Hydrogen sulfide synergistically upregulates Porphyromonas gingivalis lipopolysaccharide-induced expression of IL-6 and IL-8 via NF-κB signalling in periodontal fibroblasts

Gallic acid induces osteoblast differentiation and alleviates inflammatory response through GPR35/GSK3β/β-catenin signaling pathway in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Gallic acid (GA) possesses various beneficial functions including antioxidant, anticancer, anti-inflammatory as well as inhibiting osteoclastogeneis. However, effects on osteogenic differentiation, especially in human ligament periodontal (hPDL) cells, remain unclear. Thus, the aim of this study was to evaluate the function of GA on osteogenesis and anti-inflammation in hPDL cells and to explore the involved underlying mechanism.

METHODS

Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) treatment was used as a model for periodontitis. ROS production was determined by H2DCFDA staining. Trans-well and wound healing assays were performed for checking the migration effect of GA. Alizarin red and alkaline phosphatase activity (ALP) assays were performed to evaluate osteogenic differentiation. Osteogenesis and inflammatory-related genes and proteins were measured by real-time PCR and western blot.

RESULTS

Our results showed that GA-treated hPDL cells had higher proliferation and migration effect. GA inhibited ROS production-induced by Pg-LPS. Besides, GA abolished Pg-LPS-induced inflammation cytokines (il-6, il-1β) and inflammasome targets (Caspase-1, NLRP3). In addition, GA promoted ALP activity and mineralization in hPDL cells, lead to enhance osteoblast differentiation process. The effect of GA is related to G-protein-coupled receptor 35 (GPR35)/GSK3β/β-catenin signaling pathway.

CONCLUSION

GA attenuated Pg-LPS-induced inflammatory responses and periodontitis in hPDL cells. Taken together, GA may be targeted for therapeutic interventions in periodontal diseases.

Microbial metabolites in the pathogenesis of periodontal diseases: a narrative review

The purpose of this narrative review is to highlight the importance of microbial metabolites in the pathogenesis of periodontal diseases. These diseases, involving gingivitis and periodontitis are inflammatory conditions initiated and maintained by the polymicrobial dental plaque/biofilm. Gingivitis is a reversible inflammatory condition while periodontitis involves also irreversible destruction of the periodontal tissues including the alveolar bone. The inflammatory response of the host is a natural reaction to the formation of plaque and the continuous release of metabolic waste products. The microorganisms grow in a nutritious and shielded niche in the periodontal pocket, protected from natural cleaning forces such as saliva. It is a paradox that the consequences of the enhanced inflammatory reaction also enable more slow-growing, fastidious, anaerobic bacteria, with often complex metabolic pathways, to colonize and thrive. Based on complex food chains, nutrient networks and bacterial interactions, a diverse microbial community is formed and established in the gingival pocket. This microbiota is dominated by anaerobic, often motile, Gram-negatives with proteolytic metabolism. Although this alternation in bacterial composition often is considered pathologic, it is a natural development that is promoted by ecological factors and not necessarily a true "dysbiosis". Normal commensals are adapting to the gingival crevice when tooth cleaning procedures are absent. The proteolytic metabolism is highly complex and involves a number of metabolic pathways with production of a cascade of metabolites in an unspecific manner. The metabolites involve short chain fatty acids (SCFAs; formic, acetic, propionic, butyric, and valeric acid), amines (indole, scatole, cadaverine, putrescine, spermine, spermidine) and gases (NH₃, CO, NO, H₂S, H₂). A homeostatic condition is often present between the colonizers and the host response, where continuous metabolic fluctuations are balanced by the inflammatory response. While it is well established that the effect of the dental biofilm on the host response and tissue repair is mediated by microbial metabolites, the mechanisms behind the tissue destruction (loss of clinical attachment and bone) are still poorly understood. Studies addressing the functions of the microbiota, the metabolites, and how they interplay with host tissues and cells, are therefore warranted.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Role of Hydrogen Sulfide in Oral Disease

Oral diseases are among the most common human diseases yet less studied. These diseases affect both the physical, mental, and social health of the patients resulting in poor quality of life. They affect all ages, although severe stages are mostly observed in older individuals. Poor oral hygiene, genetics, and environmental factors contribute enormously to the development and progression of these diseases. Although there are available treatment options for these diseases, the recurrence of the diseases hinders their efficiency. Oral volatile sulfur compounds (VSCs) are highly produced in oral cavity as a result of bacteria activities. Together with bacteria components such as lipopolysaccharides, VSCs participate in the progression of oral diseases by regulating cellular activities and interfering with the immune response. Hydrogen sulfide (H2S) is a gaseous neurotransmitter primarily produced endogenously and is involved in the regulation of cellular activities. The gas is also among the VSCs produced by oral bacteria. In numerous diseases, H2S have been reported to have dual effects depending on the cell, concentration, and donor used. In oral diseases, high production and subsequent utilization of this gas have been reported. Also, this high production is associated with the progression of oral diseases. In this review, we will discuss the production of H2S in oral cavity, its interaction with cellular activities, and most importantly its role in oral diseases.

Subgingival microbiome in periodontitis and type 2 diabetes mellitus: an exploratory study using metagenomic sequencing

Purpose

To explore differences in the subgingival microbiome according to the presence of periodontitis and/or type 2 diabetes mellitus (T2D), a metagenomic sequencing analysis of the subgingival microbiome was performed.

