Mechanistic features associated with induction of metalloproteinases in human gingival fibroblasts by interleukin-1

Granzyme B promotes matrix metalloproteinase-1 (MMP-1) release from gingival fibroblasts in a PAR1- and Erk1/2-dependent manner: A novel role in periodontal inflammation

OBJECTIVE

To gain insights into how proteases signal to connective tissues cells in the periodontium.

BACKGROUND

The connective tissue degradation observed in periodontitis is largely due to matrix metalloproteinase (MMP) release by gingival fibroblasts. Granzyme B (GzmB) is a serine protease whose role in periodontitis is undefined.

METHODS

Human gingival crevicular fluid (GCF) samples were obtained from sites with periodontal disease and healthy control sites. GzmB was quantified in the GCF ([GzmB]GCF ) by ELISA. Gingival fibroblasts (GF) were cultured in the presence or absence of recombinant GzmB. Culture supernatants were analyzed by ELISA to quantify GzmB-induced release of interstitial collagenase (MMP-1). In some experiments, cells were pre-treated with the inhibitor PD98059 to block MEK/ERK signaling. The protease-activated receptor-1 (PAR-1) was blocked with ATAP-2 neutralizing antibody prior to GzmB stimulation. Systemic MMP-1 levels were measured in plasma from wild-type (WT) and granzyme-B-knockout (GzmB-/- ) mice.

RESULTS

The [GzmB]GCF in human samples was ~4-5 fold higher at sites of periodontal disease (gingivitis/periodontitis) compared to healthy control sites, suggesting an association between GzmB and localized matrix degradation. GzmB induced a ~4-5-fold increase in MMP-1 secretion by cultured fibroblasts. GzmB induced phosphorylation of Erk1/2, which was abrogated by PD98059. GzmB-induced upregulation of MMP-1 secretion was also reduced by PD98059. Blockade of PAR-1 function by ATAP-2 abrogated the increase in MMP-1 secretion by GF. Circulating MMP-1 was similar in WT and GzmB-/- mice, suggesting that GzmB's effects on MMP-1 release are not reflected systemically.

CONCLUSION

These data point to a novel GzmB-driven signaling pathway in fibroblasts in which MMP-1 secretion is upregulated in a PAR1- and Erk1/2-dependent manner.

Evodiae fructus Extract Inhibits Interleukin-1β-Induced MMP-1, MMP-3, and Inflammatory Cytokine Expression by Suppressing the Activation of MAPK and STAT-3 in Human Gingival Fibroblasts In Vitro

Periodontitis is a Gram-negative bacterial infectious disease. Numerous inflammatory cytokines, including interleukin-1β (IL-1β), regulate periodontitis pathophysiology and cause periodontal tissue destruction. In human gingival fibroblasts (HGFs), IL-1β stimulates the production of matrix metalloproteinases (MMPs) and proinflammatory cytokines via various mechanisms. Several transcription factors, such as signal transducer and activator of transcription 3 (STAT-3), activator protein 1 (AP-1), and nuclear factor-κB (NF-κB), regulate gene expression. Mitogen-activated protein kinases (MAPKs) regulate these transcription factors. However, the MAPK/STAT-3 activation signal in HGFs is unknown. We investigated the potential inhibitory effects of the extract of Evodiae fructus (EFE), the dried, ripe fruit of Evodia rutaecarpa, on MMP and proinflammatory cytokine expression in IL-1β-stimulated HGFs. EFE inhibited the expression of MMP-1, MMP-3, and proinflammatory cytokines (TNF-α, IL-6, and IL-8) in IL-1β-stimulated HGFs through the inhibition of IL-1β-induced MAPK/STAT-3 activation. Also, these results suggest that the EFE may be a useful for the bioactive material for oral care.

A review of T helper 17 cell-related cytokines in serum and saliva in periodontitis

Periodontitis is a chronic inflammatory disease with a complex underlying immunopathology. Cytokines, as molecular mediators of inflammation, play a role in all stages of disease progression. T helper 17 (Th17) cells are thought to play a role in periodontitis. Th17 cell development and maintenance requires a pro-inflammatory cytokine milieu, with many of the cytokines implicated in the pathogenesis of periodontitis. Serum and saliva are easily accessible biofluids which can represent the systemic and local environment to promote the development of Th17 cells. Here we review human clinical studies that investigate IL-1β, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, IFN-γ, sCD40L and TNF-α in serum and saliva in periodontitis. We highlight their putative role in the pathogenesis of periodontitis and place them within a wider context of animal and other clinical studies.

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.

