Periodontal ligament fibroblasts migration injury via ROS/TXNIP/Nlrp3 inflammasome pathway with Porphyromonas gingivalis lipopolysaccharide

The ROS/TXNIP/NLRP3 pathway mediates LPS-induced microglial inflammatory response

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction activated by microglia. The potential pathological changes of SAE are complex, and the cellular pathophysiological characteristics remains unclear. This study aims to explore the ROS/TXNIP/NLRP3 pathway mediated lipopolysaccharide (LPS)-induced inflammatory response in microglia.

METHODS

BV-2 cells were pre-incubated with 10 μM N-acetyl-L-cysteine (NAC) for 2 h, which were then reacted with 1 μg/mL LPS for 24 h. Western blot assay examined the protein levels of IBA1, CD68, TXNIP, NLRP3, ASC, and Cleaved Caspase-1 in BV-2 cells. The contents of inflammatory factor were detected by ELISA assay. The co-immunoprecipitation assay examined the interaction between TXNIP and NLRP3.

RESULTS

LPS was confirmed to promote the positive expressions of IBA1 and CD68 in BV-2 cells. The further experiments indicated that LPS enhanced ROS production and NLRP3 inflammasome activation in BV-2 cells. Moreover, we also found that NAC partially reversed the facilitation of LPS on the levels of ROS, IL-1β, IL-18, TXNIP, NLRP3, ASC, and Cleaved Caspase-1 in BV-2 cells. NAC treatment also notably alleviated the interaction between TXNIP and NLRP3 in BV-2 cells.

CONCLUSION

ROS inhibition mediated NLRP3 signaling inactivation by decreasing TXNIP expression.

Porphyromonas gingivalis LPS-stimulated BMSC-derived exosome promotes osteoclastogenesis via miR-151-3p/PAFAH1B1

OBJECTIVES

Porphyromonas gingivalis-LPS regulated bone metabolism by triggering dysfunction of osteoblasts directly, and affecting activity of osteoclasts through intracellular communication. Exosome, as the mediator of intercellular communication, was important vesicle to regulate osteogenesis and osteoclastogenesis. This research was designed for investigating the mechanism of BMSCs-EXO in modulating osteoclastic activity under the P. gingivalis-LPS.

MATERIALS AND METHODS

The cytotoxicity and osteogenic effects of P. gingivalis-LPS on BMSCs was evaluated, and then osteoclastic activity of RAW264.7 co-cultured with exosomes was detected. Besides, Affymetrix miRNA array and luciferase reporter assay were used to identify the target exosomal miRNA signal pathway.

RESULTS

BMSCs' osteogenic differentiation and proliferation were decreased under 1 and 10 μg/mL P. gingivalis-LPS. Osteoclastic-related genes and proteins levels were promoted by P. gingivalis-LPS-stimulated BMSCs-EXO. Based on the miRNA microarray analysis, exosomal miR-151-3p was lessened in BMExo-LPS group, which facilitated osteoclastic differentiation through miR-151-3p/PAFAH1B1.

CONCLUSIONS

Porphyromonas gingivalis-LPS could regulated bone metabolism by inhibiting proliferation and osteogenesis of BMSCs directly. Also, P. gingivalis-LPS-stimulated BMSCs-EXO promoted osteoclastogenesis via activating miR-151-3p/PAFAH1B1 signal pathway.

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.

NLRP3 Inflammasome in Autoinflammatory Diseases and Periodontitis Advance in the Management

Inflammatory chemicals are released by the immune system in response to any perceived danger, including irritants and pathogenic organisms. The caspase activation and the response of inflammation are governed by inflammasomes, which are sensors and transmitters of the innate immune system. They have always been linked to swelling and pain. Research has mainly concentrated on the NOD-like protein transmitter 3 (NLRP3) inflammasome. Interleukin (IL)-1 and IL-18 are pro-inflammatory cytokines that are activated by the NOD-like antibody protein receptor 3 (NLRP3), which controls innate immune responses. The NLRP3 inflammasome has been associated with gum disease and other autoimmune inflammatory diseases in several studies. Scientists' discovery of IL-1's central role in the pathophysiology of numerous autoimmune disorders has increased public awareness of these conditions. The first disease to be connected with aberrant inflammasome activation was the autoinflammatory cryopyrin-associated periodic syndrome (CAPS). Targeted therapeutics against IL-1 have been delayed in development because their underlying reasons are poorly understood. The NLRP3 inflammasome has recently been related to higher production and activation in periodontitis. Multiple periodontal cell types are controlled by the NLRP3 inflammasome. To promote osteoclast genesis, the NLRP3 inflammasome either increases receptor-activator of nuclear factor kappa beta ligand (RANKL) synthesis or decreases osteoclast-promoting gene (OPG) levels. By boosting cytokines that promote inflammation in the periodontal ligament fibroblasts and triggering apoptosis in osteoblasts, the NLRP3 inflammasome regulates immune cell activity. These findings support further investigation into the NLRP3 inflammasome as a therapeutic target for the medical treatment of periodontitis. This article provides a short overview of the NLRP3 inflammatory proteins and discusses their role in the onset of autoinflammatory disorders (AIDs) and periodontitis.

Er:YAG Laser Alleviates Inflammaging in Diabetes-Associated Periodontitis via Activation CTBP1-AS2/miR-155/SIRT1 Axis

Periodontitis is a significant health concern for individuals with diabetes mellitus (DM), characterized by inflammation and periodontium loss. Hyperglycaemia in DM exacerbates susceptibility to periodontitis by inducing inflammaging in the host immune system. The use of erbium-doped yttrium-aluminum-garnet laser (ErL) in periodontitis treatment has gained attention, but its impact on diabetic-associated periodontitis (DP) and underlying mechanisms remain unclear. In this study, we simulated DP by exposing human periodontal ligament fibroblasts (PDLFs) to advanced glycation end products (AGEs) and lipopolysaccharides from P. gingivalis (Pg-LPS). Subsequently, we evaluated the impact of ErL on the cells' wound healing and assessed their inflammaging markers. ErL treatment promoted wound healing and suppressed inflammaging activities, including cell senescence, IL-6 secretion, and p65 phosphorylation. Moreover, the laser-targeted cells were observed to have upregulated expression of CTBP1-AS2, which, when overexpressed, enhanced wound healing ability and repressed inflammaging. Moreover, bioinformatic analysis revealed that CTBP1-AS2 acted as a sponge for miR155 and upregulated SIRT1. In conclusion, ErL demonstrated the ability to improve wound healing and mitigate inflammaging in diabetic periodontal tissue through the CTBP1-AS2/miR-155/SIRT1 axis. Targeting this axis could represent a promising therapeutic approach for preventing periodontitis in individuals with DM.

Correlation between Inflammasomes and Microbiota in Peri-Implantitis

The activation of inflammasomes is thought to induce the inflammatory process around dental implants. No information is available on the correlation between microbiota and inflammasomes in clinical samples from patients suffering peri-implantitis. For this cross-sectional study, 30 biofilm samples were obtained from 19 patients undergoing surgical treatment for peri-implantitis because of the presence of bleeding on probing, probing depth higher than 6 mm, and radiographic bone loss higher than 3 mm. Then, soft tissue samples from around the implant were also collected. The relative abundance of bacteria and alpha-diversity indexes were calculated after analyzing the 16S rRNA gene using next-generation sequencing. The soft-tissue samples were processed for evaluation of the inflammasomes NLRP3 and AIM2 as well as caspase-1 and IL-1β. The relative abundance (mean (SD)) of specific species indicated that the most abundant species were Porphyromonas gingivalis (10.95 (14.17)%), Fusobacterium vincentii (10.93 (13.18)%), Porphyromonas endodontalis (5.89 (7.23)%), Prevotella oris (3.88 (4.94)%), Treponema denticola (2.91 (3.19)%), and Tannerella forsythia (2.84 (4.15)%). Several correlations were found between the species and the immunohistochemical detection of the inflammasomes NLRP3 and AIM2 as well as caspase-1 and IL-1β, both in the epithelium and the lamina propria. A network analysis found an important cluster of variables formed by NLRP3 in the lamina propria and AIM2, caspase-1, and IL-1β in the lamina propria and the epithelium with Prevotella dentalis, Prevotella tannerae, Tannerella forsythia, or Selenomonas timonae. Thus, it could be concluded that inflammasomes NLRP3 and AIM2 and their downstream effectors caspase-1 and interleukin-1β can be significantly associated with specific bacteria.

BML-111 inhibit H2O2-induced pyroptosis and osteogenic dysfunction of human periodontal ligament fibroblasts by activating the Nrf2/HO-1 pathway

BACKGROUND

Periodontitis is a common and harmful chronic inflammatory oral disease, characterized by the destruction of periodontal soft and hard tissues. The NLRP3 inflammasome-related pyroptosis and human periodontal ligament fibroblasts (hPDLFs) osteogenic dysfunction are involved in its pathogenesis. Studies have shown that lipoxin A4 is an endogenous anti-inflammatory mediator and BML-111 is a lipoxin A4 analog, which was found to have potent and durable anti-inflammatory effects in inflammatory diseases, but the mechanism remains unclear. The purpose of this study was to investigate whether BML-111 inhibits H2O2-induced dysfunction of hPDLFs, attenuates inflammatory responses, and identifies the underlying mechanisms.

