Regulation of matrix metalloproteinase-1 by Filifactor alocis in human gingival and monocytic cells

Possible immunomodulatory role of Filifactor alocis through beta-defensin 2 in gingival keratinocytes

OBJECTIVES

The present study aimed to investigate a possible immunomodulatory role of the periodontopathogen Filifactor alocis through the antimicrobial peptide hBD-2 on the expression of chemokines in human gingival keratinocytes.

MATERIALS AND METHODS

Cells were cultured in the presence or absence of periodontopathogenic bacteria, such as F. alocis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Treponema denticola, to evaluate the regulation of hBD-2, CXCL8 and CCL20. Furthermore, the cells were exposed or not to hBD-2 and the expression of CXCL8 and CCL20 and their receptors was evaluated.

RESULTS

All bacteria induced a significant upregulation of hBD-2, CXCL8, and CCL20 gene expressions. In addition, F. alocis significantly increased their protein levels, as detected by ELISA. Pre-incubation of the cells with the TLR2 inhibitor resulted in a significant downregulation of hBD-2 expression in F. alocis-treated cells. Gingival keratinocytes exposed to hBD-2 resulted in a significant and dose-dependent increase of all chemokines and their receptors.

CONCLUSIONS

F. alocis increased the production of chemotactic cytokines, suggesting an increase in the recruitment of immunoinflammatory cells in periodontal diseases. The chemotaxis-promoting effect is partly direct, but is also mediated via hBD-2. F. alocis stimulates the synthesis of hBD-2, which in turn could promote the expression and synthesis of these chemokines and their receptors. In addition, hBD-2 has an autostimulatory effect and stimulates the synthesis of these chemokines, so that the chemotaxis triggered by F. alocis is further fueled.

CLINICAL RELEVANCE

F. alocis and hBD-2 have a significant role in periodontitis, showing their importance for diagnostic and treatment approaches.

Non-Invasive Physical Plasma Reduces the Inflammatory Response in Microbially Prestimulated Human Gingival Fibroblasts

Non-invasive physical plasma (NIPP), an electrically conductive gas, is playing an increasingly important role in medicine due to its antimicrobial and regenerative properties. However, NIPP is not yet well established in dentistry, although it has promising potential, especially for periodontological applications. The aim of the present study was to investigate the effect of NIPP on a commercially available human gingival fibroblast (HGF) cell line and primary HGFs in the presence of periodontitis-associated bacteria. First, primary HGFs from eight patients were characterised by immunofluorescence, and cell numbers were examined by an automatic cell counter over 5 days. Then, HGFs that were preincubated with Fusobacterium nucleatum (F.n.) were treated with NIPP. Afterwards, the IL-6 and IL-8 levels in the cell supernatants were determined by ELISA. In HGFs, F.n. caused a significant increase in IL-6 and IL-8, and this F.n.-induced upregulation of both cytokines was counteracted by NIPP, suggesting a beneficial effect of physical plasma on periodontal cells in a microbial environment. The application of NIPP in periodontal therapy could therefore represent a novel and promising strategy and deserves further investigation.

Induction of TNF-α by Filifactor alocis in THP-1 macrophagic cells

OBJECTIVES

Filifactor alocis is an emerging periodontal pathogen, and macrophage-produced tumor necrosis factor-α (TNF-α) plays important roles in periodontal pathogenesis. In this study, we investigated F. alocis-stimulated TNF-α production in THP-1 macrophagic cells.

DESIGN

Phorbol 12-myristate 13-acetate-differentiated THP-1 macrophagic cells were challenged with F. alocis ATCC 35896 for various durations. TNF-α mRNA expression and protein secretion were determined using RT-PCR and ELISA, respectively. Activation of protein kinases and transcription factor proteins was evaluated by Western blot analysis.

RESULTS

Live F. alocis stimulated THP-1 cells to produce TNF-α in a dose-dependent manner. However, glutaraldehyde-killed or heat-killed F. alocis showed no effectiveness for TNF-α induction. In contrast, both live and killed Porphyromonas gingivalis robustly increased TNF-α expression. Furthermore, F. alocis was unable to stimulate TNF-α expression in Toll-like receptor 2 (TLR2) knockout THP-1 cells. F. alocis activated all three mitogen-activated protein kinases: extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). Pharmacological inhibition of ERK and JNK, but not p38, significantly reduced F. alocis-induced TNF-α production. Finally, increased levels of phospho-c-Jun were detected in F. alocis-stimulated THP-1 cells.