Platelet factor 4 upregulates matrix metalloproteinase-1 production in gingival fibroblasts

BACKGROUND AND OBJECTIVE

Periodontitis is a highly prevalent chronic inflammatory disease that causes tooth loss, morbidity and confers an increased risk for systemic disease. Tissue destruction during periodontitis is due in large part to collagen-degrading matrix metalloproteinases (MMPs) released by resident cells of the periodontium in response to proinflammatory cytokines. Platelets are immune-competent blood cells with a newly recognized role in chronic inflammation; however, their role in the pathogenesis of periodontitis is undefined. Consequently, the objective of this study was to assess the effect of platelet factor 4 (PF4), a major platelet-derived cytokine, on MMP-1 (collagenase) expression in human gingival fibroblasts (HGFs).

MATERIAL AND METHODS

HGFs were cultured in the presence or absence of recombinant PF4. Pro-MMP-1 secretion was quantified by enzyme-linked immunosorbent assay analysis of the cell culture supernatants. MMP-1 transcription was quantified by real-time polymerase chain reaction. Regulation of MMP-1 production by the p44/42 MAP kinase (MAPK) signaling pathway was examined in the presence or absence of PF4.

RESULTS

Exposure to PF4 caused a ~ 2-3-fold increase in MMP-1 transcription and secretion from cultured HGFs. PF4 treatment also enhanced phosphorylation of p44/42 MAPK, which has been previously shown to induce MMP-1 expression in fibroblasts. Blockade of p44/42 MAPK signaling with the cell-permeant inhibitors PD98059 and PD184352 abrogated PF4-induced pro-MMP-1 transcription upregulation and release from cultured HGFs.

CONCLUSION

We conclude that PF4 upregulates MMP-1 expression in HGFs in a p44/42 MAPK-dependent manner. These findings point to a previously unidentified role for platelets in the pathogenesis of periodontal diseases.

TOL19-001 reduces inflammation and MMP expression in monolayer cultures of tendon cells

Background

Tendinopathies are tendon conditions associated with degeneration and disorganization of the matrix collagen fibers, tendon cells apoptosis and inflammation through up-regulation of proinflammatory cytokines, matrix metalloproteinase (MMP) expression, and prostaglandin E₂ (PGE₂) production. Currently, the pharmacological treatment is mainly based on non-steroidal anti-inflammatory drugs (NSAIDs) use and corticosteroid injections, which both can lead to numerous side effects for patients. TOL19-001 is a diet supplementary composed mostly of spirulina and glucosamine sulfate whose antioxidant properties could be helpful to treat tendinopathies while avoiding taking NSAIDs. In this study we developed an in vitro model of tendinopathy in order to evaluate the therapeutic potential of TOL19-001.

Methods

Tendon cells were cultured on monolayer and treated with interleukin-1β (IL-1β) or ciprofloxacin (CIP), and then, MMPs, PGE2 and collagen expression was evaluated by RT-PCR or Elisa. In addition, a cotreatment with increased doses of TOL19-001 was done. Toxicity of TOL19-001 was evaluated using a metabolic activity assay.

Results

This study demonstrates that IL-1β mimics some aspects of tendinopathies with PGE2 induction, MMP expression (mostly MMP1 and MMP3), and increases of type III/I collagen ratio. CIP, meanwhile, leads to an increase of MMP2 and p65 mRNA, whereas it reduces TIMP1 expression. Scleraxis expression was also increased by CIP whereas it was decreased by IL-1β treatment. Besides, TOL19-001 cotreatment suppresses tendon cell inflammation in vitro, marked by the downregulation of PGE2, MMPs and type III collagen in IL-1β stimulated-cells. TOL19-001 also represses CIP induced-changes.

Conclusions

These findings indicate that TOL19-001 exerts anti-inflammatory effects on tendon cells, which might explain why TOL19-001 diet may improve tendon function in patients with tendon injury. Future research is required to determine TOL19-001 effect on injured or overused tendons in vivo.

The expression and regulation of matrix metalloproteinase-3 is critically modulated by Porphyromonas gingivalis lipopolysaccharide with heterogeneous lipid A structures in human gingival fibroblasts

Background

Porphyromonas gingivalis lipopolysaccharide (LPS) is a crucial virulence factor strongly associated with chronic periodontitis which is the primary cause of tooth loss in adults. It exhibits remarkable heterogeneity containing tetra-(LPS_1435/1449) and penta-(LPS₁₆₉₀) acylated lipid A structures. Human gingival fibroblasts (HGFs) as the main resident cells of human gingiva play a key role in regulating matrix metalloproteinases (MMPs) and contribute to periodontal homeostasis. This study investigated the expression and regulation of MMPs1-3 and tissue inhibitors of MMP-1 (TIMP-1) in HGFs in response to P. gingivalis LPS_1435/1449 and LPS₁₆₉₀ and hexa-acylated E. coli LPS as a reference. The expression of MMPs 1–3 and TIMP-1 was evaluated by real-time PCR and ELISA.

