Effects of Butyrate and Propionate on the Adhesion, Growth, Cell Cycle Kinetics, and Protein Synthesis of Cultured Human Gingival Fibroblasts

Microbiota metabolites in bone: Shaping health and Confronting disease

The intricate interplay between the gut microbiota and bone health has become increasingly recognized as a fundamental determinant of skeletal well-being. Microbiota-derived metabolites play a crucial role in dynamic interaction, specifically in bone homeostasis. In this sense, short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, indirectly promote bone formation by regulating insulin-like growth factor-1 (IGF-1). Trimethylamine N-oxide (TMAO) has been found to increase the expression of osteoblast genes, such as Runt-related transcription factor 2 (RUNX2) and bone morphogenetic protein-2 (BMP2), thus enhancing osteogenic differentiation and bone quality through BMP/SMADs and Wnt signaling pathways. Remarkably, in the context of bone infections, the role of microbiota metabolites in immune modulation and host defense mechanisms potentially affects susceptibility to infections such as osteomyelitis. Furthermore, ongoing research elucidates the precise mechanisms through which microbiota-derived metabolites influence bone cells, such as osteoblasts and osteoclasts. Understanding the multifaceted influence of microbiota metabolites on bone, from regulating homeostasis to modulating susceptibility to infections, has the potential to revolutionize our approach to bone health and disease management. This review offers a comprehensive exploration of this evolving field, providing a holistic perspective on the impact of microbiota metabolites on bone health and diseases.

Exploring the effect of butyric acid, a metabolite from periodontopathic bacteria, on primary human melanocytes: An in vitro study

Effects of butyric acid, a bacterial metabolite implicated in periodontitis progression, have never been examined on oral melanocytes. Herein, primary human epidermal melanocytes were used as a model for oral melanocytes. Results show the adverse effects of butyric acid (sodium butyrate; NaB) on them, which comprise marked cytotoxicity at higher concentrations (>1 mM) and robust differentiation at lower nontoxic concentrations. NaB did not alter MITF protein levels; however, it stimulated tyrosinase protein synthesis and inhibited tyrosinase activity, with no changes in cellular melanin. NaB did not affect oxidative stress, although it induced significant levels of the pro-inflammatory cytokine IL-6.

The Peri-Implant Microbiome-A Possible Factor Determining the Success of Surgical Peri-Implantitis Treatment?

The objective was to assess the effect of peri-implantitis surgery on the peri-implant microbiome with a follow-up of one year. A total of 25 peri-implantitis patients in whom non-surgical treatment has failed to solve peri-implantitis underwent resective surgical treatment. Their peri-implant pockets were sampled prior to surgical treatment (T0) and one year post treatment (T12). The natural dentition was sampled to analyse similarities and differences with the peri-implantitis samples. Treatment success was recorded. The change in microbial relative abundance levels was evaluated. The microbiota was analysed by sequencing the amplified V3-V4 region of the 16S rRNA genes. Sequence data were binned to amplicon sequence variants that were assigned to bacterial genera. Group differences were analysed using principal coordinate analysis, Wilcoxon signed rank tests, and t-tests. Beta diversity analyses reported a significant separation between peri-implantitis and natural dentition samples on T0 and T12, along with significant separations between successfully and non-successfully treated patients. Eubacterium was significantly lower on T12 compared to T0 for the peri-implantitis samples. Treponema and Eubacterium abundance levels were significantly lower in patients with treatment success on T0 and T12 versus no treatment success. Therefore, lower baseline levels of Treponema and Eubacterium seem to be associated with treatment success of peri-implantitis surgery. This study might aid clinicians in determining which peri-implantitis cases might be suitable for treatment and give a prognosis with regard to treatment success.

Proof-of-Principle Study Suggesting Potential Anti-Inflammatory Activity of Butyrate and Propionate in Periodontal Cells

Short-chain fatty acids (SCFAs) are potent immune modulators present in the gingival crevicular fluid. It is therefore likely that SCFAs exert a role in periodontal health and disease. To better understand how SCFAs can module inflammation, we screened acetic acid, propionic acid, and butyric acid for their potential ability to lower the inflammatory response of macrophages, gingival fibroblasts, and oral epithelial cells in vitro. To this end, RAW 264.7 and primary macrophages were exposed to LPSs from Porphyromonas gingivalis (P. gingivalis) with and without the SCFAs. Moreover, gingival fibroblasts and HSC2 oral epithelial cells were exposed to IL1β and TNFα with and without the SCFAs. We report here that butyrate was effective in reducing the lipopolysaccharide (LPS)-induced expression of IL6 and chemokine (C-X-C motif) ligand 2 (CXCL2) in the RAW 264.7 and primary macrophages. Butyrate also reduced the IL1β and TNFα-induced expression of IL8, chemokine (C-X-C motif) ligand 1 (CXCL1), and CXCL2 in gingival fibroblasts. Likewise, butyrate lowered the induced expression of CXCL1 and CXCL2, but not IL8, in HSC2 cells. Butyrate further caused a reduction of p65 nuclear translocation in RAW 264.7 macrophages, gingival fibroblasts, and HSC2 cells. Propionate and acetate partially lowered the inflammatory response in vitro but did not reach the level of significance. These findings suggest that not only macrophages, but also gingival fibroblasts and oral epithelial cells are susceptive to the anti-inflammatory activity of butyrate.

Interactions Between Streptococcus gordonii and Fusobacterium nucleatum Altered Bacterial Transcriptional Profiling and Attenuated the Immune Responses of Macrophages

Interspecies coaggregation promotes transcriptional changes in oral bacteria, affecting bacterial pathogenicity. Streptococcus gordonii (S. gordonii) and Fusobacterium nucleatum (F. nucleatum) are common oral inhabitants. The present study investigated the transcriptional profiling of S. gordonii and F. nucleatum subsp. polymorphum in response to the dual-species coaggregation using RNA-seq. Macrophages were infected with both species to explore the influence of bacterial coaggregation on both species' abilities to survive within macrophages and induce inflammatory responses. Results indicated that, after the 30-min dual-species coaggregation, 116 genes were significantly up-regulated, and 151 genes were significantly down-regulated in S. gordonii; 97 genes were significantly down-regulated, and 114 genes were significantly up-regulated in F. nucleatum subsp. polymorphum. Multiple S. gordonii genes were involved in the biosynthesis and export of cell-wall proteins and carbohydrate metabolism. F. nucleatum subsp. polymorphum genes were mostly associated with translation and protein export. The coaggregation led to decreased expression levels of genes associated with lipopolysaccharide and peptidoglycan biosynthesis. Coaggregation between S. gordonii and F. nucleatum subsp. polymorphum significantly promoted both species' intracellular survival within macrophages and attenuated the production of pro-inflammatory cytokines IL-6 and IL-1β. Physical interactions between these two species promoted a symbiotic lifestyle and repressed macrophage's killing and pro-inflammatory responses.

Nrf2 in the Field of Dentistry with Special Attention to NLRP3

The aim of this review article was to summarize the functional implications of the nuclear factor E2-related factor or nuclear factor (erythroid-derived 2)-like 2 (Nrf2), with special attention to the NACHT (nucleotide-binding oligomerization), LRR (leucine-rich repeat), and PYD (pyrin domain) domains-containing protein 3 (NLRP3) inflammasome in the field of dentistry. NLRP3 plays a crucial role in the progression of inflammatory and adaptive immune responses throughout the body. It is already known that this inflammasome is a key regulator of several systemic diseases. The initiation and activation of NLRP3 starts with the oral microbiome and its association with the pathogenesis and progression of several oral diseases, including periodontitis, periapical periodontitis, and oral squamous cell carcinoma (OSCC). The possible role of the inflammasome in oral disease conditions may involve the aberrant regulation of various response mechanisms, not only in the mouth but in the whole body. Understanding the cellular and molecular biology of the NLRP3 inflammasome and its relationship to Nrf2 is necessary for the rationale when suggesting it as a potential therapeutic target for treatment and prevention of oral inflammatory and immunological disorders. In this review, we highlighted the current knowledge about NLRP3, its likely role in the pathogenesis of various inflammatory oral processes, and its crosstalk with Nrf2, which might offer future possibilities for disease prevention and targeted therapy in the field of dentistry and oral health.