METHODS

The oxidative stress model was established with H2O2, and the cell proliferation activity was measured by CCK-8. ALP staining and alizarin red staining were used to detect the osteogenic differentiation capacity of cells; flow cytometry and ELISA were used to detect cell pyroptosis; we explored the effect of BML-111 on hPDLFs under oxidative stress by analyzing the results of PCR and Western blotting. The Nrf2 inhibitor ML385 was added to further identify the target of BML-111 and clarify its mechanism.

RESULTS

BML-111 can alleviate the impaired cell proliferation viability induced by H2O2. H2O2 treatment can induce NLRP3 inflammasome-related pyroptosis, impairing the osteogenic differentiation capacity of hPDLFs. BML-111 can effectively alleviate H2O2-induced cellular dysfunction by activating the Nrf2/HO-1 signaling pathway.

CONCLUSION

The results of this study confirmed the beneficial effects of BML-111 on H2O2-induced NLRP3 inflammasome-related pyroptosis in hPDLFs, and BML-111 could effectively attenuate the impaired osteogenic differentiation function. This beneficial effect is achieved by activating the Nrf2/HO-1 signaling pathway, therefore, our results suggest that BML-111 is a potential drug for the treatment of periodontitis.

PINK1-mediated mitophagy reduced inflammatory responses to Porphyromonas gingivalis in macrophages

OBJECTIVE

Mitochondria are strained by microbial stimuli in the periodontal niche. Damaged mitochondria are cleared by mitophagy. The purpose of the study was to explore whether mitophagy participated in the progress of periodontitis and whether activation of mitophagy can inhibit inflammatory responses to bacterial infection in macrophages.

METHODS

Mitophagy-related genes were measured in the healthy and inflamed human gingiva. Bone marrow-derived macrophages (BMDMs) were infected with Porphyromonas gingivalis. Dexmedetomidine, urolithin A, and resveratrol were used to activate mitophagy, while small interference RNA was utilized to knock down PTEN-induced putative protein kinase 1 (PINK1). Activation of mitophagy-related genes and colocalization of them were detected by Western blot and confocal imaging. Damages of mitochondria, accumulation of mitochondrial reactive oxygen species (mtROS), and production of IL-1β, IL-6, and TNF-α were measured.

RESULTS

Levels of mitophagy-related genes were decreased in inflamed periodontal tissues and P. gingivalis-infected BMDMs. Dexmedetomidine, urolithin A, and resveratrol activated mitophagy, leading to reduced mitochondria damages, decreased mtROS generation, and inhibited IL-1β, IL-6, and TNF-α production. PINK1 knockdown reduced dexmedetomidine, urolithin A, and resveratrol-induced anti-inflammatory effect.

CONCLUSION

Inhibited mitophagy participated in the progress of periodontitis. Activation of mitophagy may become a therapeutic target during the progress of periodontitis by reducing mtROS.

Involvement of ferroptosis in Porphyromonas gingivalis lipopolysaccharide-stimulated periodontitis in vitro and in vivo

OBJECTIVES

Ferroptosis is associated with multiple inflammatory diseases. Periodontitis is an inflammatory disease mainly caused by oral opportunistic pathogens. However, the ferroptosis-periodontitis relationship has not been thoroughly described. We here analyzed whether ferroptosis is involved in periodontitis.

MATERIALS AND METHODS

Human gingival fibroblasts (HGFs) were stimulated with P. gingivalis-LPS and ferrostatin-1 (Fer-1, a ferroptosis inhibitor), and changes in mitochondrial morphology, ferroptosis-related factors, and inflammation levels were detected. After the rat experimental periodontitis model was established, changes in ferroptosis-related factors and inflammation levels were re-evaluated in the same manner.

RESULTS

Porphyromonas gingivalis-LPS-induced mitochondrial shrinkage, an increase in mitochondrial membrane density, and upregulation of reactive oxygen species in HGFs. The expression of prostaglandin-endoperoxide synthase 2, transferrin receptor 1, and malondialdehyde and inflammation levels were upregulated, whereas the expression of solute carrier family seven member 11, glutathione peroxidase 4, superoxide dismutase, and glutathione were downregulated. Fer-1 attenuated these aforementioned changes and inflammation levels induced by P. gingivalis-LPS. The in vivo experiment results were consistent with the in vitro experiment results.

CONCLUSIONS

Ferroptosis is involved in inflammatory processes in HGFs upon P. gingivalis-LPS stimulation. Ferroptosis is observed in the gingival tissue of periodontitis rats.

Functionalized nanomaterials targeting NLRP3 inflammasome driven immunomodulation: Friend or Foe

The advancement in drug delivery systems in recent times has significantly enhanced therapeutic effects by enabling site-specific targeting through nanocarriers. These nanocarriers serve as invaluable tools for pharmacotherapeutic advancements against various disorders that enhance the effectiveness of encapsulated drugs by reducing their toxicity and increasing the efficacy of less potent drugs, thereby improving the therapeutic index. Inflammasomes, protein complexes located in the activated immune cell cytoplasm, regulate the activation of caspases involved in inflammation. However, aberrant activation of inflammasomes can result in uncontrolled tissue responses, contributing to the development of various diseases. Therefore, achieving a precise balance between inflammasome inhibition and activation is crucial for effectively treating inflammatory disorders through targeted functionalized nanocarriers. Despite the wealth of available data on the relevance of functionalized nanocarriers in inflammatory disorders, the nanotechnological potential to modulate inflammasomes has not been adequately explored. In this comprehensive review, we highlight the latest research on the modulation of the inflammasome cascade, both upregulating and downregulating its function, using nanocarriers in the context of inflammatory disorders. The utilization of nanocarriers as a therapeutic strategy holds immense potential for researchers aiming to effectively target and modulate inflammasomes in the treatment of inflammatory disorders, thus improving disease severity outcomes.

A Novel Injectable Piezoelectric Hydrogel for Periodontal Disease Treatment

Periodontal disease is a multifactorial, bacterially induced inflammatory condition characterized by the progressive destruction of periodontal tissues. The successful nonsurgical treatment of periodontitis requires multifunctional technologies offering antibacterial therapies and promotion of bone regeneration simultaneously. For the first time, in this study, an injectable piezoelectric hydrogel (PiezoGEL) was developed after combining gelatin methacryloyl (GelMA) with biocompatible piezoelectric fillers of barium titanate (BTO) that produce electrical charges when stimulated by biomechanical vibrations (e.g., mastication, movements). We harnessed the benefits of hydrogels (injectable, light curable, conforms to pocket spaces, biocompatible) with the bioactive effects of piezoelectric charges. A thorough biomaterial characterization confirmed piezoelectric fillers' successful integration with the hydrogel, photopolymerizability, injectability for clinical use, and electrical charge generation to enable bioactive effects (antibacterial and bone tissue regeneration). PiezoGEL showed significant reductions in pathogenic biofilm biomass (∼41%), metabolic activity (∼75%), and the number of viable cells (∼2-3 log) compared to hydrogels without BTO fillers in vitro. Molecular analysis related the antibacterial effects to be associated with reduced cell adhesion (downregulation of porP and fimA) and increased oxidative stress (upregulation of oxyR) genes. Moreover, PiezoGEL significantly enhanced bone marrow stem cell (BMSC) viability and osteogenic differentiation by upregulating RUNX2, COL1A1, and ALP. In vivo, PiezoGEL effectively reduced periodontal inflammation and increased bone tissue regeneration compared to control groups in a mice model. Findings from this study suggest PiezoGEL to be a promising and novel therapeutic candidate for the treatment of periodontal disease nonsurgically.

Oral intake of titanium dioxide nanoparticles affect the course and prognosis of ulcerative colitis in mice: involvement of the ROS-TXNIP-NLRP3 inflammasome pathway

BACKGROUND

Titanium dioxide (TiO2), no matter in nanoscale or micron sizes, has been widely used in food industry as additives for decades. Given the potential impact of TiO2 on the gastrointestinal epithelial and parenchymal cells, including goblet cells, the public consumers may suffer the risk of diseases caused by its widespread dissemination in food products. We therefore set out to investigate the impact of TiO2 NPs on the course and prognosis of ulcerative colitis by oral gavaging TiO2 NPs at the doses levels of 0, 30, 100, and 300 mg/kg during the induction (7 days, from day 1 to day 7) and recovery (10 days, from day 8 to day 17) phases of colitis in mice.

RESULTS

The ulcerative colitis (UC) disease model was established by administrating of 2.5% dextran sulfate sodium (DSS) solution. Our results show that TiO2 NPs significantly enhanced the severity of DSS-induced colitis, decreased the body weight, increased the disease activity index (DAI) and colonic mucosa damage index (CMDI) scores, shortened the colonic length, increased the inflammatory infiltration in the colon. The most significant changes occurred in the low dose (30 mg/kg) group of TiO2 NPs exposure during the development phase of UC and the high dose (300 mg/kg) group of TiO2 NPs during UC self-healing phase. Increased reactive oxygen species (ROS) level and upregulation of anti-oxidant enzymes including total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX) and catalase (CAT), demonstrate that the TiO2 NP exposure has triggered oxidative stress in mice. Moreover, the upregulation of caspase-1 mRNA and increased expression of thioredoxin interacting protein (TXNIP) further demonstrate the involvement of the ROS-TXNIP-NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway in aggravating the development of UC.