Results

The MMP-3 mRNA and protein were highly upregulated in P. gingivalis LPS₁₆₉₀- and E. coli LPS-treated cells, whereas no induction was observed in P. gingivalis LPS_1435/1449-treated cells. On the contrary, the expression of MMP-1 and −2 was not significantly affected by P. gingivalis LPS lipid A heterogeneity. The TIMP-1 mRNA was upregulated in P. gingivalis LPS_1435/1449- and E. coli LPS-treated cells. Next, signal transduction pathways involved in P. gingivalis LPS-induced expression of MMP-3 were examined by blocking assays. Blockage of p38 MAPK and ERK significantly inhibited P. gingivalis LPS₁₆₉₀-induced MMP-3 expression in HGFs.

Conclusion

The present findings suggest that the heterogeneous lipid A structures of P. gingivalis LPS differentially modulate the expression of MMP-3 in HGFs, which may play a role in periodontal pathogenesis.

Resveratrol modulates interleukin-1β-induced phosphatidylinositol 3-kinase and nuclear factor κB signaling pathways in human tenocytes

Resveratrol, an activator of histone deacetylase Sirt-1, has been proposed to have beneficial health effects due to its antioxidant and anti-inflammatory properties. However, the mechanisms underlying the anti-inflammatory effects of resveratrol and the intracellular signaling pathways involved are poorly understood. An in vitro model of human tenocytes was used to examine the mechanism of resveratrol action on IL-1β-mediated inflammatory signaling. Resveratrol suppressed IL-1β-induced activation of NF-κB and PI3K in a dose- and time-dependent manner. Treatment with resveratrol enhanced the production of matrix components collagen types I and III, tenomodulin, and tenogenic transcription factor scleraxis, whereas it inhibited gene products involved in inflammation and apoptosis. IL-1β-induced NF-κB and PI3K activation was inhibited by resveratrol or the inhibitors of PI3K (wortmannin), c-Src (PP1), and Akt (SH-5) through inhibition of IκB kinase, IκBα phosphorylation, and inhibition of nuclear translocation of NF-κB, suggesting that PI3K signaling pathway may be one of the signaling pathways inhibited by resveratrol to abrogate NF-κB activation. Inhibition of PI3K by wortmannin attenuated IL-1β-induced Akt and p65 acetylation, suggesting that p65 is a downstream component of PI3K/Akt in these responses. The modulatory effects of resveratrol on IL-1β-induced activation of NF-κB and PI3K were found to be mediated at least in part by the association between Sirt-1 and scleraxis and deacetylation of NF-κB and PI3K. Overall, these results demonstrate that activated Sirt-1 plays an essential role in the anti-inflammatory effects of resveratrol and this may be mediated at least in part through inhibition/deacetylation of PI3K and NF-κB.

Repetitive mechanical stretching modulates IL-1beta induced COX-2, MMP-1 expression, and PGE2 production in human patellar tendon fibroblasts

While mechanical loading is known to be essential in maintaining tendon homeostasis, repetitive mechanical loading has also been implicated in the etiology of tendon overuse injuries. The purpose of this study was to determine whether cyclic mechanical stretching regulates inflammatory responses induced by interleukin-1beta (IL-1beta) treatment in human patellar tendon fibroblasts (HPTFs). HPTFs were grown in microgrooved silicone dishes, where they became elongated in shape and aligned with the microgrooves, which is similar to the shape and organization of tendon fibroblasts in vivo. Cyclic uniaxial stretching was then applied to silicone culture dishes with a 4% or 8% stretch at a stretching frequency of 0.5 Hz for a duration of 4 h in the presence or absence of 10 pM IL-1beta treatment. Non-stretched cells in the presence or absence of IL-1beta were used for controls, respectively. The expression of cyclooxygenase-2 (COX-2), matrix metalloproteinase-1 (MMP-1), and the production of prostaglandin E2 (PGE2) were measured. In the absence of stretching, it was found that 10 pM of IL-1beta markedly induced higher levels of COX-2, MMP-1 gene expression, and PGE2 production than non-treated cells. Furthermore, cells with 4% stretching decreased the COX-2 and MMP-1 gene expression and PGE2 production that were stimulated by IL-1beta, whereas cells with 8% stretching further increased these gene products and/or expression levels in addition to the effects of IL-1beta stimulation. Thus, the results suggest that repetitive, small-magnitude stretching is anti-inflammatory, whereas large-magnitude stretching is pro-inflammatory. Therefore, moderate exercise may be beneficial to reducing tendon inflammation.