The Role of Lactic Acid on Wound Healing, Cell Growth, Cell Cycle Kinetics, and Gene Expression of Cultured Junctional Epithelium Cells in the Pathophysiology of Periodontal Disease

Lactic acid (LA) is short-chain fatty acid, such as butyric acid and propionic acid, that is produced as a metabolite of lactic acid bacteria, including periodontopathic bacteria. These short-chain fatty acids have positive effects on human health but can also have negative effects, such as the promotion of periodontal disease (PD), which is caused by periodontal pathogens present in the gingival sulcus. PD is characterized by apical migration of junctional epithelium, deepening of pockets, and alveolar bone loss. Thus, the junctional epithelial cells that form the bottom of the gingival sulcus are extremely important in investigating the pathophysiology of PD. The aim of this study was to investigate the effect of LA on wound healing, cell growth, cell cycle kinetics, and gene expression of cultured junctional epithelium cells. The results showed that stimulation with 10 mM LA slowed wound healing of the junctional epithelial cell layer and arrested the cell cycle in the G0/G1 (early cell cycle) phase, thereby inhibiting cell growth. However, cell destruction was not observed. LA also enhanced mRNA expression of integrin α5, interleukin (IL)-6, IL-8, intercellular adhesion molecule-1, and receptor activator of nuclear factor kappa-B ligand. The results of this study suggest that stimulation of junctional epithelial cells with high concentrations of LA could exacerbate PD, similarly to butyric acid and propionic acid.

Comparison of Periodontal Bacteria of Edo and Modern Periods Using Novel Diagnostic Approach for Periodontitis With Micro-CT

Ancient dental calculus, formed from dental plaque, is a rich source of ancient DNA and can provide information regarding the food and oral microbiology at that time. Genomic analysis of dental calculus from Neanderthals has revealed the difference in bacterial composition of oral microbiome between Neanderthals and modern humans. There are few reports investigating whether the pathogenic bacteria of periodontitis, a polymicrobial disease induced in response to the accumulation of dental plaque, were different between ancient and modern humans. This study aimed to compare the bacterial composition of the oral microbiome in ancient and modern human samples and to investigate whether lifestyle differences depending on the era have altered the bacterial composition of the oral microbiome and the causative bacteria of periodontitis. Additionally, we introduce a novel diagnostic approach for periodontitis in ancient skeletons using micro-computed tomography. Ancient 16S rDNA sequences were obtained from 12 samples at the Unko-in site (18th-19th century) of the Edo era (1603–1867), a characteristic period in Japan when immigrants were not accepted. Furthermore, modern 16S rDNA data from 53 samples were obtained from a database to compare the modern and ancient microbiome. The microbial co-occurrence network was analyzed based on 16S rDNA read abundance. Eubacterium species, Mollicutes species, and Treponema socranskii were the core species in the Edo co-occurrence network. The co-occurrence relationship between Actinomyces oricola and Eggerthella lenta appeared to have played a key role in causing periodontitis in the Edo era. However, Porphyromonas gingivalis, Fusobacterium nucleatum subsp. vincentii, and Prevotella pleuritidis were the core and highly abundant species in the co-occurrence network of modern samples. These results suggest the possibility of differences in the pathogens causing periodontitis during different eras in history.

Dietary Derived Propionate Regulates Pathogenic Fibroblast Function and Ameliorates Experimental Arthritis and Inflammatory Tissue Priming

Short-chain fatty acids are gut-bacteria-derived metabolites that execute important regulatory functions on adaptive immune responses, yet their influence on inflammation driven by innate immunity remains understudied. Here, we show that propionate treatment in drinking water or upon local application into the joint reduced experimental arthritis and lowered inflammatory tissue priming mediated by synovial fibroblasts. On a cellular level, incubation of synovial fibroblasts with propionate or a physiological mixture of short-chain fatty acids interfered with production of inflammatory mediators and migration and induced immune-regulatory fibroblast senescence. Our study suggests that propionate mediates its alleviating effect on arthritis by direct abrogation of local arthritogenic fibroblast function.

[Sitagliptin inhibits lipopolysaccharide-induced inflammatory response in human gingival fibroblasts by blocking nuclear factor-κB signaling pathway]

OBJECTIVES

This study was performed to clarify the effects of sitagliptin on Porphyromonas gingivalis-lipopolysaccharide (LPS)-induced inflammatory response in human gingival fibroblasts (HGFs), explore the molecular mechanism of its roles, and provide a foundation for clinical therapeutics in periodontitis.

METHODS

Healthy gingival samples were collected from the donors. HGFs were isolated with enzymic digestion method and identified. The effects of LPS and sitagliptin on cell viability were detected by cell-counting kit-8 (CCK8). The mRNA levels of inflammatory cytokines, namely, interleukin (IL)-6, IL-8, C-C motif ligand 2 (CCL2), and superoxide dismutase 2 (SOD2), were evaluated by quantity real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immune sorbent assay (ELISA) was used to measure the secretion protein levels of IL-6, IL-8, and CCL2. Western blot analysis was used to further investigate the activation of nuclear factor (NF)-κB signaling pathway. The effect of NF-κB pathway inhibitor BAY11-7082 on LPS-induced HGF inflammatory cytokines at the gene level was verified by qRT-PCR.

RESULTS

Low concentrations of sitagliptin (0.1, 0.25, and 0.5 µmol·L^-1) did not affect HGF growth in 24 and 48 h, whereas high concentrations of sitagliptin (5-1 000 µmol·L^-1) significantly inhibited cell proliferation. Sitagliptin suppressed 5 µg·mL^-1 of LPS-induced IL-6, IL-8, CCL2, and SOD2 gene expression levels in HGF in a concentration-dependent manner. Furthermore, sitagliptin significantly decreased the elevated secretion of IL-6, IL-8, and CCL2 protein induced by LPS. Western blot analysis showed that 0.5 µmol·L^-1 of sitagliptin significantly inhibited LPS-induced NF-κB signaling pathway activation. Results of qRT-PCR analysis indicated that 0.5 µmol·L^-1 of sitagliptin and 5 µmol·L^-1 of BAY11-7082 significantly inhibited LPS-induced IL-6, IL-8, CCL2, and SOD2 gene expressions.

CONCLUSIONS

Sitagliptin could significantly inhibit LPS-induced HGF inflammatory response by blocking the NF-κB signaling pathway activation.

Molecular subgroup of periodontitis revealed by integrated analysis of the microbiome and metabolome in a cross-sectional observational study

Background: Periodontitis (PT) is a multifactorial, chronic inflammatory disease that can have heterogeneous clinical presentations. The oral microbiome and its metabolites have been implicated as the causes and regulators of PT pathogenesis. In this study, we assessed the oral microbiome and its metabolome in PT patients to clarify the interactions between the microbiome and its metabolites.Methods: A total of 112 subjects were recruited. Buccal and supragingival samples were collected for microbiome analysis. Saliva samples were collected for metabolomic analyses. Microbiome and metabolome data were analyzed and further integrated for combined analysis using various bioinformatics approaches.Results: Oral metabolomic analysis identified 28 metabolites distinguishing the healthy (H) and PT groups. PT group were further clustered into two subgroups (PT_G1 and PT_G2) depending on metabolite profiles. Oral microbiome analysis revealed discriminatory bacterial species in the H, PT_G1, and PT_G2 microbiota. Interestingly, PT_G2 had significantly higher concentration of short chain fatty acids and higher abundance of pathogenic bacteria. Integrated analysis of the microbiome and metabolome showed close association.Conclusion: Our results provide evidence of a close interplay between the oral microbiome and metabolome. Multi-omics approach including microbiome and microbe-associated metabolites may serve as diagnostic biomarkers and enhance treatment prediction in periodontal disease.

