Toll-like receptors confer responsiveness to lipopolysaccharide from Porphyromonas gingivalis in human gingival fibroblasts

Lipopolysaccharides derived from Porphyromonas gingivalis and Escherichia coli: Differential and interactive effects on novelty-induced hyperlocomotion, blood cytokine levels and TLR4-related processes

Lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, activates Toll-like receptors (TLRs). Porphyromonas gingivalis (Pg) may be involved in the progression of periodontal disease. Mice exposed to a novel environment show hyperlocomotion that is inhibited by systemic administration of LPS derived from Escherichia coli (Ec-LPS). However, whether Pg-LPS influences novelty-induced locomotion is unknown. Accordingly, we carried out an open field test to analyse the effects of Pg-LPS. For comparison, effects of Ec-LPS were also studied. We additionally investigated the influence of systemic administration of Pg-LPS or Ec-LPS on IL-6, TNF-alpha, and IL-10 levels in blood, as they could be involved in the changes in locomotion. The TLR4 receptor antagonist TAK-242 was used to study the involvement of TLR4. Since Pg-LPS may block TLR4 in vitro, we analysed the effects of Pg-LPS on Ec-LPS-induced changes in behavioural and biochemical parameters. Male ddY mice were used. Pg- or Ec-LPS and TAK-242 were administered intraperitoneally. Ec-LPS (840 μg/kg), but not Pg-LPS (100, 500 and 840 μg/kg), inhibited novelty-induced locomotion, which was antagonized by TAK-242 (3.0 mg/kg). Ec-LPS (840 μg/kg) increased blood levels of IL-6 and IL-10, which were antagonized by TAK-242 (3.0 mg/kg). However, TAK-242 did not inhibit Ec-LPS-induced increases in TNF-alpha levels in blood. Pg-LPS (100, 500, and 840 μg/kg) did not alter blood IL-6, TNF-alpha, or IL-10 levels. The Ec-LPS-induced increase in blood IL-10, but not IL-6 and TNF-alpha, levels was inhibited by Pg-LPS (500 μg/kg). These results suggest that TLR4 stimulation mediates the inhibition of novel environment-induced locomotion in mice following systemic administration of Ec-LPS, while also increasing blood IL-6 and IL-10 levels. In contrast, Pg-LPS did not exhibit these effects. The present study also provides in vivo evidence that Pg-LPS can inhibit TLR4-mediated increases in blood levels of IL-10, a cytokine thought to prevent the development of periodontal disease.

A revisiting of "the hallmarks of aging" in domestic dogs: current status of the literature

A progressive decline in biological function and fitness is, generally, how aging is defined. However, in 2013, a description on the "hallmarks of aging" in mammals was published, and within it, it described biological processes that are known to alter the aging phenotype. These include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication (inflammation), and changes within the microbiome. This mini-review provides a detailed account of the progress on each of these hallmarks of aging in the domestic dog within the last 5 years. Additionally, when there are gaps in the literature between other mammalian species and dogs, I highlight the aging biomarkers that may be missing for dogs as aging models. I also argue for the importance of dog aging studies to include several breeds of dogs at differing ages and for age corrections for breeds with differing mean lifespans throughout.

MicroRNAs and Periodontal Disease: Helpful Therapeutic Targets?

Periodontal disease is the most common oral disease. This disease can be considered as an inflammatory disease. The immune response to bacteria accumulated in the gum line plays a key role in the pathogenesis of periodontal disease. In addition to immune cells, periodontal ligament cells and gingival epithelial cells are also involved in the pathogenesis of this disease. miRNAs which are small RNA molecules with around 22 nucleotides have a considerable relationship with the immune system affecting a wide range of immunological events. These small molecules are also in relation with periodontium tissues especially periodontal ligament cells. Extensive studies have been performed in recent years on the role of miRNAs in the pathogenesis of periodontal disease. In this review paper, we have reviewed the results of these studies and discussed the role of miRNAs in the immunopathogenesis of periodontal disease comprehensively. miRNAs play an important role in the pathogenesis of periodontal disease and maybe helpful therapeutic targets for the treatment of periodontal disease.

Inflammaging in domestic dogs: basal level concentrations of IL-6, IL-1β, and TNF-α in serum of healthy dogs of different body sizes and ages

Inflammaging, a "hallmark of aging," refers to a chronic, progressive increase in the proinflammatory status of mammals as they age, and this phenotype has been associated with many age-related diseases, including cardiovascular disease, arthritis and cancer. Though, inflammaging research is common in humans, there is a lack of data for this process for the domestic dog. Here, serum concentrations of IL-6, IL-1β and TNF-α in healthy dogs of different body sizes and ages were measured to determine whether inflammaging may play a mechanistic role in aging rates in dogs, similar to those found in humans. Using a four-way ANOVA, a significant decrease in IL-6 concentrations in young dogs with the rest of the age categories showing increased IL-6 concentrations was found, similar to humans. However, only young dogs have decreased IL-6 concentrations, with adult dogs having similar IL-6 concentrations to senior and geriatric dogs, implying differences in aging rates between humans and dogs. And, there was a marginally significant interaction between sex*spayed or neutered status and IL-1β concentrations with intact females having the lowest IL-1β concentrations compared with intact males, and spayed and neutered dogs. The presence of estrogen in intact females may, overall, decrease inflammatory pathways. This implies that age at spaying or neutering may be an important aspect to consider for inflammaging pathways in dogs. Furthermore, sterilized dogs often die of immune-related diseases, which could be linked to the increases in IL-1β in sterilized dogs found in this study.

Quantum dots bind nanosheet to promote nanomaterial stability and resist endotoxin-induced fibrosis and PM2.5-induced pneumonia

Endotoxin lipopolysaccharide (LPS) is a harmful substance commonly found in various environments that causes lung fibrosis. Exposure to PM2.5 also increases the risk of respiratory diseases. Through sulfur-carbon bonds and the edge S effect, GOQDs were used to bind in single-layer molybdenum disulfide (SLMoS2) nanosheets to synthesize SLMoS2@GOQDs heterojunction structures. GOQDs doping greatly increased the water solubility and stabilized of SLMoS2. SLMoS2@GOQDs with catalase-like activity protected cells from ultrastructural and cytomembrane damage and apoptosis induced by LPS. Moreover, the doping of GOQDs enhanced the escape of SLMoS2@GOQDs from cellular uptake and suppressed the release of Mo ions. Nanosheet-cell interface interactions that were regulated by quantum dots supported these positive effects. Immunofluorescence analysis and cell imaging confirmed that the nanomaterial protected against cell injury by regulating the canonical Wnt/β-catenin pathway and the secretion of relevant cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Moreover, SLMoS2@GOQDs also mitigated pneumonia caused by PM2.5 in vivo. Collectively, our findings not only provide a simple and effective approach to control lung diseases (caused by LPS or PM2.5), but also reveal the potential value of heterojunction materials in the fields of toxicology and human health, boosting the application of nanotechnology in the fields of ecotoxicology and environmental safety.