Redistributions of macrophages expressing the macrophage galactose-type C-type lectin (MGL) during antigen-induced chronic granulation tissue formation

Cell surface lectins are known to regulate trafficking of cells in the immune system, yet the role of macrophage galactose-type C-type lectin 1 and 2 (MGL1/2) is poorly understood. In this study, antigen-specific chronic inflammation was induced in a subcutaneous air pouch model in mice, and distribution of cells expressing MGL1/2 was investigated. Azobenzenearsonate-conjugated acetylated BSA, used as an antigen, was introduced into an air pouch of immunized mice, and tissue formation and distribution of MGL1/2-positive cells in the sub-dermal regions was examined. Thickness of the inflammatory tissue and number of MGL1/2-positive cells simultaneously reached the maximum at day 4 and returned to the control level at day 6 or 8. When additional antigenic challenges were given, a chronic granulation tissue, which had two distinct layers, was generated. In the chronic tissue, CD11b-positive/MGL1/2-negative cells were abundant in the area close to the antigenic stimulus, while the area far from the antigenic stimulus was dominated by MGL1/2-positive/CD11b-negative or -low cells. Flow cytometric analyses of isolated cells from the granulation tissue revealed that MGL1/2-positive cells expressed MHC class II at high levels, CD11b at low levels but no CD11c. MGL1/2-positive and -negative fractions were separated from cells in the granulation tissue and a higher level of IL-1alpha messenger RNA than negative populations was detected in the MGL1/2-positive fraction by the semi-quantitative reverse transcription-PCR method. IL-1alpha production by MGL1/2-positive cells was also immunohistochemically detected. Results suggest that MGL1/2-positive cells represent a distinct sub-population of macrophages, having unique functions in the generation and maintenance of granulation tissue induced by antigenic stimuli.

Prostaglandin E2 regulates interleukin-1beta-induced matrix metalloproteinase-3 production in human gingival fibroblasts

Prostaglandin E2 (PGE2) exerts its biological actions via EP receptors (EP1, EP2, EP3, and EP4). In the present study, we investigated whether PGE2 regulated interleukin (IL)-1beta-induced matrix metalloproteinase (MMP)-3 production in human gingival fibroblasts (HGF) derived from periodontally healthy subjects and diseased patients. In HGF from healthy gingiva, PGE2 down-regulated IL-1beta-induced MMP-3 production, whereas in HGF from periodontitis patients, PGE2 enhanced it. Butaprost (an EP2 agonist) and ONO-AE1-329 (an EP4 agonist) suppressed IL-1beta-induced MMP-3 production, and 17-phenyl-omega-trinor PGE2 (an EP1 agonist) mimicked the PGE(2) effect in HGF from healthy and periodontally diseased tissues, respectively. Analysis of these data suggests that, in HGF from healthy tissue, IL-1beta-induced MMP-3 production is down-regulated by PGE2 via EP2 and EP4 receptors, whereas in cells from periodontally diseased tissue, IL-1beta-induced MMP-3 production is up-regulated via EP1 receptors. Different regulation of IL-1beta-induced MMP-3 production by PGE2 between healthy and periodontally diseased tissues may be involved in the pathogenesis of periodontal disease.

Interleukin-1beta induces matrix metalloproteinase-1 expression in cultured human gingival fibroblasts: role of cyclooxygenase-2 and prostaglandin E2

OBJECTIVE

Matrix metalloproteinases (MMPs) degrade extracellular matrices and are responsible for excessive connective tissue breakdown in inflammatory disorders. We investigated the mechanism of MMP-1 expression in human gingival fibroblasts in response to the stimulation with interleukin-1beta (IL-1beta), and the role of inducible-type cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) in the regulation of MMP-1 expression.

MATERIALS AND METHODS

We stimulated cultured human gingival fibroblasts with r(h)IL-1beta, and examined the expression of MMP-1 mRNA and protein by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. The effect of indomethacin, dexamethasone, or cycloheximide (CHX) on the IL-1beta-induced expression of MMP-1 was examined. The expression of MMP-1 in gingival fibroblasts stimulated with PGE2 was also examined.