Influence of the FIV Status and Chronic Gingivitis on Feline Oral Microbiota

Feline chronic gingivostomatitis (FCGS) has an unclear pathogenesis with the oral microbiome and viral infections, such as feline immunodeficiency virus (FIV), thought to contribute. Although the relationship between the FIV status and FCGS is not clear, one theory is FIV-induced immune dysregulation could contribute to oral dysbiosis, promoting FCGS development. To further understand the relationship between FCGS, FIV infection, and the oral microbiome, oral cavities of forty cats fitting within 4 groups (FIV- without gingivitis, FIV+ without gingivitis, FIV- with gingivitis, FIV+ with gingivitis) were swabbed. Next generation sequencing targeting the V4 region of the 16s rRNA gene was performed for bacterial community profiling. No differences in diversity were observed, however, analysis of the data in terms of gingivitis revealed differences in the relative abundance of taxa and predicted functional output. Odoribacter spp., a bacteria associated with oral disease, was found in higher relative abundances in cats with the highest gingivitis grade. Cats with gingivitis were also found to harbor communities more involved in production of short-chain fatty acids, which have been connected with oral disease. Significant findings associated with the FIV status were few and of low impact, suggesting any connection between the FIV status and FCGS is likely not related to the oral microbiota.

Butyrate Decreases ICAM-1 Expression in Human Oral Squamous Cell Carcinoma Cells

Short-chain fatty acids (SCFA) are bacterial metabolites that can be found in periodontal pockets. The expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) within the epithelium pocket is considered to be a key event for the selective transmigration of leucocytes towards the gingival sulcus. However, the impact of SCFA on ICAM-1 expression by oral epithelial cells remains unclear. We therefore exposed the oral squamous carcinoma cell line HSC-2, primary oral epithelial cells and human gingival fibroblasts to SCFA, namely acetate, propionate and butyrate, and stimulated with known inducers of ICAM-1 such as interleukin-1-beta (IL1β) and tumor necrosis factor-alfa (TNFα). We report here that butyrate but not acetate or propionate significantly suppressed the cytokine-induced ICAM-1 expression in HSC-2 epithelial cells and primary epithelial cells. The G-protein coupled receptor-43 (GPR43/ FFAR2) agonist but not the histone deacetylase inhibitor, trichostatin A, mimicked the butyrate effects. Butyrate also attenuated the nuclear translocation of p65 into the nucleus on HSC-2 cells. The decrease of ICAM-1 was independent of Nrf2/HO-1 signaling and phosphorylation of JNK and p38. Nevertheless, butyrate could not reverse an ongoing cytokine-induced ICAM-1 expression in HSC-2 cells. Overall, these observations suggest that butyrate can attenuate cytokine-induced ICAM-1 expression in cells with epithelial origin.

Salivary Metabolomics: From Diagnostic Biomarker Discovery to Investigating Biological Function

Metabolomic profiling of biofluids, e.g., urine, plasma, has generated vast and ever-increasing amounts of knowledge over the last few decades. Paradoxically, metabolomic analysis of saliva, the most readily-available human biofluid, has lagged. This review explores the history of saliva-based metabolomics and summarizes current knowledge of salivary metabolomics. Current applications of salivary metabolomics have largely focused on diagnostic biomarker discovery and the diagnostic value of the current literature base is explored. There is also a small, albeit promising, literature base concerning the use of salivary metabolomics in monitoring athletic performance. Functional roles of salivary metabolites remain largely unexplored. Areas of emerging knowledge include the role of oral host-microbiome interactions in shaping the salivary metabolite profile and the potential roles of salivary metabolites in oral physiology, e.g., in taste perception. Discussion of future research directions describes the need to begin acquiring a greater knowledge of the function of salivary metabolites, a current research direction in the field of the gut metabolome. The role of saliva as an easily obtainable, information-rich fluid that could complement other gastrointestinal fluids in the exploration of the gut metabolome is emphasized.

Time-Course Transcriptome Analysis of Gingiva-Derived Mesenchymal Stem Cells Reveals That Fusobacterium nucleatum Triggers Oncogene Expression in the Process of Cell Differentiation

Fusobacterium nucleatum has pathogenic effects on oral squamous cell carcinoma and colon cancer, while the effects of continuously altered gene expression in normal human cells, as induced by persistent exposure to F. nucleatum, remain unclear. In this study, a microarray Significant Profiles (maSigPro) analysis was used to obtain the transcriptome profile of gingiva-derived mesenchymal stem cells (GMSCs) stimulated by F. nucleatum for 3, 7, 14, and 21 day, and the results revealed 790 (nine clusters) differentially expressed genes (DEGs), which were significantly enriched in cell adherens junctions and cancer-related pathways. On the basis of a short time-series expression miner (STEM) analysis, all the expressed genes in the GMSCs were grouped into 50 clusters according to dynamic gene expression patterns, and the expression levels of three gene clusters in the F. nucleatum-treated GMSCs were significantly different than the predicted values. Among the 790 DEGs, 50 tumor-associated genes (TAGs; such as L3MBTL4, CD163, CCCND2, CADM1, BCL7A, and IGF1) and five core dynamic DEGs (PLCG2, CHI3L2, L3MBTL4, SH2D2A, and NLRP3) were identified during F. nucleatum stimulation. Results from a GeneMANIA database analysis showed that PLCG2, CHI3L2, SH2D2A, and NLRP3 and 20 other proteins formed a complex network of which 12 genes were enriched in cancer-related pathways. Based on the five core dynamic DEGs, the related microRNAs (miRNAs) and transcription factors (TFs) were obtained from public resources, and an integrated network composed of the related TFs, miRNAs, and mRNAs was constructed. The results indicated that these genes were regulated by several miRNAs, such as miR-372-3p, miR-603, and miR-495-3p, and several TFs, including CREB3, GATA2, and SOX4. Our study suggests that long-term stimulation by F. nucleatum may trigger the expression of cancer-related genes in normal gingiva-derived stem cells.

Persistent Exposure to Fusobacterium nucleatum Triggers Chemokine/Cytokine Release and Inhibits the Proliferation and Osteogenic Differentiation Capabilities of Human Gingiva-Derived Mesenchymal Stem Cells

Fusobacterium nucleatum is one of the most frequent pathogenic bacteria causing periodontitis. The direct effect of Fusobacterium nucleatum (F. nucleatum) on oral stem cells has rarely been reported. In this study, we aimed to evaluate how gingiva-derived mesenchymal stem cells (GMSCs) respond to a direct challenge with F. nucleatum. GMSCs were isolated by the limiting dilution method and exposed to F. nucleatum at various multiplicities of infection (MOIs; F. nucleatum:cell ratios of 10:1, 50:1, and 100:1) for 24 h to 4 weeks. Our results indicated that F. nucleatum significantly inhibited cell proliferation in a dose-dependent manner and promoted cell migration and the release of chemokines/cytokines, such as CCL2, CXCL1, and IL-6. Additionally, F. nucleatum inhibited GMSC osteogenic differentiation partly by decreasing alkaline phosphatase (ALP) activity, mineralized nodule formation, and osteogenesis-related gene and protein expression. RNA-sequencing analyses indicated that F. nucleatum time-dependently activated cellular signaling pathways during the process of osteogenic differentiation. A total of 64 cell differentiation-related genes were found to be differentially expressed between non-infected and F. nucleatum-infected GMSCs at 3, 7, 14, and 21 d. Intriguingly, we discovered that the 64 cell differentiation-related differentially expressed genes (DEGs) were significantly enriched in cancer-related pathways, such as bone cancer, osteosarcoma and bone marrow cancer, which provides new insight into tumorigenesis during the process of GMSC osteogenic differentiation. In conclusion, this study demonstrates that persistent exposure to F. nucleatum promotes cell migration and chemokine/cytokine release and inhibits the proliferation and osteogenic differentiation of GMSCs. Our study provides a novel and long-time bacteria-cell co-culture in vitro model and makes a foundation for the future mechanistic studies of GMSCs under F. nucleatum infection.

