Porphyromonas gingivalis, gamma interferon, and a proapoptotic fibronectin matrix form a synergistic trio that induces c-Jun N-terminal kinase 1-mediated nitric oxide generation and cell death

Cystatin C: immunoregulation role in macrophages infected with Porphyromonas gingivalis

Background

Periodontitis is a chronic infectious disease, characterized by an exacerbated inflammatory response and a progressive loss of the supporting tissues of the teeth. Porphyromonas gingivalis is a key etiologic agent in periodontitis. Cystatin C is an antimicrobial salivary peptide that inhibits the growth of P. gingivalis. This study aimed to evaluate the antimicrobial activity of this peptide and its effect on cytokine production, nitric oxide (NO) release, reactive oxygen species (ROS) production, and programmed cell death in human macrophages infected with P. gingivalis.

Methods

Monocyte-derived macrophages generated from peripheral blood were infected with P. gingivalis (MOI 1:10) and stimulated with cystatin C (2.75 µg/ml) for 24 h. The intracellular localization of P. gingivalis and cystatin C was determined by immunofluorescence and transmission electron microscopy (TEM). The intracellular antimicrobial activity of cystatin C in macrophages was assessed by counting Colony Forming Units (CFU). ELISA assay was performed to assess inflammatory (TNFα, IL-1β) and anti-inflammatory (IL-10) cytokines. The production of nitrites and ROS was analyzed by Griess reaction and incubation with 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), respectively. Programmed cell death was assessed with the TUNEL assay, Annexin-V, and caspase activity was also determined.

Results

Our results showed that cystatin C inhibits the extracellular growth of P. gingivalis. In addition, this peptide is internalized in the infected macrophage, decreases the intracellular bacterial load, and reduces the production of inflammatory cytokines and NO. Interestingly, peptide treatment increased ROS production and substantially decreased bacterial-induced macrophage apoptosis.

Conclusions

Cystatin C has antimicrobial and immuno-regulatory activity in macrophages infected with P. gingivalis. These findings highlight the importance of understanding the properties of cystatin C for its possible therapeutic use against oral infections such as periodontitis.

NCOA4-mediated ferritinophagy promoted inflammatory responses in periodontitis

BACKGROUND/OBJECTIVES

Iron homeostasis plays a crucial role in the combat against pathogen invasion. Ferrous iron can trigger generous production of reactive oxygen species (ROS) by Fenton reaction. Nuclear receptor coactivator 4 (NCOA4), a selective cargo receptor to deliver ferritin to lysosome, may trigger release of ferritin-bound iron into the cytosol. The aim of the present study was to explore whether NCOA4-mediated ferritinophagy participated in the pathogenesis of periodontitis, and its role in promoting the periodontal inflammation.

METHODS

Inflamed and healthy periodontal tissues were harvested for immunobiological staining of ferritinophagy-related genes in the periodontal tissues, while real-time quantitative PCR (qPCR) was utilized to detect mRNA transcription. Periodontal ligament fibroblasts (PDLFs) were isolated and infected with Porphyromonas gingivalis. The mRNA transcription and protein expression of genes involved in the iron metabolism, including NCOA4, transferrin receptor 1 (TFR1), and ferroportin (SLC40A1) were detected by qPCR and western blot. Levels of labile iron pool and ROS production were detected by flow cytometry and confocal endoscopy. Small interference RNA was utilized to knock down NCOA4.

RESULTS

Elevated expression of NCOA4, ferritin heavy chain, and light chain were observed in the diseased periodontal tissues. P. gingivalis infection promoted expression of TFR1, NCOA4, and microtubule-associated protein 1-light chain 3 B (LC3B), enhanced levels of intracellular labile iron pool and ROS production. NCOA4 knockdown reduced ROS generation in PDLFs in response to P. gingivalis and mitigated production of pro-inflammatory monocyte chemoattractant protein-1 and interleukin 6. P. gingivalis triggered activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase signaling pathway. In addition, inhibitors of JNK, SP600125, and inhibitors of p38, SB203580 blocked NCOA4 transcription.

CONCLUSION

NCOA4-ferritinophagy participated in the progress of periodontitis progression. P. gingvalis-triggered ferritinophagy aggravated production of ROS and inflammatory responses in PDLFS. These findings suggest iron homeostasis plays an important role in the pathogenesis of periodontitis.

