E-selectin expression induced by Porphyromonas gingivalis in human endothelial cells via nucleotide-binding oligomerization domain-like receptors and Toll-like receptors

Integrative analysis of gene and protein expression in atherosclerosis-related pathways modulated by periodontal pathogens. Systematic review

The mechanisms modulated by periodontal pathogens in atherosclerosis are not fully understood. Aim: to perform an integrative analysis of gene and protein expression modulated by periodontal pathogens in cells and animal models for atherosclerosis.

Methods

Cochrane, PRISMA and AMSTAR2 guidelines for systematic reviews were followed. Data search was conducted in Pub-med, LILACS and Science Direct databases. Gene and protein expression data were collected from the included papers to perform an overrepresentation analysis using the Reactome Pathway Analysis tool and the KEGG database.

Results

Thirty-two papers were included in the review, they analyzed the effect of Fusobacterium nucleatum, Porphyromonas gingivalis, Streptococcus anginosus, Streptococcus sanguinis, Tannerella forsythia, and Treponema denticola or/and their virulent factors on gene and protein expression in human cells and animal models of atherosclerosis. Some of the modulated pathways include the immune system, programmed cell death, cellular responses to external stimuli, transport of small molecules, and signal transduction (p < 0.05). Those pathways are known to be involved in different stages of atherosclerosis progression.

Conclusion

Based on the performed analysis, it is possible to state that periodontal pathogens have the potential to be a contributing factor for atherosclerosis even in absence of a high-fat diet or high shear stress.

Potential Roles of Selectins in Periodontal Diseases and Associated Systemic Diseases: Could They Be Targets for Immunotherapy?

Periodontal diseases are predisposing factors to the development of many systemic disorders, which is often initiated via leukocyte infiltration and vascular inflammation. These diseases could significantly affect human health and quality of life. Hence, it is vital to explore effective therapies to prevent disease progression. Periodontitis, which is characterized by gingival bleeding, disruption of the gingival capillary's integrity, and irreversible destruction of the periodontal supporting bone, appears to be caused by overexpression of selectins in periodontal tissues. Selectins (P-, L-, and E-selectins) are vital members of adhesion molecules regulating inflammatory and immune responses. They are mainly located in platelets, leukocytes, and endothelial cells. Furthermore, selectins are involved in the immunopathogenesis of vascular inflammatory diseases, such as cardiovascular disease, diabetes, cancers, and so on, by mediating leukocyte recruitment, platelet activation, and alteration of endothelial barrier permeability. Therefore, selectins could be new immunotherapeutic targets for periodontal disorders and their associated systemic diseases since they play a crucial role in immune regulation and endothelium dysfunction. However, the research on selectins and their association with periodontal and systemic diseases remains limited. This review aims to discuss the critical roles of selectins in periodontitis and associated systemic disorders and highlights the potential of selectins as therapeutic targets.

Role of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 6 in activation of inflammation in human umbilical vein endothelial cells stimulated by Porphyromonas gingivalis-an in vitro study

Background/purpose

Porphyromonas gingivalis (P. gingivalis) could induce the activation of vascular endothelial cells and promote the formation of atherosclerosis. Nucleotide-binding oligomerization domain-like receptor family pyrin domain containing (NLRP) 6 could recognize P. gingivalis, but its role in atherosclerosis was unknown. The purpose of this study is to investigate the role of NLRP6 in the activation of inflammation in human umbilical vein endothelial cells (HUVECs) stimulated by P. gingivalis.

Materials and methods

The expression level of NLRP6 in HUVECs with or without P. gingivalis-challenge was observed. Down-regulating the expression of NLRP6 in HUVECs, the expression levels of interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein (MCP)-1 were detected. Then, the HUVECs with NLRP6-overexpressed were stimulated by P. gingivalis, the levels of inflammatory cytokines above were examined and compared with those in HUVECs triggered by P. gingivalis only. To evaluate the effect of NLRP6 on bacterial immune escape, the NLRP6 was overexpressed, and the colonies of P. gingivalis that survived in HUVECs were calculated.