Fusobacterium nucleatum Facilitates Apoptosis, ROS Generation, and Inflammatory Cytokine Production by Activating AKT/MAPK and NF-κB Signaling Pathways in Human Gingival Fibroblasts

Fusobacterium nucleatum (F. nucleatum) plays key roles in the initiation and progression of periodontitis. However, the pathogenic effect of F. nucleatum on human oral tissues and cells has not been fully evaluated. In this study, we aimed to analyze the pathogenic effects of F. nucleatum on human gingival fibroblasts (GFs) and clarify the potential mechanisms. RNA-sequencing analysis confirmed that F. nucleatum significantly altered the gene expression of GF as the stimulation time increased. Cell counting and EdU-labeling assays indicated that F. nucleatum inhibited GF proliferation and promoted cell apoptosis in a time- and dose-dependent manner. In addition, cell apoptosis, intracellular reactive oxygen species (ROS) generation, and proinflammatory cytokine production were dramatically elevated after F. nucleatum stimulation. Furthermore, we found that the AKT/MAPK and NF-κB signaling pathways were significantly activated by F. nucleatum infection and that a large number of genes related to cellular proliferation, apoptosis, ROS, and inflammatory cytokine production downstream of AKT/MAPK and NF-κB signaling pathways were significantly altered in F. nucleatum-stimulated GFs. These findings suggest that F. nucleatum inhibits GF proliferation and promotes cell apoptosis, ROS generation, and inflammatory cytokine production partly by activating the AKT/MAPK and NF-κB signaling pathways. Our study opens a new window for understanding the pathogenic effects of periodontal pathogens on the host oral system.

Time-Course Transcriptome Analysis for Drug Repositioning in Fusobacterium nucleatum-Infected Human Gingival Fibroblasts

Fusobacterium nucleatum (F. nucleatum) is a crucial periodontal pathogen and human gingival fibroblasts (GFs) are the first line of defense against oral pathogens. However, the research on potential molecular mechanisms of host defense and effective treatment of F. nucleatum infection in GFs remains scarce. In this study, we undertook a time-series experiment and performed an RNA-seq analysis to explore gene expression profiles during the process of F. nucleatum infection in GFs. Differentially expressed genes (DEGs) could be divided into three coexpression clusters. Functional analysis revealed that the immune-related signaling pathways were more overrepresented at the early stage, while metabolic pathways were mainly enriched at the late stage. We computationally identified several U.S. Food and Drug Administration (FDA)-approved drugs that could protect the F. nucleatum infected GFs via a coexpression-based drug repositioning approach. Biologically, we confirmed that six drugs (etravirine, zalcitabine, wortmannin, calcium D-pantothenate, ellipticine, and tanespimycin) could significantly decrease F. nucleatum-induced reactive oxygen species (ROS) generation and block the Protein Kinase B (PKB/AKT)/mitogen-activated protein kinase signaling pathways. Our study provides more detailed molecular mechanisms of the process by which F. nucleatum infects GFs and illustrates the value of the cogena-based drug repositioning method and the potential therapeutic application of these tested drugs in the treatment of F. nucleatum infection.

Inborn errors of mitochondrial acyl-coenzyme a metabolism: acyl-CoA biology meets the clinic

The last decade saw major advances in understanding the metabolism of Coenzyme A (CoA) thioesters (acyl-CoAs) and related inborn errors (CoA metabolic diseases, CAMDs). For diagnosis, acylcarnitines and organic acids, both derived from acyl-CoAs, are excellent markers of most CAMDs. Clinically, each CAMD is unique but strikingly, three main patterns emerge: first, systemic decompensations with combinations of acidosis, ketosis, hypoglycemia, hyperammonemia and fatty liver; second, neurological episodes, particularly acute "stroke-like" episodes, often involving the basal ganglia but sometimes cerebral cortex, brainstem or optic nerves and third, especially in CAMDs of long chain fatty acyl-CoA metabolism, lipid myopathy, cardiomyopathy and arrhythmia. Some patients develop signs from more than one category. The pathophysiology of CAMDs is not precisely understood. Available data suggest that signs may result from CoA sequestration, toxicity and redistribution (CASTOR) in the mitochondrial matrix has been suggested to play a role. This predicts that most CAMDs cause deficiency of CoA, limiting mitochondrial energy production, and that toxic effects from the abnormal accumulation of acyl-CoAs and from extramitochondrial functions of acetyl-CoA may also contribute. Recent progress includes the following. (1) Direct measurements of tissue acyl-CoAs in mammalian models of CAMDs have been related to clinical features. (2) Inborn errors of CoA biosynthesis were shown to cause clinical changes similar to those of inborn errors of acyl-CoA degradation. (3) CoA levels in cells can be influenced pharmacologically. (4) Roles for acetyl-CoA are increasingly identified in all cell compartments. (5) Nonenzymatic acyl-CoA-mediated acylation of intracellular proteins occurs in mammalian tissues and is increased in CAMDs.

Butyrate Stimulates Histone H3 Acetylation, 8-Isoprostane Production, RANKL Expression, and Regulated Osteoprotegerin Expression/Secretion in MG-63 Osteoblastic Cells

Butyric acid as a histone deacetylase (HDAC) inhibitor is produced by a number of periodontal and root canal microorganisms (such as Porphyromonas, Fusobacterium, etc.). Butyric acid may affect the biological activities of periodontal/periapical cells such as osteoblasts, periodontal ligament cells, etc., and thus affect periodontal/periapical tissue destruction and healing. The purposes of this study were to study the toxic effects of butyrate on the matrix and mineralization marker expression in MG-63 osteoblasts. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cellular apoptosis and necrosis were analyzed by propidium iodide/annexin V flow cytometry. The protein and mRNA expression of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-B ligand (RANKL) were analyzed by Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR). OPG, soluble RANKL (sRANKL), 8-isoprostane, pro-collagen I, matrix metalloproteinase-2 (MMP-2), osteonectin (SPARC), osteocalcin and osteopontin (OPN) secretion into culture medium were measured by enzyme-linked immunosorbant assay. Alkaline phosphatase (ALP) activity was checked by ALP staining. Histone H3 acetylation levels were evaluated by immunofluorescent staining (IF) and Western blot. We found that butyrate activated the histone H3 acetylation of MG-63 cells. Exposure of MG-63 cells to butyrate partly decreased cell viability with no marked increase in apoptosis and necrosis. Twenty-four hours of exposure to butyrate stimulated RANKL protein expression, whereas it inhibited OPG protein expression. Butyrate also inhibited the secretion of OPG in MG-63 cells, whereas the sRANKL level was below the detection limit. However, 3 days of exposure to butyrate (1 to 8 mM) or other HDAC inhibitors such as phenylbutyrate, valproic acid and trichostatin stimulated OPG secretion. Butyrate stimulated 8-isoprostane, MMP-2 and OPN secretion, but not procollagen I, or osteocalcin in MG-63 cells. Exposure to butyrate (2⁻4 mM) for 3 days markedly stimulated osteonectin secretion and ALP activity. In conclusion, higher concentrations of butyric acid generated by periodontal and root canal microorganisms may potentially induce bone destruction and impair bone repair by the alteration of OPG/RANKL expression/secretion, 8-isoprostane, MMP-2 and OPN secretion, and affect cell viability. However, lower concentrations of butyrate (1⁻4 mM) may stimulate ALP, osteonectin and OPG. These effects are possibly related to increased histone acetylation. These events are important in the pathogenesis and repair of periodontal and periapical destruction.

Relationship between periodontal disease and butyric acid produced by periodontopathic bacteria

Background

Periodontopathic bacteria such as Porphyromonas gingivalis produce a large amount of butyric acid as a metabolite. Though butyric acid has been reported to have an anti-inflammatory effect on inflammatory diseases in the gastrointestinal tract, it has been suggested to contribute to the progression of periodontal disease in the oral cavity. The concentration of butyric acid in periodontal tissue of patients with periodontitis patients is reported to increase with the progress of the periodontal disease state. However, the influence of butyric acid on periodontal disease progression is not well known.