Investigation of Antibacterial and Antiinflammatory Activities of Proanthocyanidins from Pelargonium sidoides DC Root Extract

The study explores antibacterial, antiinflammatory and cytoprotective capacity of Pelargonium sidoides DC root extract (PSRE) and proanthocyanidin fraction from PSRE (PACN) under conditions characteristic for periodontal disease. Following previous finding that PACN exerts stronger suppression of Porphyromonas gingivalis compared to the effect on commensal Streptococcus salivarius, the current work continues antibacterial investigation on Staphylococcus aureus, Staphylococcus epidermidis, Aggregatibacter actinomycetemcomitans and Escherichia coli. PSRE and PACN are also studied for their ability to prevent gingival fibroblast cell death in the presence of bacteria or bacterial lipopolysaccharide (LPS), to block LPS- or LPS + IFNγ-induced release of inflammatory mediators, gene expression and surface antigen presentation. Both PSRE and PACN were more efficient in suppressing Staphylococcus and Aggregatibacter compared to Escherichia, prevented A. actinomycetemcomitans- and LPS-induced death of fibroblasts, decreased LPS-induced release of interleukin-8 and prostaglandin E2 from fibroblasts and IL-6 from leukocytes, blocked expression of IL-1β, iNOS, and surface presentation of CD80 and CD86 in LPS + IFNγ-treated macrophages, and IL-1β and COX-2 expression in LPS-treated leukocytes. None of the investigated substances affected either the level of secretion or expression of TNFα. In conclusion, PSRE, and especially PACN, possess strong antibacterial, antiinflammatory and gingival tissue protecting properties under periodontitis-mimicking conditions and are suggestable candidates for treatment of the disease.

Treponema denticola increases MMP-2 expression and activation in the periodontium via reversible DNA and histone modifications

Host-derived matrix metalloproteinases (MMPs) and bacterial proteases mediate destruction of extracellular matrices and supporting alveolar bone in periodontitis. The Treponema denticola dentilisin protease induces MMP-2 expression and activation in periodontal ligament (PDL) cells, and dentilisin-mediated activation of pro-MMP-2 is required for cellular fibronectin degradation. Here, we report that T. denticola regulates MMP-2 expression through epigenetic modifications in the periodontium. PDL cells were treated with epigenetic enzyme inhibitors before or after T. denticola challenge. Fibronectin fragmentation, MMP-2 expression, and activation were assessed by immunoblot, zymography, and qRT-PCR, respectively. Chromatin modification enzyme expression in T. denticola-challenged PDL cells and periodontal tissues were evaluated using gene arrays. Several classes of epigenetic enzymes showed significant alterations in transcription in diseased tissue and T. denticola-challenged PDL cells. T. denticola-mediated MMP-2 expression and activation were significantly reduced in PDL cells treated with inhibitors of aurora kinases and histone deacetylases. In contrast, DNA methyltransferase inhibitors had little effect, and inhibitors of histone acetyltransferases, methyltransferases, and demethylases exacerbated T. denticola-mediated MMP-2 expression and activation. Chronic epigenetic changes in periodontal tissues mediated by T. denticola or other oral microbes may contribute to the limited success of conventional treatment of chronic periodontitis and may be amenable to therapeutic reversal.

Arthritic role of Porphyromonas gingivalis in collagen-induced arthritis mice

Epidemiological studies show an association between rheumatoid arthritis (RA) and periodontal disease. Porphyromonas gingivalis (P.gingivalis) is a well-known pathogen in periodontitis. This study investigated the pathogenic effects of P.gingivalis on autoimmune arthritis in vivo. Collagen-induced arthritis (CIA) mice were intraperitoneally injected with W83 and 2561 strains of P.gingivalis. Infection with P.gingivalis exacerbated arthritis score in CIA mice. Synovial inflammation and bone destruction in CIA mice infected with P.gingivalis were more severe than in uninfected CIA mice. Both W83 and 2561 strains were more pro-arthritic after arthritis symptom was fully activated. Interestingly, only W83 strain was arthritogenic before autoimmune reaction initiated. Citrullination was detected in synovial tissue of CIA mice and CIA mice inoculated with P.gingivalis, but not in normal control mice. The citrullinated area was greater in P.gingivalis-infected CIA mice than in non-infected CIA mice. This study showed that P.gingivalis exacerbated disease in a mouse model of autoimmune arthritis and increased the expression of citrullinated antigens in the synovium. The arthritogenic effects of P.gingivalis were at least in part, dependent upon the bacterial strain with or without fimbriae expression, route and time of infection. P.gingivalis-mediated citrullination may explain the possible link between periodontal disease and RA.