High Mobility Group Box 1 Protein in Osteoarthritic Knee Tissue and Chondrogenic Progenitor Cells: An Ex Vivo and In Vitro Study

OBJECTIVE

In osteoarthritis (OA), a loss of healthy cartilage extracellular matrix (ECM) results in cartilage degeneration. Attracting chondrogenic progenitor cells (CPCs) to injury sites and stimulating them toward chondrogenic expression profiles is a regenerative approach in OA therapy. High mobility group box 1 protein (HMGB1) is associated with chemoattractant and proinflammatory effects in various pathological processes. Here, we investigate the migratory effects of HMGB1 in knee OA and CPCs for the first time.

DESIGN

Immunohistochemistry, immunoblotting, and immunocytochemistry were performed to identify HMGB1 and its receptors, receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4) in OA knee tissue, chondrocytes, and CPCs. In situ hybridization for HMGB1 mRNA was performed in CPCs ex vivo. The chemoattractant effects of HMGB1 on CPCs were analyzed in cell migration assays.

RESULTS

HMGB1 expression in OA tissue and OA chondrocytes was higher than in healthy specimens and cells. HMGB1, RAGE, and TLR4 were expressed in CPCs and chondrocytes. In situ hybridization revealed HMGB1 mRNA in CPCs after migration into OA knee tissue, and immunohistochemistry confirmed HMGB1 expression at the protein level. Stimulation via HMGB1 significantly increased the migration of CPCs.

CONCLUSIONS

Our results show the chemoattractant role of HMGB1 in knee OA. HMGB1 is released by chondrocytes and has migratory effects on CPCs. These effects might be mediated via RAGE and TLR4. The in vitro and ex vivo results of this study need to be confirmed in vivo.

Cellular metabolism and IL-6 concentrations during stimulated inflammation in primary fibroblasts from small and large dog breeds as they age

The immune system undergoes marked changes during aging characterized by a state of chronic, low-grade inflammation termed 'inflammaging'. We explore this phenomenon in domestic dogs, which are the most morphologically and physiologically diverse group of mammals, with the widest range in body sizes for a single species. Additionally, smaller dogs tend to live significantly longer than larger dogs across all breeds. Body size is intricately linked to mass-specific metabolism and aging rates, which suggests that dogs are exemplary for studies in inflammaging. Dermal fibroblast cells play an important role in skin inflammation, making them a good model for inflammatory patterns across dog breed, body sizes and ages. Here, we examined aerobic and glycolytic cellular metabolism, and IL-6 concentrations in primary fibroblast cells isolated from small and large dog breeds, that were either recently born puppies or old dogs after death. We found no differences in cellular metabolism when isolated fibroblasts were treated with lipopolysaccharide (LPS) from Escherichia coli to stimulate an inflammatory phenotype. Unlike responses observed in mice and humans, there was a less drastic amplification of IL-6 concentration after LPS treatment in the geriatric population of dogs compared with recently born dogs. In young dogs, we also found evidence that untreated fibroblasts from large breeds had significantly lower IL-6 concentrations than observed for smaller breeds. This implies that the patterns of inflammaging in dogs may be distinct and different from other mammals commonly studied.

Unveiling Interindividual Variability of Human Fibroblast Innate Immune Response Using Robust Cell-Based Protocols

The LabEx Milieu Interieur (MI) project is a clinical study centered on the detailed characterization of the baseline and induced immune responses in blood samples from 1,000 healthy donors. Analyses of these samples has lay ground for seminal studies on the genetic and environmental determinants of immunologic variance in a healthy cohort population. In the current study we developed in vitro methods enabling standardized quantification of MI-cohort-derived primary fibroblasts responses. Our results show that in vitro human donor cohort fibroblast responses to stimulation by different MAMPs analogs allows to characterize individual donor immune-phenotype variability. The results provide proof-of-concept foundation to a new experimental framework for such studies. A bio-bank of primary fibroblast lines was generated from 323 out of 1,000 healthy individuals selected from the MI-study cohort. To study inter-donor variability of innate immune response in primary human dermal fibroblasts we chose to measure the TLR3 and TLR4 response pathways, both receptors being expressed and previously studied in fibroblasts. We established high-throughput automation compatible methods for standardized primary fibroblast cell activation, using purified MAMPS analogs, poly I:C and LPS that stimulate TLR3 and TLR4 pathways respectively. These results were in turn compared with a stimulation method using infection by HSV-1 virus. Our "Add-only" protocol minimizes high-throughput automation system variability facilitating whole process automation from cell plating through stimulation to recovery of cell supernatants, and fluorescent labeling. Images were acquired automatically by high-throughput acquisition on an automated high-content imaging microscope. Under these methodological conditions standardized image acquisition provided for quantification of cellular responses allowing biological variability to be measured with low system noise and high biological signal fidelity. Optimal for automated analysis of immuno-phenotype of primary human cell responses our method and experimental framework as reported here is highly compatible to high-throughput screening protocols like those necessary for chemo-genomic screening. In context of primary fibroblasts derived from donors enrolled to the MI-clinical-study our results open the way to assert the utility of studying immune-phenotype characteristics relevant to a human clinical cohort.

Porphyromonas gingivalis Mfa1 Induces Chemokine and Cell Adhesion Molecules in Mouse Gingival Fibroblasts via Toll-Like Receptors

Porphyromonas gingivalis Mfa1 fimbriae are thought to act as adhesion factors and to direct periodontal tissue destruction but their immunomodulatory actions are poorly understood. Here, we investigated the effect of Mfa1 stimulation on the immune and metabolic mechanisms of gingival fibroblasts from periodontal connective tissue. We also determined the role of Toll-like receptor (TLR) 2 and TLR4 in Mfa1 recognition. Mfa1 increased the expression of genes encoding chemokine (C-X-C motif) ligand (CXCL) 1, CXCL3, intercellular adhesion molecule (ICAM) 1 and Selectin endothelium (E) in gingival fibroblasts, but did not have a significant effect on genes that regulate metabolism. Mfa1-stimulated up-regulation of genes was significantly suppressed in Tlr4 siRNA-transfected cells compared with that in control siRNA-transfected cells, which indicates that recognition by TLR4 is essential for immunomodulation by Mfa1. Additionally, suppression of Tlr2 expression partially attenuated the stimulatory effect of Mfa1. Overall, these results help explain the involvement of P. gingivalis Mfa1 fimbriae in the progression of periodontal disease.