Main text

In this review, we have considered the relationship between butyric acid and periodontal disease with respect to the findings reported till date and the knowledge we newly obtained [Shirasugi M et al. Biochem Biophys Res Commun, 2017]. We have studied the relationship between butyric acid and periodontal disease by analyzing the effect of butyric acid on normal human gingival fibroblasts, which are a major component of periodontal tissue. We observed that gingival fibroblasts underwent cytostasis and apoptosis via extrinsic and intrinsic pathways upon long-term exposure to butyric acid. In addition, we showed that TNF-α produced by gingival fibroblasts treated with butyric acid plays an important role in inducing exogenous apoptosis.

Conclusion

Butyric acid produced by periodontopathic bacteria may promote progress of the periodontal disease state. Butyric acid is known to act as an HDAC inhibitor. Thus, we believe that advanced epigenetic analysis of the effects of butyric acid on gingival fibroblasts will help elucidate the periodontal disease pathology and facilitate discovery of new targets for periodontal disease treatment.

Effect of Butyrate on Collagen Expression, Cell Viability, Cell Cycle Progression and Related Proteins Expression of MG-63 Osteoblastic Cells

Aims

Butyric acid is one major metabolic product generated by anaerobic Gram-negative bacteria of periodontal and root canal infection. Butyric acid affects the activity of periodontal cells such as osteoblasts. The purposes of this study were to investigate the effects of butyrate on MG-63 osteoblasts.

Methods

MG-63 cells were exposed to butyrate and cell viability was estimated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mRNA and protein expression of type I collagen and cell cycle-related proteins were measured by reverse-transcriptase polymerase chain reaction (RT-PCR), western blotting or immunofluorescent staining. Cellular production of reactive oxygen species (ROS) was analyzed by 2',7'-dichlorofluorescein (DCF) fluorescence flow cytometry.

Results

Exposure to butyrate suppressed cell proliferation, and induced G2/M (8 and 16 mM) cell cycle arrest of MG-63 cells. Some cell apoptosis was noted. The mRNA expression of cdc2 and cyclin-B1 decreased after exposure to butyrate. The protein expression of type I collagen, cdc2 and cyclin B1 were decreased, whereas the expression of p21, p27 and p57 was stimulated. Under the treatment of butyrate, ROS production in MG-63 cells markedly increased.

Conclusions

The secretion of butyric acid by periodontal and root canal microorganisms may inhibit bone cell growth and matrix turnover. This is possibly due to induction of cell cycle arrest and ROS generation and inhibition of collagen expression. These results suggest the involvement of butyric acid in the pathogenesis of periodontal and periapical tissue destruction by impairing bone healing responses.

Fusobacterium nucleatum infection of gingival epithelial cells leads to NLRP3 inflammasome-dependent secretion of IL-1β and the danger signals ASC and HMGB1

Fusobacterium nucleatum is an invasive anaerobic bacterium that is associated with periodontal disease. Previous studies have focused on virulence factors produced by F. nucleatum, but early recognition of the pathogen by the immune system remains poorly understood. Although an inflammasome in gingival epithelial cells (GECs) can be stimulated by danger-associated molecular patterns (DAMPs) (also known as danger signals) such as ATP, inflammasome activation by this periodontal pathogen has yet to be described in these cells. This study therefore examines the effects of F. nucleatum infection on pro-inflammatory cytokine expression and inflammasome activation in GECs. Our results indicate that infection induces translocation of NF-κB into the nucleus, resulting in cytokine gene expression. In addition, infection activates the NLRP3 inflammasome, which in turn activates caspase-1 and stimulates secretion of mature IL-1β. Unlike other pathogens studied until now, F. nucleatum activates the inflammasome in GECs in the absence of exogenous DAMPs such as ATP. Finally, infection promotes release of other DAMPs that mediate inflammation, such as high-mobility group box 1 protein and apoptosis-associated speck-like protein, with a similar time-course as caspase-1 activation. Thus, F. nucleatum expresses the pathogen-associated molecular patterns necessary to activate NF-κB and also provides an endogenous DAMP to stimulate the inflammasome and further amplify inflammation through secretion of secondary DAMPs.

Development of an oral mucosa model to study host-microbiome interactions during wound healing

Crosstalk between the human host and its microbiota is reported to influence various diseases such as mucositis. Fundamental research in this area is however complicated by the time frame restrictions during which host-microbe interactions can be studied in vitro. The model proposed in this paper, consisting of an oral epithelium and biofilm, can be used to study microbe-host crosstalk in vitro in non-infectious conditions up to 72 h. Microbiota derived from oral swabs were cultured on an agar/mucin layer and challenged with monolayers of keratinocytes grown on plastic or collagen type I layers embedded with fibroblasts. The overall microbial biofilm composition in terms of diversity remained representative for the oral microbiome, whilst the epithelial cell morphology and viability were unaffected. Applying the model to investigate wound healing revealed a reduced healing of 30 % in the presence of microbiota, which was not caused by a reduction of the proliferation index (52.1-61.5) or a significantly increased number of apoptotic (1-1.13) or necrotic (32-30.5 %) cells. Since the model allows the separate study of the microbial and cellular exometabolome, the biofilm and epithelial characteristics after co-culturing, it is applicable for investigations within fundamental research and for the discovery and development of agents that promote wound healing.

Butyrate induces reactive oxygen species production and affects cell cycle progression in human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Short-chain fatty acids, such as butyric acid and propionic acid, are metabolic by-products generated by periodontal microflora such as Porphyromonas gingivalis, and contribute to the pathogenesis of periodontitis. However, the effects of butyrate on the biological activities of gingival fibroblasts (GFs) are not well elucidated.

MATERIAL AND METHODS

Human GFs were exposed to various concentrations of butyrate (0.5-16 mm) for 24 h. Viable cells that excluded trypan blue were counted. Cell cycle distribution of GFs was analyzed by propidium iodide-staining flow cytometry. Cellular reactive oxygen species (ROS) production was measured by flow cytometry using 2',7'-dichlorofluorescein (DCF). Total RNA and protein lysates were isolated and subjected to RT-PCR using specific primers or to western blotting using specific antibodies, respectively.

RESULTS

Butyrate inhibited the growth of GFs, as indicated by a decrease in the number of viable cells. This event was associated with an induction of G0/G1 and G2/M cell cycle arrest by butyrate (4-16 mm) in GFs. However, no marked apoptosis of GFs was noted in this experimental condition. Butyrate (> 2 mm) inhibited the expression of cdc2, cdc25C and cyclinB1 mRNAs and reduced the levels of Cdc2, Cdc25C and cyclinB1 proteins in GFs, as determined using RT-PCR and western blotting, respectively. This toxic effect of butyrate was associated with the production of ROS.

CONCLUSION

These results suggest that butyrate generated by periodontal pathogens may be involved in the pathogenesis of periodontal diseases via the induction of ROS production and the impairment of cell growth, cell cycle progression and expression of cell cycle-related genes in GFs. These events are important in the initiation and prolongation of inflammatory processes in periodontal diseases.

High concentration of sodium butyrate suppresses osteoblastic differentiation and mineralized nodule formation in ROS17/2.8 cells

Periodontitis is a destructive disease that is likely the result of the activities of different microbial complexes, including anaerobic Gram-negative periodontopathic bacteria. Butyric acid (sodium butyrate; BA) is a major metabolic by-product of anaerobic Gram-negative periodontopathic bacteria present in subgingival plaque. This study was undertaken to examine the effect of BA on the expression of osteogenesis-related transcription factors and mineralized nodule formation in osteoblastic ROS17/2.8 cells. The cells were cultured with 0 (control), 10(-5), 10(-4), or 10(-3) M BA for up to 7 days. The gene and protein expression levels of transcription factors such as Runx2, Osterix, Dlx5, Msx2, and AJ18, as well as extracellular matrix proteins such as bone sialoprotein (BSP) and osteocalcin, were examined using real-time PCR and Western blotting, respectively. Mineralized nodule formation was detected by alizarin red staining. The expression of Runx2, Osterix, Dlx5, and Msx2 decreased significantly in the presence of 10(-3 )M BA compared to the control, whereas AJ18 expression increased significantly. Mineralized nodule formation decreased markedly in the presence of 10(-3) M BA. Alkaline phosphatase activity and the expression of bone sialoprotein and osteocalcin decreased significantly in the presence of 10(-3) M BA compared to the control. These results suggest that 10(-3) M BA suppresses osteoblastic differentiation and mineralized nodule formation in ROS17/2.8 cells.