Methods

Twelve participants were divided into 4 groups based on their health conditions (periodontitis, T2D, T2D complicated with periodontitis, and generally healthy). Subgingival plaque was collected for metagenomic sequencing, and gingival crevicular fluids were collected to analyze the concentrations of short-chain fatty acids.

Results

The shifts in the subgingival flora from the healthy to periodontitis states were less prominent in T2D subjects than in subjects without T2D. The pentose and glucuronate interconversion, fructose and mannose metabolism, and galactose metabolism pathways were enriched in the periodontitis state, while the phosphotransferase system, lipopolysaccharide (LPS) and peptidoglycan biosynthesis, bacterial secretion system, sulfur metabolism, and glycolysis pathways were enriched in the T2D state. Multiple genes whose expression was upregulated from the red and orange complex bacterial genomes were associated with bacterial biofilm formation and pathogenicity. The concentrations of propionic acid and butyric acid were significantly higher in subjects with periodontitis, with or without T2D, than in healthy subjects.

Conclusions

T2D patients are more susceptible to the presence of periodontal pathogens and have a higher risk of developing periodontitis. The pentose and glucuronate interconversion, fructose and mannose metabolism, galactose metabolism, and glycolysis pathways may represent the potential microbial functional association between periodontitis and T2D, and butyric acid may play an important role in the interaction between these 2 diseases. The enrichment of the LPS and peptidoglycan biosynthesis, bacterial secretion system, and sulfur metabolism pathways may cause T2D patients to be more susceptible to periodontitis.

Lipoxin A4 promotes autophagy and inhibits overactivation of macrophage inflammasome activity induced by Pg LPS

Objective

To explore the role of lipoxin A4 (LXA4) on inflammasome and inflammatory activity in macrophages activated by Porphyromonas gingivalis lipopolysaccharide (PgLPS) one of the major causative agents of chronic periodontitis.

Methods

The mouse macrophage cell line RAW264.7 was used to produce an activated inflammation model. Markers of inflammasome and inflammatory activity and autophagy were assessed by ELISA, reverse transcription polymerase chain reaction (RT-PCR), and Western blot assay.

Results

Markers of inflammasome activity, inflammation and autophagy increased with Pg LPS concentration. They also increased with increasing exposure to Pg LPS up to 12h but decreased at 24h. However, markers of autophagy increased. Phosphorylated NF-κBp65 decreased with LXA4, which was similar to results obtained with the autophagy inducer, rapamycin.

Conclusions

LXA4 promoted autophagy and inhibited activation of inflammasomes and inflammation markers in macrophage inflammation induced by PgLPS and this action was linked to the phosphorylation of NF-κB.

MicroRNA‑199a‑3p suppresses high glucose‑induced apoptosis and inflammation by regulating the IKKβ/NF‑κB signaling pathway in renal tubular epithelial cells

Renal tubular epithelial cells (RTEC) injury induced by hyperglycemia is considered a major contributor to the pathogenesis of diabetic nephropathy (DN). However, few studies have focused on the role of microRNAs (miRNAs/miRs) in RTEC injury. Therefore, the present study aimed to investigate the role and mechanisms of miRNAs in RTEC injury. In the study, miRNAs expression profiles were determined via microarray assay in the peripheral blood samples of patients with DN. High glucose (HG)-induced injury in HK-2 cells was used as a cell model to examine the potential role of miR-199a-3p in DN. The expression of miR-199a-3p was validated using reverse transcription-quantitative PCR. The expressions of TNF-α, IL-1β and IL-6, were detected via ELISA. The protein levels of apoptosis-related proteins were determined using western blotting. Cell apoptosis and caspase 3 activity were evaluated via flow cytometry analysis and caspase 3 activity assay, respectively. Luciferase reporter assay was used to confirm the interaction between miR-199a-3p and IKKβ. miR-199a-3p was found to be significantly downregulated in the peripheral blood samples, and there was a negative correlation between miR-199a-3p expression and proteinuria in patients with DN. It was identified that miR-199a-3p expression was time-dependently decreased in the HG-induced cell damage model. Moreover, miR-199a-3p overexpression significantly improved HG-induced cell injury, as evidenced by the decrease in cell apoptosis and inflammation. Subsequent analyses demonstrated that miR-199a-3p directly targeted IKKβ, whose expression was increased, and negatively correlated with miR-199a-3p expression in patients with DN. The protective effects of miR-199a-3p overexpression on HG-treated HK-2 cells were partially reversed by IKKβ overexpression. In addition, activation of the NF-κB pathway by HG was blocked by miR-199a-3p mimics transfection in HK-2 cells. Collectively, the present findings indicated that miR-199a-3p protected HK-2 cells against HG-induced injury via inactivation of the IKKβ/NF-κB pathway, suggesting enhanced expression of miR-199a-3p as a potential therapeutic strategy for patients with DN.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