CONCLUSION

Oral intake of TiO2 NPs could affect the course of acute colitis in exacerbating the development of UC, prolonging the UC course and inhibiting UC recovery.

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

BACKGROUND AND OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Chrysophanol exerts a protective effect against Aβ25-35-induced Alzheimer's disease model through regulating the ROS/TXNIP/NLRP3 pathway

BACKGROUND

The primary pathogenic factors of Alzheimer's disease (AD) have been identified as oxidative stress, inflammatory damage, and apoptosis. Chrysophanol (CHR) has a good neuroprotective effect on AD, however, the potential mechanism of CHR remains unclear.

PURPOSE

In this study, we focused on the ROS/TXNIP/NLRP3 pathway to determine whether CHR regulates oxidative stress and neuroinflammation.

METHODS

D-galactose and Aβ_25-35 combination were used to build an in vivo model of AD, and the Y-maze test was used to evaluate the learning and memory function of rats. Morphological changes of neurons in the rat hippocampus were observed using hematoxylin and eosin (HE) staining. AD cell model was established by Aβ_25-35 in PC12 cells. The DCFH-DA test identified reactive oxygen species (ROS). The apoptosis rate was determined using Hoechst33258 and flow cytometry. In addition, the levels of MDA, LDH, T-SOD, CAT, and GSH in serum, cell, and cell culture supernatant were detected by colorimetric method. The protein and mRNA expressions of the targets were detected by Western blot and RT-PCR. Finally, molecular docking was used to further verify the in vivo and in vitro experimental results.

RESULTS

CHR could significantly improve learning and memory impairment, reduce hippocampal neuron damage, and reduce ROS production and apoptosis in AD rats. CHR could improve the survival rate, and reduce the oxidative stress and apoptosis in the AD cell model. Moreover, CHR significantly decreased the levels of MDA and LDH, and increased the activities of T-SOD, CAT, and GSH in the AD model. Mechanically, CHR significantly reduced the protein and mRNA expression of TXNIP, NLRP3, Caspase-1, IL-1β, and IL-18, and increase TRX.

CONCLUSIONS

CHR exerts neuroprotective effects on the Aβ_25-35-induced AD model mainly by reducing oxidative stress and neuroinflammation, and the mechanism may be related to ROS/TXNIP/NLRP3 signaling pathway.

Effects of NLRP3 on implants placement

Bone stability is precisely controlled by osteoclast-mediated bone resorption and osteoblast-mediated bone formation. When the balance is broken, the integrity of the bone structure will be destroyed. Inflammasomes are important protein complexes in response to pathogen-related molecular models or injury-related molecular models, which can promote the activation and secretion of proinflammatory cytokines and activate a local inflammatory response. NOD-like receptor thermal protein domain associated protein (NLRP) 3 inflammasome can promote bone resorption through the activation of the proinflammatory cytokines interleukin (IL)-1β, IL-18 and the induction of caspase-1-mediated pyroptosis. Inhibiting the production of NLRP3 inflammasome may be beneficial to improve comfort and bone stability. The presence of metal particles and microorganisms around implants can activate NLRP3 and promote bone absorption. NLRP3 inflammasome plays an important role in the maintenance of bone stability around implants, however, most studies focus on orthopedic implants and periodontitis. This article reviews the effects of NLRP3 inflammasome on bone formation, resorption and pain induced by implants, and the possibility of NLRP3 as a target for preventing peri-implantitis is discussed.

Comparison of the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress

This study was conducted to compare the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress. Increased Il-1 and Il-6 expressions, markers of inflammation, were represented by inflammation models in mouse liver and kidney tissues injected intraperitoneally with LPS. After establishing the model, the GSH level and the GSH/GSSG ratio, which are oxidative stress markers, were investigated in both tissues treated with LPS and the control group. The expression of Trx1, TrxR, and Txnip genes increased in the liver tissues of LPS-treated mice. In the kidney tissue, while Trx1 expression decreased, no change was observed in TrxR1 expression, and Txnip expression increased. In the kidneys, TRXR1 and GR activities decreased, whereas GPx activity increased. In both tissues, the TRXR1 protein expression decreased significantly, while TXNIP expression increased. In conclusion, different behaviors of antioxidant system members were observed during acute inflammation in both tissues. Additionally, it can be said that the kidney tissue is more sensitive and takes earlier measures than the liver tissue against cellular damage caused by inflammation and inflammation-induced oxidative stress.

Suppression of the NLRP3 Inflammasome through Activation of the Transient Receptor Potential Channel Melastatin 2 Promotes Osteogenesis in Tooth Extraction Sockets of Periodontitis

This study explored the role of transient receptor potential channel melastatin 2 (TRPM2)-mediated activation of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in osteogenesis during healing of tooth extraction sockets. Tooth extraction socket tissue samples were collected from patients with or without periodontitis. In a TRPM2 knockout mouse model of socket healing, mice with or without periodontitis and their wild-type littermates were used for comparing the socket healing phenotypes. Micro-computed tomography imaging, three-dimensional reconstruction of the sockets, and hematoxylin and eosin staining for histopathologic analysis were performed. Immunofluorescence, immunohistochemistry, and Western blot analysis were used for evaluation of protein expression; the mRNA levels were evaluated by quantitative RT-PCR. Osteogenic, chondrogenic, and adipogenic differentiation potential of human bone marrow mesenchymal stem cells (BMMSCs) was evaluated. Calcium deposition was evaluated using Alizarin Red S staining. NLRP3 and CASP1 were up-regulated in tooth sockets of periodontitis patients. NLRP3 knockdown promoted the osteogenic differentiation of maxillary BMMSCs under inflammatory conditions. TRPM2 was up-regulated in the tooth extraction socket tissue of periodontitis. Inhibiting TRPM2 expression mitigated the NLRP3 inflammasome and its deleterious effect on osteogenesis. Activation of the TRPM2 ion channel regulated osteogenesis of BMMSCs under inflammatory conditions via Ca²⁺ influx, the mitochondrial dynamics, and pyroptosis. Targeting the TRPM2/Ca²⁺/NLRP3 axis could be beneficial in the healing process of the tooth extraction sockets of patients with periodontitis.

Corilagin Restrains NLRP3 Inflammasome Activation and Pyroptosis through the ROS/TXNIP/NLRP3 Pathway to Prevent Inflammation

Corilagin, a gallotannin, shows excellent antioxidant and anti-inflammatory effects. The NLRP3 inflammasome dysfunction has been implicated in a variety of inflammation diseases. However, it remains unclear how corilagin regulates the NLRP3 inflammasome to relieve gouty arthritis. In this study, bone marrow-derived macrophages (BMDMs) were pretreated with lipopolysaccharide (LPS) and then incubated with NLRP3 inflammasome agonists, such as adenine nucleoside triphosphate (ATP), nigericin, and monosodium urate (MSU) crystals. The MSU crystals were intra-articular injected to induce acute gouty arthritis. Here we showed that corilagin reduced lactate dehydrogenase (LDH) secretion and the proportion of propidium iodide- (PI-)stained cells. Corilagin suppressed the expression of N-terminal of the pyroptosis executive protein gasdermin D (GSDMD-NT). Corilagin restricted caspase-1 p20 and interleukin (IL)-1β release. Meanwhile, corilagin attenuated ASC oligomerization and speck formation. Our findings confirmed that corilagin diminished NLRP3 inflammasome activation and macrophage pyroptosis. We further discovered that corilagin limited the mitochondrial reactive oxygen species (ROS) production and prevented the interaction between TXNIP and NLRP3, but ROS activator imiquimod could antagonize the inhibitory function of corilagin on NLRP3 inflammasome and macrophage pyroptosis. Additionally, corilagin ameliorated MSU crystals induced joint swelling, inhibited IL-1β production, and abated macrophage and neutrophil migration into the joint capsule. Collectively, these results demonstrated that corilagin suppressed the ROS/TXNIP/NLRP3 pathway to repress inflammasome activation and pyroptosis and suggest its potential antioxidative role in alleviating NLRP3-dependent gouty arthritis.

Geniposide suppresses NLRP3 inflammasome-mediated pyroptosis via the AMPK signaling pathway to mitigate myocardial ischemia/reperfusion injury

BACKGROUND

NLRP3 inflammasome activation and pyroptosis play a significant role in myocardial ischemia reperfusion injury (MI/RI). Geniposide was reported to show potential therapeutic use for MI/RI with its anti-inflammatory and anti-oxidative properties. However, research on the specific mechanism of geniposide has not been reported.

METHODS

The MIRI model of animal was created in male C57BL/6J mice and the hypoxia reoxygenation (H/R) model was established for the in vitro experiments. Neonatal rat ventricular myocytes (NRVMs) and H9c2 cells with knockdown of TXNIP or NLRP3 were used. Geniposide was administered to mice before vascular ligation. HE staining, 2,3,5-triphenyltetrazolium chloride (TTC) staining, echocardiography, oxidative stress and myocardial enzyme detection were used to evaluate the cardioprotective effect of geniposide. Meanwhile, pharmacological approaches of agonist and inhibitor were used to observe potential pathway for geniposide cardioprotective in vitro and in vivo. Moreover, ELISA kits were adopted to detect the levels of inflammatory factors, such as IL-1β and IL-18. The gene and protein expression of NLRP3 and pyroptosis-related factors in heart tissue were performed by RT-PCR, western blotting and immunofluorescence in vivo and in vitro, respectively.