The role of reactive oxygen species and hemeoxygenase-1 expression in the cytotoxicity, cell cycle alteration and apoptosis of dental pulp cells induced by BisGMA

Biocompatibility of dentin bonding agents (DBAs) and resin composite is important to preserve the pulp vitality after operative restoration. Bisphenol-glycidyl-methacrylate (BisGMA) is one common monomer adding into DBAs and resin. In this study, we found that exposure of human dental pulp cells to BisGMA (>0.1 mM) led to cytotoxicity, G2/M cell cycle arrest and apoptosis as analyzed by propidium iodide (PI) and PI/annexin V dual fluorescent flow cytometry. These events were associated with a decline of cdc2, cdc25C and cyclinB1 expression at both mRNA and protein levels. BisGMA also induced the expression of hemeoxygenase-1 (HO-1), an oxidative stress responsive gene, in pulp cells. Catalase could prevent the BisGMA-induced alteration of cell cycle-related genes (cdc2, cdc25C, cyclinB1) and HO-1 expression in dental pulp cells. Interestingly, Zn-protoporphyrin (2.5-5 microM), a HO inhibitor, enhanced the BisGMA-induced reactive oxygen species (ROS) production and cytotoxicity. These results suggest that exposure to higher concentrations of BisGMA may stimulate ROS production, cell cycle arrest, apoptosis and cell death. Inducing the expression of HO-1 in dental pulp cells by BisGMA is mediated by ROS production and important to protect dental pulp against the toxicity by monomers present in composite resin and DBAs.

Butyrate, a bacterial metabolite, induces apoptosis and autophagic cell death in gingival epithelial cells

BACKGROUND AND OBJECTIVE

Butyrate is produced by some types of anaerobic periodontal bacteria. Millimolar concentrations of butyrate are found in mature dental plaque from periodontitis patients. Although butyrate reportedly has a variety of effects in many mammalian cells, its effect on gingival epithelial cells is not well known. In this study, we investigated the effect of butyrate on gingival epithelial Ca9-22 cell death.

MATERIAL AND METHODS

Death of Ca9-22 cells was assessed after treating the cells with or without butyrate. A SYTOX Green dye, which exhibits strong green fluorescence once it enters dead cells through ruptured cell membranes, was used for cell death detection. Phosphatidylserine redistribution was measured using fluorescein isothiocyanate-labeled annexin V. The activity of caspase-3 was measured as the amount of cleaved substrate peptide. Anti-apoptotic bcl-2 mRNA expression was measured using real-time RT-PCR. Western blotting and fluoromicroscopic analysis with anti-microtubule-associated protein 1 light chain 3 (LC3) antibodies were performed for detection of autophagy.

RESULTS

Stimulation with millimolar concentrations of butyrate for 48 h induced Ca9-22 cell death. The stimulation also caused increased caspase-3 activity, phosphatidylserine redistribution and bcl-2 down-regulation, suggesting butyrate-induced apoptosis. However, the pan-caspase inhibitor, Z-VAD-FMK, did not inhibit cell death completely. This implies the existence of other types of cell death. In addition, markers of autophagy, namely, the conversion of LC3-I to LC3-II and increased LC3 accumulation, were observed. Moreover, inhibition of autophagy by 3-methyladenine suppressed the butyrate-induced cell death, suggesting that butyrate could induce cell death through autophagy.

CONCLUSION

These data suggest that butyrate induces apoptosis and autophagic cell death.

Effects of a bacterial lipid byproduct on human pulp fibroblasts in vitro

Butyrate, a short chain fatty acid, is a metabolic lipid byproduct of various root canal pathogens, such as Porphyromonas endodontalis. However, little is known about the effects of butyrate on cultured human pulp fibroblasts. H33258 fluorescence, flow cytometry, and protein synthesis assays were used to investigate the pathobiologic effects of butyrate on cultured human pulp fibroblasts. Butyrate exhibited cytotoxic effects on human pulp fibroblasts in a concentration-dependent manner (p < 0.05). The addition of butyrate resulted in G2/M phase arrest (p < 0.05). Butyrate also inhibited protein synthesis in a dose-dependent manner (p < 0.05). To determine whether glutathione (GSH) levels were important in the cytotoxicity of butyrate, we pretreated cells with the GSH precursor, 2-oxothiazolidine-4-carboxylic acid (OTZ), to boost thiol levels, or buthionine sulfoximine (BSO) to deplete GSH. The addition of OTZ acted as a protective effect on the butyrate-induced cytotoxicity (p < 0.05). In contrast, the addition of BSO enhanced the butyrate-induced cytotoxicity (p < 0.05). These results indicate that butyrate is cytotoxic to human pulp fibroblasts by inhibiting cell growth, cell-cycle kinetics, and protein synthesis. These inhibitory effects were associated with intracellular GSH levels.

Signaling mechanism of thrombin-induced gingival fibroblast-populated collagen gel contraction

1.--Thrombin is activated during gingival tissue injury and inflammation. Thrombin (platelet)-rich plasma has been used for periodontal regeneration with success. Thrombin and other bacterial proteases also affect the functions of adjacent periodontal cells via stimulation of protease-activated receptors (PARs). 2.--We noted that thrombin (0.1-2 U ml(-1)), human, and frog PAR-1 agonist peptide (20-240 microM) induced the gingival fibroblast (GF)-populated collagen gel contraction within 2 h of exposure. However, PAR-2, PAR-3, and PAR-4 agonist peptide (20-240 microM) showed little effect on collagen gel contraction. U73122 (phospholipase C inhibitor) and 2-APB (IP3 antagonist) were effective in inhibition of GF contraction. 3.--Thrombin-induced GF contraction was inhibited by 5 mM EGTA (an extracellular calcium chelator) and verapamil (an L-type calcium channel blocker). In addition, W7 (10 and 25 microM, a calcium/calmodulin (CaM) inhibitor), ML-7 (50 microM, myosin light chain kinase (MLCK) inhibitor), and HA1077 (100 microM, Rho kinase inhibitor) completely inhibited the thrombin-induced collagen gel contraction. Thrombin also induced the phosphorylation of ERK1/ERK2 and elevated the Rho-GTP levels in GF. 4.--However, U0126 only partially inhibited the thrombin-induced GF contraction. Similarly, wortmannin (100 nM), LY294002 (20 microM) (two PI3K inhibitor) and genistein also showed partial inhibition. Moreover, NAC was not able to suppress the GF contraction, as supported by the slight decrease in reactive oxygen species production in GF by thrombin. 5.--Thrombin also stimulated metalloproteinase-2 (MMP-2) and MMP-3 production in GF. But addition of GM6001 or 1,10-phenanthroline, two MMP inhibitors, could not inhibit the thrombin-induced GF contraction. 6.--These results indicate that thrombin is crucial in the periodontal inflammation and wound healing by promoting GF contraction. This event is mainly mediated via PAR-1 activation, PLC activation, extracellular calcium influx via L-type calcium channel, and the calcium/CaM-MLCK and Rho kinase activation pathway.