A Novel Reporter Gene Assay for Pyrogen Detection

Fever is a systemic inflammatory response of the body to pyrogens. Nuclear factor κB (NF-κB) is a central signaling molecule that causes the excessive secretion of various pyrogen-induced pro-inflammatory factors. This study explored the feasibility of a novel reporter gene assay (RGA) for pyrogen detection using RAW264.7 cells stably transfected with the NF-κB reporter gene as a pyrogenic marker. The RGA could detect different types of pyrogens, including the lipopolysaccharide of gram-negative bacteria, the lipoteichoic acid of gram-positive bacteria, and the zymosan of fungi, and a good dose-effect relationship was observed in terms of NF-κB activity. The limits of detection of the RGA to those pyrogens were 0.03 EU/ml, 0.001 μg/ml, and 1 μg/ml, respectively. The method had good precision and accuracy and could be applied to many molecules (e.g., nivolumab, rituximab, bevacizumab, etanercept, basiliximab, Haemophilus influenzae type b conjugate vaccine, 23-valent pneumococcal polysaccharide vaccine, group A and group C meningococcal conjugate vaccine, diphtheria, tetanus, pertussis [acellular, component], poliomyelitis [inactivated] vaccine, and imject alum adjuvant). The results of this study suggest that the novel RGA has a wide pyrogen detection spectrum and is sufficiently sensitive, stable, and accurate for various applications.

Cyclic compression emerged dual effects on the osteogenic and osteoclastic status of LPS-induced inflammatory human periodontal ligament cells according to loading force

BACKGROUND

Appropriate mechanical stimulation is essential for bone homeostasis in healthy periodontal tissues. While the osteogenesis and osteoclast differentiation of inflammatory periodontal ligament cells under different dynamic loading has not been yet clear. The aim of this study is to clarify the inflammatory, osteogenic and pro-osteoclastic effects of different cyclic stress loading on the inflammatory human periodontal ligament cells (hPDLCs).

METHODS

hPDLCs were isolated from healthy premolars and cultured in alpha minimum Eagle's medium (α-MEM). Lipopolysaccharides (LPS) were used to induce the inflammation state of hPDLCs in vitro. Determination of LPS concentration for the model of inflammatory periodontium was based on MTT and genes expression analysis. Then the cyclic stress of 0, 0-50, 0-90 and 0-150 kPa was applied to the inflammatory hPDLCs for 5 days respectively. mRNA and protein levels of osteogenic, osteoclastic and inflammation-related markers were examined after the treatment.

RESULTS

MTT and RT-PCR results showed that 10 μg/ml LPS up-regulated TNF-α, IL-1β, IL-6, IL-8 and MCP-1 mRNA levels (P < 0.05) and did not affect the cell viability (P > 0.05). The excessive loading of stress (150 kPa) with or without LPS strongly increased the expression of inflammatory-related markers TNF-α, IL-1β, IL-6, IL-8, MCP-1 (P < 0.05) and osteoclastic markers RANKL, M-CSF, PTHLH and CTSK compared with other groups (P < 0.05), but had no significant effect on osteogenic genes. While 0-90 kPa cyclic pressure could up-regulate the expression of osteogenic genes ALP, COL-1, RUNX2, OCN, OPN and OSX in the healthy hPDLSCs.

CONCLUSIONS

Collectively, it could be concluded that 0-150 kPa was an excessive stress loading which accelerated both inflammatory and osteoclastic effects, while 0-90 kPa may be a positive factor for the osteogenic differentiation of hPDLCs in vitro.

Reversine inhibits MMP-3, IL-6 and IL-8 expression through suppression of ROS and JNK/AP-1 activation in interleukin-1β-stimulated human gingival fibroblasts

OBJECTIVE

Periodontitis is an inflammatory disease of the supporting tissue around teeth commonly caused by gram-negative bacterial infections. Interleukin (IL)-1β, a cytokine involved in host immune and inflammatory responses, is known to induce the activation of various intracellular signaling pathways. One of these signaling mechanisms involves the regulation of gene expression by activation of transcription factors (AP-1 and NF-κB). These transcription factors are controlled by mitogen-activated protein kinases (MAPKs), which increase cytokine and matrix metalloproteinase (MMP) expression. We examined the preventive effects of reversine, a 2,6-disubstituted purine derivative, on cytokine and MMP-3 expression in human gingival fibroblasts (HGFs) stimulated with IL-lβ.

STUDY DESIGN

Western blot analyses were performed to verify the activities of MAPK, p65, p50, and c-Jun and the expression of MMPs in IL-1β-stimulated HGFs. Cytokine and MMP-3 expression in IL-1β-stimulated HGFs was measured by real-time quantitative polymerase chain reaction.

RESULTS

Reversine decreased the IL-1β-induced expression of proinflammatory cytokines (IL-6 and IL-8) and MMP-3 in HGFs. Furthermore, the mechanism underlying the effects of reversine involved the suppression of IL-1β-stimulated MAPK activation and AP-1 activation.

CONCLUSION

Reversine inhibits IL-1β-induced MMP and cytokine expression via inhibition of MAPK/AP-1 activation and ROS generation. Therefore, we suggest that reversine may be an effective therapeutic candidate for preventing periodontitis.