CONCLUSIONS

These results suggest that F. alocis induces TNF-α production in THP-1 macrophagic cells primarily by activating the TLR2, JNK, and c-Jun pathways.

S-1-propenyl-L-cysteine suppresses lipopolysaccharide-induced expression of matrix metalloproteinase-1 through inhibition of tumor necrosis factor-α converting enzyme-epidermal growth factor receptor axis in human gingival fibroblasts

Periodontal disease is the most common dental health problem characterized by the destruction of connective tissue and the resorption of alveolar bone resulting from a chronic infection associated with pathogenic bacteria in the gingiva. Aged garlic extract has been reported to improve gingival bleeding index and probing pocket depth score in patients with mild to moderate periodontitis. Although our previous study found that aged garlic extract and its constituents suppressed the tumor necrosis factor-α-induced inflammatory responses in a human gingival epithelial cell line, the mechanism underlying the effect of aged garlic extract on the destruction of the gingiva remains unclear. The present study investigated the effect of S-1-propenyl-L-cysteine, one of the major sulfur bioactive compounds in aged garlic extract, on the lipopolysaccharide-induced expression of matrix metalloproteinases in human gingival fibroblasts HGF-1 cells. Matrix metalloproteinases are well known to be closely related to the destruction of the gingiva. We found that S-1-propenyl-L-cysteine suppressed the lipopolysaccharide-induced expression and secretion of matrix metalloproteinase-1 in HGF-1 cells. In addition, S-1-propenyl-L-cysteine inhibited the lipopolysaccharide-induced phosphorylation of epidermal growth factor receptor and expression of the active form of tumor necrosis factor-α converting enzyme. Furthermore, the inhibitors of epidermal growth factor receptor tyrosine kinase and tumor necrosis factor-α converting enzyme, AG-1478 and TAPI-1, respectively, reduced the lipopolysaccharide-induced protein level of matrix metalloproteinase-1, as did S-1-propenyl-L-cysteine. Taken together, these results suggested that S-1-propenyl-L-cysteine suppresses the lipopolysaccharide-induced expression of matrix metalloproteinase-1 through the blockade of the tumor necrosis factor-α converting enzyme-epidermal growth factor receptor axis in gingival fibroblasts.

Non-Invasive Physical Plasma Generated by a Medical Argon Plasma Device Induces the Expression of Regenerative Factors in Human Gingival Keratinocytes, Fibroblasts, and Tissue Biopsies

After oral surgery, intraoral wound healing and tissue regeneration is an important factor for the success of the entire therapy. In recent years, non-invasive medical plasma (NIPP) has been shown to accelerate wound healing, which would be particularly beneficial for patients with wound healing disorders. Since the application of NIPP in dentistry has not been sufficiently understood, the aim of the present study was to investigate the effect of a medical argon plasma device on gingival cells. Human gingival fibroblasts, keratinocytes, and tissue biopsies were treated with NIPP for different durations. Crucial markers associated with wound healing were examined at the mRNA and protein levels by real-time PCR, ELISA and immunohistochemistry. NIPP treatment led to an increase in Ki67 and MMP1 at mRNA and protein levels. NIPP application lasting longer than 60 s resulted in an increase in apoptotic genes at mRNA level and superficial damage to the epithelium in the tissue biopsies. Overall, our experimental setup demonstrated that NIPP application times of 30 s were most suitable for the treatment of gingival cells and tissue biopsies. Our study provides evidence for potential use of NIPP in dentistry, which would be a promising treatment option for oral surgery.