Chronic Exposure of Gingival Fibroblasts to TLR2 or TLR4 Agonist Inhibits Osteoclastogenesis but Does Not Affect Osteogenesis

Chronic exposure to periodontopathogenic bacteria such as Porphyromonas gingivalis and the products of these bacteria that interact with the cells of the tooth surrounding tissues can ultimately result in periodontitis. This is a disease that is characterized by inflammation-related alveolar bone degradation by the bone-resorbing cells, the osteoclasts. Interactions of bacterial products with Toll-like receptors (TLRs), in particular TLR2 and TLR4, play a significant role in this chronic inflammatory reaction, which possibly affects osteoclastic activity and osteogenic capacity. Little is known about how chronic exposure to specific TLR activators affects these two antagonistic activities. Here, we studied the effect of TLR activation on gingival fibroblasts (GF), cells that are anatomically close to infiltrating bacterial products in the mouth. These were co-cultured with naive osteoclast precursor cells (i.e., monocytes), as part of the peripheral blood mononuclear cells (PBMCs). Activation of GF co-cultures (GF + PBMCs) with TLR2 or TLR4 agonists resulted in a weak reduction of the osteoclastogenic potential of these cultures, predominantly due to TLR2. Interestingly, chronic exposure, especially to TLR2 agonist, resulted in increased release of TNF-α at early time points. This effect, was reversed at later time points, thus suggesting an adaptation to chronic exposure. Monocyte cultures primed with M-CSF + RANKL, led to the formation of bone-resorbing osteoclasts, irrespective of being activated with TLR agonists. Late activation of these co-cultures with TLR2 and with TLR4 agonists led to a slight decrease in bone resorption. Activation of GF with TLR2 and TLR4 agonists did not affect the osteogenic capacity of the GF cells. In conclusion, chronic exposure leads to diverse reactions; inhibitory with naive osteoclast precursors, not effecting already formed (pre-)osteoclasts. We suggest that early encounter of naive monocytes with TLR agonists may result in differentiation toward the macrophage lineage, desirable for clearing bacterial products. Once (pre-)osteoclasts are formed, these cells may be relatively insensitive for direct TLR stimulation. Possibly, TLR activation of periodontal cells indirectly stimulates osteoclasts, by secreting osteoclastogenesis stimulating inflammatory cytokines.

OmpA-like proteins of Porphyromonas gingivalis contribute to serum resistance and prevent Toll-like receptor 4-mediated host cell activation

Porphyromonas gingivalis possesses various abilities to evade and disrupt host immune responses, by which it acts as an important periodontal pathogen. P. gingivalis produces outer membrane protein A (OmpA)-like proteins (OmpALPs), Pgm6 and Pgm7, as major O-linked glycoproteins, but their pathological roles in P. gingivalis infection are largely unknown. Here, we report that OmpALP-deficient strains of P. gingivalis show an enhanced stimulatory activity in coculture with host cells. Such an altered ability of the OmpALP-deficient strains was found to be due to their impaired survival in coculture and the release of LPS from dead bacterial cells to stimulate Toll-like receptor 4 (TLR4). Further analyses revealed that the OmpALP-deficient strains were inviable in serum-containing media although they grew normally in the bacterial medium. The wild-type strain was able to grow in 90% normal human serum, while the OmpALP-deficient strains did not survive even at 5%. The OmpALP-deficient strains did not survive in heat-inactivated serum, but they gained the ability to survive and grow in proteinase K-treated serum. Of note, the sensitivity of the OmpALP-deficient strains to the bactericidal activity of human β-defensin 3 was increased as compared with the WT. Thus, this study suggests that OmpALPs Pgm6 and Pgm7 are important for serum resistance of P. gingivalis. These proteins prevent bacterial cell destruction by serum and innate immune recognition by TLR4; this way, P. gingivalis may adeptly colonize serum-containing gingival crevicular fluids and subgingival environments.

Periodontal infection with Porphyromonas gingivalis induces preterm birth and lower birth weight in rats

Preterm birth (PTB), accompanied by low birth weight (LBW) or not, is a syndrome with tremendous risk factors and long-term health consequences for children. In recent decades, overwhelming studies have shown that periodontitis contributes to prematurity and LBW. This study was conducted to determine the link between maternal periodontitis and the pathogenesis of PTB and/or LBW through a rat infection model induced by Porphyromonas gingivalis, an important periodontopathic bacterium. The murine model was established by surgically ligating the left mandibular first molars and inoculating with P. gingivalis, and then all female rats initiated mating 6 weeks post infection. The gestational day and birth weight were recorded, and blood, amniotic fluid, and placental specimens were collected. Rats with a PTB and LBW newborns were observed in the P. gingivalis-infected group. Additionally, P. gingivalis infection significantly increased the maternal serum levels of interferon-γ and interleukin-1β, whereas no significant difference in the cytokine response was observed in the amniotic fluid. Moreover, with the translocation of P. gingivalis to placentas, remarkable changes in gestational tissues were found, followed by significantly enhanced expression of Toll-like receptor 2 (TLR2) as well as Fas and Fas ligand (FasL). These results support the concept that severe cases of periodontitis caused by P. gingivalis infection may be indicative of rats being more susceptible to PTB/LBW, probably through the activation of the TLR2 and Fas/FasL pathways within the placental tissues. This study gave us new insight into how maternal periodontopathogens might be linked to placental damage and premature pathogenesis.

Angiopoietin-like protein 2 regulates Porphyromonas gingivalis lipopolysaccharide-induced inflammatory response in human gingival epithelial cells

Angiopoietin-like protein 2 (ANGPTL2) maintains tissue homeostasis by inducing inflammation and angiogenesis. It is produced in infiltrating immune cells or resident cells, such as adipocytes, vascular endothelial cells, and tumor cells. We hypothesized that ANGPTL2 might play an important role as a unique mediator in both systemic and periodontal disease. We demonstrated an increased ANGPTL2 concentration in gingival crevicular fluid from chronic periodontitis patients. Porphyromonas gingivalis lipopolysaccharide (LPS) treatment strongly induced ANGPTL2 mRNA and protein levels in Ca9-22 human gingival epithelial cells. Recombinant human ANGPTL2 increased interleukin 1β (IL-1β), IL-8, and tumor necrosis factor-α (TNF-α) mRNA and protein levels in Ca9-22 cells. Small-interfering (si)RNA-mediated ANGPTL2 knockdown in Ca9-22 cells reduced IL-1β, IL-8 and TNF-α mRNA and protein levels compared with control siRNA (p<0.01) in P. gingivalis LPS-stimulated Ca9-22 cells. Antibodies against integrin α5β1, an ANGPTL receptor, blocked induction of these inflammatory cytokines in P. gingivalis LPS-treated Ca9-22 cells, suggesting that secreted ANGPTL induces inflammatory cytokines in gingival epithelial cells via an autocrine loop. The classic sequential cascade of P. gingivalis LPS → inflammatory cytokine induction is well established. However, in the current study, we reveal a novel cascade comprising sequential P. gingivalis LPS → ANGPTL2 → integrin α5β1 → inflammatory cytokine induction, which might be responsible for inducing potent periodontal disorganization activity in gingival epithelial cells. Via this pathway, ANGPTL2 functions in the pathogenesis of periodontitis and contributes to prolonging chronic inflammation in patients with systemic disease.