Results

NLRP6 was expressed in HUVECs and decreased after P. gingivalis stimulation. Downregulation of NLRP6 decreased the expression levels of IL-1β, IL-6, IL-8, TNF-α and MCP-1 in HUVECs. Those cytokines above in NLRP6-overexpressed HUVECs with P. gingivalis-stimulation significantly increased than in the cells with P. gingivalis-stimulation only. Furthermore, over-expression of NLRP6 decreased the colonies of P. gingivalis survival in HUVECs.

Conclusion

NLRP6 regulated the activation of inflammation in HUVECs triggered by P. gingivalis and played an important role in P. gingivalis survival in endothelial cells.

NLRC5 modulates bone metabolism and plays a role in periodontitis

INTRODUCTION

NOD-like receptor C5 (NLRC5) plays a significant role in the immune system, and is one of the largest members of the pattern recognition receptor family. Previous studies have found that NLRC5 might be involved in the regulation of various diseases, such as fibrotic diseases and cancers; however, its effect on bone metabolism-related diseases has not been reported.

METHODS

Skeletons of Nlrc5^-/- mice generated by CRISPR/Cas9 and wild-type (WT) mice were compared using X-ray, micro-computed tomography, double labeling, and histological examination. Tartrate-resistant acid phosphatase and pit-absorption assays were performed to evaluate the effect of NLRC5 on osteoclasts differentiation and osteoclastic capacity. The influence of NLRC5 on osteoblasts differentiation and bone formation were studied using alkaline phosphatase and alizarin red staining, respectively. Experimental periodontitis was induced by Porphyromonas gingivalis infection and ligature to investigate the role of NLRC5 in inflammatory periodontal bone loss.

RESULTS

Adenovirus-mediated NLRC5 overexpression in human bone marrow mesenchymal stem cells regulated osteogenesis positively. The femoral osteogenesis ability was significantly weakened in Nlrc5^-/- mice. Histology showed that the area of the femoral trabeculae in the Nlrc5^-/- mice was less than that in the WT mice, and radiology suggested that the Nlrc5^-/- mice had fewer trabeculae and a thinner bone cortex than those of the WT mice. Nlrc5 knockout decreased osteoblast mineralization and increased osteoclastogenesis in vitro. NLRC5 was downregulated in periodontitis and P. gingivalis infection. In the experimental periodontitis model, the alveolar bone loss, inflammatory cell infiltration, and inflammatory cytokines secretion (interleukin [IL]-1β, IL-6, and tumor necrosis factor alpha [TNF-α]) in the Nlrc5^-/- mice were significantly enhanced compared to WT mice.

CONCLUSION

We verified a novel role of NLRC5 in bone metabolism by regulating both osteoclasts activity and osteoblasts activity. Our results revealed a protective effect of NLRC5 against periodontal inflammation and alveolar bone destruction. NLRC5 could be a novel treatment target to prevent periodontal bone destruction.

Periodontopathic Microbiota and Atherosclerosis: Roles of TLR-Mediated Inflammation Response

Atherosclerosis is a chronic inflammatory disease with a high prevalence worldwide, contributing to a series of adverse cardiovascular and cerebrovascular diseases. Periodontal disease induced by pathogenic periodontal microbiota has been well established as an independent factor of atherosclerosis. Periodontal microorganisms have been detected in atherosclerotic plaques. The high-risk microbiota dwelling in the subgingival pocket can stimulate local and systematic host immune responses and inflammatory cascade reactions through various signaling pathways, resulting in the development and progression of atherosclerosis. One often-discussed pathway is the Toll-like receptor-nuclear factor-κB (TLR-NF-κB) signaling pathway that plays a central role in the transduction of inflammatory mediators and the release of proinflammatory cytokines. This narrative review is aimed at summarizing and updating the latest literature on the association between periodontopathic microbiota and atherosclerosis and providing possible therapeutic ideas for clinicians regarding atherosclerosis prevention and treatment.