Exogenous hydrogen sulfide prevents lipopolysaccharide-induced inflammation by blocking the TLR4/NF-κB pathway in MAC-T cells

Mastitis impairs animal health and results in economic loss. Lipopolysaccharide (LPS) may cause immune response and inflammation in the bovine mammary gland. Hydrogen sulfide (H₂S) is the third gasotransmitter that acts as an anti-inflammation regulator in many cells. Despite the importance of H₂S in regulating inflammation, the effect and mechanism of exogenous H₂S on LPS-induced inflammation in bovine mammary epithelial cells are unknown. In the present study, with NaHS as a donor of H₂S, the bovine mammary epithelial cell line (MAC-T) was applied as an in vitro model to study the role of H₂S on LPS-induced MAC-T cells. The results verified that the cell viability was diminished by LPS but restored by exogenous H₂S at a physiologically relevant concentration (10 μM). Additionally, the production of H₂S was mitigated in the LPS-induced MAC-T cells. Meanwhile, exogenous H₂S decreased the intracellular ROS production and mRNA expression levels of the pro-inflammatory cytokines, TNF-α, IL-1β, IL-8, and IL-6. Furthermore, exogenous H₂S inhibited the mRNA expression of TLR4 and activation of NF-κB signaling pathway. In summary, exogenous H₂S exerts anti-inflammatory effects through attenuating oxidative stress and blocking the TLR4/NF-κB pathway in the LPS-induced bovine mammary epithelial cells. Our findings might clarify new prophylactic approaches for mastitis.

Hydrogen sulfide exposure triggers chicken trachea inflammatory injury through oxidative stress-mediated FOS/IL8 signaling

Hydrogen sulfide (H₂S) is well known to cause irritation and damage to airway following inhalation, but the mechanism by which H₂S contributes to airway toxicity is unclear. In order to assess the respiratory toxicity of H₂S inhalation in chicken trachea, we investigated the change of oxidative stress parameters, tracheal tissue structure and transcriptome profiles of chicken trachea exposed to H₂S for 42 days. The results showed H₂S exposure induced oxidative stress and inflammation in trachea. The ultrastructural analysis revealed loss of cilia and accumulation of mucus in tracheal epithelium. Differentially expressed genes (DEGs) analysis indicated 454 genes were significantly changed, including 136 genes upregulated and 318 genes downregulated. Gene ontology and KEGG analysis showed many genes involved in response to oxidative stress, inflammatory and immune response, which might contribute to H₂S-induced tracheal inflammatory injury. Among those genes, N-acetyl-L-cysteine (NAC) treatment blocked the H₂S-triggered expression of FOS and IL8. Silencing FOS by siRNA inhibited H₂S-induced expression of IL8. Taken together, we concluded that H₂S induced oxidative stress leads to tracheal inflammation through FOS/IL8 signaling, leading to excessive mucus secretion and absence of cilia. These results provide new insights for unveiling the biological effects of H₂S in vivo and in vitro.

The Mycoplasma pneumoniae HapE alters the cytokine profile and growth of human bronchial epithelial cells

Mycoplasma pneumoniae is one of the most common pathogenic causes of community-acquired pneumonia. Hydrogen sulfide, alanine, and pyruvate producing enzyme (HapE) is a recently discovered M. pneumoniae virulence factor that can produce H₂S to promote erythrocyte lysis. However, other cytotoxic effects of HapE have not been explored. The present study examined the effects of this enzyme on normal human bronchial epithelial (NHBE) cells, in an attempt to identify additional mechanisms of M. pneumoniae pathogenesis. Recombinant HapE was purified for use in downstream assays. MTT and colony formation assays were conducted to determine the effects of HapE on cell viability and growth, while flow cytometry was used to examine changes in cell proliferation and cell cycle function. ELISA was performed to examine changes in the cytokine profile of HapE-treated cells. HapE treatment arrested NHBE cells in S phase and inhibited cell proliferation in a concentration-dependent manner. The anti-inflammatory factors interleukin (IL)-4 and IL-6 were significantly enhanced following HapE treatment. Increased secretion of pro-inflammatory factors was not observed. The effects of HapE on the respiratory epithelium may have an impact on the efficiency of host immune surveillance and pathogen elimination, and contribute to the pathogenesis of M. pneumoniae.

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

Inflammasomes serve as an intracellular machinery to initiate inflammatory response to various danger signals. However, the chronic periodontitis pathological relevance of this inflammasome activation, particularly in periodontal ligament fibroblasts, remains largely unknown. The present study demonstrated that Nlrp3 inflammasome components abundantly expressed in cultured mouse periodontal ligament fibroblasts (mPDLFs). In addition, our data demonstrated that P.g-LPS (Porphyromonas gingivalis Lipopolysaccharide), a major injurious factor during chronic periodontitis, could induce the mPDLFs migration dysfunction and the inhibition of Nlrp3 inflammasome by Isoliquiritigenin (ISO) markedly recovered the migration dysfunction in mPDLFs. And Nlrp3 inflammasome components could be aggregated to form an inflammasome complex on stimulation of P.g-LPS, as shown by fluorescence confocal microscopy. Correspondingly, P.g-LPS induced Nlrp3 inflammasome activation, caspase-1 activation, IL-1β and HMGB1 release, which were blocked by Nlrp3 inflammasome inhibitor (ISO). Interestingly, reactive oxygen species, TXNIP protein and TXNIP binding to Nlrp3 were markedly increased in mPDLFs with P.g-LPS. Furthermore, ROS generation inhibitor (Apocynin; APO) significantly reduced Nlrp3 inflammasome formation and IL-1β production in mPDLFs with P.g-LPS. And APO attenuated P.g-LPS-induced TXNIP protein expression and mPDLFs injury. In conclusion, our results demonstrate that ROS/TXNIP/Nlrp3 Inflammasome pathway is a key initiating mechanism necessary for P.g-LPS-induced subsequent mPDLFs inflammatory response leading to chronic periodontitis.