Antimicrobial actions of benzimidazoles against the oral anaerobes Fusobacterium nucleatum and Prevotella intermedia

BACKGROUND/OBJECTIVE

Benzimidazoles are widely used as proton-pump inhibitors to control stomach hyperacidity and have been found also to have antimicrobial actions against Helicobacter pylori and oral streptococci. Our primary aim was to determine if they are active also against oral anaerobes associated with gingivitis. Our major focus was on catabolism because it leads to production of inflammatory metabolites such as butyrate and ammonia. The benzimidazoles are effective in the protonated form at acid pH values and cause irreversible inhibition of enzymes associated with formation of drug-target disulfide bonds.

METHODS

Fusobacterium nucleatum ATCC 25586 and Prevotella intermedia ATCC 25611 were grown anaerobically in suspension cultures, harvested, washed and exposed to the benzimidazole lansoprazole at pH values of 4 or 5 before being washed and used for standard assays to detect inhibition of catabolic functions, uptake of the agent and lethality.

RESULTS

Lansoprazole was found to be a bacteriostatic, multi-target antimicrobial against F. nucleatum under anaerobic conditions inhibitory for amino acid fermentation and also for glycolysis of glucose or fructose. ID(50) values for fermentation of amino acids and dipeptides by F. nucleatum ranged from 0.05 mM for lysine to 0.25 mM for serine. Fructose catabolism was highly sensitive with an ID(50) value of 0.03 mM apparently related to high sensitivity of the phosphoenolpyruvate:fructose phosphotransferase system, while the ID(50) for glucose catabolism by intact cells was some 0.07 mM. Fermentation of aspartate or aspartylaspartate by P. intermedia was found to be lansoprazole-sensitive with ID(50) values of about 0.18 and 0.20 mM, respectively.

CONCLUSION

Catabolism of amino acids, dipeptides and sugars by oral anaerobes associated with gingivitis are sensitive to the inhibitory actions of lansoprazole. Thus, catabolic pathways are potential targets for use of benzimidazoles against bacteria involved in gingivitis.

Toxic and metabolic effect of sodium butyrate on SAS tongue cancer cells: Role of cell cycle deregulation and redox changes

Butyrate is a metabolite produced by oral and colonic microorganism. Butyrate has been shown to reduce colon cancer, whereas its role in oral carcinogenesis is not clear. Butyrate concentration in dental plaque and saliva ranged from 0.2 to 16 mM. In this study, we found that sodium butyrate inhibited the growth of SAS tongue cancer cells by 32% and 53% at concentrations of 1 and 2mM, respectively. Low concentrations of sodium butyrate (1-8mM) induced G0/G1 cell cycle arrest of SAS cells, whereas concentrations of 4-16 mM elicited G2/M arrest and a slight increase in apoptotic cell populations. These events were concomitant with induction of intracellular reactive oxygen species (ROS) production. An elevation in p21 mRNA and protein level was noted in SAS cells by sodium butyrate. On the contrary, a decline of cyclin Bl, cdc2 and cdc25C mRNA and protein expression in SAS cells was found after exposure to sodium butyrate. In addition, no evident increase in cdc2 inhibitory phosphorylation was found in sodium butyrate-treated SAS cancer cells. Inclusion of N-acetyl-l-cysteine (NAC) (3mM), catalase (1000 U/ml) and dimethylthiourea (DMT, 5mM), and also SOD (500 U/ml) attenuated the sodium butyrate-induced ROS production in SAS cells. However, they were not able to prevent the cell cycle arrest, apoptosis and growth inhibition in SAS cells induced by 1, 2 and 16 mM of sodium butyrate. These results indicate that sodium butyrate is toxic and inhibits the tongue cancer cell growth via induction of cell cycle arrest and apoptosis. Sodium butyrate mediates these events by mechanisms additional to ROS production.

Multi-target antimicrobial actions of zinc against oral anaerobes

OBJECTIVE

Zinc is used in oral care products as an antiplaque/antigingivitis agent. Our objective was to assess the antimicrobial actions of zinc against oral anaerobes associated with gingivitis, specifically Fusobacterium nucleatum and Prevotella intermedia, with focus on catabolism and oxidative metabolism.

METHODS

The oral anaerobes were grown in complex medium in an anaerobic chamber, harvested by centrifugation and used directly for experiments with suspensions. Biofilm growth involved super-infection by F. nucleatum of an initial biofilm formed by Streptococcus sanguis.

RESULTS

Zn(2+) inhibited catabolism of glutamate, glutamyl-glutamate, glucose and fructose by F. nucleatum cells in suspensions with ID(50) values, respectively, of 0.05, 0.005, 0.01 and 0.01 mM. The ID(50) value for inhibition of glutamate catabolism by biofilms was 0.10 mM. Inhibition of glutamate catabolism could be related to inhibition of substrate uptake and of 2-oxoglutarate reductase. Zn(2+) also inhibited catabolism of aspartate or aspartyl-aspartate by P. intermedia with ID(50) values of 0.07 and about 0.03 mM, respectively. Respiration of intact cells of F. nucleatum and NADH oxidase in cell extracts were sensitive to zinc with ID(50) values, respectively, of about 1.0 and 1.4 mM. Zinc also inhibited production of hydrogen peroxide by F. nucleatum (ID(50) = ca. 0.04 mM.) but at high concentrations acted to potentiate and enhance peroxide killing of the anaerobe.

CONCLUSION

Zn(2+) is a potent inhibitor of catabolism by F. nucleatum and P. intermedia, including catabolism of peptides, which can be degraded to yield inflammatory metabolic end products. Zn(2+) also inhibits O(2) metabolism of F. nucleatum by about 50% and hydrogen peroxide production nearly completely but also enhances killing by peroxide added to cells.

Effects of root-end filling materials and eugenol on mitochondrial dehydrogenase activity and cytotoxicity to human periodontal ligament fibroblasts

Various root-end filling materials have been used to prevent the entry of root-canal pathogens into periapical regions. Five root-end filling materials were compared regarding the cytotoxicity, apoptosis, and mitochondrial dehydrogenase (MDH) activities of human periodontal ligament (PDL) fibroblasts, with the use of a novel transwell culture system. Exposure to IRM (a ZnO eugenol-based intermediate restorative material), a 2-ethoxybenzoic acid cement (Super EBA), and amalgam for 3 days inhibited the MDH activity of PDL fibroblasts as indicated by decrease in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction by 97%, 95%, and 51%, respectively. Evident suppression of MTT reduction by amalgam and glass ionomer cement (GIC) was noted after 5 days of exposure, with 73% and 46% of inhibition, respectively. Mineral trioxide aggregates (MTA) showed little effect on MDH activity. IRM and Super EBA were cytotoxic to PDL fibroblasts as indicated by a trypan blue dye exclusion technique. GIC and amalgam showed mild cytotoxicity. IRM, GIC, and amalgam further induced apoptosis of PDL cells, as revealed by the presence of sub-G0/G1 DNA content in flow cytometric histogram. Twenty-four-hour exposure to IRM and Super EBA elevated the MDH activities to 156% and 117%, correspondingly, of that of control. Eugenol, a phenolic ingredient in Super EBA and IRM, also increases MDH activity of PDL fibroblasts by 45% and 51%, at concentrations of 0.5 and 1 mM. However, at concentrations higher than 0.5 mM, eugenol decreased the number of viable PDL fibroblasts. These results suggest that MTA is a biocompatible root-end filling material, followed by self-curing Fuji II GIC and amalgam. IRM and Super EBA ingredients induced marked cytotoxicity and transiently stimulate MDH activities, which is possibly due to their content of eugenol and induction of cellular adaptive response.