PAMPs and DAMPs as the Bridge Between Periodontitis and Atherosclerosis: The Potential Therapeutic Targets

Atherosclerosis is a chronic artery disease characterized by plaque formation and vascular inflammation, eventually leading to myocardial infarction and stroke. Innate immunity plays an irreplaceable role in the vascular inflammatory response triggered by chronic infection. Periodontitis is a common chronic disorder that involves oral microbe-related inflammatory bone loss and local destruction of the periodontal ligament and is a risk factor for atherosclerosis. Periodontal pathogens contain numerous pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide, CpG DNA, and Peptidoglycan, that initiate the inflammatory response of the innate immunity depending on the recognition of pattern-recognition receptors (PRRs) of host cells. The immune-inflammatory response and destruction of the periodontal tissue will produce a large number of damage-associated molecular patterns (DAMPs) such as neutrophil extracellular traps (NETs), high mobility group box 1 (HMGB1), alarmins (S100 protein), and which can further affect the progression of atherosclerosis. Molecular patterns have recently become the therapeutic targets for inflammatory disease, including blocking the interaction between molecular patterns and PRRs and controlling the related signal transduction pathway. This review summarized the research progress of some representative PAMPs and DAMPs as the molecular pathological mechanism bridging periodontitis and atherosclerosis. We also discussed possible ways to prevent serious cardiovascular events in patients with periodontitis and atherosclerosis by targeting molecular patterns.

The Effects of Porphyromonas gingivalis on Atherosclerosis-Related Cells

Atherosclerosis (AS), one of the most common types of cardiovascular disease, has initially been attributed to the accumulation of fats and fibrous materials. However, more and more researchers regarded it as a chronic inflammatory disease nowadays. Infective disease, such as periodontitis, is related to the risk of atherosclerosis. Porphyromonas gingivalis (P. gingivalis), one of the most common bacteria in stomatology, is usually discovered in atherosclerotic plaque in patients. Furthermore, it was reported that P. gingivalis can promote the progression of atherosclerosis. Elucidating the underlying mechanisms of P. gingivalis in atherosclerosis attracted attention, which is thought to be crucial to the therapy of atherosclerosis. Nevertheless, the pathogenesis of atherosclerosis is much complicated, and many kinds of cells participate in it. By summarizing existing studies, we find that P. gingivalis can influence the function of many cells in atherosclerosis. It can induce the dysfunction of endothelium, promote the formation of foam cells as well as the proliferation and calcification of vascular smooth muscle cells, and lead to the imbalance of regulatory T cells (Tregs) and T helper (Th) cells, ultimately promoting the occurrence and development of atherosclerosis. This article summarizes the specific mechanism of atherosclerosis caused by P. gingivalis. It sorts out the interaction between P. gingivalis and AS-related cells, which provides a new perspective for us to prevent or slow down the occurrence and development of AS by inhibiting periodontal pathogens.

SELE gene as a characteristic prognostic biomarker of colorectal cancer

OBJECTIVE

To investigate the expression and clinical value of the E-selectin gene (SELE) in colorectal cancer (CRC).

METHODS

Using gene expression profiles and clinicopathological data for patients with CRC from The Cancer Genome Atlas, and tumor and adjacent normal tissues from 31 patients with CRC from Xianyang Central Hospital, we studied the correlation between SELE gene expression and clinical parameters using Kaplan-Meier and Cox proportional hazards regression analyses.

RESULTS

Higher expression of SELE was significantly associated with a poorer prognosis and shorter survival in patients with CRC. The median expression level of SELE was significantly higher in CRC tissues compared with healthy adjacent tissue. Cox regression analysis showed that the prognosis of CRC was significantly correlated with the expression of SELE. Immunohistochemical analysis also showed that positive expression of E-selectin increased significantly in line with increasing TNM stage.Conclusion: This study confirmed that SELE gene expression is an independent prognostic factor in patients with CRC.

LOX-1 Regulates P. gingivalis-Induced Monocyte Migration and Adhesion to Human Umbilical Vein Endothelial Cells

