with and without periodontitis, and to compare these levels with those in healthy individuals. Methods: The study involved 23 participants with serologically confirmed celiac disease (CD) and 23 control subjects. The CD patients had been following a gluten-free diet (GFD) for a minimum of 1 year and had no other autoimmune disorders. The research involved collecting demographic data, conducting periodontal examinations, gathering unstimulated whole saliva, and performing enzyme-linked immunosorbent assays to measure salivary interleukin-17A, interleukin-1 beta, and interleukin-18 levels. Spearman's correlation analysis was utilized to explore the relationships between CD markers in patients on a GFD and their periodontal clinical findings. Results: The periodontal findings indicated significantly lower values in celiac disease patients adhering to a gluten-free diet compared to control subjects (p = 0.001). No significant differences were found in salivary IL-17A, IL-18, and IL-1B levels between celiac disease patients and control subjects. Nevertheless, the levels of all interleukins were elevated in periodontitis patients in both the celiac and control groups. The IL-1 Beta level was significantly higher in periodontitis patients compared to non-periodontitis patients in the control group (p = 0.035). Significant negative correlations were observed between serum IgA levels and plaque index (r = -0.460, p = 0.010), as well as gingival index (r = -0.396, p = 0.030) in CD patients on a gluten-free diet. Conclusion: Celiac disease patients on gluten-free diet exhibited better periodontal health compared to control subjects. However, increased levels of salivary IL-17A, IL-18 and IL-1B levels were associated with periodontitis. Additionally, serum IgA level was significantly inversely associated with periodontitis clinical manifestations and with salivary inflammatory mediators in CD patients on GFD.

Cystatin C: immunoregulation role in macrophages infected with Porphyromonas gingivalis.

Background: Periodontitis is a chronic infectious disease, characterized by an exacerbated inflammatory response and a progressive loss of the supporting tissues of the teeth. Porphyromonas gingivalis is a key etiologic agent in periodontitis. Cystatin C is an antimicrobial salivary peptide that inhibits the growth of P. gingivalis. This study aimed to evaluate the antimicrobial activity of this peptide and its effect on cytokine production, nitric oxide (NO) release, reactive oxygen species (ROS) production, and programmed cell death in human macrophages infected with P. gingivalis. Methods: Monocyte-derived macrophages generated from peripheral blood were infected with P. gingivalis (MOI 1:10) and stimulated with cystatin C (2.75 µg/ml) for 24 h. The intracellular localization of P. gingivalis and cystatin C was determined by immunofluorescence and transmission electron microscopy (TEM). The intracellular antimicrobial activity of cystatin C in macrophages was assessed by counting Colony Forming Units (CFU). ELISA assay was performed to assess inflammatory (TNFα, IL-1ß) and anti-inflammatory (IL-10) cytokines. The production of nitrites and ROS was analyzed by Griess reaction and incubation with 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), respectively. Programmed cell death was assessed with the TUNEL assay, Annexin-V, and caspase activity was also determined. Results: Our results showed that cystatin C inhibits the extracellular growth of P. gingivalis. In addition, this peptide is internalized in the infected macrophage, decreases the intracellular bacterial load, and reduces the production of inflammatory cytokines and NO. Interestingly, peptide treatment increased ROS production and substantially decreased bacterial-induced macrophage apoptosis. Conclusions: Cystatin C has antimicrobial and immuno-regulatory activity in macrophages infected with P. gingivalis. These findings highlight the importance of understanding the properties of cystatin C for its possible therapeutic use against oral infections such as periodontitis.

Type 17 immune response promotes oral epithelial cell proliferation in periodontitis.