Shedding of NG2 by MMP-13 attenuates anoikis

Disruption of cell-matrix interactions can lead to anoikis-apoptosis due to loss of matrix contacts. We previously showed that Nerve/glial antigen 2 (NG2) is a novel anoikis receptor. Specifically, overexpression of NG2 leads to anoikis propagation, whereas its suppression leads to anoikis attenuation. Interestingly, NG2 expression decreases in late anoikis, suggesting that NG2 reduction is also critical to this process. Thus, we hypothesized that NG2 undergoes cleavage to curtail anoikis propagation. Further, since matrix metalloproteinases (MMPs) cleave cell surface receptors, play a major role in modulating apoptosis, and are associated with death receptor cleavage during apoptosis, we further hypothesized that cleavage of NG2 could be mediated by MMPs to regulate anoikis. Indeed, anoikis conditions triggered release of the NG2 extracellular domain into condition media during late apoptosis, and this coincided with increased MMP-13 expression. Treatment with an MMP-13 inhibitor and MMP-13 siRNA increased anoikis, since these treatments blocked NG2 release. Further, NG2-positive cells exhibited increased anoikis upon MMP-13 inhibition, whereas MMP-13 inhibition did not increase anoikis in NG2-null cells, corroborating that retention of NG2 on the cell membrane is critical for sustaining anoikis, and its cleavage for mediating anoikis attenuation. Similarly, NG2 suppression with siRNA inhibited NG2 release and anoikis. In contrast, MMP-13 overexpression or exogenous MMP-13 reduced anoikis by more effectively shedding NG2. In conclusion, maintenance of NG2 on the cell surface promotes anoikis propagation, whereas its shedding by MMP-13 actions attenuates anoikis. Given that these findings are derived in the context of periodontal ligament fibroblasts, these data have implications for periodontal inflammation and periodontal disease pathogenesis.

Detection of key enzymes, free radical reaction products and activated signaling molecules as biomarkers of cell damage induced by benzo[a]pyrene in human keratinocytes

Benzo[a]pyrene (BaP) is a known carcinogenic and cell damaging agent. The underlying cell damaging pathomechanisms have not been totally revealed. Especially BaP-related induction of oxidative and nitrosative stress has not been previously investigated in detail. The presented study investigated these effects in order to elucidate the pathomechanism and as well to identify potential biological markers that may indicate a BaP exposure. Human immortalized keratinocytes (HaCaT cells) were exposed to BaP (1 μM) for either 5 min or 6 h, respectively. BaP-induced cellular damage was evaluated by immunocytochemistry analysis of multiple signaling cascades (e.g. apoptosis, Akt, MAPK, NOS, nitrotyrosine and 8-isoprostane formation), detection of nitrosative stress using diaminofluorescein (DAF-FM) and oxidative stress using 3' -(p-aminophenyl)fluorescein (APF). Our results show that BaP exposure significantly enhanced NO and ROS productions in HaCaT cells. BaP led to eNOS-phosphorylation at Ser(1177), Thr(495) and Ser(116) residues. Using specific inhibitors, we found that the Erk1/2 pathways seemed to have strong impact on eNOS phosphorylation. In addition, BaP-induced apoptosis was observed by caspase-3 activation and PARP cleavage. Our results suggest that BaP mediates its toxic effect in keratinocytes through oxidative and nitrosative stress which is accompanied by complex changes of eNOS phosphorylation and changes of Akt and MAPK pathways.

CCL3 and CXCL12 production in vitro by dental pulp fibroblasts from permanent and deciduous teeth stimulated by Porphyromonas gingivalis LPS

OBJECTIVE

The aim of this study was to compare the production of the chemokines CCL3 and CXCL12 by cultured dental pulp fibroblasts from permanent (PDPF) and deciduous (DDPF) teeth under stimulation by Porphyromonas gingivalis LPS (PgLPS).

MATERIAL AND METHODS

Primary culture of fibroblasts from permanent (n=3) and deciduous (n=2) teeth were established using an explant technique. After the fourth passage, fibroblasts were stimulated by increasing concentrations of PgLPS (0-10 µg/mL) at 1, 6 and 24 h. The cells were tested for viability through MTT assay, and production of the chemokines CCL3 and CXCL12 was determined through ELISA. Comparisons among samples were performed using One-way ANOVA for MTT assay and Two-way ANOVA for ELISA results.

RESULTS

Cell viability was not affected by the antigen after 24 h of stimulation. PgLPS induced the production of CCL3 by dental pulp fibroblasts at similar levels for both permanent and deciduous pulp fibroblasts. Production of CXCL12, however, was significantly higher for PDPF than DDPF at 1 and 6 h. PgLPS, in turn, downregulated the production of CXCL12 by PDPF but not by DDPF.

CONCLUSION

These data suggest that dental pulp fibroblasts from permanent and deciduous teeth may present a differential behavior under PgLPS stimulation.