RESULTS

IL-1beta stimulated the expressions of mRNA and protein for MMP-1, in cultured fibroblasts, in time- and concentration-dependent manners. Pretreatment of the cells with indomethacin or dexamethasone inhibited the IL-1beta-induced MMP-1 expression. CHX, a protein synthesis inhibitor, also suppressed the MMP-1 expression. IL-1beta also induced COX-2 expression in gingival fibroblasts, and PGE2, a major COX-2 product, was found to enhance MMP-1 expression.

CONCLUSION

The IL-1beta-induced MMP-1 expression in gingival fibroblasts may be mediated, at least in part, by COX-2 and its product PGE2.

Signal pathways involved in the production of MMP-1 and MMP-3 in human gingival fibroblasts

Periodontitis is associated with enhanced production of cytokines, prostaglandins and matrix metalloproteinases (MMPs). The aim of this study was to investigate the production and regulation of MMP-1 and MMP-3 in human gingival fibroblasts challenged with the cytokines interleukin-lbeta (IL-1beta), tumor necrosis factor alpha (TNFalpha) or epidermal growth factor (EGF). The results showed that gingival fibroblasts constitutively produce MMP-1 and MMP-3, and that the cytokines IL-1beta, TNFalpha and EGF increase both MMP-1 and MMP-3 production in gingival fibroblasts. The upregulation by the cytokines was apparent at 8 h of incubation and increased thereafter continuously during 48 h of incubation. The upregulation of MMPs, induced by IL-1beta or TNFalpha, was reduced by the cyxlooxygenase-2 (COX-2) inhibitor NS-398, the p38 MAP-kinase inhibitor SB 203580, and the tyrosine kinase inhibitor herbimycin A. In addition, MMP-1 and MMP-3 production, induced by IL-1beta, TNFalpha or EGF, was strongly reduced by the presence of the glucocorticoid dexamethasone. Our findings demonstrate that the cytokines IL-1beta, TNFalpha and EGF, respectively, enhance both MMP-1 and MMP-3 production in human gingival fibroblasts, and that the signal pathways COX-2, MAP-kinases and tyrosine kinases are partly involved in the production of MMPs.

Polymorphisms in the IL-1A gene are correlated with levels of interleukin-1alpha protein in gingival crevicular fluid of teeth with severe periodontal disease

Interleukin-1 (IL-1) is a potent stimulator of bone resorption and is strongly implicated in the destruction due to bystander damage seen in periodontal disease. Recent studies suggest that polymorphisms of the (IL-1) gene complex may be significant risk factors for a number of chronic inflammatory diseases. The severity of periodontal disease has been positively associated with carriage of allele 2 at position -889 of the IL-1A gene in conjunction with allele 2 of the IL-1B gene at position +3953. In this study, we tested the hypothesis that allele 2 of the IL-1A gene at position -889 might act to elevate levels of IL-1alpha protein in patients with periodontal disease. Since levels of IL-1alpha protein are low in healthy individuals, we used a group of patients with severe periodontal disease to investigate if levels of IL-1alpha protein in gingival crevicular fluid can be correlated to patient genotype. IL-1alpha levels were measured by enzyme immunoassay in 46 patients with severe periodontal disease. These patients were genotyped by PCR and allele-specific restriction digests. The carriage rate for allele 2 in the diseased population was 68%. Overall, the carriage of allele 2 was associated with almost a four-fold increase in IL-1alpha protein levels. Differences were most pronounced in non-smokers, while heavy smokers showed reduced levels of IL-1alpha protein regardless of genotype. These results suggest a mechanism whereby this genetic polymorphism acts to modulate IL-1alpha protein production and may influence the pathogenesis of periodontal disease by affecting the extent of IL-1-associated bystander damage.

Regulation of IL-1-induced gingival collagenase gene expression by activator protein-1 (c-Fos/c-Jun)

Matrix metalloproteinase-1 is probably involved in the progression of periodontal disease. The aim of this study was to investigate whether IL-1beta stimulates the expression of the activator protein 1 (AP-1) transcription factor and, consequently, if the AP-1 transcription factor participates in the regulation of collagenase gene expression in human gingival fibroblast cells. In this study, we demonstrate that the concentration of the protein components of AP-1 transcription factor, c-Fos and c-Jun, is enhanced by IL-1beta both at mRNA and protein levels, utilizing Northern blot analysis, electrophoretic mobility gel shift assay and Western blot analysis. The IL-1beta stimulated the collagenase-CAT and AP-1-CAT activities in a dose dependent manner with respect to the amount of DNA used in transfections. Further, overexpression of c-Fos and c-Jun proteins revealed a dose-dependent transcriptional activation of the collagenase promoter. These findings, coupled with the existence of AP-1 consensus DNA binding sites on the collagenase gene promoter, show that regulation of collagenase gene expression by IL-1beta involves the transcription factor AP-1 in gingival fibroblasts.