Plantamajoside inhibits lipopolysaccharide-induced epithelial-mesenchymal transition through suppressing the NF-κB/IL-6 signaling in esophageal squamous cell carcinoma cells

Plantamajoside (PMS) is a major compound of Plantago asiatica and possesses anti-tumor activity. However, the effect of PMS on esophageal squamous cell carcinoma (ESCC) and the underlying mechanism of action are unclear. The present study aimed to evaluate the effect of PMS on lipopolysaccharide (LPS)-induced epithelial-mesenchymal transition (EMT) in ESCC. The results showed that PMS inhibited viability of ESCC cell lines (Eca-109 and TE-1) in a concentration-dependent manner. PMS also inhibited LPS-induced EMT in ESCC cells. PMS inhibited LPS-induced activation of the NF-κB pathway and IL-6 expression. PMS also suppressed IL-6-induced EMT in ESCC cells. Treatment of BAY11-7082 (an inhibitor of NF-κB) or antibody against IL-6 alleviated the effect of LPS-induced EMT in ESCC cells. Besides, inhibition of NF-κB decreased IL-6 expression. In conclusion, the results indicated that PMS inhibited LPS-induced EMT through suppressing the NF-κB/IL-6 signaling in ESCC cell lines, suggesting that PMS might be a useful agent for the treatment of ESCC.

Insights into the Evolution of Host Association through the Isolation and Characterization of a Novel Human Periodontal Pathobiont, Desulfobulbus oralis

The human oral microbiota encompasses representatives of many bacterial lineages that have not yet been cultured. Here we describe the isolation and characterization of previously uncultured Desulfobulbus oralis, the first human-associated representative of its genus. As mammalian-associated microbes rarely have free-living close relatives, D. oralis provides opportunities to study how bacteria adapt and evolve within a host. This sulfate-reducing deltaproteobacterium has adapted to the human oral subgingival niche by curtailing its physiological repertoire, losing some biosynthetic abilities and metabolic independence, and by dramatically reducing environmental sensing and signaling capabilities. The genes that enable free-living Desulfobulbus to synthesize the potent neurotoxin methylmercury were also lost by D. oralis, a notably positive outcome of host association. However, horizontal gene acquisitions from other members of the microbiota provided novel mechanisms of interaction with the human host, including toxins like leukotoxin and hemolysins. Proteomic and transcriptomic analysis revealed that most of those factors are actively expressed, including in the subgingival environment, and some are secreted. Similar to other known oral pathobionts, D. oralis can trigger a proinflammatory response in oral epithelial cells, suggesting a direct role in the development of periodontal disease.

Animal-associated microbiota likely assembled as a result of numerous independent colonization events by free-living microbes followed by coevolution with their host and other microbes. Through specific adaptation to various body sites and physiological niches, microbes have a wide range of contributions, from beneficial to disease causing. Desulfobulbus oralis provides insights into genomic and physiological transformations associated with transition from an open environment to a host-dependent lifestyle and the emergence of pathogenicity. Through a multifaceted mechanism triggering a proinflammatory response, D. oralis is a novel periodontal pathobiont. Even though culture-independent approaches can provide insights into the potential role of the human microbiome “dark matter,” cultivation and experimental characterization remain important to studying the roles of individual organisms in health and disease.

An RNA-seq screen of P. gingivalis LPS treated human gingival fibroblasts

BACKGROUND

In gingival tissues, lipopolysaccharide (LPS) from Porphyromonas gingivalis (P. gingivalis) is the most critical stimulator for inducing inflammatory response. Human gingival fibroblasts (HGFs) are the major constituents of gingival connective tissues. The aim of this study was to investigate P. gingivalis LPS induced whole transcriptional profile in HGFs and the potential crosstalk between microRNAs (miRNAs) and inflammatory cytokines.

METHODS

RNA-seq was performed on HGFs with and without P. gingivalis LPS treatment. The gene expression of selected inflammatory cytokines and miRNAs induced by LPS at different time points was evaluated by quantitative RT-PCR. The protein expression of chemokines was further confirmed by ELISA.

RESULTS

Interestingly, most of the significantly changed genes (198/204) were up-regulated at 4 h after 10 μg/ml LPS stimulation, including inflammatory cytokines and miRNAs. Confirmed by quantitative RT-PCR, the mRNA levels of IL-1β, IL-6 and IL-8 showed single up-regulation peak (4 h/6 h) after 1 μg/ml and 10 μg/ml LPS treatment. Similarly, 1 μg/ml LPS induced single up-regulation peak (8 h) of miRNA-146a, -146b and -155 expression. However, 10 μg/ml LPS induced the increased expression of miRNA-146a and -155 at both early stage (2 h/4 h) and late stage (24 h).

CONCLUSION

Taken together, we investigated P. gingivalis LPS induced whole transcriptional profile, and the different behaviors of miRNA expression induced by different doses of LPS in HGFs.