RESULTS

Our results indicate that geniposide can reduce the area of myocardial infarction, improve heart function, and inhibit the inflammatory response in mice after MI/RI. In addition, RT-PCR and western blotting shown geniposide promoting AMPK phosphorylation to activate myocardium energy metabolism and reducing the levels of genes and proteins expression of NLRP3, ASC, N-GSDMD and cleaved caspase-1, IL-1β, IL-18. Meanwhile, geniposide improved NRVMs energy metabolism, which decreased ROS levels and the protein expression of TXNIP and thus suppressed the expression of NLRP3. AMPK antagonist or agonist and siRNA downregulation of TXNIP or NLRP3 were also verify the effect of geniposide against H/R injury. Further research found that geniposide promoted the translocation of TXNIP and reduce the binding of TXNIP and NLRP3.

CONCLUSIONS

In our study, geniposide can significantly inhibit NLRP3 inflammasome activation via the AMPK signaling pathway and inhibit pyroptosis of cardiomyocytes in myocardial tissues.

Kakonein restores hyperglycemia‐induced macrophage digestion dysfunction through regulation of cathepsin B‐dependent NLRP3 inflammasome activation

In hyperglycemia‐induced complications, macrophages play important roles in disease progression, and altered digestion is a key feature that dictates macrophage function. Recent evidence indicates that kakonein (Ka) possesses anti‐inflammatory activities for hyperglycemia‐induced complication. In this study, we established a mouse model of Nlrp3^+/+ and Nlrp3^−/− hyperglycemia and administering Ka, primary culture macrophages were tested by engulfing and digesting microbes. The role of macrophages in the cathepsin B–NLRP3 pathway involved in the mechanism of Ka in restoring macrophage digestion function was investigated using biochemical analyses, molecular biotechnology, and microbiology. Ka restored the function of macrophage digestion, which were same characterized by Nlrp3^−/− mice. Meanwhile, kakonein could decrease NLRP3 inflammasome products expression and NLRP3/ASC or NLRP3/Casp1 colocalization in macrophage. Interestingly, Ka suppressed inflammasome response not by reducing NLRP3 and ASC expression but by reducing cathepsin B release and activation. And Ka restored macrophage digestion and inhibited NLRP3 inflammasome activation consistent with cathepsin B inhibitor. It is concluded that Ka reduced the release of lysosomal cathepsin B and consequently inhibited NLRP3 inflammasome activation to prevent macrophage digestion. Hence, Ka may contribute to new targets for treatment of hyperglycemia‐associated dysfunction of macrophage digestion and development of innovative drugs.

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.

Effects of Hypoxic Environment on Periodontal Tissue through the ROS/TXNIP/NLRP3 Inflammasome Pathway

There is low evidence for the possible association between obstructive sleep apnea-hypopnea syndrome (OSAHS) and periodontitis, necessitating further research. This study was aimed at investigating this association. For the in vitro study, 8-day-old Wistar rats were divided into the unilateral nasal obstruction group (UNO) and the sham surgery group (SHAM). Rats in the former group were subjected to UNO by cauterization of the external nostril at the age of 8 days. Immunofluorescence analysis, quantitative real-time polymerase chain reaction, and western blot were performed to assess the expression of thioredoxin-interacting protein (TXNIP), NLR family pyrin domain-containing 3 (NLRP3) inflammasome-associated factors, and interleukin-1β (IL-1β). Throughout the experimental period, the weights of rats in the two groups were similar. The mRNA and protein expression of TXNIP and IL-1β was significantly higher in the UNO than in the SHAM groups. Compared with SHAM, NLRP3 inflammasome-associated factors were activated in the UNO group. For the in vitro study, a cellular hypoxia model was established by treating human periodontal ligament cells (HPDLCs) with cobalt chloride. The studies showed that hypoxia can induce an excessive production and accumulation of reactive oxygen species (ROS) in HPDLCs and induce abnormal expression of TNXIP, NLRP3 inflammasome-related factors, and IL-1β. More importantly, N-acetylcysteine induced reduction of ROS in HPDLCs, downregulated TXNIP expression, inhibited the expression and aggregation of NLRP3 inflammasome-related factors, and abrogated the inflammatory response to hypoxia. In conclusion, hypoxia-induced ROS can activate the TXNIP/NLRP3 inflammasome signaling pathway in response to oxidative stress, resulting in the increased expression of inflammatory factors in HPDLCs. Our findings provide evidence for the mechanism underlying the possible association between OSAHS and periodontal disease.

Microtubule affinity regulating kinase 4 promoted activation of the NLRP3 inflammasome-mediated pyroptosis in periodontitis

Background

Microtubule dynamics plays a crucial role in the spatial arrangement of cell organelles and activation of the NLRP3 inflammasome.

Purpose

This study aimed to explore whether microtubule affinity regulating kinase 4 (MARK4) can be a therapeutic target of periodontitis by affecting microtubule dynamics and NLRP3 inflammasome-mediated pyroptosis in macrophages.

Materials and Methods

The NLRP3 inflammasome-related genes and MARK4 were measured in the healthy and inflamed human gingival tissues. Bone marrow-derived macrophages (BMDMs) were infected with Porphyromonas gingivalis, while the MARK4 inhibitors (OTSSP167 and Compound 50) and small interference RNA were utilized to restrain MARK4. Apoptosis-associated speck-like protein (ASC) speck was detected by confocal, and levels of interleukin-1β (IL-1β), as well as IL-18, were assessed by ELISA.

Results

Increased staining and transcription of MARK4, NLRP3, ASC, and Caspase-1 were observed in the inflamed gingiva. P. gingivalis infection promoted MARK4 expression and the NLRP3 inflammasome in BMDMs. Inhibition of MARK4 decreased LDH release, IL-1β and IL-18 production, ASC speck formation, and the pyroptosis-related genes transcription. Furthermore, MARK4 inhibition reduced microtubule polymerization and acetylation in P. gingivalis-infected BMDMs.

Conclusions

MARK4 promoted NLRP3 inflammasome activation and pyroptosis in P. gingivalis-infected BMDMs by affecting microtubule dynamics. MARK4 inhibition might be a potential target in regulating the NLRP3 inflammasome during periodontitis progress.

NLRP3 Inflammasome Pharmacological Inhibitors in Glycyrrhiza for NLRP3-Driven Diseases Treatment: Extinguishing the Fire of Inflammation

Inflammation is the tissues’ defense response after the body is stimulated by microbial infection or damage signals, and it is initiated when pattern recognition receptors recognize pathogen-related molecular patterns and danger-related molecular patterns. The hyperactivation of NLRP3 inflammasome, the main driving force of immune outbreaks, is involved in a wide range of inflammatory diseases. Meanwhile, growing evidence has indicated that the development of NLRP3-targeted therapies offers great potential and promise for the treatment of related diseases. The search for and development of efficacious anti-inflammatory prodrugs from natural sources of plants and traditional Chinese medicines (TCMs) have received extensive attention. Glycyrrhiza, an important minister in the kingdom of TCMs, has high activity and a wide range of therapeutic effects. Studies have shown that a variety of active components found in Glycyrrhiza, such as licochalcone A, echinatin, isoliquiritigenin, and glycyrrhizin, produce a wide range of anti-inflammatory effects by discouraging NLRP3 inflammasome activation. Here, we summarize the role and mechanism of the active ingredients in Glycyrrhiza that target the NLRP3 inflammasome and treat related inflammatory diseases. We describe a favorable approach for the development of natural, safe, and efficient drugs that exploit these naturally occurring active ingredients to treat NLRP3-driven diseases.

Abnormal mitochondrial structure and function are retained in gingival tissues and human gingival fibroblasts from patients with chronic periodontitis

BACKGROUND AND OBJECTIVE

The abnormal structure and function of mitochondria in cells is closely associated with inflammatory diseases. However, the physiology of mitochondria within gingival tissues and human gingival fibroblasts (HGFs) in patients with chronic periodontitis (CP) remains unclear. The objective of this study was to investigate the structure profile and function of mitochondria in gingival tissues and in HGFs derived from patients with or without CP. These features of mitochondria in HGFs were further analyzed when HGFs were induced by lipopolysaccharide (LPS) from Porphyromonas gingivalis (P.g).

METHODS

Gingival tissues and HGFs were collected from CP and healthy patients. Mitochondrial structure was assessed by transmission electron microscopy. Tissues or cells lysis was performed for mitochondrial DNA (mtDNA) quantification, and real-time polymerase chain reaction (RT-PCR) tests were used to determine mtDNA copy numbers. Western blot analysis was used to evaluate autophagy-related protein (ATG)-5, microtubule-associated protein light chain 3 (LC3), and mitochondrial matrix protein pyruvate dehydrogenase kinase isozyme 2 (PDK2) levels in tissues and HGFs from CP and healthy individuals.

RESULTS

Tissues and HGFs from CP showed a significant greater mitochondrial structure destruction, lower mtDNA level, increased ATG5, LC3-II, and lower PDK2 protein levels than those of healthy individuals. In addition, LPS from P.g also triggered the same results in HGFs from healthy donors. Moreover, the challenge of HGFs from CP with LPS worsened these parameters.

