Vu Dang La

Naringenin has anti-inflammatory properties in macrophage and ex vivo human whole-blood models.

BACKGROUND AND OBJECTIVE Periodontitis is a chronic inflammatory disease of bacterial etiology, affecting tooth-supporting tissues. The host inflammatory response to periodontopathogens, notably the high and continuous production of cytokines, is considered a major factor causing the local tissue destruction observed in periodontitis. The aim of the present study was to investigate the effect of naringenin, a major flavanone in grapefruits and tomatoes, on the lipopolysaccharide-induced pro-inflammatory cytokine production by host cells, using two different models. MATERIAL AND METHODS The effect of naringenin was characterized using macrophages stimulated with the lipopolysaccharide of either Aggregatibacter actinomycetemcomitans or Escherichia coli and using whole blood stimulated with A. actinomycetemcomitans lipopolysaccharide, in the presence or absence of naringenin. Lipopolysaccharide-induced interleukin-1 beta, interleukin-6, interleukin-8 and tumor necrosis factor-alpha production by macrophages and whole-blood samples treated with naringenin were evaluated using an enzyme-linked immunosorbent assay. Changes in the phosphorylation states of macrophage kinases induced by A. actinomycetemcomitans lipopolysaccharide and naringenin were characterized by immunoblot screening. RESULTS Our results clearly indicated that naringenin is a potent inhibitor of the pro-inflammatory cytokine response induced by lipopolysaccharide in both macrophages and in whole blood. Naringenin markedly inhibited the phosphorylation on serines 63 and 73 of Jun proto-oncogene-encoded AP-1 transcription factor in lipopolysaccharide-stimulated macrophages. CONCLUSION The results from the present study suggest that naringenin holds promise as a therapeutic agent for treating inflammatory diseases such as periodontitis.

Cranberry Proanthocyanidins Inhibit MMP Production and Activity

Matrix metalloproteinases (MMPs) produced by resident and inflammatory cells in response to periodontopathogens play a major role in periodontal tissue destruction. Our aim was to investigate the effects of A-type cranberry proanthocyanidins (AC-PACs) on: (i) the production of various MMPs by human monocyte-derived macrophages stimulated with Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS), and (ii) the catalytic activity of recombinant MMP-1 and MMP-9. The effects of AC-PACs on the expression of 5 protein kinases and the activity of nuclear factor-kappa B (NF-κB) p65 in macrophages stimulated with LPS were also monitored. Our results indicated that AC-PACs inhibited the production of MMPs in a concentration-dependent manner. Furthermore, the catalytic activity of MMP-1 and MMP-9 was also inhibited. The inhibition of MMP production was associated with reduced phosphorylation of key intracellular kinases and the inhibition of NF-κB p65 activity. AC-PACs thus show potential for the development of novel host-modulating strategies to inhibit MMP-mediated tissue destruction during periodontitis.

Proteases of Porphyromonas gingivalis as Important Virulence Factors in Periodontal Disease and Potential Targets for Plant-Derived Compounds: A Review Article

Periodontitis is a common chronic inflammatory disorder of bacterial origin, which affects the tooth-supporting tissues. A wide range of evidences suggests that Porphyromonas gingivalis plays a key role in the initiation and progression of chronic periodontitis. This Gram-negative anaerobic bacterium produces several types of proteolytic enzymes, including gingipains, collagenases, and a dipeptidyl aminopeptidase IV. Although these enzymes have physiological functions for P. gingivalis, they have been suggested to play multiple roles in the pathogenic process of periodontitis. Indeed, P. gingivalis proteases hydrolyze a variety of serum and tissue proteins thus contributing to neutralize the immune defense system and to cause tissue destruction. Considering the key roles that P. gingivalis proteases may play in the pathogenesis of periodontitis, inhibitors of these enzymes are considered potentially new therapeutics agents. In recent years, several groups have identified natural plant-derived inhibitors effective on P. gingivalis proteases. More specifically, polyphenols isolated from cranberry and green tea were found to inhibit several proteases produced by P. gingivalis. This paper will discuss the pathological roles of P. gingivalis proteases and review the scientific literature for bioactive plant-derived compounds endowed with a capacity to inhibit these enzymes.

Anti-Porphyromonas gingivalis and Anti-Inflammatory Activities of A-Type Cranberry Proanthocyanidins

ABSTRACT A-type cranberry proanthocyanidins (AC-PACs) have recently been reported to be beneficial for human health, especially urinary tract health. The effect of these proanthocyanidins on periodontitis, a destructive disease of tooth-supporting tissues, needs to be investigated. The purpose of this study was to investigate the effects of AC-PACs on various virulence determinants of Porphyromonas gingivalis as well as on the inflammatory response of oral epithelial cells stimulated by this periodontopathogen. We examined the effects of AC-PACs on P. gingivalis growth and biofilm formation, adherence to human oral epithelial cells and protein-coated surfaces, collagenase activity, and invasiveness. We also tested the ability of AC-PACs to modulate the P. gingivalis-induced inflammatory response by human oral epithelial cells. Our results showed that while AC-PACs neutralized all the virulence properties of P. gingivalis in a dose-dependent fashion, they did not interfere with growth. They also inhibited the secretion of interleukin-8 (IL-8) and chemokine (C-C motif) ligand 5 (CCL5) but did not affect the secretion of IL-6 by epithelial cells stimulated with P. gingivalis. This anti-inflammatory effect was associated with reduced activation of the nuclear factor-κB (NF-κB) p65 pathway. AC-PACs may be potentially valuable bioactive molecules for the development of new strategies to treat and prevent P. gingivalis-associated periodontal diseases.