MyD88/ERK/NFkB pathways and pro-inflammatory cytokines release in periodontal ligament stem cells stimulated by Porphyromonas gingivalis

The present study was aimed at investigating whether human Periodontal Ligament Stem Cells (hPDLSCs) were capable of sensing and reacting to lipopolysaccharide from Porphyromonas gingivalis (LPS-G) which is widely recognized as a major pathogen in the development and progression of periodontitis. At this purpose hPDLCs were stimulated with 5 μg/mL LPS-G at various times and the expression of toll-like receptor 4 (TLR4) was evaluated. Toll-like receptors (TLRs) play an essential role in innate immune signaling in response to microbial infections, and in particular TLR4, type-I transmembrane proteins, has been shown recognizing LPS-G. Our results put in evidence, in treated samples, an overexpression of TLR4 indicating that, hPDLSCs express a functional TLR4 receptor. In addition, LPS-G challenge induces a significant cell growth decrease starting from 24 h until 72 h of treatment. LPS-G leads the activation of the TLR4/MyD88 complex, triggering the secretion of proinflammatory cytokines cascade as: IL-1α, IL-8, TNF-α and β and EOTAXIN. Moreover, the upregulation of pERK/ERK signaling pathways and NFkB nuclear translocation was evident. On the basis of these observations, we conclude that hPDLSCs could represent an appropriate stem cells niche modeling leading to understand and evaluate the biological mechanisms of periodontal stem cells in response to LPS-G, mimicking in vitro an inflammatory process occurring in vivo in periodontal disease.

Microbiota, Immune Subversion, and Chronic Inflammation

Several host-adapted pathogens and commensals have evolved mechanisms to evade the host innate immune system inducing a state of low-grade inflammation. Epidemiological studies have also documented the association of a subset of these microorganisms with chronic inflammatory disorders. In this review, we summarize recent studies demonstrating the role of the microbiota in chronic inflammatory diseases and discuss how specific microorganisms subvert or inhibit protective signaling normally induced by toll-like receptors (TLRs). We highlight our work on the oral pathogen Porphyromonas gingivalis and discuss the role of microbial modulation of lipid A structures in evasion of TLR4 signaling and resulting systemic immunopathology associated with atherosclerosis. P. gingivalis intrinsically expresses underacylated lipid A moieties and can modify the phosphorylation of lipid A, leading to altered TLR4 signaling. Using P. gingivalis mutant strains expressing distinct lipid A moieties, we demonstrated that expression of antagonist lipid A was associated with P. gingivalis-mediated systemic inflammation and immunopathology, whereas strains expressing agonist lipid A exhibited modest systemic inflammation. Likewise, mice deficient in TLR4 were more susceptible to vascular inflammation after oral infection with P. gingivalis wild-type strain compared to mice possessing functional TLR4. Collectively, our studies support a role for P. gingivalis-mediated dysregulation of innate and adaptive responses resulting in immunopathology and systemic inflammation. We propose that anti-TLR4 interventions must be designed with caution, given the balance between the protective and destructive roles of TLR signaling in response to microbiota and associated immunopathologies.

Melatonin Receptor Agonists as the "Perioceutics" Agents for Periodontal Disease through Modulation of Porphyromonas gingivalis Virulence and Inflammatory Response

Aim

“Perioceutics” including antimicrobial therapy and host modulatory therapy has emerged as a vital adjunctive treatment of periodontal disease. Melatonin level was significantly reduced in patients with periodontal diseases suggesting melatonin could be applied as a potential “perioceutics” treatment of periodontal diseases. This study aims to investigate the effects of melatonin receptor agonists (melatonin and ramelteon) on Porphyromonas gingivalis virulence and Porphyromonas gingivalis-derived lipopolysaccharide (Pg-LPS)-induced inflammation.

Methods

Effects of melatonin receptor agonists on Porphyromonas gingivalis planktonic cultures were determined by microplate dilution assays. Formation, reduction, and viability of Porphyromonas gingivalis biofilms were detected by crystal violet staining and MTT assays, respectively. Meanwhile, biofilms formation was also observed by confocal laser scanning microscopy (CLSM). The effects on gingipains and hemolytic activities of Porphyromonas gingivalis were evaluated using chromogenic peptides and sheep erythrocytes. The mRNA expression of virulence and iron/heme utilization was assessed using RT-PCR. In addition, cell viability of melatonin receptor agonists on human gingival fibroblasts (HGFs) was evaluated by MTT assays. After pretreatment of melatonin receptor agonists, HGFs were stimulated with Pg-LPS and then release of cytokines (IL-6 and lL-8) was measured by enzyme-linked immunosorbent assay (ELISA).

Results

Melatonin and ramelteon did exhibit antimicrobial effects against planktonic culture. Importantly, they inhibited biofilm formation, reduced the established biofilms, and decreased biofilm viability of Porphyromonas gingivalis. Furthermore, they at sub-minimum inhibitory concentration (sub-MIC) concentrations markedly inhibited the proteinase activities of gingipains and hemolysis in a dose-dependent manner. They at sub-MIC concentrations significantly inhibited the mRNA expression of virulence factors (kgp, rgpA, rgpB, hagA, and ragA), while increasing the mRNA expression of ferritin (ftn) or hemolysin (hem). They did not show obvious cytotoxicity toward HGFs. They inhibited Pg-LPS-induced IL-6 and IL-8 secretion, which was reversed by luzindole, the melatonin receptor antagonist.

Conclusion

Melatonin receptor agonists can inhibit planktonic and biofilm growth of Porphyromonas gingivalis by affecting the virulent properties, as well as Pg-LPS-induced inflammatory response. Our study provides new evidence that melatonin receptor agonists might be useful as novel “perioceutics” agents to prevent and treat Porphyromonas gingivalis-associated periodontal diseases.

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.

Variability of the dendritic cell response triggered by different serotypes of Aggregatibacter actinomycetemcomitans or Porphyromonas gingivalis is toll-like receptor 2 (TLR2) or TLR4 dependent

BACKGROUND

Different serotypes of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis have been shown to induce differential dendritic cell (DC) responses. This study investigates whether cytokine and CC-chemokine receptor (CCR) production by DCs stimulated with different serotypes of A. actinomycetemcomitans or P. gingivalis is Toll-like receptor 2 (TLR2) and/or TLR4 dependent.

METHODS

DCs were obtained from healthy individuals and primed at a multiplicity of infection (MOI) of 10(2) with different A. actinomycetemcomitans or P. gingivalis serotypes in the presence or absence of anti-TLR2 or anti-TLR4 blocking antibodies. TLR2 and TLR4 expression, CCR5 and CCR6 expression, and interleukin (IL)-1β, IL-10, IL-12, and IL-23 expression and secretion were quantified by flow cytometry, real-time reverse-transcription polymerase chain reaction, and enzyme-linked immunosorbent assay.

RESULTS

When DCs were stimulated with serotype b of A. actinomycetemcomitans or serotype K1 of P. gingivalis, higher levels of TLR2 or TLR4, respectively, were detected compared to DCs stimulated with the other serotypes. Similarly, higher levels of cytokines and CCRs were detected in serotype b- or serotype K1-primed DCs compared to the others, and these increased levels positively correlated with levels of TLR2 or TLR4. When TLR2 signaling was blocked using a specific anti-TLR2 monoclonal antibody, serotype b-induced cytokine and CCR expression was inhibited; when TLR4 signaling was blocked, serotype K1-induced response was inhibited.