Protease-activated receptor-1-induced calcium signaling in gingival fibroblasts is mediated by sarcoplasmic reticulum calcium release and extracellular calcium influx

Thrombin is a serine protease activated during injury and inflammation. Thrombin and other proteases generated by periodontal pathogens affect the behavior of periodontal cells via activation of protease-activated receptors (PARs). We noted that thrombin and PAR-1 agonist peptide stimulated intracellular calcium levels ([Ca2+]i) of gingival fibroblasts (GF). This increase of [Ca2+]i was inhibited by EGTA and verapamil. U73122 and neomycin inhibited thrombin- and PAR-1-induced [Ca2+]i. Furthermore, 2-APB (75-100 microM, inositol triphosphate [IP3] receptor antagonist), thapsigargin (1 microM), SKF-96365 (200 microM) and W7 (50 and 100 microM) also suppressed the PAR-1- and thrombin-induced [Ca2+]i. However, H7 (100, 200 microM) and ryanodine showed little effects. Blocking Ca2+ efflux from mitochondria by CGP37157 (50, 100 microM) inhibited both thrombin- and PAR-1-induced [Ca2+]i. Thrombin induced the IP3 production of GF within 30-seconds of exposure, which was inhibited by U73122. These results indicate that mitochondrial calcium efflux and calcium-calmodulin pathways are related to thrombin and PAR-1 induced [Ca2+]i in GF. Thrombin-induced [Ca2+]i of GF is mainly due to PAR-1 activation, extracellular calcium influx via L-type calcium channel, PLC activation, then IP3 binding to IP3 receptor in sarcoplasmic reticulum, which leads to intracellular calcium release and subsequently alters cell membrane capacitative calcium entry.

Degradation of arginine and other amino acids by butyrate-producing asaccharolytic anaerobic Gram-positive rods in periodontal pockets

The use of 20 amino acids by butyrate-producing asaccharolytic anaerobic Gram-positive rods (AAGPRs) in periodontal pockets, i.e. Eubacterium minutum, Filifactor alocis, E. infirmum, E. sulci and E. saphenum, was studied. E. minutum used only arginine and lysine, and produced substantial amounts of butyrate and ammonia as the main metabolic products from arginine, and acetate, butyrate and ammonia from lysine. Fi. alocis used arginine alone and produced butyrate and ammonia. E. infirmum, E. sulci and E. saphenum used lysine alone and produced acetate, butyrate and ammonia. The growth of these bacterial species was supported and enhanced by arginine and/or lysine enriched to culture media, but not by the other amino acids. Arginine deiminase, ornithine carbamoyltransferase and carbamate kinase activity were detected in the cell-free extract of E. minutum, suggesting that arginine was metabolised to citrulline initially, and subsequently to ornithine and carbamoyl phosphate. Ornithine and carbamoyl phosphate were further converted to butyrate, and carbon dioxide and ammonia, respectively. Enzymatic activity of arginine deiminase and ornithine carbamoyltransferase was not detected in Fi. alocis, indicating that Fi. alocis converted arginine to ornithine directly, not via citrulline, and further to butyrate.

Anaerobic cocci populating the deep tissues of chronic wounds impair cellular wound healing responses in vitro

BACKGROUND

Anaerobic cocci are estimated to be present in the deep tissues of over 50% of chronic skin wounds. While the part they play in the chronicity of these wounds is uninvestigated, anaerobic cocci have previously been shown to be involved in other chronic inflammatory human conditions.

METHODS

In this study the anaerobic microflora of the deep tissues of 18 patients with refractory chronic venous leg ulcers (mean age 80.3 years; mean duration > 24 months) was characterized using strict anaerobic culture conditions. The effect of the anaerobic organisms isolated from these tissues on extracellular matrix (ECM) proteolysis and cellular wound healing responses was studied using in vitro models.

RESULTS

Anaerobic organisms were present in the deep tissues of 14 of 18 wounds and were principally Peptostreptococcus spp. The effects of three Peptostreptococcus spp. isolated from these wounds (P. magnus, P. vaginalis and P. asaccharolyticus) on cellular wound healing responses were compared with those of two pathogenic organisms also isolated from these wounds (Pseudomonas aeruginosa and Citrobacter diversus). While the direct ECM proteolytic activity exhibited by the Peptostreptococcus spp. was limited, they did significantly inhibit both fibroblast and keratinocyte proliferation, but only at high concentrations. However, at lower concentrations peptostreptococcal supernatants profoundly inhibited keratinocyte wound repopulation and endothelial tubule formation. The magnitude of these effects varied between strains and they were distinct from those demonstrated by Pseudomonas aeruginosa and Citrobacter diversus.

CONCLUSIONS

These studies confirm the importance of anaerobic organisms in chronic wounds and demonstrate an indirect, strain-specific mechanism by which these microorganisms may play a part in mediating the chronicity of these wounds.

Potential role of anaerobic cocci in impaired human wound healing

Although more than 80% of infected and 70% of noninfected leg ulcers have been shown to harbor anaerobic organisms, their role in mediating impaired wound healing in the skin is frequently overlooked. There is now increasing evidence that the gram-positive anaerobic cocci play a role (both directly and indirectly) in mediating impaired wound healing in vivo. This article discusses the mechanisms by which these microorganisms may interfere with the inflammation, repair, and remodeling phases of the wound healing process.

Inducing the cell cycle arrest and apoptosis of oral KB carcinoma cells by hydroxychavicol: roles of glutathione and reactive oxygen species

Hydroxychavicol (HC; 10 - 50 microM), a betel leaf component, was found to suppress the 2% H(2)O(2)-induced lucigenin chemiluminescence for 53 - 75%. HC (0.02 - 2 microM) was also able to trap superoxide radicals generated by a xanthine/xanthine oxidase system with 38 - 94% of inhibition. Hydroxyl radicals-induced PUC18 plasmid DNA breaks was prevented by HC (1.6 - 16 microM). A 24-h exposure of KB cells to HC (0.5, 1 mM) resulted in 54 - 74% cell death as analysed by a 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. HC (10, 50 microM) further suppressed the growth of KB cells (15 and 76%, respectively). Long-term colony formation of KB cells was inhibited by 51% with 10 microM HC. Pretreatment of KB cells with 100 microM HC inhibited the attachment of KB cells to type I collagen and fibronectin by 59 and 29%, respectively. Exposure of KB cells to 0.1 mM HC for 24 h resulted in cell cycle arrest at late S and G2/M phase. Increasing the HC concentration to 0.25 and 0.5 mM led to apoptosis as revealed by detection of sub-G(0)/G(1) peaks with a concomitant decrease in the number of cells residing in late S and G(2)/M phase. Inducing the apoptosis of KB cells by HC was accompanied by marked depletion in reduced form of GSH (>0.2 mM) and the increasing of reactive oxygen species production (>0.1 mM) as analysed by CMF- and DCF-single cell fluorescence flow cytometry. These results indicate that HC exerts antioxidant property at low concentration. HC also inhibits the growth, adhesion and cell cycle progression of KB cells, whereas its induction of KB cell apoptosis (HC>0.1 mM) was accompanied by cellular redox changes.

Periodontal disease as a specific, albeit chronic, infection: diagnosis and treatment

Periodontal disease is perhaps the most common chronic infection in adults. Evidence has been accumulating for the past 30 years which indicates that almost all forms of periodontal disease are chronic but specific bacterial infections due to the overgrowth in the dental plaque of a finite number of mostly anaerobic species such as Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola. The success of traditional debridement procedures and/or antimicrobial agents in improving periodontal health can be associated with the reduction in levels of these anaerobes in the dental plaque. These findings suggest that patients and clinicians have a choice in the treatment of this overgrowth, either a debridement and surgery approach or a debridement and antimicrobial treatment approach. However, the antimicrobial approach, while supported by a wealth of scientific evidence, goes contrary to centuries of dental teaching that states that periodontal disease results from a "dirty mouth." If periodontal disease is demonstrated to be a risk factor for cardiovascular disease and stroke, it will be a modifiable risk factor since periodontal disease can be prevented and treated. Since the antimicrobial approach may be as effective as a surgical approach in the restoration and maintenance of a periodontally healthy dentition, this would give a cardiac or stroke patient and his or her physician a choice in the implementation of treatment seeking to improve the patient's periodontal condition so as to reduce and/or delay future cardiovascular events.

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts

BACKGROUND AND OBJECTIVE

The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair.

STUDY DESIGN/MATERIALS AND METHODS

Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining.

RESULTS

The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality.

CONCLUSION

Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.