H2S protects lipopolysaccharide-induced inflammation by blocking NFκB transactivation in endothelial cells

Hydrogen sulfide (H₂S) is a novel gasotransmitter and acts as a multifunctional regulator in various cellular functions. Past studies have demonstrated a significant role of H₂S and its generating enzyme cystathionine gamma-lyase (CSE) in the cardiovascular system. Lipopolysaccharide (LPS), a major pathogenic factor, is known to initiate the inflammatory immune response. The cross talk between LPS-induced inflammation and the CSE/H₂S system in vascular cells has not yet been elucidated in detail. Here we showed that LPS decreased CSE mRNA and protein expression in human endothelial cells and blocked H₂S production in mouse aorta tissues. Transfection of the cells with TLR4-specific siRNA knockdown TLR4 mRNA expression and abolished the inhibitory role of LPS on CSE expression. Higher dose of LPS (100μg/ml) decreased cell viability, which was reversed by exogenously applied H₂S at physiologically relevant concentration (30μM). Lower dose of LPS (10μg/ml) had no effect on cell viability, but significantly induced inflammation gene expressions and cytokines secretion and stimulated cell hyper-permeability. H₂S treatment prevented LPS-induced inflammation and hyper-permeability. Lower VE-cadherin expression in LPS-incubated cells would contribute to cell hyper-permeability, which was reversed by H₂S co-incubation. In addition, H₂S treatment blocked LPS-induced NFκB transactivation. We further validated that LPS-induced hyper-permeability was reversed by CSE overexpression but further deteriorated by CRISPR/Cas9-mediated knockout of CSE. In vivo, deficiency of CSE sensitized the mice to LPS-induced inflammation in vascular tissues. Take together, these data suggest that CSE/H₂S system protects LPS-induced inflammation and cell hyper-permeability by blocking NFκB transactivation.

Metformin Inhibits Porphyromonas gingivalis Lipopolysaccharide-Influenced Inflammatory Response in Human Gingival Fibroblasts via Regulating Activating Transcription Factor-3 Expression

BACKGROUND

Chronic periodontitis, one of the most prevalent oral diseases, is associated with Porphyromonas gingivalis (Pg) lipopolysaccharide (LPS) infection and has profound effects on type 2 diabetes mellitus (t2DM). Metformin, a well-known antidiabetic agent, has been reported to exert anti-inflammatory effects on various cells. This study aims to investigate the role of metformin on LPS-influenced inflammatory response in human gingival fibroblasts (HGFs).

METHODS

Dose-dependent additive effects of metformin on LPS-influenced HGFs were detected. Cell-counting assay was used to determine effects of metformin and LPS on viability of HGFs. Enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction (qRT-PCR) were applied to detect levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in differently treated cells. Activating transcription factor-3 (ATF3) small interfering (si)RNA transfection was used to determine the mechanism of metformin action, and the transfection efficiency was observed by fluorescence microscope. Effects of ATF3 knockdown were determined by qRT-PCR and Western blot.

RESULTS

Results showed that 5 μg/mL Pg LPS and 0.1, 0.5, and 1 mM metformin exhibited no toxicity to HGFs, and metformin inhibited LPS-influenced IL-1β, IL-6, and TNF-α production in a dose-dependent manner. Metformin and LPS could synergistically facilitate ATF3 expression, and ATF3 knockdown abolished inhibitory effects of metformin on LPS-influenced inflammatory cytokine production in HGFs.

CONCLUSION

The present study confirms that metformin suppresses LPS-enhanced IL-6, IL-1β, and TNF-α production in HGFs via increasing ATF3 expression.

Cystathionine-gamma-lyase deficient mice are protected against the development of multiorgan failure and exhibit reduced inflammatory response during burn

Considering the role of H₂S in critical illness, the aim of this study was to compare the outcome of burn in wild-type mice and in mice deficient in CSE, one of the principal mammalian H₂S-generating enzymes. Animals were subjected to scald burn. Outcome variables included indices of organ injury, clinical chemistry parameters and plasma levels of inflammatory mediators. Plasma levels of H₂S significantly increased in response to burn in wild-type mice, but remained unchanged in CSE^-/- mice. Expression of the three H₂S-producing enzymes (CSE, CBS and 3-MST) in the lung and liver, and the capacity of tissue homogenates to produce H₂S, however, was not affected by burn. In CSE deficient mice there was a significant amelioration of burn-induced accumulation of myeloperoxidase levels in heart, lung, liver and kidney and significantly lower degree of malon dialdehyde accumulation in the heart, lung and kidney than in wild-type mice. CSE deficient mice, compared to wild-type mice, showed a significant attenuation of the burn-induced elevation in circulating alkaline aminotransferase and blood urea nitrogen and creatinine levels, indicative of protective effects of CSE deficiency against burn-induced hepatic, and renal functional impairment. Multiple burn-induced inflammatory mediators (TNF-α, IL-1β, IL-4, IL-6, IL-10 and IL-12) were significantly lower in the plasma of CSE^-/- animals after burn than in the plasma of wild-type controls subjected to burns. In conclusion, CSE deficiency improves organ function and attenuates the inflammatory response in a murine model of burn.

Production of endogenous hydrogen sulfide in human gingival tissue

OBJECTIVE

Endogenous hydrogen sulfide (H₂S) has recently been shown to play an important role in inflammation, but the role of endogenous H₂S in the human gingival tissue is unknown. The aim of this study was to investigate whether gingiva had enzymes for H₂S synthesis, and whether the effect of these enzymes for H₂S production changed with periodontal inflammation.