Cranberry Proanthocyanidins: Natural Weapons against Periodontal Diseases

Cranberry ( Vaccinium macrocarpon ) is known to have a beneficial effect on several aspects of human health. Proanthocyanidins (PACs), the most abundant flavonoids extracted from red cranberry fruits, have been reported to possess antimicrobial, antiadhesion, antioxidant, and anti-inflammatory properties. Recent in vitro studies have shown that cranberry PACs may be potential therapeutic agents for the prevention and management of periodontitis, an inflammatory disease of bacterial origin affecting tooth-supporting tissues. After presenting an overview of cranberry phytochemicals and their potential for human health benefits, this review will focus on the effects of cranberry PACs on connective tissue breakdown and alveolar bone destruction, as well as their potential for controlling periodontal diseases. Possible mechanisms of action of cranberry PACs include the inhibition of (i) bacterial and host-derived proteolytic enzymes, (ii) host inflammatory response, and (iii) osteoclast differentiation and activity. Given that cranberry PACs have shown interesting properties in in vitro studies, clinical trials are warranted to better evaluate the potential of these molecules for controlling periodontal diseases.

Modulation of matrix metalloproteinase and cytokine production by licorice isolates licoricidin and licorisoflavan A: potential therapeutic approach for periodontitis.

BACKGROUND Inflammatory cytokines and matrix metalloproteinases (MMPs) produced by resident and inflammatory cells in response to periodontopathogens play a major role in the tissue destruction observed in periodontitis, which is a disease that affects tooth-supporting structures. In the present study, we investigate the effects of licorice-derived licoricidin (LC) and licorisoflavan A (LIA) on the secretion of various cytokines and MMPs by human monocyte-derived macrophages stimulated with Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) lipopolysaccharide (LPS). METHODS Macrophages were treated with non-toxic concentrations of LC or LIA before being stimulated with A. actinomycetemcomitans LPS. The secretion of cytokines and MMPs and the activation of nuclear factor-kappa B (NF-κB) p65 and activator protein (AP)-1 were assessed by enzyme-linked immunosorbent assays. RESULTS LC and LIA inhibited the secretion of interleukin (IL)-6 and chemokine (C-C motif) ligand 5 in a concentration-dependent manner but did not affect the secretion of IL-8 by LPS-stimulated macrophages. LC and LIA also inhibited the secretion of MMP-7, -8, and -9 by macrophages. The suppression of cytokine and MMP secretion by LC and LIA was associated with the reduced activation of NF-κB p65 but not that of AP-1. CONCLUSION The present study suggests that LC and LIA have potential for the development of novel host-modulating strategies for the treatment of cytokine and/or MMP-mediated disorders such as periodontitis.

Grape seed extract suppresses lipopolysaccharide-induced matrix metalloproteinase (MMP) secretion by macrophages and inhibits human MMP-1 and -9 activities.

BACKGROUND Matrix metalloproteinases (MMPs) produced by resident and inflammatory cells in response to Gram-negative periodontopathogens play a major role in the tissue destruction observed during periodontitis, a disease that affects tooth-supporting structures. In this study, we investigated the effect of grape seed extract (GSE) on MMP secretion by human monocyte-derived macrophages stimulated with Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) lipopolysaccharide (LPS) and on the activity of human recombinant MMP-1 and -9. METHODS Macrophages were treated with various concentrations of GSE prior to being stimulated with A. actinomycetemcomitans LPS. The secretion of MMPs and activation of nuclear factor-kappa B (NF-kappaB) p65 and activator protein-1 (AP-1) were assessed by enzyme-linked immunosorbent assay (ELISA). The effect of GSE on the catalytic activity of human recombinant MMP-1 and -9 was tested using fluorogenic assays. RESULTS GSE inhibited the secretion of MMP-1, -3, -7, -8, -9, and -13 by LPS-stimulated macrophages in a concentration-dependent manner. The suppression of MMP secretion was associated with inhibition of NF-kappaB p65 and AP-1 activation. Also, GSE dose-dependently inhibited the activity of MMP-1 and -9. CONCLUSION The present study suggests that GSE may be potentially used in the development of novel host-modulating strategies for the treatment of MMP-mediated disorders such as periodontitis.