CONCLUSIONS

These results demonstrate that the variability of secretion of cytokines and expression of CCRs detected in DCs stimulated with different serotypes of A. actinomycetemcomitans or P. gingivalis is TLR2 or TLR4 dependent, respectively.

Toll-Like Receptors: A Key Marker for Periodontal Disease and Preterm Birth - A Contemporary Review

The receptors of the innate immune system have evolved to recognize pathogenic bacteria in a complex manner. Out of these immune receptors, the pattern recognition receptors (PRRs) such as Toll like receptors have gained importance off late to play a key role in the activation of cascade of inflammatory cytokines in pathogenesis of preterm birth. Preterm birth has become leading cause of neonatal deaths globally. The concept of oral infection influencing the occurrence of preterm delivery has gained importance. Translocation of periodontal pathogens and inflammatory mediators play role in the pathogenesis of preterm labour. The transmembrane toll like receptors of innate immunity have been recently implicated in the association of periodontal infection and preterm labour. The TLRs are considered as a key marker and TLR blockade can be a critical method for treating women who are exposed to periodontal pathogens. This review is aimed at discussing the role of TLR in periodontal disease and its relationship with preterm birth.

Do oral bacteria alter the regenerative potential of stem cells? A concise review

Mesenchymal stem cells (MSCs) are widely recognized as critical players in tissue regeneration. New insights into stem cell biology provide evidence that MSCs may also contribute to host defence and inflammation. In case of tissue injury or inflammatory diseases, e.g. periodontitis, stem cells are mobilized towards the site of damage, thus coming in close proximity to bacteria and bacterial components. Specifically, in the oral cavity, complex ecosystems of commensal bacteria live in a mutually beneficial state with the host. However, the formation of polymicrobial biofilm communities with pathogenic properties may trigger an inadequate host inflammatory-immune response, leading to the disruption of tissue homoeostasis and development of disease. Because of their unique characteristics, MSCs are suggested as crucial regulators of tissue regeneration even under such harsh environmental conditions. The heterogeneous effects of bacteria on MSCs across studies imply the complexity underlying the interactions between stem cells and bacteria. Hence, a better understanding of stem cell behaviour at sites of inflammation appears to be a key strategy in developing new approaches for in situ tissue regeneration. Here, we review the literature on the effects of oral bacteria on cell proliferation, differentiation capacity and immunomodulation of dental-derived MSCs.

Role of Toll-like receptor 4 signaling in cutaneous chronic graft-versus-host disease

Cutaneous damage is one of the characterized manifestations in chronic graft-versus-host disease (cGVHD). When local effective immunity in the skin is altered to a dysimmune reaction, cutaneous injuries occur. Toll-like receptor 4 signaling is regarded as a central mediator of inflammation and organ injury. In this study, we found that TLR4 mRNA in peripheral blood from patients with cutaneous cGVHD was markedly increased compared with that from non-GVHD patients and healthy controls. In addition, NF-κB expression, TLR4 downstream signaling, and TLR4-mediated cytokines, including IL-6 and ICAM-1, were upregulated. Moreover, ICAM-1 was widely distributed in skin biopsies from patients with cutaneous cGVHD. We also found that LPS induced TLR4-mediated NF-κB activation and IL-6 and ICAM-1 secretion in human fibroblasts in vitro. Thus, TLR4, NF-κB, IL-6, and ICAM-1 contribute to the inflammatory response that occurs in cutaneous cGVHD, indicating the TLR4 pathway may be a novel target for cutaneous cGVHD therapy.

High acid phosphatase level in the gingival tissues of periodontitis subjects

Aim:

Periodontitis is one of the major problems slowly progressing and could affect 70% of the global population. The prevalence of periodontitis differs from mild to moderate forms of race and geographic region. The aim of this study is to determine the acid phosphatase (ACP) activity in the gingival tissues of periodontitis subjects. In this study, the activity of ACP in the gingival tissue of subjects with periodontitis was examined.

Materials and Methods:

A total of 30 subjects were selected for the study and are divided into group I (n = 15, healthy subjects in control) and in group II (n = 15, periodontitis subjects). The gingival tissue from group I and group II subjects were collected after the surgery and the ACP enzyme level was analyzed using ultraviolet spectrophotometer. Assessment of periodontitis was done based on periodontal probing depth (PPD) and clinical attachment level (CAL). The statistical analysis applied was independent sample t-test, P < 0.05 was considered as significant.

Results:

The results of group II periodontitis subjects showed statistically significant increased gingival tissues ACP level when compared with the control group I subject. The mean levels of CAL and PPD were significantly >4 mm in periodontitis subjects when compared to control.

Conclusions:

The elevated level of ACP in the gingival tissue and Gram-negative microorganisms found in sub-gingival plaque was greater in periodontitis. Based on these results, gingival tissue ACP level can be considered as an independent risk factor for evaluating the microbial status and periodontal tissue damage.

Thrombospondin-1 production is enhanced by Porphyromonas gingivalis lipopolysaccharide in THP-1 cells

Periodontitis is a chronic inflammatory disease caused by gram-negative anaerobic bacteria. Monocytes and macrophages stimulated by periodontopathic bacteria induce inflammatory mediators that cause tooth-supporting structure destruction and alveolar bone resorption. In this study, using a DNA microarray, we identified the enhanced gene expression of thrombospondin-1 (TSP-1) in human monocytic cells stimulated by Porphyromonas gingivalis lipopolysaccharide (LPS). TSP-1 is a multifunctional extracellular matrix protein that is upregulated during the inflammatory process. Recent studies have suggested that TSP-1 is associated with rheumatoid arthritis, diabetes mellitus, and osteoclastogenesis. TSP-1 is secreted from neutrophils, monocytes, and macrophages, which mediate immune responses at inflammatory regions. However, TSP-1 expression in periodontitis and the mechanisms underlying TSP-1 expression in human monocytic cells remain unknown. Here using real-time RT-PCR, we demonstrated that TSP-1 mRNA expression level was significantly upregulated in inflamed periodontitis gingival tissues and in P. gingivalis LPS-stimulated human monocytic cell line THP-1 cells. TSP-1 was expressed via Toll-like receptor (TLR) 2 and TLR4 pathways. In P. gingivalis LPS stimulation, TSP-1 expression was dependent upon TLR2 through the activation of NF-κB signaling. Furthermore, IL-17F synergistically enhanced P. gingivalis LPS-induced TSP-1 production. These results suggest that modulation of TSP-1 expression by P. gingivalis plays an important role in the progression and chronicity of periodontitis. It may also contribute a new target molecule for periodontal therapy.

Different effects of P. gingivalis LPS and E. coli LPS on the expression of interleukin-6 in human gingival fibroblasts

OBJECTIVE

Gingival fibroblasts (GFs) produce pro-inflammatory cytokines in response to stimulation with lipopolysaccharide (LPS) of Porphyromonas gingivalis, which is thought to be mediated by activation of toll-like receptors (TLR)2 and TLR4. The present study investigated the expression of interleukin (IL)-6, TLR2, and TLR4 in GFs of seven different donors upon stimulation with P. gingivalis LPS. The effects of P. gingivalis LPS were compared with those of TLR4 agonist Escherichia coli LPS and TLR2 agonist Pam3CSK4.