DESIGN

Gingival tissues were collected from patients undergoing periodontal operation including gingivitis, moderate chronic periodontitis, severe chronic periodontitis and normal controls. RT-PCR and western blotting were performed to measure mRNA and protein levels of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) for H₂S production. Immunohistochemistry was carried out to detect the location of the enzymes. H₂S levels and synthesis in gingival tissue were evaluated with modified methylene blue method.

RESULTS

The mRNA and protein of CBS and CSE were both expressed in human gingiva and raised significantly in moderate and severe periodontitis compared of that in healthy control. CBS, but not CSE, increased in gingivitis (p<0.05). However, there was no significant difference of H₂S level and synthesis among these groups (p>0.05).

CONCLUSIONS

Both CBS and CSE were expressed in human gingival tissue. The mRNA and protein levels of CBS and CSE were up-regulated in periodontitis.

Effect of endotoxemia in mice genetically deficient in cystathionine-γ-lyase, cystathionine-β-synthase or 3-mercaptopyruvate sulfurtransferase

Hydrogen sulfide (H₂S) has been proposed to exert pro- as well as anti-inflammatory effects in various models of critical illness. In this study, we compared bacterial lipopolysaccharide (LPS)-induced changes in inflammatory mediator production, indices of multiple organ injury and survival in wild-type (WT) mice and in mice with reduced expression of one of the three H₂S-producing enzymes, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3MST). Mice were injected intraperitoneally (i.p.) with LPS (10 mg/kg). After 6 h, the animals were sacrificed, blood and organs were collected and the following parameters were evaluated: blood urea nitrogen (BUN) levels in blood, myeloperoxidase (MPO) and malondialdehyde (MDA) in the lung, cytokine levels in plasma and the expression of the three H₂S-producing enzymes (CBS, CSE and 3MST) in the spleen, lung, liver and kidney. LPS induced a tissue-dependent upregulation of some of the H₂S-producing enzymes in WT mice (upregulation of CBS in the spleen, upregulation of 3MST in the liver and upregulation of CBS, CSE and 3MST in the lung). Moreover, LPS impaired glomerular function, as evidenced by increased BUN levels. Renal impairment was comparable in the CSE^−/− and Δ3MST mice after LPS challenge; however, it was attenuated in the CBS^+/− mice. MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) in lung homogenates were significantly increased in response to LPS; these effects were similar in the WT, CBS^+/−, CSE^−/− and Δ3MST mice; however, the MDA levels tended to be lower in the CBS^+/− and CSE^−/− mice. LPS induced significant increases in the plasma levels of multiple cytokines [tumor necrosis factor (TNF)α, interleukin (IL)-1β, IL-6, IL-10, IL-12 and interferon (IFN)γ] in plasma; TNFα, IL-10 and IL-12 levels tended to be lower in all three groups of animals expressing lower levels of H₂S-producing enzymes. The survival rates after the LPS challenge did not show any significant differences between the four animal groups tested. Thus, the findings of this study indicate that a deficiency in 3MST does not significantly affect endotoxemia, while a deficiency in CBS or CSE slightly ameliorates the outcome of LPS-induced endotoxemia in vivo.

The paradox of painless periodontal disease

Periodontal diseases, primarily gingivitis and periodontitis, are characterised by progressive inflammation and tissue destruction. However, they are unusual in that they are not also accompanied by the pain commonly seen in other inflammatory conditions. This suggests that interactions between periodontal bacteria and host cells create a unique environment in which the pro-algesic effects of inflammatory mediators and factors released during tissue damage are directly or indirectly inhibited. In this review, we summarise the evidence that periodontal disease is characterised by an accumulation of classically pro-algesic factors from bacteria and host cells. We then discuss several mechanisms by which inflammatory sensitisation of nociceptive fibres could be prevented through inactivation or inhibition of these factors. Further studies are necessary to fully understand the molecular processes underlying the endogenous localised hypoalgesia in human periodontal disease. This knowledge might provide a rational basis to develop future therapeutic interventions, such as host modulation therapies, against a wide variety of other human pain conditions.

Endogenous hydrogen sulfide is involved in osteogenic differentiation in human periodontal ligament cells

OBJECTIVE

Endogenous hydrogen sulfide (H2S) has recently emerged as an important intracellular gaseous signaling molecule within cellular systems. Endogenous H2S is synthesized from l-cysteine via cystathionine β-synthase and cystathionine γ-lyase and it regulates multiple signaling pathways in mammalian cells. Indeed, aberrant H2S levels have been linked to defects in bone formation in experimental mice. The aim of this study was to examine the potential production mechanism and function of endogenous H2S within primary human periodontal ligament cells (PDLCs).

DESIGN

Primary human PDLCs were obtained from donor molars with volunteer permission. Immunofluorescent labeling determined expression of the H2S synthetase enzymes. These enzymes were inhibited with D,L-propargylglycine or hydroxylamine to examine the effects of H2S signaling upon the osteogenic differentiation of PDLCs. Gene and protein expression levels of osteogenic markers in conjunction with ALP staining and activity and alizarin red S staining of calcium deposition were used to assay the progression of osteogenesis under different treatment conditions. Cultures were exposed to Wnt3a treatment to assess downstream signaling mechanisms.

RESULTS

In this study, we show that H2S is produced by human PDLCs via the cystathionine β-synthase/cystathionine γ-lyase pathway to promote their osteogenic differentiation. These levels must be carefully maintained as excessive or deficient H2S levels temper the observed osteogenic effect by inhibiting Wnt/β-catenin signaling.