CONCLUSION

Mitochondrial structure and function within gingival tissues and HGFs from CP individuals were abnormal compared to those from healthy donors, and LPS could promote mitochondrial destruction.

Porphyromonas gingivalis Induces Proinflammatory Cytokine Expression Leading to Apoptotic Death through the Oxidative Stress/NF-κB Pathway in Brain Endothelial Cells

Porphyromonas gingivalis, a periodontal pathogen, has been proposed to cause blood vessel injury leading to cerebrovascular diseases such as stroke. Brain endothelial cells compose the blood-brain barrier that protects homeostasis of the central nervous system. However, whether P. gingivalis causes the death of endothelial cells and the underlying mechanisms remain unclear. This study aimed to investigate the impact and regulatory mechanisms of P. gingivalis infection in brain endothelial cells. We used bEnd.3 cells and primary mouse endothelial cells to assess the effects of P. gingivalis on endothelial cells. Our results showed that infection with live P. gingivalis, unlike heat-killed P. gingivalis, triggers brain endothelial cell death by inducing cell apoptosis. Moreover, P. gingivalis infection increased intracellular reactive oxygen species (ROS) production, activated NF-κB, and up-regulated the expression of IL-1β and TNF-α. Furthermore, N-acetyl-L-cysteine (NAC), a most frequently used antioxidant, treatment significantly reduced P. gingivalis-induced cell apoptosis and brain endothelial cell death. The enhancement of ROS production, NF-κB p65 activation, and proinflammatory cytokine expression was also attenuated by NAC treatment. The impact of P. gingivalis on brain endothelial cells was also confirmed using adult primary mouse brain endothelial cells (MBECs). In summary, our results showed that P. gingivalis up-regulates IL-1β and TNF-α protein expression, which consequently causes cell death of brain endothelial cells through the ROS/NF-κB pathway. Our results, together with the results of previous case-control studies and epidemiologic reports, strongly support the hypothesis that periodontal infection increases the risk of developing cerebrovascular disease.

Camostat mesilate inhibits pro-inflammatory cytokine secretion and improves cell viability by regulating MFGE8 and HMGN1 in lipopolysaccharide-stimulated DF-1 chicken embryo fibroblasts

Camostat mesilate (CM) possesses potential anti-viral and anti-inflammatory activities. However, it remains unknown whether CM is involved in lipopolysaccharide (LPS)-mediated inflammatory responses and cell injury. In this project, differentially expressed proteins (DEPs, fold change ≥ 1.2 or ≤ 0.83 and Q value ≤ 0.05) in response to LPS stimulation alone or in combination with CM were identified through tandem mass tags (TMT)/mass spectrometry (MS)-based proteomics analysis in DF-1 chicken embryo fibroblasts. The mRNA expression levels of filtered genes were determined by RT-qPCR assay. The results showed that CM alleviated the detrimental effect of LPS on cell viability and inhibited LPS-induced TNF-α and IL-6 secretions in DF-1 chicken embryo fibroblasts. A total of 141 DEPs that might be involved in mediating functions of both LPS and CM were identified by proteomics analysis in DF-1 chicken embryo fibroblasts. LPS inhibited milk fat globule EGF and factor V/VIII domain containing (MFGE8) expression and induced high mobility group nucleosome binding domain 1 (HMGN1) expression, while these effects were abrogated by CM in DF-1 chicken embryo fibroblasts. MFGE8 knockdown facilitated TNF-α and IL-6 secretions , reduced cell viability, stimulated cell apoptosis in DF-1 chicken embryo fibroblasts co-treated with LPS and CM. HMGN1 loss did not influence TNF-α and IL-6 secretions, cell viability, and cell apoptosis in DF-1 chicken embryo fibroblasts co-treated with LPS and CM. In conclusion, CM exerted anti-inflammatory and pro-survival activities by regulating MFGE8 in LPS-stimulated DF-1 chicken embryo fibroblasts, deepening our understanding of the roles and molecular basis of CM in protecting against Gram-negative bacteria.

The lncRNA XIST/miR-150-5p/c-Fos axis regulates sepsis-induced myocardial injury via TXNIP-modulated pyroptosis

Myocardial injury is a severe complication of sepsis and contributes substantially to the death of critically ill patients. Long non-coding RNAs (lncRNAs) participate in the pathogenesis of sepsis-induced myocardial injury. In this study, we investigated the role of lncRNA X-inactive specific transcript (XIST) in septic myocardial injury and explored its mechanism. Lipopolysaccharide (LPS)-stimulated H9C2 cells and rats subjected to cecal ligation and puncture (CLP) were used as the in vitro and in vivo models. After exposure to LPS, XIST and c-Fos levels were upregulated, but miR-150-5p was downregulated in H9C2 cardiomyocytes and myocardial tissues. XIST affected viability, apoptosis, and pyroptosis in LPS-challenged H9C2 cells. Moreover, XIST knockdown attenuated LPS-induced injury in H9C2 cells by targeting the miR-150-5p/c-Fos axis. c-Fos could bound to the promoter of the TXNIP/XIST gene and enhanced TXNIP/XIST expression. Silencing of XIST improved cardiac function and survival rate and reduced apoptosis and pyroptosis by regulating the miR-150-5p/c-Fos axis in septic rats in vivo. Taken together, our data show that XIST/miR-150-5p/c-Fos axis affected septic myocardial injury, which may indicate a novel therapeutic strategy for sepsis-induced myocardial injury.

Galectin-7 promotes proliferation and wound healing capacities in periodontal ligament fibroblasts by activating ERK signaling

Periodontitis is a progressive inflammation condition and a primary cause of tooth loss in adults. As one of the abundant cell types in the periodontium, periodontal ligament fibroblasts (PDLFs) play an integral role in the maintenance and regeneration of periodontal tissue. Our previous work has shown that the application of Er:YAG laser increased the cell proliferation and migratory capacity of PDLFs via induction of galectin-7. In the present study, we aimed to evaluate if the forced expression of galectin-7 directly affected the cellular phenotypes of PDLFs. Our results showed that the cell proliferation, transwell migration, invasion, and wound healing capacities were all upregulated in PDLFs with the ectopic expression of galectin-7. These results suggest that therapeutic approaches to enhance the expression of galectin-7 in periodontium may accelerate tissue regeneration by recruiting more PDLFs to the injured site.

The Marine-Derived Natural Product Epiloliolide Isolated from Sargassum horneri Regulates NLRP3 via PKA/CREB, Promoting Proliferation and Anti-Inflammatory Effects of Human Periodontal Ligament Cells

Currently, periodontitis treatment relies on surgical operations, anti-inflammatory agents, or antibiotics. However, these treatments cause pain and side effects, resulting in a poor prognosis. Therefore, in this study, we evaluated the impact of the compound epiloliolide isolated from Sargassum horneri on the recovery of inflammatory inhibitors and loss of periodontal ligaments, which are essential treatment strategies for periodontitis. Here, human periodontal ligament cells stimulated with PG-LPS were treated with the compound epiloliolide, isolated from S. horneri. In the results of this study, epiloliolide proved the anti-inflammatory effect, cell proliferation capacity, and differentiation potential of periodontal ligament cells into osteoblasts, through the regulation of the PKA/CREB signaling pathway. Epiloliolide effectively increased the proliferation and migration of human periodontal ligament cells without cytotoxicity and suppressed the protein expression of proinflammatory mediators and cytokines, such as iNOS, COX-2, TNF-α, IL-6, and IL-1β, by downregulating NLRP3 activated by PG-LPS. Epiloliolide also upregulated the phosphorylation of PKA/CREB proteins, which play an important role in cell growth and proliferation. It was confirmed that the anti-inflammatory effect in PG-LPS-stimulated large cells was due to the regulation of PKA/CREB signaling. We suggest that epiloliolide could serve as a potential novel therapeutic agent for periodontitis by inhibiting inflammation and restoring the loss of periodontal tissue.

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.

Porphyromonas gingivalis Promotes Colorectal Carcinoma by Activating the Hematopoietic NLRP3 Inflammasome

Porphyromonas gingivalis (P. gingivalis) is a keystone periodontal pathogen associated with various digestive cancers. However, whether P. gingivalis can promote colorectal cancer and the underlying mechanism associated with such promotion remains unclear. In this study, we found that P. gingivalis was enriched in human feces and tissue samples from patients with colorectal cancer compared with those from patients with colorectal adenoma or healthy subjects. Cohort studies demonstrated that P. gingivalis infection was associated with poor prognosis in colorectal cancer. P. gingivalis increased tumor counts and tumor volume in the Apc^Min/+ mouse model and increased tumor growth in orthotopic rectal and subcutaneous carcinoma models. Furthermore, orthotopic tumors from mice exposed to P. gingivalis exhibited tumor-infiltrating myeloid cell recruitment and a proinflammatory signature. P. gingivalis promoted colorectal cancer via NLRP3 inflammasome activation in vitro and in vivo. NLRP3 chimeric mice harboring orthotopic tumors showed that the effect of NLRP3 on P. gingivalis pathogenesis was mediated by hematopoietic sources. Collectively, these data suggest that P. gingivalis contributes to colorectal cancer neoplasia progression by activating the hematopoietic NLRP3 inflammasome. SIGNIFICANCE: This study demonstrates that the periodontal pathogen P. gingivalis can promote colorectal tumorigenesis by recruiting myeloid cells and creating a proinflammatory tumor microenvironment. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/10/2745/F1.large.jpg.