MATERIALS AND METHODS

GFs were stimulated with P. gingivalis LPS, E. coli LPS or Pam3CSK4 and the expression of IL-6, TLR2 and TLR4 was measured by qPCR. The surface expression of TLR2 and TLR4 was measured by flow cytometry.

RESULTS

In GFs from three donors, P. gingivalis LPS and Pam3CSK4 induced a markedly lower increase in IL-6 expression than E. coli LPS. This was accompanied by significant down-regulation of the TLR2 and TLR4 expression. In GFs from another four donors, an increase in IL-6 expression upon stimulation with P. gingivalis LPS and Pam3CSK4 was similar or even higher than that induced by E. coli LPS. In GFs of these donors, all stimuli induced an up-regulation of both mRNA and protein expression of TLR2 and did not influence that of TLR4.

CONCLUSIONS

This study suggests that P. gingivalis LPS and E. coli LPS differently regulate cytokine production in human gingival fibroblasts. Regulation of the expression level of TLR2 and TLR4 by periodontal pathogens might be an important factor controlling the inflammatory response in GFs.

Aging and contribution of MyD88 and TRIF to expression of TLR pathway-associated genes following stimulation with Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Periodontal disease is a highly complex chronic inflammatory disease of the oral cavity. Multiple factors influence periodontal disease, including socio-economic status, genetics and age; however, inflammation elicited by the presence of specific bacteria in the subgingival space is thought to drive the majority of soft- and hard-tissue destruction. Porphyromonas gingivalis is closely associated with periodontal disease. Toll-like receptors (TLRs) and their intracellular signaling pathways play roles in the host response to P. gingivalis. The focus of the current study was to use microarray analysis to define the contributions of the TLR adaptor molecules myeloid differentiation factor 88 (MyD88) and Toll/interleukin-1 receptor domain-containing adaptor inducing interferon-beta (TRIF), and aging, on the expression of TLR pathway-associated mRNAs in response to P. gingivalis.

MATERIAL AND METHODS

Bone marrow-derived macrophages (BMØ) from wild-type (Wt), MyD88 knockout (MyD88-KO) and Trif(Lps2) [i.e. containing a point mutation in the lipopolysaccharide 2 (Lps2) gene rendering the Toll/interleukin (IL)-1 receptor domain-containing adaptor inducing interferon-beta (TRIF) protein nonfunctional] mice, at 2-and 12-mo of age, were cultured with P. gingivalis. Expression of genes in BMØ cultured with P. gingivalis was determined in comparison with expression of genes in BMØ cultured in medium only.

RESULTS

Using, as criteria, a twofold increase or decrease in mRNA expression, differential expression of 32 genes was observed when Wt BMØ from 2-mo-old mice were cultured with P. gingivalis compared with the medium-only control. When compared with 2-mo-old Wt mice, 21 and 12 genes were differentially expressed (p < 0.05) as a result of the mutations in MyD88 or TRIF, respectively. The expression of five genes was significantly (p < 0.05) reduced in Wt BMØ from 12-mo-old mice compared with those from 2-mo-old mice following culture with P. gingivalis. Age also influenced the expression of genes in MyD88-KO and Trif(Lps2) mice challenged with P. gingivalis.

CONCLUSIONS

Our results indicate that P. gingivalis induces differential expression of TLR pathway-associated genes, and both MyD88 and TRIF play roles in the expression of these genes. Age also played a role in the expression of TLR-associated genes following stimulation of BMØ with P. gingivalis.

MiRNA-181a regulates Toll-like receptor agonist-induced inflammatory response in human fibroblasts

MicroRNAs (miRNA) regulate the synthesis of cytokines in response to Toll-like receptor (TLR) activation. Our recent microarray study comparing normal and inflamed human dental pulps showed that miRNA-181 (miR-181) family is differentially expressed in the presence of inflammation. Prior studies have reported that the dental pulp, which is composed primarily of TLR4/2+ fibroblasts, expresses elevated levels of cytokines including Interleukin-8 (IL-8) when inflamed. In this study, we employed an in-vitro model to determine the role of the miRNA 181 family in the TLR agonist-induced response in human fibroblasts. TLR4/2+ primary human dental pulp fibroblasts were stimulated with lipopolysaccharide from Porphyromonas gingivalis (Pg LPS), a known oral pathogen, and IL-8 and miR-181 expression measured. An inversely proportional relationship between IL-8 and miR-181a was observed. In-silico analysis identified a miR-181a binding site on the 3′UTR of IL-8 which was confirmed by dual-luciferase assays. MiR-181a directly binds to the 3′UTR of IL-8, an important inflammatory component of the immune response, and modulates its levels. This is the very first report demonstrating miR-181a regulation of IL-8.

Analysis of Expression and Localization of TLR-2 by Immunofluorescent Technique in Healthy and Inflammed Oral Tissues

INTRODUCTION

Toll-like receptors (TLRs) are an important component of immune system. Among them, TLR-2 plays a dominant role in the oral tissues in initiating inflammation in chronic periodontitis. Not many studies have been done on quantitative expression of TLR-2 by using immunofluorescent techniques (IFT) in oral tissues. In this study, the expression and localisation of TLR-2 were detected in gingival tissues of chronic periodontitis patients and healthy individuals.

MATERIAL AND METHODS

Immuno Fluorescent Technique (IFT) was used for the expression and localization of TLR-2 in gingival tissue samples from 25 chronic periodontitis patients and from 25 healthy controls. Haematoxylin and Eosin staining was also done for all the samples to determine the histological characteristics of the gingival tissue samples.

RESULT

Both healthy and periodontitis gingival tissues expressed TLR-2. We found that the expression level of TLR-2 was higher in all the periodontitis patients than in healthy individuals. We also found out that the expression of TLR-2 was higher in the epithelial cells than in the connective tissue cells.

CONCLUSION

These data suggest a definite involvement of TLR-2 in initiating an inflammatory response in periodontal tissues. More studies are required to define the mechanisms and expression levels of TLR-2 in oral health and diseases.

Th2 cytokines efficiently stimulate periostin production in gingival fibroblasts but periostin does not induce an inflammatory response in gingival epithelial cells

OBJECTIVES

This study aims to clarify whether gingival fibroblasts produce periostin in response to Th2 cytokines which are elevated in periodontitis lesion and, if so, whether periostin affects the inflammatory response and matrix-protein metabolism.

DESIGN

Human gingival fibroblasts, periodontal ligament cells and the gingival epithelial cell line epi4 were stimulated with interleukin-4 (IL-4), IL-13, tumour necrosis factor-α (TNF-α) and Porphyromonas gingivalis lipopolysaccharide (LPS). Periostin expression was analysed by real-time polymerase chain-reaction (PCR) and Western blotting. The expression of the IL-4 receptor α-chain was evaluated by immunocytochemistry. The effect of periostin on the production of inflammatory cytokines and the expression of matrix protein-related genes was analysed by real-time PCR and enzyme-linked immunosorbent assay (ELISA).