CONCLUSIONS

These results demonstrate that optimal concentrations of endogenous H2S must be maintained within PDLCs to promote osteogenic differentiation by activating the Wnt/β-catenin signaling cascade.

Hydrogen Sulfide, Oxidative Stress and Periodontal Diseases: A Concise Review

In the past years, biomedical research has recognized hydrogen sulfide (H₂S) not only as an environmental pollutant but also, along with nitric oxide and carbon monoxide, as an important biological gastransmitter with paramount roles in health and disease. Current research focuses on several aspects of H₂S biology such as the biochemical pathways that generate the compound and its functions in human pathology or drug synthesis that block or stimulate its biosynthesis. The present work addresses the knowledge we have to date on H₂S production and its biological roles in the general human environment with a special focus on the oral cavity and its involvement in the initiation and development of periodontal diseases.

Acanthoic acid inhibits LPS-induced inflammatory response in human gingival fibroblasts

Periodontitis is a chronic disease that affects the gums and destroys connective tissue. Acanthoic acid (AA), a diterpene in Acanthopanax koreanum, has been reported to have anti-inflammatory activities. The aim of this study was to investigate the anti-inflammatory effects of AA on lipopolysaccharide (LPS)-induced inflammatory response in human gingival fibroblasts (HGFs). HGFs were treated with Porphyromonas gingivalis LPS in the presence or absence of AA. The production of inflammatory cytokines IL-8 and IL-6 were measured by ELISA. The expression of NF-κB and TLR4 were detected by Western blotting. The results showed that AA inhibited LPS-induced IL-8 and IL-6 production in a dose-dependent manner. In addition, AA inhibited LPS-induced TLR4 expression and NF-κB activation. In conclusion, AA inhibits LPS-induced inflammatory response in HGFs through inhibition TLR4-mediated NF-κB signaling pathway.

Metabolic changes of H2S in smokers and patients of COPD which might involve in inflammation, oxidative stress and steroid sensitivity

Oxidative stress and inflammation play crucial role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Most patients with COPD show a poor response to corticosteroids. Hydrogen sulfide (H2S ) has been implicated in the pathogenesis of COPD, but its expression and effects in lung tissue from COPD patients are not clear. In peripheral lung tissue samples from 24 patients, we found that compared with nonsmokers, the protein level of cystathionine-γ-lyase (CSE) was decreased in smokers and COPD patients. CSE mRNA increased but cystathionine-β-synthase (CBS) mRNA decreased in COPD patients. H2S donors increased glutathione and superoxide dismutase in CS exposed U937 cells and inhibited CS-induced TNF-α and IL-8 secretion. Dexamethasone alone had no effect on lipopolysaccharide (LPS) induced TNF-α release by alveolar macrophages from CS exposed rats, however the combination of dexamethasone and H2S donor significantly inhibited TNF-α release. Thus, H2S metabolism is altered in lung tissue of smokers and COPD patients. Supplementation of H2S protects against CS-induced oxidative stress and inflammation in macrophages and H2S on steroid sensitivity deserves further investigation.

Tormentic acid inhibits LPS-induced inflammatory response in human gingival fibroblasts via inhibition of TLR4-mediated NF-κB and MAPK signalling pathway

OBJECTIVE

Periodontal disease is one of the most prevalent oral diseases, which is associated with inflammation of the tooth-supporting tissues. Tormentic acid (TA), a triterpene isolated from Rosa rugosa, has been reported to exert anti-inflammatory effects. The aim of this study was to investigate the anti-inflammatory effects of TA on lipopolysaccharide (LPS)-stimulated human gingival fibroblasts (HGFs).

METHODS

The levels of inflammatory cytokines such as interleukin (IL)-6 and chemokines such as IL-8 were detected by enzyme-linked immunosorbent assay (ELISA). The expression of Toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), IκBα, p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) was determined by Western blotting.

RESULTS

The results showed that Porphyromonas gingivalis LPS significantly upregulated the expression of IL-6 and IL-8. TA inhibited the LPS-induced production of IL-6 and IL-8 in a dose-dependent manner. Furthermore, TA inhibited LPS-induced TLR4 expression; NF-κB activation; IκBα degradation; and phosphorylation of ERK, JNK, and P38.

CONCLUSION

TA inhibits the LPS-induced inflammatory response in HGFs by suppressing the TLR4-mediated NF-κB and mitogen-activated protein kinase (MAPK) signalling pathway.

Hydrogen sulfide in signaling pathways

For a long time hydrogen sulfide (H₂S) was considered a toxic compound, but recently H₂S (at low concentrations) has been found to play an important function in physiological processes. Hydrogen sulfide, like other well-known compounds - nitric oxide (NO) and carbon monoxide (CO) is a gaseous intracellular signal transducer. It regulates the cell cycle, apoptosis and the oxidative stress. Moreover, its functions include neuromodulation, regulation of cardiovascular system and inflammation. In this review, I focus on the metabolism of hydrogen sulfide (including enzymatic pathways of H₂S synthesis from l- and d-cysteine) and its signaling pathways in the cardiovascular system and the nervous system. I also describe how hydrogen sulfide may be used as therapeutic agent, i.e. in the cardiovascular diseases.