Priming effect of fibronectin fragments on the macrophage inflammatory response: potential contribution to periodontitis

Fibronectin, an extracellular matrix component, is a substrate for multiple host and bacterial proteinases found in inflamed periodontal sites. In the present study, we investigated the potential contribution of various fibronectin fragments to the inflammatory process of periodontitis. Our results showed that the smaller fragments of fibronectin (30 and 45 kDa) were the most potent inflammatory inducers as they dose-dependently increased the secretion of TNF-α, IL-1β, and IL-8 by human macrophages. The 120-kDa fragment did not induce the secretion of all the cytokines tested, while intact fibronectin only increased IL-8 secretion and to a lesser extent TNF-α secretion. Cytokine secretion was associated with increased amounts of phosphorylated ERK1/2, JNK2, and p38α MAPK in treated macrophages. The combination of fibronectin or fibronectin fragments with Porphyromonas gingivalis lipopolysaccharide had an additive effect, but no synergism appeared to occur. It was also demonstrated that gingival crevicular fluid samples recovered from patients with moderate to severe periodontitis contained more fibronectin fragments than samples obtained from healthy subjects. Finally, both Arg- and Lys-gingipains purified from P. gingivalis were found to modulate fibronectin fragmentation. In conclusion, we showed that specific fibronectin fragments that may be present in diseased periodontal sites may contribute to maintaining and amplifying the inflammatory state and that P. gingivalis gingipains may be involved in the production of these fragments.

Neutrophils in periodontal inflammation

Neutrophils (also called polymorphonuclear leukocytes) are the most abundant leukocytes whose primary purpose as anti-microbial professional phagocytes is to kill extracellular pathogens. Neutrophils and macrophages are phagocytic cell types that along with other cells effectively link the innate and adaptive arms of the immune response, and help promote inflammatory resolution and tissue healing. Found extensively within the gingival crevice and epithelium, neutrophils are considered the key protective cell type in the periodontal tissues. Histopathology of periodontal lesions indicates that neutrophils form a 'wall' between the junctional epithelium and the pathogen-rich dental plaque which functions as a robust anti-microbial secretory structure and as a unified phagocytic apparatus. However, neutrophil protection is not without cost and is always considered a two-edged sword in that overactivity of neutrophils can cause tissue damage and prolong the extent and severity of inflammatory periodontal diseases. This review will cover the innate and inflammatory functions of neutrophils, and describe the importance and utility of neutrophils to the host response and the integrity of the periodontium in health and disease.

Reduction in lipopolysaccharide-induced apoptosis of fibroblasts obtained from a patient with gingival overgrowth during nifedipine-treatment

OBJECTIVE

We have previously demonstrated that the mechanism of nifedipine (NIF)-induced gingival overgrowth is related to the observation that proliferation and cell cycle progression of gingival fibroblasts derived from NIF reactive patient (NIFr) are greater than those from NIF non-reactive patient (NIFn). Gingival overgrowth has also been reported to be a result of inhibited apoptosis of gingival fibroblasts. Apoptosis in fibroblasts is induced by lipopolysaccharide (LPS). Thus, we focused upon evaluating whether there is a difference in LPS-induced apoptosis between NIFn and NIFr.

METHODS

Both NIFn and NIFr were arrested in DMEM containing 0.5% FBS, stimulated by LPS, and assayed for apoptosis, cell cycle analysis, Western blotting, and caspase activity.

RESULTS

Compared to NIFn, the number of apoptotic cells was significantly decreased and the percentage of cells in S and G(2)/M phase was significantly increased in NIFr. The levels of Bax and cytochrome c proteins in NIFr were not up-regulated by LPS compared with NIFn. Both NIFn and NIFr displayed the following changes in protein expression: increased Bad, decreased Bcl-xL, and unchanged Bcl-2 and p53. Caspase-3 and -9 activities were significantly increased by LPS in NIFn but were unchanged in NIFr. Caspase-2 activity remained constant whilst caspase-8 activity significantly increased upon LPS treatment in both NIFn and NIFr.

CONCLUSION

Bad, Bax, cytochrome c, p53, and caspases-2, -3, -8, and -9 are pro-apoptotic proteins. Bcl-2 and Bcl-xL are anti-apoptotic proteins. Thus, the mechanism of NIF-induced gingival overgrowth might be related to decreased apoptosis in NIFr through a reduction of Bax, cytochrome c, and caspase-3 and -9.