Hypoxia and Porphyromonas gingivalis-lipopolysaccharide synergistically induce NLRP3 inflammasome activation in human gingival fibroblasts

OBJECTIVE

To investigate the effects of hypoxia and Porphyromonas gingivalis- lipopolysaccharide (P. gingivalis-LPS) on activation of the NACHT leucine-rich repeat protein 3 (NLRP3) inflammasome in human gingival fibroblasts (HGFs).

DESIGN

Periodontitis was optimally simulated using a hypoxic concentration of 1%. HGFs were stimulated using P. gingivalis-LPS (1.0 μg/ml) in normoxia and hypoxia for 3 h and 6 h, respectively. The expression levels of genes and proteins of hypoxia-inducible factor-1α (HIF-1α), interleukin-1β, gasdermin D (GSDMD) and the NLRP3 inflammasome, including NLRP3, apoptosis-associated speck-like protein containing CARD (ASC), caspase-1 and its activated forms, were measured using quantitative real-time polymerase chain reaction and western blot. ELISA was used to detect and determine levels of the inflammatory factor interleukin-1β in cell supernatants. Lactate dehydrogenase (LDH) release assay, caspase-1 activity assay and Hoechst 33342/Propidium Iodide (PI) staining were performed to further verify the presence of pyroptosis.

RESULTS

The NLRP3 inflammasome (i.e., NLRP3, ASC, caspase-1) was not affected by individual stimulation using P. gingivalis-LPS or hypoxia. However, the combination of both hypoxia and P. gingivalis-LPS stimulation significantly enhanced inflammasome activation and promoted the expression of interleukin-1β, gasdermin D and HIF-1α at gene and protein levels; PI positive cells and the release of LDH were also elevated.

CONCLUSION

Hypoxia and P. gingivalis-LPS synergistically induced NLRP3 inflammasome activation in HGFs, and subsequently high levels of interleukin-1β and GSDMD-mediated pyroptosis can cause an HGF inflammatory response, which plays an important role in the pathogenesis of periodontitis.

Trem2 mediated Syk-dependent ROS amplification is essential for osteoclastogenesis in periodontitis microenvironment

Periodontitis is the sixth most prevalent diseases around the globe, which is closely related to many systemic diseases and affects general health. As the leading cause of tooth loss, periodontitis is characterized by irreversible alveolar bone loss and activated osteoclastogenic process, which might be closely related to the activated intracellular reactive oxygen species (ROS) in osteoclasts. Here, we demonstrated triggering receptor expressed on myeloid cells 2 (Trem2) as a key regulator of osteoclastogenesis with the regulation of intracellular ROS signals in periodontitis. In the present study, the expression of Trem2 was significantly upregulated in human alveolar bones diagnosed with chronic periodontitis, as assessed by RNA-seq. In the mice model of periodontitis, the alveolar bone resorption was impeded in the presence of the conditional knockout of Trem2 in osteoclasts. Furthermore, we identified Trem2/DAP12/Syk-dependent cascade as a vital intracellular signaling for the amplification of reactive oxygen species (ROS) signals in osteoclastogenesis, while the accumulation of soluble Aβ₄₂ oligomers (Aβo) in periodontitis microenvironment further strengthened the signals and enhanced osteoclastogenesis through direct interactions with Trem2. Collectively, Trem2 mediated ROS signal amplification cascade was crucial in the process of osteoclastogenesis in periodontitis, suggesting the potential of Trem2 as a target for the prevention and treatment of bone destruction in periodontitis.

Nutraceutical Strategies for Suppressing NLRP3 Inflammasome Activation: Pertinence to the Management of COVID-19 and Beyond

Inflammasomes are intracellular protein complexes that form in response to a variety of stress signals and that serve to catalyze the proteolytic conversion of pro-interleukin-1β and pro-interleukin-18 to active interleukin-1β and interleukin-18, central mediators of the inflammatory response; inflammasomes can also promote a type of cell death known as pyroptosis. The NLRP3 inflammasome has received the most study and plays an important pathogenic role in a vast range of pathologies associated with inflammation-including atherosclerosis, myocardial infarction, the complications of diabetes, neurological and autoimmune disorders, dry macular degeneration, gout, and the cytokine storm phase of COVID-19. A consideration of the molecular biology underlying inflammasome priming and activation enables the prediction that a range of nutraceuticals may have clinical potential for suppressing inflammasome activity-antioxidants including phycocyanobilin, phase 2 inducers, melatonin, and N-acetylcysteine, the AMPK activator berberine, glucosamine, zinc, and various nutraceuticals that support generation of hydrogen sulfide. Complex nutraceuticals or functional foods featuring a number of these agents may find utility in the prevention and control of a wide range of medical disorders.

ROS-Scavenging Nanomaterials to Treat Periodontitis

The incidence of periodontitis is very high, and up to 45-50% of people are suffering from periodontitis. Periodontitis is caused by pathogens that invade teeth-supporting tissues such as gingiva, periodontal ligament, and alveolar bone. Pathogens trigger host immune responses characterized by the overproduction of reactive oxygen species (ROS). The development of effective ROS scavengers through nanotechnology has been emerging as a promising strategy for the treatment of periodontitis. Nanomaterial-based antioxidants can effectively scavenge ROS, prevent ROS-mediated tissue damage, and relieve inflammation in periodontitis. This mini-review focuses on the generation of ROS in periodontitis and its molecular mechanism of destroying periodontal tissue. Meanwhile, we summarize the research progress of ROS-scavenging nanomaterials in the treatment of periodontitis and discuss the challenges and prospects of its application.

Bixin Attenuates Experimental Autoimmune Encephalomyelitis by Suppressing TXNIP/NLRP3 Inflammasome Activity and Activating NRF2 Signaling

Multiple sclerosis (MS), an autoimmune and degenerative disease, is characterized by demyelination and chronic neuroinflammation. Bixin is a carotenoid isolated from the seeds of Bixa orellana that exhibits various potent pharmacological activities, including antioxidant, anti-inflammatory, and anti-tumor properties. However, the effects of bixin on MS have not yet been examined. To evaluate the effects and underlying molecular mechanisms of bixin on MS, experimental autoimmune encephalomyelitis (EAE) was established in C57BL/6 mice, which were treated via intragastric administration of bixin solutions. To evaluate the molecular mechanisms of bixin, quantitative reverse-transcription PCR, western blot, immunohistochemistry, flow cytometry, and enzyme-linked immunosorbent assay analyses were performed. We found that bixin significantly improved the symptoms and pathology in EAE mice, reduced the release of inflammatory cytokines TNF-α, IL-6, IL-8, IL-17, and IFN-γ, and increased the expression of the anti-inflammatory cytokine IL-10. And bixin reduced the proportion of Th1 and Th17 cells in the spleen and CNS, and suppressed microglia aggregation, and TXNIP/NLRP3 inflammasome activity by scavenging excessive reactive oxygen species (ROS) in EAE mice. Furthermore, bixin inhibited inflammation and oxidative stress via activating nuclear factor erythroid 2-related factor 2 (NRF2), and its downstream genes in EAE mice, meanwhile, these effects were suppressed upon treatment with an NRF2 inhibitor, ML385. Bixin prevented neuroinflammation and demyelination in EAE mice primarily by scavenging ROS through activation of the NRF2 signaling pathway. Taken together, our results indicate that bixin is a promising therapeutic candidate for treatment of MS.

The Promising Role of Antioxidant Phytochemicals in the Prevention and Treatment of Periodontal Disease via the Inhibition of Oxidative Stress Pathways: Updated Insights

There is growing evidence on the involvement of oxidative stress, which is simply described as the imbalance between oxidants and antioxidants in favor of the former, in the development of periodontal disease that is the most common inflammatory disease in the oral cavity. Thus, the potential of antioxidant phytochemicals as adjunctively preventive and therapeutic agents against the initiation and progression of periodontal disease is a topic of great interest. The current review firstly aims to provide updated insights about the immuno-inflammatory pathway regulated by oxidative stress in periodontal pathology. Then, this work further presents the systemic knowledge of antioxidant phytochemicals, particularly the pharmacological activities, which can be utilized in the prevention and treatment of periodontal disease. Additionally, the challenges and future prospects regarding such a scope are figured out.

Suppressing ROS generation by apocynin inhibited cyclic stretch-induced inflammatory reaction in HPDLCs via a caspase-1 dependent pathway

It has been reported that cyclic stretch could induce inflammatory reaction in human periodontal ligament cells (HPDLCs). Though reactive oxygen species (ROS) has been reported to be involved in pathogen-induced periodontal inflammatory reaction, its role in the force-related periodontal diseases has not been well clarified. This study inspected the role of ROS in the cyclic stretch-induced inflammatory reaction in HPDLCs and studied the inhibitory effect of antioxidant apocynin on this inflammatory reaction. Results confirmed that cyclic stretch induced inflammatory reaction and production of ROS in HPDLCs. This inflammatory reaction was inhibited by apocynin through blocking the production of ROS. The cyclic stretch also induced the expression of caspase-1 and NLRP3 inflammasome, which could also be inhibited by apocynin. Moreover, the cyclic stretch-induced inflammatory reaction was inhibited by caspase-1 inhibitor. Collectively, it is the first time that increased intracellular ROS was proved to play as an intermediate signal in the cyclic stretch-induced inflammatory reaction in HPDLCs, via a caspase-1-dependent pathway. The inhibitory effect of apocynin on the cyclic stretch-induced inflammatory reaction in HPDLCs shows the potential of antioxidants in the treatment of force-related periodontal inflammatory diseases.