Filifactor alocis: Recent Insights and Advances

Filifactor alocis, a fastidious Gram-positive obligate anaerobic bacterium, is a newly appreciated member of the periodontal community that is now proposed to be a diagnostic indicator of periodontal disease. Its pathogenic characteristics are highlighted by its ability to survive in the oxidative stress-rich environment of the periodontal pocket and to significantly alter the microbial community dynamics by forming biofilms and interacting with several oral bacteria. Here, we describe the current understanding of F. alocis virulence attributes, such as its comparative resistance to oxidative stress, production of unique proteases and collagenases that can cause structural damage to host cells, and dysregulation of the immune system, which enable this bacterium to colonize, survive, and outcompete other traditional pathogens in the inflammatory environment of the periodontal pocket. Furthermore, we explore the recent advancements and future directions for F. alocis research, including the potential mechanisms for oxidative stress resistance and our evolving understanding of the interactions and mechanisms of bacterial survival inside neutrophils. We also discuss the current genetic tools and challenges involved in manipulating the F. alocis genome for the functional characterization of the putative virulence genes. Collectively, this information will expedite F. alocis research and should lead to the identification of prime targets for the development of novel therapeutics to aid in the control and prevention of periodontal disease.

Filifactor alocis and Tumor Necrosis Factor-Alpha Stimulate Synthesis of Visfatin by Human Macrophages

There is little known about the effect of the periodontopathogen Filifactor alocis on macrophages as key cells of the innate immune defense in the periodontium. Therefore, the aim of the present study was to investigate the effect of F. alocis and additionally of the pro-inflammatory cytokine tumor necrosis factor-alpha (TNFα) on visfatin and other pro-inflammatory and proteolytic molecules associated with periodontitis in human macrophages. The presence of macrophage markers CD14, CD86, CD68, and CD163 was examined in gingival biopsies from healthy individuals and periodontitis patients. Human macrophages were incubated with F. alocis and TNFα for up to 2 d. The effects of both stimulants on macrophages were determined by real-time PCR, ELISA, immunocytochemistry, and immunofluorescence. F. alocis was able to significantly stimulate the synthesis of visfatin by human macrophages using TLR2 and MAPK pathways. In addition to visfatin, F. alocis was also able to increase the synthesis of cyclooxygenase 2, TNFα, and matrix metalloproteinase 1. Like F. alocis, TNFα was also able to stimulate the production of these proinflammatory and proteolytic molecules. Our results highlight the pathogenetic role of F. alocis in periodontal diseases and also underline the involvement of visfatin in the aetiopathogenesis of periodontitis.

Regulation of Cyclooxygenase 2 by Filifactor alocis in Fibroblastic and Monocytic Cells

Periodontitis is a prevalent chronic inflammatory disease triggered by a synergistic and dysbiotic microbiota present in the oral biofilm. This in vitro study is aimed at evaluating the regulation of cyclooxygenase (COX)2 expression and production by the periodontopathogen Filifactor alocis in human gingival fibroblastic (HGF-1) and monocytic (THP-1) cells and also at investigating the underlying cellular pathway mechanisms. HGF-1 and THP-1 cells were exposed either to F. alocis or to the proinflammatory cytokine tumor necrosis factor alpha (TNFα) for 1 and 2 d to examine the COX2 expression by qPCR. COX2 protein levels were evaluated by ELISA in F. alocis-stimulated cells. Both types of cells were also stimulated with a blocking toll-like receptor (TLR)2 antibody or specific inhibitors against MAPKs. F. alocis significantly (p < 0.05) increased COX2 at both transcriptional and protein levels in both HGF-1 and THP-1 cells. Moreover, the stimulatory effect of F. alocis on COX2 was more pronounced in HGF-1 cells in comparison to THP-1 cells. F. alocis upregulated the COX2 expression in a dose-dependent manner in both type cells at 1 d. TNFα also significantly (p < 0.05) increased the COX2 expression in both cells. After preincubation of HGF-1 and THP-1 cells either with a neutralizing anti-TLR2 antibody or with specific MAPK inhibitors, the F. alocis-upregulated COX2 expression was significantly (p < 0.05) suppressed at 1 d. Our in vitro study provides original evidence that F. alocis stimulates COX2 production in fibroblastic and monocytic cells through TLR2 and MAPK mechanisms, suggesting a role of this periodontopathogen in the etiopathogenesis of periodontitis.