Rheumatoid arthritis and the role of oral bacteria

Rheumatoid arthritis (RA) and periodontal disease (PD) have shown similar physiopathologic mechanisms such as chronic inflammation with adjacent bone resorption in an immunogenetically susceptible host; however, PD has a well-recognized bacterial etiology while the cause of RA is unclear. Some reports have indicated that an infectious agent in a susceptible host could be one possible trigger factor for RA, and it has been suggested that oral microorganisms, specialty periodontal bacteria could be the infectious agent (mainly Porphyromonas gingivalis). It has been reported that PD is more frequent and more severe in patients with RA, suggesting a positive association between both diseases. There have been reports regarding the detection of antibodies against periodontal bacteria while other studies have identified periodontal bacterial DNA in serum and synovial fluid of RA patients and have explored the possible pathways of transport of periodontal bacterial DNA. In conclusion, there is no question that RA and PD have pathologic features in common and there is strong evidence of an association between both diseases, but further studies, including experimental models, are needed to demonstrate the arthritogenicity of oral microorganisms.

Effects of sappanchalcone on the cytoprotection and anti-inflammation via heme oxygenase-1 in human pulp and periodontal ligament cells

Sappanchalcone has been demonstrated to possess several biological effects. However, the molecular mechanism underlying these effects is not fully understood. In this study, we examined the effects of sappanchalcone on hydrogen peroxide (H(2)O(2))-induced cytotoxicity using human dental pulp (HDP) cells, and lipopolysaccharide (LPS)-induced inflammation using human periodontal ligament (HPDL) cells. Sappanchalone concentration proportionately increased heme oxygenase (HO)-1 protein expression and enzyme activity in both HDP and HPDL cells. It also protected HDP cells from H(2)O(2)-induced cytotoxicity and reactive oxygen species production. The cytoprotective effect of sappanchalcone was nullified by HO-1 inhibitor, Tin protoporphyrin (SnPP). Sappanchalcone is seen to inhibit LPS-stimulated nitric oxide (NO), prostaglandin E(2) (PGE(2)), interlukine-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interlukine-6 (IL-6) and interlukine-12 (IL-12) release in addition to inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in HPDL cells. SnPP, a specific inhibitor of HO-1, partly blocked sappanchalcone mediated suppression of inflammatory mediator production, in LPS-stimulated HPDL cells. HDP and HPDL cells treated with sappanchalcone exhibited the transient activation of c-Jun NH2-terminal kinase (JNK) and NF-E2-related factor-2 (Nrf2). The expression of HO-1 protein by sappanchalcone was significantly reduced by pretreatment with JNK inhibitor. In conclusion, induction of HO-1 is an important cytoprotective mechanism by which sappanchalcone protects HDP cells from H(2)O(2) and in addition it also exhibits anti-inflammatory effects in LPS-stimulated HPDL cells. Thus, sappanchalcone could potentially be a therapeutic approach for periodontal, pulpal and periapical inflammatory lesion.

The anti-inflammatory role of heme oxygenase-1 in lipopolysaccharide and cytokine-stimulated inducible nitric oxide synthase and nitric oxide production in human periodontal ligament cells

BACKGROUND

Although heme oxygenase-1 (HO-1) is involved in anti-inflammation, the mechanisms of its activity in regulating periodontal inflammation are largely unclear. Therefore, the aim of this study is to investigate the anti-inflammatory properties of HO-1 in lipopolysaccharide (LPS)- and proinflammatory cytokine-stimulated inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in human periodontal ligament (PDL) cells.

METHODS

PDL cells were treated with LPS plus a combination of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta in serum-free media for 1 day. The production of NO was evaluated using a Griess reagent kit. The expression of iNOS and HO-1 proteins and mRNAs was evaluated using Western blotting and reverse transcriptase-polymerase chain reaction, respectively.

RESULTS

Proinflammatory cytokines and LPS triggered iNOS and HO-1 expression and NO production in PDL cells. HO-1 inhibitor and HO-1 small interfering RNA (siRNA) attenuated the LPS- and cytokine-stimulated NO release and iNOS and HO-1 expression. Specific inhibitors of p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinases phosphatidylinositol 3-kinase (PI3K), nuclear factor-kappa B (NF-kappaB), and protein kinase C delta (PKC-delta) greatly reduced the levels of iNOS and HO-1 expression induced by LPS plus cytokines.

CONCLUSIONS

Collectively, these data suggested that HO-1 inhibition blocked LPS- and proinflammatory cytokine-stimulated iNOS expression and NO production in PDL cells via a mechanism that involves p38, ERK, PI3K, NF-kappaB, and PKC-delta. Thus, the regulation of HO-1 activity may be a therapeutic strategy for periodontal disease.