OBJECTIVES: This study aims to investigate the effects of type 17 immune response on the proliferation of oral epithelial cells in periodontitis. DESIGN: A time-dependent ligature induced periodontitis mouse model was utilized to explore gingival hyperplasia and the infiltration of interleukin 17A (IL-17A) positive cells. Immunohistochemistry and flow cytometry were employed to determine the localization and expression of IL-17A in the ligature induced periodontitis model. A pre-existing single-cell RNA sequencing dataset, comparing individuals affected by periodontitis with healthy counterparts, was reanalyzed to evaluate IL-17A expression levels. We examined proliferation markers, including proliferating cell nuclear antigen (PCNA), signal transducer and activator of transcription (STAT3), Yes-associated protein (YAP), and c-JUN, in the gingival and tongue epithelium of the periodontitis model. An anti-IL-17A agent was administered daily to observe proliferative changes in the oral mucosa within the periodontitis model. Cell number quantification, immunofluorescence, and western blot analyses were performed to assess the proliferative responses of human normal oral keratinocytes to IL-17A treatment in vitro. RESULTS: The ligature induced periodontitis model exhibited a marked infiltration of IL-17A-positive cells, alongside significant increase in thickness of the gingival and tongue epithelium. IL-17A triggers the proliferation of human normal oral keratinocytes, accompanied by upregulation of PCNA, STAT3, YAP, and c-JUN. The administration of an anti-IL-17A agent attenuated the proliferation in oral mucosa. CONCLUSIONS: These findings indicate that type 17 immune response, in response to periodontitis, facilitates the proliferation of oral epithelial cells, thus highlighting its crucial role in maintaining the oral epithelial barrier.

Th17-to-Tfh plasticity during periodontitis limits disease pathology.

Th17 cell plasticity is crucial for development of autoinflammatory disease pathology. Periodontitis is a prevalent inflammatory disease where Th17 cells mediate key pathological roles, yet whether they exhibit any functional plasticity remains unexplored. We found that during periodontitis, gingival IL-17 fate-mapped T cells still predominantly produce IL-17A, with little diversification of cytokine production. However, plasticity of IL-17 fate-mapped cells did occur during periodontitis, but in the gingiva draining lymph node. Here, some Th17 cells acquired features of Tfh cells, a functional plasticity that was dependent on IL-6. Notably, Th17-to-Tfh diversification was important to limit periodontitis pathology. Preventing Th17-to-Tfh plasticity resulted in elevated periodontal bone loss that was not simply due to increased proportions of conventional Th17 cells. Instead, loss of Th17-to-Tfh cells resulted in reduced IgG levels within the oral cavity and a failure to restrict the biomass of the oral commensal community. Thus, our data identify a novel protective function for a subset of otherwise pathogenic Th17 cells during periodontitis.

Association of IL-4 polymorphism with severe periodontitis in a sample of Iraqi population.

INTRODUCTION: Specific bacterial plaque and environmental factors cannot be considered the only cause of periodontitis. Still, several genetic factors affect the host response to the bacteria, like gene polymorphisms in anti-inflammatory cytokines. Several studies have reported that clones of T-helper 2 lymphocytes (TH2) are generated in response to dental plaque in periodontitis patients, while in healthy individuals, they are regulated by T-helper 1 (TH1) lymphocytes. Accordingly, such patients consistently produce more IL-4 (TH2) in response to bacterial stimulation, whereas healthy controls with intact periodontal tissues produce a significantly higher level of TH1.

Macrophage-enriched novel functional long noncoding RNAs LRRC75A-AS1 and GAPLINC regulate polarization and innate immune responses.