Increase of urokinase-type plasminogen activator receptor expression in human gingival fibroblasts by Porphyromonas gingivalis lipopolysaccharide

BACKGROUND

Urokinase-type plasminogen activator receptor (uPAR) presenting on the cell surface with glycosylphosphatidylinositol (GPI) anchor is a key component in the plasminogen activator (PA)-plasmin system and plays a critical role in extracellular matrix degradation. It is believed that uPAR serves to localize and accelerate this generation system. In this study, we examined the levels of both uPA and uPAR in human gingival fibroblasts treated with Porphyromonas gingivalis lipopolysaccharide (LPS).

METHODS

Human gingival fibroblasts from the seventh to tenth doubling passages were plated at 5x10(4) cells per well in 24-well plates. The confluent-stage cells were cultured for 24 hours in alpha-MEM medium containing 2% fetal calf serum, after which they were incubated with P. gingivalis LPS. PA activity was measured using plasminogen and plasmin substrate S2251.

RESULTS

PA activity in the cell lysate was increased by LPS and reached maximum at 1 microg/ml LPS after being incubated for 8 hours. PA activity released by phosphatidylinositol-specific phospholipase C, which detaches the GPI anchor, was also increased by LPS. The activity was inhibited by amiloride, which is a specific inhibitor for uPA. LPS increased the protein and mRNA levels of both uPA and uPAR in gingival fibroblasts.

CONCLUSIONS

These findings suggest that increase of the uPAR level by LPS may play an important role in the progression of periodontal diseases through pericellular proteolysis.

Antizyme prevents ornithine decarboxylase-mediated cell death in human fibroblasts

Ornithine decarboxylase (ODC) is a key enzyme of polyamine biosynthesis essential for growth-related cellular functions. Apart from its physiological role in cell proliferation, ODC also contributes to the induction of apoptosis under certain conditions, e.g. following growth factor withdrawal. The rate of cell death is a function of its enzyme activity, ODC activity is inhibited by a regulatory protein antizyme, also known to suppress polyamine uptake. We report that forced expression of antizyme prevents ODC-mediated cell death in human gingival fibroblasts under very low serum conditions. These data suggest an important antiapoptotic role for antizyme in cell survival.

Cytokine expression in periodontal health and disease

Soluble proteins that serve as mediators of cell function and are produced by various cell types, such as structural and inflammatory cells, are collectively called cytokines. Several lines of evidence have revealed that cytokines play important roles not only in tissue homeostasis but also in the pathogenesis of many infectious diseases. Recent research on biological activities in normal periodontium and the pathogenesis of periodontal diseases has clarified the involvement of various cytokines in the biological activities observed in the sites. Cytokines play crucial roles in the maintenance of tissue homeostasis, a process which requires a delicate balance between anabolic and catabolic activities. In particular, growth factors--such as fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), transforming growth factor-beta (TGF-beta)--are thought to play important roles in modulating the proliferation and/or migration of structural cells in the periodontium and the production of various extracellular matrices by these cells. On the other hand, there is little doubt that excessive and/or continuous production of cytokines in inflamed periodontal tissues is responsible for the progress of periodontitis and periodontal tissue destruction. Particularly, inflammatory cytokines--such as IL-1 alpha, IL-1 beta, IL-6, and IL-8--are present in the diseased periodontal tissues, and their unrestricted production seems to play a role in chronic leukocyte recruitment and tissue destruction. It is possible that monitoring cytokine production or its profile may allow us to diagnose an individual's periodontal disease status and/or susceptibility to the disease. In addition, although the hypothesis is still controversial, it has been suggested that discrete T-cell subsets (Th1 and Th2) with different cytokine profiles play specific roles in the immunopathogenesis of periodontal diseases.