Eldecalcitol Inhibits LPS-Induced NLRP3 Inflammasome-Dependent Pyroptosis in Human Gingival Fibroblasts by Activating the Nrf2/HO-1 Signaling Pathway

Purpose

Periodontitis is a major chronic oral disease that is accelerated by activation of the NLRP3 inflammasome and the resulting pyroptosis. According to recent studies, active vitamin D and its analogs have been reported to have great anti-inflammatory effects. However, the anti-inflammatory mechanism of a newly found vitamin D analog, eldecalcitol (ED-71), is still unclear. This study investigates whether ED-71 could protect human gingival fibroblasts (HGFs) from LPS-induced pyroptosis and, if so, determine its underlying mechanism.

Methods

After HGFs were treated with LPS alone or with LPS and ED-71, their viability was measured by CCK8 assay. The degrees of inflammation and pyroptosis were measured via LDH assay, H₂O₂ assay, fluorescent staining, flow cytometry, and Western blots. Intracellular ROS, Hoechst 33,342, and PI stains were assessed with a fluorescence microscope. ROS inhibitor NAC, NLRP3 inhibitor MCC950, and Nrf2 inhibitor ML385 were added to further clarify the mechanism.

Results

LPS induced cytotoxicity in HGFs, as shown by CCK8 assay. LPS also increased intracellular ROS, H₂O₂ levels, release of LDH, and expression of the pyroptosis-related proteins NLRP3, caspase-1, and IL-1β. NAC and MCC950 reduced LPS-induced NLRP3, caspase-1, and IL-1β. Pretreatment with ED-71 effectively inhibited the LPS-induced pyroptosis and was associated with activation of the Nrf2/HO-1 signaling pathway. This beneficial effect of ED-71 was suppressed by ML385.

Conclusion

This study demonstrates the therapeutic effect of ED-71 on LPS-induced NLRP3 inflammasome-dependent pyroptosis in HGFs and further reveals that ED-71 can inhibit pyroptosis by activating the Nrf2/HO-1 pathway. Our results thus suggest that ED-71 is a potential candidate for the treatment of periodontitis.

Z-Guggulsterone alleviated oxidative stress and inflammation through inhibiting the TXNIP/NLRP3 axis in ischemic stroke

Ischemic stroke is a serious and life-threatening cerebrovascular thrombotic disease; however, the therapeutic strategy is limited for the complicated mechanism and narrow therapeutic window. Our previous study suggested that Z-Guggulsterone (Z-GS), an active component derived from myrrh, is a good candidate for cerebral injury. The object of this study is to investigate the exact mechanisms of Z-GS in cerebral ischemic stroke. Rats were used to conduct middle cerebral artery occlusion (MCAO) model and were treated with different dosage of Z-GS. Morphological results showed that Z-GS significantly alleviated neurological deficits, infarct volume and histopathological damage in MCAO rats. A total of 8276 differentially expressed genes were identified based on microarray analysis. Oxidation-reduction process and inflammatory response were enriched as the significant gene ontology items. TXNIP and NLRP3 were screened as the potential target genes by Series Test of Cluster (STC) analysis. The results were validated by immunohistochemistry and immunofluorescence staining. Besides, Z-GS successfully inhibited oxidative stress and inflammatory response in oxygen-glucose deprivation (OGD) treated neurons. Knockdown of TXNIP significantly decreased the expression of NLRP3 in OGD-induced neurons. In addition, Z-GS treatment scarcely changed the expressions of NLRP3 in siRNA-TXNIP pretreated cells compared with the siRNA-TXNIP alone treatment group, suggesting that the neuroprotective effect of Z-GS was dependent on TXNIP-NLRP3 axis. Taken together, this study revealed that Z-GS exerted neuroprotective property through alleviated oxidative stress and inflammation via inhibiting the TXNIP/NLRP3 axis. Z-GS could be considered as a promising candidate for the treatment of ischemic stroke.

N‑acetyl cysteine inhibits the lipopolysaccharide‑induced inflammatory response in bone marrow mesenchymal stem cells by suppressing the TXNIP/NLRP3/IL‑1β signaling pathway

N-acetyl cysteine (NAC) has been used to inhibit lipopolysaccharide (LPS)-induced inflammation. However, the molecular mechanism underlying its anti-inflammatory effects remains to be elucidated. The present study aimed to determine the effect of NAC on the LPS-induced inflammatory response in bone marrow mesenchymal stem cells (BMSCs) and elucidate the underlying molecular mechanism. First, BMSCs were stimulated by LPS following pretreatment with NAC (0, 0.1, 0.5, 1 or 2 mM). A Cell Counting Kit 8 assay was used to determine the number of viable cells and 1 mM NAC was selected as the experimental concentration. Then, the secretion of inflammatory factors, including interleukin (IL)-1β, IL-6 and tumor necrosis factor-α was evaluated by enzyme-linked immunosorbent assay. Finally, the expression levels of mRNA and proteins, including apoptosis-associated speck-like protein containing a CARD (ASC), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, thioredoxin-interacting protein (TXNIP), and thioredoxin (TRX), were evaluated by reverse transcription-quantitative PCR and western blot analysis, respectively. The results demonstrated that the secretion of inflammatory factors, which was increased by the administration of LPS, was reduced by pretreatment with NAC. Furthermore, NAC reduced the expression of ASC, NLRP3, caspase-1 and TXNIP, but enhanced that of TRX. To conclude, NAC had anti-inflammatory effects on LPS-stimulated BMSCs, which was closely associated with the TXNIP/NLRP3/IL-1β signaling pathway. Thus, NAC may be a promising treatment to attenuate the inflammatory response in LPS-induced BMSCs.

The effect of doxycycline-containing chitosan/carboxymethyl chitosan nanoparticles on NLRP3 inflammasome in periodontal disease

A polyelectrolyte complex nanoparticle comprising chitosan (CS) and carboxymethyl chitosan (CMCS) was prepared (CS/CMCS-NPs) by ionic gelation, which was then used as a doxycycline carrier (Dox:CS/CMCS-NPs). The obtained CS/CMCS-NPs and Dox:CS/CMCS-NPs were characterized for various parameters and bacteriostatic ability against Porphyromonas gingivalis. The regulation of related genes and proteins of NLRP3 inflammasome and IL-1β in human gingival fibroblasts (HGFs) was characterized by qRT-PCR, western blotting and ELISA. The results showed that Dox:CS/CMCS-NPs had an orderly morphology and an excellent cytocompatibility. P. gingivalis was strongly inhibited by Dox:CS/CMCS-NPs contrasted with control group. Dox:CS/CMCS-NPs effectively down-regulated both gene and protein levels of NLRP3 inflammasome and IL-1β in HGFs. This study provides a new method for rational application of Dox in the clinical treatment of periodontal disease and a new direction for explaining the mechanism of action of Dox:CS/CMCS-NPs and more drug-carrying nanoparticles.

Elevated microRNA-20b-3p and reduced thioredoxin-interacting protein ameliorate diabetic retinopathy progression by suppressing the NLRP3 inflammasomes

Over the years, microRNA-20b-3p (miR-20b-3p) has been found to play an essential role in human diseases; we aimed to investigate the effect of miR-20b-3p on the progression of diabetic retinopathy (DR). The DR rat models were established by streptozotocin injection and treated with miR-20b-3p mimics, silenced, or overexpressed thioredoxin-interacting protein (TXNIP). Afterward, the expression of miR-20b-3p and TXNIP, visual function, inflammatory factors, microvascular injury, vascular permeability, cell apoptosis, and angiogenesis in rats' retinal tissues were assessed. The target relation between miR-20b-3p and TXNIP was confirmed by dual luciferase reporter gene assay. MiR-20b-3p was poorly expressed while TXNIP was highly expressed in DR rats' retinal tissues. Elevated miR-20b-3p and inhibited TXNIP promoted the visual function, and restricted the inflammatory reaction, microvascular injury, vascular permeability, cell apoptosis, and angiogenesis in DR rats, thereby decelerating the development of DR. Furthermore, TXNIP was targeted by miR-20b-3p. We have found in this study that elevated miR-20b-3p could repress the levels of inflammatory factors by inhibiting TXNIP, thus attenuating the pathology of retina in DR rats, which provided new candidates for DR treatment.

Balanced oral pathogenic bacteria and probiotics promoted wound healing via maintaining mesenchymal stem cell homeostasis

Objectives

The homeostasis of oral pathogenic bacteria and probiotics plays a crucial role in maintaining the well-being and healthy status of human host. Our previous study confirmed that imbalanced oral microbiota could impair mesenchymal stem cell (MSC) proliferation capacity and delay wound healing. However, the effects of balanced oral pathogenic bacteria and probiotics on MSCs and wound healing are far from clear. Here, the balance of pathogenic bacteria Porphyromonas gingivalis and probiotics Lactobacillus reuteri extracts was used to investigate whether balanced oral microbiota modulate the physiological functions of MSCs and promote wound healing.