Antibacterial, Antiadherence, Antiprotease, and Anti-Inflammatory Activities of Various Tea Extracts: Potential Benefits for Periodontal Diseases

Porphyromonas gingivalis is a key etiologic agent of chronic periodontitis. This Gram-negative anaerobic bacterium produces several virulence factors and can induce a host inflammatory response that contributes to periodontal disease. In the present study, we investigated green tea, white tea, oolong tea, and black tea extracts with a high polyphenol content for their effects on (i) the growth and adherence of P. gingivalis, (ii) the activity of host and bacterial proteases, and (iii) cytokine secretion by oral epithelial cells. All the tea extracts inhibited the growth of P. gingivalis (minimal inhibitory concentrations ranging from 200 to 500 μg/mL; minimal bactericidal concentrations=500 μg/mL). In addition, they dose dependently reduced the adherence of P. gingivalis to oral epithelial cells. Tea extracts also inhibited the catalytic activity of matrix metalloproteinase (MMP)-9, neutrophil elastase, and P. gingivalis collagenase. Lastly, the tea extracts dose dependently inhibited the secretion of interleukin (IL)-6, IL-8, and chemokine (C-C motif) ligand 5 (CCL-5) by P. gingivalis-stimulated oral epithelial cells. No marked differences in the various effects were observed among the four tea extracts. Extracts from green tea, white tea, oolong tea, and black tea show promise for controlling periodontal disease by their capacity to interfere with P. gingivalis growth and virulence properties, host destructive enzymes, and inflammatory mediator secretion. Such extracts may be incorporated to oral hygiene products or locally delivered into diseased periodontal sites.

Naringenin inhibits human osteoclastogenesis and osteoclastic bone resorption

BACKGROUND AND OBJECTIVE Naringenin, a naturally occurring flavonoid, possesses a wide range of pharmacological properties. The purpose of this study was to investigate the effect of naringenin on human osteoclastogenesis and osteoclastic bone resorption. MATERIAL AND METHODS Naringenin was tested in a human osteoclastogenesis model using primary osteoclast precursor cells activated by receptor activator of nuclear factor-kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) for 6 days. Osteoclastogenesis was assessed by determining the number of tartrate-resistant acid phosphatase (TRAP)-stained multinuclear cells, while the secretion of factors involved in osteoclastogenesis was assessed using enzyme-linked immunosorbent assays. The effect of naringenin on bone resorption was investigated using an OsteoAssay human bone plate coupled with an immunoassay to evaluate the release of helical peptide 620-633 from the alpha1 chain of type I collagen. RESULTS Naringenin was non-toxic at the highest concentration used (50 microg/ml). Naringenin (10, 25 and 50 microg/ml) significantly inhibited osteoclastogenesis (by 29 +/- 5, 57 +/- 8 and 96 +/- 1%, respectively). Naringenin also markedly inhibited the secretion of interleukin (IL)-1alpha (by 59%), IL-23 (by 87%) and monocyte chemoattractant protein-1 (by 58%). Lastly, naringenin (10, 25 and 50 microg/ml) significantly decreased the release of helical peptide 620-633, an indicator of bone resorption activity (by 44 +/- 0.5, 73 +/- 0.5 and 86 +/- 1%, respectively). CONCLUSIONS Naringenin can inhibit human osteoclastogenesis and osteoclastic bone resorption. It thus holds promise as a therapeutic or preventive agent for bone-related diseases such as periodontitis.

Cytoprotective Effect of Proanthocyanidin-rich Cranberry Fraction against Bacterial Cell Wall-mediated Toxicity in Macrophages and Epithelial Cells

Recent studies brought evidence regarding the potential beneficial effects of cranberry polyphenols for periodontal infections. In this study, we evaluated the capacity of a proanthocyanidin‐rich cranberry fraction to protect macrophages and oral epithelial cells against cytotoxicity induced by bacterial components. U937 cells, differentiated into adherent macrophage‐like cells, as well as oral epithelial cells were treated with cell wall or lipopolysaccharide preparations from periodontopathogens. Cell viability was monitored using a commercial MTT (3‐[4,5‐diethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide) assay. The cytoprotective effect was evaluated by pre‐incubating human cells with a proanthocyanidin‐rich cranberry fraction prior to treatment with the bacterial components at toxic concentrations. Among the various bacterial components tested, Peptostreptotoccus micros cell wall was found to be the most toxic for macrophages and epithelial cells and was thus selected for further analyses. Treatment of monocyte‐derived macrophages with cell wall of P. micros (20 µg/ml) decreased the cell viability by approximately 50%. Adding the cranberry fraction prior to treating cells with P. micros cell wall dose‐dependently protected monocyte‐derived macrophages from the toxic effect. A dose‐dependent cytoprotective effect of the cranberry fraction was also observed with oral epithelial cells treated with P. micros cell wall. This study suggests that cranberry polyphenols may exert a protective effect for host cells against the toxicity induced by bacterial components. Copyright