Dissolution of type I collagen fibrils by gingival fibroblasts isolated from patients of various periodontitis categories

The classification of periodontitis in various disease categories, including juvenile periodontitis, rapidly progressive adult periodontitis and slowly progressive adult periodontitis is based mainly on differences in disease progression and age group susceptibility. Because dissolution of collagen fibers is an integral part of periodontal attachment loss, we investigated whether the clinical differences among these periodontitis/control groups are reflected in the collagen-degrading activity of gingival fibroblasts isolated from affected tissues. All fibroblast strains isolated from the 4 groups (n = 48) displayed cell-associated collagenolytic activity when seeded in contact with a reconstituted film of type I collagen fibrils. Cells from the control group (n = 14) dissolved the collagen fibril film twice as fast as those from each of the 3 disease groups (juvenile periodontitis (n = 13), rapidly progressive adult periodontitis (n = 7), and slowly progressive adult periodontitis (n = 14)). Both interleukin-1 beta and phorbolester accelerated the rate of dissolution 2-4-fold, but even after cytokine or phorbolester stimulation control cells were still considerably more effective in dissolving the collagen fibrils than cells from the disease groups. The observation made in this study, that dissolution of collagen fibrils by gingival fibroblasts from periodontally diseased individuals is significantly slower than by cells from healthy control subjects, challenges disease paradigms based on a direct relationship between collagenolytic potential and disease activity.

Immunohistochemical demonstration of the plasminogen activator system in human gingival tissues and gingival fibroblasts

The relative distribution of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator inhibitor-2 (PAI-2) was studied in cultured human gingival fibroblasts, healthy gingival tissues and inflamed gingival tissues by immunohistochemistry. In cultured gingival fibroblasts t-PA, u-PA and PAI-1 were expressed in cytoplasm; u-PA and PAI-1 were more intensely stained than t-PA; PAI-2 was not detectable in gingival fibroblasts. Following interleukin 1 beta (IL-1 beta) stimulation, the intensity of intracellular staining for t-PA was increased and a number of cells staining strongly for PAI-2 were seen; no difference in the intensity of immunostaining level was noted for the expression of u-PA and PAI-1 between IL-1 beta stimulated cells and unstimulated cells. In healthy gingival tissues, u-PA and PAI-1 displayed a wide distribution throughout all the connective tissue and epithelium; t-PA localized mainly in the connective tissue while PAI-2 showed little association with the connective tissue but did faintly stain in the epithelial layer. In inflamed gingival tissues, staining for t-PA was significantly increased in the extracellular matrix of the connective tissue, whereas staining for u-PA, PAI-1 and PAI-2 was found to be slightly increased, but no significant difference was noted for staining when compared with the healthy gingival tissues. A granular distribution of t-PA, u-PA, PAI-1 and PAI-2 was noted around areas of inflammatory cell infiltration. These immunohistochemical findings indicate that the plasminogen activator system produced by fibroblasts may be influenced by the presence of the inflammatory mediator IL-1 beta. In addition, the significant increase of t-PA in inflamed connective tissue and the wide expression of these components around inflamed cells may contribute to connective tissue degradation and may relate to the migration and localization of monocytes/macrophages in inflamed tissue.

Effects of interleukin-1 beta on matrix metalloproteinase-3 levels in human periodontal ligament cells

MATRIX METALLOPROTEINASE-3 (MMP-3), or stromelysin-1, is an enzyme responsible for the degradation of a wide range of extracellular matrix proteins. Increases in MMP-3 activity have been found in several chronic inflammatory diseases, and this increased activity is thought to be mediated by interleukin-1 beta (IL-1 beta). Because IL-1 beta has been strongly associated with inflammatory periodontal disease, the purpose of this in vitro study was to investigate the role of IL-1 beta on the regulation of MMP-3 levels in cells derived from the human periodontal ligament (PDL). Human PDL cell cultures were treated with IL-1 beta at varying concentrations (0.01-1.0 ng/ml) for 24 hour prior to analysis at either transcript or protein levels. Following the isolation of total RNA, the relative levels of MMP-3 mRNA were determined using reverse transcription-polymerase chain reaction (RT-PCR) with 32P-end-labeled primers. Immunocytochemical detection of MMP-3 protein was performed using polyclonal antibodies to human MMP-3. The results of RT-PCR analysis demonstrated a concentration-dependent increase in MMP-3 mRNA expression, with IL-1 beta treatments of 0.1 and 1.0 ng/ml significantly (P < 0.01) increased over those cells not treated with IL-1 beta. This increase in mRNA expression was paralleled by significant (P < 0.001) changes at the protein level, with an average of 27.6% of the cells stained positive for MMP-3 following IL-1 beta treatment (1.0 ng/ml), compared with control cells showing no positive staining for MMP-3. In conclusion, the results of this study demonstrate that IL-1 beta upregulates MMP-3 in human PDL cells on both an mRNA and a protein level. These findings suggest possibly important roles for IL-1 beta and MMP-3 in both normal turnover and maintenance of the PDL and in the connective tissue degradation associated with periodontal disease.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