Porphyromonas gingivalis (P. gingivalis) is one of the main periodontal bacteria. This pathogen was reported to enhance monocyte migration and adhesion to endothelial cells in atherosclerosis. The scavenger receptor lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) plays a pivotal role in atherogenesis. The aim of this study was to investigate whether LOX-1 modulates P. gingivalis-mediated monocyte migration and adhesion to endothelial cells and how it works. The results showed that the migration and adhesion of monocytic THP-1 cells to human umbilical vein endothelial cells (HUVECs) were significantly enhanced when HUVECs or THP-1 cells were challenged with P. gingivalis. Meanwhile, the expression level of LOX-1 in both HUVECs and THP-1 cells were also significantly increased by P. gingivalis stimulation. It is well known that ligand/receptor pairs monocyte chemoattractant protein-1 (MCP-1)/CC chemokine receptor 2 (CCR2), selectins/Integrins, and cell adhesion molecules (CAMs)/Integrins mediate monocyte migration and adhesion to endothelial cells. In this study, LOX-1 was demonstrated to be crucially involved in P. gingivalis-induced THP-1 cell migration and adhesion to HUVECs, by regulating expression of ligands MCP-1, intercellular adhesion molecule-1 (ICAM-1) and E-selectin in HUVECs and that of their receptors CCR2 and Integrin αMβ2 in THP-1 cells. The nuclear factor-kappa B (NF-κB) signaling pathway was proved to be involved in this process. In conclusion, LOX-1 plays a crucial role in P. gingivalis-induced monocyte migration and adhesion to endothelial cells. This result implies LOX-1 may act as a bridge in linking periodontitis to atherosclerosis.

NLRP6 Induces Pyroptosis by Activation of Caspase-1 in Gingival Fibroblasts

NLRP6, a member of the nucleotide-binding domain, leucine-rich repeat-containing (NLR) innate immune receptor family, has been reported to participate in inflammasome formation. Activation of inflammasome triggers a caspase-1-dependent programming cell death called pyroptosis. However, whether NLRP6 induces pyroptosis has not been investigated. In this study, we showed that NLRP6 overexpression activated caspase-1 and gasdermin-D and then induced pyroptosis of human gingival fibroblasts, resulting in release of proinflammatory mediators interleukin (IL)-1β and IL-18. Moreover, NLRP6 was highly expressed in gingival tissue of periodontitis compared with healthy controls. Porphyromonas gingivalis, which is a commensal bacterium and has periodontopathic potential, induced pyroptosis of gingival fibroblasts by activation of NLRP6. Together, we, for the first time, identified that NLRP6 could induce pyroptosis of gingival fibroblasts by activation of caspase-1 and may play a role in periodontitis.

LOX-1 is involved in IL-1β production and extracellular matrix breakdown in dental peri-implantitis

PURPOSE

To explore whether lectin-type oxidized LDL receptor 1 (LOX-1), interleukin 1 beta (IL-1β), matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) are involved in the nosogenesis of human dental peri-implantitis and determine the role of LOX-1 in IL-1β, MMP2 and MMP9 production in response to Porphyromonas gingivalis.

METHODS

Peri-implant crevicular fluid (PICF) was collected from ten patients with healthy implants and ten patients with peri-implantitis. The LOX-1 protein in PICF was detected by Western-blot, and the expression of LOX-1 in superficial gingiva of peri-implantitis patients was detected by immunofluorescence staining. The IL-1β, MMP2 and MMP9 proteins in PICF were detected by enzyme-linked immunosorbent assay (ELISA). THP-1 macrophages were pretreated with neutralizing antibody (LOX-1) and inhibitors (LOX-1 and c-Jun N-terminal kinase, JNK) to evaluate the role of LOX-1 and JNK in IL-1β production, as well as the role of LOX-1 in MMP2 and MMP9 production in response to P. gingivalis by quantitative polymerase chain reaction (RT-PCR) and Western-blot.

RESULTS

LOX-1, IL-1β, MMP2 and MMP9 increased in PICF of peri-implantitis patients and in THP-1 macrophages on P. gingivalis stimulation. IL-1β, MMP2 and MMP9 production in response to P. gingivalis in THP-1 macrophages was dependent on LOX-1. JNK was responsible for LOX-1 induced IL-1β production as a result of P. gingivalis infection.

CONCLUSION

LOX-1 is involved in IL-1β production and extracellular matrix breakdown is a novel inflammatory pathway trigger and potential drug target in human dental peri-implantitis.