Methods

The effects of balanced pathogenic bacteria P. gingivalis and probiotics L. reuteri extracts on gingival MSCs (GMSCs) were tested using the migration, alkaline phosphatase activity, alizarin red staining, cell counting kit-8, real-time PCR, and western blot assays. To investigate the role of balanced pathogenic bacteria P. gingivalis and probiotics L. reuteri extracts in the wound of mice, the wounds were established in the mucosa of palate and were inoculated with bacteria every 2 days.

Results

We found that the balance between pathogenic bacteria and probiotics enhanced the migration, osteogenic differentiation, and cell proliferation of MSCs. Additionally, local inoculation of the mixture of L. reuteri and P. gingivalis promoted the process of wound healing in mice. Mechanistically, we found that LPS in P. gingivalis could activate NLRP3 inflammasome and inhibit function of MSCs, thereby accelerating MSC dysfunction and delaying wound healing. Furthermore, we also found that reuterin was the effective ingredient in L. reuteri which maintained the balance of pathogenic bacteria and probiotics by neutralizing LPS in P. gingivalis, thus inhibiting inflammation and promoting wound healing.

Conclusions

This study revealed that the homeostasis of oral microbiomes played an indispensable role in maintaining oral heath, provided hopeful methods for the prevention and treatment of oral diseases, and had some referential value for other systemic diseases caused by dysfunction of microbiota and MSCs.

Contribution of TGF-Beta-Mediated NLRP3-HMGB1 Activation to Tubulointerstitial Fibrosis in Rat With Angiotensin II-Induced Chronic Kidney Disease

Fibrosis is a common phenotype that often leads to the progression of blood pressure-induced chronic kidney disease (CKD). TGF-beta plays an important role in promoting pathogenesis, and NLRP3 is a critical mediator in the progression of blood pressure-induced CKD. However, the pathophysiological roles of the TGF-beta-mediated NLRP3 pathway in modulating fibrosis in blood pressure-induced CKD have not been elucidated. The present study aims to investigate the contribution of TGF-beta-mediated NLRP3 inflammasome to renal fibrosis in rats with high blood pressure. By treating rats with angiotensin II (Ang II) for 14 days, we observed the development of fibrosis, characterized by epithelial-mesenchymal transition (EMT) markers [alpha-smooth muscle actin (alpha-SMA), MMP-2, and MMP-9]. Immunohistochemical analysis further revealed that TGF-beta and NLRP3 inflammasome activation [high-mobility group box 1 (HMGB1), IL-1beta, and NLRP3] were significantly upregulated in the kidney of rats with Ang II-induced hypertension. Interestingly, we observed that Ang II could not increase the production of NLRP3 proteins, but TGF-beta could induce NLRP3 protein expression in cultured NRK-52E cells. Furthermore, we speculated that TGF-beta played a pathogenic role in Ang II-induced CKD because TGF-beta induced the activation of NLRP3 inflammasomes and Gasdermin D cleavage expression. We also proved that the pharmacological inhibition of NLRP3 by ISO caused a decrease in TGF-beta-induced NLRP3 inflammasome activation and the expression of EMT markers (alpha-SMA and CollagenI) and Gasdermin D cleavage. Collectively, these results suggest that TGF-beta-mediated NLRP3 inflammasome activation may cause the release of HMGB1 and an increase in Gasdermin D cleavage in NRK-52E, thereby contributing to renal fibrosis in Ang II-induced CKD. These findings provide novel insights into the pathogenic role of NLRP3 in CKD associated with high blood pressure.

Targeting NLRP3 Inflammasome in Inflammatory Bowel Disease: Putting out the Fire of Inflammation

Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine, comprised of ulcerative colitis and Crohn's disease. Among the complicated pathogenic factors of IBD, the overaction of inflammatory and immune reaction serves as an important factor. Inflammasome is a form of innate immunity as well as inflammation. Among all kinds of inflammasomes, the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is the most studied one, and has been revealed to be involved in the pathogenesis and progression of IBD. Here, in this review, the association between the NLRP3 inflammasome and IBD will be discussed. Furthermore, several NLRP3 inflammasome inhibitors which have been demonstrated to be effective in the alleviation of IBD will be described in this review.

Butyrate rather than LPS subverts gingival epithelial homeostasis by downregulation of intercellular junctions and triggering pyroptosis

AIM

To investigate the effects of sodium butyrate (NaB) and lipopolysaccharide (LPS) on gingival epithelial barrier.

MATERIAL AND METHODS

We cultured human primary gingival epithelial cells and investigated the effects of NaB and LPS on gingival epithelial barrier and involved mechanisms at in vitro and in vivo levels by immunostaining, confocal microscopy, field emission scanning electron microscopy (FE-SEM), transmission electronic microscopy (TEM), transepithelial electrical resistance (TEER), FTIC-dextran flux, flow cytometry, real-time PCR and Western blot assays.

RESULTS

Our results showed that NaB, rather than LPS, destroyed the epithelial barrier by breaking down cell-cell junctions and triggering gingival epithelial cell pyroptosis with characteristic morphological changes, including swollen cells, large bubbles, pore formation in the plasma membrane and subcellular organelles changes. The upregulated expression of pyroptosis-related markers, caspase-3 and gasdermin-E (GSDME) contributed to this effect. Pyroptosis aroused by NaB is a pro-inflammatory cell death. Pyroptotic cell death provoked inflammatory responses by upregulation of IL-8 and MCP-1, and releasing intracellular contents into the extracellular microenvironment after pyroptotic rupture of the plasma membrane.

CONCLUSIONS

Our new findings indicate that butyrate is a potent destructive factor of gingival epithelial barrier and pro-inflammatory mediator, which shed a new light on our understanding of periodontitis initiation.

Taurine Alleviates Schistosoma-Induced Liver Injury by Inhibiting the TXNIP/NLRP3 Inflammasome Signal Pathway and Pyroptosis

Schistosomiasis is a parasitic helminth disease that can cause severe inflammatory pathology, leading to organ damage, in humans. During a schistosomal infection, the eggs are trapped in the host liver, and products derived from eggs induce a polarized Th2 cell response, resulting in granuloma formation and eventually fibrosis. Previous studies indicated that the nucleotide-binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is involved in schistosomiasis-associated liver fibrosis and that taurine could ameliorate hepatic granulomas and fibrosis caused by Schistosoma japonicum infection. Nevertheless, the precise role and molecular mechanism of the NLRP3 inflammasome and the protective effects of taurine in S. japonicum infection have not been extensively studied. In this study, we investigated the role of the NLRP3 inflammasome and the hepatoprotective mechanism of taurine in schistosoma-induced liver injury in mice. NLRP3 deficiency ameliorated S. japonicum-infection-induced hepatosplenomegaly, liver dysfunction, and hepatic granulomas and fibrosis; it also reduced NLRP3-dependent liver pyroptosis. Furthermore, taurine suppressed hepatic thioredoxin-interacting protein (TXNIP)/NLRP3 inflammasome activation in mice with S. japonicum infections, thereby inhibiting the activation of downstream inflammatory mediators such as interleukin-1β and subsequent pyroptosis. Our results suggest that the TXNIP/NLRP3 inflammasome pathway and mediating pyroptosis are involved in S. japonicum-induced liver injury and may be a potential therapeutic target for schistosomiasis treatment. In addition, taurine may be useful to alleviate or to prevent the occurrence of schistosomiasis-associated liver fibrosis.

Doxycycline inhibits NAcht Leucine-rich repeat Protein 3 inflammasome activation and interleukin-1β production induced by Porphyromonas gingivalis-lipopolysaccharide and adenosine triphosphate in human gingival fibroblasts

OBJECTIVE

To investigate the effect of adenosine triphosphate (ATP) on inflammasome activation by Porphyromonas gingivalis-lipopolysaccharide (P. gingivalis-LPS) stimulation and the anti-inflammatory eff ;ect of doxycycline (Dox) in human gingival fibroblasts (HGFs).

DESIGN

The optimal concentration of P. gingivalis-LPS (1.0 μg/mL) for cellular viability was determined by observing cell morphology and measuring the amount of formazan and the expression of pro-caspase-1. The expression of genes and proteins related to the NAcht Leucine-rich repeat Protein 3 (NLRP3) inflammasome, including NLRP3, apoptosis-associated speck-like protein containing CARD (ASC), caspase-1 and its activated forms, and the inflammatory factor interleukin-1β (IL-1β) and its activated forms were measured.

RESULTS

The NLRP3 inflammasome (i.e., NLRP3, ASC, caspase-1) was not affected by stimulation with P. gingivalis-LPS or ATP. However, a combination of P. gingivalis-LPS and ATP significantly enhanced inflammasome activation and IL-1β production at the gene and protein levels as measured by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, respectively. Furthermore, doxycycline addition markedly inhibited inflammasome activation and IL-1β production induced by a combination of P. gingivalis-LPS and ATP.

CONCLUSIONS

LPS, ATP, and doxycycline play critical roles in regulating host immune responses. This evidence provides guidance for the application of tetracycline drugs for the clinical treatment of periodontal disease.