RESULTS

While IL-4 and IL-13 significantly induced periostin production in gingival fibroblasts and periodontal ligament cells, no effect was observed in epi4 cells. No stimulatory effect of TNF-α or P. gingivalis LPS on the production of periostin was observed. The effect of periostin on the production of inflammatory cytokines was weak in gingival fibroblasts; however, little or no effect was observed on periodontal ligament cells or epi4 cells. No significant effect of periostin on the expression of matrix protein-related genes was found.

CONCLUSION

The results suggest that gingival fibroblasts may be a source of periostin in periodontitis lesions but periostin has only a limited role either in the inflammatory response or in matrix-protein metabolism. Thus, the role of periostin in the cellular interaction between epithelial and mesenchymal cells in gingiva may be distinct from that of skin.

Tetra- and penta-acylated lipid A structures of Porphyromonas gingivalis LPS differentially activate TLR4-mediated NF-κB signal transduction cascade and immuno-inflammatory response in human gingival fibroblasts

Background

Porphyromonas gingivalis is a major pathogen of periodontal disease that affects a majority of adults worldwide. Increasing evidence shows that periodontal disease is linked to various systemic diseases like diabetes and cardiovascular disease, by contributing to increased systemic levels of inflammation. Lipopolysaccharides (LPS), as a key virulent attribute of P. gingivalis, possesses significant amount of lipid A heterogeneity containing tetra- (LPS_1435/1449) and penta-acylated (LPS₁₆₉₀) structures. Hitherto, the exact molecular mechanism of P. gingivalis LPS involved in periodontal pathogenesis remains unclear, due to limited understanding of the specific receptors and signaling pathways involved in LPS-host cell interactions.

Methodology/Principal Findings

This study systematically investigated the effects of P. gingivalis LPS_1435/1449 and LPS₁₆₉₀ on the expression of TLR2 and TLR4 signal transduction and the activation of pro-inflammatory cytokines IL-6 and IL-8 in human gingival fibroblasts (HGFs). We found that LPS_1435/1449 and LPS₁₆₉₀ differentially modulated TLR2 and TLR4 expression. NF-κB pathway was significantly activated by LPS₁₆₉₀ but not by LPS_1435/1449. In addition, LPS₁₆₉₀ induced significant expression of NF-κB and p38 MPAK pathways-related genes, such as NFKBIA, NFKB1, IKBKB, MAP2K4 and MAPK8. Notably, the pro-inflammatory genes including GM-CSF, CXCL10, G-CSF, IL-6, IL-8 and CCL2 were significantly upregulated by LPS₁₆₉₀ while down-regulated by LPS_1435/1449. Blocking assays confirmed that TLR4-mediated NF-κB signaling was vital in LPS₁₆₉₀-induced expression of IL-6 and IL-8 in HGFs.

Conclusions/Significance

The present study suggests that the tetra- and penta-acylated lipid A structures of P. gingivalis LPS differentially activate TLR4-mediated NF-κB signaling pathway, and significantly modulate the expression of IL-6 and IL-8 in HGFs. The ability to alter the lipid A structure of LPS could be one of the strategies carried-out by P. gingivalis to evade innate host defense in gingival tissues, thereby contributing to periodontal pathogenesis.

Role of MyD88-dependent and MyD88-independent signaling in Porphyromonas gingivalis-elicited macrophage foam cell formation

Clinical studies and experimental modeling identify a potential link between periodontal disease and periodontal pathogens such as Porphyromonas gingivalis and atherosclerosis and formation of macrophage foam cells. Toll-like receptors and molecules governing their intracellular signaling pathways such as MyD88 play roles in atherosclerosis, as well as host response to P. gingivalis. The aim of this study was to define roles of MyD88 and TRIF during macrophage foam cell formation in response to P. gingivalis. In the presence of human low-density lipoprotein (LDL) mouse bone-marrow-derived macrophages (BMφ) cultured with P. gingivalis responded with significant reduction in tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The BMφ stained strongly with oil red O, regardless of whether bacterial challenge occurred concurrent with or before LDL treatment. Heat-killed P. gingivalis stimulated foam cell formation in a similar way to live bacteria. The BMφ from MyD88-knockout and Lps2 mice revealed a significant role for MyD88, and a minor role for TRIF in P. gingivalis-elicited foam cell formation. Porphyromonas gingivalis-elicited TNF-α and IL-6 were affected by MyD88 ablation and to a lesser extent by TRIF status. These data indicate that LDL affects the TNF-α and IL-6 response of macrophages to P. gingivalis challenge and that MyD88 and TRIF play important roles in P. gingivalis-elicited foam cell formation.

Porphyromonas gingivalis lipopolysaccharide regulates interleukin (IL)-17 and IL-23 expression via SIRT1 modulation in human periodontal ligament cells

Increased interleukin (IL)-17 and IL-23 levels exist in the gingival tissue of periodontitis patients, but the precise molecular mechanisms that regulate IL-17 and IL-23 production remain unknown. The aim of this study was to explore the role of SIRT1 signaling on Porphyromonas gingivalis lipopolysaccharide (LPS)-induced IL-17 and IL-23 production in human periodontal ligament cells (hPDLCs). IL-17 and IL-23 production was significantly increased in LPS-treated cells. LPS treatment also led to the upregulation of SIRT1 mRNA and protein expression. LPS-induced IL-17 and IL-23 upregulation was attenuated by pretreatment with inhibitors of phosphoinositide 3-kinase (PI3K), p38, extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase (MAPK), and NF-κB, as well as neutralizing antibodies against Toll-like receptors (TLRs) 2 and 4. Sirtinol treatment (a known SIRT1 inhibitor) or SIRT1 knockdown by small interfering RNA blocked LPS-stimulated IL-17 and IL-23 expression. Further investigation showed that LPS decreased osteoblast markers (i.e., ALP, OPN, and BSP) and concomitantly increased osteoclast markers (i.e., RANKL and M-CSF). This response was attenuated by inhibitors of the PI3K, p38, ERK, JNK, NF-κB, and SIRT1 pathways. These findings, for the first time, suggest that human periodontopathogen P. gingivalis LPS is implicated in periodontal disease bone destruction and may mediate IL-17 and IL-23 release from hPDLCs. This process is dependent, at least in part, on SIRT1-Akt/PI3K-MAPK-NF-κB signaling.

Lipopolysaccharide and hypoxia-induced HIF-1 activation in human gingival fibroblasts

BACKGROUND

We previously reported that chronic periodontal inflammation causes the accumulation of the transcriptional activator hypoxia-inducible factor-1α (HIF-1α) in human gingival fibroblasts (HGFs) in vivo. Here, evidence is provided that bacterial lipopolysaccharides (LPS) and cellular hypoxia, both associated with periodontitis, can individually, or in combination, lead to the accumulation and activation of HIF-1 in HGF in vitro.