TLR-induced immunomodulatory cytokine expression by human gingival stem/progenitor cells

During therapeutic application, mesenchymal stem cells (MSCs) may interact with their environment via their expressed toll-like-receptors (TLRs) leading to pro- or anti-inflammatory immune responses. The present study aimed to describe the gingival margin-derived stem/progenitor cells' (G-MSCs) TLR-induced immune regulatory response to specific TLR agonists. Gingival cells were obtained, immunomagnetically sorted via anti-STRO-1 antibodies and seeded out to achieve colony forming units (CFUs). G-MSCs were investigated for stem cell characteristics and TLR expression. Specific TLR agonists were applied and m-RNA expression of pro- and anti-inflammatory factors was analyzed via real-time polymerase chain reaction. G-MSCs showed all characteristics of stem/progenitor cells. All TLR agonists induced pro-inflammatory cytokines, except for the TLR3 agonist, which significantly promoted the anti-inflammatory response. (p⩽0.05, Wilcoxon-Signed-Ranks-Test). TLR-induced immunomodulation by G-MSCs could impact their therapeutic potential in vivo. Two distinctive pro-inflammatory and an anti-inflammatory TLR-induced phenotypes of G-MSCs become noticeable in this study.

Negative regulation of NOD1 mediated angiogenesis by PPARγ-regulated miR-125a

Infection with pathogens activates the endothelial cell and its sustained activation may result in impaired endothelial function. Endothelial dysfunction contributes to the pathologic angiogenesis that is characteristic of infection-induced inflammatory pathway activation. Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) is a protein receptor which recognizes bacterial molecules and stimulates an immune reaction in various cells; however, the underlying molecular mechanisms in the regulation of inflammation-triggered angiogenesis are not fully understood. Here we report that peroxisome proliferator-activated receptor gamma (PPARγ)-mediated miR-125a serves as an important regulator of NOD1 agonist-mediated angiogenesis in endothelial cells by directly targeting NOD1. Treatment of human umbilical vein endothelial cells with natural PPARγ ligand, 15-Deoxy-Delta12,14-prostaglandin J2, led to inhibition of NOD1 expression; contrarily, protein levels of NOD1 were significantly increased by PPARγ knockdown. We report that PPARγ regulation of NOD1 expression is a novel microRNA-mediated regulation in endothelial cells. MiR-125a expression was markedly decreased in human umbilical vein endothelial cells subjected to PPARγ knockdown while 15-Deoxy-Delta12,14-prostaglandin J2 treatment increased the level of miR-125a. In addition, NOD1 is closely regulated by miR-125a, which directly targets the 3' untranslated region of NOD1. Moreover, both overexpression of miR-125a and PPARγ activation led to inhibition of NOD1 agonist-induced tube formation in endothelial cells. Finally, NOD1 agonist increased the formation of cranial and subintestinal vessel plexus in zebrafish, and this effect was abrogated by concurrent PPARγ activation. Overall, these findings identify a PPARγ-miR-125a-NOD1 signaling axis in endothelial cells that is critical in the regulation of inflammation-mediated angiogenesis.

Invasive Streptococcus mutans induces inflammatory cytokine production in human aortic endothelial cells via regulation of intracellular toll-like receptor 2 and nucleotide-binding oligomerization domain 2

Streptococcus mutans, the primary etiologic agent of dental caries, can gain access to the bloodstream and has been associated with cardiovascular disease. However, the roles of S. mutans in inflammation in cardiovascular disease remain unclear. The aim of this study was to examine cytokine production induced by S. mutans in human aortic endothelial cells (HAECs) and to evaluate the participation of toll-like receptors (TLRs) and cytoplasmic nucleotide-binding oligomerization domain (NOD) -like receptors in HAECs. Cytokine production by HAECs was determined using enzyme-linked immunosorbent assays, and the expression of TLRs and NOD-like receptors was evaluated by real-time polymerase chain reaction, flow cytometry and immunocytochemistry. The involvement of TLR2 and NOD2 in cytokine production by invaded HAECs was examined using RNA interference. The invasion efficiencies of S. mutans strains were evaluated by means of antibiotic protection assays. Five of six strains of S. mutans of various serotypes induced interleukin-6, interleukin-8 and monocyte chemoattractant protein-1 production by HAECs. All S. mutans strains upregulated TLR2 and NOD2 mRNA levels in HAECs. Streptococcus mutans Xc upregulated the intracellular TLR2 and NOD2 protein levels in HAECs. Silencing of the TLR2 and NOD2 genes in HAECs invaded by S. mutans Xc led to a reduction in interleukin-6, interleukin-8 and monocyte chemoattractant protein-1 production. Cytokine production induced by invasive S. mutans via intracellular TLR2 and NOD2 in HAECs may be associated with inflammation in cardiovascular disease.