INTRODUCTION: Macrophages (Mφs) are functionally dynamic immune cells that bridge innate and adaptive immune responses; however, the underlying epigenetic mechanisms that control Mφ plasticity and innate immune functions are not well elucidated. OBJECTIVE: To identify novel functions of macrophage-enriched lncRNAs in regulating polarization and innate immune responses. METHODS: Total RNA isolated from differentiating monocyte-derived M1 and M2 Mφs was profiled for lncRNAs expression using RNAseq. Impact of LRRC75A-AS1, GAPLINC and AL139099.5 knockdown was examined on macrophage differentiation, polarization markers, phagocytosis, and antigen processing by flow cytometry and florescence microscopy. Cytokine profiles were examined by multiplex bead array and cytoskeletal signaling pathway genes were quantified by PCR-based array. Gingival biopsies were collected from periodontally healthy and diseased subjects to examine lncRNAs, M1/M2 marker expression. RESULTS: Transcriptome profiling of M1 and M2 Mφs identified thousands of differentially expressed known and novel lncRNAs. We characterized three Mφ-enriched lncRNAs LRRC75A-AS1, GAPLINC and AL139099.5 in polarization and innate immunity. Knockdown of LRRC75A-AS1 and GAPLINC downregulated the Mφ differentiation markers and skewed Mφ polarization by decreasing M1 markers without a significant impact on M2 markers. LRRC75A-AS1 and GAPLINC knockdown also attenuated bacterial phagocytosis, antigen processing and inflammatory cytokine secretion in Mφs, supporting their functional role in potentiating innate immune functions. Mechanistically, LRRC75A-AS1 and GAPLINC knockdown impaired Mφ migration by downregulating the expression of multiple cytoskeletal signaling pathways suggesting their critical role in regulating Mφ migration. Finally, we showed that LRRC75A-AS1 and GAPLINC were upregulated in periodontitis and their expression correlates with higher M1 markers suggesting their role in macrophage polarization in vivo. CONCLUSION: Our results show that polarized Mφs acquire a unique lncRNA repertoire and identified many previously unknown lncRNA sequences. LRRC75A-AS1 and GAPLINC, which are induced in periodontitis, regulate Mφ polarization and innate immune functions supporting their critical role in inflammation.

IGF2 promotes alveolar bone regeneration in murine periodontitis via inhibiting cGAS/STING-mediated M1 macrophage polarization.

Periodontitis is a chronic inflammatory disease with the destruction of supporting periodontal tissue. This study evaluated the role of insulin-like growth factor 2 (IGF2) in periodontitis by inhibiting the polarization of M1 macrophages via the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. IGF2 was enriched in the gingival tissue of murine periodontitis model identified by RNA sequencing. IGF2 application alleviated the expression of pro-inflammatory factors and promoted osteogenesis and the expression of related genes and proteins in a dose-dependent manner in periodontitis. The result of micro-CT verified this finding. Both in vivo and in vitro results revealed that IGF2 decreased the polarization of M1 macrophages and pro-inflammatory factors by immunofluorescence staining, flow cytometry, western blotting and RT-PCR. IGF2 application promoted the osteogenic ability of periodontal ligament fibroblasts (PDLFs) indirectly via its inhibition of M1 polarization evaluated by alkaline phosphatase and alizarin red staining. Then, the cGAS/STING pathway was upregulated in periodontitis and macrophages challenged by LPS, the inhibition of which led to downregulation of M1 polarization. Furthermore, IGF2 could downregulate cGAS, STING and the phosphorylation of P65. Collectively, our study indicates IGF2 can regulate the polarization of M1 macrophages via the cGAS/STING pathway and highlights the promising future of IGF2 as a therapeutic treatment for periodontitis.

IRE1α regulates macrophage polarization in type 2 diabetic periodontitis through promoting endoplasmic reticulum stress.

OBJECTIVES: The aim of this study was to investigate the effect of 4µ8c, an inhibitor targeting the endoplasmic reticulum stress-associated factor IRE1α, on macrophage polarization in an experimental model of diabetic periodontitis through ex vivo experiments. MATERIALS AND METHODS: Local alveolar bone parameters were evaluated using Micro-CT following intraperitoneal administration of 4µ8c in mice with experimental diabetic periodontitis. Surface markers indicating macrophage polarization were identified using immunofluorescence. In vitro experiments were performed employing bone marrow-derived macrophages and gingival fibroblasts. Macrophage polarization was determined using flow cytometry. Principal impacted signaling pathways were identified through Western blot analysis. RESULTS: Results from both in vitro and in vivo experiments demonstrated that 4µ8c mitigated alveolar bone resorption and inflammation in mice with diabetic periodontitis. Furthermore, it modulated macrophage polarization towards the M2 phenotype and augmented M2 macrophage polarization through the MAPK signaling pathway. CONCLUSIONS: These findings suggest that inhibiting IRE1α can modulate macrophage polarization and alleviate ligature-induced diabetic periodontitis via the MAPK signaling pathway. This unveils a novel mechanism, offering a scientific foundation for the treatment of experimental diabetic periodontitis.