METHODS

Primary gingival fibroblasts were cultured from human gingival biopsies. HIF-1α peptide from HGFs treated with Escherichia coli LPS under normoxia or hypoxia was detected by nuclear protein extraction, immunoprecipitation, immunoblotting, and immunocytofluorescence. HIF-1α transcripts were detected using reverse transcription polymerase chain reaction (PCR). The transcript expression levels of vascular endothelial growth factor-A (VEGF-A), a downstream gene of HIF-1α, were assessed by quantitative real-time PCR.

RESULTS

Two HIF-1α splicing transcription variants were found to be constitutively expressed in HGFs. E. coli LPS induced a dose- and time-dependent nuclear accumulation of HIF-1α peptide in HGFs. This accumulation could be attenuated by treatment with a Toll-like receptor 4 (TLR4)-neutralizing antibody. Under hypoxia, LPS further increased HIF-1α accumulation in HGFs. VEGF-A transcript expression was upregulated by LPS under both normoxia and hypoxia but was downregulated by pretreatment with TLR4-neutralizing antibody or the specific HIF-1α inhibitor 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole.

CONCLUSION

LPS induces the nuclear accumulation of HIF-1α in HGFs and induces HIF-1 biologic activity under normoxia or hypoxia possibly through TLR4.

Toll-like receptors and their dual role in periodontitis: a review

Innate immunity is the first line of host defense and represents inherited resistance to infection. Innate immunity works through toll-like receptors (TLRs), which recognize the conserved molecular patterns on pathogenic bacteria known as pathogen-associated molecular patterns. The periodontium is a unique environment in which oral microorganisms are in constant contact with the host immune system. The TLRs present on gingival epithelial cells are continuously stimulated, resulting in production of cytokines and defensins that help to maintain oral health. If the epithelial barrier is breached, allowing invasion of bacteria into the underlying connective tissue, the TLRs on other resident and non-resident cells of the periodontium become activated. This leads to an exaggerated release of pro-inflammatory cytokines and other biological mediators, which may cause host tissue destruction. The present review examines the role of TLRs and their signaling in periodontal health and disease.

Expression of toll-like receptors 2, 4 and 9 is increased in gingival tissue from patients with type 2 diabetes and chronic periodontitis

BACKGROUND AND OBJECTIVE

Broad evidence indicates that diabetes both increases the risk and hastens the progression of periodontal disease. Likewise, chronic inflammation or infections seem to provoke insulin resistance and thereby contribute to the development of diabetes and its complications. Innate immune responses, which appear to be altered in individuals with diabetes, are usually mediated by the recognition of pathogens through toll-like receptors (TLRs). The constitutive expression of some TLRs has been reported in healthy human gingival tissue. Interestingly, the expression of TLRs 2 and 4 is increased with the severity of periodontal disease. Considering that the inflammatory reaction is exacerbated in individuals with diabetes and periodontitis, we suspected that the expression of some TLRs might be increased in gingival tissue in these patients.

MATERIAL AND METHODS

In this study, we analyzed, by immunofluorescence, the expression of TLRs 2, 3, 4 and 9 in gingival tissues from healthy individuals and from periodontal patients with or without type 2 diabetes.

RESULTS

We found that the expression levels of TLRs 2, 3, 4 and 9 were higher in all periodontal patients than in healthy individuals. The expression of some TLRs was increased in subjects with periodontitis and diabetes relative to subjects with periodontitis but without diabetes; this increase in expression was found particularly in TLR2 and TLR9 in the connective tissue and in TLR4 at the epithelial region.

CONCLUSION

These data suggest that the expression of these TLRs 2, 3, 4 and 9 in gingival tissue is higher in individuals with diabetes because its inflammatory reaction is exacerbated. Additionally, the expression of these TLRS is positively regulated with the severity of periodontal disease.

Increased expression of C-reactive protein gene in inflamed gingival tissues could be derived from endothelial cells stimulated with interleukin-6

BACKGROUND

Epidemiological studies have suggested periodontitis as a risk factor for ischemic heart disease. High sensitive C-reactive protein (hs-CRP), a predictor of cardiovascular risk, is elevated in periodontitis patients. Therefore, local infection-induced elevation of systemic CRP could account for the relationship between the 2 diseases. However, the underlying mechanism of CRP production in the periodontal tissues has not been fully elucidated. Therefore, the aim of the present study was to clarify the mechanism of CRP production in periodontal tissues.

METHODS

Gene expression of CRP in gingival biopsies was analysed by quantitative PCR. Human gingival epithelial cells (HGECs), human gingival fibroblasts (HGFBs), and human coronary artery endothelial cells (HCAECs) were characterized for CRP-producing ability by incubating with interleukin (IL)-1β, IL-6, soluble IL-6 receptor (sIL-6R), and Porphyromonas gingivalis strain W83.

RESULTS

Gene expression of CRP is significantly elevated in periodontitis lesions compared with gingivitis lesions. HCAECs, but not HGECs and HGFBs, produced CRP in response to IL-6 and IL-1β in the presence of sIL-6R. In contrast to IL-6, the effect of IL-1β on CRP production was indirect via induction of IL-6. IL-1β was produced by HGECs and HGFBs with stimulation of P. gingivalis antigens.

CONCLUSION

These results suggest that CRP induced locally by periodontal infection may play another role in the pathogenesis of periodontal disease, and to a much lesser extent, has the potential to modulate systemic CRP level by extra-hepatic CRP production.

Macrophages from IBD patients exhibit defective tumour necrosis factor-α secretion but otherwise normal or augmented pro-inflammatory responses to infection

Defects in macrophage function have been implicated in the establishment of Crohn's disease (CD). However, the response of macrophages from CD patients to live bacteria, particularly Mycobacterium avium subsp. paratuberculosis (MAP), has not been addressed. Considering MAP has long been associated to CD, our objective was to assess whether macrophages from CD patients showed impaired inflammatory response to infection by MAP comparing to M. avium subsp. avium (MA) and other live intestinal commensal bacteria. Human peripheral blood monocyte-derived macrophages were obtained from CD patients, ulcerative colitis (UC) patients and controls. Following in vitro infection with MAP, MA, Escherichia coli or Enterococcus faecalis, cytokine levels and cell surface receptor expression were evaluated at different time points. Macrophages from CD patients showed impaired TNF-α secretion in response to bacterial challenge, but augmented IL-23 secretion and preserved IL-12 secretion and CD-40 expression. In addition, CD macrophages showed low IL-10 secretion. Macrophages from IBD patients showed increased expression of TLR-2 and -4, unaffected by infection. Differences in cytokine secretion observed after bacterial challenge were not MAP-specific, as other bacteria (E. coli and MA) showed similar effects. Macrophages from UC patients showed a less compromised TNF-α synthesis in response to mycobacterial infection than CD macrophages, with increased constitutive IL-12 secretion, and preserved IL-10 secretion. The increased IL-23 levels in response to infection and decreased IL-10 production observed in macrophages from CD patients may contribute to the inflammatory exacerbation observed in those patients.