The interleukin-1 genotype as a severity factor in adult periodontal disease

Although specific bacteria, dental plaque, and age are associated with periodontal disease, there are currently no reliable predictors of periodontitis severity. Studies in twins have suggested a genetic contribution to the pathogenesis of periodontitis, but previous attempts to identify genetic markers have been unsuccessful. The pro-inflammatory cytokines interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) are key regulators of the host responses to microbial infection. IL-1 is also a major modulator of extracellular matrix catabolism and bone resorption. We report a specific genotype of the polymorphic IL-1 gene cluster that was associated with severity of periodontitis in non-smokers, and distinguished individuals with severe periodontitis from those with mild disease (odds ratio 18.9 for ages 40-60 years). Functionally, the specific periodontitis-associated IL-1 genotype comprises a variant in the IL-1B gene that is associated with high levels of IL-1 production. In smokers severe disease was not correlated with genotype. In this study, 86.0% of the severe periodontitis patients were accounted for by either smoking or the IL-1 genotype. This study demonstrates that specific genetic markers, that have been associated with increased IL-1 production, are a strong indicator of susceptibility to severe periodontitis in adults.

Association of interleukin-1-induced, NF kappa B DNA-binding activity with collagenase gene expression in human gingival fibroblasts

During earlier examination of interleukin-1 (IL-1)-induced matrix metalloproteinase gene expression in human gingival fibroblasts a highly induced immediate early gene, I kappa B-alpha, a NF kappa B DNA-binding inhibitor, was identified. The aim now was to investigate whether recombinant (r)IL-1 beta induces the stimulation of NF kappa B and its inhibitor proteins in human gingival fibroblasts and to understand if inhibition of its activity affects collagenase gene expression. Primary gingival fibroblasts (human) were treated with rIL-1 beta to determine the effect on NF kappa B-like DNA-binding activity. IL-1 induced the production of steady-state mRNA levels of I kappa B-alpha in the cultured fibroblasts. Nuclear run-on transcription studies demonstrated that rIL-1 induction of I kappa B-alpha may be transcriptionally regulated. Using electrophoretic mobility gel-shift assays it was shown that rIL-1 activates NF kappa B-like, DNA-binding activity in these fibroblasts. NF kappa B-like DNA-binding activity was rapidly induced and turned over in gingival fibroblasts with peak activity at 30 min after rIL-1 treatment. Further, treatment with chymotrypsin protease inhibitor and antioxidant inhibitor prevented IL-1-induced, NF kappa B-like, DNA-binding activity and collagenase mRNA production. When coupled with the existence of NF kappa B consensus DNA-binding sites on the collagenase gene promoter, these findings suggest that the stimulation of NF kappa B in gingival fibroblasts by rIL-1 could play an important part in the regulation of their collagenase gene expression. The ability of IL-1 to stimulate this expression may define a pivotal role for this cytokine in the pathogenesis of periodontitis.

Expression of mRNA for matrix metalloproteinases and tissue inhibitors of metalloproteinases in periodontitis-affected human gingival tissue

It is known that the host responds to an increased concentration of collagenase [or matrix metalloproteinase (MMP)-1] by preferentially expressing mRNA for the tissue inhibitor of metalloproteinase-1 (TIMP-1) in order to overcome tissue destruction due to periodontitis. To further elucidate the relation between MMPs and TIMPs in periodontitis-affected tissues, the expression of mRNA for MMP-1, -3 and -8, and TIMP-1 and -2, in 10 gingival samples from patients and five from healthy individuals was assessed by reverse transcription-polymerase chain reaction. The diseased group showed significantly higher levels of MMP-1, -3, -8 and TIMP-1 mRNA relative to beta-actin than the control group (mean +/- SE: diseased vs healthy (%): 0.26 +/- 0.05 vs 0.018 +/- 0.0040 for MMP-1; 0.09 +/- 0.16 vs 0.063 +/- 0.016 for MMP-3; 0.068 +/- 0.017 vs 0.006 +/- 0.0010 for MMP-8; 12.66 +/- 2.90 vs 2.71 +/- 0.54 for TIMP-1; p < 0.01). TIMP-2 did not significantly differ between the two groups (1.79 +/- 0.33 vs 1.42 +/- 0.53; p > 0.05). The preferential increase in the level of MMP-3 mRNA relative to that of MMP-1 and -8 in inflamed gingiva would be relevant to tissue destruction because MMP-3 is a broad-spectrum MMP and a pivotal activator of latent MMP-1 and -8. Therefore, the overall increase in MMP-1, -3 and -8 mRNA in periodontitis-affected gingiva might account for a concerted action of MMPs during connective tissue destruction in periodontitis.